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HomeMy WebLinkAboutSusitna-Watana Hydroelectric Project Dam Configuration Review Copy AEA11-022 March 14, 2014Zz SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. Technical Memorandum 14-05-TM v1.0 Susitna-Watana Hydroelectric Project Dam Configuration REVIEW COPY AEA11-022 i 0 beafeathact ze Prepared for: Alaska Energy Authority MWH 813 West Northern Lights Blvd.1835 South Bragaw St.,Suite 350 Anchorage,AK 99503 Anchorage,AK 99508 THIS DOCUMENT IS CONSIDERED CEll CRITICAL ENERGY INFRASTRUCTURE INFORMATION DO NOT RELEASE March 14,2014 a>ALASKA 13-1405-TM-031414e& @HRE)ENERGY AUTHORITY THIS PAGE INTENTIONALLY LEFT BLANK The following individuals have been directly responsible for the preparation,review and approval of this Report. Prepared by:Brian Sadden,Project Manager Aled Hughes,Senior Principal Dam Engineer Julie Stanaszek,Senior Civil Engineer Farrokh Javarmadi,FE Specialist Reviewed by:Glenn Tarbox,Practice Lead Approved by: Julie Stanaszek,Senior Civil Engineer Approved by: Brian Sadden,Project Manager Disclaimer This document was preparedfor the exclusive use ofAEA and MWH as part of the engineering studies for the Susitna-Watana Hydroelectric Project,FERC Project No.14241,and contains information from MWH which may be confidential or proprietary.Any unauthorized use of the information contained herein is strictly prohibited and MWH shall not be liable for any use outside the intended and approved purpose. THIS PAGE INTENTIONALLY LEFT BLANK 2 ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 Clean,reliable energy for the next 100 years. 13-1405-TM-031414 CEIl TABLE OF CONTENTS 1.INTRODUCTION ........ccccsssceeeeeesenecsnenseeeeesnsnescnneeeeseseessesenoeeeeesesecaneseaneeseeesssseeneneseseess 1 2.LIMITATIONS2...cee cceccscesesececeeseessssnneneeeeeensnassucnoesesenenaneneaceesosseesesssnaeesseesenensensnonensens 6 3.GEOLOGY AND FOUNDATION uu...eeesesesnseeeeeeeeneeesseceeereeeeessenenaeesesssesensensnaneseese 7 4.SEISMIC LOAD DEVELOPMENT .......ccccssssceesseeeessessennesnasecoesenssenessnasenosesesseeesereesees 8 4.1 Development of Preliminary Seismic Design Criteria ..........ccecsssscssceeecceseesesscesceneees 9 A.V.1 Spectrum Analysis...ccessssesscscssceseccsscesesssscseseeseceeeeesseassscceeeseseetsssseeseeseees 9 4.1.2 Development of Time Histories ..........ccccsssscesessesscssessseseescsecescsnessesssenesneerseneees 9 4.2 -Selection of Time Histories...cesssssessscessecseseeesccensscecessesessseceseesesecaeseeseseesseassesens 14 A211 Interface...sseeseseesecsecsccsetsecsesseeseseseeccessscaesacseesecsseseceecsacessensesetscesseasenes 14 4.2.2 Slabs cscsscssscesssssssesscsesssssesssscsssssssssesssesesssesssssceseeseasecesseersesasenseseseeesseeetes 14 4.2.3 Crustal ...cccccsscsscssscsscsessssssssscssssssscssssessessesssseasecccsenssceeseessceseneseseesceeseesseees 16 5.CONFIGURATION DEVELOPMENT .....ssssssesssssssssssscsecsesssessssssessscssseesesssessseeseeseeese 17 INITIAL DAM CONFIGURATION (LAYOUT 2).......cscsssssensssssenesereessneseneneseesenenssenes 18 6.1 Configuration Description ...........se eeseseesceeseececeeeceeceecescesseecencesseoessceseescescescesseseteeeeees 18 6.2 Arch Dam Stress Analysis System (ADSAS)ou...eee eesseeeeseeeeeseeseesecseeesseesesseeseoes 19 6.3 FE Structural Analysis...es eseescesceseeecesccscescesesecessesessssssesssscsssesessccsscsscsseesseseeseasees 20 6.4 -LOAdS eee eeeescseccesssenceeceecesceesessseesessseessesseorssssesssssesossssesseenssssssseseeseessaeuseseeeseeseensaeses 22 6.4.1 Gravity...eccsssseceecsseceeceseccesscrsessssescsrssseesessesssssssnssssvesesssseeenssseceeseeasensssaseneses 22 6.4.2 Reservoir Hydrostatic...ccccsscsesscsscsscseesssssssessseessseenesssessessessesreeesseeseeeeeees 22 6.4.3 Uplift nce eesssscsssssssesssssssssssssssssserscesscsssssssssssecsssssesssessssetsessseenenenesesesenenees 22 6.4.4 Ground Motion...eee sseseessseaeseseseaesscecsesesecsesecsuesesesuesssesnssenenseneneesenees 23 6.4.5 Hydrodynamic...cscsssscccscsscssssesssssssesssssscssssessensseesesseseeseeesseneenenseneeeesees 24 6.5 -Static Analysis for Normal Loading Cases .........cccssesesessenseceseeesenceresceneneeseseeasnesnes 24 6.6 Dynamic AnalySis .......ccccsesesesescsesssesessesescsesesesesessensessececssesenescneneneneeacecarasesassesenensogss 24 6.6.1 Modal AnalySis........csscsccccccscsssscsscscsssssscscsssssssssesessseeesseseseeeeseseesesssenreasensesses 24 6.6.2 Response Spectra AnalySis......ccssscssseceeseesseseseesssssssessessnstsessesessceeesssseees 26 6.7 ----REC Volume ..n.....eeesccscetescesscsseseeseesccscessssesccsscsceascssseseseessenseseeneeseessesssrssseseseesnsenseees 28 7.REVISED DAM CONFIGURATION (LAYOUT 3).........cccccssssssesensssessnsseseseensensnnnenees 30 REVIEW COPY Page i 03/14/14 a a ALASKA ENERGY AUTHORITY -AEA11-022eeeminem1ot4asT4 7.1 Configuration Description...csscsssssscssssescsssssssssecsssscessssssessesssscssessesseesseesesesseenentes 30 7.2 Two-Dimensional Gravity Analysis...cesesssesssssssssssssscsesesssssesscseseeseessesessenseaes 30 7.3.Arch Dam Stress Analysis System (ADSAS)oo...cece ccescessesseesseeeeeesssereseesenneeeeeeeees 31 7A FE Structural Analysis.........cs csssssscsssssssssscsscsscssevsnssessssssessccssesasscsessesssesessesseesseneenees 32 TAL Model....c.cccccscsccscctescssssscsseesseseceesscesesesseesessssssssesssesseossseeseesssseseeseasenseseseeesees 32 7.4.2 Static Analysis...eeecscessecessesesscsssesecssssesscscsessccsseecssssssscsssessesesssessensssesentes 34 74.3 Modal Analysis...cssssscsssscscscsssscsscessssssssssssessssnsesssesssesssersseneeseneenenees 37 74.4 Transient Analysis...eesssssssscscssesscsessessccssessssscssssesesessersteeeseeseeseeasensensenees 37 TS RCC Volume ou...cceccecescsccsceeeseesceceeesescessssessssescosseessncsecessasssssseasssssseesessessesssseeesessesets 44 8.28°REVISED DAM CONFIGURATION (LAYOUT 4).......:cssscecssssssseessereeesteresenestes 45 8.1 Configuration Description...cseesscsssssecscsesesssnsssssssscsssssscessesscsestessesesarseeeeneets 45 8.2 Two-Dimensional Gravity Analysis...eeccscesseeecseesscseesesessssessssscescssscecsesenseese 45 8.3 ADSAS ceccsssssssssssnsssnsssnssssesisetusstesssessssnsssnntssassansansssonssnesanssasteansesseeeste 46 8.4 FE Structural Analysis...eteseesscsecscesesssscessssecseesscsessscsessesssssecssssscseseaseeseesensenees 48 8.4.1 Modal Analysis...essscssscscsscnssseecssseseessesssscsssssssssssssosavsesssasssaessssssonssoesnes 49 8.4.2 Transient Analysis Results 0.0.0...scscscsscseecssesssesscssssssssssssssseessssssssessosseseass 52 B.S RCC Volume oo eee eeceeeceseeeeesessescessesssssessssseseeseesacseesensaeseesseseusssssesesssesasseesseers 58 8.6 Sensitivity to Foundation Conditions...ee scesescesecsccsseseeeseseerscrseseceeeseesaeaeaeees 60 9.DISCUSSION ON STABILITY AND STRUCTURAL PERFORMANCE OF DAM ..62 9.1 General .0...eee eeeeeeeeeeeeeesscesseeseesceeceesseceessseseosceeceosseeseesssesesssseseessesecenscaceaceaeeessenrenes 62 9.2 SUMIMALY ........ceeceessessceoneccesesensnaccceeeseceesseonsseceesesoessonseseeesesessssnaaseeessseseeseseaseceeseesssenees 62 9.3.Refining the Finite Element Model and Analysis Approach ............csccsscssesseeseeeeeeees 63 9.4 Modeling of Fluid Structure Interaction scsssssssssssseessssssssesseessssessssssssssessesutssnsssesees 63 9.5 Modeling of Foundation Mass and Damping............cccssessesssssesssceccensencencenseneereeneeases 65 9.6 Element Size and Non-Linearity .........cs essscesessessesessesssseessseesesesessesesasseensesenseneeeens 65 9.7 Inclusion of Thermal Modeling Results ..........ccssssscescesessescescessseestscesesssecssssssessesseses 66 10.TYPICAL EXAMPLES OF PERFORMANCE OF EXISTING DAMS,WORLDWIDE67 LO.1 Introduction wo.ec ceeeesssceecsetcesssesensessscssesessssssssssessesesssesessssesseeeeesesesessceecarsssseess 67 10.2 Sayano-Shushenskaya Dam oo...eessessssssssesenseeacseseessseseeseseseecensecesessssestsesseseeeseeees 67 10.3 Portugués Dam ou...esecessscesseessscscensessreesessssesessessesessesseseseeseesesessssesseesssscseseesesssseees 68 REVIEW COPY Page ii 03/14/14 -Z-ALASKA ENERGY AUTHORITY AEA11-022aeniiaceeyytrmetenro-dosTMO314%4 10.4 Shapat Damo...eeeecsesssscscesseescesceaseesenseecsscesceacenscsceseeseessscesssescecseecessenesssessescesneeeees 70 10.5 Pacoima Dam oes eeessesseeceeeeeeteeceeeeeeeaceceeceessacsaceseteceecessssceseaseeseeseeseecessenseresseeaeees 73 10.6 Shasta Damm...sesesescescesseeeceeeeeesesacaceaeeaseessaceseesceecesseseseseseaseeeseeensessesessaeaneenees 74 10.7 Normalized Comparison...cesesesesscssescceesecceesessssscceaeeeseeeeeeceeeeeeeersessassseesaeeeeeeses 75 11.CONCLUSIONS AND RECOMMENDATIONG ..........c:::cccescessssssecorensesenseerseneeneesenes 77 12.NEXT STEPS .........cccesseeeeeeeeessenenenceeeeseeeeensensnenessessaenesnueeseesensnscanenssseseseussssenssosenesess 79 REVIEW COPY Page iii 03/14/14 a .ALASKA ENERGY AUTHORITY .AEA11-022SUSITNA-WATANA HYDRO tang 022 Clean,reliable energy for the next 100 years.CE List of Tables Table 1.Selected Magnitude,Distance and Epsilon wo...cssscssssesseseeseseessssesessssessesesessesnenessesasees 10 Table 2.Ground Motions for a Hypothetical nearby Crustal Event with Intraslab Design Event Shown for Comparison .........ssesssssesssesssssssssssssccssessssessesesseecsenessesessesesnesesesssseseeeessseneessseenerecesecenensees 11 Table 3.Rupture Lengths for Various Magnitudes ........cccesesesesesesessssensesesenssseseneseseesesesenseeneseenees 11 Table 4.Record Parameters for Interface Seed Time Histories M9.2-84"Percentile...14 Table 5.Record Parameters for Slab Seed Time Histories -M8.0 -69"Percentile .......escseesseeeeee 15 Table 6.Record Parameters for Slab Seed Time Histories -M7.5 -84"Percentile...15 Table 7.Record Parameters for Crustal Seed Time Histories -M7.0-84™Percentile.....cssessseeees 16 Table 8.Analyzed Dam Configurations ..........ccscssessssessensssessesesreeseenenensessesensensensssnseeesesecsesastereres 18 Table 9.Periods of Vibration and Modal Participation Mass Ratio (MPMR)of Dam...........c0 25 Table 10.Comparison of Seismic Analysis Results-Maximum Tensile Stresses..........cccceseesesereees 27 Table 11.Comparison of Seismic Analysis Results -Maximum Compressive Stresses..........00 27 Table 12.Susitna-Watana High Dam:ADSAS Estimated Dam Volumes (cubic yards).............0.4 29 Table 13.Susitna-Watana Preferred Dam:ADSAS Estimated Dam Volumes (cubic yards)..........29 Table 14.Frequency and Periods of Vibration....ccssssssssesseecsscsscecsscsssesesssssscnssensseessaseeseeeesesens 37 Table 15.Summary of Dam Layout 3 Response to 8 Earthquake Loading ...........cssssessseeseseseeee 43 Table 16.RCC Quantities (Layout 3)owe eessesseseescesessesesccssceeseeeeeseeeesnseseenseasessseasestseesosneseees 44 Table 17.Frequencies and Modal Mass Participation Ratio...cee cscsessesscsecsscsscsscsececseesesesseess 50 Table 18.Summary of Dam Response to 8 Earthquake Loadings (Layout 4)....eescseesecseeseseeees 56 Table 19.Comparison of the Results of Dam Layout 3 and Dam Layout 4.000...eee eeesereceeeeeneeee 58 Table 20.RCC Volume (Layout 4)0...sssssssesesesesssesssssssseseseessssssesesesesesensnsssesesesesesesessnessessenseaeses 59 List of Figures Figure 1.RCC Volume,Dam Layouts 2 and 3 sesssvusesecssssssssssssusssscessssssssuessssecesesssssnunuesssseccessuannaneeesses 4 Figure 2.Hazard Curves from Preliminary Seismic Hazard Assessment...........scsccscssssssessssesseeeseeeees 9 Figure 3.Uniform hazard Curve and Deterministic Spectra for Interface Event..........ccccscsssesssseees 12 Figure 4.Uniform Hazard Curve and Deterministic Spectra for Intraslab Event..........:cccceseseseseeee 13 Figure 5.Uniform Hazard Curve and Deterministic Spectra for Crustal Event .........c.cccsssessssseeees 13 Figure 6.Layout 2 (Dam J)-Crown Cantilever Stresses REVIEW COPY Page iv 03/14/14 -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEll Figure 7.Finite Element Model Upstream Side (Layout 2)....ccesescessescececssesseseccetcssceesesaseeeensens 21 Figure 8.Finite Element Model Downstream Side (Layout 2)........ccscsssssssccceeesssceeessseessssesessssseeees 22 Figure 9.Response Spectra for Susitna-Watana Dam Site Area ........ccccssssssesssseeseesesessenssnsesensens 23 Figure 10.First Six Vibration Modes Shape of the Damm...ccsssssesseseseetscesesssseeesceessessceeeseeseeeees 26 Figure 11.Layout 3 Cantilever Stresses at the Crown Cantilever...sessssssseeseeeeceseseeeccesseeseseees 31 Figure 12.Layout 3 Horizontal Stresses at the Crown Cantilever...essssesessesescesceeesessseneneeeesnees 32 Figure 13.Finite Element Model ofthe Dam (Layout 3)..........sssscssssscsssescessssseseesceseessenseseeseseeseneass 34 Figure 14.Cantilever Stress -Upstream Face (Layout 3)..........ssccsscssssssssessescessesseesceceeseeseeneeesenrsneees 35 Figure 15.Cantilever Stress -Downstream Face (Layout 3)........csssssccessssecessssecesssseceseseeceseeeeseecees 35 Figure 16.Arch Stress -Upstream Face (Layout 3)....esssssssssssssessecsssescsscscsssecesceesesssesresssorsasenes 36 Figure 17.Arch Stress -Downstream Face (Layout 3)........cssscssssccsscessscsscssesscssessesseeseesesceeneeneenenes 36 Figure 18.Envelope of Maximum Tensile Cantilever Stress due to IWT010 Earthquake -U/S View (Layout 3)...eeeeeseseeesseseescsesssssscseessssscescessesssessesesecsescsesssscsneesesesnsseesssssssssesesasesssenesssssaeeasscseeeseneeaes 39 Figure 19.Envelope of Maximum Tensile Cantilever Stress due to IWT010 Earthquake -(in psi, D/S View)(Layout 3).....ccssscscssssssccsscsscsscssssscsessesssessssseseessnssesssssscsecececcseesesseseaseaseeceaseaseaseaseneeaeness 39 Figure 20.Envelope of Maximum Compressive Cantilever Stresses due to IWT010 Earthquake - (in psi,U/S View)(Layout 3)...ccccscsesscscssscccsssssssscssssessessscssssssssssssssssssssssssesssseessssseesseseseeseseerseees 40 Figure 21.Envelope of Maximum Compressive Cantilever Stresses due to IWT010 Earthquake - (in psi,D/S View)(Layout 3)...ccssssessssessessscssscrssscsscssscssssssssescessssessessssessesssesesssssessssesensesseseseee 40 Figure 22.Residual Sliding Displacement of the Dam at the End of IWT010 Earthquake (in inches) (Layout 3)....eesscsssscssssescescsccessssscorcssssssscsssscssssssscsssacssssssssssssusssssaessesasenesseseesesseseeseneeseseeneaeenssenesnentes 4] Figure 23.Envelope of Maximum and Minimum Cantilever Stresses in Crown Cantilever for Layout 3 for Selected Event..........ssscsssesscsssssscessssssssssssssessesssesssesessessesesseseesessesesersesssarsaceesensenseaseees 42 Figure 24.Cantilever Stresses at the Crown Cantilever (Layout 4).......cscsssssssssssssessessnesesetsessenens 47 Figure 25.Horizontal Stresses at the Crown Cantilever (Layout 4)...ccsssssstesssscsseessseeseeseseeneeees 47 Figure 26.Finite Element Model of Layout 4.........cccsscsessessseressssssssseeessssenessesnesesenecsseenessenenessenenees 49 Figure 27.First Four Vibration Modal Shapes of the Dam Model ...........csssssssssssescssssersnseesenesenesenees 51 Figure 28.Envelope of Maximum Tensile Cantilever Stresses due to IWT010 Earthquake -(in psi, U/S View)(Layout 4)...cessesssscssssscsssssssssssscsssesesessssssnsesenssessssssnsnssseseseneasssesssssesesenensesssssasacnenseseneeees 52 Figure 29.Envelope of Maximum Tensile Cantilever Stresses due to IWT010 Earthquake -(in psi, D/S view)(Layout 4)......cccssssssssssssssssessssssssssssssssssesessessssssssesssecsenesenssesesesenenesenesususnessseosscessseesesaceseees 53 Figure 30.Residual Sliding Displacement of the Dam at the End of IWT010 Earthquake (in inch) (Layout 4)..ccccessecessessssesessssssssssssssscsseseseesesessesnssesnssssscsssncsecnenecscneensacsnssensesesnssssnsasavsssesesssasenesenenneasenese 54 REVIEW COPY Page v 03/14/14 -z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 oo,13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEll Figure 31.Envelope of Maximum and Minimum Cantilever Stresses in Crown Cantilever for Layout 4.....cccseccsccscsssssssesescessesessssvacssssesscssososessecscsseesessssssssessssessssscessssesceseseessenesesanensseessensasenseaseaeat®55 Figure 32.RCC Volume vs.Elevation (Layout 4)........cccssssssssesssssssseesssessesessescsessesssseseassaseesees 60 Figure 33.Effect of Foundation Deformation Modulus on Maximum/Minimum Stresses...............61 Figure 34.Finite Element Model of Dam Layout 4 with Reservoir ........ccsscssssssessseeeeeesceeseeerenees 64 Figure 35.Sayano-Shushenskaya Dam .......sccssssssssssssssesssscssessseesseseseeseessssessesssenseeseatenessessenesensenees 68 Figure 36.Completed Portugués RCC Thick Arch Dam ........csccsssssssssssseseserenesensnssesseseseseseseeesassees 69 Figure 37.Shapai RCC ARCH Damm,China ..0....cc eescssescssenensesseneenseeseesensesessesesesenesesaeenensensenenees 70 Figure 38.Contours of the Maximum Tensile Stress (MPa)on Shapai Dam Surface under the Field Records of 0.4 g (a)Linear,Massless Foundation;(b)Joint opening,Viscous-Spring Boundary....72 Figure 39.Pacoima Damou...cssesssssssesessssessesssssessssssscssssscsessecesssssesessscsssessceaseeseseeseneseeaeseseeaegesnees 73 Figure 40.Shasta Dam .......cscssscsssssssssscssssssssscssessssessescsessessesessenseseensseeseeseseesesseeeseeaesesenssneesesneenenees 75 Figure 41.Normalized Comparison of Dam Profiles...scsssssssessssssessseessssessesssssssesesseseeeeneseenees 76 List of Appendices Appendix A.Drawings: 04-01C002 Layout 2 04-01C002 Layout 3 04-01C002 Plan Development 04-01C002 Plan 04-01C001 Isometric 04-01C004 Profile A 04-01C003 Section 04-01C005 Gallery 04-03S002 Spillway 04-01C001 Seasonal Placement REVIEW COPY Page vi 03/14/14 -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 . 13-1405-TM-031414 Clean,reliable energy for the next 100 years,CEll 1.INTRODUCTION In the 1980s,the Alaska Power Authority (APA)sought a license for the Susitna Project,a hydro scheme that comprised the Devil Canyon Dam and Watana Dam together with associated powerhouses.At that time,Watana Dam was proposed as an Earth Core Rockfill Dam (ECRD)and Devil Canyon was to be a high arch dam.Both projects included underground power facilities. The projects were cancelled before a license was granted,but only after many years of study of the engineering and the environmental aspects of the development. Various updates on the Watana Dam were suggested during intermittent reviews and in 2010 the Alaska Energy Authority (AEA)-the successor organization to APA -initiated new studies in order to obtain a FERC license to construct the upper project of the two,Watana Dam (renamed Susitna-Watana Dam)and powerhouse. All the earlier engineering studies are being used to avoid repeating studies unnecessarily,or failing to take advantage of the original investment.Since the 1980s,however,worldwide developments in dam construction have been such that the type of dam to be used at the project can be prudently reevaluated. In the 1980s,the height of dam proposed at Susitna-Watana (approximately 700 feet for Stage one) presented a challenge.The few dams that had been constructed to this height were concrete thin arch dams,concrete gravity dams,and earth core rockfill dams.Over the last 30 years new design philosophies,construction methods and experience have added two other dam types that are suitable for the Susitna-Watana Dam.Concrete Faced Rockfill dams (CFRD)and roller compacted concrete (RCC)dams are both candidates for the new Susitna-Watana dam initiative. During the preparation of the Pre-Application Document (PAD),a comparison of the three potential types of dam (ECRD,CFRD and RCC)-using acceptably safe cross sections -was performed by estimating the construction costs of the facilities that are not common to the dam types.A safe project layout was configured based on each type of dam and detailed as necessary to determine the basic unit quantities associated with each development.The most economic dam that performs with the appropriate level of safety was determined to be one based on RCC methodology as recorded in Technical Memorandum 6 -Alternatives Evaluation. Following the selection of the basic arrangement -a RCC dam with the powerhouse at the base of the dam within the river channel -it is important for the feasibility study,for the license application,and for the cost estimation of the project,to undertake a first optimization of the dam configuration to ensure a safe and economic project.The examination of possible configurations was performed both using the expected normal maximum operating level (NMOL)of the pool and REVIEW COPY Page 1 03/14/14 --Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEI also for a higher dam with a NMOL equivalent to the Stage 3 proposal in the 1980s.The analysis of the higher dam was performed to ensure that any design decisions for the proposed dam would not preclude future raising. The project site is remote and necessitates a significant investment in infrastructure to enable transportation of materials,plant and construction workers to and from the site.Any reduction in imported materials can noticeably reduce the capital cost.In addition,the costs of maintaining the construction infrastructure,feeding and housing the workers,and maintaining the required supply chain are extraordinarily high,so shortening the construction period is paramount.Any reduction in the time for construction would allow generation to commence earlier to commence revenue flows. The most significant potential optimization of the project is founded on a reduction in the volume of concrete to be placed.Savings could accrue in the direct cost of the cement,fly ash,and the aggregate processing as well as the reduction in the time on site and thus the establishment costs. The focus at this stage of feasibility is to maintain a dam configuration that is safe under the expected loads (static and seismic),but minimizes the volume of RCC. This memo records the derivation of the proposed configuration.It must be emphasized that this exercise is part of a feasibility study -with the attendant iterative process -aimed at selecting a configuration that is safe and (following the applicable optimization and detailed design)will be proven to perform within FERC,and other,guidelines at reasonable cost.The intent in this memo is not to finally design all aspects of the dam shape or completely resolve all aspects of the dam shape and performance,so the level of detail of the various analyses is somewhat less than would be expected in final,detailed design. The first challenge in this exercise is the lack of sufficient site investigation focused on the projected dam foundation.Site investigations were performed in the 1980s specifically for the ECRD,and its accompanying underground power facilities.Although there are a number of drill holes at the site that have yielded useful information,additional investigations and testing are needed to collect the geotechnical data necessary for foundation characterization and to reduce geologic uncertainties that may affect engineering feasibility,location,and the general arrangement (e.g.evaluating potential displacement,frozen ground,abutment stability).Detailed design of an RCC dam will require focused and specific site investigation,including the excavation of adits in the abutments to afford visual examination,mapping and in-situ testing of the rock mass. The foundation of the ECRD was characterized in the 1980s,but during the current feasibility has not yet been fully verified,particularly in the area of the foundation of a RCC gravity structure. Geological features fracture and shear zones identified in the 1980s (such as GF5)have not yet been re-examined and characterized. REVIEW COPY Page 2 03/14/14 ---Za-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl The matter of a Watana lineament was delineated and raised in the extensive by Gedney and Shapiro (1975)based on LandSat imagery.In the extensive 1980s investigations,this lineament feature was reexamined and discounted (WCC,1982).The possibility of such feature has again been raised during this feasibility analysis even though in the earlier investigations two drill holes (DH-21 and BH-6)were drilled in a geometrical relationship with each other that further reduced the likelihood of a lineament had been "missed”.However,it is acknowledged that the existence of an "active”shear or fault through the foundation -that has the potential for displacement -might render a concrete dam (and a CFRD structure)as unsuitable options.Two vitally important drill holes are projected (together with site characterization and lineament studies)to remove the specter of a lineament from future discussions or considerations.Until the required investigations are able to be completed,an assumption has been made that the conclusions of the previous investigation are correct (that the Watana lineament does not exist nor are any "active”faults present in the dam foundation along which displacement may occur). Subsequent to the drafting of the straight axis RCC gravity dam (Layout 1)included in the (PAD), three configurations have been examined in detail for the dam.Each configuration is based on a curved gravity dam -i.e.the dam relies on its weight for the largest contribution to its stability,but also utilizes some horizontal "arch”action to enhance the stability and structural performance. Each configuration had a different curvature,and slope of the downstream face,and each was located most favorably to the topography and existing rock conditions as understood at the time each was developed (e.g.,avoiding certain geologic features). The first configuration for detailed analysis was derived by using Arch Dam Stress Analysis System (ADSAS)software -based on the trial load method -on 14 different configurations.The software provides a rapid means of analyzing the three dimensional stress distribution within a dam based on static loads.The 14 configurations comprised a range of radii using different downstream face slopes from 0.3 H:1 V to 0.85 H:1 V.Ninety eight different combinations were examined, including the PAD layout (straight dam).Each run of ADSAS provided upstream and downstream arch,cantilever and principal stresses and a dam volume.This is described in previous technical memos and in summary in section 3.1 below.The most promising arrangement was chosen for the detailed analysis.The option selected was a three centered dam (with the center section radius being 1,300 ft.and the radius of the outer sections 4,000 ft.)with a downstream slope of 0.5 H to IV. MWH presented the initial configuration to the Board of Consultants (Board)during Meeting #2 in Bellevue,WA,on March 7-8,2013.The Board opined that a somewhat simpler arrangement should be analyzed.During the associated discussions with the Board it was agreed that a single (large radius)dam with a "normal”downstream slope (0.85 H to 1V)applicable to a gravity section should be analyzed (Layout 3)-so the second analysis was performed on this configuration. REVIEW COPY Page 3 03/14/14 -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 | 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl Layout 3 was considered to be conservative,defining the upper bound of the spectrum of possible configurations -and a change from Layout 2 to Layout 3 would result in approximately 1 million extra cubic yards of RCC being needed for the dam.Layout 2 is considered the lower bound option of the appropriate dam,so a plot of volume vs.height was made for the two configurations (single curvature and three centered curves)in order to indicate the final direction of study for this stage of optimization.These curves are included as Figure 1 and show the general range of dam height vs. volume towards which the optimization should be directed. Using input from the project hydrologists with respect to the eventual desirable storage,a target volume of RCC of between 5.4 and 5.6 million was selected as desirable.With reference to Figure 1;the maximum crest elevation for the dam would be between EL 2040 ft.for Layout 2 and EL 2075 ft.for the Layout 3 configuration. 2075 "|<=Layout 2-3 centered.0.5 D/S slope "ca a e Layout 4 |pre.-|Layout 3 -3500ft radius,0.85 0/S slope |- I 2050 fon "7 "|Optimization " Scere as Pa Envelope fA Cee 2025 ::CrestElevation(EL.(ft))1975 pa 1950 focheJ 1925 A 1900 -2,500,000 3,000,000 3,500,000 4,000,000 4,500,000 5,000,000 5,500,000 6,000,000 6,500,000 RCC Volume (cy) Figure 1.RCC Volume,Dam Layouts 2 and 3 The selected operational rules for use of the low level outlet -and the surcharge required to pass any selected discharge without opening the gates -are key elements in determining the dam height, as the normal freeboard will be the total of the required surcharge for the use of the low level outlet REVIEW COPY Page 4 03/14/14 ---Z-ALASKA ENERGY AUTHORITY .AEA11-022SUSITNA-WATANA HYDRO sarang 022 Clean,reliable energy for the next 100 years.CEIll plus any PMF surcharge.In the absence of any "Employers Requirements”for the low level outlet discharges an assumption was made that for a NMOL of 2050 a total surcharge for both conditions would likely be a maximum of 15 ft.This assumption has resultedin a dam crest of 2065 being selected. Together with this assumption,an intermediate configuration of a radius of 2600 ft.with two straight gravity end sections was chosen for the third analysis (Layout 4).Each of the end sections retained a full gravity section with a downstream slope of 0.85 H to 1 V,while the central curved part of the dam included a downstream slope of 0.7 H to 1 V. For each analysis,assumptions were made of the expected foundation excavations (based on available information from the 1980s studies)and thus the foundation surface.ADSAS analysis was performed,a two-dimensional gravity analysis using CADAM was performed for selected cross sections and a Finite Element Analysis was performed using the time histories developed from the interim results of the seismic hazard analysis. The following sections describe features and attributes of each of the three analyzed configurations, together with the performance of the dam. REVIEW COPY Page 5 03/14/14 -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl 2.LIMITATIONS This memorandum presents a documentation of the iterative development of the dam layout from January 2012 through March 2014,and is a part of the feasibility level analysis of options. The geologic and engineering interpretation of subsurface conditions used to support the analysis recorded herein is based primarily on drill holes executed in the 1980s -for a different type of dam - and the reconnaissance geologic mapping,laboratory testing of selected samples etc.from that earlier program. The work presented is thus not a final and defined arrangement -and it is expected that as more geological data is gathered,and more complex analytical models are created,there will be adjustments to the details of the dam layout and cross section,as well as the precise location of the dam and the associated facilities. Derivation of the dam arrangement is thus a "work in progress”and readers of this memo should understand that stresses and safety factors recorded herein do not represent those projected for the final design -in fact some tensile stresses exhibited in some of the analyses would not be considered acceptable in the final solution.The stress results recorded here are used merely as indicators in an iterative process of feasibility analysis to confirm that the adjustments made during each iteration represent beneficial progress in selection of the dam geometry and the associated tensile stresses. Development of the detailed arrangement -and analysis with more detailed models and confirmed geological data will continue before,during,and after undertaking a comprehensive geotechnical investigation and laboratory testing program and final design. In particular,the use of a more elaborate finite element model,with more elements,and with mass incorporated in the foundations is expected to demonstrate (based on experience elsewhere)tensile stresses in the dam body below the expected capacity of the RCC. DRAFT Page 6 03/14/14 wTwwvwwvwwewwewewowoewwoewwoeoeeweoeeewewowwo-Zz ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1405-TM-031444Clean,reliable energy for the next 100 years., CEll 3.GEOLOGY AND FOUNDATION The footprint of the dam is underlain by an igneous rock mass (pluton)that is primarily composed of diorite and quartz diorite.These intrusive rocks are massive and they are generally hard,competent, and fresh to slightly weathered except within locally developed fractured,sheared,and altered zones.These rocks have been intruded by mafic and felsic dikes which are generally only a few feet wide.On either abutment,the rock is overlain by a relatively shallow later of colluvium and talus in the lower valley and glacial till in the upper slopes which soil cover is expected to range in thickness between approximately 0 and 30 feet thick beneath the dam footprint.Within the existing river channel,the rock is overlain by alluvium that is generally on the order of 65 to 80 feet thick. Several geologic structures comprised of fractured,sheared,and hydrothermally altered rock contribute to the topography at the dam site.The two most prominent rock structure orientations are northwest-southeast and north-south as seen by incised gullies on both abutments along the river. Both of these primary structures are persistent and vary in dip angle,but are near vertical on average.Several secondary joint sets have been observed at the site which are believed to be related to stress relief as a result of removal of overlying rock,glaciation,and down cutting of the river.' The geologic features have influenced the siting of the dam having located the upstream face of the dam just downstream of the N-S feature GF-4 (Acres,1982).Several other geologic features (such as GF-5)are expected to be encountered in the foundation of the dam and ancillary structures.Assuch,for the dam footprint,a rock mass zoning map was developed to divide the foundation into distinct zones based on the anticipated degree of fracturing and rock modulus. Frozen ground conditions,and rock temperature below 32°F,are expected in the left abutment and potentially the lower right abutment at the dam site.The depth of the frozen ground could be up to 200-ft.in the left abutment.The presence of ice-filled discontinuities in the rock mass could have an impact on slope stability,reducing overall shear strength,overall rock mass permeability and the effectiveness of grouting. In general,bedrock beneath the dam will be excavated to a depth so as to remove weathered and altered rock material,shape the foundation,and to key the dam into rock.This has been assumed in the analyses presented later in this report. REVIEW COPY Page 7 03/14/14 -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEll 4.SEISMIC LOAD DEVELOPMENT A seismic hazard analysis had been performed in the 1980s by Woodward Clyde Consultants.A new Site Specific Seismic Hazard Assessment was commenced and a preliminary report was prepared (FLC,2012)along with a sensitivity analysis (FLC,2013)to further identify those parameters that had a significant influence on the hazard.The subduction zone (interface and intraslab),is the dominant contributor to the hazard.Figure 2 below illustrates that the intraslab is controlling the hazard for the low periods (PGA),and for the higher periods (1.0 seconds)the intraslab controls until a return period of about 2,500 years,at which point the interface begins to dominate.A response spectrum from the seismic hazard analysis is also presented in Figure 3.The sensitivity analysis looked at the geometry of the subducting slab and the closest distance to the site using various slab geometries and thicknesses derived from recorded seismicity.The parameters that most influenced the results of the seismic hazard were shown to be the distance and also the maximum magnitude.There are crustal sources such as the Denali Fault and lineament studies are ongoing;however at this time no significant nearby faults have been identified that would generate ground motions higher than the interface or intraslab events already identified.A preliminary RTS study was also performed which suggests that the maximum RTS magnitudes may be on the order of 6.3 to 6.5 (lower than the subduction events).Although the site specific seismic hazard analysis is not finalized at this time,enough work has been completed to develop preliminary seismic design criteria and time histories suitable for use in the level of dam design appropriate to feasibility verification. REVIEW COPY Page 8 03/14/14 KeerSeaSlss)-wwwwaTwwwwaaww-Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl RetumPeriod(years)AnnualProbabilityofExceedanceReturnPeriod(years)AnnualProbabilityofExceedancePeak Horizontal Acceleration (g)1.0 Sec Spectral Acceleration (g) Figure 2.Hazard Curves from Preliminary Seismic Hazard Assessment 4.1 Development of Preliminary Seismic Design Criteria 4.1.1 Spectrum Analysis In the early design phases the dynamic analyses of the different potential configurations of the dam were commenced utilizing spectrum analysis.The selected horizontal accelerations dynamic modeling were 0.52g,0.66g and 0.82g,corresponding to return periods of 2,500,5,000,and 10,000 years (Figure 3).Spectrum analysis was prior to the development of three dimensional time histories. 4.1.2 Development of Time Histories Guidance furnished by the Federal Energy Regulatory Commission (FERC),Evaluation of Earthquake Ground Motions,was followed and a deterministic spectrum was used to develop design ground motions (Idriss &Archuleta,2007).Because the seismic hazard is made up of contributions from three different sources:subduction zone events,interface and intraslab,and crustal events, three time histories were developed for each type of event to evaluate the difference in frequency content. Table 1 contains the magnitude,distance and PGA for each of the selected events.The 84th percentile was used for all of the events,except the magnitude 8.0 event for the slab,where the 69th percentile is used.The selection of the 69th percentile helps correct for the use of the hypocentral REVIEW COPY Page 9 03/14/14 -y ALASKA ENERGY AUTHORITY ITNA-WATANA HYDRO AEA11-022SUS13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl distance in the computation of the ground motion prediction equations and is discussed in TM 13- 1404-TM-02131.A magnitude 7.5,84th percentile intraslab event is provided for comparison. Based on current field data a Vs30 of 1,100 m/s was used,as provided in Draft Revised Intraslab Model and PSHA Sensitivity Results (FCL,2013).Uniform hazard curves are provided in Figures 3 through 5 along with the deterministic response spectra for each type of event. Table 1.Selected Magnitude,Distance and Epsilon =:Rupture |Re a.oe ee eesSource[magia Distance .|.Distance |..Epsilon Depth(km)'Hormonal Interface 9.2 78 n/a 1 35 0.52 7.5 50 n/a 1 45 0.70 Intraslab 8.0 50 n/a 0.5 45 0.81 Crustal 7.0 ©7 3.5 1 0-20 0.49 Source:FCL,2012 &FCL,2013,Revised Vs30=1100m/sNotes:(1)Depth range indicates top and bottom of faults individual depths indicate the rupture depth. The seismic hazard analysis has,essentially been completed except for resolution of the crustal features -because access has been denied to the site for lineament examination. A lineament study for evaluation of crustal seismic sources in the near vicinity of Susitna-Watana is currently in progress.Design ground motions have focused on the intraslab source as the controlling source and not crustal events.To clarify why the intraslab event is the focus of study for the purposes of structural design criteria -and not a nearby or distant crustal event -ground motion calculations for crustal earthquakes were performed for several different magnitudes,for features at hypothetical distances and a single epsilon value of |(corresponding to a 84th percentile)the results of which are shown in Table 2.For ease of review,a vertically dipping strike-slip event was chosen to represent a nearby crustal event.The distance parameters in a vertically dipping strike-slip fault are straightforward and easily comparable,whereas normal and thrust faulting are complicated by dip angles,dip directions,and if the site is on the hanging wall or footwall. REVIEW COPY Page 10 03/14/14 Za ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl Table 2.Ground Motions for a Hypothetical nearby Crustal Event with Intraslab Design Event shown for Comparison Crustal 84"i ilon = Magnitude mance em)ee ocr pesto ata(Reue=Rue=Rx)PGA (9)Period of 0.5 seconds (g) 6.0 3 0.51 0.55 6.5 3 0.60 0.75 7.0 3 0.65 0.88 7.5 3 0.69 0.97*exceeds Intraslab Intraslab 69"Percentile (Epsilon =0.5) Magnitude Hypocentral Depth (km) PGA (a)Spectral Acceleration ataPeriodof0.5 seconds (g) 8.0 50 0.81 0.96 wFrwwTwwwTwwewewewoewewoeweweeewee----The Wells &Coppersmith 1994 magnitude-area relation was used to estimate the approximate rupture lengths for the magnitudes given in Table 3.The strike-slip magnitude relationship was used with an estimated rupture width of 15km. M=3.98+1.02 log (Area) Table 3.Rupture Lengths for Various Magnitudes *.Magnitude 8 Down-dip Width (km)-Rupture Length (km) 6.0 15 6 6.5 15 20 7.0 15 61 7.5 15 188 In a deterministic framework where only a magnitude,distance and epsilon are needed to perform computations,the intraslab event is almost certain to have the highest ground motion.This is supported by these hypothetical ground motion calculations for an 84th percentile strike-slip event at a distance of 3km at various magnitudes.In order for an 84th percentile (epsilon =1)strike-slip crustal event to exceed the 69th percentile (epsilon=0.5)ground motions from an M 8.0 intraslab event it would have to be located within about 3km of the dam site,have a magnitude of 7.5 and a rupture length of approximately 120 miles.No such feature has yet been discovered. REVIEW COPY Page 11 03/14/14 et a 'ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO actans e022 Clean,reliable energy for the next 100 years.CEIl Clearly,the intraslab event is dominant,and an as-yet undiscovered lineament would have to be very large and close to the site to produce an event with ground movements at the site in excess of those projected from the intraslab. 2.5 ome |Nterface M9.2,D78km Vs30=1100m/s -84th --interface M9.2,D78km Vs30=1100m/s -50th SpectralAcceleration(g)Period (s) Figure 3.Uniform hazard Curve and Deterministic Spectra for Interface Event REVIEW COPY Page 12 03/14/14 wwwwoewowwewwwwewoeweweweweweewew = - - -2 ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl ome Intrasiab M8,DSOkm Vs30=1100m/s -69th 10,000 Year Return Period ees Hntrasiab M7.5,DSOkm Vs30=1100m/s -84th -_=-Intraslab M8,DSOkm Vs30=1100m/s -50th maoN -=Intraslab M7.5,D50km Vs30=1100m/s -50th2in en We 5,000 Year Return Period am =2,500 Year Return Period 2.5 SpectralAcceleration(g)0.5 0 T T 0.01 0.1 1 Period (s) Figure 4,Uniform Hazard Curve and Deterministic Spectra for Intraslab Event 2.5 os Crustal M7.0,D7km Vs30=1100m/s -84th oe e=Crustal M7.0,D7km Vs30=1100m/s -50th 10,000 2 cc c 2a5 a oO vu L) < wil SVe a Q 7) 0.5 im 0 0.01 Period (s) Figure 5.Uniform Hazard Curve and Deterministic Spectra for Crustal Event REVIEW COPY Page 13 03/14/14 Z :ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO | AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl 4.2 Selection of Time Histories 4.2.1 Interface The catalog search for interface events included motions recorded during the Japan 2011 M 9.0 event (about 1400 recorded motions),Japan 2003 M 8.0 event (about 350 recordings)and available records for the Chile 2010 M 8.8 event (about 55 recordings).The number of interface ground motions available was then narrowed down mainly based on distance and the spectral shape. It should be noted that,for the interface scenario,the majority of the selected motions were for an M 8.8 event or M 9.0 event with similar conditions as the target event (magnitude,distance and site conditions).Hence,it is believed that the ground motion parameters (e.g.,duration and equivalent number of cycles)should be representative of the target interface scenario.See Table 4,for those earthquake records spectrally matched. Table 4.Record Parameters for Interface Seed Time Histories -M9.2-84"Percentile eventTite |station |arastimis)|redominate,|Pretominie,|Closest CURIEW 10.55 1.45 0.69 Chile (M 8.8)CURINS 2.85 0.73 1.37 85 CURIUD 10.88 0.42 2.40 VALPMEW 4.57 1.70 0.59 Chile (M 8.8)VALPMNS 0.71 0.33 3.08 %8 VALPMUD 2.02 084 1.19 CHBO28EW 2.22 0.24 4.09 Japan (M 9.0)CHBO028NS 1.79 0.22 4.47 14 CHB028US 1.35 0.11 8.94 *Arias Intensity (la)is defined as the time-integral of the square of the ground acceleration: nm ta=o 2I,2g I a(t)*dt (m/s) where g is the acceleration due to gravity and Ty is the duration of signal above threshold. 4.2.2 Slab The catalog search for slab events included motions recorded during the El Salvador 2001 M7.6 event (14 recordings),Japan 2003 M 7.1 event (about 412 of recorded motions),Chile 2005 M 7.9 event (10 recordings)and available records for the Japan 2011 M 7.0 event (about 504 recordings). REVIEW COPY Page 14 03/14/14 wwe@F@Forwewwewmwewwweiwewewawawewe----Zz ALASKA ENERGY AUTHORITY A-WATANA HYDRO AEA11-022SUSITN,13-1405-TM-031414 Clean,reliable energy for the next 100 years.'CEIl The number of slab ground motions considered was then narrowed down mainly based on distance and spectral shape. The recording distance was limited to between 50 and115 km.Chile M7.9 events were not able to be used because no records fell within this range.However,for variability one event was selected from each of the remaining events (El Salvador 2001,Japan 2003,and Japan 2011).By creating a catalog of those strong motion events that occurred on the slab,it is believed that the ground motion parameters (e.g.,duration and equivalent number of cycles)should be representative of the target slab scenario.See Table 5,for those earthquakes records spectrally matched. Table 5.Record Parameters for Slab Seed Time Histories -M8.0 -69"Percentile .wo ..Predominate.|..Predominate ClosestEventTitleStation"|Arias (m/s)|'period (sec)|Freq.(Hz)Distance(km) SDM090 11.74 0.25 3.95 El Salvador (M 7.6)SDM360 9.62 0.25 3.69 80 SDMOUP 3.35 0.18 5.50 IWTO011EW 1.39 0.40 2.48 99Japan2003 (M 7.1)IWT011NS 0.85 0.37 2.71 IWT011UD 0.55 1.61 0.62 MYGOOSEW 2.21 1.03 0.97 85Japan2011 (M 7.0)MYGOOSNS 1.76 0.21 4.66 MYGOO9UD 0.78 1.06 0.94 Table 6.Record Parameters for Slab Sced Time Histories -M7.5 -84 Percentile wa .ee .oo Predominate.-Predominate ClosestEventTitleStationArias(m/s)Period (sec)Freq.(Hz)-Distance(km) STTECO090 7.71 0.29 3.43 El Salvador (M 7.6)STTEC180 6.54 0.16 6.16 114 STTECOUP 2.80 0.31 3.19 IWTOO8EW 2.74 0.46 2.16 7Mt)IWTOO8NS 1.42 0.12 8.69 IWT008UD 0.47 0.06 16.81 IWTO10EW 7.09 0.65 1.54 401Japan201122458(M 7.0)IWTO10NS 5.21 0.. IWT010UD 1.69 0.85 1.17 REVIEW COPY Page 15 03/14/14 --Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 CEllClean,reliable energy for the next 100 years. 4.2.3 Crustal The search for the crustal time history was performed using the PEER database for those events having a magnitude ranging between 6.5 and 7.5 at distances of 10 to 30 km.Spectral shape was also considered,and the three motions that had the best fit were chosen to spectrally match.For variability three different earthquake records were chosen.See Table 7,for those earthquakes records spectrally matched. Table 7.Record Parameters for Crustal Seed Time Histories -M7.0-84"Percentile ve cee:|cae Cee bee a -Predominate.|Predominate-es ee.Event Title Station -Arias (mis):'Period (sec)Freq.(Hz)|.Ryp(km) 531E 0.41 0.53 1.88 Duzce, Turkey 531N 0.45 0.39 2.56 8.0 (M 7.14)531V 0.10 0.41 2.44 AULO000 0.05 0.59 1.69 Irpinia,Italy 9.5 (M690)AUL270 0.07 0.36 2.80 AUL-UP 0.02 0.44 2.28 ; GIL067 0.90 0.37 2.68 Loma Prieta,92 California GIL337 0.70 0.37 2.71 (M 6.93)GIL-UP 0.71 0.44 2.28 REVIEW COPY Page 16 03/14/14 wwewvwwywvwweoFowowwwewewwewemeweweweweweewew --- -- - Ze ALASKA ENERGY AUTHORITY .AEA11-022SUSITNA-WATANA HYDRO aang 022 Clean,reliable energy for the next 100 years.CEII 5.CONFIGURATION DEVELOPMENT The feasibility studies are founded on an iterative approach to arrive at the preferred solution.As noted above the process began during the preparation of the PAD at the completion of which a preferred dam type was determined -RCC.The straight dam included in the PAD was recognized to be a robust configuration that had significant potential for optimization. Subsequent to the submission of the PAD,refinement of the dam configuration has resulted in three iterations that are described below.In addition to refinements to the configuration,slight adjustments to the dam alignment have also been made in refining the design.The alignment adjustments were carried out to take into account the current understanding of foundation conditions,absent focused drilling.This understanding will be improved when focused drilling - and the excavation of adits -is carried out during planned site investigations. All configurations include a crest width of 35 feet,except the last one. REVIEW COPY Page 17 03/14/14 Zz ALASKA ENERGY AUTHORITY -A HYDR AEA11-022SUSITNA-WATAN O 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl 6.INITIAL DAM CONFIGURATION (LAYOUT 2) 6.1 Configuration Description As noted above,multiple (14)alternatives were first considered and each alternative was analyzed using ADSAS with downstream face slopes ranging from 0.3H:1V to 0.85H:1V.Ninety eight permutations were considered in total.The dam configurations analyzed are described in Table 8. Table 8.Analyzed Dam Configurations . Radii (feet)Center arc |Crest .-Dam |middie |Outer |angle |length >|"Section |Sections |(degrees)|-(feet) A 1800 Straight 91.3 4543 B 2000 Straight 79.8 4335 Cc 2200 -4350 D 2400 -4251 E 4000 -3979 F 1300 4000 30 4241 G 1500 4000 30 4171 H 1700 4000 30 4150 |1800 4000 30 4133 J 1300 4000 40 4426 K 1500 4000 40 4391 L 1700 4000 40 4287 M 1800 4000 40 4252 N*Straight -3805 *This dam was the configuration in the PAD The ADSAS program cannot model straight axes directly,so an approximation is required which involves entering the straight axes as "curves”with a radius of 999,999 ft.This technique was used to model the outer portions of the dam for the Dam A,B and N alternatives. After the analysis of the "high”dams (a possible ultimate development corresponding to the Stage 3 Watana layout included in the 1980s license application),configurations F and J were identified as the two preferred layouts with a downstream face at 0.5H:1V.A steeper downstream face would REVIEW COPY Page 18 03/14/14 wwewTwowowwwewewewewoeweweweweeeww--=--= = -_---z-ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO rang 022 Clean,reliable energy for the next 100 years.CEll result in a significant transfer of stresses from the vertical to the horizontal plane which would result in the dam no longer performing completely as a gravity structure.These two alternatives,along with Dam N were then assessed for the low dam layout being studied at this time for downstream slopes ranging from 0.4H:1V to 0.6H:1V. The preliminary stress analysis did not take into account seismic or thermal loads which will affect the stress values.These loads would result in a detrimental adjustment in the values.Both dams F and J were satisfactory alternatives as analyzed.However,the addition of these extra loads would be less pronounced for Dam J,and it was therefore selected as the configuration for further analysis. Thus the selection for "Layout 2”consists of a central portion with a curved axis of 1300 ft.radius which changes to a 4000 ft.radius at a tangent point on the abutments.The downstream face is a uniform slope of 0.5H:1V and the upstream face is vertical.The central portion is defined by a phi angle of 40 degrees.The described configuration is Dam J in the various tables above and below. The dam crest for Layout 2 remains at 2075. 6.2 Arch Dam Stress Analysis System (ADSAS) ADSAS was used in advance of Finite Element analysis in order to limit the time spent performing multiple seismic analysis at this feasibility stage of design,and the results of the ADSAS analysis provided a level of confidence that the selected dam cross section would be capable of withstanding the expected seismic loads. The results of the analysis of Dam J (Layout 2)are shown in Figure 6 for the crown cantilever. REVIEW COPY Page 19 .03/14/14 Z ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEll 2100 TDamCrest:EL 2075 ft -2050 -Reservow NMOL:EL 2050ft ;aT oo Cantilever Upstream Dam)a +Cantilever DownstreamDownstreamSlope:0.5:12000 , : w=Horizontal Upstream 1950:->io.nae=Hevizontal Dowmsteeam 1900 - : i fo::1850 +sa! :{|CantileverUpstream |yy Sy1800= :VA :_4 :Rae 'sz=:\5 1750 +--\f __* oo -ae . oeid*[ieonnitparenn /.1650.-|Horizontal Upstream '\:vA \{: : ? : .\1600 -PX ty:ae ;:¥ 1550 i ;."Dae a |Horizontal Downstream} i i 7 : : :' wooi-i oo .:.a ari Sr re ':.'Ao:i i ?poy i } m0 ne a :/- {Cantilever Downstream1400:rWA :7 a . 1350 -¢ 600 -550 -S00 -450 -400 -350 -300 -250 -200 -180 -100 -50 [']So 100 180 200 Compression Stress (psi)Tension Figure 6.Layout 2 (Dam J)-Crown Cantilever Stresses 6.3 FE Structural Analysis The three dimensional static and dynamic finite element analyses of Susitna-Watana Dam Layout 2 were performed using the Finite Element Analysis (FEA)program ANSYS,Version 14.ANSYS is a state-of-the-art commercially available general finite element method (FEM)program,which is widely used as an analytical (and research and development)tool in a number of industries, including civil/structural engineering design,including static and dynamic evaluations of dams. The ultimate development height of the dam was not dynamically analyzed because it is assumed that the results of the ADSAS calculations give sufficient indication that a safe dam raising is feasible in the future. A linear finite element model was created consisting of 5160 elements and 6658 nodes.Mostly hexagonal ("brick”)elements were used,while prism ("wedge”)elements were utilized in portions of the model where the geometry was not regular.The dam and rock foundation elements used in the model consisted of 8-node elements,with one node at each corner.Three-dimensional mass elements (added mass)attached to the nodes of the elements on the upstream face of the dam were used to simulate hydrodynamic effects of the reservoir.The weights of the added masses on the dam face were computed as noted below. REVIEW COPY Page 20 03/14/14 2 ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO tang2 Clean,reliable energy for the next 100 years.CEIl The FEM model of the dam comprises 4 elements in thickness and 20 vertical rows of elements at the crown cantilever.The rock foundation was modeled to a depth equal to the height ofthe dam,a width equal to three times the dam height and a length equal to the dam height in the upstream and downstream directions.The elements of the dam body are connected directly to the elements of the foundation neglecting any possible separation (opening)at the dam-foundation interface due to applied loadings. The rock foundation of the FEM model.was assigned stiffness in accordance with the review of existing drill holes and engineering properties of rock determined from laboratory testing and similar materials by the project geological engineers -but was assigned no mass.The deformation modulus of 3,500,000 psi,and Poisson's ratio of 0.25 were used for dynamic analysis.A massless foundation allows for transmission of the seismic ground motion time history from the boundary of the model to the dam foundation.Thus the inertial effects of the foundation mass were not included, leading to a conservative transmission of energy and an overestimate of the seismic force applied to the dam. SEP 25 2012 12206268 i re|ELEMENTS Figure 7,Finite Element Model Upstream Side (Layout 2) REVIEW COPY Page 21 03/14/14 et a ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO saaags 022 Clean,reliable energy for the next 100 years.CEIl Figure 8.Finite Element Model Downstream Side (Layout 2) 6.4 Loads 6.4.1 Gravity The gravity load was applied as a gravitational acceleration of 32.2 ft./sec”.The weight of the dam was based on the average density of concrete of 150 Ibs./ft?.No gravity loads from the foundation were included,as the foundation elements were assumed to be massless,and provided only stiffness in the model. 6.4.2 Reservoir Hydrostatic The hydrostatic reservoir load was applied in the model as a distributed force load on the dam face based on the maximum normal operating pool reservoir condition of El.2050 feet.No flood, overtopping,or any other reservoir level fluctuation and resulting load combination was considered in the dynamic analysis. 6.4.3 Uplift Uplift pressure at the dam-foundation interface could affect overall stability of the dam but has limited effect on the dam body internal stress distribution being investigated by the FE modeling.In the model for Layout 2 dam elements were continuously attached to the foundation elements and no REVIEW COPY _Page 22 03/14/14 -Z-ALASKA ENERGY AUTHORITY .AEA11-022SUSITNA-WATANA HYDRO aang 022 Clean,reliable energy for the next 100 years.CEIl uplift pressure was considered -although this boundary condition was modified for later configuration modeling. 6.4.4 Ground Motion Concurrently with the development of the FE models,the seismic hazard analysis has been ongoing, so the ground motions used for the analysis have been adjusted slightly.For the initial dynamic analysis of Layout 2 the response-spectrum analysis method was used.The Horizontal response spectra for 3 different levels of earthquake as shown in Error!Reference source not found.were used in the analyses. 2.2 =@=-2,500 yrs -m-5,000 yrs | -#°10,000 yrs|__Acceleration(Sa/g)a -----o 0.2 "=o - = 0 ¥qT v LI 0 0.5 1 1.5 2 Period (seconds) Figure 9.Response Spectra for Susitna-Watana Dam Site Area An earthquake with 2,500 year return period has been adopted as the (MCE),with a peak ground acceleration (PGA)of 0.522g.Furthermore the dam has also been analyzed for earthquakes with 0.66g and 0.82g PGA corresponding to the 5,000 yr.and 10,000 yr.event respectively.These additional events were analyzed to assess the effect of different seismic loading criteria on the stresses created within the dam. REVIEW COPY Page 23 03/14/14 2 ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEN 6.4.5 Hydrodynamic Hydrodynamic reservoir loading from the reservoir on the upstream face of the dam was estimated based on the surface area below El.2050 feet and orientation of each element using the Westergaard method and applied to the model as added masses attached to the upstream nodes for the full reservoir condition. 6.5 Static Analysis for Normal Loading Cases Analyses,using normal static loading,were performed and compared with the results of the ADSAS analysis.Some deviations in the stress distribution between the methodologies was observed;this could be attributed to the way dead load is considered.The trial load method assumes that the dam is built as separate vertical cantilever blocks resulting in the dead load being transferred vertically to the cantilevers with no "arch”action.Elastic finite element analysis considers the dam self-weight as a single block and arch stresses are developed within dam body due to the dam self-weight.The two-step odd-even cantilever method (Section 11-5.2.2 of FERC Engineering Guidelines,Chapter 11 -Arch Dams)was used to analyze the dam for dead loading conditions.The stresses determined using the odd-even cantilever method are in agreement with the trial load method,giving credence to the output of the ADSAS software. 6.6 Dynamic Analysis 6.6.1 Modal Analysis A modal analysis of the dam was performed to calculate the fundamental periods of vibration and mode shapes of the linear model.Jn response spectra analysis,modal mass is used as an indicator of the number of modes to consider in the analysis.The first twelve natural frequencies of the dam and respective modal participation mass ratios are shown in Table 14.The mode shapes for the first 6 vibration modes are shown in Figure 10. REVIEW COPY Page 24 03/14/14 yw SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1405-TM-031414 CEll Table 9.Periods of Vibration and Modal Participation Mass Ratio (MPMR)of Dam Mode Period MPMR°Sum.Of MPMR Number .Sec U/D Cross stream |Vertical U/D Cross stream |Vertical 1 0.657 0.470 0.002 0.018 0.470 0.002 0.018 2 0.495 0.002 0.074 0.000 0.470 0.076 0.018 3 0.385 0.040 0.000 0.000 0.510 0.076 0.018 4 0.313 0.080 0.005 0.001 0.590 0.081 0.019 5 0.308 0.210 0.010 0.006 0.800 0.090 0.025 6 0.262 0.012 0.003 0.007 0.810 0.094 0.032 7 0.258 0.001 0.700 0.059 0.820 0.790 0.091 8 0.254 0.002 0.061 0.730 0.820 0.850 0.820 9 0.232 0.000 0.001 0.000 0.820 0.850 0.820 10 0.224 0.000 0.001 0.000 0.820 0.850 0.820 11 0.198 0.012 0.000 0.001 0.830 0.850 0.820 12 0.189,0.000 0.000 0.000 0.830 0.860 0.820 Review of the results indicates that the first 12 vibration modes represent more than 80 percent of the total mass of the structure in all directions.Adopting twelve modes in the analysis will adequately simulate the seismic response of the structure at this stage of the design process.The fundamental period of the analyzed dam is 0.657 seconds. REVIEW COPY Page 25 03/14/14 ze ALASKA ENERGY AUTHORITY .AEA11-022SUSITNA-WATANA HYDRO 131405 tan 022 Clean,reliable energy for the next 100 years,CEIl NODAL SOLUTION cer 15 2012 NODAL SOLUTION ocr 18 2012 STEPST 15146253 STEP+1 15ratrss SUR #1 eB =2 FREC#1.83303 ”FRELHZ 09598SUN(AVG?USuM {AVG} RSYS@O RSYS= HK =,10-03 MK =,1378-03 SM ©,7678-06 SMR >.dIE-0E SK 0,1102-05 SHK ©.137R-03 Mode 1 Mode 2 MODAL SOLUTION oct 1b 2012 NOUAL SOLUTION OCT 15 2012STEP"1 15288026 srmpey 45248259 2B 03 UB 94FREQ=2,73386 WHED=3,25123Ustanya)ust a 5-0aey IMM #,1588-03 SH #,5188-06SMX=,1EVE-03 Mode 3 Mode 4 ae wo At]WObAL souution ocr 45 2012 'DAL SOLUTION cor 18 2012STEP-1 15149238 STEPAL 16103254 SUB 95 SB as FREQ=3,42258 PP ED$3.73415USUMtava)US {A¥G) SHO =,120K-05 ."SN =,4358-05 SK =,1738-05 Sg SMR =.699-06 Mode 5 Mode 6 Figure 10.First Six Vibration Modes Shape of the Dam 6.6.2 Response Spectra Analysis Elastic dynamic analysis of Susitna-Watana Dam was performed using response spectra to compute the maximum response of the dam due to earthquake loading.The data input to the model included REVIEW COPY Page 26 03/14/14 yz ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl the two horizontal and the vertical response spectra.As highlighted earlier,the dam was analyzed for three earthquake load scenarios: Earthquake with 2,500-year return period with a PGA of 0.522g Earthquake with 5,000-year return period with a PGA of 0.664g Earthquake with 10,000-year return period with a PGA of 0.8272 The maximum (tensile)and minimum (compressive)horizontal and cantilever stresses on the upstream and downstream faces of dam are summarized in Tables 10 and 11.In accordance with ANSYS convention -and for ease of comparison -tensile stresses are positive,and compressive stresses are negative. Table 10.Comparison of Seismic Analysis Results-Maximum Tensile Stresses Upstream face Downstream face Seismic Cantilever stress |Horiz.stress Cantilever Horiz.stress case (psi)(psi)stress (psi)(psi) 2,500 yrs.711 628 663 345 5,000 yrs.983 909 877 533 10,000 yrs.1300 1240 1130 752 Table 11.Comparison of Seismic Analysis Results -Maximum Compressive Stresses Upstream face Downstream face Seismic Cantilever stress |Horiz.stress Cantilever Horiz.stress case (psi)(psi)stress (psi)(psi) 2,500 yrs.-1132 -1256 -910 -917 5,000 yrs.-1403 -1538 -1122 -1105 10,000 yrs.-1721 -1868 -1379 -1324 Current dam safety practice does not judge the seismic safety of the dams based on the allowable stress criteria,and limited damages are allowed during the maximum credible earthquake.However, the computed maximum compressive and tensile stresses from a linear elastic analysis remain useful as a major indicator for the expected level of damage in a concrete dam.The maximum compressive cantilever stress and compressive horizontal stress are 1,721 psi and 1,868 psi respectively.Therefore the compressive stresses are below the probable corresponding allowable compressive stress of 2,700 psi for all earthquakes and no compressive damages are to be expected. 03/14/14REVIEWCOPYPage27 Zz ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEll The maximum cantilever tensile stress for the 2,500 year return period earthquake is 711 psi,which is in excess of the probable apparent dynamic tensile strength of RCC layers (taken as 580 psi). This overstressing is indicated only for a small area on the upstream and downstream face of the dam.Therefore the proposed dam geometry is considered safe against the developed seismic stresses in the dam body during an earthquake with return period of 2,500 yrs. The results for the 5,000-yr.and 10,000-yr.events indicate that,should these levels of ground motion be used as criteria there may well be overstress which could cause appreciable damage on the dam body which might be unacceptable.If more detailed analysis with less conservative criteria still shows overstressing,dam geometry would need to be revised to reduce developed stresses in the dam. It is also noted that the range of computed tensile stresses at the dam-foundation interface and tensile horizontal stresses between the dam monoliths are exceeding the tensile capacity of these interfaces. This reinforces the conclusion that linear elastic analyses do not present a realistic seismic response of the dam,and a more sophisticated analysis considering nonlinear contact elements at these locations is more appropriate. 6.7 RCC Volume The optimization of RCC volume -while maintaining dam safety -is the crux of these early analyses.The ADSAS program calculates the volume of concrete in the analyzed structure.It should be noted that the concrete volume predicted by ADSAS for the PAD layout (Dam N)is larger than that estimated in December 2011.This difference is due to the spacing between the cantilever sections analyzed in ADSAS.The 2011 estimate was based on sections at every 100 ft. whereas the spacing of sections used in the ADSAS model varied from 95 feet to 395 feet. The sections analyzed for the curved dams were all radial from the center of curvature.The base of each vertical element coincided with the end of a horizontal element.To ensure the entire base of each vertical element was founded on rock,the highest foundation elevation was located at the downstream toe of the dam in several instances.This would generate significant excavation at the foundation as the section would progressively get deeper into the rock abutment as it extended towards the dam's upstream face.This leads to conservative volume estimation.For the purposes of this analysis,however the volume estimations are primarily used for the comparison of the dam alternatives and serve as a measure of the relative scale of the dams.The volumes estimated for a Susitna-Watana high dam are listed in Table 12. REVIEW COPY Page 28 03/14/14 Zi SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1405-TM-031414 CEll Table 12.Susitna-Watana High Dam:ADSAS Estimated Dam Volumes (cubic yards) Dam Slope of downstream face (xH:1V) 0.3 0.4 0.5 0.6 0.7 0.8 0.85 6,416,000 7,746,000 9,047,000 10,300,000 11,525,000 12,714,000 13,295,000 6,416,000 7,767,000 9,086,000 10,372,000 11,626,000 12,847,000 13,446,000 6,370,000 7,700,000 9,002,000 10,277,000 11,523,000 12,742,000 13,340,000 6,271,000 7,589,000 8,882,000 10,149,000 11,391,000 12,607,000 13,206,000 5,911,000 7,178,000 8,432,000 9,671,000 10,896,000 12,107,000 12,708,000 6,341,000 7,655,000 8,932,000 10,174,000 11,380,000 12,550,000 13,121,000 6,305,000 7,615,000 8,891,000 10,133,000 11,342,000 12,518,000 13,093,000 I;Ol;nmsoy;ol;a]>6,176,000 7,463,000 8,719,000 9,945,000 11,139,000 12,303,000 12,873,000 6,261,000 7,574,000 8,856,000 10,108,000 11,330,000 12,521,000 13,105,000 6,379,000 7,686,000 8,950,000 10,174,000 11,356,000 12,496,000 13,051,000 6,319,000 7,620,000 8,883,000 10,111,000 11,301,000 12,455,000 13,018,000 6,233,000 7,523,000 8,780,000 10,003,000 11,193,000 12,350,000 12,916,000 6,207,000 7,496,000 8,754,000 9,979,000 11,172,000 12,332,000 12,900,000 zil/sairi[xnye5,801,000 7,079,000 8,356,000 9,634,000 10,911,000 12,189,000 12,828,000 The volumes for the selected favorable configuration for the lower dam were also estimated by the ADSAS program and the results are shown in Table 13. Table 13.Susitna-Watana Preferred Dam:ADSAS Estimated Dam Volumes (cubic yards) =:Slope of downstream face (xH:1V) Dam 0.4 0.5 0.6 0.7 0.85 J 4,521,000 |5,276,000 |6,009,000 -- REVIEW COPY Page 29 03/14/14 Zz ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO 14g 022 Clean,reliable energy for the next 100 years,CEIl 7.REVISED DAM CONFIGURATION (LAYOUT 3) 7.1 Configuration Description After being presented with the results of the analysis of the first configuration (Layout 2),the Board of Consultants suggested that a simple single radius configuration might also usefully be analyzed, so the team reassessed the work performed to derive the first configuration with the object to establish an upper envelope of conservatism in the layout.Upon examination of the original ADSAS volume calculations,the most economical of the traditional gravity sections was dam E with a single axis radius of 4000 ft.,but on examination of the topography,it was found that a radius of 3500 ft.resulted in a better angle of intersection with the abutment topographic ground contours. -This radius was therefore selected for Layout 3,but is not represented in the original volume calculations. 7.2.Two-Dimensional Gravity Analysis Using the 3500-ft single radius layout,two-dimensional analysis was performed to estimate the cross-sectional geometry that would satisfy stability criteria for the usual and unusual load cases required by the FERC Guidelines,Chapter 3,Gravity Dams.Multiple cross-sections were analyzed using CADAM,for downstream face slopes ranging from 0.7H:1.0V to 1.0H:1.0V and upstream face batters ranging from vertical to 0.2H:1.0V. As expected,the dam cross-section that satisfied two-dimensional stability criteria for all load cases -with no tension at the foundation interface (no crack forming at the foundation contact)-had a downstream face slope of 0.85H:1.0V and an upstream face batter of 0.1H:1.0V.The 2D analysis assumed zero cohesion at the dam foundation interface and included uplift applied on the dam base according to the load distribution allowed by the FERC Guidelines.This cross-section was then further refined and analyzed using ADSAS and FEM as described in the sections that follow.Post- earthquake stability was also analyzed,with modified uplift pressures applied to assumed crack lengths,for comparison to results of the FEM analysis done for stability of the cracked dam in a post-seismic condition.As reported in discussion of the FEM analysis below,permanent displacement was computed at the base of the crown monolith at the end of the earthquake event; however the dam remained stable for the post-seismic condition. A simplified analysis was also performed using PGA of .66g and .82g for the purpose of estimating the increase in dam volume required for the higher ground motions.For that condition the downstream face of the dam was estimated to require a slope of 1.0H:1V. REVIEW COPY Page 30 03/14/14 ze .ALASKA ENERGY AUTHORITY .AEA11-022SUSITNA-WATANA HYDRO 431405a022 Clean,reliable energy for the next 100 years.CEll 7.3.Arch Dam Stress Analysis System (ADSAS) In concert with the two-dimensional gravity analysis,the ADSAS program was used to perform the analysis of the dam section required to withstand the 5,000-year return period seismic event (0.85H:1.0V).A dam cross section with a 1.0H:1.0V downstream face was also analyzed. Results The stresses calculated for the cantilever and horizontal elements at the crown cantilever are shown graphically in Figure 11 and 12 below. 2010 +-----]Crest Elevation :£1 2075tt : 7 7i"Downstream Face Slope :0.85H11V ;: ,: :ay1960;«|Adis Radius:3500ft CG ee, t : :, at : :¢ 1910+- 1810 Elevation(feet)1610 1560 ++.*'.+.:.i .*ae angum Upstream Face :! T T1510+- =Downstream Face ' 1460 § / M10 FM Fr .$380 re”er Y rn Bo, -700 600 500 00 300 200 "100 0 Compressive Stress (psl) Figure 11.Layout 3 Cantilever Stresses at the Crown Cantilever REVIEW COPY Page 31 03/14/14 -Z-ALASKA ENERGY AUTHORITY 7 AEA11-022SUSITNA-WATANA HYDRO aetans 022 CEIlClean,reliable energy for the next 100 years. 2110 2060 2010 'Crest Elevation :EL 2075ft Downstream Face Slope :0.85H:1V Axis Radius :3500ft1960on 1910 "Z "ss1860+" a "a an 1810 +xv z L A 1760)6 Ri beet a fF a. ' ;'FIO poe eR PReS + ™1660 +O Face a 41610t 1560 . ' 1510 i 9400 i BFa r 4410 ee 1360 .fe re boapedo Sof Pook ed,i re Lt 280 -200 150 100 50 o so 100 1530 Compression Stress (psi)Tension Figure 12.Layout 3 Horizontal Stresses at the Crown Cantilever The ADSAS analysis shows that the vertical cantilever stresses are compressive at the upstream and downstream faces for the entire height of the dam.The maximum vertical compressive stress is less than 37%of the allowable compressive stress. The analysis also shows that there is transfer of some load horizontally to the abutments.This demonstrates that the curved axis reduces the loads carried by cantilevers,and the wedge action resulting from a curvature of the dam increases sliding stability of the dam. The analysis confirmed that the Layout 3 cross-section is stable under static loading conditions.The Layout 3 cross section was then used for 3-D analysis using finite element method software to assess the effect of dynamic loading. 7.4 FE Structural Analysis 7.4.1 Model Initially ANSYS Version 14.5 was used for analyzing Layout 3 but subsequent to the first runs, MWH upgraded to Version 15 and also made some adjustments to the foundation of the dam for Layout 4.Therefore -in order to permit reasonable comparison between the various analyses, ANSYS,Version 15.0 was used to carry out the re-analysis of Layout 3 recorded herein.The REVIEW COPY Page 32 03/14/14 Za ALASKA ENERGY AUTHORITY -WATANA HYDR AEA11-022SUSITNA-WATAN 0 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl geometric model of the dam was created directly within the "Design Modeler”of ANSYS,and subsequently used as the basis for creating the FEM mesh.The finite element model consisted of 14133 elements and 13236 nodes.The FEM model of the dam includes 2 elements (thickness)at the dam crest and 16 elements (thickness)at the dam base together with 19 elements along the height of crown cantilever.The maximum element size is thus 40 ft.for the feasibility analysis and further analysis for design development will be undertaken with a significantly (smaller and)more detailed mesh.The rock foundation was modeled to a depth equal to the height of the dam,a width equal to three times the dam height and a length equal to the dam height in the upstream and downstream directions.Three-dimensional mass elements (added mass)attached to the nodes of the elements on the upstream face of the dam were used to simulate hydrodynamic effects of the reservoir.Figure 13 shows a general 3D view of the model and a cross section of the highest monolith of the dam. Taking into account FERC and BOC observations the following modeling features were included in the FE model: ¢Nonlinear frictional contact elements were used to model the contraction joints in the dam body.These contact elements cannot transfer tensile stresses in the interface but can transfer shearing forces based on the coulomb friction criteria.During final design the distance between contraction joints will be selected based on the expected thermal performance of the dam but is expected to be between 50 to 100 ft.The distance of the contraction joints for this analysis is assumed at 200 ft.to reduce the nonlinear analysis time.A friction coefficient of 1.2 was assumed for these contacts. e In order to allow movement on the foundation,nonlinear frictional contact elements,similar to contact elements of dam monoliths,connect the dam body to the foundation.The elements of the dam-foundation contact are connected at the surface of the foundation elements (no embedment,hence no resistance against sliding other than friction).Figure 13shows all the contact elements used in the model.Assuming that the drainage system is 66%effective,uplift pressure (with an equivalent triangular distribution)at the base of monoliths was calculated and applied on contact surfaces. REVIEW COPY Page 33 03/14/14 Zz ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO saagoscroro 4.022 Clean,reliable energy for the next 100 years.CEIl wy,RASAVACATESG0777'renWAVEWANG.47;was8ErehlFag codpeasafin!it éera7OMer =i.\s+f'7Ptodeid 150 tehsil Cross section of dam model Contact elements in the model Figure 13.Finite Element Model of the Dam (Layout 3) 7.4.2 Static Analysis The initial analysis focused on the normal loading condition of dead load and hydrostatic loading. Figure 14 to Figure 17 graphically show the resulting horizontal and cantilever stresses in the dam body. REVIEW COPY Page 34 03/14/14 a-a-ALASKA ENERGY AUTHORITYSUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. AEA11-022 13-1405-TM-031414 CEll B:Transient Structural-mass Expression:$z*.0001 45 Time:2 , "ry 193.84 MaxLd2.271 tensile cantilever stress ;Le i 0 1e+004 (in)| §e+003 _Figure 14.Cantilever Stress -Upstream Face (Layout 3) 'B:Transient Structural-mass tensile cantilever stress Expression:$z*.000145 Time:2 193.84 MaxLd92.971 -29.297 -140.86 -252.43 -364 587.13 -698.7 -810.27 Min 0 1e+004 (in)EE) §e+003 Figure 15.Cantilever Stress -Downstream Face (Layout 3) REVIEW COPY Page 35 03/14/14 Za ALASKA ENERGY AUTHORITY .AEA11-022SUSITNA-WATANA HYDRO rans 022 Clean,reliable energy for the next 100 years.CEll B:Transient Structural-mass tensile arch stress . Expression:sy*.000145 °°.Oe TIM@:2 158.69 Max 99.475ae 2a i4 Le.0 1e+004 (in)Zz SS) 5e+003 Figure 16.Arch Stress -Upstream Face (Layout 3) '4 7 ;= B:Transient Structural-mass - tensile arch stress": Expression:sy*.000145Time:2 an 158.69 Max 99.475 40.263 "18.949 78.161 J .4 37-22 -255.8 gy 7315.01 -374.22 Min s|0 1e+004 (in)Zz SS Se+003 Figure 17,Arch Stress -Downstream Face (Layout 3) REVIEW COPY Page 36 03/14/14 = -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl The FE analysis indicates that the stresses in the dam body under static conditions are lower than the allowable values.The structure is in a state of compression except for two or three monoliths on the left and right side with zero horizontal stresses.Because the model includes joints at 200 ft.centers, no tensile stresses developed in the FE model. The current construction planning anticipates that the dam will be constructed in three large monoliths,corresponding to the left abutment,right abutment and central portion of the dam. Therefore the expected response of the dam to self-weight loading would be slightly different from these results.In the final design,the dam body will be modeled using three distinct monoliths and additional vertical formed joints -with shear keys -between those monoliths.The model will be analyzed for the self-weight of the dam by simulating the proposed construction schedule. 7.4.3 Modal Analysis A modal analysis of the dam was performed to calculate the fundamental periods of vibration and mode shapes of the linear model.The first 8 natural frequencies of the dam are shown in Table 14. Table 14.Frequency and Periods of Vibration Mode No 1...2 -3 4 er)6 7 .8 Frequency (hz)1.88841 |2.58056 |3.21403 |3.70938 |3.83099 |3.97313 |4.21945 |4.44512 Period (s)0.52955 |0.38751 |0.31114 |0.26959 |0.26103 |0.25169 |0.23700 |0.22497 The fundamental period of vibration is 0.529 second,smaller than the period of 0.657 seconds for dam Layout 3,thus confirming that Layout 3 is stiffer than Layout 2. Review of the modal analysis results indicates that the first 30 vibration modes represent more than 90 percent of the total mass of the structure in all directions.Rayleigh damping mass coefficient and stiffness coefficient were calculated using the first and 30"circular frequency for an equivalent 7% damping ratio. 7.4.4 Transient Analysis Three acceleration time histories were developed for each type of earthquake event as explained in Section 4.1.Two earthquake records from each type of events were used in the analyses.Transient dynamic analyses were performed for a total of eight earthquake records.Developed stresses in the dam body and sliding displacement of dam monoliths are the main parameters to assess the response of the dam against the earthquake.The results indicate that no tensile horizontal stresses develop in the dam because of the "no tension”behavior of the contact elements.However compressive REVIEW COPY Page 37 03/14/14 Za ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEll horizontal stresses develop on the upstream or downstream face of the dam depending on the direction of the earthquake loading. The envelopes of maximum (tension and compression)cantilever stress on the upstream and downstream face of the dam for the (Japan 2011)ITW010 earthquake are shown in Figure 18 to 21. (Tensile stresses are positive as usual,however,positive values are also used for compressive stresses only in these figures because of ANSYS outputs).No tensile cantilever stresses are developed along the dam-foundation interface because of the "no tension”contact elements.High tensile cantilever stresses are developed at the mid-height of the central monolith and the maximum tensile stress is around 1150 psi. Figure 22 shows the residual sliding displacement of the dam monoliths at the end of the,IW1010 earthquake.The maximum sliding exhibited at the base of the crown monolith is around 1.5 in.The magnitude of the sliding increased for the side monoliths to 2.9 in and the maximum sliding of 5 in occurred on the left side monolith.It is noted that the computed sliding displacement of each monolith is affected by dam-foundation interface geometry,friction coefficient and contact pressure, and state of the contact at the beginning of the earthquake event.Therefore the actual sliding displacements would be expected to be different from computed values at this stage.An estimation of more representative displacements awaits refined modeling which will be performed at a later stage for the chosen dam configuration. The basic structural responses of the model to eight earthquake records are similar,but different in magnitude.The detailed stress contours of the dam due to other earthquakes are not shown here but the maximum cantilever stress variations along the height of the crown monolith for eight earthquakes are plotted in Figure 23.The maximum computed stresses in the dam body and permanent displacement of dam monoliths due to the eight earthquakes applied are also summarized in Table 15. REVIEW COPY Page 38 03/14/14 a ]ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEII B:Transient Structural-mass -=2 ee max tensile cantilever stress Expression:sz*.0001 45»Maximum Over Time 1230.9 Max -256.84 Min [:.0 4e+004 (in);z -_-- 5e+003 Figure 18.Envelope of Maximum Tensile Cantilever Stress due to 1WT010 Earthquake -U/S View (Layout 3) [B:Transient Structural-massmaxtensilecantileverstress-Expression:$z*.000145MaximumOverTime 1230.9 Max ry,fies ty-256.84 Min ae eal}0 4e+004 (in)z ee $e+003 Figure 19.Envelope of Maximum Tensile Cantilever Stress due to IWT010 Earthquake -(in psi,D/S View)(Layout 3) REVIEW COPY Page 39 03/14/14 -Z-ALASKA ENERGY AUTHORITY -HYDR AEA11-022SUSITNA-WATANA O 43-1405-1M.031414 Clean,reliable energy for the next 100 years.CEII |B:Transient Structural.mass ie;max compressive cantilever stress.Expression:-sz*.000145 : Maximum Over Time 2317.3 Max e 0.00 300.00 (m)Ls.ZzaS 150.00 Figure 20.Envelope of Maximum Compressive Cantilever Stresses due to IWT010 Earthquake -(in psi,U/S View)(Layout 3) nessa renee mene ,.45.| |B:Transient Structural-mass =OAs max compressive cantilever stress 2:Expression:-sz*.000146 oo cgMaximumOverTime 2317.3 Max 1500 wm ocd0.00 300.00 (m)zZ | 150.00 Figure 21.Envelope of Maximum Compressive Cantilever Stresses due to IWT010 Earthquake -(in psi,D/S View)(Layout 3) REVIEW COPY Page 40 03/14/14 yz. SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1405-TM-031414 CEll B:Transient Structural-mass t Directional Deformation : Type:Directional Deformation(X Axis) |Unit:in|Global Coordinate System Time:50 Figure 22.Residual Sliding Displacement of the Dam at the End of IWT010 Earthquake (in inches)(Layout 3) REVIEW COPY Page 41 03/14/14 -yz ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIll Slab events -M8.0 -69th Percentile (PGA=0.81) Cantilever stress at U/S Cantilever stress D/S2100|'é 2100 "om2000aehe2000vz_.1900 «a __1900 ao.=>E x ca=1800 =1800 wec«oa <£1700 oe 7 2 1700 7o7gon@1600Af%1600 pa F"1500 *|"1500 ¢a;4 A --@--SDM --@--SDM 1400 ==--B--MYG 1400 os ---MYG1300};,1300 },, -2000 -1500 -1000 -500 0 S00 1000 1500 -2000 -1500 -1000 -500 0 500 1000 1500 Stress (psi)Stress (psi) Slab events -M7.5 -84th Percentile (PGA=0.70g) Cantilever stress at U/S Cantilever stress D/S2100-2100 i2000|2000 or - "tme Ts.¢7_.1900 £wp |1900 on vn=1800 r nip =i800 a s q A 5 'a£1700 on yd 2 1700 &a o ”$wa%1600 2,is &1600 a an a1500 15001400i=-@ -(WT010 1400 =--©=-!WTO10 bd r ----STTEC °--B--STTEC1300}7 .1300 ++:. -2000 -1500 -1000 -500 0 500 1000 1500 -2000 -1500 -1000 -500 0 500 1000 1500 Stress (psi)Stress (psi) Crustal events -M7.0 -84th Percentile (PGA=0.49g) »100 Cantilever stress at U/S 2100 Cantilever stress at D/S ae oa2000,ines 2000 es_.1900 fie aren _.1900 Mi ',=1800 gf f t 1800 Bas had 2 1700 +aieal mat &1700 oe”7 o=1600 in %1600 fey*1500 #45001400xx7-@=°AUL 1400 --@=-AUL ,o-B--Gil o--Gil1300+:1300 ||: -2000 -1500 -1000 -500 0 S00 1000 1500 -2000 -1500 -1000 -500 0 500 1000 1500 Stress (psi)Stress (psi) Interface events -M9.2 -84th Percentile (PGA=0.52g) Cantilever stress at U/S Cantilever stress at D/S21002100 2000 0 ye"r=-2000 _.1900 ct a _.1900 =1800 i =18002*s,i}2 1700 on =1700%1600 +3 1600™1500 va 1500 &1400 4 "mere Cari 1400 a f eeeo-f -Val vu -a--1300 }r -1300 }*velp -2000 -1500 -1000 -500 0 500 1000 1500 -2000 -1500 -1000 -500 0 500 1000 1500 Stress (psi)Stress (psi) Figure 23.Envelope of Maximum and Minimum Cantilever Stresses in Crown Cantilever for Layout 3 for Selected Events REVIEW COPY Page 42 03/14/14 "SY -yzw ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl Table 15.Summary of Dam Layout 3 Response to 8 Earthquake Loadings & Horiz stress Cantilever stress Sliding Event Event |Stress (psi)Displacement (in) Title Station |Location : :Compressive |Tensile |Compressive awn mon ins Slab events -M8.0 -69th Percentile (PGA=0.81) El U/S -1330 1388 -1680 Salvador SDM 4.1 6.4 13-Jan-01 DIS -1043 788 -909 Japan U/S -1175 1344 -1558 2011 MYGO009 3.8 4.4 7-Apr-11 D/S -903 848 -919 Slab events -M7.5 -84th Percentile (PGA=0.70g) El U/S -794 913 -760 Salvador |STTEC 1.8 2.2 13-Jan-01 D/S -596 695 -1330 Japan U/S -732 1149 -839 2011 IWT010 1.5 3 7-Apr-11 DIS -721 726 -1346 Crustal events -M7.0 -84th Percentile (PGA=0.49g) Irpinia,U/S -762 841 -1265 Italy AUL 0.8 1.2 23-Nov-80 DIS -538 557 -682 Loma U/S -697 1252 -916 Prieta,GIL 0.2 0.5California,: 18-Oct-89 DIS -607 363 -858 Interface events -M9.2 -84th Percentile (PGA=0.52g) Chile curt U/S -969 726 -1552 34 35M8.8).,(DIS 619 797 -634 .U/S -630 791 -1250oneVALPM 41.5 2(M 8.8)DIS -639 563 -563 The maximum tensile cantilever stress of 1388 psi occurred in the dam body during the SDM earthquake.However the average of maximum tensile stresses from all selected earthquakes is around 945 psi.This stress is beyond the projected dynamic tensile strength of the RCC hence cracking of the dam can be expected according to these results.In accordance with most dam guidelines,the dam should withstand the Operational Basis earthquake with damage acceptable in 03/14/14REVIEWCOPYPage43 --Z-ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO sarang tan 022 Clean,reliable energy for the next 100 years.CEll limited areas during the maximum credible earthquake.These damages are acceptable if there is limited release of water.The dam stability was also examined for the stability of the cracked dam in a post seismic condition.The maximum displacement calculated at the base of the crown monolith is 4.1 in.which occurred during the SDM earthquake -and the average displacement is approximately 2.15 in.This is a permanent displacement at the end of the earthquake event; however the dam remains stable for the post-seismic condition. 7.5 RCC Volume In order to establish a check on the ADSAS volume calculations,the volume of the Layout 3 dam was calculated using an excel spreadsheet in two ways:1)-per 1 ft.elevation;and,2)at 5 ft. increments along the dam crest.The spreadsheet calculated the gross volume of the dam body, adjustments were then made to the estimated volume to include the concrete between the powerhouse and the downstream face of the dam and to include volume reductions for inserts including penstocks,spillway and intakes. The volume estimates are listed in Table 10.A slight batter in the upstream direction (0.1H:1V)was included at the upstream face of the dam below elevation 1770 ft. Table 16.RCC Quantities (Layout 3) Downstream Face Slope 0.85H:1V Gross RCC volume 6,831,000 cy Quantity adjustment 416,000 cy Net RCC volume 6,415,000 cy REVIEW COPY Page 44 03/14/14 ---Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO,AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl 8.2"?REVISED DAM CONFIGURATION (LAYOUT 4) 8.1 Configuration Description Although the construction cost estimate prepared at the end of 2013 included the single radius dam, it was recognized that if the total RCC volume could be reduced to approximately 5.5 million yd', then a full season of construction could be eliminated and substantive reductions in project cost achieved.Reverting to the original comparison of volumes for the high dam,a compromise between Dams A,D and E appears promising,so a layout was prepared for a single radius.for the central part of the dam of 2600 ft.,together with straight gravity sections on either end.By using this combination,the dam foundation footprint remains almost exactly the same as that of the first revised configuration (Layout 3),and the right abutment location does not change.The left abutment rotates slightly downstream,but is Judged to be acceptable -at this level of geotechnical knowledge of the site. The updated configuration (Layout 4)for the Susitna-Watana dam thus comprises a central portion with an axis radius of 2600 ft.The dam axis changes to a straight line at a tangent point and continues to the abutments. The crest of the dam is 35 ft.wide -and at EL 2065 ft.is 10 ft.lower than previous iterations.This 10 ft.lowering of the crest level results from a reassessment of the flood and freeboard requirements for the dam at the completion of the PMP/PMF studies and after selection of an acceptable reservoir rise of 15 ft.for the efficient use of the low level outlets and for passage of the PMF.The curved section has a downstream face slope of 0.7H:1V and the straight gravity section includes a 0.85H:1V slope on the downstream face.All portions have a sloping upstream face (0.1H:1V) below EL 1770 ft.transitioning to a vertical face thereafter.The change in downstream face slope reflects the reliance on gravity at the abutments. 8.2 Two-Dimensional Gravity Analysis A preliminary check of two-dimensional stability of the 2600-ft radius dam was performed using CADAM,for the cross-section with a downstream face slope of 0.7H:1.0 V and upstream face batter of 0.1H:1.0V.Assuming zero cohesion at the dam base,the simplified analysis showed the dam _satisfied stability criteria for the normal static,flood and post-seismic conditions with a cracked base.The resultant location for all forces under the cracked condition fell within the dam base.The 2600-ft radius dam with this center cross-section was then further analyzed using ADSAS and FEM as discussed below.The FEM analysis included examination of stability of the cracked dam in a post-seismic condition.As reported below,permanent displacement was computed at the base of REVIEW COPY Page 45 03/14/14 -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years,CEI the crown monolith at the end of the earthquake event;however the dam remained stable for the post-seismic condition. 8.3.ADSAS As noted earlier in this memo,ADSAS has the capability of analyzing three centered dam configurations including those that include straight sections at both ends -as selected for Layout 4. Modeling of the curved portion of the Layout 4 dam has been carried out to assess the stresses both vertically and horizontally within the dam.The analysis omitted the straight portions at the abutments since they will perform as gravity sections.The outer sections have been defined with a -cross section that is typical for a gravity dam and the stress analysis can be performed using a traditional 2-D analysis approach. Similar to the previous configuration (Layout 3)the analysis shows that the cantilever stresses are compressive at the upstream and downstream faces for the entire height of the dam.The cantilever stresses within the dam are more evenly distributed than Layout 3;the resultant is nearer to the center of dam section and is lower in magnitude. The revised configuration results in slightly greater transfer of loading to the arches.The stresses within the arches at the extrados are compressive for the full height of the crown cantilever while the along the intrados the stresses transition from compressive to tensile about 160 ft.below the crest. The analysis shows that the upper sections of the dam,where the arch effect is most noticeable,has a larger compressive component than Layout 3.The stresses are low,relative to the allowable stresses but demonstrate that the dam shape is more efficient in accommodating the applied loads. The analysis confirmed that the dam cross-section was stable under static loading conditions.This cross section was then used for analysis using finite element method software to assess the effect of dynamic loading. REVIEW COPY Page 46 03/14/14 yz SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1405-TM-031414 CEll Crest Elevation:€t 2065ftDownstreamFaceSlope:0.70H:1VAxisRadius:26007 400 vont one]meee Upstream Face i Downstream Face CompressiveStress(psi) +200 100 Qo Figure 24.Cantilever Stresses at the Crown Cantilever (Layout 4) -}Aus Radius:2600ft Crest Elevation :EL 2065ft Downstream Face Stope :0.70H:1V 1460 --|ee -e-Upsiream 1410 Downstream 130 5 -bone +:1:ee to no more - -woo -250 -200 150 -100 -50 Qo so 400 190 200 Compression Stress (psi)Tension Figure 25.Horizontal Stresses at the Crown Cantilever (Layout 4) REVIEW COPY Page 47 03/14/14 Za ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl 8.4 FE Structural Analysis Structural analysis was performed using ANSYS v15.A new finite element model was developed for the 2™revised dam configuration (Layout 4)as shown in Figure 26.The developed finite element model is similar to the previous model of Layout 3 and has the same modeling characteristics with a new geometry and new finite element mesh.Because the foundation surface had to be re-evaluated for the slightly revised geometry,an opportunity was taken to adjust the foundation and also to use the revised foundation for the Layout 3 as recorded above.Nonlinear frictional contact elements were used between the dam and the foundation and also between dam monoliths in both Layout 3 and Layout 4. Eight earthquake time histories were used for transient analysis of the dam foundation.For each analysis,dead weight of the dam was applied in the first step and hydrostatic and dam base uplift forces were applied in the second step,with the seismic velocity time history applied in subsequent steps.Results of the Layout 4 analyses showed higher tensile cantilever stresses on the downstream face at the top of the dam.In order to reduce the tensile stresses,the dam cross section was modified for this analysis by increasing the width of the dam cross section at the top.The width of the dam crest was increased by 10 feet at crest level with no changes at the base of dam.The finite element model was revised accordingly and continued analyses were performed using the modified cross section.Figure 26 shows the finite element model for the modified cross section of Layout 4. During future runs the shape of the downstream face is expected to be adjusted to take advantage of increased cross-section in the upper part of the dam,with a small reduction in cross-section lower | down to further benefit from the adjustments described above. REVIEW COPY Page 48 03/14/14 ALASKA ENERGY AUTHORITY AEA11-022 13-1405-TM-031414SUSITNA-WATANA HYDRO CEilClean,reliable energy for the next 100 years, 248 ARERROj akiwySan' a s' me Downstream and upstream view of FE model Crown cantilever meshing and frictional contacts in the model Figure 26.Finite Element Model of Layout 4 Modal Analysis8.4.1 A modal analysis of the dam was performed and the computed periods of vibration for the first 30 free vibration modes of the dam and respective modal mass participation ratios are shown in Table 17.The mode shapes for the first 6 vibration modes are shown in Figure 27.The computed fundamental vibration frequency of the Layout 4 dam is 3 %smaller than the frequency of the Layout 3 dam.The Layout 4 dam is thinner and was expected to be more flexible than the Layout 3 its smaller radius increases its stiffness resulting in nearly equal vibrationHowever,dam. frequencies for the two configurations. 03/14/14Page49REVIEWCOPY ---Z-ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO veraneAEAt-022 Clean,reliable energy for the next 100 years.CEll Table 17,Frequencies and Modal Mass Participation Ratio Mass prticipation ratio mass participation ratio FREQUENCY |PERIOD Cumulative MODE (hz)(s)Stream Cross Stream Cross ; ar Vertical ae Vertical Direction Stream Direction Stream 1 1.82631 0.54755 4.64E-01 2.06£-04 1.12E-02 0.464 0.000 0.011 2 2.49171 .0.40133 1.96E-04 5.05E-03 |1.53E-04 0.464 0.005 0.011 3 |3.14058 0.31841 |4.15E-02 5.75E-05 2.37E-04|0.505 0.005 0.012 4 3.71290 0.26933 2.49E-01.5.61E-03 3.64E-03 0.754 0.011 0.015 5 3.76679 0.26548 1.80E-02 3.34£-03.7.63E£-04 0.772 0.014 0.016 6 4.22878 0.23647 1.94E-03_7.81£-01 6.49E-03 0.774 0.795 0.022 7 4.40551 0.22699 1.58E-02.2.13E-05 _1,90E-02 0.790 0.795 0.041 8 |4.49801 0.22232 |2.39E-03 8.53E-03.7.27E-01|0.793 0.804 0.769 9 4.89662 0.20422 5.91E-05 1.21£-02.2.14E-03 0.793 0.816 0.771 10 5.05699 0.19775 3.92E-06:4.81E£-05 6.01E-06 0.793 0.816 0.771 11 5.69345 =0.17564 7.63E-03 5.94E-05 6.24E-04 0.800 0.816 0.772 12 5.96243 0.16772 2.29E-03'4.01E-04 1.94E£-04 .0.802 0.816 0.772 13 {|6.13543 =0.16299 5.95E-03 2.34£-02.1.40E-07 0.808 0.840 0.772 14 |6.17244 =:0.16201 8.23E-02 9.30E-04 3.88E-03 0.891 0.841.0.776 15 6.33437 0.15787 4.95E-05 7.23E-05 8.94E-06 0.891 0.841 0.776 16 6.93305 0.14424 1.72E-03 5.19E-06 3.96£-03 0.893 0.841 0.780 17 7.00990 0.14266 2.53E-03 6.62E-04,2.72E-02 0.895 0.842 0.807 18 7.07257 0.14139 1.36E-03 5.52E-05 =1.05E-02)0.896 0.842 0.817 19 7.59786 0.13162 8.23E-07 1.40E-03.2.35E-04;=0.896 0.343,0.818 20 7.69704 =0.12992 1.67E-04 6.42E-05 6.19E-06 0.897 0.843 0.818 21 7.82501 0.12780 3.16E-03.8.64E-05:3.26E-02 0.900 0.843 0.850 22 8.08248 0.12372 5.63E-03 6.96E-09 8.22E-03 0.905 0.843 0.858 23 8.21690 0.12170 5.12E-06 2.71E-04 2.07E-03 0.905 0.843 0.860 24 8.26867 .0.12094 8.72E-05. 1.42E-02:3,17E-05 .0.905 0.858 0.860 25 8.68587 0.11513 2.19E-04 3.43E-05 1.07E-03 0.906 0.858 0.862) 26 |8.98427.0.11131 |2.67E-03 1.846-03 7.93E-05]0.908 0.859 0.862 27 |9.06453 0.11032 |1.74E-02 1.25E-04 3.49E-03)0.926 0.860 0.865 28 9.24927 0.10812 4.56E-04 9.18E-04 5.02E-05 0.926 0.861.0.865 29 9.40572 0.10632 7.21E-04 6.17E-03 2.33E-03 0.927 0.867 0.867 30 9.50533 0.10520 2,.84E-04 3.17E-02 2.26E-03 0.927 0.898 .0.870 REVIEW COPY Page 50 03/14/14 li-_--SS -orii/osaessssssSssssSsSeeSee -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO 1a 408TH ogee Clean,reliable energy for the next 100 years.CEIl Di Noda ow doe :>iia piteahhDenctondbatermenen9:og Proquenny|Mbt hemsCakeConetmateUryamarsine wn min ton um wae Figure 27.First Four Vibration Modal Shapes of theDam Model REVIEW COPY Page 51 03/14/14 -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO |AEA11-022 . 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl 8.4.2 Transient Analysis Results Transient dynamic analyses were performed for eight earthquake records (two earthquakes for each type of event). The envelope of maximum tensile cantilever stress on the upstream and downstream faces of the dam for the IWT010 earthquake are shown in Figure 28 and Figure 29.Figure 30 shows the residual sliding displacement of the dam monoliths at the end of the (Japan 2011),IWTO10 earthquake. A:Transient Structural-no lake oe,max_cantilever::OE;Type:Normal Stress(¥Axis),es : Unit:psi-"A eaeGlobalCoordinateSystem|-.Maximum Over Time 965.33 Max _ 830.79 696.25 -{561.71 427.17 29254815 ig23.551. =110.99 |-245.53 Min BBY Figure 28.Envelope of Maximum Tensile Cantilever Stresses due to IWT010 Earthquake -(in psi,U/S view)(Layout 4) REVIEW COPY Page 52 03/14/14 aTeSTSSEWTSEWy -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 ;13-1405-TM-031414Clean,reliable energy for the next 100 years.CEI -."as " .mee alacant cial sins A:Transient Structural-no lake max_cantilever - Type:Normal Stress(¥Axis) Unit:psi Global Coordinate System -Maximum Over Time 965.33 Max 245,53 Min Sy»*Ae°LearsaTaetwaaaPitremelcoitaly'7Byaan,i 'a . Y }.© :: iI ;a eA Poa 'i : sin SS.'ted iu,bai cise Ath a sail iiivien ai sini'',si hii Figure 29.Envelope of Maximum Tensile Cantilever Stresses due to IWT010 Earthquake -(in psi,D/S view)(Layout 4) REVIEW COPY Page 53 03/14/14 -Z- ALASKA ENERGY AUTHORITY -AEA11-022SUSITNA-WATANA HYDRO saan e022 Clean,reliable energy for the next 100 years.CEIl A:Transient Structural-no lake X Axis -Directional Deformation Type:Directional Deformation(X Axis) Unit:in Global Coordinate System Time:50 3.8025 Max 2.= 1.514 3.27710.94282 0.37088 -0.20105 -0.77299 -1.3449 Min Figure 30.Residual Sliding Displacement of the Dam at the End of IWT010 Earthquake (in inch)(Layout 4) The maximum cantilever stress variations along the height of crown monolith for eight earthquakes are plotted in Figure 31.The maximum computed stresses in the dam body and permanent displacement of dam monoliths due to eight earthquakes are also summarized in Table 19 for comparison. REVIEW COPY Page 54 03/14/14 ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl Slab events -M8.0 -69th Percentile (PGA=0.81) 2100 Cantilever stress at U/S 2100 Cantilever stress at D/S 2000 _"a.|2000 Lalo.ote her?W|1282_..1900 7 ”_.1900 me=1800 roea ae ©1300 a a ©mJ €tv o”2 1700 "on (wet 1700 ry ”iJ§1600 4 hn 7 @ 1600 +of 1500 Cm |pa ©1500 fs (| 6 ns wm |--e--sDM rs a --@--SDM14001400=--B--MYG o-B--MYG1300TT1300T7 -2000 -1500 -1000 -500 0 500 1000 1500 -2000 -1500 -1000 -500 0 500 1000 1500 Stress (psi)Stress (psi) Slab events -M7.5 -84th Percentile (PGA=0.70g) 3100 Cantilever stress at U/S 2100 Cantilever stress D/S a000-ae.|2000 x "ae,|1900 me om 1900 4 a= er ec=]4 -A £\e =1800 [4h WA =1800 *Aa81700+y.ty”8 1700 ae 2 1sc)A 4 Fad s »p bal@1600¥ve 3 1600 +r ul |"1500 a é ™1500 $n ia=-@--IWTOLO Fi «on --@--IWTOLO1400 -E--STTEC 1400 |----STTEC13007,1300 };7 -2000 -1500 -1000 -500 0 500 1000 1500 -2000 -1500 -1000 -500 0 500 1000 1500 Stress (psi)Stress (psi) Crustal events -M7.0 -84th Percentile (PGA=0.49g) Cantilever stress at U/S Cantilever stress at D/S2100ais.2100 pategfetees|20002000a'a a19001-r ._.1900 m4 tEerisaLgI.P,z 1800 a '©7 1800 "h as21700'ot Peal 2 1700 a5 rsJ31600ztrai@1600+[vt )wa1500pery -@--AUL 1500 i» -@--AUL 1400 |48 =<GIL 1400 |o-B--GiL1300tT1300t, -2000 -1500 -1000 -500 0 500 1000 1500 -2000 -1500 -1000 -500 0 S00 1000 1500 Stress (psi)Stress (psi) Interface events -M9.2 -84th Percentile (PGA=0.52g) Cantilever stress at U/S Cantilever stress at D/S2100||2100 2000 a 2000 ;1900 1900 >a '>z <=1800 i hs =1800 tr Fy£1700 "&1700 é r %1600 4 ry @ 1600 4 #iv wa1500alew|--0--cuRl eo,a @ |--@--curi1400=-f-+VALPM 14 |--B--VALPM1300T,1300 +:: -2000 -1500 -1000 -500 0 500 1000 1500 -2000 -1500 -1000 -500 0 500 1000 1500 Stress (psi}Stress (psi) Figure 31.Envelope of Maximum and Minimum Cantilever Stresses in Crown Cantilever for Layout 4 REVIEW COPY Page 55 03/14/14 Za ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO satan022 Clean,reliable energy for the next 100 years,CEll Table 18.Summary of Dam Response to 8 Earthquake Loadings (Layout 4) Arch stress Cantilever Stress Sliding Event Event |Stress (psi)Displacement (in) Title Station |Location Crown SideCompressive|Tensile |Compressive monolith |monoliths Slab events -M8.0 -69th Percentile (PGA=0.81) E|U/S -1278 942 -1830 Salvador SDM 47 6.5 43-Jan-01 D/S -995 1182 -772 Japan U/S -1277 1109 -1549 2011 MYG009 41 77 7-Apr-11 D/S -947 841 -837 Slab events -M7.5 -84th Percentile (PGA=0.70g) El U/S -1008 945 -1692 Salvador |STTEC 2.4 3.3 13-Jan-01 DIS -698 957 -855 Japan U/S -867 886 -1581 2011 IWT010 1.9 2.5 7-Apr-11 DIS -638 772 .-821 Crustal events M7.0 -84th Percentile (PGA=0.49qg) Irpinia,U/S -703 584 -1206 Italy AUL 1 1.5 23-Nov-80 DIS -573 587 -725.9 Loma U/S 801 1091 -998 Colfecia|Gl 14 1.6 18-Oct-89 DIS -634 409 -905 Interface events -M9.2 -84th Percentile (PGA=0.52g) :U/S -877 641 -1181(mes)CURI 27 3.6 .DIS -673 611 -741 :U/S -730 852 -1245(nes)|VALPM 1.6 2.2 ,D/S -615 507 -741 The average stresses and displacements for each of four earthquake events were calculated for dam Layouts 3 and 4 and are shown in Table 19.The average of maximum cantilever stresses on the upstream face of Layout 4 is generally less than similar stresses in dam Layout 3.The maximum tensile cantilever stress of 1366 psi for Layout 3 (slab event,PGA=0.81)is reduced to 1021 psi for REVIEW COPY Page 56 03/14/14 Zz ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO argos 022 Clean,reliable energy for.the next 100 years.CEIl Layout 4.The contribution of the transfer of horizontal stresses is higher in Layout 4 (compared to Layout 3);because of the shorter radius and enhanced thickness of the section at the upper part of the dam discussed earlier,resulting in reduced cantilever action and cantilever tensile stresses.The maximum tensile stress on the downstream face increases from 818 psi in Layout 3 to 1011 psi in Layout 4 (slab event,PGA=0.81g).However it is still below the maximum tensile stresses computed on upstream face of the dam. The average sliding displacement for the Layout 4 in all cases is greater than the sliding displacement of Layout 3,with the increase ranging from about 10%for slab events (PGA=0.81g), and up to 100%for crustal events.Although the sliding displacement is greater for Layout 4,the dam remains stable during the earthquake events and in the post-seismic condition. REVIEW COPY Page 57 03/14/14 -z- SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 years. ALASKA ENERGY AUTHORITY AEA11-022 13-1405-TM-031414 CEll Table 19.Comparison of the Results of Dam Layout 3 and Dam Layout 4 Arch stress Cantilever stress (psi)Sliding eedEventStress Title Location ;Crown SideCompressive|Tensile |Compressive monolith |monoliths Slab events -M8.0 -69th Percentile (PGA=0.81) U/S -1253 1366 -1619 Layout 3 4.0 5.4 DIS -973 818 -914 U/S -1277.5 1025.5 -1689.5 Layout 4 4.4 7.4 D/S -971 1011.5 804.5 Slab events -M7.5 -84th Percentile (PGA=0.70g) U/S -763 1031 -800 Layout 3 1.7 2.6 D/S -659 711 -1338 U/S -937.5 915.5 -1636.5 Layout 4 2.15 2.9 D/S -668 864.5 -838 Crustal events -M7.0 -84th Percentile (PGA=0.49g) UWS -730 1047 -1091 Layout 3 0.5 0.9 D/S -573 460 -770 U/S -752 837.5 -1102 Layout 4 1.0 1.5 D/S -603.5 498 -815.45 Interface events -M9.2 -84th Percentile (PGA=0.52g) U/S -800 759 -1401 Layout 3 1.8 2.3 D/S -629 680 -600 U/S -803.5 746.5 -1213 Layout 4 2.15 2.9 D/S -644 559 -741 8.5 RCC Volume Estimation of the RCC volume in the Layout 4 dam was carried out using the same approach as that An Excel spreadsheet was used to calculate the dam volume using twousedforLayout3. independent methods,by elevation and by station.Adjustments were made to the previous REVIEW COPY Page 58 03/14/14 Za .ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 , 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl spreadsheet to allow the straight and curved portions to be analyzed and for different downstream slopes.The spreadsheet was also refined to include the sloping portion of the upstream face. The spreadsheet accounts for the RCC fill between the dam and powerhouse and also the reduction in RCC volume arising from the penstocks,power intakes,low level outlet intake and pipes,sluice and the spillway crest. The volume of RCC in Susitna-Watana Dam in the updated configuration is as follows: Table 20.RCC Volume (Layout 4) Section RCC Volume (cy) Left Abutment Straight portion 80,970 Curved portion 513,810 Center Curved portion 3,949,590 Downstream fill 125,260 Right Abutment Curved portion 697,010 Straight portion 101,360 Total 5,468,000 As part of the ongoing development,and in preparation for the thermal analysis of the dam,the locations of the vertical construction joints between the abutments and center section have been selected to ensure the projected first season RCC placement volume could be completely placed while the river diversion was progressed and also to ensure that the RCC beneath the spillway crest would be at the required finished elevation to facilitate commencement of construction of the spillway crest at the end of the first RCC placement season.The formed vertical joints will include large shear keys,and are also expected to be grouted at the end of dam construction. REVIEW COPY Page 59 03/14/14 --Z-ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO 13-1405-TM-031444 Clean,reliable energy for the next 100 years,CEll The volume-elevation relationship for the updated configuration is shown graphically below: 2100 teow de ep.2050 if 1500 +aaae 1350 a Li 1 : 0.0 Os 19 15 2.0 25 3.0 35 40 45 5.0 $5 RCC Volume (Million cy) Figure 32,RCC Volume vs.Elevation (Layout 4) The estimated volume of RCC in the previous configuration was 6,420,000 cy.The updated configuration requires 952,000 cy less RCC to construct and thus can be completed one season earlier than Layout 3. 8.6 Sensitivity to Foundation Conditions Following the desk review of the foundation conditions -absent any site verification from a comprehensive site investigation program -the foundation was divided into two zones,each assigned different characteristics.The dynamic analyses performed for Layout 3 and Layout 4 was subject to sensitivity studies based on different characteristics of the foundation.However,the results of only the sensitivity studies of Layout 4 are reported here.Two transient analyses of Layout 4 subjected to IWT010 earthquake loading were performed and stress results are shown in Figure 33 (these results are for Layout 4 before modification to the crest width).In the first sensitivity analysis the deformation modulus of both zones was doubled (E=2Es)and in the second analysis a value of E=0.5E¢was used. The variability between foundation blocks was not subject to sensitivity analyses because the softer area of the foundation does not extend over more than one monolith or two for the size of elements detailed for this model.In further models with greater numbers of elements,this will be investigated. REVIEW COPY Page 60 03/14/14 yw A HYDRO ALASKA ENERGY AUTHORITY SUSITNA-WATAN AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEII Arch stress at U/S Arch stress at D/S2100aoe12100, 2000 vy ws 2000 Ro __1900 ry ¥_1900 ss =1800 RY.*=1800 if§1700 2 5 1300 +Hi 1600 Fey re =4e-E &1600 osteoweax1500a-"t =0.56 1500 |=90.58 1400 :|= -2E 1400 -_-=m -2€ 1300 ++-F 1300 - ?t -F -1500 -1000 =-500 0 500 1000 1500 -1500 -1000 -500 0 500 1000 1500 Stress (psi)Stress (ps!) »100 Cantilever stress at U/S 2100 Cantilever stress at D/S 2000 ae ware SS -q 2000 B-4e4 ait yak1500a)of ox.y-1900 xe efit e YS 2 aX eit=1800 ie a)ra =1800 e)fe”1700 tg --|1700 7 $Re $j ="oF fio 4 safe |[Et onal ai41500;>-a 4 BO --0--0.58 1500p "T Z oe -05E1400us=1400 we wn|eo 2E ||"=-2£1300 }:1300 :}epee -2000 -1500 -1000 -500 ©500 1000 1500 -2000 -1500 -1000 -500 0 500 1000 1500 Stress (psi)Stress (psi) Figure 33.Effect of Foundation Deformation Modulus on Maximum/Minimum Stresses Results of the analyses show that lower deformation modulus of the foundation has negligible effect on the stresses distribution in the dam.However,increasing the deformation modulus of foundation by 100%will increase maximum tensile stresses in the dam around 25 to 30 percent.The magnitude of the deformation modulus of foundation has some effect on the developed stress and requires a precise in situ and laboratory testing of the dam foundation rock to determine rock properties. REVIEW COPY Page 61 03/14/14 -Z-ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO saaang nt 022 Clean,reliable energy for the next 100 years.CEIl 9.DISCUSSION ON STABILITY AND STRUCTURAL PERFORMANCE OF DAM : 9.1 General The results of the analysis presented herein are for the purposes of defining -at feasibility level the proposed configuration of the dam structure.It is an iterative process,and has been organized so that realistic progress can be made in the absence of robust site investigation data,but taking into account the input of external parties such as the Board of Consultants.At this feasibility level of design,the focus has been comparison of various dam geometries rather than an excessively detailed "dive”into structural elements of the dam. The intent has been to arrive at a dam configuration that should maintain the required stability and safety,whilst providing the opportunity for minimization of the RCC volume and thus the shortest construction period. Thus the stability and dynamic analysis has been targeted at realizing the most promising arrangement rather than defining the final detailed geometric solution.Together with the current appreciation of the geological features of the site,the selected dam configuration will define the future site investigation and adit locations -the results from which will allow more accurate and representative analysis to be carried out together with more complete sensitivity analysis. 9.2 Summary It is acknowledged by all that a RCC dam that includes curvature represents the optimum arrangement -utilizing a substantial component of gravity action,but that redistributes stresses horizontally in a manner that enhances stability.RCC is a material that allows easy construction of somewhat complex shapes such as the three centered dam originally postulated as a possible layout. 'Layout 2 was postulated as the most aggressive layout in terms of achieving a safe project while minimizing concrete -and was recognized as one bound of the envelope of possible solutions. Layout 3 -including a gravity section while maintaining a "traditional”gravity cross section with a 0.85 downstream slope is considered to be the most conservative of the options studied,carrying the penalty of one million extra yards of RCC and one year extra construction period.Layout 4 is an attempt to provide a compromise -well within the envelope of safe and reasonable solutions -but with the benefit of the reduction of 920,000 yds?of RCC. In reviewing the results -even though the ongoing site specific seismic hazard analysis and the PMP/PMF studies have been spawning modification to the required dam criteria -it is evident that the 2D stability requirements can be achieved by Layouts 3 and 4 and the FE analysis using REVIEW COPY Page 62 03/14/14 -Z-ALASKA ENERGY AUTHORITYSUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl simplistic assumptions has shown calculated tensile stresses that are above those projected for well mixed and placed RCC.However,these can be brought down to acceptable levels by shaping of the upper part of the dam and confirmed by more refined FE analysis.RCC produced and placed by a competent contractor -even in the arduous conditions in Alaska can be expected to exhibit compressive strength of 6000 psi,and tensile strength in the mix of up to 400 psi.Under seismic loads a tensile strength of 580 psi on the lift joints can be assumed,based on experience at Olivenhain. Based on the static and dynamic analyses presented herein for Layout 4 it is clear that the simple nonlinear analysis,with massless foundation,demonstrates stress values within range of the target figures.Based on the examples and methods discussed below it is considered that more refined analysis will demonstrate values below the maximum values noted above. 9.3 Refining the Finite Element Model and Analysis Approach The main factors that influence the three-dimensional analysis of curved dams have been recently identified by several researchers (Chopra 2008,USBR 2006).The current state of the art in seismic analysis and evaluation of concrete dams is to consider these factors in the numerical simulation,as much as possible,to avoid over-conservative or under-conservative design.More careful modeling of the fluid structure interaction considering the compressibility of the water;and foundation rock inertia and damping are two major factors which are identified as contributing to a more representative and accurate model of the stresses in the structure.According to a series of example analysis it is demonstrated that (Chopra 2008): e By neglecting water compressibility,stresses may be significantly overestimated for some dams or underestimated for others, e By neglecting foundation-rock mass and damping,the stresses may be overestimated by a factor of 2 or 3. In the feasibility review of the various possible configurations water compressibility has been neglected and the foundation has been assumed to be massless -in the interests of speed of analysis. Future analytical development of the selected alternative will include Chopra's recommendations. 9.4 Modeling of Fluid Structure Interaction Water compressibility effect can be considered by performing a Fluid Structure Interaction (FSI) analysis using acoustic elements to model the dam reservoir. REVIEW COPY Page 63 03/14/14 Z ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years,CEIl ANSYS Acoustic elements,fluid30,were used to add the reservoir to the finite element model. However,transient analysis of the model using acoustic elements (Fluid30)and nonlinear elements did not converge.The divergence problem was discussed in detail with ANSYS technical support and it was concluded that the ANSYS Mechanical solver could not solve this FSI problem with the presence of any nonlinearity in the model.In discussion with ANSYS technical support team, Fluid80 element was identified as an appropriate substitute for Fluid30 element.Satisfactory results were obtained by conducting an example benchmark.Subsequently,Fluid80 elements were used for FSI analysis of Susitna-Watana dam Layout 4 and the model is shown in Figure 34.Absorbing boundary conditions were considered at the far end boundary of the reservoir to absorb the outgoing pressure waves in the reservoir.aemiamesVe}faSLCCizyomalt}maaNTeyLhteedicemerFigure 34.Finite Element Model of Dam Layout 4 with Reservoir Using FSI analysis the computed dam sliding are reduced about 50%-100%compared to the similar results from added mass model.The maximum tensile stresses derived from the two analyses appear to be close and it is concluded that the compressibility of the water does not affect the maximum tensile stresses for Susitna-Watana dam although the stress distribution was changed. MWH are performing further investigation on fluid structure interaction analysis results to improve/validate (if required)these results.Effects of size of model and size of the mesh,the REVIEW COPY Page 64 03/14/14 -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEll damping effect of reservoir and boundaries,and using explicit solver are currently under investigation. 9.5 Modeling of Foundation Mass and Damping As previously discussed with the Board of Consultants and FERC in BOC meetings,the single largest reduction in the tensile stresses could well occur as a result of adding mass (damping)to the foundation.This effect is well known in the industry and now that a proposed dam configuration has been selected,MWH is investigating the use of ANSYS software for considering mass of the foundation in the next round of finite element analysis or the use of LS-DYNA.The objective is to identify if the software is capable to consider all the main factors which affect the response of the dam including: 1.Simulating the construction sequences. .Performing thermal-stress analysis. .FSI analysis 2 3 4.Modeling of mass and damping in the foundation 5.Nonlinear contact modeling for contraction joints (geometric non-linearity) 6 .Modeling of concrete cracking (Material non-linearity) The capabilities of ANSYS or LS-DYNA for modeling some of these factors in individual models are demonstrated by software developers.However,combining all of these factors in a model for transient analysis of the arch dam would be applied carefully and verified by performing some simple bench mark examples.Along with the progressive improvement of dam layout,more advanced modeling and analysis features will be implemented to the finite element model. 9.6 Element Size and Non-Linearity Moderate sizes of elements were used to mesh the finite element model of the dam.However this mesh will be refined at the area of high tensile stresses,especially at the top part of the dam,to capture a more representative stress distribution at this area.It is anticipated that by improving the finite element model and analysis approach,as explained above,the high tensile stresses in the dam body will be reduced. If tensile overstressing still occurs in the dam body,the size of the overstressed area as well as the number of excursion above the threshold stress value and the size of each excursion would be investigated.If the results show an acceptable level of damage in the dam body no further analysis would be required.Otherwise,further analysis to model concrete cracking in the dam body REVIEW COPY Page 65 03/14/14 -Z-ALASKA ENERGY AUTHORITY ITNA-WATANA HYDRO AEA11-022SUS13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEll (material non-linearity)in addition to the contraction joints nonlinearity (geometric nonlinearity) would be required. 9.7 Inclusion of Thermal Modeling Results Thermal analysis of the dam is currently underway to determine the temperature field in the dam body based on the construction sequence shown in the Appendix.This analysis should determine the thermally induced stresses and possible cracking in the dam body.Results of thermal stress analysis of the dam body will be used to finalize the location of the contractions joints in the structural model.The computed thermal stresses will also be superimposed with the static and dynamic stresses computed by the finite element method.The results of the thermal stress analysis would be investigated closely to determine the effect of the mass concrete cooling on the contact forces between the dam monoliths.In the case of any significant reduction in the contact forces between the dam monoliths,non-linear response of dam monoliths may be affected.The temperature variations of the dam body would be considered in nonlinear transient analysis of the dam. REVIEW COPY Page 66 03/14/14 ---Z-ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO parang 022 Clean,reliable energy for the next 100 years.CEIl 10.TYPICAL EXAMPLES OF PERFORMANCE OF EXISTING DAMS, WORLDWIDE 10.1.Introduction While analysis of structural models of concrete dams are a vital tool in the design process,at the feasibility stage -of necessity -the elements of the FE model are very large,and engineers must be careful in translating individual stress output in each element to definitive drivers for large geometrical adjustments to the cross section. In essence,curved gravity dams do not usually show signs of high tensile stresses,and stress paths usually re-orient to take advantage of the horizontal transfer of load due to the "arching”action of the curved layout.For comparison to the proposed Susitna-Watana Dam,the MWH team has selected five prominent curved gravity or thick arch dams that have been designed and constructed using either CVC or RCC in highly seismic regions.Some are also in cold regions and some are located in wide valleys.All have elements of design and/or locales related to the Susitna-Watana Dam and represent precedent prototype dam structures comparisons. Each of the five dams is described below,followed by a proportionally normalized comparison (to Susitna-Watana)of the five dam geometric profiles.As indicated by the comparison,the normalized relative height of the dams and shape of the wide valleys in which they are located indicates that based on previous experience,a curved gravity dam is appropriate to the shape of the Susitna River valley at the selected dam location. 10.2 Sayano-Shushenskaya Dam The Sayano-Shushenskaya Dam as shown in Figure 34 is located on the Yenisei River,near Sayanogorsk in Khakassia,Russia.It impounds the reservoir for the largest power plant in Russia and the sixth-largest hydroelectric plant in the world (4,500 MW). The arch-gravity dam is 794 feet high with a crest length of 3,497 feet (crest to height ratio of 4.4:1.0)and a crest width of 82 feet,and a base width of 347 feet,(approximating an average downstream slope of 0.43H:1V).Similar to the proposed Susitna-Watana structure,the dam has four parts -a left-bank dam 807ft long,a section 1,089ft long,including penstocks,a spillway section 622 feet long and a right-bank dam 979 feet long.The radius of the axis is 1,968 feet. Water loading of the structure is quoted as approximately 30 million tons,with 60%load taken through the gravity action and 40%through the "arch”action. REVIEW COPY Page 67 03/14/14 -2-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl The dam is designed to withstand seismic events up to Magnitude 8.0.Similar to Susitna-Watana,it is among the highest concrete dams in the world,is located in a wide valley in a very cold region that is subject to high seismic activity,and is quite slender (slenderness ratio of 0.1033:1.0).It was constructed starting in 1961 and became operational in 1978.The average temperature at the project site in January is -27.0 °C (-16.6 °F)with the record low temperature more than double that. 'ana,*+'4. ene3pegs-S westereo:me, ane uswas :BD eas ee Po een efoe 4eSTS4gpahrseaateeitSerenenn -4 ee atBieOete "4 fi ad oe Ag aed : SER CT ie ATa)ties A way - : :a edeesCkTP Figure 35.Sayane-Shushenskaya Dam 10.3 Portugués Dam The Portugués Dam as shown in Figure 35 is a RCC single centered thick arch dam on the Portugués River,three miles northwest of the city Ponce,in Puerto Rico.Construction of the dam began in April 2008 and was finished in 2013.The dam is 220 feet high and has a crest length of 1,230 feet, with an axis radius (Raxis)of 825 feet.It is 110 feet thick at its base and 35 feet thick at its crest and a downstream slope starting from the downstream edge of the crest of 0.36H:1V (an effective downstream slope of 0.50:1.0 from the traditional intersection of the upstream edge of the crest). The dam has an uncontrolled spillway center-left side,over the river bed.The center of the dam straddles an intake and outlet structure REVIEW COPY Page 68 03/14/14 -Z-ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO 43-1405-1M031414 Clean,reliable energy for the next 100 years.CEIl The dam is located very near to the Muertos Trough subduction zone along the southern edge of the island of Puerto Rico and has been designed for a MCE of M8.25 at 19.6 km and a PGA of 0.38g. This is a modern day example of a RCC thick arch dam designed for and constructed in a wide valley with a crest length to height ratio of 5.6:1.0 in an active seismogenic zone. x Tatty wigs.eei'3 @ CwFs Figure 36.Completed Portugués RCC Thick Arch Dam REVIEW COPY Page 69 03/14/14 -Z-ALASKA ENERGY AUTHORITY .AEA11-022SUSITNA-WATANA HYDRO tans e022 Clean,reliable energy for the next 100 years.CEIl 10.4 Shapai Dam Shapai Dam as shown in Figure 37 is the first roller-compacted concrete (RCC)dam shaken by a major earthquake,M 8.0.The dam located in Sichuan Province,China is a 433-ft (132-m)high RCC three-centered arch dam with a crest width of 31 feet (9.5-m)and the bottom width is 91 feet (28-m)yielding a slenderness ratio of 0.072 (crest thickness to height).The crest length is 784 feet (239.0-m).The dam includes two formed joints and two induced joints. Completed in 2003,it is located 20 miles (32 km)from the Wenchuan earthquake that occurred on May 12,2008.The PHGA at the site was estimated to be about 0.25 to 0.50 g compared to the design acceleration of 0.1375 g.With a nearly full reservoir,420-ft (128-m)deep,at the time of the earthquake,the dam was undamaged,but the grouting and drainage galleries were flooded due to rockfall blocking the outlets.*eg> 7 , q aeas,é :r anv .oy"a af 7a"gt 4.ey oe 5 ereanens i *} 'op: aot of ee y ;x Sie Ei 'ae P cans.Yet 7 O's, ereseee4°4eran4ef ©xg,A led as Figure 37.Shapai RCC ARCH Dam,China The dam survived a major seismic event (Wenchuan,May 12,2008,M8.0)without significant damage to the structure even though the structure is only 22.5 miles from the epicenter and 20 miles from the rupture;At the time of the earthquake,the reservoir was full,but was emptied for REVIEW COPY Page 70 03/14/14 Zz ALASKA ENERGY AUTHORITY -WATANA HYDRO AEA11-022SUSITNA13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEII inspection of the dam soon after.No cracks in the face were observed and the abutments remained stable.The foundation did not exhibit any significant change in seepage. The project was dynamically analyzed for 0.4g.after the event.It was of great interest to the engineering community that Shapai performed so well in the earthquake,and linear analysis with massless foundation was immediately performed which indicated that the dam body experienced high maximum tensile horizontal stresses of up to 4 Mpa (580 psi)on the upstream face -which exceed the projected tensile stresses of the concrete. Much as Chopra has highlighted,the linear model with a massless foundation appears to be unrepresentative of the actual conditions.If it were representative,severe cracking would have been evident in the dam body. The dam was then reanalyzed using the same response spectra,but non linearity was introduced with consideration given to joint openings,and a viscous spring boundary input model was introduced to simulate damping. The results are shown in Figure 38 showing the linear results on the left and the non-linear,damped results on the right: REVIEW COPY Page 71 03/14/14 Ze .ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO 431405 022 CEIlClean,reliable energy for the next 100 years, =WO) (IV)Tensile cantilever stress on the downstream dam surface Figure 38.Contours of the Maximum Tensile Stress (MPa)on Shapai Dam Surface under the Field Records of 0.4 g (a)Linear,Massless Foundation;(b)Joint opening,Viscous-Spring Boundary REVIEW COPY Page 72 03/14/14 Za ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl For the nonlinear case including damping,the maximum tensile stresses are greatly reduced to below the design tensile strength of RCC,compared to the linear model -strongly supporting a nonlinear analysis with foundation mass.Horizontal stresses are almost completely released by the joint opening and damping. The actual performance of Shapai clearly supports Chopra's contention,and suggests that for Susitna-Watana,the future analysis with foundation mass will likely indicate stress levels within acceptable limits. 10.5 Pacoima Dam Pacoima Dam,shown in Figure 39,was completed in 1928 and is a variable radius concrete arch dam on Pacoima Creek in the San Gabriel Mountains,in Los Angeles County.It is of interest because it has been shaken by two major earthquakes,the 9 February 1971 San Fernando Earthquake of M 6.6 and then the 17 January 1994 Northridge Earthquake of M 6.8.The dam is 372 ft.high and 640 ft.long and performance has been well described in technical articles by Hansen- Roehm.At that time a number of engineers questioned the validity of the peak accelerations recorded by accelerometers located 52 ft.above the dam crest on the left abutment,but these have subsequently been confirmed. Figure 39.Pacoima Dam REVIEW COPY Page 73 03/14/14 Ze .ALASKA ENERGY AUTHORITY -YD AEA11-022SUSITNA-WATANA HYDRO ©setae 022 Clean,reliable energy for the next 100 years.CEll Since the 1971 seismic event,an extensive seismic instrumentation system was installed and the upper rock mass of the left abutment was secured to more competent rock below through the use of 35 rock anchors. The epicenter of the 1994 Northridge Earthquake was 11.4 miles southwest of the dam at a focal depth of 10.5 miles.Strong motion records indicated a peak horizontal ground acceleration of 0.53 g at the base of the dam.The acceleration records from the instrument at the upper left abutment measured a peak acceleration of 1.58 g due to the topographic amplification in the canyon.Peak accelerations of greater than 2.3 g horizontal were recorded at the dam crest. Despite being subjected to high accelerations,the dam survived the event well with the main damage being an opening of the contraction joint between the dam and the thrust block at the left abutment of approximately 2 inches.The downward movement observed of about 0.5 inches indicates that the thrust block and underlying rock mass may have moved away from the dam.The water level at the time of the 1994 earthquake was approximately two-thirds the maximum height of the dam and 13.5ft higher than the reservoir level during the 1971 earthquake. Mojtahedi and Fenves (1995)studied the response of Pacoima Dam using recorded ground motions obtained at the dam site.The analyses indicated opening-closing of contraction and horizontal joints and non-uniform seismic input.A reasonable agreement was obtained between the accelerations recorded on the dam body and the computed accelerations.Pacoima Dam is an example of the very high accelerations due to earthquake that a concrete dam can and has withstood. 10.6 Shasta Dam Shasta Dam,shown in Figure 40,is a curved gravity dam with a radius of 2800 feet,located on the Sacramento River near Summit City,California. REVIEW COPY Page 74 03/14/14 -Z-ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 CEIllClean,reliable energy for the next 100 years. Figure 40.Shasta Dam The dam was constructed in 1945,is 602 feet high and has a crest length of 3460 feet.It is 543 feet thick at its base and 30 feet thick at its crest,and was constructed in monoliths of conventional concrete.The dam has an overflow spillway at its center and a power plant on the right bank.The dam is an example of a curved gravity structure with geometry very similar to that proposed for Susitna-Watana -located in an area of high seismic activity and an even wider valley.Several fault zones are located near the dam,the nearest of which is the Battle Creek Fault Zone located approximately 27 miles south of the dam and capable of producing a M7.3 event. 10.7 Normalized Comparison The following figure shows a proportionally normalized comparison of the geometric profiles for the five dams described above,compared to Susitna-Watana (Figure 41).As indicated by the comparison,the normalized relative height of the dams and shape of the wide valleys in which they are located indicates that a curved gravity or arch-gravity dam is appropriate to the shape of the Susitna River valley at the selected dam location. REVIEW COPY Page 75 03/14/14 --Z.ALASKA ENERGY AUTHORITY AEA11-022SUSITNA-WATANA HYDRO 13-1405-TM-031414 CEIClean,reliable energy for the next 100 years. SHAPALROGARCHDAM)eres SHASTA (CURVED GRAVITY DAM} PACOIMA(TRUE ARCH DAM)PORTUGUERE(ROG THICK ARGH DAM)ereereemere -BAYANO SHUSHENSKAYA(CURVED GRAVITY DAM) --e WATAMA RCC [RCC CURVED GRAVITY DAM) -TOPOFDAM Figure 41.Normalized Comparison of Dam Profiles 03/14/14REVIEWCOPYPage76 Zz ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 . 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEIl 11.CONCLUSIONS AND RECOMMENDATIONS The development of the dam configuration and layout has been performed in the absence of robust site investigation data focused on the dam foundation,so it is evident that much evaluation and optimization remains to be undertaken.However the 2D and simple 3D analysis recorded in this memorandum has been useful to indicate the viability of the layouts proposed. The crux of the recent analysis had been to illuminate the differences in performance of the two later layouts (3 and 4)-a single centered simple curved gravity dam with a traditional downstream slope of 0.85 H:1 V and a curved dam with slightly smaller radius,but with straight gravity sections at the high abutments. Comparison of the 2D analysis shows that -assuming zero cohesion at the base -Layout 3 performed in accordance with FERC criteria,but could suffer a cracked base at higher ground motions.For Layout 4 -also assuming zero cohesion at the dam base -the simplified analysis showed the dam satisfied FERC stability criteria for the normal static,flood and post-seismic conditions with a cracked base.The resultant location for Layout 4,for all forces under the post- seismic cracked condition,fell within the dam base. With respect to the results of the nonlinear analysis using a massless foundation,the results for Layout 3 and Layout 4 were similar,with all compressive stresses within the limits of expected RCC design strengths.With regard to tensile cantilever stresses,Layout 4 exhibited a better response compared to Layout 3.The maximum tensile stress on the upstream face of the dam is reduced from 1366 psi in Layout 3 to 1025 psi in Layout 4 (slab event,PGA=0.81)and the average reduction in upstream cantilever stresses is around 15%for all earthquake events.Although the computed tensile stresses on the downstream face of Layout 4 are slightly higher than the similar stresses in Layout 3, the maximum developed tensile stress on the downstream face is still smaller than the maximum tensile stress on the upstream face.Sliding displacements predicted for each layout can be managed through design -generally being under 2 inches for the crown monolith,but sometimes over 4 inches for the side monoliths. The current state of art as recorded by Chopra -and demonstrated by the analysis of Shapai Dam after the Wenchuan earthquake -indicates that when a more detailed analysis of the recommended configuration is performed,using smaller elements,more closely spaced contraction joints and a foundation with mass (together with the resulting damping),displacements and tensile stresses will likely be below the design stresses for RCC lift joints (as suggested for extreme conditions). REVIEW COPY Page 77 03/14/14 a .ALASKA ENERGY AUTHORITY ;AEA11-022SUSITNA-WATANA HYDRO 43-1405-TM-031414 Clean,reliable energy for the next 100 years.CEll Sensitivity runs using different foundation characteristics for the massless foundation case indicate that the performance of the dam will not be compromised. For the sole purpose of finalizing the draft feasibility report -though in the absence of focused site investigation and field examination of geological features -it is proposed to use Layout 4 (Raxis = 2600 feet,downstream slope of 0.7H:1V,with straight gravity end blocks)as the chosen layout. Before completion of the feasibility report,an analysis using foundation mass will be performed to verify the performance assumptions drawn from the studies so far. REVIEW COPY Page 78 03/14/14 Z ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO AEA11-022 13-1405-TM-031414 Clean,reliable energy for the next 100 years.CEII 12.NEXT STEPS The most important next steps to finalize the dam configuration and cross sections are listed below. Some of the tasks will be performed before submission of the draft feasibility report but others must wait until access to the project site has been granted. Finalize the seismic hazard analysis and obtain concurrence for the selected seismic design criteria; Finalize the thermal analysis of the dam at all stages of construction and operation; Include the results of the thermal analysis in the structural analysis -with suitable sensitivity studies; Improve the finite element model by considering mass and damping of the foundation and using the explicit solution method; Revisit the wedge analysis of the abutments after the updated,more thorough characterization of the foundations; Revisit the individual seismic analyses of detailed structures such as the spillway piers following the overall analysis of the dam and the updating of the seismic design criteria; Increase seismic design loads and analyze the dam structure to establish fragility of various critical parts of the structure. Perform the required site investigations (drill holes;adits;seismic refraction survey etc.)on the dam foundation and dam environs; Perform in situ and laboratory testing of the dam foundation rock;and, Characterize the dam foundations and verify and delineate the geological features in the foundation. REVIEW COPY Page 79 03/14/14 Appendix A Drawings Vs a Cpag, |°oO6©bas2z3biZé5Wwgoazbe iye525ere$3$3a [e)4QO:>:=8iZiBee<8Ba<3Zz*Ee&§nn”=)"aSS:fe) fomEQDE5Mst efs <> 6SeoewiLg<<eu*s00N< ragirealze8et| Ose a) 55s2 S| PEESy m|F SESSulBeg&O15 32883|on5e2b1Oges.Ww oSOlk2aez 0223 ro) 2508is)ga.geBsar |ga)#le2)§|Z|&|3=|S|<|<|oZig 8Beetesas- g2, 0 Ques 2 lease a" [gage = [Eezs ) weetw 77]gf2&a AyaYama' DESCRIPTIONREV ift?hi BRIDGE PERMANENT |N 3228400 ps w -POWERHOUSE. WyRDAM_- _s9 PSTREAM OFFE A STOCKSN: jQUS (REMOVED AFTER CONSTRUCTION OF \\\ANAS 04-01C001 SHEET OF SITE PLAN JA.WATANA HYDROELECTRIC PROJECT (LAYOUT 3) SUSITN. -WATANA HYDROSUSITNAALASKA @@---ENERGY AUTHORITY «= =_ STATE OF ALASKA ALASKA ENERGY AUTHORITY Clean,reliable energy for the next 100 years,/@)mwu. YN, {S$CONSI STRUCTURE | "DO NORRELEASE- HEN IN "THIS DOG ENERGY. a RITICALrs im”and not suitable for"interi NOT FOR CONSTRUCTION CONCEPTUAL DESIGN PHASE This document is designated construction.As an interim document,it may contain datathatisincompleteordefineandlocatestructuresthatremain te be optimized. 10500200 12/31/2013 Designed__A HUGHES AFRISK Project No. Drawn A B SADDENroved 1 WARNING 0 % IF THIS BAR DOES NOT MEASURE 1° THEN DRAWING IS NOT TO SCALE ANSID FULL SIZEDATEBY ROCK CONTOURS DIGITIZED FROM 1980 INFORMATION/ TOPO BASED ON MATSU-NORTH BARE EARTH DATA DESCRIPTIONREV :2052Se"2065 eyi :mC) SAN :No YS CENTERED =<aay (LAYOUT#2) ae see'2080+wey "2,,_|(LAYOUT#4)|.2600 RADIUS | . THIS DOCUMENT IS CONSIDERED CElI CRITICAL ENERGY INFRASTRUCTURE INFORMATION -DO NOT RELEASE- \3500 RADIUS2(LAYOUT #3) =MPPL EL 1850--a ane y s - YT .E4887500LEGEND 3 CENTERED (LAYOUT #2) 3500 RADIUSeen(LAYOUT #3) 2 WV are SCALE WARNING Project No,10500200_|CONCEPTUAL DESIGN PHASE STATE OF ALASKA SUSITNA-WATANA HYDROELECTRIC PROJECT Sheet No. vm 0 %1°Ioote 03/07/2014 NOT FOR CONSTRUCTION ALASKA ENERGY AUTHORITY -Z-.DAM1"=200 bed -ROGK CONTOURS DIGITIZED FROM 1980 INFORMATION f IF THIS BAR DOES -|Designed__A HUGHES _|This document is designated "interim”and not suitable for Vi WwW H ®«=>ALASKA SUSITNA-WATANA HYDRO PLAN DEVELOPMENT 04-01C002PD TOPO BASED ON MATSU-NORTH BARE EARTH DATA NOT MEASURE 1°|awn AFRISK construction.As an interim document,it may contain data «=-_ ANSI D THEN DRAWING IS -_-that is incomplete or define and locate structures that remain @@-ENERGY AUTHORITY Clean,reliable energy for the next 100 yeors,REV DESCRIPTION BY DATE FULL SIZE NOT TO SCALE Approved B SADDEN t0 be optimized.SHEET OF MOL EL 2050 Sheet No. OF -01C00204 SHEET SUSITNA-WATANA HYDROELECTRIC PROJECT DAM PLAN (LAYOUT4) STATE OF ALASKA ALASKA ENERGY AUTHORITY SUSITNA-WATANA HYDRO Clean,reliable energy for the next 100 yeors. =>ALASKA =x ENERGY AUTHORITY/@)mwu. THiS DOCUMENT !S CONSIDERED CEII CRITICAL ENERGY INFRASTRUCTURE INFORMATION -DO NOT RELEASE- CONCEPTUAL DESIGN PHASE "and not sultable for ,tt may contain data ctures that remain NOT FOR CONSTRUCTION to be optimized. This document is designated "interim'construction.As an interim document, that is incomplete or define and locate stru 410500200 03/07/2014 Project No. A HUGHES AFRISK B SADDEN Date Designed Drawn Approved WARNING % IF THIS BAR DOES NOT MEASURE 1* THEN DRAWING 1S NOT TO SCALE SCALE 1"=200° ANSI D FULL SIZEDATEBYDESCRIPTION ROCK CONTOURS DIGITIZED FROM 1880 INFORMATION/ TOPO BASED ON MATSU-NORTH BARE EARTH DATA REV POWERHOUSE OMITTED FOR CLARITY THIS DOCUMENT 'S CONSIDERED CEIl NAD83ASPZ4FT CRITICAL ENERGY INFRASTRUCTURE INFORMATION -DO NOT RELEASE- SCALE wane Project No.10500200 CONCEPTUAL DESIGN PHASE STATE OF OAUTHO SUSITNA-WATANA HYDROELECTRIC PROJECT Sheet No. - 9 2 3 3/7/2014 ALASKA ENERGY AUTHORITYTee}Date ---_Sen NOT FOR CONSTRUCTION -z-_-_DRAF-IF THIS BAR DOES__|Designed MAKSIM S.This document is designated "interim”and not suitable for Ni W H &Le)DAM 04-0 1C001 -NOT MEASURE 1"|MAKSIMS.construction.As an interim document,it may contain data ,=-_SUSITNA-WATANA HYDRO ISOMETRIC ANSID THEN DRAWING IS rawn ee that is incomplete or define and locate structures that remain av DESCRIPTION ey |oate |NSO.NOTTOSCALE VApproved to be optimized.@-_ENERGY AUTHORITY Clean,reliable energy for the next 100 years.SHEET oF SOUTH LOOKING DOWNSTREAM NORTH (LEFT ABUTMENT)(RIGHT ABUTMENT) EXISTING GROUND 2150 a a 2150MBO-LOW LEVEL i:ce ee be ae ee ee ee Té outteT \-CONSTRUCTION JOINT -TOWER (aNO)INTAKES CONSTRUCTION JOINT :>SPILLWAY S|:: 2100 a rs y eb (2NO)°.a Des te fone .' ee Po,soe vs pee "|won ee :Boe ee ::7.woe 7 T 12100. 2050 | :SZNMOL,EL 2050 TTT L050 2000 2000 a ELEVATOR1950 H950 1900 --:1900 1850)-- - Zz SZMPPL,EL 1850 -1850 WBO eeeeeeee Koes L g00 ::nN GALLERY VIS ees NS H750 ::2 oN.WO ee eee ONS {1700 GROUTING AND *< |a DRAINAGE ADITS "|[1650 b ! We 4600 be ee bee ee |::600 i 4 Zz wa!TT --(COYS:fo eee51950 H550 a IEe1500)a D/P 1500 rf ::1 x : -1450 --5--Ce ce ee .a a ee 450iu::J DIVERSION TUNNEL 1400 i NTT PO LG Pr ner Gof 400 1350)a 7 GIRUUTING ANY UINAINASE fo BEen n350 :.GALLER' 4300 --bee Se ee be wba ee!ee Fe De H300V25Oee"/ee 12501200BNa/a 1200 WSO Qeee ae J.A 1150 WOO 2 ee fo ee 1100 OS INte bane foow..rn a HO50 1000 --:----:-DDTBRee A Ce De ee Hooo :a : QS ™a /.Se an 950 90!T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T T 900 -0+500+00 1+00 2+00 3+00 4+00 5+00 6+00 7+00 8+00 9+00 10+00 11400 12+00 13+00 14+00 15+00 16+00 17+00 18+00 19+00 20+00 21+00 22+00 23+00 24+00 25+00 26+00 27+00 28+00 29+00 30+00 30+65 STATIONING PROFILE [a ]SCALE:1"=120'04-01C002 DETAIL SHOWN IS OF PLAN VIEW FOR CLARITY 0 420 240 ee ee|DETAIL (1 SCALE:1"=60'- 0 60 120 el THIS DOCUMENT {S CONSIDERED CElI CRITICAL ENERGY INFRASTRUCTURE INFORMATIONNAD83ASPZ4FT-DO NOT RELEASE- )=SCALE WARNING Project No.10500200_|CONCEPTUAL DESIGN PHASE STATE OF ALASKA SUSITNA-WATANA HYDROELECTRIC PROJECT Sheet No.=_a AX 0 &1 03/07/2014 ENERGY AUTHORITYXENasworen|bee JO NOT FOR CONSTRUCTION ALASKA GY Zz DAM ROCK CONTOURS DIGITIZED FROM 1980 INFORMATION/IF THISBARDOES [Designed __AHUGHES |This documentis designated "interim”and not suitable for Ni W H ®=KA SUSITNA-WATANA HYDRO PROFILE A 04-01C004 TOPO BASED ON MATSU-NORTH BARE EARTH DATA NOT MEASURE 1”J,AFRISK construction.As an interim document,it may contain data «=_ ANSID THEN DRAWING IS oH that is incomplete or define and locate structures that remain @&_>ENERGY AUTHORITY Clean,reliable energy for the next 100 years.REV DESCRIPTION sy |DATE|FULL SIZE NOTTOSCALE |Approved _B SADDEN_|i SHEET oF 210 2100 :EL 2065 oso]EE 2050 SZ PPI ee ee ee ter tert dies eee er ce ecisnteniseerentigess ..boso Oeelo|anneene seerees epeeses Ded 6100 ||eceecececeereee ae cress esses (2000 2101 2100 :: NMOL EL 2065 1950]ewreeneecneee cess My oeecetdeerecteeesens BeinnSEE f oteseenesnseesesensnae osc ceecechanreseneeeenFeneenenecntsenscenseentcy bocce haso n0s0|----EL 2050 oe as ee L080 1Q00 -----neneene ete fesse PP APP Seen ee ieee eter ete Bene SEES EEE ETE Oe :Pete eed eee n eee tee h900 2000 cevteserneeeteeees cece lunes -.ba00 MINIMUM POWER :GALLERY POOL LEVEL : -(TYP) EL1850 <7 :. :N 1850 -- = --(1850 1Q5O)----e eee ee bette h950 TBO)vnc recneeee rect ee tees --1800 1900)-Leteteenees ep kh QE EL a.beeeneetects bee h900 once enour Guero eg AV NO : CONSOLIDATION:(TYP)roteBE DETERMINED)HI \GROUTING : 1750)ne enero ee OK SD EEA eee Qe RQ tr ESTEE Gs (1750 1B5O)----eee bec eee f.see fou bocce decceeee crettecteteeteesetes --B50"if:'DRAINS : ::(ORIENTATION OF DRAINS :If ::TO BE DETERMINED) YTOO)wnenee ene PETE TE Ts Tah TER PRET NT a Ag ee aie tale Tay Qn es QQ erentcnsebsestcresssaegeressesessaieses --{1700 T1010 rs beveeeeresveeeee ii eee aOnebebe cc cece cee eect nett ees even ee 1800 1650)rene eee ed ees fe een eee et ee bee cts ee Leer eee ete "ere 1650 De eee /beteteeee ree Sere ae ete tease aeteeteeeees bo -1750 1600)renee tee ee eee p Sets rh bake are er a cere reese eceer gr naraneers SM es RQ oso bi sec ee screens n cesses seas esseses --1600 41700 ceneeeeenenet mes wee be cee eb eee eeae cet eesens \a ee ae 1700 i \ 1550 Porcteeressetessssrtes --1550 1651 L650 POWERHOUSE;STRAIGHT GRAVITY PORTION NOT SHOWN FOR CLARITY :: 500 ECTION1500)-beveceeteeee ed Ya eRe ESET SCALE:1"=60':ESTIMATED ROCK SURFACE 04-01C002Et1475: 1450 erat ans CE ae Real ecg Og COE ERT LEED LT AC SPOE ITED E CETTE CE TONEY DuVCECESECT DD,WORE EEEEEEE ES TEEETETEOESTETLO NOSES TEESESSOSEESSOCSOOSSSIO .h4s0 1400 : Ba --1350 :\CONSOLIDATIONGROUTINGAND-GR'ROUTI NGDRAINAGEGALLERY:if \:HI \:DRAINS:ff (ORIENTATION OF DRAINS : (TO BE DETERMINED)1250)ovevecnrnen cece Mees \"coca ceebtegee bec eeeeeccdoveeettecbetctettetcateehostcerstessctveetreeerenes boo vee e deve cca ates donvuteceeeecapeseettennea ;.250 1200]reece eee wf -h200 4180)eseeeeeree \Grout CURTAIN fl150 ORIENTATION OF HOLESOBEDETERMINED) 110 H100 CENTRAL CURVED PORTION TB |0 60 120 aSCALE:1"=60'04-01C002 a THIS DOCUMENT IS CONSIDERED CEIl CRITICAL ENERGY INFRASTRUCTURE INFORMATION NAD83ASPZ4FT -DO NOT RELEASE- \-SCALE WARNING Project No._19500200_|CONCEPTUAL DESIGN PHASE STATE OF ALASKA R SUSITNA-WATANA HYDROELECTRIC PROJECT Sheat No. 0 1 03/07/2014 ALASKA ENERGY ITY --zw-SRA asnoreo ree iAMUGHES|rua goamtlO1OR CONSTRUCTION ©MWH.|ge al acic DAM 04-01C003ROCKCONTOURSDIGITIZEDFROM1980INFORMATION/IF THIS BAR DOES igned__A reir?|is document is designated "interim”and not suitable for ®ALASKA - - TOPO BASED ON MATSU-NORTH BARE EARTH DATA NOT MEASURE 1°orawn ©SHOYMERMAN construction.As an interim document,it may contain data =-SUSITNA-WATANA HYDRO TYPICAL SECTIONS ANSI D THEN DRAWING IS oY that is incomplete or define and locate structures that remain @&->ENERGY AUTHORITY Clean,reliable energy for the next 100 years, REV DESCRIPTION BY |DATE]FULL SIZE NOT TO SCALE Approved ___B SADDEN |to be optimized.SHEET oF PRECAST CONCRETE - 4 ROW GROUT CURTAIN {EXACT ORIENTATION TO BE DETERMINED) -DRAINS {EXACT ORIENTATION _..TO BE DETERMINED) CONSOLIDATION GROUTING DETAIL.[2|SCALE:1"=5'04-01C003[ee GROUTING AND DRAINAGE GALLERY IN RCC THIS DOCUMENT IS CONSIDERED CEII CRITICAL ENERGY INFRASTRUCTURE INFORMATION ROCK ANCHORS (TYP) 1 ROW GROUT CURTAIN (EXACT ORIENTATION TO BE DETERMINED)Wie]LEcvc DRAINS (EXACT ORIENTATION TO BE DETERMINED) SECTION [A|SCALE:7"=5'04-01C004|ee GROUTING AND DRAINAGE ADIT IN ROCK NAD83ASPZ4FT -DO NOT RELEASE- ED /\SCALE WARNING Project No,10500200_CONCEPTUAL DESIGN PHASE STATE OF ALASKA SUSITNA-WATANA HYDROELECTRIC PROJECT Sheet No. -J iNT NX 18 ee le ae NOT FOR CONSTRUCTION ©)MWH ALASIA ENERGY AUTHORITY Zz DAM TOPO BASED ON MATSU NORTH BARE EARTHOATA™To eS ere cRNA Conetucton,As annem documert,may contin dats ®«=>ALASKA _SUSITNA-WATANA HYDRO GALLERY 04-01C005 REV DESCRIPTION BY |DATE FOUL SIZE THOTT SCALE Approved __8 SADDEN|thats incompite or joeotmeed 'hat remain @™&_ENERGY AUTHORITY Ctean,retiable energy for the next 100 years,TYPICAL DETAILS sueer oF NMOL EL 2050 SZ2050 . 2000 re ans cee Sees hae |CONCRETE ---_| 1950 --""5 GROUT ENRICHED RCC GROUTINGANDDRAINAGEGALLERY 4900 rr eee eee eee MINIMUMPOWER = >1959 -POOLLEVELEL 1850-7, ORIENTATION OF GROUT HOLES AND DRAINS TO BE DETERMINED GATE IN FULLY RAISED POSITION 64'HX 44'WRADIALGATE EL 2065 PIER G SPILLWAY .i 164" EXISTING GROUND 1650 . | J fem So cessssssstseasseseee . 1600... a ASSUMED EXISTING ROCK SURFACE ooo oaa(e)m bee ee viene {1d}. ROCK ANCHOR (TYP)Hi ELEVATION SCALE:1”=30° ASSUMED EXISTING ROCK SURFACE SECTION 'B ieSCALE:1"=50°94-03S001,04-010002Celt 0 50 100 a cs| THIS DOCUMENT IS CONSIDERED CEll CRITICAL ENERGY INFRASTRUCTURE INFORMATIONNAD83ASPZ4FT-DO NOT RELEASE- DHPAL 1.SCALE WARNING Project No._10500200 CONCEPTUAL DESIGN PHASE STATE OF ALASKA SUSITNA-WATANA HYDROELECTRIC PROJECT Sheet No.yA'o %1 ALASKA ENERGY AUTHORITY -zZXENasnoreo|Smmeeend [Oe -Sneroit NOT FOR CONSTRUCTION MWH «>as 04-03S002ROCKCONTOURSDIGITIZEDFROM1980INFORMATION/IF THISBAR DOES |Designed__AHUGHES_|This document is designated "interim”and not suitable for ®ALASKA SUSITNA-WATANA HYDRO SPILLWAY CREST PROFILE - TOPO BASED ON MATSU-NORTH BARE EARTH DATA NOT MEASURE 1”J.AFRISK construction.As an interim document,it may contain data ;ANSI D THEN DRAWING IS -_----that is incomplete or define and locate structures that remain @&_>ENERGY AUTHORITY Clean,reliable energy for the next 100 years,SECTIONS -1REVDESCRIPTION.BY |DATE]FULL SIZE NOTTOSCALE [approved _B SADDEN_to be optimized.SHEET OF THIS DOCUMENT IS CONSIDERED CEil CRITICAL ENERGY INFRASTRUCTURE INFORMATION i TeteSareeaeae at PARTS LIST PART NUMBER MATERIAL VOLUME SEASON 1-N PURPLE 15303850.5 ft*3 SEASON 1-S PURPLE 9264492.9 ftA3 SEASON 2 RED 24651751.8 ft43 SEASON 3 MAGENTA 26013022.5 fRt*3 SEASON 4 -N CYAN 18536396.9 ft*3 SEASON 4 -S CYAN 7907155.5 ftA3 SEASON 5 YELLOW 26563647.7 ft*3 SEASON 6 -NN GREEN 3132450.6 ft*3 SEASON 6 -NS GREEN 2232988.2 ft*3 SEASON 6 -CN GREEN 1176222.1 ft*3 SEASON 6 -CS GREEN 609030.7 ft*3 SEASON 6-S GREEN 5626041.4 43 NAD83ASPZ4FT -DO NOT RELEASE- |_|scate WARNING Project No.10500200 CONCEPTUAL DESIGN PHASE STATE OF ALASKA SUSITNA-WATANA HYDROELECTRIC PROJECT Sheet No. TS ly 0 2 1 oa ayrie014 NOT FOR GONSTRUGTION ALASKA ENERGY AUTHORITY - a :-_--___--|iF THIS BAR DOES Designed MAKSIM S.This document is designated "interim"and not suitable for NI W H ®=DAM 04-0 1C€001SPNOTMEASURE1"|MAKSIM S.construction,As an interim document,it may contain data '«a SUSITNA-WATANA HYDRO RCC SEASONAL PLACEMENT av DESCRIPTION ay |oate |ronceze |"NOrTOSCALES |Acproved Thats Incomplete OF ce opimzed.oman @&-_>ENERGY AUTHORITY Clean,reliable energy for the next 100 years.SueET or