The URL can be used to link to this page

Home My WebLink AboutAPA1385I,. 1- . __ , . --' () '·"---~ I " I,, ':1-. i:~ 1.· ~ •. ,. '. -. ., I I -.. I I: I -· I I, I I ~- ~· '. . < \~ - ALASKA POWER AUTHORITY SUSITNA HYDROELECTRIC PROJECT INFORMATION PACKAGE FOR INTERNAL REVIE\'V. BoARD r1EETI NG #1 --:- JULY 23, 1980 ;'.:c. -.-::.::.·!:::.~-:.:':!~~ • ...~~~~"':!:!:'~ ...... !..~--"' --~~:!":. -:"'--f'\ "-,/ ,, ·" , .... :1 II If I • I I I I I I I I I I I I I I· I I I I OFFICE MeMORANDUM TO: See Distribution FROAf: N. H. Cl i pstone Date: File: uuly 10, 1980 P5700.13 .. 10 SUBJECT: Susitna Hydroelectric Project Internal Review Board Meeting #1 Attached is a copy of the· agenda and a bound val ume of support material (Review Board M·embers _only) for this meeting. We look forward to seeing you on the 23rd of July. The meeting will be in the Board Room, Niagara Falls, starting at 8:30 a.m. NHC/jmh . Di stt'i buti on: J. D. Lawr·ence C. A. Debelius J. D. Gill I. Hutchison V. Singh S. ·Thompson D. MacDonald J .. MacPherson L. Wolofski D. Hepburn H. Eichenbaum N1gel H. Clipstone Project Administrator 0 •• I I I I I I I I I I I I .I I I I I I TABLE OF CONTENTS 1.0 EXCERPTS FROM ACRES PLAN OF STUDY (PROPOSAL) 1.1 Executive Summary 1.2 Slope Stability Studies, Task 2 1.3 Seismic Sudies, Task 4 1.4 Geotechnical Exploration, Task 5 2o0 MAPS OF THE PROPOSED EXPLORATORY PROGRAM, 1980 3.0 REPORTS BY OTHERS 3.1 Foundations and Materials, Section 0, 1979 Corps of Engineers Report 3.2 Exc;:rpt from "Reconnaissance of the Recent Geology of the Proposed Devils Canyon and Watana Dam Sites, Susitna River, Alaska 11 by Kachadoorian and Moore 3.3 Excerpt from "Earthquake Assessment at the Susitna Project 11 by Krinitzsky 3.4 List of References (Available at the Buffalo Office) I ,··:0 <.,.:..: ' ·t , •• I I , I I'' I. I I .I . I -•. ·I I ,·I ·'I tl •. .. :· .. , ··,, ... ."'-, f' ;= . .. _ .. '. ., ,, -·:,-. '\ ', \ . ~.· •• ;r,.· r t ~ II i1 i J\ •• ·~ r i EXECUTIVE SUMMARY 1 -INTROQUCTION This ?1 an of Study (POS) has been prepared by Acres Arneri can Incorporated in resp-onse to the request of the A 1 ask a Power Aut hori~y to provide a prl:gram leading to a license application to the Federal Energy Regulatory Comm .. ~ssion for construction of the Susitna Hydroelectric Project. Maj~r contribucors to the plan and proposed participants in its implementation include R & M Consultants Incorporated (R & M), Terrestrial Environmental Specialists Incorporated· (TES), Frank Mool in Associates {FNA), t·loodward-Clyde Consultants {WCC), Salomon Brothers, and Cook Inlet Region Incorporated/ Holmes and Narver (CIRI/H & N). · The complete plan is made up of three major parts in addition to this executive summary. Part A sets forth the study plan itself and includes the establishment of program objectives, an overview of the study approach 3 a budget sum!flar:y> a logistical plan, detailed activity descriptions, a proposed project schedule, and a summary assessment of work which must be continued beyond the point of 1 icense application. ?art B is devoted to implementation of the plan. Key personnel assignments, an organizational structure, and coordination procedures are contained therein. Supplemental information in Part C provides supporting materials such as evidence of the qua 1 i fi cations of proposed corporate team members, deta i 1 ed resumes for key project personnel, and similar items. 2 -BACKGROUND A series of studies conducted initially by the Bureau of Reclamation and I subsequently by the Corps of Engineers 1ed to the recommendation that a two dam system should be constructed on the Susitna River. The upper dam at I Watana would be an 810-foot-high earthfill structure and the lower a 635-foot-high concrete thin arch dam at Devil Canyon. Transmission Tines \'IOuld extend north and south to Fairbanks and Anchorage respectively, for a total of 365 miles. The total project \'las 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 with the State of Alaska under ~~ovisions of Section ~03(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 facil 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 tue detailed studies required before a definite construction decision can be m~de.. An alternative to consummating the cooperative agreement with the Corps of Engineers is to fi ria nee the study entire 1 y \'lith State resources, contracting with a private engineering firm to do those I ! ~~~(~ I L---------------~--------------------------------·--------------------~ ?I~ I· 11' .11 '11 11 11 IJ 11 IJ IJ fJ f] I-, J 1 ~ iJ iJ IJ ,.----------------------------=·-----....:...--...., - 2 studies necessary to prepare and file a license application... Acres American 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 threefold: (1) Estab1 ish technical, economic and financial feasibility; (2) Evaluate the envjronmental consequences of designing and constructing the Susitna Project; and (3) File a complete 1 icense application with the FERC. Included within these overall objectives are certain specific items which must be satisfied. This latter group includes assessment of alternatives, preparation of an optimal development plan~ cost estimates, risk analysis, environmental and social factor evaluations, annua1 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 within this time frame, Acres has assembled a team \vhich brings to the Susitna project a unique combinatioo of capability and expertise, largely Alaska based .. The group provides: · (i) A powerful design/project/construction management team experienced in studies, economic evaluation, risk analysis, alternatives assessments, licensing, design, financing ~nd construction of large hydroel~ctric projects. (ii) Strong northern and subarctic experience. (iii) ( i v) (v) (vi) A skilled and readily available field exploration team \'lith facilities, personnel and equipment experienced in a11 aspects ,of hydrologic and geotechnical design and exploration, particularly in the vicinity of the Susitna site. An exceptional team of environmental specialists with first-hand knowledge and experience of the project area and ready to wo~< closely with state environmental agencies in effectively meeting the requirements of the plan of study. A capability for detailed seismic studies by renowned experts as wel1 as a comprehensive external revie\v. A logistic support capability \'lhich dra\vs heavily upon the skills of ,, ~ Alaskan Natives whose land selections are in the project al·ea. :~~~(~1·'----___________ _____, -· ":ft -I~! -··l ,{ ... •-* - 3 (vii) financial advice from an investment banking firm skilled in handling tax-exempt bond issues. The combined knowledge, 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 every case, task and subtask objectives are explicitly defined, as are proposed approaches, 1 evel s of effort, and schedules.. The thirteen major tasks are: Tas~ 1 -Power Studies 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 Tasks are presented in Section 8 of this Executive Summary. 5 -COSTS A~D SCHEDULES The Budget Summary is shown in Table A.3.1. The entire POS ca1ls for the expenditur.~ of $19.7 mi11ion in 1979 dollars over a period of two and one half years from study initiation to filing the license. app1ication for thr.se minimum efforts necessary to estab 1 ish feasibility frcm a technic a 1 , economic, and environmental standpoint. An additional amount of $3.4 million is required to conduct effective public participation, financing and local project management programs and to satisfy certain non-discretionary funding requirements. Subsequent costs during the estimated 30-month period through award of the FERC license are estimated as$ 26.2 million, including provision of an estimated $8 mill ion for the construction of a pioneer access road. The proposed project schedule is shown in Plate A2.1.. Initial site facil fties will be operational by March 1980 to support field investigations \'lhich will commence at that time. By the end of the first year of study, sufficient data will have been accumulated to make definitive recommendations as to continuation of the -study program. The second year will i nvo 1 ve continuation of field investigation efforts and development of conceptual designs along with initial mitigating measures. Field investigatiQns continue in the th·ird year and beyond, but sufficient information ~'lill 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 revie\'1 boards recommended to and selected by APA. Finalization i I • - 4 of the 1icense application including all exhibits will occur in the 30th month and a final review will be conducted at that time. 6 -ANTICIPATED DIFFICULTIES Thr·oughout the development of the POS, a number of potentiai prob1 ems have bef~n identified and the difficulties associated with m·anaging their resolution have been noted. Certain areas in particular have been long staDding concerns of many interested parties in Alaska: · (1) . (2) (3) (4) (5) The matter of generating a concept for optimal development calls for careful study of projected demand and alternative means of sat'fsfying it. Without such a foundation, it is simply impossible to assure the Power Authority that the proper project will be planned in the right place and constructed in time to meet the energy needs of the Rail belt. Data acquisition wi 11 present diffi cu 1 ties~ for seasona 1 and weather constraints as \'/ell as certain land use restrictions will lead to peaK 1 oadi ng of site support faci 1 it i es and the necess fty for use of spe:ci a l equipment not normally readily available in Alaska because of conflict- ing demands from other projects. The financial risks of such a large project must be reduced insofar as possible, for investor confidence is a prerequisite to successful financinge It follows that a set of detailed risk analyses must be conducted concurrently with the development of designs~ Parti~ularly important design problems to be resolved invoTve earth- quake 'hazards, ice occurrence, slope stability in long narro\·1 reservoirs, and the long term effects of silt deposition in the upper reservoir. Careful and complete environmental studies \'lill 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 Oepartr-~ent of Fish and Gaae, yet the objectivity of that agency insofar as reviews and approvals are concerned, must be retained. In addition, compliance with all ap~lica ble State and Federal environmental laws wil1 require strong coordination efforts. {6) Preparation of the license application itself must be accomplished at the very time new FERC regulations will be promulgated. (7) (8) Informing and involving the public is necessary and important~ but conflicting desires will be expressed and determination of h0\'1 the public interest can best be served will be difficult. Control and ~.::oordination of the efforts of a11 parties involved in implementing this plan demands effective management. ;i: - 5 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 so, the requirement to maintain a high degree of flexibility in adaptfng to ne\'1 problems is clear, for there is simply no 'day to anticipate every diffi- culty \vhich may be encountered. The plan provides a large measure of flexibility and a \vell defined chain of command as well as positive steps for addressing the noted problem areas: (1) Careful studies of projected loads and possible alternatives for 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 succ~ss 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 wil1 be undertaken by the Alaskan office of \<ICC, \vhere intimate knO\'/Tedge of the local scene is available.. Insofar as hydroelectric altern.atives are concerned, Acres will contribute its own extensive experience in planning, designing, and managing hydroelectric projects ranging in size fro111 500 kilovJatts to thousands of megawatts .. Optimal development of the Susitna River itself will flow naturally from these preliminary studies if the proposed project is shovm to be 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 C IRI /H & N, \·lhose earlier experiences on the Trans-Alaska Pipeline and whose intimate ~nowl_edge of project lands selected by Native Corporations will be important factors., The question of equipment availability and its operation 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 \oJhich is self-contained and fully equipped for the purpose. (3) Financial planning efforts by the prominent investment banking finn of Sa 1 oman Brothers \'li 11 be camp 1 emented on the Acres team by the work of Mr. J. G. Warnock v1ho successfully 1 ed the bond offering support documentation effort on the 5225 MW Churchill Falls project in Canada. The risk analyses will be undertaken by Dr. C. B. Chapman whose past experiences in this special area have supported certain 1 arge po\>~er projects in North America and abroad. (4) Of the many potential design problems, none is of more serious concern than seismicity. wee (California) will conduct exhaustive studies in this area and their work \'-lill be subjected to close scrutiny and confirmatory studies to be managed by an external board at a level of effort of $1 million. Ice studies, slope stability studies, permafrost studies and sedimentation studies are included in the plan. Much of the field ~·1ork will be undertaken by R & i1 and the primary design efforts by Acres. ~~ .___ ____ _ I i: j. i' ,, ' j ' i I I l I~ :, j j I j :j j I 1.>' .. :. .· • . . : :· \ . \ l • • ••• . • • \ ' ') . . .:.. ! . . . ~ . ' .. -6 (5) The en vi ronmenta 1 effort wi 11 be conducted by TES whose~ core staff \\fi 11 be augment.ed by principal investigators from the faculty of the University of Alaska and other consultants with exten;;i ve 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 dir~~ctly to APA in all such cases. Revie~t/~), approval S 1 , and coordination \vith ADF & G and \vith other State and Federal agencies wi 11 be sought throughout to minimize 1 ate st<.\ge non-concurrences .. FERC has confirmt~d that all studies need not have been completed at the time of filing, provided that a plan for completing them is included 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 regulations as they are published. Acres will lead this. effort and "1ill 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 \vell as a positive control on response to every public concern. (8) The management expertise gained in Alaska on large pr·ojects by Ff·1A \'-lill be heavily re1ied upon in the establishment of cost and schedule controls as well as in the preparation of realistic constr'uction cost estimates, schedules and projected cash flows. 8 -ACTIVITY DESCRIPTIONS As stated ·; n Section 4, the Acres approach to the Sus i tna POS wi 11 be in terms of a series of 13 tasks, each \'lith its specific objectives.. Sumt~tary descriptions of these tasks follow. 8.1 -TASK 1: POWER STUDIES (i) Task Objectives 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 gro~rth, to develop and rank. a series of feasible, optimum expansion scenarios and finally to determine the environmental impacts of the se:1 ec~ed optimum ·scenarios. (ii) Task Output The primary output of rask 1 will be a report dealing with the selection and ranking of optimum system expansion scenarios for the Alaska Railbelt Region. The final version of this report will be submitted for review and approval by Alaska Power Authority on or about Week 48 of the Study. Preliminary findings of the study will be discussed with Alaska Power Authority on or about Week 30 of the Study. Such a discussion wi 11 center on whether or not ~1ork on the [Q l,__ ____ s_u_s ..... it_n_a_D_e_v_e_lo_p_m_e_n-ts_h_o_u_l_d_c_on_t_i_n_u_e--or_w_h_e_t-he_r_a_n_o_t_h-er_,_p_o_s_s-ib_l_y _______ --..l I I I I i I I l ~ • • .. • • • • '>S :. • I •• ~ . : : .-~" • I i . . • . . -. l . ,I .j ., ' f f t1 f I I - 7 more viable alternative should be examined. Design Transmittals outlining intermediate stages of the power studies will 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 Expansion Sequences Subtask 1.05 -Expansion Sequence Impact Assessments Subtask 1. 06 -Pm'ler A 1 ternat ives Study Report 8.2 -TASK 2: SURVEYS AND SITE FACILITIES (i) Task Objectives {ii) (iii) 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 subtask s \'lhich must be performed prior to licensing; to resolve real estate issues associated \'lith the proposed project in sufficient detail to permit preparation of Exhibit F of the FERC license application; and to undertake initia) studies of proposed reservoir areas and access roads. Task Output The primary outputs of this task will be major portions of certain exhJbits r·equired for FERC 1 icense application and data rlhich will be necessary inputs for many of the remaining exhibits. Specifically, this task will contribute to Exhibit 0 (demon-:trating evidence of compliance with State water and land use laws), Exhibit E (providing water rights data and plans for perfecting rights to use water for project operation), Exhibit F (statement of land ownership). !n addition, surveys and mapping will be essential portions of Exh'ibit J (general project map) and Exhibit K (detailed project map showing boundaries, survey data, 1 and O\'lnershi p, and feature 1 ocat i ens). In addition to the data collection and exhibit preparation) a number of tangible products will be acquired or constructed and will generally be suitable for use during the post-application phase and beyond. In this latter category are included camp facilities, airfield~ and similar semi-permanent items. · List of Subtasks Subtask 2.01 -Provision for Land Use F'ayments and Directed Inspection Services Subtask 2.02 -Provision of Field Camps and Associated Logistic Support Subtask 2.03 -Design and Construct~on of Airstrip Subtask 2.04 -Land Status Research Subtask 2.05 ~ Land Acquisition Analysis Sub task 2 .. 06 -Right-of-Entry . ! I l ' f . ! ~ ~~~(~ i I ~--------------------------------------------------------------------~ I I 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 Reservoir 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 Task Objectives The basic objectives of this t~sk are to undertake and report on all hydrologic, hydraulic, ice,and climatic studies necessary to complete the feasibility design of the project and to provide sufficient material for the FERC license application. (ii) Task Output -Data Index System A data index system listing all the available hydrologic and climatologic data will be compiled and circulated. Hard copies of the more relevant data items ~·till be stored in the project office in Anchorage and copies made available to those requesting it. All the additional hydrologic and climatologic field data co 11 ected as part of this study wi 11 be documented on either computer printout sheet-s or type\·lrittt:n tab1es. -Written Sections and Drawings for Inclus:on in the FERC License Application Exhibit H -proposed reservoir operating rules, predicted reservoir behavior, and downstream water quality and flow conditions. Exhibit I -dependable poltlel' flm·1, critical design low fl0\'1 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 -spillway design flood and capacity and freeboard allowancea ~I ~~~nm,i.__! --~-----------.... :li. ·.m ~ 1_, lr· .til F: " ' .j' "r· I ~~~. 1;1 ' ~ •~ . -.tJ I . ' . I '(1 fr jJ ~ F ,. \ . jM jU F . ~ . IJ ;iJ 41 - 9 -Hydrologic Appendix to Engineering Report The detailed technical appendix will contain sections on the follC\'Iing type of studies: hydrology (resource and floods)~ reservoir" operation, hydraulic, sediment yield, river morphology, ice engineering, and climatic studies for transmission line design and hydrologic and hydraulic studies for the access road. - A Series of Design Transmittals These will summarize the pertinent design parameters obtained from the studies outlined above. (iii) list of Subtasks 3.01-Revie\·1 of Available i-iaterial 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 Obje~tives To .. determine the earthquake ground motions which 'ilill provide the seismic design criteria for the major structures associated with the Susitna Hydroelectric Project, to undertake prelimin.ary evaluations of the seismic stability of p1oposed earth-rockfill and concrete dams, to assess the potential for reservoir induced seismicity and landslides, and to identify sons which are susceptible to seismically-induced failure along the proposed transmission line and access road routes. (ii) Task Outout The data collection programs and studies outlined in this task will be sufficiently comprehensive for FERC license applications. Thorough presentations of conclusions, eva1uations and data are also desirable for projects that are being carefully reviewed by permitting agencies. Wood\·tard-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. Based upon our past experience, we believe that the Susitna Hydropower Project will undergo close scrutiny~ and that the reports of the project shou 1 d be camp 1 ete and thorough. ~·le propose to complete the reporting of the seismic geology and siesmology investigations with this philosophy as a guide. \ ~~~rn \I ~--------------------------------------------------------------------- !~ .•. ~ 1 I ~· .~ ~ ...i1 i' '~ •• ~~ -10 :rhe primary products of this task will include: -Technical reports containing thorough documentation of all \-tork done during the first year. -Final technical reports containing thorough documentation for all studies during the first tv/O 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 wi11 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 -p·reliminary Reservoir Induced Seisiificity Subtask 4.04 -Remote Sensing Image Analysis Subtask 4.05 -Seismic Geology Reconnaissance Subtask 4.06 -Evaluation and Reporting Subtask 4.07 -Preliminary Ground t~otion Studies Subtask 4.08-Preliminary Analysis of Dam 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- ! nduced Failure 8.5 -TASK 5: GEOTECHNICAL EXPLORATION (i) Task Objectives To determine the surface and subs-urface geology and geotechnical conditions for the feasibility studies of the proposed Susitna Hydroelectric Project, including the access roads and the transmission lines. ( i i) Task Outpu_! The primary outputs of Task 5 will consist of comprehensive i documentation of geotechnical exploration undertaken at the Devil I Canyon and Watana sites, reservoirs, and access roads and I transmission line routes. This documentati'ln will include the 1 following: 1 -geologic maps It -geologic sections ~ descriptive and graphic borehole logs i ~~~~(~~~---------de_s_c_r_i_pt_,_·v_e __ t_e_st __ t_r_e_nc_h __ 1_o_g_se ____________________________________ ~J -field inspection borehole and test trench logs -photogeologic maps -borehole rock core photographs -law level air photointerpretation -seismic and resistivity bedrock profiles -radar imagery interpretation maps geotechnical exploration program summaries (1980~ 1981, 1982) -data summaries for o --in-hole seismic testing --borehole camera studies --laboratory testing. geotechni ca 1 exploration summary reports (1980, 1981) (iii) List of Subtasks Subtask 5.01 -Data Collection and Review Subtask 5.02 -Photointerpretation Subtask 5. 03 -Exploratory Program Design (1980) Subtask 5.04 -Exploratory 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 8.6 -TASK 6: DESIGN DEVELOPMENT (i) Task Objectives -11 To undertake planning studies, to evaluate, analyze and review all previous engineering studies related to hydroelectric development of the Upper Susitna River Basin and to develop preliminary engineering des'ign and cost information for Watana and Devil Canyon. Dam sites with all associated intake, outlet works, spill\'/ays 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 ~latana to Devil Canyon to eliminate the high dam at that site. A Development Selection Report will be issued on or about vleek 65 of the Study for review and approval by Alaska Power Authority~ Preliminary findings of the study will be discussed on or about Week 50, in order to - establish \'lhether or not work on two dam sites should continue or whether more viable alternatives exist and should be examined. Design transmittals will be issued at appropriate points in the study. All necessary input from parallel tasks including hydrology, geotechnical, economic, seismic survey and environmental studies \-Jill be factored into the planning studies and the development of the various features of the project. Engineering evaluation criteria and project definition v-till be developed. rf sites are found to be 1 . • I l technically viab1e 3 ecoDomically feasible and environmentally ~~~~I~ IIL--..---.-----:------------------1 ,_-~---·C: .•.. ·.· ~' ' :" '·· a· · ..•.... -. . . ' )") ' ~· - CJ I' ' .-. . r• ... .. '·.> I ' . ' .•...... ·f} I I ••• I I •• ••• I ··I_ I -1 ).::, .. 1.2 SLOPE STABILITY STUDIES, TASK 2 I Subtask 2.15 ... Slope Stability and Erosion Studies I I I I I I I· I I I I I I I I I I ' (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) Approac~ 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 risk analysis to ensure that all potential difficulties have been accounted for. 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 license application, much more detailed 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 wil1 be 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_will 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 will have been drilled in other project tasks to accomplish 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 describing 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 ty~e and its consistency. Included in this report will be a discussion of erosion control for general site grading .. (d) Schedule \4eeks 47 to 54 5-48 . . . _ _,.. ' 0 ·I~ , '.. ' ' ' () ' -,) ·, :······... ); .. • ,i). ' 1--~--~·-· -~-~-···-' ''"'" ·---~-~ I ,, ~0 • ~ ~.! I ·a 1-.·· ·_. I I I I ·-· ~-- 1 I I. 1,' •• Q --· ':'; 1.3 SEISHIC STUDIES, TASK 4 --. ; . ~--·--------~-- ..... I ... . . 1981 TASK . 1980 • < DESCRIPTION ~1N fEe MAR APR UAY dUN Jll. AUG SEP OCT NOV DEC JAN fEO UAR APR 11/!V JIJN '-'Ul. AUG SEP ~-ct NOV DEC • ' 4.01 DATA REVIEW .,. ;311117&1 l:ilal . . . j ··-' J . 4.02 SHORT-TERM -~ -mac UZliZI !ZJ. m: am:: < . Di MONITORING PROORMt • ' 4.03• RESERVOJ~·INDUCED I I •• . ~-if'-~sa -~ fl:ll ·liD 1:1 --~ 8 4. J0 SEISMICITY . ! . ..:.t 0 ' :E 4.04) REMOTE SENSING m:a r:;. ' In w IMAGE ANALYSIS ll) . ~ ~ >-4.05 SEISMIC GEOLOGY mil~ . ., ~ a ~ g RECONNAISSANCE 1 0 -tJJ C) 4.06, EVAWATION a ' . 11.m::iii2 ~ mila a::::a -· 1.~ I'.IIZm ~ Di3 r.m:ma ar:m; ~ a:a ~ . :: 4.12 REPORTING j U') w (I) 4.09 LONG ·TERM : ~ . . MONITORING ffiOGRAM . 4.U SEISMIC GEOLOGY' cz ;t.a&m; ~--a:r8J ~--FIELD STUDIES . . REVIEW MEETINGS ~ u:a Fa ID .. . (!) z 4.07, GROUND MOTlON plli3ID ,151 ~Dill ----llCIG; ;taa:za ii ra .. IU: I ttl 4.13 STUDIES . z . .. ffi z . . .. tamm ~ llml iU 4 .oa, DAM STABILITY . ~ 4.14 :l SOILS SUSCEPTIBLE . 0 F::ui 1 1MB l: 4 .15 TO SEiSM!CALLY • •• ... ~ . INOUCEO FAILURE . ~ . . . . . SUS I TNA HYDROELECTR-IC PROJECT . . PLAN OF STUDY . PI .ATE T4.1• TASK 4 SCHEDULE I l I I I I I I I I I I I. I I I I I I A~5a5 -TASK 4: SEISMIC STUDIES . (i) Task Objectives . To determine the earthquake ground motions which will provide the seismi~ design criteria for the major structures associated with the Susitna Hydroelectric Project, to undertake preliminary evaluations· of the seismic stabi 1 i ty of proposed earth-rockfi 11 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 collection programs and studies outlined in this task will be sufficiently comprehensive for FERC license applications. Thorough presentations of conclusions, evaluations and data are also . desirable for projects that are being carefully reviewed by permit- ting agencies. Complete reporting of the seismic geology and seismology investigations will be made with this philosophy as a guide. This task will be conducted primarily by Woodward-Clyde Consultants with review by Acres and field support by R&M Consultants. The ground motion study data wi11 be utilized in Task 6 for design studies. Identification of seisim1cally susceptible soils for the r.Qad 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.ihal technical reports containing thorough documentation for al1 studies· during the first two years. -Monthly management reports during the course of· the investigatione The technical reports will be accompanied by geologic maps showing locations of all controlling features, fault lines, etc. Management repc>rts wi 11 deal with technical and financial progress with respect to plan. 5-79 • I " I -· I I ,. I I ., •• I I I I "I ! ~· . 'L !. :I • :I Subtask 4.01 -Review of Available Data (a.) Objective To acquire, compile and review existing data and identify the earthquake setting of the Susitna River basin area. (b) Approach . Data obtained· under this subtask will be used to plan the details of the seismologic investigations (Subtasks 4s02~ 4.03~ 4.09 and 4$10) and the seismic geology field reconnaissance (Subtask 4a05). Avail- able geo1Qgica1, seismological, an~ geophysical data for the region . will be gathered from sources such as Woodwar.d-Clyde files, the DeRartment of Geologic and the Geophysical Institute of the Univer- sity of Alaska, the·Alaska Geological Survey, the u.s. Geological Survey and the major call eges and univer>siti-es involved in research pertinent to the project. In addition, researchers with on-going programs of study will be contacted and the current status of their research will be obtained by discussions and written correspondence. '!he acquisition of geological data will be cr,ncentrated :1n structural features of the earth that may repre$ent mgj~r_active faults.. The geomorJJhic expressio'hs of these features will ~1 so be ider1tified from the available data. Geophysical data regarding the structure of the earth wili be acquir- ed and reviewed. Regional gravity and magnetic data ar~~ particularly useful in identifying major discontinuities in the cru~t o·f the earthe These discontinuities may be. along faults that coald produce large earthquakes and surface fault ruptures. !f availdble~ other . types of geophysicai data such as seismic refractioi1,. seismfc reflec- tion and electrical resistivity may also be of us~ in identifying major active fau 1 ts.. · Seismological data will be acquired for the project area.. Thi.s data includes historical information on past earthquake~~ instrumental data from the Geophysical Institute of the University-of Alaska~ and regional instrumental data from the u.s. Geological Survey. The geological, seismological and geophysical data will 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 epi.center clusters or alignments identified by others. These maps will provide a-basis for the pro- · posed geological an~ seismological studies. In addition to the data acquired for the project area~·data relating to reservoir-induced seismicity will also be csmpiled. The world- wide data on reservoir-induced seismicity will 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 world-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 .:. I. I I •• I I I I I I I I I ,I .I z ~. I I I ;:; I The specific products of this subtask include: -Historical earthquake 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 como1ete- ness level of the catalog.with respect to magnitude~ focal depth and spatial location. -.Summary of .recent reg; ona 1 monitori na Microearthquake monitoring by the University of Alaska Geophysical Institute and the u.s. Geo,logical Survey. will be reviewed 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 natwork studies. -·recto'lic model .Based on available seismologic and geologic data, a preliminary kinematic tectonic model will be developed for the region within approximately 200 miles of the site.. This model will be modified as needed by studies in later subtasks and will provide the basis for understanding the i nterre 1 a ted geo 1 ogi c source · a.r'eas for future earthquake activity in the Alaskan interior-. 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....t!!e seismicity of continental Alaska was stimulated by the majo~ earthquake and involved the initiation of regional microearthquak:e monitoring and the augmentation of geological fnvtstigations to improve understanding of the tectonics of Alaska. The seismological environment of the Susitna Project is characterized by two major earthquake sources: -shaliow earthquake activity occurring along crustal faults such as the Denali fault, with depth of focus less than approximately 1?.-" miles; and -earthquake activity in a Benioff zone which has a depth range of 30 to 90 mi.les and is associated with the subduction of the Pacific plate bene~th Alaska. 5-82 (. ( I I I I I I l I I I I I I I 0 seismological data t to inves- uake 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. Woodward-Clyde Consultants has previously conducted regional studies of seismic geology and seismicity over broad regions of Alaska. The 'past regional evaluations have be&n for the. Trans-Alaska Pipeline System, the proposed Offshore Continental Shelf regions surrounding Alask·a, and for the proposed Alcan Gas .Pipelinee These past regional studies provide data regarding the earthquake sources in Alaska, Ftndthey also provide up-to.:date know- ledge of the current status of research in the area. (d) Schedule Weeks 0 through 22 5-83 ' . "'"; '• •· .. -~:.'>(".,~: """ ....... ~"""' I I I I I I I I I I I I I I I I I I I ?ubtask 4.02 -Short-term Seismologic f1onitoring. Program (a} Objective Establish initial monitoring system, obtain and analyze basic seismo- logic data on potential earthquake sources \'lithin 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 of Existing Data Further limited analysis ·of existing regional earthquake data will be undertaken to enable sufficiently accurate and appropri- ate selection of maximunt earthquake sources and associated attenuation relationships. Source studies will be carried out on several of the largest historical earthquakes, including the ~904 and 1912 events, in order to constrain their location, 0~ ()local depth and causative geological structureo The maxi.mum ~ earthquake potential of the subduction zone beneath the Susitna site is poorly understood, and it will be of significant value to use the historical data to properly charact~rize this source. These studies will also be dire'cted to the evaluation of the seismic attenuation characteristics of deeper earthquakes to enable the proper utilization of the results of the Alaskan . (()'ASES study by Woodward-Clyde Consultants (1978) and other V 'nUdies in selecting appropriate attenuation relationships • required for Subtask 4.07 and 4.13. {2) Establishment of a Monitoring Network Since the study area is in a remote but seismically act1ve area additional detailed earthquake source data will be collect~d by installing and operating a localized microearthquake recording network. C. The network will be established and operated during the summer · of 1980. The area covered will include the region within "Cfd with station spacing of 5 to 10 miles will be installed to \1' <( , ·( record microearthquake activity down to magnitude of 1.0 or _ ~r less. Low-power radio telemetery w_ill be used to make the field ~~d operation as efficient as possible. Helicopter support wi11 be ~:~ -used for i nsta 11 at ion and mai ntenanceo &'" Initial station deployment will b.e guided by the information obtained during the data review (Subtask 4.01). It will be required_to monitor known significant geologic featuress such as the Susitna fault. 5-84 • • • I It .I I I I I I I I I I I I -1 . , I II. ·I During the course of the study, some of the stations may t~ moved to study specific areas of activity. Data analysis will . be carried out to locate active seismic sources and evaluate their spatial extent and focal depth. These analyses will also be used tv establish causative stress orientations based on focal mechanism studies, to evaluate seismic attenuation~ and to evaluate the statistical features of the microearthquake activity. Specific results to be obtained r·elative to source and wave propagation assessment include the association of larger earth- quakes {such as the 1904 and 191~ events) with probable source· structures, depth determination of the Benioff Zone of deeper seismic activity and attenuation characteristics of subduction zone earthquakes$ Seismic source location in tenns of maximum earthquake potential in the Benioff Zone will be performed. Comparisons will be made with sei!;mic activity in other compar- able tectonic ar·eas to assess attEmuation and maximum earthquake potential. The scope of these studies will be modified as necessary on the basis of the resutlts· obtained as the work progresses • . Liaison will be maintained with data call ection by the Univer- sity of Alaska Geophysical Institute and the u.s. Geological Survey. The recording period is initially planned as three months; ·however, if this should net!d to be modified, appropriate recomnendati ons wi 11 be made duri ntl the course of the study .. (c) Discussion The present location and focal mechanism level using the Geophysical Institute network is approximately magnitude 2~112 or larger. The data obtained from the propos~d monitoring program will supplement the existing rerjional network operations and will provide needed accuracy and detection threshold. In addition, the results obtained will provide the information ne'eded. to accurately site the long-term network stations (Subtask 4.09) and to select appropriate instrumen- tationo They will also aid in planning the seismic geology recon- naissance (Subtask 4.05). (d) Schedule Weeks 21 through 52 5-85 I ~1 "' :; ••• .. • • ~ .. ~ # •• ~ .. ·.··~ ................. : •• •• ,.·~ ...... .,_. ~: ....... "","' ....... ~ .. ' -~· ·: ... ,.·· ~· "';"• • ., ."' ... ".:~--... :""~ .. I I I I I I I ~ I I· I I I I I I I I I I Subtask 4.03 -Preliminary Reservoir Induced Sei_smici·ty (a) Objective (b) Evaluate the potential for the possible future occurrence of reservoir-induced seismicity (RIS) in the Susitna Project area. Approach ~ · . 0 ~ Tne results of this eval. uation will) be .used to establi.sh scenarios of possible outcomes of the occurrenc~ reservoir induced seismicity. Woodward-Clyde Consultants has recently completed a major analysis of geologic, seismologic and hydrologic factors associated with past cases of reservoir-induced seismicity.. The resu1ts of this study .also will be applied to the known factors for the Susitna project in order to statistically relate the Susitna Project to the potential for RIS. The resulting potential 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 paten~ tial for the occurrence of reservoir-induced seismicity as a result of the danming of the Susttna River. A comparison will be made of depth~ volume, regional stress, geologic settti.!l9 and faulting at the Susitna dam sites with the same parameters a~the world's deep and/ or very large r~servoirs. Based on this comparison, the probability of reservoir-induced seismicity at the Susitna dam sites will be assessed. A description of known cases of RIS emphasizing th~ rel~tionship between fi 11 i ng of the reservoir and the 1 ength of "t1me 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 actfon. that can be taken if RIS is antic·ipated or detected during filling of t "' . ue reservo1r. (c) Discussion The activities associated 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 It I I I I I I. 1 .. .. ) I I I I •• I " I I -m IK ms r • Subtask 4 .. 04 -Remote Sensing Imag~ Analysis (a) Objective . Select and interpret available remote sensing imagery to identify topographic features that may be associated with active faulting. (b) Approach 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 produce . future earthquakes and future surface fault ruptures. Remote .. sensing imagery and aerial photography relevant to approximately([iffifkm~ radius about the dam site will be selected for a lineament--anaTYsiso · This·remote sensing data includes available Landsat, SLAR (side- landing airborne radar}, Skylab photography; high altitude U-2, or RB-57 color infrared photographs, and black-and-white aerial photo- graphs. The remote sensing and high altitude imagery and aerial photographs will be interpreted in terms of the geology~ geomorpho- logy and structure of the study regiona Interpretation will help to identify lineaments and other features that may. be related to active faults. Seismicity clusters and alignments identified during the seismicity eva'luation in Subtask 4.02 will be compared with the lineaments identified by the imagery interpretation and the knO\'In 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 with active faults. It will be important to distinguish these lineaments frcxn similar features tl1at result from non-tectonic geologic processes. · {c) Disc•.tssion The activities in this tas will be closely coordinated with the ·~·\g'O photo interpretation studi s being conducted for the dam sites reservoir and construct material areas {Subtask 5.02) to ensure that informationrequests and analyses are not duplicated .. Following ,f an init.ial aerial and ground reconnaissance it.may oe decided that ~ ~low-sun-angle aerial photography should be acquired for specific ~ eomorphic features that may be fault-related. For this purpose, ' ow-sun-angle col or infrared and black-and-white photography at a jr cale of approximately·l: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 undetectable with conventional vertical aer'ia1 photographs~ 5-87 I I I I I I I I .I I. I I I I I I I I I· 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 1 ineaments t'lithin 100 km of the project area tlill be pro- duced as a gufde for Subtasks 4. OS and 4.11. The 1 ineament map wi 11 be supplemented by mapped faults from Subtask 4.01, in order to com- pare known faults with lineaments of various origins. (d) Schedule . Aerial photographs will be ordered during the first month. rne analysis will be performed during weeks 10 through 26. 5-88 ('" ( I I I I • i I I I I I I I J Subtask .4. 05 -Seismic Geo 1 ogy Reconnaissance (a) Objective Perform 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 utilize 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 fauit capable of impacting the project area due to its being ~ (associated with a large earthquake or c~able of producing a future__..\"D surface fault rupture. Features within @?'finles of the prOJect area will be studied during the reconnaissance, with each lineament and fault being identified by number. In addition, regional reconnais- sance of major features such as the Denali fault and the Castle Mountain fault 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 projects. Those features that are interpreted to originate from youthful faulting!t or features of unknown ori·gin that may be due to youthful faulting, will be studi eel further in the field and subjected to reconnaissance-level geologic mapping. The reconnaissance-1 evel geologic mapping will be oriented. 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 will require detailed study during the field season of 1981. These activities will be coordinated with the geologic mapping tasks associated in Subtask 5.0~. (c) Discussion The Susitna River area is in a complex tectonic area that is poorly known geologically. Previous work by Kachadoorian and Moore empha- sized the structoral complexity of this area, and the large number of linear features at the surface that may be due to faulting or to other origins. These surface features require· field investigation to identify their origins. In order to identify the origins of some features~ it may require detailed mapping~ tren~ing, borings, or ! ~ 5-89 . 1M- -I I I I I I I I I- I I I I I I ,. I I I geophysical data. Despite thorough investigations, however~ it may not. be possible to obtain definitive infonnation 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 as 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 will be undertaken in the Seismic Geology Field Studies1 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 critical facilities. In addition, all field observation~ will be tabulated for 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 afterrSubta~k 4.04 is complete. Subtask 4.02 should either proceed concurrently with this subtask or it should precede this subtask. 5-90 ( • I I I I I I I I •") I I I I •• I II I Subtask 4.06 ... Evaluation and Reporting (a) .Qbjectives Complete a preliminary evaluation of the seismic environment of the project~ define the earthquake source parameters required for ear-th- quake engineering input in design and document the studies in reports suitable for use in design studies (Task 6). (b} Aeproach The approach of this subtask will be to provide a probabilistic analysis of earthquakes concerning control of active faulting, and to ·estimate maximum credible 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. (c) 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 all study. work undertaken and the findings thereof. Overall management and coordination of Subtasks 4.01 to 4.05 is also incorporated in this subtask. {d) Schedule Weeks 18-through 52 I 5-91 I I •• •• I I I I· I· I I I I I I I 'I I I - Subtask 4.07 -Preliminary Ground Motion Studies (a) Objective • . . Undertake a preliminary estimate of the ground motions (ground shaking) to which proposed project facilities may be .subjected' during earthquakes • (b) Approach IThe ground motion characteristics to be estimated Hacl ude peak. para- meters (peak accelerations, velocitiesj 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 wi(l be refined if necessary on the basis of additional infonnation gathered during the second year. (See Subtask. 4.13). In consideration of ground motions,. the tenns ... seismic exposuren and .. seismic risk 11 are sometimes used interchangeably. However~ for the purposes of this proposal they have twa distinctly different mean-· ings: - 11 Seismic Exposureu is used to define the nature of the earthquake-: induced ground motion characteristics at a specific site; - 11 Seismic Riskr• is used to define the risk as the probability of' structural damage or destruction by an earthquake at the project site. It reflects the degree to \'.ilich 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 jnto account the frequency of occurrence of earthquakes from all significant seismic sources. and the attenuation of ground motion fran each soorce to the locations of project faci 1 ities. Earthquakes of various magnitudes, up to the magnitudes of maximllll credible events, will be cons,idered. Attenuation relationships will be derived from examination and analyses of earthquake recordings made in similar tectonic environments and in similar subsurface geologic conditions~ including available recordings from Alaska. wee has recently cond~cted 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=-Castle Mountain fault) as wel.l as. offshpre faults \:i (e.g.,. Benioff zone), will be extremely valuable· to the progress study. 5-92 ........... ,, ( ( I ·' I I I I I I I .~· I I I I I I I ' I I ., The end products of this subtask wi 11 consist of estimates of the prob-ability of exceedence during selected time periods {e.g., 100 years) of various levels of ground motions at the locations 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 and corresponding amplitudes of ground motions that may be cons.idered in.selecting project seismic design criteria will be discussed. For the dams ground motion criteria ·11 be onsistent with round motions asso i maximum credi ea h uakes.. For less cr1t1ca project components, ground motion characteristics having a higher probability of exceedence would be used as design criteria. (c) 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 \-~hen the best available data and technology are employed. The fact is recognized in the above approach and con- siderable attention will be devoted to determining the reliability of the estimated aesign criteria. The key interrelationships of this subtask and others are the . following: Projections of earthquake recurrence and identification of maximum credible earthquak~s is an essential input to this subtask and will be ztccomplished in Subtask 4.06 •. The results of this subtask consti- tute. essential input to Subtask 4.08 (Preliminary Analysts of Dam Stability) and Subtask 4.15 (Identification of Soils Susceptible to Seismically Induced Failure Along the Transmission Line and Access Road Routes}. The products of this task include the following: -Estimates of the probability 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 \~eeks 24 through 52 · 5-93 I ',, I .--=--- I ~J . I ·-1'~ ' w_,; -:.-·- 1.4 ·0 ~- GEOTECHNICAL EXPLORATION; TASK 5--. . . •) •, 0. I, " I I I ·I I I fJ I I I I I •• 1. 1 I A.5.6 -TASK 5: GEOTECHNICAL EXPLORATION {i) Task Objectives .. To determine the surface and subsurface geology and geotechnical conditions f9r the feasibility studies of the proposed Susitna Hydroelectric Project, including the access roads and the transmis- sion lines. (ii) Task Output 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 primary outputs of Task 5 will consist of comprehensive documen- tation of geotechnical 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 1ogs -descriptive test trench logs · -field inspection borehole and test trench logs -photogeologic maps -borehol~ 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 --1 aboratory testing. -geotechnical exploration summary reports (1980, .1981) (iii) List of Subtasks Subtask 5.01-Data Collection and Review Subtask 5.02 -Photointerpretation Subtask 5.03 -Exploratory Program Design (1980) Subtask 5.04 -Exploratory Program (1980) Subtask 5a05 -Exploratory Program Design (1981) Subtask 5.06 -Exploratory Program (1981) Subtask 5.07 -Exploratory Program Design .(1982) S~ibtask 5.08 ... Data Cumpilation (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 will be initiated prior to submission of the FERC license application, but is not an essential prerequisite 5-105''. I ·- I I I I I I I I I I I I I I I I I to that submission~ The 1980 geotechnical exploration pro~ ---~ \Jill be designed to identify and investigate in limited detail those geological and geotechnical conditions which will significantly aff~ct the feasibility of the proposed dam projects. Limited prepl anning ~pportunities and climatic constraints are such that investigations in 1980 will be somewhat limited in scope, and the data limited in detail. Emphasis will therefore be placed on identifying and investigat.ing to the 1haximwn extent the most adverse geotechnical condition~ encountered • . The objectives of the 1981 geotechncial 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. ·Exploration 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 still be somewhat limited, the exploratory program \'lill be designed to establish with reasonable confidence the feasibility and total cost of the project, access roads and transmission lines. The exploratory program in 1982 will be yet more detailed. This and subsequent programs will pe aimed at providing greater certainty in the design of major dams 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 wil1 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. Full account has been taken of ~hese 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 ( ( (_ •• .. I I I. I I I I I I I I I I I ) -. I I 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 corridor& and the Susitna River basin. (b) A2proach Data to be ccllected at this stage include, but are not limited to the fo 11 ovli ng: . -previous regional and site geologic~l mapping and studies -published or unpublished geological and geotechnical data and reports from federal, state, academic or private sources -air photos and high level ERTS photos of the project ar.ea, including tne proposed access road and transmission lin~ 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 determine the design of the exploratory investigation progra~. The data and results of review will be assembled into a brief report with appropriate appendices. These documents will be made ava~lable for subsequent use by all project design and study groups. Borehole rock cores from previous investigations will also be examined in 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 \iith the construction of large embankments, access roads and transmission lines will be collected. Discussions will be held with the u.s Corps of Engineers concerning details of the past field studies. This task \'Jill be undertaken by Acres' Anchorage staff with appropri- ate support from R&M Consultants. (c) Schedule Week 0 through 9 5-107 I I I I I I I I I I I I I I I •• 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 1 i ne corridors, 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 scale obtained under Task 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 sca·~e. They will, however> serve to establish·preliminary surface geology, including geomorpho- logy5 geologic history, glacial geology, li::hology and stratigraphy, structural geology, permafrost characteristics and geohydrology and engineering geology. Land forms wi11 be identified. Alluvial or glaciofluvial 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 rQck types will bt2 identified. Photo analysis will also be used to generally delineate or. infer permafrost areas and buried channels. Groundw·ater 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 perfonmed early in the first field season (1980). (c} Discussion New air photos produced under Task 2 will be available at the end of the first field season. These low level, high resolution, large scale photos will have two purposes: -preparation of sec-ond year exploratory investigation program -production of accurate topographic maps on which to base subsequent geological mapping and design studies. Photointerpretation under this subtask wi11 be undertaken by Acres• Anchorage staff and closely coordinated with the photointerpretation work done by wee (Subtask 4.05) in order to eliminate unnecessary duplication of work. 5-108 ( ' ( ( I t I I I I -I I I I I I I I I I ~ I - I The results of photpinterpretation will be documented in the form of brief su(Olary reports and appended photographs and maps to high 1 i ght the principal findings. (d) Schedule Weeks s· through 41 5-109 •• I I I I I I I I I I I I I I I I I_ Subtask: 5.03 -Exploratory Program Design (1980) (a) Objective Design the geotechnical exploratory investigation programs for 1980 for Watana and Devil Canyon damsites, dam construction materials, and reser·voir areas, and along the access road route. (b) Jpproac:!:!_ 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 will also be required. Generally, these exploratory investigations will consist of geologic mapping, auger drilling and sampling, test trenching, seismic and resistivity studies, airborne radar imagery techniques and laboratory testing. In cases \'/here environmental damage is a problem or accessibility is poor, test trenches will be replaced by shallow auger drilling by helicoptero 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 ~Y airbor.ne radar imagery techniques -types and numbers of laboratory tests. Investigations for access roads will be confi-ned to geologic mapping and radar imagery. Table A5.4 and A5.5 detail the type and extent of investigations and laboratory testing that are currently proposed el~ewhere. The design of the explor·atory investigations will be flexible enough to permit changes during the execution of the work ... These changes will become evident as the field studies proceed. (c) Discussion Work under this subtask will be performed by Acres• Anchorage staff with support in logistical planning provided by R&M and close liaison with wee. In the design of the exploratory investigations, 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 boreholes 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 Kachadoqrian. A total of 19 auger and diamond drill 5-110 0 ( ( -.. - Area Oamsite Dam Con- struction Materials Reservoir Basin ---- --·-. ----:, d -._"_ .... ?· ' --- TABLE A5.4 PROPOSED 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 PRUJECI SIRUCIURES/FACILIIIES Oev11 Canyon-Dam & Reservo1r Watana Dam & Reservoir 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 aad saddie dam site One established and two new borrow ~reas yes 20 -10 ft. deep holes in the two proposed borro~ areas 2 -1,000 ft. lines in the two pro- posed borrow are as 30 trenches in the three borrow areas 6 -1,000 ft. lines in the three borrow areas yes 10 ~ 10 ft, deep holes 2,000 ft. 100 ft. 10,000 ft. yes 1 .... 5,000 ft. 1 i ne at wr.oposed spillway site · 2 -Oblique 1,500 ft. 1lii:nes across river withfm ,upstream portion of dam 600 ft. + 4,000 ft. at right and~ left abutments Four established and tw~ new borrow areas yes , 20 -10 ft. deep holes im the two proposed ·borra~ areas 2 -1,000 ft. lines in 1tJbe 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 right bank relict channel lOP ft. 20,000 ft. - U1 I ...... ,_. N --------(} ------ Area Damsite Oam Construction Matert a1s Reservoir Basin Access Road Route (Approx. 50 miles} Geologic Mapping Oiamond Driiling In-hole Seismic Borehole Camera Test Trenching Auger Drilling Diamond Drilling Test Trenching Geologic Mapping Portable Auger Drilling Diamond Drilling Geophysical/Seismic Reservoir Slope) f1on i tori ng ) Geologic Mapping Airborne Radar Imagery Portable Auger Drilling H~llow Stem Auger} Diamond Drilling ) TABLE A5.5 PROPOSED GEOTECHNICAL EXPLORATORY PROGRAM -1981 POwER SIROCIURES/FACilliiES Oev1l Canyon Oam & Reservotr Watana Oam & Reservo1r yes 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 dee:p holes t 1 -200 ft. slnpe indicators yes 2 holes in relict channel, right abutment 2 holes in right ab.utment spillw~y and dam) 2 holes in left abutment (power-house and dam)** 1000 ft. 1200 ft. 15 trenches Six borrow areas from 1980 program plus two new areas 12 -30 ft. deep holes 12 -50 ft. deep holes in six borrow areas 30 trenches in two new areas yes 10 -10 ft. 3 -100ft. 1000 ft. 1 -200 ft. deep holes deep holes, 1 -200 ft. slope indicator --- \Jther ACCESS ROAD rgs mH es (20:( of tot.a 1 25 -10 ft ~ deep llo las 15 -50 ft. deep hGles - length) I • I I I I ~ I I I ) I I I I I I I ., I holes and 26 test pits have been made in the construction materia1 areas. A total of 69,600 feet of seismic surveys has also been completed., • These investigations have tentatively shown the Hatana site to be suitable for an earth and rock-fill dam. The dam foundation contains small she.ar 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 a1 i gnment downstream of the dam may represent discontinuity of some kind. Discontinuous permafrost exists locally. Overburden depth in the r'lverbed at the · site appears to be less 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 o availab.ility and suitability of the construction materials, confirm good quality rock in the spillway and powerhouse are~ and define the buried channel and identify its geohydrologic properties. -Devil Canyon Site At the Devil Canyon damsite, 13 boreholes totalling 1,350 feet have bee~ 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 geo1ogic 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 Devil 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 t~rough 20 5-113 ! I I I I I I I . I I I I I I I I I I I I §.ubtask 5.04 -Exploratory P.rogram (1980) (a} Objective (b) Perfor~ initial surface and subsurface investigations at Watana and Devil Canyon sites and reservoir areas and access road routes to establish general and specific geological and foundation conditions. Approach Th~ program \'lill essentially be designed to -obtain more details on the surface and subsurface geology and · foundation conditions at the Watana and Devil Canyon damsit~$ .. -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 geotechnical conditions fn 1jmited 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• Anchorage office personnel with input frcm the Buffalo.design qroup as needed. Seismologic input Will be provided by WCC and logistical support by R&M. All field operations will be performed by R&M with appropriate technical inspection and supervision by Acres and to a lesser extent the wee staff. (c) Damsites The proposed e.xpl oratory investigations \'lill supplement previous work in establishing general and specific surface and subsurface geologic and foundation conditions at the Devil Canyon and Watana damsita areas. The investigations will comprise geologic mapping, diamond drilling, 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 permeabi.l ity of bedrock -location, orientation, width, continuity, fi11ing characteristics and capability of major discontinuities in bedrock such as faults 5-114 ( ( ( I ID I I I I I I I I I I I I I ) I ~ I I -orientation, frequency~ opening, continuity and filling of joints in bedrock -permafrost characteristics including location_, temperature profile and soil type -groundwater regime Emphasis will be placed on locating and studying adverse geological features. Such features will include faults, excessive depths of overburden in riverbeds and buried channels which 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 supplement and verify the previous geological mapping carried out by~ the U.s. Corps of Engineers and the U.S. Geological Survey (Kachadoorian). · The photointerpretation (Subtask 5.02} will be checked in the field_, and adverse geologic features and conditions suggested in the photointerpretation will 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 fi'eld. The geologic mapping will be perfonned primarily by Acres' Anchorage office personnel with assistance from R&M. Geophysical seismic refraction and resistivity studies will be carried out primarily to qetermine bedrock depth in deep overburden areas such as buried relict channels and the riverbed area. This work will be done at both damsites. Seismic work can be misleading in pennafrost regimes and resistivity provides a reasonab1e alternative. Bedrock depth profiles will be prepared from these studies. Airborne radar imagery will be used to delineate the areas of pennafrost. The geophysical work~ inclt~ding the interpretation, will be undertaken by R&M, with .;~view and 1 i ai son by Acres • Anchorage office personnelc (d) Construction Materials " The exploratory investigations for construction materials \'lill comprise geological mapping, portable auger drilling, geophysical seismic and resistivity studies) test trenching and laboratory testing. The geologic mapping~ drilling, trenching and geophysical work will generally be used to establish the limits, depth, stratigraphy, type and properties of the borrow materials. The 1imits, type and proper- ties of potential quarry rock will be similarly determined. The · explorations will also serve to verify the photointerpretation and previous studies by the Corps of Engineers. Ground\'later and permafrost conditions ~1ill be investigated and extensive soil sampling undertaken. Rock outc.rops will be mapped and test trenches excavated by sma 11 track-mounted backhoes to a depth of about 13 feet. 5-115 I I I I I I I I I I I I I I I I I I I Geophysical techniques~ such as seismic refraction and resistivity will be used to prove· the depth of the potential borrow materials and. the groundwater depth. Airborne radar imagery or 1 ow sun angle air photos will be used to assist in identifying the permafrost areas. A moderate amount of 1 aboratory testing of the borrow material wi 11 be conducted at this stage. The testing will comprise routine soil identification tests including unit weight, moisture content, consis- tency, Atterberg 1 imits and gradation. Standard Proctor compaction tests wi 11 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 performed on fmpervious and pervious materials. Potential concrete aggregate samples will be tested for sodi urn sulfate soundness,. acidity and Los Angeles abrasion character- istics. All field exploration work under this subtask will be undertaken by R&M. Laborator·y testing on borrow material will be performed by R&M with some assistance from wee . Design liaison, supervision and review will be provided by Acres' Anchorage office personnel. {e) Reservoir Areas The exploratory investigations to be carried out for the reservoir areas will include geologic mapping, portable auger drilling and geophysical seismic refraction surveys. The primary aim will be to map those geological features and geo.tech- nical conditions in the reservoir area which may seriously affect. the reservoir performance. Such features may include previous buried channels or faults in the reservoir rim which may jeopardize the reservoir watertightness, faults whicn may be activated under reser- voir impounding and natural slopes which may become unstable or erodible vlith reservoir impounding or reservoir drawdown .. The geologic mapping will be on a reconnaissance scale ... The air- photo interpretation (Subtask 5.02) will be checked on the ground ~nd specific adverse features suggested in the photointerpretation ~ll be investigated. The distribution, type and properties of overburden and bedrock materials will be checked against the photointerpreta- tion. Portable auger drills will be used to drill shallow holes to assist in estab1 ishing the subsur-face geology and geologic history. Low sun angle air photos or airborne radar imagery techniques will be uti 1 ized to help delineate general permafrost areas which may cause unstable slopes once the reservoir is impounded. Specific test areas will be identified in which auger borings utilizing a modified CRREL core barrel will be used to sample permafrost. Thenna1 probes \iill be installed in the holes to determine temperature profiles~ 5-116 ( .( ( I -. 1 I I I I I I I I I I I I I II I I •• zq No buried channels have been found to date in the reservoir rim.. If such chann.els are ~uggested in the photointerpretation, geophysical seismic studies wi 11 be initiated to determine the depth ~and nature of·the overburden and channel widths. A relatively minor amount of laboratory testing will also be under- taken in this phaseo 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 review will be provided by Acres • Anchorage office personnel. (f). Schedule Weeks 20 through 40 5-117 a == • --· Yi I IIRfitl ! T • ~" ,, ..... · .. ·. ·-···· ·.· -=-~;_:c., . . i :-' - . . , . ·I I -·1, I I I I I ·I . ; '. ,:; . .;;0~"- 1 0 .I • ,., ,, I ····- . '~--::..··:.;.;::::.::- ::"::• ;, . ~· ~ ' ~ • ,' ·.<. .. :: . . - ·· 2·.·0 MAPS OF THE PROPOSED EXPLORATORY PROGRAM, - 1980 ;' :.-.";.. ,, ' ; I - /71'1 J-~ ,;· '' '· i'/r c ,<cc iJ",;-;.;:,v ff CO/(f!Pr. i!tJti!¢/N'tc-s /9 ,g ' . '--------, .. ~ . \ \ ' ALASKA POWER AUT SUSITNA HYOROELECTRh 'vVATANA DAMSITE I NVESTI I I I ~I I -I I r t :I I I I I I I (} ~· ' lFGEND -~OH 'iJ . DRILL HOt£ S -···-····--SEISMIC LINES ~"""".!"'-.. .:;.:~·:-..:!."'->q LIMITS OF TEST 1 HENCH lNG AREA NOTE: INFORMATION FROM U.S. ARMY CORPS OF ENGINEERS, PLATE 8-2 ' ... ,~---""'' ---~· =· "" ~ 0 .. ....... ' " \ \ / / s---J (-...,. r-.. ) 1 '\ .,.,. r ( ___ ,; ~, "'"L f"'Q_ f !L. 2l~ -0.._ __ __ ' n SUSITNA H • ---~-· -· .. :;.: .. ::...:..... · -~-__ . -.!~~~ElECT RIC PROJECT -......... ~,. .... ,_. ____ ,_._,._ ___ ,.,_ .. - \VAT/J.NA Df~rv1SI fE I NVESTJGA·i-JON I I NOT(S . l. lOf'OuP.4?Hit CQ,lO\P.S t.r{t !:.!.$: D 01'1 A[RlAL PH!IlOGq.Af'Hl" DATtO 10 JUS:: 19'1"8 'li"Hillt:Al :::..TUM lS Mt .tJ-,1 50. lfvtL (M S U {). 8/1-/ 51..-3 r ----I .S£/SfiJJC LIA'c k,:{Y_2oo_/ -~.;;;..o...;;;;~._,.,.....,~- ~zooO ~--2.100~ """ " :><10 ...........___. .. _t_ __ ,_.l ~..&U; .._ 'UT ---·. --·-·,.--,..--~--.. "', .. ,,. <• $0U1 HC!::IiTRAt. RAIL 6€L1 ~qE.f,, Al. .t.S I<: A Sv'P?LfW::.NTAL r E ASlSIUTY STUD'I' UPPER SUSITNA RIVER BASIN WATANA DAM DETAIL PLAN t I. I I I I I I I I I I I I I I I I· I 1- • r • SWJTCHYARD El 1410~> / : __ _ -----«· --·~· ~ -.. _...,. __ --~-"""'""- D~W! .S • '<l'l t looQI.L (;1.""-~0\.. I I I I 1---- I -1-· .. . . I .... -.... ..._ ........ ...... .,, -----'""" --.......... -:-=::::--·-· .. -· -·\0:-~ ~- -· -.. -.. -.... -_:_~ ......... ;:,_ ~ ... ~ -" ............. ~-... .~-.. ,.~ ....... -..... .:-... - ':'-"""'· ---- -,.. ....... .. . -- .,-~ . --·--·-. -~-::. .. -...... ... ~ -=----.::"" .. -:-___ ... .. -.. ; ... ~----·-----"':"""' """":. -:::---· -. . =-...... ---? ~.F .. CQiif'!. .Of t r..Cl'HfH ~------if--·~~· , "'" "" ---~--~----w·•·• -·--·-· -· ---· ~--- 2500 • 90•00 2"100 - 2~00 • 2200 - 2100 2000 l900 1800 1700 1600 1-1500 .~ 1400 "- ~ 1~00 z 1200. 0 ~ 1100 > ~ 1000 UJ 900 800 95•00 " L.-.------------·---- --~~ ~·· ··-.....,... ~"' .. - tiOt-00 liSt PO FOR EMBANlo;MENT SECTIONS 2() .SEPT 1978 ....... -~ ..... ,-.-.. --.·---·- ANDESITE DIKE ~ PO~?HORY-~ ~-Dti· 21 BOTTOM 70' 0/S . SEGTION A-A :...---"-.... - 125.::._00 .. '- 140.!.00 L(GEIO SU'ift.'.:E \..fnE TOP OF ROCJ<; \..IN( FQUr:O:.iiON 8F.:DROCI'i EXC!.Vr.TIOS t ~ ~ SHtAR 2DN£ 0 /S IXWINSTRf:AM tl/S UPSTREAM 0/B OVERBURDEN WE WATERS EDGE DH u: .2500 .2400 .2~00 .noo .21QO -2000 ,!900 .1800 .noo .1600 .1500 ... ----_,400 .r~oo .1200 .1100 .1000 .900 • 800 ORtl.L H01.E JtNf,RT £ l f. VAT ION TOP Of ROCK .f XC4VAl'l01i LINE NOT£: lOP Of ROCK UN!;: 5 !X~.e.v~~~~._ ~ '.! SUoJEC1 TC CH~N:i£ FOR lOCATION Of' CRt'S!;·SEC1J~ S::::: PI.ATE 0-<1 .-----------·--~"'''~'-·-. SOUTHCE:NlfiAL R~:-.~E'Ll A=<E:., ;.~:.SY:t. SUPPL£MEIHA!.. ; ~~SlBlLI1 l' S1i.::n' UPP(R SUSITN.e. RIVER e::.SlN WATANA DA~.:. SECTION AU1NG DAM AXIS ----__..,.,..,.. __ ,; __ ._, __ ------------·-__ .. __ , ___ _ -------··-·----. ... ,_.,. ... .... _,.,_, .. -<'Mi·----.;. ....... ~-.... --,. .. -... ..., .... ~ ' .. '"!~ . ...:::-- II -~!I I I I I I I NOTE; lNFORMA110N FROM US t.RMY CORPS Of ENGINEERS. PLATE B.:r lV ON 2..5 H 0 ON DRILL HOLES ~-··---SEISMiC UNES ...-~~ LIMns OF lEST TRENCHING AREt. DEVIL CANYON DAMSITE INVESTIGATION I . I I , ' . ~ .:::;, I I. I I I I I I I --1 . . I c::.:::..:.!::;;,-,..;::;,.~ ·.:: :.··;.::-':-.::,.·"' I, I I -1! 3.1 FOUNDATIONS & MATERIAL, SECTION D, 1979 CORPS OF ENGINEERS REPORT ' ' ' ,. ' ' I ' I I ' I I. ' ' i ' SECTION D FOUNDATION ANDDMATERIALS TABLE OF CONTENTS Item SUMMAr-'/ OF CHANGES Chanties to the 1976 Interim Feasibility Report Chan~es in Design REGIONAL GEOLOGY Physiography Inferred Geologic History Regional Tectonics Seismicity Rock and Soil Units Rock Structure DEVIL CANYON Seismic Refraction Survey Material Requirements \~ATANA SITE Scope of Investigations Field Reconnaissance 'rest Pits Seismic Refraction Investigations Instrumentation Site Geology Introduction Foundation Conditions Valley \~all Conditions Relict Channel Spillway ~ Permafrost Ground Water Reservoir Geology Dam Design Dam Foundation Treatment Embankment Design Powerhouse_and Underground Structur~s Intake Structure Spfllway Seepage Control, Relict Channel i Page, D-1 D-1 0-1 D-4 D-4 D-4 D-6 D-6 D-7 n-A -- D-10 D-10 D-10 D-12 D-12 0-12 0-12 D-13 D-13 D-17 D-17 D-18 · D-19 D-21 D-22 0-23 D-24 D-25 D-26 D-26 D-27 D-29 D-29 D-30 D.-30 I r I r I TABLE OF CONTENTS (cant) ( Item PagE! ~ I , Construction Materials 0-31 Material Requirements D-31 [ Sources of Materials Q.-31 I General, D-31 Rock Shell 0-31 I Core Materia 1 D-33 Filter Materials 0-34 I Concrete Aggregates D-35 Gradation Envelopes r I LIST OF CHARTS ( Number Title Page I 0-1 Soils Gradation Envelope -Borrow .Area E ( Test Pits 1 through 5 0-37 I D-2 Soils Gradation Envelope -Borrow Area D Test Pits 8 through 19 0-38 [ D-3 Gradation Envelopes -Borrow Area E I Superimposed on Fine Filter D-39 D-4 Gradation Envelopes-Fine :,~ter and ( Impervious Core D-40 D-5 Gradation Envelopes -Coarse Filter and \ . I Borrow Area E D-41 0-6 Gradation Curve -Composite Sample No. 1 0-42 [ 0-7 Gradatio11 Curve -Composite Sample No. 2 0-43 I 0-8 Specific Gravity and Permeability Report D-44 D-9 Compaction Test Report -Method A 0-45 f D-10 Compaction Test Report -Method D D-46 D-11 Triaxial Compression Test Report I -Q Test, I ·Composite Sample No. 1, 3.5% W.C. 0-47 D-12 Triaxial Compression Test Report II -Q Test~ I Composite Sample No. 1~ 7.5% w.c. 0-48 I D-13 Triaxial Compression Test Report III -Q Test, .Composite Sample No. 1, 1lo5% W.C. D-49 ·[ D-14 Triaxial Compression Test Report IV - R Test, I Composite Sample No. 1, 7.5% W.C. D-50 0-15 Triaxial Compression Test Report IV -Back Pressure l. .and Pore Pressure Test Data 0-51 D-16 Triaxial Compression Test Report V - R Test, I Composite Sample No. 1, 3.5% W.C. 0-52 D-17 Triaxial Compression Test Report V -Back Pressure I and Pore Pressure Test Data D-53 I ·ii r· I c, I I 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 feasibil·ity ~f the Watana da~site. ~s 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, pag~s 0 .. 1 through D-9; \~atana Site, pages D-10 through 0-12; and the paragraph on Seismology at Devil Canyon, page D-7, of Appendix 0, 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 e:.<p1oration 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 reinfor':e the basic concepts of that report fo11ows. . . 1 •. Nothing was found during tl)is phase of the study to cast doubt on the feasibility of~ a dam at_th~_t'/atana ciamsite. All exploration and geologic studies reinforced the concept that a large earth and rock:fill or a concrete gravity dam could be built in this general vicinity .. 2. Detailed surveys \~ere 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 shown in the 1976 report'" The detailed survey:showed the va11ey 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 the 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 supp~··t this conclusion, the regional and site geology as well as the rock structure are discussed in much greater detail in this supplemental report. D-1 I I I I I I I I I -I I I \,) I I I I I I I 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 permafrost were jdentified and a number of temperature measuring devices were installed. The earlier assumption that perma- frost does exist over much of this area was confirmed; however, it was detennined.tha~ this is a very "warm 11 permafrost, ranging from 0° c to -1° C. Premafrost was encountered in bedrock in the left abutment of the dam ~nd its effects 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 thi~ report. 5. The 1976 report envisioned-rather large amounts of gravel avail- able for construction 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 impervious core material were discovered near the damsite. Because of the apparent shortage of gravel and an excess Oi impervious material, the dam section ha~ 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 spill\'lay. The remainder will come from excavation of underground f~cilities 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 excavation to bedrock under the core and fil.ters only. H0\'1- ever, because the evidence of the limited drilling performed is incon- clusive, it was considered adviseable to require removal of in situ gravels beneath the entire embarlkment. If additional drilling supports a less conservative approach, the change ~an 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 mate~ial, approximately of the same width as the core, has been added. Th1s was done because large amounts of semipervious material are available and estimates shovt that it can be placed within the dam at a considerably lower cost than the rock she11 material. The total thickness of these impervious and semipervious zones was determined by considering their effect on total stability of the dam and the difficulties of placing materi·als whi-ch require careful moisture control in the arctic environment. Laboratory tests performed on these materials indicate that optimum moisture will be a rather criti- ca 1 facto1n in their compaction. Therefore, the use of such mate~i a 1 s has been held to within reasonable limitsv , ! f c· 1 r· ( [ { r \ f ( .. [ r. [ r l ( r l " ( ~/ l , . l I L I I I I I I 1-, I I I ' ' ' 8. The ~976 report showed ~ vertical access shaft to the low-level· d,,·ain system \-Jhich passed through the embankment of the dam. This has now been changed to a tunnel through the right abutment, thereby e1imin- ating any structures in the dam embankment. 9'. A grout gallery has been added to the lower portions of the dam to facilitate grouting and to accommodate the process of thawing the permafrost. Use of the gallery will allow embankment placement and curtain grouting to proceed simultaneously, resulting in a shortened construction schedule. The gallery will also pi"'ovide fo~ "read-out" stations for instrumentation in the foundation and lower levels of the embankment and for general access. 10. The spillway location as shown in the 1976 report has been shifted southwest to a location, \>ihich 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; ho\-Jever, studies indicate that it is not a problem ~nd~ therefore, no remedial action is required. .. .. -·-. ·--·· .. . 12. The diverison tunnel ·portals have been shifted to ensure their'· location in reasonably sound rock. 13. Pl·ofessional services of Ellis Krinitzsky of the Waterways Experiment Station and Reuben Kachadoorian and Henry J. Moore from the. U.S. Geological Survey were obtained by contr~ct to perform seismic studies and evaluate the earthquake risk at these sites. Their WOl~ was divided into two phases. Kachadoorian and Moore of USGS performed the . field reconnaissance to 1ook for active faults and other geologic hazards. Krinitzsky's work was aimed at assessing the potential earthquakes. which couid 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 darnsites and reservoirs did not uncover evidence of recent or active faulting along any of the kncn1n or inferred faults. In their work they did not uncover evidence of the Susitna F,~.ult, which was. previously thought to exist a short distance west of the Watana damsite. Krinitzsky's work assessed the possible occurra.nce of earthquakes at the damsite and the motions that are likely to be a!;sociated with earthqauke activity. His findings indicate that the desi'gn of the proposed dams to withstand such activity is within the state of the art of seismic design. 14. In the fa11 of 1978, the consulting firm of Shannon & Wilson was engaged to perfonn refra<:;tion seismograph work at both the Watana 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 I I I I I I I I I I I I I I I I I I I 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 forms related to the lithology and geology of the region. From its preglacial channel in the Alaska Range, it passes through a broad, glaciated, intennontane valley characterized by knob and kettle topo- graphy and by braided river channels.. Turning westward along the northern edge of the Copper River 1 owl ands, the river' enters a deep, V:-shaped valley and,traverses the Talkeetna Mountains, emerging into an outwash plain and broad va11ey which it follows to the sea. Three regional topographic lows, still identifiable today, are the Susitna R~ver-Chu1itna River area downstream of the Devil Canyon site, the middle reach of the Susitna River from Prairie C-r.eek to \llatana 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·m since glacia- tion has modified the original drainages. One possible interpretation is that the ancestral Susitna River may have followed the course of the present 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 Watana Creek in the Fog Creek area and leaves the ancestral valley to flow westward into the steep, V-shaped Devil Canyon area.. Glaciation probably blocked its former southwest course forcing the river to find a new outlet in Devil Canyon. Once established in a v1estward course~ the Susitna River downcut its channel rapidly and became ent:-e:nched in Devil C1nyon. INFERRED GEOLOGIC HISTORY The upper Susitna River basin is a complex geologic area with a variety of sedimentary, igneous, and metamorphic rock types. These range.from Pennsylvanian to Pleistocene in age and have undergone at least three major periods of tectonic deformation. D-4 r f ( ~ "( ( l { t { (' \. [ l [ J f f f _( ... I : J I L I I I I I I ,, ·r.:~ I I· I I I I I . .• The oldest outcrops in the area are Pennsylvanian and Permian aged metavolcanic flows and tuffs, 1oca11y containing limestone interbeds that have subsequently been altered to marble •. This transitional shelf environment continued throughout the Triassic and into e~rly 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 massive outpour~ng of lavas··-- in the eastern Alaska Range, resulting in regiona} subsidence. The first major tectonic upheaval in the Susitna area a~curred in mid to late Jurassic time and consisted of large plutonic intrusions accompanied by uplift and intense metamorphism. Erosiona·1 remnants 'of these intrusives include amphibolites, greenschists, diorites~ and acidic granitic types in the upper Hatana reservoir areas. This uplift,. · a1"tq .subsequent erosional period, was fol1o\~ed by marine deposition of argillite and graywacke in late Cretaceous. These rocks are·exposed ·in the northwestern half of the uoper 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 time. 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. ~·, _.,. .. ,u•~ , .. o~--"' •:; .,.,., . 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 f1ows., pyroclastics, and associated· near-surface intrusives occurred concurrent with and following the intrusion of the plutons .. The third major tectonic event was a period of extensive uplift and erosion i'n middle Tertiary to Quaternary. Uplift of 3,000 feet has been measured in the southern Ta 1 keetna ~tounta ins. The widespread erosion that occurred during this period removed thick rock sequences from the Susitna basin area. Glaciation has been the prime erosion agent during the past.severa1 million years. At least two, and probably more~ 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 1ate Pleistocene rejuvenated the ~rosion cycle until the streams, with their increased D-5 I I I I I I I I I I I I I I I I I I I • gradients, became incised Within glaciated valleys. The area currently is undergoing continued stream erosion, anti is covered in many areas With a veneer of glacial and alluvial clay, silt, sand, and gravel de(:)osits. REGIONAL TECTONICS The arcuate structure of southcentral Alaska reflect both the magni- -tude and direction of regional tectonic forces caused by the collision of the Nqrth American and Pacific Plates. The Talkeetna Mountains and adjacent Susitna River basin are believed to have been thrust north- westward onto the North American Plate from their parent continenta1 blocks. It was this ~hrusting action which caus·ed most of the stru~ tural features now seen in the upper Susitna basin • .. ·--'""" ................ _________ -• -.... -------."",_...., ...-.. "'" • .. ~ ........... _,. ~·' lj... 0 .. '~ Two major tectonic features bracket the basin area. The Denali Fault, about 43 miles north of the ~amsites and active during the Holocene, is one o.f the better known Alaskan faults. A second frac- ture~ the Cast)e Mountain Fault, is 75 miles south of the river basin. The Susitna basin is roughly subdivided by the northeast-southwest trending Talkeetna Thrust, which roughly parallels the location of the Susitna Fault, as referred to in the 1976 Interim Feasibility R~port. The Talkeetna River. 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 evidence of movement in the Talkeetna River and Hatana 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 Hatana damsite. The major alpine orogeny which fanned many of the basins' present northeast- southwest trending compressional structures occurred in conjunction with the Talkeetna Thrust in late 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 ~ne proposed Oevii Canyon damsite. These faults have the northeas-c-southwest trend typical of the major structures within the area. No faults with recent movement have been observ~~ within the upper Susitna River basin. SEISMICITY A sei smo logi ca 1 assessment of the basin area \'las prepared by Dr. E.L. Krinitzsky of the U.S. Army Engineer Waterways Experiment Station in the summer of 1978, under contract with the A·laska pistrict, D-6 I _{ ( ( I r { [ { f l ' r 1 t ' [ 1 I I. ' ·, ·I- ' ' ' ' ' ' \ ' ""} I ' ' ' ' ' ' it ' ' .4 . --~· . . ' a .. 4 • • ... • \ • • • ' • -~ •• :· •• • • ~ t \ ~ • • • ~ .4 : ! Corps of Engineers. Field reconnaissance to loot< for active faults and other geological hazards was conducted QY u.s. Geological Survey under the di retti on of Reuben Kachadoori an and Henry J. f4oore. These reports are included as Exhibits 0-3 and 0-2 in th·,s appendix. They t·ecognize that tt.~ Devil Canyon and Watana damsites are in a t"egion of high seis- micity and· major faults. However~ the geologic reconnaissance of the proposed Devil Canyon and Watana damsites and reservoir areas by th~ 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 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 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 the USGS field \vork.. He assumes an earthq~ake 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 majol" active fault could exist near the damsites, Krinitzsky has assigned a 11 f1oating" 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 "floating" ,arthquake 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 fonnation names have not been applied to most of these units and they are instead assigned lithologic defcriptions f.or correlation al'_ld mapping purposes. The distribution of various rock units that underlie the proposed reservoir are shown on P1ate 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 details concerning the rock units are included in the U.S. Geological Survey's Open File Report 78-558-A, Reconnais- sance Geologic Mao and Geqchronolooy, Talkeetna Mountains·Quadrangle, D-7 £, ' . \ • ' • I . I .· \ '•' '.. ~ ' :-. ·.. -\· '., \ ' . . ·) . ~ -.~ ' ; . \• ' . \ \ , .. ' '' ·• '\ I I I I I I I I I I I I I I I I I I Corner of H~ This report is included The upper reaches 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 level.· 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 t;onglomerates, sandstones, and claystones is exposed a 1 ong the 1 0\'/er reaches of t·Jatana Creek directly upstream from its mouth. · The downstream reaches of the reservoir area are under1ain by a sequence of argillites and graywackes.. Exposed vJithin the immedi.ate 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\vash and lake sediments, colluvium including slopewash and talus, alluvium and local slide debris. ROCK STRUCTURE Rocks within the reservoir area have undergone a complex deforma- tion sequence, including uplift, intrusion, thrust faulting~ folding, shearing, and associated metamorphism. The most significant structural feature within the reservoir area is the Talkeetna Thrust which strikes northeastward across the lower reservoir area and is roughly parallel o-a . ' .: ' '' ·\. . .. . ~ ' . . > ;... •. . . f • (( l f r. f r { l. ( ~ 1 [ t ~ l l I r· 5-! { I ' I I I I I I I. --.. ) I I I I I I I to the lower reaches of ~~atana Creek. The Talkeetna Thrust, within the Watana reservoir area, has displaced the volcanic unit over the much younger 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 Talkeetna Thrust near Kosina Creek. Woether this shear zone represents a signifi~ant feature is not known. The most significant rock structure jn the immediate dam area is the intrusive diorite pluton or Tertiary~ageo It is observable for 4 miles parallel to the river and 2 mi1es north and south and is prob- ably of great depth. Upstream and downstream border zones developed with several different metamorphic and igneous rock varieties. Two 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° W to 60° ~~ and dips from 70° to 9u 0 either SW or NE. The two shears can be seen in the right valley wall, but not on the left valley wall. The left 'tlall is obscured by a slide block at the upstream shear, and the left wall at the dO\IJnstream shear has a rock face that parallels the shear direction making observations difficult. The up- stream shear zone has been named 11 The Fins," and has an observable width in excess of 400 feet. It includes seven near vertical rock fins averaging 5 to 25 feet in \'lidth bounded on both sides by altered and crushed rock. The downstream shear zone, named "Finger Buster,.~ is some- what less distinct and is partially covered by slope debris. It has an estimate.d width of 300 feet.. Another northwest trending shear zone$ simi·1ar to the t\vo shears mentioned above, occurs downstr~am from the damsite in the vicinity of Tsusena Creek. Fracture patterns including both joints and local shears have been mapped within accessible areas in the vicinity of the damsite. Details of this mapping are shown on Plates 0-3 and D-4. Fractures include both cooling type jointing and structural deformation jointing resulting from the regional tectonic forces of uplift and thrust faulting. Shear-~ tension, and relief joints resulting from unloading by erosion of over- lying sediments and/or melting of glacial ice are a11 present within ·the damsite area. A joint diagram plotted on an equal area sterr:agraphic projection is shown in Figure 0-6 •. The dominant fracture orientation 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 observed within the area. a , D-9 I I I I I I I I I' I I I I I I I I I I DEVIL CANYON SEISMIC REFRAGTION SURVEY . . During September 1978, seismic refraction surveys \'/ere 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 D-1). The seismic line near the centerline of the left abutment saddle dam was alined to expand information derived from drilling 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, Exh7bit 0-1). A lower velocity zone of rock sandwiched between competent phyllite indicates the possi- bility of a shear zone 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 gravels or glacial materials several hundred feet, thick overlying bedrock. This. confirms the existence of material well in excess of the requirements far the project. -· -. _..._ • ..J • ~ ., • ..t.. ~ •.. ~ ..L.I ,-.r_ & The 1 oca1:1 on map anu se·i sm1 c ve a oc1 ~Y pro·n 1 es rrom ~ne :m~xmon Wilson report and included in Exhibit D-1 to this appendix. MATERIAL REQUIREMENTS Concrete Requirements 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 cubic yards of processed aggregate. ' The USBR 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. 0-10 ( ( r l l {u I f r { f l l I. { [ [ f r ( ·"' -, ' ' \ t ( (' 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 \alas tested by the USBR 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 locatad above river 1eve1 (elevation 910 to 920 feet) with conservative back s1opes through the ridges and benches, approximately 6,000,000 cubic yards of material is available in this location with all the resulting excavation in the reservoir area. St...ismic refraction surveys indicate that usable gravel exists to approximate1yelevation 870 feet, so additional material could be retrieved if needed by bailing from below the water surface. P1acement of the coffer dam, sizing of · the diversion tunrlf=1, and the. ability to control the flow in the river at 'Aa.tana dam \'lill ultimately affect .the method of exploitation of this source. The locations of the test nits are shown on Plate D-1 and the . . detailed logs can be found in the U.S. Bureau of Reclamation's Alaska Geologic·Report #7, Devil Can~on Project, dated March 1960e Labo~atory investigations of the aggregate samples '.'(ere reported in USBR Report #C-932 by their Concrete Laboratory Branch, dated 21 December 1959, Pet~ographic 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 dior·ites, diorites., granites, andesites, dacites:. metavolcanic rocks, ap1ites, breccias, schists, phyllites, argillites, and amphibolites.,. Th~ gravel particles are stream worn and generally rounded in shape.. The sand grains vary from nearly rounded to sharply angular in shape, averaging sub~ngular. 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 Materia 1 Regui rements. The saddle dam on the left abutment, associated with the concrete gravity dam, will require approximately 835,000 cub.ic yards of material. These materials will be obtained from the same sources as discussed in the Interim Feasibility Report .. D-11 I I I I I I I I I I I I I I I I I I I WATANA SITE SCOPE OF INVESTIGATIONS Field Reconnaissance Geologic reconnaissance and mapping of the reservoir area and dam- site wer~ 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 rock outcrops were not obscured by the leaves on the trees and the dense ground foiiagec Through the months of March and April, geologic mapping of the lower canyon was done from the frozen surface of the river, which allowed access to areas otherwise 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, identify, 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 Pits ,. During 1978, explo~ations 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 area \'lere used to define the depth of overbur:1en~ 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 hales were also used to determine the extent of deposits in the barrow areas and to verify the existence of quantities necessary . for embankment construction. Locations of explorations are s<'hown on Plate D-2. togs 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 Materials Labora- tory in Troutdale, Oregon. D-12 ' r (" f . f f { f ( ( { r ( ~ I f I l_ I ( r ( .--' [ I . A total of 27 test pits were dug in four areas as follows: 1. The mouth of Tsusena Creek (Borrow Area 'E'}-6 test pits. 2. The glacial till borrow area (Borrow Area '0') -14 test pits. 3. Upper Tsusena Creek, north of Tsusena Butte, (Borrow Area •c•) - 1 test pit .. 4. Middle Tsusena Creek - 6 test pits. The loc.ations of Test Pits 1 through 5 and 8 through 21 are shown on Plates D-12 and D-11. The ~~mainder of the test pits are located in areas which are not presently considered as borrow 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. ~eismic Refraction Surveys A seismic refraction exploration program consisting of 22~500 1 i nea 1 feet of seismic refraction 1 i nes was campi eted by Dames and ~1oore, Consultants, in 1975. Results of thos.e 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, Consultants, 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 con.finned the existence of a buried channel in the relict channel area and in general supported conclusions relating to shear zones in tne abutments as interpreted from the recent core borings and geologic reconnaissance .. The Shannon and \~ilson survey also confirmed the existence of large 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 water 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 v1ith diesel oil \-!here they extend through permafrost zones to prevent freezing. A total of 10 piezometers were installed at the following locations. D-13 I I- I I I I I I •• I I I I I I I I I TABLE D-1 Surface· Tip Location Elevation Elevation Date Set Size -OR-14 2,340 2,271.0 26 Apr 4" 2,340 2,295 .. 2 19 Aug 1-1/21• DR-20 2,207 2,123.8 30 May 1-1/2" OR-18. 2,172 2,107.0 21 Jun l-1/2" DR-17 2-,167 2,136.3 8 Jun 1-l/2" DR-16 2t099 2,053.8 5 Jun 1-1/2,. AP-1 2,202 2, 188.6 20 Jun 1-1/2" AP-2 2,200 2,189.0 20 Jun 1-1/2" DR-19 2,151 2,109.0 3 Jul 1-l/2n DR-22 2,229 2,005.5 3 Aug 1-1/2" DR-26 2,295 2,229.5 11 Aug 1-1/2 .. · All locations are shown on Plate D-2 and Plate D-11 .. Plotted data is shown on Plates D-16 through D-18. Subsurface Temperature: Th~ principal temperature logging device consisted of a 3/4-inch galvanized pipe, \'lith the 1 ower end capped and tsealed. The pipe was filled with a mixture of ethylene glycol and water (50/50) or arctic grad~ diesel fuel. Readings were taken using a digita1 volt-ohm meter and a single thermister 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 sho\t~n in Table D-20 D-14 I J I I I I I I I q I I I I I I J ;·g I - I It I I I I I I I I) I I I I I I 4. I ·I TABLE D-2 Date Buried Location Installed Leng!P_ Stief< Up Depth Fluid AP-8 23 Jun 64* 4.2' 58.9' Diesel AP-9 23 Jun 21 t 3.2' 17.8 1 Diesel DH ... l2 3 Jul 129' 1.:. 8 f 127.2' Diesel DH-23 17 Jul 76' o.s• 75.5' Antifreeze OH,·24 1 Aug 86' 1. 2' 84 .. 8' Antifreeze Df<-18 21 Jun 251 1 3.4' •247 .6' Diesel DR-19 3 Jul 83' 3.9' 79.1' Diesel DR-22 3 Aug 492' 2.o• 490.0' Antifreeze DH-28 30 Aug 124' 1. o• 123.0' Antifreeze OR-26 (3/4" pipe) 11 Aug 68' DR-26 3.8' 64.2' Antifreeze (1-1/2" pipe) 11 Aug gge 3.4 1 95o6 1 Antifreeze DR-14 19 Aug 65i 2.8' 62.2e Antifreeze DH-21 23 Aug 160' 2.0' 158.0' Antifreeze DH-25 15 Aug so• 4.0' 76.0' Antifreeze All locations are shown on Plate D-2 and Plate D-11. The plotted temperature data can be found on Plates 0-13 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 fi11ed devices described above. Ambient Temperature: The ambient temperature was obtained using a standard high-low Mercury thennometer placed in the shade on the right abutment riverbank approximately 4 feet above the ground-a Prior to this phase of the project, there was no ambient temperature data available for this section of Alaska. Data obtained is shown on Tabie 0-3. D-15 I r I TABLE D-3 f ( •• Date High °F Low °F Date High o.F Low t)F ' ~ 23 Mar 78 22 0 23 May 78 60 39 I 24 Mar 78 24 13 24 May 78 60 32 25 Mar 78 28 19 25 May 78 61 40 r 27 Mar 78 32 10 26 May.78 41 36 I 28 Mar 78 26 13 27 May 78 64 29 Mar 78 40 6 28 May 78 --36 r 30 Mar 78 35 6 29 May 78 58 33 31 Mar 78 36 5 30 ~1ay 78 63 36 I 1 Apr 7B 31 5 31 r~ay 78 66 40 {'_ 2 Apr 78 28 -4 1 Jun 78 54 36 3 Apr 78 28 3 2 Jun 78 58 38 I 4 Apr 78 36 4 3 Jun 78 68 41 5 Apr 78 36 . 20 4 Jun 78 68 38 f 6 Apr 78 33 11 5 Jun 78 57 39 7-8 Apr 78 40 28 6 Jun 78 66 44 I 9 Apr 78 41 10 11 Jun 78 72 44 r-10 Apr 78 43 13 12 Jun 78 62 39 11 Apr 78 38 20 14 Jun 78 57 40 t I 12 Apr 78 · 38 15 16 Jun 78 58 34 13 Apr 78 40 30 19 Jun 78 52 33 r 14 Apr 78 44 32 20 Jun 78 61 33 I 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 "8 -~ '· 18 Apr 78 43 21 28 Jun 78 59 37 I 19 Apr 78 44 20 30 Jun 78 62 43 20 Apr 78 48 24 1 Jul 78 57 41 f · 21 Apr 78 44 25 2 Jul 78 62 43 I 22 Apr 78 45 30 4 Jt.(l 78 70 47 23-24 Apr 78 47 32 7 Jul 78 62 40 { 25-26 Apr 78 50 26 8 Jul 78 73 43 30 Apr 78 59 32 9 Jul 78 70 49 I 1 r~ay 78 60 34 10 Jul 78 66 42 { 9 f1ay 78 64 30 11 Ju1 78 71 10 May 78 72 33 12 Jul 78 so ·--- 11 ~1ay 78 70 33 14 Jul 78 59 50 12 r~ay 78 65 40 16 Jul 78 58 47 [ 13 May 78 72 30 26 Jul 78 66 45 .. 14 May 78 · 72 31 27 Jul 78 78 40 I 15 May 78 66 36 28 Jul 78 74 55 l. 16 May 78 55 32 29 Jul 78 78 39 17 May 78 60 30 30 Jul 78 82 46 I 18 May 78 64 37 31 Jul 78 84 52 19 May 78 60 37 1 Aug 78 80 58 f 20 May 78 75 24 9 Aug 78 71 46 21 May 78 70 43 10 Aug 78 68 54 •• 22 May 78 --36 11 Aug 78 66 49 r D-16 ( I . I I • I' ' ' ' ' ' i t. ' ,. Accurac of Subsurface Tern erature Data: Resistance measurements were o "'a1ne us1ng a e1t ey vo ... am me er, 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 re't iable 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 OoOOd C. General Comments The dri 11 i ng in the permafrost was performed with core dri 11 s, and rotary drills, 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 pennafrost, and it is necessary to rely heavily on the instrumentation for a true evaluation of the location .and depth, at \vhich 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 "mud .. as the circulation m~dium, which tends to thaw the permafrost. Upon inspection of the plotted data'for the locations in this area it 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 11 freeze back.u At location DR-26, 3/4 inch and 1-1/2 inch pipes were installed to determine 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 0-15~' that there is a degree of convection in the upper zones, whi 1 e \vi th 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 question. This is due to damage received during installatton 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.ocation 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 Lp during installation. SITE GEOLOGY Introduction The river valley at the site has a V-shaped 10\'ler or bottom canyon deeply incised into an upper, much broader, U-shaped river valley of considerable extent and width. D-17 I I I I I I I I I I I I I I I I I I I The lower river valley floor ranges from 300 to 600 feet wide and has side slopes of 35 to 60 degt'ees with locally s~attered rock outcrops that rise in near. vertical .. cliffs. The incised portion of the canyon · extends from subr1ver level upward about SOu feet to approximate eleva- tion 2,000 feet, where it ranges in width from 1,500 to 3,000 feet. Above elevation 2,000 faet, there is a distinct flattening of the valley s~opes and ~h~ Q~~~ ~!"9adens out into a very wide fanner river va.lley W1dth of th1s former valley base level is from 8 to 10 miles in the lower reservoir area, narrows to about 1 mile in the midreservoir ar:a · upstream of Jay Creek and widens to more than 20 miles in the upper reaches of the reservoir. · Foundation Conditions The. site was mapped ario 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 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 up 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- diorite, and quartz diorite \'lith 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 wide·ly spaced with depth. Fracture zones found at all depths tend to be tight or recemented with calcite or silica. The northwest trending joints and high angle shears mapped in the 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 surfaces. Shears are D-18 ~ { f (f ( ... l f f I l { r l f t i f [ l f -f _, l l I • ' I I I I I I I I ) I I I I j I " I I ~ ......... spaced_from-a few feet to more than 100 ~eet 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 rehea1ed breccias are relatively competent rock, but a primary breccia zone downstream of the axis on the. 1eft abutment includes locally decomposed materials. · Valley Conditions The river valley bottom was explored vlith 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~ cobb)es, 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 were also noted. r~ost of -the gravels are fresh, but a few are coated \'lith plastic fines. Alluvial materials in some areas were frozen to depths in excess of 50 feet and possibly al1 the way to bedrock at the time of drilling. The bedrock is a diorite that in most holes is very closely fract'.Jt~ed in the upper 10 to 20 feet. Fractures become more wide 1y spaced \'ii th depth; hO\'Iev~r, local zones of closely spaced fractures occur throughcut. Joints are both open and rehealed or cemented with calcite and silica. The rock be1m~ rivar level is mostly fresh and hard to very hard. Shear . zones occur in several of the holes and include some thin clay gouge coatings and slickensides. Soft ch1oritic materials were also encountered in one shear zane, and iron staining with pyrite mineralization is common .. 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 10 feet. This confirms the near vertical nature of most shearing. Geologic mapping in rock ;:xposures along the river- bank also indicates the near vertical nature. of shearing. An andesite porphyry dike was penetrated at depth by DH-21. 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 three 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 eleva.tion 1 ,971 feets . 0-19 I I; I I I I ' I I I I I I I I I I. I I 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 encou.ntered 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 c1ayey silts are stiff and plastic. Rock in the three axis holes is a hard quartz diorite~ whereas in DH-28 do\tn?tream of the embankment, it is an andesite 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 two type rocks is in the location of the underground powerhouse and will be closely explored during design. inves .. tigations. It is assumed the underground pm-Jerhouse will be locat~d in the dioritic rock.· Weathering is primarily staining ot:t 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 emban~ent, appears to have been drilled in an andesite porphyry breccia contact zone adjacent to the d1orite pluton. Much of the core is brecciated, moderately \'leathered to highly altered, and recove~ed 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, \'lith the greater depths in the holes farthest upslope. Overburden consists of gravelly sand with cobbles and small boulders. · Bedrock is moderately hard, but weathered, closely fractured and iocally 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 emplacements 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 slickensides occur on some fracture surfaces. Iron staining occurs on many fracture surfaces and fine dis- seminated pyrite mineralization occurs more wi.de1y. D-20 ( r { l [ 1 r { i I ( 1 ·l 1 I I f {' ( I I ,. I I I I I I I r I I I I I I e. I ' . I .. 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 originally explored with two seismic lines and the results presented in the Feasibility Report, Appendix 1 a$ Exhibit D-1. Subsequent 1978 explorations include 1,814 linear feet of drilling~ borrow explorations near Deadman Creek and 23,600 feet of seismic refraction lines. The-11 dri"llnoles 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 confinn the existence of the deeply buried bedrock surface depression discovered durjng the 1975 seismic investigations., The lo\'lest 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 driiling to date. • Outwash occurs over much of the area, consisting of·gravelly, , silty 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 nan-.PJastic. · 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 surface tills are normally consolidated while the tills from greater depths 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 nonp·lastic or only moderately plastic. Smaller gravel sizes are rounded, while larger sizes are more subrounded to subangular. Naterials are poorly sorted with 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 gravels with soma silts. Sandy alluvial units have a tendency to cave during dri11ing and several appear to have relatively high permeabilities. Most of these river deposits were less than .. so fet;t in thickness but in DR-22, directly above bedrock, the a11uv1al un1t was 159 feet thick. . D-21 I I. I I '·· I I I I lit: I I I I I I I I' •• I A·t least two deposits of lake sediments were encountered during drilling. The larger of these was named "Lake ~toller" and occurs in DR-13, DR-15, DR-26, and DR-27 in varying thicknesses. Maximum thick- ness is 60+ feet in DR•13. Lake 1-loller deposits .appear to be confined between elevations 2,240 and 2,305 feet. Another apparent 1ake deposit was penetrated in DR-18 and DR~20. Maximum thickness of this deposit is 33 feet and appears to be coufined between elevations 2,130 and 2,190 feet.. Both lake deposits may represent eitht!r quiet lake deposition during an interglacial period., or possibly preglacial lakes formed during glacial retreats. The lake deposits consist primarily of highly to moderately plastic clays and silts with local gravel and sand lenses. ~.., .oil ... ---\,.. .• ... · $ 'l. ~.; •. ~ ..... ,.:... "'I· ~ '* .. ~ SpillwaY, The original location of the Saddle Spillway in the Interim Feasi- bility Report, Appendix I, Plate D-3!» was found to lie directly upon . two adverse structures •... The overburden depths increased from 9 feet at DR-17 on the left side of the proposed alinement to 231 feet at OR-18 on the right or east side of the spillway. This depth of overburden prevailed throughout the length of th~ spillway, including the proposed gate structure area. The glacial tills, clay, and intennittent sand lenses of the over- burden would have required additional excavation and flatter sides1opes. Added expense would also have resulted from increased foundation require- ments for the gate structure and from the full length lining which would have been required in the spillway channel. To avoid these disadvantages a change of the channel alinement was made. The new proposed alinement lies approximately sao· 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 alinem~nt will also avoid potential structural problems from the second adverse structure, the shear zone titled 11 The Fins" (Plate o.:4) which will now parallel the spillway for its entire length. Rock qua-lity is such that excavated rock will be used as dam shell rock. As a result of the move, it is anticipated that sound bedrock will be encountered at a maximum depth of 25 feet at the gate structure and will continue dolfm spillway for at least 2,500 feet. As the spill'11ay dips down to Tsusena Creek, deeper glacial till is 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 f ( l ,. 1 l. { r l 1 ( . q i t l " 1 [ l. J r { l ' \ ' ' ' ' ' ' ' I ., I I t ' I t. I I Permafrost The Watana damsite lie~ 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 where arctic vegetation has effectively insulated the ground surface. Depths of permafrost within the discontinuous zone are variable and often change drastically within short distances depending .o~ exposure, ground cover, soil charac~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 abu~~ent which faces north and is either continuously shaded or receives only low angle rays from the sun ~-.as explored with core drilling equipment. Five·holes were drilled and pressure tested by pumping water into the drill holes at selected intervals using a double packer. Observation of drill water returns and pressure tests showed that permafrost exists for the enti-re depth of the holes. Holes drilled in the right ~butment, where the sun 1 s rays are most effective, did not indicate any perma- frost. Within the relict channel areas, on the terrace north of :be right abutment, indications of permafrost were observed as reflected by ground water conditions and water table measurements, drill action~ and sampling. Drill hole DR-27 was sampled and ice lenses were retrieved from a depth of 30 through 36 feet. Permafrost was also 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 l.ayer. 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 11 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 obtai1led since installation due to the fact that heat was introduced into the regime by drilling and equilibrium may not yet be reestablished. However, it appears that the readings do support the conclusion that permafrost is not as widespread or as deep as was previous believed. Of equal significance is the fact that the temperature probes indicate that the temperatures within the permafrost are generally within 1 degree of freezing. Construction in cold regious has shown that, within this ra11ge, ·materials can be excavated with considerably 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 materia1 can be ripped, left exposed to the. sun for a D-23 I I I. I ·~ I I J I I I J: I I 1: I I I I few hours and.then handled in the normal fashion~ The fragile nature of the permafrost regime as indicated by temperature -studies will be of prime importance in the scheduling related to foundation grouting. Pennafrost barely within the frozen range will be much easier to thaw and foundation gr·outing wiil be facilitated. 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 "Instrumentation.,. Ground Water Ground water conditions in the terrace area north of the spillway alinement were ex""mined during exploratory drilling, but the use of. drilling mud used for most of the rotary drilling made direct water tabie measurements difficult. Pervious zones were occasionally encoun- tered where loss of drilling mud was noted: Examples are DR-22 where mud 1osses were experienced of approximately 5C gallon: per foot of hole r.~illed between elevations 2,025 and 2,000 feet and 1oss{:)s of approximately 14 gallons per foot of hole drilled betwe.en elevation 1 ,9Li0 and 1,855 feet. In a very few instances water tab 1 es co~1 d be measu·,.ed at the time of drilling. A notable example of artesian head was ·neasured while drilling OR-13 and DR-14. In both of these holes the £~round water was under sufficient head to rise from elevation 2,240 and ~,270 feet, respectively, to elevation 2,300 + feet when the overlying clay layer was penetrated by the drill. - A discussion of the overburden units encounter~d in the terrace area can be found under the heading "Relict Channel A~ea.11 It wi11 be noted in that discussion that at least twQ deposits of lake sediments were encountered \-Jhi ch appear to be rather e.xtensi ve. As migh-t be expected, perched water was encountered above the hi-gher deposit, lake Wollers in some holes because of the impermeability of·the material. In the alluvial zones bet\'leen 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~ approximate elevation 2,190 feet, the glacial tills were very compact and can be expected to be relatively imper.vi.ous. The over consolidation of these materials· as previously stated js 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 ~his channel is necessary depends on the pervious nature of the materials 0-24 I t ( f { 1 r { f !. ( .t t l l [ [, [ {· ( / J \ I . • I I I I I I I I I I I I I i '') ~ I I '· encountered. While a more detailed program of exploring~ sampling~ and testing will be undertaken to ensure that pervious layers will not present 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 be1ief can be found under the heading "Seepage Control, Relict Channel." Reservoir Geology The Watana reservoir -includes seven general zones of geology~ as indicated by Plate D-5 (Watana Reservoir Surficial Geology). Glacial . fill, out\.Jash, and preglacial iake 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 a11uvia1 units with metamorphics such as the Vee Canyon schist. The predominat- ing dioritic gneiss and amphibolite is laced with bands of mica schist, pyroxenite. and augen gneiss that are inferred to correspond \'lith contact and shear zones trending northeast. The area around Jay and Kosina Creeks and do~,amstream to \~atana Creek inGl udes two 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 mi.xed 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 Talkeetna Thrust as identified by the U.S. Geological Survey. Downstream o-f Watana Creek lie the remaining two units, starting with moderately metamorphosed sediments (phyllite, argi11ite, graywacke) with t\-Io 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, Jranites !» and migmatites of !:c'le 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 mos·t of t..~e lo\~er canyon elevations are covered \vith only shallow overburden deposits~ sloughing will be minor and have minimal effects upon the reservoir. Deep overburden deposits, mostly of glacial origin, occur above. approxi- mate elevation 2,000 feet where the slopes f1atten out into a broad river valley ba!'a' 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,n is located upstream of the axis on the south bank opposite "The Fins" shear-. Several old and potential landslides are identified by Kachadoorian - and Moore in their reconnais.sance of the project area. . . D-25. I I •• I' I I I I. I I I. I ·I I • • I In general tenns, the geo1ogy in the immediate damsite is controlled by the'diorite intrusive believed to oe the top of a stock which uplifted the surrounding sediments and volcanics and was later eroded by glaciers. Subsequent glacial and stream deposition has masked much of the flat upland areas and stream valleys. DAM DESIGN Dam Foundation·rreatment Main Dam: Foundation conditions are more than adequate for con- struction of an earth-rockfill dam. The underlying rock is a diorite or.granodiorite which, in nonfractured fresh samples, had unconfined compressive strengths·that ranged from 18,470 to 29,530 psi. Only the uppermost 20 to 40 ·feet of this rock is closely fractured and suffj- 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 length and width of. the impervious core. Foundation treatment v1ithin the rock excava- tion area will include removal of a11 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 inplace 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 proper placement of embankment materials. Exploratory drilling in 1978 has shown the mat~rials in the river channel to be a well graded mixture of grave 1 s and cobb 1 es as good, or bette1", than the materia 1 s that would be used to replace them. As the exploration program ·continues, these gravels will be more completely explored and it may be demonstrated 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 the. 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 ga 11 ery wi-11 be provided from the PO\verhouse on the 1 eft abutment and, by adit, from the downstream toe of the right abutment. Grouting will be on a single line of holes utilizing split spacing~ stage grout- ing techniques. Grout holes will be slanted upstream and may be included D-26 ( r f· 1 t: I f i . l ( t 1 I [ l f I . •• • I I I I I I I .~ . ;' . ·I I I I I I I L I I to intercept the dominant high a~gle northwest tending fracture system. Preliminary grout hole depths are estimated at two-thirds the height of the embankment to a maximum depth of 300 feat 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, inclination, grout mixtures, and grouting·methods will be dependent on the results of future explorations, permeability studies, test grouting, and perma- . frost thawing investigations. Rock permea·bility test t'"esults are shown on the drill l.qgs presented on Plates D-28 through 0-37. Coefficients of permeability (K) were computed in feet per minute times lo-4. Permeability coefficients ranged from 0.0 to 23.1 and ave~age 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 a.t the greater depths in the axis area.. Right abutment dri11 holes had perme- ability coefficients that ranged from 0.0 to 23 .. 09 and average~d 5 ... 47. DH-10 was the only hole tested that had relatively 10\'1 permeability coefficients throughout. Dr-i11 water returns had simi1ar patterns with variable percentage losses. DH-7 and DH-9· had 0 percent ~eturns through- out. and DH-8 and DH-11 maintained high percentages of dri11 \"Jater returns throughout. · The existence of perma..frost in the 1 eft abutment and the possib i- 1 i ty of minor amounts in the right abutment necessitates assessment of the problem of thawing a zone in the foundation bedrock suffici-ently wide and deep to allow proper installation of the grout curtain. In anticipation of this need, the U.S. Anny Cold Regions Reseal'";ch and Engineering Laboratory was asked to do a des~ study on tha\ving ~tb;e per- manently frozen bedrock. The Technical Note which \•/as-submitted 1\:n 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 addi·tion to their suitability as engineering materials. As a result of these cc.m- sider-ations3 the embankment contains a central section consisting of~ an impervious core buttressed on the downstream s:ide by a semipervious zone. D-27 . I I I I I I I I I I I I I I I I I . I I .. _: .·-----~ ·>.. . -.'_;-.. ·-.. . . ~ .-.. ·:. ·_ ... ---: __ : .· . ~ Thi:s centra 1 section is supported, both upstre!am 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 will be obtained by selectin~ the coarser grained materials while the finer materials will be placed in the impervious zone. These materials, as discussed under "Embankment Mdterials," have been shown by exploration and test to be a well graded mixture, \vhich, when compacted, has a very good shear streng·~..tl and a r1i gh degree of impermeability. 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 tile gravelly sand deposit at the mouth of Tsusena Creek. · Chart D-3 shows an envelope of gradations 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 migration of fines into the filter material. Proven sources of gravel which can yield large quantities of material are scarce within short hau1 distances of the project. For this reason~ the decision was made to use mJterial from the rockfi11 source as a coarse filter. Chart D-5 is an envelope of the required gradation which \"#ill 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.. fl1s indicated, the rockfi11 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 she=tls was made when reconnaissance and eJ<ploration 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 rockfi11 dam, and, if rockfill is used, these slopes will be re- fined in accordance with sound engineering pratctice. Refraction seism1c D-28 r 1 r f 1 1 i I I. I ·L •• I I I I I I I ~~ ., I t I I I I I t. I I lines in the borrow areas show velocities which·could represent large deposits of gravels or glacial materials but rather extensive explora- tions \'li 11 be required to verify 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 pr.eference 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 Canycn 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 undergrbund facilites, but the location and design of the various structures may have to be adjusted in some areas. "The Fins 11 and 11 Fingerbuster 11 Shear Zones shown on Plate D-3 and discussed in paragraph 11 Rock Stt .. ucture" 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 common i·n the site area and were 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 and construction of the underground structures. '\} Prior to pm'lerhouse excavation, exploratory adits located near the crown of the various chambers will be driven to confirm final design criteria. The chambers wi 11 be constructed \'/i th straight \'Ia 11 s 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. Use of stee1 channeling and remedial concrete is anticipated in local areas where fallout may occur or in fracture zones having a substantial \'lidth of crushed rock. ~lire mesh will be uti1 ized where necessary as a temporary facility prior to placing concrete. A thin layer of wire reinforced shotcrete may be placed on the main powerhouse chamber walls and crO'tln as a protective measure-against rock raveling. Additional shotcrete will be utilized~ a$ required, to sea1 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 I •• I I I ·.~ I I I • I I I I I I be designed so that there is a minimum of t\'lo tunne1 diameters of sound rock above the heading where they go underground4 Initial tunnel sup port wi 11 be by pattern bo 1 ts, with stee 1 channeling and wire mesh . where necessary in closely fractured areas. Major shear zones will require steel supports. Hydraulic and geologic considerations will necessi~ate final concrete linings for all but the access tunnels, and steel l1ners for the_penstock~. Grout rings will be required in the penstock portal areas. The ~~o diversion tunnels are to be separated by a minimum of four tunnel d1ameters to provide greater structural stability. Downstream diversion tunnel portals will have to be located to avoid the 11 Finger Buster" shear zone to insure adequate portal construction conditions. Spi 11way 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 CreeJ< 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 \•lhich, when separatsd from the boulders can be used in the impervious or semiper- vious zones. Seepage Control -Relict Channel The relict channel area 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 till, some of which has been reworked by alluvial action. For this reason, consid- eration was given to the possibility of seepage through t~e area where rock. contour·s are below the proposed reservoir elevation. However, preliminary seepage calculations indicate that even in the relict channel area. where the head differential approaches 350 feet, and using a very conservative 'k' 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 1 ayer a~lsumed to be 80 feet thick. Assuming such a 1 ayer 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 veloGities 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 "D," ground water was encountered in alluv·ial layers between elevation 2,240 D-30 J f ( l I ( 4 l I .f!!l. ~ I I I I I I I ~} .._;:, -·-.. . I I i ' ' f I I, ' I .. \. and 2,280 feet with an artesian head which exceeded the proposed reser- voir level by 100 feet. In spite of this high head condition, no evidence was found indicating seepage out of this layer into either Deadman Creek o'f· Ts us en a Creek. Indeed, it is probab 1 e that the effect of this artesian water, which evidently has its access to the alluvial l~yer in the upper reaches o! T~usena or De~dman Creek, would be to resist flow from the reservo1r 1nto the aqu1fer. Because mud losses in DR-22, located at the center of the relict channel, indicated the possibility of penneable layers at approxitiiate elevations 1,900 and · 2,000 feet, a falling head permeability test was performed at this hole .. 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 to 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 riprapv Sources of Materials General: Several sources of embankment materials were investigated in the damsite area. These sources included two 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 \'lill be generated by required excavation for the dam foundation, underground facilities, and the spillway channel~ All rock excavation from the spillway channel will be incorporated into the rock shell zone of the dam. The overburden encountered in th~ 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 fnnii two quarry locations shown on Plates D-10 and D-11 • D-31 I I I. I I. I I I I I I I I 1: I I I I fl Quarry sites were 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 left abutment is an outcrop of igneous rock ranging in elevation from approximately 2,300 to 2,630 feet. The total volume of the hill above the surrciunding 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 development would 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 material in the hill is a diorite on the western 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 an~ 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 down,hi11. If properly developed, virtually all.of the material removed from the qua~ry 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 •s•) could be developed by excavating rock from the open faces visible on Deadman Creek and continuing the development of a face to the westward, maintaining the face between elevation 1,700 and 2,000 feet. Stripping 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 rockfill shell 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 'A 1 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 haul distance is greater and the D-32 I ~ ( t f. I r f i ', I ( J 1 { I 1 I i net environmental impact of the Quarry 'A' on the left abutment i.s sma11, this area is a less desirable source of embankment materials. Core Material: Imperviou~ 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 'D' 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 traGk- 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 If/ere 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 surface 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, permeabt1ity·, 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 area 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 was not possible. The coefficient of permeability (K2o) for the minus l-inch fra.ction 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 \'lith an adequate shear strength at the optimum water content, acceptable con- solidation values even when loaded to 32 tons/sq ft and a n·arrow 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 low optimum moisture content of 7.5 percent. The results of the triaxial compression tests indicate -chat in the unsaturated and undrained condition the glacial tills will be s·ensitive D-33 -. . . . ~ . . ~ . " .. __ ,." ... I • I I, ... I I I I I I I I I I I I I I I to moisture·oontents higher than optimum but that if placed on the dry side of optimum they wi11.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 for both the impervious and semi pervious zones. The speci fi cations \'li 11 need to provide for close. controls of the moisture content and the quality ... assurance programs will have to be adequately staffed to provide for c~reful che:k~ of moisture content in the pervious and semipervious f1ll. Oeta1led laboratory reports of the tests conducted are included as Charts D-6 through 0-29. The materials from Borrow Area 0 can be used with 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 only the silty, sandy gravel above the clays \'/ill result in the floor of Borrow Area •·o• 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. Approximate1~ 630 acres will be restored. Filter Material: The nearest source of clean sands and gravels for use 1n the f1ne filter of the embankment dam is an alluvial 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 comp9sed 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 materiais 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 8 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 removal of material larger than 12 inches :to prQ._dute fine filter material. An envelope. of gt·adation curves derived from tests of samples from TP-1 through TP-5 is shown in Chart D-1 •. All of the samples are from the first 8 feet of material. All .of this material lies. above D-34 ( { t r 1 \ 1_ 1 1 i " I I I I I t I I I I I I I I I " . : the water table and can be t.aken by front loaders.. The quantity of material available in the first 8 feet is approximately 3.7 million cubic yards. After the boulders are encountered at a depth of 8 feet, the oversize material will have to be removed and material below the \'later table will have to be bailed frorn 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 repres~nts an excellent source of essential filter materials. The second area in which clean san9s 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- abJe 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 i.ndicate that adequate materials may not be obtained from the sources closer to the damsite. Explorati·on at Site 1 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 v1ith 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 first 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 gr·avels 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 represents the most economical source of concrete aggregate and the nearest 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 0-35 I I I I I I I I I I I I I I I • - I I I granitic rock with the remainder composed of basait, andesite, and. ryholite.. Chert is present·;n such small quantities as to be nondele- terious. The quarry site on the left abutment (Quarry Source 1 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 producing the concrete aggregate incidental to the production of embankment material. The conc~ete aggregates would be produced from the diorites in the quarry to 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 invol~ed (10 miles), it is .not anticipated that this source. would be explo1ted 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 adjc.cent 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 cou1d be produced from Borrow Area E with a resulting haul distance of 2.3 miles. D D-36 ( ( 1 l l ( l r f ' 1 l i { I f f l ( /f ' I. -·1 -I I I I. ~ .. ~ I ~ .,_ 1 f I I I I I I I I I I I I ( -· ( li!.Z.Z~.ooo l ... ~. ·-. ~-. . \~ .- 3 228,000 ..._,~~ ... -- ' ... 3..227,000 .-- ........ __ ~.... . ... ' ... . . .................. j• • .. 0 0 0 N ,., ,.... w ..... 1 ( ..... *'*('""~ . I ... 'i " . -. f f '· ..._. :-' . ... - . .. ' .. .. - . . ... -. - 0 g 114'!1rl: ..: ... ~· ... w 0101'\ITtr &(;Hilt llUUHVU Rli<OI.Il!. UltHl tl~tn; 1·1-~SlVCS Gliii~O ltlFll; UI~USI'fU ·~orsnr. uuL1 ......G;t X ~ .:f( ctoux;.u: tCI<I£CL (Is •af[O"!!I-,. stntrtOJ<t vUh SUI'~Iit tllliStl!Ut ~(l;llit£ 11lUIIl(Q W IJlnt;J.'It; .l Sl!iU 1011£ 14\1/HIIIo WTI11 Ill!' 'l't'n'lCAl JUlaf· >Mnt llr.r- :wt:at"t.c..at. 0 SAIIQ, S&~DS100i( ~ SILT, $llUIOXt h / j: n.u. ;<tl)l Ill' l'tlHUI. UlfOUD ~~ 'l>11tw liiP. ~Tnt n:. S1'!s:T. ~ ~ ~ [;] .ItT a IIQ BLDl Ill. a. DtOa FRAC •ons, IDU\:Dt~S !~0~ J'!Pt $110"'!1 I~ECCU (UStD 11/ROCil rttEI . lOIRE VI &TIDIIS &liE RED avert I lOTH[ BOULDER BI!QWII a.n 0101111£ HActu•to 0 D»U' iPilU. IIOU G <gff.J Ct ~UITf. II 111i:Hlr lttt ~n .. 11£11 s $UfO u -SlOOIE wz ~11!£1(0. I. OIOWlll liAS INtRUDED UD Ul'llfl.W ~TS .UQ U:>tS•US. l•OtSITfS U( IUEUID TO It I. Uf•rt~7llloft. lllTUt:l•.toa HD>f U~Lin!D UO &lTPtED If tllt•nt ~I.Cllllllt. 2. CliCill C~At lWO AlUJYIIJ:I &fP(&I'll!l tuJt ~EEXISllli'IO tCOSIDUl CHIW~ElS Ul UPPtil Clwt'Oll ·~S.. SOUTHCENTRAL RAlL.BELl' .:1,.\'rE.A • ALASKA SUPPLEMENTAL FEASISIUn" STUDY UPPER SUSITNA RIVER BASIN WATANA DAMSIT:E SURFICIAL GEOLOGY WEST SHEET AL.t.SU O!STRICT, c:l<IPS «: a,.-:;lll!t.Ells &lirlfi;.~'CE .,._ .A\..A:Siit:&. PLATE .fb1 -- • i ~I ·I -I I ·I I. ~ I i I I I I I I I I I ( c SOUTHCENTRAL R~LBELT AREA. ALASKA SJPPLE!.E:NTAL FEASIBILITY STUDY UPPER SUSITNA RIVER BASIN WATANA DAMS tTE SURACIAL GEOLOGY EAST SHEET •L lSI( A DIS"f iiiCl, (X)<{PS Of (H<"~E!tS Ao,(.oQ'1£Gt., .... ~ I I I I I I ~ 2500-90"t00 95<;00 I 2400- 2~00 - 2200- I 2100- 2000 1900 - I t800 1700 • 1600 I. 1-1500 - :ilJ400 "- :2;. 1300 . z 1200 ll 0 ~ 1100 . > ~ 1000 - \&J 900 - I BOO . I I I I (_ II . ! I 100 ... 00 105 +00 I GRID BASE STATJONJNG N 3,224,898.674 E 744,915.063 IOO+oo 110'1-00 115"!"00 120;t00 FOR EMBANKMENT SE.CTIONS 20 SEPT 1978 SECTION A-A l.E GENP SURFACE LINE TOP OF' ROCK LINE i'O\JNDATION BEDROCK EXCAVATION UNE rs.;;;a SHEAR ZONE DIS OOWNSTREAM U/S 0/B W.E. OH I.E --2500 •. 2400 .2300 .2200 .2100 .2000 .1900 .1800 .rroo .1600 .1500 '"i ·--~ ---.1400 -1300 .1200 .1100 .1000 .900 .800 UPS! REAM OVERBURDEN WATERS EDGE DRILL HOLE INVERT EI..EVATION TOP Of ROCK EXCAVA!ION l.INE NOTE' TOP Of' ROCK LINE 8 EXCAVATION LINE SUBJECT TO CHANGE. FOR LOCATION OF CROSS· Sf:CTiON S....~ PLATE D-4 SOUTHCENTRAL RAILBELT ARii:A, At.ASI<A SUPPLEMENTAL FEA.SIBILlTY STUDY UPPER SUSITNA RIVER BASIN WATANA DAM SECTION ALONG DAM AXIS PLATE 0-7 - I I I I· I I •t I~; I I I I I I . I I I 11 I I ... 0 0 ~ H '3 '200 OOQ TALKEETNA THRUST .PE.R RtFERENCE 2 l /: ) 0 ~ ... \ . . _:~ lOD1£$ ~--;;,1 "'"TltUi t!QI!I~• utr M~ft!lfll~ i:lmss-tnnotoe• ••t< '-'~'-"' "' e.l:S(c o. t ••n1l0 o~ t-CnD"-r\.ltr t•t. U)flt fl.t"r;-;x;:.uuts ·a_·u ~.,.li'~F-44': .. 2 • lt'tlU o• "••Plt ""ns morofl•U •11n ~nuu•;:£ -z •. o.:~~' .u «<tt ~ "'~.• · ~~:.:~t~ fA"'<;n;l'M~o\~~'g~m,;r~t~·m.c.m•m~:s,~:,..~;Mi?': :,1 llll mt tllUIUUt II I~ !<01 ll<Jtl IClliO fl< '"'' Ul.Ut. I<~C'f ~:: Ql •HU Ul $11~•·· IS\nll), ~IIlli Sl~l•'tS ~w: '''~' ltJI'.jl(;U!t"l-. U&1\llt$ 14HI ~(U. DLUTtfl. ~. ,200 llltll CO•HHIR HI~ UIW Atti~HIJ J.S '"li~l ... U.i't llllll 01 ilt~:U!tt: ~ lflltl. !> •. WO Pti!'!1Ub$l I)~ t•Tli\'IIUtHI 1·~on AtTIO" U:!&~ U1 S~()«. 6 • SLIOI~. ·~~ .U I•Dtt:'l.HP D! Sliftl..lCl 11PliE$S.tf>'!l:. l'no!ll nt: l'¢<tth- ll1Dt Hti.S JW~ <R(H SUSC[Pllll( 10 'lASS 'lCtt•l£.¥1 '~t£1 ll~U'tf':>ll IWl\ltliOC[ l!i1( M~l Btl~ SIIOII~. 1 '"~' •nus ~·o..,. u CllCUt 11\t mnuo ku$ . .,,..,:!:" Wtti'IC?e. nn ~ • 1!01 DtlttUO n 11.11PI,C. O(ll.ll t~ lll•PI~~ 1!\ lH~•rt;[~ lO: 'Qt~tilt CO•l•C:l$, lO'IfS or I)ISliiR'l~Cl, A~D llll•ttl.,.tll!!) •!It!$. ttl :3.200,000 I ' tU._AI!J -v;o·-v- -vv~zV .31111 12l --""--1 ---l- lDl"Q(if{~~Htt ST~ wll[ft • lUt, Sl~l&"' to'!: •It'll i'QO* CtllilOU!t llil_fJIYJ.l$ t.__ f(t't .·l'J:'(( "'-E.-t-: !i[ ~ tEYlt lft£1. II &rPJ«JJio«U lOUliC" ~f t.&:al t'J; SJ!tU. c•~J«J• oo"" DIP or s:n .. :t t:;.~l:; BUi$ • stbltti•Tlll1 Ill! tl.~ Slt.~tlti~i:: >rna DIP Ill: V[UICll t21 BEDS ~ HPROII!Ill[ Dll· S!Mtl I ME, S~OVIM( U,lS !ill. .... !'~ttU.1[ tt:e:l1l!ll. llilllCl Utt • .SH.Oii1 .. C. t~ts;" :,&fi•-.JOXUtU~ :!.:;c.r (II. flOw JOL tlnOJC, SCifA!1"t:.l.:.~ .. ·tll:tlK(, til: .. Y(.l ICAl 121 JOI~T!.; IWCUNEO ill. •u:"~Ool ~l.tS U:! llliiOLOCIC Snt!OtS Cl1Cill liLt ~'1$1; 1110:1,.--=tw;; Ul·PU·'lt\ s::>li$"' ·~l!t!l SDIISl U: .::.0."1.::t ~:l;10~1t:IC n:~ UkCO~SOll 011(0 tll$11 C: ltlUVIlL DEJ'OSIU U~CO•SOllOlTEO fiN[ •tU>VUL O[POSll$ • Cl1T. Sl!.!. •·:.~~~ft CI:-'':"S COUOll Oll[D UP OED SIDI!IE~l1~ D[PDSilS • All tlUHC lTP£$ lllt£510~[ H 0 IURDlt .Ul lTH$ r .. uuctous ~DC~ I Mrt ~IIi& tt£1&HOt,.,. ~.-. rmnr.s 1flRDUGij Pill. ".11( Rlf1R£~C£5 I~'.'J ... .\ '""il *''t;(l~l :n. n.e;s. c:t, ·~!~~s .. txttn~~ ~~ :t:":Jt:S1¥tS . .tilt~ ~::-~•a "'t'U...WRtK I eli ~u•rc HINS iLJQ ·suts, ••:!:sl\-::: ... b $-I'Sll.TS ltlllt to,t!= ~l.:.1S$.1J. t•~ E:! ~ :tU.»$t, D~~~t:. "'· lt ll.¢ '1\!U-S:lU'~ ~~tlkt~ ~ttH1C$ .... ~·-~c; ~~~~~nt-s. ·c:::.:JJ;-\'!!:. ~s Of VUlt lt"::>-;;lll!l &;,1UHD• ~ 41oc'J'"'_J..t10~·ts.~ t.: 'tc:J::t; ~'!ll)lll&HOII. """"IiollllliC&. ~illtt1tl".ltilt:.'lf .c. ~t1S Dr CoO~ 'IQ•:etn.u;:;, I. US t;tOLO::IC1l ·sunU 1:113,36!) SE~IES llDfC!:~::,., ~ll,~[['fU ~--:• l)tUDqliJCl[, SH(£lS Cl, C2, 03, Du. 2. .,.[CO•••ISSUCt OIOLOGIC IW' A•D GEDCII,OIIO!.a;;-<. li¥l.Ut1U I'(!:;J~~Uf&l' t1u•oRhGL£. !iO«t~tA~ r.IRT or nc•on•or l)<l,.;~n.::::.t: .. •oro so:;t"""'~ to•HER Of llllll ()JlDU•Olt, ausu.• !WU HH 3ilf'.::n 'll·~ I!'RtliHI•ART), US ClOlOCICAl. $URvt'f, titlll.O ru ... Q:..lfGQ-I.l t!)21; CSCJTU .• [1 .U • SOUTHCENTRAL RAILBELi ,t.gEA • Al.A~l<A SJPPLEMENTAL FEASIBll..iiY STUDY UPPER SUSITNA RiVER BASIN WA'TANA RESERVOIR SURFICIAL GEOLOGY ~;.:.S.CA IXSlftiCT, CO'IPS CT E¥..1AiCEIU • "(;'QO loG{ • .l.t..r.sq PlATE D-S j I I I I I I I I I I I I I i 11 I - ( I I I I I ' i I I I I I I I I I ... I I .,- . ....._ / 'SWITCHVARO EL. 1410.!: • .... IV ON 2.5H \ I \ • \ t ~---• AGGREGATE SOURCE: •• _ . "'---CONCRETE -- ,_, .. ---.. •..__pt' .. """ ---. ,~ .. I l RA!LBELT AREA • SOUTHCENTRAL FEASIBIUTY STU!n' SlJ?PLEMENTAL if' SlN UPPER SUSITNA RIVER B ... DEVIL CANYON a EXPLORATIONS SITE PLAN a Elt':i•-.t£~n "'STRICT_, CCl<'!PS. A~ASI(A "" ASI<A •V.."'''.r.G{. ·~ -~ f'"...ATE D-1 I I I I r. I ·, I I I I I I I I • I I I I I I I ! 200' r-----·------· SPILLWAY _SECTION t". .••• r ..::t[ ·r C'olliUtC s~lt· r .. toe"•o• MONOLITH i ORIGINAL GROUND SURFACE.} ASSUMED EXCAVATION LINE 26' OIA. DIVERSIO~A. -·~ TUNNEL 'L.J ,--......,...,,. .~I.Ji~L <;~J:§L~6J.11Z s •• -AXIS OF DAM METAL TRASK RACK INTAKE STRUCTURE . 'TOP OF DAM <i_ EL 1075 LOW LEVEL SLUICES --FOR-EMERGENCY DRAWDOWN M_AX. POOL EL~ UPSTREAM ELEVATION DEVELOPED ALONG C[ OF DAM EL 975 I ~WALL/ TOPO EL. 87 .fl-.~ • .L / / SCALE: I" ~ 100' d . EL li33.5 L26 1 DIA. / '"""""-". I /v'\ \ \ \ ' /PLUG .J... ' \ \ \. \ \. -, SECTION ' .. ' I 1400 1000 800 400 200 DIVERSON TUNNEL PROFILE SCALE: t":ol00 1 ...... ....... ..-::: \ .. .,.,.,. " DIA. PENSTOCK ~~~~-.MA~ T W Et.. 924 ;;.,...,=='<,.....-~-SlOP lOG SLOT SECTION THRU PENSTOCK AND P.QWER PLA~L SCALE: !";roo• TYPICAL NON-OVERFLOW . SECTION 10' d Sf/ crt \ac:)w ... ' J EL 1085 ', ------ EL.. 843 • 0 ' '"""HIC: ·sc.a.L£ , •• scf .. o• EL ~ .. I ~I' FINE FILTER , 1 'I• , · · 2 COARSE FILTER . 3 RIP RAP FILL~ ----rORIGINAL GROUND LINE ------ DE~Jl.~. CANYON AUXILIA-RY EARTH FILL DAM lid f1 .t;,' DO' .. •::' • I .l'tAf'...; 3CALI:.• f • #UJ•·a• SOUTt!C:ENTRAL RAILBELT AR£.4<,. ALASKA SUPPLEMENTAL FEA.SIBILI:'t'lf :STUDY UPPER SUS ITN A RIVER BASIN DEVIL CANYON ~'M CONCRETE GRAVLTY DAM ELEVATION AND SECaaDNS ./lLASKA OtSTRICT, CORPS OF OiGEI:RS ,.!<C><OI\IGt. Al.;.I5I<.A FEBRUARY 1979 PlAtE 6 '1'\ ·:· :_-., ... I . I . .. I ==!::::-::;-:::;::.::::-..:::::-:--: I I ·- ~ < • •• ~. << ,, I· -· . . .•.. _· ':···-__ ' ' - .I- I I I ·J -~. . ' 3. 2 EXCERPT FR0~1: - ''RECONNAISSANCE OF THE RECENT GEOLOGY OF THE PROPOSED . DEVILS CANYON AND WATANA DAr1 SITES# SUSITNA RIVER, AU\Sl<A 11 Bv: REUBEN l<ACHAOOORIAN AND HENRY J. MooRE -::;.·.· I I I I I I - r . (I ' ' I 1 ' ' f "'~ ·-~ • .....: .. • ..... -.. ... PRELIMINARY REPORT OF THE RECENT GEOLOGY OF THE PROPOSED DEVILS CA~~ON AND WATANA DAMSITES, SUSITNA RIVER, ALASKA. by • Reuben Kachadoorian and Henry J. MOore ABSTRACT At the request of the Corps of Rngineers, the u.s. Geological Survey conducted a reconnaissance of the recent geology of the proposed Devils Canyon and Watana damsite areas, Susitna River, Alaska. -The purposes of the reconnaissance were to look for active faults and other geologic hazards. Field work by the Geological Survey was conducted . . between July 25, 1978 and August 7, 1978 using a helicopter whi.ch vas shared jointly and in cooperation Y!th personnel of the Corps of Engineers. . the geologic reconnaissance of the proposed Devils Canyon and I Watana damsite and reservoir areas did not uncover any evidence for recent or active faulting along any of the known or inferred faults,. Recent movement of surficial deposits'has occur-red as the result of mass wasting proeesses and, possibly, by seismic shaking and minor displacemen~s of bedrock along joints. Landsliding· has occurred in the past and future landsliding appears probable. The occurrence of unconsolidated glacial debris~ alluvium, and Tertiary sediments at elevations below the proposed reservoir water • ""1-,..... • " -....... levels may slump and slide into the reservoirs when they are inundated. ' . ·~ .;..:-"" ,. ·Some of these sediments may be permanently frozen and, locally, may be 1 I I I I I I I I I I I I I I I I I I I ice-rich which increases the probability of slumping and sliding wen the sediments are thawed by the water impounded behind the dams. The tectonic framework of the Devils Canyon and Watana damsite areas is not well understood· The present knowledge of the area • indicates that the sei.smicity of the region -ranges in depth from less ,• than lC km to greater than 175 km- Additional detailed geologic and seismic st.udies are necessary in order to reliably evaluate the potential geologic hazards in the region of the proposed dam and reservoir sites. .2 t ( c l l. • ( [. [ l { ( i.. { [ ~ [ [ [. I { .el I i i RECOMMENDATIONS I 'lbe c:onc:J.usions presented in this report are based on a i reconnaissance study o.f the proposed Devils Canyon and Watana dam and I) reservoir sites, and, therefore, should be considered to be preliminary • . ~ * A thorough evaluation of the geotechnical problems of the proposed dam and reservoir sites will require mere data. It 'Will be necessary to * i (1) map the Healy, Alaska, Quadrangle, at a scale of 1:250,000, from the Talkteena Mountains Quadrangle to the Denali Fault, about 80 km (48 miles) north of the damsites, (2) map the proposed Devils Canyon and - Watana damsites at an appropriate scale to determL'e the bedrock structure and distribution of unconsolidated sediments overlying the -~- bedrock, ( 3) map the reservoir sites at a scale of h 6.3, 360 in ord-er to (a) establish the type and distribution of unconsolidated sediments and I i bedrock, (b) locate additional potential landslide areas:t and {c) determine the nature and distribution of permafrost, (4) tn~t~ate a seismic monitoring program of the dam and reservoir areas, (5) continue -the active fault study, (6) redetermine t.he altitudes of the Vert~cal Angle Benchmarks, and (7) collect detailed data on the suspended :loads I and bed loads of the Susitna River in order to determine if the reservoir filling rates are acceptable. I ~ I I ' ·I 39 I ,,,. I I •••• I I ..•. ,,: /~· I n . ., -· I I I .... . . • • • < ·t I ... ~ ' -._·_ '-.~·.'~~···-.-~--~.:.....: .. ~---.-: 3. 3 EXCERPT FR0~1 : __ .;.:.:.: 1'EARTHQUAKE ASSESS- MENT AT THE SUSITNA PROJECT I ALASKA'' BY: . E. La: KRINITZSKY .. ~ I I .I I I I I I I I I I I . I I I I I I PART VI: CONCLUSIONS 58. The geological-seismological investigations to date were made on reconnaissance levelso The Devils Canyon and lol'atana dams.ites are in a region of high seismicity and major faults. However, no move- ments wer!?! found on the faults that might be indicative of earthquakes .. Also, no seismic activity was identified -as associated with these faults, though the data suffers from inexactness in the accuracy of locations. No active faults were found at the damsites. Active faults of appreciable length 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 damsites. The magnitude 7 is in conformity with general fault lengths in this area and with worldwide 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 wi.th possible more severe motions. An earthquake of magnitude 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 Denali.fault attenuated to the sites pJ:ovides motions of 0.28 g, 40 em/ sec, 22 em, and 10 sec. 61. A closer snecification of which sets of peak motions to apply .. and the appropriate time histories will await further field studies .. 18 ( .. ( I s r •• i i i i -I -I I 62. Possible induced seis~city from reservoir loading is not a factor .needing additional design but is accounted for in the existing moi,lons. However, water wav:es from possible earthquake-triggered land- slldeu and possible overstressed conditions in rock pose problems !"or which at present there is a paucity of data and a need for further evaluation • 19 I I '·' ··I·'· . . ,-_~ .:_;· LIST OF-, REFERENCES (AVl\ltABLE AT THE BUFFALO 0FFlCE:) -----·-------------- SUSITNA MATERIALS COLLECTION l}.~_f_i:J·t~ . o \-i;l., Alaska Dept. of Commerce ALASKA POWER & ECONOMIC DEVELOPMENT PROGRAM 2 Vol~ Alaska Power Adm. Alaska Power Authority A.rct:to Env.Uonmental Information & Data Center Bacon, Glenn . . JOBS AND POWE~-FOR ALASKANS: A PROGRAM FOR POWER & ECONOMIC ~~L- OPMENT INVENTORY TYPE CALCULATIONS FOR SOMF. POTENTIAL HYDROELECTRIC: !PRO- JECTS IN ALASKA ANCHORAGE-FAIRBANKS TRANSMISSION: ECONOMIC FEASIBILITY STUDr ~EPORT. DRAFT .. FUTURE POWER REQUIREMENTS-REPORT OF THE TECHNICAL ADVISORr~OMMIT TEE ON ECONOMIC ANALYSIS & LO~~_PROJECTIONS FUTURE ALASKA POWER SUPPLIES ~ REPORT OF THE TECHNICAL ADVISQ~Y COMMITTEE ON RESOURCES & ELECTRIC POWER GENERATION RE~ORT OF THE TECHNICAL ADVISORY COMMITTEE ON ENVIRONMENTAL CONSIDER AT£0N & CONSUMER AFFAIRS SUS~TNA HYDROELECTRIC PR08ECT; A DETAILED PLAN OF STUDY SUSJ:TNA HYDR9ELECTRIC PROJECT: PLAN OF STODY FOR PROJECT FEASlBIL- ~T~ ~ND FERC LICENSE AP~LICATION CLIMATOLOGICAL DATA ARCHEOLOGY·IN THE UPPEa SUSITNA _RIVSR BA$IN . ---------------.----- Behlke, Dr. Charles E. . . SUSITNA MATERIALS continued AN INVESTIGATION OF SMALL TIDAL POWER PLANT .POSSIBILITIES ON C®OK INLET, ALB.SKA Bishops, Daniel M. A HYDROLOGIC RECONNAISSANCE OF THE SUSITNA RIVER-BELOW DEVIL*S CANYON Burrows, Robert L. SEDIMENT TRANSPORT IN THE TANANA RIVER IN THE VICimi'l'Y OF FAIRBANKS 1 ALASKA Carlson, Robert F. EVALUATION OF THE NATIONAL WEATHER SERVICE RIVER FORECEASE SYSTEM MODEL FOR USE IN NORTHERN REGIONS~. Federal Power Comm:i:ssion ALASKA PO'r."ER SURVEY Gray, T.J. Hartman, Charles w. Henry, J. Kaiser Co. Inst. o1= Water Resources Univ. of Alaska Johnson, Roy W, Jones~ & Jones THE 1976 ALASKA POWER SURVEY, VOL. I & II - TIDAL POWER (COOK INLET} ENVIRONMENTAL ATLAS OF ALAS~~ REASSESSMENT RE~ORT ON UPPER SUSITNA RIVER HYDROELECTRIC DEVELOP- MENT FOR THE STATE OF ALASKA . STUDY OF THE BREAKUP CHARACTERISTICS OF THE CHENA RIVER.BASIN USING ERTS IMAGERY HARNESSING COOK INLETts TIDAL ~CTIVITY .. u·PPER SUS!TNA Rl!VER, ALASKA: AN INVENTORY & EVALUATION OF ENVI;RON- MENTALtt AESTHETICS & RECREATIONA!t RESOURCES + .: ~ - - - - ----- - -~·--- - - - - - Lamke, R.D. Naske, Claus M. Project Software & Development Inc. .Salomon Brothers Scu11y, David R. Shira, Donald·L. u.s. ARmy Corps of Engineers SUSITNA MATERIALS COntinued FLOOD CHARACTERISTICS OF ALASKAN STREAMS THE POLITICS OF HYDROELECTRIC POWER IN ALASKA: RAMPART & DEv:tla CANYON, A CASE STUDY PROJECT/2: SA1'~I.F.: RUN ACTIVITY-ON-ARROW NORTH CAROLINA MUNICIPAL POWER AGENCY, No. 3. PROPOSAL SURFACE WATER RECORDS OF COOK IN:f.,ET BASIN, ALASKA, THROUGH SE:~'!r. 1975 HYDROELECTRIC POWER PLANT SITING IN GLACIAL AREAS OF ALASKA i) COOK INLET & TRI:BUTARIES, HARBORS & 'RIVERS IN ALASKA~~ SURVEl! REPORT COPPER RIVER & GULF COAST. HARBORS & RIVERS IN ALASKA SURVE)!' REl?0R'r DRAFT & F'EVISED DRAFT ENVIRON:tv1ENTAL IMPACT STATEMENT. . (HYDROlS'LEC- TR~C ~OWER DEVELOPMENT ~ SUSlTNA RIVER BASIN, SOUTHCENTRAL RAIL BELT AREA F~AL ENVIRONMENTAL !MPACT STATEMENT (as above) . . HARBORS & ~ETERS IN ALASKA. . SURY"~Y M'J?ORT, YUKON & KUSKOKV'1IN RIVER BAS:ENS . R.YDROELECTRIC POWER & RELATED PURPOSES -INTERIM FEASIBILITY REPORT SOUTH CENTRAL RAILBET:r ?.~El-\1 ALASKA U~PER SUSIT~A RIVER BASIN . ------------------SUSITNA MATERIALS cont. • .a..Lued u.s. Army Corps of Engineers INTERIM REPORT NO. 2 1 COOK INLET & . TRIBUTARIES 1 PART NO. 1 - HYDROELECTRIC POWER, BRADLEY LAKE 1 ALASKA NATIONAL HYDROELECTRIC POWER RESOURCES STUDY -PRELIMINARY INV~--. . TORY OF HYDRO POWER RESOURCES, PACIFIC NORTHWEST 1978 SEISMIC REFRACTION SURVEY.. SUSITNA HYDROELECTRIC. PROJEC~11 WATANA DAMSITE 1 DEVIL t S CANYON DAMSITE REPBRT ON RA!JS..PART CANYON DAM & LAKE YUKON RIVER BASIN REVIEW OF REPORTS: COOK INLET fi TRIBUTARIES 1 COPPER RIVER & GU~lf A COAST 1 'TANANA RIVER BASINS 1 YUKON & KUSKOKWIN BASINS 1 SOUTHClmN!rRAL• RAILBELT Am!A. PUBLIC HEARING-~ FAIRBANKS, ALASKA 1974 REVIEW OF REPORTS ••• as above ANCHORAGE & FAIRBM~~S PUBLIC ME~~NG 1975 REVIEW OF SOUTHCENTRAL ALASKA. HYDRO POWER POTENTIAL, ANCHORA.GE SOUTHCENTRAL-RAILB'E~T1 AREA, ALASKA. {HYDROELECTRIC POWER STUOY- PUBL<EC HEARIN~, ANCHORAGE ALASKA,) 197 4 . . SOUTHCENTRAL RAILBE!DT AREA, ALASKA UPPER SUSITNA RIVER BASIN. INTERIM FEASIBII.!ITY REPORT • Appendix 1 & 2. . . 'sOUTHCENTRAL RAILBELT AREA, ALSKA UPPER SUSITNA RIVER BASIN. MAIN :REPORT GJ SUBSURFACE GEO?HYS<CCAL EXPLORA~ION, PROPOSED WATANA DAMSITE ON THE SUSITNA RIVER ------ - - - - - - - - - - --: -SUSITNA MATERIALS Cu.ilcinued u.s. Army Corps of Engineers UeS. Bureau of Rec ... amation u.s. Dept. of commerce u.s. Dept. of Energy U.S~ Dept. of the Interior TANANA RIVER BASIN, HARBORS & RIVERS IN ALASKA SURVEY REPORT- TRANSCRIPT OF COORDINATION CONFgRENCE FOR SOUT~CENTRAL RAILBE~ AREA, ALASKA INVESTIGATION DEVIL CANYON PROJECT, ALASKA FEASIBILITY REPORT ENGINEERING GEOLOGY REPORT, FFt'1-S.;' .. BILITY STAGE, DEVIL CANYON D~l " ' REPORT ON THE POTENTIAL DEVELOPMENT OF WATER RESOURCES IN THE; SUSITNA RIVER BASIN OF ALASKA. DISTRICT MANAGER 1 S RECONNAISSANCE REPORT VEE CANYON PROJECT_, SUSITNA RIVER ALASKA: ENGINEERING GEOLOGY OF VEE CANYON DKMSITE . ALASKA ECONOMY: YEAR END l?ERFORMANCE REPORT 1978 CLIMATE OF ALASKA: CLIMATOGRAPHY OF THE U.S. ANALYSIS OF I~:U?ACT ON HYDROELECTRIC POTENTIAL OF 'l'HE ADMINISTru\TION' RECOMMENDATIONS FOR THE ALASKA D-2 LANDS HYDROELECTRIC ALTERNATIVES FOR THE ALASKA RAILBE!lT UPJ?ER SUSITNA RIVER PROlJ'ECT: POWER MARKET ANALYSES ~\LASKA NATURAL RESOURCES & THE R.AMJ?ART PROJEC'l' VOL. I & II •• ---~--------------- u.s;·Dept. of the Interior U.S • Fi·sh & Wi:'ldl:tfe Service u~s. Geologi:cal Uurvey SUSITNA MATERIALS continued - ALASKA -RECO~lNAISSANCE REPORT ON THE POTENTIAL DEVELOPMENT OF' WATER, RESOURCES IN THE TERRITORY OF ALASKA ANALYSIS OF IMPACT H.R. 39 ON THE HYDROELECTRIC POTENTIAL OF ALASKA DEVIL CANYON PROJECT 1 ALASKA REPORT OF THE COMMISSION OF RECLAMATION DEVIL CANYON PRO~ECT -ALASKA STATUS REPORT FUTURE POWER REQUIREMENTS :·REPORT OF TBE TECHNICAL ADVISORY CO~ TEE ON ECONOMIC ANALYSIS & LOAP PROJECTIONS SUSITNA RIVER BASIN: A REPORT ON THE POTENTIAL DEVELOPMENT OF WATER RESOURCES IN SUSITNA RIVER BASIN SUBSTANrriATING REl?ORT ON THE FISH & WILDLIFE RESOURCES OF THE YUKON · AND KUSKOK\iiN RIVER BASINS WATER RESOURCES DATA FOR ALASKA WATER YEAR 1977 wa:::,e:R. RESOURCES (SURFACE ! SUBSURFACE) OF THE COOK INLET BAS'CN • ROUGH FINA1~ DRAFT