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Photoelectronic composition by 
caupohnu office op state pmnitnc 

VC 87402— 950 1-75 2,500 

California state 
Water Project 

Volume in 



Bulletin Number 200 
November 1974 

state of CalHomia 

The Resources Agency 

Department of Water Resources 

The Resources Agency 

Department of Wa ter Resources 



Volume ill 
Storage Facilities 



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 


P.O. Box 388 

Sacromento, California 95802 
Moke checks payable to STATE OF CALIFORNIA 
California residents add sates tax. 


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 

y John R. Teerink, Director 

Department of Water Resources 
The Resources Agency 
State of California 







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 


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 



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 


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 



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 


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 



Mechanical Installation 59 

Spillway 59 

Excavation 59 

Concrete 59 

Concrete Production 60 

Reservoir and Other Clearing 60 

Initial Reservoir Filling 60 

Bibliography 61 


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 



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 



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 


General 141 

Description and Location 141 

Purpose 141 

Chronology 141 

Regional Geology and Seismicity 143 

Design 143 

Foundation 143 

Site Geology 143 



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 




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 



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 


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 



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 


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 



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 


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 



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 


General 271 

Description and Location 271 

Purpose 273 

Chronology 276 

Operation 276 

Design 279 

Dams 279 

San Luis 279 



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 


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 



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 



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 


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 



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 


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 



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 



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 


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 



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 



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 


Appendix A: CONSULTANTS 475 





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 


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 



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 

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 



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 


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 

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 


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 


FIGURES— Continued 


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 




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 


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 


Clifford J. Cortright Division Engineer 

John W. Keysor Chief, Design Branch 

Howard H. Eastin Chief, Construction Branch 


Thomas H. T. Morrow Chief, Division of Land and Right of Way 


H. G. Dewey, Jr. Division Engineer 

James J. Doody Deputy Division Engineer 

State of California 
Department of Water Resources | 


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 




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 


Senior Engineer, Water Resources 
Chief, Dams and Canals Unit, Civil 

Design Section 
Division Engineer, Division of Safety of 

Chief, Engineering Services Section, 

Design Branch 
Construction Supervisor 
Chief, Project Geology Section 
Principal 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 
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 


■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 


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 

Chief, Engineering Services Section, 

Design Branch 
Construction Supervisor 
Chief, Project Geology Section 
Principal 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 
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 


Chief, Program Analysis Office 


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 



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 

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. 


Figure 1. Location Mop — State Water Project Reservoirs 



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 

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 



Name of Reserv'oir 














































































Lake Oroville 








Lake Del Valle 



O'Neill Forebav 



i Little Panoche.- ... 





iHderberry Forebav 









' 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) 


1^, r CH. iM^nT^. 


LAKE '^^ 



->'f II A >-»!ii 

■ ,0\'-' ' 1 



I M '""t*>'-:i.^ , / x;===;=::::!«' l.OVaLTON 

-. S |i ' - ^ ^ ° 

Figure 2. Upper Feather River Division 




ELEV 900' 


Edward hvaTt 







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 

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- 











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 




rc HJci 


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- 





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- 

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- 


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 

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 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 ^ 


■^« Sacramento 














Figure 9. Location of Construction Project OfRces 



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. 


Figure 10. Location Map — Frenchman Dam and lalt^ 



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 


A statistical summary of Frenchman Dam and Lake 
is shown in Table 2, and the area-capacity curves are 
shown on Figure 12. 


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- 


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. 


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 


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 feet 


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 


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 


Type: Reinforced-concrete conduit beneath dam at base of left abut- 
ment, valve chamber at midpoint — discharge into impact dissi- 

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 




t 5960 



, z 

2 9940 

i ^ 5920 

























19 20 29 30 39 40 







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 

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- 


Figure 13. General Plan and Profile of Dam 




Figure 14. Embankment Sections 


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 

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. 


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- 

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- 


Figure 15. locotion of Embankment Instrumentation 


Figure 16. General Plan and Profile of Outlet Works 

















> 5530 





ELEV. 5588 


Lip of Outlet Tower 
Elev. 5517^ 

40 80 




Figure 17. Outlet Works Rating Curve (24-lnch Hollow-Cone Valve) 



1 1 

■ SP 



1 • 


ELEV, 55 

f t 







it 5570 


Ul 5560 




a: 5550 




5 5540 


> 5530 










<o / 
^ / 

o / 

It 1 
<y 1 







1 1 1 1 
Lip of Outlet Towery 

Elev. 5517 i ---r 
1 1 1 — i: 1 1 

r " 

2 3 4 5 6 7 



10 11 


Figure 18. Outlet Works Rating Curve (8-Inch Globe Valve) 


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- 

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. 


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- 


Figure 20. Location of Borrow Areas and Frenchman Dam Site 


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 

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 


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 

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). 


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 ; 


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 


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- 

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 


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. 


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- 


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. 



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. 


Figure 26. Location Map — Antelope Dam and lake 



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- 

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 


A statistical summary of Antelope Dam and Lake is 
shown in Table 4, and the area-capacity curves are 
shown on Figure 28. 


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. 


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 

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 

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. 



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 


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 


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 

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 


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 


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 





1 1 





EL. 5 





















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 

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. 


^^ 1^ 'M^&\!ptfe| ^H: 

Figure 29. General Plan and Profile of Dam 


Figure 30. Embankment Section 


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- 

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. ■ 


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. 


Figure 31. General Plan and Sections of Outlet Works 



ELEV. 5002.0' ^ 



60 80 100 


Figure 32. Outlet Works Rating Curves 






Fiqure 33. General Plan and Sections of Spillway 


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 


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 

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 


Figure 36. Location of Borrow Areas and Antelope Dam Site 


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). 


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 

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 


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. 


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. 


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. 





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 


V STA. 244-7 

Figure 39. Location of Embonlcment Instrumentation 




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 

, 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. 


Figure 40. location Mop — Grizzly Valley Dam and Lake Davis 




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 

Figure 41. Aerial View — Grizzly Valley Dam and lake Davis 


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. 


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. 


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 

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. 


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 


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 


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 


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 


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 

Capacity, stream maintenance 222 cubic feet per second 

Design delivery to pipeline 8 .25 cubic feet per second 



AREA IN 1,000 

4.5 4 3. 


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- 

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 


Figure 43. Dam — Plan, Profile, and Sections 


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- 

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 

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. 


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 

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 













Figure 44. Location of Embankment Instrumentation 


Figure 45. General Plan and Profile of Outlet Works 




EL. 5760 

EL. 5740 

EL. 5700 



EL. 5651 


EL. 5651 


80 120 160 



Figure 46. Outlet Works Rating Curve 


Figure 47. General Plan and Profile of Spillway 


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- 

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- 


Jjj L 

Figure 48. Location of Borrow Areas and Grizzly Valley Dam Site 


Figure 49. Completed Embankment 





- ,<" -■ ' 

^^^^^^^^^^^^^^ \ 



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 


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. 


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 

Figure 52. Outlet Works — Butterfly Valve in Outlet Structu 

Figure 53. Spillway Chute 


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. 



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 

, 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. 




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 


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 

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 

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- 

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 

TABLE 8. Statistical Summary of Oroville Dam and Lake Oroville 


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 


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 


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 


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 


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 









16 J4 12 10 8 6 4 









400 800 1200 1600 2000 2400 2800 3200 3600 4000 


Figure 57. Area-Capacity Curves 


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- 

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 


Figure 58. Model of Multiple-Arch Concrete Don 


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 

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 

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 

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 


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. 



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- 

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 



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Figure 59. Embankment Plan 


Figure 60. Embankment — Selected Sections and Profile 


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- 




Scale of Milts 

Dredge Tailings 







Figure 62. Location of Borrow Areas and Oroville Dam Site 


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 

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 



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 

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- 


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 




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Figure 64. Stability Analysis Summary 


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 



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 

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 

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, C = Zone I condition, so no 
further construction stability studies were deemed 

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. 


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 


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- 

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- 

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- 


M li. 

s ii 


^ ; ; 

Figure 67. Core Block 


Figure 68. Diversion Tunnels Nos. 1 and 2— Draft-Tube Arrange 


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- 

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 

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. 


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 

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 

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 

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 


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 

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 

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- 


Figure 69. Grout Envelope 


Figure 70. Intake Structures Plan 


Figure 71. Diversion Tunnel No. 1 — Intoke Portal Sections 


Figure 72. Diversion Tunnel No. 2 — Intake Pcrlol Sections 


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. 


^^;\ a" 

I I I I I 




' I 

J I I -J 

Figure 73. Diversion Tunnel Outlet Structures — Plan and Sections 


Figure 74. Miscellaneous Tunnels 


Figure 75. Palermo Outlet Tunnel 


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 

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 

The outlet requirements of this turnout are the 
same as for the outlet tunnel, i.e., a maximum dis- 
charge of 40 cfs. 


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 


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 

\'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 

Adjacent trunnion pins are not interconnected to 
the pier anchorage but are connected to a common 


Figure 76. General Plan of Spillwoy 


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Figure 77. Flood Control Outlet — Plan and Elevation 


Figure 78. Spillwoy Chute— Plon, Profrle, and Typicol Secti 


Figure 79. Emergency Spillway — Sections and Details 
















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Figure 81. 

Spillway and Flood Confrol Ouflet Rating Curves 


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 

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- 

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. 


Figure 82. Flood Control Outlet — Elevations and Sect! 


Figure 83. Bidwell Canyon Saddle Dam— Plan and Profile 





Figure 84. Bidwell Canyon Saddle Dam — Sections and Details 


Figure 85. Parish Camp Saddle Dom— Plan, Profile, and Sections 


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 


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. 


Figure 86. Location of Borrow Areas ond Parish Camp Saddle Dam Site 



Dam. The following is a summary of the in- 
strumentation in Oroville Dam: 

Hydraulic Piezometers 
Hydraulic Piezometers 
Electric Pore Pressure 

Dynamic Electric Pore 

Pressure Cells 
Cross-arm Settlement 

Fluid Level Settlement 

Surface Settlement 


Horizontal Movement 

Soil Stress Meters, 

7'/^-Inch Diameter 

Soil Stress Meters, 
18-Inch Diameter 

Dynamic Soil Stress 
Cells, 30-Inch 

Concrete Stress Meters 

Concrete Deformation 
' Accelerometers 

I Resistance Thermometers 


Sumber General Location 

54 In dam embankment 
2 In dam foundation rock 
2 In rock next to grout 

6 In dam embankment up- 
stream of Zone 1 
In dam embankment down- 
stream of Zone 1 


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 

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 

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). 

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 







NO. I 



Figure 87. Western Pacific Railroad Relocation — Tunnel Locations 


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 

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 

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 


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 

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- 

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 



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 

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 

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 


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 

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 


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 

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- 

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 

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 


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. 

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. 


TABLE 9. Major Contracts — Oroville Dam and Appurtenances 


Low bid 




Total cost- 



Prime contractor 

Tunnels Nos. 4 and 5, Western 
Pacific Railroad Relocation... 







Peter Kiewit Sons' Co. 

Bridge Over North Fork Feather 
River, Western Pacific Rail- 
road Relocation 







Pacific Bridge Co. 

Bridge Over Feather River at 
Oroville, Western Pacific Rail- 
road Relocation 







John C. Gist 

Roadway Structures and Tun- 
nels Nos. 2 and 3, Western 
Pacific Railroad Relocation 






9/ 8/61 

Ball & Simpson, Inc. 

Tunnel No. 1, Western Pacific 
Railroad Relocation 





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 







Ball & Simpson, Inc. 

Diversion Tunnel No. 1 







Frazier-Davis Construction Co. 

Palermo Outlet Works 







Morrison-Knudsen Co. 

Section Headquarters at Siding 
No. 3, Western Pacific Rail- 
road Relocation 







El Rey Builders, Inc. 

Oroville Dam 







Oro Dam Constructors 

Oroville Seismograph Station... 







El Rey Builders, Inc. 

Left Abutment Access Road 






4/ 9/63 

Piombo Construction Co. 

Oroville Construction Headquar- 







A. Teichert & Son 

Middle Fork, Feather River 







Bethlehem Steel Co. 

Employee Housing 




7/ 9/63 


Nomellini Construction Co. 

Oroville-Quincy Road Reloca- 

tion, Oroville-Forbestown 
Road to Middle Fork Bridge.. 





1/ 3/64 


Piombo Construction Co. 

Construction Overlook Modifi- 







A. Teichert & Son 

Pioneer Cemetery and Grave 






9/ 2/64 

Frank P. Donovan 

Headquarters and _ Employee 
Housing Landscaping 







Frank M. Smith 

Thermalito Power Canal Relo- 






11/ 5/65 

Osborn Construction Co. 

Bidwell Bar Emergency Cross- 

Frank P. Donovan 

Temporary Access Road, Middle 
Fork Bridge North to County 





12/ 3/64 

6/ 5/65 

Crooks Bros. Construction Co. 

Clearing Oroville Reservoir Site.. 







C. J. Langenfelder & Son, Inc. 

Oroville Dam Spillway 







Oro Pacific Constructors & 

George Farnsworth Construc- 
tion Co. 


TABLE 9. Major Contracts — Oroville Dam and Appurtenances — Continued 


Low bid 




Total cost- 



Prime contractor 

Oroville-Feather Falls Road Re- 

Oroville Feather Falls Road Re- 
location, South Fork Feather 
River Bridge and Roadway, 
Station 422-l-SO to Lumpkin 

Construction Overlook Reloca- 

Bulkhead Gates for Diversion 
Tunnel No. 1 

West Branch County Road Mod- 
ifications, Bennum and Lunt 

Oroville Operations and Main- 
tenance Center — Thermalito 

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- 

Oroville Completion Contract 
No. 3. 

Oroville Division Landscaping.. 

Oroville Dam Spillway Fencing.. 















































7/ 9/66 

11/ 4/66 
12/ 9/66 






1/ 8/70 
9/ 3/71 




2/ 3/67 

10/ 3/67 

4/ 4/68 





5/ 1/70 

O. K. Mittry & Sons 

Rothschild, Raffin & Weirick, 
Inc. & Piombo Construction 

Baldwin Contracting Company, 

Berkeley Steel Construction Co., 

A. Teichert & Son, Inc. 

Baldwin Contracting Co., Inc. 
Harms Brothers 

Christensen & Foster 

George R. Osborn Construction 

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- 

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 


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 

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- 


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 

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- 

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 

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- 


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 

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 

Figure 95. Stage 2 D, 

Figure fo. 3iag 


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 

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- 

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 


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 


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 

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- 


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 


Figure 107. Haul Route 


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 

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. 


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 

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 

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 



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 


Figure 114. Transfer Conveyor 


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- 

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 


f « |t-, ff ',:, 

^rl| -'Z/ i^fS 


^ I I 

■ ?^'\. I: 

■ ' 1 1 !^-* 

1 f? 1 

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Figure 115. Electrical Grounding Grids 




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 

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- 



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. 


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 

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 

After the water was controlled, work began on the 
building of the form for the 30-foot-long upstream 

Figure 118. Lowering Stoplogs 


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- 


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- 

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- 


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- 




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 

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- 

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 


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 

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 

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 


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 

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 






It ill 






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- 

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. 





, Goi 

' Hal 



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 

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. 


Figure 119. location Mop— ThermolHo Dlvoreion Dam 




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 

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). 


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. 


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 


Figure 121. General Plan and Profile of Dam 


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. 



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 


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 


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 


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 


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 


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 


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 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. 


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 

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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Figure 122. Spillway Rating I 


8 '^'^ -V Kit *»j.<.rl' 


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Figure 123. Spillway Sections 


Figure 124. Power Canal Headworki — Plan, Profile, and Sections 


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- 

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 

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- 

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. 


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 


Low bid 




Total cost- 



Prime contractor 

Oroville Dam' 





















3/ 4/69 




1/ 4/68 

Rodney Hunt Machine Co. 

Furnishing Fixed Dispersion 
Cone Valve and Operator 

Furnishing Radial Gates and 

Willamette Iron and Steel Co. 
Berkeley Steel Construction Co., 


Abbett Electric Corp. 

Furnishing Stop Logs and Lift- 

1 Thermalito Dam coDStnicted under this contract. Estimated &nal coBt 99,000,000. 


Figure 125. West Bank Diversion Plan 


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 

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 


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 


Figure 127. Channel Bypass, Closure, and East Bank Diversion Plan 


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 


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 

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 



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 

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- 

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 


Figure 129. Locglion of Concrete Mixes Used in Dam Structure 


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- 

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 

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 in Thermalito Diversion Dam 
consists of 64 foundation drains that are monitored 
quarterly and three crest monuments that are moni- 
tored annually. 



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. 




Figure 130. location Map— Tharmalito Forcboy and Aftarbay 





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 


TABLE 12. Statistical Summary of Thermallto Foraboy Dam and Forebay 


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 


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 


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- 


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 


Thermalito Powerplant Bypass 

Capacity 10,000 cubic feet per second 

TABLE 13. Statistical Summary of Thermalito Afterbay Dam and Afterbay 


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 


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 


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- 


Tail channel 

Maximum generating flow 16,900 cubic feet per second 

Maximum pumping flow 9,000 cubic feet per second 


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 






9 4 






































126 + OC 

O 1 M. 















JEL ' 










3 4 96 7 89 10 II 





Figure 133. Area-Copacity Curves — Thermalito Forebay 



5 4 3 2 

10 20 30 40 50 60 


Figure 134. Area-Capacity Curves — Thermalito Afferbay 



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 



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- 


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. 


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 

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. 


Figure 135. General Plon of Foreboy Main Dam 



J. r^ 


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Figure 136. Forabay Dam — Sections and Details 


r n « ^ 5 





Figur* 137. Forebay — Ruddy Creek and Low Danu Sections 


Figure 138. Afterbay Dam — Sections and Details 



1 ^J 





U ^ 



1 II 



Figure 139. Afterbay Dam Defaili 


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 

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 

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 


Unit Weight in Pounds 
Per Cubic Foot 

Static Shear Strengths 

B Angles in Degrees 

Cohesion in Tons Per Square Foot 





































Zone lA 

Zone 2A 

Zone 4A. ._. 


Foundation in Columbia Soils 
Southwest of River Outlet. . 
Northeast of River Outlet.. 
Foundation in Red Bluff for- 
mation was treated as 
basement rock 



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, 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 



i " 

P ^ 


A I 

1^ V 

Figure 141. Power Canal Sections 


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 

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 

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 

Water is released from this structure for down- 
stream project use, streamflow maintenance, and wa- 


TABLE 15. Data for Gates and Hoists — ^Thermalito Afterbay 


of Gates 

of Gates 


Gate Travel 


Inches per 


Invert of 

Gate Opening 


Flow Sensing 

Gate and 




Each (pounds) 



96' sq. 

72' sq. 

30' so. 

60" by 72' 

96' dia. 

72' dia. 

30* dia. 

72' by 84' 



Flow Tubes 
Flow Tubes 






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- 

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 




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Figure 143. Typical Turnoul — ^Thermalito Power Canal 


Figure 144. Western Canol and Richvole Canol Outlets 


Figure 145. Western Canal and Richvale Canal Outlets — Isometric View 


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Figure 146. Pacific Gas and Electric Outlet 



Figure 147. Pacific Gas ond Electric Outlet — Isometric View 


Figure 148. Sulter-Butte Outlet 


Figure 149. Sutter-Butfe Outlet — Isometric View 

V ^ 


Figure 150. River Outlet 



Figure 151. River Outlet Headworks ond Fish Barrier Weir — Isometric View 


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 

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 - 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- 

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 

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. 


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. 


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 


Low bid amount 

Final contract cost 

Total cost-change orders 

Starting date 

Completion date 

Prime contractor 







Guy F. Atkinson 


Power Canal 



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. 


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- 

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 

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- 

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- 

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. 


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 

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 


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 

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 

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). 


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 


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- 

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. 


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 

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. 



Figure 164. Location of Miscellaneous Channels 


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 

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 


^^^ il'H^Bi 

■»— "^ 


~"r>-*";-' . 




^^BP^^t^jj^-t-^.-^^ , 


Figure 165. Western Canal and Richvale Canal Outlets — Upstrean 

Figure 166. Pacific Gas and Electric Lateral Outlet Conduit 


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 


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 


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 

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 

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. 


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. 


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. 


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- 

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 



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. 












kElSO toao 










Figure 172. location Map — Clifton Court Foreboy 




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 


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 


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 


TABLE 17. Statistical Summary of Clifton Court Foreboy 


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 

Above maximum probable delta flood sur- 
face S feet 

Above maximum operating surface 6 feet 


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 

No spillway necessary 
Top of embankment is above all surrounding ground 


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 


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. 



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 


Figure 174. Embankment Sections 




{••^l.l'Sii! I. 



Figure 175. General Plan of Forebay — North 


Figure 176. General Plan of Forebay — South 


Figure 177. Gated Control Structure 


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 


Static Shear Strengths 

B Angles in Degrees 

Cohesion in Tons Per Square Foot 

Unit Weight in Pounds 
Per Cubic Foot 














Oto 8 feet 















8 feet and lower 

Sandy Silt 




Riprap and Filter 



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. 


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- 

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 

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. 







ri: \ 

Figure 179. Closure EmbankmenI 


NO. 2 



NO. 3 

Figure 180. Drainoge System 


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 

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- 


Excavation was performed under four categories: 
Forebay, Borrow Area A, structural, and ditch and 

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 

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 

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 


and used as uncompacted ballast outside of the em- 
bankment around the southern portion of the Fore- 

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 

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 


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 

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, 

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 

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 of Clifton Court Forebay was ac- 
complished by using (1) settlement gauges, (2) slope 
indicators, (3) plastic tubes, and (4) structural monu- 

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 








« ; 1 







5S5* 5* 

5 * * fc ■* 













•<? •« •« 



Figure 181. Test Installations 


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. 



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. 
















Figure 182. Location Mop — Bethany Dams and Reservoii 



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. 


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 


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 


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 


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 


California Aqueduct from Delta Pumping Plant 

Capacity lO,300 cubic feet per second 


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 


South Bay Pumping Plant 

Capacity 330 cubic feet per second 

North San Joaquin Division of California Aqueduct 

Capacity.. -. 10,000 cubic feet per second 







150 100 














UJ 220 








S '»° 




TY — - 


















10 20 30 40 50 


Figure 183. Area-Capacity Curves — Bethany Reservoir 


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- 

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 

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 


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. 



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 


Static Shear Strengths 

S Angles in Degrees 

Cohesion in Tons Per Square Foot 

Unit Weight in Pounds 
Per Cubic Foot 















Forebay Dam 

Adjacent Dams 






















Adjacent Dams 


to 0.50 of a ton per square foot for s 


Bethany Forebay Dam — Plan, Profile, and Sections 


Figure 187. Dam No. 1 — Plan, Profile, and Sections 


Figure 188. Dam No. 2 — Plan, Profile, and Sections 


Figure 189. Dam No. 3 — Plan, Profile, and Sectio, 


1 J 

Figure 190. Dam No. 4 — Plan, Profile, and Sections 




Figure 191. Location of Borrow Areas and Bethany Forebay Dam Site 


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 

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 

The piezometers are connected to an instrument 
panel in a well at the downstream toe of the Forebay 

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- 

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. 


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). 


Figure 192. Foundation Excovotion and Drainage Details — Dam No. 3 


Figure 193. Location of Foreboy Dam Instrumentatioi 


Figure 194. Outlet Works — Plan and Profile 



40 60 80 


Figure 195. Outlet Works Rating Curve 


Figure 196. Connecting Channel — Plan, Profile, and Sectio 


Figure 197. Temporary Spillway 


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 


Low bid amount 

Final contract cost 

Total cost-change orders 

Starting date 

Completion date 

Prime contractor 

Forebay Dam 







O.K. Mittry & 


Bethany Dams 

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. 


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. 


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. 


Figure 200. Locotion of Borrow Areas ond Adiocent Dams 


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 

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 


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 

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- 

Zone 4 (riprap bedding) material was dumped and 
spread on prepared surfaces in layers not exceeding 12 
inches after compaction. 


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 

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. 


i.. Ik. 



California Department of Water Resources, Bulletin No. 117-12, "Bethany Reservoir Recreation Development 
Plan", December 1970. 
























Figure 202. Location Mop — Del Voile Dam and Loke Del Voile 



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 

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 


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. 


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. 


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 


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 


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 


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 


Del Valle Pumping Plant 

Capacity, in or out 120 cubic feet per second 


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 



1200 1000 800 


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). 



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 

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 

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 


Figure 205. General Plan of Dam 



Figure 206. Embankment — Sections and Profile 


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 

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 

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 



Weight in Pounds 
Per Cubic Foot 

Static Shear Strengths 

6 Angles in Degrees 

Cohesion in Tons Per Square Foot 





















Zone IB 




Zone 3 







Figure 208. Conservation Outlet Works-Plan, Profile, and Sections 


Figure 209. Inclined Intake Structure 


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- 

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 

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 

Figure 210. Conservation Outlet Works Rating Curve 

I Jt 

! * 



inch (psi) at the valve vault to 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 

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. 


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 

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- 














\ 1 


\ * 










3 3 3;: 

Figure 211. General Plan of Flood Control Outlet Works 


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 

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 

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 

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. 


Id Nl N0llVA3n3 3DVdans' a3iVM 

Figure 212. Flood H/drographs 


Figure 213. Spillway Stilling Basin 


Figure 214. Single-line Eleclricol Diag 


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. 


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. 


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 

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 

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- 

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 


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- 

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- 


Figure 216. Location of Borrow Areas and Del Voile Dam Site 


TABLE 26. 

Compaction Data 

—Del Valle Dam 




























2 7 

In-place dry density — pounds 
Standard deviation 

per cubic foot. 


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 

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 

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 

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- 


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. 


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 

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. 


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 

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 


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 


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 

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 

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- 

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 



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- 

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- 


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 

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 

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. 


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. 



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. 










Figure 227. Location Map — San Luis Joint-Use Storage Facilities 



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 

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. 



Figure 228. Aerial View — San Luis Dam and Reservoir 


Figure 229. San Luis Reservoir Recreation Areas 


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. 


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- 

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. 


TABLE 27. Statistical Summary of San Luis Dam and Reservoir 


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 


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 


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 


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 


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 


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 


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 


Type: Glory hole with reinforced-concrete conduit and stilling basin 

Crest elevation 225 feet 

Crest length 184 . 4 feet 

Crest diameter 59. feet 

Conduit diameter 11.8 feet 

Peak maximum probable routed 

outflow.. 3,250 cubic feet per second 

Maximum surface elevation 228 feet 


North San Joaquin Division of California Aqueduct 

Capacity 10,000 cubic feet per second 


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 


San Luis Canal 

Capacity 13,100 cubic feet per second 


TABLE 29. Statistical Summary of Los Bonos Detention Dam ond Reservoii 


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 


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 


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 


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 

Type: Zoned earthfiU 

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 


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 


Storage at maximum probable flood 13,236 acre-feet 


leath dam at base of right 

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 



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, 

The detention dams were completed and put into 
operation in 1966. 


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 


133d-3dOV QNVSnOHl 
Nl 39Va01S dlOAd3S3a 






133d-3yOV QNVSnOHl 

Nl 30Vds loaiNoo-aooid 

Figure 231. Flood Diagram — Los Bonos Reservoir 


Figure 232. General Plan and Sections of San Luis Dam and O'Neill Forebay 




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 



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 

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- 

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 

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. 


Figure 236. Los Banos Detention Dam — Plan, Profile, and Sections 


Figure 237. little Ponoche Detention Dam— Plan, Profile, and Sections 


Figure 238. Spillway and Outlet Works — Son Luis Dam 


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. 


Figure 240. Spillway — O'Neill Forebay Dam 





'b * is 




\'"«i ''■ ' ' 

t < 

\' : 

\ 1 j • 1 ■ ■ ■ 

• •. i I > i i : 

I > 

■ \y 

ii' « 

Figure 241 . Los Bonos Detention Dam — Spillway and Outlet Plan and Spillwoy Profile 


Figure 242. Los Banos Detention Dam — Outlet Profile 


Figure 243. li„|e Panoche Detention Dom-Spillwoy Plan and Sections 



Instrumentation at San Luis Dam and O'Neill Dam 
consists of the following: 

San Luis Dam 


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 


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 

! Los Banos 

Embankment 20 

Spillway 46 

Outlet works 20 

, Abutments 14 

[Abutment piezometer wells 2 

iToe drain 1 

Weir, outlet tunnel drain 1 

Little Panoche 


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. 


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. 


Figure 244. Location of Instrumentotion — Son Luis Dam 



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 


_, "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 


_, "Final Construction Report, Los Banos Creek Detention Dam", Specifications No. DC-6080, December 


, "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 


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) 



< t M M TT I I I I I I I I I I I I ' ' " ' ■ ' ~r~r 

Figure 245. Location Map — Cedar Springs Dam and Silverwood Lake 





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 


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 


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 


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 


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 


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 


Open concrete-lined channel and chute from terminus of Mojave 
Siphon to flip bucket on reservoir floor 
Capacity 1,990 cubic feet per second 


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 


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 




























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 


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 


Figure 248. Dam Site Plan 



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. 


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 

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 


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 

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- 

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. 



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 




San Andreas 

Design Earthquake 

Relative Importance 

Applied Horizontal 



Granite shear zone, 
Harold formation 












(includes approacli and crest walls and crest 

Spillway chute and stilling basin 

Outlet Works 
Inlet tower and trashrack.. 


Gate chamber . 


Mojave Siphon Inlet Works 






Figure 250. Embankment Plan 




!t •" 

/'-L-^ — 1 — 7 

'^ — ^I— — "^ — *" 

^T 1 1 

-'.-V , « 

V ' 1 

_ •! 1 1 

A 5 

\^-~2l~ — *-— u. 

' tn 


1 ^^ T 

\ \ '' r 

--K:^ . 

ift \ '\ \ - 

- S»« 

li\ \ '' V 

\ ij^o K 

' \ \\ 

° ;;; 

• i ; 



^ \ 

Figure 251. Embankment Sections 


Figure 252. Embankment — Sections and Details 


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- 

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 


TABLE 33. Materiol Design Parameters — Cedar Springs Don 



Static Shear Strengths 
8 Angles in Degrees 
Cohesion in Tons Per Square 


Weight in Pounds 
er Cubic Foot 














Zone 1 . 





















Zone 2 

Zone 3, Quarry 

Zone 3, Streambed 

Zone4A _.. 

Zone 5 

Foundation, Harold for- 


• 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 

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 



Figure 254. Location of Instrumentation — Sections 






Figure 255. Location of instrumentation — Plan 



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 

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, 


Figure 257. Miller Canyon Debris Barrier 


i 'i 

Figure 258. Cleghorn Canyon Debris Barrier 




\ '^\ 


Figure 259. San Bernardino Tunnel Approach Channel 


Figure 260. Access Tunnel and Drainage Gallery Plan 



-'"■'--— ^ 

^5l ■ 


























Figure 261. Access Tunnel and Drainoge Gollery — Profiles and Sections 



Figure 262. 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- 

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. 


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 

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 


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- 

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 


Figure 265. Outlet Works — Plan and Profile 


/vj . 



/ / — 


Figure 266. General Arrangement of Gate Chamber 


Figure 267. Inlet Works— Plan and Profile 



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 


designed as a "U" section with the following loading 

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 

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- 

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 

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 




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- 

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 

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 


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 

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 

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 

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 


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- 

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- 

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 

Control \'alves. Two control valves, one 12-inch 


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 

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 

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. 



I k J 


. ^ 5 


i i i 

ill! i M 



< \U 

^""■V't- ,1 ,1 ,1 

J s , 6 »B ^ *Bi 

J ' « k -s^ i 

I II f ^^ I 

% I ? I ,» * j>. 5 

M H I > ^^ ! 

J I I I I < i? i 





\ ii t^ 

Figure 270. Control Schematics 


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- 

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 

Stage II Pump 

Quarry Irrigation 



Low bid amount 

Final contract cost 

Total cost-change orders 

Starting date 

Completion date 

Prime contractor 







Clifford C. Bong & 




?43 1,628 




R. L. Thibodo 

Construction Co. 









Pylon, Inc. 

Moulder Bros. 


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. 


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 

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 


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- 

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- 

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). 


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. 


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 

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 



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 

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 

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- 

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 + 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 

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 


added to the concrete to reduce friction in the slick- 

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 

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 
+ 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- 

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 



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- 

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 

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 


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 

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 

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- 


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. 


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- 

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- 

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 

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. 


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. 



Lanning, C. C, "Cedar Springs Dam", USCOLD Issue No. 32, U. S. Committee on Large Dams Newsletter, May 

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. 




III I ' I I M I M I I I ' > > 



■+-* ■ I I |-p 





















Figure 278. Location Map — Perris Dam and Lake Perris 



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. 



Figure 279. Aeriol View — Perris Dam and Lake Perris 



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- 


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 


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 


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 



Type: Ungated ogee crest with concrete baffled chute and riprapped 

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, 


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 


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 



2000 1600 1200 




O 1540 


NWS EL 1588 
















— A R F A 








80 100 





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. 


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- 

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 


Figure 281. Embonkirienf Plan 





JTr I I 

Figure 282. Embankment Sections 


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- 

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 


Unit Weight in Pounds 
Per Cubic Foot 

Static Shear Strengths 
e Angles in Degrees 
Cohesion in Tons Per Square 






























Zone 3 


Foundation . 

• Free-draining material. u»c effective stress valu 



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. 


Figure 283. Embankment Instrumentation 


Figure 284. Inlet Works — Plan and Profile 


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 

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 

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 

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 


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 

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 

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 

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- 


Figure 285. Outlet Works — Plan and Profile 



Figure 286. Outlet Worb Tower 


Figure 287. Outlet Works Delivery Facilitiej 


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- 

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 

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- 


Figure 288. Spillway — Plan, Profile, and Sections 


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- 

4. Venturi metering readout equipment. 

5. Emergency power supply. 

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. 





/ ^CR 


10 200 300 400 500 

Figure 289. Spillway Rating Curve 


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 

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- 

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- 

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 


Low bid amount 

Final contract cost 

Total cost-change orders 

Starting date 

Completion date 

Prime contractor 

Perris Dam Con- 


Perris Dam Con- 







Perris Dam Con- 

2254,000 (Est.) 


12/74 (Est.) 

Jesse Hubbs & Sons 

' Reflects bid-price adjustments. 

' Includes 32,260,925 (or recreational facilitic 

* As of November 1974. 


Figure 290. Location of Borrow Areas and Perris Dam Site 


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- 

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 

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 



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 

When the decision was made to forego any future 

Figure 294. Embanltment Construction Activity 


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. 


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 

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 

The 40-foot-long steel-liner sections of '/2-inch plate 



ir. "'T^3iiB| 



y '^BSikif^^^^^^^^^^^l 


1 ^^^^^S/Jg^^^^^^^^^^^^t 

Figure 297. Tower Outlet Portal 

Figure 298. Outlet Works Delivery Manifold 









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. 


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. 




5/ oso 



























Figure 300. Location Mop — Pyramid Dam and Lai<e 




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 


Figure 302. Dam Site Plan 


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. 


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 

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 


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 


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 


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 


Improved Gorman Creek (interim) 

Design flow 850 cubic feet per second 

Pyramid Powerplant (future) 

Maximum generating flow 3,128 cubic feet per second 


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 


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 

Capacity, stream maintenance 1,000 cubic feet per second 

Capacity, reservoir drainage 3,200 cubic feet per second 




Z 2400 










1 '<yg 1 *i 

Eltv. 257S 

M 1 


6QQ 4» 2no 1 























Min. W. S. El*»^34n 







60 SO 100 120 140 


Figure 303. Area-Capacity Curves 



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 

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 


1915 and 1965, approximately four other earthquakes 
occurred which could have produced an estimated in- 
tensity of 6 or greater at the Dam site. 



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- 

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- 


i Ml 
i it 


I I i 

I I 

Figure 304. Embankment Sections 


Figure 305. Embankment Plan 


Figure 306. Interim Dam — Plan, Sections, and Detoils 




Figure 307. Interim Dam — Sections and Profile 


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 


—Pyramid Dam 


Unit Weight in Pounds 
Per Cubic Foot 

Static Shear Strengths 
Angles in Degrees 
Cohesion in Tons Per Square 



























* The same parameters were used in transition and drain zones. 


than would otherwise be necessary, providing addi- 
tional freeboard, and compacting the rockfill as much 
as possible without adversely affecting the permeabili- 
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: 

Type of Instrument Installed Data Obtained 

Piezometers (Hydraulic) 21 * Pore Pressure 


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 

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 

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- 



Figure 308. Exploration Adits — Section and Details 


Figure 309. Diversion Tunnel — Plan and Profile 


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 

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 

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 

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- 



Figure 311. Valve Chamber 
















t- - 































* It 











\ / 
































Figure 312. Outlet Works Rating Curves 


Figure 313. Air Shaft 


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 

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 


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- 

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. 



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- 

1. With releases through the gated passage equaling 
inflow, up to the gate capacity, 4 feet above peak 

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 

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. 


Figure 318. General Plan of Spillway 








i33d Nl N0I1VA3-I3 


Figure 319. Spillway Profile 

■^.if*^'-' -^^^'Hu :£- ':' v - . 

Figure 320. Spillway Flip Structure During Discharge 



Figure 321. Spillway Headworks Structure 


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 

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 

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. 



Figure 322. Interstate 5 Embankments 


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 



Cohesion (C's), psf 



Angle of internal friction 

(9), degrees 



Total Stress 

Cohesion (C), psf 



Angle of internal friction 

(9), degrees 



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 

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 

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. 


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- 

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 


Low bid 



Total cost- 




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... 























7/ 6/71 


9/ 6/74 


2/ 8/71 
2/ 1/74 


6/ 7/74 

1/ 6/75 

Bill Anderson Co. and Bill An- 
derson Co., Inc. 


Wismer & Becker Contracting 

Kasler Corp., Gordon H. Ball, 
Inc., & Robert E. Fulton Co. 

Ray N. Bertelson Co., Inc. and 
Ray N. Bertelson Co. 


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^ 



- .', , -.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 


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 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 

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- 

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 




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 

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. 


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 

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 



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. 


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 • ■^■:^-' 

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- ■'">•- V 


f ' 










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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 

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 

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- 


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 


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