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Full text of "Report to U.S. Department of the Interior and State of Idaho on failure of Teton Dam"

BOSTON PUBLIC LIBRARY 



3 9999 06317 344 5 



GOVDOC 



REPORT TO 



U.S. DEPARTMENT OF THE INTERIOR AND STATE OF IDAHO 



ON 



FAILURE OF TETON DAM 



BY 



INDEPENDENT PANEL TO REVIEW CAUSE OF TOTON DAM FAILURE 



DECEMBER 1976 



D.236A 




REPORT TO 
U. S. DEPARTMENT OF THE INTERIOR AND STATE OF IDAHO 



ON 



FAILURE OF TETON DAM 



BY 



INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Wallace L. Chadwick, Chairman 

Arthur Casagrande 

Howard A. Coombs 

Munson W. Dowd 

E. Montford Fucik 

R. Keith Higginson 

Thomas M. Leps 

Ralph B. Peck 

H. Bolton Seed 

Robert B. Jansen, Executive Director 

IDAHO FALLS, IDAHO 
DECEMBER 1976 



For sale by the Superintendent o( Documents, U.S. QoTemment Printing Office, Washington, D.C. 20*02 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 

Wallace L Chadwick, Chairman 

Arthur Casagrande 

Howard A. Coombs 

Munson W Dowd 

E. Montford Fucik 

R. Keith Higginson 

Thomas M. Leps 

Ralph B. Peck 

H. Bolton Seed 

Robert B. Jatisen, Executive Director 



December 31, 1976 



Honorable Thomas S. Kleppe 

Secretary 

U.S. Department of the Interior 

Washington, D.C. 



Honorable Cecil D. Andrus 
Governor 
State of Idaho 
Boise, Idaho 



Gentlemen: 

Immediately following the failure of the Teton Dam on June 5, 1976, 
you joined in ordering an investigation and established for this purpose 
the Independent Panel to Review Cause of Teton Dam Failure. The Panel 
has completed its charge and herewith submits a report on its findings. 

Pursuant to your instructions, the Panel has conducted a comprehen- 
sive study of the failure, including review of planning, design, construc- 
tion, and operation of the dam and reservoir. Extensive field exploration, 
laboratory testing, and data analysis have been accomplished. 

In briefest summary, the Panel concludes (1) that the dam failed by 
internal erosion (piping) of the core of the dam deep in the right founda- 
tion key trench, with the eroded soil particles finding exits through 
channels in and along the interface of the dam with the highly pervious 
abutment rock and talus, to points at the right groin of the dam, (2) that 
the exit avenues were destroyed and removed by the outrush of reservoir 
water, (3) that openings existed through inadequately sealed rock joints, 
and may have developed through cracks in the core zone in the key trench, 
(4) that, once started, piping progressed rapidly through the main body 



m 



Page 2 December 31, 1976 

Letter to Honorable Thomas S. Kleppe and Honorable Cecil D. Andrus 



of the dam and quickly led to complete failure, (5) that the design of 
the dam did not adequately take into account the foundation conditions 
and the characteristics of the soil used for filling the key trench, and 
(6) that construction activities conformed to the actual design in all 
significant aspects except scheduling. 

The Panel is hopeful that its findings will not only shed light on 
the Teton Dam failure, but will also assist in the design of safe dams 
at other sites. 

Respectfully submitted. 



Arthur Casagrande Wallace L. Chadwick, Chairman 



/^TiMLu/^ ^ ^ /Cf-J^lUt/. 




Munson W. Dowd 




Thomas M. Leps 



H. Bolton Seed 



IV 



SUMMARY AND CONCLUSIONS 



The Independent Panel to Review Cause of Teton Dam Failure has completed its task, as charged by 
the Secretary of the United States Department of the Interior and the Governor of the State of Idaho 
in letters from Secretary Kleppe, dated June 11, 23, and 30, 1976. The Panel submits its report 
herewith. These pages present a summary and conclusions. 

Teton Dam failed on June 5, 1976, when the reservoir was at El. 5301.7, 3.3. ft below the spillway 
sill. Although downstream warnings are believed to have been timely, deaths of 14 persons and 
property damage estimated variously from 400 miUion to one bilhon dollars have been attributed to 
the failure. 

Construction of Teton Dam was authorized on September 7, 1964, by PubUc Law 88-583. The dam is 
situated on the Teton River, three miles northeast of Newdale, Idaho. Prior to 1963, the proposed 
dam was known as Fremont Dam. 

Teton Dam and its reservoir were principal features of the Teton Basin Project, a multipurpose 
project embodying flood control, power generation, and supplemental irrigation water supply. The 
dam was a central-core zoned earthfill structure, with a height of 305 ft above the riverbed and 405 ft 
above the lowest point in the foundation. Provisions for seepage control included a key trench in the 
foundation rock above El. 5100 and a cutoff trench to foundation rock below that elevation. A grout 
curtain extended below these trenches. 

Investigations of site possibiUties for a dam on the Teton River commenced as early as 1904 and 
continued at various times until bids for construction of Teton Dam were invited on July 22, 1971 . A 
construction contract was awarded on December 13, 1971. The embankment was topped out 
November 26, 1975. Filling of the reservoir commenced October 3, 1975, and continued until the 
failure on June 5, 1976. 

The Panel's approach to its assignment has been to: 

(1) obtain, analyze and evaluate all relevant information which could be obtained in document 
form from the United States Bureau of Reclamation, the United States Geological Survey, the 
construction contractor, and any other available and knowledgeable source regarding the regional and 
site geology, pre-siting investigations, siting decisions, pre-design investigations, design, contract 
specifications and drawings; construction practices, progress and inspections; in-progress changes, if 
any; pre-failure operation; mechanism of failure, including sworn eyewitness accounts; and actions of 
respective authorities during and immediately following failure; 

(2) supplement the documentary information by such further inquiry, including public hearings, as 
became necessary; 

(3) make (a) detailed studies of the post-failure condition of the dam, its auxiliary structures and its 
foundation, by inspection, dissection and subsurface drilling; (b) special tests on foundation 
materials; (c) detailed geologic maps and joint surveys; (d) tests of remnant materials; (e) detailed 
stress analyses; (0 studies of photographs for comparison of post-failure conditions with 
pre-construction and construction conditions; (g) measurements of post-failure geodetic positions of 
surface and subsurface points, as determined before failure and before filling of the reservoir; 

(4) contract with various organizations for special studies required by the Panel; 



(5) evaluate relevant data in order to sort out those of greatest significance in determining cause; 

(6) complete a report of the results of the foregoing activities prior to January 1 , 1977. 

The approach was initiated by telegrams, dated June 11 and June 14, 1976, to the Director, 
Engineering and Construction, U.S. Bureau of Reclamation, Denver, and by setting the Panel's first 
working session and its inspection of conditions at the site for the week of June 28-July 2, 1976. The 
telegrams requested information concerning (1) site geology in plan and sections with any test results 
on foundation materials; (2) site exploration with detail of drill logs, exploration trenches, borrow 
materials and tests; (3) grout records in detail showing non-average takes by location and depths, the 
patterns used and records of any interconnections; (4) foundation preparation showing both before 
and after conditions; (5) design memoranda for embankment, spillway, diversion structures and 
outlets; (6) basic drawings and technical specifications; (7) any outside report regarding the site or 
designs; (8) construction history of borrow pits, material preparation placement, progress, inspection, 
in-place tests; (9) seepage measurements or observations; (10) eyewitness accounts on progress of 
failure; (11) hydrology of the site; (12) seismicity of the site; (13) drain designs and drainage 
observations; (14) post-failure changes in spillway or auxihary outlet structures; (15) any changes in 
precise level or horizontal control survey points; (16) changes in topography up and downstream; 
(17) photos of the foundation as approved at the start of embankment placement, particularly in the 
key trench and the cutoff trench; (18) record of any seeps or springs in the cutoff and core contact 
area; and (19) records of cofferdam seepage and pumpage from the foundation area. 

Prior to the Panel's convening for its first session, the Department of the Interior had recorded sworn 
testimony of 37 eyewitness observers of pre-faOure and during-failure conditions, of whom 14 were 
Bureau of Reclamation staff and employees, 13 were employees of the construction contractor, and 
10 were from the general pubUc. In parallel with these eyewitness accounts, there became available 
several excellent photographic sequences in still and later in motion picture form. In order to 
supplement these eyewitness accounts with any available observations of failure-related, but 
pre-faOure conditions, a public call was issued, and two pubhc hearings were held in Idaho Falls on 
July 21, 1976. 

During its first working session, the need for professional staff and technical and administrative 
support was recognized. To fill this need, the services of Robert B. Jansen, as Executive Director, 
were secured through the cooperation of the Governors of Idaho and California. Also, the services of 
Clifford Cortright, Staff Engineer, and Larry James, Staff Geologist, and Frank Sherman, also a staff 
geologist, were secured within a few days of Mr. Jansen's appointment. Through the excellent 
cooperation of the Office of the Secretary, Department of the Interior, suppordng properties, 
services, technicians and administrative assistance have been made available to the Panel through 
various bureaus of the Department. 

Because of the importance of determining existing embankment and foundation conditions, the Panel 
early addressed the Director, Design and Construction, USER, Denver, requesting specific work on 
the right abutment to permit detailed examination of the remnant there, and excavation to uncover 
both the auxiliary outlet tunnel for internal inspection and the site of the large, lower spring observed 
early on June 5, 1976. 

Response was prompt, and on July 16, 1976, the Bureau of Reclamation awarded its Contract No. 
DC-7232 to Gibbons and Reed, Salt Lake City, to cover the required work. Actual dissection of the 
right remnant of the dam started July 26, 1976. This excavation proceeded expeditiously, in five-foot 
vertical increments, to El. 5200, with trenching in each incremental level to allow taking of samples as 



VI 



well as inspection of the core remnant for any evidence of water channeling, or cracking, and of the 
manner in which the key trench was excavated, sealed, fitted and compacted. 

The Bureau's response to the Panel's request for records, data and descriptions was also prompt. A 
large volume of information was furnished. Many of these records have been supplemented by others 
furnished to the Panel's staff at the site in response to oral and written requests. 

Further information was sought on the manner in which the grout curtains were closed and in which 
the core was built into the key trench. This information was desired both from the Bureau of 
Reclamation as designers and construction engineers of the dam, and of the contractor, who 
implemented that construction. Accordingly, a questionnaire was directed concunently to the 
Director, Design and Construction, USER, and to the Chief Executive Office of Morrison-Knudsen, as 
the sponsoring member of the constructing contractor, Morrison-Knudsen-Kiewit. 

The USBR response was quite complete. The contractor's response is in two parts. One is from the 
prime contractor per se, and the other is from the grouting sub-contractor, McCabe Bros., Inc. The 
prime contractor's answer was rather general. 

Staff investigations started immediately upon appointment of the various staff members. Their efforts 
have been interested, diligent, competent, and tireless. They have greatly expedited the completion of 
the Panel's task and the compilation of its report. The Panel met in Denver on June 28 and 29 to 
organize and initiate its inquiry through information presentations by the Bureau of Reclamation. A 
site inspection was made on June 30. Information meetings were held with the Bureau engineers at 
the site during the following day. Working sessions were continued in Denver on July 2. The Panel 
met again in working session in Idaho Falls Augusts through 5, again Octobers through 7, 
November 1 through 3, and December 7 through 10. Between its working sessions, individual Panel 
members worked with the staff, and independently on assignments from the Panel. Frequent 
individual visits were made to the site exploratory work. 

Careful study was made of all eyewitness accounts of their observations prior to the breach. All 
available photographs of the failure events were studied and arranged in chronologic sequence. All 
available relevant documentary records have been reviewed for significant content. Continuous 
professional examination was conducted of ail trenching in the right abutment embankment remnant. 
Detailed mapping of the bedrock joints and fractures in and adjacent to the right abutment key 
trench was conducted between Stas. 11+00 and 16+00. Laboratory testing of undisturbed samples of 
Zone 1 (core) material was carried out. Subsurface water loss tests were conducted at many locations 
near the centerUne right abutment grout curtain. Surface ponding tests were conducted at the key 
trench invert at prominent joints crossing the invert. Hydraulic fracturing tests were made in drill 
holes in the left abutment core remnant. Analytic studies were made to assess the stress conditions on 
sections of the embankment and key trench in the zone of failure. 

The Panel's conclusions are summarized below: 

1. The records show that the pre-design site selection and geological studies were appropriate and 
extensive. The pilot grouting program carried out in 1969 forecast the difficulties to be experienced 
in construction of the final grout curtain. 

2. The design followed USBR practices, developed over a period of many years from experience 
with other Bureau projects, but without sufficient consideration of the effects of differing and 
unusually difficult geological conditions at the Teton Damsite. Every embankment can be said to 



vn 



have its own personality requiring individual design consideration and construction treatment. 
Treatment of such individuaUties produces most of the continuing advances in dam design and 
construction technology. 

3. The volcanic rocks at the Teton Damsite are highly permeable and moderately to intensely 
jointed. Water was therefore free to move with almost equal ease in most directions, except locally 
where the joints had been effectively grouted. Thus during reservoir filling, water was able to move 
rapidly to the foundation of the dam. Open joints existed in the upstream and downstream faces of 
the right abutment key trench, providing potential conduits for ingress or egress of water. 

4. The vnnd-deposited nonplastic to sUghtly plastic clayey silts used for the core and key trench fill 
are highly erodible. The Panel considers that the use of this material adjacent to the heavily jointed 
rock of the abutment was a major factor contributing to the failure. 

5. Construction of the project was carried out by competent contractors under formal contracts 
administered in accord with well-accepted practices. Controversy between the contractors and Bureau 
of Reclamation officials which might have affected the quality of the work seems not to have 
occurred. Construction activities conformed to the actual design in all significant aspects except 
scheduling. 

6. One construction condition which affected the Bureau's ability to control the rate of fdling of 
the reservoir was the delay that occurred in completion of the river outlet works. However, the Panel 
beUeves that the conditions which caused the piping and consequent failure of the dam were not 
materially affected by the fact that the reservoir was filled at a more rapid rate than had been 
originally plaimed. A slower rate of filling would have delayed the failure but, in the judgment of the 
Panel, a similar failure would have occurred at some later date. 

7. The records show that great effort was devoted to constructing a grout curtain of high quaUty, 
and the Panel considers that the resulting curtain was not inferior to many that have been considered 
acceptable on other projects. Nevertheless, the Panel's on-site tests and other field investigations 
showed that the rock immediately under the grout cap, at least in the vicinity of Stas. 13+00 to 
15-hOO, was not adequately sealed, and that additional unsealed openings may have existed at depth in 
the same locality. The leakage beneath the grout cap was capable of initiating piping in the key trench 
fill, leading to the formation of an erosion tunnel across the base of the fill. The Panel considers that 
too much was expected of the grout curtain, and that the design should have provided measures to 
render the inevitable leakage harmless. 

8. The geometry of the key trenches, with their steep sides, was influential in causing transverse 
arching that reduced the stresses in the fill near the base of the trenches and favored the development 
of cracks that would open channels through the erodible fill. Arching in. the longitudinal direction, 
due to irregularities in the base of the key trenches, and arching adjacent to minor irregularities and 
overhangs, undoubtedly added to the reduction of stress. 

9. Stress calculations by the finite element method indicated that, at the base of the key trench 
near Stas. 14+00 and 15+00, the arching was great enough that the water pressure could have 
exceeded the sum of the lateral stresses in the impervious fill and the tensile strength of the fill 
material. Thus, cracking by hydrauUc fracturing was a theoretical possibility and may have led to flow 
of water in the base of the key trench between Stas. 14+00 and 15+00, and erosion of the key trench 
fill. 



vm 



10. Close examination of the interior of the auxiliary outlet tunnel showed no distress of any kind 
such as would be expected had the right abutment, through which the tunnel passes, been subjected 
to significant settlement or other structural change. Geodetic resurveys showed only minor surface 
movements as a result of reservoir filling and emptying. Accordingly, differential movements of the 
foundation are not considered to have contributed to the failure. 

11. The Panel found no evidence that seismicity was a factor in failure of the dam. 

12. The dam and its foundations were not instrumented sufficiently to enable the Project 
Construction Engineer and his forces to be informed fully of the changing conditions in the 
embankment and its abutments. 

13. Following its first working session, the Panel reported that it then seemed apparent that the 
failure resulted from piping, a process by which embankment material is eroded internally and 
transported by water flowing through some channel in the embankment section. That conclusion 
remains vaUd. The Panel's investigations since that time have been directed particularly to 
determining the most probable manner in which such piping erosion started. The Panel beUeves that 
two mechanisms are suspect. Either could have worked alone or both could have worked together. 
One is the flow of water against the highly erodible and unprotected key trench filling, through joints 
in the unsealed rock immediately beneath the grout cap near Sta. 14+00 and the consequent 
development of an erosion tunnel across the base of the key trench fill. The other is cracking caused 
by differential strains or hydraulic fracturing of the core material fiUing the key trench. This cracking 
would also result in channels through the key trench fill which would permit rapid internal erosion. 

In either case, leakage occurring through the key trench ultimately initiated further erosion along the 
downstream contact of the core and the abutment rock. Since the core material was both easily 
erodible and strong, any erosion charmels in the core, along the contact with the rock, readily 
developed into large turmels or pipes before becoming visible along the downstream parts of the dam. 

It should be noted that this description of the failure mechanism does not provide a final answer to 
the specific cause of failure of Teton Dam. Clearly many aspects of the site and the embankment 
design contributed to the failure, but because the failed section was carried away by the flood waters, 
it will probably never be possible to resolve whether the primary cause of leakage in the vicinity of 
Sta. 14+00 was due to imperfect grouting of the rock below the grout cap, or cracking in the key 
trench fill, or possibly both. There is evidence to support both points of view. Nevertheless, while the 
specific cause may be impossible to estabhsh, the narrowing of the possibiUties to these two aspects 
of design and construction is likely to serve as an important but tragic lesson in the design and 
construction of future projects of this type. 

14. The fundamental cause of failure may be regarded as a combination of geological factors and 
design decisions that, taken together, permitted the failure to develop. The principal geologic factors 
were (1) the numerous open joints in the abutment rocks, and (2) the scarcity of more suitable 
materials for the impervious zone of the dam than the highly erodible and brittle windblown soils. 
The design decisions included among others (1) complete dependence for seepage control on a 
combination of deep key trenches filled with windblown soils and a grout curtain; (2) selection of a 
geometrical configuration for the key trench that encouraged arching, cracking and hydraulic 
fracturing in the britUe and erodible backfill; (3) reliance on special compaction of the impervious 



ix 



materials as the only protection against piping and erosion of the material along and into the open 
joints, except some of the widest joints on the face of the abutments downstream of the key trench 
where concrete infilling was used; and (4) inadequate provisions for collection and safe discharge of 
seepage or leakage which inevitably would occur through the foundation rock and cutoff systems. 

The difficult conditions of the site called for basing the design on the most unfavorable assumptions 
compatible with the geologic conditions concerning the behavior of the water and its possible effect 
on the embankment. Instead of placing so much dependence on the key trenches and grout curtain, 
measures should have been developed to render harmless whatever water did pass, irrespective of the 
reasons. 

In final summary, under difficult conditions that called for the best judgment and experience of the 
engineering profession, an unfortunate choice of design measures together with less than conventional 
precautions was taken to ensure the adequate functioning of the Teton Dam, and these 
circumstances ultimately led to its failure. 



FOREWORD 



As a basis for this report, the Independent Panel to Review Cause of Teton Dam Failure read and 
evaluated a large volume of documents, records, and data, the larger part of which was obtained from 
the United States Bureau of Reclamation, the designing and constructing agency for the Teton Dam. 
Additionally, the Panel carried out numerous independent inquiries; and through contracts, 
administered by the Department of the Interior, conducted detailed exploratory excavations in the 
right bank remnant of embankment which survived the failure. All of that remnant was dissected, 
seeking evidences of cause of failure. 

Exploratory core drilling was done for the Panel, seeking better to evaluate subsurface foundation 
conditions and adequacy of foundation grouting. Independent geological mapping was carried out, 
particularly of the bedrock foundation joint systems. Physical testing was done on undisturbed 
samples of fill material from the remnant of the dam on the right abutment. Using several 
laboratories, additional tests were made of the characteristics of the foundation materials. Analytical 
studies were made to permit estimating the stresses within the embankment. The results of some of 
the investigations carried out for a separate investigative unit identified as the U.S. Department of the 
Interior Teton Dam Failure Review Group, under the chairmanship of Mr. Dennis Sachs, have been 
suppUed to the Independent Panel, and have been carefully evaluated. Also the results of the field and 
laboratory studies conducted by the Independent Panel were made available to the Interior Group. 

An effort was made by the Independent Panel to evaluate all available, relevant information. To aU of 
this information the Panel has applied its best professional judgment, and it is satisfied that its 
conclusions regarding the cause of failure are sound. However, to permit others to reach their own 
judgments concerning the Panel's findings, the Panel has attempted to hst and reference, as much as 
has been practicably possible, the principal source information upon which it relied in making its 
judgments. 

The Panel is grateful to the Secretary of the Interior and to his office, and to the Governor of Idaho 
and his office, for their support and understanding throughout the Panel's review. The administrative 
counsel and aid received from the Secretary's office has maximized the time available for the 
technical and analytical work of the Panel. The cooperation which the Panel received from all levels 
of the Bureau of Reclamation has been of great assistance. 



XI 



CONTENTS 

Page 

LETTER OF TRANSMITTAL iii 

SUMMARY AND CONCLUSIONS v 

FOREWORD xi 

ABBREVIATIONS xx 

TERMINOLOGY xxi 

ACKNOWLEDGEMENTS xxiii 

CHAPTER 1. INTRODUCTION 1-1 

CHAPTER 2. CHRONOLOGY OF FAILURE AND USBR REACTIONS 2-1 

June 3, 1976 - Observation, Small Seeps Downstream of Dam 2-1 

June 4, 1976 - Further Small Seeps Downstream 2-5 

June 5, 1976 - First Observations - Leaks at Els. 5045 and 5200 2-6 
June 5, 1976 - 8:00 A.M. to 10:00 A.M. - Development of Additional Leakage at Els. 2-8 

5045 and 5200 

Development of Upstream Whirlpool 2-17 

Reaction of Bureau of Reclamation Personnel to the Emergency 2-20 

CHAPTERS. PANEL INVESTIGATIONS 3-1 

Post-failure Excavation ^.IQ 

Soil Sampling and Testing 2-15 

Embankment Stress Analysis 2.17 

HydrauUc Fracturing Tests in Boreholes 2-17 

Post-failure Foundation Investigation 2-1 g 

Inspection of Auxiliary Outlet Works 2-39 

Rock Joint Survey 2-39 

Comparison of Pre-failure and Post -failure Surveys 2.39 

Model of the Right Abutment 2-39 

CHAPTER 4. SITE SELECTION AND PROJECT SITE INVESTIGATIONS 4-1 

Early Studies 4-1 

Selection of Teton Damsite 4-4 

Core Drilling at Teton Damsite and Reservoir Area 4-4 

Other Exploration 4-8 

Reservoir Leakage Studies 4-8 

Rock Core Testing 4-9 

Pilot Grouting Program 4-9 

Comments 4-11 

CHAPTER 5. GEOLOGY 5-1 

Regional Geology 5-1 

Geology of Dam and Reservoir Site 5.5 

Findings of Engineering Significance Based on 5.37 

Available Geologic Information 5.37 



xiii 



CHAPTER 6. SEISMICITY 6-1 

Historical 6-1 

Geologic Setting 6-1 

Faulting 6-1 

Seismometer Array 6-5 

Recordings Monitoring Dam Failure 6-7 

Comments 6-7 

CHAPTER?. CONSTRUCTION MATERIALS 7-1 

Borrow Areas 7-1 

Materials as Placed 7-5 

Project Materials Testing Program 7-7 

Panel's Investigative Zone 1 Soils Testing Program 7-8 

Comments 7-10 

CHAPTERS. PROJECT DESIGN 8-1 

Design of Dam g-1 

Design of Auxiliary Outlet Works g^ 

Design of River Outlet Works g^ 

Design of Spillway g^ 

Comments g.9 

CHAPTER 9. PROJECT CONSTRUCTION 9-1 

Contract and Subcontract Awards 9.J 

Specified Construction Schedule 9.I 

Diversion and Care of River 9.J 

Site Preparation 9.2 

Project Surveying Records 9.3 

Foundation Grouting and Treatment 9.3 

Dam Construction 9.JO 

Auxiliary Outlet Works 94 1 

River Outlet Works 9.I3 

Spillway 9. 14 

Comments 9. 14 

CHAPTER 10. RESERVOIR FILLING EXPERIENCE 10-1 

Hydrographic Record Prior to 1976 Water Year lO-i 

Reservoir Outlet Works lO-i 

Comparison of Reservoir Filling Rates 10-6 

Comments 10-15 

CHAPTER 1 1 . MEASURES TAKEN TO MONITOR SAFETY OF DAM 11-1 

Surveillance Plan 1 1 .1 

Instrumentation H.l 

Measurements 1 1 .3 

Inspection 11. 5 

Analysis 1 1 .7 

Reporting 1 1 .g 

Comments 1 1 .g 



XIV 



CHAPTER 12. CAUSE OF FAILURE 
Review of Surface Manifestations 
Physical Conditions Along Failure Path 
Untenable Failure Hypotheses 
Most Probable Steps in Development of Failure 
Initial Breaching of the Key-trench Fill 
Summary 



12-1 
12-1 
12-1 
12-3 
124 
12-5 
12-18 



APPENDIX A. USER LIST OF TETON DAM FAILURE EXHIBITS 

APPENDIX B. PANEL CORRESPONDENCE 

APPENDIX C. WITNESS ACCOUNTS OF FAILURE 

APPENDIX D. FINITE ELEMENT ANALYSES 

APPENDD( E. POST-FAILURE JOINT MAPPING 

APPENDIX F. POST-FAILURE EXPLORATION 

APPENDIX G. LIST OF ADDITIONAL REFERENCES ON FILE 



XV 



FIGURES 



Page 

1-1 Location Map 1-2 

1-2 Teton Dam, General Plan and Sections 1-3 

1-3 Teton Dam, Embankment Details 1-4 

1-4 Teton Dam, Auxiliary Outlet Works 1-5 

1-5 Teton Dam, River Outlet Works 1-6 

1-6 Teton Dam, Spillway 1-7 

1-7 Inundation Map 1-8 

2-1 Pre-failure Leakage on June 5, 1976 2-2 

2-2 Section A-A along Approximate Path of Failure 2-3 

2-3 North canyon wall about 1300 feet downstream, 2-4 

June 3, 1976 

2-4 North canyon wall about 1500 feet downstream, 2-4 

June 3, 1976 

2-5 Muddy flow at about El. 5045 2-10 

2-6 Close-up of leak shown in Fig. 2-5 2-10 

2-7 View from top of embankment toward leak at El. 5200 2-12 

2-8 Close-up of leak shown in Fig. 2-7 2-12 

2-9 Flow increasing. Dozers sent to fill hole at El. 5200 2-13 

2-10 Dozers lost in hole 2-13 

2-11 Approximately 11:30 a.m. 2-14 

2-12 Second hole in face of dam 2-14 

2-13 About 11:50 a.m. 2-15 

2-14 Dam crest breaching 2-15 

2-15 Early afternoon, June 5, 1976 2-16 

2-16 Late afternoon, June 5, 1976 2-16 

3-1 Exploration trenches 3-11 

3-2 Transverse trenches exposing key trench invert and grout cap 3-1 1 

3-3 Removal of Zone 1 material by crane and skip 3-12 

3-4 Obtaining block samples 3-12 

3-5 Exploration of Zone 1 and Foundation Key Trench 3-16 

3-6 Bore Hole, Sta. 26+00 3-19 

3-7 Bore Hole Hydraulic Fracturing Test, Sta. 27+00, 3-20 

Water Surface Recession Rates 

3-8 Bore Hole HydrauUc Fracturing Test, Sta. 26+00, 3-21 

Water Surface Recession Rates 

3-9 Post-failure exposure of the grout cap 3-23 

3-10 Grout cap severed at Sta. 13+96 and missing to Sta. 14+26. 3-23 

Open fracture shown in Fig. 3-12 is behind the ladder. 

3-11 Three vertical joints crossing alignment where grout cap 3-24 

is missing between Stas. 13+96 and 14+26. 

3-12 Two-in. open fracture crossing grout cap ahgnment near 3-24 

Sta. 13+90. See Fig. 3-10 for location. 

3-13 Rock structure along grout cap ahgnment, Stas. 13+30 to 3-26 

13+96 



XVI 



3-14 Rock structure along grout cap alignment, Stas. 13+30 to 3-26 

13+96, upstream profile 

3-15 Rock structure along grout cap alignment, Stas. 13+30 to 3-27 

13+96, downstream profile 

3-16 Test ponds for joint transmissibility tests, looking downstream 3-27 

3-17 Joint Transmissibility Testing 3-29 

3-18 Vertical brick riser for ponding test at Sta. 13+90 3-30 

4-1 Map of Teton Basin Showing Alternative Sites 4-2 

4-2 Teton Damsite, Areal Geology, Sheet 1 of 2 4-5 

4-3 Teton Damsite, Areal Geology, Sheet 2 of 2 4-6 

44 Teton Damsite, Geologic Cross Section Along Cutoff Trench 4-7 

5-1 Surface Geology Rexburg Bench 5-2 

5-2 Geologic Cross Section Rexburg Bench 5-3 

5-3 Geologic Cross Section Rexburg Bench 5-4 

5-4 Profile Teton Dam Along Grout Cap 5-6 

5-5 Geologic Section Showing Pre- and Post-Construction Exploration 5-7 

5-6 Exploration and Observation Wells in Vicinity of Dam 5-13 

5-7 Water Level Elevations in Observation Wells 5-14 

5-8 Prevalent horizontal joints 5-15 

5-9 The ash-fiow tuff upstream of dam axis 5-15 

5-10 Slab-like structure in Unit 1 5-16 

5-1 1 Joint pattern in Unit 2 5-16 

5-12 Prominent vertical joints in right wall of canyon 5-18 

5-13 Transition from predominantly flat-lying to near-vertical 5-18 

jointing 

5-14 Effect of Pump-in Test at DH-303 5-25 

5-15 Geology & Explorations in Right Abutment Key Trench 5-26 

5-16 Geologic Sections Across Fissures 5-27 

5-17 Rock fissure near Sta. 4+34 5-28 

5-18 Interior of fissure shown in Fig. 5-17 5-28 

5-19 Opening in upper right wall of Teton Canyon 5-30 

5-20 Joint in right wall of Teton Canyon 5-30 

5-21 Locations of Bench Marks and Survey Stations 5-35 

6-1 Seismic Risk Map of the United States 6-2 

6-2 Generalized Late Mesozoic-Cenozoic Tectonic Map of 6-3 

Intermountain West 

6-3 Epicenters for Intermountain Seismic Belt 6-4 

6-4 Location of Seismic Stations 6-6 

6-5 Portion of Seismogram from Station GMI 6-8 

7-1 Location of Explorations for Borrow Areas "A", "B", 7-2 

and "C" 

7-2 Location of Explorations for Borrow Areas "A", "B", 7-3 

and "C" 

7-3 Location of Explorations for Borrow Area "C" Extension 7-4 

9-1 Slush Grout Distribution and Density Zone 1 Foundation 9-5 
Sta. 11+41 to 16+00 



xvii 



9-2 Foundation formation and contact beneath Zone 2 and 9-7 

Zone 5 
9-3 Foundation formation and contact beneath Zone 2 and 9-7 

Zone 5 
9-4 Right abutment excavation showing the variable qualities 9-8 

of foundation for the various embankment zones and for the 

key trench invert. Zone 1 is approximately El. 5145 
9-5 Right abutment (to left in photo) showing minimal stripping 9-9 

(vegetation only) in preparing Zones 2 and 5 foundation. 

Zone 1 is approximately El. 5170 

10-1 Teton Watershed Showing Gaging Stations 10-2 

10-2 Summary Hydrographs Teton River near St. Anthony 10-3 

10-3 Frequency Curves of Monthly Runoff Volumes, Teton River 104 

near St. Anthony 

10-4 Frequency Curve of Spring Flood Peaks, Teton River 10-4 

near St. Anthony 

10-5 Area-Capacity-Discharge Curves 10-5 

10-6 Flood Control Rule Curve 10-9 

10-7 Teton Reservoir Inflow, Outflow, and Contents, 10-13 

January 1 to June 5, 1976 

11-1 Monuments for Measuring Surface Movement 11-2 

11-2 Observation Wells in Vicinity of Dam 1 1 A 

12-1 Kpe Eroded by Water Flowing Along Open Joint 12-7 

12-2 Pipe Eroded by Water Flowing Along Reentrant Step in Rock 12-7 

12-3 Fissure in Fill Produced by Hydrostatic Pressure in 12-7 

Rock Joint Along Reentrant Step 

12-4 Piping Stage I 12-8 

12-5 Piping Stage II 12-8 

12-6 Piping Stage III 12-8 

12-7 First Order Arching in Fill Over and Between Walls of 12-10 

Key Trench 

12-8 Second Order Arching Produced by Longitudinal Topography 12-10 

of Rock Surface in Key Trench 

12-9 Contours Showing Ratio of Vertical Stress in Embankment to Overburden 12-1 1 

Pressure for Conditions With and Without Key Trench at Sta. 15-K)0 - 

Before Wetting of Soil in Key Trench 

12-10 Development of Longitudinal Fracture Pattern 12-14 

12-11 Computed Values of Minor Principal Stress in Rane of Section Sta. 13+70 12-15 

12-12 Computed Values of Normal Stress on Transverse Section in ksf Sta. 13+70 12-16 

12-13 Longitudinal Section Through Center-line Crest and Grout Cap 12-17 



xvui 



TABLES 



Page 

3-1 Joint Transmissibility Testing 3-25 

3-2 Grout Curtain Water Loss Testing in Right Abutment 3-31 

Key Trench 

3-3 Grout Curtain Water Loss Testing at Spillway Weir 3-34 

3-4 Teton Dam, October 1976, Drill Hole Water Tests 3-35 

Near Right End of Dam 

4-1 Summary of Foundation Rock Properties 4-10 

5-1 Typical Descriptions of Lake and Stream Sediments 5-8 

Underlying the Vicinity of Teton Dam 

5-2 Descriptions and Results of Water Pressure Tests 5-10 

5-3 Cross-Index of Numbering Systems for Wells and 5-20 

Drill Holes 

5-4 Summary of Exceptionally High Water Losses 5-22 

5-5 Comparison of Pre- and Post-Failure Elevations of Benchmarks 5-32 

5-6 Comparison of Distances Between Survey Stations 5-33 

5-7 Elevations of Points on the Right Abutment Grout Cap 5-36 

7-1 Summary of Permeability Tests for Zone 1 Materials from 7-9 

Borrow Area "A" 

7-2 Summary of Triaxial Shear Tests for Zone 1 Materials 7-1 1 

7-3 Post-Failure Tests Performed for Independent Panel 7-12 

7-4 Summary of Classification Test Data. Samples From Remnant 7-13 

of Key Trench Fill, Right Abutment 

9-1 Embankment Placement Specifications 9-12 

10-1 Runoff Volume Forecasts of Inflow to Teton Reservoir 10-8 

in Calendar Year 1976 

10-2 Snow Water Equivalents as Percent of 1958-76 Averages 10-10 

11-1 Measurements of Monuments on Dam 11-5 



XIX 



ABBREVIATIONS 



acre-ft acre-foot 

a.m. midnight till noon 

AOW auxiliary outlet works 

avg average 

cfs cubic feet per second 

cm centimeter 

cu ft cubic foot 

cu in. cubic inch 

cu yd cubic yard 

DH drill hole 

diam diameter 

El. elevation (always in feet) 

Fig. Figure 

ft foot 

gpm gallons per minute 

in. inch 

kip 1 ,000 pounds 

km kilometer 

ksf kips per square foot 

kw kilowatt 

lb pound 

max maximum 

min minimum 

M.M. Modified Mercalli scale of earthquake intensities 

NP non-plastic 

PI plasticity index 

p.m. noon to midnight 

pcf pounds per cubic foot 

psf pounds per square foot 

psi pounds per square inch 

ROW river outlet works 

rpm revolutions per minute 

sec second 

sq ft square foot 

Sta. Station 

T ton 

yr year 



XX 



TERMINOLOGY 

Effective stress cohesion parameter 
Centerline 



CH 




GP 




GW 




MH 




ML 




DH-651AB 



E 

e 

Es 
g 
k 
K 



Soil classification according to Unified 
Soil Classification Chart. (See Fig. 3-7, 
"Earth Manual," USBR.) 



Numerals designate driU hole number. DH-651 A 
indicates that DH-651 was abandoned and a new 
start undertaken. DH-651B designates the 
third start at the same drill site. DH-651 AB 
refers to all three holes. Thus the log 
DH-651 AB is a composite log containing 
information obtained in the course of drilUng 
DH-65 1 , DH-65 1 A and DH-65 1 B. 

Modulus of deformation 
Unit strain 

Secant modulus of elasticity 
Acceleration of gravity 
Coefficient of permeability 
Modulus number 



av 

lineament 



Left, i.e., left 
abutment, left 
bank, etc. 



Ratio of horizontal principal stress ( a 3) to 
vertical principal stress ( 0., ). 

Average coefficient of permeability 

A hne on an aerial photo that is structurally 
controlled. The term is widely applied to 
lines representing sedimentary beds, faults, 
joints, and rock boundaries. 

Refers to that side of the river channel 
to the viewer's left when he is facing 
downstream. 

Poisson's ratio 



Mt 



Earthquake magnitude based on measurement 
of the amplitude of surface (Love) waves 



XXI 



TERMINOLOGY (cont.) 

Nx drill hole A 2.98-in. diam hole drilled or cored in 
rock. Similarly, Bx, Ax, and Ex holes 
are respectively 2.38 in., 1.89 in., and 
1.485-in. diam. 

Sj^ Standard deviation 

tan <i> ' Effective stress friction parameter 

2:1 Slope designation, horizontal units to 

vertical units 



xxu 



ACKNOWLEDGEMENTS 



The Panel gratefully acknowledges the fine help it has received from many individuals during its 
review. Accepting the risk that some who should be mentioned may be overlooked, special thanks are 
due Secretary Thomas S. Kleppe for his own and his staffs support and assistance, including Under 
Secretary Kent Frizzel; Executive Assistant Loren J. Rivard; Assistant Secretary Albert L. Zapanta; 
Assistant Secretary Jack 0. Horton; Deputy Assistant Secretary Richard R. Hite; Deputy Assistant 
Secretary Dennis N. Sachs; Justin P. Patterson, Assistant Solicitor for ProcuVement; and John R. 
little, Jr., Regional Solicitor in Denver. 

The Panel also is very grateful to Governor Cecil Andrus for his aid, particularly in talking with 
Governor Edmund G. Brown, Jr., of California to obtain Mr. Jansen's leave of absence to assist with 
the review. Panel member Keith Higginson has helpfully maintained a continuing contact with 
Governor Andrus and his office. 

The interest and capable assistance of James F. Kelly, Director, Office of Administration and 
Management Pohcy; James E. Johnson, Chief, Procurement and Grants; William S. Opdyke, 
Procurement Analyst, Department of the Interior; and M.S. Greenlee, Chief, Property and Purchasing 
Branch, Engineering and Research Center, Denver, have been especially helpful by freeing the Panel 
of many contract and administrative tasks which it otherwise would have been required to perform 
personally. 

The fine support of the Bonneville Power Administration, the National Park Service, including the 
Division of Graphic Systems, the Bureau of Indian Affairs, the Government Printing Office, and the 
United States Geological Survey in supplying technical and administrative people and services has 
been greatly appreciated. These people responded to the Panel's need with interest and dihgence. 

The Bureau of Reclamation responded to the Panel's many needs for data and information promptly 
and with candor and interest. Special thanks are due Harold G. Arthur, Donald J. Duck, Sammie D. 
Guy, and others in the Bureau's Denver organization. Sam Rey from Grand Coulee and D.D. McClure 
from Boise were especially effective in getting the office set up and supplied in Idaho Falls and at the 
damsite. Thayne O'Brien continued that fine service. 

At the damsite the help and assistance of Robert R. Robison, Project Construction Engineer, have been 
candid and fully responsive. This cooperation has been duplicated by all of the Bureau's on-site staff, 
particularly by Pete Aberle, Stanley White, Dan Magleby, Ralph MulUner, and Ken Hoyt. The 
cooperation of Brent Carter of the Regional Office was appreciated. 

The work of Gibbons and Reed under Superintendent George Tackett in carrying out the dissection 
and other work on the right abutment was capable, responsive, and interested. 

Important laboratory and analytical investigations in support of the Panel's work were also carried 
out by Northern Testing Laboratories, Geo-Testing, Inc., J.M. Duncan and G. Jaworski of the 
University of California at Berkeley, R.E. Bieber of Dynamic Analysis Corporation, K. Arulanandan 
of the University of Cahfornia at Davis, the U.S. Bureau of Reclamation laboratories at Denver and at 
the damsite, and the Waterways Experiment Station at Vicksburg. 

ExhibiGraphics Group was especially helpful in its expeditious construction of the model of the dam. 



xxiu 



This report would not be in being, however, except for the special competence and untiring 
dedication of Robert B. Jansen, Executive Director, and other professional staff, namely Clifford J. 
Cortright, Staff Engineer, Laurence B. James, Staff Geologist, and Frank B. Sherman, geologist. 
Jacque Steele well coordinated the Idaho Falls office and kept an immense number of drafts of texts 
flowing smoothly under considerable pressure. 



XXIV 



CHAPTER 1 
INTRODUCTION 



Construction of Teton Dam was authorized on September 7, 1964, by Public Law 88-583. The dam is 
situated on the Teton River, three miles northeast of Newdale, Idaho, as shown on Fig. 1-1. Prior to 
1963, the proposed Teton Dam was known as Fremont Dam, and some records remain under that 
name. 

The Teton Dam and Reservoir are the principal features of the Teton Basin Project, a multipurpose 
project, which when completed was to serve the objectives of flood control, power generation, 
recreation, and supplemental irrigation water supply for 111,250 acres of farm land in the Upper 
Snake River Valley. Appurtenant features of the dam are (1) a 16000 kw generating and pumping 
plant on the left bank, (2) river outlet works and a gate chamber shaft on the left bank, (3) auxiliary 
outlet works and an access shaft in the right bank, (4) a three-gate chute-type spillway on the right 
bank, and (5) the 72-in. Enterprise-East Teton Feeder Pipeline and Canal Outlet Works Control 
Structure on the left bank. In this report, right and left designations are made looking downstream. 
The reservoir had a total capacity of 288,000 acre-ft. It extended 17 miles upstream, and had a 
surface area of 2100 acres. 

The dam was a central-core zoned earthfill structure, whose maximum section rose 305 ft above the 
original valley floor, and 405 ft above the lowest point in the foundation. The plan and cross section 
of the dam are shown in Fig. 1-2, from the construction contract documents. Embankment details are 
shown in Fig. 1-3, from the contract documents. This drawing (Fig. 1-3) includes the foundation 
design grouting patterns. Details of auxiliary outlet works, river outlet works, and spillway are 
provided in Figs. 1-4, 1-5, and 1-6, respectively. The crest elevation before camber was 5332, and its 
length was about 3,100 ft. The volume of the embankment was about 10 million cu yds. 

At the damsite the Teton River occupies a steep-walled canyon incised in rhyolitic ash-flow tuff, a 
hard rock derived from distant volcanoes now long extinct. Extensive joints are common in this rock 
and are particularly numerous near the surface of the abutment. An important feature in the dam is a 
key trench excavated through this highly jointed surficial layer and later backfilled with embankment 
to provide a barrier to reservoir leakage. 

The construction contract was awarded December 13, 1971, and work commenced in February 1972. 
The embankment was topped out November 26, 1975. Closure for storage occurred October 3, 1975. 

Tlie dam faUed on June 5, 1976, when the reservoir water level was at El. 5301 .7. That level was 22.6 
ft below the maximum water level and 3.3 ft below the spillway sill. 

The inundation downstream was disastrous, and the loss of the lives of 14 persons has been associated 
directly or indirectly with the failure. Property damage has been estimated at various amounts from 
$1 billion downward. The current best estimate seems to be $400 million. The area which was 
inundated has been shown on maps by the Corps of Engineers, U.S. Army, and by the United States 
Geological Survey. The outlines mapped by the latter are shown on Fig. 1-7. 

Immediately following the Teton Dam failure, the Governor of Idaho and the Secretary of the 
Interior agreed on the need for an independent engineering and geological review of the cause of that 
failure. 



l-I 




ST. ANTHONYl 



a.'t- 



t03 



^<f SUGAR 






NEWDALE 



(33> 



TETON 



CITY,^ ^/ 



7 > TETON DAM" 



sovs 



^^/ 



MENAN ; 



BUTTESLv/O^ 






%S- 



REXBURG 



THORNTON 



SCALE IN MILES 



10 



Si 



RIGBY 



1 



^i^ 



RIRIE; 




^UCON 



26< 



'.^^- 



•^^v- 
v 



^^ 



■^-^ 



20026<)191' 



IDAHO 
FALLS 



LOCATION MAP 



j-,y>-^ J _M U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

rHj. I I. INDEPENDENT PANEL TO RFVIEW CAUSE OF TETON DAM FAILURE 



1-2 



€ Open drain e' bottom width 
i Open dram lo'txjtiom width^ 



Sla32tS9H\ V\l 

N 8I7.S60 00 h~^ I f, 



Sta 
N t 
E 666.499 14 






Intake stnjcture- 



C Left abutment county 
rood connection 
'""^Tipc o*OORood'Sta.32i-96 64Dam 
Begin Road constructioiT- 




Swi tchyard ^ 

■^ (completion contracf}^^ 



,<' 



Original 
ground 
surface 




C Auxiliary outlet works 





Storage area for completion ipecifieotionz 

^^£^pXEnterpnse-Eos^ Teton 

^^Jeeder pipelini 
Drainage ditc^ 





'Cut slope of key trencti 



<i Enbonkment 
measurement point — - 



I*"-— € Crest of dam 

i 

-35 



Bottom of strippi 




,4 Gravel surfacing 
Slope; per ft i Slope; per ft. ju-^ 



' I— /J.5 H ^. 




^ — 3 O' Camber 
.— Crest Without camber -El 5332 



'\ 



~ Slope vanes deperiding on camber - 

O 




v. ^ ® 



CREST DETAILS AT MAXIMUM CAMBER 



iCresI of iom— q 
Limits cf cutoff trencti "Vfj'rC^^^ f ' '■'•'2 



JL 



. <• JW * ■=' * 



above El 5030 — 



~EI 5302 



200 Taiirace channelAstorog^^ area for 

'" completion specifications 




SCALE OF FEET 



RESERVOIR CAPACITY ALLOCATIONS 



'Riprap 

ling OS directed 



Assumed firm formation 
I Grout cap and foundation key trencti 

I0*\ [r^^Grout holes atopprox id crs 
'0 TJ h^^^Grout holes at approx 2d crs 



PURPOSE 


ELEVATIONS 


CAPACITY 
ACRE - FEET 


Joint use 


5189 3 to 5310 


100.000 


Inactive 


50400 to 5/893 


87.700 


Oeod 


5025' to 5040 


470 


Total Reservoir Caoacitv 


2S«.2» * 



.~,^^y'S67'W\,^>^.\\'''yP'CAL ABUTMENT SECTION A-A 

\.VVn 816,580^ 
664. 163 33 < 

^ -^ yy\ EMBANKMENT EXPLANATION 

Qj Selected cloy. silt. sand. gravel, and cobbles compacted by tamping 
, — T-'^* . L rollers to 6-inch layers 

\ ^-"^^f^^ ' © Selected sand, grovel, and cobbles compacted by crawler-type tractors 
to 12 -inch layers 
(T) Miscellaneous material compacted by rubber-tired rollers to 

12- inch layers 
(T) Selected silt. sand, gravel, and cobbles compacted by rubber- tired 
|-|6^ rollers to iz-inch layers 

@ Rockfill placed in 3-foot layers 



Includes 4.300 of allowance for loo year sediment deposition 
A surcharge of 9.270 af ( Max W.S El 5324 3} with a spillway discharge 
of I7.870cfs and a river outlet discharge of 3.400c fs is provided 
to protect against the inflow design flood which has a peak of 22.400 
c fs and a l5-doy volume of 200,000 a f 

RESERVOIR AREA \N HUNDREDS OF ACRES 

5 >0 i9 20 23 : 

RESERVOIR CAPACITY IN THOUSANDS OF ACHE FEET 



/'Reinforcement 
bar or equal 



Place bar 
vertically ' 



t Crest of dam 



Top of joint use 
capacity, El 53200-. 



Mar w. S 

El 5324 3-. 



i, 



3' Riprap - 



EMBANKMENT MEASUREMENT 
POINT DETAIL 



StO 0*0000 
N 819.500 00 
E €64.07392 



r Contractors coffer dam 
and disposal area 
El 5ioa^ 






© 





\-^_^^Width varies depending on volume of zone 2 in f he stockpile 
' iPfC res t El. 5332 



Spillway 



Max water surface £1 5324 5 



i-Crest El 5305 00 





^e 



^River outlet works 
-Sill El 5141.00 



-Sill El 504000 



Capacity 



'-Discharge limited 
to 850 C-f-S 



Auxiliary outlet works 



' Embankmerrt measurement 
points — --_^ 



Thickness varies depending 

on volume of rockfill available 



GENERAL PLAN 



SCALE OF FEET 



^-f ^(irigmni ground surface 
"• si 1 -^-""^ rZ.~rt-i^i*^ of cutoff trench below El 5030 — ^ 



'Top of dead capacity. El 50400 

Stripping as directed - 



Assumed firm 
formation - - 



'EViSfD ST0R*2E anCA fOD COMPlfTION SPECIF 

as wortp iw Lcrrcw DjrEo b-htj 



UOVEO SmitCMYA 



] KMOVEO aovtlMUEUT BVIL0IH63 



ADDED- POUEfl ANO iNTEHC0UNecr CttLE THENCH. 



CHAHGE IN TAILItACE CHANNEL 





AUXILIARY OUTLET WORKS DISCHARGE rN HUNDREDS OF CFS 

I Z 3 4 9 

OUTLET WORKS DISCHARGE IN THOUSANDS OF C FS 

4 a 12 16 20 

SPILLWAY DISCHARGE IN THOUSANDS OF CFS 

AREA-CAPACITY' DISCHARGE CURVES 




■^5 rEt.504r5 



-*3 j-tf 



Zone (z) blanket under zone (T) -^ 



f= 



.'- El 4920 -Cutoff trench reference line 
j for establishing cut slopes 



^20' Thick over river valley reduced ^@ 
proportionally up the abutments 
to a minimum of 5' measured vertically 
but not less than 14' measured horizontally, 



f*- Grout tioles at opprox 10' crs 
MAXIMUM SECTION WITHOUT CAMBER 



I aujAvs TuinK SAf€TV 



UNITED STATES 

0£PAtiTU£NT OF THC INTC/tlOa 

BUftEAU OF RECLAMATION 

TETON BASIN PmOJeCT 

LOwen TETON DIVISION - IDAHO 

TETON DAM 

GENERAL PLAN AND SECTIONS 






549-0-8 



SCALE OF FEET 



FIG. 1-2. 



U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



1-3 




Cl/^ 1 Q "J S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

rlLr. I ~0. INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAflURE 



1-4 




N 819.246 5a 
E 66S.</2 53 
P( Sfa Ttil 96 

P r Sto. 7+5574 

B • so 00 
r '29 45' 
L -53.2! 



NSiaj03 04 
E 664.606 71 
Pt StO I6t98 29 
PC. Sta 16*80.09 
PTStalTta 
A •40' 00' 
» "50.00' 
r • 18-20' 
L • 34 91' 



Original ground surface 




z 














1, 























■^ 




5 

1 


^S/// fl 5047.00 
1 


^ 







Discharae 
imifto to 
850 C-fs. 



I /-^'^ 0'»4 0' Outlet gates 
-H' ''' ^-— - — —Crown grouting only ^ 20't crs .SO'i deep 

^r*"!*— Sfo 19*50 ,''^?*r-?''-5* 0/0 tunnel- 

" ^'"^ '2r ^s-oo- 



Compacied embankment'^ '■♦ 

//Ktom -—Section d-d 

REFERENCE POINT DETAILS 



Sta 13.15 *''^'" 
S/o ;5*?o 

Orof/ioje fto/es@20't crs.^o'* deep 



£7-5 Oio funne/ 



_ ^ J ^Original ground surface 

-PI. Sta 34t48 24 
El. 5023 88 

rSto 35*04 




Grout holes 5o'i deep 



SECTION ON € ADIT AND SHAFT 



Vent hole in ttighest break m excavation 

— Pipe for backfill grouting 

Grout holes @ 20'* crs.. 20't deeporos directed, 
rotate adjocentbandsof grout holes 45'- 

-Alternate location of grout holes - -^ 

Drainage holes @ 20'± crs.. 20'* deep- 
In portal section 
Portal section to Sta 15*75 
5t0}5*75 toSta irt72 17 

l5'Stal8*0975 toSto.l9tl5 

12' Sta I9ti5 to portal section 

15" In portal section 



Pipe for crown grouting one hole 
20'± crs.. 20'i deep downstream 
of Sta 19*30 



SECTION A- A 




40 VC ^ El 4996 00 

PT Sta 34*6824 
El 5013 88 
PC.St0 34f28 24 

El. 5024 13 



AUXILIARY OUTLET WORKS DISCMARGE IN 100 CFS- 

DISCHARGE CURVE 



NOTES 

For general notes see Dwg 40-0-6123 and 40-0-7008 

Spacing of transverse construction joints m funnel linmq shall not 

exceed 50 
Rubber waterstop sfiotl be placed m all transverse construction joints 

in tunnel lining, gate chamber and shaft 
For tunnel support details see Dwg 549-0-38 



Construchon joint -- 



■ ''^ 8 Line 



5^ In 9 lining _ 

b' Inl^ond 14" lining 

7'ln I5'and I8''lining 




Pipe for foundation 
)/' grouting 



TUNNEL CONSTRUCTION 
JOINT DETAIL 



10 Unsupported and 
rogk beH supported. 
14 steel rib supported 



o - ' - - ' ■ 

°.-4<&i. 

6 -re -72 



73 I10VC0 IHTiMC STHUCTUHE I4 FECT 00»MSTHe»M 



°«fe- 



MMOU COHfieCTIOHS 



•AflY OUTLET WOIIKS ( 



^ ftlUIDVS TMIflK SAf €TV 



reo STATES 

DEPARnue/VT Of THE 'NTE^iO^ 

Bu9EAy Of KECLAVAT'Ott 

TETON BASIN PROJECT 

LOWEft TETON DIVISION - IDAHO 

TE TON DAM 

AUXILIARY OUTLET WORKS 
GENERAL PLAN AND SECTIONS 




SECTION B-B 



FIG. 1-4. 



U. S DEPARTMENT Of THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE Of TETON DAM fAlLLIRE 



1-5 




^iz' Riprap 



15 For concrete 
encasement - 



SECT/ ON J' J 



3' Riprap 
Assumed surface of 
firm fermo^on— ^ _^^ 

18' Bedding-^ 



IB Bedding-^ 
SECTION A- A 



Pervious bockfilH 



^b' Perforated 5 P drams 



SECTION C-C 



SCALE OF FEET 



SECT/ON E-E 



PROFILE ON € DRAINAGE CHANNEL 



m* 


1 


Maximum water surface, ei 5324 3- 

{ { 1 ' 1 


1 
-i-. 




i 


I 




y 


y 




1 






y. 


i 












/ 




i 1 


9316 






/ 


/' 










/ 


/ 












5312 




/ 


/ 
















/ 




















/ 






















/ 








i 












1 
1 






1 











Hondroil- 

3 - zq-b' t /5'-6' Radiol gotes 

Ei 53320 







Sta 


26 


>/5 


^ 


I 


12" 


5 P dram- 
S-0023'_ 

4- 


a- 


12"- 
— i-i 


2i 

i1 




J- 


- 


m 



'^'- 



DISCHARGE IN THOUSANDS OF C F S 

SPILLWAY DISCHARGE CURVE 

surcharge of 9270 a f. [Maximum water surface 
El 5324.3) in combination with a spillway discharge 
of I7.B70 cfs and on outlet capacity of 3.40Ccfs. 
are provided to protect against the inflow design 
flood whicti has a peak of 22.400 cfs and a i5-doy 
volume 200.000 f 

NOTES 

Far general notes see drawings 40-D-6I23 and 40-0-7006 
Where approach clHinnel and outlet channel excavation is in 
suitable formation the excavation shall be completed 
to the channel profile omitting riprap and bedding 
as directed by the contracting officer 




CHANGE in TAILR*CC CHAHHCL SHILLING BASIM HAlSCO 
7 F££T AND MOVED « fEET UPSTHEAM 



^ HUMPVS THtnn SAftTV 



ED STATES 



BUfEAU OF ItECLAIIIATlON 
TETON BASIN PROJECT 
LOWER TETON DIVISION - IDA 



TETON DAM 

SPILLWAY 
GENE RAL PLAN AND SECTIONS 




x..^ ^ C U. S. DEPARTMENT OF THE INTERIOR — STATE OF IDAHO 

FIG. 1 -b. INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



1-7 



\ 



n 



AREA INUNDATED BY FLOODWATER 
FROM TETON DAM 



\ 



■\ 



■A 



V 



POCATELLO 



TETON 


DAM^ 


X 




ST 


ANTHONY- 

1^ 




^\ TETON 
^ \ / RIVER 




A 


7 




. NEW DALE \ 


fjf)\^ 


'"""'T^'r^ 


^ 




~- TETON \ 






t 




-SUGAR CITY 




/ 




T 




-REXBURG l\ 





RIGBY 





/ISh 


|i^ 






IDAHO FALLSy/ jB 


V) 


/ 


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r 




m/f 




R1VERSIDE< 


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rl^ 


■i BLACKFOOT 


^ 





i 



.s^' 



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10 



10 



SCALE IN MILES 



20 



INUNDATION MAP 



REFERENCE DATA: 

U S GEOLOGICAL SURVEY 



rjJ^ -i ~7 us DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

r Hj. \~ I . INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



1-8 



Candidates for a panel of review were considered from lists suggested by the National Academy of 
Engineering, the National Academy of Science, and other organizations. 

The selection of the Panel members was confirmed in appointment letters signed by the Secretary on 
June 11, June 23, and June 30, 1976. Copies of these letters are included in Appendix B. The 
June 30 letter states the Panel's charge. 

As a result of the various consultations, the Independent Panel to Review Cause of Teton Dam 
Failure was established with membership as follows: 

WALLACE L. CHADWICK, Chairman, former president of the American Society of Civil Engineers, 
and a consultant on water projects and dam safety. 

ARTHUR CASAGRANDE, Professor Emeritus at Harvard University and engineering consultant on 
dams and foundations. 

HOWARD A. COOMBS, Professor Emeritus of Geology at the University of Washington, and 
consulting geologist on dams and power projects. 

MUNSON W. DOWD, Chief Engineer of the Metropohtan Water District of Southern Cahfornia. 

E. MONTFORD FUCIK, Chairman of the Board, Harza Engineering Company, and designer and 
consultant on major dams. 

R. KEITH HIGGINSON, Director of the Department of Water Resources, State of Idaho. 

THOMAS M. LLPS, consulting engineer on major water projects and a member of the consulting 
board retained by the State of California to investigate the failure of the Baldwin Hills Dam in 
southern California in 1963. 

RALPH B. PECK, consulting engineer. Professor Emeritus of Foundation Engineering, University of 
Dlinois at Urbana, and recipient of the National Medal of Science from President Ford in 1975. 

H. BOLTON SEED, Professor of Civil Engineering at University of California at Berkeley, a member 
of the California Seismic Safety Commission, and a consultant on seismic design of embankment 
dams and on nuclear power plants. 

Organizational work started with telegraphic requests to the Director, Design and Construction, 
United States Bureau of Reclamation, for specific information and data. These requests were dated 
June 11 and June 14, 1976. Copies are included in Appendix B. Subsequently, the office of the 
Secretary of the Interior, working with the Panel Chairman, undertook a detailed plan for 
administering the Panel's work. Several alternatives were considered, and the respective advantages 
and disadvantages weighed. In the interest of best preserving complete independence for the Panel, a 
contract plan of organization and administration was accepted wherein the Panel Chairman became a 
prime contractor, and the other panel members and professional staff became subcontractors, with 
the contract obligation to prepare a series of interim and progress reports, and a main report. 

The intent of the "no fee" contract was contained in a letter dated July 16, 1976. The definitive 
contract was also dated July 16, 1976, but was finalized on October 4, 1976. However, because of 
the urgency of its task, the Panel actively pursued its purpose from the time of its appointment. 



1-9 



On June 30, 1976, the Panel was able to retain as its Executive Director, Robert B. Jansen, a civil 
engineer who was formerly Chief, Division of Safety of Dams, and Deputy Director of Water 
Resources in California. Mr. Jansen served as chairman of the State Engineering Board of Inquiry in 
the Baldwin Hills Dam failure investigation in 1963 and is on leave of absence through the 
cooperation of the Governor of California. 

On July 3, 1976, selection of the principal members of the Panel staff was completed by the 
assignment of consulting engineer Clifford J. Cortright as Staff Engineer, and consulting geologist 
Laurence B. James as Staff Geologist. Mr. Cortright is former chief of the Division of Safety of Dams, 
and of the Division of Design and Construction of the California Department of Water Resources. Mr. 
James was until recently Chief Engineering Geologist for the California Department of Water 
Resources. 

Other members of the Panel staff, on special assignment from their regular government positions, 
were Frank B. Sherman, geologist from the Idaho Department of Water Resources; technicians 
Romeo Singson, Thomas E. Chinn, and Doug Burkhard from the National Park Service; technicians 
Dwight P. Berger and Clifford L. Cole, draftsman Robert E. McDonald, and office assistant Jacque J. 
Steele from the Bonneville Power Administration; and draftsmen John Carillo and Robert M. Nilchee 
from the Bureau of Indian Affairs. In addition, the services of geologist Gerald Maughan were 
obtained from Northern Testing Laboratories for a short period. 

The Panel's contract required that a final report be completed by the Panel by December 31, 1976. 
The Panel was also requested to make a preliminary report as of August 1, 1976, and progress reports 
as of the first of each following month, until the fmal report was made. 

During the month of June, 1976, Secretary of the Interior Thomas S. Kleppe appointed Dennis N. 
Sachs, Deputy Assistant Secretary for Land and Water Resources, as Chairman of an Interior 
Department Teton Dam Failure Group, composed of Federal employees, and also named Mr. Sachs as 
liaison with the Independent Panel to Review Cause of Teton Dam Failure. Throughout the program 
of the Panel, close coordination was maintained with Mr. Sachs to assure that unnecessary duplication 
of field and laboratory effort was avoided, while preserving the independence of the investigating 
organizations. 

To conduct its investigation most effectively, the Independent Panel estabhshed offices in Idaho Falls 
and at the Teton damsite. Data collection and technical analyses were accomplished at both locafions. 
Daily overseeing of field investigative work was done by Panel staff at the dam, while general 
management of the program was provided in Idaho Falls. 



1-10 



CHAPTER 2 

CHRONOLOGY OF FAILURE AND USBR REACTIONS 

(Panel Charges Nos. 1 1 and 13) 



The record shows that the first indication of grave difficulties at Teton Dam was observed at about 
7:00 a.m. on Saturday, June 5, 1976, and that the breach of the dam was complete before noon of 
that day. Because of the dramatic events during the final hours preceding that breach, an excellent 
photographic record, both still and cinematic, exists of the various stages of heavy erosion, of 
progress of that erosion, of the final failure itself, and of post-failure flows. Because the related events 
were not so dramatic, records of the symptoms of erosion and of the erosion itself during the time 
prior to the major erosion are minimal. However, sworn witnesses who were questioned by special 
agents of the Department of the Interior reported observations of some of these early events. 
Although timing is approximate, being based on individual memories, the Panel has pieced together 
the following sequence. For locations, refer to Fig. 2-1. A section along the observed hne of failure is 
shown in Fig. 2-2. The record of eyewitness accounts is included in Appendix C. 



JUNE 3, 1976 - OBSERVATION, SMALL SEEPS DOWNSTREAM OF DAM 

From testimony of Peter P. Aberle, Field Engineer, USBR, Teton Dam Project: 

Starting on about June 3, 1976, I observed small springs in the right abutment 
downstream from the toe of the dam. These springs were clear water and did not appear 
to be serious in nature, but warranted monitoring by visual observation as frequently as 
routine inspections of the entire operation at the dam. 

From testimony of Harry Parks, Supervisory Surveying Technician, Teton Dam Project: 

About June 3, 1976, I observed a small stream of water appearing along the bottom of 
the waste area about 1400 feet downstream from the toe of the dam. I was on the top of 
the south rim when I observed this water and so I could not say at this time whether the 
water was clear, muddy, etc. I was aware that Robison and Aberle were watching the flow 
on at least one occasion. 

From testimony of Robert R. Robison , Project Construction Engineer: 

While there were rumors as early as April 1976 that there were leaks at the dam, there is 
no basis to these rumors, because there were no leaks. 

On June 3, 1976, several small seeps in the rhyoUte (volcanic rock) appeared about 1400 
to 2000 feet downstream from the toe of the dam in the north abutment wall. The water 
was clear and all of these seeps totaled about 100 gallons of water per minute. This was 
felt to be a good sign because the dam was being filled and it indicated the water table 
gradient was acting in a normal manner. The water was clean enough to drink and if there 
had been a problem the water would have been turbid. I felt the area should be 
monitored by sight inspections and other mechanical means, the latter of which were 
never put into effect. 1 took pictures of the seepage [Figs. 2-3 and 2-4] and reported the 
matter to the E&R Center, Bureau of Reclamation, Denver, Colorado. 



2-1 



SEQUENCE OF EVENTS 

ABOUT 1300 FEET & 1500 FEET DOWNSTREAM FROM 
TETON DAM SPRINGS FLOWING CLEAR ABOUT 100 GPM 
FROM NEAR VERTICAL JOINTS EL, 5028-5035. JUNE 3, 1976 
SPRING FLOWING CLEAR ABOUT 20 GPM. JUNE 4, 1976 
MUDDV FLOW AT RIGHT DOWNSTREAM TOE 
ESTIMATED 20 TO 30 CFS AT EL. 5045. 8.30 A.M. 

2 CFS FLOW FROM ABUTMENT ROCK AT EL. 6200. 9:00 A.M. 

LEAK DEVELOPING ABOUT 15 FEET FROM RIGHT 
ABUTMENT AT EL 5200 FLOW ABOUT 15 CFS 10:30 A.M. 

WHIRLPOOL FORMING AT ABOUT STA 14+00. 11:00 A.M. 

AREA ERODED BY MUDD\ FLOW ABOUT 11:15 A.M. 

HEADWARD EROSION BETWEEN 11: 15 AM. AND 11:50A.M. 

SINK HOLE DEVELOPED ABOUT 1150 AM. 




NOTE: 

SEE FIG. 2-2. FOR 
FAILURE SECTION A-A 



SCALE IN FEET 



PRE-FAILURE LEAKAGE ON JUNE 5.1976 



FIG. 2-1. 



U S DEPAHTMENT of the INTFRrOR STATE OF IDAHO 

INDEPENDENT PANEL lO REVIEW CAl'SE OF TETON DAM FAlLliRE 



2-2 



5200 




800 



NOTE: 

SEE FIG 2-1 FOR LOCATION 



REFERENCE DATA: 

US. BUREAU OF RECLAMATION 

DWG NO 549 -D- 8 



SCALE IN FEET 



SECTION A-A 
ALONG APPROXIMATE PATH OF FAILURE 

rj,- O O U S DfPARTMtNT OF THE INTEBIOR STATE Of JDAHO 

riLl. C.~ ^. INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM fAllUBE 



2-3 




. > 



Fig. 2-3. North canyon wall about 1300 feet downstream from Teton Dam. 
Clear water from several small seeps flowing about 60 gpm. 
June 3, 1976. 




t*. 






Fig. 2-4. North canyon wall about 1500 feet downstream from Teton Dam. 
Clear water flowing from rhyolite about 40 gpm. June 3, 1976. 



2-4 



From testimony of Kenneth C. Hoyt, Construction Inspector, Teton Dam Project: 

Before June 5, I saw seepage in the bottom beyond the toe of the dam. This seepage was 
visible for about two or three days prior to June 5, and was 150 feet downstream of the 
toe of the dam. I never saw the seepage clearly, do not know the condition or volume. It 
was a slight flow and was of no great concern to me as it appeared rather natural. 

No other records have been found by the Panel of leaks or seepage on June 3 or earUer, although 
public inquiries were made and replies were invited. 



JUNE 4, 1976 - FURTHER SMALL SEEPS DOWNSTREAM 

From testimony of Wilburn H. Andrew, Mechanical Engineer, Teton Dam Project: 

At 9:00 a.m. on Friday, June 4, 1976, Stites and I walked around the right abutment 
(north side) area at the toe of the dam for the purpose of looking for leaks. We were 
doing this because one or two spring leaks had developed further down the stream in the 
abutment wall about the day before. We did not see any leaks around the toe of the dam 
or any where on the downstream face of the dam. 

From testimony of Dick R. Berry, Survey Technician, Teton Dam Project: 

On June 4, 1976 I recall seeing seepage near the right abutment wall below the toe of the 
dam. The water was clear and not really running ~ just settlement. There were no 
leakages or seeps at the dam. 

From testimony of Stephen Elenberger, Construction Inspector, Teton Dam Project: 

On Friday, June 4, 1976, I was working the 4:00 p.m. to 12:30 a.m. shift at the dam. Up 
until dark, which occurred at about 9:00 p.m. or shortly thereafter I made several 
observations of both the downstream side and the upstream reservoir. I had been alerted 
to pay particular attention for possible leaks because there were small spring Uke areas of 
water on the north side of the canyon well below the toe of the dam. These springs were 
clear water and had been visible for two or three days. 

Until darkness I did not see any sign of a leak in the toe of the dam at the north or right 
abutment at about 100 feet from the top of the dam near the north or right abutment. 
The entire downstream face of the dam showed no sign of any problems. I also did not 
see anything unusual in the reservoir or upstream side of the dam. There was no sign of a 
whirlpool. 

From testimony of CUfford Felkins, Surveying Aide, Teton Dam Project: 

On Friday, June 4, I noticed for the first time some wetness in the waste area near the 
right abutment wall of the dam. There was no water flow, just wetness. 

From testimony of Robert R. Robison: 

On June 4, 1976, a small seepage occurred about halfway between the toe of the dam and 
the end of the spiUway along the north abutment. This flow was approximately 20 



2-5 



gallons per minute and I had no concern because the water was clear. I checked this leak 
at about 4:30 p.m. on June 4 before leaving the dam and determined that there was no 
problem. At this time I also observed the entire downstream face of the dam and 
observed nothing unusual. I also observed that there was nothing unusual on the upstream 
reservoir side of the dam. 

The record contains no other statements of observations of seepage prior to June 5. As of darkness on 
June 4, seepage had been observed from springs 1400 to 2000 feet below the toe of the dam in two 
groups with a reported total flow of 100 gpm and from a small spring midway on the right side, 
between the toe of the dam and the spillway. This latter flow was reported to be 20 gpm. Apparently 
these flows were not measured. 



JUNE 5, 1976 - FIRST OBSERVATIONS - LEAKS AT ELS. 5045 AND 5200 

The first record of observations of leakage on June 5 begins at 7:00 a.m. Testimony regarding 
observations prior to 8:00 a.m. follows: 

From testimony of CUfford Felkins: 

On Saturday, June 5, 1976, I arrived at the dam at about 7:00 a.m. ... On June 5, the 
first thing that I saw cormected with the later events of the dam collapse was a water flow 
coming from the toe of the dam. It was a steady flow of water, but I cannot estimate the 
volume. To the best of my recollection the water flow was clear. I noticed this flow while 
I was standing across the river on the canyon wall from the spillway. I was with Harry 
Parks and we came to the survey office . . . and reported the leak to Jan Ringel. This was 
about 8:15-8:30 a.m. 

From testimony of Dick R. Berry: 

On Saturday, June 5, 1976, I arrived at the Project office before 7:00 a.m. Harry Park's 
Volkswagen was in the parking lot ... I had no watch with me at work on that date. 

At 7:20 a.m., on June 5, I left the Project Office and drove down the upper south rim 
road to check three site [sight] rods. . . . While checking the site [sight] rods I saw a 
small seepage on the north side downstream face of the dam, right at the abutment and 
dam joint. This was approximately one-third of the way up the dam, but not as high as 
the change in slope. There was slight erosion, slow flow of water, but I do not recall it 
being muddy. The seepage appeared to be almost new. I returned to the office and Harry 
Parks, who was in the crew, reported the seepage to Jan Ringel about 7:35 a.m. 

From testimony of Myra H. Ferber, Survey Technician, Teton Dam Project: 

On Saturday, June 5, 1976, I reported to work at the Dam at 7:00 a.m. for the purpose 
of doing scheduled survey work. At about 7:30 a.m. Harry Parks, Richard Berry, Clifford 
Felkins, all surveyors, and myself, proceeded downstream from the dam on the south or 
left canyon wall to check sitings [sightings] .... While checking the sitings [sightings] we 
saw a small leakage about 100 feet below the top of the dam near the right abutment on 
the downstream face of the dam. The water was flowing down the face of the dam and 
washing away fill at the toe of the dam. We then proceeded to the office and reported the 
leak to Jan Ringel. 



2-6 



From testimony of Harry Parks: 

On Saturday, June 5, 1976, I arrived at the project office a couple of minutes before 

7:00 a.m We left the office about 7:35 a.m. . . and traveled down the south rim road 

downstream for the purpose of checking survey sights in order to perform a survey on the 
spillway on the north side of the dam. At about 7:50 a.m. a member of the survey party 
noticed water seepage. I then observed the water which was running out of the toe of the 
dam at about 50 feet from the north abutment wall ["ponding" on the berm at El. 
5041.5] . I cannot estimate the volume but it was barely what could be called a stream at 
all. The water appeared muddy, but this may have been caused by the material over 
which it was flowing. We drove back to the office and I reported the water leakage about 
8:00 a.m. to Jan Ringel. 

From testimony of Jan Ringel, Civil Engineer, Teton Dam Project: 

On Saturday, June 5, 1976, I arrived at work at 7:00 a.m. I had two survey crews 

working Mr. Parks checked the staffs for the spillway control on the south side of the 

dam opposite the spillway. They were on the canyon rim and noticed the lower leak on 
the dam near the toe at about 5,041.5 elevation. At about 7:30 a.m. Parks reported 
sightings to me. I drove down to the powerhouse and walked over to the leak. The water 
was muddy. The water was running between the rocks on the right abutment and not 
through the dam. I estimate the water flow to be about 20-30 cfs at this time. I did not 
detect any increase at that time. 

The only other noticeable thing at this time was some springs at the base of the dam 
against the abutment - 200 feet below the other. This had been there for one or two 
days previous. This was clear water running at about 10 gallons per minute. Mr. Aberle 
and Mr. Robison had previously checked this. 

During a conference on October 29 requested by the Panel staff with Messrs. Robison, Aberle, Ringel, 
Parks, Isaacson, and Rogers, Mr. Ringel supplemented the foregoing sworn testimony by stating that 
he first examined the leakage at El. 5045 and that he noticed that water which had been flowmg 
down the right groin during the night of June 4, or early in the morning of June 5, had eroded a 
shallow channel that had not been there at 9:00 p.m. on the preceding night. He said that there was 
no water in this channel when first observed during the morning of June 5 but that it was damp in 
places (see letter of October 31 , 1976 from Robert B. Jansen to Panel Members in Appendix B). 

From testimony of Harold F. Adams, Mechanic, Gibbons and Reed Company, Teton Dam Project: 

On Saturday, June 5, 1976, I arrived at Gibbons and Reed yard behind Bureau office at 
7:00 a.m. to work on equipment. As I drove in I saw a small trickle of water on 
downstream slope of dam against the north abutment and about 100 feet from top of 
dam. About 30 feet out there was a wet spot. 

From testimony of David Burch, Mechanic, Gibbons and Reed Company, Teton Dam Project: 

I arrived for work at 7:00 a.m. on June 5, 1976. As 1 was driving up the canyon to the 
G-R shop I noticed a seepage down the north side of the dam. The seepage was slight and 
started at about the 5200 level near the change of the slope and ran down the abutment 
wall towards the toe of the dam. You could not actually see water running — just the 



2-7 



dampness. I could not tell if the water was clear or muddy because it was just dampness. I 
mentioned to some of my co-workers that the dam was leaking. 

From testimony of Perry W. Ogden, Mechanic, Gibbons and Reed Company, Teton Dam Project: 

On Saturday, June 5, 1976 ... I arrived at shop at 7:00 a.m., went right to our shop area. 
I was out of view of most of dam, but could see top part. Shortly after I arrived, Dave 
Burch told me there was a wet spot on the downstream side of dam. I walked over to the 
visitor's viewpoint on south rim and saw a wet spot at about 100 feet from top of dam 
against abutment. No flowing water - just a wet spot. 

It seems reasonable to conclude that the seeps at El. 5045 and El. 5200 were both active as early as 
7:00 a.m. The record does not permit determining which was activated first. Neither appears to have 
existed at 9:00 p.m. on June 4. 



JUNE 5, 1976 - 8:00 A.M. TO 10:00 A.M. - DEVELOPMENT OF ADDITIONAL LEAKAGE AT 
ELS. 5045 AND 5200 

From testimony of Peter P. Aberle: 

Between 8:20 a.m. and 8:30 a.m. on Saturday, June 5, 1976, I received a call from Jan 
Ringel at my home and he told me of a leak at the right abutment toe area of the dam. 
Ringel estimated the leak to be about 20 to 30 sec. ft. I asked my wife to call Mr. 
Robison and I left for the dam. I drove directly to the powerhouse area and briefly 
inspected the leak from the left side abutment area. 1 noted that the water was muddy 
and estimated the volume to be the same as that given me by Ringel. I do not beheve the 
water was running long because there was very little erosion in the gravel at the toe of the 
dam. 

At approximately 9:00 a.m. I went to the project office and met Mr. Robison and Jan 
Ringel. Mr. Robison and I walked out on the top of the dam and walked down the 
downstream face of the dam to a leak located at the 5200 feet elevation, near the right 
abutment wall. The water in this leak was running at about 2 sec. ft. and was only very 
slightly turbid. The leak appeared to be coming from the abutment rock. [*] The leak at 
the toe of the dam was running turbid water from the abutment rock at an estimated 
volume of 40 to 50 sec. ft. 

From testimony of Robert R. Robison: 

I... arrived at the Reclamation Office at about 9:00 a.m. Aberle and I drove to the 
downstream toe of the dam and I observed a major leak at the downstream toe at the 
right abutment at about 5045 elevation. The water was flowing at about 50 cubic feet per 
second, was moderately turbid and was coming from the abutment rock. [*] This was 

♦During the October 29 conference with the Panel staff, Mr. Robison stated that the flow first 
observed at El. 5045 was from the talus, not formation rock. Mr. Robison was asked whether the 
talus at the toe of the right canyon waU could have carried appreciable flow without such flow being 
apparent on the surface. He replied that such a condition was entirely possible. He said that in 
retrospect he believes that the leak seen issuing from the abutment at El. 5200 on June 5 was also 
from talus, as well as the seepage discovered between the toe of the dam and the spillway stilling 
basin on June 4. 



2-8 



not connected to the other seepages mentioned above. I felt this seepage was coming 
straight out of the abutment rock and not through the dam. 

1 also saw another leak at about 5200 elevation in the junction of the dam embankment 
and the right abutment. The water was sUghtly turbid and issuing from the rock at about 

2 cubic feet per second. The water from this leakage was not flowing at a great enough 
volume to even reach the toe of the dam. 

At about 10:00 a.m. I observed a large leak developing about 15 feet from the right 
abutment in the dam embankment at an approximate elevation of 5200. This leak was on 
the downstream face of the dam and was adjacent to the smaller leak at the same 
elevation. At first the flow of water was about 15 cubic feet per second and it gradually 
increased in size. The water was turbid. 

During the October 29 meeting with Panel staff, Mr. Robison said that from his vantage point looking 
directly into the hole at El. 5200, it was a tunnel about 6 ft in diameter running roughly 
perpendicular to the dam axis and extending back into the embankment for about 35 ft, as far as he 
could see. 

From testimony of Dick R. Berry: 

We then started work on the spillway at about 8:30 a.m. Just before we went into the 
spillway I saw a wet area at the end of the sage area just off the abutment on the 
downstream face of the dam. I do not recall this being running water, just a wet area. 

From testimony of Myra H. Ferber: 

At about 8:30 a.m. we checked the water elevation in the reservoir on the upstream side 
of the dam. The water elevation was 5301+ feet and I did not notice anything unusual 
about the reservoir water — specifically there was no indication of a whirlpool. 

From testimony of Jan R. Ringel: 

At about 8:50 a.m. Mr. Aberle and Mr. Robison arrived at the dam. I briefed them lightly 
and we drove over the top of the dam to the right abutment. At this time Mr. Robison 
and Mr. Aberle walked down the downstream face of the dam to look at the leak. I drove 
the pickup around the rim road to meet them at the bottom. When I arrived, I walked 
directly to the right abutment. I stopped momentarily at the powerhouse and took some 
pictures of the leak. . . . [Figs. 2-5 and 2-6] 

From testimony of David Burch: 

At about 9:30 a.m. I noticed a wet spot appear on the north side of the face of the dam. 
This spot was about 100 feet from the abutment and probably 125 feet from the top of 
the dam. The damp spot appeared to be about 3 or 4 feet in diameter from my viewpoint 
at the trailer. There was not any water flowing from the damp spot at that time. 

At 10:00 a.m. I observed water coming from the above described spot. The water was 
coming at a steady flow and was muddy. 



2-9 







^^r>^-'^-'*'" 



Fig. 2-5. 



Muddy flow at about El. 5045 at right downstream toe estimated 
20 to 30 cfs (9,000 to 1 3,500 gpm) 8:30 a.m. June 5, 1976. 




Fig. 2-6. Close-up of leak shown in Fig. 2-5. Muddy flow through rock on 

right abutment at about El. 5045. 8:30 a.m. June 5, 1976. 



2-10 



From testimony of Jerry Dursteler, Master Mechanic, Gibbons and Reed Company, Teton Dam 
Project: 

On Saturday, June 5, 1976, Perry Ogden and I arrived at the company yard behind the 
Reclamation offices at about 10:00 a.m. . . . When at the office, I heard water running. I 
drove downstream from the dam on the upper south rim road to look at the spillway and 
to see if water was flowing over it. I saw wetness on the downstream face of the dam and 
seepage against abutment wall. This was about at the slope change in the dam. I cannot be 
more specific. The water was muddy, but was merely a light stream. I went back to my 
truck. By then the wet spot had started flowing. This was a very small flow. I returned to 
my office and told Adams and Burch there was a problem. The three of us walked behind 
the Reclamation offices on the south side of the dam to look at the dam. The leakage had 
increased considerably and started eroding a hole. This was about 10:15 a.m. 

The foregoing testimony, covering the period from 8:00 a.m. to 10:00 a.m., includes the history of 
the leak which developed a short distance south and about at the same elevation as the 2 cfs spring 
observed earlier. One observer (Berry) noted it as a wet spot at 8:30 a.m. At 9:30 a.m. David Burch 
reports seeing a wet spot appear on the north side of the face of the dam 100 ft from the abutment 
and 125 ft below the crest. He estimated the spot to be 3 or 4 ft in diameter. He stated that at 
10:00 a.m. water was flowing from that spot. Dursteler reported development of flow from a wet 
spot at about the same time followed by increasing flow. 

Beginning at about 10:00 a.m., the record of leaks expands both in eyewitness statements and in 
photographs taken by several photographers. These records clearly show the leakage at El. 5045. 
Although the outflow at that level was not measured, the eyewitness accounts show an increase after 
the first observations by Parks at about 7:50 a.m. Ringel reported 20-30 cfs to Aberle at about 
8:30 a.m. Aberle later concurred in that estimate. Subsequently, Aberle and Robison estimated 40 to 
50 cfs. 

The records clearly show the development of leakage near the abutment at El. 5200, first the small 2 
cfs flow from the abutment followed about 10:30 a.m. by the 15 cfs flow from the embankment 
(Figs. 2-7 and 2-8). Later, following a progressive upward erosion of the original embankment leak, a 
sinkhole or crater developed just below the crest above the 15 cfs flow at El. 5200. Successive 
photographs show this development clearly; also the upward erosion from El. 5200 toward the 
sinkhole (Figs. 2-9 through 2-16). 

Although it is spectacularly shown in the photographs, little notice of this development seems to have 
been taken by people on-site. The following quotations seem to be the only testimony as to its 
observation. 

From testimony of Clifford Felkins: 

I do not recall the time when we first observed the upper water seepage. We were standing 
near the top of the dam in the spillway and observed the second hole beginning to form 
just as we were coming out of the spillway. We were leaving the spillway on the 
instruction of Pete Aberle who told us to get out. 1 did not actually see any water come 
out of the upper hole because the dam caved in and the two holes became one large one. 
The water that came through was muddy. I cannot estimate the volume but it was a lot of 
gallons. The volume increased very rapidly. 



2-11 




Fig. 2-7. 



View from top of embankment toward leak at El. 5200 near right abutment. Approximately 
10:30 a.m. Junes, 1976. 




Fig. 2-8. Qose-up of leak shown in Fig. 2-7. Turbid flow about 15 cfs. Approximately 10:30 a.m. 

June 5, 1976. 



2-12 




Fig. 2-9. Flow increasing. Dozers sent to fill hole at El. 5200. About 10:45 a.m. June 5, 1976. 




Fig. 2-10. Dozers lost in hole. About 1 1 :20 a.m. June 5, 1976. 



2-13 




Fig. 2-1 1. Approximately 1 1:30 a.m. June 5, 1976. 




Fig. 2-12. Second hole in face of dam. A few minutes after 1 1 :30 a.m. June 5, 1976. 



2-14 




Fig. 2-13. About 11:50 a.m. June 5, 1976. 




Fig. 2-14. Dam crest breaching. 1 1 :55 a.m. June 5, 1976. 



2-15 




Early afternoon June 5, 1976 




Fig. 2-16. Late Afternoon June 5, 1976. 



2-16 



From testimony of Jerry Lynn Walker, Superintendent, Gibbons and Reed Company, Teton Dam 
Project: 

While I was standing on the visitor's observation point and after the two M-K dozers were 
lost a crack developed above the hole. The crack was in the shape of a semi-circle with the 
arc at the top; was about 30 feet above the hole; and I would estimate that it may have 
been as much as 100 feet in total length. The earth started sluffing down from the crack 
towards the hole and caused an offset in the earth on the face of the dam as it sank. As 
the earth fell in a small hole developed above the crack. I would estimate this was about 
10 to 15 feet above the crack and was initially six or seven feet in diameter. I then left 
the visitor's observation point and drove to the top of the dam. I would estimate that I 
reached the top of the dam at about 1 1 :40 a.m. 



DEVELOPMENT OF UPSTREAM WHIRLPOOL 

Aberle reports a "loud burst of water" at a time which he now estimates at 10:30 a.m.* From his 
testimony, that burst was coincident with development of the leak at El. 5200, 15 ft to the left of the 
right abutment. Aberle also reported that he observed a whirlpool in the reservoir surface upstream at 
Sta. 13+00 (about 150 ft from the spillway) and about 10 to 15 ft into the water from the riprap. He 
estimated the whirlpool to have been 0.5 ft in diameter when first observed. Although he reports the 
whirlpool to have formed in clear water, he also reported "I noticed that the water along the right 
bank was turbid about 150 feet upstream from the dam and about 15 to 20 feet out from the edge of 
the abutment. This turbid water was first noted at 9:30 a.m. by me before the whirlpool started and 
was thought to be turbid due to wave action." 

From testimony of Alvin J. Heintz, Construction Inspector, Teton Dam Project: 

As I was talking to Aberle we noticed a small whirlpool forming in the reservoir on the 
upstream side of the dam. The whirlpool was about two feet in diameter, close to the 
north or right abutment and about 10 to 15 feet out from the dam. . . . 

I remained on the top of the dam near the north end and helped direct two dozers 
pushing riprap into the whirlpool. While working 1 saw the downstream flow of water 
increase in volume and the whirlpool increase in size. 

From testimony of Charles L. Entwisle, Construction Inspector, Teton Dam Project: 

As I approached the north or right side a small whirlpool about 10 feet from the 
upstream face of the dam just off the right abutment was forming in the reservoir. The 
time of this was about 10:50 a.m. The whirlpool was about two feet in diameter and the 
vortex eye was about six inches. It appeared to be stationary, but grew in size as I 
watched it. 

From testimony of Jan Ringel: 

At approximately 10:50 a.m. a whirlpool developed on the upstream face of the dam. 
This was at the right of the dam about 1 5 to 20 feet away from the dam. 

♦Revised from 10:00 a.m. to 10:30 a.m., as discussed during October 29 conference with Panel staff. 



2-17 



Robison reported: 

At about 1 1 :00 a.m. I saw a whirlpool developing on the upstream side of the dam in the 
reservoir at about 10 to 15 feet into the water from the face of the dam and less than 100 
feet from the abutment wall. I had looked for a whirlpool at about 10:30 a.m. and had 
not seen one. The whirlpool was approximately six feet in diameter, was stationary, and 
appeared to be increasing in size. The water on the reservoir side was clear. 

The approximate elevation of the whirlpool was 5295. 1 would estimate that at this time 
the volume of water going through the upper leak on the downstream face of the dam 
was 100 cubic feet per second. . . . 

When I noted the whirlpool developed at about 1 1 :00 a.m. I realized there was imminent 
danger of the dam collapsing. From this time on there were numerous people making 
telephone calls alerting people in the area of the danger. 

In their meeting with Panel representatives on October 29, Robison and Aberle agreed that the 
whirlpool was probably not as close to the abutment as they previously had estimated. They said that 
it may have been as far out as Stas. 13+70 or 13+80. 

From testimony of Alfred D. Stites, Construction Inspector, Teton Dam Project: 

I arrived at the top of the dam at about 10:40 a.m. and within three or four minutes I 
noticed a whirlpool forming in the reservoir on the upstream side of the dam about 22 
feet into the water from the face of the dam. The whirlpool was approximately \^A feet in 
diameter at the outset, briefly got smaller, and then began increasing in size. The water in 
the area of the whirlpool appeared to be shghtly muddy. 

David Burch reported: 

I had started pushing riprap from the face of the dam towards a whirlpool or funnel 
which had developed on the reservoir side of the dam shortly after 1 1 :00. The whirlpool 
was directly across from the spot where the hole appeared on the downstream face of the 
dam. When I first saw the whirlpool, it was very small, maybe a foot across and was very 
muddy and it was surrounded by clear water. I saw no other mud on the upstream side. 
The water on the reservoir side was very calm. There was very little wind. The whirlpool 
was about 20 feet out from the upstream face of the dam and about 100 feet from the 
north abutment. We tried by using the riprap to build a ramp to the whirlpool but never 
succeeded. 

Sometime after 10:15 a.m. Dursteler started taking pictures of the downstream canyon 
walls and some of the face of the dam. I took pictures from the visitor's viewpoint, 
downstream rim and from the Morrison and Knudsen yard. 

Ogden reported: 

Burch arrived with a dozer and the two of us crossed the dam and started pushing riprap 
into whirlpool. This probably about 10:00 a.m. or so. Whirlpool developed at this time 
about 4 feet in diameter. 



2-18 



Walker testified: 

By the time I had arrived at the dam at 10:30 a.m. two D-8 dozers ... had been 
dispatched to the top of the dam to work on the upstream face and push riprap into the 
whirlpool which had developed. 

John P. BeUegante, Excavation Superintendent, Morrison-Knudsen and Kiewit, Teton Dam Project, 
testified: 

Others had found whirlpool on upstream face and were directing dozers to push riprap 
into whirlpool area. Whirlpool was about 18 inches in diameter near the north abutment 
wall about 15 feet from upstream face of the dam. I did not notice it getting bigger. 

Jay N. Calderwood, General Excavation Foreman, Morrison-Knudsen and Kiewit, Teton Dam Project, 
testified: 

I . . . worked on pushing riprap into the whirlpool, which was on the upstream side about 
12 feet to 14 feet in water near the right abutment, not far out. The whirlpool was about 
20 feet to 30 feet in circumference and 5 feet to 6 feet in depth. It continued to get 
larger. 

From testimony of David O. Daley, Equipment Operator, Morrison-Knudsen and Kiewit, Teton Dam 
Project : 

... I operated a Gibbons and Reed dozer trying to fill in the whirlpool on the upstream 
reservoir side of the dam. 

The whirlpool was about 30 feet out into water and about 20 feet in circumference. The 
pool was rather close to the north wall. 

Vincent M. Poxleitner, Jr., Project Engineer, Morrison-Knudsen and Kiewit, Teton Dam Project, 
testified: 

By the time I got to the top of dam, whirlpool had developed on upstream side of dam. I 
cannot give times. The whirlpool about 25 feet from upstream face of dam and 75 feet 
from right abutment. About 3-1/3 feet to 4 feet in diameter. 

Henry L. Bauer, resident farmer on the north side of Teton Canyon, reported: 

Time approximately 11:15 a.m. to 11:30 a.m. I saw a truck dump material on the upper 
face of the dam as 1 approached. I noticed a whirlpool 8 feet across against abutment and 
face of dam. Large commotion and muddy water. Water away from whirlpool was 
semi-clear. Then a large part of time [dam] - 20 feet wide and 20 feet high sluffed off 
into the whirlpool - one big chunk. This created extra commotion in whirlpool and 
boiled up more. In a matter of one minute the top section of the dam dropped and the 
dam had collapsed. I never looked at my watch. . . . 



2-19 



REACTION OF BUREAU OF RECLAMATION PERSONNEL TO THE EMERGENCY 

Pinpointing of the beginning of the period of emergency at the Teton Dam and Reservoir would be 
difficuh. There is no question in retrospect that the sequence of events observed on the morning of 
Saturday, June 5, 1976, indicated a rapidly developing emergency. Developments during earher days 
of that week undoubtedly have some significance and may have pointed, though more subtly, to 
adverse circumstances threatening the integrity of the dam. To assess the performance of Bureau of 
Reclamation personnel, therefore, events and conditions during the week prior to failure must be 
examined. 

Project employees knew of the probabihty that flows in the Teton River would exceed, and had 
exceeded, the capacity of the completed auxiliary outlet works and that completion of the 
construction of the unfinished river outlet works was necessary to assure control of reservoir filling. 

Project personnel had been carefully reviewing runoff forecasts for the watershed and foresaw that 
the reservoir would fill at rates greater than the 1-ft-per-day criterion originally prescribed. In view of 
the delay in the completion of the river outlet and to obtain benefit from greater generating head, 
they asked for relaxation of that requirement. 

The trends of rising water in the observation wells were being monitored. Frequency of readings was 
about once a week until the spring of 1976, when it was increased to about twice a week. Inspectors 
were on the alert for signs of seepage at the dam or in the canyon downstream. They made daily 
inspections of these areas. 

During the first week in June, 1976, the Project Construction Engineer gave oral instructions to 
designated field people to be on the alert. He made personal inspections of the dam and its environs. 
He took photographs of the seepage discovered on June 3, 1976 and dispatched a report on the 
situation to the Engineering and Research Center in Denver. Again on June 4, he examined additional 
seepage which had appeared downstream from the dam. He judged it not to be dangerous because he 
found the water to be clear. On June 5 at 8:30 a.m., when he was notified by telephone of the 
leakage from the dam itself, he left his home immediately and arrived at the project office at about 
9:00 a.m. He went to the downstream toe of the embankment and examined the leakage. Within half 
an hour after his arrival, he entered discussions with the Project Manager for the contractor to 
determine remedial measures. At that point he judged the situation to be critical but beUeved that the 
leakage could be controlled, since it appeared to be coming from the abutment rather than from the 
dam. 

He made telephone calls to the Bureau of Reclamation Regional Office in Boise and to the 
Engineering and Research Center in Denver to alert them to the situation. He considered notification 
of residents downstream; but since he did not believe that an emergency situation was then imminent 
and did not want to cause a panic he decided against such notification. 

As the leak at El. 5200 turned into a hole with a "loud burst" at about 10:30 a.m., he ran to the 
project office and at about 10:43 a.m. notified the Sheriffs Offices of Madison and Fremont 
Counties of the hazard and advised them to alert the citizens of potential flooding. The Project 
Construction Engineer did not hesitate in notifying the citizenry of the hazard at that time. Power 
supply and communication to the project facihties were interrupted at 1 1 :57 a.m. 

At 12:10 p.m., he left the damsite to go to Rexburg to place telephone calls to Bureau of 
Reclamation officials in Boise and Washington, D.C., notifying them of the coUapse of the dam. 



2-20 



On the day of the failure, there was no schedule of work shifts for Bureau of Reclamation employees 
that would have required personnel at the dam on a 24-hour-a-day basis. 

In general, Bureau of Reclamation personnel appeared to have been dutifully responsive during the 
emergency on June 5, 1976. Supervisory Surveying Technician Harry Parks, for example, spotted a 
small seepage at the right groin of the dam at a time reported between 7:25 and 7:50 a.m. and 
immediately saw that it was reported to his supervisors. Without delay, those supervisors went to the 
leak and assessed the situation. Other observations were made and responded to as the morning went 
on. 

Jan R. Ringel, civil engineer at the project, was one of the supervisors who received the first report of 
leakage. After evaluating the situation, he telephoned the field engineer. Within half an hour both the 
field engineer and the project construction engineer had arrived at the dam. 

USER personnel acted promptly and responsibly throughout the emergency to protect the pubUc and 
the project. They directed the contractor to mobilize all possible equipment and they took initial 
steps to open the river outlet. Efforts to close the erosion conduit at El. 5200 by pushing 
embankment material into the downstream exit were futile. Likewise, efforts to close the upstream 
entrance by pushing riprap into the opening were foredoomed because of inability to move physically 
a sufficient mass of properly graded material into the opening fast enough to abate the rapid erosion. 
Any possible success of such an effort would have required several thousand cubic yards of readily 
available stockpiled material and almost instant mobilization of a considerable fleet of loaders, dump 
trucks and bulldozers. Neither the material nor the equipment was available. 

The concern of USBR personnel for the people downstream was apparent. They sounded the warning 
as soon as failure could be foreseen. 



2-21 



CHAPTER 3 
PANEL INVESTIGATIONS 



The Panel's approach to its assignment to review the cause of Teton Dam failure has been to: 

(1) obtain, analyze and evaluate all relevant information which could be obtained from the United 
States Bureau of Reclamation, the United States Geological Survey, the construction contractor, and 
any other available and knowledgeable source regarding the regional and site geology, pre-siting 
investigations, siting decisions, pre-design investigations, design, contract specifications and drawings, 
construction practices, progress and inspections, in-progress changes, if any, pre-failure operation, 
mechanism of failure, including sworn eyewitness accounts, and actions of respective authorities 
during and immediately after the failure; 

(2) supplement documentary information, as it was received, by supplemental inquiry, including 
public hearings, written requests and responses, and oral inquiries where appropriate; 

(3) make (a) detailed study of the post-failure condition of the dam, its auxihary structures and its 
foundation, by inspections, dissection, subsurface drilling; (b) special tests of foundation materials; 
(c) detailed geologic maps and joint surveys; (d) tests of remnant materials; (e) detailed stress 
analyses; (f) studies of photographs for comparison of post-failure conditions with pre-construction 
and construction conditions; (g) measurements of post-failure geodetic positions of surface and 
subsurface points, to compare with data available before filling of the reservoir; 

(4) evaluate relevant data in order to sort out those of greatest significance in determining cause; 

(5) report the results of the foregoing activities to the extent possible by completion of all of the 
investigation work involved by December 31, 1976. 

This approach was initiated by telegrams, dated June 1 1 and June 14, 1976, to Director, Design and 
Construction, U.S. Bureau of Reclamation, Denver, and by setting the Panel's first working session 
and inspection of conditions at the site for the week of June 28-July 2, 1976. The telegrams 
requested a data book, available if possible before the meeting, to present (1 ) site geology in plan and 
sections with any test results on foundation materials, (2) site exploration with detaU of drill logs, 
exploration trenches, borrow materials and tests, (3) grout records in detail showing non-average 
takes by location and depths, patterns used and record of any interconnections, (4) foundation 
preparation showing both before and after conditions, (5) design memoranda for embankment, 
spillway, diversion structures and outlets, (6) basic drawings and technical specifications, (7) any 
outside reports re site or designs, (8) construction history of borrow pits, hauling, placement, 
progress, inspection, in-place tests, (9) any seepage measurements or observations, (10) eyewitness 
accounts on progress of failure, (11) hydrology, (12) seismicity, (13) drain designs and drainage 
observations, (14) any changes in spillway or auxihary outlet structures, (15) any changes in precise 
level or horizontal control survey points, (16) changes in topography upstream and downstream, (17) 
photos of foundation as approved at start of embankment, particularly in the cutoff trench, (18) 
record of any seeps or springs in the cutoff and core contact area, and (19) record of cofferdam 
seepage and pumpage from the foundation area. 

Prior to the Panel's convening for its first session, the Department of the Interior had recorded sworn 
testimony of 37 eyewitness observers of pre-failure and during-failure conditions. Of those 37 



3-1 



persons, 14 were Bureau of Reclamation staff and employees, 13 were employees of the construction 
contractor, and 10 were from the general pubUc. In parallel with these eyewitness accounts, there 
became available several excellent photographic sequences in still and later in motion picture form. In 
order to supplement these eyewitness accounts with any available observations of failure-related but 
pre-failure conditions, a pubUc call was issued, and two pubUc hearings were held in Idaho Falls on 
July 21, 1976. 

All members of the Panel were present for the June 28-July 2 working sessions, and for the 
June 30-July 1 site inspections. An interim report, covering the Panel's activities up to July 2, was 
forwarded to the Secretary of the Interior and the Governor of Idaho on July 2, 1976. The full text 
of that report is attached in Appendix B. 

During this first working session, the need for professional staff and technical and administrative 
support was recognized. To fill tlie professional need, the services of Robert B. Jansen, as Executive 
Director, were secured through the cooperation of the Governors of Idaho and Cahfornia. Also, the 
services of Qifford J. Cortright, Staff Engineer, and Laurence B. James, Staff Geologist, were secured 
within a few days of Mr. Jansen's appointment. Soon thereafter, geologist Frank B. Sherman joined 
the professional staff. Through the excellent cooperation of the Office of the Secretary, Department 
of the Interior, supporting properties, services, and technical and administrative assistance have been 
made available to the Panel through various bureaus of the Department. 

Simultaneously with its July 2 report the Panel addressed the Director, Design and Construction, 
USBR, Denver, saying: 

The following activities represent the Panel's highest priority and are recommended for 
immediate implementation. It should be recognized that additional activities will be 
proposed in the coming months. 

1. The remnant of the right-abutment keyway fill to the left of the spillway should be 
excavated to permit inspection of conditions below Elevation 5301. Down to Elevation 
5301 the remnant can be removed in any manner that will not disturb the material below. 
Below Elevation 5301 the remnant can be removed in any stages and by any means, 
provided that a width of undisturbed material remains with a minimum horizontal 
thickness of five feet on each side and a minimum vertical distance of ten feet above the 
bottom of the original trench. The material within the five-foot envelope on each side 
should be removed by hand, where directed by the Panel's representative, as required to 
permit appropriate samphng to allow description of conditions of soU, rock, and any joint 
treatment disclosed by the excavation, to allow observation of any indications of piping 
or other defects. The bottom ten feet should be removed in two Ufts. These hfts should 
be preceded by excavating trenches at places selected by the representative of the Panel 
to a depth of five feet with appropriate sampling and observation. 

2. Any debris remaining on the face of the central part of the abutment, especially 
where the grout cap remains intact, should be carefully cleaned to permit detailed 
inspection. 

3. The area of the lower spring (50 cfs) should be exposed. Any original material still in 
place should be left undisturbed. The details of jointing of the rock in this area should be 
carefully examined. 



3-2 



4. AU steps necessary to assure safety at the remaining left section of the dam can be 
carried out promptly. 

5. In order to provide some quantitative evaluation of permeability in the rocks in the 
right abutment, detailed studies should be made on enlarged photographs of 
representative areas of each joint type near the keyway. 

Total footage of open joints per unit of area (e.g., one square yard) should be determined 
by direct measurements on enlargements of the photos, using a rehable scale with which a 
grid system is drawn on the enlargement. 

The details of this survey, including best lighting (either direct sun during the forenoon or 
on a cloudy day) should be developed in a pilot program. 

6. An item of prime importance is the nature of the joint system in the right abutment 
on either side of the keyway. Particularly important is the identification of major, 
throughgoing joints on the downstream side of the keyway that might provide access of 
water to the embankment. 

Primary and secondary joint systems should be plotted on a new topographic map. 
Symbols may be used to indicate wide and continuous joints in contrast to the numerous, 
smaller joints. Any evidence of springs or watercourses along or through the joints should 
be indicated on the joint map. 

Response was prompt, and on July 16, 1976, the Bureau of Reclamation awarded its Contract No. 
DC-7232 to Gibbons and Reed, Salt Lake City, to do the requested excavation. Notice to proceed 
was issued July 23, 1976, and mobilization started on July 23. Actual removal of the right remnant 
of the dam started July 26, 1976. This excavation proceeded expeditiously, by five-foot working 
levels, or platforms, to El. 5200, with trenching of each platform in accord with the Panel's need to 
inspect the core remnant for any evidence of water channeUng or cracking and of the marmer in 
which the key trench was excavated, sealed and filled. 

A large volume of information was furnished, with oral perspective and explanations, during the 
Panel's sessions June 28, 29, and 30. A list of the related exhibits is contained in Appendix A. Many 
of these records have been supplemented by others furnished to the Panel's staff at the site, and by 
oral and other written requests. 

Further information was desired on the manner in which the grout curtains were closed and in which 
the core was buUt into the key trench. This information was desired both from the Bureau of 
Reclamation as designers and constructors of the dam, and of the contractor who implemented that 
construction. Accordingly, on August 18, 1976, a questionnaire was directed concurrently to the 
Director, Design and Construction, USBR, and to the Chief Executive Officer of Morrison-Knudsen, 
as the sponsoring member of the construction contractor, Morrison- Knudsen-Kiewit, requesting 
descriptions of: (Refer Appendix B) 

a. The manner in which axial grout distribution and closure were assured when the up 
and downstream grout travel was relatively unhmited. Details of any doubts over the 
effectiveness of this axial distribution in any particular location along the three grout 
curtains between Station 18+00 and Station 2+00 will be helpful. Likewise, details of 
difficulties in obtaining assurance of axial closure at any stations or grout holes along this 
same stretch of curtain will be helpful. 



3-3 



b. The manner in which the key trench between Station 18+00 and Station 2+00 was 
prepared to receive the first embankment material. Compare the way in which this trench 
was prepared with "broom clean." If there were differences in clean-up between 
particular stations, because of weather, or any other cause, please describe such 
differences in detail. 

c. The manner in which any fissures or open joints in the key trench walls and floor 
were sealed between Station 18+00 and Station 2+00; that is, the manner in which, and 
the places where, slush grouting, dental concrete, gunite, or shotcrete may have been 
used, also the extent to which such sealing was general. Were any joints left unsealed and, 
if so, where? If known, please indicate the particular stations, if any. 

d. The method of material selection, preparation, placement and compaction, in the key 
trench, of the "specially compacted earthfill" shown in the cross section marked 
"Foundation Key Trench" on USER Drawing 549-D-9. If special difficulties were 
encountered in selection, preparation, placement or compaction at any points along the 
length from Station 18+00 to Station 2+00, please describe each. 

e. The method of material selection, preparation, placement and compaction in the key 
trench between Station 18+00 and Station 2+00 of the core material. If special 
difficulties were encountered in selection, preparation, placement or compaction at any 
points along the length from Station 18+00 to Station 2+00, please describe each. 

f. The manner in which the contact area under the core of the dam outside of the key 
trench was prepared to receive the first core material. If special difficulties were 
encountered at any location along the length of dam between Station 18+00 and Station 
2+00, please describe. 

g. The manner in which core material was selected, prepared, placed, and compacted 
outside of the key trench between Station 18+00 and Station 2+00. If special difficulties 
were encountered, please describe in detail by specific location. 

h. Similarities and significant differences in the appearance of the walls and floor of the 
key trenches in the right and left abutments. 

The answers of the addressees are contained in full in Appendix B. The USER response is quite 
detailed. The contractor's response is in two parts. One is from the contractor per se, and the other is 
from the grouting subcontractor, McCabe Bros., Inc. The prime contractor's answer was rather 
general and not sufficiently responsive. 

The full Panel met in technical working session again on August 2-5, 1976. At that time the 
excavation was well started. That work was inspected. Because of the need to know the physical 
properties of the in-place materials of the right remnant and the subsurface conditions under that 
remnant, the Panel appended to its progress report a list of additional physical work, analyses and 
tests required to be conducted. The report included the following statements: 

A. Purpose 

In its report of July 2, 1976, the Panel listed five potential causes of the piping failure of 
Teton Dam, and on the same date, in a letter to the Director, Design and Construction of 
the Bureau of Reclamation, listed items of highest priority recommended for action by 



3-4 



the Bureau to provide data for choosing among the potential causes. In its dehberations 
during its meeting of August 3-5, the Panel concluded that the field evidence virtually 
excludes massive seepage around the end of the grout curtain as a Ukely cause. 
Accordingly, the foUowing detailed program was developed to aid in discriminating 
among the other four hypothetical causes, namely whether the massive seepage or piping 
took place (1) through the grout curtain, (2) through the core at the core-to-rock contact, 
(3) through the core above the base of the keyway core-to-rock contact, or (4) through a 
crack in the core. The program is in part a particularization of the work recommended on 
July 2, and in part a supplement to that work. 

B. Investigation of Bottom of Key Trench and Grout Curtain 

The purpose of the program is twofold: first, to determine if any cracks encountered in 
the rock in the bottom of the key trench, either up- or downstream, are open enough to 
permit flows of water through them; and second, to test the watertightness of the grout 
curtain under the grout cap and under the spillway. The section of the key trench to be 
tested extends from Station 12-1-50 to 14-H50. 

To test the water-carrying characteristics of cracks in the bottom of the key trench, it is 
proposed to pond water over selected cracks and observe the drop in the level of ponds. 
Each pond can be formed by placing a dike of stiff mortar on the low side of the crack, 
high enough to produce a depth of water of about 6 inches over the crack. Visual 
observation of the loss of water wUl permit a rough idea of whether the crack is relatively 
open or tight. At open cracks, an approximate measurement should be made of the 
outflow per Unear foot of crack per minute. It is suggested that the wider cracks be tested 
first, and then the narrower ones. 

Tests should be made both upstream and downstream of the grout cap. It is envisioned 
that between 10 and 20 representative cracks should be tested in the proposed section. 
The cracks tested should be distributed throughout the length of the section. If most of 
the cracks leak substantially, additional tests might be made to verify the conclusion that 
most cracks would transmit water easily. 

To test the watertightness of the grout curtain, it is proposed to drill through the grout 
cap and the spillway crest into the rock below, and to watertest these holes. The holes 
should preferably be of Ax size and cores should be obtained from each hole to permit 
observation of any grout that may fill cracks in the rock. The holes through the grout cap 
should be drilled to a depth of 10 feet below the bottom of the grout cap, watertested, 
drilled 10 feet more and tested again. If pressure is used, it should not exceed 10 psi at 
the collar. The rate of flow in each stage of the hole should be recorded. If the second 
stage of any hole shows large leakage, a third 10-foot stage should be drilled and tested. 

It is suggested that tests be carried out on the centerline of the grout curtain 
approximately at Stations 12+65, 13+05, and 13+40. At each station, three holes should 
be drilled, one vertical, one inclined 22-1/2° from the vertical toward the abutment, and 
one incUned 45° into the abutment. At each location, three holes should be drilled, in 
each stage, before starting the water testing. 

It is also suggested that holes be drilled at about the center of each of the three spillway 
bays. Three holes should be drilled at each location, one vertical, one at an angle of 30° 
toward the river, and one at an angle of 30° away from the river. The holes through the 



3-5 



spillway crest should be drilled and watertested in three stages of 25 feet each, so that the 
grout curtain will be tested to the depth of the adjacent key trenches. 

If large water takes are observed at any location, additional holes should be drilled on 
each side to determine the extent of the open zone. 

C. Investigation of Key-Trench Fill 

As the key trench fill on the right abutment is excavated in accordance with the Panel's 
recommendation of July 2, detailed studies should be made of the variations in the degree 
of compaction of the fill material by penetration tests, and samples should be taken for 
investigation of erosion resistance, stress-strain characteristics, and such other purposes as 
may become desirable as the investigation proceeds. The specific studies are as follows: 

1. Field Investigations and Routine Laboratory Tests 

a. Observations and Sampling in Trenches 

Immediately upon completion of excavation of an approximately 30-foot long section of 
exploratory trench, the following observations and sampling should be performed: 

With a shovel or spade, make a fresh exposure by removing a vertical slice at least one 
inch thick, at locations spaced approximately 7 to 8 feet. In this fresh exposure make a 
rapid survey of variations in consistency along a vertical Une, using a screwdriver or other 
convenient hand tool; also examine variations in types of materials; then perform 
penetration tests with the Proctor Needle on several representative layers, to define the 
entire range of strengths, with special attention to the weakest layers or lenses. For the 
penetration tests on the weakest materials, it will probably be necessary to use the largest 
diameter "point." Prepare a log of all observations and penetration tests, including 
thickness of representative layers. 

To facihtate recording the logs, it will be desirable to develop a simple classification 
system which should be based on the BR test data of the Zone 1 fill and on initial 
experience in surveying the trenches. 

b. Sampling 

(1) Hand-cut block samples. Samples, usually about 8 inches square and about 12 
inches high, should be taken of representative materials, but with particular emphasis on 
the weakest materials. Usually three such samples should be taken at each location, side 
by side, of material that is essentially similar. 

Each sample should be wrapped in Saran wrap, or similar plastic film, and then covered 
with at least a 1/4-inch thick layer of microcrystalline wax by dipping several times into 
the wax melted to the correct temperature. (Do not overheat the wax, which would 
change its properties.) 

Use a grade of wax as used in soils laboratories for such purposes. Then place a clearly 
written identifying label on one side of the sample and again wrap in one layer of plastic 
film, taking care to place the film smoothly over the label to ensure that it can be read 
easily. 

(2) A Bag Sample should be taken at each location where block samples are taken and 
placed in a plasfic bag which is closed tight. Usually about 10 lb. will be sufficient. 



3-6 



(3) Storage of Samples should be in a shed with appropriate shelves to provide space for 
samples taken from an estimated 100 locations and equipped with a humidifier (to 
maintain humidity at greater than 80% relative humidity) and heated in winter to a 
temperature above 40°F. 

c. Observation of Features That May be Related to Potential or Actual Piping 

Special attention must be paid to careful observation of fissures, holes, and any signs 
indicating that the originally placed fill was disturbed. Such features should be identified, 
sketched, described and photographed. Particular care should be exercised in identifying 
such features immediately adjacent to the downstream rock face and the bottom of the 
key trench. If such features are discovered, it will be necessary to proceed with the 
greatest of caution in further excavation to protect vital evidence of erosion. At such 
junctures, the field staff will have to make ad hoc decisions how to proceed. Mr. Jansen 
should be notified immediately. When particularly meaningful discoveries are made, Mr. 
Jansen will confer by telephone with available geotechnical panel members. 

d. Laboratory Tests 

Preferably in a field laboratory, the following tests should be performed on representative 
samples: 

(1 ) Natural water content. 

(2) Grain size analyses. 

(3) Liquid and plastic Umit tests. (Report actual test results; not the computed plasticity 
index in lieu of the measured plastic Umit.) 

(4) Unconfined compression tests. 

e. Miscellaneous Comments 

The depth of the exploratory trenches should not exceed 6 feet to faciUtate operations. 

During removal of fill immediately adjacent to the rock slopes of the key trench, all loose 
rock should be removed to ensure safety of the men who wiU work later at lower levels. 

2. Evaluation of Erosion Potential of Zone 1 Material 

In view of the fact that the failure of Teton Dam has already been attributed to internal 
erosion of the Zone 1 material, it is important to establish the vulnerabUity to erosion of 
this particular material in comparison with that of other soils customarily used as core 
materials. This is particularly true since visual inspection and classification-test data of 
Zone 1 materials would appear to indicate that these soils would be highly susceptible to 
erosion. 

To establish the erosion potential of this soil, it is recommended that selected samples be 
sent to two laboratories for independent evaluation as follows: 

a. A series of 10 samples should be sent to the Waterways Experiment Station at 
Vicksburg, Mississippi, for performance of the pinhole test as now standardized by that 
laboratory. Grain-sized distribution curves and liquid and plastic limit values should be 



3-7 



determined for each of the test samples and the results used to establish the relative 
erodibiUty of Teton Dam Zone 1 materials. 

b. A series of 10 samples should be sent to a second laboratory speciaUzing in measuring 
the erosion potential of soOs (e.g., the SoO Mechanics Laboratory of the University of 
California at Davis) where the erodibiUty can be evaluated and compared with data for 
other soils by means of two or more appropriate types of tests. As before, grain-size 
distribution curves and liquid and plastic limit values should be determined for each test 
sample. 

In all cases, the erosion tests should be performed on the undisturbed block samples cut 
from the right abutment key trench. The selected samples should be representative of the 
range of materials and densities found in the trench, with particular emphasis on materials 
that appear to be most erodible, as established in the field survey. To the extent 
practicable, the two independent laboratories should be sent similar suites of samples. 

3. Determination of Stress-Strain Characteristics for Use in Finite-Element Analyses 

To determine the possibility of hydrauUc fracturing or of crack formation in the Zone 1 
material, it is desirable to evaluate the stress distribution within Zone 1 . This can best be 
achieved by finite-element analyses incorporating reahstic representations of the 
stress-strain characteristics of the compacted loessial soU used to fill the key trenches and 
to form the main core of the embankment. 

The stress-strain properties should be determined by several series of drained triaxial 
compression tests on representative samples cut from the Zone 1 section of the dam. At 
least 3 series of tests should be performed, each series including one test at each of four 
confining pressures, approximately 15, 40, 70 and 100 psi. Samples should be 1.4 inches 
in diameter and approximately 3-1/2 inches high and should not be saturated before 
testing. Stress-strain relationships should be recorded up to the point of failure. 

At least one series of the drained tests should be conducted by stress-control techniques 
to investigate the creep characteristics under loads sustained for several days. 

An additional two series of tests should be performed on samples tested as discussed 
above, but with specimens saturated prior to testing. 

Representative grain-size distribution curves and liquid and plastic limit values should be 
determined for the samples in each series. 

D. Embankment Stress Analysis 

It is requested that additional finite element stress analyses be made of the embankment 
fill. This work would constitute an expansion of a pilot analysis submitted to the Panel 
on August 3, and would incorporate the following specific requirements; 

1. Three cross sections of the original right abutment embankment between Stations 
12+00 and 15+00, and one axial section of the right abutment embankment (Stations 
12+00 to 20+00) should be analyzed. The three transverse stations utilized, and the 
details of analytical formulation, are to be selected after review of the shape of detailed 
as-built cross sections. 



3-8 



2. The displayed results should include vertical stress, minor principal stress and strain. 

3. The stresses should be those developed by layered construction, as opposed to the 
"gravity-turn-on" option. 

4. In addition, stresses should be calculated to reflect the effect on the embankment of a 
reservoir rise to Elevation 5300. 

5. Two complete sets of stresses should be computed for each section: 

a. One adopting a core stiffness factor K of 470, as measured by the USER on a 
composite, reconstituted triaxial sample under rapid shearing; and 

b. One utilizing a K of 200, a value judged to be a probable lower limit for the Zone 1 

mi. 

The foregoing finite element analyses should be undertaken at once, under the guidance 
of Mr. Leps and Dr. Seed, with a target dehvery date of perhaps October 15. 
Concurrently, a suite of triaxial shear tests on representative samples should go forward, 
as covered in the previous section, to provide appropriate verification of the K-parameter 
range assumed in requirement 5, above. 

E. Modifications in Program 

Field conditions may require modification of some of the details of the recommended 
program. Moreover, as the findings accummulate, the results may suggest changes, 
additions, or deletions. The field staff is encouraged to make changes that appear 
appropriate and to inform the Panel promptly. If major changes seem desirable, the staff 
should communicate with the Panel. 

The fuU Panel met again for technical working sessions and site inspection on October 4 through 6, 
1976. At that time, drUUng was requested into the foundation in the vicinity of fissures near Dam 
Sta. 4+00, described in USBR construction reports. This was in addition to driUing described in the 
schedule of August 5, 1976. One of the drill holes at that location was to extend into deep underlying 
sediments where samples could be taken for compression testing. At its October meeting, the Panel 
decided to have a model fabricated of the right abutment to help in visualizing features relating to the 
failure. It was also decided to perform hydrauhc fracturing tests in bore holes at various sections of 
the intact portion of the embankment overlying the left abutment. 

On October 4, members of the Panel entered the dewatered auxihary outlet works. The tunnel was 
inspected for its fuU length and was found to be in sound condition with no sign of distress which 
could be related to the failure. 

The Panel conducted technical working sessions in the period November 1-3, 1976 with eight of the 
nine Panel members in attendance. On November 1 , inspection was made of the sluiced key trench; of 
the drilhng sites; of the foundation areas uncovered by excavation and sluicing of debris on the right 
abutment between the spillway and the river. An examination of the remaining lower right canyon 
wall was made by boat. 

Panel technical working sessions were held December 7-10, 1976 with all members parficipating. The 
recently completed model of the right abutment was examined. Detailed work was done in drafting 
the Panel's report due on December 31 , 1976. 



3-9 



POST-FAILURE EXCAVATION 

Contract DC-7232 was executed for three primary purposes: (1) exploration as necessary in the 
Panel's investigation of the cause of failure; (2) excavation of a 4,000-ft-long chaiuiel downstream 
from the spillway stiUing basin and auxiliary outlet downstream portal for the purpose of permitting 
internal inspection of the auxiliary outlet and to restore it to service for river diversion; and further to 
unwater the right abutment for examination, especially in the region of the 50 cfs leak at the right 
toe of the dam at El. 5045; and (3) resloping the left portion of the dam embankment for public 
safety and to prevent uncontrolled damming of the river by sUdes. 

All requirements under purpose (1) were determined by the Panel and controlled by the Panel's 
on-site representatives, acting through the Contracting Officer of the USER. As suggested above, the 
Panel's primary interest under purpose (2) was examination of the unwatered auxiUary outlet tunnel, 
of the lower portion of the right abutment, and of the vicinity of the 50 cfs leak at El. 5045. 

Exploration of Zone 1 in Right Abutment Key Trench. 

Exploration, excavation, and sampling of Zone 1 materials and examination of the foundation 
structure in the right abutment foundation key trench proceeded generally as outhned in the Panel's 
July 2, 1976 letter to Mr. Arthur, with minor on-site modifications. 

The near vertical face of the right wall of the breach was sloped for safety in successive vertical Ufts to 
form horizontal working platforms using a 3/4-cu-yd dragUne. Materials of all zones in each 5 -ft 
platform to El. 5301 were excavated by a 2-cu-yd backhoe and a 5-cu-yd bucket loader. 

A series of longitudinal and transverse backhoe trenches (Fig. 3-1) was excavated to El. 5296, and a 
series of drive samples was obtained. 

Outside the key trench between the spillway and Sta. 12+50 the general foundation level over the full 
base width of the right abutment remnant was about El. 5295 to El. 5300. The excavation was 
entirely in Zone 1 at each level below El. 5296 and was made by the 2-cu-yd backhoe and 5-cu-yd 
bucket loader, also in increments of 5 ft, preceded by transverse trenches at both key trench walls. 
The transverse trenches were excavated by hand through the final 1 ft of Zone 1 to the rock surfaces. 
Close inspection, photographing, and mapping were done in these excavations. 

Transverse trenches were excavated similarly to expose the key-trench invert whenever excavation 
neared that depth (Fig. 3-2). 

At El. 5280, the 2-cu-yd backhoe was walked from the excavation, while egress was still possible, and 
replaced with a small combination backhoe and bucket loader. The excavation of Zone 1 materials 
from the key trench, preceded by exploration trenches at the side waUs and invert by backhoe and 
hand shovel, was made in the same 5-ft vertical increments to El. 5215. Excavated material was 
hoisted from the key trench by the dragUne until it reached its operational limit at El. 5260. 
Thereafter, material was removed from the key trench in skips hoisted by a truck-mounted crane 
equipped with a 160-ft boom until it in turn reached its operational Umit at El. 5210 (Fig. 3-3). The 
backhoe was hoisted from the key trench and a small dozer was lowered in turn. The remaining 
materials were then dozed to the El. 5 140 rock bench or to the river's edge as final excavation to rock 
was accomplished by hand methods. 

Below El. 5265, in addition to the transverse trenches, longitudinal exploration trenches were 
continuously excavated on key-trench centerline, 5 ft from both key-trench walls and at intermediate 
positions. 



3-10 




Fig. 3-1 



Exploration trenches 




Fig. 3-2 Transverse trenches exposing key-trench invert and grout cap 



3-11 




' f 



•a 







Fig. 3-3 Removal of zone 1 material by crane and skip 




Fig. 3-4 Obtaining block samples 



3-12 



Ninety-two 9-in. cube samples and 47 3 in. x 36 in. Shelby tube drive samples were obtained at 
selected locations (Fig. 3-4). 

Final exposure of aU rock surfaces was carefuUy made by hand shovel throughout. Exposures in all 
trenches were carefully examined for paths of seepage, erosion channels, foundation bond, quality of 
foundation cleanup, rock nests, extreme variation of materials characteristics, extremely dry or overly 
wet layers, cracks and other indications of stress or displacement, and the integrity of the grout cap. 
The rock surfaces were examined and surveyed for joint and fracture patterns, intrusions of soil or 
extrusions of pre-failure filling, and evidence of pressure grout filling, displacement, or adjustment. 

Related location surveys were made. Photographs were taken. 

Upon completion of the removal of all soil by mechanical means to the water's edge, the rock 
surfaces of the key trench and of the right abutment were sluiced clean with fire hose nozzles 
supplied from water trucks positioned on the abutment near El. 5295. 

Observations During Exploration. 

The materials comprising Zone 1 appeared to be quite uniform and weU compacted. Moisture 
contents were found to be slightly less than the USBR laboratory optimum. Penetration resistance 
readings using the Proctor needle varied from 1500 to 2600 psi, and decreased slightly with 
decreasing elevation of location. PracticaUy all materials classified as nonplastic, inorganic sUts (ML). 
Some visual distinction was possible, mainly in color, with brown, tan, gray, and black being present. 
The black color was due to a slight organic content in those soils, probably obtained from the near 
surface layers of the borrow pits. Variations in caliche contents were also present. Sizes larger than 
the No. 4 screen were practically nonexistent but, when present, were usually caliche clods or small 
caliche granules. Only one layer, near El. 5265, appeared to be clay, with a plasticity index of 7 and 
with 93 percent passing the No. 200 screen. 

A possible erosion channel was noted adjacent to the upstream wall of the key trench at Sta. 13+00, 
El. 5261, but upon careful uncovering it proved to be localized and its cause undeterminable. 

The first evidence of distress in the compacted fill was noted near El. 5270 and was judged to be 
localized horizontal slickensides attributable to overcompaction from extensive traffic during 
placement and abutment wheel rolling in the confined area of the key trench. 

Only one vertical longitudinal crack was encountered. It was 1/16 in. to hairline in width, located 
about 2 ft from the upstream key-trench wall and traceable from El. 5267 to 5280 near Sta. 12+40 
This crack may have been caused by differential settlement induced by the narrow horizontal bench 
on the upstream key-trench wall near El. 5265. 

In all respects, the remnant of Zone 1 appeared to be a well-constructed impervious fill meeting all 
the requirements specified in the contract documents. 

The embankment foundation contact in the key trench was excellent and well bonded where 
observed at many locations in the side wall, transverse invert trenches, and the longitudinal trenches 
extending to the top of the grout cap. Foundation cleanup was excellent. No rock nests, shattered 
foundafion surfaces, or remaining grout spills were encountered. No dry, pervious, or low density 
layers or lenses were found. 

A few locahzed, saturated pockets of Zone 1 material were encountered along the upstream wall of 
the key trench, as were several on the invert of the key trench at the upstream edge of the grout cap 



3-13 



where direct access of reservoir water was afforded by the interconnected joint and fracture 
structure. 

The rock surfaces at the key-trench walls and invert are highly jointed and fractured, but the rhyoUte 
rock is hard, dense, and strong. On the walls the joints and fractures are numerous and closely spaced. 
The openings are frequent and range up to 1 in., especially above El. 5280. 

There was no evidence of the joints and fractures having been surface treated by slush grouting. The 
Zone 1 fiU where placed against the open joints was found to bridge across them. Some local 
overhangs of hmited extent were present under which the Zone 1 material was found in an 
uncompacted and saturated state. 

As the Zone 1 fill was progressively and alternatively explored by trenches and excavated full width, 
it was found intact and undisturbed from El. 5332 to 5265. At El. 5265, the embankment was found 
to be cracked transversely at vertical and steeply dipping angles. WeU-defmed shear zones appeared. 
Hydraulically transported filling was found in some of the cracks. Wet clay coatings were also present. 
It was concluded that these cracks were associated with incipient sliding of the remnant of fill toward 
the face being eroded by the flood waters and that the filling was due to the flow of bank storage into 
the cracks as the failure progressed. Hence, the cracks were judged to be due to the consequences of 
the failure. 

Finally, at the lower elevations, near El. 5225 and the rock bench at El. 5220, the well-defined, 
concentrated cracks disappeared, but the shear pattern became more intense and extensive until the 
embankment everywhere exhibited distress for horizontal distances in excess of 20 ft from the face of 
the breach. The shearing pattern was diamond-shaped, and the general configuration formed cupped 
or bowl-shaped surfaces concave toward the river, with the surfaces gradually becoming subtangent to 
the key-trench walls. 

The longitudinal exploration trenches exposed the bench at 5220 and extended to the deeper key- 
trench invert beyond. Here the sheared zones were found concentrated at the key-trench profile 
break and appeared to be controlled by that break. 

Near Sta. 13+15, at El. 5215, the embankment for the first time was found extremely wet 
continuously across the width of the key trench. Some free water was encountered. The fill was 
extremely muddy over the surface of the grout cap. Between the grout cap and the upstream key- 
trench wall, the backhoe sank up to the axle. Even under the lighter ground pressure of the small 
dozer, the fill was spongy and quick. The in-place embankment remaining at this elevation was very 
limited in axial extent, being about 15 ft. A transverse vertical face was cut by hand 3 to 4 ft to the 
key-trench invert rock. By probing over this vertical surface, a softer, wetter horizon was detected. 
Penetration resistance readings were in the 170-psi range while readings above were in the 400-psi 
range and those below averaged 330 psi. Because this horizon was everywhere within 15 in. of the 
rock, and in such close proximity to the face of the breach it was not possible to determine if this 
wetter horizon existed pre-failure or was created during the failure. 

At Sta. 1 3+ 25 and El. 5206 on centerline of grout cap, the in-place embankment terminated, and all 
of the soil then remaining on the abutment foundation was identified as disturbed material which had 
sloughed down from the steep face of the breach. 

Beyond that location, all the remaining soil on the abutment was gradually removed by the small 
dozer pushing the soil either to a stockpile on the bench at El. 5140 or completely down to the edge 



3-14 



of the river. By hand shovel, the grout cap was exposed ahead of the dozer operation to avoid any 
possible damage or displacement of the grout cap. 

Care was also used in removing the soil immediately adjacent to the rock by hand, initially without 
water, so that any existing clues to the cause of failure might not be accidently destroyed. The rock 
surfaces were then sluiced clean as previously described. 

Channel Excavation. 

Following the failure, the river flow stabilized with the reservoir at about El. 5056 and an 
intermediate pool in the breach at approximately El. 5053. The level of the intermediate pool was 
controlled by an extensive bar of large rocks. The auxiliary outlet portal was blocked by debris 
deposited in the stilling basin; consequently, a trapezoidal channel bypassing the bar was excavated, 
commencing 4,000 ft downstream from the stilHng basin, and was completed sufficiently by 
September 27 to attempt a controlled lowering of the intermediate pool by gradual removal of the 
portion of the bar near the stiUing basin which had been partially reinforced as a cofferdam at the 
head end of the bypass channel. Unfortunately, the cofferdam eroded very rapidly, lowering the 
intermediate pool to El. 5036 with consequent rapid erosion of Zone 1 of the left remnant in the 
river channel. To avert uncontrolled releases of the remaining reservoir storage, the cofferdam was 
quickly reestablished, again raising the intermediate pool to El. 5053 and arresting the erosion of 
Zone 1 . 

A temporary gated, double-barrelled culvert control structure of 1,000-cfs capacity was then 
constructed in the river bypass channel. After testing it by closing the gates and filling the lower pool 
thus formed at the spillway stilling basin, the cofferdam was removed and the river channel at the 
dam was slowly excavated to permit controlled draining of the reservoir through the bypass control 
structure. In this manner, the residual reservoir and intermediate pool were reduced to a negligible 
capacity by lowering the river channel invert, and the remaining abutment and the vicinity of the leak 
at El. 5045 were unwatered for inspection (Figs. 2-5 and 2-6). 

SOIL SAMPLING AND TESTING 

Undisturbed, hand-cut block samples, 9 in. x 9 in. x 9 in. in dimension, and 3 in. x 36 in. Shelby tube 
drive samples together vwth 10-lb bag samples taken nearby were obtained at the locations shown in 
Fig. 3-5. 

Selected block samples, representative of the range of materials and densities found, and spanning the 
mass of the embankment remnant on the right abutment, were sent to various laboratories for 
identification tests and tests of designated engineering properties. To the extent practicable, two 
laboratories were sent similar samples for comparative purposes. 

The dispersive characteristics of Zone 1 material were investigated by pinhole tests at the Waterways 
Experiment Station and the erodibiUty by flume tests and rotating cylinder tests by the University of 
CaUfornia at Davis. 

The stress-strain properties were investigated by drained triaxial compression tests at both placement 
moisture and saturated moisture contents by Northern Testing Laboratories, Billings, Montana, and 
by the Earth Sciences Branch, USBR, Denver, Colorado. Unconfined compression tests at varying 
moisture contents were also made by the latter. 

Special horizontal permeability tests were made by the University of California at Berkeley. 



3-15 



DAM CREST EL 5332,0 



5210 



TOTAL SAMPLES 



SPILLWAY WALL 



GENERAL FOUNDATION LEVEL OF ZONE 1 



REMOVE MATERIAL BETWEEN TRENCHES AND 
IR-DI-1 DI-2 HAND EXCAVATE FINAL 1 FT TO ROCK 












BREACHED FACE 
OF EMBANKMENT 






SAMPLES 




ZONE-1 EL. 


DRIVE 


BLOCK 




5301 


4 








5296 


4 








5290 










5285 


5 




4 




5280 


8 








5275 






4 




5270 


8 




24 


c 


5265 






4 




5260 






4 




5255 


8 




18 




5250 






4 


/ 


5245 








SLOUGH -^/ 


5240 


6 




12 


/ 


5235 






3 


/ i 


5230 






3 


/ / 


52275 
5225 
5222.5 
5220 


4 




6 
6 


/ U 



- TRENCH 
.0- SAMPLE 



•HAND EXCAVATE IN THIS VICINITY 
WITH EXTREME CARE 



TRANSVERSE TRENCHES 5 FT DEEP AT KEY 
TRENCH WALLS. HAND EXCAVATE FINAL 
1 FT. TO ROCK 



N OT E S 



©&© SLOPE BACK TO SAFE SLOPE 



FROM EL 5332 TO EL 5301 EXCAVATE IN ANY 
MANNER THAT WILL NOT DISTURB MATERIAL 
BELOW 



TRENCH DESIGNATION 

5285 U3 
5250 IE 
5245 IR 



— THIRD TRENCH ON UPSTREAM 
WALL . INVERT EL 5285. 

— TRANSVERSE TRENCH INVERT IN 
EMBANKMENT AT EL 5250 

— TRANSVERSE TRENCH INVERT ON 
ROCK AT EL 5245 



SAMPLE DESIGNATION 

5285 U3-1 FROM TRENCH 5285 U3. 

5260 IR U3-1 FROM TRENCH 5260 IR UPSTREAM 

5260 IR D3-1 FROM TRENCH 5260 IR DOWNSTREAM. 

TRENCH AND SAMPLE LOCATIONS ARE SCHEMATIC ONLY. 



TESTING PROGRAM 



SAMPLE 



RECEIVING 
LABORATORY 



TEST 



U C -BERKELEY 



HORIZONTAL 
PERMEABILITY 



* 



NORTHERN TESTING 

DRAINED TRIAXIAL 
FIELD MOISTURE 
SATURATED 



USER 

DRAINED TRIAXIAL 

SATURATED 

FIELD MOISTURE 

FIELD MOISTURE 

STRESS CONTROLLED 
UNCONFINED COMPRESSION 



A 
U.S.C.E.- WES 



PINHOLE 
DISPERSION 



U.C- DAVIS 

ROTATING 
CYLINDER 
EROSION 



U.C. - DAVIS 



FLUME EROSION 



EXPLORATION OF ZONE 1 AND 
FOUNDATION KEY TRENCH 



FIG. 3-5. 



V S DEPARTMENT OF THE INTERIOR STATE Of IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



3-16 



Gradation analysis and Atterberg limit determinations were made on all samples by the Teton Project 
Laboratory, including those samples shipped to the other laboratories for testing. 

The results of all tests are discussed in Chapter 7, and the complete reports have been placed in the 
Panel's records. Samples not tested are stored at the USER laboratories in Denver. 



EMBANKMENT STRESS ANALYSIS 

Interest developed early within the Panel as to the possibility of tension cracking of Zone 1 
transversely within the key trench due to arching between the steep side walls of the narrow trench or 
due to differential settlement at any abrupt changes in the longitudinal slope of the key-trench invert, 
or due to the tendency of the embankment mass to pull away from the abutments as the dam settled. 
The Panel recognized that the state of stress within the embankment due to these factors would be 
intimately associated with and influenced by the intergranular forces imposed as the reservoir filled 
and saturation gradually spread through the embankment volume. A two-dimensional pilot study of 
the state of stress within Zone 1 at Sta. 14+00 was made at the Panel's request by Dynamic Analysis 
Corporation, Saratoga, Cahfornia. The finite element analytical methods for soils developed in recent 
years primarily by the University of Cahfornia at Berkeley were employed. 

The results of these pilot studies, available to the Panel at its August meeting, were considered 
sufficiently revealing to warrant expanding the studies to three transverse sections at Stas. 12+70, 
13+20, and 13+70 and to a longitudinal section along the key trench from Sta. 12+00 to Sta. 20+00. 
The University of California at Berkeley also undertook a two-dimensional fmite element stress 
analysis of the embankment at Sta. 15+00. The results of these analyses are included in Appendix D 
and reviewed in Chapter 12. 



HYDRAULIC FRACTURING TESTS IN BOREHOLES 

Hydraulic fracturing tests were made in boreholes in the left portion of the remaining embankment at 
stations where the geometry of the key trench and the height of the overlying embankment were 
similar to those at the stations where the initial breach of the right key-trench fill occurred. The 
principal purpose was to determine, by comparing the results of the field tests with those of 
calculations, appropriate in-situ values of soil properties needed for finite-element analyses of stress 
conditions in the right key trench. 

Three tests were performed. Sta. 26+00 was selected for the first test upon determining that the key 
trench and embankment-foundation geometry were analogous to that of Sta. 15+00. 

The test procedure involved drilhng a vertical hole directly over the key-trench centerline to a 
predetermined depth and subjecting an exposure of Zone 1 over a selected length of the hole near the 
bottom to a gradually increasing head of water. The length of hole so pressured was restricted by 
sealing an internal standpipe in the drill hole with a cement plug at the top of the length selected for 
testing and introducing water into the standpipe. 

By observing the recession rate of the imposed head, a normal rate of seepage for the conditions 
estabhshed was determined. The head was then increased by increments and the recession rates 
observed. If an increment was reached for which the recession rate suddenly increased by a larger 
magnitude, the fill in the region of the hole was deemed to have been fractured by the hydrostatic 
pressures created by the head then imposed. 



3-17 



At Sta. 26+00 it was believed that the hole could be safely wash-bored to 150 ft and the plug set at 
that depth (Fig. 3-6). However, at 101.3 ft (El. 5211.7) a sudden loss of drill water occurred. 
Fracturing is believed to have occurred at that elevation and head. Through a misunderstanding, 
drilling of the hole continued to a depth of 1 50 ft with continued loss of drilling water and the 
injection of several thousand gallons of water into the adjacent soil. A 3-in. plastic pipe was sealed in 
the hole with the cement plug and the hole was extended for 39 ft beyond by drilling with air. Soil 
wetted by the previous drill water loss became lodged behind the drill bit and in forcefully freeing the 
drill string the plastic pipe was pulled from the plug. The hole was temporarily abandoned. 

A second attempt was made at Sta. 26+25 by drilling a 4-in. hole with air to a depth of 150 ft, sealing 
a 3-in. plastic pipe in the hole with a cement plug at El. 5163, and extending the length of hole to be 
pressured 20 ft to El. 5143 by using air to faciUtate drilling. Again wet drill cuttings lodged behind 
the drill bit, this time causing a momentary increase in air pressure, apparently sufficient to fracture 
the hole as evidenced by the sudden entry of water into the hole, most Ukely from the adjacent hole 
at Sta. 26+00. 

Because Sta. 13+70 had also been analyzed and because Sta. 27+00 was analogous, a third test hole 
was located at that station and angered 109 ft to El. 5210. Nx casing was sealed in the hole at that 
elevation, and the hole was extended 20 ft with a split spoon drive sampler. The hole was then 
incrementaUy pressured as previously described. The test results are shown on Fig. 3-7. 

As revealed by the water level recession rates, no fracturing occurred even with the water level raised 
to the top of the hole at El. 5317. 

The hole at Sta. 26+00 which had been originally cased to 150 ft with 6-in. casing was restored by 
sealing Nx casing with a new plug at 152 ft and by cleaning out the original 39-ft-long hole extension 
with the split spoon drive sampler for 28 ft. The hole was then tested. Although some sloughing of 
the hole may have taken place during the test, the average head was assumed measured to the 
midheight of the restored hole, or El. 5147. The results are shown on Fig. 3-8 and indicate that the 
Zone 1 fill was fractured when the water surface was 20 ft below the top of the hole, or El. 5293. 



POST-FAILURE FOUNDATION INVESTIGATION 

Early in its investigation the Panel recognized the desirability of identifying the most probable path 
or paths of the leakage that led to failure of the dam. Efforts were directed to determine whether 
critical leakage had passed through, around, or under the dam, or had followed a combination of 
routes; also to establish the precise path or paths insofar as possible from the evidence remaining at 
the site. 

A geologic program was developed to investigate the following possible avenues of leakage through 
the foundation: 

1 . Around the right end of the dam. 

2. Through the grout curtain. 

3. Through large cavities discovered near the right end of the dam during its construction. 

4. Through sedimentary deposits underlying the volcanic rock foundation. 



3-18 




3-19 



10 109 



20 — 99 



30 89 



tt* 
I 



O 60- 

[- 

X 
H 
0. 



100- 




BORE HOLE HYDRAULIC FRACTURING TEST, 
STA. 27+00 WATER LEVEL RECESSION RATES 



U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

"AILURE 



_ _^^ _ — us DEPARTMENT OF THE INi tRIUR M«i t ur lUflHU 

r ICj. O"" / . INDEPENDENT PANEL TO REVIEW CAUSE OK TETON DAM FAN 



3-20 



I 100- 




BORE HOLE HYDRAULIC FRACTURING TEST 
STA. 26+00 WATER LEVEL RECESSION RATES 

_, _ ^^ Q Q L S DfPARTMfNT Of THE INTERIOR NTATI 

r 1 Ij . O O. INDEPENDENT PANEL 1 O RE VI E\X tAUSEOFTETt 



3-21 



Investigation of Possibility of Flow Around End of Dam. 

As an initial step, a review was undertaken of the records of subsurface exploration performed by the 
Bureau of Reclamation prior to construction of the project. This effort produced convincing evidence 
that flow around the dam was possible through interconnecting joints, but the Panel concluded that 
at the time of the failure there was insufficient hydraulic gradient between the end of the dam and 
the leak at El. 5200 to account for the large flow that was estimated to have broken out at this point. 
The analysis leading to this finding is developed in Chapter 5. 

Investigation of the Grout Curtain. 

At its August 5th meeting, the Panel developed a program for the investigation of the key-trench 
invert and of the grout curtain. The purpose of the program was to determine if the joints and 
fractures intersecting the key-trench invert could pass water and if the grout curtain beneath the 
grout cap and under the spillway weir was watertight. The section tested in the right abutment key 
trench extended from grout cap centerline Sta. 12+60 to 14+ 26.* 

The removal of all the loose soil covering the right abutment revealed the post-failure condition of the 
grout cap (Fig. 3-9). The cap was found intact and continuously in position from the spillway to Sta. 
13+96. Between Stas. 13+96 and 14+26, the cap was entirely missing (Fig. 3-10). However, the 
original rock invert of the trench in which the cap concrete had been placed was undisturbed, as 
shown by the preservation of the original line drill holes. Three prominent, nearly vertical joints, 
striking approximately N20°W, cross this gap, the ends of which appeared to be determined by the 
presence of the two joints at the ends of the gap (Fig. 3-11). A 2-in. open vertical fracture striking 
S68W (Fig. 3-12) crosses the alignment beneath the cap at Sta. 13+90. This fracture was ponded for a 
joint transmissibility test and is identified as U13 in Table 3-1. 

Between Stas. 13+30 and 13+96 (Figs. 3-13, 3-14, and 3-15) where the original side walls of the key 
trench were washed away during the failure, the cap exhibited a remarkable degree of resistance to 
the failure forces as evidenced by the large amount of rock plucking immediately adjacent both 
upstream and downstream and the surface erosion of the concrete. 

The cap concrete was eroded flush with the adjacent rock surfaces between Stas. 14+ 26 and 14+46. 
Extensive concrete erosion was also present between Stas. 14+65 and 14+75. This erosion is 
attributed to flows occurring during failure. Beyond Sta. 14+95 the cap is again missing at least as far 
as the river level at El. 5052. 

Wherever the original contact between cap concrete and rock foundation was exposed, it was found 
tight and intimate, indicating the absence of pre-failure displacement or separation. This observation 
was particularly striking at Stas. 14+ 26 and 14+65. 

Transverse cracks, only one of which was more than hairline width, are spaced approximately 20 ft 
apart along the grout cap (Appendix E). These cracks are attributed to shrinkage during loss of heat 
of hydration with the possible exception of those cracks near 13+90 which could have been caused 
by a slight rotational force on the cap at the time the cap was severed at 13+96. 



*Because they are on differing lines, the stations along the grout cap and along the axis are not the 
same. 



3-22 




Fig. 3-9 Post-failure exposure of the grout cap 




Fig. 3-10 Grout cap severed at Sta. 13+96 and missing to Sta. 14+26. 

Open fracture shown in Fig. 3-12 is behind the ladder 



3-23 




Fig. 3-1 1 Three vertical joints crossing alignment where grout cap is 

missing between Stas. 13+96 and 14+26 




Fig. 3-12 2 in. open fracture crossing grout cap 

alignment near Sta. 13+90 (see Fig. 
3-10 for location) 



3-24 









TABLE 3-1 














JOINT TRANSMISSIBILITY TESTING 












Location, 
















Intersection 


Submerged 


Max Depth 


Volume 










of Strike 


Length 


of 


of 




Joint 






w/Grout Cap 


of Joint 


Water 


Pond 


Loss 


No. 


Dip 


Strike 


tSta. 


ft 


ft 


gal 


gpm 


Ul 


35W 


N25W 


13+50 


5.4 


0.7 


37.7 


0.01 


U2 


31W 


N25W 


13+45 


4.4 


0.7 


12.0 


None 


U3 


49W 


N25W 


13+41 


3.4 


0.6 


3.3 


None 


U4 


44W 


N30W 


13+32 










Pond 1 








2.6 


0.5 


2.4 


None 


Pond 2 








1.8 


0.4 


2.3 


None 


Pond 3 








2.1 


0.6 


4.6 


None 


U5 


45W 


N20W 


13+30 










Pondl 








3.0 


0.6 


3.1 


0.09 


Pond 2 








1.2 


0.4 


0.4 


None 


Pond 3 








2.0 


0.8 


4.6 


0.38 


U6 


45W 


N30W 


13+27 


2.2 


0.5 


18.0 


1.09 


U7 


21W 


N25W 


13+23 










Pondl 








4.1 


0.5 


4.4 


0.01 


Pond 2 












2.1 


None 


U8 


38W 


N20W 


13+15 


2.4 


0.4 


2.9 


None 


U9 


30W 


N15W 


13+03 


2.7 


0.4 




None 


UIO 


25W 


N 8W 


13+00 


8.0 


0.6 


26.4 


0.10 


Ull 


25W 


N 5W 


12+93 










Pond 1 








2.7 


0.5 


16.3 


0.08 


Pond 2 








3.4 


0.7 


10.7 


None 


U12 


90 


N24W 


13+96 


27.5 


1.0 


120.1 


None 


U13 


90 


S68W 


13+90 


3.7 


3.7 




>28.5 


Dl 


25W 


NlOW 


13+50 


5.8 


0.8 


14.2 


0.58 


D4 


42W 


N13W 


13+32 


4.9 


0.9 


— 


— 


D5 


36W 


N25W 


13+30 


6.0 


0.6 


6.8 


0.21 


D7 


78E 


N33W 


13+23 


3.9 


1.0 


32.1 


0.09 



Notes: 



Ponds numbered from upstream. 

Stations on grout cap centerline. 

Joint Ul — Return flow from intersecting joints upstream of grout cap. 

Joint Dl — Joint truncated at outcrop affording free egress. 

Joint D4 — Could not effectively pond joint. 

Joint D5 — Return flow appeared downstream on canyon wail, Sta. 13+50, 

20 ft downstream, El. 5185. 
Joint U6 — Return flow appeared from joint 6 ft downstream of grout cap, 

N30W, 77E. Pond also submerged a fracture, N50W, 72E. 
Joint U5 — Pond 3 — Return flow at same location as from Joint U6. 
Joint UIO — Return flow from intersecting joints upstream of grout cap. 
Joint U13 - Capacity of water supply was 28.5 gpm. Could not raise water 

surface higher. Return flow appeared along horizontal joint, 

Sta. 13+97, El. 5155, 2.5 and 5.5 ft downstream of grout cap. 



3-25 




-^i^ 



Fig. 3-13 Rock structure along grout cap alignment Stas. 13+30 to 

13+96 




Fig. 3-14 Rock structure along grout cap alignment Stas. 13+30 to 

13+96, upstream proGIe 



3-26 




Fig. 3-15 Rock structure along grout cap alignment Stas. 13+30 to 

13+96, downstream profile 




Fig. 3-16 Test ponds for joint transmissibility tests, looking downstream 



^.o? 



Joint Transmissibility Testing. 

The transmissibility characteristics of the rock foundation at the grout cap were first tested under a 
low gravity head by constructing small impoundments with mortar and stone over selected joints and 
fractures (Fig. 3-16). The ponds and joint traces were cleaned with air and water. The volume of the 
ponds and any loss rates were determined by metering water into the ponds. The dip, strike, and 
submerged length of each joint were measured. Twelve ponds were prepared upstream and four 
downstream of the grout cap between grout cap Stas. 12+93 and 13+96 (Fig. 3-17). These ponds 
were not in contact with the cracks in the grout cap. Also, as previously reported, one vertical joint 
(U13) where exposed by rock plucking over a considerable height below the top of the grout cap near 
Sta. 13+90 was tested by constructing a vertical riser against the rock face and about the joint (Fig. 
3-18). The loss rate results and associated data for these tests are shown in Table 3-1. 

The tests revealed that water could pass freely through the shallow joints and fractures beneath the 
grout cap at several locations in the vicinity of grout cap Stas. 13+27, 13+30, and 13+90under the 
low gravity heads imposed by the tests. 

Grout Curtain Testing in Foundation Key Trench. 

The watertightness of the grout curtain at depths below the base of the grout cap and at the 
concrete-rock interface was tested by drilling Nx -sized holes at selected locations and inclinations 
along the grout cap centerline after the joint transmissibihty ponding tests had been completed. 

The locations initially designated by the Panel at Stas. 12+65, 13+05 and 13+40* were augmented on 
the basis of the results obtained in testing the original holes and in the joint transmissibihty tests. The 
additional holes were located at Stas. 13+30, 13+77, 14+10, and 14+26. Inclinations were chosen for 
optimum intersection angles with the predominant joint planes. 

The holes were staged downward, usually in two stages of approximately ten-foot lengths. The upper 
stage was tested with the packer set above the concrete-rock interface to include the effect of the 
watertightness of the contact. Applied pressure at the collar of the hole was Umited to 10 psi in all 
tests except in one instance. In that case, upper stage, DH-621, the pressure was raised to 18 psi for 
comparison of loss rates at 10 psi pressure. The rate increased from 7.9 gpm to 13.0 gpm under those 
conditions. 

After pressure water-testing by stages, each hole was subjected to a gravity water test by equalizing 
inflow with outflow as observed by stabilizing the water level at the top of the hole. 

At each hole cluster, usually three holes per cluster, the hole previously tested was filled with thick 
grout after testing to avoid undetected water escape routes by possible hole interconnections when 
testing the next hole. Upon completion of testing of all holes in the cluster, the last hole tested was 
left open for possible future examination. 

Twenty-three holes were drilled and water tested. The results and associated data for these tests are 
shown in Table 3-2. 

The tests revealed that water could pass through the rock structure beneath the grouted portion of 
the key-trench foundation at the depth tested. The larger losses (up to a maximum of 14.1 gpm) 
occurred in the upper stages (10 ft below base of grout cap). Maximum loss observed at 10 psi 
pressure in the second stage (10-20 ft below base of grout cap) was 5 gpm. Return flows were 
observed from joints and fractures downstream from the grout cap. The greater losses occurred from 
the angle holes. 

* Holes were actually drilled at Stas. 12+75, 13+15, and 13+50 respectively 



3-28 




JOINT TRANSMISSIBILITY TESTING 



U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

NDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAIlURt 



3-29 




Fig. 3-18 Vertical brick riser for ponding test at Sta. 13+90 



3-30 





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3-32 



Grout Curtain Testing at Spillway Weir. 

TTie spillway weir cutoff serves as the grout cap beneath the spillway control structure and affords 
continuity of the grout cap beneath the embankments flanking each side of the spillway. During 
construction the rock formation beneath the entire area of the spillway control structure was treated 
extensively by blanket grouting to a depth of 80 ft on a primary hole spacing of 15 ft and closed to 
7-1/2 ft. Tlie grout curtain beneath the spillway weir location was then grouted after the blanket 
grouting was completed. That curtain was slightly modified to avoid interference with the access shaft 
of the auxiliary outlet by placing the center and upstream row of holes on the same alignment as the 
spillway weir cutoff. (See Chapter 9.) 

As part of the Panel's investigation, nine holes were drilled and water tested, three each at the center 
of each spillway bay at dam crest centerline Stas. 10+82, 11+06, and 11+30. One hole in each bay 
was angled to the left, one to the right, and one vertical. The grout curtain in this vicinity was tested 
for watertightness with some modifications suited to the above conditions. The water test holes were 
located just upstream of the center row of curtain grout holes. The water test holes were drilled and 
water tested in three stages of 30 ft each for the vertical holes and three stages of 35 ft each for the 
inclined holes in order that the final stage would extend beyond the depth of the consoUdation 
grouting. 

Water test procedures and pressures were the same as those used for the foundation key trench. Every 
hole was filled with grout after being tested to avoid creating water escape routes by interconnections 
between holes. The results and associated data for these tests are shown in Table 3-3 and Appendix F. 

DH-609 was extended an additional stage to a length of 145 ft to examine the region where the 
consolidation grouting pattern terminated and the curtain grouting pattern continued. 

The tests indicated that the rock formation beneath the spillway control structure as grouted is 
reasonably impermeable within generally accepted standards. 

Grout Curtain Testing Near Right End of Dam. 

The following two sections of this chapter discuss the Panel's investigation of cavities discovered near 
the right end of the dam and of sedimentary deposits that underlie the volcanic rock foundation. 
Three holes, designated DH-650, DH-651 AB, and DH-652, drilled primarily for these two studies, also 
provided an opportunity to test a section of grout curtain lying between Stas. 3+00 and 4+50 (Fig. 
5-5). The results of water pressure tests conducted at these holes within this interval are given in 
Table 3-4, and the drilling logs are contained in Appendix F. 

In DH-650 several large water losses were recorded during the pressure testing. However, a survey of 
the alignment of DH-650 by the USER under observation of Panel staff indicated that the hole had 
been deflected from S19°E to S26°E. The water pressure tests therefore were performed in segments 
of the hole lying upstream of the grout curtain. 

At DH-651 no significant pressure losses were measured. For DH-652 a loss of 12.8 gpm occurred in 
the 301.3-307.7 ft interval, indicating the probable existence of an ungrouted joint. All other losses 
measured at DH-652 were minor. 

The water pressure tests near the right end of the dam did not disclose excessive losses. The reader is 
referred to Chapter 5 for comments concerning rock permeability beyond the right end of the dam. 



3-33 






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3-34 



TABLE 3-4 

TETON DAM 

OCTOBER 1976 

DRILL HOLE WATER TESTS 

NEAR RIGHT END OF DAM 



DH-650 



Location: On dam at Sta. 3+00 approximately 4.7 ft upstream of centerline 

Bearing: S19E (A survey conducted after completion indicated this hole had been deflected to S26°E) 

Dip: 60°below horizontal 

Elevation: 5332 Total Depth: 351.5 ft 



Depth 






Interval* 


GPM 




90.U- 97.7 


32.1 


Hole cased to 90 ft. Lost drilhng 


99.8-104.8 


32.9 


water return at 91.6 ft — never 


103.1-127.4 


28.3 


recovered. 


127.6-162.6 


13.4 




160.6-197.2 


8.4 




197.6-232.6 


0.0 




232.6-267.5 


20.3 




267.5-302.5 


6.1 




301.7-331.7 


2.1 




331.5-351.5 


0.0 





*Footages measured along axes of holes from collar. 

All pressure tests conducted at 10 psi measured at hole collar. 

Geologic logs are contained in Appendix F. 



3-35 



TABLE 3A (cont.) 



DH-651 



Location: On dam axis at Sta. 4+34 

Dip: Vertical 

Elevation: 5332 Total Depth: 622.4 ft 



Depth 




Interval* 


GPM 


80.0-100.0 


0.2 


100.0-120.0 


0.2 


120.0-140.0 


1.0 


140.0-160.0 


0.4 


160.0-180.0 


0.0 


180.0-200.0 


0.0 


200.0-220.0 


0.5 


219.9-239.9 


0.4 


239.9-259.9 


0.5 


259.9-279.9 


0.4 


279.9-299.9 


0.6 


299.9-319.9 


1.3 


319.9-359.9 


0.6 


359.9-399.9 


1.3 


399.9-439.9 


0.2 


432.4-472.4 


0.0 


479.3-519.3 


0.4 


517.7-527.2 


2.2 


518.2-535.9 


1.2 


530.8-543.7 


6.2 


546.1-552.3 


9.3 


546.1-566.1 


2.1 


559.3-581.2 


2.7 


560.0-600.0 


35.0 



Note: Lost 75% drilling water at 47.2 ft 
in Zone 1 fill. 



Concrete/Zone 1 contact at 78.8 ft. 



Packer in grouted zone. 



Packer in casing at 499.7. 
Packer in casing at 539.4. 

Hole drilled to 600 ft, but bottom 
"washed in" to 580 ft. Could not get 
10 psi at 35 gpm. 



*Footages measured along axes of holes from collar. 

All pressure tests conducted at 10 psi measured at hole collar. 

Geologic logs are contained in Appendix F. 



3-36 



TABLE 3-4 (Cont.) 



DH-652 



Location: On dam at Sta. 5+10, 5.5 ft upstream of centerline. 

Bearing: NI8W 

Dip: 60° below horizontal 

Elevation: 5332 Total Depth: 450 ft 



Depth 






Interval* 


GPM 




95.0-130.0 


0.4 


Hole collar is 0.4 ft above dam crest. 


130.0-165.0 


0.4 




165.0-200.0 


1.4 




200.0-235.0 


0.1 


Note: Hole cased to 90 ft, then driven 


235.0-270.0 


0.8 


to 94 ft 


267.9-302.9 


1.2 




301.3-307.7 


12.8 


Lost drilUng water at 303 ft. 


307.7-347.7 


0.8 




347.7-387.7 


0.3 




387.4-427.4 


0.1 




425.0-450.0 


0.5 





*Footages measured along axes of holes from collar. 

All pressure tests conducted to 10 psi measured at hole collar. 

Geologic logs are contained in Appendix F. 



3-37 



Investigation of Cavities Near Right End of Dam. 

Extensive fissures were exposed in the foundation of the dam during excavation for the key trench 
near Stas. 3+55 and 4+34. These are described in Chapter 5. Treatment entailed drilling 8-in.-diam 
holes into the cavities from ground surface through which high-slump concrete was poured, Figs. 5-15 
and 5-16, Sections D-D^ and E-E^. 

Under the guidance of the Panel staff three holes, designated DH-650, DH-651 AB, and DH-652, were 
drilled to explore for possible additional cavities undetected by the original investigation and to check 
the effectiveness of the grouting that had been undertaken. These holes were located near the right 
end of the dam, respectively at Stas. 3+00, 4+34, and 5+11.2 (Fig. 5-5). Holes DH-650 and DH-652 
were inclined 60 degrees below horizontal and oriented to parallel the axis of the dam and to 
intersect the cavities well beneath the key trench invert. DH-651 was located directly above the 
largest cavity and was drilled vertically through the concrete fillihg. 

Core samples obtained from the concrete-rock interface in the cavities disclose a tight bond, 
indicating an effective watertight seal at the contact points penetrated by the drills. This exploration 
revealed that the large cavities at those points drilled and tested were effectively sealed. 

Investigation of Sedimentary Deposits. 

Sedimentary deposits of unknown thickness underhe the volcanic rocks on which the dam rests. The 
possibility of seepage from the reservoir passing beneath the dam through permeable lenses within 
these deposits is considered in Chapter 5. The deep sediments are generally much less permeable than 
the overlying jointed volcanic foundation and consequently are judged a less likely avenue of 
significant leakage. 

The deep vertical hole, designated DH-651, at Sta. 4+34 has been described in connection with the 
exploration of deep cavities near the right end of the dam. An additional purpose of this hole was to 
explore and sample the underlying lake and stream deposits. The drilling of DH-651 was terminated 
in the lake and stream deposits at a depth of 622 ft due to frequent blocking of the Nx-diameter core 
barrel by small rounded pebbles. The drill rig was moved 10 ft to Sta. 4+24 and a new hole, 
designated DH-651 A, was started. Again difficulties necessitated a restart and the rig was shifted to 
drill DH-651 B at Sta. 4+19. To improve core recovery in the deep sediments, the hole was enlarged to 
permit use of a 5-in. core barrel. Notwithstanding the use of the larger barrel, only a limited length of 
core could be obtained. Because of persistent blocking, primary emphasis was shifted from obtaining 
core to determining whether the sediments were comparatively thin beneath the dam or if a thick and 
lenticular section existed. The remainder of the hole to its final depth of 885 ft was drilled largely 
with rock bit cores being taken only when finer grained sediments were encountered. 

An Nx-size core sample of silt with a liquid limit of 33 and a plasticity index of 8 was obtained from 
DH-651 at a depth of 595.3 to 596.2, beneath the water table which was at a depth of 312 ft. Three 
specimens were prepared from this sample and were tested for one-dimensional consolidation by 
Geo-Testing, Inc., San Rafael, California. The results are presented in the form of pressure-void ratio 
curves. The curves, when interpreted according to the customary procedures, indicate 
preconsoUdation loads well below the existing overburden pressure. This results either from a high 
degree of disturbance associated with samphng at such great depths, from an imperfect fit of the stiff 
samples within the consolidation ring on account of difficulty of trimming the specimens, or both. In 
any event, the disturbance has so increased the compressibility of the samples that the results are not 
considered representative of the compressibQity of the in-situ material. 



3-38 



INSPECTION OF AUXILIARY OUTLET WORKS 

The auxiliary outlet works stoplogs were set at the intake on October 2, 1976 and the tunnel was 
drained and inspected by the Panel's on-site representative, accompanied by project personnel. 

The tunnel was again inspected by Panel members, staff, and project personnel during the October 
Panel meeting. No offsets, open cracks, or other evidence of displacement, or evidence of 
overstressing were found. Resurveys on pre-failure bench marks at the gate chamber were made 
without finding any evidence of settlement. 



ROCK JOINT SURVEY 

Under the direction of the Panel, detailed maps of the joints in the right abutment were prepared to 
help determine the probable paths by which water from the reservoir reached the leaks that appeared 
downstream immediately prior to and during the failure, and establishing channels for the transport 
of Zone 1 material. The maps covered the entire area on the right abutment that had been covered 
with the dam embankment, with particular emphasis placed on mapping of the key trench. The base 
for this mapping consisted of plats to a scale of 1 in. = 5 ft covering the area extending 10 ft both 
upstream and downstream of the grout cap and from the spillway to the river channel. Topography 
witliin the trench was defined by contours drawn at 5-ft vertical intervals. Joints 10 ft or longer were 
numbered and mapped on the plats and their attitudes shown by conventional dip and strike symbols. 
Significant observations were recorded, and all notes were cross-referenced to the maps by joint 
numbers. The key trench joint maps were supplemented with two geologic cross sections drawn 
parallel to the axis of the key trench respectively 10 ft upstream and 10 ft downstream of the grout 
cap centerUne. The cross sections were needed to define the numerous comparatively fiat-lying joints 
which could not be shown effectively on the areal maps. The joint map and related geologic sections 
covering the key trench appear in Appendix E. 

Major joints in the right abutment lying outside of the key trench were mapped on aerial photo 
overlays. A total of twelve 24-in. by 24-in. photos was required to cover the abutment to a scale of 1 
in. to 20 ft. Two additional geologic cross sections were prepared in connection with this phase of the 
mapping program. Both these sections were oriented parallel to the centerline of the dam, one 150 ft 
upstream and the other 100 ft downstream of the centerline. These and other data from the joint 
survey are included in Appendix E. 



COMPARISON OF PRE-FAILURE AND POST-FAILURE SURVEYS 

At the Panel's request, post-failure resurvey was made of networks and bench marks established at the 
damsite and in its environs prior to the failure. The results are shown in Tables 5-5 and 5-7 and Fig. 
5-21. No significant horizontal or vertical movement was measured that is pertinent to the cause of 
failure. Results of surveys of monuments on the dam are discussed in Chapter 1 1 . 

MODEL OF THE RIGHT ABUTMENT 

The Panel retained ExhibiGraphics Group, a firm in Salt Lake City, to construct a model of the right 
abutment of Teton Dam to a scale of 1:400. The model has facihtated visualization of principal 
features of the dam and its foundation that relate to the mechanics of failure. It shows drill holes, 
observation wells, structures, foundafion zones, major rock jointing, points of leakage, and the 
whirlpool of June 5, 1976. It has removable elements which show pre-failure and post-failure 
conditions. 



3-39 



CHAPTER 4 
SITE SELECTION AND PROJECT SITE INVESTIGATIONS 

(Panel Charge No. 3) 



EARLY STUDIES 

Consideration was given to possible water resources development on the Teton River in eastern Idaho 
by the Bureau of Reclamation and others as early as 1904. At various times since that time, 
reconnaissance investigations have been made on damsites on the Teton River and its tributaries. 
More detailed investigations have been made at several sites beginning in 1932. Nearly all of the sites 
then studied, however, were on the Upper Teton River or its tributaries. This area is far upstream 
from the present Teton Dam in a considerably different geologic environment. 

None of the early investigations included the Teton (Fremont) site. However, much of the 
information obtained from these studies is helpful in understanding the geologic conditions at the 
Teton site. 

U.S. Geological Survey. 

The U.S. Geological Survey conducted some of the first investigations of the hydrologic and geologic 
features of the Teton River watershed, and during the 1960's participated with the USBR in 
inspections of the canyon near the present damsite. 

U.S. Corps of Engineers. 

The Teton damsite as such was investigated by the Corps of Engineers in July 1957 by the boring of 
two diamond drill holes in the vicinity. One boring 146 ft deep was located in the river channel and 
the other was on the left abutment. The one in the channel showed that the alluvium was about 100 
ft deep, while the abutment hole was in rhyolite for its entire depth of 285 ft. 

U.S. Bureau of Reclamation. 

In 1946 two damsites were investigated by the USBR on Canyon Creek, a tributary of the Lower 
Teton River, and a report titled "Reconnaissance Geologic Report on Canyon Creek Damsites near 
Newdale, Idaho," dated March 1947 was prepared by M.H. Logan and C.J. Okeson. The report 
concluded that storage would be expensive at either site and that seepage losses could be expected 
from the reservoirs. Locations of alternative damsites are shown in Fig. 4-1. 

During August and September 1956, field examinations were made downstream from the Teton site 
at the Newdale site at the mouth of Teton canyon, three miles north of the town of Newdale. An 
earthfill diversion dam about 46 ft high was considered at this point where topography of the area 
was suitable for a diversion canal northward and westward to the North Fork of the Snake River, and 
ultimately onto the Snake Plain. It was believed that fioodflows diverted onto the Snake Plain would 
sink and add to the groundwater supply to the southwest. Tlie damsite was considered worthy of 
further consideration and four diamond drill holes were completed approximately along the 
considered axis. Hole No. 1 was on the left abutment, Nos. 2 and 3 on the valley floor, and No. 4 on 
the right abutment. All but Hole No. 3 penetrated bedrock. Percolation tests were performed in the 
overburden and in the bedrock. 

The subsequent report by M.J. Athearn, titled "Reconnaissance Geologic Report, Teton River 
Diversion, Newdale Damsite," dated March 1957, concluded that the Newdale site was infeasible. 



4-1 




SHOWING ALTERNATIVE SITES 



rj/^ A A L' ^ DEPARTMENT OF THE INTERIOR MAIt Ut iw^rt^ 

rHj. ^- I INDEPENDENT PANEL TO HiVlE» CAUSE OF TETON DAM EAIIURE 



4-2 



The Bureau of Reclamation prepared a reconnaissance geologic report on Teton Dam and Pumping 
Plant site in January 1961 and a special report in March 1962. At that time the dam was planned as 
an earthtlll about 310 ft high above stream level, with a chute spillway on the right abutment. Ample 
quantities of impervious material were estimated to be available within one mile of the damsite in the 
tableland on either side of the canyon. Sand, gravel, and volcanic rock for construction purposes were 
also obtainable nearby. 

In October 1961, representatives of the Teton County Wheatgrowers Association proposed that the 
Bureau of Reclamation consider storage in the vicinity of the mouth of the North Fork Teton River 
as an alternative to the Teton site. They felt that a diversion from a reservoir in this location could 
serve a much greater area of new land. (Fig. 4-1.) 

At that time the USBR cited storage capacity for flood control, ease of diversion to the Enterprise 
and East Teton canals, and the more climatically suited lands of the Rexburg Bench as important 
reasons for placing the storage as far downstream in the Teton Canyon as possible. Upstream from the 
mouth of the North Fork, the gradient of the river steepens considerably and the USBR pointed out 
that the suggested reservoir would therefore have less capacity. 

The Teton River canyon upstream from the Teton site was believed by Bureau geologists to have been 
subjected to some faulting as evidenced by displacement in the relatively young basalt flows that cap 
the canyon rim. Any such faults were difficult or impossible to discern in the rhyolite or welded tuff 
in the canyon walls. Preferably, any damsite would have to be located some distance from these faults 
and in an area where there was competent rock on both sides of the canyon. 

In November 1961 a Bureau geologist looked at five possible sites in the stretch of the river from 
Linderman Draw upstream to the mouth of North Fork. From these observations, it was concluded 
that the best site for a dam in this reach would be about one-half mile upstream from Linderman 
Draw, with the second choice about one-half mile downstream from Spring Hollow. Damsites farther 
upstream would have less capacity because of the steep gradient of the river. Linderman Draw is on 
the south side of the Teton River canyon 9.6 miles upstream from the Teton damsite, and Spring 
Hollow is on the north side about 12 miles upstream. 

Following are excerpts from a report entitled "Teton Basin Project, Lower Teton Division," made by 
the U.S. Bureau of Reclamation, March, 1962: 

. . . Fremont storage is closer to points of use than are the present sources of water 
distributed by the Enterprise and East Teton Canals. By supplying these uses from 
the proposed new storage, an appreciable water economy could be effected by 
savings in canal losses now experienced in the diversions .... 

. . . Fremont Reservoir could be operated on a forecast basis to reduce floodflows 
to the 2,000-cubic-foot-per-second bankfuU capacity for most floods on lower 
Teton River. This regulation would also effect a large reduction of floodflows in 
lower Henrys Fork and a significant reduction of flows in Snake River below 
Henrys Fork. . . . 

. . . The channel capacity in the lower reach of the Teton River is about 2,000 cubic 
feet per second, and general inundation occurs with a discharge of 4,000 cubic feet 
per second. . . . 



4-3 



SELECTION OF TETON DAMSITE 

The reservoir was finally located as far downstream in the Teton River Canyon as elevation, 
topography, and geology would permit in order to minimize the cost of the conveyance system for 
water between the reservoir and the project lands. Alternative upstream sites were rejected because of 
smaller storage capacity and more difficult canal construction. Downstream, the topography was 
judged to be unfavorable. Engineers and geologists from USER offices in both Denver and Boise 
participated in the final site selection. 



CORE DRILLING AT TETON DAMSITE AND RESERVOIR AREA 

About 100 core drill holes were bored at the damsite in the period 1961-1970. Locations of holes are 
shown in Figs. 4-2, 4-3, and 4-4. 

1961-62. 

The USBR started its diamond drilling program at the damsite and reservoir area in July 1961 . Four 
drill holes were completed and two others started in that year. In 1962, driUing started in July and 
ended in November with the completion of the two holes started the previous year and the boring of 
six additional holes. Thus, twelve holes were drilled in the 1961-1962 period - ten near the damsite 
and two in the reservoir area about 9.6 miles upstream from the damsite. The total footage of drill 
holes was 5,107 hn ft. 

1967. 

A total of 36 holes was drilled at the damsite in 1967, as follows: 

Canyon Bottom 6 

River Outlet Works 10 

Power and Pumping Plants 4 

Right Abutment 4 

Left Abutment 7 

Spillway 5 

1968. 

Ten more holes were bored this year, consisting of six for the river outlet works, two on the left 
abutment, and two for the pump canal discharge line. In addition, three holes were drilled in the 
basalt riprap source area two miles downstream from the damsite. 

1969. 

Fourteen holes were completed at the damsite in 1969, comprising four for the river outlet works, 
two on the left abutment, one for the auxiliary outlet works, and seven for the spillway. In addition, 
seven shallow auger holes were bored in the spillway area. 

1970. 

Thirty holes were drilled at the damsite during 1970, including ten to check the pilot grouting results 
(nine on the left abutment and one in the canyon bottom). The other 20 were located as follows: ten 
at the river outlet works, six at the powerplant, three on the right abutment, and one on the pump 
canal discharge line. The holes drilled in 1970 to verify the results of the pilot grouting program are 
discussed later in this chapter. 

Percolation tests, using single mechanical packers, were made in the drill holes in intervals of from 10 
to 60 ft. Most of the sections were tested for 5 minutes each at pressures of 25, 50, or 100 psi. 



44 



M - J.a,4fl a 9 



4 D H -ZI2 <«« 



X 



X 




^ ' 



\ 



X 



\(t Crest of dom 



Outline of dam 



X 



.^■ 



rfp 



X 



X 



SILT . 



%. 



■x^ 



--~^<^^^^ 



SILT 







:r5C.i— - 






SLOPEWASH ■ ' ; ', -< 

X . 



. ' 0,M -105 .» 



D H -104 ^V , \ 










0M.405 • 



X 



\ OH- 407 ^^ 
\ \ 



, ^ Outlet works 



K 



\ 



\ c 



Mo1c^ Line Sheet 2 o1 2 



EXPLANATION 



Motcn Line Sneet 2 of 2 



U\-TCO STATtS 

oef^^mfftT Of rue M'enio^ 

BUMAU V ItCCLAMATlOU 



I 1 SII.T - LooiuJy lo moJ^rdtrly coBp«tl«d windblown silt on the uplaniJsi 

L , I '^Jlly touerh iliv slopni.tah on Ihe valley clde*. 

• SluPKn'ASH - I IfhCly to nodaracelv conpacted, gruvtl- to boulder-sllc , 

1 I .injii.ljr -ind pl.iiy frdgm^nti oi rhvolltc In j allty soil matrix. 

I I lAUS - A.unul-uluo ^1 luo.t-. piji, jnd anguUr (r.iKBcnt* al rhyullt. 

I I At.U'VllM - Str.,.r^dep..,Hcd .lit. *.,nd . gr-vel . jrid s«™^ cobbler. 



□RHYOLITE {OB WEiDED TUFF) - Light brown to purple-gray. liBhlly 
viodrrately veauulat, potphyrltlc, lightly to locally hlj 



:ly to 
, potphyrltlc, lightly to locally highly 
trutjtuTed and Jointed, relatively lliiht weight. 



• DH-lOl UtAMOND DKII.L HOLE - vertUal 
*~-^ DH-20I DIA.-WSD DRILL HOLE - angle 

• AP-Sl PUWFH AlCER HOLE 

^^^* ^i^^ Ai-PHOXlMAn BOHSDAPV 6ETVEEK GEOLOGIC USIIS 



100 100 



TerON OAMSITE 
AREAL GEOLOGY 



Revised Moy '97' 



549- 125- 266 



CT/^ yl O ^^ DiPARTMENT OF THE INTERIOR — STATE OF IDAHO 

rlLj. ^~Z. INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



4-5 



Match Line Street I ot 2 



Molch L'"e Sfeei i o) 2 



i 




549 125 267 



CJf-^ A O U S OlfAlTMENT OF THE INTEKlOll STATE OF IDAHO 

rlVj. ^ v^ INOfPENDINT PANEl TO REVIEW CAUSE OF TETON DAM PAItUU 




CD 



EXPUNATIOH 

SILT - Windblown alli on ihc upland*, locally ic 
on [he viUcy aide*. 

SLOPEUASH - Llihily (o nodaraccly canpacted. gti 



1 • ' » I ALUIVIUH - Scream-dapoalted silt. sand, gravel, and ui^me 

1^ ff I USALI - Iniracanyon bacalc riow, dark purple to black, < 
I IT ) slightly vesicular, fairlv frenh, hard, hfhly frt 



Light brown to purplc-|ray, danai co 
porphyrltlc. lightly to locally hlthly 
and jointed, relatively light nelshl. The upprr 



I 1, T I RKYOLITE (OB WELDED TUFF 
I iL I Boderately vealcu 



viireo srjres 
otPU*TM€'iT Of THE mnnioi^ 

BU1CAV or DEZLtltaTION 



TETON OAMSITE 
GEOLOG/C CaOSS SECTION ALONG CUTOFF TRENCH 






DIAMOHD DRILL HOLE - 



Revised May 1971 



549-125-274 



FIG. 4-4. 



U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Percolation tests showed many sections of rliyolite to be relatively impermeable, but individual cracks 
or joints were capable of transmitting large quantities of water - over 100 gpm. 

Extended pump-in tests were made in five of the drill holes on the right abutment. These were drilled 
on a dip of 60° (30° from vertical). (Fig. 4-3). (The following depth figures refer to vertical 
measurements.) In DH-301 , water pumped into the hole at a rate of 290 gpm raised the water level in 
the hole 159 ft, and water pumped in at a rate of 460 gpm raised the water level 171 ft. In DH-302, a 
pump-in test for 19 hours at a rate of 450 gpm raised the water level 57 ft. In DH-303, water pumped 
into the hole for two weeks at a rate of 450 gpm raised the water level 185 ft. In DH-202, pumping at 
a rate of 165 gpm maintained the water level at the collar of the hole. In DH-203, water pumped in at 
a rate of 400 gpm raised the water level 200 ft (from the bottom of the hole, which was dry). During 
these extended pump-in tests, no water was found to leak from the abutment, although there were 
rises in the water levels in some of the surrounding holes on the right abutment. Chapter 5 contains 
more information on water testing of drill holes. 

The Bureau's bore-hole television camera was used to examine some of the drill holes on the right 
abutment and some of the grout-check holes on the left abutment. The camera observations showed 
many cracks and joints of apparent random orientation. The widest crack measured was 1.7 in.; most 
cracks were 0.1 to 0.5 in. wide. 



OTHER EXPLORATION 

In the period 1961-70, in addition to the core drilling programs, geological mapping of the joints 
appearing in outcrops in the canyon walls was carried out. In 1967 a magnetometer survey was made 
along the line of the proposed cutoff trench, to determine if any large cavities were present in the left 
abutment. The results of this survey were reported to be inconclusive. 



RESERVOIR LEAKAGE STUDIES 

The estimation of reservoir leakage was a major consideration in all the investigations leading to the 
final design. The bulk of the core drilling and permeability testing for this purpose was done in direct 
coordination with the dam foundation investigations. 

The Teton River normally loses water to the surrounding ground in the reach of the canyon where 
the dam is located. Although the water table has a regional gradient toward the southwest, locally in 
the vicinity of the damsite it slopes 5-1/2 ft per mile to the northwest. In addition to the regional 
water table, there is a well defined perched water table which, prior to reservoir fiUing, was 100 ft or 
more above the regional water table. 

In a report titled "Ground-water Aspects of the Lower Henrys Fork Region, Idaho," 1967, by E.G. 
Crosthwaite, M.J. Mundorff, and E.H. Walker of the U.S. Geological Survey, estimated seepage losses 
from the proposed Teton Reservoir were 49 cfs (rounded to 50 cfs, or 36,000 acre-ft per year). This 
figure was offered as only "an order of magnitude," and was compared with an estimate of 8 to 42 
cfs made by Okeson and Magleby of the Bureau of Reclamation in 1963. 

The Independent Panel regards reservoir loss rates as primarily of economic importance and not 
related directly to the safety of the dam. 



4-8 



ROCK CORE TESTING 

In 1970 the USER laboratories in Denver made various tests of Nx and Bx core specimens of 
foundation rock selected from the Teton damsite. These tests were conducted to determine the 
physical and mechanical properties. The cores were taken from holes DH-1, DH-D, DH-L, DH-S6, 
DH-SIO, and DH-108. The test results are summarized in Table 4-1 . 

The properties of each of the rock types tested — basalt and rhyolite — were found to be fairly 
uniform in their relationships, with the basalt having high elasticity and strength (averaging about 9.4 
million psi and 13,600 psi, respectively) and the rhyoUte having lower corresponding values (averaging 
1.6 milUon psi and 5,960 psi, respectively). 

Tests of Nx rock cores from holes DH-402 and DH403 at the site of the Teton Powerplant were 
made in 1970. They showed comparable average properties of basalt and rhyolite, namely 7.1 million 
psi and 13,000 psi versus 2.3 million psi and 6,860 psi, respectively. 

The core specimens from these drill holes were subjected to petrographic examination at the Denver 
laboratory. 



PILOT GROUTING PROGRAM 

To assist in appraising the feasibiUty of the Teton damsite, the Bureau of Reclamation conducted a 
pilot grouting program on the left abutment of the Teton damsite in 1969. This program consisted of 
grouting and pressure testing 23 holes, including previously drilled exploratory holes as well as new 
curtain and blanket grouting holes. Curtain holes generally are part of an in-line series of relatively 
deep borings that are grouted with the objective of influencing seepage patterns. Blanket holes are 
usually shallower borings arranged in an areal pattern and grouted with the intent of strengthening 
the foundation. 

There were significant grout takes in several holes. The grout injection in two exploratory drill holes 
alone exceeded the originally estimated take for pressure grouting in the entire program. Final 
quantities injected into these two holes were 15,720 sacks of cement and 17,787 cu ft of sand. In the 
blanket grouting effort the largest grout take in any hole was 1 ,626 sacks of cement. 

In addition to other results, the basalt interflow was shown to be very hard but intensely jointed. The 
gravel layer between the basalt and the rhyohte accepted grout. 

The curtain holes showed exceptionally high takes at depths less than 70 ft and considerable grout 
travel, up to 300 ft downstream. Subsequently, after thickening the grout using cement-sand mixes 
and calcium chloride, the leaks tended to seal. Due to a persistent surface leak located 300 ft 
downstream of Sta. 33+00, stages from 30 to 70 ft could not be completed to refusal. Grouting of 
curtain holes at depths less than 30 ft was abandoned, since the key trench was expected to be at 
least that deep. 

In 1970 ten holes were drilled in the area of the pilot grouting to check the effectiveness of that 
grouting. Most of the water tests took very Httle water. Geologic logs were prepared showing the 
detailed water loss information, description of joints, and occurrences of grout found in the core. The 
drill cores contained numerous seams of grout ranging in width from about 1/50 of an in. to 4 in. The 
grout was generally well bonded to the rock. The USER bore hole television camera was used in some 
of these drill holes to observe and measure the thickness and attitude of grouted cracks. Much of 



4-9 



Avg. 



TABLE 4-1 
SUMMARY OF FOUNDATION ROCK PROPERTIES 

Teton Damsite - Teton Basin Project 
Elasi- Compressive 



Specimen No. 


Rock 


ticity* 


Poisson's 


strength. 


Absorption 


Specific 


(DH-Depth) 


type 

Basalt 


10^ psi 


ratio 


psi 


%by wt 
0.28 


gravity 


SI 0-5 1.7 


14,500 


2.83 


SlO-55.3 


Basalt 


9.4 


— 


15,800 


0.20 


2.83 


SlO-55.5 


Basalt 


— 


— 


10,400 


0.27 


2.86 


108-50.7 


Basalt 


— 


— 


— 


0.30 


2.80 



9.4 



13,600 



0.26 



2.83 



1-318.1 


Rhyolite 


- 


- 


6,990 


4.48 


2.28 


1-319.0 


Rhyolite 


1.7 


0.10 


7,260 


3.87 


2.34 


1-320.9 


Rhyolite 


2.1 


0.13 


6,400 


3.92 


2.30 


1-321.6 


Rhyolite 


1.4 


0.12 


6,050 


4.07 


2.29 


D-29.7 


Rhyolite 


1.5 


0.12 


5,040 


3.82 


2.38 


D-31.9 


Rhyolite 


1.5 


0.13 


3,640 


4.77 


2.36 


D-32.3 


Rhyolite 


1.7 


0.17 


3,780 


4.42 


2.37 


D-34.1 


RhyoUte 


1.4 


0.11 


4,160 


4.33 


2.37 


L-249.0 


Rhyolite 


1.1 


0.13 


6,000 


5.04 


2.24 


L-249.9 


Rhyolite 


1.6 


0.15 


7,400 


4.84 


2.25 


L-251.7 


RhyoUte 


1.6 


0.17 


6,820 


4.34 


2.27 


1.252.6 


RhyoUte 


1.7 


0.16 


7,230 


4.32 


2.27 


S6-262.8 


RhyoUte '■ 


**0.5 


**0.10 


6,880 


3.42 


2.40 


S6-265.3 


RhyoUte 


1.9 


0.25 


6,460 


3.48 


2.39 


S6-265.7 


RhyoUte '■ 


**0.7 


**0.20 


5,600 


3.83 


2.38 


S6-266.6 


RhyoUte 


1.2 


0.13 


6,060 


3.61 


2.39 



Avg. 



1.6 



0.15 



5,960 



4.16 



2.33 



*Secant modulus of elasticity (E ) at 1000 psi stress, first cycle. 
**Ej and \i at 500 and 700 psi stress for S6-262.8 and S6-265.7, 
respectively; these omitted from averages. 



Note: Specimens with no E values were unsuitable for the test; 
DH-108 specimens broke in preparation. 



4-10 



the grout in the upper 50 to 70 ft of the holes was found in cracks and openings about parallel to the 
nearly horizontal flow planes in the rhyolite. 

From review of the drill logs and the pilot grouting data, it was concluded by the designers that it 
would be more economical to remove the upper 70 ft of the foundation than to conduct the grouting 
necessary to seal this horizon. Accordingly, a foundation key trench about 70 ft deep was provided 
above El. 5100 in both abutments seeking to intercept the more open-jointed rock and to reach a 
groutable horizon in the more sound rock. 



COMMENTS 

The final location of the Teton Dam was largely based upon factors not directly related to the 
foundation conditions at the site nor the type of materials avaUable for the construction of the dam. 
The location was selected primarily because of the increased reservoir volume, as compared with 
upstream sites, and the lower costs of constructing the conveyance system from the reservoir to the 
project lands. 

The investigations of the geology in the region of the damsite and the foundation conditions at the 
site were sufficiently detaUed to indicate to the designers that the selected site was as favorable for 
the construction of a dam as any of the other sites studied. 

The foundation exploratory drilling, geologic mapping, pumping tests, groundwater observations, and 
pilot grouting tests which had been completed prior to the adoption of the final design for Teton 
Dam were sufficiently detailed to provide the designers with adequate knowledge of the site 
conditions. The jointed character of the foundation rock, with the large water-carrying capacity of 
the joint system, was well documented from the results of the core borings, water testing of drill 
holes, groundwater table studies and the pilot grouting tests. The presence of the basalt tlow in the 
canyon at the base of the left abutment was also well defined. Therefore, it can be concluded that the 
preliminary investigations had disclosed the major characteristics of the foundation and abutments 
needed to develop a satisfactory design. 



4-11 



CHAPTER 5 
GEOLOGY 

(Panel Charge No. 1) 



REGIONAL GEOLOGY 

Teton Dam is located in a steep-walled canyon incised by Teton River into the Rexburg Bench, a 
volcanic plateau draining into the Snake River Plain. The exposed rocks are almost entirely of 
volcanic origin (Fig. 5-1), but these are covered on the high lands flanking the canyon by a layer of 
aeolian sediments up to 50 ft tliick. 

The volcanic rocks consist of quaternary basaltic cones and flows underlain and interfingered by 
rhyolite. Rhyolite accumulations include welded ash-flow sheets, lava flows, airfali and waterlaid 
tuffs, and tuffaceous sediments. 

Deep water wells have encountered lenses of sediments of late-Tertiary age enclosed within the 
volcanic units (Haskett, Gordon 1., 1972). They are known locally as "lakebed" or "lake and stream" 
sediments. Lenses range from a few thousand square feet to several square miles in areal extent and 
from a few feet to over 900 feet in thickness. These deposits are believed to have accumulated within 
intermittent lakes created where volcanic flows dammed ancient stream courses. They were buried to 
their present depths by subsequent volcanic outpourings. 

The relationships of the geologic units are shown on Geologic Sections, Figs. 5-2 and 5-3. 

Regional Tectonic Activity. 

The region surrounding Teton Dam is one of volcanic and tectonic instability. Steep escarpments 
along major fault zones and records of the occurrence of earthquakes within liistoric time attest to 
continuing seismic activity. However, as discussed in Chapter 6, the Panel's investigation disclosed no 
evidence that earthquakes contributed in any way to the failure of the dam. 

Regional Groundwater Geology. 

An extensive network of joints has rendered the otherwise dense volcanic rock of the Rexburg Bench 
into a liighly permeable aquifer. An indication of the magnitude of its permeability is found in the 
performance of wells which tap it. For example, a well located about three quarters of a mile 
downstream from the mouth of Teton Canyon, VA mile from Teton Dam, reportedly produces 1,800 
gpm with a water level drawdown of only two feet. 

Groundwater replenishment is achieved by precipitation on the surface and percolation from streams. 
Streamflow measurements by the Bureau of Reclamation along the course of Teton River in August 
and October 1961 indicated that the stream lost from 25 to 50 cfs through percolation downstream 
from the site of the dam, but that streamflow losses in the upstream reaches were negligible. 

Groundwater also occurs within the buried lake and stream deposits which contain sand and gravel 
lenses. However, these deposits are generally regarded as poor aquifers in comparison to the jointed 
volcanic rocks. In some areas they form the base upon which perched water bodies accumulate. Local 
well drillers are known to terminate drilling when these sediments are encountered because of the 
lower probability of developing a satisfactory well within them. 



5-1 



R40E 



Fault inferred by 

US Geological Survey 

from photos- 

42E 



Fault Inferreii b)/ ; , 

U.S. de.ologL:aL.Sju4«W l,. 

from sections A-A'j 
B-B' 







ALLUVIUM -Unconsolidated sedimentory deposits in nver 
valleys Predominontly sand and grovel, locally interbedded 
with basalt flows Thickness ronges from a few to over 
300 feet. Yields small to large quantities of water, 

BASALTIC CONES -Accumulation of volconic debris^ flow 
breccia, cinders, ond thin flows buill up into cones, 
BASALT FLOWS -Aphonific to porphyritic bosoU including 
flows of the Snake River group ond flows from local vents. 
iniertlow zones of scoriaceous ond rubbly material 
normolly yield lorge quonlities o( water. 
RHYOLITE - Silicic volconic rocks including flows and 
pyroclastics with oil degrees of induration Age ranges 
from late Tertiary into Pleistocene. Yields small lo lorge 
Quantities of water. 

PRE-TERTIARY-Ufidifferentioted rnonne sediments 

consisting of ihm bedded sondsione. limestone, ond shale. 

Not reoched by Rexburg Bench wells, 

CLOSED DEPRESSION OF UNKNOWN ORIGIN. 

DIP-STRIKE OR DIRECTION OF DIP COMPONENT. 

FAULT. MAPPED. INFERRED OR PROJECTED. 

LOCATION OF GEOLOGICAL CROSS SECTION. 

USBR EXPLORATORY HOLE OR OBSERVATION WELL. 

PRIVATE IRRIGATION WELL. 

ABANDONED OR SUSPENDED IRRIGATION WELL. 

SELECTED PRIVATE WELL. 



REFERENCE DATA 

US. Bl'REAl OF RECLAMATION 

DWG NO. 549-100-50 



FIG. 5-1. 



SURFACE GEOLOGY 
REXBURG BENCH 



(J S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAISE OF TETON DAM fAILI'HF 



5-2 



WHITE OWL BUTTE 



6/41-27 dda^ 
LONG HOLLOW -X 




SECTION B-B' 
CITY OF TETON TO WHITE OWL BUTTE 



HIGHWAY 20 
7/41-36dd2- 
TETON RIVER- 
FAULT INFERRED 
BY U. S. G. S. 

7/41-24dc- 
7/41-24ac- 
7/4 1-1 3 c a- 



CANYON CREEK CANAL, 

6/42-7dbd- 





A^gg^otf ^ . ^-V 



Tv 



rREGIONAL 
i WATER TABLE 



702' 



Tv 



980' 
■OLD RHYOLITE SURFACE 



SECTION A-A' 
VICINITY OF TETON DAMSITE 



5800 



5600 



5400 



5200 



5000 



4800 



4600 



4400 



4200 



Qal 



QIa 



6200 



6000 



5800 



5600 



5400 



5200 



5000 



4800 



4600 



4400 



200 



LEGEND 

ALLUVIUM 

BASALT FLOWS 

RHYOLITE 

LAKE AND STREAM 
DEPOSITS 

WATER BEARING, 
REPORTED 

PERCHED WATER TABLE, 
REPORTED DURING 
DRILLING 

WATER LEVEL, MEASURED 
OR REPORTED 

6/41-36cdd-DESIGNATES 
SE V4 SE V4 SW V4 Sec. 36 
T6NR41E 



b 


a 


b|a 


d 



LOCATIONS SHOWN IN FIG. 5-1. 
REFERENCE DATA: 

U. S. BUREAU OF RECLAMATION 
DWG. NO. 549-100-54 



GEOLOGIC CROSS SECTIONS 



REXBURG BENCH 



FIG. 5-2. 



U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



5-3 



7/4 2-36 aac^ 
CANYON CREEK-^ 
6/42-2 cab-. 



6/40-35bdd 
5/40-3 da~^ 
5/40-3 db 




3800 



3600 



SECTION C-C 



LEGEND 



LOCATIONS SHOWN IN FIG 5-1. 
REFERENCE DATA: 
U S. BUREAU OF RECLAMATION 
DWG. NO. 549-100-55 



Qal ALLUVIUM 



I Qb I BASALT FLOWS 

I Tv I RHYOLITE 

I QIa I LAKE AND STREAM DEPOSITS 

• WATER BEARING, REPORTED 

^ WATER LEVEL. REPORTED OR MEASURED 



GEOLOGIC CROSS SECTION 
REXBURG BENCH 



y,.--, r- O U S DSPARTMINT OF THE INTE«rO« ST«TE Of IDAHO 

rHj. 0~0 JNDEPENDENT PANEl TO BIVIEW CAUSE OF TETON DAM FAILU«1 



5-4 



GEOLOGY OF DAM AND RESERVOIR SITE 

The walls of Teton Canyon at the damsite consist of late-Tertiary rhyolite welded tuff which has 
undergone various degrees of welding. It is probably part of the Huckleberry Ridge Member of the 
Yellowstone Group that was emplaced approximately 2 million years ago as determined from 
radiometric measurements (Christiansen and Blank, 1972). Alluvium has been deposited in the 
channel of the canyon to a depth of about 100 ft, and the high lands near the ends of the dam are 
mantled up to 30 ft with aeolian sediments. The relationship between these formations and those that 
underlie the ash-flow deposits are shown diagrammatically on Fig. 5-4. 

Rhyolite (Welded Ash-Flow Tuff). 

Rhyolite is a term used for all silicic lavas in the older literature and reports. More recently the air fall 
nature of these volcanic rocks has been recognized and thus they may be classified as welded ash-flow 
tuffs. Welded ash-fiow tuff comprises most of the foundation for Teton Dam. Exposures at the site 
and cores from drill holes display varying degrees of welding. The rock is light weight, has a 
porphyritic texture with coarse-grained feldspar phenocrysts within a fine-to-medium-grained tuff 
matrix, and has variable jointing. Upstream from the dam axis, the tuff is divisible into three units. 
This division is based largely on variations in intensity and character in rock jointing and is described 
more fully under the subsequent paragraph on that subject. 

Physical and mechanical properties of the welded tuff from Teton damsite as determined by 
laboratory tests on selected drill core specimens are given in Table 4-1 . 

The contact between the ash-flow tuff and underlying sedimentary deposits as partially established 
from the logs of foundation drilling appears to be an erosion surface of moderate relief (Fig. 5-5). 
Possibly, an ancient deep valley existed in this area with its channel about 400 ft below the elevation 
of the present streambed. 

Lake and Stream Sediments. 

Lake and stream sediments that interfinger the volcanic rocks consist of a variety of sedimentary 
types described in the logs of exploratory drill holes as tuffaceous conglomerate, agglomerate, 
sandstone, tuff, lapilli tuff, ash, tuffaceous sediment, volcanic ash, sand and gravel, boulders and 
cobbles, and interlayered silt and gravel (Table 5-1). 

Water pressure tests were conducted within the lake and stream deposits in a few deep drill holes. 
Table 5-2 summarizes this information and sets forth all significant water losses that were recorded. 
The results suggest that some zones witliin the lake and stream deposits are significantly permeable. 

Because of the lenticular structure of the lake and stream sediments, it has not been possible to 
correlate sand, gravel, or other apparently permeable members from one drill hole to another. 
However, behavior of groundwater levels in hole DH-506 suggests that Teton Reservoir was connected 
hydraulically with the lake and stream deposits. 

DH-506 is located on the right abutment on the projection of the axis of the dam about 500 ft 
beyond the end of the embankment (Figs. 5-5 and 5-6). It was drilled to a depth of 644.5 ft, the 
bottom 53.5 ft penetrating lake and stream deposits. A steel pipe piezometer was installed to a depth 
of 643.7 ft. A cement seal was emplaced between 576.4 and 566.5 ft to isolate the piezometer from 
shallower groundwater bodies. 



5-5 



STA .344-00 STA.30 + 00 

r^ — h 



ST A. 2 0+00 



STA 10 + 00 



STA. 2+20 



EL.5300 



EL. 5200 




EL 5100 WELDED ASH-FLOW TUFF 

(RHYOLITE 



EL. 5000 



EL. 4900 



EL 4800 LAKE AND STREAM DEPOSITS 



EL 4700 



AUXILIARY OUTtET 
WORKS TUNNEL 



LAKE AND STREAM DEPOSITS 



EL. 4600 



REFERENCE DATA: 

ABERLE, PETER P . AUGUST 1976 



PROFILE OF TETON DAM ALONG GROUT CAP 



FIG. 5-4. 



L S DEPARTMENT OF THE INTERIOR STATE Of IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



5-6 



<^ 0> u> faTn 

f^ cy CVJ JnT - 

iDtD_ Ed w5!2 

~—(D m' ^,U3U) I" 8" 

-TO w CM S *£!?' ' 



....,,, \ 









,.,.,.,. ^^ ^ 



-^=^ 



if'" 




-~-&#>- 



EXPLANATION 




DH600 SERIES HOLES ARE 
POST-FAILURE. 



REFERENCF DATA 

US BUREAU OF RECLAMATION 

DWG NO GEOL -T. -022 



ELEV 4447 



TYPICAL CROSS SECTION 



GEOLOGIC SECTION SHOWING PRE- AND 
POST- CONSTRUCTION EXPLORATION 

FIG. 5 - 5 . ,„„i„'r,r '?;:;. °o v"'.,;:'"™ v, ';tv„°',.T,z.., 



TABLE 5-1 

TYPICAL DESCRIPTIONS OF LAKE AND STREAM SEDIMENTS 

UNDERLYING THE VICINITY OF TETON DAM 

As Abstracted From U.S. Bureau of Reclamation Drill Hole Logs 



Drill 


Vertical 


Core 


Hole No. 


Depth Interval 


Recovery 




(feet) 


(%) 


1 


440443 


100 


(Fig. 4-4) 


443-454 


100 




454-456 


22-100 




456-467 


75-100 




467-477 


9 




477-482 


33 


5 


442-448 


15 


(Fig. 5-5) 


448-491 


10-78 


9 


276-288 


3 


(Fig. 5-6) 


288-291 


? 




291-299 


58 




299-309 







309-314 







314-324 







324-334 


22-38 




334-335 


38 




335-347 


95 




347-351 







351-359 


22 




359-377 







377-378 


40 




378-379 







379-384 


45 



Description 



Tuff (soft, friable) 

Tuff (quite hard and dense) 

Siltstone (quite well consolidated) 

Siltstone or sUt (quite soft) 

Boulders and cobbles 

Sand and gravel 

Gray /white tuff (very soft) 
Tuffaceous conglomerate 

Tuff (dense, fine grained) 

Tuff (well consolidated) 

Silt (nonplastic, compacted, quite dense) 

Gravel (rounded) 

Not described 

Gravel 

Silt (compacted) 

Silt (soft) 

Silt (lightly compacted) 

Gravel 

Silt (lightly compacted) 

Gravel 

Silty sand (75% fine sand, 25% fines) 

Gravel 

Silt and silty clay 



102 
(Fig. 4-4) 



501 
(Fig. 5-5) 



276-290 

290-302 
302-326 
326-335 
335-413 
413421 

421-506 

539-549 

549-556 



100 

100 

100 

50 





36 







Tuff (or tuffaceous sandstone). Firm, 
cannot be broken with hands. 

Sandstone (tuffaceous, firm) 

Siltstone (or tuff, fairly hard) 

Lapilli tuff (fairly hard) 

Sand and gravel 

Sandy clay (80% medium plastic fines, 
20% fine sand) 

Claystone (fairly hard, quite brittle) 

Lapilli in a medium to well-consolidated 

fine tuff matrix 
Gravel (particles W to 2" across) 



5-8 







TABLE 5-1 (cont 


•) 


Drill 


Vertical 


Core 




Hole No. 


Depth Interval 
(feet) 


Recovery 

(%) 


Description 






503 


216-226 


30 


Ash (crumbles in fingers) 


(Fig. 5-6) 


226-296 


96 


Tuffaceous sediment 




296-306 


20 


Sand and gravel 




306-344 





Interpreted to be gravel with layers 
of sand and/or silt 


504A 


507-510 


100 


Volcanic ash (fairly well consolidated) 


(Fig. 5-5) 


510-517 


99 


Lapilli tuff (medium to well consolidated) 


506 


591-645 


72-100 


Tuff and lapilli tuff (medium to well 


(Fig. 5-5) 






consolidated, jointed) 


507 


343-351 


84 


Ash (crumbles with finger pressure) 


(Fig. 5-6) 


351-365 


90 


Tuffaceous sediment (scratches with 



365-372 



hard fmgernaU pressure) 
Sand and gravel 



5-9 



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5-11 



The hydrograph from the water stage recorder at drill hole 506 shows a fairly close correlation 
between groundwater levels in the lake and stream deposits, with other observation wells located in 
the right abutment, and with reservoir stage (Fig. 5-7). Thus, these observations would suggest a fairly 
extensive permeable zone to exist within the lake and stream deposit in the right abutment area. 
However, the effectiveness of DH-506 as a piezometer within the lake and stream deposits is subject 
to question. The log of the hole shows that the cement seal was placed in rock containing joints 
stained by moving water and that water pressure tests conducted within this interval showed 
significant losses as follows: 

Depth 
Interval Tested 



Pressure 


Length of Test 
(min) 


Water Loss 


(psi) 


(gpm) 


50 


5 


8.9 


100 


5 


13.6 


50 


5 


4.9 


100 


5 


6.4 



(ft) 

565-570 
570-575 



Thus it is possible that the cement seal is bypassed by open joints in the surrounding rock and 
therefore that the water levels and hydrographs recorded for this piezometer are not the true levels 
within the lake and stream deposits. 

Basalt. 

Basalt was encountered beneath the alluvium near the left wall of the canyon during site exploration 
and was subsequently exposed when the channel section for the dam was excavated (Fig. 5-4). Basalt 
was also exposed in the foundation for the power and pumping plant and in outcrops in the spillway 
stilling basin. Its source is believed to be an unidentified vent near the mouth of Teton Canyon, 
whence it flowed upstream over the thin veneer of alluvium covering the floor of the gorge to an 
elevation of about 5005 ft. The river eroded the basalt from the right side of canyon but left it on the 
left side, where it was subsequently buried with alluvial debris. 

Joints. 

Joints are prevalent in the volcanic rocks. They are exposed prominently in the walls of the canyon 
and are evident in the drill cores obtained during site exploration. In the right abutment, they are 
largely either steeply dipping or near horizontal in attitude. Flat-lying joints prevail upstream of the 
dam axis and vertical joints dominate downstream (Fig. 5-8). 

Joints in the reservoir walls are part of an extensive interconnecting system that transmits and stores 
groundwater beneath the Rexburg Bench. Regionally, they render the volcanic rock highly 
permeable, providing multidirectional flow paths. 

The three separate units of welded ash-flow tuff identified in the right wall of the canyon upstream of 
the dam are apparent in Fig. 5-9. They are described as follows: 

Unit 1 , the uppermost layer, consists of lenticular and tabular plates mainly 2 to 6 in. thick, but some 
are up to 18 in. thick (Fig. 5-10). The plates are nearly horizontal and parallel the joint foliation in 
the rock. Open partings between plates are % in. to 2 in. wide. Some are coated with calcite layers up 
to Va in. thick. Caliche and silt fill some of these openings in the upper 5 to 6 ft of the unit. High 
angle joints are scarce. 



5-12 




DH302 
• 14-DH 5 
21-DH 501 



10A&B-DH 506 



• 9-DH 6 



8* 



7-"C' 



REFERENCE DATA: 

U. S. BUREAU OF RECLAMATION 

DWG. NO. 549-100-116 



500 1000 

SCALE IN FEET 

LEGE N D 

• CURRENTLY OBSERVED 

O DESTROYED DURING CONSTRUCTION * 

NOTE 

FOR A CROSS INDEX OF WELL NUMBERING 
SYSTEMS, SEE TABLE 5-3. 

'EXCEPT DH507 WHICH WAS DESTROYED 
DURING THE FLOOD FOLLOWING DAM FAILURE. 



EXPLORATION AND 

OBSERVATION WELLS 

IN VICINITY OF DAM 



FIG. 5-6. 



V S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



5-13 



5400 




4900 



I JANUARY 



JULY 



1976 



SEE FIG 5-6 FOR LOCATIONS D.H. 506 EQUIPPED 
WITH CONTINUOUS WATER STAGE RECORDER. 
ELEVATIONS SHOWN FOR THE OTHER WELLS 
ON JUNE 5, 1976 WERE EXTRAPOLATED FROM 
JUNE 1 WATER LEVEL MEASUREMENTS 



WATER LEVEL ELEVATIONS 
IN OBSERVATION WELLS 



FIG. 5-7. 



U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



5-14 




Fig. 5-8 Showing prevalent horizontal joints upstream and dominating 

vertical joint system downstream of dam in right wall of 
canyon (post-failure photo) 




r^» '^ 



■A'-f"y 







Fig. 5-9 The ash-flow tuff upstream of dam axis is divided into three units 

(post-failure photo) 



5-15 



i'' ....^.r'K ; i .' ■ .. . < 'i'./^' ->'-^' -!•■' 










Fig. 5-10 Slab-like structure in Unit 1 of ash-flow tuff exposed in rim of 

downstream wall of keyway in right abutment, (post- failure 
photo) 






UNIT 2 



Fig. 5-1 1 Joint pattern in Unit 2 of ash-flow tuff, right 

wall of canyon upstream from key trench, 
(post-failure photo) 



5-16 



Unit 2, the inteimediate layer, is gradational witii the overlying Unit 1 , the contact occurring at about 
El. 5250 ft. Jointing is moderate to intense. Horizontal partings prevail, but east-west trending high 
angle joints spaced at 10 to 20 ft intervals also are prominent (Fig. 5-11). Minor random joints are 
generally spaced 1 to 2 ft apart. Most joints are open from 1/8 in. to 1 in. and are coated or filled 
with calcium carbonate. Flow lineations due to flattened lapilli fragments and flattened vugs are near 
vertical. Contact with the underlying unit is marked by a breccia zone 6 in. to 2 ft thick consisting of 
rock fragments cemented with calcium carbonate. The contact zone is located at about El. 5185 ft. It 
is nearly flat lying, but in some places it is a wavy, irregular surface with openings ranging from 1/4 to 
3 in. 

Unit 3 forms bold outcrops in the lower abutment from El. 5060 to 5185 ft (Fig. 5-9). Near vertical 
joints are prominent and can be traced for over 100 ft. The dominant joint trend is northwesterly 
with lesser northeasterly trends. Spacing is commonly 5 to 10 ft, with openings ranging from 1/4 in. 
to as much as 3 in. Most joints are stained with iron and manganese oxides. Separation along the 
dominating low angle joint planes has led to the development of prominent benches along the canyon 
wall. 

As previously mentioned. Unit 2 is not recognizable in the right wall of the canyon downstream of 
the dam. Here extensive, steeply dipping joints prevail (Fig. 5-12). The transition from predominantly 
near-horizontal to near-vertical jointing occurs near the axis of the dam (Fig. 5-13). 

DH-505, located at the extreme right end of the dam (Fig. 5-5), is slanted into the abutment at an 
angle of 30 degrees below horizontal and is oriented N20W along the projected bearing of the axis of 
the dam. It encountered several open joints. No grout was detected in the drill core; notwithstanding, 
the hole had been completed on November 20, 1974 subsequent to emplacement of the grout 
curtain. During drilling, all water return was lost at a depth of 70 ft and was not regained throughout 
the remainder of the operation. No water pressure tests were made because of caving and ravelling 
conditions. However, percolation tests made at two depth intervals are summarized as follows: 



Date 



11/12/74' 



(A) 



Drill 












Hole 




Vertical 


Quantity 






505 


EI. 


Depth 


Injected 


Duration 


Discharge 


(ft) 


(ft) 


(ft) 


(gals) 


(min) 


(gpm) 


199.8 


5234 


100 


2300 


40 


57.5 



11/19/74 
12:40 p.rn.'^) 



399.8 5134 



200 



5705 



90 



11/19/74 
2:15 p.m. 



(B) 



399.8 5134 



200 



7970 



135 



(A) Unable to raise water level to surface. 

(B) Unable to raise water level above El. 5136. 

The drillers of DH-505 reported open joints between Els. 5272 and 5274 and a 0.6-ft seam at 5248 ft 
(Fig. 5-5). Thus, the existence of permeable joints beyond the end of the dam is established. 



5-17 




Fig. 5-12 Prominent vertical joints in right wall of canyon downstream of the 

axis of the dam. (post-failure photo) 




■ ■ 4* ^ 



\>V-4 «H -' "S" 






p^. 



K' 



•'} 



:vv?' 










Fig. 5-13 Transition from predominantly flat-lying 

to near-vertical jointing occurs near axis 
of dam. (post-failure photo) 



5-18 



During filling of the reservoir in Spring 1976, water levels were monitored in a number of observation 
wells located in vicinity of the dam. Water levels in these holes responded to the rise in the reservoir 
stage, indicating hydraulic interconnection through the joint systems. The locations of these wells and 
hydrographs reflecting the correlations are shown on Figs. 5-6 and 5-7. 

Some confusion arises as a result of the several different systems that have been used for numbering 
water level-observation wells. The Bureau of Reclamation has assigned two separate numbers to wells 
which were drilled for foundation exploration and later included in the groundwater monitoring 
program. In addition, the U.S. Geological Survey has assigned numbers following its customary well 
numbering system. Furthermore, local irrigation and domestic wells are often referred to by the 
owner's name. Table 5-3 provides a cross-index of these well designation practices. 

The rapid rise of the water table in response to reservoir filling indicates that joints in the canyon 
walls extend into and beyond the right abutment, and that the rock is permeable. It is apparent from 
Fig. 5-7 that at holes DH-5, DH-6, DH-503, DH-506, and Observation Wells Nos 7 and 8, the rise in 
water table was more rapid than that of the reservoir level during May and the first week of June 
1976. This condition is attributed to fiow through dominant horizontal joints that exist in rock Units 
1 and 2 exposed in the right wall of the reservoir. As the reservoir reached the levels of these joints, 
water appears to have flowed along them and to have caused a more rapid rise in water elevation in 
the drill holes. A particularly rapid rise in groundwater occurred in DH-5 when the reservoir stage 
reached El. 5250, commencing about 18 days before failure of the dam. Since DH-5 is located 
downstream of the key trench, this rise indicates that some water from the reservoir was bypassing 
the dam, possibly flowing around the right end through interconnecting joint avenues. However, on 
the day of failure the water level in DH-5 was 104 feet lower than the reservoir. 

During geologic exploration of the site, prior to commencement of dam construction, water pressure 
testing of Nx-diameter drill holes in and near the dam abutments had in several instances shown high 
water losses. A listing of tests in which leakage exceeded 50 gpm is shown in Table 5-4. In addition to 
the customary pressure tests, experiments were conducted wherein water was pumped into drill holes 
in the right abutment. The injections were metered, and the effects on groundwater levels in other 
drill holes in the abutment area were observed. Fig. 5-14 depicts the results of a pump-in test at 
DH-303 wherein over 24 acre-ft was injected over a 15-day period. Running at maximum capacity, 
the pump for this test delivered a discharge of 440 gpm to DH-303 without filling it. Water levels rose 
in holes DH-5, 6, 204, 301, and 302 during the period of injection and dropped abruptly upon its 
termination. Results of the pump-in test at DH-303 confirm the openness and intercommunication of 
the joint system in the volcanic rock in the right abutment between DH-204 near the wall of the 
canyon and DH-6 which is located about 11 00 ft west of the right end of the dam. 

Maps of the rock joints and geologic sections along the right abutment key trench invert prepared 
after failure of the dam are contained in Appendix E where additional photographs and detailed 
descriptions of joints are also found. The mapping program is discussed further in Chapter 3 under 
the section entitled Rock Joint Survey. 

Rock Cavities. 

During excavation of the dam foundation, large openings were uncovered in left and right abutment 
key trenches. Near the right end of the dam, two large fissures were exposed near Stas. 3-H55 and 
4-H34. These are shown in plan and cross-section in Figs. 5-15 and 5-16. Figs. 5-17 and 5-18 show the 
exterior and interior of the fissure near Sta. 4-H34. Both fissures trend generally east-west and cross 
the axis. 



5-19 



TABLE 5-3 

CROSS-INDEX OF NUMBERING SYSTEMS FOR WELLS AND DRILL HOLES 

USED FOR MONITORING WATER LEVEL ELEVATIONS 



USBR 
Observation 
WeU No. 


USBR 
Exploration 
Hole 
Designation 


uses No.** 


1 


6N/41E-llcdl 


2 




7N/41E-25cbl 


4 




7N/42E-6ddl 


5 




7N/42E-8cal 


6 


Site A 


7N/42E-17bcl 


7* 


SiteC 


7N/42E-19abl 


8* 




7N/42E-19ccl 


9* 


DH-6 


7N/42E-19cdl 


10 A* 


DH-506 


7N/42E-19dcl 


108* 


DH-506 


7N/42E-19dcl 


11* 


DH-503 


7N/42E-29bdl 


12* 


Corps Engrs 

No. 2 


7N/42E-29bcl 


13A* 


DH-507 


7N/42E-30ad 



13B* 


DH-507 


7N/42E-30adl 


14* 


DH-5 


7N/42E-30abl 


15 


Site D 


7N/42E-32bbl 


17 


DH-8 


7N/43E-16cbl 



Local Designation and Comments 

Qyde Packer Irrigation Well. 
Equipped with Stevens A-35 Recorder. 

Trupp Irrigation Well. 

Remington Irrigation Well. 

Schwendiman Well. 

Equipped with Stevens A-35 Recorder. 

Remington Irrigation Well. 

Angle Hole - Dip 30° From Horizontal. 

Deep Piezometer Monitors Underlying 
Lake and Streambed Deposits. 

ShaUow Piezometer. 



Deep Piezometer. Destroyed June 5, 
1976. Monitored "Lake and Streambed 
Sediments." 

Shallow Piezometer. Destroyed 
June 5, 1976. 



Equipped with Stevens Type F Recorder. 
Plugged at About 400 ft. 



5-20 



TABLE 5-3 (cont.) 





USBR 




USBR 


Exploration 




Observation 


Hole 




Well No. 


Designation 
DH-7 


uses No.* 


18 


7N/43E-21aal 


19 




7N/42E-15abl 


20* 


DH-504 


7N/42E-19ddcl 


21* 


DH-501 


7N/42E-19dcd2 



Local Designation and Comments 

Piezometer Open to Basalt Below 
467 ft. 

Supply Well, Hog Hollow Recreation Area. 



Angle Hole - Dip 60° From Horizontal. 



* Observation wells located in vicinity of dam, Fig. 5-6. 

**Designates well location based on Township, Range, Section, Quarter-section, and Quarter-quarter 
section. Final number indicates whether the well was 1st, 2nd, 3rd, etc., to be drilled in the area. 



5-21 



Drill 
Hole 
No. 



TABLE 5-4 

SUMMARY OF EXCEPTIONALLY HIGH WATER LOSSES* 

EXPERIENCED IN DRILL HOLES IN RIGHT ABUTMENT 

DURING WATER PRESSURE TESTING 

(Locations shown on Figs. 5-5 and 5-6) 



Depth Interval 



102 



301 



(ft) 

51.8- 
61 - 
41 - 
73.3- 
117 ■ 
102 
141 
100.6- 
169.7- 
190.3 
160.3- 
210.2- 
190.2- 
160.2- 
222.6- 
242.4- 
251.9- 



61.8 

71 

71 

83.3 
127 
132 
151 
160.6 
179.7 
200.3 
200.3 
220.2 
220.2 
220.2 
232.6 
252.4 
261.9 



27 - 77 
71.9-100.4 
140.4-190.4 
179.3-229.2 
254.6-304.6 
294.0-344 
15.5-306.1 



29 - 

49 

84.7- 

94.7- 
104.7- 
134.5- 
144.5- 
164.2- 
174.6- 
215.7- 
235.5- 



39 

59 

94.7 
104.7 
114.7 
144.5 
154.5 
174.2 
184.6 
235.7 
255.5 



Water Pressure 


Water Loss 


(psi) 


(gpm) 


25 


68.7 


25 


56.6 


25 


60 


35 


70 


25 


52.3 


50 


58 


25 


54.5 


50 


55.2 


50 


56.5 


25 


64.6 


25 


55.7 


25 


42.1 


35 


55.1 


50 


52 


25 


62.1 


25 


59.7 


40 


62.5 


85 


52.4 


25 


59.8 


90 


50.1 


95 


54.6 


100 


51.6 


100 


54.6 


6 


112 


50 


120 


50 


110 


50 


100 


25 


150 


25 


100 


25 


162 


90 


57 


20 


150 


20 


150 


90 


74 


100 


32 



''Arbitrarily selected as losses exceeding 50 gpm. 



5-22 



TABLE 5-4 (cont.) 



Drill 
Hole 

No. 



301 

(cont.) 



302 



303 



Depth Interval 
(ft) 

255.5-271.7 
270.2-290.2 
289.5-309.5 
349.5-389.5 

24 - 39 

49.4- 59.4 
89.3- 99.3 
99.2-109.2 

126.4-136.4 

173.2-183.2 

181.8-191.8 

191 -211 

201 -211 

211.2-221.2 

269.5-289.5 

311.7-331.7 

370.9-390.9 

42.5- 52.2 
52.3- 60.3 
60.3- 70.3 
70 - 80 
80 - 90 
90 -100 
98.8-109.8 

119.6-129.6 
188.6-198.6 
267.7-277.7 



Water Pressure 


Water Loss 


(psi) 


(gpm) 


50 


53.7 


50 


70 


50 


90 


30 


100 


50 


112 


90 


62.1 


30 


157 


20 


164 


50 


79.6 


15 


170 


15 


150 


20 


150 


25 


120 





180 





165 





170 





180 


10 


115 





75 





75 





75 





93 


80 


100 





179 





165 





176 





110 



504 



505 



597 Pump-in test 11/20/74. 

Pumped in 6,589 gal 
from 8.00 a.m. to 4:00 p.m. 
Water level at 4:00 p.m., 
185.0 ft. 

Excerpt from USER drill hole log: 

No percolation tests taken because of caving and ravelling 
conditions. 

Seam at 1 7 1 .3 where drill rods dropped 0.6 ft after loosening 
chuck. 

120.6-123.5 "Void determined to be at least 3" wide" 

124-131 "Void determined to be at least 3" wide" 



5-23 



TABLE 5-4 (cont.) 



Drill 
Hole 

No. 



Depth Interval 
(ft) 



Water Pressure 
(psi) 



Water Loss 
(gpm) 



505 
(cont.) 



137.1-138.9 "Void space up to 1" locally along joint" 

139.8-141 "Scattered void spaces mostly less than 1/2" 
open along joint" 

143.3-144.6 "Scattered void spaces mostly less than 1/2" 
open along joint" 

"Hole at depth 199.8. Pumped through wire line rods with 
rods pulled back to 160.0 ft. Pumped in 2300 gallons 
in 40 minutes. (57.5 gpm) — unable to raise water level 
to surface." This test was performed 1 1/12/74 after 
installation of grout curtain. No grout was found in 
the core. 



5-24 



500 



PUMP IN RATE AT 
DRILL HOLE 303 IN 
GALLONS PER MINUTE 



4998 



4996 



4994 



w 
w 



2 

O 

i 



> 



DC 

i 



4992 



4990 



4988 



4986 



4984 



4982 



4980 



REFERENCE DATA; 

U.S. BUREAU OF RECLAMATION 




11 16 

SEPTEMBER 1970 



EFFECT OF PUMP-IN TEST AT DRILL HOLE 303 
ON WATER LEVELS IN NEIGHBORING DRILL HOLES 



FIG. 5-14. 



V. S DEPARTMENT OF THE fNTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



5-25 



DH 13 
O 

63 

DH ^S 
DH. 302 



EXPLANATION 

Vertical sir track drlli hole iho^lnj 
depth Xa top of fissjre 






tical. 



Core drill hole - location shown Is the 
intersection of the hole with the floor 
of the keyway trench. Depth shown is 
from original grojtid Surface. 

Boirders Of fissure «nes. lnclud)nQ 
lonei 'iHed «ith broken rock - dashed 
where inferred. 



■ loose rock mtercepti 




NOTE 

R«t9r to 4wg. 549-147-134 
for gtolQgie $»eliang. 



SCALE OF FEET 



I lUMvs THiriK SAfCTV 



LOWER rtrON DIVISION ' IDAHO 

GEOLOGY a EXPLORATIONS IN 
RIGHT ABUTMENT KEYWAY TRENCH 



?». «r G 4 SwEEHEr 



'-mm tnh i im\ — ,«.nT-m 

SKtrriQit I a49-l4T-l3a 



FIG. 5-15. 



U S DEPARTMENT Of THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



5-26 



ELEVATION 


^ 


9 Vt'OlA CASEO HOLC 


sno 






stas 






5?»0 




^^-««.«^.^____^_^^ 


S2r5 




/ 


sm "^^H 


^^L^ ^ TOP OF CONCRETE 


56 rO^^^^^ 


^^^^^^^^^^^^^^^^^■_ 


sies 


^^^^^^HBHP^S 


S2eo 


^^^^^^HBr s* 


5255 


iO rO^ 


5230 


SECTION D-D' 




^H Placed 4-27-74 






■■ Ploced 5-6-74 



Rock ourijne in fissure openings estimoted 



ELEVATION 

3280 

S2T5 

S2ro 

sees 

seeo 

sess 

S2S0 

SZ4S 

S240 

SZ35 

S230 




aS/a'O/A CASED MOLE 




SECTION E-E' 



SECTION C-C' 



CLCVATIOH 

5«0 

«55 

«50 

«<5 

5X40 

5«5 

- sno 

«/5 

5«0 

5//5 

St 10 

StOS 

StOO 

SISS 

5190 

- sies 

5180 

SI75 

5170 

5IS5 




SECTION B-B' 



CLeviTION 
5tt0 

«55 

5150 

5145 

5t40 

»?M 

5250 

5225 



HOTC 

R»l»f to amg 549-147-155 ler plan 




SCftLE OF FEET 



I Mjaavs niinn SMETV 



GEOLOGIC SECTIONS ACROSS FISSURES IN 
RIGHT ABUTMENT KEYWAY TRENCH 



.„.„i?>.<i^-i? cm«i- . . 



""\ 549-147-134 



„ ^, r- ^^ U 5 DEPARTMENT OF THE INTEKIO* STATE OF IDAHO 

rlLl. 0~ It3. INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



5-27 










V— . 



/T*»* 




Fig. 5-17 



Rock fissure near Sta. 4+34 discovered during excavation 
of i<ey trench of the dam. Crevice extends through axis 
of dam for nearly 100 ft both upstream and downstream. 
(1974) 



f 




Fig. 5-18 



Interior of fissure shown in Fig. 5-17. Photo taken 10 ft 
from upstream wall of key trench. Spot in background 
is light from a bulb suspended through a 6-in. vertical 
drill hole located about 25 ft from camera. (1974) 

5-28 



The fissure near Sta. 4+34 was entered and explored by a Bureau of Reclamation employee for a 
distance of about 100 ft both downstream and upstream of the dam axis and an estimated 100 ft 
below the key trench invert. An interview with him is summarized in a memorandum dated 
November 16, 1976, contained in Appendix B. He described the cavity downstream as fairly 
consistently about 4 ft wide with a floor strewn with angular blocks of rock measuring up to 4 or 5 ft 
on a side. Upstream from the keyway, the roof and floor of the cavity were reported lined with 
stalactites and stalagmites up to 3/8 in. in diameter. About 100 ft upstream from the keyway wall the 
fissure pinched and turned so that the end could not be seen. It was reported that in winter vapor 
could be seen emerging from the downstream segment and that this segment was warm and could be 
entered in winter without a coat. Conversely, upstream of the keyway the air was reported to be cold. 
The end of the downstream segment was blocked by a large rock "the size of a pickup truck." A 
room or passage could be seen beyond, but the opening into it was too small to enter. In one place 
the cavity walls were described as covered with a red coating "which rubbed off on our clothes." 

The interior of the fissure at Sta. 3+55 was not examined since it was too narrow to permit entry. 
High-slump concrete was poured into both fissures during project construction. (Fig. 5-16 and 
Appendix B document dated August 25, 1976.) The extent to which the uppermost parts of the 
cavities may have been sealed by this procedure is uncertain. However, the concrete-rock contact was 
drilled at three points during post-faUure exploration, and in each instance the rock cores obtained 
displayed a tight bond between grout and rock (Chapter 3). 

The Bureau of Reclamation has referred to these cavities as tensional cooling cracks modified by 
ascending hot gasses and water vapor (Gebhart, L.R., et al, March 1974). Disruption caused by steam 
ascending from the saturated lake and stream deposits upon which they were emplaced could possibly 
have been a contributing factor. Another theory is that they are tension cracks that developed as the 
result of tectonic deformation. 

Additional description of these fissures and their treatment is contained in a memorandum to the 
Director of Design and Construction of the U.S. Bureau of Reclamation from the Project Engineer, 
Newdale, Idaho, dated March 14, 1974. Appendix E. 

Several other large fissures are exposed in the right waU of the canyon, one-eighth to one-quarter-mile 
upstream from the dam (FigS. 5-19 and 5-20). The walls of a few of these openings are curved and 
parallel with configurations such that opposite walls "fit" like the mating pieces of a jigsaw puzzle. 

Subterranean cavities in the region are commonly reported by local well drillers. A water well driUed 
in Section 18, northwest of the right abutment, is said to have encountered a void into which the drill 
bit dropped about 6 ft. At another well, the well bailer was lost in a cavity. The hole was 
subsequently abandoned and a new well started a few feet away. During this redriUing, the cavity was 
again encountered and the lost bailer snagged and fortuitously retrieved. 

The genesis of the cavities that have been observed or reported is controversial and perhaps academic. 
However, there is no question that they increase the permeability of the abutment and may serve as 
significant feeders to other joint conduits. Other cavities may lie undiscovered deep in the dam 
foundation. 

Faults. 

Although Teton Dam is situated in a seismically active region, there are remarkably few identifiable 
faults in vicinity of the damsite. The closest two faults are located, respectively, about 10 miles 
upstream and 10 miles downstream. 



5-29 




Fig. 5-19 Opening in upper right wall of Teton Canyon 

1/8 to 1/4 mile upstream from dam. (post-failure 
photo) 




Fig. 5-20 Joint in right wall of Teton Canyon 1/8 to 1/4 

mile upstream from dam. (post-failure photo) 



5-30 



The U.S. Geological Survey has suggested the possible existence of a northeast trending fault in the 
right abutment of the dam (Oriel et al, 1973). Its approximate location is shown on Figs. 5-1 and 5-3 
as inferred by the USGS from aerial photographs and from geologic sections prepared as part of the 
Bureau of Reclamation's groundwater investigation of the Rexburg Bench (Haskett, 1972). The aerial 
photographs of the area west of the dam were interpreted as showing surface breaks in slope similar 
to lineaments sometimes manifested by eroded fault scarps. In some of the geologic sections, based 
upon information from water well logs, the ends of the lenses of volcanic and sedimentary deposits 
show a near-vertical alignment, suggesting possible truncation by a fault plane (Figs. 5-2 and 5-3). 

Inspection of the area through which faulting was inferred has failed to disclose positive evidence of 
the existence of a fault. Furthermore, as discussed in Chapter 6, no significant earthquakes were 
detected on the day of the failure by the sensitive seismographs that monitor this region. Should this 
fault exist near the riglit abutment as postulated, it is improbable that it played a significant role in 
the failure of the dam. 

Foundation Deformation. 

Teton Dam rests directly upon a foundation of welded tuff and basalt which in turn overUe the lake 
and stream deposits (Fig. 5-4). Physical properties of the volcanic rocks indicate these rocks to be 
strong and rigid except where locally weakened by joints (Table 4-1 ). 

Logs of exploration holes drUled into the lake and stream sediments describe some lenses of 
sediments as soft, friable, or hghtly compacted (Table 5-1). These descriptions imply that the deposits 
are compressible. However, they could undergo further consolidation in place only if subjected to 
pressures that exceeded maximum historic loads. The heaviest loading at the site probably existed 
when the tuff was first emplaced, before Teton Canyon was incised by the river. Subsequent removal 
of rock during erosion of the canyon reduced this initial load and was undoubtedly attended by some 
elastic rebound. Construction of Teton Dam and filling of the reservoir restored only a fraction of the 
initial load inasmuch as the combined weight of water and embankment was considerably less than 
that of the rock that earlier occupied the reservoir site. While the weight of the dam and impounded 
water surely caused some elastic strain in the foundation, significant settlement is not expected to 
have occurred. 

Clearly, the lake and stream deposits have borne the weight of the overlying ash-flow tuff since its 
deposition about 2 million years ago, and they have had the ensuing period during which to 
consolidate. At the dam the load is presently approximately 570 ft of rock and soil on the right 
abutment, over 200 ft on the left abutment, and about 290 ft of alluvium and rock in the river 
channel. 

That no significant deformation has occurred at the dam since its construction is evidenced by the 
results of geodetic and leveling surveys conducted before and after its failure. Tables 5-5 and 5-6 
compare pre- and post-failure elevations and positions of survey stations, the locations of which are 
shown on Fig. 5-21. Table 5-7 makes a comparison of benchmark elevations along part of the right 
abutment grout cap. No significant changes in elevation or position of the unmolested stations are 
indicated to have occurred. 

Inspections of the auxiliary outlet tunnel that passes through the right abutment disclosed no 
observable cracks in the concrete lining, providing further evidence that no significant deformation 
has occurred in this abutment, at least along the tunnel alignment, since completion of construction. 



5-31 



TABLE 5-5 

COMPARISON OF PRE- AND POST-FAILURE ELEVATIONS 

OF BENCHMARKS IN VICINITY OF TETON DAM 



Benchmark Designation* 




Elevations in Feet 










Pre-failure 

5299.22 


(Date of Survey) 


Post-failure 


Change, ft 


Tri Station BEV 


(4/24/72) 




5299.18 


-.04 


Tri Station CORA 


5289.62 


(4/24/72) 




5289.62 


.0 


Tri Station DOT 


5280.96 


(4/25/72) 




5280.93 


-.03 


Tri Station ALICE 


5298.20 


(4/24/72) 




5298.16 


-.04 


Photo Pt. 3-19 


5323.69 


- 




5323.72 


+.03 


Tri Station No. 7 


5310.54 


(7/24/69) 




5310.52 


-.02 


Station 0+00 


5335.79 


(5/7/74) 




5335.67 


-.12 


SS Bolt 17+79 Lt. 


5331.95 


(4/16/76) 




5331.91 


-.04 


Pt. 16+25 P.I. R.O.W. 


5322.63 


(10/17/74) 




5322.67 


+.04 


Tri Station No. 3 


5290.51 


(4/19/72) 




5290.44 


-.07 


SS Bolt 34+35.5 Rt. 


5038.43 


(8/18/75) 




5038.33 


-.10 




5038.41 


(6/3/76) 




5038.33 


-.08 


4' X 4' Gate 


5045.88 


Prior to 

6/5/76 


D/S Lt. 

D/S Rt. 

U/S Lt. 
U/S Rt. 


5045.80 

5045.81 
5045.82 
5045.82 




Tri Station B-Pt.-9 


5271.76 


(4/19/72) 




5271.71 


-.05 


Cor. No. 3 


5342.37 


(10/17/74) 




5342.35 


-.02 



*Locations shown on Fig. 5-21. 



5-32 



Tri. Sta 



TABLE 5-6 
COMPARISON OF DISTANCES BETWEEN SURVEY STATIONS 
MEASURED BEFORE AND AFTER FAILURE OF TETON DAM 



To 



Tri. Sta. 



Distance 
Before 



*Distances computed from coordinates. 
See Fig. 5-21 for locations. 



Distance 
After 



Change in 

Distance 

(ft) 



Trupp 


B-Pt-6 


3,323.586 


3,323.615 


.029+ 


Trupp 


B-Pt-5 


2,148.384 


2,148.332 


.052- 


Trupp 


Klatt 


1,387,410 


1,387.452 


.042+ 


Klatt 


B-Pt-5 


2,078.905 


2,078.873 


.032- 


Klatt 


B-Pt-6 


2,496.616 


2,496.609 


.007+ 


B-Pt-5 


B-Pt-6 


1,651.849 


1,651.826 


.023- 


B-Pt-5 


B-Pt-3 


3,555.890 


3,555.838 


.052- 


B-Pt-5 


B-Pt-9 


2,901.992 


2,902.008 


.016+ 


B-Pt-6 


B-Pt-9 


2,980.990 


2,980.964 


.026- 


B-Pt-6 


B-Pt-3 


2,868.941 


2,868.934 


.007- 


B-Pt-9 


B-Pt-3 


1,476.568 


1,476.533 


.035- 


B-Pt-9 


#3 


982.586 


982.600 


.014+ 


B-Pt-9 


#2 


2,459.435 


2,459.432 


.003- 


B-Pt-3 


#3 


♦1,810.686 


1,810.632 


.054- 


B-Pt-3 


#2 


1,654.797 


1,654.787 


.01- 


#3 


#2 


2,005.236 


2,005.210 


.026- 


#2 


_ Omega 


* 1,577.374 


1,577.364 


.01- 


*2 


- Gamma 


* 1,028.444 


1,028.677 


.233+ 


#2 


29BD 


* 2,048.537 


2,048.538 


.001 + 


Omega 


Beta 


2,182.560 


2,182.517 


.043- 


Omega 


29BD 


* 2,723.499 


2,723.470 


.029- 


Omega 


— Gamma 


1,246.310 


1,246.286 


.024- 


29BD 


#7 


* 3,367.434 


3,367.481 


.047+ 


29BD 


Beta 


* 3,122.492 


3,122.493 


.001 + 


29BD 


12-8-A 


* 2,995.038 


2,994.899 


.039- 


Pot #1 


Boot 


2,149.352 


2,149.365 


.013+ 


Pot#l 


- Alice 


2,809.447 


2,809.482 


.035+ 


Pot #1 


Pot #2 


1,656.547 


1,656.536 


.011- 


Pot#l 


#7 


1,670.932 


1,670.939 


.007+ 


12-8- A 


Beta 


* 2,513.037 


2,512.972 


.065- 


12-8- A 


#7 


* 2,672.141 


2,672.082 


.059- 


12-8- A 


T-Pt-A 


* 1,985.313 


1,985.315 


.002+ 


Pot #2 


AUce 


2,056.381 


2,056.397 


.016+ 


Pot #2 


- Boot 


2,319.802 


2,319.667 


.135- 


#7 


T-Pt-A 


♦1,591.714 


1,591.633 


.081- 


*1 


— Alice 


1,976.380 


1,976.340 


.04- 


#7 


- Boot 


2,255.677 


2,255.518 


.159- 



5-33 



TABLE 5-6 (cont.) 









Distance 


Distance 


Tri. Sta* 


To 


Tri. Sta. 

Alice 


Before 


After 


Boot 


1,336.178 


1,336.005 


Boot 


— 


Bev 


1,937.760 


1,937.606 


Boot 


_ 


Spur 


643.659 


643.706 


Spur 


_ 


Alice 


1,385.799 


1,385.761 


Spur 


— 


Bev 


1 ,609.437 


1,609.380 


Spur 


_ 


Cora 


1,757.141 


1,757.113 


Alice 


— 


Bev 


1,025.878 


1,025.854 


Bev 


— 


Eye 


2,353.080 


2,353.064 


Bev 


— 


Cora 


1,052.972 


1,052.960 


Cora 


— 


Eye 


1,533.391 


1,533.360 


Eye 


— 


Spur 


1,796.022 


1,796.008 



Change in 
Distance 
_(ft) 

.173- 
.154- 
.047+ 
.062- 
.057- 
.028- 
.024- 
.016- 
.012- 
.031- 
.014- 



5-34 




5-35 



TABLE 5-7 

A COMPARISON OF 

ELEVATIONS OF POINTS ON THE RIGHT ABUTMENT 

GROUT CAP AS DETERMINED FROM SURVEYS 

MADE BEFORE AND AFTER FAILURE 

OF THE DAM 



Grout Cap 


Elevations in Ft 




Station 


Pre-failure 


Post-failure 


Change, ft 


11+72 


5275.617 


5275.618 


+.001 


12+09 


5254.120 


5254.119 


-.001 


12+16 


5250.483 


5250.462 


-.021 


12+50 


5223.524 


5223.514 


-.01 


12+60 


5222.320 


5222.312 


-.008 


13+27 


5198.422 


5198.415 


-.007 



Survey points consisted of straight lengths of Number 6 reinforcing bar which were embedded in the 
concrete grout cap. During dam construction, the contractor bent over or cut off those bars that 
threatened damage to his rubber-tired equipment. The stations included in this table were inspected 
by a Panel representative and judged to be unmolested. 



5-36 



FINDINGS OF ENGINEERING SIGNIFICANCE BASED ON AVAILABLE GEOLOGIC 
INFORMATION 

1. The volcanic rock surrounding Teton Dam is moderately to intensely jointed and, consequently, 
is permeable. At the damsite a blocky and slabby structure is displayed on the right abutment 
between El. 5185 and the canyon rim. A severely jointed zone is located above El. 5280. Both 
flat-lying and steeply dipping open joints are prevalent above 5185. Groundwater was therefore free 
to move with almost equal ease in most directions within the upper two zones, except locally where 
the joints had been effectively grouted. On reservoir filling, water moved rapidly to the foundation of 
the right end of the dam, as indicated by the observation well hydrographs of Fig. 5-7. Open joints 
also existed in the upstream and downstream faces of the right abutment keyway trench, providing 
potential conduits for access or egress of water. See maps, geologic sections, and photos. Appendix E. 

2. The rock beyond the right end of the dam is jointed and permeable. The log and water testing at 
drill hole 505 (drilled after emplacement of the grout curtain) suggest exceptionally high permeability 
above El. 5250. (Table 5-4 and Fig. 5-5.) 

3. Pump-in tests at drill hole 303 established the existence of interconnecting open joints between 
driU holes 5, 6, and 204; in other words, underground conduits exist on the downstream side of the 
dam througli which water could travel from the right end of the dam to the canyon wall. These holes 
are all located either downstream or beyond the end of the grout curtain; therefore, it is doubtful 
that grouting significantly affected the carrying capacity of these joint paths. On the basis of these 
observations, it appears that no natural watertight barrier existed at the end of the dam and that it 
was possible for some water to follow the shortest path or paths around the end of the grout curtain 
and re-enter the canyon downstream. However, the maximum elevation of groundwater at DH-5, the 
only observation well near the downstream side of the dam, approached 5200 ft, which is 
approximately the level of the leak observed on the morning of the failure. Thus the avaUable 
evidence argues that there was insufficient hydraulic gradient between DH-5 and the canyon wall to 
provide the high velocity underflow leading to the breakout that was observed at El. 5200 on the 
downstream side of the dam. 

4. The lake and stream deposits beneath the right wall of the canyon contain permeable members 
which may connect hydraulically with the reservoir and with drill hole 506 beyond the right end of 
the dam. Whether such members extend beneath the dam and interconnect with vertical joints or 
fissures that extended upward to the base of the embankment is not known. However, the lake and 
stream deposits beneath the Rexburg Bench are generally much less permeable than the overlying 
volcanic rocks. Although some leakage under the dam may have occurred through these sediments, 
flow through joints in the welded tuff was more likely a significant factor in the failure process. 

5. A comparison of geodetic surveys completed before and after failure of the dam indicates that 
no significant deformation of the dam foundation or vicinity occurred since construction of the 
project was undertaken. 



5-37 



REFERENCES 

Aberle, Peter P., Pressure Grouting Foundation on Teton Dam, Volume 1, Proceedings of the 
Specialty Conference Sponsored by the Geotechnical Engineering Division of the American Society 
of Civil Engineers on Rock Engineering for Foundations, August 15-18, 1976, University of 
Colorado, Boulder, Colorado. 

Christiansen and Blank, 1972, U.S. Geological Survey Professional Paper 729-B. 

Corbett, Marshall K., August 5, 1976, Testimony on the Teton Dam Disaster, Given before the 
Conservation, Energy and Natural Resources Subcommittee of the House Government Operations 
Committee Hearings. 

Crosthwaite, E.G., Mundorff, M.J., and Walker. E.H., 1967, Ground-Water Aspects of the Lower 
Henry's Fork Region, Idaho, U.S. Geological Survey, Water Resources Division, in cooperation with 
the U.S. Bureau of Reclamation and the Idaho Department of Reclamation. 

Curry, Robert R., August 5, 1976, Hazard Geology of the Teton Damsite with Special Reference to 
Reduction of Future Geologic Siting Errors for Dam Projects Involving Public Risk, Testimony to the 
Conservation, Energy, and Natural Resources Subcommittee of the House Government Operations 
Committee, Hearings on the Teton Dam Disaster. 

Gebhart, L.R., Harber, W.G., and Gilbert, J.D., March 29, 1974, Travel Report, U.S. Bureau of 
Reclamation, Engineering and Research Center, Denver, Colorado. 

Haskett, Gordon I., 1972, Groundwater Geology of Rexburg Bench, Idaho, U.S. Bureau of 
Reclamation Report. 

Oriel, S.E., Prostka, H.J., Schleicher, D., and Hackman, R.J., June 1973, Preliminary Report on 
Geologic Investigations, Eastern Snake River Plain and Adjoining Mountains, U.S. Geological Survey, 
Denver, Colorado. 

Prostka, H.J., and Hackman, R.J., 1974, Preliminary Geologic Map of the NW 114 Driggs l'^ by 2P 
Quadrangle, Southeastern Idaho. 

U.S. Bureau of Reclamation, June 1976, Teton Dam Geology, Geology and Geotechnology Branch, 
Division of Design, Engineering and Research Center, Denver, Colorado. 



5-38 



CHAPTER 6 
SEISMICITY 

(Panel Charge No. 2) 



HISTORICAL 

In general terms the region of Teton Dam is included in Zone 3 on the Seismic Risk Map of the 
United States, Fig. 6-1 (Algermissen, 1969). This is the zone of highest risk. Furthermore, the dam 
lies from 35 to 50 miles west of the great Intermountain seismic belt, a complex system of faults 
aligned in a north-south direction as shown on Fig. 6-2, numbers 1 to 13 inclusive. The general 
seismicity of the region is also indicated by the clusters of epicenters, as shown on Fig. 6-3 in the 
Yellowstone Park and the Jackson Hole area to the south of Yellowstone Park. 

However, it should be emphasized that the highly seismic areas mentioned above almost surround the 
long aseismic protrusion to the northeast of the Snake River plain; this is best seen on Fig. 6-2. It is in 
this relatively seismically quiet platform of Cenozoic volcanic and sedimentary rocks that Teton Dam 
was buUt. 

Prior to 1932 earthquake data are based almost exclusively on felt and damage reports. Furthermore 
from 1932 to 1961 no seismograph stations were operating in Idaho. Pre-instrumental epicentral 
locations may have errors of 10 to 20 mUes. Since 1961 many seismometers have been installed and 
these have been especially valuable in identifying the location and magnitude of the smaller seismic 
events. In the period 1969-74, five earthquakes were located within 30 miles of the damsite and two 
of these had magnitudes greater than 3. 



GEOLOGIC SETTING 

The geologic history has been described in the previous chapter. It will suffice here to restate a few 
comments on the regional geologic setting. 

The eastern Snake River plain is a northeast trending depression formed in late Cenozoic time with 
concurrent volcanism. Rhyolitic ash-flow tuffs lie beneath the younger basalts which make up much 
of the surface of the Snake River plain. At Teton Dam the two-million-year-old ash-flow tuffs are 
several hundred feet thick. 

Teton canyon is incised in this thick rock unit as a result of local uplift across the path of the river. 
Remnants of younger basalts are found in places along the canyon bottom. Downwarping, and 
possibly adjustments by faulting, continued until late Cenozoic time and undoubtedly the broad, 
regional picture is one of structural deformation continuing up until the present. 



FAULTING 

Fig. 6-2 shows the distribution of the major active faults, particularly the Madison (3), Hebgen (4), 
Yellowstone (5) and the Grand Valley fault zone (7). Teton Dam is located approximately 25 miles 
south of the Island Park caldera (6). 

The largest historic earthquake in the Intermountain seismic belt was in 1959 at Hebgen. The ground 
rupture of 15 miles with a 20-ft normal displacement produced a 7.1 magnitude earthquake 



6-1 




SEISMIC RISK MAP OF THE UNITED STATES 

ZONE — NO DAMAGE 

ZONE 1 — MINOR DAMAGE: DISTANT EARTHQUAKES MAY CAUSE DAMAGE 

TO STRUCTURES WITH FUNDAMENTAL PERIODS GREATER THAN 10 

SECONDS; CORRESPONDS TO INTENSITIES H AND Xt 

OF THE M. M," SCALE 

ZONE 2 -MODERATE DAMAGE; CORRESPONDS TO INTENSITY lELE OF THE MM/ SCALE. 

ZONE 3-MAJOR DAMAGE; CORRESPONDS TO INTENSITY •VTTT AND HIGHER OF THE MM.' SCALE. 

This map is based on the known distribution ot damaging earthquakes and the 
M.M.' intensities associated with these earthquakes; evidence of strain release, 
and consideration of major geologic structures and provinces believed to be 
associated with earthquake activity. The probable frequency of occurrence of 
damaging earthquakes in each zone was not considered in assigning ratings to 
the various zones. See accompanying text for discussion of frequency of 
earthquake occurrence. 



♦ Modified Mercalli Intensity Scale of 1931. 



SEISMIC RISK MAP 

OF THE UNITED STATES 

r T /-- ^ i ' "* DEPARTMENT OF THI INTERIOR STATE OF IDAHO 

rllj. D I. INDEPENDENT PANEL TO REVIEW t AL SE OF TETON DAM FAILURE 



6-2 



ROCKY MOUNTAIN TRENCH 
MISSION FAULT ZONE 
MADISON FAULT ZONE 
HEBGEN FAULT ZONE 
YELLOWSTONE CALDERA 
ISLAND PARK CALDERA 
GRAND VALLEY FAULT ZONE 
EAST CACHE FAULT ZONE 
WASATCH FAULT ZONE 
SEVIER FAULT ZONE 
HURRICANE FAULT ZONE 
PAUNSAUGUNT FAULT ZONE 
ESCALANTE DESERT CALDERA 
RIO GRANDE VALLEY 




REFERENCE DATA: 

KINGS TECTONIC MAP OF NORTH 

AMERICA (1969 

U. S GEOLOGIC SURVEY 

TECTONIC MAP OF THE 
UNITED STATES" {1962] 



GENERALIZED LATE MESOZOIC - 

CENOZOIC TECTONIC MAP OF 

INTERMOUNTAIN WEST 



FIG. 6-2. ,N 



U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

DEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



6-3 




A X 

A 3a 

^ •VTT- VTTT 

MAGNITUDES (1963-1972) 

• 3.0- 3.9 (NOT ALL EVENTS PLOTTED) 

• 4.0-4.9 






5.0-5.9 
6.0-6.9 
7.0- 7.9 



REFERENCE DATA: 

U.S.G.S. 1962 

"TECTONICS MAP OF THE U.S. 



EPICENTERS FOR INTERMOUNTAIN 
SEISMIC BELT 

r'T/^ O Q US DEPARTMENT Of THE INTERIOR STATE OF IDAHO 

r llj. O O. INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



6-4 



approximately 60 miles from Teton Dam. In 1964 a 5.8 magnitude earthquake was recorded in 
Madison Valley 25 mUes north of Hebgen. 

Other large earthquakes in the belt have magnitudes ranging from 6.5 to 7. However, except for the 
Hebgen event, no earthquake within 50 mUes of Idaho, or in Idaho, had a magnitude above 6.5. The 
nearest major fault to the dam is at Jackson Lake 35 miles to the east. 

Fig. 5-1 in the previous chapter indicates a fault passing close to the dam. On the basis of low swales 
or flexures in the surface aeolian sediments it has been interpreted as passing between core holes 
DH-5 and DH-6. However, Bureau of Reclamation personnel (Klein and Boch, 1973) suggested that 
neither of these deep, inclined holes showed evidence of faulting. 

Another fault, with a northeasterly inferred extension, has been mapped at White Owl Butte ten miles 
south of Teton Dam. It is doubtful if this inferred extension passes within several miles of the dam. 
Nevertheless, Greensfelder, in a recent seismicity study of Idaho, has suggested that the maximum 
acceleration at the damsite may reach a value as high as 0.25g. 



SEISMOMETER ARRAY 

To observe effects of water impounded by the dam, plus the weight of the dam, the U.S. Geological 
Survey installed three stations: Big Bend, Dry Creek and Garns Mountain. Their locations are shown 
on Fig. 6-4 under the code designations BBI, DCI and GMI. 

The Energy Research and Development Administration (ERDA) and the Idaho National Engineering 
Laboratory (INEL) had stations at Hamer (HID) and Taylor Mountain (TMI), localities indicated on 
Fig. 6-4. 

An additional station was installed at the Teton Dam project office and a strong-motion 
accelerometer was placed in the Teton Dam powerhouse. 

The results of the monitoring study by the U.S. Geological Survey can be summarized as follows: 

1. The most sensitive Teton Dam seismic monitoring station has a magnitude threshold of —0.1 Mi 
in the immediate vicinity of the dam. 

2. No seismic events other than identified blasts were observed within a 30-km radius of the Teton 
Dam site during the period April 1, 1976 - June 9, 1976. 

3. The closest and largest earthquake during this same period was located southwest of Victor, 
Idaho, at a distance of 60 km from the dam, and had a magnitude of 1 .7 Mr . 

4. No seismic events of magnitude 2.2 Mj^ or greater were observed within a 30-km radius of the 
dam during the period June 16, 1974 - March 31, 1976. All of the events within 20 km of the dam 
have been confirmed as blasts. 

5. No increase in seismicity around the dam was observed as the reservoir was filling. 

6. For at least four hours, the seismic monitoring network recorded ground motion generated by 
the release of the flood waters and the breakup of the dam. 

7. The strong-motion instrument at the base of the powerhouse has not been recovered. 



6-5 



112" 



111' 



110° 




SCALE 1 : 1.000,000 
O TETON DAM PROJECT SEISMIC STATIONS 

V^ IN EL SEISMIC STATIONS 



REFERENCE DATA; 

U. S. GEOLOGIC SURVEY 



LOCATION OF SEISMIC STATIONS 

j^ f /^ C A ^' ^ DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

rl(j. O ^. INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



6-6 



RECORDINGS MONITORING DAM FAILURE 

Ground motions induced by flooding water during the failure of Teton Dam were recorded at all 
seven stations in the U.S. Geological Survey array including the most distant, 78 miles from the site. 

The initial recording began at 1 1 :47 a.m. and vibrations continued for four hours. Fig. 6-5 is a 
portion of the seismogram from station GMI showing ground motion induced by the flood waters. 



COMMENTS 

Although the Teton Dam was constructed in a general region of high seismicity and a localized region 
of moderate seismicity. there were no seismic events triggered by filling the reservoir and there is no 
reason to believe that earthquakes were in any way responsible for the failure. 



6-7 



.GROUND MOTION DUE TO 
FLOODING COMMENCED 
APPROXIMATELY 11:47AM JUNE 5,1976 




"" ■ A r .^ 



SEVEN -IN. LONG SEGMENT FROM 30 IN. CIRCUMFERENCE CONTINUOUS RECORD. 
SUCCESSIVE HORIZONTAL LINES REPRESENT ONE COMPLETE REVOLUTION OF THE 
SEISMOGRAPH DRUM, AN INTERVAL OF15M1N. AS REPORTED TO THE PANEL, BY A 
REPRESENTATIVE OF THE USGS.THE GROUND MOTION RECORDED HERE IS 
DISTINCT FROM THAT OF AN EARTHQUAKE. 



PORTION OF SEISMOGRAM 
FROM STATION GMI 



REFERENCE DATA: 

U S GEOLOGIC SURVEY 



FIG. 6-5. 



U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



6-8 



REFERENCES 

Algermissen, S.T. (1969) "Seismic Risk Studies in the United States," Fourth World Conference on 
Earthquake Engineering, Santiago, Chile. 

Gilbert, J.D. (1963) Map. "Earthquake Occurrence along the Idaho-Wyoming Border 1904-1972," 
Memorandum, U.S. Bureau of Reclamation, to Chief, Hydraulic Structures Branch, March 30th. 

Klein, Ira E. and Bock, R.W. (1973) "Review of Construction, Teton Dam, Idaho," Travel Report to 
Director of Design and Construction, Nov. 23rd. 

McKelvey, V.E. (1976) Letter to Senator Henry Jackson, June 11th. 

Oriel, Stephen S. (1973) Prostka, Harold J., Schleicher, David and Hackman, Robert J., "Preliminary 
Report on Geologic Investigations, Eastern Snake River Plain and Adjoining Mountains," Draft 
report, U.S. Geological Survey. 

Navarro, R., Wuollet, G., West, J., King, K. and Perkins, D. (1976) "Seismicity of the Teton Dam 
Area, June 16, 1974 - June 9, 1976," U.S.G.S. Open File Report 76-555. 

Greensfelder, Roger W. (1976) "Maximum Probable Earthquake Acceleration in Bedrock in the State 
of Idaho," Research Project No. 79 for Idaho Dept. of Transportation. 

Smith, Robert B. and Sbar, Marc L. (1974) "Contemporary Tectonics and Seismicity of the Western 
U.S. with Emphasis on the Intermountain Seismic Belt," Bull. Geol. Soc. of America, vol. 85, no. 8, 
pp. 1205-1218. 



6-9 



CHAPTER 7 
CONSTRUCTION MATERIALS 

(Panel Charge No. 4) 



A general description of the Teton Dam embankment is included in Chapter 1. (Figs. 1-2 and 1-3.) 
The canyon width at river level is about 750 ft (El. 5050 ±) and at the canyon top the vwdth is about 
1,700 ft (El. 5320+). The abutments rise steeply 280+ ft above the canyon floor. 

The dam embankment consisted of five zones of the following approximate volumes: 

Zone 1 5,186,327 cu yds 

Zone 2 2,393,364 cu yds 

Zone 3 906,560 cu yds 

Zone 4 591,275 cu yds 

Zone 5 793,675 cu yds 

The upstream slope above El. 5185 was protected with a 3-ft thickness of basalt rock riprap measured 
normal to the surface. 



BORROW AREAS 

General. 

Embankment materials utiUzed at the Teton site consisted of the ML aeolian silts covering the 
uplands in Borrow Area "A" just north of the right abutment; GP and GW river-deposited gravel in 
the bottom of the Teton River Canyon immediately upstream of the Dam in Borrow Areas "C" and 
"C" Extension; and basalt from quarries developed about 3-1/2 miles north of the site. The borrow 
areas are shown in Figs. 7-1, 7-2, and 7-3. In addition maximum utilization was made of the material 
from the required excavations for embankment and structure foundations, the two outlet tunnels, the 
powerhouse, the tailrace channel, and the borrow pits. 

Required Excavation. 

The surface of the foundations occupied by the embankment and appurtenant structures was stripped 
of soil containing root concentrations, organic materials, and any unstable silts and clay. The stripped 
material was wasted in the disposal areas immediately upstream and downstream of the dam. The 
materials from foundation and structural excavation below the stripping were selectively placed in 
appropriate zones of the dam. River sands and gravels were placed in Zones 2 and 4. Loose rock and 
rock excavation were placed in Zone 5. Mixtures of clay, silt, sand, and rock fragments were placed in 
Zone 3. The construction separately of portions of Zones 2, 3, 4, and 5 was permitted where possible 
to minimize the stockpiUng of required excavation. 

Borrow Area "A". 

Materials for Zone 1 and Zone 3 that were not available from required excavation were borrowed 
from Borrow Area "A". This area contained substantial deposits of caliche (a soil inclusion formed by 
cementation of material by calcium carbonate) and relatively hard cemented layers of overburden. 
Close control and selective excavation were required to avoid extensive deposits of caliche and 
cemented soils, as well as deposits of MH and CH lower-density soils. Occasionally, shallow layers of 
caliche and soils easy or moderately hard to excavate were blended in cut. Some relatively thick 
layers of caliche and cemented soils that would not break down readily under rolling had to be 



7-1 



'SLA. 



■see Dwg 543-0-ie7 



^ ^^r~> 



h^ 



'tiiO^i 



^ft« Pump discharge/ 



riV- 



j5" 



-7 



/AP-I204 



j-#a'* 



!3A 38 , 



BORROW AREA "D"- 

fs« On^ 549- D -167) 



-y^ 



/lie ^^^K^BORROw:iliREA ^-B-fK^^ 



--AP-e25y^ ,' 



'^Proposed ROW'' 



j: 



>" 



/^ 



^^ 






^£ Lef/ abutment county "- 
""rf connection 



V. 



E4E^ 



Di 



'■:^ 



^BORROW AREA 
EXTENSION STOCKPILE AH 

~ ~\ AP-BIT 






AP~A3e9 



r APrABSa' 
f AP-A283 



.>^i/ 



if 



\ \' 



yy/. 



AP-A3r6 « AP-AZee 



♦ -AP-A20I" 1 

T ■ I fAP-ASlV • AP-A 

i i /' ' -"^ I- 

^ AP-AZ09 • AP-A19 / 



Match hne Dwg 549-0-50J- 



I TP-CBOB ,--=^^~^ 



»-A267f J AP-A852 t AP-A247_ • *^'* 
■P-A?/ " 4 AP-*2'2 ^ AP-AIO o AP-A: 

^*JaP-A253 4 AP-Ae46 



Test embankment 



4 AP-A£46 4 AP-Ae32 

T f AP-A3J0 

A AP-A20B )|*P-*"8 i ap-asoB 

t 4 •,-*' j^^'g;:? ^^ |ap-a3ob I 



NOTES 

For logs of opiorotions for Borrow Areo 
V see the following drowings 

SECTIONS l-l AND 2-2 _ 549-0-I6B 

SECTION 3-3 549-D-I69 

SECTIONS 4-4 AND 5-5 549-0-170 

SECTIONS 6-6 AND 7-7.... 549-0-171 

SECTIONS e-8 AND 10-10 .549-a-l7^ 

SECTIONS 9-9 ANOII-M ...J49-0-I73 

for log:; of e^ipioroTions for Areo 
Vsee the following drawings 

SECTIONS l-l AN0 2-2... 549-0-181 

SECTION 3A-3A 549-0-182 

SECTIONS 3B-3B AND 4-4_ ___549-D-lB3 

SECTION 5-5 549-0-184 

SECTION 6-S S49-0-IB5 

SECTION 7-T_ 549-0-186 

SECTIONS 8-8 THRU 10-10 549-0-187 

For logs of explorottons for Borrow Area 
'c* see the following drawings 

SECTIONS l-l THRU 3-3 549-0-186 

SFCTIONS -1-4 THRU 7-7_ J49-0-I89 

SECTIONS 8-8 THRU 10-10 549-0H90 

For doto frofn test embonkments see the following 
drowings 

BORROW AREA PHE-WETTING OATA 549-0-323 

SUMMARY OF FIELD AND LABORATORV TESTS. 549-0-324 

For togs of dragline and backhoe tesi pits see the 
following ' Log of test pit or auger hole ' 
TP-C 208 
TP-C209 
TP-C2I0 



AP-ABIS ,^ AP-A6 
AP-AeS4 



SCOLEOF FEET 



EXPLANATION 

• AP- flZBO 6 Incfi power auger hole 

■ TP- CIO Jest pit exco voted by bock hoe 

I IP- A3 Test pit e»cavoted by drogime 

a Quoffy blost test site 

I TP-C208 Tesi piteiCQvoted by drogime 

and bock hoe 



o-W 



LOCiTIOM Of r^ - CZOI.CZO*. AttO Clio *ODtO 



net CHtt/tCL 



) nuunvs tmihk SAfCTY 



0£P*RTMC»T or TMC IHTiRIO^ 

ewetu Of RtCLtf^Tion 
reroN basin project 

LOWER TETON DIVIS ION - I DAMO 

TETON DAM 

LOCATION OF EXPLORATIONS FOR 
BORROW AREAS 'A', 'B'AND'C 

rao IfJ^, ^»»mo-,to ^C^>^ J> »T - - - 



549 -D- 165 



—Test embankment areo site No 1 



FIG. 7-1. 



U S DEPARTMENT OF THE JNTEHIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



-Match Line Dwg 549-D-I65 



.-Test embankment area site No z 



Uotch line Dwg 549-0-503 



m 




SCALE OF FEET 



EXPLANATION 

• AP-A300 . e Inch power auger hole 

■ TP-CI3 Test pit e« CO voted by bQchhoe 

I TP-Ai Test pit eicovQted by dragline 

a Ouorry blosf test site 



NOTES 

For logs of eiplorotions for Borro* Areo V 
see the following drawings 

SECTIONS ie-l2 THRU I4-I4_._ 549-D-I74 

SECTIONS 15-15 AND 16-16. _549-0-l75 

SECTIONS 17-17 AND l8-r8 549-D-IT6 

SECTIONS 19-19 AND ^0-^0 549-0-177 

SECTION 21-21 549-D-I78 

SECTIONS 22-22 AND 23-21. 549-0-179 

SECTION 24-24 549-D-IBO 

For logs of eiplorotions for Borrow Areo V 
see The foliowing drawings 
SECTIONS e-e thru io-io 549-D-190 



) RUtwvs n«int( SAf €TV 



OCPAnTMdur OF ThC ihtEriOD 
aUHtAV OF R£CI."il*TIOH 

TETON BASIN PROJECT 
LOW£/t TETON DIVISION' IDAHO 

TETON DAM 

LOCATION OF EXPLORATIONS FOR 
BORROW AREAS >'. 'fl; AND C 

.__.■!-_ .„..,"... .,tiZ</2^^^«t 

•- --^^ •• "aiiVv.r.iigS;&y»raT3i.- 

549-D- 



FIG. 7-2. 



U S DEPARTMENT OF THE JNTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIE^)l' CAUSE OF TETON DAM FAILURE 



7-3 




STATE OF IDAHO 



rlLr. / ~0. INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



7-4 



excavated to uncover the required quantity of suitable underlying Zone 1 type materials. Such 
required excavations and those that were unsuitable for Zone 1 by reason of excess quantities of 
caliche or hardpan were used in Zone 3. 

Borrow Areas "C" and "C" Extension. 

Materials for embankment Zones 2 and 4 that were unavailable from required excavation were 
borrowed from Areas "C" and "C" Extension. Seventeen percent of the necessary material was 
obtained from required excavation. Zone 4 was designed to faciUtate the construction of the 
diversion cofferdam. After diversion of the river. Borrow Areas "C" and "C" Extension were subject 
to flooding during spring runoff. To assure an adequate supply of Zone 2 material when needed, all 
but 400,000 cu yds of the required Zone 2 quantity was stockpiled above the canyon wall upstream 
of the left abutment. As construction progressed, the volume of Zone 2 anticipated from required 
excavation and Zone 2 shrinkage factors were continuously monitored. By varying slightly the 
boundary between Zone 1 and Zone 2, the embankment was completed with the material available in 
the stockpile. 



MATERIALS AS PLACED 

Zone I. 

Zone 1 is the impervious central core obtained from Borrow Area "A" located on the north side of 
the river canyon near the right end of the dam. 

Material in Borrow Area "A" was about 5 to 6 percent dry of the specified moisture content. Water 
was added by either ponding or by ripping and sprinkling. Material was excavated either with a wheel 
excavator in an 8-ft cut, or by scrapers. It was compacted by 12 passes of the USBR standard 
sheepsfoot roller. Zone 1 was placed in 6-in. compacted lifts with moisture and density control tests 
determined by the rapid compaction control method (Earth Manual, 1974 — Designation E-25). 

The earthwork construction control records show the following average values for Zone 1 material for 
2,608 tests: 

Ratio of fill dry density to maximum 

USBR dry density = 98.2 percent 

Optimum moisture minus field moisture = 1 .3 percent dry 

Fill dry density, minus No. 4 = 99.5 pcf 

Fill moisture content, minus No. 4 = 18.6 percent 

Zone 2. 

Zone 2 is the inner downstream shell and the upstream shell of the embankment and also forms the 
drainage blanket beneath Zone 3 and between Zone 3 and the abutment foundation surfaces. It 
consists of a mixture of fines, sand, gravel and cobbles obtained from required excavations and 
Borrow Area "C" and "C" Extension in the riverbed deposits upstream from the dam. Zone 2 was 
compacted in 12-in. lifts by either crawler-type tractors or vibratory compactors. Density 
requirements were controlled by the Relative Density Test (Earth Manual Designation E-12). The 
average relative density for 176 construction control tests was 94 percent. 

Permeability tests were made during construction on 18 laboratory-compacted specimens. As 
reported by USBR, the coefficient of permeability ranged from 0.7x10'" cm/sec to 39.3x10'^ cm/sec 
and averaged 9.4x10 cm/sec for 16 of the specimens. Two specimens tested at extremes of 2980 
and 1784x10'^ cm/sec. 



7-5 



Coarse and fine fractions, as determined by record tests during construction were: 

Fraction Average Range 

Plus 3-in. 10 percent to 30 percent 

Plus No. 4 66 percent 45 to 76 percent 

Minus 200 4.5 percent 2 to 12 percent 

Zone 3. 

Zone 3 is an intermediate downstream shell utilizing material from Borrow Area "A", unsuitable for 
Zone 1, and Zone 1-, 2-, or 4-type materials. Zone 3 material was compacted in both I2-in. lifts with 
six passes of a 50-ton pneumatic-tired roller and in 6-in. hfts with 12 passes of a 4000-lb/ft sheepsfoot 
roller. Construction control methods used were the same as for Zone 1 . 

The earthwork construction control records show the following average values for 118 tests: 

Ratio of fill dry density to maximum 

USER dry density =97.4 percent 

Optimum moisture minus fill moisture = 1 .5 percent dry 

Plus No. 4 =1.6 percent 

Fill dry density, minus No. 4 = 97.5 pcf 

Fill moisture content, minus No. 4 =18.4 percent 

Zone 4. 

Zone 4 is the toe segment of the upstream shell utilizing the semipervious silty sands and gravels from 
the required excavations of the cutoff trench and Borrow Area "C" and "C" Extension, and also 
formed part of the cofferdam for river diversion. Downstream Zone 4 is the berm at the downstream 
toe of the dam utilized for storage areas near the power and pumping plant. Zone 2 type material 
from Borrow Area "A" was also placed in Zone 4. 

Zone 4 material was compacted in 12-in. hfts with four passes of a 40,000-pound crawler-type 
tractor. Density requirements were controlled by the Relative Density Method (Earth Manual 
Designation E-12). The average relative density for 94 construction control tests was 98 percent. 

Coarse and fme fractions, as determined by record tests during construction, were: 

Fraction Average Range 

Plus 3-in. 8 percent to 31 percent 

Plus No. 4 61 percent 12 to 75 percent 

Minus No. 200 6 percent 2 to 15 percent 

Zone 5. 

Zone 5 is the outer layer of the upstream and downstream shells, utilizing cobbles, boulders and rock 
fragments from the required excavations of the cutoff trench, the foundation key trench, abutment 
cleanup, river outlet works, auxiliary outlet works, spiUway, and Borrow Area "C" and "C" 
Extension. Zone 5 material was placed in 3-ft hfts and compacted by travel of the hauling and 
placement equipment. 



7-6 



PROJECT MATERIALS TESTING PROGRAM 

Soil Samples. 

Seventy-two soil samples were acquired by the Earth Sciences Branch, Denver Laboratory, during the 
project design period. The first 45 samples (51B-1 through 518-45, Denver Laboratory index 
number) were acquired in May 1969. Thirty-nine were disturbed fine-grained materials from three 
prospective impervious borrow areas and six were gravel and sand from two prospective pervious 

borrow areas. Two samples (51B-X46 and 51B-X47) were composited of materials from 
representative test pits in Borrow Area "A" (TP-A2) and Borrow Area "B" (TP-B2). 

Undisturbed 6-in.-diam Denison-type samples were obtained from the embankment during 
construction at approximately 10-ft vertical intervals while drilling hole DH-DNGP-1 for geophysical 
testing of the embankment and represent the interval between El. 5133.5 and El. 4940.5. The hole 
was located 100 ft upstream of Sta. 20-1-00. Twenty samples from that hole (51B-48 through 51B-67) 
were sent to the Denver Laboratory for both static and dynamic soil analyses. One composite sample 
(51BX68), representing the full length of the hole, was prepared for the various soil tests scheduled. 

Four hand-cut undisturbed samples (51B-70 through 51B-73) were obtained from the cutoff trench 
during construction at the following locations: 



kment £ Station 


Elevation 


19-H00.7 


4944.6 


19+01.2 


4945.9 


19-^04.7 


4949.3 


20-^51.3 


4944.0 



Laboratory Tests on Borrow Materials. 

Gradation and Atterberg limits were determined for each sample from Borrow Areas "A" and "B" 
and specific gravity and moisture-density relationships were determined for four selected samples, 
two from each borrow area. All samples from TP-A2, Borrow Area "A", were composited to form 
one sample (51B-X46). All samples from TP-B2, Borrow Area "B", were composited to form one 
sample (51B-X47). Tlie composite samples were tested for gradation, Atterberg limits, specific 
gravity, moisture-density relationships, permeability, one-dimensional consolidation, triaxial shear 
strength, the modulus of deformation, and Poisson's ratio. 

Sample No. 51 B-X46, which classified as ML material, consohdated about 6 percent under a 300 psi 
loading, developed shear-strength parameters of tan ^'= 0.64 and c'= 1 1.3 psi under lateral confining 
pressures of 25, 50, and 100 psi. Permeability was 0.32 ft/yr under a 100 psi loading. 

Sample No. 51 B-X47, which classified as CL material, consohdated about 6.5 percent under a 300 psi 
loading and developed shear-strength parameters of tan i^' = 0.58 and c' = 11.6 psi under lateral 
confining pressures of 25, 50, and 100 psi. Permeability was 0.18 ft/yr under a 100 psi loading. All 
tests were made on specimens compacted near maximum dry density (12,500 ft-lbs/cu ft compactive 
effort) and at either 2 percent dry of optimum moisture content or at optimum moisture content. 

The materials from borrow areas "C" and "D" are streambed gravels and sands. Two samples (51 B-38 
and 51 B-39) from Borrow Area "C" were tested for gradation and relative density. 

Laboratory Tests on Embankment Samples Obtained During Construction. 

Gradation, Atterberg limits, field moisture, and density were determined for the 6-inch undisturbed 
samples obtained from Zone 1 in Drill Hole DH-DNGP-1. These materials classified as silt or silty clay 



7-7 



(ML or CL-ML). Sample 51B-X58 was composited and remolded using approximately one-half of 
each undisturbed sample, and gradation, Atterberg limits, specific gravity, moisture-density 
relationship, one-dimensional consoUdation, and triaxial shear strength were determined. Specimens 
compacted to about 98 percent of USER maximum dry density at optimum water content for 
one-dimensional consolidation and triaxial shear testing consolidated about 7 percent under a 300 psi 
loading and developed shear -strength parameters of tan ^' = 0.70 and c' = 0.02 psi under lateral 
confining pressures of 15, 30, 75, and 100 psi. All specimens were back-pressured for complete 
saturation and then sheared under consolidated-drained conditions. 

The USER maximum dry density was 102.9 pcf at an optimum moisture content of 18.2 percent. 
The average dry density and moisture content of all the undisturbed embankment samples were 105.1 
pcf and 21.2 percent, respectively. 

Laboratory tests to determine soil behavior under dynamic loadings scheduled for sample No. 5 1 B-68 
have not been made. 

Samples 51E-70 through 51B-73 were tested for horizontal permeability in their undisturbed state. 
All were classified as silt or silty clay. Dry density varied from 85.7 to 89.4 pcf. The maximum 
horizontal permeabiUty was 18.1 ft/yr under a hydraulic gradient of 43. Permeability decreased at 
higher gradients. 

Summary of Laboratory Test Data for Zones 1 and 2. 

A summary of permeabihty tests for Zone 1 materials is shown in Table 7-1 and a summary of triaxial 
shear tests on Zone 1 materials is provided in Table 7-2. 

Riprap. 

The quarry sites finally selected and used for riprap were known as Hobbs No. 2 and Hobbs No. 2 
extension, located 3-1/2 miles north of the damsite. The rock, which is a massive vesicular to dense 
basalt, was exposed in bold outcrops with large talus blocks also present. The specific gravity ranged 
from 2.27 to 2.88. The loss by Los Angeles abrasion test was 7 percent at 100 revolutions and 31 
percent at 500 revolutions. 

Concrete Aggregate. 

Sand and gravel for concrete aggregate were obtained from Falls River streambed deposits about 6 
miles north of the damsite. Aggregate was processed at the pits into 3 in., 1-1/2 in., 3/4 in. and sand 
fractions. The gravel was subrounded with about 13 percent subangular and 4 percent flat particles. It 
was composed mainly of basalt, quartzite, and glassy volcanics with lesser amounts of schist, chert, 
and obsidian. The loss by Los Angeles abrasion test was 5 percent at 100 revolutions and 26 percent 
at 500 revolutions. 

The sand was subangular to angular and contained the same rock types found in the gravel plus 
quartz, feldspar, amphibole, garnet, and magnetite. Generally, the fineness modulus was about 3.10. 
A considerable percentage of both the gravel and sand was alkali reactive. 



PANEL'S INVESTIGATIVE ZONE 1 SOILS TESTING PROGRAM 

As described in Chapter 3, undisturbed samples were obtained from Zone 1 during exploration of the 
right abutment remnant and tested for engineering properties in a number of laboratories in 
accordance with the schedule shown in Table 7-3. The locations from which the samples were 
obtained are shown in Fig. 3-5. 



7-8 



TABLE 7-1 

SUMMARY OF PERMEABILITY TESTS 

FOR ZONE 1 MATERIALS FROM 

BORROW AREA "A" 



Lab 










Coefficient 




Sample 


Field 


Depth 


Smaller Than 




of 


USBR 


Number 


Designation 


Sampled 


No. 200 Sieve 


PI 


Permeability 


Exhibit 






(ft) 


(percent) 




(ft/yr) 


(Appendix A) 



Remolded* (Vertical) 



51B-X46 


TP-A2 


0-18.0 


74 


NP 


0.32 


1.3, Table 3 


F-21 


A-4 


0-10. 


68 


3.1 


0.37 


1.3, Table 10 


F-81 


A-13 


0-20. 


68 


10.0 


0.01 


1.3, Table 10 



*USBR Designation E-13, 3" high sample in 8" permeability cylinder loaded to equivalent weight of 

mi. 



Undisturbed* (Horizontal) 



51B-70 


20+51.3 


94 




95 


NP 




12.3 




24,Memo Chief, 


51B-71 


19+00.7 


93.4 




93 


6 




13.0 




Earth Sciences 


51B-72 


19+04.7 


88.7 




88 


NP 




8.5 




Branch, 10/6/75 


518-73 


19+01.2 


92.1 




97 


3 




6.4 






*High-pressure 


permeability 


test apparatus 


under 


lateral 


pressure 


of 


55 psi. 


hi 


-place density. 



85.7-89.4 pcf. Average for Zone 1, 100 pcf. 



146 
Record Tests 



Remolded* (Vertical) 






See Exhibit 


0.02- 


39, Earthwork 




3.57** 


Central Data 



*USBR Designation E-13. 
** Kav. = 0.47 ft/yr 



7-9 



All laboratories also made classification tests on the samples which they tested for other properties. 

Classification Tests. 

Table 7-4 shows the physical properties of representative samples taken from the Zone 1 material of 
the right abutment remnant. 

Triaxial Compression Tests. 

Five series of tests were made to determine the stress-strain characteristics of Zone 1 material for use 
in finite element stress analyses. These tests were made under consolidated-drained conditions at 
confining pressures of 15, 40, 70, and 100 psi on 1.4-in.-diam specimens, 3-1/2 in. long. Three series 
were made with the specimens at placement moisture content and two at saturated moisture content. 
One of the series at placement moisture and one at saturated moisture were conducted by 
stress-control techniques to investigate the creep characteristics under loads sustained for several days. 
Guided by the results of these tests and those of the Project Soils Testing Program, strength and 
stress-strain parameters were developed for use in the fmite element analyses as discussed in 
Appendix D. 

Permeability Tests. 

Seven tests were made on specimens cut from undisturbed block samples for permeability in a 
horizontal direction. Three tests were made with the specimen saturated and four unsaturated. The 
overall average horizontal coefficient of permeability was 5x10 cm/sec. 

Erosion and Dispersion Tests. 

Although the highly erodible character of windblown silts of the type used in Zone I are well known 
to the engineering profession, the erodibility characteristics of these soils were determined by both 
quantitative and qualitative tests. The quantitative test procedures used were the flume test and the 
rotating cylinder test. The qualitative tests used were the crumb test, the dispersion ratio test and the 
pinhole test. 

The flume and rotating cylinder tests which are specifically designed to test soil erodibility indicated 
clearly that the materials tested were highly erodible. The pinhole, crumb, and dispersion ratio tests, 
which are primarily designed to test the dispersive character of soils yielded mixed results. The results 
of the erosion and dispersion tests coupled with field observations of the material as it was excavated 
from the remnant on the right abutment, leave no doubt that the Zone I material was highly 
erodible. 

Unconfined Compression Tests. 

Uncontmed compression tests were made on undisturbed specimens at placement moisture and on 
specimens compacted at various moisture contents to densities comparable with that of the 
undisturbed sample to assess the stress-strain relationships (brittleness) of Zone 1 material when 
placed at moisture contents both dry and wet of optimum. These tests confirm that Zone 1 material, 
when compacted dry of optimum, is brittle as evidenced by the shape of the stress-strain curves. The 
complete reports of tests are available in the Panel's records. 



COMMENTS 

Zone 1 — Core Material. 

As has been described above, the Zone 1 material which formed the core comprised more than half of 
the volume of the dam. Tlie material is a fine, wind-blown silt, primarily an ML material. As 



7-10 



oa £ 



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£ a 


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a 3 




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7-11 



TABLE 7-3 
POST-FAILURE TESTS PERFORMED FOR INDEPENDENT PANEL 





Samples 




Laboratory 


Supplied 

5255D4-I 


Tests Made 


Northern Testing 


Drained triaxial shear at field moisture 


Laboratories 


5250IR-U3-2 


Drained triaxial shear at saturation 


Billings, Montana 




moisture 




5270D3-1 


Spare 


Earth Sciences Branch 


5270U2-1 


Drained triaxial shear at field moisture 


USBR 


5755U4-1 


Drained triaxial shear at field moisture 


Denver, Colorado 


5255D5-1 


Drained triaxial shear at saturation 
moisture 




5270D4-2 


Unconfmed compression 




5270D5-1 


Spare 




5270U5-1 


Spare 




5285U4-1 


Spare 


Corps of Engineers 


5240D5-1 


Pinhole dispersion 


Waterways Experiment 


5255D4-2 


Pinhole dispersion 


Station 


5270U3-1 


Pinhole dispersion 


Vicksburg, Mississippi 


5250IR-D3-1 


Pinhole dispersion 




5260IR-D2-1 


Pinhole dispersion 


University of California 


5240D5-2 


Rotating cyUnder erosion 


Davis, California 


5255D4-3 


Rotating cylinder erosion 




5270U3-2 


Rotating cylinder erosion 




52501R-D3-2 


Rotating cylinder erosion 




5260IR-D2-2 


Rotating cylinder erosion 




5240D5-3 


Flume erosion 




52351E-D4-1 


Flume erosion 




5270U3-3 


Flume erosion 




5255U3-1 


Flume erosion 




5255D3-1 


Hume erosion 


University of California 


5270U5 


Horizontal permeability 


Berkeley, California 


5270D3-2 


Horizontal permeability 


Teton Project Laboratory 


All 


Classification 


Newdale, Idaho 







7-12 



TABLE 7-4 
SUMMARY OF CLASSIFICATION TEST DATA 
SAMPLES FROM REMNANT OF KEY-TRENCH FILL 
RIGHT ABUTMENT 







Approx. Std. 


Usual 


Property 


Mean 
26.4 


Deviation 

0.8 


Range 


Liquid limit 


23-31 


Plasticity Index 


3* 


- 


0-11 


Water Content 


22 


5 


14-32 


% less than 200-mesh 


80 


6 


55-95 



No. of samples tested for each property was approximately 150 

* 40% of samples non-plastic 

Usual classification ML, occasional samples CL 



7-13 



compacted in the dam at less than optimum water content, it was very brittle and, because of its 
composition, extremely susceptible to erosion by flowing water. These two properties of the Zone 1 
material, erodibility and brittleness, were prime factors which contributed to the faUure of Teton 
Dam. The brittle nature of the Zone 1 material substantiaUy increased the potential for cracking, and 
would sustain cracks once opened. The very high erodibility of the Zone 1 material permitted rapid 
piping of the material when subjected to flowing water through cracks in Zone 1 and along open 
joints at the foundation contact of Zone 1. 

The strength of the Zone 1 material was a factor in the failure mechanism. The material, as 
compacted in the dam, permitted continuous erosion channels (pipes) to be formed in the core 
without any evidence of their existence becoming visible from the exterior of the dam. There is no 
doubt that channels had developed within the dam, in Zone 1 and possibly also in Zone 2, before the 
leaks were noticed at the downstream face of the dam on the morning of June 5th. The large volumes 
flowing from the leaks, the "loud burst" that was heard when the leak at El. 5200 broke out of the 
dam, and the observation of the 6-ft-diam tunnel in the dam reported by Mr. Robison, the Project 
Construction Engineer, all point to the probability that the Zone 1 material had been eroding for 
some time before the visible signs of faUure appeared on June 5, and that the combination of 
erodibihty and strength of this material had led to the formation of a major tunnel or pipe. Had the 
material been weaker, the internal erosion might have caused caving near the place where erosion 
initially took place, and continuing erosion might have resulted in a sink hole appearing on the 
surface of the dam. 

Thus, it can be concluded that the nature of the Zone 1 material, and the manner in which it was 
utilized, were major factors leading to the failure of the Teton Dam. 

Zone 2. 

Zone 2 was intended to form "... a blanket and chimney drain in the downstream shell ... to assure 
positive control of the phreatic line during periods of high reservoir levels and to provide drainage 
control of seeps through the foundation. . . ." (p. 24, USBR "Design Considerations," October 1971). 

Record permeability tests made on remolded samples of Zone 2 material during construction raise 
some question about the suitability of this material for a drainage blanket and chimney drain. These 
test results suggest that much of the Zone 2 material may have been nearly as impervious as the Zone 
1 material. 

Grain-size analyses of large-volume samples of Zone 2 material taken from the remnant on the left 
side showed that between 5 and 1 1 percent of the material was finer than the No. 200 sieve. This 
suggests a low permeability. Further evidence that the Zone 2 material is less pervious than planned is 
the fact that Zone 2 of the dam remnant on the left is standing on very steep slopes, which a 
non-cohesive, free-draining sand and gravel would not do. 

The low permeability of the Zone 2 material probably prevented the leakage which was occurring 
through the erosion channels in Zone 1 from making an earlier appearance at the downstream face of 
the dam. 



7-14 



CHAPTER 8 
PROJECT DESIGN 

(Panel Charges Nos. 5 and 7) 

Teton Dam was designed under the direction of the Office of Design and Construction, U.S. Bureau 
of Reclamation, at the Denver Federal Center. Its Division of Design had responsibility for 
supervision and coordination of the design program. 



DESIGN OF DAM 

USBR design notes* indicate recognition of the difficulties presented by conditions at the damsite. 
Early consideration was given to control of seepage issuing from the foundation under the 
embankment and to prevention of piping due to cracks in the core. Some of the measures considered 
as the design evolved were: (1) excavation to groutable rock in key trenches; (2) excavation, dental 
treatment, special compaction, and slush grouting under the core outside the key trenches; (3) drains 
or pervious blankets on the downstream side of the cutoff trench; (4) blanket grouting, slush 
grouting, guniting, or special compaction of earthfill in the cutoff trench bottom; (5) downstream 
drain holes or tunnels; and (6) semipervious zones on the upstream and downstream sides of the core 
so that cracks in the core would not result in failure by piping. Not all of these measures were 
adopted in the final design. 

The designer's notes identify the core material as a silt, or soil classification ML. It is labelled as 
abundant, inexpensive, strong in frictional resistance, low in permeability, erodible, and susceptible to 
cracking. Late in 1970, apparently to avoid damaging the environment by disturbing the alluvial 
materials downstream from the dam, the designers decided to use as much as possible of the silt, with 
a corresponding reduction of sand and gravel requirements. 

The design finally adopted for the Teton Dam and its appurtenances is shown in Figs. 1-2 through 
1-6. A description of this design follows: 

The seepage barrier in the central part of the dam consisted of a wide impervious zone of silty 
material in the embankment proper and a grout curtain in the foundafion rock. In the abutments it 
consisted of an impervious backfill of the same silty material in a key trench excavated to a depth of 
about 70 ft through the heavily jointed rock and, beneath the backfUl, a continuation of the grout 
curtain. Beneath the spillway structure on the right abutment, the key trench was omitted and the 
grouted cutoff extended downward from the base of the structure. 

A substantial transition zone of selected sand and gravel was provided upstream of the seepage barrier 
in the embankment (but not in the key trenches). 

Downstream of the impervious core of the embankment proper was a drainage or filter zone of 
modest dimensions, consisting of selected sand and gravel. It extended to the bedrock of the valley 
floor and was then continued downstream beneath a random zone and a downstream rockfill zone. 
No transition material was placed between the impervious core and the alluvium on the bedrock 
vaOey bottom and no transition zone was provided in the key trench downstream of the grout cap 



♦Notes by W.G. Harber, USBR file, dated March 1967, November 1969, May 1970, and October 
1970. 



8-1 



against the bottom or side of the bedrock trench. Instead, the core material in the key trench was 
placed directly against the rock by "special compaction" of a 2-ft thickness at a moisture content 
specified to be somewhat above that of the rest of the backfill and compacted by small hand-operated 
compactors or by rubber-tired equipment. 

The specifications provided for grouting under pressure any faults, joints, shear zones, springs, or 
other foundation defects, when determined necessary by the contracting officer. There were no 
provisions for treatment of such foundation defects by the surface appUcation of slurry grout. 

During post-failure investigative excavation of the embankment remnant on the right abutment 
between the spillway and about Sta. 13-I-00, no evidence was found that joints had been treated on 
the bottom of the key trench in that area. Actual construction procedures are covered in Chapter 9. 

No drainage system was provided for either abutment, and no downstream piezometers were called 
for. 

Thus, the final design depended for seepage control almost exclusively on the impervious core, the 
key trench backfill and on the grout curtain. Although the upstream face of the impervious core in 
the embankment proper was protected by a transition zone, the only downstream defense against 
cracking in the impervious fill or against concentrated leakage through it was the drainage zone, and 
this did not extend into the key trenches. In fact, there is reason to question whether there was an 
effective downstream drainage zone anywhere since Zone 2 material does not appear to have been 
adequately permeable (Chapter 7). 



Foundation Details. 

The foundation treatment specified at Teton Dam was based upon an examination of drill hole data 
such as rock type, extent of fracturing, driU hole water losses, and on the pilot grouting done in 1969. 
It consists basically of four elements, as shown on Figs. 1-2 and 1-3: 

(1 ) 70-ft-deep, steep-sided key trenches on the abutments above El. 5 1 00. 

(2) A cutoff trench to rock below EI. 5 100. 

(3) A continuous grout curtain along the entire foundation, extending about 1000 ft into the 
right abutment and about 500 ft into the left abutment. The grouting pattern consists of one row of 
grout holes with two outer rows of grout barrier holes, except in certain areas below El. 5100 where 
the foundation was less jointed and where only one or two Unes of holes were placed. Actual 
techniques and patterns adopted during construction varied from those specified in design. (Chapter 
9.) 

(4) Excavation to rock under Zone 1 on the abutments. 



Stripping. 

Stripping was required beneath all embankment zones outside of the cutoff trench. Stripping depths 
used to arrive at the specifications estimate were based on drill hole logs, test pit logs, and 



8-2 



descriptions and photographs in the design data. These data indicated that the foundation below El. 
5040, with the exception of the existing river channel, would have to be stripped to an average depth 
of approximately three feet. 

Outside the cut slopes of the cutoff trench and key trenches, the embankment foundation area was to 
be stripped to uncover material equal in strength to the overlying embankment materials. The valley 
floor downstream, underlying Zones 2 and 5, was to be stripped to expose Zone 2 type material to 
insure proper drainage characteristics in the downstream toe, and the abutments were to be shaped to 
provide a reasonably smooth surface that would permit adequate compaction of the embankment 
against the foundation with Uttle or no special compaction. 

In accordance with the USBR design practice of not requiring stripping to rock under coarse-grained 
zones, stripping specifications did not require removal of in-situ impervious soils from the abutments 
prior to placement of the Zone 2 blanket drain. As apphed at Teton Dam, this requirement is based 
on the USBR's premises that: 

(1) "If the rock is open, any normal flow would be continued in the jointed rock." 

(2) "Concentrated normal flows which would surface could be handled by the Zone 2 gravel 
drain." 

(3) "Flows large enough to cause washing of silt beneath the gravel blanket into rock 
openings were not expected." 

Stripping was not required under the El. 5041.5 downstream berm or under the fill on the southeast 
side of the powerplant tailrace charmel. 

Key Trenches. 

A foundation key trench was to be excavated above El. 5100 on each abutment to intercept the more 
open rock joints and to reach a groutable horizon. The trench was to be excavated 70 ft deep, 
measured from the original ground surface, as shown in Fig. 1-3. 

A bottom width of 30 ft was selected to provide space for construction equipment and for three lines 
of grout holes. In response to questions posed after the failure, the USBR stated that although the 
hydraulic gradient was recognized as somewhat higher across the key trench than the normal USBR 
standard, laboratory tests on the material did not indicate that there would be a problem with piping. 

Spillway Treatment. 

The key trench was omitted under the spillway. The bottom of the trench was sloped at 1.5:1 from 
the edges of the spillway cut down to the 70-ft trench depth. It was anticipated that blanket grouting, 
closely spaced closeout holes, and large-volume grout injection would be required to seal the 
foundation under the spillway. 

The decision not to continue the key trench under the spillway was based on a desire to avoid 
differential settlement that might crack the spillway structure. The rock foundation under the 
spillway was judged to be adequate to carry the design load and was considered suitable for blanket 



8-3 



and curtain grouting. The cutoff beneath the spillway crest formed a portion of the grout cap for 
deep grouting of the right abutment. 

Cutoff Trench. 

The design width of the cutoff trench varies on the basis of a reference width of 30 ft at El. 4920, as 
shown on "Cutoff Trench Plan," (Fig. 1-3). The El. 4920 reference line was used to dimension the 
cutoff trench and does not indicate the bottom of excavation. Above El. 5030 on the abutments 
where overburden is shallow, the top of the cut slope for the cutoff trench is referenced to the 
intersection of outer slopes of Zone 1 with the bottom of stripping. This intersection line is shown in 
Fig. 1-3, and in "Typical Abutment Section A-A," Fig. 1-2. 

Across the canyon floor the specifications estimate provided for excavation through recent 
river-deposited gravel and into the rock in the bottom of the cutoff trench. On the abutments the 
cutoff trench was to be excavated through weathered and loose or open-jointed rock to a firm 
relatively tight horizon. In addition, irregularities were to be removed and the remaining surface 
sloped to 0.5:1 or flatter. 

Grouting. 

Erosive seepage under the embankment was to be prevented by injecting the foundation with grout. 
Foundation investigations at the damsite indicated that large grout quantities would be required to 
produce a tight curtain, and that special procedures would be required to prevent excessive travel of 
the grout. 

Water tests in core drill holes indicated the abutments above El. 5100 to be very pervious. In these 
areas, therefore, three rows of grout holes were to be provided, with the outer rows 10 ft upstream 
and 10 ft downstream from the center. 

The pilot grouting program in 1969 demonstrated that conventional grouting procedures would result 
in grout travel far beyond the limits of the intended grout curtain. From a design standpoint, grout 
extending more than about 100 ft from a vertical plane through the grout cap was judged to serve no 
useful purpose and measures were taken to restrict treatment to the curtain area. 

The stated purpose of the two outer rows of grout holes, spaced at 20 ft except in the basalt area, was 
to restrict grout travel "by pumping thick mixes and provide an upstream and downstream barrier to 
allow the centerline row of holes to be grouted effectively under pressure with less chance of travehng 
distances of several hundred feet downstream or upstream." The outer rows were "not expected to be 
completely solid barriers. . . ." 

Except where interrupted by the auxiliary outlet works access shaft, a continuous grout cap was to be 
provided in rock formation for the fuU length of the dam. Concrete in the grout cap was to be placed 
approximately to the general level of the adjacent bottom of the trench after final cleanup. In 
estimating specifications quantities, grout cap excavation was assumed to range in depth from the 3-ft 
minimum up to 8 ft when crossing zones of intensely jointed rock. In the vicinity of the test areas for 
blanket grouting and curtain grouting, the centerUne of the cutoff trench and the key trench was to 
be located so that the pilot grouting would become part of the final grout curtain. 

Specifications permitted the contractor to construct the grout cap in the form of a stairway on the 
abutments. Steps, if constructed, were to be formed by extending the cap above the adjacent bottom 
of the trench. 



8-4 



The grout cap in the bottom of the key trench was placed in a notch with minimum specified 
cross-sectional dimensions of 3 ft deep by 3 ft wide. A detail is shown in Fig. 1-3. Excavation of this 
notch required some use of explosives, with the attendant probability of some fracturing of the rock 
adjoining the grout cap. Since this rock was already extensively jointed and fractured in its natural 
state, blasting for the grout-cap notch would have tended to worsen its condition. 

Specific measures were not taken to assure seaUng of the upper part of the rock under the grout cap, 
such as gravity grouting in closely spaced blanket holes. 

Blanket grouting was to be provided for special treatment of open cracks, jointed areas, zones of high 
grout take, and other defects disclosed in the bottom of the cutoff trench or found during curtain 
grouting. Blanket grouting was not general, however. Blanket holes, if required, were to be located by 
the contracting officer as the work progressed. 

Large open joints or cracks in the bottom of the key trenches and cutoff trench were to be treated by 
(1) cleaning out the crack with air and/or water jets, (2) setting grout pipe nipples in the crack, (3) 
sealing the surface by caulking and/or grout, (4) drilling, if required, and (5) low-pressure grouting 
through the nipples. Evidently Uttle of this treatment was actually done, at least in the part of the 
key trench exposed by the Panel's investigations. Actual foundation treatment is described in Chapter 
9. 

The older alluvium beneath the intercanyon basalt on the left side of the river bottom was 
investigated by water testing drill holes during the test grouting program in 1969 for the purpose of 
determining the groutability of the alluvium and overlying basalt. The results of the pilot grouting led 
to the conclusion that the estimated 5- to 15-ft thickness of alluvium between the basalt and rhyolite 
was groutable with a cement grout. For economic reasons, the alternative of chemical grouting was 
not specified. 

Embankment Details. 

The USBR volume titled "Design Considerations for Teton Dam," dated October 1971, documents 
the basic concepts of the embankment design. As seen on Fig. 1-2, the dam is composed of five zones. 
In addition, a thickness of 3 ft of riprap was placed on the upstream slope above El. 5185. 

For economic and environmental reasons (primarily opposition to downstream channel borrow), 
consideration was given early in the design to building a nearly homogeneous dam predominantly 
composed of sUt. However, for an embankment of the required height, the upland silts were found to 
have some undesirable characteristics, including a high percentage of fines, some caliche, a low 
maximum dry density of about 100 pcf, and a tendency to crack when subjected to differential 
settlement. Since Teton Dam would rest on about 100 ft of unconsolidated overburden and since it is 
in a seismicaUy active region, the designers concluded that a homogeneous dam involved unacceptable 
risks and that the core of aeolian sOt should be surrounded by sand and gravel for earthquake crack 
protection. 

In addition to the Zone 1 silt and the Zone 2 sand and gravel, the design provides the third, fourth, 
and fifth zones to permit maximum utilization of required excavations for foundations and 
structures. 

Embankment Zoning. 

Zone 1 is the impervious core intended to form the water barrier of the dam. It was specified to 
consist of ML and CL type soils. 



8-5 



CH and MH type materials in the borrow areas were to be avoided or blended in the borrow cut with 
silty material to preclude layers of low-strength clay in the dam. CaUche and cemented soil that 
would break down under the roller could be blended and placed in Zone 1. Material predominantly 
composed of caliche and cemented hard layers of soU was allowable in Zone 3. 

Zone 2 was intended to form a blanket and chimney drain in the downstream shell for the purpose of 
controUing the phreatic line during periods of high reservoir levels and to provide control of seepage 
through the foundation. The Zone 2 blanket was extended up the abutment so that there was a layer 
of Zone 2 between Zone 3 and the foundation in all sections of the embankment. Test pit logs in the 
borrow area indicated that the available material was predominantly gravels that tended to be 
deficient in fines. From the designers' standpoint, mixing the surface layer of silty sand with the 
underlying gravel was regarded as a desirable procedure when it could be accomplished in the normal 
excavation process; moreover, if concentrations of silty, sandy gravels were encountered in the 
borrow area, they could be utilized in Zone 2 provided they could be reduced to an acceptable 
moisture content. Such material was to be placed next to Zone 1 and in the upstream shell, reserving 
the more pervious gravels for the Zone 2 chimney next to Zone 3 and the blanket under Zone 3. 

Zone 3 is composed of miscellaneous material placed in the downstream part of the embankment to 
accommodate material unsuitable for Zone 1 because of rocks larger than 5 in. or layers of caliche or 
hard-cemented materials that were excavated in the borrow areas. The top elevation of Zone 3 could 
be varied according to the quantity of material that became available from required excavation. Zone 
1, 2, and 4 type materials were allowed in Zone 3. 

Since Zone 3 was to provide structural stability, some degree of moisture control was regarded as 
essential. The best practicable placement moisture for the specified compaction effort was judged as 
probably sUghtly dry of optimum. It was recommended by the designers that placement moisture in 
Zone 3 be maintained approximately as recommended for Zone 1 . 

Zone 4 is a part of the upstream toe where silty sands and gravels were used to construct a cofferdam 
for river diversion. Zone 4 material was also used for the berm at El. 5041.5 at the downstream toe of 
the dam and for the storage areas downstream from the control and warehouse structure. 

Zone 5 is the outer shell composed of rock from the required excavations in the cutoff trench, key 
trenches, abutment cleanup, river outlet works, auxiliary outlet works, spillway, and Borrow Area 
"C" and "C" Extension. 

The riprap for upstream slope protection was basalt obtained from sources in the region near the 
dam. 

Crest Details. 

Teton Dam is located in Earthquake Zone 3 on the Seismic Risk Map of the United States (Fig. 6-1). 
At the crest, earthquake design considerations included heavy slope protection at the top of the 
embankment and sand and gravel fills around the silty core to provide filter blanket protection in the 
event the core was cracked. A 35-ft-wide crest was adopted to provide space for zones meeting these 
criteria. The crest was cambered 3.0 ft to allow for settlement. 

Special Compaction. 

"Special compaction" was required in the bottom of the cutoff trench and in the key trenches. For 
the specifications estimates, an average vertical depth of 12 in. of "specially compacted" material was 
assumed in the bottom of the cutoff trench below El. 5040 and above El. 5 1 50 and in the bottoms of 



8-6 



the key trenches; however, the depth was expected to vary considerably, depending on the roughness 
of the foundation. Where a smooth surface was exposed, consideration was to be given to obtaining 
compaction at the embankment-foundation contact by placing the material adjacent to bedrock at 
optimum or slightly wet of optimum moisture content, by using a thicker initial layer, up to 12 in., 
and by increasing the number of roller passes to obtain compaction. An average of 24 in. of specially 
compacted earthfill, measured horizontally, was to be placed against the slopes of the key trench; also 
24 in. of such compacted material measured horizontally would be required in the bottom of the 
cutoff trench against steep abutment slopes between Els. 5040 and 5 150. 

The Panel's investigation did not indicate that the fill against the rock in the key trench was wet of 
optimum. 

Stability Analyses. 

The embankment was analyzed for stability by the USER standard procedure for stability analysis 
with the least factor of safety being determined by a computer program using an automatic search 
technique. 

Design parameters for friction and cohesion were adopted as follows: 

Material Cohesion Tan ^ ' 

Zones 1 and 3 11.6 psi 0.58 

Zones 2, 4 and 5 0.70 

The parameters used for Zone 2 were also used for the alluvial foundation. The permeabilities of the 
materials were determined from laboratory tests. Pore water pressures for the high-level steady state 
and for the drawdown stage were computed from flow nets. 

The analysis indicated safety factors considered by the designers to be conservative for rapid 
drawdown, high-level steady state, and the construction condition. Safety factors were calculated by 
the USER to be as follows: 

Construction Condition 1 .47 

High-Level Steady State 1.69 

High-Level Steady State With Earthquake 

(with pseudo static factors, Horiz. = 0.1 , 

Vert. = 0.0) 1.32 

Rapid Drawdown 2.36 

The Independent Panel has not reviewed these stability analyses further, since they are not regarded 
as pertinent to the failure. 

Filter Criteria. 

In USER practice, filter criteria are used to design narrow filters but may be relaxed when zones of 
pit-run sand and gravel are incorporated in the embankment, as was the case at Teton Dam. The 
Bureau filter criteria for subrounded particles are: 



_, 50 percent size filter material 

Rcr,= r?r T" — ;: r~T = 12 to 58 and 

->" 50 percent size base material 

_ 15 percent size filter material 

15 15 percent size base material 



8-7 



Although much of Zone 3 material was the same as Zone 1 silt, a filter was not included between 
Zone 3 and the Zone 5 rockfill since Zone 2 upstream from Zone 3 was expected to control the 
phreatic line and prevent Zone 3 from becoming saturated. 

Consideration of Differential Settlement. 

Design consideration was given to possible differential settlements and subsequent cracking of the low 
plasticity Zone 1 fill due to the steep rock abutments and deep key trenches. However, the USBR has 
stated in response to questions after the failure, that its experience with such material had not 
indicated that tension would develop in the embankment, even with such foundation configuration. 

Instrumentation. 

According to the statements made after the failure, devices for measuring internal movements and 
water pressures were considered by the USBR to be unnecessary at the Teton Dam because 
instrumentation was "not normally used for structures which are constructed of materials previously 
instrumented at other dams and for which [there are] satisfactory performance records." 
Performance records were said to be available for dams "constructed with similar material and on 
similar foundations." 



DESIGN OF AUXILIARY OUTLET WORKS 

The auxiUary outlet is a concrete-lined tunnel through the right abutment, with a diameter of 6 ft 
upstream of the gate chamber and 7 ft 6 in. downstream from that point. (The latter diameter was 
increased from 7 ft 3 in. after the design was done.) Its centerline coincides with the projected 
centerUne of the spillway for most of its length. Details of this facihty are shown in Fig. 14. The 
auxiliary outlet works were designed to accommodate streamflow for the period from October 1 to 
April 30, during which time the river outlet works were to be completed, and for passing riverflow 
while any future repairs or inspection of the river outlet works was taking place. A discharge rating 
curve is shown in Fig. 1-2. 

The tunnel and adit, the gate and shaft chambers, and the access shaft were excavated in densely 
welded ashflow tuff for their entire distances. 

DESIGN OF RIVER OUTLET WORKS 

The river outlet works through the left abutment include a 1 1 1-ft-high, 13.5-ft-diam intake structure, 
a 2,127-ft-long, 13.5-ft-diam tunnel; and a 320-ft-high, 18.5-ft-diam gate chamber shaft. The tunnel 
was buUt to serve as the main outlet works and as the intake to the powerplant. Details of this facility 
are shown in Fig. 1-5. A discharge rating curve is provided in Fig. 1-2. 

Most of the tunnel was driven, and the intake and gate chamber access shafts were excavated, in 
densely welded ashflow tuff. 



DESIGN OF SPILLWAY 

Details of the spillway at Teton Dam are shown in Fig. 1-6. 

The spillway design was based on requirements for passing a flood with a peak inflow of 22,400 cfs 
and a 15-day volume of 200,000 acre-ft with a reservoir level at El. 5324.3. A discharge rating curve is 
shown in Fig 1-2. 



8-8 



COMMENTS 

From a design standpoint, the appurtenant structures of the dam had no direct relationship to the 
failure. On June 5, 1976, the reservoir water had entered the approach charmel of the spillway, but 
did not reach its crest. The spillway therefore was not required to function. Nothing in the operation 
of the auxiliary outlet works indicated any deficiency in design. Construction of the river outlet was 
incomplete, so its design was not tested during the emergency. 

The capability of rapid lowering of a reservoir during a crisis is an important consideration in sizing 
outlet facilities. There are no widely accepted rules for satisfying this general requirement. In fact, 
many important dams have no facilities to permit emptying the reservoir quickly. In the case of 
Teton Dam, the combined capacity of the two outlets, if both had been operable, was 
approximately one-third more than necessary to pass reservoir inflows during the ten days preceding 
the disaster. The capacity in excess of this requirement was enough to enable lowering the reservoir 
level about one foot per day. This indicates that a moderate emergency capability was designed into 
the outlet system. 

Comments on the relationship of the design to the failure are presented in Chapter 12. 



8-9 



CHAPTER 9 
PROJECT CONSTRUCTION 

(Panel Charges Nos. 6 and 8) 



CONTRACT AND SUBCONTRACT AWARDS 

The final design of Teton Dam was completed in early 1971 , and the drawings and specifications were 
issued under Specifications No. DC-6910, Volumes 1 to 4. Invitations for construction bids to cover 
all items of the dam and associated facilities, except major electrical and mechanical items at the 
power and pumping plant, were issued on July 22, 1971. Bids were received on October 29, 1971. 
Contract award was made to the joint venture of Morrison-Knudsen-Kiewit on December 13, 1971, 
and notice to proceed was given on December 14, 1971 . The contract award totalled $39,476,142. 

The contractor awarded a number of subcontracts during the progress of the project, such as the one 
to McCabe Bros. Drilling Company for drilling and foundation grouting for the dam. 



SPECIFIED CONSTRUCTION SCHEDULE 

The required overall schedule is given in Par. 15 of the General Conditions and the schedule details 
are deferred to a contractor-prepared schedule under Par. 17. The basic requirement was that all work 
be completed within 1800 days of notice to proceed. Accordingly, the contract completion date was 
November 17, 1976. Because of change orders, the date was extended to October 27, 1977. 

The detailed schedule, as mutually amended and agreed to between the contractor and the USBR in 
early 1976 has been examined only to the extent necessary to evaluate compliance with critical dates 
for certain features required for handling water storage and controlled release. A comparison of 
required and attained dates is given below: 

Item Completion Date 

Contractor's Approved 

Schedule Actual 

Auxiliary Outlet Works (In Service) Aug. 31, 1975 Oct. 3, 1975 

Embankment (Essentially Complete) Nov. 15, 1975 Nov. 26, 1975 

Spillway (Essentially Complete) May 30, 1976 June 4, 1976 

River Outlet Works Mar. 31, 1976 (Incomplete June 5, 1976) 

The significance of the delay in completion of the river outlet works is discussed in Chapter 10. 



DIVERSION AND CARE OF RIVER 

Diversion of the river was a responsibiUty of the contractor, and was initially handled by a 70-ft-high 
embankment cofferdam located under the upstream toe of the main dam. The contract required a 
13.5-ft-diam Uned river outlet tunnel through the left abutment. The cofferdam was constructed on 
river aUuvium with underseepage controlled by pumped wells downstream. The crest elevation was El. 
5100, providing a diversion capacity of about 5300 cfs. Diversion through this left abutment tunnel, 



9-1 



later to be converted to serve as the permanent river outlet works, was commenced on June 8, 1973, 
following a 14-month tunnel construction period. 

Immediately thereafter, construction was started on the auxiliary outlet works tunnel through the 
right abutment. This 6.0 to 7.5-ft-diam lined tunnel, with intake invert at El. 5047, was completed in 
September, 1975; and on October 3, 1975 the river outlet tunnel entrance was closed by placement 
of stoplogs and all subsequent diversion of river flows past the damsite was made through the 
auxihary outlet. Since these works had a maximum rated capacity of slightly more than 850 cfs, river 
flows in excess of that capacity, a common occurrence in late winter and spring, could only partially 
be passed, with storage of the remaining flow. 



SITE PREPARATION 

Clearing. 

The specifications required clearing and stripping at the dam and powerhouse sites only. 

Excavation. 

In regard to the damsite, the specifications required stripping of all loose topsoil and organic materials 
from the entire site, excavation of alluvium from the riverbottom cutoff trench, and excavation of 
blasted rock from the two abutment key trenches. From photographs of construction, it is clear that 
stripping of the abutment areas under Zone 1 was taken down to the bedrock surface, but under the 
other embankment zones relatively shallow stripping was done, leaving slopewash and talus materials 
in place. Excavation volumes originally planned were estimated as follows: 

Abutment Stripping 100,000 cu yds 

Abutment Key Trenches 350,000 cu yds 

Cutoff Trench 650,000 cu yds 

This work was carried out essentially as planned, except that it was apparent from as-excavated cross 
sections that the planned 1/2:1 key trench side slopes specified in the design were somewhat 
impracticable in the initial 20 to 40 ft depths below bedrock surface because of the loose, intensely 
jointed nature of rock at those depths. Accordingly, it was necessary to lay back the slopes of the 
upper third to half of the trench depth to inclinations varying from 1:1 to 2:1, substantially 
increasing the rock excavation volume. 

Damsite excavation was initiated on April 17, 1972, working at the left end of the cutoff trench area, 
and was essentially completed by late 1973. 

Drainage. 

Excavation of the cutoff trench through alluvium to a depth of about 100 ft in the river bottom 
portion of the site between about Stas. 17-1-00 and 24-K)0 required extensive drainage of seepage from 
beneath both upstream and downstream cofferdams and from the abutments. The control facilities 
used consisted principally of pumped wells in the alluvium and pumped sumps on the cutoff bottom 
at rock surface. These systems have not been studied in detail because of their unlikely relationship to 
the failure of the dam. 



9-2 



PROJECT SURVEYING RECORDS 

Information available to the Panel indicates that the project was provided with conventional second 
order surveying controls for both horizontal and vertical reference points. The local horizontal 
controls were tied to first order geodetic surveys at distance of 15 to 30 miles from the project. 
Vertical controls were based on available U.S. Coast and Geodetic Survey bench marks. Details of 
project survey data relating to settlements and deflections are presented in Chapters 5 and 11. The 
Panel believes that the surveying work was conventional and acceptable. 



FOUNDATION GROUTING AND TREATMENT 

General. 

It is clear from the great volume of records, summaries, reports and data that, during construction, 
special emphasis was placed on foundation grouting. Because it is impracticable to attach all this 
information, a summary is given here. A more extensive description is given in the paper by Peter P. 
Aberle, published by the American Society of Civil Engineers in Rock Engineering for Foundations 
and Slopes, 1976. Vol. 1, and entitled: "Pressure Grouting Foundation on Teton Dam." The total 
grouting program entailed drilling 118,000 lin ft of grout hole and injecting nearly 600,000 cu ft of 
cement, sand and other materials, at a contract cost of $3,800,000. 

Site Conditions. 

From preconstruction geologic evaluation of the damsite, it was apparent that much of the 
foundation bedrock to depths of at least up to 100 ft was highly pervious, and that curtain grouting 
would be difficult, extensive and expensive. To obtain a quantitative assessment of the problem, a 
Pilot Grouting Program was carried out on the left abutment in 1969, as described in Chapter 4. This 
program showed that it would be extremely costly to attempt to curtain-grout the upper 70 ft of 
foundation bedrock for the dam above El. 5100. Accordingly, the decision was made to excavate the 
relatively ungroutable rock to a depth of about 70 ft on both abutments from El. 5100 upward to the 
ends of the dam, and to begin the grout curtain under a concrete grout cap in the center of the 
excavation. The trenches, for economy, were designed to be deep, narrow and steep-sided. 

In addition to the major adjustment to site conditions of locally substituting a key trench filled with 
impervious Zone 1 for a grout curtain through highly jointed, pervious bedrock, the designers 
concluded that extensive curtain grouting beneath key and cutoff trenches would be required. To 
indicate the scope, the bid items included provision of 55,000 barrels of cement, and 1,700 cu yds of 
sand, together with 260,000 cu ft of pressure grouting. Actual quantities of cement injected were 
over twice the bid quantities. 

Grout Curtain. 

The drawings and specifications called for three rows of deep grout holes along most of the axis of 
the key and cutoff trenches, with wide latitude retained by the USBR to direct and modify specific 
details. The center row of grout holes, intended to form the impermeable curtain, was provided with 
a concrete grout cap. nominally 3 ft wide by 3 ft deep in a drilled and blasted notch in rock. In the 
key trenches, the specified grouting sequence was: First, the downstream row of holes on 20-ft 
centers; second, the upstream row of holes on 20-ft centers; and third, closure along the center row of 
holes working through the grout cap. These center holes were spaced on 10 ft centers, with split 
spacing where the primary holes did not indicate a fight curtain. It is important to recognize that, as 
this procedure was actually carried out, neither the upstream nor the downstream rows constituted 
grout "curtains" as the term is conventionally understood. Actually full closure along the two outer 



9-3 



rows was neither attempted nor attained. Both the grouting procedures and hole spacing along the 
outer rows were such that gaps could be judged to be inevitable. The outer rows were intended to be 
only semi-pervious grout barriers against which the center row of grout holes could reasonably be 
fully and successfully grouted. 

Accordingly, it is the Panel's view that a triple or 3-row grout curtain was not constructed. Instead it 
should be termed a single-row curtain. 

The Panel has reviewed and analyzed the grouting records and reports, including review of the 
specifications, reports and records, sufficiently to assess the methodology and scope and to judge the 
effectiveness. Perhaps more importantly, in what were judged to be the critical reaches of the grout 
curtain between key-trench Stas. 3-1-00 and 15-1-00, the Panel had coring and water pressure testing 
carried out along the center row of grout holes to assess directly the probable effectiveness of the 
grouting. The testing has been reported in Chapter 3, with results summarized in Tables 3-2, 3-3 and 
3-4. 

With particular reference to those tests in the general failure area between Stas. 13-H50 and 14-1-26, the 
results show that more than 40 percent of the 30 water loss tests, run at depths up to 34 ft below key- 
trench invert, exceeded 0.1 gpm/ft of hole. Twenty percent of the tests exceeded a loss of 0.5 gpm/ft, 
and 7 percent exceeded 1.0 gpm/ft. Accordingly, the tests indicate that in the critical key-trench area 
the grout curtain was not fully closed. 

The Panel's water loss tests under the spillway at depths of up to 145 ft, as more fully reported in 
Chapter 3, and in two properly positioned holes in the grout curtain near the right end of the dam at 
depths up to 300 ft, showed satisfactory grouting. A third hole near the right end showed high water 
losses but in a subsequent survey was found to be located out of the grout curtain. 

Blanket Grouting. 

Par. 100 of the specifications requires "blanket grouting" in the key trench and cutoff trench, as 
directed by the USER. No definition of the term is given, but it appears that it entailed drilling and 
grouting both uniformly and randomly spaced and angled holes to shallow depths (20 to 35 ft) to 
intercept and plug open joints. The results of the work are shown on USBR drawings. The scope of 
the blanket grouting done was limited, and the areas so treated were almost exclusively in the bottom 
of key and cutoff trenches, and at only a few local spots. A major exception was at the spillway crest 
structure where a close pattern of 80-ft-deep "blanket" grout holes is shown under the entire 
structure. 

Slurry Concrete. 

A review of the drawings and specificafions has failed to show that it was expected to treat open 
bedrock joints at the Zone 1-to-bedrock contact with slurry concrete. USBR Project Office records 
show, however, that a total of about 1830 cu yds was placed at the instigation of that office (Fig. 
9-1). This was accomplished principally by pouring slurry into open joints and the more obviously 
open cracks. This procedure was discontinued above about El. 5210. Fig. 9-1 illustrates the extent of 
slurry grout or concrete placement on the side slopes of the key trench and in the stripped bedrock 
areas upstream and downstream from the key trench on the right abutment, principally beneath Zone 
1. It is particularly evident on Fig. 9-1 that, in the failure area, significantly large open joints existed 
at the top of the downstream face of the key trench at axis Sta. 14-1-00 and near the downstream toe 
of Zone 1 opposite Sta. 15-1-00, where slurry takes totaled 100 or more cu yds. 

These large takes under gravity placement conditions identified the rock as being extremely pervious, 
indicating that grave incompatibility existed between the highly erodible Zone 1 fill and its 
unde rlying intensely j ointed foundation . 



94 




LEGEND 



O 0-5 CUBIC YARDS 

O 6-10 CUBIC YARDS 

Q 11-20 CUBIC YARDS 

( J 21-30 CliBIC \ARDS 



-40 CUBIC YARDS 



o 




41-50 CUBIC Y'ARDS 



GREATER THAN 50 CUBIC Y'ARDS 



REFERENCE DATA: 

TETON DAM FAILURE EXHIBIT NO. 4 



SLUSH GROUT DISTRIBUTION AND 
DENSITY ZONE 1 FOUNDATION 

STA. 11 + 41 TO 16+00 



FIG. 9-1. 



NDEPINDENT PANEL 



9-5 



9-6 



River Alluvium. 

At the maximum sections of the dam, where the bedrock canyon was filled with up to 100 ft of 
alluvium, the design permitted constructing the upstream and downstream shells of the dam on this 
material, except for stripping away organic and loose materials. A cutoff trench down to bedrock, 
with bottom width actually constructed a minimum of 80 ft wide, was required to control 
underseepage. 

In view of the generally coarse-grained nature of this alluvium, which from upstream areas provided 
the "silt, sand, gravel and cobbles" utilized for fill as Zone 2, there was no engineering justification 
for fully removing all alluvium under the outlines of the dam. 

It is believed that there were no aspects of construction activities involving treatment of the river 
alluvium left in place under the dam that had any significant influence on the failure. 

Talus and Overburden on Abutments. 

The Drawings and Specifications, as interpreted, permitted slopewash materials, overburden and talus 
to be left in place under the dam, in all areas outside of the Zone 1 fill (Figs. 9-2, 9-3, 94 and 9-5). 
Under Zone 1, stripping to bedrock was required. Stripping of overburden was subject to the 
Construction Engineer's judgment as to the amount necessary to uncover reasonably strong materials. 

It seems conclusive, from examination of as-excavated cross sections taken at 10-ft intervals along the 
axis between Stas. 14+50 and 15+50, as well as construction photos and oral inquiry, that a 
substantial thickness of talus was left under the dam downstream from the Zone 1 fill. This 
conclusion is based on interpretation of the original topography, as against the belief that steep 
bedrock cliffs existed under that topography together with an admittedly subjective evaluation of the 
cross sections. No direct evidence remains, all overburden and talus in the vicinity, together with a 
large but unknown volume of the blocky bedrock cUffs having been washed away following the 
failure. However, supplemental inquiry of the project construction staff confirms that substantial 
volumes of talus were left in place under the outer zones of the dam. 

If, as is believed, a large volume of bouldery talus existed along the canyon wall under the 
downstream slope of the dam in the vicinity of axis Sta. 15+00 to Sta. 17+00, it could have provided 
an exit conduit for the initial, relatively restricted leakage across or under the key trench at about 
Sta. 14+00, and increasing leakage fiows could have had explainable exits at the groin of the dam at 
El. 5200 and El. 5045 where the large flows of muddy water were seen on June 5. 

Quality Control. 

The Panel has not undertaken a detailed review of construction quality control procedures or 
personnel, except indirectly through examinations of reports on physical characteristics of the 
construction materials used in the dam, of the Construction Engineer's reports, and through review of 
certain design and construction decisions. 

Based on its contacts with the USBR project construction staff, the Panel considers that the project 
was properly staffed with knowledgeable, interested, supervisory personnel, and that all required 
aspects of quality control were faithfully carried out. If any substantive questions regarding 
construction quality control could be raised, it would seem that it would not be in the areas of tests 
or reports which are clearly designated by long standing USBR practice, but rather in the areas of 
reaction to and exercise of judgment in matters more related to fundamentals of conceptual design 
than to execution of construction. 



9-6 




Fig. 9-2 



Foundation formation and contact beneath zone 2 and zone 5 










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Fig. 9-3 



Foundation formation and contact beneath zone 2 and zone 5 



9-7 




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9-8 




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9-9 



DAM CONSTRUCTION 

General embankment construction started in late June 1972 with placement of Zone 2 downstream 
from the cutoff trench near the left abutment. It was essentially completed by November 26, 1975. 
The necessary operations of stripping, excavation, dewatering, grouting, borrow pit and quarry 
development, and fill placement generally progressed concurrently throughout that period. Key dates 
througliout the construction were as follows: 



Chronology. 

Feb. 22, 1972 
Mar. 17, 1972 
Apr. 17, 1972 
Apr. 25, 1972 

July 11, 1972 
July 17, 1972 
Oct. 20, 1972 

Dec. 1,1972 
Dec. 13, 1972 
Apr. 10, 1973 



First construction equipment arrived. 
Started excavation of river outlet works. 
Started excavation of left key trench. 
Started fill placement downstream from 

cutoff trench. 
Started excavation of right key trench. 
Started stripping at spillway. 
Started drilling and grouting operations 

in left key trench. 
Fill operations suspended. 
Set first steel hner in river outlet works. 
Fill operations resumed. 



River outlet works tunnel grouting completed. 
River diverted through river outlet works. 
Started excavation of auxUiary outlet works 

and upstream cofferdam at El. 5100. 
Grouting begun in cutoff. 
First Zone 1 fill in cutoff. 
All fill operations shut down. 
Completed grouting left abutment. 
Resumed till placement. 

Fill operations shut down, majority at El. 5130. 
Resumed fill placement. 

Completed concreting auxiliary outlet works tunnel. 
Closed river outlet works and diverted river to 

auxiliary outlet. 
Completed Zone 1 placement. 
Dam essentially complete, 200 ft of fill 

placed in 6.7 months. 
Modifications to river outlet works to permit 

project use as power and irrigation water 

outlet, including concrete elbow, trash racks, 

gates and repainting liner. Repainting 

incomplete as of 6/5/76. 

Embankment Materials. 

The sources and physical characteristics of the embankment materials are presented in Chapter 7. 

Placement Procedures. 

The five zones of the dam embankment were constructed in accordance with accepted practices and 
their placement was controlled by the project inspection forces exercising the specification 
provisions. 



June 5, 1973 
June 8, 1973 
June 25, 1973 

Sep. 17, 1973 
Oct. 18, 1973 
Nov. 7, 1973 
Dec. 12, 1973 
Apr. 4, 1974 
Nov. 27, 1974 
Apr. 29, 1975 
May 9, 1975 
Oct. 3, 1975 

Oct. 21, 1975 
Nov. 26, 1975 

Oct. 1975- 
June 1976 



9-10 



Specification requirements for placement are abbreviated in Table 9-1. 

Permissible variations in compaction equipment were made by also using vibrating rollers on Zone 2, 
sheepsfoot rollers on Zone 3, and 40,000-lb crawler tractors on Zone 4. 

The sources and engineering properties, excavation, hauling, stockpihng, and handUng of the 
embankment materials, and the achievement of the density requirements as revealed by the 
earthwork construction control records are presented in Chapter 7. 

The plans and specifications contain a provision for specially compacted earthfill Zone 1 at steep and 
irregular abutments and on rough and irregular embankment foundations to include ". . . each 
layer . . . shall be compacted by special rollers, mechanical tampers, or by other approved 
methods . . . moisture and density shall be equivalent to that obtained in the earth fill placed in the 
dam embankment . . . ." This provision was nothing more than a requirement for a method of 
compaction in confined locations. For example, no special treatment regarding increased moisture 
content was specified. The project office did require selective placement of material having a slightly 
higher moisture content but the average was only 0.7% wetter than that for the normally compacted 
fill and was still 0.5% dry of optimum moisture. Wheel rolling by loaded trucks, and power tamping 
by gasoUne or air hammers were used. 

Embankment was placed during four construction seasons, 1972 through 1975, commencing June 15, 
1972 and terminating November 26, 1975. Embankment was not placed during the cold winter 
months. 



AUXILIARY OUTLET WORKS 

The auxiliary outlet (Fig. 1-4) is located in the right abutment of the dam. The concrete-lined tunnel 
is 6 ft in diam upstream of the gate chamber and 7 ft 6 in. downstream. A 7-ft-6-in.-diam adit and an 
8-ft-diam shaft provide access to the gate chamber. 

The auxiliary outlet diverted the Teton River while the river outlet was being modified and 
completed for use as a permanent power and irrigation water outlet. 

Tunneling Experience and Geology — Right Abutment. 

The auxiliary outlet tunnel, adit, and gate chamber access shaft were driven in consistently hard, 
hghtweight, densely welded, crystal rich, rhyoUtic ash flow tuff. Tunneling conditions were excellent 
throughout. Shears and numerous joints subparallel with the tunnel alignment were present. No water 
flows were encountered. 

In some areas, hydrothermal alteration adjacent to joints and locally disseminated through the rock 
has discolored the tuff reddish brown to brick red, but had little or no other apparent effect on the 
character or quaUty of the welded tuff. 

Two prominent, well-developed joint sets were observed. The joints of one set generally strike on an 
average of about N30°W. Joints of the other set generally strike on an average of about N60°W. The 
joints of both sets are vertical to steeply inclined. Joints of the N30°W striking set appear to be the 
strongest, most consistent of the two sets except between tunnel Stas. 21-1-40 and 27-H80 where joints 
of the N60°W striking set not only are very strongly developed and generally closely spaced, but form 
virtually all of the joints present.. 



9-11 



TABLE 9-1 
EMBANKMENT PLACEMENT SPECIFICATIONS 





Compacted 












Lift 


Moisture 


Compaction 


No. of 


Density 


Zone 


Thickness 


Control 


Equipment 


Passes 


Control 


1 


6 in. 


1/2 to 1-1/2% 


5-ft X 5-ft 


12 


Average compaction 






dry of optimum 


4,000 lb/ft 
sheepsfoot 




not less than 98% 
of std. AASHO 


2 


12 in. 


Thoroughly 


40,000-lb 


4 


Relative density 






wetted 


crawler-type 
tractor or 
approved 
alternate 




not less than 6S% 
but no more than 
20% of tests less 
than 70% 


3 


12 in. 


Most 


SOT pneumatic- 


6 


Best practicable 






practicable 


tired roller 




degree 


4 


12 in. 


Optimum 


SOT pneumatic- 


6 


Maximum obtainable 






amount 


tired roller 




by the specified 






required 






procedure 


5 


36 in. 


None 


Hauling and 


Equip- 


Maximum amount 








placement 


ment 


possible 








equipment 


routed 





9-12 



Only minor seeps or drips occurred locally from joints and rock bolts in the tunnel crown and from 
joints in the crown of the adit near its intersection with the gate chamber. However, numerous seeps 
ranging in volume from heavy drips to wet or damp rock reportedly developed between Stas. 29+20 
and 34+1 1 .5 (the downstream portal) during the spring runoff following the completion of the tunnel 
excavation. 

It was reported that water and a small volume of grout leaked into the tunnel at Sta. 17+73 from a 
spillway blanket grout hole located 18 ft upstream from dam centerline Sta. 11+04 (dam ^ Sta. 
11+06.5 = spillway Sta. 18+30), and a very small amount of grout also leaked into the tunnel at Sta. 
16+81 from a grout hole 18 ft upstream from dam f^Sta. 10+78. 

Control Works. 

Flow through the auxiliary outlet is controlled by two tandem 4-ft x 4-ft hydraulically operated high 
pressure shde gates located beneath the gate chamber. Control stations are located in both the shaft 
house at El. 5332 and the gate chamber at El. 5048. The control cabinet equipment is located in the 
shaft house. At the time of failure the permanent electric power facilities, including duct banks in the 
crest of the dam, had not yet been installed. However, a temporary power source was available and 
the gates were open at that time. 

Means for unwatering the tunnel upstream of the control gates are provided by sectionaUzed steel 
stoplogs which were designed to be set in position by a barge-mounted crane under balanced head 
conditions. 

Schedule. 

Excavation for the auxiUary outlet commenced April 13, 1973. All concrete was completed July 28, 

1975. On October 3, 1975 the river flow was diverted from the river outlet to the auxihary outlet. 

Post-failure Condition. 

As discussed in Chapter 3, no unusual conditions were found during the Panel's inspection of the 
unwatered auxiliary outlet tunnel on October 4, 1976. 

There is no known aspect of the auxiUary outlet works construction that is believed to have a bearing 
on the failure of the dam. 



RTVER OUTLET WORKS 

The river outlet works (Fig. 1-5) are located in and on the left abutment of the dam. They consist of 
a 13.5 ft diam Uned tunnel, controlled at mid-length by an hydraulically operated, 10.5 ft by 13.5 ft 
wheel gate. The gate shaft extends from the crest of the dam vertically to the gate chamber. The 
downstream end of the tunnel, as finally completed, branches into four steel pipes, each being 
controlled by a 4 ft by 4 ft outlet gate. 

The river outlet works were constructed in two stages: The first stage consisted only of tunnel and 
shaft excavation and lining. At the end of this stage, the tunnel was utihzed as a free-fiow conduit for 
initial diversion of the river around the damsite. The tunnel was begun in March 1972 and went into 
service for diversion in June 1973. This service extended to October 1975. At that time the auxihary 
outlet works were put in service. Whereupon, the upstream end of the river outlet tunnel was plugged 
and second stage construction began. That stage principally included constructing a permanent 
intake, installing gates and associated operating equipment, constructing penstocks, and recoating the 



9-13 



steel liner in the downstream half of the tunnel with coal tar enamel. This work was not quite 
complete on June 5, 1976, although the required completion date was March 31 , 1976. 

Control Works. 

The 10.5-ft by 13.5-ft wheel gate previously mentioned was completely installed and in operating 
condition by May 17, 1976. There was reservoir pressure on its upstream face at all times after 
May 14. 

The 4 ft by 4 ft outlet gates were in operating condition on June 5, but it is indicated that they had 
not yet been connected to the available power source. They were fully open at that time, the 
openings serving as access and ventilation for the tunnel Uner coating work still in progress. 

Schedule. 

The only item of Stage 2 River Outlet Works construction which was incomplete on June 5 is 
believed to have been coating the steel tunnel Liner. This work must have been virtually complete, 
since communications from the project office stated that completion had been expected by June 10. 

Post-failure Condition. 

It has not yet been possible to unbury, dewater and inspect the river outlet works. 



SPILLWAY 

No detailed discussion is offered of spillway construction because it has not been found to have any 
influence on the dam failure. Two items of interest are noted, however: (1) the spillway was 
operational on June 5; and (2) according to oral reports by project personnel, there was no indication 
at any time of discharge of groundwater from the spillway underdrains, before, during, or after the 
dam failure. 



COMMENTS 

For construction of the grout curtain, the Panel considers that reliance on a single curtain with 
nominal hole spacing of 10 ft and with holes inclined in only one direction was unduly optimistic. 
The use of smaller hole spacing, cross-angled holes, and multiple curtains would have been justifiable 
in the light of known rock conditions. It is not suggested, however, that even these measures would 
have provided adequate closure for the embankment as designed. 

In view of the known presence of a maze of open joints in the bedrock under all of Zone 1 
embankment, the Panel would not have concurred with the decision to limit blanket grouting 
essentially to the bottoms of the key and cutoff trenches. 

In going forward with the initial filling of the reservoir, the USER clearly had arrived at the judgment 
that the Contractor's construction was completely acceptable from the standpoint of the structural 
safety of the dam. Probably the only significant aspect of project construction wherein a failure to 
meet design requirements may be judged to have occurred was the contractor's failure to meet the 
approved construction schedule for completion of the river outlet works. 



9-14 



CHAPTER 10 
RESERVOIR FILLING EXPERIENCE 

(Panel Charges Nos. 9 and 12) 



The Teton River drains an area of about 1 ,000 square miles on the west side of the Teton Range in 
Wyoming and Idalio, as shown in Fig. 10-1. It is the largest tributary of the Henrys Fork of the Snake 
River. The drainage area above the Teton Dam is 853 square miles. Principal tributaries of the Teton 
above the damsite are Canyon, Bitch, Badger, Leigh, and Teton Creeks. Canyon Creek enters Teton 
River within the reservoir area five miles upstream from the dam. The other tributaries and the 
headwaters of Teton River drain the west slopes of the Teton Range and provide most of the flow of 
the river. 

The Teton River basin includes a broad agricultural valley cut by a narrow 20-mile-long canyon. 
Elevations range from 4800 to more than 13,000 ft. 

Precipitation in the Teton basin varies from about 13 in. per year at Sugar to over 40 in. per year in 
the Teton mountains. Average annual precipitation at Driggs in the upper valley is about 15 in. Most 
of the annual precipitation occurs in the form of snow. 



HYDROGRAPHIC RECORD PRIOR TO 1976 WATER YEAR 

Characteristics of flows at the gaging station Teton River near St. Anthony, about five miles 
downstream of Teton Dam, are shown on the summary hydrograph in Fig. 10-2. Approximately 37 
percent of the annual runoff in an average year occurs in May and June as a result of snowmelt. The 
average annual runoff at this station is about 580,000 acre-ft. 

Frequency curves of runoff volumes for the months of April and May are shown on Fig. 10-3. A 
frequency curve of springtime flood peaks is shown in Fig. 10-4. The two largest flows of record 
occurred in the winter as a result of rain and snowmelt on frozen ground in the lower areas of the 
basin. Instantaneous peaks were: 

Feb. 12, 1962 11,000 cfs 

Feb. 3, 1963 7,280 cfs 

These floods were of short duration compared with the spring snowmelt floods. 



RESERVOIR OUTLET WORKS 

Low-level reservoir discharge was to be accomplished through the river outlet works in the left 
abutment and by the auxiliary outlet works in the right abutment. The design capacities of these 
facilities at a maximum water surface elevation of 5324.3 ft were 3,400 cfs and 850 cfs, respectively. 
The area and capacity curves of the reservoir and discharge ratings for the spillway and outlets are 
shown on Fig. 10-5. 



10-1 



u 

Z : 

I 



< 
Q 



Z 

< 

UJ 




MAXIMUM LINE REPRESENTS 
MAXIMUM FLOW RECORDED 
FOR EACH DAY OF THE YEAR 
FOR THE PERIOD OF RECORD. 

10X LINE INDICATES FLOWS 
THAT WERE EXCEEDED 10 X 
OF THE TIME 



REFERENCE DATA: 

DEPARTMENT OF WATER RESOURCES 

STATE OF IDAHO 



SUMMARY HYDROGRAPHS 
TETON RIVER NEAR ST. ANTHONY 



FIG. 10-2 



U. S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



1 15 31 15 29 15 

\m — JANUARY J^ FEBRUARY— «^« MARCH 



16 30 

SEPTEMBER — -\ 



10-3 



H 

I 
w 

o 
o 

o 






X 
H 

I 



600 
400 

200 

100 
80 

60 
40 

20 



99.99 



PERCENT PROBABILITY OF EXCEEDENCE 

99 90 70 50 30 10 1 



0.01 

























































































F 


ERIOD. 

1929-1974 






































.-■" 


.." ' 
















.- 










^ 














>• 












^^^ 












_^* 















^ 


^^^ 








MAY-!*,' 


' 












^^ 


<^ 










^^ 














^ 


^APRIL 








.-"' 










^ 


^-^ 




















^ 


^ 











































































0.01 1 10 30 50 70 90 99 

PERCENT PROBABILITY OF NONEXCEEDENCE 

FIG. 10-3. FREQUENCY CURVES OF MONTHLY 
RUNOFF VOLUMES, TETON RIVER NEAR ST. ANTHONY 



99.99 



(J 
1 

I 



< 



10000 
8000 

6000 
4000 



2000 



1000 
800 

600 
400 



200 



99.99 



PERCENT PROBABILITY OF EXCEEDENCE 

99 90 70 50 30 10 



0.01 





























^^ 
























































^^ 


























,^' 


























^ 
























^ 


y^ 




















^ 


X 


y 


















^ 


^ 


y 




















> 


^ 






















































































































































































>FR 


lOO: 




























1891 
1903 


-18S 

-19f 


)3 
19 
























1920 


-19" 


'3 

































0.01 1 10 30 50 70 90 99 

PERCENT PROBABILITY OF NONEXCEEDENCE 

FIG. 10-4. FREQUENCY CURVE OF SPRING 
FLOOD PEAKS, TETON RIVER NEAR ST. ANTHONY 



99.99 



REFERENCE DATA : 

DEPARTMENT OF WATER RESOURCES 

STATE OF IDAHO 



U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



10-4 



RESERVOIR AREA IN HUNDREDS OF ACRES 

10 15 20 



25 



5400 



RESERVOIR CAPACITY IN THOUSANDS OF ACRE FEET 

50 100 150 200 250 



30 



300 



in 

z 
o 

I 

w 
w 

w 
(J 

(A 

D 

ai 
w 



o 

w 
w 



5300 



5200 



5100 



5000 




2 4 6 8 10 

AUXILIARY OUTLET WORKS DISCHARGE IN HUNDREDS OF CFS 



12 3 4 5 

OUTLET WORKS DISCHARGE IN THOUSANDS OF CFS 



4 8 12 16 20 

SPILLWAY DISCHARGE IN THOUSANDS OF CFS 



24 



REFERENCE DATA: 

U. S. BUREAU OF RECLAMATION 

DWG. NO 549-D-8 



AREA-CAPACITY-DISCHARGE CURVES 

W-. y^ ^/-\ r- U. S. DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

f llj. \\J — O. INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



10-5 



COMPARISON OF RESERVOIR FILLING RATES 

Reservoir Filling Anticipated. 

The following is taken from "Design Considerations for TETON DAM," by the U.S. Bureau of 
Reclamation, Denver, Colorado, October 1971 : 

The performance of the foundation, of the abutments, and of the embankment of Teton 
Dam during initial filling and reservoir operation is extremely important. Instructions for 
observing and reporting performance of the structure will be issued in "Designers' 
Operating Criteria." It is most likely, however, that initial filling or partial fiOing, and 
some reservoir operation wUl occur prior to issuance of the operating criteria. The 
instructions contained here are tentative and are applicable until such time as the final 
criteria are issued. 

During the initial filling for periods when the reservoir surface is either rising or falling 
more than 1 foot per day, and for at least the first year of reservoir operation, frequent 
inspections of the embankment, of the abutments, and of foundation areas should be 
made to check for seepage or for significant rises in the water table downstream from the 
dam. 

Measurable seepage should be collected and measured; seepage areas should be mapped 
and photographed; and reservoir water surface elevation and other pertinent data should 
be recorded. Generally, the results of the inspections should be reported monthly to the 
Director of Design and Construction. . . . Adverse seepage conditions may require more 
frequent reports, and any unusual developments noted during any inspection should be 
reported immediately. In this event further instructions will be furnished by the Director 
of Design and Construction. . . . 

After the completion of the required portions of the river outlet works and the 
installation of protection for various parts of the work, the Teton River would be 
diverted through the river outlet works by the construction of the upstream cofferdam. A 
downstream cofferdam will also be required to exclude high tailwater from the 
powerplant area, tailrace, and spillway stilling basin. 

In routing the 25-year spring flood through the diversion tunnel and channels as described 
above, the water surface in the reservoir would rise to elevation 5075 and the discharge 
would be 4,200 cfs. The 25-year spring flood has a peak of 5,000 cfs and a 15 -day volume 
of 111,000 acre-feet. The tailwater in the 110-foot minimum downstream diversion 
channel would be at about elevation 5029 for a discharge of 4,200 cfs. A hydrauHc jump 
will occur in the 19-foot-wide channel lining for a discharge of 4,200 cfs. 

After the spillway, auxiUary outlet works, and dam embankment have been completed as 
required by the specifications, the river outlet works should be closed on October 1 of 
the final winter period. This should be accomplished by installing the intake bulkhead 
gate at elevation 5141, opening the 24-inch slide gate in the diversion inlet, and instaOing 
the diversion inlet stoplogs. The stoplogs were designed to seat in flowing water with a 
depth up to about 9 feet. Before the stoplogs are installed all rocks, gravel, and debris of 
all kinds must be removed from the seats and sill in order to give a watertight contact. 

When the river outlet works is closed the auxiliary outlet works must be fully open and 
must be kept fully open until the river outlet works has been completed ready for 
service. . . . 



10-6 



After May 1 the flow in the Teton River exceeds the maximum allowable release from the 
auxiliary outlet works of 850 cfs, and the capacity of the river outlet works is needed in 
order to control the rate of filling in the reservoir. 

It is anticipated that with the river outlet works completed for service by May 1 , storage 
in the reservoir could be commenced. . . . 

Unless adverse performance develops, unrestricted filling rates will be permitted to 
elevation 5200. Above elevation 5200 initial filling should not exceed 1 foot per day. . . . 

This quotation shows that a flood of the magnitude of the actual spring flow of 1976 was anticipated 
in designing the outlet facilities. The possible consequences of operating with a single outlet during 
the spring runoff were known. 

The following is an excerpt from U.S. Bureau of Reclamation letter dated August 4, 1976 (after the 
failure) from Acting Regional Director, Boise, Idaho, to Director of Design and Construction, 
Engineering & Research Center, Denver, Colorado, subject: Teton Forecast Information as 
Requested (Re: Faxogram Dated July 30, 1976): 

Runoff volume forecasts of the inflow to Teton Reservoir were made as soon after the 
first of each month as data was available from January 1, 1976 to June 1, 1976. These 
forecasts [Table 10-1] and the flood control rule curve [Fig. 10-6] were used to 
determine what reservoir space would be needed to regulate downstream flows to 2500 
c.f.s., the safe channel capacity. [Table 10-1] presents the volume forecasts, the flood 
space required by the rule curve on May 1 , and the space available on the date of the 
forecast. [Fig. 10-6] is used to convert the forecast to a May 1 estimated residual on 
those months prior to May 1. Historically, runoff volumes of this magnitude would 
produce daily inflows of 4000-4500 c.f.s. per day for several days during the height of the 
snowmelt season. Anticipating that the main river outlets would be available during that 
period, it was estimated that the filling rate would be from 2 to 2.5 feet per day during 
the peak inflow. Had the main river outlets been available the fill rate prior to June 5 
would have been Umited to approximately 2 feet per day on or near the 18th of May, the 
time of peak inflow to the reservoir. . . . 

Reservoir Filling Experienced. 

Construction of the dam was started in February 1972. Initially, river flow was directed through the 
middle of the canyon so that excavation could proceed on both abutments. 

Construction of the river outlet works tunnel was begun in June 1972. During construction, diversion 
was made through a channel at the right abutment. This channel permitted excavafion of the cutoff 
trench to the left of the channel. 

Diversion through the river outlet works was commenced on June 8, 1973. This diversion enabled 
construction of the cutoff trench on the right side and placement of embankment in the trench. 

At the end of water year 1975 (October 1 , 1 974 through September 30, 1975), Teton River flows 
were at about the normal rates for that time of year. However, reservoir storage in the Snake River 
system was well above normal as a result of unusually high 1975 runoff. Runoff of the Teton River 
continued near normal through the fall and early winter months. 



10-7 



TABLE 10-1 

RUNOFF VOLUME FORECASTS OF INFLOW 

TO TETON RESERVOIR IN CALENDAR YEAR 1976 

(Volumes in Thousands of Acre-ft) 









May-Sept. 


Flood Control 




Forecasting 


Forecasted 




Est. Residual 


Space Required 


Flood Control 


Period 


Volume 


% Normal 


Forecast 


on May 1 


Space Available 


Jan.-Sept. 


616 


122 


470 


125 


238.2 


Feb.-Sept. 


612 


128 


489 


140 


230.6 


Mar.-Sept. 


591 


130 


492 


140 


224.1 


Apr.-Sept. 


617 


146 


544 


175 


217.4 


May-Sept. 


584 


157 


584 


200 


175.2 


June-Sept. 


391 


140 




95 1 


53.8 



Flood control space required on June 1. 



Reference: USBR Communication dated August 4, 1976. 



10-8 



200 



at 

< 

o 
o 
o 



o 

CO 



160 



a: 

% 120 

I 
O 

O 
ei 

X 
\- 



b- 80 

< 



O 
Z 

a: 

w 

O 40 

< 

UJ 

> 
< 

















^ 












'^J^^ 


^ 








^ 






^ 


^ 






^"^^ ^ 


^ 


hjji- 


.jjs:^ 








^ 






AVER 


\GE PROBABLE 
NEAR ST. 


RUNOFF. TETON RIVER 
ANTHONY 



100 



200 



300 



400 



500 



600 



700 



800 



FORECASTED RUNOFF OF THE TETON RIVER AT ST. ANTHONY 
INDICATED DATE THROUGH SEPT 30 (lOOO ACRE-FT) 



REFERENCE DATA: 
BUREAU OF RECLAMATION 



FLOOD CONTROL RULE CURVE 



r^T^ 10-^ "-' ^ DEPARTMENT OF THE INTERIOR STA 

r IVJ. lvy~0 INDEFENDENT PANEL TO REVIEW CAUSE OF TE 



TATE OF IDAHO 
TON DAM FAILURE 



10-9 



Diversion continued through the river outlet works until October 3, 1975 when the auxiliary outlet 
was put into operation to enable placement of second-stage concrete in the intake and gate chamber 
of the river outlet works and to install outlet gates, pipe, penstock manifold, and metalwork and 
equipment. From that date until the failure of the dam, all diversion was througli the auxiliary outlet 
works. Chapter 9 discusses the details and schedules of outlet works construction. 

Snow surveys in the Teton River watershed which were begun in January 1976 indicated heavy snow 
accumulations. Table 10-2 shows 1976 snow course measurements in percentages of normal for two 
Teton basin snow courses. 

TABLE 10-2 
Snow Water Equivalents as Percent of 1958-76 Averages 



Pine Cr. Pass 


State Line 


(%) 


(%) 


191 


191 


142 


129 


141 


141 


141 


136 


193 


233 



Jan 1 
Feb 1 
Mar 1 
Apr 1 
May 1 

As of March 1, 1976, the reservoir water surface was at EI. 5164.7 ft and the auxiUary outlet was 
discharging 295 cfs. The reservoir level was rising about 0.2 ft per day. 

A memorandum from the USBR Project Construction Engineer to the Director of Design and 
Construction dated March 3, 1976, when the reservoir stood at El. 5165.1, requested approval to 
exceed the 1-ft-per-day tllhng rate. Pertinent excerpts from the memorandum follow: 

. . . have been monitoring the observation wells. . . . These observations show that there 
are several of the wells in which the water level is rising. Drill Hole No. 5 [No. 14 in Fig. 
5-6] indicates a significant rise in the water table, but we do not feel that this well is truly 
representative of the area in which it is located. . . . 

In addition to the well readings, daily inspections of the constructed works, including the 
auxihary outlet works and the river outlet works access shafts, the river outlet works 
tunnel, and the area below the dam, are made. No leaks have been detected to date along 
the abutments or along the embankment downstream of the fill. However, moisture had 
become apparent on the walls of the river outlet works shaft up to elevation 5130. 

There are no significant leaks to date and total leakage in the shaft is estimated to be ^/i 
gallon per hour emitting through hairline cracks in the shaft lining. Water is leaking 
through the concrete hning upstream of the gate shaft in the river outlet works tunnel at 
approximately 2 gaUons per minute. 

In the auxiUary outlet works shaft, beginning on February 9, we have detected small leaks 
and they are presently apparent up to elevation 5067 with an estimated flow of i4 gallon 
per hour. . . . 

. . . request . . . approval to deviate from the 1 foot per day filling rate set forth in the 
design considerations. . . . feel this . . . desirable for the following reasons: 



10-10 



1. The reservoir filling curve and snow forecast information shows that if we do get 
permission for this deviation, we will be able to fiU the reservoir this coming runoff 
period. This would allow our clearing contractor to sweep the reservoir and complete his 
work. This would make it possible to open the reservoir to the public for recreation in the 
summer of 1977. 

2. The . . . construction schedule includes testing the turbines and generators. ... A near 
full reservoir will permit tests at the higher operating heads. 

3. Filling the reservoir . . . would enable us to observe the effectiveness of the curtain 
grouting. 

4. A full reservoir would make it possible for full power generation this year subsequent 
to testing the generators. 

5. We have in the past experienced flows considerably above that which we can release 
from the auxiUary outlet works during March and April. If we experience this again this 
year before the river outlet works is complete, we will not be able to maintain the 
recommended 1 foot per day filling rate. 

In addition to reading the wells as we have in the past, we will continue to provide daily 
inspection of the downstream area of the dam; and upon melting of the ice on the 
reservoir, we will initiate a bi-weekly reservoir reconnaissance to detect any outflows into 
fissures or vents which might occur as the water rises behind the dam. 

Our present releases from the reservoir average 300 cubic feet per second. From the 
available information on inflows, it appears that approximately 6 percent of the water is 
being lost either to seepage or to bank storage. . . . 

On March 23, 1976, the Director of Design and Construction sent a memorandum to the Project 
Construction Engineer which stated: 

The Design Considerations for Teton Dam, pubhshed in October 1971, restricted the 
fluctuation of the reservoir to 1 foot per day during the first year of operation to observe 
performance of the foundation and abutments of the dam. In May 1975, a program for 
monitoring ground-water conditions at the damsite and reservoir prior and during initial 
filling was established. This program, consisting of 19 observation wells, is superior to the 
normal monitoring program as it would give advance warning of the development of 
unusual ground-water conditions. A review of the ground-water monitoring from 
September 1975 to February 1976, contained in your referenced memorandum, indicates 
a predictable buUdup of the ground-water table for Teton Dam and reservoir. 

The preUminary reservoir filling curves developed for the 1976 runoff season indicate that 
the reservoir filhng will exceed 1 foot per day with required releases only during the 
month of May when the maximum daily increase will be approximately 2 feet. 

The normal development of the ground-water table to date and the well system being 
used for monitoring will allow relaxing the filling rate from 1 to 2 feet per day. 

Daily inspection of the embankment, abutments, and foundation areas should be 
continued during filling. 



10-1 1 



Teton River flow in 1976 is shown in Fig. 10-2 for comparison with the historic river flows. These 
1976 flows are identified as computed reservoir inflows and were determined by adding reservoir 
storage changes to outflows. This hydrograph differs from natural flows of the Teton River near St. 
Anthony by the amount of reservoir loss to bank storage. 

Beginning in early April, river flows rose well above average and continued well above normal until 
the dam failure on June 5. During two periods, April 12-14 and May 17-23, the flows exceeded all 
previous flows for those dates. April and May 1976 runoff volumes (approximately 61,000 acre-ft 
and 170,000 acre-ft on a computed basis) are estimated to have 15 percent and 2 percent 
probabiHties of exceedence (Fig. 10-3), respectively. 

Storage commenced at the beginning of October 1975. The reservoir filled slowly and steadily until 
April 5, 1976, when increasing inflows accelerated the rate of'fill. Fig. 10-7 shows the reservoir filling 
sequence from January 1 to June 5. Outflows were held constant at about 300 cfs until early May 
when they were increased to about 800 cfs and subsequently to a maximum of 963 cfs on May 28. 

The 2-ft-per-day rate was exceeded on April 13, 14, and 15 during warm weather in the Teton River 
drainage area. The reservoir rises on these days were 2.6 ft, 3.1 ft, and 2.3 ft, in sequence. From 
April 16 through May 10, the 2-ft-per-day criterion was not exceeded except for a 2.1 -ft rise on 
May 5. From May 11 until June 5, the 2-ft-per-day requirement was exceeded with an average daily 
rise of 3.0 ft and a maximum rise of 4.3 ft on May 18. During the period of May 12 to June 5, the 
auxiliary outlet was discharging at a rate higher than its capacity of 850 cfs. 

On May 14, 1976 when the reservoir level stood at El. 5236.9, the USER Project Construction 
Engineer sent a Faxogram to Director of Design and Construction, Denver, reporting current status of 
the reservoir filling and of the river outlet works construction. The following are excerpts: 

1. ...we do not expect that painting of the tunnel liner downstream of the 
wheel-mounted gate will be completed before June 10, 1976. Further acceleration of the 
painting to enable earUer opening of the river outlet works is not feasible. 

2. The spillway gates are in place but not fully operational. Completion ... for possible 
control of the reservoir at capacity is not expected before June 1, 1976. 

3. ... Should the need for any water release through the river outlet works become 
imperative before completion of the painting, the resultant interruption would involve 
claims by the contractor for delay and additional cleanup and sandblasting. . . . 

We request your comments for flood control operation. 

Response to this message is dated June 4, 1976. The message was in the mails on the day of failure 
and said in part: 

We . . . conclude that the river outlet works need not be used prior to completion of the 
painting unless problems directly related to filling of the reservoir develop in the 
foundation, embankment or structures. It is imperative however that both the spillway 
and river outlet works be made operational as soon as possible. 

In a statement before the Subcommittee on Conservation, Energy and Natural Resources of the 
Congressional Committee on Government Operations, on August 5, 1976, R.R. Robison, Project 
Construction Engineer, said: 



10-12 



I- 
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■♦- JUNE 



1976 



TETON RESERVOIR INFLOW, OUTFLOW, 
AND CONTENTS, JANUARY 1 TO JUNE 5,1976 



Fwf-^ iO— 7 ^^ DEPARTMENT 

\\J \\J I INDEPENDENT PANEL 



OF THE INTERIOR STATE OF IDAHO 

TO REVIEW CAUSE OF TETON DAM FAILURE 



REFERENCE DATA: 

DEPARTMENT OF WATER RESOURCES 

STATE OF IDAHO 



10-13 



During the period from October 3, 1975, to May 3, 1976, releases through the auxiliary 
outlet works were limited to required downstream flows, 300 ft /s, and all flows in 
excess of 300 ft-^/s were taken in storage resulting in a reservoir depth of 185 feet. From 
May 4 through May 11, 1976, the flow through the auxiUary outlet was gradually 
increased to 850 ft-^/s. From May 4, 1976, until the time of dam failure, the auxiliary 
outlet works was operated at or above its design capacity of 850 ft-'/s. 

On March 3, 1976, I requested that the filUng rate be relaxed - at this time, there was a 
depth of 135 feet in the reservoir (Elevation 5170). On March 23, 1976, I was given 
permission to increase the filling rate to 2 feet per day because of the normal 
development of the ground water table at that time and no springs had developed below 
the dam, indicating the filling was not causing problems. Results of the monitoring of the 
ground water conditions received by the Engineering and Research Center for the period 
through May 13, 1976, did not indicate a radical change in the water level in the wells 
inconsistent with the rise in reservoir elevations, and no springs had developed. The 
decision was then made to fill the reservoir to the spillway. (The rapid rise of the right 
abutment wells subsequent to that date was not viewed as indicating emergency 
conditions inasmuch as the left abutment wells downstream from the dam were not 
affected, so the readings were transmitted routinely and reached the E&R Center after 
the failure.) 

H.G. Arthur, Director of Design and Construction, stated before the same Subcommittee on 
August 6, 1976: 

With regard to the filling of the reservoir, discussed yesterday by Mr. Robison, the design 
considerations required that above elevation 5200, the reservoir was not to be fdled faster 
than 1 foot per day. This criterion has been used for many years by the Bureau for initial 
filUng of reservoirs and it is considered a desirable rate for testing the abutments and the 
embankment. With structures available to control to this rate, time would be available to 
take remedial measures if problems developed. If desirable for project purposes, the initial 
rate is exceeded when the dam performs satisfactorily. 

Exceeding the initial filhng criterion at Teton Dam was not an unusual procedure. Initial 
reservoir filling criteria were increased in the initial fiUing of 36 instances on Bureau 
reservoirs. In eight instances, the reservoir filling rates experienced exceeded the 
maximum rate of 4.3 feet which occurred during filling of Teton Reservoir. No problems 
were encountered in any instance due to relaxation of the initial reservoir filling criterion. 

Hypothetical Filling Rate. 

The first day in the spring of 1976 when the actual rise in reservoir exceeded one foot per day was 
AprU 8. Tlie water level on the preceding day had been recorded at El. 5175.5. Assuming 
hypothetically that both outlets had been fully operable and that a maximum rise of 1 ft per day had 
been observed each day thereafter, the reservoir water surface would have risen to about El. 5234 ft 
by June 5, which was 59 days later. 

The USBR criterion actually allowed unUmited filling rates up to El. 5200, which was reached on 
April 22. If it had been possible to adhere to the 1-ft-per-day rule after this date, the reservoir would 
have risen to El. 5244 by June 5, as compared with El. 5301.7 measured just prior to failure. 

The maximum inflow rates occurred in the period May 18-21, inclusive, with flows of 4044 cfs, 3664 
cfs, 41 1 1 cfs, and 3947 cfs, respectively. The combined capacity of the two outlet works for these 



10-14 



reservoir levels would have been about 3600 cfs which would have been more than adequate to 
maintain the 1-ft-per-day limit in reservoir rise. Under such an hypothetical operating regimen the 
safe downstream channel capacity, estimated by the USER at 2500 cfs, would have been exceeded by 
as much as 30 percent for short periods. 



COMMENTS 

The 1976 spring flow was within the probabilities considered in design. Runoff forecasts based on 
snow surveys gave warning that river flows would be of such above-normal volume that both outlets 
would be required to hold the reservoir rise to the prescribed rate. Actual flows compared closely 
with these forecasts. 

The river outlet works and auxiliary outlet works of Teton Dam were designed with a total capacity of 
4250 cfs at maximum water level. However, even though the approved construction schedule required 
construction to be completed by March 31, 1976, only the auxiliary outlet works were in operation 
through June 5, 1976. This resulted in virtual non-control of the reservoir filling rate during the late 
spring of 1976. 

The records of Teton River hydrology were well known to the Bureau of Reclamation. The design 
criteria recognized that it would be necessary to have the river outlet works in operation after May 1 , 
1976 in order to control the rate of filling so as not to exceed a 1-ft-per-day increase when the 
reservoir surface elevation was above 5200 ft. This design fill rate was relaxed to 2 ft per day on 
March 23, 1976, but the new rate was exceeded on three days in April and during the entire period 
from May 1 1 to June 5. 

If both outlets had been operable on March 31, 1976, as required by the specifications, their 
combined discharge capacities would have been enough to control reservoir filling to the originally 
prescribed rate after that date. However, because information on the internal condition of the dam 
and its foundation was minimal, there can be no assurance that Project staff would have been able to 
see any reason to modify the March 23 operating plan. 

The paucity of instrumentation and the decision to allow an increased rate of filling had no 
demonstrable influence on the failure. The short time within which the chain of events occurred that 
culminated in the catastrophe suggests that there would have been insufficient reaction time to take 
advantage of instrumental warnings. Nevertheless, the possibiUty exists that a more conservative 
approach to instrumentation and rate of filling could have averted the disaster. Had the rate of filling 
not exceeded 1 ft per day, and had foundation piezometers been located downstream of the cutoff, 
the piezometers might have given early warning of rapidly rising piezometric levels while the 
hydraulic gradients causing erosion were relatively small. Time would then have been available for 
lowering the pool and investigating the phenomena. It is equally possible, however, that the slower 
rate of fiUing would only have delayed the date of the failure. 



10-15 



CHAPTER 1 1 

MEASURES TAKEN TO MONITOR SAFETY OF DAM 

(Panel Charge No. 10) 



SURVEILLANCE PLAN 

Procedures. 

Instructions for observing and reporting performance of the structures at the Teton damsite were to 
be issued in the "Designers' Operating Criteria." It was seen as likely that some reservoir operation 
would occur prior to issuance of these guidelines. Tentative instructions provided in the "Design 
Considerations for Teton Dam," USER, October 1971, were in effect until such time as the final 
criteria were issued. Those criteria had not been issued at the time of the Teton Dam failure. 

As stated in the preceding chapter, during the initial filling for periods when the reservoir surface 
was rising or faUing more than 1 ft per day, and for at least the first year of reservoir operation, 
frequent inspections of the embankment, of the abutments, and of foundation areas were to be made 
to check for seepage or for significant rises in the water table downstream from the dam. 

These tentative instructions of 1971 also required that measurable seepage should be collected and 
measured; seepage areas should be mapped and photographed; and reservoir water surface elevation 
and other pertinent data should be recorded, and that the results of the inspections should be 
reported monthly to the Director of Design and Construction. Any unusual developments noted 
during any inspections were to be reported immediately. In such an event, further instructions were 
to be furnished by the Director of Design and Construction. 

Assignment of Responsibility. 

The Project Construction Engineer had primary responsibility for surveillance of the dam and 
reservoir. He was required to report unusual conditions to the Director of Design and Construction in 
Denver. As reservoir fiUing began the Project Construction Engineer gave general instructions to 
members of the field forces to be alert for any adverse developments. 



INSTRUMENTATION 

Monuments. 

Measurement points were to be installed by the contractor in rows parallel to the dam axis upon 
completion of the outer surfaces of the dam embankment to an elevation 10 ft above each of the 
measurement points. Plarmed spacing in each row was approximately 250 ft as shown in Fig. 11-1 
with numbers and elevations as shown in the table below: 





Approximate 


Between 


Number 


Location 


Elevation 


Stations 


of Points 


350 ft upstream 
1 50 ft upstream 
22.5 ft upstream 
22.5 ft downstream 
250 ft downstream 
500 ft downstream 


5199 

5279 
*. 

». 

5215.75 
5127.17 


16+07 and 23+56 
15+00 and 25+00 
6+25 and 31+25 
5+00 and 30+00 
16+25 and 26+25 
17+50 and 22+50 


4 
5 

10 

11 

5 

3 


Total 






38 



♦Camber determines elevation 



11-1 




D MONUMENT NOT INSTALLED 
■ MONUMENT IN PLACE 
X MONUMENT DESTROYED 




200 



200 



400 600 



SCALE IN FEET 



MONUMENTS FOR 
MEASURING SURFACE MOVEMENT 



PJ/^ HH A U S DEPARTMENT OF THE INTERIOR ST 

FlVJ. I I I. INDEPENDENT PANEL TO REVIEW CAUSE OF T 



TATE OF IDAHO 
ETON DAM FAILURE 



11-2 



Under his contract the contractor was required to furnish materials for and to place the embankment 
measurement points where shown, or as designated by the Government. 

The Government was to assist the contractor by determining the approximate locations for the 
measurement points and on completion of each row of points was to establish them as benchmarks 
for elevations and targets for horizontal control. Periodic Government surveys to 0.01 ft on these 
points were to be started for the measurement of cumulative settlement and for horizontal deflection 
of each with respect to the centerline of crest. Further details of the embankment measurement point 
installation are described in Designation E-32 of the USER Earth Manual, first edition, revised 1968. 

On June 5, 1976, only nine of the upstream points had been installed and were being monitored. Five 
of these points were destroyed when the dam failed. As shown in Fig. 11-1, none of the downstream 
points were placed. 

Some settlement was expected along the spillway walls. To determine the magnitude of such 
settlement and any deflection of the walls, readings were obtained on measurement points as soon as 
the structures were constructed, prior to backfill placement, and periodically as construction 
progressed. As previously stated in Chapter 7, no movement was significant. 

Flow Measuring Facilities. 

Devices such as weirs to measure seepage flows downstream from the dam had been planned but had 
not yet been constructed at the time of failure. The reported flows were estimated from visual 
observation. 

Groundwater Measuring Devices. 

Nineteen exploratory borings located in a large region surrounding the dam were used as observation 
wells (Fig. 1 1-2). These holes, however, were not specifically located for the purpose of surveillance 
of the dam. They did serve to indicate rise in water level in the area in the vicinity of the reservoir, 
but their value in monitoring the safety of the dam was incidental and minimal. 

Abutment Seepage Instruments. 

No provision was made for monitoring seepage flows inside the abutments. 

Strong Motion Instruments. 

The U.S. Geological Survey had a strong motion accelerometer installed in the Teton Dam 
powerhouse which was destroyed at the time of failure. For other seismometer installations refer to 
Chapter 6. 



MEASUREMENTS 

The water table in the right abutment was observed through drill holes and wells for several years 
before construction of the dam. In May 1975 a program for measuring groundwater conditions at the 
damsite and reservoir prior to and during initial filling was established. This program was expected by 
the USBR to give advance warning of the development of unusual groundwater conditions. Readings 
of water levels in the wells were taken weekly until the spring of 1976, when the frequency of 
readings was increased to about twice a week. The results are discussed in Chapter 5. 

Surveys were made periodically of horizontal and vertical movement of the surface monuments which 
had been installed on the dam. The results are shown in Table 11-1. 



11-3 




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11-5 



INSPECTION 

Daily inspection was made of the constructed works, including the auxiliary outlet works and the 
river outlet works access shafts, the river outlet works tunnel, and the area below the dam. Patrol 
examination was made of the abutments and the canyon walls downstream in search of leakage. 

Surveillance inspections were made during reservoir fiUing as a part of the regular duties of the 
inspectors. In addition, the project photographer who recorded the observation well readings also 
inspected the abutments at least twice each week. 

A daily report dated August 2, 1976 by Inspector Lyman G. Rogers, USER, states: 

As construction work started up this spring and reservoir was fiUing, Inspector Gary 
Larson was instructed to check for leaks in A.O.W. shaft and sides of spillway and 
spillway drains. Inspector Frank Emrick was instructed to check for leaks in R.O.W. 
shaft. Inspectors Alfred Stites and Ken Hoyt were instructed to check for leaks along left 
and right abutments downstream of face of dam. This work was done along with their 
regular inspection duties. I also checked along the abutments at least twice a week. 

In a memorandum of November 9, 1976 to the Project Construction Engineer from Field Engineer 
Peter P. Aberle, the following description of surveillance procedures was given (Appendix B, under 
letter to Robert Jansen dated November 12, 1976): 

. . . The area downstream of the spillway area was observed from across the river on a 
daily basis by the inspection forces and myself and leaks of any consequence could be 
detected by watching for water flows from the drain downstream of the spillway along 
the right abutment into the river. AH inspectors were instructed to be aware for leakage 
and to report these leaks immediately. 

During the month of May, the contractor (MK-K) cut a small hole into a water storage 
pond which was located higlr on the right abutment for the purpose of draining it. Water 
from this pond drained into the gully located to the right of the spillway. This water was 
detected almost immediately by the inspection forces and reported which shows the 
awareness of the program. 

About ten days prior to June 4, I received a call from Mr. Duane Buckert, Project 
Manager for MK-K, stating that their Office Engineer, Vince Poxleitner, thought he saw a 
leak downstream of the spillway. This was checked out by the inspection forces and 
found to be negative. 

After well no. 6 [DH-6] showed an exceedingly rapid increase of the water level, 1 made 
an inspection of the right abutment about 1200 to 1700 feet downstream of the dam and 
the gully in this area. This inspection was made on or about June 1, 1976, and no leaks 
were noted. 

On Thursday, June 3, 1976, when the two leaks were found downstream of the spillway, 
I checked along the canyon downstream of these leaks an additional 500 feet and found 
no leaks. 

On the morning of June 5, as I drove to the powerhouse area, I again visually checked the 
spillway drains and the gully to the right of the spillway and saw no leaks. 



11-6 



At least once a week I instructed the shift inspector to remind all inspectors to watch 
daily for possible leaks. These reminders were also made by myself several times during 
the weekly safety meeting held by the inspection forces each Monday morning. 

As soon as the ice cleared from the reservoir area, the reservoir was inspected two to three 
times per week. The shoreline was patroled near the damsite and potential land slides 
were noted and reported throughout the reservoir area. . . . 

After the failure, Aberle reported that the small springs in the right abutment downstream from the 
dam "warranted monitoring by visual observation as frequently as routine inspections of the entire 
operation at the dam." 

Such inspections were made. On the morning of June 4, 1976, for example, engineer W.H. Andrew 
and inspector A.D. Stites walked around the right abutment area at the toe of the dam looking for 
leaks. Andrew reported that they were doing this because "one or two spring leaks had developed" 
farther down the stream in the abutment wall "about the day before." 

Later on June 4, until dark, inspector Stephen Elenberger made several observations of "both the 
downstream side and the upstream reservoir." He says that he had been alerted to pay particular 
attention for possible leaks because there were small spring-like areas of water on the north side of 
the canyon below the toe of the dam. 

Regarding the seepage downstream in the north abutment waU, Project Construction Engineer R.R. 
Robison says that "I felt the area should be monitored by sight inspections and other mechanical 
means, the latter of which were never put into effect." Robison inspected this seepage late in the 
afternoon of June 4, 1976 and examined the dam itself, both upstream and downstream. 



ANALYSIS 

The need for monitoring and analyzing water levels in weUs and drill holes at and near the damsite 
was apparently recognized by the Bureau of Reclamation, and attention was given to study of the 
data from this effort. Tlie procedures for processing of well observation data were transmitted in a 
memorandum attached to a letter to Robert Jansen dated November 12, 1976: 

... It was our intent that the readings should be compiled and forwarded to the Regional 
Office and Denver office personnel interested in this data at least once each month. 
Subsequent to the water being stored in the reservoir, Mr. [Keith] Rogers would receive 
the data and plot them on the charts as they were submitted in the field. I would review 
them periodically at least once each week to see if there was any significant changes in 
the water level shown. Approximately once each month we would assign a cutoff date 
that the charts would be brought up to date, the readings would be recorded and the data 
sent off to the various offices. The reservoir started filhng so rapidly in the spring that 
recordings were read at more frequent intervals. Periodically we would meet with Mr. 
Robison and would look over the readings and discuss the changes noted. The last month 
before the dam failure, we noted a significant rise in water level shown on these readings. 
This was discussed with representatives of Director of Design and Construction, Denver. 
It was decided to make a special effort at this time to compile the data from the 
observation wells in order to forward them at a closer interval than in the past. . . . 



11-7 



As can be seen in Fig. 11-2, two observation wells were located on the left abutment downstream 
from the dam and one was nearby in the canyon bottom. However, there was only one drill hole 
downstream from the dam axis on the right abutment to serve as an observation well. While more 
holes in this vicinity would have faciUtated analysis, the Bureau regarded the monitoring system as 
adequate. 



REPORTING 

SurveUlance activity was conducted as part of the general inspection program, and any observations 
related to safety of the project structures were made on that basis. Adverse developments, however, 
were reported separately from the routine inspection reports. Construction personnel were instructed 
to make oral reports to their supervisors if they observed any questionable conditions at the dam. 

The Project Construction Engineer was expected to make monthly inspection reports to the Director 
of Design and Construction in Denver. Unusual observations were to be reported immediately. Project 
Construction Engineer Robison did this either by telephone, faxogram, or mail. 



COMMENTS 

For a dam of this size and complexity, facilities for measurement usually would include surface 
monuments for gaging vertical and horizontal movement, cross-arm settlement devices and/or slope 
indicators to measure internal embankment movement, piezometers to monitor water pressures 
within the fill and in its foundation, weirs or other devices to measure seepage, wells for observation 
of water levels in the reservoir environs, and instruments such as accelerometers to measure earth 
tremors. 

Inspectors responsible for visual observation should be provided with standard operating instructions 
to guide them in their regular patrols. These observers would be trained to interpret potentially 
adverse conditions and to report significant fmdings promptly. The assignment of responsibility 
should be well documented and well understood by all concerned persoruiel. 

Several key members of the construction force made inspections on a regular basis, supplementing 
their construction assignments. Definition of responsibihties was apparently adequate. Information 
from pertinent observations was communicated reUably through the chain of supervision. The major 
deficiency in the surveillance program was in instrumentation. While considerable attention was given 
to well measurement in the vicinity of the dam, most of the wells were too far away to give direct 
indication of its performance. None of the wells was located specifically to monitor behavior of the 
embankment or its abutments. Without good instrumentation in the foundation and with none inside 
the dam itself, observers at the site were Umited in the judgments that they could make related to 
safety. 

In summary, project staff complied sensibly with preliminary operating criteria specified by USBR 
designers. Most instructions given at the site were oral, but it is beUeved that they were followed 
conscientiously. However, the dam and its foundation were not instrumented sufficiently to enable 
the Project Construction Engineer and his forces to be informed fully of the changing conditions in 
the embankment and its abutments. 



11-8 



CHAPTER 12 
CAUSE OF FAILURE 



REVIEW OF SURFACE MANIFESTATIONS 

Any satisfactory explanation of the failure must be in accordance with the known chronology and 
eyewitness accounts. The facts are summarized as follows: 

Before June 3, no springs or other signs of increased seepage were noticed dowstream of the dam. On 
June 3, clear-water springs appeared at distances of about 1300 and 1500 ft downstream, issuing from 
joints in the rock of the right bank. 

During the night of June 4, water may have flowed down the right groin from about El. 5200, 
inasmuch as a shallow damp channel was noticed early on the morning of June 5. Shortly after 7:00 
a.m. when the first observations were made on June 5, muddy water was flowing at about 20 to 30 
cfs from talus on the right abutment at about El. 5045, and a small trickle of turbid water was 
flowing from the right abutment at El. 5200. Both flows were at the junction of the embankment and 
the abutment, referred to as the groin, and both increased noticeably in the following three hours. 

At about 10:30 a.m. a large leak of about 15 cfs appeared on the face of the embankment, possibly 
associated with a "loud burst" heard at that time, at El. 5200, about 15 ft from the abutment and 
adjacent to the smaller leak previously observed at the same elevation. The new leak increased and 
appeared to emerge from a "tunnel" about 6 ft in diameter, roughly perpendicular to the dam axis 
approximately opposite dam axis Sta. 15+25, and extending at least 35 ft into the embankment. The 
tunnel became an erosion gully developing headward up the embankment and curving toward the 
abutment, as shown in Fig. 2-1 and in the photographs. Figs. 2-1 1 and 2-13. 

At about 11:00 a.m., a vortex appeared in the reservoir at about Sta. 14+00, as shown in Fig. 2-1, 
above the upstream slope of the embankment. At 11:30 a.m., a small sinkhole appeared temporarily, 
ahead of the gully developing on the downstream slope, near the crest of the dam. Shortly thereafter, 
at 11 :55 a.m., the crest of the dam began to collapse at a point between the vortex and the head of the 
enlarging gully (Fig. 2-14). The failure then continued as a simple enlargement of the discharge 
channel by the reservoir. 

From the time observers arrived at the site and first observed the small muddy flows, to the breaching 
of the dam, was about five hours. If it is assumed that such flows began on June 4, immediately after 
Inspector Elenberger's last visit at about 9 p.m., the surface manifestations of the developing erosion 
channel could not have existed more than 15 hours before the final breaching of the dam. 

No other pre-failure observations are known except for the rise in water levels in various drill holes 
being used as observation wells. This information is shown in Fig. 5-7. 



PHYSICAL CONDITIONS ALONG FAILURE PATH 

Introduction. 

The path along which the erosion developed is defined in plan with a considerable degree of certainty 
by the surface manifestations described previously. The subsurface conditions along this path played 
a vital part in determining the nature of the failure. In the following comments, the term "failure 



12-1 



section" is frequently used. This term is intended to refer to that section of the dam generally 
between dam axis Stas. 13+50 and 15+25. 

Conditions Upstream from Grout Curtain and Key Trench. 

The open-jointed nature of the welded tuff in the right abutment, both upstream and downstream of 
the axis of the dam, is described in detail in Chapter 5. In the early stages of design, during the test 
grouting program, it was concluded that the upper 70 ft of the rock on both abutments was too open 
for successful grouting; consequently the key-trench design was adopted. The open nature of the 
joints on the upstream face of the right abutment key trench was confirmed by the Panel's 
investigation after removal of the key-trench fill. At the failure section, part of the abutment rock has 
been removed by the erosive action of the escaping floodwaters. There is no reason to beheve that the 
eroded rock was less open-jointed than that which remains. "Hence, there can be no doubt that 
reservoir water had ready access to the entire upstream face of the key trench, including the portion 
adjacent to the faUure section. 

Beneath the level of the base of the key trench, the rock was also jointed and permeable, as judged by 
the water tests in exploratory drill holes and by the grout takes in the curtain. Since the curtain was 
confined to the key trench, there is no doubt that the rock at depth, upstream of the curtain, was 
permeable, albeit possibly less so than that in the upper 70 ft. Inspection of the face of rock 
remaining along the right abutment after the erosion by the escaping floodwaters disclosed many 
open joints below key-trench level, some partly fiUed with grout, both upstream and downstream of 
the grout curtain. 

Conditions at Key Trench. 

The geometry of the key-trench excavation is shown in Figs. 3-1, 3-3, and 3-13. In addition to the 
steep sides of the general excavation, many local irregularities are present. These include near-vertical 
faces and occasional overhangs. 

Tlie geometry of the local steep faces and overhangs is related to the jointing. Concentrations of 
joints, largely trending N30'^W, exist between Stas. 13 + 00 and 13 + 50, and in the vicinity of Sta. 
14 + 00 where erosion has removed the grout cap and exposed the rock beneath. The jointing is 
described in Chapters 3 and 5 and in AppendLx E. 

Tlie grout curtain and grout cap have been described in detail in Chapters 8 and 9. The ponding or 
joint transmissibUity tests conducted by the Panel, described in Chapter 3, demonstrated that water 
can flow readily beneath the grout cap at several locations near the failure zone. Water tests in drill 
holes on the center line of the grout curtain near the failure section also demonstrated the existence 
of passages through which water emerged downstream. 

Tlie key-trench fiJl was investigated extensively as the remnant on the right abutment was excavated. 
The material, as indicated in the specifications, consisted of windblown clayey silts. As described in 
Chapters 7 and 9, it was compacted generally on the dry side of optimum, contained occasional lenses 
or layers more plastic than the rest, and was placed against the rock walls of the key trench with no 
rock treatment or transition. Loose zones were noted beneath occasional overhangs or against open 
joints. 

Conditions Downstream from Key Trench. 

The jointing in the rock exposed in the downstream face of the key trench appears generally less 
prominent and open than upstream, except in the vicinity of Sta. 14+00 where several sets of major, 
throughgoing joints are apparent. These joints are located just to the right of the mass of rock eroded 
by the floodwaters; others undoubtedly existed within the eroded mass. 



12-2 



The right abutment was originally partly covered with products of rock weathering and 
accumulations of talus. These materials were removed where Zone 1 was in contact with the 
abutment, but not at the foundation contact with Zones 2 and 5. As described in Chapter 9, 
pervious talus existed beneath the groin of the dam on the right abutment downstream of Zone 1 . 
The downstream toe rested on alluvium. A stockpile of riprap existed downstream of the toe along 
the right abutment at the time of failure. Thus there was considerable pervious material in contact 
with the right-abutment rock wall into which moderate quantities of clear or muddy water could have 
escaped for a limited time without detection. 

The geometry of the mass of rock bounded by the downstream face of the key trench and the face of 
the right abutment immediately downstream of the key trench deserves attention. The outer part of 
the mass was removed by the floodwaters. It was transected by nearly vertical joints, of which the 
lower portions still remain (Figs. 3-9 and 3-1 1), which constituted a short path from the key trench 
to the portion of Zone 2 resting on the right-abutment talus at about El. 5200. 



UNTENABLE FAILURE HYPOTHESES 

Seismic Activity. 

As indicated in Chapter 6, there is no evidence of seismic activity at the time of failure. The only 
earth motions recorded were those clearly caused by the escape of the turbulent fioodwaters from the 
reservoir. Therefore seismic activity was not a cause of failure. 

Settlement. 

Settlement of the dam and its surroundings, possibly associated with compression of the Miocene lake 
and stream sediments, has been suggested as a cause of cracking leading to penetration of water and 
erosion. 

Settlement observations were made on surface reference points on the embankment (Table 11-1). 
Because the reference points were estabhshed when the dam was almost completed, the records do 
not include the immediate settlements due to the weight of the embankment. They do include, 
however, post-construction settlements due to this weight plus the settlements associated with filling 
the reservoir and any distortions due to the subsequent failure. The maximum observed movements 
prior to the failure were on the order of 2 in., a value by no means unusual during first filling of 
reservoirs. The settlements of a large number of successful earth dams have been many times this 
value. Indeed, one of the advantages of earth dams is their ability to accommodate large settlements 
of the foundations and of the fill itself, as well as large differential settlements among various parts of 
the dam and its appurtenant works. Furthermore, had appreciable abutment settlements actually 
occurred, distress would have been visible in the concrete lining of the auxiliary outlet tunnel beneath 
the spUlway structure. Tlie tunnel, when inspected after the failure, was in excellent condition and 
displayed no cracks that could be attributed to causes other than normal shrinkage. 

A resurvey of fourteen principal control points used in construction of the dam was made after the 
failure (Table 5-5). One control point was located as far as 6500 ft from the axis of the dam, beyond 
the influence of the weight of the dam; two were located close to the ends of the dam; others were at 
intermediate distances. Indicated differences in elevation of reference points before and after failure 
of the dam ranged from a settlement of 1.5 in. to a rise of 0.5 in. Tliese differences might be 
considered to be within the tolerances for construction surveys run across a canyon, and not to be 
significant. It would be reasonable to conclude that a movement of as much as 0.5 in. might have 
occurred as a consequence of removing the weight of the failed portion of the dam. On the 



12-3 



assumption that the thickness of the Miocene sediments is 100 ft, the constrained modulus of 
elasticity of the sediments, to account for a rise of 0.5 in. on removal of 100 ft of embankment, is 
about 500,000 psi. This value corresponds to the in-situ modulus of many basalts and other flow 
rocks on first loading. Hence, settlement due to compressibility of the Miocene sediments should have 
differed little from that which would have occurred if they had been replaced by rhyoUte. It should 
be noted that since the Miocene sediments are thicker than 100 ft, their calculated modulus is even 
greater. 

On the basis of the preceding discussion the Panel concludes that settlement of the dam or its 
foundation did not contribute to the failure. 

Reservoir Leakage. 

High water losses in various exploratory drillholes near the dam and along the reservoir rim have been 
cited as a factor indicative of potential failure. Large losses of water beneath or around earth dams or 
through the reservoir rim may have an influence on the economics of a project but they have no 
relation per se to the safety of the dam, provided that the foundation and abutment treatment, to be 
discussed, is designed and executed in accordance with good practice. Therefore, the Panel does not 
consider the question of reservoir losses to be pertinent to the cause of failure of the dam. 

Seepage Around End of Grout Curtain. 

As concluded in Chapter 5, seepage around the end of the grout curtain was not a cause of failure. 



MOST PROBABLE STEPS IN DEVELOPMENT OF FAILURE 

Appearance of Springs. 

As the reservoir level rose, more and more water gained access to the joints in the rhyolite, joints that 
increased in width in a general way with increasing elevation, especially above about 5200 ft. As a 
result of flow beneath and around the ends of the grout curtain, as well as through the "windows" 
existing in it, a general rise of groundwater levels occurred downstream of the dam. This rise led to 
the appearance of clear-water springs 1300 to 1500 feet downstream of the toe a few days before the 
failure. These springs, although predating the failure only sUghtly, were not in themselves indicators 
of developing defects, but were normal accompaniments of reservoir filling. 

Development of Erosion Tunnel. 

Between about Stas. 13+40 and 15+00, particularly unfavorable conditions existed, as described 
previously: (1) a geometry of the key trench especially favorable to arching, to poor compaction, 
and to cracking of the Zone 1 material; (2) significant water passages through the rock just beneath 
the grout cap and possibly through the grout curtain at greater depth; (3) a concentration of 
throughgoing joints beneath and alongside the key trench; and (4) an erodible fill within the key 
trench and in contact with the jointed rock downstream from the key trench. As a result of these 
conditions one or more erosion tunnels formed across the bottom of the key trench permitting water 
to flow readily from the open joints upstream to those downstream of the key trench and grout 
curtain. The manner of formation of the initial tunnel deserves detailed discussion and is treated in 
the next section. 

As erosion enlarged the tunnel or tunnels, the discharge of water increased. The discharge, being of 
increasing amount and containing eroded silty soils, could escape only through passages of 
appreciable size. Some of the outflow undoubtedly entered the generally interconnected joint system 
downstream of the cutoff and spread through the rock mass, but a large part passed nearly 
horizontally, near El. 5220, through or around the narrow block of rock between the downstream 



124 



face of the key trench and the right abutment wall. Flow through this rock mass was faciUtated by 
the concentration of joints intersecting the downstream wall of the key trench between Stas. 13+40 
and 14+00. Part of the flow emerged from the rock against the Zone 1 fill on the right abutment, 
turned downstream, and flowed along the interface. Since the silty fill beneath minor overhangs and 
along near-horizontal joints was sheltered from overburden pressure, it too was vulnerable to erosion. 
The water and suspended silt continued along the interface until it reached Zone 2 or the pervious 
surficial soils and talus left beneath Zone 2. Another part of the flow remained in the rock near the 
abutment, where weathering and relaxation left more open joints than at greater depth, and then 
emerged into Zone 2 or the talus beneath it. Once the pervious zones were reached and as long as the 
outflow did not exceed their capacity, water flowed through the pervious materials near the groin of 
the right abutment and through the riprap stockpile at the toe. 

Development of Erosion Gully. 

During the night of June 4, however, the leakage began to exceed the capacity of the pervious 
materials, whereupon it emerged at El. 5200 and flowed briefly down the surface. Dampness and 
slight erosion were noted along the groin the next morning. Early in the morning, as flow continued 
to increase, muddy springs appeared at both El. 5045 and El. 5200. Soon the spring at El. 5200 was 
seen to be the mouth of an erosion tunnel extending along the rock at the base of the earthfill close 
to the groin. Progressive erosion led to continued increase in size of the tunnel until finally at about 
10:30 a.m. the water pressure was great enough to break suddenly and violently through the Zone 2 
fill and erupt on the face of the dam. Thereafter the erosion tunnel became an erosion gully, working 
headward first up the groin and then along the initial passage through the key trench. The gully 
extended upstream by successive collapses of the roof of the tunnel, including the sinkhole that 
appeared briefly at El. 5315, toward the vortex over the upstream end, culminating in collapse of the 
roadway at the crest of the dam. 



INITIAL BREACHING OF THE KEY-TRENCH FILL 

Conditions Favoring Erosion and Piping. 

It was recognized by the USBR early in design, and confirmed by the Panel's investigation, that the 
Zone 1 material placed in the key trench and against the abutments was highly erodible. Wherever 
this material would be subjected to the action of flowing water, it would be attacked and washed 
away rapidly. Seepage through the material could also produce backward erosion due to 
grain-by-grain removal at points of emergence of flow lines where such points consist of voids 
unprotected by filters. The latter process develops slowly. Hence, it is unUkely to have played a 
significant role in the failure of Teton Dam, because the failure developed with remarkable rapidity. 

Therefore the initial breaching of the key-trench fill can be attributed to erosion by direct contact 
with flowing water. This contact could have occurred under two conditions: Where the fill was in 
contact with open joints through which water was flowing, and through cracks in the fill itself. The 
physical conditions in the vicinity of Sta. 14+00 were conducive to both possibilities, and it is 
possible that both existed simultaneously. 

The erodibility of the fill material itself is, moreover, dependent on its density and state of stress. 
Where loose, as in local zones where compaction is difficult or impracticable, the erodibihty is 
substantially greater than where the fill is dense. Where the intergranular pressures are low, erosion 
can take place more readily than where they are high. Furthermore, if the water pressure exceeds the 
intergranular pressure, tension develops in the soil skeleton, and if the tension exceeds the tensile 
strength of the soil, the soil may crack by the process known as hydrauUc fracturing. If the total 



12-5 



stress in the soil at a soil-rock interface is less than the water pressure in a joint at the interface, the 
soU may separate from the adjacent rock as a consequence of hydrostatic pressure, and the 
separation tends to propagate and allow greater access of the water to the soil. 

Some or all of these conditions occurred near the base of the key trench near Sta. 14+00 and, 
separately or in combination, were responsible for the original breach of the key-trench fill. The 
evidence is reviewed, for clarity of presentation, under the following two headings, although the two 
topics cannot, in fact, be completely separated. 

Evidence of Attack on Fill by Flow in Rock Joints Along the Contact. 

The mechanism of erosion under these conditions is illusirated by Fig. 12-1 , in which is depicted an 
idealized joint in the bottom of the key trench. The joint is not sealed by dental concrete or slush 
grout; consequently, horizontally flowmg water under pressure would attack the base of the Fill and 
begin to form a pipe. If the joint occurred at a step in the rock surface, Fig. 12-2, the erosion would 
occur even more readUy because of the reduction of stresses in the reentrant corner due to arching, as 
will be discussed in greater detail in the next section, and because of the likelihood of poor 
compaction of the fill in the corner. Furthermore, under high water pressure, the pipe is likely to 
enlarge by separation of the fill from the rock surface, as illustrated in Figs. 12-2 and 12-3. 
Conditions corresponding to Figs. 12-1 and 12-2 have been observed in the key trench near Sta. 
14 + OU as documented in Chapter 3; indeed, several instances of overnanging as well as near-vertical 
steps were noted. 

In reality, the key trench at the failure section contained a giout cap overlying a single-line grout 
curtain flanked by two other lines of grout holes intended to contain the flow of grout from the 
curtain grouting. The investigations earned out at the request of the Panel, described in Chapter 3, 
demonstrate clearly that openings or windows existed in the grout curiain near the failure section, 
particularly at shallow depth beneath the grout cap. These conditions are illustrated diagrammatically 
in Figs. 12-4 to 12-6. The diagrams show how the initial formation of pipes along transverse joints, as 
illustrated in Figs. 12-1 to 12-3, associated with even modest seepage beneath the gtout cap, can 
develop (Fig. 12-5) into larger cavities upstream and downstream of the giout cap, and how the 
cavities may unite under the high hydraulic gradient between them to form a single erosion tunnel. 
After this occurs, enlargement of the tunnel is restricted only by the capacity of the adjacent joints to 
deliver and carry away the through-flowing water. 

The Panel's investigations leave no doubt that all the conditions for creation of the initial breach by 
this mechanism existed between about Stas. 13+40 and 15+00. lire results of ponding tests on 
throughgoing joints demonstrated the existence of zones of ready leakage beneath the grout cap at 
the places shown in Fig. 3-17 and the existence of deeper windows in the grout curtain is indicated in 
Table 3-2. 

Furthermore, the topography of the bottom of the key trench in the vicinity of the failure showed a 
concentration of steps and overhangs conducive to arching and poor compaction. 

Evidence of Attack on Fill Through Cracks in Fill. 

Cracking of cohesive soils in the impervious sections of earth dams is a well known phenomenon 
associated with tensile strains due to differential settlements among portions of the dam or between 
the embankment and its foundation. A variety of defenses is available to the designer to reduce the 
potential for cracking and to render harmless those that occur. The mere presence of cracks, 
therefore, is not an indication of unsatisfactory design or performance. At Teton Dam, however, it is 
apparent that cracks through the key trench would inevitably lead to rapid erosion and would thus 
constitute remarkably efficient avenues for breaching the seepage barrier and initiating failure. 



12-6 




\t>77777777Z 



/ — Pipe eroded by water 

/ 1 lowing in open rock joint. 

I 

Open )oint in rock 




Hydrostatic 
pressure in open 
rock joint 



77777777777777 

Zone of reduced stresses 
in fill due to arching 

Pipe formed by combination of 

1) Soft or poorly compacted 
fill and 

2) Erosion by water (lowing 
in open joint 



Pipe eroded by water flowing along 
open joint 

Fig. 12-1 



Pipe eroded by water flowing 
along re-entrant step in rock 

Fig. 12-2 



Low stresses due 
to arching- 




^7777777777777? 

Initial separation of till trom rock surface, due 
to hydrostatic pressure, propagates upward as 
tissure into the fill. If water flows longitudinally 
in joint, the fissure will be eroded and form 
a pipe. 



Hydrostatic 
pressure 



Fissure in fill produced by hydrostatic pressure in rock joint 
along re-entrant step 

Fig. 12-3 



EROSION DIAGRAMS 



FIGS.12-1. THROUGH 12-3. 



U S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



12-7 



Downstream 



Upstream 



Grout Barrier 



r 



Pipes eroded on top 
of open joints 




Fig. 12-4 



Flow through open rock 
joints and windows in 
grout curtain 

Grout Barrier 



Downstream 



Grout Barrier 




Upstream 

High gradient causes 
breakthrough over 
grout cap 



Fig. 12-5 



Grout Barrier 



Piping Stage H 



Downstream 



Grout Barrier 




Upstream 



Fig. 12-6 



Flow through pipe 
shortcircuited across 
keytrench 



Grout Barrier 



Piping Stage HI 

EROSION DIAGRAMS 

r;j/-^Q "lO^/l T'UD/^T T/^U "lO^^ U S. DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

rHjO. 1^ '+. 1 rllvLIUvjri 1^ O. independent panel to review cause of TETON DAM FAILURE 



12-8 



Cracking is associated with zones of low compressive stresses in the fill. Such zones are related to 
differences in compressibility of materials in adjacent portions of the dam, or between the 
embankment and its foundation or abutments. The weight of the embankment overlying a 
compressible material is partly transferred to adjacent less compressible materials as a result of 
shearing stresses developed in the embankment. This process of stress transfer is commonly referred 
to as arching. 

In a qualitative sense, arching is illustrated in Fig. 12-7 which depicts an idealized cross section 
through the key trench of Teton Dam. The rigidity of the rock walls, combined with their steep 
slopes, causes a high degree of arching or stress transfer to the abutments, and a corresponding zone 
of low stresses in the fill at the bottom of the trench. Because of its importance, this arching 
transverse to the key trench is designated as first-order arching. In a longitudinal direction, however, 
the profile of the bottom of the key trench contains major steps or irregularities; in the depressions 
the compressible materials cause load to be transferred to the adjacent rock surfaces. Arching of this 
type, Fig. 12-8, is designated as second-order. Finally, local smaller steps and overhangs occur that 
lead to a third order of arching (Figs. 12-2 and 12-3) that may not only be significant in itself but is 
especially likely to be associated with poor compaction. All three orders of arching may occur 
simultaneously and the reductions of stress are additive. That the conditions in the key trench near 
Sta. 14+00 were conducive to all three orders is evident from a study of the cross sections, the 
longitudinal sections, and numerous photographs. The occurrence of a high degree of arching near 
Sta. 14+00 combined with the presence in this area of joints capable of delivering and carrying away 
large quantities of water make cracking a highly probable potential cause of breaching of the 
key-trench fill. 

The qualitative discussion of arching represented by Figs. 12-7, 12-8, and 12-3 can be supplemented 
by quantitative studies carried out by the finite-element method. Although this method of analysis 
has been applied to the calculation of stresses in earth dams for some years, it is still under 
development. At the present time, the techniques are practicable for two-dimensional analyses. The 
most refined techniques require the determination of nine different soil parameters, determined from 
triaxial tests. The parameters do not take into account the influence of time, although allowances can 
be made for the effect of yielding, and the computational procedures permit allowing for the 
progressive construction of the embankment. Thus, the numerical results of stress and displacement 
calculations, although themselves quantitative, are best used in a qualitative or semi-quantitative 
manner. 

Soil parameters for analyses at critical locations were selected by members of the Panel on the basis 
of five triaxial tests, some performed by the USBR during design of the dam and some performed by 
the USBR and Northern Testing Laboratories according to procedures specified by the Panel, and on 
the basis of experience in testing other materials. A range of values was chosen for the principal 
parameters to take some account of variations in properties from those represented by the samples 
tested. Details of the materials tested and of the tests are described in Chapter 3. 

Two-dimensional analyses were performed for cross sections at Stas. 12+70, 13+70, and 15+00 on the 
right abutment and at Sta. 27+00 on the left abutment. The sections on the right abutment were 
chosen by the Panel as being representative of the portion of the key trench where the seepage barrier 
was initially breached. Similar sections at Stas. 26+00 and 27+00 were analyzed to permit comparing 
certain predictions based on the finite-element analysis with field observations carried out in the 
portion of the embankment remaining after the failure, as discussed in the next subsection. 

The values of vertical normal stress throughout the embankment and key-trench fill are shown as 
fractions of overburden pressure in Fig. 12-9 for Sta. 15+00. For comparison, the figure also shows 



12-9 



7777. 




Zone of low 
stresses in fill 



First order arching in fill over and 
between walls of key trench 

Fig. 12-7 




Zone of low 
stresses in fill 



Second order arching produced by 
longitudinal topography of rock surface 
in key trench 

Fig. 12-8 



EROSION DIAGRAMS 



FIGS. 12-7 THROUGH 12-8. 



11 S DEPARTMENT OF THE INTERIOR STATE OF IDAHO 

INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



12-10 



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12-11 



the stresses that would exist if there were no key trench; that is, if there were no redistribution of 
stresses due to arching. The results demonstrate the marked reduction of stress due to first-order 
arching as a result of the presence of the key trench. Because the results are two-dimensional, they 
give no information about the second-order arching associated with the longitudinal configuration of 
the key trench (Fig. 12-8), or about the third-order arching illustrated in Figs. 12-2 and 12-3. 

Hence, the finite-element studies confirm and to a degree quantify the importance of the arching 
associated with the key trenches adopted for the abutments of Teton Dam. 

The analyses were carried out under the direction of members of the Panel. The details of the 
analyses and an assessment of their pertinence are contained in Appendix D. 

Considerations of Hydraulic Fracturing. 

Within the limitations of the vahdity of the assumptions, the finite-element method of analysis also 
permits calculation of whatever other components of stress are considered to be of interest. It is thus 
possible, in principle, to compute the minimum total compressive stress at any point within the dam 
and to compare the sum of this stress and the tensile strength of the fill material with the porewater 
pressure. If the sum of the normal stress and tensile strength is less than the porewater pressure, the 
possibiUty exists that cracks will develop by a mechanism known as hydrauhc fracturing. 

Hydraulic fracturing has often been induced in the impervious zones of earth dams by creating 
sufficient head in water-filled drill holes in the dams. Measured values of water pressure to cause 
fracturing, indicated by sudden loss of water from the drill hole, have compared favorably with the 
sum of reasonable values of tensile strength of the material and the total minor principal stress 
calculated by the finite-element procedure. 

Because of the agreement between calculated and observed values of water pressure to cause 
hydraulic fracturing around drill holes, field tests in drill holes have been used to check the 
reasonableness of soil parameters determined by laboratory tests for finite-element analyses, or to 
determine the most appropriate value of one of the more significant parameters. Such tests were 
carried out at the request of the Panel near the left abutment at Stas. 26+00 and 27+00 where the 
key trench sections closely resemble those at Stas. 15+00 and 13+70 in the right abutment, in order 
to verify the general applicabihty of the parameters selected from the soil tests and to aid in selecting 
the applicable value of Poisson's ratio. The details of the procedure and of the interpretation are given 
in Appendix D. 

The possibiUty of hydraulic fracturing in dams as a result of water pressure from a reservoir appUed 
against an impervious zone has also been investigated by the finite-element procedure. This is 
accompUshed by comparing the sum of the minimum total compressive stress and the tensile strength 
at a point in the zone with the water pressure at that point. In computing the stresses in the soil, the 
effects of consohdation, swelUng and creep are not fully considered. However, this limitation can be 
overcome to some extent by considering a range of soil parameters and by utilizing observed field 
performance as an additional guide in selecting the most suitable values. 

In determining the water pressures, consideration should be given to the head losses associated with 
whatever seepage may occur. If a completely impervious grout curtain should be achieved, for 
example, full hydrostatic pressures corresponding to the reservoir level would be exerted against the 
cutoff and the possibiUty of hydraulic fracturing would be maximized. At the other extreme, if the 
efficiency of the grout curtain is very low, the water pressures exerted against the cutoff would be 
greatly reduced and, for a reasonably symmetrical section, would approach half the values 



12-12 



corresponding to the reservoir level. The potential for hydraulic fracturing would be 
correspondingly reduced. 

Thus, depending on personal evaluations of the efficacy of a grout curtain and of the applicabihty of 
the stress analyses, there are likely to be differences of opinion concerning the possibility of hydraulic 
fracturing in any given case. Nevertheless, the results of such calculations when appUed to the right 
abutment of Teton Dam between Stas. 12+70 and 15+00 lead to interesting conclusions. The 
abbreviated discussion in this section is treated more fully in Appendix D. 

The results for Sta. 13+70 illustrate the findings. They show that the minor principal stress Ues in the 
plane of the cross section and, at the upstream face of the key trench, is inclined downward at about 
30° in the downstream direction, as illustrated in Fig. 12-10. Thus, the first cracks would form in a 
direction parallel to the axis of the key trench rather than across it. Computed values of the minor 
principal stress in the plane of the section at Sta. 13+70 are compared with the full hydrostatic 
pressures for reservoir level at 5300 ft in Fig. 12-11. The comparison shows that hydraulic fracturing 
would occur in a zone along the upstream face and the lower portion of the key-trench fill. Thus, 
water would be distributed longitudinally to any nearby sections where transverse cracking might 
occur. 

The possibility of transverse cracking is shown in Fig. 12-12, in which the computed values of normal 
stress on the transverse section at Sta. 13+70 are compared with hydrostatic pressures for reservoir 
level at 5300 ft. Hydraulic fracturing is indicated across the entire bottom of the key trench up to a 
height of approximately 15 ft. Thus, the analysis indicates that cracking due to hydraulic fracturing 
could have been responsible for initial breaching of the seepage barrier, if full hydrostatic pressures 
developed on the upstream face of the key trench. Similar results, with more extensive zones of 
fracturing, are found for the sections at Sta. 15+00. On the other hand, no fracturing is indicated for 
the section at Sta. 12+70. 

With the reservoir level at El. 5255, as it was on May 20, 1976, the calculations indicate that the 
hydrostatic pressures in the upstream jointed rock would have been sufficient to cause hydraulic 
fracturing only in the bottom 10 ft of the key trench at Sta. 15+00, but not at Stas. 13+70 and 
12+70. This condition is shown by the longitudinal section. Fig. 12-13, drawn through the centerline 
of the key trench. The shaded area indicates a very small zone near Sta. 15+00 where on May 20 the 
water could move through hydraulically induced fractures. The extent of the zone on May 25 with 
reservoir elevation at 5275, and on June 5 with reservoir elevation at 5300, are also shown. 
Downslope of about Sta. 16+00, hydraulic fracturing would not have occurred because the key trench 
became either very shallow or nonexistent. 

Fig. 12-13 summarizes the extent of the zone of hydraulic fracturing as estimated from the results of 
the analytical studies. It indicates that a substantial zone of vulnerability could have developed no 
earlier than two weeks before failure actually occurred, and that the location of the zone coincides 
closely with the zone in which piping finally developed. These coincidences lend support to the 
hypothesis that hydraulic fracturing of the soil in the key trench is a highly probable mechanism for 
the initial breaching of the seepage barrier. 

On the other hand, in the calculations made to determine the zones susceptible to hydraulic 
fracturing, it has been assumed that full hydrostatic pressure acts on the upstream face of the 
impervious fill. In reality, because the grout curtain had windows and flow occurred through it, the 
actual pressures against the upstream face and beneath the key trench upstream of the grout curtain 
would be less than full reservoir pressure. Hence such comparisons indicate greater potential for 



12-13 




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12-17 



hydraulic fracturing than actually existed. Even so, allowing for some reduction in water pressure due 
to seepage, sufficient disparity exists between water pressures and lateral soil stresses at sections such 
as Stas. 13+70 and 15+00 to enable fracturing to occur. This would be accentuated as the key-trench 
fill became saturated and arching effects became more pronounced. 

It is perhaps paradoxical that if, on the one hand, the grout curtain were not effective, failure would 
result directly from the underseepage whereas, on the other hand, if the grout curtain were fully 
effective, failure would tend to develop as a result of hydraulic fracturing. 



SUMMARY 

Upstream of the seepage barrier there was ample opportunity for reservoir water to reach the barrier 
in quantity through the joint system in the rock. The physical conditions were fully satisfied for 
water flowing under high pressure to attack the lower part of the key-trench fill along open joints, 
some of which were found to transmit water freely through the grout curtain, particularly through 
the upper part near the grout cap. The attack was fully capable of quickly developing an erosion 
tunnel breaching the key trench. Arching at local irregularities, loose zones of fill at reentrants, and 
local cracking may have contributed to the success of the attack and determined the precise location. 
Hydraulic fracturing, according to analytical studies, may also have been responsible for the initial 
breaching of the key-trench fill. Conditions were favorable for escape of the water and eroded solids 
into the joints of the rock downstream, for discharging the water against and along the interface of 
the right abutment of the dam and the embankment, and for development of the erosion features 
that ultimately breached the entire dam. 

The precise combination of geologic details, geometry of key trench, variation in compaction, or 
stress conditions in fill and porewater that caused the first breach of the key-trench fill is of course 
unknown and, moreover, is not relevant. The failure was caused not because some unforeseeable fatal 
combination existed, but because (1) the many combinations of unfavorable circumstances inherent 
in the situation were not visualized, and because (2) adequate defenses against these circumstances 
were not included in the design. 



12-18 



APPENDIX A 

USER LIST OF TETON DAM FAILURE EXHIBITS FURNISHED TO INDEPENDENT PANEL 



No, 



As of July H, ly/b 
(Items 1 through 35) 

(Updated to 10/21/76) 



TETON DAM FAILURE EXHIBITS 



Panel Information Packet 

1.1 Brochure on Lower Teton Division, Idaho, dated 1 S^^ 

1.2 Comparison - Specifications vs. Final Quantities (DC-6766) 

Teton Dam, Pilot Grouting (Table) 

1.3 Construction Materials Test Data 
1.^ Design Considerations 

1.5 Drawing of Teton Dam Left Abutment Cut-off Trench, Station t33+20 to 

Station 3'++00, dated 8/17/72 

1.6 Drawing - Teton Dam - Location of Explorations for Borrow Areas "A," 

"B," and "C" 

1.7 Earthwork Construction Data, dated June 1975 

1.8 Earthwork Control Analysis (2 printouts - Zone Number Dam 1, Run No. 1^, 

and Zone Number Dam 3, Run No. 7) 

1.9 Final Environmental Statement (including pertinent letters) 

1.10 Geological Survey letter regarding Teton Dam (Memo from Commissioner Stamm 

transmitting letter dated June II, 1976 from V. E. McKelvey of 
the Survey to Senator Henry M. Jackson) 

1.11 Geological Survey Questions and Answers Regarding Teton Dam (Wire 

message dated June 18, 1976 - Questions and Answers dated June 15, 
1976) 

1.12 Key Events and Key Personnel - Teton Dam, Design and Construction, 

Denver Office, from I/I/69 to present (June 28, I976) 

1.13 L-IO - Final Report on Foundation Pilot Grouting 

l.!** List of Teton Dam Material in Central Files, Library, etc., at 
E&R Center 

1.15 List of Teton Original Drawings on file in PN 700 as of 6/15/76 

1.16 Listing of correspondence and reports on Teton Dam Project on file in the 

Regional Geology Office 

1.17 Listing of Key Personnel - Teton Project Office - 1967 to present 

1.18 Morr i son-Knudsen wire message dated June II, 1976, regarding their part 

in building Teton Dam 

1.19 News Release - Teton Dam Failure - Department of the Interior, dated 

6-9-76 

1.20 News Release - Panel Named to Review Cause of Teton Dam Failure - 

Department of Interior, dated 6-10-76 

1.21 Preliminary Geologic Map of the NW ]/k Driggs 1° by 2 Quadrangle, 

Southeastern Idaho (USGS) 

1.22 Progress Chart - DC-69IO (showing maximum section, with dates of 

construct ion) 

1.23 Records available at Teton Project Office (Faxogram from Project 

Construction Engineer, Newdale, Idaho to Regional Director, Boise) 
1.2'+ Resume of Facts and Findings - Teton Dam, Idaho 



A-1 



TETON DAM FAILURE EXHIBITS - Continued 
No. 

1.25 Seismic monitoring program - Teton Dam and Reservoir (including memo- 

randum from Acting Chief Geologist Robert C, Davis to D. J, Duck, 
d&ted July 20, 1973 and Preliminary Report on Geologic investigations. 
Eastern Snake River Plain and Adjoining Mountains, a draft report 
by Steven S. Oriel, Harold J. Prostka, David Schleicher, and 
Robert J. Hackman, USGS , June 1973) 

1.26 Testimony, Vol H, Vol V, Civil Case No. I-7I-8R, Trout Unlimited et al 

vs. Rogers C.B. Morton et al 

1.27 Water Surface Elevations - March, April, May, and June 1976 

1.28 Wire Message from R, R. Robison to Commissioner of Reclamation, 

Director of Design and Construction, and Regional Director, Boise, 
subject, "Failure of Teton Dam, Teton Project, Idaho," dated 
June 6, 1976 

2. Teton Dam Book 

3. Plans and Specifications Packet 

3.1 Plans and Specifications - DC-69IO - with supplemental notices 

(Four volumes - 10 supplemental notices) 

3.2 Abstract of Bids 

3.3 Record of Subsurface Investigations 

3.^^ Specifications No. DC-6766 - Teton Dam, Pilot Grouting - with one 
supplemental notice 

k. General Plan Sketch 

5. Maximum Section Sketch 

6. Profile Sketch 

7. Prints of slides- Location of Damsite - Construction through Failure 

8. Photographs of Failure 

9. 8mm Film of Dam Failure 

10. 16mm Film of Dam Failure 

11. Record of Filling of Teton Reservoir (2-page memorandum with the following) 

11.1 Memorandum of March 3. 1976 from Project Construction Engineer to 

Director of Design and Construction, subject, "Monitoring Ground 
Water Conditions - Teton Project, Idaho" 

11.2 Memorandum of March 23, 1976 from Director of Design and Construction 

to Project Construction Engineer, subject, "Reservoir Operating 
Criteria - Teton Dam - Teton Basin Project, Idaho," 

11.3 Faxogram from Project Construction Engineer to Director of Design and 

Construction dated May ]k, 1976, subject, "Status of Construction 
of Teton Dam and Filling of Reservoir - Teton Project, Idaho" 



A-2 



TETON DAM FAILURE EXHIBITS - Continued 
No. 

11.^ Daily Records of Reservoir Filling (Same as Exhibit 1.27) 

11.5 Record of observation well from October 1975 to June 1976 (6 sheets) 

12. Geology Handout 

12.1 Introduction 

12.2 Part I 

12.3 Part II 
12. ^4 Index 

12.5 Letter of June 1^, 1976 to Director of Design and Construction from 

Regional Director with attachments, as follows: 

12.5.1 Maps of the reservoir seepage loss study, including 

isopachs, water table contour for 2-2-76 and 6-1-76, 
and cross sections 

12.5.2 "500 series" geologic drill logs DH-501 through -507 

12.5.3 Water level data from observation wells 

12.5.'+ Hydrographs of Teton Reservoir and observation wells 

12.6 Seismicity reports including four sent to the Bureau by U.S. 

Geological Survey in letters dated: 

12.6.1 April 26, 1976 

12.6.2 February 19, 1976 

12.6.3 September 19. 1975 
12.6.'+ September k, 1975 

12.6.5 Memorandum on the geologic and seismic factors of Island Park 
and Jackson Lake Dams dated March 30, 1973 

12.7 Two reports 

12.7.1 "Preliminary Report on Geologic Investigations, Eastern 

Snake River Plain and Adjoining Mountains" by the 
USGS, sent by cover letter dated July 20, 1973 

12.7.2 "Groundwater Investigations of the Rexburg Bench," 

by the Bureau of Reclamation, February 1972 

12.8 Laboratory test data of foundation rock core specimens covered by 

memorandums dated: 

12.8.1 November 2^, 1970 

12.8.2 December 1, 1970 

12.8.3 December 2, 1970 

12.9 Final Construction Geology Report for the Spillway (Draft) 

12.10 Drawings 

12.10.1 Teton Dam - pian View of Fissures Exposed in Haul Road 
Cut - Drawing No. 5't9-100-I76 - July I976 



A-3 



TETON DAM FAILURE EXHIBITS - Continued 
No. 

12.10.2 Profiles of Right Abutment 200 and 250 Feet Upstream 

of Dam Axis, Un-numbered - post June 5, 1976 

12.10.3 Construction Geology of Spillway - Drawings No. S'+S" 

100-12'4 to -132 - December 1975 
12.10.U Generalized Geologic Section A-A' Drawing No. 5^*9-100-152 - 
March 1976 

12.10.5 Geologic Map of Cutoff Trench, Stations 2+60 to 34+20 - 

Drawings No. 5^9-100-158 to -168 - June 1976 

12.10.6 Geologic Section Along Upstream Grout Curtain, 

Stations -5+10 to ^49+00 - Drawings No. 5U9-IOO-I69 to 
-172 - June 1976 

12.10.7 River Outlet Works Tunnel Geology, Stations 7+72.5 to 

28+97.0 - Drawings No. 549-l'+7-100 to -115 - April 1973 

12.10.8 River Outlet Works Tunnel Gate Shaft Geology - Drawings 

No. 549-l'+7-117 to -118 - April 1973 

12.10.9 River Outlet Works Tunnel Gate Chamber Geology - Drawing 

No. 5^+9-1^7-119 - April 1973 

12.10.10 River Outlet Works Tunnel Intake Shaft Geology - Drawing 

No. 5^9-1^7-120 - April 1973 

12.10.11 Geology and Explorations in Right Abutment Keyway Trench - 

Drawing No. 549-I'+7-133 - April 197^+ 

12.10.12 Geologic Sections Across Fissures in Right Abutment Keyway 

Trench - Drawing No. 5^9-1^7-13'+ - April 197^+ 

12.10.13 Auxiliary Outlet Works Geology, Stations 6+63 to 3'++I1.33 - 

Drawings No. 549-l'+7-400 to -419 - October 197^ 

12.10.14 Auxiliary Outlet Works Shaft and Adit Geology - Drawing 

No. 549-147-420 - October 1974 

12.10.15 Auxiliary Outlet Works Access Shaft Geology, el 508O to 

el 5290 - Drawing No. 549-147-121 - October 1974 

12.10.16 Location of Exploration and Surface Geology - Drawings 

No. GEOL-76-020 and -021 - June 1976 

12.10.17 Geologic Section Along Downstream Grout Curtain - Right 

Abutment Drawing No. GEOL-76-022 - June 1976 

13. Prints of Slides (Geology) 

14. Seismicity 

14.1 Epicenters with Modified Mercalli Epicentral Intensity V or Greater 

through 1970 
]k.2 Maximum Epicentral Intensity (Modified Mercalli) per 10,000 sq. km. 

through 1970 

14.3 Horizontal Acceleration in Rock with 10% Probability of Being Exceeded 

In 50 Years (2 sheets, one redrawn from the other) 

14.4 Figure 2. --Location of seismic stations near Teton Dam 

14.5 Figure 6, --Port ion of seismogram showing ground motion induced by flood- 

ing waters 



A-4 



TETON DAM FAILURE EXHIBITS - Continued 



No. 



15. Regional Environmental Geology of Southeastern Idaho, by Steven S. Oriel 

(Unedited remarks prepared for presentation to Review Group June 15, 1976) 

16. Composite Drawing of Grouting Profile (Same as 12.10.6) 

17. Photographs of Key Trenches (Grouting) 

18. Grout Profile of Right Abutment (This is included in Exhibit 32.) 

19. Handouts on Embankment 

19.1 Teton Dam Earthwork Control Data - "Part C - Earthwork Construction 

Data" from L29 Reports - May 1972 to November 1975 

19.2 Teton Dam - Earthwork Information from Weekly Progress Reports - 

June 1973 to December 1975 

19.3 Sequence of Earthfill Placement from L29 Reports - June 1972 to 

October 1975 
19.'+ Maximum Sections and Earthwork Control Statistics of Earth-fill Dams 
Built by the Bureau of Reclamation - June 1973 

19.5 Measurement Points (with observation dates) (seven sheets) 

19.6 Right Abutment Cross-Sections Before and After June 5, I976 - Stations 

100 through ^+00 Upstream of the Dam Axis (seven sheets) 

19.7 Memorandum dated June k, I976 from Project Construction Engineer to 

Director of Design and Construction, subject, "Filling of Teton 
Reservoir, Teton, Project, Idaho, with drawing showing location of 
springs . 

19.8 Teton Flood Data 

19.9 Memorandum dated June k, I976 to Project Construction Engineer from 

Director of Design and Construction, subject, "Status of Construction 
of Teton Dam and Filling of Reservoir - Specifications No. DC-69OO - 
Morr ison-Knudsen-Kiewit , Contractor - Teton Dam, Power and Pumping 
Plant - Teton Basin Project, Idaho" 

20. Photographs of Key Trenches (Embankment) 

21. Letter from R. Keith Higginson, State of Idaho Department of Water Resources, 

to Wallace L. Chadwick, dated June 21, 1976, requesting additional information 
for the Panel 

21.1 Draft of Reply, dated 6/2V76 

21.2 Corrected Reply, dated 7/8/76 

22. Chart - Bureau of Reclamation Organizations at Engineering and Research Center - 

March 1976 

23. Eye Witness Accounts - Interrogatories by Division of Investigation Special Agents, 

Office of Audit and Investigation, Office of the Secretary, on Behalf of the 
Teton Dam Project Review Committee, dated June 25, I976 



A-5 



TETON DAM FAILURE EXHIBITS - Continued 

No. 

23.1 Analysis of Eye Witnesses to Teton Dam Failure, June 5, 1976, 
dated July 2, 1976 plus three more accounts 

2k. Denver Laboratory Test Data entitled "Sample Index Sheets" 

25. Observation Well Maps (Readings through June 20, 1976) 

26. Slurry and Grout Used to Fill Cracks & Fissures in Abutment (Six pages) 

27. Drawings 

27.1 549-D-5 Location Map 

27.2 5^9-D-6 Vicinity Map 

27.3 S^+g-D-S General Plan and Sections 
27. U 5i49-D-9 Embankment Details 

28. Set of Six Grout Summary Sheets - Main Dam - Final Quantities (taken from 

October 25, 1975 L-10 Report) 

29. Preliminary Report on Failure of Teton Dam, by Harold G, Arthur 

30. Pressure Grouting Foundation on Teton Dam, by Peter P. Aberle 

31. Questions and Answers Concerning the Failure of Teton Dam - prepared by the 

Bureau of Reclamation 

32. Foundation Grouting Profile and Plan Drawings - Drawings No. 5^9-1^7-150 

through -195 (with index) 

33. Preconstruct Ion Geologic Report, Teton Damsite, April 1971 

3'+. Photographs of Teton Dam construction and prefailure (from project files) 
35. Volume of material washed away by failure of Teton Dam - dated 6-I8-76 



A-6 



TETON DAM FAILURE EXHIBITS 
(Added Subsequent to July 8, 1976) 

No, 

36. Sequence of Failure Photographs (taken by Gibbons and Reed employee) 

37. Chronology of Failure (from Interim Report of Interior Teton Dam Failure 

Review Group) 

38. Aerial Photographs (Only one set available. Furnished to Mr. Jansen for 

panel use, 7/27/76) 

Teton Dam Earthwork Control Data Book 

Teton Dam Earthwork Control Statistics, Zones 1 and 3 

Map showing Observation Wells located near Teton Dam 

10/21/76 
(Exhibits added subsequent to July 30, 1976) 

Transcript of Hearings before Conservation, Energy, and Natural Resources 
Subcommittee of the Committee on Government Operations, House of 
Representatives, Congress of the United States, August 5, 1976 

Transcript of Hearings before Conservation, Energy, and Natural Resources 
Subcommittee of the Committee on Government Operations, House of 
Representatives, Congress of the United States, August 6, 1976 

Transcript of Hearings before Conservation, Energy, and Natural Resources 
Subcommittee of the Committee on Government Operations, House of 
Representatives, Congress of the United States, August 31, 1976 

Prepared Statement of Robert R. Curry Presented to Conservation, Energy, 
and Natural Resources Subcommittee Hearing, August 5, 1976 

Prepared Statement of Marshall K, Corbett Presented to Conservation, Energy, 
and Natural Resources Subcommittee Hearing, August 5, 1976 

Prepared Statement of H. Anthony Ruckel Presented to Conservation, Energy, 
and Natural Resources Subcommittee Hearing, August 5, 1976 

Prepared Statement of Robert W. James Presented to Conservation, Energy, 
and Natural Resources Subcommittee Hearing, August 5, 1976 

Prepared Statement of R. R. Robison Presented to Conservation, Energy, 
and Natural Resources Subcommittee Hearing, August 6, 1976 

Prepared Statement of H. G. Arthur Presented to Conservation, Energy, and 
Natural Resources Subcommittee Hearing, August 6, 1976 

Prepared Statement of Gilbert G. Stamm Presented to Conservation, Energy, 
and Natural Resources Subcommittee Hearing, August 31. 1976 

7 

A-7 



10/21/76 
TETON DAM FAILURE EXHIBITS - Continued 

Teton Dam Disaster - Thirtieth Report by the Committee on Government 
Operations to the S'+th Congress, Based on a Study Made by its 
Conservation, Energy, and Natural Resources Subcommittee, September 23, 
1976 (House Report No. 9^-1667) 

Summary of Bureau of Reclamation Comments on Testimony Presented to 
Conservation, Energy, and Natural Resources Subcommittee of the 
House Committee on Government Operations 

Seismicity of the Teton Dam Area, June 16, 197^-June 9, 1976, by 

R, Navarro, G. Wuolet, J. West, K. King, and D. Perkins (Open File 
Report 76-555) 

Drawing No. 5^+9-125-268, Geologic Cross Section Along Spillway Site, 
Revised Apri 1 1976 

Transcript of Meeting of Teton Dam Failure Review Group, Idaho Falls, 
Idaho, September 15, 1976 



8 

A-8 



APPENDIX B 

PANEL CORRESPONDENCE 



f-^")^-\" United States Department of tlie Interior 

l.-uJ-.!/} (;i 1 ic:i". n\ iiii", .si:(:i(i,iAii.v 

-■;rj;'-:'/' washincmon, d.c. wno 

TO ^LLZliEi'MiY 
In i^cpl.y Refer To: 
LBR 501/930. /» ,,,,, ,.,,. , ,^_,^ 

lir. Uallace L. Chadv;lck 

Suite 904 FOR SlCKATUilE 

52^3 Went 6th Street 

Los Angeles, California 90014 

Dear Mr. Chadwlck: 

This will confirm discussions with you concerning your appointment 
to a non-Federal pariel for the independent review of the causes of 
the Teton Dam failure. 

Ve are establishing this panel as a joint undertaking with 
Governor Cecil D. Andrus of Idaho. The Governor and I would appre- 
ciate your serving as chairman. The following meabers v/ill serve 
with you: 

Mr. Ralph B. Peck 
1101 Uarra Sands Drive, SE. 
Albuquerque, New Mexico 87123 
tel. 505-293-2484 

Mr. Arthur Casagrande 

Pierce Hall 

Harvard University 

Caicbridgc, Massachusetts 02133 

Home address: 16 Roclanont Road 

Bolriont, Massachusetts 02178 

tel. 617-495-2343 

Mr. Thomas M. Leps 
177 Watkins Avenue 
Atherton, California 94025 
tel. 415-325-9032 

Mr. H. Bolton Scod 

Professor of Civil Engineering 

University of California 

441 Davis Hall 

Berkeley, California 94672 

tel. 415-642-1262 



B-1 



Mr. R. Keith Hig;;lnson 
Director, Ichilio Dcpartr.:!nt 

of Natural Resources 
373 West Frnnklin Street 
Boise, Iclalio 83702 
tel. 208-334-2215 

Mr. E. Montford Fucik 
President nnd Chairman 
Harza Engineering Company 
150 South Wacker Drive 
Chicago, Illinois 606C6 
tel. 312-855-7000 

Mr. Munson U. Dowd 

Chief Engineer 

Metropolitan Water District of 

Southern California 
1111 Sunset Boulevard 
Los Angeles, California 90012 
tel. 213-626-4282 

Your appointaient papers v;ill be forv;£rded se;-'irately . In the r:eantic-.e, 
you may make arrangements to neet with the pare] members and plan your 
review. The Department of the Interi.-ir will finance all expenses 
associated with your independent investigaticr.. Upon completion of you: 
review, the panel should report its findings and recor^:endations 
simultaneously to Governor Andrus and the Secretary. 

Vc Lhank you for undertaking this important public sei-vice. 

Sincerely yours. 



(Sgd) Thon2s S. KIsppe 





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Secretary of the Interior 



cc: Messrs. Peck, Leps, Cas.igrnnde, Seed, Higginson, Fucik, and 
• Dowd 
Governor Cecil D. Andrus 

bcc: 

Secretary's Files 

Secretary's Rendini; Files— I'.FCl.AMATTi^N (2) 

AssiEt.int Si'crotary - LV," 

Under Scrri't;iry 

Regional Director, Uoise, Idniio 

Director of Design and Construction, EiU Center, Denver, ColornJo 



B-2 




Lnitcd Scares Dcparm^ent of die Interior 

OFi-ICE or THE SECRETARY 
WASHINGTON, D.C. 20240 



RE 



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jUii r; 1 



IC 



.W. L. CHADWiC 



JUN 



X X 



^j75 



Dr. Howard A. Coombs 
3856 A6th Avenue, NE. 
Seattle, Washington 98105 

Dear Dr. Coombs: 

This will confirm discussions with you concerning your appointment 
to a non-Federal panel for the independent review of the causes of 
the Teton Dam failure. 

We are establishing this panel as a joint undertaking with 
Governor Cecil D. Andrus of Idaho. The Governor and 1 appreciate 
your willingness to serve. The following are the other panel 
members : 

Mr. Wallace L. Chadwick, Chairman 

Suite 904 

523 West 6th Street 

Los Angeles, California 90014 

tel, 213-623-6954 

Mr. Arthur Casagrande 

Pierce Hall 

Harvard University 

Cambridge, Massachusetts 02138 

Home address: 16 Rockmont Road 

Belmont, Massachusetts 02178 

tel. 617-495-2843 



Mr. Thomas M. Leps 
177 Watkins Avenue 
Atherton, California 
tel. 415-325-9032 



94025 




Mr. H. Bolton Seed 

Professor of Civil Engineering 

University of California 

441 Davis Hall 

Berkeley, California 94672 

tel. 415-642-1262 



'-^^6-191^ 



B-3 



Mr. R. Keith Higginson 
Director, Idaho Department 

of Natural Resources 
373 West Franklin Street 
Boise, Idaho 83702 
tel. 208-38A-2215" 

Mr. E. >iontford Fucik 
President and Chairman 
Harza Engineering Company 
150 South Wacker Drive 
Chicago, Illinois 60606 
tel. 312-855-7000 

Mr. Munson W. Dowd 
Chief Engineer 
^ o Metropolitan VJater District of 
hi^ Southern California 

J'//'^^h-^lll\ Sunset Boulevard 
•P L '^ £i>^W Los Angeles, California 90012 
Vul-'-"'£i^^===^^^— ___ tel. 213-626-4282 

Your appointment papers will be forwarded separately. In the 
meantime, Mr. Chadwick will be in touch with you and the other 
panel members to plgn your review. The Department of the Interior 
will finance all expenses associated with the panel's independent 
investigation. Upon completion of the review, the panel should 
report its findings and recommendations simultaneously to 
Governor Andrus and the Secretary. 

We thank you for undertaking this important public service. 

Sincerely yours. 



(sgdj Tom KleppG 
Secretary of the Interior 



Enclosure 



cc : /Mj 



Mr. Chadwick, Chairman 
Governor Cecil Andrus 

Messrs. Casagrande, Leps, Seed, Higginson, Fucik, and Dowd 
(NOTE: Dr. Coombs' tel. no. is 206-522-9242) 



B-4 



LOS x.WJELES, CALIFORNIA 
JUNE 11, 1976 

MR. HAROLD G. ARTHUR, DIRECTOR 
DESIGN & CONSTRUCTION 
USER, BUILDINo 67 
DENVER FEDERAL CENTER 
DENVER, COLORADO 80225 

UNABLE TO REACH YOU BY TELEPHONE. HAVE BEEN ADVISED BY DON GIAMPOLI 
THAT I^^ULD CONVENE PANEL WHICH HAS BEEN APPOINTED TO REVIEW 
TETON DAM PROBLEM AND THAT YOU WILL BE CONTACT FOR THAT PANEL WITH 
USER. TRYING TO ASSEMBLE ^IROUP FOR WEEK, JUNE 28 AT PLACE AND TIME 
TO BE DETERMINED. SUGGEST THAT PANEL WILL BE GREATLY AIDED BY HAVING 
A DATA BOOK AVAILABLE IF POSSIBLE BEFORE MEETING. THAT BOOK TO 
PRESENT FOLLOWIN'J INFORMATION (1) SITE GEOLOGY IN PLAN AND SECTIONS 
WITH ANY TEST RESULTS ON FOUNDATION MATERIALS (2) SITE EXPLORATION 
WITH DETAII OF DRILL LOGS, EXPLORATION TRENCHES, BORROW MATERIALS 
AND TESTS, (3) GROUT RECORDS IN DETAIL SHOWING NON-AVERAGE TAKES 
BY LOCATION AND DEPTHS, PATTERNS USED AND RECORD OF ANY INTER- 
CONNECTIONS, (4) FOUNDATION PREPARATION SHOWING BEFORE AND AFTER 
CONDITIONS (5) DESIGN MEMORANDA FOR EMBANKMENT, SPILLWAY, DIVERSION 
STRUCTURES AND OUTLETS, (6) BASIC DRAWINGS AND TECHNICAL SPECIFICA- 
TIONS, (7) ANY OUTSIDE REPORT RE SITE OR DESIGNS, (8) CONSTRUCTION 
HISTORY, BORROW PITS, HAULING, PLACEMENT, PROGRESS, INSPECTION, 
IN PLACE TESTS, (9) ANY SEEPAGE MEASUREMENTS OR OBSERVATIONS, (10) 
EYEWITNESS ACCOUNTS, PROGRESS OF FAILURE. 

WILL APPRECIATE YOUR CALL RE THESE SUGGESTIONS, AREA 
CODE 213-623-6954, ADDRESS 904 PACIFIC MUTUAL BUILDING, 523 WEST 
SIXTH STREET, LOS ANGELES, CALIFORNIA 90014. 

W. L. CHADWICK 
B-5 



LOS ANGELES, CALIFORNIA 

JUNE 14, 1976 

HAROLD ARTHUR, DIR. OF DESIGN & CONSTRUCTION 
USER, BUILDING 67 - DENVER. FEDERAL CENTER 
DENVER, COLORADO 80225 

REFERENCE MY TELEGRAM JUNE 11 RE DATA FOR TETON DAM PANEL, PLEASE 

ADD FOLLOWING: 

1. HYDROLOGY 

2. SEISMICITY 

3. DRAIN DESIGNS AND DRAINAGE OBSERVATIONS 

4. ANY CHANGES IN SPILLWQY OR AUXILIARY OUTLET STRUCTURES 

5. ANY CHANGES IN PRECISE LEVEL OR HORIZONTAL CONTROL SURVEY POINTS 

6. CHANGES TOPOGRAPHY UP AND DOWN STREAM 

AT 

7. PHOTOS OF FOUNDATION AS APPROVED -AMJ START OF EMBANKMENT, 

PARTICULARLY IN CUTOFF TRENCH 

8. RECORD OF ANY SEEPS OR SPRINGS IN CUTOFF AND CORE CONTACT AREA 
AND 

9. RECORD COFFERDAM SEEPAGE AND PUMPAGE FROM FOUNDATION AREA. 

THANKS. 

W. L. CHADWICK 

Dictated to me 6/14/76 from Dorval/Montreal Airport 
8:40 A.M. - Called in to W. U. 9:00 A.M. 

COPY TO DONALD A. GIAMPOLI 



>/J.V 



B-6 







STATE OF IDAHO 

DEPARTMENT OF WATER RESOURCES 



Cecil D. AndfUJ 
Governor 

r:. Keith Hi(jginson 
D/reclor 



Statehousc 

Boise, Idaho 83720 

(208) 384-2215 



June 21, 197 6 



OFFICIAL 
FILE COPY 



JIJM 25 i97G 



Mr. Wallace L. Chadwick 
904 Pacific Mutual Building 
523 West Sixth Street 
Los Angeles, CA 90014 

Dear Mr. Chadwick: 



m^ 



ItJFCr'-'.ATiOiJ 
COPY_TO^_ 

RQMTP TO _ ' 

Xoo 



IJIO^^ 








•I I 



__^y-^ 



V~' 



In addition to the information you have requested, I would 
like the Bureau to furnish the panel with the following: 

(1) Operating criteria for outlet works during period 
Oi initial filling. 

(2) Statement of condition and operability of outlet works 
on date of failure. 

(3) History of reservoir filling from date of closure 

of diversion to failure giving reservoir contents, rate of rise 
of water level and water surface elevations. 

I would also like some information concerning the decision- 
making process and authority within the Bureau of Reclamation 
during the construction of a dam such as Teton. 



Very truly yours, 




Director 



RKH/slg/- 

Cr- "Mr. Harold Arthur 



B.7 



United States Department of the Interior 

OFFICE OF THE SECRETARY 
WASHINGTON, D.C. 20240 



Dear Mr. Chadwick: 



JUN 2 31976 



You may already be aware of an Interior Department Teton Dam Failure 
Review Group. In addition to establishing with Governor Andrus 
your independent Blue Ribbon Panel, I felt it was appropriate to 
establish this "in-house" group to determine the cause of failure 
and recommend measures to prevent recurrences of such failures. 

I have appointed Dennis N. Sachs, Deputy Assistant Secretary for 
Land and Water Resources, as Chairman of the Review Group. I have 
drawn other members of the Review Group from the Bureau of Reclamation, 
Geological Survey, Tennessee Valley Authority, Corps of Engineers, 
and the Soil Conservation Service. 

I envision your Blue Ribbon Panel and the Interior Review Group 
conducting their investigations essentially independent of each 
other. Nonetheless, there may be certain matters related to the 
investigations about which the two groups should consult. I have, 
therefore, directed Mr. Sachs to meet with you at your earliest 
convenience to discuss whatever coordination may be appropriate. 

Thank you for your continued cooperation. 




Secretary of the Interior 



Mr. Wallace L. Chadwick 

Suite 904 

523 West 6th Street 

Los Angeles, California 90014 



■rtc «--* 9m» J i' *v»r =^.- 



J - ■ < ' '■ 



CONSERVE 
iAM ERICA'S 
ENERGY 




w. L c^;';CV,.ci^ 



Save Energy and You Serve America! 



B-8 



United States Department of the Interior 

OFFICE OF THE SECRETARY 
WASHIXGTOX, D.C. 20240 




Dear Mr^ Chadwick: 



JUN 3 01976 






This will confirm our discussion of June 23, 1976, concerning the 
charge to the independent panel for its review of the Teton Dam 
failure. 

The panel should determine the cause of the failure of Teton Dam. 
In so doing, the panel should examine, among other matters relative 
to the cause of the failure, the following: 



(1 

(2 

(3 

(4 

(5 

(6 

(7 

(8 

(9 

(10 

(11 

(12 

(13) 



The geology of the site. 

Seismicity of the site. 

Preconstruction investigation. 

Embankment construction materials. 

Embankment designs. 

Embankment construction and construction control. 

Foundation design. 

Foundation construction and construction control. 

Reservoir filling. 

Measures taken to monitor the safety of the dam. 

Reaction of Reclamation personnel to the emergency. 

Status of outlet works construction and ability to pass 

Teton river water. 
Such other matters that the panel may determine appropriate 

to its charge. 



If the facts warrant, the panel should also make findings as appropriate 
with regard to measures that can be taken to avert recurrence of failure. 

The findings of the panel are needed as soon as possible. To that end, 
the entire resources of the Department of the Interior are available 
to the paitiel. Also, the panel will be authorized to secure the services 
of other organizations as may be required to reach its findings. 



.CONSERVE 
^AM ERICA'S 
ENERGY 




Save Energy and You Serve America! 



B-9 



-2- 



The panel is requested to provide me and Governor Andrus with a 
preliminary report by August 1, 1976, and with status reports 
by the first of each month following until the final report is 
made. 

The Governor concurs with the charge and other arrangements 
indicated in this letter. We thank you for undertaking this 
important service. 

Sincerely yours. 





Secretary of the Interior 



Mr. Wallace L. Chadwick 

Suite 904 

523 West Sixth Street 

Los Angeles, California 9001A 



B-10 



July 2, 1976 



Honorable Thomas J. Kleppe, Secretary 
United States Department of the Interior 

Honorable Cecil D. Andrus, Governor 
State of Idaho 

Gentlemen: 

The undersigned non-Federal Panel for Independent Review of the Causes 
of the Teton Dam Failure has proceeded with your charge. In doing so 
it has organized for continuing its investigation, including appoint- 
ment of Mr. Robert B. Jansen as the Panel's Executive Director. Pro- 
cedural details are being developed for implementation. 

The Panel met in Denver for one and one-half days for the purpose of 
obtaining from the Bureau of Reclamation and the United States Geological 
Survey information and data of relevance to the failure. Response was 
free and unrestrained. As a result, the Panel has received a large mass 
of pertinent technical data, information and reports to review and 
analyze. The Panel also spent two days, except for travel time, at 
the dam site. During travel to the site from Idaho Falls the extent 
and nature of the downstream damage were observed. At the site, 
inspections of general, construction, and geological conditions were 
observed during numerous helicopter over-flights. Additional and closer 
inspections were made of the left and right abutments, while walking and 
climbing along them. Inspections were also made from a powered boat. 

A major portion of one day at the site was devoted to examination of 
data and photographs and obtaining personal statements concerning many 
construction details, including the manner in which the key and cutoff 
trenches were treated prior to placement of overlying embankment. 

Only tentative hypotheses of causes of failure can be considered at this 
time, because of the need to study all of the various factors which may 
support each particular hypothesis or negate it. At this time, however, 
it seems apparent that the failure resulted from piping. This is a 
process by which embankment material is eroded internally and transported 
by water flowing through some channel. Piping may be initiated by several 
detailed causes and, unfortunately, most of the direct evidence appears 
to have been destroyed by the violence of the failure itself. The Panel 
is planning to examine all obtainable evidence in detail and has prepared 
a program of field explorations to pinpoint, if possible, which of the 
following potential causes is responsible: 



B-11 



1. Massive seepage through the grout curtain, impinging forcibly 
against the contact between the downstream part of the dam 
and the rock abutment . 

2. Piping through the core at the core-to-rock contact at the 
right abutment . 

3. Piping through the core at levels above the base of the 
keyway core-to-rock contact. 

4. Piping through a transverse tension crack in the core in 
the right abutment area. 

5. Massive seepage around the end of the grout curtain, directed 
by the foundation joint system against the contact between 
the downstream part of the dam and the rock abutment. 

The Panel will continue its investigation independently, and in accord 
with the best professional practice. This necessarily requires weighing 
of many data and many factors by full analysis and free exchanges within 
the Panel. Your need for an early preliminary report is understood. 
The Panel will meet again during the week of August 2 to review the 
data, observations and information developed in the interim, anticipating 
a preliminary report to you early in August. 

Included in the Panel's on-going inquiry will be a public fact-finding 
meeting in Idaho Falls prior to its next session, soliciting any 
relevant information as to the cause of the Teton Dam failure. 

It is intended to establish a temporary office of the Panel in Idaho 
Falls at an early date. 

The Panel is presenting today to the Director, Design 5 Construction of 
the Bureau of Reclamation, a list of exploratory work which will be 
necessary for its additional information. In doing so the Panel wishes 
to release the Bureau of Reclamation from any further restraint on all 
site-changing physical work which the Bureau considers necessary to 
reduce hazards to safety. 

The support you have given to the Panel is greatly appreciated, as also 
is the excellent cooperation of all members of the United States Bureau 
of Reclamation and Geological Survey of whom the Panel has inquired. 

Respectfully submitted. 



Wallace L. Chadwick, Chairman 
Independent Panel for Review of 
Teton Dam Failure 



8-1 : 



July 2, 1976 



Mr. Harold G. Arthur 

Director of Design and Construction 

Bureau of Reclamation 

Denver Federal Center 

Denver, Colorado 80225 

Re: Teton Dam Investigation 

Dear Mr. Arthur: 

The following activities represent the Panel's highest priority and are 
recommended for immediate implementation. It should be recognized that 
additional activities will be proposed in the coming months. 

1. The remnant of the right -abutment keyway fill to the left of 
the spillway should be excavated to permit inspection of conditions below 
Elevation 5301. Down to Elevation 5301 the remnant can be removed in any 
manner that will not disturb the material below. Below Elevation 5301 
the remnant can be removed in any stages and by any means, provided that 
a width of undisturbed material remains with a minimum horizontal thick- 
ness of five feet on each side and a minimum vertical distance of ten 
feet above the bottom of the original trench. The material within the 
five-foot envelope on each side should be removed by hand, where directed 
by the Panel's representative, as required to permit appropriate sampling 
to allow description of conditions of soil, rock, and any joint treatment 
disclosed by the excavation, to allow observation of any indications of 
piping or other defects . The bottom ten feet should be removed in two 
lifts. These lifts should be preceded by excavating trenches at places 
selected by the representative of the Panel to a depth of five feet 

with appropriate sampling and observation. 

2. Any debris remaining on the face of the central part of the 
abutment, especially where the grout cap remains intact, should be care- 
fully cleaned to permit detailed inspection. 

3. The area of the lower spring (50 cfs.) should be exposed. Any 
original material still in place should be left undisturbed. The details 
of jointing of the rock in this area should be carefully examined. 

4. All steps necessary to assure safety at the remaining left 
section of the dam can be carried out promptly. 

5. In order to provide some quantitative evaluation of permeability 
in the rocks in the right abutment, detailed studies should be made on 
enlarged photographs of representative areas of each joint type near the 
keyway. 



B-13 



Total footage of open joints per unit of area (e.g., one square 
yard) should be determined by direct measurements on enlargements of the 
photos, using a reliable scale with which a grid system is drawn on the 
enlargement. 

The details of this survey, including best lighting (either 
direct sun during the forenoon or on a cloudy day) should be developed 
in a pilot program. 

6. An item of prime importance is the nature of the joint system 

in the right abutment on either side of the keyway. Particularly important 
is the identification of major, throughgoing joints on the downstream 
side of the keyway that might provide access of water to the embankment. 

Primary and secondary joint systems should be plotted on a new topographic 
map. Symbols may be used to indicate wide and continuous joints in con- 
trast to the numerous, smaller joints. Any evidence of springs or water- 
courses along or through the joints should be indicated on the joint map. 

7. On the basis of the evidence presented to it by the U.S. 
Geological Survey, the Panel does not consider that the failure was 
in any way related to seismic activity in the vicinity of the site. 
There is no record of significant seismic activity at the site either 
on the day of the failure or in the year preceeding the failure. No 
additional investigations of seismicity, other than those currently in 
progress by the U.S.G.S., are recommended. 

Sincerely yours. 



Wallace L. Chadwick, Chairman 
Independent Panel for Review of 
Teton Dam Failure 



B-14 




IN REPLY „„„ 
REFER TO: 222 

510. 



United States Department of the Interior 

BUREAU OF RECLAMATION 

OFFICE OF DESIGN AND CONSTRUCTION 

ENGINEERING AND RESEARCH CENTER 

P.O. BOX 25007 

BUILDING 57. DENVER FEDERAL CENTER 

DENVER, COLORADO 80225 



Memorandum 



JUL 



8 1976 



To: 



Mr. Wallace L. Chadwlck, Chairman, Independent Panel for 
Review of Teton Dam Failure 



From: Director of Design and Construction 

Subject: USER Reply to R. Keith Hlgglnson Letter 

A further review of our correspondence reveals that an error was made 
In response to Question No. 2 of Mr. Hlgglnson's June 21, 1976 request 
to Mr. Wallace L. Chadwlck for further Information on Teton Dam. 

The Initial response to Question No. 2 had Indicated that the electrical 
power was not available for operating the river outlet works gates; 
however, power was available for operating the gates on and following 
May 17, 1976. 

it was not possible to immediately operate the river outlet works gates 
on June 5, 1976, due to the contractor's sandblasting and painting 
operations for the downstream liner of the river outlet works. 



•— ^ I ^^ 








B-15 



jUL'^^^i^'" 



WALLACE L. CHADWICK 

90< PACIFIC MUTUAL BUILDING 

SaS WEST SIXTH STREET 

LOS ANGELES, CALIFORN lA 9 O O I 4 



July 24, 1976 



Mr. Harold G. Arthur, Director of Design and 
Construction, United States Bureau of Reclamation 
Building 67, Denver Federal Center 
Denver, Colorado 80225 

Dear Mr. Arthur: 

Reference is made to Secretary Kleppe's letter 
of June 30, 1976 supplementing his and Governor Andrus ' 
original charge to the Independent Panel to Review the 
Cause of Teton Dam Failure, particularly to items 9, 
10 and 12. 

It will be a great help to the Panel if you can 
furnish the following additional information, or if pre- 
viously supplied, give references to facilitate ready find- 
ing: 

1. Were 1976 runoff forecasts made during March, April, 
and May, for use in estimating the Teton reservoir 
filling rate, and comparing the expected rate with 
the actual. 

2. Was an operating rule curve developed for use in pro- 
gramming reservoir filling and releases, particularly 
any releases required to control filling rate. 

3. What schedule was used for progressing erection of the 
river outlet gates and controls, the auxiliary outlet 
gates and controls, and the spillway gates and controls 
On what dates were such facilities completed and ready 
for use. Copies of any original schedules and pro- 
gressive changes will be appreciated. 



B-16 



Mr. Harolo o, Arthur 
July 24, 1976 
Page 2 



4. When was each gate hoist commissioned? 

5. When and how frequently were walkover surveillance 
inspections made as the reservoir filled. Copies of 
daily logs or diary entries of each surveillance in- 
spection will be appreciated. In the absence of logs 
or other records, a written statement of the inspector 
or inspectors will be helpful. 

Thank you for your cooperation. 



Very truly yours, 




WLC:ecs 



cc : Panel Members 
R. B. Jans en 



y 



B-17 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 

Wallace L Chadwick. Chairman 

Arthur Casagrande 

Howard A. Coombs 

Munson W. Dowd 

E Montford Fucik 

R, Keith Higginson 

Thomas M. Lcps 

Ralph B Peck 

H Bolton Seed 

Robert B Jansen, Executive Director 

August 5, 1976 

Honorable Thomas S. Kleppe, Secretary 
United States Department of the Interior 
Interior Building 
Washington, D.C. 20240 



Honorable Cecil D. Andrus, Governor 
State of Idaho 
Capitol Building 
Boise, Idaho 83720 



Gentlemen: 

The Independent Panel to Review Cause of Teton Dam Failure has continued 
its work under your charge. The Panel conducted technical working sessions 
in Idaho Falls August 3 through 5, 1976, with all members present. Included 
in these sessions was a visit to the damsite on August 3, 1976, to review the 
progress which has been made to date in the exploration being performed on 
the right abutment by the Bureau of Reclamation for observation by the staff 
of the Panel. 

The following is a report of the progress which has been made by the 
Panel since its report to you dated July 2, 1976. 

Organization 

A small but capable staff has been assembled, based both at the site 
and in Idaho Falls, under the direction of Mr. Robert B. Jansen. The coopera- 
tion of Governor Andrus, and of Governor Brown of California in making 
Mr. Jansen available for this important responsibility, is much appreciated. 
Mr. Clifford J. Cortright has been actively at work as staff engineer since 
July 3. Likewise, Laurence B. James is at work as staff geologist. The entire 
staff has unique experience and expertise with which to serve the Panel. 

Through the assistance of Secretary Kleppe and the Bonneville Power 
Administration, a secretary-office manager and two technicians have been 
provided for temporary aid to the Panel. In addition, Mr. Higginson has 



B-18 



Page 2 August 5, 1976 

provided a geologist from his staff to assist the Panel. All this assis- 
tance, as well as the support and help received from numerous people in the 
Secretary's office, is much appreciated by each member of the Panel. Also, 
the Panel appreciates the full cooperation it has received from the Bureau 
of Reclamation. 

Public Meeting 

On July 21, 1976, the public was invited to bring into either of two 
public meetings, conducted in Idaho Falls, information regarding pertinent 
first-hand observations prior to the failure of the dam on June 5, 1976. 
Response was somewhat disappointing because only four individuals testified. 
A transcript was taken. 

Site Work 

On July 16, 1976, the Bureau of Reclamation awarded Contract No. DC-7232 
to Gibbons S Reed to carry out, among other things, work requested by the 
Panel in its letter of July 2, 1976 to Mr. H. G. Arthur. Work under that 
contract was started at the site on July 23. On August 3, at the time of 
the Panel's visit, the right remnant of Teton Dam had been removed to about 
Elevation 5301 and the first exploratory trenches had been cut, permitting 
the first in-situ observations. Initial progress has been good. Work was 
also in progress directed toward uncovering the downstream portal of the 
auxiliary outlet tunnel. The proposed detailed mapping of right abutment 
bedrock joint systems has progressed well. 

Accomplishments of the Panel 

Since its last meeting, the Panel members have reviewed the extensive 
documentation received from various sources and the Bureau of Reclamation. 
A fine chronological photographic record has been compiled showing the 
progressive development of seepage on June 5. Unfortunately, to this date, 
no photographs are available of the early development of this seepage. 
Search will be continued for such photographs. 

A chronological statement has been compiled of the sequence of observa- 
tions by various individuals during the period from June 3 to late in the 
day of June 5, 1976. 

Following a detailed discussion of the five hypotheses which were 
enumerated in the Panel's report to you dated July 2, 1976, the Panel 
developed a schedule for specific laboratory and field tests and for analyses 
which will be of assistance in reaching conclusions. A copy of that schedule 
is attached. 



B-19 



Page 3 August 5, 1976 

A preliminary finite element analysis has been made, for the Panel, to 
indicate possible stress conditions across the embankment at Station 14+00. 
The results of this analysis were used as a basis for planning the further 
analyses included in the attached schedule. 

Hydrographic studies have been made through the offices of Mr. Higginson 
seeking to relate (1) the 1976 runoff expectancy to historic flows, (2) the 
Teton Dam project's expected rate of reservoir filling, and (3) the actual 
rate of filling. Such studies will be continued and related to historic 
reservoir operation. 

The Panel has scheduled its next technical working session for October 4, 
5, and 6 in Idaho Falls. 

The Panel appreciates your continuing interest and support. 

Very truly yours. 



Chairman 
End . 



B-20 



SCHEDULE FOR LABORATORY AND FIELD TESTS AND ANALYSIS 
APPENDED TO PANEL REPORT OF AUGUST 5, 1976 



A. Purpose 

In its report of July 2, 1976, the Panel listed five potential causes 
of the piping failure of Teton Dam, and on the same date, in a letter to 
the Director, Design and Construction of the Bureau of Reclamation, listed 
items of highest priority recommended for action by the Bureau to provide 
data for choosing among the potential causes. In its deliberations during 
its meeting of August 3-5, the Panel concluded that the field evidence 
virtually excludes massive seepage around the end of the grout curtain as 
a likely cause. Accordingly, the following detailed program was developed 
to aid in discriminating among the other four hypothetical causes, namely 
whether the massive seepage or piping took place (1) through the grout 
curtain, (2) through the core at the core-to-rock contact, (3) through the 
core above the base of the keyway core-to-rock contact, or (4) through a 
crack in the core. The program is in part a particularization of the work 
recommended on July 2, and in part a supplement to that work. 

B. Investigation of Bottom of Key Trench and Grout Curtain 

The purpose of the program is twofold: first, to determine if any 
cracks encountered in the rock in the bottom of the key trench, either up- 
or downstream, are open enough to permit flows of water through them; and 
second, to test the watertightness of the grout curtain under the grout 
cap and under the spillway. The section of the key trench to be tested 
extends from Station 12+50 to 14+50. 

To test the water-carrying characteristics of cracks in the bottom 
of the key trench, it is proposed to pond water over selected cracks and 
observe the drop in the level of ponds. Each pond can be formed by placing 
a dike of stiff mortar on the low side of the crack, high enough to produce 
a depth of water of about 6 inches over the crack. Visual observation of 
the loss of water will permit a rough idea of whether the crack is 
relatively open or tight. At open cracks, an approximate measurement 
should be made of the outflow per linear foot of crack per minute. It is 
suggested that the wider cracks be tested first, and then the narrower 
ones . 

Tests should be made both upstream and downstream of the grout cap. 
It is envisioned that between 10 and 20 representative cracks should be 
tested in the proposed section. The cracks tested should be distributed 
throughout the length of the section. If most of the cracks leak sub- 
stantially, additional tests might be made to verify the conclusion that 
most cracks would transmit water easily. 



B-21 



To test the watertightness of the grout curtain, it is proposed to 
drill through the grout cap and the spillway crest into the rock below, 
and to water-test these holes. The holes should preferably be of AX size 
and cores should be obtained from each hole to permit observation of any 
grout that may fill cracks in the rock. The holes through the grout cap 
should be drilled to a depth of 10 feet below the bottom of the grout cap, 
water tested, drilled 10 feet more and tested again. If pressure is used, 
it should not exceed 10 psi at the collar. The rate of flow in each stage 
of the hole should be recorded. If the second stage of any hole shows 
large leakage, a third 10-foot stage should be drilled and tested. 

It is suggested that tests be carried out on the centerline of the 
grout curtain approximately at Stations 12+65, 13+05, and 13+40. At 
each station, three holes should be drilled, one vertical, one inclined 
22-1/2° from the vertical toward the abutment, and one inclined 45° into 
the abutment. At each location, three holes should be drilled, in each 
stage, before starting the water testing. 

It is also suggested that holes be drilled at about the center of 
each of the three spillway bays. Three holes should be drilled at each 
location, one vertical, one at an angle of 30° toward the river, and one 
at an angle of 30° away from the river. The holes through the spillway 
crest should be drilled and water-tested in three stages of 25 feet each, 
so that the grout curtain will be tested to the depth of the adjacent key 
trenches. 

If large water takes are observed at any location, additional holes 
should be drilled on each side to determine the extent of the open zone. 

C. Investigation of Key-Trench Fill 

As the key trench fill on the right abutment is excavated in accordance 
with the Panel's recommendation of July 2, detailed studies should be made 
of the variations in the degree of compaction of the fill material by 
penetration tests, and samples should be taken for investigation of erosion 
resistance, stress-strain characteristics, and such other purposes as may 
become desirable as the investigation proceeds. The specific studies are 
as follows: 

1 . Field Investigations and Routine Laboratory Tests 

a. Observations and Sampling in Trenches 

Immediately upon completion of excavation of an approximately 30-foot 
long section of exploratory trench, the following observations and sampling 
should be performed: 



B-22 



With a shovel or spade, make a fresh exposure by removing a vertical 
slice at least one inch thick, at locations spaced approximately 7 to 8 
feet. In this fresh exposure make a rapid survey of variations in consis- 
tency along a vertical line, using a screwdriver or other convenient hand 
tool; also examine variations in types of materials; then perform penetra- 
tion tests with the Proctor Needle on several representative layers, to 
define the entire range of strengths, with special attention to the 
weakest layers or lenses. For the penetration tests on the weakest 
materials, it will probably be necessary to use the largest diameter "point". 
Prepare a log of all observations and penetration tests, including thickness 
of representative layers. 

To facilitate recording the logs, it will be desirable to develop a 
simple classification system which should be based on the BR test data of 
the Zone 1 fill and on initial experience in surveying the trenches. 

b. Sampling 

(1) Hand-cut block samples . Samples, usually about 8 inches 
square and about 12 inches high, should be taken of representative materials, 
but with particular emphasis on the weakest materials. Usually three such 
samples should be taken at each location, side by side, of material that 

is essentially similar. 

Each sample should be wrapped in Saran wrap, or similar plastic film, 
and then covered with at least a 1/4-inch thick layer of microcrystalline 
wax by dipping several times into the wax melted to the correct temperature. 
(Do not overheat the wax, which would change its properties.) Use a grade 
of wax as used in soils laboratories for such purposes. Then place a clearly 
written identifying label on one side of the sample and again wrap in one 
layer of plastic film, taking care to place the film smoothly over the label 
to ensure that it can be read easily. 

(2) A Bag Sample should be taken at each location where block 
samples are taken and placed in a plastic bag which is closed tight. 
Usually about 10 lb. will be sufficient. 

(3) Storage of Samples should be in a shed with appropriate 
shelves to provide space for samples taken from an estimated 100 locations 
and equipped with a humidifier (to maintain humidity at greater than 80% 
relative humidity) and heated in winter to a temperature above 40°F. 

c. Observation of Features That May be Related to Potential or 
Actual Piping . 

Special attention must be paid to careful observation of fissures, 
holes, and any signs indicating that the originally placed fill was dis- 
turbed. Such features should be identified, sketched, described and 
photographed. Particular care should be exercised in identifying such 



B-23 



features immediately adjacent to the downstream rock face and the bottom 
of the key trench. If such features are discovered, it will be necessary 
to proceed with the greatest of caution in further excavation to protect 
vital evidence of erosion. At such junctures, the field staff will have 
to make ad hoc decisions how to proceed. Mr. Jansen should be notified 
immediately. When particularly meaningful discoveries are made, Mr. Jansen 
will confer by telephone with available geotechnical panel members. 

d. Laboratory Tests 

Preferably in a field laboratory, the following tests should be per- 
formed on representative samples: 

(1) Natural water content. 

(2) Grain size analyses. 

(3) Liquid and plastic limit tests. (Report actual test 
results; not the computed plasticity index in lieu of the measured plastic 
limit.) 

(4) Unconfined compression tests. 

e. Miscellaneous Comments 

The depth of the exploratory trenches should not exceed 6 feet to 
facilitate operations. 

During removal of fill immediately adjacent to the rock slopes of 
the key trench, all loose rock should be removed to ensure safety of the 
men who will work later at lower levels. 

2 . Evaluation of Erosion Potential of Zone 1 Material 

In view of the fact that the failure of Teton Dam has already been 
attributed to internal erosion of the Zone 1 material, it is important to 
establish the vulnerability to erosion of this particular material in 
comparison with that of other soils customarily used as core materials. 
This is particularly true since visual inspection and classification-test 
data of Zone 1 materials would appear to indicate that these soils would 
be highly susceptible to erosion. 

To establish the erosion potential of this soil, it is recommended 
that selected samples be sent to two laboratories for independent evalua- 
tions as follows: 

a. A series of 10 samples should be sent to the Waterways 
Experiment Station at Vicksburg, Mississippi, for performance of the 
pinhole test as now standardized by that laboratory. Grain-size distribu- 
tion curves and liquid and plastic limit values should be determined for 



B-24 



each of the test samples and the results used to establish the relative 
erodibility of Teton Dam Zone 1 materials. 

b. A series of 10 samples should be sent to a second laboratory 
specializing in measuring the erosion potential of soils (e.g., the Soil 
Mechanics Laboratory of the University of California at Davis) where the 
erodibility can be evaluated and compared with data for other soils by 
means of two or more appropriate types of tests. As before, grain-size 
distribution curves and liquid and plastic limit values should be determined 
for each test sample. 

In all cases, the erosion tests should be performed on the undisturbed 
block samples cut from the right abutment key trench. The selected samples 
should be representative of the range of materials and densities found in 
the trench, with particular emphasis on materials that appear to be most 
erodible, as established in the field survey. To the extent practicable, 
the two independent laboratories should be sent similar suites of samples. 

3 . Determination of Stress-Strain Characteristics for Use in Finite- 
Element Analyses 

To determine the possibility of hydraulic fracturing or of crack forma- 
tion in the Zone 1 material, it is desirable to evaluate the stress distri- 
bution within Zone 1. This can best be achieved by finite-element analyses 
incorporating realistic representations of the stress-strain characteristics 
of the compacted loessial soil used to fill the key trenches and to form 
the main core of the embankment . 

The stress-strain properties should be determined by several series 
of drained triaxial compression tests on representative samples cut from 
the Zone 1 section of the dam. At least 3 series of tests should be performed, 
each series including one test at each of four confining pressures, approxi- 
mately 15, 40, 70, and 100 psi. Samples should be 1.4 inches in diameter 
and approximately 3-1/2 inches high and should not be saturated before 
testing. Stress-strain relationships should be recorded up to the point of 
failure. 

At least one series of the drained tests should be conducted by stress- 
control techniques to investigate the creep characteristics under loads 
sustained for several days. 

An additional two series of tests should be performed on samples tested 
as discussed above, but with the specimens saturated prior to testing. 

Representative grain-size distribution curves and liquid and plastic 
limit values should be determined for the samples in each series. 



B-25 



D. Embankment Stress Analysis 

It is requested that additional finite element stress analyses be 
made of the embankment fill. This work would constitute an expansion of 
a pilot analysis submitted to the Panel on August 3, and would incorporate 
the following specific requirements: 

1. Three cross sections of the original right abutment embankment 
between Stations 12 and 15, and one axial section of the right abutment 
embankment (Stations 12+00 to 20+00) should be analyzed. The three 
transverse stations utilized, and the details of analytical formulation, 
are to be selected after review of the shape of detailed as-built cross 
sections. 

2. The displayed results should include vertical stress, minor 
principal stress and strain. 

3. The stresses should be those developed by layered construction, 
as opposed to the "gravity-turn-on" option. 

4. In addition, stresses should be calculated to reflect the effect 
on the embankment of a reservoir rise to Elevation 5300. 

5. Two complete sets of stresses should be computed for each section: 

a. One adopting a core stiffness factor K of 470, as measured 
by the USBR on a composite, reconstituted triaxial sample under rapid 
shearing; and 

b. One utilizing a K of 200, a value judged to be a probable lower 
limit for the Zone 1 fill. 

The foregoing finite element analyses should be undertaken at once, 
under the guidance of Mr. Leps and Dr. Seed, with a target delivery date 
of perhaps October 15. Concurrently, a suite of triaxial shear tests 
on representative samples should go forward, as covered in the previous 
section, to provide appropriate verification of the K-parameter range 
assumed in requirement 5 . above . 

E. Modifications in Program 

Field conditions may require modification of some of the details of 
the recommended program. Moreover, as the findings accumulate, the 
results may suggest changes, additions, or deletions. The field staff 
is encouraged to make changes that appear appropriate and to inform the 
Panel promptly. If major changes seem desirable, the staff should 
communicate with the Panel. 



B-26 



UNITED STATES DEPARTMENT OF THE INTERIOR J.TATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



August 18, 1976 



Wallace L. Chadwick, Chairman 

Arthur Casagrande 

Howard A. Coombs 

Munson W. Dowd 

E. Monllord Fucik 

R Keith Higginson 

Thomas M. Leps 

Ralph B Peck 

H Bollon Seed 

Robert B. Jansen. Executive Director 



Mr. H. G. Arthur, Director 
Design and Constiniction 
U.S. Bureau of Reclamation 
Building 67, Denver Federal Center 
Denver, Colorado 80225 



Mr. William H. McMurren 

President & Chief Executive Officer 

Korrison-Knudsen Co., Inc. 

P. 0. Box 7808 

Boise, Idaho 83729 



Gentlemen; 

Reference is made to this Panel's charge from the Secretary of the 
Interior and the Governor of Idaho to revie"!? the cause of Teton Dam failure. 
It vdLll be of important assistance to the Panel in this review if the 
construction techniques used, particularly on the right abutment, are as 
thoroughly understood as may be possible in the absence of personal obser- 
vations. As an aid to such an understanding, the following questions have 
been prepared. Your full and candid answers to these questions will be 
a significant aid to the work of the Panel aaid will be much appreciated. 

Please describe: 

a. The manner in which axial grout distribut5.on and closure were 
assured when the up and downstream grout travel was relatively unlimited. 
Details of any doubts over the effectiveness of this axial distribution in 
any particular location along the three grout curtains between Station ]&!-00 
and Station 2+00 will be helpful. Likt\7ise, details of difficulties in 
obtaining assurance of axial closure at any stations or grout holes along 
this same stretch of curtain will be helpful. 

b. The manner in which the key trench between Station 18+00 
and Station 2+00 was prepared to receive the first embankment material. 
Compare the way in which this trench was prepared with "broom clean". If 
there were differences in clean-up between particular stations, because 

of weather, or any other cause, please describe s-ach differences in detail. 



B-27 



Pc^ije 2 Aui^-ust 1&, 1976 

Letter to MeoRro. H. G. Arthur and William H. McMurren 



c. The ii)Oiiner In v.hich any fiGsurcs or open jo-Jjita in the key- 
trench wjills an.i floor were scaled between Station 18+00 and Station ?fOO; 
that is, the maxxnor in which, and the places •••.here, aluch grouting, dental 
concrete, gunite, or shotcrete may have bec-n used, also the extent to 
v.hich rrTJch sealing was general, V/ere any joints left unsealed rmd, if so, 
where? If J-inov.Ti, please indicate the perti.cular stations, if any. 

d. The method of material selection, preparation, placement 
and ccir.paction, in the key trench, of the "specially compacted earthfill" 
S5hcvr-n in the cross section Biarked "Foundation Key Trench" on USER Dravdng 
r..^9_T)_g, If special difficulties were encountered in eelectJon, preparation, 
plncejiient or coitpaeticn at any points along the length from Station ISfOO 

to Station 2+00, pleaoe describe each, 

e. The method of rcatorial selection, preparation, plaeea-Cnt, and 
ccGpaction in the key trench between Stat?, on 3 8+00 and Station 2+00 of the 
core raaterial. If special difficulties wore encountered in oelection, 
preparatic-n, placement or co;3paction at any points along the length from 
Station IS+CO to St^ition 2+00, ple:ise cieBcribe each. 

f. The r.ianner in which the contact area under the cere of the 

dan: outside of the key trench was prepared to receive the firet core inater-ial. 
If special difficulties were encountered at any location along the length 
of dia between Station 13+00 and Station 2+00, please dobcidbe, 

g. The maiinor in \fhic-h core :a?itei"ial was solceteid, prepared, 
placed, and cocipsjctcd outside of the key tre^-jcb, betv-'een Station 18+00 

end Station 2+00, If Bpecial difficulties v^ere encountered, please de:jcribe 
in detail by specific location. 

h, SiEllarltlGS and significant differences in the appearance of 
the walls and floor of the key trenches in the right end left nbutaerits. 

The infcnuation Eju^ht thix^ugh this questionnaire is of special 
inpoi-tance to the PcriSl in its reviev/ and ecirly receipt of your rncrvvers 
v.'ill be much appreciated. However, it is realized that the ta.?k of prepara- 
tion is a large one. For tMs reason, if it v.ould be advantageous to you 
find perttsit earliei* answer, the task rriay be biiDken into tr.vo phsse-s, with 
priority given to Phase I covering the length of fciindation from Station 
15+00 to the spiir.vay centerline, and Phase II covering from Station 18+00 
to Station 16+00 and from the spillway centoi^llne to Station 2+00. Pax-tial 
replies are encouraged, that is ti-anemittals for individual questions v/ill 
be helpful. 



B-28 



Page 3 

Letter to Messrs. H. G, Arthur and Williaa H. I.TcMiurren 



Auguet ]a, 1976 



Please accept our appreciation in advance for your cooperatjon in 
supplying this important Eaipplenenting infoixnation. 

Very truly yours, 




B.29 



UNITED STATES DEPARTMENT OF THE INTERIOR — STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 

Wallace L Chadwick, Chairman 

Arthur Casagrande 

Howard A Coombs 

Munson W Dowd 

E Montford Fucik 

R. Keith Higginson 

Thomas M Leps 

Ralph B Peck 

H Bolton Seed 

Robert B Jansen, Executive Director 

August 20, 1976 
MEMO TO R. B. Jansen: 



I have completed review of the Inspector Daily Reports with special 
attention to foundation preparation and embankment placement at the right 
abutment during the 1975 season, which is the period of interest to us. 
I have attached highlighted copies of those Inspector Daily Reports which 
bear some information that is helpful to us. Steven Johnson's reports are 
most informative. R. Jones' are not bad; but Doug Janic's and Jerry Smith's 
only recite equipment employed and are of no value for our purpose. 

The Special Inspection Report file covers special subjects, almost 
90% of which are the Hobbs Riprap Quarry, a few reports on the powerhouse, 
and the record of the abutment dental concrete. We checked the record, as 
given in the Special Inspection Report, against the summary that we had 
previously shown on the drawing that we presented to the Panel at their 
last meeting. The record agrees with the summary. 

In summary, from review of these reports, I find no glaring violations 
of the specifications, but I don't consider them a real reliable source of 
information of that type. The photographic record, of course, is much 
better and speaks for itself. 



Clifford J. Cortright (/ 
Staff Engineer 



Ends , 



B-30 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Wallace L Chadwick. Chairman 

Arthur Casagrande 

Howard A Coombs 

Munson W, Dowd 

E. Monllord Fucik 

R Keith Higginson 

Thomas M Leps 

Ralph B Peck 

H Bolton Seed 

Robert B. Janscn. Executive Director 



August 2A, 19 76 



Mr. Robert R. Robison 

Project Construction Engineer 

Teton Project Office 

P.O. Box 88 

Newdale, Idaho 83436 



Dear Mr. Robison: 



On August 19, 1976, representatives of the Teton Dam Failure Review 
Group, the Teton Project Office, and the United States Department of the 
Interior - State of Idaho Independent Panel to Review Cause of Teton Dam 
Failure met in the Idaho Falls office of the Panel to discuss coordination 
of their activities. 

With regard to the Schedule for Laboratory and Field Tests and Analyses 
appended to the Panel Report of August 5, 19 76, several modifications and 
clarifications were made and mutually accepted. 

The drilling and water testing of the grout curtain will be performed 
by crews and equipment from the Boise Regional Office of the USER. The 
holes, water testing, and core will be logged by the Regional geologists 
and also independently by the Panel's on-site representatives. 

The holes will be of NX size. 

The depths of the final stages of both the vertical and inclined holes 
in the three spillway bays will be sufficient to penetrate the rock beyond 
the 80-foot depth of the foundation consolidation grouting beneath the 
spillway control structure. 

Soils samples to be later identified for testing by Northern Testing 
Laboratories will be delivered with special handling by Bureau personnel 
to Billings, Montana. Samples to be tested by the Earth Sciences Branch 



B-31 



Page 2 August 24, 1976 

Letter to Mr. Robert R. Robison 

and samples to be stored will be delivered under special handling by 
Bureau personnel to Denver, Colorado. Space will be made available in 
advance in the humidity room there to receive and store the samples. 

The Teton Project Office Laboratory will perform the following tests: 

(1) Natural Water Content 

(2) Grain Size Malyses 

(3) Liquid and Plastic Limit Tests 

The Earth Sciences Branch will perform unconfined compression tests 
and drained triaxial compression tests. Detailed special instructions for 
these tests will be supplied by Panel representatives later. 

Panel representatives will arrange for shipment of samples to be 
tested at the Corps of Engineers' Waterways Experiment Station, Vicksburg, 
Mississippi, and the University of California at Davis, California. 
Purchase Orders for testing at those laboratories other than those of the 
USBR have been arranged by Department of the Interior purchasing agents. 
Samples for testing will be selected and detailed instructions for testing 
will be issued to those laboratories by Panel representatives. 

Sincerely, 



Robert B. Jansen 
Executive Director 



cc: 

Dennis Sachs 
Sara D. Guy 



B-32 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 

Wallace L Chadwick, Chairman 

Arthur Casagrande 

Howard A Coombs 

Munson W Dowd 

E. Montford Fucik 

R. Ketth Higginson 

Thomas M- Leps 

Ralph B Peck 

H Bolton Seed 

Robert B Jansen, Executive Director 

September 8, 1976 



TO: Robert B. Jansen 

SUBJECT: Review of Report, "Right Abutment Excavation," Teton Basin 
Project, by Teton Project Office, Newdale, Idaho, 
November, 1975 

I have reviewed subject report available at the Project Office. 

The report was prepared in analyzing the contractor's claim for 
contract adjustment arising from alleged delays caused by the Government 
not giving timely direction for the removal of rock overhangs during the 
stripping of the right abutment. 

1 find nothing in the text which affords a clue to the cause of 
failure. The timing and manner of overhang removal performed within 
the Zone 1 foundation area in no way appears related to the failure. 

Two photos, P549-147-2557NA, 10/10/72, and P549-147-2974NA, 8/8/73, 
do show a bench or profile irregularity in the keyway invert excavation 
estimated to be near Station 12+70 and Elevation 5220 which may have 
had some influence on the failure. 



J (U Clifford ^J. Cortright 



B-33 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Wallace L. Chadwick, Chairman 

Arthur Casagrande 

Howard A. Coombs 

Munson W Dowd 

E. Montford Fucik 

R. Keith Higginson 

Thomas M Leps 

Ralph B Peck 

H Bolton Seed 

Robert B Jansen, Executive Director 



October 6, 1976 



Honorable Thomas S. Kleppe, Secretary 
United States Department of the Interior 
Interior Building 
Washington, D.C. 20240 



Honorable Cecil D. Andrus, Governor 
State of Idaho 
Capitol Building 
Boise, Idaho 83720 



Gentlemen: 

The Independent Panel to Review Cause of Teton Dam Failure has con- 
tinued its work under your charge. The Panel conducted technical working 
sessions in Idaho Falls on October 4 through 6, 1976, with all members 
attending. On October 4, inspections were made of investigative excava- 
tions at the damsite and of the auxiliary outlet works, which has been 
dewatered recently. 

The following is a report on progress by the Panel since its report 
to you of August 5, 1976. 

Organization 

Through the cooperation of the National Park Service, two technicians 
have been assigned to the Panel for temporary assistance in preparation 
of illustrations for the Panel's report. Also, a draftsman will be pro- 
vided by the Bureau of Indian Affairs on October 12. 

Site Work 

Satisfactory progress is being made on work requested by the Panel's 
letter of July 2, 1976 to Mr. H. G. Arthur, under USBR Contract No. DC- 
7232 with Gibbons and Reed Co. At the time of the Panel's inspection of 
the damsite on October 4, 1976, the general level of excavation, by five 
foot stages, of the embankment remnant on the right abutment was at 



B-34 



Page 2 October 6, 1976 

Letter to Honorable Thomas S. Kleppe and Honorable Cecil D. Andrus 

Elevation 5210 and inspection trenches had been excavated at each stage 
to Elevation 5205. Trenches are being surveyed, logged, and photographed. 
Penetration tests are being made and soil samples are being taken for 
laboratory testing. A total of 92 nine-inch cube samples have been taken, 
distributed throughout the length and depth of the excavation. Arrange- 
ments have been made for specific tests at the Northern Testing Laboratory 
in Billings, the University of California at Davis, the Waterways Experiment 
Station of the Corps of Engineers in Vicksburg, and the USER laboratories 
at Teton Dam and Denver. All of this work is pursuant to the schedule 
appended to the Panel's report of August 5, 1976. Shipments of soil 
specimens from the dam were made to the Billings and Denver laboratories 
during the week of September 13 and to the Davis and Vicksburg laboratories 
during the week of September 27. 

The Panel received for its consideration during the technical work 
sessions of October 4-6 the results of two finite element analyses of 
transverse sections of the embankment conducted by Dynamic Analysis Corpora- 
tion. These are being studied by the Panel. Copies of these analytical 
results have been supplied to the Interior panel for its use. Two other 
analyses are in progress. 

As exploratory excavation on the right abutment has progressed to 
lower elevations in recent weeks, signs of distress have appeared in the 
dam embankment in the form of cracks and general distortion. This evidence 
is being carefully studied by the Panel in an attempt to ascertain whether 
it relates to the cause of failure, or is a post-failure condition resulting 
from collapse of the adjoining dam mass. 

Quite satisfactory progress has been made in the channel excavation 
to lower the river. This work had advanced so that the Panel was able to 
enter the dewatered auxiliary outlet works tunnel on October 4. Inspection 
was made of the full length of the facility and it was found to be in 
sound condition, with no visible evidence of distress that could be related 
to the failure of the dam. 

Drilling into the foundation of the spillway was begun by the USSR 
early in September. Nine holes have now been completed. Water pressure 
testing so far has indicated the grouted rock under this structure to be 
reasonably impermeable, within generally accepted standards. 

Drilling is underway into the foundation in the vicinity of fissures 
near Dam Station 4+00, described in the USER construction reports. This 
is in addition to drilling described in the schedule of August 5, 1976. 
One of the drill holes at that location, which has now progressed to a 
depth of about 300 feet, will extend into deep underlying sediments where 
samples can be taken for compression testing. The Panel also will have 
tests made on core samples taken from these sediments during the Bureau's 
preconstruction drilling. 



B-35 



Page 3 October 6, 1976 

Letter to Honorable Thomas S. Kleppe and Honorable Cecil D. Andrus 

The Panel continues its review and analysis of data and the drafting 
of material intended for use in the final report. 

In addition to participation in the technical working sessions of 
the Panel, individual members have periodically consulted with the staff 
in the Idaho Falls office and have made inspections of work at the damsite, 

Arrangements have been made for construction of a model of the dam 
to facilitate visualization of various features that are regarded as 
pertinent in analysis of the failure. 

The Panel appreciates the attention given by the office of the 
Secretary of the Interior to finalizing its definitive contract. 

The continuing support which you and your staffs have extended to 
the Panel is deeply appreciated, as is the cooperative response of the 
Bureau of Reclamation to the Panel's requests. 

The next technical working sessions of the Panel are scheduled for 
November 1-3, 1976, in Idaho Falls. 

Respectfully submitted. 



Wallace L. Chadwick, Chairman 
Independent Panel to Review Cause 
of Teton Dam Failure 



B-36 




CONTRACTORS 

ENGINEERS 

DEVELOPERS 



O MORRISON-KNUDSEN COMPANY. INC. 



EXECUTIVE OFFICE 

ONE MORRISON-KNUDSEN PLAZA / PO 60X7808 / BOISE. IDAHO 83729 /USA 

TELEX: 368439 

PHONE: (208) 345-5000 



E. M. Armstrong 

EXECUTIVE VICE PRESIDENT 



October 7, 1976 



Mr. Wallace L. Chadwick 

United States Department of the Interior 

State of Idaho BECEIVED 

Independent Panel to Review Cause of 

Teton Dam Failure ^'■■'> ' ■' " •':.'• 

539 9th Street ^ . ,,.,. 

Idaho Falls, Idaho 83401 >V. L Cn.%u.^;v;W 

Re: Teton Dam 

Dear Mr. Chadwick: 

In its letter of August 18, 1976, the Panel has asked certain 
questions with regard to construction techniques used in the 
construction of Teton Dam with special attention to the right 
abutment. The Contractor, a joint venture composed of 
Morrison-Knudsen Company, Inc. and Peter Kiewit Sons' Co., 
hereby submits the following answers to those questions: 

a) The best information available to the Contractor with 
regard to this question is that contained in a letter 
submitted to the Contractor by its grouting subcontractor, 
McCabe Bros. Drilling, Inc., dated August 25, 1976 and 
appended hereto as an attachment. 

b) The key trench between 2+00 and 18 + 00 was prepared 
by using air and water. The cleanup was more extensive 
between Station 3+00 and 4+35 due to open joints and 
fissures. 

c) All fissures or open joints were backfilled with dental 
concrete or slush grout at the direction of the Bureau of 
Reclamation. To the knowledge of the Contractor, no 
joints were left unsealed. 



B-37 



MORfilSON-KNUDSEN COMPANY. INC. 

Letter to Mr. Wallace L. Chadwick, dated October 7, 1976 
Page two 



d) This material came out of the borrow area designated 
by the Bureau of Reclamation. In general, material of 
higher plasticity and optimum moisture was selected from 
the pit. Preparation of the material was by pre-irrigation. 
Placement was accomplished in 3" lifts and compacted by 
using air operated tampers and plate tampers and wheel 
rolling with heavy equipment. To the Contractor's knowledge, 
there were no difficulties encountered in any of these areas. 

e) Material selection was accomplished by the same method 
described in d) , above. The pit was prepared in the follow- 
ing manner: A cut depth was determined by topographic notes 
to establish the desired drainage pattern. The pit was then 
divided into material blocks. Three-inch holes were then 
augered to the depth of cut required on a 200 foot grid and 
proctor optimum moistures were determined for drill cuttings 
and noted for the respective section of the pit. Moisture 
was added to the pit by sprinkling the required amount of 
water for the design cut on the area at least 3 weeks prior 
to excavation. Constant monitoring was possible by utilizing 
a Speedy Moisture Teller. Placement and compaction were in 
accordance with Bureau of Reclamation specifications. 

f) This area was blown clean with air and water. The rock was 
badly fractured and cleanup was a little more difficult 

on the right abutment than it was on the left abutment. 
There were areas on the right abutment which required the 
treatment described in c) above 

g) This material was handled as described in d) and e) above. 

h) The rock on the right abutment was more fractured than that 
on the left abutment and there were more fissures in the 
key trench in the right abutment than in the left abutment 
key trench. 

Very truly yours, 

MORRISON-KNUDSEN-KIEWIT 
A Joi«-trT?fentur 

E. M. Armstrong 
EMA: jl 



B-38 




'i'^i^^ch fei. 



C 1 



.N «i 



I'M ■«- 



DIAMOND CORE DRILLING 
PRESSURE GROUTING 



ROTARY DBILLII. G 

FOUNDATION TESTING 



BOX 1892. IDAHO 



FALLS. 
PHONE 



IDAHO 83401 
5 2 2 • 5 < 3 7 



August 25, 1976 



Morrison-Knudsen Company, Inc. 
P. 0. Box 127 
Newdale, Idaho 83436 




A-G Z\ 1376 



Co.nlfecf No. 25 P4 



Attention: Mr. Duane E. Buckert 



Dear Sir: 



Re: Letter from 'Independent Panel to Review 
Cause of Teton Dam Failure' to Morrison 
Knudsen Co., Inc. for information on 
Construction Techniques. 



Referring to Question: 



The Manner in wliich Axial grout Distribution 
and Closures were assured when the up and 
dovmstream grout travel was relatively 
iinlimited. 



There were three grout lines; a downstream, a center and a up- 
stream. The dovmstream grout line was fi-om Station 2 + 20 to l6 + 00, 
the upstream grout line v.as from Station 2 + 28 to 1$ + 94 and the 
center grout line was from Station 2 + 23 to Station 18 + 00 and on. 
Most of the grout p.ipples were 2" diameter. The Area holes were 
Located over fairly large cracks and the nipples were set to inter- 
cept the cracks at different depths, some being set vertically over 
cracks with cencrete poured around them. The dov.nstream boles were 
vertical with 20 ft, centers. The upstream holes v.sre at a 30 ajigle 
A-d-th 20 ft. centers, except one vertical at Station 5 + 28 and one 
fan hole at 2 + 28 37 • The center line holes were at a 30 angle 
with 10 ft. centers. 

There were no closure holes on the downstream line. There are 
three fan holes at Station 2+20; one at 15 , one at 30 ,and one 
at 45 . The upstream line has the follo',-ri.ng closui-es: 3 holes on 
5'centers, 6 holes on 6' centers, 1 hole on 7' center, 2 holes on 
9' centers, 1 hole on 10' center, 3 holes on 11' centers, 2 holes on 
12' centers and 2 holes on 13' centers. As directed by the contract- 
ing officer, the holes from Station 9 + 22 to 10 + 00 in the upstream 
line were deleted. 



B-39 



'j^h^^r^h /§/^o^ 



DIAMOND CORE DRILLING ROTARY DRILLING 

PRESSURE GROUTING FOUNDATION TESTIS G 



Page 2 



BOX 1892. IDAHO FALLS. IDAHO 83401 

PHONE S2E.5137 



The primary holes were staggered from each other on the three 
grout lines. The Area holes that were set close to cracks were 
grouted first. We drilled the holes until we lost 50^ or more of our 
drill water. Then commenced grouting at the bottom stage of the hole, 
Kost of the area holes were intermittently grouted if the take was 
500 cu. ft., with a waiting period of three hours. Eventually that 
stage of the hole wo\ild come up to the desired pressure required by 
the inspector. At that time vje set the packer up to the next stage 
and progressed out of the hole through the different stages and 
finished grouting by hooking the nipple and grouting to the speci- 
fied pressure. If the above hole v;as required to go deeper, we then 
drilled to the specified depth or \intil we had a water loss of 50^ 
or more and then set the pacxer at the directed settings and grouted 
the different stages at required pressures until we staged up to the 
previous stage grouted, therby completing the entire hole. 
Closures were added to area holes. 

There are primary holes every 80 ft., secondary holes every 80 
ft. and closui'e holes every i+Oft. on the dov.nstream and upstream 
grout lines. The priiTiary holes v;ere drilled and grouted first, the 
secondary holes were drilled and grouted second and the closure holes 
were drilled and grouted last as directed. All grouting of holes vjas 
accomplished in the same manner described above for the Area holes. 

The centerline holes have a primary every 80 ft., a secondary 
every 80 ft. and an intermediate hole every AO ft. with closure holes 
every 20 ft. The primary holes were drilled and grouted first, the 
secondary holes were drilled and grouted second, the intermediate holes 
were drilled and grouted third and the closure holes were drilled and 
grouted last as directed. Of course the centerline has a more complex 
pattern than the dov.Tistream and upstream grout lines and is designed to 
serve as a closure line for the downstream and upstream grout lines, 
with many closure holes being added. 

Good packer settings were accomplished with the very minimum of 
difficulty. 

A large percent of the holes where the water loss vras negligible, 
v.-e were able to drill to the complete depth of the hole, in this case 
we grouted from the bottom stage up, until the hole was completely 
grouted. 

about 98 or 9^ of the stages in all holes were water tested, with 
the exception of the top 20 ft. in many, holes. The migration of water 
from the water tests and the grout travel into other drilled holes was 
very minimal. All holes were completely backfilled with grout after all 
stages v.'ere co.-.pleted. All grout leaks to surface areas were calked 
irmediately and continously lontil leakage stopped. 

Referring to Question: Details of any doubts over the effectiveness of 

this Axial distribution in any particiilar- location 
along the three grout cm^tains between Station 
18 +00 and Station 2 + 00. 
B40 



'//M'M'/hvf'i 



'SO 



Page 3 



DIAf/OND CORE DRILLING - — F.OTARY DRILLl 

FRCSSURE GROUTING FOUrJDATION TcrTi 

BOX 1692. IDAHO FALLS. IDAHO 83401 

PHONE E.22.5<37 



The only doubt that we have been concerned vdth was the high 
percent of Calcium Chloride being used. The highest percent used 
as directed by the inspectors was 10^ for a short time, later this 
was lowered to 8^. 

As an example, if the hole was 100 ft. deep and we were grouting 
with about 3% or more Calcium Chloride, intermittently grouting the 
bottom stage and finally the bottom stage came up to pressure, then 
we stage grouted the hole up to the surface. At this time we were 
directed to deepen the hole to 130 ft. We then drilled the hole down 
to 90 ft. and had a total water loss. Then we set the packer above the 
water loss in the bottom stage of the hole and started grouting until 
the stage came up to pressure; sometimes this stage reqviired intermittent 
grouting. This condition has happened many times when using Calcium 
Chloride. The question we have asked ourselves about the above problem 
is: Is this same condition happening in the grouting of large or small 
cracks and fissures, causing a honey-comb effect? Thereby causing many 
more closure holes to be drilled and grouted on the centerline than other- 
wise would be necessary. 

Referring to Question: Details of difficulties in obtaining assur- 
ance of Axial closure at any station or grout 
hole along the same stretch of curtain. 

V/e had no difficulty in grouting up to the desired pressure in all 
stages of all closm^e holes. If one closure hole took more than the 
minimum amount of grout in any one stage, we were then ordered to drill 
and grout additional closui^e holes. 

Referring to Question: Similarities and significant differences 

in appearance of the walls and floor of the 
Key trench in the right and left abutments. 

The left abutment had a few caverns in the vjalls, the floor of the 
key trench appeared to be good solid rock. Directly up the grout line on 
the right abutment, 75 to 125 ft. above the tower on the steepest slop, 
we had some grout leaks around some large boulders. As we were calking 
these leaks, nu-.nerous bats were flying ou-t of the cracks that we were 
attempting to calk. 

The right abutment from about Station 13 + 00 to Station 11+50 
appeared to be very badly fractured with small cracks in the walls and 
the floor of the trench. From Station 11 + 50 to 10 +00 it appeared to 
be good solid rock. From Station 10 + 00 to 7 + 50 it appeared to be 
good solid rock on the walls and floor of the key trench, with some 
small vi sable fissm-es. From 7 + 50 to 2 + 00 the walls and floor 
appeared to be of good sound rock ivith a very little small fractirring 
with the exception of nuinerous large faults visable in the walls aiid 
floor of the key trench. 



B41 






■yM^^?^-;//^ 3^it<i 



'j^j 



►'-' 1 



DIAMOND CORE DRILLING 
PRLSSURE GROUTING 



ROTARY DRILLING 

FOUNDATION TESTING 



BOX 1892 



IDAHO 



FALLS. IDAHO 83401 
PHONE 522-5437 

Page 4 

The lake bed sediments that underlay the riolite formation along 
the extreme length and width of the dam at depth were drilled and 
grouted to the desired pressiires for a short distance on the outer end 
of the left abutment. 

All work described above was completed as directed by the 
contracting officer, The Bureau of Reclair.ation. 



Very truly yours, 



McCAEE BROS. DRILLING, INC. 



Edwin L. McCabe 
President 



i_ 



EL.M:RJN 



B-42 




IN REPLY 
REFER TO 



510. 



210 



United States Department of the Interior 

BUREAU OF RECLAMATION 

OFFICE OF DESIGN AND CONSTRUCTION 

ENGINEERING AND RESEARCH CENTER 

P.O. BOX 25007 ' ' ' 

BUILDING 67, DENVER FEDERAL CENTER 

DENVER, COLORADO 80225 JC) 



! i O 



OCT 19 1976 

Mr. Wallace L. Chadwick 
Chairman, Independent Panel to 

Review Cause of Teton Dam Failure 
Post Office Box 1643 
Idaho Falls, [D 83^01 

Dear Mr. Chadwick: 

Draft answers to the questions regarding the Teton Dam failure 
posed to Mr. McMurren of Morr i son-Knudsen Company and to me in 
your letter of August 18, 1976 were handed to you on October k. 
We are enclosing our final responses to these questions which 
we ask that you use instead. 

The material you received earlier was subsequently reviewed in 
this office by our grouting expert, Mr. Lloyd R. Gebhart, and 
others. Certain portions were discussed with project personnel, 
several minor changes were made in the text, and the photographic 
references were corrected. 

We understand that the Morr i son-Knudsen Company is giving you their 
answers to these questions in a separate transmittal. The answers 
we have given are, therefore, attributable only to Bureau of 
Reclamation project and Denver Office records and observations. 
We believe they accurately describe the situation at the damsite 
as it existed during construction and the construction techniques 
used. 



Sincerely yours, 



j/0 



Arthur 




H. G 

Di rector 

Design and Construction 



Enclosures 



^o\'^"r'0/v Copy to: 




'-^?6-l9T^ 



Morr i son-Knudsen Company, Inc. 
Post Office Box 7808 
Boise, Idaho 83729 
Attention: Mr. W. K. Smith 
(with copy of enclosures) 



B43 



Please describe : 

A. The manner in which axial grout distribution and closure were 
assured v;hen the up and downstream grout travel was relatively 
unlimited. Details of any doubts over the effectiveness of this 
axial distribution in any particular location along the three grout 
curtains between Station 18+00 and Station 2+00 will be helpful . 
Likewise, details of difficulties in obtaining assurance of axial 
closure at any stations or grout holes along this same stretch of 
curtain will be helpful . 

GROUTING REQUIREMENTS 

(A) Grouting requirements between Station 2+00 and Station 18+00 consisted 
of a triple curtain between Station 2+00 and 16+00 and a single curtain 
between 16+00 and 18+00. Blanket holes were located in areas where 
joints and fissures were exposed in the curtain area and also a blanket 
grouting program was performed under the spillway weir section. The 
minimum depth requirements for the curtain holes were 260-60-160-60-260 
feet for 80-foot patterns on the centerline curtain on 10-foot centers. 
In the spillway area, the maximum depths were increased to 310 feet. 

Specifications drawings required that both the upstream curtain and 
downstream curtain be drilled on 20-foot centers with no provisions for 
spaced closure. However, these curtains were split spaced and closed to 
depth. Specifications drawings also required that both the upstream and 
downstream curtain consist of vertical holes. After excavation of the 
key trenches was completed, it was determined that angle holes on one 
of the two outer curtains would readily intercept more joints and, 
therefore, the upstream curtain holes were drilled on angles 30 degrees 
from vertical. Specifications required AX (1-7/8- inch) diameter size holes 
be drilled and that holes be down staged if water losses larger than 
50 percent occurred. When partial water losses occurred, the percentage 
amount was determined by the onsite inspector and grouting of these 
partial water loss stages consisting of 50 percent or larger was strictly 
adhered to. 

In the vicinity of the spillway section, an exception was made in regard 
to the centerline curtain insofar that between Station 10+00 and Station 
11+37, the centerline curtain was eliminated and incorporated with the 
upstream curtain. This was done because the alinement of the centerline 
curtain was in the same alinement as the AOW gate chamber shaft and 
because a positive curtain was better protection for the shaft when 
located upstream of the shaft. This was accomplished for <two reasons. 
First , double coverage could be given to the adit and shaft by enveloping 
the curtain between the shaft and the reservoir, and secondly , curtain 
holes could be extended to their full design depth rather than having to 
be shortened to prevent intersection with the shaft and adit concrete. 
Curtain holes enveloping the AOW tunnel had to be shortened to prevent 
intersecting the tunnel concrete . H(jwever, radial holes from within the 
tunnel in the curtain area were deepened to overlap the curtain holes by 
30 feet . 



B-44 



GROUTING ORGANIZATION 

U.S. Bureau o f Reclamation 

The grouting organization for the Bureau of Reclamation consisted of 
one Supervisory Civil Engineer and primarily, three Construction 
Inspectors. The Supervisor had approximately 12 years of inspection 
and supervisory experience in the field of grouting. Three primary 
Construction Inspectors had grouting experience varying from 2 to 5 
years prior to arriving on Teton Dam. 

Each of the three primary inspectors was responsible for one shift on a 
three-shift basis and supervised additional inspectors when grouting 
operations were separated and additional inspectors were required. When 
grouting operations were separated, the primarj' inspector was able to 
contact subordinate inspectors through the contractor's communications 
system to discuss any problems. 

Contractor (McCabe Brothers Dril ling Company) 

The contractor usually had a work force which varied from 18 to 27 men. 
The Company is owned by three brothers and each brother was a shift 
foreman. A mechanic was on duty on day shift to make necessary repairs. 
Other workmen consisted of pump operators and drillers. 

CONTROL OF GROUTING OPERATIONS 

Order of Grouting 

When the contractor determined the area that he wanted to grout in, 
grout holes on the upstream and downstream curtain were located by Bureau 
inspectors. These locations were previously determined from profile 
drawings from which the proper spacings were determined. Blanket holes 
were located in the field to fit the rock foundation conditions except 
those required beneath the spillway weir which were located on a pattern 
basis. Location of grout holes for the centerline curtain was also 
determined from a profile drawing prepared prior to concrete placement in 
the grout cap. Pipe nipples v;ere embedded in the concrete as the concrete 
was placed. Angles for the pipe were accurately determined with a 
machinist's protractor and the pipe nipples were set above the concrete- 
rock contact at all times so that this contact would be drilled and 
grouted if a bond did not occur. 

When grouting was initiated within a specific area, the blanket holes were 
drilled and grouted prior to any grouting performance or curtain holes . 
The contractor usually worked in an area 400 to 500 feet long. Therefore, 
Initial curtain grouting consisted of drilling on five to six pattern 
holes. As drilling and grouting progressed on the original pattern holes 
to depth, it was sometimes necessary to initiate drilling and grouting on 



B-45 



intermediate and final closure holes simultaneously to facilitate the 
contractor's operations. However, a lag of 40 feet in vertical distance 
was always adhered to with respect to adjacent related holes. 

The upstream curtain was grouted in similar fashion to the downstream 
curtain; however, no holes were drilled on the upstream curtain until 
those patterns on the downstream curtain in vicinity of the holes on the 
upstream curtain to be drilled were completed. 

Grouting on the centerline curtain was initiated after all other grouting 
in the vicinity was completed. As previously mentioned, the centerline 
curtain was grouted on 10-foot centers with the 10-foot center holes 
split to 5-foot centers or less if a grout take of 20 cubic feet or more 
per stage occurred. This criterion was adhered to, with two exceptions. 
At Station 10+25 stage 0-20 feet, a grout take of 28 cubic feet was not 
split as most of the grout injected leaked to the surface within a few 
feet of the holes. Also, a grout take of 1,003 cubic feet at Station 
11+37 stage 220 to 245 was only split on one side. However, this take 
is near the gate chamber adit, and the area was super-saturated with 
grout holes from within the adit and access shaft. 

Five-foot-closure holes were drilled and grouted at Stations 11+09, 8+19, 
6+34, 6+46, 6+22, and 15+28 to check areas of doubt . However, these holes 
were not required as the adjacent 10-f oot-closure holes previously grouted 
were tight . 

DAILY DIRECTION DY THE BUREAU SUPERVISION 

As grouting was initiated in each area, a drilling and grouting instruction 
sheet was made by the Bureau supervisor. On this sheet were listed holes 
that were available for drilling and grouting by the contractor as 
determined by the Bureau supervisor. This sheet was made on a daily basis 
and was updated taking into consideration the work that had been previ- 
ously completed, and the work that was expected to be completed during 
that particular day. Special instructions and safety notes were also 
added to tliese sheets from time to time. On rare occasions, it would be 
necessary for the field inspector to make additions to the sheet if field 
operations made it necessary. This daily sheet v;as made for the purpose 
of keeping unity by having a single organized program within the Bureau 
inspection forces and it was also available to the contractor so he could 
plan his operations accordingly. Examples of these sheets are attached 
at the suggestion of Cliff Cortright, Panel Representative. 



B-46 



LOG BOOK KEPT BY INSPECTORS 

From the plan and profile drawings kept in the Bureau Office, log books 
were made which contained a profile of grout holes as located in the 
field. In these log books, the onsite grouting inspector kept a running 
record of all dril7-ing and grouting that was performed. The log books 
were passed from inspector to inspector (shift to shift) . This record 
contained the history of each hole and was available to the inspector at 
all times at the pump site for the purposes of back-checking for related 
grout takes, water losses, water test information, surface leaks, and 
performance dates of adjacent holes. Copies of pages from several log 
books are attached to show the types of information contained. 

DAILY WRITTEN REPORTS 

In addition to the log books, each field inspector was required to write 
a daily report which gave a brief description of the holes drilled and 
grouted as to location, depth, water tests, grout takes, equipment 
problems, conversations with the contractor's representative, and 
instructions to the contractor. Also, a drill sheet was made for each 
hole drilled and a grout sheet for each hole grouted . The drill sheet 
was passed on from shift to shift until that particular hole was completed 
or the hole was stopped for grouting at which time it was turned in to 
the Bureau supervisor at the end of the graveyard shift. The drill sheet 
contained drilling information such as rock hardness, color oi v/ater 
return, time of drilling, and water losses. The grout sheet was also 
passed on from shift to shift until that particular hole was completed or 
the hole was ready to be redrilled to a deeper depth at which time it 
was turned in to the Bureau supervisor at the end of the graveyard shift. 
The grouting sheet gives a complete history of a grout hole. This 
history may be very complex; however, all information relating to the 
hole is recorded in -ninute detail in relation to time. The grout sheet 
primarily contains information relating to water tests, packer settings, 
initial grout mixes, final grout mixes, pressures, surface leaks, amount 
of grout take per hour, total grout take, holding pressures, back pres- 
sures, suction, etc. A copy of a drill and a grout report (see attached 
examples) are appended to the daily written report. 

After the daily reports in conjunction with the drill and grout reports 
were turned over to the Bureau supervisor by the field inspector at 
8:30 a.m. each morning, they were reviewed and checked for accuracy. 
The results from the drill and grout reports were then immediately 
plotted on a plan and profile drawing. These results were plotted each 
day on the same drawing and thoroughly studied by the supgrvisor to 
correlate grout takes from hole to hole and curtain to curtain. 

Profile drawings from each curtain were usually overlain for a positive 
checl: so that no gaps in the overall curtain area would occur. From 
each days' information as it was plotted, depth of holes could l)e changed 
and additional holes added as required. The daily drilling and grouting 



B-47 



instruction sheet discussed above was determined from the plan and 
profile drawing. 

RECORDS BY THE CONTRACTOR 

The records made by McCabe Brothers Drilling Company are extensive and 
were kept diligently by the employees of the contractor. Drill logs were 
made by each driller of each hole drilled on each shift. Grout pump 
operators kept a running record of all grout injected which contained 
the time, number of batches, cubic feet per batch, and the grout mix. 
A record of all water tests was also made which stated the hole number 
stage and amount of take . 

Drillers recorded drill bit serial numbers used each shift with corres- 
ponding drilling depths. 

A profile of each curtain in the vicinity of the work area was kept 
current daily and given to each foreman . This profile was reviewed 
with the inspector and correlated with the Bureau Daily Drilling and 
Grouting Sheet. A time log on each grout pump was kept by pump operators. 

GROUT MIXES, CAJ.CIUM CHLORIDE, SAND, PRESSURES, WATER TESTS 

Grout mixes were designed to fulfill the scope of the specifications 
and design criteria. It was desirous that grout travel be limited to 
within 100 feet of the curtain area and that the upstream and downstream 
curtains be constructed as barrier curtains for the centerline curtain 
which was the final closure curtain. \\Tien large grout takes on the 
upstream and downstream curtain were encountered, grout mixes were 
readily thickened . Calcium chloride was used to increase hydration and 
decrease the initial set time and was rarely used when a hole was being 
pumped under pressure . 

When a hole was relatively wide open and the grout mix used was an 0.8:1 
W-C ratio (by volume), the hole would accept grout at the rate of 250 cubic 
feet of cement per hour (maximum pump rate) and the pressure on the hole 
gage would be zero and the hole would have extreme suction. This 
indicated tliat the grout was traveling away from the hole area and, in 
order to restrict travel, the hole was pumped intermittently (500 cubic 
feet with delays ranging from 3-8 hours) by using calcium chloride. When 
pressures began to register on the hole gage during a pumping sequence, 
the calcium chloride was discontinued and pumping would then usually 
continue to refusal . Precautions were taken to prevent slugging a hole 
prematurely . 

Sand was used when evidence showed that a large void had been encountered 
and that the sanded mix would be readily accepted. For instance, the 
blanket holes in the spillway area accepted large amounts of grout; however, 



B-48 



sand was used in onlj' one liole as no large voids were encountered 
during drilling ol these holes. Although other holes accepted grout 
quite readily, no voids of consequence were detected by the drillers 
when water losses occurred and, therefore, a sanded grout mix was not 
used in this area. 

Calcium chloride was added to accelerate hydration of the grout mix 
and control travel within the curtain area. Laboratory and field experi- 
ments were perform.ed to determine the optimum amount of calcium chloride 
to be used to achieve setting after the grout reached the area to be 
grouted. Numei'ous variables, such as mix water temperature, sand tem- 
perature, cement temperature, air temperature, rate of take of the hole, 
and distance of hole from the mix plant, affected the set-up time and 
the injection time . A hole that was wide open would usually accept 
grout at the rate of 250 cubic feet of sand and cement or cement per 
hour. The lapsed time between mixing and injecting the grout at this 
rate varied between 6 and 8 minutes. An initial set-time of 12 to 16 
minutes was therefore desirable, so that the grout could adequately reach 
its destination before prematurely setting. 

Due to these temperature variances of the grout ingredients, it was 
impossible to develop a usable criteria to accurately predetermine amount 
of calcium chloride required to attain the desired set time. A more 
feasible set of criteria was used based on grout temperatures at the 
grout pump. From 2 to 3 percent by weight of cement of calcium chloride 
was added when the mix water temperature ranged between 75 and 80 degrees 
F. and up to 6^ percent of calcium chloride was required when the mix 
water temperature was in the 35 to 40 degrees F. range. Eight percent 
calcium chloride was used for a short interval when near freezing water 
was used by the contractor, however, set times were uncontrollable and 
the percentage was ultimately lowered . Grout would reach the critical 
temperature of 90 degrees F. when using the warmer mix water and near 
70 degrees F. when using the colder mix water. Grout temperatures were 
monitored constantly at the pump by the pump operator and the inspector 
so that the propei' amount of calcium chloride required could be constantly 
adjusted . Water was added to the grout mix at the pump on rare occasions 
when tlie grout began its initial sot in the tub before it could be 
injected. It was of utmost importance that, when calcium chloride was 
being used in a grout mix, the temperature of the grout mix be kept as 
high as possible without prematurely setting in the tub before it could 
be injected. Adding lesser amounts of calcium chloride only prolonged 
the sot time and increased grout travel distances which was undesirable 
in holes which were determined to be wide open. The use of calcium 
chloride on the centerline curtain holes was very limited. 

Pressures used during grouting and water testing consisted of 10 jjsi. at 
the hole collar and were increased by 0.75 psi per foot of depth of the 
packer setting normal to the rock surface at the hole collar. Pumping 
pressures wore kept at the design pressure at all times unless surface 
leaks occurred or when the hole acceptance rate was greater than the 
capacity of the pump. 



B49 



For grouting of the downstream and upstream curtains and blanket holes, 
a maximum of 5:1 water-cement ratio by volume was used. An 8:1 maximum 
ratio was used on the centerline (final closure) curtain. All packer 
settings were water tested prior to grouting and the starting grout mix 
was determined by the amount of water accepted in the 5-minute water 
test period. On the upstream and dowaistream curtain and blanket holes, 
the following criteria were used: 

Water accepted in 5 minutes Starting Grout Mixture 

30 c .f . or more 3:1 w/c ratio 

20 - 30 c.f . 4:1 w/c ratio 

20 c.f. or less 5:1 w/c ratio 

For the centerline curtain, these criteria were modified to: 

Water accepted in 5 minutes Starting Grout Mixture 

30 c.f. or more 5:1 w/c ratio 

20 - 30 c.f . 6:1 w/c ratio 

20 c.f. or less 8:1 w/c ratio 

Grout mixes were changed when it was felt that a thicker mix would be 
readily accepted by the hole . When to change mixes was a judgment 
decision made by the onsite inspector and was based on rate of take, 
drilling characteristics, pumping pressure, and intuition or so called 
"feel of the hole" by the inspector. Only basic criteria were specified 
as mix changes could be based on hole behavior and this was quite 
variable even within different stages within the same hole . 

Wlien large grout takes were encountered in any portion of any hole at 
lower than normal pressures, the grout mix was progressively thickened. 
Sand or calcium chloride was used only after it was definitely determined 
that a hole would accept thick mixes . Once it was determined that a 
hole was wide open, intermittent grouting was performed by injecting 
500 cubic feet of cement or cement and sand and then washing the hole 
with just enough water to clear the hole . Grouting was resumed after 
a 4-hour interval . Two percent of bentonite by weight of the cement 
in a batch was added to all mixes containing sand to facilitate keeping 
the sand in suspension during pumping. 

EQUIPMENT 

Grout pumps used by the contractor consisted of Gardner-Denver 6"x3"x6" 
and 5"x2j"x5" air operated duplex piston type in conjunction with a 
25-cubic-foot agitator tubs and circulating system grout lines. Pumps 
were usually located within 50 feet of the hole being pumped which 
facilitated the pumping of thick mixes. Pumps were identified by 



B-50 



number and operating logs were kept. Pumps v/ere cleaned after each 
pumping interval and were dismantled every 110 hours at which time 
piston swabs were replaced and liners checked. This maintenance 
schedule was strictly adhered to by the contractor and throughout the 
duration of the grouting program a pump breakdown occurred only once 
while a hole was being pumped. 

Pressure gages consisted of Ashcroft 0-100 lbs. for low pressure and 
0-300 lbs . for higher pressure . The gages were internally filled with 
glycerin for dampening purposes from pump surges which made them 
extremely long lasting. The gages were activated by an oil filled 
diaphram in contact with the grout mixture . 

Communications between persons at the grout pumps at the grout hole and 
the mixing plant were achieved by the use of waterproof mine telephones 
These telephones were also equipped with signal lights for use in 
ordering batches. Three separate light systems, one for each mixer, 
were incorporated to facilitate operations between a grout pump and its 
designated mixer at the plant . This system was used to call pei'sonnel 
to the telephone who may have been at some distance from the telephone . 
Telephones were located at the office, repair shop, mixing plant, and 
at each grout pump located at the grout hole. The main telephone line 
had numerous outlets and the telephones were equipped with extensions 
so they could be readily moved. 

REPORTS 

Monthly Reports (L-lO's) were submitted for construction and design 
review. These reports contained plan and profile drawings of all the 
work performed during the month and a summary of holes grouted . The 
hole summary sheet contained all information pertinent to each hole 
such as stages, pressures, mixes, water tests, surface leaks, and 
holding pressures. A summary sheet is attached. A general narrative 
was also included which stated the amount of drilling accomplished, 
the total amount of cement and sand injected, and also the number of 
■water tests performed. 

SUMMARY 



Tlie'upstream-downstream curtains were not intended to be closed beyond 
20-foot centers . The purpose of these two curtains was to act as barriers 
for the centerline curtain which was the intended main-line of final 
closure. Final closure of the centerline curtain was rather easily 
attained. The number of 5-foot closure holes was negligible and 22--foot 
closures wore required only twice (Stations 2+60 and 3+10). To eliminate 
doubts during the time of grouting, holes were extended or extra holes 
added . Full confidence in the effectiveness of the grout curtain as a 
barrier was obtained by the meticulous drilling and grouting operations 
and method of closures. 



B-5] 



In regard to the attached letter submitted by McCabe Brothers to 
Morrison-Knudsen Company, dated August 25, 1976, we generally agree 
with all statements except for Paragraphs No . 1 and No . 2 on page 3 . 
High percentages of calcium chloride ivere seldom used and the situation 
of water losses occurring higher in the hole after grouting than when 
the water loss had originally occurred did not exist . Water losses 
did however occur at times at the same location or immediately below 
the original water loss, which is a normal occurrence. 



B-52 



(Drilling and Grouting Instruction Sheet) 



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B-53 



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(Drilling and Grouting Instruction Sheet) 



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B-56 



GROUTING INSPECTOR'S RIZPORT ^''"'^'^^ ^''flki^P^PU ■ 
fcatureT^.A^ _.ZP_r"?;>V.__ \nspf.C70R. Aj.^/(^c/:cV}/.'^. 

(DAM, TUN NTLS, SPILLWAY, ETC.) ^ /"/' / / 



(DAM, TUNNTLS, SPILLWAY, ETC.) 
SPECS N0j^C^-(e 'U LINE 



(A.B.C ETC.) 



._ RELIEVED BY 






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DEPTH DRILLED 


IpO 


PROPOSED FINAL DEPTH 


f^P 


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P 



CEMENT SUMM AR Y (C.F.) 1 




PLACED 


WASTED 
gov't CON! R. 


WITH PACKER 


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TOTAL ^ 






"N 



STAGE 
DEPTH 



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REMARKS 



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Tlii;, fcporl jliould •■.lio^ .Q-<-uir i.ii-1t — r,'.' /■.Vd" OT 'lln'^-i n.-o'!rn.--nr^ q i yen cncli hole \r^\v6 A / > J/ / 
Rtiiiofko coliiiriti: npcOKl'TToks, d 1 H icuHiri, l>ocK prc-sourc, r C'coiniric-ndolions, cic. 
Jvcosons for 'vVuslt' otiould be c/ploiricd in di-lciil. Vr/C to be incoiufcd by volume. 

B-57 



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GROUTING INGP[:CTPRS RLPORT SHLtT_oK_ 

fuojuc r. :-/:^J:<i 6i . .Q^Jm _ _ _•_':"' . J^f-. Qj. .^..'. ...%h\? ■xh<i i-y? 1 9 .?^' 

FEATURE 5/^' //o<^^P '/._ /S/' /)n /^y- O^'X'. <^j{- INSPECTOR -,^^^ •j/t:^-<^-0='--' _ 

{DAM.'ruNNEi.s, SPILLWAY, ETcO".:.::, ■■;„"' '■' r? '""/"' I ' 

SPECS UO. .DC-.(^SlJ^ LINE_/2_'^Vr_. RELIEVED n\_ K c f^ _Aj J cj<i .^ / 

(A.B.C ETC.) 



HOLE NO. 


DEPTH DRILLED 


S'o 


PROPOSED FINAL DEPTH 


f^ 


PREVIOUSLY GROUTED 


(:p 



CEMENT SUMM ARY (C.F.) 1 


\ 


PLACED 


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gov't 


CON! R. 


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WITHOUT PACKER 








TOTAL 









STAGE 
DEPTH 


TIME 


CEMENT 


"w/c 


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PRESSURE 


R E f,1 A R K S 


TOTAL 


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SACKS 
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This report iliould shorv a toir.plfic record of Itie Ircotrncnl givtn coch hole listed. 
RcrnorKs column: (Record Icoks, d i f firulticD, bock prciiurc, reconirr»endotioris, ttc. 
Reotons for 'Woote' oliculd be tuploirud in dctoil. W/C to \>b nnoiured by volume. 

B-58 



ceo hr.O • / * 



Sample Drill Report 



71744 {7-71) 

lluirliU of Kr clHinalior 



INSPECTOR'S DRILL RFXORD 
(FOR GROUT OR DRAINAGE HOLES) 



PROJECT_ Z^/_^J^ QA^-/Z^- SPECS. NO. 



VC G7/0- 



\ 



f-EATURE 



Tp ro r^ ?/?/^ TYPE HOLcs_ ^£:4/^'^_n 



DETAIL •^^'±L.'^ .^'ll BIT SIZE 

(RT. ACUT., D/Vf-RS/ON TUNNEL. SPV/Y.. ETC.; 



B^DRA/NAGE, ETC.) 



HOLE 


DRILL TIME 


DEPTH (FEET) 


PERTir^ENT INIORWATION* 


SHIFT 
& DATE 


IHSP. 
INIIIALS 


START 


STOP 


riJOM 


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'NOTr D/;/'TnoF coNcnr.iE ir any, eokmahon c.iian1.i.s. water i osi or gain. cave. etc. 

B-59 



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DIAMOND COMC DHILLINC 

PRCSSUnC CROUTINC 




HOTARY DRILLING 
rOUNDATION 7CDTINC 



BOX 1692. IDAHO FALLS. IDAHO 83401 

PHONC 522.5437 



August 25, 1976 



Korri son-Knud.sen Company, Inc. 
P. 0. Box 127 
J^ewdale, Idaho 83j^36 



Attention: l-'r. EHiane E. Buckert 






/noffis^n-Knud-^en - Kiewil 
ConUod No. 7b9A 



Gentlemen: 



Re: Letter from 'Independent Panel to 
Review Cause of Teton Dam Failure' 
to Korrison-Knudsen Co. Inc. for 
Information on Construction Teclinioue: 



Referring to Question: 



The Marnier in which AjJial grout distribution 
arid Closures were assured -when the up and 
downstream grout ti-avel v.-as relatively 
unlimited. 



There vjere tlur-ee grout lines an upstream, a center and a dov-Tt- 
stream. The dov.'nstream grout line vras from Station 2 -f 20 to I6 + 00; 
The upstream grout line ^.■as from Station 2 + 28 to 15 + % and the 
center grout line v.as from Station 2 + 23 to Station 18 + 00 and on. 
Most of the grout nipples were 2" diajneter. The Area holes were 
located over fairly large cracks ajid the nipples were set to inter- 
cept the cracks at different depths, soi.ne being set vertically over 
cracks with concrete poui-ed around triem. The downstream boles were 
vertical with 20 ft. centers. The upstream holes were at a 30 angle 
with 20 ft. centers, except one vertical at station 5 + 28 and one 
fan liole at 2 + 28 37 . The centerline holes were at a 30 angle 
•with 10 ft. centers. 

TJierc are no closure holes on the downstream IJne. Thoj-e jlt-c 
three fan liolcs at station 2 + 20; one at 15 1 one at 30 and ojie 
at A5 . The upstream line has the follGrnng closures: 3 holes on 
5' ccntcr.s, 6 hoi os- on 6' cenLcrs, 1 hole on 7' center, 2 holes on 
9 ' center, 1 hole on 10' ce/iter, 3 holes on 11* centers, 2 })oles on 
12' centers, and 2 holes on 13' center.';. As directed by tlie 
contracting officer, the ?iolcs from :;tation 9' I- 22 to 30 l- 00 in tlie 
\ipstrcajn lii>e v/ere deleted. 



B-61 






Page 2 



DIAMOND cone DRILLING — ROTARY DRILLING 

PRtSSURC GROUTING rOUNDATION TCSTING 

BOX 1092. IDAHO FALLS. IDAHO 83401 

PHONC 522.S437 



The primary holes vere stacgered from each other on the three 
grout lines. The Area holes that were set close to cracks were 
grouted first. V?e drilled the holes until we lost 5C^ or more of our 
drill water. Then commenced grouting at the bottom stage of the hole, 
wost of the area holes were intermittently grouted if the take was 
500 cu. ft., with a waiting period of t}'iree hours. Eventually that 
stage of the hole v/ould come up to the desired pressure required by 
the inspector. At that time we set the packer up to the next stage 
and progressed out of the hole thi-ough the different stages and 
finished grouting by hooking the nipple and grouting to the speci- 
ficed pressure. If the above hole v/as required to go deeper, we then 
drilled to the specificed depth or ujitil v^e had a v;ater loss of 50/o 
of more and then set the packer at the directed settings and grouted 
the different stages at req\iired pressures until we staged up to the 
previous stage grouted, thereby completing the entire hole. 
Closures were added to area holes. 

There are primary holes every 80 ft. , secondary holes every 80 
ft. and closure lioles every /4O ft. on the downstream and upstrea/n 

gi'Out lines. The priinary holes were drilled and grouted first, the 

secondai^y holes were drilled and grouted second and the closure holes 

were driDled and grouted last as directed. All grouting of holes v.'as 

accomplished in the same marnier described above for the area holes. 

The centerline holes have a primary every 80 ft., a secondary 
every 80 ft. and an intermediate bole every 40 ft. with closure holes 
every 20 ft. The priinary holes were drilled and grouted first, the 
secondary holes were drilled arid grouted second, the intermediate holes 
were da^illed and grouted third and the closui'e holes were drilled and 
grouted last as directed. Of com^se the centerline has a more complex 
pattern than the dowTstream and upstream grout lines and is designed to 
serve as a closure line for the downstream and upstream grout lines, 
Vv'ith many closure holes being added. 

Good packer settings Avere accomplished with the very minimum of 
difficulty. 

A large percent of the holes where the v.'ater loss v;as negligible, 
we were able to drill to the complete depth of the hole, in i.his case 
ve grouted from the bottom stageup, until the hole was completely 
grouted. 

About 9S or 99fo of the stages in all }ioles were water tested, with 
the exception of tlie top 20 ft. in many liolcs. The migration of water 
from the water tests and the grout travel into other drilled holes v.as 
very minijnal. All holes were completely backfilled with grout after all 
stages were completed. All rroiit leaks to surface areas were calked 
imrncdiately ajid contJnously until leakage stopped, 

I?efej'rin£^ to Question: Details of any doubts over the effectiveness of 

tliis Axial disLr'roution in any particular location 
B-62 






DIAMOND CORC DRILLING — ROTARY DRILLING 

PRtSSURC GROUTING TOUNDA TION TESTIN C 

BOX 1892. IDAHO FALLS. IDAHO 83401 

PHONE 512-5437 



Page 3 

The only doubt that we have been concerned with was the high 
percent of Calciiim Chloride being used. The highest percent used 
as directed by the inspectors was 10/J for a short time, later this 
was lowered to &fo. 

As an exajnple, if " tlie hole was 100ft. deep and we were grouting 
with about 3% or more Calcium Chloride, intermittently grouting the 
bottom stage and finally the bottom stage cajne up to pressui^e, then 
ve stage grouted the hole up to the surface. At this tjjne we were 
directed to deepen the hole to 130 ft. We then drilled the hole down 
to 90 ft. and had a total water loss. Then we set the pacl^er above the 
water loss in the bottom stage of the hole and started grouting until 
the stage came up to pressure - sometimes this stage required intermittent 
grouting. This condition has happened many times v;hen using Calcium 
Chloride. The question \ie have asked ourselves about the above problem 
is - Is this sa-me condition happening in the grouting of large or small 
cracks and fissures, causing a honey-comb effect. Thereby causing many 
more holes to be drilled ajid grouted on the centerline than otherwise 
would be necessaa^y. 

Referring to Question: Details of difficulties in obtaining assurance of 

axial closure at any station or grout hole along 
the same stretch of curtain. 

Me had no difficulty in grouting up to the desired pressure in a ll 
stages of all closure holes. If one closure hole took more than the 
minimum ajnount of grout in any one stage, we vera then ordered to drill 
and grout additional closure holes. 

Referring to Question: Similarities and significant differences in the 

appearance of the walls and floor of the Key 
trench in the right and left abutments. 

The le^t abutment had a few caverns in the v/aDls and the floor of 
key trench appeared to be good solid rock. Directly up the grout line, 
75 to 125 ft. above the tower on the steepest slop, we had some grout 
leaks around some large boulders and as v/e were calking these leaks, 
numerous bats were flying out of the cracks that v^e were attempting to 
calk. 

The right abutmentfrom about Station IS hOO to Station 11+50 
appeared to be very badly fxactured with small cracks in the v.-alls and 
the floor of the trench. From Station 11 +50 to 10 +00 it appeared to 
be good solid rock. From Station 10 hOO to 7 +50 -it appeared to be 
good solid rock on the walls and floor of the key trench, with some 
smaLl vi sable fissures. From 7 + 50 to 2 + 00 the walls and floor 
appeared to be of good soujid lock with a very little small frocturip^ 
vith tlic exception of nujncrous large faults viscible in the v;alls and 
floor of the key trench. 

B-63 






DIAMOND CORC DRILLING 
PRtSSURC GROUTING 



ROTARY DRILLING 
FOUNDATION TESTING 



BOX 1 8 9 Z 



IDAHO FALLS. 

P H O N C 



DAHO 034O1 
. 2 2 • S 4 3 7 



Page A 



The lcJ<e bed sediments that underlay the riolite formation along 
the extreme length and vddth of the dam at depth were drilled and 
grouted to the desired pressures for a short distance on the outer end 
of the left abutment. 

All work described above was completed as directed by the 
contracting officer, Bureau of Reclajnation. 



Very truly your, 



McCABE BROS. DRILLING, INC. 



t.i:^.. 



t ■■ / / 



* -I-v.' ~^ I 



Edwin L. HcCabe 
President 



ELJ-^:rjn 



B-64 



Please describe: 

B. The manner in which the key trench between Station 18+00 and 

Station 2+00 was prepared to receive the first embankment material . 

Compare the way in which this trench was prepared with "broom clean." 

If there were differences in clean-up between particular stations, because 

of weather, or any other cause, please describe such diffei'ences in 

detail . 

(B) The key trench between Station 2+00 and 18+00 was all cleaned in 

basically the same manner. Laborers using hand shovels and bars would 
first remove any loose rock or earth materials from the rock foundation. 
An air jet was then used to clean any remaining finer material down to 
a clean rock condition . Any grout which had been spilled in key trench 
areas was loosened by paving breaker and cleaned by air jet . Cleanup 
of key trenches and all abutment areas generally progressed to 2 to 10 
feet above the elevation of the zone 1 fill. Material accumulated during 
cleanup was removed by a rubber-tired backhoe . 

Prior to placement of each lift of specially compacted Zone 1 material, 
the abutment rock which had been cleaned by shovels and air jets was 
always sprayed with water to assure a proper bond with the fill material . 

No particular areas in the foundation key trench received a different 
type of treatment from the rest of the key trench. The air jet and 
water treatment method of cleaning the abutment rock was considered 
superior to broom clean because the use of air jets and water resulted 
in a more thorough cleaning of cracks and irregularities in the rock 
surface then with the broom method . 



B-65 



Please describe: 

C. The manner in which any fissures or open joints in the key trench walls 
and floor were sealed between Station 18+00 and Station 2+00; that is, the 
manner in which, and the places where, slush grouting, dental concrete, gunite, 
or shotcrete may have been used, also the extent to which such sealing was 
general. Were any joints left unsealed and, if so, where? If known, please 
indicate the particular stations, if any. 

(C) The excavation for the right abutment keyway trench disclosed two unusually 
large fissures that cross the floor and extend into the walls of the keyway 
near the toe of the walls. On the floor of the keyway, the fissures were 
filled with rubble; but at both locations, the contractor excavated a trench 
about 3 to ^ feet wide and about 5 feet deep. Both fissures apparently 
were developed along joints that strike about N80 W and are vertical to 
steeply inclined. The largest fissure crossed the keyway from station k+^-k 
of the upstream face to station 3+^5 on the downstream face. The strike 
of a smaller fissure was about N75 W and crossed the keyway trench from 
station 5+33 of the upstream face to station 5+11 of the downstream face. 

The largest and most extensive open zone extended into the upstream wall 
from the toe of the keyway wall near station k--kk . The opening at the toe 
v;as about 5 feet wide ai-d 3 feet high. There was a rubble-filled floor about 
k feet below the lip of the opening. A few feet in from the wall the fissure 
was about 7 feet wide, but a very large block of welded tuff detached from 
the roof and/or the north wall rested in the middle. Beyond the large block 
about 20 feet in from the opening the fissure narrowed to about 2-1/2 feet 
wide. The rubble floor sloped gently away from the opening and the vertical 
clearance was about 10 feet. About 35 feet in, the rubble floor sloped 
rather steeply and the roof tilted sharply upward. About 50 feet in from the 
opening, the vertical clearance was about ^0 feet and the fissure curved out 
of sight at the top. About 75 feet back, the fissure curved slightly south- 
ward out of view. The smaller fissure was mostly rubble-filled and was open 
only at the upstream face. The opening was about 1 foot square at the face 
and the fissure appeared to be rubble-filled about 5 feet back from the face. 

The continuation of this fissure intersected the downstream wall of the 
keyway near station '+'-21. The opening was about 4 feet wide and k feet high. 
A rubble-filled floor lay about 4 feet below the lip of the opening. The 
large opening extended only about 5 feet back from the face and then a foot 
wide fissure at the north edge continued about 10 feet back and about 10 feet 
upward before going out of view. 

The other large open zone extended into the upstream wall from the toe of the 
wall near station 3+66. The opening at the toe of the wall was about 1-1/2 feet 
wide and 1-1/2 feet high. From the opening, the fissure extended about 10 feet 
down to a rubble floor and about 15 feet back before going out of view. The 
continuation of this fissure intersected the downstream wall of the keyway at 
about station 3+^5. There was no open fissure at the downstream wall but 



B-66 



there was a 3-1 /2-foot-wide zone of very broken rock with open spaces up 
to 0.8 foot wide. About 2-1/2 feet north, there was an open joint about 
10 feet long and 0.2 feet wide that dipped about 78 degrees south. 

At both the upstream and downstream locations of the fissure zones, broken 
rock extended to about midway up the keyway walls. Above the broken zones 
there appeared to be filled fissures about 0.5 foot wide that extended 
vertically to the top of the keyway cut. 

Two 9-5/8- inch-d iameter holes were bored to intersect the open fissure that 
extended into the upstream and downstream walls of the keyv;ay trench. One 
hole was located 72 feet upstream from dam axis station k+Gk and the other 
was located 75 feet downstream from dam axis station U+02. The upstream 
extension of the fissure was encountered at a depth of 68 feet and the 
downstream extension was encountered at a depth of 58 feet. The holes were 
cased with 8-5/8- inch-d iameter steel casing. High-slump concrete was poured 
through these casings into the fissures. Ninety-five cubic yards of concrete 
was placed in the upstream hole and 233 cubic yards was placed in the down- 
stream hole in April 197^. 

Three 3- Inch-d Iameter vertical drill holes were bored 77 feet downstream from 
dam axis station 3+30 to explore for a possible open fissure indicated by 
earlier horizontal drill holes bored from the floor of the keyway trench. 
The vertical holes encountered some voids and some soft, broken, or loose 
rock; however, these voids did not appear to be of sufficient volume to 
warrant drilling large diameter holes for backfilling with concrete. 

In May 197^, an additional 18 cubic yards of high-slump concrete was placed 
in the 8-5/8- i nch-d iameter-cased hole which intercepts the open fissure 
75 feet downstream from station ^++02. A total of 251 cubic yards of high- 
slump concrete was placed in this hole. Drawings No. 5^9-1^7-133 and -13^+ 
(Exhibits 12.10.11 and 12.10.12) show the location of the holes, the esti- 
mated outline of the fissures, and the concrete that was placed into the 
f i ssures . 

Other open joints or holes were observed on the floor of the kyeway near 
centerline at stations 5+03, 5+68, and 6+18 and about 5 feet left of 
centerline between stations 6+03 and 6+08. The roles were rubble filled at 
shallow depths and their lateral extent, if any, was covered by rubble. 
Heavy calcareous deposits were associated with all of the open zones except 
for a 0. 2-foot-wide open joint between stations 6+03 and 6+08. 

The joints between station 5+03 and 6+08 were filled with grout during the 
grouting operation. 

Dental concrete was placed in an open jointed area on the spillway floor at 
approximate station 9+00 where the 1-1/2:1 slope of the key trench meets 
the sp i I Iway f loor . 



B-67 



The surface grouting on the abutments began because of the numerous joints 
in the rocks. This grouting was started on July 29, 197^ and was completed 
about August 6, 1975. 

The joints in the rock between elevation 5055 and 5205 were grouted to 
refusal by mixing grout in the mix trucks and placing it in the crack or 
joint by making a funnel out of the zone 1 material around the cracks and 
dumping it in out of the trucks. The smaller cracks, approximately 1/2 inch 
to 2 inches wide, were grouted witha 0,7 to 1 mix by volume. For gravity 
filling the larger cracks, approximately 3 to U inches wide, a sand-cement 
grout was used. These cracks were marked and filled by inspectors for zone 1 
special compaction placing. 

Occasionally, the batch plant could not place grout in these cracks daily. 
Therefore, the zone 1 special compaction was held up until the cracks could 
be grouted. At times, the fill would get ahead of the special compaction a 
foot or 2, but this was not a problem because the batch plant operated on 
two shifts and grout could be placed during the graveyard shift when the 
fill was shut down . 

The foundation keyway and abutment rock above elevation 5205 had fewer open 
joints than below this elevation. Generally the rock in the keyway was more 
massive and the joints and cracks very small; hence, the slurry grouting above 
elevation 5205 became impracticable. It was noted also that the fewer large 
joints above elevation 5205 were usually filled with rubble or silt which also 
added to the difficulty of treating these joints. 

Please refer to the detailed geologic maps of the abutment and key trench 
areas for a description of the joints and fissures. The panoramic photos 
of key trenches and zone 1 foundation rock will also reveal the more massive 
nature of the rock in the key trenches. 

No fissures or large joints were knowingly left untreated. A tabulated list 
of the locations where slurry grout was used is attached. 

The fissures crossing the key trench at stations 3+55 and ^3^ were 
excavated similar to the grout cap trench and filled with concrete. 



B-68 



SLURKY GROUT USfD TO FILL CRACKS AND 
FISSURLS IN RIGHT ABUTMENT 



Cc) 



Date 


Station 


Offse 


t 


Volume in Cu. 


Yds 


8-14-74 


16+50 






1.00 




8-19-74 


16+30 


340' - 3 


55' 


1.00 




8-22-74 


16+10 


300' - 3 


50 'us 


2.00 




9-3-74 


15+95 


75' ds 




1.00 




9-3-74 


1 5+95 


250' us 




1.00 




9-5-74 


16+00 


15' ds 




4.00 




9-5-74 


16+20 


74' ds 




4.00 




9-5-74 


16+20 


176' us 




4.00 




9-5-74 


15+90 


64' ds 




2.00 




9-5-74 


15+90 


150' us 




2.00 




9-6-74 


16+00 


35' ds 




1.00 




9-6-74 


16+10 


45' ds 




1.00 




9-6-74 


16+20 


74' ds 




1.00 




9-10-74 


16+00 


190' ds 




6.00 




9-10-74 


16+00 


15' - 90 


'ds 


6.00 




9-10-74 


16+00 


300' us 




6.00 




9-13-74 


16+00 






4.00 




9-17-74 


16+00 


60' ds 




2.00 




9-24-74 


15+70 


50' & 75' 


'ds 


20.00 




9-25-74 


15+70 


50' & 75' 


'ds 


48.00 




10-3-74 


15^80 


125' ds 




9.00 




10-3-74 


15+50 


48' us 




0.50 




10-3-74 


15+60 


75' us 




0.50 




10-4-74 


16+20 


300' us 




8.00 





B-69 



Date 


Station 


Offset 


Volume in Cu. 


Yds 


10-4-74 


16+75 


150' us 


1.50 




10-4-74 


16+50 


128' ds 


0.50 




10-7-74 


15+60 


35' us 


6.00 




10-10-74 


15+70 


40' ds 


1.00 




10-10-74 


15+70 


135' ds 


3.00 




lO-n-74 


15+80 


10' ds 


2.00 




10-11-74 


15+80 


csnterline 


4.00 




10-11-76 


15+80 


265' us 


38.00 




10-11-74 


15+80 


258' us 


3.00 




10-11-74 


15+80 


223' ds 


3.00 




10-14-74 


15+50 


125' ds 


0.25 




10-14-74 


15+50 


273' ds 


5.75 




10-15-74 


15+40 


100' us 


0.50 




10-15-74 


15+50 


273' - 278'us 


35.50 




10-16-74 


14+80 


35' us 


0.50 




10-16-74 


15+50 


273' - 278'us 


0.50 




10-16-74 


15+30 


30' us 


17.00 




10-17-74 


15+30 


30' us 


0.50 




10-17-7.4 


14+80 


35' us 


8.50 




10-17-74 


15+40 


12' ds 


8.50 




10-18-74 


15+50 


50' ds 


6.00 




10-18-74 


15+30 


12' us 


6.00 




6-3-75 


14+63 


84' us 


5.00 




6-3-75 


14+37 


82' us 


3.00 




6-6-75 


-14+70 


110' us 


39.50 




6-10-75 


1 5+20 


150' ds 


13.50 




6-11-75 


15+20 


150' ds 


1.00 





B-70 



D^te 


Station 


Offset 


Volume in Cu. 


Yds 


6-11-75 


15+15 


115' ds 


4.25 




G-n-75 


15+10 


90' ds 


1.50 




6-11-75 


15+00 


60' ds 


1.25 




6-11-75 


14+90 


30' ds 


0.50 




6-11-75 


14+78 


3' ds 


7.00 




6-11-75 


14+25 


35' us 


5.50 




6-11-75 


14+40 


80' us 


3.00 




6-11-75 


15+30 


110' us 


1.50 




6-11-75 


15+35 


115' us 


1.00 




6-11-75 


1 5+60 


150' us 


1.00 




6-11-75 


15+80 


245' us 


2.00 




6-11-75 


15+40 


120' us 


17.00 




6-11-75 


15+25 


106' ds 


1.00 




6-13-75 


15+00 


105' ds 


0.25 




6-13-75 


15+00 


40' ds 


8.75 




6-13-75 


15+00 


29' ds 


15.00 




6-13-75 


14+63 


15' ds 


0.25 




6-13-75 


14+30 


15' us 


1.50 




6-13-75 


14+03 


30' us 


2.00 




6-13-75 


14+25 


15' us 


0.25 




6-13-75 


15+30 


center! ine 


2.00 




6-13-75 


15+50 


190' us 


5.00 




6-13-75 


15+00 


123' ds 


3.00 




6-13-75 


15+00 


111' ds 


7.75 




6-13-75 


15+00 


98' ds 


2.00 




6-13-75 


14+80 


15' ds 


0.25 




6-13-75 


14+75 


7' us 


0.25 





B-71 



Date 


Station 


Offset 


Volume in Cu. 


Yds 


6-13-75 


14+60 


95' us 


2.75 




6-13-75 


15+40 


120' us 


0.50 




6-13-75 


15+50 


220' us 


1.00 




6-13-75 


15+50 


245' us 


1.50 




6-16-75 


3+60 


us slope trench 


37.00 




6-16-75 


4+43 


us slope trench 


7.00 




6-16-75 


3+44 


ds slope trench 


10.00 




6-16-75 


4+21 


ds slope trench 


10.00 




6-18-75 


15+00 


125' ds 


7.00 




6-18-75 


15+00 


120' ds 


110.00 




6-19-75 


14+80 


115' ds 


12.00 




6-19-75 


15+00 


120' ds 


27.50 




6-19-75 


15+00 


150' ds 


7.50 




6-19-75 


15+00 


140' ds 


20.00 




6-19-75 


15+00 


90' ds 


4.00 




6-19-75 


15+00 


75' ds 


2.00 




6-19-75 


15+00 


150' ds 


14.50 




6-19-75 


15+00 


70' ds 


1.00 




6-19-75 


15+00 


127^ ds 


1.50 




6-20-75 


15+00 


103' ds 


0.25 




6-20-75 


15+00 


105' ds 


0.25 




6-20-75 


15+00 


50' ds 


0.25 




6-20-75 


15+00 


68' ds 


0.25 




6-20-75 


14+45 


10' ds 


0.25 




6-20-75 


14+40 


5' ds 


3.50 




6-20-75 


14+.30 


centerline 


0.25 




6-20-75 


14+50 


100' us 


0.25 




6-20-75 


14+60 


110' us 
B-72 


0.50 





Date 



Station 



Offset 



Volume in Cu. Yds 



6-20-75 

6-20-75 

6-20-75 

6-20-75 

6-20-75 

6-20-75 

6-20-75 

6-20-75 

6-20-75 

6-20-75 

6-20-75 

6-20-75 

7-1-75 

7-1-75 

7-1-75 

7-1-75 

7-1-75 

7-1-75 



7-1-75 



7-1-75 
7-1-75 
7-1-75 
7-1-75 
7-2-75 
7-2-75 



7-2-75 



7-2-75 



14+70 


120' us 


14+52 


104' us 


14+18 


10' us 


15+00 


140' ds 


14+95 


85* ds 


14+95 


75' ds 


14+90 


30' ds 


14+15 


5' ds 


14+45 


90' us 


14+25 


25' ds 


15+20 


115' ds 


15+20 


120' us 


Key v/ay rt. 

of spillway 
II 


110' us 
115' us 


II 


120' us 


II 


100' us 


II 


12'us 


II 


25' ds 


II 


60' ds 


II 


80' ds 


II 


75' ds 


II 


100' ds 


II 


125' ds 


15+10 


205^ us 


15+15 


210' us 


14+50 


110' us 


14H85 


130' us 



0.25 



6.00 

0.50 

4,00 

1.00 

4,00 

12.00 

1.00 

5.00 

1.00 

1.00 

1.00 

6.00 

0.25 

3.00 

0,25 

7.00 

0.25 

1.25 

12.00 

0.50 

0.50 

29.00 

12,00 
2.00 

1.50 

9.50 



B-73 



Date 


Station 


Offset 


Volume in Cu. 


Yds 


7-2-75 


14+35 


100' us 


9.00 




7-2-75 


14+50 


10' ds 


1.00 




7-2-75 


15+10 


75' ds 


0.50 




7-2-75 


15+25 


125' ds 


1.00 




7-9-75 


14+30 


100' us 


9.00 




7-9-75 


14+55 


centerline 


8.00 




7-9-75 


14+90 


160' us 


14.00 




7-9-75 


14+90 


225' us 


6.00 




7-9-75 


14+18 


2' us 


1.00 




7-9-75 


14+80 


55' ds 


6.00 




7-9-75 


14+85 


80' ds 


2.00 




7-9-75 


14+90 


101' ds 


2.00 




7-10-75 


14+10 


8' us 


2.00 




7-10-75 


14+25 


5' ds 


2.00 




7-10-75 


14+30 


10' ds 


6.00 




7-10-75 


15+00 


210' us 


1.00 




7-10-75 


15+20 


115' ds 


7.00 




7-10-75 


1 5+40 


150' ds 


6.00 




7-11-75 


4+18 


27' ds 


16.00 




7-11-75 


4+42 


27' us 


12.00 




7-11-75 


15+20 


115' ds 


28.00 




7-11-75 


15+30 


132' ds 


1.00 




7-11-75 


15+40 


150' ds 


1.00 




7-11-75 


13+85 


10' us 


5.00 




7-11-75 


14+50 


23' ds 


1.00 




7-11-75 


14+70 


125' us 


28.00 




7-11-75 


14+00 


98' us 


2.00 




7-11-75 


14+10 


107' us . 


3.00 






B-74 







DAte 


Station 


Offset 


Volume in Cu, 


Yds 


7-11-75 


14+40 


122' us 


1.00 




7-11-75 


14+60 


125' us 


1.00 




7-11-75 


15+00 


148' us 


4.00 




7-11-75 


14+80 


133' us 


10.00 




7-11-75 


13+85 


8' us 


4.00 




7-11-75 


15+10 


80' ds 


4.00 




7-14-75 


1 3+75 


20' us 


1.00 




7-14-75 


13+80 


78' us 


14.00 




7-14-75 


14+10 


108' us 


1.00 




7-14-75 


14+50 


30' ds 


12.00 




7-14-75 


14+45 


25' ds 


2.00 




7-14-75 


15+10 


80' ds 


2.00 




7-18-75 


15+20 


135' ds 


7.00 




7-18-75 


15+10 


125' ds 


30.00 




7-18-75 


15+00 


120' ds 


17.00 




7-18-75 


15+20 


125' ds 


8.00 




7-18-75 


15+00 


50' ds 


1.00 




7-18-75 


15+10 


68' ds 


3.00 




7-21-75 


15+00 


110' ds 


3.00 




7-21-75 


14+90 


95' ds 


3.00 




7-21-75 


14+60 


55' ds 


2.00 




7-21-75 


14+45 


40' ds 


4.50 




7-21-75 


13+90 


85' us 


5.00 




7-21-75 


14+07 


107' us 


3.00 




7-21-75 


14H25 


125' us 


0.50 




7-21-75 


14+10 


5' ds 


24.00 




7-24-75 


14+00 


15' U5 


13.00 





B-75 



Date 


Station 


Offset 


Volume in Cu. Yds 


7-24-75 


14+02 


10' us 


11.00 


7-28-75 


14+25 


145' us 


6.50 


7-28-75 


14+06 


110' us 


1.00 


7-28-75 


13+85 


97' us 


2.00 


8-1-75 


13+85 


95' us 


1.00 


8-1-75 


14+00 


100' us 


7.00 


8-4-75 


13+85 


9' us 


33.00 


8-4-75 


14+12 


115" us 


7.00 


8-4-75 


14+12 


138' us 


13.00 


8-4-75 


14+12 


168' us 


11.00 


8-4-75 


13+96 


7' us 


8.00 


8-5-75 


14+00 


100' ds 


2.00 



B-76 



Please describe: 

D. The method of material selection, preparation, placement and 
compaction, in the key trench, of the "specially compacted earthfill" 
shown in the cross section marked "Foundation Key Trench" on USER 
Drawing No. 549-D-9 . If special difficulties were encountered in 
selection, preparation, placement or compaction at any points along 
the length from Station 18+00 to Station 2+00, please describe each. 

(D) The material selected for zone 1 special compaction in the foundation 
key ti'ench was excavated in Borrow Area "A" with a Barber Greene wheel 
excavator. Borrow Area "A" material was pre-wet by irrigation sprin- 
klers . The wheel excavator removed material in cuts up to 13 feet in 
depth and the material received a thorough blending of gradation and 
moisture by this method. Selection of the best available material for 
compacting with hand tampers was accomplished by the contractor's qualify 
control engineer and pit foreman. The Bureau inspector in the foundation 
key trench area inspected the special material on the basis of moisture 
and also the amount of caliche as well as the suitability of the mate- 
rial for compaction against the rock. The contractor's quality control 
personnel and the Bui'eau inspector selected material with moisture 
content near optimum, low caliche content, and highest possible plas- 
ticity available from the borrow area. 

Moisture was controlled in specially compacted material by mixing dry 
material with material which was too wet to reduce moisture content or 
by adding water to material which was too dry . Special compaction 
material was deposited near the abutment and then placed by dozers and 
laborers using hand shovels. Proper moisture content was determined 
hy the inspector and checked by the lab test . 

Material was compacted using gasoline and air tampers in irregular 
areas along the abutments and key trench and by a loaded Euclid 74-TD 
end dump truck or by a loaded Caterpillar model 992 front end loader. 
Material was compacted in 3-inch lifts by the gasoline and air tampers 
and in C-inch lifts by the loaded equipment method. If a laboratory 
test of specially compacted material revealed that moisture limits 
were exceeded, failing material was removed, reworked, and then replaced. 
The area was recompacted when failure was due to low density. Rework 
area was generally 50 to 100 feet on each side of the test failure. 

Between Stations 2+00 and 18+00, a total of 425 density tests of the 
specially compacted material were taken in the foundation key trench 
and along the right abutment zone 1 foundation. The average optimum 
moisture content of this material was 19.1 percent and placed at an 
average of 0.6 percent dry of optimum. The average "c" value of this 
material was 98.2 percent and "d" value averaged 97.2 percent. The 
silty material was difficult to compact in the foundation key trench 
special compaction area and along the abutment in the special 



B-77 



compaction areas. This is illustrated by the fact that of the 425 
tests taken between Stations 2+00 and 18+00, 114 tests failed either for 
moisture or density deficiencies and required reworking or additional 
compaction; however, these areas were retested after being reworked and 
brought up to specifications requirements. 

Field experience with this silty material demonstrated that the 
Inherent nature of the material, particularly its low plasticity, made 
compaction by hand tampers difficult and a very concentrated effort was 
required to obtain a good job. However, there were no areas not placed 
to specifications requirements and particular attention was given to 
obtaining both moisture and density uniformity along the abutment rock 
contact in these special compaction areas. 

Please refer to our reply to Question F., "Cleanup and Special Compac- 
tion - General" for additional information. 



B-78 



Please describe : 

E. The method of material selection, preparation, placement, and 
compaction in the key trench between Station 18+00 and Station 2+00 
of the core material . If special difficulties were encountered in 
selection, preparation, placement or compaction at any points along 
the length from Station 18+00 to Station 2+00, please describe each. 

Material in the key trench core area was selected by the same method 
as in paragraph (D) . The borrow area was prepared in the following 
manner: A cut depth was determined from topographic notes to estab- 
lish the desired drainage pattern. The borrow pit was then divided 
into material blocks . Three-inch holes were augered to the depth of 
cut required on a 200-foot grid and proctor optimum moistures were 
run on the drill cuttings and noted on the borrow pit drawings. 
Moisture was added to the pit by sprinkling the required water for 
the design cut on the area at least 3 weeks prior to excavation. 
Constant monitoring was possible by utilizing a speedy moisture 
teller. Material on the zone 1 fill received extra water from water 
trucks if required. The material was spread in about 8- to 9- inch-thick 
uncompacted lifts and rolled with two Caterpillar 825B self-propelled 
sheepsfoot rollers with cai'on wheels and two Ferguson SP-120-P 
self-propelled sheepsfoot rollers. T-.vo Caterpillar motor graders 
with scarifier attachments provided supplemental scarifying on 
embankment as moisture was being added. 

The method of excavation in the borrow pit by the Barber Greene wheel 

excavator resulted in a very homogeneous mixture of zone 1 material . 
Moisture and gradation reached a high degree of uniformity by the 
mixing action of the wheel excavator and the subsequent loading into 
the trucks by the belt . Further uniformity was attained by spreading 
and working of the material on the fill . The average density of all 
zone 1 fill placed was 98.3 percent of laboratory maximum with an 
average optimum moisture of 19.6 percent and placed at an average 
of 1.0 percent dry of optimum. 

No special difficulties were encountered in placing the core material 
to the required density. 



B-79 



Please describe: 

F. The manner in which the contact area under the core of the dam outside 
of the key trench wa's prepared to receive the first core material. If 
special difficulties were encountered at any location along the length 
of dam between Station 18+00 and Station 2+00, please describe. 

(F) CLEANUP AND SPECIAL COMPACTION - GENERAL 

Placement of zone 1 embankment at Teton Dam began in the cutoff trench on 
October 18, 1973 with zone 1 material being transported by beltline conveyor 
from the left abutment to the trench bottom. Special compaction of the 
zone 1 material began on October 19, 1973, initiated by two laborers 
operating pneumatic tamping hammers and gas powered wackers along the 
perimeter of the embankment area from station 17+75 on the dam axis to 
station 19+50, 200 feet upstream. 

While the zone 1 dam embankment material consisting of clay, silt, and sand 
could have rocks with dimensions of 5 inches or less, the zone 1 embankment 
material placed in locations requiring special compaction consisted of clay, 
silt, and sand v\/ith rock fragments having maximum dimensions of no more than 
1 inch. Any portion of the dam embankment where zone 1 material was placed 
and could not be adequately compacted by sheepsfoot roller was specially 
compacted. These areas include zone I material adjacent to rock abutments, 
concrete structures, and any steel pipe or steel structures which would be 
embedded in the zone 1 embankment. Special compaction was accomplished for 
an average horizontal distance of 2 feet from any surface contacted by the 
zone 1 embankment. Standard procedure for placing a lift of zone 1 fill 
consisted of dumping the material from belly dumps and placing the lift with 
dozers to a depth which would equal 6 inches when compacted. An uncompacted 
lift of 9 inches generally compacted to a depth of 6 inches. Areas of fill 
which could not be placed by dozer were placed by laborers with hand shovels. 
Equipment such as dozers and sheepsfoot rollers were not allowed to contact 
tiie abutment or any other surface requiring special compaction of adjacent 
embankment material to assure that no damage would occur to the surface 
and that no rock would be loosened or dislodged from the abutment. 

Abutment cleanup along the zone 1 embankment consisted of removal of all 
vegetation, including roots, larger than one-fourth inch in diameter, leaving 
clean rock. Any earth attached to the rock was removed by a ; r jet or hand 
shovel. Any grout which had been spilled in key trench areas was chipped out 
by jack hammer and cleaned by air jet. Cleanup of abutments generally prog- 
ressed 2 to 10 feet above the elevation of the zone 1 fill. Material accumu- 
lated during cleanup was removed by rubber-tired backhoe. 

Prior to placement of each lift of specially compacted zone 1 material, the 
abutment or other surface which had been cleaned by handwork and air jets 
was always sprayed with water to assure a proper bond of the fill material 
to this surface. A [minimum of eight passes was made by a loaded Euclid Jk-JD 



B-80 



end dump or other approved piece of rubber-tired equipment over specially 
compacted areas forcing the clay material into the wetted cracks in the 
rock abutment. (See photo P5^9-1^7-5732 , Exhibit 3^-) All surfaces were 
clean prior to placement. Areas not reached by wheel rolling were power- 
tamped by gasoline or air tampers to such a degree that the compaction and 
density requirements were met. (See photo P5^9- 1^7-5731 , Exhibit 3^.) 

Before placing a new lift of specially compacted zone 1 material, the 
previous lift was scarified by discing the surface. Any areas which could 
not be reached by the disc were scarified by hand with shovels to assure 
a good bond with the following lift and to prevent a smooth bonding surface 
which could possibly allow movement of water along this boundary in the 
future. Moisture was controlled in specially compacted material by mixing 
dry material with material which was too wet, to reduce moisture content, 
or by adding v^/ater to material which was too dry. Material was worked 
to the proper moisture content near the abuiment and then placed. It was 
difficult to adjust the moisture content of material already in place along 
the abutment. Proper moisture content was determined by the inspector and 
checked by the lab test. Following a test, failing material was removed, 
reworked and then replaced to correct a failure in moisture content. The 
area was recompacted when failure was due to low density. Rework area was 
generally 50 to 100 feet on each side of the test failure. 

Material was specially compacted around 36-inch pipe encasing dewatering 
pumps station 18-1-85, 75 feet upstream and at station 19+70, 175 feet 
upstream. (See photo P5^9- 1^7-325^ NA , Exhibit 3^.) Plastic dewatering 
pipes at the bottom of the trench were also embedded in specially com- 
pacted earthfill. Saturated material along the upstream and downstream 
toe of the embankment was removed with a Case 58OB backhoe. The areas 
were then backfilled with gravel to prevent water from pooling or saturating 
placed embankment material. Zone 1 material was then specially compacted 
over the gravel beds, or French drains, using a rubber-tired 992 front 
loader with its bucket filled with zone 1 material. 

Special compaction of zone 1 fill continued from station 18-1-50 to 
station l8-f-75, I90 feet upstream to 200 feet upstream, elevation ^937 to 
504 1 , using gas-powered plate wackers around the pump encasement and drains. 
Rock abutments were cleaned of all vegetation and loose material by hand- 
work and air jets as construction of the embankment progressed. 

By October 29, 1973, the pipe from the dewatering pump at station I8+85 
was embedded in specially compacted material to elevation 4961. An area 
6 feet wide for a depth of k feet above the pipe was compacted with gas- 
powered plate wackers, from the pump to the downstream toe of the embank- 
ment. With a 'i-foot depth of material over the pipe, it was possible for 
a sheepsfoot roller to compact the fill in this area. On November 7, 1973, 
the two 50-hp dewatering pumps were removed from the embankment and the 
36-inch pipe encasements were filled with concrete. Special compaction 
with wackers began around the zone 1 belt tower footings on this date at 



B-81 



station 16+65 on the right abutment. This was the last day of fill place- 
ment as snow closed the embankment for the season. 

The contractor resumed embankment operations on April k, 197^. with zone 1 
material being placed and compacted at the toe of the right abutment and 
around the base of the beltline tower. After dropping through the tower, 
the material was loaded and spread by a Cat. 966 loader. The fill was 
compacted adjacent to the abutment by wheel rolling with the Cat. 966 loader 
and around the tower legs with gas-powered plate wackers. An access ramp 
was constructed for scrapers at the base of the tower during this operation. 
Elevation of the fill around the tower legs on April 11, 197^ was 5015.5 feet. 

Laborers continued to clean the basalt formation at station 21+55 on the 
left abutment. Mud and grout along the grout cap on both abutments and 
loose debris were removed to a waste area on the downstream slope of the 
embankment by a Cat. 988 loader. Fill was compacted along the rhyolite 
wall of the right abutment with pneumatic tamping hammers. The abutment 
was wetted by a Cat. 63IB water wagon to assure proper bond with the 
embankment . 

On April 29, 197^, a 6,000 gallon Cat. 63IB water wagon compacted fill 
material adjacent to the abutment making eight passes of the wheel at each 
locat ion . 

By May 29, 197^, areas of special compaction of zone 1 included material 
around the legs of zone 1 beltline tower station I6+58, 50 feet upstream 
from the dam axis, the right zone 1 abutment station 16+50 to sta- 
tion 17+50, 100 feet downstream to 3^0 feet upstream from centerline, 
and the left abutment from station 22+50 to station 2^+00, 100 feet downstream 
to 300 feet upstream. Average elevation of embankment was 5022 feet. 

On July 8, 197^, the contractor began using a Pierce Arrow pavement breaker 
or Hydra Hammer, with shoe area of the hammer approximately 1 square foot, 
for special compaction along the abutment and the materials handling tower 
supports, (See photo P5^9- 1^7-^590 NA , Exhibit 3^.) 

On July 11, 197^, special compaction v/as interrupted to blast overhanging 
rock on the left abutment. Blasting, scaling, and cleanup continued for 
several days and special compaction resumed following this operation. 
Grout leaks from construction of the grout curtain in the right cutoff 
trench appeared along the right abutment special compaction area. Wet 
material was removed by motor patrol and new material was placed and 
compacted . 

A "Ho-pac" compactor arrived for use on July 17, 197^ and a Case 58OB back- 
hoe with special vibrator attached to the end of the backhoe to be used for 
compaction arrived on July 22, 197^. Use of the "Ho-pac" v^as discontinued 
because of the high number of passes required to get adequate compaction. 
When it was not possible to compact zone 1 fill in very deep voids on the 
irregular abutments, it was necessary to fill these voids wivh backfill 



B-82 



grout to form an impervious rock foundation sealing off voids so earthfill 
material could not penetrate the foundation and cause an unstable embankment. 
A standard grout mix of 0.7-'l water-to-cement ratio was used for most backfill 
grouting operations. 

On November 27, 197^, the contractor terminated operations for the season, 
resuming work on April 18, 1975, with cleanup on rock abutments. Standing 
water along the abutment on May 19, 1975, was drained toward the center of 
the fill and pumped downstream and fill material was scarified with an 
International TD15C dozer pulling discs and allowed to dry. Any material 
considered too wet along the abutments was removed by a Cat. \kE patrol, 
picked up by scrapers, and hauled to the zone 3 embankment to dry. 

When construction of the right cutoff trench embankment began on June 10, 
1965, a Cat. 966 rubber-tired loader was used for special compaction. 
After all concrete repair was complete at the Auxiliary Outlet Works gate 
shaft and right spillway counterforted wall station 10+55, elevation 5295 
special compaction began on July 22, 1975. Gasoline-powered plate wackers 
were used there. 

On October 20, 1975, cleanup of grout and debris began around the River 
Outlet Works gate shaft. Hand shovels and air jets were again used to clean 
the foundation. Placement of zone I material around the shaft began on 
October 2k, 1975 with same special compaction procedures used as at previous 
concrete structures. By November 1, 1975, special compaction around the 
shaft was finished completing zone 1 special compaction on the dam 
embankment . 



B-83 



Please describe: 

G. The manner in which core material was selected, prepared, placed, and 
compacted outside of the key trench, between Station 18+00 and Station 2+00. 
If special difficulties were encountered, please describe in detail by 
specific location. 

(G) There is no significant difference between this operation and the operation 
described in the answer to (E) previously given. The key trenches, except 
for special compaction areas, were a continuation of the zone 1 fill opera- 
tion. The key trenches were wide enough to permit the spreading and rolling 
equipment to place the key trench areas in a concurrent operation with the 
main body of zone 1 fill. The method of selection, preparation, placement, 
and compaction was the same outside of the key trench areas as inside them. 
We do not know of any particular difficulties associated with this operation. 

The following description of the training procedures used for construction 
personnel and quality control efforts will provide an insight into efforts 
made to select and prepare the zone 1 material for placement in the 
embankment : 

Prior to the start of zone 1 placement in the fall of 1973, the Bureau 
of Reclamation supervisory personnel met with those from Morr i son-Knudsen- 
Kiewit to determine how to precondicion and excavate material from Borrow 
Area "A." It was decided that, for the short construction season left. Bureau 
materials technicians would work in the pit directly with M-K-K personnel 
and that the Bureau would provide laboratory facilities for preplacement 
testing. This would help train M-K-K personnel for control of the pit 
during the following construction season. 

During the winter shutdown following the 1973 construction season, the 
Bureau conducted a training session covering testing procedures for 
earthwork and concrete. Bureau laboratory personnel conducted the session 
in the project laboratory. 

M-K-K requested that their supervisory personnel be allowed to attend 
these sessions. After completion of the initial training session, M-K-K 
requested that the Bureau have an additional day's training covering 
earthwork testing so that they could hove additional personnel receive 
this training. This was done. 

Prior to and during the early part of the 197^ construction season, M-K-K 
had three people work in the Bureau project laboratory to receive training 
before they were allowed to work in M-K-K 's mobile laboratory, which was 
set up in Borrow Area "A" specifically for preplacement testing of the 
material for specifications compliance prior to placement in the dam. 
From the start of the 197'+ construction season and through completion of 
the dam, M-K-K handled the preconditioning and testing of the borrow area 
prior to placing. The Bureau of Reclamation tested the material as 



B-84 



delivered to the dam for specifications compliance. The Bureau provided 
technical assistance and provided special testing whenever requested by 
M-K-K to maintain adequate control of the borrow area. Considerable 
control testing was needed in Borrow Area "A" due to the wide range of 
optimum moisture contents. The optimum moistures ranged from approxi- 
mately 16 percent to 2k percent. It was difficult to determine visually 
or by hand tests whether the material from the pit was within the speci- 
fications limits from placement moisture. 



B-85 



Please describe: 

H. Similarities and significant differences in the appearance of the 
walls and floor of the key trenches in the right and left abutments. 

(H) The walls and floor of the l<ey trench in the right abutment generally 
appeared to have more cracks in the rock than the walls and floor of 
the key trench in the left abutment. 

Both abutments, however, have a highly fractured zone in the top of 
the canyon wall in the rhyolite. 

Profiles through the key trenches are, of course, quite different because 
of the 1-1/2:1 slope adjacent to the spillway on the right abutment key 
trench . 

It is recommended that similarities and differences of the key trenches 
can best be understood by inspecting the panoramic color photos with 
geologic overlays and the detailed geologic maps made of the key trenches 
during construction. 



B-86 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Wallace L Chadwick, Chairman 

Arthur Casagrande 

Howard A Coombs 

Munson W Dowd 

E Montford Fucik 

R Keith Higginson 

Thomas M Leps 

Ralph B Peck 

H Bolton Seed 

Robert B Jansen, Executive Director 



TO: 

FROM: 

SUBJECT; 




October 27, 1976 



Robert R<^Jansen 



Clifford J. Cortright 



Review of "L-29 Construction Reports," Teton Basin Project; 
Lower Teton Division, May 1972 through December 1973 



I have reviewed subject reports available at the Project Office, 

I find no obvious statements in the reports affording a direct clue 
to the cause of failure. 

Copies of individual pages of the reports have been obtained wherever 
they appear to supply factual basic information of value in preparation 
of the Panel's report. 




^r/^^(?M2uf^ 



B-87 



UNITED STATES DEPARTMENT OF THE INTERIOR — STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Wallace L Chadwick, Chairman 

Arthur Casagrande 

Howard A. Coombs 

Munson W Dowd 

E Monlford Fucik 

R- Keith Higginson 

Thomas M. Lcps 

Ralph B Peck 

H Bolton Seed 

Robert B. Jansen. Executive Director 



October 31, 1976 



TO: 



Panel Members 



FROM: 



Robert B. Jansen 



SUBJECT: Meeting with R.R. Robison and His Staff on October 29, 1976 

At 8:30 a.m. on October 29, 1976, C.J, Cortright and I met with 
Project Construction Engineer R.R. Robison and members of his staff 
(P.P. Aberle, Jan Ringel, Harry Parks, Lynn Isaacson, and Keith Rogers) 
in Mr. Robison 's office at the Teton Dam. This meeting had been arranged 
at my request to afford opportunity to amplify and clarify various records, 
especially on project surveillance procedures, and observations in the 
period June 3-5, 1976. I had provided in advance a list of initial 
questions, as follows: 

R.R. Robison 

1. What were the procedures for collecting, plotting, analyzing, 
and reporting on surveillance data? e.g., observation wells. 

2. What were the time intervals in each step of this process? 

3. What reports did you make, oral or written, on the dam's 
condition in June? 

4. Can you provide any more information on the Project Technical 
Record? 

P.P. Aberle 



1. In your statement, you said that you wrote down the time of 
collapse as 11:57 a.m. on June 5. Into what record was this 
written? 

Harry Parks 

1. In your statement, you said that you saw seepage at 7:50 a.m. 
on June 5, 1976 coming out of toe about 50 feet from the north 
abutment wall. You saw leakage 50 feet from the north abutment 
above 5200 elevation at about 10:30 a.m. Can you describe these 
more fully and reconcile them with the observations of others? 



B-88 



Page 2 October 31, 1976 

Letter to Panel Members 



Harry Parks (Cont'd) 

2. Who was the first to see distress in the dam, and what did 
he see? 

Jan Ringel 

1. Did you inspect the leak alone at 8:00 a.m. on June 5, 1976? 
Or did somebody from the survey crew accompany you? Did you 
inspect leaks other than what was reported to you by the surveyors? 

General Question 

1. What was the time of each significant observation on June 5, 
1976, as you can reconstruct it now? 

In response to the first three questions, Mr. Robison described the 
oral instructions that he had given and the specific assignments that he 
had made to watch for any adverse conditions at the dam. He also discussed 
his communications with USER offices in Boise and Denver. He and Mr. Aberle 
described their personal efforts in making patrols and in reviewing inspec- 
tors' reports. I asked for, and Mr. Robison agreed to provide, a written 
description of all this activity so that it can be documented for the Panel's 
report. 

Regarding the fourth question, Mr. Robison said that the construction 
report data already made available to the Panel constitutes the Project 
Office's contribution to date to the Project Technical Record. He also 
agreed to provide us with copies of his weekly construction reports. 

Mr. Aberle said that his entry of the time of dam collapse was made 
on a desk pad in the Project Office. 

Responding to our first question to him, Harry Parks commented that 
he and his survey party were at such a distance from the seepage area at 
7:50^^ a.m. that all they saw was an apparent ponding of water at the toe 
of the dam. They were really too far away to say that it was "coming out 
of the toe." As to the location of the leakage at El. 5200, we were 
referred to the photography of the leak, which Parks and the others suggest 
is the best record. Parks recalls that he and his crew members all saw 
the water on the 5041.5 berm at the same time. He and Ringel confirm that 
Parks went into Ringel 's office alone to report the leakage. 



B-89 



Page 3 October 31, 1976 

Letter to Panel Members 



Jan Ringel said that immediately after being alerted by Parks, he 
went alone to the toe of the dam to inspect the reported leakage. He 
did not see other active leakage at that time, but he did note that water 
had been flowing down the right groin during the night of June 4, or early 
in the morning of June 5. This was evidenced by a shallow eroded channel 
that had not been there at 9:00 p.m. on the preceding night. Although 
there was no water in this erosion channel, it was damp in places. 

In reply to the general question about the times of significant 
observations on June 5, there appeared to be agreement in retrospect that 
the loud burst and the concurrent rapid enlargement of flow at approxi- 
mately El. 5200 occurred at about 10:30 a.m. rather than 10:00 a.m., as 
had been previously reported. Mr. Robison said that when this happened 
he did not have his car and he ran all the way to the office to telephone 
the sheriffs. The call to the Sheriff of Fremont County was logged at 
10:43 a.m. 

The times earlier and later in the morning as reported in the sworn 
statements are regarded by the Project staff as more accurate. Robison, 
Aberle, and Ringel agree that Robison and Aberle arrived separately at the 
dam headquarters building, but nearly at the same time - about 8:50 a.m. 
Since they almost immediately proceeded down to see the leakage, they 
believe that the reported time of this observation was reasonably accurate. 
The 11:57 a.m. time of collapse is seen as precise ("within one-half minute 
or so") because it was marked by the power outage and consequent stopping 
of an electric clock at the Project Office, whose power came through the 
system in the canyon just below the dam. 

Mr. Robison reports that the flow first observed at El. 5045 was from 
the talus, not formation rock. I asked him if the talus at the toe of the 
right canyon wall could have carried appreciable flow without such flow 
being apparent on the surface. He believes this to be entirely possible. 

When asked to describe the hole at El. 5200, Mr. Robison said that 
from his vantage point looking directly into it, the hole was a tunnel 
about six feet in diameter running roughly perpendicular to the dam axis 
and extending back into the embankment for about 35 feet - as far as he 
could see. 

Regarding the early stages of this leak, which developed a short 
distance south and about at the same elevation as the 2 cfs spring at 
El. 5200, the "wet spot" observed by Berry at about 8:30 a.m. is believed 



B-90 



Page 4 October 31, 1976 

Letter to Panel Members 



by Robison, Aberle and Ringel to have been a damp part of the erosion 
channel which they have described. They say that they noticed that this 
channel had curved out a little ways from the abutment, as can be seen 
in photographs . 

Robison and Aberle also question the wet spot location reported by 
David Burch as 100 feet from the abutment. They say that examination 
of the failure photographs alone shows this distance to be inaccurate. 

Parks says that the seepage observed by Berry and Ferber between 
7:00 a.m. and 8:00 a.m. was at the toe, on the 5041.5 berm, and not at 
El. 5200. 

Answering a question about the location of the whirlpool on June 5, 
Robison and Aberle agreed that it was probably not as close to the abutment 
as they previously had estimated. Robison said that it was directly 
opposite the sinkhole on the downstream face. He and Aberle would now 
estimate that it may have been as far out as 13+70 or 13+80. (This would 
put it more in line with a section through the grout-cap break, the 
sinkhole, and the leaks at El. 5200 and El. 5045.) 

We also discussed whether seepage and leakage amounts were all esti- 
mated by visual observation or if some measuring devices were used. Robison 
and Aberle said that devices were planned but not yet installed. They both 
have considerable experience in flow measurement and estimating, and they 
believe that their judgments of the spring and leakage flows are reasonably 
accurate . 

Robison also informed us that the first observations of springs 
flowing from formation rock downstream from the spillway stilling basin 
on June 3 (the only flows observed from formation rock in the pre-failure 
period June 3-5) resulted from his dispatching Ken Hoyt, Construction 
Inspector, to that area to conduct surveillance. Hoyt thus made his 
discovery of the springs, which were observed later by Robison and by 
Aberle. 

I asked how much discharge was actually passed through the auxiliary 
outlet on June 5. Robison said that it got up to about 900 cfs, compared 
with the specified operational limit of 850 cfs. Aberle said that the 
gates were open about 69 percent. They had consulted with the designer 
to get guidance on how much to exceed the limit and were told that up 
to even 1,000 cfs would probably be all right. However, they decided not 
to push it that far, so as to avoid possible damaging vibration. 



B-91 



Page 5 

Letter to Panel Members 



October 31, 1976 



Mr. Robison raised the subject of treatment of the rock joints and 
cracks in the key trench. He says that during construction he and his 
men did not observe openings in the rock such as are now exposed in 
the breach on the right abutment. He says that if they had, they would 
have done something about them. Robison also stated that slush grouting 
is uncommon in USER practice and that the designers did not expect the 
construction forces to initiate such treatment. 

Sincerely, 




cc: 

C.J. Cortright 

L.B. James 



B-92 




IN REPLY 
REFER TO: 

510.- 



1300 



United States Department of the Interior 

BUREAU OF RECLAMATION 

OFFICE OF DESIGN AND CONSTRUCTION 

ENGINEERING AND RESEARCH CENTER 

P.O. BOX 25007 

BUILDING 67, DENVER FEDERAL CENTER 

DENVER, COLORADO 80225 

'1 

NOV 3 1976 




Mr. Robert^&nsen 

P.O. BOX/K43 

Idaho P^ls, ID 83401 



Dear Mr. Jansen: 

Please refer to Mr. Chadwick's two telegrams dated June 11 and 14, 
1976, addressed to me. I understand from Mr. Guy of my staff that 
all the requested information has been supplied except item 9, 
"Record Cofferdam Seepage and Pumpage from Foundation Area". We 
do not have very much data on these activities. 

Drawing No. 549-147-170 which is contained in exhibit 32 shows the 
arrangement of the dewatering effort in the cutoff trench and the Q 
on November 30, 1973. I have enclosed an additional copy of this 
drawing for your ready reference. The contractor submitted a rather 
voluminous claim for differing site conditions in the cutoff trench. 
Exhibit E of the contractor's April 11, 1975 claim contains the report 
"Changed Conditions - Cutoff Trench Excavation - Teton Dam" by 
Woodward, Thorfinnson & Associates. This report contains photographs 
of some seepage into the COT. Also of interest would be the USER 
report entitled "Cutoff Trench Report". Both reports are available 
at the Teton Project Office. 

Seepage through the cofferdam occurred in June of 1974. The following 
is quoted from the 1974 L-29 Monthly Construction Report: 



^^OUJT-O^^^ 




'^p-e-AQi* 



"River Runoff - The flow of the Teton River has been above 
normal through the month due to an above normal snowpack 
in the drainage area and continued above normal temperatures. 
The water flow through the river outlet works tunnel peaked 
at approximately 4,100 c.f.s. on June 20 with the upstream 
pool elevation at 5074.2. A temporary bulkhead previously 
installed at the upstream portal of the auxiliary outlet 
works tunnel prevented any water flows through the auxiliary 
outlet works tunnel. Some seepage occurred through the up- 
stream zone 4 and zone 2 embankment and around the zone 4 
and left abutment contact. Pumps were installed by the 
contractor to prevent this seepage from flooding the zone 1 
embankment." 



B-93 



The locations of these seepages are approximately as follows: 

Through cofferdam at centerline station 23+40 

Around left end of cofferdam at centerline station 24+OOd: 

Project photographs P549-147-4397 NA and P549-147-4426 show the 
upstream and downstream views of the cofferdam In June of 1974. 
You may also wish to discuss the cofferdam and COT seepage locations 
and quantities with specific project personnel. 




H. A^. Arthur 

Director 

Design and Construction 



Enclosure 



B-94 




IN REPLY 
REFER TO: 

510.- 



1300 



United States Department of the Interior 

BUREAU OF RECLAMATION 

ENGINEERING AND RESEARCH CENTER 

P.O. BOX 25007 

BUILDING 67, DENVER FEDERAL CENTER 

DENVER, COLORADO 80225 



NOV 3 W6 




Mr. Robert, 
P.O. Box/L643 
Idaho ^lls, 

Dear Mr. Jans en: 



83401 



The information requested by the Independent Panel to Review the Cause 
of Teton Dam Failure in your letter of October 12, 1976, is listed 
below in the same numbering format as in your request. Exhibits 24 and 
39 were the sources for the information. 

1. Grain size distribution 

a. Borrow area investigations, zone 1, design. - During the 
design phase, two borrow areas were investigated for zone 1 
material, "A" and "B". Only "A" was used in construction of 
the dam. In exhibit 24 are the grain size curves for each 
borrow sample and the standard properties summary (memorandum 
of May 27, 1970). Twenty-one samples 51B-1 through 51B-21 
representative of area "A" were tested. 

Clay (< 0.005mm) 14 percent, standard deviation = 5.7 percent 
Silt (0.005 to 0.074mm) 66 percent, standard deviation = 13.7 

percent 
Sand (0.074mm to No. 4 size) 19 percent, standard 

deviation = 11.3 percent 



deviation = 11.3 percent 

nples contained gravel, 12 percent and 30 percent 
actively 



:ing 



Two samp 

respectively 
Test pit A2 (18-foot depth) samples were composited for 

shear, percolation, compaction, and compression testir 
Grain sizes for the composite sample (51Bx46) were: 

Clay - 10 percent, silt - 74 percent, and sand - 16 percent 

b. Undisturbed samples from cutoff trench, zone L - Results 
of tests are discussed in a memorandum of October 6, 1975, a 
part of exhibit 24. The four samples were obtained between 
stations 19+00.7 and 20+51.3. Mean grain size distribution is; 
Clay - 19 percent, silt - 74 percent, and sand - 7 percent. 




'■'^6-19'''^ 



Bj95 



c. Dynamic analysis testing, zone 1. - Samples, Denison type, 
taken from a hole about 100 feet upstream centerline at about 
station 20+00 with embankment at about elevation 5130. Two- 
foot long samples were taken at 10-foot intervals and were 
numbered 51B-48 through 51B-67(20), exhibit 24, "Testing for 
Dynamic Analysis". 

Clay 23 percent, standard deviation = 6.5 percent 
Silt 71 percent, standard deviation = 7.2 percent 
Sand 6 percent, standard deviation = 3.4 percent 
Inplace dry density, 105.1 pcf, standard deviation = 6.5 per- 
cent 
Inplace water content, 21.2 percent, standard deviation 

= 2.8 percent 
Proctor density - 102.9, moisture 18.2 

Atterberg limits 

a. Borrow area investigations, zone 1 design. - See discussion 
under l.a. Of the 21 samples tested 14 were nonplastic. The 
remaining had a mean liquid limit of 27 and standard deviation 
of 1.6; plasticity index of 4, and standard deviation of 2.0. 
See exhibit 24, memorandum of May 27, 1970. 

b. Undisturbed samples from cutoff trench, zone 1. - See l.b. 
Two samples were nonplastic and the other two averaged 26 for 
LL and 4-1/2 for PI. 

c. Dynamic analysis testing, zone 1. - See I.e. None of the 
20 samples were nonplastic. LL = 27, standard deviation = 1.2; 
PI = 5, standard deviation = 1.9. 

Permeability tests 

a. Borrow area investigations, zone 1, design. - See discussion 
under l.a. Composite sample (x-46) had permeability of 0.32 
feet per year, placed at a dry density of 98.8 pcf, 21.9 percent 
moisture, and a 100 psi load. See exhibit 24, memorandum of 
May 27, 1970. 

b. Undisturbed samples from cutoff trench, zone 1. - See l.b. 
The four samples were taken to perform horizontal permeability 
tests on the undisturbed samples. In place densities varied 
from 85.7 to 89.4 pcf. Lateral pressure of 25, 55, and 75 psi 
were applied to the outside of the membranes. Testing was 
performed in the high-pressure permeability test apparatus which 
uses pressurized permanent water to dissolve entrapped air and 
usually shows a higher permeability than a standard permeability 
test. Pressures in the permanent water were held at 5 psi below 
the applied lateral pressure. Hydraulic gradients were varied 
from 36 to 495. Coefficients of permeability at 55 psi varied 
from 3.2 to 13.0 feet per year. 



B-96 



c. Dynamic analysis testing, zone 1. -No test. 

d. Construction control record tests, zone 1. - Data sheets 
for record tests are in exhibit 39 following the zone 1 con- 
struction control tests (form 7-1352). Number of tests = 147, 
mean = 0.47 feet per year, standard deviation = 0.67, the range 
of values was 0.02 to 3.57 feet per year. Fourteen tests had 
values over 1.0 feet per year. When these are excluded, values 
are: Mean = 0.29 feet per year, standard deviation = 0.24. 

e. Construction control record tests, zone 2. - Data sheets 
for these large permeability tests are at the end of exhibit 39. 
The 14 test values ranged from 0.71 to 2979.6 with a mean of 
137 feet per year and a standard deviation of 474. 

Triaxial tests 

a. Borrow area investigations, zone 1, design. - See discussion 
under l.a. Composite sample (x-46) was tested in an unconsoli- 
dated undrained test. Tan 0'= 0.64 and c'= 11.3 psi corrected 
for pore pressure. Nonlinear parameters for constitutive models 
were not obtained as standard practice at the time these tests 
were made. See exhibit 24, memorandum of May 27, 1970. 

b. Undisturbed samples from cutoff trench, zone 1. - No test. 

c. Dynamic analysis testing, zone 1. - See I.e. Testing was 
done on remolded specimens made from composited material from 
the 20 samples. Tests were consolidated drained. Tan 0' = 0.70, 
c' = 0.2 psi. The tests were run with back pressure to insure 
saturation. Nonlinear parameters for the hyperbolic stress- 
strain constitutive model were only calculated for the "raw" lab 
data. Values for use in finite element analysis should be 
obtained from corrected and/or smoothed lab stress-strain curves. 
Preliminary parameters are: K = 470, n = 0.12, Rf = 0.78, 

G = 0.35, F = -.17 (slope indicates decrease in "G" with increase 
in confining pressure), d = 3.8. See exhibit 24 for plots. 

Compression tests 

a. Borrow area investigations, zone 1, design. - See discussion 
under l.a. Composite sample (x-46) was tested. Placement dry 
density of 96.0 pcf, moisture content of 19.9 percent, degree of 
saturation of 72.5 percent. Maximum consolidation was 10.3 per- 
cent under 600 psi load and 10.4 percent saturated under 600 psi 
load. See exhibit 24, memorandum of May 27, 1970. 

b. Undisturbed samples from cutoff trench, zone 1. - No test. 



3 

B-97 



c. Dynamic analysis testing, zone 1. - See I.e. Testing was 
done on remolded specimens made from composited material from 
the 20 samples. Placement conditions were: dry density = 
100.1 pcf, moisture = 18.5 percent, degree of saturation = 
75.2 percent. Maximum consolidation was 7.95 percent at 
300 psi load and 8.05 percent saturated under 300 psi load. 
See exhibit 24 for plots. 



Very truly yours. 




■?•/: 



G. Arthur 
Director 
Design and Construction 



B-98 



November 3, 1976 



Mr. Harold G. Arthur 

Director of Design and Construction 

U.S. Bureau of Reclamation 

Bldg. 67, Denver Federal Center 

Denver, Colorado 80225 



Dear Mr. Arthur: 



It has come to our Panel's attention that regularized inspections 
of Teton Dam construction were made by representatives of your Denver 
organization, with records of related observations in the form of trip 
reports. Because we have not found such records in the docuraents pre- 
viously furnished our Panel by your office, we will appreciate receiving 
the file of these reports and any related responses as early as is 
reasonably possible. 

Thanks in advance for your usual cooperation. 

Very truly yours. 



Wallace L. Chadwick 
Chairman 

cc: 

Dennis Sachs, USBR, Washington, D.C. 



B-99 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Wallace L Chadwick. Chairman 

Arthur Casagrande 

Howard A, Coombs 

Munson W Dowd 

E Montford Fucik 

R. Keith Higginson 

Thomas M. Lcps 

Ralph B Peck 

H Bolton Seed 

Robert B Jansen, Executive Director 



November 3, 1976 



Honorable Thomas S. Kleppe, Secretary 
United States Department of the Interior 
Interior Building 
Washington, D.C. 20240 



Honorable Cecil D. Andrus, Governor 
State of Idaho 



Capitol Building 
Boise, Idaho 83720 



Gentlemen: 

The Independent Panel to Review Cause of Teton Dam Failure has the 
following progress to report. 

Technical working sessions were conducted in Idaho Falls in the period 
November 1-3, 1976, with eight of the nine Panel members in attendance. 
On November 1, inspection was made of the drilling sites and the foundation 
areas uncovered by excavation on the right abutment. An examination of the 
lower right canyon wall was accomplished by boat. 

Excavation of the embankment remnant on the right abutment has been 
completed and the rock surface has been sluiced. The grout cap is missing 
in the 30-foot interval between Stations 13+86 and 14+16. It is fully 
intact above this breach and extends continuously although severely eroded 
at several locations below this point to Station 14+85, beyond which it is 
missing at least to the present river level. 

Mapping of joints and cracks in the right abutment rock continues. 
This has been facilitated by the sluicing which was completed during the 
last week in October. 

In mid-October, ponding tests were performed on rock joints adjacent 
to the grout cap between Stations 12+73 and 13+40 on the right abutment. 
There was resultant flow under the cap at one point. In view of this, the 
Panel's planned program for drilling and water testing in that area has 
been expanded and is underway. Additional ponding tests are also being 
made. 



B-lOO 



Page 2 November 3, 1976 

Letter to Honorable Thomas S. Kleppe and Honorable Cecil D. Andrus 

Initial results have been received from two of the four laboratories 
performing tests on soil specimens taken from the dam remnant on the right 
abutment. These data are being studied by the Panel. 

During the technical working sessions of November 1-3, consideration 
was given to finite-element stress analyses prepared by the Dynamic 
Analysis Corporation and by the University of California at Berkeley. 

To obtain field correlation with these analytical data, a hole is 
being bored into the left abutment embankment at Station 26+25 for a 
hydraulic fracturing test. 

Investigative exploration near the right end of the dam is well 
advanced. Drilling and water testing of nine holes in the foundation under 
the spillway crest indicated that the grouted rock at that location was 
satisfactorily impermeable. The boring at Station 4+34 was terminated 
at a depth of 600 feet, having penetrated the sediments underlying the 
volcanics for an interval of about 80 feet. Sediment samples will be 
tested. A larger-diameter hole is being started nearby, at Station 4+29, 
with the objective of exploring the sediments to greater depth and for 
taking other specimens that can be tested. The angle holes on either 
side of the 600-foot hole have been completed and water tested. The 
results of all these borings are being analyzed by the Panel. 

A model of the right side of the dam and its abutment is being fabri- 
cated by a firm in Salt Lake City. It is expected to be ready for the 
Panel's use by November 15. The model should facilitate visualization of 
principal features that relate to the mechanism of failure. 

The contractor's work in the river channel continues, with the objective 
of lowering the water level in the pool just below the dam during the next 
six weeks. Once this is accomplished, the Panel will make inspection of 
the base of the right abutment. 

The Panel has continued its analyses of the data collected and of 
the hypotheses of failure previously reported. Progress has been made in 
the assembling and drafting of material intended for use in the final report, 
which is still expected to be ready for submittal by December 31, 1976. 

In all phases of its work, the Panel has been helped immeasurably by 
the consistent cooperation of you and your agencies. Your support has been 
essential and is appreciated. 



B-101 



Page 3 November 3, 1976 

Letter to Honorable Thomas S. Kleppe and Honorable Cecil D. Andrus 



The next technical working sessions of the Panel are scheduled for 
December 7-10, 1976. 



Respectfully submitted. 



Wallace L. Chadwick, Chairman 
Independent Panel to Review Cause 
of Teton Dam Failure 



B-102 




United States Department of the Interior 



IN REPLY 
REFER TO: 



BUREAU OF RECLAMATION 
TETON PROJFXT OFFICE 
P.O. BO.X 88 
• NEWDALE, ID,\HO 8343fi 

/T November 12, 1976 



Mr. Robert J^sen 
Executi veBi rector 
Independent Panel 
539 Qtystreet 
Idahj/Falls, ID 83401 

Dear Mr. Jansen: 



Enclosed are project memorandums concerning processing of 
observation well data and the project's observation program 
for reservoir leakage, which you requested. 

Sincerely yours. 




Robert R. Robison 

Project Construction Engineer 



Enclosures 



cc: Director of Design and Construction, Denver, Colorado 
Attn : 1 300 

Regional Director, Boise, Idaho 
Attn : 200 

Teton Dam Repository, Washington, DC 
Attn: 1600 
Mr. Dennis Sachs, Deputy Assistant Secretary, Washington, DC 



^<.-°^r^^. 







B-103 



OPTIONAL FORM NO. 10 

^!AY U?? EDITION 

GSA FPMR (t\ cFB) lOI-n.f 



UNITED STATES GO\ERNMENT 

Memorandum 



TO 



Project Construction Engineer 



date: Nov. 10, 1976 



FROM 



Contract Administration 



subject: Compiling Data for Observation Wells 

Subsequent to the receipt of a letter from the Regional Director, subject, 
monitoring ground level water wells, assignments were made to the various 
divisions for gathering and reporting this data. Contract Administration 
was assigned the responsibility of compiling the data received from field 
observations. Mr. Mike Brenchley was given the responsibility of developing 
a system of graphs and charts upon which the data from the observations could 
be compiled showing locations and number of wells observed. Charts were developed 
on which to compile the readings. Due to Mr. Brenchley resigning, the responsi- 
bility was given to Mr, Keith Rogers. 

It was our intent that the readings should be compiled and forwarded to the 
Regional office and Denver office personnel interested in this data at least 
once each month. Subsequent to the water being stored in the reservoir, Mr. 
Rogers would receive the data and plot them on the charts as they were submitted 
in the field. I would review them periodically at least once each week to see 
if there was any significant changes in Ihe water level shown. Approximately 
once each month we would assign a cutoff date that the charts would be brought 
up to date, the readings would be recorded and the data sent off to the various 
offices. The reservoir started filling so rapidly in the spring that recordings 
were read at more frequent intervals. Periodically we would meet with Mr. 
Robison and would look over the readings and discuss the changes noted. The 
last month before the dam failure, we noted a significant rise in water level 
shown on these readings. This was discussed with representatives of Director 
of Design and Construction, Denver. It was decided to make a special effort at 
this time to compile the data from the observation wells in order to forward them 
at a closer, interval than in the past. 



bcc: CA, Joseph Lynn Isaacson 11-10-76 // ^ /y 






Noted: 




^iy^'^^'tr^-^f'-ir 



Project Construction Engineer 




Buy U.S. Savings Bonds Regularly on the Payroll Savings Plan 

B-104 



OITIO'JAL FOr.M tiO. 10 

MAY Itei EDITION 

CSA FPWR (41 CFft) lOl-ll.t 



UNITED STATES GOVERNMENT 

Memorandum 



TO 



Project Construction Engineer 



date: Nov. 9, 1976 



i-ROM : Field Engineer 



subject: Observation Program for Reservoir Leakage 

At the time of closure of the river outlet works on October 3, 1975, 
an observation program for leakage of the reservoir was initiated. 
Mr. Al Stites, who was assigned to the inspection of the river outlet 
works area, was assigned to observe for leaks on the left abutment 
and powerhouse area, Mr. Frank Emrich, who was assigned to inspection 
of works in the R.O.W. gate chamber and shaft areas, was assigned to 
watch for leaks through the concrete in these areas. These leaks were 
measured and estimated as to the amount of water. However, they were 
very minimal at all times. 

Mr. Gary Larson was assigned to watch for leaks in the A.O.W. shaft, 
spillway drains and the area to the right of the spillway. It was 
felt by the project forces that if any leakage would occur around 
or through the right abutnent, it would initially show up in the gully 
located to the right of the spillway. 

The area davnstream of the spillway area was observed from across the 
river on a daily basis by the inspection forces and myself and leaks 
of any consequence could be detected by watching for water flows from 
the drain downstream of the spillway along the right abutment into the 
river. All inspectors were instructed to be aware for leakage and to 
report these leaks immediately. 

During the month of May, the contractor (MK-K) cut a small hole into 
a water storage pond which was located high on the right abutment for 
the purpose of draining it. Water from this pond drained into the 
gully located to the right of the spillway. This water was detected 
almost immediately by the inspection forces and reported which shows 
the awareness of the program. 

About ten days prior to June 4, I received a call from Mr. Duane 
Buckert, Project Manager for MK-K, stating that their Office Engineer, 
Vince Poxleitner, thought he saw a leak downstream of the spillway. 
This was checked out by the inspection forces and found to be neg- 
ative. 

After well no. 6 showed an exceedingly rapid increase of the water 
level, I made an inspection of the right ebutrnent about 1200 to 1700 
feet downstream of the dam and the gully in this area. This inspection 
was made on or about June 1, 1976, and no leaks were noted. 



/.i-S 



W 
M 



Buji U.S. Savings Bo>ids Regularly on the Payroll Savings Plan 

B-105 



On Thursday, June 3, 1976, when the two leaks were found downstream of 
the spillway, I checked along the canyon downstream of these leaks an 
additional 500 feet and found no leaks. 

On the morning of June 5, as I drove to the powerhouse area, I again 
visually checked the spillway drains and the gully to the right of 
the spillway and saw no leaks. 

At least once a week I instructed the shift inspector to remind all 
inspectors to watch daily for possible leaks. These reminders were 
also made by myself several times during the weekly safety meeting 
held by the inspection forces each Monday morning. 

As soon as the ice cleared from the reservoir area, the reservoir was 
inspected two to three times per week. The shoreline was patroled near 
the damsite and potential land slides were noted and reported throughout 
the reservoir area. ^,^ v X^^ ^ i , 



J^lXu^- 



NOTED: ^t^^^^" .-^2^ 

Project Construction Engineer 



B-106 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Wallace L Chadwick. Chairman 

Arthur Casagrande 

Howard A Coombs 

Munson W Dowd 

E Montlord Fucik 

R Keith Higginson 

Thomas M, Leps 

Ralph B Peck 

H Bolton Seed 

Robert B. Jansen, Executive Director 



November 16, 1976 



TO: 
FROM 



:^ 



R.B. Jansen, Executive Director 
L.B. James, Staff Geologist 



SUBJECT: Exploration of the Rock Fissure Passing Through Station 4+34 
at Teton Dam 

The subject fissure, which was exposed during excavation of the keyway 
in the right abutment, was entered and examined shortly after its discovery 
by Mr. Steve Ellenberger, Construction Inspector for the U.S. Bureau of 
Reclamation. This fissure is shown in plan and cross-section on USBR 
Drawings Nos . 549-147-133 and 134, which are being reproduced for Chapter 5 
of the Panel's report. There follows a siommary of the interview I had with 
Mr. Ellenberger on November 11, 1976 during which he described his observa- 
tions. 

Mr. Ellenberger described that portion of the fissure that lies down- 
stream of the keyway as averaging about 4 feet wide, except for some places 
where he could "outstretch his arms without touching either wall." At one 
place he noted a white popcorn-like lining on the walls, and at another a 
coating of red substance that rubbed off on his clothes. Blocks of rock 
with dimensions up to 4 to 5 feet on a side were encountered which he 
climbed over or crawled under as he made his way downward. Passage was 
finally blocked by a rock "the size of a pickup truck." He could look 
through a narrow opening into a room or passage that lay beyond, but could 
not see the end of the fissure. At this furthest point from the entrance, 
he judged that he had traveled laterally about 100 feet from the downstream 
wall of the keyway and that he was roughly 100 feet below keyway invert 
elevation. The walls remained fairly consistently 4 feet apart to this 
depth and showed no indication of converging below this point. 

The segment of fissure lying upstream of the keyway was described as 
1 to 1-1/2 feet wide and steep, but apparently flattening toward the north 
with depth. It was lined with stalactites and stalagmites, mostly about 
3/8 inch in diameter. One stretch was coated with a mineral lining which 
displayed a "popcorn-like" appearance. Mr. Ellenberger edged his way 
laterally through this crack for about 100 feet where he squeezed through 
an opening into a chamber about 4 feet by 4 feet by 5 feet in dimensions . 



B-107 



Page 2 November 16, 1976 

Memo to R.B. Jansen from L.B. James 

SUBJECT: Exploration of the Rock Fissure Passing Through Station 4+34 
at Teton Dam 

He noted that the joint continued beyond this chamber but that its walls 
converged and turned. He was unable to explore further and could not 
determine whether the fissure reopened or pinched out entirely beyond 
this point. 

Mr. Ellenberger noted that on cold days vapor could be seen emitting 
from the segment of the fissure that extended downstream of the keyway 
and this segment seemed warm and could be entered in winter without a 
jacket. Conversely, in the upstream segment he felt cold. 



cc: 

Panel Members 
C.J. Cortright 
F . B . Sherman 



B-108 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Wallace L Chadwick. Chairman 

Arthur Casagrande 

Howard A Coombs 

Munson W Dowd 

E. Montford Fucik 

R Keith Higginson 

Thomas M Leps 

Ralph B Peck 

H Bolton Seed 

Robert B Jansen, Executive Director 



November 18, 1976 



TO: Robert B. Jansen 

FROM: Clifford J. Cortright 

SUBJECT: Review of L-29 Construction Reports, Teton Basin Project, 
Lower Teton Division, January 1975 through April 1976 

I have reviewed subject reports available at the Project Office. 

I find no statements in the reports that can be directly associated 
with the cause of failure. In fact, these reports are totally devoid 
of any statements commenting on the quality of construction, disputes, 
conformance with specifications, or discussions of problem situations 
encountered and the manner in which they were solved. Several photos, 
although taken from a distance, do give some insight into the general 
nature of the quality of the embankment foundation beneath Zones 1, 2, 
and 5 along the right abutment . Zone 1 in the key trench appears 
excavated into the rhyolite rock formations . Zone 1 elsewhere was 
stripped only to the rhyolite surface. The foundation for Zones 2 and 5 
appears to be stripped of vegetation only. 

Prints and captions of these photos are attached for later reference 
if needed. 



End . 

Photos P549-147-5480 
-5733 
-5735 
-5859 
-5876 
-5883 



B-109 




Project Photo P 549-147-5480 NA 4/1/75 Embankment at 5145 



B-110 




Project Photo P 549-147-5733 NA 5/27/75 Embankment at 5150 



B-li; 




Project Photo P 549-147-5735 NA 5/27/75 Embankment at 5 1 50 



B-112 




Project Photo P 549-147-5859 6/26/75 Embankment at 5170 



B-113 




Project Photo P 549-147-5876 NA 7/22/75 Embankment at 5185 



B-114 




..--^^■*S- 







*r. 




«^ 



jj-- 



ML-. 



^"^ "^ 






^«. 



^^ 



Project Photo P 549-147-5883 NA 7/22/75 Embankment at 5 1 85 



B-115 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Wallace L Chadwick, Chairman 

Arthur Casagrande 

Howard A. Coombs 

Munson W Dowd 

E. Montlord Fucik 

R. Keith Higginson 

Thomas M Leps 

Ralph B Peck 

H. Bolton Seed 

Robert B. Jansen. Executive Director 



November 22, 1976 



TO: Robert B. Jansen 

FROM: Clifford J. Cortright 

SUBJECT: Teton Project Time Lapse Photo Record 



The following Project Photographer's time lapse photo roll numbers 
were viewed by either Mr. Cole or myself: 

9, 27, 29, 39, 97, 113, 115, 120, 125, 127, 133, 135, 
148, 150, 155, 158, 162, 171, 175 and 179 

The rolls viewed were selected on the basis that they might be 
informative with regard to foundation preparation and embankment place- 
ment at the right abutment in the general vicinity of the failure and 
that they might afford some insight into the cause of failure. 

Unfortunately, the camera setup was usually at quite some distance 
from the main area of interest and no revealing detail of the abutment 
rock surface, quality of foundation cleanup, or manner of embankment 
placement against the abutment is visible. 

A 16 mm reel exposed May 19, 1976 was also previewed. The canyon 
wall above the downstream right abutment groin and portions of the down- 
stream embankment slope are visible in the background while the camera 
was recording a slope dressing operation by bulldozing. At the distance 
recorded, the degree of detail is not very great. No evidence is apparent 
of failure -related phenomena such as moisture, seepage, or leakage. 




B-116 



UNITED STATES DEPARTMENT OF THE INTERIOR — STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 



Wallace L Chadwick, Chairman 

Arthur Casagrande 

Howard A Coombs 

Munson W Dowd 

E Montford Fucik 

R. Keith Higginson 

Thomas M. Leps 

Ralph B Peck 

H "olton Seed 

Rojert B Janscn. Executive Director 

December 1, 1976 

TO: Robert B. Jans en 

FROM: Clifford J. Cortright 

SUBJECT: Review of L-29 Construction Reports, Teton Basin Project, 
Lower Teton Division, January 1974 through December 1974 

I have reviewed subject reports available at the Project Office. 

I find no statements in the reports that can be directly revealing 
as to the cause of failure. 



^^.^^^w/^/tA^^ 



B-117 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 

Wallace L Chadwick, Chairman 

Arthur Casagrande 

Howard A. Coombs 

Munson W. Dowd 

E. Montford Fucik 

R. Keith Higginson 

Thomas M. Leps 

Ralph B Peck 

H Bolton Seed 

Robert B Jansen, Executive Director 



December 10, 1976 



Honorable Thomas S. Kleppe, Secretary- 
United States Department of the Interior 
Interior Building 
Washington, D.C. 20240 



Honorable Cecil D. Andrus, Governor 
State of Idaho 



Capitol Building 
Boise, Idaho 83720 



Gentlemen: 

The Independent Panel to Review Cause of Teton Dam Failure has continued 
with its work under your charge and submits the following report of its 
progress . 

The Panel held its final technical working sessions in Idaho Falls 
December 7 through 10, 1976, with all members participating. On December 7 
the Panel examined the recently completed model of the right side of the dam 
and its abutment. This model depicts well the principal site features which 
are pertinent to the failure. 

Site Work 

Mapping of joints and cracks in the rock of the right abutment of the 
dam has been completed and the results are being analyzed. 

Ponding and water-pressure testing of the foundation along the grout cap 
on the right abutment have been completed. The tests accomplished in that 
area, during the past month, showed some water flow through the jointed rock 
under low pressure immediately under the grout cap. This evidence of the 
rock condition supplements the ponding test results reported by the Panel on 
November 3, 1976. 

The Panel's program of hydraulic fracturing tests in three borings 
in the dam embankment remnant on the left side of the canyon has been 
completed. 



B-118 



Page 2 December 10, 1976 

Letter to Honorable Thomas S. Kleppe and Honorable Cecil D. Andrus 

Investigative exploration of the foundation near the right end of the 
dam to assess the possibility of differential settlement is approaching 
completion. The previously reported drilling of a large-diameter hole into 
the deep underlying sediments has been advanced to a depth of about 900 
feet, having penetrated the sediments for an interval of about 400 feet. 
With the completion of this drill hole, the Panel's investigation at the 
damsite will be concluded. 

Excavation of the river channel and related work under Bureau of 
Reclamation Contract No. DC-7232 with Gibbons and Reed Co., have progressed 
so that some lowering of the reservoir and the intermediate pool just down- 
stream from the dam has been possible. This has exposed more of the founda- 
tion rock for inspection. 

Laboratory Testing 

Soils testing results have been received from all five laboratories 
providing support services to the Panel: Northern Testing Laboratories in 
Billings, Montana; Waterways Experiment Station of Corps of Engineers in 
Vicksburg, Mississippi; Bureau of Reclamation laboratory in Denver, the 
University of California laboratory at Davis, and Geo-Testing, Inc., of 
San Rafael, California. The results have been analyzed and are being used 
in developing the Panel's conclusions. 

Analyses 

Analyses of data collected from record examination and from field 
investigation and testing have been essentially completed. The results have 
been used to weigh the various hypotheses of failure reported earlier. 

As investigation results have been obtained and correlated between data 
sources, the full record has been supplied to the Interior Review Group. 

Final Report 

The preparation of material for the Panel's final report has progressed 
on schedule, and the report will be completed by the contract date of 
December 31, 1976. This completion within schedule has been facilitated greatly 
by the continuing full support forthcoming from your offices. 

Respectfully submitted. 



Wallace L. Chadwick, Chairman 
Independent Panel to Review Cause 
of Teton Dam Failure 



B-119 



UNITED STATES DEPARTMENT OF THE INTERIOR - STATE OF IDAHO 
INDEPENDENT PANEL TO REVIEW CAUSE OF TETON DAM FAILURE 

Wallace L. Chadwick, Chairman 

Arthur Casagrande 

Howard A. Coombs 

Munson W. Dowd 

E. Montford Fucik 

R. Keith Higginson 

Thomas M. Leps 

Ralph B. Peck 

H Bolton Seed 

Robert B. Jansen, Executive Director December 11, 1976 



Memorandiim 



To: 



Robert B. Jansen 
Executive Director 



Prom: Laurence B. James 
Staff Geologist 

Subject: Bore Hole Photography 
DH652 

In response to your request, I have reviewed the letter to you on this 
subject from Don C. Banks, Chief, Engineering Geology and Rock Mechanics 
Division, Waterways Experiment Station, U.S. Army Corps of Engineers dated 
3 December 1976, including attachments. Attachments include a location 
map and profile, narrative borehole camera log, final log (computer print- 
out), joint pole diagram, joint rosette, joint classification, tabulation 
of joint orientations and tabulation of joint effective porosities. 

The joint rosette shows that the predominant joint orientation is north- 
westerly similar to that observed in exposures in the walls of Teton 
Canyon. This is a particularly significant finding because while many 
joint characteristics may be determined by examination of drill core, it 
is not possible to determine the strike of joints from such inspection. 
Thus the survey indicates that a northwesterly joint orientation persists 
near the right end of the dam. It also confirms the existence of a large 
number of low- angle joints in the vicinity of the drill hole. 






j6. Vc^ini^ 



B-120 



o 









o 



!' T ,'^> /'"■""' n 






rjQN-RECORD COPY i. 

■^'^'i-J DEC 1^13/6 



■M -■ . 



i-/^A(.;urr AM 



To: 



Deceni)Gr 15, 1976 

Teton Independent Panel, Idaho Falls, 
Attn: Cliff Cortwrlght 



Tron: 
Subject: 



"' ' Project Construction Enginepr, NewdalfiTldatJO" 



Survey Data for Dan Station 12+00 
Idaho 



ROUIE TO INITIALS DATE 



lyfjii 



Idiho 



Te ton -B3&4IV-P re j(?GJ: 



ORIG. TO: 



^•V 



ucstrean of dcnx:gPV'?o>'2S set' by" 



Dam station 12+33.27 150.00 feat 

cc-ordinazes frc^ Jr\ station v7 sighting Tri sfelriTjrr-^BtJ'Sf^ — tt|tri-?f!!2f?4f 

used wa5 a 7-2 theodolite transit end a H. P. distance trsiter. Tnen 

station 12+33.27 78.00 feet uDStf-^o-iin was set from station 12^'-33.27 

150.00 feet upstream by using a 100 foot chain and a T-2 thc-Ddi>lite transit 

sighting Tri station f7 a TH43 transit and a 100 foot chain \JaS then used 

on rettaindsr of control points. 



Setting instrUiT'snt on station 12+38.27 78.00 feet upstrea^n ar.d back 
sichting s^iation 12+38.27 159 feet upstrean, a deflection ^'C\>fiQ. of 
90^'OQ' v/as turned to the right and a distance of 8.5^ feet i-,'2s chained 
to set the bisect of th& delta angle of P. I. 12+33.27 78.00 f£-et upstrsan. 
Then setting on this point a deflection cngle of 12°30' "Aas turned to the 
left, back sighting station 12+33.27 73.00 feet upstrca.w and a distance 
of 56.81 feet was theoretically chained. This distance was later 
found to be 45.81 fest. Station 1U50.CG, 7S.C0 feet UDSt?v:-arj should have 
read 12+00.00 73.00 feet upstreac. Thsn a deflection angle of 90'^00' 
was turned left, back siqhting station 12+38.27 78.00 fset upstream, 
bisect of the angle point. Points station 11+90.00 52M feet upstrea!^ 
and station 11+90.00 10.00 feet dcwnstrean vsere thsn chained out. These 



SJ 



'+- 
G 
i- 



r features including setting 

dff-vnstrea 



f/: 



last Uio points wer-e used for lcr:ating all oths. 

grout cap center line points and 15.00 feet upstrsan and 15,00 feet 

The stations that were used for the Independent Panel investigations would 

be affected on the block samples, trenchs, and the stationing on the grout 

cap. Only tiie drill holes on the left side of the spillway would be affected. 

The points tnat vsere located on tiie 100 foot dcwnstream and the 150 foot 

upstrea^i line of dam axis for geology control, would also be affected. In 

essence, 10 feec should ba added to all stations. 

We have subsequently tied liie point at d^m station 12+00, 10 feet do^-mstream 
to Tri station "2" and "CLWIA", in order to insure that stationing is correct. 

We regret this incident and apologize for the great Inconvenience caused. 




4 
I 

{ 

i 
(. 

f. 



B-121 



PI. IZ+ 38.17 
A '12** 30 Rt. 
R= ZSO' 
T-- 17. 38' 
L = 54. 54' 




RI. 11 + 49.4 
A= 05* 26'^ 



IT 

150" u/s 



B-122 



APPENDIX C 



WITNESS ACCOUNTS OF FAILURE 



INTERROGATORIES BY DIVISION OF INVESTIGATION SPECIAL AGENTS, OFFICE 
OF AUDIT AND INVESTIGATION, OFFICE OF THE SECRETARY, ON BEHALF OF 
THE TETON DAM PROJECT REVIEW COMMITTEE 



June 25, 1976 



Name: 
Address: 

Employer: USBR Contractor_ 

Title of Position: 
How Long Employed: 
All of Teton Project? 



Wheredjcl yoiJ observe events of failure? (Exact location if possible) 

Why were you there? 

What time did you arrive at scene? 

Who alerted you of possible problem? What Time? 

How long did you stay? 

Did you change locations? 

State your description of what you saw from each site . 
Did you see: 

1. The lower water seepage? Where was it? What time noted? What 
color was the water? Estimated volume? How fast did it increase? 

2. The upper water seepage? Where was it? What time noted? What 
color was the water? Estimated volume? How fast did in increase? 
When were you aware that the dam was in eminent danger? When did 
you realize that it would collapse? 

3. The whirlpool upstream? Was there more than one? Estimate its 
circumference when first seen. Describe its activity - enlarging? 
moving? Did you realize the significance? Where was it? What time 
observed? How long was it visable? 

Any tremors earlier? 

Check inspection route on previous shifts. 



C-1 



BUREAU OF RECIAi>gVTION .^'INESS STATEMENTS TO .TETON DAM t, .LURE 



Peter P. Aberle, Field Engineer 356-7631 

Fifth West South 
Rexburg, Idaho 83440 

Andrew L. Anderson, Electrical Engineer 356-3924 

53 S. Third E. 
Rexburg, Idaho 83440 

Wilbum H. Andrew, Mechanical Engineer 

Virginia H. Perkins Dormitory #32, 356-2579 

Ricks College, Rm 59 

Rexburg, Idaho 83440 

Richard Berry, Surveyor 
275 So. First East 
Rexburg, Idaho 83440 

Stephen Elenberger, Construction Inspector 
Victor, Idaho 

Charles L. Entwisle, Inspector 624-3012 

440 N. 7th W. 

St. Anthony, Idaho 83445 

Clifford W. Felkins, Surveyor 745-7922 

430 N, 3 W. 
Rigby, Idaho 83442 

Myra Ferber, Surveyor 624-4106 

Box 124 

St. Anthony, Idaho 83445 

Alvin J. Heintz, Inspector 624-7982 

151 N. 2nd E. 

St. Anthony, Idaho 83445 

Kenneth C. Hoyt, Inspector 624-3228 

Rt. 1, Box 202-12 

St. Anthony, Idaho 83445 

Harry A. Parks, Surveyor (Chief of Crew) 624-4273 

Kit Circle Trl. Ct. #5 
St. Anthony, Idaho 83445 

Jan R. Ringel, Engineer (Supr.) 624-3873 

520 Targhee St. 

St. Anthony, Idaho 83445 

Robert R. Robison, Pro j . Constr. Engineer 356-7218 

581 Taurus Drive 

Rexburg, Idaho 83440 

Alfred D. Stites, Inspector 624-3885 

P.O. Box 15 5 

St. Anthony, Idaho 83445 



C-2 



STATE OF Idaho ) 

) SS 

COUNTY OF Madlscn ) 



Ir Peter P. Aberle , Rb, 1. Box 2k7Cf "Rexhurn, Tdaho 

^ , being duly 

sworn make the following voluntary statement to Vincent L. I>.rran / 

who has identified himself to me as a Special Agent of the D. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I have "been employed as Field Engizieef, &S-13, Teton Dam Project, Bureau 
of Reclamation, Newdale, Idaho, since K.arch I976 and have a total of 15 
years service with the Bureau of Reclamation. From October 1972 to 
August 197^,1 served as Chief of Grouting, and from August 1974 to 
March 197^, I served as Chief Inspector and Chief of Grouting. 

Starting on about June 3, 197^, I observed small springs in the right 
abutment downstream from the toe of the dam. These springs were clear 
vater and did not appear to be serious in nature, but warranted monitoring 
by visual observation as frequently as routine inspections of the entire 
operation at the dam. 

Between 8:20 and 8:30 a.m. on Saturday, June 5, I976, I received a call from 
Jan Ringel at my home and he told me of a leak at the right abutment toe 
area of the dajn. Ringel estimated the leaJc to be about 20 to 30 sec. ft. 
I asked ray wife to call I-lr. Eobison and I left for the dam. I drove directly 
to the powerhouse area and briefly inspected the leak from the left side 
abutment area. I noted that the water was muddy and estiivated the volume 
to be the same as that given me by Ringel. I do not believe the water was 
running long because there was very little erosion in the gravel at the toe 
of the dam. 

At approximately 9:00 a.m. I went to the project office and met 1-tr. Robison 
and Jan Ringel. Mr. Robison and I walked out on the top of the dam and 
walked down the dawnstream face of the -iun to a leak located at the 5200 
feet elevation, near the right abutment wall. The water in this leak was 
running at about 2 sec. ft. and was only very slightly turbid. The leak 
appeared to be coming from the abutment rock. The leak at the toe of the 
dam was running turbid water from the abutment rock at an estimated volume 
of ho to 50 sec. ft. 



C-3 



At about 9:30 a.m. lir. Pobiscsn and I went to the office area and discussed 
the matter with Mr. Buckert and asked him to mobilize two dozers and a 
front end loader in order to channel water away from the powerhouse area and 
to riprap a channel to the tailrace area. 

At about 10:00 a.m. I was coming out of Buckert 's office, when I hep'^d a 
loud burst of water. I ran down to the visitor's view point and saw that 
a leak had occurred at the 5200 ft. elevation about 15 feet from the right 
abutment wall. The water was muddy and flowing at a volume of about 
5 sec. ft. I went back to Buckert 's office and asked him to mobilize 
all possible equipment and we discussed what mi^t be needed to open the 
liver outlet tunnel. At about 10:30 to 10:^5 a.m. two dozers went down the 
face of the downstream side to move rock into the leaking area at the 
5200 elevation. The reason for the delay in the dozer operation was the 
fact that men had to be called from home since Saturday was not a working 
day for most einployees. 

At 11:00 a.m. Alfred Stites and T saw a whirlpool begin to form at station 
1300 (about 150 feet from the spillway) and about 10 to 15 feet into the 
water from the edge of the riprap. We were standing on the top of the dam 
toward the north end and the whirlpool was forming in the upstream reservoir. 
As we watched this two dozers were coming across the top of the dam from 
the left and I instructed them to push riprap and zone 2 material to-r^ard 
and into the whirlpool. I saw only one whirlpool and as I watched it, it 
gradually grew larger. The whirlpool was approximately O.5 feet in 
diameter at the beginning and was located in an area consisting of clear 
water. I noticed that the water along the right bank was turbid about 
150 feet upstream from the dam and about 15 to 20 feet out from the edge 
of the abutment. This t\arbid water was first noted at 9:30 a.m. by me 
before the whirlpool started and was thought to be turbid due to wave 
action. I wish to point this out due to the possibility of abutment failure. 
At about 11:15 a.m. the two dozers working on the downstream face of the 
dam at 5200 elevation began having problems. One of the dozers was falling 
into the opening and the second was trying to pull the other dozer out. 
At approxi-T^tely 11:30 a.m. both dozers were lost into the hole caused by 
the flow of water. 

At about ll:ilO a.m. I left the top of the dam heading for the office and 
I noticed that at H'.k'^ a.m. the two dozers working on the upstream side 
of the dam began leaving the work area. I was standing in front of the 
project office which is located beyond the south end of the dam and saw 
the top of the dam collapse into the rushing water. I looked at my watch 
and it, was 3.1:57 a.m. and I wrote this time down. 

I vas of the opinion that the collapse of the dam was definitely going 
to happen shortly after 11:30 when the two dozers were lost. 



C-4 



A nunber of the Bureau of Reclamation employees were Involved in controlling 
crowds of onlookers on both sides of the dam, from the time of the collapse 
until late in the afternoon. I cannot at this time estimate the number of 
onlookers . 

I have carefully read the foregoing stattment consisting of two and 
one-quarter pages and declare it to be true and correct. 



Off, . r?. cduj^ 



Peter P. Aberle 



Subscribed and s^{om to before 

me this '^Z''^^ d ay of June I976 

Vincent L. Duran, Special Agen-tiJ 
U. S. Department of the Interior 



C-5 



COPY 



State of Idaho 

ss 

County of Bonneville 

I, Andrew L. >jiderson, 53 S. Third E. , P.exburg, Idaho, being duly 
svom make the following voluntary statement to Vincent L. Duran, who has 
identified hir^elf to me as a Snecial Agent of the U.S. Department of the 
Interior, No threats or promises have been made to obtain this state- 
ment. 

I am employed as Electrical Engineer, GS-12, Teton Dam Project, Bureau 
of Reclamation, Jlevdale, Idaho, I have worked thsre since Novem.ber 197li, 
Previous Bureau ot" Reclamation experience of 12 years. 

At Teton I was working on all electrical work, primarily in power house. 
On Saturday, June 5, 1976, I was at home at 11:00 a.m. I received a 
call from Peter Aberle. He told me dam was leaking and wanted me to 
come out to get river outlet gates open to release water. I arrived at 
dam between 11:1$ and 11:20 a.m. I got pickup at office and went to 
outlet shaft house — left side and UDStream at dam. This took about 
five minutes. I noticed heavy equic.ment on far side of dam on top and 
Robison's vehicle. Did not notice specifically v;hat they were doing 
on the whirlpool. I vent into shaft house to check power to gates. 
There was power, disconnect switch was off and locked. This was normal 
condition because of work in the outlets. The auxLllary shaft on right 
side of dam was open ani water flowing. 

After determining we had power I went over to Robison on top of dam - 
right side. At this time, no later than 11:30 a.m., I saw leak inside 
right abutment about l/3rd way down. Also saw one bulldozer at the 
opening stuck at top of opening. Asked Robison wnat he wanted m.e to do. 
He instructed m.e to go to power house area and get the gates operational 
at the penstocks and check for workers in the outlet. On v;ay down I met 
Wilburn Andrew, he told me power house secure and he was going to notify 
fishermen down stream. I continued down and met Dick Cuffe and Hopkins. 
They were lea-.-ing and told me to leave also. I checked gates, everyone 
leaving and bulldozers were falling in hole. I went up top, saw huge 
hunks of dam falling. V/ithin two or three minutes Aberle came in and 
said dam breached. Time was about 11:57 a.m. 

Seepage water was muddy and the increase was very rapid but cannot estimate 
the volume. I was of the opinion there was eminent danger wnen I talked 
to Robison at about 11:30 a.ra. Within six hours most of water gone from 
the reservoir. 



C-6 



I have carefully read the foregoing statement, consisting of 2 pages 
smd declare it to be true and correct. 



/s/ A. L. Anderson 

Andrew L, Anderson 



Subscribed and sworn to before me on 
this 18th day of June, 1976. 

/s/ Vincent L. Duran, Special Agent 

Vincent L. Duran, special Agent 
U.S. Department of th'- Interior 



C-7 



STATE OF Idaho ) 

) SS 

COUNTY OF Madison ) 



I» Wllbu^.i IT. Andrew , 2>7 N« 2ndW.. Rexburg, Idaho 

____^ , being duly 

sworn make the following volvintary statement to Vincent L. Duran 



who has identified himself to me as a Special Agent of the U. S. 
Department of the Interior. No threats or promises have been made to 
obtain this statement. 

I am employed as a mechanical engineer^ GS-12, Teton Dam project. Bureau 
of Reclamation, Newdaie, Idaho and have held this position since January 20, 
1975. I have been employed by the Bureau of Reclamation since August 1972, 

At 9:00 a.m. on Friday, June U, 1976, Stites and I walked around the 
right abutment (north side) area at the toe of the dam for the purpose 
of looking for leaks. We were doing this because one or two spring 
leaks had developed further down the stream in the abutment wall about 
the day before. We did not see any leaks around the toe of the dam 
or any where on the downstream face of the dam, 

Qn Saturday morning, June 5, 197^, Peter Aberle telephoned me at home 
and asked me to come to the dam immediately because there was an emergency, 
I arrived at the dam sometime between 10:15 and ±0:30 a.m. and reported 
to Mr, Robison at the Project office, Robison told me there were some 
bad leaks in the dam and asked me to check all the valves in the powerhouse 
to be certain they were closed, V/hile driving from the office to the 
powerhouse, I observed the uoper seepage in the downstream face of the 
dam at about 5200 elevation and anshort distance from the right (north) 
abutment wall. There was a sizeable flow of water which was muddy, b^ct 
I cannot estimate the solurae, 

I went into the powerhouse and checked the various butterfly valves 
and assured myself they were all closed. This was in preparation 
to the possibility of opening the river outlet tunnel. I went outside 
the powerhouse with a camera and took a picture of the upper leakage 
at the 5200 elevation near the right abutment. I did not notice that 
there was a sizeable increase in the volume of water flowing through 
the dam opening. After talcing the picture, I ran into Dick Guffe 
and Lloyd Hopkins at the nower house and they told me there were four 
fishermen about one-quarter mile or more dovmstreara of the dam. I 
drove downstream to try to locate the fishermen and found the fishermen 
near a residence and out of sight of the dam. I j-Blled to the fishermen 
to leave the area iTJuediately and they advised ms that they would do so. 
The fishermen were in a rubber raft when I located them on the river. 

1 
C-8 



1^ 

I drove back upstream ^ the powerhouse and saw a crane evacuating 
the area and Barry Roberts advised me that I should leave the 
powerhouse area and go to higher ground, I would estimate the time 
to be about 11:1; J a.m. I drove up to the south rim road and observed 
the top of the dam collapse, I would estima"b the collapse of the dam 
to have been at about 11: U5 avra, but this is not an exact time, 
I was not checking the time in the face of all the turmoil. 

The river outlet tunnel was never opened because it had to be=evacuated 
before it was completely cleared of equiomsnt, 

I had no IXill realization that the dam was actually going to collapse 
until I saw the top fall. I never saw the activity at the top of 
the dam, including the whirlpool, because all of my activities were 
in the powerhouse and the downstream area. 

I remained at the dam site until about 8:30 p.m. Much of this time 
was spent working on crowd control, but I cannot estimate the number 
of people who came to the dam. At about 7:U0 or 8:ijO p.m. I observed 
several springlike flows of water on the face of the rock wall upstream 
of the grout curtain on the north or right side. I made this 
observation from the south side of the dam, I noticed one flow 
was approximately 25 feet unstream from the grout curtain and about 
100 to 125 feet down from what had been the top of the dam. I would 
estimate this flow at about 200 gallons cer minute. There were no 
observable leaks or flows of water from the rock face within 200 feet 
downstream of the grout curtain, 

I have carefully read the foregoing statement consisting of one and 
three-quarter pages and declare it to be true and correct. 



Wilbum H. Andrew 



Subscribed and sworn to before 
me this ;y^-'-4- day of June 1976 



Vincent L. Buran, Special Agent 
U. S. Department of the Interior 



2 

C-9 



STATE OF IDAHO 

ss 

COUNTY OF MADISON 

I, Dick R. Berry 269 S. First E.^ Rexbur p, - Idaho 

^__^__ ____, being duly sworn make the 

following voluntary statement to Vincent L. Duran, who has identified himself 
to me as a Special Agent of the U.S. Department of the Interior. No threats 
or promises have been made to obtain this statement. 

I am employed as Survey Technician, GS-5, Teton Dam Project, Euieau 
of Reclamation, Kevdale, Idaho and have held this position since 
September 1975 • I had previously been e:nrployed vith the Soil Conservation 
Service, U. S. Department of Agric\ilture since May 197^. 

Qa June 4, 1976 I recall seeing seepage near the right abutment wall 
below the toe of the dam. The water was clear and not really running— 
J\ist settlement. There were no leakages or seeps at the dam. 

Qa Saturday, June 5, I976, I arrived at the Project Office a little 
before 7:00 a.m. Rarry Park's Volkswagen was in the parking lot. 
Clifford Felkins and I arrived in a white Chevrolet pickup truck. These 
were the only two vehicles in the parking lot at the time. I had 
no vatch with ms at work on that date. 

At 7:20 a.m. on June 5^ I left the Project Office and drove down the 
upper south rim road to check three site rods on the south rim across 
from the spillway. I was checking the site rods for the purpose 
of going to the spillway and doing survey work on its walls. While 
checking the site rods I saw a small seepage on the north side 
downstream face of the dam, ri^t at the abutment and dam joint. 
This was approximately one -third of the way up the dam, but not 
as high as the change in slope. There was slight erosion, slow flow 
of water, but I do not recall it being muddy. The seepage appeared 
to be almost new. I returned to the office and Earry Parks, who was 
In the crew, reported the seepage to Jan Ringel about 7:35 a.m. 
We then drove across the dam £md parked just south of the spillway. 
I checked the water level in the reservoir on the upstream side, but 
do not recall the level. Tne water was very calm and there was 
no discoloration and no evidence of a whirlpool. 



C-10 



We then started work on the spillway at about 8:30 a.m. Just 

before we vrent into the spillway I saw a wet area at the end 

of the sar^i area just off the abutment on the dcr,^nstream face 

of the dam. I do not recall this being running water, just a 

vet area. We went into the sp ill way and surveyed the left wall. Hy 

view of the leak was blocked. At about 10:15 a.m. I heard noise 

from a lot of equipn:ent. At 10:30 a.m. I went to the top of the 

spillway to start the right wall and noted that the upper hole 

had expanded to 35 feet in diameter with a flo-rf- of muddy water 3 to 4 

feet wide and six inches deepf . There was a dozer trying to fill in 

the hole. 

At 11:00 a.m. I was back at the top of the spillway and saw the hole 
had expanded toward the top of the dam and had elongated to 100 feet 
and took more of the face of the dam. There was a lot of activity 
on the dam. I recall sayin^^sor.^thigg about sounding like a waterfall 
sometime about 11:15 a.m. i~^ 1±:30 a.m. We continued to survey 
\intil about 11:U0 a.m. at which time Aberle called ns out of the 
spillway because of danger. I arrived at the top of the spillway 
at about 11:45 a.m. and saw that there was a little bridge of dam 
material across the top. I thought at this time that the dam was 
gone. At about 12:00 noon I saw the top of the dam break through. 

At 11:45 a.m. I saw ii«i- dozer^ leaving the upstream face just before 
the top collapsed. I also believe there was a pickup truck going 
across the top. I evacuated to the north side. I observed the dam 
until about 12:15 p.m. and then head for St. Anthony, Idaho. I was 
not involved in crowd control. 

I was not aware of aay earthquake or tremors. 

I have carefully read the foregoing statement, consisting of one 
and three -quarter pages and declare it to be true and correct. 



P-J/^R 



Dick R. Barry 



^ 



Subscribed and sworn to before 
me this 22nd day of June I976. 




Vincent L. I>.iran, Special /.ront 
U. S. Department of the Interior 



C-11 



STATE OF Idaho ) 

) SS 
CXDUNTY OF Hadlson ) 



I, Charles L. Entwisle , ^^40 N. Seventh W. , Si^^r 



.<y j-. Anthony, Idaho , being duly 

sworn make the following voluntary statement to Vincent L. Duran 



who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

For three and one-half yoars I have been employed as Construction Inspector, 
GS-9, Teton Dam Project, Bureau of Reclamation, Newdale, Idaho. I have 
been employed by the Bureau since May 7» 1962. 

On Saturday, June 5, 1976, at about 9:30 a.m., I received a telephone 
call from Jan ^ingel who asked me to come to the dam because there was 
an emergency. I arrived at the dara at about 10:30 a.m. Upon my arrival 
at the office I answered the telephone and was told by Wilburn Andrew 
that the butterfly valves at the power house were secured. I then proceeded 
to the top of the dam to relay the information to Robert Bobison. As I 
approached the top of the dam I saw a washout area about ^0 feet square in 
the downstream face of the dam near the north or right abutment and about 
one-third the way up the face. There were two dozers pushing material 
into the openings. The water was muddy, but I cannot estimate the volume. 

I proceeded out across the top of the dam to see Robison. As I approached 
the north or right side a small whirlpool about 10 feet from the upstream 
face of the dam just off the right abutment was forming in the reservoir. 
The time of this was about 10:50 a.m. The whirlpool was about two feet 
in diameter and the - S^r^ ^ wa^ about six inches. It appeared to be 
stationer}'', but grew in size as I watched it. Two dozers were activated 
and began pushing rip rap into the whirlpool. 

The downstream leakage and the whirlpool grew in size and the two dozers 
working on the downstream side were washed away by the water. I would 
estimate the time of this to be about 11:30 a.m., but this is strictly a 
guess. Shortly after this the downstream face washed out to within 10 feet 
from the top of the dam. At this point I felt the dam was going to wash 
away. 

The two dozers working on the whirlpool were told to evacuate and as 
they moved across the top of the dam to the south side the top of the dam 
collapsed. To my recollection the collapse occurred at about 12 noon. 



C-12 



I immediately after the collapse drove down the north side of the river 
warning people of the collapse and returned to the project office about 
12:30 p.m. Throughout the afternoon we were working on safety precautions 
for on-lookers coning by, but I cannot estimate how many people were there. 

I have carefully read the foregoing sta.tement, consisting of 2 pages, and 
declare it xo be true and correct. 




M^ 



UL 



Charles L. Entwisle 



Subscribed and sworn to before 
me on this ^(^^'^day of June 1976. 




Vincent L. Duran, Special Agent 
U.S. Department of the Interior 






C-13 



STATE OF Idaho ) 

) SS 
COUirrY OF Madison ) 



I, Clifford Felklns r _ li^O W. ^-r ri w.^ '^^Z'^Y, '^'^'^'^'^ 

, baing duly 

sworn make the following volvmtary statement to Betty J. Foves ' 

her 

who has identified )S£fcelf to me as a Special Agent of the U. S. 
Department of the Interior. No threats or promises have been made to 
obtain this statement. 

I am employed as a Surveying Aid, GS-3, Teton Dam Project, Bureau of 
Reclamation, Newdale, Idaho and have held this position since May 3^ 1976. 
I have had no other Federal Service except with the U. S. Navy. 

On Friday, June 4, I noticed for the first time some wetness in the 
waste area near the right abutment wall of the dam. There was no 
water flow, Just wetness. 

On Saturday, June 5, 1976, I arrived at the dam at about 7:00 a.m. driving 
a little Chevrolet pickup truck and parked it in the parking lot at the 
Project Office. Harry Parks had arrived a little before me and had 
parked his Volkswagen in the parking lot. My pickup truck is white. These 
were the only two vehicles in the parking lot. 

On June 5^ the first thing that I saw connected with the later events 
of the dam collapse was a water flow coming from the toe of the dam. It 
was a steady flow of water, but I cannot estimate the volume. To the 
best of my recollection the water flow was clear. I noticed this flow 
while I was standing across the river on the canyon wall from the spillway. 
I was with Harry Parks and we came to the survey office, which is a building 
immediately^behind the Project Office, and reported the leak to Jan Eingel. 
This was a^5oiiiE'8:30 a.m. We then went back to the spillway, which is 
located on the north or right side of the dam in order to check the alignment 
of the walls on the spillway. During part of the time when we were working 
on the alignment of the spillway the leak was out of o\ir view. We started 
our work on the alignment from the top of the spillway on the left hand side. 
This was approximately 9:15 a.m. We worked our way halfway down the spillway 
on the left hand side. When we were working the lower half the leak was 
out of our view. When we completed ovir work on the left side of the spillway, 
we came up to the top of the spillway by walking along the left side, but 
outside the spillway. VJhile we were making our way to the top of the dam, 
at about 10:15 a.m., we observed a hole on the rifjht abutment (north side) 
about one-third of the way up the dam, just below the chEinge in elevation, 



C-14 



I wOTild estimate the hole was about 10 foot In diameter at this time. 
A cat was 'beginning to move riprap Into the hole. I was personally 
concerned about the trouble at the dam, but nevertheless continued 
on to the zap of the spillway to begin work on the righti side alignmeijit. 
When we reached the top of the dam I observed another cat moving into 
the dam to begin work, but I did not see where it went. 

We be^in our work on the right side of the spillway, working down. We 
could see the construction supervisors from Morrison-Knudsen and Bureau 
supervisors directing operations and making observations of the dam. 
We tried to continue our work, but naturally were distracted by the 
activity and kept watching the supervisors running around. We were 
never at a point where we observed the whirlpool which later formed 
on the reservoir side of the dam. We did see two more cats move onto 
the dam and begin pushing riprap into the reservoir side of the dam. I 
would estimate this was around 11:00 a.m. 

I do not recall the time when we first observed the upper water seepage. 
We were standing near the top of the dam in the spillway and observed 
the second hole beginning to form just as we were coming out of the 
spillway. We were leaving the spillway on the instruction of Pete Aberle 
who told us to get out. I did not actuetlly see any water come out of 
the upper hole because the dam caved in and the two holes became one 
large one. The water that came through was muddy. I cannot estimate 
the voltime, but it was a lot of gallons. The voliome increased very rapidly. 

I noticed the two cats on the top of the dam just before the dam collapsed. 

I recall that there was also a pickup truck on the top of the dam. When 

the dam collapsed between 11:^5 and 12:00 noon, the cats and the pick 

up truck had just left the top of the dam, proceeding to the left side (south), 

I never really believed that the dam was going to fail. When they told 
\is to get out of the spillway I knew the dam was in imminent danger. I 
could not really believe the dam had collapsed even after the event had 
occurred. 

Just before we came out cf the spillway, right before 11:30 I heard what 
appeared to be soimd like water rushing and there was a slight vibration. 
I would estimate that this occurred when the dam was actually crvunbling. 

After the dam collapsed we collected our equipment and got into a Jeep 
and drove immediately to St. Anthon;/, Idaho, stopping along the way 
at a farm house in order to call our families in St. Anthony Jind Ri^iby. 
I would estimate we left the dam shortly eiter 12:00 noon. I noticed 
before we left that there were a lot of members of the public observing 
the dam from the visitor's observation platform on the other side. Since 
we were across the river we did not assist in crowd control. 



C-15 



I have carefully read the foregoing statement consisting of two and a 
fraction pages and declare it to be true and correct. 



Subscribed and sworn to before me 
this 22nd day of June I976. 





h 




U^^^i^OJ 



Betty J, f^yif} Special Agent 
U. S. Department of the Interior 



C-16 



STATE OF 


) 




) ss 


couirrY OF 


) 



I, 



Myra \. Ferber 



box 12^, St. Anthony, Idaho 



, being duly 



sworn make the following volvintary statement to 



Vincent L.Duran 



who has identified himself to me as a Special Agent of the U. S. 
Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am employed as a Survey Technician, GS-4, Teton Dam Project, Bureau of 
Reclamation, Newdale, Idaho and have held this position for one and one- 
half years. I previously worked at the Project as a secretary for one 
and one-half years. 



On Siturday, June 5i 1976, I reported to work at the Dam at 
the purpose of doing scheduled survey work. At about 700 2. 
Richard Eerry , Clifford Felkins, all surveyors, and myself, 
stream fron the dam on the south or left side canyon wall to 
in preparation for survey work on the spillway on the north 
of the dam. While checking the sitings we saw a small leaka 
feet below the top of the dam near the right abutment on the 
face of the dan. The water was flowing down the face of the 
washing away fill at the toe of the dam. Ue then proceeded 
g ^frTTTi -^.n » ■■' ou_rp£^^j-^t^. and reported the leak to Jan Kin 



7:00 a.m. for 
m. ii^ Parks, 
proceeded down- 
check sitings 
or right side 
ge about 100 
downstream 
dam and 
to the office 
gel. 



Vejthen proceeded across the dan to do our survey work. At about 8:30 a.m. 
we checked the water elecation In the reservoir on the upstream side of 
the dam. The vrater elevation vfas 5301+ feet and I did not notice anything 
unusual about the reservoir water — specifically there was no indication 
of a whirlpool. From there we started survey work on the left wall of 
the spillway and I was unable to observe the leak in the dam. At about 
10:15 a.m. we finished surveying the left wall and went up to the top 
of the spillway. At this time I noticed that the leak in the dam had 
opened to about 10 to I5 feet in diameter. The vfater was turbid and 
flowing fast, but I cannot estimate the volume. 

At about 10:^5 a.m. to 11:00 a.m. we prepared to survey the right wall of 
the spili'way. Before leaving the position of being able to see the face 
of the dam I noticed two dozers were going down the downstream face toward 
the hole. 



C-17 



Again while we were surveying the spillway I was unable to obsein^c 
the leak. At about 11:^5 a-.m. Peter Aberle called us out of the 
spillway and we started tov.-ard the top. Just before Aberle called 
us I heard a loud noise, which sounded like water forcing though the 
leak area. 

At 2.bout 11:5D a.m. I arrived at the. top, of the spinLlway and ea w t -w o - 1^^.<^A<^ 

^cc^:^(~o~sc'zz ''^c'^-i >' z\[j D-^HgT^ar. z'jz t . — the narvlT 3ldj3--to i f-j. J - '-4n:r— rrcuth - 
^^idc; Shortly thereafter the remaining portion of the top of the 

dam on the north side collapsed, I would estimate the time to have 

been 11:57 a.m. I went hone at about 12:15 ^'^' 

I have carefully read the foregoing statement consisting of one 
and one-third pages and declare it to be true and correct. 



Ferber 



H^a A, 



Subscribed anch sworn to before me 
this ^^^^zA^y of -Jui^e 1976. 

^ , (/ . /.Ij-^T ^ - ry-^^^ ]-~i'^£ ^\ 

Vincent L. Duran, Special Agent <^ 
U. S. Department of the Interior 




C-18 



STATE OF Idaho ) 

) SS 
COUNTY OF Madison ) 



I^ Alvin -T. Heintz , I05 N. Second E. , St. Anthony, 

Idaho , being duly 

sworn make the following voluntary statement to /incent L. Duran , 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

Since October 1971, I have heen employed as Construction Inspector, 
CS~$, Teton Dam Project, Bureau of Reclamation, Newdale , Idaho, I have 
heen employed by the Bureau since 1955» 

At about 10:30 a.m. on Saturday, June 5» 1976, Pete Aberle telephoned 
me at my home and asked me to come to the dam because there were some 
leakage problems. I arrived at the office at about 10:55 a.m. and after 
finding no one in the office drove across the top of the dam and found 
Aberle on the north or right end of the dam near the spillway. I would 
estimate the tine to be 11:00 a.m. 

As I drove across the dam I could see water spewing from the downstream 
face of the dam near the north or right side abutment. I cannot estimate 
the elevation of the leak. The v^ater v/as flowing rapidly and was eroding 
fill materials thereby making it muddy. There were two dozers on the 
face of the dajn pushing rock into the hole. 

As I was talking to Aberle we noticed a small whirlpool forming in the 
reservoir on the upstream side of the dam. The whirlpool was about two 
feet in diajneter, close to the north or right abutment and about 10 to 
15 feet out from the dam. This was the only whirlpool I saw and to my 
knowledge it stayed in the same location. 

I remained on the top of the dam near the north end and helped direct 
two .dozers pushing riprap into the whirlpool. V/hile 'ro:."i:i;'g I saw the 
downstream flow of water increase in volume and the whirlpool increase in 
size. I cannot give estimates of the volime of water or the sii^ie of 
the whirlpool or times of any significant increases. 

At about 11:45 a.m. , we instructed the two dozers on the top of the dam 
to leave and I went off the north or right side of dam. The top of the 
dam collapsed at about 11:50 a.m. This time estimate is not specific. 
I never really considered that the dam -.jould fail until the last minute. 
To my knowledije there was no earthquake before the problems began. 




C-19 



Shortly after the collapse I left the north side and proceeded down- 
stream to i.-a.^-in-residcnts. I returned to the offices on the south side 
of the dam i=M. assist/'^ i" crowd control. I cannot estinate the number 
of people who cair.e to the dan after the failure, but v/e had problems 
keeping people off the rim edges and the dam itself. 

I have carefully read the foregoing statement, consisting of 1 and l/8th 
pages, and declare it to be true and correct. 




Alvin J. }Ieintz 



Subsc>?d.bed and sworn to before me on this 
c^?-*^ day of June 1976. 

Vincent L. Duran, Special Agent 
U.S. Department of the Interior 



C-20 



STATE OF IDAHO 

ss 
COUNTY OF MADISON 



It Kennetii C. Hoyt » Rt. 1^ Box 202-12 ^ St. AnthcnVj 

Ifffthn * being duly sworn make the 

following voluntary statement to Vincent L. Duran, who has identified himself 

to me as a Special Agent of the U.S. Department of the Interior. No threats 

or promises have been made to obtain this statement. 

I have been employed as Construction Inspector, GS-9> Teton Dam Project, 
Bureau of Reclamation, ITewdale, Idaho since March 30, 19T5/ and I have 
a total of l6 years service with the Bureau of Reclamation. 

Before June 5*1 saw seepage in the bottom beyond the toe of the dam. 
This seepage was visible for about two or three days prior to June 5» 
and was 150 feet downstream of the toe of the dam. I never saw the 
seepage clearly, do not know the condition or volume. It was a slight 
flow and was of no great concern to me as it appeared rather natural. 

On Friday, June h, I saw nothing unusual at the dam. There were no 
leaks or no whirlpools up to 4:30 p.m. when I qviit work. 

On Saturday, June 3, 19T6, at about 10:30 a.m., Pete Aberle called my 
home and left a message with my wife that I should be on standby to 
come to work on the midnight shift that ni^t. I caLI ed Aberle back 
about 10:40 a.m. and he told me to come to the dam immediately. I 
drove to the dam and arrived on top of the dam at about 11:15 a.m. I 
saw a large stream of water running off the downstream side of the dam 
at about 5*200 slope and about 20 to 30 feet from the right abutment. 
(The elevation for the water level was 5*324 feet elevation. 
The- elevation of the opening to the spill water was 5*306.) The 
stream of water was at about the change in slope elevation. The water 
was muddy. I also saw two dozers pushing rock into the hole created 
on the downstream face. 

I also saw a whirlpool on the upstream face of the dam in reservoir 
water. The whirlpool was about 150 feet across the top of the dam from 
the spillway and about 15 feet out from the face of the dam into the 
vater. It was rather close to the rock and abutment wall. The 
whirlpool was about 10 feet in diameter. There were two bulldozers 
pushing riprap into the pool. The water was clear. The dozers were 
creating discoloration in the water. When I saw the whirlpool I felt 
the dam was ^one. The vhirlpool gradually grew and was visible 
until I left the dan. 



C-21 



Someone said the dozers on the downstream face were gone. I looked and 
saw then tumblins do-.m stream. Shortly thereafter the dozers on the 
top of the dam pulled back and headed to the south aide of the dam. I 
foUcved the dozers in a piclrap truck. When I got to the river outlet 
shaft house on top of the dam I turned around and saw the top of the dam 
collapse. I looked at my watch and noted the time to "be 11:58 a.m. 

Thereafter, I spend time controlling crowds. There were a number of 
people wandering around. I cannot estimate the number at this time. 
It was a very dangerous situation. 

At about 2:00 p.m., Andrew Ancerson and I went one mile upstream to 
check the water elevation, which at the time was 5^217 feet. At 
2:30 p.m. the water level was 5AT0 feet. There was no one around the 
area. At the time I could see a lot of water running out of rock on 
the riglit abutment across from the boat ramp. This was water in the 
rocks from the reservoir. There was no such water prior to the filling 
of the dam. 

I am not aware of any earthjjuak.e tremors in the area. 

I have carefully read the foregoing statement, consisting of 2 pages, 
and declare it to be true and correct. 



Kenneth C. Hoyt ^ 



Subscribed ar^d sworn to before me 
on this ^2^=^)-d£LY of June 1976. 




iW-!^ ^LrA tri o^Sf 



Vincent X. I>aran, Special Agents 
U.S. Department of the Interior 



C-22 



STATE OF IDAHO 

ss 
CX)UNTY OF MADISON 

I . Harry Parks . Kit Circle Trailer Court, 

Space 5 J St. Anthony, I daho , being duly sworn make the 

Betty J. Foyes .._„_^ 
following voluntary statement to Vincent L. Duran,/who ha^e identified h^'csw 
themselves 
to me as ^ Special Agents of the U.S. Department of the Interior. No threat 

or promises have been made to obtain this statement. 

I am employed as Supervisory Surveying Technician (Party Chief), GS-8, 

Teton Dam Project, Bureau of Reclamation, Ilewdale, Idaho, and I have 

held this position since April 1975 • I previously worked for the 

Bureau of Reclamation at Forest Grove, Oregon from November I968 to April 

1975* I have been employed by the Bureau of Reclamation since November 19d1. 

About June 3, 1976, I observed a small stream of water appearing 
along the bottom of the vaste area about l400 feet downstream from 
the toe of the dam. I was on the top of the south rim when I observed 
this water and so I could not say at this time whether the water was 
clear, muddy, etc. I was aware that Roblson and Aberle were watching 
the flow on at least one occasion. 

On Saturday, June 5^ 197^, I arrived at the project office a couple 
minutes before 7:00 a.m. I was driving a green Volkswagen, I parked 
the Volkswagen in the Reclamation parking lot. I was the first person 
to park a vehicle in the lot and Chris Felkins arrived shortly thereafter 
driving his white Chevrolet pickup truck. We left the office about 
7t35 a.m. in a survey truck and traveled down the south rim road 
downstream for the purpose of checking the siirvey si^ts in order to 
perform a survey on the spillway on the north side of the dam. At about 
7:50 a member of the survey party noticed water seepage. I then 
observed the water which was running out of the toe of the dam at about 
50 feet from the north abutment wall, I cannot estimate the volume 
but it was barely what could be called a stream at all. The water 
appeared muddy, but this may have been caused by the material over 
Vhich it was flowing. We drove back to the office and I reported 
the weter leakage about 8:00 a.m. to Jan Ringel, 

After reporting the water, we departed the project office and drove 
across the top of the dam and parked our vehicle near the spillway 
bridge on the dam. At about 8:20 a.m. I checked the water elevation 
on the reservoir or upstream side of the dam, near the spillway inlet, 
and it was 5301.7 clevaticn. This W3.s about three feet of the gate leve? 
of the spillway. At this time I noted nothing unusual on the 
reservoir side of the clam so x'ar as the water was concerned. There 

was no whirlpool and in fact the water was unusually calm. There was no 



C-23 



discoloration of the water. There vere no fishermen or any other 
persons on the reservoir side at this time. This area is posted 
against fishing. 

I went down into the spillway and made no observation of the 
downstream face of the dam at this time. I was working in the 
spillway and ray view was blocked of the da.7nstreajn face of the dam, 
and it was not until about 9^30 a.m. that I could see a dozer 
coming off the top of the dam to work on the downstream side. 
At about 10:30 a.m. I came up to the top of the spillway. I walked 
onto the sage area and observed a leakage about 50 feet from the 
north abutment and somewhere above the 5200 elevation. I cannot 
estimate the volume of the water but it was a running stream. 
I would estimate the hole was about five feet in diameter and the 
water was muddy. We watched the water about five minutes and 
tterhpleamay have increased as much as a foot during this time. 
He does not recall seeing any dozers working at the hole at this 
time. 

We then went back down the spiUvray to continue our survey work. 

I was aware of a lot of activity at the top of the dam in that 

there were a lot of people moving about and tiio dozers moved across 

the dam. Between 11:15 a.m. and 11:30 a.m. I could hear water flowing 

and made tl'C assumption that it was coming out of the hole, but I 

could not see it from where I was working. At about 11:^5 a.m. Pete 

Aberle called to the survey crew and told us to leave the area. 

I did not have the feeling at that time that the dam was in imminent 

danger of collapse smd if I had, I would have left the spillway earlier. 

I would estimate that it was close to 11:50 when I reached the 

top of the dam. At this time the hole on the da^mstream face of 

the dam had eroded almost to the top and muddy water was rushing 

out of it. There was a pickup truck on the top of the dam and two 

dozers. Tne dozers were pushing riprap into the water on the upstream 

side. 

I did not see the whirlpool which developed on the upstream side 
of the dam. I did not see the water on the upstream side of the 
dam at all until the dam broke. I was standing a few feet from 
the spillway bridge in the middle of the road. I saw half of xhe 
top of the dam go and shortly thereafter the other half (upstream) 
went. I was wearing a watch but did not note the time, but it was 
close to noon. 

The first time that I became aware that there '/ra.s imminent danger 
of the dam collapsing was when edge of the hole carae close to the 
bottom of the road. This was shortly after 11:50 a.m. 



C-24 



I am not aware of any earthquake tremors. The only tremors I am 
sware of vms vhen the spillvay tremored a little bit about 11:45 
and I bel-f^^vd this was caused by the rush of the vater. 

I departed from the north side of the dam at about 12:05 p.m. 

I did not paxticip3.te In any crowd control operation, since there 

were no members of the public on the north side at that time. 

I have read the above statement consisting of two and one-quarter 
pages and declare it to be true and correct. 



(^^^$^^^^^-^ ^.^^ 



Harry Parks 



Siibscribed and sworn to before rae 
this 22nd day of June 1976 



^jUfM 



J-L^r^^ l U^ CJl 



c-<J__y Q/-J) 



Vincent L. I>i.iran, Special^ Agent ' 
U. S. Itepartnent of the Interior 



6^1.^ 



u^e^, 



Betty J. Fovps, Spacial Agent 
U. S. Deparment oi the Interior 




C-25 



STATE OF Idaho ) 

) SS 
COUNTY OF Madison ) 



I, Jan B. Pjpgel , y^O Tar^ee Street, St. Anthony, 

Idaho , being duly 

sworn make the following volxmtary statement to Vincent L. Duran , 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement, 

I am employed as Civil Engineer, GS-11, Teton Dam Project, Bureau of 
Eeclamation, Newdale, Idaho. In this function I act in the capacity of 
Chief of Surveys and Principal Inspector. I have been employed on the 
project since September 1972. I previously had one and one-half years 
service with the Bureau of Eeclamation. 

On Saturday, June 5j 197^, I arrived at work at 7:00 a.m. I had two 
survey crews working. V^ office is in a trailer behind the office complex 
at the project, l-tr. Parks checked the staffs for the spillway control 
on the south side of the dam opposite the spillway. They were on the 
canyon rim and noticed the lower leak on the dam near the toe at about 5^0^1.5 
elevation. At about 7:30 a.m. Parks reported sightings to me. I drove 
down to the powerhouse and walked over to the leak. The water was muddy. 
The water was running between the rocks on the right abutment and not 
through the dam. I estimate the water flow to be about 20-30 cfs at this 
time. I did not detect any increase at that time. 

The only other noticeable thing at this time was some springs at the base 
of the dam a^inst the abutment — 200 feet below the other. This had been 
there for one or two days previous. This was clear water running at about 
10 gallons per minute. Mr. Aberle and Mr. Robison had previously checked 
this. 

At about 8:20 a.m. I telephoned Mr. Aberle at his home in Rexbvirg. At 
about 8:50 a.m. Mr. Aberle and Mr. Robison arrived at the dam. I briefed 
them lightly and we drove over the top of the dam to the right abutment. 
At this time Mr. Robison and Mr. Aberle walked down the downstream face 
of the dam to look at the leak, I drove the pickup around the rioi road to 
meet them at the bottom. When I arrived, I walked directly to the right 
abutment. I stopped momentarily at the powerhouse and took some pictures 
of the leak, then proceeded to the riprap stockpile where Mr. Robison and 
Mr, Aberle were observing and deciding what to do with the water running 
out of the abuticen o . We -chen proceeded "oo che pickup and went to the 
Morrison-rCnudsen Company and Pe^er rCiewit Sons' Office to contact Mi*. 3uci:erw 



C-26 



to mobilize some equipment, namely two dozers and one front end loader 
to make a channel from the water source to the river bo that the va^er -ivould 
not get into the powerhouse. After cur conversation with Mr. Buckert we 
retiimed to the office to get some help. We called Mr. Al Stites and 
?■&". Al Heintz to check on the contractor's work and look for other leaks 
along the canyon. Mr. Robison wanted to know the reservoir water elevation 
so I returned to the right abutnent wheie Mr. Parks was working in li.e 
spillway to get this inforination because he had read it at approximately 
8:00 a.m. that morning. The reservoir was at elevation 5301.7. I then 
returned to the office to give this information to I'lr. Robison. I then 
went but the front door of the Bureau of Reclamation office to talk to 
Kr. Aberle, who was returning fa'om Morrison ruiudsen Company and Feter 
Kiewit Sons' office. This was approximately 10:30 a.m. 

At about 10:30 a.m. I heard water running, i-tr. Aberle and I ran dovm to 
look over the side of the Canyon. At this time we discovered the upper 
leak on the right side at approximately 5200 elevation, and approximately 
15 feet from the abutment. The water was washing zone 5 material - varying 
sizes, dOT-m the slope. The water was a muddy color and was running at 
10-20 CFS, I would guess verj' rougily. 1-ir. /vberle ran back to the 
Morrison-1-Cnudsen Company and Peter Kiewit Sons ' to inform them of the new 
development and I ran into the Bureau office to tell I'jr. Robison. I then 
vent back down to the pc-./-erhGuse to get the gates open if someone was 
available. Stites was there. I saw the two cats working on the downstream 
face of the dam. I told Andrew to prepare to open the gates but this was 
never done. 

I then drove up to the top of the dam. At approximately 10:50 a.m. a 
whirlpool developed on the upstream face of the dam. This was at the right 
of the dam about 15 to 20 feet away from the dam. Gibbons and Reed dozers 
were pushing in riprap. I cannot estimate the circumference of the whirlpool 
or its activity. I only saw it miomentarily. I realized then that we had 
big trouble. I did not watch continuously. 

When the whirlpool developed two dozers from Gibbons and Reed Company 
immediately started working on the upstream face of the dam trying to push 
riprap and zone 2 material into the whirlpool to stop the leak. 

I saw a pickup truck going to Wilbur Peterson and Sons, the clearing 
contractor. John Blo-^-ers and Miller went to get a cat. I went to tell 
them where we needed work. They did not have a key to the cat. I went 
and got one for them and returned to the dam. This occurred bet^^^een 
11:00 - 11:30 a.m. V/hen I returned to the dam the cats on the upstream 
face were pulling off. This was about 11:40 a.m. The operators of the 
downstream cats were running across the dam. The dam collapsed at 11:57 a.m. 



C-27 



I recall that there vas a farmer in a green pickup truck at the dam on 
the north side soEP.etime "between 9:00 and 11:00 a.m. The man said "what 
is going on here?", "Is it seriotis? " I told him yes, the dara is ■breaking. 
The man said "I am going to get out of here. I have a farm down below," 
I do not know the name of the man and carnot identify him. 

Within two hours of the collapse of the dam, there were at least 15 people 
on the north side of the dam around the spi3-lway and on the edge of the 
collapsed area. There was considerable problems with crowd control 
throughout the afternoon, 

I am not aware of any earthquake tremors. 

I have carefully read the foregoing statement consisting of two and 
one-half pages and declare it to be tine and correct. 




'Jan R. Ringai 



S\ibscribed and sworn to before 

me this Q "^ -^ day of June 1976 

Vincent L. I>aran, Special Agent <3 
U, S, Department of the Interior 



C-28 



STATE OF Idaho ) 

) SS 

COUNTY OF Madison ) 



I, Bobert R. Eoblson / 58I Taiirus Drive, Pexburg, Idaho 

, being duly 

sworn make the following voluntary statement to Vincent L. Puran and Be- ^ty J. 
have themselves . Foyes 

who hJSXXidentif ied KXitSXO to me as X Special Agente'of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am einployed as Project Construction Engineer, GS-lk, Teton Dam Project, 
Bureau of Reclamation, Ilewdale, Idaho and have held this position since 
August 1971 • I have been employed by the Bureau of Reclamation since 
1951 • I received a B.Sidegree in engineering in 195D from the University 
of Utah. 

While there vere rumors as early as April 197^ that there were leaks 
at the dam, there is no basis to these rumors, because there were no 
leaks. 

On June 3, 1976, several small seeps in the rhyolite (volcanic rock) 
appeared about ihOQ to 2000 feet dcr,mstream from the toe of the dam 
in the north abutment wall. The water was clear and all of these 
seeps totaled about 100 gallons of water per minute. This was felt 
to be a good sign because the dam was being filled and it indicated 
the water table gradient was acting in a normal manner. The water was 
clean enough to drink and if there had been a problem the water wo\ild 
have been turbid. I felt the area shovLLd be monitored by sight 
inspections and other mechanical means, the latter of which were never 
put into effect. I took pictures of the seepage and reported the 
matter to the ESJt Center, Bureau of Reclamation, Denver, Colorado. 

On, June k, 1976, a small seepage occirrred about halfway between the 
toe of the dam and the end of the spillway along the north abutment. 
This flow was approximately 20 gallons per minute and I had no 
concern because the water was clear. I checked this leak at about 
^:30 p.m. on June h before leaving the dam and determined that there 
was no problem. At this time I also observed the entire do-rt-nstream 
face of the dam and observed nothing unusual. I also observed that 
there was nothing unusual on the upstream reservoir side of the dam. 



/r / . ^.. 



r 



C-29 



On June 5* 1976, at 8:30 a.m. I received a telephone call at my 
home from Pete Aberle's vife. She told me that Ringel had called 
Aberle and said there was a large leak in the dam. I left my 
home immediately and arrived at the Reclamation Office at about 
9:00 a.m. Aberle and I drove to the downstream toe of the dam 
and I observed a major leaJc at the dovmstream toe at the right 
abutment at about 50^5 elevation. The vater vas flowijig at about 
50 cubic feet per second, vas moderately turbid and was ccming 
from the abutment rock. This vas not connected to the other seejiages 
xnentioned above. I felt this seepage vas coming straight out of the 
abutment rock and not throu^ the dam. 

I also saw another leak at about 5200 elevation in the jxmction of 
the dam embankment and the right abutment. The vater vas slightly 
turbid and issuing from the rock at about 2 cubic feet per second. 
The vater from this leakage vas not flowing at a great enough volume 
to even reach the toe of the dam. 

At about 9:30 a.m. Aberle and I vent to the south rim area of the 
dam and located Duane Buckert, Project Ifenager for Morrison-Khudsen 
and Kiewit. We discussed control measures and decided to excavate 
a channel at the toe of the dam to protect the pCT/erhouse. At this 
point I felt that the situation vas critical but we coiold control 
the leaks, since they vere coming from the abutment rock. I made 
calls to the Bureau of ReclHmation Regional Office in Boise, Idaho 
and talked to Harry Stivers, Assistant Regional Director, since 
the Regional Director vas not available, and the E&R Center, Bureau 
of Reclamation, Denver, Colorado. These calls vere only for the 
purpose of alerting those offices to the problem. I also considered 
the matter of alerting area residents at this time, but decided that 
an emergency situation vas not imminent and he did not want to cause 
a panic. These calls were made between 9:30 and 10:00 a.m. 

At about 10:00 a.m. I observed a large leak developing about 15 feet 
from the ri^t abutment in the dam embankment at an approximate 
elevation of 5200 feet. This leak vas on the downstream face of 
the dam and vas adjacent to the smaller leak at the same elevation. 
At first the flov of vater vas about 15 cubic feet per second and it 
gradually increased in size , The water vas turbid. By about 10:30 a.m. 
two Morrison-Khudsen dozers were sent to the area of this leak and 
instructed to push rock into the hole. 

At about 10:30 a.m. to 10:^5 a.m., I notified the sheriff's offices 
in Ifedison and Fremont Counties and advised them to alert citizens 
of potential flooding from the Teton Dam and to be prepared to evacuate 
the area da^nstream. I also received a call from Ted AustiJi, a 
radio announcer in St. Anthony, Idaho and advised him of the possible 
dan~er. There vas no equivocc-ion on ny part aDOU"& advising people 
of the danger at this tirte. 



fn 






C-30 



At about 11:00 a.m. I saw a whirlpool developing on the upstream 
Bide of the dam in the reservoir at about 10 to 15 feet into the 
vater from the face of the dam and less than 100 feet from the 
abutment wall. I had looked for a whirlpool at about 10:30 a.m. 
and had not seen one. The whirlpool ■inis approximately six feet 
in diameter, was stationary, and appeared to he increasing in 
size. The water on the reservoir side was clear. The approximate 
elevation of the whirlpool was 5295* I would estimate that at this 
time the vol\ime of water going through the upper leak on the downstream 
face of the dam was 100 cubic feet per second. 

At ahout 11:00 a.m., or soon thereafter, two Gibbons and Reed dozers 
came across the top of the dam and were directed to begin pushing zone 2 
and riprap material, into the whirlpool area. The dozers had to create 
a ramp down the face of the upstream side of the dam in order to 
get the riprap into the whirlpool and were never completely effective. 

At about 11:30 a.m. the two Morrison-Khudsen dozers on the downstream 
face of the dam were lost in the washout area and carried downstream 
by the rush of water. I may possibly be the individual in the center 
of the Time magazine picture, walking away from the dozers as they 
were falling into the washout area. 

At about 11:^5 a.m. the two Gibbons and Reed dozers working on the 
upstream whirlpool were piilled off their job of pushing riprap into 
the whirlpool and they proceeded to leave the top of the dam, heading 
for the south side. At this time I was on the road heading tCT,fard 
the Project Office and I sa;/ the top of the dam collapse from this 
location. I did not note the time, but when I got to the office 
the clocks had stopped at about U.:5T a.m. because of power failure 
and I assume this was the time of the collapse. Aberle told me 
he noted the time of collapse to be 11:57 a.m. 

At 12:10 p.m. I departed the dam site for Rexburg, Idaho, in order to 
place telephone calls to Bioreau officials in Boise, Idaho and Washington, 
D. C. 

When I noted the whirlpool developed at about 11:00 a.m. I realized 
there was imminent danger of the dam collapsing. From this time on 
there were numerous people making telephone calls alerting people 
in the area of the danger, 

I am not aware of any earthquakes or eart^ tremors which may have 
caused the viltimate collapse of the dam. 

Contractor personnel were b\isy during the morning hours attempting 
to clear equipment out of the river outlet tvmnel on the south side 
of the dam in anticipation of opening the river outlet tunnel to 

relieve the pr^s^uro o; t;.e vator o:; :;;i2 d^m. ■Z'^'^ ccn^-ac^or 's 
employees had to evacuate the tiimi-^l bofore they had accorrLnlished 
their task. I doubi; t'n&x. the openinii of the tunnel i,-ould have been 
effective in preventing the collapse of the dam. 



C-31 



At the time of the dam collapse there vas no schedule of work shifts 
for Bureau of Reclamation employees that would have required persons 
at the dam 2k- hours a day. On Saturday June 5^ 1976, the only 
scheduled Bureau of Eeclajnation workers were the survey crews. Theic 
were scheduled quality control inspections according to the work 
"being done, but there were no scheduled physical plant inspections 
of the dam on a routine basis by the inspectors. 

I have carefully read the foregoing statement, consisting of three 
and one-qu2rter ixiges and declare it to be true and correct to the 
best of my kncrwledge and belief. 



,,^^y^- .M^ 



Robert R. Robison 



Subscribed and sworn to before 
me this 23rd day of June 1976 

V^>-<uJ) /,,.<iW~ ^/-j^ivj fk. dJJ 

Vincent L. D-oran, Special Agent ^ 
U. S. Department of the Interior 

Betty J/ Foyes, /Special Agent U 
U. S. itep^-tmen-f/ of the Interior 



/L 



C-32 



a^ 



STATE OF Idaho ) 

) SS 
COUNTY OF Madison ) 



I, Alfred B, Suites , p. 0. Box 1^$, St. Anthony. loaho 

, being duly 

sworn make the following volxintary statement to Vincent L. Duran , 

who has identified himself to me as a Special Agent of the U. S. 
Department of the Interior. Ko threats or promises have been made to 
obtain this statement. 

I am emrjloved as a Construction Inspector, GS-9, Teton Dan Project, 

Bureau of Reclamation, Newdale, Idaho, I have held this position 

since June 1962 and have l6 years service with the Bureau of Reclamation, 

On Saturday, June 5, 1976, Jan Ringel telcDhoned me at my home and 
asked me to come to the dam immediately because there were Droblems. 
I arrived at the dam site about 10:15 a,m. and Itingel told me there 
was a leak in the downstream face of the dam and asked me to see about 
getting a dozer 'Do channel water away from the powerhouse. At about 
10:30 I proceeded to the pcfcrhouse and saw a leak in the dam on the 
downstream face at about 5200 elevation and near the. right abutment wall. 

Vfhen I arrived at the dam I talked to John Bellagante, who was preparing 
to take a dozer to the leak area, I also ran into Llewellyn Payne, wno 
was going intxs the river outlet tunnel with three other men to remove 
equipment in order that the tunnel could be openad, 

I then walked up the do-.-mstream face of the dam and passed the two 
dozers which were working at the 5200 elevation and trying to fill in 
the hole. The seenage water was muddy, but I carjiot estinate i.he volume, 
I arrived at the top of the dam at about 10: UO a.m. and within three or 
four minutes I noticed a whirlcool forming in the reservoir on the uostream 
side of the dam about 22 feet into the vrater from the face of the dam,-=nd. 
s w^U. t^?-^r^^--;;::r :^=^s^t^£;£ ? i ^r=jT7s: :=:^^ The whirlpool was approximaoely 

1.\ feet in diameter at the outset, briefly got smaller, and then began 
increasing in size. The water in the area of the whirlpool 
appeared to be sligntly muddy. I watched the whirlpool for possibly 
five minutes and then ran back dovm the dovn-.stream face of the dam to the 
area of the powerhouse on the left side (south). Before I left the top 
of the dam two dozers were beginning to nush riprap into the whirlpool. 
This was about 10: Ii5 a.m. or shortly thereafter. 



C-33 



When I arrived at the powerhouse aarea I noted that one of the dozers 
working on the doi-mstream face was falling into the washed out area 
and the other dozer was atternpting to pull it out. A very short time- 
thereafter both dozers were washed away in the stream of water. The 
volume of water at this point had increat>cl tremendously and the water 
was very muddy. 

Shortly after 11:00 a.m. Payne and his fellow workers evacuated the 
river outlet tunnel and three other -oersons in the powerhouse area 
were evacuating notorized equipir.ent to higher gi^und near the dam. 
I drove to the upoer south rim oposite the spillway and observed 
the washout area on the downstream face continually increase and portions 
of the dam falling into the vacuum. This was during the period 
11:30 a.m. until almost 12: DO noon when the top of the dam. finally 
collapsed. I felt that the dara was definitely going to collapse shortly 
after 11: Ou a.m. when the two dozers were washed away. 

I remained at the dam until about 10:30 p.m. and much of this time 
was spent trying to keep spectators behind the visitors point 
on the south rim. I cannot estimate the number of spectators that 
were there during the day. 

During the afternoon, after the water had receded, it appeared to me 
that the grout cap was still in place. I noticed some water was 
riinning out of the right abutment, uostream of the grout cap, but I 
did not observe any water running out of the abutment dovmstreara of 
the grout cap. 

I have carefully- read the foregoing statement consisting of one and one-half 
pages and declare it to be true and correct. 



Alfred D. Stites 



Subscribed and .sworn to before 
me this '2,7'^ day of June 1976 




Vincent L. Duran, Special A^en,-^ 
U. S. Department of the Interior 



C-34 



STATE OF IDAHO 

ss 

COUNTY OF MADISON 



T Stephen ELenberger, ^ Victor, Idaho, 



, being duly sworn make the 



following voluntary statement to Vincent L. Duran , who has identified him'.el 
to me as a Special Agent of the U.S. Department of the Interior. No threats 

or promises have been made to obtain this statement. 

I have been employed as a Construction Insoector, GS-7, Teton Dam Project, 
Bureau of Reclamation, Newdale, Idaho for four and one-half years and have 
a total of nii^ years vrith the Bureau, ^'^AOOUT "^ 

On Friday, June Ii, 1976, I was working the IjrOO p.m. to 12:30 a.m. shift 
at the dam. Up until dark, which occurred at about 9:00 p.m. or shortly 
thereafter I made several observations of both the downstream side and 
the upstream reservoir. I had been alerted to pay particular attention for 
possible leaks because th=re were small spring like areas of water on the 
north side of the canyon well below the toe of the dam. These springs were 
clear water and had been visible for two or three days. 

Unliil darkness I did not see any sign of a leak in the toe of the dam at 
the north or right abutment at about 100 feet from the top of the dam 
near the north or right abutment. The entire dowTnstream face of the 
dam showed no signs of any problems. I also did not see anything unusual 
in the reservoir or upstream side of the dam. There was no sign of a 
whirlpool. 

I was not at the dam on Saturday, June 5, 1976, and can furnish no infor- 
mation about the events of that day. 

I have carefully read the foregoing statement, consisting of 1 page, and 
declare it to be true and correct. 



Stephen Elenberger 



Subscribed and ^swom to before 
me on this^/^ay of June 1976. 

Vincent L.'' Duran, Spe^cial Agent ^ 
U.S. Departm.ent of the Interior 



C-35 



GIBBONS & REED-CONTRACTOR WITNESS STATEMENTS 



Harold F. Adams 
Route 3, Box 259 
Rigby, Idaho 

Dave Burch, Mechanic 
P.O. Box 384 
Ashton, Idaho 

Jerry Dursteler, Master Mechanic 524-1396 

280 Wilson Drive 
Idaho Falls, Idaho 

Perry Ogden, Mechanic 356-7920 

Rexburg, Idaho 

Lynn Walker, Superintendent 458-4304 

Behind June's Bar 

Teton 



C-36 



COPY 



STATE OF Idaho ) 

) SS 
CXDUNTY OF I^dison ) 



If Harold F. Adams , Rt. 3. Box 259. 



BJRby, Idaho , being duly 

sworn make the following voluntary statement to Vincent L. Duran t 

who has identified himself to me as a Special Agent of the U. S. 
Department of the Interior. No threats or promises have been made to 
obtain this statement. 

I am employed as a mechanic with Gibbons and Reed Company on the Teton Dam 
Project, Ifewdale, Idaho. I jiist started on that project about June 1, 1976. 
Previously with company three years. 

On Saturday, June 5^ 19T6, I arrived at Gibbons and Reed yard behind 
Bureau office at 7:00 a.m. to work on equipment. As I drove in I saw a 
small trickle of water on dOT/nstreara slope of dam against the north abutment 
and about 100 feet from top of dam. About 30 feet out there was a wet 
spot. 

At about 8:00 a.m. I walked from the shop out to south rim to look at 
leak again. Now small stream coming out from where we saw wet spot. At 
about 9:30 or 10:00 a.m. Dursteler told us to look at leak. From south 
rim I saw a 6 or 8 inch diameter flow of water. Dursteler said we had 
trouble . 

I went about 2 miles downstream out of site of dam to get equipment out 
of possible danger area. Just before leaving I told my wife to be on the 
alert because of leak. I was (sic) downstream about 30 or 40 minutes. 

When I got back water flo\7 had increased and Gibbons and Reed dozers out 
on top of dan working. The time was between 10:00 and 3JL:00 a.m. I 
watched from visitor viewpoint. 

I would estimate dam collapsed at top somewhere around 11:30 a.m. and the 
dozer had gotten off just before that. 

I cannot be specific about times. No earthquake or tremor. I never saw 
upstream side during the day. 

I was in the area until 5:30 p.m. but did not get involved in crowd control. 



C-37 



I thou^t dam votild go at about 9:30 a.m. vhen the flo^r of vater had increased, 

I did take note of ^fol-rison and Khudsen tractor activity and saw them get 
washed away. I do not know the time. 

I have carefully read the foregojjig statement, consisting of 3 
pages and declare it to he true and correct. 



/g/ Harold F. Adams 



Subscribed and sworn to before me 
this 22nd day of Ji-sie IJTo 



/s/ Vincent L. Dirran. S-cecial Aront 
Vincent L. i/oran, opeciaj. Aq^enz 
U.S. Department of the Interior 



C-38 



COiT 



STATE OF Idaho ) 

) SS 
COUOTY OF ^^dison ) 



1, "Rs.vidBurch , P.O. Box "^Sh 



Ashton , Idaho , being duly 

sworn make the following voluntary statement to Betty J. Foyes , 

herself 
who has identified ki.E^s;«li^ to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am eE'iployed as a mechanic vith Gibbons and Reed, the contractor who is 
"bunding the Irrigstion canals at the Teton Dam Project, Nevdale, Idaho. 
I have been employed by Gibbons and Reed since May 30, 1976, and was 
formerly employed by i-'orrison-Khudsen and FCiewit on the Teton Dam Project 
in the same capacity for almost four years. 

I arrived for work at 7: CO a.m. on June 5^ 1976. As I was drivimg up the 
canyon to the G-H shop I noticed a seepage dawTi the norxh side of the dam. 
The seepage was slight and started at about the 5200 level near the change 
of the slope and ran drr.-ra the abuxment wall t awards the toe of the dam. 
You could noo actually see waT:er innaing — j'list the dampness. I could not 
tell if the water was clear or muddy because it was just dampness. I 
mentioned to some of my co-vorkers that the dam was leaking. We were not 
concerned at that time that there was any real problem and we went on with 
our work at the G-R trailer. 

At about 9:30 a.m. I noticed a wet spot appear on the north side of the face 
of the dam. This spot was about 100 feet from the abutment and probably 
125 feet from the top of the dam. The damp spot appeared to be about 3 or 
h feet in diameter from my viewpoint at the trailer. There was not any 
vater flowing from the damp spot at that time. 

At 10:00 a.m. I observed water coming from the above described spot. The 
vater was coming at a steady flow and was muddy. 

At approximately 10:30 we went down in the canyon to the beaver slide to 
get our equipment — a scraper and a D-3 cat. There was another D-3, cat 
in the field south of the project parking lot on the canal and we also 
brought that to the dam. Me put the 2 D-o cats to work on the upstreain 
ffiae of the dam driving them tron the south to the north side. This was 
about 11:00 a.m. when we got on top of the dam. 



C-39 



When I crossed the top of the dam driving my D-8 cat there was a large 
flow of water coining from the hole in the dan on the downstream side. I 
voTjld estiinate that the hole was 10 to 12 feet in diar.eter and the water 
was muddy and rocky. The V.-K dozdr operators were pxising riprap and gravel 
Into the hole, vrnen the M-K dozers were caught in the hole, M-K personnel 
asked me to try to save xheir dozers by me backing my cat over the facp 
of the dam and pulling then out, but it was too late. The dozer on the 
extreme righthamd side of the Time i-la^zine photograph. Page 57, is mine. 
I am the man on the left of the t->ro individuals standing near the cat in the 
picture. The other man who is standing to my rigit is the H-K employee 
who had requested my help in pulling out their cats. The red truck to my 
left belongs to Owen Daley, an M-K employee. 

I had started pushing riprap from the face of the dam towards a whirlpool 
or funnel which he-d developed on the reserA'oir side of the dam shortly 
after 211 ;00. The whirlpool was directly across from the spot where tne 
hole appeared on the da,ra,stream face of the dam. Vfnen I first saw the 
whirlpcol, it was very small, na;^'be a foot across and WcLS very muddy and 
it was surrounded by clear water. I saw no other mud on the upstream side. 
The water on the reservoir side was very calm. There was very little 
wind. The whirlpool was about 20rjLeet o^^t from the urstream face of the 
dam and about 100 feet from the north ab\itm.ent. We tried by xising the 
riprap to build a ramp to the whirlpool but never succeeded. TrfO M-K men 
then came and took the cat I was driving and tne one Ferry was driving 
since neither of us are cat operators. It was after I got off the cat 
that the picture was taken which appears in Time magazine. Perry and I 
left at this point to obtain a 9o5 cat loader to laod fines to help plug 
the hole on the downstream side. At the time we left the two M-K men 
were operating the cats at the top of the dam, having lost theirs in the 
hole. There wa^ also a pickup truck on the top of the dam. I was sitting 
In the 938 Loader near the M-K shops when the dam collapsed at about 12:00 
noon or a little later. 

I first became aware that the dam was in danger of collapsing when the 
water started running through the hole on the downstream face of the dam 
at 10:00 a.m. 

I at no time felt earthquake tremors at the dam. 

I saw only one whirlpool on the reservoir side of the dam and when I left 
the dam I would estimate it was 20 feet in diameter. 



C-40 



I have read the above statement consisting of foxor and one-half handwritten 
pages and declare it to be true and correct. 



/s/ David L. Burch 
David L. Burch 



Subscribed and sworn to before 
me this 22nd day of June 1976 



/s/ Betty J. Foyes 

Betty J. Foyes, special A.?;en-c 
U. S. Department of the Interior 



C41 



STATE OF IDAHO 

ss 

COUNTY OF MADISON 



I. 



Jerry Dursteler^ 280 Wilson Drlv^ 



Idaho Falls, Id^io » being duly sworn maka the 

following voluntary statement to Vincent L. Duran, who has identified hiiTisei f 
to me as a Special Agent of the U.S. Department of the Interior. No threats 
or promises have been made to obtain this statement. 

I am employed as Master Mechanic, Gibbons and F.eed, Teton Dan Project, 
ITewdale, Idaho. I have been on this job since February 1976. 

On Saturday, June 5^ 197^, Perry Ogden and I arrived at the company 
yard behind the Eeclamation offices at about 10:00 a.m. \le came to 
do maintenance work on equipment. Wp.en at the office, I heard water 
running. I drove daiv^ls^re^3l from xhe dam on ohe upper south rim road 
to look at the spillway and to see if water ■^ras flcr,Jing over it. I 
saw witness on the da^mst:reara face of the dam and seepage against 
abutment wall. This was about at the slpe change in the dam. I cannot 
be more specific. The water was muddy, but was merely a lirht stream. 
I went back to u^f truck. By then the wet spot had started flaring. 
This was a very small flew. I returned to ny office and told Adarn^ and 
Burch there was a problem. The three of us walked behind the Reclamation 
offices on the soutside of the dam to look at the dam. The leakage 
had increased considerably and started eroding a hole. This was about 
10:15 a.m. 

I then returned to my office and Perry Ogden and I started towsird the 
dam in a truck. We ran into Itobison and agreed to move v^o dozers out 
on top of the dam for whatever purpose. I radioed Lynn Walker and asked 
him to come to the site. Ogden and Burch moved two dozers onto the dam, 
I reisadned in the office area taking pictures of the downstream canyon 
va3J.s and soma of the face of the dam. I took pictures from the visitor's 
viewpoint, downstream rim and from the Morrison and Knudsen yard. 

Between 10:15 and 10:30 a.m. two Morrison Knudsen dozers were pushing 
material ?jito the downstream face of the hole. Tae hole was very large 
with a big stream of water. Gibbons and Eeed dozers got onto the 
top of the dpm, I saw Morrlson-Knudsen dozers wash out but have no idea 
of the time. 



C42 



John Bellaganti and Owen Daley operated Gibbons and Reed dozers 
pushing rock into the vhirlpooi area on the upstream side of the 
dam. I never saw the vhirlpooi. I watched activities, but cannot 
give tine e^jrosnts. I was waxching pricsrily from the visitor's 
observa-cion point. Gibbons and Heed dozers were pulled out and 
just bai-ely cleared the top of the dam when it collapsed. 

I "believe the tir^ elenent was two hours from the time I arrived, 
"therefore the dam collapsed about 12:00 noon. 

During the events the ai-ea at the visitor's center was completely full. 
I do not know any of the people who were on the visitor center. 

During ray observation t.he water was muddy and the area of leakage 
grew big~er at a very fast pace. I am not aware of any earthquake- 
like tremors. 

I have carefully read the above statement consisting of one smd one-half 
pages and declare it to be true and correct to the best of my knowledj^e 
and belief. 





'Jerry i'-<irsteler 



Subscribed and sworn to before 
me this 22nd day of Jime 1976 




■.^r^; /y - 1 '^■LCi-r 



<\o I, 



Vincent 1,. L^iran, opacial Azenz O 
U. S. Department of tne Interior 



lersteler stated orally that at about 10:30 a.m., when the Morrison- 
Khudsen dozers were los-u on the downstream side 01' the dajn he realized 
the collapse of the dam night be iuminen-c. 



C43 



STATE OF ItiahiJ I 

) 

COiraTY OF Madison ) 



, being duly 

sworn make the following volxmtary statement to v-i.nf°nt t,. Th^rf^.n r 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am employed as a mechanic ^ri.th Gibbons and Eeed Company doing Canal 
construction -work at Teton Dam Pro.lect, llewdale, Idaho. I have been with 
Gibbons and Eeed at Project since February 1976. Previously with Itorrison- 
Khudsen-Kiewit at the project about 2 years. 

On Saturday, June 5» 197^, I was scheduled to do maintenance on equipment 
at the shop area behind the Reclamation offices. I arrived at shop at 
7:00 a.m., went right to o\ir shop area. I was out of view of most of 
dam, but could see top part. Shortly after I arrived, Dave Burch told me 
there was a wet spot on the downstream side of dam. I walked over to 
visitor's viei^rpoint on south rim and saw a wet spot at about 100 feet 
from top of dam agairist abutment. No f lairing water — jvLst a wet spot. 

Between about 8:30 a.m. and 9^00 a.m., Dursteler arrived at work and told 
me water was running through dam. I went to Reclamation office and talked 
to Robison. He asked for pTI dozers we could get to dam area. I went 
down road and got dozer and returned to top of dam with dozer. Tliis 
was about 9:30 a.m. On damstream face there was good flow of water and 
a hole about 30 feet in diameter. Morrison and. Khudsen dozers vrorking on 
this hole. Burch arrived with a dozer and the two of us crossed the dam 
and started pushing riprap into whirlpool. This probably about 10:00 a.m. 
or so. Whjjrlpool developed at this time about k feet in diameter. 

Sometime after this Belle gante came up and told me the dozers on downstream 
face were gone . He and Daley came up and took over Burch and my dozers . 
About 10 minutes later Burch and I drove a pickup to the southside of dam 
and went to viewpoint. 



C44 



I stood on viewpoint about one hour watching, with exception of one phene 
call to my wife. During this ham.' the dam kept eroding and more water 
flowing. I was certain dan was going to collapse. The Gibbons and Reed 
dozers cleared out almost last few minutes and came across dam. Jtist about 
noon when dam collapsed. I recall looking at my watch right after top 
fell and it was 11:55 a.m. 

No earthquake or tremors. 

!I5iere were a large number of visitors. Visitor area full and vas lined up 
along entrance road. 

I have cEirefully read the foregoing statement, consisting of 3 

pages cind declare it to be true and correct. 



/s/ Perry Ogden 



Subscribed and sworn to before me 
this 22nd day of June 1976. 



/s/ Vincent L. Duran. Special A^ent 
Vincent L. Lraran, :apacia-L Arsno 
U.S. Department of the Interior 



C45 



STATE OF IdElho ) 

) SS 
(XJONTY OF Madison ) 



1 Jerry Lynn WnlVer , Teton Trailer Court, Teton, Idaho 

~ ' ~" (Temporary) 

695 East 1st North, Pleasant Grove, Utah (perm anent) , being duly 

sworn make the following voluntary statement to Betty J. Foyes , 

who has identified himself to me as a Special Agent of the D. S. 

JDepartment of the Interior. No threats or promises have heen made to 

obtain this statement. 

I am employed as Superintendent, Gibbons and Beed Construction Company, 
and have held this position for about 12 years. I have been employed 
by Gibbons and Reed at the Teton Dam Project, Bureau of Reclamation, 
Hewdale, Idaho for about three months. Gibbons and Reed has had a 
contract since about April 1976 to construction irrigation canals 
and a water pipeline to other canals below the dam. 

On June 5; 1976, I arrived at the Teton Dam about 10:30 a.m. because 
subordinate Gibbons and Reed employees had called me on the radio at 
ny home to advise me that the dam vas leaking. I would estimate that 
I vas called about 10:15 a.m. I immediately went to a point just 
downstream from the visitor's observation point, on the southside of 
the dam. At that time I observed a hole approximately 3' in diameter 
located at the 5200 elevation, near the abutment wall (north). There 
vas a sizeable flow of muddy water coming from a portion of the hole 
and it had begun to wash out a trench. There was a dozer coming down 
the slope of the dam toward the hole. At this point I knew the dam 
vas gone and I went back to my office to call my family. I then returned 
to observe the dam after making one other call. The time which elapsed 
vas probably I5 minutes. Tois would place my return to the dam shortly 
before 11:00 a.m. By then the second dozer was in position and the 
two dozers were trying to push rock into the growing hole. The hole weis 
growing fast and was about 10 to 12 feet in diameter at this time. 
Bie stream of muddy water had increased in volume correspondingly. 

By the time I had arrived at the dam at 10:30 a.m. two D-8 dozers belonging 
to Gibbons and Reed had been disp-atched to the top of the dam to 
vork on the upstream face and push riprap into a whirlpool which had 
developed. Tjo of my mechanics had obtained the D-8 dozers and had 
begun this work. The two l-'orrison-Knudsen dozers on the downstream 
face of the dam were lost at about 11:15 to the "b?st of -rr^r recollection. 
At this point I went to the top of the dam to order ny v^-o dozers 
to stop n-or'i:: and leave xhe cou of t'-ie dr::.Tn. vrnile I vas standing en 
the visitor's observation point and after the two M-K dozers were lost 



€46 



a crack developed above the hole. The crack vas in the shape of 

a Genii-circle with the arc at the top; vas about 30 feet above 

the tole; p-'.d I woiild estimate that it may have been as much as 100 

feet in total length. The earth starting sluffing down from the 

crack towards the hole and caused an offset in the earth on the face 

of the dam as it sank. As this earth fell in a small hole developed 

above the crack. I would estimate this wb.s about 15 to 15 feet 

above the crack and was initially six or seven feet in diameter. 

I then left the visitor's observation point and drove to the top 

of the dam. I would estimate that I reached the top of the dam 

at about ll:4o a.m. My cats were eilready coming across the top of 

the dam towards the south side. As soon as I saw that my cats were 

getting off the dam, I drove back to the visitor's observation point 

and observed that while my cats were about one-third of the way across 

the top of the dam sluffed down about 100 feet. About 11:55 a.m. the dam 
failed. 

I at no time was in a location where I could observe the whirlpool 
vhich had formed on the upstream side of the dam. 

I at no time felt earthquake tremors at the dam site either before June 5 
or on June 5> 1976. 

About 7:30 plm. on June 5> 197^, after the water was down to the lowest 
ievel it would reach at that point, I was at the upper curve of the M-K 
access road on the south rim of the dam and I observed a six inch 
stream of water coming out of theahorthside abutment rock. The water 
was clear as a bell. The water was coming from a spot about 100 
feet dawn from where I would estimate the crest of the dam had been. 
We took some photographs and I may be able to furnish a picture of 
this occurrence. We have some other photographs of the collapse of 
the dam and I will make arrangements to have a set of the photographs 
furnished to the Department of the Interior. 

I have carefully read the foregoing statement consisting of one and 
one-half pages and declare it to be true and correct. 



<z: 



^/<>'7>>^-C^^ t>CX^^^ 




J«j^^ Lyn^ Walker 



Siibscribed and sworn to before 
me this 23rd d ay of June I976 

Betty J. Foy^;:, 3j;3cial /A^;n^ 
U. S. Departr^ntlybf the Interior 



ZAl 



MDRRISON-KNUDSET^I , KIEWITT EMPLOYEE WITNESS STATEMENTS 



John P. Bellegante 
Teton Villa Apts. 
Rexburg, Idaho 

Duane E. Buck^.rt 
Kit Circle #14 
St. Anthony, Idaho 

Jay M. Calderwood 
Victor , Idaho 

Roy C. Cline 
Kit Circle #22 
St. Anthony, Idaho 

David 0. Daley 

330 W. 8th St., Space 6 

St. Anthony, Idaho 

Llewellyn L. Payne 
P. O. Box 37 
Ashton, Idaho 

Vincent M. Poxleitner, Jr, 
P.O. Box 22 
Teton City, Idaho 

Barry W. Roberts 
Kit Circle No. 1 
St. Anthony, Idaho 

Donald D. Trupp 
P.O. Box 3 
Newdale , Idaho 



C48 



COPY 



STATE OF Idaho ) 

) SS 
COUNTY OF Had i son ) 



I, John P. Eellegante , 262 N. Second W. , 

Rexhurg, Idaho , being duly 

sworn make the following volvintary statement to Vincent L. Duran , 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am employed as excavation superintendent, Morrison-Knudsen and Kiewit 
at Teton Dam Project, Uewdale , IdEiho. I have worked there since March 
1975. 

On Saturday, June 5? 1976, at about 1C:00 a.m., Duane Buckert telephoned 
me and told me the dam v/as leaking and to come to project. I arrived 
at the project at 10:30 a.m. and went directly downstream of the dam 
in the area of the powerhouse. Buckert told me by radio he wanted to 
try and fill in hole. I saw a leak near north abutment side at about 
5250 feet elevation. There v/as a fast flow of water down slope and 
there were several gallons per minute coming down, '..'ater was muddy. 

Prior to Saturday, thei-e were leaks on north side at toe elevation of 
dam. These were on north side. There were three that I know of. Clear 
water on these leaks. This was about Tuesday or Wednesday. 

On Saturday, I went on top of dam, got a dozer and Instructed Owen Daley 
to get another dozer. The tvro of us went dovm and started pushing 
rock into face of leak on the downstream face. This was about 10:^0 a.m. 
To my knowledge there was no increase in the leakage. 

Hy dozer settled into hole created by leak. I got a cable at top of 
dajn and hooked the tvro dozers together. We were unsuccessful and both 
dozers went with the vfater. I would estimate this to be about 10:55 a.m. 
to 11:00 a.m. I looked dovm into the hole, '..'hite water was gushing 
out of the north abutment through the rocks and creating the muddy water. 

I then went to top of dan. Others had found whirlpool on upstreajn face 
and were directing dozers to push riprap into whirlpool area, '..'hirlpool 
was about 18 inches in diameter near the north abutment vrall about 15 feet 
from upstream face of the dam. I did not notice it getting bigger. I 

could feci the Lv.~. r.rca scttlin- and rullei -he do::era out. ^ozc.rz -.-.•cnt 
to southside a,nd I went to northside. I cannot ;?ivo tine elements of this. 



C49 



Shortly aftervrards, the dan collapsed. I do not know the time. At 
no point did I think the dain vras going to collapse. These were the 
last thoughts I had until innediately before it went. 

I proceeded do'm the northside rin with others notifying people and 
eventually returned to office on southside. I was in the area until 
abDut 5=00 p.m. 

I have carefully read the foregoing statement, consisting of 3 
pages and declare it to be true and correct. 



/s/ John P. Bellegani 



Subscribed and sworn to before me 
this 19th day of June 1976. 



/s/ Vincent L. Duran, S~;^cial A-ent 
Vincent L. Dura.n, Special Agent 
U.S. Department of the Interior 



C-50 



ccfpy 



STATE OF Idaho ) 

) SS 
CX)DNTY OF Madison ) 



I, Duance I!, guckert , Kit Circle #14 



St. Anthony, Idaho , being duly 

sworn make the following volxintary statement to Vincent L. IHiran ^ 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am Project Manager, F.orrlson-Knudswn-Klewit on Teton Dam Project, Newdale , 
Idaho. I have been on the project for two years. 

On Saturday, June 5, 1976, I arrived on job at approximately 8:30 a.m. 
and drove out on top of dam. As I drove out I saw water coming out of 
side at abutment below toe of dam. Tlie water was clear. I was told 
Robison had been notified. Robison, Aberle, Ringel and I met regarding 
this leak and decided to channel this water to reduce erosion and keep 
away from power house. I agreed to get people and went to the office to 
make telephone calls to employees, '.."hile doing this, Aberle came in about 
10:00 a.m. and told me another leak had appeared. 

At about 10:20 a.m. I went out and saw leak on downstream face of dam. This 
leaJc at about elevation 5200 and about 10 or 12 feet out from abutment. The 
area eroded out was about six feet by six feet. The flow, I cannot estimate, 
but it vras muddy and erosion vjas occurring. I sent two dozers in to 
push rock into the hole. I then went down into tunnel area at power- 
house to get it cleaned out for possible opening. The erosion was increasing 
at the leak area. 

I went back up on top of the dam and ran into Robison. He told me two 
dozers had been lost on the downstream face. We talked about opening the 
river outlet tunnel. This was about 11:00 to 11:20 a.m. A whirlpool had 
developed on the upstream reservoir of dam. I did not actually see the 
whirlpool, but saw dozerspushing materials in. 

I proceeded to office when Poxleitner told me he did not believe the 
dam would hold. This was sometime around 11:20 a.m. I then went to the 
office and made telephone calls to notify area residents of the danger. 
During this time I observed the increasing turbulence of water, but did 
not actually see the final collapse. I saw the dozers on top of dajn 
leaving and coll:irr:inr cr-rth bf^hini them. The ti~e of 11:57 a.m is close 
to the actual time of failure. 



C-51 



I realized the loss of dam when I heard about the whirlpool at atout 
11:30 a.m. This was the first tine the facts really dawned on me. 

I was not iir.-olved in crowd control. This was handled by the Bureau 
of Reclamation. 

I have carefully read the foregoing statement, consisting of 2. pages 
and declare it to be true and correct to the best of my knowledge. 



/s/ Duane E. Buckeri 



Subscribed and sworn to before me this 
19th day of June I976. 



/s/ Vincent L. Duran, S-pcclal Aront 
Vincent L. Du^an, Special A;:pnt 
U.S. Department of the Interior 



C-52 



COPY 



STATE OF Idaho ) 

) SS 
COUNTY OF Kadison ) 



J Jay M. Calderwood Victor, Idaho 



, being duly 



sworn make the following voluntary statement to Vincent L. Dvuran ^ 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am general excavation foreman for Motrison-Knudsen and Kiewit on Teton 
Dam Project. I worked on the project at Hewdale , Idaho, from March 1972 
to present. 

On Saturday, June 5i 1976, Pay Short , timekeeper, telephoned me at 
home and told me there was a leak in the dam. I arrived at the dam at 
11:30 a.m. I went directly on top of dam. I saw a hole about 20 feet 
in circumference, about 15 feet from right abutment and about 2/3rds 
way up from bottom. 

There was a large anount of water, muddy and washing the hole bigger all 
the time. I thought then we could not stop the water and the dan would 
go. I jumped on a dozer on top of dan, worked on pushing riprap into 
the whirlpool, which was on the upstream side about 12 feet to 14 feet 
in water near the right abutment, not far out. The whirlpool was about 
20 feet to 30 feet in circumference and 5 feet to 6 feet in depth. It 
continued to get larger. 

I pulled the dozer back to southside and within two minutes the top fell 
in. This was about 11:50 a.m. or thereabouts. V:hen I looked at my watch, 
it was 12:00 noon anci the dan had collapsed about 5 to 10 minutes before. 

I have carefully read the foregoing statement, consisting of 1-1/2 
pages and declare it to be true and correct. 



/s/ Jay Calderwood 



Subscribed and svjorn to before me 
t^^is 19th day of June 1976. 



/s/ Vincert L. I>jran, t-~^ecial A.rent 
Vincent L. ./jL-an, ^pc-ciai A.;c.r.^ 
U.S. Department of the Interior 



C-53 



COPY 



STATE OF Idaho 



) SS 



COUNTY OF Kadison ) 



I, Roy C. Cline 



Kit Circle #22 



St. Anthony, Idaho 



, being duly 



sworn make the following voluntary statement to Vincent L. Duran 



who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am employed as master mechanic at Morrison-Knudsen-Kiewit on the Teton 
Dam Project. I have been on the project since January 1972. 

On Saturday, June 5. 1972, at abDut 10:30 a.m., Duane Buckert telephoned 
me and told me there was a leak. I arrived at 11:00 a.m. and went 
directly to the powerhouse, I saw a stream of water from right abutment 
about 3/^'-th way up the dam. Volume was equivalent to vfhat would run out 
of a 10- inch pipe. It appeared clear at the time. I proceeded to make 
a roadway behind pov/er in preparation to opening the river outlet. I 
did this and then moved a truck. At about 11:30 a.m. , I looked at the 
dam from powerhouse and saw the two dozers had disappeared, the hole was 
big, and a Isirge volume of muddy water. I cannot estimate the size of 
hole or volume of water. I moved crane and other equipment to top on 
southside. I'hen I reached the top I saw the final collapse of the dam 
top. I would estimate I arrived at top and saw collapse at about 11:55 a.ni. 
I proceeded to office and arrived at noon. 

I felt the collapse was imminent at about 11:30 a.m. when dozers were 
gone, and I began leaving the powerhouse hole. 



I left the area shortly after 12:00 noon. 

I have carefully read the foregoing statement, consisting of 
and declare it to be true and correct. 



pages 



/s/ Roy C. Cline 



Subscribed and sworn to before me 
this 19th day of June I976. 



/s/ Vi 



ncpn1 



^t'-. 



^ ^ .-^ n T_ 3 T i_ .- 



Vincent L. luran, Jriecial A.xcnz 
U.S. Benartment of the Interior 



C-54 



COPY 



STATE OF Idaho ) 

) SS 
COITNTY OF I-edison ) 



I David 0. Daley ^ 330 '•'. 8th Gt. , I'pace 6, 



St. Anthony, Idaho ^ being duly 

sworn make the following voluntary statement to Vincent L. Jura.n , 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am employed as equipment operator vfith Korrison-Knudsen-Kievjit on 
Teton Dam Project, I\ev;dale, Idaho. I have worked there since liarch 15 1 
1972. 

On Saturday, June 5i 1976, at 10:10 a.m., I got a call asking me to 
come to the dam. The timekeeper cp.lled and did net give r.c details. 
I arrived at 10:25 S--^-- I stopped at office briefly and then v;ent on to 
dam. I sav; leaJv on north side within 15 to 20 feet of abutment and 
about 100 to 150 feet from top of dam. A small stream of v;atcr was 
flowing, but could not :5ee if rr.ter muddy, v-j-o^ that point on the hole 
got bigger and more i.-ater flo>:ed. Water definitely muddy. 

I would guess Eellegante and I lost our dozers in the flovf of v/ater on 
the dovrnstream face at about 11:15 3..m. The two of us went up to the 
top of dam and I operated a Gibbons and Jeed dorrer trying to fill in 
the whirlpool on the upstream reservoir side of the dam. 

The whirlpool was about 30 feet out into vrater and about 20 feet in 
circumference. The pool v;as rather close to the north wall. I operated 
one dozer about one-half hour before we pulled then out. We got dozers 
on top of dam and headed toward southside of the da.m. This was about 
11:^5 a.i^. or possibly a little later. As we were driving off the dam the 
top caved in. 

I never believed the dam i;as going to collapse until the lE,C3t minute 
when we pulled the dozers off. I cannot give specific or estimated time 
of collapse. I have heard it was 11:57 a.m. 

After the collapse I watched the v:ater go down the river a short while 
and then left for home. I did not get involved with onlookers. 



C-55 



I have carefully read the foregoing statement, consisting of 
pages and declare it to be true and correct. 



/s/ David O.ren Daley 



Subscribed and sworn to before ne 
■this 19th day of June 1976. 



/s/ Vincent L. Duran , Sprc ial Af-en 
Vincent L. Duran, Sp-ncial Arent 
U.S. DeTiartrient of tYe Interior 



C-56 



COPY 



STATE OF Idaho ) 

) SS 
COUNTY OF Kadison ) 



I, Llewellyn L. Fayne , P.O. Box 37, 



Ashton, Idaho , being duly 

sworn make the following voliintary statement to Vincent L. Duran 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement, 

I am employed as concrete superintendent with I'orrison-Knudsen and 
Kiewit, on the Tetan Dan Project, Newdale, Idaho. I have worked there 
for three years and one month. 

On Saturday , June 5 > 1976 , Duane Buckert called my house and left a 
message for me to come to the dam. I got the message about 10:00 a.m. 
and arrived at 10:20 a.m. I travelled "by the lower road and arrived 
at the powerhouse. As I approached I could see muddy vjater in river but 
not the actual leak. As I got closer, I could see the leal:, v.'hich v?as 
about 75 - 100 feet from top of the dam on north side against abutment 
and zone material. I cannot estimate volume and at this time I 
did not see ictual hole. 

After my arrival I got Archie J. Zuern, Claude Rhodes, Ilichael Powell 
and Charles PoT/ell and went into the river outlet tunnel. The purpose 
was to get painting equipment out in order to let vfater through, -ie 
went into the tunnel about 10:30 a.m. At the time, one dozer was 
working on downface of the dam and another was on its vray. I was in 
and out of the tunnel and v/atching leak so could pull men if danger 
became too great. 

The leak grew larger - vfater was muddy, and at about 11:20 or 11:30 a.m. 
the tvro do:rers were washed out. 'v'e went into the tunnel one more time 
to move anything, "ie left for the top of the dajn shortly thereafter 
on foot. The water vras flowing heavily and began coning around the 
powerhouse, '.''hen I was about half- way up, I could see dozers working 
on top. I could see the dam washing out and radioed to move the cats 
because the dam vfas going. I saw the dam go, but cannot make a guess. 
I did not look at a watch and just never gave the time factor a thought. 

At about the time the dozers were lost - 11:30 a.m. , I was scared and 

h?-d the fc*?!!*!^ the dam t-'wH "oin"" to coI'^tt^^^^ 



C-57 



Ve worked on croud control as rauch as we could. Also number of cars 
that cane to' the dan. 

I have carefully read the foregoins statement, consisting of 2y 
pages and declare it to be true and correct. 

/s/ L. L. Payne 



Subscribed and cKorn to before me 
this 19th d ay of June 1976. 



/s/ Vincent L. Dnran. 5; -fecial Arent 
Vincent L. Duran, Special Acont 
U.S. Department of the Interior 



C-58 



COPY 



STATE OF Idaho ) 

) SS 
COUNTY OF Madison ) 



I, Vincent H. Poxleitner, Jr. , P.O. Box 211 



Tetftn, Idaho ^ being duly 

sworn make the following vol\intary statement to Vincent L. Duran 

who has identified himself to me as a Special Agent of the 0. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am employed by Ilorrison-Knudsen, Kiewit, at the Teton Dam Project. I 
have been employed here since June 22, 1973. I a™ the Project Engineer. 

On Saturday, June 5, 1976, Duane Buckert, Project Manager, telephoned 
me at home shortly after 9:00 a.m. He asked that I come to the dam 
immediately because there was a leak. I arrived within 15 minutes at the 
office. As I came through gate saw v.'ater running out of downstream face 
of dam. The leak vras on right-hand side of dam just off the abutment at 
about 5150 to 5200 elevation. The water was turbid from vrhat I could 
see. The volume was the equivalent of what you see coming out of 12" 
pipe. 

Buckert was moving a tractor across top of dam and I followed him out 
on top of dam. This v/as about 10:00 a.m. The flow had not changed 
much and was turbid. V.'e hc.d another dozer on its way to work on dov:nface. 
Talked to Piobison at his office, then Buckert at powerhouse, then back 
up to top of dam. 

By the time I got to top of dam, whirlpool had developed on upstream side 
of dam. I cannot give times. The whirlpool about 25 feet from upstream 
face of dan and 75 feet from right abutment. About 3-2" feet to ^ feet 
in diameter. Stayed constant for awhile. There were two Gibbons and 
Reed dozers pushing riprap into hole. I did not feel the dam vras going 
to callapse. I thought everything was salvageable. I was working to 
change operation of the dozers on upper side to build a ramp in order 
that trucks could bring in material. 

The dozers on downface viere having trouble. The TD I5 was tied to the 
eight, which rfas nosed into the hole. I went to get another dozer to 
help them and by the time I got turned around they were gone. 

I would ostir'.ata it v;au about. 11:00 a.n. .-hortly after dozers were t^onc. 
I wan on top of r.,D.:^.. '-^'o i^ozors r^till '.rorliing on upstream face. Did not 
pay attention to whirlpool. 



C-59 



Shortly thereafter I rcoved tvro pickup trucks off the dam. At about 
11:30 a.m., I would estimate, I called Euckert and told him dam going 
pretty fast and to have 3ureau of Reclamation get people out dounstreara. 

About 10 or 15 r.inutes later we pulled the dozers off the upstream face 
of dam. Th^y '.v'c-nt to southside and I went to ncrthside of dam. Within 
one minute or one and a half minutes the dam collapsed. At 11:55 5.-^' 
the dam collapsed. I looked at my watch when this happened. I went down 
stream within two or three minutes to help people. I did not return 
until about 1:00 p.m. 

I have carefully read the foregoing statement, consisting of 3 pages and 
declare it to be true and correct. 

/s/ V. M. Fcxleitnor, Jr. 



Subscribed and sworn to before me 
this 19th day of June, 1976. 



/s/ Vincent L. Duran, S-pccial A-ent 

Vincent L. Duran, Special Agenr, 
U.S. Department of the Interior 



C-60 



COPY 



STATE OF Idaho ) 

) SS 

CXDUNTY OF I'adison ) 



I^ Barry N. Roberts , Klx Circle No. 1, 



St. Anthony, Idaho , being duly 

sworn make the following voluntary statement to Vincent L. Duran , 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am employed as office engineer of IIorrison-Knudwen , Kiewit Teton Dam 
Project, Mevfdale , Idaho. I have been on the project since December 1973' 

On June 5i 1976, I came to the office shortly after 9=00 a.m. on personal 
business. Ringel, nobison and Aberle followed me through the gate and 
proceeded across the dam. As I came in I noticed the downstream rifrht 
side of daiii wa.s wet. This was at the slope change and against the 
right abutment. I cannot estimate the volume. 

Shortly before 10:00 a.m. , Robison requested of Buckert assistance in 
getting river outlet operational and dozers to '.•:ork on the downstream 
slope. For the next half hour I •..'as in the uarehouse. 

At about 10: ^'-5 a.m. I was in the powerhouse -ee—^ to get opening of 
river outlet operational. At this tine there was considerable water 
coming thrrough the dam. I cannot estimate the volume. There was no 
chasm. The leakage area vras considerably larger than vrhen I a.rrived. 
r did some work in the power house area and at about 11:;.0 a.m. everj'one 
at the powerhouse decided to evacuate. I thought at this time the dam 
was going to break. . 

On the way up several people stopped on the south ridge. '/Jater flowing 
and there wa.s a small bridge on the top of the dam on right side. I 
proceeded to visitors overlook and by the time I arrived the dam had 
collapsed. I estimated the collapse at ll:i^5 a.m. This was estimated 
because I had no watch with ne. 

I did not see anything on the upstream face of dam. Everything I did was 
on downstream side. 



C-61 



I do not recall seeing the dozers working on downstream face or their 
loss. 

I have carefully read the foregoing statement , consisting of 2-l/Ur 
pages and declare it to he true and correct. 



/s/ Earry W. Roberts 



Subscribed and sworn to before me this 
19th d3.y of June, 1976. 

/s/ Vincent L. I>jran, c-pociol A-ent 
Vincent L, Juran, Special A^jcnt 
U.S. Denartnent of the Interior 



C-62 



COPY 

STATE OF Idaho ) 

) SS 
OOUim OF I'adison ) 



I, Donald u. Trupp , P.O. Box 3, 



Newdale , Idaho , being duly 

sworn make the following voluntary statement to Vincent L. Duran , 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I ajn employed as medical supervisor with Morrison-Knudsen and Kiewit, 
Teton Dam Project, Ne'.fdale, Idaho. I began working on the project 
April 19, 1972. 

On Saturday, June 5, I976, at ahout 10:30 a.m. I was approaching the 
dam on the upper south rim road and saw v;ater leaking through the 
dam on the downstreair. side , north side and approximately l/':- to I/3 dovm 
from top and close to the side. The hole was four to six feet in 
diameter with muddy water flowing. I v:ent to the first aid office on 
the project and at about 10:35 a.n. telephoned my wife. I stayed in 
trailer and Korrison-Knudsen office the rest of the time. I saw the 
flow gradually increase and saw the dozers vforking on downstream side 
of dam. I saw them having problems. 

I did not see the whirlpool activity on the upstream side of the dam. 
I saw the dam collapse, but cannot estimate the time. I only saw the 
progressive increasing of the lealiage. 

At about 11:30 a.m., I telephoned relatives in V/ilford, Idaho, and told 
them they had better be ready for danger, because I thought the dsjn might 
collapse . 

I recall at eight minutes to 12:00 noon, by my watch, several of us put 
out the alarm and the dam collapsed very shortly after this. 

I have carefully read the foregoing statement, consisting of 2 pages 
and declare it to be true and correct. 



/s/ Donald D. Trupp 



Subscribed and sworn to before me 
this 19th d ay of June 1976. 

/s/ V incent L. 'Turrn, Z-^-oi'l A -eni 
Vincent L. Juran, Gpecial Agent 
U.S. Oenartnent of the Interior 



C-63 



Wia?lvESS STATEI-ENTS BY OTHERS 



Henry L. Bauer 

Box 173 

Teton City, Idaho 

Dave Christensen 

1420 Benton St., Apt. 1 

Idaho Falls, Idaho 

Ted V. Gould 
455 N. South W., 
St. Anthony, Idaho 

Richard B. Howe 
Rexburg, Idaho 

John F. Lee 
276 N. First E. 
Rexburg , Idaho 

Eunice J . Olson 
223 North 4th East 
St. Anthony, Idaho 

Mr. Lynn Schwendiman 
Mrs. Lee Ann Schwendenan 
Rt. 1, Box 122 
St. Anthony, Idaho 



C-64 



COPY 



STATE OF Idaho ) 

) SS 
COUNTY OF r.adison ) 



I, Henr:/ L. Bauer , Box 173. Teton City, Idaho 

, being duly 

sworn make the following voluntary statement to Vincent L. Duran , 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 
I am retired. 

I farmed on northside of Teton River where the dam built for ^0 years. My 
farm v.'as upstream of ivhere the dan ultimately built. I always thought the darn 
would be beneficial. 

On Saturday, June 5< 1976, I stopped on the northside of dan approximately 
1/2 mile upstream. 1fe-^- .,^i; j i^j l"., ■..",■ ' a L 1,. l/n—r^li uj^^j.u... . This was 
between 10:30 and 11:00 a.m. I looked over the reser^'oir for about 20 
to 30 minutes. The watervas very calm, there was no wind. The reservoir 
1,000 feet wide at this point. 

I decided to go dovm to dan. Tine approximately 11:15 a.m. to 11:30 a.m. 
I saw a truck dump material on the upper face of the dan as I approached. I 
noticed a whirlpool 8 feet across "S^siJ^'St abutment and face of dam. Large 
commotion and muddy vrater. l/'ater av.-ay from vmirlpool v.-as semi-clear. Then a 
large part of time - 20 feet wide and 20 feet high sluffed off into whirlpool — 
one big chunk. This created extra comm.otion in whirlpool and boiled up more. 
In a matter of one minute the top section of the dam dropped and the dam 
had collapsed. I never looked at my watch and am not sure of the time of 
collapse . 

1 did not see dozers working on the upper side at the v/hirlpool area. 

I talked to a m.an in pea greoipickup truck — he said to get out of area and 

warn everyone I could. I first stopped at Ken Remington potato farm, vfarned him, 

and continued to v:arn others. 

I saw no fishermen in the reservoir when I made obscr'/ations. I saw no other 
people on canyon. 

No eairthquake or tremor — no water ripple as a result. 



C-65 



I have carefully read, the foregoing statement, consisting of 
pages and declare it to be true and correct. 



/s/ Henry L. Bauer 



Sutscribed and sworn to before me 
this 2?rd d ay of June 1976. 



/s/ Vincent L. Duran, Special A;::ent 
Vincent L. Duraji, Special Agent 
U.S. Department of the Interior 

/s/ Betty J. Foye? , cT)ncial Af^ent 
Betty J. Foyes, Special Agent 
U.S. Department of the Interior 



C-66 



STATE OF Idaho ) 

) SS 
COUNTY 0? Madison ) 

I, Dave ChriPtensen, 1420 Benton St., Apt. 1, Idaho Falls, Idaho, 

being duly sworn make the following voluntary statement to Ivan L. 

Kestner, who has identified himself to me as a Special Agent of the 

U. S. Department of the Interior. No threats or promises have been 

made to obtain this statement. 

I am a Receiving Foreman at the Idaho Supreme Company Plant, Firth, 
Idaho. On June 5, 1976, my parents, wife, and children and I, visited 
the Teton Dam at approximately 10;00 a.m. and remained 10 or 15 
minutes. Our observations were made solely from the observation 
platform at the dam, and we did not view the reservoir or the reservior 
side of the dam. Upon arrival we saw a muddy stream coming from the 
mountain wall adjacent to the far or north end of the dam. We could 
see the muddy water mingling at the bottom of the dam with the com- 
paratively clear water flowing through the dam outlet. This stream 
originated at about 20 to 30 feet from the dam bottom. As we watched 
we could see a free flow of water, volume unknown, but no gush of 
water. Just before leaving we noticed a darker wet streak on the dam 
face, starting from a point about 2 feet wide, about 30 or 40 feet 
from the place where the dam joined the mountain, and very near the 
top of the dam. This streak grew 15 or 20 feet wide as it reached 
the bottom of the dam. When we left about 10:15 a.m. we could see no 
signs of employee activity of any nature. We did see a bulldozer parked 
on top of the dam. 

I have carefully read the above statement and declare it to be true and 
correct. 



/s/ David Wayne Christensen 



Subscribed and sworn to this 
23rd day of June 1976. 

/s/ Ivan L. Kestner 

Ivan L. Kestner, Special Agent 
U.S. Department of the Interior 



C-67 



STATE OF Idaho ) 

) SS 

COUNTY OF lladison ) 



I, Ted V. Gould ^ 435 N. South W. , St. Anthony, Idaho 



_, being duly 



sworn make the following volxintary statement to Vincent L. Duran 



who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am self employed. 

Saturday, June 5i 1976, I v;as going to Teton, Idaho, to work on my trucks. 
This was about 3:30 a.m. I had t'.:o-Nay radios on sa.T.e frequency as Gihbins 
and Reed arxi others and heard talk about leak being at dam, I thougli. little 
of this, but continued to hse:*- talk regarding equipment movement and the 
leakage. Then I heard someone say there was a hole in the dam. 

I arrived about 900 a.m. and '.rent to visitor vievrpoint. Lmall hole about 
half-vray up about 20 feet into dam on downstream side. The v;ater vjashing av.'ay 
material and this ma,de it muddy. The dozers were just heading toi.'ard area to 
fill in rock at the hole area. The hole gradually got bigger and more water 
flowing as I vra.tched. More and more volume. One dozer, D-8, started slipping 
into washed out area and D-I5 tried to pull out. Unsuccessful and about 
10:00 am. the dozers washed away. 

Then big chunks of dirt fell out of hole and water appeared to be running out 
of side abutment rock. 

I was back in my truck about this time and heard someone on the radio mention 
vfhirlpool on upstrea.m face and I heard the person talking ^rliat there vjas 
big trouble and proba.bly not be able to stop. This vras possibly about 
10:30 a.m. 

I left shortly thercrfter and went to Teton to check on my parents. At 
about 11:00 a.m. , I hearal a radio message over Gibbons and read about top of 
dam going pusing riprap into whirlpool. 

I called my .dfe and told her about the incident. I talked Gibbons and 
Reed over the radio and he told me top washing out and dam going. This 
was about 11:30 a.m. I did not see the actual collapse. 



C-68 



I v/as back at the dam at about 5'-?0 p.n. and saw water mnninr: out of 
abutnent on the south side right where the dan abutted against canyon wall. 

I have carefully read the foregoing statement, consisting of 2^ pages and 
declare it to be true and correct. 

/s/ Ted '■■'. Gould 



Subscribed and s'.:orn to bsfore rae 
this 2?i-d d ay of June 1976. 



/s / Vincent L. Duran, S^ocial Aroni 
Vincent L. Imuran, special A.rcnt 
U.S. Department of the Interior 



C-69 



IXoyd Hopkins, 56 K. Second W. , Rexbnrg, Idaho 

Employed as Supervisor;,'' Electrician by Wismer and Becker at Teton Ttam 
Project, Newdale, Idaho, 

Hopkins said dyrinn; the period 6:00 T5.r5. to 7:30 p.m. on Friday, Juno h, 
1976, he wns at the da^. aroimd the ncwtr house area, which is located on 
the south or left side at the downstrerjn foot of the dnn. He said he 
observed the entire doT-nstream face of the da-n more than once during this 
period and saw no evidence of any leaks or water running anjn-.'here on 
the face of the dam. 

Hopkins s:iid at about 10:00 a.m. on Saturday, June 5, 1976, rick Cuffe, 
his supervisor, a?ked him to eo to the dam because there were problems. 
He said he went directlv to th mover house and arrived at about 10:30 a.m. 
He said upon his arrival he s''.w a leak in the dcwnstre.im face of the 
dam near the north or ri'ht abutment and belc; the tor of the da-i. He 
said he could not be mere snecific about the location nor cculd he estimate 
the voluTi^e of water. He said the water was muddv. He said he saw one 
dozer fa]lin~ in the hole created by the leak nnd another dczer trv-i.r? 
to pull it out. He said shortly after this the two dozers were washed 
away by the water, but he cannot estimate the time. 

Hopkins aid he checked the availability of electricity at the power house 
in order to possibly cnen the river outlet tunnel. He said while he was 
doing his work several ^^^n were in the tunnel moving equipment out in 
order that the tunnel could be opened. 

Hopkins said that at about 11:00 he and the several other workers in the 
tunnel and powerhouse area decided f^ere was eminent danrer and evr>cuated 
the area. He s = id he went to the Bureau of Reclar.ation offices onthe 
south or left side of the dam. He said when he pot to the offices he 
saw two doners, which vere working at the too of the dsm., orpnarinrr to 
withdraw from the top of the dam. He said he does not know what time this 
was, but he knovis the top of the dam callaosed shortly thereafter. He 
said he did not see the collanse, because he was nreparing to leave for 
Rexburg, Idaho, and do what he could to protect his hom.e from the flood. 



This is not a signed statement because Mr. Hopkins was departing for 
California. 



C-70 



COPY 



STATE OF 
COUNTY OF 



) ss 



Idaho 



Fresnont 



J Elizabe'-i"! A. Havard 



P.O. Box 342, St. Anthony, Id. 83445 



, being duly 



sworn make the following voluntary statement to Ivan L. Kestner 



who has identified himself to me as a Special Agent of the U. S. 
Department of the Interior. No threats or promises have been made to 
obtain this statemenr. 



C-71 



I an enployed as an Engineering Clerk, GS-4, Targhee National Forest. 
St. Anthony, Idaho, and have been so eirployed for three years. I have 
25 years of Federal Service. 

On J\me 5, 1976, I visited the Teton Dam in the oorpany of my son. Dale 
Howard, and his wife and his three daxighters. We arrived at approximately 
9:30 a.m. or 9:45 a.m. and spent seme time observing and taking photographs. 
linnediately \jpcn arrival our attention was drawn to a stream of water 
beginning about one third the distance fron the top pf the dam, and 
running down the angle between the dam face and the adjoining rock wall. 
This was on the far or n'^rth side of the dam. I have no way of estimating 
the flow of water other than to say it rauinded me of a small woodland 
stream. As we watched for about half an hour the stream grew noticeably 
larger and it was visibly creating a gully. We wondered whether scmething 
should not be done about this, but we saw no signs of any activity 
associated with the stream and ccncluded it was a normal ^lencmencn. 
At perhaps 10:00 a.m. or 10:15 a.m. we noted a wet spot en the dam face, 
slightly below the level at v;hich the stream originated. This grew as 
a visible wet spot and eventually began falling in. We were on the point 
of leaving the dam when a large collapse into this hole occurred. We 
then came back to watch further. This was approximately 11: 00 a.m. 

Some minutes after this a small bulldozer came dcwn the face of the 
dam and the operator appeared to inspect the hole in the ccmpany of a 
second man v*io walked down. This dozer then left and we saw ccnsiderable 

activity in tenrs of picl-oip truck ncvcrren-ts fraii this tirr.e on at tiie d£.r."i 
top and nearby areas. About 11:15 a.m. a larger bulldozer arrived at 

2 



C-72 



the gra^?ing fissure in the dam face and began pushing in earth and rock 
fron below the hole. It was joined by the snailer bulldozer vdiich began 
moving earth and rock to a position in v^ich tlie larger dozer could push 
it into the' fissure. In all I believe the dozers worked about 20 to 30 
minutes before the earth gave way beneath the dozers and they were lost. 
For a fav minutes an attsnpt was made to retrieve the larger dozer, 
vdoich went into the hole first ,:j;^<!j3v- by pulling it free witli a chain or 
cable fron the smaller dozer. Then both dozers were lost in the mud 
slide. 

We remained on the cbservation platform adjacent to the Reclamation 
^ministration Building until dam collapse occurred at approximately 
12:00 noon. I'iy son had been taking pictures v/ith his Yashika camera 
with telephoto- lens until he ran out of filjn just before the top of 
the dam collapsed. I then began taJcing pictures with iry Instamatic 
camera. 

^^ obervations and that of my party were limited to the face of the 
dam as described above. I took no particular note of the surrounding 
terrain and had no opportunity to see the resesvoir lake behind the dam. 
■Hie stream we originally noted ^^eared to be clear water until it 
began washing away the bank and became mudd^. The flow fron the hole 
in v*iich the bulldozers were lost was a mud flew xontil it kcaivie mi:.ed 
water and mud. 



C-73 



I have read the above statsnent cxxisistirsg in all of four typed pages, 
including this page, aiid I declare thcc it is true and correct. 



SubscrJi>ed and s^ram to before me 
tliis 22nd day of June, 1976. 



^^ ^•^Q^ 




Ivan L. Kestner, Special 7-!gent 
U.S. DepartTTrant of thie Interior 



C-74 



COPY 



STATE OF IDAHO ) 

) SS 
COUNTY OF MADISON ) 



I, Richard B Kowe , of Rexburg, Idaho 

, being duly 

sworn make the following volxintary statement to Ivan L. Kestner , 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I am a reporter for the KID Radio AM and Television Station, Idaho Falls, 
Idaho. On the morning of June 5, 1976, the day of the Teton Dam collapse, 
I piloted a light aircraft near the dam, passing about three miles north 
and 1000 feet above the dam. I was too distant to note seepage or breaks 
on the dam face, but did clearly observe the reservoir lake behind the 
dam. No turbulence or unusual features were visable in the water or 
the adjacent landscape. This observation took place about 10:00 a.m. 

At approximately 11:45 a.m. on the same day, June 5, I learned that 
a warning had been given that the Teton Dam was in danger of collapse. 
I immediately went to the airport at Rexburg and flew to the dam with 
cameraman Paul Jenkins, arriving within minutes after actual collapse 
of the dam. I estimate our arrival at about 12:00 noon. I began broadcast- 
ing an account of the flood, as visible from the air, and Jenkins secured 
the only TV film footage taken in close proximity to the time of collapse. 
His footage was seen on CBS Network Television that evening. 

I-have carefully read the foregoing statement, consisting of one page only, 
and I declare it to be true and correct. 



(signed) Richard B. Howe 



Subsdribed and sworn to before me this 
22nd day of June, 1976. 



(signed) Ivan L. Kestner 

Ivan L. Kestner, Special Agent 
U.S. Department of the Interior 



C-75 



STATE OF IDAHO ) 

) SS 
COUNTY OF MADISON') 

I, John F. Lee, 276 N. First E. , Rexburg, Idaho, being duly sworn 

make the following voluntary statement to Vincent L. Duran, who has 

identified himself to me as a Special Agent of the U. S. Department 

of the Interior. No threats or promises have been made to obtain 

this statement. 

I am self-employed. 

On Saturday, June 5, 1976, I leaving house to go fishing when my 
daughter called and told me heard dam breaking. I told her would 
stop by the dam and look. As I drove into visitors overlook on south 
rim at about 11:40 a.m. there was a hole in notth side of dam about 
3/4 way up on downstream side. The hole appeared to be 30 feet in 
diameter. I could not see water, but dirt was caving in from all 
sides. Small chunks like scoop shovels. Scill could see white 
gravel at floor of canyon and muddy water running. My brother Ore E. 
Lee, v.'ho was with me, commented that the dam going. The chunks of 
earth falling were now as big as a pickup. No water visible- looked 
air pressure blowing out from canyon wall. I looked bottom of canyon 
now a fuel tank going toward power house going upstream. Then large 
chunks of dirt, size of house falling in. The increase in size of 
chunks happened in about 30 seconds. Then water came over north rim 
of dam top and left area. This about 11:55 a.m. I did not look at 
watch. As I leaving Don Ellis, KRKX, came in to broadcast and I 
listened to his Broadcast as I heading home. 

All the action at the north canyon wall on downstream side. Appeared 
water coming out wall at first. 

Water hit Rexburg at my home at 2:32 p.m. 

I have carefully read the foregoing statement, consisting of 2 pages 
and declare it to be true and correct. 



/s/ John F. Lee 



Subscribed and sworn to before me 
this 24th day of June, 1976. 

Is/ Vincent L. Duran 

Vincent L. Duran, Special Agent 
U. S. Department of the Interior 



C-76 



STATE OF IDAHO ) 

} SS 
COUNTY OF FREMONT ) 



^' Eunice ^' gison ' 22? North Ath F^^t 

St. Anthony. Idaho ^ being duly 

sworn make the following vol\antary statement to 'van L. Kestner 



who has identified himself to me as a Special Agent of the D. S. 

Department of the Interior. . No threats or promises have been made to 

obtain this statement. 

I am the Resource Clerk, GS-5, Targhee National Forest, St. Anthony, Idaho 
(U.S.Forest Service) and reside at St. Anthony, Idaho. 

On the morning of June 5, 1976 I visited the Teton Dam with two guests, 
Ms. Myrtle Worfolk and Hiss Heather Chapman, both residents of Griffith 
Australia. We arrived at the dam at approximately 10:30 a.m. and upon reaching 
the observation platform found that two bulldozers were beginning work 
on the visible face of the dam at a point where a mud leak appeared to have 
developed. At that time the flow from the fissure had a lava-like appearance 
and seemed to consist solely of mud. It was absorbed into the dam face to 
a large degree. We watched as the bulldozer operators attempted to scrape 
earth and rocks into the fissure. At approximately 11:00 a.m. I became aware 
that the hole was growing in an accelerated way and the two bulldozers were 
In danger. Within a very short time the dozers were lost and the operators 
scrambled to safety. We continued to watch until approximately 12:00 noon 
when total collapse occurred. I never had opportunity to look at the reservoir 
lake and \ did not observe any other leaks or fissures other than that dealt 
wrth by the two bulldozers. Just prior to actual collapse Project Engineer 
Robison caused us to move back from the observation platform for safety. 

Ms. Worfolk and Miss Chapman each had cameras and took pictures of the collapse 
but to date I have been unable to retrieve these pictures. 

I have carefully read the above statement ajjd;:^eclare it true and correct. 

7 



Subscribed and sworn to ~t^ 

before me this 22nd day of C/ 

June, 1976. „,^^^ 



^3..».^..^.-- ^fxj^v^^ 



Ivan L. Kestner, Special Agent 
U.S. Department of the Interior 



C-77 



COPY 



STATE OF Idaho ) 

) SS 

COUNTY OF^'3,dlson ) 

y Mr. Lynn Schv.'endlnan 

M,' Mrs. Lee Ann Schwendema n ^ Rt. 1, Box 122, 

St. Anthony, Idaho , being duly 

sworn make the following voluntary statement to Betty J. Foyes 

who has identified himself to me as a Special Agent of the U. S. 

Department of the Interior. No threats or promises have been made to 

obtain this statement. 

I, Lynn Schevrendeman am employed at the Idaho Stud Mill, St. Anthony, Idaho and 
on Saturday morning, June 3t Lee Ann vfas notified by GB radio that the Teton 
Dam was leaking. This v^as 11:00 a.m. exactly. 

We drove out to the dajn, leaving our residence about 11:00 a.m. and arrived at 
the visitor's observation center on the south side of the Teton i3am about 11:30 
a.m. or thereabouts, '..'e took a camera and film with us. When we got to the dam 
there was just a big hole about Z/'^rds of the way down on the downstream face 
of the dam, about 75 'to 100 feet from the north abutment. The water was 
pouring out of the hole and it had more the appearance of boiling mud than 
water. 

The two dozers working on the downstream side of the dam had already fallen in 
the hole and we could see one of them bouncing on top of the vjave of water 
going down river. There were no vehicles on top of the dam to the best of 
our recollection. 

Vfe vrould estimate that the top?of the dam collapsed about 11:55 a.m. As the 
dam continued to collapse v.e were impressed by the fact that in the area about 
halfway down the dam, as evidenced by the dark arc-shs.ped area on the south side 
of the breaJc in our picture number k, the dirt had apparently not packed since 
it came off like sand rather than in chunks. The same is true of the abutment 
side of the J^ hole. Vihat dan fill v;as on the north side (canyon side) of 
the dam went fastest. There was no indication that there was any breakage on 
the abutment ;rall itself. I£ looked like a natural canyon wall. It 
looked like all that went was just the fi3.1 part. 

We had no impression of earthquakes or tremors » just the roar of the water. 
Vie took Polaroid pictures, seven in number of the hole in the dam and the dam 
collapsing. The Ko. 4 picture mentioned above is one of the 7. '^^e wish to 
retain the originals at the suggestion of Senator Richard Egbert (State 
Senator fro;:; jr?;,^^}. 



C-78 



';.'e have read the above statement consisting of two and cne-quarter pages 
and declare it to be true and correct to the best of our knowledce and 
belief. 

/s/ Lynn Gchv.'Gndiir'.an 
Lynn Jchv.'endiman 

/s/ L ee Ann L'ch'.."endirfa n 
Lee Ann uchNendiman 



Subscribed and svrorn to before 
me this 23rd day of June 1976. 



/s/ Eetty J. Fo^^e3 

Ectty J. Foyes, Cpecial A.3ent 
U.S. Derartnent of the Interior 



C-79 



LAW ENFORCEMENT OFFICIALS - NoCificaticn Of Dam Collapse. 

Ford Smith, Sheriff of Madison County (County aeat - Rexburg) advised 
in a telephone interview of June 21, 1976, that the Teton Dam was located 
on the joint boundary of Madison and Fremont Counties. He said he was 
advised by his dispatcher of the threatened dam collapse at a time he 
(Smith) recalls as 10:50 a.m., June 5, 1976. he said the dispatcher 
called him immediately after receiving telephone notification from 
someone at the dam„ He said that in the excitement generated by the 
call, the call from the dam was not logged officially by the dispatcher, 
and calls in general v/ere not logged for sometime thereafter. Sheriff 
Smith said he did not immediately accept the warning as valid, but he 
concluded that the matter was too serious not to act on the call and he 
began telephoning everyone he Knew in the potential flood path, starting 
with a citizen residing one and one-half miles from the dam. He said 
he believes it was 11:40 or 11:45 p.m. that he was told the dam was 
actually gone. He said none of his officers reached the dam site prior 
to the collapse but individual officers had driven as far as the village 
of Teton, warning households as they went, before they were turned back 
by flood v;aters. entering Rexburg. 

Blair K. Siepert, Chief of Police, Rexburg, Idaho, advised that his office, 
like the Sheriff's, made no official record of notice of the impending 
dam collapse. He said he was on a fishing trip and near Felt, Idaho 
about 25 miles above the Teton Dam, v/nen he learned that the dam had 
collapsed or was on the point of collapsing. H^ said he "drove liUe 
hell" to return to Rexburg, arriving at 1:45 p.m., a short time before 
flood waters reached the town. 

Thomas F. Stegelmeier, Sheriff of Fremont County (Ccuntyseat - St. Anthony) 
advised on June 22, 1976, that his office officially logged a warning 
from the dam of pending collapse as of 10:43 a.m., June 5, 1976. He 
said he immediately telephoned the Project Engineer, Robert Robison, 
at the dam and confirmed that Robison wanted persons living below the 
dam warning of the danger of collapse. Stegelmeier said he telephoned 
Ted Austin of Radio Station KIGO who also placed a call to Robison. 
He said Austin and Deputy Sheriff Craig Reinhart then left in the same 
vehicle for the dam, but it is his understanding that the dam had collapsed 
or was in the final stages of collapse before their vehicle reached the 
diua. He said there were false radio accounts that St. Anthony was wiped 
out by flood, but in actual fact the flood was diverted by the terrain 
and did not damage property in St. Anthony. 

Ivan L. Kestner, Special A'gent 



C-80 



APPENDIX D 



FINITE ELEMENT ANALYSES 



APPENDIX D 

HYDRAULIC FRACTURING AND ITS POSSIBLE ROLE 

IN THE TETON DAM FAILURE 

by 

H. Bolton Seed, T.M. Leps, J.M. Duncan and R.E. Bieber 



INTRODUCTION 

In recent years, cracking leading to excessive loss of drill water in the cores of a number of 
embankment dams has been attributed to the phenomenon of hydraulic fracturing; that is, a 
condition leading to the creation and propagation of a thin physical separation in a soil whenever the 
hydrauhc pressure exerted on a surface of the soil exceeds the sum of the total normal stress on that 
surface and the tensile strength of the soil. A similar condition has also been suspected of occurring in 
the cores of several embankment dams due to reservoir water pressures. This has usually been the case 
in compressible cores of dams with more rigid outer shells, where the tendency for the core to settle 
or compress more than the shells results in a major reduction in stresses within the core. As a result, 
water pressures may exceed the sum of the normal stresses and tensile strength of the soil on certain 
planes within such zones of reduced stress, and cracking may develop along these planes. 

To date there does not seem to have been any case reported where similar hydraulic fracturing has 
occurred as a result of construction of a steep-walled key trench although the conditions required to 
produce hydraulic fracturing are as well-developed for this type of construction (compressible fill 
adjacent to relatively rigid rock) as they are for the cores of rockfill dams (compressible impervious 
soil adjacent to relatively stiffer rockfill). Accordingly the possibility of hydrauhc fracturing 
developing in the key trench of Teton Dam was considered to merit serious consideration, and 
detailed studies have been conducted to investigate this possibility. 

The general hypothesis whereby failure could have occurred as a result of internal erosion due to 
leakage through cracks in the key-trench fill caused by hydraulic fracturing is illustrated schematically 
in Fig. 1. If the grout curtain were fully or highly effective, the highly pervious nature of the 
upstream rock along vertical and horizontal joints would lead to a condition of essentially full 
hydrostatic pressures developing along some zones of the upstream face of the key trench. Even if the 
cutoff allowed some seepage under the key trench, high water pressures might still develop against the 
upstream face of the key-trench fill. As shown in Fig. 1 , step 1 , these pressures could cause fracturing 
of the fill wheie it came in contact with the joints. The resulting cracks would tend to be along the 
minor principal planes and would propagate longitudinally along the wall of the trench, permitting 
water to have access to the wall over a considerable length of the key trench. 

In a coincident or second step (step 2 in Fig. 1 ) the water pressures thus developed would tend to 
produce multiple fractures along transverse planes with low normal stresses acting on them due to the 
arching action of the fill over the soil in the key trench. This would provide access for the water to 
the downstream face of the key trench. 

Once this stage was reached, further fracturing could occur along minor principal planes for soil 
elements adjacent to the downstream wall of the key trench, again permitting the water to flow 
longitudinally until it found a convenient egress through open joints in the downstream rock. Erosion 
along the resulting flow path would ultimately lead to a piping failure of the embankment as 
discussed in a later section. 



D-1 



Section 




Vertical joint 




'^Vertical 
joint 



1. Flow in vertical upstream 
■joint to face of key trench 
followed by longitudinal 
hydraulic fracturing of 
fill near face of trench 
allowing water to spread 
along face 



Vertical joint 




Vertical 
joint 



Transverse hydraulic 
fracturing producing 
multiple fractures 
through soil in key 
trench and giving water 
access to downstream 
side of trench (may 
occur before Step 1) 



Vertical joint 




Longitudinal hydraulic 
fracturing of soil near 
downstream face of key 
trench allowing water to 
spread along face and 
find egress through open 
downstream joints in rock 



FIG. 



SCHEMATIC DIAGRAMS SHOWING DEVELOPMENT OF HYDRAULIC FRACTURING 
AND FLOW OF WATER THROUGH KEY TRENCHES 



D-2 



Analysis for Predicting the Possibility of Hydraulic Fracturing. 

In many cases where hydraulic fracturing is beUeved to have occurred, its development resulted by 
accident during driUing or monitoring operations. In recent years experimental and analytical studies 
have been developed for investigating the possibility of its occurrence. Experimental studies include 
laboratory tests on large models, which clearly showed that high water pressures induced in vertical 
holes could produce observable extensive fracturing in earth materials, and field bore hole tests where 
high pressures induced by filling the hole with water led to fracturing at the bottom of the hole and 
an initially rapid loss of water from the hole. Analytical studies have involved studies of the stress 
conditions causing fracturing at the bottom of drill holes and the stress conditions in the shell and 
core materials in embankment dams. These latter studies, accomplished by means of the finite 
element method of analysis, have shown that this procedure has the capabihty to show where zones 
of low pressure will occur in the cores of embankment dams and thus where hydraulic fracturing 
might be anticipated. It has been used in design studies of such dams in the past few years. 

It should be recognized that the use of finite element analyses to predict stress conditions in cores 
and key trench materials in this way requires the use of the most sophisticated analysis techniques 
and even then they should desirably be used in conjunction with some types of field test program to 
provide some check on the validity of the calculations. Furthermore, potential errors in the results 
would suggest that they are more useful as a guide to judgment than as an absolute indication of 
stress conditions. 

The best method of stress analysis of this type is one which determines the stresses on the basis of a 
reasonable representaUon of the non-linear stress-strain relationships for the construction materials 
and foUows a step-by-step sequence representative of the construction sequence for the embankment 
under consideration. Such features are embodied in the finite element computer program ISBILD 
which was developed at the University of California, Berkeley (Ozawa and Duncan, 1973). For some 
of the analyses described in this appendix, Bieber (1976) developed a computer program which 
employs the same analysis procedures and stress-strain relationships as ISBILD. Results from Bieber's 
program were compared with results from ISBILD for a simple problem to insure that the new 
program would produce results which conform to those from ISBILD in all essential respects. 

The computer program ISBILD employs hyperboUc stress-strain relationships which model several 
important aspects of the stress-strain behavior of soils, including (1) nonUnearity, or decreasing 
modulus with increasing strain, (2) stress-dependency, or increasing stiffness and strength with 
increasing confining pressure, and (3) realistic variations of Poisson's ratio with strain and confining 
pressure. The parameters employed in the hyperbohc stress-strain relationships are listed in Table 1, 
together with descriptions of their physical significance and explanations of their roles in finite 
element analyses; a more complete description of these parameters is contained in a recent report by 
Wong and Duncan (1974). 

Using this procedure, two types of analyses may be performed — a total stress analysis using 
undrained stress-strain parameters, or an effective stress analysis using drained stress-strain 
parameters. Both approaches have limitations. For example, an effective stress analysis may be used, 
incorporating drained stress-strain parameters, to evaluate the effective stress acting on any plane 
within the soil mass. Gradually increasing water pressures may be introduced by means of nodal point 
loads, representing buoyancy and seepage forces, and the resulting changes in effective stress may be 
calculated. If this type of analysis is performed using hyperbolic stress-strain and strength parameters 
determined from conventional laboratory tests conducted with positive (compressive) values of 03, 
which are often used to represent the non-linear stress-strain properties of soils, the modulus of the 
soil will approach zero as the calculated value of 03 approaches zero simply due to the method of 



D-3 



stress-strain formulation. This is an inherent characteristic of the hyperbolic stress-strain relationship 
which employs the following approximation of the variation of initial tangent modulus with 
confining pressure: 



Ei = Kp, 



(^f 



where E: = initial tangent modulus 

K = modulus number 

p = atmospheric pressure 

Oo = minor principal effective stress 

n = modulus exponent 

Because the modulus approaches zero as the effective stress is reduced, the soil tends to swell without 
limit and the calculated effective stress never reaches zero. The calculated effective stress therefore 
never becomes tensile, and the results of such analyses never indicate any likelihood for hydraulic 
fracturing, even for the most critical conditions where hydraulic fracturing would inevitably occur. 

Alternatively a total stress analysis may be used to assess the possibility of hydraulic fracturing. Using 
this approach the total stresses acting on any plane within the soU mass are evaluated and hydraulic 
fracturing is presumed to occur whenever the water pressure exceeds the sum of the total normal 
stress and the tensile strength of the soil; alternatively the procedure may be visualized as one in 
which the effective stress on any plane is determined by subtracting the water pressure from the 
computed total stress. If the resulting effective stress is tensile and equal to or greater than the tensile 
strength of the soil, the inference is drawn that hydraulic fracturing would occur under the conditions 
analyzed. This total stress procedure is overly-conservative because it ignores the tendency of the soil 
to swell as the effective stresses on any plane are reduced; in effect the method assumes no tendency 
to swell during a reduction in stress equal to the water pressure. Furthermore the effects of creep 
movements in the soil under sustained loads are not considered. These limitations can be 
compensated for in the analysis by using a somewhat higher value of Poisson's ratio (expressed by the 
parameter G, see Table 1) than that which actually applies for the soil involved, and a range of other 
soU parameters. The best method to determine the appropriate value of G is to conduct field 
fracturing tests and compare the stresses required to cause fracturing with those computed using 
different values of G in the analysis. The value giving best agreement with field conditions is the value 
most likely to give the best assessment of the overall distribution of stresses and thereby the hydraulic 
fracturing potential from the analytical studies. Accordingly this procedure was selected for use in the 
present study. 

An added comphcation in the case of Teton Dam arises from the possibihty that the soil in some 
sections of the key trench may have become saturated by seepage. Stations of primary interest range 
from about 12+50 to 15+50 and while it seems reasonably clear that the key trench fill for stations at 
12+70 and 13+70 would not have time to become saturated as the water level in the reservoir rose 
above the base of the trench at these locations, the same cannot be said for the key trench fill at Sta. 
15+00. At this location the base of the trench is at El. 5 105 and the water level stood in the reservoir 
at about El. 5160 for a period of 4 months prior to April 1, 1976. Thereafter it rose to El. 5300 in a 
further period of 2 months. 

Whether or not these water head conditions would be sufficient to cause water to seep into and 
saturate the key trench fill depends on the permeabihty of the fill. Unfortunately data on this 



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D-5 



property of the Zone 1 fill are highly variable. Preconstruction values determined by the Bureau of 
Reclamation show an average value of 0.25 x 10'" cm/sec and 146 tests on record samples taken 
during construction tend to confirm this result, showing values ranging from 0.02 x 10'° to 
3.6 X 10'^ cm/sec. On the other hand, horizontal permeabHity tests on 3 undisturbed samples taken 
during construction gave permeability coefficients ranging from 3 x 10'" to 13 x 10'" cm/sec while 
four similar tests at the University of California on samples taken from one block of soil from the key 
trench fill gave values ranging from 0.3 x 10"" to 4.3 x 10"" cm/sec. 

It seems reasonable to conclude from these data that the coefficient of permeabiUty of the in-situ 
Zone 1 fill varies mainly from about 0.1 x 10"" to 5 x 10"" cm/sec. 

If the average permeabihty were 1 x 10'" then a simple computation would show that for a head of 
55 ft, such as would exist near the bottom of the trench at Sta. 15+00 from Jan. 1 to April 1, 1976, 
the water would flow horizontally into the fill for a distance of only about 6 or 7 ft. At higher 
elevations the water penetration would be even less. 

On the other hand, if the coefficient of permeability of the fill were of the order of 5 x 10'" cm/sec, 
as indicated by the undisturbed sample tests, the water would penetrate into the bottom of the fill a 
distance of 30 to 40 ft prior to April 1, suggesting, that by June 1 , the major part of the key trench 
fill at Sta. 15+00 could have increased in degree of saturation. This raises the possibility that in this 
vicinity, arching of the soil over the key trench would occur not only due to the original differential 
compressibihty of the soil and rock at the key trench elevation, but also due to some additional 
tendency of the fill in the key trench to settle slightly as a result of the wetting action. Although 
settlement due to wetting may be very small, it can never-the-less have a pronounced effect on the 
stress distribution in the key trench. 

Because of the uncertainty regarding the extent of wetting in the key trenches at the deeper sections, 
analyses of stress distribution were made for both conditions and a determination of the most Ukely 
condition was made by comparing the computed stress distribution with the results of field tests to 
measure the in-situ stresses at which hydrauUc fracturing developed. The secondary effect of 
settlement due to wetting can be taken into account in a finite element analysis of stress distribution 
using a computer program written by Nobari and Duncan (1972) and this program was used, together 
with measured values of compression of the Teton Dam Zone 1 material due to wetting, to compute 
the stress distribution at Sta. 15+00 for the wetted key trench condition, in addition to the stress 
distribution for the normal fill placement condition. 

The purpose of the field test program was thus two-fold: (1) to investigate whether the soils in the 
vicinity of Station 15+00 showed any indication of having been saturated prior to the failure and (2) 
to investigate the appropriate value of Poisson's ratio or G, as used in the computations, to provide 
computed stresses in agreement with in-situ conditions. 

The value of G determined by the field tests corresponds to a sudden or short-term application of the 
water pressure. In a dam, the rate of application of the water pressure by a rising reservoir is much 
slower. The effect of the difference in rate of loading, with respect to the value of G, has not been 
systematically investigated, and thus represents an element of uncertainty in predictions of the 
potential for fracturing. 

Selection of Significant Soil Characteristics. 

As previously noted, the computation of the stress distribution in an embankment using the program 
ISBILD requires the determination of nine different soil parameters. These parameters are readily 



D-6 



determined from triaxial compression tests and a number of such tests were conducted for this 
purpose. Since the primary interest in Teton Dam centers on the Zone 1 material, testing programs 
were Umited to this material. 

Tests were performed on both laboratory-compacted samples and on undisturbed samples cut from 
the key trench fill after the failure occurred. The results of these tests are summarized in Table 1. 

As may be seen from the data presented in this table, the test data show considerable scatter for some 
of the parameters involved. However, in determining the stress distribution within the Zone 1 
material, the most significant of the highly variable parameters are K (the modulus number), n (the 
modulus exponent) and G, the factor determining the relationship between major, minor, and 
intermediate principal stresses. 

Because of the wide scatter in these values shown by the test data, it was decided to perform a 
parameter study to determine the effect of the values of K and n, within the range indicated by the 
data, on the values of the stresses computed to develop in the Zone 1 fill. Accordingly stress analyses 
were made for the conditions at Stations 15+00 for the following conditions 



(1) K = 250; 


n = 0.07 


(2) K = 1000, 


n = 0.07 


(3) K = 250 


n = 0.50 



Other parameters were maintained constant at their most likely values (e.g. G = 0.35; Y = 117 Ib/ft^; 
c = 1650 psf, (j>= 31°; etc.). The results of these studies are shown in Figs. 2 and 3. Fig. 2 shows 
computed values of the major principal stress and Fig. 3 shows computed values of the minor 
principal stress at a number of representative points both in the key trench and throughout the Zone 
1 fill. It may be seen that, in spite of the wide variations in K and n, the values of the computed 
stresses do not change appreciably, indicating that the stress analysis procedure is insensitive to 
reasonable variations in these parameters. In view of this it was considered appropriate to use 
representative values, based on the test data and on experience with determinations of parameters for 
other soils. On this basis, the following parameters were selected for use in all further analyses: 



Y 


= 1171b/ft3 


c 


= 1650 psf 


<f> 


= 31° 


K 


= 470 


n 


= 0.12 


Rf 


= 0.79 


F 


= 0.10 


d 


= 4.0 



The value of G was left variable at this stage pending the completion of field tests to determine the 
stresses at which hydraulic fracturing occurred in the field. Three such tests were conducted in the 
embankment and key trench fill near the left abutment at Stations 26+00 and 27+00, where the key 
trench sections closely resemble those at Stations 15+00 and 13+70 on the right abutment 
respectively. 

Field Tests for Hydraulic Fracturing 

Several field tests were performed to measure the water pressures required at different points in the 
Zone 1 section in the unfailed portion of the dam to measure the water pressure required to cause 



D-7 








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D-9 



hydraulic fracturing. Previous studies have shown that this water pressure should be closely equal to 
the sum of the minor principal stress at the point in question and the tensile strength of the soil at 
that point. 

Sections chosen for study were Station 26+00, where the stress conditions were considered to be 
somewhat similar to those at Station 15+00 on the right abutment and Station 27+00, where 
conditions were similar to those at Station 13+70 on the right abutment. 

Test No. 1 - Station 26+00 

The first test was performed at Station 26+00 where fracturing was induced at El. 5210 under a water 
head of 101 ft, corresponding to a pressure of 6.3 ksf. The location of the test, superimposed on the 
cross-section at Station 15+00, is shown by point A in Figs. 4 and 5. Also shown in the figures are the 
computed stress conditions required to cause hydrauUc fracturing in the vicinity of A for three 
different values of the parameter G and for the case where the key-trench fill is assumed to be 
unwetted (Fig. 4) and wetted (Fig. 5). It was estimated that the tensile strength of the Zone 1 fill was 
about 0.4 ksf for this purpose. It will be seen that, in Fig. 4 the computed stress required to induce 
fracturing at point A is about 6.5 ksf for G = 0.35, while in Fig. 5, the computed fracturing pressure 
is about 6.3 ksf for G = 0.35. Both of these computed results are in excellent agreement with the 
measured pressure causing fracturing in the field, but results for other values of G are significantly less 
favorable. 

Test No. 2 

The second test was performed at Station 26+00 in a depth range between Els. 5133 and 5161, and 
fracturing developed when the head of water acting on the soil reached an average elevation of 5293. 
As described in Chapter 3, it seems reasonable to believe that fracturing occurred at about El. 5147 so 
that the corresponding head causing fracturing would be 146 ft of water or a pressure of 9.1 ksf. The 
location of such a test position superimposed on the cross-section at Station 15+00 is shown by point 
B in Figs. 4 and 5. Also shown in the figures are the computed stress-conditions required to cause 
hydraulic fracturing in the vicinity of B for three different values of the parameter G and for the case 
where the key-trench fill is assumed to be unwetted (Fig. 4) and wetted (Fig. 5). It may be seen that, 
in this case also, reasonably good agreement is obtained between the measured pressure required to 
cause hydrauhc fracturing (9.1 ksf) and the computed pressure for the case where G = 0.35 and the 
key-trench fill is assumed to be unwetted (8.8 ksf). Poorer agreement is obtained for higher and lower 
values of G. However the much lower values indicated for all values of G by an analysis performed for 
a wetted key-trench fill suggests that this type of analysis would not provide reahstic results for the 
section under investigation, and indicates that the key-trench fill was probably not wetted before the 
failure. It might also be noted that the results of this test indicate the tensile strength of the fill to be 
of the order of 0.4 ksf (see Chapter 3). 

Test No. 3 

The third test was performed at Sta. 27+00 in a hole drilled to El. 5190. The hole was then filled with 
water to El. 5315 but no evidence of hydrauhc fracturing was observed. The pressure at the bottom 
of the hole under this head was 7.8 ksf. The location of this test point superimposed on the 
cross-section at Station 13+70 is shown in Fig. 6. It may be noted that for G = 0.35, the 
corresponding value of the computed pressure required to cause hydrauhc fracturing at this location 
is only 6.4 ksf. It seems likely, based on the results shown in Figs. 5 and 6, that a computed pressure 
in good agreement with the field test result might have been obtained if the analysis had been made 
for G = 0.4. 

However in view of the good results obtained for Station 15+00 using G = 0.35 and an unwetted key- 
trench fill condition, together with the uncertainties necessarily introduced by other aspects of the 



D-10 




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analyses it was concluded that analyses based on these conditions would provide an adequate 
indication of the stress distributions in the embankment at sections of primary interest and a useful 
guide to the associated potential for hydrauhc fracturing. Having thus established a reasonable set of 
analysis parameters and conditions, computations of stress conditions were then made for the 
embankment sections at Stas. 12+70, 13+70 and 15+00. The results of these analyses are described 
below. 

Analysis of Section at Sta. 12+70 

An ideahzed cross-section through the embankment at Sta. 12+70 is shown in Fig. 7. Before 
discussing the computed values of stresses developed throughout the embankment it is useful to note 
the stress conditions in a soil element adjacent to the upstream face of the key trench. Such an 
element is shown in Fig. 8 together with the orientations of the major and minor principal stresses. 
Since hydrauhc fracturing is hkely to occur first on the plane with the lowest value of normal stress it 
will always tend to be initiated on the minor principal plane, which for the element shown is inclined 
inwards at about 30° to the vertical. On the centerUne of the trench the minor principal plane will be 
essentially vertical while on the downstream side of the face of the trench it will be inclined at the 
opposite direction to that shown in Fig. 8. Whether or not fracturing will occur on such planes 
depends on the relative values of the water pressure on the face of the trench and the minor principal 
stresses in soil elements adjacent to the wall of the trench. 

A comparison of these stresses is shown in Fig. 7. Values of the minor principal stress developed in 
different elements of the finite element mesh are shown directly in the elements in ksf units and the 
hydrostatic water pressures assumed to develop in a highly jointed rock for a reservoir level of 5300 
(the elevation at the time the dam failed) are shown adjacent to the elements in parentheses. It may 
be seen that for this section hydrauhc fracturing of the type described above is only indicated for the 
outer rows of elements in the bottom part of the trench (shown shaded) and elements on the 
downstream side would only fracture if full hydrostatic pressure could develop in this area. In these 
elements and zones, however, the analyses would indicate the onset of hydraulic fracturing which 
could be expected to propagate from any point of initiation in a longitudinal direction, providing the 
possibihty of full hydrostatic pressures developing over a substantial area near the lower part of the 
upstream face of the key trench. The resulting fractures are illustrated schematically in Fig. 9. 

With regard to the possibility of hydrauhc fracturing in the transverse direction it is necessary to 
compare the hydrostatic water pressures with the sum of the normal stress on the transverse section 
and the tensile strength of the soil as illustrated in Fig. 10. A comparison of the computed normal 
stress on the transverse plane with the full hydrostatic pressures is shown in Fig. 1 1 . It may be seen 
that the analysis indicates that the stresses developed at all elevations in this section would be 
sufficient to preclude the possibility of transverse fracturing. 

However with the reservoir level at El. 5300 the study would indicate that full hydrostatic water 
pressures could move through fractures along the upstream face, and along the downstream face, 
possibly finding egress through transverse fractures which might form at other sections of the 
embankment. This possibihty is explored further below. 

It is appropriate to point out at this stage that the walls of the key trench were not smooth as shown 
schematically in the sections used for analyses. Thus in addition to fracturing along the faces of the 
key trench, longitudinal movement of water might also be facihtated by zones of lower compaction 
underlying projections on the face, thereby compounding the conditions discussed above. 

For simphcity in explanation, the grout curtain has been assumed to be fully or neariy fully 
impermeable. Under this condition, full reservoir pressure can reasonably be assumed to act on the 



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Transverse fracturing occurs if u>0^ +ts 

where; u = water pressure 

tgs tensile strength of soil 



FIG. 10 



MECHANISM FOR TRANSVERSE 
FRACTURING IN KEY TRENCH 



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D-19 



upstream face of the key-trench fill. It is evident, however, that the calculated potential for hydraulic 
fracturing depends greatly on the actual water pressure. Since the efficiency of single-line grout 
curtains in rock, when determined by piezometric observations upstream and downstream of the 
curtains, has in reality turned out to be remarkably low, the actual water pressures are established by 
the conditions of flow through the foundation and curtain, and may be substantially less than full 
reservoir pressure. Therefore, the susceptibUity to hydraulic fracturing determined by the foregoing 
calculations represents an upper limit. 

Analysis of Section at Station 13+70 

Analyses similar to those presented above, but for the embankment cross-section at Station 13+70, 
are shown in Figs. 12 and 13. Fig. 12 shows values of the minor principal stress at element locations 
throughout Zone 1, together with values of the hydrostatic water pressures in the upstream jointed 
rock for a reservoir level of 5300 (the level on the day of the failure). The shaded zone shows those 
parts of the key trench where the water pressure exceeds the sum of the minor principal stress and 
the estimated tensile strength of the key trench fill, and thus where inclined longitudinal fracturing as 
shown in Fig. 8 can be expected to occur. It may be seen that such fracturing could extend about 40 
ft above the base of the key trench at this section and that longitudinal flow of water along fractures 
could occur aU the way across the section. 

Fig. 13 shows values of the normal stresses on the transverse section, together with values of the full 
hydrostatic pressure on the day of failure. Here it is apparent that transverse fracturing could occur to 
a height of about 20 ft above the base of the trench. 

A combination of the two hydrauhc fracture patterns shown for Sta. 13+70 would provide a 
continuous flow path for water from joints in the upstream rock to open joints in the downstream 
rock, providing a mechanism for erosion of the highly erodible Zone 1 fUl. 

The question might be raised whether, in fact, full hydrostatic pressures could be developed on the 
downstream side of the key trench fill. Until a continuous flow path developed, piogressive fracturing 
could readUy lead to the development of full hydrostatic pressures in aU parts of the fracture system. 
Once the water found an outlet path, some loss of pressure would inevitably occur. If this loss of 
pressure was appreciable, the fracture might close, and if this happened flow would stop. Cessation of 
flow, however, would quickly lead to reestabhshment of full hydrostatic pressure conditions, which 
would result in reopening of the crack. Thus, once a continuous seepage path had been established 
from upstream to downstream, it seems likely that flow would continue, perhaps on an intermittent 
basis in the early stages but on a continuing basis as progressive erosion developed in the key trench 
and later the embankment fdl. 

Analysis of Section at Sta. 15+00 

Analysis of the stress conditions for the embankment sections at Station 15+00 are shown in Figs. 14 
and 15. Fig. 14 shows values of the minor principal stress at element locations throughout Zone I 
together with values of the hydrostatic water pressures in the upstream jointed rock for a reservoir 
level of 5300. It is apparent that for these stress conditions, hydrauhc fracturing in a longitudinal 
direction could at this stage extend through virtually the full area of the key trench, although very 
high pressures would prevent its development in the upper center part of the trench. Hydrauhc 
fracturing would also be indicated in a substantial zone near the base of the Zone 1 material in the 
main body of the embankment. 

Somewhat similar results are indicated in Fig. 15 which shows the distribution of normal stress on the 
transverse section at this station. Again the low values of lateral stress developed in the key trench 



D-20 




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D-24 



would indicate that hydraulic fracturing could extend through the full depth of the trench except for 
a small zone in the upper part of the trench on the downstream side. 

Summary of Results 

In assessing the significance of the zones of potential hydraulic fracturing shown in Figs. 7 to 15, it 
should be noted that the determinations were made by comparing the stresses developed in the 
embankment and key trench fills with the full hydrostatic pressures in the adjacent rock on the day 
of failure when the reservoir elevation was 5300. On dates prior to this, the stress levels in the fill 
would be essentiaUy the same, but the reservoir level and corresponding hydrostatic water pressures 
would be substantially lower so that the potential zones of hydraulic fracturing would be greatly 
reduced. 

For example with the reservoir level at El. 5255 (as it was on May 20, 1976) the hydrostatic water 
pressures in the upstream jointed rock would only be sufficient to cause hydrauhc fracturing in the 
bottom 10 ft of the key trench at Station 15+00 and none at all for Stas. 13+70 and 12+70. This 
condition is best illustrated by the longitudinal section drawn through the centerline of the key 
trench on the right abutment shown in Fig. 16. The analysis indicates only a very small zone in the 
vicinity of Sta. 15+00 where the water could move horizontally and vertically through 
hydraulically-induced fractures on this date, May 20, and for a reservoir level of 5255. 

As the water level rose, the extent of the zone in which fracturing could occur naturally increased, 
but reference to Figs. 11 and 12 will show that even when the reservoir level rose to El. 5275 
hydrauhc fracturing would still not yet have developed at the bottom of the key trench at Station 
13+70. This reservoir elevation was reached on May 25, 1976 and Fig. 17 shows the estimated extent 
of the zone of hydraulic fracturing in the key trench on this date. 

Finally, by the time the reservoir reached El. 5300 on June 5, 1976, transverse hydraulic fracturing 
would become possible in the bottom section of the key trench at Station 13+70 and it would extend 
to a greater height at Sta. 15+00 as shown in Fig. 18. Note however that it is never likely to occur 
beyond about' Sta. 1 6+00 because the key trench downslope of that station was either very shallow or 
non-existent, and it does not seem likely that it would develop upslope of about Station 13+20 
because the stress conditions beyond that point are unfavorable to its development. 

Figs. 16, 17 and 18 provide an excellent summary of the extent of the potential zone of hydraulic 
fracturing, as estimated from the results of the preceding analytical studies. It is interesting to note 
that they only indicate the development of a substantial zone of vulnerability due to this cause in the 
10 days before failure actually occurred and that the location of the indicated zone of fracturing 
coincides closely with the zone in wliich piping finally developed (between about Stations 13+50 and 
15+00). 

While the potential for hydraulic fracturing to provide a fiow path for water through the key trench is 
a significant aspect of any potential failure mechanism, it must be coupled with the possibility of 
erosion of soil and therefore the possibility of removal of eroded material through open joints in the 
downstream rock, at least in the early stages of failure development. Accordingly also plotted on the 
longitudinal sections shown in Figs. 16, 17 and 18 is the approximate location of the bottom of the 
open-jointed, highly pervious rhyolite in the vicinity of the key trench. 

Consideration of the position of this material in conjunction with the estimated extent of the zones 
of hydrauhc fracturing on May 20 (Fig. 16), May 25 (Fig. 17) and June 5 (Fig. 18) would seem to 
indicate that it was not until the reservoir elevation reached about El. 5290 on June 1 that the 



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complete flow path through highly pervious rock, through extensively fractured key trench fill and 
again into highly pervious rock would exist to permit the initiation of internal erosion and the 
mechanism which finally could lead to failure of the dam. 

The remarkable coincidence of the critical zones for hydraulic fracturing, and the time at which it 
could develop, with the zone of failure and the time of failure would seem to lend considerable 
support to the hypothesis that hydrauhc fracturing of the soU in the key trench may well have been a 
contributory cause to the failure of Teton Dam. However it should be noted that the potential zones 
of hydraulic fracturing would tend to be reduced if water pressures on the upstream face of the 
trench were substantially lowered as a result of leakage through the grout curtain. Thus the analysis 
presented above indicates an upper bound on the extent of hydraulic fracturing which might have 
occurred. 

The hydraulic fracturing hypothesis presented above necessarily raises other questions concerning the 
dam failure. Foremost among these would have to be the question of why failure was initiated on the 
right abutment rather than the left. The key trench sections were remarkably similar on both sides 
and an analysis similar to that described in the preceding pages for stations on the left abutment of 
the dam would undoubtedly lead to somewhat similar results with regard to the potential for 
hydraulic fracturing. 

In the final analysis therefore it must be considered that if hydraulic fracturing were responsible for 
the leakage through the key trench fill, initiation of failure on one side of the damsite rather than the 
other would be related to the question of minor geologic details and the fact that the joint system in 
the rhyoUte was more extensively developed and adversely aligned to facilitate seepage and internal 
erosion on the right abutment than on the left. However the hypothesis would seem to indicate that 
if this mechanism of failure developed, given similar rock conditions in the left abutment, it would 
only have been a matter of time before seepage and internal erosion occurred on that side also. 

Finally, it is worthy of note that, although it is assumed that hydraulic fracturing will occur in a 
fine-grained soil whenever the water pressure exceeds the sum of the minimum compressive stress and 
the tensile strength of the soil at a given point, the phenomenon is not yet fully understood and 
deserves research on a variety of materials under different boundary conditions and under controlled 
laboratory conditions. When a better physical understanding of the creation and propagation of 
cracks by water pressure has been achieved, the criteria for initiation of hydrauhc fracturing utilized 
herein may require modification. 

Significance of Key Trenches 

The preceding discussion necessarOy attaches considerable significance to the role of the key trenches 
in reducing the stresses in the key trench fill and thereby facihtating hydrauhc fracturing and 
accompanying erosion. In order to further investigate the effects of the key trenches on the stress 
distribution and to provide a qualitative rather than a quantitative assessment of their significance, a 
series of studies was conducted for the conditions at Sta. 15+00 in which the vertical stresses 
developed in the embankment were expressed as a proportion of the total weight of overburden, for 
all points in the embankment. TTre results are expressed as contours showing the developed vertical 
stress as a fraction of the direct overburden pressure. Analyses were made for four conditions. 

1. For the actual section at Sta 15+00 with no allowance for wetting of the Zone 1 fill in the 
key trench or the embankment. 

2. For the section at Sta 15+00 if the key trench had not been constructed and with no 
allowance for wetting of the Zone 1 material. 



D-29 



3. For the actual section at Sta 15+00 with allowance for wetting of the Zone 1 fill to the 
extent indicated in Fig. 13. 

4. For the sections at Sta. 15+00 if the key trench had not been constructed but the Zone 1 
fill had been wetted to the extent indicated in Fig. 13. 

The comparative results for analyses 1 and 2 above are shown in Fig. 19 and for analyses 3 and 4 
above in Fig. 20. The effects of arching over the key trench and the considerable reduction in stresses 
in the key trench fill resulting from the presence of the key trench is readily apparent from these 
figures, confirming the fact that the use of key trenches on the sides of the abutments invited the 
development of arching, stress reduction and the accompanying onset of hydraulic fracturing and 
internal erosion. 

Mechanism of Failure by Hydraulic Fracturing 

The discussion presented in the preceding pages has shown clearly how the phenomenon of hydraulic 
fracturing could provide a continuous flow path through the key-trench fill in critical locations, if all 
features of the grout curtain had functioned adequately. The flow path in the early stages of its 
development would necessarily start in highly pervious rock, pass through fractures in the key-trench 
fill and then continue through highly pervious rock. 

Whether the initial flow started by hydrauUc fracturing or leakage in the rock just below the grout 
cap, the flow path would have to develop into a continuous pipe through the embankment in order to 
lead to the massive seepage which developed in the one or two hours just prior to complete failure 
and which through accompanying erosion led to the breaching of the embankment. It is of interest to 
speculate therefore on the manner in which this transition might have developed. 

Playing a key role in this aspect of failure was undoubtedly the specific character of the joint systems 
in the rock in the vicinity of Station 14+00 and the highly erodible nature of the Zone 1 fill. As 
observed in the field, there were a number of open joints in the rock plunging down to and below the 
base of the key trench on the upstream side of the key trench between Stas. 13+90 and 14+10. 
Similar but narrower joints could readily be identified at locations 10 to 20 ft on both sides of this 
zone. 

Readily identifiable exit paths for water on the downstream side of the key trench in this vicinity 
could similarly be noted as follows: 

(a) a Umited number of open vertical joints in the relatively sound rhyolite below about El. 
5200 

(b) a maze of open horizontal and vertical joints in the highly fractured and jointed rhyoUte 
between about Els. 5200 and 5240. 

and (c) a 25 ft thick layer of highly pervious talus and slope wash between Els. 5240 and 5265. 

Characteristically the primary open vertical joints in the downstream pervious rock angled in plan at 
about 45° from the dam axis towards the river, so that water entering this joint system would be 
expected to flow primarily in this direction until it encountered a more accessible outlet path near 
the face of the abutment rock, where joints were abundant in aU directions. 

Thus the general path of seepage and erosion, both as evidenced by the field and analytical studies 
and by the observed backward path of erosion towards the whirlpool during the failure itself would 



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D-32 



indicate that failure was probably initiated in the key trench in the vicinity of Sta. 14+00, and then 
progressed downstream approximately along the section ABC shown in Fig. 21. A cross-section 
througli the embankment along section ABC is shown in Fig. 22. 

The overall progression of piping leading to failure might thus be visualized as follows: 

Several days before the final failure, leakage through the key trench fed water at a slowly 
increasing rate into a number of diagonal joint systems; a portion of this flow entered the 
joints directly, and a portion entered via the overlying highly fractured rhyolite and talus 
above El. 5200. As the joint systems began to fill with water, aided by water flow around 
the end of the right abutment key trench fill, quiet discharges of water occurred several 
days before the actual failure. Some of the discharges emerged along the base of the 
canyon wall downstream from the dam (see locations 1 and 2 in Fig. 21) and some moved 
as subsurface flows into the contact zone of talus and heavily jointed rock beneath the 
Zone 2 and Zone 5 portions of downstream part of the embankment (Fig. 22). 

Thus the critical escape route for leakage was the multitude of partially filled void spaces 
in the loose slabby rock just beneath the Zone 1 fill downstream from the key trench. 
Significantly, materials partially filling void spaces in this zone of rock would be 
unaffected by overburden pressures from the overlying fiU because of the sheltering 
action of the loose rock structure. Accordingly, the leakage conveyed to this medium by 
flow across the key trench at Station 14+00 and thence flowing downward and to the left 
towards Sta. 15+00, found not only an almost free exit in the near-surface rock but also 
escaped in channels that were of such size that they could easUy convey soil particles 
eroded from the core of the dam. Thus of paramount importance was the possibihty for 
leakage flows occurring immediately along the core-to-rock interface to loosen and erode 
the compacted silt from Zone 1. Although the fill was probably well-compacted, those 
parts of the fill beneath minor overhangs would inevitably be sheltered from overburden 
pressures and thus locally vulnerable to erosion. 

In this way the initial seepage probably eroded a small channel along the base of the dam, 
both upstream and downstream as shown in Fig. 23(a), with the seepage flowing under 
the Zone 2 material, down the talus on the upper part of the right abutment and finally 
emerging as the leak at the toe of the dam on the morning of the failure. 

As the flow continued, further erosion along the base of the dam and a resulfing 
concentration of flow in this area, led to a rapid increase in the size of the eroded channel 
as shown in Fig. 23(b). At this stage water probably began to emerge at the contact of the 
embankment with the underlying rock at about El. 5190 to 5200. 

Progressive erosion led to continued increase in the size of the channel along the base of 
the dam, and perhaps some erosion of the soil above Zone 2 as shown in Fig. 23(c), until 
finally the water pressure was sufficiently great to break suddenly and violently through 
the Zone 2 fill and erupt on the face of the dam as shown in Fig. 23(d). 

Beyond this point the progressive formation of sinkholes, both upstream and 
downstream, as illustrated in Fig. 23(e), provided an ever-accelerating mechanism for 
internal erosion, finally leading to complete breaching of the dam as illustrated in Fig. 
23(0. 



D-33 







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(A, B,C, OF F) 



CONCEPTUAL MECHANISM OF PROGRESSIVE 



IVJ.^O FAILURE ALONG SECTION A-B-C 



D-36 




5340 

5300 

5260 

5220- 

5180- 

5140- 





(CONT D, E,F) 



CONCEPTUAL MECHANISM OF PROGRESSIVE 



PIP Q "^ CONCEPTUAL MECHANISM OF PR 
r \\J.C.O FAILURE ALONG SECTION ABC 



D-37 



This general concept of the mechanism appears to be consistent with the photographic 
record of the development of the failure. 

It should be noted that even this rather detailed description of the failure mechanism does not 
provide a final answer to the specific cause of failure of Teton Dam. Clearly many aspects of the site 
and the embankment design were contributory to the failure, but because the failed section was 
carried away by the flood waters, it will probably never be possible to resolve whether the primary 
cause of leakage in the vicinity of Station 14+00 was due to imperfect grouting of the rock just below 
the grout cap, or to hydraulic fracturing in the key trench fill, or possibly both. There is evidence to 
support both points of view. Nevertheless, while the specific cause may be impossible to estabUsh, 
the narrowing of the possibilities to these two aspects of design and construction is likely to serve as 
an important lesson in the design and construction of future projects of this type. 



D-38 



REFERENCES 

Bieber, Ray E. (1976) "TETON DAM: Finite Element Stress Analysis Study," Report DAC/1222 to 
Independent Panel to Review Cause of Teton Dam Failure, October 15, 1976. 

Nobari, E.S. and Duncan, J.M. (1972) "Effect of Reservoir Filling on Stresses and Movements in 
Earth and Rockfill Dams," Geotechnical Engineering Report No. TE 72-1 to the Office, Chief of 
Engineers, U.S. Army Waterways Experiment Station, University of California, Berkeley, January. 

Ozawa, Y. and Duncan, J.M. (1973) "ISBILD: A Computer Program for Analysis of Static Stresses 
and Movements in Embankments," Geotechnical Engineering, Report No. TE 734, University of 
California, Berkeley, December. 

Wong, Kai S. and Duncan, J.M. (1974) "Hyperbohc Stress-Strain Parameters for NonUnear Finite 
Element Analyses of Stresses and Movements in Soil Masses," Report No. TE 74-3 to National 
Science Foundation, Office of Research Services, University of California, Berkeley, July. 



D-39 



APPENDIX E 

POST-FAILURE JOINT MAPPING 



This appendix includes the following items: 

1. GEOLOGIC EXPLANATION AND LOCATION MAP 

A legend of geologic units and symbols and a map showing 
the locations and orientations of geologic sections in 
the right abutment. 

2. STRIP MAPS OF THE RIGHT ABUTMENT KEYWAY FROM SPILLWAY TO 
RIVER CHANNEL showing joints 10 ft and longer. 



3. GEOLOGIC SECTIONS 

A-A parallel to dam centerline 100 ft downstream 

B-B^ parallel to grout cap 10 ft downstream 

C-C^ parallel to grout cap 10 ft upstream 

D-D parallel to dam centerline 150 ft upstream 

4. EXPLANATION OF FIELD OBSERVATIONS 

5. TABULATION OF JOINT CHARACTERISTICS CROSS REFERENCED TO 
GEOLOGIC SECTIONS 

6. FIGS. E-1 THROUGH E-24 

Photos of joints in right abutment of Teton Dam 

7. Memorandum from Project Construction Engineer, Newdale, Idaho, 
to U.S. Bureau of Reclamation, Director of Design and 
Construction, Denver, Colorado, dated March 14, 1976, 
Subject: Proposed Treatment of Fissures and Cavities in 
Right Abutment Key Trench 



E-1 



GEOLOGIC UNITS 



Tsv, 



WELCea ASH-PLOW "niFP tT»v). Tertlmry silicic volcaaics of rfarellte co^Msl- 
tlon. The tuff is variably welded, generally porphyritic with light 
colored feldspar phenocrysts up to 1/4 inch within a fine- to Beditn- 
gralned tuff Batrix. Very lightly to locally aoderately vesicular 
with vesidas (up to 3/8" in siie). Moderately to lightly jointed 
(Joints spaced Bostly fro* 1 to 6 feet) with intensely jointed zones 
(joints spaced less than O.S ft. apart). Joints are tight to open 
up to 1/4", but locally up to 4 inches. Many joints are stained with 
liaonite, heaatite, aanganese and soae calcite. Most of the flow is 
characterized by a fainV to distinct foliation that is caused by 
flattened, wavy streaJcy, light colored puiice fragments (and soae 
lapilli) and by soae zones or areas of flattened or elongated 
vesicles. The rock generally is hard; hand size speciaens break with 
a Boderate haaaer blow. The color is variable fro« light gray to 
sediua gray with shades of red, brown and purple. 

The welded ash-flow toff fotaatlon exposed upstreaB of the grout curtain 
is divisible into 3 units: Tsvj, TsV2, and TSV3. These units are 
difficult to trace or differentiate downstreaa of the grout curtain. The 
middle unit, Tsv^, appears to pinch out or terainate downstream of the 
grout curtain and the upper platy tmit, Tsvj, appears to thicken down- 
streaa of the grout cap. 

Light gray-brown in i^^per part grading to light to 
■ediia gray in lower part and fonu Irregular ragged out- 
crops. Platy: Lenticular and tabular plates aostly 2 
to 6 inches thick but soae \if> to 18 and 24 inches thick. 
The plates dip at low angles and are about parallel to the 
faint foliation. Spaces between plates are 1/4 inch up 
to 2 inches open. Soae plates are coated with calcite 
up to 1/4 inch; caliche and silt fill aany of the openings 
in the upper S to 6 feet of the unit. The near vertical 
jointing strikes N 30* - 60* E and N 60* - 90* E, spaced 
froB about 3 to 10 feet apart. Most of these joints are 
tight, planar and saooth and about half are stained with 
iron, aanganese and calcite. 

Gradational with upper platy unit and is Barked at 
lower contact by a breccia zone. The unit, which is 
about 60 feet thick upstreaa of the grout cap, dips gently 
downstreaa (westward) and appears to pinch out or term- 
inate against a strong NN trending joint about 15 feet 
downstreaB from the grout cap. 

Medita to dark gray. Forms aany near vertical cliffs 
along the abutment upstream of the grout cap. Joint- 
ing, much of which is foliation jointing, is moderate 
to locally intense, (aostly 1-2 feet), mostly high 
angle and trends N 10* to 40* W. Host joints are tight, 
planar to wavy and saooth, but some joints are rough 
and open up to 4 Inches. Calcite coats aany of the 
joints and fills some joints up to 1/2 inch thick. Iron 
and Banganese stains aany of the joints. The foliation, 
which is faint to distinct, appears to dip at high angles 
in contrast to the low dipping foliation in the over- 
lying and underlying units. 

Breccia Zone - This zone forms the contact between Tsv2 and Tsvj 
and is quite irregular and varies from a single zone about 2 
inches thick up to several zones that occur over a thickness 
of up to about 10 feet. The zones consist of breed ated and 
crushed rock fragaents, frca less than 1/2 inch up to 12 
inches thick, ceaented together by a white, brown to dark 
gray calcine up to 1-1/2 inches thick. Openings in the 
breccia zone are irregularly shaped and vary from 1/4 inch 
up to 4 inches in size. The upper and lower contacts in 
soae places are planar, but in other places are wavy and 
irregular. Through the grout cap area this zone occurs as a 
proadnent low dipping, calcite filled joint about 1-1/2 inches 
thick. 

Qtaracter i zed by the bold massive blocky outcrops and the 
proainent benches in the lower part of the abutment. The 
near vertical jointing is very prominent and many joints can 
be traced over 100 feet. The major joint trend is N 15* - 
40* W. Spacing is mostly 5 to 10 feet with openness varying 
froa tight to 1/4 inch, locally 1 to 4 inches. Most joints 
" are saooth and are stained with iron and manganese oxides 

and soae calcite. The foliation planes are near horizontal 
and are froa a few inches to about 3 feet apart ; soae are 

USBR DWG. NO. 549-100-299 ^i^^; ^?*'*"' ""eT" *° ^^' "^''' '^°^" ^' ■""''' 



Tsv. 



TSV: 



SYMBOLS 



Pill Geologic M«ps 



g^ J'-^ Trace of dipping joint with strike and dip shown at 

observation point. Joint is dashed where projected or 



cdW 



72 




approximate, queried where inferred. Joint niaiber (84) 
refers to accoapanying tabulation with detailed descrip- 
tion. Additional observation points nuabered (2), (3), etc. 

Trace of vertical joint. 

Horizontal joint. Trace shown on cross sections only. 

Openness of joints. 

Single line » tight to open less than 1/2 inch. 
Double line ■ open 1/2 to 2 inches. 
Double line with inches noted ■ open greater than 
2 inches with maximm openness shown. 

Grout filling joint. 




Strike and dip of foliation. 

Contact. Solid line where exposed, dashed where 
projected or approximate, queried where inferred. 

Area of surface grout covering rock. 

U»it of concrete grout cap. Solid line denotes hairline 
to 1/8" open crack. Dashed line (heavy) represents pour 
line or lift line. 

Grout nipple. 




Geologic Cross Sections 

Joint NiBber. Sequential nuaber fro« 1 to ? on each drawing. 

Tight Joint. Open less than 1/2 inch. 

Circled Joint; Denotes grout occurrence in joint. 

Tlfht Horizontal Joint. H denote* a horizontal or near 
horizontal joint which has no trace plotted on plan aap. 

Open Joint. Open greater than 1/2 inch. 

Graphic representation of proninent foliation and closely 
spaced jointing. 



Unconsolidated debris washed down froa rock surface con- 
posed of heterogeneous mixture of silt, gravel, cobbles 
and angular fragments of welded ash-flow tuff. 



Notes : 

1. For detailed description of each Individual joint, refer to 
accc^>anying tabulation by Joint Niaiber. 

2. Length of joint trace In cross section portrays the continuity at depth. 

3. All joint traces shown with apparent dips. 



USBR DWG. NO. 549-100-299 



E-3 





LOCATION MAP 



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E-18 



TETON DAM 
POST FAILURE ROCK SURFACE JOINT SURVEY 

EXPLANATION 



ITEM 



DEFINITIONS 



1. Joint Number (and observa- 
tion points 1, 2, 5j etc. 
if needed) 

2. Strike 



3. Dip 



4. Continuity (feet) 

D 

MC 

C 

5. Openness 

T 



EO 

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P 

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S 

R 



Sequential number from 1 to ? on 
each photograph, section or plan 
map. 

Strike taken at observation 
point. 

Measured maximum dip at observa- 
tion point. 

Measured on surface trace. 
Discontinuous; <50' 
Moderately Continuous; 50-100'. 
Continuous; > 100' 
Note: Joints <10' in length 
not mapped ixnless unusual condi- 
tion existed. 



Tight; <l/2" 
Open; 1/2-2" 
Excessively Open; > 2" 



(maximixm openness noted), 



Planar 

Irregular 

Curved 

Wavy 

Offset 




(Range of offset in inches or feet), 



Smooth; deviation from plane <l/4' 
Rough; deviation from plane > 1/4" 



E-19 



8. Pilling, coating, or 
stain 

A . Natural 

10 

MO 

CT 

CP 

CV 

SL 

B. frrout 

GT 

GV 

9. Remarks 

Pertinent observation 
not covered in above 
items. 



Estimated ^ of joint surface 
by each type present. 

Iron Oxide (red, yellow, rust), 
Manganese oxide (black stain 

or dendrites). 
CaCO ; <1/16" 
CaCO^; 1/16-1" 
CaCO^;> 1" 
Silt'' 



<l/4" 
>l/4" 



Hydrothermal alteration, evidence 
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of unusually thick CaCO^. Foliation 
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Fig. E-1 Right wail of Teton Canyon upstream of dam axis showing 

intensive jointing in uppermost rock zone, (post-failure) 




Fig. E-2 Ash-flow tuff in right wall of Teton Canyon upstream of key 

trench. Note near-horizontal planes of separation, (post-failure) 



E40 




Fig. E-3 Right wall of Teton Canyon downstream from grout cap. (post- 

failure) 




Fig. E-4 Right wall of canyon between dam and spillway stilling basin, 

(post-failure) 



E-41 



^jkyv,,^-0fc:3^i^^^ 




Fig. E-5 Downstream face of 

key trench in right 
abutment, (post-failure) 















Fig. E-6 Upstream face of key 

trench in right abutment, 
(post-failure) 



E42 




Fig. E-7 Downstream face of key trench in right abutment at El. 5290. 

(post-failure) 




Fig. E-8 Intensively jointed ash-flow tuff in downstream 

face of right abutment key trench at El. 5290. 
(post-failure) 



E43 




Fig. E-9 Open joint in upstream face of right abutment 

key trench at Sta. 12+40, El. 5290. (post-failure) 




Fig. E- 1 Open joint in downstream face of right 

abutment key trench at El. 5290. (post- 
failure) 



E44 




Downstream of wall of right abutment key trench. Elevation in 
center of photo is about 5290. (post-failure) 







.MKT; ^ 






Fig. E-12 View along grout cap; key trench, and spillway in background, 

(post-failure) 



E-45 



•'^"'-^ "^ 





m 



r 



Fig. E-13 Rim of upstream wall of right abutment key trench, (post-failure) 



■a *■ '-.'l^M 'T"»« ?■• . ^Jp^i- -"^ST Ik-^-ii. .iai^^ -^^ ^••» ^ I - -1 ■ ■- 



^•*Vl 



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Fig. E-14 Upstream face of right abutment key trench at Sta. 12+70. 

Fill at El. 5240. (post-failure) 



E-46 






K": 



■^. 



ft^i 







Fig. E-15 Upstream wall right abutment key trench at Sta. 12+65. 

Elevation of fill is 5240. (post-failure) 




Fig. E-16 Downstream wall of right abutment key trench, (post- 

failure) 



E-47 



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Fig. E-17 Key trench excavation on right abutment, (post-failure) 




0m:&mm^ 



Fig. E-18 Right abutment of dam immediately downstream from grout 

cap. (post-failure) 



E^8 




Fig. E-19 Fissure at rim of right 

wall of canyon 1/8 to 
1/4 mile upstream from 
dam. (post-failure) 




Fig. E-20 One of several large 

fissures near rim of 
canyon right wall 1/8 to 
1/4 mile upstream from 
dam. (post-failure) 



X'^4 a:^^ 



E49 




M 



Fig. E-21 Prominent rock joints in vicinity of missing grout cap segment 

bottom of photo, (post-failure) 







Fig. E-22 Photo overlaps Fig. E-21. (post-failure) 



E-50 



'J 










^-«^ 



Fig. E-23 Joint system near missing segment of grout cap Sta. 14+00 behind 

ladder in lower center, (post-failure) 




Fig. E-24 View across grout cap 

toward prominent joint 
near Sta. 13+30. (post- 
failure) 



E-51 



March 14, 1974 

Memorandum 

To: Director of Design and Construction, Denver, Colorado 
Attn: 1300 and 220 

Prom: Project Construction Engineer, Newdale, Idaho 

Subject: Proposed Treatment of Fissures and Cavities in Right 
Abutment Key Trench - Specifications No. DC-6910 - 
Morrison-Xnudsen-Kiewit, Teton Dam, Power and Pumping 
Plant, Teton Project, Idaho 

The geology of the fissures and cavities which have recently been 
exposed in the excavation for the right abutment key trench is 
described in the attached report. Preliminary drawings numbers 
549-147-131 and 549-147-132, and photographs of the fissure zones 
and cavities are also included. 

The following proposed treatment of the fissure zones and related 
cavities as discussed with members of your staff is s\immarized as 
follows : 

1. Locate the cavities with pilot angle holes upstream and down- 
stream from the foundation key trench using an air-trac drill 
set up on the original ground surface. The estimated pilot 
hole footage is about 500 lin. ft. 

2. Drill 10-inch diameter holes (8" casing) to intersect cavities 
at locations determined by the pilot drilling and approxi- 
mately as shown on Drawing No. 549-147-131. Ten-inch diameter 
holes as follows: 

a. One 10-inch diameter hole to intersect cavity in fissure 
zone at Station 4+44 upstream. The estimated depth of 
this hole is 60 feet. 

b. One 10-inch diameter hole to intersect cavity in continua- 
tion of above fissure zone at Station 4+21 downstream. The 
estimated depth of this hole is 70 feet. 



E-52 



c. One 10-inch diameter hole to intersect cavity in fissure 
zone at Station >66 upstream. The estimated depth of 
this hole is 70 feet. 

d. The need for a 10-inch diameter hole in the continuation 
of the above fissure zone downstream at Station >i-45 is 
questionnable; however, the final determination of the 
need for a larger hole in this area should be based on 
the results of the pilot hole drilling. 

3. Pill the cavities v/ith high slump backfill concrete discharged 
into the 10-inch diameter holes (S" cased) described above. 
Discussions with the prime contractor indicate that backfill 
concrete using a 4-bag mix will be the most economical filler 
material for these cavities. It is anticipated that a local 
ready mix concrete supplier will furnish the concrete to the 
prime contractor at a substantially lower price than can be 
batched on the job with the contractor's batching facilities, 

4. Place nipples in the voids along fissure zones in the bottom 
of foundation key trench and embed in concrete during place- 
ment of grout cap. Trenches 3 to 5 feet deep and about 3 feet 
wide have been excavated along the strike of the two main 
fissure zones as shown on drawing No. 549-147-132. Nipples 
will be placed in open joints or holes in the floor of the key 
trench near centerline at Stations 5+03, 5+63, and 6+18; and 
about five feet left of centerline between Stations 6+03 and 
6+08. 

5. Intersect fissure zones at various depths in the bottom of key 
trench with grout holes, then grout voids using grout mixes 
and procedures previously established on the project for grout- 
ing similar areas. 



E-53 



The estimated cost for accomplishing this proposed work is as 
follows: 



Work or Material 

1. Mobilization and demobilization 
of drill equj.pment 

2. Air-trac pilot holes 

3. Ten-inch diameter holes with 
8-inch casing 

4. Backfill concrete 

5. Block cavern entrances 



Quantity Unit Price Amount 

For the lump sum of 1,000.00 

300 lin.ft.,5.00 1,500.00 

200 lin.ft.,35.00 7,000.00 

350 cu. yds., 30. 00 10,500.00 

For the lump Siim of 1,000.00 



Total estimated cost 



S 21,000.00 



E-54 



It is critical that this work begin as soon as possible to avoid 
delaying the contractor in his scheduled grouting program on the 
right abutment. Backfilling of the cavern areas with concrete 
should precede grouting to prevent leakage of more costly grout 
into the large voids. The contractor has indicated that pilot 
drilling could begin during the week of March 18 and begin filling 
the cavities in earlj"- April. 

I suggest that representatives from yoiir office visit the project 
during the week of March 18 for an examination of the fissure and 
cavity zones and discuss with our staff the proposed treatment of 
these areas. To expedite the early commencement of the treatment 
work, it is requested that authority be granted this office to 
proceed with price negotiations with the contractor. 

Your early reply v/ould be appreciated. 



Enclosures 

cc: Regional Director, Boise, Idaho 
Attn: 200 w/Enc. 



Note to Regional Engineer ; 

Vi'e would appreciate having a member of your staff present during 
the visit of the Denver Office representatives to the Teton Project, 



E Robisontlc 3-14-74 

be: AO, PCE, OE, ?E, Aberle 



E-55 



Appendix E 



Attachment to letter dated March 14, 1974 addressed to Director of 
Design and Construction, Denver, Colorado, from Project Construction 
Engineer, Newdale, Idaho. 

GEOLOGY 



The excavation for the right abutment keyway trench has disclosed two 
unusually large fissures that cross the floor and extend into the walls 
of the keyway near the toe of the walls. On the floor of the keyway, the 
fissures are filled with rubble; but at both locations, the contractor has 
excavated a trench about three to four feet wide and abqut five feet deep. 
Both fissures apparently were developed along joints that strike about 
N80°W and are vertical to steeply inclined. The largest fissure crosses 
the keyway from station 4+44 of the upstream face to station 4+21 at the 
downstream face. The other crosses from station 3+66 on the upstream 
face to station 3+45 on the downstream face. A smaller fissure strikes 
about N75°W and crosses the keyway trench from station 5+33 of the upstream 
face to station 5+11 at the downstream face. 

The largest and most extensive open zone extends into the upstream wall 
from the toe of the keyway wall near station 4+44. The opening at the 
toe is about five feet wide and three feet high. There is a rubble-filled 
floor about four feet below the lip of the opening. A few feet in from 
the wall the fissure is about seven feet wide, but a very large block of 
welded tuff detached from the roof and/or the north wall rests in the 
middle. Beyond the large block about 20 feet in from the opening the 
fissure narrov;s to about 2h feet wide. The rubble floor slopes gently 
away from the opening and the vertical clearance is about ten feet. About 
35 feet in, the rubble floor slopes rather steeply and the roof swings 
sharply upward. About 50 feet in from the opening, the vertical clearance 
is about 40 feet and the fissure curves out of view at the top. About 75 
feet back the fissure curves slightly southward out of view. The smaller 
fissure is mostly rubble filled and is open only at the upstream face. The 
opening is about one foot square at the face and the fissure appears to be 
rubble filled about five feet back from the face. 

The continuation of this fissure intersects the downstream wall of the 
keyway near station 4+21. The opening is about four feet wide and four 
feet high. A rubble-filled floor lies about four feet below the lip of 
the opening. The large opening only extends about five feet back from 
the face then a foot wide fissure at the north edge continues about ten 
feet back and about ten feet upward before going out of view. 

The other large open zone extends into the upstream wall from the toe of the 
wall near station 3+66. The opening at the toe of the wall is about Ih feet 
wide and 1% feet high. From the opening, the fissure extends about 10 feet 
down to a rubble floor and about 15 feet back before going out of view. The 
continuation of this fissure intersects the downstream wall of the keyway at 
about station 3+45. There is no open fissure at the downstream wall but 



E-56 



there is a 3.5 feet wide zone of very broken rock with open spaces up to 
0,8 foot wide. About 2.5 feet north, there is an open joint about 10 feet 
long and 0.2 foot wide that dips about 78 degrees south. 

At both the upstream and downstream locations of the fissure zones, broken 
rock extends to about midway up the keyway walls. Above the broken zones 
there appears to be filled fissures about 0.5 foot wide that extend 
vertically to the top of the keyway cut. 

Other open joints or holes were observed on the floor of the keyway near 
centerline at stations 5+03, 5+68, and 6+18 and about five feet left of 
centerline between stations 6+03 and 6+08, The holes were rubble filled 
at shallow depths and their lateral extent, if any, was covered by rubble. 
Heavy calcareous deposits were associated with all of the open zones except 
for a sharp, 0.2 foot wide open joint between stations 6+03 and 6+08. 

The fissures have developed along planes of weakness, probably joints but 
possibly faults in the welded tuff. Ancient fumarole activity probably was 
common throughout the region considering the volume of trapped gases that 
would have been associated with the ash flow or flows that formed the welded 
tuff. Violent hot spring and geyser activity probably occurred in connection 
with the fumaroles. Such activity is believed to have occurred in the dam- 
site area in both the right and left abutments of the dam a few hundred feet 
back from the canyon. The ancient Teton River apparently had some controlling 
influence since there is no evidence of such activity in the welded tuff that 
forms the canyon walls. A high area of pre-welded tuff sediments upstream 
from the inlet portal of the river outlet works also may have been related 
to the hot spring and geyser activity. The thinner body of the welded tuff 
cooled more rapidly and the sediments formed a base for water moving through 
the welded tuff. 

In the initial fumarole activity, hydrothermal fluids developed from the 
ash flow deposit are believed to have caused alteration and some opening 
along joints and zones of weakness in the welded ash flow tuff. Ground 
water moving through the welded tuff probably became superheated and built 
up a considerable pressure, very likely the release of pressure that occurred 
when the water reached joints or vents that were open to the surface, causing 
the water, at least in part, to flush to steam and to move with great force 
through the joints or vents and surface as violent hot springs or geysers. 
The violent activity is believed to have eroded the softer, hydrothermally- 
altered rock adjacent to existing open joints and vents. Continued activity 
further altered and eroded the rock, resulting in open fissures and vents 
that have been encountered in the abutments. Apparently the large fissures 
developed in zone of numerous smaller, interconnected fissures. Blocks of 
welded tuff isolated by the small fissures eventually collapsed into the 
void spaces created by the small fissures to develop the large fissures 
floored by welded tuff rubble. 



E-57 



APPENDIX F 



POST-FAILURE EXPLORATION 



DRILL 


LOGS 




Hole Designation 




Appendix No 


DH601 




F-1 


DH602 




P-2 


DH603 




P-3 


DH604 




P-4 


DH605 




P-5 


DH606 




P-6 


DH606A 




P-6A 


DH607 




P-7 


DH607A 




P-7A 


DH608 




P-8 


DH609 




P-9 


DH610 




P-10 


DH611 




P-11 


DH612 




P-12 


DH613 




P-13 


DH614 




P-14 


DH615 




P-15 


DH616 




P-16 


DH617 




P-17 


DH618 




P-18 


DH619 




P-19 


DH620 




P-20 


DH621 




P-21 


DH622 




P-22 


DH623 




P-23 


DH624 




P-24 


DH625 




P-25 


DH626 




P-26 


DH627 




P-27 


DH628 




P-28 


DH629 




P-29 


DH630 




P-30 


DH631 




P-31 


DH632 




P-32 


DH650 




P-33 


DH650 Hole 


Survey- 


P-33A 


DH651 




P-34 


DH651B 




P-34A 


DH652 




P-35 


DH652 Hole 


Survey 


P-35A 


WATER PRESSURE TEST 


RESULTS 


DH-601 thru 


609 


P-36 


DH-610 thru 


632 


P-37 


DH650 




P-38 


DH651 




P-39 


DH652 




P-40 



APPENDIX P-1 



HOLE DESIGNATION: DH-601 
BEARING: N74°W 

ANGLE: 30 to right from vertical 
DEPTH: 109.2 ft. 



LOCATION: 



ELEVATION 

Started: 

Finished: 



Right bay spillway 
at STA 10+60.4 2 ft. 
downstream of up- 
stream grout curtain 
: 5299 

9/8/76 

9/11/76 



LOG: 

0-5.4 ft. Concrete spillway apron (good bond with rock) 

5.4-bottom WELDED ASH-FLOW TUFF 

5.4-20.0 light gray, slightly porphyritic with phenocrysts up to 1/16" in 

diameter, low density rock 
20.0-30.0 prominent "banding", red-purple tint to a medium gray, "bands" 

are flattened pumice fragments and aligned vesicles with probable 

vapor phase minerals 

light to medium gray, slightly porphyritic 



30.0-101.0 

101.0-109.2 medium to dark gray, markedly vesicular, vesicles flattened 
60 to core axis 



Core breaks : 

5.4 '-20. 0' typical core fragment is 0.8' long, range 0.1 '-1.0', most breaks 

are planar, oriented 60 to the core axis, and have a dark 

surface stain 
20.0' -30.0' typical core fragment is 0.4' long, range from less than 0.1' 

to 1.0', most breaks are smooth-surfaced, planar or arcuate joints 
30.0'-109.2' typical core fragment is 1.5' long, range 0.4 '-4. 0'; most breaks 

are planar, oriented at an angle of 60 to the core axis 



Prominent Features 
9.2' 



40.1'-40.7' 



52.0'-54.7' 
62.3'-63.5' 



68.3'-69.8' 



77.2'-78.0' 



79.6'-80.2' 



chalky grout to 1/8" filling a smooth planar joint 
oriented 60 to the core axis 

grout to 1/8" filling a rough- surfaced, irregular 
fracture oriented roughly 10 to the core axis 
grout to 1/4" filling a rough- surfaced, irregular 
fracture which is Bughly parallel to the core axis 
grout to 1/8" filling a smooth-surfaced, planar 
to arcuate joint roughly parallel to the core axis 
calcite (0,5' thick) over silt (O.l' thick), over 
sand filling a rough fracture roughly parallel to 
the core, sand terminates on a smooth, planar joint 
surface oriented 35 to the core axis; sand grain- 
size increases downward 

grout to 1" filling a rough- surfaced fracture oriented 
about 30 to the core axis, bottom portion of fracture 
filled with layered medium sand 

intersection of a smooth planar joint and a rough- 
surfaced planar fracture, both calcite coated and 
oriented 30 to that core axis 



APPENDIX P-2 



HOLE DESIGNATION: 
BEARING: — 
ANGLE: Vertical 
DEPTH: 94.7 ft. 



DH-602 



LOCATION: 



ELEVATION 

Started: 

Finished: 



Right spillway bay 
at STA 10+63.4 2 ft. 
dovimstream of up- 
stream grout curtain 

; 5299 

9/4/76 

9/8/76 



LOG: 

0-4.7 ft. Concrete spillway apron (good bond with rock) 

4.7-bottoin WELDED ASH-FLOW TUPF 

4.7-17.2 light gray, slightly porphyritic with phenocrysts to 1/16" in 

diameter; light weight rock with scattered pumice fragments 
17.2-30.0 pinkish-gray, with prominent light-colored bands oriented 

roughly perpendicular to the core axis 
30.0-94.7 medium to dark gray, slightly porphyritic 

Core breaks : 

4.7'-17.2' typical core fragment is about 0.8' long, range 0.3'-1.3', 

most breaks are planar and are roughly perpendicular to the 

core axis 
17.2'-30.0' typical core fragment is about 0.3' long, range from less than 

0.1' to 0.8', most breaks are smooth- surfaced, planar, and 

roughly perpendicular to the core axis 
30.0 '-94.7' typical core fragment is about 1.8' long, range from less than 

0.1' to more than 5.0' 

Prominent Features 

4.7'-7.8' grout to 1/8" filling a calcite-lined arcuate joint 

parallel to the core axis 
7. 8' -8.1' pumice fragment 
11.1 '-11. 6' pumice fragment 
13.0'-14.2' minor grout in a rough- surfaced arcuate joint 

roughly parallel to the core axis 
43.0'-43.5' vesicular zone, vesicles flattened approximately 

80 to the core axis 
49.1 '-49. 5' vesicular zone, vesicles flattened approximately 

80 to the core axis 
70.6 '-73. 9' rough- surfaced, irregular fracture with vapor phase 

coatings; core broken from 71.0 '-72. 3' 
74.3'-76.1' rough- surfaced, irregular fracture with vapor phase 

coatings; core broken from 74.4 '-76.8' 
77.4 '-78. 1' grout to 1/8" thick partially filling a rough- surfaced 

irregular fracture oriented 10 to core axis 
88.3'-89.7' rough- surfaced, irregular fracture approximately 

parallel to the core axis, core broken 89. 5 '-89.7' 



APPENDIX P-3 



HOLE DESIGNATION: 

BEARING 

ANGLE: 

DEPTH: 108.7 ft. 



DH-603 



S74E 
30° to left 



from vertical 



LOCATION: 



ELEVATION 

Started: 

Finished: 



Right bay of spillway, 
STA 10+66.4 2 ft. 
downstream of up- 
stream grout curtain 
; 5299 

9/11/76 

9/15/76 



LOG: 

0-5.1 ft. Concrete spillway apron (good bond with rock) 

5.1-bottom Y/ELDED ASH-FLOW TUFF 

5.1-22.2 light gray, slightly prophyritic with phenocrysts up to 1/16" in 

diameter; scattered pumice fragments up to 3" in diameter; low 

density rock 
22.2-38.0 prominent "bands" of collapsed pumice fragments and aligned 

vesicles oriented 60° to the core axis; red-gray color 
38.0-108.7 medium gray, porphyritic 



Core breaks: 



5.1'-22.2' 
22.2'-38.0' 



typical core fragment about 1.0' long, range 0.7'-2.0', most 
joints are smooth, planar and oriented 60 to the core axis 

typical core fragment is 0.5' long, range 0.2' -1.0' most joints 
are rough- surfaced and parallel to the "bands" which are angled 
60 to the core axis 
38.0'-108.7' typical core fragment is 1.0' long, range 0.4' to more than 

3.0', breaks are smooth, planar joints roughly 60 to core axis 



Prominent Features 



10.7' 
11.2'-11.3' 

15.0'-15.8' 

40.3'-40.5' 
53.1'-53.3' 
55.5'-56.6' 

57.0' 

63.8'-64.7' 

65.8'-69.3' 

84.9'-85.4' 
88.4'-88.8' 
91.0'-91.4' 
97.7'-98.5' 



piimice fragment approximately 3" in diameter 

grout to 1/4" filling a smooth planar joint oriented 

at 60 to the core axis ^ 

rough- surfaced arcuate core bresQc roughly 10 to 

the core axis 

pumice fragment with vapor phase minerals 

vesicular zone with voids up to 3/4" in diameter 

large void approximately 1/2" in diameter, lined 

with quartz crystals 

grout to 1/4" filling smooth joint, calcite lined, 

40 to core 

grout to 1/16" present in layers angled 10 to the 

core axis 

grout to 3/4" filling planar joint oriented roughly 

parallel to the core axis 

vesicular zone, voids to 3/4" 

grout to 3/4" partially filling voids 

grout and silt at intersection of 2 joints 

layers of aligned vesicles oriented from 10 to 

roughly parallel to the core axis 



APPENDIX P-4 



HOLE DESIGNATION: DH-604 
BEARING: N74°W 

ANGLE: 30° to right from vertical 
DEPTH: 109.7 ft. 



LOCATION: Center bay of spill- 
way at STA 10+86 2 ft. 
downstream of up- 
stream grout curtain 

ELEVATION: 5299 

Started 9/18/76 

Finished 9/21/76 



LOG: 

0-6 ft. Concrete spillway apron (smooth contact with rock) without apparent 

adhesion, some suggestion of chalky cement 
6-bottora WELDED ASH-FLOW TITPF 
5.9-21.9 light gray, slightly porphyritic with phenocrysts up to 1/16" in 

diameter, 2 large pumice fragments, light weight 
21.9-29.0 prominent "bands" of collapsed pumice fragments oriented 50 to 

the core axis, core breaks frequently parallel to "bands", red to 

purple gray color 
29.0-48.0 fev/ light-colored "banded" zones, breaks not necessarily through 

"bands", less intense reddish color 
48.0-109.7 light to medium gray, porphyritic, prominently vesicular below 

104.5' 



Core breaks : 

5.9'-21.9' typical core fragment is about 0.8' long, range 0.2'-1.8', most 

core breaks are smooth, planar joints oriented 50 to the core axis 
21.9'-29.0' typical core fragment is 0.4' long, range 0,l'-0.7', m.ost breaks 

are through, or parallel to light-colored "bands" at 60 to core axis 
29.0 '-48. 0' typical core fragment is 0.4' long, range 0.1'-1.8', most breaks 

are smooth- surfaced planar joints oriented 60 to the core axis 
48.0'-109.7' typical core fragment is approximately 2.0' long, range 0.4 '-4. 0', 

most breaks are smooth-surfaced planar joints oriented about 60 

to the core axis 



Prominent Features 



14.2' 

15.4'-16.4' 
15.7'-17.1' 
42.5'-44.0' 

61.7'-62.2' 

62.3'-62.5' 
81.5'-83.0' 
95.5' 

95.8'-95.4' 

108.1'-109.0' 



pumice fragment to 1-1/4" 

calcite coated planar joint --it 10 to core axis 

pumice zone 

rough- surfaced, arcuate fracture with silt coatings, 

oriented approximately 10 to the core axis 

calcite filled (to 1/16" thick) planar joint at 20 

to the core axis 

vesicular zone 

grout to 1" filling a rough- surfaced fracture or void 

grout to 1/4" filling a planar joint or fracture 

perpendicular to the core axis 

grout to 1/8" filling a smooth planar joint oriented 

at 10 to the core axis 

grout to 3/8" filling a planar joint oriented at 15 
to the core axis, the joint surface has irregularities 
or offsets parallel to flattened vesicle layers which 
are roughly perpendicular to the core axis 



APPENDIX P-5 



HOLE DESIGNATION: 

BEARING: 

ANGLE: Vertical 
DEPTH: 96 ft. 



DH-605 



LOCATION; 



ELEVATION 

Started: 

Finished: 



Center bay of spill- 
way, STA 10+89 2 ft. 
downstream of up- 
stream grout curtain 
; 5229 

9/16/76 

9/18/76 



LOG: 

0-5.8 ft. Concrete spillway apron (core break at contact, but bond appears 

to have been satisfactory) 
5.8-bottora WELDED ASH-PLOW TUPF 
5.8-21.5 light gray, slightly prophyritic (phenocrysts to 1/16" in diameter), 

rare pumice fragments mostly less than 3/4" in diameter; very 

light weight rock 

light reddish gray, bands of aligned vesicles and collapsed pumice 



21.5-25.3 



25.3-40.5 



40.5-96.0 



fragments, many core bresiks through "bands", breaks "bands" 

oriented roughly 80 to core axis 

medium gray with few "bands" of collapsed pumice oriented roughly 

80 to core axis, some light-colored "bands" of probable vapor phase 

minerals are aligned roughly parallel to the core axis 

light gray, slightly porphyritic, amygdules and phenocrysts to 1/8" 

in diameter 



Core breaks : 
5.8'-21.5' 

21.5'-25.3' 

25.3'-40.5' 
40.5'-96.0' 



typical core fragment is about 1.0' long, range 0.4 '-2. 2', most 

breaks are wavy or planar smooth- surfaced joints 

typical core fragment is 0.4' long, range 0.1'-0.5'; most breaks 

are rough- surfaced and parallel the "banding" at 80 to the core 

axis 

tjrpical core fragment is 0.6' long, range 0.1'-2.0'; most breaks 

are smooth- surfaced 

typical core fragment is about 1.7' long, range 0.4'-more than 3.0'; 

most breaks are smooth- surfaced planar joints oriented 70 -80 

to the core axis 



Prominent Features 



7.8'-8.4' 
14.6'-14.9' 

15.2'-15.5' 

16.4'-16.5' 

17.2' 

26.3'-27.1' 
29.7'-30.1' 

41.1'-41.5' 

42.4'-44.0' 

92.1'-92.4' 



arcuate joint oriented approximately 10 to the core axis 
grout to 1/4" thick filling a planar, silt lined joint 

oriented 15 to the core axis 
g""out and chalky grout to 1/8" filling an arcuate joint 

roughly parallel to the core axis 
flattened pumice fragment, an apparent orientation of 

60 to core axis 

chalky grout to 1/4" in smooth- surfaced joint, angled 

40 to the core axis 
wavy, arcuate joint roughly parallel to the core axis 
grout and calcite in rough- surfaced, irregular 

fracture angled about 20 to core axis 
aligned vesicle layers oriented about 70 -80 to core 

axis 



to core axis. 



arcuate joint oriented approximately 10° 
partially filled with calcite to 1/16" 

grout to 1/8" thick in smooth planar joint at 25 to 
core axis 



APPENDIX P-6 



HOIE DESIGNATION: DH-606 
BEARING: S74°E 

ANGLE: 30° to left from vertical 
DEPTH: 40.6 ft. 



LOCATION: Center bay of spill- 
way STA 10+92 2 ft. 
downstream of up- 
stream grout curtain 

ELEVATION: 5299 

Started: 9/21/76 

Finished: 9/22/76 



LOG: 

0-7.1 ft. Concrete spillway apron (poor bond with rock) 

7.1-bottom WELDED ASH-FLOW TUPF 

7.1-24.0 light gray, slightly porphyritic with phenocrysts to 1/16", 

scattered pumice fragments to 1-1/2" in diameter 
24.0-40.6 prominent "banding" caused by collapsed pumice fragments and layers 

of aligned vesicles, few bands below 37.7' 

Core breeJcs : 

7.1'-24.0' typical core fragment is 1.2' long, range 0,2'-4.0', most breaks 

are rough- surfaced planar joints which cross the core at an 

approximate angle of 70 
24.0'-40.6' typical core fragment is 0.3' long, range 0.1'-0.8', most core 

breaks are smooth-surfaced planar joints oriented 60 to the 

core axis 



Prominent Features 



11.1 '-11. 9' smooth- surfaced, partially calcite filled (honeycomb 
structure) arcuate joint oriented roughly 10 to core 
axis, chalky grout coating on some calcite 
grout to 1" filling a planar joint oriented 45 to 
the core axis 



18.1' 
18.3'-18.8' 
31.1'-31.4' 
38.9'-39.0' 



silt coating on a rough- surfaced joint oriented 

10 to the core axis 

4 layers of silt and calcite oriented approximately 

55 to the core axis 

scattered grout filling voids in a vesicular zone 

aligned roughly 80 to the core axis 



APPENDIX P-6A 



HOLE DESIGNATION 

BEARING: 

ANGLE: 

DEPTH: 111 ft. 



DH-606A 



S74E 
30° to left 



from vertical 



LOCATION: Center bay of spill- 
way STA 10f92 2.7 ft, 
downstream of up- 
stream grout curtain 

ELEVATION: 5299 

Started: 9/29/76 

Finished: 9/29/76 



LOG: 

0-7.1 ft. Concrete spillway apron (poor bond with rock silt coatings on 

rock surface) 
7.1-bottom WELDED ASH-PLOW TUPP 
7.1-24.1 



24.1-43.0 



light gray, slightly porphyritic with phenocrysts to 1/16", 
scattered pumice fragments to 3", low density rock 

prominent "banding" caused by flattened vesicles and pumice fragments 
oriented 60 to the core axis, medium gray with a pink or red tone 



43.0-111.0 dark gray, slightly porphyritic, several vesicular zones 

Core breaks : 

7.1 '-24. 1' typical core fragment is approximately 1.5' long, range 0.3' to about 

3.0', most joints are smooth-surfaced, planar, darkstained, and 

oriented 60 to the core axis 
24.1 '-43. 0' typical core fragment is approximately 0.4' long, range O.l'-l.O', 

most breaks parallel the "banding" at 60 to the core axis 
4 3.0 '-111. 0' typical core fragment is 0.9' longi range 0.1'-3.0', most breaks 

are smooth planar joints oriented 50 -60 to the core axis 



Prominent Features 



17.1 '-17. 4' pumice fragment 

17.4 '-17. 7' grout to 3/4" thick in an irregular joint angled 

35 to the core axis 
19.8'-20.5' rough- surfaced, irregular fracture oriented roughly 

parallel to the core axis 
30.1 '-30. 4' vesicular zone, layers of aligned vesicles 60 to the 

core axis 
50.1'-50.5' grout to 3/8" in a smooth, planar joint oriented 

roughly 30 to the core axis, joint surfaces are 

calcite lined 
55.8'-58.0' grout partially filling 1/4" wide joint with calcite 

lining roughly parallel to the core axis 
62. 2 '-62.7' vesicular zone 



APPENDIX P-7 



HOLE DESIGNATION: DH-607 LOCATION: Left bay of spillway 

BEARING: N74W at STA. 11+11 2 ft. 

ANGLE: 30 to right from vertical downstream of up- 

DEPTH: 8.4 ft. stream grout curtain 

ELEVATION: 5299 

LOG: 

0-5.7 ft. Concrete spillway apron (good bond with rock) 

5.7-bottom WELDED ASH-FLOW TUFF 

5.7-8.4 light gray, slightly porphyritic with fine-grained matrix 

Core breaks : typical core fragment is 0.2' long, from badly broken zones 
to fragments 0.5' long 

Prominent Features 

4.2' layer of aligned vesicles oriented roughly 20 to the 

core axis 
7.8' intersection of two rough- surfaced planar joints angled 
20 and 60 to the core axis, both with silt coatings 



APPENDIX P-7A 



DH-607A 
M74vV 
30 to right from vertical 



HOLE DESIGNATION 

BEARING 

ANGLE: 

DEPTH: 109.5 ft. 



LOCATION: 



ELEVATION: 



Left bay of spillway, 
STA 11+11.6 2.7 ft. 
downstream of up- 
stream grout curtain 
5299 



Started: 9/29/76 
Finished: 10/2/76 

LOG: 

0-5.7 ft. Concrete spillway apron (good contact with rock) 

5.7-bottom V/ELDBD ASH-FLOW TUFF 

5.7-24.0 light gray, slightly porphyritic with fine-grained matrix, 

phenocrysts to 1/16" in diameter; scattered pumice fragments to 1" 

difcmeter, some fragments slightly flattened perpendicular to the 

core axis 
24.0-28.8 closely spaced light-colored bands angled 80 to the core axis; 

raedi-om to dark gray with purple-pink tones 
28.8-109.5 light to medium gray, porphyritic, amydules to 1/8" in diameter 



Core breaks : 
5.7'-24.0' 



24.0'-28.8' 



28.8'-109.5' 



typical core fragment 0.9' long, range 0.2'-1.8', most breaks 
are smooth, planar, and angled 60 to the core axis 
typical core fragment 0.3' long, range from less than 0.1'-1.2', 
most breaks are parallel to the "banding" 

typical core fragment is 1.5', range 0.2 '-5.7', most breaks 
are smooth, planar joints 



Prominent Features 



5.9'-6.7' rough- surfaced, irregular fracture roughly 10 to 

core axis 
21.9'-22.2' rough, irregular fracture oriented 30 to core axis, 

silt coatings 
24.5' grout and calcite filling a planar joint oriented 

approximately 30 to the core axis 
45.8'-47.3' layers of aligned vesicles with some chalky grout 

fillings 
50,5' grout and chalky grout to 3/8" thick filling a smooth 

planar joint oriented roughly 35 to the core axis 
60,0'-60.6' grout to 3/8" filling a smooth-surfaced arcuate 

joint angled roughly 10 to the core axis 
70.0 '-70. 2' scattered grout in vesicle layers oriented approximately 

70 to the core axis 



APPENDIX P-8 



HOLE DESIGNATION: 

BEARING: 

ANGLE: Vertical 
DEPTH: 125.8 ft. 



DH-608 



LOCATION; 



ELEVATION 

Started: 

Finished: 



Left bay of spillway 

at STA 11+14.6 2 ft. 

dovmstream of upstream 

grout curtain 
: 5299 
9/25/76 
9/28/76 



LOG: 

0-6.1 ft. Concrete spillway apron (poor bond with rock) 

6 . 1-bottom WELDED ASH-PLOW TUFF 

5.8-21.2 light gray, slightly porphyritic with phenocrysts to 1/16" in 

diameter, rare pumice fragments to 3" in diameter 
21.2-33.0 prominent light colored "banding" oriented roughly perpendicular 

to the core axis, pinkish-gray hue 
33.0-104.0 medium gray, slightly porphyritic, amygdules of quartz and feldspar 
104.0-125.8 fairly prominent "banding" caused by layers of aligned vesicles 

and collapsed pumice oriented roughly 80 to the core axis 

Core breaks : 

5.8'-21.2' typical core fragment is 0.8' long, range 0.3'-1.6', most breaks 

are along planar joints having smooth to slightly rough surfaces 
21.2'-33.0' typical core fragment is 0.3' long, range 0.1'-0.5', most breaks 

are along smooth, planar joints oriented roughly perpendicular 

to the core axis 
33.0'-125.8' typical core fragment is about 1.0' long, range 0.1 '-2.5', 

most breaks are along rough- surfaced planar joints 

Prominent Features 



rough- surfaced, irregular fracture roughly parallel 

to the core axis, pumice fragments 1"— 3" in diameter 

at 12.6', 12.9', and 13.6', fracture surface has 

silt coating 

grout coated, rough- surfaced, arcuate joint with iron 

staining oriented roughly 10 to the core axis 

grout to 1/2" thick filling a zone of intersecting 

joints 

grout 1" thick filling a calcite lined joint oriented 

perpendicular to the core axis 

rough- surfaced, irregular fracture roughly parallel 

to the core axis, grout filled to 3/8" 

grout to 1-1/4" filling a planar joint oriented 
at 10 to the core axis 

111.3'-113.1' rough- surfaced, irregular fracture oriented roughly 
parallel to the core axis, grout filled below 112.6* 

123.4 '-123. 8' planar joint oriented 30 to the core axis, grout 
and calcite to 1" thick 



12.1'-14.0' 

63.0'-64.1' 
76.3' -78.0' 
78.6'-78.7' 
83.8'-85.5' 
105.3'-105.8' 



APPENDIX P-9 



HOLE DESIGNATION: DH-609 
BEARING: S74°E 

ANGLE: 30° to left from vertical 
DEPTH: 145 ft. 



LOCATION: 



ELEVATION 

Started: 

Finished: 



Left bay of spillway 

STA 11+17.6 2 ft. 

downstream of upstream 

grout curtain 
: 5299 
10/2/76 
10/6/76 



LOG: 

0-6.2 ft. Concrete spillway apron (good bond with rock) 

6.2-bottom WELDED ASH-FLOW TUFF 

6.2-25.7 light gray, slightly porphyritic, fine-grained matrix with 

phenocrysts up to l/l6" in diameter 
25.7-40.0 dark gray color with reddish/purple hue with prominent light-colored 

"bands" angled 40 to the core axis 
40.0-145.0 medium gray, slightly porphyritic, occasional banding and layers 

of aligned vesicles angled approximately 70 to core axis 



Core breaks ; 
6.2'-25.7' 



25.7'-40.0' 



typical core fragment is 1.7' loi^gj range 0.3'-3.0', most breaks 
are smooth planar joints angled 30 to the core axis 
typical core fragment 0.3' long, range 0.1'-0.8', breaks are 
rough- surfaced and angle 40 -50 to the core axis 
40.0'-145.0' tjrpical core fragment is 0.8' long, range 0.1'-2.5', 2 sets of 
joints, one angled 30 to core axis, the other roughly 70 to 
the core 



Prominent Features 



14.2'-14.4' 

16.0'-16.2' 

41.7'-42.2' 
64.7'-65.3' 

65.3' 



rough- surfaced planar joint filled with silt up to 

1/8" thick, oriented 35 to the core axis 

grout to 1/16" partially filling a silt lined smooth 

joint angled 45 to the core axis 

laj'-ers of aligned vesicles with flattened voids up to 1/2" 

arcuate joint with silt coating oriented roughly 10 

to core axis 

joint open to 3/8" partially filled with calcite, 

angled 40 to core axis 



65.5 '-66.4' broken core from vesicular zone, limonite stain on 
vapor phase minerals, grout filling voids between 
66.2' and 66.4' angled 40 to the core axis 
87.3'-87.5' aligned layers of vesicles angled 50 to the core axis 
102. 3' -104. 3' rough- surfaced irregular fracture roughly parallel 
to the core axis, silt filled 



APPENDIX P-10 



HOLE DESIGNATION: DH-610 
BEARING: Parallels grout cap 
ANGLE: 42° to right from vertical 
DEPTH: 24.8 ft. 



LOCATION: 



ELEVATION: 



ON GROUT CAP AT 
STA 12+73 
5222.1 



LOG: 

0-4.8 ft. 
4.8-24.8 



Concrete grout cap (good bond with rock) 

WELDED ASH-FLOW TUEF 

uniform medixom gray with porphyritic texture, fine-grained 

matrix with phenocrysts to imrn in diameter 



typical joint spacing 0.6', ranging from 0.1' to 1.3'; most 
are smooth- surfaced with a dark stain and are oriented 
approximately 40 to core axis; a few joints are oriented 
at 20 to the core axis 



Prominent Features 



5.6 '-5.5' smooth arcuate joint, approximately 10 to core axis 
13.5 '-14. 8' smooth arcuate joint roughly parallel with core axis 



APPENDIX P-11 



HOLE DESIGNATION: DH-611 
BEARING: Parallels grout cap 
ANGLE: 20^° to right from vertical 
DEPTH: 23.9 ft. 



LOCATION: 



ELEVATION: 



ON GROUT CAP AT 
STA 12+74 
5222 



LOG: 

0-3.9 ft. 
3.9-23.9 



Concrete grout cap (good bond with rock) 

WELDED ASH-FLOW TUFF 

a unifonn medium gray with porphyritic texture, fine-grained 

matrix; lines of vesicles at 30 to core axis are common 

below 22.0' 

typical joint spacing 0.5', ranging from 0.3' to 1.0'; most 
are smooth- surfaced with a dark stain and make an angle of 
approximately 50 with the core axis, some at 20 to the core 
axis 



Prominent Features 



6.3' 



6.8' 



smooth planar joint with calcite coating, angled 40° to 
core axis 



smooth planar joint with calcite filling (to 1/8"), 
angled 40 to core axis 
8.7 '-9. 3' roiogh- surfaced core break at approximately 10° to 
the core axis, silt coatings on the fracture surface 



APPENDIX F-12 



HOLE DESIGNATION: DH-612 
BEARING: Parallels grout cap 
ANGLE: Vertical 
DEPTH: 23.5 ft. 



LOCATION: 



ELEVATION: 



ON GROUT CAP AT 
STA 12+75 
5222 



LOG: 

0-3.5 ft. 
3.5-23.5 



Concrete grout cap (good bond with rock) 

WELDED ASH-FLOW TUPF 

a uniform medium gray with porphvritic texture, fine-grained 

matrix; lines of vesicles at 10 to core axis are common 

between 15.0'-17.3' 

typical joint spacing 0.4', ranging from 0.05'-l.l'; most 
are smooth-surfaced with a dark stain and make an angle of 
approximately 70 with the core axis, some at 40 to core axis 



Prominent Featur es 
22.9' 



minor grout coatings on smooth planar joint angled 
at 45 to core axis 



APPENDIX F-13 



HOLE DESIGNATION: DH-613 
BEARING: Parallels grout cap 
ANGLE: 45 to right from vertical 



LOCATION: 



ELEVATION: 



ON GROUT CAP AT 
STA 13+15 
5206 



DEPTH: 



24.8 ft. 



LOG: 
0-4.8 ft. 

4.8-24.8 



Concrete grout cap (good bond but rock is badly broken 0.15 ft. 

below contact) 

WELDED ASH-FLOW TUFF 

medium gray, porphyritic texture, coarse-grained; amygdales 

common (to 3/8") 



core is marked by smooth-surfaced arcuate joints nearly parallel 
to the core axis in the upper part, making fracture density 
meaningless; there are no natural breaks below 19.5' 



Prominent Features 



6. 3 '-7. 9' aligned vesicles with vapor phase minerals 

13. 5 '-14. 0' smooth arcuate joint partially filled with calcite, 

joint originally open to 1/4"; angled 10 to core axis; 

truncated by joint at 14.0' 
14.0' smooth planar joint at 50 to core axis, calcite coated 
18.1'-20.0' aligned vesicle layer and arcuate joint rovighly parallel 

to core axis, partial calcite filling of vesicle layer 



APPENDIX F-14 



HOLE DESIGNATION: DH-614 
BEARING: Parallels grout cap 
ANGLE: 22g° to right from vertical 
DEPTH: 24.4 ft. 



LOCATION: ON GROUT CAP AT 

STA 13+15 
ELEVATION: 5206 



LOG: 

0-4.4 ft. Concrete grout cap (good bond with rock) 

4.4-24.4 WELDED ASH-PLOW TUPF 

light to medium gray, porphyritic; amygdales filled with vapor 

phase minerals (to 3/8") up to 10^ of rock 

typical joint spacing greater than 1.0', ranging from 0.4 '-2. 0' 
except for intensely jointed zones 5.6'-6.3' and 11.8'-13.0' 

Prominent Features 

4.6 '-5.6' smooth planar joint and aligned vesicle layer, both 

roughly parallel to core axis 
12.0 '-12. 4' chalky grout in planar joint at 25 to core axis 
18.5' void space in aligned vesicle layer 
21.8' core break through limonite stained "band" at 25 

to core axis 
23.6 '-24.4' aligned vesicles with vapor phase minerals at 10 

to core axis 



APPENDIX F-15 



HOLE DESIGNATION: DH-615 
BEARING: Parallels grout cap 
ANGLE: Vertical 
DEPTH: 24.9 ft. 



LOCATION: ON GROUT CAP AT 

STA 13+15 
ELEVATION: 5206 



LOG: 

0-4.9 ft. 
4.9-24.9 



Concrete grout cap (good bond with rock) 

WELDED ASH-FLOW TUFF 

mediiim gray, slightly porphyritic, coarse-grained; vesicles 

and aligned vesicles are common 

typical joint spacing above 13.0' is 0.6', ranging from 0.1'- 
2.4', below 13.0', typical spacing is greater than 2.0', ranging 
from 1.5 '-more than 4.0' 



Prominent Features 
5.0'-6.0' 
9.2'-11.0' 



11.1' 



rc-igh fracture at approximately 10 to core axis 

aligned vesicles and bands of light colored minerals 
at 10 to core axis 

grout coating on smooth planar joint roughly 30 to 
core axis 



APPENDIX P-15 (Con't.) 



Prominent Features (Con't«) 



12.2'-12.6' rough fracture with probable vapor phase minerals 
roughly 15 to core axis 



15. 2 '-15. 7' rough fracture with dark staining oriented 15 -20 

to core axis 
22. 2 '-23. 5' rough fracture with dark stain, 30 to core axis 



APPENDIX P-16 



HOLE DESIGNATION: DH-616 LOCATION: ON GROUT CAP AT 
BEARING: Parallels grout cap STA 13+29 

ANGLE: 47-g-° to right from vertical ELEVATION: 5197 
DEPTH: 24.3 ft. 

LOG: 

0-4.3 ft. Concrete grout cap (good bond, but rock badly broken) 

4.3-24.3 WELDED ASH-FLOW TUFF 

mediian gray with porphyritic texture, some "banding" in lower 

portion 

very few joints, a typical spacing would be greater thaji 2.0', 
some unbroken core longer than 5.0' 

Prominerit Features 

4.7'-6.1' smooth arcuate joint with calcite coating nearly 

parallel to core axis, paralleled by rough fracture 

4.7'-5.5' 
5.9' calcite coating on smooth planar joint, 30 to core 

axis 
6.3' calcite coating on smooth planar joint, 30 to core 

axis 
13.4 '-13. 8' aligned vesicles with significant void space, dark 

stain 
15.1' core break nearly perpendicular to core axis through 

layer of limonite stained probable vapor phase minerals 
17.5' grout filled, smooth, planar joint roughly 20 to core 

axis 
20.2' grout filled, smooth, planar joint roughly 20 to core 

axis 



APPENDIX P-17 



HOLE DESIGNATION: DH-617 
BEARING: Parallels grout cap 
ANGLE: 21° to right from vertical 
DEPTH: 23.9 ft. 



LOCATION: 



ELEVATION: 



0.9 ft. upstream 
grout cap center- 
line at STA 13+30 
5197 



LOG: 

0-3.9 ft. 
3.9-23.9 



Concrete grout cap (good bond with rock) 

WELDED ASH-FLOW TUEF 

medium gray with porphyritic texture; some vesicle alignment 

below 11.5' at an angle of 60 to core axis 



typical joint spacing 1.5', ranging from 0.2'-more than 6.0'; 
most are smooth- surfaced, dark stained, and make an angle of 
approximately 40 with the core axis 



Prominent Features 



4.0 '-4. 7' smooth arcuate joint and rough fracture, both 

nearly parallel to core axis 
4.7 '-6.7' smooth arcuate joint roughly parallel to core axis 
8.0'-10.0' smooth arcuate joint roughly parallel to core axis, 

partially filled with grout 



APPEITOIX F-18 



HOLE DESIGNATION: DH-618 
BEARING: Parallels grout cap 
ANGLE: Vertical 
DEPTH: 24.2 ft. 



LOCATION: 



ELEVATION: 



ON GROUT CAP AT 
STA 13+30 
5197 



LOG: 

0-4.2 ft. 
4.2-24.2 



Concrete grout cap (good bond with rock) 

WELDED ASH-FLOW TUFF 

medium to dark gray, porphyritic; aligned vesicles below 14.0', 

light colored "bands" of collapsed piomice and vapor phase 

minerals present, but not obvious (oriented roughly perpendicular 

to core axis) 



typical core fragment is 1.3' long, range 0.1'-1.9', most breaks 
are through "bands", smooth- surfaced joints are not common 



Prominent Features 



4. 9 '-5. 9' smooth, dark stained joint at 15 to core axis 
15. 8 '-16. 8' rough- surfaced fracture with dark surface stain at 
10 to core axis 



APPENDIX P-18 (Con't.) 



Prominent Features (Con't. ) 



16.9'-17.4' 

21.6'-22.3' 
22.8' 



rough- surfaced fracture with dark surface stain 

at 10 -20 to core axis 

smooth, planar joint at 10 to core axis 

smooth planar joint roughly perpendicular to core 

axis, partially filled with calcite 



APPENDIX P-19 



HOLE DESIGNATION: 

BEARING: 

ANGLE: 

DEPTH: 26.7 ft. 



DH-619 
Parallels grout cap 
31 to left froni vertical 



LOCATION: 



ELEVATION: 



ON GROUT CAP AT 
STA 13+31 
5197 



LOG: 
0-6.7 ft. 

6.7-26.7 



Concrete grout cap (concrete appears to lie on a smooth joint 
surface oriented 60 to the core axis, no apparent adhesion) 
WELDED ASH-PLOW TUPF 

medium to dark gray porphyritic rock with crystalline matrix; 
aligned vesicles below 15.0', average spacing of 0.5' 



typical joint spacing 1.2', ranging from 0.3'-2.6'; 
smooth- surfaced, planar with a dark stain 



most are 



Prominent Features 

10.1'-10.6' 
11.6'-12.2' 



18.9'-19.3' 



21.9' 



25.1' 



smooth arcuate joint, roughly 25 with core axis 

smooth arcuate joint with chalky grout coating, 

roughly 25 to core axis 

smooth planar joint making 40 angle with core 

axis is calcite lined and filled with 3/4" of 

calcareous silt 

rough- surfaced fracture with calcite lining filled 

with calcareous silt (to 3/8") 

joint up to 1/2" wide filled with grout and silt 



APPENDIX F-20 



DH-620 
Parallels grout cap 
44 to right from vertical 



HOLE DESIGNATION 

BEARING 

ANGLE: 

DEPTH: 100 ft. 



LOCATION: 



ELEVATION: 



1.4 ft. downstream 
of grout cap center- 
line at STA 13+46 
5189 



LOG: 

0-4.4 ft. Concrete grout cap (good bond, but rock is badly broken along 

rough, dark-stained fractures 
4.4 to 100 WELDED ASH-PLOW TUFF 

dark gray, porphyritic, general increase in the number of "bands" 

of collapsed pumice and vapor phase minerals with depth, "bands" 

are prominent below 50.0' 

typical core fragment is 0.9' long, breaks occur primarily at 
dark stained, planar joints above 45.0', along or through "bands" 
below 45.0' 



Prominent Features 



7.2' rough- surfaced fracture at 30 to core axis, silt filled 

to 3/8" 
7.7' smooth, planar joint at 30 to core axis, silt filled to 

3/8" 
7.6 '-8. 0' smooth planar joint at 30 to core axis 
20.7' rough- surfaced fracture at 50 to core axis, calcite 

filled (to 3/4") 
24.8' smooth planar joint at 45 to core aais 
25.0'-25.3' planar joint at 30 to core axis, partially filled 

with grout 
25.5 '-26,1' smooth arcuate joint with dark surface stain oriented 

15 to core axis 
26.1' smooth planar joint at 45 to core axis, partially filled 

with calcite 
41.1 '-41. 6' smooth planar joint at 30 to core axis, grout lined 

and filled with silt (to 3/8") 
41.8 '-42