The URL can be used to link to this page

Home My WebLink AboutAPA2350[}{)&L§J~£!\c§~&®©@ Susitna Joint Venture Document Number Please Return To DOCUMENT CONTROL ·TI ' , .~~· z-_,. '·-·---~--.. -··-· '-----·-------__ .:,_ . ' _, -~.-··"~-~·---··--·· -~--·-·- ALASKA POWER AUTHORITY SUSITNA HYDROELECTRIC PROJECT INFORMATION PACKAGE FoR FIRST SPECIALIST CONSULTANTS PANEL f1EETING OCTOBER, 1980 ALASKA POWER AUTHORITY LIBRARY COPY PLEASE DO NOT ~.EMOVE FROM OFFICE! 1 ' \ t•< 1 4 Acres American Incorporated 900 Liberty Bank Building Mai·n at Court Buffalo, New York 14202 Telephone (716) 853-7525 -1 l , I .. : ....... ~ .. ' ('· ALASKA POY./ER AUTHORITY SUSITNA HYDROELECTRIC PROJECT INFORMATION PACKAGE FoR FIRST SPECIALIST CoNSULiANTS PANEL MEETING OCTOBER, 1980 /, l ... '' I ... ' ,;:r.:;:~ --:."' TABLE OF CONTENTS .. 1 -EXCERPTS FROM ACRES PLAN OF STUDY (PROPOSAL) 1.1 Executive Summary. 1.2 Slope Stability Studies, Task 2 1.3 Seismic Studies, Task 4 1.4 Geotechnical Exploration, Task 5 1.5 Design Development, Task 6 2 -PROJECT MAPS, EXPLORATION . . 2.1 Summer, 1980 -t~atana Exploration & Proposed \1atana Exploration~ Winter, '1980 . · 2.2 Summer, 1980 -Devil Canyon Exploration & Proposed Devil Canyon Expl oratio1.n·, \-linter, 1980 2.3 -Devil Canyon Arch Dam 3 -NOTES OF FIRS:r IN-HOUSE REVIEltJ PANEL ~1EETING 4 -REPORTS BY OTHERS 4.1 Founda·tians and r~ateria1s, Section D, 1979 Corps of Engineers Report 4.2 Excerpt from "Reconnaissance of the Recent Geology of the Proposed Devil Canyon and Watana Dam Sites, Susitna fdver, Alaska" by Kachadoorian and Hoare (1979 COE Report) 4.3 Excerpt from 11 Earthquake Assessment at the Susitna Project 11 · by Krinitzsky (1979 COE Report) 4.4 Selected Sections from Devil Canyon Engineering Geology Report :.~ 1 I l~_,,:,..,,_ ... ,......._ ·--.· ·-r="' ., ["··-·'"''"·' [. ·. r ~~-·~!l·---~~-.. -·~-. .. r~--·-1---..,. f'•''-·-, r-·"-'"'\ ,~. ··~·1-:::-ir-~----.. -.~. (''"-'!\ ,~···-., r-~ .. , r--·]_ t.. ' . J.' < L -:---"1 _r--t ····I~ _J-1 ~~ I''~~.~ .-. . .. __ __ .. _ . ..J ........ .' •. .... •. . .1 . ..~ • _ .. J "'·· • . l. __ ... ...-.._ .... ~. ....... _.,-~ ""'"·-. r ~-. :_... ·-· . . .. J.. ~----· ·~. J ·i~ I N ) ./'" .,_ -\ r I ,... ~ IQ \. ~t i I MID] I ..... )' v l1 ,......, ... . I ,.. ,.. • -~ t t.lilU : ) 0 l ) '~ 0~ ' ~~' 0 \ ,. & ~ ~ ~v ~94211 !A1 · ~ \ \ --' ,f~ ....-J / ~ '1 I O....J .... , { ,.. __ '"'t SIISITNC l.4XC \ ~'> / PftOPOS£0 OAMSIT(S • EXISTING STAiiOUS f1 US G $ GAGING SU'r•Ok (4) 1Hcw tounst PIWPOS£0 SUltOtlS Q S tfOW COUUH 0 STill AUfl01t GA.GittC. v Ja'AT(fl lh(l }-( SlOI._.fiH DISC.CUIG( () 'ft.lf(A QUALITY :~·SITNA HYDROELECTRIC P.ROJECT PLATE TJ.l• PROPOSED DATA COLLECTION Sl'ATION S . IH THE SUSITNA BASIN-1900 M • a • .. ....... 4 a II • t $ i ; i A'GI W•4J :; 1 w I:" • ' •• -... .. ............. '. . ..• 0-l'!'tl~-1£ f r - f' I' r f J 1 -EXCERPTS FROM ACRES PLAN OF STUDY (PROPOSAL) f l I I l l ! ! ' 1 j f_-_· 'f ~~ .J, · .. -~·' Open Letter to the Public Acknowledgement TABLE OF CONTENTS TABLE OF CONTENTS . -----------------------------------------------------1 LIST OF TABLES -------------------------------------------------------ii LIST OF PLATES --------------------------------------------------------iii Page ~ -PROGRAM OBJECTIVES ---------------------------------------------1-1 A2 -STUDY APPROACH -------------------------------------------------2-1 A3 -BUDGET-SUMMARY-------------------------------------------------3-1 A4 -RESPONSE TO PUBLIC COMMENT -----· ... -----------------··-------------4-1 AS -DETAILED ACTIVITY DESCRIPTIONS ---------------------------------5-l A5.1 _ -Introduction -------------------------------------------5-1 A5.2 -Task 1: Power Studies ---------------------------------5-2 A5.3 -Task 2: Surveys & Site Facilities ---------------------5-25 AS. 4 -Task 3: Hydro 1 ogy --------...:-·-------------------...:-------5-50 A5.5 -Task 4: Seismic Studies -------------------------------5-79 A5.6 -Task 5: Geotechnical Exploration ----------------------5-105 A5.7 -Task 6: Design Development ----------------------------5-129 A5~B -Task 7: Environmental Studies ---------~---------------5-193 A5.9 -Task 8: Transmission ----------------------------------5-289 A5.10 -Task 9: Construction Cost Estimates and Schedules -----5-303 A5.11 -Task 10: Licensing --------------------------------~----5-313 A5.12 -Task 11: Marketing and Financing -----------------------5-333 A5.13 -Task 12: Public Participation Program------------------5-363 A5.14 -Task 13: Administration --------------------------------5-379 A6 -POST LICENSE APPLICATION SUBMISSION ACTIVITIES -----------------6~1 A7 -PROJECT SCHEDULES -----------------------~----------------------7-1 AB -LOGISTICAL PLAN ------------------------------------------------8-1 i I -i-J': i .. . . ,-"'"111r--~--. .. ·~--::'"---~------..,-···--·~·---····~---.w·· .. ---~-·-·-·-··---~-···-·--·---... ~--·---·--·-·-····---·· . -. '1-····--~----··--~--·-----···---··-·r--··-·--·---·-----·---~---···-~------.. ---------:-:-~-;;. --~:.:)t'",_ ~ II • J ··-·-.. JIIt'111 ___ 111MllliJilltbe ·a .. i\ • :ll ~· ~· ~:1 EXECUTIVE SUMMARY 1 -INTRODUCTION This Plan of Study (POS) has been prepared by Acres American I ncorpor·ated in res~onse to the request of the Alaska Power Authority to provide a program leading to a license application to the Federal Energy Regulatory Commission for construction of the Susitna Hydroelectric Project. Major contribucors to the plan and proposed participants in its implementation include R & N Consultants Incorporated (R & M), Terrestrial Environmental Specialists Incorporated· (TES), Frank r1oo1 in Associates (FMA.), tioodward-Clyde Consultants (WCC), Sa 1 oman Brothers, and Cock Inlet: Region Incorporated/ Holmes and Narver (CIRI/H & N). The complete plan is made up of three ma~jor parts in addition to this executive summaryG Part A sets forth the study p1an itself and includes the establishment of program objectives, an overview of the study approach~ a budget surmnary, a logistical plan, detailed activity descriptions, a proposed p·raject schedule, and a summary assessment of work which must be cent i nued beyond the point of 1 i cense app 1 i cation. P a.rt 8 is devoted to implementation of the plan. Key personnel assignments, an organizational structure, and coordination procedures are contained therein. Supplemental i.nformation in Part C provides supporting materials such as evidence of the qual ifi cations of proposed corporate team members, deta i 1 ed resumes for key project personne1, and similar items. 2 -BACKGROUND A series of-studies conducted initia11y by the Bureau of Reclamation and subsequently by the Corps of Engineers led to the recommendation that a two dam system should be constructed on the Susitna River. The upper-dam at Watana would be an 810-foot-high earthfill structure and the lower a 635-foot-high concrete thin arch dam at Devil Canyon. Transmission lines would extend north and south to Fairbanks and Anchorage respectively, for a total of 365 miles. The total project was selected by· the Corps as the best of several alternati·ves to contribute to satisfaction of a projected energy demand of 15 billion kilowatt hours by the year 2000. The Corps• recommendation resulted in Congressional authorization to proceed with detailed feasibility studies in a cooperative effort \vith the State of Alaska under ~~ovisions of Section 203(e) of the Water Resources Development Act of 1976. Should feasibility be demonstrated, study costs· would be reimbursed by the State.. Amendments are currently being sought to faci 1 i- tate the funding process and expedite study initiation • • It is the intent of the State of Alaska, through the Alaska Power Authority, to undertake tile detailed studies required before a definite construction decision can be m~der An alternative to consummating the cooperative agreement with the Corps of Engineers is to fi'nance the study entirely \·lith State resources, contracting with a private engineering firm to do those - 2 studies necessary to prepare and fi 1 e a 1 i cense app 1 i cation. Acres Amer·i can Incorporated was selected as one of three private engineering firms to prepare plans of study. 3 -PROJECT OBJECTIVES The primary objectives of the proposed study are threefo 1 d: (1) Estab 1 ish technical, economic and financial feasibility; (2) Evaluate the env~ronmental consequences of designing and constructing the Susitna Project; and (3J File a complete license application with the FERC. Included within these overall objectives are certain specific items which must be satisfied. This latter group includes assessment of alternat·fves~ preparation of an optimal development plan, cost estimates, risk analysis, environmental and social factor evaluations, annual system power cost estimates, preparation of the application itself, a public participation program, preparation of a plan for financing, minimization of study costs consistent with the satisfaction of other objectives, and maximization of employment opportunities in Alaska---including affirmative actions for native hire. 4 -PROPOSED APPROACH Acres proposes to accomplish the essential objectives of the POS within a period of two and one half years. January 1, 1980 is the projected start date. In order to satisfy all of the objectives Nithin this time frame, Acres has assemb 1 ed a team \vh i ch brings to the Susitna project a unique combinatioo of capability and expertise, largely A1aska based. The group provides: (i) A powerful design/project/construction manag€ment team experienced in studies, economic evaluation, risk analysis, alternatives assessments, licensing, design, financing and construction of large hydroelectric projects. (ii) Strong northern and subarctic experience. (iii) A skilled and readily available field exploration team ~'/i.th facilities, personnel and equipment experienced tn all aspects of hydrologic and geotechnical design and exploration, particularly in the vicinity of the Susitna site. (iv) An exceptional team of environmental specialists with first-hand knowledge and experience of the project area and ready to work closely with state environmental agencies in effectively meeting the requirements of the plan of study. (v) A capabil·ity for detailed seismic studies by renowned experts as Ne11 as a comprehensive external review. (vi) A 1 ogi st i c support capabi 1 i ty wh f ch draws heavi 1y upon the ski 11 s of Alaskan Natives whose land selections are in the project area. fiji, ~----------·--------------------------------------------~--·----------~ ;;u;:' -•• , . . .. ...---~<.· I - 3 (vii) financial advice from an investment banking firm skilled in handling tax-exempt bond issues. The combined knowledge 3 experience, and equipment of the Acres team will be brought to bear upon the project objectives through the accomplishment of thirteen specific tasks, each one of which is subdivided into a number of subtasks. In e·very case, task and s ubtask objectives are exp 1 ici t1 y defined, as are proposed approaches, levels of effort, and schedules. The thirteen major tasks are: Task 1 -Power Stud1es Task 2 -Surveys and Site Facilities Task 3 -Hydrology Task 4 -Seismic Studies Task 5 -Geotechnical Exploration Task 6 -Design Development Task 7 -Environmental Studies Task 8 -Transmission Task 9 -Cost Estimates and Schedules Task 10 -Licensing Task 11 -Marketing and Finance Task 12-Public Participation Task 13 -Administration Summary descriptions of the work to be undertaken in each of these Ta s~s a-re presented in Section 8 of this Executive Summary. 5 -COSTS ANO SCHEDULES The Budget Summary is shown in Table A.3.1. The entire POS caT1s for the expenditur.~ of $19.7 million in 1979 dollars over a period of two and one half years from study initiation to filing the license application for thr.se minimum efforts necessary to establish feasibility from a technica1~ economic, and environmental standpoint. An additional amount of $3.4 million is required to conduct effective pub1ic participation, financing and local project management programs and to satisfy certain non-discretionary funding requirements& Subsequent costs during the estimated 30-month period through award of the FERC 1icense are estimated as$ 26.2 million, including provision of an estimated $8 million for the construction of a pioneer access road. The proposed project sc.hedule is shown in Plate A2.1. Initial site facilities wi11 be operationa1 by r·1arch 1980 to support fie1d investigations which wil1 commence at that time. By the end of the first year of study~ sufficient data.wi11 have been accumulated to make definitive recommendation~ as to continuation of the stuqy program. The second year wi11 involve continuation of fieid 1nvesti gat ion efforts and deve·1opment of conceptual designs along with initial mitigating·measures. Field investigatiQns continue in the third year and beyond, but sufficient information will have been accrued to permit the preparation of drafts for all required licensing exhibits by the end of the 29th month. Review will have been conducted throughout, both internally by panels of in-house experts and externally by independent review boards recommended to and selected by APA. Fina1ization !Am~ L ----------------------------------~--------------------------------~ ""' f - 4 of the license application including all exhibits will occur in the 30th month and a final review will be conducted at that time. 6 -ANTICIPATED DIFFICULTIES Throughout the development of the POS, a number of potential problems have been identified and the difficulties associated with managing their reso)ution have been noted. Certain areas in particular have been Tong staDding concerns of many interested parties in Alaska: (1) The matter of generating a concept for optimal development calls for careful study of projected demand and alternative means of satfsfyi ng it. Without such a foundation., it is simply hnpassible to assure the Power Authority that the proper project wi 11 h~ plan ned in the right place and constructed in time to meet the energy needs of the Rail belt. ( 2) Data acquisition ~~; 11 present di ffi cu 1 ties, for seasona 1 and weather constraints as well as certain land use restrictions will lead to peak loading of site support facilities and the necessity for use of special equipment not normally readily available in Alaska because of conflict- ing demands from other projects. ( 3) T'he fi nanci a 1 risks of such a 1 arge prcj ect must be reduced insofar as possible~ for investor confidence is a prerequisite to successful financing. It follows that a set of detailed risk analyses must be Conducted COncurrently Nith the develOpment Of designs. r ( 4) Parti s:._ul arly important design prob 1 ems to be reso 1 ved i nvo T ve earth- quake hazar':is, ice occurrence, slope stability in long narrow reservoirsD and the 1ong term effects of silt deposition in the upper reservoir. (5) tareful and complete environmental studies will be required~ yet the proposed study period is shorter than the time for some full cycle studies of certain species. A great deal of expertise is to be found in and should be sought from the Alaska Department of Fish and Game> yet the objectivity of that agency insofar as reviews and approvals are concerned, must be retained. In addition~ compliance with a11 applica- ble State and Federal environmental laws will require strong coordination effortso (6) Preparation of the license application itself must be accomplished at the very time new FERC regulations will be promulgated. (7) Informing and involving the public is necessary and important, but conflicting desires will be expressed and detennination of how the public interest can best be served will be difficult. (8) Control and coordination of the efforts of a11 parties involved in implementing this plan demands effective management. I I ·~~--~-----------~~~. 1'r· .\Ji •.;;;::!, ·.~· ID[ mlrr ~., , .... I - 5 I lMi 7 -METHODS FOR RESOLVING DIFFICULTIES Certain unique features and approaches are woven into the fabric of the POS as the basis for resolving the various problem areas noted aboVe. Even sa, the requirement to maintain a high degree of flexibi1ity in adapting to new problems is clear, for there is simply no 'flay to anticipate every diffi- culty which may be encountered. The plan provides a large measure of flexibility and a well defined chain of command as we11 as positive steps for addressing the noted problem areas: (1) Careful studies of projected loads and possible alternatives for 1 satisfying them will rely heavily upon use of models developed in Alaska for this purpose. Sophisticated computer programs which have been used by Acres with great success in the past in the analysis of major hydroelectric projects \'lill also be employed. Power marketing studies and a careful analysis of non-hydroelectric alternatives wi11 be undertaken by the Alaskan office of Y/CC, where intimate knowledge of the local scene is available.. Insofar as hydroelectric a1tern.atives are concerned, Acres will contribute its own extensive experience in planning, designing, and managing hydroelectric projects ranging in size frcf!1 500 kilowatts to thousands of megawatts. Optima1 deve1opment of the Susitna River itself 11'1ill flow naturally from these preliminary studies if the proposed project is shown to bl~ the best alternative by the end of the first year of study. (2) Data acquisition will be accelerated because site facilities will be furnished on time and of sufficient capacity by CIRI/H & N, Nhose earl i e~ e:<peri ences on the Trans-A 1 ask a Pipe 1 i ne _?_Dd_w~_ose_j nt i mate ~n~~l.edge_.of proJe.~t lands selected by Native Cqrporations will be important factors. The question of equipment avai1abi1ity and its ope~ation in a sub-arctic environment has been accounted for through selection of R & M to undertake major geotechnical investigations and surveys. R & M is the only finn in Alaska which is self-contained and fully equipped for the purpose. (3) Financial planning efforts by the prominent investment banking firm of Sa 1 oman Brothers wi 11 be camp 1 emented on the Acres team by the work of Mr. J. G. Warnock ~t1ho successfully 1 ed the bond offering support documentation effort on the 5225 ~1W Churchill Falls project in Canada. The risk analyses will be undertaken by Dr. c. B. Chapm~n whose past experiences in this special area have supported certain large power projects in North America and abroad. ( 4) Of the many potential design prob 1 ems, none is of more serious concern than seismicity. WCC (California) will conduct exhaustive studies in this area and their wor~ will be subjected to close scrutiny and confirmatory studies to be managed by an .external board at a level :..tf effort of $1 million. Ice studies, slope stability studies~ permafrost studies and sedimentation studies are included in the plan. Much of the field work will be undertaken by R & H and the primary design efforts by Acres. ~----------------------------~~--------~------------------~----------~ - 6 (5) The en vi ronmenta 1 effort wi 11 be conducted by TES whose core staff vJi 11 be augmented by principal investigata·rs from the faculty of the University of Alaska and other consultants with extensive Alaskan experience. ADF & G will be asked to conduct certain studies~ but their objectivity will be preserved because they will be funded by and will report directly to APA in all such cases. Reviews, approva1s~ and coordination with ADF & G and with other State and Federal aaencies -wi11 be sought throughout to minimize late stage non-concurrences. FERC has confirmed that all studies need not have been completed at the time of filing, provided that a plan for completing them is inc1ud€d in the application. (6) A separate small team has been set up to ensure close monitoring of the preparation of numerous exhibits as well as to evaluate new regu1ations as they are published~ Acres will lead this effort and will seek advice from time to time from legal consultants. (7) A strong public participation program will include three major public meeting events and eight workshop sessions as well as a positive control on response to every public concern. (8) The management expertise gained in Alaska on large projects by FHA will be heavily relied upon in the establishment of cost and schedule controls as well as in the preparation of realistic construction cost estimates, schedules and projected cash flows. 8 -ACTIVITY DESCRIPTIONS As stated ·;n Section 4~ the Acres approcch to the Susitna POS wi11 be fn terms of a series of 13 tasks, each with its specific objectives. Surrn.tary descriptions of these tasks follow.· 8.1 -TASK 1: POWER STUDIES (i) Task Objectives (ii) To determine the need for power in the Alaska Railbelt Region~ to develop forecasts for electric load growth in the area, to consider viable alternatives for meeting such load growth, to develop and rank a series of feasible, optimum expa.nsion scenarios and finally to determine the environmental impacts of the selec~ed optimum scenarios. . Task o~~QUt The primary output of Task l wi 11 be a report de a 1 i ng with the· selection and ranking of optimum system expansiop scenarios for the Alaska Rai1belt Region. The final version of this report wil1 be submitted for review and approval by Alaska Power Authority on or about \~eek 48 of the Study. Preliminary findings of the study 'l'lil1 be discus sed ~tlith A 1 ask a Pov1er Authority on or about Week 30 o.f the Study. Such a discussion will center on whether or not work on the I I ! iji -----su_s_i_t_n_a_O_e_v_e_l_o_pm_e_n_t-sh_,o_u_l_d_c_on_t_i_n_u_e_o_r_\1/_h_e-th_e_r_· --a-n-ot..,...h_e_r_,_p_o_ss-1-·b_l_y_· ------1 i HUlUU l !L-------------------------__,_.~ - 7 more viable alternative should be examined. Design Transmittals outlining intermediate stages of the power studies 'flill also be issued. (iii) List of Subtasks Subtask 1.01 -Load Forecasting Methodology Subtask 1.02 -Development of Load Growth Scenarios Subtask 1.03 -Selection of Alternatives Subtask 1.04 -Selection of Viable E~pansion Sequences Subtask 1.05 -Expansion Sequence Impact Assessments Subtask 1.06 -Power Alternatives Study Report 8.2 -TASK 2: SURVEYS AND SITE FACILITIES . ( . \ 1 j (ii) Task Objectives To provide for safe, cost effective, and environmentally acceptable logistical support of all project field activities; to conduct those surveys.necessary to furnish data for use in other subtasks which must be performed prior to licensing; to resolve real estate issues associated with the proposed project in sufficient detail to permit preparation of Exhibit F of the FERC license application; and to undertake initial studies of proposed reservoir areas and access roads. Task Outout - The primary outputs of this task will be major portions of certain exhjbits required for FERC license app1ication and data which will be necessary inputs for many of the remaining exhibits. Specifica1ly) this task wi11 contribute to Exhibit 0 (demon~trating evidence of compliance with State water and 1 and use la\vs), Exhibit E (providing water rights data and plans for perfecting rights to use water for [ project operation)) Exhibit F (statement of land ownership). In 1 addition, surveys and mapping will be essential portions of Exhibit J I (general project map) and Exhibit K (detailed project map showing f boundaries, survey data, land ownership, and feature locations). In addition to the data collection and exhibit preparation, a number of J tangible products will be acquired or constructed and will generally be suitable for usa during tbe post-application phase and beyond. 1 1 In this latter category are included camp facilities, airfie1d, and similar semi-permanent items. · (iii) List of Subtasks Subtask 2.01 -Provision for Land Use Payments and Directed Inspection Services Subtask 2.02 ·· Provision of Field Camps and Associated Logistic Support Subtask 2.03 -Design and Construction of Airstrip 1:.. Subtask 2.04 -Land Status Research· _ Subtask 2.05 -Land Acquisition Analysis ~ Subtask 2.06 -Right-of-Entry I !Am~!.,.___--------------....~ r---:.:.=.:-:::~-~-~ • Subtask 2.07 -Site Specific Surveys Subtask 2.08 -Aerial Photography and Photogrammetric Mapping Subtask 2.09 -Control Network Surveys Subtask 2.10 -Access Roads Subtask 2.11 -Map and Photo Search - 8 Subtask 2.12 -Field Reconnaissance of Ressrvo~r Areas Subtask 2.13 -Marketability and Disposal Study for Reservoir Area Subtask 2.14 -Cost Estimates for Reservoir Clearing Subtask 2.15-Slope Stability and Erosion Studies Subtask 2.16 -Hydrographic Surveys 8.3 -TASK 3: HYDROLOGY (i) Task Objectives The basic nbjectives of this t:3sk are tn undertake and report on all hydrologic, hydraulic, ice,and climatic studies necessarJ to complete the feasibility design of the project and to provide sufficient material for the FERC license application. (ii) Task Outout -Data Index System A data index system listing all the available hydro1~gic and climatologic data will be compiled and circulated. Hard copies of the more re 1 evant data items ~·d 11 be stored in the pr·oj ect office in Anchorage and copies made available to those requesting it. ATl the additional hyd~ologic and climatologic field data collected as part of this study will be documented on either computer printout sheets or typewritten tables. -Written Sections and Drawings for Inclusion in the FERC License Application Exhibit H -proposed reservoir operating rules) predicted reservoir behavior, and downstream water quality and flow conditions. Exhibit I -dependable po'tler fl0\'1, critical design low flow period, flow duration curves and tailwater rating curves. Exhibit K -reservoir shorelines for maximum and minimum reservoir water levels and reservoir water level area and capacity curves. Exhibit L-spillNay design flood and capacity and freeboard allowance • • I ----------------------------------------------------------------------~ I I I I ·~[ ... ·. .=ii ~, ' 'J IDr t, ~[j'; 41 r' 1 --------------------~-------------------------------------------·---·-- (iii) -9 -Hydrologic Appendix to Engineering Reoort The detailed technical appendix will contain sections on the fa 11 owing type of studies: hydro 1 ogy (resource and floods) , reservoir operation, hydraulic, sediment yield, river· morpho1ogy, ice engineering, and climatic studies for transmission line design and hydrologic and hydraulic studies for the access road. - A Series of Design Transmittal~ These will summarize the pertinent design parameters obtained from the studies outlined above. List of Subtasks 3.01 -Review of Available Material 3.02 -Field Data Index and Distribution System 3.03 -Field Data Collection and Processing 3.04 -Water Resources Studies · 3.05 -Flood Studies 3.06 -Hydraulic and Ice Studies 3.07 -Sediment Yield and River Morphology Studies 3.08 -Climatic Studies for Transmission Line 3.09 -Access Road Studies 8.4 -TASK 4: SEISMIC STUDIES (i) Task Objeetives To,petermine the earthquake ground motions which \·~i11 provide the seismic design criteria for the major structures associated with the Susitna Hydroelectric Project, to undertake preliminary evaluations of the seismic stability of proposed earth-rockfill and concrete dams, to assess the potentia 1 for reservoir-induced seismic 1 ty and landslides, and to identify soils which are susceptible to seismically-induced failure along the proposed transmission line and access road routes. (ii) Jask Output The data collection programs and studies outlined in this task will be suffJciently comprehensive for FERC license applications. Thorough presentations of conclusions, evaluations and data are also desirable for projects that are being carefully reviewed by p~rmitting agencies. Woodward-Clyde Consultants has completed previous similar projects in Alaska and other states where permitting agencies, or other interested groups or agencies, are closely scrutinizing a project. Ba5ed upon our past experience~ we believe that the Susitna Hydropower Project ·r~ill undergo close scrutiny, and that the reports of the project should be complete and thorough. We propose to complete the reporting of the seismic geology and siesmology investigations with this philosophy as a guide. Wi~----------~-------, . -,---------~----·-·r::.~- ~-.. ·-·n••··-~··~···u~ m I .. -10 ihe primary products of this task will include: -Techni ca 1 reports containing thorough documentation of a 11 ~1ork done during the first year. -Final technical reports containing thorough documentation for all studies during the first two years. -Monthly management reports during the course of the investigation. The technical reports will be accompanied by geologic maps showing locations of all controlling features, fault lines, etc. Management reports will deal with technical and financial progress with respect to plan. (iii) List of Subtasks Subtask 4.01 -Review of Available Data Subtask 4.02 -Short-term Seismologic Monitoring Program Subtask 4.03-Preliminary Reservoir Induced Seismicity Subtask 4.04 -Remote Sensing Image Analysis Subtask 4.05 -Seismic Geology Reconnaissance Subtask 4.05 -Evaluation and Reporting Subtask 4.07-Preliminary Ground Motion Studies Subtask 4.08 -Preliminary Analysis of Jam Stability Subtask 4.09 -Long-term Seismologic Monitoring Program Subtask 4.10 -Reservoir Induced Seismicity Subtask 4.11 -Seismic Geology Field Studies Subtask 4.12 ~ Evaluation and Reporting Subtask 4.13 -Ground Motion Studies Subtask 4.14 -Dam Stability Consulting Services Subtask 4.15-Soil Susceptibility to Seismically- Induced Failure 8.5 -IASK 5: GEOTECHNICAL EXPLORATION (i) Task Objectives To determine the surface and subs-urface geo Togy and geotechnica 1 conditions for the feasibility studies of the proposed Susitna Hydroelectric Project, including the access roads and the transmission lines. (ii) Task Output The primary outputs of Task 5 ~tlill consist of comprehensive documentation of geotechnical exploration undertaken at the Devil Canyon and Watana sites, reservoirs, and access roads and transmission line routes. This documentatiJJn 'tli11 1nc1ude the following: -geologic maps l I -geologic sections l~APft[PI .... _______ -_d_e_s_c_r1_;p_t_i_v_e_a~n-d--gr_a_p_h_i_c_b_o_r_e_ho_1_e __ l_og_s ______________________________ j', ~ HU0£0 -descriptive test trench logse _ [ ~ field inspection borehole and test trench logs -photogeologic maps -borehole rock core photographs -low level air photointerpretation -seismic and resistivity bedrock profiles -radar imagery inter~retation maps -geotechnical exploration program summaries (1980, 1981~ 1982) -data summaries for --in-hole seismic testing --borehole camera studies --laboratory testing. geotechni ca 1 exp 1 oration summary reports (1980 ~ 1981) . (iii) List of Subtasks Subtask 5.01 -Data Co11ection and Review Subtask 5.02 -Photointerpretation Subtask 5 .. 03 -Exp 1 oratory Program Design (1980) Subtask 5.04 -Exploratory Program (1980) Subtask 5.05 -Exploratory Program Desigr. (1981) Subtask. 5. 06 -Exp 1 oratory Program (1981) Subtask 5.07 -Exploratory Program Design (1982) Subtask 5.08 -Data Compilation 8.6 -TASK 6: DESIGN DEVELOPMENT (i) Task Objectives -11 To undertake planning studies, to evaluate, analyze and revie~" all previous engineering studies related to hydroelectric development of the Upper Susitna River Basin and to develop preliminary engineering des'i gn and cost i nfonnat ion for Watana and De vi 1 Canyon Dam sites with all associated intake, outlet works, spillways and power facilities to allow preparation of a project feasibility report .. (ii) Task Output The primary output of Task 6 will be a logical and systematic development of the requisite project features. Alternative sites for dams and power developments will be evaluated. Alternative arrangements at each site will also be considered. One such alternative will involve a 30 mile long tunnel from Watana to Devil Canyon to eliminate the high dmn at that site. A Development Selection Report will be issued on or about Week 65 of the Study for revie\v and approval by Alaska Power Authority .. Preliminary findings of the study will be discussed on or about Week 50, in order to establish whether or not work on two dam sites should continue or I whether more viable alternatives exist and should be examined. i Design transmittals will be issued at appropriate points in the I study. All necessary input from parallel tasks including hydrology, 1 geotechni ca 1, economic, seismic survey and environment a 1 studies wi 11 J be factored into the planning studies and the development of the i various features of the project. Engineering evaluation criteria and 1 project definition will be developed. [f sites are found to be I ~l~------t-e-c-hn_i_c_a_ll-y~v-ia_b_l_e_,_e_c_o_no_m_i_c_a_11-y--f-e-as-i-b-l--ea-n-d--en-v~i-r-o-nm_e_r._.t_a_11-y----------~~ ---~--·-·•--«-:;···---~----~ .. -·-·· ... , '. -~~~---.. ,__.~ .. --.. ~-~----------~~ .. ------·--·-----.. f ~~ I [ ' (,, [_ [. l ,--12 1 acceptable, additional studies and investigations will be conducted to establish the feasibility of the project and the optimum scale and .sequence of development. (iii) List of Subtasks Subtask 6.01 -Review of Previous Studies Subtask 6.02 -Investigate Tunnel Alternative Subtask 6.03 -Evaluate Alternative Susitna Developments Subtask 6.04 -Evaluation of Arch Dam at Devil Canyon Site Subtask 6 ... 05 -Development Se 1 ecti on Report • Subtask 6.06 -loJatana/Devi1 Canyon Staged Development Alternatives Subtask 6.07-Preliminary Hatana Dam Alternatives Subtask 6.08-Preliminary Devil Canyon Dam Alternatives Subtask 6.09 -Establish Watana Design Criteria Subtask 6.10 -Establish Devil Canyon Destgn Criteria Subtask 6.11-Preliminary Design \~atana Dam Subtask 6.12 -Preliminary Design Devil Canyon Dam Subtask 6.13 -Dam Selection Report Subtask 6.14 -Spi 1 hvay Design Criteria Subtask 6.15 -Watana Spillway Alternatives Subtask 6.16 -Devil Canyon Spillway Alternatives Subtask 6.17-Pr.eliminary Design Hatana Spillway Subtask 6.J8 -Preliminary Design Devil Canyon Spillway Subtask 6.19 -Spillway Selection Report Subtask 6.20-Access and Camp Facilities Subtask 6.21 -Watana Diversion Scheme Subtask 6.22 -Devil Canyon Diversion Scheme Subtask 6. 23 -Optimize ~Jatana PoHer Development Subtask 6.24 -Optimize Devil Canyon Power Development Subtask 6.25 -Optimize Dam Heights Subtask 6.26 -Preliminary Design Watana Pm'/er Development Subtask 6.27 -Preliminary Design Devil Canyon Pov;er Development Subtask 6.28 -Power Development Report Subtask 6.29 -Watana General Arrangement Subtask 6.30 -Devil Canyon General Arrangement Subtask 6.31 -Feasibility Report 8.7 -Task 7 -Environmental Studies {i) Task Objectives The environmental program is designed to evaluate primarily the Susitna Hydroelectric Project and associated facilities, with respect to environmental impacts. To accomplish this, a comprehefisive program of studies has been developed in the following disciplines: socioeconomics, archaeological and historical resource~~ geology, land use and recreation, water resources, · f~sh ecology, \'lildlife ecology and plant ecology .. Access roads, s1te facilities and transmission corridors will also be studied for environmental compatibility. ~ The overall objectives of the environmental studies are to describe. the existing environmental conditions, evaluate alternatives in light of the existing conditions and, for the selected alternatives, lpn(~ predict future conditions \'lith and without the proposed project so HUH that changes (impacts) caused by the project may be assessed. To n·~~~ ----------------------------- ·-~" .,,,~'~''"'-~-~· -"'" "•" ·-··-,, J -. f ( ' f Subtask 2.15 -Slope Stability and Erosion Studies (a) Objective~ Estimate the extent to which cleared slopes will maintain stability; estimate the risk that continued reservoir operation will cause one or more slopes to fail; and estimate costs of minimizing slope failure risks .. (b) . Approach · Field data collected during the reconnaissance under Subtask 2.12 will be used. as. the basis for analyzing the potential for slope stability probJems. To the extent that such problems appear to exist, alterna~ tive means of slope protection will be considered. It will be assumed that slope protection will be required if there is a danger of failure during continued operation. (c) Discussion Risk estimates developed during this study will be used ultimately in the fisk analysis to ensure that all potential difficulties have been accounted for. The costs of providing appropriate slope protection necessarily become a pa~t of the total project cost estimate to be considered ultimately in determining project financibility and viability .. Subsequent to submission of the license application, much more detailed and vigorous erosion control studies wili be required to minimize damage caused by a concentrated flow of water over newly constructed slopes or in areas. where the natural vegetative cover has bee~ removed. The objective of this post-application task will b~ to issue recommendations and delineate problem areas where an added degree of caution should be exercised. A two part study is contemplated to fulfill these needs. This task will be limited to the general site earthwork and is not intended to address erosion of the downstream channel of the dam site. · Input from the first phase of the detailed erosion study \'lill come from an evaluation of soil types obtained from project test borings and laboratory test data. Air photo studies· will also be used. It is presently anticipated that a sufficient number of test borings wi11 have. been dri 11 ed in other project tasks to accomp 1 ish this study without additional test borings. Nevertheless, samples of surficial soil may be collected for identification and classification purposes, and laboratory tests may be performed. A report d~scribing areas of varying degrees of erosion susceptibility will be prepared. Some of the factors that will be considered in this evaluation will be the soil type and its consistency. Included in this report will be a discussion of erosion control for general site grading. (d} Schedule Weeks 47 to 54 5-48 .. -l·· -···--·-·····--. ---. . , - Subtask 2.15 -Slope Stability and Erosion Studies (a) Objectives Estimate the extent to which cleared slopes will maintain stability; estimate the risk that continued reservoir operation will cause one or more slopes to fail; and estimate costs of minimizing slope failure risks. {b). 8oproach · Field data collected during the reconnaissance under Subtask 2.12 will be used. as. the basis for analyzing the potential for slope stability prob]ems. To the extent that such problems appear to exist, a1terna~ tive means of slope protection will be considered. It will be assumed that slope protection \vill be required if there is a danger of failure during continued operation. (c) Discussion Risk estimates developed during this study will be used ultimate1y in the risk analysis to ensure that all potential difficulties have been accounted fo~. The costs of providing appropriate slope protection necessarily become a part of the total project cost estimate to be considered ultimately in determining project financibility and viability. Subsequent to submission of the iicense application, much more detai1ed and vigorous erosion control studies will be required to minimize damage caused by a concentrated flow of water over newly constructed slopes or in areas where the natural vegetative cover has been removed. The objective of this post-application task will be to issue recommendations and delineate problem areas where an added degree of caution should be exercisedQ A two part study is contemplated to fulfill these needs. This task will be limited to the general site earthwork and is not intended to address erosion of the downstream channel of the dam site. · Input from the first phase of the detailed erosion study will come rrom an evaluation of soil types obtained from project test borings and laboratory test data. Air photo studies· will also be used. It is presently anticipated that a sufficient number of test borings wi11 have been drilled in other project tasks to accomplish this study without additional test borings. Neve\theless, samples of surficial soil may be collected for identification and classification purposes, and laboratory tests may be performed. A report d.escri bing areas of varying degrees of erosion suscept i bi 1 ity will be prepared. Some of the factors that will be considered in this evaluation will be the soil type and its consistency. Included in this report will be a discussion of erosion control for general site grading. (d) Schedule Weeks 47 to 54 . : .. cww•mt•rn·rmrrt'r-, eetetr,L.. ~ 5-48 \ '.. >' A.S.S TASK 4: SEISMIC STUDIES . (i) Task Objectiv~ To determine the earthquake ground motions which will provide the seismic design criteria for the major structures associated v1ith th~ Susitna Hydroelect_ric Project, _to undertake preliminary evaluations of the sei srnic stabi 1 ity of proposed earth-rockfill and concrete dams, to assess the potential for reservoir induced seismicity and landslides, and to identify soils which are susceptible to seismi- cally-induced failure along the proposed transmission line and access road routes~ (ii) Task ·Output . . The data co 11 ecti on programs and studies outlined in this task ~"i 11 be sufficiently comprehensive for FERC license applications. Thorough presentations of conclusions, evaluations and data are a1so desirable for projects that are being carefully reviewed by permit- ting agencies. Complete reporting of the seismic geology and seismology investigations will be made ~tJith this philosophy as Z; guide.. This task wi 11 be conducted pri mari"ly by Woodward-Clyde Consu 1 t ants with revi e\v by Acres and fie 1 d support by R&~ Consultants. The ground motion study data will be utilized in Task 6 for design studies. Identification of seisimica11y susceptible soils for the road and transmission routes will be inputs to Task 2 and 8 studies. Field activities will be coordinated with the Task 5 activities. The primary products of this task will include: -Technical reports containing thorough documentation of all work done during the first year. -F~nal technical reports containing thorough documentation for all studies· during the first two years. -Monthly management reports during the course of the investigation. The techni ca1 reports wi 11 .be accompanied by geo 1 ogic maps. showing locations of all controlling features, fault lines, etc. Management reports will deal with technical and financia.1 progress with respect to plan. 5-79 I - , L Subtask 4.01 -Review of Available Data (a) Objective . To acquire, compile and revie\'i existing data and identify the earthquake setting of the Susitna River basin area. (b) .Approach Data obtaine~ under this subtask will be tised to plan the details of the seismologic investigations (Subtasks 4&02, 4.03~ 4.09 and 4.10) and the seismic geology field reconnaissance (Subtask 4.05). Avail- able gealQgical, seismological, an~ geophysical data for the region . will be gathered from sources such as Woodward-Clyde files~ the DeP.artment of Geologic and the Geophysical Institute of the Univer- sity of Alaska, the-Alaska Geological Surv~y~ the u.s. Geological Survey and the major call eges and universiti-es i nvo1 ved in research pertinent to the project. In addition, researchers \'lith on-going programs of study will be contacted and the current status of their research will be obtained by .discussions and written correspondence. · The acquisition of geological data will be concentrated on structural features of the earth that may repre$ent m~j-~~~1:.~ ~~ faults. The geomorph1c expressions of these features will also 5e identified from the available data. Geophysical data regarding the structure of the earth \'li11 be acquir- ed and reviewed. Regional gravity and magnetic data are particularly useful in identifying major discontinuities in the crust of the earth. These discontinuities may be along faults that could produce large earthquakes and surface fault ruptures. If available, other . types of geophysical data such as seismic refraction, seismic reflec- tion and electrical resistivity may also be of us.~ in identifying . 11ajor acti'!e faults. Seismological data will be acquired for the project area. This data includes historical information on past earthquake~, instrumental data from the Geophysical Institute of the University o.f Alaska,. and regional instrumental data from the U.S. Geo1ogica1 Survey .. The geological, seismological and geophysical data \~11 be compiled in order to obtain a thorough current knowledge of the tectonics of the Susitna River area. The end product will consist of maps that identify faults, lineaments, and epicenter clusters or alignments i denti fi ed by others. These maps wi 11 pro vi de a basis for the pro- · posed geological and seismological studies. In addition to the data acquir.ed for the project area, data relating to reservoir-induced seismicity 'tli11 also be cG>mpiled. The world- wide data on reservoir-induced seismicity wi11 provide a partial basis for evaluating whether or not induced earthquakes may be gener- ated in the Susitna River area. Woodward-Clyde Consultants has an extensive file on \1/orld-wide data on reservoir-induced earthquakes, and is currently being retained for further· research in reservoir- induced seismicity by the u.s. Geological Survey. 5-81 ' ""•re•r•m·!M'tr1P ee•m rntt::.•··. * ::;:w= 4f r . r r [ [ [ [ [ [ The specific products of this subtask include: -Historical earthauake map and catalog A catalog of reported earthquakes with magnitude 4.0 and larger from 1899 to the present will be prepared for the region within 200 miles of the site. For the larger earthquakes in the period, the geologic and engineering effects will be discussed. Data quality as a function of time will be evaluated to estimate the complete- ness 1cvel of the catalog with respect to magnitude, focal depth and spatial location. -Summary of recent regional monitoring Microearthquake monitoring by the University of Alaska Geophysical Institute and the u.s. Geological Survey will be reyiewed and sum- mary· plots of seismicity data will be prepared. Results and inter- pretations based on these data will be review~ with appropriate personnel in governmental and academic organizations. Of particu- lar importance is evaluation of the accuracy of focal depth deter- minations based on these netv1ork studies. -·Tecto'lic model . Based on available seismologic and geologic data, a preliminary kinematic tectonic model will be developed for the region \vithin approximately 200 miles of the site. This model wil1 be modified as needed by studies in later subtasks and will provide the basis for understanding the interrelated geologic source areas for future. earthquake activity in the Alaskan inter·ior. Applications and implications of seismic gap theory will be considered. (c) Discussion The seismicity and seismic sources of the Alaskan interior have only recently begun to be studied in sfgnificant detail. Interest in~ seismicity of continental Alaska was stimulated by the majorc:r[64 earthquake and involved the initiation of regional microearthquake monitoring and the augmentation of geological inv~stigations to improve understanding of the tectonics of Alaska. The seismological environment of the Susitna Project is characterized b,y two major earthquake sources: -shallow earthquake activity occurr·ing along crustal faults such as the Denali fault, with depth of focus less than approximately 12 miles; and -earthquake activity in a Benioff zone which has a depth range of 30 to 90 miles and is associated with the subduction of the Pacific plate beneath Alaska. 5-82 - ' . ,' """'*""eetenree·efftma...;eeree•erewwr 'T. ~ ( ( ( Geological studies are used, along with seismological data, to inves- tigate the shallow earthquake sour~es. The deeper-focus eartQgyake ~~~~ot_g~.l..t_§X~,es?_ed_2L_the ea.r:th~ J!!.~St be ~ n~st~gaj:ed-._ US~9. ... Se)~O~QJ.fE_.l aata .f_Ql!lbi ned Wi ~_b_fl..'-kj_.!]_e.m_at i<;, ~-~~ng of the-rese~t-dait~tonj_c~illVrf~~_Afa~kg~ 1nterior. Tfie occurrence of past--r~thquaRes within the region;-such as the· 1904 and 1912 -magni-tude 7 to 8 ·earthq~akes ~ indi- cates that both the shall 0\'1 and deeper sei sm1c zones may have the potential for generating earthquakes with ground mbtions significant to the project .. The Susitna River area is within a zone of active seismicity that extends from the Aleutian trough on the south into central and ·northern interior Alaska. W6odward-Clyde Consultants ha~ previously conducted regional studies of seismic geology and seismicity over broad regions of Alaska. The past regional evaluations have been for the Trans-Alaska Pipeline System, the proposed Offshore Continental Shelf regions surrounding Alaska, and for the proposed Alcan Gas .Pipeline. These past regional studies provide data regarding the earthquake sources in Alaska, ~nd they also provide up-to-date know- ledge of the current status of research in the area. (d) Schedule Weeks 0 through 22 5-83 b r r r r r r r r 1 [ I 1 l ( i --,-~ , .. ~ '-\_ Subtask 4.02 -Short-term Seismologic Honitoring Program ( a) 0 b j ect i v e Establish initial monitoring system, obtain and ana1yze oasic se1smo- 1ogic data on potential earthquake sources within the Susitna River area and supply information required to implement a more thorough long-term monitoring program (Subtask 4.09). (b) Approach This subtask involves two major packages of work: (1) Analysis oflxisting Data Further limited analysis ·af existing regional earthquake data will be undertaken to enable sufficiently accurate and appropri- ate selection of maximum earthquake sources and associated attenuation relationships. Source studies will be carried out. on several of the largest historical e~rthquakes, including the J..904 and 1912 events, in order to constrain their location, 0~ (Vocal depth and causative geological structure. The maximum ~ earthquake potential of the subduction zone beneath the Susitna site is poorly understood, and it \~·ill be of significant value to use the hi stori ca 1 data to properly characterize this source. These studies will also be directed td the evaluation of the seismic attenuation characteristics of deeper earthquakes to enable the proper utilization of the resu1ts of the Alaskan . C1fASE5 study by Woodward-Clyde Consultants (1978) and other ~ies in selecting appropriate attenuation relationships required for Subtask 4.07 and 4.13. (2) Establishment of a Monitorina Network Since the study area is in a remote but seismically active area additional detailed earthquake source data will be collected by installing and operating a localized microearthquake recording network. The network will be established and operated during the suwmer of 1980. The area covered will include the region within approximately 30 miles of the dam sites. Eight to ten recorders 'with station spacing of 5 tc 10 miles will be installed to record microearthquake activity down to magnitude of 1.0 or less. low-po~"Jer radio telemetery \'till be used to make the field operation as efficient as possible. Helicopter support will be used for installation and maintenance8 . Initial station deployment will be guided hy the information obtained during the data review (Subtask 4.01)s It will be required to monitor known significant geologic featuresa such as the Susitna fault. 5-84 .. < "#_ ,_ ..... r During the course of the study, some of the stations may be moved to study specific areas of activity. Data analysis will be carried out to locate active seismic sources and evaluate their spati a1 extent and focal depth. These analyses will also be used to establish causative stress orientations based on focal mechanism studies, to evaluate seismic attenuation~ and to evaluate the statistical features of the microearthauake activity. • Specific results to be obtained relative to source and wave propagation asse!:isment include the association of 1 arger earth- quakes (such as the 1904 and 1912 events) with probable source structures, depth determination of the Benioff Zone of deeper· sei srnic activity and attenuation characteristics of subducti.on zone earthquakeso Seismic source location in tenns of maximum earthquake potentia 1 in the Benioff Zone will be performed. Comparisons will be made w·ith seismic activity in other compar- able tectonic areas to assess attenuation and maximum earthquake potentia 1. The scope of these studies will be modified as necessa~y on the basis of the resu1ts obtained as the work progresses. Liaison will be maintained·with data collection by the Univer- sity of Alas.ka Geophysical Institute and the u.s. Geolagica1 Survey. The recording period is initially planned as three months.; however, if this should need to be modified, app.ropriate recomnendations will be made during the course of the study. (c) Discussion The present location and focal mechanism level using the Geophysica1 Institute network is approximately magnitude 2~112 or larger. The data obtained from the proposed monitoring program wi11 supplement the existing re1ional network operations and will provide needed accuracy and detection threshold. In addition, the results obtained will provide the information needed to accurately site the long-term network stations (Subtask 4.09) and to select appropriate instrumen- tation. They will also aid in planning the seismic geology recon- naissance (Subtask 4.05). {d) Schedule Weeks 21 through 52 5-85 -t'.l -....... Subtask 4.03 -Preliminary Reservoir Induced Seismicity (a) Objective Evaluate the potential for the possible future occurrence of reservoir-induced seismicity (RIS) in the Susitna Project area. (b) Approach ~.,.. 0 f) The results of.this evaluation will\ be used to establish scenarios of possible outcomes of the occurrenc~ reservoir induced seismicity. Woodward-Clyde Consultants has recently completed a major analysis of geologic, seismo1ogic and hydrologic factors associated with past cases of reservoir-induced seismicity. The results of this study .also wi 11 be app 1 i ed to the known factors for the Susitna project in order to statistically relate the Susitna Project to the potential for RIS. The resulting potenti a1 will be evaluated in terms of possible scenarios for the occurrence of induced activity, and the possible outcome of such occurrences will be discussed. This analysis will result in a quantitative assessment of the poten- tial for the occurrence of reservoir-induced seismicity as a result of the damning of the Susitna River. A comparison \vil1 be made of depth,' volume, regional stress, geologic set~ing and faulting at the Susitna dam sites with the same parameters atihe \'lorl d • s deep and/ or very large r~servoirs. Based on this comparison, the probabi1ity of reservoir-induced seismicity at the Susitna dam sites wil1 be assessed. A description of known cases of RIS emphasizing the relationship between filling of the reservoir and the length of time to the first and largest earthquakes and the relevance of these data to the Susitna dam sites will be discussed. · Scenarios will be presented that discuss possible courses of action that can be taken if RIS is anticipated or detected.during filling of the reservoir. (c) Discussion The activities as~ociated with this task will be closely coordinated with the hydraulic studies aimed at assessing the potential impact on the reservoir water level of a reservoir-induced slide. (See Subtask 3. 06). {d) Schedule Weeks 23 through 50 5-86 I ' _;old_Jiiiliii39t#Wirrma'!Ii!'¥eer·-tiBifY£ists >4·Smrtlrt ~ :jq,,_A, p Ill ( I.''. I. ~· [ L i I Subtask 4.04 -Remote Sensing Image Analysis (a) Objective ___,.:::._..__ . Select and interpret available remote sensing imagery to identify topographic features that may be associated with active faulting. (b) Approach (c) Data obtained under this subtask will be used during the Seismic Geology Reconnaissance (Subtask 4.05) and the Seismic Geology Field Studies (Subtask 4.11) to identify youthful faults that may oroduce . future earthquakes and future surface fault ruptures. Remote sensing imagery and aerial photography relevant to approximately([()c)km~ radius about the dam site will be selected for a lineamerltanarY'sis. This'remote sensing data includes available Landsat:t SLAR (side- land·i ng airborne radar), Skyl ab photography; high altitude U-2~ or RB-57 col or infrared photographs, and bl ack-and-~ihite aerial photo- graphs. The remote sensing and high altitude imagery and aerial . photographs will be interpreted in terms of the geology~ geomorpho- 1 ogy and structure of the study region. Interpretation will help to identify lineaments and other features that may be related to active faults. Seismicity clusters and alignments identified during the seismicity evaluation in Subtask 4.02 will be compared with the lineaments Jdentified by the imagery interpretation and the known faults on existing maps to assess the possible relationship of the epicentral locations, surficial linea- ments and mapped faults. The imagery interpretation will be conduc- ted by geologists experienced in lineament evaluation and in the recognition of features associated ~Mth active faults. It will be important to distinguish these lineaments from similar features that resu1 t from non-tectonic geo 1 ogi c processes .. Discnssi·on • \ g'O The activities in this 1Nil1 be closely coordinated with the photo interpretation studi s being conducted for the dam site, reservoir and construct material areas (Subtask 5.02) to ensure that information requests and analyses are not duplicated. Following an initial aerial and ground reconnaissance it.may be decided that ·low-sun-angle aerial photography should be acquired for specific !geomorphic features that may be fault-related. For this purpos\~_, lo\'1-sun-angle color infrared and black-and-white photography at a )scale of approximately·1:24,000 is proposed. This has proven exceed- ingly valuable in delineating subtle topographic features that may be fault-related. The long shadows cast by the low-sun-angle highlight subtle topographic features related to faults, such as scarps or off- sets, that would be uridetectable with conventional vertical aerial photographs. ~ 5-87 , ---------------:r-~-~ ----··~----·-"··~~-----~----·-·---·-··--.. -------~-----~----·-----~~~~:::;J~~ --~·e*i'9Pi11Waiterfirtr flfNRnif±iitf'' -'Mt¥5 iGi?rW 1%~Utt£a,. Color infrared photography has also proven extremely useful in delineating subtle features in the terrain such as a contrast in vegetation or in surface moisture. Such features are often associa- ted with faults where ground water is either closest along the fault zone or on only one side of the fault.. ( A map of lineaments within 100 km of the project area will be pro- duced as a guide for Subtasks 4.05 and 4.11. The lineament map will be supplemented by mapped faults from Subtask 4.011 in order to com- pare known faults with lineaments of various origins. (d) Schedule . Aerial photographs will be ordered during the first month~ The analYsis will be performed during weeks 10 through 26. ( ( 5-88 ~ ',, ~ . ,, .. ' . _,.,. wwzrramre.emsmi1Hile4r+Df't15at:ren?aartttmzsvmwv,¢·~- Subtask 4.05 -Seismic Geology Reconnaissance (a) Object i ve Periorm a reconnaissance investigation of known faults in the Susitna River area, and of lineaments that may be faults, identify active faults and establish priorities for more detailed field investiga- tions. (b) Approach This task will utiiize the data obtained from Subtask 4.01 and the aerial photographic interpretations outlined in Subtask 4.04 as a basis for planning aerial and ground reconnaissance. The aerial reconnaissance will systematically cover all lineaments and faults identified in previous subtasks. A field analysis will be made in order to identify whether or not each feature may be an active fault capable of impacting the project area due to its being . ~- '(associ a ted with a 1 arge ea.rth. quake or c*ab 1 e of producing a future./ \"D surface fault rupture. Features within e_Q)'ftnl es of the proJect area will be studied during the reconnaissance, with each lineament and faul·t.. being identified by number. In addition, regional reconnais- sance of major features such as the Denali fault and the Castle Mountain fauit which may extend as far as 200 miles from the project area will be investigated. Interpretations regarding the origin of each feature will be made by expert seismic geologists with past experience on similar proj~cts. Those features that are interpreted to originate from youthful faulting, or features of unkno\vn ori·gin that may be due to youthful faulting, will be studied further in the field and subjected to reconnaissance-level geologic mapping. The reconnaissance-level geologic mapping will be ori~nted'toward identifying whether or not the bedrock units near the feature suggest the presence or absence of a fault. In addition, the Quaternary geomorphic surfaces and stratigraphic units in proximity to each feature will be studied to aid in identifying whether or not faulting has occurred in young units. The reconnaissance-level mapping, at a scale of 1:63,360, will aid in identifying those features that wi11 require detailed study during the field season of 1981. These activities will be coordinated with the geologic mapping tasks associated in Subtask 5.04. (c) Discussion The Susitna River area is in a complex tectonic area that is poor1y known geologically. Previous work by Kachadoorian and Moore empha- sized the structural complexity of this area, and the large number of linear features at the surface that may be due to faulting or to ether origins. These surface features requite field investigation to identify their origins. In order to identify the origins of some features, it may requi r_e deta i 1 ed mapping, tre~d·i ng, borings, o~ I ~ 5-89 geophysical data. Despite thorough investigations) however~ it may not be possible to obtain definitive information regarding the origins of all the lineaments. Woodward-Clyde Consultants has conducted seismic geology reconnais-( sance investigations over large regions of Alaska and in many other seismically active areas of the world. Based upon that experience~ we estimate that reconnaissance-level investigations a~ proposed in this subtask will define the origins of about 90 percent of the lineaments identified on remote sensing images. If these features are considered to be controlling faults for the design of dams and other important facilities, further detailed investigations wi11 be undertaken in the Seismic Geology Field Studies, Subtask 4.11. The products of this subtask will consist of a map that identifies recently active faults and features of unknown origins that may be faults significant to one or more dam sites and other critica1 facilities. In addition, all field observations will be tabulated fm .. each lineament studied, and preliminary estimates of the maximum credible earthquake and faulting, along with the recurrences of faulting, will be made for each active fault and other features that may be· faults. (d) Schedule Weeks 24 through 39 This task can begin after Subtask 4.04 is complete. Subtask 4.02 should either proceed concurrently with this subtask or it should precede this subtask. 5-90 d I:' ( -. Subtask 4.0~-=--!v~luation and Reporting (a) Objectives (b) (c) Complete a preliminary evaluation of the seismi~ environment of the pl·oj ect, def·i ne the earthquake source parameters required for earth- quake engineering input in design and document the studies in reports suitable for use in design studies (Task 6). Approach The approach of this subtask will be to provide a probabilistic analysis of earthquakes concerning control of active faulting, and to ·estimate· maximum credib1 e earthquakes for each active fault. These analyses will be completed by an interdisciplinary team utilizing the reconnaissance-level information obtained from Subtask 4.01 to 4.05. Reporting will be in a format suitable for use in selecting the design basis earthquakes, and will include thorough documentation that will be suitable for FERC and peer group review. Discussion A panel of leading experts in seismology investigation and seismic design of major structures will be convened during this activity .to review and comment on a11 study \'/Ork undertaken and the findings thereof. · Overall management and coordination of Subtasks 4.01 to 4.05 is a1so incorporated in this subtask. (d) Schedule Weeks 18.through 52 I 5-91 p;;:s;tbo;:'' 4 Subtask 4.07 -Preliminary Ground Motion Studies (a) Objective Undertake a preliminary estimate of the ground motions (ground ( shaking) to \vhich proposed project facilities may be subjected during earthquakes. (b) ~roach The ground motion characteristics to be estimated ;;,cl ude peak para- meters (peak accelerations, velocities, and displacements), response spectra (describing the frequency content of ground shaking) and significant duration (describing the time duration of strong ground shaking). This initial assessment of ground motions will be made using information from the seismic geology (Subtask 4.05) and seis- mology (Subtask 4.02) studies~ The ground motion estimates wi11 he refined if necessary on the basis of additional infonnation gathered during the second year. {See Subtask 4.13). In consideration of ground motions, the terms nseismic exposuren and "seismic risk" are sometimes used interchangeably. However, for the purposes of this proposal they have two distinctly different mean- ings: - 11 Sei smic Exposure" is used to define the nature of the earthquake-: induced ground motion characteristics· at a specific site; -"Seismic Risk 11 is used to define the risk as the probabi1it~y of structura 1 damage or destruct·i on by an earthquake at the project site. It reflects the degree to \'fhi ch the structure has been designed to cope with earthquakes. Ground motions will be estimated using a probabilistic approach, usually called a seismic exposure analysis. In this approach, the probability of exceeding various amplitudes of ground motion is estimated, taking into account the frequency of occurrence of earthquakes from all significant seismic sources and the attenuation of ground motion fran each source to the locations of project facilities. Earthquakes of various magnitudes, up to the magnitudes of maximum credible events, will be con.s,idered. Attenuation relationships will be derived from examination and analyses of earthquake recordings made in similar tectonic environments and in l similar subsurface geologic conditions, including available ~ recordings from Alaska. wee has recently conduc:ted a comprehensive ~ state-of-the-art analysis of seismic exposure in Alaskan offshore ~ ~ areas (OASES, 1978). The results and data of this previous study, ~~~which included assessment of activity for major onshore faults (e.g., '~ ... ~· Denali Fault, Cast 1 e Mount a i'n fault) as we 11 as. offshore faults ~ ' (e.g., Benioff zone), will be extremely valuable to the progress ~ · study. 5-92 ( ( r t {c) The end products of this subtask will consist of estimates of the probability of exceedence during selected time periods (e.g., 100 year·s) of various 1 evel s of ground motions at the 1 ocat ions of each proposed major dam and other major facilities. For the long trans- mission lines and major access roads, the probability estimates will be given for appropriate segments of the systems. Probability levels an~ corresponding amplitudes of ground motions that may be considered in selecting project seismic design criteria will be discussed. For the dams, ground motion criteria will~consistent with grouQd motions associated with maximum credible earthquakes. For less critical project components, ground motion characteristics having a higher probability of exceedence would be used as design criteria. Discussion . It is widely recognized that neither the occurrence of future earth- quakes nor the resulting ground motions at a site can be predicted with great~accuracy even when the best available data and techno1ogy are employed. The fact is recognized in the above approach and con- siderable attention wil1 be devoted to determining the reliability of the ~stimated de.si gn cr'iteri a. The key interrelationships of this subtask and others are the following: Projections of earthquake recurrence and identification of maximum credible earthquakes is an essential input to this subtask and will be accomplished in Subtask 4.06. The results of this subtask consti- tute. essential input to Subtask 4.08 (Preliminary Analysis of Dam Stability) and Subtask 4.15 (Identification of Soils Susceptible to Seismically Induced Fai1ure Along the Transmission Line and Access Road Routes) • The products of this task ·include the following: -·Estimates of the probabi1ity of exceedence during selected time periods (e.g., 100 years) of various degrees of ground motion at the location of each proposed major dam and other major project components. - A discussion of and recommendations for project ground motion design criteria. (d) Schedule Weeks 24 through 52 5-93 o. \; au:ay:::a (\ l ~ t ~ ~ ,, F ~. t "' -:;-, " ' l i .-: I ' ·~ f I ! l l .. I ~~ TASK DESCRIPTION DATA REVIEW SHOOT-TERM MONITORING PROG.'~AM ...._ RESERVOJ'l ·INDUCEP S f•t JO ~ SEJSMlClTY .:.1 0 ~ ,4.04 REMOTE SENSING w . IMAGE ANALYSIS U) ol G 14 05 SEISMIC GEOLOGY g RECONNAISSANCE 0 ld Cl 14.06, EVAWATION a ~ 4.12 REPORTING U) w (/) 14.09 LONG-TERM MONITORING PROGRAM 4.ll SEISMIC GEOLOGY flELD STUDIES REVIEW MEETINGS - I GflOUNO MOTION .13 STUOtES - 4 •08• DAM STABILITY 4.14 SOILS SU SCEPTIDLE TO SEISMICALLY- INDUCED fAILURE *--""•~ • d • • - 1980 -·-· ~ t-II!;"'"-:r.:~""""'" '~.. __ ··~-·r~ ... ~{_.. __ , ... ~.. ,Jt;, t ... ~~-.,-~·_.,H.,.,; ...,.~~-~ .. ,_ ' ~ '-J ., ~~'-' '" '';~!4'"~~~ !!.-~,.:.;...~"~"" .; ll .-.2: ,"!:.-,~ .. ~~. ...... .... • ';;: L..: ';:.,::,~~ :·;;,.lim . ..~ . - i9BI JAN I fEB I MAR I APR J UAV I JUH I JlL I, AUG I SEP I OCT I NOV I OEC I JAt~ I fED I UAfll AM IIAf.V I JUt• I JUL I AU a I SEP I OCT I NOV I PEC -~~ ·, ~!{.@ ~w;n:;n;c;t:·nr:m:·rrnm~f ~~;m.~~ am ~~~1m I~ P'wcr;;=ltjlf.!'ljiYl...,tn;,wn·t~l~ n-r - ua IIZa .. ~I ml'WJ ~ ~'i'ft1XPT~~~-~''x:rm".:~ IUli:llll pam.:'!mam:arfm;cu:szt mu am11 I'DQ!l!'i: ·r a~~ SUSlTNA HYOROELECTRlC PROJECT PLAN OF STUDY ( [ A.5.6 -TASK 5: GEOTECHNICAL EXPLORATION (i) Task Objectives .. To determine the surface and subsurface geology and geotechnical conditions for the feasibility studies of the proposed Susitna Hydroelectric Project, including the access roads and the transmis- sion lines. (ii) I2sk Output ( i i;) The Task 5 studies will be designed to provide input to the Task 6 design studies and will provide support to the Task 4 studies. The primar·y outputs of Task 5. wi 11 consist of comprehensive documen- tation of geotechnica1 exploration undertaken at the Devil Canyon and Watana sites, reservoirs, and access roads and transmission line routes. This documentation will include the following: -geologic maps -geologic sections -descriptive and graphic borehole logs descriptive test trench logs -field inspection borehole and test trench logs -photogeologic maps -borehole rock core photographs -low level air photointerpretation -seismic and resistivity bedrock profiles -radar imagery interpretation maps geotechnical exploration program summaries (1980,. 1981~ 1982) -data summaries for --in-hole seismic testing --borehole camera studies --laboratory testing. -geotechnical exploration summary reports (1980, 1981) List of Subtasks Subtask 5.01 -Data Collection and Review Subtask 5.02 -Photointerpretation Subtask 5.03 -Exp lo·ratory Program Design (1980) Subtask 5.04 -Explo·ratory Program (1980) Subtask 5.05 -Exploratory Program Design (1981) Subtask 5.06 -Exploratory Program (1981) Subtask 5.07 -Exploratory Program Design (1982) Subtask 5.08 -Data Compilation (iv) Subtask Scope Statements For the purposes of this Plan of Study, .the geotechnical exploratory programs are essentially divided into first-, second-and third-year stages (1980, 1981 and 1982). Exploratory work to be undertaken in 1982 and beyond is not included in Task 5 activities~ Preparation of the. program for 1982 is nevertheless included on the understand- ing that the 1982 program wi11 be initiated prior" to submission of the FERC license application, but is not an essential prerequisite ' 5-105" . ..... ....... ._ Li . . ·~.:' tis ' to that submission. The 1980 geotechnical explor,ation program will be designed to identify and investigate in limited detail those geo1ogical and geotechnical conditions which will significantly affect the feasibility of the proposed dam projects. Limited pre~lanning opportunities and climatic constraints are such that ( investigations in 1980 will be somewhat 1 imited in scope, and the data limit12d in detail. Emphasis will therefore be placed on identifying and investigating to the 1haximum extent the most adverse geotechnical conditions encountered. The objectives of the 1981 geotech~cial exploration program will be to investigate in more detail those geological and geotechnical conditions, both general and adverse, which will significantly affect the design and construction of the proposed dam projects. ·Explol .. ation along the routes selected for the access roads and transmission lines will also be undertaken in 1981. Although the scope of the exploratory work and the data produced in 1981 will sti 11 be somewhat 1 i.mited, the exploratory program will be designed to establish with reasonable confidence the feasibility and total cost of the project, access roads and transmission 1 i nes. The exploratory program in 1982 will be yet more detailed. This and subsequent programs will be aimed at providing greater certainty in the design of major darns and structures with a view towards further ensuring the safety of structures while minimizing potential project cost ov·erruns due to unforeseen geotechnical design conditions. The geotechncal exploration programs will be specifically designed to be complementary to the work already completed. The geotechnical exploration programs in the field will also be severely constrained by difficulties of access and maneuverability of equipment imposed by weather conditions and the requirements for ( environmental preservation. Fu11 accour.t has been taken of these constraints in developing this Plan of Study. · A detailed discussion of the individual subtasks follows. It should be stressed that the exploration program design is based on the assumption that Watana and Devil Canyon are the selected sites. 5-106 .·. \\ (_ Subtask 5.01 -Data Collection and Review . (a) Objective Collect and review all existing geological and geotechnical data pertaining to the Susitna Project area, including the access road and transmission line corridors and the Susitna River basin. (b) Approach Data to be collected at this stage include, but are not limited to the following: . -previous regional and·site geo1ogicG1 mapping and studies published or unpublished geological and geotechnical data and reports from federal, ~tate, academic or private sources -air photos and high level ERTS photos of the project area, including tne proposed access road and transmission line -geophysical survey, remote sensing and seismicity studies and data pertaining or relevant to the project A short field visit will be made to the proposed damsites for prelim- inary geologic interpretation. This will assist in making the pre- liminary damsite and dam alignment selections in Task 6. This in turn will determi1ne the design of the exploratory investigation program. The data and results of review wi11 be assembled into a brief report with appropriate appendices. These documents wi 11 be made available for subsequent use by all project design and study groups. Borehole rock cores from previous investigations will also be examined iti Anchorage~ Contacts will be made with the University of Alaska to gather geologic and geotechnical data. A check will be made for·mining interests in the project areas. Data pertaining to geological and geotechnical problems associated with the construction of large embankments, access roads and transmission 1ines will be collected. Discussions will be held with the U.S Corps of Engineers concerning details of the past field studies. This task wi 11 be undertaken by Acres' Anchorage staff with appropri- ate support fr·om R&M Consu ·1 tants. (c) Schedule Week 0 through 9 5-107 Subtask 5.02 -Photointerpretation (a) Objective Perform air photointerpretation and terrain analysis of the Watana ( and Devil Canyon damsite areas, reservoir areas, construction material borrow areas and access road and transmission line corridor~, and identify adverse geological features and geotechnical conditions that would signficantly affect the design and construction of the project features. {b) Approach 'Photointerpretation will be based on available air photography obtained under Subtask 5.01, and new aerial photos of a larger sca1e obtained under Ta~k 2 for the damsites, reservoirs, and construction materials borrow areas, access road and transmission line corridors. The initial photoanalysis will utilize existing air photos obtained ·either from private or government sources. These photos are believed to be high level and consequently small scale. Tney will, however, serve to establish preliminary surface geology, including·geomorpho- logy, geologic history, glacial geology, lithology and stratigraphy, structural geology, permafrost characteristics and geohydrology and engineering geology. Land forms \'fill be identified. Alluvial or gl aciofl uvial deposits of previous sand and gravel, glacial deposits of impervious till and floodplain deposits of poorly drained, com- pressible silty materials will be located. The distribution, quality and stratigraphic relationships of rock types will be identified. Photo analysis will also be used to generally delineate or. infer ( permafrost areas and buried channels. Groundwater regimes will also be studied and unstable and/or erodible slopes identified. A short field study will be required to verify the photo- interpretation analysis. This will be perfonned early in the first field season (1980). (c) Discussion New air photos produced under Task 2 will be availcible at the end of the first field season. These low level, high resolution, large seale photos w·ill have two purposes: -preparation of second year exploratory investigation progrcm -production of accurate topographic maps on which to base su'Jsequent geological mapping and design studies. Photointerpretation under this subtask will be undertaken by Acres• Anchorage staff and closely coordinated with the photointerpretation work done by WCC (Subtask 4.05) in order to ·eliminate unnecessary duplication of work. · ~ 5-108 .;~.,' 44 ( The resu 1 ts of photoi nterpretat ion wi 11 be docume~1ted in the form of brief summary reports and appended photographs and maps to highlight the .Pri nci pa 1 findings. (d) Schedule Weeks 5 through 41 5-109 Subt ask 5. 03 -Exp 1 or a tory Program Design ( 1980) (a) Objective Design the geotechnical exploratory investigation programs for 1980 for Watana and Devil Canyon damsites, dam construction materials, and reservoir areas, and along the access road route .. (b) Approach The design of the various exploratory investigations will be based on the results of the data collection and review study (Subtask 5.01) and the air-photo interpretation study (Subtask 5 .02). Input from the preliminary access road studie·s under Task 2 wili also be required. Generally, these exploratory investigations will consist of geologic mapping, auger drilling and sampling, test trenching, seismic and resistivity studies, airborne r·adar imagery techniques and 1 aboratory testing. In cases where environmental damage is a prob 1 em or accessibility is poor, test trenches will be replaced by shallow auger drilling by helicopter. The design will specify the following detai 1 s: · -area to be geologically mapped -position and extent of seismic and resistivity lines -areas to be investigated by ai rbor.ne radar imagery techniques -types and numbers of 1 aborator;! tests. ( Investigations for access roads will be confined to geologic mapping ( (c) and radar imagery~ Table A5.4 and AS.S detail the type and extent of investigations and laboratory testing that are currently proposed elsewhere. The design of the exploratory investigations will be flexible enough to permit changes during the execution of the work_ These changes will become evident as the field studies proceed. Discussion . Work under this sub task '.Vi 11 be performed by Acres • Anchorage staff with support in logistical planning provided by R&M and close 1iaison with wee. In th.a design of the exploratory inve::tigations, full advantage wi11 be taken of the extensive investigations previously undertaken. These include drilling, test pitting, geologic mapping and seismic surveys by the US Corps of Engineers at Watana damsite, and the drilling investigations and seismic studies at Devil Canyon by the US Corps of Engineers and the US Bureau of Reclamation. -Watana Site At the Watana damsite area, 17 boreholes have been drilled for a total of 3,340 feet and 11 borenoles have been drilled, totalling 1,815 feet in the right bank spillway and buried channel area. Reconnaissance reservoir mapping and fault mapping has been per- formed by Kachadoqri an. A tot a 1 of 19 auger and diamond dri 11 ·------------.,_.-~~5:-· .. 11 ._. -- ( ' Area Oams·i,te ... ? ., ! Dam Con- struction I 1 I <.n Materials ' J-& I 1 l-' l-' Reservoir Basin ... ~ .._, \,. ._.t,;.,wf TABLE A5.4 PROPOS-ED GEOTECHNICAL EXPLORATORY PROGRAM -1980 Exploration Geologic Mapping Geophysical (seismic and resistivity) Diamond Drilling Airborne radar imagery Geologic Mapping Portable Auger Drilling Geophysical {seismic and resistiv1ty) Test Trenches Airborne Radar Imagery Geologic Mapping Portable Auger Drilling Geophysical (seismic) Diamond Drilling Airborne Radar Imagery PROJECI SIRUCIORES/FACILIIIES Oev11 Canyon·Ooot & Reservoir watana Dam & Reservo1r yes 3 -900 ft. lines at buried channel site 3 -Oblique 450 ft. lines across river channel 2 -1,000 ft. lines on right abutment 1000 ft. + 3,500 ft. at right and left abutment -and saddle dam site One est ab 1 i shed and two new borrow areas yes 20 -10 ft. deep holes in the two proposed borrow areas 2 -1,000 ftl' lines in the two pro- posed but row are as 30 trenches in thr three borrow areas 6 -1,000 ft. lines in the three borrow are as yes 10 ~ 10 ft, deep holes 2,000 ft. 100 ft. 10,000 ft. yes . 1 - 2 5,000 ft. line at proposed spillway site Oblique 1,500 fta lines across river within upstream portion of dam 600ft. + 4,000 ft. at right and left abutments four established and two new borrow areas yes 20 -10ft. deep holes in the two proposed borrow areas 2 -1,000 ft. lines in the two proposed borrow areas 30 trenches in threen of borrow areas 8 -1,000 ft. lines in four of the borrow areas yes .10 -10 ft. deep holes 6,000 ft. at site of r1ght bank relict channel lOP ft~ 20,000 ft. ., I , :;. .~ -t>" ., .-. ~·~.., I t- ~{'; • • ~ ~ ~-' 1:., ( I ""· " I I <1 /'1 - ~--~---·~ -~, -... ~ ,, -__...,., $ .,, "" ,, ~ ~ c=:r:!! 'r ~ 'L~ r-·~ ~ ~-~ ~ < . .....:.,... "" ... ·~ "' "" ... • TABLE A5.5 PROPOSED GEOTECHNICAl EXPLORATORY PROGRAM -1981 REH SIRlJCTIJI{ES/FACJlll IES ,...._~ ~ ~ ~ ·~ -""1; lP "'.~ _. -""' -' __ ,., "" Area Type of Exploration Devil Canyon Dam & Reservo1r Watana Dam & Reservo1r . Other . 01 I ~ )-A N Oamsite Geologic Mapping yes yes Dam Construction Materials Reservoir Basin Access Road Route (Approx. · 50 miles) ""' Diamond Drilling in-hole Seismic Borehole Camera Test Trenchin~ Auger Drilling Diamond Drilling Test Trenching Geologic Mapping Portable Auger Drilling Oi amond. Ori 111ng Geophysical/Seismic Reservoir Slope) Monitoring ) Geologic Mapping Airborne Radar Imagery Portable Auger Drilling Hollow Stem Auger) Diamond Drilling } ~ 4 holes in right abutment (power- house and dam) 4 holes in left abutment (saddle dam and diversion tunnel) 3 holes in riverbed* 1500 ft. 1500 ft. 15 trenches Three borrow areas from 1980 program plus two new areas · 10 -30 ft. deep holes 10 -50 ft. deep holes in five borrow areas 30 trenches in two new areas yes 10 -10 ft. 3 -100 ft. 1000 ft. 1 -200 ft. deep holes deep holes, 1 -200 ft. slope indicators 2 holes in relict channel, right abutment 2 holes in right abutment spillway and dam} 2 holes in left abutment (power- house and dam)** 1000 ft. 1200 ft. 15 trenches Six bo~row areas from 1980 program p 1 us b1o new areas 12 -30 ft. deep holes 12 -50 ft. deep holes in six borrow areas 30 trenches in two new areas res 0 -10 ft. 3 -100 ft. 1000 ft. 1 -200 ft. deep holes deep holes, 1 -200 ft. slope indicator ACCESS ROAD yes 10 miles (20% of total length) 25 -10 ft. deep hoies 15 -50 ft. de~p holes l.~ ho 1 es and 26 test pits have been made in the construction materia 1 areas." A total of 69,600 feet of se ... , smic surveys has also been co~p1eted. These investigations have tentatively shown the Watana site to be suitable for an earth and rock-fill dam. The dam foundation contains small shear zones but no major shear zones have been found. Construction materials appear to be available and .suitable. Although the important Susitna fault traverses the reservoir~ no active faults have as yet been proven in the reservoir. There has been a suggestion that the Tsusena Creek alignment downstream of the dam may represent discontinuity of some kind. Discontinuous permafrost exists locally. Overburden depth in the riverbed at the · site appears to be 1 ess than 80 feet. A deep buried and potentially leaky channel exists in the right abutment. Further studies at Watana are required to prove the absence of major faults in the riverbed and in the abutments, to delineate permafrost zones and identify its characteristics, prove the availability and suitability of the construction materials, confirm good quality rock in the spillway and powerhouse area and define the buried channel and identify its geohydro1ogic properties. -Devil Canyon Site At the Devil Canyon damsite, 13 boreholes totalling 1,350 feet have been drilled in the dam area and another eight boreholes totalling 735 feet have been drilled in the left abutment buried channel area. Nineteen test trenches have been excavated in potential borrow areas. A total of 3,300 feet of seismic surveys have been performed. Although there has been little geologic mapping of the abutments at Devil Canyon, the investigations have shown this site to be suitable for a concrete gravity structure. Major shear zones have not been found in the dam foundation area but minor shear zones are present. Although no active faults have been found in the reservoir, a deep buried channel exists in the left abutment. Some potential construction material areas have · been identified. Further studies at De vi 1 Canyon are required to prove the absence of major faulting in the riverbed and abutments or active faults in the reservoir. Studies are also needed to determine the site geology in more detail, to delineate and evaluate the left abutment buried channel and to prove the availability and suitability of construction materials. (d) Schedule Weeks 12 through 20 5-113 Subtask 5.04 -Exploratory P.rogram (1980) (a) Objective Perform initial surface and subsurface investigations at Watana and Devil Canyon sites and reservoir areas and access road routes to establish general .~nd specific geological and foundation conditions. (b) Approach The program will essentially be designed to -obtain more details on the surface and subsurface geology and · foundation conditions at the Watana and Devil Canyon damsites. -complete the preliminary evaluation of the availability and suitability of the various construction materials required, i.e. fine and coarse aggregate, fine and coarse rockfill, impervious earth fill, pervious and semipervious granular fill and riprap. -determine the surface geology and geotechnicai conditions in ljmited detail to the Watana and Devil Canyon reservoir areas. -provide· preliminary geologic assessments of the proposed access road routes. Field work programs will generally be designed by Acres• AnchGrage office personnel with input from the Buffalo design qroup as needej .. ( Seismologic input will be provided by \~CC and logistical support by (. R&M. All field operations will be performed by R&M with appropric:te technical inspection and supervision by Acres and to a lesser extent l the wee staff. (c) Damsites The proposed exploratory investigations will supplement previous \liork in establishing general and specific surface and subsurface geolo~ic and foundation conditions at the De vi 1 Canyon and Watana damsite areas. The investigations will comprise geologic mapping, diamond drillin3, geophysical, seismic and resistivity' studies and airborne radar imagery, to substantiate and augment the available information on -depth, distribution, type, stratigraphy and properties of over- burden -distribution, type, quality, degree of weathering and permeabili·.y of bedrock -location, orientation, width, continuity, filling characteristic! and capability of major discontinuities in bedrock such as fault~ 5-114 , ...... ..,.f*"-~~-·-~--·---~-~---··--~ .. ,~·---·~ ............................. -···--·-··-··••"""'•· ··-···· ~ ............ -..... -----··· I' "'MU .. + ¥ ( I ; (d) -orientation, frequancy, opening, continuity and filling of joints in bedrock permafrost characteristics including location, temperature profile and soil type -groundwater regime Emphasis w111 be placed on locating and studying adverse geological features. Such features will include faults, excessive depths of overburden in riverbeds and buried channels 'mnch will signficantly effect the design and cost of a dam project at a given site. The geologic mapping at Watana and Devil Canyon damsites wi11 be undertaken to supplament and verify the previous geological mapping carried out by the U.S. Corps of Enginee-rs and the U.S .. Geo1ogica1 Survey {Kachadooricn). The photoi nterpretat ion ( Subtask 5. 02) wi 11 be checked in the fie Td, and adverse geo 1 ogic features and conditions suggested ·in the photointerpretation wi 11 be investigated on the ground.. The geologic mapping will utilize the most recent topographic maps. Aerial photos and survey lines normal to the river will be used as reference in the field. The geologic mapping will be performed primarily by Acres' Anchorage qffice personnel with assistance from R&M. Geophysical seismic refraction and resistivity studies will be carried out primarily to determine bedrock depth in deep overburden areas such as buried re1ict channels and the riverbed area. This work will be done at both damsites. Seismic work can be misleading in permafrost regimes and resistivity provides a reasonable alternative. Bedrock depth profi 1 es wi 11 be prepared from thes.e studies.. Airborne radar imagery will be used to delineate the areas of permafrost. The geophysical work, including the interpretation, will be undertaken by R&M, with review and 1 i ai son by Acres' Anchorage office personnel. Construction Materials <.~--~~~~~~~~ The E!xploratory investigations for construction materials will comprise geological mappinj, portable auger drilling, georhysical seismic and resistivity studies, test trenching and labora1:ory testiing. The !~eologic mapping, dri'lling, trenching and geophys·ical work \'li11 generally be used to establish the limits, depth, strc:ltigr·aphy, type and properties of the borrow materials. The 1 imits, type and proper- ties of potential quarry rock will· be similarly de!tenninedo The expl <>r·ati ens will also serve to verify the photo interpretation and previous studies by the Corps of Engineers. Groundwater and perm.afrost conditions ,.~ill be investigated and extens·lve soil samp'l i ng undertaken. Rock outc.rops wi 11 be mapped and test trE~nches excavated by small track-m·ounted backhoes to a depth of about 13 feet. 5-115 l ' • .1 . ' <., •• .:1 Geophysical techniques such as seismic refraction and resistivity will be used to prove· the depth of the potential borrow materials and the groun~water depth. Airborne radar imagery or low sun angle air photos will be used to assist in identifying the permafrost areas. A moderate amount of laboratory testing of the borrow material will be conducted at this stage. The testing will comprise routine soil identification tests including unit weight~ moisture content, consis- tency, Atterberg limits and gradation. Standard Proctor compaction tests will also be performed on pervious and impervious material and permeability of compacted impervious materials assessed., Some dynamic shear strength tests under high . confining pressures will also be perfonned on i'mpervious and pervious materials. Potential concrete aggregate samples will be tested for sodium sulfate soundness,. acidity and Los Angeles abrasion character- ; sties .. All field exploration work under trds subtask will be undertaken by R&M. Laborator·y testing on borrow material vlill be perfonned by R&M with some assistance from \~CC • Design liaison, supervision and revie\·1 will be provided by Acres• Anchorage office personnel. (e) Reservoir Areas The exploratory investigations to be carried out for the reservoir araas wi11 include geologic mapping, portable auger dr·illing and geophysical seismic refraction surveys. The primary aim will be to map those geological features and geotech- nical conditions in the reservoir area which may se~iously affect the reservoir performance. Such features may include previous buried channels or faults in the reservoir rim which may jeopardize the reservoir watertightness, faults which may be activated under reser- voir impounding and natural slopes which may become unstab"l e or erodible with reservoir impounding or reservoir drawdown. The geologic mapping will be on a reconnaissance sc~le. The air- photo interpretation (Subtask 5.02) will be checked on the ground and specific adverse features suggested in the photointerpretation will be investigated. The distribution:. type and pr-operties of overburden and bedrock materials will be checked against the photointerpreta- tion. Portable auger drills will be used to drill shallo~ holes to assist in estab'lishing the subsurface geology and geolog•ic history. Low sun angle air photos or airborne radar imagery techniques will be uti 1 i zed to he 1 p de 1 i neate genera 1 permafrost areas M1 i ch may cause! unstable slopes once the reservoir is impounded. Specific test areas will be identified in which auger borings utilizing a modifi:d CRREL core barrel 't~ill be used to sample pen11afrost. Thermal probes will be i nsta 11 ed in the ho 1 es to determine te~mper·ature profi 1 es .. 5-116 ( ( I "'"-~'"--·-~------' -1 ·.· ~~~--~'"''""~---·· --:· ··-···-~~-··------·--·---· -~··----------~-·---~---·--·----·-·~"-·-~~---~ c ~ ~ : " . . 1, '· c. ··, .~: ..~ -:, ,-, . .•. rwkml¥--"'"·Aeytre.,~li#. ".Ji,.-IA;.i.r"'&!l~~~-'h-w->.1-...i..~'-' ,. J No buried channels have been found to date in the reservoir rim. If such chann,els are suggested in the photointerpretation, geophysical seismic studies \'lill be initiated to determine the depth and nature of"the overburden and channel widths. A relatively minor amount of laboratory testing \'Jill also be under- taken in this phase. This will comprise routine soils identification tests on those samples taken in the reservoir studies. All field and laboratory work undertaken under this subtask will be performed by R&M. Design liaison, supervision and revieH \'Jill be provided by Acres• Anchorage office personnel. (f). Schedule Weeks 20 through 40 5-117 No buried channels have been found to date in the reservoir rim. If such chan~els are suggested in the photointerpretation, geophysical seismic studies will be initiated to determine the depth and nature of· the overburden and channel widths. A relatively minor amount of laboratory testing ~t1ill also be under- taken in this phase.. This will comprise routine soils identification tests on those samples taken in the reservoir studies. All field and laboratory work undertaken under this subtask will be performed by R&M. Design liaison, supervision and revieH will be provided by Acres' Anchorage office personnel. (f). Schedule Weeks 20 through 40 . . 5-117 I. l l L t l A.5.7 -TASK 6: DESIGN DEVELOPMENT (i) Task Objectives To undertake planning studies, to eva1uate, analyze and review a11 previous engineering studies related to hydroelectric development of the Upper Sus itna River Bas in and to develop pre 1 imina.ry engineering design and cost information for Watana and Devil Canyon Dam sites with all associated intake, outlet works, spillways and power facilities to allow preparation of a project feasibility report. (ii) Task Output The primary output of Task 6 will be a logical and systematic devel- .opment of the requisite project features. Alternative sites for dams ·and power developments will.be evaluated. Alternative arrangements at each site will also be considered. One such alternative will involve a 30-mile long power tunnel from Watana to Devil Canyon to eliminate the high dam at that site. A Development Se 1 ect ion RerJort wi 11 be issued on or about Week 65 of the Study for review and approval by A1aska Power Authority. Preliminary findings of the study will be discussed on or about Week 50, in order to establish whether or not work on two dam sites should continue or whether more viable alternatives exist and should be examined. Design transmittals will be at appropriate points in the study .. All necessary input from parallel tasks including hydrology, geotechnical, economic, seismic, survey, and environmental studies will be factored into the planning studies and the development of the various features of the project~ Engineering evaluation criteria and project definition will ba developed. · If sites are found to be technically viable, economically feasible and e:nvironmentally acceptable, additional studies and investigations will be co~ducted to establish the feasibility of the project and the optimum scale and sequence of development. (iii) List of Subtasks Subtask 6.01 -Re~view of Previous Studies Subtask 6.02 -Investigate Tunnel Alternative Subtask 6.03 -Evaluate Alternative Susitna DevE~lopments Subtask 6.04 -Evaluation of Arch Dam at Devil Canyon Site Subtask 6.05 -Development Selection Report Subtask 6.06 -Watana/Devil Canyon Statged Deve1opment Alternatives Subtask 6.07 -P~"~l iminary Watana Dam A iternatives Subtask 6 .. 08 -Pr·elim·inary Devil Cany1;n Dam Alternatives Subtas.k 6.09 -Establish Watana Design Criteria Subtask 6.10 -Establish Devil Canyon Design Criteria Subtask 6.11 -Preliminary Design Watana Dam Subtask 6.12 Pl"eliminary Design Dev"il Canyon Dam Subtask 6.13 -Dam Selection Report Subtask 6.14 -Spillway Design Criteria Subtask 6.15-Watana Spillway AlternatiVE!S Subtask 6.16 -Devil Canyon Spillway J~lteronatives Subtask 6.17 -Prelimina.ry Design Watana Spillway Subtask 6.18 -Preliminary Design Devil Canyon Spillway 5-129 ~\ .... 0 ' ... :~.~'; l l L l l~ l Subtask 6.19 -Spillway Selection R~port Subtask 6.20 -Access and Camp Facilities Subtask 6.21 -Watana Diversion Scheme Subtask 6.22 ~ Qevil Canyon Diversion Scheme Subtask 6 .. 23 -Optimize Watana Power Development Subtask 6.24 -Optimiz~ Devil Canyon Power Development Subtask 6"25 -Op·timi ze Dam Heights Sub task 6 .. 26 -Pre1 imi nary Des·i gn Watana Pm'ier Development Subtask 6.27 -Preliminary Design Devil Canyon Power Development Subtask 6.28 -Power Development Report Subtask 6.29 -Watana General Arrangement Subtask 6.30 -Devil Canyon General Arrangenent Subtask 6.31 -Feasibility Report (iv) Subtask Scope Statements Plate T5.1 illustrates the interr~lationship of various subtask studies and the logical input of various other tasks. The subtasks have been specifically arranged to make maximum use of input from various other tasks including Tasks 1 through 5 and 7 through 9. A detailed discussion of the objectives, the methodologies and associ a ted costs and scheduling for each subtask fo 11 ows.. Note that for the purpose of this plan of study, it has been assumed. that only Watana and Devil Canyon sites will be considered for additional field exploration and analysis.· However, in the initial subtasks, all pOSS·ible sites and modes of development on the Susitna wi.ll be examined to confirm that the Watana/Devi1 Canyon arrangement is the ·most appropriate. 5-130 •,l \::"J L Subtask 6.01 -Review of Previou§ Studies and Reports (a) Objective Assemble and review all available engineering data, siting and economic studies relating both to the Susitna hydropower development and to alternative potential sites. (b) Approach (c) Reports and also field reconnais.sance studies generated by various agencies ·including USBR, the Corps of Engineers, Kaiser and others wi 11 be reviewed to assess the design assumptions for the sites. Information obtained from these reports, including reservoir storage and power head, site evaluation, geologic and seismic conditions, topographic features and other special physical and environmental constraints, will be tabulated. Total potential for power development at each site and the associated costs will be assembled in tabular form; costs will be updated to current levels for comparison. Sites· studied will inciude a11 those identified in the previous reports. Layouts for all sites and special constraints for each site wi11 be identified. All conceptual design parameters wfll be developed to update the cost of each site to a uniform level in order to rank the sites. The task will include the indexing of all basic information that could be used in analysis under Subtask 6.03. Indexing will include all basic infonnation on· nature, type and extent of geotech- nical investigations previously completed, maximum level of develop- ment considered for e~ch site, type and. size of dam selected, type and size of spillway considered for each site studied, and on-line dates considered in the previous reports. Other data to be indexed will include reservo1r storage, average, maximum and minimum flow, regula- ted flow, power capacity and energy development at each site, equiva- 1 ent construction costs and other factors, such as special ·environ- mental and seismic impact on each siteo · Discussion The level of study previously undE!rtaken for·· each site varies consid- erably, not only with respect to geotechnical investigations and preliminary planning, but also in relation to hydrologic and economic assessment. Project ranking techniques and cost updating criteria will necessarily have to include additional cost parameters and analysis. These data will be used at the specified ·~,evel of develop- ment as an input to Task 6q03u In orde1~ to meet the overat11 objectives of the subtask:~ a critical r1~vie~/ and assessment will b<~ made of all technica~ infonnation on power capacities; and othe!r constraints for the de.vel opment of each site will be identified. Previous work has identified six dam sites for which ranges of heights and power installation have been considered. These sites wi11 be analyzed in order to select the projects which are both technically feasible and economically attractive for initial construction and are compatible with the plan 5-131 : t t l l l for hydropower development of the entire basin. It is likely that some of the sites wi11 be rejected in initial screening because of poor foundations or because of very high cost of development. Previous studies have demonstrated that the Watana and Devil Canyon sites are probably the mas~ favored; but if the studies under this task indicate othen~ise discussions \~ith the Alaska Power Authority will be scheduled immediately. All cost data from the previous reports will be updated to 1980 cost levels. As project costs are highly dependent not only upon site foundation conditions) size of spillway and outlet works~ but also upon whether a low level outlet is provided, costs wi11 be adjusted to a conmon design. (d) Schedule Weeks 25 through 40 _. I 5-132 c: ( r r L, l l< f l. i_ul:i_task 6.02 -Investi.aate Tunnel Alternatives (a) Objective To investigate the feasibility of a scheme for development of the Susitna River el imi n·~ti ng the Devi 1 Canyon project by the substitution of a tunnel-supplied power plant fed from the Watana dam site. (b) Approach A pre 1 imina ry rev i ew of the proposed ~Ja t a na{Dev il Canyon deve 1 o pment of the Susitna River suggests that a feasible alternative, which would allow the elimination of the major reservoir formed by the Devil Canyon dam, would comprise the construction of a. power tunnel starting at, or near, thd curre~ly proposed W~ana site and terminating ~ a power plant near the proposed Devil Canyon site as illustrated in Plate T6.2. In addition to the reduced en vi ronment a 1 impact brought about by the .elimination of the Devil Canyon dam and lake, the tunnel alternative would eliminate a major dam, reduce the size of one p~er plant, and allow a much larger proportion of the construction work to be located underground, shielded from severe Alaskan winters. Potential disadvantages of the tunnel alternative include lOss of power output due both to head losses in the tunnel and to the neces- sity to maintain flow in the river between Watana and the lower power plant tailrace. The considerable len~h of the tunnel ~uld require the provision of several constru~ion adits with corresponding environmental impacts during constrwctiono In order to make an initial assessment as to whether this alternative should be carried forward into more d~ailed evaluation, the following activities are proposed: (1) On the basis of the material assembled in Subtask 6.01, a number of tunnel alternative arrang~ents will be identified. Some preliminary concepts are shown in Plate T6.2. Several others incorporating different tunnel alignments and intake/power plant locations will be identified. {2) These initial alternatives will be subjected to a gross screening to eliminate those least 1 ikely to meet economic, technical or environmenta 1 requirements. P'rel imi nary layouts will be develop- ed for those remaining and major dimensional and design charac- teristics will be establishedo (3) Preliminary quantity and cost estimates will be prepared for the selected tunnel alternatives, together with corresponding cash flows. 5-133 , , : ~;-'~;}<c ' ,. .~. . ._.., · ~A• ........ .Wnr?'tw*" ~. l (4). Estimates of capacity and energy for each of the alternatives will be developed. (5) The most attractive of the tunnel alternatives will be compared from the technical, economic, and environmental standpoints with other options for the river development identified in Subtask 6.03. (c) Discussion The tunnel alternative to the Devil Canyon project would appear~ from initial review, to have some rather attractive features which may warrant careful evaluation. From the environmental standpoint, the elimination of the large Devil Canyon reservoir must be a significant step~· This may, of course, be offset to some extent by the increased live storage to be provided at Watana and by the possible wid~r spread of construction activity during tunnel construction. Initial "order of magnitude" cost estimates seem to indicate at least a trade-off level of cost for the tunnel alternative, without assessing the impact on the schedule and power generation capabilities of the long power tunnel. (d) Schedule Weeks 30 through 50 .. 5-134 ,~·.'' c : l. t ( Subtask 6~03-Evaluate Alternative Susitna·Developments (a) Objective (b) To identify the most appropriate scheme for development of the Susitna River on the initial basis of technical feasibility ~nd cost. ~oproach Primary input for this subtask from the cost and technical standpoints will be derived from the review of previous studies {Subtask 6.01) and from the investigation of the .. tunnel alternatives .. (Subtask 6.02}. Further input will be provided from the hydrological studies under- taken in Task 3 and from the public participation program carried out under Task 12. This subtask will involve the development~ comparison and subsequent ranking of all reasonably feasib1e combinations of sites and power facilities identified either in the previous studies or in the course of kres studies to this tin. e. Economic parameters for a range of dam heights and power i::stall arions will be developed for ea.ch site and for the complete river devel :1pment; these wi"ll be analyzed by computer to identify the most promising scheme. Specific activities will include: Evaluation of six previously identified sites including Susitna ·1 and II~ Denali, Vee, Watana and Devtl Canyon and other sites, for· which data will be obtained from the review of literature (Subtask 6.01). . -Data on rated head, regulated flow, yield and power available from previous reports for these sites wi 11 be developed and the va1 ue and cost of power for each site Will be compared. Only previous 1ayouts and engineering information generated will be evaluated. -Data on foundation conditions, availability of construction materials, limits of development of each site~ access conditions, seismic and environmental conditions for each site wil1 be reviewed in site-ranking studies~ -Sites with extremely poor foundation conditions and other serious constraints related to seismic or environmental impact will be rejected. A summary report on this ranking study will be prepared. · (c) Discussion : By this stage of the study, costs of alternative power and energy will be available for economic comparison and development of cost-benefit ratios of each individual site, and by combination for each set of developments discussed above. It would appear from previous. studies that the combination of Watana and Devil Canyon sites is the most promising development, and it is expected that the results of this 5-135 l I I ' ~~ ( ~~ L t. t l work will verify this. However, if the results of the study indicate otherwise, the layout, costs and details of the alternative arrange- ment will be brought to the same level as the studies for the 1979 report by the Corps of Engineers for the Watana and Devil Canyon sites. The evaluation will· rank the sites or the combination of various sites with power capability at each, and establish associated costs and cost-benefit ratios for each combination studied. Alterna- tives will include combinations of Watana dam sites and power tunnels. The results of these studies will be documented in the form of a memorandum which will form a basis for further studiese The report will explain the mechanics of the evaluation process and the rationale of specific site and combinations of sites, foundation suitability and availability of construction materials. Economic· comparisons from cost/benefit analysis will indicate the environmental impact on each such site. The selected alternative will be that which proves to be the most favorable for development of the Upper Susitna Basin. · (d) Schedule Weeks 40 through 60 5-1.36 ( ; (~ If l J· '- . Subtask 6.04 -Eva'luation of Arch Dam at Devil Canyon Site {a) Objective To make a preliminary assessment of the feasibility of an arch dam at the Devil Canyon site. (b) Approach Th~ ori g ~na·l deve 1 opment at the De vi 1 Canyon site recommended by the Corps o·f Engin~ers incorporated a 635 foot high double curvature thin arch dam with a crest length of 1,370 feet.. Following critical comment by the OMB, the Corps, in their Supplemental Feasibil·ity Report (1979), proposed an alternative which wou'ld replace the arch dam with a more costly gravity dam. The primary rationale was the r·educed sensitivity of the gravity dam to foundation and abutment conditions. · We will critically review the feasibility of an arch darn at the Devil Canyon site from both economic and technica1 aspects, as well as the overall safety aspect. The review. and evaluation will comprise. the following: -Assembly and review of all available material relating to the arch dam design recommended in the Corps• report and earlier in Bureau of Reclamation reports. - A cr~itical examination of all geotechnical data relating to the foundation and abutment conditions at the proposed dam site. These data may well include further information obtained in the course of the ongoing field investigati0nso - A critical review of the seism·ic conditions at the site, particularly in the light of material developed in the course of Task 4 Seismicity Studies. - A review of current design practice in relation to high arch dam design in seismically sensitive areas. · ... The development of the draft design of an arch dam appropriate-to the conditions at Devi ·1 Canyon~ Design wi 11 be accompanied by associated schedule and cost estimate, including impact on · associated structures. : -Review of proposed design by Special Consultants and modificat·tons as required. -Final evaluation of feas·ibi lity of the arch dam from the technical, economic and safety standpoints and development of a recommendation as to ~hether an arch dam or another design of dam should be carried through to the licensing documentation. 5-137 ·-r ,,., (c) Discussion The arch dam design at De vi 1 Canyon w·as supp 1 emented with an a 1 tern a-( tive conventional gravity design by the Corps in the 1979 Supplemental '"" Report. Economic feasibility of the project using more conservative design approaches was demonstrated. An underlying concern regarding the safety of arch dams in high zones is evinced by the recent decision regarding the Auburn dam. However, it is of interest to note that as reported in a recent issue of Water Power and Dam Construction, April 1979~ not (Jne failure of a concrete dam directly caused by earthquakes has ever ;:leen recorded. Linear analytical techniques for evaluation of the response of con- crete str·uctures to seismic forces have evolved, the most widely used being the finite element technique. Acres recently utilized this technique to evaluate the Karun high arch dam proposed in Iran with a height of 325 meters. In general, concrete dams perform very well when subjected to earthquakes. Of the types available, arch dams generally have proven to perform the best and buttress dams have been subject tu the severest. damage because of abrupt change in section and the resultant stress concentrators. The V-shape canyon with a ratio of 2.15 (width at crest level--1,370 feet to depth--635 feet) is favorable for a doub1e curvature arch dam. As an example, the experience of dam building in Japan can be cited. The average se·ismic intensity experienced at various types of Japanese dams (in 12 point scale) is: -gravity dams ··············~· 9.8 -arch and arch gravity •••••• ~ 10 -.rockfi 11 dams ............... c 8. 5 Such high arch dams as Kurobe (186m), Nagovado (155m), Iagisawa (131 m)~ Takane (130 m), Kawamata (120 m) and others were built in areas with earthquake intensity 10 to 11 points. There are a number of approa~hes which can be used to condition the abutments of arch dams to weaknesses of the rock. Str~sses in the foundation may be reduced, not only by increasing the abutment thick- ness of the arch, but also by using abutment pads. In addition to being a very satisfactory means of spreading arch thrusts, abutment pads prov·i de an efficient means of bridging faults and other weakness- es in the foundation. Abutment pads are applied on the world's highest arch dams at Ingury (U.s.s.R. 271 m) and were proposed for the · Auburn dam (U.S.A. 209 m). Severe weather conditions will cause serious problems for both dam types. Besides the necessity to prevent freezing and tracking of concrete during construction, a serious consideration will be consoli- dation of the dam body and rock base • ... 5-138 ' - ( (_ I I ~~ : ........ I In Russian dams built in Siberia, grouting joints between monoliths were replaced by slots 1.2 m wide backfilled with concrete after cooling the monolith below the average annual temperature (the average annual temperature in the core of the dam is 2oC to 3°C higher than the average annua 1 temperature Jf the area). If the area average temperature is below zer(\? the concrete should be cooled to a tempera- ture of not more th~n +1 to +2°C. Such a procedure involves a long time and high cost. The Russi an Mamakan and Zeya dams are hamm1:rhead type (buttress type). This type of dam provides E:asy access to the slots from the hollow spaces. Concreting of the slots is performed after warrsdng up the surfaces of slots by means of electric heaters. After fi 11 i ng the reservoir,· the temperature of the dam body wi 11 rise and the concrete plugs will be compressed. Another problem is prevention of the negative eff;:ct on the stress state of the dam caused by freezing of the downstr·eam part of the dam. Static analysis and model tests performed for gravity dams located in Siberia (annual average temperature -2°C to -4°C) showed that for the winter, the frost can penetrate to the center of the dam~ causing opening of the horizontal·joints and, as a consequence, tensile stresses on the upper face of the dam (reductions in the compressive stresses of up to 30 percent were demonstrated). For this reason, hammerhead or massive buttress dams with heating inside the hollows were bui 1 t in Russi a (Mamakan, Zeya, Bratsk ~ Buchtarma) instead of massive gravity dams. At the Mamakan dam, the e 1 ectric heating system is in operation. for one to one and a half months a year, and the capacity of the heaters is 80 kW. Another method of preventing freez- ing. is to insulate the downstream face of the dam. Consolidation of an arch dam is much easier because arch dams do not have long-itudinal construction joints. Concreting of the slots after cooling the monolith below the average temperature will produce an effect similar to heating gravity monoliths. In general, arch dams, since they are more flexible and smaller volume working structures, can cope more easily with severe temperature conditions than gravity dams. Nonethe 1 ess, some improvements of the presently proposed arch da.m are likely to be necessary. (1) An abutment pad should be used. It functions as a transition structure between arch and rock, and as such, may be thickened, widened and reinforced as necessary. In addition, the abutment pad may be used to improve symmetry of the canyon profile. (2) A two-center~ed dam layout with two separate pairs of lines of centers, one for each side of the dam, shou 1 d b~ used to tope. with the unsymmetrical shape of the canyon~ (3) The slenderness of the dam is ~~5 6 = 0.135 (base tt!ickness to hs·ight), and it requires reevaluation in light o~ seismic and temperature conditions. 5-139 l 13, - The slenderness coefficient should probably be increased to 0.16 aad the base thickness to 0.16 x 635 = 101.6 feet (31 m) • . Note, however, that even if it i.s corsi dered th?t an earthfi 11, rockfill dam or concrete-gravity dam should be considered for FERC licensing application, some background information should be developed for s1 arch dam. Later studies may possibly indicate technical feasibility or economic and environmental desirability, and the option to revert to the arch design should be maintained open for as long as possible. (d) Schedule Week~ 45 through 65 5-140 2 - 1N . ~ q -. PROJECT MAPSI EXPLORATION b I;, l l ----- - PtASN - •rr nnrn e u ·~u•t • II till{ MILl -U ... IOTUt MIU *U Os• ~~L~Ct, •nn I UCUIDOI II llMU ltUlllt • IIWU Ul SIIDIII Ill llfUll S!j((n ANO taH*IT D-1. 1 L.:.TIIIf Ill" lU;n •us nt soaw 111 SKUl 11•11 u ! Al!MY SOUTHCENTRAL RAIL BELT AREA • ALAS!<~ SJPPLE!.ENTAL FEASIBIUTY STUDY UPPER SUSITNA RIVER BASIN WATANA DAMSI_TE EXPLORATION PLAN . ... ~--~.J JNV. NO. DACWB$.. PLATE D-2. .-, 1 1 : I I I \ \ i \ L l 1 ·'l r- ' ' ' ' ' ' ' ' ' ' ' ' I t>OT£S . I. lo-.1(';1\l..f'rilC COOilQo..RS I.R( fi~S£:0 00 t.(i!IJ.L PHOlOGRJ.Ptl\' l:l~O 10 JUI;t G7tl "'(RTICAL 01.1UM IS II(AH &I< l['V[L IMSU 1Cf'6D Lu ' 1'\ 4-....-)"-5~ts..,_,i '-) ~~~~ SL -~~-4 St.-so-s- 0 Bil-l .(Jo/lc/IIU£ .LCc.IPT/DA/ ,..!L_:-!.; .SE!SilJIC .I..JA~ I <tao S '-' """~-er. · Pr~ va YVt I B . I Of"l~ s \) t" 5-, t=: t. l ~so' ' zooo T 8H -~ )&H-6 T B'H -~ I ~00 '. ~)'\-'I'-«. ~YCI~ Vl"r+i ~0 0 bOe ~€"() A ?;t.)oor!ui-1... '2. z. s,., (p 00 4-~ll ~::~.~~· :::0 '01800 7 so. fi 401 1 I Propoo•.J T e.tt-9 '13 H 10 ---t J9gb w~.,f-t.r- _ _, '"'~· y.,'l'"~ v~ .... r- : -'--_L_,. Pr~]Y2·~ }$"01 1 s-o' ......________,zooo ~--2100 1j HZ'3000 ~~ ~~-.---. .,.o /'' ... , -· • ,{/'Do $:1 \) v. SOUTHCENlRAL RAJLBELT AREA, ALASKA SU'PL(Mf:HTAL fEASIBILITY STUDY UPPER SUSITNA RIVER BASIN WATA.NA DAM OE1AIL PLAN Al.~a 1JSl•oc:1. CO'•S " (I<C..CtM ,_,o<)lll.r..t:.~·· fEBRUARY 1979 /ZEVIIUU.I I '6jt;j!"() ··-·ptGIIKC I ji!~AlvmM.Il !>c-,s,mc .e.'4'EJ 0 ~v 0 0 = a !l SUSITNA RNER \. ~ --~II/ ~,=--'\. -~-'8o-S ~~~~==~~====~ a :c ooll uoo· 2000 6 ~---"~- ~ €'VIS")"' I i-/0/60 , ;l.f!A.IVM4Err IJ~~r / 7CJi /''TS -mea ;;awv --~w:w.-~-·-· Co {.~ :;\ ~~ q 1] T~ ~ TEsT P/1"' 41) PH-I .ITUCEIZ 1/0L£' SL·'-J-----1 5 ElSI7liC L./,.IE LEGEND •" 'lt.Sl rrn ... DOIOU.IQ.[ • .,. AUC[OIQ.[ Qs• 'uswc. uc .!!!11 1~ S.lt"'lt llll'l n:)tJ\U ""'' lit ro.Jltl II 11111111 ~1. I, 141• ~U t••tt lll ..,_tal ot IC\UDI Atll C. 1110 tv\ IGLl 110<11'11 Dl MD ltMft UaU NIO U-2'P~ 111 P\..&n Do-L ). N•l lAO u.r Ul alJ,I ~·20 )II J,PIUII.t.1 AIIU.. SU rul'l •1• c. rc. lOCA11C:.. Of 1' ;..J M: 11' n-~. su n.an a-z. SOUTHCENTRAL RAIL BELT AREA, ALASKA SJPPLEMENTAL FEASIBIUTY STUDf UPPER SUSITNA RIVER BASIN WATAN~ DAMSITE QUARRY SOURCE 8 B BORROW AREA D ALAS<• DIS10ICT. CXliiPS IY ['<G .. ttiiS .t.V...c:JI'II.c:t. ALUIU r~t;ullc $ -~ ('. ~· •e" .~ '.> ~~ t-~ • ; ' ·• <C .. z : ~ iii p .J ::l ~ .. . .. i .... co ., :l .. a:~LLJ • .. ~!:w_<r !; i :1 2: {/) LLJ .. 11 a: ::E 0: ~ . d~ <r:<( § i II W '4 0 ~ ... zoet~ . ~ ~ (J a:.,.!::zo lj y -c VI <( 0: ~ . :g~!;£~ .. ll.t '-) A ... :1 :::: (!l 2 ... a: ~ ~ ~ t ~ ~ .. ~ 0... ;/ ~ :> ·:l ~ G: to "" -.1 I ~ ~ k J ~ "' ~ t< II( ~ ~ I i .~ \1.) " ~, ~~ ~ "" ~ V\ ... ~ ~ ~ ;: "" ~ !~ ~· !: ~!i a ~!l -r "' ~ or .. I ..... ~ ~ " ~I tl: !-... .!.. • [J -.~:~ ~ I • ' o·q \ , ~::,...-" S~/ \ () ~ . 06 ~ . < \ ~ ~ I .. I ~ 0 § \ ~" g ~ -..;.. --~~-P-PQ~cl ____ ---- V.....? I ~-+-t' V" <;~ J ~ ~; c.. L) tj .(> .5 -------- S L -CO 0 -;I S',. } c_, i / ~~ ·-1Cl8D ~u,.,.,.,.,.,,.. \S tl-I 1 '2.) 4 "---- . 1 \ \ ~~---~---.... -~--·--~-.,......-:..-.~" -----·----... ·----~--~--------- _____ ... ----· -·-... ,:;.._ .. ......... -... ~:<0:. . -.. ~·;._"'· ~:. .. : 11•~1. .. ,._ . ..,,.--... _ ,.; ,_... -- ~ ,rw • '"'O.{' ·'- a.. D~ • 0. , •O <:::::-::-:-:-. • .~jt::i=~ .. ,... . ........ ~(" . . .. ·, ', ' "'-, ' · .. \ \. ..,., C-..,., '\ _.. J4 ,;<"'-' ' fill'(: ................ )~:.• -..:-/ "·. ~ o"'•lo{ .,:o!J -•n·• / . w ,. /1 < .•. ,.... - I rP-B0-10 o-·-~;; ~~ J/:..:::....· I I ' / "--~· I I CQ • ~ .-' .-' • NCRETE AG<;R£GATE S · · \ 0 TP-~o-'1 ·• · OURCE -z. 'V ?:! .:.. t" ?:! .• _,..,... ... -,: • 0 TP-t~-1 I ·-si<=< .· ~ / . "'"' ' ' . . -_/ . \-0 rP-;;o-e ~ ,~ ..... · .:: IIH··I: I O '-.._E!·t~/ """ "'" . -. :_;i~'l'S' :-:~· ... ·. ~--~f!_II_·G:J. TFJ9~ OtOO ... '...,, \. '' '!::>·-~ ··-..,.•" ; ----_ ... -, __ _ I . • TP· fO •). .. -·' 0 / '": ~ ........ ~~.s ,;,·s:o --,~ \ --:~ • -~~~" 1\~. r ... ;;---. ~o -:-..~, • '--'-...-. ,· ~ ... \ ; I -......; ,:-'· --~--. ;zP -~--~~ I .\.._ '?~ 'J1J-Z' . • 811-1 ,_~'"1-~ s.::$r..•:r L,.-.~r 6 BP·S ,-;vr,.:.~. :: _c 0 TP-6 TEST ~Jr SOU1HCEN1RAL RAILBELT AR(A, ALASKA SJPPLEMENTAL ftASIBILITY STUDY UPPER SUSITNA RIVER BASIN DEVIL CANYON SITE PLAN a EXPLORATIONS &LAS<& ll<STRICT, r.o<IPS or fi<!Oifj£LIIS A""'o<JII~(. AL~ FIGU.f!E 2 ··=~ I p ,;:;: I } I .. .. ;; ., . . ~ • •" ·~ ... :L' ,,--.. ""'-: .. ""! I '., \ ' ' ' ' (\' \ \ I I "15 I or 0 I N 01 I 5 Ill I N l l r. ~ .~ ll SUSITNA HYDROELECTRIC PROJECT INTERNAL REVI~A BOARD MEETING #1 ,. GEOTECHNICAL AND SEISMIC ASPECTS JULY 23, 1980 NOTES ON MEETING l l l I [ ' ' TABLE OF CONTENTS Agenda of First Internal Board Review Meeting Objectives of Meeting Summary of Meeting Attachment A -Existing Geotechnical & Seismic Data Viewgraphs Attachment 8 -1980 Geotechnical Program Attachment C -1980 Seismic Studies Viewgraphs Time & Location: [ SUSITNA HYDROELECTRIC PROJECT. AGENDA OF IST INTERNAL BOARD REVIEW MEETING -GEOTECHNICAL AND SEISMIC ASPECTS Wednesday, July 23, 1980, 8:30 a.m. (all day) Board Room, Niagara Falls Office Ontario, Canada [ In Attendance: Project Team Rev·; ew Board [ J. Lawrence D. MacDonald c. Debeliu.s J. ~iacPherson [ J. Gili L. Wo1ofski I . Hutchison D. Hepburn v. Singh H. Eichenbaum [ S. Thompson J •• , ·-~ i>' .. ' • .. . . .J. ....._ .......... Puroose: To review work plan for 1980 Task 4 (Seismic Studies) and Task 5 [ (Geotechnical Investigations) and preparation for Exter.nal Review Board Meeting (tentatively scheduled for late August). ll· t~oderator: John D. Lawrence .i; [ L < < l l [ Agenda: L" NOTE: l Time 8:30 AM 9:00 AM 10:00 AM 10~15 At~ 11:15 AM 12:00 1:00PM 2:00 PM 2:30 PM ~ • 1 r:= nM' ,J; v r· 3:30 PM Topic Introduction Existing geologic, geotechnical & seismic data Break 1980 Geotechnical Field Program Discussion Lunch 1980 Seismic Studies Discussion Wrap-up & ·summary of 'Board Views o ........... k OICQ Soeaker ---·--I ! • J. D. Lawrence I ~ · ~~ ·,~·-rl...il--" , I So Thompson & V~ Singh J. Gill V. Singh Scope and schedule of External Review P.ane1 Meeting Speakers are requested to hand out detailed agendas of their presentations during the meeting. I • I . .. ~~ I .. I r . [:· ,;,;! [ [ ~: [ [ [ [ [ .. [ [ L .. t L ~~ l. SUSITNA HYDROELECTRIC PROJECT INTERNAL REVIEW BOARD MEETING #1, JULY 23, 198Q PRIMARY.OBJECTIVES 1. Familiarization \'• •. :...-"1 , .. 2. Review of: -proposed dam locations and types (preliminary concepts only) ' -geotechnical exploration program scope and schedule -proposed seismic and reservoir induced sa;smicity programs -potential tunneling problems (preliminary concepts only) 3. Recommendations for scope of first external review panel meetin~ (late August) .... ..... ' - I l I r [ I' [ ( [ [ [ [ [ .. _[ [·. ,,)' [ [ L t SUSITNA HYDROELECTRIC PROJECi INTERNAL REVIEW BOARD MEETING #1, July 23, 1980 ACRES CONSULTING SERVICES OFFICE, CANADA SUMMARY In Attendance: Introduction Project Team J. Lawrence c. Debelius J. Gi 11 R. Henschel I. Hutchison V. Singh S. Thompson J. Hayden Review Board August 4, 1980 P5700 .13 .10 D. MacDonald J. MacPherson L. ~~o 1 of sky John Lawrence began the meeting with introductions of all participants, followed by a brief summary of the agenda and speakers. A series of slides and talk was used to give general background on the Susitna Study Project, the various subcontractor·s fonni ng the study team, and their ro 1 e in over- all project. This portion was concluded with slides taken along the Su- sitna River ValleY:~ starting in glacial headwaters and progressing into the lower river basin. John Hayden gave a brief summary of the current status on all the various subtasks, with the exception of Tasks 4 and 5 which were discussed later in detail. Existing Geologic, Geotechnical and Seismic Data Virendra Singh summarized the geotechnical data currently available for the four sites of interest; i.e., Denali, Vee, Devi~ Canyon and Watana. ·This data includes a· surrnnary of investigation completed by others at each site, significant features identified and conclusions about each site. (see attached copies of view graphs.) Some additional data had only recently been received and review and compilation (subtask 5.01) had been consequently delayed. 'tr - I I I [ ( I [ [ [ I [ [ [ [ [. l [ t t SUSITNA INTERNAL REVIEW PANEL MEETING -cont 1 d page 2 Stewart Thompson gave a brief review of the regional and site specific geology for both proposed damsites. The geologic history is very complex and not well understood. Infonnation at both sites is somewhat limited due to poor rock exposures. Field mapping program of damsites and reser- voirs is currently planned but access is very difficult. A series of slides were presented showing general conditions and geology. At Devil Canyon there is believed to be a relict channel and possible shear zone on the left abutment which needs further investigation as it may have serious impact on site suitability or type of dam. Also, possible stress relief features (open fractures) exist in the left abutment which need to be drilled and verified. It was recommended that in order to prove the abutment suitable for an arch dam it may be necessary to excavate adits in due course. Slope stability in the reservoir also needs to be investi- gated. Permafrost conditions, thick overburden and steep slopes combined with thawing and wave action produced by reservoir can potentially result in localized beaching, slides and slope failures. There is a need to identify potential problem areas and evaluate effects of such failures. It was suggested that such slides will most probably occur and the effort in the study shouTd be directed towards a means of handling the problem. The large waves created by earthquakes or landslides was discussed. Ade- quate freeboard would have to be maintained in the reservoir to handle such cases. 1980 Geotechnical Field Program Jim Gill reviewed the geotechnical program as originally developed far the Plan of Study and the permitting requirements for the program. BLM is lead agency, however, most activities are located on native lands. There is presently a problem with the Chickaloon Village lawsuit over disputed - ( [ r ~· "' [, " i [ [ [ [ l' ) [ [ [ [ L L L L L SUSITNA INTERNAL REVIEW PANEL METTING -cont 1 d page 3 land ciaims which is interfering with field progr~ams. We are not allowed to work on disputed lands until the matter is settled. The major area affected is borrow area Gat Devil Canyon (see map). Based on a review of existing data, budget and logistics, the original program as developed in the Plan of Study was revised for 1980 with the intention of providing an increa.sed amount of diamond drilling this year with sufficient work in borrow areas to confirm materials and overlap next years program. The revised program as shown in Figs. J. thru 5, and detai1ed in Tables 1 thru 4 was discussed. Following the recent site visit by S. Thompson, L. Wolofsky·and P. r~1orris, the program was reviewed and revised somewhat further. Based on their recommendations the total number of diamond drill holes to be completed this year was revised to 3 at each site. (Watana BH-6, 2 & 8; Devil Canyon- BH 1~ 2, & 4.) The philosophy behind this change was to reduce the expen~ ditures during 1980 while still maximizing the data obtained, and leaving e~~ugh flexibility to allow for changes in layout which may result from Task 6 studies and which would then be investigated in 1981. Presently . BH-6 at Watana is complete and BH-2 is underway. The auger drilling pro- gram is complete, but had some difficulties as the materials generally contained boulders, particularly in borrow area E, and it was not possible to get holes as deep as originally planned. This results in need for deep test pits (probably in fall/winter) to obtain samples for 1ab testing. Other areas which require some further discussion and development include: -application of SLAR and low sun angle photos for identification of penna- frost high moisture contents (>7%) from thawing frozen materials in borrow areas will make handling and suitability of materials very questionable. t'.l // I I _I I I [ [ I [ I [ .I~ . [ .l .. L l [ l. SUSITNA INTERNAL REVIEW PANEL r~EETING -cant' d page 4 -intrumentation consisting of thermal probe and piezometers has to be evaluated further and the type and means of installation resolved. -existing piezometers installed by the Corps of Engineers should be reinstated and read if possible. Interpretation of readingsis current- ly difficult as riser pipes are filled with diesel fuel. possibility of using technical climbers at Devil Canyon for mapping. Discussion: A gener~l discussion of the morning's topics raised the following points: -at Devil Canyon there is a need to look at earth/rockfill dam alternatives and possible borrow sources for construction materials. all available geotechnical data pertaining to Devil Canyon is to be reviewed in Buffalo and commented on by the end of September. methods of sampling permafrost in rock and the significance to design need to be reviewed. Past projects have used 11 Chi11er 11 set-up with good results. There is a question of what temperature to use for solution to prevent formation of ice during drilling. -spillway designs and locations need to be determined at both sites . -it is desirable to minimize 1980 program and keep enough money and flexi- bility to allow for layout changes in structures. Emphasize features this year which will have a major impact on site suitability . -there is a need to advance layout studies to late 1980 to allow suffi- cient time for design of 1981 investigati.on program. -tunnel alternative layouts are underway. Any investigation (for tunnel) will be done in 1981, but will be a major change to the original Plan of Study. -there is a need to resolve which load growth forecast the dam designs f I I I I [, ~~ I' ~~ ( 1: I' .( [ [ L [ L l SUSITNA INTERNAL REVIEW P.A.NEL MEETING -cant' d page 5 are to be based on. It is possible to have range of schemes for vari- ous forecasts. -the earthquake factor to be used in design has to be established so pre- liminary work can start. A figure of 0.68 mentioned in previous Corps reports is a peak acceleration for 1 cycle and not for periods of strong ground motion which is likely to be 1/2 to 2/3 of this. An acceleration of 0.5 g is considered adequate for preliminary design. The impact of such a factor on dam design should be evaluated as soon as possible. 1980 Sesmic Studies; Virendra Singh summarized the seismological studies presently being per- formed by Woodward-Clyde Consultants, which include installation of a micro seismic monitoring network and identification and evaluation of potential activity of faults within the project area. The primary objective of these studies is to define the maxfmum probable earthquake distance from site~ and attenuation at the sites such that an appropriate earthquake factor and gound motion can be selected for design. wee is also supposed to evaluate potential for reservoir induced seismicity. It is expected that a site meeting in late August will be held by wee with a preliminary report in October and a final report in Nove.'llber (see viewgraphs). Discussion There was some discussion about reservoir induced seismicity (RIS). wee Preliminary evaluation of historical data indicates about a 90% probability of reservoir induced seismicity for Watana and a 50% probability for Devil Canyon. General consensus was that (RIS) would occur, but that magnitude of resultant earthquake would be less than the maximum probable design earthquake and should therefore not have any significant affect on design. ..... ·•·. - I ~~ ~~ Jl :! ! ! 1: !' I' I. I. I, I I, l l l:. I~ l SUSITNA INTERNAL REVIEW PANEL MEETING -cont'd page 6 wee studies are geared toward developing the maximum probable earthquake in project area and attenuation curves to each site. Acres is to select design earthquake. It is considered that three months of monitoring of the micro-seismic network would be sufficient this season, and that it is not necessary to monitor all winter. Reservoir induced seismicity is a potential psychological problem to people rather than a design problema There is some concern over the Susitna fault as to whether or not it really is a fault, and if so, whether it is active. The location is within about 2-3 miles of Watana damsite. There was considerable discussion over what earthqJake factor to use in preliminary designo Previous reports give values up to 0.68g, which is greater than any known values used for existing dam designs. It was felt that this value is the maximum peak acceleration for one cycle and not the value for the period of strong ground motions of significant duration which would be used for design. Normally the value for design would be 2/3 to 1/2 of the peak. It was suggested that value for preliminary de- sign should be O.Sg and it would be worthwhile to examine literature on existing dams in high seismic areas to get a feel for what effect it will have on the design of Watana or Devil Canyon. After reviewing the prob- lem in-house the next step would be to consult outside expertise via the proposed review panel. A recent ICOLD report has case histories of large dam failures in China due to earthquake. It includes very detailed analy- sis of failure mechanisms which might prove useful. There is a need to develop approximate layouts of both developments by early '81 so that investigation programs can be developed. It was gen- erally considered better to spend extra time in the office now (earlier than originally scheduled) developing layouts based on assumptions rather - 1 ;( ~ tli '! 'I I' I I': ~~ I. I ~~ I. (, [ ' l [ L l SUSITNA INTERNAL REVIEW PANEL MEETING -cont'd page 7 than having to potentially waste time in the field on exploration of non-feasible schemes. Conclusions Wrap-Up -Some of the key points which came out of the meeting were: 1) The schedule for layout studies must be re-examined and accelerated, such that preliminary layouts are available in early '81. This will allow for flexibility in the design of the '81 drilling program. 2) The type, layout and discharge channels for spillways must be examined. 3) Earthquake factor to be used in preliminary design must be deter mined. Very little precedence exists for such high seismic regions. It was suggested that we assume O.Sg until more data from wee becomes available in the near future. Acres should review current designs for dams in highly seismic areas with the possibility of requesting outside opinions/expertise. 4) Devil Canyon will require adits to verify abutments for an arch dam prior to design. In the original POS it had not been planned to use adits until Phase II work. It will be possible to use borehole data and down-hole camera, geophysical logging and instrumentation both to verify that the site appears suitable and that adits should subse- quently be used to confirm this8 5) To apply for the FERC license there has to be sufficient data for a specific dam layout at a specific site to prove feasibility. Some flexibility may be allowed for relatively minor changes after licens ing, but a major change such as type of dam, or location may not be acceptable to FERC. It presently appears that it is not possible to - l.l .P,: IJl, ~~ ... IJ ~ ti. l [ L l l SUSITNA INTERNAL REVIEW PANEL MEETING -cont 1 d page 8 prove suitability of Devil Canyon site for arch dam by mid 1982 in view of the need for adits not currently schedu1ed. Therefore it will prob- ably be necessary to submit a license application for both dams with a type of dam other than an arch at Devil Canyon, or submit separate applications as data becomes available. It remains to be detennined if there is any way to delay submission of Devil Canyon section of license application to allow sufficient time to satisfactorily prove the suitability of the Devil Canyon site for an arch dam or other dam type. There is also a problem with licensing if investigations prove that one of the sites is not suitable, and a new site has to be inves- tigated. Data must be reviewed as it becomes· available and discussions held with FERC people has been very cooperative in this respect thus far. 6) The question of reservoir slope stability and how we al"e going to han- dle it needs to be a.ddressed further. From preliminary site reconnais- sance it is obvious that beaching, thawing and slope instability will occur with reservoir filling. There is a need to identify those area which are likely to present problems, and to detennine what effects they will have on the reservoir and what measures, if any, have to be taken. This problem will be aggravated by tha proposed 100-150 foot annual fluctuation in reservoir levels at Watana. Aesthetically it could be a problem but should not have serious engineering impacts on operation of the reservoirs; It was proposed that an in-house revi~w be made of reports for similar projects to determine what alternatives have been used. ! 'I :a· I :I I, I e· ! I I. • ~ . I I . I, 1:. (J I: I. SUSITNA INTERNAL REVI~A PANEL MEETING -cont 1 d age 9 External Review Panel At present the status of the External Review Panel, originally scheduled for late August, is unclear. A five member review panel was recommended to APA by Acres. These recommendations are currently being reviewed by the APA Board of Directors. The last word was that APA may appoint another fir~ to interface with the panel. It is like!y that this firm would then have Acres make a presentation to the panel and then make its own recom- mendations to APA based on finds by the review panel. Scheduling of all this is still undecided as the other finn has not been selected yet. It was suggested that earliest possible meeting might be in late September. In light of this situation it was suggested that we (Acres) should recom- mend to APA a separate meeting of a smaller panel of outside consultants (possibly members scheduled for the APA review panel) in the near future to review our programs, since the external APA review panel may be too late to accomplish anything useful. This matter was to be looked into further by John Lawrence . Closing Another meeting of the Internal Review Panel and Project Team was tenta- tively scheduled for later this year to review the completed field data and earthquake data from Woodward-Clyde . If possible, site visits for review panel member will be arranged at convenient times in the summer program, with possible on-site meetings. Reported ~.• / .. ~ // ' .~' by '/I. '-j,.-f-~ ,._. .IJ. Robert Hense he 1 / ·~ .. I I :( '.1· . 'I I . . I I I' . I; I I,, ~ ~~ t L l . ~" A TT ACH~1ENT A .I ~ I ( I .~ ; I I I I. I' I I li, I; . -" ( ! I " EXISTING GEOTECHNICAL & SEISMIC DATA I. GENERAL A. Geology and Seismic Reports B. Site Specific Data II. SITE SPECIF!C DATA-GEOTECHNICAL A. Dena 1 i Site B. Vee Canyon C. Devil Canyon -Investigations -Significant Features -Summary and Conclusions D. Watana -Investigations -Significant Features Summary and Conclusions III. DISCUSSIONS ( 01 . ' I . ~ \. ~ ' . ~~~~..-~·~~~~,~F;.;;M~~;~~~~~ ~.~ .... -~...=--....._-.....~ :;! ~ wm ... _. .. ~. ··~-··:::::== 7'-~""' ·•••• -....... -_.,..,.. • .,_-:,.., • ..,,_·~~·-~· !i1 • / "'-~f~ N )J ·-· \ I . . ( J . !~ (~ I Q <. 11 . I o L,"\ J /till»' \ ' -071 0 . +"' 'a v JJ -r""' ... t-· ~ 'gp" ... Lo II lUI ~n I I \ ~ U'll;tC \ \ ....-J r..// _J, . ~ \ 1 I ·~ l ;,... .,. "'t rrcN£ , 4t·t)~ \ ~~ SVSITNC l ~. '-.._ , LAX£ \ /1 \ f U~fs\:_ .;~,_---G r _...., \..,....-rlf ...__:.J . PROPOSED OAt.ASITES • EXISTING STAHONS [j 0 S 0 S GAGIHG STU10H • SH<.'W COllfiSl PHOPOSE.O SfATIONS Q SHOW COUMI>( 0 Sf"[ AMfLO* GAGihCi V W.&Uft lhll H S(OIU(HT OISC~.UG[ (} WAT(H QU&l.ITY SUSITNA HYDROELECTRIC PROJECT PLATE T3.1•PROPOSEO DATA COLLECTION STATIONS IN THE SUSITNA BASIN-1900 ~-T~/~-76 11 . t. k ~. ti s BoREHot. 5s fi#IV zoo· oe£ p I+ tEST PIT..S . LA-s T£.srs JOO' 't. Peem4' i=~o.s"i-ee7"# A-SoTs. (o~P.R&ssrG!..S. STRATA-~OJ~ AoaOn, . M A-~, ~t)~ EAR.TH--QUAit£ MA-(.;NJ~r;$. S_S" A-r 4D ~P!..S.s .m DEf\JliLT . ml~)\!_ES-flGA~Cf.ON_: ~ 1 e; s e -· sc; us a R · s BoREHOLes #'IJ zoo· CS~P IT t esr· PITS · 11 .:A LA-s Tssr.s ~ON~~&.. t C/+flo.Al 6~~QP,TION I.NDEX TEST$ . PE.T~o6~t-t?*;~ 1 R E!.ATJvet y Le>ess SA Nos A-Nb 6~~vsw IJ ·OF: Oi'l~NOWN TH! (.~A}S$~ 11 -PERVIO~ s'na~rA .. F2t&11r A-eo-rm~Nr . ~ JOO' 't. PeemtT r=P-o~r-ac-rH A.Sors. L. (o~?R5.SSU~L.£ STRATA-~OT"t+-A>aon. L MA-~I'PAU~ EAf<.TH--Q\jA~5. MA-~NJ'TV~ L S .. S" A. r 40 rn,!.. s s , .. , iJ ... " '·' - • fiMtlLE~18.L_ ~?OUJ~~E;~ .. ~ ~ PeRVJoc;s ---A-DEQuttT& o,s-TO s-Mit..5 HAUL 11 E PRO~.~-~ i\1\ s.: ll .1· DeeP PE.ernA t=P-o~r (om P ~6$$ r S!.S Fo VNOA-Y"Iai".! N\7' !....S. Exc..ES$f'Y5 Fov;vc~"'i'JON TREAlM~.?·rr Pe.Rv;ou~ sr~H-rA-.-~Jt:tHT' A ~\J'r.' DeeP GuTeFr= L I G..~ I F~eT"JOJ\J IJ.s U.MM A RY : ~ Mov~ SIT'E sooo' D/..5 E~re:~-.ssJv£ Fl£!..~ IN~rssrifbAT'Io~..s REQu1!< E-D - .fl .n n n n n n n~ D D 11 - VEE CANIYQN ... JSTRI:JC.TU.RF,: 470~ HI~H t=AP-nl l)AM :1 1<7 bO-I b 2 lJ s B R fi 13. BoREl-\oLEsJ l~-T~LF ~ !S0 1 J'AA~. l J b D 0 ~ER.. Tl<ENC,.H E.S n . n5lGN1 FICAN 1 · J=fATU.E ES: _ VER"i 'STEG.P C.A.N'(ON ( 0~,) . ' 12.S 1 Ov 61?_ s v !2..D~N PooR QuA-t.JI~ R6c:..K SttDOL.E DAM 40o' OVS r<.. Sue.D EN .. n PSR:MAF~Ost 10 >G:>o' . D P.CCI<.LJNE 85L.DW E X/STIN<':J. ~ _ . . . e)vs12 s.1. JM.~ I ~RlA L 50V Rc-_~5.· . ~· w . Nor DELI.Nt=A-TP.D ' . GLA<-Io -FLUVlA~ Fof2.. SMBI+..N~WJ~r -R IVE:.R. C.HitNN'G.L FOJ< .466, ~ .• r· • ,r:., ( r . f~> ~-' ~-.·! ' rtt ~ . ~' ~ ,. ~· >' ' ' ,, ~\ ' ,, i ' I) - n . I . ,. ~ . . J r£mh?ARY: n E~TeN~Jve. G RooTPNG ~ Ds:T~ItS'~ FOUNO~fJON A.NO' ~f!Jti'.-MGI<J (g E){PLoKA·T10N RS:.GUI~E~ IJ P H.o T T UNNSL S ~ e<:o n.~ F'i1 ErN 0 £ l:) 11 . . ' . ff re#)FLS A-<;~~€GATe' A VI+N .. Awela~J ~ Peoc.c.~st...v~ es.a•c. · I ~· • f' •-~ - / . ~ Jcrs-o-:s3 ~ us B R~ R£eoNNAISSANe.e. n 1Cf7S'") COE ~ ,, . ·~. p ~/\~ J CoE· n l '78 n l . ~ H ~0 1 TO ~CO' DeGP 27 Tssr Ptrs f ! /.g A u't e H6e,e s .. \ I n 4 7' 's-' l.. F SE:I.S:/?11~ ~ U .L NS f~UMEJ.i TA-TIC.Al ~ lO Pte'2orne.re RS 13 Te.MP. P ~osss ~~G~JFI(flNT. EEATURt;.~ ' U 300 '-,00' ~~ DS \JA~L.S'\', 30" ··~0 41 S~O~.i Al-.. 1 e~ot 0 ~J"!j~,~~~·fJ ~ -.~C'J .... C;· ~~c-... ~ (.; r--~ ~ ~ · · . ~ ' [ S •-40 W€A1(-;S~S C /C~(!6\ A Lt. u v p,,i M - . FRO¢. s.N J?.:) ~0 ~17"' t R s~t~ r c.. HANNG.!.... uP yo 4S"t o ee ~,; F I L.. L. E 0 W l T H-G ~ ~<:.. !A L AN 0 A~t.,UVIA~ n;n..s" . {\lEAK.. vE.R.ri~AL. sH E.,4~ ?;ONe,! . . .. , f~~.~c:-~ STRUCTURES '9 m , >?wm&i11!: £bi£ 4 Roc.K C.ONDJTICJNs-PAVORitsLr-. Sc::Jvne; "SUPP012TS 2SG2'-'12SD 11 ADD1TION/Jr)._ G..'/-. PL..Of<A-JION n Gsr~e~~~--RCX..K ~TRU~rt)'f2-E. fl .. -RIVER. CHANNSL -FO~ LAKE 'FAVLT'IN6l r; LEAI<A-6 e. ~ . g lGHI A-BU!.-SLJ DE. 13l..0Gk (.~J (; -OVS-R. 8 tJ eD~N [ IH-1~ K N s:.s S ll L 5!= r ~tJr. -PSI2..mt4F!2o'.sT [ 6 0~ A-ea+.s -~E:. DS.f:o.!SI~ lci SPILLWfo'( -8Ul2JSD ~rt2~r:4 ·· · C..HANN6L- r D0'~4\~r :sr/2~AM -~l • ~~ ~ $tiSI IJJA-. FAULt~ t l' , - 11 [ l . I . :J: ~ [ . [ l ATIACHMENT B 11 . • 11 I ' .J L [ l [ I I • - I I • : • ll :: . >- ... ; " . l. .. ~t., 1 l""'uc-r-t r '\ flVDnQri cc-n!C f"'lr"'· ~ rr-CT ~ '-' l I I ·~ J ·~ I I I \ -: --1 1. ~ r-i \ '-I.! = , TASK 4 & 5 INTERNAL REVIEW MEETING JULY 23 , 1980 1980 GEOTECHNICAL PROGRAM 1. Scope of Geotechnical Work Contained in the Acres Plan of Study. 2. Scope of 1980 Geotechnical Investigations Under Bureau of Land Management Permit No. AK-017-0096. 3. Spring 1980 Revised Program. 4. Currant 1980 Geotechnical Program. ACRES AMERJCAN INCORPORATED Consulting Engineers 2207 Spenard Road Anchorage, Alasr.a 99503 Telephone sc; 276·48SS Telex 91·642:3 ACriES SUF - 1'1 i ' j I) . ' ,, ~:• L L ' J .. ·-.. ~t: :: .. -· '~"·· . ~: 4! ..:.k-: .. ~. ':" ~---~ .. ··- • .6 • -· ""'-•• .. .. ... • ··~~.:r :: .. /"'": -. ::--..,. -.:. . ... ~ .. ~,.,-.. . ~-<.·•/C.,··-..... ... ":.. ";~ -~.).; . ·:. ..... • • ,.::..r .; :J .... • • .•... ~:r :-.. .-.. .; !"~~ ........ -......: .. - ca. -· ~ , ~ • .;..: :~ • i -... , ~·· -· .. -... ~;:-· ·-~~ ...... ~ .. _. . i. • ... '· ':" ... i' -...... :. ·:-.--· t .. . " .... --~~ ··.: -~... . . . ... .. ~ -,(; ~c ' . . ' e~o• ·-'~ •':.~ • •• (J .. : ..... r .... ·\.t . . . . " ,. -~ ...... -.... ·~· -".. ~· ·-. :--> ... .. • \...;.~._ - -• t ···-· ---1" .-,, -... .. ~ :. . . : .. ,. :: ··-,..... ---1 e.~~-·· -~ . .. . " ..,.,., .. ·;:-1-r . ; .. -· ff~ ~ .. '. • --·· -~== .... s , --•!:: ........ ~ -·:. .. . --'i. ~ . • l ..... --....... lr· -........ ~,.--:...._ .. ·~ ·::-~ . ~ .... ... • ' ~ •••• ~ ! -.. • ..... _ .._..... ........ !:•i:. _;. ~-.•. ~ \.•. • -i-... . ~· .___,.--· • ;....?",:. : • • -.• .. -~ ' .. . .. .. ~:. r: '" '·--;.___:.. _____.... ~ . r .. . ,. !.. • ·..._. ................. . .. '. "" .. .. !'•· . ..... . -.. . ....... -·· .. .•· .· . -· . . -.... . . . . . . . . ·. .. -:•·-·• ..... .. ... · .. . .. -..... ,_ - . . : . .:. . . .:' ........... ;. · . J • .• . ...... . ·:. ·: : . : ... ;:'It t .. ';· . :-:.-- •• Ul •• .. . ... .. .-.. •'-... : ~· \ '~.;.--.. •r:r. "':.. : ....... __ _, .• .l - ... •-:. ; . ... . J , .. -=· ... ·.· .· ·-:· . .. , -.. .. ~ . ·. ~--...... -' ... ~,~~~·-~--~~~-,_ ... _. __ ~.-.. -•. ,..1: , •.._ .. .-~ ~,:. c ~ · .. ,.... .:...-• . • 1~ •.. ""-...... ,.. ·-· --, .. ,. . .. ;'--I • • • • ~ •. .· :-... ! -~-.. ~ --...._.,..---... -.... '--'----... _-·~-. ------.: .-; -.. • 1 .. ··...... . -. , ... _ ... ~ . • I ... . .I -. ~ .... , .. .. .. · . . . . ... ~ ... .. . • ... -~' .;.. .. . .. ---.. '· . ! :-... J. ·-... .• 1 • _J: , ' . i.: ... : •• , '•i . I.' { , . .· ~ . . --... ~ . . ~ -.: . . ! ·-... ~-~· . _, )}-'. -. ·. ... . ·-.· -. 0 .-or-..... -;.,_: \ "~ .. . · . .:": ... , ·-4, • . . . . . , . ..-.. •• ,._ .... J·. ---·· : . . . ·.--. ;,· -~--;: .. . ~ ,-,. . ~ ~ . . . . _.,~ ; i .. . I •. -;-t:-. } . . ··-·. I : ,, ':.}. : " .. :-.. -···, ,· ... ~ -··. J ..• : ! i .:,.. -~ ·!."',' ,. ...---.. .. -I ~ .. : -· .... :-.,r .... '.' . .. ·-~-· .. ·..:: -~ ~ .. . . . :. . t' ~ ·. :r---. ~. . -..... !:. :.. • ...-..· ·' - \ -: •t• •• ,..~---... •• . .:. . 1., ... ;.-- : . . if.: . • ! .. r I -· . -=---~· .. ·-------- ·. -· ... ~- -. ... . . ·-· :'• .. · . . ,· ·-·- . --- . . • . . ~·. I t" ;,. • • .. .. : ' ----... ,-. . .. .... --· ... .,. ,II:. ..., . ·· . '"'· .. .. .... .. c:: • .. : - .. ... '-- ~:. ..,.-' ...... · -.. "·r ........... . . -)%" • .. . ""·~-~. . . ......... .J • ....... ... _ .... .. -.. -...:. ·-.. ... : . .. . · ...... ., ... •. -. .,......-.· I . :~ . . 7't . -.. ····~ . • ... -... ,. • . . -. ·~ ~·:. ~: .. ~ .... •·· . -~ -· .. . . .. . . ...... ·--. -... "'---:· .... . .. ,. r . .. - ~-~--=---'·- ·-. .... . . . . \I PIJ tJ • i !IBJI-1 1!.~---~~ rl!!'!! ,_ !JIL -"'·' ~ _..l :..,.,....., .. -o..f ~ 4 ·-· j ........ ~ tl'!ll!la. .,.;,;"~"' -,;J :!:--...... ~ ·-, r.;,:;.. ... :,.;' .•. ~ £.~1~ ~ ~ ~ ;;;;,:;t ;.''~ !!:'?~ !!"~ L---~ .) ...... "----·--~4~ ... 1 ~ ~; .. ,,.;-~ P~l~t. .,_,vc;; ,P;('tJ~d!.-?""7 /IPI'IlOX. .4.ociJT/aAJ £-ictl. R r. n sur. .e r. I? 8 vr. I I ~ r. 4'lltJT. I I A! r. ,?ddT. J!T. uour. ~r. /}Qur. LT. /JOvr LT Adt/T ~~v~~ ~ ~~~c:.e % I J Hou t9ZillJVT/I l;yCJ. i.t:AI~)If p~ 1/t/t/.t(V oo Tt!c.r,v~s 1 sP~'I/JI. res rAY~ jl$0 .l/S6 - - - ;t~s· 6o• -- I ,o• I J.S'O-Jllo' I 55° l.ltto -.roo' I I 1--'EIZr.l j'()-/OlJ~ I v~~r. I l.tJo-Joo I vc~r 1 /PO-JtJo I 4 boca 7i'O --~-~~------------~~---------~---_ ... __ _ GlfO~OGIC Jr,evc ru~c VEJlJCirV IJIS t:tJ-41T/..VvJrY i Pcllflic/IQ/1.//Y I . GetH<>GIC sr/tu~ru,e4 (;A.<tP4'n~N/ft. C<>Nr4~T~ P.f~MC4d/'1Ti' CA'm~.c-. .) ,/ . / . VE'L. e>C./J'Y P/s~o.vr,r~.l,hTY tJtJ/tteO "H~M..vs~ ( ~~-,YP(S' &Gor1'/YJJ'~ 1 ~ . • OV£'~8U.tPev' T&'/C& .VtiSJ' co,e.eE~~,re IV/ Se%J'~'< / OVcJ( 8U~~A/ TH/Ck"-'dSS Ct:IA!~e~41K t4y'Sc/S/'~tlt" / OVG~ .ov/l.oGAI T.HICKAIIS"r.t coll,eli"t./':f/C ~f6"/.I/1uc ) GtSoL.oGJc Jr~ucruL e ( FQtJtr ,-» ,( ~~~ cN4~_.,£", ? ) 1 p~.£m_, cAmE~Z~ c;k>/AYJ T/l£'~fruUO~ / .,0/cZ""'"'o.Tc·<. I VE/tT I /OtJ-15'0 I OVE./(. Oli~I.?Ei""N T,Y/CA:...Vli"J'S GtOI.OGY ~~I(? / Pt:ll.m rHc/l./lJIIt"~~ .JT/?.b't:ru/t£ t0° tPo-J.ro' GEt::'LOG/C $/~V~V~ (~OW<f"~//OVt6) I Vifl/'.1 I /OtJ -lf"O I ove~ QuJl.~l'iA/ TtYtcx.VOsi Fau.v .P~n-~ "/J'#.t:i1 ,1 "EA.T I /OIJ-/S"IJ .Pl!~,. rtJA:. c oF/'t:'"< <7,y.,.PJ o l/l5 .<..OvA:.. a ti' A/ Ptiit!'11 • T,Y/c-t: NcS'I _r-:ot'-'Jo~ns~.V .J ro~ Cor'ri!~P4-'F7 ,4.VP / ... /(..dt"'/.i /MOl C4 TP.<:. . PeA:~ C4~f:,(4/ GcO- .PA'Yi"t~! TIT~~,,, Ttt~f / /" ~ ~ _, € #*'if d'-' (. ~ ;-.Y' .PcA?."'t'"' d/"r/ rt• .. J ~ ~ .. . • · . .. . ··-· . • .. 'I• .,,_' "· ~ ::·. ,;' :·. ' - I) '' .. ... ... ~ ~ ~ ~ ~ ~ ~ I f I t I f ~ "-r,~i;:;~.;;';;;;-?-:":-?,~;-;¥;~··-;:.,...~----..-···--'-·--:---~-:-·~··~~. ----·····"· ~-1--·-··· ?----···---·3!:~ ... ·----~-~--~--~---·-----·-~~-"·----~·-· ~ H~ .. . . - 11 'v ~ '!J v "' \, "' ' .... ~ ~ ~ 1: ~ .._ ... c< ~ ~ 4 ,, '' ~ ~ ~ ~ ~ fl ~ ~ f'J ~ ~ ~ ~ I! "" ~ ( ~ ~ "l ~ ~ ~ ~ ~ [ ~ " ~ () Q ~ ~ ~ ~ ~ "" "-~ ·I: :-..' .f\ "~~ (ij ~ ~ I" ~ ~ ... ~ ~ ,, ~ '~ ,, ~ " ~ '~ ~ ) " ""' ~ ~ ~ t " ~ ' ~ ~~ ' ~ ~ ~ \J tJ ~ ~ 1\t t!l ""' '\ ..... " ~ \. ~ ~ ""'' ~' ~ v, ~~ ~ '\ ~ ~ ~ ~ ~ ~. ~ ~ ~ :', ~ )' ~ ~ ~ ~ '-1..:, ~· ~ ~ ~ ~ ~ r ~ ~ :i ~ ~ ....,. 1· ? ~ ~ ~ ~ ~ ~ ~ ~ ~ ' ~ ~ ~ ~ ~ ~ ~· '-\ ~ ~ N ~ ·~ ~ ~ v 14 ~ ~ ~ ~ ~ .. \) ~ ~ ~ ~ ~ rq ~ ·~ ~ ~ ~ ~ ~ ~-~ .. ~ \;; ~ ~ •• ~-~ ~ ~ ·~ "' ~ \J ~ ~ ...., '-'-""'" I ~ ~ ~ ~ 1Y· . -.. -. ~ ~·~ ~ ~ ~ ~ ~ . . .. '4 ' ~ ' \) ~ ~ ~ i:: .. ~ ~ ~ ~ ~ ..., " ,, ~ l:, . .. 0 ~ ~ ~ ~-\ti ~-~-~ "" . " lU ~ ~ ~ ~ ~ ~ ~ ~ ~ '::.., -. ~ ~ ~ ' I;' • )t ... <:1 "' " ' " ' .. ~· ~ t» ~ ~-Q• li:\ r -~ ~ ~ ~ Q ~ ~ : ~ o--. a-~ ~ "-.! .. ~ ..... -«.,..· ~ ~-. ~· I ' ,., . . '-1 . . ~ ',~ ~ ~ " . -..... ~ ~ 1.:;: ~~ \'\ ~ ·~ ~ ~ ~ \1 ~ ~ ~ ~ ~ ~ " ~ ~-u "" l.\ ~ '.::~. ~ ~ .... ..... . ... .. to "4 "" ""( ~ ~ ~ L~l-~ ~ '(.., . . ~ ..,J ~;--., ' t'( ~ ~ ~ t) ~ l I I t ~ f ..... ~ ""' ~ ~ " ~ ~ "' "' - [ 11 ' 1: l! J ~~ [ ' li. ~~ I~ I' ~-~ ~- I ' ',;t. ~~~ ,, . J, r ' . IJII>J~ :'l !:0'1 r:r c- I c:.- I g~ -... I 2'- j toe ..~r. I ~~ l ~--.. 1(:1 . S!! I ol ' l --.,-~"" ,.:.1:1 ~ ·~ ~ \1 ~ ... ,.. ~ ~ ~ ~ 'IQ .... ~ ~ • \~ ~ ~ ..., ... ~ .... I:J ") ,. ,.., ~I "'' .I. II I ~----------------------------------------------~~ - [ I I. I' . --- l ~~ [ [ 1'1 ,, ' [, ~~ I' ,, l I~ m·· ,, ~~ I. ~~ I ~ ' ' ~ ".' t 11 ··' ' ,:J .. i. t [ L l I I I I i! 0 .... c • 1~-~ l I ~ 0 - I ~ Q 0 • z e e: ·[ 10 ' } lj . ~~ I' _::..~ - 1.~ t I, I; I. I. ·m· . . ... . l . . t L ATIACHMENT c -<:.I f ' ' ' l l ft. ·-~ 1980 SEISMIC STUDIES I. GENERAL WC~ Project Team -Status of 1980 Activities -Monitoring of Program II. SUSITNA VALLEY SEISMIC SETTING -Seismotectonic Setting -Available Historiccl & Instrumented Records -Limitations of the Record Data . III. PURPOSE OF THE PROGRP~ -Definition of Seismic Event -Source of Seismic Event -Surface Rupture Potential IV. STATUS OF PROGRAt~ ~ Office Studies -Field Studies Microseismic Network V. DISCUSSIONS - r ~. I . i : ~CC PRINC!PAt-IN ... CHARGE I. ~~ . I , I_ l: .. WCC PROJECT HANAGER G. E. Brogan •' • • L.. Cl.uff, D. Packe= R.. Forbes, T. Turcot-te W .. Savage (~·~---------------~~-~-~ ... -- l: l. r ~· ,, .~. 14 658A-4000 WOOD~ARD-CL YOE CONSUL 1 Ar:TS PROJECT ORGAUI ZA Tl ON ~ -~· • 10 J~ 1980 • - r . !' •••• IJ. u· . I . I ; ~. : . I. I ! lu ! : -. £: . 1: t ~ ,• .. 1·. I . "" =:J l . . . . . . (j 0.·. ·\}} .. , .LLl ~· . . t= J ~ }-' --t Ul .0. ~ . 0 !~ [ ~~ I· ~· I t· 'I I m· 14 I. I [_ [; . I~ . I. ' . . .. ( [ - - l ±=c-i+kJ\ c PrL .P 4P.., T \ V\C..l ? Lf:T ~ oP ~Tub'{ ~u f.Pit;JJ I ( t I. I .. i~ .· •.cr-\ - l Iii l. F -~ c :: -c. ...; • -.-> \.:J 0. -...s <: •• I ~ .;•. '-'J """ ;:-./ ,. / 1 J .• 1 I . I : . '. ! l . '. : l .• '; j ' ""' 3-\ ~~ o~ £A12ri+QUtW.E.5 -~L\DW Ue:c\-\~UAY.E - 14-A. t pA-ct fElL fX-A-T.E· . CoNrtT-CT lD I T ~·' f\) N · f\ · pL~\:C... CRuST .. b~ .. ID r:>,. "~ """\:.-\ -0 F-J\.G,. \ tJ ~-c-\ \'J ~ l rV ~E-W \() f-f--?:: o IJ E - [ ; i r. -·---· -·-. ··-·.-. --·· .. _ .. ··------~------ r : [· [ . ( . 1 ~ f ; ~ ' ~. ~ :. ~ . t ! F : t r l. l r ; L • r ; . ~ [ . . t} . ~ = A WE1TfHU1 OE.~filt BON.i=..R. ~~~6t _FP.Ut.!J ~. M J F~Ul5 ea ~· ,r ~ ~~~ ~=---~,~ ---)------;-.1-------r--1 c.RUS1n ~LOC.t\ • I j & ! SCAle l'N Mtl.ES ' • ',i \ ') ~ • l I l ... . . .. • . · . · . ... < .. ,;. ••••••• ....... ·,-4 .. c :..., .. , ...... ·jr._···~:, ••.• -·.-. '-'o····.~· ··: ~-· •.;, .• .= .-.. ,. ., ... '(IIIII# --= -· "'. --~ ... . -~ ·- "' c::a ·" .. .a. 0 " • •· •. ,_~ ......... -• .. • c. c.. .l • • • -.._. -• •• • • .,.. ·I ·. ... . . ... . .. ~.., -~· .c, .·.·~ '-, .-:: .. ; .... :· •.. c:. --c e-.. ~ ~ .. ·-• . -o· o • · .. ~ ~·, !::· .... · 4.4'·-~ " -:::; .. ": -. . . . .... :-"':"~. . "" .. : •" • Q. 0 I • ,;: .,•.:*'! • .:.~ • • • • - -•.: c. . E E • 'Z. -N == ... : •... ~: :-:· -.... -.... ,.. = ..:=-· •• ~· ... "·• •• :z 0 -,_ <:: C: c: ·~'. . -e - . = ~ 0-1":11 '-..... " .. : c = :::.. .. 1--~-· ·= . · ... --~ ., .. ·-. ...., ......... -=-QI~··:·. .---.-. ~ ...... ~ ... =~·.:. . . . •. . ·· .... . '· .... .... ... .· .. ·-..:~:-.., Q :--~ -= · ... · . =--·.-. ·:-I z ·. :s ·-,. • ,. ..a .'CQ ..=. .. . .. .... ---..... t:l •: .· ; = ~ .... :. .,• ·.·".· ..... _. == ~_,_,... .., .0 •. .-·· e ~· Z-.-:. . ,; ·. ·:·.::·~ ... . : .·. ·•· . -~ .· · .. • ;....... . . .:..:;, .. \ ... :·.·. ..... "' .. , -·. -: ~ _..... .• "t::. ~:·:·· .. ~ . .;,; :. ~· .! ,' •. '• : ; -;'; :... ·~~ I" .. :.: • ... .. :..:.1 ·-.:. ·-· .... .; . .:--·-:~'-,. __ · ...... . " 1 :-::· • "' !~··" .·.--.. ~ ....... . ~ ·. ·:.1.. ... .• -~:..; ·-: ;~ .• ·::'!' ·"' -4 ~ ......... • . ,· ;•. :.-: .· .··t:.'f~ _._ . -f.. ' • ..... ;. •• .• r•l --.~ • •• • •• -·· • •J . .-~. ~-... :::· ... ....,; ·· . .:.-.~· ." .. ,. .· ·. . ~ ,.. ~ ' ' -. -'~.· . •. -~;....~'·:-............ : ••. • ••••• -! ~.,:. . '. -~.--::.:::_... (·: ;: : .:.:~ •. ~.:.:-:.··: ' -~~-· · ....... :,;: -: .. :-·-. .,. ""•:. ·: ~. ~. -:·: .,. •. ~-·,.··.*:.·~· .. -· ~~.,~-':-·~· .~~· ... p • -~-.'· .... ,:. -::'~ • • ,. • ,.'f• -• • " ........ • ••. ··:.-· ... :.-:o·· •• • .•• ··: ..... -.:. • ~·-··-:.r:, .... -.:: ·• .. ., .. " : . I .. ·;:~~;.:§'.:;.:·::.._'"!:-: l .... ;.~ : ... -... -,;,.::.:,~~·; ... , . -.~ .. :-:~ ; .. ... . . ·. . . . .:..-[.::.~:·· -;~a ·- .. ·-·· - , . . - r, •• : ·•·. · .. ..... -.. .• . ; . . . . . . . . .. .; . .:·. .... -... . . . . . -~· . .• " ·---· . -.... • ........ -· .. -. --:~ ...... :. .·· .... • •• •• .... • tt ~~.:.~ ;~-: ~... . • • .r·::: ••• ., • ""' . ·.-·~ .•. .. .• .: 1• • .. -. . ... . . .. - ··-. . . .. . .. ·. . . ·.• -· k .. . '· . .. · .. .. •' d - -----· -- - . . . .. .• .. .# ~ • ... . , I .. [ r:, t £ B ·I B ll ·~ I ~ I I I I I I I I A\J A\L~~LE ffis.L~$_ £:. )US"T\<..U\1\CZ..AJtS<Q bAT A \ s --L\11\\\t._~ ~~~~ lh.s.~ ~~ Qb~_,t- . ~ \Lta_4 Jo o trR~ b~""C'~ ~~ ~OT cus:;e_l'-( }~~\~t&-. b~Cou PLI ~ ~,1 'l 4 ~ £ ·11 ~ ·~ ~~ I l ' ' I I I I I I I I • • J I I I i l . ! . . . i r i ~ : I I • • • ... r ~(:} ~t-· 0 --0 :z -~ 0 \P l- $ ·-Ul ill \J} i-- _J _J ~ 4_ 0 2 -o! () Q -\iJ F JlJ \{) -Q! -r -- 0 • fj ~ :z -ti • ~ \.f1 ~ UJ . -.. . UJ ·o :> :> 1--. -- t \P <i I lll ~ :\1 <i gl :) G ·o . :I' uJ }--\5 D! . 4 . u lU -~ ~ \P \) -Ul -\D ~. e e ~ . \ ~· I -~ I I I I I I I ~ '-~ ~ • • ::=>. 1 t= -I ~~ ~-'.!!. ~ ~ ~ c~ :;:, e~ : '2> ~ \.~~ :::::..:"" ~ -f(~ --._..._. . Wf I l\ ~ "'* I ~I .... i ~'b,li ~ .... -~ l . .. • w .....J >-!-- ·\P !l () lJ) :z 0 :z 0 -L !{ ~· a e:l· fl. • • • • f . ~ '~ ·i~J:''t'""-:-;-;::z:r.:·~--.--r~·~-c-·•-:-':-•--~w~·~--~··~-·····-:-·~·· ··--~·~·--.... , .... .,,.T. ·~--·--·•·-·•·-...-·-~:~ .. ~·-··-"'\r--~---~-------~-~--~.~~~ ] I~ ;. ·~,,, ,. ·,,1 ~ -.-. . .... n tl fj E tJ I Ei El tl I] fl ttl • I IMA 0 GEOGRAPHJC LOCATIONS OF SElSMJC ·STATIONS. - • ·~·i ., '-! ~~-~ . '! ·;,·! '. •! '! ·~j . I 1 I I :~ j l I f • [ ! l "•'-... -~~ I ~ t . . <-. . .. q ' • , T . ;s .' • • •• b • 0 . . ' N VOLCANIC lliOGE . ----··-~--·-... -··.. ·-·-·-A I cs;kt:~I~~:~,~ISULA I TAENCI ~-------~?9 :tuo kn ~ -. ] no·- ..... :t \00 ·-t: lU a \1<\ ·- l~l\h 160 ·~ 100 ... 200 I .. Q(\ t= f\00 Q\ ~ ~f\() • Notes: ~~.j~~~·~~~,~-~-m.~~ .. ----~"''"~~ ""'': ..... •' ·' -~· ;.·;·~ .·· ... :-~""'' -~P·-;, i~oo~~"· '~·~=~1~~~;:~~:.~··.:::_. ~~~~)'-~''~"' 0 ~ .. ~ .. ~~~~::-~:>:~ .... ·.:·: ~ .'\'\ ,, .~· .... '~':·~·-'' ,,,, ...... . --..... , ... -····'·'5>~ ....... ·.:-.-~······'''''' .... 4 .;.;,·.'' ~ .. , .·.'~ ·:'. ........... ~ ~ Up • soo Os ~ 260 I) Op and Os are Inferred avera go values from p and 1 wovo volocltlet. II) Location and dlpa or IUbductlng plotos no achomatlo, Ill) Soo volumo I I Sootlon 2, ~ \ l .. ,,.1 [ , . . ) [ I • 0 I f It [ 81 .. Cl, :::t' ~ a) -~ g . ~ - 8 -,... &n - -z < c a: -< t.:.. Cf.>UJ a::z ~0 ·oN i-. zu. sj·o u.. ;;oQ .-z • . c:: !. I l i -• . ~ ::t" -8 . c :::t" - C::: I ' l • N, ., - s· . ::JI1' an - 8 • -e:: .. ,. - :r:w r-m 0.. wu.. ~ro~o~------~8~----------~--------~ ~ . -w • 0 tG "' -l.U ":l '=' ..., 0 -.. t.r. ..... -;--VT ..,.... -~ c ff> l:JI ,1:) 0 =r • tC -"' ~ =-- [ [ ~ E I L - 1 l 1 ,If( ~J [ [ [ ( L L~·- f ,,.. lL \) ~ lU - > .l.ll tJ_ .. . i ~ ~ \!J. Q DL [J_ ~ _J ~ D \fl _j \l1 . . DL .. l1.l --LL. \J \1j tr----- • • • • [ [ I .. ~- l • I -.. ,... . ~~ ~I ~~ " R\5. WP.t1Et \J.t.Vt'n ~ 260 I ,, 1 f • 240- I I 220·1 20C>·· • 180. 140· 120· • 100·-~t}'2 ~37 • s • • • • • • • ~31 -~, .. CE'llL_ ~ • CMr~o..- • • • . W£;TER \JOLUME r:-:-2 • ~ • • • • • • • ~··· • . "' .. • • • • • • ·-. - • . , £§ • • • • • • • 4Q-. Ar>ot~am..te+,o 1 't.OOO r'l's•r•cW'a . withOut ••~'ed RIS not ~ne-d • ~ : . • • 20·. -- . . ·l -~ ~ •• ~ •• • • • 0~.--~~----· -·-~-~-·--·-····-·;~~~·-·---·-·-·--~··~~~~~-~·~·~~~-~--~-·=~~~·~·~··-·~~-------------~.-----------~. 10 100 1,000 10,000 100,000 500,000 Reservoir CaoacHv in 1 oerrf Oo;.arit~mic scale) EXPLANATION; A=~;ned as. of R 1S, m1ximum m~"itude-~ 5 ; .Al::.=ptr:d c:ase' of. R tS, maximum-J"na9t'titude 3-5. Ac::::;:rte-0 c:.;w of R IS, m:zximum-m..gnltude S 3 Ou~t;Oflf:..b&e e2se-of R lS Not RJS ,..~ Th• 1o!·•~"9 ,...,., YOtt"l \Otlertr net c-Ion~ ~~• of insutfic....,.., a-!a: ~~nan. • Sharaonlhl. •.e1' • N""'x (USSR) c:l4-ptl't i• ;,. e)tetss. ot 2SS m. • 4 -REPORTS BY OTHERS ·r.,.,.....,..~ ,,I :\ ., -- ! ', lr I-t ··r' ~· I' r r I' l l~' l f l 1: (, ll ' ( I I· •• I. ~' If SECTION 0 FOUNDATION AND MATERIALS TABLE OF CONTENTS Item SUMr~ARY OF CHANGES Changes to the 1976 Interim Feasibility Report Changes in Design REGIONAL GEOLOGY Physiography Inferred Geologic History Regional Tectonics Seismicity Rock and Sail Units Rock Structure DEVIL CANYON Seismic Refraction Survey Material Requirements \~AT ANA SITE Scope of Investigations Field Reconnaissance Test Pits Seismic Refraction Investigations Instrumentation Site Geology Introduction Foundation Conditions Va 11 ey \~a 11 Conditions Relict Channel Spillway Permafrost Ground ~1a tar Reservoir Geology Dam Design Dam Foundation Treatment Embankment Design Powerhouse and Underground Structur~:s Intake Structure Spillway Seepage Control, Relict Channel i - Page D-1 0-1 D-1 D-4 D-4 D-4 0-6 D-6 0-7 D-8 D-10 D-10 0-10 D-12 D-12 0-12 0-12 D-13 D-13 D-17 D-17 0-18 · D-19 D-21 0-22 0-23 D-24 0-25 D-26 0-26 D-27 0-29 D-29 D-30 0-30 r' " '.·~ l~ f l f I' ' : TABLE OF CONTENTS (cent) Item Construction Materials Material Requirements Sou·rces of Materials General, Roc!< She11 Core Material Filter Materia~s Concrete Aggregates Gradation Envelopes Number 0-1 D-2 D-3 D-4 D-5 D-6 D-7 D-8 o ... g D-10 0-11 0-12 D-13 0-14 D-15 D-16 0-17 LIST OF CHARTS Title Soils Gradation Envelope -Borrow ft.rea E Test Pits 1 through 5 Soils Gradation Envelope -Borrow Area D Test Pits 8 through 19 Gradation Envelopes -Borrow Area E Superimposed on Fine Filter Gradation Envelopes -Fine Filter and Impervious Core Gradation Envelopes -Coarse Filter and Borrow Area E Gradation Curve -Composite Sample No. 1 Gradation Curve -Composite Sample No. 2 Specific Gravity and Permeability Report Compaction Test Report -Method A Compaction Test Report -Method 0 Triaxial Compression Test Report I -Q Test, Composite Sample No. 1, 3.5% W.C. Triaxial Compression Test Report II -Q Test, Composite Sample No. 1, 7.5% W.C. Triaxial Compression iest Report III -Q iest, .Composite Sample No. 1, 11.5% W.C. Triaxial Compression Test Report IV - R Test, Composite Sample No. 1, 7.5% w.c. Triaxial Compression Test Report IV -Back Pressure and Pore Pressure Test Data Triaxial Compression Test Report V - R Test, Composite Sample Mo. 1, 3.5% W.C. Triaxial Compression Test Report V -Back Pressure and Pore Pressure Test Data ii Page D-31 0-31 0-31 0-31 D-31 0-33 0•34 D-35 D-37 D-38 0-39 D-40 D-41 0-42 D-43 D-44 D-45 D-46 D-47 D-48 D-49 D-50 D-51 D-52 D-53 ·-~~--------:-·~~~-~-~-·--v~·~--.. ... "r---:-'-.. ---~·~---.. ---.. --.-----~-·-----··-·--------·-----·----·-.. -- • . 0 ' - ( [ I [ { ( ( \ .. - 1 f t ·I I !· ( ~ l r [ j 1··· ,, "' r r ~ l {, • I l SUMMARY OF CHANGES CHANGES TO THE 1976 INTERIM FEASIBILITY REPORT. In 1978, The Alaska District, Corps of Engineers, performed addi- tional field explorations and geologic studies to verify the feasibility .of the Watana damsite. As a result of these studies, considerably more information is now available concerning the site and the regional geology of the area .. Therefore, the entire sections on Regional Geology, pages 0-1 through 0-9; Watana Site, pages D-10 through D-12; and the paragraph on Seismology at Devil Canyon, page D-7, of Appendix D, Foundations and Materials, of the 1976 Interim Feasibility Report are deleted and replaced by this supplemental report. No changes to the Vee Canyon and Denali sites have been made. Plate D-3, Watana -Site Plan and Centerline Profile is deleted and replaced with revised drawings. Several new plates showing geologic sections, borrow areas, and exploration logs have been added. These are listed in the index. CHANGES IN DESIGN As a. result of the additional field exploration and geologic studies~ a more knowledgeable assessment of the proposed project can now be made. A summary of the items which reflect changes to the 1976 Interim Feasi- bility Report, or reinforce the basic concepts of that report fo11ows. 1. . Nothing was found during .tbi s phase_ of ~he study to cast doubt on the feasibility of.a dam a~ the...J.1.~_tana damsite. All exploration and geologic studies reinforced the concept that a large earth and rockfill or a concrete gravity dam could be built in this general vicinity. 2. Detai 1 ed surveys were performed at the Watana site. It was found that the topography used· for-· the 1976 report was. in error by approximately 15 feet. Therefore, the elevations shown on the plates or sections in this supplement are 15 feet lower than those sho\ir\ in the 1976 report.. The detailed survey showed the valley section to be a little wider than previously assumed and therefore, the crest length of the dam and the total quantities within the dam are somewhat larger. 3. The explorations at :th~ damsite indicate that the rock is as good or better than previously ass.umea:·-·Foundation rock is considered adequate to support either an earth-rockfill structure or a concrete gravity dam .. · To support this conclusion, the regional and site geology as we11 as the rock structure are discussed in much greater detail in this supplemental report. D-1 0 -------------l-~-r---------------------------~-~~ r t [ '~ [ ' ' . ( II I l - 4. The 1976 report recognized that the Watana damsite is an area of marginal permafrost and, therefore, permanently frozen ground could be expected in the vicinity. In the 1978 exploration program, specific locations of p~rmafrost were jdentified and a number of temperature measuring devices \~ere irrstalled. The earlier assumption that perma- frost does ex1 st over much of this area vtas confirmed; ho~1ever, it was de·tennined that this is a very "warm" permafrost, ranging from 0° C to -1° C. Premafrost was encountered in bedrock in the left abutment of the dam ~nd 'its effacts on the grouting in this area are discussed in this supplemental report. Permafrost was also encountered in the imper- Vious borrow area; however, because of its marginal temperature, it tends to be soft and can be easily excavated. A more detailed dis- cussion is contained in the body of this report~ 5. The 1976 report envisioned rather large amounts of gravel avail- able for constructi6n of the shells of the dam and limited amounts of impervious core material. The·recent·explorations indicate that this is not the case since gravels in~large quantities were not verified but large quantities of imper~ious core material were discovered near the damsite. Because of the apparent shortage of gravel and an excess o·1 impervious material, the dam section has been completely revised. The gravel shells have been changed to rock shells. This change to rockfill has allowed the use of a somewhat steeper slope on the upstream face of the dam. A large portion of the rock will come from required excavation of the spillway. The remainder will come from excavation of underground facilities and access roads and from a large borrow source on the left abutment. 6. The foundation excavation has been increased to require the entire foundation of the dam to be stripped to bedrock. The 1976 report envisioned exeavation to bedrock under the core and filters only. H0\'1- ever, b~cause the evidence of the 1imited drilling performed is incon- clusive, it was considered adviseable to require remova1 of in situ gravels be~eath the entire embankment. If additional drilling supports a less conservative approach, the change can be made under subsequent feature design. 7. The core has been widened somewhat from that shown in the 1976 report and a zone of semipervious material,·approximate1y of the same width as. the core, has been added. This was done because large amounts of semipervious material are available and estimates sho~o.t that it can be placed within the dam at a considerably lower cost than the rock shell material. The total thickness of these impervious and semipervious zones was determir,ed by considering their effect on total stability of the dam and the_difficulties of placing materi·als which re.quire careful moisture control in the arctic environment. Laboratory tests performed on these materials indicate that optimum moisture will be a rather criti- cal factor in their compaction. Therefore, the use of such materials has been held to within reasonab1e limits. D-2 -1· ·····~ .. .. __ .............. -------...... , ··---'t ,L -i) (. I I l I I l I I ~' . • . ;;;t ~· ar 8. The ~976 report showed a verti ca 1 access shaft to the 1 o~o.~-1 eve 1 drain system \~hich passed through the embankment of the dam. This has now been changed to a tunnel through the right abutment$ thereby elimin- ating any structures in the dam embankment. 9·. A grout ga 11 ery has been added to the 1 m·Jer portions of the dam to facilitate grouting and to accommodate the process of thawing the permafroste Use of the gallery will allow embankment placement and curtain grouting to proceed simultaneously, resulting in a shortened -construction schedule. The gallery will also provide for 11 read-out 11 stations for instrumentation in the foundation and lower 1eve1s of the embankment and for general access. 10. The spillway location as shown in the 1976 report has been shifted southwest to a location which insures rock cut for its entire · length. The rock and overburden material from this large excavation will be utilized in the dam embankment. 11. The 1976 report discusses a potential problem of seepage along a relict channel in the right abutment. The 1978 explorations verified the existence of this channel; however, studies indicate that it is not a problem and~ therefore~ no remedial action is required • .... ~. ~ . ·• ... -·-·-·-· ... _ 12. The diverison tunnel portals have been shifted to ensure their location in reasonably sound rock. 13.. Professional services of Ellis Krinitzsky of the Natert'lays Experiment Station and Reuben Kachadoorian and Henry J. Moore from the U.S. Geological Survey were obtained by contract to perform seismic studies and evaluate the earthquake risk at these sites. Their work W?S divided into two phases. Kachadoorian and Moore of USGS performed t~e field reconnaissance to look for active faults and other geologic hazards. Krinitzsky's work was aimed at assessing the potential earthquakes which could be associated with such faulting. The u~ss report recognized that this is a highly seismic region; however, the geologic reconnaissance of the proposed Devil Canyon and Watana damsites and reservoirs did not uncover evidence of recent or active faulting along any of the known or inferred faults. In their work they did not uncover evidence of the ~usitna Fault, which was previously thought to exist a short distance west of the Watana damsite. Krinitzsky's \~Jork assessed the possible occurrance of earthquakes at the damsite and the motions that are likely to be associated with earthqauke activity. His findings indicate that the design of the proposed dams to withstand such activity is Nithin the state of the art of seismic design. 14. In the fall of 1978, the consulting firm of Shannon & Wilson was engaged to perform ·refrac.;ti on seismograph work at both the Wa tan a and Devil Canyon damsites. This work supplemented the drilling infor- mation. The location maps and seismic velocity profiles from the Shannon & Wilson report are included as Exhibit D-1 to this appendix. 0-3 REGIONAL GEOLOGY PHYSIOGRAPHY . The area of study is located within the Coastal Trough Province of southcentral Alaska. The Susitna River is a glacially fed stream which heads on the southern slopes of the Alaska Range, and flows by way of a continuously widening valley to the tidewaters of Cook Inlet. Within the upper 200 river miles, the Susitna passes through a variety of land fonns related to the lithology and geology of the region. From its preglacial channel in the Alaska Range, it passes through a broad, glaciated~ intermontane valley characterized by knob and kettle topo- graphy and by braided river channels. Turning west\-Jard along the northern edge of the Copper River lowlands, the river enters a deep, V-shaped valley and traverses the Talkeetna Mountains, emerging into an.outwash plain and broad valley which it follows to the sea. Three regiona.1 topogra.phic iows, still identifiable today, are the Susitna R~ver-Chulitna River area downstream of the Devil Canyon site, the middle reach of the Susitna River from Prairie Creek to Watana Creek, and the Oshetna River area at the Susitna Big Bend. These may represent drainage base levels that existed during the glacial periods. Whether they were interconnected at one time is not knm-1n since glacia- tion has modified the original drainages. One possible interpretation is that the ancestral Susitna River may have followed the course of the p~esent Watana Creek and continued southwest along an ancestral valley through the area now occupied by Stephan Lake, Prairie Creek, and the Talkeetna River. The Susitna River, presently incised 500 feet into that broad, ancestral, U-shaped valley, makes two sharp right-angle turns downstream of ~latana Creek in the Fog Creek area and leaves the ancestral valley to flow westNaY~d into the steep, V-shaped Devil Canyon area. Glaciation probably blocked its former southwest course forcing the r·:ver to find a new out1 et in De vi 1 Canyon. Once estab 1 i shed in a \ltestward course, the Susitna River downcut its channel rapidly and became entrenched in Devil C1nyon. INFERRED GEOLOGIC HISTORY The upper Susitna River basin is a complex geologic area \v.:th a variety of sedimentary, igneous, and metamorphic rock types. These range fl•om Pennsylvanian to Pleistocene in age and have 11r1dergone at least three major periods of tectonic deformation. D-4 ·~( I E; ~- ' ' ) [ l l . . i " - The oldest outcrops in the area are Pennsylvanian and Permian aged metavolcanic fiows and tuffs, locally containing limestone interbeds that have subsequently been altered to marble .. This transitiona1 shelf environment continued throughout the Triassic and into edrly Jurassic times, with alternate deposition of basalt and thin sedimentary inter- beds. Metavolcaniclastics include altered marine sandstones and shales. This deposition was contemporaneous with a m~ssive outpouring of lavas,._- in the eastern Alaska Range, resulting in regional subsidence • ... .... The first major tectonic upheaval in the Susitna area occurred in mid to ,.ate Jurassic time and consisted of large plutonic intrusions accompanied by uplift and intense metamorphism. ·Erosiona·l remnants ·of these_intrusives include amphibo1ites, greensch_ists, diori.tes, and acidic granitic types in the upper Hatana reservoir areas. This uplift, . .. an~ _subsequent' erosionar period, .was "followed by .marfne deposition of argi 11 i te and graywacke in 1 ate .. Cretaceous. These rocks are· exposed -in the northwestern half of the upper Susitna basin and include the phyllites of the Devil Canyon site. ~ The second major tectonic event occurred in middle to late Cretaceous .. Most of the structural features in the Talkeetna Mountains~ including thrust faulting, complex folding,.and uplift, occurred at that timeb As ·a result of the thrust faulting, Pennsylvanian and Permian volcanic flows and tuffs were thrust over the much younger"late Cretaceous argillite and graywacke. · """~ --..•••• ..._po.f .. ...,____ ., :a -·• ... , ... -.,. . ~ • ,.. .. ..... In early Tertiary, approximately 65 million years ago~ the north- western portion of the upper Susitna basin was intruded by plutons of igneous rock. The diorite pluton .that underlies the Watana site is one of these intrusives.. Deposition of undifferentiated volcanic flows., pyroclastics, and associated near-sut'face intrusives occurred concurrent with and following the intrusion of the plutons. The third major tectonic event was 3 period of extensiVe uplift and erosion ·;.n middle Tertiary to quaternary. Uplift of 3,000 fe.::t has beeH measured in the southern Talkeetna rtlountains. The widespread erosion that occurred during this period removed thick rock sequences from th~ Susitna basin area. Glaciation has been the prime erosion agent during the past several million years. At least two, and probably mora; periods of glaciation occurred within the upper Susitna basin area. The central and eastern portions of·the area may have been partially covered by glacial lakes during the latter glaciations. Renewed uplift in late Pleistocene rejuvenated the ~rosion cycle until the streams) with their increased 0-5 I' . ' ~· - gradients, became incised within glaciated vaileys. The area currently is undergoing continued stream erosion, and is covered in many areas with a veneer of glacial and alluvial clay, silt, sand, and gravel deposits. REGIONAL TECTONICS The arcuate structure of southcentra1 Alaska reflectboth the magni- tude a·nd direction of regional tectonic forces caused by the collision of the North American and Pacific PlatesQ The Talkeetna Mountains and . . . adjacent· Susitna River basin are believed to have been thrust north- westward onto the North American Plate from their parent continental blocks. It was this thr·ustin~ action which caused most of the struc- tura 1 featur-es now seen in the upper Sus i tna basin . ... • .. .. .,....,__, _________ .., ........... -------........ ; .,.. ~ ....... , .......... , .... _ .... 4~ Two major tectonic features bracket the basin area. The Denali Fault, about 43 miles north of the damsites and active during the Holocene, is one of the better known Alaskan faults. A second frac- ture, the Castle Mountain Fault, is 75 miles south of the river basin. The Susitna basin is-roughly subdivided by the northeast-southwP.st trending Talkeetna Thrust, which roughly parallels the locatio.n of the Susitna Fault, as referred to in the 1976 Interim Feasibility Report. The Talkeetna Rive~ is a surface expression of the southern portion of both structures; however, Kachadoorian and Moore were unable to locate . evidence of faulting in the Tsusena Creek area and, therefore, expressed doubt that the Susitna Fault exists. They found ~vidence of movement in the Talkeetna River and Watana Creek valleys and postulated that the Talkeetna Thrust could be a projection of this feature. Such a projection passes about 4 miles to the south of Watana damsite. The major alpine orogeny which formed many of the basins• present northeast- southwest trending compressional structures occurred in conjunction with the Talkeetna Thrust in 1ate Cretaceous. Another contemporary zone of intense shearing, roughly parallel to the Talkeetna Thrust, is located about 15 miles east of the Talkeetna Thrust • . . Two poorly exposed normal faults of probable Cenozoic age have been projected from gravimetric data as occurring in the Chulitna River valley about 15 miles northwest of the prQposed Devil Canyon damsite. These faui ts have the nol"theast-south•.vest trend typi ca 1 of the major structures within the area. No faults with recent movement have been observed within the upper Susitna River basin. . . . SEISMICITY A seismological assessment of the basin area was prepared by Dr. E.L. Krinitzsky of the U.S. Army Engineer Waterways Experiment Station in the summer of 1978, under contract with the A1aska 9istrict, D-6 - _{ ( 1. [ f f { { { ( ' t ,. t f t ~ [ f. ( i I. .... . l lr h' . l .· lr I It ~ } r~ lr ... Corps of Engineers. Field reconnaissance to lao~ for active faults and other geological hazards was conducted Qy U.S. Geological Survey under the direction of Reuben Kachadoorian and Henry J. Noore. These reports are included as Exhibits D-3 and D-2 in th·.s appendix. They recognize that the Devil Canyon and Watana damsites are in a region of high seis- micity and major faults. However, the geologic reconnaissance of the proposed Devil Canyon and Watana damsites a.nd reservoir areas by the US~$ exp~rts did not uncover evidence of recent or active faulting along any of the kncwn or inferred faults. The tectonic framework of the region is not well understood because of the lack of local seismic moni- toring stations. Present knowledge indicates that historical earthquakes tn the area often have hypocenter depths in excess of 50 km. Such events are associated with movement along the Benioff zone and often are. not directly associated with loca1 surface faulting~ The Denali Fault in the A1aska Range, approximately 43 miles to the north, is the dominant · ·surface feature in this area. The Susitna Fault, previously thought · to exist west of the Watana damsite, was not confirmed in recent geologic mapping by the USGS team, nor did they find any evidence of faulting in the river channel at either of the damsites. The results of the core drilling and geolggic reconnaissan~e at the damsite are strong eviden~e that no major faulting exists under the Watana damsite. The lack of significant shearing in DH-21, the 600-foot cross river hole, reinforces this conclusion~ .. .. Krinitzsky's work assessed the possible occurrence of earthquake activity based on the USGS field work. He assumes an earthquake of magnitude 8 along the Denali Fault, however, these motions are not critical when attenuated to the damsites. To account for the possibility that a major active fault could exist near the damsites, Krinitzsky has assigned a 11 f1oating 11 earthquake of magnitude 7 which could occur in the near vicinity of the dam. This generates the most severe design motions. The rational for the ufloating 1 ' earthquake and a table of associated motions is included in his report (Exhibit D-3). This. criteria is within the state of the art for earthquake design for large dams, and therefore, should not preclude proceeding with detailed design of the projects. ROCK AND SOIL UNITS The proposed Watana damsite and reservoir area is underlain by a complex series of metamorphic, igneous, and sedimentary rock. Specific formation names have not been applied to most nf these units and they. are instead assigned lithologic descriptions for correlation and mapping purposes~ The distribution of various rock units that underlie the proposed reservoir are shown on Plate 5. Following is a brief descrip- tion of the various rock units, beginning at the upper end of the res- ervoir and proceeding downstream to the damsitee Additional informa- tion and descri'ptive details concerning the rock units are included in the U-S. Geological Survey's Open File Report 78-558-A, Reconnais- sance Geologis Mao and Geochronology, Talke?tna Mountains·Quadranole, D-7 }I: ) ~~ tl l ~;,4 \ lt } lt I ~-~ l.:L.' ll ) Corps of Engineers. Field reconnaissance to lao~ for active faults and other geological hazards was conducted qy U.S. Geological Survey under the direction of Reuben Kachadoori an and Henry J. t~oore ~ These reports are included as Exhibits D-3 and D-2 in th~s appendix. They recognize that the .Devil Canyon and Watana damsites are in a region of high seis- micity and major faults. However, the geologic reconnaissance of the proposed Devil Canyon and Watana damsites ~nd reservoir areas by the USGS experts did not uncover evidence of recent or active faulting along any of the known or inferred faults. The tectonic framework of the region is not well understood because of the lack of 1oca1 seismic moni- toring stations. Present know1edge indicates that historical earthquakes tn the area often have hypocenter depths in excess of 50 km. Such events ~re associated with movement along the Benioff zone and often are. not directly associated with local surface faulting. The Denali Fault in the Alaska Range, approximately 43 miles to the north, is the: dominant · ·surface feature in this area. The Susitna Fault, previously thought · to exist west of the Watana damsite, was not confirmed in recent geologic mapping by the· USGS team., nor did they find any evidence of faulting in the river channel at either of the damsites. The results of the core drilling and geologic reconnaissance at the damsite are strong evidence that no major faulting exists under the Watana damsite. The lack of significant shearing in DH-21, the 600-foot cross river hole, reinforces this conclusion •.. •' ·~ Krinitzsky's work assessed the possible occurrence of earthquake activity based on tne USGS field work. He assumes an earthquake of magnitude 8 along the Denali Fault, however, these motions are not critical VihP.n attenuated to the damsites. To account for the possibility that a major active fault could exist near the damsites, Krinitzsky has assigned a "f1oating 11 earthquake of magnitude 7 which could occur in the near vicinity of the dam. This generates the most severe design motions. The rational for the ufloating 1 ' earthquake and a table of associated motions 1s included in his report (Exhibit D-3). This. criteria is within the state of the art for earthquake design for 1arge dams, and therefore, should not preclude proceeding with detailed design of the projects. ROCK AND SOIL UNITS The proposed Watana damsite and reservoir area is underlain by a complex series of metamorphic, igneous, and sedimentary rock. Specific formation names have not been applied to most of these units and they. are instead assigned lithologic descriptions f.or corre1at"ion and mapping purposes. The distribution of various rock units that underlie the proposed reservoir are shown on Plate 5. Following is a brief descrip~ tion of the various rock units, beginning at the upper end of the res- ervoir and proceeding downstream to the damsite. Additional informa- tion and descri'ptive detdils concerning the rock units are included in the U.S. Geological Survey•s Open Fi1~ Report 78-558-A, Reconnais- sance Geologic Mao and Geochronology, Talkeetna ~tounta.ins ·quadratt~ D-7 ,.~ ·~~;~~·--·~. ·;,;;:,;;,""7·";-;:;.:;·· ...... ',,_ .......... ,..... ._,. "''""" ... , ___ , ___ .. ,._,, ___ ,,_~---.. ~----"'"""""" ........ ., .... , __ , •..... . y~ _.,,li.<,. 'A-'< __ .,. ___ ,__."--· •'-'"-""""~~""'~~,., .. ,.,.-l'/..,. .... • 1> · -..... ···,I ·~ t -···-:rJ 'l I,~ [ I . rr ~~ Northern Part of Anchorage Quadrangle, and Southwest Corner of Healy Quadranole~ Alaska, by C:ejtey, et. al., 1978. This report i·s included at the Sack of this appendix as Exhibit Sa The upper reachjs of the reservoir are underlain by an amphibolite unit. These are metamorphic rocks including greenschists, diorites, and local marble interbeds. Directly downstream of this unit is a zone of granitic types that are exposed north of the river at elevations above th~ proposed reservoir 1 evel.· The oldest rocks exposed within the area are farther downstream within the middle reservoir reaches and include both volcanics and lime- stone units. The volcanics consist mostly of metamorphosed basalt and andesite flows and tuffs that outcrop in the vicinity of Jay Creek and downstream from Kosina Creek. The limestone unit consists of marble interbeds that occur locally within the volcanics. The volcanics are overlain farther downstream by a volcanic unit of younger age consisting of a series of metamorphosed basaltic flows with interbeds of chert, argillite, and marble. This unit is exposed both near the mouth of Watana Creek and on the higher slopes west of Watana Creek. A much younger series of interbedded conglomerates, sandstones, and claystones is exposed along the lower reaches of Watana Creek directly upstream from its mouth. The downstream reaches of the reservoir area are underlain by a sequence of qrgi11ites and graywackes. Exposed \vithin the immediate damsite area is a granitic body intruded into these metasediments. It consists primarily of diorite with upstream and downstream margins that include associated schist, gneiss, and composite igneous and metamorphic rock types. Andesite flows and dikes are associated with this diorite pluton. · Other granitic intrusives occur east of the reservoir area. Locally, these intrusives are overlain by a series of younger igneous flows and tuffs and related shallow intrusives~ Overburden units in the proposed reservoir area include deposits of glacial till and drift with associated out\~ash and lake sediments, colluvium includinq slooewash and taius, alluvium and local slide debris. "" . .. ·-"""'"-. "'' ROCK STRUCTURE Rocks within the reservoir-area have undergone a complex deforma- tion sequence, including uplift, intrusion, thrust faulting, fo1ding, shearing, and associated metamorphism. The most significant structural feature \vithin the rr-servoir ar.t;a is the Talkeetna Thrust which stt"ikes northeastward across the lowe.t" reservoir area and is r-oughly parallel 1'··~-.,---·-~····------~ .. ----·----"··---------·-····"-'''-''"'-'"---···-·-' -~--~···-·"' ' ·-· { ('' {' I I I· I I F t r ( \ I l {I tl t . . • > li-:'~1 ~ !r '! f ~~ { !' f f-...1"' ~£: I i () ' to the lower reaches of Watana Creek. The Talkeetna Thrust, within the Watana reservoir area, has displaced the volcanic unit over the much YO~.nger metasediments. A northeast striking shear zone that dips steeply southeasterly, and is roughly parallel to the Talkeetna Thrust, crosses the reservoir area about 15 miles east of the Ta1keetna Thrust near Kasina Creek. Woether. this shear zone represents a significant feature is not known. The most significant rock structure jn the irrmediate dam area is the intrusive diorite pluton o·f Tertiary .. age. It is observable for 4 miles parallel to the river and 2 rni1es north and south and is prob- ably of great depth.· Upstream and downstream border zones developed with sev~ral different metamorphi-c and igneous roc!< varieties. T~tJO distinct northwest trending shear zones have been mapped in the vicinity ·of the damsite. One is 3,400 feet upstream and the other 2,500 feet downstream from the proposed dam axis. Attitudes vary with strikes ranging from N 40° \~ to 60° W and dips from 70° to 9ll 0 either s~: or NE. The two shears can be seen in the right valley wall, bt:t not on the left valley wail. The left wall is obscured by a slide block at the upstream shear, and ~he left wall at the downstream shear has a rock face that parallels the sh~ar direction making observations difficult. The up-str~am shE~r ~Qn{! has been named ·~The Fins," and has an observab 1 e · width in excess crf 400 feeto It includes seven near vertical rock fins averaging 5 tt' 25 feet in width bounded on both sides by aitered and crushed rock. The downstream shear zone, named "Finger 8uster 11 , is same- what less distinct and is partially covered by slope debris. It has an · estimat.e.d width of 300 feet.. Another northwest trending shear znne, simi·l ar to the b'lo shears ment·i oned above, occurs downstream from the damsite in the vicinity of Tsusena Creek. Fracture patterns including both joints and local shears have been mapped within accessible areas in tha vicinity of the damsite. Details of this mapping are shown on Plates D-3 and D-4. Fractures include both cooling type jointing and structural deformation jointing resulting from the regiona·l tectonic farces of uplift and thr·ust f·au1ting. Shear, tension, and relie-F joints resu'lting from unloading by erosion of over- lying sediments and/or melting of glacial ice are all present within ·the damsite area. A joint diagr·am platted on an equal area sterc-ographi'c pt~ojet;tiort i~ shown in Figure D-6 •. The dominant fracture ori-..:ntation ·· · is to the northwest, but fractures strike in several directions. The major joint sets are N 50° W and the minor joint sets are N 30° E as ·obser'Ved within the area .. 0-9 ' :!'"' I ''n I I f t f i t .. t .. ~ DEVIL CANYON SEISMIC REFRACTION SURVEY . During September 1978, seismic refraction surveys were undertaken at Watana and Devil Canyon damsites by Shannon and Wilson, geotechnical consultants. At Devil Canyon, the seismic survey consisted of three lines, each approximately 1,100 feet long. One of these lines was located near the proposed alinement of the saddle dam on the left abut- ment and the remaining two lines were located near an abandoned airstrip on the alluvial fan at the confluence of Cheechako Creek and the Susitna. River (see Plate 0-1).· The seismic line near the centerline of the left abutment saddle dam was a1ined to expand information derived from dr~lling accomplished on this site by the U.S. Bureau of Reclamation (USSR) in 1957. The refraction profile correlated well with the top of rock from the drilling data (see Sheet No. 10, Exhibit 0-1). A lower velocity zone of rock sandwiched between competent phyllite indicates the possi- bility of a shear z.one at .. the low point of. the saddle. This correlates with hole DH-6 which indicated shearing in the 20 feet of bedrock pene- trated by the boring.--· ---· ... -.. ·· ·· -··· .... The seismic lines on the Cheechako Creek aggregate deposit were alined to establish the depth to bedrock beneath these deposits and thereby confi·rm the quantity of material available for borrow. The velocities for the material in the alluvium indicate that the area is composed of a layer of sands and gravel5 o~ glacial materials several hundred feet thick overlying bed~ock. This confirms the existence of material well in excess of the requirements for the project. The location map and seismic velocity profiles from the Sh~nnon & Wilson report and included in Exhibit D-1 to this appendix. MATERIAL REQUIREMENTS Concrete Reguir~~ents Material requirements for Devil Canyon dam are based on a concrete gravity dam. Under this proposal approximately 2.6 million cubic yards of concrete will be required, most of which will be mass concrete. The remainder will be structural concrete for the appurtenant structures to the dam, including the powerplant. With stockpile losses, this amount of concrete will require approximately 3 million cubi~ yards of processed aggregate. The USSR located an extensive deposit of material which will yield concrete aggregate of adequate quality in an alluvial fan approximately 1,000 feet upstream of the proposed dam axis. The fan was formed at the confluence of Cheechako Creek and the Susitna River. D-10 I Thirteen test pits and trenches were dug in the fan area by Bureau of Reclamation personnel in 1957. About 1,300 pounds of minus 3-inch material ~1as tested by the USSR for basic aggregate suitability studies~ An additional 200 pounds of material was collected by Corps of Engineers personnel in 1975 from the existing Bureau tE:;t pits and the riverbank. This material was tested by the North Pacific Division Materials Labora- tory in 1978 • If the excavation of materials is confined to that part of the ·alluvium 1ocatad above river level (elevation 910 to 920 feet) with conservative back slopes through the ridges and benches, approximateiy 6,000,000 cubic yards of material is available in this location with all the resulting excavation in the reservoir area. S~ismic refraction surveys indicate that usable gravel.exists to approximately.elevation _870 feet, so additional material could be retrieved if needed by bailing ·rrom·below the water surface. Placement of the coffer dam, sizing of the diversion tun~1, and the ability to control the flow in the river at Watana dam will ultimately affect the method of exploitation of this source. The locations of the test pits are shown on Plate D-1 and the detailed logs can be found in the U.S. Bureau of Reclamation's Alaska Geo 1 ogi c Report #7, Deyi 1 Canyon Project., d.a ted March 1960. Laboratory investigations of the aggregate samples were reported in USBR Report #C-932 by their Concrete Laboratory Branch, dated 21 December 1959. Petrographic analyses of the fine (sand sized) particles and coarse (gravel size) particles indicate that the sands and gravels in the fan are composed of quartz diorites, diorites, granites, andesites, dacites, metavolcanic rocks, aplites, breccias, schists, phylli.tes, argillites, and amphibolites. The gravel particles are stream worn and generally rounded in shape. The sand grains vary from 1early ro~nded to sharply angular in shape, averaging subangularo The specific gravity (BSSD) of the material ranges from 2.68 to 2.80. Results from both labs indicate that the material in the Cheech~ko Creek fan is of adequate quality for use· as concrete aggregate. Embankment Material Requirements. The saddle dam on the left abutment, associated with the concrete gravity dam, will require approximately 835,000 cubic yards of material .. These materials will be obtained from the same sources as discussed in the Interim Feasibility Report. D-11 '-~ { ' ~ i' l WATANA SITE f SCOPE OF INVESTIGATIONS Field Reconnaissance Geologic reconnaissance and mapping of the reservoir area and dam- site were conducted concurrently with subsurface investigations through- out the spring and early summer of 1978. The work of the geologic teams was made e~sier in the early spring as l·ock outcrops were not obscured by the leaves on the trees and the. dense ground foliage. Through the months of March and April, geologic mapping of the lower canyon was done from the frozen surface of the r·i ver, which a 11 owed access to areas otherwi.se inaccessible after the ice had melted and high summer flows on the river had begun. Within the damsite area the primary purpose was to find, idsntify, and trace the surface expressions of discontinuities and shear zones as an aid in directing the drilling program and to provide preliminary geologic mapping of the site~ Within the reservoir area, the primary thrust of the reconnaissance was toward identification· of slopes, which by reason of shape, structure or overburden mantle could develop minor slumps and slides as a result of permafrost degradation or seismic action. Borings and Test Pit~ During 1978, explorations were conducted in the dam foundation and relict channel area. Core borings in the valley walls and floor were used to explore the quality and structure of the foundation rock and to obtain representative samples for testing. Borings in the relict channel a rea 'flere used to define the depth of overbur:ien, the extent of penna- frost, the location of the water table and to examine, by drilling and sampling, the nature and condition of the materials. Shallow auger holes were also used to determine the extent of deposits in the borrow areas and to verify the existence of quantities necessary for embankment construction. Locations of explorations are shown on Plate D-2. Logs are shown on Plates D-19 through D-37; and core photos are shown on Plates D-38 through D-45 .. Test pits were dug in potential borrow areas -utilizing tractor- mounted backhoes. Bulk sack samples were retrieved from each test pit for testing later at the North Pacific Divison ~1aterials Labora- tory in Troutdale, Oregon .. D-12 ' I f. ( .,•' I l L -----,·---~-----,.,,=:::r If IJ r t [ ~- t [ t ' ' t t ~ .. Ji .. t ?" A total of 27 test pits were dug in four areas as follows: lo The mouth of Tsusena Creek (Borrow Area 'E')-6 test pits. 2o The glacial till borrow area (Borrow Area 'D') -14 test pits. 3. Upper Tsusena Creek, north of Tsusena Butte, (Sorrow Area 'C') 1 test pi.t. 4. Middle Tsusena Creek -6 test pits. The locations of Test Pits 1 through 5 and 8 through 21 are shown on Plates 0-12 and D-11. The remainder of the test pits are located in areas which are not presently considered as borrm'-1 areas; however: they may be located on Plate D-2. The logs of all the test pits are shown on the appropriate borrow area Plates D-19 through D-22. Seismic Refraction Surveys A seismic refraction exploration program consisting of 22,500 lineal feet of seismic refraction lines \~as completed by Dames and Moore, Consultants, in 1975. Results of those investigations were presented as Exhibit D-1, Section D, Foundation and Materials, in the 1976 Interim Feasibility Report. In the fall of 1978, an additional seismic refrac- tion survey was completed by Shannon and Wilson, Consult3nts, which includes 47,665 feet of seismic refraction lines. Locations of these additional seismic explorations are shown on Plate D-2, and the location map and seismic velocity profiles are presented as Exhibit D-1. The survey confirmed the findings of the Dames and Moore study. It confi~med the existence of a buried channel in the relict channel area and in general supported conclusions relating to shear zones in tpe abutments as interpreted from the recent core borings and geologic reconnaissance. The Shannon and t~i 1 son survey a 1 so confirmed the existence of 1 arge quantities of borrow materials on Tsusena Creek in the proposed borrow area. Instrumentation Instrumentation conducted under this phase of the project consisted of the installation and data reading of ground \'later measurement devices, temperature logging devices, and the recording of the ambient temperature. Ground Water: All piezometers installed were of the open well point type and were filled with diesel oil where they extend through permafr~.st zones to prevent freezing. A total of 10 piezometers were installed at the following locations~ D-13 -- r·· ; 1 • TABLE 0-1 Surface Tip Location Elevation Elevation Date Set Size DR-14 2,340 2,271.0 26 Apr 411 2~340 2,295.2 19 ,A,ug 1-1/2" DR-20 2,207 2' 123.8 30 May 1-1/2" OR-18 2,172 2,107.0 21 Jun 1-1/2" DR-17 2,167 2,136.3 8 Jun 1 .... 1;2u DR-16 2,099 2,053.8 5 Jun 1-1/2il AP-1 2,202 2' 188.6 20 Jun 1-1/2 11 AP-2 2,200 2' 189.0 20 Jun 1-1/2 11 DR-19 2,151 2, 109.0 3 Jul 1-1/2" DR-22 2,229 2,005.5 3 Aug 1-1/2 11 DR-26 2,295 2,229 .. 5 11 Aug 1-1/2 11 All locations. are shown on Plate D-2 and Plate 0-11. Plotted data is shown on Plates 0-16 through 0-18. Subsurfa~e Temperatur~: Th~ principal temperature logging device consisted of a 3/4-inch galvanized pipe, with the lower end capped and sealed. The pip.e was filled with a mixture of ethylene glycol and water (S0/50) or arctic grade diesel fuel. Readings were taken using a digital volt-ohm meter and a single thenn·ister which was lowered into the pipe. At location DR-26 both a 3/4-inch galvanized and a 1-1/2-inch PVC pipe were installed to determine if readings could be duplicated in a pipe of larger diameter. A total of 14 devices were installed at the locations shown in Table 0~2. D-14 ~ [ Ct'' TABLE D-2 Date Buried Location Insta 11 ed Length Stick Up Depth Fluid AP-8 23 Jun 64' 4.2' 58.9' Diesel AP-9 23 Jun 21 I 3.2' 17.8' Diesel DH-12 3 Jul 129 I 1. 8' 127.2 1 Diesel DH-23 17 Jul 76' 0.5' 75.5' Antifreeze DH-24 1 Aug 86 1 1. 2' 84.8 1 Antifreeze DR-18 21 Jun 251' 3.4' •247. 6' Diesel DR-19 3 Jul 83 1 3.9 1 79.1 1 Diesel DR-22 3 Aug 492 1 2.o• 49o.o• Antifreeze DH-28 30 Aug 124' 1. o• 123.0' Antifreeze DR-26 (3/4" pipe) 11 Aug 68' 3.8' 64.2 1 Antifreeze DR-26 (1-1/2u pipe) 11 Aug ggr 3.4 1 95.6' Antifreeze DR-14 19 Aug 65' 2.8' 62.2' Antifreeze DH-21 23 Aug 160' 2 .. 0 1 158.0' Antifreeze OH-25 15 Aug 80' 4.0' 76 .. 0 1 Antifreeze All locations are shown on Plate D-2 and Plate D-11. The plotted temperature data can be found on Plates D-13 through D-15. A second type of temperature logging device, installed at DR-22, consisted of a multipoint thermistor string. The purpose of this instal- lation was to act as a check against the 3/4-inch fluid filled devices described above. Ambient Temperature: The ambient temperature was obtained using a standard high-low Mercury thermometer placed in the shade on the right abut~ent riverbank approximately 4 feet above the ground. Prior to this phase of the project 7 there was no ambient temperature data available for this section of Alaska. Data obtained is shown on Table 0-3. D-15 - TABLE 0-3 r Date J:!igh 0 f Low °F Date. High O·f Low "F ·' 23 Mar 78 t'\2 0 Z3 r4ay 78 60 39 ~. [ 24 Mar 78 24 13 24 May 78 60 32 25 Mar 78 28 19 25 May 78 61 40 27 Mar 78 32 10 26 Hay 78 41 36 r 28 Mar 78 26 13 27 May 78 64 29 Mar 78 40 6 28 May 78 36 30 Mar 78 35 6 29 May 78 58 33 [ 31 Mar 78 36 5 30 f·1ay 78 63 36 1 Apr 78 31 5 31 f4ay 78 66 40 2 Apr 78 28 -4 1 Jun 78 54 36 3 Apr 78 28 3 2 Jun 78 58 38 ~ 4 Apr 78 36 4 3 Jun 78 68 4·1 5 Apr 78 36 20 4 Jun 78 68 38 6 Apr 78 33 11 5 Jun 78 57 39 [ 7-8 Apr 78 40 28 6 Jun 78 66 44 9 Apr 78 41 1.0 11 Jun 78 72 44 10 Apr 78 43 13 12 Jun 78 62 39 [ 11 Apr 78 38 20 14 Jun 78 57 40 12 Apr 78 38 15 16 Jun 78 58 34 13 Apr 78 40 30 19 Jun 78 52 33 [ 14 Apr 78 44 32 20 Jun 78 61 33 15 Apr 78 40 38 21 Jun 78 63 16 Apr 78 39 29 22 Jun 78 46 17 Apr 78 38 21 27 Jun 78 55 .38 r 18 Apr 78 43 21 28 Jun 78 59 37 .:: 19 Apr 78 44 20 30 Jun 78 62 43 20 Apr 78 48 24 1 Jul 78 57 41 r 21 Apr 78 44 25 2. Jul 78 62 43 22 Apr 78 45 30 4 Jul 78 · 70 47 1 •• -/ 23-24 Apr 78 47 32 7 Jul 78 62 40 r 25-26 Apr 78 50 26 8 Jul 78 73 43 30 Apr 78 59 32 9 Jul 78 70 49 ~J 1 r~ay 78 60 34 10 Jul 78 66 42 II 9 r1ay 78 64 30 11 Jul 78 71 10 May 78 72 33 12 Jul 78 50 11 ~1ay 78 70 33 14 Ju1 78 59 5;1 12 May 78 65 40 16 Jul 78 58 47 Jj 13 r~ay 78 72 30 26 Jul 78 66 45 14 May 78 72 31 27 Jul 78 78 40 15 May 78 66 36 28 Jul 78 74 55 [ 16 May 7e 55 32 29 Jul 78 78 39 17 May 78 60 30 30 Ju1 78 82 46 18 May 78 64 37 31 Ju1 78 84 52 L 19 May 78 60 37 1 Aug 78 80 58 20 May 78 75 24 9 Aug 78 71 46 21 May 78 70 43 10 Aug 78 68 54 22 t4ay 78 --36 11 Aug 78 66 49 u D-16 L --T~"-~---"-.. '-~·..,·-·---·--~···-···--·· .. --- '-':: - [ 1·: 'U I ·[ l~ r, r .::~ ,.., Accuracy of Subsurface Temoera_!ure Data: Resistance measurements were obta1ned us1ng a Ke1tnley volt··ohm meter, which allowed readings to the nearest ohm. With a span of 225 ohms per degree centigrade, 1 ohm represents 0.005° C. The temperature data in this report has been reported to 0.01° C and is re1iab1e to that degree of accuracy. To verify the accuracy of each thermister, its resistance was measured in an ice bath. It was found that the thermistors are very stable and do not tend to drift from their original resistance at 0.00° C. General Comments The drilling in the permafrost was performed with core drills and rotary dri11s, which introduce a large amount of heat into the ground. Where the permafrost temperature is only slightly below the freezing point, this tends to melt the permafrost and makes identification very difficult. Therefore, the drilling operation may or may not reflect the existence of permafrost, and it is necessary to rely heavily on the instrumentation for a true evaluation of the location and depth, at which permafrost exists.. By December of 1978, the temperature logging devices may not have stabilized due primarily to the fact that the drilling · -method used was rotary \'lith drilling "mudu as the circulation medium, which tends to thaw the permafrost. Upon inspection of the plotted data~for the locations in this area i't can be seen that the temperatures are gradually approaching the 0° C point. Through a continual program of monitoring these points, a great deal can be learned about 1'freeze back." At location DR-26, 3/4 inch and 1-1/2 inch pipes were installed to detennine if convection currents in the pipe would affect the accuracy of the near surface readings. It can be seen from the temperature plots, shown on Plates D-13 through D-15; that there is a degree of convection in the upper zones, while with depth the two readings are very similar. At location DR-22, the string had 14 thermistors in a 150 foot length. The data obtained from this string has not been included in this report since its reliability is in guestinn. This is due to damage received during installation as well as the ract that the thermistors are of a lower quality and adequate calibration could not be obtained prior to installation. At l~cation DH-12 the 3/4-inch pipe temperature logging device was lost when it was decided that the bore- hole camera should be run in this boring. At location DH-25 no data is available because the 3/4-inch pipe froze t:p during installation. SITE GEOLOGY Introduction The river valley at ~he site has a V-shaped lower or bottom canyon deeply incised into an upperJ much broader, U-shaped river valley of considerable extent and width. D-17 r . ' r.~ [ [ r· [ ,., ',.· r r r. [ ,,) . i~. 1.+ I~ The lower river valley floc~ ranges from 300 to 600 feet wide and has side slopes of 35 to 60 degrees with locally scattered rock outcron:; that rise in near vertical cliffs. The incised portion of the canyon · extends from subriver level upward about 500 feet to approximate eleva- tion 2,000 feet, where it ranges in width from 1,500 to 3,000 feet. Above elevation 2,000 feet, there is a distinct flattening of the valley s 1 opes and the area broadens out into a very wide· fanner river va 11 ey. Width of this fanner valley base ievel is from 8 to 10 mi1es in the lower reservoir area, narrows to about 1 mile in the midreservoir area upstream of Jay Creek and widens to more than 20 miles in the upper reaches of the reservoir. Foundation Conditions The. site was mapped arid explored with 17 core holes, 12 of which are on the dam axis shown in this report. Six of the holes are angle .holes, five were drilled normal to the dominant structural trend, and one drilled acr·oss the river valley. The exploration plan with hole locations is presented on Plate D-2. The river valley is filled with alluvium consisting of gravels, cobbles, and boulders in a matrix of sand or silty sand. Overburden depths in the valley bottom range from 40 to 80 feet and may exceed 100 feet in places. Overburden depths on the valley slopes range ~P to 10 feet deep on the left abutment and up to 20 feet on the right abutment. However, overburden upstream of the left abutment is more than 56 feet deep. · · · · . Overburden on the valley slopes is mostly glacial debris and talus consisting of various gravel and sand mixtures and some silts, with cobbles and small boulders. The underlying rock is diorite, yrano- dior1te, and quartz diorite with local andesite porphyry dikes and more widely scattered·minor felsite dikes. Most of the rock, although frac- tured, is relatively fresh and hard to very hard within 5 to 40 feet of top of rock. Overburden ~nd rock stripping depths along the dam axis are shown in cross section on Plate. D-7. Fractures are closely to moderately spaced at the bedrock surface, generally becoming more widely spaced with depth. Fracture zones found at all depths tend to be tight or recemented with calcite ur silica. The northwest trending joints and high angle shears mapped in t~e rock outcrops are found at different depths within most drill holes and - ·range from single fractures to broken zones more than 20 feet thick .. Broken rock within the shear zones is locally decomposed but consists mainly of moderately hard to very hard fragments. Many· fractures have thin clay gouge seams and slicken sides. Pyrite and chlorite minerali- zation is found as coatings on many f~acture surfaces. Shears are 0-18 r lr: ., L r r [. ~' I t t L The lower river valley floor ranges from 300 to 600 feet wide and has side slopes of 35 to 60 degrees with locally scattered rock outcrops that rise in near vertical cliffs. The incised portion of the canyon · extends from subriver level upward about 500 feet to approximate eleva- tion 2,000 feet, where it ranges in width from 1,500 to 3,000 feet. Above elevation 2,000 feet, there is a distinct flattening of the valley s 1 opes and the ar~a broadens out into a very wide· fanner river va 11 ey. Width of this former valley base level is from 8 to 10 miles in the lower reservoir area, narrows to about 1 mile in the midreservoir area upstream of Jay Creek and widens to more than 20 mi1es in the upper reaches of the reservoir. Foundation Conditions The. site was mapped arid explored with 17 core holes, 12 of which are on the dam axis shown in this report. Six of the holes are angle ~ales, five were drilled normal to the dominant structural trend, and one drilled across the river valley. The exploration plan with hole locations is presented on Plate D-2. The river valley is filled with alluvium consisting of gravels, cobbles, and boulders in a matrix of sand or silty sanda Overburden depths in the valley bottom range from 40 to 80 feet and may exceed 100 feet in places. Overburden depths on the valley slopes range yp to 10 feet deep on the left abutment and up to 20 feet on the right abutment. However, overburden upstream of the left abutment is more than 56 feet deep. · · . Overburden on the valley slopes is mostly glacial debris and talus consisting of various gravel and sand mixtures and some silts, with cobbles and small boulders~ The underlying rock is diorite, grano- diorite, and quartz diorite with local andesite porphyry dikes and more widely scattered·minor felsite dikes. Most of the rock, although frac- tured, is relatively fresh and hard to very hard within 5 to 40 feet of top of rock. Overburden ~nd rock stripping depths along the dam axis are shown in cross section ,n Plate. D-7. Fractures are closely to moderately spaced at the bedrock surface, generally becoming more widely spaced with depth. Fracture zonas found at all depths tend to be tight or recemented with calcite ur silica. The northwest trending joints and high angle shears mapped in t~e rock outcrops are found at different depths within most drill holes and - range from single fractures to broken zones more than 20 feet thick. Broken rock within the shear zones is locally decomposed but consists mainly of moderately hard to very hard fragments~ Many· fractures have thin clay gouge seams and slicken sides~ Pyrite and chlorite minerali- zation is found as coatings on many fracture surfacas. Shears are D-18 . '. lil ~, ,.. > [,' ' .. I . ., ,. spaced from a few feet to more than 100 feet apart, and since the shears are mostly vertical, greater lengths of sheared material were recovered in vertical drill holes. In addition to the shears, primary and rehealed breccia zones occur in some areas adjacent to the andesite porphyry dikes. Most of these rehealed breccias are relatively competent rock, but a primary breccia zone downstream of the axis on the left abutment includes locally decomposed materials. ·Valley Conditions The river valley bottom was explored \'lith s1x core drill holes. Three holes are on the axis and three are about i.,OOO feet downstream of centerline in the toe area. River alluvium varied in depth from 44 to 78 feet. This alluvium consists of gravels, cobbles, and boulders imbedded in sands with local gravelly or silty sand lenses. The gravels and larger sizes are mostly subrounded to rounded with occasional large· boulders. Most large sizes are of dioritic composition, but metamorphic and other rock types \1/ere a 1 so noted. Most of the grave 1 s are fresh, but a few are coated with plastic fines. Alluvial materials in some areas were frozen to depths in excess of SO feet and possibly all the way to bedrock at the time of drilling. The bedrock is a diorite that in most holes is very closely fractured in the upper 10 to 20 feet. Fractures become more widely spaced with depth; however, local zones of closely spaced fractures occur throughout. Joints are both open and rehealed or cemented with calcite and silica. The rock below river level is mostly fresh and hard to very hard. Shear zones occur in several of the holes and include some thin clay gouge coatings ana slickensides. Soft chloritic materials were also encountered in one shear zone, and iron staining with pyrite mineralization is cowman. It should be noted that DH-21 was drilled essentially across the river from the left to the right abutment. No major fault or significant change in materials was seen although six minor shear zones were encountered in the hole. Most of these zones are less than 3 feet thick, whereas, some of the vertical holes penetrated sheared material for distances of more than :a feet. This confirms the near vertical nature of most shearing. Geologic mapping in rock ~~posures along the river- bank also indicates the near vertical nature. of shearing. An andesite porphyry dike was penetrated at depth by DH-2.1 .. This dike has an apparent thickness of about 13 feet, and the contacts with the diorite are tight and contain no notable planes of weakness • . The left abutment was explored with five drill holes, three on the dam axis and one each upstream and downstream of the embankment. Over- burden depths in the downstream hole and the thr~e axis holes are less than 10 feet. This overburden consists of small subangular to sub- rounded boulders in silt, sand, and gravel. Overburden in DH-28, located approximately 1,000 feet downstream of the axis at elevation 1,971 feet, D-19 ' r ' 1_,.~ [ . i consists of 6 feet of silty clay overlaying 2 feet of sand. DH-25, located ·about 750 feet upstream of the axis at elevation 2,045 feet, penetrated a vertical depth of 56 feet of glacial and alluvial deposits and had not yet encountered rock when it was abandoned. Overburden in DH-·25 consists primarily of gravelly, silty sand with boulders to a depth of 15 feet, underlain bY. gravellY~~ clayey silt. Gravels are sub- rounded to rounded and the·clayey silts are stiff and plastic. R~ck in the three axis holes is a hard quartz dio.rite~ whereas in OH-28 down~tream of the embankment, it is an ~ndesite porphyry. The relationship between the quartz diorite as a plutontic rock and the andesite porphyry as a surface flow rock is not clearly understood. This contact area between the t\vo type rocks is in the location of the underground powerhouse and will be closely explored during design inves- tigations. It is assume~ the underground powerhouse will be located in the diori-f:ic rock~· Weathering is primarily staining on fracture surfaces. Fracture spacings vary from very close to moderately spaced; spacing increases with depth. Fractured zones, encountered in all holes, are from less than 1 to more than 20 feet thick and are separated by from 10 to more than 50 feet of relatively undisturbed rock. Many fractures include thin seams of clay gouge, slickensides, secondary pyrite, and breccia. DH-28, downstream of the embankment, appears to have been drilled in an andesite porphyry breccia contact zone adjacent to the diorite pluton. Much of the core is brecciated, moderately weathered to high1y a1tered, and recovered in small fragments. Several zones of clay gouge were noted • . Right abutment conditions were explored with six core drill holes along the proposed dam axis. Three of these holes were angle holes drilled normal to the dominant structural trends. Overburden depths within the six holes range from 4 to 20 feet, with the greater depths in the holes farthest upslope. Overburden cons.sts of gravelly sand with cobbles and small boulders. Bedrock is moderately hard, but weathered, closely fractured and locally sheared in the upper 10 to 40 feet. The rock is diorite or quartz diorite with zones of quartz diorite breccia. The quartz diorite breccia is healed, probably formed during emplacement, and is not con- sidered a zone of weakness. Fractured zones encountered during drilling are similar to those noted on the left abutment. Shears range up to 22 feet thick and are separated from each other· by about 10 to 100 feet of competent rock. Very thin films of clay gouge and slicRensides occur on scm~ fracture surfaces. Iron staining occurs on many fracture surfaces and fine dis- seminated pyrite mineralization occurs more widely. D-20 ( . , . . -. Relict Channel Area The relict channel is a suspected ancestoral Susitna River channel north of the right abutment under the broad terrace area b~tween Deadman and Tsusena Creeks. Ground surfaces within the Relict Channel area are between elevation 2,100 and 2,300 feet along low elongated ridges and shallow depressions. This area was origi·nally explored with tt>Jo seismic lines and the results presented in the Feasibility Report, Appendix 1 as Exhibit 0-1. Subsequent 1978 explorations include 1,814 linear feet o~ drilling, borrow explorations near Deadmari Creek and 23,600 feet of seismic refraction 1 i nes. The 11 dri.ll ho 1 es range from 21 to 494-feet in depth and were mostly noncore rotary holes supplemented with drive samples and some bedrock coring. the results of these 1978 explorations confirm the existence of the deeply buried bedrock surface deoression discovered durjng the 1975 seismic investigations •. The lowes~ bedrock elevation encountered in drilling was in DR-22 at 1,775 feet, MSL or 454 feet below ground surface. · Overburden consists of both glacial and alluvial materials occurring in varying sequences that are difficult to correlate with the limited drilling to date4 Outwash occurs over much of the area, consisting of·grave11y, siity sands or silty, gravelly sands in varying· proportions, with some local cobbles and boulders and more widely scattered clay lenses. These materials are mostly loose and the fines are predominantly non- .Plastic. · · · · Glacial till is the most abundant overburden material found within the relict channel area. These tills occur in three separate sequences in the deepest drill holes, separated by lenses of alluvial materials •. The n~ar s~J~"face tills are normally consolidated while the tills from greater ~epths are highly over consolidated and dense. It is quite probable that· this over consolidation was caused by glacial loading in the geologic past. All of the tills contain fines that are nonplastic or only moderately plastic. Smaller gravel sizes are rounded, while larger sizes are more subrounded to subangular. Materials are poorly sorted wi~h little or no indi'cation of bedding. The tills vary con- siderably in thickness from only a few feet to a maximum of 163 feet in DR-18. · · · . -·--·· . .. .. · -..... _. · · · · · · · ········ ·· · · Apparent river deposited alluvial lenses which represent inter- .glacial periods, separate many of the till units. These deposits consist of sandy gl"'avels with some silts. Sandy alluvial units have a tendency to cave during drilling and seve~al appear to have relatively high permeabilities. Most of these river deposits were less than 50 feet in thickness but in DR-22, directly above bedrock, the alluvial unit was 159 feet thick.. .. 0-21 r r 1 p ' I f { I At least two deposits of lake sediments were encountered during drilling. The larger of these was named "lake Hollern and occurs in DR-13, DR-15, OR-26, and DR-27 in varying thicknesses. Maximum thick- ness is 60+ feet in OR-13.. Lake \~oller deposits .appear to be confinec• between elevations 2,240 and 2,305 ·feet. Another apparent lake deposit was penetrated in DR-18 and DR-20. Maximum thickness of this deposit is 33 feet and appears to be confined bet\•Jeen elevations 2,130 and 2,190 feet. Both lake deposits may represent either quiet lake deposition during an interglacial period, or possibly preglacial lakes formed during gl~cial retreats. The lake deposits consist. primarily of highly to moderately plastic clays and silts with local grave1 and sand 1enses. ~ . ~ -~ .. • ~ . . .... ·;· • "'-" .. • .. • ~ • :r ... .:-w.J •. ~~ ... ·., . ..... .., .. -~, .... -... . . , Spillway The original location of the Saddle Spil)way in the Interim Feasi- bility Report, Appendix I, Plate 0-3, was found to lie directly upon .. two adverse structureso .. The overburden depths increased from 9 feet at DR-17 on the left side of the proposed alinement to 231 feet at DR-18 on the right or east si'de of the spillwaye This depth of overburden prevailEd throughout the length of th& spillway, including the proposed gate structure area. The glacial tills, clay, and intermittent sand lenses of the over- burden would have required additional excavation and flatter sideslopes. Added expense woYlo also have resulted from increased foundation require- ments for the gate structure and rrom the fu11 length iining whieh weuld have been required in the spillway channe'l. To avoid these disadvantages a change of the channel alinement was made. The new proposed alinement lies approximately 800 feet laterally to the left (southwest) of the original design and will be in rock cut from inlet to final outlet at Tsusena Creek. This alinement wi11 also avoid potential structural problems from the second adverse structure, the shear zone titled "The Fins 11 (Plate 0-4) which wil·l now parallel the spillway for its entire length. Rock quality is such that excavated rock will be used as dam shell rock. As a result of the move, it is anticipated that sound bedrock wil1 be encountered at a maximum depth of 25 feet at the gate structure and will continue down spillway for at least 2,500 feet. As the spillway dips down to Tsusena Creek, deeper glacial till i's again encountered, so the final section of the outflow may not be totally founded on bed- rock. The plunge pool at Tsusena Creek will be contained by existing rock cliffs. D-22 ( ' J ( A I ·····---;-·-·-·---·" """'"l, ·"""" '"'.\owa;O .. ; •. : -~-·-----~---~--------··----.. ~·-··-·~··~·~·-··-··~·--·'"·"-·'"·""''""""·"""""~--·---··--···· c••···--·--·-·--··.,·--:""""~··~···::--·~;:;,"\::·~,..,~~; . -I """""$ *I t r· \ r· ~ I l• \ r L I,. r ... r r r r ) \ . " ~ r ' 1 ' \ \A 2 r ) \ .-· i< [ . ;/ " r;::;; •. ~:) Permafrost ---The Watana damsite lies within the discontinuous permafrost zone of Alaska. For this reason it is to be expected that permafrost would be found during the exploratory effort, particularlY on north facing slopes and areas ~~here arctic vegetation has effectively i nsu1ated the ground surface. Depths of permafrost within the discontinuous zone are vari ab 1 e and often change drasti'ca 11Y within short distances depending _on exposure, ground cover, soil chara~eristics and other factors. Permafrost conditions at Watana as indicated by the exploratory work done to date appear to be typical for the zone. The left abutment which_faces north and is either continuOusly _shaded or receives only low angle rays from the sun was explored with core drilling equi~nt. FiVe· ho 1 es were dri 11 ed and pressure tested by pumping ~~a ter into the drill hales at selected intervals using a double packer. Observation of drill water returns and pressure tests. showed that permafrost exists for the entire depth of the holes. Holes drilled in the right abutment, where the sun's rays are most effective, did not indicate any perma- frost. Within the relict channel areas, on the terrace north of :he right"abutment, indications of permafrost were observed as reflected by ground water conaitions and water table measurements. dri11 action, and sampling. Drill hole DR-27 was sampled and ice lenses were retrieved f1·om ~-depth of 30 through 36 fee·t. Permafrost 1~as a 1 so encountered during test pit activities. However, in general, permafrost in the spillway and relict channel area, while encountered as near as 1 foot to the surface, is expected to be confined to a relativelY shallow layer. This expectation has been reinforced by the fact that ground water has been encountered at various depths. In order to study the thermal regime · of the permafrost and to more accurately define the lower limits of the frozen zone, temperature probes were installed at 13 locations. These locations are shown on Table 1 under the heading "Instrumentation" and the graphs of readings taken to date are shown on Plates D-13 through D-15. It is still. too early to reach definite conclusions from the limited data obtained since installation due to the fact that heat was introduced into the regime by drilling and equilibrium may not yet be reestablished. ~owever, it appears that the readings do support the conclusion that pe~frost is not as widespread or as deep as was previous believed. Of equal significance is the fact that the temperature probes indicate that the tempera"ures within the pe~frost are generally within 1 degree of freezing. Construction in cold regious has sho~tn that, within this range, mater•ia 1 s can be excavated with cansiderab ly less dificulty than in areas where the permafrost temperatures are lower. ·particularlY in borrow areas, where a rather large area can be exposed, degradation is rapid and by alternating from side to side in the area, the material can be ripped, left exposed to the_ sun for a 0-23 Jf' ' ~· . i \' I l f [ r r [ \· .c:-·· .. . ~,.~ few hours and.then handled in the normal fashion;. The fragile nature of the permafrost reg·ime as indicated by temperature studies wi 11 be of prime importance in the scheduling related to foundation gtouting. Pennafrost barely within the frozen range will be much easier to thaw and foundation grouting wi 11 be faci 1 ita ted. As explorations at the damsite continue, the installation of frost probes will be expanded to provide detailed knowledge of the extent of existing permaforst areas as well as their. condition. A discussion of design type of probes installed and the degree of accuracy to be expected from· data readings can be found under 11 Instrumentation.11 . Ground Water Ground water conditions in the terrace area north of the spillway alinement \vere ex.,mined during exploratory drilling, but the use of drilling mud used for most of the rotary drilling made direct water table measurements difficult. Pervious zones were occasionally encoun- tered where loss of drilling mud was noted. Examples are DR-22 where mud losses were exp~rienced of approximately SO gallons per foot of hole drilled between elevations 2,025 and 2,000 feet and 1osses of approximately 14 galions per foot of hole drilled between elevation 1,940 and 1,855 feet. In a very few instances water tables could be measured at the time of drilling. A notable example of artesian head was measured while dri 11 i ng OR-13 and DR-14. 1n both of these holes the ground \·later was under sufficient head to rise from elevation 2,240 and 2,270 feet, respectively, to elevation 2,300 + feet when the overlying clay layer was penetrated by the drill. - A discussion of the overburden units encountered in the terrace area can be found under the heading 11 Relict Channel Area." It will be noted in that discussion that at least two deposits of lake sediments were encountered which appear to be rather extensive. As migh~ be expected, perched water was encountered above the higher deposit, Lake Woller, in some holes because of the impermeability of the material. In the alluvial zones between the lake deposits water wa~ usually encoun- tered although~ as previously noted, in only one instance was this water under artesian head. Below the lower lake deposit, appr·oximate elevation 2,190 feet~ the glacial tills were very compact and can be expected to be relatively impe~vious. The over consolidation of these materials as previously stated is probably due to being overloaded by the weight of ice in glacial times. The significance of ground water conditions in this area lies in the fact that the deep deposits in the relict channel area will be under a head of approximately 400 feet from the proposed Watana reser- voir. The decision· as to whether or not an impervious cutoff across this channel is necessary depends on the pervious nature of the materials D-24 ( ( ·•. encountered. While a more detailed program of exp1oring, sampling, and testing will be undertaken to ensure that pervious layers wi11 not pres~nt a seepage danger in this area, it is presently believed that no impervious barrier is required. A more detailed discussion of the rationale in support of this belief can be found under the heading "Seepage Contra 1, Re 1 i ct Channe 1 •. " Reservoir Geology The Watana reservoir includes seven gener.al zones of geology, as indicated by Plate 0-5 (\~atana Reservoir Surficial Geology). Glacial _fill, outwash, and preglacial lake deposits predominate in the mean- dering reaches of the river upstream of the Oshetna River confluence. -The next zone extends downstream along the incised channel to Jay · Creek and Kosina Creek, and includes localized sedimentary and alluvial units \'lith metamorphi cs such as the Vee Canyon schist. The predomi nat- ing dioritic gneiss and amphibolite is laced with bands of mica schist, pyroxenite, and augen gneiss that are inferred to correspond with contact and shear zones trending northeast. The ~rea around Jay and Kosina Creeks and downstream to Hatana Creek in~ludes t\vo zones \•lith outcrops of high grade schist and basalt flows at the river level. The surround- ing hills are composed of volcanics with limestone interbeds on the south, and mixed volcanics and near surface intrusives to the north for a minimum of 10 miles. The Watana Creek area consists of basalt flows and semiconsolidated predominately clastic sediments overlain by thick glacial and outwash deposits. This area also contains the Ta1keetna Thrust as identified by the U.S. Geological Survey. Do\'Jnstream of Watana Creek lie the remaining t\'iO units, starting \~ith moderately metamorP.hosed sediments (phyllite, argillite, graywacke) with ~Jo bands of schist. The final unit starts just upstream of Deadman Creek and includes all materials downstream to Fog Creek below the damsite. The predominate types are the diorites, ]ranites, and migmatites of ~he damsite pluton. The Watana reservoir includes many permafrost areas, especially on north facing slopes. Frozen overburden will tend to slough as the reservoir is filled and the permafrost degrades. Since most of the lower canyon elevations are covered with only shallow overburden deposits, sloughing will be minor and have minimal effects upon the reservoir. Deep overburden deposits, most1>' of glacial origin, occur above approxi- mate elevation 2s000 feet where the slopes flatten out into a broad river valley base level. Most of these glacial deposits will be stable due to the flat topography. . Some rock and overburden landslide~deposits have occurred within the reservoir area. One such slide deposit, known as the "Slide Block," is located upstream of the axis on the south bank opposite "The Fins'' · shear. Several old and potential landslides are identified by Kachadocrian and Moore in their reconnaissance of the project area. 0-25 .. I f r f I i ( 1 i l 1 l In general tenns, the geology i'n the immediate damsite is controlled by the diorite intrusive believed to be the top of a stock which uplifted the surrounding sediments and volcanics and was later eroded by glaciers. Subsequent g1acia1 and stream deposition has masked much of the flat upland areas and stream valleys. DAM DESIGN Dam Foundation'Treatment Main Dam: Foundation conditions are more than adequate for con- struction of an earth-rockfi11 dam. The underlying rock is a diorite or_granodiorite which, in nonfractured fresh samples, had unconfined ~ompressive strengths·that ranged from 18,470 to 29,530 psie Only the uppermost 20 to 40 feet of this rock is closely fractured and suffi- ciently weathered to require removal within the core area. Stripping .depths along the centerline section are shown on Plate D-7. Stripping to sound foundation rock is required for the entire lenQth and width of the impervious core. Foundation t~eatment within the rock excava- tion area will include removal of a~l loose and highly fractured rock and soft materials, cleanup, and dental treatment. If there are any zones where more than an 8 foot width of soft materials is removed, the dental concrete will be contact grouted to the adjoining rock. Stripping to rock will also be required under the remainder of the embankment area. However, in this area excavation will not include removal of the inp1ace rock. Only the loose and severly weathered surface rock will be removed. Steep or overhanging rock walls will be trimmed to a smooth shape for propar placement of embankment materials. Exploratory drilling in 1978 has shown the materials in the river channel to be a well graded mixture of gravels and cobbles as good, or better, than the materials that would be used to replace them. As the exploration program continues, these gravels will be more completely explored and it may be demonstr?.ted at that time that there is no need for their removal beneath the shell zones. Should this prove to be the case, the change can be made during feature design. Provision has been made for a 6-by 8-foot concrete grouting gallery with concrete lining to be constructed in foundation rock under the impervious core. This gallery will begin at elevation 1,900 feet on the left abutment and will terminate at elevation 1,800 feet on th~ right abutment. It will provide access for drilling and grouting which, in some areas may be delayed to allow thawing of permafrost. Access to the gallery will be provided from the powerhouse on the left abutment and, by adit, from the downstream toe of the right abutment. Grouting will be on a single lin~ of holes utilizing split spacing, stage grout- ing techniques. Grout holes will be slanted upstream and may be included D-26 - 'I '' . i ( ( [ I I l . '':: to intercept the dominant high angle northwest tending fracture system. Preliminary grout hole depths are estimated at two-thirds the height of the embankment to a maximum depth of 300 feet with primary spacing of 20 feet, secondary spacing of 10 feet, and tertiary spacing of 5 feet with additional holes as required. Determination of final grout hole depths, spacing, inc1ination, grout mixtures, and grouting methods will be dependent on the results of future explorations, permeability studies, test grouting, and perma- . frost thawing investigations. Rock permeability test results are shown on the dri1l logs presented on Plates D-28 through D-37. Coefficients of permeability (K) were computed in feet per minute times lo-4. Permeability coefficients ranged from 0 .. 0 to 23 .. 1 and average 4.9 for those holes that were tested. Drill holes in the left abutment area indicated very low permeability due to permafrost. River section hole DH-1 had variable permeability coefficients that range from 0.48 to 2.52 and averaged 1.98. Drill water returns in the river holes were quite variable throughout the entire hole depths and tended to drop off to low percentages at the greater depths in the axis area. Right abutment drill holes had perme- ability coefficients that ranged from 0.0 to 23.09 and averaged 5.47. DH-lO 'Has the only hole tested that had relatively lo\v permeability coefficients throughout. Drill water returns had sirni1ar patterns with variable percentage losses. DH-7 and DH-9 had 0 percent returns through- out and DH-8 and DH-11 maintained high percentages of drill water returns throughout .. The existence of perm~frost in the left abutment and the possibi- lity of minor amounts in the right abutment necessitates assessment of the problem of thawing a zone in the foundation bedrock sufficiently wide and deep to allow proper installation of the grout curtain. In anticipation of this need, the U.S. Anny Cold Regions Research and Engineering Laboratory was asked to do a desk study on thawing the per- manently frozen bedrock. The Technical Note which was.submitted in response to the request is included as Exhibit D-4. Embankment Design Design of the dam embankment at Watana damsite has been based on the availability and proximity of construction materials in addition to their suitability as engineering materials. As a result of these con-t ~iderations, the embankment contains a central section consisting of an r 1mpervious core buttressed on the downstream sjde by a semipervious zone. D-27 - ~ r [ This central ~ection is supported, both upstream and downstream, by suitable fine and coarse filters and rockfill shells. A typical cross- section of the embankment is shown ori Plate D-9. The impervious core and semipervious zone will be constructed using the glacial tilT which is readily available in the area. The semi- pervious material wi11 be obtained by selecting the coarser grained materials while the finer materials will be placed in the impervious zone. These materials, as discussed under 11 Embankment Materials," have been shown by exploration and test to be a well graded mixture, which~ when compacted, has a very good shear strength and a high degree of jmpermeability. Tests have shown that this material is quite sensitive to moisture control; therefore, special attention must be paid to this aspect of the design and construction. The 14,000,000 cubic yards required are available within a very reasonable haul distance and will only require removal of oversize boulders prior to use. The fine filter material can be obtained from the gravelly sand deposit at the mouth of Tsusena Creek. ·Chart D-3 shows an envelope of gradation~ from this source superimposed onto the envelope for the fine filter as established by engineering design criteria. This comgarison indicates that the Tsusena Creek source can provide material within the ranges of sizes necessary to protect the core and semipervious zone against piping or mig·ration of fines into the filter material. Proven sources of gravel which can yield large quantities of material are scarce within short haul distances of the project. For this reason~ the decision was made to use material from the rockfill source as a coarse filter. Chart 0-5 is an envelope of the required gradation which will provide proper filtering action for the fine filter material. A curve has been superimposed on this envelope which represents the materials expected from the rockfill source. As indicated, the rockfill will provide the proper filter action. The maximum size material in the coarse filter and the lift thickness for placement will, of course, be limited to ensure design criteria are met. The decision to utilize rockfill rather than gravel for the embank- ment she11s was made when reconnaissance and exploration indicated that dependable deposits of gravels which would provide the necessary quanti- ties could not be verified within reasonable haul distances of the dam- site. On the other hand, rockfill can be readily obtained as discussed under "Embankment Materials." Riprap for wave protection can be obtained from the same source. It is recognized that the 1 vertical on 2 to 2.25 horizontal side- slopes shown on the typical cross section for the dam are conservative for a rockfill dam, and, if rockfill is used, these slopes will be re- fined in accordance with sound engineering practice. Refraction seismic D-28 ( ( ···-····----·--··-~--··--········-··--·--~-···--····-·----·-~--"--·---~·-·····--·-"<··----~-·---~-.---···""..,_..;;;:~j I;' - }; ) lf ~ l ~ ! l: lines in the borrow areas show velocities which could represent 1arge deposits of gravels or glacia~ materials but rather extensive e~plora tions \'lill be required to ver1fy the true nature and quantity of the materials. Should these explorations reveal that suitable gravel deposits in the area are sufficiently extensive to provide the large quantities required for the dam shell sections, the gravel will be used in preference to borrowing quarried rock for rockfill. Powerhouse and Underground.Structures An underground powerhouse is well suited to meet the restrictions of subarctic weather and other environmental factors. Topographically, the narrow Susitna Canyon is well situated for this type of underground construction. The diorite pluton that underlies the foundation area is expected to.be competent for excavation and support of underground facilites, but the location and design of the various structures may have to be adjusted in some areas. 11 The Fins" and "Fingerbusteru Shear Zones shown on Plate 0-3 and discussed in paragraph nRock Structure 11 are the two most significant shears within the damsite area. Other northwest trending steep angled minor shears involving displacements of a fraction of an inch up to a few feet are corranon i·n the site area and \vere noted in many of the drill holes. These minor shears appear to represent mass adjustments to regional stress and compensation can be made for them in design ana construction of the underground structures. Prior to pmverhouse excavation, exploratory adits iocated near the crown of the various chambers will be driven to confirm final design criteria. The chambers will be constructed with straight walls as required for maximum dimensions, and not notched or cut irregualarly for support of interior powerhouse facilities. Rock support will include pattern bolts consistent with wall and crown conditions. U$e of steel channeling and remedial concrete is anticipated in local areas where fallout may occur or in fracture zones having a substantial width of crushed rock. Wire mesh will be utilized where necessary as a temporary facility prior tc placing concrete. A thin layer of wire reinforced shotcrete may be placed on the main powerhouse chamber wails and crown as a protective measure against rock raveling. Additional shotcrete wi 11 be uti 1 i zed, as requi red·:s to sea 1 surfaces and retain rock strengths. Construction methods in the large chambers will include controlled blast- ing and rock removal in lifts from the top downward. Gutter and floor sloping for drainage will be provided in the interior structures between chambers. Intake Structure Consolidation grouting may be necessary for the intake structure foundation and the bridge pier footings. The higher bridge pier footings will also be recessed into sound rock. Tunnel portals will D-29 - t:. t IJ [ I' [ [ I. l.i be designed so that there is a minimum of two tunnel diameters of sound rock above the heading where they go underground. Initial tunnel support will be by pattern bolts, with steel channeling and wire mesh where necessary in closely fractured areas. ~1ajor shear ·zones will require steel supports. Hydraulic and geologic considerations will necessitate final concrete linings for all but the access tunnels, and steel liners for the penstocks. Grout rings will be required in the penstock portal areas. The t~o diversion tunnels are to be separated by a minimum of four tunnel diameters to provide greater structural stability. Downstream diversion tunnel portals will have to be located to avoid the •'Finger Busteru shear zone to insure adequate portal construction conditions. Spi llwa,t The gated spillway has been relocated about 800 feet southeast of the alinement presented in the 1976 report so that it will be constructed in a through rock cut. The spillway will be unlined beyond the spill- way gate structure and apron. The new spillway alinement extending from the Susitna north valley wall to Tsusena Creek and the spillway gradient are shown on Plates B-2 and B-5. It is anticipated that, with the exception of minor amounts of waste, all the excavated materials from the spillway will be used in the dam embankment. The· major part of the excavation is in rock and this material will be used in the shell sections. The overburden materials are glacial till which, when separated from the boulders can be used in the impervious or semiper- vious zones. Seepage Control -Relict Channel The relict channel a1ea is an overburden terrace underlain by a bedrock depression, and extends northward from the right abutment for about 6,000 feet. This terrace is composed of glacial tili, some of which has been reworked by alluvial action. For this reason, consid- eration was given to the possibility of seepage through the al~ea where rock contour·s are below the proposed reservoir elevation. However, preliminary seepage calculations indicate that even in the relict ch~nnel area~ where the head differential approaches 350 feet, and using a very conservative 'k 1 value of 500 feet per day, the seepage would be less than 0.02 cubic feet per second per foot of width for a pervious layer assumed to be 80 feet thick. Assuming such a layer to be 200 feet wide, the seepage would be in the order of 4 cubic feet per second, which is a minor amount. The exit velocities associated with such seepage wo~d be too low to cause serious piping or erosion. Investigations during the summer of 1978 support this conclusion. In holes DR-13 and DR-14, located in the vicinity of Borrow Area no," ground water was encountered in alluvial layers between elevation 2,240 D-30 \ ,, - ( ( .. . \ ,-c. . ' and 2 280 feet with an artesian head \vhi ch exceeded the proposed reser- voir ievel by 100 feet. In spite of this high head condition, no evidence was found indicating seepage out of this layer into either Deadman Creek or Tsusena Creek. Indeed, it is probable that the effect of this artesian watery which evidently has its access to the ai1uvia1 layer in the upper reaches of Tsusena or Deadman Creek, would be to resist flow from the reservoir into the aquifer. Because mud 1osses in OR-22, located at the center of the relict channel, indicated the possibility of permeable layers at approximate elevations 1,900 and · 2,000 feet, a falling head permeability test was performed at this holeo The oermeabilities calculated from this test are a further indication the seepage through the terrace would be minor or nonexistent. Conse- quently, it was unnecessary to include any cutoff through the saddle and relict channel area. CONSTRUCTION MATERIALS Material Requirements Embankment: Approximately 57,792,000 cubic yards of embankment materials will be required to construct an earthfill dam at Watana site. The impervious core is estimated to require 7,373,000 cubic yards and the semipervious fill zone 6,077,000 cubic yards of material. The fine filters are estimated tc require 5,621,000 cubic yards of material and the coarse filters 2,201,000 cubic yards. The pervious rock shells, which make up the largest portion of the dam, will require approximately 36,297,000 cubic yards. Slope protection on the upstream side of the dam is estimated to require 223,000 cubic yards of riprapw Sources of Materials Genera 1: Severa 1 sources of embankment rna teri a 1 s· were investigated in the damsite area. These sources included ~do quarry locations which could yield rock shell and coarse filter materials, a source of glacial till which could produce core material, and two areas containing rela- tively clean sands and gravels for the fine filter material. Additional embankment materials will be generated by required excavation for the dam foundation, under·ground facilities, and the spillway channel. A 11 rock excavation from the spillway channel will be incorporated into the rock shell zone of the dam. The overburden encountered in the excavation for the spillway channel will be glacial till which can be processed by removal of oversize material for use as core material. Rock Shell Materials: Rock shell materials may be obtained fr·om two quarry locations shown on Plates D-10 and D-11 . 0-31 .J,. . . I [ [ [ l [ Quarry sites \'/ere located on the left abutment of the dam (Quarry Source 'A') and in the northwest quadrant of the confluence of Deadman Creek and the Susitna River (Quarry Source'S'). The Quarry Source (A) on the 1 eft abutment is an ou·~crop of igneous rock ranging in e 1 evati on from approximately 2,300 to 2,630 feet. The total volume of the hill above the surrounding terrain is approximately 200 million cubic yards of rock. Development would consist of open faces on the north flank of the dome with the final quarry floor at an elevation of 2,300 feet • This type of deveiopment wou.ld maintain the visible profile of the hill essentially as it is now. The resulting quarry floor could provide an ideal site for parking areas, visitor facilities, and perhaps, the switchyard. The materia 1 in the hi 11 is a di cri te on the \<Jestern side and a rhyodacite porphory on the eastern half. The appearance of outcropings and exposed faces of each material indicates that the hill is composed of sound rock. The product of th.is quarry will be used for the rockfill shell zones of the dam and in the coarse filter and riprap. This site (Quarry 'A') represents the nearest source of adequate quantities of rock materials for the dam. From the approximate center of the quarry to the approximate center of the dam is a distance of 4,000 feet and .movement of material would be downhill. If properly developed, virtually all of the material removed from the quarry will be used in the dam and the oversize material, overburden and weathered waste material can be disposed of immediately adjacent to the quarry in the reservoir area upstream of the dam. The quarry source at the confluence of Deadman Creek and the Susitna River (Source 'B') could be developed by excavating rock from the open faces visible on Deadman Creek and continuing the development of a face to the west\'lard, maintaining the face between elevation 1,700 and 2,000 feet. Strtpping and clearing would be minimized by developing a long, narrow quarry paralleling the river and using the quarry floor as a haul road for the length of development. If exploited in this way, the quarry could yield 17,000,000 cubic yards of material. The rock exposed in this area is a moderately weathered diorite. The product of this quarry could be used on the rockfi11 she11 sections of the dam. The distance from the center of the Quarry 'B' to the center of the dam is approximately 2 miles. The only reason for utilizing this quarry source instead of the Quarry 1 A' on the left abutment would be the lessened environmental ~ . impact since the quarry at Deadman Creek would be entirely in the reservoir area. However, since the hau1 distance is greater and the D-32 ( l ( _./ { net environmental impact of the Quarry 'A' on the 1 eft abutment i.s small, this area is a less desirable source of embankment materials. Core Material: Impervious and semipervious materials can be excavated from the glacial tills which are present at the damsite. The most logical source of glacial till appears to be in an area denoted as Borrow Area 'DJ which lies between Deadman Creek and the saddle on the north side of the dam (see Plate D-11). Exploration in this area was accomplished by drilling with a track- mounted, self-propelled auger and a Failing 1500 rotary drill, by test pitting with a backhoe, and by use of seismic refraction methods. Five holes were completed using the air rotary drill, 14 holes were completed using the auger, 14 pits were completed with the backhoe, and 4 seismic refraction lines were extended across the proposed 1imits of the borrow area. The material in the area is composed of a su~face layer of natural ground cover of roots and moss, approximately 2 feet of boulders and organic silts underlain by the tills which are classified as gravelly silty sands. The tills range from 15 to 25 feet thick and usually over- lie a clay, sandy gravelly clay and silty sandy.·gravel .. Sack samples from the test pits (in Borrow Area D) were tested at the North Pacific Division Materials Laboratory to determine gradations, compaction~ consolidation characteristics, permeability·, and triaxial shear strength. Gradation tests were run on each sample from each test pit. An envelope of the gradation curves derived from the tests of samples from Test Pits 8 through 19 is shown on Chart D-2. Because the range of gradations of materials from the test pits centrally located in the atea is limited, a composite sample was formed. Use of a composite sample was necessary to provide adequate material for a representative testing program since retrieval of large bulk samples from the site v~as not possible. The coefficient of permeability (K2o) for the minus 1-inch fraction of the till material, compacted to 95 percent of maximum density with an optimum water content of 7.5 percent equals 10.90 X lo-6 em/sec. This relatively low coefficient of permeability is coupled with an adequate shear strength at the optimum water content, acceptable con- solidation values even when loaded to 32 tons/sq ft and a narrow band of gradation throughout the central portion of the outlined borrow area. The shape of the compaction curves indicates that moisture content is critical in obtaining maximum densities with a pronounced peak at the relatively 1ow optimum moisture content of 7.5 percent. The results of the triaxial compression tests indicate that in the unsaturated and undrained condition the glacial tii1s will be sens~tive D-33 ( I I ' ~~ to moisture·contents higher than optimum but that if placed on the dry side of optimum they will .maintain strength essentially equal to those obtained when placed at optimum. The results of this testing program indicate that the glacial tills can be placed and compacted to provide a suitable material fo~ both the impervious and semipervious zones. The specifications will need to provide for close controls of the moisture content 3nd the quality~ assurance programs will have to be adequately staffed to provide for careful checks of moisture content in the pervious and semipervious fill. Detailed laboratory reports of the tests conducted are included as Charts D-6 through D-29. The materials from Borrm'-1 Area o· can be used hri-+-.h very little processing. The ground cover and organic silts and boulders will be stripped from the surface and disposed of as designated near the mouth of Deadman Creek in the reservoir area. The remainder of the material can be utilized in the core of the embankment if oversize (12 inch plus) ·material is removed by mechanically raking in the pit or on the embank- ment fill. Less than 10 percent of the material will be too large to use in the core. Since removal of oniy the silty, sandy gravel above the clays will result in the floor of Borrow Area rol being above reservoir elevation, it will be necessary to contour and seed the borrow area after the completion of removal of materials as a restora- tion measure~ Approximately 630 acres will be restored. Filter Material: The nearest source of clean sands and gravels for use 1n the fine filter of the embankment dam is an aliuvial deposit formed by materials washed out of Tsusena Creek and deposited at the confluence of Tsusena Creek and the Susitna River on the right bank of the Susitna (Borrow Area 'E', see Plate D-12). Haul distance to the dam ranges from 3 to 5 miles. ·This area was explored by digging 5 test pits to a depth of 8 feet using a backhoe mounted on a small tractor. The material in this area is composed of approximately 2 feet of organic, sandy silt overlaying 6 feet of clean, well graded sands and gravels having maximum size particles of up to 4 inches in diameter. The materials are sound, well rounded particles, The bottoms of the test pits indicate the possibility that the materials deeper than 8 feet below the ground surface contain up to 50 percent of boulders in excess of B inches in diameter and ranging up to 24 inches in diameter. The 6 feet of material which lies above the boulders may be used in the embankment with required processing limited to some blending and .remova 1 of materia 1 1 arger than 12 inches to produce fine fi 1 ter material. An envelope of gradation curves· derived from tests of samples from TP-1 through TP-5 is shown in Chart 0~1. All of the samples are from the first 8 feet of material. All .of this material lies above D-34 ( t [ 1 \ 1 t. l I > -· -.·-~·····l--·-···;;,~,;;c:r~···:-----·~--·---'-···--· .. ·-~---·-··-·--~·----.. ··-· --~····-----····-------..... -~ .. ·-···········-·---.·~~ .. ---------··--·--:--:J~~{~. :-:" .· . ,\ ' - [ [ the \vater table and can be taken by front loaders. The quantity of material available in the fi~st 8 feet is approximately 3.7 million cubic yardso After the boulders are encountered at a depth of 8 feet 1 the oversize material will have to be removed and material below the water table will have to be bailed from the area. A dike will be maintained to separate the borrow operations from the river so that all turbidity created by the excavation of materials will be filtered or settle prior to entering the Susitna River. In terms of grading, particle soundness and proximity, this area represents an excellent source of essential filter materials~ The second area in which clean sands and gravels were located is in the upper reaches of Tsusena Creek, north of Tsusena Butte (Borrow Area 'C'). The materials are sound, well rounded particles and are well graded with maximum sizes generally less than 4 inches. Consider- able exploratory effort would be necessary to ensure quality and quantity of materials before this could be considered an acceptable source. Because of the haul distance of 12 miles, this source will not be con- sidered unless further explorations and testing ipdicate that adequate materials may not be obtained from the sources closer to the damsite. Exploration at Site 'C' was accomplished by digging one test pit~ reconnaissance of the area on foot and from helicopter, and with a seismic survey. Concrete Aggregates: Approximately 310,000 cubic yards of concrete wi 11 be requi r·ed to construct the appurtenant structures for an embank- ment dam at Watana damsite. Most of this will be structural concrete placed in tunnel linings, the powerplant, gate structures, intake struc- tures, and spillway channel lining. Maximum size aggregate will be 3 inches in all but the smaller structures or those with closely spaced reinforcing. The most readily available source of concrete aggregate is available at the confluence of Tususena Creek and the Susitna River (Borrow Area 'E'). The materials from the fir~t 8 feet in the alluvium • can be utilized with only limited screening. As oversize.materials are encountered at greater depths, the larger particles will be crushed for use in the concrete aggregate, thereby achieving maximum utilization of gravels from the area and also to increase the tensile strain resis- tance of the concrete which will lessen problems with thermal cracking in the more massive sections. Since Borrow Area E r8?'resents the most economical source of concrete aggregate and the neare~t acceptable source of essential filter material. maximum utilization of the material in this area is required. - A petrographic analysis of sands and gravels from Borrow Area E was conducted by the Missouri River Division Laboratory at Omaha, Nebraska. The results show the material to be approximately 70 percent D-35 l· ~ ,~; r t~ . granitic rock with the remainder composed of basait, andesite, and ryholite. Chert is present in such small quantities as to be nond~1e terious. The quarry site on the left abutment (Quarry Source 'A') is con- sidered an alternate source of concrete aggregate. If material from the quarry were used in the embankment dam aggregate could be produced by placing a crushing and screening plant in the quarry and prt1ducing the concrete aggregate incidental to the production of embankmen~ material. The concrete aggregates would be produced from the dio\ites in the quarry tci avoid the potential of problems caused by the reaction of the alkalis in the concrete with the rhyodacite porphory in the eastern half of the hill. The materials in upper Tsusena Creek (Borrow Source 'C') would produce excellent concrete aggregate; however, because of the haul distance involved (10 miles), it is.not anticipated that this source would be exploited to· produce concrete aggregate unless embankment · materials are also taken from the same source. It is anticipated that because of the relatively small quantities of required concrete aggregate compared to the large quantities of the various classes of embankment materials, that concrete aggregates will be produced incidental to the production of embankment material and stockpiled adjacent to the batch plants used. The first concrete required on the project will be that required to line the diversion tunnels and form gate and trashrack structures for river diversion. The aggregate for this work could be produced from Borrow Area E with a resulting haul distance of 2.3 miles. D-35 ( . --.,:_ . ·: . -, .J . . -.0 • •' \ • : • ' • . . \ I i \ 1 I j I I I I I ! I I 1 ·I I ! II i I l I I t l \ l1 I . w u 0: ::l 0 (/) w ~ Cl lo.l 0: l!l ~ w t~ tu 0: u . Z J ( 8 I \''• ' '. \ .. .. , ·II. \ } '· ' l \ I I f I l I I I t I '· i,'' .. • -~·" ........ ;, ... '1 ~ : > ~·· ~"!..' , •• .. . . . : . ". ~ ... l, • .. • .. 4 ;. ,_ .. • ' 0 ... ...: • ' ~ • \ ' ~I .. \ ' • -~ \. ~ ~.·.; ". '!<.:·, _ _', \' •. ' • OOO'.LU :1 • . .. ... #. ·~ ~ • •i<p·~~ ~>~.: .. ;t~-~ .. ~~-.. /1'~-,,"" ~ ~~.: "'':.. :0 .,. t: ·,~:r"N~~:~· !'l~lo>~t"':; • Cl -~ • • "' • ~ ,. l • . ''< ~· o' _:,.::. ·-·. • • • • • •. " • . . ' ~ ' ' '' .. ' \ [ \ \ \ .' ' "' .. ... ... . ~ i) z ... ... 0 "' ... ... 0 1.1 3NJ1 H:l.t\'1'1 J. I t r t ------------·-··· ----------------------·--·-------~ -c--··· ~-= L_.~QQ_. ~ I ~--·-·-____ 4~'L-, ---·· -~~- ·• CRf.ST _EL J<l !<!.§ AXIS OF OAM -~ _j I ~AX ..f~OL EL !;'!,_115Q~··· / 2'1" DIA EL 1'155 .L!AX T W EL 9Z4 LOG SLOT !..~.:J --AXIS OF DAM .2s~r ~L.:l~;'>§l il 0.75/ if/ ' ' &, ,;~il ~~--, ASSUMED TOP OF ROCK SPILLWAY Sf-CTION ~~ SECTION THRU PENSTOCK AND POWER PLANT ----sCAt::E~ocr---_TYPICAL 1\!.Ql'J-OVfBFLOW SECTIOl:L •o• rl $tl aa" ~.c::-:::-===;... ...,..j """»-< .-st.u.t. (--«::I··fj~ MONOLITH ~ ORiGINAL GROUND SURFACE/ ASSUMED EXCAVATION LINE 26' OIA. ~~~~~£E~ METAL TRASH RACK ;fNTAKE STRUCTURE , , ,CJ,~-~-r--r . ;TO;: OF 1 DAM 1 t.L.I~:>:>,-! <i:. EL 1075 LOW LEVEL SLUICES -FOOEMERGEN-cYiifiliwoOwN' UPSTREAM ELEVATION Lj -~~X..£001. EL.J.'l~5 oEVECO?Eo"Alo'NG<toFDAM SCALE: I" ,. 100' I' V'\ ' \ /. \ / ' I \ /~-----/ \ -/ ~ ---;/' \ / ' I ' FINE / -'-" \~--]I:;L_.J.~L TOP OF WAlL f ~2_~:L /zs' DIA. ,PUIG SECTION d '- tL!!?L_ I --L. I' ~ ----- .. EL.lL'!~ -~~ " -----·-=--··'·-···--· .:,..-.-=.==-=~·,,"'""'-" I .EL...Jl'l3 ' 1400 =====-::::-::.:·-::::· ::;;..;:=""'""""'-·---·-· .... -. =-=......,.__-===-. . --.. . . -- 1200 1000 t .eoo roo DIVERSON TUNNEL PROFILE SCALE: 1":1001 ' . '100 200 0 ,.A.I" .. t ICAJ,.( 1•• 10'•0 .. ··--__rORIGINAL GROUND LINE -----------~ DEVIL CANYOt-.J .. AUXILIARY EARTI-I FILL D~M .cl d •o• .,~ ""=-=· I I .II.U'OC •tA\.l• r• 160"•0• -~~..,•~·-·~MNt<W:W4 ~ SOUTHCENTRAL RAIL BELT AREA, ALASKA SUPPLEM!'.NTAL FEASIBILITY STUDY UPPER SUSITNA RIVER BASIN DEVIL CANYON DAM CONCRETE GRAVITY DAM ELEVATION AND SECTIONS AlAS<A DISTRICT, WIPS Dr £'<GIN£ERS Allf'!toOIII"'-C • AU,S.u FEBRUARY 1979 PLATE 6 c e COH!. Of (>-IGINHR$ 2500-90";00 95';00 2.<;00- 2300- 2200. 2100- 2000- J900 -~t 1800 - I 1700. 1600 ... 1500 - ~ 1400 ..... :; 1300 • 2: 1200 - 0 !i 1100 - ~ ...J 1000 • w 900 - BOO • _,._,.._ ~-- 'l,., 'b., ~·a<!>· fbx. <!>'( JOo .. oo 105700 1101·oo ustoo 12o;too 125+oo zy {L-1:30-+0!L ! GRID BASE STATIONING FOR CM3ANKMENT SECTIONS 20 SEPT 1978 -••. • ~-1~5:>00 140_!..00.. N 3,224,898.674 E 744,915.063 1oo•oo -----CREST ELEV. 2195 -NORMAL .POOL ELEV. 2185 -, . ., 1 OH IO ----~,.,:;;,.P 17 GLACII\l TILL H. II ... ;;.:;:.;..:-1 • D •• ~:::.--..-: 78'0F RIVER ld GLACIAL g~:g _>_::.:.;.:-;c;UARTZ DIORITE AllUVIUM TILL ~··~ORITE-. ~ANDESITE DIKE WE. WE. OH·S . :;.---. ~P NDE:~ITE d! ~DH·U BOTIOM ISO' DIS DH·7 · ~RftJ ~~~y MODERATElY TO HIGHLY fRACTURED 5' GLACIAL .-·9"" IO 1 ~"ELSIT"' DIKE TILL . ~ DIORITE ·,~ -. ·-;-;::?" :· . 1 MOt>.'RATE TO HIGHLY FRACTURED ZONE ·5 DH-4 . ; I OH-9 BDTIOM 175' DIS H . ,"ELEV •s 146:3 SUSITNA RIVEfL_ ~-. ----------·------ 73' ote-~-~w"'"",· ....... ..Y~• I~~ y~-j>-' I DH·7 BOTTOM 4 5• D/S "'~IVCRSIOO TUNNELS ~~( l£.1'148.75 LIGHT 10 MODER A ~OUARii! IE. 144853 FRACTURED ZONE \ ·,DitRITE ANDESITE PORPHORY '\ DIKE ~DH·21 BOTTOM 70'01S SECTION A-A ~'=' LEGtNO SURfACE LINE TOP OF ROCK LINE 0!; ... ~~,. FOUNDATION BEDROCK EXCAVATION L.INE ~ SH!:AR ZONE DIS OOWNSTREAM U/S 0/B WE. DH I.E --2500 .2'100 .2300 .2200 .2100 -2000 .1900 .1800 .1'700 .1600 .1500 .1'100 -1:300 .1200 .1100 .1000 .900 .BOO UPSTREAM OVERBURDEN WATERS EDGE DRILL HOLE INVERT ELEVAiiON TOP OF ROCK EXCAVATION. LINE NOTE! TOP or ROCK LINE 6 EXCAVATION LINE SUBJECT TO CHANGE. rOR LOCATION Oi-" C.'lOSS·SECTION SEE PLATE 0-4 SOUTHCENTRAL RAILBELT AREA, ALASKA SUPPLEM!:NTAL FEASIBILITY STUDY UPPER SUSITNA RIVER BASIN WATANA DAM SECTION ALONG DAM AXIS &l&$1(~ 0!5-lft.C.T. (X)I:IP.S CY (~l"'l[[lltS .. ...:;....,...""',. .c ... ~ ... PlATE0-7 ·~iiJIWtlf\li t i!IJ@Willlilll!IJI*DIL I SJIIII .. Uf.jlktt.t 24Z4¥4lk JUS 3 £t4il¥!f]I!IA.C .¥P. N1!! Y!i1 QJAP · •...,...wma•""'s'*'+'Wwn-• .. 'll: . F:i .. J . ' '.:.· PRELIMINARY REPORT OF THE RECENT GEOLOGY OF THE PROPOSED DEVILS CANYON AND WAIANA D~~S!TES, SUSITNA RIVER, ALASKA • by Reuben Kachadoorian and Henry J. ~~ore ABSTRACT At the request of the Corps of Engineers, the U.So Geological Survey conducted a reconnaissance of the recent geology of the proposed Devils Canyon and Watana damsite areas, Susitna River, Alaska. The pu~poses of the reconnaissance ~ere to look for active faults and other geologic hazards-Field work by the Geological Survey was conducted .,. ,...._ .... . . betveen July 25, 1978 and August 7, 1978 using a helicopter wh~ch ~as shared jointly and in cooperation ~th personnel of the Corps of Engineers. '!he geologic reconnaissance of t·he proposed Devils Canyon and' ,., ... ~ . Wat4na damsite and reservoir areas did not ?ncover any evidence for recent or active faulting along any of the known or inferred faults- Recent movement.of surficial deposits has occurred as the result of mass wasting processes and, possibly, by seismic shaking and minor displacemen~s of bedrock along joints. Landaliding'has occurred in the past and future landsliding appears " .... ~ ... ~--" f probable. The occurrence of unconsolidated glacial debris~ alluvium, a~~ .. -~ertiary sediments ~r; .:.~eva~ions below the proposed reser-1oir wate_r levels may slump and slide into ~he reservoirs Yhen they are inundated • . ....... : ... Some of these sediments may be permanently f••ozen and, locally, may be 1 ., ... ' . 1 ' .:.] ~~ !f; '·j ice-rieh ~~ch increases the probability of slumping and sliding when the sedicents are thawed by the ~ater impounded behind the dams. The tectonic framework of the Devils Canyon and Watana damsite areas is not w-ell understood. The present know-ledge of the area .. r indicates that the seismicity of the region ranges in depth from less .. .....::1 [ r I ,. i' ~ [; 1 • ~ l 1 ' :r. ~ t . ' ' than lC km to greater than 175 km. Additional detailed geologic and seismic studies are necessary in order to reliably evaluate the potential geologic hazards in the region of the proposed dam and reservoir sites. 2 - "" <.. ... .. •. li!t 1 • -.. ~ I F~ r • I , ~ .I I' .• .,, \-.- [ ! • .t,··.· ; '··~ - - RECCMMENUAT!ONS T.h~ conclusions presented in this report are based on a reconnaissance study of the proposed Devils Canyon and 1j.lata.na dam and reservoir sites, and, therefore, should be considergd :o be prel±Minaryft A thorough evaluation of the geotechnical problems of the proposed dam and reservoir sites will require more data. It ~11 be necessary to (1) map the Healy, Alaska, Quadrangle, at a scale of 1:150,000~ f=om the Talkteena Mountains Quadrangle to the Denali Fault, about 80 km (48 miles) nor~h of the damsites, (2) map the proposed Devils Canyon and Watana damsites at an appropriate scale to determine the bedrock structure and distribution of unconsolidated sediments. o:verlying the bedrock, (3) map the reservoir sites at a scale of 1:63,360 in order to (a) establish the type and distribution of unconsolidated sediments and bedrock, (b) locate additional potential landslide areas, and (c) determine the nature and distribution of pe~afrost, (4) in~tiate a seismic monitoring program of the dam and reservoir areas, (5) continue the active fault study, (6) redetermine the altitude$ of the Vertical Angle Benchmarks, and (7) collect detailed data on the suspended loads and bed loads of the Susitna River in order to deter=ine if the reservoir filling rates are acceptable. 39 . I ' < PART VI: CONCLUSIONS .r 58. The geological-seismological investigations to date were made on reconnaissance level.s. The Devils Canyon and Watana damsites are in a reg£on of high seismicity and major fa~lts. However, no move- r ; ' ments wer~ found on the faults that might be indicative of earthquakes. r f ' Also, no seismic activity was identified as associated with these faulcs, though the data suffers from inexactness in the accuracy of locations. r-No active faults were found ac the damsites. Active faults of appreciable y. iength are required if large earthquakes are to be generated in close proximity of the proposed structures. 59. The area was provided with a floating earthquake of magnitude 7 placed at a short distance from the damsitas. The magnitude 7 is ~n conformity with general fault lengths in this area and with world~de experiences between such faults and resulting earthquakes. However, ( further field studies will be mad'e to determine conclusively whether . or not there are faults closer to the sites with possible more severe motions. An ea~thquake of magni,tude 8 from the Denali fault at a distance of 80 km was evaluated by attenuating the event to the damsites. 60. Peak motions were assigned for the earthquakes following the practices of the Corps of Engineers. The magnitude 7 earthquake near the damsites has motions that are: acceleration 0.68 g, velocity 68 em/sec, displacement 30 em, and duration 12 sec.. An earthquake at the f I' Denali fault attenuated to the sites provides motions of 0.28 g, 40 em/ sec, 22 em, and·lO sec. 61. A closer specification of which sets of peak motions to apply and the appropriate time histories will await further field studies. 18 ,- r l ' 7 ·, . r . ' r ' F L ' f! ! ' j r ~ .. · ... 62. Possible induced seism~city from .reservoi:t• loading is not a factor needing additional design but is accounted for in the existing motions. However, water waves from possible earthquake-triggered land- ollde~ and possible overstressed conditions in rock pass problems for which at present there is a ~aucity of data and a need for further evaluation .. 19 -- .. ~ I , r. :w- r r . r r t. r ! r~ ~ \ ~ • . ,[ .. ~ .. . UI~TI'ED STATES DEPA:\Tl:·i:Er,T OF THE I!U&{IO?. El.JrtE.4.U OJ? RECL.t-.!.!..ATIOH ENG!Nf:~:rtiNG GEOLOOY REPORT F'EA.SI~ILITY ST.P.GE DE\''IL CJ.Jrt ON DPJr1 ' . Alas}~ Geologic Report No. 7 Alasl':-9. District Headquarters JU.Deeu, Alasl~a l.farch 196o • . . c '---·-·----·-·--. -·--.,.~ ....... _... ..... ___,_ ---"'---~i'-""'" .. - . . .. -( ( ! I •J CONTLNTS Abstract •...••••••••.• , •.••••.••.....•••....•.......•..•...••• Introd.uction ............................................... -••• Purpose of the Investigations Report .•.••••• , ••.•.•• . . . . . . . . . . . . . . . . . . . . . ~ . Perfor~d. . . . . . . . . . . . . . . . . . . . . . . . . . ' . . . . . . . . . Purpoae of the D:rilling ...................................... . Terrain Condi tiona ••••••.••.••••••.••••••••.••.•••.••••••••••• I I • e • I • • • t e • e • e 6 e • • t • e a I a .. •••• !oce.tion (Pls.te l, Fig'J.re 1) .. Topog:re.phy (Figure 2 ) ....................................... . Clima.te ( Ts.bl~s I and !I) .•.• , ••. " •.•••• o ••••••••••••••••••• lir-e a •••••••••••••••• Table I: Cli:tr.s.tic Ds.ta--Devil Ca.nyon T'a.ble II: CliL"latic Data--Freeze end Ice ConditionD .•.•••• Vegetation •••• ~~ •• , ................. o ••••••••••••••••••••••••• General GeologJT ••• 0 ••••••••••••••••• 0 •••••••••• " •••••• e ••••••• .Bedrock ••••• • • ~ • • • • • • • • • • • • • • • • • • • • • , • ; • 0 • • 0 • • • • • • • 9 • • • • • • • • StrU.cture {F'igtire 3). • • • • • • • • • • • o • • • a • • • • • • • • "e • • • • • • •••• Pen.e..frost •• ., •. ft ••••••••••••••• o ........ ., ........ o ............ . Recent Deposita ••.••• • • • • • 0 • ' • • • • • • • • • • • • • • • ~ • • • • • • • • • • • • • • l~r·'aines •.•••••••.••.••.•••••••••.•• ~ o ................. , .... . Otlt vas h • • • • • Jt • o • • • • • • • • • • tJ • • • • • • • • • • •• o • • • • ... ., • • o • • ••• o • • ., Terraces •••••••••• ,;) ................ co ••• Q ••••••••••••••••• Tal us and l"'\l b b le , • • • • • • • • • , • • • • • • ~ • ~ • • • • • • • • • • • • , • • o • • • • • • S;;amp depoa 1 ta • • • • # • • • • • • • • • • • • • • • ' • • ' • • • • • • • • • • • • • ~ • • • • • • Seismic Acti;~ty (Figure 60-2) •••..•..•.••. o••Q••••••••••••• Engineering 0-eolos:r .••••••••••••••••• ., o •••••••••••••• .. . ' ..... Reaerv-oir ••• ., • I •• e ........ 0 ••••••••• . . . . . . . . . . . . . . . . . . . . ' ~ . . D8.!!18 1 "te •• ' c 0 • 0 ••••••••••••••••••••••••••••• ' ••••••• I •••••••• (Ple.te 17) .. • • • • • • • • • • 9 • • • 0 f • • • • • • • • • • • • • • • • left Abutnent "Spillway, Sa~e •••••••••••••••• , ...... I 4 • e I I •• 4' e • e e • I _. A f • Right Abutment (Plate 20). . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~ . . . River Section •••••••• tl .................................... . General ••••••••••••••••••••• • • • • • • • • • • 0 • • • • • • • • • • • • • • • • • • Powerhouse ......... o ••••••••••••••••••••••••••••••••••••••••• Undergrouud. Poverhouse ••••••••••••.••••••• 1 • " ................ . Spillway and Diversion T~ls .•••• o•••··~····~~····•••••••• Highvey Geolos:r ............................................. . '.I'l:le lo'-...ter Route ••••••••••••••••••••••••••••••••••••••••••• l!'l:le tJpper Rout~ • • .. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • o Access Road Tunnel •••••••••••••••••••• • • • • • • • • • • 0 • • • • • • • • Const.rtlct.ion :rtateriala •••••••••• , ••••••••••••••••••••••••• Government Camp •••••••••••••••••••••••••• o ., , ..... ~ ••••••••••• • • • • • • • • • • • • c • • • • • • • • • • • • • • • • • Construction !~at.eria.ls ••• Concrete Agg:rege.te and Pervious • • • {Figure 3). . ~ . . . . . . . . . . . . . Il:!Iperv-ious l·S!.tteria.J. ••••••••••••• o ••• I) ..................... . Concrete Water Supply ••••••••••••• ~~··•••••••••••~'~••e•••••• Ripr ap •••••••••• o • o ................. o •••••••••••••••••••••• ...... _ _._. ____ _ .~ - - Page 1 2 2 2 2 3 3 4 4 6 ~ I 8 9 9 9 10 10 11 11 11 12 12 1.2 12 12 13 13 14 15 15 15 16 J.6 17 18 18 l9 19 20 2.0 21 21 21 22 22 ( .... ( .... ,CONTENTS--Cant inued Page. Trangrn:isaion Linea. 5 ••••••••• o •••••••••••••••••••••• •• • • • • • • 2.2 .I,oc·ation ................................ , ........... , ........ . Explanation of Geological Terir.s Used. , •..•.... , .•.•.•••. , Al.l uv 1 um •.••••.•... o • ~ ••••••••••••••••••••• , ............ , Bogs •••••••••••••••••••••••••• ' • t •••• s ••••• , • ' • ' ~ •• .-••• i~oraine 1 end and la.ters.l •••.••...•••.•.....•••...••••.• l~ua keg •••••••••••• ~ •••••• " ........................... ,. •• S~id.es and sl't.lll!ps ...................................... . Terraces , .. ~ . 9 •••••••••• & •••••••••••••.• ., • , , • ., .......... . Till, rubble .............. , ................ , ..... , .... . T111 1 sa...'ley .•..•...•••...•••••.••.••• ,. ...••......• ct •••• Till, 'Uil.SOrted •••••••••••••••••••••••..••••••.••••••••• Vegetation ••••.•••••••••. ~ •..•••..••••....••••.••.•.••••• Permafrost ....... _. ......................................... , Geological Log of the Transmission Routes.~·············· 22 22 ~ 23 23 23 23 23 23 2< .,; 23 ·23 24 . 24 Conclll.Sions ............................ ; .......... , • . • • . . • • • • • • 26 Reco~nd.stions .••.••.•...••••••• ,. • • • . . . . . . • . • . . • • . • . • . . . • • • • 27 Appendix Original C~ologic Logs of Exploration (8 drawings) Concrete L~bora.tory Rei.>Ort No. C-933 (Rock core tests)_ Petrographic ~.eoorcmdtll!l !1o. 57 .. 35 (Outcrops) Petrogrephic l·~Jr~.ore.ndum Jio.. 57-70 (Rock cores ) Petrogrc.phic l·~more.odum no. 57-79 (Rock cores ) PetrQgraphic l~morandum Ho. 58-152 (Rock cores) Petrographic Memorandum No. 59-3 (Aggregate) Plates (Photographs) Plate 1--Airphoto of Project Area. Plate 2--~-all airstrip upstream from axis. Plate 3--I.ooking upstrea:cl a.t fa.n Ple.te 4--Aeria.l of e.xis and saddle lakes Pla.te 4A--Sa.d.dle a.:rea on left abutu~nt. lookiog upstream P.late Plate Plate Plate Plate Plate Plate Plate - from near outlet of large lake 5--Turbulence in river 6--Typical vegetation on left abut~nt 7--Typical. vegetation on right abutm~nt '8--Vegetation in gullias on right 'at utrrent 9--Vegetation along acceas road (about 3 miles from d.nm) 10--Typical outwash in trench between Spill~ay Lake and Saddle 11--Talus at toe of left abutment 12--Prom.inence at top of left a.but!!lent ahO'\ling dip of bedJs into a:but1r..ent. This knob is ty:pica.l of loose blocks requiring scaling • i1 .A-1 A-6 .4.-7 A-8 A-8 A-13 . . ·''-'-····•"-...;·~------~· ... ··-............ ~" --.~---,.,_, .. __ ·~----... ~ . ..-...------' l l -.-atl. . L, ' . f / \ ... ... ·' . .. _·.:c ~ONT::.t.\'TS--Continuo d Plate 13--Typica.l major jointa. Face of left abut-cent Plate 14--Cloaeupa of shear zone expoaed in S-4 on right sbut=ont Plate 15-~Test Pit K-94 on left ab~t~~nt as3dle ' . ~· Pla.te 16-·-!s.ce of s.ggreg:.tc trenob upcrtra&m frou, axl:; and abov-: fan s.ri!a Plate 17--I.eft 3.buttt.ent. Tal--..en from Tl"iangula.tion Station B,agg Plate 18--She~ zone co left abutma~t ne~r DH-11 Pla.te 19--I.cf-: ab·.l't:~nt.. Cloaeuy of face shO"'.J"ing join.ting Plate 20--Right ~but~n~ Plate 21--.tu:ia. looking upatre~ from belO\I DE-ll Plate 22--Core f~o~ DE-l. Illustrates f~acturing and joiuting Plate 23--Surfs.ca potterhou~e site. too king upatream Plate 24--!n~ake eraaa for api~1~ay and diversion tunnels Pla.te 25 ·-Ch.rtlat o'!' di·..re':"aion tunnels. looking ~lovn!}tream Plate .26--rropoaed ncceas road route. Aerial viev Plate 27 __ g.,a.Jl 1e.l:eG o.bcut 3 ~ilea from camp Plate 28--Roed cut in ~~~ioal dcpoaita on present access road Plate 29--Ty:p!crll. t:.r:;.:~cria.la in eGkcr up~treOL1 from axis on left. side of river Fl~te 30--Typical terrain ~t proposed campsite-ridge in center of .Photo Plate 31--Lookin; d~~tre~ at axia and poaaible campsites Ple.te 32--P..eri~ of terre.in ncar ~~a.silla ?late 33-·looking west ~cross Stwitna River at MP-246.9 near Talkeetne Plate 34--Looking Nw from ~TY across Susitna River Pla.te 35--Gold Creek Station Plate 36--Chulitn~ River Plate 37--·!-'iena..'la River at MP-353.6 Plate 38--Slide caused by th~wed permafrost at MP-349.5 Plate 39~-Terrain at Eeely, MP-368 Plate 40--T:Y:Pic~ muskeg terrain near Clear 1-rll' -405 · Pls.te 41--Terre.in e.t Nene.na. MP -422 Figures Figure l--Vicini ty Me.p (Sw.Ul !Scale) Figure · 2--Vicir.:ity M~p (Large sca.le) . Figure 3--Area..l Geology and Ioco.tion of Exploration Figure 4-.. Geology of ~ft A'Qutroont--Iaoruetric View Figure 5--Geologic:: Sections A.A. and. :SB Figure 6 --Geologic Sections CC, DD, s.nd D 'D F1gur~ 7-~ologic Sections Along Riv~r Figure 8--Geology of UndergroWJd Po-werhoWle Figure 9--Geology of Trs.nsmisaion Lines: Anchorage to Talkeetna Figure 10-.... Geology of Tra.ns!ilis&:lon Linos: Talkeetna to Lagoon Figure 11--C~ology of Tr~rnisaion Lines: ~goon to F~irbf~-~ Figure 12--Geology ot Tra.n.emiasion tin.::!s .. : Cantwell to Denali Da....~ite Figure 60-2--I.oca.tio~ of Earthquake Epicenters e.:o.d U. S, Weather Stationa 111 ------------------------·..._,.-.· ~<11'.-~-...r---------... --.. ..----__ .. to ___ -~·. - / \ L·: ......... ...__ __ _ ·. .DEV lL C.A!!YON PROJECT DEVIL C/J\YOri D.l'J-1 FEASIBILITY REPORT E!iGINE:i·:RinG GEOLOGY APPENDIX Abstract I It is believed sufficient geologi~al a.nd. la.bore.tory st.udies were per- formed to provide adequcte ~t~ for feasibility designa ?~d estimates. Bot~ __ e.b.:ut~nt.u of the d:!r...oi te are e.lJ;"I!:lst deYoid of o·v·erburden; the rock is a. y_er:~_ ha.rq .l~hy~g t~.... It is complexly i'ractu=edJ a.nd broken by thrc:e j_oi~it sets. Tlle bedding dip cauees the strata on tbe left a.bu·b::1.ent to o,:-erhe.ng tlle Susiatna Ri Yer. At lee.ut 35 or rrore feet of broken, looae blocks of· p!:lylli te will_heYe to ·be ___ removed to provide a satisfactory dam fou.tids'tion ..;::~n the ebut'G!:3nts. The center portion of the dam axis is underlain by 35 ._cu:·_p:;ore feet of allt~vial me.tericW.s.; the eY..act thickness of the del>osit and the "Wo..ter depth a.t the axis ·· couJ.d not be det.er!!lin~d. N~~_!!lajpr g~.QJ-9g:f:.c~.-Pr..o.b.le~--§.ppea.l:. __ tq_ exist; s.o.~ qente 1 .,rork ".W'1ll_'Q.e_reg_u.:!.:.;:-.eq_:in_ shear and fa.uJ.t zones t~~~-i.n:t.e.rl~ .. ce bt"'t.h-abutJLents ··~ Extenai ve gro~ng 'W'ill be required to effectively see~ the foundation. The rock in the rigfr~ ... J;~.bg~~~:t opJ_J.J.~~y_and di ve.ra.icn...tur...nel.s~ s.ppeJ.l:" su~:fAciently_qpr;met~p'!;_ to_ miniu.d.ze. the need for exter.si ve steel sup- ports. T'ne es.rth dike r\;quired on the left a.but:ne~t sa.ddJ.e vill be founded on a de.ep d.eposi t of h1:.~lly co~a.ct J pr~izlly :pervious glac.i.g deno~_i t~. A SUI'!' ace :pov~ouse e.tthe·-tOe . of 'the -Tight e.butment vill require e~tenu i ve scaJ.ing o~ the cliff a above it a.nd some aeep footings to reach firm rock under the river. _The geological situation anueara excellent for the consideration of an undergrouoa RP"Jerb.ou.se on :the r~g!lt~bu~ment; tb.e probien:.a-involved appear less- costly thau those likeljr to be encountered in a surfece ~-erhouse. Ample supplies of concrete aggregate are a.ve.i1a'ble clooe to the dam. Impervious materi~ls can be obtained only by selective processing of the gla.cio.l debrio in the general area:. There a.re ~le oupplies of ma.teria.lrJ for construction of eith~r an 'tupper" or ."!.J:rt¥er" e.ccess read from Gold Creek. Portions of the proposed transmission linea to Anchorage, FairbE!.L'"'l.ka 1 end Denali Ds.m vill tre.Yerse permafrost 1 muskeg and bogs, aDd mud1'lowa and landslides. · ---I r-c;nsiderable additional detailed foundetion investigation •1Lll be l r·equj.red :prior to C(Y.mpletion of final designa. f,._.,_.. • ·~ •, r -··"·-.·.----," .... _ I ....,.J ~--~ .... --.-.... , ............ ~ .. ,;- - ( ( ( \ \ ·u The &rea has b~~J!._e:.xtensi vely __ gla.c,:i.ate.d...· Gia.T'lt striations evidenced by ·-nu~roun east-west depressions (Plate 1) can. be attri- buted to gla.cio.l erosion of atee:p-dipping xretam:n-phic b.eds with an ea.st-;test strike and a varying hardness. Bedrock The bedrock gen~rally is terrr~d ~~llit~ probably of l~sozoic age. (In one of the drill cores at the d?m a small fossil was found; this was sent to t~e F~aakan Branch of the USGS who heve te:atati vely identified 1 t s.s being of CretaceoUE1 age. ) This rock has a bedded and lacinated annearance simil~r-to the shale from __...._.. ___ ..----s.,---"' .. --... ·---.1.-o ~hieb it vaa derived; ho•ever, these small l~nae generally are ~t an angle to the strike and dip of the present massive beds. The rock is very hard and brittle (see An~endix--L~boratory Re~ort · Ho-.c-.::93'3). It containe . .E~e.-rous gu;_;tz_etringerf? that we;e injected soon after consoliQ~tion of the bedD and aBain after the beds were upturned to their present poai tion. __patai :).,~JLdescri:p_:.~. tions of tt;_: phY.~~~~!:~_co~~e.:r:.ent~-~o~}>.~_.?:t"e. in -~h~LJ'.e±.ro~- graphic men1orand~ in the_ a.ppendi~~~.:_Q.f_t.hia_r..epo..t=t,----··--~----=----'-.. Structure (Figure 3). Throughout the irnmediate .. area,_i!_he " • '-·-------·---• 0 bedrock has ~n approxir-stely east-~est strike with a di~ of 55 to. -75 .. 0 -tlouth -(P1ite-··12) :--It-ia·-dir:fi"cUl.t"' to -obtC\in ·acc·Ui~e_sUP..s=.--· --,...--.. -----.. ... "be.<;~'d~~ of the cross -laminations and accompanying jointing in the Qutcrops.--·------··· -----·· · ·· -·-·--·~ -· -·----· · ..... ·-·-.. .... '-! ___ _ One well-developed and two poorly-developed seta of joints occur in the damsi te. t:U"ea.. The ~ster _j_Q.i_nt e-et he.s a strike that averages ..H2SH but varies betYeen NlO'w and N45W (Plate 13). The dip of this 9et sverages 80 o east but varies from 75 • east to vertics.l. T'neSe jOints' eene,:rall~arP .S~~d._ 8.00:Ut_,4.._:t.o-5 -feet apart_, al t!-~OUgh from.2-in~t~~~-fQ9t a~.ac1Dg_£as been po~ed!. ~~ of the~e joints are filJ.ed rl th quartz that often contains minute pyrite crystals. ~~.~V..,9_.17linol:~j9iBLse:ta_a.tu.k.e-.a1moat_p_~all~J,.-t.o_;t..he-he.d..Q...~p,g.;_o.ru:_ of_ them is a~most horizontal but '.ri th occaa ions.l. dips ·between -15 • -...__._ , __ _. "'• -· .... ______ ---~-__ , .-_ _ __....... ' -~ _:Q..orth and 15 south and an e~.t.::-w.e.st_strlke. T'ne o.tl:.e.:r_ se..t has. a steep ...nortn....dip..~~=-si._~~~s~_min~~~--va.r.ies ~ f;:o~ 3 inches to es much as_ 30 __ 1;'~et in the set tb.at-~:i:kes-~~a.st-west. A fourth, apparently isolated, joint set occurs in the viCiDlty-ot the Shag triangulation stationo T'nis set strikes l'f55E 1 dips 80 o north 1 and hes a spacing of from 3 to 15 ft!et. · 1 ... ~.p.. b~vt_h~:r.~~~~+l;d.:t~vh_.t!~o_ped-ahepTi ___ ~r ~~~~t zonestochcur. in,!J;:e '\1 .c u.J...ta_o~ .. o _ S.l.u.cS • ...O.A... ·~-~-~;!;pJJ:~n. ne~ a...~...J.. appear o ave a gen-.ij era.l strike of S25E and a dip of from 80 northeast to ver·t.ical. 9 .. •· _..,. __ ~ ... ,, ..,--_ _,..;.. __ ----------· ......... >1-<0"~ "~" --·-'It'_..._~--_,.....----.:: ..... _ ..... _.'"' --·-~· . I . -_.,. .~ .. _,_ .. ---~----------,c--~r-... ., ____ .,...~·-« _..,.. ''"'',-;-_...._. __ ,--~~-~"'"'"~.._~-~~..-we~ .. --.-~ .... ..,~:-'"¥"'---~ ·~.,..,..,___ •;; .. _,.., .. _.,..,.._~--~ ·v>~,:i - * C .. .. I •.. "-~· . .. .. -Q On the le:f't a.butment, ~he larger zoner. ~i1LS9U.&EL.JJ.P. t:.o 2 fe~ th~c~~ The zones on the right ~ide of the canyon 1 although con- taining intens~ly sheared rock, g~n~relly u=e verJ tight, well · heo.led, and extrex=ly he.rd (Pl~te 14) Q T'nese zones have ca.uaed the formatioD of steep V·shaped gulliec in the ca~yon wall~~· Their tr~ce &.bove the cs.nyon rim is con~ee..led. by overburd.en. Becs.w:.e of the lack of marker beds 1 it was oct possible to determine if the fauJ.ting resulted in major d.ispla.cemeilt of the beds. PertlS.frost According to present in~orcation on the limits of con- tinuous permafrost in Alsska and as a result of our inveatlgations, the damsite area appears to be south of this zone. It is, however, in the zone of ~or~~~erm;fyos~: Shallow and apparently thin lenses and pockets of ~rmafrost were encountered occasionally in the road coll..Struction. T'nese sporadic occurrences vere evidenced by lenses of ice, frozen soil, and continuously thavi~ fro~en ground8 Permafrost was not en~ountered in ~~e bench. area adjacent to the left abut~nt. It is doubtful it any permafrost occurs st the dal:!lSite proper a.ltllougb. there l!l5Y be occasional pockets in the dike area south of the left abutment.. Temperature mee..sure~nts were not rr.ad.e in the drill holes on the axis because pract.ically all of them were in hard rock; thus, even if permafroot was present, it would have no de$tructive influ=nce on the proposed structures. Recent De?Osits The areas north and south of the canyon rim often a.re mantled vith glacial ~~d nonglacial depoaito of Quaternary age. The glacial tl'a.terials priD'.arily consist of outwash (Ple.te 10) and moraines (Plnte 16)i'these ere composed of erratic lense~ and layers of sand, rounded to angular gravel and cobbles, boulders 1 e. small amount of ~il t, aud considerable rock flour. Some of the older glacial depooits exhibit consiicrable weatheringj this is evidenced by heavy iron steins and the aJ~~st co~lete alteration of pebbles and co·obles. T'ne nonglacial C!!.terials pri!!la.rily are river terraces and fa.na, talus (Plate 11)1 out1.."!1sh, and svamp deposits. Their constituents range from rock flour and silt to sand, gravel, and bou.lder.s. In many areas it is not possible to i~diately differ- entiate the glacial and no~ial materi~s; a distinction generally can be made only by a broad. inspection of the m:lr.phological charac- teristics of the various types of depoa~ts. The most distinguishing feature of the nonglacial deposits is their co~cn occurrence in strata or ls.ye:r;-.s. However 1 this se:zre identif'ic!!!.tion method eeld.om can be applied to the fine-grained materi~ because turbulence in • " . ' 10 ...... _..,_ ·-· .,. ___ ....._ ______ __,_ ________ -...;._,,.,..---~---=-. ------------'""'"""' ... -·-... ·----. ·--.. .. * · •• . ·-,..,.::."'~ ........... "'-... . -.... ·-... ._.....,-. .. .,: .. __ , ·---- - l_ ( .. -· \::; the depositing waters ~as resulted in minute croes~~dding and fold- in~ of these ~teriala. ~ A third category of tUlcon~ol.idated depos11~ is a.llu\"is.l material nov being d:epos i ted or moved by the Susi tn~s. River. For the m::lat :p;J:t; ~~i.a d.epos it is granular vi th numerous boulders , and heavily corita.mine.ted by rock floUl·. M~raines. To._::~~-,~~~--~ . .'PPS_~,!_.P.r.edg,:~ri:a§..:t~ n_grth of Jhe_... Susitna. River and cover a eo:o.sid.era.ble portion of the a.rea. south of .. ...,:_,..,. .~--. .. --.... - the river. Th.ey are fr·om a fev inches to severe.!. feet thick. O'.ring to comparatively recent surfece erosion processes, they have loat di~t1ngu1ahing surficial chera.cteristics. Tney contain materials ranging from rock flour up to boulders 8 feet in diameter (Plate 15). In the mapped area, there vas s high percentage of material larger the.n 4 inches in diai:t:eter 1 and the largest boul.d.er see11 \ISS 3 feet. Because of the high conteut of rock flour, and with the exception of occe.sione.l gre:.nular pockets or stringer! of sand, the ~aip.ea. l!houJ.d ~e impe::-v'1.ous. r'~'-~ ·/.) <!.. ··----- Outwash. A thin layer of this material l!'.a.n.tles a portion of the vesternmost part of the bench south of the left abutment. Elaevhere in this area}· the outwash may be as much as 90 feet thick but is veneered by moraine. It con~sis ts primarily of fine-to m:adiu:I!l•grain sand, witb. roUD.ded to subrounded pebbles-,· ·cobbles} and boulders up to 14 inches in d.ie.mzter. Tile material a:p:pa.rently w-aa d.eposlted in a V ··sha.:?ed valley in front of an s.dve.ncing glacier (Plate 10). The ~eight of the glacial ice and subsequently depos- 1 ted 1I';Ors.inal materiel consolide.ted the outwash to a rels.ti vely high d~naity. Terraces. River-deposited terra.ces.occur south of the river in the eester.n part of the me.p:ped area.. They are compo~ed of eoe.rse and fine sand, subrounded to rounded gravel, e.nd boulders up to 3 feet in diameter. The terrace gravels on the ·canyon floor (referred to throughout this re::port as a "fan") extend to about 65 feet above river level, vith an unkn~-.n thickn.ess below river level. The gravel in the fan at the floor of the canyon is over-. lain by 3 to 5 feet of clean, medium-to co!U'se-grained sa."'ld. Approximately 210 feet of gravel occurs above river level in the terrace remnant upon which Triangulation Station Ho is located (P~ate 16) .. The terraces formed by Cheechako Creek occur about 22 feet belov the fan terrace on the floor of Devil Canyon and about 27 feet below the first terrace. The highest Cheeche.ko terrace is a flat about 270 feet vide, and the lower and youngest terrace ia about 140 feet vide. The gravel in these terraces is coarser than the • 'I . -. ._auc = ' I .. ® . ~ . ... ' ! ·. . . -. .,. ........ ' - . J \....- gravel in the previously mentioned Susitna Rive~ terraces. Granite boulders up to 10 feet ~n diar~t~r mantle the surf&ce. Talus s.nd rubble . This unsorted, e.ngular to eubs.ogular material occurs in the aoutbvestern part of the left abutment bench, vith o.ccs.niona.l deposits near the base of the gullies and cliffs in the csnyon ··(P1a.te 11). This t:D.terial is derived from the adjacent outcrops, and the blocks range fro~ a fev inches to 15 feet in maximum dimension. The deposits in the bench area probably do not e~ceed 10 feet in ~~ickness, vhereas those in the canyon average about 20 feet in thickness and may be a.s nru.ch e.s 40 :feet. Swamp deposits. Rimming the lakes on the bench of the left abutment and 1n areas of poor drainage are deposi 'ts of moss and shrubs mixed •ith fine sand a:od silt. Theee deposits genereJ.ly are less tha:a. 3 feet thick and. s.re underlain by moraine e.nd outvash. Seis~c Activity (Figure 60-2) T.he damsite is in a zone of major seismic activity. According toU. S. Coe.s:Cancf Geodetic Survey re:pOrt.s:;-u-:-s:-E.eologicel Su_~~y Professional P~per No. 69 (1912), ani Gutenberg and Richter's book, Seismicity of the Earth and P~sociated ?henooena, there bave been a.t ·least ~e.rthqu.ak.e epieenters wi t.hi?_:-a rs.d_i.':l~~<?f __ ~5~-mil:e_s of the site. T\ielve of tfiese qua.r:.es hs.d a Richter-Gutenberg iilsgni- tude of 2. 0 or g-res.ter. The remaining 33 ea.rthq,ua.kes had a msgni- tude of 5.0 to 6~9· ~o epicenters ~ere located within 25 miles of the site. On May 29, 1931 1 an earthquake nf unknown Inactrnitude occurred near the Chulitna River about 15 ~les nPrtheast of the site; on July 3, 1929, a 6.5-rna.gnitude earthquake occurred near the Talkeetna R.i. ver about 25 miles sou-the~t of the site. Some of th~se shocks caused considerable major dama.ge to structures in .Anchorage · and Fairbanl-"..s ~ and major earth move~nts and landslides along the highways and railroad. ENGINEERTI~G GEOLOGY Reservoir .Ti.me limitations e.nd access d.iff"icul ties did not permit a ground inspection of the reservoir baein. However, aerial recon- naissance and a study o.f existing geologica.J. date. indice..te the res- ervoir basin vill be tight. Since the basin ie ritmned by th.' high uplands oi' the Talkeetna 1-bunte.ins 1 there a.ppee.rs no possibility of loss into other drainage basins. PJJ.y eround-vater percolation into f-ractures in the reservoir rock 'WOuld be stored and vould drain back into the reservoir during low ~cter. • .. l2 I I I I I I I I i . ' { - .,..._,.. .. Extcnsi ve ri~nse tirr.be~· o~curs along the lo'l,;er eltnrations in the res:rvoir basin. Tne vegetaticn is simila~ to that described in previous parts of thia report. Da.msite Left Abutment (Plate 17) The most crittcal engineering geological problerr~ occur on this side of the canyon. These are a result of the_ov~rhap_gi~ cliffs formed by the southerly dipping beds; and what appears to hav-e-been more stru·:tura.l ~disturbance in this cbutment ( sho·v~n in DH-9 and DH-10 and in F'ig'.lre 4). E.aul.:t~~g_has caused ahea.r...._zones -that a~e ap~roximately normal t~_the river (Plate 18) and also roughly par;_lle-f'"t-he canyon rim. The sheared rock is not well healed; thus., extensive fracturing vith open crevices is cormr.:cm. However. pressure tests in DH-9 and DH-10 did not result in severe . -----. _ ..... -. - water losses l even in faul tad zones in the hole a. DH:..8 apparently encountered only minor faulte~ areas and showed hec~y wa~er losses ·to a depth of about 118 feetj but, f~om this poi~t to th: bottom of the hole at 150 feet, or within about 15 feet of the cliff face, there was practically no water lost in the pressure tests. (Thi~ angle hole iJaS-drilled to1o~ard the cliff fe.~e for the specific pur •. pose o·i det~rlrlning the decrease or inc:.-ease in 1.'ra..ctu!'e_ qpenings in the direction of the cliff fer:e.) DH-1 a"Due.rent.lY en~ounte!'r::d 1~ 1;~1~. or:. n~_.faul ti~; ho"«ever, severe wate:-""-=·iosses ~~urred tnroug.."'l- out all but the last 10 feet of the hol.i..~:-· _.._. ----.. ---·-... -·-. - The overhangtng beds on this side of the canyon have resulted in large blocks (Plate 6) that, in some cases, are dis- tinctly separated from the adjacent bed~ock. Sene of these blocks are as much e.s 25 feet in horizontal dimension and 50 feet in ver-· tical dimension. During small earthqualce tremors, sli&-~t movements of these blo~ks can be felt. Because of these loo~e blocks and the vari~ble results from the water pressure tests, shelves ("kitchens") were excavated into the ab"..ltment face (Figure 4). The initial plan was to determine the depth to ~O\L~d rock from the cao- yon face. The first shelf, S-1, ~as started ebout 60 feet belov the canyon rim on the nose of a ridge downstream from the downstream toe of the dam. This excavation had to be abandoned befo::.-e reaching unbrol~en, ma.saive rock, because the blasti:r...g loosened great quanti- ties of loose rock above the shelf. Loose rock for about 10 f'ee't. in e. horizontal direction was removed before the excavation had to be abandoned. Excavation then -w·as started at S-2, auout 170 feet below the canyon rim on the cliff face (Plate 19) of the left abut- ment. This excavation also had to be halted because each blast loosened increasing quantities of rock above the shelf) and it became too dangerous for furth~r ;.;ork.. This ehelf is believ:d to 13 --~· -·-·-------· -...... ~-----------~----. -... ,_..._., ... .., .. ~~~ - :.-i- I \.. 't . ' "-..: . • -'J () ha,.rc a~t·ually pen~trat~.d abt:~ut. 20 f~et int.o the eli ff fa ~e; however, a.n a~curute m~asu~ement. o:-a log of the shelf ;,•a.s not. pos:Jiblc b:ca.us-; cf. the cov<:ring o:' loose ;ocl' .. s.:'ter the final bla3t. Remov·al of this -loos':! ma.t~ria.l could not b~ attez:::pted b~cauoe of danger from o-.rerhanging blocks . . Besed upon the aforementioned investigations 1 it is a~ti: .. mated that a minimum of 35 to 50 feet of ::ocl~ will have to be removed from the present surfa~e befor; firm rock is reached. It will no't be possible to obtain a "clzan" excavation a'l!rface because of the blocky a..11:J ov:rha.nging nature of the formation; 1 therefore, . },_,;. extensive d~ntal woD>...tray be required./Jod~Jt:!(--:J;et~u-o ,The left a'b.~t!-"'.ent _ of_the -.axch .is_nes.r a faul ~ zone trznd.ing sout.h- east f'rot: 'DH-9 and .the shear or fault zone that roughly :paralle~. the canyon rim in this same. BJ:ea . (Figure 4). Shif:ting the laft ·aou~ment upstream would r~quire constru~tion of a thrust block (because of the loss of topographic elevation)) but the thrust from the arch then ~auld react against e considerably larger and firmer . . rock mass. "Spillvay" Saddle ·-Becsuse of' favorable topog;-aphy, it ini tie.lly ~as :ple.nn~d to USe a ~ontrolled overflo;; spillway chute 8-·~TOSS the no~~h ... soutJ."-1 saddle to the left of t~e left.abutment (?l~te 4 and 4A). Several drill holes in this sa1dle dis~losefr a a:ep buried channel appar- ently st~ikiu~ about esst and west through the lake-filled depres- sions on both s.ides of the saddle (Figure 5, Section BB) and over- lying e. severely faulted area. The maxim~tm depth of the valley fill in this channel is about 90 feet. The.fill r~terial is com- posed primarily of-~ell-consolidated out~ash, ~ith about a 10-foot veneer of moraine (Plate 15). qontinuous strata o~ pervious ~~te rial probably occur in the o~t~aah. Tne moraine venee~ may have sufficient imper\~ous material to form a moderately ef~ective blan- ket. It is necessary to effectively seal this char~el fill~ es the lm/est point in the underlying bedrock surface is almost 170 feet below the ::1.3Ximum water surfa.ce in the reservoir. T.ne per- colation path fr9m the reservoir probably vould not exceed 3,000 feet. Tne lack of suitable foundation ana other design considera- tions resulted in the abandonment of this·saddle area for a spillvay. Ro-w-=ver, since the lowest elevation in the saddle is 1375; it vill be neceasar~y to const1~ct a dike across it approximately Boo feet long with a caxi~~m height of 80 feet. The area selected for the dike is slightly upstreaxn from the saddle (Figure 5, CC). Because 14 -· ,;~ ' ' ..... ------:-.... -~ . .:..-............ ·-...... ----"'"'~----· -...... -. : i ' '" ·-~. ·w-•~ I - . .. lj the fo~~d~tion ~terials have been cornpected by relatively hiah ice loaC.S, they e.:ppear to be ss.tisfa.ctory insofar W3 beo.r:Lng cs.:pa.ci ty is concerned. for the e.fo:r-e::enticned dike. Water r:2:e.sure1ents in the drill holes throughout the left abutment areas indicate the ground vater ia.tributary to the su~ lakes in the depresoion. Thia a:lao may ind.ica.te that some of the underlying materials are relatively impervious .• Right Abut~nt {Plate 20) Only & minor a.mount of dental \fork should be required for the d.e.m foundation in this abutESnt. The ebut.rnent is intersected by shear zones s trikir.g ~~_:!:._Eo!·r.<.aJ. 19--tn~L -~tre.~~---~wever·;--· Shelves S-3 a..""ld s-4 ·diacloEled tha.t the rock in these zone!S is com- petent vith only thin seems of gouge (Plate 14). Tne only :problem oi' any magnitude will be the scaling of locae blockH in the knii"e ridgeo on the right abut~nt iD order to protect the poverhouse and dam .excavation against rockfa.ll.s. Seepage through the a.butJtent should be an acceptcble mini~~ as the joints on this aide of the cllDyon e.re well healed, The dip of the bedding is favorable for she.ping this s.butii'..ent for the arch (Figure 5, Section AA) i • River Section _ The high velocity o~ the river in the canyon ~~·ae it impracticable to drill holes in the center of the river. An attempt vas maae to determine at least a rough bedrock profile under the river by z:cs:ans of angle holes drilled from e:a.ch "oa.nk. Because of vertical cliffs to the vater edge (Plate 21), it was not possible to drill intersecting angie holes: That is, holes started on directly opposite sides of the river drilled at angles to intersect each other under the rive~. The drilling that was e..ccoUiplished a.p:pea.r~ to give an approximation of the maximum depth to bedrock beneath the river (Figure 7). According to this drilling, the rnQxiz:mun de:pth to bedrock from the vater surface is about 85 feet (Figure 7, Sectiqn BB). Because 1.t ve.s not :possible to In.essure the depth of Yater 1 the stree.mf'ill can be estimated only roughly as about 35 feet in maximum thickness. According to pressure tests in th~se holes, severe fractures and open joints occur from the bed.rock sur- face to about 25 feet below this surface. Below ·~is 25-foot depth, ,however, the rock tighte!l9 emd only nomina.l water loaaes occurred (Figure 7, Sections AA, BB 1 CC). None of the holes indicated fa1llj;.~- 1ng paralleling the river. -.-··~· --- ----------··-·---· General To expose finn foundation. rock, :part1c::ule.rly on the left abutment, will req,uire the removal o:f up to 35 or 50 f.eet of loose 15 . .. . i .. , ~~;:· : ··-..,. -:.;:;_.:... -:--.... -..,...... 1<--.... --.,---·.......:. ~-----------'!'~'---. --.··--_,..._____ ~ ...... .... ..... --... .. .:. .... -· .. . - "" --- [ ~ ' ' ~ ~; t: . . ; I ~l .. r \ (! blocks. There is no appreciable dept~ of vea~hered rock. B~cause of the extensive fracturing and open joints (Plate 22) considerable grout take cen be expected. Such grouting is necessal7 to consol- idate the fractured roclc and reduce ee~page through the foundation. ---:J:.,aboratory tests (Appendix--L9.boratory R2port No. C-933) · on cores representative of th~ foundation rock have disclosed that Young's modulus fo·;· unfr~ctured founcla.tion rock exceeds 7,000,000 psi. Poisson•a ratio is about 0.18. Tne unconfined compressive strength is as high as 37,000 psi. Tneee tests disclosed that the rock acts priL~ily as ~ elastic material and practically no per- manent "set" occurs. Although these initial tests indicate excel- lent foundatio~ conditions, it ~s highly desirable that during final design investigations, in-situ r~asurements ere taken of the elastic properties of the rock. This recommendation is based upon the fact the severely fractured in-place condition of the rock ~~y result in lower moduli than obtained in the laboratory tests. Powerhouse Present pla.'tls establish the :powerhouse location along the toe of the right wall of the ca.."'lyon) dowr.Lstr.:a.m from the dam (Plate 23) Figtire 3). Tnis wi~l require e~tensiv~ excavation into the right abutm:nt to obtain sufficient room for the structure (Figure 5J Section AA). Conside~able scaling will b: required on the cliffs end knife ridges auove this excavation to :pro·vide pro- tection during construction and to prevent oajor ro~kfalls during operation. The poverhouse and tailrace st~uctures should be founded on the bedrock balow the streamfill~ Under(~rou..TJ.d Pov.erhouse The rastricted topogr~phy, the possible need for extensive ' -scaling, and favorabl~ geological conditions indicate the dasira~ bility of consid~ring an underground pow~rhouse in the ri~~t abu~~·--- ~1;1-~.... Tne unusual competency of the rock~ii"lfi-cat-=s-·:uiepossibility of excavating an underg:-aund ~har.ber with a l'r'..inimum of roof and wall support (Figure 8). Additional investigation of the chamb~r site by deep drill holes and a pilot tunnel will be required to fully outline potential roof and wall support problems. Because PQrtions .. 16 .. .,. ···---. --·:..----..---------~.:-------·-· . -... -· ... ---~----... ' -. ..:....-_ .. _ .. ----.. t l t 1 ... e ( .t . . Oo ' l l of the exco.ve.tion will be belo,.; river level, extensive grouting rua.y be necessary for the lower part of the chamber to prevent ·"e.tel" inflows through the open fractures. The topography on the right side of the river is partic- ularly· favorable f'cr the construction of shr.,rt penstock and ta.il- race.tunnels. The drilling done to date lends further support to an ~derground plant as the co:re indicates the rock tig..iltens .:i th depth and the frscturing decreases. Furthermore, the size of installation required for a 580,000-kw powerplant may preclude the construction of a surface pl~t because of nUDerous and costly excavation difficulties that will result from the steep terrain and extensive fracturing of bedrock near the surface. Spillvay a.nd Di yerc;ion l".mnels In present plans, these structures are located in and on the rig.i-!t, abutment (Figure 6, Section DD a."ld D 'D). The spillway. intake can be founded on bedroc}:. with a rnini:D:"J.In a.mo"'.l..."lt of over- burden excavation. Rock cuts of 1/4:1 to 1/2:1 should be feasible in the intake area (Plat~ 24). Some difficulty may be experienced 'W"ith ove:rexcavation on the so'..ltheast or left side of the excavation, owing to the adverse dip of t~e bedding. Prior to final design of the intake excavation, suffi~ient ~illing should be perto~med in · this area to determine the de:pth o:t' ·overburden and. extent a~J. sever- ity of the jointing and fracturing in the bedrock. E~ca~se cuts of 50 and more feet in height. vill be required, extensive jointin$ in the rock on the right side of the intake nu3.i result in movement. of loos~ blocks during const!Uction. ~1is problem is not believed to "'be too serious ~s no c.la.y seams are kno"n-n to exist in the bedroclt. T'ne diversion a:'ld spill-way -~;-1.lnnels will penetrate the same type of rock. Nothing is knGnm ~~t present of th~ character- istics of the phyllite bedrock at diversion tUlln~l gradient; hovcver, as mentiQned in the powerhouse discussion, it is believed that this rock would have a minimum of fracturing and be exceedingly cqmpetent for tunnel operations. With the exception cf s~®el ~pport~--~o~ about 100 feet of the inlet (Plate 24) and outlet areas and in nar- ~-ow shear~z.E~l-.2"ockboiti:£l.g_fq~pqut-1.5~..P.~r.C:~Il~-.Qf ~f1e tup.nel - ""l:'ane;ttC.SE:.~~~d be adequate._ This bolting is suggested bece.use of ~e olockiness caused by the three joint seta. If the nature of the a;hear zones on this abutment is the same at tunnel depth as it is at the surface, these zones should offer only minor difficulty in the tunnel excavationo 17 -...-·-· ·-.. __,__ __ ---==-:----:-:--::----::---------:-=--::---::----------l -____.. ... -...... -, ... -··· .,. -· --.... . .. .... . '~ -..--· ._,,. __ -.. . >"" __ .,. __ 1 u r ·'t i ,.;. Jm f. u r t-. r t . ~' ·. ~ '• [. t ,I r k :\ -· The occasional open joints, surface springs, and an~~lt indicate th~t minor waterflo~s vill be enc~~tered in the tunnels • . ~ the rock is very competent) none of these flova should be of sufficient ~itude to seriously interfere vith construction. -One problem requiring further etudy is the closeneas of the le.rge d.is.:m.eter tunnels., 'r'ae rock is . of a. D-'\ture the.t would tr~~mit blasting vibrations vith only nominal dampening effects. T.hereforeJ blasting in one tUIL~l could c~use rockfalls in the adjacent tunnel. Extensj.ve rock bolting would offer considerable ~rotection against such an eventuality. f T"ne comments m!l.d.e in regard to the spillvay inta!-:e exce.va.- tion also vould apply to the excavations required for the intakes and outlets of the tunnels. T'.o.e only difference msy occur at the outlet of the tunnel if it de.ylig..'r:lts into an open cha.n."'lel cut throug.."l a talus de:poni t of' undetermined depth (Pla.te 25). T-~o possible routes he~re been suggested for the access highv~y to the d.eJr!.si te. One route would closely pa.....-nllel the existing. road nigh on the slope .of the Talkeetna. Hounta.ir.s, vherea.s the second or lower route would be a.J.ong the south be.nk of--the Susitns. River. The Ia\fer Route The lower route vill traverse te~ace deposits immediately south of the river from Gold Creek to a.bout 1@-6) vitb. e. stretch of bedrock from !-1? -2 ~ 5 e...'ld MP-3. At !.P -6 , the . road leaves the river a.nd clil!ios a bencli that may req_uire nu.meroua avi tchbc.cka beca.use of the steep gradient; . From the top of the bench to the d.a.msi te, the road vill follow the south rim of the canyon; althoUl";o. long stretehes of bea)"'Cck will occur~ swamp and z:mgkeg arees vill ba.ve . ~-~ to be bypassed {Pla:t-e 17) c T"nis sec;tion of tb.e road also il'ill he.ve to b~!dge deeply incioed gullies. The lover route will require placement of embe.nkr:ents on sve.mp and muskeg a.ree.s. It is believed that such areas are :probably not over 15 or 20 feet deep; thus the soft ma~erial could be com~ pletely ret!X:Ived, or consolidated by overloading of the emhan.kment. The latter method has been used with conaidereble success in simi- lar si tua.tiona 1 pe.rticuls.rly when it is accompanied by tb.e detona- tion of low-velocity charges along the toea of the proposed embank- ments and at varying depths from the ~urface to underlying aound material. 18 .. • .. -·-.. ot -... --" ... ~ ...... _, ____ _ --.. ----·-----.--·~---·-..,·-·--------____ ,. .. -,, ... ~ .... -.. --------·-.. .. ---__ *'.,.., . . . ·-·-........ ~.~~---..,.~-· -......... ~,.... "'"""';'"'"""~·,·-·-·,....,:·-----~~-""-............ ~·-·~~~ ............. --,":~.---··----,~ .,._, __ ,...,_. - G. r t2 \ '· • -, ~ .. . -ui a.:. 0 0 0 (f). (.') lU 0: t- en 4,-.---- --·. .. ' I I I , I J 1\. I ' --~ .... ---~--···-~---1 ' LATERAL' ! STR_AIN ' l -·+···--·-+--·-l ' ! ! -......... -.... . I I -.. -t-... -··-·t--.. i····--.---· ----- --J. G R f\ Y W A C K ~ I .--· j(SPECIMEN 12A-1243)------- AXIAL STRAIN , .......... --.. . -~-. -· .... -;-·----- 1 I ' I • l I l 3 ---· ____ l ______ ._j__ I ' I I ! -o-~---,-.... -.,- ' I . 2 ; . I I i • J .•• ·-'---..!-I . ~I . o -· .. ·---·r - , I I ; ! I ·---· .;..._ ----,----. ~ I · I I . I . I f i ----1--··--·r---·--! . ·---i---- 1 I I I I ,. : I : I I -~-.,. - . .,.. ---: i I I . I , 1-----o------+·-·-·--i--,--v--o----·--... -. i-. I l • •• .j.- l +· • i ' ·~ I. ' -... i I --··--+-·--·t-·· : i -·-4,; --~ .. . +-·-. ··-, I . -·-·------1 I I I -0 • l : . . -t---·--r . -.. _._ .,..... ... i ; 1 ·--...;..---! .. --·+--·---i ' i I I l . . ' l--l"r--------wr"l----·4·-..,._----.---·---···- '1 . I ., It : • --..J _______ .:. --,_.J--- ! : I t t • ; ~ : i I i I . I I I 1-+---:-· ~--t---+~ ---l·--: ·1 ··--1 ·-r----·r--- 1 1 l I i ! l . I ' I • I • , ,---l---~--~r·-·t-~·--t·--·· t~· -r--- • I I l I I i I l I I I I I• I ~--lr·· -1---·--~---· --,-----··-!-·-·-··t----+----r------t--1- l ~ I I I I I I I I ! l__ 100 200 300 500 STRAIN-MILLIONTHS FIGURES .. STRESS STRAIN CURVES, FIRST LOADING CYCLE TYPICAL DEVJ·L CAN'YON DAM SITE FOUNDATION ROCK . -... _ .... .,.., ill' ,_t __ ... J • •• .. 11'- • I --·--"'" ......... .,..:: • "'! :::-...:_ .... ,'"'::.~ . -. .,., ,:...,.. ~-~ "'"""*'"'----· -... --- . .. . ·-. _ _..... .. _.,.,.. '14"'- .--.. -·-----· -f "' "'--~:--_ ..... _...~-·--...,....- ~ --· ~--· ·• . ..,. .. -· ... --.. -----~ .... I W$ J.L A4 :Curved surface on is illusion caused by tric projection. is fou It is believed to be fltraight plane.--------- lit ISOMETRIC VIEW DEVIL CANYON DAM GEOLOGY-LEFT ABUTMENT 852-906-25 ~one burden Figure 4 ---.. '"" ....... --,..,_ ~ i l' q Q.) !... ;J Ol L1... c <U Q)"t:) t.: L.. 0 :J N..O ..._ ..._ Q) n ..... 1\l I I (,"' ...... • t • ~ ·•· ·o Om c:.-0 0 Q) -~~ (.) !... c ll I I I J •.J Ill ~ 'I I \ 1/j ' \ I ;, i I . ' l I 1/ l I l/ I ·w ·~. I-I D· ~ I l().• • t I ,;:r: ,.....lD 1-lcrj ·o:·:Z:\1 <1.·0-·w. lli ,1'1 .. ,,, I(') ~I -I ol l{)f ~I (Ill ~~ I • 1 !I ' ' !' ; I • I 0 0 0 '£!. /\ ____ ;' \ / I , I I I , , / j,l -~- Jl ;.;:;·, -~~ ~ wl{tilfl:tfi!t: ·/-.. _ fa tt: lli' · ,~0-~ -~-•f! !'!&n':'!!rt ...... -' ?0;., ...... -= ilif 1!'. h itriiJ• !4 ' ~-··~ -:;---.. fl -~· ,. ------------~---~· w 'r1~ v&v'··~.;:;~::..;~~~~:;~!D _[ :r t --:-r I r f r-s; t ·-~ l L I I l u i - L ii I -I ...,L.:' -·-1 c - tOr • 0 " __ th doke .--1-£ ::~I ~--_ J' . . nd of 1-' -~· cc • oH 1 ----ocreie -,;,o~ ;' esl trench No I ·-OHio ·-·;DH 9 I dcm I Dam crest ( Elr.;SS)·-·, , ~-•. ~~~\(Proj) -••· --: __ T_.. ·· • ..... • -1 ' , .. ~ ~.,;.-··}!''"· .,..~,•nr .. -.;·~·-K"' .:;." ,., J!!'·'·· ~~!!. •'· •• ' ,, .l '\ ;.;;f(ff>'' ;;'I _,/ 1\ s-' --·---------.--L / . ·:r ---- ~~-- J '' --·PHY ,~ -,..,--"" LLlTE _ .. "'-___ _.;;/ J4A• ,J4 17-•~ -, ~. f!l----~.:~,t(_ II 12-~:.""' I 12A --14 B ~~-" y !<,. 0 ·$ '6' b 'b ""' '9 0 <. 0 ~ ._p ~ I • -1.:;.:;:: 1- i w I w • u.. z Q 0, ~ "'J: ~ I z 0 I ··-r 1-l ·--<::t I > Spillway an::l ~ 1 d1versian ~ .. ·-.::·-::...,. l -----;:---I I ' J::o :.tJ ..J w . I NOT£: L)l-'l~ and 14A encoun1ered river wat'er at 50.0' and 56.1' respec1h:.:. j 01-i 14~ reentered rock at 59.0. An attc>mpt to relocate rock beyond 1l:e j 50-..,::>oi point tn DHl4 by probing with the dril: rods wos unsuccc~:-=_. becuuse t"he S1'>1ft undercurrents in the river bent the dn II rod tic ... -:: --eom. l --t ~:c EXPLANATION /Ill Ill':-~-.... ---·"'---·-----.... ............. -~~~--"'-·--...-...T----~-=-----... ~· ~· -~---~----------·~---· ------~-----· --~---· _____ · -----·:------~---·-···_j [/if _____ Shear ond fault zones. I I I I -~-r J ___ I I I ~ 1}7,; ~d .f.J]f' ,;J..~ r_ i ~ t:/1;. ~~//~ ·#-1/ ,.,,( . ?»;Jli . cv-;1' 1};1 .. _-PHY LLJT E-" J;· '-1-" ~ J' :t~ SECTION A-A I I i _L-----~-----'----- SECTION 8-8 ---------------- Dam crest { EL 1455) -~, ______ J_ / ---_7/ / , /.~ /ill' !" . ~ ·#;p 7:::..--J1soo 13001-w w u. z z 0 1100 j: <1: > ~ P HY ''· :1 r/ --,----LLI TE -···-w J w ··ltC }. _i;-·Spillwoy and -~~"er.lon <unnel I ------ 900 J700 ~ Intermixture of slope wosh ~----·and alluvial or channel fill. [fit1 ____ Glacial Till @!l7illl Phyllite (contains beds of I:!::ZMJ ____ graywacke and argillite) -G-.'~ ---fstimoted location of steel supports in tunnel 200 0 2'00 ( .... , •• tIt I HORIZ, SCAI..E OF FEET UNITCO STATI!S ., D£PAIQTM£NT c;F THE l"'TERIOA BUR.!:'At.; OF ,l:f£CL.A~ATJON DeVIL. CANYON Pt:lOJeCT-AL.ASKA DEVIL CANYON DAM GEOLOGIC SECTIONS -...,,~"""" till' 1_!·_:1~--S~JBMITT.ED-----_----------i. -T.RACEC _ _::_~~--R£COMM£iVbED--.--_---_.;a.~ 852-906-2.1 C\ r [ -f I [I r fJ , \ 100 0 100 ~ L---•• 5-·~C-A-L~E~~~f~E~E~T~----~ R-~ __ .. -SECTION A-A -- ( . ) ... L IJ . ' --------·-'r»- .. , __ ........... __ do 11 ~!'J:--1· ___ .... ,..~~ ' ~ ___ ......._. ___ .__ .. c ___ _. __ .._.< --..--·--- 8 ISOMETRIC EXPLANAHON ~a· Avrro9e d1p on<\ ~trHt of pi·,Jihfe Avtro9• dip 0 lD strlkt or JOIOh ....---Faults or shoor ~onas. _..1-- ..>-- VIEW 1080 • 'j' Sul"foct eltv"t'o"• abo,. "orners of pow<:rplonl chomb"!" I ------------ --- ~·y \ -•= NT AND BE:::l • ..,;G ROSET'rE UNITE.:: STATES t:EPARTMEN"!';r ..-HE INT£:1!10/f 1!1 UtH:A U t:F" -:;c L.A MA TION 0~/L CA~YON•~OJECT-ALASKA DEVIL C.LVYON DA!r1 GEOLOGY C.:= UND£F:P.OUND Of!At'll'l ___ "f:-~ !'.'----· SIJtJMirr:::;: _____ _ TRACED_.!,.%.~-___ Rf:COIJIJCr.;E: ::J. ---___ --__ CHECKED-/-1..~---__ .APPI'fO VC:., _____ • D€N VC'f• C~-:1* ADO._ F£1J~ .-•-"'