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VC 87402— 950 1-75 2,500
California state
Water Project
Volume in
Storage
Facilities
Bulletin Number 200
November 1974
state of CalHomia
The Resources Agency
Department of Water Resources
STATE OF CALIFORNIA
The Resources Agency
Department of Wa ter Resources
BULLETIN No. 200
CALIFORNIA
STATE WATER PROJECT
Volume ill
Storage Facilities
NOVEMBER 1974
NORMAN B. LIVERMORE, JR. RONALD REAGAN JOHN R. TEERINK
Secretary for Resources Governor Director
I The Resources Agency State of California Department of Water Resources
Copies of this bulletin at $5.00 each may be ordered from:
State of California
DEPARTMENT OF WATER RESOURCES
P.O. Box 388
Sacromento, California 95802
Moke checks payable to STATE OF CALIFORNIA
California residents add sates tax.
FOREWORD
This is the third of six volumes which record aspects of the planning, financing, design,
construction, and operation of the California State Water Project. The subjects of the other
volumes are: \'olume I, History, Planning, and Early Progress; \'olume II, Conveyance Facilities;
\'olume I\', Power and Pumping Facilities; \'olume \\ Control Facilities; and \'olume \'I,
Project Supplements.
The State Water Project conserves and distributes water to much of California's population and
irrigated agriculture. It also provides electric power generation, flood control, water quality
control, new recreational opportunities, and enhancement of sports fisheries and wildlife habitat.
Construction of the first phase of the State Water Project was completed in 1973. The $2.3
billion reimbursable cost is being repaid by the water users and other beneficiaries. It is expected
that another $0.7 billion will be spent during the next decade to construct authorized facilities
for full operation.
This volume discusses storage facilities of the State Water Project and how the various dams
and reservoirs function in the Project as a whole. The individual dams and reservoirs are de-
scribed in detail, the extent of coverage varying with the size, importance, and uniqueness of the
individual facility. Geologic conditions at each site are discussed and construction highlights are
presented.
y John R. Teerink, Director
Department of Water Resources
The Resources Agency
State of California
TABLE OF CONTENTS
Page
FOREWORD iii
ORGANIZATION AND POSITIONS OF RESPONSIBILITY xxxvi
ABSTRACT xli
CHAPTER I. GENERAL
Overview 1
Upper Feather River Division 2
Oroville Division 3
North San Joaquin Division and South Bay Aqueduct 4
San Luis Division 6
South San Joaquin and Tehachapi Divisions 6
Mojave Division 7
Santa Ana Division 7
West Branch Division 8
Design 8
Construction 8
CHAPTER II. FRENCHMAN DAM AND LAKE
General 13
Description and Location 13
Purpose 14
Chronology 14
Regional Geology and Seismicity 14
Design 14
Dam 14
Description 14
Stability Analysis 14
Settlement 14
Construction Materials IS
Foundation 15
Instrumentation 18
Outlet Works 18
Description 18
Structural Design 18
Mechanical and Electrical Installations 18
Spillway 18
Description 18
Hydraulics 18
Structural Design 18
Construction 24
Contract Administration 24
Diversion and Care of Stream 24
Foundation 24
Dewatering 24
Excavation 24
Grouting 24
Handling of Borrow Materials 24
Impervious 24
Drain 24
TABLE OF CONTENTS— Continued
Page
Slope Protection 24
Embankment Construction 24
Impervious 24
Drain 26
Slope Protection 26
Outlet Works 26
Spillway 26
Excavation 26
Anchorage 27
Concrete Placement 27
Concrete Curing 27
Backfill 28
Concrete Production 28
Reservoir Clearing 28
Closure 28
Bibliography 29
CHAPTER III. ANTELOPE DAM AND LAKE
General 31
Description and Location 31
Purpose 32
Chronology 32
Regional Geology and Seismicity 32
Design 32
Dam 32
Description 32
Stability Analysis 33
Settlement 33
Construction Materials 33
Foundation 33
Outlet Works 36
Description 36
Structural Design 36
Mechanical Installation 36
Spillway 36
Description 36
Hydraulics 36
Structural Design 36
Construction 40
Contract Administration 40
Foundation 40
Dewatering 40
Excavation 40
Grouting 40
Handling of Borrow Materials 40
Impervious 40
Pervious 40
Slope Protection 42
Embankment Construction 42
TABLE OF CONTENTS— Continued
Page
Impervious 42
Pervious 42
Slope Protection 42
Outlet Works 42
Excavation 42
Concrete 42
Spillway 42
Excavation 42
Concrete 42
Concrete Production 42
Reservoir Clearing 42
Closure 43
Instrumentation 43
Bibliography 45
CHAPTER I\'. GRIZZLY VALLEY DAM AND LAKE DAVIS
General 47
Description and Location 47
Purpose 48
Chronology 48
Regional Geology and Seismicity 48
Design 48
Dam 48
Description 48
Stability Analysis 49
Settlement 49
Construction Materials 49
Foundation 49
Instrumentation 51
Outlet Works 51
Description 51
Hydraulics 51
Structural Design 51
Mechanical Installation 51
Spillway 51
Description 51
Hydraulics 51
Structural Design 51
Grizzly \'alley Pipeline 51
Construction 56
Contract Administration 56
Diversion and Care of Stream 56
Excavation for Dam and Dewatering Foundation 56
Handling of Borrow Materials 56
Embankment 56
Outlet Works 56
Excavation 56
Concrete 58
TABLE OF CONTENTS— Continued
Page
Mechanical Installation 59
Spillway 59
Excavation 59
Concrete 59
Concrete Production 60
Reservoir and Other Clearing 60
Initial Reservoir Filling 60
Bibliography 61
CHAPTER V. OROVILLE DAM AND LAKE OROVILLE
General 63
Description and Location 63
Purpose 65
Chronology and Alternative Dam Studies 65
Construction Schedule 67
Regional Geology and Seismicity 67
Design 68
Dam 68
Description 68
Configuration and Height 68
Construction Materials 71
Laboratory Testing 73
Test Fills 74
Stability Analyses 74
Other Earthquake Considerations ^ 77
Settlement, Pore-Pressure, and Crest-Camber Studies 77
Foundation 77
Site Geology 77
Exploration 78
Excavation Criteria 78
Grouting 78
Core Block 78
Grout Gallery 81
Tunnel Systems 81
Diversion-Tailrace Tunnels 82
River Outlet 83
Diversion Tunnel Intake Portal Structures 83
Diversion-Tailrace Tunnel Outlet Portal Structures 88
River Outlet Access Tunnel 88
Powerhouse Emergency Exit Tunnel 88
Core Block Access Tunnel 88
Palermo Outlet Tunnel 88
Spillway 92
Headworks 93
Chute 100
Emergency Spillway 100
Saddle Dams 100
Location 100
TABLE OF CONTENTS— Continued
Page
Description 100
Site Geology 105
Embankment Design 105
Foundation Grouting 105
Construction Materials 105
Stability Analysis 105
Instrumentation 107
Dam 107
Spillway 107
Saddle Dams 107
Relocations 107
Western Pacific Railroad 107
Tunnels 107
Bridges 109
Feather River Bridge 109
West Branch Bridge 109
North Fork Bridge 110
Feather River Railway 110
Oroville-Quincy Road 1 10
Forbestown Road to Bidwell Bar Bridge 110
Bidwell Bar Bridge to Original County Road Ill
Bidwell Bar Bridge 1 1 1
Canyon Creek Bridge 112
Oroville-Feather Falls Road 113
B. Abbott Goldberg Bridge 113
U.S. Highway 40A 114
Nelson Bar County Road 114
Bennum Road 114
Lunt Road 114
U.S. Forest Service Roads 114
Construction..... 114
Contract Administration 1 14
Early Contracts 1 16
Relocations 116
Diversion Tunnel No. 1 116
Palermo Outlet Works 1 17
Initial Dam Construction Activities 118
Diversion of River and Dewatering of Foundation 118
Foundation Preparation 119
Stripping 119
Core Trench Excavation 119
Grout Gallery Excavation 1 19
Core Block Excavation 1 19
Factors Affecting Contractor's Progress 120
Core Block 120
Grout Gallery 121
Core Block Access Tunnel 122
TABLE OF CONTENTS— Continued
Page
Production of Embankment Materials 122
Pervious 122
Impervious 123
Training Dikes 125
Materials Hauling Facilities 125
Dam Embankment 125
Chronology 125
Construction Equipment 126
Construction Operations 126
Electrical Installation 128
Grounding Grids 128
Lighting and Power Systems 128
Structural Grouting of the Core Block 128
Diversion Tunnel No. 2 130
Equalizing Tunnel 13
Valve Air-Supply Tunnel 13
River Outlet Works 13
River Outlet Access Tunnel 13
Emergency Exit Tunnel 13
Closure Sequence 13
Spillway 13
Clearing 13
Excavation 13
Drain System 13
Concrete 134
Electrical Installation 134
Gate Installations 134
Grouting Program 134
Grout Curtain 135
Blanket Grouting 135
Envelope Grouting 135
Reservoir Clearing 135
Saddle Dams 136
Foundation 136
Construction Materials 136
Mine Adit Plug 137
Construction of Embankment 137
Bibliography 139
CHAPTER VI. THERMALITO DIVERSION DAM
General 141
Description and Location 141
Purpose 141
Chronology 141
Regional Geology and Seismicity 143
Design 143
Foundation 143
Site Geology 143
TABLE OF CONTENTS— Continued
Page
Strength 143
Overpour Section 143
Description 143
Hydrology 143
Structural Design 144
Spillway Gates and Hoists 144
Stability 144
Nonoverpour Sections 144
Thermalito Canal Headworks 144
Radial Gates and Hoists 148
Foundation 148
Stability Analysis 148
Embankment Section 148
Description 148
Construction Materials 148
Stability Analysis 148
Construction 148
Contract Administration 148
Diversion and Care of River 150
West Bank 150
Channel 150
Closure 150
East Bank 152
Foundation 152
Excavation 152
Preparation 152
Grouting 152
Embankment Construction 152
Description 152
Random Backfill 152
Impervious Core 152
Select Backfill 152
Consolidated Backfill 152
Riprap 152
Concrete Production 153
Construction Phases 153
Concrete Mixing and Materials 153
Concrete Placing and Formwork 153
Radial Gates and Hoists 153
Spillway Gates 153
Canal Headworks Gates 153
Hoists for Radial Gates 153
Trunnion Beams and Stressing Operation 155
Slide Gates and Operators 155
Other Installations 155
Reservoir Clearing 155
Instrumentation 155
Bibliography 157
TABLE OF CONTENTS— Continued
CHAPTER VII. THERMALITO FOREBAY, AFTERBAY, AND
POWER CANAL Page
General 159
Description and Location 159
Purpose 162
Chronology 162
Regional Geology and Seismicity 163
Design 163
Dams 163
Description 163
Stability Analysis 163
Settlement 163
Construction Materials 169
Foundation 169
Instrumentation 169
Forebay Inlet-Outlet 170
Thermalito Power Canal 170
Canal Section 170
Filter Subliner 170
Lining 170
Drainage Structures 170
Turnouts 172
Tail Channel 172
Afterbay Irrigation Outlets 172
Afterbay River Outlet 172
Flood Routing 173
Relocations — Thermalito Complex 184
OroviUe-Chico Road Bridge 184
Oroville-Cherokee Road Overhead Crossing 184
Oroville-Cherokee Road Bridge 184
Nelson Avenue 184
Larkin Road 184
Oroville-Willows County Road 185
State Highway 162 185
Construction 185
Contract Administration 185
Foundation 185
Stripping 185
Excavation — Forebay 185
Excavation — Afterbay 185
Grouting 186
Embankment Materials and Construction 186
Impervious — Forebay 186
Impervious — Afterbay 187
Pervious — Forebay 187
Pervious — Afterbay 187
Riprap 187
"Top-Out" Operation 187
TABLE OF CONTENTS— Continued
Page
Thermaljto Power Canal 188
Excavation 188
Horizontal Drains 189
Filter Subliner 189
Concrete 189
Weeps 190
Stone Protection 190
Recreation Area 190
Tail Channel 191
Excavation 191
Placement of Channel Protection 191
Miscellaneous Channel Excavation 191
Irrigation Outlets 193
Western Canal and Richvale Canal 193
PG&E Lateral 193
Sutter-Butte Canal 194
River Outlet 194
Headworks 195
Fish Barrier Weir 195
Concrete Production 196
Reservoir Clearing 196
Closure 196
Instrumentation and Toe Drain Observations 196
Seepage 196
Forebay 196
Afterbay 196
Tail Channel 197
Bibliography 199
CHAPTER VIII. CLIFTON COURT FOREBAY
General 201
Description and Location 201
Purpose 201
Chronology 201
Regional Geology and Seismicity 201
Design 202
Dam 202
Description 202
Foundation 202
Construction Materials 202
Stability Analysis 207
Settlement 207
Control Structure 207
Intake Channel Connection 208
Intake Channel Closure 208
Piping and Drainage Systems 208
Construction 208
Contract Administration 208
TABLE OF CONTENTS— Continued
Page
Dewatering and Drainage 208
Reservoir Clearing 211
Excavation 211
Forebay 211
Borrow Area A 211
Structural 211
Ditch and Channel 211
Handling of Borrow Materials 211
Embankment Construction 212
Compacted Material 212
Uncompacted Material 212
Slope Protection 212
Closure Embankment 212
Breaching Levees 213
Control Structure 213
Concrete 213
Mechanical Installation 213
Concrete Production 213
Electrical Installation 213
Instrumentation 213
Bibliography 217
CHAPTER IX. BETHANY DAMS AND RESERVOIR
General 219
Description and Location 219
Purpose 219
Chronology 220
Regional Geology and Seismicity 220
Design 221
Dams 221
Description 221
Stability Analysis 221
Settlement 221
Construction Materials 221
Foundation 228
Instrumentation 228
Outlet Works 228
Forebay Dam 228
Outlet to South Bay Aqueduct 228
Outlet to California Aqueduct 228
Spillway 228
Construction 235
Contract Administration 235
Diversion and Care of Stream 235
Foundation 235
Grouting 235
Handling of Borrow Materials 237
Embankment Construction 237
TABLE OF CONTENTS— Continued
Page
Spillway 238
Outlet Works 238
Concrete Production 238
Mechanical and Electrical Installations 238
Reservoir Clearing 238
Placing Topsoil and Seeding 238
Embankment Test Installation 238
Bibliography 239
CHAPTER X. DEL VALLE DAM AND LAKE DEL VALLE
General 241
Description and Location 241
Purpose 242
Chronology 242
Regional Geology and Seismicity 242
Design 243
Dam 243
Description 243
Stability Analysis 243
Settlement 243
Foundation 243
Construction Materials 246
Instrumentation 246
Conservation Outlet Works 246
Flood Control Outlet Works 251
Spillway 251
Description 251
Hydraulics 253
Structural Design 253
Mechanical and Electrical Installations 253
Flood Control Outlet Works 253
Conservation Outlet Works 257
Construction 257
Contract Administration 257
Diversion and Care of Stream 257
First Construction Season 257
Second Construction Season 257
Third Construction Season 257
Foundation 257
Dewatering 257
Excavation 257
Flood Cleanup 258
Dam Foundation Grouting 258
Blanket Grouting 258
Curtain Grouting 258
Embankment Materials 258
Impervious 258
Transition 259
TABLE OF CONTENTS— Continued
Page
Filter 259
Drain 259
Outer Shell 259
Random 259
Slope Protection 259
Embankment Construction 261
Impervious and Transition 261
Filter and Drain 261
Outer Shell 261
Random 262
Slope Protection 262
Instrumentation 262
Conservation Outlet Works 262
Outlet Portal 262
Inlet Portal 262
Tunnel 262
Concrete 262
Grouting 263
Installation of 60-Inch Steel Pipe 263
Intake Structure 263
Hydraulic Testing 264
Testing Butterfly Valves 264
Inlet Control Building 264
Flood Control Outlet Works and Spillway Tunnel 264
Description 264
Inlet 264
Pressure Tunnel 265
Trashrack 265
Spillway Crest, Shaft, and Gate Chamber 265
Downstream Portal 266
Spillway Tunnel 266
Gates 267
Gate Chamber Access 267
Stilling Basin 267
Return Channel 268
Concrete Production 268
Reservoir Clearing 268
Closure 268
Bibliography 269
CHAPTER XI. SAN LUIS JOINT-USE STORAGE FACILITIES
General 271
Description and Location 271
Purpose 273
Chronology 276
Operation 276
Design 279
Dams 279
San Luis 279
TABLE OF CONTENTS— Continued
Page
O'Neill Forebay 280
Los Banos Detention 280
Little Panoche Detention 280
Inlets, Outlets, and Spillways 280
San Luis Reservoir 280
O'Neill Forebay 280
Los Banos Reservoir 284
Little Panoche Reservoir 284
Instrumentation 289
Recreation 289
Bibliography 291
CHAPTER XII. CEDAR SPRINGS DAM AND SILVERWOOD
LAKE
General 293
Description and Location 293
Purpose 294
Chronology 295
Regional Geology 297
Seismicity 297
Major Faults 297
Design Criteria for Maximum Credible Accident 297
Design Criteria for Embankment 298
Design Criteria for Structures 298
Design 298
Dam 298
Description 298
Foundation 298
Embankment Layout 302
Grouting 302
Construction Materials 302
Stability Analysis 302
Seismic Considerations 302
Settlement 303
Instrumentation 303
Debris Barriers 303
Description 303
Miller Canyon 306
Cleghorn Canyon 306
San Bernardino Tunnel Approach Channel 306
Drainage Gallery and Access Tunnel 306
Exploration Adit 306
Drainage Gallery 306
Access Tunnel 306
Spillway 3
Description 3
Excavation 3
Backfill 3
Drainage 3
TABLE OF CONTENTS— Continued
Page
Hydraulics 313
Structural Design 3 14
Outlet Works 315
Description 315
Hydraulics 315
Structural Design 315
Mojave Siphon Inlet Works 319
Description 319
Hydraulics 319
Structural Design 3 19
Las Floras Pipeline 320
Hydraulics 320
Valve Vaults 320
Blowoff Structures 320
Energy Dissipator Structure 320
Mechanical Installation 320
Outlet Works 320
Slide Gates 320
Fixed-Cone Dispersion Valve 322
Lubrication System 323
Service Facilities 323
Heating and Air-Conditioning System 323
\'entilation System 323
Domestic (Potable) Water Supply System 323
Las Floras Pipeline 323
Shutoff Valve 323
Flow Metering 323
Control Valves 323
Air- Vacuum Valve 324
Electrical Installation 324
Operating Equipment 324
Emergency Engine-Generator Set 324
' Equipment 324
' Construction 326
Contract Administration 326
Exploration Adit 326
' Diversion and Care of River 326
Dam Foundation 327
Dewatering 327
Excavation 327
Cleanup and Preparation 327
Handling of Borrow Materials 327
Description 327
Impervious 327
Pervious and Slope Protection 328
Waste Areas 328
Embankment Construction 328
Impervious 328
TABLE OF CONTENTS— Continued
Page
Pervious 329
Slope Protection 329
Riprap 330
Spillway 330
Open-Cut Excavation 330
Structural Excavation 330
Concrete Placement 330
Mojave Siphon Inlet Works 330
Excavation 330
Concrete Placement 331
Concrete Piles 331
Mojave Siphon Extension 331
Pipe Installation 331
Debris Barriers 331
Drainage Gallery 331
Concrete Placement 331
Drainage Gallery Extension 332
Access Tunnel 332
Completion 332
Concrete Placement 332
Outlet Works Tunnel 332
Excavation 332
Concrete Placement 333
Air Shaft Tunnel 334
Excavation 334
Concrete Placement 334
Concrete Production 334
Grouting 33
Dam Foundation 33
Spillway 33
Tunnel 33
Gate Chamber 33
Air Shaft 33
Reservoir Clearing 33
Bibliography 33
CHAPTER XIII. PERRIS DAM AND LAKE PERRIS
General 339
Description and Location 339
Purpose 340
Chronology 340
Regional Geology and Seismicity 340
Design 341
Dam 341
Description 341
Stability Analysis 344
Settlement 344
Construction Materials 344
Foundation 345
Instrumentation 345
TABLE OF CONTENTS— Continued
Page
Inlet Works 345
Description 345
Hydraulics 345
Pipe Structural Design 348
Outlet Works 348
Description 348
Intake Channel 348
Outlet Works Tower 348
Outlet Works Tower Mechanical Installation 348
Outlet Works Tunnel 349
Outlet Works Delivery Facility 349
Delivery Facility Mechanical Installation 353
Spillway 355
Description 355
Hydraulics 355
Construction 356
Contract Administration 356
Dam Foundation 356
Excavation 356
Grouting 356
Handling of Borrow Materials 358
Clay Borrow Area 358
Lake Borrow Area 358
Embankment Construction 359
Mandatory Waste Area No. 2 361
Inlet Works 361
Outlet Works 361
Outlet Works Delivery Facility 362
Spillway 362
Clearing and Grubbing 362
CHAPTER XIV. PYRAMID DAM AND LAKE
General 365
Description and Location 365
Purpose 367
Chronology and Alternative Dam Considerations 367
Regional Geology and Seismicity 368
Design 369
Dam 369
Description 369
Foundation 369
Construction Materials 369
Stability Analysis 374
Settlement 375
Instrumentation 375
Drainage Adits 375
Diversion Tunnel 375
Intake Tower 375
Stream Release Facility 378
Fixed-Cone Dispersion Valves 382
TABLE OF CONTENTS— Continued
Page
Shutoff Valves 383
Spillway 384
Grouting 384
Overpour Weir 384
Head works Structure 384
Approach Walls 384
Radial Gate 384
Bulkhead Gate 384
Concrete Chute 384
Earthquake Criteria 384
Concrete and Steel Structures 389
Hydrodynamic Pressures 389
Earth Pressures 389
Materials and Design Stresses 389
Electrical Installation 389
Interstate 5 Embankments 389
Description 389
Shear Strength Properties 391
Stability Analyses 391
Borrow Areas 391
Culvert Reinforcement 391
Culvert Extensions 391
Construction 392
Contract Administration 392
Diversion Tunnel 392
Excavation 392
Concrete 392
Diversion and Care of Stream 393
Foundation Preparation 393
Overburden 393
Shaping 393
Cleanup 394
Grouting 394
Channel Excavation 394
Embankment Materials 394
Impervious 394
Rock Shell 394
Transition and Drain 395
Embankment Construction 396
Impervious 396
Shell 397
Transition and Drain 397
Spillway 397
Drainage 397
Reinforcing Steel 397
Concrete Production 397
Forms 398
Concrete Placement .'. 398
TABLE OF CONTENTS— Continued
Page
Radial Gate 399
Access and Air-Supply Tunnel 399
Adits 400
Completion of Outlet Works Intake Structure 400
Diversion Tunnel Plug 401
Mechanical and Electrical Installations 401
Instrumentation 402
Bibliography 403
CHAPTER XV. CASTAIC DAM AND LAKE
General 405
Description and Location 405
Purpose 407
Chronology 407
Regional Geology and Seismicity 409
Design of Elderberry Forebay 409
Operation 409
Embankment 409
Emergency Spillway 409
Outlet Works 409
Design of Castaic Dam 409
Diversion Tunnel 409
Hydraulics 409
Structural Design 412
Grouting 415
Embankment 415
Description 415
Stability Analysis 415
Construction Materials 415
Test Fill 418
Settlement 418
Seepage Analysis 418
Transition and Drain 418
Upstream Slope Protection 418
Dam Axis Alignment Changes 418
Foundation 419
Site Geology 419
Excavation 419
Spillway 419
Flood Routing 419
Approach Channel 419
Weir 419
Transition 421
Chute 421
Stilling Basin 421
Return Channel 421
Retaining Wall Design 421
Floor Design 422
Open-Cut Excavation 422
TABLE OF CONTENTS— Continued
Page
Drainage 422
Foundation 422
Outlet Works 422
Hydraulics 432
Structural Design of High Intake Tower 432
High Intake Tower Access Bridge 433
Instrumentation 433
Castaic Lagoon 433
Mechanical and Electrical Installations 437
High Intake Port \'alves 437
Low Intake Gate System 440
High Intake Auxiliary Equipment 440
Turnout Guard \'alves 449
Stream Release Facilities 454
Stream Release Regulating \'alves 454
Stream Release Guard \'alves 454
Construction 459
Contract Administration 459
Foundation Trench 459
Diversion Tunnel 459
Open-Cut Excavation 459
Underground Excavation 459
Pervious Backfill and Riprap Placement 460
Structural and Tunnel Lining Concrete 460
Diversion and Care of Stream 460
Dam Foundation 461
Excavation 461
Grouting 463
Foundation Preparation 464
Handling of Borrow Materials 464
Impervious 464
Filter and Drain 464
Pervious 464
Random 465
Soil-Cement 465
Downstream Cobbles 465
Embankment Construction 465
Impervious 465
Filter and Drain 465
Pervious 465
Random 466
Soil-Cement 466
Downstream Cobbles 466
Boat Ramp and Parking Area 466
Outlet Works 466
High Intake Tower — Excavation 466
High Intake Tower — Concrete Operations 467
Access Bridge Piers 468
TABLE OF CONTENTS— Continued
Page
Access Bridge Girders and Deck 468
Low Intake Tower 468
Penstock 469
Spillway 469
Excavation 469
Concrete 470
Flip-Bucket Piles 470
Structural Backfill 470
Castaic Lagoon Control Structure 471
Clearing, Grubbing, and Erosion Control 471
Reservoir Clearing 471
Clearing and Grubbing of Other Areas 471
Erosion Control 472
Bibliography 473
APPENDIXES
Appendix A: CONSULTANTS 475
Appendix B: ENGLISH TO METRIC CONVERSIONS AND
PROJECT STATISTICS 479
FIGURES
Figure
Number Page
1 Location Map — State Water Project Reservoirs xlii
2 Upper Feather River Division 2
3 Oroville Division 3
4 South Bay Aqueduct and Part of North San Joaquin Division.. 4
5 San Luis Division S
6 Mojave Division 6
7 Santa Ana Division 7
8 West Branch Division 9
9 Location of Construction Project Offices 10
10 Location Map — Frenchman Dam and Lake 12
11 Aerial View — Frenchman Dam and Lake 13
12 Area-Capacity Curves 15
13 General Plan and Profile of Dam 16
14 Embankment Sections 17
15 Location of Embankment Instrumentation 19
16 General Plan and Profile of Outlet Works 20
17 Outlet Works Rating Curve (24-Inch Hollow-Cone Valve) 21
18 Outlet Works Rating Curve (8-Inch Globe Valve) 22
19 General Plan and Profile of Spillway 23
20 Location of Borrow Areas and Frenchman Dam Site 25
2 1 Embankment Construction 26
22 Completed Embankment 26
23 Outlet Works Concrete Placement 27
24 Spillway Chute 27
25 Spillway Flip Bucket 27
26 Location Map — Antelope Dam and Lake 30
27 Aerial View — Antelope Dam and Lake 31
28 Area-Capacity Curves 33
29 General Plan and Profile of Dam 34
30 Embankment Sections 35
31 General Plan and Sections of Outlet Works 37
32 Outlet Works Rating Curves 38
33 General Plan and Sections of Spillway 39
34 Temporary Diversion Pipe and Outlet Works Conduit 40
35 Drilling Grout Hole — Left Abutment Auxiliary Dam 40
36 Location of Borrow Areas and Antelope Dam Site 41
37 Outlet Works Control Structure 42
38 Spillway 43
39 Location of Embankment Instrumentation 44
40 Location Map — Grizzly Valley Dam and Lake Davis 46
41 Aerial \'iew — Grizzly Valley Dam and Lake Davis 47
42 Area-Capacity Curves 49
43 Dam — Plan, Profile, and Sections 50
44 Location of Embankment Instrumentation 52
45 General Plan and Profile of Outlet Works 53
46 Outlet Works Rating Curve 54
47 General Plan and Profile of Spillway 55
<
FIGURES— Continued
Figure
Number '^'S^
48 Location of Borrow Areas and Grizzly Valley Dam Site 57
49 Completed Embankment 58
50 Control House at Dam Crest 58
51 Control House at Dam Toe 58
52 Outlet Works — Butterfly Valve in Outlet Structure 59
53 Spillway Chute 59
54 Spillway Approach and Log Boom 60
55 Location Map — Oroville Facilities 62
56 Aerial View — Oroville Dam and Lake Oroville 63
57 Area-Capacity Curves 65
58 Model of Multiple-Arch Concrete Dam 66
59 Embankment Plan 69
60 Embankment — Selected Sections and Profile 70
61 1964 Cofferdam 71
62 Location of Borrow Areas and Oroville Dam Site 72
63 Dredge Tailings 73
64 Stability Analysis Summary 75
65 Embankment Model on Shaking Table 76
66 Grouting 78
67 Core Block 79
68 Diversion Tunnels Nos. 1 and 2 — Draft-Tube Arrangement .... 80
69 Grout Envelope 84
70 Intake Structures Plan 85
71 Diversion Tunnel No. 1 — Intake Portal Sections 86
72 Diversion Tunnel No. 2 — Intake Portal Sections 87
73 Diversion Tunnel Outlet Structures — Plan and Sections 89
74 Miscellaneous Tunnels 90
75 Palermo Outlet Tunnel 91
76 General Plan of Spillway 94
77 Flood Control Outlet — Plan and Elevation 95
78 Spillway Chute — Plan, Profile, and Typical Sections 96
79 Emergency Spillway — Sections and Details 97
80 Hydrologic and Hydraulic Data 98
81 Spillway and Flood Control Outlet Rating Curves 99
82 Flood Control Outlet — Elevations and Sections 101
83 Bidwell Canyon Saddle Dam— Plan and Profile 102
84 Bidwell Canyon Saddle Dam — Sections and Details 103
85 Parish Camp Saddle Dam — Plan, Profile, and Sections 104
86 Location of Borrow Areas and Parish Camp Saddle Dam Site.. 106
87 Western Pacific Railroad Relocation — Tunnel Locations 108
88 Feather River Bridge 109
89 West Branch Bridge 109
90 North Fork Bridge 110
91 Bidwell Bar Bridge 112
92 B. Abbott Goldberg Bridge 114
93 Diversion Tunnel No. 1 Intake Portal After Backfilling 117
94 Stage 1 Diversion 118
FIGURES— Continued
Figure
Number
Page
95 Stage 2 Diversion Earth Dike 119
96 Stage 3 Diversion 1 19
97 Wood Forms— Core Block 120
98 Steel Cantilever Panel Forms — Core Block 120
99 25-Ton-Capacity Cableway 120
100 Rail-Mounted Steel Towers 121
101 Grout Gallery 121
102 Bucket Wheel Excavator 122
103 Initial Set-In of Excavation 122
104 Transfer Conveyor and Bucket Wheel Excavator 123
105 Pervious Loading Station 123
106 Impervious Loading Station 123
107 Haul Route 124
108 Automatic Car Dumper 125
109 Conveyor Across Feather River 126
110 Traveling Stacker at Reclaim Stockpile 126
1 1 1 Reclaim Tunnel 126
112 Distribution Conveyors on Right Abutment 127
113 Truck-Loading Hopper 127
1 14 Transfer Conveyor 127
115 Electrical Grounding Grids 129
116 Cracking of Core Block 130
117 Wedge Seat Removal in Diversion Tunnels 131
118 Lowering Stoplogs 132
119 Location Map — Thermalito Diversion Dam 140
120 Aerial View — Thermalito Diversion Dam 141
121 General Plan and Profile of Dam 142
122 Spillway Rating Curve 145
123 Spillway Sections 146
124 Power Canal Headworks — Plan, Profile, and Sections 147
125 West Bank Diversion Plan 149
126 Channel Bypass (Aerial View) 150
127 Channel Bypass, Closure, and East Bank Diversion Plan 151
128 Cofferdam Closure 152
129 Location of Concrete Mixes Used in Dam Structure 154
130 Location Map — Thermalito Forebay and Afterbay 158
131 Aerial \'iew — Thermalito Forebay 159
132 Aerial View — Thermalito Afterbay 159
133 Area-Capacity Curves — Thermalito Forebay 161
134 Area-Capacity Curves — Thermalito Afterbay 162
135 General Plan of Forebay Main Dam 164
136 Forebay Dam — Sections and Details 165
137 Forebay — Ruddy Creek and Low Dams Sections 166
138 Afterbay Dam — Sections and Details 167
139 Afterbay Dam Details 168
140 Thermalito Power Canal 170
141 Power Canal Sections 171
FIGURES— Continued
Fjure p
Number
142 Typical Horizontal Drain — Thermalito Power Canal 174
143 Typical Turnout — Thermalito Power Canal 175
144 Western Canal and Richvale Canal Outlets 176
145 Western Canal and Richvale Canal Outlets — Isometric View .... 177
146 Pacific Gas and Electric Outlet 178
147 Pacific Gas and Electric Outlet — Isometric View 179
148 Sutter-Butte Outlet 180
149 Sutter-Butte Outlet — Isometric View 181
150 River Outlet 182
151 River Outlet Headworks and Fish Barrier Weir — Isometric View 183
152 Grouting Foundation of Forebay Main Dam 186
153 Hand Placement of Forebay Dam Adjacent to Powerplant Wing-
wall 186
154 Afterbay Dam Construction 187
155 Placement of Zone 4A— Afterbay Dam 187
156 Riprap Placement 188
157 Slide at Left Side of Power Canal 188
158 Placing Type II Drain Pipe Along Toe of Slope and Type B
Filter Material on Invert of Power Canal 189
159 Placement of a Slope Mat 189
160 Reinforcing Steel Being Placed in Canal Invert 189
161 Slip Form Lining Operation on Thermalito Power Canal Transi-
tion Slopes 190
162 Closeup of Slip Form Lining Operation on Thermalito Power
Canal Transition Slopes 191
163 Bedding Placement on Tail Channel 191
164 Location of Miscellaneous Channels 192
165 Western Canal and Richvale Canal Outlets — Upstream View .. 193
166 Pacific Gas and Electric Lateral Outlet Conduit 193
167 Sutter-Butte Canal Outlet 194
168 Sutter-Butte Canal Outlet Conduits 194
169 Sutter-Butte Canal Outlet Intake 195
170 River Outlet 195
171 River Outlet— Fish Barrier Weir 195
172 Location Map — Clifton Court Forebay 200
173 Aerial View — Clifton Court Forebay 201
174 Embankment Sections 203
175 General Plan of Forebay — North 204
176 General Plan of Forebay — South 205
177 Gated Control Structure 206
178 Control Structure and Inlet Channel Connection to West Canal
and Old River (in background) 207
179 Closure Embankment 209
180 Drainage System 210
181 Test Installations 214
182 Location Map — Bethany Dams and Reservoir 218
183 Area-Capacity Curves — Bethany Reservoir 220
184 Bethany Forebay 220
FIGURES— Continued
Figure
Number
Page
185 Bethany Reservoir 221
186 Bethany Forebay Dam — Plan, Profile, and Sections 222
187 Dam No. 1 — Plan, Profile, and Sections 223
188 Dam No. 2— Plan, Profile, and Sections 224
189 Dam No. 3— Plan, Profile, and Sections 225
190 Dam No. 4— Plan, Profile, and Sections 226
191 Location of Borrow Areas and Bethany Forebay Dam Site 227
192 Foundation Excavation and Drainage Details — Dam No. 3 229
193 Location of Forebay Dam Instrumentation 230
194 Outlet Works— Plan and Profile 231
195 Outlet Works Rating Curve 232
196 Connecting Channel — Plan, Profile, and Sections 233
197 Temporary Spillway 234
198 Bethany Forebay and Excavation for Adjacent Dams 235
199 Foundation Grouting — Bethany Forebay Dam 235
200 Location of Borrow Areas and Adjacent Dams 236
201 Bethany Forebay Dam Construction 237
202 Location Map) — Del Valle Dam and Lake Del Valle 240
203 Aerial View— Del Valle Dam and Lake Del Valle 241
204 Area-Capacity Curves 243
205 General Plan of Dam 244
206 Embankment — Sections and Profile 245
207 Location of Embankment Instrumentation 247
208 Conservation Outlet Works — Plan, Profile, and Sections 248
209 Inclined Intake Structure 249
210 Conservation Outlet Works Rating Curve 250
211 General Plan of Flood Control Outlet Works 252
212 Flood Hydrographs 254
213 Spillway Stilling Basin 255
214 Single-Line Electrical Diagram 256
215 Left Abutment Excavation and Curtain Grouting 259
216 Location of Borrow Areas and Del Valle Dam Site 260
217 Embankment Construction 261
218 Combined Outlet Works 262
219 Concrete Saddles for 60-Inch Pipe 263
220 Sloping Intake Structure 263
221 Tunnel Supports 264
222 Trashrack 264
223 Spillway Crest 265
224 Spillway Shaft Excavation Support 265
225 Tunnel Crown Placement Forms 266
226 Stilling Basin 267
227 Location Map — San Luis Joint-Use Storage Facilities 270
228 Aerial \'iew — San Luis Dam and Reservoir 271
229 San Luis Reservoir Recreation Areas 272
230 President John F. Kennedy and Governor Edmund G. Brown
Pushing Plungers to Detonate Explosives for Ground Breaking 276
FIGURES— Continued
Figure
Number P^g^
231 Flood Diagram — Los Banos Reservoir 277
232 General Plan and Sections of San Luis Dam and O'Neill Forebay 278
233 Placing and Compacting Embankment — San Luis Dam 279
234 Wheel Excavator Cutting on 50-Foot-High Face 279
235 Basalt Hill Rock Separation Plant 279
236 Los Banos Detention Dam — Plan, Profile, and Sections 281
237 Little Panoche Detention Dam — Plan, Profile, and Sections 282
238 Spillway and Outlet Works — San Luis Dam 283
239 Trashrack Structure and Access Bridge — San Luis Dam 284
240 Spillway— O'Neill Forebay Dam 285
241 Los Banos Detention Dam — Spillway and Outlet Plan and Spill-
way Profile 286
242 Los Banos Detention Dam — Outlet Profile 287
243 Little Panoche Detention Dam — Spillway Plan and Sections .... 288
244 Location of Instrumentation — San Luis Dam 290
245 Location Map — Cedar Springs Dam and Silverwood Lake 292
246 Aerial View — Cedar Springs Dam and Silverwood Lake 293
247 Area-Capacity Curves 295
248 Dam Site Plan 296
249 Fault Uncovered During Excavation 297
250 Embankment Plan 299
251 Embankment Sections 300
252 Embankment — Sections and Details 301
253 Determining the Plasticity Index Number of the Impervious
Zone 302
254 Location of Instrumentation — Sections 304
255 Location of Instrumentation — Plan 305
256 Installation of Piezometer Tubing 306
257 Miller Canyon Debris Barrier 307
258 Cleghorn Canyon Debris Barrier 308
259 San Bernardino Tunnel Approach Channel 309
260 Access Tunnel and Drainage Gallery Plan 310
261 Access Tunnel and Drainage Gallery — Profiles and Sections.... 311
262 Spillway 312
263 Perforated Drain Pipes in Spillway Chute 313
264 Shear Keys in Spillway Chute 314
265 Outlet Works— Plan and Profile 316
266 General Arrangement of Gate Chamber 317
267 Inlet Works— Plan and Profile 318
268 Flume and Chute 319
269 Initial Reservoir Filling 319
270 Control Schematics 325
271 Embankment Construction 326
272 Compacting Zone 1 Material 328
273 Performing Field Density Test on Zone 3 Material 328
274 Zone 3 and 4 Material 329
275 Zone 5 Embankment Shell Material 329
FIGURES— Continued
Figure Page
Number
276 Rock Bolts in Dome of Outlet Works Gate Chamber 332
277 Placing Concrete in Gate Chamber 333
278 Location Map — Perris Dam and Lake Perris 338
279 Aerial \'iew — Perris Dam and Lake Perris 339
280 Area-Capacity Curves 341
281 Embankment Plan 342
282 Embankment Sections 343
283 Embankment Instrumentation 346
284 Inlet Works— Plan and Profile 347
285 Outlet Works— Plan and Profile 350
286 Outlet Works Tower 351
287 Outlet Works Delivery Facilities 352
288 Spillway — Plan, Profile, and Sections 354
289 Spillway Rating Curve 355
290 Location of Borrow Areas and Perris Dam Site 357
291 Excavation in Clay Borrow Area 358
292 Excavation in Lake Borrow Area 358
293 Rock Production 359
294 Embankment Construction Activity 359
295 Pneumatic Roller on Embankment Zone 2 360
296 Tower Concrete Placement 361
297 Tower Outlet Portal 362
298 Outlet Works Delivery Manifold 362
299 Concrete Placement in Spillway 362
300 Location Map — Pyramid Dam and Lake 364
301 Aerial \'iew — Pyramid Dam and Lake 365
302 Dam Site Plan 366
303 Area-Capacity Curves 368
304 Embankment Sections 370
305 Embankment Plan 371
306 Interim Dam — Plan, Sections, and Details 372
307 Interim Dam — Sections and Profile 373
308 Exploration Adits — Section and Details 376
309 Diversion Tunnel — Plan and Profile 377
310 Intake Tower 378
311 Valve Chamber 379
312 Outlet Works Rating Curves 380
313 Air Shaft 381
314 8-Inch-Diameter Fixed-Cone Dispersion \'alve 382
315 36-Inch-Diameter Fixed-Cone Dispersion Valve 382
316 42-Inch-Diameter Shutoff Valve 383
317 Shutoff \'alves and Butterfly Valve — Accumulator System 383
318 General Plan of Spillway 385
319 Spillway Profile 386
320 Spillway Flip Structure During Discharge 387
321 Spillway Headworks Structure 388
322 Interstate 5 Embankments 390
FIGURES— Continued
Figure
Number ^^S^
323 Old Highway 99 Bridge Bents Uncovered in Downstream Shell
Area of Dam 393
324 Shaping Excavation on Right Abutment 393
325 Presplit Face of Shaping Area on Right Abutment 393
326 Air-Water Jet Cleanup of Foundation 394
327 Dump Truck Used for Embankment Material Hauling 395
328 Rear-Dump Rock Wagon Used for Embankment Hauling 395
329 Spreading and Compacting of Contact Material on Foundation 396
330 Rolling of Impervious Fill 396
331 Compacting Pervious Material With 10-Ton Vibratory Roller.. 397
332 Prefabricated Steel Form Used for Spillway Walls 399
333 Concrete Placement in Spillway Headworks Invert 399
334 Concrete Placement in Spillway Chute Slab 399
335 Location Map — Castaic Dam and Lake 404
336 Aerial View — Castaic Dam and Lake 405
337 Site Plan 406
338 Area-Capacity Curves 408
339 Diversion Tunnel — Plan and Profile 410
340 Diversion Tunnel — Plan and Profile (Continued) 411
341 High Intake-Shaft Intersection 413
342 Diversion Tunnel Intake Structure 414
343 Outlet Works Energy Dissipator 415
344 Embankment Plan 416
345 Embankment Sections 417
346 General Plan and Profile of Spillway 420
347 Spillway and Stilling Basin 421
348 Spillway Rating Curve 421
349 Outlet Works— Plan and Profile 423
350 Outlet Works — Plan and Profile (Continued) 424
351 Outlet Works — Low Intake Tower 425
352 Outlet Works — High Intake Tower 426
353 Access Bridge 427
354 High Intake Tower and Access Bridge 428
355 Stream Release Facility 429
356 Outlet Works Stream Release 430
357 General Plan of Turnouts 431
358 Outlet Works Turnouts 432
359 Instrumentation — Plan and Section 434
360 Castaic Lagoon Control Structure Sections 435
361 Castaic Lagoon Control Structure — Erosion Control 436
362 Castaic Lagoon Control Structure 437
363 Single-Line Diagram — Intake Tower 438
364 Single-Line Diagram — Stream Release Facilities 439
365 Butterfly Valve Assembly 441
366 Port Valves — Hydraulic Scheme 442
367 Low Intake Gate 443
368 Low Intake Sluiceway 444
Figure
Number
FIGURES— Continued
Page
369 General Arrangement of Tower Mechanical Features — Eleva-
tion and Plan 445
370 General Arrangement of Tower Mechanical Features — Eleva-
tion and Plan (Continued) 446
371 General Arrangement of Tower Mechanical Features — Plan and
Section 447
372 Tower Jib Crane 448
373 20-Ton Polar Bridge Crane 450
374 General Arrangement of Bulkhead Gate 451
375 General Arrangement of Bulkhead Gate and Lifting Beam 452
376 General Arrangement of Bulkhead Gate, Thimble Seal Plate, and
Guide 453
377 Turnout \'alve — Hydraulic Schematic 455
378 General Plan of Stream Release and Turnouts 456
379 Stream Release Facility — Plan and Sections 457
380 Hydraulic Schematic 458
381 Foundation Exploration Trench 460
382 Flood Damage to Lake Hughes Road Bridge 461
383 Dam Site at Beginning of Work 461
384 Block Slide at Right Abutment 462
385 Dam Under Construction — \'iew Across Dam Toward Left
Abutment 462
386 Excavating Slide Area at Left Abutment 463
387 Grouting Through Embankment at Left Abutment — White
Lines Show Limits of Core Zone 463
388 Scraper Spreading First Load of Embankment in First Approved
Dam Foundation Area 464
389 Loading of Pervious Borrow at Elizabeth Canyon 465
390 Soil-Cement Batch Plant 466
391 Spreading Soil-Cement 466
392 Compacting Soil-Cement 466
393 Downstream Cobble Slope Protection 467
394 East Abutment Boat Ramp 467
395 Concrete Placement — High Intake Tower 467
396 High Intake Tower Bridge Under Construction 468
397 Low Intake Tower 468
398 General \'iew of Penstock Under Construction 468
399 Tunnel Penstock 468
400 Spillway Stilling Basin and Chute Excavation 469
401 Spillway Construction 470
402 Castaic Lagoon Control Structure 471
%;
%»
TABLES
Number
1 Statistical Summary of 20 Completed Reservoirs and Their Dams 1
2 Statistical Summary of Frenchman Dam and Lake 14
3 Major Contract — Frenchman Dam 24
4 Statistical Summary of Antelope Dam and Lake 32
5 Major Contract — Antelope Dam 40
6 Statistical Summary of Grizzly Valley Dam and Lake Davis 48
7 Major Contract — Grizzly Valley Dam 56
8 Statistical Summary of Oroville Dam and Lake Oroville 64
9 Major Contracts — Oroville Dam and Appurtenances 115
10 Statistical Summary of Thermalito Diversion Dam 143
11 Major Contracts — Thermalito Diversion Dam 148
12 Statistical Summary of Thermalito Forebay Dam and Forebay .. 160
13 Statistical Summary of Thermalito Afterbay Dam and Afterbay 160
14 Material Design Parameters — Thermalito Forebay and Afterbay
Dams 169
\5 Data for Gates and Hoists — Thermalito Afterbay 173
16 Major Contracts — Thermalito Forebay, Afterbay, and Power Ca-
nal 185
17 Statistical Summary of Clifton Court Forebay 202
18 Material Design Parameters — Clifton Court Forebay 207
19 Major Contract — Clifton Court Forebay 208
20 Statistical Summary of Bethany Dams and Reservoir 219
21 Material Design Parameters — Bethany Dams 221
22 Major Contracts — Bethany Forebay Dam and Bethany Dams .... 235
23 Statistical Summary of Del Valle Dam and Lake Del Valle 242
24 Material Design Parameters — Del \'alle Dam 246
25 Major Contract — Del Valle Dam and Reservoir 257
26 Compaction Data — Del Valle Dam 261
27 Statistical Summary of San Luis Dam and Reservoir 274
28 Statistical Summary of O'Neill Dam and Forebay 274
29 Statistical Summary of Los Banos Detention Dam and Reservoir 275
30 Statistical Summary of Little Panoche Detention Dam and Reser-
voir 275
31 Statistical Summary of Cedar Springs Dam and Silverwood Lake 294
32 Design Earthquake Accelerations — Cedar Springs Dam Complex 298
33 Material Design Parameters — Cedar Springs Dam 303
34 Major Contracts — Cedar Springs Dam and Appurtenances 326
35 Statistical Summary of Perris Dam and Lake Perris 340
36 Material Design Parameters — Perris Dam 344
37 Features of Performance Monitoring System — Perris Dam and
Lake Perris -^45
38 Major Contracts — Perris Dam 356
39 Statistical Summary of Pyramid Dam and Lake 367
40 Material Design Parameters — Pyramid Dam 374
41 Major Contracts — Pyramid Dam 392
42 Statistical Summary of Elderberry Forebay Dam and Forebay .. 407
43 Statistical Summary of Castaic Dam and Lake 408
44 Material Design Parameters — Castaic Dam 415
45 Major Contracts — Castaic Dam and Appurtenances 459
State of California
The Resources Agency
DEPARTMENT OF WATER RESOURCES
Ronald Reagan, Governor
Norman B. Livermore, Jr., Secretary for Resources
John R. Teerink, Director
Robert G. Eiland, Deputy Director
Robert B. Jansen, Deputy Director
Donald A. Sandison, Deputy Director
DIVISION OF DESIGN AND CONSTRUCTION
Clifford J. Cortright Division Engineer
John W. Keysor Chief, Design Branch
Howard H. Eastin Chief, Construction Branch
DIVISION OF LAND AND RIGHT OF WAY
Thomas H. T. Morrow Chief, Division of Land and Right of Way
DIVISION OF OPERATIONS AND MAINTENANCE
H. G. Dewey, Jr. Division Engineer
James J. Doody Deputy Division Engineer
State of California
Department of Water Resources |
CALIFORNIA WATER COMMISSION '
IRA J. CHRISMAN, Chairman, Visalia
CLAIR A. HILL, T 'ice Chairman, Redding
Mai Coombs Garberville
Ray W. Ferguson Ontario
Ralph E. Graham San Diego «
Clare W. Jones Firebaugh k,
William P. Moses San Pablo j,
Samuel B. Nelson Northridge
Ernest R. Nichols Ventura ^
Orville L. Abbott
Executive Officer znA Chief Engineer jj^
Tom Y. Fujimoto '..
Assistant Executive Officer
i;
AUTHORS OF THIS VOLUME
*]
George A. Lineer
Donald H. Babbitt
Gordon W. Dukleth
Robert C. Gaskell
John H. Lawder
John W. Marlette
Preston E. Schwartz
Gene L. Anderson
Alfred J. Castronovo
H. John Garber
Leon M. Hall
Cortland L. Lanning
Samuel J. Linn, Jr.
George C. Myron
Fleming E. Peek
Donn J. Stafford
Henry E. Struckmeyer
Lorimer E. Erikson
Ted E. Rowe
James L. Zeller
Curtis A. Canevari
Dale E. Martfeld
Herman Neibauer
William C. Baer
Menzo D. Cline
Gale G. Hannum
John A. Hartung
Donald E. Wiles
Arthur C. Gooch
EDITOR
Senior Engineer, Water Resources
Chief, Dams and Canals Unit, Civil
Design Section
Division Engineer, Division of Safety of
Dams
Chief, Engineering Services Section,
Design Branch
Construction Supervisor
Chief, Project Geology Section
Principal Engineer, Water Resources
(Retired)
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Construction Office Manager
Construction Management Supervisor
Construction Supervisor
Associate Engineer, Water Resources
Associate Engineer, Water Resources
Associate Engineer, Water Resources
Water Resources Engineering Associate
Construction Supervisor
Water Resources Engineering Associate
Construction Supervisor
Mechanical Construction Supervisor
Chief, Program Analysis Office
IN THE DESIGN AND CONSTRUCTION OF THESE PROJECT WORKS, POSITIONS OF
MAJOR ENGINEERING AND RELATED RESPONSIBILITY WERE HELD BY:
■nos H. Adams
)bert F. Adams
larles G. Anderson
;ne L. Anderson
thur B. Arnold
loyd S. Arnold
»rge D. Atkinson, Jr
tenn L. Atkinson
jnald H. Babbitt
»ger A. Baker
trvey O. Banks
ith G. Barrett
hn L. Baugh
bn H. Beaver
iss D. Billings
maid P. Bisio
,rry L. Blohm
rold P Brock
iin A. Buchholz
thur J. Bunas
Iliam E. Busby
lester A. Bush
n E. Bussell
ilson M. Cantrell
in A. Cape
vid B. Carr
in Carrillo
larles H. Carter
_,/de P. Cass
fin Castain
■ fred J. Castronovo
Ux A. Champ
l.'fbert H. Chan
p L. Chatterly
I'lrold F. Christy
k Coe
mold T. Cook
• itford J Cortright
Jin W. Cowin
lul H. Davies
Lvere J. Davis
1 G. Dewey, Jr.
tV. Dickinson
rge T. Dodds
I diaries I. Donald
Jnes J. Doody
tanklin E. Drake
lirdon W. Dukleth
!,inuel S. Dulberg
-(idrew F. Dywan
'jilliam T Easterday
l)ward H. Eastin
Jbert W Ehrhart
Iben G. Eiland
'I Iliam J. Ellis
Iroy F. Eriksen
Shirl A. Evans
John K. Facey
Ray N. Fenno
Herbert B. Field
John W. Flynn
Samuel Fong
J. Henry Fredericks
Harald D. Frederiksen
Wallace D. Fuqua
Norman K. Gadway
H. John Garber
Robert C. Gaskell
William R. Gianelli
Paul H. Gilbert
Austin E. Gilligan
Raymond D. Gladding
Alfred R. Golz6
Bernard B. Gordon
Seymour M. Gould
Leemon C. Grant
Edgar L. Grider
Edward R. Grimes
John P. Grogan
David J. Gross
Carl A. Hagelin
Leon \4. Hall
William D. Hammond
Robert G. W. Harder
Robert E. Harpster
John A. Hartung
Marvin J. Hawkins
Richard L. Hearth
Charles \'. Heikka
Edward Henry
Harold H. Henson, Sr.
Marcus O. Hilden
Vincent D. Hock
A. J. Hoffman
Norman W. Hoover
Jack E. Horn
Kenneth E. Houston
Ralph E. Houtrouw
Herbert C. Hyde
Calvin M. Irvine
Joey T. Ishihara
Ernest C. James
Laurence B. James
Robert B. Jansen
Ade E. Jaskar
Arnold W. Johnson
Richard W. Johnson
Takashi T. Kamine
John W. Keysor
Frank C. Kresse
George H. Kruse
Edward J. Kurowski, Jr.
V'ictor J. LaChapelle
Robert F. Laird
Cortland C. Lanning
John H. Lawder
Frank \'. Lee
Carl G. Liden
Eugene M. Lill
Samuel J. Linn, Jr.
Clifford \'. Lucas
Mark S. Lyons
Alexander Mailer
John W. Marlette
Calvin M. Mauck
Fred L. McCune
Robert L. McDonell
Donald H. McKillop
Manuel Mejia
Leo Meneley
Edward A. Menuez
Robert K. Miller
Don R. Mitchell
Albert J. Moellenbeck, Jr.
John E. Mooner
Andrew J. Morris
Thomas H. T. Morrow
George C. Myron
Alexander S. Nadelle
Harold Nahler
Don H. Nance
Herman Neibauer
Jerome S. Nelson
Theodore Neuman
Philip M. Noble
Gene M. Norris
Harry L. O'Neal
AlanL. O'Neill
John E. O'Rourke
Raymond W. Oleson
Donald E. Owen
George L. Papathakis
Wilferd W. Peak
Fleming E. Peek
Charles W. Perry
X'ernon H. Persson
Carleton E. Plumb
Marian Pona
George E. Purser
Joseph A. Remley
Robin R. Reynolds
Eldred A. Rice
Gordon A. Ricks
Paul C. Ricks
Raymond C. Richter
Raymond L. Ritter
Ted E. Rowe
Harold E. Russell
Robert E. Rutherford
Ray S. Samuelson
Joseph R. Santos
John E. Schaffer
Walter G. Schulz
Preston E. Schwartz
James B. Scott
James G. Self
Joseph H. Sherrard
Clyde E. Shields
W. Burt Shurtleff
Cecil N. Smith
Stephen E. Smith
Ross G. Sonneborn
Donn J. Stafford
Donald C. Steinwert
Malcolm N. Stephens
Elmer W. Stroppini
Henry E. Struckmeyer
Steinar Svarlien
Fay H. Sweany
Mark A. Swift
John R. Teerink
Donald P. Thayer
Medill P. Theibaud
Robert S. Thomas
Harrison M. Tice
Albert C. Torres
L. O. Transtrum
Theodore W. Troost
Lewis H. Tuthill
Owen I. L'hlmeyer
Austin V'arley
Arthur C. \'erling
John C. X'ernon
Jack D. Walker
Joseph D. Walters
William K. Warden
William E. Warne
Carl A. Werner
Ray L. Whitaker
Addison F. Wilber
Donald E. Wiles
Kenneth G. Wilkes
James V. Williamson
Jeff A. Wineland
Roy C. Wong
Dee M. Wren
Robert E. Wright
Robert H. Wright
Jack G. Wulff
Burton O. Wyman
Richard A. Young
James L. Zeller
Kolden L. Zerneke
AUTHORS OF THIS VOLUME
George A. Linear
Donald H. Babbitt
Gordon W. Dukleth
Robert C. Gaskell
John H. Lawder
John W. Marlette
Preston E. Schwartz
Gene L. Anderson
Alfred J. Castronovo
H. John Garber
Leon M. Hall
Cortland L. Lanning
Samuel J. Linn, Jr.
George C. Myron
Fleming E. Peek
Donn J. Stafford
Henry E. Struckmeyer
Lorimer E. Erikson
Ted E. Rowe
James L. Zeller
Curtis A. Canevari
Dale E. Martfeld
Herman Neibauer
William C. Baer
Menzo D. Cline
Gale G. Hannum
John A. Hartung
Donald E. Wiles
Senior Engineer, Water Resources
Chief, Dams and Canals Unit, Civil
Design Section
Division Engineer, Division of Safety of
Dams
Chief, Engineering Services Section,
Design Branch
Construction Supervisor
Chief, Project Geology Section
Principal Engineer, Water Resources
(Retired)
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Senior Engineer, Water Resources
Construction Office Manager
Construction Management Supervisor
Construction Supervisor
Associate Engineer, Water Resources
Associate Engineer, Water Resources
Associate Engineer, Water Resources
Water Resources Engineering Associate
Construction Supervisor
Water Resources Engineering Associate
Construction Supervisor
Mechanical Construction Supervisor
Arthur C. Gooch
EDITOR
Chief, Program Analysis Office
IN THE DESIGN AND CONSTRUCTION OF THESE PROJECT WORKS, POSITIONS OF
MAJOR ENGINEERING AND RELATED RESPONSIBILITY WERE HELD BY
Amos H. Adams
Robert F. Adams
Charles G. Anderson
Gene L. Anderson
Arthur B. Arnold
Floyd S. Arnold
George D. Atkinson, Jr.
Glenn L. Atkinson
Donald H. Babbitt
Roger A. Baker
Harvey O. Banks
Keith G. Barrett
|ohn L. Baugh
|ohn H. Beaver
Ross D. Billings
Ronald P. Bisio
Harry L. Blohm
Harold P. Brock
|ohn A. Buchholz
Arthur J. Bunas
William E. Busby
Chester A. Bush
jBen E. Bussell
Wilson M. Cantrell
(ohn A Cape
David B. Carr
|ohn Carrillo
Charles H. Carter
Clyde P. Cass
|ohn Castain
Alfred J. Castronovo
Vlax A. Champ
Herbert H. Chan
lay L. Chatterly
Harold F. Christy
lack Coe
Harold T. Cook
Clifford J. Cortright
lohn W. Cowin
Paul H. Davies
Devere J. Davis
H. G. Deviey, Jr.
|im \'. Dickinson
.jeorge T. Dodds
Charles I. Donald
lames J. Doody
franklin E. Drake
Cordon W. Dukleth
5amuel S. Dulberg
lAndrew F. Dywan
William T. Easterday
Howard H. Eastin
Robert W. Ehrhart
ilobert G. Eiland
William J. Ellis
Lerov F. Eriksen
Shirl A. Evans
John K. Facey
Ray N. Fenno
Herbert B. Field
John W Flynn
Samuel Fong
J. Henry Fredericks
Harald D. Frederiksen
Wallace D. Fuqua
Norman K. Gadway
H. John Garber
Robert C. Gaskell
William R. Gianelli
Paul H. Gilbert
Austin E. Gilligan
Raymond D. Gladding
Alfred R. Golz6
Bernard B. Gordon
Seymour M. Gould
Leemon C. Grant
Edgar L. Grider
Edward R. Grimes
John P. Grogan
David J. Gross
Carl A. Hagelin
Leon M. Hall
William D. Hammond
Robert G. W. Harder
Robert E. Harpster
John A. Hartung
Marvin J. Hawkins
Richard L. Hearth
Charles \'. Heikka
Edward Henry
Harold H. Henson, Sr.
Marcus O. Hilden
Vincent D. Hock
A. J. Hoffman
Norman W. Hoover
Jack E. Horn
Kenneth E. Houston
Ralph E. Houtrouw
Herbert C. Hyde
Calvin M. Irvine
Joey T. Ishihara
Ernest C. James
Laurence B. James
Robert B. Jansen
Ade E. Jaskar
Arnold W. Johnson
Richard W. Johnson
Takashi T. Kamine
John W. Keysor
Frank C. Kresse
George H. Kruse
Edward J. Kurowski, Jr.
X'ictor J. LaChapelle
Robert F. Laird
Cortland C. Lanning
John H. Lawder
Frank \'. Lee
Carl G. Liden
Eugene M. Lill
Samuel J. Linn, Jr.
Clifford \'. Lucas
Mark S. Lyons
Alexander Mailer
John W. Marlette
Calvin M. Mauck
Fred L. McCune
Robert L. McDonell
Donald H. McKillop
Manuel Mejia
Leo Meneley
Edward A. Menuez
Robert K. Miller
Don R. Mitchell
Albert J. Moellenbeck, Jr.
John E. Mooner
Andrew J. Morris
Thomas H. T. Morrow
George C. Myron
Alexander S. Nadelle
Harold Nahler
Don H. Nance
Herman Neibauer
Jerome S. Nelson
Theodore Neuman
Philip M. Noble
Gene M. Norris
Harry L. O'Neal
Alan L. O'Neill
John E. O'Rourke
Raymond W. Oleson
Donald E. Owen
George L. Papathakis
Wilferd W. Peak
Fleming E. Peek
Charles W. Perry
Vernon H. Persson
Carleton E. Plumb
Marian Pona
George E. Purser
Joseph A. Remley
Robin R. Reynolds
Eldred A. Rice
Gordon A. Ricks
Paul C. Ricks
Raymond C. Richter
Raymond L. Ritter
Ted E. Rowe
Harold E. Russell
Robert E. Rutherford
Ray S. Samuelson
Joseph R. Santos
John E. Schaffer
Walter G. Schuiz
Preston E. Schwartz
James B. Scott
James G. Self
Joseph H. Sherrard
Clyde E. Shields
W. Burt Shurtleff
Cecil N. Smith
Stephen E Smith
Ross G. Sonneborn
Donn J. Stafford
Donald C. Steinwert
Malcolm N. Stephens
Elmer W. Stroppini
Henry E. Struckmeyer
Steinar Svarlien
Fay H. Sweany
Mark A. Swift
John R. Teerink
Donald P. Thayer
Medill P. Theibaud
Robert S. Thomas
Harrison M. Tice
Albert C. Torres
L. O. Transtrum
Theodore W. Troost
Lewis H. Tuthill
Owen I. L'hlmeyer
Austin Varley
Arthur C. X'erling
John C. Vernon
Jack D. Walker
Joseph D. Walters
William K. Warden
William E. Warne
Carl A. Werner
Ray L. Whitaker
Addison F. Wilber
Donald E. Wiles
Kenneth G. Wilkes
James \'. Williamson
Jeff A. Wineland
Roy C. Wong
Dee M. Wren
Robert E. Wright
Robert H. Wright
Jack G. Wulff
Burton O. Wyman
Richard A. Young
James L. Zeller
Kolden L. Zerneke
lit
ABSTRACT
The storage facilities of the State Water Project are discussed in this volume.
Twenty reservoirs and their associated dams are now in operation. They are
located throughout the Project over a distance of about 650 miles. Three addition-
al dams will be constructed in the future to complete all authorized storage
facilities; however, these are not included in the discussion of the individual
storage facilities presented in this volume.
Five of the existing dams were designed and constructed by other agencies:
four by the U. S. Bureau of Reclamation as part of the Federal-State Joint-Use
Facilities and one by the City of Los Angeles Department of Water and Power.
All of these facilities constructed by others were partially funded by the Depart-
ment of Water Resources, and the Department also is their operator, except for
the small forebay constructed by Los Angeles Department of Water and Power.
The more interesting and unique aspects of the design and construction details
of each dam are discussed under the appropriate headings. Included are descrip-
tions of site geology, seismicity, embankments, outlet works, spillways, and
equipment.
The volume is written in the language of engineers and engineering geologists
engaged in design and construction acitivities throughout project development.
Highly technical discussions and extensive details are avoided in an attempt to
interest the largest cross section of readers. Design analyses and alternatives
studied generally are included whenever they are related to major decisions and
unusual physical features. Difficulties which arose during construction or after
start of operations also are discussed. These difficulties probably were no greater
or less than encountered by others involved in similar major projects.
Consulting firms and boards were selected and retained by the Department to
provide broad experience and expertise in several areas of project work. Exten-
sive model-testing programs designed to ensure appropriate and economic design
were utilized and supervised by the Department.
xli
Figure 1. Location Mop — State Water Project Reservoirs
xlii
CHAPTER I. GENERAL
1 Overview
There are 20 completed reservoirs in the State Wa-
ter Project, the locations of which are shown on Fig-
ure I. Fifteen were built and are operated by the
Department of Water Resources, and four (San Luis
Joint-Use Facilities) were built by the U.S. Bureau of
Reclamation and now are operated by the Depart-
ment. The last of the 20 completed reservoirs. Elder-
berry Forebay, was built and is operated by the City
of Los Angeles Department of Water and Power as
part of the Pyramid-Castaic power development. Ta-
ble 1 presents a brief statistical summary of the 20
completed reservoirs and their dams, all of which are
discussed in this volume.
The first project dams to be constructed were
Frenchman in the Upper Feather River watershed
and Bethany Forebay at the head of the South Bay
.Aqueduct. Both prime contracts were let in 1959. Oro-
ville Dam, the largest dam of the Project, was started
in 1962, and reservoir storage began in November
1967. Other work on the Project proceeded southward
during the 1960s and early 197(is with Pyramid, the
last dam in the initial phase of the Project, completed
in early 1974.
Virtually all of the project yield of 4,230,000 acre-
feet annually comes from two sources: the Feather
River watershed above Oroville Dam, and surplus
winter and spring runoff from other watersheds
tributary to the Sacramento-San Joaquin Delta. Sur-
plus water in the Delta is pumped into San Luis Reser-
voir for summer and fall releases. Thus, Oroville Dam
and San Luis Dam are the two key conservation fea-
tures of the State Water Project.
Nine of the existing 20 reservoirs are involved in the
generation of power, with all but one utilizing
pumped storage. In the Oroville Division, two pump-
ing-generating plants, Edward Hyatt Powerplant un-
derground in the left abutment of Oroville Dam and
Thermalito Powerplant, involve four reservoirs —
Lake Oroville, Thermalito Diversion Pool, Ther-
malito Forebay, and Thermalito Afterbay. Pumping-
generating plants also are located between San Luis
Reservoir and O'Neill Forebay and between Pyramid
Lake and Elderberry Forebay. The ninth reservoir,
Silverwood Lake, is the forebay for Devil Canyon
Powerplant.
Pyramid, Castaic, and Silverwood Lakes and Lake
Perris are large reservoirs located near the metro-
politan areas of Southern California, where water sup-
plies primarily are imported. The three aqueducts
TABLE 1 . Statistical Summary of 20 Completed Reservoirs and Their Dams
Reservoirs
Dams
Name of Reserv'oir
Gross
Capacity'
(acre-feet)
Surface
Area
(acres)
Shoreline
(miles)
Structural
Height
(feet)
Crest
Elevation^
(feet)
Crest
Length
(feet)
Volume
(cubic
yards)
55,477
22,566
84,371
3,537,577
13,328
580
11,768
57,041
28,653
4,804
77,106
2,038,771
56,426
34,562
13,236
74,970
131,452
171,196
28,231
323,702
1,580
931
4,026
15,805
323
52
630
4,302
2,109
161
1,060
12,700
2,700
623
354
976
2,318
1,297
460
2,235
21
15
32
167
10
1
10
26
8
6
16
65
12
12
10
13
10
21
7
29
139
120
132
770
143
91
91
39
30
121
235
385
88
167
152
249
128
400
200
425
5,607
5,025
5,785
922
233
181
231
142
14
250
773
554
233
384
676
3,378
1,600
2,606
1,550
1,535
720
1,320
800
6,920
1,300
600
15,900
42,000
36,500
3,940
880
18,600
14,350
1,370
1,440
2,230
11,600
1,090
1,990
4,900
/•537,000
380,000
253,000
Lake Oroville
80,000,000
154,000
10,500
1,840,000
5,020,000
2,440,000
1,400,000
Lake Del Valle
4,180,000
77,645,000
O'Neill Forebav
3,000,000
2,100,000
i Little Panoche.- ...
1,210,000
7,600,000
20,000,000
6,860,000
iHderberry Forebav
6,000,000
46,000,000
Totals
6,765,817
54,642
491
168,450
266,599,500
' M maiimum normal operating level.
which supply water to Southern California (Cali-
fornia, Owens Valley, and Colorado River Aque-
ducts) cross the San Andreas fault system and likely
could be disrupted, at least temporarily, by fault
movement. In view of this, these four reservoirs were
constructed as large as practicable to provide a reserve
water supply should such an event occur.
Two reservoirs, Oroville and Del Valle, are drawn
down prior to the flood season to create an adequate
storage capacity to control downstream floods. Costs
allocated to flood control were borne by the Federal
Government. Although incidental flood control bene-
fits accrue to many of the other reservoirs in the sys-
tem, no federal flood control payments were made.
Substantial recreation benefits are derived from
reservoirs throughout the Project, with the Upper
Feather River reservoirs built primarily for this pur-
pose. Recreation use, in general, has greatly exceeded
predictions, and onshore recreation developments
have lagged the demand.
Additional reservoirs, Abbey Bridge and Dixie Ref-
uge in the Upper Feather River watershed and Buttes
in the Mojave Division, are planned for future con-
struction. The first two will be used primarily for
recreation and the third to regulate water deliveries.
The following sections briefly describe the dams
and reservoirs and relate them to the remainder of the
State Water Project.
Upper Feather River Division
Beginning with the northernmost features of the
Project, three of five authorized reservoirs (Figure 2)
i_^-
1^, r CH. iM^nT^.
!
LAKE '^^
^''^^==^-
CRESCcN
MILLS
->'f II A >-»!ii
■ ,0\'-' ' 1
OUINCY
V
I M '""t*>'-:i.^ , / x;===;=::::!«' l.OVaLTON
-. S |i ' - ^ ^ °
Figure 2. Upper Feather River Division
CK V
\
LAKE OROVILLE
ELEV 900'
OROVILLE DAM.
Edward hvaTt
CK VII
THERMALITO FORE BAY
FISH HATCHERY
'^THERMALITO
DIVERSION
DAM
Figure 3. Oroville Division
have been completed: Frenchman Lake, Antelope
Lake, and Lake Davis. All five reservoirs are, or will
be, located on the upper tributaries to the Feather
River — a river system with a drainage area in excess
of 3,600 square miles above Oroville Dam. The three
completed reservoirs have a combined storage capaci-
ty of 162,414 acre-feet and provide for local irrigation,
recreation, and incidental flood control. All of the
dams are of earthfill construction and vary in height
from 120 to 139 feet. Frenchman Dam, the largest of
the dams, is a 139-foot-high earth embankment con-
taining 537,000 cubic yards of material. The largest
reservoir in the group is Lake Davis, which has a gross
capacity of 84,371 acre-feet.
Oroville Division
About 90 miles downstream on the Feather River at
Oroville and about 100 miles upstream from the Sacra-
mento-San Joaquin Delta is the Oroville Division
(Figure 3 ) . Included in this division are Oroville Dam
and the Oroville-Thermalito power complex. Oroville
Dam, one of the two principal conservation features of
the Project, impounds 3, 537, .577 acre-feet of water. In-
cluded in this storage capacity is provision for flood
control. The reservoir has a surface area of 15,805
acres and a shoreline of 167 miles.
This 80,000,000-cubic-yard embankment dam,
which is the highest earthfill dam in the United States
at the present time (1974), rises 770 feet above
streambed excavation and has a crest length of 6,920
feet.
Power at Oroville Dam is produced by the Edward
Hyatt Powerplant and the Thermalito power facili-
ties, which in turn encompass a diversion dam, a pow-
er canal, a forebay, and an afterbay. Edward Hyatt
Powerplant is located underground in the .'eft abut-
ment of Oroville Dam. It contains three conventional
generators and three motor-generators coupled to
Francis-type reversible pump-turbines. The latter
units provide for off-peak pumped-storage operations.
Releases from Edward Hyatt Powerplant are di-
verted from the Feather River by the 143-foot-high
Thermalito Diversion Dam, a concrete gravity over-
pour structure with a 560-foot-long radial gate crest
section. These releases pass at a maximum rate of
16,900 cubic feet per second (cfs) through the 10,000-
foot-long Thermalito Power Canal and Thermalito
Forebay to Thermalito Powerplant. The Thermalito
Diversion Pool, Power Canal, and Forebay have a
common water surface to accommodate flow reversals
for the pumped-storage operation.
Thermalito Forebay Dam is a 1 5,900-foot-long em-
bankment with a maximum height of 91 feet. The
powerplant intake structure is an integral part of the
Dam. This plant is equipped with one Kaplan turbine
and three pump-turbines and operates under a static
head of 100 feet.
Thermalito Afterbay has a gross capacity of 57,041
acre-feet and stores plant discharges for the pumped-
storage operation as well as reregulates flows for re-
turn to the Feather River. The afterbay dam is a
42,000-foot-long earth structure with a maximum
height of 39 feet.
Migrating salmon and steelhead blocked by the de-
velopment are diverted from the River into the
Feather River Fish Hatchery by the Fish Barrier
Dam, located '/j rnile downstream of Thermalito Di-
version Dam. This 91 -foot-high, concrete, overpour
structure is discussed in Volume VI of this bulletin.
North San Joaquin Division and South
Bay Aqueduct
The initial and northernmost reach of the Califor-
nia Aqueduct, designated the North San Joaquin Divi-
sion, is 68 miles long (Figure 4). Principal features
consist of Clifton Court Forebay in the Delta, the
Delta Fish Protective Facility, 3 miles of unlined in-
^AVWARD
CLIFTON COURT FOREBAY'
'. C INTAKECHANNELt
DELTA PUMPING PLANT
BETHANY RESERVOIR^
SOUTH BAY PUMPING PLANT
DYER CANAL
.IVERMORE
TUNNEL\ y PIPELINE
CANAL
DEL VALLE BRANCH PIPELINE
AND PUMPING PLANT
N SAN JOAOUIH DIVISION
CH. X
/
Figure 4. South Bay Aqueduct and Part of North Son Joaquin Division
1 take channel, Delta Pumping Plant, Bethany Reser-
voir, and 64 miles of coprrete-lined canal and
1 appurtenant structures. The Division terminates at
I O'Neill Forebay. The design capacity of this aqueduct
reach decreases from 10,300 cfs at its head to 10,000 cfs
at its terminus.
Water released from Oroville Dam flows down the
Feather and Sacramento Rivers, and the surplus wa-
ters in the Sacramento-San Joaquin Delta then are
diverted into the California Aqueduct at Clifton Court
Forebav. This forebay provides storage for off-peak
pumping at Delta Pumping Plant and minimizes any
adverse effects on existing Delta channels by diverting
i and storing large amounts of water at high tide. It has
1| a surface area of 2,109 acres. The water is diverted
I from the Delta into the Forebay from adjacent Delta
I waterways, namely Old River and West Canal, and is
. regulated by an intake structure with five automatical-
j ly controlled radial gates.
The water eventually will be conveyed to Clifton
; [ Court Forebay through the planned 43-mile-long Pe-
ripheral Canal. This unlined canal will start at the
1 Sacramento River 18 miles south of the City of Sacra-
: mento and will skirt the eastern perimeter of the Del-
j ta. It will be hydraulically isolated from the Delta
: channels and will connect to the east side of the Fore-
I bay.
I Bethany Forebay Dam was included in the initial
i construction of the South Bay facilities. The 890-acre-
' foot forebay, formed by the 119-foot-high 300,000-cu-
' bic-yard embankment, was used to provide operation-
I al flexibility as well as conveyance capability. Ini-
I tially, water was supplied to the South Bay Aqueduct
from the federal Delta-Mendoia Canal through a small
unlined canal. An interim pumping plant at the toe of
the Dam lifted the water from the unlined canal into
the forebay. South Bay Pumping Plant, located on the
forebay, lifts the water 545 feet to the head of the
42-mile-long South Bay Aqueduct. The plant has since
been expanded to the present 330-cfs capacity. During
' construction of the California Aqueduct and Delta
Pumping Plant in the North San Joaquin Division,
the forebay was expanded into the present Bethany
Reservoir. Four embankments similar to the Forebay
' Dam were constructed, a channel was excavated to
connect two sections of the Reservoir, and the Califor-
nia Aqueduct was cut into the north and south ends
of the Reservoir. The Reservoir functions as a 1 '/2-mile
reach of canal and provides operational flexibility for
Delta Pumping Plant, located 2 miles to the north.
Regulatory storage for South Bay Aqueduct now is
provided in the 100-acre-foot Patterson Reservoir and
the 77,106-acre-foot Lake Del Valle (Patterson Reser-
voir is discussed in Volume II of this bulletin). Lake
Del \'alle is located on Arroyo Del \'alle near the
midpoint of the South Bay Aqueduct. Project water is
pumped into Lake Del \'alle and released from it
through a 120-cfs branch pipeline and Del \'alle
Pumping Plant. The Lake, formed by 235-foot-high
Del \'alle Dam, also provides flood control for Liver-
more X'alley and conserves local runoff. This embank-
ment structure contains 4,150,000 cubic yards of earth
materials. The conservation function was established
by agreement with a local agency and is incidental to
project operation. Local runoff is stored when project
SAS LUIS RESERVOIR
N SAN JOAQUIN DIVISION
O'NEILL FOREBAY
rcHJci
''CALIFORNIA AQUEDUCT
G s :;\-
Figure 5. San Luis Di>
operations permit and is released into the stream
channel as requested by the local agency.
San Luis Division
The 106-mile-long reach, designated the San Luis
Division, constitutes the Federal-State Joint-Use
Facilities (Figure 5). It includes, among other fea-
tures, San Luis Dam and Reservoir and appurtenant
pumping-generating facilities. This entire division
was designed and built by the U.S. Bureau of Recla-
mation and is operated by the Department of Water
Resources on a cost-sharing basis, which is discussed
in Chapter XI of this volume.
San Luis Reservoir, located at the head of this reach,
provides 2,038,771 acre-feet of off-line storage, of
which 1,067,908 acre-feet is the State's share. The main
dam is an earthfill structure 385 feet high with a crest
length of 18,600 feet. A total of 77,645,000 cubic yards
of material was used in its construction. Water deliv-
ered to O'Neill Forebay through the California Aque-
duct and Delta-Mendota Canal is pumped during
off-peak periods into San Luis Reservoir. On-peak
power is generated from releases made through the
eight reversible units in the San Luis Pumping-Gener-
ating Plant, located at the toe of the main dam.
O'Neill Forebay, with a gross capacity of 56,426
acre-feet, serves as a regulation pool for the San Luis
Pumping-Generating Plant and also as a gravity diver-
sion pool for flows continuing south in the California
Aqueduct. The reservoir has a surface area of 2,700
acres. The forebay dam required 3,000,000 cubic yards
of material and has a maximum height of 88 feet and
a crest length of 14,350 feet. The distance across the
Forebay in the direction of the flow of the California
Aqueduct is about 3 miles.
Los Banos and Little Panoche Detention Dams
located south of San Luis Reservoir protect the Aque-
duct, the Delta-Mendota Canal, and other improve-
ments from floodflows. Los Banos Detention Dam
also provides a 470-acre recreation pool. The reser-
voirs have a capacity of 34,562 and 13,236 acre-feet,
respectively. The Dams are 167 and 152 feet high and
contain 2,100,000 and 1,210,000 cubic yards of earth
materials, respectively.
Because of en route deliveries, the flow capacity of
the California Aqueduct through the San Luis Divi-
sion decreases from 13,100 to 8,350 cfs, 7,050 cfs of
which is for the State Water Project. Dos Amigos
Pumping Plant, located 16 miles south of O'Neill
Forebay, provides a 113-foot lift in the Aqueduct.
South San Joaquin and Tehachapi Divisions
The last reach of the California Aqueduct in the
Central \'alley, designated the South San Joaquin Di-
vision, is 121 miles long and primarily is canal. Three
pumping plants (Buena Vista, Wheeler Ridge, and
Wind Gap) with a total lift of 956 feet are located
within this reach. The aqueduct capacity decreases
from 8,100 to 4,400 cfs reflecting en route deliveries to
water users. Volume I of this bulletin contains a dis-
• TEHACHAPl DIVISION
WEST BRANCI
VENTURA
^ FERNAND
Figure 6. Mojave Division
ussion of the events which brought about the dispar-
ty in flows between this division and the San Luis
)ivision to the north.
The next reach of aqueduct, designated the Tehach-
pi Division, crosses the Tehachapi Mountains. A. D.
"dmonston Pumping Plant, located at the northern
lase of the Tehachapi Mountains, has the capability to
ift 4,410 cfs nearly 2,000 feet in a single lift through
wo 12'/2-foot-diameter, underground, discharge lines.
These discharge lines enlarge to a 14-foot diameter
bout halfway up the slope. At the top of the lift, these
ines are joined by a manifold.
Three 2 3 '/2-foot and one 20-foot-diameter tunnels,
otaling 7.9 miles in length, are joined by siphons to
arry the water through the summit region of the
fehachapis. The longest tunnel, 4% miles, is the 20-
oot-diameter Carley V. Porter Tunnel. The longest
iphon, the 2,452-foot-long Pastoria Siphon, conveys
he water across Pastoria Creek between Tehachapi
Tunnels Nos. 2 and 3. It consists of a single, elevated,
92-inch-diameter, steel pipeline designed for 2,680
fs. A similar parallel pipeline is required to bring this
each up to ultimate planned capacity.
Tehachapi Afterbay, at the southern end of this di-
ision, provides minor regulatory storage to accom-
nodate flow mismatch between A. D. Edmonston
'umping Plant and the downstream pumping plants.
t consists of a concrete-lined, trapezoidal, canal sec-
ion, 24 feet deep, over most of its 0.6-mile length. The
Vest Branch bifurcates from the California Aqueduct
t the southern end of the Afterbay. The Afterbay is
,iscusssed in Volume II of this bulletin.
.dojave Division
Extending southeasterly from the Tehachapi After-
>ay is the 102-mile-long reach of Aqueduct designated
he Mojave Division (Figure 6). The Aqueduct con-
ists of 93.4 miles of concrete-lined canal and a total of
.9 miles of pipeline. At the head of this reach, two
hutes accommodate a 132-foot total drop in the verti-
al alignment. Midway along the Division, the Pear-
ilossom Pumping Plant, with a capacity of 1,380 cfs,
ifts the water 540 feet, the high point along the entire
California Aqueduct alignment.
Silverwood Lake, a 74,970-acre-foot, in-line, storage
eservoir, is located at the end of this division. The
^ake, formed by Cedar Springs Dam, regulates deliv-
ries in the system, provides emergency storage of
vater for use during aqueduct outages, and furnishes
vater-oriented recreation. Cedar Springs Dam is a 7.6-
nillion-cubic-yard earth and rockfill dam 249 feet
ligh with a crest length of 2,230 feet.
ianta Ana Division
. The remaining reach along the California Aque-
luct, designated the Santa Ana Division, is 34 miles
ong and terminates at Lake Perris, a 13 1,4 5 2 -acre-foot
.eservoir (Figure 7). Flows are released from Silver-
vood Lake into the 3.8-mile-long 12 '/-foot-diameter
hn Bernardino Tunnel. This high-head pressure tun-
Flgure 7. Santa Ana Division
nel, with a capacity of 2,020 cfs, is directly connected
to the Devil Canyon Powerplant penstock. The plant,
situated at the mouth of Devil Canyon at the southern
base of the San Bernardino Mountains, is a 119,700-
kilowatt installation which operates under a normal
static head of 1,418 feet. The penstock, which varies in
diameter from 9/2 feet to 8 feet, is an elevated steel
pipeline. The Powerplant houses two impulse tur-
bines rated at 81,000 horsepower each and two genera-
tors rated at 63,000 kVA each.
The Santa Ana Valley Pipeline, which comprises
about 28 miles of buried high-pressure pipe 9 to 10 feet
in diameter, conveys a flow of 444 cfs to the Project's
terminal reservoir in Riverside County. This design
flow capacity has been recalculated recently at 469 cfs
due to a lowering of the pipeline outlet to Lake Perris.
Lake Perris, the terminus of the "main line" Califor-
nia Aqueduct, regulates deliveries and provides emer-
gency storage and recreation. Perris Dam, of zoned
earthfill construction, is 128 feet high and has a crest
length of over 2 miles. The embankment required 20
million cubic yards of fill.
West Branch Division
The West Branch originates at Tehachapi Afterbay
and extends southerly about 32 miles toward Los An-
geles (Figure 8). Water flows by gravity southward
from the Afterbay about 1'/^ miles to Oso Pumping
Plant. This plant has a capacity of 3,128 cfs against a
maximum static head of 231 feet. It is an indoor-type
installation housing eight electric motor-driven
pumps which require a total of 93,800 horsepower.
The eight pumping units are manifolded to five 9-foot-
diameter discharge lines.
From the end of the Oso Pumping Plant discharge
lines, a concrete-lined canal extends 2.7 miles in a
southwesterly direction to Quail Lake, a small regula-
tion pool discussed in Volume II of this bulletin. From
Quail Lake, the canal continues 2.3 miles to a transi-
tion to the temporary Gorman Creek Improvement
Facilities. The Improvement Facilities, primarily an
8-foot-base-width concrete-lined channel, extend 6
miles to Pyramid Lake, a 171,196-acre-foot, in-line,
storage reservoir. To utilize the 740-foot drop up-
stream from this reservoir, a pipeline will replace the
Gorman Creek Improvement and a power plant will
be installed with initial operations planned for 1982.
Pyramid Dam is a 400-foot-high zoned earth and rock-
fill embankment, with a crest length of 1,090 feet.
From Pyramid Lake, which also functions as a pow-
er pool, water is diverted through the 30-foot-diameter
7.15-mile-long Angeles Tunnel to Castaic Pow-
erplant. Maximum flow through the concrete-lined
tunnel during periods of peak demand will be 18,400
cfs. A surge tank is located near the downstream por-
tal of the Tunnel. The chamber is 1 20 feet in diameter
and 383 feet high, with 158 feet of its height above-
ground.
Castaic Powerplant will have a generating capacity
of 1,200 megawatts. Six pump-turbines with motor-
generator units are being installed. Companion Unit
7 Powerplant contains a 50-megawatt generator which
can be used in the pump-starting process.
The plants discharge into the 28,231 -acre-foot Eld-f
erberry Forebay, from which the water is either
pumped back to Pyramid Lake or released into Castaic
Lake immediately downstream of the forebay dam.
Elderberry Forebay Dam is a 200-foot-high, 6,000,000-
cubic-yard, zoned embankment.
The power facilities between Pyramid Lake and
Castaic Lake are joint-use facilities of the City of Los
Angeles and the Department of Water Resources. The \
City constructed and operates Castaic Powerplant,
Unit 7 Powerplant, and Elderberry Forebay.
Castaic Dam is a 42S-foot-high earthfill embank-
ment with a crest length of 4,900 feet creating a reser-
voir with a capacity of 323,702 acre-feet. Ap-
proximately 46 million cubic yards of material was
used in its construction. Castaic Lake provides opera-
tional and emergency storage and water-oriented rec-
reation.
Design
The Department's staff located in Sacramento de-
signed all the storage facilities except those previously
credited to the U. S. Bureau of Reclamation or the Los
Angeles Department of Water and Power. The same
engineers designed or reviewed all significant changes
made during the construction process.
Appendix A of this volume mentions the consult-
ants and others outside the Department who con-
tributed to the design and construction of the storage
facilities.
The latest available design techniques were em-
ployed, hydraulic model studies were run on all major
structures, and extensive, sometimes innovative, ex-
ploration and soils-testing programs were conducted.
This work is covered in the chapters on the various
dams. For example. Chapter V of this volume includes
discussions of the early application of the finite ele-
ment technique to the design of the Oroville Dam
grout gallery and of the embankment seismic analysis
that led to the finite element analysis currently being
used on dams. ■
Construction
Construction contracts for storage facilities of th(
State Water Project were awarded and administerec
in accordance with provisions of the State Contrac
Act, Sections 14250 to 14424, Government Code, Stat
utes of the State of California. The State Contract Ac
requires that bids be solicited in writing and that th(
contract be awarded to the lowest responsible bidder
To comply with the Act, the following procedure
were employed:
1. Prequalification of prospective contractors — t
two-phase prequalification procedure was used to es
_^
c ^
OROVILLE
PROJECT
OFFICE
■^« Sacramento
PERIPHERAL CANAL
SOUTH BAY,
PROJECT OFFICE
NORTH SAN JOAQUIN
PROJECT OFFICE
NORTH SAN JOAQUIN
DIVISION
U.S.B.R.
PROJECT
vOFFICE ^
SOUTH SAN JOAQUIN
PROJECT OFFICE
WEST BRANCH
DIVISION
TEHACHAPI DIVISION
PALMDALE^ROJECT OFFICE
r?P/^ MOJAVE DIVISION
TEHACHAPI -WEST
BRANCH^
PROJECT OFFICE
Figure 9. Location of Construction Project OfRces
SANTA ANA DIVISION
10
tablish qualified bidder lists of those contractors desir-
ing to bid. First, if the required financial statement
indicated that the contractor had the necessary re-
sources, the request for prequalification was processed
further. Second, the contractor's ability was assessed
based on the firm's overall experience and other uni-
form factors.
2. Advertisement and award of contracts — Public
notice of a project was given once a week for at least
, two consecutive weeks in a newspaper published in
the county in which the project was located and in a
trade paper of general circulation in either San Fran-
cisco or Los Angeles, as appropriate. A "Notice to
Contractors", in each case, was sent to all contractors
on the list of qualified bidders. This document gener-
ally described the requirements and extent of the
work and indicated the time and place for receiving
!the bids.
Contracts were awarded to the lowest responsible
bidder. Responsible bids were those meeting all the
conditions of bidding stated in the bidding require-
ments and determined to be reasonable in cost when
compared with the engineer's estimate.
The Department's organization for supervision of
construction activities consisted of project offices at
selected locations throughout the State and a head-
quarters construction office located in Sacramento
(Figure 9). Each project office was responsible for all
project construction work within a particular geo-
graphical area and was staffed with construction en-
gineers, inspectors, engineering geologists, and labo-
ratory and other technicians. The headquarters con-
struction office provided administrative and liaison
services to the project offices. Factory inspection of
materials and equipment to be incorporated in the
work was performed by an equipment and materials
section of the headquarters construction office.
11
Figure 10. Location Map — Frenchman Dam and lalt^
12
CHAPTER II. FRENCHMAN DAM AND LAKE
I General
lOescription and Location
Frenchman Dam is a 139-foot-high, homogeneous,
;arthfill structure with internal blanket and chimney
Irains. The spillway is located on the right abutment.
it has an unlined approach channel; a 50-foot-wide,
ingated, ogee crest; a 30-foot-wide rectangular chute;
ind a flip-bucket terminal structure. The outlet works
s located along the base of the left abutment.
Frenchman Lake has a capacity of .')5,477 acre-feet at
spillway crest, a water surface area of 1,580 acres, and
a 21-mile shoreline.
Frenchman Dam and Lake are located entirely
within the Plumas National Forest on Little Last
Chance Creek, a tributary of the Middle Fork Feather
River. The site is about 15 miles northeast of Portola
and about 30 miles northwest of Reno, Nevada. The
nearest major roads are State Highways 70 and 49 and
U. S. 395 (Figures 10 and 11).
Figure 11. Aerlol View — Frenchman Dam and Lake
13
A statistical summary of Frenchman Dam and Lake
is shown in Table 2, and the area-capacity curves are
shown on Figure 12.
Purpose
The principal purposes of Frenchman Lake are rec-
reation and irrigation water supply. Flood control is
an incidental benefit but was not considered to be a
purpose. Operation studies indicate that the reservoir
is capable of supplying an average of 10,000 acre-feet
annually for irrigation through controlled releases
without an adverse effect on the lake storage for recre-
ation.
Chronology
Investigations of water and recreation development
in the Upper Feather River Basin resulted in pub-
lished reports in 1955 and 1957 (see Bibliography). In
1957, the Legislature authorized construction of five
dams in this development. One of these was French-
man Dam.
Preliminary design work included economic com-
parisons of rockfill and homogeneous earthfill dam
sections as well as economic comparison of four sites
on Little Last Chance Creek. From this work, the type
of dam and final location were chosen. Final design
work was initiated in 1959. Construction began in
September 1959, and the Dam was completed in 1961.
Regional Geology and Seismicity
The Dam and reservoir are in the northern Sierra
Nevada on the southeast corner of the tilted Diamond
Mountain fault block. Pre-Cretaceous granitic rock
was covered by Tertiary volcanic and pyroclastic
rocks. Subsequent erosion of the volcanic series of
rocks carved deep canyons and, in places, completely
uncovered the older granitic rocks. The Dam and res-
ervoir are mainly on the volcanic series of rocks.
Frenchman Dam is near a seismically active area along
the California-Nevada border.
Design
Dam
Description. The 139-foot-high embankment was
designed as a homogeneous, rolled, earthfill structure
with internal sloping and horizontal drains located
downstream from the axis. Embankment general plan
is shown on Figure 13, and sections are shown on
Figure 14.
Stability Analysis. Stability of the Dam was deter-
mined by the Swedish Slip Circle method of analysis.
Cases analyzed included loading of full reservoir and
critical lower reservoir levels along with earthquake
loading. Earthquake loading involved a foundation
horizontal acceleration of O.lg in the direction of in-
stability of the mass being analyzed.
Settlement. Since the Dam was to be founded on
rock, no foundation settlement was anticipated; there-
fore, settlement analyses were conducted on embank-
ment material only. Tests indicated a maximum
TABLE 2. Statistical Summary of Frenchman Dam and Lake
FRENCHMAN DAM
Type: Homogeneous earthfill
Crest elevation 5,607 feet
Crest width 30 feet
Crest length 720 feet
Streambed elevation at dam axis 5,478 feet
Lowest foundation elevation 5,468 feet
Structural height above foundation 139 feet
Embankment volume 537,000 cubic yards
Freeboard above spillway crest 19 feet
Freeboard, maximum operating surface 19 feet
Freeboard, maximum probable flood 0 feet
FRENCHMAN LAKE
Maximum operating storage 55,477 acre-feet
Minimum operating storage 2,335 acre-feet
Dead pool storage 1,840 acre-feet
Maximum operating surface elevation 5,588 feet
Minimum operating surface elevation 5,520 feet
Dead pool surface elevation 5,517 feet
Shoreline, maximum operating elevation 21 miles
Surface area, maximum operating elevation.. 1,580 acres
Surface area, minimum operating elevation. . 171 acres
Drainage area _ 82 square miles
Average annual runoff 27,000 acre-feet
SPILLWAY
Type: Ungated ogee crest with lined chute and flip bucket
Crest elevation 5,588 feet
Crest length 50 feet
Maximum probable flood inflow 32,000 cubic feet per second
Peak routed outflow 15,000 cubic feet per second
Maximum surface elevation 5,607 feet
Standard project flood inflow 14,200 cubic feet per second
Peak routed outflow 7,950 cubic feet per second
Maximum surface elevation 5,600.5 feet
OUTLET WORKS
Type: Reinforced-concrete conduit beneath dam at base of left abut-
ment, valve chamber at midpoint — discharge into impact dissi-
pator
Diameter: Upstream of valve chamber, 36-inch concrete pressure
conduit — downstream, 30-inch steel conduit in a 6-foot - 6-inch
concrete horseshoe conduit
Intake structure: Uncontrolled low-level tower with concrete plug
emergency bulkhead
Control: Downstream control structure housing 24-inch fixed-cone
dispersion valve and 8-inch globe valve — 30-inch butterfly guard
valve in valve chamber
Capacity 165 cubic feet per second
14
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60
69
Figure 12. Area-Capacity Curves
consolidation of 4% for 8 tons per square foot. Most
of the settlement was expected to occur during con-
struction. A nominal crest camber of 12 inches was
provided.
Construction Materials. An alluvial terrace 2
miles upstream of the Dam site was selected for bor-
row on the basis of surface examination, auger holes,
and testing of materials sampled.
Natural moisture ranged from 12 to 51% and specif-
ic gravity from 2.66 to 2.80. Shear tests showed an
angle of internal friction of 30 degrees and a cohesion
of 500 pounds per square foot (direct shear, con-
solidated-quick; and triaxial shear, consolidated-un-
drained, and consolidated-drained tests were run).
Permeability range was determined to be 0.0007 to
0.0010 of a foot per day. Riprap and bedding were
found at the Dam site, but filter and drain materials
had to be imported.
Foundation. At the Dam site three members, or
layers, of the Tertiary volcanic series of rocks dip
about 40 degrees southwest into the right abutment.
One of these members, an olivine basalt flow, forms
most of the left abutment down to the stream channel.
Pyroclastic rocks, mainly an andesite tuff breccia, un-
derlay the channel section and lower half of the right
abutment. The pyroclastic rock in the channel was
covered by alluvium which was removed during foun-
dation excavation. Capping the right abutment is a
layer of hornblende andesite.
A normal fault, dipping 30 degrees to the southwest
and striking nearly perpendicular to the dam axis,
passes through the intake tower foundation and along
the left side of the channel section. The fault zone,
from 2 to 4 feet wide, contains brecciated to clayey
sheared rock and seams of fat clay. Rock several feet
on either side of this zone is strongly fractured and
platy. The fault forms the contact between the tuff
breccia and altered basalt in the channel section down-
stream from the cutoff.
A grout curtain approximately 50 feet in depth was
placed across the entire length of the dam foundation.
A second grout curtain approximately 100 feet deep
was placed upstream of this curtain and was intended
to grout any cavities not reached by the 50-foot cur-
tain.
13
Figure 13. General Plan and Profile of Dam
16
<3-
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Figure 14. Embankment Sections
17
Instrumentation. Instrumentation at Frenchman
Dam included (1) embankment settlement monu-
ments, (2) piezometers, (3) electric pressure cells, (4)
a cross-arm settlement unit, (5) observation wells, and
(6) a seepage measurement weir (Figure 15).
Outlet Works
Description. The outlet works is located along the
base of the left abutment. It consists of ( 1 ) a low-level
intake tower with a concrete bulkhead that can be
lowered to seal the opening; (2) a 36-inch, reinforced-
concrete, pressure conduit from intake to valve cham-
ber; (3) a valve chamber containing a 30-inch butter-
fly valve located just upstream of the dam axis; (4) a
30-inch, steel, outlet pipe installed in a 78-inch
horseshoe conduit from the valve chamber to the
downstream terminus; and (5) a control structure
with discharge valves and stilling basin at the toe of
the Dam (Figure 16). Access to the valve chamber is
through the horseshoe conduit. A bulkheaded, 18-
inch, penstock wye was installed on the 30-inch outlet
pipe 11 feet upstream from the control structure to
provide for possible future power development. A
gauging weir is located downstream from the stilling
basin to provide measurement of flow through the
outlet works.
Because of the wide range of flows to be controlled,
two discharge valves were installed: a 24-inch fixed-
cone dispersion valve to control high flows for irriga-
tion (up to 88 cubic feet per second with reservoir at
elevation 5,520 feet) and an 8-inch globe valve to con-
trol low flow for maintaining fish life in the stream (as
low as 1 cubic foot per second). Rating curves are
-shown on Figures 17 and 18.
Structural Design. The intake structure is a tower
approximately 34 feet high with outside dimensions of
5 feet by 5 feet and an inside diameter of 36 inches. It
was designed as a vertical cantilever, fixed at the base.
Loading cases included: (1) construction condition,
no embankment in place, and a horizontal wind pres-
sure of 15 pounds per square foot; and (2) at-rest earth
pressure of the finished embankment and reservoir
pressure. Trashracks were designed for a differential
hydrostatic head of 40 feet. Yield point stresses were
allowed in the trashbars while normal working
stresses were allowed in the supporting concrete
members.
Upstream and downstream conduits are composed
of monoliths approximately 25 feet long with water-
stops at each joint upstream of the embankment chim-
ney drain.
The 30-inch outlet pipe was fabricated from '/-inch
steel plate with a yield point of 30,000 pounds per
square inch. It has a '/2-inch mortar lining. The pipe is
set on saddles inside the horsehoe conduit and is de-
signed with allowable stress of 16,000 pounds per
square inch in tension and 12,000 pounds per square
inch in compression.
Mechanical and Electrical Installations. A 120-
volt, 3, 000- watt, gasoline-operated, generating set is
provided at the control structure to supply power for
lighting and ventilating. All valves were intended to
be operated manually; however, because of the time
required to develop sufficient hydraulic pressure by
hand to operate the 30-inch butterfly valve, a motor-
driven linkage powered by the generator set was in-
stalled in February 1963.
A ventilating system operated by a '/^-horsepower
motor with an output of 406 cubic feet per minute was
installed in the control house to ventilate the valve
chamber and conduit.
Spillway
Description. The spillway is located on the right
abutment. It consists of an unlined approach channel;
a 50-foot-long, ungated, ogee crest; a transition chute
section; a 30-foot-wide rectangular chute; and a flip-
bucket terminal structure (Figure 19). Two bridges
cross the spillway: one at the crest for connecting U.S.
Forest Service roads, and one at the lower end to pro-
vide access to the control structure.
Hydraulics. Reservoir storage above the spillway
reduces the standard project flood from a peak inflow
of 14,250 cubic feet per second (cfs) to an outflow of
7,950 cfs with 6'/2 feet of freeboard and the maximum
probable flood from a peak inflow of 32,000 cfs to an
outflow of 15,000 cfs without any freeboard.
Structural Design. Crest walls were constructed
monolithically with the ogee crest and were designed
for (1) normal earth loads plus live loads on the
bridge, and (2) normal earth loads plus seismic load-
ing. The crest is anchored with No. 10 reinforcing
bars embedded 6 feet into the rock foundaton on ap-
proximately 5 '/2-foot centers. The upstream end is pro-
vided with a 6-foot-deep cutoff and a 25-foot-deep
grout curtain. The crest was designed for loads trans-
ferred from the walls and for uplift conditions during
maximum spillage.
Walls and floors of the transition and chute sections
were constructed monolithically. Floors are anchored
with No. 9 reinforcing bars embedded 6 feet into the
rock on approximately 5-foot centers in both direc-
tions.
The flip bucket was designed with a 50-foot-radius
vertical curve with a 20-degree upward deflection.
The floor upstream of the cutoff is anchored with
three rows of No. 9 bars embedded 6 feet into the rock
foundation at 6-foot centers in both directions. A 4-
inch pipe surrounded by filter material is provided
beneath the concrete floor to drain the bucket founda-
18
Figure 15. locotion of Embankment Instrumentation
19
Figure 16. General Plan and Profile of Outlet Works
20
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ELEV. 5588
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Lip of Outlet Tower
Elev. 5517^
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DISCHARGE -CFS
120
160
Figure 17. Outlet Works Rating Curve (24-lnch Hollow-Cone Valve)
21
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DISCHARGE-CFS
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22
Figure 18. Outlet Works Rating Curve (8-Inch Globe Valve)
_lJ
Construction
Contract Administration
General information for the construction contract
for Frenchman Dam is shown in Table 3. The princi-
pal features included in the contract, designated as
Specification No. 59-19, were an earthfill dam, spill-
way, outlet works, and relocation of portions of U. S.
Forest Service roads.
TABLE 3. Major Contract — Frenchman Dam
Specification 59-19
Low bid amount 21,809,110
Final contract cost 21,708,093
Total cost-change orders 222,485
Starting date 9/15/59
Completion date 10/18/61
Prime contractor Isbell Construction Com-
pany
Diversion and Care of Stream
Diversion of Little Last Chance Creek during con-
struction was the responsibility of the contractor. The
outlet works was utilized. Between the time the foun-
dation excavation was begun and the outlet works
completed, streamflow was pumped around the job
site through a 6-inch aluminum pipe extended along
the left abutment.
A cofferdam upstream of the toe of the Dam was
placed and the impounded water transported to the
outlet works at the base of the intake tower by a 36-
inch reinforced-concrete pipe. This pipe was left in
place and plugged with concrete at its junction with
the base of the intake structure after its use for diver-
sion was discontinued. Downstream water require-
ments during the remainder of the construction
period were fulfilled by means of a 6-inch bypass be-
tween the diversion pipe upstream of the concrete
plug and the outlet conduit.
Foundation
Dewatering. A 1 5-foot-wide cutoff trench was ex-
cavated to bedrock between the cofferdam and the
upstream toe of the Dam. A 24-inch, perforated, corru-
gated-metal pipe with a 12-inch riser was installed and
the trench was backfilled with drain rock. Water ac-
cumulating in the pipe was removed by pumping
from the riser.
Excavation. A total of 50,953 cubic yards of un-
suitable foundation material was removed from the
streambed and abutments. Cavities in the right abut-
ment were filled with concrete. The largest was mined
to a depth of nearly 50 feet. It contained a preserved
redwood tree trunk, V/^ feet in diameter and approxi-
mately 20 feet long, estimated to be 10 million years
old. Portions of this trunk were preserved for display.
An auxiliary grout curtain 100 feet in depth was
placed around the upstream limits of the cavity area.
To reduce the possibility of seepage through a fault
zone in the stream channel, all sheared and strongly
fractured rock was removed to a depth of several feet
below the cutoff surface. A 5-foot-deep trench that
varied from 10 to 20 feet in width was excavated along
the fault in the cutoff area and then backfilled with
embankment material.
Grouting. A total of 6,567 cubic feet of grout was
injected into the foundation. Where surface leakage
occurred, the most effective treatment was intermit-
tent low-pressure pumping of thick grout. The grout
then was permitted to harden in the hole, which was
redrilled and regrouted in the succeeding stage. Uplift
due to grouting was negligible (maximum recorded
was '/^ inch).
Handling of Borrow Materials
Impervious. Impervious borrow material was ob-
tained from lenticular to thickly bedded terrace depos-
its 2 miles upstream from the Dam site (Figure 20).
Mixing of these deposits was accomplished by power-
shovel excavation from a vertical face approximately
30 feet high. In-place samples indicated that field
moisture was from 1 to 5% above optimum. It was,
therefore, necessary to blend freshly excavated materi-
al with that which had been spread and dried. A total
of 515,632 cubic yards of excavation yielded 487,330
cubic yards of compacted impervious fill.
Drain. Due to the fact that the contractor was una-
ble to find suitable sand in the area for the drain, he
imported 11,000 cubic yards of sand from Reno, Ne-
vada (30 miles) and blended it with 5,000 cubic yards
of local crushed andesite.
Slope Protection. Approximately 22,000 cubic
yards of riprap (1 cubic yard maximum size) was
obtained from the andesite quarry located on the right
abutment downstream from the Dam. Between 10,000
and 15,000 cubic yards of smaller rock for crushing
into rock spalls and riprap bedding also was obtained
from this source.
Embankment Construction
Impervious. The impervious fill was placed in
designated lanes parallel to the axis of the Dam by six
bottom-dump trucks and two scrapers. It then was
spread into 6-inch lifts by bulldozers and mixed by
disking. Compaction was accomplished by six passes
of two double-drum sheepsfoot rollers in tandem,
pulled by a tractor. Areas inaccessible to or missed by
the larger unit were compacted by 12 passes of a single
sheepsfoot roller pulled by a tractor.
Special compaction near abutments and structures
was accomplished by gasoline engine-operated hand
compactors. Where this equipment was used, it was
necessary to scarify and wet the top of each lift before
placing the next one to avoid laminations.
Design recommendations for embankment compac-
24
Figure 20. Location of Borrow Areas and Frenchman Dam Site
25
tion were: (1) rejection of material with a maximum
dry density of less than 104 pounds per cubic foot, (2)
a desirable relative compaction of 98%, and (3) rejec-
tion of material below 95% relative compaction. Aver-
age dry density for all rolled fill tested was 107.0
pounds per cubic foot (pcf) ranging from 90.7 to 115.2
pcf, with an average relative compaction of 97.7%
ranging from 91.4 to 103.8%. Average dry density for
specially compacted fill (hand-held compactors) was
107.8 pcf, ranging from 100.9 to 117.2 pcf, with an
average relative compaction of 98.8% ranging from
94.5 to 102.9%. Only borrow materials with maximum
dry density exceeding 104 pcf were drawn from the
borrow areas. Areas within the borrow where light
materials were known to exist in substantial quanti-
ties were avoided. Fill with a relative compaction of
less than 95% was either rejected or reworked and
retested. The embankment under construction is
shown on Figure 2 1 and the completed Dam on Figure
22.
Drain. The horizontal portion of the drain was
compacted by four passes of a tractor, while the slop-
ing portion was compacted with two passes of a vibra-
tory roller. The decision to change methods of
compaction was made after tests showed that the vi-
bratory roller method of compaction resulted in high-
er and more uniform compaction than the specified
method. To ensure satisfactory compaction upstream
of the drain, the impervious material was lapped 1 to
2 feet over the drain during compaction, then
trimmed back to a neat line.
Slope Protection. Bedding was end-dumped onto
w^mm
Figure 21. Embankment Construction
the upstream dam slope which had been trimmed to
firm material. Riprap then was end-dumped onto the
bedding and selectively placed by a clamshell bucket
and hand labor. Rock spalls were end-dumped on the
downstream face of the Dam, shaped, then compacted
by backing a vibratory roller over the slope with a
tractor.
Outlet Works
Rough excavation was done with a ripper-equipped
tractor and a 2 '/^-cubic-yard shovel. Light to moderate
blasting was necessary in areas of basalt. The fault
zone parallel to the stream through the Dam site was
encountered for about the first 100 feet upstream of
the outlet structure. Loose material was excavated to
a depth of 3 to 13 feet below grade and backfilled to
foundation grade with concrete. Where pyroclastics
were encountered, initial excavation was made to
within 0.3 to 0.5 feet above final grade elevation, and
final grading was done the day before concrete was
placed. This prevented rapid deterioration of the
foundation surface and eliminated the need for spray-
ing with protective asphalt covering. All areas of over-
excavation were backfilled to foundation grade with
concrete. Inasmuch as this concrete was placed during
the summer, there was no need for cold-weather pro-
tection. Placement generally was routine and was ac-
complished with a truck crane and a bottom-dump
bucket (Figure 23).
Spillway
Excavation. A total of 34,016 cubic yards was ex-
cavated for the spillway. Blasting was required only in !
the approach channel at the crest and at the upper part ;
26
Figure 23. Outlet Works Concrete Placement
T of the chute. Overexcavation was required at and be-
I low the crest where blocks of andesite were loosened
; by the blasting or taken from the foundation during
' ripping operations. Before the spillway slab was
; placed, cavities and areas that had been overexcavated
were backfilled with concrete to foundation grade.
Because the pyroclastic and sedimentary rocks in the
i foundation of the spillway deteriorated rapidly when
I dried or rewetted, it was necessary to spray them with
a protective coat of asphalt to prevent slaking.
■ ' Anchorage. Anchor bars were replaced by shear
' keys for about 100 feet in the middle of the chute when
I it became apparent that the foundation rock in this
'■ area would not provide sufficient anchorage for the
bars.
Concrete Placement. The floor of the spillway
i was placed by means of a steel slip form that was
' I drawn uphill with a winch to strike off the concrete.
' I Forms for the crest and wall were constructed of ply-
■ j wood backed by studs and walers.
'• I Placement of the spillway concrete was started in
■ j the fall of 1960 and completed in the spring of 1961.
" I The sequence of construction was the floor slab first,
I then the crest, flip bucket, outlet works bridge and,
' I finally, the walls and crest bridge. A total of 1,678
I cubic yards of concrete was placed in the spillway and
83 cubic yards in the bridges crossing the spillway
(Figures 24 and 25).
Concrete Curing. If mean daily temperatures fell
below 40 degrees Fahrenheit, the contractor was re-
. I quired to maintain concrete temperatures above SO
degrees Fahrenheit for the first three days after place-
ment and above 32 degrees Fahrenheit for the next
three days. To accomplish this, a plastic tent was
placed over the walls of the spillway chute and steam
was piped in from a steam generator for six days. The
tent then was removed and a curing compound ap-
plied.
The high walls of the spillway crest were protected
by 2'/2-inch-thick batting with an aluminum reflective
surface. Single layers were placed between the vertical
Figure 25. Spillway Flip Bucket
27
studs and a double layer over the open concrete at the
top. Six days later, the forms were stripped and a
curing compound applied.
Portable heaters were placed under the deck of the
crest bridge to supplement the steam in the plastic
tent, and blowers were used to circulate the air. The
contractor suspended operations after December 6,
1960, and unstripped forms were left in place until the
following spring.
Backfill. Uncompacted backfill behind the spill-
way walls was obtained from waste material rejected
during the processing of other rock.
Concrete Production
Concrete was produced at a semiautomatic batching
plant located about one-half mile upstream from the
Dam. Coarse aggregate was obtained from a pit near
Reno and sand from Washoe Lake, approximately 17
miles south of Reno. Mixing water was obtained di-
rectly from Little Last Chance Creek but, when the
stream became dirty from eroded materials, it was
necessary to truck water in from a different location.
Concrete was mixed in 7-cubic-yard truck mixers for
a minimum of 80 revolutions at the rate of 8 to 10
revolutions per minute. The normal load did not ex-
ceed 6 cubic yards.
An air-entraining agent was used in the concrete to
provide resistance to deterioration from freezing and
thawing cycles which occur in the project area.
H
Reservoir Clearing
The reservoir area below elevation 5,588 feet was
cleared of sagebrush, trees, down timber, rubbish, and
farm buildings. Trees were cut off 1 foot above the
ground. Fencing in the reservoir area was left in place
as long as practical to fulfill existing grazing require- ,
ments and was later removed by department person-
nel.
Closure
Storage in Frenchman Lake was begun in 1961 by
closing the 6-inch bypass valve on the inlet tower.
Early in March 1962, it became apparent that the res-
ervoir level would not be high enough by the start of '
the irrigation season (March 15) to release water-
right entitlements (up to 94.4 cubic feet per second)
through the outlet works. The need to pump water to
meet downstream requirements during the closure
was eliminated by executing individual agreements
with downstream water-right holders. The maximum
storage in 1962 was 13,811 acre-feet; therefore, only ;
fish and stream maintenance and water entitlement
releases were made in that year. j
In February 1963, the reservoir rose above the mini- |l
mum recreation pool of 21,425 acre-feet. It exceeded -i
43,000 acre-feet in May 1963 and dropped to a low of
31,383 acre-feet in October 1964. The first spill was in
April 1965, and the reservoir has spilled in about half
of the succeeding years. It has remained above a pool
of 36,000 acre-feet since October 1964.
28
BIBLIOGRAPHY
California Department of Water Resources, "A Plan for the Development and Operation of Recreation Facilities
at Frenchman Reservoir, Upper Feather River Basin", March 1961.
, Bulletin No. 59, "Investigation of Upper Feather River Basin Development: Interim Report on Engi-
neering, Economic and Financial Feasibility of Initial Units", February 1957.
, Bulletin No. 59-2, "Investigation of Upper Feather River Basin Development", October 1960.
"Design Report for Frenchman Dam", December 1966.
California Department of Public Works, "Northeastern Counties Investigation: Report on Upper Feather River
Service Area", April 1955.
. , "Program for Financing and Constructing the Feather River Project as the Initial Unit of the California
Water Plan", February 1955.
Diller, J. S., "Geology of the Taylorsville Region", U. S. Geologic Survey Bulletin 353, 1908.
29
Figure 26. Location Map — Antelope Dam and lake
30
CHAPTER III. ANTELOPE DAM AND LAKE
General
Description and Location
Antelope Dam consists of two zoned earth embank-
ments: a 120-foot-high main dam and a 60-foot-high
auxiliary dam. The spillway is located on a ridge be-
tween the embankments. It is an open channel struc-
ture with a 60-foot-long ungated weir. An outlet
works, consisting of a low-level intake tower, a 36-inch
steel-lined pressure conduit, and a control valve struc-
ture, is located along the base of the right abutment of
the main dam.
Antelope Lake has a capacity of 2 2,. '566 acre-feet, a
water surface area of 931 acres, and a 15-mile shore-
line.
Antelope Dam and Lake are located entirely within
the Plumas National Forest on Upper Indian Creek,
a tributary of the North Fork Feather River, 43 miles
by road northeast of Quincy. The nearest major roads
are State Highways 70 and 89 (Figures 26 and 27).
Figure 27. Aerial View — Antelope Dam and Lake
31
A statistical summary of Antelope Dam and Lake is
shown in Table 4, and the area-capacity curves are
shown on Figure 28.
Purpose
The purposes of Antelope Lake are streamflow
maintenance and recreation. Flood control is an inci-
dental benefit. Operation studies indicate that the res-
ervoir is capable of releasing 20 cubic feet per second
from April I through June 30 and 10 cubic feet per
second during the remainder of the year without an
adverse effect on the recreation water level of the
Lake. These flow quantities were determined with the
guidance of the Department of Fish and Game to be
sufficient to provide fishery enhancement in the
stream below the Dam. They also will meet down-
stream water rights. Surface drawdown will vary
from 2 to 12 feet, averaging less than 6 feet.
Chronology
Investigations of water and recreation development
in the Upper Feather River Basin resulted in pub-
lished reports in 1955 and 1957 (see Bibliography). In
1957, the Legislature authorized construction of five
dams in this development. One of these was Antelope
Dam.
Preliminary design involved studies of three em-
bankment axes, and the final alignment selected was
based on minimum embankment quantity. Final de-
sign work was initiated in 1961. Construction began in
August 1962, and the Dam was completed in 1964.
Regional Geology and Seismicity
Antelope Dam is near the northern extremity of the
Sierra Nevadas on the westward-tilted Diamond
Mountain fault block. The site is in a relatively small
granitic area surrounded by Tertiary and older vol-
canic and metavolcanic rocks. Pliocene and Pleisto-
cene volcanic rocks of the southern Cascade Range
and Modoc Plateau lie as close as 20 miles north of the
site. Volcanically active Mount Lassen lies approxi-
mately 50 miles to the northwest. Honey Lake Valley,
which consists chiefly of Quaternary Lake deposits
and other alluvium, is about 10 miles to the northeast
and belongs to the Basin and Range provinces. Rela-
tively small deposits of Tertiary auriferous gravels,
deposited by the ancient Jura River, occur within the
Indian Creek drainage basin and partially have been
reworked to form a portion of the Quaternary allu-
vium and terrace deposits found adjacent to the Dam
site.
Studies of seimicity from 1769 to 1960 indicated the
Dam site is in a seismically active area. Most of the
earthquakes affecting the site originated in Genessee
Valley, Honey Lake Valley, and Mount Lassen Na-
tional Park. Maximum intensity experienced at the
site probably was 7 on the Modified Mercalli scale.
Design
Dam
Description. Both the 1 20-foot-high main dam and
the 60-foot-high auxiliary dam were designed as zoned
TABLE 4. Statistical Summary of Antelope Dam and Lake
ANTELOPE DAM
Type: Zoned earthfiU
Crest elevation.
Crest width
Crest length
Streambed elevation at dam axis-
Lowest foundation elevation
Structural height above foundation.
Embankment volume
Freeboard above spillway crest
Freeboard, maximum operating surface.
Freeboard, maximum probable flood
ANTELOPE LAKE
Maximum operating storage.
Minimum operating storage.
Dead pool storage
Maximum operating surface elevation.
Minimum operating surface elevation..
Dead pool surface elevation
Shoreline, maximum operating elevation
Surface area, maximum operating elevation.
Surface area, minimum operating elevation.
Drainage area
Average annual runoff.
5,025 feet
30 feet
1,320 feet
4,918 feet
4,905 feet
120 feet
380,000 cubic yards
23 feet
23 feet
Ofeet
22,566 acre-feet
500 acre-feet
500 acre-feet
5,002 feet
4,950 feet
4,950 feet
15 miles
931 acres
57 acres
71 square miles
20,900 acre-feet
SPILLWAY
Type: Ungated ogee crest with lined chute and flip bucket
Crest elevation.
Crest length
5,002 feet
60 feet
Maximum probable flood inflow 32,500 cubic feet per second
Peak routed outflow 23,400 cubic feet per second
Maximum surface elevation 5,025 feet
Standard project flood inflow 18,300 cubic feet per second
Peak routed outflow 12,900 cubic feet per second
Maximum surface elevation 5,017 feet
OUTLET WORKS
Type: Steel-lined reinforced-concrete conduit beneath dam at base
of right abutment — discharge into impact dissipator
Diameter: 36 inches
Intake structure: Uncontrolled low-level tower
Control: Downstream control structure housing 10- and 24-inch
butterfly valves — guard valve, 36-inch slide gate on intake tower
Capacity 136 cubic feet per second
32
^lT
AREA IN 100 ACRES
8040
1 1
NORMAL WATER
SURFACE
^
^
-
EL. 5
002.0".
^
><
"^
1-
UJ
UJ
^
'^
^
z
o
/
V.
APACIT
Y
SURFACE
AREA
V
<
>
_l
(
\
4800
CAPACITY IN 1000 ACRE FEET
Figure 28. Area-Capacity Curves
earthfill structures consisting of upstream impervious
zones of decomposed granite and downstream pervi-
ous zones of streambed sands and gravels. The em-
bankment plan is shown on Figure 29, and the sections
are shown on Figure 30. No instrumentation of the
embankment was planned during design.
Stability Analysis. Embankment slope stability
was analyzed by the Swedish Slip Circle method. Sat-
isfactory safety factors were established under all an-
ticipated loading cases. These cases included full
reservoir and other critical reservoir levels along with
earthquake loads. Earthquake loading was assumed to
be an acceleration of the foundation (O.lg) in the di-
rection of instability of the mass being analyzed. De-
sign strength for the impervious material was
determined by soil testing while that for the gravels
was based on published information for similar
material.
Settlement. No rigorous settlement analysis was
made. Consolidation tests indicated that practically all
settlement would occur during construction. A cam-
ber of 1% of the fill height was provided.
Construction Materials. On the basis of surface
examination, boring logs, and soil test data, decom-
posed granite at a site in Antelope Creek about two-
thirds of a mile upstream of the Dam was selected for
impervious borrow. In-place moisture ranged from
4.4 to 13.8%, averaging 6.9%. Specific gravity values
ranged from 2.67 to 2.80, averaging 2.74. In-place dry
densities ranged from 92.2 pounds per cubic foot (pcf)
to 100.8 pcf A maximum dry density of 122.6 pcf at an
optimum moisture content of 11.5% was obtained
from material that had a field value of 100.8 pcf in-
dicating a shrinkage factor of approximately 18%. Di-
rect shear tests on impervious fill showed a strength
of 33 degrees for effective stress analyses, and a
strength of 3 1 degrees and cohesion of 200 pounds per
square foot for total stress analyses. Permeability of
the compacted material ranged from 0.0002 to 0.09 of
a foot per day, averaging about 0.01 of a foot per day.
Streambed sands and gravels from within the reser-
voir area were selected for the pervious embankment.
Areas of free-draining material were delineated based
on exploration with backhoe trenches. Sampling was
accomplished in the trenches. Average compacted dry
density was found to be 137 pcf. Permeability for com-
pacted samples in this density range was from 1 to 7
feet per day. Testing showed that permeability de-
creased rapidly as density increased to 140 pcf.
Strength of the material, based on testing of similar
materials, was assumed to be 38 degrees.
Foundation. Rock occurring at the Dam site is
biotite granodiorite, which has a shallow cover of allu-
vium along the stream channel.
The channel section consisted of jointed fresh rock
overlain by varying depths of silty sandy alluvium
which was removed during construction. Outcrops of
vertical and overhanging rock were shaped to a '/4:1
maximum slope against which the embankment
material could be compacted. A cutoff trench of varia-
ble width and a single grout curtain consisting of two
2S-foot grouted zones (total depth .SO feet) were pro-
vided for the main dam.
33
^^ 1^ 'M^&\!ptfe| ^H:
Figure 29. General Plan and Profile of Dam
34
Figure 30. Embankment Section
35
The auxiliary dam foundation consisted of decom-
posed granodiorite up to 35 feet in depth. All organic
material and loose decomposed rock were removed
from the embankment area. A cutoff trench to firm
decomposed rock was provided near the middle of the
impervious zone. No grout curtain was planned under
the auxiliary dam.
No evidence was found of major faults, although the
presence of slickensided fractures and a narrow shear
zone in the left abutment of the auxiliary dam indicat-
ed minor displacements.
Outlet Works
Description. The outlet works is located along the
base of the right abutment of the main dam. It consists
of an intake tower with a hydraulically operated, 36-
inch, slide gate and metal trashrack; a 36-inch, steel-
lined, pressure conduit; and two discharge valves (10-
and 24-inch butterfly valves) in a control structure at
the toe of the Dam. Plan and sections of the outlet
works are shown on Figure 31.
The discharge valves are located in an impact-type
energy dissipator. Only the 10-inch valve was intend-
ed for throttling service; the 24-inch valve was intend-
ed to operate fully open when needed. Rating curves
are shown on Figure 32. Operators are located im-
mediately above the valves in the valve house. The
reinforced-concrete dissipator structure has a width of
11 feet and a length of 17 feet, which discharges into
a channel, returning the flow to the creek.
Structural Design. The intake structure is a tower
approximately 30 feet high with an inside diameter of
36 inches and minimum wall thickness of 1 foot. It was
designed as a free-standing tower capable of with-
standing a wind pressure of 1 5 pounds per square foot
as well as normal operating loads when inundated by
the reservoir. Trashracks were designed for a differen-
tial hydrostatic head of 40 feet with yield stresses al-
lowed. The racks are welded to a cover plate which has
lifting hooks to enable removal of the entire assembly.
The slide gate and its hydraulic cylinder are en-
closed in a concrete box which sits on top of the verti-
cal inlet. The gate was designed for a S6-foot head
acting uniformly over the entire gate disc in the direc-
tion of seating; a minimum factor of safety of 5 was
required. Four hydraulic lines and the 4-inch, cast-
iron, air pipe were placed in a riprap-protected trench
that extends from the intake structure to the operating
vault at the crest of the Dam (Figures 29 and 30).
A 12-inch bypass valve was installed at the base of
the intake tower for stream diversion during construc-
tion.
The conduit is a 36-inch-inside-diameter, steel-
lined, reinforced-concrete, cut-and-cover section. The
conduit was designed so that the X-'nch steel liner
would carry all of the internal pressure, and external
loads would be carried by the concrete (minimum
thickness 10 inches). There are six 1 '/j-foot-thick seep-
age-cutoff collars which extend V/-^ feet from the top
and sides of the conduit at 25-foot spacing.
Mechanical Installation. The 36-inch slide gate
originally was intended to operate by means of a hand-
operated hydraulic pump in the vault at the crest of
the Dam. Due to the time required to operate the
valve, a linkage was installed that is driven by an elec- f
trie motor powered by a 12-volt battery. All other 1
valves are operated directly by hand. ■
Spillway
Description. The spillway is located on the ridge
between the main dam and the auxiliary dam. It con-
sists of an unlined approach channel; a 60-foot-long,
curved, ungated, ogee crest; a transition section; a 40-
foot-wide rectangular chute; and a flip-bucket termi-
nal structure (Figure 33). A bridge, open to the pub-
lic, crosses the spillway at the crest and connects U.S.
Forest Service roads in the area.
Hydraulics. Reservoir storage above the spillway
reduces the standard project flood from a peak inflow
of 18,300 cubic feet per second (cfs) to a peak outflow
of 12,900 cfs with 8 feet of freeboard, and maximum
probable flood from a peak inflow of 32,500 cfs to a
peak outflow of 23,400 cfs with no freeboard.
Structural Design. Crest walls are cantilevered
from the crest and were designed for two situations:
backfill loads plus live loads on the bridge and backfill
loads plus seismic loading.
The crest is anchored with No. 10 reinforcing bars
embedded 6 feet into the rock foundation on approxi-
mately 5/4-foot centers in both directions. The up-
stream end is provided with a 6-foot-deep cutoff that
acts as a shear key. A 25-foot-deep grout curtain was
provided in the cutoff invert. The crest was designed
for loads transferred from the walls and for uplift
conditions with water above the crest. The influence
of anchor bars was discounted in these analyses.
Walls and floors of the transition and chute sections
were constructed monolithically. Floors are anchored
with No. 9 reinforcing bars embedded 6 feet into the
rock on approximately 5-foot centers, in both direc-
tions. The flip bucket has a 50-foot radius and a 20-
degree upward deflection. A shear key is placed near
the center of the bucket, and the floor upstream of the
key is anchored with No. 9 bars embedded 6 feet into
the rock foundation at 5-foot centers. A 4-inch pipe
drain is provided beneath the bucket.
36
Figure 31. General Plan and Sections of Outlet Works
37
SOIOr
NORMAL POOL^
ELEV. 5002.0' ^
FIELD
MEASURED
DESIGN
COMPUTATIONS
60 80 100
DISCHARGE (CFS)
Figure 32. Outlet Works Rating Curves
120
140
160
38
_|
Fiqure 33. General Plan and Sections of Spillway
39
Construction
Contract Administration
General information for the construction contract
for Antelope Dam is shown in Table 5. Principal fea-
tures involved the construction of an earthfill em-
bankment and spillway and the furnishing and
installation of materials and equipment for a gated
intake tower, a steel-lined conduit, and two butterfly
discharge valves. Miscellaneous road work also was
included in the contract. The contract was designated
Specification No. 62-20.
TABLE 5. Major Contract — Antelope Dam
Specification 62-20
Low bid amount - 22,909,774
Final contract cost ?3,254,049
Total cost-change orders 278,735
Starting date..:..__ 8/29/62
Completion date -- 7/7/63
Prime contractor Norman I. Fadel, Inc.
and Granite Construc-
tion Company
Foundation
Dewatering. Dewatering of the foundation posed
no problems other than the capping of several small
springs encountered in the main dam foundation.
Stream diversion was accomplished through a tempo-
rary pipeline laid through the foundation area (Figure
34).
Excavation. A total of 71,652 cubic yards of
material unsuitable for foundation was removed from
the streambed, abutments, and auxiliary dam saddle
area. Excavation was accomplished with dozers, a
backhoe, and hand labor to finish cleaning the abut-
ments. Blasting was employed to shape foundation
rock outcrops to proper slope. Where foundation
material was subject to ripping, as on the right abut-
ment and for the full length of the auxiliary dam, a
well-defined cutoff trench was excavated. The main
dam channel and left abutment were massive rock,
and no cutoff trench was excavated.
Grouting. Grout caps were necessary at only three
locations: at the bottom of the left abutment of the
auxiliary dam (Figure 35), at each side of the spillway
crest, and on the upper left abutment of the main dam.
A single grout curtain 50 feet in depth was placed in
two 25-foot zones for the full length of the main dam.
Several 100-foot holes were grouted, and a secondary
grout curtain across the outlet works foundation was
added. Although no grouting of the auxiliary dam was
assumed necessary during design, a short reach of the
foundation was grouted because of a shear found in
that area. A total of 724 cubic feetof grout was injected
into the foundation.
Handling of Borrow Materials
Impervious. Impervious material was obtained
from an area two-thirds of a mile upstream of the Dam
on Antelope Creek (Figure 36). The borrow pit was
moisture-conditioned by a sprinkler system prior to
excavation and by a water truck during excavation.
A total of 318,981 cubic yards of excavation yielded
271,353 cubic yards of compacted impervious fill.
Pervious. Pervious material was obtained from an
area 1 mile upstream of the Dam on Indian Creek
(Figure 36). A design modification during construc-
Figure 34. Temporary Diversion Pipe ond Outlet Works Conduit
Figure 35. Drilling Grout Hole— Left AbulmenI Auxiliory Don
40
Figure 36. Location of Borrow Areas and Antelope Dam Site
41
tion utilized more impervious material, which was in
abundant supply, and reduced the required yardage of
pervious material which was in limited supply. A total
of 113,097 cubic yards of excavation yielded 95,305
cubic yards of in-place pervious fill.
Excavation of pervious material presented a prob-
lem because a high percentage of the total quantity
was below the water table. Best results were obtained
by step excavation. One portion of the pit was lowered
2 to 3 feet below the general area; then borrow was
taken from the higher area of the pit. This procedure
allowed drainage of the gravels and escape of water to
the stream by gravity.
Slope Protection. Riprap was quarried from sev-
eral locations near the Dam site. Riprap particle size
varied from a maximum of one cubic yard down to
one-half of a cubic foot. A total of 13,526 cubic yards
of riprap was placed on the upstream face of the Dam.
Pervious fill was employed as bedding for riprap.
Embankment Construction
Impervious. Impervious fill was placed parallel to
the axis in 6-inch lifts and compacted by 12 passes of
a sheepsfoot roller as specified. Design recommenda-
tions for compaction were as follows: (1) minimum
field dry density of HI pcf, (2) field densities for 80%
of the samples to be greater than 97% of laboratory
Figure 37. Outlet Works Control Structure
dry density, and (3) an absolute minimum dry density
of 95% of laboratory maximum. Material that did not
meet these criteria was either rejected or reworked.
Pervious. Pervious material was spread and com-
pacted by four passes of a crawler tractor. On numer-
ous occasions, excessive moisture caused hauling and
compacting equipment to bog down in the placed
material. Special effort was required to haul and place
the driest pit material.
Slope Protection. Riprap was end-dumped on the
slope and placed with a rock rake to the 3-foot thick-
ness specified.
Outlet Works
Excavation. The entire length of the outlet works
conduit is founded in rock (Figure 34). When rock
was not encountered at grade, overexcavation was di-
rected to sound rock and backfilled to subgrade with
concrete. Blasting was required to shape the trench
and to obtain foundation grade. A backhoe was used
to remove material, and all foundation overbreak was
backfilled with concrete.
Concrete. Placement generally was routine and
was accomplished with a truck crane and a bottom-
dump bucket (Figure 37).
Spillway
Excavation. The major portion of the excavation
was made with a shovel which loaded trucks for haul
to the waste area. Some blasting was necessary to exca-
vate near the flip-bucket end of the spillway. After
rough excavation of the shear key trenches, hand labor
was used for final shaping.
Concrete. Placement generally was routine and
was accomplished with a truck crane and a bottom-
dump bucket. The completed spillway is shown on
Figure 38.
Concrete Production
Concrete was produced using a portable batch plant
stationed near the Dam site and transported with
three transit mix trucks. Coarse aggregate was ob-
tained from dredger tailings near Oroville. Sand was
supplied from the Pentz pit on Dry Creek. The con-
tractor attempted to produce coarse aggregate from
Indian Creek gravel but discontinued the operation
due to high cost and low quality. Mixing water was
obtained directly from Indian Creek.
As the concrete was placed during the summer,
there was no need for cold-weather protection during
construction.
An air-entraining agent was used in the concrete to
provide resistance to deterioration from ensuing
freezing and thawing cycles.
Reservoir Clearing
Clearing of the Dam site and reservoir area was
started in September 1962, immediately following the
42
Figure 38. Spjilwoy
removal of merchantable timber. Merchantable tim-
ber previously had been flagged by the U. S. Forest
Service and removed under another contract. In gen-
eral, the contractor's clearing method consisted of us-
ing a bulldozer to push over standing timber and move
it into piles for burning. This initial rough clearing
was followed by brush-raking most of the reservoir
area. Raking proved to be insufficient since many logs,
trees, and limbs were wholly or partly covered and
were not gathered into the burning piles.
The contractor stopped this operation after burning
permits were terminated in 1963. He started again late
in the fall of that year but, before he could take care
of the buried material, the ground froze making re-
moval of the debris virtually impossible. Final cleanup
was made in the spring of 1964 after the reservoir was
partially filled. Floating debris was gathered by hand
at the edge of the reservoir and placed on open rafts
which were towed by motor boats to selected locations
where the debris was burned at a later time.
Closure
Storage commenced in Antelope Lake during Janu-
ary 1964 even though some minor work remained to
be done. During the spring, only stream maintenance
releases were made, and storage rose to a maximum of
12,565 acre-feet by June. In October and November,
all but 3,103 acre-feet of storage was released, in ac-
cordance with prior rights, to the downstream facili-
ties of Pacific Gas and Electric Company. In January
1965, the Lake was filled and the first spill occurred.
Instrumentation
Embankment instrumentation was not included in
the construction contract. After the reservoir filled,
however, seepage appeared on the downstream face.
Seven observation well piezometers were installed
from the crest, seven from the downstream face of the
Dam, and one from the downstream face of the auxil-
iary dam in the fall of 1965 (Figure 39). In addition,
a 4'/2- to 5-foot-deep trench was excavated in the down-
stream face of the main dam at Station 17-1-10 from
elevation 5,000 to 4,917 feet. The trench was partially
filled with 3 feet of crushed aggregate, then brought
to original grade with material excavated from the
trench. The observation wells and the trench appar-
ently punctured impervious layers accidentally creat-
ed during placement of the downstream shell. The
wells and trench now provide vertical drainage paths,
and no further seepage has appeared on the surface.
Embankment stability was reviewed using the data
from these installations, and it was determined that
seepage, as observed, had not significantly affected the
stability of the Dam.
43
ANTELOPE VALLEY DAM AND RESERVOIR
PIEZOMETER AND SEEPAGE LOCATIONS
EXPLORATION TRENCH
STA. 164-42
9T*- 16 + SO
STA. 17-1-20
STA. 174-26
STA. It + OO
STA. 1*4-04
STA. 16 + 26
STA, 16 + 90
STA. 17410 E»pl. tffich
STA. 174-34
STA. 174-90
STA. 16400 S««D 9U
STA. 164-30
AUXILIARY 0AM DRAIN
y-AUXILIARY DAM
V STA. 244-7
Figure 39. Location of Embonlcment Instrumentation
44
H
BIBLIOGRAPHY
California Department of Water Resources, Bulletin No. 59, "Investigation of Upper Feather River Basin Devel-
opment: Interim Report on Engineering, Economic and Financial Feasibility of Initial Units", February
1957.
, Bulletin No. 59-2, "Investigation of Upper Feather River Basin Development", October 1960.
, "A Plan for the Recreation Development of Antelope Valley Reservoir", March 1962.
California Department of Public Works, "Northeastern Counties Investigation: Report on Upper Feather River
Service Area", April 1955.
, "Program for Financing and Constructing the Feather River Project as the Initial Unit of the California
Water Plan", February 1955.
45
Figure 40. location Mop — Grizzly Valley Dam and Lake Davis
46
CHAPTER IV. GRIZZLY VALLEY DAM AND LAKE DAVIS
General
Description and Location
Grizzly Valley Dam is an earth and rockfill struc-
ture about 800 feet long at the crest with a structural
height of 132 feet. An ungated, broad-crested, open-
chute spillway is located on the right abutment. The
outlet works consists of an inclined intake structure
on the left abutment, a low-level intake, a 36-inch out-
let conduit along the base of the left abutment, and a
downstream control house. The reservoir, which is
now named Lake Davis, has a capacity of 84,371 acre-
feet of water and a water surface area of 4,026 acres.
The Dam is located 8 miles north of Portola within
the Plumas National Forest on Big Grizzly Creek, a
tributary of the Middle Fork Feather River. The near-
est major road is State Highway 70 (Figures 40 and
41).
Figure 41. Aerial View — Grizzly Valley Dam and lake Davis
47
A statistical summary of Grizzly Valley Dam and
Lake Davis is shown in Table 6, and the area-capacity
curves are shown on Figure 42.
Purpose
The primary purposes of Lake Davis are recreation,
fish and wildlife enhancement, and domestic water
supply. During the planning stage, integration of the
yield from Lake Davis with that from Frenchman
Lake by a canal to Sierra Valley was considered.
Transportation charge for delivering Lake Davis wa-
ter to the Frenchman service area was beyond the
ability of the agricultural interests to pay; thus, this
portion of the State Water Project was abandoned
as financially infeasible. Agricultural water now
released from Lake Davis is for the fulfillment of prior
rights, about 900 acre-feet per year. Incidental flood
protection is afforded by the reservoir but was not
considered as a project purpose.
Chronology
Investigations of water and recreational develop-
ment in the Upper Feather River Basin resulted in
published reports in 1955 and 1957 (see Bibliogra-
phy). In 1957, the Legislature authorized construction
of five dams in this development. One of these was
Grizzly Valley Dam.
After an economic comparison of four sites and four
dam heights, the axis of the dam was chosen and the
normal pool level was established at elevation 5,775
feet. Detailed design work was initiated in 1963. Con-
struction began in October 1964 and was completed in
1967.
Regional Geology and Seismicity
Grizzly Valley is one of several fault block valleys
found in the Sierra Nevadas and parallels the north-
west structural trend of the northern Sierra Nevada.
The former lake that periodically occupied Grizzly
Valley in the geologic past was finally drained when
Big Grizzly Creek cut its present gorge at the valley
outlet. Granitic rocks outcrop near the valley floor.
Andesitic lava flows and pyroclastics cap the adjacent
higher ridges. Andesitic dikes cut the granitic rocks
and are believed to be feeder dikes to the Tertiary
andesitic volcanics. The crustal forces which caused
the formation of the Valley also produced strong joint-
ing, fracturing, and minor faulting in the bedrock at
the Dam site.
Seismicity is believed to be only moderate, and no
active faults were observed in the area. The site is near
the seismically active area along the California-Ne-
vada border.
Design
Dam
Description. The 132-foot-high dam was designed
as a zoned earthfill structure. Plan, profile, and sec-
TABLE 6. Statistical Summary of Grizily Valley Dam and Lake Davis
GRIZZLY VALLEY DAM
Type: Zoned earth and rockfiU
Crest elevation 5,785 feet
Crest width 30 feet
Crest length 800 feet
Streambed elevation at dam axis 5,670 feet
Lowest foundation elevation.. 5,653 feet
Structural height above foundation 132 feet
Embankment volume 253,000 cubic yards
Freeboard above spillway crest 10 feet
Freeboard, maximum operating surface 10 feet
Freeboard, maximum probable flood 0.6 feet
LAKE DAVIS
Maximum operating storage. 84,371 acre-feet
Minimum operating storage 90 acre-feet
Dead pool storage 90 acre-feet
Maximum operating surface elevation. 5,775 feet
Minimum operating surface elevation 5,700 feet
Dead pool surface elevation 5,700 feet
Shoreline, maximum operating elevation 32 miles
Surface area, maximum operating elevation.. 4,026 acres
Surface area, minimum operating elevation.. 25 acres
Drainage area. 44 square miles
Average annual runoff 25,000 acre-feet
SPILLWAY
Type: Ungated broad crest with lined chute and flip bucket
Crest elevation 5,775 feet
Crest length 30 feet
Maximum probable flood inflow 17,500 cubic feet per second
Peak routed outflow 2,420 cubic feet per second
Maximum surface elevation 5,784.4 feet
Standard project flood inflow 9,220 cubic feet per second
Peak routed outflow 1,190 cubic feet per second
Maximum surface elevation 5,780.8 feet
OUTLET WORKS
Type: Steel-lined reinforced-concrete conduit beneath dam at base
of left abutment — discharge into impact dissipator
Diameter: 36 inches
Intake structure: Two-level inclined structure with 30-inch butter-
fly shutoff' valves — low-level intake tower with concrete plug emer-
gency bulkhead
Control: Downstream control structure housing 10- and 30-inch
butterfly valves for stream release and a 16-inch butterfly valve
at the beginning of Grizzly Valley Pipeline — 24-inch butterfly
guard valve in low-level intake conduit at junction with inclined
structure
Capacity, stream maintenance 222 cubic feet per second
Design delivery to pipeline 8 .25 cubic feet per second
48
jkAi
AREA IN 1,000
4.5 4 3.
CAPACITY IN 1,000 ACRE FEET
Figure 42. Area-Capacity Curves
tions of the Dam are shown on Figure 43. Zone 1 is
compacted clay, Zone 2 is an upstream section of
decomposed granite, Zone 3 is rolled rockfill, and
Zone 4 is transition material consisting of a graded
mixture of crushed rock and fine sand.
Stability Analysis. Embankment stability was de-
termined by the Swedish Slip Circle method of analy-
sis. Adequate safety factors existed for all loading
conditions. Loading conditions analyzed included full
reservoir and other critical reservoir levels coupled
with earthquake loads. Earthquake loading assumed a
horizontal acceleration of the foundation in the direc-
tion of instability of the soil mass being analyzed. The
acceleration used was O.lg. Zone 1 and 2 material
parameters were based on soil testing. Material
parameters for the other zones were selected after a
review of available information on the properties of
similar materials.
Settlement. Settlement analyses based on labora-
tory tests indicated the core could settle 4 to 5 inches
at the maximum section after saturation. A camber of
12 inches at the maximum section, more than twice
the long-time postconstruction settlement, was pro-
vided.
Construction Materials. Sediments from the
former lakebed about one-half mile upstream of the
Dam site were selected for the impervious borrow on
the basis of surface examination and auger holes.
Natural moisture ranged from 20 to 30% and specific
gravity from 2.72 to 2.79. Shear tests showed a
strength, effective stress basis, of 30 degrees with zero
cohesion and a strength, total stress basis, of 11.3 de-
grees with 2,000 pounds per square foot (psf) cohe-
sion. Permeability was determined to be 0.0002 of a
foot per day.
Decomposed granite for the upstream transition
was located adjacent to the lake sediments. Natural
moisture was as low as 8%, and specific gravity was
in the same range as the clayey sediments. Shear tests
showed a strength of 35 degrees with zero cohesion,
effective stress basis; and a strength of 20 degrees with
2,000 psf cohesion, total stress basis. Permeability was
determined to be 0.02 of a foot per day.
The rockfill and transition material was assigned a
strength of 38 degrees, zero cohesion, based on pub-
lished data for similar materials. The permeability
rate was greater than 2 feet per day. Streambed sands
and gravels were explored by backhoe trenching.
Holes were drilled at the proposed quarry site for
determination of rock quality and thickness of weath-
ered layer.
Foundation. The Dam site is in a deep gorge. Bed-
rock consists of a biotite-hornblende granodiorite,
which is strongly joined and irregularly weathered.
There are numerous outcrops of fresh rock on the
abutments. A 50-foot-wide andesite dike cuts the
granodiorite along the right abutment parallel to the
stream channel. The dike rock is more resistant to
weathering and is less jointed than the granodiorite.
Channel fill consisted of gravel, sand, and angular
blocks of andesite and granodiorite from 1 to 5 feet
across. Depth of overburden at the Dam site averaged
about 8 feet.
Foundation preparation consisted of removing allu-
vium, weathered granodiorite, and hard rock excava-
tion to eliminate overhangs and steep slopes. A deeper
cutoff trench was provided beneath the core to obtain
foundation rock with less jointing and thus more im-
permeability. The grout curtain consists of 25- to 50-
foot-deep holes across the foundations for the entire
49
Figure 43. Dam — Plan, Profile, and Sections
50
length of the Dam and dike and holes 100 feet in depth
in the streambed.
Instrumentation. Settlement monuments are pro-
vided on the edge of the crest and downstream face
(Figure 44).
Outlet Works
Description. The outlet works (Figure 45) con-
sists of a 36-inch-diameter reinforced-concrete con-
duit with a %-inch steel lining beneath the
embankment along the base of the left abutment, a
low-level intake, an inclined intake, and a downstream
control structure.
The inclined intake is equipped with 30-inch butter-
fly valves at elevations 5,740 feet and 5,760 feet to
permit withdrawal of water at selected levels for con-
trol of quality and temperature. The low-level intake
is a free-standing tower with an opening at elevation
5,700 feet for drainage of the lower portion of the
reservoir. A 24-inch butterfly valve is located in the
connecting conduit at the base of the inclined intake
to control flow from the low-level intake. A tempo-
rary 3-foot-diameter hole was provided through the
base of the low intake for diversion during construc-
tion.
The downstream control structure contains a 10-
inch butterfly valve for normal streamflow mainte-
nance; a 30-inch butterfly valve for larger releases; and
a 16-inch stubbed-off branch for connection of Grizzly
Valley Pipeline, which was installed under a later con-
tract by another agency. Both valves discharge into an
impact-type dissipator structure.
Hydraulics. Outlet works components were sized
to provide normal streamflow during the lower flow
seasons and to allow drainage of the reservoir in one
season with normal runoff. The outlet works rating
curve is shown on Figure 46.
Structural Design. The low-level intake structure,
approximately 37 feet high, was designed as a free-
standing tower. The outside dimensions are 5 feet by
5 feet and the inside diameter is 36 inches. A concrete
bulkhead that can be lowered to seal the tower open-
ing is provided inside the trashrack for dewatering the
conduit.
The inclined intake has a concrete-box section with
inside dimensions of 6 feet by 6 feet. This structure
was designed for external loading of the reservoir and
embankment where applicable.
The concrete conduit was designed for external
loads of the Dam and reservoir. The steel liner is capa-
ble of withstanding the internal pressure due to a full
reservoir. Concrete cutoff collars are constructed out-
side the conduit at 40-foot centers along the reach
passing under the dam core. Control houses are locat-
ed at the toe and crest of the Dam.
Mechanical Installation. All valves are operated
manually by handwheels or hydraulic cylinders.
Spillway
Description. The spillway is located on the right
abutment about 250 feet from the main embankment.
It consists of an unlined approach channel; an ungated
broad-crested weir; a 30-foot-wide, rectangular, con-
crete chute; and a flip-bucket terminal structure (Fig-
ure 47). A bridge crosses the spillway at the crest
connecting U. S. Forest Service roads.
Hydraulics. Storage above the spillway reduces
the standard project flood from a peak inflow of 9,220
cubic feet per second (cfs) to a peak outflow of 1,190
cfs while retaining 4 feet of freeboard on the Dam and
reduces the maximum probable flood from a peak in-
flow of 17,500 cfs to a peak outflow of 2,420 cfs with
0.6 of a foot of freeboard.
Structural Design. Crest walls were designed for
normal earth loads plus live loads on the bridge and
for normal earth loads plus a seismic acceleration of
O.lg. They were constructed monolithically with the
crest.
At the crest, anchor bars were designed to resist
uplift resulting from passage of floods. The upstream
end is provided with a 6-foot-deep key. The crest was
designed for loads transferred to it from the walls.
Walls and floors of the transition and chute sections
were constructed monolithically. Shear keys were
placed at each contraction joint. Design considered
backfill loads and loads due to spillage.
The flip bucket discharges with a slight downward
deflection 100 feet above streambed. The floor up-
stream of the cutoff (Figure 47) is anchored with two
rows of No. 8 bars embedded 9 feet into the rock
foundation at 7'/2-foot centers.
Grizzly Valley Pipeline
Grizzly Valley Pipeline supplies water for munici-
pal and industrial use in Plumas County. The facility
was designed to take 8.25 cfs with the water surface in
Lake Davis at elevation 5,750 feet.
Grizzly Valley Pipeline was designed and con-
structed under the direction of the Plumas County
Flood Control and Water Conservation District. The
Department of Water Resources' role was limited to
review and approval of the plans and monitoring of
construction.
51
GRIZZLY VALLEY DAM
SURFACE MONUMENT AND DRAINAGE LOCATIONS
LOW -LEVEL
O^ INTAKE
:^ STRUCTURE
NTAKE
STRUCTURE
PLAN
I
RIGHT SIDE LEFT SIDE.
OUTLET
STRUCTURE
6 DRAIN PIPE
4" WEEP HOLE
6 DRAIN PIPE
4" WEEP HOLE
TOE DRAINS
Figure 44. Location of Embankment Instrumentation
52
Figure 45. General Plan and Profile of Outlet Works
53
97BOr
UPSTREAM VALVES
30" BUTTERFLY-INLET AT
EL. 5760
30" BUTTERFLY- INLET AT
EL. 5740
24" BUTTERFLY-INLET AT
EL. 5700
DOWNSTREAM VALVES
30" BUTTERFLY ^- AT
EL. 5651
10" BUTTERFLY (J.- AT
EL. 5651
S700
80 120 160
DISCHARGE IN CFS
240
Figure 46. Outlet Works Rating Curve
54
Figure 47. General Plan and Profile of Spillway
55
Construction
Contract Administration
General information for the contract for the con-
struction of Grizzly Valley Dam is shown in Table 7.
The work was performed under the provisions of
Specification No. 64-22. The principal features in-
volved in the construction of Grizzly \'alley Dam and
reservoir were a zoned embankment consisting of an
impervious earth core and rock shells with river grav-
el transition zones; a concrete, chute-type, ungated
spillway; outlet works; the clearing of the reservoir;
and the relocation of portions of existing U.S. Forest
Service roads.
TABLE 7. Major Contract— Grizzly Valley Dam
Specification — 64-22
Low bid amount 31,833,131
Final contract cost _ 32,269,382
Total cost-change orders 366,020
Starting date 10/20/64
Completion Date.... 9/29/67
Prime contractor Pascal & Ludwig, Inc.
Diversion and Care of Stream
Diversion of Big Grizzly Creek during construction
was the responsibility of the contractor. During the
first construction season, stream diversion was made
through a temporary pipe. Diversion during the sec-
ond season was through the outlet works. The 36-inch-
diameter opening in the base of the intake tower was
plugged with concrete after its use for stream diver-
sion was discontinued.
Excavation for Dam and Dewatering Foundation
The left abutment was stripped with a "Yo-Yo"
tractor anchored to a large tractor acting as an anchor.
In contrast to the left abutment, the right abutment
consisted of many steep overhanging outcrops of fresh
rock. The slope was shaped by blasting and backfilling
with concrete. A cutoff trench was provided in the
foundation under the Zone 1 core upstream of the
axis. The total amount of foundation excavation was
about 65,000 cubic yards.
Grouting was done in two stages. In the first stage,
a curtain 25 feet in depth was extended across the
entire length of the dam foundation. Below elevation
5,770 feet on the foundation, a second stage was ex-
tended to a depth of 50 feet. Two holes were extended
to a depth of 75 feet. The total grout take of 1,837 cubic
feet was about half the estimated 3,500 cubic feet.
After stripping and grouting were completed, arte-
sian water problems were encountered. Holes V/^
inches in diameter were drilled into the foundation,
pipes were grouted in, and the water table lowered by
pumping. Drains up to 24 inches in diameter also were
installed and pumped. After the fill material was com-
pacted around the drains, they were sealed with con-
crete.
Handling of Borrow Materials
Borrow materials were obtained from the areas
shown on Figure 48.
Impervious Zone 1, compacted clay, was disked in
place to aid drying, spread on a stockpile, and disked
again before being brought to the Dam. Excavation
across layers varying from fat clay to decomposed
granite was necessary to ensure that the embankment
was homogeneous in texture and uniform in moisture
content. A total of 101,750 cubic yards of clay was
placed in the Dam.
Semipervious Zone 2, decomposed granite, was
delivered directly to the fill. A total of 54,592 cubic
yards was placed in the Dam.
Pervious material for Zone 3 and riprap were quar-
ried from an andesite knoll on private land two-thirds
of a mile south of the Dam and from the designated
area in granodiorite adjacent to, and immediately
downstream from, the Dam on the left bank. The bulk
of Zone 3 rock came from the andesite knoll quarry
where excavation was shifted between several areas
but finally confined to an 80- by 150-foot swale sur-
rounded on three sides by fines and overburden.
The material was processed by ripping, blasting,
and raking to comb the rocks from the fines. The rock
then was pushed into piles where a loader, equipped
with a rock bucket, sifted the remaining fines from the
piles and loaded the material into dump trucks for
placement in the embankment. A total of 84,442 cubic
yards of rock fill was placed in the Dam.
Zone 4 material, the transition zone, was produced
by crushing, screening, and blending river-run sand
with the andesite. This material was delivered to the
Dam in dump trucks. A total of 13,953 cubic yards of
transition zone material was placed in the Dam.
Embankment (Figure 49)
Zone 1 material was spread, leveled, scarified, and
rolled with 12 passes of a sheepsfoot roller with each
lane overlapping the last one rolled. Due to the con-
fined working area in the bottom of the Dam, it was
necessary to compact Zone 1 material in a direction
normal to the dam axis. At elevation 5,680 feet, the
working area had expanded sufficiently to permit
placing and rolling to be done parallel to the dam axis.
Zone 2 material was spread by loaders, leveled, and
watered before being compacted by a vibratory
smooth-drum roller.
Zone 3 material was end-dumped on the Dam and
dozed into place. To obtain proper filtration. Zone 3
material within 9 feet of the downstream edge of Zone
4 contained at least 20% material smaller than 4 inches
in size.
Zone 4 material was end-dumped in position, then
spread and compacted by a large tractor.
Outlet Works
Excavation. Blasting was required in most of the
trench for the outlet pipe. Overexcavation was back-
56
Jjj L
Figure 48. Location of Borrow Areas and Grizzly Valley Dam Site
57
Figure 49. Completed Embankment
^^1^
4
^^^■■■■l^^^M|Ham^mte|
L-,
- ,<" -■ '
^^^^^^^^^^^^^^ \
/
^^^^HV^^^^vT
filled with concrete to the subgrade of the conduit.
Metal chairs were set in the backfill concrete to sup-
port the steel liners.
Concrete. Dewatering of the trench was difficult,
and a number of small pumps located in strategic areas
were utilized to keep free water to a minimum during
concrete placement. Concrete was cured with white
pigmented compound and was protected with insulat-
ing blankets where necessary.
To avoid flooding of the conduit by winter runoff,
both low-level and inclined intakes were placed under
adverse weather conditions to elevation .\694 feet.
Mi.xing water was heated to maintain placement tem-
perature at approximately 50 degrees Fahrenheit. Af-
ter placement, the structures were tented with
polyethylene and heated by salamanders. The balance
of the concrete for the two structures was placed un-
der favorable weather conditions and cured by normal
methods. Both control houses are concrete block
structures with reinforced-concrete slab roofs (Fig-
ures 50 and 51). A total of 1,412 cubic yards of con-
crete was placed in the outlet works.
Figure 50. Control House at Dam Crest
Figure 51. Control House at Dam Toe
58
Mechanical Installation
Butterfly valves in the sloping intake and the outlet
structure (Figure 52) are operated directly by hand,
while the 24-inch butterfly valve at the base of the
sloping intake is operated by a hand-pump hydraulic
unit. The concrete bulkhead inside the trashrack of
the low-level intake is used for dewatering the outlet
to allow visual inspection. It is raised and lowered by
a diver using an A-frame hoist.
Spillway
Excavation. The spillway required little blasting.
Overexcavation was backfilled to subgrade with con-
crete. The end key was excavated to sound rock.
Concrete. Spillway slabs were struck off with a
slip form and hand-finished from plank bridges with
rubber floats. Spillway walls were formed with metal
forms. Due to temperatures below freezing, the con-
crete was cured using wet rugs covered by insulating
blankets. This resulted in suitable curing tempera-
tures for the slab and walls.
The spillway bridge was constructed during warm-
er weather; thus, only wet rugs were used in curing.
A total of 520 cubic yards of concrete was placed in
the spillway, and 299 cubic yards were placed in the
bridge and culvert headwalls.
The completed spillway chute is shown on Figure
53 and the spillway approach with log boom on Figure
54.
Figure 52. Outlet Works — Butterfly Valve in Outlet Structu
Figure 53. Spillway Chute
59
Figure 54. Spillway Approach and Log Boom
Concrete Production
Concrete was manufactured with a 3-cubic-yard
batcher located about one-third of a mile upstream
from the Dam site. During 1965, coarse aggregate was
obtained from Graeagle, a small town about 20 miles
from the Dam site. Because production at this plant
was uncertain, in 1966 the contractor elected to im-
port concrete aggregate from Oroville, about 95 miles
away. Mixing water was obtained directly from Big
Grizzly Creek. Concrete was mixed and transported
to placement in 6-cubic-yard transit mix trucks.
An air-entraining agent was used in the concrete to
provide resistance to deterioration due to freezing and
thawing cycles which occur in the vicinity.
Reservoir and Other Clearing
Merchantable timber was felled and decked on the
access roads, quarry areas, and Dam site in November
1964 and in the spillway area early in 1965. The re-
mainder of the clearing was begun on March 29, 1966
and completed on September 29, 1967. Reservoir clear-
ing was done to the normal high water line, elevation
5,775 feet. The downstream two-thirds of the shore-
line was cleared of all vegetation between the 5,765-
and 5,775-foot contours. Water storage in Lake Davis
was begun in the fall of 1966 prior to completion of
clearing, and the level rose higher than anticipated,
inundating several of the burn piles below the 5,765-
foot contour. The contractor was forced to use a great
deal of hand labor during the summer of 1967 because
of high water and wet ground.
Initial Reservoir Filling
No problems were encountered in filling the reser-
voir. Storage was started on October 18, 1966 and rose
to 53,507 acre-feet in June 1967. In succeeding years,
storage dropped during the summer months but in-
creased during the rainy season. The first spillage oc-
curred in January 1969, and storage has remained
above 70,000 acre-feet since that time.
60
BIBLIOGRAPHY
California Department of Water Resources, Bulletin No. 59, "Investigation of Upper Feather River Basin Devel-
opment: Interim Report on Engineering, Economic and Financial Feasibility of Initial Units", February
1957.
, Bulletin No. 59-2, "Investigation of Upper Feather River Basin Development", October 1960.
, Bulletin No. 117-3, "Lake Davis: Recreation Development Plan", July 1965.
, Bulletin No. 128, "Lake Davis: Advance Planning Report", May 1965.
California Department of Public Works, "Northeastern Counties Investigation: Report on Upper Feather River
Service Area", April 1955.
, "Program for Financing and Constructing the Feather River Project as the Initial Unit of the California
Water Plan", February 1955.
61
CHAPTER V. OROVILLE DAM AND LAKE OROVILLE
General
Description and Location
Oroville Dam, on the Feather River, is the highest
earthfill dam in the United States. It rises 770 feet
above streambed excavation and spans 5,600 feet be-
tween abutments at its crest. The 80,000, 000-cubic-
yard embankment is made up of an inclined impervi-
ous clay core resting on a concrete core block, with
appropriate transitions and rock-filled shell zones on
both sides.
The spillway, located on the right abutment of the
Dam, has two separate elements: a controlled or gated
flood control outlet, and an uncontrolled emergency
spillway. The flood control outlet consists of an un-
lined approach channel, a gated headworks, and a
lined chute extending to the River. The emergency
spillway consists of a 1,730-foot-long, concrete, over-
pour section with its crest set 1 foot above normal
maximum storage level. Emergency spill would flow
to the River over natural terrain.
Two small embankments, Bidwell Canyon and Par-
ish Camp Saddle Dams, complement Oroville Dam in
containing the 3,537,577-acre-foot Lake Oroville.
They are 47 and 27 feet high, respectively.
Most of the water released from the Lake passes
through Edward Hyatt Powerplant, located in the left
abutment of Oroville Dam. The plant's 678.75-mega-
watt output is achieved by means of three convention-
al generators rated at 123.2 MVA each, driven by
vertical Francis-type turbines, and three motor-gener-
ators, rated at 115 MVA each, coupled to Francis-type
reversible pump-turbines. The latter units allow off-
peak pumped-storage operations. The underground
powerhouse measures approximately 550 feet long, 69
feet wide, and 140 feet high.
The intake for the Powerplant is a sloping concrete
structure located on the left abutment just upstream
from the Dam. It consists of two parallel intake chan-
nels, one each for the two 22-foot-diameter penstock
Figure 56. Aerial View — Oroville Dam and Lake Oroville
63
tunnels. The intake openings are protected by stain-
less-steel trashracks. Beneath the trashracks and on
top of the intake channels are guide rails for a shutter
system. Each shutter is approximately 40 feet square.
The setting of the shutters determines the level from
which water is withdrawn from the reservoir and, in
turn, the temperature of the water. Temperature of
the water is critical for local agricultural purposes,
mainly rice, and for the downstream fishery. Emer-
gency closure of the penstocks can be accomplished by
means of hydraulically activated roller gates posi-
tioned at the base of the channels at the entrance of the
penstocks.
Discharges from the underground powerplant are
conveyed to the Feather River by two 35-foot-diame-
ter former diversion tunnels. The "river outlet" also
is included in one of these tunnels. This facility, with
a maximum release capability of 5,400 cubic feet per
second (cfs), was used to make downstream releases
until the reservoir reached the penstock intake level.
It is being preserved to serve the same function in the
event there is ever a prolonged total outage of the
Powerplant.
Another outlet serves Palermo Canal on the left
abutment at the Dam's mid-height. This tunnel outlet
can release up to 40 cfs.
The Dam backs water into areas previously oc-
cupied by two railroads, a U. S. highway, and three
county roads. These facilities had been principal arter-
ies for access to and from the Oroville community and
the State in general. In order to provide service to all
who used these facilities, relocations were designed
and constructed prior to the filling of Oroville Reser-
voir.
Table 8 shows the statistical summary of Oroville
Dam and Lake Oroville, Figure 55 is a location map,
Figure 56 is an aerial view, and Figure 57 contains the
area-capacity curves.
Oroville Dam is situated in the foothills of the Sier-
ra Nevada above the Central Valley and is 1 mile
downstream of the junction of the Feather River's
major tributaries. The Dam is located 5 miles east of
the City of Oroville (Figure 55) and is approximately
85 miles north of Sacramento. Nearest major roads are
State Highway 70, adjacent to the west city limits of
Oroville, and State Highway 99, six miles farther
west.
TABLE 8. Statistical Summary of Oroville Dam and Lake Oroville
OROVILLE DAM
Type: Zoned earthfill
Crest elevation 922 feet
Crest width-- 50.6 feet
Crest length - --- 6,920 feet
Streambed elevation at dam axis 180 feet
Lowest foundation elevation-- 152 feet
Structural height above foundation 770 feet
Embankment volume 80,000,000 cubic yards
Freeboard above spillway crest 21 feet
Freeboard, maximum operating surface 22 feet
Freeboard, maximum probable flood 5 feet
LAKE OROVILLE
Maximum operating storage 3,537,577 acre-feet
Storage at flood control pool 2,778,000 acre-feet
Minimum operating storage 852,000 acre-feet
Dead pool storage 29,638 acre-feet
Maximum operating surface elevation - 900 feet
Surface elevation of flood control pool 848.5 feet
Minimum operating surface elevation 640 feet
Dead pool surface elevation 340 feet
Shoreline, maximum operating elevation 167 miles
Surface area, maximum operating elevation.- 15,805 acres
Surface area, minimum operating elevation.. 5,838 acres
Drainage area - 3,611 square miles
Average annual runoff 3,500,000 acre-feet
SPILLWAY
Emergency: Ungated ogee (left 930 feet) and broad crest (right 800
feet), discharge on hillside above river
Crest elevation-- 901 feet
Crest length 1,730 feet
Flood control: Gated broad crest with lined channel and dispersion
chute blocks — Eight submerged radial gates 17 feet - 7 inches
wide by 33 feet - 6 inches high
Sill elevation. 813.6 feet
Total sill width ..-. 140.7 feet
Combined spillways: All 8 gates open
Maximum probable flood inflow.. 720,000 cubic feet per second
Peak routed outflow 624,000 cubic feet per second
Maximum surface elevation 917 feet
Flood control: All 8 gates open
Standard project flood inflow 440,000 cubic feet per second
Peak routed outflow 150,000 cubic feet per second
Maximum surface elevation 900 feet
POWERPLANT INTAKE
Edward Hyatt Powerplant: Multilevel, twin, sloping intakes each
with roller gate shutofl' and 13 removable shutters
Maximum generating release 16,900 cubic feet per second
Pumping capacity 5,610 cubic feet per second
OUTLET WORKS
River outlet: Two 72-inch-diamcter conduits through tunnel plug
controlled by two 54-inch fixcd-conc dispersion valves each of
which is guarded by a 72-inch spherical valve — intake, diversion
tunnel intake — auxiliary inlet, uncontrolled vertical shaft —
discharge into tailrace tunnel
Capacity - 5,400 cubic feet per second
Palermo outlet tunnel: A 72-inch-diameter lined tunnel with a valve
chamber and energy dissipator immediately downstream of grout
curtain — control, 12-inch fixed-cone dispersion valve
Capacity 40 cubic feet per second
64
.li
AREA IN 1000 ACRES
2
000
eoo
600
400
0 1
8
16 J4 12 10 8 6 4
2 0
f
d
APAC
TY
AREA'^
\
^
0
400 800 1200 1600 2000 2400 2800 3200 3600 4000
CAPACITY IN 1000 ACRE-FEET
Figure 57. Area-Capacity Curves
Purpose
Oroville Dam and its appurtenances comprise a
multipurpose project encompassing water conserva-
tion, power generation, flood control, recreation, and
fish and wildlife enhancement. The Lake stores win-
ter and spring runoff which is released into the
Feather River as necessary, to supply project needs. A
pumped-storage capability permits maximization of
the value of power produced by these releases. The
dependable capacity of Edward Hyatt Powerplant
and downstream Thermalito Powerplant combined is
725 megawatts, with an energy output of over two
billion kilowatt-hours per annum. The Federal Gov-
ernment shared in the cost of the Dam, which pro-
vides 750,000 acre-feet of flood control storage. The
15,805-acre surface of the Lake with a 167-mile shore-
line provides water-oriented recreational opportuni-
ties.
Chronology and Alternative Dam Studies
Various plans for development of the Feather River
have been studied by state and federal agencies begin-
ning in the 1920s. The River, a major tributary to the
Sacramento River in California's great Central Valley,
has a particularly erratic streamflow record. In some
years, it has been practically dry in the late summer
and fall and, in other years, has produced devastating
floods. A major project was needed to control the
floods and to assure a firm water supply for the val-
ley's irrigation needs. Later planning included export-
ing some of the conserved water to the State's south
coastal area around Los Angeles. Since, historically,
the flow of the Feather River has been well below
normal for as many as four consecutive years, the stor-
age had to be great enough to provide carryover stor-
age from wet years to dry years.
In the late 1940s, the State compared development
at the Oroville site with developments on the North
Fork at Big Bend and on the South Fork at Bidwell
Bar. The conclusion, quoting the August 1949 report
(see Bibliography), was that "major storage capacity
can most feasibly and economically be provided at the
Oroville site".
Work then was concentrated on feasibility studies
for the State Water Project (then known as the
Feather River Project), which was authorized by the
State Legislature in 1951. A concrete gravity dam
similar to Shasta Dam was assumed at Oroville for
these studies.
In 1956, the State Legislature authorized the prepa-
ration of final designs, plans, and specifications for
Oroville Dam. First, the type of dam to be constructed
at the site had to be selected. Initially, gravity, multi-
ple-arch, straight-buttress, and arch-buttress concrete
dams were studied (Figure 58).
One of these designs was of the concrete-buttress
65
Figure 58. Model of Multiple-Arch Concrete Don
66
type consisting of a series of massive head buttresses
60 feet thick and spaced 1 20 feet center to center across
Oroville Canyon. Later, to eliminate the extremely
high buttresses that would have been required in the
deeper part of the Canyon, an arch-buttress alterna-
tive was developed. The central deepest portion of the
Canyon was to be spanned by an inclined arch abut-
ting against a massive buttress on either side. The
remainder of the dam would have consisted of a mas-
sive head buttress similar to that proposed for the
straight-buttress dam. Preliminary design studies of
this hybrid dam showed it to be economically and
engineeringly attractive. Detailed design studies,
which included a structural model, were undertaken.
Designs for multiple-arch dams were suggested by the
foremost concrete dam designers in the world at the
time.
The Oroville Dam Consulting Board (discussed in
Appendix A) advised the Department of Water Re-
sources on these studies and on the final design and
construction of the Dam and appurtenant structures.
Concurrent with these design studies, extensive
damsite geologic and construction materials investiga-
tions were being undertaken. The materials investiga-
tions were centered in the vast fields of tailings located
10 to 15 miles downstream of the site that had been
produced by dredgers working over the flood plain of
the Feather River for gold. This gravelly cobbly
material originally was explored for a source of con-
crete aggregate and later proved to be an ideal material
for pervious shells for the earthfill dam. The dredger
tailings, consisting of washed sands and gravels, var-
ied in depth from IS to 50 feet. Normal dredger opera-
tion stacked the gravel and cobbly material on top of
the sand. The sand deposit was not usable for concrete
aggregate but could be used to blend with the tailings
to form transition zones for an earth or rockfill dam.
Preliminary analyses showed that an embankment
dam utilizing the dredger tailings could be construct-
ed at approximately the same cost as the most competi-
tive concrete dam. Further exploration located a
source of impervious core material near the tailings.
An intensive study was undertaken to determine the
feasibility of hauling the borrow materials an average
of 1 1 miles to the dam. The use of a conveyor, a truck,
and a rail haul was investigated. The high capital in-
vestment made a conveyor uneconomical. The cost of
a high-speed road required for truck haul and the cli-
matic conditions made trucks impractical. Daytime
temperatures in the Oroville area reach 100 degrees
Fahrenheit for more than 30 days each summer. At
those temperatures, difficult service conditions would
have been created for tires then available. In the win-
ter, the area is frequently shrouded by fog which
would have forced the trucks to reduce their speeds.
The Department, in its economic studies, made the
choice of rail haul based on the use of the old Western
Pacific Railroad tracks for nearly one-half the haul
distance. This was possible since the relocation of the
railroad would be completed by the time construction
of the dam commenced. This selection later was veri-
fied by the successful contractor, and all the other
bidders adopted a railroad as the most economical
means of transporting the materials to the damsite.
These design studies were completed and results
gathered and reviewed in the fall of 1958. Preliminary
costs estimated for the earth dam and the arch-buttress
concrete dams were nearly the same when the power
facilities were included, but continuing damsite explo-
ration indicated that extensive foundation treatment
would be required for a concrete dam. The conclusion
was that an embankment dam should be constructed.
The next phase of design was to develop the section
of the embankment dam. Included in these studies
were preliminary designs of vertical, inclined, and
sloping thin-core dams. The inclined core was selected
as the section for final design.
Construction Schedule
First construction in the Oroville area was on U. S.
Highway 40A (now State Highway 70) and Western
Pacific Railroad relocations in 1957. The State Legisla-
ture annually appropriated limited funds to continue
this work until 1960, when the California voters ap-
proved the bond issue (the "Burns-Porter Act") to
construct the State Water Project.
Work at the Dam site started in the summer of 1961
with the award of a contract for constructing the first
of the two diversion tunnels. The contract for con-
struction of the Dam, including the second diversion
tunnel, was awarded in the summer of 1962. The spill-
way, reservoir clearing, saddle dams, and other work
were accomplished by separate contracts awarded one
to four years after the main dam contract.
The embankment was topped out in October 1967.
Storage in the reservoir commenced the following
month with closure of Diversion Tunnel No. 1. The
spillway was completed in early 1968 as was all other
work, except the powerplant and cleanup contracts,
which were completed within the following two
years.
Regional Geology and Seismicity
Oroville Dam lies in the foothills on the western
slope of the Sierra Nevada, a westerly tilted fault
block with a core of granitic rock. A series of tightly
folded, steeply dipping, metamorphic rocks overlies
the granite core along its western and northwestern
flanks.
Geologic formations in the Oroville area are
grouped into an older, steeply dipping, "Bedrock Se-
ries" containing mostly dense, hard, metamorphosed
volcanic and sedimentary rocks and a younger, overly-
ing, "Superjacent Series" of nearly flat-lying, non-
deformed, sedimentary rocks and volcanic flows.
During recorded history, the Oroville area largely
has been unaffected by earthquakes. The most signifi-
cant earthquake in the northern Sierra Nevada before
1934, when location of earthquakes by seismographs
67
became routine, was the temblor of 1875 which proba-
bly occurred on the Mohawk Valley fault near Quin-
cy, about 40 miles east of Oroville. Fissures 2 feet wide
and rejuvenated hot springs along the fault trace were
reported. A maximum intensity was not assigned for
the epicenter because the area was uninhabited and
consequently no damage reported. The intensity as-
signed the Oroville area was V (Modified Mercalli).
No known active faults are within 20 miles of Oro-
ville Dam. The active Mohawk Valley fault is about 40
miles east of Oroville, and the San Andreas fault is
about 130 miles west.
The foothill fault system parallels the Sacramento
Valley for about 160 miles. An unnamed branch of
this system is about 27 miles east of the project area.
This fault system generally is regarded as inactive.
Evidence suggests that the most recent movement oc-
curred over 70,000,000 years ago.
Design
Dam
Description. Oroville Dam is a zoned earthfill
structure with a maximum height of 770 feet above its
lowest streambed excavation. The dam embankment
crest, at elevation 922 feet, is 50.6 feet wide and ap-
proximately 5,600 feet long from the gated spillway to
the left abutment. The embankment plan is shown on
Figure 59. Selected sections and the profile of the Dam
are shown on Figure 60. The materials used in each
zone and the compaction methods were:
Zones 1, lA, and IB — Impervious core from the
deposit adjacent to the pervious borrow areas consist-
ing of a well-graded mixture of clays, silts, sands, grav-
els, and cobbles to 3-inch maximum size. Compaction
was in 10-inch lifts by 100-ton pneumatic rollers.
Zones 2 and 2A — Transition zones consisting of a
well-graded mixture of silts, sands, gravels, cobbles,
and boulders to 15-inch maximum size (6% limit on
minus No. 200 sieve material). Compaction was in
15-inch lifts by smooth-drum vibratory rollers.
Zone 3 — Shell zone of predominantly sands, grav-
els, cobbles, and boulders to 24-inch maximum size; up
to 25% minus No. 4 U.S. Standard sieve sizes permit-
ted. Compaction was in 24-inch lifts by smooth-drum
vibratory rollers.
Zone 4 — Impervious core from selected abutment
stripping contains between 15 and 45% passing No.
200 U.S. Standard sieve with 8-inch maximum size.
Compaction was in 10-inch lifts by a 100-ton pneu-
matic roller.
Zone 4A — Buffer zone designed to compress, with
same grading requirements as Zone 4 but less strin-
gent compaction requirements. Compaction was in
15-inch lifts by a smooth-drum vibratory roller.
Zones 5A and 5B — Drainage zones consisting of
gravels, cobbles, and boulders with maximum of 12%
minus No. 4 sieve size permitted. Compaction was in
24-inch lifts by a smooth-drum vibratory roller.
The only processing of embankment materials re-
quired, other than a minor amount of moisture condi-
tioning, was screening of the core material to remove
plus 3-inch rock.
Elevation 900 feet was selected as the normal water
surface while the concrete dams were being consid-
ered. Factors influencing the selection were: a 3.5-
million-acre-foot reservoir was needed, the ridge near
Parish Camp Saddle Dam is narrow, and this saddle
and the ones at the spillway site and Bidwell Canyon
were slightly below elevation 900 feet. In addition to
these physical factors, the height of the Dam was un-
precedented.
Configuration and Height. Because the shear
strength of the core material is lower than the shear
strength of the material in other major zones of the
Dam, the thickness and relative position of the core
played an important role in selection of the section for
the Dam. Although the most economical design was
determined to be a section with a thin vertical core,
the consolidation characteristics of the embankment
materials dictated the selection of an inclined core
section. The core material is more than twice as com-
pressible as the shell materials under the loads in a
dam the height of Oroville. With a vertical core, there
was the chance that resultant differential settlement at
the shell-core contact could have caused "arching" and
horizontal cracks through the vertical core. With an
inclined core, these effects would be less likely to oc-
cur and the inclined core section did not affect materi-
ally the cost of the Dam. Settlement and stress
measurements made in the embankment during con-
struction verified the wisdom of the selection in that
only a harmless degree of arching occurred even in the
sloping core.
The curve in the axis of the Dam (Figure 59) im-
proved the appearance and gained some possible arch-
ing to keep the core in compression.
A 400-foot-high cofferdam (Figure 61), which was
incorporated into the final embankment, served to di-
vert the Feather River and protect the Dam site dur-
ing construction. This solution was the result of
studying several sizes of diversion tunnels and em-
bankment-placing schemes in which the standard
project flood with a peak flow of 440,000 cfs was rout-
ed past the Dam. The plan for protecting the Dam
during the first flood season by making allowance for
the fill to be overtopped is discussed later in this chap-
ter in describing the core block. During the second
and third years, considerable storage was required be-
hind the Dam to route the flow through the tunnels.
It was doubtful if the impervious material in the main
core could be placed at a rate great enough to provide
the required dam height, particularly in the first full
year of embankment placement. The high-cofferdam
scheme reduced the required embankment placement
rate during this shakedown year to little more than
one-half the average rate required to complete the re-
mainder of the Dam. When the need for the cofferdam
68
~
x±J- -^^
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—
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—
-X-.. fi-±
[:* -ttl
E--:,^x±
tt-2--ix
— ^.
X-t — ■
- -. — =
A-r ■ '^
8
3| ir:^
- =
■I-ix- •
- jU . -.- -. ^
1^4- ■ ■ ■
ili- ■ ^-^
'
\ti- - ■
• -J
t^' ■
■ ^-
^
i\- ■ ■
- _j^
. - \: - :
. - ^'
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- . _
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i
1 § 1
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Figure 59. Embankment Plan
69
Figure 60. Embankment — Selected Sections and Profile
70
Figure 61. 1964 CofFerdam
had passed, the contractor elected to remove the bulge
it caused in the upstream slope and to use the gravels
in the Dam.
Construction Materials. Availability of suitable
earth and rock materials was one of the key elements
in the economy of an embankment dam at the Oroville
site. Materials in and around the dredge tailing fields
south and west of the City of Oroville (Figure 62)
provided an abundant supply of all types of earth and
rock materials for the major embankment zones.
The impervious borrow area was selected in favor
of other areas explored because its proximity to the
pervious borrow area would allow common transpor-
tation facilities and because a more uniform material
could be obtained. The specifications required excava-
tion by shovels on a vertical face to blend the material
which was coarser at depth. The depth of the excava-
tion was selected to produce the desired gradation.
Design exploration work in the Oroville dredger
tailings was accomplished in two basic phases (see
Bibliography). The first phase was accomplished in
1956-57 at the time when a concrete dam was
proposed for the Oroville site.
The primary problem in exploration of the dredger
tailings was that of obtaining representative samples
from the loose gravels and sands occurring above and
below the static water level. The coarseness of the
material presented problems in sampling. Ordinarily,
water level in the dredger tailings was located approx-
imately at the interface between coarse gravels and
sand. Large excavations by dragline were considered;
however, the problem of obtaining representative
samples, particularly beneath the water table, forced
, consideration of other means of exploration. Drilling
I of this kind of deposit appeared to be infeasible with
' standard types of equipment. However, a "hole exca-
vator" manufactured and operated by Par-X Placer
Equipment Company of Benicia, California, was
located. This unique piece of equipment appeared to
be suitable for excavating holes through these loose
coarse gravels and into the sand beneath the water
table. The excavator consisted of a carrier beam and
attached clamshell bucket mounted on, and operated
from, the back of a 2'/2-ton truck. A hydraulically con-
trolled winch enabled the operator to raise the boom
to the vertical from its horizontal transporting posi-
tion, to raise or lower the boom, to crowd the bucket,
and to open and close the bucket. The longest boom
available was 41 feet, which limited the depth of hole
using the clamshell bucket to 37 feet. The bucket could
be locked in 90-degree positions or rotated freely,
much as a percussion bit. The bucket was used to
penetrate gravels and intervals of sand above the wa-
ter table. Sand beneath the water table was excavated
with a piston-operated cylindrical sucker which drew
material through a hinged door on the bottom. The
average operating capacity of the sucker was approxi-
mately 2 cubic feet. After this piece of equipment was
removed from the hole, the sand was emptied into a
riffled sluice box, which was used to prevent excessive
washing and loss of fines.
A major problem with excavation of any type of
hole in a tailing deposit is run-in or caving of the hole.
To prevent these conditions, telescoping, continuous,
and butt-jointed casings were used. In most cases, all
three types of casing were used in each hole. Telescop-
ing casing, consisting of six sections each 46 inches
high and ranging from 62 to 50 inches in diameter, was
used as a starter for all holes. A 12-foot length of 38-
inch-diameter casing was used inside the telescoping
casing to extend the depth of hole. While excavating
in the gravelly materials, the casing had to be driven
within a few inches of bottom in order to prevent
excessive run-in and contamination of samples. Suck-
er casing was butt-jointed and fit inside the 38-inch-
diameter casing. The inside diameter of the sucker
casing was 17% inches, and this casing was driven
ahead of the hole when excavating sand beneath the
water table.
Exploration procedures and equipment went
through various periods of evolution, and attempts
were made to analyze the results with regard to suffi-
ciency and accuracy of data, samples obtained, and
cost of conducting such types of exploration. During
1956-57, 70 holes on a 1,000-foot grid spacing were
drilled through the dredge tailing deposit in an area
which was selected because of location and apparent
suitability. For practical considerations, the samples
were split and run through screens at the test pit.
Initially, only the minus '/-inch material was sent to
the laboratory.
Shortly after the investigation for concrete aggre-
gates was completed, it was determined that Oroville
Dam would be a zoned embankment type. In 1959, the
second phase of the overall tailings exploration pro-
71
OR0\/ILLE DAM
SPILLWAY-
Scale of Milts
LEGEND
Dredge Tailings
Ptrvious
borrow
area
LOCATION OF BORROW AREAS
AND
OROVILLE DAM SITE
Figure 62. Location of Borrow Areas and Oroville Dam Site
72
gram was undertaken to verify the existence of the
required additional volume of material suitable for the
outer zones of the embankment-type dam and to deter-
mine its physical properties. Since quality and basic
grading were known in at least one area as a result of
concrete aggregate exploration, quantity became the
prime consideration. Also, it was desirable and neces-
sary to delineate broad areas of tailings with distin-
guishable and characteristic grading. The first step
was to evaluate aerial photographs and block out simi-
lar-appearing areas of the tailings so as to plan an
exploration program. Detailed gradings, as obtained
during concrete aggregate investigations, were not re-
quired but immediate results were needed to provide
necessary design data. It was decided that the hole
excavator, used during concrete aggregate explora-
tion, would be too slow; therefore, exploration by
dragline pits and bulldozer trenches was selected. A
program was planned in which approximately four
pits would be excavated in each section of the dredger
tailing field. A I'/^-yard dragline and a large bulldozer
were used, and the completed program consisted of
the excavation of 71 dragline pits and 129 bulldozer
trenches.
Procedure on the pit exploration started with the
bulldozer leveling a site between two linear ridges of
dredge tailings (Figure 63). By pushing the material
from the ridge into the adjoining valleys at each side,
an attempt was made to obtain an average thickness of
gravel. This procedure reduced the depth of dragline
excavation and gave relative assurance that the sand
table would be reached. After leveling by the bull-
dozer, the dragline was moved in and test pits were
excavated through the gravel and several feet into the
sand so that an uncontaminated sand sample could be
collected and an accurate elevation could be obtained
I
,j^M^^^
Figure 63. Dredge Tailings
on the sand table. After the pit was excavated, one
large representative sample of the entire thickness of
gravel penetrated was taken from the wall of the pit
with the dragline bucket. This sample was placed in
a separate pile adjacent to the pit. The sample pile
contained approximately 10 cubic yards of gravel and,
from this pile, several 40-gallon drum samples were
taken with a backhoe. Drum samples were trans-
ported to the laboratory for analysis and testing.
It was intended to use the dozer to obtain supple-
mentary information on gravel thickness, as well as to
prepare test sites; however, cuts through the gravels
proved impractical due to raveling of the material in
cut slopes. Instead, most of the 129 trenches were used
as an aid to a visual classification of the coarse tailings.
In the visual classifications, the amount of No. 200 to
No. 4 sieve size material and the amount of minus No.
200 sizes were estimated. Generalized classifications
were used which consisted of clean, sandy, silty, and
clayey gravels. These classifications were delineated
on a base map and the volumes were computed for
each classification, based upon the thickness of gravel
determined during pit excavation. It was estimated
from the exploration that a total volume of over 140
million cubic yards of coarse tailings were available.
Test pits of the type excavated by dragline averaged
approximately 20 feet deep.
Exploration was started in the impervious borrow
area with a wide spacing of large-diameter holes. The
Par-X excavator was tried; however, this method of
excavating holes was abandoned for a faster method.
Thirty-inch-diameter bucket augers were employed,
and it was soon found that because of the compactness
and gravelly nature of the borrow area, it was neces-
sary to use heavy-duty drill rigs with extra-heavy kel-
leys. Also, it was necessary to use a variety of bucket
types in order to continue holes when drilling became
difficult.
To expedite the exploration and testing programs,
it was desirable once again to do the coarse grading in
the field and to transport only the finer materials to
the laboratory for further testing. The entire borrow
area was drilled with 56 holes on a 750-foot grid spac-
ing, and materials were sampled and graded from each
hole in the first phase. Holes averaged 42 feet in depth
and were drilled to the static water level or to volcanic
sediment underlying the borrow area. The deepest
;iole was 60 feet, and it was not necessary to case holes
in this material. By carefully selecting materials from
each 5-foot interval, it was not necessary to use the
splitter or to process the entire sample being drilled.
The 750-foot hole spacing was later split to 375 feet,
requiring an additional 83 holes.
Laboratory Testing. The large materials made it
impractical to attempt detailed laboratory testing on
prototype material. However, it was considered desir-
able ( 1 ) to include the effect of maximum particle size
on embankment design parameters to the extent prac-
73
tical from the standpoint of laboratory equipment de-
sign, and (2) to carry the testing into the range of
loads expected within the embankment mass of the
prototype structure. To this end a special, high-capaci-
ty, compression apparatus was designed and con-
structed at the Department's Bryte Laboratory with
the capability of handling, in a cylindrical testing
chamber, specimens up to 27 inches in diameter with
varying heights up to 60 inches. This apparatus is
capable of applying axial loads of up to 650 pounds per
square inch (psi) through a hydraulic piston. In these
test chambers, it was possible to test samples contain-
ing up to 6-inch rock sizes for compression, consolida-
tion, and permeability characteristics under max-
imum estimated prototype load. As a secondary result,
it was also possible to determine particle degradation
under compressive loads representative of maximum
embankment height.
For establishing the efficiency of the compactive
processes used on the shell and transition materials, a
special, laboratory, vibratory, density test was devel-
oped as a standard against which to compare the max-
imum density obtained by compaction equipment in
the field. This test utilized a 27-inch by 30-inch cylin-
der and external vibration.
Maximum density for the impervious samples was
determined in conventional laboratory compaction
tests but modified to permit using various maximum
particle sizes (^-inch, 1/2 inches, 3 inches, 4 inches,
and 6 inches). A compactive effort of 20,000 foot-
pounds per cubic foot was used.
An unusual undertaking of the laboratory investiga-
tions was the performance of triaxial shear tests on
samples of materials for the three major zones, using
samples up to 12 inches in diameter and lateral pres-
sures up to 650 psi (see Bibliography). The equipment
utilized had been constructed by the U. S. Army
Corps of Engineers and was operating in its South
Pacific Division Laboratory at Sausalito, California.
In these studies, samples of materials containing parti-
cle sizes up to a maximum of 3 inches were tested
using confining pressures of up to 125 psi. Samples
containing particle sizes up to a maximum of I'/i
inches were tested using confining pressures up to 550
psi for gravels and 650 psi for clayey gravels. Further
testing of the embankment materials was undertaken
after the Dam was under construction. These tests
were run on even larger samples at the test facility
constructed by the Department at the Richmond Field
Station of the University of California (see Bibliogra-
phy). The later tests showed the earlier results to be
1 to 2 degrees conservative.
Test Fills. It was desirable to verify the practical-
ity of achieving laboratory densities and related physi-
cal properties in the field using prototype materials
excavated, transported, and compacted in a conven-
tional manner by commercially available modern con-
struction equipment. To this end, an extensive test-fill
program was conducted. Various compactors (sheeps-
foot, pneumatic-tired, segmented-pad, pneumatic-vi-
bratory, smooth-drum vibrator, crawler-tractor, and
hydraulic-monitor) and various combinations of layer
thickness, roller coverages, and moisture content
ranges were tried on 14 different test fills. Over 150
different processes of placing and compacting materi-
al were tested. The fills were built in the proposed
borrow areas using pit-run materials representative of
the three major zones of the embankment.
Because of the large maximum particle sizes in the
test fill materials, it was necessary to scale up the
conventional field density determinations and, to ac-
complish this, the Department of Water Resources'
field density determination method was developed.
By this method, field measurements were made on
samples weighing over 1,000 pounds taken from den-
sity holes to 6 feet in diameter. This test and the spe-
cial laboratory density tests and equipment discussed
earlier in this chapter were used to control construc-
tion of the Dam.
Stability Analyses. The slopes of the Dam were
determined by use of the modified Swedish Slip Cir-
cle, the sliding wedge, and infinite slope methods of
analysis. A O.lg horizontal seismic acceleration was
included in the conventional analyses to determine
the factor of safety during an earthquake. Total stress
or effective stress basis soil strengths were used, de-
pending on the condition being analyzed. Results of
these analyses indicate factors of safety substantially
in excess of those the Department uses in the design
of embankment dams of lesser heights. Properties
used and the results of these analyses are summarized
on Figure 64.
Because of the configuration of the cross section of
Oroville Dam with the sloping core, it was found that
the core material had relatively little effect on overall
stability of the downstream slope. The predominant
influence of the downstream shell, with a high friction
angle and cohesion equal to zero, caused the minimum
factor of safety for a downstream failure to occur un-
der an "infinite slope"-type analysis. This fact was
borne out in an extensive study by the Department
and was confirmed in studies by Moran, Proctor,
Mueser and Rutledge Consulting Engineers. Since an
infinite slope-type failure in a coarse-grained material,
such as Oroville Zone 3, would take the form of insig-
nificant shallow raveling and would not involve deep-
seated sliding, analysis of the downstream slope by
deep wedges and circles was limited to only a few
trials to compute the order of magnitude of safety
factors which pertained.
The upstream slope stability was analyzed for three
different cases of Zone 1 shear strength. Case 1 as-
sumed the "effective stress" core shear strength
of<f> = 34 degrees, C = 0, which did not include the
effects of pore pressures due to shearing. Case 2 as-
sumed the "total stress" core shear strength of <^ = 14
degrees, C = 0.3 tons per square foot, which included
the effects of full pore pressures due to shearing. Case
74
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Figure 64. Stability Analysis Summary
75
3 assumed the unrealistically conservative core shear
strength of <^ = 0, C = 0, or, in effect, a "fluid" core.
This latter condition, a "limiting case", was analyzed
only as a matter of interest and does not have any real
status by comparison with the more realistic analyses
of Cases 1 and 2.
In addition to these analyses, two additional condi-
tions were analyzed by Moran, Proctor, Mueser and
Rutledge Consulting Engineers. These additional con-
ditions were (1) end of construction, and (2) rapid
drawdown from elevation 900 feet to elevation 590
feet. Although the material properties used in these
analyses differed slightly from the final values used by
the Department, the results of this work demonstrated
that the conditions studied were not critical to em-
bankment stability and they were not pursued.
While Oroville Dam is located in a region of low
historical seismic activity in California, design to re-
sist earthquakes was a major consideration in develop-
ment of the final embankment section. Analytical
methods available in the early 1960s for earthquake-
resistant design of earth embankments were, at best,
only an approximation and somewhat empirical in
their approach as to what actually happens in an em-
bankment during an earthquake; therefore, it was de-
cided to make further earthquake studies for Oroville
Dam. In 1961 and 1962, a series of model tests was
conducted for the Department by the Engineering
Materials Laboratory of the University of California
at Berkeley (see Bibliography) under the supervision
of Professor H. B. Seed (Figure 65) . These tests were
conducted on a 1:400 scale model of the embankment,
using horizontal earthquake accelerations up to 0.5g.
They yielded some informative qualitative results but
left some points unresolved due to the difficulty of
scaling the influence of pore-water pressures during
dynamic loading. If the prototype dam was subjected
to a dynamic force which tended to cause movement
along some potential shear surface, the deformation
would be accomplished by either dilation or consoli-
dation of the Zone 3 shell material, depending upon
the load at any given location in Zone 3. The resulting
dilation or consolidation would cause internal pore
pressure changes which could not be included in a
model study program but which could significantly
affect embankment stability. However, since it was
known from previous laboratory testing what range of
Figure 65. Embankment Model on Shaking Table
76
i
loading caused the Zone 3 material to change from
dilation to consolidation during shear, it was conclud-
ed that additional analytical work could help resolve
the uncertainties remaining from the model study
program. One additional series of analytical studies
was made for the upstream slope of the Dam. For this
analysis, the undrained strength of Zone 3-type
materials was utilized in conjunction with results of
pulsating load test performed on sands at the Univer-
sity of California. Seismic coefficients of up to 0.25g
were used. Also, the stability of the upstream slope of
the Dam was analyzed for a design earthquake equal
to the 1940 El Centro earthquake (peak acceleration
0.2Sg). Seismograph records of this earthquake were
the best strong-motion records available at the time
and were considered representative of the most severe
ground motions which could be anticipated at the site.
The results of these studies supported the conclu-
sions of earlier work that the dam embankment was
designed conservatively with respect to earthquake
loading in the light of currently accepted engineering
practice.
Other Earthquake Considerations. It is interest-
ing to note that inherent in the conventional embank-
ment design were these additional earth-
quake-resistant features:
1. Dam embankment is founded directly on bed-
rock or, in the case of the outer shells, on a minor
amount of sand and gravel with a density greater than
that of the embankment, thus eliminating any possi-
bility of foundation liquefaction.
2. The embankment zoning scheme provides a wide
crest and wide transition zones of well-graded sand
and gravel between shells and core. The transition is
dense and relatively impervious.
3. The 22 feet of freeboard above normal maximum
water level required for maximum floods is more than
would normally be required for any possible combina-
tion of earthquake-caused reservoir waves and crest
slumping.
4. Core material is a dense, plastic, erosion-resist-
ant, extremely impervious material with a wide range
of particle sizes. All material was placed at contacts
with bedrock of concrete structures at an initial water
content from 1 to 3% above optimum to ensure that
a plastic zone is in contact with these more rigid ele-
ments. The sloping core was placed at or slightly wet
of optimum to provide additional protection against
potential cracking.
Settlement, Pore-Pressure, and Crest-Camber
Studies. Settlement, pore-pressure, and crest-cam-
ber studies were performed for Oroville Dam to ( 1 )
determine if pore pressures developed during con-
struction would be detrimental to embankment stabil-
ity, (2) estimate how much of the overall settlement
would occur during and after construction, and (3)
determine what effects postconstruction settlement
would have on the dam crest so that compensating
design provisions could be made for crest camber. Sev-
eral gradations and moisture contents of Zone 1
material were tested and used in the analyses to pro-
vide a range of possible results.
These studies indicated that construction pore pres-
sures which could develop would not be significantly
detrimental to embankment stability. They would not
approach the 0 = 0, C = 0 Zone I condition, so no
further construction stability studies were deemed
necessary.
Settlement was studied at two important locations
within the embankment: one at the maximum height
of Zone 1 material, which was on a vertical line 242.5
feet upstream from the dam axis, and one at the dam
crest, on a vertical line 10 feet upstream from the dam
axis. These studies showed that regardless of grading,
not over 2.5 feet of postconstruction dam crest settle-
ment (due to simple consolidation) should be an-
ticipated at the maximum dam section.
The third objective was to design crest camber to
compensate for postconstruction settlement using the
above results of the previously mentioned studies.
Some additional factors are summarized as follows:
Postconstruction consolidation
of Zone 1 due to embankment load 0.6 feet
Additional settlement of Zone 1
due to water load 0.3 feet
Additional settlement of Zone 2
and Zone 3 due to full load 0.9 feet
Vertical deformation due to
embankment shear strain 1.8 feet
Safety factor 1.4 feet
Total design camber at maximum
section 5.0 feet
The actual settlement after seven years is less than
1 foot but is still continuing at a slow rate.
Foundation
Site Geology. Oroville Dam is founded on an un-
named metavolcanic rock formation, one of several
units within the "Bedrock Series". The rock is
predominantly amphibolite, a basic rock rich in am-
phibole with abundant veins of calcite, quartz, epi-
dote, asbestos, and pyrite. It is hard, dense, greenish
gray to black, fine to coarse grained, and generally
massive, although foliated or schistose structures are
not uncommon. Average attitude of regional foliation
strikes 12 degrees west of north and dips 77 degrees
east. Rock at the site is moderately to strongly jointed
and is transected by steeply dipping shears and schist-
ose zones. Three prominent joint sets impart a blocli-
ness to the rock, but individual joints are relatively
tight. The depth of weathering was found to be sub-
stantial and varied greatly from place to place.
Two major shear areas exist beneath the Dam,
which are about mid-height on each abutment. Both
are steeply dipping and strike normal to the axis of the
Dam.
77
Fresh rock was exposed on the bank of the river
channel and in minor outcrops on the abutments.
Weathering of rock approached 100 feet in depth in
the sheared zones.
Exploration. Subsurface geologic exploration was
initiated by the U. S. Army Corps of Engineers in
1944 with the drilling of two core holes, one on each
abutment. In 1947, the U. S. Bureau of Reclamation
drilled six core holes at the site. Explorations by the
Department of Water Resources were begun in 1952
and those required for design were completed in 1959.
They included the following:
1. Exploratory Adits — Four 5-foot by 7-foot adits
were driven, two on each abutment, together with
drifts and cross cuts, totaling 5,251 linear feet.
2. Core Borings — 175 borings were drilled varying
in size from EX to NX, and in depth up to 200 feet,
totaling 18,600 linear feet.
3. Seismic Surveys — Supplementing a "depth of
weathering" survey by the U.S. Bureau of Reclama-
tion in 1950 was a 1957 program consisting of 4,350
linear feet of spreads to determine modulus of elastici-
ty and depth of weathering.
4. Special Studies — Detailed evaluation of bedrock
properties was made by carrying out the following
special investigations:
a. X-ray diffraction and solubility tests on clay
gouge in shear planes
b. Compression tests on rock cores
c. Studies of blasting effects in the diversion tun-
nels
d. Test grouting
e. Rock-joint attitude mapping
f. Measurement of ground water levels and
spring flows
g. Bedrock-stripping methods, eliminating rip-
ping and blasting
h. In situ rock modulus tests
Additional information was gained from explora-
tion for the underground powerplant and other struc-
tures.
Excavation Criteria. The excavation criteria for
the various parts of the foundation were:
Concrete Core Block — Sound hard rock consist-
ing of fresh to slightly weathered rock, with un-
stained to slightly iron-stained fractures.
Embankment Core Trench — Sound hard rock
that would be impervious after grouting. Trench
slopes 1:1 or flatter downstream and Yi-.l upstream.
Seams and shear zones excavated to a depth approxi-
mately equal to their width. Irregular rock to be
removed to permit compaction of the core.
Embankment Shells and Transitions — Weath-
ered rock exhibiting definable rock structure of a
strength equal to that of embankment materials
placed thereon.
Grouting. A single cement grout curtain of 200-
foot maximum depth was provided in the foundation
beneath the core (Figure 66).
Forty-foot-deep foundation drain holes with a max-
imum spacing of 80 feet were specified to angle down-
stream from the grout curtain discharging into the
grout gallery.
Slush and shallow blanket grouting were provided
to fill surface voids or to improve the strength of frac-
tured areas of the core trench foundation.
Core Block
The 283,000-cubic-yard, lean-concrete, core block is
composed of 18 monoliths (Figure 67). The primary
structure has a flat top at elevation 250 feet. An up-
stream parapet rises to elevation 300 feet. Maximum
height to the top of the parapet is about 120 feet. The
base thickness at maximum section is about 400 feet
and the crest length of the parapet is 900 feet.
The purposes of the core block were to ( 1 ) elimi-
nate the need to compact impervious core material in
the irregularly eroded inner gorge of the Feather Riv-
er, (2) reduce possibility of transverse embankment
settlement cracks, (3) reduce maximum height of the
core, and (4) expedite embankment construction. The
core block with a 50-foot-high parapet served as a po-
tential overflow structure. This allowed the expedited
placement of about 2,000,000 cubic yards of embank-
ment in the upstream half of the stream channel in
advance of the critical 1964 embankment construction
season, in which the 400-foot-high cofferdam would be
incorporated into the Dam to provide flood protec-
tion.
78
M li.
s ii
^.
^ ; ;
Figure 67. Core Block
79
Figure 68. Diversion Tunnels Nos. 1 and 2— Draft-Tube Arrange
80
Because of its position (buried under the dam em-
bankment) and its low irregular shape, the core block
as a whole did not lend itself to a simple structural
analysis. Little information was available at the time
of design on stresses that might be imposed on the
structure by the zoned embankment. However, the
parapet was recognized as the critical component. It
was determined that, with certain assumptions made
for embankment soil properties, the parapet would
tend to separate from the remainder of the block. Un-
der one loading condition, the parapet was the toe of
the 1.6:1 downstream toe of the 1964 cofferdam. Com-
pressible Zone 4A was included upstream of the rigid
core block to provide some room for base spreading of
this slope. The other loading condition had three con-
tributing factors: (1) embankment base spreading
caused by the core block being upstream of the crest,
(2) tendency of the embankment loads to arch across
the core, and (3) projection of the parapet.
Instrumentation was provided in the core block,
particularly in the parapet, to observe stress and
strains under these loading conditions. The parapet
survived the first condition but cracked under the
other, as is explained in the section on construction.
The core block contains an extensive gallery system.
The grout gallery extends through the upstream por-
tion. A bypass gallery connects it to a gallery that was
constructed to provide access to the underground
powerplant. Later, this connection was plugged to
separate the dam gallery system from the Powerplant
in case either flooded. A recess off one of the galleries
contains one of the dam structural performance in-
strumentation terminals. Also included is a drainage
system with three pump chambers. Two of the cham-
bers contain SO-horsepower, vertical, turbine pumps
with encapsulated windings to protect against water
damage. The third contains a 75-horsepower submers-
ible pump. A level control consisting of electrodes is
located in a well within the No. 2 pump chamber. The
submersible pump motor starter and a duplex sump
pump controller are located at the connection of the
grout gallery with the powerhouse emergency exit
tunnel. All three pumps are connected to a 16-inch
discharge pipeline. This pipeline uses the tunnel for-
merly connected to the Powerplant and galleries as
the route to the terminus in the crown of Diversion
Tunnel No. 2.
Grout Gallery
The reinforced-concrete, 5-foot by 7-foot, grout gal-
lery is located under the core from the core block up
the right abutment to approximate elevation 780 feet
and up the left abutment to approximate elevation 820
feet. From these locations, each leg extends to the
downstream face of the Dam (Figure 59). Under the
core, the gallery generally is in a trench approximate-
ly 15 feet deep with a 10-foot bottom width and '/:!
side slopes. In some areas, the trench is imperfect and
the concrete projects a few feet into the core. The
reaches extending downstream start the same as under
the core and end fully projecting into the embank-
ment.
Purposes of the gallery were to ( 1 ) reduce the con-
flict between the grouting and embankment-placing
operations, (2) provide an exit for the foundation
drain holes, (3) provide the capability to regrout un-
der the higher portions of the embankment if neces-
sary, and (4) provide access to the core block gallery
system and the facilities located therein. Based on eco-
nomic considerations, the grout gallery was terminat-
ed before it reached the crest of the Dam. It was
determined that the remaining 100- to 150-foot height
of dam remaining on the abutments did not justify the
cost of the additional length of gallery.
The gallery in the trench is lightly reinforced con-
sidering the embankment loads on it, compared to
structures designed using approximate methods. It
was analyzed at the University of California using one
of the first applications of the finite element method.
Internal stresses and reactions of such a structure de-
pend to a great degree on the relative stiffness of the
concrete and the foundation rock. The finite element
method readily handled these variables whereas other
techniques available at the time could not. The result
was a much more economical structure than the previ-
ously planned projecting gallery that was being
analyzed by conventional methods or an overrein-
forced trenched gallery. More than six years of satis-
factory performance have proven the validity of the
analysis.
Tunnel Systems
A multiplicity of tunnels was required in conjunc-
tion with the construction and operation of Oroville
Dam and Edward Hyatt Powerplant (Figure 68).
Construction of the tunnels was accomplished under
four major contracts. The first diversion tunnel and
the Palermo outlet tunnel were let under separate con-
tracts in 1961. The contract for the dam embankment
included construction of the second diversion tunnel
along with connecting portions of the powerplant
draft-tube tunnels, a portion of the river outlet access
tunnel, and the core block access tunnel. Tunnels di-
rectly serving the underground powerplant were con-
structed under the initial contract for the Powerplant.
These tunnels, which include the powerhouse access
tunnel, high-voltage-cable tunnel, penstock tunnels
and branches, and the remaining portions of the draft
tubes, are described in Volume IV of this bulletin.
All tunnels were excavated in the moderately joint-
ed metavolcanic rock of the left abutment. A series of
drill holes was used and exploration adits were ex-
cavated to locate major shear zones. The location of
the powerplant machine hall, the major underground
excavation of the complex, was established on the ba-
sis of this exploration. Location of the machine hall, in
turn, was a major factor controlling the layout of the
tunnel systems.
81
All tunnels in the complex are concrete-lined. The
designed concrete-lining section is that thickness be-
tween the inside tunnel surface and a designated line
called the "A" line. In this thickness, no materials
were allowed to remain permanently which would
reduce the integrity of the concrete section. No rock
was allowed to project into the section, and all timber
was required to be removed prior to concrete place-
ment. Structural-steel tunnel support and other metal-
work, which did not interfere with the reinforcement
steel, was allowed to remain in the section.
Overbreak was anticipated in the excavation of the
tunnels and a designated thickness of excavation and
concrete lining (9 inches in the case of the diversion
tunnels, 6 inches or less for smaller diameter tunnels)
was paid for outside of the "A" line. The limit of
payment was designated the "B" line.
Diversion-Tailrace Tunnels. The alignment and
profiles of the two 3S-foot-diameter, 4,400-foot-long,
diversion tunnels were selected to (1) bypass the dam
construction area, (2) provide for convenient connec-
tion to the underground powerplant for use as tailrace
tunnels, and (3) keep the total tunnel length to a mini-
mum. A circular section was chosen for the tunnels
since they are subjected to high external hydrostatic
heads.
Diversion Tunnel No. 1, nearest the Feather River,
has an intake invert elevation of 210 feet and an outlet
invert elevation of 182 feet. The center reach of the
tunnel is depressed to permit connection of the draft-
tube tunnels from generating units Nos. 3 through 6.
The intake invert of Diversion Tunnel No. 2 is at
elevation 230 feet and the outlet invert at elevation
-207.5 feet. Draft-tube tunnels from units Nos. 1 and 2
connect directly to this tunnel and surge openings for
units Nos. 3 through 6 are provided.
More than 50 years of good streamflow records
were available on which to base the design of a se-
quence to provide flood protection during construc-
tion. They indicated the normal start of a 4'/2-month
flood season was November 15. The following covers
the highlights of the sequence as it actually occurred:
1. Diversion Tunnel No. 1 was completed in No-
vember 1963 allowing embankment to be placed in the
stream channel upstream of the core block. Had the
riverflow exceeded about 12,000 cfs that winter, this
embankment would have been flooded and the core
block parapet would have acted as a weir, preventing
erosion of the embankment material already placed.
2. Diversion Tunnel No. 2 was completed in No-
vember 1964 in time to combine with Diversion Tun-
nel No. 1 and the 400-foot-high cofferdam, to protect
the Dam from actual floods up to the U.S. Army
Corps of Engineers' standard project flood (frequency
about 1 in 400 years and about twice the flood of
record). As discussed later in the section on construc-
tion, this combination withstood a new flood of
record.
3. When no longer needed for diversion, the tun-
nels were plugged upstream of the reaches utilized for
the tailrace. Plugging of Diversion Tunnel No. 2 took
place in August 1966, when the embankment was high
enough to protect against the standard project flood
with only Diversion Tunnel No. 1 functioning.
4. Tunnel No. 1 was plugged in November 1967
when the embankment was topped out and the spill-
way essentially was complete. Gates were lowered at
the intake to Tunnel No. 1 to dewater the tunnel for
plug construction. This act marked the beginning of
filling Lake Oroville.
Two criteria were considered for determining the
size of the tunnels: (1) the flood conditions just dis-
cussed, and (2) the most economical diameter for use
as a tailrace for power generation. The two 35-foot-
diameter tunnels were required to control the design
flood while holding the embankment placement rates
to reasonable quantities. The most economical tailrace
was estimated to be 3 1 feet in diameter but would have
required a tailrace surge chamber. The two 35-foot
tunnels allowed one tunnel to flow free and, by inter-
connections, eliminated the need for a surge chamber.
As velocities during diversion would reach over 100
feet per second, special effort was required to ensure
a high-quality surface for flow. High-strength con-
crete was used, and a concrete finish was specified
which allowed no abrupt irregularities and only mini-
mal gradual irregularities. Tunnel intersections were
plugged with the inside surface smooth and mono-
lithic with the tunnel interior. The only irregularities
allowed in the diversion flow path were the gate slots
in the intake structure for Diversion Tunnel No. 1
and in the exit portal structures for both tunnels. The
slots were constructed with offset downstream edges
to minimize turbulence and negative pressures in the
slots.
Bell mouths were used at each tunnel to reduce inlet
head loss and prevent cavitation of the adjacent tunnel
lining. Because Diversion Tunnel No. 1 required clo-
sure gates, a rectangular bell was formed and transi-
tioned to the circular tunnel. Hydraulic model studies
of the tunnels were conducted by the U.S. Bureau of
Reclamation at Denver, Colorado (see Bibliography).
Both diversion and tailrace modes were tested.
The concrete tunnel lining was designed for the i
maximum external hydrostatic head expected. Up-
stream of the plug locations, this was the maximum
construction flood pool head minus the hydraulic
gradeline for the peak diversion discharge (equivalent
to velocity head plus intake head loss). Between the
plugs and the dam grout curtain, full hydrostatic pres-
sure of Lake Oroville would come to bear. Drain holes
were therefore drilled through the lining into the rock
to reduce local pressures, and an external loading of
50% of the lake head was assumed for design. Down-
stream of the grout curtain, the drain holes were con-
tinued and external hydrostatic head was assumed
equivalent to the height of overburden. Any load from
the disturbed surrounding rock was assumed to be
82
borne by temporary supports and was not added to
loading of the concrete lining.
Structural concrete for the lining was specified to
attain an ultimate strength of 5,000 psi in one year.
The one-year strength was specified since full loading
would not occur until the reservoir filled.
Nominal reinforcement was used to minimize
cracking due to shrinkage and temperature changes.
All portions of the tunnels are contact-grouted to
ensure good contact between tunnel lining and the
rock.
Pressure grouting from within the tunnel included
a continuation of the grout envelope constructed
around the Powerplant and consolidation grouting of
the rock immediately surrounding the tunnel plugs.
The grout envelope involves radial holes on a regular
pattern throughout the reach near the Powerplant,
grouted in an interval between 40 and 50 feet from the
tunnel lining (Figure 69).
After the 150-foot-long concrete plugs were placed
near the center of both tunnels, the knockout plugs for
the draft-tube tunnel connections then were removed.
The draft-tube connections, 18 and 21 feet in diame-
ter, had metal form panels to partially outline the
knockout plugs, facilitating their removal and mini-
mizing the roughness of the opening.
Large ports connect Diversion Tunnel No. 2 with
the draft-tube tunnels of units Nos. 3, 4, 5, and 6. This
allows Tunnel No. 2 to act as a surge chamber to
receive water from or supply it to the draft tubes and
Diversion Tunnel No. 1 during load changes. Tunnel
No. 2 operates at atmospheric pressure during all
powerplant operation modes with the flow normally
half filling the tunnel. To provide atmospheric pres-
sure to the upstream end of Tunnel No. 1, an 8-foot-
diameter pressure-equalizing tunnel connects the tail-
race tunnels directly downstream from the tunnel
plugs.
Maximum discharge through Tunnel No. 1 during
generation is 12,000 cfs (picking up flow from units
Nos. 3 through 6). Discharge through Tunnel No. 2
is 6,000 cfs (units Nos. 1 and 2).
River Outlet. The river outlet is located just
downstream of the plug in Diversion Tunnel No. 2.
Two 72-inch-diameter steel conduits were cast into
the plug. Stream releases are controlled by two 54-
inch fixed-cone dispersion valves that are backed up
by 72-inch spherical valves. Access to the valves is
gained through a tunnel from the Powerplant. The
river outlet valves are capable of a combined discharge
of 5,400 cfs with full reservoir. A steel liner is used
inside the tunnel where discharges impinge and a baf-
fle ring protrudes into the flow path to help still the
discharge. An air supply for the valves is provided
through a small-diameter tunnel above and parallel to
the tailrace tunnel. This tunnel allows air to be drawn
by the valves from an area downstream, clear of the
valve discharge turbulence.
The 72-inch, spherical, shutoff valves have double
seats, are hydraulic cylinder-operated, and are de-
signed to sustain the maximum transient pressure
without exceeding the allowable design stresses. The
valves are provided with an electrohydraulic activat-
ing and control system. Each seat is separately con-
trolled and operated by oil. The operating controls are
arranged for the following operations:
1. Normal opening and closing of the valve and
upstream and downstream seats from the valve cham-
ber at elevation 233 feet.
2. Emergency remote closing of valve and down-
stream seat from equipment control chamber at eleva-
tion 290 feet.
The 54-inch fixed-cone dispersion valves (Howell-
Bunger valves) are actuated by electric motors which
can be operated locally or remotely from the equip-
ment control center. Additionally, handwheels were
provided for emergency operation of the valves.
The valves were carefully designed by the Depart-
ment because of the severe service expected and the
history of problems with similar valves experienced
by other agencies. Special consideration was given to
vane design; stiffness was emphasized in order to
reduce any tendency toward vibration and possible
fatigue failure. Smooth ground surfaces and faired
edges of components exposed to high-velocity flow
and full-penetration welds throughout were specified.
Extensive nondestructive examination was performed
on all welds during the construction phase.
Hydraulic model studies of the river outlet were
conducted by the U.S. Bureau of Reclamation in Den-
ver, Colorado.
Diversion Tunnel Intake Portal Structures. In-
take excavations were shaped to efficiently train
streamflows into the tunnel intakes during the diver-
sion mode. Cut slopes in overburden were laid back to
safe slopes to preclude slides, and steep cuts in rock
were rock-bolted and covered with heavy wire mesh.
The plan of the intake structures is shown on Figure
70 and sections on Figures 71 and 72.
The intake structure of Diversion Tunnel No. 1 is
a rectangular bell mouth transitioning to the^5-foot-
diameter tunnel. A center pier with an elliptical nose
is incorporated into the structure to accommodate
steel bulkhead gates to dewater the tunnel for plug
placement. The gate slots are positioned as far back on
the transition as practical to take advantage of arching
of the partial circular section and thus its ability to
resist external loads. Horizontal prestressed rods were
installed in the pier and attached to the gate-slot as-
sembly to carry gate loads forward to the more mas-
sive pier section. This assembly consists of 1-inch steel
plates lining the slot and a steel grillage connecting
the downstream slot faces so as to carry gate loads to
the prestressed tendons. Heavy plate was used for the
slot liner to maintain true alignment of the bearing
surface and slot liner after prestressing loads are ap-
plied.
83
Figure 69. Grout Envelope
84
Figure 70. Intake Structures Plan
85
Figure 71. Diversion Tunnel No. 1 — Intoke Portal Sections
86
Figure 72. Diversion Tunnel No. 2 — Intake Pcrlol Sections
87
The closure gates, 17 feet - '/J inches wide by 36 feet -
6 inches high, were built up from wide-flange struc-
tural sections and provided with rubber seals. They
were positioned in a chimneylike structure above the
gate slots prior to closure and lowered into place by
a frame and cable system. Low streamflows were
necessary to allow gate seating. A trial lowering was
required for each gate, prior to final closure, to ensure
that adequate sealing could be accomplished.
The intake walls and roof of Diversion Tunnel No.
1, upstream of the gate, were designed for an external
hydrostatic head equal to the velocity head plus the
entrance head loss during peak discharge while divert-
ing the standard project flood. The closure gates and
the structure downstream of the gates were designed
for the maximum water surface in the reservoir dur-
ing plug construction. Normal working stresses occur
with a load of 440 feet of water, and yield is not exceed-
ed with a full reservoir (elevation 900 feet).
Diversion Tunnel No. 2 intake is a circular bell
mouth. The headwall and wingwalls are anchored to
the rock face with grouted No. 1 1 bars. No provisions
for gating were required as the intake is 20 feet higher
than Diversion Tunnel No. 1 and was out of water
during construction of the plug and river outlet (Tun-
nel No. 1 remaining open during this period). A con-
crete trashrack was constructed at the intake face to
guard the river outlet valves from submerged debris.
An auxiliary intake for the river outlet was placed at
elevation 340 feet and connected to the tunnel by an
18-foot-diameter shaft. This intake supplies water to
the river outlet should the tunnel intake be closed by
silt. This intake also is provided with a concrete trash-
rack. The trashracks are designed to withstand a dif-
ferential head of 20 feet.
Diversion-Tailrace Tunnel Outlet Portal Struc-
tures. Both tunnels have similar outlet portal struc-
tures consisting of a concrete headwall and a
50-foot-long concrete trough with a semicircular in-
vert (Figure 73). Gate slots are provided in the
troughs for installation of a bulkhead gate to dewater
the tunnels. The gates extend from trough invert to
normal tailwater surface, elevation 225 feet. The
troughs are anchored to the rock with grouted bars
and are designed to resist the forces of external head
to elevation 225 feet with the interior dewatered. The
headwalls also are anchored to the portal face with
grouted bars. These bars are designed to resist a 10-
foot hydrostatic head behind the wall.
Above the headwalls, working areas and concrete
slabs are located on which trashrack hoisting equip-
ment is mounted. The trashracks are held above the
troughs on the portal face during generation of power
and lowered into slots provided in the trough during
the pumping cycle. Design of the trashracks is covered
in Volume IV of this bulletin.
River Outlet Access Tunnel. The river outlet ac-
cess tunnel (Figure 74) connects the valve chamber in
Diversion Tunnel No. 2 with the northern end of the
powerplant machine hall.
The 8-foot-diameter tunnel extends from elevation
262 feet in the powerhouse to the river outlet control
chamber at elevation 290 feet, an enlarged portion of
the tunnel which contains the control equipment. It
continues to an 8-foot-diameter reach extending from
the chamber to the diversion tunnel (invert elevation
at intersection-elevation 233 feet). Metal stairs were
installed in the inclined portions. The control cham-
ber enlargement is 1 5 feet in diameter and 3 3 feet long.
It was placed at elevation 290 feet to preclude flooding
of the powerhouse with maximum tailwater during
spillage of the maximum probable flood (maximum
water surface elevation 287 feet) . A panel downstream
of the valve chamber is designed to pop out when a
head of 15 feet bears on it; thus, the tunnel will not
serve as a passage to flood the powerhouse should a
failure of a river outlet component occur.
The concrete lining is 22 inches thick in the valve
control chamber and 12 inches thick in the 8-foot-
diameter tunnel. The lining will support the external
hydrostatic head of full reservoir. As the tunnel is
within the zone of influence of the powerplant drain-
age system, the actual head on the structure will be
somewhat less.
Powerhouse Emergency Exit Tunnel. The pur-
poses of the powerhouse emergency exit tunnel,
shown on Figure 74, are to provide an alternate means
of escape from the underground powerhouse in case
of emergency and to act as an access to the grout
gallery from the powerhouse. This tunnel, 8 feet in
diameter and approximately 570 feet in length, is dis-
cussed in Volume I\' of this bulletin.
Core Block Access Tunnel. The purpose of the
core block access tunnel is to convey seepage water
from the core block to Diversion Tunnel No. 2. It is
a former exploration adit and was a planned low-level
connection between the core block and powerhouse.
It was plugged near the powerhouse wall to reduce the
chance of flooding in either facility due to this inter-
connection. The tunnel is 7/4 feet in diameter and
approximately 780 feet in length.
A 16-inch-diameter steel pipe was installed in the
tunnel to convey discharge from the core block drain-
age pumps. This pipe terminates in the vertical hole
above Diversion Tunnel No. 2. The tunnel will con-
vey water from the core block to the diversion tunnel
should a failure of the drainage pumps occur.
The concrete tunnel lining is 10 inches thick. This
thickness is sufficient to resist the external hydrostatic
pressure of full reservoir and yet be convenient for
placement of concrete.
Palermo Outlet Tunnel. Because the construction
of Oroville Dam terminated the previous method of
supply to Palermo Canal, a tunnel outlet (Figure 75)
was designed to make releases into the Canal down-
stream of the Dam.
88
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Figure 73. Diversion Tunnel Outlet Structures — Plan and Sections
89
Figure 74. Miscellaneous Tunnels
90
Figure 75. Palermo Outlet Tunnel
91
The outlet tunnel is concrete-lined and is approxi-
mately 2,430 feet long. The intake portal invert is set
at elevation 548.25 feet. A 6-foot-diameter level tunnel
connects the intake with a valve chamber located im-
mediately downstream of the intersection with the
dam grout curtain. Downstream of the chamber, a
6-foot - 6-inch horseshoe section continues to the
downstream portal on a slight downhill grade. A wall
divides the downstream reach into a water-carrying
passage and a 3-foot-wide access walkway. The outlet
valve is connected to a steel conduit which is embed-
ded in a concrete plug immediately upstream of the
valve chamber.
The intake portal structure consists of a short
length (approximately 27 feet) of cut-and-cover tun-
nel section with invert elevation 549 feet. Slots are
provided for a trashrack and bulkhead gate and a bulk-
head gate is held in place above the intake. To dewater
the tunnel, a diver is required to connect a hoist rope
to the gate and remove the pins which hold the gate
in its storage position.
Tunnel lining upstream of the dam cutoff was de-
signed to resist the external hydrostatic head of full
reservoir. Downstream reaches were designed to re-
sist the maximum pressure used during tunnel grout-
ing. This was assumed to be 25 psi. Drain holes were
drilled through the lining in the downstream reach to
ensure that ground water pressures on the lining do
not exceed this design pressure. A grout curtain is
provided upstream of the valve vault to mesh with the
curtain under the Dam.
The outlet facility in the tunnel consists of a 12-
inch-diameter rated discharge valve backed up by a
30-inch-diameter butterfly valve. Discharge is made
through a steel hood into an energy dissipator.
The downstream portal structure consists of a con-
crete headwall and wingwalls paralleling the channel
to retain material which may ravel from the cut slopes.
Immediately downstream of the portal, a reinforced-
concrete Parshall flume with a throat width of 5 feet
was constructed in the channel and equipped with a
recorder.
During construction of Oroville Dam, water for
Palermo Canal was obtained from Oroville-Wyan-
dotte Irrigation District's Kelly Ridge penstock,
which is approximately 2,600 feet downstream of the
outlet portal. A 16-inch turnout pipe connects to an
access door in the penstock (elevation 583 feet) ap-
proximately 240 feet northeast of the point where the
penstock crosses the Canal. The buried turnout pipe
terminates near the Canal with a 10-inch-diameter,
40-cfs, rated, discharge valve enclosed in a reinforced-
concrete energy dissipator. The valve is located at ele-
vation 547 feet. If, in the future, there arises some
emergency situation where water becomes unavaila-
ble from Lake Oroville in the required quantity, the
needed water can again be supplied by Kelly Ridge
penstock.
The outlet requirements of this turnout are the
same as for the outlet tunnel, i.e., a maximum dis-
charge of 40 cfs.
Spillway
The spillway for Oroville Dam (Figure 76) is locat-
ed in a natural saddle on the right abutment of the
Dam. This location allows spillway discharges to en-
ter the River, well downstream of the toe of the Dam
and powerplant tailrace. The spillway consists of a
combined flood control outlet and an emergency weir.
The flood control outlet consists of an unlined ap-
proach channel with approach walls shaped to make
a smooth transition to the outlet passage, a headworks,
and a chute. The headworks structure (Figure 77) has
eight outlet bays controlled by top-seal radial gates, 17
feet - 7 inches wide by 33 feet high. A concrete chute
(Figure 78), 178 feet - 8 inches wide, extends 3,050 feet
from the flood control outlet down the side of the
canyon to a terminal structure (chute blocks) where
the water plunges into the Feather River.
The emergency spillway is an ungated, concrete,
overpour weir located to the right of the flood control
outlet and is made up of two sections ( Figure 79) . The
right 800-foot section is a broad-crested weir on a
bench excavation. The left 930-foot section is a gravity
ogee weir up to 50 feet in height. Except for a narrow
strip immediately downstream of the weir, the terrain
below the weir was not cleared of trees and other
natural growth because emergency spillway use will
be infrequent.
The flood control outlet was sized on the basis of
limiting Feather River flow to leveed channel capacity
of 180,000 cfs during occurrence of the standard
project flood (peak inflow 440,000 cfs). This limita-
tion applies at the confluence of the Feather and Yuba
Rivers approximately 35 miles downstream of the
Dam. It was estimated that a runoff of 30,000 cfs could
be expected within this 35-mile reach of the Feather
River during the standard project flood. Therefore,
the flood control outlet was designed for a controlled
release of 150,000 cfs. The normal reservoir water sur-
face previously had been set at elevation 900 feet.
To meet these criteria, a flood control reservation of
750,000 acre-feet was needed. The criteria also gov-
erned the size and location of the flood control outlet
gates. The outlet must release 150,000 cfs at water
surface elevation 865 feet to control the flood shown
on Figure 80.
The standard project flood has a probability recur-
rence interval of approximately 450 years. If data re-
ceived indicate a flood is developing greater than the
standard project flood, release through the flood con-
trol outlet may be increased above 150,000 cfs but may
not exceed 90% of the inflow. When the reservoir fills
above elevation 901 feet, flow occurs over the emer-
gency spillway. The emergency spillway, in conjunc-
tion with the flood control outlet, has the capacity to
pass the maximum probable flood release of 624,000
92
cfs for the drainage area (peak inflow 720,000 cfs)
while maintaining a freeboard of 5 feet on the em-
bankment. The maximum probable flood has a proba-
bility recurrence interval in excess of 10,000 years.
Hydrologic and hydraulic data are shown on Figure
80.
\'arious types of spillways were studied and mod-
eled to arrive at the final structure. The original de-
sign consisted of a control structure with radial gates
to pass the total spillway design flood. A short con-
crete apron was to extend downstream from the con-
trol structure, and then the flows were to be turned
loose down the hillside in an excavated pilot channel.
As the spillway would operate on the average of every
other year, this plan was determined to be unaccepta-
ble based on the large quantities of debris that would
be washed into the Feather River and could ultimate-
ly affect power operations. Adding a converging con-
crete-lined channel and chute to the original head-
works structure created major standing-wave prob-
lems throughout the system. These problems were
resolved by separating the flood control structure
from the spillway structure as shown on Figure 76.
The rating curve for the flood control outlet (Fig-
ure 81) is based on these hydraulic studies.
Concrete for the spillway chute, weir, and flood
control outlet structure above elevation 865 feet was
specified to obtain a strength of 3,000 psi in 28 days;
concrete for the lower portions of the flood control
outlet, below elevation 865 feet, was specified to ob-
tain a strength of 4,000 psi in 28 days; and concrete
immediately behind the prestressed trunnion anchor-
ages was specified to obtain a strength of 5,000 psi in
28 days.
Steel reinforcement conforms to intermediate or
hard-grade billet steel as specified in ASTM Designa-
tion A15 or A408.
Post-tensioned tendons for the gate trunnion an-
chorages have an ultimate strength of 160,000 psi.
Structural steel for the main members of the radial
gates and bulkhead gates conforms to ASTM Designa-
tion A441. Secondary gate members and trunnion
beams are of A36.
Head works. The top of the 570-foot-long head-
works is coincident with the top of the Dam (eleva-
tion 922 feet). The gated outlet passages are placed in
an excavated channel depressed from the emergency
spillway approach channel. The invert of the outlet is
elevation 813.6 feet.
Four bridges or service decks are provided: the crest
of the structure is a roadway used for maintenance
purposes, including placement of stoplogs; the radial-
gate hoist deck is at elevation 886.5 feet; the spillway
road bridge providing access to the right abutment by
way of the dam crest is at elevation 870 feet; and a
walkway for inspection of the gates and trunnions is
at elevation 847 feet.
Because the headworks structure is founded on
competent rock, sliding was not considered a factor in
stability. The structure was analyzed for safety
against overturning.
The embankment grout curtain was extended un-
der the headworks. It consists of a single line with a
maximum depth of 50 feet.
Drain holes were drilled into the foundation rock
downstream of the grout curtain. Uplift pressures
were assumed to be 100% of reservoir head at the
upstream edge, reducing in a straight line to 33% at
the drains and zero at the downstream toe.
Reinforced-concrete piers, 5 feet thick, separate the
gated water passages. The piers also support the breast
wall and service decks and provide anchorage for the
gate trunnions. The pier noses are steel-armored to
reduce wear, and guides for stoplogs are welded to the
leading edges.
The crest service bridge is made up of reinforced-
concrete slabs spanning between the piers. The total
width is 21 feet. The spillway road bridge deck is of
similar construction but the total width is 34 feet.
Reinforced-concrete bents were required on the
downstream end of the piers to support the bridge.
The maintenance deck involves individual rein-
forced-concrete slabs, 18 inches thick, supported on
the piers in 4-inch-deep notches. Blockouts are pro-
vided in the deck for access to ladders which lead to
the gate head seal assemblies. It was designed for a live
floor load of 250 pounds per square foot. In addition
to the live load, a seismic acceleration of O.lg parallel
to the axis of the structure was investigated assuming
the deck acts as a strut between the piers.
The hoist deck, a downstream continuation of the
maintenance deck, was designed to support the weight
of the gate hoists, the maximum force caused by lifting
the gates, and a live load of 250 pounds per square foot
on the working surface.
The walkway for inspection of gates and trunnions,
a 15-foot-wide reinforced-concrete slab spanning be-
tween the piers immediately downstream of the gate
trunnions, also was designed to support a live load of
250 pounds per square foot.
The skinplates for eight 17-foot- 7-inch by 33-foot
top-seal radial gates were designed as a continuous
plate spanning horizontally between vertical support-
ing members. Bending stresses in the plate were deter-
mined by treating the member as a continuous beam;
however, horizontal tension also was checked. The
load on the skin assembly is transmitted to the trun-
nions through horizontal girders and canted arms.
The outlet gate trunnion assemblies consist of welded-
steel trunnion rings to which the three end-frame
struts are connnected, steel shoes rigidly attached to
the piers (e.g., by a trunnion beam), and trunnion
pins.
Adjacent trunnion pins are not interconnected to
the pier anchorage but are connected to a common
93
Figure 76. General Plan of Spillwoy
94
*■ M.
Figure 77. Flood Control Outlet — Plan and Elevation
95
Figure 78. Spillwoy Chute— Plon, Profrle, and Typicol Secti
96
Figure 79. Emergency Spillway — Sections and Details
97
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Figure 81.
WS ELEVATION FEET
Spillway and Flood Confrol Ouflet Rating Curves
99
support beam. At the end piers, support beams act as
simple cantilevers. Post-tensioned embedded steel
rods, at an alignment approximately parallel to the
maximum resultant hydrostatic pressure, anchor the
support beams to the piers. Twenty-four 1%-inch-di-
ameter tendons anchored 37 feet -6 inches into the
piers are used for each gate trunnion.
As the radial gates are submerged (Figure 82), rub-
ber seals are required on all four sides of the gate. The
bottom seal is a rubber bar mounted in the sill plate.
The gate rests on this bar, and its weight effects a tight
closure. The side and top seals are hydraulically ac-
tuated, double-stem, rubber seals. Hydrostatic pres-
sure is applied behind the seals by a direct connection
to the reservoir with a two-way activated valve to re-
lieve internal pressure when moving the gate. The
side seals slide on and seal against embedded steel
plates in the walls. Because sliding occurs when gates
are opened or closed, the seal noses are teflon-clad.
The friction factor assumed between the teflon-clad
seals and the stainless-steel plates was 0.1.
The flood control outlet radial gates are operated by
electric-motor-powered cable-drum hoists located on
the hoist deck. The gates may be operated locally or
remotely from the Oroville Area Control Center.
Normal power for hoist operation is supplied through
a buried distribution line from Edward Hyatt station
service power system. Standby power is available lo-
cally in the form of a S5-kW generator operated by a
liquid-propane-gas-fueled engine. Normal power sup-
ply is sufficient to operate all gates simultaneously.
A set of stoplogs is provided to dewater outlet bays
to allow maintenance work to be performed on the
radial gates.
Five interchangeable leaves are stacked in slots in
the pier noses and make up the set required to close off
one gate bay. The gate leaves are each 8 feet - 10 inches
high and were constructed of '/j-'nch-thick skinplate
and box-shaped ribs. Rubber seals are used on all four
sides ("J" seals on the top and sides, and wedge-shaped
seals on the base). Each leaf is provided with a 4-inch
gate valve to refill the volume between the radial gate
and stoplog and thus equalize the pressure for gate
removal. The stoplog leaves were designed for a hy-
drostatic head of 87 feet (elevation 813 feet to eleva-
tion 900 feet).
The bottom stoplog seal was modified after initial
use. A softer rubber bar-type seal was used to com-
pletely seal the bottom corners.
Also, a modified slide gate with regular ropes as
operators was installed on the bottom stoplog to has-
ten the filling time of the space between the stoplogs
and the radial gates.
Chute. Except for the terminal structure, the
chute walls are cantilever type varying from 20 to 34
feet in height. The walls are structurally independent
of the chute invert slab. The reinforced invert slab has
a minimum thickness of IS inches and is anchored to
the rock with grouted anchor bars and provided with
a system of underdrains.
The terminal structure, designed to dissipate large
flows, is more massive and is keyed into the rock foun-
dation to resist forces from the flow. Its walls are
gravity type; its invert slab is thicker and keyed into
the rock. Mounted on the invert are four 23-foot-high,
43-foot-long, chute blocks designed to separate the
solid flow of water.
Energy of this separated jet is absorbed in a plunge
pool excavated in the Feather River at the foot of the
chute. No concrete lining is used in the plunge pool
as rock of adequate quality exists near the ground
surface.
Emergency Spillway. The grout curtain was con-
tinued under the left reach of the emergency weir
near the upstream face, and formed drains are used
under the downstream half. The crest of the emer-
gency weir to the right, which is only 1 foot above the
excavated channel, is keyed 2 feet into the foundation.
Both weir sections were checked for overturning and
shear friction safety factor and found to be satisfac-
tory.
Saddle Dams
Location. Bidwell Canyon and Parish Camp Sad-
dle Dams are low dams which complement Oroville
Dam in containing Lake Oroville. Bidwell Canyon
Saddle Dam is located at the head of the Bidwell Bar
Canyon arm of the reservoir and is V/i miles southeast
of Oroville Dam (Figure 55). Parish Camp Saddle
Dam is located on the narrowest ridge enclosing the
Lake on the West Branch arm of the Lake and is 12
miles north of Oroville Dam.
Description. Bidwell Canyon Saddle Dam is an
earth and rockfill dam consisting of two separate em-
bankments. The main dam encompasses the former
Miners Ranch Dike built by Oroville-Wyandotte Irri-
gation District as part of its South Fork project. The
west dam meets the main dam at a knoll at the middle
of Bidwell Canyon and extends to Kelly Ridge. In
addition to containing Oroville Reservoir with a nor-
mal pool at elevation 900 feet on its north side, the
main dam also contains Miners Ranch Reservoir with
a maximum pool at elevation 888 feet on its south side.
The plan and profile are shown on Figure 83, and
sections and details are shown on Figure 84.
Parish Camp Saddle Dam is an earth and rockfill
embankment which extends 260 feet across Lime Sad-
dle, the maximum height being 27 feet. The plan, pro-
file, and sections are shown on Figure 85.
Construction of Parish Camp Saddle Dam included
plugging a collapsed mine adit found near the Dam.
100
Figure 82. Flood Control Outlet — Elevations and Sect!
101
Figure 83. Bidwell Canyon Saddle Dam— Plan and Profile
102
.i
i!
A
Figure 84. Bidwell Canyon Saddle Dam — Sections and Details
103
Figure 85. Parish Camp Saddle Dom— Plan, Profile, and Sections
104
Site Geology. Bidwell Canyon Saddle Dam is
founded on a metavolcanic rock consisting mainly of
a foliated amphibolite. Amphibolite varies considera-
bly in its degree of weathering throughout the area,
with depths ranging from 2 to as much as 18 feet.
Fresh exposures generally are dense and tough with a
dark bluish or greenish gray color.
Parish Camp Saddle Dam is founded on phyllite, a
metavolcanic rock of the Calaveras group, with the
exception of a small portion of the left abutment
which has blocky metavolcanic rocks of the Oregon
City formation. The phyllite is moderately weathered
to decomposed, with the weathering ranging from 5 to
as much as 16 feet. Weathered phyllite has a fairly high
clay content. The Oregon City formation is fresh,
dense, black, metavolcanic rock.
Embankment Design. Bidwell Canyon Saddle
Dam's main dam was designed as a zoned embank-
ment matching the Miners Ranch Dike's zoning, ex-
cept that a "downstream wing" was added to the core
late in the design period so that random material
rather than the scarce rockfill material could be used.
Bidwell Canyon Saddle Dam's west dam was de-
signed as a homogeneous structure except for a down-
stream horizontal blanket drain, a compacted rockfill
upstream toe, and rock slope protection. The blanket
drain is located 5 feet below the normal reservoir wa-
ter surface and contains an 8-inch perforated collector
pipe which drains into Miners Ranch Reservoir
through an 8-inch pipe. The rockfill toe was included
for stability purposes to avoid a flatter upstream slope
which would have extended a considerable distance
down the Canyon.
Parish Camp Saddle Dam was designed as a homo-
geneous dam with rock slope protection. The mine
adit plug constructed near Parish is of common imper-
vious embankment. Since the adit portal had caved,
i blocking access for exploration, the conservatively di-
mensioned plug was constructed to control possible
seepage through the narrow ridge.
Foundation Grouting. The grout curtains for
both dams are 25 feet deep in a vertical plane. The
holes were inclined 20 degrees off vertical along the
plane in order to cross the nearly vertical cleavage and
schistosity. Selected grout holes were deepened to 50
; feet to explore beneath the curtain. The curtain for
; the main dam is an extension of the curtain for the
1 Dike. An initial hole spacing of 10 feet was used with
' intermediate holes drilled as necessary to close out the
curtain.
Construction Materials. Borrow Areas F and G
located outside proposed recreation areas just to the
north of Bidwell Canyon Saddle Dam were chosen as
the sources of impervious material (Zone IB). This
material consists of decomposed to strongly weath-
ered schistose amphibolite.
Material excavated from Kelly Ridge tunnel ap-
proach channel of the South Fork project by Oroville-
Wyandotte Irrigation District had been spoiled adja-
cent to the north side of Miners Ranch Dike. This
material was suitable for Zone 3B and was designated
Stockpile H (Figure 83).
The transition zone and drain material (Zone 2B),
the downstream rock toe of the main dam (4B), and
riprap were supplied by the contractor from approved
outside sources.
Impervious material (Zone IP) for Parish Camp
Saddle Dam was developed by excavating the weath-
ered phyllite in the two borrow sources not in a
proposed recreation area. Excavation for a permanent
access road, located through one borrow area, was
designated as the primary source, with the remainder
of the material supplied by Borrrow Area C immedi-
ately to the northwest of the Dam site (Figure 86).
Zone 2P, the transition, was supplied by the con-
tractor from an approved outside source.
Material for the mine adit plug was obtained from
Borrow Area E located in the reservoir area 400 feet
north of the adit (Figure 86).
Stability Analysis. Stability of the embankments
was determined by the Swedish Slip Circle method of
analysis. Adequate safety factors were found for all
loading conditions. Seismic forces of O.lg in the direc-
tion of instability were included in the earthquake
analysis. Analysis of the upstream slopes included sev-
eral lake levels assuming a horizontal phreatic line at
maximum pool elevation 900 feet. The downstream
slope of the Bidwell main dam was analyzed for a
steady-state seepage condition with the downstream
tailwater at maximum water level in Miners^ Ranch
Reservoir, elevation 888 feet. The narrow width and
flat slope required for construction obviated the need
for stability analysis of the mine adit plug.
Embankment properties used in the stability com-
putations were determined by exploration and labora-
tory testing of the impervious zones, while standard
properties were used for the transition zones, shell
zones, and riprap.
105
Figure 86. Location of Borrow Areas ond Parish Camp Saddle Dam Site
106
Instrumentation
Dam. The following is a summary of the in-
strumentation in Oroville Dam:
Instrument
Hydraulic Piezometers
Hydraulic Piezometers
Electric Pore Pressure
Cells
Dynamic Electric Pore
Pressure Cells
Cross-arm Settlement
Devices
Fluid Level Settlement
Devices
Surface Settlement
Points
Horizontal Movement
Units
Soil Stress Meters,
7'/^-Inch Diameter
Soil Stress Meters,
18-Inch Diameter
Dynamic Soil Stress
Cells, 30-Inch
Diameter
Concrete Stress Meters
Concrete Deformation
Meters
' Accelerometers
Accelerometer
I Resistance Thermometers
Extensometers
Sumber General Location
54 In dam embankment
2 In dam foundation rock
2 In rock next to grout
gallery
6 In dam embankment up-
stream of Zone 1
In dam embankment down-
stream of Zone 1
2
36 In dam embankment
100 Along crest of dam and
on upstream and down-
stream slopes
i 2 In embankment down-
stream of Zone 1
32 Embedded in core block
and grout gallery
adjacent to fill
material
27 In dam embankment
15 In downstream Zone 3
9 In core block and grout
gallery adjacent to
foundation rock
8 In downstream face of
core block parapet
2 In dam embankment
1 In dam foundation
62 In core block and dam
foundation
3 In core block
Spillway. Instruments used were strain meters,
pore pressure cells, and pore pressure cells modified
for use as piezometers. Strain meters were embedded
in Pier 8 and in the breast wall above Bay 6 as the
concrete was placed. Pore pressure cells were placed
in holes drilled into the rock foundation under Bays
3 and 6 as the piers were constructed. Piezometers
were placed in the concrete around Bays 5 and 8.
Saddle Dams. Crest settlement points are the only
instrumentation in Bidwell Canyon Saddle Dam and
Parish Camp Saddle Dam. There are eight of these at
Bidwell and three at Parish Camp Saddle Dam (Fig-
ures 83 and 85).
Relocations
Western Pacific Railroad
Relocation of the Western Pacific Railroad out of
the Feather River Canyon, site of Oroville Dam and
Lake Oroville, was part of the initial work required
before major construction for the Dam could start
(Figures 55 and 87).
The 23 miles of relocated railroad begins at the east-
erly end of the City of Oroville. From that point, it
crosses the Feather River about 1 mile upstream from
the town, traverses northward along the westerly
slopes of North Table Mountain, and then connects
with the original railroad alignment along the easterly
side of the North Fork Feather River. The relocated
line passes through five tunnels and over three major
bridges. The reconnection point is about one-quarter
mile upstream from the shoreline of the maximum
operating pool level of the reservoir. Four complete
passing tracks approximately 7,000 feet in length are
included in the relocated line. Station buildings and
appurtenant facilities were built at a location near
railroad tunnel No. 1.
The original reconnaissance for relocation of the
railroad was performed during the early 1950s, with
the final location survey being completed in 1955.
An agreement with Western Pacific Railroad Com-
pany established the criteria for design. The design
was based on then-current railroad design data. These
data called for a maximum grade of 1%. The grade was
reduced at curves to compensate for curve resistance
and at bridges and tunnels. The maximum degree of
curve was 4°30'. Cut sections were constructed to a
40-foot minimum width and embankment sections
were constructed to a 26-foot minimum width with an
additional 1 foot of width provided for each 15 feet of
fill over the initial 15 feet. Both cut and embankment
sections were widened 1 5 feet for passing track and an
additional 14 feet for storage track where required. All
culverts were sized by the use of Talbot's formula,
using a 4-inch rainfall and a C factor suitable to the
area drained.
Tunnels. The length of the five railroad tunnels
measured between portal faces is as follows: (1) 2,410
feet, (2) 2,923 feet, (3) 2,583 feet, (4) 4,407 feet, and
(5) 8,825 feet. Due to the long lengths of tunnels Nos.
4 and 5, ventilating chambers were incorporated into
the design. The typical portal wall, at each end of the
tunnels, is a 2-foot - 6-inch-thick, reinforced-concrete,
portal structure flanked by retaining walls at varying
angles. The retaining walls are of different heights
and lengths to fit the topography at each location.
The geometry of the tunnel cross section is typical
for all five tunnels. The wall section above the spring-
line is circular with a radius of 9 feet, which makes the
clear width of the tunnel 18 feet. The height from the
top of the rail to the springline measures 15 feet.
Eight-inch, wide-flange, steel ribs fitting the tunnel
geometry were encased in the concrete wall along
with other reinforcement, e.g., rock bolts with chain-
link fabric, steel liner plates, and lagging materials as
needed to support the various excavation conditions.
Concrete placement of the tunnel lining was per-
formed pneumatically. The lining was constructed
with contraction joints spaced at 40 feet maximum on
centers. Four-inch formed drains were installed along
each tunnel spaced at 8-foot intervals both vertically
and horizontally. Refuge niches, car setoff niches, and
107
PARISH
CAMP
SADDLE
DAM
^^P^-
c<^TUNNEL
NO. I
WEST
BRANCH
BRIDGE'
WESTERN PACIFIC
RAILROAD RELOCATION
Figure 87. Western Pacific Railroad Relocation — Tunnel Locations
108
other safety and operating openings were provided
along each tunnel.
The design and construction supervision was done
by the Department except for track laying. Western
Pacific Railroad approved all design drawings prior to
award of construction contracts and laid the track.
Bridges. The three major bridges built in conjunc-
tion with the relocation of the railroad are: (1)
Feather River Bridge, (2) a combination highway-
railroad bridge across the West Branch Feather River,
and (3) North Fork Bridge. In addition to the above,
a short-span arch bridge was constructed across Dark
Canyon, and many single-lane underpasses were built
to provide access to property on both sides of the
railroad.
All design was based on a Cooper E-72 live load with
O.Ig earthquake loading.
Feather River Bridge. The crossing of the Feather
River approximately 1 mile north of the City of Oro-
ville was designated the Feather River Bridge (Figure
88). This bridge was designed by an engineering con-
sultant to the Western Pacific Railroad Company us-
ing 1956 American Railway Engineering Association
(AREA) specifications. Horizontal alignment of the
Bridge is on a 3°00' curve with a track grade of 0.88%
ascending eastward.
A riveted-deck plate-girder structure was selected as
the most economical design for this bridge. The cen-
terline of track span lengths, center to center of piers,
vary from 90 to 128 feet, for a total length of bridge of
1,012 feet in ten spans. Two plate girders were in-
stalled on 8-foot centers to support the 16-foot-wide,
lightweight-concrete, ballast trough. The girders vary
in length from 125 to 88 feet and their depths vary
from 9 to 10 feet.
Supporting this superstructure are reinforced-con-
crete cylindrical piers founded on spread footings
placed into bedrock, which vary in height from 44 to
77 feet. The top 44 feet of the cylindrical piers are 10
feet in diameter. They are 12 feet in diameter for the
remainder of their length. Piers for a future track
were installed 18'/^ feet upstream of the new bridge
and on the same footings. These piers rise above the
maximum normal water surface.
Principal considerations used in the design of the
piers, due to their almost complete submergence in
the Thermalito diversion pool, were: (1) mass to be as
small as practicable, (2) form to require the accelera-
tion during earthquakes of the least practicable
amount of water, (3) superstructure square rather
than skewed, (4) least practicable interference with
and resistance to streamflow, and (5) as much duplica-
tion of forms as possible.
The consultant's plans and specifications were in-
corporated into contract documents, the work was ad-
vertised, and construction was supervised by the
Department of Water Resources.
West Branch Bridge. The relocations of the West-
ern Pacific Railroad and U.S. Highway 40A (now
State Highway 70) converged at a common location to
cross the West Branch Feather River. This crossing is
located approximately 2 miles west of the confluence
of the West Branch and the North Fork of the Feather
River, 1 1 miles northeast of the City of Oroville. A
combination highway-railroad bridge was the logical
choice.
The West Branch Bridge (Figure 89) is a riveted-
steel, cantilevered, Warren truss with verticals. The
single-track railroad is on an 18-foot-wide, light-
weight-concrete, ballast trough supported by steel
Figure 89. West Branch Bi
109
stringers and floor beams attached to the lower chord
of the truss. The highway is four lanes on a 56-foot-
wide concrete roadway supported by steel stringers
and floor beams on the top chord of the truss.
The truss-span layout includes a .?60-fo()t approach
truss, two 432-foot anchor spans, and a 576-foot main
span consisting of a .^6()-foot suspended span and two
108-foot cantilevers. In addition, there are 10 highway,
welded-steel-plate-girder, approach spans. Si.x spans
(79 feet, three at 80 feet, \i5 feet, and 79 feet-.?
inches) are located on the south end and four spans
(133 feet, two at 80 feet, and 79 feet - 3 inches) are
located to the north. Total length of the structure is
2,731 feet.
The three main piers supporting the truss sections
are 216 feet, 2S2 feet, and 257 feet in height. They are
founded on spread footings placed against undis-
turbed rock excavated to near-vertical lines. The other
piers and abutments are reinforced concrete on spread
footings.
The Bridge Department of the Division of High-
ways, California Department of Public Works (now
the Department of Transportation), designed and
supervised construction of the Bridge. The contract
documents were reviewed and approved by the De-
partment of Water Resources and the Western Pacific
Railroad Company.
Conventional construction methods were used in
the pier-footing excavations and in constructing the
piers themselves, except for the main piers. These
piers were constructed using the slip form method of
concrete placement.
Truss erection started at the southwest end of the
Bridge (nearest Oroville) and proceeded toward the
middle of the main span. Then, at the northeast end,
erection proceeded until it connected with the already
erected portion of the main span.
North Fork Bridge. In order for the relocated
Western Pacific Railroad tracks to join the existing
tracks at the North Fork of the Feather River, a bridge
had to be constructed across the River (Figure 90).
The agreement between the Department of Water
Resources and the Western Pacific Railroad Company
required the railroad to design this bridge. The agree-
ment called for either a cantilever truss structure or a
reinforced-concrete arch bridge. A consultant for the
railroad prepared contract documents for both
proposals. These contract documents were furnished
to the Department, who subsequently called for bids
on both proposals. The bid for the reinforced-concrete
arch bridge was the least costly and was selected for
construction. The Department supervised the con-
struction.
The reinforced-concrete arch structure has arch
spans of 191.5, 308, and 257.5 feet, six east approach
spans 22.5 to 28 feet long, and abutments for a total
length of 1,010.5 feet. The 1 19-foot-high concrete
arches vary in width from 20 to 30 feet. They are
founded on concrete pedestals placed on bedrock.
Figure 90. North Fork Bridge
The single-track railroad is on 20-foot-wide, con-
crete, ballast trough with a parabolic soffit. The bal-
last trough is supported by walls rising from the arch.
These walls vary in thickness from 9 feet at the piers
to 2 feet at mid-span. They vary in height from 130
feet at the piers to approximately 5 feet at mid-span.
Feather River Railway
The Feather River Railway extended from the town
of Feather Falls above the South Fork arm of Lake
Oroville to its junction with the Western Pacific Rail-
road in the Feather River Canyon 2 miles upstream of
Oroville Dam. As explained in Volume \T of this
bulletin, the lumber formerly carried by the railroad
is now trucked in accordance with a settlement be-
tween the Department and the owners.
Oroville-Quincy Road
The relocated Oroville-Quincy Road begins ap-
proximately 5 miles due east of the City of Oroville
and extends 8.1 miles north to the original Oroville-
Quincy Road (Figure 55). The north and south
reaches of the new road are separated by an arm of the
reservoir that is spanned by the Bidwell Bar Bridge.
The general location of the entire road was dictated in
part by the site selected for Bidwell Bar Bridge, which
was built at the only feasible site for a major bridge in
that area.
The portion of the old Oroville-Quincy Road now
inundated by Lake Oroville originally crossed the
Feather River Canyon at Bidwell Bar and continued
generally north, rising from the canyon west of
Mount Ratchel.
Forbestown Road to Bidwell Bar Bridge. From its
southern end at Forbestown Road, the relocated route
extends 3.8 miles north to Bidwell Bar Bridge. Loca-
tion of its beginning was influenced by the location of
110
i
the Miners Ranch Reservoir to the west. Beginning at
elevation H50± feet, the Road rises to elevation 2,156
feet at its highest point. It joins the south approach to
Bidwell Bar Bridge at elevation 9.')0 feet. For part of
its length, the Road follows the eastern limit of the
Loafer Creek recreation area. Cross slopes range from
moderate to steep. Several alignments for the southern
reach were studied before the present alignment was
accepted. Its precise location was the result of negotia-
tions between Butte County and the Department and
also reflected the wishes of the Department of Parks
and Recreation for a road in the vicinity of the Loafer
Creek recreation area. Subsequent to completion of
the Road, Butte County relocated a portion of the
southerly end of the Road so that it aligned with Olive
Highway.
Inasmuch as this was a relocation of a Federal-Aid
Secondary Highway with an average daily traffic
count exceeding 400 vehicles, the criteria chosen are
those appropriate for a road with an average daily
travel of 400 to 1,000 vehicles in rolling or mountain-
ous terrain.
Drainage structures were designed to carry runoff
from 100-year storms as determined by the procedure
defined in the "California Culvert Practice" of the
Division of Highways. The calculations to determine
the runoff were based on a 100-year record storm.
Bidwell Bar Bridge to Original County Road. The
northern section of Oroville-Quincy Road extends 3.9
miles north from Bidwell Bar Bridge, following the
configuration of the ground above Oroville Reservoir
at elevations from 945 to 1,060 feet. The road crosses
Canyon Creek on a 780-foot-long bridge and continues
along the south side of Canyon Creek. It connects with
the original county road about 1 mile northwest of the
Canyon Creek crossing. Cross slopes for almost the
entire length of the Road are extremely steep.
Butte County was responsible for design and con-
struction of this part of the road relocation. The
County contracted with its consultant. Porter, O'Bri-
en and Armstrong Engineers, to prepare the plans and
specifications for this portion of the Road. Both the
Department of Water Resources and Butte County
agreed on the design standards used. Total cost to the
Department for design and construction work was not
to exceed $4,900,000. The Department retained the
responsibility for acquisition of right of way.
Roadway fills extending below the high water ele-
vation of the reservoir were designed to resist the ero-
sive action of 3-foot waves. The compacted embank-
ment was protected by a 15-foot zone of pervious
material and a 3-foot zone of rock slope protection.
The compacted embankment consisted of material
with a gradation of 85% passing a '/j-'nch sieve, 50%
passing a No. 8 sieve, and 10% passing a No. 70 sieve.
This material, frequently found in the roadway exca-
vation after overburden was stripped, was designed to
give the compacted embankment below elevation 905
feet the free-draining characteristic needed for a reser-
voir drawdown rate of 0.0038 of a foot per minute.
Pervious material selected or proces.sed from roadway
excavation, with no more than 10% passing a No. 4
sieve, was utilized below elevation 911 feet to act as
filter material between the compacted embankment
and rock slope protection.
Because of the steep transverse slopes where the
road alignment is adjacent to the reservoir, viaducts or
steep embankment supported by retaining walls were
required. Following consideration of the viaducts and
the many types of retaining walls, metal bin-type
walls were selected.
Transverse members of the metal bin walls are
spaced 10 feet apart, tying the front and rear walls of
the bins. The walls are made up of modules 1.33 feet
high. The bins were predesigned by the manufacturer
for walls of six heights with corresponding bin
widths. Base plates serve to establish the wall at prop-
er line, grade, and batter. To facilitate adjustments, 8
inches minimum of loose material was placed below
each footing. Native material was satisfactory for
backfilling and was compacted in 1-foot layers. The
bins were set on a 1:6 batter.
To provide adequate road width at gullies crossing
the roadway, it was necessary to build concrete foun-
dation walls on which the metal bin walls were placed.
These concrete foundation walls were anchored to
bedrock by dowels grouted into drilled holes in the
bedrock.
Bidwell Bar Bridge. Bidwell Bar Bridge (Figure
91), the key feature of the Oroville-Quincy county
road relocation, crosses the Middle Fork arm of Lake
Oroville about 1 mile upstream from the former cross-
ing at Bidwell Bar. The inundated Bidwell Bar cross-
ing was the location of the historic Bidwell Bar
suspension bridge, said to be one of the first suspen-
sion bridges erected in the West. The historical bridge
was removed and is to be reassembled at a new site at
the Kelly Ridge recreation area. The Bidwell Bar
Bridge originally was designated the "Middle Fork
Feather River Bridge". After construction, it was re-
named after the geographical and historical site inun-
dated by Oroville Reservoir.
The Department of Water Resources designed, and
was the contracting agency for, the Bridge.
Selection studies for the Bridge were based upon an
investigation of several types of existing structures.
Types other than cantilever or suspension bridges
were quickly eliminated due to site conditions, span
length requirements, and economics.
Studies for a cantilever bridge emphasized the dif-
ficulties of fitting an economical structure to the steep
slopes at the selected site. Two piers over 300 feet in
height would have been necessary to support the
bridge. Even with piers of such height, the balance
between anchor, cantilever, and approach span was
111
Bidwell Bar Bridge
such that considerable uplift would have resulted at
the abutment. The steep side slopes also would have
required massive roadway excavations to make the
near-right-angle turns in the approach roadway onto
and off the bridge.
Preliminary studies in the design of the suspension
bridge were made using the basic design approaches
presented in "A Practical Treatise in Suspension
Bridges" by D. B. Steinman.
The economics of locating the piers as far shore-
ward as possible was apparent. In addition to allowing
the use of shorter piers, this geometry allowed the use
of unloaded rather than loaded backstays. Use of un-
loaded backstays was necessitated by the requirement
to use curved roadway approaches for smooth access
to and from the Bridge.
It was apparent from preliminary cost estimates
that a suspension bridge was the obvious choice. Aes-
thetical characteristics of the Bridge are an advantage
which has been gained at no cost.
The main cables are covered with a plastic cable
covering developed by the Bethlehem Steel Company.
This bridge is the first to use a cable protection system
other than the painted wire wrapping introduced by
John A. Roebling in 1845. An obvious advantage in
using the plastic (glass-reinforced acrylic) cable cov-
ering is found in comparing its estimated 50-year life
without maintenance to the two- to three-year re-
painting cycle required by the painted wire-wrapping
system.
The main cables are anchored in tunnels by utiliz-
ing prestressing tendons. This bridge is the first major
structure to use this method of anchorage. The pre-
stressed tunnel anchorage was the most economical
type that could be used. Plain details, smaller mem-
bers, and easier access resulted in a small tunnel re-
quiring less excavation and concrete than would have
been necessary with others. Another advantage of-
fered by the prestressed anchorage is that the entire
concrete tunnel plug is compressed. Consequently,
there was no elastic elongation of the anchorage dur-
ing the spinning of the cables, and an accurate zero
point of movement for connecting the cable strands to
the anchorage was available.
Canyon Creek Bridge. Canyon Creek Bridge
spans the arm of Oroville Reservoir 2.75 miles north
of Bidwell Bar Bridge and immediately south of the
former confluence of Canyon Creek and its east fork.
Studies indicated that the most economical structure
for the Canyon Creek crossing would be a steel-plate-
girder bridge. The crossing selected required a struc-
ture 780 feet long. The Bridge has four spans: 195 feet,
250 feet, 196 feet, and 134 feet in length. It was de-
signed for two lanes of traffic with H20-S16-44 live
loading (AASHO).
Pier footings were designed for direct bearing on
sound rock. Excavation was planned to reach about 35
feet below original ground. Pier footings, 8 feet by 24
feet, were anchored to the hillside by 1/^-inch rock
112
bolts. Piers 2 and 3 contained three horizontal bolts,
three bolts at 1 5 degrees with the horizontal, and three
at 30 degrees with the horizontal. A reinforced-con-
crete bench was installed at ground level to absorb the
horizontal reaction of the tension bolts, thus avoiding
a horizontal thrust on the base of the piers. In main-
taining a length-to-depth ratio of not greater than 20,
the outside dimensions of Piers 2 and 3 were 8 feet by
24 feet. Each pier consisted of a hollow interior shaft
with dimensions of 16 feet by 5 feet - 4 inches. Exter-
nal vertical edges of the piers were rounded on a 4-foot
radius.
Canyon walls rising 400 to 600 feet above Canyon
Creek Bridge generally shield the Bridge from any
high-velocity winds striking it in the normal direc-
tion. The only direct approach for the wind is from
the southwest. Prevailing winds in the locality blow
from either the southeast or the northwest, reaching
a maximum velocity of 90 miles per hour. A wind load
of 32 pounds per square foot was used in the design of
the Bridge.
Seismic loading was based on the assumed period of
vibration of historical earthquakes in the area. For
Canyon Creek Bridge, this period was estimated to be
3.3 seconds. On this basis, as outlined in the Division
of Highways' "Bridge Planning and Design Manual",
the seismic force used to design the Bridge was .031
times the dead load. The dead load of the submerged
portion of piers included the weight of a column of
water 24 feet in diameter.
The reinforced-concrete deck is supported by two
parallel steel girders spaced 20 feet apart. The deck, 34
feet wide and lO'/j inches thick, cantilevers 7 feet from
each side of the girders. A 30% impact load was used
in the design of the deck.
The steel girders were designed as continuous mem-
bers over Piers 2 and 3 and simply supported over Pier
4 and at the abutments. Expansion bearing assemblies
at both abutments and at the stream channel side of
Pier 4 allow for longitudinal movement of the girders.
Fixed bearings support the girders at Piers 2 and 3 and
at the bank side of Pier 4.
Interior cross frames were located as required at
25-foot maximum spacing to give lateral support to the
girders. The frames were bolted or welded to the web
stiffeners 6 inches in from the flanges. Diagonal lacing
is used in the plane of the bottom chord of the frames.
An inspection catwalk supported on the lower chord
of the cross frames runs the full length of the Bridge.
Oroville-Feather Falls Road
The Oroville-Feather Falls county road relocation
(Figure 55) is a 10-mile-long replacement for a por-
tion of Lumpkin Road, inundated by Lake Oroville
near Enterprise. It is located on the South Fork of the
Feather River approximately 10 miles east of Oroville.
The new alignment was based on least cost and loca-
tion was governed primarily by the type and length of
the bridge crossing. The structure ultimately was
located 1% miles upstream from the old road. Adop-
tion of the route was effected through an agreement
with Butte County which also established design cri-
teria and provided for concurrent review of the design
by the County. Although the character of the former
road was extremely poor, the replacement design cri-
teria were based on current design standards The
realignment was extremely advantageous from the
standpoints of design, right of way, traffic interrup-
tion, and service.
The agreement with Butte County provided for
passing lanes to compensate for the increased amount
of truck traffic required to transport the lumber
products of the Feather River Pine Mills that were
formerly conveyed by railroad (see Feather Falls Rail-
way).
The project was divided into two contracts because
of the timing involved in both design and construc-
tion. The first contract included a portion of the road
south of the B. Abbott Goldberg Bridge, and all of the
road north of the Bridge, to the existing road. The
second contract included that portion of the road from
the beginning of the relocation to the first contract.
In terms of overall service, the relocation is 2'^ miles
longer than the original road.
B. Abbott Goldberg Bridge. Adequate bridge sites
were limited due to the steep character of the terrain.
The bridge site selected resulted from the best eco-
nomic compromise between a narrow bridge crossing
and the steep topography for the road alignment. A
suspension bridge, a deck truss bridge, and a welded-
plate-girder bridge were considered. No other types
were appropriate for this site. The suspension bridge
was eliminated due to the questionable characteristics
of the decomposed granite in the anchorage areas.
A program for foundation exploration and testing
revealed a deep layer of decomposed granite near the
ends of the Bridge. Due to the instability pf this
material, it was more economical to span these areas.
Span lengths necessary to avoid these critical end
areas exceeded the economic limit for the plate-girder
alternative; therefore, it was abandoned in favor of the
deck truss design (Figure 92).
Bridge design was in accordance with the American
Association of State Highway Officials "Standard
Specifications for Highway Bridges", dated 1961, as
supplemented by the State of California "Bridge Plan-
ning and Design Manual". Live load used was the
H20-S 16-44 AASHO loading and an alternative load-
ing of two 24,000-pound axles 4 feet apart. A 15%
impact factor was used for the truss design, and a 30%
impact factor was used for the deck and approach
spans.
Pier foundations required special consideration.
The decomposed granite overburden is approximately
50 feet deep at the pier locations with the canyon slope
at roughly 30 degrees from horizontal. Any yielding
or movement in the slope at the piers will produce a
113
Figure 92. B. Abbott Goldberg Bridge
lateral force that must be resisted by the foundation.
The design force against the pier from a potential slide
in an active state was based on an effective wedge of
soil that would be retained by the pier. An anchor
shaft foundation, well socketed into fresh granite, was
chosen as the most acceptable means of withstanding
the large soil loads imposed on the piers. Closed-end
cellular-type abutments were used to reduce the earth
surcharge on the critical soil.
Interaction between the main truss members and
the lateral bracing members was investigated using
criteria recommended in the text "Modern Framed
Structures" by Johnson, Bryan, and Turneaure. Par-
ticipating stresses that would be developed were
found to be quite significant.
Analysis of the truss also considered the loading
conditions that would exist during various stages and
types of erection. These calculations determined that
eight members required selection based on erection
stresses governing over other loading conditions.
A deck Warren truss with two side spans of 308 feet
and a center span of 440 feet, for a total length of 1,056
feet, was selected for the superstructure. The super-
structure uses two component trusses spaced at 20-
foot centers. They are 24 feet in depth (center to cen-
ter between the top and bottom cord) and are
haunched to 36 feet in depth at the piers. All truss
panel points are spaced at 22-foot intervals. The
bridge roadway is 34 feet wide, consisting of two 14-
foot traffic lanes plus a 2-foot safety curb and barrier
railing on each side.
The truss expansion bearings and the slab roadway
approaches are supported on the abutments. Fixed
bearings for the truss are placed over the piers. Piers
2 and 3 are 12- by 36-foot hollow-shaft construction for
the top 100 feet above the ground, changing to a 14- by
28-foot section for the remaining exposed portion,
with approximately a 24-foot by 32-foot solid section
below the ground. Pier 2 extends 149 feet above the
ground surface and 102 feet below, while Pier 3 ex-
tends 140 feet above the ground surface and 75 feet
below. Both pier shafts are anchored into rock.
U.S. Highway 40A
As discussed in Volume VI of this bulletin, the 21
miles of U.S. Highway 40A (now State Highway 70)
that parallel the Western Pacific Railroad through the
Feather River Canyon were relocated by the Division
of Highways. Previously, it has been mentioned that
this relocation shares a bridge with the railroad at the
West Branch arm of the reservoir.
Nelson Bar County Road
Bennum and Lunt Roads modifications were neces-
sary to improve traffic access across the West Branch
arm of Oroville Reservoir and replace traffic patterns
provided by the old Nelson Bar Bridge.
Bennum Road. Bennun Road modifications begin
at Highway 70 near the northwest corner of Section
29, T.21N., R.4E. and extend northwest for approxi-
mately 1.65 miles along the west side of the West
Branch arm of the reservoir to connect with the Pentz
Magalia Road (a paved road connecting Highway 70
and Paradise). A channelized intersection on High-
way 70 was incorporated with this facility to provide
safety for vehicles turning left into Bennum Road.
Lunt Road. Lunt Road modifications begin at
Highway 70 near the center of Section 4, T.2 1 N., R4E.
and extend northwest 0.65 of a mile to connect with
the Nelson Bar County Road (a paved road serving
the area in the vicinity of Concow School).
The above modifications to Bennum and Lunt
Roads provide ready access via paved road from one
side of the reservoir to the other in the vicinity of the
West Branch arm, utilizing the West Branch Bridge
and Highway 70 (relocated Highway 40A).
Bennum and Lunt Road modifications were de-
signed and constructed by the Department. The chan-
nelization on Highway 70 at the intersection with
Bennum Road was designed by the Division of High-
ways, incorporated into the Department's plans, and
constructed at its expense. On completion, Bennum
and Lunt Road modificiations were incorporated into
the road system of Butte County.
U.S. Forest Service Roads
U.S. Forest Service roads to provide access for fire
suppression and recreational use in the vicinity of the
upper end of Oroville Reservoir on the North Fork of
the Feather River were lengthened and improved.
Construction
Contract Administration
General information about the major contracts for
the construction of Oroville Dam and appurtenances
is shown in Table 9. Other contracts relating to the
underground powerplant in the left abutment are dis-
cussed in Volume IV of this bulletin.
114
TABLE 9. Major Contracts — Oroville Dam and Appurtenances
Specifi-
cation
Low bid
amount
Final
contract
cost
Total cost-
change
orders
Starting
date
Comple-
tion
date
Prime contractor
Tunnels Nos. 4 and 5, Western
Pacific Railroad Relocation...
57-03
28,499,235
310,442,272
?6,378
5/24/57
12/30/60
Peter Kiewit Sons' Co.
Bridge Over North Fork Feather
River, Western Pacific Rail-
road Relocation
57-13
1,538,660
1,580,940
5,971
2/10/58
6/29/60
Pacific Bridge Co.
Bridge Over Feather River at
Oroville, Western Pacific Rail-
road Relocation
58-01
1,169,265
1,293,159
50,068
4/29/58
3/16/60
John C. Gist
Roadway Structures and Tun-
nels Nos. 2 and 3, Western
Pacific Railroad Relocation
59-16
5,720,320
6,255,568
155,824
8/11/59
9/ 8/61
Ball & Simpson, Inc.
Tunnel No. 1, Western Pacific
Railroad Relocation
60-07
2,069,090
1,948,032
16,228
8/ 1/60
11/ 3/61
Frazier-Davis Construction Co.
Roadway and Structures, Oro-
ville to West Branch Feather
River, Western Pacific Rail-
road Relocation
60-08
3,612,652
4,074,149
153,271
9/15/60
4/20/62
Ball & Simpson, Inc.
Diversion Tunnel No. 1
61-05
6,193,685
7,675,552
407,498
8/18/61
12/27/63
Frazier-Davis Construction Co.
Palermo Outlet Works
61-15
724,261
801,118
23,910
11/16/61
5/17/63
Morrison-Knudsen Co.
Section Headquarters at Siding
No. 3, Western Pacific Rail-
road Relocation
61-17
164,997
168,324
3,727
12/11/61
7/13/62
El Rey Builders, Inc.
Oroville Dam
62-05
120,863,333
135,336,156
7,503,716
8/13/62
4/26/68
Oro Dam Constructors
Oroville Seismograph Station...
62-11
31,226
39,469
742
7/19/62
10/26/62
El Rey Builders, Inc.
Left Abutment Access Road
62-13
452,388
549,400
65,742
7/14/62
4/ 9/63
Piombo Construction Co.
Oroville Construction Headquar-
ters
62-27
938,000
989,965
46,964
11/16/62
10/25/63
A. Teichert & Son
Middle Fork, Feather River
Bridge
62-30
4,436,104
4,859,714
96,006
2/11/63
8/11/65
Bethlehem Steel Co.
Employee Housing
63-04
659,095
618,543
7/ 9/63
4/27/64
Nomellini Construction Co.
Oroville-Quincy Road Reloca-
tion, Oroville-Forbestown
Road to Middle Fork Bridge..
63-35
1,053,196
1,521,868
359,825
1/ 3/64
8/25/65
Piombo Construction Co.
Construction Overlook Modifi-
cations
63-38
138,483
138,196
1,063
12/18/63
5/15/64
A. Teichert & Son
Pioneer Cemetery and Grave
Relocation
64-17
78,918
70,314
903
6/11/64
9/ 2/64
Frank P. Donovan
Headquarters and _ Employee
Housing Landscaping
64-30
37,043
40,982
2,046
7/24/64
9/22/64
Frank M. Smith
Thermalito Power Canal Relo-
cations
64-31
64-44
935,480
34,098
963,647
31,189
12,111
10/30/64
9/28/64
11/ 5/65
11/11/64
Osborn Construction Co.
Bidwell Bar Emergency Cross-
ing
Frank P. Donovan
Temporary Access Road, Middle
Fork Bridge North to County
Road
64-51
327,904
379,909
8,303
12/ 3/64
6/ 5/65
Crooks Bros. Construction Co.
Clearing Oroville Reservoir Site..
65-05
3,515,970
3,594,943
187,433
4/12/65
5/20/67
C. J. Langenfelder & Son, Inc.
Oroville Dam Spillway
65-09
12,249,850
13,702,871
615,781
6/25/65
2/20/68
Oro Pacific Constructors &
George Farnsworth Construc-
tion Co.
115
TABLE 9. Major Contracts — Oroville Dam and Appurtenances — Continued
Specifi-
cation
Low bid
amount
Final
contract
cost
Total cost-
change
orders
Starting
date
Comple-
tion
date
Prime contractor
Oroville-Feather Falls Road Re-
location
Oroville Feather Falls Road Re-
location, South Fork Feather
River Bridge and Roadway,
Station 422-l-SO to Lumpkin
Road..
Construction Overlook Reloca-
tion
Bulkhead Gates for Diversion
Tunnel No. 1
West Branch County Road Mod-
ifications, Bennum and Lunt
Roads
Oroville Operations and Main-
tenance Center — Thermalito
Annex
Oroville Peripheral Dams
Oroville Operations and Main-
tenance Center
Oroville Completion Contract
No. 1
Butte County Road Relocation,
Glen Drive Improvement
Oroville Reservoir Service Area
Boat Ramp
Oroville Dam Crest Improve-
ments
Oroville Completion Contract
No. 3.
Oroville Division Landscaping..
Oroville Dam Spillway Fencing..
65-23
65-26
65-59
66-05
66-27
66-41
66-42
66-52
67-43
67-44
67-53
69-07
69-19
69-34
71-20
$2,347,401
2,773,236
123,887
67,000
341,220
194,296
373,066
1,651,406
112,680
93,394
104,331
394,628
249,765
66,655
14,952
$2,565,225
2,919,468
123,657
69,747
371,168
194,024
499,420
1,708,603
110,131
119,120
109,895
423,391
278,959
69,521
14,947
$119,344
152,926
11,512
1,451
68,353
52,393
2,469
3,932
473
-9,965
28,933
1,967
12/23/65
8/10/65
1/19/66
1/28/66
7/ 9/66
11/ 4/66
12/ 9/66
1/23/67
9/15/67
8/31/67
9/20/67
3/10/69
8/14/69
1/ 8/70
9/ 3/71
9/20/67
1/11/68
6/17/66
7/30/66
2/ 3/67
9/29/67
10/ 3/67
4/ 4/68
7/20/68
12/18/67
12/11/67
7/21/69
5/ 1/70
3/24/70
10/13/71
O. K. Mittry & Sons
Rothschild, Raffin & Weirick,
Inc. & Piombo Construction
Co.
Baldwin Contracting Company,
Inc.
Berkeley Steel Construction Co.,
Inc.
A. Teichert & Son, Inc.
Baldwin Contracting Co., Inc.
Harms Brothers
Christensen & Foster
George R. Osborn Construction
Co.
A. Teichert & Son, Inc.
VV. H. Lindeman & Sons, Inc.
Oman Construction Co., Inc.
A. Teichert & Son, Inc.
Economy Garden Supply
Dalzell Corp.
Early Contracts
Relocations. The earliest contracts at Oroville
were for relocations. Construction aspects of the relo-
cations can be found with the design discussion. Costs
are, however, contained in Table 9.
Diversion Tunnel No. 1. The contractor estab-
lished an equipment and maintenance area on the
right bank of the Feather River opposite the intake
portal for the 4,400-foot-long 3S-foot-diameter tunnel
and erected a Bailey bridge to provide access to the
work area. Later, another Bailey bridge was erected
across the River to gain access to the work area at the
downstream portal.
Open-cut excavation was begun at the intake portal
on October 2, 1961 and, on November 14, 1961, a 12-
inch-wide crack developed over and nearly perpen-
dicular to the centerline of the tunnel. The partially
completed portal collapsed shortly after the crack de-
veloped.
Twenty-five-foot rock bolts on S-foot centers were
installed on the left wall to increase the stability of the
slope. One-inch-diameter slot and wedge-type rock
bolts 20 and 25 feet long were installed on a S-foot-
square pattern and torqued to 250 foot-pounds. The
rock above the portal was grouted, and most of the
muck pile was left in place to buttress the portal slope
116
while reinforcement of the rock progressed. Thirty-
foot crown bars (No. 18 rebars) were installed in
holes drilled on 12-inch centers over the arch of the
portal face and grouted in place. Arch ribs were in-
stalled on wall plates to form an umbrella which was
then lagged solid with timber. Timber cribbing was
placed 30 feet up each side of the umbrella and back-
filled with tunnel muck. The umbrella then was cov-
ered with approximately 1,800 cubic yards of
well-graded dredger tailings which were allowed to
assume their natural angle of repose { Figure 93 ) . Tun-
nel excavation resumed on January 9, 1962. Open-cut
excavation at the outlet portal began on July 10, 1962
in hard, strongly jointed, fresh to slightly weathered
amphibolite. No problems were encountered with
this portal.
A 38-foot section of the tunnel near the downstream
portal was left unexcavated through the 1962-63 rainy
season to prevent flooding of the tunnel from the
downstream end. However, on October 13, 1962, a
flood with a peak flow of 1 36,000 cfs overtopped the
upstream training levee and flooded the tunnel from
that end as well as taking out the downstream Bailey
bridge. This flood occurred a month earlier than the
start of the historic flood season. A flood with an even
larger peak, 191,000 cfs, inundated the work and dam-
aged the replaced bridge on January 31, 1963.
Rock conditions encountered were considered fair
to good for excavation of a large bore. Problems with
excavation and support were greatly minimized be-
cause the tunnel crossed geologic structures at nearly
right angles to strike.
The contractor used the top heading method of
driving the circular tunnel, excavating initially as a
horseshoe section 28 feet high and 40 feet wide at
springline. A 10-foot-square exploratory crown drift
was driven 20 to 25 feet ahead of the main heading for
the first 100 feet of tunnel from the upstream portal.
The tunnel was driven using diesel-powered rub-
Figure 93. Diversion Tunnel No. 1 Intake Portal After Backfilling
ber-tired equipment. Drilling of the top heading was
done from two three-deck jumbos on truck chassis.
The bench was removed for the entire length of the
tunnel after excavation of the top heading had been
completed. The average rate of advance for the top
heading was 20.5 feet per 24-hour 3-shift day, while the
average rate of advance for the bench was 83.2 feet.
The tunnel was supported throughout with W12X58
(12WF58) four-piece ribs spaced from 1.5 to 6 feet on
centers. Ground water was not a problem. The sum of
all estimated initial flows into the tunnel during exca-
vation amounted to 115 gallons per minute.
Openings 5 to 10 feet long were excavated, rock-
bolted, and concrete-lined for future connections to
draft tubes Nos. 3 through 6. Concrete bulkheads then
were installed.
A 20-foot-diameter 10-foot-high opening was ex-
cavated in the tunnel arch and rock-bolted prior to
excavation of the 10-foot-diameter, 38-foot-high, verti-
cal rise for later connection to the equalizing tunnel.
This excavation was lined and a concrete bulkhead
installed.
The tunnel lining reinforcement was modified in
the future tunnel plug reach so that some of the con-
crete lining could be removed to key the plug.
Concrete was mixed in an on-site batch plant, trans-
ported by a variety of methods, and placed in four
steps. A subinvert was placed to fill overbreak, make
a good working surface, and hold steel arch forms.
Curbs were placed on the subinvert to tie down the
bottom of the arch form. The arch then was placed
and finally the invert. The 48-foot-long arch form was
mounted on a jumbo which moved on rails placed on
the subinvert. Static forms were used for the invert.
Pumpcretes and slicklines conveyed the arch concrete
and belts conveyed the invert concrete.
The grouting program for the tunnel included en-
velope, contact, and consolidation grouting. High-
pressure envelope grouting was done in the tunnel
plug and draft-tube sections before lining the tunnel
with concrete, as discussed later in this chapter. Con-
tact grouting was done throughout the length of the
tunnel after tunnel lining was completed. Consolida-
tion grouting of the tunnel plug and a section at the
inlet portal followed contact grouting.
Construction of the tunnel for the diversion mode
was completed and water turned into the tunnel in
November 1963.
Palermo Outlet Works. Initial work on the 2,430-
foot-long 6-foot-diameter tunnel consisted of divert-
ing drainage at the intake and outlet portals.
The upstream portal was cut in moderately to
strongly weathered, moderately hard, blocky am-
phibolite and deep soil cover at slopes of l'/4:l, and 2:1
above the bench. Because of the blocky nature of the
rock at the intake portal, drill steel was installed to
serve as crown bars to support the arch.
Downstream portal excavation encountered fresh
to slightly weathered, hard, strongly jointed amphibo-
117
lite with a thin soil cover. The cut was excavated at a
slope of I'/j:!.
Both upstream and downstream portal cuts were
excavated with a ripper-equipped tractor with only a
minimum amount of blasting required to loosen large
blocks.
Rock conditions encountered in the tunnel were
considered good for normal tunneling operations in a
small bore. The amphibolite was generally fresh, hard,
moderately blocky and jointed, with support required
at each portal and in only three zones of sheared
weathered rock within the tunnel. Where support was
required, W4X13 steel beams were used for 17% of the
length of tunnel.
The tunnel was driven using rail-mounted equip-
ment on a 24-inch-gauge track. Three hydraulically
operated drifters were mounted on a jumbo for drill-
ing the face. Mucking was accomplished with an air-
operated mucking machine modified by shortening
the bucket arms for operation in a small bore. Two
muck trains were used for hauling the muck. Each
train was composed of six 30-cubic-foot side-dump
cars powered by a S5-horsepower, 6-ton, diesel loco-
motive.
The valve chamber and tunnel plug are located at
the grout curtain for Oroville Dam tunnel Station
24 + 08 (Figure 69). The valve chamber was moved 25
feet upstream from the design location primarily to
take advantage of better rock conditions but also to
locate the tunnel plug and grout curtain coincident
with the grout curtain for the Dam. (Construction of
Palermo outlet started before design of the Dam was
finalized.)
Curtain grouting was done from the tunnel to
reduce or eliminate the need for deep high-pressure
grouting adjacent to Palermo outlet works during cur-
tain grouting on the main dam and to reduce reservoir
pressure on the concrete lining of the tunnel down-
stream from the tunnel plug. To further reduce hy-
drostatic pressure on the concrete lining, drain holes
were drilled along the tunnel downstream from the
valve chamber. The curtain consisted of a single ring
of EX grout holes oriented radially at intervals of 22/2
degrees in a plane that is transverse to the tunnel
alignment and that dips 75 degrees upstream. Holes
varied from 60 to 130 feet in length in order to reach
elevations above and below the tunnel corresponding
to the estimated upper and lower limits of the
proposed grout curtain for the Dam.
Initial Dam Construction Activities
The prime contractor for Oroville Dam (including
Diversion Tunnel No. 2 and Thermalito Diversion
Dam) was notified to proceed with the contract work
on August 13, 1962 and began preconstruction activi-
ties during that week. The first work performed, un-
der the largest (in dollars) civil works contract up to
that time, was the building of an access road to the
outlet portal of Diversion Tunnel No. 2 and the con-
118
struction of the piers for a Bailey bridge.
By the end of the month, the contractor's survey
crews were staking out the locations for the conveyor
belts to handle embankment materials.
Clearing of the Dam site was begun in September
1962. By November 1962, the clearing crew, equipped
with ten logging dozers and chain saws, had com-
pleted the operation. Most of the area was covered by
scrub oak, digger pine, and manzanita.
There were 31 exploration holes from 82 to 145 feet
deep and five exploration tunnels in the dam founda-
tion. The exploration holes which generally were un-
der the core were filled with grout. Parts of the
exploration tunnels under the core and transition
zones were backfilled with concrete. In addition, the
portals of all five tunnels were filled with embank-
ment materials.
The Western Pacific Railroad had been relocated
out of the reservoir area prior to the start of construc-
tion. Approximately 1.06 miles of abandoned track
was removed and used in the contractor's rail facili-
ties, and an interconnection between the relocated
Western Pacific Railroad and the original line was
constructed for an interchange yard.
Diversion of River and Dewatering of Foundation
The diversion of the Feather River and dewatering
of the foundation were carried out in four stages.
For Stage 1 (Figure 94), the River was allowed to
remain in its natural channel while the lower lifts of
blocks 1 through 7 and 9 of the core block were being
placed.
Stage 2 (Figure 95) was started on July 18, 1963,
when the River was diverted through block 8 by
means of an earth dike across the channel upstream of
the core block. A similar earth dike downstream per-
mitted dewatering of the remaining foundation.
Stage 3 (Figure 96) of the diversion was provided
by a 30-foot by 22.5-foot sluiceway through block 12.
On September 4, 1963, the River was diverted through
this opening allowing block 8 to be dewatered and its
construction resumed.
The final diversion, stage 4, was made through Di-
version Tunnel No. 1 on November IS, 1963. The
sluiceway was backfilled with concrete in four lifts.
The first three lifts were placed by means of a rubber-
tired front-end loader. The crown lift was placed with
a pumpcrete machine.
Foundation Preparation
Stripping. Stripping was started in the general
area of the core block, the temporary diversion flume,
and batch plant and cableway areas. The next goal was
the area to be covered by the 1964 embankment, fol-
lowed by the upper reaches of the right and left abut-
ments. The final areas to be excavated were the areas
downstream of the core block, from the river channel
to approximate elevation 500 feet.
The principal method used was the loading of
trucks by shovel for hauling to disposal areas. A part
of the excavation was of sufficient depth to permit
direct loading by the shovel. However, much of the
area to be worked was in steep terrain, with shallow
cuts. In this case, bulldozers were used to push the
material downslope to the shovel. Gradalls were used
in areas too small for dozers to operate. The most
satisfactory method in the less steep areas was the use
of scrapers. Depth of cut could be controlled, and the
resulting surface was uniform. A minor amount of
ripping was required to remove hard projections in
weathered areas. The stripping for Zones 2 and 3 re-
sulted in a foundation equal in soundness to that of the
embankment to be placed thereon and consisted of the
removal of topsoil, overburden, and weathered rock to
a surface of definable rock structure.
Core Trench Excavation. Core trench excavation
provided a foundation for the impervious Zone 1 em-
bankment and included the removal of moderately
weathered rock to expose a hard dense surface. The
bulk of the excavation was systematically drilled and
blasted and the material loaded by shovel.
Foundation preparation in the core trench, subse-
quent to the initial excavation and immediately prior
to impervious embankment placement, consisted of a
thorough cleanup of the sound rock surface. Surface
preparation included handbarring and high-velocity
air or air-water cleaning to remove all loose or un-
sound rock. Fissures, seamg, shear zones, or small
areas of adverse slopes were filled or corrected with
backfill concrete. Slush grouting also was done where
open seams were encountered.
Grout Gallery Excavation. Grout gallery excava-
tion provided a trench within the core trench for the
concrete grout gallery. As this excavation was general-
ly in sound rock, drilling and blasting were required.
Final cleanup was performed by washing downslope
with water jets.
Core Block Excavation. All decomposed, weath-
ered, or crushed rock or similar unsuitable foundation
material were excavated to hard fresh rock which pro-
vided an impervious foundation after grouting. Final
foundation cleanup was performed with water jets
after the forms were in place and just prior to placing
concrete. After initial stripping, surficial weathered
material and foundation excavation for the core block
including channel alluvium involved removing about
238,000 cubic yards of material. For comparison, the
concrete volume of the core block was 283,000 cubic
yards.
Figure 95. Stage 2 D,
Figure fo. 3iag
119
Factors Affecting Contractor's Progress. Actual
excavation overran estimated bid quantities by a sub-
stantial margin. Bid quantities are compared with cur-
rent actual excavation quantities in the following
tabulation:
Bid Estimate Actual Pay Estimate
Class of Excavation (cubic yards) (cubic yards)
Stripping 2,860,000 4,844,300
Core Trench 690,000 1,112,200
Grout Gallery 30,300 55,500
In general, the requirement that excavation for
stripping and core trench be carried to a surface de-
fined in accordance with foundation requirements re-
sulted in the removal of more weathered rock than had
been contemplated. At least four slides developed in
areas in which excavation was considered complete.
The largest occurred on the left abutment, upstream
from the core trench. A section approximately 150 feet
in length and 40 feet high moved away from the hill-
side in a broken mass. Heavy rains in December 1964
saturated the material, and apparently small cracks
above this slide became filled with water. This result-
ed in the formation of a much more extensive slide, the
top of which extended above elevation 700 feet. Ulti-
mately, about 100,000 cubic yards of material was
removed from this slide area.
Core Block
The core block is a mass concrete structure 900 feet
long and is positioned approximately 700 feet up-
stream of the long chord and parallel to the dam axis.
Wood forms, constructed in place (Figure 97), were
used for concreting on foundation rock, and their use
continued until the blocks reached sufficient height to
use steel forms. From this point, steel cantilever panel
forms were used. A hydraulic crane, operating on top
of the blocks, was used to raise and set forms (Figure
98). The crane was moved from block to block by
means of a high line. The high line, the same one used
at Glen Canyon Dam, was of 2S-ton capacity (Figure
99). The main cable or "gut" line was 3 inches in
diameter and spanned 1,400 feet. Two rail-mounted
steel towers on opposite sides of the canyon provided
the anchorage and support for the cable (Figure 100).
The towers had a 400-foot travel parallel to the River.
A tramway traveled on the cable and carried an 8-
cubic-yard placing bucket. All points within the core
block area could be reached with this piece of equip-
ment.
The majority of the concrete in the core block was
two-sack 6-inch maximum size aggregate with pozzo-
lan to effect a lower heat of hydration for the mass
concrete. In areas around the galleries and the up-
stream face of the core block, an enriched three-sack
mix with pozzolan was used. Working limit of the
slump as delivered was 1'/^ inches and a maximum
temperature of 50 degrees Fahrenheit was required.
The temperature of the concrete for the core block
was controlled by cooling of aggregate and by the use
of cold water.
25-Ton-Capacity Cablewoy
120
The cooling plant was composed of five silos, each
of 210-ton capacity; three refrigeration units; and
three boilers. Cooling of the rock was accomplished by
evaporation. The silos were filled from the top with
moist aggregate, sealed, and a partial vacuum applied.
Under reduced pressure, the moisture from the aggre-
gate evaporated, causing a cooling effect or heat loss.
The cooled material then was discharged from the
bottom of the silos onto an insulated belt and carried
to the finish screens at the top of the batch plant. This
cooling plant was more theoretical than practical and
any deviation from ideal conditions caused a chain of
troubles. It was found that the use of ice in place of
water was more reliable than the elaborate aggregate
cooling plant. On subsequent portions of the contract,
ice was used in place of the aggregate cooling plant.
The concrete batch plant was a fully automatic unit
with three 4-cubic-yard mixers. The cement silo con-
tained 7,000 barrels and the pozzolan silo had 265 tons
of storage. The mixers discharged into a "gob hopper"
where the fresh concrete was held momentarily until
dumped into the rail-mounted transfer cars. Then the
concrete was transported from the batch plant to the
cableway loading dock by rail. Two 8-cubic-yard hop-
per cars were constructed for this purpose, and each
was pulled by a small diesel locomotive. An 8-cubic-
yard pneumatic bucket on the high line was used for
concrete placement.
Treatment of cracks which developed in the core
block are covered in a later section of this chapter.
Grout Gallery
The grout gallery is located in rock below the final
excavation in the core trench (Figure 101). Construc-
tion was initiated early in October 1963. However, the
first 14 months of activity amounted to only a small
effort and was used to take up work slack at the core
block and Thermalito Diversion Dam which was in-
cluded in the construction contract for the Dam.
With the Zone 1 embankment placement scheduled
to begin in December 1964, the contractor accelerated
gallery construction. However, heavy rains created
difficult working conditions and slowed progress con-
siderably. Despite weather shutdowns and associated
difficulties, the contractor was able to construct the
gallery from the core block up both abutments well
ahead of the embankment placing operations.
Concrete for the grout gallery was delivered from
the core block plant and the Thermalito Diversion
Dam plant prior to construction of the grout gallery
plant in October 1964. This plant was a fully auto-
matic unit with a single 3-cubic-yard mixer.
During the mixing cycle, aggregate, sand, and ice
were weighed in batch amounts and delivered to the
mixer by belt. The cement and pozzolan were
weighed separately in a weigh hopper mounted above
the mixer and were discharged directly into the mix-
ing drum. Admixtures were metered by commercial
dispensers and entered the mixer with the mixing wa-
ter. A 3-cubic-yard wet-batch hopper was located di-
rectly below the discharge gate of the mixer, and the
fresh concrete was held there momentarily before be-
ing dumped into agitator trucks for transportation to
the site. Two 1 -cubic-yard buckets and a truck crane
were used for placement.
The gallery segments were about 30 feet long and
constructed in two lifts, which consisted of an invert
placement and an arch placement. Interior forms were
the same as had been used in the core block galleries.
They were steel panels of 2-foot sections and were
assembled at the placing site while the walls of the
excavation served as the outside form for the trench
section of the gallery. Exterior forms were required
only in the projected section of the gallery. These
were made of plywood or shiplap panels and assem-
bled in place.
During the construction period, access ports were
Figure 100. Rail-Mounted Steel Towers
Figure 101. Grout Gallery
121
left open at various locations along the gallery for ease
of access and to facilitate grouting operations. These
were sealed as the embankment progressed upward.
At the left and right grout gallery portals, two fans
powered by ^-horsepower, squirrel-cage, induction
motors were installed to provide ventilation through
the gallery.
Core Block Access Tunnel
The core block access tunnel is located in the left
abutment of Oroville Dam. It is appro.ximately 780
feet long and has a finished inside diameter of 7.5 feet.
At a point approximately 30 feet from the end of the
tunnel, there is a drain shaft that empties into Diver-
sion Tunnel No. 2.
Approximately 566 feet of left exploratory tunnel
No. 3 were utilized for the access tunnel, and the
remaining 214 feet were driven by a subcontractor.
The tunnel was lined by means of a pumpcrete set-
up using steel panel forms. The concrete with 1 '/-inch
maximum size aggregate was supplied from a plant
located on the right abutment, upstream from the in-
let portal to Diversion Tunnel No. 1.
Production of Embankment Materials
As discussed in detail near the beginning of this
chapter, material for construction of the Oroville
Dam embankrhent came from borrow areas adjacent
to the Feather River and the Oroville Airport, south-
west of the City of Oroville (Figure 62). In addition
to mining the material for the dam embankment,
training dikes, weirs, and a spillway were constructed
in the borrow areas to prevent dredger tailing sands
from being carried into the river channel during high
river stages.
Figure 102. Bucketwheel Excavator
Pervious. The contractor used three different and
distinct methods of excavating the dredger tailings.
These methods were:
1 . A bucketwheel excavator with a conveyor system
2. Two dragline buckets and haul by bottom-dump
wagons
3. A scraper spread push-loaded by dozers
Approximately two-thirds of the pervious material
was excavated by the bucketwheel excavator. The re-
mainder was removed by the other methods.
The bucketwheel excavator had a rotating wheel 30
feet in diameter and was equipped with eight buckets
of 1.8-cubic-yard-capacity each (Figure 102). The ex-
cavator dug 30-foot-wide strips into the piles of
dredger tailings, rotating through an arc of 90 degrees
before moving along parallel to the face of the piles.
For the first three passes, material was delivered to a
field conveyor system from the belt mounted on the
excavator (Figure 103). On the fourth and successive
passes, when the distance from the excavation to the
conveyor was excessive, a 200-foot-long transfer con-
veyor was joined to the excavator (Figure 104). When
the width of excavation reached 300 feet, the field
conveyor system was moved. Tractors, at intervals of
150 to 200 feet, moved along the length of the portable
system and skidded the conveyor assembly approxi-
mately 2 feet sideways. This produced a severe bend-
ing in the rails which straightened out as the succeed-
ing sections were skidded. As the tractors reached the
end of the conveyor system, the direction of travel was
reversed and another 2 feet of move accomplished.
This procedure continued until a full 300-foot move
was made and the conveyor was again adjacent to the
excavator. The moving of the portable conveyor sys-
122
tern usually was done on weekends when production
was not needed for embankment placement.
The portable conveyor usually fed a fixed conveyor
located at the edge of the borrow area being mined.
The fixed conveyor, which was up to 3 miles long,
moved material into a hopper which discharged to an
elevating belt that fed a shuttle belt which distributed
material over ten hoppers at the loading station. These
loading hoppers loaded 40-car trains (Figure 105).
The train loading station was moved along with the
permanent conveyor after the northern borrow areas
were excavated.
Two draglines equipped with 1 1-cubic-yard buckets
loaded a fleet of 100-ton bottom-dump trucks that
hauled the material excavated by the draglines to a
loading station. The trucks dumped into a hopper that
fed the elevating belt; otherwise, the loading station
was identical to the one used to load the trains.
The scraper spread was virtually the same spread
used in the impervious material excavation and oper-
ated in the pervious area during "down time". The
spread consisted of single- and double-unit pushcats
assisting 20- to 50-cubic-yard-capacity scrapers in ex-
cavating, loading, and hauling the material.
An elevating belt loader was used by the contractor
to mine areas inaccessible to other excavating units.
The hopper of the loader was fed by several dozers.
The load discharged directly into a hopper set over the
fixed conveyor system or into the hauling units, which
hauled to a loading station.
Impervious. The impervious material was of the
Red Bluff formation deposited as a river flood plain in
an area immediately adjacent to the Oroville Airport.
In March 1964, the contractor began excavating the
material with a diesel power shovel equipped with a
3-cubic-yard bucket. A nearly vertical face was ex-
cavated with the material hauled by bottom-dump
trucks to the loading station for processing. Process-
ing consisted of screening the material to reject all
rock and clay lumps in excess of 3 inches. This method
of excavation proved to be unsatisfactory since the
compacted clay close to the surface did not break
down during excavation or screening.
In July 1964, the contractor was allowed to change
the excavation method. Scrapers were push-loaded
down a 3:1 slope, cutting a thin slice through each
stratified layer to the full depth of the pit.
The scrapers dumped into hoppers feeding two vi-
brating screens where the plus 3-inch material was
removed. This was the only processing of the impervi-
ous material required other than minor moisture con-
ditioning. Material passing the screens was
belt-conveyed to a shuttle conveyor that distributed to
ten metal bins from which ten railroad cars could be
loaded simultaneously (Figure 106).
Figure 104. Transfer Conveyor and Bucketwheel Excavator
Figure 105. Pervious Loading Static
Figure 106
Impervious Loading Station
123
Figure 107. Haul Route
124
During the winter season, placement of clayey Zone
1 material occasionally was interrupted by rainfall;
however, delays were minimized by protecting bor-
row material from saturation. A selected area was
sloped to drain and covered for protection during the
rainy season. During the 1964—65 rainy season, an 8-
mil clear polyethylene cover was used. An asphalt
membrane was used during subsequent rainy seasons.
Training Dikes. A system of training dikes was
constructed around the pervious borrow areas to pre-
serve and maintain the existing channel of the Feather
River.
A sheet piling weir was included in each dike sys-
tem so that the water levels on each side of the dikes
would be equal and thus prevent washing of the dikes
due to differential pressures.
Materials Hauling Facilities
The haul facilities consisted of a railroad (Figure
107) that ran through the borrow areas and along the
Feather River to a car dumper at the Dam site, and a
system of belts and transfer points that delivered the
material to a truck hopper on the embankment. It took
approximately 14 minutes to load a train under nor-
mal conditions at either type loading station and ap-
proximately 50 minutes for a train to make a round
trip from the borrow area to the dumper and back.
The average haul distance was about 12 miles.
When the train arrived at the Dam site, it would
pull onto the dumper, spotting the first two cars over
the dumper. After spotting, the locomotive would de-
tach itself from the gondola cars, go to a tail track, pick
up a train of empties, and return to the borrow area
for reloading. The dumper inverted the two spotted
cars (Figure 108) and then proceeded to empty the
rest of the train two cars at a time. A "pusher bar"
built into the car dumper moved the cars. The cars
Figure 103. Automatic Car Dumper
were equipped with rotating couplings so that it was
not necessary to uncouple them for dumping. When
a complete train was emptied, it was allowed to roll
down an inclined grade to the tail track to await haul-
ing back to the borrow area. Forty-five to fifty trains
were dumped in a 24-hour period, a rate compatible
with the production from the borrow areas. Embank-
ment placement rates averaged nearly 500,000 cubic
yards per week. The borrow and hauling functions
frequently had to operate on Saturdays to keep up
with the placement. The surge piles at the Dam pro-
vided the needed flexibility in the system.
The car dumper discharged onto a conveyor belt
which carried the embankment material across the
Feather River. This belt and other components of the
conveyor system at the Dam are discussed in a subse-
quent section of this chapter.
Each train was powered by tandem, diesel electric,
2,500-horsepower locomotives pulling 42 railroad gon-
dola cars. Although the contractor had four complete
trains with 12 spare gondola cars, only three sets of
locomotives were used at one time, with the fourth set
being used for switch engines or for standby. This was
possible since one train of gondolas was being unload-
ed while the other three were on the tracks.
Dam Embankment
The maximum section of the multizoned earthfill
embankment is shown on Figure 60. Zones 1, lA, IB,
4, and 4A are impervious material. The mass of the
Dam is made up mainly of Zone 3 (the pervious shell)
and Zones 2 and 2A (transition zones). A drain sys-
tem made up on Zones 5A and 5B was included in the
downstream shell.
Chronology. The first embankment placement in
Oroville Dam was made upstream of the core block on
September 16, 1963. The maximum height for the em-
bankment, prior to April 1, 1964, was planned to be
elevation 290 feet, 10 feet below the parapet wall of the
core block. This would allow a flood to pass over the
core block without damage to the upstream embank-
ment. The winter of 1963-64 was dry, work proceeded
ahead of schedule, and the contractor was allowed to
place fill above this elevation on the right abutment
outside of the channel area. This action helped to as-
sure that the 1964 cofferdam would be completed to
elevation 605 feet prior to the 1964—65 winter, so that
the River could be diverted through the diversion tun-
nels. In December 1964, less than a month after the
605-foot elevation was reached, a new flood of record
(approximately 250,000 cfs) occurred and was con-
trolled through the diversion tunnels with negligible
downstream damage. Without the partially completed
Dam, the disastrous floods of 1955, in which 38 lives
were lost and $100,000,000 damage occurred, would
have been exceeded. After the flood subsided, place-
ment of the material downstream of the core block
was started. Three years later, on October 6, 1967,
Oroville Dam was topped out at elevation 922 feet.
125
Figure 111
Construction Equipment. The placing equip-
ment on the embankment included:
14 100-ton bottom-dump trucks
3 Dozers
3 Loaders
2 6,000-gallon water trucks
1 Truck ballasted with steel plate to give 100-
ton wheel-load equivalent
1 100-ton compactor
1 100-ton contractor-fabricated compactor
3 Compactor rollers used in triplex
In addition, several pieces of equipment not normal-
ly found on a construction project were used:
1. The conveyor carrying material over the Feather
River from the car dumper was 2,380 feet long and
carried up to 12,000 tons per hour on a steel cable belt
72 inches wide (Figure 109). It delivered to a traveling
stacker that traversed 1,400 feet of stockpile; its belt,
96 inches wide, discharged at a distance of 60 feet over
a reclaim tunnel (Figure 110).
2. The reclaim tunnel, constructed of 1,590 feet of
multiple-plate arch, had an interior height of 18 feet.
Gates and feeders in the tunnel roof consisted of 23
specially designed undercut gates, feeding one of two
rail-mounted traveling chute cars, which fed a 72-inch
belt (Figure 111). Selection could be made through 19
gates and vibrating feeders to proportion and blend
sand into the cobbles to produce material for the tran-
sition zone.
3. Four multipurpose distribution conveyors (Fig-
ure 112) carried material from the stockpile to the
1,000-ton truck-loading hopper (Figure 113). Each of
the conveyors was set up for a haul of 2,300 feet or less.
Each was powered by two 1,000-horsepower motors.
The conveyor was made up of steel sections 25 feet
long.
4. A crawler-mounted pivoting and luffing transfer
conveyor (Figure 114) fed the truck-loading hopper
and completed the system for delivery of fill material.
The transfer conveyor was designed initially to be set
up in a 12-degree down position. Then, as the fill
progressed, and by a series of ramps, the angle was
increased to its maximum 16-degree up position. This
provided for a possible range in the truck-loading hop-
per of 140 feet, with a single position of the feeding
conveyors.
5. A bin stored up to 1,000 tons as a surge for truck
loading. Through four hydraulically operated gates, it
loaded two 100-ton trucks in as little as 8 seconds. The
bin was portable, and it was usually kept above the
elevation of the fill so that the trucks were loaded
downhill to assist acceleration to maximum speed.
This resulted in the minimum number of trucks need-
ed for hauling.
Construction Operations. Zone 4, the impervious
upstream core below elevation 290 feet, was construct-
ed of selected fine material obtained from the abut-
ment stripping operation. A 100-ton pneumatic roller
126
^■Jl
was specified for compaction. The lift of Zone 4 cover-
ing foundation rock was placed 2 to 3 inches thick and
hand-compacted with gasoline-powered whackers and
air-operated "Pogo Sticks". The abutment rock was
covered in the same way as the embankment pro-
gressed; then the 100-ton roller made four coverages
(two passes equal one coverage) of all the material
accessible to it.
Zone 3 was constructed of coarse dredger tailings
which contained sound rock with a specific gravity of
approximately 2.9. This material, which was mostly
minus 6-inch with some larger cobbles, was suitable
for use in its natural state. Bottom-dump trucks depos-
ited their loads in 60-foot-long windrows which were
spread by rubber-tired dozers. The required lift thick-
ness was a maximum of 24 inches after compaction.
Two coverages of the towed triple vibratory roller
were used for compaction.
The downstream face of the Dam was constructed
to an approximate slope by stepping in successive lifts.
The final surface finishing was done with dozers trim-
ming up the slope. Then, two 30-foot-long railroad
rails were dragged down the slope.
Selected rock material from the Oroville Dam spill-
way excavation was placed in parts of the outer up-
stream Zone 3. Side-by-side test fills were constructed
to compare the characteristics of the shot rock with
the dredger tailings. Gradation, placing, and compac-
tion of the spillway rock were similar to that required
for Zone 3 dredger tailings, except the maximum size
was decreased to 18 inches.
Zone 4A, a special compressible zone obtained from
abutment strippings, was constructed just upstream
of the core block to compress horizontally when high
lateral soil pressures built up due to base spreading
during the 1964 construction season. To obtain the
moderate compaction required, only equipment travel
was used since the specified coverage by the triplex
vibratory roller gave too much compaction.
Zone 1 (the impervious core of the Dam) and Zone
IB (the 1964 cofferdam core) materials were con-
veyed to the embankment on the materials handling
system. In order to deliver these materials to the em-
bankment within the allowable moisture content lim-
its (plus or minus 1/2% of the designated moisture
content of the minus U.S. No. 4 sieve fraction), water
was added by spray bars at the conveyor transfer
points and in the reclaim tunnel.
The material was deposited on a scarified and mois-
tened surface in 100-foot-long windrows and spread
by rubber-tired dozers. Placing and spreading were
done parallel to the dam axis. Four coverages of a
100-ton pneumatic roller were required for compac-
tion. Rolling of Zones 1 and IB generally was done
parallel to the dam axis. Areas inaccessible to the 100-
ton roller were compacted in 6-inch lifts by a ballasted
truck loaded to give a wheel load equivalent to the
100-ton roller. Areas inaccessible to the ballasted truck
were compacted by hand-operated compactors. This
^a^fc*:>.S
Figure 114. Transfer Conveyor
127
abutment contact material, with not less than 60%
minus No. 4 sieve size, generally was manufactured on
the embankment by running Zone 1 material over a
portable vibrating screen.
Zone 2 serves as a transition filter zone between the
fine-grained impervious Zone 1 and the coarse-
grained Zone 3. This material is a combination of
gravel and sand occurring naturally in the borrow
areas or produced by blending the underlying sands
with the gravels. Placing and compaction of Zone 2
were similar to Zone 3. The one exception was that
the maximum lift thickness was 15 inches after com-
paction.
To impound and measure seepage into the down-
stream Zone 3 embankment at elevation 242 feet, a
small earth barrier was constructed of Zone lA
material. Zone 2A filters Zone 1 A. Materials and plac-
ing procedures were the same as for Zones 1 and 2.
Zone 5A, a horizontal drain, was constructed at ele-
vation 235 to 245 feet from downstream Zone 2 to the
downstream face. Zone 5B, a vertical drainage zone 20
feet wide, was constructed immediately downstream
from Zone 2. These zones were added after embank-
ment construction was underway because there was
concern over the amount of fines in the pervious
material that was being delivered to the Dam site. To
ensure that the downstream shell would remain dry,
these zones were incorporated into the Dam. Zones
5A and 5B were placed and compacted in the same
manner as Zone 3.
A zone of riprap was placed on the upstream face of
the embankment from elevation 605 to 922 feet and on
the downstream face of the mandatory waste area at
the downstream toe. Riprap for the upstream face was
graded rock up to 1 cubic yard in size. At the down-
stream toe, rock fragments from '/j to 2 cubic yards in
size were used. Most of the riprap was spillway rock
placed as the outer 6 feet, measured perpendicular to
the slope. The shot rock was hauled directly from the
spillway to the Dam.
Electrical Installation
Electrical work on Oroville Dam consisted of the
installation of two grounding grids along with two
test grids and the installation of the lighting and pow-
er systems in the grout gallery, core block, and instru-
ment houses.
Grounding Grids. Grounding grids (Figure 115)
were installed in two areas in the embankment as part
of the powerplant grounding system and were con-
nected under a completion contract covered in V'ol-
ume 1\' of this bulletin.
When the embankment reached elevation 290± feet,
the area for the location of grounding grid No. 1 was
bladed and "V" trenches were cut in the pattern of the
grid. Electricians placed the copper cables in the tren-
ches and cadwelded the cross connections forming the
grid. Sand backfill was placed over the cables and
embankment operations continued. Prior to the em-
bankment reaching elevation 615 feet in the location
for grounding grid No. 2, the grouting subcontractor
drilled four cable drop holes from the embankment
foundation to the crown of Edward Hyatt Power-
plant. Using a "fish" line, the drops were fed into the
holes from the Powerplant and pulled up to the foun-
dation level using the winch of a y^-wn truck. Prior to
grouting the holes, the drops were supported from the
top by wire mesh grips looped over 2-inch, schedule
80, steel pipe placed over the holes. Before grouting
began, the bottom of the holes at the powerhouse
crown were caulked. Using a small "tremie", about 25
feet of grout was placed in the bottom of each hole and
allowed to set, forming a plug capable of holding the
remaining grout needed to fill the hole.
When the embankment reached elevation 615 feet,
grounding grid No. 2 was installed similar to ground-
ing grid No. 1.
Lighting and Power Systems. In the grout gallery,
the power system consists of a 480- volt, 3-phase, power
distribution system which supplies power to each of
six electrical equipment panels and two gallery ven-
tilating fans. A 1 /4-inch rigid conduit was installed
throughout the gallery with pullboxes located at 200-
foot maximum intervals. Three No. 2 and one No. 12
RHW insulated conductors were pulled into the con-
duit. The No. 2 conductor provides power, and the
No. 12 conductor is used as a switch bus connecting
each of the lighting push-button stations for common
lighting control.
The 480-volt 3-phase power is supplied to the sys-
tem from the Powerplant through a distribution
board located in the grout gallery at Station 36-1-75,
the grout gallery connection to the emergency exit
tunnel. Connected to grounding grid No. 1, a No. 4/0
bare copper ground cable was installed throughout
the gallery system to provide grounding of all conduit
and electrical equipment.
Structural Grouting of the Core Block
As mentioned in the discussion of the core block
design, compressible Zone 4A material apparently
limited upstream horizontal earth pressures on the
unreinforced parapet protecting it through the initial
loading condition. However, when the downstream
fill was placed, pressures from that direction caused a
rotation of the parapet and cracking as shown on Fig-
ure 1 16.
The presence of cracking was first indicated in Oc-
tober 1965, when contact was lost with piezometer
No. 8, upstream of the core block at elevation 250 feet.
Tubing to the piezometer had been routed through
the core block concrete, near the top surface, and
beneath the parapet. In April 1966, the last instrument
routed beneath the "hinge point" was lost. Indications
continued through the summer of 1967, although no
adverse conditions were visible from within the gal-
leries except for a joint in the sump which started
leaking water at a rate of approximately 35 gallons per
128
f « |t-, ff ',:,
^rl| -'Z/ i^fS
:p
^ I I
■ ?^'\. I:
■ ' 1 1 !^-*
1 f? 1
■' Ji ?
^
4
u
«?
& ,
i^;
1
?5
;j :;',
R^
Figure 115. Electrical Grounding Grids
129
Stream
Flow
Figure 116. Cracking of Core Block
minute. Exploratory core drilling from the gallery
system was initiated in the suspect area beneath the
parapet wall. Open cracks, several inches wide, were
estimated by drilling action and visually observed by
a 20-foot-long periscope.
To minimize any further disruptive movements
which might be produced by future reservoir loading,
and to prevent reservoir seepage into the galleries and
through the core block, the cracks and all monolith
joints in the core block were filled with a neat grout.
Six thousand sacks of cement were injected under
pressure into the interlaced cracks and joint system.
The grout mixes used varied from one sack of cement
for one gallon of water to one sack of cement for five
gallons of water. Drilling and grouting were done in
stages from August 1967 through February 1968. Final
check drilling, with 450 feet of water head in the pervi-
ous zones acting on the core block, indicated the
cracks and joints were effectively filled and sealed off
from any significant reservoir seepage. The grouted
cracks and joints were instrumented to detect any fu-
ture movements. There has been only minor harmless
movement in the five years since the instruments were
installed.
Diversion Tunnel No. 2
Diversion Tunnel No. 2 was excavated from the
outlet portal to within 54 feet of the inlet portal to
protect against possible floods. Open-cut excavation of
the outlet portal channel began on January 3, 1963,
disclosing that the left channel wall contained unsuit-
able rock; therefore, the slope was changed from Y^-.l
to I'/::!- In addition, the left wall and headwall were
both rock-bolted with expansion-shell groutable rock
bolts before starting excavation of the crown drift. A
5-foot-square pattern with chain-link fabric and head-
er steel was used. Thirty-foot-long crown bars (No. 18
rebars) were installed on 12-inch centers 2 feet above
the tunnel "B" line and grouted.
Excavation similar to that for the outlet portal was
started on the inlet portal in February 1964. Because
of the extremely weathered rock at this portal, the
contractor chose to drive an 1 1- by 1 1-foot exploratory
crown drift through the 54-foot plug that was left in
for flood protection. After a 1-inch-wide crack was
observed over the portal at Station 3-1-20, the face was
moved 3'/4 feet upstream in order to accommodate the
revised structural support. The additional support
steel and knee braces were anchored in concrete. Ad-
ditional 15-foot rock bolts were installed above the
portal face. Tunnel excavation resumed and removal
of the rock plug was completed on July 31, 1964.
Tunnel excavation, concreting, and grouting were
accomplished in the same manner as in Diversion
Tunnel No. 1, except that the invert was concreted
with a slip form and a steel liner was placed down-
stream of the river outlet location. To facilitate con-
version of the tunnel into its role as a tailrace tunnel,
the draft-tube stubs; auxiliary intake shaft and river
outlet, air supply, and pressure-equalizer tunnels were
excavated, lined, and capped off with removable con-
crete knockout plugs during the initial construction
period. The main tunnel was completely excavated
and lined prior to November 1964.
Diversion Tunnel No. 2 was in service as a diver-
[
130
sion facility for the winter seasons of 1964—65 and
1965-66. During the summer of 1965, draft-tube stubs
Nos. 5 and 6 were opened up, completely constructed,
and resealed.
In the summer of 1966, Diversion Tunnel No. 2 was
closed permanently by the installation of the mass
gravity concrete plug. Streamflow continued through
the adjacent lower Diversion Tunnel No. 1. Concur-
rent with this was the partial construction of the valve
chamber and draft tubes Nos. 3 and 4 and removal of
the knockout plugs from draft tubes Nos. 1, 2, 5, and
6. The knockout plugs for the auxiliary intake shaft
and river outlet, air supply, and equalizer tunnels also
were removed at this time.
Installation of the last 14 feet of 72-inch conduits
and the valves was delayed for the 1966-67 winter
season due to manufacturing problems with the con-
duit and valves. This necessitated installing bulkheads
at the upstream end of the conduits to prevent flood-
ing of Diversion Tunnel No. 2 and constructing a
blockout for the valves and a portion of the conduit at
the downstream end of the tunnel plug.
Wedge seats (Figure 117) for the plug were excavat-
ed from the tunnel lining by blasting. The deepest
holes at the upstream end of the wedges were 1 foot,
and succeeding holes progressing downstream in each
wedge were shortened to develop the taper. All loose
material was removed with chipping guns prior to
placing concrete. Stainless-steel grout stop was in-
stalled around the full circumference of the plug at
each end. This was done concurrently with the con-
crete work.
Concrete was placed in seven lifts of varying depths
because of the installation of the two 72-inch conduits
in the plug. An 18-foot-long blockout was left in the
downstream end of the plug from elevation 223 feet
up. This was to allow easy installation of the remain-
Figure 117. Wedge Seat Removal in Diversion Tunnels
der of the conduits and the spherical valves.
Under the specifications, the plug was to be 2'X-sack
6-inch maximum size aggregate concrete. The con-
tractor proposed to pumpcrete the placement, which
would require 4'/2-sack I'/j-inch concrete. This was ap-
proved with the requirement that the concrete be
cooled to keep temperature rise equal to or less than
that which would have been encountered using the
mass concrete.
To accomplish this stipulation, the contractor in-
stalled 1-inch-diameter, thin-wall, steel tubing in all
but the top lift of the plug which had been specified
to be pumped. The tubing was on 3y2-foot centers and
circulated cold water from a cooling plant at the
downstream portal. The cooling was discontinued af-
ter 14 days on each lift.
Equalizing Tunnel
The 8-foot-diameter pressure-equalizing tunnel
connecting the two diversion tailrace tunnels (Figure
68) was excavated and concreted in conjunction with
construction of Diversion Tunnel No. 2.
In the vertical portion of the tunnel, stopper and
jacklog drills were used exclusively, working from a
temporary platform. Fifteen-foot rock bolts were in-
stalled around the perimeter of the collar before exca-
vation started, and additional 10-foot rock bolts were
installed within the raise following each succeeding
blast. The installation of the rock bolts stabilized the
area as no movement was noted.
While the raise was being driven, the contractor
decided to continue excavation up to the valve air-
supply tunnel. The additional raise excavation at this
time probably was faster and safer than sinking a shaft
from the valve air-supply tunnel down to the equaliz-
ing raise.
The horizontal portion of the tunnel was mucked
out with a slusher bucket attached to an air-operated
tugger. Support consisted of rib steel left over from
Diversion Tunnel No. 1 placed on 4-foot centers.
Valve Air-Supply Tunnel
The 8-foot-diameter, valve, air-supply tunnel (Fig-
ure 68) begins approximately 158 feet downstream
from the equalizing tunnel, rises vertically 30 feet,
then parallels the main tunnel until intersecting with
the extension of the equalizing tunnel rise. Excavation
and equipment used were essentially the same as used
for the equalizing tunnel.
River Outlet Works
Between April and November 1967, the valve cham-
ber was completed and the river outlet works was
installed. The remaining portions of the conduits, two
72-inch spherical valves, and two 54-inch hollow-cone
valves connected to the conduits through the concrete
plug in Diversion Tunnel No. 2 were installed the
previous summer and fall. The outlet works was put
into service November 15, 1967, on the day following
the closure of Diversion Tunnel No. 1.
131
The operating center for the river outlet is the Sta-
tion 1 control cabinet within the river outlet control
chamber. The 480-volt 3-phase pov/er was provided to
the cabinet by the Oroviile Powerplant completion
contractor. From this cabinet, lighting circuits were
provided for the grout gallery, emergency exit tunnel,
river outlet control chamber, river outlet access tun-
nel, and river outlet valve chamber. Power also was
provided for the 220-volt, single-phase, spherical-
valve-pit, sump pump. Power, control, and position
indicator lamps for the fixed-cone dispersion valve
operators were provided. Station 2 cabinets for local
control of the spherical valves were mounted in the
valve chamber.
River Outlet Access Tunnel
Convergence of the valve air-supply tunnel, equaliz-
ing tunnel, valve chamber enlargement, and the river
outlet access tunnel in the same immediate area (Fig-
ure 68) presented a delicate excavation situation.
Overbreak was experienced in the river outlet access
tunnel collar, and many IS-foot-long rock bolts were
installed along with wire fabric. The lower portion of
the access tunnel was horizontal, and several 10-foot
rock bolts were installed to stabilize this portion im-
mediately behind the collar. The remaining 90% of
the tunnel was inclined approximately 35 degrees and
was excavated essentially the same as the other small
tunnels. It was necessary to build a working platform
from which to drill due to the steep slope. No struc-
tural steel was used.
Emergency Exit Tunnel
Portal excavation on the 8-foot-diameter emergency
exit tunnel (Figure 68) was started May 14, 1964, after
Oroviile Dam grout gallery excavation essentially was
completed beyond the portal location. Crown bars
(No. 18 rebars) were installed on 12-inch centers and
grouted to stabilize blocky, slightly iron-stained, fresh
rock at the opening. Nine W4X 13 steel ribs were in-
stalled on 4-foot centers in the portal area. Jacklegs
were used to drill all holes, and an overshot mucker
and shuttle car were used for removing shot rock. Five
8-foot-long rock bolts were installed on 4-foot centers
in the arch throughout the 575 feet of tunnel. Numer-
ous seams crossed the tunnel but did not create any
problem.
Closure Sequence
By the fall of 1967, the river outlet in Diversion
Tunnel No. 2, the connections between Diversion
Tunnel No. 2 and the Powerplant, and the other tun-
nels were complete. Connections to Diversion Tunnel
No. 1 had bulkheads so that releases could be made
through the river outlet while Diversion Tunnel No.
1 was being converted to its tailrace mode. The main
dam and saddle dams were topped out, the spillway
was nearly completed, and the reservoir was cleared.
Tunnel No. 1 remained to be plugged and converted
to a tailrace (Figure 68).
In 1966, the Oroviile Dam Consulting Board ex-
pressed two concerns about the closure of Diversion
Tunnel No. 1, which started on November 14, 1967.
The first was a concern that after the first bulkhead
gate was positioned, the force of the flowing water
might be too great for the second gate to seat com-
pletely. The second concern involved a question of
whether the bulkhead gates were sufficiently strong
in the event of rapid filling of the reservoir immediate-
ly after closure. The planned earlier closure had been
delayed by several factors to the start of the normal
storm season. Measures, including the addition of the
stoplogs and the concrete plug behind the steel bulk-
head discussed later, were added to the closure se-
quence to assure its success.
For the seating of the gates, concrete stoplogs (Fig-
ure 118) were placed across each opening during clo-
sure. By producing quiet water at the bulkhead gate,
a diver was able to clean the slots so that the gate could
be lowered without the pressure of running water.
(By prior arrangement with upstream dam owners,
the riverflow was held to less than 1,000 cfs.) After the
first bulkhead gate was dropped into place, the stop-
logs were removed from that side, moved to the other
side, and the procedure was repeated. There was a
substantial amount of leakage around both gates after
they were dropped into place. The contractor succeed-
ed in sealing the right gate by pumping a 1:1 mix of
bentonite and Silvacel followed by fine sand into the
edges of the gate. This was ineffective on the left gate.
A section of 2-inch hose wedged between the slot and
the gate on the left side succeeded in diverting the
flow to the invert where it could be picked up in a
drain.
After the water was controlled, work began on the
building of the form for the 30-foot-long upstream
Figure 118. Lowering Stoplogs
132
plug to buttress the bulkhead gates. A 35-foot-diame-
ter wood form was constructed adjacent to the trailing
edge of the divider in the intake structure of the tun-
nel. The steel bulkhead gates served as the upstream
form. The placing operation was continuous except
for minor breakdowns of equipment and a few shut-
downs to allow the air to clear in the tunnel. No at-
tempt was made to completely seal off the top lift of
the plug as its only function was to provide safe work-
ing conditions in the tunnel while the permanent plug
was being constructed.
As soon as the upstream plug was completed, the
contractor moved to the permanent plug near the mid-
point of the tunnel. The wedge seats were removed in
the manner used in Diversion Tunnel No. 2, and an
18-inch drain pipe was installed in the invert of the
tunnel. The permanent plug then was constructed in
five 7-foot lifts. Cooling pipes were installed in an
identical method to Diversion Tunnel No. 2.
Prior to placing the last lift, the contact grout sys-
tem was installed. A multiple header hookup was used
on both pressure lines of the system with a return line
connected to the vent pipe at the crown.
The 18-inch drain pipe installed in the plug at the
invert was backfilled by placing a 90-foot piece of 10-
inch thin-wall pipe inside the drain line and support-
ing it off the invert on chairs. Concrete was pumped
through the thin wall into the drain pipe and forced
to the upstream end. Pumping continued, forcing the
concrete to reverse direction and flow back over the
thin wall and out the downstream end of the drain
pipe. The 10-inch line was cut and left in place.
While the tunnel plug was being completed, drain
holes were drilled in the downstream half of the tun-
nel and, as soon as the tunnel plug was completed, the
plugs connecting to the draft-tube and pressure-equal-
izing tunnels were removed. All work in Diversion
Tunnel No. 1 was completed on March 15, 1968.
The steel bulkheads on the draft tube-tunnel No. 2
connections were removed from the floor of the tun-
nel shortly thereafter. Downstream demands were
met by releasing water stored in the Thermalito facili-
ties.
Spillway
Clearing. Appro.ximately 1 1 5 acres, 40 in the spill-
way and chute and 75 in the emergency spillway area,
were cleared of brush and trees. The area below the
emergency spillway was not cleared.
Excavation. The three major methods used to ex-
cavate the spillway were as follows: bottom-loading
scrapers and pushcats, a loader with cats feeding the
belt and bottom-dump wagons hauling the material,
and two large shovels.
In general, the scrapers were used to strip the area
to rock. The shovels were used to excavate the rock
after it was drilled and shot. The loader was used
similarly to the scraper operation, the main difference
being that it was possible to work this operation in
rougher terrain as up to eight dozers were used to
push material to the feeding hopper. A road was grad-
ed out below the hopper and the bottom-dump wag-
ons could drive under the hopper to load.
All drilling for blasting was done by percussion-
type drills mounted on tracks and powered by air. The
patterns varied greatly from area to area. The most
generally used pattern was 8 by 8 feet; however, pat-
terns ranging all the way from 2'/2 by 2/4 feet to 15 by
1 5 feet were used depending on the area, type of rock,
and excavation objective. Excavation near structure
lines had to be controlled to avoid damage to the rock
to be left in place, and 840,000 tons of riprap for Oro-
ville Dam had to be produced.
In part of the emergency spillway, an additional 10
feet of excavation was required to reach acceptable
foundation rock, resulting in considerable additional
time for excavation and placement of the backfill con-
crete to subgrade.
Approximately 90% of the chute foundation re-
quired blasting to reach grade. The only extra excava-
tion directed was removal of a few clay seams in the
foundation and a few areas where slope failures oc-
curred.
The depth of overburden in the approach channel
was deeper than estimated and the slopes had to be
changed from '^-A to I'/i-.l to prevent sloughing as the
excavation reached the final grade.
The slopes in the flood control outlet gate section
proved to be of a lower quality rock than anticipated.
There were several large seams running parallel with
the chute. The planned anchor bars were replaced
with grouted rock bolts, pigtail anchors, and chain-
link surface covering in that area.
Drain System. The foundation drains designed
for the spillway included nearly vertical NX holes
drilled 65 feet into the foundation rock of headworks
Monoliths 25 and 26 and extensive perforated pipe
systems on the foundation surface under the head-
works, chute, and higher portions of the emergency
spillway weir. Much of the drain system on the foun-
dation surface was modified during construction.
The original 4-inch-diameter, horizontal, pipe
drains under the chute were redesigned in accordance
with a recommendation from the Oroville Dam Con-
sulting Board. The pipes were placed on a herring-
bone pattern to give them a downward slope and
enlarged to a 6-inch diameter. The longitudinal collec-
tor system was enlarged proportionally and modified
slightly. The effect of these modifications was to in-
crease the system's capacity and its self-cleaning abili-
ty. The pipes remained on the foundation enveloped
in gravel which projected into the reinforced-concrete
floor of the chute.
Similar drain pipes were impractical to place on
irregular rock surfaces under the headworks and
emergency spillway weir. The contractor was allowed
to substitute wooden formed drains of equal cross-
133
sectional area. These forms were cut to fit the irregu-
lar rock surface and remained in place after the con-
crete was placed over them.
Concrete. Concrete placement started on January
26, 1966. Mass concrete was placed monolithically in
all monoliths (other than 25 and 26, which contain the
gates) between the transition section at Station 18 -|- 30
on the emergency spillway and the east end of the
flood control outlet at dam Station 20-1-61.66. Mass
concrete also was placed in the emergency spillway
weir to the west of the transition. An on-site plant
discharged into 4-cubic-yard concrete buckets posi-
tioned on low-boy trucks which hauled to the placing
area where the concrete was handled and placed using
a track-mounted crane. Six-inch vibrators were used
to consolidate concrete. Concrete was placed in the
monoliths in lifts of 7 feet - 6 inches. Wooden starter
forms were used until 7-foot - 6-inch, cantilever, steel
forms could be used. An adjustable steel form was
used to form the curved or ogee section of Monoliths
1 through 20. The uppermost lift of the ogee section
was formed using wooden forms. Seven screed ribs
were shaped to the desired curve, between which pa-
nels were added as concrete was placed. When the
concrete would hold its shape, the forms were
removed and the surface finished. Structural concrete
was placed in Monoliths 25 and 26 of the flood control
outlet, the approach walls, the chute walls and invert,
and the terminal structure.
Flood control outlet concrete was placed by a track-
mounted crane. When the concrete reached an eleva-
tion that could not be reached by the crane, a con-
veyor-belt system was used. This conveyor system was
used mainly in the Monolith 26 half of the flood con-
trol outlet. The conveyor-belt system was used less in
Monolith 25 due to a more accessible area for a crane
to be positioned at Monolith 24.
Concrete placing for the spillway chute invert be-
gan on September 8, 1966. A conveyor-belt system was
used to transport the concrete from the chute banks to
point of placement. Concrete was transported from
batching plant to a conveyor reclaim hopper by "bath-
tub" trucks.
A 40-foot, steel-beam, slip form was used to screed
the concrete to invert grade. This slip form, along
with the discharge portion of the conveyor, rode on
steel rails positioned along each side of the chute slab
being placed. The slip form was propelled by the use
of a winch geared to keep pace with the placing of
concrete. This slip form was used chiefly on the steep-
er area of the chute. A smaller slip form was used to
screed concrete for the chute wall footings.
Chute invert concrete in the area of lesser slope near
the flood control outlet was placed by a truck-mount-
ed crane and concrete bucket. Terminal structure con-
crete of the chute also was placed in this manner.
Rigid wood forms were constructed to contain the
concrete in the chute walls. Windows were cut in the
backs of the wall forms through which concrete was
vibrated until it reached that level. A truck-mounted
crane and concrete bucket were used to place the con-
crete in forms. A leveling platform was made from
timbers to position the crane while working on the
steep portion of the chute invert. The total volume of
concrete placed was 165,000 cubic yards.
Electrical Installation. Lists were made of all elec-
trical conduits and equipment to be installed prior to
placing each lift of concrete. The lists were reviewed
whenever necessary to ensure the installation of con-
duits in their proper places. The ground cable was
completed as concrete was placed. All electrical con-
duits were in place before the electricians started
cleaning the conduits and blowing lines into them for
use in pulling the conductors through the conduits.
The standby generator was placed in the control
room. After it was started and checked, it was used to
operate the hoists because the temporary source of
power had been removed.
As the radial gates were installed, temporary cir-
cuits were run to the hoist motors so the hoists could
be operated and the gates checked before the controls
were activated.
Gate Installations. The concrete was blocked out
of the piers in the immediate vicinity of the trunnion
beams. The trunnion beam was placed over the ten-
sioning tendons and set to final alignment. The bear-
ing plates then were brought into contact with the
beams. When the trunnion beams and the bearing
plates were positioned, concrete was placed in the
blocked-out areas. After the concrete had achieved its
design strength, the rods were tensioned to design
loading and no rod failures occurred. After the ten-
dons were tensioned, the voids between the rods and
the sleeves were grouted.
The side-seal plates were aligned by swinging an arc
with a chain from the centerpoint of the trunnion.
After the plates were in proper position along the arc
of the gate, the plates were adjusted parallel to the
walls of the bay by transits. By the time the gates were
to be placed, the radial wall plates were within '/z inch
of their proper position.
The contractor chose to erect the gates in the bays
in their operating position. This method was used
because there was not enough work space to bring the
gate skins into the bay in one piece. Erection of the
radial gates was done as follows: (1) two halves of the
skin with the side seals attached were moved into
place; (2) horizontal and vertical members were bolt-
ed to the skins; (3) canted-arms and trunnions were
bolted in place; (4) the gate was leveled and aligned
and the two halves welded together; and (5) the gate
was lowered to its closed position and final adjust-
ments made to position the gate and seals.
Grouting Program
Foundation grouting for Oroville Dam consisted of
curtain grouting a single row of holes the full length
of the core trench and spillway crest, extending a max-
134
1!-
1,
imum depth of 200 feet into rock; blanket grouting of
the core trench and core block foundation; envelope
grouting over Diversion Tunnels Nos. 1 and 2 and the
Powerplant; and a minor amount of curtain grouting
from the Palermo outlet works tunnel (Figure 66).
Grout Curtain. The grout curtain for Oroville
Dam is located approximately along the upstream one-
third point of the core trench on the abutments and
the core block in the channel. This curtain was drilled
and grouted from the grout gallery to where the gal-
lery reached about elevation 750 feet, and from the
rock surface between elevation 750 feet and the dam
crest at elevation 922 feet. The dam and spillway cur-
tains join on the upper right abutment at dam Station
21 + 29. The plane of the curtain dips 75 degrees up-
stream where grouted from the gallery section and is
vertical where grouted from the rock surface. To con-
trol leakage and grout placement, the curtain was di-
vided into three zones.
Zone 1 extended 50 feet into rock and was drilled
and grouted in a minimum of two stages with a max-
imum hole spacing of 10 feet. Grouting pressures of 50
to 100 pounds per square inch (psi) were used in the
gallery; 25 to 50 psi from the rock surface.
Zone 2 extended 100 feet below foundation eleva-
i| tion 500 feet; above elevation 500 feet, the depth
' equaled one-fourth the potential reservoir head and
was drilled in one stage using packers with a max-
imum hole spacing of 20 feet. The normal grouting
pressure was 150 psi.
Zone 3 extended 200 feet below elevation 500 feet,
one-half the potential head above elevation 500 feet,
and was drilled in one stage using packers with a max-
imum hole spacing of 40 feet. The grouting pressure
ranged from 200 to 300 psi.
The total grout take was 23,763 cubic feet of cement
and the average was 0.28 of a cubic foot per foot of
0 i hole.
Blanket Grouting. The blanket grouting program
j consisted of shallow low-pressure grouting of most of
,1 the core trench and core block foundation upstream
ifrom the grout curtain. This sealed the many joints
I and shear zones that cross the foundation and also
J : consolidated areas of strongly fractured or weathered
',, I rock. Most blanket grouting in the core block was
, done after concrete placement.
, Spacing and depth of blanket holes were governed
[by the nature and extent of foundation defects en-
1 (Countered and by grouting results as the operation
i progressed. In areas of weathered or closely fractured
■ ; foundation, final hole spacing was as close as 5 feet and
holes were arranged more or less in an equilateral
pattern. In areas of fresh sparsely fractured founda-
tion, such as portions of the core block and lower
abutment core trench, holes were up to 40 feet apart.
(The general practice was to space the initial holes
oi |from 20 to 30 feet apart, then reduce the spacing if the
itli I initial holes took grout or if there was severe surface
leakage. Final spacing of most holes upstream from
the grout gallery ranged from 10 to 20 feet apart. In
addition to grouting from the core trench surface
ahead of embankment placement, 123 holes were con-
nected to the gallery with pipes and grouted under an
embankment cover of 100 feet to allow grouting at
pressures of 50 to 100 psi and eliminate surface leak-
age. Most holes were inclined 40 to 70 degrees from
horizontal and were aimed to cross steeply dipping
joints and shears a few feet below the foundation sur-
face. In general, holes ranged from 10 to 30 feet deep;
a few holes were as deep as 70 feet. The total grout take
was 13,745 cubic feet of cement and the average was
0.23 of a cubic foot per foot of hole.
Envelope Grouting. A grout canopy, extending
700 feet downstream from the tunnel plug section,
was constructed over both diversion tunnels and
around the underground powerplant to reduce inflow
into the plant and protect the concrete lining of the
diversion tunnels from a potential reservoir pressure
of 300 psi. The grout curtain for Oroville Dam extends
from the grout gallery to the downstream end of the
envelope to produce a continuous curtain above the
powerplant area (Figure 69).
Drilling and grouting were begun shortly after the
top heading excavation was completed through the
draft-tube section. All holes in each ring were drilled
to the full depth of the first grouting zone as the drill-
ing jumbo progressed downstream from ring No. 1.
Grouting operations followed six to eight rings be-
hind the drilling jumbo.
Reservoir Clearing
Clearing of the reservoir was planned to enhance
recreational use. Vegetation was not removed in cer-
tain areas to be submerged to provide fishery enhance-
ment. Public beach areas were grubbed of stumps and
roots. The plan also included an agreement with the
U. S. Forest Service and State Division of Forestry for
the prevention and suppression of fires during clear-
ing.
Elevation 640 feet was established as the lowest
stage to which the reservoir would be drawn down
under extreme conditions. Clearing of the area below
elevation 640 feet consisted of removal of all loose
floatable material. This included drift along the
streams, logs, windfall trees, and miscellaneous im-
provements. The area between elevations 640 and 900
feet, with the exception of areas of vegetation reten-
tion, was cleared of all trees, brush, and improve-
ments. All stumps and roots were grubbed out of the
840 acres of planned beach areas. In the remaining
7,660 acres above elevation 640 feet, stumps 6 inches or
less in height were allowed to remain.
Approximately 1,100 acres of vegetation retention
was provided above elevation 640 feet for the enhance-
ment of the reservoir fishery. In these areas, all conif-
erous trees over 25 feet in height and deciduous trees
over 60 feet in height were cut down and tied to their
135
stumps with wire rope. A total of nearly 7,000 trees
over 12 inches in diameter were cut and anchored
with '/^-inch galvanized wire rope, and a total of about
5,000 trees 12 inches or less in diameter were cut and
anchored with '/-inch galvanized wire rope.
The work of clearing timber and brush, between
elevations 640 and 900 feet, was performed in three
separate operations: (1) cutting timber and brush, (2)
raking and piling cut material for burning, and (3)
burning and final cleanup.
Cutting of timber and brush was performed with
dozer equipment and chain saws. The method of cut-
ting timber and brush was dependent upon roughness
of terrain and access. Dozers equipped with sharp cut-
ter blades, set at an angle, were used for cutting timber
and brush on flat and moderately steep terrain. On
steep terrain, a second dozer with a heavy-duty winch
cable was used to control the downhill movement of
a dozer with a cutter blade and to haul it back up the
slope. This operation of using two dozers on steep
terrain is known as a "yo-yo" method of cutting and
stripping hillsides. Chain saws were used for cutting
in areas not accessible to dozer equipment or for cut-
ting large trees in heavily timbered areas.
The work of raking and piling cut timber and brush
was performed by hand labor and by dozers equipped
with brush rakes or regular dozer blades. On steep
terrain, a "yo-yo" method was used to pile material in
windrows. In areas not accessible to heavy equipment,
chain saws were used to fell the timber and cut materi-
al into shorter lengths to facilitate hand piling and
burning. Dozers and labor crews were used to collect
and push together unburned chunks until completely
burned.
Burning was restricted to the winter months or as
permitted by the Division of Forestry. The work of
raking and piling was contingent upon availability of
equipment, manpower, terrain, and accessibility. At
certain locations, the interval of time between cutting,
piling, and burning actually spanned a period of six
months or more, which allowed the cut timber to dry
and brush to cover the ground during the late summer
months. To prevent the spread of wild fires, and
before piling and burning in these areas were permit-
ted, the contractor was required to provide adequate
fire breaks near the uncut timber and brush lines at
elevation 900 feet.
Work of grubbing areas for recreation was per-
formed after all clearing was completed. Grubbing
was performed by dozers equipped with regulation
dozer blades and with a single ripper tooth clamped
and mounted on the left end of the dozer blade. The
ripper tooth was mounted at one end of the blade so
that stumps being rooted out would be visible to the
operator.
The contractor cleared approximately 12 dwellings
located at Bidwell Bar, Bidwell Bar Canyon, and En-
terprise and disposed of them by burning.
The Department removed all buildings located
136
along the Western Pacific Railroad and buildings
located at Bidwell Bar. These buildings were burned
in 1964 prior to the reservoir clearing contract.
Saddle Dams
Construction of the Saddle Dams commenced in
December 1966. The contract specifications allowed
275 days to complete the work on both dams. Comple-
tion was timed to precede closing of the second diver-
sion tunnel at Oroville Dam and commencing of
storage in Lake Oroville. The planned date for com-
pletion of Oroville Dam and start of storage in the
reservoir was October 17, 1967. The actual start was
on November 14, 1967.
Foundation. All foundation excavation at both
dams was done by common means, using scrapers and
dozers with rippers. Excavation was started January
10, 1967 and essentially was completed on February
28, 1967.
The Bidwell Canyon Saddle Dam foundation out-
side the cutoff trench was stripped to expose strongly
or moderately weathered rock. The cutoff trench was
excavated to fresh rock or firm moderately weathered
rock. The bottom of the trench was cleaned of loose
materials with hand tools and air jets.
The downstream Zone 3 foundation within Miners
Ranch Reservoir was not dewatered during embank-
ment construction. It had been determined by prob-
ing, prior to construction of the Saddle Dam, that this
area consisted of strongly weathered rock which was
stripped of topsoil during construction of Miners
Ranch Dike.
Ground water issued from the spoil pile adjacent to
the upstream left abutment of the main dam during
foundation excavation. Water also flowed from the toe
of the Miners Ranch Dike. These flows were drained
from the foundation area by placing a French drain of
coarse rock at the base of Zone 3 and by digging a
drainage trench through the spoil pile north of the
Dam.
Excavation for Parish Camp Saddle Dam founda-
tion outside the cutoff trench exposed strongly and
moderately weathered phyllite over most of the area.
The cutoff trench was excavated to fresh or firm mod-
erately weathered phyllite.
The grout curtain for both dams was 25 feet deep in
a vertical plane. Holes were inclined 20 degrees off
vertical along the plane in order to cross the nearly
vertical cleavage and schistosity. The ends of the cur-
tain extended to foundation elevation 917 feet on all
abutments. Stage grouting was used where necessary.
In the more weathered areas where excessive amounts
of grout might have leaked to the surface, a 10-foot-
deep upper stage was drilled and grouted at 10 psi
before drilling and grouting the remaining 15 feet of
hole. In fresher rock, it was possible to grout the entire
hole with a single hookup at a pressure of 25 psi with-
out surface leakage.
Construction Materials. Impervious borrow for
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Bidwell Canyon Saddle Dam was obtained by strij>
ping near-surface, strongly weathered, decomposed
amphibolite. Initially, material was taken from the
two designated borrow areas north of the west dam.
When these sources were depleted, one of the areas
was extended farther northward and a new borrow
area was opened near the east end of the main dam.
These new sources were explored with bulldozer tren-
ches excavated by the contractor at the direction of the
Department. To help alleviate the shortage of imper-
vious borrow, the design of the west dam was modi-
fied to reduce the quantity of impervious material
required in the embankment. This modification per-
mitted the use of more rocky material in the outer
limits of the west dam impervious section. Such
material could be obtained by excavating deeper in the
designated borrow areas.
Pervious borrow initially came from the designated
source, a rock spoil pile adjacent to the main dam
made up of material from portal excavation of tunnels
leading in and out of Miners Ranch Reservoir. When
this stockpile was nearly depleted, a few thousand
cubic yards of rock was hauled from a spoil pile of rock
wasted during construction of the Oroville-Quincy
Road relocation near Bidwell Bar Bridge. This source
was abandoned when it was found to be more econom-
ical to rip and remove rock from one of the designated
impervious borrow areas which had already been
stripped of impervious material.
Filter material. Zone 2B, was trucked into the area
from the Feather River dredger tailings and was pro-
duced by mixing the necessary ingredients, utilizing
a dragline and a dozer. The proportions of different
materials had to be changed somewhat when mechani-
cal analysis tests indicated an increase in that portion
passing the No. 200 screen. This condition was con-
trolled by frequent testing of the material at the
source. Zone 4B is clean, coarse, dredger-tailing cob-
ble.
Impervious borrow for Parish Camp Saddle Dam
was obtained from the weathered surface of the Cala-
veras phyllite, which was decomposed to gravelly clay
and clay. The material came from excavation of the
access road to the dam and from the designated bor-
row area just northwest of the dam. Pervious material
was imported by the contractor.
A small amount of riprap for Bidwell Canyon Sad-
dle Dam was obtained from the designated pervious
borrow source adjacent to the main dam by separating
out the larger rock fragments using dozers equipped
with rock rakes. Most of the riprap was imported by
the contractor from a department-owned spoil pile at
Thompson Flat north of Oroville which contained
rock excavated from a deep cut during construction of
the Western Pacific Railroad relocation. This riprap
also was separated out with dozer-mounted rock rakes.
All riprap placed on the dams was fresh, hard, and
durable metamorphic rock.
Mine Adit Plug. Work under the contract includ-
ed placing compacted impervious embankment to cov-
er the portal of an abandoned, collapsed, mine adit
one-third mile northwest of Parish Camp Saddle Dam.
This embankment was designed to prevent possible
leakage from the reservoir.
The contractor stripped the area around the adit
portal with dozers and a backhoe. The portal was
found to be completely collapsed and was not opened
during excavation. Water flowing from the adit at
about % of a gallon per minute was sealed off with
placement of the compacted embankment.
Construction of Embankment. Impervious ma-
terial (Zone IB, IP, and mine adit embankment) was
excavated by scraper units which picked up both clay
and weathered rock for placement. After placement,
the lift was cut to a thickness that would produce a
finished layer not more than 6 inches in depth by a
grader and rolled by a 5-foot by S-foot, double, sheeps-
foot roller.
Filter material (Zones 2B and 2P), after being
placed in layers that resulted in a thickness of not
more than 12 inches after compaction, was moisture-
conditioned to prevent bulking. Compaction was ac-
complished by four passes of a large tractor.
Pervious material (Zones 3B and 3P) was placed
and compacted in the same manner as Zones 2B and
2P. Care was taken to distribute the embankment
material to produce a well-graded mass of rock with a
minimum of voids.
By agreement with Oroville-Wyandotte Irrigation
District, Miners Ranch Reservoir was lowered as far
as possible during Zone 4B placement. Underwater
placement was accomplished by dumping, starting
from the edge of the water and proceeding parallel to
the longitudinal axis of the dam. This procedure was
followed until the top of the material was 1 foot above
the surface of the water. Thereafter, the material was
placed in layers not to exceed 2 feet in thickness after
compaction with a large tractor.
Riprap was placed to its full thickness in one opera-
tion. Care was taken not to displace the adjacent
material. Riprap was placed on the upstream faces of
the embankment with front-end loaders but had to be
straightened and rearranged with a truck crane and a
clam bucket to produce a well-graded mass with a
minimum of voids.
0*
137
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BIBLIOGRAPHY
California Department of Public Works, "Report on Comparison of Oroville, Big Bend and Bidwell Bar Reservoir
Sites for Development of Feather River", August 1949.
California Department of Water Resources, "Basic Data Report on Test Fills of Proposed Embankment Materials
for Oroville Dam", December 1961.
Chadwick, W. L. and Leps, T. M., "Inspection and Review of Oroville-Thermalito Project Facilities, Oroville
Thermalito Diversion Dam, Thermalito Forebay Dam, Thermalito Afterbay Dam, Feather River Hatchery
Dam", February 1973.
Daehn, W. W., "Development and Installation of Piezometers for the Fluid Measurement of Pore-Fluid Pressures
in Earth Dams", ASTM, 1962.
Golz6, Alfred R., "Oroville Dam", Western Construction Magazine, April 1962.
Golz6, A. R., Seed, H. B., and Gordon, B. B., "Earthquake Resistant Design of Oroville Dam", Proceedings of
ICOLD, 1967.
Gordon, B. B., Hammond, W. D., and Miller, R. K., "Effect of Rock Content on Compaction Characteristics of
Clayey Gravel", ASTM, STP 377, June 1964.
Gordon, B. B. and Miller, R. K., "Control of Earth and Rockfill for Oroville Dam", ASCE Journal of the Soil
Mechanics and Foundation Division, May 1966.
Gordon, B. B. and Wulff, J. G., "Design and Methods of Construction, Oroville Dam", Edinburgh, Scotland,
Communication, 8th Congress on Large Dams, 1964.
Hall, E. B. and Gordon, B. B., "Triaxial Testing Utilizing Large Scale, High Pressure Equipment", ASTM,
Special Tech. Pub. 361, 1963.
Kruse, G. H., "Instruments and Apparatus for Soil and Rock Mechanics", ASTM-392, pp. 131-142, December
1965.
Kulhawy, F. H. and Duncan, J. M., "Stresses and Movements in Oroville Dam", ASCE Journal of the Soil
Mechanics and Foundation Division, July 1972.
Lanning, C. C, "Oroville Dam Diversion Tunnels", ASCE Journal of the Power Division, October 1967.
Marachi, N. D., Chan, C. K., and Seed, H. B., "Evaluation of Rockfill Materials", ASCE Journal of the Soil
Mechanics and Foundation Division, January 1972.
O'Neill, A. L. and Nutting, R. G., "Material Exploration for Oroville Dam", 66th Annual Meeting, American
Society for Testing Materials, June 1963.
Schulz, W. G., Thayer, D. P., and Doody, J. J., "Oroville Dam and Appurtenant Features", Journal of the Power
Division, American Society of Civil Engineers, Volume 87, No. 902, July 1961.
Stroppini, E. W., Babbitt, D. H., and Struckmeyer, H. E., "Foundation Treatment for Embankment Dams on
Rock", ASCE Journal of the Soil Mechanics and Foundation Division, October 1972.
Thayer, D. P., "Oroville Test Fill Experience in Compacting Granular Material", Proceedings 7th Congress on
Large Dams, Volume IV.
Thayer, D. P., Gordon, B. B., and Stroppini, E. W., "Soil Mechanics Aspects of Oroville Dam", American Society
of Civil Engineers, Water Resources Engineering Conference, May 1963.
Thayer, D. P. and Stroppini, E. W., "Hydraulic Design for Oroville Spillway", ASCE Hydraulic Conference,
August 1965.
Tuthill, L. W., Adams, R. F., and Mitchell, D. R., "Mass Concrete for Oroville Dam", SP-6 Symposium on Mass
Concrete, ACI, 1963.
United States Bureau of Reclamation, "Hydraulic Model Studies of the Diversion Tunnels for Oroville Dam",
Hydraulics Branch Report No. HYD-502, January 18, 1963.
, "Hydraulics Model Studies of the Flood Control Outlet and Spillway for Oroville Dam", Hydraulics
Branch Report No. HYD-510, September 30, 1965.
.., "Hydraulic Model Studies of the River Outlet Works at Oroville Dam", Hydraulics Branch Report No.
HYD-508, October 11, 1963.
Western Construction Magazine, "Big Show Starting at Oroville Dam", May 1963.
Wilber, A. F., and Mims, J. R., "Construction Procedure at Oroville Dam", ASCE Conference Paper, Denver,
Colorado, May 16-20, 1966.
139
Figure 119. location Mop— ThermolHo Dlvoreion Dam
140
CHAPTER VI. THERMALITO DIVERSION DAM
General
Description and Location
Thermalito Diversion Dam is located on the
Feather River approximately '/ of a mile upstream
from the Oroville-Chico highway truss bridge and 4'/2
miles downstream from Oroville Dam. The nearest
major road, State Highway 70, crosses the Feather
River about 2 miles downstream of the Dam (Figure
119).
Thermalito Diversion Dam (Figure 120) consists of
a 62S-foot-long, concrete, gravity section with an ogee
spillway; a canal-regulating headworks structure; and
an earth embankment section at the right of the canal
headworks (Figure 121).
Purpose
Thermalito Diversion Dam diverts water into
Thermalito Power Canal for power generation at
Thermalito Powerplant and creates a tailwater pool
for Oroville Powerplant. The impounded reservoir
acts as a forebay when Edward Hyatt Powerplant is
pumping water back into Lake Oroville. The reservoir
also is used for incidental recreation.
Chronology
The concept of Thermalito Diversion Dam evolved
in 1956 when a canal to a powerplant and offstream
afterbay was first proposed. The Diversion Dam site
formerly was considered for an afterbay. The pump-
storage concept required more afterbay storage than
was available at the Diversion Dam. Detailed design
Figure 120. Aerial View — Thermalito Diversion Dam
141
Figure 121. General Plan and Profile of Dam
142
work was initiated in 1961, and work on the Diversion
Dam was started in October 1963 and completed in
March 1968. A statistical summary of Thermalito Di-
version Dam is shown in Table 10.
Regional Geology and Seismicity
The Dam site is approximately 4 miles west of Oro-
ville Dam, and the section on regional geology and
seismicity contained in Chapter V of this volume ap-
plies to the Diversion Dam as well as to Oroville Dam.
Design
Foundation
Site Geology. Rocks of the Jurassic Oregon City
formation comprise the foundation of the Diversion
Dam. This formation is composed of a sequence of
metamorphosed volcanic and sedimentary rocks. Two
rock types were exposed in the dam foundation: me-
taandesite, which is a massive, fine-grained, equiangu-
lar rock; and metaconglomerate, which contains
volcanic cobbles in a medium- to coarse-grained
ground mass. Both rock types are extremely hard,
dense, and durable where fresh. Shear zones and well-
developed joints cut the rock at various angles, creat-
ing a blocky or slabby appearance; however, no major
shear zones were found in the foundation.
Strength. Inspection of the foundation rock, sur-
face geologic mapping, and core hole logs indicated
that foundation strength would not be a critical factor
in the stability of a dam of this height. Therefore, no
strength testing of the rock was performed. Grouting
was necessary to consolidate the foundation and mini-
mize seepage.
Overpour Section
Description. The spillway consists of a concrete,
gravity, overpour section with a crest across the chan-
nel of the Feather River. An energy dissipator is pro-
vided at the toe of the spillway to prevent scouring of
the channel and possible undermining of the Dam.
Hydrology. Spillway capacity of 320,000 cubic
feet per second (cfs) was determined from a study of
the economics, operational requirements, and physi-
cal limitations of the site. This capacity is in excess of
the controlled releases for the standard project flood
from Oroville Reservoir (150,000 cfs). Discharges in
excess of 320,000 cfs will not overtop the abutments of
the nonoverpour sections but will flow over the spill-
way bridge above the gates; however, no major dam-
age will occur with discharges up to the peak spillway
discharge of 650,000 cfs at Oroville Dam. The Ther-
TABLE 10. Statistical Summary of Thermalito Diversion Dam
THERMALITO DIVERSION DAM
Type: Concrete gravity
Crest elevation 233 feet
Crest width 24 feet
Crest length 1,300 feet
Streambed elevation at dam axis 105 feet
Lowest foundation elevation 90 feet
Structural height above foundation 143 feet
Volume of concrete 154,000 cubic yards
Freeboard above spillway crest 28 feet
Freeboard, maximum operating surface 8 feet
THERMALITO DIVERSION POOL
Maximum operating storage 13,328 acre-feet
Minimum operating storage 12,090 acre-feet
Dead pool storage 5,849 acre-feet
Maximum operating surface elevation 225 feet
Minimum operating surface elevation.. 221 feet
Dead pool surface elevation 197.5 feet
Shoreline, maximum operating elevation 10 miles
Surface area, maximum operating elevation.. 323 acres
Surface area, minimum operating elevation.. 308 acres
SPILLWAY
Type: Gated ogee crest with slotted-bucket energy dissipator — 14
radial gates 40 feet wide by 23 feet high
Top elevation of gates 226 feet
Ogee crest elevation. 205 feet
Crest length 560 feet
Maximum probable flood inflow 650,000 cubic feet per second
Peak routed outflow 650,000 cubic feet per second
Maximum surface elevation 246 feet
INLET-OUTLET
Edward Hyatt Powerplant
Maximum generating release 16,900 cubic feet per second
Pumping capacity 5,610 cubic feet per second
Thermalito Power Canal
Maximum generating flow 16,900 cubic feet per second
Maximum pumping flow 9,000 cubic feet per second
OUTLET WORKS
To Oroville Fish Hatchery: 60-inch reinforced-concrete pipe with
60-inch slide gate shutoff on upstream side of dam — flow regula-
tion at hatchery
Capacity 100 cubic feet per second
River Release: 60-inch reinforced-concrete pipe — control, 42-inch
fixed-cone dispersion valve — guard valve, 60-inch slide gate on
upstream side of dam
Capacity 400 cubic feet per second
143
malito Diversion Dam spillway rating curve is shown
on Figure 122.
Structural Design. The spillway section (Figure
123, Sections D and E) was constructed of mass con-
crete with a 2-foot-thick surface of high-strength con-
crete on the spillway face. The vertical upstream face
is recessed 6 feet downstream from the dam axis to
reduce the volume of concrete required.
The 25-foot-radius, slotted-bucket, energy dissipa-
tor was designed to withstand the forces resulting
from falling water during an occurrence of the design
flood as well as to resist the tailwater loading. Uplift
forces are resisted by the weight of the concrete
bucket. Waterstops were placed at contraction joints
to prevent the buildup of excessive uplift forces dur-
ing spillway operation. Concrete gravity retaining
walls at both ends of the energy dissipator contain the
turbulent flow of the slotted bucket and prevent
scouring of the abutments.
Thirteen 5-foot-thick piers and two 3-foot-thick
training walls support the radial gate trunnion an-
chorage assemblies. The piers also support the bridge
over the spillway section and will accommodate stop-
logs. The spillway bridge, at elevation 233 feet, was
designed to provide access across the Dam, serve as the
hoist platform for the radial gates, support mainte-
nance equipment, and allow placement of stoplogs.
Removable railings were placed along the curb on the
upstream side of the bridge to provide access to the
stoplogs. Permanent railings are located on the down-
stream side of the bridge.
Spillway Gates and Hoists
Each of the 14 radial gates on the spillway crest
consists of a curved skinplate welded to vertical ribs
which in turn are welded to two horizontal girders.
The loads are transmitted by radial arms which are
bolted to the horizontal girders and to the trunnion
assembly. The load from the gates is transmitted into
the piers by prestressed anchorage assemblies. The 14
hoists are electric motor-operated, conventional, wire-
rope type designed for 90 kips, with the load equally
divided between the four wire ropes. The hoists can
be controlled either on-site, at the local control build-
ing, or from the Oroville Area Control Center.
Stability
Stability analyses were performed on all sections of
the Dam under various conditions of loading.
The monoliths are not keyed together, and no provi-
sions were made for bonding the vertical joints.
Waterstops are provided to prevent leakage through
these joints.
Curtain grouting was done through a grout gallery
in the Dam. Spacing and depth of the holes are de-
scribed in the construction section of this chapter.
Although foundation drainage is provided, it was
assumed, for conservative design purposes, that the
drains would remain inoperative.
144
Water and pressure profiles over the spillway were
calculated, and the loads resulting from the static and
dynamic pressures on the crest, headwater, and tail-
water and from velocity were incorporated into the
stability analyses. No "over-turning factor" as such
was determined; however, a sliding factor (ratio of
vertical to horizontal forces) of 0.87 was calculated for
the critical section. Due to the extremely uneven sur-
face of the foundation, it was believed that sliding
could not occur and, therefore, more emphasis was
placed on the shear friction factor. Another factor
which would resist sliding but was disregarded in the
analysis was the bearing provided by placing the
downstream toe of the Dam directly against the slope
of the excavation.
It was assumed that earthquakes would not occur J
simultaneously with riverflows in excess of 150,(X)0 I
cfs. Increases in stress due to a horizontal seismic ac-
celeration factor of O.lg were small and did not govern
design in any case.
Nonoverpour Sections !
A nonoverpour concrete section (Figure 123, Sec-
tion F) with a 24-foot-wide crest at elevation 233 feet
adjoins each side of the spillway section. The design
and stability analyses were the same as for the over-
pour section. The crest accommodates vehicles and is
provided with curbs and railings similar to the spill-
way bridge.
Three 60-inch-diameter outlets equipped with elec-
trically operated slide gates are provided in the abut-
ments. The one in the right abutment provides a water
supply outlet for the Feather River Fish Hatchery of
100 cfs. The other two are in the left abutment: one
providing for a minimum river release of 400 cfs, and
the other for a possible future water demand. A 42-
inch-diameter fixed-cone dispersion valve with an
electric motor operator is located in a valve vault just
downstream of the left abutment. It is used to make
river releases. The valve discharge impinges onto the
spillway apron parallel to the dam axis. Since the head
and flow are constant, except for short periods, only
on-site control was provided.
Thermalito Canal Headworks
Due to the extemely high value of head for power
generation, it was imperative to minimize head loss.
This was accomplished by increasing the velocity of
the water at a constant rate through the approach
channel.
Warped transitions were adopted both upstream
and downstream from the headworks structure (Fig-
ure 121). This was done to minimize head loss
through the structure and thus better meet pump-
storage requirements. Sizing was based on a capacity
of 16,900 cfs.
Piers were designed to support the gates, bridge,
breastwall, and hoist platform and resist the resultant
forces due to their respective critical loading condi-
tions (Figure 124). Under normal loading conditions,
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ELEVATION IN FEET
Figure 122. Spillway Rating I
145
8 '^'^ -V Kit *»j.<.rl'
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Figure 123. Spillway Sections
146
Figure 124. Power Canal Headworki — Plan, Profile, and Sections
147
seismic acceleration was included in the design.
Piers are 5 feet thick with vertical and horizontal
reinforcing steel in both faces. Prestressed tendons are
embedded to provide anchorage for the gates.
The left side of the headworks structure is flush
with the face of Monolith 1 (Figure 121, Section A).
A 4-foot-thick wall at the downstream face of the
monolith connects the Dam to the left counterfort
wall. The breastwall is formed by three reinforced-
concrete vertical walls, simply supported between
piers and endwalls (Figure 124, Section A). The pur-
pose of the breastwall is to protect Thermalito Power
Canal from high floodflows.
A bridge across the headworks structure provides
access to the Dam and left bank of the Canal. It con-
sists of a reinforced-concrete slab, continuous between
the piers and walls. A platform, simply supported be-
tween the piers and walls, is situated at the top of the
breastwall and is used to support gate hoist equip-
ment. Live loads used for design included 100 kips for
the gate, 25 kips for the hoist, 2.5 kips for the motor,
and 25% of the gate weight for impact.
Radial Gates and Hoists. The three gates are of
similar design to the spillway gates. The gate hoists
are identical to the spillway gate hoists except for the
spacing of the wire ropes. These gates were designed
to be used either fully open or fully closed.
Foundation. The base of the canal headworks
structure extends to sound rock of the same quality as
the foundation of the Dam. Hydrostatic pressure is
relieved by the placement of weepholes in the up-
stream transition walls and by underdrains emptying
into the River on the downstream side of the struc-
ture.
Stability Analysis. Stability of the headworks
structure was investigated with criteria similar to the
Dam. Foundation conditions were considered compa-
rable to the Dam. Grouting was performed directly
from the surface and similar foundation drainage was
provided.
Embankment Section
Description. The embankment section (Figure
123, Section J) of the Dam between the Canal and the
right abutment provides freeboard only. The down-
stream toe is at elevation 228 feet, 3 feet above normal
water surface of the Power Canal, and the crest is at
elevation 246 feet. In addition to riprap for protection
from wave action, a 4-foot concrete parapet with a top
elevation of 250 feet is situated on the upstream side
of the crest of the embankment. The crest serves as an
access road to the hoist platform of the canal head-
works.
Construction Materials. Pervious material for the
embankment was obtained from foundation excava-
tion and supplemented with dredger tailings from
downstream borrow areas that were designated for
use in construction of Oroville Dam. Impervious
material was obtained from abutment stripping.
Stability Analysis. Stability of embankment sec-
tions was determined by the Swedish Slip Circle
method of analysis, assuming reservoir-level criteria
similar to that assumed for the gravity dam. A seismic
acceleration factor of O.lg was incorporated into the
design forces. The slope stability safety factor did not
fall below 1.1 for the most adverse condition analyzed.
Construction
Contract Administration
General information for the major contracts for the
construction of Thermalito Diversion Dam is shown
in Table 11. Thermalito Diversion Dam and its ap-
purtenances were constructed as part of the Oroville
Dam contract (Specification No. 62-05). Associated
mechanical and electrical equipment was furnished
under separate contracts.
TABLE 11.
Major Contrac
s — Thermalito Diversion Dam
Specifi-
cation
Low bid
amount
Final
contract
cost
Total cost-
change
orders
Starting
date
Comple-
tion
date
Prime contractor
Oroville Dam'
62-OS
64-25
64-26
64-43
65-47
67-40
3120,863,333
20,876
24,004
751,000
103,963
43,755
3135,336,156'
16,081
25,255
778,830
155,393
45,270
37,503,716
838
38,448
8/13/62
6/29/64
6/25/64
12/11/64
1/12/66
7/17/67
4/26/68
3/ 4/69
10/18/66
9/22/66
4/15/68
1/ 4/68
Rodney Hunt Machine Co.
Furnishing Fixed Dispersion
Cone Valve and Operator
Furnishing Radial Gates and
Hoists
Willamette Iron and Steel Co.
Berkeley Steel Construction Co.,
Inc.
Abbett Electric Corp.
Furnishing Stop Logs and Lift-
1 Thermalito Dam coDStnicted under this contract. Estimated &nal coBt 99,000,000.
148
Figure 125. West Bank Diversion Plan
149
Figure 126. Channel Bypau (Aerial View)
Diversion and Care of River
West Bank. First-stage construction work for
stream diversion consisted of an embankment and
earth-filled timber crib which enclosed the right abut-
ment and Monoliths 1 through 9 (Figures 125 and
126). This offered flood protection up to elevation 180
feet. A diversion channel through Monolith 8 also was
excavated to prepare for second-stage diversion. The
earth-filled timber crib was constructed in the founda-
tion area of Monolith 10, and the remainder of the
enclosure was an earth embankment extending up-
stream and downstream of the crib and tied into the
right bank. This structure served as a precautionary
measure in the event of a flood and did not actually
encroach on, or divert, the normal flow of the Feather
River.
Channel. Second-stage stream diversion (Figures
127 and 128) called for enclosure of the foundation
area of Monoliths 10 through 19 and diversion of
riverflow through a 15-foot by 15-foot opening
through Monolith 8. Flood protection was to elevation
180 feet.
Timber cribbing was set adjacent to Monolith 9,
both upstream and downstream. The earth section of
the cofferdam was composed of rockfill ballast, clay
core, and sheet piling driven vertically through the
core to sound rock (Figure 127). It was constructed to
extend out into the River as far as practical without
losing material by erosion. Prior to the closure at-
tempt, rock was stockpiled at the River's edge on both
sides near the upstream closure point. The actual clo-
sure was made from the left bank. To accomplish this,
all available earth-moving equipment was utilized.
Progress was slow due to erosion of embankment
material nearly as fast as it was trucked in. At one
time, large rock was positioned by the high line to
check the loss of fill material. Work continued around
the clock for three days before the closure was success-
ful. When the River was finally diverted, the remain-
ing cofferdam construction was routine. Two 36-inch
150
dewatering pumps were placed into operation near
the downstream end of the cofferdam to take care of
seepage water.
Closure. Third-stage diversion consisted of clos-
ing the 15-foot by 15-foot opening through Monolith
8, thus forcing the River to flow over the completed
spillway structure.
Sudden closure of the 15-foot by 15-foot opening
would have been a construction advantage but, due to
flow requirements downstream of the Dam, this pro-
cedure was not permissible. As a result, the bulkhead
gate was lowered in increments allowing gradual fill-
ing of the reservoir and at the same time, to a disadvan-
tage, increasing steadily the hydrostatic pressure on
the gate. Movement of the gate continued in this man-
ner to within 16 inches of closure and, at that point,
it became immovable.
Concrete blocks were then set upstream in the path
of the opening. Progressively smaller rocks were
dumped over the blocks, followed with application of
earth and straw, until the flow was reduced enough to
allow men to enter the opening.
To control the remaining flow, a box chamber was
constructed along the downstream side of the bulk-
head at the invert of the opening by welding two
15-foot by 2-foot by '/j-inch steel plates together and to
the bulkhead. A 10-inch gate valve was mounted on
top at the end of a 5-foot pipe riser. A line then was
connected and extended to the downstream end of the
Monolith 8 opening, making it possible to open the
valve and relieve hydrostatic pressure.
Water leaking through the chamber at the invert
level was collected by two French drains positioned
along the invert and piped into the access gallery prior
to placing the first lift of concrete. Before placing the
second lift, the 10-inch gate valve was closed and the
downstream section of pipe removed.
After the third and last lift was placed and cured,
grout was pumped into the French drains and also
through a preinstalled grout system located in the
crown of the 15-foot by 15-foot opening to complete
the closure.
Cofferdam sheet pilings, which were easily pulled,
were salvaged by the contractor, and the more dif-
ficult pieces were left in place at the time of the first
high water. Rains came in late October and early No-
vember, flooding the construction area on November
2, 1964. More flooding occurred on November 9 and
wet weather continued intermittently into December.
Heavy rain occurred December 18, 1964 and con-
tinued through December 23, resulting in a record
peak flow of 253,000 cfs upstream of Oroville Dam.
The peak flow at the Diversion Dam was reduced to
187,000 cfs by the restrictive action of the diversion
tunnels at Oroville Dam. The highest elevation of the
River at the Diversion Dam site was 206.7 feet.
When the River subsided, the remaining cribbing
that had not been removed had been washed out. The
downstream cofferdam embankment was eroded to
i
Figure 127. Channel Bypass, Closure, and East Bank Diversion Plan
151
Figure 128. Cofferdam Cloture
elevation 1 SO feet and scattered along the river chan-
nel. A few pieces of twisted sheet piling protruding
through the muck and debris marked the location of
what was once the cofferdam. In midsummer of 1965,
the upstream portion of the cofferdam was leveled to
elevation 175 feet by the contractor.
East Bank. The fourth stage of stream diversion
consisted of the placement of an earth dike to provide
flood protection for future closure of the railroad
bypass, which was located at the left abutment of the
Dam.
Foundation
Excavation. At the abutments, the overlying soils
and weathered material were removed and wasted in
the designated waste area. The exposed rock was
found to be badly fractured. Further excavation by
drilling and shooting was necessary to reach a suitable
foundation.
Streambed excavation consisted of removing river
gravels that varied from 15 to 25 feet in depth. The
exposed rock provided a satisfactory foundation, and
it was not necessary to drill and blast as had been
expected. A power shovel, end-dump trucks, and trac-
tors were used to excavate and transport waste materi-
als to a designated area upstream of the Diversion
Dam. All material wasted within the reservoir was
placed below dead storage, elevation 175 feet.
Canal headworks excavation included a portion of
the Power Canal, upstream and downstream transi-
tion wall foundations, headworks foundation, and the
intake channel. The excavated material was used in
the first-stage cofferdam.
Preparation. The foundation at Thermalito Di-
version Dam is a blocky, well-jointed, metavolcanic
rock which was easily cleaned. The only difficult area
was a fractured trough formed by two intersecting
shears that cut diagonally across Monoliths 3, 4, and
5. The fractured material was excavated to a depth
equal to the width of the shear zones, which varied
from 3 to 5 feet.
Foundation cleanup was done using high-pressure
water hoses to remove most of the loose material.
Loose and detached rocks were removed by prying.
Air-water jets and pneumatic siphons were used for
final cleanup.
Grouting. Blanket grouting was used to consoli-
date areas of weathered or fractured rock and to seal
open cracks and shear zones. Grout holes at spacings
of 5 to 35 feet were drilled from 10 to 30 feet deep.
Spacing and depth of holes were governed by the na-
ture and extent of the foundation defects encountered.
Most of the holes were inclined to penetrate steeply
dipping seams and shear zones a few feet below the
foundation surface. Holes normally were tested and
grouted at 30 pounds per square inch (psi).
Curtain grouting was accomplished from a 5-foot by
7-foot horseshoe gallery within the Dam between Sta-
tion 5-1-70 and Station 12-1-25 (Figure 121) and from
the surface of the excavated foundation beyond the
limits of the gallery. The maximum spacing of the
holes was 10 feet. Zone 1 holes, drilled to a maximum
depth of 25 feet, were stage-grouted at pressures up to
100 psi. Zone 2 holes, drilled to a maximum depth of
75 feet, were stage-grouted at pressures up to 200 psi.
Embankment Construction
Description. The embankment provides flood
freeboard only. No unusual problems were encoun-
tered in the placement of embankment. A major por-
tion of the material was obtained in borrow areas close
to the job site. The embankment material was divided
into five separate classifications.
Random Backnil. Random backfill with a max-^
imum size of 24 inches, free of organic material, was
placed on the upstream and downstream faces of the
embankment. This material also was used as fill for
the parking and storage area adjacent to the upstream
face of the Dam and the service road adjacent to the
downstream face of the Dam.
Impervious Core. Impervious core material w«
placed from the canal headworks to the right abut
ment. This material conformed to Oroville Dam Zon<
1 embankment described in Chapter V of this volume
Select Backfill. Select backfill was placed behinc
the retaining walls. The material conformed to Oro
ville Dam Zone 3 material with a maximum size of I',
inches. Zone 3 requirements also are described ii
Chapter V of this volume.
Consolidated Backfill. Consolidated backfill wa
used in the trench for the 60-inch water pipe leadinj
to the Feather River Fish Facilities. This material wa^
granular with a gradation specified for concrete sand
Riprap. Riprap was hard, dense, durable, rocl
M'.
1S2
fragments free from organic, decomposed, and weath-
ered material. It was obtained from canal excavation
previously stockpiled and was placed on the upstream
slope in such a manner that a well-graded blanket was
produced.
Concrete Production
Construction Phases. Construction of Thermalito
Diversion Dam was accomplished in four phases: (1)
construction of Monoliths 1 through 9 and the canal
headworks, (2) construction of Monoliths 10 through
20, (3) plugging the diversion opening through
Monolith 8, and (4) filling the railroad pass through
Monolith 20. During the second phase. Monoliths 1 1
through IS were left low during the winter of 1964-65
for passage of floodflows. After the River had subsided
sufficiently in the spring of 1965, these low monoliths
were completed to grade.
Concrete Mixing and Materials. The concrete ag-
gregates were stored in seven 320-cubic-yard timber
bunkers. Clam gates at the bottom of the bunkers
regulated the flow of the material onto a 30-inch con-
veyor belt. The cement used was Type II (low alkali)
supplied by Calaveras Cement Company of Redding,
California. Ice used as part of the mixing water for
cooling the mass concrete was produced by an ice
plant located on the job site.
The bulk of the mass concrete was a 2 '/-sack mix
with 6-inch maximum size aggregate. Mixes with up
to four sacks of cement were used on a selective basis
(Figure 129).
The last day the batch plant was used to mix con-
crete for the Diversion Dam was October 6, 1965.
From September 18, 1965 through November 9, 1965,
concrete was transported from Oroville Dam batch
plant. Transportation from this plant to the job site
was by transit mix trucks.
For the remaining small-volume concrete items
(curbs, control house, cable trench, radial-gate walls,
and sill-plate blockouts), a portable concrete mixer
was set up on the right abutment near the high line.
Concrete for the diversion opening plug in Mono-
lith 8 and the railroad bypass in Monolith 20 was
obtained from Oroville Dam spillway batch plant.
Concrete Placing and Formwork. Transportation
of the concrete was accomplished in two stages. Eight-
cubic-yard, rail-mounted, side-delivery, transfer cars
transported the concrete from the batch plant to the
high-line dock. Attached to the high line was an 8-
I cubic-yard bucket, which received the concrete from
; transfer cars and conveyed it to the placement area.
i From October 1964 to May 1965, placing operations
continued on a three-shift basis. With the beginning of
summer weather and higher daytime temperatures,
placing operations were restricted by state specifica-
I tion to two hours before sunset and two hours after
j sunrise. The contractor developed a nozzle that pro-
I duced a fine mist or fog. Operation of this device over
the concrete placement area reduced the surrounding
air temperature by 10 to 15 degrees, allowing the re-
sumption of a three-shift concrete operation.
The mass concrete in the Dam was placed in y'/j-foot
lifts. Steel forms cantilevered from the previous lifts
were used on the spillway monoliths. The cantilever
supports were supplemented by rods welded to pins
embedded in the previous lift.
The slotted bucket was formed by using screed rails
to hold the 2-foot by 6y2-foot form panels in place. As
placement progressed, more panels were added until
the surface was completely formed. After the concrete
had set sufficiently, the forms were removed in the
order of assembly.
Wooden forms for the dentates were constructed at
the job site.
Concrete was cured for ten days by continuous ap-
plication of water with rainbird sprinklers and spray
pipes. Concrete surfaces subject to direct sunlight
were covered with burlap and kept wet by sprinklers.
The bridge over the spillway section has 56 pre-
stressed beams. For fabrication, the contractor con-
structed a jig on the right abutment within reach of
the high line for ease of handling. Four beams were
cast at a time, using the post-tension method for pre-
stressing.
Radial Gates and Hoists
Spillway Gates. Spillway gates are 40 feet wide by
23 feet high. The gates were assembled by setting the
two horizontal beams on a level H-beam jig. The four
skinplate sections were then assembled and bolted
loosely to the horizontal beams with the upstream face
up. The skinplate assembly then was squared up and
dogged where necessary before butt welding the skin-
plate sections together. After the gates were fully as-
sembled, the joints between the horizontal beams and
the vertical ribs and the edges of the back-up strip on
the downstream side of the plate were welded by a
single filler pass. The gate was turned over so the
downstream face of the skinplate was up. The diago-
nal braces between the beams then were welded in
place, the bottom struts were welded bracing the gate
bottom, and the gate arms were bolted on.
While setting the side seals to the required '/-inch
compression tolerance, it was found that the "/«-inch
adjustment of the side-seal angle bars did not provide
the proper seal compression. The slots were elongated
% of an inch for additional adjustment.
Canal Headworks Gates. The assembly and in-
stallation of the 26.67-foot-wide by 25.8-foot-high ca-
nal gates were similar to the spillway gates, except
that the arms were bolted on after the skinplate assem-
bly was in place in the canal bays. The presence of the
breastwall (Figure 124) prevented setting the gate as
a unit.
Hoists for Radial Gates. The first radial-gate hoist
unit delivered to the job site was mounted on H-beams
153
Figure 129. Locglion of Concrete Mixes Used in Dam Structure
154
and used as a portable test apparatus. Each gate was
checked for operation, and final adjustments were
made on the wall and sill plates. The plates then were
secured with second-stage concrete. As the remaining
hoists arrived, they were installed, serviced, and
checked for operation.
Trunnion Beams and Stressing Operation. Trun-
nion beams were slipped over the tendons positioned
in the piers and held to the correct elevation by field-
fabricated pipe stands. The center section of the
trunnion beams was to be filled with grout. Instead,
two 3-inch holes were cut in the two horizontal stiff-
ener plates and later filled with beam encasement con-
crete.
The trunnion beam tendons were post-tensioned by
anchoring the jacking end of the tendon with grip
nuts. This method of tendon anchorage proved satis-
factory, as any loss of stress through seating of the
wedge could be checked by returning the jack to the
required pressure and checking the tightness of the
nut.
Slide Gates and Operators. Three 60-inch slide
gates were installed on the upstream face of the Dam.
The one on the right abutment near the canal head-
works releases water to the Feather River Fish Hatch-
ery, and the other two are mounted side by side near
the left abutment. One is a guard valve for the fixed-
cone dispersion valve, and the other is connected to a
pipe stub for future use. The gates are of the rising
stem type provided with stem extensions and their
installation was routine.
Other Installations
Installation of the outlet conduits, fixed-cone dis-
persion valve, sump pump system, ventilating system,
and electrical connections also was routine.
Reservoir Clearing
Clearing of the Dam site and diversion pool area
consisted mainly of removing scrub pine and oak.
Instrumentation
Instrumentation in Thermalito Diversion Dam
consists of 64 foundation drains that are monitored
quarterly and three crest monuments that are moni-
tored annually.
155
BIBLIOGRAPHY
Amorocho, J. and Babb, A., "Thermalito Diversion Dam Model Studies", Department of Irrigation, University
of California, Davis, 1963.
California Department of Water Resources, SpeciHcation No. 62-05, "Specifications Proposal and Contract for
Construction of Oroville Dam", Addendum No. 1, 1962.
, Specification No. 64-25, "Specifications Bid Instructions and Bid for Furnishing Slide Gates for
Thermalito Diversion Dam", 1964.
-, Specification No. 64-26, "Specifications Bid Instructions and Bid for Furnishing Fixed Dispersion Cone
Valve and Operator for Thermalito Diversion Dam", 1964.
, Specification No. 64-43, "Specifications Bid Instructions and Bid for Furnishing Radial Gates and
Hoists for Thermalito Diversion Dam", 1964.
_, Specification No. 65-47, "Specifications Bid and Contract for Electrical Equipment for Thermalito
Diversion Dam," 1965.
_, Specification No. 67-40, "Specifications Bid Instructions and Bid for Furnishing Stop Logs and Lifting
Beam for Thermalito Diversion Dam", 1964.
157
GENERAL
LOCATION
SUTTER-BUTTEt
CANAL OUTLET
Figure 130. location Map— Tharmalito Forcboy and Aftarbay
1S8
CHAPTER VII.
THERMALITO FOREBAY, AFTERBAY,
AND POWER CANAL
General
Description and Location
Thermalito Forebay is an 1 1,768-acre-foot offstream
reservoir contained by Thermalito Forebay Dam on
the south and east and by Campbell Hills on the north
and west. It is located approximately 4 miles west of
the City of Oroville.
Thermalito Afterbay is a 57,041-acre-foot offstream
reservoir contained by Thermalito Afterbay Dam on
the south and west and by higher natural ground on
the north and east. It is located approximately 6 miles
southwest of the City of Oroville.
Thermalito Power Canal, which also is included in
this chapter, is a concrete-lined canal about 10,000 feet
in length. It conveys water in either direction between
Thermalito Diversion Dam and Thermalito Forebay
for power generation or pumping at Edward Hyatt
and Thermalito Powerplants.
Excess material from the Canal and other excava-
tions was placed in recreation areas and shaped to
make the areas more productive for recreation use.
Nearest major roads are State Highway 99 border-
ing the west side of the Afterbay, State Highway 70 to
the east of the Forebay and over the Power Canal, and
State Highway 162 passing south of the Forebay and
across the Afterbay (Figures 130, 131, and 132). Statis-
tical summaries of the dams and reservoirs are shown
in Tables 12 and 13, and area-capacity curves are
shown on Figures 133 and 134.
Figure 131. Aerial View — Thermalito Forebay
Figure 132. Aerial View — ^Thermalito Afterbay
159
TABLE 12. Statistical Summary of Thermallto Foraboy Dam and Forebay
THERMALITO FOREBAY DAM
Type: Homogeneous and zoned earthfiU
Crest elevation 231 feet
Crest width 30 feet
Crest length.... 15,900 feet
Lowest ground elevation at dam axis 170 feet
Lowest foundation elevation 140 feet
Structural height above foundation 91 feet
Embankment volume 1,840,000 cubic yards
Freeboard, maximum operating surface 6 feet
THERMALITO FOREBAY
Maximum operating storage 11,768 acre-feet
Minimum operating storage 9,936 acre-feet
Dead pool storage.. 15 acre-feet
Maximum operating surface elevation 225 feet
Minimum operating surface elevation 222 feet
Dead pool surface elevation. 185 feet
Shoreline, maximum operating elevation 10 miles
Surface area, maximum operating elevation.. 630 acres
Surface area, minimum operating elevation.. 592 acres
SPILLWAY
No spillway necessary
The capacity of Thermalito Powerplant bypass exceeds the peak
maximum probable flood inflow. Should the bypass fail to operate,
the entire volume of the maximum probable flood could be con-
tained within the freeboard above the maximum operating eleva-
tion.
INLET-OUTLET
Thermalito Powerplant
Maximum generating release 16,900 cubic feet per second
Pumping capacity 9,000 cubic feet per second
Thermalito Power Canal
Maximum generating flow 16,900 cubic feet per second
Maximum pumping flow _ _ 9,000 cubic feet per second
OUTLET
Thermalito Powerplant Bypass
Capacity 10,000 cubic feet per second
TABLE 13. Statistical Summary of Thermalito Afterbay Dam and Afterbay
THERMALITO AFTERBAY DAM
Type: Homogeneous earthfiU
Crest elevation 142 feet
Crest width 30 feet
Crest length 42,000 feet
Lowest ground elevation at dam axis 105 feet
Lowest foundation elevation 103 feet
Structural height above foundation 39 feet
Embankment volume 5,020,000 cubic yards
Freeboard, maximum operating surface 5.5 feet
THERMALITO AFTERBAY
Maximum operating storage 57,041 acre-feet
Minimum operating storage 2,888 acre-feet
Dead pool storage. 753 acre-feet
Maximum operating surface elevation 136.5 feet
Minimum operating surface elevation 123 feet
Dead pool surface elevation 113 feet
Shoreline, maximum operating elevation 26 miles
Surface area, maximum operating elevation.. 4,302 acres
Surface area, minimum operating elevation.. 2,190 acres
SPILLWAY
No spillway necessary
The river outlet capacity of 17,000 cubic feet per second exceeds the
peak maximum probable flood inflow. Should the river outlet
gates fail to operate, the entire volume of the maximum probable
flood from both the Forebay and Afterbay could be contained
within the freeboard above the maximum operating surface eleva-
tion.
INLET-OUTLET
Tail channel
Maximum generating flow 16,900 cubic feet per second
Maximum pumping flow 9,000 cubic feet per second
OUTLET WORKS
River outlet: Gated structure through dam — control, five 14-foot
by 14-foot radial gates
Capacity 17,000 cubic feet per second
Sutter Butte outlet: Four 7-foot-wide by 6-foot-high rectangular
conduits — control by slide gates on headworks — discharge over
measuring weir into open channel
Design delivery 2,300 cubic feet per second
PG&E lateral outlet: One 30-inch-diameter reinforced-concrete con-
duit— control by slide gate in wet well — discharge into stilling
basin with measuring weir
Design delivery 50 cubic feet per second
Richvale Irrigation District outlet: Three 72-inch-diameter rein-
forced-concrete conduits — control by slide gates on headworks —
discharge through Dall flow tubes into open channel
Design delivery.. 500 cubic feet per second
Western Canal outlet: Five 96-inch-diameter reinforced-concrete
conduits — control by slide gates on headworks — discharge through
Dall flow tubes into open channel
Design delivery 1,200 cubic feet per second
160
230
225
7
6
AREA- ACRES
9 4
IN THOUSANDS
3
2
0
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CAPACITY-ACRE FEET IN THOUSANDS
12
13
14
Figure 133. Area-Copacity Curves — Thermalito Forebay
161
AREA-ACRES IN THOUSANDS
5 4 3 2
10 20 30 40 50 60
CAPACITY-ACRE FEET IN THOUSANDS
Figure 134. Area-Capacity Curves — Thermalito Afferbay
70
Purpose
The purposes of the Forebay are to convey generat-
ing and pumping flows between Thermalito Power
Canal and Thermalito Powerplant, provide regula-
tory storage and surge damping for the Hyatt-Ther-
malito power complex, and provide recreation. Since
Edward Hyatt and Thermalito Powerplants operate
in tandem and are hydraulically matched, the regula-
tory storage is utilized only for start-up and shutdown
flow mismatch.
The purposes of the Afterbay are to provide storage
for the water required by the pumpback operation to
Lake Oroville, provide power system regulation, pro-
duce uniform flow in the Feather River downstream
from the Oroville-Thermalito facilities, and provide
recreation. Outlets are provided to the Feather River
and to furnish water to local districts where service
from the River was interrupted by construction of the
reservoir.
162
Chronology
Early in the 1950s, the original concept for power
development downstream from Oroville Dam was to
construct a number of small dams and plants within
the Feather River channel. This concept later was
modified to provide a diversion dam, a power canal, a
power plant, and an offstream afterbay. A major con-
sideration involved in selecting the offstream afterbay
was that surges in the Feather River past the City of
Oroville which would be caused by power plant re-
leases could not be overcome in the onstream afterbay
schemes. By 1957, a forebay was proposed for the de-
velopment. In economic studies which followed, it
was determined that any of three alternatives could be
constructed for about the same cost: ( 1 ) the forebay as
built, (2) a smaller forebay southwest of the Nelson
Avenue Bridge, or (3) the originally proposed canal
without any forebay. The forebay as built was selected
because it could provide more operational flexibility,
drainage problems could be minimized, and more rec-
i
reation could be provided. A pumped-storage concept
for the power facilities had been proposed in 1957 but
was not considered in these alternative studies. Even-
tual adoption in 1958 of pumped storage and raising
the crest of the Afterbay Dam by 5 feet to provide
necessary additional storage did not affect the
proposed forebay design.
Plans for Thermalito Forebay and Afterbay were
completed in June 1965, a construction contract was
awarded on October 18, 1965, and final inspection of
the completed work was made on April 18, 1968. The
Power Canal was constructed under a separate con-
tract which was awarded on September 8, 1965. Work
on this facility was completed in October 1967.
Within months after storage began in the Afterbay
(November 1967), high piezometric levels were ob-
served along U.S. Highway 99 and farther west. In
February 1968, the water level in the reservoir was
lowered to about elevation 1 19 feet, and a program of
exploration and reservoir bottom sealing was initiat-
ed. As the work accomplished under this program
later was found to be ineffective, a number of pumped
wells were installed along the west and south sides of
the reservoir. Operation of this system of wells,
termed the Afterbay Ground Water Pumping System,
successfully lowered the piezometric level in the sur-
rounding land.
Regional Geology and Seismicity
The oldest rock exposed in the forebay and afterbay
area is the Older Basalt formation, a series of basalt
flows which form the Campbell Hills. Three separate
basalt flow members of the formation have been desig-
nated: Lower, Middle, and Upper. Two interflow lay-
ers of volcanic sediments separate the flows.
Compact sediments of the Red Bluff formation
overlie the basalt flows and form the dam foundations
throughout most of the contract area. The Red Bluff
formation is a flood-plain deposit ranging in classifica-
tion from clay to gravel. Materials near the surface
have weathered in place to clay, clayey sand, and
clayey gravel. Leaching has created discontinuous
iron-cemented horizons a few feet beneath the surface.
Locally, streams have eroded through the surficial
weathered zones, and excavations have shown that
Red Bluff materials are cleaner at depth.
Unconsolidated fine- to coarse-grained alluvium oc-
curs along stream channels such as Ruddy Creek in
the Forebay and Grubb Creek in the forebay and tail
channel areas. Approximately 150 acres of alluvium,
known as Columbia fine sandy loam (silt and lean
clay), lie within the southeast corner of the Afterbay.
Most of the Columbia soil is underlain at 10 to 15 feet
by relatively clean sandy gravel. Dredge tailings, con-
sisting of loose gravel overlying sands, cover the area
between the Columbia soil and the Feather River and
extend in both directions along the River for a dis-
tance of approximately 5 miles.
The section on seismicity contained in Chapter V of
this volume applies to the structures discussed in this
chapter as well as to Oroville Dam.
Design
Dams
Description. Thermalito Forebay Dam is approxi-
mately 15,900 feet long with a maximum height of 91
feet and an average height of 25 feet. The 30-foot-wide
crest is at elevation 231 feet, providing a 6-foot free-
board. This dam involves two relatively high sections
joined by low reaches of embankment. The high por-
tions are termed: main dam, located adjacent to Ther-
malito Powerplant, and Ruddy Creek Dam, located in
the watershed near the Power Canal terminus. The
plan of the main dam is shown on Figure 135, and
sections and details of the entire dam are shown on
Figures 136 and 137.
Thermalito Afterbay Dam is approximately 42,000
feet long with a maximum height of 39 feet and an
average height of 24 feet. The 30-foot-wide crest, at
elevation 142 feet, provides a SYi-ioot freeboard at
maximum operating pool. There is a 12-foot-high sad-
dle dam approximately 1,000 feet in length at the
northwest corner of the Afterbay. Sections and details
of the Afterbay Dam are shown on Figures 138 and
139.
The design intent was to construct basically homo-
geneous dams with locally available materials. Zoned
embankments with more dredger tailings and basalt
rockfill were considered but deemed too complicated
for the heights involved. Therefore, slopes were flat-
tened and more local material was used.
The portion of the main Forebay Dam adjacent to
the powerplant wingwall is the only location where a
zoned section was required. The water side slope was
steepened between the plant and Station 3 + 75F (Fig-
ure 135) to minimize encroachment into the approach
channel. Transition to a flatter and more economical
homogeneous section is completed at Station 5 + 50F.
The land side transition from zoned to homogeneous
section is completed at Station 2-l-OOF. Remaining
dam sections for the Forebay and all sections for the
Afterbay are essentially homogeneous with protective
facing. Downstream blanket and toe drains, including
perforated pipe in a trench filled with pervious
material, were added to the homogeneous sections.
Stability Analysis. Stability was determined main-
ly by the Swedish Slip Circle method of analysis. In
zoned sections, the sliding wedge method of analysis
also was used. The infinite slope method was used to
check the stability of all outer shell slopes. In addition
to the reservoir loading at the full level and at other
critical levels, a seismic acceleration of O.lg was ap-
plied horizontally in the most unfavorable direction to
each section analyzed. Material strengths were based
on soils testing.
Settlement. Foundation settlements were predict-
ed to be negligible in all but the 91-foot-high main
Forebay Dam. There, an embankment camber of 6
inches was provided.
163
Figure 135. General Plon of Foreboy Main Dam
164
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165
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Figur* 137. Forebay — Ruddy Creek and Low Danu Sections
166
Figure 138. Afterbay Dam — Sections and Details
167
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Figure 139. Afterbay Dam Defaili
168
Construction Materials. Materials used in em-
bankments were obtained from the following sources
(the letter F after the embankment zone number sig-
nifies Forebay Dam; the letter A, Afterbay Dam):
1. Impervious
Zone IF — Designated stockpiled material from
Thermalito Powerplant excavation.
Zone lA — Mandatory afterbay excavation, op-
tional channel excavation, dam foundation excava-
tion, structure excavation, tail channel excavation,
outlet channel and connecting channel excavation,
and roadway excavation.
Zone 2F — Mandatory forebay excavation, option-
al channel excavation, dam foundation excavation,
structure excavation, tail channel excavation, road-
way excavation, and excess material from stockpile
for Zone IF.
Select Zones IF and lA are coarser materials se-
lected from these sources to filter the blanket drains
composed of Zone 3 material.
2. Pervious
Zone 2A — Transition material from Borrow
Area Z (dredger tailings west of Feather River,
south of Afterbay) or furnished by the contractor
from outside sources.
Zone 3 — Transition material from Borrow Area
Z.
Zone 4F — Designated stockpiled rock material
from Thermalito Powerplant contract, rock from
mandatory forebay excavation, and Borrow Area Y
(base of Campbell Hills within Forebay, near Ther-
malito Powerplant).
Zone 4A — Borrow Area Z and other designated
areas of coarse dredger tailings.
3. Riprap
Designated stockpiled Thermalito Power Canal
excavation (Rock Stockpile No. 1), designated
stockpile Oroville Dam spillway excavation (Rock
Stockpile No. 2), designated state-owned quarry 2
miles upstream of Thermalito Diversion Dam and
approved contractor's sources.
Material design parameters for the construction
materials are shown in Table 14.
Foundation. The forebay low dam is founded en-
tirely on Red Bluff formation; the main dam, partially
on basalt and partially on Red Bluff formation; and
the Ruddy Creek Dam, on Red Bluff formation.
The Afterbay Dam is founded on Red Bluff forma-
tion except at the southeast corner of the reservoir
where the foundation is Columbia loam.
The dam on the compact Red Bluff material was
designed with a 5-foot-deep cutoff trench. On the Co-
lumbia loam, the trench was omitted, but the seepage
path was lengthened by including relocated Oroville-
Willows Road on a 50-foot-wide berm on the down-
stream side and a 100-foot-wide blanket on the up-
stream side. In addition, the entire reservoir floor was
compacted.
Instrumentation. Instrumentation at Thermalito
Forebay Dam consists of embankment settlement
monuments and downstream open-tube piezometers
and measuring wells.
Instrumentation at Thermalito Afterbay consists of
TABLE 14.
Material Desig
n Parameters —
Thermalito Forebay and After
say Dams
Specific
Gravity
Unit Weight in Pounds
Per Cubic Foot
Static Shear Strengths
B Angles in Degrees
Cohesion in Tons Per Square Foot
Effective
Total
Material
Dry
Moist
Saturated
e
C
e
C
Forebay
2.75
2.75
2.91
2.85
2.85
2.75
2.78
2.91
2.91
2.85
2.80
2.80
114
109
155
135
125
93
117
155
150
120
96
96
130
126
161
138
127
118
134
161
155
122
122
122
135
134
164
150
144
121
137
164
161
140
124
124
33
30
45
45
45
32
30
45
40
45
30
26
0
0.15
0
0
0
0.2
0.15
0
0
0
0.10
0.05
16
15
0.4
1.0
Aftirlay
Zone lA
Zone 2A
Zone 4A. ._.
_.
Foundation in Columbia Soils
Area:
Southwest of River Outlet. .
Northeast of River Outlet..
Foundation in Red Bluff for-
mation was treated as
basement rock
--
169
109 open-tube piezometers (95 functional) located
downstream of the dam and alongside the tail channel.
In addition, piezometric level is monitored in 171 pri-
vately owned farm wells located in adjacent areas.
Forebay Inlet-Outlet
Flow into and out of the Forebay occurs in the
normal course of power production. Thermalito Pow-
erplant on the west and the Power Canal on the east
each provide for these flows depending on whether
generation or pumpback is taking place. A bypass gate
is provided at the plant for release of water from the
Forebay to the Afterbay in the event of powerplant
shutdown. Flows up to 10,000 cubic feet per second
(cfs) can be discharged.
Thermalito Power Canal
Thermalito Power Canal extends from a headworks
structure, which is a portion of Thermalito Diversion
Dam, to Thermalito Forebay (Figure 140). The canal
invert is level to facilitate conveyance in both direc-
tions. It was designed to convey a maximum flow of
17,000 cfs for the generating cycle of pumped-storage
operation. Maximum flow in the pumping cycle is
9,000 cfs. Canal cross-section dimensions were set for
convenience of doubling the canal capacity at a later
date in connection with a possible second Oroville
Powerplant. Bridge pier foundations were deepened
to allow for this expansion.
The area traversed by the Canal contained ground
water which stood at a considerable height above in-
vert for most of the length. Ground water levels were
higher to the north of the canal alignment and gener-
ally followed the natural topography.
The Canal traverses an area with a wide variety of
soil and rock material which vary considerably in
strength from sound rock to weak clay.
Figure 140. Thermalito Power Canal
Canal Section. Preliminary design analysis in-
dicated that for a canal with a flat invert at elevation
196.7 feet and I'/j:! side slopes, a 60-foot bottom width
would yield the most hydraulically efficient section.
The significant factor in selecting the bottom width
was that it must be reasonably matched with possible
second-stage construction. A 48-foot bottom width
was chosen for initial development because it pro-
duced a favorable economic balance between the cost
of additional head loss and savings in excavation and
lining costs when considering future expansion. If the
60-foot section had been selected, widening problems
would have been compounded for the second-stage
canal to permit it to match the same water surface
elevation. Typical sections are shown on Figure 141.
A transition section was provided between the Ca-
nal and the Forebay to minimize head losses. This
section is 2,830 feet long.
Filter Subliner. Two types of material were used
for the 9-inch filter blanket placed under the concrete
lining. Type A (placed on soil excavation) was 65 to
90% sand with %-inch maximum size, 0 to 8% passing
No. 100 sieve and nothing passing No. 200 sieve. Type
B (for rock excavation) was 35 to 60% sand, with a
maximum size of 1/4 inches, and nothing passing No.
30 sieve. The filter was necessary to transport ground
water into the canal lining weep holes and prevent
piping of foundation materials.
Lining. Changes in pressures on the lining can
result from fluctuations in ground water levels and
from fluctuations in canal water surface elevation
caused by changes in power operations. The lining,
weep holes, and filters were designed to satisfy rapid
fluctuations, even to the point of negative waves
formed during emergency shutdowns.
Design of the canal lining specified 6-inch concrete
slabs reinforced with No. 4, steel, reinforcement bars
without expansion joints but with grooved joints
placed at 15-foot centers to relieve expansion stresses.
The lining is anchored at each end of the Canal to
prevent movement at the ends. The top of the lining
is at elevation 228 feet.
Weep holes were placed in the lining to allow
ground water and water trapped behind the lining to
flow freely into the Canal from the filter subliner.
Holes were constructed from 1 '/4-inch-diameter, mold-
ed, plastic pipe with a perforated conical tip embed-
ded in the filter material. There are three weep holes
for each top lining panel and one in each of the re-
maining 15- by 15-foot panels of canal lining.
Sides of the transition section into the Forebay were
lined with 1 foot of stone protection over 6 inches of
filter material. This stone material was specified to be
9 inches maximum and 1/2 inches minimum size.
Drainage Structures. Interception of ground wa-
ter flows and surface drainage on and above the cut
slopes is critical to the stability of the canal side slopes.
Surface drainage pipes receive intermittent use. Drop
170
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Figure 141. Power Canal Sections
171
inlets were installed with seepage rings to prevent
seepage along the pipeline which would soon endan-
ger the stability of the drainage structure and the ca-
nal section.
Horizontal drains were placed in localized areas to
allow ground water in the cut banks above the canal
lining to be collected and drained into the Canal (Fig-
ure 142). Each horizontal drain consists of a 2-inch-
diameter, perforated, steel pipe connected to a 6-inch-
diameter, asbestos-cement, collector pipe.
Turnouts. Two canal turnouts were provided
(Figure 143). One is for California Water Service
Company, and the other is for Thermalito Irrigation
District. California Water Service Company convey-
ance and treatment facilities had to be relocated due
to severance caused by the Canal.
The Thermalito Irrigation District outlet provides
releases to replace water from its facility which was
inundated by Lake Oroville.
Tail Channel
The tail channel hydraulically connects Thermalito
Powerplant with the Afterbay. This channel is ap-
proximately V/i miles long and was constructed with
a 70-foot bottom width and 2:1 side slopes. It was sized
to ensure that when Thermalito Powerplant is pump-
ing and the Afterbay is at minimum water surface
elevation, the water surface profile through the chan-
nel will be high enough to maintain adequate submer-
gence on the pumping units. The channel section is
lined with a 1-foot-thick layer of stone slope protec-
tion on a 6-inch layer of bedding.
Afterbay Irrigation Outlets
Irrigation outlet structures are incorporated into
Thermalito Afterbay Dam to supply irrigation water
to various water districts whose diversion facilities
were taken out of service as a result of construction of
the Afterbay. The irrigation outlet facilities (Figure
130) regulate, measure, and record deliveries. Sizes of
the outlets were determined by the necessity to meet
discharge requirements at minimum reservoir level
and match existing water levels in the canal systems.
These structures include Western Canal and Richvale
Canal outlets combined in one structure, located in
the northwest corner of the Afterbay; Pacific Gas and
Electric Company (PG&E) lateral outlet, on the west
side of the Afterbay south of State Highway 162; and
Sutter-Butte Canal outlet, on the south side of the
Afterbay.
Western Canal outlet consists of five 96-inch-diame-
ter conduits through the dam. The Richvale Canal
outlet parallels these with three 72-inch-diameter con-
duits, all resting on a concrete slab base (Figures 144
and 145). Each conduit is equipped with a slide gate
at the upstream end to control flow and a Dall flow
tube for measurement purposes. It was decided to use
Dall flow tubes for measurement in this structure in-
stead of a less expensive weir, as in the Sutter-Butte
Canal outlet, because of the small head available when
the reservoir is at minimum level. Conduits discharge
into concrete-lined transition sections providing
smooth flow conditions into the canals. Bulkheads are
provided at the upstream and downstream end of the
structure which enable the conduits and gated intakes
to be dewatered. Stability analyses of the structure
were made for several cases of loading, the more se-
vere of which was for drawdown and for seismic load-
ing. The minimum safety factor against sliding is 2.00
and against overturning is 1.47. Other stability results
are considered to be adequate.
The PG&E lateral outlet (Figures 146 and 147) con-
sists of a 30-inch-diameter conduit, a small intake
training structure with provisions for bulkheading, a
wet well upstream of the dam centerline containing a
30-inch-square slide gate, and an outlet stilling box
with a weir for measuring flow.
The Sutter-Butte Canal outlet (Figures 148 and
149) consists of four 7-foot-wide by 6-foot-high rectan-
gular conduits founded on a concrete base slab, slide
gates, a headwall with provisions for bulkheading,
training walls, and an outlet channel approximately
1,200 feet long connecting to the existing Sutter-Butte
Canal. The concrete base slab overlies a 2-foot-thick
drain blanket. Flow is measured by a control weir in
the outlet channel approximately 400 feet down-
stream of the conduit outlet.
Stability analyses were made for several different
cases of loading, with the two most severe being for
drawdown and seismic loading. The minimum safety
factor against sliding is 1.35 and for overturning is
1.33. All other stability results were considered to be
adequate.
The controls for all irrigation outlets were designed
to automatically adjust the slide gates to accommodate
constantly changing head caused by afterbay fluctua-
tions. Each gate may be operated from any of three
control stations: at the gate hoist operator, in the sepa-
rate outlet control houses, or in the remote control
station located in the Oroville Area Control Center at
the foot of Oroville Dam.
Each local control house is supplied with power
from PG&E. The houses contain motor control cen-
ters, supervisory control cabinets, and standby en-
gine-generator sets with appurtenances. The PG&E
lateral outlet has a battery for emergency power
rather than an engine-generator set.
Table 15 lists the pertinent data for the slide gates
and electric motor-operated hoists installed on the
various outlet structures.
Afterbay River Outlet
The river outlet (Figures 150 and 151) is situated in
the southeast corner of the reservoir (Figure 130), a
location most convenient for discharge to the Feather
River.
Water is released from this structure for down-
stream project use, streamflow maintenance, and wa-
172
TABLE 15. Data for Gates and Hoists — ^Thermalito Afterbay
Outlet
Number
of Gates
Size
of Gates
Conduit
Size
Gate Travel
Speed
Inches per
Minute
Invert of
Gate Opening
Elevation
Flow Sensing
Method
Gate and
Operator
Assembly
Weight
Each (pounds)
Western
5
3
1
4
96' sq.
72' sq.
30' so.
60" by 72'
96' dia.
72' dia.
30* dia.
72' by 84'
6
6
3
6
105.0
105.0
109.2
102.75
Flow Tubes
Flow Tubes
Weir
Weir
13,000
8,000
3,000
8,000
PG&E
Sutter-Butte
ter-right commitments. Streamflow maintenance
requires a minimum release of 600 cfs at this point.
The outlet discharges the net water used in power
generation for each day uniformly over a 24-hour peri-
od. In winter months, high riverflows to Lake Oro-
ville result in full generation, and afterbay releases can
be as high as 17,000 cfs. During other months, only
peaking generation occurs and releases are about 6,000
to 8,000 cfs. Releases to 8,000 cfs can be accomplished
at any afterbay stage above minimum operating level,
elevation 123 feet. Full discharge of 17,000 cfs is possi-
ble only with reservoir stage at or above elevation 127
feet. High flows in the Feather River restrict dis-
charge through the outlet. Nearly full pool in the Aft-
erbay is required for 17,000 cfs through the outlet with
150,000 cfs in the River (the standard project flood
release at Oroville Dam).
Releases are controlled by five 14-foot by 14-foot
radial gates with rubber "J" seals at the top and sides.
The bottom is sealed by a rubber bar embedded in the
invert. The gate position is automatically controlled
and set remotely from the Oroville Area Control Cen-
ter.
Outlet gates extend from invert elevation 105 feet to
top elevation 1 19 feet. A concrete breastwall contains
the reservoir above elevation 119 feet. Slots are pro-
vided both upstream and downstream of the radial
gates to accommodate bulkhead gates to dewater each
bay. Concrete counterfort walls form the sides of the
outlet channel and retain the embankment at the head-
works and channel. A service bridge crosses over the
gates at elevation 142 feet, and a bridge for Oroville-
Willows County Road spans the channel immediately
downstream at elevation 135 feet.
Five electric motor-operated hoists are located on
the machine deck of the headworks structure at eleva-
tion 142 feet to operate the radial gates. Each hoist
consists of an operator with accessories mounted on a
support base.
An unlined trapezoidal channel, with a bottom
width of 160 feet and length of approximately 1,000
feet, carries the discharge from the headworks to the
River. Concrete piers, in a pattern determined by hy-
draulic model study, were constructed in the concrete-
lined headworks outlet channel to spread the flow and
dissipate energy before the discharge enters the un-
lined trapezoidal channel. Approximately 800 feet
downstream of the headworks, where the channel nar-
rows, a weir was constructed to prevent anadromous
fish from moving up the channel into the Afterbay
and also for measuring discharge. The weir has an
ogee-shaped crest at elevation 133 feet, with a length
of approximately 168 feet. Metal racks were installed
on the crest downstream of the weir crest to prevent
migration of fish but were removed when subsequent
operation indicated they were not required. A bridge
and walkway provide access for service of the racks.
Downstream of the weir is a paved channel about 117
feet in length which extends to the river channel.
The headworks structure and fish barrier weir were
analyzed for overturning and sliding for both normal
and seismic conditions. The minimum safety factors
for the headworks are 1.92 against overturning and
1.32 against sliding. The minimum safety factors for
the barrier weir are 3.4 against overturning and 1.66
against sliding.
A control house located near the outlet contains the
motor control center, supervisory control cabinet, wa-
ter-level and temperature recorders, and standby en-
gine-generator set with its appurtenances. The
control house is supplied with 3-phase, 480-volt, 60-
cycle power.
Flood Routing
The volume of local inflow during the maximum
probable storm was calculated to be 3,800 acre-feet for
the Forebay and 5,200 acre-feet for the Afterbay. This
would be produced by approximately 17 inches of
rainfall in a 72-hour period. Ninety percent runoff
would be expected due to the impervious surface of
the drainage area.
Thermalito Powerplant bypass can discharge the
forebay runoff into the Afterbay. The river outlet or
one of the other afterbay outlets can discharge the
combined local inflow, because the afterbay water sur-
face would be at least 5 feet higher than the River or
inundated lands in the area, even during the max-
imum probable storm over the entire Feather River
drainage. Therefore, construction of spillways was
unnecessary.
173
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175
Figure 144. Western Canol and Richvole Canol Outlets
176
Figure 145. Western Canal and Richvale Canal Outlets — Isometric View
177
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Figure 146. Pacific Gas and Electric Outlet
178
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Figure 147. Pacific Gas ond Electric Outlet — Isometric View
179
Figure 148. Sulter-Butte Outlet
180
Figure 149. Sutter-Butfe Outlet — Isometric View
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Figure 150. River Outlet
182
88
Figure 151. River Outlet Headworks ond Fish Barrier Weir — Isometric View
183
Relocations — ^Thermalito Complex
Construction of the Thermalito complex required
the relocation of many utilities and roads serving the
area. It also required, where relocation was not made,
structures to cross the complex or abandonment of
little used roads. Where abandonment took place,
other facilities were provided to handle the traffic
(Figure 130).
Construction of the Power Canal required a bridge
on the Oroville-Cherokee Road, the Oroville-Chico
Road, and relocated Highway 40A (now State High-
way 70). A bridge also was constructed across the
Western Pacific Railroad relocation on the Oroville-
Cherokee Road. Power Canal construction also re-
quired the relocation of the Thermalito water treat-
ment facilities.
Construction of the Forebay required relocating
about 4,600 feet of Nelson Avenue with a bridge
across the Forebay.
Construction of the tail channel and Afterbay re-
quired relocation of Oroville-Willows Road, State
Highway 162, and abandonment of sections of Tres-
Vias and Larkin Roads.
All facilities were replaced in kind or updated to the
then-current design standards. The bridges were de-
signed and built to AASHO specifications and the
California "Bridge Planning and Design Manual".
They were designed for like loading of HS20-44 or
H20-S 16-44 with an alternate loading of two 24,000-
pound axles 4 feet apart. The Department of Water
Resources designed and constructed all the relocations
except for State Highway 162, which was done by the
State Division of Highways (now the Department of
Transportation).
Following is a brief synopsis of the work performed
on each road.
Oroville-Chico Road Bridge. The Oroville-Chico
Road Bridge is a continuous, three-span, reinforced-
concrete, box-girder structure supported on rein-
forced-concrete abutments and two reinforced-con-
crete piers. The two end spans are 60 feet long and the
center span is 150 feet long, for a total length of 270
feet. Total deck width is 36 feet - 10 inches which in-
cludes two 14-foot- 0-inch vehicle lanes and a 5-foot
-11-inch-wide curb on the east side. The boxgirder is
a three-cell unit 28 feet - 5 inches wide from outside to
outside and 8 feet - 0 inches deep from the roadway
deck to outside bottom. The two abutments are found-
ed on spread footings, and the two 8-foot - 0-inch-di-
ameter columns are cast-in-place and extended to a
maximum of 44 feet below canal invert with a mini-
mum penetration of 8 feet into sound rock.
The entire structure was constructed prior to exca-
vation of Thermalito Power Canal. This resulted in a
shorter construction time with a minimum amount of
false work required to support the cast-in-place super-
structure.
The road alignment was shifted slightly to produce
a more perpendicular and thus shorter bridge across
the Canal.
Oroville-Cherokee Road Overhead Crossing. The
Oroville-Cherokee Road overhead crossing of the
Western Pacific Railroad relocation is a 140-foot-long
bridge which has a three-span, continuous, reinforced-
concrete, "T"-beam superstructure supported by rein-
forced-concrete piers and abutments. It provides a 32-
foot roadway consisting of two 12-foot lanes and two
4-foot shoulders. A 3-foot - 2-inch safety curb with
barrier railing is located along one edge of the bridge,
and a 1-foot- 10-inch safety curb with barrier railing
is located along the other edge of the bridge.
Oroville-Cherokee Road Bridge. The Oroville-
Cherokee Road Bridge across the Canal is a continu-
ous, five-span, reinforced-concrete, box-girder struc-
ture supported on reinforced-concrete abutments and
four reinforced-concrete piers. The total length of the
Bridge is 575 feet. One approach span is 65 feet long
and the other is 110 feet. The lengths of the three
interior spans are 1 10 feet, 144 feet, and 144 feet. Road-
way width, sidewalks, curbs, and boxgirders are iden-
tical to the Oroville-Chico Road Bridge. The two
abutments are founded on a cast-in-place concrete pile
system. The four 8-foot-diameter reinforced-concrete
piers are cast-in-place and extend 8 feet minimum into
sound rock.
Nelson Avenue. Approach embankments and a
bridge across the Forebay were constructed on an
alignment north of the existing road to minimize the
bridge length. The east approach embankment over-
lies the Forebay Dam.
The bridge has a six-span, reinforced-concrete, "T"-
beam superstructure 430 feet long supported by rein-
forced-concrete piers and abutments. It provides a 28-
foot clear roadway, a 5-foot sidewalk, a 2-foot safety
curb, and barrier railings on each edge of the deck.
Five piers have been provided for future construction
of a parallel bridge.
Larkin Road. The Larkin Road Bridge was built
to replace a county road which was severed by the tail
channel.
The Bridge has a four-span, reinforced-concrete,
"T"-beam superstructure 265 feet long supported by
reinforced-concrete piers and abutments. It provides
a 28-foot clear roadway, a 5-foot sidewalk, a 2-foot
safety curb, and a barrier rail on each edge of the deck.
Except for a short section of this county road, Lar-
kin Road was abandoned south of State Route 162.
Traffic from this road was rerouted to the Oroville-
Willows Road. (Recent maps indicate that Larkin
Road has been renamed Wilbur Road and that old
Oroville-Willows Road is now called Larkin Road.)
The county agreed that sections of Tres-Vias Road
across the tail channel and the Afterbay could be aban-
doned if other access was provided. A single bridge
crossing was used on Larkin Road to provide access to
the Tres-Vias Road.
184
Oroville-Willows County Road. The Oroville-
Willows County Road was relocated around the
southern end of Thermalito Afterbay. The work con-
sisted of slightly over 2 miles of new alignment with
a bridge spanning the river outlet headworks.
The bridge is 96 feet long with a simple-span, com-
posite, plate-girder superstructure supported at the
ends by the walls of the river outlet headworks. It
provides a 28-foot clear roadway, a 4-foot - 1-inch side-
walk, a 1-foot - 7-inch safety curb, and a barrier railing
on each edge of the deck.
State Highway 162. State Highway 162 was placed
on an embankment and a 670-foot-long bridge im-
mediately south of its preproject alignment. The total
length of the relocation was 4,300 feet. The embank-
ment has adequate width for expansion to four lanes
while the bridge will carry only the present two lanes
of traffic. Embankment was included in the afterbay
dam construction.
Construction
Contract Administration
General information about the major contracts for
the construction of Thermalito Forebay, Afterbay,
and Power Canal is shown in Table 16. There were
two principal contracts. The first was for construc-
tion of Thermalito Forebay and Afterbay under the
provisions of Specification No. 65-27. The most note-
worthy features included forebay and afterbay em-
bankments, tail channel, road relocations, outlet
structures and gates, and installation of department-
furnished equipment. The second was for the con-
struction of the Thermalito Power Canal, Specifica-
tion No. 65-37, which included earthwork, concrete
lining, and turnouts for the Canal.
TABLE 16. Major Contracts — Thermalito Forebay, Afterbay,
and Power Canal
Thermalito Forebay
and Afterbay
Specification
Low bid amount
Final contract cost
Total cost-change orders
Starting date
Completion date
Prime contractor
65-27
214,452,680
216,265,321
21,387,113
10/25/65
4/1/68
Guy F. Atkinson
Co.
Thermalito
Power Canal
65-37
35,549,348
27,061,410
21,222,438
10/7/65
10/15/67
Morrison-Knudsen
Co.
Foundation
Stripping. Foundations of both the Forebay and
Afterbay Dams were stripped of all organic material
and Recent alluvium. Stripping was approximately 10
inches deep under the major portion of the dams and
over 5 feet deep in Ruddy Creek, Grubb Creek, and
other small drainage channels.
Excavation — Forebay. Foundation excavation in
the Forebay was of two major types. One type was the
Red Bluff formation and the other was basalt rock.
Basalt rock extended from the Powerplant to Station
8-I-40F, while the remainder of the forebay dam foun-
dation was Red Bluff formation. The foundation was
excavated down to the basalt and curtain-grouted in
this reach because it was economically feasible to do
so. The grouting is discussed in a later section.
The main dam included a deep cutoff trench where
it is founded on the Red Bluff formation to control
seepage into the tail channel. A pervious water-bear-
ing stratum was found near the bottom of design
depth for the trench. The trench was deepened and
extended to Station 15 + 37F, the southern limit of the
Ruddy Creek channel. The pervious stratum still ex-
isted at that point, but any extension of the trench
would have required considerable excavation. The
deep trench was terminated since the tail channel
slope was about 1,000 feet away. This treatment was
effective and seepage into the tail channel has not
caused any problems.
The method used to dewater the excavated trench
was to place rock in drainage trenches on both sides
of the cutoff trench invert and carry it above the limits
of the wet zone. These trenches channeled water to 24-
and 18-inch, perforated, riser pipes (sumps) from
which water was pumped by submersible booster
pumps until the fill reached within approximately 2
feet of the top of the pipe, at which point the water
table was stabilized. The sumps were pumped dry,
pumps removed, and immediately the riser pipes were
backfilled with lean concrete. One and one-half-inch
riser pipes, which were laid parallel to the slope and
on 24-foot centers, penetrated the drain rock and ex-
tended to the surface. They were used to grout the
drain rock when the fill reached the top of the cut.
Beyond Station 15-(-37F, the cutoff trench had a
12-foot bottom width with a depth of 5 feet except
when pervious strata were encountered. Then auger
holes were drilled to find the depth of the pervious
strata, and deepening of the trench was accomplished
if a satisfactory cutoff could be achieved within a max-
imum of 10 feet. If a satisfactory cutoff could not be
achieved, a compacted impervious blanket 3 feet thick
was added upstream, extending 100 feet from the toe
of the dam.
Excavation — Afterbay. Foundation excavation in
the Afterbay also comprised two major types. One
type was the Red Bluff formation and the other Co-
lumbia loam. Red Bluff formation was treated in the
same manner as in the Forebay beyond Station
15 + 37F.
The Columbia loam area in the southeast portion of
the Afterbay and in the vicinity of the river outlet
required close attention to prevent uncontrolled seep-
age into the River. Areas under the dam and the 100-
foot blanket upstream of the dam were excavated to a
depth of 3 feet to reduce the permeability, increase the
strength, and assure removal of roots remaining from
mature walnut trees that formerly grew in the area.
185
After excavating and grubbing operations were com-
pleted, the foundation was scarified, moisture-condi-
tioned, and compacted with a 75-ton pneumatic roller
prior to placement of Zone lA compacted embank-
ment.
Areas 400 by 2,000 feet, adjacent to Western Canal,
were stripped to a depth of 2 feet and compacted.
Once this area was compacted, the adjoining area re-
ceived the same treatment, with the stripped material
wasted on the previously treated area.
Grouting. The grout curtain under the main Fore-
bay Dam was continuous with the powerplant grout-
ing and included the length of the dam resting on
basalt foundation as well as an extension 100 feet out
onto the Red Bluff formation (Figure 152). In this last
area, emphasis was placed on grouting the rubble lens
at their contact. Eighty-five holes were drilled on the
curtain line in three zones: (1) from the surface to 25
feet and pressure-tested at 25 pounds per square inch
(psi); (2) from 25 feet to penetration of the interflow
in the basalt and pressure-tested at 50 to 65 psi, de-
pending on the depth of penetration; and (3) max-
imum depth of 100 feet and pressure-tested at 75 to 85
psi.
Grouting was conducted through a double-line
(feed-return) system. Generally, the top 25 feet were
tight; occasional holes took one or two sacks. Zone 3
holes also took only a few sacks of cement. Almost all
of the grout was pumped into Zone 2 (interflow inter-
cept) with one hole taking 614 sacks. Most mixes start-
ed at 7:1 and were reduced to 5:1 or 4:1.
In addition, 29 holes were drilled for blanket grout-
ing fault areas and for contact grouting at the wing-
wall of the Powerplant. They were bottomed nor-
mally about 10 feet deep.
No grouting was performed in the Afterbay be-
Figure 152. Grouting Foundation of Foreboy Main Dan
cause only Red Bluff and Columbia soils were encoun-
tered.
Embankment Materials and Construction
Impervious — Forebay. Zone IF and 2F material
in the Forebay Dam was generally coarser and less
uniform than Zone lA material in the Afterbay Dam.
Close attention was given to assure that the coarser
portions of the Zone 2F materials were routed to the
outer limits of the zones and Zone iF materials were
blended by controlled excavation to make them homo-
geneous.
Zone 2F material was compacted in all impervious
portions of the embankment except for the designated
Zone IF. Zone IF material was excavated from a
stockpile located approximately 1,000 feet to the east
of the main dam. Material was originally excavated
from the Thermalito Powerplant area.
Zone 2F borrow areas contained many different
strata of fine and coarse material. Excavation was per-
formed normal to the strata with scrapers loaded
downward on the slopes to assure blending of the
strata. Sand lenses that were exposed in the Channel
"H" excavation were blanketed.
Excavated material was transported to the embank-
ment by scrapers and placed parallel to the dam axis
in 8- to 10-inch loose lifts. It was then leveled and
scarified with a bulldozer with a "Trinity Scratcher"
or a motor patrol with a scarifier. The embankment
lift was compacted with 12 passes of a sheepsfoot
roller. All rolling was performed parallel to the dam
axis, except where insufficient space prevented this
procedure from being followed. Zone iF material
placed in contact with the powerplant wingwall was
compacted with hand equipment (Figure 153). A rela-
tive compaction of 97% was required for Zone IF and
95% for Zone 2F.
186
Figure 154. Afterbay Dan
Figure 155. Placement of Zone 4A — Afterbay Dam
When embankment showed an insufficient relative
compaction, the areas were reroUed or the material
removed and wasted.
Impervious — Afterbay. Suitable material excavat-
ed from the cutoff trench was utilized to backfill the
already excavated cutoff trench or was compacted as
Zone lA embankment. The main source of material
for Zone lA embankment was required channel and
structure excavation. Approved borrow areas selected
by the contractor also were used. The specifications
allowed the contractor to spoil required excavation
and excavate for borrow at his own expense to shorten
haul distances.
Transportation and placement of the Zone lA
material were performed in a manner similar to Zone
IF and 2F placement in the Forebay Dam (Figure
154).
Pervious — Forebay. Zone 3, a sandy gravel, was
placed on the entire upstream face of the dam and at
designated areas on the downstream side. Zone 4F
material, basalt rockfill, was placed on the entire
downstream face of the Forebay Dam and on the up-
stream face at designated areas. It was obtained from
two places: Borrow Area Y, an extension of the inlet
channel to Thermalito Powerplant, and stockpiled
powerplant excavation.
Prior to placing Zone 3 and 4F material, the con-
tractor elected to construct the Zone IF or 2F embank-
ment to about dam crest elevation. This resulted in a
restricted working area which precluded compaction
by the specified method of four passes of the treads of
a crawler tractor. Tests of alternate compaction meth-
i ods with vibratory rollers showed that one pass of a
72-inch vibratory roller on Zone 3 material and one
pass of a 54-inch vibratory roller on Zone 4F material
would result in compaction slightly higher than speci-
fied. Consequently, this method of compaction was
adopted throughout the operation.
Both zones were loaded at the source with rubber-
tired loaders and transported to the embankment in
16-cubic-yard, bottom-dump, highway trucks. A bull-
dozer was used to spread the material in 12-inch lifts.
Pervious — Afterbay. Placement of Zone 3 and 4A
material consisted of a blanket of Zone 4A material on
the entire downstream face of the dam (Figure 155)
and Zone 3 material on the upstream face of the dam.
Zone 3 material was obtained from Borrow Area Z.
Most of Zone 4A material was excavated from the
river outlet structure area, with the remainder from
optional borrow areas.
The contact point between Zone lA embankment
and Zone 3 and 4A material was watered and wheel-
rolled with loaded trucks. Transportation and place-
ment of material were accomplished in the same man-
ner as for Zones 3 and 4F in the Forebay.
Riprap. Riprap was hauled to the dams utilizing
end-dump highway trucks and trailer rigs and
dumped in stockpiles along the upstream toe of the
dams. Placement was performed with rubber-tired
front-end loaders with chain wrapping on the front
wheels for better traction (Figure 156). The loaders
carried the rock from the stockpiles to the top of the
slope and windrowed a lift for a distance of 50 to 100
feet longitudinally, then added another windrow be-
low it. This procedure was continued until the bottom
was reached.
"Top-Out" Operation. A small, self-loading, pad-
dle-wheel scraper; a blade; and compaction equipment
187
Figure 156. Riprap Plor
were employed to finish the top 2 feet of the impervi-
ous portion of the dams because they were too narrow
for larger equipment to maneuver. The pervious por-
tions of the dams were brought to grade at a later date.
The top surface was fine-graded and a 4-inch layer of
the aggregate base material was placed.
The aggregate base material was trucked to the em-
bankment from a screening plant located at Borrow
Area Z. Once at the embankment road, the material
was dumped in two windrows, one on each half of the
road; a spreader box was used to distribute the materi-
al to the required thickness and width of the road.
After spreading was completed, the surface of the road
was bladed and compacted with a three-legged roller.
Final compaction was performed with a vibratory
roller.
Thermalito Power Canal
Excavation. Canal excavation was started west of
State Highway 70 using double-bowl diesel-electric
scrapers. Excavation progressed eastward in a pion-
eering fashion, with the contractor constructing haul
roads to and from various spoil areas prior to serious
excavation in any particular area. Spreads of scrapers
with bulldozers later were added to the excavation
effort.
Nearly all of the excavated material required rip-
ping prior to its removal with scrapers. Bulldozers
operated singly or in tandem to push-load the non-
electric scrapers. Electric scrapers were self-loading
with all eight wheels pulling but occasionally needed
assistance. Softer earth material was excavated with
the electric scrapers while the others were used mostly
in weathered and decomposed rock, in wet areas, and
in the small confined areas of the canal prism. The rate
of production in the canal excavation averaged 25,000
to 28,000 cubic yards per eight-hour day.
Between the Oroville-Cherokee Road Bridge and
the Oroville-Chico Road Bridge, areas of unsuitable
material were encountered below the elevation of the
canal invert and beyond the established slope lines
above the operating roads. These areas were overex-
cavated and refilled. The invert was refilled with com-
pacted embankment or with Type B filter material,
depending on the subsurface water conditions en-
countered. Side slopes above the canal lining were
filled with free-draining material from canal excava-
tion to eliminate slide conditions.
Bedrock was drilled and shot. Typical drill holes
were 20 feet deep on 8-foot centers. Shot rock was
loaded into dump trucks with front-end loaders and,
using the canal invert as a roadway, the material was
hauled to the designated riprap stockpile area or wast-
ed in spoil areas. The stockpiled rock was used as
riprap on the forebay embankment under the Ther-
malito Forebay and Afterbay contract. More than half
of the excavated rock broke into pieces too small to be
used for riprap, even though normal rock excavation
methods were used. The high loss probably resulted
from weathered shear zones or closely spaced joints in
the bedrock. A total of 207,000 cubic yards of excavat-
ed rock was stockpiled.
Beginning in early August 1966, the first indication
of serious slide trouble became apparent when earth
slides developed in both cut banks 1,000 to 2,000 feet
west of Oroville-Cherokee Road Bridge. Fissures and
cracks observed at various other locations along the
canal gave evidence of possible future slides. These
slides and indications of slides were not of any great
magnitude at first; however, attempts to remove the
slide material triggered further movement. The slides
were attributed to failure, or "breaking down", of un-
supported lone formation clay, which was exposed
during canal excavation (Figure 157).
188
After the first earth slides, seasonal rains com-
menced which further aggravated slide conditions.
Existing slides became more extensive, and new slides
developed in areas where the slopes had been standing
satisfactorily. Additional movement of the earth slides
west of the Oroville-Cherokee Road Bridge blocked
the canal invert, causing surface drainage water to
pond for a distance of one-half mile. Consequently, the
contractor was directed to let the earth slides stand
until studies were made. It was concluded that the
slides should be removed and replacement of the slide
material with compacted backfill began in early Feb-
ruary 1967, on a two-shift-per-day schedule, five days
a week. Later, the contractor went to a three-shift
schedule, six days a week. Corrective work was com-
pleted in May 1967, and all canal excavation was com-
pleted in June 1967.
Horizontal Drains. In areas where ground water
was found seeping through the cut slopes, horizontal
drains were installed to intercept and remove this sub-
surface water. Average depth of the holes was 172 feet,
with a depth range of 80 to 300 feet.
At several locations, horizontal drains were in-
stalled in the canal prism below the operating roads.
These drains were not anticipated in the design, so a
contract change order provided for a collector system
and for disposing of the water. These drains extend
through the canal lining.
Filter Subliner. Type A filter material was placed
with a clamshell a few inches below final grade prior
' to the trimming operation, with the remainder being
placed by the lining machine at trimming. Where
Type A filter material was found to be above elevation
218 feet, it was removed and replaced with Type B
filter by means of a cutoff plate attached to the front
I of the lining machine (Figure 158). Type B filter for
I rock sections also was placed on the slopes by a clam-
: shell and trimmed with a lining machine. Filter
I material in the invert was spread with a motor grader
I and trimmed concurrent with trimming of the side
\ slopes. Filter material was placed by clamshell and
I trimmed to line and grade by less automated methods
I in other areas inaccessible to the lining machine.
I Concrete. The canal lining consists of 6-inch-
j thick reinforced concrete with transverse grooved
I joints on 1 5-foot centers. One longitudinal construc-
i tion joint was placed at the canal centerline. Longitu-
j dinal grooved joints were placed on 1 5-foot centers on
] the side slopes and at distances of 7 feet and 20 feet on
leach side of the centerline in the invert.
j Reinforcement steel for the canal lining consists en-
jtirely of No. 4 bars placed on 12-inch centers each
iWay. Precast mortar spacers were attached to the steel,
land the invert and side slope mats were placed on the
ifilter blanket with a mobile crane (Figures 159 and
I 160).
Figure 158. Placing Type II Drain Pipe Along Toe of Slope and Type
B Filter Material on Invert of Power Canal
Figure 160. Reinforcing Steel Being Placed in Conol Invert
189
The contractor's paving (lining) train was made up
of a lining machine followed by a finishing jumbo and
a curing jumbo. The jumbo spanned the full width of
the paving operation, one side slope and half the in-
vert.
All power to the lining machine was supplied by a
diesel motor-generator mounted over the low driving
track. Travel and support were provided by two inde-
pendent tracks driven by an electric motor mounted
on each unit. Line and grade were controlled by elec-
tric probes attached to the lining machine, activated
by piano wire stretched along the invert and the oper-
ating road.
Concrete was delivered to the lining machine by
8-cubic-yard mixer trucks and deposited on a belt
which conveyed the concrete to a 4-cubic-yard, travel-
ing, dump car mounted on the front of the lining
machine. Consolidation of the concrete was accom-
plished by horizontal vibrators running the full
length of the lining machine and mounted in the bot-
tom of the baffled hopper at the finish gradeline. Once
the concrete was consolidated, it passed under a
smooth pan located below the structural members of
the machine. Beyond the smooth pan, there was a
short gap; then the concrete passed under an 18-inch-
wide floating pan.
The longitudinal grooves were cut first using cut-
ting edges protruding 3 inches below the lining ma-
chine's leading pan. The transverse grooves were cut
by transverse bars located at the rear of the lining
machine which were forced into the concrete by hy-
draulic rams aided by vibration. The grooved joints
obtained by this method were not satisfactory. They
required more hand finishing than appeared practical,
so other methods were explored. The contractor final-
ly elected to place plastic strip joints both longitudi-
nally and transversely. Observation of the breaks and
appearance in the lining at the plastic strip joints in-
dicated that good results were obtained.
Concrete placements, referred to as "hand lining"
were made in areas inaccessible to the canal lining
machine and in the transition area west of State High-
way 70. A small paver (Figures 161 and 162) was
designed by the contractor and used to place concrete
in these areas.
Concrete placed was well consolidated and required
only a small amount of hand finishing. The cove at the
toe of the side slopes was placed first in alternating
IS-foot sections. Side slopes then were placed in the
remaining 15-foot-wide sections. Alternating the ini-
tial concrete placements provided a firm foundation
and solid side forms for the paving screed during the
final placements. The invert was placed last.
The operation that actually controlled construction
progress on the canal lining was the concrete finish-
ing. Concrete repair was required in a few areas that
were placed in the early part of the lining operation.
Concrete for the canal lining was produced in an
automatic batch plant located to the right of the canal,
Figure 161.
Slip Form Lining Operation on Thermalito Power Canal
Transition Slopes
west of the Oroville-Cherokee Road Bridge, in Spoil
Area B. Concrete temperature control was accom-
plished by the addition of ice to the batch water. The
contractor was able to maintain the temperature at or
below 80 degrees Fahrenheit.
Structural concrete was delivered to the site in
transit mixers from a commercial plant.
Weeps. Due to anticipated problems and slow rate
of progress in installing the canal weeps as designed,
plastic tube-type weeps were substituted. The plastic
weep consisted of a 2-inch-diameter by 12-inch-long
tube, conical on the bottom and open at the top with
an internally fitted plastic cap. Weeps were installed
by placing each weep over a steel insert and driving
it into the wet concrete.
Stone Protection. Where the canal section is 400
feet wide, the specifications gave the contractor the
option of placing crushed stone or rock material ob-
tained from the canal excavation or other sources. The
contractor interpreted this as allowance for the use of
uncrushed river gravel screened from local Feather
River aggregate sources. However, it was the Depart-
ment's intention to require the use of crushed or angu-
lar rock material — not round, uncrushed, river gravel.
Consequently, a contract change order was issued
clarifying the requirements.
Recreation Area. In cooperation with the Califor-
nia Department of Parks and Recreation, site prepara-
tion work for the north forebay recreation area
adjacent to State Highway 70 was included in the
power canal contract. This recreation area originally
consisted only of a spoil area, but a contract change
order provided for a swimming lagoon and beach adja-
cent to the spoil area and canal outlet.
190
Closeup of Slip Form Lining Operation on Thermalito
Power Conal Transition Slopes
Figure 163. Bedding Placement on Tail Channel
Work in the area consisted of clearing and grub-
bing; stripping embankment foundations; placing
compacted embankment for access roads, parking
areas, and building pads; placing 24-inch-diameter,
corrugated-metal, pipe culverts and culvert markers;
final shaping and grading to the design contours; and
the construction of a 24-foot-wide, reinforced-con-
crete, boat ramp. A separate contract change order
provided for the application of a soil sterilizing agent
to a beach area prior to placement of aggregate base
material and processed sand.
Tail Channel
Excavation. Dewatering was performed with one
6-inch, one 8-inch, and one 12-inch, 50-horsepower,
centrifugal pumps. Water was piped to the Van
Gilder drain about 1 '/j miles west of Larkin Road.
In some areas, the bottom of the excavation became
too saturated due to excessive ground water and
would not support the weight of the scrapers and
other equipment. In these areas, material was excavat-
ed with draglines. Where overexcavation occurred,
the areas were brought back to grade with Zone 4F
material. Usable material from the tail channel was
placed in appropriate zones of the forebay and after-
bay embankments and the remainder was wasted. Fi-
nal trimming of the slopes was performed with a small
bulldozer, and the invert was brought to grade with a
blade.
Placement of Channel Protection. Upon comple-
tion of slope trimming, placement of the stone slope
protection and bedding material commenced with a
Gilli-K-Hike (Figure 163). Power to the belt was pro-
vided by a diesel engine-generator mounted adjacent
to the hopper on a platform at the bottom of the ma-
chine, and the power to move the unit was provided
by a bulldozer located on the operating road and a
rubber-tired side-dump truck on the invert of the
channel. Stone slope protection and bedding material
were transported with side-dump trucks. The bedding
material is dredge tailing sand and gravel which was
processed at the Thermalito Powerplant batch plant.
The slope protection is the same material as forebay
Zone 4F. An average of approximately 1,000 feet of
slope protection was completed per two-shift day.
Invert protection material, which is the same as
slope protection material, was trucked with bottom-
dump and end-dump, 18-wheel, highway trucks from
Borrow Area Y and Zone 4F stockpile and spread with
two large bulldozers. Final grading was performed
with blades. Immediately after placement of the invert
protection was completed, the sump pump located at
Larkin Road was removed, and the ground water was
allowed to fill the channel invert.
Miscellaneous Channel Excavation
Channels "A" through "G" are located within the
limits of the Afterbay while Channel "H" is within
the limits of the Forebay (Figure 164). They were
excavated through high ground to provide hydraulic
continuity in the reservoirs.
The contractor exercised his option of extending
the minimum lines of Channels "A", "C", "D", and
"H" to obtain suitable materials for embankment at
reduced haul distances. Sand strata that were exposed
during the excavation of several of the channels were
blanketed with a layer of impervious material.
191
192
Figure 164. Location of Miscellaneous Channels
i
Irrigation Outlets
Western Canal and Richvale Canal. Western Ca-
nal and Richvale Canal outlet structures were built
immediately north of the existing canal alignment so
that the canal could be used during construction (Fig-
ure 165). At the upstream end, the structures are con-
nected by a retaining wall, footing, and cutoff wall.
The entire area between the two structures and the
adjoining area for the structures themselves were ex-
cavated in one operation. This made dewatering easier
since drainage channels could be cut across the entire
area and fewer sumps were required.
Dewatering was accomplished by digging trenches
around the structures. These trenches led to sumps
where the water was pumped out and discharged into
Western Canal. Two weeks after commencement of
discharging water into Western Canal, it was discov-
ered that a delta was developing in the Canal from
sediments deposited from the pumped water. Subse-
quently, water from the excavation was discharged
onto the ground where it either evaporated or seeped
back into the ground. The foundation for the main
cutoff wall was overexcavated and formed instead of
placing concrete directly against the excavation.
The cylindrical forms for the five 92-inch-diameter
(Western Canal) and three 72-inch-diameter (Rich-
vale) Dall tubes had to be anchored securely because
they were subject to extreme uplift pressure as the
concrete placement was brought up.
It was difficult to place concrete under both the
flow tubes and thimbles embedded in concrete at the
barrel intakes without developing voids. These voids
were filled by drilling a hole at the lowest and highest
points of each void and pumping grout into the lower
hole until it came out the upper hole. Holes in the
metal were filled by threading the hole and screwing
a plug into it. Plugs were ground until flush with the
walls.
Each exit wall was placed in three sections. The first
section was formed, the concrete placed and allowed
to set, and the forms stripped, usually in about 6 days.
Fill then was compacted behind the wall. In this case,
however, the contractor was directed not to strip the
forms until test cylinders showed a strength of 2,500
psi to assure that the stress at the base of this concrete
section due to the backfill load would not be exceeded.
For the two sections most removed from the outlet
structure, the slope was flatter and material was
placed behind the walls to grade. Concrete then was
placed from trucks and finished with a slip form that
moved up and down the sloping surface.
PG&E Lateral. This structure is a single-barrel
30-inch-diameter conduit approximately 180 feet long,
with a small intake and exit works.
Structural excavation was performed with a
backhoe for the conduit section and with a bulldozer
for the exit structure and weir. Minor adjustments
were made by hand labor for the cutoff collars and the
float well.
Concrete placement began with the bottom sections
of the six cutoff collars. Subgrade slabs of the inlet,
exit, and wet well were placed next.
Conduit concrete (Figure 166) was placed in a se-
ries of sections as determined by construction joints.
Each section was placed in two lifts, the first of which
was made with the inside conduit forms and all of the
m
^^^ il'H^Bi
■»— "^
^^i^H
~"r>-*";-' .
1
-«^^I|m*>:
V.
^^BP^^t^jj^-t-^.-^^ ,
■<-"'■■
Figure 165. Western Canal and Richvale Canal Outlets — Upstrean
View
Figure 166. Pacific Gas and Electric Lateral Outlet Conduit
193
reinforcing steel in place. The concrete was placed in
the bottom section and brought up to a level an inch
or two below the invert. This anchored the reinforc-
ing and inside forms, thus preventing the forms from
floating during the placement of the second lift. Out-
side forms then were installed and weighted in place
and the second lift placed through the top.
Sutter-Butte Canal. Sutter-Butte outlet structure
(Figure 167) consists of an approach and headworks
section, four 6- by 7-foot rectangular conduits approx-
imately 340 feet long, and an exit structure. A rectan-
gular, modified \'-notch, sharp-crested weir was
constructed 370 feet downstream of the exit structure.
Incorporated in the headworks section are 4- by 6-foot,
steel, slide gates and hoists.
Canal excavation was performed in conjunction
with the structural excavation. The small plug at the
entrance to the old Sutter-Butte Canal was removed
during the closure sequence.
Rough excavation was performed with scrapers,
bulldozers, a motor grader, and a backhoe. Final trim-
ming was performed with a small bulldozer, and cut-
off collar excavation was performed with a small
rubber-tired backhoe.
During structural excavation for the headworks
structure cutoff collar, water-bearing pervious strata
were exposed. As a result, the approach channel was
blanketed with impervious material and the structure
backfill modified to increase the length of the water
percolation path. Dewatering was accomplished by
excavating drainage ditches along the outside of the
conduit slab and by utilizing the cutoff collar excava-
tion as cross drainage.
Bottom slabs of the conduits were placed in alter-
nate 25-foot-long sections for the full width of the
structure. The walls and top slab of the conduit sec-
tions were placed next, in a like manner (Figure 168).
Placement of the downstream transition section in-
cluded the first lift of the exit piers. Embedded in
these piers were the downstream stoplog guides. Dur-
ing placing operations, movement of the forms pushed
the right exit wall guide out of plumb by more than
1 inch parallel to the structure centerline. It was re(>o-
sitioned and epoxy-bonded concrete replacement was
made in 2-foot lifts.
Construction of the slabs and walls of the upstream
approach and headworks (Figure 169) was done simi-
lar to those of the exit works. Higher wall placements
were made in two lifts, the maximum height being 14
feet. Headworks piers were made in three lifts with
the breastwall concrete incorporated in the top two
lifts. The counterforts were placed to full height in
one lift.
River Outlet
The river outlet structure (Figure 170) is located in
the southeast corner of the Afterbay (Figure 130).
Prior to commencement of excavation, sheet piles
were driven and a cofferdam was constructed across
the entire width of the canal just downstream of the
fish barrier structure to keep the river water from
entering the construction site.
Immediately upstream of the cofferdam, two elec-
tric centrifugal pumps, 8- and 12-inch, were installed
to pump the ground water from between the fish bar-
rier and the cofferdam into the River.
Another cofferdam was built just downstream of
the headworks structure for flood protection purposes
during the rainy season. During the winter months of
1966, the ground water between the two cofferdams
was allowed to reach the water surface elevation of the
River, thus equalizing the hydrostatic pressure about
the cofferdam at the River. After the rainy season, the
water once again was removed and construction pro-
ceeded normally.
Figure 167. Sutter-Butte Conal Outlet
Figure 168. Sutter-Butte Canal Outlet Conduits
194
Figure 169. Sutter-Butte Canal Outie; '.r.:^:.^
Headworks. The headworks structure was built
on in-place gravels. The foundation was excavated to
elevation 95 feet and brought back to subgrade with
compacted, semipervious, Zone 3A material. Sub-
grade was at elevation 101.0 feet for the entrance slab
and at elevation 99.5 feet for the radial-gate slab.
Blockouts were provided in the piers to receive the
radial-gate wall plates. This permitted the wall plates
to be adjusted to final position with the radial gates in
place. Stoplog guides were installed upstream and
downstream from the radial gates.
The county road bridge and service bridge slabs
were hand-screened and finished without the aid of a
mechanical finishing machine. Each bridge slab was
covered with carpet and kept wet for curing.
The county road bridge abutments and the radial-
gate end walls were counterforted without using hori-
zontal construction joints.
Figure 170. River Outlet
Fish Barrier Weir. The fish barrier weir structure
(Figure 171) is located on the bank of the Feather
River approximately 860 feet southeast of the river
outlet headworks.
A hammer, powered by compressed air supplied by
a 900-cubic-foot-per-minute rotary compressor, was
used to drive the sheet piling cutoffs under the weir.
The downstream cutoff was driven to tip elevation 80
feet with head or cutoff elevation 99 feet in the chan-
nel invert. Upstream sheet piling was driven to tip
elevation 60 feet with head or cutoff elevation 101 feet
in the channel invert. No difficulty was encountered
in driving the downstream sheet pile tips to elevation
80 feet but, when the upstream sheet pile tips reached
elevation 70 feet, 1-inch penetration required 150 to
300 hammer blows. It was agreed that 150 blows per
inch of penetration of the sheet piling would be ac-
cepted as refusal.
Figure 171. River Outlet — Fish Barrier Wei
195
The structural excavation was performed by a drag-
line with a 3-cubic-yard bucket and end-dump trucks.
Excavated material was wasted in old dredger ponds
or used for channel dikes between the fish barrier and
the river outlet headworks.
Sheet piling was capped by the concrete slabs of the
structure. Concrete for the 3:1 sloped exit slabs was
placed using slip forms.
Face forms for the ogee crest of the weir were
stripped within two hours after concrete was placed,
and all surfaces received a hardwood float finish.
Falsework to support the service bridge slab was
composed of 6- by 8-inch bents with 6- by 6-inch caps.
Telltales were used to check any deflection during
concrete placement. The maximum deflection was '/
inch. The slab surface was hand-finished without any
problems.
Concrete Production
Except for two sections of the river outlet approach,
walls and minor drainage structures, all structural
concrete used on the afterbay outlets was produced at
the batch plant located at the site of Thermalito Pow-
erplant. The remainder was produced at a plant in
Oroville. Control of actual batching operations was
done by department personnel.
Concrete was transported from the Thermalito
Powerplant batch plant by agitator trucks with an
8-cubic-yard capacity. The remaining concrete was
delivered to the job from Oroville by various transit
mixers, ranging in capacity from 6 to 1 1 cubic yards.
Water cure was required on structures for a period
of 10 days. This was accomplished by covering the
structures with water-saturated carpets kept wet by
soaker hoses. Carpets were kept in place for 4 days
following the 10-day curing period.
Membrane curing was allowed on subgrade place-
ments, surfaces to be backfilled, and scattered miscel-
laneous structures. Membrane curing compound was
white-pigmented "Hunts".
Reservoir Clearing
Clearing was required within the entire construc-
tion area and the entire area below the maximum res-
ervoir water levels. Within the cleared area all trees,
structures, and obstructions were leveled to the exist-
ing ground line and all combustible material was
burned.
Grubbing was required only under embankment
foundations where tree roots, pipes, or other material
were buried within the top 3 feet of the foundation.
Trees were pushed over with a large bulldozer, and
the roots were removed with a ripper attachment on
the same equipment.
All known wells within the reservoir and wells that
were discovered during the course of construction
were backfilled in accordance with specifications.
Designated wells located outside the reservoir were
preserved for observation of piezometric levels.
Closure
Since no flowing stream or irrigation ditches exist-
ed in the Forebay, closure did not present any prob-
lems. In the Afterbay, the main closure problem
centered around the Western Canal. The outlet struc-
ture was built adjacent to the existing canal and, upon
completion in the spring of 1967, the Canal was re-
routed so that water ran through the completed struc-
ture and the dam was constructed across the old canal
alignment. The original inlet for Western Canal on
the Feather River had to be maintained until the Fore-
bay was filled and could feed Western Canal through
the tail channel. At that time, October 1967, the After-
bay Dam was closed across the old Western Canal just
north of the river outlet. Closure of the Sutter-Butte
Canal presented no problems because it was possible
to supply water through existing facilities outside the
Afterbay during the period of closure. The PG&E
lateral canal was shut down during the period of clo-
sure, and Richvale Canal was not yet in service when
the Afterbay was constructed.
Instrumentation and Toe Drain Observations
Instrumentation was observed from the time of in-
stallation throughout the entire construction period.
After filling of the reservoirs, flows from the em-
bankment toe drains were estimated to average less
than '/^ gallon per minute (gpm), and many drains
remained dry. No unusual settlement or alignment
deviations are evident in the embankment nor is there
any evidence of deterioration of slope protection.
Seepage
Forebay. When the Forebay was filled, water in
the piezometers between Stations 78 + 00 and 91+00
rose rapidly. Seven relief wells failed to alleviate the
situation and, by April 1968, the piezometric surface
was above ground level. The situation was corrected
in September 1968 by drilling 11 more wells and'col-
lecting water in an open ditch, then pumping back
into the reservoir. In June 1969, the system was im-
proved by cutting off the well casings about 4 feet
below ground level and installing a 10-inch, perforat-
ed, asbestos-cement pipe to interconnect the relief
wells. A 100-gpm submersible pump now returns the
water to the reservoir.
Afterbay. A similar situation was observed along
Highway 99 when the Afterbay was filled. After low-
ering the water surface and an unsuccessful attempt to
blanket probable sources of leakage with bentonite,
the Afterbay Ground Water Pumping System was
proposed and implemented.
The Afterbay Ground Water Pumping System in-
volves 15 irrigation-type wells spaced around the west
and south sides of the reservoir. Eleven of the wells are
along the west side, situated between the dam and
Highway 99. The remaining four are located on the
south side along Hamilton Road. The total pumping
capacity is about 28,000 gpm.
196
The purpose of the system is to mine the ground
water on the immediate land side of the dam, thereby
lowering the piezometric level in the surrounding
ground. The pumped water is returned to the After-
bay.
Criteria used for setting the number of wells, their
size, and location included data collected from the
ground water monitoring program, topographic low
points, known geologic data under the floor of the
reservoir, results of two aquifer pumping tests, and
availability of land. The total depth of each well
drilled was based on judgment of interval of aquifer
intercepted to produce an adequate drawdown. The
depth of casing and perforation was determined from
logs and resistivity tests on the drilled holes.
Each pump is controlled separately by start and
stop probes set at the desired high and low ground
water level.
Tail Channel. Excavation of the tail channel ex-
posed an area of pervious material in the left bank just
downstream of Thermalito Powerplant. This area has
been monitored for seepage and signs of movement.
Seepage from the Forebay enters the tail channel
through this stratum but has not caused any damage
or movement. This is considered beneficial since it
lowers the water table in the area, alleviating the need
for relief wells outside the Forebay adjacent to the
Powerplant.
197
BIBLIOGRAPHY
Bucher, Kenneth G., "Hydraulic Investigation of the Thermalito Afterbay River Outlet", Water Science and
Engineering Papers 1029, Department of Water Science and Engineering, University of California, Davis,
June 1969.
California Department of Water Resources, Bulletin No. 117-6, "Oroville Reservoir, Thermalito Forebay, Ther-
malito Afterbay: Water Resources Recreation Report", December 1966.
199
GENERAL
LOCATION
DELTA
PUMPING*
PLANT
BVHON TRACT
DELTA FISH»«"
PROTECTIVE
FACILITY
EL \ PESC40ER0
TRACY
PUMPING 1
PLANT
N>
kElSO toao
BETHANY FOREBAY OAtt
\ CHRlSTeNSEN f
/»•>
BETHANY
DAMS.
tamooNeo
CANAL
SOUTH BAY-
PUMPING PLANT
BETHANY ,
RESERVOIR
OUTLET FACILITIES'
Figure 172. location Map — Clifton Court Foreboy
MILES
200
CHAPTER VIII. CLIFTON COURT FOREBAY
General
Description and Location
Clifton Court Forebay is a shallow 28,653-acre-foot
reservoir at the head of the California Aqueduct. It
was formed by constructing a low dam inside the
levees of Clifton Court Tract. The Forebay is located
in the southeast corner of Contra Costa County about
10 miles northwest of the City of Tracy adjacent to
Byron Road (Figures 172 and 173).
A gated control structure connected to West Canal,
a channel of Old River, allows Sacramento-San Joa-
quin Delta water to enter the Forebay. Water leaves
the Forebay through a designed opening in the east
levee of the Delta Pumping Plant intake channel just
north of the Delta Fish Protective Facility. Until the
latter connection was made, the intake channel was
connected to Italian Slough, located on the west side
of Clifton Court Tract, to furnish water for initial
operation of the California Aqueduct. A statistical
summary of Clifton Court Forebay is shown in Table
17.
Purpose
Clifton Court Forebay provides storage for off-peak
ri pumping and permits regulation of flows into Delta
Pumping Plant. This regulation dampens surges and
^ drawdown which would be caused during peak pump-
> ing periods. When the water surface of the Delta chan-
' nels falls below that of the Forebay because of tidal
action, the control structure gates can be closed to
prevent backflow. Inflows to the Forebay generally
are made during high tides and can be controlled with
gates to reduce approach velocities and prevent scour
in the adjacent Delta channels. Sediment removal has
proven to be an additional benefit of the Forebay
which will result in reduced canal maintenance costs.
Ultimately, the planned Peripheral Canal will supply
the Forebay with water, bypassing the Delta channel
system.
Chronology
Preliminary design of Clifton Court Forebay began
in March 1965.
Exploration drilling for the Forebay commenced
April 13, 1966, the design plans and specifications
were completed on July 6, 1967, the contract was
awarded on November 27, 1967, and all work was
completed on December 17, 1969.
Regional Geology and Seismicity
Clifton Court Forebay is located at the southwest-
ern edge of the Sacramento-San Joaquin Delta, where
the flat Delta basins merge with the gentle slopes at
the base of the Coast Range. These two physiographic
regions intersect approximately along the sea-level
contour in the southern and western edges of Clifton
Court Tract.
The Forebay is entirely underlain by Quaternary
alluvium consisting of deltaic sediments in the central
Figure 173. Aerial View — Clifton Court Forebay
201
TABLE 17. Statistical Summary of Clifton Court Foreboy
CLIFTON COURT FOREBAY DAM
Type: Zoned earthfiU
Crest elevation
Where exposed to delta waterway 14 feet
Where not exposed to delta waterway 11 feet
Crest width 20 feet
Crest length 36,500 feet
Lowest ground elevation at dam axis —10 feet
Lowest foundation elevation —16 feet
Structural height above foundation 30 feet
Embankment volume 2,440,000 cubic yards
Freeboard
Above maximum probable delta flood sur-
face S feet
Above maximum operating surface 6 feet
CLIFTON COURT FOREBAY
Maximum operating storage* 28,653 acre-feet
Minimum operating storage 13,965 acre-feet
Dead pool storage not applicable
Maximum probable delta flood surface ele-
vation 9 feet
Maximum operating surface elevation* 5 feet
Minimum operating surface elevation —2 feet
Dead pool surface elevation not applicable
Shoreline, maximum operating elevation* 8 miles
Surface area, maximum operating elevation.. 2,109 acres
Surface area, minimum operating elevation.. 2,088 acres
SPILLWAY
No spillway necessary
Top of embankment is above all surrounding ground
INLET WORKS
Control: Concrete structure with five 20-foot-wide by 25-foot - 6-
inch-high radial gates
Design flow 10,300cubic feet per second
Design velocity 2 feet per second
OUTLET
Intake channel connection:
Design flow 10,300 cubic feet per second
Design velocity 2. 5 feet per second
• Without Peripheral Canal.
and northern portions and alluvial fan deposits along
the southern and western margins.
No known active faults occur at, or adjacent to,
Clifton Court Tract. The area is located approximate-
ly 21 miles from the nearest known active fault, the
Calaveras fault, and about 45 miles from the San An-
dreas fault. Seismic considerations similar to those
used on the California Aqueduct intake channel and
its related structures were applied to the Forebay.
Design
Dam
Description. The dam, which has a maximum
height of 30 feet, has two basic compacted zones and
is ballasted with uncompacted material (Figure 174).
Zone 1 material, which consists of fairly uniform inor-
ganic silty and sandy clays, was placed on the reser-
voir side of the embankment. The balance of the
embankment proper, designated Zone 2, consists of
inorganic clays, sands, and silts. Waste materials, such
as peats and soft organics, were placed as ballast on the
outside of the embankment where needed for stability
and were designated Zone 3. Slopes are protected
from wave action with soil-cement consisting of nine
pounds of cement per cubic foot of soil.
Foundation. The dam alignment rests almost en-
tirely on deltaic sediments which consist of nonorgan-
ic flood-plain deposits covered by a blanket of organic
and peaty soils. The organic blanket ranges in thick-
ness from less than 1 foot to over 12 feet. In general,
the organic soils have low shear strengths and low
densities. They include soft organic clays, organic
silts, and peat in various stages of decomposition. At
first it was thought that the organic soil should be
removed, but the existing Clifton Court levees, which
had been constructed on this soil at steeper side slopes
than planned for the Forebay, showed that the organic
soil was usable as a foundation. Reinforcing the same
existing levees to serve as forebay embankments was
ruled out because the strengths of both levee and foun-
dation were indeterminable.
Construction Materials. Embankment materials
were excavated from the floor of the Forebay (Figures
175 and 176). Zone 1 material was limited to Borrow
Area A, Zone 2 material was selected from excavation
throughout the Forebay, and Zone 3 material was ex-
cavation that proved to be unsuitable for placement in
Zone 2. Sand and sandy silt for use in soil-cement were
obtained from an old streambed within the Forebay, '
and the filter material was obtained from the Pacific '
Coast Aggregates Company located in the City of
Tracy.
202
Figure 174. Embankment Sections
203
m
i
11
{••^l.l'Sii! I.
+
+
Figure 175. General Plan of Forebay — North
204
Figure 176. General Plan of Forebay — South
205
Figure 177. Gated Control Structure
206
Stability Analysis. The embankment was designed
using the Swedish Slip Circle method of analysis em-
ploying a seismic force of 0.1 5g applied in the direc-
tion that would produce the lowest factor of safety for
the condition being analyzed. Soil properties used in
the analyses are given in Table 18.
Settlement. Probable total consolidation of the
embankment foundation was computed to be from 1.4
feet to 2.1 feet, including a postconstruction consolida-
tion range of 0.7 to 0.9 of a foot. Specifications re-
quired that the compacted embankment be con-
structed in stages of 4 feet and in several marginal
areas in stages of 3 feet. It was required that a period
of at least six weeks be allowed to elapse before mak-
ing any additional placement upon a previous stage.
This permitted consolidation to take place and mini-
mized the buildup of pore pressures in the weak foun-
dation material so that it could support the next em-
bankment stage.
Control Structure
To regulate flow into Clifton Court Forebay and to
isolate the Forebay from the Delta, a gated control
structure was required (Figures 177 and 178). It will
serve only as emergency control once the Peripheral
Canal is completed. This structure consists of five 20-
foot-wide by 25.5-foot-high radial gates, housed in a
reinforced-concrete gate bay structure. The gate
structure includes a 10-foot-wide bridge for vehicular
traffic, one set of stoplog slots, and a hoist platform. A
riprapped earthen transition extends from both the
inlet and outlet of the structure. A 1,000-foot-long rip-
rapped channel with a 300-foot base width connects
the control structure to West Canal. A log boom was
provided at the channel inlet to discourage boats from
entering the area (Figure 178).
The control structure was designed for a maximum
head differential across the gates of 6 feet of water
under normal design stresses. For the extreme case, a
head differential of 12 feet of water, one-third over-
stress, was allowed. The control structure inlet chan-
nel was sized to accommodate 16,000 cubic feet per
second (cfs), the maximum tidal flow from West Ca-
nal, at an average velocity of 3 feet per second (fps).
Riprap was placed in the portions of the earth transi-
tion where the average velocity could exceed 3 fps.
The structure itself was designed to pass a continuous
flow of 10,300 cfs with resulting velocities between 5
and 7 fps through the gate bays, depending on reser-
voir stage. If a high tide were to coincide with low
water in the reservoir during the interim operating
period, the full flow of 16,000 cfs could pass through
the structure without causing any damage.
Figure 178. Control Structure and Inlet Channel Connection to West
Canal and Old River (in background)
TABLE 18. Material Design Parameters — Clifton Court Forebay
Specific
Gravity
Static Shear Strengths
B Angles in Degrees
Cohesion in Tons Per Square Foot
Unit Weight in Pounds
Per Cubic Foot
Effective
Total
Construction
Material
Dry
Moist
Saturated
e
C
e
C
e
c
Foundation
Clay
Oto 8 feet
--
--
118
120
120
117
122
122
90
125
125
120
35
38
35
35
"6
0
'6
0
18
18
25
0.15
0.15
0.2
'-'-
8 feet and lower
Sandy Silt
--
Sand
Embankment
Riprap and Filter
--
207
The foundation consists of alternating layers of lean
clay and sand below the organic and peaty soils. The
structure was set on the uppermost layer of sand. To
control uplift caused by high water levels in the Delta,
it was necessary to excavate a cutoff trench at least 1
foot into the underlying clay strata. This trench com-
pletely encircles the control structure and is filled
with compacted impervious material. It was judged
desirable to construct the embankment adjacent to the
structure at an early date to prevent differential settle-
ment that could damage the structure. A surcharged
fill was placed over the structure abutments to obtain
most of the settlement before the structure concrete
work was initiated. Pressure from this fill was 2,000
pounds per square foot (psf) greater than the
proposed structural load to obtain more rapid consoli-
dation of the embankment foundation. Preconsolida-
tion duration was selected so that when structural
excavation began, settlement rates for both the struc-
ture and the adjacent embankment foundations would
be approximately equal.
The five 20-foot-wide gate bays were formed by
counterforted abutment walls at each edge of the
structure and by reinforced-concrete piers between
the bays. The piers were designed as columns with
cross-section widths sufficient to block out stoplog
slots. The floor slab of the gate structure was designed
as a one-way slab on an elastic foundation. The deck
slab, which constitutes the hoist and maintenance
platform and vehicular bridge, was designed as a sim-
ple span which would support hoist equipment and a
H20-S 16-44 bridge load. Studies indicated that for all
static loading and uplift conditions, the resultant
forces fall within the middle one-third of the founda-
tion. For earthquake loading, the resultant falls within
the middle one-half of the foundation. Five 20-foot-
wide by 25.5-foot-high, tapered, radial gates are sup-
ported within the gate bays by means of the hoist
cables and trunnion beams. A standby generator was
provided for use in case of utility power failure.
Intake Channel Connection
The opening from the Forebay to the Delta Pump-
ing Plant intake channel (Figure 172) was designed to
pass 10,300 cfs, the maximum capacity of the plant, at
an average velocity of 2.5 fps. The opening is an earth-
lined channel extending into the Forebay with a level
invert at elevation —15.5 feet (U.S. Coast and Geo-
detic Survey sea-level datum of 1929). The invert of
the flare section within the Forebay slopes upward at
35:1 and daylights at original ground. The flare sec-
tion, like the level portion, was designed for a max-
imum velocity of 2.5 fps.
Intake Channel Closure
The closure embankment (Figure 179) was pro-
vided to close permanently the earlier connection of
the intake channel to the Delta at Italian Slough and
provide a base for the permanent Clifton Court road
crossing of the intake channel. It consists of granular
fill topped with compacted Zone 1 material and a
sheet-piling core in the center of the embankment
extending from elevation 9 feet, the top of the granu-
lar fill, to elevation 23 feet, 8 feet below the channel
invert. Existing riprap was removed for 10 feet on
each side of the sheet piling. Granular material was
used to assure speedy placement of a stable fill under
water. The closure embankment was placed to eleva-
tion 15 feet, 1 foot above the adjoining embankment,
to allow for postconstruction consolidation.
Piping and Drainage Systems
Four pump structures were installed between the
embankment of Clifton Court Forebay and the origi-
nal levee to drain accumulated surface water and seep-
age (Figure 180). Each structure consists of a vertical,
72-inch, reinforced-concrete pipe placed on a 1-foot-
thick concrete pad; a 24-inch, reinforced-concrete, in-
let pipe; a 900-gallon-per-minute centrifugal pump
equipped with a 1,200-rpm electric motor; and auto-
matic controls actuated by a metal float. Water is dis-
charged into the Forebay from each pump through an
8-inch steel pipe installed through the embankment.
Construction
Contract Administration
General information about the construction con-
tract for Clifton Court Forebay is shown in Table 19.
TABLE 19. Mojor Contract — Clifton Court Forebay
Specification 67-45
Low bid amount }i4,421,606
Final contract cost 35,904,116
Total cost-change orders ?2S4,95 3
Starting date 12/12/67
Completion date.. 12/17/69
Prime contractor Gordon H. Ball Enter-
prises
Dewatering and Drainage
Dewatering was the contractor's responsibility and
the work was divided into two separate operations:
first, maintaining the water surface in all drainage
ditches at elevation — 13 feet or lower until filling of
the Forebay commenced; and second, dewatering and
draining the area where the control structure was to
be located to elevation —20 feet. Dewatering to eleva-
tion — 1 3 feet was accomplished by cleaning and deep-
ening existing ditches and using existing pumps.
Interceptor ditches were constructed to tie in existing
ditches.
In accordance with specifications, the dewatering
operation around the control structure was extended
more than 25 feet beyond the outer limits of the con-
trol structure. The contractor, in sequence, excavated
a 1:1 trench in sandy material to elevation —26 feet,
placed a 3-foot blanket of washed concrete sand in the
trench, installed pervious concrete pipe 8 inches in
diameter, and backfilled with another 3 feet of sand.
208
J^-l
mm
mm
b'-'i^i
n
^'^^Z'^-f
ri: \
Figure 179. Closure EmbankmenI
209
PUMP
NO. 2
BYRON
TRACT
CLIFTON COURT
ROAD
PUMP
NO. 3
Figure 180. Drainoge System
210
Within a day, the pipe had become completely choked
and ceased to function. The piping project was aban-
doned in favor of open drainage with pumped disposal
from two 30-inch-diameter riser pipes.
Reservoir Clearing
Clearing and grubbing, accomplished throughout
the construction period, consisted of removing all
trees, stumps, brush, culverts, downed timber, tanks,
fences, buildings, privies, cesspools, leaching lines,
discarded equipment, and debris. In addition, all exist-
ing ditches were backfilled. Grubbing was minimal
because the Forebay was built on large parcels of open
farmland.
Stripping was complicated by several factors. First,
the rich soil, deep roots, warm days, and rains caused
quick regrowth and second, the weak foundations
necessitated the halting of restripping.
The contractor was required to pump, clean, and
flush all septic tanks; remove all filter material from
leaching lines; and dispose of the material outside of
the Forebay. Pit privies were dug out and excreta
deposits removed and disposed of outside the forebay
area. Septic tanks and leach lines were dug out with
small backhoes and the debris hauled to approved
waste areas.
Large-diameter pipes through the old levees were
excavated by a dozer, or a grader, and smaller pipes
were removed by using a rubber-tired backhoe
equipped with a loader bucket. Because of the critical
nature of this work, removal of pipe from the old
levees was paid for as structural excavation and back-
fill.
Excavation
Excavation was performed under four categories:
Forebay, Borrow Area A, structural, and ditch and
channel.
Forebay. Forebay excavation included material
used for Zones 2, 2A, and 3, all of which was utilized
in embankments and the various toe details or was
spoiled. The contractor had two separate excavation
operations: one for stripping surface organic materials
which were placed in ballast fills or in waste banks,
and another for the underlying material which was
placed as Zone 2 and 2A embankment.
Forebay stripping excavation equipment consisted
of scrapers, jeep tractors pulling scrapers, and double-
engine scrapers. Large dozers were used exclusively as
pushers at both the pit and the fill.
The other forebay excavation equipment spread
consisted of a belt loader drawn by a large dozer. Bot-
tom dumps were loaded from the attached conveyor
belt. Because of soft ground, a dozer was needed to
assist the bottom dumps in and out of the area. Where
conditions were too wet or too soft for the belt loader
to operate, the scraper spread was used to complete
the required excavation.
Borrow Area A. Material from Borrow Area A
(Figure 176), the southwest portion of the Forebay,
was used in Zone 1 embankment. It was mostly imper-
vious material and fairly plastic. The contractor was
unsuccessful in excavating this material with the belt
loader, and the bottom dumps were too heavy for use
on the wet clay material. Most of Borrow Area A was
excavated with a scraper spread.
Structural. The bulk of structural excavation con-
sisted of the removal of control structure surcharge.
Also included was removal of unsuitable material un-
der the control structure surcharge and excavation for
keys, cutoff trenches, concrete transitions, piping,
drainage pump structures, float wells, and control
building footings.
Ditch and Channel. Ditch and channel excava-
tion was separated into two general types: that dug
with scrapers, and that dug with backhoe or dragline
equipment.
The trenches around the perimeter of the Forebay
that drain water to one of the four pump sumps were
excavated with scrapers and blades. These trenches
were either vee trenches or vertical wall trenches and
usually were constructed in Zone 3 material. Vee tren-
ches were cut with a blade and are similar to a swale.
Vertical wall trenches were excavated by using self-
loading scrapers (paddle wheels).
The existing trenches to be crossed by the new em-
bankment were first cross-sectioned and then excavat-
ed until suitable material was reached. This exca-
vation, for the most part, was done with a Gradall
which reached down and removed the mud and silt
from the bottom until firm material was found. When
these excavations were not filled quickly with Zone 1
material, fine silt particles carried by ground water
tended to accumulate on the bottom of the trench,
leaving an undesirable situation necessitating reexca-
vation. Once these trenches were backfilled with Zone
1 material, they did not cause any further trouble.
Handling of Borrow Materials
Impervious borrow material (Zone 1) was obtained
from Borrow Area A. In place, this material was well
above optimum moisture. When exposed to the wind
and sun, the surface dried sufficiently to allow the top
18 inches to be taken at about 2% above optimum
moisture. By the time it was transported, disked, and
rolled, the material usually was at optimum moisture
for compaction and little water had to be added at the
embankment.
Zone 2 material was selected from various areas in
the Forebay outside of Borrow Area A. This material
was dry and required constant watering and disking
to bring the moisture content up to optimum. Because
of the availability of Zone 2 material in the northern
part of the Forebay, it was used as ballast on the out-
side of the embankment from Station 229 + 80 to
363+80 (Figure 175) and was designated Zone 2A.
Zone 3 material was stripped from Borrow Area A
211
and used as uncompacted ballast outside of the em-
bankment around the southern portion of the Fore-
bay.
Zone 4 material was supplied from an aggregate
plant in Tracy and was used only in the closure em-
bankment section.
Riprap required for purposes other than protection
of the interior embankment slopes was obtained from
department-owned stockpiles at Bethany Reservoir.
Processing consisted of primary and secondary blast-
ing and the use of a grizzly. Riprap was loaded with
a loader, or wheel loader; a large dozer kept the materi-
al worked up into a pile at the pit. Eleven 10-cubic-
yard dump trucks with special beds were used in the
4'/2-mile haul to the Forebay.
Embankment Construction
Compacted Material. Zone 1 and Zone 2 materi-
als were placed in the same manner, except that Zone
2 material required constant watering at the embank-
ment. The foundation was not strong enough to sup-
port the construction equipment, but it was found
that when an uncompacted 3-foot lift was dozed out
onto the foundation, equipment could travel over it.
Once the initial uncompacted lift was placed, compac-
tion proceeded smoothly. Material was brought to the
fill by either scrapers or bottom dumps and placed in
horizontal layers not exceeding 6 inches after compac-
tion. Spreading equipment included a large dozer and
a rubber-tired dozer which also pulled a larger hy-
draulic-operated double disc.
Compaction was accomplished by two pieces of
equipment on each spread: first, a tractor with an
attached dozer blade pulling a sheepsfoot roller; then
a large, four-drum, electric power packer weighing 50
tons, the most effective piece of equipment. The pow-
er packer could be depended upon to obtain maximum
densities in high fill areas. Relative compaction tests
were taken in areas where compaction results were
questioned, and good results were verified. The re-
quired relative compaction was 92%.
After completing each stage, the area was sloped to
drain. When the 42-day waiting period was over, the
embankment was disked and moisture-conditioned
prior to placing another stage.
Uncompacted Material. Zone 2A and Zone 3
materials were placed in lifts not exceeding 12 inches
and scrapers were routed over them. No difficulty was
experienced with these placements.
Slope Protection. There were two alternatives for
slope protection. Alternative A slope protection was
riprap material which was to be imported as this large
quantity was not available locally. Alternative B slope
protection was soil-cement for which sand available in
the Forebay could be used as aggregate. No contractor
bid on Alternative A because of the higher cost.
The soil-cement mixing was done in a batch plant
with automatic controls. Spreading was accomplished
by a spreader box continuously fed by dump trucks.
The method of compaction was by two passes with a
steel-wheeled roller and no more than five passes with
a pneumatic roller. The steel-wheeled roller was
equipped with a special side roller that worked off the
hydraulic system. It forced the small steel wheel into
the side of the soil-cement, allowing it to roll the outer
edge to obtain the desired stair-step effect. Curing was
done by foggers that were installed on water trucks
and worked off a high-pressure system on each truck.
The soil-cement slope protection, where subjected
to severe wind wave action, has required maintenance
since construction. Due to insufficient cement con-
tent and/or poor quality aggregate, certain layers of
soil-cement have eroded badly, allowing the soil-ce-
ment slabs above to break up due to lack of support.
Such locations have been repaired by placing riprap
over the failure.
Closure Embankment. The closure embankment
required removal and disposal of the existing bridge
on Clifton Court Road that crossed the intake channel,
removal of in-place riprap under the closure embank-
ment, furnishing and placing the various categories of
zoned closure embankment material, driving steel
sheet piling, and rebuilding the road.
Bridge removal and pile driving were done from
two large barges. One barge was equipped with a 40-
ton crane with an 80-foot boom, and the other was
equipped with a pile driver. The crane also was used
to set and drive the sheet piling, and a clamshell
bucket was used to remove the riprap.
A gravity drop hammer was used to place the steel
sheet piling, and a vulcan, air-driven, single-action
hammer was used to drive the sheets. These sheets
were easily driven to the planned elevation, and Zone
4 material was then brought in on both sides of the
sheet piling. Large amounts of the material had been
stockpiled to facilitate the work, and trucks continued
to bring material to the stockpiles as the closure was
made.
After the Zone 4 material had been brought up to
grade. Zone 1 embankment was placed. Aggregate
base was spread on top, compacted, and oiled with 0.3
of a gallon of SC 250 per square yard. This area was
covered with a layer of sand to allow automobile traf-
fic to pass through the work.
Riprap was stockpiled on both sides of the closure
and was placed as soon as the embankment had been
topped out. After the riprap was placed, a guard rail
was installed on each side of the road.
Construction of the closure embankment and
breaching of the existing levee between Clifton Court
Forebay and the California Aqueduct intake channel
were coordinated. This was done so that water flow-
ing into the California Aqueduct intake channel
would not be less than 500 cfs for longer than any
3-day period, nor less than 2,000 cfs for longer than a
15-day period. The work was done at the end of the
212
irrigation season. Work on the closure began on Octo-
ber 21, 1969 and was completed on October 30. The
intake channel embankment was breached on October
31.
Breaching Levees. The West Canal levee was
breached after forebay embankments, control struc-
ture, and riprap within the entrance to the Forebay
were completed. Levee freeboard within the breached
section was removed; then a section in the center of
the breach was cut, thus enabling water to flow into
the entrance to the control structure. The remainder
of the levee was removed by a dragline, and riprap was
placed underwater in the new passageway. When this
was complete, the Forebay was filled to elevation — 5
feet by allowing water to flow through the control
structure at a rate of 500 cfs.
In order to breach the embankment between the
intake channel and the Forebay, the water in the in-
take channel was lowered to elevation —5 feet. The
breach was excavated to elevation —4.5 feet when the
closure embankment cut off the flow from Italian
Slough. Vertical openings of 150 square feet were
made below elevation —4.5 feet and 700 square feet
below elevation —2.0 feet to supply water to the in-
take channel from the Forebay. The Department con-
trolled the water level in the Forebay to elevation -|- 2
feet until the breach was completed. Excavation was
done by a dragline, and riprap was placed in the open-
ing underwater.
Control Structure
Concrete. The contractor used standard, %-inch,
exterior-grade plywood to form the inlet and outlet
transition walls, but forms were not nailed to the studs
in the conventional manner. Plywood was laid loose
inside the 2- by 4-inch uprights, and only the vertical
walers were nailed. This required closer spacing on
the studs and walers but, according to the contractor,
took less time and labor.
The contractor made good use of new products,
such as the various developments in styrofoam and
adhesives, which were used to seal the forms against
grout leaks at the bottom, joints, and drilled holes.
Form work was done in the yard close to the struc-
ture. Concrete work on the control structure was
begun on January 9, 1969 and completed on June 26,
1969.
Water cure for the general concrete work was tried
in several ways. Use of carpets and plain burlap was
not satisfactory, but cotton and burlap mats were
heavy enough to stay in place. Water was introduced
from the top by sprinklers to keep water flowing over
the burlap. These mats could be draped over the wall
immediately after the forms were stripped and cone
holes dry-packed. A curing foreman worked seven
days a week.
Mechanical Installation. The gates were erected
in sections by the subcontractor in his Hayward, Cali-
fornia yard. He supplied the five motor-operated gate
hoists complete with gear motor and gear-motor
brakes, shoe brakes, gear reducers, limit switches and
drives, couplings, shafting, shaft bearings, drum sup-
port bases, and wire ropes.
It was necessary to modify the bottom seal plate to
make it fit the side seal. Bottom seal plate bolts, which
were installed earlier, had to be removed. This in-
volved chipping out concrete to a sawed line, drilling
in cinch anchors and bolts, and grouting as required
by the plans. The gates were tested in the field by both
the contractor and the Department.
Concrete Production
The contractor set up a batch plant approximately
700 feet from the control structure. The 1%-cubic-yard
batches were discharged into 1 '/^-cubic-yard buckets
which were hauled two at a time by truck to the con-
trol structures, where a crane hoisted them to the
work. Vibration was done by 3-inch electric and pneu-
matic vibrators. Sixty-cubic-foot-per-minute compres-
sors supplied the air.
Twenty-eight-day strengths of the I'/j-inch max-
imum size aggregate 5 '/-sack mix used in the control
structure averaged 4,300 pounds per square inch (psi) ,
ranging from 3,310 to 5,360 psi. The design value for
28 days was 3,000 psi. The 7-day strengths averaged
2,400 psi, ranging from 1,890 to 3,210 psi, and the
91-day strengths averaged 4,980 psi, ranging from
4,130 to 5,770 psi. These figures were based on 38 tests
taken from 3,219 cubic yards of concrete between
January 8, 1969 and June 26, 1969.
Seven tests were made on four other mixes used in
the 133 cubic yards of miscellaneous concrete. Test
results indicated that the concrete was of satisfactory
strength.
Electrical Installation
Electrical installation at Clifton Court Forebay in-
cluded work at the control structure, control building,
and pump structures. Cathodic protection and a stand-
by generator also were provided. Excavation for the
conduit between the control house and the control
structure was done by a rubber-tired backhoe with a
loader bucket. Initially, compaction was obtained by
using whacker compactors. Later, the entire length of
the trench was compacted by a large air tamper which
straddled the trench and pounded the earth with
equipment operating much like a pile driver.
Instrumentation
Instrumentation of Clifton Court Forebay was ac-
complished by using (1) settlement gauges, (2) slope
indicators, (3) plastic tubes, and (4) structural monu-
ments.
To monitor settlement of the embankment founda-
tion during construction and subsequent operation, 64
settlement gauges (Figure 181) were installed at speci-
fied locations. During construction, areas which ex-
perienced large settlements were watched for
213
>
1
T
■1
1
1
« ; 1
;;
j
j
Hi
^52
?H
5S5* 5*
5 * * fc ■*
5
<J
i
;-
^
J
i
5
?
?^^
K<»«
??^??!
•<? •« •«
-^rfijiwj
5—
0
Figure 181. Test Installations
214
evidence of potential failure and the rate of fill place-
ment was controlled accordingly. Settlement during
the period of construction ranged generally between
0.5 to 2.0 feet with a maximum of 2.5 feet at Station
252 + 00 (Figure 175). Following completion of con-
struction and filling of the Forebay in late October
1969, settlement rates became nominal. During a sev-
en-month period, from May to December 1970, max-
imum settlement was 0.07 of a foot.
During construction, 8 slope indicators and 83 plas-
tic tubes were installed at seven locations on the fore-
bay side of the embankment to detect and monitor
possible horizontal ground movement caused by em-
bankment construction. The plastic tubing was in-
stalled at 75-foot centers along two parallel lines at
distances of 100 and 180 feet from embankment cen-
terline. Although movement was noted in both the
slope-indicator pipes and plastic tubes, none was con-
sidered indicative of horizontal movement in the
foundation. Movements were erratic and frequently
reversed direction, indicating the probable influence
of adjacent drainage ditches and heavy-equipment op-
eration. All of these instruments are now inundated.
Permanent bench marks installed on the control
structure have been monitored periodically since July
1969. During the period July 1969 to October 1969,
when the structure became operational, settlement of
0.14 of a foot occurred.
215
BIBLIOGRAPHY
California Department of Water Resources, Specification No. 67-45, "Specifications Bid and Contract for Clifton
Court Forebay, State Water Facilities, North San Joaquin Division, Contra Costa County, California", 1967.
217
SENERAL
LOCATION
^
DELTA
PUMPING
PLANT.
DELTA OPERATIONS
AND MAINTENANCE
CENTER -
BETHANY FOREBAY DAM
SOUTH BAY-
PUMPING
PLANT
BETHANY RESERVOIR;
^OUTLET
FACILITIES
JETHANY
DAMS
tLTAMfi!!!-
l580>
CALIFORNIA
\1 AQUEDUCT^
Figure 182. Location Mop — Bethany Dams and Reservoii
218
CHAPTER IX. BETHANY DAMS AND RESERVOIR
General
Description and Location
Bethany Reservoir is a 4,804-acre-foot pool on the
California Aqueduct, l'/2 miles down the canal from
Delta Pumping Plant. The Reservoir is impounded by
five earth dams.
The facility is located approximately 10 miles
northwest of the City of Tracy in Alameda County.
The nearest major roads are U. S. Highway 50 and
Interstate 580 (Figure 182).
A statistical summary of Bethany Dams and Reser-
voir is presented in Table 20 and the area-capacity
curves are shown on Figure 183.
Purpose
Bethany Reservoir serves as a forebay for South Bay
Pumping Plant and as an afterbay for Delta Pumping
Plant. The Reservoir also serves as a conveyance facil-
ity in this reach of the California Aqueduct and pro-
vides water-related recreational opportunities.
TABLE 20. Statistical Summary of Bethany Dams and Reservoir
BETHANY DAMS
Type: Homogeneous earthfill
Crest elevation 250 feet
Crest width 25 feet
Crest lengtli 3,940 feet
Streambed elevation at dam axis 170 feet
Lowest foundation elevation 129 feet
Structural height above foundation 121 feet
Embankment volume 1,400,000 cubic yards
Freeboard above spillway crest 5 feet
Freeboard, maximum operating surface 7 feet
Freeboard, maximum probable flood- 2 feet
BETHANY RESERVOIR
Maximum operating storage 4,804 acre-feet
Minimum operating storage 4,200 acre-feet
Dead pool storage 150 acre-feet
Maximum operating surface elevation 243 feet
Minimum operating surface elevation 239 feet
Dead pool surface elevation 190 feet
Shoreline, maximum operating elevation 6 miles
Surface area, maximum operating elevation.. 161 acres
Surface area, minimum operating elevation __ 150 acres
SPILLWAY
Type: Ungated broad crest with unlined channel
Crest elevation 245 feet
Crest length 100 feet
Maximum probable flood inflow 6,410 cubic feet per second
Peak routed outflow. 1,560 cubic feet per second
Maximum surface elevation 248 feet
INLET
California Aqueduct from Delta Pumping Plant
Capacity lO,300 cubic feet per second
OUTLET WORKS
Emergency outlet: Reinforced-concrete conduit beneath Forebay
Dam at base of right abutment, valve chamber at midpoint —
discharge into impact dissipator
Diameter: Upstream of valve chamber, 60-inch pressure conduit —
downstream, 48-inch steel conduit in a 78-inch concrete horseshoe
conduit to manifold — 24-inch pipe from manifold to dissipator
Intake structure: low-level, uncontrolled
Control: 24-inch butterfly valve at manifold — 48-inch butterfly
guard valve in valve chamber
Capacity 121 cubic feet per second
OUTLETS
South Bay Pumping Plant
Capacity 330 cubic feet per second
North San Joaquin Division of California Aqueduct
Capacity.. -. 10,000 cubic feet per second
219
300
250
SURFACE
200
AREA IN AREA
150 100
50
0
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10 20 30 40 50
RESERVOIR STORAGE IN HUNDREDS OF ACRE-FEET
Figure 183. Area-Capacity Curves — Bethany Reservoir
Chronology
The five dams were built under two separate con-
tracts. A single dam, designated the Forebay Dam, was
constructed initially to create a reservoir to supply
South Bay Pumping Plant (Figure 184). This initial
pool was designated Bethany Forebay. After a few
years of operation and with the construction of the
California Aqueduct underway, the second contract
was awarded for construction of four smaller dams
southeast of the Forebay Dam. These four dams al-
lowed expansion of the initial reservoir and provided
the most economical conveyance facility for this por-
tion of the California Aqueduct (Figure 185). The
resulting pool is designated Bethany Reservoir.
The initial dam designation, Forebay Dam, has
been retained; the later dams are referred to as Betha-
ny Dams No. 1 through No. 4, or adjacent dams.
During the initial operational period of the South
Bay Aqueduct (before December 1967), water was
pumped into the Forebay from an interim canal join-
ing the Delta-Mendota Canal. This interim canal was
abandoned upon completion of the reservoir enlarge-
ment, and service from the California Aqueduct com-
menced.
Detailed design of the Forebay Dam was started in
1958, and construction was completed in 1961. Design
of the four adjacent dams and expanded reservoir was
started in 1965, and construction was completed in
1967.
Regional Geology and Seismicity
Bethany Reservoir is located in an area on the east
flank of the Altamont anticline of the Diablo Range.
Recent alluvium and sedimentary rocks of the Upper
Cretaceous Panoche formation are the two geologic
units present. Recent alluvium consists of clay and
sandy clay with minor lenses of silt, sand, and gravel.
The Panoche formation consists of interbedded
shales, sandstones, and siltstones with occasional hard,
Figure 184. Bethany Forebay
220
Figure 185. Bethany Reservoir
calcareous, boulder concretions within the sandstone
beds. The strongest earthquakes in the area in historic
times are thought to have originated either on the San
Andreas, Hayward, or Calaveras fault systems, all of
which pass through the San Francisco Bay area. It is
doubtful that any of these earthquakes in the project
area exceeded an intensity of VII on the Modified
Mercalli scale.
Design
Dams
Description. The 119-foot-high Forebay Dam was
designed as a homogeneous rolled earthfill with inter-
nal sloping and horizontal drains located downstream
from the axis of the dam. The plan, profile, and sec-
tions of the Forebay Dam are shown on Figure 186.
Adjacent dams, 50 to 121 feet in height, are of the
same design except for the drainage system. These
dams have strip drains comprised of granular materi-
als surrounding perforated drain pipes in place of the
Forebay Dam's continuous pervious blanket drain.
The plan, profile, and sections of each of the four
adjacent dams are shown on Figures 187 through 190.
Stability Analysis. Stability of the embankment
sections was investigated by the Swedish Slip Circle
method of analysis. Cases analyzed included full reser-
voir and critical lower reservoir levels combined with
earthquake loading. Earthquake loading was simulat-
ed by the application of a horizontal acceleration fac-
tor of O.lg in the direction of instability of the mass
being analyzed.
Settlement. No detailed settlement analysis was
made. Consolidation tests indicated, however, that
practically all settlement would occur during con-
struction. A camber of 1% of the fill height was pro-
vided for each of the five dams.
Construction Materials. On the basis of surface
examination and auger holes, a knoll adjacent to the
right abutment of the Forebay Dam was selected as
the primary borrow area for that dam (Figure 191),
and another knoll between Dams Nos. 3 and 4 was
selected as the borrow area for Dams Nos. 1 through
4. Suitable materials from required excavations also
were used in the dams. In the areas above the water
table, natural moisture was well below the 15% op-
timum while, in a few areas where water was encoun-
tered, moisture ranged from 11.1 to 28.6%. A
summary of material design parameters is shown in
Table 21. Soils were tested for material parameters by
the Department of Water Resources. Pervious materi-
als were unavailable on the site and were imported.
TABLE 21. Material Design Parameters — Bethany Dams
Specific
Gravity
Static Shear Strengths
S Angles in Degrees
Cohesion in Tons Per Square Foot
Unit Weight in Pounds
Per Cubic Foot
Effective
Total
Construction
Material
Dry
Moist
Saturated
e
C
e
C
e
C
foundation
Forebay Dam
Adjacent Dams
Embankment
2.74
2.72
2.73
2.73
92
105
115
105
114
122
132
123
121
130
136
131
32
.32
'6
'o
20
15
23
18
0.25
0.6
0.25*
0.6
8
5
23
22
0.50
0.25
0.25
Adjacent Dams
1.3
to 0.50 of a ton per square foot for s
221
Bethany Forebay Dam — Plan, Profile, and Sections
222
Figure 187. Dam No. 1 — Plan, Profile, and Sections
223
Figure 188. Dam No. 2 — Plan, Profile, and Sections
224
Figure 189. Dam No. 3 — Plan, Profile, and Sectio,
225
1 J
Figure 190. Dam No. 4 — Plan, Profile, and Sections
E
226
il
Figure 191. Location of Borrow Areas and Bethany Forebay Dam Site
227
Foundation. Abutments of all five dams are in
sandstones and shales of the Panoche formation.
Foundations in the channel sections are either
Panoche formation or alluvial deposits consisting
mainly of clay. Panoche formation shales and sand-
stones are strongly weathered, jointed, and fractured
and part easily along bedding planes. Many joints,
fractures, and bedding planes were coated heavily
with iron and manganese oxides, and a few joints and
seams are gypsum-filled. The alluvium is weak and,
except at Dam No. 3, does not increase appreciably in
strength to the depths penetrated.
All organic material was removed. It ranged in
depth from less than 1 foot on the abutments to about
8 feet in the channel sections. In addition to this strip-
ping, cutoff trenches were excavated through allu-
vium into stable rock of the Panoche formation. This
rock was susceptible to air slaking when exposed. All
foundation areas in this formation were excavated
within 1 2 to IS inches of final grades, and final excava-
tion was made just before embankment placement.
The foundation excavation plan for Dam No. 3 (Fig-
ure 192) is illustrative of all dam foundations.
A shear seam extends through the channel portion
of the forebay dam foundation; however, there is no
evidence of recent geological movement. The right
abutment contains a joint system that appears to be
the result of shearing stresses produced by regional
folding.
Instrumentation. Four types of instrumentation
were installed in the Forebay Dam (Figure 193): (1)
surface settlement points, (2) hydraulic piezometers,
(3) a cross-arm settlement unit for measuring differ-
ential settlement at different embankment levels, and
(4) base-plate installations for measuring foundation
settlement.
The piezometers are connected to an instrument
panel in a well at the downstream toe of the Forebay
Dam.
Surface settlement points were installed on all adja-
cent dams, and both Dams Nos. 1 and 3 are instru-
mented with two porous tube-type piezometers.
Outlet Works
Forebay Dam. In the first phase of operation, wa-
ter was diverted by gravity from the Delta-Mendota
Canal, about 2 miles away, through an interim canal
to the right abutment toe of the Forebay Dam. It was
then pumped into the Forebay through the outlet con-
duit.
In the second phase of operation, water is delivered
by gravity to Bethany Reservoir through the Califor-
nia Aqueduct. The Aqueduct enters the Reservoir
through a topographic saddle about 750 feet to the
southwest of the left abutment. The original outlet
works of the Forebay Dam will be used only to empty
the Reservoir in case of emergency.
The outlet works is located on the right abutment.
It consists of a low-level intake structure, with trash-
rack; a 60-inch-diameter, reinforced, cast-in-place,
concrete conduit upstream of a valve chamber; and a
48-inch steel pipe installed in a 96-inch, horseshoe-
shaped, concrete, access conduit between the valve
chamber and the downstream portal structure. A 48-
inch butterfly valve in the valve chamber provides
shutoff for dewatering the downstream facilities.
Beyond the portal structure, five 24-inch lines
branch from the 48-inch steel conduit and extend to
the former interim forebay pumping plant. The 48-
inch steel conduit and the manifold are encased in
concrete. These five branch lines were capped when
the interim pumping plant was removed from service.
A 24-inch, steel pipe blowoff extends from the end
of the manifold to a reinforced-concrete energy dis-
sipator in the stream channel. This blowoff is con-
trolled by a 24-inch gate valve.
An investor-owned utility company supplies the
power to a load center for valve chamber lighting and
ventilating and for driving the valve operators.
The plan and profile of the outlet works are shown
on Figure 194, and the rating curve is shown on Fig-
ure 195.
Outlet to South Bay Aqueduct. An unlined in-
take channel at the southwest margin of the Forebay
supplies water to South Bay Pumping Plant.
Outlet to California Aqueduct. A connecting
channel, designed to carry 10,000 cubic feet per second
(cfs) at a velocity of 2 feet per second, supplies water
to the expanded Bethany Reservoir (Figure 196). The
outlet from Bethany Reservoir into the California
Aqueduct consists of a check structure located at the
southwest edge of the expanded reservoir.
Spillway
Since the Reservoir was constructed in two phases,
two spillways also were constructed. The temporary
forebay spillway (Figure 197) was constructed under
the Bethany Forebay Dam contract at the location
where the California Aqueduct later entered the Res-
ervoir. This spillway was replaced by a permanent
spillway constructed under the canal embankment
Specification No. 63-28.
The permanent spillway consists of a straight, un-
lined, trapezoidal, earth channel located in a saddle
about 200 feet beyond the left abutment of the Fore-
bay Dam. The control structure is a reinforced-con-
crete broad-crested weir located midway along the
spillway alignment. The spillway channel is unlined
because the need for its operation is extremely unlike-
ly. The maximum probable flood (peak inflow 6,410
cfs) can be accommodated fully by the outlet facilities
to the California Aqueduct (capacity 10,000 cfs).
228
Figure 192. Foundation Excovotion and Drainage Details — Dam No. 3
229
Figure 193. Location of Foreboy Dam Instrumentatioi
230
Figure 194. Outlet Works — Plan and Profile
231
250
40 60 80
DISCHARGE IN CFS
Figure 195. Outlet Works Rating Curve
232
Figure 196. Connecting Channel — Plan, Profile, and Sectio
233
Figure 197. Temporary Spillway
234
Construction
Contract Administration
General information about the major contracts for
the construction of Bethany Forebay Dam and Betha-
ny Dams is shown in Table 22.
TABLE 22. Major Contracts — Bethany Forebay Dam
and Bethany Dams
Specification
Low bid amount
Final contract cost
Total cost-change orders
Starting date
Completion date
Prime contractor
Bethany
Forebay Dam
59-22
?877,870
?876,339
226,456
11/25/59
3/9/61
O.K. Mittry &
Sons
Bethany Dams
66-17
51,716,650
?2,057,838
?87,448
5/10/66
12/13/67
Rivers Construc-
tion Co. Inc.
Diversion and Care of Stream
Streamflow through the Forebay Dam site (Specifi-
cation No. 59-22) was controlled during construction
by a small earth embankment and retention pond ap-
proximately 1,300 feet upstream from the Dam site.
A drainage ditch was provided around the South
Bay Pumping Plant site during excavation of the in-
take channels and later was converted for permanent
hillside drainage and erosion prevention of the chan-
nel cut slopes.
Diversion facilities were unnecessary for the four
dams constructed under Specification No. 66-17.
Foundation
Material from all dam foundation excavations suita-
ble for use as compacted embankment, riprap, or top-
soil was stockpiled for later use. Unsuitable material
was wasted in the reservoir area. A total of 64,000
cubic yards was excavated for the foundation of the
Forebay Dam and 333,000 cubic yards for the founda-
tion of Dams Nos. 1, 2, 3, and 4 (Figure 198).
Figure 198. Bethany Forebay and Excavation for Adjacent Da
Figure 199. Foundation Grouting — Bethany Forebay Dam
Seepage water accumulated in the middle 100 feet of
the cutoff trench of the Forebay Dam. This was con-
trolled by embedding a slotted 2-inch-diameter pipe in
a gravel-filled trench and pumping from an 8-inch
riser set at the low point. One-inch vent pipes were
installed at the one-third points of the 2-inch pipe on
each side of the riser. After the embankment was
placed 10 feet above the foundation, sand-cement
grout was forced into the drain system through the
8-inch riser to force out the remaining water and seal
the system.
Water was encountered in the vicinity of the in-
terim canal crossing under Dam No. 1 and was con-
trolled by pumping.
Grouting
A concrete grout cap, 3 feet wide by 3 feet deep, was
placed in the foundation of each cutoff trench along
the centerline. The trench for the grout cap was ex-
cavated mainly with a rotary bucket wheel trencher
which worked well in the soft shales and sandstones
and usually left a smooth uniform cut. Because the
shales tended to air slake severely, the concrete grout
cap was placed as soon as possible after trench excava-
tion. Grout nipples were set on 5-foot centers in the
grout cap.
The split-spacing method was used for drilling and
grouting the curtain along the entire length of Betha-
ny Dam (Figure 199) and the adjacent dams. Primar-
ily, holes were drilled and grouted at 40-foot spacing,
and secondary holes were set midway between the
primary holes. The spacing similarly was "split"
twice more, so that the final spacing of the grout cur-
tain holes was 5 feet except on the higher portions of
the forebay dam abutments where the spacing was 10
feet. The specification provided for the holes on 10-
foot spacing to be 50 feet deep and the intermediate
holes to be 25 feet deep.
Both stage and packer grout methods were used.
235
Figure 200. Locotion of Borrow Areas ond Adiocent Dams
236
During stage grouting, holes were drilled to partial
depth, grouted, and then cleaned out by flushing with
water before the grout in the hole had set. After the
grout in the surrounding rock had set, the hole was
drilled an additional interval, stage-grouted, and
flushed out again. This process was repeated until the
required depth was reached. During packer grouting,
the hole was drilled to full depth, and then packers
were set at depth in the hole to isolate selected inter-
vals for grouting.
Handling of Borrow Materials
The borrow materials for all dams were obtained
from designated borrow areas, foundation, spillway,
and connecting channel excavations (Figures 191 and
200). Where possible, the material was placed directly
in embankments being constructed; surplus material
was stockpiled for future use. It was unnecessary to go
to Borrow Area B under the forebay dam contract
because all material was obtained from other areas of
surplus. A total of 285,079 cubic yards of excavation in
borrow areas plus suitable material from the founda-
tion and spillway excavation yielded 289,712 cubic
yards of compacted embankment for the Forebay
Dam. A total of 1,037,338 cubic yards of compacted
Zone 1 embankment from designated channel excava-
tions and foundation excavations was placed in the
four adjacent dams.
Impervious borrow areas (Zone 1 material) were
moisture-conditioned by sprinkling to near-optimum
moisture content prior to excavation. At times during
construction of the Forebay Dam, the premoistening
operations were poorly executed, delaying and com-
plicating embankment placement and compaction.
The processed filter and drain materials (Zones 2
and 3) for all dams were obtained from commercial
aggregate sources in the Tracy area.
There was enough suitable rock in borrow areas
and other areas of required excavation to supply all of
the riprap and the riprap bedding (Zone 4). Rock was
stockpiled as excavation progressed, then hauled to
the dams by 5-cubic-yard, rubber-tired, front-end
loaders.
Embankment Construction
Zone 1 embankment, the bulk of all the dams, was
placed by controlling the distribution and gradation
of materials throughout the fill to avoid lenses, pock-
ets, streaks, and layers of material differing substan-
tially from surrounding fill. Embankment materials
were spread in successive horizontal layers, not ex-
ceeding 6 inches in thickness after compaction. As
hauling and spreading of the material had a drying
effect, an adjustment to the moisture content was
made with a water truck, followed immediately by
disking for mixing just prior to compaction.
The contractor was required to keep the compacted
materials adjacent to the abutments 2 to 3 feet higher
than the rest of the fill to provide a good seal between
the abutment and the fill.
Good compaction results were obtained when mois-
ture control, rolling of lifts, and rock removal were
done properly. Compaction improved as the work
progressed. The low densities found early in construc-
tion of the Forebay Dam were not considered critical,
and it was reasoned that the overburden weight of the
upper material would sufficiently consolidate the low-
density areas. Twelve years after the completion of
the Forebay Dam, settlement gauge readings showed
a maximum settlement of 5 inches, well within the
anticipated amount. The Forebay Dam during final
construction stages is shown on Figure 201.
Figure 201. Bethany Forebay Dam Construction
237
The overall average in-place dry density for Betha-
ny Dams Zone 1 was 107.3 pounds per cubic foot
(pcf), ranging from 95.2 to 120.4 pcf The average
relative compaction was 98%, ranging from 91 to
106%.
Zone 2 (filter) material was placed in layers not
more than 12 inches thick after compaction, and Zone
3 (drain) material was placed in layers not more than
15 inches thick after compaction.
In Dam No. 2, obtaining the proper density of the
sloping drain was difficult. A maximum of 4% mois-
ture before compaction was specified. This was in-
creased to 8% before obtaining the required 70%
relative density. The increased moisture content was
supplied throughout the construction of all four of the
adjacent dams. The moisture content for the sloping
drain zone was not specified in the forebay dam con-
tract, and the zone was placed without incident. As
the Forebay Dam became higher, the drain became
longer and placement lagged. Until additional trucks
were used, the elevation of the drain zone fell below
the other zones.
The average relative density for Zone 2 material in
the Bethany Dams was 71%. Forty-seven (63%) of the
74 tests taken were above the 70% relative density
specified. Zone 3 material was placed with little dif-
ficulty.
Zone 4 (riprap bedding) material was dumped and
spread on prepared surfaces in layers not exceeding 12
inches after compaction.
Spillway
Excavated material from the temporary forebay
spillway, where suitable, was placed in the embank-
ment. The remainder was wasted in the reservoir area.
This spillway structure site was overexcavated and
backfilled to grade with concrete.
After the permanent spillway for the extended res-
ervoir was built, the Aqueduct was excavated on the
alignment of the temporary forebay spillway. Suitable
material from this excavation was used in the aque-
duct embankment, while the remainder was spoiled in
designated areas.
Outlet Works
Excavation for the outlet works of the Forebay Dam
followed excavation of the dam foundation. Outside
the cutoff, alluvial material was removed to sound
rock. From the intake structure to the walk-in portal,
shotcrete protective coating was applied to prevent
slaking; then the trench was backfilled to subgrade
with concrete. Downstream of the walk-in structure.
the trench was backfilled to subgrade with compacted
impervious embankment.
The outlet works conduit, including 2-foot by 6-
inch cutoff collars at the construction joints, was
monolithically cast in 32- and 33-foot sections. Six-
inch, "dumbell", rubber, water stops and '/z '"ch of
expansion-joint filler were placed in the construction
joints. A 48-inch-inside-diameter steel pipe was placed
on concrete saddles spaced at 16 feet inside the 8-foot-
diameter, walk-in, horseshoe conduit.
Concrete Production
Concrete was supplied by a commercial ready-mix
plant and was mixed and transported to the placement
site in transit mix trucks. The manually operated, 3-
cubic-yard, batch plant was located 2 miles north of
the City of Brentwood on State Highway 4. Transit
mix trucks varied in capacity from 5 to 9 cubic yards.
The haul distance to the site was about 20 miles, and
the average haul time was 45 minutes, with an average
unloading time of 15 minutes.
Mechanical and Electrical Installations
A ventilating fan, operated by a '/^-horsepower mo-
tor with an output of 406 cubic feet per minute, was
installed in the storage and equipment house. This
ventilating equipment was connected to the portal
structure by an 8-inch-diameter cast-iron pipe. Air
was blown into a 9-inch-diameter aluminum duct
through the walk-in conduit and discharged at the
valve vault.
A 50-amp load center also provides power for the
lighting system and the 24-inch valve operator.
Reservoir Clearing
The reservoir area below elevation 240 feet was
cleared of all trees, brush, rubbish, fences, and a tim-
ber bridge. Trees were cut off within 1 foot of the
ground.
Placing Topsoil and Seeding
Topsoil placed on the downstream slopes of all
dams was selected from the stockpiles that contained
the most fertile loam. Ammonium sulfate fertilizer
was spread evenly at the rate of 400 pounds per acre,
and seed was sown at the rate of 60 pounds per acre.
Immediately following seeding, the seeded areas were
covered uniformly with layers of straw and anchored
by rolling the entire area with a punching-type roller.
Embankment Test Installation
The instrumentation described earlier in this chap-
ter was observed continuously during construction
and now is observed on a scheduled basis.
238
i.. Ik.
I
BIBLIOGRAPHY
California Department of Water Resources, Bulletin No. 117-12, "Bethany Reservoir Recreation Development
Plan", December 1970.
239
PLEASANTON
/
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^y
DEL VALLE
PUMPING
PLANT
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MILES
I
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DEL VALLE
BRANCH
PIPELINE
'DEL VALLE DAM
LAKE
DEL
VALLE
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Figure 202. Location Mop — Del Voile Dam and Loke Del Voile
240
CHAPTER X. DEL VALLE DAM AND LAKE DEL VALLE
General
Description and Location
Del Valle Dam is a 235-foot-high zoned embank-
Tient containing 4,150,000 cubic yards of material.
The spillway control structure is an 84-foot-diameter,
|ingated, glory-hole intake located 1,600 feet southeast
)f the Dam beyond the right abutment. The spillway
intake discharges into a 30-foot-diameter vertical shaft
oined by an elbow transition to a 28-foot-diameter,
,893-foot-long, nearly horizontal tunnel. An 18-foot-
iiameter, flood control, outlet works tunnel dis-
:harges into the spillway tunnel at the elbow. High-
)ressure slide gates located at the elbow control the
low through the flood control outlet. A smaller con-
ervation outlet is located between the spillway and
Dam. It consists of an inclined, multilevel, reinforced-
concrete, intake structure; a 78-inch-diameter pres-
sure tunnel; a valve vault at the axis of the Dam; and
a 60-inch-diameter steel pipe inside a 9-foot - 6-inch,
horseshoe-shaped, walk-in tunnel beyond the valve
vault.
Lake Del Valle has a capacity of 77,106 acre-feet, a
surface area of 1,060 acres, and a 16-mile shoreline.
The Dam and Lake are located in Arroyo Del Valle,
just south of Livermore Valley, approximately 4 miles
from the City of Livermore in Alameda County. Ar-
royo Road, a paved city street and county road, affords
access from Livermore to the Dam site. The nearest
major roads are U. S. Highway 50 (also Interstate 580)
and State Highway 84 (Figures 202 and 203).
Figure 203. Aerial View — Del Valle Dam and Lake Del Valle
241
A statistical summary of Del V^alle Dam and Lake
Del \'alle is shown in Table 23, and the area-capacity
curves are shown on Figure 204.
The 320-foot-deep Del \'alle Shaft, which served as
access to the Hetch Hetchy Aqueduct tunnel, was
plugged with a combination of concrete plugs and fill
material under Specification No. 67-55. The Shaft and
its access were submerged by Lake Del Valle. The
Shaft had been used for access during construction of
the tunnel and was considered for the same purpose
for construction of a future parallel tunnel. With the
existence of Lake Del Valle, this future construction
scheme was abandoned.
Purpose
The purposes of the project are to provide reg-
ulatory storage for the South Bay Aqueduct (30,000
acre-feet), flood control for Alameda Creek (38,000-
acre-foot reservation), conservation of storm runoff,
recreation, and fish and wildlife enhancement.
The U. S. Army Corps of Engineers has made pay-
ments of approximately $4,900,000 toward the con-
struction and the capitalized operation and
maintenance costs of the flood control features of the
Dam and reservoir. Possible additional appropriations
are pending.
Local storm runoff is impounded by the Dam and
later released at the convenience of downstream water
users. The Department of Water Resources has re-
ceived payment for these conservation benefits from
the water agencies involved.
Chronology
The State started preliminary surveys at the site in
1957 and final design in 1964. Dam construction was
begun in March 1966 and completed in 1968.
Regional Geology and Seismicity
The Dam and reservoir are located in the Diablo
Mountain Range, a part of the Coast Ranges. Geologic
formations in the area consist mainly of sedimentary
rocks folded into northwest-trending anticlines and
synclines. The oldest rocks in the area, Jurassic gray-
wackies, cherts, shales, and serpentines of the Francis-
can group, crop out in an extensive area south of the
reservoir. Younger Cretaceous sandstones and shales
of the Panoche formation are present at the Dam site
and extend for several miles west where the Panoche
formation is in fault contact with Franciscan rock
along the Williams fault. Above the right abutment of
the Dam, soft sandstones and siltstones of the Miocene
TABLE 23. Statistical Summary of Del Valle Dom and Lake Del Valle
DEL VALLE DAM
Type: Zoned earthfill
Crest elevation 773 feet
Crest width _.. 25 feet
Crest length.... 880 feet
Streambed elevation at dam axis 550 feet
Lowest foundation elevation. 538 feet
Structural height above foundation 235 feet
Embankment volume 4,150,000 cubic yards
Freeboard above spillway crest 28 feet
Freeboard, maximum operating surface 69.8 feet
Freeboard, maximum probable fiood 8.4 feet
LAKE DEL VALLE
Storage at spillway crest elevation 77,106 acre-feet
Maximum conservation storage 40,000 acre-feet
Storage at flood control pool 39,000 acre-feet
Minimum conservation storage 9,863 acre-feet
Dead pool storage _ 3,317 acre-feet
Maximum conservation surface elevation 703.2 feet
Surface elevation of flood control pool 702 feet
Minimum conservation surface elevation 638 feet
Dead pool surface elevation 609 feet
Shoreline, spillway crest elevation 16 miles
Surface area, spillway crest elevation. 1,060 acres
Surface area, maximum conservation eleva-
tion 708 acres
Surface area, minimum conservation eleva-
tion _ __ 285 acres
SPILLWAY
Type: Glory hole with concrete-lined tunnel and stilling basin
Crest elevation 745 feet
Crestlength 264 feet
Crest diameter 84 feet
Tunnel diameter 28 feet
Maximum probable flood inflow 64,000 cubic feet per second
Peak routed outflow 44,200 cubic feet per second
Maximum surface elevation 764.6 feet
Standard project flood inflow 23,500 cubic feet per second
Routed outflow 7,500 cubic feet per second
Water surface elevation 749 . 7 feet
INLET-OUTLET
Del Valle Pumping Plant
Capacity, in or out 120 cubic feet per second
OUTLET WORKS
Conservation: Lined tunnel under right abutment, valve chamber
at midpoint — upstream of valve chamber, 78-inch-diameter pres-
sure section — downstream, 60-inch steel conduit in a 144-inch con-
crete horseshoe tunnel — intake, five-level inclined structure with
42-inch shutoff butterfly valves — downstream control, 42-inch
fixed-cone dispersion valve — discharge into spillway stilling
basin — 66-inch butterfly guard valve in valve chamber
Capacity 400 cubic feet per second
Flood control: 18-foot-diameter lined tunnel under right abutment-
intake, bell-mouth entrance — transition to 28-foot-diameter spill-
way tunnel — control in transition by two pairs of 6-foot-wide by
7-foot - 6-inch-high, high-pressure, slide gates in tandem
Capacity with surface elevation
at spillway crest 7,000 cubic feet per second
242
AREA IN ACRES
1200 1000 800
CAPACITY IN 1000 ACRE- FT.
Figure 204. Area-Capacity Curves
'Cierbo formation rest unconformably upon the
Panoche sandstones and shales. Overlying the Cierbo
formation are the Plio-Pleistocene Livermore gravels
which extend for about 5 miles northeast of the Dam.
Del Valle Dam is near seismically active regions in
California. There are three major active fault zones
within 30 miles of the Dam: Calaveras (8 miles), Hay-
ward (12 miles), and San Andreas (30 miles).
Design
Dam
I Description. The Dam is a rolled earthfill struc-
ture consisting of a central impervious core, granular
ihells, and random stability zones upstream and
Hownstream. The plan of Del Valle Dam is shown on
ngure 205.
I Internal embankment drainage is provided by an
nclined drain downstream of the impervious core and
|)lanket drains on the downstream abutments which
onnect to a drain in the stream channel. Protective
liters are provided between the core and downsteam
nclined drain, between the core and upstream shell,
rnd between the channel and abutment foundations
]nd drains (Figure 206).
, Stability Analysis. Selection of the preliminary
'ection was based on geologic investigations, availabil-
cy and characteristics of materials, known character-
istics of foundation materials, and seismic con-
iderations. After preliminary design was completed,
lore extensive drilling and testing for final design
jCvealed poorer foundation conditions and strengths
|lian had been anticipated during preliminary designs.
I^s a result, the embankment slopes were flattened and
stability sections of random fill were added upstream
and downstream.
Stability of embankment sections was analyzed by
the Swedish Slip Circle and sliding wedge methods of
analysis. Adequate factors of safety were calculated
for the final embankment sections under all cases of
loading. These cases of loading included full reservoir
and other critical reservoir levels along with earth-
quake loads. Earthquake loading involved a horizontal
force equal to the weight of the soil mass being
analyzed, multiplied by an earthquake acceleration
factor.
Because of the close proximity of major faults and
less than desirable foundation conditions, the Depart-
ment's Earth Dams Consulting Board recommended
(1) the use of an earthquake acceleration of 0.1 Sg, (2)
conservative embankment and cut slopes, (3) wide
impervious embankment sections, and (4) freeboard
design to include consideration of landslides and
seiches.
Settlement. Measurements of settlement in proto-
type dams of impervious material indicated that most
of the settlement occurs during fill placement. A
nominal camber of 1% of the fill height was provided
to allow for postconstruction settlement.
Foundation. The Dam is founded upon sand-
stones and shales of the Panoche formation. Geologic
structure is complex owing to faulting and folding.
Most of the shears or faults are small but, in the right
side of the channel, there was a shear large enough
that soft sheared material was required to be removed
to prevent seepage under the core along the shear
zone. Beds in the left abutment either are overturned
243
Figure 205. General Plan of Dam
244
_^_^
Figure 206. Embankment — Sections and Profile
245
or steeply dipping into the abutment. Beds in the right
abutment dip from 34 to 63 degress into the abutment.
Sandstones become increasingly abundant in the up-
per right abutment, and many of the sandstone beds
have open cracks. The lower flank of both abutments
had considerable volumes of terrace material and
slopewash that were unsuitable for foundation.
Foundation excavation involved removal of weath-
ered or otherwise weak materials from the abutments,
removal of the stream gravels and terrace materials,
and clean-out of soft materials from the shear zone
described above. The excavation under the core was
specified to be about 3 feet deeper than that for the
remaining foundation so as to expose less permeable
material.
A grout curtain, consisting of two rows of holes,
was provided at the centerline of the core contact. The
grout holes were spaced at 5-foot intervals and were
up to 100 feet in depth. Blanket grouting of shallow
holes on a 10-foot grid was required in areas where
weak permeable material was identified beneath the
core.
Construction Materials. Construction materials
for the Dam were obtained from various sources.
Material design parameters for these materials, as de-
termined by soils testing, are presented in Table 24.
Zone lA, the impervious core, consists of clayey
soils of the Livermore formation obtained from a loca-
tion on the north arroyo slope upstream from the
Dam. Zone IB flanks Zone lA on each side and was
obtained from an alluvial terrace located between the
aforementioned borrow area and the stream channel.
Zones 2A, 2B, and 3 were composed of streambed
gravels excavated as far as 5 miles upstream of the
Dam. Zone 2A is the processed transition between the
core and drain. Zone 2B is the processed gravel drain,
and Zone 3 is pit-run gravels forming the embank-
ment shells. Zone 4 is a random material from manda-
tory excavations.
Instrumentation. Instrumentation at Del Valle
Dam consists of 3 1 piezometers, 8 Carlson pore-pres-
sure cells, 9 porous-tube piezometers, 37 surface
monuments, and 8 slope indicators. This instrumenta-
tion was designed to monitor pore pressures, settle-
ments, and horizontal movements (Figure 207).
Conservation Outlet Works
The conservation outlet works (Figure 208) is used
to release natural streamflows in Arroyo Del Valle
and convey regulated inflow and outflow of South
Bay Aqueduct water between Del Valle Pumping
Plant and the reservoir. During construction of the
Dam, the conservation outlet tunnel was used to di-
vert natural streamflows around the Dam. After con-
struction, the diversion intake was plugged with
concrete from its inlet to the elbow at the base of the
inclined intake.
The conservation outlet works consists of a mul-
tilevel, inclined, reinforced-concrete, intake structure
on the right abutment; an upstream reach of 78-inch-
diameter, concrete-lined, pressure tunnel; a valve
vault near the axis of the Dam; and a 60-inch-diameter
steel pipe inside a 1 14-inch-diameter, horseshoe-
shaped, walk-in tunnel extending from the valve vault
to a control structure near the left wall of the spillway
stilling basin.
The inclined intake structure (Figure 209) consists
of a 7-foot-square reinforced-concrete conduit from
elevation 710 feet to elevation 600 feet; a transition to
a 78-inch-diameter circular conduit; and an elbow and
thrust block near streambed level. To provide for se-
lective level releases for water quality control, 42-inch-
diameter butterfly valves and trashracks were in-
stalled at elevations 690, 670, 650, 630, and 620 feet.
The tunnel transitions from a 78-inch diameter to a
60-inch diameter with a steel liner immediately up-
stream of the valve chamber.
The valve vault contains a 60-inch butterfly valve
for emergency shutoff, two air-vacuum valves, and a
mechanical-type coupling for ease in assembly of the
valves and steel pipeline. Dimensions of the valve
vault are sufficient to install, operate, and remove the
butterfly valve and operating mechanism.
^
TABLE 24. Moteriol Design
Parometers — D
•1 Valle Dam
Specific
Gravity
Unit
Weight in Pounds
Per Cubic Foot
Static Shear Strengths
6 Angles in Degrees
Cohesion in Tons Per Square Foot
Effective
Total
Material
Dry
Moist
Saturated
e
C
B
C
2.72
2.72
2.76
2.78
2.76
114
114
139
116
146
114
104
131
131
143
152
129
135
135
151
136
156
134
24
24
38
38
38
29
30
s
0
0
0
0
0
14
14
38
38
38
16
16
0.6
Zone IB
0.6
Zone2A
0
Zone2B.
0
Zone 3
0
Zone4
0.6
Foundation
0.6
246
247
Figure 208. Conservation Outlet Works-Plan, Profile, and Sections
248
Figure 209. Inclined Intake Structure
249
The walk-in conduit is a concrete-lined, 1 14-inch-
diameter, horseshoe-shaped section with a concrete
walkway and concrete pipe supports. This walkway
provides room for removal of the emergency shutoff
butterfly valve. Peripheral drain holes are placed be-
tween Stations 15+45 and 19 + 65 (Figure 209) at 30-
foot spacing to relieve the external hydrostatic pres-
sure.
A sump and sump pump were installed at the down-
stream end to remove seepage entering the walk-in
conduit. A ventilation system was provided, consist-
ing of a fan near the downstream control structure
and an air duct running from the fan to the valve
vault.
The downstream control structure was constructed
as an integral part of the left wall of the spillway
stilling basin. It consists of a wye branch and thrust
block, a 60-inch by 42-inch reducer, and a 42-inch fix-
ed-cone dispersion valve. The valve allows the flow to
discharge into a 10-foot by 9-foot chamber which con-
fines the spray and directs the flow into the stilling
basin. A control house was constructed above the
valve to provide room for (1) valve operating equip-
ment, (2) sump pump operating equipment, and (3)
walk-in tunnel ventilating fan.
The conservation outlet works was designed to (1)
release 400 cubic feet per second (cfs) at the minimum
conservation pool, water surface elevation 638 feet,
and (2) to pass a flow of 120 cfs between the reservoir
and Del Valle Pumping Plant. To reduce pumping
cost, project water from the South Bay Aqueduct can
be discharged by gravity through the branch pipeline
into the downstream end of the outlet and into Arroyo
Del Valle to replace natural flow which is being stored
in the reservoir.
The 42-inch butterfly valves in the sloping intake
were designed to operate either fully open or fully
closed, and the 60-inch butterfly valve in the vault
beneath the dam crest remains open except in an
emergency. Releases to the stream are controlled by
the 42-inch fixed-cone dispersion valve at the down-
stream end. Flow between the reservoir and Pumping
Plant is controlled in the plant. The rating curve for
the conservation outlet works is shown on Figure 210.
The sloping intake may be dewatered for inspection
and was designed for this condition with an external
water load imposed by a reservoir water surface at
elevation 710 feet. The thrust block was designed to
spread the load of the intake structure at the base of
the structure near streambed level.
Maximum allowable load on the foundation was
4,000 pounds per square foot. Trashracks are remova-
ble and were designed for yield stress at a differential
head of more than 20 feet of water. Steel bulkheads
were provided to allow closure of the openings should
repair of the butterfly valves be necessary. The bulk-
heads were designed to resist the water load with the
reservoir at elevation 710 feet.
The pressure tunnel was designed to resist the full
reservoir head both internally and externally (applied
individually) assuming no support from the sur-
rounding rock. The valve vault was designed for an
external pressure of a full reservoir. The walk-in tun-
nel from the valve vault to the tunnel portal was de-
signed to resist the external water pressure, which was
assumed to vary linearly from 68 pounds per square
FLOW-IOOO C.F.S.
Figure 210. Conservation Outlet Works Rating Curve
I Jt
! *
2S0
JM^
inch (psi) at the valve vault to 0 psi at the downstream
control structure. Rock loads from the tunnel roof
u ere assumed to be resisted by the support installed
during construction and were not added to the load on
concrete sections. The walk-in conduit from the
downsteam tunnel portal to the control structure was
designed to support the load of the pervious backfill
assuming the vertical load is equivalent to the weight
of the overburden and the lateral load is one-third the
\ ertical load.
The outlet control structure contains the welded
steel wye, embedded in concrete, which connects to
the discharge valve and connects the outlet works
\\ith the Del \'alle Branch Pipeline and Pumping
Plant. Retaining walls on each side of the control
structure were designed as cantilever walls. The wall
on the left side contains the fill on top of the structure,
while the wall on the right side forms the stilling basin
wall.
The 60-inch-diameter steel pipe and branches were
fabricated from steel plate which has a minimum yield
strength of 30,000 psi and an allowable stress of 15,000
psi. Saddle supports are spaced at 7-foot centers to
eliminate the necessity of stiffener rings on the steel
pipe. An expansion joint was placed near the midpoint
of the pipe alignment to permit expansion and con-
traction of the steel pipe due to a change in tempera-
ture of up to 30 degrees Fahrenheit.
Flood Control Outlet Works
The flood control outlet works is located in the
right abutment and connects with the spillway tunnel
( Figure 2 11 ) . It consists of a reinforced-concrete trash
frame, a bell-mouth entrance, an 18-foot-diameter tun-
nel 216 feet long, and a junction structure with a 28-
foot-diameter spillway tunnel. A concrete plug in the
junction structure contains a transition to two sluice-
ways for the purpose of making flood control releases.
Each sluiceway has two 72-inch by 90-inch, high-pres-
sure, slide gates in tandem for regulation and emer-
gency shutoff. These sluiceways discharge through a
: 10-foot by 12-foot conduit directly into the spillway
tunnel. A gate chamber housing the hydraulic opera-
tors was provided above the sluiceways. Access to the
I gate chamber is by a stairway in a 9-foot-diameter,
jconcrete-lined, vertical shaft from the spillway over-
llook parking area to a 9-foot-diameter, concrete-lined,
access tunnel which slopes at 0.5% to the gate cham-
ber. The control house over the vertical shaft contains
electrical panels, ventilation equipment, and a standby
engine-generator for emergency operation of the out-
let works.
The flood control outlet works was designed to re-
lease up to 4,400 cfs with the reservoir surface at eleva-
tion 702 feet. To provide for emergency reservoir
drawdown, the design discharge is 7,000 cfs with the
reservoir water surface at the spillway crest, elevation
745 feet. The 4,400-cfs flow corresponds to the capaci-
ty of Arroyo Del Valle below the Dam, and the 7,000-
cfs flow can be carried with minor damage. The intake
trash frame was designed so that the velocity through
the net area would not exceed 5 feet per second for a
flow of 7,000 cfs. Except for a case of extreme emer-
gency, the slide gates will not be operated at more than
90% open.
The intake structure was placed directly on Zone 3
fill rather than on existing rock formations to mini-
mize excavation into the hillside. Two expansion
joints were provided in the conduit between the tun-
nel portal and the intake structure to allow for differ-
ential settlement between the intake structure and the
tunnel. The trash frame was designed for a yield stress
at 20 feet of differential head.
The 18-foot-diameter, reinforced-concrete, tunnel
lining from the stoplog slot in the intake structure to
approximately 50 feet downstream of the tunnel por-
tal was designed to support 30 feet of overburden, and
the reinforcement in the concrete lining is sufficient
to resist the full reservoir head. The flood control
tunnel and spillway junction was designed to with-
stand the internal pressure of full reservoir head, as-
suming no support from the surrounding rock.
The gate chamber was designed for full hydrostatic
head, with normal allowable stresses for water at the
lip of the spillway, elevation 745 feet, and no more
than one-third overstress for water at the spillway
design flood elevation of 765 feet. Allowance was
made in the gate chamber dimensions to give suffi-
cient clearance for installation, operation, and re-
moval of slide-gate bonnets, hydraulic operators, and
gate leaves. The access tunnel and shaft were designed
to support 30 feet of highly fractured overburden, and
the concrete lining was designed for full hydrostatic
head due to a water surface elevation of 765 feet.
Spillway
Description. The first type of spillway investigat-
ed was an open chute on the left abutment. This alter-
native was abandoned because of an extensive shear
zone that made the location undesirable for a spillway
structure.
Both side-channel and glory-hole spillways were
considered for the right abutment, but these also were
abandoned because of the high cuts that would be
necessary. A failure of the cut slope could cause rock
to slide into the intake structure and render the spill-
way inoperable.
The design selected was a glory-hole spillway locat-
ed on a knob 1,600 feet southeast of the Dam.
At this location, cut-slope heights were minimized.
The spillway intake structure was located 50 feet from
the base of the cut slope at its nearest point (Figure
211) in order to provide a space to catch small slides
should they occur. The unlined approach apron is on
a relatively flat plane at elevation 738 feet and is sloped
at 5% in two directions for drainage. The inlet con-
sists of an 84-foot-diameter ungated crest at elevation
745 feet. Antivortex vanes are placed at the one-third
points on the circumference. A log boom prevents
large debris from entering the glory-hole spillway in-
251
--J
^
^
5
!
3
^
1^
n\
I
\
\
\ 1
\
\ *
\\
w^
V
.
1
\
Ai
1
\i
3 3 3;:
Figure 211. General Plan of Flood Control Outlet Works
2S2
take. A transition connects the ogee crest to a 30-foot-
diameter shaft at elevation 697.60 feet, which extends
to an elbow at elevation 678.92 feet. The elbow reduces
the diameter uniformly to 28 feet at the point where
it connects with the spillway tunnel. The flood con-
trol outlet works, previously described, connects at
this elbow. An air vent leads from near the top of the
elbow to the top of one of the antivortex vanes. The
spillway tunnel extends downstream 1,893 feet from
the elbow to the downstream portal, and a 28-foot-
diameter cut-and-cover conduit, 111 feet in length,
ends at the transition to the stilling basin. The transi-
tion is 100 feet long and changes from a semicircular
section to a rectangular section. Within this length,
the invert elevation falls 15 feet.
Hydraulics. The Federal Government, acting
through the U. S. Army Corps of Engineers, par-
ticipated in the flood control aspects of the project and
initially required that the maximum discharge during
the standard project flood be not more than 7,000 cfs
(the capacity of the downstream channel allowing
only slight damage). This limitation was placed on an
occurrence of the standard project flood with reser-
voir level at the spillway lip and the flood control
outlet not being used. Routing of the standard project
flood (spillway weir elevation 745 feet) resulted in a
peak discharge of 7,500 cfs. To reduce the peak dis-
charge to 7,000 cfs, it would have been necessary to
raise the weir elevation and the dam crest. The Corps
decided that the additional cost of construction to low-
er the discharge was not warranted and set the final
criteria for the maximum discharge during the stand-
ard project flood at 7,500 cfs. Discharge during the
maximum probable flood would be 44,200 cfs with a
maximum water surface of about 765 feet, leaving 8
feet of freeboard above the resulting water surface.
Flood hydrographs are shown on Figure 212.
The spillway stilling basin (Figure 213) was de-
signed so that the hydraulic jump would not move
upstream into the conduit. To avoid negative pres-
sures on the floor of the basin, the vertical curve was
made flatter than the trajectory of a free-discharging
jet. The stilling basin will contain a full hydraulic
jump for all flows up to 7,500 cfs. Model studies indi-
cate a partial jump is contained for flows up to 10,000
cfs. A flip sill was placed at the downstream end of the
stilling basin to create a discharge trajectory with im-
pact greater than 80 feet from the structure for flows
ranging between 10,000 cfs and 44,200 cfs and to keep
the dynamic load on the sill to a minimum. The ex-
cavated portion of the return channel was designed to
carry flows up to 4,400 cfs without expanding to an
overbank condition. This is the capacity the natural
downstream channel can carry without causing flood
damage. Water is released through the flood control
outlet works when the reservoir surface reaches eleva-
tion 702 feet during the flood season.
Structural Design. The crest structure and ap-
proach structure are located in the Panoche forma-
tion. Bearing tests conducted on similar foundation
material indicated a maximum allowable foundation
pressure of 3,000 pounds per square foot.
The crest structure was analyzed as a gravity struc-
ture. The loads on the weir were calculated with the
water surface at elevations 745 and 764.6 feet. Full
uplift pressures along with horizontal and vertical
seismic forces were considered. The concrete in the
throat transition and shaft was analyzed as horizontal
rings subject to uniform lateral rock loads and hydro-
static pressures. The antivortex piers are concrete
structures cantilevered vertically from the spillway
crest.
The concrete tunnel lining and stilling basin de-
signs considered static and dynamic forces of flood-
flows as well as loading due to the reservoir and
backfill. Where dynamic loading is critical, one-third
overstress (one-quarter in end sill) is allowed and,
where static loading is critical, normal stresses are
allowed.
Structural design of the stilling basin considered
loading of the backfill as well as static and dynamic
loading of water during flood discharge. One-quarter
overstress was allowed in the end sill when dynamic
loads were considered. A drainage system under the
transition and stilling basin, consisting of intercon-
nected longitudinal and transverse vitrified clay pipes,
relieves uplift pressure, distributes pressures uniform-
ly, and provides a drainage path for the water.
Mechanical and Electrical Installations
Power to operate the mechanical equipment at Del
Valle Dam is supplied from Del Valle Pumping Plant
to the outlet control house, located at the downstream
toe. From there, power is extended to the other facili-
ties at the Dam (Figure 214). The Pacific Gas and
Electric Company supplies 480-volt, 3-phase, 60-cycle
power to Del Valle Pumping Plant. Only the motors
that drive the gate operators, sump pumps, and ven-
tilators can make direct use of this power. For all other
uses, the power is transformed to 120 volts, single
phase.
Flood Control Outlet Works. The high-pressure
slide gates in the flood control outlet can be opened or
closed in 15 minutes by a motor-driven hydraulic op-
erator. The control panel is in the gate chamber. Air
for ventilation is supplied through an 18-inch alumi-
num conduit. Air for the slide gates is furnished by
two 24-inch aluminum ducts routed through the ac-
cess tunnel and shaft from the intakes in the control
house located over this shaft. An emergency genera-
tor, capable of producing the power to operate the
flood control outlet works in case of power failure,
was installed in this control house.
253
Id Nl N0llVA3n3 3DVdans' a3iVM
Figure 212. Flood H/drographs
2S4
Figure 213. Spillway Stilling Basin
255
Figure 214. Single-line Eleclricol Diag
256
Conservation Outlet Works. The 42-inch butter-
fly-valve operators in the sloping intake are activated
from a motor-driven pump in a control house located
above the intake. The operator for the 60-inch butter-
fly valve is activated by a motor-driven pump located
in the conservation outlet works valve chamber. Oper-
ating time for all butterfly valves is four minutes. Two
10-inch vacuum valves were installed on the down-
stream side of the 60-inch butterfly valve within the
valve chamber. Air for ventilation is supplied by a
blower in the conservation outlet works through an
,j 8-inch aluminum conduit in the walk-in tunnel.
I The fixed-cone dispersion valve in the conservation
outlet works can be opened or closed in five minutes
by a motor-driven hydraulic operator in the outlet
control structure. A sump and sump pump that drain
the walk-in tunnel are located on the right side of the
outlet control structure and empty into the spillway
basin through a 2 '/2-inch, galvanized, steel pipe. The
6-inch, manually operated, blowoff valve for the con-
servation outlet works empties into the same chamber
! as the 42-inch fixed-cone dispersion valve.
; Construction
' Contract Administration
General information about the contract for the con-
struction of Del Valle Dam and reservoir. Specifica-
tion No. 66-01, is shown in Table 25. This contract
included the construction of the Dam and its appur-
tenant structures.
TABLE 25. Major Contract — Del Valle Dam and Reservoir
Specification 66-01
Low bid amount 216,577,802
Final contract cost ?16,520,404
Total cost-change orders 3242
Starting date --. 3/28/66
Completion date... 9/17/68 _
. Prime contractor Green Construction Co.
I & Winston Bros. Co.
Diversion and Care of Stream
First Construction Season. During the summer of
the first construction season, 1966, a trench was ex-
cavated across the valley at the upstream toe of the
Dam. Collected water was pumped into a 12-inch pipe
I running along the county road and discharged into a
; settling basin below the Dam site. A ditch was ex-
I cavated from the settling basin to the stream for re-
' turn flow. The original streambed between the return
I point and the downstream toe of the Dam then was
I used as a spoil area for tunnel muck from both the
! flood control and conservation outlets.
The foundation for the Dam was excavated, the cur-
tain grouted through a grout cap, and embankment
placed to the original level of the streambed. A flood
; control channel was excavated from the downstream
I toe of the Dam to return floodflows to the original
I channel. That winter, a maximum streamflow of 5,600
cfs caused only minor damage.
Second Construction Season. In the spring of
1967, a cofferdam was installed around the inlet end of
the conservation tunnel, and 36-inch and 24-inch cor-
rugated-metal pipes were installed through the coffer-
dam into the tunnel. The contractor's plan was to
divert the stream through the conservation tunnel
when the flow fell below 50 cfs so embankment place-
ment could begin. This occurred on May 11, 1967.
The only water flowing downstream through the
conservation outlet works during the summer was
leakage through the cofferdam which was diverted by
a 12-inch pipeline through the tunnel to facilitate the
remaining work on the outlet.
By the fall of 1967, the Dam had been topped out,
but the flood control outlet works was not yet opera-
ble. The diversion plan for the winter utilized the
reservoir as a temporary detention basin by releasing
the flows through the conservation outlet works. This
diversion operation would control a 100-year flood
with the maximum reservoir stage at the invert eleva-
tion of the flood control outlet works, 40 feet above the
crown of the conservation outlet works. A steel bulk-
head was available to place in the stoplog slot of the
flood control intake should a larger flood occur. The
empty reservoir capacity would have contained the
entire maximum probable flood volume well below
the crest of the spillway. The winter of 1967hS8 was
exceptionally dry, and stream diversion during this
period did not present any problems.
Third Construction Season. Following an ex-
tremely dry winter, the streamflow was low enough
to allow placement of the permanent plug in the diver-
sion portion of the conservation outlet works on May
16, 1968. The storage of water behind Del Valle Dam
essentially began on that date.
Foundation
Dewatering. During streambed excavation and
curtain grouting, the diversion across the channel at
the upstream toe of the Dam adequately dewatered the
foundation. Before any embankment could be placed,
it was necessary to cut off all flow into the excavated
area. This was accomplished by installing a system of
French drains just downstream of the cutoff trench.
These drains joined a rock-filled sump 50 feet down-
stream of the upstream toe of the Dam. A 15-foot
length of 24-inch corrugated-metal pipe was placed
vertically at the low point of the sump, and the water
collected was pumped into a 12-inch discharge line by
a float-controlled pump.
Excavation. The first area excavated was the foun-
dation for Zones 1 A and 3 and upstream Zones IB and
2A. The excavated material was hauled to Zone 3 and
4 stockpiles. Inspection of the exposed foundation re-
vealed that it was suitable for acceptance of Zone lA
material without the additional 3-foot depth of excava-
tion required by the plans and specifications.
257
The second area excavated was in the vicinity of the
upstream and downstream portals of the conservation
outlet works and most of the foundation area below
elevation 668 feet between the two portals. A bench
was constructed along the right abutment to facilitate
construction of the conservation outlet works during
the winter season. The excavated material was loaded
at the base of the abutment and hauled to the Zone 4
stockpile.
When excavation of the lower part of the right abut-
ment was completed, isolated pockets in the Zone 1 A
area of the streambed were cleaned out and the materi-
al hauled to the Zone 4 stockpile downstream of the
Dam.
The third major area excavated was the streambed
between the downstream limit of Zone lA and the
downstream toe of the Dam. All material suitable for
Zone 3 was placed directly in upstream Zone 3 and
remaining material was hauled to the Zone 4 stock-
pile.
The shear zones were excavated and filled, complet-
ing the preparation of the streambed portion of the
foundation on October 10, 1967. The embankment for
the Dam then was placed to the original level of the
streambed in accordance with the plans and specifica-
tions, except that Zone 2A material was temporarily
substituted for Zone 2B material. Otherwise, silt from
the winter flows would have infiltrated Zone 2A
material, destroying the drainage characteristics. Af-
ter the flood season, surplus Zone 2A was trimmed
back and replaced with Zone 2B material.
In January 1967, work commenced on the fourth
area to be excavated, the upper portion of the right
abutment below the access road. Dozers side-cast
material from the cut where it was loaded at the base
of the abutment and hauled to the upstream spoil area.
Boulders were separated and hauled to the upstream
riprap stockpile by end-dump trucks.
In February 1967, stripping commenced on the fifth
and last area, the left abutment. The material was
hauled to Zone 3 and 4 upstream stockpiles. In May,
a surface crack appeared at Station 33+00 normal to
the dam axis revealing a slide potential on the abut-
ment. Four thousand cubic yards were placed and
compacted between Stations 29+50 and 37 + 50 ex-
tending from the streambed (elevation 555 feet) to
elevation 620 feet to stabilize the abutment and pre-
vent a slide.
Flood Cleanup. Cleanup of foundation debris re-
sulting from the first season flooding was completed
on May 27, 1967. Material suitable for Zone 3 was
spread to dry in upstream areas, and material suitable
for Zone 4 was hauled to a stockpile.
Dam Foundation Grouting
Dam foundation grouting included blanket grout-
ing to seal near-surface voids and curtain grouting to
form a barrier against seepage beneath the Dam. The
blanket holes were drilled and grouted before the cur-
tain holes to control surface leaks while grouting the
curtain holes.
The starting grout mix (water-cement ratio) for
both blanket and curtain grouting was originally 7:1,
gradually increasing in thickness to \ A or Y^: I as neces-
sary. The starting mix was later changed to 5:1.
Grouting pressures were controlled carefully lie-
cause the foundation could be deformed easily with
grouting pressures exceeding 1 psi per foot of hole
depth. The pressures were limited to 0.50 to 0.75 psi
per foot of hole depth.
Blanket Grouting. Drilling and grouting of the
blanket holes were done in one or two stages, depend-
ing upon the water-pressure test results. The holes
were drilled to a depth of 15 feet, washed, and water-
tested at a maximum pressure of 10 psi. If the water
loss exceeded 0.5 cubic feet per minute, this interval
was grouted and then the interval from 15 to 25 feet
was drilled and grouted. If the water loss was less than
0.5 cubic feet per minute, the hole was completed to
a depth of 25 feet, then washed, water tested, and
grouted. In areas of very disturbed rock, no water
testing was done.
Initially, the blanket holes were arranged in a trian-
gular pattern over the entire Zone 1 foundation area.
Later, the plan was modified to concentrate the blan-
ket grouting near the grout curtain and the upstream
portion of the Zone I foundation. Two additional
rows of blanket holes were added: one 10 feet up-
stream from the curtain with holes on 10-foot centers
and the other 20 feet downstream from the curtain
with holes on 20-foot centers.
Curtain Grouting. The curtain grout holes were
arranged in two parallel lines, about 15 feet apart,
running the full length of the Dam near the center of
the Zone 1 embankment foundation. Initially, pri-
mary holes 100 feet deep on 40-foot centers were
drilled and grouted; then 75-foot-deep secondary holes
between the primary holes were drilled and grouted.
In areas of relatively high grout take, the spacing was
split even farther, with additional holes 50 feet deep.
Final spacing was l'^, 5, or 10 feet for the curtain
holes. The curtain holes were drilled and grouted in
stages of 25 feet (Figure 215).
To test the effectiveness of the curtain grouting, 32
holes were drilled and grouted in a plane midway
between the two grout curtains. These holes were
drilled at angles of 40 to 60 degrees with respect to the
curtain holes. Most of these holes were tight when
water-tested or they had negligible grout takes.
The grout take was far less than anticipated. Only
47,163 cubic feet of the estimated 150,280 cubic feet
were used.
Embankment Materials
Impervious. Zone lA material was acquired from
Borrow Area L located approximately 4,000 feet east
of the Dam site on terrain that slopes into Arroyo Del
258
Figure 215. left Abutment Excavation and Curtain Grouting
Valle (Figure 216). This material is composed of clays
and sandy clays from the Livermore formation. Prior
to excavation, the contractor prewet Borrow Area L
to moisture-condition soils which would be used in
the embankment. During initial excavation in the
southwest corner, unsuitable sands and gravels were
encountered. The contractor then moved to other
areas and obtained acceptable materials although the
borrow was heterogeneous at times. Scrapers were
loaded downhill so that materials from the different
strata would be mixed, resulting in a more homogene-
ous embankment.
Transition. Zone IB is the impervious transition
between the Zone lA and Zone 2A filter. Zone IB is
more coarsely graded than Zone lA and was obtained
from alluvial soils in Borrow Area P, located about
3,000 feet upstream of the Dam site adjacent to the
southern limit of Borrow Area L. This material was
old alluvial soils from stream-terrace deposits. The
borrow deposits occurred in two zones: an upper zone
I of impervious soils derived primarily from the Liver-
more formation and a lower zone of semipervious ter-
race deposits. The alluvium in Borrow Area P
contained erratic lenses of gravel and clay. Satisfac-
tory mixing and blending was achieved by prewetting
the surface prior to excavation and crosscutting the
I alluvial fans. The bulk of Zone IB was taken from the
I northeast portion of the borrow area.
Filter. Zone 2 A in the downstream portion of the
embankment is the filter between Zone IB and the
pervious drain. Zone 2B. In the upstream portion of
the Dam, Zone 2A acts as a drain during reservoir
drawdown. Material for Zone 2A was processed from
materials obtained in Borrow Area S, which extended
from the Dam site to a point about 5 miles upstream.
The processing plant was established approximately 3
miles upstream from the Dam site, in the Arroyo Del
Valle stream channel. The processed material, fairly
well-graded from the '/-inch size to the No. 200 sieve
size, was hauled from the plant to the embankment in
25-cubic-yard-capacity bottom-dump wagons. Ma-
terial in Borrow Area S was, in general, a homogene-
ous sandy gravel composed of subrounded to rounded
particles of resistant sandstone, cherts, schists, and
assorted igneous and metamorphic rocks. The materi-
al particle size generally was less than 8 inches.
Drain. Zone 2B is the drain zone designed to con-
vey seepage from the core and abutments to the down-
stream toe. Zone 2B is a coarse material with 100%
passing the 4-inch sieve with no more than 5% permit-
ted to pass the No. 4 sieve. This material was proc-
essed by the same plant previously described. Material
was obtained from Borrow Area S. Due to the grada-
tion of material in Borrow Area S, an excess of Zone
2B resulted while obtaining the necessary quantity of
Zone 2A and cobbles. By change order, the contractor
was permitted to place the 30,000 cubic yards of sur-
plus Zone 2B material in the Zone 3 embankment
above elevation 755 feet at no additional cost.
Outer Shell. Zone 3 forms a portion of the outer
shells of the Dam. Zone 3 comprises the bulk of
materials placed in the embankment, some 2,171,834
cubic yards. Material for Zone 3 was stream-channel
gravels excavated from Borrow Area S. Some Zone 3
material also was acquired from foundation excava-
tion.
Random. Zone 4 is a random zone forming por-
tions of the upstream and downstream shells. This
zone accounted for the second largest quantity of
material placed in the embankment. Materials for
Zone 4 were acquired from stockpiled material from
the dam foundation, open-cut excavations, spillway
tunnel and shaft excavations, conservation tunnel ex-
cavations, and from the specified borrow areas after
stockpiles were exhausted. Zone 4 materials are clayey
gravels, sandstones, shales, and talus.
Slope Protection. Cobbles also were obtained dur-
ing the processing of materials from Borrow Area S
and were placed on the embankment slopes for ero-
sion protection. By change order, the upstream cobble
thickness was reduced to 1 foot. The reduced quantity
conformed more nearly to the amount available after
obtaining the necessary quantities of Zone 2A and
Zone 2B material. The specifications required all
material to be coarser than 3 inches.
Riprap required for upstream slope protection, still-
ing basin outlet, and downstream channel was ob-
tained approximately 26 miles from the Dam site. The
source was existing stockpiles of large rock removed
during excavation of the California Aqueduct. The
rock was reduced to proper size by a pneumatic im-
259
Figure 216. Location of Borrow Areas and Del Voile Dam Site
260
TABLE 26.
Compaction Data
—Del Valle Dam
lA
IB
2A
2B
3
4
97.6
2.6
121.2
4.8
97.6
2.6
131.8
5.2
79.4
13.3
130.3
5.7
110.5
19.5
114.6
3.9
101.5
4.7
143.2
5.8
97 0
2 7
In-place dry density — pounds
Standard deviation
per cubic foot.
116.4
6.3
pact hammer mounted on the boom of a backhoe. It
was transported in 12-cubic-yard truck-trailer units. A
minor amount of riprap was obtained from stockpiled
boulders from foundation excavation.
Embankment Construction
Table 26 shows the as-built relative compaction and
in-place dry density of the various zones within the
Dam. Placement and compaction of embankment
materials is shown on Figure 217.
Impervious and Transition. Placement of Zone
lA material began during October 1966 following
completion of the backfill of all shear zones in the
foundation. The bedded borrow materials were loos-
ened prior to and during excavation by a tractor-
mounted ripper. In some areas, the material was very
hard and rock-like in nature but was sufficiently bro-
ken down by the disking and compacting operations
to be removed easily. The contractor transported and
spread Zone lA material using a scraper operation.
Zone IB construction procedures were the same as for
Zone 1 A. Placement of Zone IB began during Septem-
ber 1966 by backfilling overexcavated foundation
shear zones. Zones 1 A and IB were placed, spread, and
compacted parallel to the dam axis in layers not ex-
ceeding 6 inches in compacted thickness.
Following placement of each layer, the materials
were blended and mixed by means of a disc pulled by
a tractor. Any necessary moisture corrections were
made prior to rolling by use of 10,000-gallon water
wagons. Material placed against abutments generally
was placed with a higher moisture content to obtain
more plasticity and wheel-rolled with a rubber-tired
tractor.
Compaction of Zones lA and IB was achieved with
two tandem-roller tractor combinations. The four
rollers were double-drum, sheepsfoot, tamping roll-
ers, 5 foot by 5 foot in size.
The standard deviation for in-place densities for the
first period of Zone lA and IB placement was 4.6
compared to the overall value of 2.6 at the end of the
job. A standard deviation of 3.0 or less was considered
acceptable control.
Compaction test data indicated that moisture con-
trol was good. Prewetting in the borrow area and effi-
cient disking of the fill contributed to the good control
achieved.
Filter and Drain. Zone 2A material was loaded
from stockpiles at the processing plant with a 2'/-
cubic-yard-bucket rubber-tired loader. Then, it was
hauled to the embankment in 25-cubic-yard loads with
a bottom-dump wagon powered by a rubber-tired
tractor.
Zone 2B material was loaded at the processing plant
with a 4-cubic-yard-bucket rubber-tired loader and
hauled to the embankment by scrapers powered by
rubber-tired tractors.
Both Zones 2A and 2B were placed in layers not
exceeding 15 inches after compaction with sufficient
moisture content to preclude bulking. Following
dumping on the embankment, the Zone 2A and 2B
material was leveled to required thickness with a rub-
ber-tired dozer and moisture was added. Sufficient
time was allowed to permit penetration of added mois-
ture. Zones 2A and 2B then were compacted with two
passes of vibratory rollers. The compaction equip-
ment consisted of three smooth-drum vibratory roll-
ers connected in a triangular pattern and drawn with
a large tractor.
Outer Shell. Initial placement of Zone 3 began
during September 1966, with material from the down-
stream Zone 2 foundation excavation being hauled
directly into upstream Zone 3. After this source was
exhausted. Zone 3 material was excavated from Bor-
row Area S using scrapers pushed by large tractors.
The material then was hauled and placed in the em-
bankment.
261
Zone 3 was placed in layers not exceeding 15 inches
in compacted thickness. Moisture conditioning was
required on materials containing over 15% finer than
the No. 4 sieve size. Compaction was achieved with
two passes of the vibratory compactor used for Zones
2A and 2B.
Moisture conditioning was required on the embank-
ment for most Zone 3 material. In order to achieve the
required density, the contractor was directed to satu-
rate the area prior to compaction. Satisfactory results
were obtained using this method.
Random. Zone 4 material was placed in 8-inch
compacted layers with moisture conditioning pro-
vided in a manner similar to Zone lA and Zone IB. It
was compacted by six passes with a sheepsfoot tamp-
ing roller having the same characteristics mentioned
under Zone lA. Zone 4 material had been stockpiled
both downstream and upstream from the embank-
ment. Material was excavated, hauled, and placed in
the embankment with scrapers. Moisture was added
on the stockpiles and embankment with 10,000-gallon
water wagons.
The in-place dry density of Zone 4 averaged 116.4
pounds per cubic foot. Considering the range of
materials used, the density was uniform.
Slope Protection. The cobbles and riprap were
dumped and spread on the slopes. No testing was re-
quired for these materials.
Instrumentation. Reading of the embankment in-
struments (Figure 207) commenced upon installation
and continued during the construction period. The
responsibility was transferred to operating personnel
after the Dam was completed.
Shortly after installation, 24 of the 3 1 hydraulic pie-
zometers located in the embankment core gave ques-
tionable readings. The remaining 7, along with the
foundation piezometers, however, were believed to be
able to provide adequate information to monitor the
performance of the Dam.
Conservation Outlet Works
Outlet Portal. Excavation of the outlet portal of
the conservation outlet works was started in April
1966. Because of the close proximity of the spillway
tunnel outlet, the portals for the two tunnels were
excavated at the same time (Figure 218).
To avert loss of the portal by a landslide, a unique
construction technique was employed. The first 100
feet of the cut-and-cover tunnel adjacent to the portal
resembled a fully supported tunnel. The excavation
was made, 6-inch WF tunnel supports with invert
struts were installed on 2-foot centers, and invert con-
crete was placed to anchor the supports. Solid lagging
was placed entirely around the outside of the sup-
ports, and grout was placed in the narrow space be-
tween the lagging and the excavation in those
locations where compaction of backfill would be dif-
ficult. Then structural backfill was placed, and the
218. Combined Outlet Works
crown was placed later from the inside as in a tunnel
section. The driving of the tunnel was not started
until after the backfill over the first 100 feet of cut-
and-cover sections was completed. There is little ques-
tion that this method of construction protected the
tunnel portals from a major slide. During excavation,
a crack developed just downstream of the tunnel por-
tal and the formation was shored with heavy timbers.
Tunnel supports and struts then were placed between
timbers, invert was placed, backfill was completed,
and shoring was removed without a slope failure.
Inlet Portal. Excavation for the inlet cut-and-cov-
er section commenced on July 1, 1966, following a
procedure similar to the one used at the outlet portal.
The 18 feet of cut-and-cover conduit adjacent to the
tunnel portal was supported and the remaining 32 feet
was unsupported.
Tunnel. The tunnel was driven on a three-shift-
per-day basis from the outlet end, through the valve
vault area, to Station 9-t-53. Excavated material was •
stockpiled downstream for use in the Dam. The re-
mainder of the tunnel was driven from the inlet end.
Seepage water was encountered in all tunnel sections
and was controlled by pumping through a 4-inch line.
Continuous pumping was required during concreting
of the tunnel.
Concrete. Invert placement for the walk-in tunnel
included the lower 9 inches of the walls and was i
formed with steel channels set on wooden headers.
The form was an open structure utilizing a manually .
operated strike-off to maintain the invert radius. The
crown form was a steel horseshoe structure supported ,
on an overhead needle beam. Concrete was placed by
a pumpcrete machine through an 8-inch line. Internal
vibrators were used inside the form, and form vibra- ,
tors were spaced along the form surfaces. An invert ,
section was placed in the afternoon and the corre-
sponding crown section the following morning.
262
Figure 219. Concrete Saddles for 60-Inch Pipe
The 9-foot-diameter pressure section was monolith-
ically cast in 30-foot sections using forms split into
three sections. Concrete was placed in the same man-
ner as in the crown of the walk-in tunnel.
The final 180-foot downstream section of the walk-
in tunnel was cut and cover. The invert was placed as
in the supported section, and the same interior
horseshoe steel form was used for the crown. Exterior
1 forms were 30-foot-long steel panels that extended just
above the springline. This portion of the forms was
'first filled with concrete, then steel trusses with slop-
ling panels were attached to the side forms, and con-
crete placement was resumed through the nonformed
area at the crown.
Grouting. Grout pipes were installed throughout
all supported sections of the tunnel. Contact grouting
ifilled the voids behind the concrete lining for the en-
[tire length of supported tunnel. Average grout take
|for both the 6-foot - 6-inch pressure tunnel and the
'9-foot - 6-inch walk-in conduit was 3'/2 sacks per linear
[foot of tunnel.
Consolidation grouting for the purpose of cutting
!3ff the flow of water in lenses parallel to the tunnel
ijxtended from Station 4+70 to Station 15+42 and
was tied into the grout curtain of the Dam. Four hun-
Idred and thirty-five holes, 15 and 25 feet in depth,
totaling 7,335 feet in length were used. The average
STout take was 0.49 of a cubic foot of grout per linear
["oot of grout hole.
Installation of 60-Inch Steel Pipe. Forms for the
Concrete saddles (Figure 219) which support the 60-
inch pipeline in the walk-in section were prefabricat-
';d in the contractor's carpenter shop. Reinforcing
'jteel also was formed into cages for easier installation,
-•lacement started at the upstream end and continued
Progressively downstream. Concrete was transported
lo the placement area by buggies and placed by hand
jihoveling.
A single railroad rail was installed on the pipe sup-
ports and fastened to the supports. The rail supported
the special equipment carriage used to transport the
60-inch pipe and butterfly valve. The carriage was
equipped with two flanged rail wheels on one side and
two plastic-tired wheels on the opposite side. The
plastic-tired wheels traveled along the walkway of the
tunnel, and the railroad wheels guided the carriage
along the railroad rail. The 60-inch conduit was in-
stalled in 20-foot - 10-inch sections that were loaded
onto the special equipment carriage and hand-pushed
to the placement position. Dry packing was inserted
between the asbestos friction surface and the pipe sup-
ports as pipe was placed.
The prefabricated bifurcation unit, connecting the
60-inch conduit in the walk-in section to the 60-inch
Del Valle Branch Pipeline, was encircled with straps
welded to the reinforcing steel protruding through
the invert slab to prevent flotation during concrete
placement. The conduit trench was overexcavated
from 2 to 9 inches and backfilled with selected bed-
ding material. Spark gap tests were made of the coal-
tar-coated exterior as well as the wrapped joints, and
all defects were repaired prior to backfilling. A blind
flange was bolted to the end of the Branch Pipeline at
Station 3 + 35.
Intake Structure. The trench for the intake struc-
ture (Figure 220) was excavated on a 1'/:! slope and
was 5 feet deep by 10 feet wide. The trench was ex-
cavated with a backhoe starting at the top. A dozer
pushed the material down the slope where it was
removed during foundation cleanup. Because the
foundation was composed of highly fractured sand-
stone and shale, consolidation grouting was necessary
to minimize the possibility of settlement and to pre-
vent erosion of the foundation due to fluctuations of
the water surface.
263
The excavated surfaces were covered with 1 inch ot
gunite, anchor bars were placed in drilled holes (but
not grouted), and consolidation grouting was started.
While injecting consolidation grout, cross-flow into
the anchor bar holes grouted many of the bars in place.
The remaining bars were grouted in place before any
concrete was placed. The first concrete was placed in
the thrust block. Ten linear feet of 1 '/-inch grout pipe
was installed through the block for consolidation
grouting in that area.
The slab was placed with a 5-foot-long by 7-foot-
wide, weighted, steel panel used as a slip form. The
form was pulled up the slope with a pneumatic hoist
and was guided by steel channels welded to the No. 10
grouted anchor bars. The concrete was dumped and
vibrated above the leading edge of the form. Four
placements were required to complete the invert.
The inclined sections were monolithic placements.
Walls were placed first with an hour lapse in time
allowed to minimize shrinkage before placing the top
slab. The heavy network of reinforcing steel within
the forms necessitated use of %-inch maximum size
aggregate in the concrete mix.
Hydraulic Testing. After the 42-inch fixed-cone
dispersion valve and the 60-inch butterfly valves were
installed, the entire system was tested hydraulically
by filling the intake structure with water to elevation
700 feet. Leakage that developed at the flexible coup-
ling expansion joint in the walk-in section of the con-
servation tunnel was repaired and the line was satis-
factorily retested.
Testing Butterfly Valves. After all five 42-inch
butterfly valves were installed (June 27, 1968), the
operator and hydraulic lines were tested. A leakage
test of each butterfly valve also was conducted by fill-
ing the space above the valve with 1 foot of water.
Minor leaks resulting from improper seating were
corrected.
Inlet Control Building. The conservation outlet
works intake structure is operated from the inlet con-
trol building. The building is located above the intake
structure on the conservation outlet works service
road and is connected to the intake structure by the
inlet control conduit.
The building rests on a concrete slab foundation
and is of masonry block construction, with a metal
roof deck and built-up, mopped-on, roof surface.
Machinery installed in the building includes a pow-
er package with hydraulic pumps; two 44-volt, 3-
phase, 60-cycle, dripproof, electric motors; a 20-gallon,
heated, hydraulic fluid reservoir; and a control panel.
Flood Control Outlet Works and Spillway Tunnel
Description. The 2,340-foot-long spillway tunnel
and flood control outlet works are located in the right
abutment of Del Valle Dam. The complex is com-
posed of three sections: the 2 1 5-foot-long, 18-foot-di-
ameter, pressure tunnel extending from the trashrack
at the inlet to the gate chamber; the gate chamber and
141-foot-high shaft; and the main 2,004-foot-long 28-
foot-diameter tunnel extending from the gate cham-
ber downstream to the stilling basin. The entire sys-
tem is lined with reinforced concrete.
Inlet. The abutment at the inlet portal was
stripped to firm sandstone, the face of the tunnel por-
tal was cut, and tunnel supports of the cut-and-cover
section were placed. Prior to starting tunnel excava-
tion, thirteen No. 18 bars were placed in holes drilled
30 feet horizontally into the abutment 1 foot - 8 inches
outside and around the crown of the tunnel. They
Figure 221. Tunnel Supports
Figure 222. Trashrack
264
Figure 223. Spillway Crest
Figure 224. Spillway Shaft Excavation Support
were then pressure-grouted in place forming a protec-
tive shield in the abutment at the portal. By having
these bars extend 5 feet out of the abutment and weld-
ing the first three structural steel supports of the cut-
and-cover section of the tunnel portal to them, they
acted as anchors and gave additional protection to the
portal during the tunnel operations (Figure 221).
Tunnel supports were placed for the full length of the
portal protection structure and lagged solidly.
Pressure Tunnel. The pressure section was ex-
cavated by conventional drilling, shooting, and muck-
ing methods. Steel posts and arches, with 4-inch
timber lagging, supported the crown and walls while
excavation of the tunnel was in progress. Concrete
was placed in the pressure section, utilizing an 18-foot-
diameter, full-circle, 24-foot-long, steel form. The
form was split at the invert and hinged at the quarter
points, allowing the lower halves to be raised or low-
ered by hydraulic jacks. The form was moved on an
overhead rail trolley, raised into final position by
jacks, and tied down to the structural steel posts by
steel rods welded to the form. The ends of the form
were bulkheaded against the rock sides with lumber.
Concrete was placed with a pumpcrete machine
through two 8-inch slicklines discharging at the 10
o'clock and 2 o'clock positions on the crown.
Contact grouting of the flood control outlet works
was completed on January 9, 1968. Consolidation
grouting was started at the completion of contact
grouting and continued until completed on January
22. Consolidation grouting of the gate chamber started
on January 23 and was completed on February 9, 1968.
A portion of the pressure tunnel, near the portal, was
grouted from the ground surface with good results.
Trashrack. The flood control trashrack is a rein-
forced-concrete structure 34 feet high composed of a
16-foot-radius, semicircular, grid frame with 2-foot-
thick beams and columns and 4-foot-square openings
(Figure 222). It is joined to the upstream end of the
tunnel with a transition section and headwall.
The foundation of the trashrack structure was ex-
cavated to firm sandstone. Zone 3 material was placed
and compacted to the required density and elevation.
A 2-foot-thick, reinforced-concrete, footing slab then
was placed and the trashrack constructed upon it.
Concrete placements were made in 8-foot-high lifts
using a mobile crane bucket. The concrete was cured
by wrapping with burlap and sprinkling with water.
Spillway Crest, Shaft, and Gate Chamber. A 5 '/i-
inch hole was drilled on the centerline of the vertical
spillway shaft from the bench at approximate eleva-
tion 738 feet downward to the elevation of the gate
chamber. A 1-inch steel cable was lowered through
this hole and attached to a 6-foot-square metal plat-
form. With this platform, an 8-foot-square shaft was
raised to the surface at elevation 738 feet. The spillway
shaft was sunk from this elevation. Holes were drilled,
loaded, and shot on concentric circles. The material
then was dozed into and dropped through the 8-foot-
square shaft and removed through the spillway tunnel
from the lower level.
A 4-foot-wide concrete collar with an inside diame-
ter of 64 feet then was placed around the perimeter of
the excavation at elevation 734.5 feet. A concrete crest
structure (Figure 223) was placed on top of the collar
at this elevation. The collar was used to anchor the
structural-steel shaft supports. Trimming of the shaft
then proceeded from the top. Successive structural
steel rings (Figure 224) were suspended, lagged, and
braced as the shaft was sunk to elevation 652 feet.
Here, at the elevation of the crown of the gate cham-
ber, a 33-inch, wide-flange, steel, ring beam was in-
stalled. Excavation of the gate chamber and elbow
265
then commenced. Arch sets bracing the walls and
crown of the gate chamber were installed and welded
to the ridge beam. Tunnel muck was removed through
the spillway tunnel.
Concrete placement in the gate chamber, elbow,
and shaft was made with four 12-inch and two 8-inch
steel pipe trunks spaced at intervals around the circu-
lar spillway shaft. The trunks were positioned be-
tween the inner and outer layer of reinforcing steel.
Each trunk was attached to an individual hopper at
the top of the shaft. Concrete was dumped into the
hoppers and then dropped through the pipes into final
position. A concrete mix with I'/j-inch maximum size
aggregate and a 4- to 5 '/-inch slump was used. The mix
fell a maximum of 5 feet from the end of the trunk. No
gates were used and no segregation was noted. Con-
crete placement in the shaft was made in three lifts.
One foot of first-stage concrete was removed from
the invert of the transition between the gate chamber
and the tunnel. A pneumatic impact hammer mount-
ed on a diesel wheel tractor with backhoe attachment
was used to remove the bulk of the concrete. Fine
grading was done with hand-operated pavement
breakers. In preparing the joint for second-stage con-
crete, the top 2 inches of first-stage concrete was
sawed.
A prefabricated form section was lowered down the
spillway shaft and skidded into place on a heavy tim-
ber track placed on pipe rollers. To prevent this form
from floating, No. 8 reinforcing bars were grouted
into the invert of the gate chamber and welded to steel
plates secured to the main structural members of the
form. She-bolts in the sides and crown of the gate
chamber were attached to the form in a similar man-
ner. Interior timber bracing running from crown to
invert and from side to side also was installed.
The drilling and grouting of the spillway shaft was
accomplished from a platform suspended from a
crane. Horizontally oriented rings with 8 to 10 grout
holes each were located at elevations 727, 717, 707, 697,
and 673 feet. A ring of 19 grout holes was located at
elevation 662 feet and a ring of 23 grout holes at eleva-
tion 652 feet. In addition, 18 grout holes of various
orientations were located near tunnel Station 9-1-82,
in the elbow area.
Downstream Portal. With one exception, the
downstream portal of the spillway tunnel was con-
structed in the same manner as the upstream portal of
the flood control outlet tunnel; that is, as soon as the
lagging of the umbrella section was completed, struc-
tural backfill was placed from the footings to the
springline.
Spillway Tunnel. The tunnel was driven by the
top heading and bench method. First, all material was
removed between the crown and 2 feet below spring-
line from the outlet portal to the gate chamber, a dis-
tance of 1,893 feet. Structural steel sets were placed
and lagged as the tunnel advanced. The material be-
low springline then was removed commencing at the
outlet portal. As the bench was removed, the steel
supports were extended to the invert elevation. This
extension was made by temporarily supporting the
top heading posts and arches with a 6-inch by 18-inch
by 30-foot-long soldier beam.
Concrete tunnel lining was placed in two phases:
the invert and crown. The invert was formed in 28-
foot sections with an 8-foot-long, 90-degree-arc, metal
slip form. Guide rails 40 feet long allowed the 8-foot
slip form to clear the end of each 28-foot section. The
form was pulled along the guide rails by two air win-
ches.
Concrete was placed in the invert by a swivel belt
conveyor system discharging into the forms and sup-
plied directly by transit mix trucks. Concrete first was
placed to the top of the reinforcing steel mat and vi-
brated. The next lift was placed over the mat and
forced ahead of the leading edge of the slip form. Fin-
ishers worked from a wooden platform spanning the
slip form rails. Finishing started as soon as the con-
crete cleared the form.
Crown placements were formed with two identical
28-foot-long steel forms (Figure 225). The forms were
moved on a rail-mounted jumbo and positioned to line
and grade with hydraulic jacks and an electrically op-
erated "Tugger" hoist.
Crown concrete was placed by two pumpcrete ma-
chines discharging through 8-inch slicklines at the 2
o'clock and 10 o'clock positions on the crown. The
concrete was consolidated with form vibrators mount-
ed on the form ribs at spacings of 7 feet longitudinally
and 6 feet circumferentially. Fourteen to sixteen vi-
brators were used for the 56-foot-long section. Two
and one-half-inch internal vibrators also were used
between the form face and rock walls.
Figure 225. Tunnel Crown Placement Forms
266
L
Complete filling of the crown was achieved by in-
serting 4-inch pipes through the lining at each end of
the arch form and injecting sand-cement mortar after
all concrete was placed. A total of 3 10.5 cubic yards of
mortar was injected behind the arch section from Sta-
tion 10+36 to Station 29+17. Mortar was injected
prior to tunnel contact grouting.
Contact grouting commenced near the downstream
portal and progressed upstream. Leakage at construc-
tion joints and grout flow to other holes occurred as
far as 60 feet from the injection hole. The relatively
high grout take of almost ten sacks of cement per
linear foot of tunnel is probably attributable to the
excessive fracturing and overbreak along the tunnel
crown during the driving of the tunnel.
The initial spacing and location of consolidation
grout rings in the spillway tunnel and shaft were
based on recommendations of the project geologist.
Several additional grout rings were installed in areas
of abrupt change in bedding attitude and areas of ex-
cessive overbreak. Two multiring grout curtains were
located in the prolongation of the dam axis. Each cur-
tain consisted of six rings of 16 holes each, with S-foot
spacing between rings.
Gates. Flow through the flood control outlet
works is controlled by four hydraulically operated
slide gates located in the gate chamber.
The cylinders, bonnets, and frames were lowered
down the spillway shaft by a mobile crane onto a
metal cart which transported them to the final loca-
tion.
Prior to positioning the gate bodies, the hydraulic
cylinders were hoisted to within 4 feet of the gate
chamber crown with individual 15-ton coffin hoists
and tied off with 1-inch cable safety straps to the pad
eyes embedded in the crown. The cylinders remained
suspended until the concrete deck of the gate chamber
Figure 226. Stilling Basin
was placed. They then were lowered into position on
top of the frames.
Gate Chamber Access. Entrance to the flood con-
trol outlet works gate chamber is through a concrete-
lined shaft and tunnel. The upper level of the shaft
terminates at elevation 773.5 feet in the flood control
outlet works control building located near the north
end of the right abutment access road.
The contractor first placed a 12-foot-diameter con-
crete ring at the shaft location and started excavation
by hand. As the shaft was sunk, loose material was
removed by hand loading into a clamshell bucket.
Conventional drilling, shooting, structural-steel ring
placing, and lagging methods were used. Waste
material was loaded into dump trucks and hauled to a
Zone 4 stockpile. The tunnel invert, elevation 640 feet,
was reached on October 1 3, 1966. The tunnel then was
excavated for a distance of 9 feet. The first two struc-
tural steel rings were set and lagged. Excavation of the
tunnel then was started from within the gate chamber
area. A shuttle buggy was used to remove material
from the tunnel. Material was loaded into the shuttle
buggy with an air mucker, dumped into the gate
chamber, and hauled out through the flood control
tunnel with a front-end loader.
The first concrete was placed in the vertical elbow
section to elevation 652 feet, or 12 feet from the shaft
base. Concrete was placed up the shaft in 20-foot lifts.
A 9-foot-diameter, full-circle, steel form was lowered
into place wth a truck crane and secured by welding
to the structural steel rings. Because of the limited
work area, all reinforcing steel for the entire 1 30 feet
of shaft was installed prior to the first concrete place-
ment. Concrete was placed by mobile crane bucket.
After completion of tunnel concreting, a concrete
walkway was formed and placed along the length of
the tunnel.
The same form used in the shaft was used in the
tunnel. Concrete in both the tunnel and horizontal
elbow section was delivered and placed by a double-
ram pumpcrete machine positioned just outside of the
flood control intake.
Grout pipes were installed as the concrete was
placed, and grouting of the access shaft and tunnel
started on September 25, 1967 and was completed on
October 12, 1967. Grout takes generally were low.
Stilling Basin. The stilling basin (Figure 226) for
the spillway and flood control outlet tunnel is a rein-
forced-concrete structure 267 feet long, 30 feet wide,
and 38 feet high. The basin is supported on a 62-foot-
wide, drained, concrete footing. The stilling basin
foundation was soft sandstone partially saturated with
water. Continual seepage during construction of the
basin drains made installation difficult. The sandstone
tended to disintegrate and become suspended in the
water. The sandy water filled the sumps and plugged
the dewatering pumps which had to be changed fre-
quently.
267
The stilling basin was excavated during July 1967.
Concrete placement started on August 10, 1967 and
was completed on December 14, 1967. Construction of
the basin drains proceeded simultaneously with the
concreting. The final concrete placements were de-
ferred until all construction equipment was removed
from the spillway tunnel.
Wall sections were placed in two lifts, each 25 feet
in length. A 6-inch polyvinylchloride waterstop was
placed in all construction joints. The floor slab was
concreted in alternate panels staggered on either side
of the centerline. A 6-inch waterstop also was installed
in the slab construction joints.
All concrete in the structure was placed by a mobile
crane bucket. The floor slab was cured by flooding
and the walls by draping with carpets kept moist by
soaker hoses.
Return Channel. The channel from the end of the
stilling basin flip bucket extends approximately 800
feet downstream in line with the tunnel from where
it turns in a northerly direction and merges with Ar-
royo Del Valle. The upstream portion of the channel
is confined between dikes constructed of Zone 3
material, cobbles, and riprap. Downstream from the
turn, the channel is confined between banks excavated
in stream gravels. The elevation of the channel invert
is 535.6 feet at the discharge end of the stilling basin.
Grade of the invert rises to elevation 540 feet at its
intersection with the original creek channel.
A small 15-foot-wide channel is located along the
center of the return channel for conveying reservoir
releases to supplement the streamflow.
The excavation, placement of cobbles on the invert,
and placement and compaction of Zone 3 material in
the dikes proceeded without difficulty. Placement of
riprap in the return channel, however, was a slow and
tedious process. Material was dumped as close as pos-
sible to the final location. Each rock then was picked
up individually with an orange-peel bucket and depos-
ited in final position.
Concrete Production
Concrete for the major portion of the project was
supplied from a portable batch plant operated by a
subcontractor.
The prefabricated plant was automatic and inter-
locked, and 1 2 different mixes could be set on the plant
controls for immediate selection. The mixer was a
4-cubic-yard tilt mixer. Additional equipment which
was part of the plant included a storage building for
block ice and a crusher, pozzolan and cement bulk
storage silos, and an overhead shuttle conveyor system
for transporting truck-loaded aggregates to stockpiles.
There also was an underground reclaiming tunnel
and conveyor system to feed aggregates from the
stockpiles through washing and finishing screens to
the weigh hoppers and finally to the tilt mixer.
Mixed concrete was transported from the plant to
the placement locations with three mixer trucks
equipped with tilt mixers.
The remainder of the concrete was supplied by a
commercial plant in Pleasanton, 8 miles from the Dam
site.
Reservoir Clearing
Clearing operations started on the hillside above the
flood control inlet and outlet portals, moved to the
dam foundation and abutments, and then progressed
upstream to the borrow areas and the reservoir.
Heavy grubbing was done with three large dozers
equipped with rippers and brush blades. Small brush
was removed by laborers using power saws and ma-
chetes. Stumps were removed with the dozers and
later buried in designated waste areas. Brush and
burnable logs were piled and burned. Small logs were
removed and piled.
Closure
The permanent plug closing the diversion opening
in the conservation outlet works was placed on May
16, 1968, without incident. All work was completed on
September 17, 1968 and, by the end of the year, the
water was 23 feet below the invert of the flood control
outlet works, the reservoir's lowest outlet. The first
flood control releases were made on February 25,
1969, and since then the reservoir has been operated
within the planned range.
268
BIBLIOGRAPHY
California Department of Water Resources, Bulletin No. 117-2, "Del Valle Reservoir: Recreation Development
Plan", December 1966.
, Bulletin No. 132-72, "The California State Water Project in 1972", June 1972.
, Bulletin No. 132-72C, "The California State Water Project SUMMARY: nineteen-seventy-one". Appen-
dix C.
, Specification No. 66-01, "Specifications Bid and Contract for Del Valle Dam and Reservoir, State Water
Facilities, South Bay Aqueduct, Del Valle Division, Alameda County, California", 1966.
269
y
GENERAL
LOCATION
O'NEILL
FORE B A Y
SAN LUIS DAM
SAN LUIS
RESERVOIR
SAN LUIS
PUMPING-GENERATING
PLANT
Figure 227. Location Map — San Luis Joint-Use Storage Facilities
270
CHAPTER XI. SAN LUIS JOINT-USE STORAGE FACILITIES
General
Description and Location
The San Luis Joint-Use Facilities serve the U.S.
Bureau of Reclamation's San Luis Unit of the Federal
Central \'alley Project and the State Water Project
(Figure 227). They extend along the west side of the
San Joaquin \' alley from O'Neill Forebay to Kettle-
man City, about 106 miles. The joint-use storage facili-
ties consist of San Luis Dam and Reservoir (Figure
228), O'Neill Dam and Forebay, Los Banos Detention
Dam and Reservoir, and Little Panoche Detention
Dam and Reservoir (O'Neill Dam and Forebay for-
merly were identified as San Luis Forebay Dam and
Forebay).
The route for conveying project water to state serv-
ice areas in the San Joaquin Valley and Southern Cali-
fornia is through the 500,000-acre federal San Luis
service area on the west side of the San Joaquin Valley.
%
'.'•y*^
Figure 228. Aerial View — San Luis Dam and Reservoir
271
Figure 229. San Luis Reservoir Recreation Areas
272
The San Luis Unit of the Central Valley Project was
authorized by Act of Congress, PL 86-488, which
became law on June 3, 1960 (74 Stat. 156). Each
project required development of the San Luis Dam
site, west of Los Banos, for storage of surplus flows
pumped from the Sacramento-San Joaquin Delta.
Therefore, the best development for California and
the United States was to integrate the storage, pump-
ing, and conveyance facilities for coordinated opera-
tion. An agreement between the State and the United
States was entered into on December 30, 1961 to
achieve those results.
The agreement provided that the Bureau of Recla-
mation would design and construct the Joint-Use
Facilities. It was agreed that cost sharing would be on
the basis of approximately 55% state and 45% federal.
The State was granted responsibility for operation
and maintenance under the same approximate cost-
sharing formula.
The Bureau of Reclamation publishes reports on its
projects, similar to the Department of Water Re-
sources' Bulletin 200. Reports covering the Joint-Use
Facilities are or will become available in the near fu-
ture. Accordingly, this chapter is intended to provide
only sufficient information for continuity in Bulletin
200 coverage of the State Water Project.
San Luis Dam is located at the base of the foothills
on the west side of the San Joaquin Valley in Merced
County. It is 12 miles west of the City of Los Banos on
San Luis Creek and 2 miles west of O'Neill Dam.
Several highways traverse the locality. Located to the
east are Interstate Highway 5 and State Highway 33.
Relocated State Highway 152 extends through the
site between San Luis and O'Neill Dams and across
the intake channel leading to the San Luis Pumping-
Generating Plant. This highway connects Los Banos
and the Gilroy-HoUister area over Pacheco Pass. Los
Banos Detention Dam is 7 miles southwest of the City
of Los Banos in Merced County. The nearest highway
is Interstate 5, about 1 mile to the east of the Dam site.
Little Panoche Detention Dam is located in Fresno
County 20 miles southwest of the City of Los Banos.
The nearest major highway is Interstate 5, about 3
miles to the east of the Dam site. The Dam is located
at a stream constriction about 2 miles west of the San
Joaquin Valley floor.
Purpose
San Luis Reservoir and Lake Oroville are the two
key conservation features of the State Water Project.
San Luis Reservoir provides offstream storage for ex-
cess winter and spring flows diverted from the Sacra-
mento-San Joaquin Delta. In periods of excess runoff,
water is pumped into San Luis Reservoir from
O'Neill Forebay via San Luis Pumping-Generating
Plant. San Luis Reservoir is sized to provide seasonal
carryover storage. Hydroelectric power generation.
on a nondependable schedule, is a project benefit but
only an incidental purpose. There are extensive recre-
ational developments around the reservoirs, as shown
on Figure 229, as well as fish and wildlife benefits.
Los Banos Detention Dam provides flood protec-
tion for San Luis Canal, Delta-Mendota Canal, City of
Los Banos, and other downstream developments. In
addition, a 470-acre lake is provided for recreation.
San Luis Dam is a 385-foot-high 77,645,000-cubic-
yard embankment with a crest length of 18,600 feet.
The gross capacity of San Luis Reservoir is 2,038,771
acre-feet of which 1,067,908 acre-feet are allocated to
the State. The spillway consists of a glory-hole inlet,
shaft, conduit, chute, and stilling basin. San Luis
Pumping-Generating Plant serves as the inlet-outlet
works for the Reservoir. Four tunnels near the left
abutment connect the plant to an inlet-outlet struc-
ture in the Reservoir. A control shaft and reservoir
intake for the Pacheco tunnel, a future outlet to the
west, were constructed to serve the San Felipe Divi-
sion of the Central Valley Project. This tunnel stub is
approximately 2 miles long.
O'Neill Forebay, with a gross storage capacity of
56,426 acre-feet, has several inlets and outlets. San
Luis Pumping-Generating Plant functions as both an
inlet and an outlet. The California Aqueduct entering
from the north and O'Neill Pumping Plant on the left
abutment of O'Neill Dam serve as inlets. Finally, the
San Luis Canal reach of the California Aqueduct starts
on the southeast edge of the Forebay. O'Neill Dam
contains 3,000,000 cubic yards of embankment. It has
a crest length of 14,350 feet and a maximum height of
88 feet. The forebay spillway is a glory-hole inlet dis-
charging into a cut-and-cover conduit.
Los Banos Detention Dam is a 2,100,000-cubic-yard
embankment with a structural height of 167 feet and
crest length of 1,370 feet. The spillway is a concrete
chute located on the left abutment. The outlet works
consists of a vertical intake tower, a tunnel with a gate
chamber, and a discharge line with hydraulically oper-
ated slide gates. Los Banos Reservoir has a gross
capacity of 34,562 acre-feet.
Little Panoche Detention Dam is a 152-foot-high
embankment with a crest length of 1,440 feet. The
embankment volume is 1,210,000 cubic yards. Parallel
cut-and-cover conduits for the spillway and outlet
works are located under the embankment on the right
abutment. The spillway has a glory-hole inlet, while
the intake to the outlet works is a vertical tower. Little
Panoche Reservoir has a gross capacity of 13,236 acre-
feet.
Tables 27 through 30 are statistical summaries of the
dams and reservoirs.
Little Panoche Detention Dam provides flood pro-
tection for San Luis Canal, Delta-Mendota Canal, and
other downstream developments.
273
TABLE 27. Statistical Summary of San Luis Dam and Reservoir
SAN LUIS DAM
Type: Zoned earth and rockfiU
Crest elevation SS4 feet
Crest width - - - 30 feet
Crest length 18,600 feet
Streambed elevation at dam axis 241 feet
Lowest foundation elevation 169 feet
Structural height above foundation.,- 385 feet
Embankment volume 77,645,000 cubic yards
Freeboard above spillway crest 10.1 feet
Freeboard, maximum operating surface 11.2 feet
Freeboard, maximum probable flood.. 8.2 feet
SAN LUIS RESERVOIR
Storage at spillway crest elevation 2,038,771 acre-feet
Maximum operating storage 2,025,795 acre-feet
Minimum operating storage 79,200 acre-feet
Dead pool storage 8 acre-feet
Maximum operating surface elevation 542 . 8 feet
Minimum operating surface elevation 326 feet
Dead pool surface elevation 281.1 feet
Shoreline, spillway crest elevation 65 miles
Surface area, spillway crest elevation. 12,700 acres
Surface area, maximum operating elevation.. 12,520 acres
Surface area, minimum operating elevation.. 3,600 acres
SPILLWAY
Type: Glory hole with reinforced-concrete conduit and stilling basin
Crest elevation 543 . 9 feet
Crest length 95.2 feet
Crest diameter 30.3 feet
Conduit diameter 9.5 feet
Peak maximum probable routed
outflow. 1,030 cubic feet per second
Maximum surface elevation 545.8 feet
INLET-OUTLET
San Luis Pumping-Generating Plant: Four vertical intake towers
each with a 23-foot - 3K-inch-wide by 23-foot - 7-inch-high roller
gate shutoff and a 24-foot - 6-inch-wide by 29-foot-high emer-
gency bulkhead gate in tandem
Maximum generating release 13,120 cubic feet per second
Pumping capacity 11,000 cubic feet per second
OUTLET
Pacheco Tunnel
Length (initial contract) 1.8 miles
Length (ultimate) 10,3 miles
Diameter 13 feet
Capacity (when completed) 670 cubic feet per second
TABLE 28. Statistical Summary of O'Neill Dam and Forebay
O'NEILL DAM
Type: Homogeneous earthfill
Crest elevation 233 feet
Crest width 30 feet
Crest length 14,350 feet
Streambed elevation at dam axis 167 feet
Lowest foundation elevation 145 feet
Structural height above foundation.. 88 feet
Embankment volume 3,000,000 cubic yards
Freeboard above spillway crest 8 feet
Freeboard, maximum operating surface 9 feet
Freeboard, maximum probable flood 5 feet
O'NEILL FOREBAY
Storage at spillway crest elevation.. 56,426 acre-feet
Maximum operating storage 53,730 acre-feet
Minimum operating storage 35,700 acre-feet
Dead pool storage 10,220 acre-feet
Maximum operating surface elevation. 224 feet
Minimum operating surface elevation 217 feet
Dead pool surf ace elevation 202 feet
Shoreline, spillway crest elevation 12 miles
Surface area, spillway crest elevation 2,700 acres
Surface area, maximum operating elevation . . 2,670 acres
Surface area, minimum operating elevation.. 2,450 acres
SPILLWAY
Type: Glory hole with reinforced-concrete conduit and stilling basin
Crest elevation 225 feet
Crest length 184 . 4 feet
Crest diameter 59. 0 feet
Conduit diameter 11.8 feet
Peak maximum probable routed
outflow.. 3,250 cubic feet per second
Maximum surface elevation 228 feet
INLET
North San Joaquin Division of California Aqueduct
Capacity 10,000 cubic feet per second
INLET-OUTLET
San Luis Pumping-Generating Plant
Maximum generating release 13,120 cubic feet per second
Pumping capacity 11,000 cubic feet per second
O'Neill Pumping-Generating Plant
Maximum generating release 3,600 cubic feet per second
Pumping capacity 4,200 cubic feet per second
OUTLET
San Luis Canal
Capacity 13,100 cubic feet per second
274
TABLE 29. Statistical Summary of Los Bonos Detention Dam ond Reservoii
LOS BANGS DETENTION DAM
Type: Zoned earthfiU
Crest elevation
Crest width
Crest length
Streambed elevation at dam axis.
Lowest foundation elevation
384 feet
30 feet
1,370 feet
228 feet
217 feet
Structural height above foundation 167 feet
Embankment volume 2,100,000 cubic yards
30.5 feet
56.2 feet
5.8 feet
Freeboard above spillway crest
Freeboard, maximum recreation surface.
Freeboard, maximum probable flood
LOS BANCS RESERVOIR
Storage at spillway crest elevation.
Maximum recreation storage
Dead pool storage
Maximum recreation surface elevation.
Dead pool surface elevation
Shoreline, spillway crest elevation
Surface area, spillway crest elevation
Surface area, maximum recreation elevation-
Surface area, minimum recreation elevation..
34,562 acre-feet
20,600 acre-feet
8,000 acre-feet
327.8 feet
295.2 feet
12 miles
623 acres
500 acres
380 acres
SPILLWAY
Type: Ungated ogee crest with lined chute and stilling basin
Crest elevation.
Crest length
353.5 feet
20 feet
Peak maximum probable routed
outflow 8,600 cubic feet per second
Maximum surface elevation 378.2 feet
OUTLET WORKS
Type: Lined tunnel under left abutment, valve chamber at mid-
point— discharge into stilling basin
Diameter: Upstream of valve chamber, 78-inch pressure conduit —
downstream, 70-inch steel conduit in a 126-inch concrete horse-
shoe tunnel
Intake structure: Uncontrolled tower
Control: Downstream control, two 42-inch-square, high-pressure,
slide gates — guard valve, one 60-inch-wide by 72-inch-high, high-
pressure, slide gate in valve chamber
Capacity 1,255 cubic feet per second
TABLE 30. Statistical Summary of Little Panoche Detention Dam and Reservoir
LITTLE PANOCHE DETENTION DAM
Type: Zoned earthfiU
SPILLWAY
Type: Glory hole with reinforced-concrete conduit and stilling basin
676 feet
30 feet
1,440 feet
641.5 feet
88.5 feet
28.5 feet
556 feet
524 feet
152 feet
1.210.000 cubic vards
9.5 feet
Streambed elevation at dam axis
Lowest foundation elevation
Structural height above foundation
Peak maximum probable routed
outflow _.
Maximum surface elevation
OUTLET WO
Type: Reinforced-concrete conduit ber
abutment — discharge into stilling bas
Diameter: 9 feet - 6 inches
Intake structure: Uncontrolled tower
Control :_None
3,200 cubic feet per second
670.4 feet
Freeboard above spillway crest 34.5 feet
Freeboard, maximum probable flood 5.6 feet
LITTLE PANOCHE RESERVOIR
Storage at maximum probable flood 13,236 acre-feet
RKS
leath dam at base of right
in
590 feet
Shoreline, maximum probable flood
Surface area, maximum probable flood
Surface area, dead pool elevation
10 miles
354 acres
30 acres
1,040 cubic feet per second
275
Chronology
Final design of the San Luis features started in 1961 .
The first construction contract for relocation of State
Highway 152 was awarded in August 1962. The offi-
cial San Luis Unit ground-breaking ceremonies were
held on August 18, 1962. The event was highlighted by
the presence of President John F. Kennedy (Figure
230). The contract for construction of San Luis and
O'Neill Dams and the Pumping-Generating Plant
was awarded on January 8, 1963.
Construction of San Luis and O'Neill Dams was
completed on August 4, 1967. Water was first pumped
to storage in San Luis Reservoir on April 12, 1967.
Essentially, it was filled for the first time on May 31,
1969.
The detention dams were completed and put into
operation in 1966.
Operation
Primarily during winter and early spring, surplus
water in the Sacramento-San Joaquin Delta is pumped
into the North San Joaquin Division of the California
Aqueduct and flows by gravity into O'Neill Forebay.
The federal diversion is pumped into the Forebay
from the Delta-Mendota Canal by O'Neill Pumping
Plant. From the Forebay, water either flows south
through the San Luis Canal or flows through the in-
take channel to the San Luis Pumping-Generating
Plant, where it is pumped into San Luis Reservoir.
The maximum static head on the Pumping-Generat-
ing Plant is 327 feet.
During the remainder of the year, when down-
stream water demand is greater than direct Sacra-
mento-San Joaquin Delta diversions through the
California Aqueduct and the Delta-Mendota Canal,
water is released from San Luis Reservoir to augment
the flow. Power is generated as the flow passes
through the Pumping-Generating Plant into the Fore-
bay. Additional power for the Federal Central V^al-
ley Project is generated by reversal of flow through
O'Neill Pumping Plant from the Forebay to the Del-
ta-Mendota Canal.
The reservoirs are operated to minimize electrical
energy costs for pumping and to deliver water on
demand. They also are operated at a normal maximum
operating level 1 foot below the maximum storage
elevation to prevent loss of water through the spill-
ways by wave overtopping.
Under the coordinated operation to satisfy the fu-
ture maximum demands on the state and federal
projects, there will be large storage withdrawals from
San Luis Reservoir. The hydraulic machinery of the
Pumping-Generating Plant was designed to function
with the reservoir level reduced to elevation 326 feet,
a fluctuation of 218 feet.
Operational limitations on storage in Los Banos
Reservoir are shown on the flood control diagram
(Figure 231). Between September 20 and March IS of
any year, 14,000 acre-feet of space will be maintained
insofar as possible for control of flood waters under
the following conditions:
1. Releases from Los Banos Reservoir shall be re-
stricted, insofar as possible, to flows which will not
exceed 1,000 cubic feet per second (cfs) in Los Banos
Creek below Los Banos Detention Dam.
2. The rate of change (increase or decrease) of
flows in Los Banos Creek below the Dam shall not
exceed 200 cfs during any two-hour period.
During the remainder of the year, inflow from Los
Banos Creek may be used to raise the recreation pool
above elevation 327.8 feet.
The outlet works for Little Panoche Reservoir is
ungated. Water is stored behind the Dam above cur-
rent dead storage only during the period that the in-
flow from Little Panoche Creek exceeds the capacity
of the outlet works.
Figure 230.
President John F. Kennedy and Governor Edmund G. Brown Pushing Plungers to
Detonate Explosives for Ground Breaking
276
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Figure 231. Flood Diagram — Los Bonos Reservoir
277
Figure 232. General Plan and Sections of San Luis Dam and O'Neill Forebay
278
Design
Dams
San Luis. The 385-foot-high San Luis Dam is a
zoned earthfill (Figure 232) with a rock face section
on a 3:1 slope upstream above elevation 400 feet, and
an 8:1 slope of random material below elevation 400
feet, steepening to 2J4:1 below elevation 310 feet (Fig-
ure 233). The downstream slope is 2:1 above and 2/4:1
below elevation 450 feet, flattening to a 6: 1 slope below
elevation 400 feet. The Dam incorporates a chimney
drain below elevation 500 feet connected to a founda-
tion blanket drain. This drain system terminates in toe
drains. The dam crest is at elevation 554 feet.
The foundation for San Luis Dam, in the channel of
San LuisCreek, consisted of up to 160 feet of alluvium.
Excavation for the Dam was in excess of 100 feet in
depth into the alluvial deposits terminating on a com-
petent, firm, clayey, gravel formation extending to
Panoche bedrock.
The double foundation trenches involved the re-
moval of 5,570,000 cubic yards of material. The foun-
dation trenches provide for a proper gradient to
control seepage underflow, a foundation capable of
supporting the superimposed loads, and an embank-
: ment section capable of resisting static and dynamic
sliding forces. The abutments mostly consist of in-
terbedded shale and sandstone units. There are con-
, glomerates in the lower left abutment which were
penetrated by the four inlet-outlet tunnels.
The rock foundation was grouted with primary
holes at 10-foot centers. Where grout takes were
heavy, the spacing was split to obtain satisfactory re-
sults. The curtain extended to a normal depth of 160
feet with a maximum depth of 300 feet. The deepest
holes were drilled to intercept faults in the outlet
iworks tunnel alignments to improve conditions for
Itheir excavation. The average grout take was nearly
0.4 of a cubic foot of cement per foot of hole.
Embankment materials for Zone 1 were the alluvial
valley fills from within both the San Luis and O'Neill
ireservoir basins. The largest portion was excavated by
a large wheel-type loader (Figure 234). The sand,
gravel, and cobbles of Zone 2 were obtained from
ichannel deposits along San Luis Creek, beginning up-
.stream of San Luis Reservoir. Zone 3 consisted of
•miscellaneous material, including that removed in
foundation excavation which was moved directly to
jplacement in the embankment. Material for rock fill,
|bedding, and riprap was quarried from Basalt Hill,
iaigh on the right abutment. It was separated at the
3-inch size with some of the material passed through
1 crusher to manufacture bedding for riprap (Figure
J35). Zone 4 consists of the fraction less than 8 inches
md Zone 5 that fraction greater than 8 inches.
Figure 233. Placing and Compacting Embankment — San Luis Dam
Figure 234. Wheel Excavator Cutting on 50-Foot-High Fa
Figure 235. Basalt Hill Rock Separation Plant
21—87401
279
O'Neill Forebay. This 88-foot-high dam is homo-
geneous with riprap protection from 2 feet below
minimum pool to the dam crest on the upstream face.
The upstream slope is Z'/zil above elevation 215 feet
and 3/2:1 below. The downstream slope is constant at
2:1. The downstream section has a foundation blanket
drain and a toe drain.
The Dam is founded entirely on alluvium except for
the abutment at O'Neill Pumping Plant. Exposed
gravels in San Luis Creek upstream of the Dam were
blanketed with S feet of impervious material. Grout-
ing was done at the abutment, but seepage control
otherwise is obtained by the cutoff trench. The em-
bankment materials are from the same sources as for
San Luis Dam.
Los Bancs Detention. Figure 236 shows the plan
and sections of 167-foot-high Los Banos Detention
Dam.
The foundation consists of shales, sandstones, and
conglomerates. The channel of Los Banos Creek con-
tained alluvial deposits which were removed under
Zone 1 of the Dam.
Foundation preparation included construction of a
grout cap. Grout holes were drilled at 10-foot centers
to a maximum depth of 110 feet. The grout take was
small, averaging 0.19 of a cubic foot of cement per foot
of hole.
The embankment contains three zones: Zone 1, the
core, contains a clay, silt, and gravelly material to 5
inches maximum size; Zone 2 is stream sand and grav-
el from the reservoir area; and Zone 3 is miscellaneous
material from required excavations and suitable site
stripping. Riprap was obtained from a basalt quarry
about 17 miles west of the project.
Little Panoche Detention. Figure 237 shows the
plan and section of Little Panoche Detention Dam.
Foundation for the Dam is the Panoche formation
consisting of sandstone, siltstone, and clay shale. A
cutoff trench was excavated to fresh formation. To
prevent air slaking, the final 1 foot of excavation for
the Dam and concrete structures was deferred until
covering could proceed expeditiously.
The foundation was not grouted. Grouting was un-
necessary because water will not be in reservoir reten-
tion longer than five days at a time, which is not long
enough to allow seepage to become established. Fur-
thermore, siltation is expected to form a bottom blan-
ket.
The embankment contains two zones. The majority
of Zone I embankment was obtained from selected
material from required excavation, with the balance
taken from the reservoir area.
Zone 2 embankment generally was that material
which was unsuitable for Zone 1. Mostly, it is sand,
gravel, cobbles, and fragments of sandstone and, in the
reservoir borrow area, normally was overlain by Zone
1.
The contractor chose to develop a quarry on private
land southeast of Ortigalita Peak to obtain riprap. It
was in greenstone of the Franciscan formation.
Inlets, Outlets, and Spillways
San Luis Reservoir. The San Luis Pumping-Gen-
erating Plant is the only inlet-outlet for San Luis Res-
ervoir. Four 17 '/^-foot-diameter concrete and partly
steel-lined tunnels, located in the left abutment, con-
nect the plant to the four trashrack tower structures
(Figures 238 and 239). Each of these tunnels services
two pump-turbines.
The tunnels are about 2,1 50 feet long and were driv-
en from both portals simultaneously. The geology of
the site, and particularly the existence of faults, in-
fluenced the method of construction. The normal con-
crete lining is 2 feet - 5 inches thick. The thickness at
special sections through faults, and in areas of low
rock cover, is a minimum of 3 feet - 6 inches. The
downstream portions of the tunnels are steel-lined.
As inlets, the tunnels can convey 11,000 cfs and,
operating as reservoir outlets, they can discharge
13,120 cfs.
The spillway, with a capacity of 1,030 cfs at water
surface elevation 545.8 feet, is sized to pass the max-
imum probable floodflow. However, because the San
Luis Pumping-Generating Plant has a capacity to dis-
charge a flow of 13,120 cfs while generating, the spill-
way will be used only if the Pumping-Generating
Plant is inoperative during a flood. Under such condi-
tions, the flow would pass into a glory-hole-type inlet
structure, through a 9-foot - 6-inch conduit under the
Dam on the left abutment, and into a rectangular
chute. At the downstream end of the chute, the flow
would enter a stilling basin, then discharge into the
approach channel of the Pumping-Generating Plant.
O'Neill Forebay. As stated previously, there are
four inlets and outlets for O'Neill Forebay: (1) San
Luis Pumping-Generating Plant, (2) O'Neill Pump-
ing Plant, ( 3 ) North San Joaquin Division of the Cali-
fornia Aqueduct, and (4) San Luis Canal. O'Neill
Pumping Plant has six reversible units. Each has its
own 10-foot-diameter discharge line to the Forebay
which carries water at a 700-cubic-foot-per-second
rate. The inlet from the North San Joaquin Division
portion of the California Aqueduct is a simple transi-
tion, while the outlet to the San Luis Canal essentially
is a canal check structure.
280
Figure 236. Los Banos Detention Dam — Plan, Profile, and Sections
281
Figure 237. little Ponoche Detention Dam— Plan, Profile, and Sections
282
Figure 238. Spillway and Outlet Works — Son Luis Dam
283
Figure 239. Trashrack Structure and Access Bridge — San Luis Da
The spillway (Figure 240), with a capacity of 3,250
cfs at water surface elevation 228 feet, is capable of
carrying the maximum probable floodflow from the
Forebay. Also, it is expected to be used infrequently
because the reversible O'Neill Pumping Plant has a
capacity to discharge 3,600 cfs while generating,
which is well in excess of the spillway design flow.
During a plant outage, floodflows will pass into a glo-
ry-hole spillway adjacent to the Pumping Plant,
through an 11-foot -9-inch-diameter conduit under
the Dam, and into a stilling basin at the toe of the
Dam. After being stilled, the flow will enter the fore-
bay wasteway and pass through a siphon under the
Delta-Mendota Canal. Here, it is returned to the chan-
nel of San Luis Creek.
Los Bancs Reservoir. The outlet works located in
the left abutment of the Dam will discharge a max-
imum of 1,225 cfs and consists of an 84.5-foot-high,
trashracked, intake structure; a 6.5-foot-inside-diame-
ter (ID), 5 10- foot-long, circular tunnel; a gate cham-
ber housing one 5-foot by 6-foot, hydraulically
operated, high-pressure, emergency gate; and a 70-
inch ID, 497-foot-long, steel conduit (within a 10.5-
foot ID, concrete, horseshoe tunnel) which branches
into two outlets pipes, each controlled by a 3.5-foot-
square, hydraulically operated, high-pressure, slide
gate. The outlets discharge the water into a stilling
basin which, in turn, empties into the existing channel
of Los Banos Creek downstream from the structure.
Plan and profiles of the outlet works are shown on
Figures 241 and 242.
The concrete chute spillway has a discharge capaci-
ty of 8,600 cfs and is located in the left abutment of the
Dam. It has an uncontrolled 20-foot-long ogee crest at
elevation 353.5 feet. Water reaches the spillway crest
through an inlet channel to the crest, then flows
through an open chute of variable width down to the
stilling basin located near the toe of the Dam.
Little Panoche Reservoir. The outlet works, locat-
ed adjacent to the spillway near the right abutment of
the Dam, will discharge a maximum of 1,040 cfs and
consists of a 90.5-foot-high, trashracked, intake struc-
ture and a 6-foot - 6-inch ID, 592-foot-long, ungated,
reinforced-concrete pipe that empties into a stilling
basin adjacent to the spillway stilling basin. These
stilling basins, in turn, flow into Little Panoche Creek
channel downstream of the structure. The plan and
profile of the outlet works are shown on Figure 243.
The spillway, with a glory-hole-type inlet has a dis-
charge capacity of 3,220 cfs and is located in the em-
bankment on the right abutment. It discharges
through a 9-foot - 6-inch-diameter conduit into a still-
ing basin at the toe of the Dam.
284
Figure 240. Spillway — O'Neill Forebay Dam
285
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iiiisi
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'b * is
i-'^J
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Figure 241 . Los Bonos Detention Dam — Spillway and Outlet Plan and Spillwoy Profile
286
Figure 242. Los Banos Detention Dam — Outlet Profile
287
Figure 243. li„|e Panoche Detention Dom-Spillwoy Plan and Sections
288
Instrumentation
Instrumentation at San Luis Dam and O'Neill Dam
consists of the following:
San Luis Dam
Monumentation
Surface settlement 117
Spillway tunnel 14
Spillway chute and basin 110
Trashrack structure 10
Hydraulic piezometers 1 19
Internal vertical and horizontal
movement devices 4
Base plates — foundation settlement 3
Observation wells 16
Toe drains 8
Seepage measurements 5
Slide monitoring 1
Area control 60
O'Neill Dam
Monumentation
Embankment 42
Spillway conduit 13
Spillway chute and basin 16
Toe drains 3
Ground water observation wells in
agriculture settings 34
Ground water observation wells at dam
and appurtenant features 15
The location of certain instrumentation at San Luis
Dam is shown on Figure 244.
The following instrumentation was installed at Los
Banos Detention Dam and Little Panoche Detention
Dam:
! Los Banos
Monumentation
Embankment 20
Spillway 46
Outlet works 20
, Abutments 14
[Abutment piezometer wells 2
iToe drain 1
Weir, outlet tunnel drain 1
Little Panoche
Monumentation
Embankment 23
Spillway conduit 18
Spillway stilling basin 25
Outlet conduit 24
Outlet stilling basin 21
Abutment 16
Toe drain 1
The location of the embankment monuments and
the toe drains is shown on Figures 237 and 240.
Recreation
Although the drawdown of San Luis Reservoir (dis-
cussed under "Operation") will not be an annual oc-
currence, it affects the recreation potential of the
Reservoir. Therefore, to realize the greatest return
from multipurpose benefits, proportionally greater
outlay is invested in recreation facilities at O'Neill
Forebay where maximum reservoir fluctuation will
be only 8 feet.
During construction of San Luis Dam, some of the
embankment materials were excavated from the fore-
bay reservoir area. This excavation was performed
with the objective of improving the forebay topogra-
phy in the interest of creating better beach and bottom
areas for the recreational environment. Also, it creat-
ed a greater storage capacity to minimize drawdown.
It is projected that the Forebay will receive considera-
bly greater recreation patronage because of the more
stable water surface.
Native vegetation in the area is predominantly
grasses, with scattered trees at the higher elevations
around San Luis Reservoir. Mainly, the land had been
used for grazing and livestock production. For the
most part, the locations chosen for recreation were
barren. At an early stage, the State planted trees to
provide areas around the reservoirs more conducive to
recreation enjoyment.
The California Department of Parks and Recrea-
tion is responsible for project recreation. It funds the
onshore improvements and manages the recreation
facilities. The Department of Water Resources pro-
vides interpretive services to the public at Romero
Overlook, an attractive visitor facility which is adja-
cent to State Highway 152 and beyond the left abut-
ment of San Luis Dam.
289
Figure 244. Location of Instrumentotion — Son Luis Dam
290
BIBLIOGRAPHY
United States Bureau of Reclamation, "Agreement Between the United States of America and the Department
of Water Resources of the State of California for the Construction and Operation of the Joint-Use Facilities
of the San Luis Unit", Contract No. 14-06-200-9755, December 30, 1961.
, "Final Construction Report, Completion of Dos Amigos (Mile 18) Pumping Plant Switchyard and
Appurtenant Works", Specifications No. DC-6255, April 1970.
"Final Construction Report, Completion of San Luis Pumping-Generating Plant and Switchyards",
Specifications No. DC-6185, June 1970.
, "Final Construction Report, Dos Amigos (Mile 18) Pumping Plant", Specifications No. DC-5982, April
1969.
_, "Final Construction Report, Forebay Pumping Plant and Appurtenant Works and Forebay Dam
Spillway", Specifications No. DC-6033, December 1971.
, "Final Construction Report, Little Panoche Creek Detention Dam", Specifications No. DC-6236, May
1972.
_, "Final Construction Report, Los Banos Creek Detention Dam", Specifications No. DC-6080, December
1966.
, "Final Construction Report, San Luis Dam and Pumping-Generating Plant and Forebay Dam", Specifi-
cations No. DC-5855, February 1970.
, "Final Construction Report, San Luis Canal, Reach 1", Specifications No. DC-5900, September 1970.
, "Final Construction Report, San Luis Canal, Reach 2", Specifications No. DC-5977, August 1971.
, "Final Construction Report, San Luis Canal, Reach 3", Specifications No. DC-6148, December 1969.
, "Final Construction Report, San Luis Canal, Reach 4", Specifications No. DC-6280, June 1971.
, "Final Construction Report, San Luis Canal, Reach 5", Specifications No. DC-6344, July 1971.
_, "Final Construction Report, Pacheco Inlet Channel and Tunnel to Station 198-1-55", Specifications No.
DC-6160, April 1971.
-, "History, General Description, and Geology", Volume I, San Luis Unit Technical Record of Design
and Construction.
, "San Luis Dam and Pumping-Generating Plant, and O'Neill Dam and Pumping Plant — Design",
Volume n, San Luis Unit Technical Record of Design and Construction.
, "San Luis Dam and Pumping-Generating Plant, and O'Neill Dam and Pumping Plant — Construction",
Volume in, San Luis Unit Technical Record of Design and Construction.
, "Dos Amigos Pumping Plant and Pleasant Valley Pumping Plant — Design", Volume IV, San Luis Unit
Technical Record of Design and Construction.
-, "Dos Amigos Pumping Plant and Pleasant Valley Pumping Plant — Construction", Volume V, San Luis
Unit Technical Record of Design and Construction, September 1974.
., "Waterways and Detention Dams — Design", Volume VI, San Luis Unit Technical Record of Design
and Construction.
, "Waterways and Detention Dams — Construction", Volume III, San Luis Unit Technical Record of
Design and Construction.
, "Designer's Operating Criteria, San Luis Canal", July 1966.
, "Pile Driving Report on San Luis Canal, Reach 3", Specifications No. DC-6148.
, "Preliminary Design of Canal Sections, San Luis Canal", July 1961 (revised September 1961).
_, "Final Embankment and Grouting Report, San Luis Dam and Pumping-Generating Plant and Forebay
Dam", Specifications No. DC-5855, December 1968.
-, "Final Report, Test Apparatus Installation, San Luis Dam", Specifications No. DC-5855, November
1967.
An Act of Congress Authorizing the San Luis Unit, Central Valley Project, Public Law 86-488, 86th Congress,
S. 44, (74 Stat. 156), June 3, 1960. (United States Bureau of Reclamation)
291
GENENAL
LOCATION
< t M M TT I I I I I I I I I I I I ' '" ' ■ ' ~r~r
SOUTHERN PACIFIC R.R.
Figure 245. Location Map — Cedar Springs Dam and Silverwood Lake
292
CHAPTER XII.
CEDAR SPRINGS DAM AND
SILVERWOOD LAKE
General
Description and Location
Cedar Springs Dam is a rolled earth and rockfilled
dam with a structural height of 249 feet and a crest
; length of 2,230 feet. The spillway is an ungated con-
j Crete chute with the outlet works located in a tunnel
I directly beneath; both have a common energy dissipa-
I tor. The reservoir is supplied project water from Mo-
jave Siphon which terminates at the inlet structure on
the left abutment of the Dam directly west of the
spillway (Figures 245 and 246) . Construction work on
the Dam was started November 10, 1968 and com-
pleted during the summer of 1971. Initial reservoir
filling started on January 5, 1972.
The embankment consists of a zoned earth-rock sec-
tion that utilizes thick shells of rolled rockfill and
dumped large rock, both upstream and downstream of
the impervious core. Alignment of the embankment is
buttressed by a downstream knoll so that downstream
deflection compresses the core. In addition, the core is
thickened in such critical areas as in the convex down-
stream curvature of the Dam and throughout the left
abutment area where a shear zone exists.
Figure 246. Aerial View — Cedar Springs Dam and Silverwood lake
293
Special consideration for earthquake loading was
given to ail zones, including the filter and transition.
The embankment was constructed to accommodate a
shear movement of 5 feet and still retain a sufficient
zone thickness to function as designed. Zone 2, located
next to the core, consists of silty and gravelly sands of
the Harold formation and is used to provide both a
sealing material in the event of rupture and a usable
transition section.
In 1968, Cedar Springs Reservoir was officially re-
named Silverwood Lake. At about the same time,
plans were being completed for the construction of
large-scale recreation facilities.
Large quantities of borrow waste and channel exca-
vation material were utilized during construction to
form beaches and boat ramps. On the west side of the
reservoir, rerouted State Highway 138 incorporates
several scenic, overlook, parking areas. On the oppo-
site side of the reservoir from Highway 138, an emer-
gency fire road was constructed to a greater width
than normally required to include a portion of the
California riding and hiking trail. When possible, the
reservoir water level will be maintained within a
range of 30 inches during any seven-day period from
March 1 to September 1. A statistical summary of
Cedar Springs Dam and Silverwood Lake is shown in
Table 31, area-capacity curves on Figure 247, and a
Dam site plan on Figure 248.
Cedar Springs Dam lies 10 miles due north of the
City of San Bernardino on the West Fork of the Mo-
jave River near the junction of State Highways 173
and 138. The reservoir drainage area covers 34 square
miles.
Purpose
Cedar Springs Dam and Silverwood Lake are part
of the California Aqueduct and provide regulatory
and emergency storage. The reservoir's primary pur-
poses are to firm deliveries to water users along the
Aqueduct, provide recreation, and assure continuity
of discharge through Devil Canyon Powerplant.
TABLE 31. Statistical Summary of Cedar Springs Dam and Silverwood Latce
CEDAR SPRINGS DAM
Type: Zoned earth and rockfiU
Crest elevation 3,378 feet
Crest width 42 feet
Crest length 2,230 feet
Streambed elevation at dam axis 3,165 feet
Lowest foundation elevation 3,129 feet
Structural height above foundation 249 feet
Embankment volume 7,600,000 cubic yards
Freeboard above spillway crest 23 feet
Freeboard, maximum operating surface 23 feet
Freeboard, maximum probable flood 5 feet
SILVERWOOD LAKE
Storage at spillway crest elevation 74,970 acre-feet
Maximum operating storage 73,031 acre-feet
Minimum operating storage 39,211 acre-feet
Dead pool storage... 3,967 acre-feet
Maximum operating surface elevation 3,353 feet
Minimum operating surface elevation 3,312 feet
Dead pool surface elevation 3,235 feet
Shoreline, spillway crest elevation 13 miles
Surface area, spillway crest elevation 976 acres
Surface area, maximum operating elevation.. 962 acres
Surface area, minimum operating elevation.. 690 acres
SPILLWAY
Type: Ungated ogee crest with lined channel and stilling basin
Crest elevation 3,355 feet
Crest length 120 feet
Maximum probable flood inflow 51,000 cubic feet per second
Peak routed outflow 3 2,250 cubic feet per second
Maximum surface elevation 3,373 feet
Standard project flood inflow 27,500 cubic feet per second
Peak routed outflow 21,000 cubic feet per second
Maximum surface elevation 3,368 feet
INLET WORKS
Open concrete-lined channel and chute from terminus of Mojave
Siphon to flip bucket on reservoir floor
Capacity 1,990 cubic feet per second
OUTLET WORKS
Stream release facility: Lined tunnel under spillway, valve chamber
at midpoint — discharge onto spillway
Diameter: Upstream of valve chamber, 13-foot pressure tunnel —
downstream, 13-foot concrete horseshoe tunnel
Intake structure: Uncontrolled tower with provision for steel plug
emergency bulkhead
Control: Stream maintenance, 30-inch fixed-cone dispersion valve
and two sets of two S-foot-wide by 9-foot-high, high-pressure,
slide gates in tandem within valve chamber
Release at minimum storage 5,000 cubic feet per second
Las Flores Pipeline: Stream release from Mojave Siphon
Capacity 23 cubic feet per second
OUTLET
San Bernardino Tunnel: Lined tunnel 12 feet - 9 inches in diam-
eter— six-level intake tower — inlets controlled by 60-inch butter-
fly valves
Capacity _. 2,020 cubic feet per second
294
W S. AREA 100 ACRES
^
^
"^
^^0^^
'^
^
^
X
\
/
\
\,
A
^ CAPACn
Y
N
X
/
AREA
/
\
/
\
\
\
CAPACITY- 1,000 ACRE FEET
Figure 247. Area-Capacity Curves
Cedar Springs Dam has features which were de-
signed to enable it to withstand overtopping by wave
action in the event it should occur. The central core
and adjacent zones have been capped by a paved crest
road. The downstream section, which is constructed
of massive rocks, is capable of passing large flows safe-
ly. Added safety from a seiche overtopping the Dam
is provided by the reservoir's irregular shape and the
23-foot surcharge and freeboard distance between the
normal water surface and the dam crest.
The outlet works and spillway were constructed on
the left abutment of the Dam and utilize a common
energy-dissipating basin and river return channel.
Downstream release controls consist of two pairs of 5-
by 9-foot, high-pressure, slide gates and a 30-inch
fixed-cone dispersion valve located inside a tunnel
constructed at streambed elevation. The outlet tunnel
was used during construction of the Dam to divert
floodflows around the dam embankment. In case of an
emergency, a full reservoir can be dewatered in ap-
proximately one week.
The dam spillway is an ungated, 120-foot-wide, rec-
tangular, lined chute that is located directly over the
outlet works tunnel. Because the spillway crosses a
fault zone, extra precautions were taken in the design
to minimize loss of operating capabilities if t move-
ment should occur. These included having the wall
steel continuous through the concrete joints, con-
structing shear keys into the fault zone material in-
stead of anchor bars, and providing sufficient area in
the spillway to prevent backwater on the weir in the
event there is local movement downstream in the
chute.
Chronology
Final design of a 216,000-acre-foot storage reservoir
and dam commenced during July 1964. In April 1965,
the Department of Water Resources' Consulting
Board for Earthquake Analysis concluded that, while
the probability of a fault offset occurring through the
damsite was small, it would be assumed that such a
fault displacement could happen. As a result, it was
295
Figure 248. Dam Site Plan
296
y
decided to limit the size of Silverwood Lake to approx-
imately 75,000 acre-feet.
To make up the resulting loss of storage capacity,
other alternative and supplemental sites to Cedar
Springs Dam were studied. In all cases, the cost per
acre-foot of storage was considerably more than for
the original plan. Therefore, the most practical solu-
tion was to build a dam on the original site to a size
deemed safe for the foundation conditions and to ad-
just the system elsewhere. The reduced size of the dam
then became a factor in the final sizing of the Aque-
duct to Lake Ferris, which is discussed in Volume II
of this bulletin.
Design of the Dam and reservoir was completed
August 9, 1969, and construction began shortly there-
after. The dam embankment was completed during
March 197 1 . The spillway and outlet works essentially
were completed by April 1971.
Regional Geology
Cedar Springs Dam is in the northwest portion of
the San Bernardino Mountains, near the boundary of
the Transverse Ranges geomorphic province with the
Mojave Desert. Bounded on the south by the San An-
dreas fault and on the north by a series of east-west
faults, the San Bernardino Mountains form an east-
west-trending block about 55 miles long and up to 30
miles wide. Rock types are mainly gneissic and gra-
nitic rocks of the Mesozoic Age. Pre-Cambrian gneiss,
which includes some scattered bodies of marble, is
dominant in the southwest portion of the range. Terti-
ary to Quaternary continental sediments and older
and recent alluvium are found locally along structural
troughs and valley floors.
Cedar Springs Dam is 7 miles from the San Andreas
fault and 10 miles from the San Jacinto fault. Several
faults, some associated with the San Andreas, pass
through the reservoir area. These faults have steep
dips and trend about N 70° W. However, two faults
near the Dam site strike roughly N 60° E and N 40° E.
The Cleghorn fault, which offsets older alluvium in
Cleghorn Canyon, is about 2 miles south of the Dam.
Seismicity
It was necessary to consider the effects of a fairly
large earthquake in design of the Dam and appurten-
ant structures because of the Dam's proximity to the
San Andreas and San Jacinto fault zones. Instrumen-
; tally determined epicentral data are available from
I 1937, and records of earthquake intensities are avail-
, able from 1857 to date (1974).
', Major Faults. During the 1857 earthquake, the
; ground along the San Andreas fault was fractured
from San Bernardino to Cholame Valley, a distance of
about 200 miles. An estimated 20 feet of horizontal
displacement of the land surface occurred near Gor-
man, 95 miles northwest of the Dam.
I San Jacinto fault was the source of two earthquakes
I during the past 70 years estimated to have Richter
magnitudes of 6.8 and 6.3. These caused severe damage
near Hemet, San Jacinto, and San Bernardino — 47, 43,
and 18 miles southwesterly of the Dam, respectively.
Cleghorn fault trends in a general northwest-south-
east direction in the reservoir area about l'/2 miles
south of Cedar Springs Dam.
Sierra Madre fault zone is located about 20 miles
southwest of Cedar Springs Dam. It is considered to
be active, but it is improbable that earthquakes as-
sociated with this fault would damage Cedar Springs
Dam.
Two presumably active faults were discovered dur-
ing excavation of the foundation material near the axis
of Cedar Springs Dam (Figure 249) and have been
traced a distance of from 1 to 3 miles. Vertical dis-
placement of 3 to 5 feet has been measured at an ex-
posed fault in the exploration trench. It is highly
improbable during the life of the Dam that displace-
ment along these faults in any direction will exceed 5
feet. Separation of the fault wall is not expected, even
if movement should occur. The basis for these assump-
tions can be found in the Bibliography.
Design Criteria for Maximum Credible Accident.
The maximum credible accident is defined as a major
earthquake producing a 3- to 5-foot displacement in
the foundation, occurring when the reservoir is at
maximum water surface with spillway and outlet
works operating at maximum discharge.
Six possible conditions that could result from the
maximum credible accident were analyzed, resulting
in 20 specific provisions being incorporated into de-
sign to protect against their effects. Provisions includ-
ed selecting a material for the impervious core that can
deform plastically without cracking, thickening tran-
Figure 249. Fault Uncovered During Excavation
297
sition zones to accommodate a 5-foot displacement
along a fault while maintaining sufficient thickness to
operate as designed, not placing the core on known
faults, providing additional freeboard to guard against
overtopping, and locating the spillway so that the
chute does not cross a fault until it is 400 feet down-
stream of the crest.
Design Criteria for Embankment. The dam em-
bankment was designed to withstand earthquakes by
including a horizontal force in the stability analyses.
This force was equivalent to an acceleration of 0.1 5g
multiplied by the mass of the material in a sliding
wedge or slip circle and was applied in the direction
of greatest instability. The embankment was designed
to meet the required factor of safety against sliding
with this horizontal force and the normal static forces
applied.
Two conditions resulting from the maximum credi-
ble accident were applied in the design stability analy-
ses for the dam embankment: (1) a full reservoir was
assumed against the face of Zone 3 downstream of the
impervious core, and (2) upstream Zone 2 was as-
sumed liquefied with all loss of strength. These condi-
tions were additive to the normal static forces plus the
force due to the 0.1 Sg horizontal earthquake accelera-
tion.
Design Criteria for Structures. Earthquake loads
applied to the structures of the complex were scaled
as to the importance of the structure and the conse-
quences of its failure. The earthquake accelerations
that were used in design are listed in Table 32.
Design
Dam
Description. The dam embankment is a zoned
rockfill structure with a core consisting of an impervi-
ous, imported, plastic material (Zone 1) flanked by
narrow zones of nonplastic native materials (Zone 2).
Figures 250, 251, and 252 show the embankment plan.
sections, and profile, respectively. Transition zones
are provided on each side of the core consisting of
either streambed sands and gravels or fines produced
from the processing of material for the downstream
shell (Zone 3). The upstream shell is rolled quarry-
run rock (Zone 4A). The inner portion of the down-
stream shell is rolled processed rock (Zone 5).
A plastic clay was chosen for the core because of its
ability to deform rather than crack if the foundation
should settle or shift during an earthquake. Even if the
clay should crack, it has the added characteristic to
resist erosion.
Because of the seismic hazard, the core and filters
were made thicker than usual. A wide cross section
resulted at the elevation of the normal reservoir water
surface. Rather than have a wide crest, the slopes were
extended upward to a narrower higher crest to pro-
vide additional freeboard above the normal water sur-
face. Additional embankment was relatively inex-
pensive and provided greater safety against overtop-
ping by a reservoir seiche, as well as allowing a nar-
rower, less expensive spillway.
Blankets of streambed gravels were provided under
the upstream and downstream rock shells of the Dam.
The primary reason for these blankets was to provide
a filter over the minor faults passing through the foun-
dation. This will prevent piping through the rockfill
embankment downstream should seepage develop
through the shear zones of the faults. Upstream, the
filter material could enter any developing crevice,
thus helping to develop a seal within the crevice.
Foundation. The downstream two-thirds of the
dam foundation is granitic rock and the upstream one-
third is slightly indurated silty sand of the Harold
formation. The Harold formation is in a nearly verti-
cal contact with the granitic rock. Movement along
both the granite rock-Harold formation fault and in-
tersection fault displaced alluvial stream gravels, in-
dicating the fault system was active during recent
geologic time. As a precaution, the Dam was designed
TABLE 32. Design Earthquake Accelerations — Cedar Springs Dam Complex
Structure
Foundation
Percent
San Andreas
Design Earthquake
Relative Importance
Applied Horizontal
Acceleration
Spillway
Crest
Granite
Granite shear zone,
Harold formation
Granite
Granite
Granite
50
75
50
SO
50
100
40
100
100
40
0.2Sg
O.lSg
(includes approacli and crest walls and crest
structures)
Spillway chute and stilling basin
Outlet Works
Inlet tower and trashrack..
0.25g
Gate chamber .
0.2Sg
Mojave Siphon Inlet Works
Chute
O.lOg
298
I
i
i
Figure 250. Embankment Plan
299
m
/'y^\
!t •"
/'-L-^ — 1 — 7
'^ — ^I— — "^ — *"
^T 1 1
-'.-V , «
V ' 1
_ •! 1 1
A 5
\^-~2l~ — *-— u.
' tn
\\^~~"~r~>
1 ^^ T
\ \ '' r
--K:^ .
ift \ '\ \ -
- S»« 0
li\ \ '' V
\ ij^o K
' \ \\
° ;;;
• i ;
\\
-'-r
^ \
Figure 251. Embankment Sections
300
Figure 252. Embankment — Sections and Details
301
to maintain a minimum distance of 200 feet between
the dam axis and the granite rock-Harold formation
fault contact. Removal of the alluvium, colluvium, and
highly weathered and badly fractured bedrock was
specified under the embankment to ensure a founda-
tion at least as strong as the embankment rockfill.
Embankment Layout. To minimize potential
cracking, the core was located entirely on the granite
rock portion of the foundation. This condition re-
quired the dam axis to be bent sharply near the center.
The core at the bend was thickened and buttressed
against the knoll located between the left abutment
and the river channel. The axis then was arched to-
ward the reservoir on both sides of the bend to further
ensure against cracking due to embankment creep un-
der reservoir pressure.
Grouting. To ensure the imperviousness of the
foundation, a grout curtain up to 150 feet deep was
required beneath the Zone 1 material, with a second-
ary grout curtain 25 feet deep upstream of the main
grout curtain. Blanket grouting (holes up to 25 feet
deep) of the foundation under embankment Zones 1
and 2 was specified to strengthen and seal the founda-
tion where fracturing might be a problem. The
specifications provided for slush grouting, if neces-
sary.
Construction Materials. Zone 1, clay material,
was required to be highly impermeable, plastic
enough to withstand large deformations without
cracking, and sufficiently workable to be used with
heavy equipment.
Initial explorations showed that no clay material
was located in the lake area. An extensive search was
conducted to find suitable material that would have a
Plasticity Index greater than 15 and have the Liquid
Limits fall between 30 and 50. Bucket auger holes
were drilled at Summit \'alley and in dry lakebeds as
far as 40 miles away. An unnamed lakebed 20 miles
northeast of the Dam site was selected since it showed
the desired clay quality (Figure 253).
Zone 2 material (silty sand), used for transition
between pervious and impervious material, occurs
naturally in the Harold formation as a weak sandstone
lying between the ridges of the granite mountains in
the area.
River deposits throughout the reservoir area were
found to contain adequate material for Zone 3 (sand
and gravel). Natural river deposits smaller than 18
inches generally produced a satisfactory filter be-
tween Zones 2 and 4 and between Zones 2 and 4A.
Zone 4A is the rolled, quarry-run, upstream, rock-
fill shell. Zone 4 was designed as a processed, coarse-
graded, rolled rockfill to provide stability and free
drainage downstream. Zone 5, the coarsest of all, was
placed as the farthest downstream shell and was in-
tended to be dumped because of its size. Riprap was
required to be of a more select gradation and functions
as slope protection for Zone 4A. Fines resulting from
the production of Zone 4 and 5 material were used in
Zone 3.
Stability Analysis. Embankment stability was
analyzed by the infinite slope, sliding wedge, and slip
circle methods. The soil properties used in the stabil-
ity analysis are shown in Table 33.
Zones 1 and 2 and the Harold formation in the
foundation were unable to immediately dissipate con-
struction pore pressures. Because of this, uncon-
solidated undrained strengths for these materials were
used for postconstruction stability determination.
Flow nets used in stability analyses assumed Zones
3, 4, 4A, and 5 were infinitely pervious, except during
drawdown when Zone 4A was assumed to be as per-
meable as Zone 3. Zones 1 and 2 were assumed to have
the same permeability with a horizontal-to-vertical
permeability ratio of 16. For rapid drawdown, the
upstream phreatic line was determined by Casa-
grande's approximate method with a minimum drain-
age time of six days.
Seismic Considerations. Design considerations
for seismic activity necessitated placing large shells of
rolled rockfill both upstream and downstream of the
core, removal of all alluvial material under the Dam,
and provisions of ample freeboard above the normal
water surface. The large size dense rock used provided
the Dam with highly stable zones as the major sup-
porting elements. Removal of all alluvial materials
eliminated any possibility of liquefaction of founda-
tion materials during an earthquake. With the rolled
rockfill shells, settlements and deflections due to
earthquake shaking will be minimized, and the
amount of slumping to be expected will not lower the
crest to the elevation of the maximum probable flood
water surface.
Figure 253. Determining the Plasticity Index Number
of the Impervious Zone
302
TABLE 33. Materiol Design Parameters — Cedar Springs Don
Specific
Gravity
Unit
P
Static Shear Strengths
8 Angles in Degrees
Cohesion in Tons Per Square
Foot
Weight in Pounds
er Cubic Foot
Effective
Total
Construction
Material
Dry
Moist
Saturated
d
C
6
C
e
C
Zone 1 .
2.78
2.70
2.71
2.71
2.70
2.70
2.70
2.69
lOS
117
127
127
130
120
105
124
126
131
137
137
130
136
143
143
144
141
24
35
38
40
43
42
38
36
0.2
0
0
0
0
0
0
0
16
16
24
26
26
27
0.2
1.0
1.0
1.5
1.5
1.5
4
*
23
1.5
Zone 2
Zone 3, Quarry
Zone 3, Streambed
Zone4A _..
Zone 5
Foundation, Harold for-
1.0
• Free-draining material, us
effective strcs
s values.
Design criteria included the possibility of an earth-
quake seiche. Configuration of the reservoir is such
that seiche waves probably will be of short duration.
Design features providing for seiches include a sub-
stantial freeboard (23 feet) above maximum operating
water surface, an ample zone of large open-graded
;rockfill (plus 2-foot sizes) on the downstream slope of
,the Dam, and a paved road on the crest of the Dam.
j Settlement. Laboratory consolidation testing was
jperformed on Zone 1 material to determine the
Amount of settlement that could be expected from the
consolidation of the central impervious core. Tests
.were run on this material at 1% above optimum mois-
ture content compacted to 95% of maximum dry den-
sity. The consolidation tests on these as-compacted
specimens showed an initial buildup of a large amount
bf compression in a short period of time followed by
|i slow uniform rate of compression buildup for the
'duration of the test. Tests that were postsaturated in-
ilicated that approximately 1% settlement would take
jlace in the dam core. The dam embankment was
increased in height by approximately \.5% to com-
Ijensate for long-term settlement.
i Instrumentation. Test apparatus and facilities in-
jtalled in the foundation and embankment of Cedar
Springs Dam (Figures 254 and 255) made possible the
!;athering of data to study its structural behaviour dur-
ng construction. A monitoring program now has
l»een made part of the regular maintenance procedure.
Instruments which were installed include piezome-
lers, slope-indicator casings, surface settlement points,
'nd crest settlement monuments.
Six pneumatic piezometers were installed in the
oundation of the Dam and 15 in the embankment,
hese piezometers are observed from instrumentation
erminal well No. 1 on top of the Dam. Seven founda-
ion piezometers are observed from instrumentation
terminal well No. 2 (Figure 256).
Three slope-indicator installations were made for
Cedar Springs Dam and are located upstream of the
centerline of the Dam.
Seventeen crest settlement monuments are located
on the crest of Cedar Springs Dam, and 15 surface
settlement points are located on the upstream slope of
the Dam.
A seepage measuring weir has been constructed at
the toe of the main dam to monitor and record em-
bankment and foundation seepage.
Two instrumentation terminal wells were con-
structed under the main dam contract. The wells are
located on the dam crest. These structures contain
terminal facilities for the foundation and embank-
ment piezometers and include the measuring panels,
air tanks, filters, and all appurtenant equipment for
operation of the piezometer system.
A reservoir head-level recording and indicating sys-
tem was installed and consists of a servo-manometer,
two mechanical counters, a gas purge tube, and a sen-
sor tip anchored to a concrete bench mark monument.
The system records and indicates reservoir water sur-
face level from elevation 3,230 feet to elevation 3,370
feet.
Debris Barriers
Description. Debris barriers were placed up-
stream on either side of the deeply cut San Bernardino
Tunnel approach channel. They were designed to
protect the tunnel approach channel from debris
originating in Miller and Cleghorn Canyons (Figures
257, 258, and 259). The debris capacity was based on
either a 10-year rainstorm coming after the San Ber-
nardino Tunnel approach channel was excavated and
before reservoir filling, or a lOG-year storm following
10 normal storm years after the reservoir has been
filled.
303
CEDAR SPRINGS DAM \
LOCATIONS OF I N S TR U M E N T A T 10 n\
Figure 254. Location of Instrumentation — Sections
304
LEGEND
• PIEZOMETER
# flCCELER0GR4PH
O SLOPE INDICATOR
CEDAR SPRINGS DAM
LOCATIONS OF INSTRUMENTATION
Figure 255. Location of instrumentation — Plan
305
*M«^^
Figure 256. Installation of Piezometer Tubing
Miller Canyon. This barrier (Figure 257) is L-
shaped with a crest length of 980 feet at elevation 3,304
feet. It was built of random fill material excavated
from the San Bernardino Tunnel approach channel
and has a downstream rock face. The crest width is 30
feet, and upstream and downstream slopes are 2'/^:l. A
rock-covered, 130-foot-wide, spillway section was in-
cluded in the right abutment to pass floodflows
around the San Bernardino Tunnel approach channel.
Cieghom Canyon. This 580-foot-long barrier
(Figure 258), with crest at elevation 3,300 feet, was
built of random fill excavated from the San Bernar-
dino Tunnel approach channel and has a rockfill
downstream face.
San Bernardino Tunnel Approach Channel
The San Bernardino Tunnel approach channel
(Figure 259), a 10-foot-wide trapezoidal section, con-
nects the intake tower approach channel, constructed
under the intake tower contract, to the reservoir floor
at elevation 3,230 feet. The San Bernardino Tunnel
approach channel was excavated in granitic material
beneath Borrow Area B-3 at Station 7-1-50 and joins
the intake tower approach channel at Station 40 + 00.
At Station 28-1-00, the material encountered changed
from granite to Harold formation.
Drainage Gallery and Access Tunnel
Exploration Adit. An exploration adit was con-
structed in the left abutment of Cedar Springs Dam to
(1) determine the site geology by paralleling the fault
inside the left abutment of the Dam, (2) cross the
main shear zone in two locations for inspection and
fault monitoring, (3) determine tunnel support re-
quirements, (4) create a permanent drain between the
fault and the dam embankment, and (5) provide ac-
cess to a valve chamber that would convert the diver-
sion tunnel to an outlet works.
This adit, which is now the drainage tunnel and
part of the access tunnel, was constructed 1,480 feet in
length as an unlined horseshoe-shaped section. The
first 710 feet were aligned along the centerline of the
Cedar Springs Dam access tunnel and served as the
top drift for that tunnel. Under the main dam con-
tract, the remaining 770 feet of exploration tunnel in
the left abutment of the Dam was converted to a con-
crete-lined drainage gallery (Figures 260 and 261).
A standard 4-inch by 4-inch, wide-flanged, struc-
tural-steel rib was selected as the support to carry the
varying loads. Rib spacing was on 4-foot centers.
Drainage Gallery. The main drainage gallery pre-
vents ground water buildup in the left abutment of
the Dam, particularly the area upstream of a local
shear zone that runs east-west. This shear zone acts as
a barrier that would develop a hydrostatic head on the
downstream toe of the left abutment if no provisions
were made for drainage.
A drainage pocket exists in the downstream founda-
tion formed by the core, the left abutment, and the
knoll. Positive drainage was provided through the left
abutment by adding a short tunnel to the drainage
gallery which terminates under the embankment
rockfill at the base of the pocket. An 8-foot-long con-
crete plug was designed for the end of the gallery
which had openings large enough to carry water
freely but small enough to prevent the rockfill from
passing through.
The drainage gallery is a concrete-lined horseshoe-
shaped section 5 feet by 6/2 feet. The length of the
gallery is 723 feet with an invert slope of .005 toward
the access tunnel. Drain holes, approximately 100 feet
in length, were drilled on 20-foot centers alternating
between sets of four with two vertical and two hori-
zontal holes and sets of four with all four holes at 45
degrees. The invert contains a collection ditch which
permits the seepage to drain into one of two weir
boxes. The first weir box is located directly above the
outlet works tunnel and empties through a 14-inch
drain hole into the outlet tunnel at the crown. The
other weir box is located at the access tunnel entrance,
Station 19-1-90, and empties into an outside drainage
ditch.
The reinforced-concrete tunnel lining was analyzed
as an elastic arch supporting a hydrostatic load of 50
feet, which was estimated to be the equivalent of 19
feet of rock load on the lining. This loading resulted
in a concrete lining 12 inches thick, with only a nomi-
nal amount of temperature steel reinforcement.
Access Tunnel. Besides drainage, the main pur-
pose of the access tunnel is to provide outside access
to the outlet works gate chamber. Design was similar
to the drainage gallery except for the length of the
drain holes. Drainage from the gate chamber and part
of the drainage gallery flows along the access tunnel
floor to the portal where it is measured in a Parshall,
flume.
306
Figure 257. Miller Canyon Debris Barrier
307
i 'i
Figure 258. Cleghorn Canyon Debris Barrier
308
p
8S
\ '^\
i
Figure 259. San Bernardino Tunnel Approach Channel
309
Figure 260. Access Tunnel and Drainage Gallery Plan
310
1
-'"■'--— ^
^5l ■
n
o
hi
o
<M
u.
Q
2
o
h-
^
UJ
-I
o
_l
2
3
5
CO
<
rr
tr
o
u
u.
Figure 261. Access Tunnel and Drainoge Gollery — Profiles and Sections
23—87401
311
Figure 262. Spillway
312
Spillway
Description. The spillway (Figure 262) for Cedar
Springs Dam is located on the left abutment, approxi-
mately 300 feet from the embankment, and was de-
signed to convey all floodflows around the Dam site
and back to the natural river channel. It consists of an
approach channel, crest structure, chute, stilling ba-
sin, and return channel.
The approach channel to the spillway weir is
trapezoidal in cross section and is 120 feet wide at the
bottom with l'/4:l side slopes. The channel is unlined
except for the first 65 feet immediately upstream of
the weir. This reach is lined with concrete to block
downstream leakage and reduce uplift.
The spillway chute is rectangular in cross section,
concrete-lined, and 120 feet wide. Side walls vary in
I height from 10 to 13 feet. The outlet works tunnel
enters the spillway chute just upstream from the still-
, ing basin. The hydraulic jump-type stilling basin is
120 feet wide, is 160 feet long, and has cantilever side
walls 45 feet high.
The spillway return channel is trapezoidal in cross
section and is 130 feet wide at the bottom with 3.1 side
slopes. A bridge carries State Highway 173 traffic
across the channel downstream from the stilling ba-
sin.
Excavation. Spillway excavation upstream from
Station 32+00 was in granitic rock. Downstream
from that point, excavation was in alluvium, slope-
, wash, and Harold formation. Except for that portion
I of the chute that crosses a small east-west fault (Sta-
;tion 22 + 70 to 23 + 60), the spillway is founded on
hard rock. The excavation was all in open cut and had
■ a maximum depth of 200 feet at the weir. The granitic
rock portion was used in the dam embankment.
Backfill. Impervious backfill, which corresponds
to the requirements for Zone 2 dam embankment, was
placed behind the spillway approach and crest struc-
ture walls. This backfill prevents seepage around the
spillway. The remainder of the walls were backfilled
jwith pervious material.
! Drainage. A drainage system is located under the
ispillway floor slabs and along the wall heels in the
l:hute and stilling basin to help relieve uplift. The
|:hute drainage system consists of lateral-perforated
;irain pipes placed in a herringbone pattern with the
|3erforations down and surrounded by drain material
.(Figure 263 ) . In the stilling basin, the drainage system
|:onsists of perforated drain pipes bedded in concrete
in a rectangular pattern, with the perforations up and
I 4i^in material placed over the pipe.
! Hydraulics. The spillway was designed to carry
jhe maximum probable flood with 5 feet of freeboard
«tween the maximum reservoir water surface and
he crest of the Dam. For design, it was assumed that,
I'rior to the maximum probable flood, the reservoir
yould be completely full, the spillway discharging the
Figure 263. Perforated Drain Pipes in Spillway Chute
base flow of the stream ( 1,000 cubic feet per second),
and all outlet facilities inoperable. The maximum
routed outflow for these conditions is 32,250 cubic feet
per second (cfs) with the reservoir water surface at
elevation 3,373 feet.
The 120-foot-long spillway weir is ogee-shaped and
has a 45-degree, sloping, upstream face to improve
discharge efficiency. The downstream surface consists
of circular arcs which approximate the profile of the
lower nappe of the standard project design flood dis-
charge of 2 1,000 cfs. This ogee shape was developed to
prevent negative pressures that would cause cavita-
tion on the surface of the weir for flows up to the
maximum probable flood.
Wall heights for the chute vary from 10 to 13 feet
and were chosen to allow for freeboard above the wa-
ter surface profile of the maximum probable flood.
The vertical curves of the invert of the chute were
designed to be flatter than was required to conform to
the trajectory of a free-discharging jet. This was done
to insure that positive pressures are maintained on the
chute invert.
The stilling basin is used to still both the spillway
and the outlet works flows. Chute blocks are provided
at the upstream end, and dentates are provided at the
downstream end of the basin. Model studies showed
that the selected basin would operate satisfactorily for
all flows up to maximum probable flood. These model
studies also verified the riprap size required, both ad-
jacent to the stilling basin and in the downstream
return channel.
The return channel is lined with riprap to Station
40 + 00 (Figure 262) just downstream from State
Highway 173 bridge and is unlined from that point to
the end. Riprap was not placed downstream from Sta-
tion 40 + 00 because erosion of the channel in this
reach would not have any adverse effects. Heavy rip-
rap is provided at the stilling basin to protect the
channel from turbulence caused by the hydraulic
jump. Heavy riprap also is provided at the down-
stream end of the lined portion of the channel to pro-
vide a control section for tailwater if the downstream
channel erodes.
313
Structural Design. The spillway approach chan-
nel wails between Station 17-1-47 and Station 17-1-87
(Figure 262) are slabs that are anchored to the ex-
cavated slope. The approach walls between Station
17-1-87 and Station 18-1-12 are a combination of an-
chored slabs and cantilever walls. This second section
of walls affects the transition of the side slopes of the
approach channel from l'/,:l to vertical and are back-
filled with impervious material. Reinforcement is con-
tinuous through all the construction joints and
waterstop was placed in the designated construction
joints.
The weir is a concrete gravity structure anchored to
the foundation with grouted anchor bars. Reinforce-
ment is continuous and waterstops are in all of the
construction joints.
Crest structure walls are cantilever with a portion
of the weir acting as a wall toe. To prevent spillway
leakage, the walls were backfilled with impervious
material. Weakened contraction joints are provided in
the crest walls at Station 18-1-12 and Station 18-1-44.
Reinforcement is continuous through them and
waterstop was placed in the joint at Station 18-1-12.
Spillway chute walls are cantilever and decrease in
height as the water gains velocity. A transition of per-
vious backfill that meets Terzaghi's filter criteria was
placed behind the walls to prevent drain water wash-
out. The toe of the spillway walls forms a portion of
the chute floor and was designed to have the water
load offset the overturning moment of either the soil
or water load. The longitudinal steel in the walls, ex-
cept for four expansion joints, is continuous for the
entire length of the chute. This unorthodox construc-
tion was included to prevent spillway wall breakage
resulting in possible chute blockage in the event the
fault crossing the spillway was to move.
Chute slabs are 15 inches thick and are anchored to
the foundation. Where the chute crosses a local shear
fault, shear keys are provided because grouted anchors
alone would not be effective in the broken rock and
soil (Figure 264). Longitudinal construction joints,
with waterstop and continuous reinforcement, are
placed at a spacing of approximately 33 feet. Lateral
construction joints with continuous reinforcement
were placed as required, except in the fault zone
where a joint was placed at each shear key.
The outlet works transition to the spillway trans-
fers the flow from the outlet works tunnel to the spill-
way chute. It consists of a rectangular box section of
varying height and width. The width gradually wid-
ens from 20 feet at the tunnel portal to 35/2 feet over
a distance of 11 1 feet. The top of the sections is a slab
2 feet thick and was designed as a beam fixed at the
ends, supporting a uniform load equivalent to 6 feet of
water. This load accounted for the depth of flow over
the spillway from the maximum probable flood plus
an allowance for vibration and impact. The bottom
slab varies in thickness from 2 feet at Station 27-1-96
to 3 feet at Station 28-1-55. This slab was designed as
a beam fixed at the ends with a uniform uplift applied
due to a water surface at the elevation of the spillway
chute drains. This assumes the French drain below
the bottom slab is plugged. The slab that covers the
portal excavation at Station 11 + 96 was designed as a
two-way slab fixed on three sides supporting a uni-
form construction load of 12 feet of wet concrete.
Walls of the box section are essentially gravity walls
and carry nominal reinforcement.
A transition section, 70 feet long and 120 feet wide,
with walls varying in height from 10 to 45 feet con-
nects the chute to the stilling basin.
The stilling basin is a rectangular structure 120 feet
wide and 160 feet long, consisting of two parallel can-
tilever walls with a concrete floor between the toes of
the walls. Its walls are anchored to the rock founda-
tion and are divided into seven sections by contraction
joints placed approximately 33 feet apart to minimize
cracking due to temperature stresses. Floor slabs are
independent of the wall sections and are anchored to
the foundation with grouted anchor bars. Floor slabs
between the cantilever walls were designed to with-
stand the uplift loads imposed on them from the hy-
draulic jump for the standard project flood. The end
Figure 264. Shear Keys in Spillway Chute
314
slabs between Station 30+53 and Station 30 + 85 were
designed to resist the dynamic effects of the flow im-
pinging on the dentates. The slabs are divided by three
transverse contraction joints located at Station 28+55,
Station 28 + 90, and Station 30 + 53 and by three longi-
tudinal contraction joints located on the centerline
and at the toes of the wall sections. All contraction
joints are waterstopped due to the high differential
heads produced by the hydraulic jump.
Chute blocks before the stilling basin and dentates
at the end of the basin were designed to resist the
dynamic effect of the flow impinging on them.
Outlet Works
Description. The outlet works (Figure 265) con-
sists of an intake tower, an upstream pressure tunnel,
a gate chamber, a downstream tunnel that discharges
into the spillway chute, and an air intake that also acts
as an emergency exit. The primary purpose of the
outlet works is to release normal reservoir inflow and
emergency reservoir drawdown. During construc-
tion, the outlet tunnel was used to divert the river
around the dam embankment.
The outlet works tunnel was driven through gra-
nitic rock which varies from moderately weathered to
fresh. A local shear zone crosses the outlet works at
approximately a right angle. The fault zone extends
approximately from Station 22 + 70 to Station 23 + 50.
Drain holes are located in the horseshoe tunnel down-
stream from the gate chamber to lower the hydrostatic
head on the tunnel lining.
This was the first contract in which the Depart-
ment specified that construction of all tunnels was to
be by lump-sum bid item. This, in effect, placed all
responsibility for tunnel support systems on the con-
tractor.
Hydraulics. Downstream water rights for the Mo-
jave River require that all natural inflow to Silver-
wood Lake be released. Downstream river releases
between '/j and 23 cfs generally are made from the
Mojave Siphon via the Las Flores Pipeline (Figure
248). Flows between 23 and 5,000 cfs usually are
released through the outlet works. Flows above 5,000
cfs either are stored in the reservoir for later release
or discharged over the spillway.
Flows through the outlet works up to 300 cfs are
controlled by a 30-inch fixed-cone dispersion valve.
The valve was designed to deliver the required flows
at minimum operating pool, elevation 3,312 feet. Two
5-foot by 9-foot slide gates are used to control flows
between 300 cfs and 5,000 cfs. Both the valve and the
gates are located in the gate chamber (Figure 266).
Structural Design. The intake structure was de-
signed to meet both construction and operation condi-
tions. Loading conditions for construction were
analyzed with and without backfill along with consid-
eration for an earthquake acceleration of 0.2 5g hori-
zontally and 0.125g vertically. The operating con-
dition considered was with the reservoir water level at
maximum operating pool, elevation 3,355 feet. Dead
load consists of tower weight, submerged surrounding
backfill, and weight of water. Earthquake force, loca-
tion of resultant force, and allowable increase of nor-
mal working stresses for loads of short duration were
considered the same as during construction.
The pressure tunnel upstream of the control gates
consists of a steel-lined branching conduit 39 feet long,
26 feet of tunnel transition, and a circular tunnel 504
feet in length. The portal section was designed to re-
sist a combined external load of 43 feet of backfill plus
a hydrostatic load due to the reservoir at maximum
operating pool. Between Stations 12 + 27 and 14 + 00,
the tunnel section was designed for separate internal
and external hydrostatic loads due to the reservoir at
maximum operating pool. The internal load was con-
sidered separately to allow for rapid initial filling of
the reservoir when insufficient time is available to
develop the full external water load. Between Stations
14 + 00 and 17 + 81, the tunnel section was designed for
an external hydrostatic load with the reservoir at max-
imum operating pool.
The transition section and rectangular conduits be-
tween Stations 17 + 81 and 18 + 35 were designed for
separate internal and external hydrostatic loads when
the reservoir was at maximum operating pool. Con-
crete lining for the gate chamber was designed to
withstand full hydrostatic pressure head when the res-
ervoir was at maximum flood pool, elevation 3,373
feet; a rock load due to 20 feet of rock; and a concen-
trated load of 20 tons acting through any of the ten
lifting hooks. A steel liner extends from the beginning
of the rectangular conduit at Station 17 + 07 to the
upstream end of the gate body and from the down-
stream end of the gate body to Station 18 + 84. Its
primary purposes are to protect the concrete lining
from cavitation by high-velocity flows and prevent
seepage between the upstream pressure tunnel and
the downstream horseshoe tunnel. The upstream steel
liner and stiffeners were analyzed as a rectangular
frame and designed for a hydrostatic head of 178 feet.
The horseshoe tunnel at Station 18 + 67 was de-
signed as an integral part of the gate chamber. The
load transmitted from the gate chamber was assumed
to be uniformly distributed onto the tunnel arch. This
load was combined with an external hydrostatic load
that decreased from a hydrostatic head of 178 feet at
Station 18 + 84 to 25 feet at Station 19+17. The re-
maining downstream portion of the tunnel was de-
signed for an external hydrostatic load of 25 feet above
its invert. External hydrostatic pressure on the tunnel
lining in the later reach of tunnel is relieved by drain
holes drilled through the concrete lining into the sur-
rounding rock.
The reach of tunnel crossing the shear zone is pro-
vided with extra reinforcement and a thicker concrete
section.
315
Figure 265. Outlet Works — Plan and Profile
316
/vj .
\
ii
/ / —
-H-
Figure 266. General Arrangement of Gate Chamber
317
Figure 267. Inlet Works— Plan and Profile
318
!
Mojave Siphon Inlet Works
Description. Project water is supplied to Silver-
wood Lake through the Mojave Siphon, a portion of
the California Aqueduct which crosses under the Mo-
jave River. The Mojave Siphon enters the Lake on the
left abutment ridge approximately 1,500 feet west of
the spillway and consists of a transition structure, con-
crete chute, and a flip-bucket energy dissipator (Fig-
ures 267 and 268). The concrete chute through the
ridge is on a slope of approximately 0.1% toward the
reservoir. It follows down the ridge to a flip-bucket
energy dissipator at elevation 3,231 feet. This chute
was modified in 1974 at the grade change to form a
Parshall flume section to measure inflow. The picture
was taken during initial reservoir filling but does not
show the Parshall flume (Figure 269).
The siphon barrels have transitions to square con-
duits that open into an open rectangular section
which narrows to the 20-foot chute width. A center
pier was constructed in the open transition to stabilize
discharges and provide slots for a bulkhead gate to
allow dewatering of the individual siphon barrels.
Only the 1,200-cfs barrel of the Mojave Siphon has
been completed. The second barrel with a capacity of
800 cfs has not been scheduled for construction. The
summit of the inlet works, elevation 3,373 feet, occurs
at the end of the open transition. This allows 2 feet of
freeboard above the maximum reservoir stage when
the maximum probable flood is routed through.
Hydraulics. To deliver the full design discharge of
1,990 cfs, a maximum energy gradeline is required at
the end of the Siphon at an elevation of 3,388 feet. The
chute width of 20 feet was established to meet the
above requirement while allowing the chute invert to
be placed above the maximum reservoir stage.
Subcritical flow is maintained in the upper portion
of the chute, with the flow passing through critical
depth at the chute vertical curve. A vertical-curve ra-
dius was selected to ensure positive pressure at all
points on the invert.
Four feet of freeboard was provided on the walls at
the siphon outlet and 2 feet for the remainder of the
chute. A flip-bucket energy dissipator was used at the
chute terminus to eliminate erosion in the vicinity of
the structure during initial filling of the reservoir and
in cases of extreme drawdown.
Structural Design. The closed portion of the tran-
sition structure was designed for the following load-
ing cases:
1. External fill load to elevation 3,378 feet plus a
surcharge of 2 feet to account for vehicular loads and
internal hydrostatic head to elevation 3,386 feet.
2. External loads above only, with no internal hy-
drostatic head.
The open section of the transition was designed as
a "U" channel section with the same external fill and
internal hydrostatic design loads.
A bulkhead gate was designed for the maximum
water depth while one barrel is operating (12 feet).
Yield strength of the material is not exceeded if the
gate is loaded to its top (13 feet).
Weakened-plane contraction joints are located at 25-
foot intervals along the upper chute and 30-foot inter-
vals down the steep portion. Expansion joints are
located at 100-foot intervals along the entire chute.
The upper portion of the chute was backfilled with
pervious material and was provided with drains, while
the lower portion of the chute was backfilled with
riprap and bedding to a depth of 8 feet. The chute was
Figure 268. Flume and Chute
Figure 269. Initiol Reservoir Filling
319
designed as a "U" section with the following loading
cases:
1. No water in chute, saturated backfill, uplift equal
to 50% of fill height.
2. Water in chute, saturated backfill, no uplift.
The nip-bucket energy dissipator was partially
backfilled with riprap and bedding material was used
to stabilize the lower chute section.
Loading on the structure includes:
1. Fill pressure taken as an equivalent fluid weigh-
ing 50 pounds per cubic foot.
2. Hydrodynamic load of the design discharge on
the flip bucket.
3. Uplift due to the maximum tailwater surface
with supercritical flow within the dissipator.
Cast-in-place concrete piles were used under the
structure to resist uplift and to support the structure
should erosion or softening of the foundation take
place.
Las Flores Pipeline
Las Flores Pipeline (Figure 248) provides water to
the downstream water right owners and to the De-
partment's operation and maintenance buildings. It is
a buried, mortar-lined, 18-inch-inside-diameter, weld-
ed-steel pipeline that diverts water from the Mojave
Siphon and delivers it to an energy dissipator struc-
ture located adjacent to relocated State Highway 173
below Cedar Springs Dam. Components of Las Flores
Pipeline include the steel pipe, two valve vaults, two
blowoff structures, and an energy dissipator struc-
ture.
Hydraulics. The 23-cfs design flow of Las Flores
Pipeline was calculated from the maximum capacity
of an irrigation system that was removed to construct
the Dam. One of the design requirements was to deliv-
er water downstream of the Dam at an elevation high
enough to be diverted into an existing Las Flores
Ranch ditch. The terminal end of Las Flores Pipeline
was designed with a river turnout so that no water
rights were established or denied by replacing parts of
the Las Flores Ranch's previous irrigation system.
Valve Vaults. There are two underground, con-
crete, valve vaults located on Las Flores Pipeline. One
is located at Mojave Siphon and the other at a high
point in the Pipeline just east of the return channel.
They contain the emergency, regulatory, vacuum re-
lief, and air valves. Pervious material was backfilled
against the vault walls. The vault has an aluminum
roof which can be taken off should removal of a valve
be necessary.
Blowoff Structures. There are two blowoffs: one
at the West Fork of the Mojave River and one at the
return channel. They consist of a standard AWWA
18-inch tee, a blind flange bolted to the tee, a 4-inch
steel riser pipe welded to the blind flange, and a 4-inch
steel gate valve screwed onto the riser pipe.
Energy Dissipator Structure. The impact-type en-
ergy dissipator was constructed as a box with an inter-
nal beam baffle. Water leaving the energy dissipator
structure is turned into the Las Flores distribution
pipe to flow by gravity to Las Flores Ranch. An over-
flow weir returns excess flow to the Mojave River via
a small riprapped channel.
Mechanical Installation
Functions of the mechanical features are to control
the release of water to the Mojave River and to provide
the essential station services for operation and mainte-
nance personnel and for safeguarding the operation of
the outlet works.
Outlet Works. In the gate chamber (Figure 266)
of the outlet works, there are two 5-foot by 9-foot,
regulating, high-pressure, slide gates; two 5-foot by
9-foot, emergency, high-pressure, slide gates; a iO-
inch-diameter fixed-cone dispersion valve; and a 36-
inch-diameter, emergency, high-pressure, slide gate.
The emergency gates, installed upstream of the
regulating gates and the fixed-cone dispersion valve,
are used for isolation purposes. They will shut off the
flow if the regulating gates or the fixed-cone disper-
sion valve malfunction and also will permit normal
maintenance and repair of the downstream water-
ways, regulating gates, and fixed-cone dispersion
valve.
Controls for the 36-inch-diameter shutoff valve
(slide gate) and the fixed-cone dispersion valve, which
are in tandem, were designed to move each individual
valve to either a fully open or fully closed position by
a single push-button command. Each valve may be
stopped in any position and then moved in either di-
rection. The shutoff valve cannot be operated unless
the fixed-cone dispersion valve is closed, and the fixed-
cone dispersion valve cannot be operated unless the
shutoff valve is open.
Slide Gates. Although the slide gates are of two
different sizes and serve two different functions, all
five slide gates, for reasons of economics and uniform-
ity, were constructed under the same specifications
with a few minor exceptions. The guard gates do not
have an air vent for air admission to the downstream
side of the gate leaf nor gate creep adjustment, and the
regulating gates do not have a 2-inch bypass line across
the gate body. The major components of the gates are
the gate body, the seats, the gate leaf, and the operator.
The gate body is of welded-steel construction and
was designed to resist the internal water pressure or
external pressure caused by reservoir seepage. The
body is embedded in concrete, except the bonnet cov-
er section. The bonnet cover section was designed to
withstand the full reservoir head. The 5-foot by 9-foot
guard and regulating gates are bolted together at their
faying surface and "O" rings added for watertight-
ness. All bolted joints in the bodies become a perma-
nent assembly after the gates are embedded, except the
bonnet joints, which remain accessible.
The seats, which are renewable, are bronze and are
320
i-foJ-
lis'
10
bolted to the body to function as top and side seals.
The gate leaf also is of welded-steel construction
and is secured to the gate stem by a nut, tightened
against an adjusting nut on the stem. The leaf is fitted
with bolted bronze seats on the top and sides and is
overlain with stainless steel on the bottom edge to
function as the bottom seal. The seats bear on the
corresponding seats in the body.
The seating surfaces are metal-to-metal and their
watertightness depends on their close contact when
forced together by the hydrostatic pressure and by the
downward force of the moving parts. A small amount
of leakage is expected.
The bottom seals of the two 5-foot by 9-foot, regulat-
ing, slide gates and the 36-inch-diameter emergency
gate were changed to rubber seals. This change was
made to reduce water leakage and prevent damage to
the lip area of the leaf.
The sliding seating surface.^ are lubricated by means
of the centralized, automatic, lubricating system in the
gate chamber. Application of lubricant to the seating
surfaces before each operation provides a lubricating
film to reduce friction, lessen the possibility of scor-
ing, and improve the degree of sealing obtained.
The operator is a hydraulically driven cylinder
which is bolted to the gate bonnet. The cylinders for
the 5-foot by 9-foot gates have a 26'/2-inch diameter
with an 8-inch-diameter rod and, for the 36-inch-diam-
eter gate, the cylinder has a 13-inch diameter with a
4-inch-diameter rod. A hydraulic system installed in
the gate chamber provides power for the operators.
To mechanically hold the gate leaf in the fully open
position, a handwheel is provided at the top centerline
of the cylinder for screwing a stud into the top end of
the piston rod, thus holding the stem piston and the
gate leaf in a fixed position. If, in an emergency or by
accident, hydraulic pressure is applied above the pis-
ton when the stud is engaged, the stud will break and
allow the gate to close. Stud breakage should occur at
approximately 150 pounds per square inch (psi) and
does not result in damage to the equipment. The cylin-
der must be dismantled and a new stud installed after
breakage occurs.
A mechanical, gate-leaf, position indicator is oper-
ated by a vertical rod attached to a stuffing box in the
bonnet cover. Position of the gate leaf can be observed
in the gate chamber by a pointer on the rod and an
attached scale. Position of the regulating gate leaves
also can be read remotely by means of the rotary shaft
encoders and remote display unit.
Gate-leaf creep adjustment is provided for the regu-
lating gates. The mechanisms to achieve the adjust-
ment are part of the hydraulic system which provides
power to the cylinder operators.
Before adoption of two slide gates and one fixed-
cone dispersion valve to control the release of water,
a large fixed-cone dispersion valve, fixed-wheel gate,
and butterfly valve also were considered. They were
rejected chiefly because of higher overall cost.
Based on agreements with the water users and tech-
nical considerations, the gates were designed accord-
ing to the following criteria:
Design Flow and Head Criteria
1. Two 5-foot by 9-foot regulating gates shall pass
300 to 5,000 cfs at 173 feet of head and 8,000 cfs
at 200 feet of head under flood condition.
2. All five gates shall be capable of operating un-
der a maximum static head of 200 feet.
3. The gate body for all gates shall be capable of
withstanding 77 psi of static internal pressure
and 77 psi of static external pressure plus all
additional surge pressure which may result
from gate operation.
Operation Criteria
1. The regulating gates shall control the flow rate
with an accuracy of approximately + 2'X% at
all gate positions within the normal range of
regulated flows.
2. The gate shall be operable both locally in the
gate chamber and remotely from the monitor
control building.
3. Opening and closing time for each 5-foot by
9-foot gate shall be 15 minutes and for the 36-
inch-diameter gate it shall be 3 minutes.
4. If required, two gates may be operated simul-
taneously.
5. Both local and remote indication of regulating
gate position shall be provided.
Design Stresses and Loading Criteria
1. The design stresses shall be governed by the
applicable provisions of the ASME Boiler and
Pressure Vessel Code, Section VIII. Where a
material is not listed in the Code, a design
stress of '/ of the ultimate or '/, of the minimum
yield strength of the material shall be used.
2. A seismic loading of 0.3g shall be included in
all design loads.
3. All parts shall be designed in consideration of
buckling. No part shall have a ///-ratio of more
than 80, where /is defined as the unsupported
length of the part and r is the "least radius of
gyration" of the part.
4. Gate-leaf deflection shall not exceed 0.005 of an
inch.
The rectangular configuration of the 5-foot by 9-
foot slide gates was based on the optimum width-to-
height ratio of 0.5:0.6 published in the U. S. Army
Corps of Engineers' design manual, "Hydraulic De-
sign of Reservoir Outlet Structures", and the Tennes-
see Valley Authority's Technical Report 24. The
36-inch-diameter slide gate was determined by con-
figuration of the pipe required for the fixed-cone dis-
persion valve. It should be noted that the gate
dimensions refer to the cross-sectional area of the pas-
sageway of the gate. The cross-sectional area was
321
based on the flow to be passed through at a specified
head and a discharge coefficient of 0.7.
The design of the slide gates, in many respects, fol-
lowed the design for those gates installed at the De-
partment's Del \'alle Dam and reservoir. The gate
leaves were constructed in a welded-box-girder form
for rigidity. The bottom of each gate was tapered at 45
degrees. Model studies made by the Corps of Engi-
neers indicated that a 45-degree lip was the best con-
figuration to reduce vibrations, downthrust, negative
pressures, and turbulence.
Fixed-Cone Dispersion \ 'alve. This 30-inch valve
is a cylindrical-type, free-discharge, regulating-cone
valve commonly known as either a fixed-cone disper-
sion valve, a hollow-cone valve, or Howell-Bunger
valve. The major components of the valve and opera-
tor are the cylindrical valve body, sliding gate, worm
gear units, bevel gear drive assembly, screw operator
assembly, body sleeve, and valve operator.
Seating is accomplished by a fixed seat attached to
the central cone in the body and a movable seat, which
is part of the sliding gate. To open the valve, the gate
is moved upstream by the screw assembly which, in
turn, is rotated by the worm gear units on the sides of
the valve. These are driven by two sloping shafts
through the bevel gear drive assembly to the input
shaft, which is driven by the valve operator.
The valve was designed based on the following:
1. The 30-inch-diameter fixed-cone dispersion
valve shall pass a minimum of 305 cfs at a minimum
total discharge head of 120 feet.
2. A maximum static head of 185 feet was specified.
3. The valve shall be operable both locally in the
gate chamber and remotely from the monitor control
building.
4. Opening and closing time shall be three minutes
in each direction.
5. The valve and the companion flange shall be de-
signed in accordance with all applicable requirements
of the ASME Boiler and Pressure \'essel Code, Sec-
tion \'III, Unfired Pressure Vessels, unless otherwise
specified.
6. A liberal factor of safety shall be used throughout
the design of the valve and its components. For com-
ponents for which allowable stress state or factor of
safety is not established, the factor of safety based on
the minimum ultimate tensile strength of the material
and most adverse conditions to be encountered is not
less than the following:
Cast Steel 6
Cast Iron 10
Forged Steel 6
Stainless Steel 6
Bronze 6
Structural Steel Plate (for
brackets and supports) 5
The design of the body and the ribs comply with the
following minimum requirements:
1. Under maximum head, all stress combinations
fall within a maximum shear stress theory of failure
envelope having coordinate boundaries of % of the
minimum tensile strength or % of the minimum yield
strength of the material, whichever is less.
2. Internal pressure corresponding to maximum
head acting on the body shell plus a differential pres-
sure of 15 psi acting across the ribs shall not produce
any stress combination which will fall outside of a
minimum shear stress theory of failure envelope hav-
ing coordinate boundaries of the endurance limit of
the material. The endurance limit shall be defined as
a stress equal to 45% of the minimum ultimate tensile
strength of the material.
3. The minimum body shell and rib thickness are 1
inch.
The complete drive mechanism, including shafting,
was designed for the following conditions:
1. Under normal operating torque, all stress combi-
nations are within the maximum shear stress theory of
failure envelope that has coordinate boundaries which
provide the minimum factors of safety as specified
earlier in this section.
2. Under a stalled motor torque at maximum oper-
ating torque, plus the torque due to the inertia of the
rotating parts, all stress combinations in the drive fall
within a maximum shear stress theory of failure enve-
lope having coordinate boundaries of 75% of the mini-
mum yield strength of the material.
3. The maximum twist of the shaft under normal
operating conditions will not exceed one degree in a
length equal to 20 shaft diameters.
The valve was made of various types of material to
best suit the requirements for the different valve com-
ponents. The materials used are as follows:
Pan Material Used
\'alve body; bolting flange; A285 Firebox Grade C,
radial ribs; valve gate; Plate Steel; A515,
stiffening ring; seat ring Firebox Grade 65,
Plate Steel
Companion flange A27, Grade 70-36
cast steel normalized
and tempered
The dispersion-cone surface is made straight to pre-
vent cavitation due to the creation of low pressure
areas on the surface or seat. Cavitation and pitting of
valve parts will occur if the valve is operated at less
than 10% of its gate opening.
Two pilot tubes installed at the leading edge of one
rib and one static pressure tap installed in the valve
body are used to measure the flow through the valve.
The valve is operated by a SMB-00 limitorque valve
control operator having a 15-foot-pound, 3-phase, 60-
hertz, 440-volt, 1,800-rpm, weatherproof, continuous-
duty motor. The torque limit switch and the limit
switches automatically will stop the motor operator in
the event of an obstruction in the gate path or the
failure of a limit switch.
Shop tests consisted of a hydrostatic test on the
valve at 120 psi for 60 minutes for any evidence of
valve distress, a leakage test at 80 psi for 30 minutes
322
v\ ith leakage not exceeding one-half gallon per
minute, and a stroking test of three full opening and
three full closing strokes. Field tests consisted of three
full opening and three full closing strokes in the in-
stalled position.
These tests were conducted to ensure that the
equipment was free from defects prior to acceptance
by the Department.
Lubrication System. A centralized lubrication
system was installed in the gate chamber to meet the
lubrication requirements for the five slide gates and
the fi.\ed-cone dispersion valve. The system works au-
tomatically in conjunction with the gate and the valve
operating systems through an electrical interconnec-
tion. Whenever a gate or valve is energized for opera-
tion, the electrical system simultaneously actuates the
lubrication system. The lubrication system also is ca-
pable of being manually controlled.
The system consists of a central station, piping,
valve manifolds, valving, control mechanism, and ac-
cessories.
Service Facilities. The service facilities consist of
(1) heating and air-conditioning system, (2) ventila-
tion system, and (3) domestic water supply system.
These facilities are mainly in the monitor and control
building and gate chamber of the outlet works. They
are provided for maintaining and safeguarding the
operation of the outlet works.
Heating and Air-Conditioning System. A central
heating and air-conditioning system is provided in the
offices and equipment room of the monitor and con-
trol building to maintain comfortable working condi-
tions for personnel and proper ambient temperature
for the electronic equipment.
The cooling unit has a capacity of 37,000 BTU per
hour and is supplied with 208-volt, single-phase, 60-
hertz power from the motor control center and uses
R-22 refrigerant. The electric heater has a capacity of
48,000 BTU per hour and is supplied with 480-volt,
3-phase, 60-hertz power from the same center. The fan
used in both the heating and the cooling phases has a
capacity of 1,460 cubic feet per minute (cfm) and is
supplied with 120-volt, single-phase, 60-hertz power.
Selection of the components for the air-conditioning
system was based on (1) an inside cooling tempera-
ture of 80 degrees Fahrenheit and an inside heating
temperature of 65 degrees Fahrenheit, and (2) consid-
eration of reliability and minimum maintenance since
the electronic equipment in the equipment room is
highly sensitive to heat and moisture.
Ventilation System. The ventilation system con-
sists of individual fans and blowers installed in the
gate chamber, drainage gallery, and two instrumenta-
tion wells for the protection of equipment.
The system was designed to provide a sufficient
number of air changes to avoid any danger of asphyx-
iation in addition to removal of heat and moisture. An
airflow switch was installed at the drainage gallery to
operate an alarm which will warn individuals enter-
ing the gallery when the blower is not providing prop-
er ventilation.
The blower located in the gate chamber is designat-
ed as Blower 1. It ventilates the gate chamber by draw-
ing air into it through the access tunnel and then
discharging it through the ventilation shaft. The
blower located at the remote end of the drainage gal-
lery, designated as Blower 2, takes its air from the
gallery and discharges it into the outlet works tunnel.
Both of these fans are rated at 1,000 cfm, '/j-inch S.P.,
1,174 rpm, and are provided with 480-volt, 3-phase,
60-hertz power.
An 8-inch centrifugal exhaust fan is provided to
ventilate each instrumentation terminal well. These
fans are rated at 175 cfm and operate on 120-volt, 3-
phase, 60-hertz power.
Domestic (Potable) Water Supply System. The
potable water system provides treated water in the
monitor and control building for domestic use.
Raw water is taken from the Las Flores Pipeline and
collected in a sump in the valve vault at Station
19-1- 16. It is pumped to the treatment plant located in
the monitor and control building through a steel pipe-
line.
The treated water is stored in a 350-gallon tank in
the same building ready for dechlorination and distri-
bution. The treated water has turbidity of 1 part per
million and chlorine level not below 0.2 of a part per
million. The water pressure at the fixture is between
20 to 50 psi.
Las Flores Pipeline. Mechanical equipment for
the Las Flores Pipeline is located in two valve vaults
at Stations 1 +98 and 19-|- 16. The equipment includes
a shutoff valve, flow metering, control valves, and an
air-vacuum valve. They are required for proper opera-
tion of, and measuring the flow through, the Pipeline
(Figure 248).
Shutoff \'alve. The shutoff valve is located in the
first valve vault at Station 1 -1-98 and is used for closing
off all flow to Las Flores Pipeline during periods of
maintenance and repair. It is an 18-inch, 150-pound,
manually operated, rubber- seated, butterfly valve and
is flanged at both ends.
A butterfly valve was selected because it is more
economical and simpler in operation and maintenance
than gate and plug valves.
Flow Metering. The flow-metering equipment in-
stalled in the second valve vault at Station 19+16 is
used to measure all flow through Las Flores Pipeline.
The metering equipment consists of a 14-inch and a
6-inch flow tube in parallel complete with pressure
tap connections and flow transmitters.
The flow transmitters, which transmit the electrical
signals to the monitor and control building for record-
ing and totalizing the flow, are mounted on the vault
wall.
Control \'alves. Two control valves, one 12-inch
323
and one 6-inch, were installed downstream of the 18-
inch and 6-inch flow tubes inside the valve vault at
Station 19+16. They regulate the flow through Las
Flores Pipeline and control the amount of flow
through each flow tube for proper metering.
Air-\'acuum \'alve. There are two 2-inch air-vac-
uum valves installed in Las Flores Pipeline to release
air during pipeline filling and to admit air into the
Pipeline if a vacuum condition occurs. The air-vac-
uum valves are 150-pound rated with both ends
flanged. Each valve is complete with a 2-inch, 150-
pound, flanged, solid-disc, gate valve for shutoff.
Electrical Installation
Normal electrical service is supplied by a utility
company and standby electrical power is provided by
an engine-generator set for all electrical features at the
Cedar Springs Dam and reservoir facilities. Electrical
power is fed to the intake gate chamber and access
tunnel. Las Flores outlet vault, outdoor lighting, and
instrumentation well buildings from the control
building.
Operating Equipment. All the equipment neces-
sary for remote monitoring and control of Cedar
Springs Dam and reservoir are contained in the con-
trol building. Data, status, and alarm information are
transmitted to the Castaic Area Control Center.
Remote closing and opening of the intake slide gate is
provided from the control building and Castaic Area
Control Center by means of the digital comparator
module, supervisory equipment, and site processor.
Local controls and annunciations for Las Flores
outlet and cone valves are located at the valve sites and
duplicated at the control building. All other local con-
trols are only at the sites although duplicate annuncia-
tions are provided at the control building.
Emergency Engine-Generator Set. An engine-
generator set is provided as an emergency source of
power for the operation of the entire facility, includ-
ing the slide-gate hydraulic system, fixed-cone disper-
sion valve operator, lubrication system, air-con-
ditioning system, ventilating fans and blowers, instru-
ments, controls, and lights. The engine-generator set
is located in the engine-generator room of the monitor
and control building.
The engine is a 4-cycle, 6-cylinder, water-cooled en-
gine. It has overhead valves, 339-cubic-inch displace-
ment, and produces 105-brake-horsepower at 1,800
rpm. The engine is equipped with a built-in flyball
close regulating governor for speed regulation. The
engine operates satisfactorily with liquid propane gas
(LPG) fuel at an elevation of 3,400 feet.
The generator was designed for a continuous out-
put of 55 kW at 0.8 power factor, 277/480 volts, 3
phase, 4 wire, 60 hertz at 1,800 rpm.
The fuel for the engine-generator set is stored in a
500-gallon storage tank which is sufficient to meet the
full-load fuel requirements of the engine for a period
of 96 hours.
Engines using diesel, natural gas, and LPG fuels
were investigated. An LPG-fueled engine was selected
because of the low initial cost of the unit and also
because LPG fuel is easily stored and remains usable
indefinitely. LPG-fueled engines are easier to start
under extreme temperature conditions, which is the
case at Cedar Springs Dam site.
Equipment. The following electrical equipment
was installed at the Cedar Springs Dam and reservoir
facilities:
Control Building
1. Motor control center
2. Servo-manometer-type water-level indicating
and recording instruments
3. Supervisory and site processor consoles
4. Telephone system equipment
5. Engine-generator set
6. Miscellaneous electrical equipment such as
lighting, air-conditioning and heating, ventila-
tion, and potable water-pump starter
Gate Chamber
1 . Hydraulic consoles and lubricating equipment
2. Motor control panels
3. Air-shaft ventilation equipment
4. Access tunnel lighting
Instrumentation Well Buildings
1. Seismic equipment
2. Panel boards and transformers
3. Lighting and ventilation equipment
Las Flores Outlet \ 'ault
1. Flow-metering equipment
2. Motor control panels
3. Lighting
A single-line diagram of Cedar Springs Dam facilities
is shown on Figure 270.
324
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m
. ^ 5
ill
i i i
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ill! i M
Yi'i
)yi
< \U
^""■V't- ,1 ,1 ,1
J s , 6 »B ^ *Bi
J ' « k -s^ i
I II f ^^ I
% I ? I ,» * j>. 5
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Figure 270. Control Schematics
32S
Construction
Contract Administration
General information about the major contracts for
the construction of Cedar Springs Dam and appurte-
nances is shown in Table 34. The principal contract,
Specification No. 68-30, included the Dam, relocation
of forest service roads, part of State Highway 173,
access roads, inlet works, a portion of the Mojave Si-
phon, and the outlet works tunnel and control struc-
ture.
Exploration Adit
Portal excavation for the exploration adit, which
later became the access tunnel, began in September
1967. A trench was dug extending north from the
portal across State Highway 138 (Figure 248). Tem-
porarily, the Highway had to be relocated around the
north end of the trench while a conduit pipe for access
to the proposed tunnel was being placed in the trench
and the Highway rerouted over the top. Tunnel exca-
vation began in October 1967 and was completed in
March 1968. Two jacklegs were used to drill holes 4 to
7 feet deep. The drilling pattern was a 26-hole burn
cut and a 14- to 26-hole "V" cut. Muck was loaded into
muck carts with an air-powered mucker.
Tunnel support from the portal to Station 26 + 03
(Figure 260) consisted of temporary timber sets
placed on centers of 4 and 8 feet. Wood sets consisted
of 10-inch by 10-inch caps and 6-inch by 8-inch posts.
A 36-foot section between Stations 22+48 and 22 + 84
was driven 14 feet wide and left unsupported. It was
used as a car pass area. From Station 26 + 03 to the end
of the adit, W4X13 (4WF13) horseshoe steel sets were
used for support. While driving the adit, support gen-
erally followed the face by less than 10 feet but, in
places, as much as 70 feet of tunnel was left unsupport-
ed for several days.
Diversion and Care of River
During the first winter (1968-69), two delays
amounting to 24 calendar days were a result of two
storms. The first storm caused flood conditions so se-
vere the entire vicinity was declared a disaster area by
the Governor of California. All construction work,
including excavation for the spillway and reservoir
clearing, was halted by this storm. A second storm
Figure 271. Embankment Construction
closed all routes to the job site and washed out haul
roads to the spillway. Major excavation operations
were resumed on March 3, 1969.
After April 1, 1969, construction began on a small
dam at the site of the Las Flores diversion structure to
bypass summer streamflow around the construction
area. A 36-inch-diameter corrugated-metal pipe was
laid through the Dam site. Since no rainfall occurred
during the summer of 1969, the system remained dry.
Because streamflow in the Mojave River was insuffi-
cient to meet construction needs, the Department de-
veloped a 2,250-gallon-per-minute well in the Mojave
River, 9 miles downstream, and pumped water to the
area of use.
During the first phase of dam construction, the Riv-
er was diverted through the Dam site west of the right
abutment to allow completion of right abutment exca-
vation and foundation grouting. By October 1969,
right abutment excavation, core trench excavation,
and foundation grouting had progressed sufficiently
to permit commencement of construction of the flood
diversion channel located along the right abutment
(Figure 271).
The completed flood channel was triangular in
shape and was formed by the excavated right abut-
ment slope and a 5:1 filled slope on the left. The invert
of the channel was at approximate elevation 3,165 feet.
By April 1970, the first-stage embankment reached
elevation 3,305 feet. Because the contractor demon-
TABLE 34. Major Contracts — Cedar Springs Dam and Appurtenances
Exploration Adit
Interim Water
Supply Facility
Cedar Springs
Dam
Stage II Pump
Quarry Irrigation
System
Specification
Low bid amount
Final contract cost
Total cost-change orders
Starting date
Completion date
Prime contractor
67-36
Ji251,130
?293,822
28,634
7/31/67
4/29/68
Clifford C. Bong &
Co.
67-50
?39S,353
?43 1,628
338,561
10/2/67
4/9/68
R. L. Thibodo
Construction Co.
68-30
?25,376.422
328,148,654
3429,060
11/12/68
8/18/71
Morrison-Knudsen
Co.
69-13
334,238
331,538
362
4/25/69
7/1/69
Pylon, Inc.
71-09
324,084
325,280
3925
5/21/71
8/13/71
Moulder Bros.
326
strated that he could complete the outlet works, the
spillway past Station 23+90, the spillway stilling ba-
sin, and the dam embankment to elevation 3,300 feet
by November 1, 1970 (Figure 251), he was allowed to
close the flood channel and proceed with construction
of stage two of the dam embankment.
In an emergency, the outlet works are capable of
passing the standard project flood with a maximum
water surface at elevation 3,295 feet. After November
I 1970, floodflows were stored behind the Dam or di-
1 verted through the outlet works.
Dam Foundation
Dewatering. Seepage of water into and along the
bottom of the excavation for the Dam was controlled
by using drain trenches and sumps. During stage 1
construction, the water was pumped from the sumps
into either the diversion channel or the pipeline sup-
! plying Las Flores Ranch. Zone 1 and 2 embankment
j contact materials were placed over the dam founda-
tion in the dry.
Excavation. Stripping for the Dam began on the
left abutment knoll in December 1968. The contractor
I used a large tractor with a slope board. Two additional
! tractors were added to the left abutment stripping
i operation. The metamorphic rock exposed was severe-
I ly weathered and friable to a depth of 10 feet. Below
I the severely weathered zone, the rock was moderately
, to slightly weathered, weak to moderately strong, and
1 closely fractured. The stripping operation on the right
I abutment was accomplished by a large tractor with a
i double-shank parallelogram ripper.
I Alluvium with an average thickness of about 30 feet
and a maximum thickness of about 50 feet, including
some slopewash at the base of both abutments, was
i excavated from the channel. The slopewash was 10 to
i 20 feet thick in both the left and right channel areas
I and generally consisted of silty sand.
I Minimal excavation was required in the Harold for-
, mation under Zones 3 and 4A, since it was as fresh on
; the surface as at depth. Further excavation was re-
\ quired in the granite under Zones 1 and 2 to remove
j all weathered rock to a depth sufficient to ensure that
I the foundation would be impervious after grouting.
1 This resulted in the formation of a core trench, the
excavation of which was accomplished using conven-
tional excavating equipment without the need for any
] blasting.
j Ground water was encountered in the alluvium ex-
I cavation from 50 feet upstream of centerline to 200
; feet downstream of Station 21-1-75 (Figure 250). The
water table was at elevation 3,167 feet. In addition,
small seeps occurred as a result of cuts between eleva-
tions 3,180 and 3,185 feet in fractured rock associated
: with faults 1 and 5 (Figure 254).
i Cleanup and Preparation. Prior to placing Zone
i 1 contact material in the core trench, all loose rock,
I soil, and waste materials were removed using hand
labor and a backhoe. This was followed by a thorough
cleaning using air and/or water jets immediately prior
to placement of the contact material. No slush grout-
ing was performed as it would have resulted in a rigid
membrane inconsistent with the general design con-
cept of a flexible embankment. Grout caps were
placed in excavation where rock was too highly frac-
tured or too soft to adequately anchor pipe nipples and
hold the required grouting pressure.
Foundation cleanup prior to placing Zone 2 materi-
al was the same as described for Zone 1. Embankment
for Zone 3 was placed upon either Harold formation
or granitic rock. After excavating overlying sands and
gravel, loose material was either recompacted or
removed prior to placing Zone 3. Boulders larger than
18 inches excavated from the dam foundation were
utilized in Zones 4A and 5 of the embankment. No
further cleanup was required. Foundation cleanup
prior to placing Zone 4 material was the same as de-
scribed for Zone 3.
Little foundation cleanup was required for Zone 4A
because most of it rests upon the upstream Zone 3
embankment. In those areas where Zone 4A was
placed upon the dam foundation, all overlying topsoil,
slopewash, and alluvial materials were removed prior
to placement. Foundation preparation prior to placing
Zone 5 was the same as described for Zone 4A.
Handling of Borrow Materials
Description. Materials for construction of the em-
bankment were obtained from mandatory excavations
and designated borrow areas. All materials from the
mandatory excavations, meeting the requirements of
the specifications, were used in the embankment in
lieu of wasting.
Impervious. Borrow Area A (Figure 245) was the
source of impervious material for Zone 1 of the Dam.
A total of 1,182,000 cubic yards of material was ex-
cavated to supply material for the core. The borrow
source was an unnamed dry lake just north of State
Highway 18 and approximately 20 miles from the
Dam site. The contractor built his own 45-foot-wide
haul road from the borrow area to the specified stock-
pile area in the reservoir. The dry lake materials were
prewetted before removal from the borrow area for
dust control purposes.
Elevating belt loaders towed by tractors were used
to excavate the clay to a depth of 3 to 5 feet in each
pass. Maximum depth of excavation in the borrow
area was 29 feet. At the Dam site, tandem bottom-
dump trucks deposited the material into windrows in
the reservoir area. The windrows were spread into
lifts for moisture conditioning, using tractors. A
sprinkler system was used to apply water to the dry
material. Discs and scarifiers mixed the material to
assure complete and uniform distribution of the wa-
ter. After moisture conditioning to optimum moisture
content, the material was picked up and hauled to the
Zone 1 embankment in scrapers.
327
Pervious and Slope Protection. Silty sands and
gravelly sands for Zone 2 material were obtained in
part from areas located in the reservoir. Of approxi-
mately 483,000 cubic yards of Zone 2 material, 108,300
cubic yards were excavated from the west side of the
valley floor and the remainder from required excava-
tion for the spillway return channel and inlet works
excavation.
The bulk of Zone 3 materials came from streambed
sand and gravel on the dam foundation and in the
upstream channel area.
Excavation in the borrow areas was accomplished
by cutting across deposits of sand, gravel, and cobble
and through lenses and layers of differing gradation to
produce a uniform mixture of materials within speci-
fied grading limits. Scrapers, push-loaded by dozers,
were used to haul the material to the embankment.
Boulders too large to be picked up by the scrapers
were loaded by end loaders into rear-dump trucks for
hauling to the rock embankment area of the Dam.
Excavation from the four borrow areas was completed
in March 1971. A total of 1,348,000 cubic yards of Zone
3 material was excavated.
About 85% of the rockfill portion of the Dam for
Zones 4, 4A, and 5 was excavated from a quarry locat-
ed in the reservoir area about 1 mile south of the Dam.
The remainder was obtained from stockpiles and man-
datory excavations.
By October 1969, overburden in the rock quarry
area had been stripped to such an extent that large
areas of hard rock were exposed. The basic equipment
used to drill the rock consisted of air tracs, a drill, and
compressors. In November, a rotary drill was brought
to the job site and put on this work.
Suitable rock was hauled in 75-ton rear-dump
trucks, either directly to the dam embankment or to
a rock-separation and processing plant. Waste materi-
al was hauled either to mandatory waste areas or used
in haul roads. Shot rock was loaded by either a 15-
cubic-yard shovel or a loader.
Rock processed through the plant was rear-dumped
into the plant hopper bins onto a hydraulically oper-
ated grizzly scalper which removed oversize rock for
Zone 5 material. The remaining rock passed onto a
conveyor belt which fed the separation plant. \'ibrat-
ing screens in the separation plant divided the materi-
al into the required sizes for Zones 3, 4, and 4A. Rock
for the various zones was collected in bins which fed
dump trucks used to haul the material to the Dam.
The oversize rock scalped off for Zone 5 material was
loaded into end dumps by an end loader equipped
with a tined bucket. The trucks hauled the rock direct-
ly to the Zone 5 embankment. Excavation in the rock
quarry was completed in March 1971. A total of
4,629,000 cubic yards of material was excavated.
Waste Areas. More than 7,500,000 cubic yards of
material, stripped as overburden from borrow area
sites and unsuitable embankment materials excavated
from mandatory excavations, was wasted in five man-
datory waste areas and two optional waste areas.
An estimated 2,300,000 cubic yards of waste materi-
al was placed in a mandatory waste area located at the
upstream toe of the Dam. Another waste area was
developed adjacent to the rock quarry to serve as a
recreation beach.
Materials placed in spoil areas did not require any
compaction other than that derived by routing con-
struction equipment over the fill. Dozers were used to
level the material after it was dumped on the fill.
Embankment Construction
Impervious. The first Zone 1 contact material was
placed in the core trench in October 1969. The contact
material was compacted at optimum moisture content
plus 2 to 3%. The moisture-conditioned material was
hauled from Zone 1 stockpiles to the core trench in
both scrapers and end-dump trucks. A front-end load-
er was used to place the material. Then it was com-
pacted in nominal 4-inch lifts by a rubber-tired dozer.
At least two passes were made on each lift: one parallel
Figure 272. Compacting Zone 1 Material
Figure 273. Performing Field Density Test on Zone 3 Moteriol
328
to the dam axis and the other perpendicular to it. This
method of placement, with minor modifications, was
used to place all of the Zone 1 contact materials.
Placement of contact material to a depth of 12
inches was followed by the placement of Zone 1 em-
bankment in the conventional manner using sheeps-
foot rollers (Figure 272). The material was spread and
leveled by a rubber-tired dozer and compacted by self-
propelled, four-drum, sheepsfoot rollers. Twelve
passes with the sheepsfoot roller were required to
compact the material to a maximum depth of 6 inches
and to a required compaction of 95%. The top layer
of foundation contact material, compacted by a wheel-
roller, was scarified to a depth of 2 inches prior to
placing Zone 1 embankment. A total of 1,090,000 cubic
yards of Zone 1 material was placed in the dam em-
bankment.
Pervious. Filter blankets lying on each side of the
impervious Zone 1 core consist of Zone 2 materials of
the Harold formation.
Placement of Zone 2 contact material commenced
in the core trench near the center of the east portion
of the Dam. The material was hauled from stockpiles
in the spillway return channel to the core trench
where it was dumped. Then it was leveled with dozers
and compacted in 3- to 4-inch lifts by a rubber-tired
dozer in the same manner as described for the Zone 1
contact material. This method of placement, except
for special problem areas, was used to place all Zone
2 contact material.
Zone 2 embankment placed over Zone 2 contact
material was hauled in rear-dump trucks, leveled by
dozers, and compacted by self-propelled, four-drum,
sheepsfoot rollers to a required minimum compaction
of 95%. The material was compacted in 12 passes to a
maximum thickness of 6 inches. A total of 483,000
cubic yards of material was placed in the Zone 2 em-
bankment.
The gradation of Zone 3 material varies in size from
No. 200 screen to 18 inches. The upstream Zone 3
Figure 275. Zone 5 Embankment Shell Material
material was extended in a thick blanket along the
foundation and under the Zone 4A embankment all
the way to the upstream toe of the Dam. The materials
were leveled by dozers and moisture-conditioned on
the fill by water tankers. The material was compacted
by two passes of a vibratory roller. Lifts were limited
to a depth of 24 inches. Compaction tests were per-
formed for every 10,000 cubic yards of material placed
(Figure 273).
The minimum compaction required was 95%. A
total of 1,949,000 cubic yards of Zone 3 embankment
material was placed.
Materials for Zone 4 embankment, lying down-
stream of Zone 3, varied in size from 3 to 30 inches.
The rock for Zone 4 was hauled in rear-dump trucks
and spread on the fill by dozers. No moisture condi-
tioning was required. Lifts were limited to 36 inches
after compacting (Figure 274) with two passes of a
vibratory roller. A total of 776,000 cubic yards of Zone
4 material was placed in the dam embankment.
Placements for Zone 4A embankment commenced
on June 24, 1969. A total of 2,460,000 cubic yards of
Zone 4A material, varying from sandy gravel to 30-
inch rock, was placed in the embankment.
Little foundation cleanup was required for Zone 4A
since most of this material rests upon the upstream
Zone 3 embankment. In those areas where Zone 4A
was placed upon the dam foundation, all overlying
topsoil, slopewash, and alluvial material were
removed prior to placement.
Rock was leveled on the fill by dozers, moisture-
conditioned by water tankers, and placed in 36-inch
lifts. Compaction was accomplished with two passes
of a vibratory roller.
Slope Protection. No moisture conditioning or
compaction was required on Zone 5 embankment
rock. Dressing of the 2'/4:l downstream slope of the
Dam was done by dozers. A total of 784,000 cubic
yards of Zone 5 material was placed in the dam em-
bankment (Figure 275).
329
Riprap. Riprap for the upstream face of the Dam
from elevation 3,305 feet to the dam crest varied in size
from 3 inches in diameter to 2 cubic yards in volume.
Lifts were limited to a depth of 5 feet.
Spillway
Open-Cut Excavation. Spillway excavation was
started in December 1968 in the upper reach of the
spillway and in the return channel. The material ex-
cavated from the upper reach of the spillway that was
unsuitable for embankment was wasted at the dam
toe, while the material excavated from the return
channel was either wasted in the downstream waste
area or used to build the construction facility earth
pad. The initial construction equipment used to strip
the vegetation and overburden consisted of dozers
equipped with rippers and slope boards, push dozers,
and scrapers.
After stripping the vegetation and overburden, the
initial excavation was in weathered granite. As the
excavation progressed deeper, the material ranged
from decomposed granite to hard rock. The rock was
moderately to highly fractured. Air drills were used
where rock was too hard to be ripped. In some isolated
areas, rock had to be blasted. In addition, some boul-
ders were encountered that had to be shot and pushed
over the side of the cut into the reservoir area where
they were later reshot for use in the dam embankment.
All materials suitable for dam embankment were
placed in the various rockfills of the Dam.
By the end of July 1969, the excavation of the upper
approach channel, crest section, and chute to the inter-
section of the outlet works had been completed except
for final foundation cleanup and structural excava-
tion. Open-cut excavation for the spillway from the
intersection of the outlet works to the end of the still-
ing basin essentially was completed by December
1969, except for fine grading and structural excava-
tion. A total of 2,2.'i4,750 cubic yards of material was
excavated for the spillway.
Structural Excavation. Structural excavation for
the spillway included the shear keys and drain ditches
below the bottom surface of the spillway floor slab.
Some of the hard granitic rock in the spillway chute
was difficult to blast to grade which resulted in con-
siderable overexcavation.
Drain trenches were excavated using a backhoe
with a blade and by laborers using jackhammers. Rock
too hard to be excavated with the backhoe was drilled
and shot prior to excavation. Final cleanup of the
foundation prior to placing concrete was done with
air-water jets.
Concrete Placement. The first floor concrete
placement for the spillway was on the 2% slope sec-
tion of the chute. The concrete was placed using a
conveyor system which discharged the concrete into
the form ahead of a screed. The concrete was screeded
by a steel slip form pulled up the slope by winches.
Floor concrete placement on the 22% slope section
of the chute was somewhat slower than those place-
ments made on the 2% slope and caused more segrega-
tion problems.
For concrete placemenis on the lower reach of the
50% slope section, a 60-ton truck crane and 1-cubic-
yard buckets were used to handle the concrete. A con-
veyor belt system was used as the placement pro-
gressed uphill and out of reach of the crane.
Floor concrete placements for the stilling basin
were made using either a crane and bucket method or
a conveyor belt system. The conveyor belt system was
supplied by transit mix trucks. This method also was
used to place the floor concrete for the approach chan-
nel and the ogee crest section. All forming was done
with wood. All floor placements were completed by
the time the contractor placed the cover slab over the
outlet works tunnel portal.
The first concrete placement for the walls was made
on the right side of the spillway at the vertical curve
transition between the 2 and 22% slopes of the chute.
The wall form consisted of steel panels faced with
plywood. Prior to placing the concrete, considerable
effort was spent anchoring the form to prevent grout
leaks.
A 30-foot conveyor with rubber wheels on the bot-
tom and track-guided wheels at the top was used to
elevate the concrete to the top of the form where it was
discharged through hoppers and tremie pipes. The
concrete was vibrated by working off a platform at the
top of the form. This method of placement, with mi-
nor modifications, was used to place all wall concrete
except in the stilling basin walls, warped approach
walls, and ogee crest walls.
Concrete in the stilling basin walls was placed using
concrete buckets handled by a 60-ton truck crane. The
45-foot-high walls were placed in three lifts, which
varied from 11 feet to about 19 feet in height.
Concrete for the warped approach walls and for the
ogee crest walls was placed using conventional wood
forms. The warped walls were placed in six lifts using
holding forms while the crest walls were placed in
three lifts. These placements were made using con-
crete buckets and a truck crane.
Mojave Siphon Inlet Works
Excavation. Excavation for the inlet works was all
open cut. The cut was a maximum of 150 feet deep in
the granitics and varied from 25 to 60 feet in Harold
formation on the lake side of the ridge. Cut slopes of
1 : 1 , with 1 5-foot-wide berms every 40 feet in elevation,
were used in the granitics. Cut slopes of l'/2:l with a
similar berm arrangement were used in the Harold
formation where they were subject to submergence by
the reservoir.
Excavation commenced in the vicinity of Station
15-1-00. The excavation work for the first nine months
was, for the most part, confined to the reach between
Stations 12-1-00 and 18-1-00 and was on an intermittent
basis, depending upon the availability of scraper units
330
'OK
from other phases of the work. The work during this
period basically was a dozer and scraper operation.
When excavation had progressed to elevation 3,380
feet, a small slide on the fault plane was observed in
the approximate area of Station 17 + 00, centerline
right, at about elevation 3,450 feet. The contractor was
directed to perform additional excavation from Sta-
tion 14 + 00 to Station 19 + 00 to correct this problem.
Approximately 77,000 cubic yards of material was
removed above the fault plane. Major equipment used
to remove the slide consisted of dozers with rippers,
scrapers, track drills, end-dump trucks, and an end
loader.
Excavation was completed in September 1970. Prac-
tically all of the excavated material was wasted at the
upstream toe of the Dam. Exclusive of the slide, a total
of 727,100 cubic yards of material was excavated for
the inlet works structure.
Structural excavation for the concrete inlet works
key and drain trenches under the chute floor slabs was
performed using a backhoe or jackhammers, depend-
ing on the nature of the rock. Considerable care was
exercised to prevent shattering the rock beyond the
excavation neat lines.
Concrete Placement. Floor placements for the
upper reach of the chute and the transition structure
were made by chuting concrete directly into the ply-
wood-faced forms. The walls were placed using con-
crete buckets handled by a 60-ton truck crane. Floor
and wall placements for the 41% slope of the chute
and for the dissipator structure also were made using
the crane and bucket method. The contractor used a
job-built slip form screed to place concrete in the in-
vert of the 41% slope of the chute. Two cables pow-
ered by an electric winch were used to pull the slip
form up the slope at a slow rate of speed while vibrat-
ing the concrete just ahead of the screed. A total of
2,634 cubic yards of concrete was placed for the inlet
works structure.
Concrete Piles. Holes for the 24-inch-diameter,
30-foot-long, cast-in-place, concrete piles under the in-
let works dissipator structure were drilled using a
crane-mounted auger drill rig. No particular prob-
lems were encountered in placing a total of 374 feet of
piling.
Mojave Siphon Extension. Open-cut excavation
for the Mojave Siphon pipeline extension commenced
just north of relocated State Highway 173. Excavation
progressed uphill (southerly) toward the inlet works
structure, and then the remaining reach of the excava-
tion under State Highway 173 was performed. Dozers
and scrapers were used to excavate a total of 33,400
cubic yards of material for the pipeline.
Pipe Installation. The first section of the 126-
inch-diameter Mojave Siphon pipeline extension was
placed in the open-cut trench 250 feet south of the
existing Mojave Siphon. Pipelaying, like the open-cut
excavation, proceeded uphill (southerly) toward the
inlet works structure, except for the first 250 feet
south of the existing Mojave Siphon which was in-
stalled last. The pipe installation sequence consisted of
laying the pipe to grade, testing the rubber gasket ring
for sealing, grouting the outside portion of the joint,
installing bond cable at each joint, grouting the inside
portion of the joint, and backfilling the pipe. A total
of 1,177 linear feet of pipe was installed.
Debris Barriers
Two debris barriers were constructed under this
contract. One barrier is located in Miller Canyon in
the southeast fork of the reservoir and the other in
Cleghorn Canyon in the southwest fork of the reser-
voir.
These barriers were constructed across the
streambeds of the two canyons to catch debris coming
down the canyons after closure of the diversion chan-
nel through Cedar Springs Dam. Consequently, con-
struction of these barrier dams was prohibited prior to
closure of the diversion channel.
Immediately following construction of the debris
barriers and prior to reservoir filling, a large-magni-
tude flood overtopped the Miller Canyon dam and
washed out a section containing the spillway. Just
before reservoir filling, this section was replaced
along with a 48-inch corrugated pipe to bypass flow
during reconstruction.
Drainage Gallery
The drainage gallery. Station 0 + 00 to Station
8 + 22, was driven initially for exploration purposes, as
part of the exploration program discussed previously.
Except for mucking out the caved-in materials of the
exploration adit, no excavation was required in the
drainage gallery. One extensive cave-in had to be
mucked out at the beginning of the tunnel in the vicin-
ity of Station 1 + 50 (Figure 260). The remaining
work in the tunnel, prior to placing concrete, consist-
ed of laying track, bringing in utility lines, providing
for drainage, realigning existing steel sets, reinstalling
fallen lagging, and installing additional lagging where
required.
The tunnel section between Stations 8 + 22 and
8 + 64 (Figure 260) was driven northward from the
dam foundation under the main dam contract.
Concrete Placement. The first concrete place-
ment in the invert of the drainage gallery tunnel was
between Station 8 + 00 (approximately 22 feet from
the drainage gallery extension) and Station 6+70.
Subsequent invert placements in the drainage gallery
proceeded toward its intersection with the access tun-
nel. From Station 8 + 00 to Station 4 + 60, the concrete
placements were made using a concrete pump located
outside at the drainage gallery extension portal. A
6-inch slickline was used to convey the concrete di-
rectly into the invert forms. Usually, additional ce-
ment over the structure's design requirements was
331
added to the concrete to reduce friction in the slick-
line.
The remaining reach of the drainage gallery tunnel
invert from Station 4 + 60, and its intersection with
the access tunnel, w as placed with the concrete pump
located inside the tunnel. The concrete was pumped
from the pump hopper directly into the invert forms
using a 6-inch slickline. Length of placements varied
from about 60 to 110 feet.
The first arch placement in the drainage gallery was
made at its intersection with the drainage gallery ex-
tension, and subsequent placements proceeded to-
ward its intersection with the access tunnel. A total of
14 arch placements, varying in length from 48 to 68
feet, were made using a concrete pump and slickline
from inside the tunnel. Collapsible steel forms were
used for these placements.
Drainage Gallery Extension. The drainage gal-
lery extension was driven using a crawler-mounted
drill. Steel supports, heavily cribbed, were required
only at the portal, as sound rock was encountered as
the excavation progressed. Most of the blasted rock
was mucked out through the portal using an end load-
er except muck from the last round, which was
removed through the drainage gallery using a mucker
and train.
Concrete for the 6-foot-diameter drainage gallery
extension was monolithically placed using a concrete
pump and a slickline. The concrete was transported
from the batch plant in transit mix trucks which dis-
charged their loads directly into the pump hopper.
The upstream 8-foot-long plug was placed in a similar
manner.
Access Tunnel
Completion. Work began with mucking out sand
and drainage water from the exploration adit tunnel
and extending the track into the existing timber-sup-
ported tunnel. Mucking out the invert; laying track;
and installing air, water, and electric lines were con-
tinued until the intersection of the access tunnel and
drainage gallery was reached. At the intersection, the
crown of the tunnel had caved in from Station 2 .S + 65
to Station 25-f 88 in the access tunnel and to Station
0 + 90 in the drainage gallery tunnel. The cave-in
brought down all the previously installed supports.
The cave-in was mucked out and the crown was resup-
ported with several 4-inch and 6-inch-wide steel sets
and timber lagging.
While one mining crew continued work in the
previously driven part of the access tunnel and in the
drainage gallery tunnel, another crew started driving
the access tunnel from Station 2.*! + 88 toward the out-
let works gate chamber. Fairly good rock usually was
encountered in the access tunnel as it was driven to-
ward the gate chamber. In the vicinity of Station
27 + 87, three steel sets, W4Xl.^, on ."i-foot centers were
used in a faulted area. In the remaining reaches, the
tunnel was either driven bald-headed or rock-bolted
(bolts were % of an inch by 6 feet long), depending
upon the nature of the granitic rock. The tunnel was
advanced in 4- to 7-foot rounds.
Concrete Placement. The first concrete invert
placement for the access tunnel was between Stations
28 + 97 and 29 + 62 near the outlet works gate chamber,
and subsequent invert placements proceeded toward
the portal. The concrete was transported by rail from
the batch plant. A concrete pump with a 6-inch slick-
line was used to place the concrete. Placements varied
from about 55 to 135 feet in length.
Concrete arch placements for the access tunnel
commenced after the drainage gallery arch was com-
pleted. Placements started at the gate chamber. Sta-
tion 29 + 78, and progressed to the portal at Station
19 + 90. A total of 16 arch placements, averaging 68
feet each, were required. The method used to place the
concrete was the same as described for the drainage
gallery arch placements.
Outlet Works Tunnel
Excavation. The initial excavation of the gate
chamber was a continuation of the access tunnel exca-
vation. A tunnel with a width of 10 feet and a height
of 1 1 feet - 6 inches was driven to the centerline of the
gate chamber and then to the air tunnel portal, thus
completing the first phase of the outlet works excava-
tion.
After completing the excavation of the air tunnel,
the contractor resumed excavation in the gate cham-
ber by driving an 8-foot-diameter shaft from the floor
of the gate chamber (elevation 3,196.30 feet) to the top
of the dome. The dome at the top of the shaft was
rock-bolted with 10-foot-long rock bolts on 3-foot cen-
Flgure 276. Rock Bolls in Dome of Outlet Works Gate Chombe
332
J
ters. A rod then was hung at the centerline of the gate
chamber from the top of the dome to the springline of
the dome from which a platform was attached. This
enabled the miners to drill 17 feet - 8 inches in any
direction above the springline from the lower end of
the rod. The entire top 120-degree peripheral portion
of the dome above the springline at elevation 3,212.30
feet then was drilled out and shot in one blast. The
30-degree slope bench formed by the blast served as a
funnel, in effect, since the muck rolled down into the
8-foot-diameter shaft to elevation 3,213.50 feet where
it was removed. The rest of the dome then was rock-
bolted on approximately 3-foot centers with rock bolts
varying from 6 to 10 feet in length. The center shaft
was enlarged to a diameter of 15 feet, and the remain-
ing rock above the springline was drilled, shot, and
rock-bolted (Figure 276). The chamber below the
springline was excavated in three separate rounds
working outward from the center of the 15-foot shaft
on a 17-foot -8- inch radius. The walls of the gate
chamber between the springline and the floor (eleva-
tion 3,196 feet) also were rock-bolted. The contractor,
throughout the tunneling, used the proper amount of
tunnel supports without arguing that more support
was needed for various reasons. This was due in large
part to the lump-sum bid item for tunnel work which,
in effect, made the contractor responsible for the
amount of tunnel support used.
The major equipment used to excavate the gate
chamber included jackleg drills, stoppers, a mucker on
rails, a mucker on tracks, five to seven 4-cubic-yard
muck cars on rails, and an 8-ton motor-driven locomo-
tive.
The outlet works tunnel was driven upstream from
Figure 277. Placing Concrete in Gate Chamber
the downstream (north) portal where the tunnel dis-
charges onto the 50% slope of the spillway floor. As
soon as the fractured rock over the north portal was
stabilized with the installation of crown bars into the
overburden, a 3-set steel umbrella was installed at the
portal and drilling commenced. The first shot opened
cracks in the rock above the portal, and additional
cribbing had to be installed along the sides and above
the portal. The fractured rock at the portal extended
into the tunnel for about 75 feet to Station 27-1-21 and
was supported by W6X15 steel sets on 4- to 5-foot
centers, with considerable lagging. From Station
27 + 21 to Station 26-1-79, the granitic rock was fairly
good, and no supports were required.
The rock from Station 27-1-21 to Station 23-f 50, a
point of contact with a shear zone, varied from slightly
fractured to sound rock. As a result, this reach of the
tunnel was either supported by W6X15 steel sets on 5-
to 6-foot centers or rock-bolted with rock bolts vary-
ing from 6 to 10 feet long, depending upon the nature
of the rock.
In the faulted area reaching from Station 23 + 50 to
approximate Station 22+96, fault 1 was highly frac-
tured and contained clay gouges. This area was sup-
ported by W6X15 steel sets on 3- to 4-foot centers and
required extensive lagging. Between Stations 22+96
and 18 + 65, where the excavation broke into the previ-
ously excavated gate chamber dome, the quality of the
rock varied considerably.
In November 1969, driving of the 13-foot-diameter
circular section of tunnel was commenced, leaving 3
feet of material in the invert to be excavated later.
From Station 17 + 81 to Station 13 + 68, the lightly
fractured granite required rock bolts only in isolated
areas to pin loose rock. Between Station 13+68 and
the upstream portal, several 6-inch steel sets were re-
quired to support the rock.
Major equipment used to excavate the outlet works
included a drill jumbo, two end loaders, and five air
compressors.
The open-cut excavation for the outlet works intake
structure was performed in conjunction with the
open-cut excavation required for the spillway ap-
proach channel. Nine steel sets, with considerable lag-
ging, were used to support the portal.
Concrete Placement. The first two placements
for the gate chamber were made to level the founda-
tion to allow setting of jack plates and anchor bolts for
the steel-plate liner supports. The concrete was trans-
ported from the batch plant to the gate chamber in
transit mix trucks (Figure 277).
For three months, the work in the gate chamber was
limited to placing, fitting, and welding the steel-plate
liner sections. Fit-up of the liner sections took longer
than expected due to plate distortion and warping.
Embedment of the upstream steel-plate liner was
done in two lifts and the downstream liner in three
333
lifts. All placements were made with a concrete pump
and slickline.
Three concrete placements were required in the
sidewalls between the upstream and downstream lin-
er to elevation 3,194 feet. Placements were made using
conveyor belts to span the gate chamber.
Conventional wood forms were used for these
placements. The floor, remaining walls, and dome
placements were made in five segments using a pump
and slickline and conventional wood forms. Concrete
was transported by rail through the access tunnel.
Invert placements for the 13-foot-diameter portion
of the outlet works tunnel upstream of the steel-plate
liner in the gate chamber were made in seven sections.
The first five placements were made using a 60-foot
conveyor belt which discharged the concrete directly
into the form. The last two placements were made
using a concrete pump and an 8-inch slickline. The
concrete pump and slickline method of placement
proved to be the most effective, reducing the placing
time by approximately 50%.
Ten arch placements, starting from the gate cham-
ber and varying in length from 48 to 56 feet, were
required to reach the upstream portal at Station
12-f71. All placements were made using a concrete
pump and an 8-inch slickline.
The first invert placement for the downstream
horseshoe section of the outlet works was made for the
downstream transition from Station 18 + 84 to Station
19+17. This placement and the next six placements
from Station 18 + 84 to Station 24+36 were made us-
ing a concrete pump with an 8-inch slickline. The
remaining placements, except for the last one at the
downstream portal, were made using a conveyor belt.
The last invert placement was made using a concrete
pump, set at the portal, and an 8-inch slickline.
Prior to placing concrete in the arch of the down-
stream horseshoe section, 1-foot-high stub (curb)
walls were placed on each side of the centerline.
Transit mix trucks discharging directly into the steel
forms were used for these placements, which were
made well ahead of the arch placements. The arch
placements were made using a concrete pump with an
8-inch slickline.
The outlet works intake structure was built using
wood forms faced with plywood. The concrete was
placed using a truck crane and 2-cubic-yard concrete
buckets.
Air Shaft Tunnel
Excavation. Excavation for the air tunnel was a
continuation of the outlet works gate chamber. The
tunnel was driven through sound granitic rock and no
supports were required. The method, equipment, and
labor used to drive the tunnel essentially were the
same as for the access tunnel excavation.
Excavation of the air shaft was started on July 2,
1969. By July 7, 1969, the shaft had been driven 46 feet
from the invert of the air tunnel by miners working
off a platform pinned to the shaft. Work was suspend-
ed at that time until a cable and air hole could be
drilled from the ground surface to the heading in the
shaft. Excavation of the air shaft resumed with drill-
ing from the ground surface of an 8-inch-diameter
hole in the center of the shaft. This hole was to serve
as a cableway for raising a man-cage used as a work
platform by the miners in excavating the shaft at high-
er elevations (Figure 261). Work continued using the
platform until the shaft had been raised 87 feet from
the invert. Then the miners began using the man-cage
to excavate the shaft. The cage was hoisted from the
ground surface using a 30-ton truck crane. The man-
cage was used to excavate all but the top 25 feet of the
raise. This reach was excavated from the top of the
shaft.
Concrete Placement. The first placement consist-
ed of 15 feet of invert and stub wall in the air tunnel
to the centerline of the air shaft. The concrete was
delivered to the top of the air shaft and lowered 180
feet down the air shaft in a 1-cubic-yard bucket where
it was dumped and vibrated into the forms.
The first air-shaft placement was made from the
invert to elevation 3,230 feet and included 8 feet of the
tunnel walls and arch. Six subsequent placements
were made to elevation 3,376.5 feet or to 2 feet below
the finished floor of the air-shaft louver house. Two
shaft placements were made monolithically using two
6-inch slicklines extending from the top of the shaft to
within 3 feet of the bottom of the placement. This
method of placement for the air shaft produced good
workability without segregation.
The first air-tunnel invert and stub walls placement
incorporated the invert of the air shaft. The remaining
78 feet of the invert and stub walls were placed using
a truck-mounted pump located downstream of the
gate chamber in the outlet works tunnel. Two con-
crete placements were required to complete the air-
tunnel arch. Placements were made using a pump
located at the upstream end of the tunnel, adjacent to
the outlet works gate chamber. A 6-inch slickline was
used to place the concrete in collapsible steel forms.
Concrete Production
Three principal concrete mixes were used in the
construction of the spillway, inlet works, and tunnels.
A mix with 3-inch maximum size aggregate, 306
pounds of cement, and 70 pounds of pozzolan was
used for the spillway and inlet works floor slabs and
large walls, and for the entire intake structure. Thin
walls of the spillway and inlet works have concrete
with a mix of 1 '/2-inch maximum size aggregate, 400
pounds of cement, and 70 pounds of pozzolan. All
concrete placed in the underground works consisted
of a mix of I'^-inch maximum size aggregate, 447
pounds of cement, and 100 pounds of pozzolan. Using
waterwashed and shaded aggregate, together with
100% ice, concrete was held below 53 degrees Fahren-
heit during summer placement. This placement tern-
334
perature was only 3 degrees above optimum for this
type of work.
A fully automatic 4-cubic-yard plant was used to
batch the concrete for Cedar Springs Dam structures.
The plant included a 4-cubic-yard tilting-drum mixer
and individual batches of 6,000-pound capacity for the
four sizes of aggregate. Cement and pozzolan were
batched cumulatively in a 6,000-pound batcher. Ice
was batched into a 2,000-pound batcher with adjusta-
ble feed discharge directly onto a belt. Water was me-
tered through a 3-inch meter. Based on a 2 '/^-minute
mi.xing cycle, the capacity of the plant was 80 cubic
yards of concrete per hour.
Grouting
Dam Foundation. The curtain grouting program
for the dam foundation involved a high-pressure, 150-
foot-deep, main curtain and a low-pressure, 25-foot-
deep, secondary curtain. One-and-one-half-inch-diam-
eter pipe nipples were installed in all grout holes.
Grouting was done by the split-spacing method. Pri-
mary holes were 150 feet deep on 20-foot centers with
, 50-foot-deep intermediate holes between the primary
I holes. The main curtain crosses the entire length of
I the Dam in a mid-position under Zone 1 and was
combined with a line of holes in the secondary cur-
tain.
Grouting of the main curtain was accomplished by
a combination of stage and packer grouting in the
following sequence: first stage was drilled to a depth
of 25 feet and stage-grouted from the nipple; second
stage was drilled the next 25 feet, a packer was set at
the top of this stage, and grouted; primary holes were
^ completed by drilling the third stage the remaining
' depth of hole (150 feet); packer grouting from 100 to
150 feet; and subsequently setting a packer at a depth
of 50 feet and packer grouting from 50 to 100 feet.
Blanket grouting was done in fractured areas and
[where grouting of the first stage in the main and sec-
londary curtains did not appear to be adequate to seal
the upper 25 feet. Blanket grouting consisted of single
: lines of shallow holes (up to 25 feet deep) on 10-foot
i spacings, upstream and downstream of the curtain.
I Pressures of 10 to 15 pounds per square inch (psi)
were used, although up to 25 psi was used occasional-
ly.
Spillway. Curtain grouting for the spillway foun-
dation was done by a procedure similar to that for the
'dam foundation except a secondary curtain was not
! included; maximum depth of drill holes was 125 feet
I in the bottom and 50 feet on the side slopes; and for
[the third stage, the packer was set at 90 feet, and the
Imaximum pressure was 125 psi instead of 150 psi.
j Tunnel. Contact grouting was performed in the
: tunnels to fill any voids between the concrete tunnel
i lining and the surrounding rock. Contact grout was
injected through 1 '/j-inch-diameter pipe set in the tun-
inel lining near the crown. Grouting of a hole was
I considered to be complete when 30 psi could be main-
tained for 15 minutes with no significant grout take.
Consolidation grouting consisted of low-pressure
shallow-hole grouting of the fractured rock surround-
ing the tunnel. This was accomplished by drilling and
grouting a series of holes in a ring pattern equally
spaced around the tunnel perimeter and perpendicu-
lar to the tunnel centerline. Grout pipe, l'/4 inches in
diameter, was installed prior to placement of the con-
crete lining. Grouting of each ring usually was started
at the tunnel invert, and every other hole was grouted
progressing upward to the crown. Grouting was ac-
complished by setting a packer inside the pipe and
grouting with a pressure of 50 psi. The intermediate
holes on each ring then were drilled and grouted to fill
any voids between the primary holes.
Gate Chamber. Contact grouting was conducted
in the gate chamber dome by using seven consolida-
tion grout pipes which were located evenly through-
out the dome.
Consolidation grouting consisted of 61 holes includ-
ed in six rings of 10 each, plus one hole at the top of
the crown. Holes were drilled 20 feet into rock and
grouting was accomplished in one stage. The rock
surrounding the dome was hard to drill with diamond
bits, and low grout takes were recorded.
After reservoir filling, moisture was noted on about
50% of the gate chamber walls and ceiling. To main-
tain a dry condition for the electrical equipment, the
Department contracted for additional contact grout-
ing using a chemical grout. Seeping plugged grout
holes, construction joints, and fine-line cracks were
drilled, caulked, and pressure-grouted with acrylo-
mide grout. The treatment proved to be about 95%
effective. Additional grouting is planned in the gate
chamber air shaft where moisture continues to be a
problem.
Air Shaft. Consolidation grouting was conducted
in the air shaft for a vertical distance of 203 feet above
the air intake tunnel. The grouting consisted of rings
of four holes each on 15-foot centers. Grout take was
low in most areas and 22 holes were tight. The only
area with appreciable grout take was the south side of
the shaft between elevation 3,201 feet and elevation
3,225 feet. Additional chemical grouting also is
planned for the air shaft where moisture from seeping
construction joints now drips from the walls.
Reservoir Clearing
Clearing in the reservoir to elevation 3,354 feet con-
sisted of the removal and disposal of all trees, down
timber, brush, rubbish, fences, floatable material, and
buildings. Cesspools and septic tanks were pumped
out and filled with sand. Any trees between elevation
3,354 feet and the spillway weir crest at elevation 3,355
feet were left standing at the request of the U.S. Forest
Service. It was believed that many of these trees would
live because of infrequent inundation, and those that
die can be used by campers for firewood.
335
Reservoir clearing commenced in December 1968 except for commercial timber, was disposed of by
and was completed in June 1971. A spread of four burying or burning. All burning was performed in
bulldozers was used to clear the reservoir area, except accordance with the project fire plan approved by the
for inaccessible areas which had to be cleared by labor- U.S. Forest Service. Merchantable pine timber in the
ers using hand and power tools. Combustible material, Miller Canyon area was logged by a subcontractor.
336
BIBLIOGRAPHY
Lanning, C. C, "Cedar Springs Dam", USCOLD Issue No. 32, U. S. Committee on Large Dams Newsletter, May
1970.
Sherrard, J. L., Cluff, L. S., and Allen, C. R., "Potentially Active Faults in Dam Foundations", Volume XXIV,
No. 3, The Institution of Civil Engineers Geotechnique, September 1974.
Stroppini, E. W., Babbitt, D. H., and Struckmeyer, H. E., "Foundation Treatment for Embankment Dams on
Rock", ASCE Journal of Soil Mechanics and Foundation Division, October 1972.
337
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338
CHAPTER XIII. FERRIS DAM AND LAKE FERRIS
General
Description and Location
Perris Dam is a zoned earthfill structure with a
maximum height of 128 feet. The Dam is over 2 miles
in length and impounds a reservoir with a gross stor-
age capacity of 131,452 acre-feet within a horseshoe
ring of rocky hills. Approximately 20 million cubic
yards of fill material comprise the embankment.
Structures appurtenant to the Dam include a tun-
neled outlet works connecting to distribution facilities
of The Metropolitan Water District of Southern Cali-
fornia (MWD) and an open-channel ungated spill-
way. Water is discharged into Lake Perris by an
extension of the Santa Ana Valley Pipeline, termed
the "inlet works".
Perris Dam and Lake Perris, the terminal storage
facility on the California Aqueduct, are located in
northwestern Riverside County, approximately 13
miles southeast of the City of Riverside and about 65
miles east of Los Angeles. Perris, the nearest town, is
about 5 miles to the southwest (Figures 278 and 279).
The reach of the State Water Project terminating at
the Lake is designated the Santa Ana Division.
A statistical summary of Perris Dam and Lake Per-
ris is shown in Table 35, and the area-capacity curves
are shown on Figure 280.
m
«
Figure 279. Aeriol View — Perris Dam and Lake Perris
339
Purpose
Lake Perris, a major feature of the State Water
Project, is a multiple-purpose facility with provisions
for water supply, recreation, and fish and wildlife en-
hancement.
Chronology
Prior to 1965, the capacity of Lake Perris was set at
100,000 acre-feet. At that time, this storage volume
satisfied the requirements of MWD, the only water
contractor taking deliveries from this facility.
The Metropolitan Water District studies in 1965 of
water service expansion concluded that increasing the
capacity of Lake Perris would increase the security of
service and improve flow regulation. The Department
of Water Resources then was requested by MWD to
study reservoir enlargement, and two amendments to
the water service contract between the Department
and MWD followed. Amendment No. 4, dated No-
vember 19, 1965, provided that the Department would
acquire all lands necessary for a reservoir with a
capacity of 500,000 acre-feet and would perform plan-
ning and design work which would enable MWD to
select the appropriate ultimate reservoir size. Amend-
ment No. 5, dated October 10, 1966, stated that the
Dam and appurtenant facilities initially would be con-
structed to impound 100,000 acre-feet and provisions
would be made so that the Dam could be raised, in any
number of stages, to impound a maximum of 500,000
acre-feet of water. Final design of the facilities was
completed in accordance with Amendment No. 5, and
construction of the Dam commenced in October 1970.
Increased recreation potential and the adverse im-
pact of reservoir enlargement on the onshore recrea-
tion development, along with reevaluation of MWD
future demands, resulted in the decision to construct
the facilities in one stage with a capacity somewhat
above 100,000 acre-feet. Studies immediately follow-
ing showed that a dam 10 feet higher, providing a
storage capacity of 120,000 acre-feet, could be con-
structed with the funds available. Redesign of the
Dam took place in April 1971 and the contractor, who
had begun construction but had been limited to work-
ing on items unaffected by the enlargement, was given
immediate notice to proceed with construction in ac-
cordance with the new plans.
All construction was completed by February 1974,
except for some minor project modifications and ini-
tial recreation facilities.
Regional Geology and Seismicity
The Dam site is located on the Perris block, a large
down-dropped block of Cretaceous granitic rock
which contains some schist and gneiss. During earlier
times, these crystalline rocks were sculptured into
ridges and valleys by erosional processes. Later, the
Perris block dropped down, changing the drainage
pattern and filling the valleys with alluvium. Today,
only the higher former ridges protrude through the
alluvial surface forming a landscape of flat valleys and
low ridges.
TABLE 35. Statistical Summary of Perris Dam and Lake Perris
PERRIS DAM
Type: Zoned earthfiU
Crest elevation.. 1,600 feet
Crest width. 40 feet
Crest length 11,600 feet
Streambed elevation at dam axis 1,480 feet
Lowest foundation elevation 1,472 feet
Structural height above foundation 128 feet
Embankment volume 20,000,000 cubic yards
Freeboard above spillway crest 10 feet
Freeboard, maximum operating surface 12 feet
Freeboard, maximum probable flood. 5.8 feet
LAKE PERRIS
Storage at spillway crest elevation 1 3 1 ,452 acre-feet
Maximum operating storage 126,841 acre-feet
Minimum operating storage 37,013 acrc-fect
Dead pool storage 4,100 acre-feet
Maximum operating surface elevation 1,588 feet
Minimum operating surface elevation 1,540 feet
Dead pool surface elevation 1,500 feet
Shoreline, spillway crest elevation 10 miles
Surface area, spillway crest elevation 2,318 acres
Surface area, maximum operating elevation.. 2,292 acres
Surface area, minimum operating elevation. , 1,540 acres
340
SPILLWAY
Type: Ungated ogee crest with concrete baffled chute and riprapped
channel
Crest elevation.
Crest length
1,590 feet
16 feet
Maximum probable flood inflow 17,500 cubic feet per second 1 4 ll
Peak routed outflow 320 cubic feet per second 'Bj
Maximum surface elevation 1,594.4 feet Hh,
INLET WORKS wl
Buried 8-foot - 6-inch concrete pipeline from terminus of Santa Ana !i
Valley Pipeline above right abutment — energy dissipated by I
hydraulic jump inside pipeline
Capacity 469 cubic feet per second
OUTLET WORKS
Type: 12-foot - 6-inch-diameter lined tunnel under left abutment,
with a steel delivery manifold
Intake structure: Five-level vertical tower with 72-inch shutoff
butterfly valves
Control: Regulation of flow at delivery manifold by water users
Design delivery 1,000 cubic feet per second
UlowofT structure: 6-foot-wide by 12-foot-high slide gate down-
stream of delivery manifold with bolted bulkhead at downstream;
terminus ,; !■ '
Capacity _ 3,800 cubic feet per second '.Wi
2800
SURFACE AREA -ACRES
2000 1600 1200
1580
1560
Z
O 1540
\
NWS EL 1588
/
\
\
\^
y
y
y
^
\
^
A
~ CAPAC
ITY
^
\,
— A R F A
X
/
>
\
f
\
60
CAPACITY
80 100
1000 ACRE-FEET
120
140
160
Figure 280. Area-Capacity Cu
The Dam is located in one of the most active seismic
areas in Southern California. There are seven faults
w ithin 20 miles of the site which have been classified
as active. These faults are: San Andreas; San Jacinto;
Elsinore; Agua Caliente; and the Casa Loma, Loma
Linda, and Hot Springs branches of the San Jacinto.
The southwest margin of the San Jacinto fault zone is
the Casa Loma fault, which is within 6 miles of the
Dam site and 1 mile from the edge of Lake Perris. The
Elsinore fault zone is located approximately 17 miles
southwest of the Dam site.
During the 33 years of available seismograph
records, 31 earthquakes with Richter magnitudes of
3.0 to 3.9 were recorded within a 10-mile radius of the
Dam site, and 15 were recorded with magnitudes over
4.0 within a 30-mile radius of the site. Two of the
earthquakes, within a 20-mile radius, were of major
proportions, with magnitudes of 6.0 and 6.9. One of
these occurred in 1918; its epicenter was only 16 miles
southeast of the Dam site. Buildings and water mains
1 in the town of San Jacinto were destroyed.
Design
Dam
Description. Perris Dam has a zoned earthfill sec-
tion with a sloping clay core (Figure 281). Except for
short reaches on the left abutment and at the rock
outcrops, the Dam is founded on an alluvial founda-
tion.
Necessary freeboard to prevent overtopping of the
Dam during maximum flood was computed assuming
a maximum wave height plus run-up caused by a wind
of 100 miles per hour. The dam crest thus was estab-
lished at elevation 1,600 feet. This provides a free-
board of 12 feet above normal pool. The maximum
section (Figure 282) is 128 feet high.
The dam alignment was initially predicated on the
ultimate development ( SOO,000-acre-foot lake). Left
abutment location was selected to yield the most fa-
vorable rock contact for the large dam, even though
considerable shaping was required for the lower por-
tion. The rock outcrops at the valley center were used
341
Figure 281. Embonkirienf Plan
342
tt
iHTiT
<jn
JTr I I
Figure 282. Embankment Sections
343
as a turning point, and the right-leg alignment fol-
lowed the shortest line to topography of sufficient
elevation. Because embankment construction was un-
derway when the decision was made to change the
reservoir capacity, the alignment described earlier in
this chapter was not changed.
The core of the Dam is constructed of a plastic clay,
and the outer zones are composed of silty sand. The
downstream silty sand zone contains a vertical
crushed-rock drain, and a horizontal drain underlies
the downstream shell. A filter zone of silty sand was
placed between the core and the vertical drain. Em-
bankment zones were made a minimum of 12 feet in
width to allow efficient placement and compaction.
Riprap protects the upstream face of the Dam from
wave erosion. Riprap at the downstream toe also pro-
tects the exposed face of the horizontal drain. The
remainder of the downstream slope was planted with
a stand of grass for surface runoff protection.
Stability Analysis. Slip circle and sliding wedge
analyses were made to determine the stability of the
embankment under all anticipated loading conditions.
Satisfactory safety factors were attained for the sec-
tion as designed. Critical loading cases were: upstream
slope, reservoir at critical level and earthquake load;
and downstream slope, full reservoir with earthquake
load. Earthquake loading utilized in these analyses
was assumed to be a horizontal acceleration of the
foundation in the direction of instability of the soil
mass being analyzed. The assumed acceleration was
0.1 5g. Material strengths utilized in these analyses
were derived as follows: Zones 1 and 2 and foundation,
soil testing by the Department; and Zones 3 and 4,
estimates based on material strengths determined for
similar materials (Table 36).
Dynamic finite element analyses were made by the
University of California and a private engineering
firm. These analyses showed that the Dam was stable
under severe earthquake shaking and that substantial
increased stability could be gained by achieving high
density in Zone 2 material. Therefore, compaction
near the maximum department laboratory standard
was required for this material.
Settlement. Analyses were made for the Dam and
alluvial foundation to estimate the additional amount
of embankment required to compensate for settlement
during construction and to establish the crest camber
necessary to compensate for postconstruction settle-
ment.
Anticipated settlement of the embankment during
construction was calculated by summing consolida-
tion as horizontal layers were placed successively.
This was found to be 2.4 feet. Postconstruction settle-
ment occurs mostly in the foundation when saturation
takes place. The settlement was estimated to be 3.6
feet. The 4-foot camber supplied at maximum section
was a summation of the anticipated postconstruction
settlement of the embankment and the foundation.
Construction Materials. The sloping impervious
core (Zone 1) is a plastic clay material obtained from
a borrow area 5 miles northeast of the Dam site. Inves-
tigation was made of ways to furnish water to this
borrow area after construction to provide a fishing
and waterfowl observation site. Lack of funding by
potential operating agencies and possible conflicts
with the main recreation area resulted in abandon-
ment of this concept. Therefore, the borrow area was
designed as a free-draining excavation with flat slopes
so the land could be returned to its original use of
grain farming.
Zone 2, the semipervious upstream and down-
stream shells and downstream dam facing, was ob-
tained from a borrow area within the lake area and
from required structural excavations. Two alternative
borrow areas were considered. The first was located
as close as possible to the Dam and was formed by
simple excavation lines. The second contemplated ex-
cavations along the north shore for recreational en-
hancement. Slopes for beaches and boating facilities
along with peninsulas formed of waste materials were
provided in the final configuration of the borrow area.
This alternative was requested by the Department of
Parks and Recreation and general layout criteria were
furnished by them. As the second borrow alternative
TABLE 36. Material Desig
n Parameter
— Perris Dam
Specific
Gravity
Unit Weight in Pounds
Per Cubic Foot
Static Shear Strengths
e Angles in Degrees
Cohesion in Tons Per Square
Foot
Effective
Total
Construction
Material
Dry
Moist
Saturated
e
C
e
C
9
C
2.76
2.75
2.70
2.70
2.74
112
121
127
125
116
128
134
134
139
143
140
136
23
33
40
40
33
0.4
0
0
0
0
f,
40
40
15
0.6
1.0
0
0
1.0
3
33
1.3
0
Zone 3
•
Foundation .
• Free-draining material. u»c effective stress valu
344
I
ltd I
obviously would be more costly, each was included in
the specifications on separate schedules, and potential
contractors were required to bid on each. The Depart-
ment then could award the contract on the basis of
either schedule, depending upon the differential cost
and availability of funds.
The horizontal and vertical embankment drains are
composed of a clean drain rock (Zone 4) enveloped by
sandy gravel transitions (Zone 3). Originally, it was
planned that Zone 3 and 4 material and riprap would
either be quarried and crushed granitic rock obtained
from the ridge near the left abutment of the Dam or
hauled from designated sources outside the project
area. The materials investigation revealed insufficient
quantities of clean gravels within reasonable haul dis-
tance of the site and demonstrated that crushed rock
would be the most economical alternative. The grada-
tion of Zone 3 material was established on the basis of
the Terzagi filter criteria with respect to the gradation
of Zone 2 (silty sand) and Zone 4 materials.
An on-site quarry was established as the source for
riprap. Average rock size required for riprap was 170
pounds, ranging from 20 to 2,000 pounds. The hori-
zontal width of the riprap layer was established at 10
feet. Crushed rock bedding was provided beneath the
riprap for a transition to the fine-grained underlying
embankment material. A width of 12 feet satisfied the
minimum thickness requirements and allowed room
for efficient placement and compaction.
Foundation. The main portion of the foundation
for Perris Dam is alluvium within a broad valley be-
tween two granitic ranges, Bernasconi Hills and Rus-
sell Mountains. The alluvium, consisting of a mixture
of silty sand and clayey sand, is deposited over granitic
bedrock. A layer of decomposed granite, up to 60 feet
in thickness, overlies much of the intact bedrock. The
alluvial foundation is divided by granite outcrops near
the central region of the site. North of the outcrops,
the alluvium is relatively shallow, averaging less than
40 feet. South of the outcrops, the bedrock dips form-
ing a subsurface canyon, and the maximum alluvium
depth is over 250 feet.
The left abutment of the Dam is granitic rock of the
Bernasconi Hills, whereas the right is formed by ris-
ing alluvial ground surface. The embankment is
founded on rock in the vicinity of the outcrops.
Instrumentation. Instrumentation is provided at
Perris Dam to monitor embankment and foundation
settlement, internal pore pressures, and response of
the embankment and foundation to ground motions
from earthquakes (Figure 283). Facilities at the site
are consistent with those provided at other project
dams; however, portions of the instrumentation sys-
tem are somewhat more elaborate because of the
unusual foundation conditions.
Control panels for monitoring instrumentation are
located in two terminal buildings. Instrumentation
and other features of the performance monitoring sys-
tem for the Dam and Lake are described in Table 37.
TABLE 37. Features of Performance Monitoring System —
Perris Dam and Lake Perris
1. Lake horizontal movement net:
Total of 13 instrument stands.
2. Level line:
25 miles of bench marks around Lake; 1 kilometer spacing.
3. Lake-level gauge.
4. Embankment and foundation instrumentation:
24 piezometers.
27 crest settlement monuments.
5 accelerometers; crest of dam, on foundation below crest,
near the rock-alluvium contact 77 feet below the embank-
ment, in alluvium downstream of the Dam, and in rock out-
crop downstream of the Dam.
2 cross-arm settlement devices.
5. Seismographs:
1 instrument located at Instrumentation Terminal No. 1.
1 instrument installed on the dam crest.
6. Open-tube piezometers:
13 cased holes downstream of Dam.
Inlet Works
Description. An S'/j-foot-inside-diameter inlet pipe-
line joins the Santa Ana Valley Pipeline at vent struc-
ture No. 1 on the crest of the hill near the right abut-
ment of Perris Dam (Figure 284). The inlet pipeline,
located in a cut section, descends 190 feet in elevation.
Ninety feet of drop occurs in the first 400 feet of
length. It then rises slightly over the next 670 feet
before descending at vent structure No. 2 over the
final 2,630 feet to the terminus at the outfall basin.
The outfall basin structure is located beneath the
lake surface and is protected by a 30-foot-wide con-
crete apron extending beyond the end of pipe on a 2:1
slope. A terminal stilling basin, 70 feet wide, 150 feet
long, and 35 feet deep, was provided to minimize
churning of silt into the Lake by water jet.
Because the inlet works is located near a recreation
area, the selected design was based on maximum
safety and minimum adverse environmental effects on
the surrounding area. During the preliminary design
stage, three alternatives were investigated. Two open-
chute alternatives with high-velocity flow were elimi-
nated for public safety reasons. The high-velocity bur-
ied pipeline alternative best satisfied the above
considerations at a feasible cost.
Hydraulics. The inlet works was designed to sat-
isfy two hydraulic requirements for conveying project
water. The first requirement was a summit invert ele-
vation of 1,698 feet. This elevation provides sufficient
static head to achieve the required flow at upstream
turnouts on the Santa Ana Valley Pipeline. The sec-
ond requirement was sizing the inlet works to convey
a maximum flow of 560 cubic feet per second (cfs)
into the reservoir.
345
Figure 283. Embankment Instrumentation
346
Figure 284. Inlet Works — Plan and Profile
347
The energy of the water downstream of the Pipe-
line summit partially is dissipated by hydraulic jumps
inside the Pipeline. The profile grade was selected to
prevent the jump from being swept out. The Pipeline
was sized to prevent blowback due to air entrainment
induced at the jump. Vents are provided at locations
where pipe flow changes from full to partially full.
Because the maximum velocity is in excess of 60 feet
per second, 2 inches of concrete cover over the inside
reinforcement was selected for protection against
abrasion. The pipe joints were beveled to minimize
cavitation.
Pipe Structural Design. A low-pressure (43
pounds per square inch) reinforced-concrete pipe was
selected to resist internal hydrostatic pressure due to
the hydraulic jump and to support 20 feet of earth
cover.
Outlet Works
Description. The outlet works is located at the left
abutment of the Dam and consists of a multiple-level,
vertical, intake tower; concrete and steel-lined tunnel;
and concrete-encased, steel-pipe, delivery facilities
(Figure 285). The delivery facilities connect to the
water user's distribution facilities and provide a gated
outlet to the downstream channel. Control and moni-
toring of the outlet works take place primarily from
a control building jointly used by the Department and
MWD.
Intake Channel. The purpose of the intake chan-
nel is to convey reservoir water to the outlet works
tower when the reservoir water surface elevation
drops below the original ground surface at the tower
site. The channel has a trapezoidal cross section 40 feet
wide at the bottom with 4:1 and 3:1 side slopes and is
partially lined with impervious earth blanket.
Outlet Works Tower. The cylindrical, reinforced-
concrete, outlet works tower with a 26-foot inside di-
ameter is 105 feet high above foundation elevation and
is capped by a deck supporting a 20-ton gantry crane
(Figure 286). The tower contains 10, hydraulically
operated, 72-inch, butterfly valves which release water
to the outlet works tunnel from five selected levels
within the reservoir, two valves per level. The quality
of water released can be selected. Two tiers of valves
(four valves) at the selected withdrawal depth are
opened for delivery at the maximum rate (1,000 cfs).
Steel cylindrical hoods on the discharge end of the
eight upper valves direct the flow downward. Direct-
ing the flow downward minimizes the possibility of
air entrainment and damage to downstream compo-
nents of the outlet works. Hoods are not provided for
the lower valves as no change in flow direction occurs
between the valve and tunnel. A movable fish screen
outside of the operating intake valves excludes small
debris and fish from the system.
The tower was designed to resist stresses resulting
from the vertical dead load and the effect of seismic
forces with full reservoir conditions. For the dynamic
analyses, the tower was assumed to act as a vertical
cantilever fixed at the base.
The seismic forces on the concrete shell of the tower
include lateral inertial forces due to dead load and
lateral dynamic forces due to two cylinders of water
with diameters equal to the inside and outside diame-
ters of the tower. The earthquake input was 60% of
the San Andreas design earthquake acceleration spec-
trum, as recommended by the Department's Consult-
ing Board for Earthquake Analysis. This design
spectrum suggests a horizontal acceleration of one-
half gravity for rigid structures. The input was re-
duced because foundation conditions, including fairly
intact rock, were considered better than those for
which the design earthquake was developed. Two per-
cent of critical damping was used.
The moments and shears used for design were cal-
culated by means of an elastic model analysis. Final
design moments and shears were determined by com-
puting the root-mean-square values of the moments
and shears generated in the first five modes of vibra-
tion. The tower, because of its moderate height, is a
relatively rigid structure with a first mode period of
0.33 of a second. For this reason, the higher modes do
not contribute significantly to the seismic loading.
Inelastic yielding, in the event that the design earth-
quake is exceeded, probably would be confined to one
hinge area at the base of the tower.
The outlet works tower footing was designed to
transfer all superstructure loads into the foundation
rock by means of a spread footing anchored to the
rock. It was assumed that the footing would receive
the shears from the superstructure shell above and
transfer them to the rock mass below, primarily by its
shear resistance. The compressive stresses are trans-
ferred to the rock in direct bearing since the footing
concrete was placed against an undisturbed rock sur-
face. The tensile stresses due to overturning moment
are transferred by the anchor bars which are grouted
into the rock mass.
Access to the tower is provided by a 109/^-foot-long
16-foot-wide bridge from the outlet works access road.
This road follows the south lake shore to Bernasconi
Pass and then connects to Ramona Expressway. The
bridge was designed for HS 20-44 loading.
Outlet Works Tower Mechanical Installation. Ten
72-inch-diameter, rubber-seated, butterfly valves were
installed in the intake tower in two vertical rows. The
port valves can be operated locally from the control
cabinet on the tower operating deck and remotely
from the joint MWD-Department control building.
The valves are intended to operate in the fully open
or closed positions. Each of the valves in one vertical
row, however, is capable of operating partially opened
at differential heads_of up to 93 feet and discharging
348
free flows up to 60 cfs for filling the tower.
Each valve is actuated by its own hydraulic motor
and screw drive-type operator. The valve operators
are capable of opening or closing the valves under a
t maximum differential head of 30 feet and closing un-
[1 der full reservoir head. The hydraulic system for oper-
r. ating the valves consists of two vane-type oil pumps;
an oil reservoir; solenoid-operated, 4-way, control
valves; flow control valves; strainers; piping; valves;
t and appurtenances. The system was designed to oper-
j|; ate with a maximum hydraulic oil pressure of 2,000 psi
5, and operating time of 5 minutes per valve stroke. Two
„( valves can be operated simultaneously.
A structural-steel maintenance platform stored in
the tower above normal reservoir level is provided for
servicing the upper four tiers of valves. The lower
valve tier at elevation 1,503 feet is serviced from the
tower base at elevation 1,495 feet.
One trolley of the 20-ton gantry crane raises and
lowers the maintenance platform on stainless-steel
guides embedded in the tower wall.
The platform was not designed to support the
weight of the valves, operators, or hoods. These items
must be removed from the tower during disassembly
by the gantry crane.
A bulkhead gate is provided for closure of the but-
terfly valve intake openings to facilitate repair or re-
moval of the butterfly valves. It is 9 feet - 4 inches high
by 9 feet - 5'/ inches wide and weighs approximately
9,000 pounds. The bulkhead is stored off the tower in
the on-site maintenance facility.
The gate, with lifting beam attached, is lowered
vertically into slots on the outside of the tower by one
of the 10-ton trolleys on the 20-ton gantry crane and
dogged in front of the valve opening to be closed.
A 20-ton-capacity, electric, cab-operated, outdoor,
traveling, gantry crane was installed on the tower
deck. The crane operates on rails anchored to the
tower deck and is equipped with two 10-ton-capacity
trolleys which service both the inside and outside of
the tower. The crane also is used to provide hoist
service as necessary on the tower deck and inside the
tower and to position the fish screens.
Capacities and speeds are as follows:
Rated capacity of crane, tons 20
Number of trolleys 2
Rated capacity each trolley, tons 10
Length of lift, feet 125
Length of travel, feet 13
Hoist speed, feet per minute (fpm) .. 14-20
Trolley travel speed, fpm 4—6
Gantry travel speed, fpm 4-6
Master control devices for the functions of the crane
were installed on the console in the operator's cab.
Stainless-steel wire rope is used on the crane hoists
since operation of the fish screens requires submerged
service for extended periods of time.
Screens to cover operating intake ports are provided
to prevent passage of fish and debris into the delivery
system. The screens are '/j-inch-square mesh covering
structural-steel frames. One frame is suspended by the
gantry crane over two operating valve tiers for each of
the vertical valve rows. Rails are provided on the out-
side of the tower for guidance during up and down
movement and for holding the screens horizontally in
place.
A washing system designed to remove minor debris
and algae from the fish screens is provided in the
intake tower. Two washing stations, one for each fish
screen, are located at elevation 1,591 feet.
A variable-spray-pattern wash nozzle is mounted on
a flexible ball joint at each platform. Water to the
washing stations is supplied by a six-stage, deep-well,
vertical, turbine pump mounted at elevation 1,600
feet. The pump has a rated capacity of 90 gallons per
minute at a total head of 265 feet and a speed of 3,450
rpm.
Outlet Works Tunnel. The outlet works tunnel is
a 12-foot -6-inch-inside-diameter pressure conduit
about 2,100 feet long, located in the left abutment of
the Dam (Figure 285). It conveys water from the out-
let works tower to the delivery facilities which serve
MWD (Figure 287). The tunnel was provided with a
reinforced-concrete lining upstream of the axis of the
dam impervious core. From the core axis to the down-
stream portal, steel liner with concrete backfill was
used.
The steel liner was designed to withstand external
pressure due to ground water equal to the depth of
cover over the tunnel or to elevation 1,590 feet, which-
ever was greater. A study of types of liner plate in-
dicated that, due to the greater stiffener spacing
possible, the use of ASTM A572 steel was the most
economical. Liner thickness was set at J^ of an inch so
as to adequately withstand the entire internal hydro-
static pressure to elevation 1,590 feet and to provide
rigidity for handling.
The reinforced-concrete lining upstream of the axis
of the impervious core was designed to withstand ex-
ternal hydrostatic head due to reservoir water surface
at elevation 1,590 feet. The section reinforcement was
designed to withstand the entire internal pressure,
with the hydraulic gradeline at the same elevation. An
overstress of 25% was allowed for transient overpres-
sure loading. A nominal lining thickness of 18 inches
was used for most of the tunnel.
Outlet Works Delivery Facility. The delivery fa-
cility is located adjacent to and below the left abut-
ment and delivers water to MWD's Ferris control
facility (Figure 287).
The delivery facility consists of a 12-foot - 6-inch-
diameter steel conduit extending from the west portal
of the outlet works tunnel to a 12-foot - 6-inch-inside-
diameter (ID) service outlet manifold, a service outlet
manifold, three branch lines extending from the mani-
349
Figure 285. Outlet Works — Plan and Profile
350
1
Figure 286. Outlet Worb Tower
351
Figure 287. Outlet Works Delivery Facilitiej
352
fold, and a terminus release gate. The conduit, mani-
fold, and branch lines are all concrete-encased with
the approximate length of conduit and manifold 353
and 141 feet, respectively. The appro.ximate overall
lengths of the 4-foot - 6-inch ID branch line and the
6-foot - 6-inch ID branch line are approximately 110
and 88 feet, respectively, measured from the center-
line of the service outlet manifold. Each of these lines
near the downstream end is equipped with a butterfly
valve. The two valves are located in a single valve vault
and are accessible through hatch covers. The valves
are operated in the fully open or fully closed position
only and thus are not used to regulate flow. Regula-
tion is accomplished by the MWD control facility.
The third branch line, a provision for future expan-
sion, has a 7-foot - 6-inch ID and terminates with a
dished bulkhead.
A blowoff structure was provided at the service
manifold terminus to permit emergency evacuation of
the Lake. The original design involved a spherical
head at the outlet manifold terminus. To remove the
head with the pipe full of water would require the use
of explosives. Subsequent to the construction period,
this evacuation concept was reconsidered and a 6-foot
by 12-foot slide gate was provided to increase the flexi-
bility of the system. The maximum discharge through
the slide gate is approximately 3,800 cfs. A bolted bulk-
head is installed downstream of the gate to ensure that
large releases cannot be made inadvertently and to
allow for exercising the gate.
To avoid differential settlement, the conduit and
manifold were designed to be supported on sound
rock. Bedrock of an irregular nature was overexcavat-
ed and backfilled with concrete.
The 6-foot - 6-inch branch line has a capacity of 325
cfs, and the 4-foot - 6-inch line has a capacity of 175 cfs.
The additional stubbed-off branch line provides for a
total ultimate capacity of 1,000 cfs.
The 12-foot - 6-inch conduit provides a velocity of
approximately 8 feet per second (fps) at a discharge
of 1,000 cfs. The conduit also provides for a maximum
release of 3,800 cfs at 31 fps through the slide gate at
reservoir water surface elevation 1,588 feet.
Although the tunnel liner and the delivery facility
conduits are encased in concrete, the total internal
pressure is resisted by the steel conduit. Allowable
stress for the maximum load case is 25,000 psi. Max-
imum internal pressure occurs with hydraulic grade-
line at elevation 1,590 feet, plus 25% of the total static
I head for transient overpressure. Welded joint effi-
I ciency was considered to be 100% and all joints were
I required to be radiographed. The required minimum
i 28-day strength of the concrete was 3,000 psi.
Delivery Facility Mechanical Installation. One
78-inch-diameter and one 54-inch-diameter valve are
located in branch conduits near the interface with
'• facilities of the water contractor (MWD). The valves
; are housed in a common vault. Each valve is metal-
seated with a hydraulic cylinder operator and a com-
mon hydraulic control system. Each delivery facility
valve was designed for a working water pressure of 50
psi and to withstand a 50-psi differential water pres-
sure across the closed valve disc from both the up-
stream and downstream direction.
Each delivery butterfly valve was designed to with-
stand opening and closing under the following condi-
tions:
Constant Head Maximum Flow Maximum Flow
\ alve Upstream of During Opening During Closing
Size Valve of Valve of Valve
(inches) (feet) (cfs) (cfs)
54 100 175 610
78 100 325 1,280
Both valves and their operators primarily were de-
signed for fully open or fully closed operation, but the
valves can be closed under emergency conditions, ei-
ther independently or simultaneously, in approxi-
mately 5 minutes.
The hydraulic control system was designed for an
operating pressure of 2,000 psi and, in order to mini-
mize the cycle time for the oil pumps, a bladder-type
hydropneumatic accumulator is used to maintain
pressure on the system to keep the valves fully open.
Since Perris Dam is located in an active seismic
area, a seismic acceleration of 0.5g was used in the
design of the valves and their appurtenances.
One large dewatering and two small drainage
pumps are located in a pump-house structure adjacent
to the main outlet works conduit. All three pumps are
complete with automatic controls, discharge lines, and
appurtenances. The dewatering pump is used for
dewatering the main outlet works conduit, and the
drainage pumps are used to remove any extraneous
water from the valve vault.
The dewatering pump is a vertical-shaft single-suc-
tion type with a rated capacity of 500 gallons per
minute (gpm) at a total head of 30 feet. The drainage
pumps are the submersible type with a rated capacity
of 10 gpm, each at a rated head of 40 feet.
The outlet works release facility slide gate is located
downstream of the delivery branches at the end of the
delivery conduit. The gate provides a waterway 6 feet
by 10 feet. The gate leaf is cast steel, 7.25 feet wide by
12.5 feet high, and weighs approximately 20,000
pounds.
The gate is operated by a hydraulic cylinder located
on the concrete structure above the gate.
Preliminary design considered two gate-leaf alter-
natives: (1) a welded-steel gate, and (2) the cast-steel
gate which finally was selected. Historically, high-
pressure slide gates of this type have been cast. The
basic configuration lends itself to sound casting prac-
tices and was found to be less expensive due to the
extensive weldments in the alternative design.
A hydraulic operator is provided for opening and
closing the slide gate. The hydraulic system consists of
a hydraulic cylinder and piston rod, pumps, ac-
353
Figure 288. Spillway — Plan, Profile, and Sections
354
cumulators, and a control cabinet. The cylinder has a
31-inch bore and 146.5-inch stroke. The operator was
designed to open the gate under an unbalanced head
of 92 feet. The system operates at 1,500 psi and utilizes
two pumps to obtain an opening and closing rate of
approximately 1 foot per minute. If electrical power to
the system is interrupted and emergency operation of
the system is required, one pump is designed to re-
ceive power from the emergency engine-generator set
and operate the hydraulic system. Two oil accumula-
tors precharged with nitrogen are connected to the
system to provide holding capacity in the up position.
The system was designed for local-manual operation
for opening and closing cycles.
The outlet works control room, located in the joint
control building, contains facilities for controlling
and monitoring contract water deliveries to MWD.
Southern California Edison Company supplies 480-
volt 3-phase power to the building which is located in
close proximity to the delivery facility. The control
room houses:
1. Controls for operating the tower and delivery
butterfly valves.
2. Position indicators for MWD butterfly delivery
valves and department valves.
3. Reservoir and tower water surface elevation in-
dicators.
4. Venturi metering readout equipment.
5. Emergency power supply.
Spillway
Description. The spillway is located beyond the
right dam abutment (Figure 288). It consists of an
8 50- foot-long, unlined, trapezoidal, approach channel
22 feet wide; a reinforced-concrete control structure;
a concrete baffled chute; a short section of riprapped
channel; and an unlined channel terminating far
enough downstream to eliminate erosion adjacent to
the toe of the Dam. The spillway crest elevation is
1,590 feet, a nominal 2 feet above the maximum oper-
ating water surface to prevent it from being over-
topped by waves. The crest length is 16 feet. When the
lake level was raised 10 feet, as discussed earlier in this
chapter, no major changes were made in the channel
or concrete structure, except for being moved vertical-
ly to accommodate the revised pool level and horizon-
tally to best suit the topography.
Hydraulics. The spillway was designed for emer-
gency use only because the probability of spilling is
extremely remote. Normally, the reservoir will be
drawn down during the winter season sufficiently so
that the maximum probable flood volume (8,340 acre-
feet) can be stored without spilling.
If the reservoir is full at the time of a flood, releases
can be made to MWD through the outlet works. The
sizing of the spillway was based on the requirement
that a sustained inflow from the Santa Ana Valley
Pipeline of 560 cfs can be discharged without excessive
encroachment on the embankment freeboard. This
discharge is greater than the routed outflow resulting
from an occurrence of the maximum probable flood
with full reservoir. The spillway rating curve is
shown on Figure 289.
y-
/
/
/
/ ^CR
■ST
10 200 300 400 500
DISCHARGE IN CUBIC FEET PER SECOND
Figure 289. Spillway Rating Curve
355
Construction
Contract Administration
General information about the major contracts
relating to Perris Dam is shown in Table 38. Perris
Dam and its appurtenant structures were constructed
under two main contracts.
The zoned earth embankment, spillway, and outlet
works approach channel were constructed under the
first contract (Specification No. 70-25). Most of the
cost increase shown in Table 38 for this first contract
resulted from the decision to increase the reservoir
capacity to 120,000 acre-feet as described earlier in this
chapter.
The inlet works and outlet works were constructed
under the second contract (Specification No. 71-11).
Dam Foundation
Excavation. Four 6-foot-deep trenches were ex-
cavated approximately along the centerline of the
Zone 1 embankment at Stations 25 + 00, 40 + 00,
88 + 00, and 105 + 00 to determine if low-density
materials or other objectionable materials occurred
within the designated excavation limits. Samples were
taken from these pits to determine in-place densities
and moisture contents and for relative compaction
tests. By this process, it was determined that a mini-
mum depth of excavation of I foot for the impervious
reservoir blanket upstream of the Dam, 3 feet for Zone
2 embankment, and 6 feet for Zone I embankment
would be necessary.
Excavation began in the blanket area near the right
abutment. The first materials excavated were stock-
piled in mandatory waste area No. I for later use in
the blanket.
Excavation proceeded generally in a southerly di-
rection from the right abutment toward the left, with
the excavated materials used directly for construction
of the reservoir blanket and Zone 2. During these
operations, the waste strip was constructed at the
downstream dam toe, as called for on the plans.
A trench was excavated along the center of the Zone
1 foundation, primarily for further exploratory pur-
poses. This trench extended below the general Zone
1 foundation elevation, had a bottom width of 1 5 feet,
and had a minimum depth of 10 feet, except where
rock was encountered. At Station 90 + 00, sand lenses
were encountered, and the depth of the trench was
increased to 25 feet. Between Stations 24 + 00 and
27 + 00, an ancient streambed consisting of permeable
clean sand was encountered and the trench was deep-
ened about 20 feet. This trench, backfilled with Zone
1 material, forms a partial cutoff beneath the Dam.
During the geologic exploration for Perris Dam,
three 40-foot-deep trenches were excavated by drag-
line beneath the dam foundation and later filled with
loose material. These had to be reexcavated, and the
material was replaced with compacted Zone 2 materi-
al.
The left abutment, which is on a granitic rock for-
mation, required shaping and grouting. About 70,000
cubic yards of solid rock was excavated between Sta-
tion 120 + 00 and the extreme left end of the Dam.
Drilling and blasting were required for foundation
excavation. Material removed beyond Station 122+00
was hauled from the embankment foundation to man-
datory waste area No. 2. Rock excavation beyond Sta-
tion 122 + 00 extended as much as 40 feet below
original ground. Most of the excavation was required
for shaping the foundation surface of the impervious
Zone 1.
A small volume of rock also was excavated along the
downstream toe of the dam embankment in the vicin-
ity of Station 64 + 00. After it was decided to increase
the reservoir capacity, it was determined that further
rock excavation would not be necessary in this loca-
tion.
Grouting. The grouting plan for Perris Dam con-
sisted of a single line of curtain grout holes on an
alignment starting 260 feet upstream of Station
120 + 00 and extending approximately 750 feet to the
crest of the Dam at the left abutment. Due to the
steeply dipping joints in the bedrock, the holes were
drilled at an angle of 60 degrees from the horizontal.
At Station 127+00, the curtain alignment angled to
the east and extended up the rock face of the left abut-
ment foundation to elevation 1,600 feet. Split-spacing
TABLE 38. Major Contracts — Perris Dam
Perris Dam and
Lake Perris
Perris Dam Inlet
and Outlet Works
Completion of Perris
Dam and Lake Perris
Completion Contract
No. 2
Specification
Low bid amount
Final contract cost
Total cost-change orders
Starting date
Completion date
Prime contractor
70-25
$27,394,995
231,362,749
222,537,778'
10/10/70
11/15/72
Perris Dam Con-
structors
71-11
26,974,810
27,197,504
2176,919
10/13/71
10/6/73
Perris Dam Con-
structors
73-01
$2,051,552
22,608,6372
2260,847
3/29/73
2/1/74
Perris Dam Con-
74-39
2231,169
2254,000 (Est.)
9/5/74
12/74 (Est.)
Jesse Hubbs & Sons
' Reflects bid-price adjustments.
' Includes 32,260,925 (or recreational facilitic
* As of November 1974.
356
Figure 290. Location of Borrow Areas and Perris Dam Site
357
grouting techniques were used, and the final hole
spacing was 10 feet. A grout cap was not employed,
and the amount of grout injected was very small be-
cause of the tightness of the rock. Most of the grout
take was due to shallow fissures in Zone 1 foundation;
however, two intervals of high take were encountered
at Station 120 + 00 and from Stations 124 + 80 to
125 + 60. It was estimated that 8,600 cubic feet of grout
would be needed, but only 1,429 cubic feet were actu-
ally required.
Along the extreme left abutment, a rather deep fis-
sure was encountered in the rock extending up the
abutment to the full height of the embankment. This
fissure contained broken rock and rubble that would
have allowed the passage of surface water from the
slopes above the left abutment down through the rock
drain materials into the dam foundation. To prevent
this, a concrete plug was placed against the rock con-
tact line in the fissure at approximate elevation 1,595
feet, and a gunited surface ditch was constructed
across the crest of the Dam at the extreme left abut-
ment.
Handling of Borrow Materials
Clay Borrow Area. To obtain the estimated
8,670,000 cubic yards of Zone 1 material required for
the Dam as originally designed, an excavation pattern
was established having a maximum excavated depth of
about 40 feet with provisions for draining the entire
area. By contract change order, the estimated amount
of required Zone 1 material was reduced to 4,690,000
cubic yards. Because the original surface area of the
site available to the contractor was not changed, the
required depth of excavation was reduced drastically.
The clay borrow area (Figure 290) was located in
a lake area subject to inundation during periods of
heavy rainfall, but rainfall during the construction
period was small and did not interfere with borrow
operations. Advance moisture conditioning, when
necessary, was accomplished by a sprinkler system.
Clay borrow was excavated with a tractor-mounted
l)elt loader (Figure 291) and hauled directly to the
Dam using 100- to 150-ton-capacity bottom-dump
Figure 292
n Lake Borrow Area
Figure 291. Excavation in Clay Borrow An
trucks. Due to the presence of material in the clay
borrow area which contained excessive amounts of silt
and sand unsuitable for Zone 1 embankment, the final
configuration of this borrow area was somewhat ir-
regular in shape. It was shaped, however, to drain
with maximum slopes of 10:1. Topsoil material was
stripped from the borrow, stockpiled around the outer
perimeter, and replaced on the excavated surfaces af-
ter completion of construction.
Lake Borrow Area. Two alternative lake borrow
plans (within the reservoir area) were included in the
contract specifications and each required separate
bids. One alternative utilized a simple geometric pat-
tern for excavation in the reservoir close to the Dam
and the other required a more complex excavation
configuration for the recreation development along
the north reservoir margin. Although the borrow as-
sociated with the recreation plan was bid slightly
higher, the amount was well within the facility alloca-
tion and therefore the contract was awarded on the
basis of that alternative.
Zone 2 material was obtained from the lake borrow
area which extends along the northerly shoreline a
distance of approximately 4 miles. The shoreline was
excavated in a series of coves and fingers of land to
provide maximum potential for recreation. Excava-
tion was accomplished with the same type of equif)-
ment as was used in the clay borrow area (Figure
292).
The original contract provided for stripping of all
vegetative matter from the borrow area and placing it
upon the fingers of land which were mandatory waste
areas. No provisions were made for ultimate develop-
ment of these waste areas, and the strippings as placed
did not bring them above the originally contemplated
high water line. When the reservoir capacity was in-
creased from 100,000 to 120,000 acre-feet, provisions
were made to relocate this shoreline to conform to the
corresponding higher water surface. At the request of
the Department of Parks and Recreation, sufficient
material was excavated from the lake borrow area to
358
J
Figure 293. Rock Productic
place the mandatory waste areas above the normal
lake level and provide for maximum recreational use.
The embankment drain system consists of 1.3 mil-
lion cubic yards of coarse material (Zone 4) of 6-inch
maximum size and 1.5 million cubic yards of transi-
tion material (Zone 3) of I'/j-inch maximum size. Ap-
proximately 240,000 cubic yards of riprap was used for
slope protection, upstream and downstream. All of
the above materials, with the exception of approxi-
mately 14,000 cubic yards of Zone 3 material, were
obtained from the designated rock source located up-
stream of the left abutment of the Dam.
The rock source was laid out on benched faces ex-
tending from a maximum elevation of approximately
2,070 feet to the lowest level at approximate elevation
1,665 feet. The height of the faces varied from 50 feet
to 30 feet. The rock was blasted from the quarry and
hauled to the nearby rock-crushing plant located east
of the quarry (Figure 293).
Initially, an excessive amount of fines were pro-
duced, due mainly to overburden contamination and
excessive blasting. Plant operations were revised to
separate these fines.
Coordination of the placement of Zones 1 and 2
with Zones 3 and 4 initially was deficient because the
loading and hauling equipment used was capable of
placing Zone 1 and 2 material faster than the rock-
crushing plant could produce the material for Zones
3 and 4. This lack of coordination resulted in nonuni-
form elevations of the various embankment zones
transverse to the dam axis. In an attempt to reestablish
uniform zone elevations, the contractor ceased place-
ment of Zones 1 and 2 and purchased supplemental
Zone 3 material from an alternate source. However,
only 14,000 cubic yards of supplemental Zone 3
material was placed before heavy rains caused that
effort to be terminated.
The quarry and crusher plant operations were later
revamped, and the rate of production of Zone 3 and 4
material increased sufficiently to permit the zone ele-
vations to be regained, and the embankment construc-
tion proceeded to completion.
Embankment Construction
The Dam was constructed in a series of three
reaches. Embankment construction began at the low-
est point along the foundation in the vicinity of Sta-
tion 85-f 00. When the grouting was completed at the
left abutment, efforts were concentrated in that area.
Embankment construction then proceeded with a
slight slope toward the north to enable loaded trucks
to climb to the higher area where embankment was
being placed. General embankment construction ac-
tivity is shown on Figure 294.
The upstream face of the Dam from the crest down
to elevation 1,540 feet was faced with a layer of riprap
10 feet in horizontal width underlain by a layer of
Zone 4 bedding material 12 feet in horizontal width.
Riprap and bedding were placed continuously as the
other embankment zones were placed. To reduce con-
gestion, ramps were constructed down the upstream
face of the Dam for use by empty trucks. These ramps
consisted of Zone 4 material placed upon the riprap
blanket and overlain with Zone 3 material. Zone 3
material was removed upon completion of each sec-
tion but Zone 4 material was allowed to remain. A
layer of riprap also was placed along the downstream
toe of the Dam above the toe drain.
A layer of topsoil, having a horizontal thickness of
12 feet, was to have been placed on the downstream
face of the Dam above the riprap. It was anticipated
that this material would be stripped from the dam
foundation and stockpiled. Because there was little
vegetative matter in this material, it was used in the
lower layer of the upstream blanket, and no stockpil-
ing was done. Zone 2 material was used in place of
topsoil for the downstream facing.
The original design of the embankment provided
for a layer of blanket material 3 feet thick extending
1,000 feet upstream from the toe of the embankment.
Blanket material was obtained primarily from excava-
tion of the dam foundation and was the first work
undertaken.
When the decision was made to forego any future
Figure 294. Embanltment Construction Activity
359
enlargement of the Dam above crest elevation 1,600
feet, the 8:1 embankment fillet at the upstream toe no
longer was needed for ultimate stability. Elimination
of this fillet would have resulted in movement of the
toe downstream for a considerable distance. By then,
however, the work on the blanket had progressed for
about four months; thus, no change was made and the
blanket was constructed to the original upstream lim-
its. The area between the original and revised up-
stream toes was covered with Zone 2 material for at
least a 3-foot depth.
The initial problem in producing Zone 3 and 4
material for the horizontal drain in sufficient quantity
(previously discussed) created the necessity of con-
structing Zone 1 and 2 material in lifts approximately
3 feet in height and wide enough to allow for place-
ment and compaction. When the horizontal drain was
brought to its maximum required depth, the place-
ment of Zone 1 and 2 material proceeded in a more
efficient manner.
Zone 1 material was placed in layers not exceeding
6 inches in compacted thickness. Compaction was
achieved by 12 passes of a sheepsfoot roller. The initial
12-inch depth of Zone 1 material next to rock founda-
tion was compacted in 4-inch lifts with rubber-tired
rollers. The optimum moisture content of this materi-
al averaged 14% with an average field dry density of
1 14 pounds per cubic foot. The relative compaction
obtained was approximately 98%.
Zone 2 material also was placed in layers and com-
pacted to a 6-inch thickness by four passes of a sheeps-
foot roller, followed by four passes of a pneumatic
roller (Figure 295). The facing and blanket materials
were placed and compacted in the same manner as the
Zone 2 material.
Two test fills were constructed in Zone 2 to deter-
mine the compaction characteristics of the materials
for the zone. One fill was compacted with 75-ton rub-
ber-tired rollers and the other with 50-ton rollers. Av-
erage densities obtained with either roller were
within specification requirements. After a further tri-
al period, the 50-ton rollers continued to prove satis-
Figure 295. Pneumatic Roller or. Eu.bankment Zone 2
factory and they were used throughout construction.
The average compacted dry density of this material
was 125.9 pounds per cubic foot, and the average op-
timum moisture was 11.2%. The relative compaction
averaged 101%.
Zones 3 and 4 comprise the horizontal and vertical
drains. The horizontal drain consists of a lower 3-foot
layer of Zone 3 overlain by a 6-foot layer of Zone 4 and
topped with another 2 '/2-foot layer of Zone 3 material.
The vertical drain has a reverse slope configuration
extending from the upstream end of the horizontal
drain to an elevation approximately 12 feet below the
dam crest (Figure 281). The drain consists of two
12-foot-wide Zone 3 strips enclosing a 12-foot-wide
Zone 4.
Zone 3 was placed in layers not exceeding 18 inches
in compacted thickness with a moisture content not
exceeding 5% by weight. It then was rolled with two
passes of a vibratory roller weighing over 20,000
pounds, operated at a frequency from 1,100 to 1,500
vibrations per minute. Zone 4 was placed in layers not
exceeding 24 inches in compacted thickness and rolled
with one pass of the same roller used for Zone 3.
The riprap was hauled to the site from the quarry
in end-dump trucks. It was dumped directly upon the
slopes and placed in final position with a grader.
The design provided for a longitudinal drain trench
at the downstream toe of the Dam. The rock drain
zones join this toe drain, which consists of a perforat-
ed, concrete, drain pipe 12 inches in diameter en-
veloped with drain rock.
The downstream face of the Dam was hy-
dromulched immediately after construction to pre-
vent surface erosion; however, the stand of grass
obtained by the first winter was insufficient. Fine
material eroded from the embankment was deposited
in both the toe drain material and the drain pipe,
necessitating extensive cleanup. To prevent any re-
currence, major revisions were made along the toe of
the embankment. Layers of Zone 4 and Zone 3, topped
by a paved surface, were placed along the top of the
riprap blanket to intercept surface runoff from the
slope above. Downdrains carry the water over the toe
drain to the original ground beyond. Cleanouts for the
perforate toe-drain pipe are provided by 48-inch ac-
cess wells at 400-foot intervals.
Better erosion protection than originally provided
by the hydromulching process was supplied by apply-
ing straw at the rate of 4 tons per acre and incorporat-
ing it into the soil with a roller.
Instrumentation previously described (Table 37)
was observed from the time of installation to comple-
tion of construction. Operations and maintenance
personnel continue monitoring all instruments. The
accelerometers had to be set at a higher than normal
triggering threshold during completion of embank-
ment construction because construction equipment
set off recording devices.
360
Mandatory Waste Area No. 2
Mandatory waste area No. 2, located upstream from
the left abutment of the Dam, was intended primarily
to provide access to the Perris Dam outlet tower
bridge. After it was determined that there would be
insufficient material wasted in this area to provide the
required access, revisions were made to require mini-
mum limits of the waste area, which then was filled
completely, thus supplementing the waste with
material from the lake borrow area.
Inlet Works
Trench excavation for the inlet pipeline required
blasting in areas between Station 1+20 and Station
14 + 90 (Figure 281). A bulldozer, equipped with a
ripper, and a dragline removed the rock from the exca-
vation. For pipe bedding and backfill, the contractor
was permitted the option of consolidating (by satura-
tion and vibration) imported free-draining material,
consolidating excavated rock after processing for
specified gradation, or compacting excavated semi-im-
pervious alluvial materials. The alluvial material was
used and backfill was compacted with small, self-pro-
pelled, vibrating compactors for the first 6 feet of cov-
er. The remaining backfill was compacted with a
sheepsfoot roller.
Outlet Works
The channel invert was excavated with scrapers on
a level grade for a length of approximately 2,700 feet.
The maximum depth of excavation was 40 feet. Three
feet of Zone 2 blanket material was placed over the
entire excavation surface. Excavated material was
placed in the reservoir blanket area. Only a negligible
amount of rock excavation was necessary.
Two steel girders were set into place with two
cranes after being sandblasted and coated with inor-
ganic zinc silicate at the job site. The bridge deck was
formed, and three gradelines were set to guide the
finishing machine during concrete placement.
The entire tower basin between elevation 1,495 feet
and 1,482 feet was excavated in sound rock by drilling
and blasting. The shattered rock was loaded on dump
trucks with rock beds and hauled to a mandatory
waste area. The 50-foot-diameter tower base was ex-
cavated by drilling and blasting with material being
removed by a crawler crane equipped with a 5-cubic-
yard dragline bucket. Material was loaded and hauled
away as described in previous paragraphs.
The 9-inch holes for the foundation anchor bars
were drilled, holes were filled with grout, and No. 18
anchor bars were vibrated into place with a form vi-
brator. Concrete for the tower base then was placed.
The interior form for the tower barrel was erected
to full height with the aid of an interior scaffold. The
interior form consisted of a double thickness of ply-
wood backed by wooden strongbacks and metal wal-
ers. After the reinforcement steel was erected, port
thimbles and valves were securely set in place. The
Figure 296. Tower Concrete Placement
thimbles were supported on pipes set in the previous
concrete lift of the barrel.
The exterior forms, comprised of a metal shell with
Finn forms attached, permitted placements of con-
crete in 16- and 17-foot lifts (Figure 296). Six lifts
were cast (excluding the base and the tower deck)
using 1 '/2-inch maximum size aggregate concrete ex-
cept around the thimbles where %-inch aggregate was
used.
Forms for the last 5 feet of the tower barrel and the
tower deck were prefabricated in the contractor's yard
and set on the tower using a crawler crane.
Concrete for the intake tower and other structures
was produced in a 150-cubic-yard-per-hour-capacity
batch plant located near the outlet works. Aggregates
were obtained from a commercial source in Riverside.
Concrete was moved to the work site in 7-cubic-yard
transporters. Water used to cure the concrete was ap-
plied by a sprinkling system.
Most of the outlet works tunnel was driven through
hard, fresh, granitic rock, but some weathered and
fractured rock was encountered in the vicinity of the
portals. The tunnel was unsupported except for a few
steel sets at each portal and a few rock bolts at several
places in the tunnel (Figure 297). Ground water did
not constitute any problem and only minor seepage
was encountered.
After holing through, about five weeks were re-
quired to remove protruding ribs of rock within the
tunnel excavation control line. A concrete subinvert
was placed tangent to the control line to facilitate the
setting of steel-liner sections and concrete-lining
forms.
The 40-foot-long steel-liner sections of '/2-inch plate
361
^^■\'i>.
ir. "'T^3iiB|
^^Y^^^^^SBu^H
^
y '^BSikif^^^^^^^^^^^l
!>
1 ^^^^^S/Jg^^^^^^^^^^^^t
Figure 297. Tower Outlet Portal
Figure 298. Outlet Works Delivery Manifold
V
^
^^
^
|Mi«m
^^
ff
^m
Figure 299. Concrete Plocement in Spillway
were longitudinally placed and seam-welded. A con-
crete pump was used to place the concrete backfill. A
wire-mesh bulkhead was placed at the end of each
section to contain the concrete. All tunnel concrete
was mixed at the on-site batch plant.
Tunnel grouting consisted of contact grouting
throughout with additional skin grouting next to the
steel liner. Grout was mixed outside of the tunnel.
After mixing, the grout was pumped to a hopper in-
side the tunnel where it was remixed. From the remix
hopper, the grout was pumped into the grout lines.
Skin grouting was accomplished through '/2-inch
holes drilled in the steel liner. These holes were
plugged and welded upon completion of grouting.
Due to exceptionally good rock, no consolidation
grouting was necessary. Grout curtains were located
at Station 36+55 and Station 36+70.
Outlet Works Delivery Facility
The construction of this facility and associated ap-
purtenances was performed in conjunction with other
outlet works construction (Figure 298). No unusual
construction methods were employed and no difficul-
ties were encountered.
Spillway
Excavation for the spillway was made initially with
a crawler crane equipped with a 5-cubic-yard dragline
bucket and later with a small scraper. As excavation
progressed, it became apparent that the original loca-
tion of the foundation for the concrete-slab crest struc-
ture would be unsatisfactory. The crest structure was
relocated 100 feet upstream where sound rock had
been encountered. Approximately 100 cubic yards of
concrete was placed in the spillway chute and weir
(Figure 299).
Clearing and Grubbing
Clearing and grubbing consisted of the removal of
all trees, concrete, and other debris in the contract
area, as well as the removal of all vegetation over 1 foot
in height within the lake area. Because of the concern
for Russian thistle control, the reservoir area below
elevation 1,578 feet had to be kept continually clear of
all vegetation over 1 foot in height during the entire
construction period.
Tumbleweed control in the entire project area was
necessary to adhere to provisions of the California
Agricultural Code. Tumbleweeds were cut and wind-
rowed. Spring tooth harrows then were pulled
through the windrows. Burning the tumbleweeds
before harrowing yielded excellent results.
In addition to the work required within the reser-
voir area, a house, garage, and passive radio-repeater
station within the project area were removed. All
trees, broken concrete, rubble, and other debris with-
in the reservoir area were buried in a pit located 3,200
feet upstream from the Dam. The major portion of the
initial clearing and grubbing was completed in No-
vember 1970.
362
o
v:
5/ oso
PUMPING
PLANT-
■ TEHACHAPI AFTERBAY
COTTONWOOD
POWERPLANT
OUAIL
CANAL
eCNCRAL
(location
GORMAN
, OUAIL
±AKE.
PEACE VALLEY
PIPELINE-
:o
PYRAMID
LAKE
PYRAMID^
DAM
I
PYRAMID
POWERPLANT
CASTA IC
CREEK
ELIZABETH LAKE
CANYON CREEK-
KcASTAIC
POWERPLANT
ANGELES
; TUNNEL
\ELDERBERRY-
FORE BAY
m
CASTAICI
LAKE
HUGHES ROAD
CASTAX
LAKE
CASTAIC
CASTA fC DAM
LAGOON
SOUTHERN
PACIFIC R.R
Figure 300. Location Mop — Pyramid Dam and Lai<e
364
CHAPTER XIV. PYRAMID DAM AND LAKE
General
Description and Location
Pyramid Dam is a 6,860,000-cubic-yard earth and
rockfill embankment with a height of 400 feet and a
crest length of 1,090 feet.
The spillway for Pyramid Lake is located on the
right abutment of the Dam in a deep excavation that
furnished much of the rockfill for the embankment.
The spillway is comprised of two elements: a con-
trolled or gated spillway and an emergency spillway.
The controlled spillway consists of an unlined ap-
proach channel, gated headworks, and lined chute.
The emergency spillway consists of a 365-foot-long,
concrete, overpour section with its crest set 1 foot
above normal maximum storage level, discharging
into an unlined chute.
There are two outlets from the Lake. The 30-foot-
diameter 37,775-foot-long Angeles Tunnel starts in
the left abutment just upstream of the toe of the Dam.
This tunnel conveys generating flows to, and pump-
ing flows from, Castaic Powerplant. Tunnel features
at the Dam are the submerged intake and the emer-
gency closure gate located in a vertical shaft excavated
in the abutment 600 feet upstream of the dam crest.
The capacities of the Tunnel are 18,400 cubic feet per
second (cfs) generating and 17,300 cfs pumping. The
other outlet is the stream release facility which con-
sists of valving in the former diversion tunnel. The
capacity of this outlet, with water surface elevation
2,500Teet, is 1,000 cfs.
Figure 301. Aerial View — Pyramid Dam and Lake
365
Figure 302. Dam Site Plan
366
The Lake inundates the lower part of three embank-
ments on Interstate Highway 5. Culverts under the
embankments had to be reinforced and extended, and
ballast fills had to be constructed to counteract the
effects of saturation caused by the Lake. The required
excavations and embankments were designed so they
could accommodate recreation developments.
A statistical summary of Pyramid Dam and Lake is
shown in Table 39. Figure 300 is the location map,
Figure 301 an aerial view of the Dam, and Figure 302
the Dam site plan. The area-capacity curves are shown
on Figure 303.
Pyramid Dam and Lake are located on Piru Creek
near Pyramid Rock in a narrow gorge which was tra-
versed by abandoned U. S. Highway 99, approximate-
ly 14 miles north of the town of Castaic (Figure 300).
The nearest major highway is Interstate 5, which
crosses the two easterly arms of the Lake.
Purpose
Pyramid Dam and Lake comprise an essential fea-
ture of the West Branch of the California Aqueduct.
They provide (1 ) en route regulatory storage for Cas-
taic (pumped-storage) Powerplant, (2) an afterbay
for Pyramid Powerplant to be operational about 1982,
(3) regulatory storage for a possible future pumped-
storage plant in the Piru Creek arm, (4) emergency
storage for water deliveries from the West Branch, (5)
recreational opportunities, and (6) incidental flood
protection.
Chronology and Alternative Dam Considerations
Studies for routing project water via Piru Creek
were started by the Department of Water Resources
in 1953. In December 1959, Department Bulletin No.
79 recommended that a reservoir, located approxi-
mately at the Pyramid site, be sized to impound 56,000
acre-feet. In 1960, the Department signed a contract
for the delivery of project water from the West Branch
to three contracting agencies. Two years later, it was
determined that the West Branch should have delivery
and storage capacities as large as economically feasi-
ble. Subsequent studies in 1964-65 concluded that the
TABLE 39. Stotistical Summary of Pyramid Dam and Lake
PYRAMID DAM
Type: Zoned earth and rockfill
Crest elevation
Crest width
Crest length
Streambed elevation at dam axis
Lowest foundation elevation
Structural height above foundation
Embankment volume 6,8
Freeboard above spillway crest
Freeboard, maximum operating surface
Freeboard, maximum probable flood
2,606 feet
35 feet
1,090 feet
2,224 feet
2,206 feet
400 feet
50,000 cubic yards
27 feet
28 feet
4 feet
PYRAMID LAKE
Storage at spillway crest elevation 171,196 acre-feet
Maximum operating storage 169,902 acre-feet
Minimum operating storage 4,798 acre-feet
Dead pool storage 4,798 acre-feet
Maximum operating surface elevation 2,578 feet
Minimum operating surface elevation 2,340 feet
Dead pool surface elevation 2,340 feet
Shoreline, spillway crest elevation 21 miles
Surface area, spillway crest elevation _ 1,297 acres
Surface area, maximum operating elevation., 1,291 acres
Surface area, minimum operating elevation.. 176 acres
SPILLWAY
Emergency: Ungated ogee crest with unlined channel
Crest elevation 2,579 feet
Crest length 375 feet
Flood control: Gated broad crest with lined channel and flip bucket —
one radial gate 40 feet wide by 31 feet high
Top elevation of gate 2,579 feet
Sill elevation 2,548 feet
Sill width 40 feet
Combined spillways: Gate open
Maximum probable flood inflow.. 180,000 cubic feet per second
Peak routed outflow 1 50,000 cubic feet per second
Maximum surface elevation 2,602 feet
Standard project flood inflow 69,000 cubic feet per second
Peak routed outflow 52,300 cubic feet per second
Maximum surface elevation 2,596.7 feet
INLET
Improved Gorman Creek (interim)
Design flow 850 cubic feet per second
Pyramid Powerplant (future)
Maximum generating flow 3,128 cubic feet per second
INLET-OUTLET
Angeles Tunnel: A 30-foot-diameter lined tunnel to Castaic Power-
plant — uncontrolled inlet tower — upstream shutofF, 25-foot by 32-
foot coaster gate
Maximum generating release 18,400 cubic feet per second
Pumping capacity... 17,300 cubic feet per second
OUTLET WORKS
Stream release: 15-foot-diameter lined tunnel under the right
abutment with valve chamber at midpoint — intake, uncontrolled
tower with steel plug emergency bulkhead — control, series of
rated valves in conduits through tunnel plug — discharge from
fixed-cone dispersion valves into tunnel downstream of valve
chamber
Capacity, stream maintenance 1,000 cubic feet per second
Capacity, reservoir drainage 3,200 cubic feet per second
367
VWTER SUWFACE AREA M ACNES
2600
Z 2400
S
2300
2200
IS
00
1600
1400
N.W
N
5
1 '<yg 1 *i
Eltv. 257S
M 1
n
6QQ 4» 2no 1
s
K
^
,^
X'
^
^
N
^
k
/
/
/
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\^
A
/
\
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/
Min. W. S. El*»^34n
V
\
V
'
\
20
60 SO 100 120 140
CAPACITY IN THOUSANDS OF ACRE-FEET
Figure 303. Area-Capacity Curves
160
aoo
maximum, feasible, operating, water elevation at the
Pyramid site was 2,578 feet.
During the preliminary design period, various
types of dams were investigated for this site. These
included concrete gravity, concrete thin arch, con-
crete arch gravity, and earth and rockfill. The con-
crete thin arch had the lowest cost; however, it was
rejected because the thin right abutment ridge ap-
peared inadequate to support a structure of the height
being considered, and spillage during floods would
cause adverse vibrations of the foundation rock. The
earth-rockfill section was chosen over the remaining
alternatives because of lower cost and better resistance
to damage due to earthquake-associated movements.
Construction started in the fall of 1969. Included in
the initial contract were: the diversion tunnel, access
road and bridge, and site development excavation for
Angeles Tunnel intake. This work was identified as
essential in a construction sequence that would allow
initial project deliveries to pass down the West Branch
on schedule. The remaining contracts for the Dam
and other works were deferred for several months
pending resolution of a temporary cash-flow problem
existing at the time.
A subsequent contract for Angeles Tunnel intake
civil work was awarded in September 1970, and the
contract for the Dam and spillway was awarded in
June 1971. The latter contract included provisions for
an interim dam to be constructed to divert project
flows into Angeles Tunnel in October 1971. The in-
terim dam was later incorporated into the upstream
toe of Pyramid Dam.
The dam embankment was topped out in March
1973 and storage commenced that spring. The reser-
voir filled a year later.
Regional Geology and Seismicity
The Dam site is at the southern edge of the Ridge
Basin. The north boundary of the Ridge Basin is
formed by the San Andreas fault, the southwest and
southeast boundaries are formed by the San Gabriel
fault and by nonmarine Pliocene sediments, and the
northeast and east boundaries are formed by granitic
rocks and by a metamorphic complex. Prominent
faults in and near the Ridge Basin are the Liebre and
Clearwater faults in the northern portion of the Basin
and the Bee Canyon and San Francisquito faults to the
east.
In the general region, which includes Pyramid Dam
and Lake, several major earthquakes have been record-
ed. The 1857 Tejon earthquake was estimated to be
among the largest in California history. It is thought
to have had its epicenter on the San Andreas fault in
the Carrizo Plain, approximately 50 miles northwest
of the Dam site. The 1952 Kern County earthquake
had its epicenter on the White Wolf fault, about 25
miles north of the site. Estimates are that it had a
Richter scale intensity of 7 in the dam area. Between
368
1915 and 1965, approximately four other earthquakes
occurred which could have produced an estimated in-
tensity of 6 or greater at the Dam site.
Design
Dam
Description. The zoned earth-rockfill embank-
ment (Figures 304 and 305) consists of a central clay
core with flanking shells of quarried rock. Transition
drain zones are included between the core and shell.
A blanket drain is extended from the transition drain
zones to the toe of the Dam to complete the down-
stream drain system. Random zones were designated
in the downstream shell and in isolated parts of the
upstream shell for quarried rock of lower permeabili-
ty than the remainder of the shell. Thin zones were
included on the faces of the Dam for dumping the
uncompactable plus 30-inch rock. Very durable riprap
available from processing the streambed deposit for
transition drain zones was specified for use within the
anticipated range of normal reservoir fluctuation.
A 90-foot-high interim dam (Figures 306 and 307)
was located at the upstream toe of Pyramid Dam, the
bulk of its mass being included in the upstream shell.
It was a central core structure with a single transition
zone located downstream of the core, a downstream
shell constructed to Pyramid Dam shell zone specifi-
cations, and an upstream shell of semipervious rock-
fill.
Extensive waste areas were designated at the up-
stream toe up to elevation 2,400 feet, and a buttress of
random fill and select spoil was placed on the up-
stream right abutment.
A single-line grout curtain with a maximum depth
of 150 feet was injected into the foundation under the
core. Abutment drainage is provided by two former
exploration adits.
Foundation. The deeply incised gorge through
the Dam site contained Piru Creek and old U.S. High-
way 99. The Highway was abandoned in the summer
of 1970 upon completion of Interstate 5 adjacent to the
area. The overall width occupied by the stream chan-
nel and highway at the Dam site ranged from 200 to
350 feet.
The abutments are narrow, the right abutment be-
ing just thick enough to contain the Dam with the
help of the buttress. Natural abutment slopes along
the axis of the Dam generally were from 1:1 to 2:1 with
some steep cliffs and overhangs and a major highway
cut at 0.4:1. These slopes were flattened by controlled
blasting to 1 : 1 under the core and transitions and 1/4:1
in other areas.
Sands and gravels deposited in the stream channel
ranged up to 25 feet thick, while fills associated with
Highway 99 ranged up to 50 feet thick. Channel and
fill materials were excavated to provide a bedrock
foundation under the embankment.
The rock consists of thin beds of argillite. The beds
strike nearly parallel to the dam axis and dip favorably
upstream at 40 to 50 degrees. Pyramid argillite is inter-
mediate in hardness between shale and slate and is a
unique unit within the Ridge Basin group, being con-
siderably more competent and resistant than the re-
mainder of the group. It has a stratigraphic thickness
of approximately 1,800 feet at the Dam and grades on
three sides into softer, characteristic, ridge basin sedi-
ments. On the fourth side, the argillite grades into
conglomerate sandstone and sedimentary breccia that
is adjacent to the San Gabriel fault zone.
Construction Materials. The impervious core of
Pyramid Dam is clayey shale material found in the
reservoir area 1 mile upstream from the Dam site.
This material is divided into Zones lA and IB. Zone
lA was taken from the lower slopes of the borrow area
and consists of slopewash material that washed down
from the in-place shales above. Slopewash material
was specified for Zone 1 A because it was believed that
the weathered in-place shales used in Zone IB might
not break down fine enough for the tight core desired.
The bulk of the material for the filter and blanket
drain zones was processed from the Piru Creek sand
and gravel deposits in the reservoir area. Zone 2A
(minus '/-inch material) flanks both sides of the core,
acting as the fine half of the transition between the
core and the shells. Zone 2B ('/- to 6-inch material)
was the coarse half of the downstream transition and
also acts as a chimney and blanket drain system for the
downstream shell. An intermediate transition Zone
2D (minus 6-inch material) was added during con-
struction after segregation occurred in Zone 2B. Fine
Zone 3B replaced Zone 2B upstream at that time be-
cause Zone 2D required the stream gravels. Zone 2C
(minus 3-inch streambed material) is the transition in
the interim dam. Zone 3 A is the rockfill shell of fresh
to slightly weathered rock. It is compacted except on
the outer slopes where oversized rock was dumped.
Zone 3B is finer material than 3A and was used both
upstream and downstream in the random zones and as
noted above in the upstream transition between Zones
2A and 3A.
The primary design problem was to determine if
available sources could produce suitable rockfill
materials. This problem at Pyramid Dam was more
complex than usual because there was some question
that the excavated argillite would retain its rockfill
characteristics through chemical changes or other
breakdown processes after it was placed in the em-
bankment. Test quarries, test fills, and special tests
were used to make the determination.
Two rocks were quarried: argillite that would be
representative of the spillway and other required ex-
cavations, and sandstone found 1,000 feet downstream
of the Dam.
After careful examination of both the sandstone and
argillite quarry materials, and after considering the
economies of the various material sources in the re-
369
i Ml
i it
l>l=
I I i
I I
Figure 304. Embankment Sections
370
Figure 305. Embankment Plan
371
Figure 306. Interim Dam — Plan, Sections, and Detoils
372
t
'1U
Figure 307. Interim Dam — Sections and Profile
373
quired excavations, the sandstone was eliminated
from further consideration as a borrow source for the
following reasons; (I) much of the material is poorly
cemented and would easily break down to sand-size
particles upon rolling; (2) separation of the softer
rock from the harder portion would have been dif-
ficult; (3) if the material did become fresher and hard-
er with depth, an excessive amount of material would
be wasted in reaching the better material underneath;
and (4) large amounts of argillite material had to be
removed from mandatory excavations such as the
spillway and core shaping site development, and these
materials were considered suitable for rockfill. There-
fore, the test fills were confined to the argillite. They
were 90 feet by 150 feet in plan. Various lift thick-
nesses were compacted by 5- and 10-ton vibrating roll-
ers. The rock showed favorable characteristics. Design
properties and specification requirements for place-
ment and compaction were obtained.
Special tests used to resolve the question of whether
the rock would break down in the dam embankment
were: (1) standard solubility and wetting-drying tests,
(2) a petrographic analysis, and (3) excavation into a
20-year-old highway fill. The first two tests provided
technical reasons why the rock exposed in the third
test was found to be sound after the surface material
was removed. It was concluded that the surface of the
rock weathers because it is free to relax and crack.
Some weathering is therefore expected on the down-
stream face of the Dam.
Stability Analysis. Embankment stability was
analyzed by the infinite slope, sliding wedge, and
Swedish Slip Circle methods of analysis. The rock
(argillite) foundation is significantly stronger than
the embankment materials. Consequently, the rock
surface is treated as a limiting boundary for failure
planes after a few trial analyses. Material properties
used in the analyses are given in Table 40. These val-
ues were based on the results of a detailed exploration
program, the test quarry and fill previously discussed,
and an extensive soil- and rock-testing program.
Core materials were explored and laboratory-tested
by conventional methods. Special attention was given
to the gradation tests to assure that nonrepresentative
breakdown of the residual soil was avoided in the test-
ing process. Gentle hand-sieving was required.
Sand and gravel explorations and testing were rou-
tine except for handling of shales that were mixed
naturally into the alluvial deposit. The exploration
program did not disclose the true quantity of shales
present. They broke down during processing of the
material during construction and reduced the permea-
bility of the fine transition zones, thus requiring addi-
tional tests and reevaluation of the embankment
design during construction. The lower permeabilities
were determined to be acceptable. Shell materials
from the quarry were tested in large samples at the
Richmond Laboratory discussed under Chapter V of
this volume. These tests provided the design parame-
ters and, as part of the testing program, proved that
much smaller samples would have provided accepta-
ble results.
Seismic forces for the stability analyses were ap-
proximated by a steady horizontal force acting in the
direction of instability. The force was taken as 0.1 5w,
where "w" is the moist or saturated embankment
weight, whichever was applicable. The procedures for
applying the seismic forces to the Swedish Slip Circle
analysis, given in the U. S. Army Corps of Engineers'
design manuals, were modified to expedite a computer
solution, and forces were applied at the center of mass
for each infinitesimal slice rather than at the base.
This conventional earthquake analysis was consid-
ered at the time of the design to be an approximate and
somewhat empirical approach. Consideration was
given to using the then-developing, two-dimensional,
finite element analysis which had been tried on dams
with crest lengths several times longer than their
heights. However, the shortness of the crest and shape
of the canyon made this analysis inapplicable to Pyra-
mid Dam. The 0.1 5g factor provided conservative
slopes, and the following features were included in the
embankment to emphasize earthquake-damage-resist-
ant considerations: providing a plastic core thicker
TABLE 40. Material Design
Parameters-
—Pyramid Dam
Specific
Gravity
Unit Weight in Pounds
Per Cubic Foot
Static Shear Strengths
0 Angles in Degrees
Cohesion in Tons Per Square
Foot
Eff'ective
Total
Construction
Material
Dry
Moist
Saturated
$
C
0
C
e
C
•Rockfill
2.54
2.75
2.54
113
104
115
124
165
135
129
165
40
26
60
I'.b
40
14
60
0"2
1.0
40
12
60
Core
1.2
1.0
* The same parameters were used in transition and drain zones.
374
than would otherwise be necessary, providing addi-
tional freeboard, and compacting the rockfill as much
as possible without adversely affecting the permeabili-
ty-
Settlement. A crest camber of approximately one-
half of 1% of the fill height was provided to compen-
sate for long-term embankment settlement. The
adequacy of the assigned camber was checked with
data, which were analyzed from one-dimensional con-
solidation tests using samples initially compacted to
95% of relative compaction. These samples were con-
solidated under incremental loads without the addi-
tion of moisture until maximum test loads were
reached. Then, they were immersed in water under
maximum test load to induce further consolidation.
Various maximum test loadings were used to simulate
various embankment heights. These procedures veri-
fied that the allowance for camber was reasonable.
Instrumentation. Following is a summary of
structural performance instrumentation initially in-
stalled in the Dam:
Number
Type of Instrument Installed Data Obtained
Piezometers (Hydraulic) 21 * Pore Pressure
Slope-Indicator
Installations 3 Internal Deflection
Internal Settlement
Water Surface Elevation
Embankment Monuments S Surface Settlement
Surface Deflection
Crest Monuments 13 Surface Settlement
Surface Deflection
Drainage, Right Adit Flow Rate
Drainage, Left Adit Flow Rate
Seepage, Access Tunnel Flow Rate
Drainage, Dam Toe Flow Rate
• Four in the foundation and 17 in the embankment
Drainage Adits
Two 9-foot by 7-foot former exploration adits have
been retained and improved to provide drainage of the
abutments. One 900-foot adit is in the right abutment
with portal at elevation 2,450 feet and the other 650-
foot-long adit is in the left abutment with portal at
elevation 2,450 feet (Figure 308). Structural steel sup-
port was used in portals and areas of weak rock, while
the remaining portions of the tunnels were either
rock-bolted or left unsupported. (Construction of the
adits was accomplished by a lump-sum bid contract.)
The structural-steel-supported sections were lined
with reinforced concrete and contact-grouted while
the remaining sections were lined with shotcrete.
Drain holes initially were drilled in all reinforced-
concrete-lined reaches farther than 100 feet from the
portal to protect the concrete. Later, drain holes were
drilled in shotcreted sections to increase the area of
influence of the abutment drainage system. Rings of
four holes, 25 feet in length, were drilled at 20-foot
intervals.
The concrete-lined section is of uniform dimensions
and was designed to resist the worst of the following
loading cases:
1. A rock load of one bore diameter in height.
2. A. rock load of one-half bore diameter in height
plus a hydrostatic head of 25% of the overburden
depth.
3. A uniform grouting pressure of 30 pounds per
square inch.
Dead load is included in all the above loading cases.
Diversion Tunnel
The diversion facility is a 15-foot-diameter con-
crete-lined tunnel approximately 1,350 feet long
through the right abutment ( Figure 309) . This tunnel
was used to divert streamflow during construction of
the Dam and now is used to carry controlled down-
stream releases.
During the flood season of 1972-73, the embank-
ment was required to be above elevation 2,445 feet.
The tunnel was sized to pass the standard project
flood with maximum water surface elevation at 2,441
feet. The inflow of 69,000 cfs would have been reduced
to an outflow of 11,300 cfs. Space requirements for
future stream release facilities also were considered in
sizing the tunnel.
For design, the tunnel was divided into a reach up-
stream and a reach downstream of the grout curtain.
The loading on the concrete lining for the upstream
portion is due to an external hydrostatic head result-
ing from the normal reservoir water surface at eleva-
tion 2,578 feet with tunnel dewatered and dead load.
Loading on the downstream reach is dead load plus
external hydrostatic head to ground surface or 25% of
reservoir head, whichever is greater.
The concrete lining also was checked for internal
pressures to the hydraulic gradeline for maximum di-
version discharge. The internal load was distributed
between hoop reinforcement and the surrounding
rock by equating the deformations.
Intake Tower
The intake to the former diversion tunnel is a 1 19-
foot-high reinforced-concrete tower (Figure 310)
which has an internal diameter of 1 5 feet. The 1 19-foot
height includes an 18-foot-high trashrack. The base of
the tower contains a 30-foot-radius elbow which con-
nects to a 40-foot-long, cut-and-cover, conduit connec-
tion to the tunnel. The elbow and conduit also are 15
feet in diameter. The tower rests on a 10.25-foot-thick
by 70-foot, horizontal, hexagonal, slab base. The tower
and conduit are founded on fresh bedrock.
There were two openings in the tower. The lip of
the upper opening is at elevation 2,340 feet which
provides 100 years of silt storage below this intake.
The reinforced-concrete trashrack frame which ex-
tends above this opening was included in the initial
tower construction. The other 1 5-foot-diameter open-
ing was at the base of the elbow at streambed eleva-
tion.
A
375
Figure 308. Exploration Adits — Section and Details
376
Figure 309. Diversion Tunnel — Plan and Profile
377
Figure 310. Intake Tower
The low-level intake provided for initial diversion
flows. It was blocked when the interim dam was com-
pleted and later plugged with concrete except for two
30-inch-diameter and one 10-inch-diameter temporary
conduits. This allowed water to pond behind the Dam
to elevation 2,293 feet. Stream releases during con-
struction were controlled through the conduits by
sluice gates (30-inch) and a butterfly valve (10-inch).
Floodflows passed over the interim spillway the first
winter of dam construction and through the upper
tower opening the second.
After the second winter, the trashracks were added
and the temporary conduits were plugged. The trash-
rack on the top of the structure can be removed so a
bulkhead can be placed on the intake opening to dewa-
ter the upstream part of the tunnel. Such a bulkhead
was used to provide a dry working area during con-
struction of the stream release facility. The bulkhead
also can be used on the Castaic Dam outlet works
low-level intake.
The intake tower is considered a free-standing
structure and was analyzed for the following loading
cases:
1. Tower submerged and discharging 1,000 cfs
(standard operation).
2. Tower submerged and discharging 11, 300 cfs (di-
version condition).
3. Reservoir at normal water elevation 2,578 feet,
with seismic load.
4. Tower bulkhead closed and empty with external
hydrostatic head to elevation 2,578 feet.
Normal working stresses were applied to Cases 1 and
4. Stresses resulting from Case 2 and 3 loadings were
allowed one-third overstress.
The trashracks were sized to limit the velocities to
2 feet per second during a discharge of 1,000 cfs, and
the trash bars were designed to fail at stresses result-
ing from a differential head of 20 feet through the
trashrack.
Stream Release F'acility
The stream release facility at Pyramid Dam utilizes
the former diversion tunnel as a conduit and releases
all natural reservoir inflows on an equal-rate basis to
a maximum of 1,000 cfs. Inflows above 1,000 cfs are
stored temporarily until reservoir inflows drop below
1,000 cfs. If temporary storage capacity is not suffi-
cient, inflows will be routed through the spillway.
A valve chamber (Figure 311) is located in the di-
version tunnel near its midpoint and contains five
steel conduits: one emergency, 78-inch with a butter-
fly valve; two 42-inch; one 24-inch; and one 12-inch.
Each of the last four conduits is equipped with a fixed-
cone dispersion valve and a shutoff valve. Access to
the chamber is gained through a tunnel from the
downstream portal area.
Pressure flow is maintained in the tunnel from the
intake to a tunnel plug at the upstream end of the
chamber and in the conduits, which extend through
the plug to the valves. The flow from the valve system
discharges into a steel-lined energy-dissipating cham-
ber. From the dissipating chamber, the water flows as
open-channel flow in the tunnel to the downstream
portal. The tunnel is sloped to maintain supercritical
flow.
As a safety measure for the Dam, it is possible to
draw down the reservoir 100 feet below the normal
water surface in approximately 12 days. This can be
accomplished by opening the 78-inch butterfly valve
in the emergency conduit and opening the 40-foot-
wide by 31-foot-high, spillway, radial gate. This re-
sults in a maximum discharge of approximately 3,200
cfs through the butterfly valve, which would operate
during the entire drawdown period, and 20,000 cfs
through the spillway gate, which operates only during
the first 30 feet of drawdown.
The shutoff valves and the 78-inch butterfly valve
are capable of being opened and closed with the reser-
voir at elevation 2,578 feet.
The series of rated fixed-cone dispersion valves is
capable of accurately releasing discharges from near
zero to 1,200 cfs. This system was designed to release
a minimum of 1,000 cfs at water surface elevation
2,500 feet. Rating curves for the outlet works are
shown on Figure 312.
The tunnel plug was designed to resist hydrostatic
loads equivalent to the reservoir at elevation 2,602 feet
(maximum water surface) on the full face, and the
valve anchor block was designed to resist the thrust on
the block from the conduits.
The valve-chamber concrete lining is undrained
and was designed to resist the full external hydrostatic
pressure of the reservoir. The steel conduits through
the valve chamber were designed to resist an internal
hydrostatic pressure equivalent to the reservoir at nor-
378
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Figure 311. Valve Chamber
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Figure 312. Outlet Works Rating Curves
380
Figure 313. Air Shaft
381
mal water surface elevation 2,578 feet and a water-
hammer load of 50% larger head.
The energy-dissipating chamber was designed to
resist external hydrostatic pressure prorated between
100% of full reservoir at the grout curtain at Station
16-f20 (Figure 309) and 25% at the drained down-
stream tunnel reach at Station 17-1-38. Steel plates
anchored to the concrete lining are used to protect the
inside surface of the concrete.
The concrete lining of the valve-chamber access
tunnel and air-supply tunnel was designed to resist an
external hydrostatic head equal to one-half the height
of overburden. The finished dimensions of the access
tunnel are sufficient to allow passage of foot traffic
and small maintenance carts. The air-supply tunnel
(Figure 313) was designed to limit air velocities to 150
feet per second (fps) and the access tunnel was de-
signed to limit the air velocity to 37 fps (25 mph),
assuming the air demand to be two and one-half times
the design valve discharge.
Fixed-Cone Dispersion Valves. Two 36-inch-di-
ameter, one 16-inch-diameter, and one 8-inch-diame-
ter, cylindrical-type, free-discharge, regulating, cone
valves (commonly known either as hollow-cone, Ho-
well-Bunger, or fixed-cone dispersion valves) were in-
stalled to control stream release and downstream
water deliveries. Each valve installation consists of a
valve body, valve gate, operating power screws and
gear units, interconnecting shafting, electric motor-
driven operator, and companion flange.
A centralized lubrication system is provided to lu-
bricate the power screws on ail valves. The system
provides a forced continuous supply of grease to the
valve power screws during valve operation. This sys-
tem has sufficient capacity to lubricate the two 36-
inch-diameter valves if operated simultaneously.
The valves may be operated from the motor control
center in the access tunnel or a hydraulic cabinet in
the valve chamber. The valves also may be controlled
from the Pyramid Dam control building and area con-
trol center at Castaic. Each valve operator is provided
with a handwheel for manual operation.
Design criteria employed was as follows:
1. Valves were designed for a maximum head of 350
feet.
2. All valves were designed to withstand a seismic
load of 0.5g.
3. The 8-inch-diameter valve will operate approxi-
mately 75% of the time at flow rates from 0.5 to
29 cfs.
4. The 16-inch-diameter valve will operate approxi-
mately 20% of the time at flow rates from 21 to
120 cfs.
5. The 36-inch-diameter valves will operate approx-
imately 5% of the time at flow rates from 120 to
600 cfs, each.
Research data obtained from the Oroville river out-
let fixed-cone dispersion valves indicated that flow
through these valves was not increased when valve
openings exceeded 80%. At openings of greater than
80%, the discharge area at the cone exceeded the valve
inlet area and excessive vibrations occurred in the
valve body. As a result of this investigation, design
criteria for the Pyramid valves required that the max-
imum valve stroke be limited to the 80% value.
In order to reduce cavitation effects at small valve
openings, the valve gate seats and downstream edge of
Figure 314. 8-lnch-Diameter Fixed-Cone Dispersion Valve
Figure 315. 36-lnch-Diameter Fixed-Cone Dispersion Valve
382
Figure 316. 42-lnch-Diameter Shutoff Valve
Shutoff Valves and Butterfly Valve — Accumulator System
the deflector cone of the 8-inch- and 16-inch-diameter
valves are overlayed with Stellite since they are in
service most of the time. The deflector cone on the
8-inch valve (Figure 314) is fabricated of stainless
steel. The valve gate seat,and downstream edge of the
deflector cone of the 36-inch-diameter valves (Figure
315) are overlayed with stainless steel.
Flow through the valves is measured by means of
flowmeters installed upstream of the valves.
Valve tests under flow conditions were conducted
after completion of construction. The purpose of the
tests was to measure the performance of the valves in
order to evaluate original design concepts. Measure-
ments and data taken were as follows:
1. Valve vibration
2. Valve displacement
3. Tangential and circumferential strain in the
valve bodies
4. Flow rate through the valves
5. Valve-operator voltage and current measure-
ments
The test results correlated extremely well with the
expected data.
Shutoff Valves. Two 42-inch-diameter, one 24-
inch-diameter, and one 12-inch-diameter, conical,
plug-type, shutoff valves are located in the valve cham-
ber (Figure 316). They serve as guard valves to the
two 36-inch-diameter, one 16-inch-diameter, and one
8-inch-diameter, stream-release, fixed-cone dispersion
valves. Each plug valve is equipped with an oil hy-
draulic-cylinder operator and dual seats for both
opened and closed valve positions.
The valves were designed for a 1 5-pound-per-
square-inch (psi) operating pressure and to open and
close under the following conditions:
\'alve Size Shutoff head Flow rate
(inches) (feet) (cfs)
42 325 870
24 325 184
12 325 42
Each valve-operator hydraulic cylinder was de-
signed to operate with an oil pressure between 1,500
psi minimum to 2,000 psi maximum under the operat-
ing conditions described. However, for normal opera-
tion, the valve control system is required only to
operate the valves under balanced head conditions.
The operating mechanism is designed to be self-lock-
ing so that hydraulic cylinder pressure is not required
to hold the plug in the open or closed positions.
The valve control system incorporates an accumula-
tor bank of sufficient capacity to operate the shutoff
valves in case of power failure (Figure 317).
Each shutoff valve is capable of opening and closing
in three minutes under the maximum flow condition;
however, for normal operation, the control is designed
so that the valve will operate only when its corre-
sponding fixed-cone dispersion valve is closed. The
shutoff valves may be operated from the motor control
center in the access tunnel or the hydraulic cabinet in
the valve chamber. They also can be controlled from
the Pyramid Dam control building.
383
Spillway
The spillway (Figures 3 18, 3 19, and 320) consists of
a depressed concrete-lined channel controlled by a 40-
foot-wide by 31-foot-high radial gate for passing in-
flows through the Lake and a 365-foot-long overpour
weir with crest at 1 foot above the maximum operat-
ing water surface elevation of 2,578 feet, with an un-
lined channel to discharge very large inflows.
Routing the standard project flood through the
spillway reduced the inflow of 69,000 cfs to a 52,300-
cfs release. This flood is expected to occur only once
in 200 years. The maximum probable flood inflow of
180,000 cfs is reduced to a 150,000-cfs release. The
gated passage has the capacity of 20,000 cfs to pass a
flood of 10-year recurrence interval without overtop-
ping the weir.
Freeboard requirements for the Dam during an oc-
currence of the maximum probable flood are as fol-
lows:
1. With releases through the gated passage equaling
inflow, up to the gate capacity, 4 feet above peak
stage.
2. With spillway gate and all outlet works inopera-
ble, 2 feet above peak stage.
Grouting. The embankment grout curtain ex-
tends across the abutment between the Dam and spill-
way, under the controlled channel, and 50 feet under
the overpour weir. All of the grout holes were 50 feet
deep.
Overpour Weir. The overpour weir is a concrete
gravity block with rounded upstream and down-
stream crest edges. This block extends below channel
elevation a sufficient depth for stability.
Stability of the block was checked for all discharges
up to the maximum probable flood peak with an earth-
quake acceleration of 0.2g and reservoir water surface
at elevation 2,579 feet.
Headworks Structure. The headworks structure
(Figure 321) consists of the concrete floor and walls,
gate, bridge, and machinery deck which act as a unit
and were analyzed as such.
This structure is founded on competent rock, and
the sliding factor was not a problem. Therefore, de-
sign was based on a shear friction safety factor of 4 and
an overturning resultant falling within the middle
one-third of the base under normal operating condi-
tions. For seismic loading with the reservoir at flood
stage or the bulkhead gate in place, the resultant was
required to fall within the middle one-half of the base.
The entire foundation slab has underdrains down-
stream of the grout curtain. For design, uplift pressure
was applied over the entire base of the structure with
full head applied at the upstream edge, reducing lin-
early to zero at the downstream end. The headworks
carry the water load and seismic loads transmitted
from the gate to the foundation through prestressed
rods from the trunnion anchorage. The bridge deck
live and dead loads are transmitted axially through the
walls. The foundation slab was designed to transmit
forces on the base of the wall to the underlying rock
for any loading systems on the walls.
Approach Walls. The approach walls to the head-
works structure give a smooth transition into the gate
opening. These walls were placed against cut slopes.
Weep holes were installed in the walls to reduce hy-
drostatic loading and anchor bars were installed to
maintain stability. Wall loading includes hydrostatic
head to elevation 2,578 feet. Weep holes were assumed
50% effective, and the horizontal load is carried by the
anchor bars.
Radial Gate. One 40-foot-wide by 31-foot-wide
gate was installed in the structure. Under regular op-
erating conditions, normal stresses were allowed in
the structural design of the gate and trunnion anchor-
ages. Overstresses were allowed for certain condi-
tions, such as seismic loading and flood conditions
with the gate closed.
Bulkhead Gate. The bulkhead gate consists of sev-
eral noninterchangeable leaves whose size was limited
by the crane lifting capacity. Slots are provided in the
headworks to accept the gate which is used when it
becomes necessary to dewater and then service the
radial gate. Steel bearing and seal plates are provided
in the slots and floor. The design load on the gate
consists of hydrostatic head to elevation 2,578 feet.
Concrete Chute. A concrete chute conveys dis-
charge from the headworks structure to the down-
stream slope of the abutment ridge. Concrete for the
walls and invert slab was placed directly against the
rock, and grouted anchor bars and drains were used
under the entire chute. The chute terminates with a
gravity flip bucket.
Earthquake Criteria
Because Pyramid Dam was constructed in an area of
high seismic activity, particular attention was paid to
the inclusion of seismic loads in design of structures.
In a structural complex, such as a dam and appur-
tenant structures, arrangement is of prime impor-
tance. Situations were avoided where failure of one
component would impair the operation or cause the
failure of another component. Design loads that were
applied to each structure were conservatively scaled as
to the importance of that structure and the conse-
quence of its failure.
Design earthquake accelerations were based on the
San Andreas design earthquake developed by the Con-
sulting Board for Earthquake Analysis. This design
earthquake is applicable to structures on foundations
of alluvium; it can be reduced when dealing with
foundations of more competent material. A reduction
factor was derived assuming 100% of the San Andreas
design earthquake for alluvium foundations and 50%
for foundations of hard rock. A straight-line variation
between design intensity and seismic velocity in the
foundation material was assumed.
384
Figure 318. General Plan of Spillway
385
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386
Figure 319. Spillway Profile
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Figure 320. Spillway Flip Structure During Discharge
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387
Figure 321. Spillway Headworks Structure
388
The structures at Pyramid Dam were founded on a
hard argillite with an in-place modulus of deformation
near 1.5 million psi. To determine the maximum re-
sponse of structures on this foundation, an interpola-
tion was made between the given response of
structures on alluvium and an arbitrary value of that
on rock, with a modulus equal to that of concrete. The
seismic velocity characteristic of the material was used
as the scale of comparison. An earthquake with a mag-
nitude of 60% of San Andreas design earthquake was
chosen as the maximum to be experienced by struc-
tures at this site.
Design earthquake loadings used for specific struc-
tures were as follows:
1. Spillway weir and gated passage — Failure of the
gate passage will not affect the Dam nor result in a
progressive loss of the reservoir. A design earthquake
of 40% of the San Andreas design earthquake was
used.
2. Outlet tunnel intake tower — Failure of this
structure will not result in a loss of water from the
reservoir nor impair the safety of another structure.
Its failure, however, would require draining the reser-
voir for reconstruction; therefore, a design value of
50% of the San Andreas design earthquake was used.
3. Outlet tunnel downstream portal — The same cri-
teria exist for this structure as for the outlet tunnel
intake tower, except that draining the reservoir would
not be required. A design value of 40% of the San
Andreas design earthquake was used.
4. Features inside the outlet tunnel — History has
shown that earthquake damage to tunnels resulting
from vibration alone appears near the portals and lit-
tle or no damage occurs inside. No specific design
criteria were therefore set. Features, however, have an
adequate safety factor applied to static loads.
Concrete and Steel Structures. For structures
having relatively long natural periods of vibration,
various modes of vibration were investigated. The
natural period of each mode was calculated and the
corresponding acceleration from the design earth-
quake was applied. For structures with short natural
periods, less than 0.1 of a second, a uniform accelera-
tion was assumed.
The design assumed that components of earthquake
acceleration occur in all directions and must be con-
sidered acting simultaneously. Vertical accelerations
were taken as approximately two-thirds of horizontal
accelerations. As the components probably will not
maximize at the same instant, full value was used on
one component and a reduced value applied to the
others.
Hydrodynamic Pressures. Hydrodynamic pres-
sures on the face of structures were determined from
Westergaard's formula. These pressures on sub-
merged structures were based on an equivalent cylin-
der of water, modified where appropriate.
Earth Pressures. Earth pressures on structures
due to an earthquake were derived by assuming Cou-
lomb's wedge was accelerated into the structure. A
critical wedge of fill was determined for various val-
ues of lateral acceleration and the angle of internal
friction of material.
Materials and Design Stresses. Temporary stresses
in structure due to design earthquake loads were al-
lowed to approach the yield stress of the material.
Steel used for structural members and concrete rein-
forcement had a relatively high elongation between
yield and ultimate strength to provide a large capacity
for energy absorption.
Electrical Installation
Equipment for remote monitoring and control of
the Pyramid Dam and Lake facilities is located in the
Pyramid control building on the left abutment. Local
controls for the spillway and stream release facility
are located at the spillway and in the valve chamber,
respectively. Normal electrical services are supplied
by a utility company, whereas standby electrical pow-
er is provided by engine-generator sets. One set is in
the control building while the other is on the right
abutment near the spillway.
Interstate 5 Embankments
Description. Parts of three embankments for In-
terstate 5 were inundated by Pyramid Lake (Figure
322). These fills cross Liebre Gulch, West Fork Liebre
Gulch, and an unnamed canyon in the vicinity of the
old highway maintenance station. Stabilization of the
embankments for this condition involved reinforcing
and extending culverts beneath the fills and placing
additional ballast fill and slope-protection material.
The improvements discussed here were designed, and
the construction supervised, by the Department of
Water Resources with review by the California De-
partment of Transportation.
The ballast fills at Liebre Gulch and West Fork
Liebre Gulch consisted of widening the existing high-
way fill berm at elevation 2,600 feet by a minimum
construction width and sloping to the streambed at
4'/4:l. Stability of the fill at the maintenance station
site required raising the berm to elevation 2,620 feet
and increasing its width to a total of 200 feet. The same
fill slope was used here.
The level berms at the top of the ballast fills formed
a portion of the relocation corridor for utility lines
which traversed the lake area.
389
1
Figure 322. Interstate 5 Embankments
390
Shear Strength Properties. Shear strength proper-
ties were determined from saturated, consolidated-un-
drained, triaxial shear tests with pore pressure
measurements. r- j . .
rounaation tmbankment
Landslide Material
Effective Stress
Material
(Fill)
Cohesion (C's), psf
200
200
Angle of internal friction
(9), degrees
30
34
Total Stress
Cohesion (C), psf
500
500
Angle of internal friction
(9), degrees
IS
23
Stability Analyses. Embankment stability was
analyzed by sliding wedge and Swedish Slip Circle
methods for the following cases:
Case I Critical pool elevation, horizontal phreat-
ic line
Case II Pool elevation 2,570 feet, phreatic line at
elevation 2,578 feet
Case III Sudden drawdown from water surface
elevation 2,578 feet to toe of fill
The safety factor of the existing highway fill under
dry conditions was determined first. Ballast fill was
added to return the embankment safety factor to this
value under reservoir conditions described under
Cases I and II. The safety factor under Case III condi-
tions was required to be above unity.
Borrow Areas. Borrow areas for embankment
materials were chosen for ease of access between the
area and fills, to blend best into the existing surround-
ings while enhancing recreation potential, and to help
solve an existing slope instability problem on the
highway.
One borrow area was located on Liebre peninsula,
a finger of land extending westerly between Liebre
Gulch and West Fork Liebre Gulch. This borrow area
was excavated in such a manner as to provide a use
area above normal water surface and a beach slope
into the reservoir. Access berms and recreation areas,
including grading for a boat ramp, also were provided
by the borrow at maintenance station fill. Excavation
for materials for the easterly fill slopes involved flat-
tening the side slope of an unstable existing highway
cut.
Culvert Reinforcement. The concrete arch cul-
verts at Liebre Gulch and West Fork Liebre Gulch,
approximately 16 feet in height and width, previously
had shown signs of higher than expected strains. To
reinforce these culverts to handle the combined loads
of the existing fill (which would be saturated by the
reservoir) and the ballast fill, structural-steel arches of
the culvert shape were placed inside. A gunite lining
was added to fill the voids between the arches and to
provide a smooth inside surface.
The culvert at the maintenance station fill is a cor-
rugated-metal pipe. To reinforce the culvert in
reaches of added load, a smaller corrugated-metal pipe
was placed concentrically inside and the annular
space filled with grout.
As culvert reinforcement reduced the flow areas,
flood hydraulics were investigated. The contribution
to spillway design flood from each drainage area was
determined and routed through the culvert into the
main reservoir. It was found that none of the subreser-
voirs formed behind the fills overtopped the highway
during this event.
Culvert Extensions. Prestressed-concrete cylin-
der pipe with a 12-foot -6-inch inside diameter was
used for the Liebre Gulch and West Fork Liebre
Gulch extensions. Historically, areas around the inlets
and outlets to these culverts have been subject to ex-
tensive landslides. There is a predominant bedding in
the soft sedimentary rock of the area and the land-
slides are largely dip slope. Since saturation by the
reservoir might reactivate the sliding, the inlets and
outlets were located in the safest possible sites with
the primary inlets placed above the streambeds to al-
low for slides and silt accumulation below them.
Thirty-inch-diameter concrete pipe was used to pro-
vide lower secondary inlets to the culverts. The sec-
ondary inlet at Liebre Gulch assured nearly balanced
water levels on both sides of the embankments during
initial filling and balanced water levels during subse-
quent drawdowns. In addition to these functions, the
secondary inlet at West Fork Liebre Gulch conveys
water into and out of the small subreservoir (water
behind the fill) at that site as the primary intake is set
above the maximum operating surface elevation.
391
Construction
Contract Administration
General information about the major contracts for
the construction of Pyramid Dam is shown in Table
41. The principal construction contract, Specification
No. 71-03, included construction of the dam embank-
ment and excavation and concrete construction for
the spillway. Work done under other contracts includ-
ed excavation of the diversion tunnel, excavation of
exploratory adits in each abutment, construction of an
access road and bridge, construction of ballast fills to
stabilize the slopes of Interstate 5 embankments which
were inundated by Pyramid Lake, mechanical and
electrical work required for completion of Pyramid
Dam outlet works, and a seepage weir at the down-
stream toe of Pyramid Dam. Features of the Angeles
Tunnel, which extends from Pyramid Lake to Castaic
Powerplant, also were constructed under other con-
tracts.
Diversion Tunnel
The diversion tunnel was one of several tunnels
constructed for the Department on a lump-sum bid
item. This approach was tried after major overruns
occurred in support system costs on other tunnels.
Safe working conditions were obtained even though
less tunnel support was required.
Excavation. Excavation of the 1,233-foot-long di-
version tunnel was started on January 8, 1970. Excava-
tion was performed by conventional tunneling
methods using a job-built rubber-tired jumbo on
which were mounted one burn drill and four stopers.
This jumbo, which had been used on the Angeles
Tunnel, was modifed to fit into the diversion tunnel
bore. Drilling and blasting operations were started
from the south portal. The jumbo was moved out of
the tunnel after each drilling cycle. Blasted material
was removed by a front-end loader which backed out
of the tunnel and deposited the muck in a temporary
disposal area just outside the portal. Front-end loaders
removed muck from the temporary location and
hauled it to the designated spoil location just east of
the portal. The tunnel was excavated full section to a
nominal 17-foot diameter, except the valve transition
area which was a nominal 21-foot diameter and the
valve chamber, a nominal 33-foot diameter. Few dif-
ficulties were encountered.
Horizontal and vertical survey control for driving
the tunnel was maintained by the use of a laser system.
Limited use was made of steel tunnel supports since
the surrounding rock was competent. Five-inch, wide-
flange, horseshoe-shaped ribs were used at the portal
areas and in a short zone of less competent rock within
the tunnel.
Ventilation for the tunnel during driving was pro-
vided by an in-line fan mounted above the south por-
tal. Air was conducted to the heading by a 40-inch-
diameter fan line salvaged from the Angeles Tunnel.
The fan line was suspended from the tunnel roof by
short rock bolts.
Concrete. Tunnel concrete placement started at
the upstream portal and was divided into six seg-
ments. Invert and arch placements were made uf>-
stream of the valve chamber, in the chamber, and
downstream of the chamber. Concrete was produced
at the Angeles Tunnel south adit batch plant and
hauled to the job site by transit mix trucks, which
backed into the tunnel to discharge into hoppers. Con-
crete was pumped from the hoppers through a 6-inch-
diameter slickline onto a conveyor belt and then to the
placement where it was vibrated into place.
The 119-foot-high, reinforced-concrete, intake
structure and the reinforced-concrete outlet structure
were founded on bedrock. A total of 3,990 cubic yards
TABLE 41. Major Contracts — Pyramid Dam
Specifi-
cation
Low bid
amount
Final
contract
cost
Total cost-
change
orders
Starting
date
Comple-
tion
date
Prime contractor
Pyramid Dam Adits
Pyramid Dam Initial Facilities..
Pyramid Dam and Lake
Completion of Angeles Tunnel
Intake Works and Pyramid
Dam Outlet Works
Ballast Fills for Interstate 5
Pyramid Lake Gauging Stations.
Completion of Pyramid Dam...
67-30
69-21
71-03
71-10
71-27
73-43
74-40
3239,250
2,498,484
22,036,875
4,552,630
4,222,222
47,216
418,796
?259,018
2,558,028
26,533,214
4,902,094
4,479,582
57,797
460,000
(Est.)
-48,838
760,662
347,981
870,189
1,522
10/18/67
10/13/69
5/26/71
7/ 6/71
1/19/72
11/14/73
9/ 6/74
3/25/68
2/ 8/71
2/ 1/74
4/18/74
7/10/73
6/ 7/74
1/ 6/75
(Est.)
Bill Anderson Co. and Bill An-
derson Co., Inc.
Shea-Kaiser-Lockheed-Healy
Shea-Healy
Wismer & Becker Contracting
Engineers
Kasler Corp., Gordon H. Ball,
Inc., & Robert E. Fulton Co.
Ray N. Bertelson Co., Inc. and
Ray N. Bertelson Co.
392
of concrete was required for these facilities.
Forms for these structures were built in place or as
close as possible to the site in order to minimize han-
dling and transporting. Concrete was placed by using
a mobile crane and a 2-cubic-yard bucket.
Diversion and Care of Stream
In June 1971, Piru Creek was diverted into Pryamid
Dam diversion tunnel through the low-level intake
controlled at that time by one 30-inch slide gate at the
base of the diversion tunnel intake tower. The diver-
sion was accomplished by construction of a 6-foot-
high dike across the stream channel. Dewatering of
the dam foundation was accomplished by the use of
several small pumps situated in low areas. During the
fall of 1971, the interim dam was constructed to eleva-
tion 2,320 feet, and an interim spillway with a crest
elevation of 2,293 feet was cut through the right abut-
ment ridge. The interim dam permitted diversion of
project flows through Angeles Tunnel and natural
streamflow though two low-level, 30-inch, slide gates
in the diversion tunnel intake tower. All natural in-
flows during the 1971-72 runoff season were passed
through the slide gates except those resulting from a
Christmas-week storm. During this storm, a flow of
approximately 300 cfs flowed over the crest of the
interim spillway.
Foundation Preparation
Overburden. Overburden in the foundation area,
comprised of streambed material, old highway fill,
and weathered shale, was excavated with rubber-tired
front-end loaders with 7-cubic-yard buckets assisted
by bulldozers. The material was hauled by dump
trucks and rock wagons. Overburden was disposed of
in the mandatory waste area at the upstream toe of the
Dam, in the buttress fill, and the upstream waste area.
Removal of the highway fill in the downstream area
of the foundation revealed four old highway bridge
bents of reinforced concrete (Figure 323). These were
located in the pervious shell section of the Dam, and
they were left in place as they did not hinder place-
ment or compaction of the embankment.
Shaping. The right abutment of Pyramid Dam
was very steep and irregular. Extensive shaping exca-
vation was performed to provide a uniform surface for
placement of impervious embankment and to flatten
the slope in the area of the old Highway 99 cut slope
(Figure 324). Drilling for this excavation started at
the end of the Dam in January 1971, and excavation to
the stream channel was completed in March 1971. The
slopes of the excavation were presplit with an average
hole spacing of 30 inches. This produced a neat line
excavation with deviations limited, in general, to
within 12 inches of the drilled line (Figure 325). Lifts
normally were 30 feet deep.
Five areas on the dam abutments had overhangs.
These were designated as shaping areas in the plans
and were required to be laid back to a slope of 1/4:1
<
, ..'" m^
1
-?
- .', , -.t y
» .
Figure 323.
Old Highway 99 Bridge Bents Uncovered
Downstream Shell Area of Dam
figure 32o. Prespiit face ot Snuplng Area on Right Abutment
393
in shell areas and 1/2:1 in the core zone. It was re-
quired that these areas be removed by the presplit
method. Presplit hole spacing was varied from 18
inches to .^6 inches, and it was found that a spacing of
30 inches gave excellent results.
Cleanup. After overburden material was removed,
the final cleanup prior to placement of embankment
was accomplished. In the rock shell zones, this consist-
ed of machine removal of loose material. Backhoes and
graders were used for this operation. In the core zone,
great care was taken to remove all loose and weathered
material to expose fresh solid rock. Final cleanup was
by air and water jets (Figure 326). Several deep holes
encountered in the stream channel in the core zone
were backfilled with concrete to provide a uniform
surface which facilitated placement and compaction
of the impervious material.
Grouting. The Pyramid Dam grout curtain con-
sists of a singe line of holes with 10-foot maximum
spacing. Grouting was accomplished in three zones by
the split-spacing stage-grouting method, usually with
a primary 40-foot spacing. Zone depths were 0 to 25
feet, 25 to 50 feet, and 50 to 100 feet. The third zone
was extended to 200 feet in three holes in the channel.
The holes were drilled normal to the slope. In the
three zones, the pressures at the grout nipple (sur-
face) were 15 psi, 35 psi, and 75 psi. The foundation
was tight, and the average grout take was only 0.13 of
a bag per foot of hole.
Channel Excavation
Alluvium in Piru Creek downstream from the Dam
was excavated to form the downstream spillway chan-
nel. Excavation and disposal of this material was per-
formed in a manner identical to that used for
overburden excavation.
Embankment Materials
Impervious. The borrow area for the impervious
material was located in the lake area about 1 mile
upstream from the Dam. It was divided into two sub-
areas: one lying along the east side of the stream chan-
nel contained slopewash material and the second was
higher on the slopes immediately east of the first and
was comprised of weathered in-place shales. While
both materials were very clayey, slopewash material
was somewhat finer than the weathered shale. It was
used in the upstream portion of the core, while weath-
ered shale went into the downstream portion of the
core.
Clearing and grubbing of the impervious borrow
area, which had a brush and grass cover, were done
with bulldozers and a small labor crew. The original
intent was to strip up to 18 inches of surface material
prior to borrowing but, because of the light vegetative
cover, this was not necessary and stripping depth
averaged less than 6 inches.
Following clearing and stripping, the area was
sprinkled by a portable water system to bring the
Figure 326. Air-Water Jet Cleanup of Foundatloi
material to the desired moisture content. Ripping was
used to enhance the water penetration, and loading
operations were shifted to ensure that properly condi-
tioned materials were delivered to the Dam. In gen-
eral, this system worked very well, and only minor
supplemental sprinkling was done at the Dam site. It
was somewhat more difficult to moisture-condition
the weathered shale than the slopewash material. This
was because the weathered shale was situated on
steeper slopes and water did not penetrate the shale
fragments as easily as it did the more uniform slope-
wash.
Bulldozers pushed the impervious material to front-
end loaders which, in turn, loaded the hauling units.
Two types of haul units were used: dump trucks
(Figure 327), which could haul approximately 20 cu-
bic yards bank measure, and tractors with rear-dump
wagons that had a capacity of approximately 15 cubic
yards (Figure 328) . The haul route was downslope on
old Highway 99 to the upstream toe of the Dam and
then up a 15% grade on a 40-foot-wide haul road tra-
versing the face of the Dam.
Rock Shell. Rock for the upstream and down-
stream shells of the Dam is a hard shale (argillite)
obtained primarily from the spillway excavation.
Other sources were: the abutment shaping areas, over-
burden removal, channel excavation, material that had
been stockpiled under the initial facilities contract
which included the access roads and the Angeles Tun-
nel gate-shaft bench excavation, and an auxiliary bor-
row area above the left abutment.
Drilling for excavation of the spillway began in July
1971. Initial drilling was accomplished with crawler-
mounted, air-powered, self-propelled, percussion
drills. The air supply was a compressor plant at the
downstream toe of the Dam. An 8-inch air-supply
pipeline extended from the compressor plant up the
west limit of the excavation to the top of the spillway
1
394
Hauling
Figure 328. Rear-Dump Rock Wagon Used for Embankment Hauling
cut. After adequate access and working areas had been
developed, truck-mounted, diesel-powered, rotary
drills were used for drilling production holes. A typi-
cal drill pattern used with these units was 6y4-inch
holes on a 22-foot by 22-foot grid. The maximum lift
thickness was 50 feet. The holes were loaded with
ammonium nitrate and fuel oil (ANFO) with dyna-
mite primers. Detonation was by electric blasting
caps. The ANFO was delivered by bulk trucks and
loaded into the holes with the fuel oil being added as
the ammonium nitrate was fed into the hole. The larg-
est blast of the operation comprised 67,225 pounds of
explosive. The average powder factor for the spillway
excavation was 0.6 of a pound of powder per cubic
yard of rock. The cut slopes of the spillway were pre-
split. Although this was not required by the specifica-
tions, the contractor considered this to be economical
as it saved barring down and cleanup of the slopes that
would have been required with conventional blasting.
The specifications were written to preclude the
bulldozing of rock so that breakdown during handling
would be minimized. Therefore, it was necessary for
the contractor to build haul roads from the excavation
site, i.e., the spillway ridge, to the dam embankment.
This involved roads traversing a maximum difference
in elevation of approximately 800 feet and required
the use of a 15% haul-road gradient. Two roads were
constructed: one to the downstream part of the un-
lined spillway, and the other from the upstream side
of the Dam to the top of the spillway excavation. The
downstream road involved a fill of almost 900,000 cu-
bic yards with material from stripping approximately
25 feet of weathered rock from the spillway chute area.
As the chute excavation was brought down, this road
material was removed and placed in the Dam, if suita-
ble, or otherwise in the waste area. The upstream haul
road was cut into the steeply dipping slope of the right
abutment until, at a point about 150 feet below the
dam crest, it swung out onto the upstream buttress
fill.
The haul units used for transporting rock from the
spillway excavation were the same types as used for
the impervious material. They were loaded by rubber-
tired front-end loaders, some of which had a special
steel tread to protect the tires in the rocky material. A
spread of one loader and five haul units could excavate
and haul about 5,000 cubic yards in a 10-hour shift.
Maximum daily production for two 10-hour shifts was
approximately 30,000 cubic yards.
Transition and Drain. Materials for the filter and
drain zones of the Dam were obtained from the stream
channel of Piru Creek upstream from the Dam. The
sands and gravels were dozed into piles and then load-
ed into the dump trucks and rear-dump wagons by
rubber-tired front-end loaders. They were hauled to a
stockpile in the lake area about I'/z miles upstream
from the Dam site. From the stockpile, they were
pushed by bulldozer to a processing plant which sepa-
rated them into desired fractions.
The specifications provided for production of three
types of material from the stream-channel borrow
ar^a. These were: (1) minus %-inch material for the
filter zone. Zone 2A; (2) '/-inch to 6-inch material for
the drain zone. Zone 2B; and (3) plus 6-inch rock for
riprap. After placement of the first drain zone materi-
al, it was noted that undesirable segregation occurred
at the interface between drain and transition zones
due to the tendency for the larger rocks in the drain
to roll to the outside when a lift was placed. Because
of concern that this segregation would permit migra-
tion of fines from the filter zone into the drain, a
change order was issued to provide for an additional
transition zone. This added zone comprised a mixture
of the drain and filter zone materials and was designat-
ed Zone 2D.
395
The processing plant consisted of a grizzly for re-
moval of plus 6-inch rock and two sets of vibrating
screen decks for separation of the minus 6-inch materi-
al into the two desired fractions. The added transition
zone, which was essentially a pit-run material with
plus 6-inch rock removed, was produced by blanking
off the lower screens of the vibrating decks. Produc-
tion rates varied from 230 cubic yards per hour when
producing Zones 2A and 2B to 300 cubic yards per
hour for Zone 2D.
After production was started, it was found that the
dry screening contemplated by the specifications did
not remove enough fines to produce filter material
with the specified 10% maximum of material passing
the No. 200 mesh screen. Wet screening was consid-
ered but, after study and additional permeability test-
ing, it was concluded that the allowable amount of
material passing the No. 200 screen could be increased
to 1 5% without detriment to the Dam. A change order
was issued to cover this modification.
The proportion of %-inch by 6-inch drain zone rock
in the borrow pit turned out to be less than contem-
plated, so a shortage of this material developed. This
problem was alleviated by lowering the top elevation
of the downstream drain blanket and replacing the
upstream drain zone with a zone of weathered rock
obtained from dam overburden and spillway excava-
tion. It was still necessary, however, to produce about
100,000 cubic yards of minus %-inch material in excess
of what was needed in order to generate the necessary
quantity of drain rock.
The riprap, drain rock, and transition materials
were hauled to the Dam site by the same equipment
and over the same haul route that was used for the
impervious fill.
Embankment Construction
Pyramid Dam embankment was constructed in two
stages. A low interim dam at the upstream toe of the
main dam was built in the fall of 197 1 to divert project
flows through Angeles Tunnel. Construction of the
interim dam also provided an excellent opportunity to
check out the specified placing and compaction proce-
dures before construction of the main dam. It was
found that the specified methods worked well, and no
problems were experienced in obtaining desired com-
paction of the fill when these methods were properly
followed.
Impervious. Placement of impervious fill in the
interim dam commenced in August 1971. The first
step was to cover the foundation area with contact
material which was placed about 2% above optimum
moisture and wheel-rolled with a rubber-tired front-
end loader with a loaded bucket (Figure 329).
Throughout placement of the core sections, the con-
tact material was placed about 2% wetter than the
remainder of the impervious fill so that it would easily
conform to irregularities in the rock surface. As the
fill progressed, a layer of contact material 10 to 15 feet
wide was brought up ahead of, and compacted prior
to, the rest of the embankment. The abutment contact
line generally was maintained 1 to 2 feet higher than
the plane of the embankment, with the surface sloping
gently away from the abutment. These measures were
taken to ensure coverage of the foundation with the
wetter material and to preclude the possibility of loose
material rolling into a low area against the abutment
and being poorly compacted.
After compaction of contact material to an ap-
proved elevation, the impervious embankment was
Figure 329. Spreading and Compacting of Contact
Material on Foundation
Figure 330. Rolling of Impervious Fill
396
1
raised to that elevation. After being dumped by the
hauling units, the material was spread with a bull-
dozer into 8-inch loose lifts, then processed by at least
two passes of a disc. At this time, if any supplemental
moisture was required, it was added by a water wagon.
After disking, the lift was compacted by 12 passes of
a self-propelled, four-drum, sheepsfoot roller (Figure
330). Compaction of the fill was closely monitored
with an average of one relative compaction test being
taken for each 2,500 cubic yards of fill placed. The
average relative compaction for the impervious em-
bankment was 98.5%.
Shell. Rock shell material was dumped and spread
in 3-foot-thick layers and then rolled with two passes
of a vibrating drum roller (Figure 331). Both self-
propelled and towed rollers were used. The compact-
ing and grading of this material were closely moni-
tored by testing. These tests involved considerable
effort as a field density test required the excavation
and weighing of 1,000 to 1,500 pounds of rock, and
mechanical analyses required the screening of several
thousand pounds of material.
Transition and Drain. Material for the transition
and drain zones was spread in 18-inch lifts. Transition
material was compacted by two passes of a vibrating
roller and drain material by one pass. Here again,
compacting and grading were closely monitored by
daily field testing.
Spillway
After the spillway area was e.xcavated down to the
elevation of the unlined chute, the cut for the 40-foot-
wide concrete-lined chute was made using presplit-
ting to shape the cut slopes against which concrete
lining was placed.
■ ^::^W :r^P • ■^■:^-'
» T
^'t":-^
..^;»i^
0L-^
- ■'">•- V
^'^
f '
}
1^
1
^
■^
^^^
riia^i^k^'
'■^
n^^
-■ ..-i*^\
I
Figure 331.
Compacting Pervious Material With 10-Ton
Vibratory Roller
Drainage. The spillway underdrain system plans
called for horizontal, triangular-shaped, gravel-filled,
outlet drains to be cut into the east slope of the spill-
way excavation at 10-fooi vertical intervals. This
would have been extremely difficult to do, and the
contractor proposed an alternate system which was
adopted. This consisted of embedding 4-inch plastic
pipes in the reinforced-concrete wall leading from
gravel drains under the invert slab and discharging
into the chute. The originally detailed gravel-filled
drains were intended to provide drainage for the wall
lining as well as for the invert slab. This function was
provided by drilling horizontal drainage holes into the
rock at points where the plastic drains returned into
the chute.
Drain holes in the 2% slope portion of the chute
invert were made by installing 4-inch-long pieces of
4-inch-diameter plastic pipe in the invert concrete as
the concrete was finished. Later, a drill rig was
brought in to drill the drain holes. This method gave
a neat hole in the invert as spalling of concrete by the
drills was eliminated. For the horizontal drain holes in
the spillway wall, plastic pipe sleeves were substituted
for the originally detailed steel to eliminate rust and
consequent staining.
Reinforcing Steel. Installation of reinforcing steel
was more or less routine except that this operation,
like all others involved in the spillway work, was com-
plicated by the steep slope of the chute. Inconvenience
was caused by the fact that carpenters, ironworkers,
and laborers had to work in close quarters on the steep
slope.
Concrete Production. All concrete for the work
was produced by a job-site, automated, batching and
mixing plant with an 8-cubic-yard tilting-drum mixer
with a theoretical capacity of 1 20 cubic yards per hour.
This was larger than needed but was on hand from the
Angeles Tunnel contract. Ice was added to the mix to
hold the temperature as near 50 degrees Fahrenheit as
possible. It was brought to the site in 300-pound blocks
and chipped and blown into the mixer as needed. Bulk
cement and pozzolan were stored in silos at the plant,
and aggregates were stockpiled by the delivery units
and then loaded into the batching bins by a front-end
loader via a rinsing screen. The specifications re-
quired that all aggregate be shaded on the day of use.
In lieu of this, the Department approved the contrac-
tor's proposal that the aggregate piles be sprinkled for
cooling.
Concrete for the headworks walls, broad-crested
weir, and all chute invert sections contained 3-inch
maximum size aggregate. Concrete for the chute walls
and operating deck contained I'/j-inch maximum size
aggregate. Slumps ranged from I to 2 inches for the
inverts and massive wall placements. An average
slump of 3 inches was used for the chute wall place-
ment.
397
Forms. The basic form used for the wall place-
ments was a 32-foot-long, prefabricated, steel form
complete with struts which spanned the spillway
width and formed both side walls at one setup (Figure
332). Form heights were adjusted by addition or re-
moval of panels. A system of jacks and ratchets ena-
bled adjustment of the form for sloping walls. This
unit was pulled up the slope by a double-drum hoist
which was anchored at the top of the 85% slope. The
form assembly was supplemented by wooden panels
where necessary, and transverse joints in the walls
were formed with wood.
The invert slab of the spillway was formed with a
10-foot-long by 40'X-foot-wide, steel, slip form with a
weight of approximately 60 tons. This was comprised
of six 27-inch WF beams spanning the chute slab.
These beams were tied together by four 6-inch WF
beams at the top and a '/-inch-thick skinplate on the
bottom. The spaces between the beams were filled
with concrete. The form was suspended by steel
wheels riding on 75-pound rails which were support-
ed by a system of 3-inch pipe posts and No. 1 1 rein-
forcing steel braces grouted into the rock in the wall
sections of the spillway. The rails were set V/i feet
above spillway invert grade. The slip form was pushed
forward (upslope) during concrete placement by two
6-inch hydraulic rams which were clamped to the
rails. The cylinder stroke was 6.5 feet so several
strokes were required to complete a 30-foot slab.
While the cylinders were being retracted and re-
clamped, the slip form was anchored by cable to the
double-drum hoist at the top of the slope.
The headworks structure walls were formed with a
combination of steel and wood forms and were placed
in 14'/2-foot lifts.
Concrete Placement. The concrete was hauled to
the placement site in transit mix trucks. Two five-man
labor crews, one for concrete placement and one for
cleanup, worked a normal day shift; an additional la-
bor crew worked a night shift to sandblast, clean up,
and prepare for placements. Consolidation of the con-
crete primarily was done with 6-inch immersion-type
vibrators. In some instances, 3J4-inch vibrators were
used to supplement the larger ones and to consolidate
in congested areas.
The first portion of the lined spillway to be placed
was the invert slab of the upper chute, which was on
a 2% slope. Concrete for the ten 30-foot-long sections
was placed by crane and bucket, with the crane being
situated on the invert of the unlined spillway. The
concrete was struck off by a rail-mounted screed, 3
feet long and 40'/ feet wide. This screed was a segment
of the slip form to be used on the steeper slopes and
was moved by hydraulic cylinders clamped to the
rails. A platform from which the finishers worked was
pulled behind the screed. A steel trowel finish was
specified for the invert, and cold weather, which pre-
vailed at that time, retarded the concrete set and
caused long finishing hours. In general, these place-
ments proceeded well and the contractor was able to
make one 30-foot section per day.
The headworks structure was the second spillway
feature to be placed. The major problem encountered
in this work was in connection with placement of the
invert slab. An attempt was made to place the entire
invert in one placement (2,000 cubic yards) by utiliz-
ing "drop pipes" in conjunction with one crane and
4-cubic-yard-capacity buckets. The drop pipes consist-
ed of five 10-inch-diameter steel pipes along each side
of the headworks (Figure 333). Concrete was dumped
directly from buckets into the center of the invert and
dropped through the pipes along the sides. Small hop-
pers about 2 feet square were mounted on top of the
pipes. Concrete was conveyed from the transit mix
trucks to the hoppers by chutes. Discharge of the con-
crete from the trucks through the gently sloping
chutes was very slow. The large aggregate tended to
roll down the chutes, jump over the hoppers, and fall
among the workmen below. Concrete also plugged the
pipes several times; it tended to stack at the pipe out-
lets and had to be flattened and moved with vibrators.
Surprisingly, little segregation was noted at the pipe
outlets. After ten hours of placing, and with only
about one-third of the invert done, the contractor
elected to stop the placement and make a construction
joint. Prior to placing the second lift of the invert, the
inlets of the drop pipes were lowered, chutes steep-
ened, and an additional crane brought in. These
changes increased the placement rate significantly,
and the remainder of the invert was completed with-
out any major problems.
After completion of the headworks concrete, the
chute walls in the 2% slope section were placed. Both
walls were placed simultaneously and were formed by
a steel-form strut assembly. Except for tight clear-
ances due to the narrow wall, no major problems were
encountered and the contractor was able to place a
section every other day.
After completion of the walls on the 2% slope, the
invert of the 85% slope section was placed. The slip
form performed well and produced a good surface that
required little additional hand finishing. Movement of
the slip form was slowed by trouble in attaching the
ram clamps to the rail. Attaching and releasing these
clamps was a major factor in delaying many of the
placements. The concrete was spotted in front of the
slip form by a 120-ton crane with up to 220 feet of
boom. This crane was able to reach the lower 3 sec-
tions from the toe of the unlined spillway slope, the
next 1 1 sections from the right adit bench, and the
remaining section from the top of the 85% slope.
When operating with the maximum length of
boom, placements were slow due to the flexibility and
resultant "bounce" of the boom. Also, in several areas,
the operator was operating "blind" and had to spot the
bucket by telephone, radio, or hand signals. Despite
398
these conditions, one invert section per day was placed
(Figure 334).
In placing the wall sections on the steep chute, the
same problems with operation of the crane were en-
countered as for the invert. Also, due to the steep
slope, the tops of the walls had to be formed as place-
ment progressed.
The final feature of the spillway to be placed was
the flip structure at the end. It was placed in four lifts,
and no major problems were encountered except for
some difficulty in slip forming the invert, which was
on a 40-foot radius. A 3-foot-long slip form on curved
pipe rails was used for this.
In general, the concrete for the lined spillway
turned out well despite the narrow battered walls and
steep slope. Considerable repair work was required
along the tops of the walls. The concrete was well
consolidated and reasonably well finished.
Radial Gate
The 31-foot-high, 40-foot-wide, radial gate was fab-
ricated by Hopper, Inc. in Bakersfield, California. Pri-
or to shipment, the entire gate was fabricated with
two 8-inch pipe spreaders, assembled in the shop, and
checked for correct spacing and alignments. Tempo-
rary installation of the same two spreaders in the field
facilitated correct positioning of the trunnion girders.
On October 30, 1975, the gate was lowered to contact
the sill plate and was found to have a %-inch bow in
the bottom edge. Under the direction of the manufac-
turer, the gate was straightened by the alternate ap-
plication of controlled heating and cooling to within
a tolerance of plus or minus '/ inch. Final adjustment
of the gate sill plate was made by lowering the gate
and adjusting the plate to meet the bottom edge. The
gate installation was quite good as attested by the fact
that, when the reservoir was filled, leakage past the
side seals was nil and only a couple of damp spots
showed up downstream of the bottom seal.
Access and Air-Supply Tunnel
Driving of the access tunnel was started on July 1,
1971 and completed on July 23, 1971. The contractor
worked 27 ten-hour shifts in driving the tunnel an
average of 28 feet per shift.
The air-supply tunnel is a circular tunnel 5 feet in
diameter and 90 feet in length connecting the crown
of the access tunnel with the crown of the valve cham-
ber of the Pyramid Dam diversion tunnel. This tunnel
was completed in six 10-hour shifts with an average
advance of IS feet per shift.
The equipment used by the contractor was left over
from the Angeles Tunnel job. The jumbo was contrac-
tor-built and modified to adapt it to the access tunnel
size and shape. The 8-foot by 1 1-foot access tunnel was
driven about 1 foot oversize at the contractor's request
as he elected not to reduce the basic size of the jumbo.
The contractor was not paid for the extra concrete
lining in the overexcavation. The jumbo was on rub-
Figure 332. Prefabricated Sfeel Form Used for Spillway Walls
Figure 333. Concrete Placemen
Heodworks Invert
'rttn^
Figure 334. Concrete Placement rn Spillway Chute Slob
399
ber tires, diesel-powered, and mounted with four
pneumatic drills — two upper and two lower. These
drilled 45 holes, 1/2 inches in diameter, and a 3-inch
"burn" hole for each round. Compressed air for the
drilling initially was supplied by three 600-cubic-feet-
per-minute (cfm), portable, air compressors. Later,
two 900-cfm, portable, air compressors were used. At
the end of tunnel driving, compressed air was sup-
plied by two 2,000-cfm and two 1,200-cfm stationary
air compressors. These last compressors also supplied
air to other drilling operations on this contract and to
the Angeles Tunnel intake works contract.
After drilling of a round was completed, the holes
were loaded (using the jumbo as the loading plat-
form) with caps being used to control the sequence of
the blast.
After a shot was set off, the tunnel was ventilated
using a 7'/2-horsepower ventilating fan with a 35,000-
cfm capacity.
The muck pile was removed from the face and
hauled out of the tunnel by a front-end loader. After
the muck pile was completely hauled out, the jumbo
returned to the face to resume drilling.
There were no problems or delays during tunnel
driving. No water was encountered. The tunnel was
monitored for explosive and hazardous gases, but
there was never any indication of their presence.
No steel supports were used in the tunnel. After the
driving operation was completed, the contractor elect-
ed to place shotcrete, approximately '/2-inch thick, in
two areas intersected by beds of Pyramid shale which
were much softer and more fractured than the Pyra-
mid argillite.
Preparations for lining the access tunnel and the
air-supply tunnel were begun on June 26, 1972. Work
included scaling loose material from the walls and
crown and removing loose muck from the invert. The
first concrete placement of the tunnel lining was made
on July 11, 1972, and the concreting was completed
with the placing of the portal structure on October 26,
1972.
Six concrete placements were made for the tunnel
invert. Sixteen placements were required for the walls
and crown, two for the air-supply tunnel, and one for
the portal structure.
All concrete for the tunnels was produced at the
job-site, central, batch plant and transported into the
tunnel in transit mix trucks. Concrete for the invert
section was a standard design five-sack mix with I'/j-
inch maximum size aggregate. Wall and crown section
concrete was the same mix except that sand content
was increased to approximately 40% to facilitate
pumping.
The initial invert placement was made using manu-
ally operated buggies. Due to the excessive amount of
labor required for this method of placement, the re-
mainder of the invert was placed using a belt con-
veyor. Use of the over 200-foot-long, self-propelled,
conveyor belt enabled invert placements to proceed
with a minimum of labor and with no major problems.
The concrete was consolidated with 6-inch and 3-inch,
pneumatic, immersion vibrators. Inconsistent slump
of the concrete and lack of competent finishers were
the primary problems encountered in the invert place-
ments. Scheduling of reinforcing steel installation to
prevent congestion in the tunnel was another persist-
ent problem.
A 6-inch hydraulically operated pump was used for
the first placement of the walls and crown. Plugging
of the 8-inch slickline occurred several times during
this placement, so this pump was replaced with an
8-inch mechanically operated pump for the remainder
of the wall and crown sections. This pump performed
satisfactorily and could handle the desired 4 inches or
less slump concrete. Up to 450 feet of slickline was
used. Air sluggers were used along the slickline to aid
in moving the concrete.
A 45-foot-long steel form was used for the normal
section of the walls and crown. This form was mount-
ed on dolly-type wheels and was hinged at the crown.
A system of ratchets and jacks folded and lowered the
form, which enabled easy and fairly rapid spotting
and removal of the forms for each placement. The
form was towed along the previously placed invert
sections by an air tugger mounted on the form. Al-
though the form had access and inspection windows,
the large amount of overbreak in the tunnel enabled
access inside the forms for concrete placement and
consolidation.
Consolidation of the wall and crown areas was done
with 6-inch and 3-inch, pneumatic, immersion vibra-
tors as well as external form vibrators.
Adits
The adits in the abutments were excavated under an
earlier contract. Invert paving and shotcrete lining
were added under the dam contract.
Concrete in the left adit invert was placed by labor-
ers pushing buggies from the portal. This was so dif-
ficult that the contractor changed the method for the
right abutment. Concrete in the right abutment was
placed by a 6-inch pump through a 4-inch slickline. It
had '/-inch maximum size aggregate. The left adit re-
quired 167 cubic yards and the right adit 290 cubic
yards of concrete.
After placement of the inverts, shotcrete was ap-
plied to the walls and crown. A dry mix was used with
water being added at the nozzle. The pot was posi-
tioned at the portal and was fed by transit mix trucks.
As much as 900 feet of hose was required to reach the
ends of the adits.
Completion of Outlet Works Intake Structure
Contract work for the completion of the outlet
works intake structure was started on July 26, 1972.
In order to place concrete in the intake tower plug,
maintain the required water level upstream of the in-
terim dam, and provide water release facilities during
the winter of 1972-73, it was necessary to install 30-
400
inch pipe extensions on the two low-level, 30-inch,
slide gates and a 10-inch pipe extension on the low-
level, 10-inch, butterfly valve.
One interim slide gate was not provided with seal-
ing surfaces and a 1-inch bolt had been left under the
gate during a previous contract. As the gate was under
approximately 30 feet of head, partial sealing was ac-
complished from the outside with gravel and cotton-
seed hulls. The remaining leakage was collected in a
6-inch pipe, which was grouted full after completion
of the plug.
During the period when the contractor was placing
concrete for the intake plug, he completed the installa-
tion of the vertical trashracks, checked and prepared
the horizontal trashrack for proper fit, and installed
the seals for an 18-foot-diameter dished head.
The other 30-inch slide gates remained in operation
until May 8, 1973 and then were grouted full. The
10-inch pipe was extended through the diversion tun-
nel with a 12-inch pipe to allow the contractor to
complete valve chamber work while maintaining a
minimum flow of 10 cfs in Piru Creek. The 18-foot-
diameter dished head was installed on the intake
tower on May 8, 1973 to permit the reservoir level to
rise above the intake tower.
During the summer and fall of 1973, the 10-inch
butterfly valve was operated to maintain minimum
flows in Piru Creek. On December 11, 1973, the 10-
inch butterfly valve was found inoperative and could
not be closed. An attempt was made to seal the valve
from the outside with a steel cap fitted with a rubber
sealing surface. This was done by divers at a depth of
223 feet. Due to poor visibility and extreme depth, the
sealing was unsuccessful. It was essential that the pipe
be sealed and the dished head removed from the tower
to provide discharge capabilities through the outlet
works.
On January 7, 1974, equipment and materials were
moved in for grouting the 10-inch pipe. The next day,
the grouting pipe was installed and the 10-inch pipe
grouted with an expansive cement-pozzolan slurry.
On January 9, 1974, the inside 10-inch valve was
opened and the pipe was found to have only minor
leakage. The valve was removed, a blind flange in-
stalled, and the concrete blockout and cleanup com-
pleted on January 11, 1974.
On January 17, 1974, the equalizer plug on the 18-
foot-diameter dished head was pulled and the dished
head removed from the intake tower. On January 18,
1974, the horizontal trashrack was lowered onto the
intake tower. During lowering of the trashrack, the
cable sling became entangled under the trashrack, pre-
venting seating. Divers completed the seating of the
trashrack on January 19, 1974.
Diversion Tunnel Plug
On June 6, 1973, the contractor installed a concrete
chipping machine (scabbier) in the diversion tunnel
plug area to remove the required 1 inch of surface
concrete. This machine was equipped with a rotating
arm, a scabbier unit on each end of the arm, and seven
vibrating scabbier heads in each unit. The machine
was self-centering on supporting wheels and was air-
and hydraulically operated. Considerable adjustment
and changes were required before the scabbier became
fully operational. The machine did an extremely effec-
tive job of providing a rough irregular surface for the
plug concrete. Areas in the valve chamber and plug
that could not be reached with the scabbier were bush-
hammered by hand. On completion of the concrete
chipping, the piping and reinforcing steel were in-
stalled in the plug.
The first concrete was placed in the tunnel plug on
August 7, 1973. The diversion tunnel was too small for
concrete trucks so permission was given to pump con-
crete from the diversion tunnel entrance to the plug
and valve chamber area. The maximum pumping dis-
tance was 830 feet with a vertical lift of 39 feet. The
pumping was done by a concrete pump through a
6-inch slickline. The mix used had I'/j-inch maximum
size aggregate and contained 400 pounds of cement
and 70 pounds of pozzolan. This mix was pumped
satisfactorily with a slump of 4 to 5 inches at the
pump. The slump loss in the slickline was 1 inch.
Vibration of the concrete was effectively handled
with 6-inch vibrators. Concrete was obtained from a
plant located near the work site until November 15,
1973. After that, concrete was obtained from a sup-
plier at Castaic. Concrete was mixed and transported
to the job site by transit mix trucks.
Total concrete placement in the tunnel plug and
valve chamber was 898 cubic yards.
Mechanical and Electrical Installations
The contractor moved the westerly 42-inch plug
valve into the valve chamber on October 27, 1973.
Transporting of the valve through the diversion tun-
nel was accomplished with a four-wheeled cart with
wheels sloped to conform to the curvature of the tun-
nel. The cart was pulled into the chamber by an elec-
tric winch. Rock bolts with lifting eyes were installed
at the center of the tunnel just ahead of the valve deck,
and four 10-ton chain hoists were used to lift the valve
above the deck elevation. Steel I-beams were installed
under the valve, four sets of wheels were placed under
the valve, and the valve was transported along the
beams to the deck. The valves then were jacked into
position over the anchor plates and lowered. All valves
were transported in a similar manner.
Installation of the 78-inch valve was delayed be-
cause the contractor's proposed anchorage was not
satisfactory, and considerable revision for the valve
and operator was required to prevent uplift during
valve stroking. The 78-inch valve was moved into the
tunnel on November 10, 1973, and final positioning
was completed on December 5, 1973.
The piping for the tunnel plug and valve chamber
was fabricated and hydrotested to 275 psi in position
401
or outside the tunnel, depending on the pipe size,
length, and installation problems. This was accom-
plished in two phases: the upstream inlet sections
ahead of the valves and the downstream discharge sec-
tions. This procedure tested all the field welds except
the nipple weld to the pipe flanges at the valves. The
Department accepted radiographing of these welds in
lieu of the specified hydrotest. All welds were ul-
trasonically tested prior to hydrotesting or radio-
graphing. All welding was satisfactory except about 6
inches of longitudinal factory weld just upstream of
the 78-inch valve which was satisfactorily repaired.
Installation of the fixed-cone dispersion valves start-
ed as soon as the downstream sections of pipe were
installed and aligned. Piezometer piping was installed
as main piping was completed.
In the Pyramid Dam outlet works, epoxy coating
was applied to all metalwork and valves in the disper-
sion chamber, to the interior of all piping 4 inches and
larger, to the sump pumps and appurtenances, and to
all exterior ferrous and galvanized surfaces exposed to
water. Exposed ferrous metalwork and galvanized
piping within the valve chamber which was not ex-
posed to water was primed with a red-lead alkyd and
finished with machinery enamel.
Coatings generally were not applied until all major
work items had been completed. This procedure pro-
vided a better-appearing finished product and elimi-
nated considerable touchup work although it did
require additional surface preparation where metal-
work had become rusted.
Miscellaneous mechanical work included the air
ventilation fan and duct systems, and sump pumps in
the valve chamber. With the exception of the sump
pumps, the work was performed without difficulty.
The sump pumps are operated by water-level pres-
sure switches and were found to be extremely difficult
to adjust and maintain. The pump transfer relay did
not function correctly and was replaced.
Electrical installation for the Pyramid outlet works
included the embedded conduit in the valve chamber,
surface runs in the valve chamber and diversion tun-
nel, electrical-duct shaft, completion of the conduit
runs to the spillway motor control center, control
cabinets, and all devices required to complete the elec-
trical installation. Electrical work was completed as
equipment was installed and made ready for opera-
tion.
Instrumentation
All 21 piezometers functioned properly for a period
after installation but, by July 1973, all those above
elevation 2,300 feet had failed. The plastic tubing to all
of these tips contained vertical runs, and it is surmised
that the riser tubing failed in the vicinity of elevation
2,260 feet due to high consolidation of the impervious
material in this area. The slope-indicator data showed
that embankment settlement in this area was approxi-
mately 6 feet.
Open-tube piezometers were installed in holes
drilled from the crest of the Dam to the inoperative
piezometers. The drilling fluid in these holes evident-
ly caused temporary hydraulic fracturing of the core,
and some of the drilling fluid was lost. The fracturing
was determined to be possible because the effective
overburden pressure in the core had been reduced by
the stiffer transition and shell zones carrying the
weight of the core. Extensive exploration and supple-
mental analyses showed that there was no permanent
affect on the Dam. Performance of the Dam since then
has verified this conclusion. A finite element stress
analysis is being conducted to check the details of the
estimated stress conditions.
The slope-indicator installations were comprised of
.S-foot sections of extruded aluminum tubing approxi-
mately 3 inches in diameter. The tubing has four
tracking grooves which guide the slope-indicating de-
vice. It was found that the grooves in the tubing had
a slight twist which caused a rotation in the grooves
as the individual sections of tubing were added. When
this was discovered, slope indicator No. 3 had rotated
over 8 degrees. At this time, measures were taken to
correct this and eliminate future rotation. This was
done by using a spanner wrench to twist the added
section of tubing in the desired direction while it was
riveted to the previously installed section. This
proved successful and, thereafter, installations were
held within the prescribed tolerance of plus or minus
3 degrees of the specified orientation. Another prob-
lem was that the settlement of the embankment tend-
ed to move slope indicators Nos. 2 and 4 away from
the dam abutment. This required correction as each
section was added. A great deal of survey crew time
was required to monitor the orientation and location
of the slope indicators.
402
BIBLIOGRAPHY
Marachi, N. D., Chan, C.K., and Seed, H. B., "Evaluation of Rockfill Materials", ASCE Journal of the Soil
Mechanics and Foundation Division, January 1972.
Stroppini, E. W., Babbitt, D. H., and Struckmeyer, H. E., "Foundation Treatment for Embankment Dams on
Rock", ASCE Journal of the Soil Mechanics and Foundation Division, October 1972.
I
403
6ENCKAL
LOCATION
Figure 335. location Map — Castaic Dam ond Lake
404
CHAPTER XV. CASTAIC DAM AND LAKE
General
Description and Location
Castaic Dam rises 425 feet above streambed excava-
tion and spans 4,900 feet between abutments at its
crest. The 46,000, 000-cubic-yard embankment is made
up of a central impervious core flanked by pervious
shells with appropriate transition zones.
The spillway is located at the right abutment of the
Dam and consists of an unlined approach channel; a
360-foot-wide, ungated, ogee weir; and a 5,300-foot-
long lined chute with energy dissipator.
The outlet works provides delivery of water
through a 19-foot-diameter penstock installed inside
the 27-foot-diameter, former, diversion tunnel. Down-
stream control is provided through a valving complex
for stream releases up to 6,000 cubic feet per second
(cfs), delivery to water users up to 3,788 cfs, and reser-
voir emergency releases. Upstream control is pro-
vided by a multiple-level, high, intake tower equipped
with 72-inch butterfly valves.
Elderberry Forebay located at the upper end of, and
separated from the right arm of, Castaic Lake provides
regulatory storage for Castaic Powerplant.
Downstream of the Dam, Castaic Lagoon, a former
borrow area, now serves as a recreation area and a
recharge basin.
Castaic Dam and Lake are located about 45 miles
northwest of Los Angeles and about 2 miles north of
the community of Castaic at the confluence of Castaic
Creek and Elizabeth Lake Canyon Creek (Figures 335,
336, and 337). Elderberry Forebay Dam (owned and
operated by Los Angeles Department of Water and
Power, LADWP) is located 3/2 miles upstream of Cas-
taic Dam on Castaic Creek. The weir that contains
Castaic Lagoon is located V/i miles downstream of
Castaic Dam where Lake Hughes Road crosses Castaic
Creek. The nearest major highway is Interstate High-
way 5, about 2 miles to the west.
Figure 336. Aeriol View — Castaic Dam ond Lake
405
Figure 337. Site Plan
406
Purpose
Castaic Lake was built to accomplish the following:
(1) provide emergency storage in the event of a shut-
down of the California Aqueduct to the north, assur-
ing water deliveries to the West Branch water users;
(2) act as regulatory storage for deliveries during nor-
mal operation; and (3) provide a setting for recrea-
tional development by state and local agencies for the
Southern California area. Although flood control is
not a primary purpose, inflows of up to 61,000 cfs will
be reduced to the capacity of the downstream channel.
Elderberry Forebay serves three purposes: (1) pro-
vides 18,000 acre-feet of live storage which can be util-
ized by Castaic Powerplant during off-peak hours for
pumpback into Pyramid Lake, (2) provides submer-
gence for the pump-generator when Castaic Lake is at
its lower operating levels, and (3) reduces daily and
weekly fluctuations in Castaic Lake.
Castaic Lagoon originally was a borrow area for the
construction of Castaic Dam. Now, its purposes are
(1) to provide a recreation pool with a water surface
at a constant elevation of 1,134 feet, and (2) to func-
tion as a recharge basin for the downstream ground
water basin.
TABLE 42. Statistical Summary of
Chronology
Studies by the Department of Water Resources in-
dicated that storage of any appreciable amount at the
terminus of the West Branch Aqueduct would be pro-
vided most logically and economically at the Castaic
Dam site. Planned storage capacity of Castaic Lake has
varied from 150,000 acre-feet in 1959, to 370,000 acre-
feet in 1960, to 100,000 acre-feet in 1961, and to 350,000
acre-feet in 1963. The final decision to increase the
capacity of Castaic Lake from 100,000 acre-feet to
350,000 acre-feet was made to utilize the optimum ca-
pability of the site in providing terminal storage for
regulatory and emergency requirements. With the
construction of Elderberry Forebay by LADWP, stor-
age in Castaic Lake was reduced to 323,702 acre-feet.
Final design was started in January 1964, excavation
was started in August 1965 in a foundation trench, and
the completion contract was finished in June 1974.
Statistical summaries of Elderberry Forebay Dam and
Forebay and of Castaic Dam and Lake are shown in
Tables 42 and 43, respectively. The area-capacity
curves are shown on Figure 338.
Elderberry Forebay Dam and Forebay
ELDERBERRY FOREBAY DAM
Type: Zoned earthfiU
Crest elevation 1,550 feet
Crest width 25 feet
Crest length 1,990 feet
Streambed elevation at dam axis 1,370 feet
Lowest foundation elevation 1,350 feet
Structural height above foundation 200 feet
Embankment volume 6,000,000 cubic yards
Freeboard above spillway crest 20 feet
Freeboard, maximum operating surface 10 feet
ELDERBERRY FOREBAY
Maximum operating storage* 33,004 acre-feet
Normal maximum operating storage 28,231 acre-feet
Minimum operating storage 19,041 acre-feet
Dead pool storage 811 acre-feet
Maximum operating surface elevation 1,540 feet
Normal maximum operating surface elevation 1,530 feet
Minimum operating surface elevation 1,480 feet
Dead pool surface elevation 1,412 feet
Shoreline, spillway crest elevation 7 miles
Surface area, maximum operating elevation __ 492 acres
Surface area, spillway crest elevation 460 acres
Surface area, minimum operating elevation.. 379 acres
* Storage above elevation 1,530 feet to be utilized only during the
months of May and June when additional storage on the Cali-
fornia Aqueduct may be required.
SPILLWAY
Emergency: Ungated ogee crest with lined channel, discharge into
draw
Crest elevation 1,540 feet
Crest length 420 feet
Service: Glory hole with reinforced-concrete conduit and stilling
basin — 10-foot-high stoplogs provided at crest
Top of stoplogs 1,540 feet
Crest elevation 1,530 feet
Crest length, elevation 1,540 feet. 173 feet
Crest length, elevation 1,530 feet- 126 feet
Crest diameter 54.9 feet
Conduit diameter 21 feet
Combined spillways: No stoplogs in service spillway
One-in-l,000-year-flood inflow 28,747 cubic feet per second
Outflow with 5 feet of freeboard.. 28,747 cubic feet per second
INLET-OUTLET
Castaic Powerplant tailrace
Maximum generating release 18,400 cubic feet per second
Pumping capacity 17,300 cubic feet per second
OUTLET WORKS
Type: High-level, spillway conduit beneath dam along base of right
abutment; low-level, reinforced-concrete conduit with valve
chamber adjacent to glory-hole spillway — discharge into spillway
conduit downstream of elbow
Diameter: High-level, 21 feet — low-level, 7 feet
Intake structures: High-level, slide gates on spillway shaft; low-
level, uncontrolled box with stoplog emergency bulkhead
Control: High-level, two 8-foot-wide by 9-foot-high slide gates at
elevation 1,498 and six 8-foot-wide by 12-foot-high slide gates at
elevation 1,477 on spillway shaft; low-level, single set of two 5-
foot-wide by 6-foot-high, high-pressure, slide gates in tandem
within gate chamber
Capacity 17,000 cubic feet per second
407
TABLE 43. Stalislical Summary of Castaic Dam and Lake
1
CASTAIC DAM
Type: Zoned earthfill
Crest elevation 1,535 feet
Crest width ..- 40 feet
Crest length 4,900 feet
Streambed elevation at dam axis 1,200 feet
Lowest foundation elevation 1,110 feet
Structural height above foundation 425 feet
Embankment volume 46,000,000 cubic yards
Freeboard above spillway crest 20 feet
Freeboard, maximum operating surface 20 feet
Freeboard, maximum probable flood 5 feet
CASTAIC LAKE
Maximum operating storage 323,702 acre-feet
Minimum operating storage _ 18,590 acre-feet
Dead pool storage _ 18,590 acre-feet
Maximum operating surface elevation 1,515 feet
Minimum operating surface elevation 1,280 feet
Dead pool su rf ace elevation 1,280 feet
Shoreline, maximum operating elevation 29 miles
Surface area, maximum operating elevation. _ 2,235 acres
Surface area, minimum operating elevation.. 372 acres
SPILLWAY
Type: Ungated ogee crest with lined chute and stilling basin
Crest elevation 1,515 feet
Crest length 360 feet
Maximum probable flood inflow 120,000 cubic feet per second
Peak routed outflow 78,400 cubic feet per second
Maximum surface elevation 1,530 feet
One-in-400-year-flood inflow 61,000 cubic feet per second
Peak routed outflow 27,200 cubic feet per second
Maximum surface elevation 1,522.7 feet
INLET
Elderberry Forebay outlet
Capacity.. 17,000 cubic feet per second
OUTLET WORKS
Type: Lined tunnel under right abutment — upstream of tunnel plug,
19-foot-diameter pressure tunnel — downstream, 19-foot-diameter
steel conduit in a 27-foot-diameter tunnel to delivery manifold
and stream releases
Intake structures: Low-level uncontrolled tower with provision for
steel plug emergency bulkhead and 6-foot by 10-foot coaster gate
shutofi' at junction with high intake; high-level vertical nine-
level tower with 72-inch butterfly shutoff valves
Control: Regulation by water users beyond downstream delivery
manifold — stream release, series of rated valves in a structure
immediately downstream of the deliver)' mainfold
Design deliveries 3,788 cubic feet per second
Capacity, stream maintenance 6,000 cubic feet per second
Capacity, reservoir drainage 11,000 cubic feet per second
RESERVOIR SURFACE AREA (100 Ac.)
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Figure 338. Area-Capacity Curves
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408
Regional Geology and Seismicity
Castaic Dam site, approximately 10 miles southeast
of Pyramid Dam, is approximately 3 miles northeast
of the San Gabriel fault and 1 3 miles southwest of the
San Andreas fault. The section on regional geology
and seismology in Chapter XIV of this volume applies
to Castaic Dam as well as Pyramid Dam.
Design of Elderberry Forebay
Elderberry Forebay was designed and constructed
by the City of Los Angeles Department of Water and
Power.
Operation
Castaic Powerplant, located between Pyramid Lake
and Elderberry Forebay, generates during peak de-
mand periods when the value of energy is high and
pumps water back to the higher level of Pyramid Lake
during off-peak periods when the value of energy is
low. On a daily basis, approximately 18,000 acre-feet
of water is used for power generation during the day,
8,000 acre-feet of which is pumped back at night. This
leaves a daily flow of about 10,000 acre-feet through
Elderberry Forebay to Castaic Lake. On weekends, a
full 18,000 acre-feet of live storage from the Forebay
(a 60-foot drawdown) can be pumped to Pyramid
Lake using off-peak power. Then, during the week,
this drawdown can be replenished with part of the
daily 18,000-acre-foot flow from Pyramid Lake.
Under normal operating conditions, minimum wa-
ter surface in Castaic Lake may be at about elevation
1,435 feet each year, which is 45 feet below the mini-
mum operating surface of the Forebay. Under these
conditions, the Forebay is necessary to supply sub-
mergence for the Castiac Powerplant tailrace.
Embankment
The 160-foot-high forebay embankment is a zoned
earthfill with free-draining material in the upstream
rapid drawdown area. The downstream section,
where drawdown will be more gradual, is of pervious
material protected from the wave wash of Castaic
Lake by V/i feet of soil-cement. The depth of Castaic
Lake on the toe of the forebay embankment will be at
least 55 feet under normal operation. A core trench is
provided to sound rock under the impervious Zone 1
material.
Emergency Spillway
An emergency spillway discharges across a ridge
east of the left abutment and into a draw that returns
to Castaic Creek near the toe of the Forebay Dam. The
spillway consists of an unlined approach channel with
side slopes protected by riprap; a 4-foot-high, ungated,
ogee crest; and a concrete-lined chute.
Outlet Works
The outlet works of the Forebay consists of a high-
level and a low-level outlet.
The high-level outlet is a 64'/2-foot-diameter glory-
hole-type intake with a 40-foot-diameter shaft. The
intake has 12 stop-gate bays around its crest and slide
gates at two levels below the crest. Closing of the stop
gates on the crest will raise the Forebay 10 feet, to the
level of the emergency spillway crest. Below the slide
gates and above the elbow of the outlet, the diameter
of the shaft reduces from 40 to 21 feet. At the toe of
the Forebay Dam, the 21-foot pipe discharges into a
transition to a flume which empties into a concrete-
lined stilling basin. Backwater from Castaic Lake
stands above the top of the elbow at the base of the
shaft, except in case of emergency draining of the
system.
The low-level slide-gate outlet consists of an intake
structure with a trashrack; a 10-foot-diameter pressure
conduit; a gate chamber containing two 5- by 6-foot,
motor-driven, remotely operated, pressure gates; and
a 7-foot-diameter outlet pipe that discharges into the
21-foot-diameter, high-level, outlet discharge line.
Design of Castaic Dam
Diversion Tunnel
The diversion tunnel for Castaic Dam served to di-
vert floodflows during construction of the embank-
ment and now serves as part of the outlet works. The
diversion tunnel passes through the right abutment
under the embankment. The finished tunnel is a circu-
lar concrete-lined section, 19 feet in diameter from
intake to Station 25-1-90 and 27 feet in diameter from
that point to the outlet. The total length of the tunnel
is 3,766 feet (Figures 339 and 340).
A reinforced-concrete channel extends from the di-
version tunnel outlet portal to an energy dissipator.
The channel and dissipator were utilized to pass flood-
flows during construction. Later, the channel was
modified to meet the needs for turnouts and stream
release facilities. The stilling basin was designed for
use with the stream release facilities as well as the
diversion tunnel.
The diversion tunnel contract provided for con-
struction of the diversion facilities plus the necessary
provisions for their later incorporation with the deliv-
ery and stream release facilities. The upstream portal
structure included a foundation pad for a low intake
tower and a tower barrel to an elevation above the
diversion tunnel soffit. At Station 20-1-18, provisions
were made for a high-level intake. The downstream
facilities consisted of a concrete channel with a semi-
circular to rectangular transition section, a rectangu-
lar channel, and a hydraulic-jump energy dissipator
(stilling basin) at the downstream end. The down-
stream structure also included provisions for a deliv-
ery penstock and was designed to serve as the
foundation for the delivery branch bifurcations and
stream release structure.
Hydraulics. The diversion tunnel, as designed and
constructed, could have passed the standard project
flood, which has a peak inflow of 58,000 cfs, with a
maximum reservoir water surface elevation of 1,306
feet and a peak discharge of 14,600 cfs. The diameter
409
'f
'U tj
§1 1^!!^ 1!
\i\l^
\i
Figure 339. Diversion Tunnel — Plan and Profile
410
Figure 340. Diversion Tunnel — Plan and Profile (Continued)
411
of the tunnel was determined by the hydraulic criteria
of delivering a maximum flow of 3,788 cfs to the water
users with the reservoir water surface elevation at
1,421 feet and a hydraulic gradeline elevation of 1,400
feet at The Metropolitan Water District of Southern
California/ Department of Water Resources delivery
point. With the reservoir water surface at elevation
1,380 feet, the tunnel and related system have to dis-
charge downstream releases of up to 6,000 cfs, plus
delivery to water users of 1,600 cfs. It also was neces-
sary to design the shaft-tunnel intersection to permit
1969-70 floodwaters to pass unobstructed through a
partially completed intersection structure. With the
stream release facilities installed, maximum release is
reduced to approximately 8,000 cfs (water surface ele-
vation 1,515 feet). In case of emergency, two fixed-
cone dispersion valves can be removed from the
stream release facilities increasing the capacity to ap-
proximately 11,000 cfs.
The energy dissipator at the end of the channel
chute was designed to control downstream erosion.
Energy is dissipated by use of a hydraulic jump, which
mainly is controlled by downstream backwater condi-
tions. Chute blocks and a dentated sill were added as
further aids to stabilize and contain the hydraulic
jump. Design of these facilities was verified by model
studies.
The dissipator structure was sized to operate with
a discharge of 20,000 cfs. Final design of the outlet
works, which was completed after the stilling basin
was constructed, lowered maximum discharge to
14,600 cfs during diversion and approximately 11,000
cfs upon completion of the work. Tailwater for the
jump is controlled by a downstream weir (elevation
1,136 feet) located at the new Lake Hughes Road
crossing. The dissipator floor was set at elevation
1,090 feet to provide the necessary tailwater for the
development of a hydraulic jump and to prevent
sweep-out.
Structural Design. It was anticipated that the en-
tire length of the diversion tunnel would require
structural-steel support. Due to the varying nature of
material encountered, support loading varied. Sup-
port of the tunnel, except in designated reaches, was
the responsibility of the contractor. A minimum sup-
port was designated for a short reach at each portal.
Special rib placement and shapes were required for
the high intake-shaft intersection supports. An invert
strut was designed for use through reaches of material
exhibiting lateral yielding tendencies. An umbrella of
structural steel was designed for both intake and out-
let portals to ensure stability of the cut faces and to
provide safe working areas. The design also included
grouted crown bars installed around the soffit of tun-
nel portal excavations to tie the umbrella structure to
the portal face and to provide overhead protection
during initial rounds of excavation. The upstream
structural-steel umbrella was incorporated into the
section of cut-and-cover tunnel required between the
low intake tower and tunnel portal.
Cut slopes at the portals were designed to be no
steeper than 1.67:1, with 15-foot-wide berms at eleva-
tion intervals of 40 feet. The resulting minimum
equivalent slope for cuts involving one or more
benches was approximately 2:1. Cut slopes were deter-
mined by the following criteria:
1. Stability analyses by the circular arc and/or slid-
ing wedge methods.
2. Comparison of design cut slopes with stable
natural slopes in similar material in the immediate
vicinity.
3. Design slopes parallel to or flatter than the aver-
age bedding plane of the formation in the cut.
The tunnel's concrete lining was divided into three
reaches, each with different loading conditions: (1)
from upstream portal to high intake-shaft intersec-
tion, loads are hydrostatic head to ground surface and
dead load; (2) from high intake-shaft intersection to
Station 25+90, loads are hydrostatic head to reservoir
normal water surface and dead load; and (3) from
Station 25 + 90 to downstream portal, loads are hydro-
static head to ground surface and dead load (Figure
339). Rock load was taken as a uniform pressure
around the concrete lining of one bore diameter of
material. Concrete lining also was designed to with-
stand internal pressures to hydraulic gradeline during
maximum diversion flow.
The reach of diversion tunnel in the vicinity of the
high intake-shaft intersection (Figure 341) was de-
signed to constitute the initial stage of the shaft-tunnel
intersection, which was completed under the outlet
works contract. No reinforcement was placed in the
areas where concrete was to be removed at a later
time.
The tunnel intake structure (Figure 342) was de-
signed to function both as a diversion during dam
construction and later as a base for the low-level intake
tower in the outlet works. The tower base was located
a sufficient distance from the portal to be relatively
free of slides and be a part of the portal approach floor.
The critical design forces (hydrostatic and earth-
quake) on the tower were considered of sufficient
magnitude to require the use of foundation piling
around the perimeter of the tower base. Piling was
designed for tension with the bearing floor serving as
a pile cap and tie. A pile friction of 500 pounds per
square foot was used.
Primary concern for the channel section was that it
carry the standard project flood. However, to accom-
modate the future stream release facility and to pro-
vide room for penstock valving, channel width was
increased from 40 to 60 feet downstream at the bifur-
cation. The cantilever walls of the transitions, chan-
nel, and chute sections were designed to withstand
level backfill within 2 feet of the top. Earthquake load-
ing of O.lg was added. The structure was provided
with a side drainage system.
412
Figure 341. High Intake-Shaft Intersection
413
Figure 342. Diversion Tunnel Intake Structure
414
Although counterforts generally are more economi-
cal for walls of the height used for the energy dissipa-
tor, a gravity structure was designed to increase
stability. This was achieved by designing the walls as
tapered cantilevers with thickened bases. The addi-
tional concrete required for this design increased the
weight of the structure and produced the desired sta-
bility (Figure 343).
Grouting. The design grouting program for the
tunnel called for a grout curtain, consolidation grout-
ing, and contact grouting. The grout curtain consisted
of two rings of holes from 80 to 150 feet deep located
near the dam axis so as to mesh with the dam grout
curtain. Consolidation grouting consisted of rings of
six holes 20 feet deep. Contact grouting was required
throughout the length of the tunnel.
Embankment
Description. The basic embankment section con-
sists of a central impervious core flanked by pervious
shells and a zone of random material contained within
the downstream pervious shell. Internal embankment
drainage is provided by an inclined drain, down-
stream of the impervious core, connected to a blanket
drain in the channel and on the abutments up to eleva-
tion 1,450 feet. Protective filters are positioned be-
tween the core and inclined drain and between the
core and upstream shell. Various details of the em-
bankment are shown on Figures 344 and 345.
Stability Analysis. Embankment stability was
analyzed by the infinite slope, sliding wedge, and
Swedish Slip Circle methods of analysis. Seismic
forces used in stability analyses were approximated by
applying a steady horizontal force acting in the direc-
tion of instability. The steady force was assumed at
0.15 times the moist or saturated embankment weight,
whichever was applicable. The design properties of
the compacted embankment materials are shown in
Table 44.
Design features providing protection against failure
from seismically induced displacements included fil-
F!gure 343. Outlet Works Energy Dissipator
ters and an inclined drain at least twice as thick as
would be specified for the same zoned embankment in
a nonearthquake area, a substantially increased imper-
vious core width, and plasticity requirements for the
core materials. These features were intended to pre-
vent concentrated leakage and piping along any plane
of differential transverse movement. A minimum
plasticity index of 7% was specified for impervious
core materials, resulting in an average plasticity index
of core materials in the range of 10 to 15%. It is gener-
ally accepted that the higher the plasticity index of a
fine-grained soil, the greater the ability to deform
without cracking and thus the higher the resistance to
concentrated leakage.
An extensive drainage system in the downstream
shell and in the natural sand and gravel downstream
of the Dam was provided to collect core and founda-
tion seepage and transport it to Castaic Lagoon. A
weir to determine seepage quantities was provided at
the seepage outfall facility adjacent to the Lagoon.
Construction Materials. The impervious core was
selected from unweathered (Zone IB) and weathered
(Zone 1 A) Castaic formation materials obtained from
required excavation. Additional Zone 1 A material was
TABLE 44. Material Design
Porameters-
—Castaic Do
„
1
Specific
Gravity
Unit Weight in Pounds
Per Cubic Foot
Static Shear Strengths
6 Angles in Degrees
Cohesion in Tons Per Square
Foot
1
EfFective
Total
Construction
Material
Dry
Moist
Saturated
8
C
e
C
e
C
2.72
2.72
2.70
2.70
2.70
2.70
113
113
131
131
131
120
130
130
140
140
140
135
135
135
145
145
145
30
30
38
38
38
35
0
0
0
0
0
0
18
18
35
0.15
0.15
0
20
20
35
l.S
Zone IB
l.S
*
Zone2B
*
•
0
' Free^ainiog
: effective stress valu
I
41S
Figure 344. Embankment Plan
416
Figure 345. Embankment Section
417
obtained from selected borrow areas. Transition
material (Zone 2A) and drain material (Zone 2B) are
processed streambed sands and gravels from required
excavation and pervious borrow areas. Pervious shell
material (Zone 3) is streambed sands and gravels from
required excavation and pervious borrow areas. Ran-
dom material (Zone 4) consists of terrace sands and
gravels from required excavation and sandstones with
some shale of the Castaic formation.
Soil-cement for upstream slope protection was pro-
duced by mixing cement with excess Zone 2A materi-
al. Cobbles for downstream slope protection were
obtained during the processing of streambed deposits
for Zones 2A and 2B.
Test Fill. A test fill was constructed at the Dam
site in October 1966 to determine more adequately the
reaction of Castaic formation materials to procedures
being considered for construction of the impervious
cores. Extensive field and laboratory testing con-
firmed that weathered and unweathered plastic
materials from the Castaic formation would break
down during excavation and compaction to form an
impervious mass with a shear strength at least equal
to that used in design.
Settlement. Settlement of the zoned embankment
is caused primarily by consolidation of the central
impervious cores. Consequently, laboratory consoli-
dation testing and analysis concentrated on materials
to be used in constructing the core. Because there is no
proven analytical settlement approach known to de-
termine that portion of core consolidation which oc-
curs after completion of an embankment, a camber of
approximately 1% of the fill height was provided to
compensate for long-term embankment settlement.
Seepage Analysis. Seepage under the central im-
pervious core is controlled by excavation for the core
foundation to sound unweathered bedrock, by grout
curtain construction, and by blanket grouting of frac-
tured or sheared bedrock zones outside the area of the
grout curtains. The design called for a main grout
curtain 1 50 feet in depth, flanked by two curtains with
depths of 70 feet, and two outside curtains with depths
of 40 feet. Some of this grouting was deleted, as is
discussed later. Seepage that does occur under the core
should be concentrated in sandstone layers contained
in the bedrock.
Seepage through the impervious core, based on
flow-net analysis, was estimated to be less than 0.25 cfs
with the reservoir at normal pool. The analysis as-
sumed a horizontal to vertical permeability ratio of 9
for the core and infinite permeability for Zones 2A,
2B, and 3. A vertical permeability of 0.01 of a foot per
day was used for the core.
Transition and Drain. The transition zones pre-
vent movement of fine-grained core material into the
surrounding pervious zones due to seepage forces, and
the drain ensures drainage of the downstream shell.
Materials used for the transition and drains were proc-
essed by separating sands and gravels at approximate-
ly the '/z-'nch particle size and using oversize and un-
dersize materials for drain and transition zones, re-
spectively. To satisfy recommendations of the
Department's Earth Dams Consulting Board, some
smaller grain sizes were blended with the oversize
material to prevent segregation when placing and
compacting the drain zone. Specification limits for the
transition (2A) and drain (2B) materials were
derived to fit the anticipated processing scheme previ-
ously described.
Upstream Slope Protection. Due to the relatively
short period of wind-velocity recording and the topo-
graphic differences at the Dam site, a wind velocity of
60 miles per hour (mph) in any direction was used for
a conservative determination of maximum wave
height. The reservoir configuration results in a max-
imum fetch (length of reservoir over which wind can
blow) of approximately 5 miles and an effective fetch
(an equivalent length that a wave could traverse with-
out being dampened) of 1.6 miles.
Wave run-up was investigated for a 60-mph wind,
an effective fetch of 1.6 miles, and a 3'X:1 embankment
slope. The vertical wave run-up on riprap and smooth
(soil-cement) facings was found to be 2.4 feet and 6.1
feet, respectively. Under conditions of wave run-up
and the standard project flood maximum water sur-
face, the riprap and soil-cement-protected slopes
would have a freeboard of 9.7 feet and 6.0 feet, respec-
tively. The soil-cement facing was assumed smooth to
determine an extreme wave run-up condition; actual-
ly, the stairstep method of soil-cement construction
results in a corrugated surface.
A cement content of 8% by weight and a total soil-
cement thickness of 2 feet was provided. To aid drain-
age immediately behind the facing during drawdown
of the reservoir, Zone 3 material containing less than
3% by weight passing the No. 200 sieve was placed
within 10 feet horizontally of the soil-cement.
The riprap alternative included in the bid docu-
ments apparently was not economically feasible and
no contractor bid on that alternative.
Dam Axis Alignment Changes. Slides occurring
in the east (left) abutment during foundation excava-
tion raised concern that the scheduled deep excava-
tions for the dam foundation at the easterly extremity
of the Dam would undermine the stability of Lake
Hughes Road and the ridge downstream of the Dam
( Figure 344) . To avoid this, the alignment of the dam
axis was moved upstream by changing it from the
8,000-foot-radius curve to a line tangent to the curve
running easterly at Station 45-1-20 (Figure 345). To
further eliminate excavation in the vicinity of Lake
Hughes Road and to take advantage of the more com-
petent foundation, a second change was made along a
400-foot-radius curve to the northeast from Station
56-f 50 to Station 60 + 97 and then along a tangent line
418
to the south end of the visitor's construction overlook.
The alignment change to the tangent line at Station
45 + 20 departed from the original axis location at a
very small rate. The locations of the various zones of
embankment were brought into proper relationship
with the new axis by varying outer and contact slopes
slightly through a small height differential. The align-
ment change from the tangent to the 400-foot- radius
curve at Station 56+50 would have been simple, ex-
cept that there was insufficient room to extend the
downstream Zone 2 A and the 2B chimney. At the time
of this change, Zone lA at the east abutment was
being built upward along a 1:1 foundation cut slope at
its southern limit. The existing alignment also located
Zones 2 A and 2B on the 1:1 slope. To correct this
situation, Zone 1 A material was carried to higher ele-
vations in this area until there was sufficient room to
extend Zones 2A and 2B and also accommodate a sec-
tion of Zone 3 adjacent to the slope.
Earth buttresses were added during construction to
stabilize this area and an old landslide area on the right
abutment. This construction included the earthwork
for a boat ramp and parking lot on the left abutment
as discussed later in this chapter.
Foundation
Site Geology. The entire project area is underlain
by the Castaic formation. Bedrock under the embank-
ment is composed of approximately two-thirds shale
interbedded with one-third sandstone. Silty shales and
sandy shales comprise approximately 90% of the shale
areas; clay shales comprise approximately 10%. Gen-
erally, the bedrock is not exposed at the ground sur-
face, being covered by sand and gravel alluvium up to
85 feet thick in the channel, by terrace deposits up to
200 feet thick on the right abutment, and by landslides
over 100 feet thick on the left abutment.
Fresh shale is moderately hard. Bedding thickness
ranges from '/j to 1 foot. Some areas contain soft clay
seams varying from a thin coating to '/ of an inch thick
along bedding planes. Weathered shale is soft to mod-
erately hard and contains gypsum in joints and along
bedding planes.
Fresh sandstone is soft to moderately hard. Bedding
thickness ranges from 'X inch to 15 feet with most beds
between 1 and 4 feet. Grain size ranges from fine to
coarse, with fine grains predominating. The grains
range from very weakly cemented to moderately well
cemented with clay. Some beds contain hard sand-
stone concretions up to 5 feet in diameter.
Tight, soft, clay gouges caused by shearing or fault-
ing both across and parallel to bedding planes occur in
zones that vary from a fraction of an inch to 2 feet in
thickness.
Ebccavation. Removal of the overburden materials
and highly weathered bedrock under the embankment
was specified in order to provide a foundation at least
as strong as the embankment materials to be placed on
it. Another requirement was that Zone lA and IB
materials be placed on fresh, undisturbed, Castaic for-
mation. This requirement necessitated the design of a
cutoff trench.
Spillway
The spillway extends along the ridge line that com-
prises the right abutment of the Dam. It is approxi-
mately 5,300 feet long and consists of an approach
channel, weir, transition, chute terminating in a still-
ing basin, and return channel (Figures 346 and 347).
During the early design phase, several spillway loca-
tions were studied, including an alignment directly
through the ridge into Grasshopper Canyon with a
return channel down Grasshopper Canyon to Castaic
Creek. Other alternatives included a dual-purpose
stilling basin for the spillway and outlet works. Final
design selection was based on economy and safety.
Flood Routing. The spillway protects the Dam
against the maximum probable flood (spillway design
flood) which has a peak discharge of 120,000 cfs and
a three-day volume of 86,600 acre-feet. There is 5 feet
of freeboard above the resulting water surface. Design
of the structures based on this flood is allowed to have
stresses above normal. This conforms to the U.S.
Army Corps of Engineers' design criteria.
The l-in-400-year flood is the greatest flood for
which design is based on normal stresses. This flood
has a peak discharge of 61,000 cfs and a three-day vol-
ume of 57,300 acre-feet.
Approach Channel. The approach channel con-
veys floodflows from the reservoir to the weir, limit-
ing the velocities in the immediate vicinity of the
upstream slope of the Dam. It was designed to mini-
mize excavation costs and limit approach velocities to
5 feet per second in the unlined portions of the chan-
nel and 15 feet per second in the area where riprap is
used.
Hydraulic model tests of the original configuration
showed unsatisfactory flow conditions. Other wall
alignments were tested for the approach walls. Final
wall alignments were based on the results of the model
studies.
Weir. The control structure of the spillway con-
sists of an ungated, concrete, ogee weir with a crest
elevation of 1,515 feet and net length of 360 feet. The
weir length is based on economic studies which com-
pare length of weir to height of dam embankment.
The spillway during the maximum probable flood has
a discharge of 78,400 cfs and a surcharge above weir
crest of 15 feet. The spillway rating curve is shown on
Figure 348.
The weir structure was analyzed as a gravity struc-
ture. Stability against sliding and overturning was
analyzed, and the magnitude and distribution of the
foundation reaction resulting from the weight of the
weir and the applied loads were determined. The weir
structure is anchored to the rock foundation to in-
crease its effective weight. For computing the stabil-
419
5
— r-|S
t
»
8
11*
%
Figure 346. General Plan and Profile of Spillway
420
!l
Figure 347. Spillway and Stilling Basin
ity, the critical sliding plane was assumed as the
surface passing from the bottom of the upstream shear
key to the bottom of the toe curve slab at the down-
stream end.
Transition. The transition, immediately down-
stream of the weir, directs the flow into the 85-foot-
wide chute with a minimum of turbulence. The flare
angle for the transition was checked for contractions
in supercritical flow. Various flare angles were tested
in the hydraulic model. The design angle used gave
the most satisfactory model study results.
Chute. The chute extends between the end of the
transition at Station 25 + 54 and the beginning of the
stilling basin at Station 51+00 (Figure 346).
Hydraulic model tests showed the flow down the
transition and the chute to be satisfactory for the max-
imum discharge of 78,400 cfs, except for a short area
where wave action approached the top of the wall.
Wall heights were increased in this area to maintain
freeboard.
Stilling Basin. The spillway stilling basin was de-
signed to still all flows up to the 400-year flood. It will
traject all the discharges that exceed the 400-year flood
to a point not less than 100 feet downstream.
Freeboard to contain the hydraulic jump was the
controlling factor in determining the wall height re-
quired. The length and radius of the flip bucket were
chosen to yield a trajectory length of greater than 100
feet and to resist all dynamic, hydrostatic, and soil
loads applied to it during spillway operation and dur-
ing the design earthquake. Following standard prac-
tice, it is assumed for design purposes that there will
be no seismic action during maximum probable flood
conditions.
Return Channel. Immediately downstream of the
flip bucket, a channel approximately 400 feet long re-
turns all flows to Castaic Lagoon. Channel side slopes
and floor are protected from erosion by riprap sized
to resist return flows that occur when the flip bucket
trajects the flow.
Retaining Wall Design. The active and passive
states of earth pressure in the pervious backfill were
MAX. W
ELEV.
1530.0
^
^
^
^
30 40 SO
DISCHARGE IN 1,000 cfs
Figure 348. Spillway Rating Curve
421
computed. Soil load was determined under the effect
of earthquake loading.
For various retaining wall design conditions where
normal stresses were allowed, the resultant of the ap-
plied forces is within the middle one-third of the base.
For improbable conditions (such as water in the spill-
way at the time of an earthquake) where the allowable
stresses are increased by one-third over normal
stresses, the resultant of the applied forces is within
the middle one-half of the base.
The approach, transition, and chute walls are of the
cantilever type and vary in height from 7 to 26.5 feet.
Near the end of the chute, at Station 49-f-08, the wall
changes from cantilever to counterfort. Counterfort
walls vary in height from 26.5 feet at Station 49 + 08
to 70 feet at the start of the stilling basin (Station
51+00).
The use of gravity, cantilever, and counterfort walls
for the stilling basin was investigated. Counterfort
walls were selected on the basis of economy and ease
of construction.
Floor Design. The impervious blanket in the
aproach channel extends upstream from the spillway
crest structure approximately 300 feet to create a per-
colation barrier to control seepage below and around
the spillway crest structure. The blanket is a 3-foot-
thick, compacted, impervious material. Three feet of
riprap was placed over the impervious blanket in the
approach channel.
The floor slabs in the transition and chute were
designed in approximately 30- by 35-foot panels. Sta-
bility without the use of anchor bars and ease of con-
struction were considered when the size and thickness
of the floor slabs were selected. All transverse contrac-
tion joints were provided with a cutoff and drains.
The floor slabs were designed to resist uplift when the
downstream transverse drain in a panel is plugged and
no water is flowing in the spillway channel.
Open-Cut Excavation. All construction slopes,
except in the area of the stilling basin, are %:\. Near
the stilling basin, the maximum construction slopes
are 1/2: 1. which provides more stability. The extra
slope stability was required because the excavation in
the area of the stilling basin is deep and was left ex-
posed for a considerable period of time. Permanent
slopes do not exceed 2:1 on the eastern side of the
spillway excavation nor l'/^:l on the western side.
Berms, in general, are spaced 40 feet vertically. The
berms are 15 feet wide and slope at 7/2:1 from the toe
to the heel of the berm. Where necessary, a pneumati-
cally applied mortar was provided for erosion protec-
tion.
Drainage. To reduce uplift, drainage was pro-
vided under the downstream end of the crest toe, floor
slabs of the transition chute, and stilling basin, thus
adding to the stability of the structure. The under-
drain system consists of a drainage gallery, cross
drains, wall heel drains, and French drains.
Foundation. The final selection of alignment and
grade of the spillway weir, chute, and stilling basin
achieved acceptable foundation conditions and satis-
fied all the hydraulic requirements. The upstream
starting point placed the foundation of the weir crest
structure in fresh Castaic formation that was not fault-
ed nor otherwise disturbed. The location of the still-
ing basin was governed by locating the flip bucket in
fresh Castaic formation. The stilling basin floor is 10
feet deeper than required for hydraulics to ensure that
the entire foundation of the structure is in fresh Casta-
ic formation.
Outlet Works
During the early design phases, several configura-
tions were considered for the outlet works. These in-
volved principally the intake tower and the
downstream facilities. These studies included (1) a
free-standing tower with its base at elevation 1,200
feet, (2) a sloping intake similar to the one at Lake
Oroville for Edward Hyatt Powerplant, and (3) the
final design that was built. The first two plans were
eliminated because of topographic and geologic condi-
tions. All plans considered multiple intakes to satisfy
water quality requirements. The outlet works (Fig-
ures 349 and 3 50) utilizes the existing diversion tunnel
to convey water under the Dam. Several modifications
and additions to the diversion tunnel were required.
A low intake tower (Figure 351) is located on the
diversion tunnel intake structure. The tower is 15 feet
in diameter, 100 feet high, and draws water from the
reservoir above elevation 1,280 feet, minimum reser-
voir pool.
A multiple-level, high, intake tower (Figure 352) is
located above the diversion tunnel and is connected to
it by a vertical shaft. An access bridge (Figures 353
and 354) spans from the right abutment of the Dam
to the high intake tower. A fixed-wheel gate was
placed upstream of the shaft and diversion tunnel in-
tersection to shut off discharges through the low in-
take.
A 19- foot-diameter steel penstock, located in the 27-
foot-diameter diversion tunnel, terminates at a bifur-
cation at Station 50+50. This bifurcation reduces and
separates into two 9-foot - 6-inch-diameter penstocks.
The stream release facility (Figures 355 and 356) is
composed of these two penstocks and three smaller
lines that branch from the left 9-foot - 6-inch branch.
Fixed-cone dispersion valves and a pressure-reducing
valve are used to regulate stream releases. The control
valves are protected by butterfly guard valves.
Turnouts just upstream from the bifurcation (Fig-
ures 357 and 358) deliver water to the various water
users. These turnouts enter vaults containing guard
valves which are operated either fully open or fully
closed. This permits each water user to regulate the
flow rate with his own downstream valving. Meter
vaults are located downstream of the guard valve
vaults.
422
Figure 349. Outlet Works — Plan and Profile
423
Figure 350. Ouflet Works — Plan and Profile (Continued)
424
Figure 351. Outlet Works — low Intake Tower
425
/
V ^
^R
\\Jl/
/ \
^""'^
\
\
L
I ^
i~ivS
<^ \
1 1
1
-s
'"" t"
r. o"/;j
^w
^-\
-
■5
ri 1
Vx
1
-/
J /
1
(
•:
-1-y
— V M /_ 1
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Figure 352. Outlet Works— High intake Tower
426
Figure 353. Access Bridge
427
Figure 354, High Intake Tower and Access Bridge
428
Figure 355. Stream Release Facility
429
Figure 356. Outlet Works Stream Release
430
Figure 357. General Plan of Turnouts
431
Figure 358. Outlet Works Turnouts
Hydraulics. The hydraulic criteria used to design
the delivery system were based on contract commit-
ments and maximum deliveries as follows:
Yearly Contract Maximum Delivery
The Metropolitan Water
District of Southern
California (MWD) 2,000,000 acre-feet 3,650 cfs
Castaic Lake Water
Agency (CLWA) 41,500 acre-feet 103 cfs
X'entura County Flood
Control District
(\CFCD) 20,000 acre-feet 35 cfs
Totals 2,061,500 acre-feet 3,788 cfs'
* Design flow with reservoir surface at elevation 1,421 feet.
The head available to make these deliveries was estab-
lished at 21 feet (reservoir water surface elevation
1,421 feet — hydraulic gradeline elevation 1,400 feet at
the Department/MWD delivery point). From the
just-mentioned criteria, tunnel, pipe, and turnout
sizes were selected. The sizes of the turnouts are as
follows: two 150-inch, one 132-inch, and one 78-inch
for MWD; one 60-inch for CLWA; and one 30-inch for
\'CFCD. The required port area per level at the high
intake tower was 88 square feet, based on a velocity
through the ports of approximately IS feet per second.
This was based on operating two levels of ports for
maximum delivery.
All natural inflow is to be measured for release to
the downstream water rights owners. Flows up to
6,000 cfs are released at the same rate as the inflow.
Flows above the maximum outflow rate of 6,000 cfs
are stored until this excess inflow can be safely
released. Downstream flow releases are through two
96-inch, one 30-inch, and one 10-inch fixed-cone dis-
persion valves, and one 8-inch pressure-reducing
valve.
To minimize cavitation problems, the fixed-cone
dispersion valves will not be operated less than 10%
open. The 8-inch pressure-reducing valve can dis-
charge O..') to 8 cfs between minimum total net head of
156 feet and 320 feet of maximum static head.
Reservoir drawdown time from elevation 1,515 feet
(maximum water surface) to elevation 1,400 feet is
about 14 days. Maximum discharge with the fixed-
cone dispersion valves removed is approximately
11,000 cfs.
A fish barrier was required to prevent the passing
of fish from the reservoir into the system. The fish
screens are movable and cover any two adjacent ports
in a vertical row. The units travel inside the trashrack
on rails with a clear distance of at least 6 inches be-
tween the trashrack system and the screen. Openings
with movable covers are provided to allow the screen
unit to pass protruding hardware on the outside of the
tower.
The fish screens consist of stainless-steel mesh with
%-inch clear opening attached to a frame of stainless-
steel tubing. The mesh was designed to withstand 5
feet of differential head, and the frame was designed
to withstand 10 feet of differential head.
Structural Design of High Intake Tower. The
superstructure arrangement was chosen to accommo-
date mechanical and electrical equipment and to sat-
isfy structure requirements.
in design of the operating deck, five live load
sources were considered. In design of the intake
tower, six loading cases were considered, including
seismic forces with tower dry and with v\ater both
inside and outside the tower. San Andreas design
earthquake spectra, as developed by the Department's
Consulting Board for Earthquake Analysis, was used
432
I as the basis for determining design accelerations for
! the tower. For determination of design base moment
and shear, 60% of the San Andreas spectral accelera-
tion was used. This reduction was based on considera-
tion of the seismic response of the foundation material
and on the relative importance of the high intake sys-
tem and the consequences of its failure. The calculated
modal periods of the tower were 0.78 of a second, 0.12
of a second, and 0.045 of a second for the first three
modes. The 8% damping factor used in the seismic
' response analysis resulted in acceleration factors of
0.25, 0.33, and 0.30 for the first three modes.
The tower was treated as a moment-deflecting can-
tilever. For the controlling seismic case, the base mo-
ment and shear are a result of the dead- weight inertial
load of the tower and superstructure, internal hydro-
dynamic load, and external hydrodynamic load. Dy-
namic and hydraulic model studies, conducted at the
University of California at Davis, verified the design
assumptions (see Bibliography).
The intake shaft was designed to transfer base mo-
ment and shear to the foundation rock. A joint was
designed for the shaft at elevation 1,262 feet to prevent
transfer of the moments to the tunnel. Tower and
shaft dead weight were included with the maximum
moments from flexural design. Hoop reinforcement
was designed to provide tensile reinforcement to resist
diagonal tensile stresses associated with moment and
shear in horizontal planes during an earthquake.
Placement of shotcrete was specified after the com-
pletion of each 6 feet of shaft excavation, thus prevent-
ing air slaking and minimizing the need for lagging.
Excessive lagging would reduce the effectiveness of
the shaft concrete contact with the rock. A consolida-
tion grouting program also was specified to fill voids
and structural defects in the surrounding rock and
between the rock and shaft concrete.
Trashracks protect all the tower intake ports and
the traveling fish screens from logs and other debris.
Maximum spacing of the trashrack tubes was set at 4
inches, based on the maximum-size debris that can
pass through downstream facilities. Stainless steel was
chosen because of its low maintenance requirement
and long service life.
High Intake Tower Access Bridge
The high intake tower access bridge, in combina-
tion with an approach ramp, provides access to the
Castaic outlet works high intake tower from the near-
by crest of the Dam. A curved bridge alignment was
required to permit an efficient arrangement of equip-
ment in the tower. This alignment also located the
abutment a safe distance from the top of an adjacent
cut slope and allowed for an economical design of the
abutment.
The bridge is 504 feet long with a superstructure
consisting of four simple spans of welded-plate girders
acting compositely with a lightweight concrete deck.
The girders are supported by the high intake tower,
reinforced-concrete piers which are socketed into
rock, and a reinforced-concrete abutment. The super-
structure is highly articulated to accommodate ex-
treme earthquake movements. It provides a clear
roadway width of 16 feet between barrier railings.
Design was in accordance with the 1965 AASHO
specifications and with the State of California "Bridge
Planning and Design Manual". The bridge was de-
signed for a live loading of HS20-44 and an alternative
loading of two 24,000-pound axles, 4 feet apart.
Instrumentation
Castaic Dam instrumentation consists of 15 pneu-
matic foundation piezometers, 16 pneumatic embank-
ment piezometers, 18 hydraulic piezometers, 13
open-tube piezometers, 8 embankment slope indica-
tors, 9 abutment slope indicators, 69 embankment sur-
face monuments, 15 embankment soil stress cells, 7
embankment accelerometers, 1 foundation accelerom-
eter, and 2 accelerographs. Monuments also are locat-
ed along the top of the spillway walls and on other
concrete structures. The instrumentation was de-
signed to monitor pore pressures and vertical and
horizontal movements, as well as acceleration re-
sponse of earth motion and dynamic stresses resulting
from seismic activity (Figure 359). Seepage is meas-
ured at the end of the embankment drainage system
and in the spillway drainage gallery.
Castaic Lagoon
As previously mentioned, the Lagoon was initially
a borrow area immediately downstream from the toe
of Castaic Dam. Maximum elevation of the floor of the
Lagoon is 1,125 feet. A minimum of 2 feet of fine-
grained, mandatory, spoil blanket was required over
most of the Lagoon to control seepage. Where Castaic
formation was exposed, no cover was required. The
west side of the Lagoon was excavated to enhance the
recreation development.
The control structure for the Lagoon is a 170-foot-
long by 350-foot-wide concrete apron under the new
Lake Hughes Road Bridge. A rectangular discharge
channel near the east abutment of the Bridge carries
streamflows up to approximately 12 cubic feet per
second. A standard Parshall flume with a throat width
of 2 feet and a depth of 1 foot - 6 inches was installed
near the upstream edge of the apron for flow measure-
ment. Downstream releases are recorded by a flume-
recording well. Flows greater than the capacity of the
Parshall flume pass over the entire 350-foot width of
the apron. The control structure is designed to pass
the standard project flood discharge from the spill-
way.
Details and sections of the lining of the approach
channel are shown on Figure 360. Downstream ero-
sion control consists of riprap as shown on Figure 361.
The bridge abutments form a portion of the control
structure walls. Cantilever walls of varying height
flank these abutments upstream and downstream to
complete the control structure walls (Figure 362).
433
Figure 359. Instrumentation — Plan and Section
434
H
360. Castaic Lagoon Control Structure Sections
43S
Figure 361. Castoic Lagoon Control Structure — Erosion Control
436
Mechanical and Electrical Installations
The mechanical features of the outlet works consist
of three major systems: (1) the high intake valves,
operating system, and auxiliary equipment; (2) the
turnout guard valves and operating systems; and (3)
stream release regulating system.
The flow of water into the outlet works is con-
trolled by the high intake tower port valves for normal
reservoir operating levels and the low intake gate for
low reservoir levels. The high intake auxiliary equip-
ment provides emergency power, handling, mainte-
nance, and repair capabilities. The turnout guard
valves and support equipment provide closure capa-
bility for the performance of maintenance work on
water user pipelines and meet the needs of any outlet
works emergency. The stream release regulating sys-
tem provides for release of normal streamflow, storm
inflow, and emergency drainage of the reservoir.
Separate normal electrical service is supplied by a
utility company, and standby electrical power is pro-
vided by engine-generator sets for the intake tower
and stream release facilities. A single-line diagram for
the intake tower is shown on Figure 363 and the
stream release facilities on Figure 364.
All equipment necessary for remote monitoring and
control of the intake tower is contained in the tower,
while the outlet works control building contains all
the equipment for the stream release facilities. Data,
status, and alarm information is transmitted to Castaic
Powerplant and Castaic Area Control Center. Emer-
gency closure of the intake tower valves and the fixed-
wheel gate may be accomplished from the Castaic
Area Control Center.
Local controls and annunciations for the intake
tower are located in the tower. Local controls and
I
annunciations for the stream release facilities are
located in the outlet works control building with du-
plication at the valves.
High Intake Port Valves. The high intake port
valves consist of 22 hydraulic motor-operated, 72-inch-
diameter, rubber-seated, butterfly valves with provi-
sions for future installation of 14 additional 72-inch-
diameter valves.
The valves are located within the tower on four
vertical rows with nine tiers. The tiers are on 17-foot
centers from elevation 1,357 to elevation 1,493 feet.
Only the bottom two tiers contain valves in all four
rows. The remaining valves are on the two opposing
rows. Two rows of port thimbles without valves are
blocked with a blind flange until future use is re-
quired.
A hydraulic power and control unit was installed on
the operating deck (elevation 1,526 feet) to provide
power to the hydraulic motors. The valves are set to
open or close in a five-minute operating time, and
controls are provided to operate any combination of
valves on a given tier. The valves are designed for a
normal operating condition to pass 765 cfs in free
discharge with a static head of 30 feet.
Each valve in any one row of the tower is capable
of operating partially opened to provide a free dis-
charge flow of 80 cfs at a differential head of 30 feet.
The partially open condition is used to fill the tower.
Except for filling the tower, the valves are used only
in the fully opened or fully closed position.
The port valve thimbles were designed with an el-
liptically shaped bell-mouth-type entrance based on
the equation — — -|- —^ — = 1 where constants
1296 100
are selected to suit the space available for the port.
437
M'Bi
I
I
Figure 363. Single-Line Diagram — Intake Tower
438
Figure 364. Single-Line Diagram — Stream Release Facilities
439
The port valves were designed to meet AWWA
C504 Class 7SB or better rating (Figure 365). The
valve disc is offset from the stub shafts with disc posi-
tion set to create a closing torque imbalance. Should
a failure occur in the operator that allows the disc to
rotate freely, the valve will be closed automatically by
hydraulic forces caused by the flow of water. The
valves were installed with the shafts in a vertical posi-
tion to provide the most suitable location of the opera-
tor and to minimize disc vibration. Mounting holes
were made on the downstream valve body flange to
permit future installation of hoods when four valves
per tier are installed. The hoods are to direct the flow
in a downward direction. Model studies indicate that
the four-valve-per-tier configuration could cause
pockets of air to be trapped if no hoods are used.
Three different models of the worm gear-type valve
operator are used to match the emergency torque re-
quirements of each tier. The hydraulic motors used on
the operators are a constant displacement, multiple
axial-piston, rotating type. The valve shaft is attached
to the operator by a splined adapter which fits into the
operator drive sleeve.
A 10-gallon-capacity lube oil reservoir was installed
on the operating deck. It is connected by tubing to
each operator housing. This oil lubricates the operator
and provides a positive head inside each limit switch
and operator housing to prevent water intrusion.
The hydraulic power system is rated 2,000 pounds
per square inch (psi) at 20 gallons per minute (gpm).
Power is provided by an electric motor-driven pump.
The system contains directional control valves, relief
valves, check valves, and other auxiliary equipment as
shown on Figure 366.
Low Intake Gate System. The low intake gate is
located at the upstream interior wall of the high intake
tower. The gate is of the vertical-lift fixed-wheel type,
with upstream seals and skinplate (Figure 367).
The gate normally is in the closed position and will
be used only for delivery of water when the reservoir
level is below the level of the tower outlet valves or for
emergency drainage of the reservoir. The gate is ap-
proximately 1 1 '/^ feet wide by 1 1 feet high and is de-
signed for a maximum head of 322 feet. The gate is
connected by a 306-foot guided stem extending verti-
cally to a hydraulic gate operator cylinder located on
the top deck of the tower.
Preliminary design of the gate-stem system indicat-
ed the possibility of a resonating condition produced
by flow under the partially open gate.
Model studies (see Bibliography) showed that pres-
sure fluctuations in the flow at the gate lip were near
the resonant frequency of the gate-stem system and
that the magnitude of the load fluctuations were such
that failure of the gate stem was possible. The original
design of the sluiceway and gate was modified to
reduce the vibrations. The modifications are shown
on Figures 367 and 368.
A hydraulic cylinder operator is provided for open-
ing and closing of the low intake gate. The operator
has a 14-inch bore and a 192-inch stroke. The operator
was designed to open the gate under an unbalanced
head of 213 feet and close the gate under an un-
balanced head of 307 feet. The hydraulic system is a
dual pressure system incorporating separate pumps
for opening and closing. Opening pressure is 1,500 psi
and closing pressure 750 psi. The dual system was
used due to the great difference in force required be-
tween raising and lowering the gate. The operator was
designed for local-manual operation for both opening
and closing the gate and for remote-manual opening
of the gate.
High Intake Auxiliary Equipment. The high in-
take auxiliary equipment (Figures 369, 370, and 371)
consists of a 6-ton tower jib crane, 20-ton polar bridge
crane, maintenance platform, fish-screen hoists, bulk-
head gates, emergency engine-generators, and a fish-
screen washing system.
A 6-ton-capacity, cab-operated, outdoor, full-revolv-
ing, leg-braced, jib crane was installed at the top of the
outlet works high intake tower (Figure 372). The
crane is trunnion-mounted and revolves on a rail an-
chored to the edge of the tower. The crane's purpose
is to install and remove the valve maintenance bulk-
head gates, trashrack panels, and fish screens. The
motors for the hoist, jib motion, and trolley travel
controls are regulated stepless adjustable voltage, di-
rect-current, regenerative-braking, and static-revers-
ing. Separate operation is provided for each control.
The controls are interlocked so that the jib and trolley
drives will no^ operate while the hoist is being raised
or lowered. Capacities and speeds are as follows:
Rated capacity of crane, tons 6
Rated capacity of hoist, tons 6
Rated hoisting speed,
feet per minute (fpm) 25-30
Jib travel speed, fpm at centerline of rail .... 4-6
Trolley travel speed, fpm 4-6
Maximum lift, feet 210
Operating reach, feet 0-12
440
Figure 365. Butterfly Valve Assembly
441
Figure 366. Port Valves — Hydraulic Scheme
442
Gate Stem Guide
TOP VIEW
Roller Track
Seol Plotes
D
SECTION A-A
1 0 1 2 3 4 5
Lla-i-il 1 1 1 1 1
Scole of Feet
Figure 367. Low Intake Gate
443
Vortex Suppressor Vones
(Added to Final Design)
Elev. 1212.5
B U-C
nvert Elev. 1208.05
'i'-f'". '
- "■ *'.
4 *
f ■*
"« .'
.
: •-
f,-
~
'••-;
- 6' .
."*>.
* *•'•*
SECTION A-A
SECTION B-B
SECTION C-C
5 0 5
■ •••■' I
Stole of Feet
Figure 368. Low Intake Sluiceway
444
Figure 369. General Arrangement of Tower Mechanical Features — Elevation and Plan
445
Figure 370. General Arrangement of Tower Mechanical Features — Elevation and Plan (Continued)
446
Figure 371. General Arrangement of Tower Mechanical Features-Plan and Section
447
Figure 372. Tower Jib Crane
448
A 20-ton-capacity, electric, cab-operated, indoor,
overhead, revolving. Polar bridge crane was installed
in the outlet works high intake tower operating bay
(Figure 373). The crane revolves on a rail anchored to
the inside tower wall. The primary use of the crane is
to install, remove, or perform maintenance on the
tower port valves and valve operators, and to position
the valve maintenance platform. The crane also is
used for low-level gate removal, low-level gate hydrau-
lic-cylinder servicing, and handling of miscellaneous
equipment in the operating bay. The motors for the
hoist, bridge, and trolley travel controls are of the
same type as previously mentioned for the jib crane
and were designed so that the hoist may be operated
at full load simultaneously with the operation of the
trolley and bridge drives. Capacities and speeds are as
follows.
Rated capacity of crane, tons 20
Number of trolleys I
Rated capacity of hoist, tons 20
Rated hoist speed, fpm, with maximum
working load 1-10
Bridge travel speed with maximum working load:
Bridge, rpm 0.47-0.70
Truck speed at wheels, fpm 50-75
Trolley travel speed, fpm, with maximum
working load 20-30
Diametric span, feet 35
Length of lift, feet 200
The maintenance platform consists of a portable
maintenance platform and trolley. Its main function is
to aid in the servicing of the tower port valves and any
maintenance work in the tower below the gate service
deck. Its secondary function is to aid in the storage of
the low intake gate stems when the platform is stored.
Four 7 '/-ton-capacity fixed hoists are provided to
position the fish screens in front of the tower port
valves. The hoists are located on the top of the high
intake tower adjacent to the jib crane. Each hoist has
a lifting speed of 9 to 10 feet per minute and a max-
imum lift of 175 feet. Each hoist consists of a parallel
shaft gear reducer, gear motor, magnetic brake, and
two hoist drums with stainless-steel wire ropes. The
control for the fish-screen hoist was designed for local-
manual or remote-automatic operation.
Two structural-steel bulkhead gates are provided to
facilitate removal or repair of the high intake tower
port valves. The gate system is composed of two bulk-
head gates, a lifting beam, four gate guides, and gate
seal plates mounted around each valve port (Figures
374, 375, and 376). The gate body was constructed of
sixWl2Xl06 (12WF106) beams welded to a skinplate.
The gate was designed to seal at all depths up to 168
feet by the use of a counterweighted linkage system
which extends or retracts dogging bars. The lifting
beam also has a counterweighted linkage system to
operate its hooks so that the lifting beam can be au-
tomatically attached or detached from a gate in its
parked condition. The gate must be installed or
removed from the tower under a balanced head condi-
tion.
The two emergency engine-generator sets are lique-
fied petroleum gas-fueled. One set provides emer-
gency power for equipment in the high intake tower,
and the other set provides emergency power to the
stream release and turnout facilities. The engine-gen-
erator set for the stream release and turnout facilities
is a continuous-duty rated unit of 100 kW. The high
intake engine-generator set is a continuous-duty rated
unit of 75 kW.
Generator
Tower
Stream Release
and Turnout
115 kW
100 kW
1,800
+ 2%
Standby Power 85 kW
Continuous Power 75 kW
rpm 1,800
Voltage Regulation + 1%
The fish-screen washing system uses reservoir wa-
ter to clear away debris attached to the four fish
screens on the high intake tower. The system consists
of two 165-gpm, 400-foot total dynamic head, submers-
ible pumps and a piping manifold system supplying
water to four spray stations and four hose valves. The
washing system manifold was installed just below the
operating deck. The pumps were installed in two 12-
inch wells in the high intake tower walls at a distance
of approximately 150 feet below the supply manifold.
The spray nozzles were selected by testing several
types. The type chosen provided a flat spray with a
15-degree spray angle.
Turnout Guard Valves. All turnout guard valves
are adjustable, steel-seated, butterfly valves. The 42-
inch, 78-inch, and 132-inch valves are operated by hy-
draulic cylinders. The 30-inch valve is electric motor-
operated. Control for each valve is provided remotely
at the Castaic Area Control Center and locally at the
valve hydraulic control cabinet. These valves are de-
signed to operate under the following conditions:
Maximum Emergency
Valve Static Maximum Operating Total Downstream
Size Head Flow Time Head at Maximum
(inches) (feet) (cfs) (minutes) Flow (feet)
132 322.9 6,600 10 271
78 322.7 2,300 5 301
42 323.1 1,050 5 188
30 323.2 340 5 306
The valves normally are in the fully open or fully
closed position. The 132-, 78-, and 42-inch valves are
opened under a balanced head condition by means of
a bypass system.
The operators used on the valves were based on
torque required during emergency closure. The high-
er torques required by the 1 32-, 78-, and 42-inch valves
were suitable for hydraulic cylinder operators. The
motor operator for the 30-inch valve is a worm gear
type with handwheel.
449
Figure 373. 20-Ton Polar Bridge Crane
450
Figure 374. General Arrangement of Bulkhead Gate
451
o
o
o
o
iipfflli
i' " !i
siyi
-tMiJ
I
Pi
hit
E
II
:^-l
Figure 375. General Arrangement of Bulkhead Gate and Lifting Beam
452
Is ^
J-[~ f ■•» i.<l S SS.
S'i *8 i-5 i„ s «;
M> il fft ',5 ' 58
ll ^ £« «« ^3 < «S
1le
Figure 376. General Arrangemerit of Bulkhead Gate, Thimble Seol Plate, and Guide
453
ff
The hydraulic power for each cylinder-operated
valve is provided by its own system. Each system is
housed in a control cabinet installed in its own valve
vault. 1 he hydraulic power system for each of the
13 2-, 78-, and 42-inch valves are pump-operated at a
pressure of 2,000 psi (Figure 377).
The turnout valves are to be locked whenever they
are in the open or closed position. In the open posi-
tion, the 132-, 78-, and 42-inch valves are locked to
overcome the closing tendency of butterfly-type
valves by interference, fitted, clamping sleeves which
are released by each valve's hydraulic power system
prior to closing the valve. The holding power is equal
to 25% of the maximum force of the hydraulic cylin-
der. In the closed position for the 1 32-, 78-, and 42-inch
valves, a hand-operated mechanical lock is used to ef-
fect a holding power greater than the maximum force
of the hydraulic cylinder. The 30-inch valve is locked
in the open or closed position as a consequence of the
worm gear-type operator.
Stream Release Facilities. The stream release
facilities (Figure 378) consist of five discharge regu-
lating systems installed on or within vaults in the
concrete facility structure. The structure is located at
the end of the 228-inch penstock as shown on Figure
379.
Two 96-inch, one 30-inch, and one 10-inch fixed-
cone dispersion valves and one 8-inch pressure-reduc-
ing valve are provided as discharge regulating valves.
The guard valves provided for the stream release
system are:
1. A 114-inch valve installed upstream of each 96-
inch fixed-cone dispersion valve.
2. A 42-inch valve installed upstream of the 30-inch
fixed-cone dispersion valve.
3. An 18-inch valve installed upstream of the 10-
inch fixed-cone dispersion valve.
4. An 8-inch manually operated plug valve installed
upstream of the 8-inch pressure-reducing valve.
Stream Release Regulating Valves. Each fixed-
cone dispersion valve is controlled by its electric mo-
tor operator and gear reducer. Each operator can be
controlled locally in the gate chamber and remotely
from the Castaic Area Control Center.
The fixed-cone dispersion valves were designed in
accordance with the following requirements and de-
sign criteria:
Minimum
Minimum
Opening
Maximum
Total
Discharge
and
Valve
Static
Discharge
@ Minimum
Closing
Diameter
Head
Head
Total Dynamic
Time
(inches)
(feet)
(feet)
Head (cfs)
(minutes)
96
350
111
3,000
10.9
}0
}50
149
337
4.0
10
}S0
162
39
1.0
The critical dimensions for the net discharge areas of
the valves are based on a discharge coefficient of 0.8.
Special features were included in the design of these
valves to provide additional stiffness in the valve body
and ribs. These features were incorporated to prevent
vibration and progressive failure of ribs which have
been previously experienced at other facilities.
An 8-inch pressure-reducing valve was installed in
the stream release facility, which discharges 0.5 cfs at
a minimum total head of 156 feet and 8 cfs at a max-
imum total head of 320 feet.
Stream Release Guard Valves. The 1 14-, 42-, and
18-inch guard valves are butterfly valves. The 1 14-inch
valve is hydraulic cylinder-operated and the 42- and
18-inch valves are electric motor-operated. The valves
were installed in vaults inside the stream release struc-
ture.
The valves are required to operate under the follow-
ing conditions:
Valve
Maximum
Maximum
Operating
Size
Static Head
Flow
Time
(inches)
(feet)
(cfs)
(minutes)
114
m.9
5,500
10
42
323.6
490
5
18
314.5
58
5
8
320.0
8
—
The function of the valves is to shut off flow to the
fixed-cone dispersion valves to allow their mainte-
nance and repair.
The stream release valves are locked whenever they
are in the open or closed position. The locking system
for the 1 14-inch valves is the same as that for the cylin-
der-operated turnout valves. The 18- and 42-inch
valves are locked in the open or closed position due to
the self-locking worm gear operator.
The operators used on the valves were based on
torque required during emergency closure. The high-
er torques required by the 1 14-inch valves were suita-
ble for the use of a hydraulic cylinder operator. Motor
operators for the 18-inch and 42-inch valves are a
worm gear type with handwheel.
The hydraulic power for both 114-inch valves is
provided by a single pump-operated system with an
operating pressure of 2,000 psi (Figure 380).
454
«i!Pii
I i .
t * ? { - ; ^5 ("-Sis
Figure 377. Turnout Valve — Hydraulic Schematic
455
- Jo a ;
" 'til'
w
Figure 378. General Plan of Stream Release and Turnouts
456
^
^:^
\^
' if
1
7tLd°"
i^
3
m
1=
Figure 379. Stream Release Facility — Plan and Sections
457
Figure 380. Hydraulic Schemotic
458
Construction
Contract Administration
General information about the major contracts for
construction of Castaic Dam and appurtenances is
shown in Table 45. Most of the contract work was
included in three large contracts. All contract work
was administered by the Castaic Project Office located
near the Dam.
Foundation Trench
Between August and December 1965, in advance of
the large contracts, a trench was excavated to bedrock
in the vicinity of the dam axis. Approximately 475,000
cubic yards of material was removed in forming a
combination foundation excavation and exploration
trench.
Diversion Tunnel
Open-Cut Excavation. Excavation for the outlet
channel and the stilling basin for the diversion tunnel
began in April 1966. It involved the excavation of a
bowl-like basin in which the south portal, outlet chan-
nel, and stilling basin were situated. Materials from
ripping and scraping operations were disposed of in
spoil areas with the exception of selected materials,
which were stockpiled near the Dam site. Small land-
slides were encountered in the east-slope excavation
where aquifers or shears were intercepted.
The upstream portal approach was excavated to ele-
vation 1,200 feet and to a point where the tunnel cover
was well within the Castaic formation. The excava-
tion was 50 feet below original ground with a floor
width of 90 feet.
Miscellaneous excavations were performed for foot-
ings for the portal protective structures, keyways
beneath the sloping outlet channel footings, and a cut-
off trench that was dug around the stilling basin and
backfilled with impervious fill. A dragline and scraper
were used to excavate 85,000 cubic yards of material.
Underground Excavation. The north (upstream)
tunnel heading was excavated to a 23-foot-diameter
and finished to a 19-foot-diameter circular section.
The south (downstream) heading was excavated to a
30-foot diameter and has a finished section with a 27-
foot diameter. In the vicinity of the transition section
between the north and south headings, trenches for
nine cutoff collars were excavated.
North heading tunnel excavation was done by the
top heading method after completion of the portal
protective structure. Drilling was accomplished from
a jumbo by four pneumatic auger drills with carbide-
insert dragline bits. An imbalance in the loading of the
holes, lack of relief cut in the center of the face, and
concentration along the lower rib sections contribut-
ed to larger than normal overbreak and perimeter
shattered areas.
Construction of a reinforced-concrete junction sec-
tion for the high intake structure was provided by
enlarging the tunnel diameter by V/^ feet from Station
20-1-68 to Station 20-1-16. From Station 20+ 3 1 to Sta-
tion 204-46, the roof was enlarged an additional 4 feet
(Figure 341).
Final excavation operations provided for a semi-
circular invert section to final rough grade. It left cut
rock benches along both sides as foundation for sup-
port posts. A 4-inch-thick, concrete, mud slab was
FABLE 45. Major Contracts-
Castaic Dam ar
d Appurtenances
Specifi-
cation
Low bid
amount
Final
contract
cost
Total cost-
change
orders
Starting
date
Comple-
tion
date
Prime contractor
65-42
66-16
67-20
67-28
68-31
68-37
68-38
71-21
73-15
3398,620
8,580,940
43,389,724
1,080,406
13,725,362
61,275
106,382
335,415
666,186
3412,269
12,896,281
63,681,552
1,121,834
15,457,729
63,316
144,673
443,065
796,336
311,383
465,826
7,576,510
42,945
1,750,360
23,985
56,892
37,558
8/11/65
4/ 9/66
5/19/67
6/22/67
2/17/69
10/ 8/68
10/ 8/68
9/27/71
6/25/73
12/22/65
10/ 4/68
11/ 8/71
5/ 4/68
6/ 9/73
8/ 5/69
3/ 8/73
4/20/72
5/24/74
Tomei Construction Co.
Castaic Dam Diversion Tunnel. .
Castaic Dam and Reservoir
Castaic Project Facilities
Castaic Dam Outlet Works
Soil Stress Measuring and Re-
cording System for Castaic
Dam
Peter Kiewit Sons' Co.
Western Contracting Corp.
Montgomery Ross Fisher, Inc.
Polich-Benedict Constructors
Aerojet-General Corp.
Strong Motion Acceleration Mon-
itoring Systems (Incl. Wheeler
Ridge and A.D. Edmonston
Slope Indicator Co.
Drainage and Paving for Castaic
Dam
F. W. Richter Assoc.
Completion of Castaic Dam
Altfillisch Construction Co.
459
placed over the invert to protect the rock from slaking
and softening.
In the course of excavating the top heading, struc-
tural support distortion and one major cave-in oc-
curred as a result of improper blocking and cribbing,
softening of blast-shattered foundation rocks by water
seepage, and weight of the ground above.
Pervious Backflll and Riprap Placement. Pervi-
ous backfill consisted of carefully selected rock, 100%
passing No. 8 screen and 1% passing No. 4 screen. It
was spread into striplike lifts adjacent to the walls of
the stilling basin with a crawler tractor followed by at
least five passes of the same equipment. A total of 2,600
cubic yards of quarried riprap was placed over the top
of the compacted backfill.
Structural and Tunnel Lining Concrete. A pro-
tective coating was needed on excavated surfaces
which were to receive concrete to prevent breakdown
and sloughing of the structure foundation material
when it became exposed to air and water. A 3-inch-
thick, concrete, protective slab was placed over ex-
cavated foundation, except for the steeper slope above
the stilling basin where pneumatically applied mortar
was employed. The actual thickness of the protective
slab varied considerably because of problems in ex-
cavating a smooth surface in the dipping and folding
planes of shale and sandstone. Consequently, there
was a significant overrun in the quantity of concrete
used.
Most of the structural concrete was used in con-
struction of the outlet channel structure. It is basically
a rectangular channel with a transition from the circu-
lar tunnel to a rectangular cross section, a transition
in the size of the channel, and a vertical curve to a
steep slope which terminates at a large rectangular
energy dissipator. Floor slabs are as much as 6 feet
thick, and the 52-foot-high walls are over 8 feet thick
at the base.
The tunnel, including portal structure, consists of a
1,756-foot section having a 19-foot inside diameter and
a 2,010-foot section having a 27-foot inside diameter.
The entire tunnel lining contains steel reinforcement.
Spacing was sufficient to permit the use of a standard,
1 '/2-inch maximum size aggregate, lining mix except in
the area of the high intake shaft intersection, where
spacing of bundled bars required a mix containing
X-inch maximum size aggregate. A total of 64,868 cu-
bic yards of concrete was placed.
Diversion and Care of Stream
Dewatering operations started May 25, 1967, with
pumping from the dam foundation exploration
trench. This trench, excavated to bedrock on a previ-
ous contract, crossed the stream channel in the vicin-
ity of the dam axis (Figure 381). As the water table
was lowered, dam foundation excavation was extend-
ed outward from the exploration trench. Ditches at
the bases of cut slopes diverted ground flows to sump
holes where the water was pumped and discharged
downstream. The low summer flows of 1967 from
Castaic and Elizabeth Lake Canyon Creeks were inter-
cepted upstream of the Dam site and piped across the
excavation areas.
In August 1967, the creek flow was diverted into a
diked section built along the west side of the canyon
floor. A ditch and dike were provided just upstream of
the Dam to divert Elizabeth Lake Canyon flows to the
right abutment. Construction of an intermediate
channel, with a bottom width of approximately 40
feet, along the right abutment was started in early
November 1967. Runoff from rains in the last part of
November overtopped this channel and flooded the
lower parts of the dam foundation excavation. The
system was adequate for the remainder of the 1967-68
wet season.
Early in 1968, as the upstream Zone 3 foundation in
the channel excavation area was exposed, a ditch to
intercept ground water was dug along the base of the
upstream toe of the dam excavation slope.
Water was pumped and piped from sumps within
the ditch. As the embankment was built, the ditch and
a section immediately above were backfilled with cob-
bles encased in a well-graded drain material to create
an aquifer. Riser pipes with deep well pumps were
installed in the cobbles. This arrangement kept up-
stream seepage from reaching most excavation areas
and provided a reliable water source for construction
purposes.
In October 1968, the diversion tunnel was available
for the contractor's use.
Ditching was done to dewater material in the La-
goon. A channel section also was excavated at the Lake
Hughes Road Bridge to facilitate the flow of water by
that area.
Figure 381. Foundation Exploration Trench
4«0
Castaic Canyon pervious borrow was dewatered by
ditching and sump pumping. A double-barreled cul-
vert of open-ended, railroad, tank cars was installed
between the diverion tunnel inlet and Castaic Canyon
borrow pit operations to handle large flows of water.
Between January 18, 1969 and January 29, 1969,
15.17 inches of rain fell in the Castaic area. The peak
floodflow through the project area was estimated to be
18,000 cfs. Erosion and silting occurred at the Dam
site and locations in the Lagoon. Landslides occurred
in various areas, and heavy erosion occurred under the
Lake Hughes Road Bridge at the south end of the
Lagoon.
Rainfall continued to delay the work during Febru-
ary 1969. An additional 11.87 inches of rainfall was
recorded during that month. The floodflow through
the project area at the end of February peaked at
32,000 cfs. The damages sustained during the January
flooding were increased. A section of the Lake Hughes
Road Bridge was destroyed, and extensive repairs
were necessary (Figure 382).
The dam embankment was restored to prestorm
conditions by May 1969, and the minimum embank-
ment elevation of 1,315 feet was reached by November
1, 1969 in accordance with the specifications for flood
protection.
During the 1969-70 wet season (December through
March), the contractor took precautions in the left
abutment area by diking, sandbagging, and ditching to
minimize aggravation of landslide conditions by
storm runoff and to minimize interference with the
work being conducted there. Dewatering operations
of the upstream borrow areas continued by ditching
and sump pumping to the diversion tunnel. Late rains
of the 1969-70 season ponded in the excavation areas
of Castaic Canyon below the tunnel invert. This water
remained while operations continued in Elizabeth
Lake Canyon.
The lagoon control structure was completed, and
the low-level tunnel inlet was bulkheaded by the out-
let works contractor prior to the 1970-7 1 rainy season.
Storms at the end of November 1970 flooded borrow
operations upstream of the Dam. Continued releases
from runoff and impounded water in the reservoir
threatened a long-term inundation of the lagoon area.
The gates to the diversion tunnel were closed, and no
further releases were made from the reservoir during
the contract since the embankment was high enough
to contain the inflow.
The pervious borrow operations were confined to
the only remaining borrow area, the Lagoon. This
necessitated deeper excavations in this area than origi-
nally planned. Ditches and the sump at the south end
were deepened and higher head pumps installed.
Dam Foundation
Excavation. Excavation for dam foundation in-
cluded removal of all streambed sands and gravels,
landslide material, terrace deposits, soil deposits, and
weathered rock required to reach competent founda-
tion material (Figure 383). The extreme upstream
portion of the Dam within the stream channel was to
rest upon streambed sands and gravels excavated to
elevation 1,190 feet leaving about 60 feet of sand and
gravel but, when excavation reached this elevation,
large silt deposits were discovered. These deposits
were removed under a change order, exposing bed-
rock.
Foundation excavation began at the easterly side of
the channel section immediately north of the explora-
.1^^^
^S%=f-'
^r
"s-
Figure 382. Flood Damage to Lak
Figure 383. Dam Site at Beginning of Work
461
tion trench excavated under the contract for Castaic
Dam foundation trench. Scrapers were used for most
of this excavation, aided by a dragline in areas inac-
cessible to the scrapers. The dragline also was used to
construct sump holes for dewatering the foundation.
Streambed sands and gravels were stockpiled for later
use in embankment construction and, as embankment
areas became available, the excavated streambed sands
and gravels went directly to Zone 3 dam construction.
Other material went to waste piles and haul-road con-
struction.
As previously discussed, storms and inadequate
stream diversion at the end of November 1967 caused
flooding of the low portion of Zone 1 excavation. The
area required pumping and truck removal of muck
(thick, saturated, shale, foundation tailings) for sev-
eral days. Final removal of muck was done by pumper
trucks of the type used in oil fields. The interceptor
system at the upstream toe of the Dam, completed
during January 1968, eliminated the need for the
dewatering sumps within the channel area and exca-
vation of the channel section was advanced toward the
right abutment.
Above streambed level, the excavation procedure
established by the contractor was to start successive
cuts within the abutment areas which would intercept
the dam foundation at predetermined elevations to
coincide with his embankment construction schedul-
ing. Major problems encountered during the founda-
tion excavation were ( 1 ) the uncovering of an existing
slide mass not previously detected at the base of the
upstream right abutment, (2) the easterly sliding
movement of a triangular-shaped block of Castaic for-
mation in the right abutment above the aforemen-
tioned slide mass (Figure 384), and (3) the massive
slides at the left abutment (Figures 385 and 386).
It was determined that the slide mass at the base of
the upstream right abutment required removal. This
was initially accomplished with a scraper operation.
As excavation continued, the area at the base of the
excavation became limited, and water seepage became
a major problem because the slide mass extended be-
low streambed level. The contractor utilized a drag-
line to excavate and load the remaining material and
to progressively lower sump holes for dewatering.
The lowest elevation reached in the slide removal area
was about 120 feet below streambed. The base of the
hole was cleaned, and filling with Zone 3 compacted
embankment was started on January 13, 1969. About
50 feet of the excavation had been backfilled to ap-
proximate elevation 1,150 feet by January 20, 1969,
when heavy rains started. Early attempts to dewater
the slide excavation were futile. Rain continued peri-
odically, completely inundating the dam embankment
area and heavily silting the slide excavation area, bury-
ing the dragline and pumping equipment in the hole.
Between March 21, 1969 and April 16, 1969, a dredge
pumped silt to an area upstream of the Dam in the
lower reach of Castaic Canyon. Dewatering of the
hole and removal of remaining sediment was started
April 16, 1969 and was finished May 23, 1969. On May
29, 1969, backfilling of the slide excavation area was
completed.
The triangular-shaped block of Castaic formation,
between Stations 25-1-00 and 26-1-80, on the right
(west) abutment was sliding easterly along a horizon-
tal clay seam at elevation 1,200 feet. It was decided to
excavate at higher elevations to relieve the driving
force and to remove a portion of the block.
Excavation of a portion of the sliding block was
accomplished between July 17, 1969 and August 7,
1969. Much of the material excavated was clean hard
sands and gravels and was utilized directly in the adja-
cent Zone 3 embankment construction. Zone 3 em-
bankment then was rapidly constructed to elevation
1,250 feet. Grouting was performed to fill large voids
t Right Abutment
Figure 385. Dam Under Construction — View Across Dam
Toward Left Abutment
462
.
- ^^
y^iyitlam^Stl ^
fc *1i«W^
Figure 386. Excavating Slide Area at Left Abutment
and stabilize the area around the slide block. A berm
was built on the upstream toe of the Dam at the right
abutment to elevation 1,300 feet to permanently stabil-
ize this area.
After the first major slide occurred at the left abut-
ment on April 26, 1969, slides became a continuing
problem during excavation above and within the dam
foundation of the left abutment. Slide scarps were
sloped back, and overburden above the cuts was
removed to stabilize the area. At times, it was evident
that any work performed to advance the dam founda-
tion at the embankment contact would precipitate
sliding. In this situation, embankment was built to a
predetermined elevation. Narrow sections of this
material then were excavated to good foundation with
a resulting buttressing on either side of the exposed
foundation. The foundation was quickly prepared and
permanent embankment placed. This process was re-
peated as many times as necessary to complete the
embankment.
The equipment used to perform the major portion
of excavation for dam foundation were scrapers and
tractors for support and pioneering. Shaping of cut
slopes was done primarily with a large tractor
equipped with a slope board. Loaders with a 12-cubic-
yard capacity were used during excavation of the
channel area. A dragline with a 14-cubic-yard capacity
was used extensively for this work from the time of
arrival on the site through August 1968. The material
from the loaders and dragline operations was trans-
ported by off-highway end-dump units.
Grouting. This work consisted of the construction
of grout curtains beneath the Dam and spillway and
for blanket grouting as necessary in the exposed core
zone dam foundation.
Curtain grouting was used to provide a continuous
barrier against leakage and to reduce hydrostatic pres-
sures in the downstream foundation. Originally, it
Figure 387. Grouting Tlirough Embankment at Left Abutment —
White Lines Show Limits of Core Zone
was planned to grout the main center curtain through
a concrete grout cap. The cap was placed and used
between dam Stations 39 + 65 and 46 + 00. However,
grout leakage, uplift, and cracking of the grout cap
occurred during grouting of the upper 10 feet of the
foundation, even though very low pressures were
used. Construction of the grout cap and grouting of
the upper 10 feet of the foundation therefore were
discontinued. Instead, a core trench 10 feet deep along
the curtains was excavated for removal of the overbur-
den after grouting operations were completed. The
bottom width of the trench varied from 20 to 50 feet,
depending on the number of grout curtains used and
the geologic conditions. The trench was backfilled
with Zone lA embankment material.
Most of the grout cap was removed due to require-
ments of foundation shaping. Excavation for this
shaping also made it necessary to deepen the outer
grout curtains and sections of the center curtain be-
tween Stations 42 + 80 and 45 + 00.
Excavation of the core trench was discontinued in
the east abutment at Station 52 + 20 because of slide
conditions. Also, due to the need for buttressing ex-
cavated areas against sliding in the east abutment, as
discussed previously, grouting was done through the
embankment from Station 53+60 to Station 61+00.
Grouting of the spillway section was delayed to al-
low for rebound resulting from excavation in the area
immediately adjacent to the approach channel. This
grouting was done through pipe installed in the con-
crete at the spillway crest section.
Shallow grouting was performed in the core zone
channel sections to restrict seepage from the dam
foundation. Blanket grouting also was done through
the embankment at the east abutment to consolidate a
small area of foundation that had been disturbed by
sliding (Figure 387).
463
An anticline at the easterly side of the channel sec-
tion was treated with deep blanket grouting upstream
and downstream of the grout curtain along the anticli-
nal axis. Additional holes on a closer spacing and an-
gled holes were grouted at the intersection of the
anticline and the grout curtain.
Foundation Preparation. Initial excavation for
dam embankment foundation was cut to within 12
inches of final grade. Removal of this final 12 inches
and cleaning of surfaces was limited to a period of two
days, within which time embankment placement was
started (Figure 388). This was necessary due to the
rapid deterioration of the Castaic formation, especial-
ly the shales, when exposed to air.
In the filter and shell zones, final cleanup was often
accomplished with motor graders and tractors with
slope boards. At times, the cleanup for these zones was
accomplished more conveniently by a grader.
Foundation cleanup for the core zone was more
critical. A clean undisturbed surface was necessary to
obtain a tight seal with the embankment material
placed in direct contact. Gradalls produced the
desired results. Slush grouting was used in several
areas to fill voids in shallow, jointed, and fractured
rock. Occasionally, a tremie pipe was used to assure
penetration of grout into narrow deep (10 to 20 feet)
voids. Upon completion of this grout treatment, the
area was covered immediately with embankment con-
tact material.
Handling of Borrow Materials
Impervious. Soils designated foundation contact
for the core zone were selected from the high intake
excavation, the spillway basin, portions of impervious
borrow areas, selected portions of previously built em-
bankment, and Borrow Area D. Borrow Area D was
established for this purpose after dam construction
had started and was located immediately north of the
spillway approach channel.
Soils for the construction of Zones lA and IB came
from required excavations mainly in the spillway,
dam abutments, and designated borrow areas adjacent
to the Dam and spillway. The areas known to have
large deposits of acceptable material were prewetted
by irrigation sprinklers. Additional wetting of imper-
vious material was done in the stockpile by sprinklers
and tanker trucks.
Excavation of the lower channel section of the spill-
way, starting in 1967, yielded large quantities of Zone
1 material lying above the Castaic formation. Approxi-
mately 700,000 cubic yards of this material was stock-
piled in the lagoon area.
Borrow Area "T-South" immediately downstream
of the Dam on the left abutment was left intact and
deleted from the contract as a source of material, after
the landslides had occurred. This was done because it
was believed excavation in this area could jeopardize
the stability of the ridge downstream of the left abut-
ment and possibly portions of Lake Hughes Road.
Castaic Ridge borrow area. Borrow Area "T-East"
near the upstream left abutment, and excavations
above the spillway cut designated spillway shaping
west and spillway shaping east, were established to
replace the material from "T-South". These areas
were prewetted in the same manner previously dis-
cussed.
Filter and Drain. Material for Zones 2A and 2B
was obtained from the lagoon and upstream Castaic
Creek pervious borrow areas. Hauling to the separa-
tion plant was done primarily with off-road belly
dumps powered by tractors. Other hauling units were
used as needed.
Problems with grading of Zone 2B material were
evident from the start of stockpiling at the plant and
the first placements in the embankment. Huge remov-
als, in relation to the amount placed in the embank-
ment, were required because of improper grading. Ac-
tions taken to bring the grading within the specified
range were as follows: decreasing the spacing on the
grizzly to allow initial removal of oversize material;
revising the screen sizings at the plant; installing a
crusher to reduce oversize rock, thereby increasing
the amount of intermediate rock sizes available; pro-
viding washing facilities; and reducing handling of
the material to a minimum. The most satisfactory re-
sults were obtained when material was loaded from
the plant hopper and taken directly to the embank-
ment.
Pervious. The first sections of Zone 3 were placed
using material that had been taken directly from foun-
dation excavation and foundation excavation material
that had been stockpiled. Sands and gravels excavated
for placement of the seepage discharge line also were
stockpiled for use in Zone 3 embankment areas. Exca-
vation of pervious borrow areas started in the Lagoon
during August 1968 and in Castaic Creek Canyon in
Figure 388. Scraper Spreading First load of Embonkment ir
First Approved Dam Foundation Area
464
November 1968, and continued from Castaic Canyon
through November 1970.
Excavation of the pervious borrow areas was per-
formed mainly with the large-capacity dragline and
shovel loader. Off-highway end- and bottom-dump
units were used for hauling material to the embank-
ment. Belt loaders fed by dozers and other large load-
ers were used intermittently to load hauling
equipment. Large scrapers also were used extensively
at times for hauling to the Zone 3 embankment.
Random. The random section of embankment
was constructed of material obtained from required
excavations. Sandstones and terrace sands and gravels
were used, the latter being preferred. Required exca-
vation from the Lagoon which did not meet Zone 3
requirements, but was of good Zone 4 quality, also was
utilized. Sands and gravels that underlaid the impervi-
ous material from Borrow Area D were allowed be-
cause it gave the contractor the benefit of a shorter
haul than from stockpiled terrace sands and gravels.
Soil-Cement. Material for the production of soil-
cement for the upstream-face slope protection was
designated to be terrace sands and gravels from re-
quired excavation meeting specified grading stand-
ards. The contractor was permitted to use surplus
Zone 2 A material with the addition of fines; however,
the addition of fines was discontinued at an early date,
thus producing a stronger material.
The contractor's plant was a twin-pugmill continu-
ous-mix plant. Material was stockpiled near the plant
and fed into the hopper with a front-end loader.
Material then was moved into the pugmill, where the
correct amount of cement and water was added and
the mixing took place. After mixing, material was lift-
ed by a belt to a loading hopper, where it was trans-
ferred into bottom-dump trucks to be hauled to the
upstream face of the Dam.
Figure 389. Looding of Pe
-vious Borrow at Elizabeth Canyon
Downstream Cobbles. The material was obtained
from the separation plant and from the stockpile of
oversize material removed from the embankment
areas. The contractor elected to place cobbles in a
2-foot-thick course rather than the specified 1 foot to
facilitate placement, alleviate a greater selection proc-
ess, and make greater use of the material available.
Embankment Construction
Impervious. Contact material was placed in a
slightly wetter condition than the soils in the general
core zone embankment. The purpose was to cause it
to mold into irregularities in the foundation and thus
seal effectively. The contact material was pushed into
place by rubber-tired dozers from adjacent embank-
ment or uncompleted foundation areas, leaving the
prepared foundation undisturbed. Compaction was
by wheel rolling with heavy equipment.
Hauling to Zone lA and Zone IB areas of the em-
bankment was done by scrapers. Immediately follow-
ing placement, front-end loaders equipped with rock
buckets removed oversize material. The embankment
was disked, and final moisture adjustments were made
with tankers equipped with spray bars. Compaction
was performed with self-propelled sheepsfoot rollers
and a vibratory roller. The lift thickness was 6 inches
after compaction. Twelve coverages by the rollers
were required. Leveling between embankment lifts
was done with motor graders and dozers.
Filter and Drain. Material for Zone 2 A, the transi-
tion zone between the dam core and the other zones,
was hauled to the Dam and placed from single- and
twin-bowled power scrapers. Each 12-inch lift was
leveled by a motor patrol, watered, and then compact-
ed with two passes of a three-drum vibrating roller.
The material from the plant consistently met grading
requirements, and satisfactory compaction was never
a problem.
Inspection trenching of Zone 2B material, the chim-
ney and blanket drain, revealed that the finer fractions
on the grading scale tended to migrate to the bottom
of the lifts. Testing showed that in-place densities
were far exceeding what had been expected. To allevi-
ate this condition, wetting for particle lubrication was
reduced to a minimum, only that traffic necessary for
placement was allowed on the zone, and compaction
was reduced to one pass of the vibrating roller on the
24-inch lift. Otherwise, the hauling and placing was
similar to that of Zone 2 A material. The blanket drain
was increased to a depth of 10 feet in a faulted area to
the right of the dam axis.
Pervious. End-dumped material in the Zone 3 em-
bankment was leveled into 15-inch lifts and pushed
into place by track and rubber-tired dozers. Oversize
material was removed with rock buckets having prop-
erly sized openings and mounted on front-end loaders
(Figure 389) . The embankment was wetted with tank-
er trucks and compacted by two coverages of the
three-drum vibratory rollers.
465
Figure 392. Compacting Soil-Cement
Random. Hiuling and placing of Zone 4 embank-
ment materials was done primarily with the power
scrapers. Compaction was accomplished in four cov-
erages by pneumatic rollers with wheel loadings of
30,000 pounds. The 10-inch embankment lifts were
watered and scarified as necessary, depending on the
types of materials being utilized. No major problems
were encountered with this zone, other than main-
taining area and slope control.
Soil-Cement. Bottom dumps hauled and wind-
rowed the material at the work site (Figure 390). The
material was graded into position with a spreader box
attached to a tractor (Figure 391). The soil-cement
was compacted with a IS-ton pneumatic roller. The
roller was unable to propel itself through the loose
lifts and had to be towed to make the initial passes.
This problem was solved by attaching a grid-type
roller to a tractor for a breakdown pass as it was
spreading the soil-cement. The pneumatic roller was
equipped with a side-mounted hydraulically operated
wheel to contain the outer lift edge during rolling
operations (Figure 392). This wheel was modified as
to angle of mount and tire size to increase its effi-
ciency during the work. Required densities were
achieved easily and usually exceeded.
The soil-cement was cured by water trucks during
working hours and by irrigation sprinklers at other
times.
Downstream Cobbles. The downstream dam
slope was overbuilt and then brought to finished
grade with a crane-operated dragline or grader. Place-
ment of cobble was done with a crane equipped with
an orange-peel bucket (Figure 393).
Boat Ramp and Parking Area. A boat ramp and
parking area were built at the east abutment to in-
crease the stability of the area due to slides and to
make use of materials that otherwise would have gone
to waste (Figure 394).
The boat ramp and parking area were constructed
primarily of sandstones from spillway excavation and
excavation from borrow areas where removal was
necessary to reach Zone 1 material deposits. These
areas of embankment were compacted to Zone 4 em-
bankment standards. The embankment slope below
the ramp surface was protected with concretions ob-
tained from excavation and designated Type I\' rip-
rap. Pervious material meeting dam embankment
specifications was used for loose material, and the
ramp and parking area were paved with asphalt in a
completion contract.
Outlet Works
High Intake Tower — Excavation. A 4-foot-diame-
ter pilot hole was excavated from ground level to the
intersection with the diversion tunnel, and a tractor
with backhoe was used to enlarge the hole to the re-
quired dimensions. The excavated material fell into
the diversion tunnel and was removed to a designated
466
spoil area by a loader. Along with conventional
backhoe methods, drilling, shooting, and hand labor
were used in the excavation.
The sequence of operation was to excavate a max-
imum of 6 feet to the required dimension; install the
required welded wire fabric, rock bolts, and structural
support steel; and apply 4 inches of shotcrete. After
excavating to elevation 1,346.6 feet, a shaft support
collar with support beams was placed to hold the
structural support members as excavation progressed.
For reasons of safety and to expedite the work, a
second arch over the tunnel intersection was omitted;
an 8-inch channel collar bracing and flanges were
welded to the in-place tunnel arch.
The in-place concrete in the tunnel crown was suc-
cessfully removed by controlled blasting. Thin-wall
tubing had been installed previously by the diversion
tunnel contractor, making the blasting operation effi-
cient. After blasting, large pieces of concrete were
broken up with pneumatic hammers and removed
from the tunnel.
Excavation for the low intake gate slot was nar-
rowed '/, of a foot downstream to avoid removing one
of the in-place tunnel support posts and invert struts.
The invert and sides of the slot were overexcavated
and protected with concrete to prevent air slaking of
the Castaic formation material.
High Intake Tower — Concrete Operations. Rein-
forcing steel was installed in three stages: (1) shaft-
tunnel intersection to the shaft control joint, (2) shaft
control joint to the welded splice connection just be-
low the shaft collar, and (3) welded joint to the intake
tower.
The No. 14 and No. 18 reinforcing bars required
butt welding at splice points. All welding was 100%
X-rayed. The variable-diameter horizontal steel that
required butt welding was set up in a jig in the reverse
order in which it was to be used. A hydraulic bender
was used to eliminate tangent ends and properly align
bars prior to welding. The bars then were hoisted and
lowered into position using a crane. Hydraulic jacks
were used for final alignment. Back-up strips were
used to weld the vertical No. 18 bars that were not
accessible for conventional welding as well as the No.
11 bars that had to be removed in the shaft-tunnel
intersection for the installation of a sluiceway liner.
Tower reinforcement was erected by first setting a
skeleton template and anchoring it to concrete an-
chors on the ground to maintain alignment. Remova-
ble scaffolding then was set at the base of the template.
Vertical bars were hoisted into place in pairs using a
truck or tower crane. Horizontal bars were loaded on
the scaffold and hand-hoisted into position.
Concrete construction for the high intake tower and
shaft was by conventional methods. Wooden forms
were used to shape and confine the concrete in the
shaft, and metal forms were used for the tower above
elevation 1,350 feet. Concrete was placed using buck-
ets and tremie pipes (Figure 395).
Figure 395. Concrete Placement — High Intake Tower
467
gure 396. High Intake Tower Bridge Under Construction
Figure 397. Low Intake Tower
Access Bridge Piers. A crane-mounted hole digger
equipped with a telescoping Kelly bar, a 4-foot rotary
drilling bucket, and a lO-foot-diameter auger and
reamer were used to excavate the required holes (Fig-
ure 396). Initially, a 10-foot-diameter hole was ex-
cavated using the 10-foot-diameter auger. The hole
was then reamed to 1 1 feet - 4 inches using a drill
extension reamer. An 1 1-foot-diameter casing con-
structed of '/-inch steel plate was lowered into the
hole to support the shaft walls.
Hoop reinforcing steel, having a minimum amount
of vertical reinforcement, was fabricated above-
ground. After the cage was lowered into the pier exca-
vation and supported, longitudinals were lowered
into place and secured.
Concrete was placed by crane and bucket using a
hopper aboveground and tremie pipes. The steel cas-
ing was removed in sections as concrete placement
progressed. At no time was it necessary to place the
concrete above the bottom of the casing. Steel forms
were used to confine the concrete aboveground.
Access Bridge Girders and Deck. Upon comple-
tion of the bridge abutment and piers, preassembled
girders were delivered to the job site and set in place
using one track-mounted and one truck-mounted
crane.
Crane and buckets were used to place spans Nos. 3
and 4 of the bridge deck, with spans Nos. 1 and 2
placed by conveyor belts. High winds and the crew's
lack of familiarity with lightweight concrete caused
placing and finishing difficulties. It was necessary to
refinish parts of the span with a coat of epoxy-sand
compound.
Low Intake Tower. Concrete was first removed
from the tunnel section at the intersection of the
tower (Figure 397). Reinforcement then was welded
to the vertical reinforcement stubbed out of the tun-
Figure 398. General View of Penstock Under Construction
Figure 399. Tunnel Penstock
468
nel for the low intake structure. Concrete was placed
in stages up to the elevation for the precast-concrete
trashrack beams. The beams were set, the ends en-
cased in concrete, and the tower cap and seal plate
placed.
Initially, a 24-inch pipe and slide-gate unit was to be
installed to control the flow of water through the di-
version tunnel plug during construction of the high
intake tower. However, due to delays in completion,
an additional 30-inch, corrugated-metal-pipe, slide-
gate unit was installed through the diversion tunnel
plug, and a temporary bulkhead gate was installed on
top of the tower. These were to control flow through
the tunnel prior to installation of the low intake gate
located at the high intake tower.
After installation of the slide gates, access platform,
and ladder, storm runoff raised the water elevation in
Castaic Lake enough to cause silting in and around the
gates. This necessitated building an earthfill dam out
to the tower so that grouting of the bypass piping,
removal of the temporary bulkhead gate, and installa-
tion of the metal trashracks could take place.
Penstock. The penstock (Figure 398) includes the
wye branches for the turnouts and the bifurcation for
the dispersion structure. Some difficulty was ex-
perienced when installing the penstock (Figure 399)
sections because of flat spots, out of roundness, and
misalignment in the sleeve-type coupling areas.
Modification of the downstream side of the pen-
stock was necessary in most of the valve vaults because
of misalignment of the upstream and downstream sec-
tions in the areas of the valve couplings. The 78-inch
penstock-to-turnout coupling outside the valve vault
was not installed correctly and later started to leak.
This section eventually had to be welded together.
Concrete removal consisted of roughening the exist-
ing concrete in the area to receive the tunnel plug
liner, removal of concrete for keying the penstock sup-
Figure 400. Spillway Stilling Basin and Chute Excavafion
port piers, and removal of various areas of the diver-
sion channel invert and walls. Surface roughening and
pier concrete removal were accomplished by use of a
tractor-mounted hoe ram and men working from a
high scaffold using hand-held pneumatic tools. The
outline of the area for concrete removal was first
sawed to a depth of 2 inches. The contractor was per-
mitted to remove and replace some of the reinforce-
ment steel in the pier areas to facilitate and expedite
the work.
After removal of the required concrete in a given
area, a backhoe was used to excavate and clean up to
the required lines and grade. Immediately following
excavation, the area was cleaned of all loose and
semidetached material, and 3 inches of foundation
protection shotcrete or concrete was applied.
Placing of concrete was by conventional methods:
crane and buckets for the outside work, pumps for the
tunnel plug concrete, and conveyor belts for the pen-
stock piers.
Because of delays, it was necessary to construct a
bypass channel through and around the work area to
carry the runoff during the 1970-71 rainy season.
This was accomplished by building a 4-foot retaining
wall across the turnout area at turnout Station 49-1-17
down to the stream release area. The wall normally
was 1 foot inside the vertical reinforcement. In the
stream release and dispersion area, the excavated slope
was steepened and the face shotcreted to provide
a bypass channel outside the work area. Water re-
entered the paved channel at Station 53-f 70.
Major difficulty was encountered in maintaining
specified tolerances on the penstock diameters and
installing the couplings according to the manufac-
turer's instructions. During filling and hydrotesting
of the penstock, a crew was maintained to inspect and
adjust the penstock coupling to a point where no ap-
preciable leakage occurred. After the hydrotesting
was completed, the penstock was drained, the test
head and other testing equipment removed, and the
necessary protective-coating repair made. After mini-
mal cure time for the coating elapsed, the penstock
was refilled to within 20 feet of the surface elevation
of Castaic Lake.
Spillway
Excavation. Initial excavation (Figure 400) was
carried to within 2 feet of final grade. Rebound gauges
were installed and monitored. Depending upon the
rate of rebound and the contractor's schedule for start-
ing structural concrete, sections of the spillway were
released for final excavation prior to expiration ot the
stipulated' five months. Where the foundation had
been cut and cleaned to final grade, protection re-
quirements called for concrete placement or applica-
tion of an asphaltic emulsion covering within 24
hours. Structural concrete was placed within 30 days
in the areas protected with the asphaltic emulsion^
Much of the early excavation material was stockpiled
469
for later use in the dam embankment. However, large
quantities of unweathered shales were wasted.
Slides occurred between spillway Stations 53+00
and 54 + 00 on both sides of the excavation in the vicin-
ity of the main dewatering sump hole. The slides
probably were due to the fluctuating action of the
water table. Other sliding took place along a bedding
plane in the vicinity of Station 50 + 00 at the easterly
side of the excavation. Slopes were flattened to control
the sliding. Ground water inflow was intercepted on
the slopes and directed to sump holes for pumping.
Investigation disclosed an unstable condition exist-
ing in the left foundation at the flip bucket. A block
of Castaic formation was subject to slippage along a
shear plane. Because of area limitation and economy,
the block was stabilized by pinning it in place with
grouted rock bolts.
The heavy rains at the end of January and again in
February 1969 flooded and silted the stilling basin. In
March 1969, a dredge pumped silted material from the
basin to portions of the Lagoon. Dredging was com-
pleted in March 1969, and dewatering of the basin was
started immediately. Well points were established at
the right side of the excavation in the vicinity of Sta-
tion 53 + 50 at the end of April 1969.
Excavation for the remaining structural section was
worked back from Station 37 + 00 to the crest section.
The major portion of the approach channel section
was left in place to facilitate its use in dam embank-
ment.
Sliding occurred on the easterly side of the spillway
excavation between Stations 12 + 70 and 17 + 00. This
area was unloaded and buttressed. However, addition-
al sliding seemed imminent at Station 12 + 50 when
keyways were cut for the wall upstream of the crest
in the approach channel. Rock bolts were placed at
this location to ensure its stability.
Excavation for the drainage and access gallery was
begun by sawing into the foundation material to the
appropriate lines and depth and then excavating with
a track-mounted backhoe. The wall-footing excava-
tion was made using a tractor with rippers, scrapers,
and motor graders. Excavation for the transverse
drains was made with a backhoe, or a backhoe in con-
junction with sawing, as was done in the gallery. Final
cleanup was by hand. Considerable overbreak oc-
curred during these operations, and large quantities of
backfill concrete were used.
Concrete. Standard wooden forms were used to
confine the concrete for the spillway invert and a
weighted steel slip form was used to strike the con-
crete to grade. Forms for the spillway walls were made
from 1-inch resin-treated plywood and were support-
ed with appropriate horizontal and vertical members.
Forms for the ogee-crest section and the flip-bucket
section were constructed to shape the concrete to the
desired configurations. These forms were removed
board by board, starting from the bottom, to allow for
finishing of the concrete prior to its final set.
Invert and footing steel was supported by concrete
and steel chairs. The major portion of the spillway
wall steel was secured in place with galvanized metal
chairs.
Construction of the spillway (Figure 401) pro-
gressed from Station 37 + 00, down the chute section
to the flip bucket, and then from Station 37 + 00 back
to the crest. The order of concrete placement, not
including that placed for foundation protection, was
(1) keyways, (2) wall footings, (3) gallery and invert
slabs, and (4) walls. Placements were performed con-
currently as conditions permitted.
Concrete was batched and mixed in a central batch
plant. Concrete was hauled to the job site in 8-cubic-
yard agitator transports and discharged into 2- or 4-
cubic-yard buckets. The buckets were hoisted into
placing position by motor cranes. All permanently
exposed concrete surfaces were water-cured. Mem-
brane curing was allowed for surfaces that were to be
backfilled.
Flip-Bucket Piles. Design studies after the start of
construction indicated that additional support for the
flip-bucket section in the stilling basin would be re-
quired during periods of heavy discharges. A design
change was issued calling for the installation of verti-
cal and battered cast-in-place piles beneath the section.
Structural Backfill. The designated backfill be-
hind the spillway walls was Zone 3 material meeting
gradation requirements below the 6-inch size. The
contractor was permitted to use surplus Zone 2A
material for this operation since it met gradation re-
quirements in this range.
Originally, no provisions had been made to protect
the backfill from erosion in the steep chute area of the
spillway. Intense rains late in the 1970-71 season
washed and heavily eroded backfill in this area. The
backfill surface was the ultimate collection area for
Figure 401. Spillway Construction
470
runoff. The damaged backfill was repaired and a 6-
inch layer of riprap bedding was placed on a lowered
backfill surface. Cobble slope protection, as specified
for the downstream slope of the Dam, then was placed
from just above the start of the chute section to the
stilling basin area.
Castaic Lagoon Control Structure (Figure 402)
Foundation excavation and concrete placement for
this structure started in November 1968. Wingwalls
were constructed first. Reinforcing steel for the wing-
walls was doweled and anchored into the Lake
Hughes Road Bridge abutments.
Storms in January 1969 caused erosion around some
of the bridge pilings (Figure 382). The contractor
attempted to prevent further erosion by placing rip-
rap lining on the diversion channel at the Bridge.
However, the extremely heavy flows at this location
from the February 1969 storms undercut and dis-
placed the pilings and the westerly section of the
bridge collapsed. Cleanup of storm debris, structural
repair, bridge repair by Los Angeles County, and dam
closure of the diversion channel caused delays in con-
struction of the major portion of the structure until
the following year.
The flooding that occurred in 1969 indicated the
need for additional protection to prevent erosion
downstream of the lagoon control structure during
periods of heavy water flows. It was determined that
much of the damaging erosion was because of the deg-
radation of the streambed downstream and immedi-
ately adjacent to the State's right of way, resulting
from the removal of streambed gravels by another
contractor. An extended riprap design was provided,
and performance of the work was directed by a con-
tract change order. The work consisted of grading and
shaping the area immediately downstream of the
structure, laying a blanket for riprap consisting of
Zone 2B drain material, and placing Type IV riprap
Figure 402. Castaic Lagoon Control Structure
(native sandstone concretions). The riprap extended
well below normal streamflow depth; therefore, the
change order provided for dewatering of the area dur-
ing placement of the riprap. However, due to the time
of year and the contractor's upstream pumping diver-
sions, no water was encountered. This work was per-
formed during October and November 1970.
Clearing, Grubbing, and Erosion Control
Reservoir Clearing. The reservoir area to be
cleared extended 4 miles up Elizabeth Lake Canyon
and 2'/4 miles into Castaic Canyon from the Dam. Eliz-
abeth Lake Canyon was heavily wooded and brush-
covered. Castaic Canyon had relatively few trees or
brush-covered areas. Two areas in Elizabeth Lake
Canyon about 1 mile from the Dam were designated
for vegetation retention to approximate a more nor-
mal habitat for some fish species.
The clearing subcontractor moved onto the job in
early November 1969 and began clearing operations
with the removal of floatable debris from the stream
channel areas. Reservoir clearing work was restricted
because of unfavorable fire load indexes. However,
some tree felling, brushing, channel debris removal,
stacking, and burning in Elizabeth Lake Canyon was
done during the spring of 1970. At the end of the first
season of reservoir clearing in June 1970, it was es-
timated that this work was 60% complete. The reser-
voir clearing was completed on April 24, 1971.
The clearing operations consisted of felling and
bucking trees for burning or hauling to approved dis-
posal sites, dozing of brush-covered areas, hand clear-
ing of slopes where equipment could not operate, and
removal of channel debris. Downed trees and floatable
debris were removed from between elevations 1,515
feet and 1,525 feet and in the vegetation retention
areas. Anchorage of large downfalls was allowed in
remote and inaccessible parts of the vegetation reten-
tion areas. Unburned debris and fire residue were bur-
ied as specified. Some trees and shrubs were removed
by private concerns to landscape areas under develop-
ment.
Clearing and Grubbing of Other Areas. The
prime contractor performed the remainder of the
work under the contract item "clearing and grub-
bing". Clearing and grubbing of the dam foundation
started on July 5, 1967. This work was extended to
borrow areas, excavation areas, and structure and
roadway locations throughout the contract period as
the scheduled work was performed.
Other items of work included removal of buildings,
water tanks, water lines, property improvements, and
the county road bridge across the Dam site area. The
bridge was dismantled in July 1967, with the contrac-
tor salvaging much of the timber. The bridge pilings
were removed during excavation operations. Disposal
of the material was by burning, burying, or removal
from the job site. No major difficulties were encoun-
tered.
471
Erosion Control. Erosion control for designated
areas called for seeding on slopes less than 1 5% and for
seeding and mulching on slopes 15% or steeper. No
seeding was required within the reservoir area. All
seeding was done toward the conclusion of the con-
tract as areas were completed and dressed. Work was
started in September 1971.
Mulching was done with straw which was applied
with an air-blowing spreader. Coverage was governed
by the number of bales to the acre. The mulch then
was worked into the ground with rollers equipped
with protruding studs. The less steep areas were
disked prior to seeding.
Seeding and fertilizing were accomplished in one
operation. Batches of 1,500 pounds of fertilizer and
225 pounds of seed were suspended in water in a 1,500-
gallon mixing tank. Agitation maintained the suspen-
sion, and the mixture was evenly distributed over a
3-acre area. Following seeding, mulched areas were
rerolled. The seed was raked into the soil in the flatter
areas. The erosion control work was completed in
November 1971.
Ai«
Dev
472
BIBLIOGRAPHY
Amorocho, J., Babb, A. F., and Ross, J. A., "Hydraulic Model Investigations of the Castaic Dam High Intake
Tower", Water Science and Engineering Papers 1046, Department of Water Science and Engineering,
University of California, Davis, June 1971.
Devries, J. J., Amorocho, J., and Ross, J. A., "Hydraulic Model Study of the Castaic Low Intake Gate", Water
Science and Engineering Papers 1049, Department of Water Science and Engineering, University of Califor-
nia, Davis, July 1971.
Godden, W. G., Tuncag, M., Wasley, D. L., "Model Analysis of the Castaic Reservoir Intake Tower", College
of Engineering Office of Research Services, University of California, Berkeley, California, September 1970.
Gordon, B. B., and Wulff, J. G., "The Effects of Changes in the State of the Art on Heights of Earth and Rock
Dams — Oroville and Castaic Dams", Proceeding of Western Water and Power Symposium, Los Angeles,
California, April 1968.
Perry, C. W., and Kruse, G. H., "Instrumentation for Pore Pressures and Seismic Effects — State Water Project
Dams", Proceeding of Western Water and Power Symposium, Los Angeles, California, April 1968.
Ross, J. A., Amorocho, J., and Babb, A. P., "The Castaic Dam Diversion Facilities, A Hydraulic Investigation",
Water Science and Engineering Papers 1022, Department of Water Science and Engineering, University of
California, Davis, August 1968.
Ross, J. A., Jones, W. C, Amorocho, J., and Babb, A. F., "Hydraulic Model Investigations of the Castaic Dam
Release Facilities", Water Science and Engineering Papers 1042, Department of Water Science and Engineer-
ing, University of California, Davis, November 1970.
, "Hydraulics of the Castaic Dam Spillway (Laboratory Model Studies)", Water Science and Engineer-
ing Papers 1023, Department of Water Science and Engineering, University of California, Davis, August
1968.
473
APPENDIX A
CONSULTANTS
475
APPENDIX A
CONSULTANTS
Several major consulting boards were employed by the Department to advise on the dams covered in this
volume. These boards were composed of men, acknowledged to be experts in their fields, who could bring to the
Project many years of experience gained from their work on other major water projects around the world.
Earth Dams Consulting Board
Mr. Wallace L. Chadwick
Mr. Julian Hinds
Mr. Roger Rhoades
Dr. Philip C. Rutledge
Mr. B. E. Torpen
Earthquake Analysis Board
Dr. Clarence Allen
Dr. Hugo Benioff
Dr. John Blume
Dr. Bruce Bolt
Dr. George Housner
Dr. H. Bolton Seed
Dr. James L. Sherard
Mr. Nathan D. Whitman
Oroville Dam Consulting Board
Mr. A. H. Ayers
Mr. John Hammond
Mr. Raymond A. Hill
Mr. J. Donovan Jacobs
Mr. Thomas A. Lang
Mr. Roger Rhoades
Dr. Philip C. Rutledge
Mr. Byram W. Steele
Mr. B. E. Torpen
The Board advised the Department's engineers with
regard to design and construction of Del Valle, Casta-
ic, Pyramid, Cedar Springs, and Perris Dams and
other proposed dams.
The Board advised the Department concerning the
evaluation of seismic effects to be anticipated at any
given site or area and on the development of rational
procedures for seismic design in regard to hydraulic
structures.
The Board advised the Department's engineers on de-
sign and construction for Oroville Dam first when a
concrete dam was being considered and later on the
earth dam. They also advised on the other dams and
appurtenances in the Oroville Division.
Many other individuals furnished consulting services and several universities, especially the Berkeley and Davis
Campuses of the University of California, furnished technical support as did the U.S. Bureau of Reclamation and
several engineering firms.
477
APPENDIX B
ENGLISH TO METRIC CONVERSIONS
AND PROJECT STATISTICS
479
CONVERSION FACTORS
English to Metric System of Measurement
Quantity
English
unit
Multiply by
To get
metric equivalent
Length
inches
2.54
centimeters
feet
30.48
0.3048
0.0003048
centimeters
meters
kilometers
yards
0.9144
meters
niles
1,609.3
1 .6093
meters
kilometers
Area
square inches
6.4516
square centimeters
square feet
929.03
square centimeters
square yards
0.83613
square meters
acres
0.40469
4,046.9
0.0040469
hectares
square meters
square kilometers
square mi les
2.5898
square ki lometers
Volume
gallons
3,785.4
0.0037854
3.7854
cubic centimeters
cubic meters
liters
acre-feet
1,233.5
1,233,500.0
cubic meters
liters
cubic inches
16.387
cubic centimeters
cubic feet
0.028317
cubic meters
cubic yards
0.76455
764.55
cubic meters
liters
Velocity
feet per second
0.3048
meters per second
mi les per hour
1.6093
kilometers per hour
Discharge
cubic feet per second
0.028317
cubic meters per second
or
second-feet
Weight
pounds
0.45359
ki lograms
tons (2,000 pounds)
0.90718
tons (metric)
Power
horsepower
0.7460
kilowatts
481
PROJECT
OPERATIONAL STATUS
DIXIE REFUGE
>fESEflVOJ/>
ANTELOPE LAKE"^
ABBEY BRIDSE
R/tSERVQM
I OPERATIONAL
I I FOR FUTURE CONSTRUCTION
FRENCHklAN LAKE
WATER SERVICE
I I AREA OF CONTRACTING
AGENCIES
FIRST YEAR OF SERVICE
1968
; LJtKE o/tftyjM^
V
■DWARO HYATT {
m.r POWERPLAlir
THEHItALtrO M^ , J
pomeitPLAHT 9 - v^
%^-*^ \.THERMALirO
CALHOUN
PUMPINt PLAtfT
/ TRAVIS ^ \
.^ef)MP(He PLANT ^^J^^ PUmPlHG
A/OffTH BAY AQUEDUCT
^^-.-r -^— 1968
/ CORi
/ PUUPINi
J CANAL
23 DAMS AND RESERVOIRS
I Lake
SS.'
Antclopr Lake-- 22.566
Lake Davi>.._ 84.371
Abbey Bridge. 45,000
DiBie RefugC' 16.000
Lake Oroville J. 537. 577
Thermaliio DlverBion
Pool I. (.328
Fimh Barrier Pool 580
Thermalito Forebey .... 1 1 ,768
Thermaliio Afierbay.... 57,041
Cliflon Court Forebay.. 28,653
Belhany 4.804
Lake Del Valle 77.106
San Lui« 2,038.77 1
ONeiU Forebay 56.426
Loa Banot . _, 34.562
Liiile Panorhe 13.236
Bullet 21,800
Silverwood Lake 74,970
Lake Perrit Ml 452
Pyramid Lake 171.196
Elderberry Forebay 28,231
Ca»taic Lake 323.702
Total* 6.848,617
12.700
3.700
1,297
460
2.235
554 18.600
380
000
253
000
500
000
400
000
80,000
000
10
000
1.840
000
020
000
:oo
000
'^
000
000
100
210
130
000
000
7
600
000
20
000
000
6
860
000
6
000
000
46
000
000
70
62g
500
AQUEDUCTS
outh Ba A Iduct
• rioharal Canal
.moen..A,a..uc.<«..n
in.,:
A. D. Edmon.lon Pumpl
A. D. Edroonaton Pumpln|
Plani
TWMchapl Aftwbayt^n La
Subtotal, main line
ali/omla Aquaduct (branc
lie fWrts
hea):
C 1 1 B h
482
STATISTICS
RECREATION
POWERPLANTS [J
22 PUMPING PLANTS Q
Number
Units
Normal
Sialic
Head
dm)
Tol.l
Dciiifi
(cubic
•econd)
Toi.l
powtfr)
Maximum
Energy
Edward Hyatt (pumped
Thermaliio (pumped iio
North Bay Aqueduct:
t Of age) 3
age)- .- 3
500/660'
33
0
0 381
205
233
518
1,926
540
331
810
9,000
120
120
10,303
5,049
1,380
126
126
120,000
600
900
1,000
333,000
136.000
140,000
308,000
,040,000
93,800
10,500
6,500
16,000
91.000,000
5,000.000
166.000.000
2,000.000
313,000.000
1 .761.000,000
647.000,000
446.000,000
20.000,000
SI. 000. 000
3.691,000.000
Trav.s
6
Cordelia
South Bay Aqueduct:
Del Valle
J
g
Slate Share
10<^
Wheeler Ridge
9(3
A D Edmonaton
14lJ
California AqueducI fbr
.„ch..,.
J
Badger Hill
"
.
Polonio
^
Peripheral Canal
9(3
Total, State Share
;',:„:;:;.: ::::;:;-
^jj^
^^
^^
^^^
483
PROJECT
(METRIC
23 DAMS AND RESERVOIRS
1,363.60 6,396 268.8
16 44 131 16 1
0.72 21 1.6
14.52 2SS 16.1
70.36 1,741 41.8
69.60 1.093
43 12,802
26.89 235
>.29 904
i.669 59.363
536 15,291
AQUEDUCTS
L«nKlh (kilomriers)
.6,., C.„., P,.e„„e Tu„ue, 31
North Bay Aqueduct - 42 6 23 0 IQ 6 0 0
Souih Bay Aqu«ducl 69.1 13. S S3.0 2.6 0
Tehuchapi Afterbay thru
CalHomi. Aqueduct (bnncham)!
=,^ = = =
484
STATISTICS
UNITS)
RECREATION
• RECREATION AREAS
<>^ FISHING ACCESS SITES
■OS KseHyojR
•SERVOtR AND
RATING PLANT
COASTAL BRANCH %
w
SAN LUIS oeispo _j;,-«fc
POWCRPLANT
8 POWERPLANTS
n
":
"'"' H^ld „'."'"p.r
Output
3L„
Ed».rd Hy.
,25/206^ ,,2 0
26/30 i^ 478.6
30/100^ 371,6
\':,z
1,003,000,000
~
" ■
s.„....o.
jj
6,645,000,000
'-' SF'
',Z
■
r;
iiii,E:H
.'jlVnZ
rEvH;.
485
10
8764
10 8764
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MAY 2 p 1977
^#n^W4
jUN 1 6 1984
M/iy 2 6 mv
•■.fSSClt-lBRAHY
^Ufti6 1971
t lys?
jUNl2RtC'0
'^'IVRRCIIiflM/''-
e;rp28^Sn
*i^F^ 2 8 REC'O
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