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HomeMy WebLinkAboutBradley Lake Final Supporting Design Report Vol 1 1988Alaska Power Authority FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CONTRACT BRADLEY LAKE HYDROELECTRIC PROJECT FEDERAL ENERGY REGULATORY COMMISSION PROJECT NO. P-8221-000 VOLUME 1 REPORT Prepared By STONE & WEBSTER ENGINEERING CORPORATION MARCH 1988 . , r K .• •' TABLE OF CONTENTS . .... . . 1 ~ •• '-J. ., TABLE OF CONTENTS FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION COuTRACT VOLUME 1 -REPORT VOLUME 2 -DESIGN CRITERIA VOLUME 3 -DAM AND SPILLWAY STABILITY ANALYSIS VOLUME 4 -CALCULATIONS VOLUME 5 -CALCULATIONS VOLUME 6 -CALCULATIONS VOLUME 7 -CALCULATIONS VOLUME 8 -CALCULATIONS VOLUME 9 -CALCULATIONS 0216R-4460R/CG 1 ' c' ,~- 1 I TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN_REPJRT GENERAL CIVIL CONSTRUCTION COnTRACT VOLUME 1 REPORT 1.0 INTRODUCTION 2.0 DESIGN AND GENERAL TECHNICAL DATA 2.1 DESIGN 2. 2 -DESIGN LOADS 2.3 STABILITY CRITERIA 2.4 MATERIAL PROPERTIES 2.5 GENERAL. TECHNICAL DATA 3.0 SUITABILITY ASSESSMENT 3.1 SPECIFIC ASSESSMENTS 4.0 GEOTECHNICAL INVESTIGATIONS 4.1 CHRONOLOGY OF INVESTIGATIONS 4.2 BORING LOGS, GEOLOGICAL .REPORTS AND LABORATORY TEST RESULTS 5.0 BORROW AREAS AND QUARRY SITES 5. 1 -BORROW AND QUARRY AREAS 5.2 OTHER MATERIAL SOURCES 6.0 STABILITY AND STRESS ANALYSIS 6. 1 GENERAL _ 6. 2 DIVERSION TUNNEL INCLUDING INTAKE STRUCTURE 6.3 MAIN DAM 6.4 SPILLWAY 6.5 POWER TUNNEL AND PENSTOCKS 6.6 POWERHOUSE/SUBSTATION EXCAVATION, COFFERD~ AND_TAILRACE CHANNEL 6.7 POWERHOUSE 6.8 REFERENCES 7.0 BASIS FOR SEISMIC LOADiNG 7.1 GENERAL 7.2 SEISMOTECTONIC SETTING 7.3 SEISMIC DESIGN 0216R-4460R/CG ii TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CO~~CT VOLUME 1 REPORT 8.0 SPILLWAY DESIGN FLOOD BASIS 8.1 STUDY METHODOLOGY 8.2 WATERSHED MODEL CALIBRATION 8.3 PROBABLE MAXIMUM FLOOD 8.4 SPILLWAY DESIGN FLOOD 8.5 MODEL TEST 9.0 BOARD OF CONSULTANTS 9.1 INDEPENDENT BOARD OF CONSULTANTS 9.2 FERC BOARD OF CONSULTANTS APPENDIX A Plates Exhibit F 1 2 3 4 5 6 7 8 9 10 13 14 15 16 17 18 19 20 Figures F.6.2-5 F.6.2-6 DRAWINGS Title General Plan General Arrangement -Dam, Spillway and Flow Structures Concrete Faced Rockfill Dam -Sections and Details Spillway -Plan, Elevations and Sections Power Conduit Profile and Details Intake Channel and Power Tunnel Gat: Shaft -Sections -and Details Civil Construction Excavation at Powerhouse -Plan Civil Construction Excavation at Powerhouse -Elevations 90 MW Pelton Powerhouse Construction Diversion -Sections and Details Main Dam Diversion -Channel Improvements General Arrangement -Permanent Camp and Powerhouse Barge Dock Powerhouse Substation and Bradley Junction Main One Line Diagram Martin River Borrow Area Waterfowl Nesting Area Powerhouse Access Roads Mean Horizontal-Response Spectrum Design Acce~erogram 0216R-4460R/CG iii - APPENDIX B TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME 1 REPORT ATTACHMENTS B.l Construction ·schedule Contract Dat·es B.2 Meetings of the Independent Board of Consultants Meeting No. 1 May 12 and 13, 1983 Meeting No. 2 July 11 to 15, 1~83 Meeting No. 3 September 25 to 27, 1984 Meeting No. 4 November 4 and 5, 1985 with response November 25, 1985 Meeting No. 5 January 28, 1986 of Meeting No. 6 May 6 .to 8, 1986 with response dated May 21, Meeting No. 7 August 12 to 14, 1986 with response dated October 20, 1986 ·Meeting No. 8 December 8 to 10, 1986 1986 Site Visit by Mr. A. Merritt on December 11, 1986 Meeting No. 9 May 5 to 7, 1987 Meeting No. 10 December 17 and 18, 1987 B.3 Meetings ·of the FERC Board of Consultants Meeting No. 1 Meeting No. 2 March 6 ·and 7, 1986 May 28 and ·29, 1986 with response dated July 11, 1986 Hydraulic Mode1 Test of Spillway July 9, 1986 Meeting No. 3 August .18 to 20, 1986 with response dated October 28, 1986 Meeting No. 4 Meeting No. 5 Meeting No.; 6 0216R-4460R/CG . Hydraulic Model Test Spilh.·ay and Diversion ·Tunnel August 29 and September 25, 1986 January 27, 1987 with response dated January 29, 1987 May 26 to 28, .1987 with response December 7 and 8, 1987 with response iv TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CO~~CT VOLUME 2 DESIGN CRITERIA 1.0 Civil Design Criteria 2.0 Geotechnical Design Criteria 3.0 Structural Design Criteria Part A General Design Criteria Part B Special Requirements for Major Structures Section 1. Section 2. Section 3. Section 4. Section 5. Section 7. Main Dam Diversion Main Dam Spillway Power Tunnel Lining, Intake and Gate Shaft Steel Liner and Penstock Tailrace 4.0 Hydraulic Design Criteria 1. Main Dam Diversion 2. Tailrace 3. Hydraulic Turbines, Governors and Spherical Valves 4. Spillway 5. Power Intake, Tunnel and Penstock 5.0 Architectural Design Criteria 0216R-4460/CG v TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CONTRACT . VOLUME 3 DAM AND SPILLWAY STABILITY ANALYSIS DAM STABILITY REPORT Section Section Title 1.0 INTRODUCTION 1.1 PURPOSE 1.2 SCOPE 1.3 DAM SAFETY CRITERIA .2.0 DESCRIPTION OF PROJECT FEATURES 2.1 GENERAL 2 .. 2 MAIN DAM 2.3 UPSTREAM COFFERDAM 3.0 DESIGN EARTHQUAKE REGIME 3.1 SEISMOTECTONIC SETTING 3.2 DESIGN RESPONSE SPECTRA 3.3 ACCELEROGRAM DEVELOPMENT 4.0 ALTERNATIVE METHODS OF ANALYSIS 4.1 GENERAL STABILITY CRITERIA 4.2 PSEUDOSTATIC METHOD 4.3 SARMA/NEWMARK METHOD 4.4 FINITE ELEMENT METHOD 4.5 SELECTION OF SARMA METHOD . 5.0 SARMA ANALYSIS METHODOLOGY 5.1 MATERIALS PROPERTIES AND EARTHQUAKE SELECTION 5.2 LEASE II ANALYSIS 5.2.1 Static Analysis 5.2.2 Critical Circles and Accelerations 5.3 SARMA ANALYSIS 5.3.1 Data Requirements 5.3.2 Processing 5.3.3 Analytical Output 5.3.4 Significance of Results 6.·0 BRADLEY .LAKE EMBANKMENT ANALYSES 6.1 EARTHQUAKE RECORDS 6.2 INPUT PARAMETERS 6.3 DESIGN CASES 6.4 LEASE II ANALYSES 6.5 SARMA ANALYSES 6.6 INTERPRETATION OF RESULTS 0216R-4460R/CG vi TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT - GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME 3 DAM AND SPILLWAY STABILITY bNALYSIS Section Section Title 7.0 8.0 6.7 6.'7 .1 6.7.2 6.7.3 6.7.4 6. 7-.5 -6. 7.6 6.7.7 6.7.8 6.8 7.1 7.2 7.3 -7.4 SPECIAL STUDIES Megathru~t (a = .SSg) DBE .(ah = .37Sg) _ Influence of Downstream Berm Fa:iled Concrete Face Varying Embankment Height Planar Slip Surfaces La Union Accelerogram Parametric Analyses COFFERDAM CONCLUSION CRITICAL CASES SUMMARY OF CRITICAL FAILURE SUR~ACES PREDICTED DISPLACEMENTS _ RESPONSE TO VARIOUS EVENTS BIBLIOGRAPHY LIST OF FIGURES Figure Title 1 Project Location_Map 2 Main Dam Area ~ General Arrangm:nt 3 Main Dam Sections 4 (Not Used) 5 MCE ,Response.Spectra-Mean and Chosen 6 Rockfil1 rriction Angles 7 Intermediate av/ah Ratio 8 Selected Sliding Surfaces -Mai3 Dam 9 Critical Acceleration Plots 10 Permanent Deformation Plots 11 MCE Response/Displacement Plots 12 Megathrust Response/Displacement Plots 13 DBE Response/Displacement --Plots 14 Flow Through Dam Without Face 15 Dam Height vs. Acceleration and Displacement 16 Wedge Stability: S1oped Slidin5 Planes 17 _ Wedge Stabili-ty: Horizontal Sliding Planes 18 La Union Response/Displacement ?lots- 19 Response Spectrum-La Union.E-N Record· 20 Response Spectrum--Taft Record - 21_ Arias Inten~ity _ _ 22 Taft Response/Displacement Plot 0216R-4460R/CG vii TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN·REPORT GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME 3 DAM AND. SPILLWAY STABILITY ANALYSIS SPILLWAY STABILITY REPORT Section Section Title 1.0 INTRODUCTION l.i PURPOSE 1.2 SCOPE 1.3 SPILLWAY SAFETY CRITERIA 2.0 DESCRIPTION OF PROJECT FEATURES 2.1 GENERAL 2.2 OGEE SECTION 2.3 .NON-OVERFLOW SECTIONS 2.4 GEOLOGIC CONDITIONS 3.0 .DESIGN EARTHQUAKE REGIME 3.1 SEISMOTECTONIC SETTING 3.2 DESIGN RESPONSE SPECTRA 3.3 ACCELEROGRAM DEVELOPMENT 4.0 STABILITY CRITERIA 4.1 GENERAL 4.2 LOADS 4.2.1 Deadweight 4.2.2 Ice 4.2.3 Hydrostatic 4.2.4 Earthquake 4.2.5 wind 4.2.6 Uplift 4.2.7 Temperature 4.3 LOADING CONDITIONS 4.4 ACCEPTANCE CRITERIA 4.4.1 Stability Requirements ·4.4.2 Min.imum Allowable Stress 4.4.3 Shear-Friction Factor of Safety 5.0 METHODS OF ANALYSIS 5.1 STA,.TIC METHOD 5.2 FINITE ELEMENT METHOD 5.3 SARMA METHOD 6.0 STATIC ANALYSIS 6.1 STABILITY ANALYSIS 6.2 RESULTS 7.0 FINITE ELEMENT ANALYSIS 7.1 STRESS ANALYSIS 7.2 RESULTS 0216R-4460R/CG. viii TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME 3 DAM AND SPILLWAY STABILITY aNALYSIS Section Section Title 8.0 8.1 8.2 9.0 9.1 9.2 SARMA ANALYSIS STABILITY ANALYSIS RESULTS CONCLUSIONS CRITICAL CASES SUMMARY OF STABILITY CONDITIONS 10.0 BIBLIOGRAPHY Figure 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15. 16 17 18 19 LIST OF FIGURES Title Project Layout Map General Arrangement -Main Dam Area General Arrangement -Spillway Project Response Spectra Hybrid Accelerogram Static Spillway Model . Case I -Static Analysis-Base El 1124 Case II -Static Analysis-Base 31 1124 Case IV-Static Analysis-Base.31 1124 Finite Element Model -Base El 1160 Finite Element Model -Base El 1150 Finite Element Model -Base El 1124 Finite Element Analysis: Case III -Max. Tensile Stresses· -Base El 1160 Finite Element Analysis: Case III -Max. Compressive Stre~ses -Base El 1160 Finite Element Analysis: Case V -Max. Tensile Stresses - Base El 1160 Finite Element Analysis: Ccse V -Max. Compressive Stresses -Base El 1160 Finite Element Analysis: Case III -Max. Tensile Stresses -Base El 1150 Finite Element Analysis: Case III -Max.· Compressive Stresses -Base El 1150 Finite Element Analysis: Case V -Max. Tensile Stresses - Base El 1150 20 Finite Element Analysis: · Ccse V -·Max. Compressive Stresses -Base El 1150 21 Finite Element Analysis: Case III -Max. Tensile Stresses -Base El 1124 0216R-4460R/CG ix Figure 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 0216R-4460R/CG TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME 3 DAM AND SPILLWAY STABILITY dNALYSIS LIST OF FIGURES Title Finite Element Analysis: Case III -Max. Compressive Stresses -Base El 1124 Finite Element Analysis: Case V -Max. Tensile Stresses - Base El 1124 Finite Element Analysis: Case V Max. Compressive Stresses -Base El 1124 SARMA Analysis Model, Ogee Sections -Sheet 1 SARMA Analysis Model, Ogee Sections -Sheet 2 SARMA Analysis Model, Non-Overflow Sections SARMA Analysis: Base El 1160 -Ogee SARMA Analysis: Base El 1150 -Ogee SARMA Analysis: Base El 1130 -Ogee SARMA Analysis: Base El 1124 -Ogee SARMA Analysis: Base El 1160 -Left Abutment SARMA Analysis: Base El 1124 -Right Abutment Spillway Stability Analysis Sun~ary -Sheet 1 Spillway Stability Analysis Sun~ary -Sheet 2 Spillway Stability Analysis Summary -Sheet 3 X HYDRAULIC TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN R~PORT · GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME 4 CALCULATIONS Cale:::ulation Title · -No. SPILLWAY CREST SHAPE H-027 FLOOD ROUTING-P.M.F. THROUGH SPILLWAY H-028 FLOOD ROUTING -FLOOD OF RECORD THROUGH H-033 BRADLEY LAKE & DIVERSION TUNNEL DESIGN THRUSTS -POWER PENSTOCK NEAR H-036 MANIFOLD SIMPLIFIED DAM BREAK ANALYSES AND WATER H-046 SURFACES PROFILES WAVE RUNUP AND FORCE ON DAM PARAPET H-048 TAILRACE CHANNEL SLOPE PROTECTION H-050 PROTECTION AGAINST WAVES FOR THE H-066 UPSTREAM COFFERDAM & PQWER TUNNEL. INTAKE ROCK PLUG ICE FORCE ON DAM PARAPET H-068 INVESTIGATION OF NEED FOR A~RATION OF s·PILLWAY FLOW H-077 RIPRAP DESIGN H-079 FILLING'BRADLEY LAKE RESERVOIR H-081 0216R-4460R/CG xi TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME 5 CALCULATIONS GEOTECHNICAL Calculation Title No. ROCK STRESS IN CIRCULAR TUNNEL LININGS G(Ak)-04 AND SELECTION OF EXTERNAL WATER PRESSURE CRITERIA GROUND WATER SEEPAGE LOADS ON DIVERSION TUNNEL LINER ~~Ak)-08 VERIFICATION OF INTAKE GEOMETRY FOR THE POWER AND DIVERSION INTAKES AT THE BRADLEY LAKE RESERVOIR G{Ak)-10 EXTERNAL ROCK & GROUND WATER LOADS ON POWER INTAKE AND GATE SHAFT STRUCTURES G-(Ak)-22 FINAL STABILITY ANALYSIS: BRADLEY LAKE G{D)-24 MAIN DAM PENSTOCK -MANIFOLD THRUST BLOCK EMBEDMENT LENGTH AND STABILITY ANALYSIS G~Ak)-29 ROCK MODU1I FOR POWER TUNNEL TRANSIENT STUDY G{Ak)-31 DESIGN OF ROCK SUPPORT FOR THE MAIN POWER INTAKE STRUCTURE PLINTH AND TOE SLAB GEOMETRY -MAIN DAM 0216R-4460R/CG xii G(Ak)-35 G(D)-38 TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT . GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME.6 CALCULATIONS · . . GEOTECHNICAL · Cai.=ulation Title No. GROUNDWATER INFLOW & LEAKAGE INTO POWER TUNNEL' .d-<Ak)-41 EVALUATION OF SHEAR STRENGTH OF ROCK MASSES AT TH.E BRADLEY LAKE SITE G-(Ak)-47 . EVALUATION OF EXTERNAL LOADS ON POWER · TUNNEL LINER G-(Ak)-48 ·VERIFICATION OF CONFINEMENT TO PREVENT HYDRAULIC JACKING OF THE POWER TUNNEL G~Ak)-49 TAILRACE SLOPE· STABILITY & PROTECTION G·(A)-50 DESIGN OF ROCK BOLTS FOR DIVERSION G(A)-58 TUNNEL & GATE SHAFTS DAM TOE PLINTH .LOADS G(A)-60 POWER TUNNEL INTAKE EXCAVATION DESIGN G ' -70 MANIFOLD & PENSTOCK THRUSTBLOCK STABILITY CONSIDERING SHEAR ZONE FEATURE POWERHOUSE CELLULAR SHEETPILE COFFERDAM STABILITY ANALYSIS EVALUATION OF CONCRETE LINER REQUIRE1:1ENTS FOR THE MAIN . POWER TUNNEL MAIN DAM FACE SLAB DESIGN SPILLWAY: SARMA DISPLACEMENT ANALYSIS SPILLWAY OF THE UPSTREAM COFFERDAM TOE AND ABUTMENT PLINTH DOWEL EMBED. LENGTHS AND QUANTITIES ' . 0216R-4460R/CG xiii G -86 ~(Ak)-89 G(Ak)-90 . G(Ak).:_93. G -98 G -104 G · -106 TABLE OF CONTENTS (Conti~ued) FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME 7 CALCULATIONS STRUCTURAL Title WIND LOADS FOR DESIGN CRITERIA' · SNOW & ICE LOADS FOR DESIGN CRITERIA SEISMIC DESIGN DATA MAIN DAM DIVERSION TUNNEL LINING AND GATE CHAMBER ANALYSIS . POWER .TUNNEL INTAKE POWER TUNNEL GATE CHAMBER AND LINING 'DESIGN AND ANALYSIS . GATEHOUSE CONCRETE STRUCTURE 0216R-4460R/CG x'iv Calculation No. SDC.l SDC.2 SDC~3 SC-133-3 SC-151-16 SC-152-21 SC-152-32 TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME 8 CALCULATIONS STRUCTURAL Title DAM PARAPET MAIN DAM TOE PLINTH DESIGN SEGMENTS A, B, C, D ABUTMENT DESIGN SPILLWAY STABILITY ANALYSIS - STATIC ANALYSIS FINITE ELEMENT ANALYSIS OF SPILLWAY FOR SEISMIC LOAD COMBINED WITH DEAD WEIGHT, ICE THRUST, AND WATER LOADS SPILLWAY TRAINING WALLS 0216R-4460R/CG XV Ca1::u1ation No. s::-191-26 s::-191-27 s.:::-191-29 ~-201-BA s:::-201-34 s:::-20s-23 TABLE OF CONTENTS (Continued) FINAL SUPPORTING DESIGN REPORT GENERAL CIVIL CONSTRUCTION CONTRACT VOLUME 9 CALCULATIONS STRUCTURAL Calculation Title No. PENSTOCK AND MANIFOLD ANCHOR BLOCKS SC-261-25 MAIN DIVERSION & MAIN INTAKE BULKHEADS SS-132-2 MAIN DAM DIVERSION PENSTOCK DESIGN SS-134-12 POWER TUNNEL INTAKE TRASH RACKS SS-153-10 POWER PENSTOCK THRUST RINGS AND MISC. COMPONENTS SS-261-16A REQUIRED THICKNESS OF STEEL LINER UNDER INTERNAL AND EXTERNAL PRESSURE SS-261-17A STRESS ANALYSIS OF FLANGE WITH 108" INSIDE DIAMETER SS-261-17B ·LOCAL STRESSES DUE TO GEOMETRY DISCONTINUITY AT REDUCERS AND MITERED ELBOWS SS-261-17C REQUIRED THICKNESS OF ELLIPSOIDAL HEADS FOR PENSTOCK SS-261-17D STRESS ANALYSIS OF POWER PENSTOCK WYE BRANCH SS-261-17F PENSTOCK ACCESS FLANGE BOLTS SS-261-18 0216R-4460R/CG .xvi SECTION 1. 0 INrnODU.CTI ON v~\ 1.0 INTRODUCTION As part of the documents for the Application for License for the Bradley Lake Hydroelectric Project, the Applicant issuerl a "Preliminary Supporting Design Report." In that document the Applicant stated that a "Final Design Report" would be submitted to the Commission fer review and approval prior to the award of each construction contract. There will be seven major construction contracts awarded for project facilities. The scheduled dates for the submittal of Final Supporting Design Reports for each phase to the Comrnissioc for approval and the dates for starting each phase of construction are shewn on Construction Schedule Contract Dates Appendix B (Attachment B.1 ).._ The seven construction contracts consist of:. First-Contract·-Site Preparation Contract (completed August 1987) • Clearing, grubbing and removing overburden in diversion structure, camp, road, and powerhouse a=eas • Rock excavation • Construction of access road and bridg:s to permanent facilities and Martin River borrow area • Quarry and placing riprap • Site grading and stockpiling topsoil • Diversion tunnel excavation • Placing concrete and reinforcing steel for the intake structure· of the diversion tunnel • Construction of the temporary and permanent camp facilities including utilities • Construction of the airstrip • Construction of . the barge dock including sheet pile cells, approach roads and local dredging • Placing rock bolts and slope protection in powerhouse and diversion tunnel excavations • Improvement of channel downstream of diversion tunnel outlet 0216R-4429R/CG 1-1 • Installation of conununication tower power supply and main damsi te power supply cable and install television/phone service microwave and light fiber optic cables. (Owner installed) Second Contract -General Civil Construction Contract • Construction of diversion outlet structure and gate shaft • Completion of the concrete and steel lining of the diversion tunnel • Excavation of the power tunnel • Construction of the power tunnel concrete and steel lining including intake and vertical gate shaft • Installation of the power penstock • Rock excavation for all permanent structures including tailrace channel • Construction of the dam, spillway and cofferdams • Electrical and mechanical work for the diversion tunnel gate shaft and fish by-pass facilities • Electrical and mechanical work for the power tunnel gate shaft Third Contract -Transmission Line Clearing Contract • Clearing of the transmission line right-of-way • Disposal of vegetative matter Fourth Contract -Powerhouse Construction Contract • Construction of the powerhouse including installation of equipment • Construction of powerhouse substation Fifth Contract -Transmission Line Construction Contract • Construction of transmission line • Construction of Bradley Junction transmission line intertie 0216R-4429R/CG 1-2 • • • Sixth Contract -Middle Fork and Nuka Diversions. and Reservoir Clearing Contract • Construction of Nuka Diversion • Construction 9f Middle Fork Diversion • Reservoir Clearing Seventh Contract -Rehabilitation and Recreational Facilities Construction Contract • Rehabilitation Activities Martin River Borrow Waterfowl Nesting Area Campsites, Staging Areas and Concrete Batch Plant Areas • Recreational facilities The Final Supporting Design Report for the Site Preparation Contract was submitted by the Applicant in March 1986 and wEs approved by FERC, May 20, 1986. The Final Supporting Design Report for the General Civil Construction Contract is submitted by the Applicant to de~onstrate that the work proposed under this Contract is safe and adequ.:=te to fulfill their stated functions. The revised Exhibit F drawings for the General Civil Construction Contract are included herein. Final Exhibit F drawings and a Final Supporting Design Report will be submitted by the Applicant for Commission approval for the Powerhouse Contract, and Middle Fork and Nuka Diversions, and Reservoir Clearing Contract in June 1988. Unless otherwise noted, all elevations given in this report are based on Bradley Lake Project Datum . 0216R-4429R/CG 1-3 SECTION 2.0 DESIGN AND GENERAL TECHNICAL DATA 2.0 DESIGN AND GENERAL TECHNICAL DATA 2.1 DESIGN The following design data are furnished to indicate to the Commission staff the applicable codes, guides, regulations, and standards which are utilized in the engineering and design documents reqdred for the Bradley Lake Hydroelectric Project. Attached to this report are the Design Criteria that are the basis of the design of the General Civil Construction Contract structures as listed below: • Main Darn including Upstream Cofferdam • Spillway • Power Tunnel including Intake, Gate Shaft, Steel Lining and Power Penstocks • Diversion Tunnel including Gate Shaft, Diversion Penstock and Outlet Portal • Powerhouse excavation • Tailrace 2.1.1 Codes, Guides and Regulations Where specific standards and design criteria are not covered in these design data, the latest edition of the followir..g codes and standards will apply: 2.1.1.1 General ANSI A58.1 UBC AAC 0216R-4430R/CG Minimum Design Loads for Build:ngs and Other Structures; American National Standards Institute Uniform Building Code; Internatknal Conference of Building Officials Alaska Administrative Code, Section 13AAC50 (incorporates UBC provisions for Alaska Building Code) 2-1 OSHA-AK OSHA-US General Safety Code, Vol. I, II-, and III, Occupational Safety and Health Standards, Alaska Department of Labor, Division of Occupational Safety and Health, 1973 and as amended in 1983 and the Construction Code, 1974 and as amended in 1982 U.S. Department of Labor Occupational Safety and Health Administration, OSHA 2206 General Industry Standards (29 CFR 1910'), and OSHA 2207 Construction Industry (29 CFR l926/1910), as supplement to the State of Alaska's General Safety Code UL~FRD Fire Resistance Directory Underwriters Laboratory 2.1.1.2 Concrete ACI 207.~ lR ACI 207.2R ACI 210R ACI 211.1 ACI 214 ACI 301 Mass Concrete for Dams and Other Massive Structures; American Concrete Institute Effect of Restraint, Volume Change, and Reinforcement on Cracking of Massive Concrete; American Concrete Institute Erosion Resistance of Concrete in Hydraulic Structures; American Concrete. Institute Standard Practice for Selecting Proportions for Normal, Heavy Weight, and Mass Concrete; American Concrete Institute Recommended Practice for Evaluation of Strength Test Results for Concrete; American Concrete Institute Specifications for Structural American Concrete Institute Concrete for Buildings; ACI 302.1R Guide to Concrete Floor and Slab Construction ACI 306 Cold Weather Concreting; American Concrete Institute 0216R-4430R/CG 2-2 ACI 315 ACI 318 ACI 322 ACI 336.2R ACI 336.3R ACI 347 ASTM C33 ASTM ClSO CRD-Cll9 Manual of Standard Practice for Detailing Reinforced Concrete ·Structures; American Concrete Institute Building Code Requirements for Reinforced Concrete and Commentary; American Concrete Institute Building Code Requirements for Structural Plain Concrete; American Concrete Institute Suggested Design Procedures for Combined Footings and Mats; American Concret.e Institute Suggested Design Construction Procedures for Pier Foundations; American Concrete Institute Recommended Practice for Concrete =ormwork; American Concrete Institute Specification for Concrete Aggregates; American Society for Testing and Materials Specification for Portland Cement; American Society for Testing and Materials Method of Test for Flat and Elo:J.gated Particles in Coarse Aggregate; U.S. Army, Corps of Engineers CRSI CRSI Handbook; Concrete Reinforcing Steel Institute 2.1.1. 3 Steel AISC 0216R-4430R/CG Manual of Steel Construction; Anerican Institute of Steel Construction, Inc., 8th Edition 2-3 AISC AISC AISC AISI ASME VIII Specification for the Design Fabrication and Erection of Structural Steel for Buildings with Commentary; American Institute of Steel Construction Codes of Standard Practice for Steel Buildings and Bridges with Commentary; American Institute of Steel Construction Specification for Structural Joints Using ASTM A325 and A490 Bolts Specifications for the Design of Cold-Form Steel Structural Members with Commentary; American Iron and Steel Institute Boiler and Pressure Vessel Code; American Society of Mechanical Engineers ASTM . Various Standards, American Society for :resting and Materials AWS Dl.l AWS Dl.4 AWWA C200 AWWA C206 AWWA C207 AWWA C208 AWWA DlOO 0216R-4430R/CG Structural Welding Code; American Welding Society Reinforcing Steel Welding Code; American Welding Society Steel Water Pipe 6 Inches and Larger; American Water Works Association Standard for Field Welding of Steel Water Pipe; American Water Works Association Standard for Steel Pipe Flanges for Waterworks Services - Sizes 4 in. through 144 in.; American Water Works Association Standard for Dimensions for Steel Water Pipe Fittings; American Water Works Association Standard for Welded Steel Tanks for Water Storage; American Water Works Association 2-4 AWWA Dl02 AWWA Mll Standard for Painting Steel Water-Storage Tanks; American Water Works Association Steel Pipe Design and Installation; American Water Works Association 2.1.1.4 Roads and Bridges AASHTO HB-12 Standard Specifications for Highway Bridges, ·Twelfth Edition; American Associations of State Highway and Transportation Officials AASHTO ISB Interim Specifications -Bridges; American Association of State Highway and Transportation Officials AASHTO WSB-3 Standard Specifications for Welding Structural Steel Highway Bridges; American Association of State Highway and Transportation Officials AASHTO LTS-1 Standard Specifications for Structural Supports for Highway Signs; Luminaires, and Traffic Si~nals; American Association of State Highway and Transportation Officials AASHTO CD-2 A Policy on Geometric Design of Rural Highways; American Association of State Highway and Transportation Officials AASHTO HDG Highway Drainage Guidelines; American Association of State Highway and Transportation Officia:s AASHTO HDG-7 Hydraulic Analyses for the Location and Design of Bridges; American Association of State Highway and Transportation Officials AASHTO GSH-4 Guide Specifications for Highw3y Construction; American Association of State Highway and T=ansportation Officials 0216R-4430R/CG 2-5 AASHTO HLED-.1 A Guide American for Highway Landscape Association of State and · Environmental Design; Highway and Transportation Officials AASHTO GWP-1 A Design Guide for Wildlife Protection and Conservation for Transportation Facilities 2.1.1.5 Design Guides SEAOC A'i'C 3-06 NFPA DOT/PF SJI Recommended Lateral Force . Requirements and Commentary, Structural Engineers Association of California Tentative Provisions for :the Development of Seismic Regulations for Buildings; Applied Technology Council National Fire Protection Association · Alaska Department of Transportation and Public Facilities, Design Standards for Buildings Standard Specifications an~cLoad-Tables Steel Joist Institute .(SJI) Addi tiona! design guides and references are listed in the Desl.gn Criteria which are in Volume 2 of this Supporting Design Report. 2.2 DESIGN LOADS· The following qesign loads · are being considered with the loading combinations described in Section 2.3 for the Design of Structures.· 0216R-4430R/CG 2-6 2.2.1 Dead Loads Mass Concrete Reinforced Concrete Steel Water Ice Salt Water Silt -Vertical -Horizontal Backfill -Dry -Moist -Submerged Sound Rock 2.2.2 Backfill Loads 145 150 490 62.4 56 64 120 85 120 135 85 170 lbs/ft 3 lbs/ft 3 lbs/ft 3 lbs/ft 3 lbs/ft 3 lbs/ft 3 lbs/ft 3 lbs/ft 3 lbs/ft 3 lbs/ft 3 lbs/ft 3 lbs/ft 3 The lateral earth pressure against vertical faces of structures with cohesionless horizontal backfill is computed using the equivalent fluid pressures calculated from: p = KwH Where: p = unit pressure K = pressure coefficient w = unit weight of fill H = height of fill For structures free to deflect or rotate about the base the pressure coefficient is computed from Rankine's theory, using the following equation: Ka = tan2 (45-0/2) Where 0 =angle of internal.friction (degrees). 0216R-4430R/CG 2-7 For structures restrained from bending or rotation, the at-rest pressure coefficient is used: K = 1 -sin 0 0 For inclined walls, sloping backfill, soil wall friction, compaction induced pressures and surcharge pressures refer to Geotechnical Technical Guidelines GTG-6.15-1, Determination of Lateral Pressures on Buried Structures in Granular Soils, for applicable equations. Where vehicular traffic can run adjacent to the structure, a surcharge loading of 300 lbs/ft 2 . is applied. 2.2.3 Snow and Ice Loads Roofs, decks, and structural features which will carry snow or ice loads are designed in accordance with the technical document ETL 1110-3-317, U.S. Dept. of Army with additional provisions where more severe icing is considered likely. 2.2.4 Floor Loads Gate Shaft Equipment Platforms (Diversion and Power Tunnels) 2.2.5 Hydraulic Loads 250 lbs/ft 2 All structures are designed for full lateral water pressures, including hydrodynamic and uplift forces, where applicable. 2.2.6 Uplift Uplift (or internal hydrostatic pressure) is assumed to act over 100 percent of the affected area of the structure. 0216R-4430R/CG 2-8 Uplift pressure is equivalent to the full wc.ter pressure acting on a foundation or structure where no head differ:ntial exists across the structure. The foundations and structures are analyzed for flotation, if applicable. Foundation drain holes are provided for the spillway downstream of the foundation grout curtain. The drain holes are drilled into the foundation rock and terminate within the drainage gallery. The projected pressure at the drains is based upon the effectiveness of th: drainage system expressed as drain efficiency. For example, a drainage efficiency of 100 percent corresponds to a reduction of the projected pie~metric pressure elevation to tailwater elevation at the line of drains. The expression for the drainage efficiency is: (HW-DL) DE = (HW-TW) x 100 where DE = drainage efficiency, percent HW = headwater elevation, feet DL = projected piezometric level at the line jf drains, feet TW = tail water elevation or foundation elevation (whichever is greater ) feet The drainage efficiency for the drains at the sp~llway is assumed to be 50 percent with the drains operative and with proper maintenance of drains. 0216R-4430R/CG 2-9 2.2.7 ·seismic Loads The Bradley Lake Project is located in a seismically active region. All major Project structures except the barge dock and airstrip are founded on or excavated in rock. Design acceleration values given in this design data are horizontal accelerations in rock and are amplified or attenuated up through soil as applicable in design. 1 •. Main Dam The main dam, as well as the spillwar, is designed for an earthquake with the response spectrum shown in Appendix A on Figure 6.2-5, Mean Horizontal Response Spectrum, and a normalized peak acceleration of 0.75 g which represents the maximum credible earthquake (MCE). The dam is ·designed for this severe acceleration· to maintain wat'er retaining integrity. The field studies conducted to date have not revealed any geological structure in the dam site area which could be conSidered active. 2. Intake Structure and Gate Shaft for Power Tunnel The hydraulic gates and associated equipment for the power tunnel have been specified to be designed for an earthquake with the response spectrum shown in Appendix A on Figure 6.2-5, Mean Horizontal Response Spectrum, and a normalized peak acceleration of 0.75 g with a SO percent increase ·in allowable stresses. The intake gates are designed to operate during and after a major seismic event to close the water passageway of the power conduit. To assure the gates remain operable, .air-oil acc1llllulators are provided with. a tank size to permit independent closure of each gate before recharging is required by the ·hydraulic power pack. ·An additional engine-pump will be provided as a backup to operate the gates in case the accumulator system becomes inoperable. 0216R-4430R/CG 2-10 The concrete structures have been design=d for a pseudostatically applied horizontal acceleration of 0.7Sg with a SO percent increase in allowable stresses. 3. Permanent Outlet Facilities in Diversion Tuncel The primary hydraulic gates and associated equipment for ·the permanent outlet facilities are designed for an earthquake with the response spectrum shown in Appendix A on Figure 6.2-3, Mean Horizontal Response Spectrum, and a normalized peak acceleration of 0.7S g with a SO percent increase in allowable stresses. The outlet gates are designed to operate during and after a major seismic event specifically to open the main (downstream) gate to effect reservoir drawdown. The ~uard gate (upstream) is normally open. To assure the gate remains operable, air-oil accumulators are provided with a tank size to permit one open-close cycle of one gate before rechc.rging is required by the hydraulic power pack. An additional engine-pump will be provided as a backup to operate· the gates in case the accumulator system becomes inoperable. The diversion penstock has been des±gned~for a 0.75g horizontal ground acceleration with the penstock empty, and a 0. 3Sg horizontal ground acceleration with the penstock full of water, with a 50 percent increase in allowable stresses. The concrete structures have been designed for a pseudostatically applied horizontal acceleration of 0.75g. 4. Power Tunnel Fully embedded installations will react in conc,ert with the surrounding rock mass, unless actual rupture and displacement of the rock mass occurs. The power tunnel crosses the Bradley River and Bull Moose Faults, each of which are assumed to De capable of independent .earthquake generation, ·implying surface and subsurface rupture .potential. In addition, these faults are ·capable of rupture in response to events on adjacent larger faults .• 0216R-4430R/CG. 2-11 It is considered impossible for the design to withstand or accommodate rock mass rupture. Other than safety-related issues, no consideration other than those consistent with normal tunnel design is applied. In the event rupture should occur, the power tunnel will be dewatered and repairs made. 5. Steel Liner and Penstock The steel liner and penstock will be encased· in concrete in excavated rock tunnels as shown on Plate 6. Once installation is complete, the fully embedded installation will react in concert with the surrounding rock mass. The portion of the penstock extending into the powerhouse and not encased in concrete is designed for an effective seismic acceleration of 0.7Sg. The closure of two penstock inlets into the powerhouse is by the spherical valves located within the powerhouse. The future powerhouse penstock is closed off by a high pressure spherical head. 6. Other Project Structures and Facilities The other project structures are designed for an effective seismic acceleration of 0.35 g consistent with or exceeding U.B.C. Zone 4 with the exception of the upstream cofferdam which is designed for a seismic acceleration of O.lg. 2.2.8 Temperature and Thermal Loads Expansion and contraction resulting from temperature changes, moisture changes, creep in component materials, and movement resulting from differential settlement will be combined with other forces and loadings for maximum effects. The minimum design temperature is -30°F -and the maximum design temperature is +85°F. 0216R-4430R/CG 2-12 2.2.9 Horizontal Ice Loads The design ice thickness for · Bradley Lake is 28 inches. Using charts developed by E. Rose in the paper "Thrust Exerted by Expanding Ice Sheet" Trans. ASCE Vol. 1 ·and 2," 1947, page 871 and also included in the USBR book "Design of Small Dams" figure 220, ·the 28 inch thickness of ice results in a horizontal ice load of 12 kips per linear foot, .assuming no lateral restraint to ice and a temperature rise of 15°F/bour. Excessive ice buildup on trashracks, gates, gate guides, and critical areas of stru~tures will be prevented by providing adequate submergence or heating of such equipment. 2.2.10 Wind and Wind Related Loaqs Wind data at the site has been gathered since August 1979. The analysis of the limited data indicates that highest winds occur from October through April with several events exceeding 70 mph during this period (maximum 106 mph recorded in the project area away from the coast). The 100 year return period speed has been estimated at 115 mph in the area with the predominate direction of the winds toward the northwest. Wind loads developed for the Bradley Lake project are based on the 1985 Uniform Building Code formula for wind pressure: where: p = c = e c = q p = C C q I e q s (UBC 11-1) design wind pressure combined height, exposure and gust factor coefficient as given in UBC Table No. 23-G pressure coefficient for the structure or portion of structure under consideration as given in UBC Table No. 23-H qs = wind stagnation pressure at the standar1 height of 30 ft as set forth in UBC Table 23-F I = importance factor as set forth in UBC Section 23ll(h) 0216R-4430R/CG 2-13 f Wind Load Application Wind loads are applied orthogonally to buildings and structures in only one direction at a time. For tanks or structures supported on four legs in an elevated position wind load .is applied diagonally. Wind loads are not combined . with earthquake loadings; however, . they are applied in combination with snow loads, with snow loads reduced to account for removal by wind action. Wind Load Exposure and Importance Factors Area Main Dam Diversion Outlet Structures Main Dam Diversion Gatehouse Power Tunnel Gatehouse Main Dam Structures Miscellaneous Structures Wind Driven Loads Exposure B c c c B Importance Factor 1.0 1.15 1.15 1.15 1.0 Design Wind Speed (mph) 120 120 120 120 100 Wind driven ice ride-up on the Main Dam face slab results in an estimated ice load on the parapet of 3 kips per linear foot acting parallel to the face slab. This is based on a design wind speed of 120 mph. The Main Dam parapet was also designed for a broken wave loading based on a sustained wind speed of 120 mph. 2.3 STABILITY CRITERIA 2.3.1 Main Dam Stability The main dam is a compacted rockfill founded on competent bedrock with an upstream concrete face slab membrane. A general plan and sections of the 0216R-4430R/CG 2-14 darn are shown in Appendix A Exhibit F Plates 2 and 3. The following criteria are being considered in the stability analysis: 1. Reservoir Elevations • • • Probable Maximum Flood Normal Maximum Operating Minimum Operating 2. Tailwater Elevations • • • Probable Maximum Flood Normal Maximum Operating Minimum Operating 3. Uplift and Seepage Forces 1190.6 1180 1080 1081 1067 1061 • At Base -full reservoir pressure at upstream face • Internal -full reservoir pressure at upstream concrete membrane, dropping to tailwater hydrostatic pressure within embankment • Upstream concrete membrane is impervio~s compared to rockfill. No excess pore pressures develop for construction or drawdown loading conditions. 4. Embankment Geometry • Crest Elevation -1190 • Foundation Elevation-1075 (at Axis), 1030 (at Extremity of D/S Toe) • Alignment of Axis -Straight • Crest Width -18 Feet 5. Slope Protection • Upstream Slope -Reinforced concrete face slab membrane • Downstream Slope -Oversized rockfill layer 0216R-4430R/CG 2-15 6. Material Properties • Rockfill Dry/Moist Unit Weight Saturated Unit Weight Shear Strength ·· 135 lbs/ft 3 145 lbs/ft 3 • Internal Friction 48° • Cohesion 0 .Shear Wave Velocity Damping 800 ft/sec 15% Permeability -Pervious relative to upstream concrete. membrane • Dam Concrete Face Slab Strength -3,000 psi compressive strength @ 28 days • Water Unit Weight 62.4 lbs/ft 3 · 7. Silt ...:.~~-NO-silt loads 8. Ice and Wind Loads These ioads are listed in Section 2.2.3 for ice loads and Section 2.2.10 for wind loads. 9. Earthquake • Horizontal earthquake with the response spectrum shown on Figure 6. 2-5 ~ Mean Horizontal Response Spectrum, and a normalized peak 0.75 g acceleration. • Vertical earthquake acceleration is applied separately as appropriate • 0216R-4430R/CG . 2-16 10. Method of Analysis • Static analysis -two dimensional Simplified Bishop Method of Slices using circul~r sliding surfaces, infinite .slope analyses, and sliding wedge failure analysis. • Dynamic Analysis -two dimensional permanent displacement method by Newmark, utilizing Sarma seismic amplification from base to top of dam. 11. Loading Combinations Case I -Normal Conditions • Normal Maximum Reservoir El. 1180 • Dead Loads Case II -Unusual Condition -Probable Maximum Flood (PMF) • Maximum Reservoir El. 1191 • Uplift and Seepage Forces • Dead Loads Case III -Extreme Condition -Earthquake • Normal Maximum Reservoir El. 1180 • Uplift and Seepage Forces • Dead Loads • Maximum Credible Earthquake Case IV -Construction Condition • Reservoir Water Surface at El. 1065 • Dead Load • Earthquake (0.1g) 0216R-4430R/CG 2-17 .> Case V -Reservoir Drawdown • · Drawdown from spillway crest to top of cofferdam eievation 1090 • Uplift and Seepage Forces • Dead Load • Design Basis Earthquake (0.3Sg) 12. Factors of Safety •• Static Loading Condition Normal Operating Maximum Reservoir Reservoir Drawdown Construction Condition. Maximum Reservoir Level • Dynamic Loading Condition Required Minimum Factor of Safety 1.5 1.2 1.3 1.2 The loss of freeboard and damage to the dam during an earthquake event described in the subsection 9, Earthquake, should not cause catastrophic failure of· the dam. 13. Sections to be Analyzed • The embankment· is analyzed for a unit width slice through a section at the maximum height. • Abutment geometry is considered for strain compatibility • Crest conditions are considered for local topographic amplification effects 2.3.2 Spillway Stability The spillway is a concrete agee section founded on competent bedrock in · a saddle on the right side of the main dam. The spillway is shown in Appendix A Exhibit F on Plate 4. The .following criteria were considered for the stability analysis of the spillway. 0216R-4430R/CG 2-18 1. Reservoir Elevation • • • Probable Maximum Flood Normal Maximum Operating Normal Minimum Operating 1190.6 1180 1080 2. Tailwater Elevation • Tailwater elevation will have no direct effects on spillway stability as the toe is well above tailwater pool level. 3. Uplift At Base • 100% of full reservoir pressure at the upstream face varying linearly to SO% rese=voir pressure at the drains, then varying to zero pressure at downstream face of apron. This condition assumes the drains to be periodically inspected and cleaned out. as required. For the PMF condi ti::m, uplift pressure at the upstream face shall be taken to be 100% of the maximum water surface headwater pressure. Internal • 100% of the full reservoir pressure at the upstream face decreasing linearly to zerc at downstream face. • For (PMF) Flood Discharge Cond:. tion the uplift should be assumed to vary from SO% bead rise above normal headwater pressure at upst=eam face decreasing linearly to zero at the downstream face. Uplift shall be assumed to act over 100% of base area. For all Usual and Unusual cases, when the :omputed stress without uplift does not meet the minimum allowable stress then the base is assumed to crack and the uplift on that por:ion not in compression is assumed to be 100% of the upstream head. For the extreme earthquake loadings, the uplift is not rev~sed in non-compressive sections due to the rapid cycling of seismic loads. 0216R-4430R/CG 2-19 4. 5. 6. Dead Weights • • Silt • Ice Concrete 145.0 lbs/ft 3 Water 62.4 lbs/ft 3 No silt loads 12 kips/ft applied at elevation 1179 (based on 28 inch ice thickness and developed as described in Section 2.2.9) 7. Earthquake The horizontal earthquake loads.are based on the response spectrum shown on Figure 6.2-5, Mean Horizontal Response Spectrum and a normalized peak acceleration of 0.75 g. The horizontal earthquake water loads are based on either the Westergaard added mass approach or the Zangar formula: where Pe = C E w h P = increase in water pressure in psf at any elevation due e to horizontal earthquake C = dimensionless coefficient from Figure 222 USBR "Design of Small Dams" E = earthquake intensity w = unit weight of water in pounds/cu. ft. h = total depth of reservoir at section studied in feet 0216R-4430R/CG 2-20 The combination of the earthquake loads are described in Spillway Stability Report which is included in Volume 3 of this report. 8. Temperature Loading from volumetric changes due t"o temperature was not considered in the analysis since the joints are not grouted. While the loadings were not evaluated, consideration was given to temperature effects in location of contraction joints and material selection. 9. Wind The wind loads are developed from the formula listed in Section 2.2.10.- 10. Loading Combinations Case I -Normal Conditions -=~-. Normal Maximum Reservoir El. 1180 . • Uplift and Seepage Forces • Dead Loads • Ice at El. 1179 Case II -Unusual Condition-Probable Maximum Flood (PMF) • Maximum Reservoir El. 1190.6 (rounded for design to El. 1191) • Uplift and Seepage Forces • Dead Loads 0216R-4430R/CG 2-21 Case III -Extreme Condition -Earthquake s Normal Maximum Reservoir El. 1180 e Uplift and Seepage Forces • Dead Loads • Ice at El. 1179 • Maximum Credible Earthquake (0.7Sg) Case IV-Unusual Condition -Construction Earthquake • Reservoir Water Surface at El 1065 e Dead Load e Construction Basis Earthquake (O.lg) or wind load Case V -Extreme Condition -Reservoir Drawdown • Drawdown·from spillway crest to minimum reservoir elevation 1080 • Uplift and Seepage Forces • Dead Load • Maximum Credible Earthquake (0.7Sg) 0216R-4430R/CG 2-22 11. Factors of Safety • Allowable Stresses -Maximum Case IV Case V Case I Case II Case III-Construe-Low Normal Unusual Extreme tion Res. Concrete 3000 psi Compression, psi Tension, psi Factor of Safety 1000 60 3 Rock: (40 ksf = 280 psi) Bearing Capacity, psi Factor of Safety • Sliding 140 2.0 1500 90 2 185 1.5 30CO 270 1 250 1.1 1500 90 2 185 1.5 Based on shear friction factor of safety computed by where 0216R-4430R/CG Q = CA + N tan 0 H Q = Shear Friction Factor of Safety C = Unit Cohesion A = Area Base Section in Compression N = Summation Normal Loads Including Uplift 0 = Internal Friction Angle 45° Concrete at Lift Lines 45° Concrete on Sound Rock H = Summation Horizontal Shearing Loads .2-23 3000 270 1 250 1.1 Case IV Case v Case. I Case II Case III Construe-Low Normal Unusual Extreme tion Res Sliding Shear Friction in Concrete Factor of Safety· 3.0 2.0 1.0 2.0 1.0 On Rock Foundation Joints and Faults Factor of Safety 4.0 3.0 N/A 3.0 N/A 2.4 MATERIAL PROPERTIES 2.4.1 Concrete Materials As part of the General Civil· Contract a concrete testing laboratory will develop concrete mixes for various required concrete strengths. These mixes will have the following specified compressive strengths at 28 · days and maximum aggregate size: Class AS 4000 psi 3/4 in. Class AL 4000 psi 1 l/2 in. Class BS 3000 psi 3/4' in. Class BL 3000 psi 1 1/2 in. Class BLX 3000 psi 3 in. Class cs 6 2500 3/4 in. Class CL 7 2500 1 1/2 in. 2.4.2 -Reinforcing Steel Reinforcing steel will be required in bar sizes No. 4 through No. 18 bars. All bars will conform to the Specifications for Deformed Billet Ste~l Bars for Concrete Reinforcement, ASTM A615, Grade 60 including Supplement Sl. Welded wire fabric will conform to ASTM A185. 0216R-4430R/CG 2-24 2.4.3 Water Stops Water stops are either. copper:, natural rubber, synthetic rubber, neoprene or polyvinyl chloride. Water stops are provided, where required, in: • expansion and contraction joints • vertical and horizontal construction joints communicating with dry interior spaces. 2.4.4 Structural Steel Structural steel will be ASTM A36 (Minimum yield stress = 36 ksi) or ASTM A572 (Minimum yield stress = 50 ksi) or ASTM A588 (Minimum yield stress = 50 ksi). 2.4.5 Structural Connections 1. Bolted Connections Bolts and hardware will conform to ASTM A325 Type 1 Class E for high strength connections or ASTM A307 for normal strength connections. High strength bolted connections will be f=iction type joints due to reversible wipd and seismic loading. 2. Welded Connections All structural welded connections will be in accordance with AWS Dl.l. Pressure vessel welding requirements will ~e in accordance with ASME VIII, Pressure Vessel Code. 0216R-4430R/CG 2-25 2.4.6 Tunnel Steel Liner and Penstock The tunnel steel liner and penstock will be constructed from high strength steel plates conforming to ASTM A710 with minimum yield strength for up to 1-1/4 inch plates of 90,000 psi, for over 1-1./4 to 2 inch plates of 75,000 psi, for over 2 inch to·4 inch plates of 65,000 psi. 2.5 GENERAL TECHNICAL DATA 2.5.1 Reservoir Elevation of Existing Lake Surface, feet Elevation of Maximum Operating Pool~ feet Elevation at Minimum Operating Pool, feet Elevation at Emergency Drawdown, feet Elevation at Probable Maximum Flood, feet Area of Reservoir at Full-Pool, acres Area of Reservoir at Minimum Pool, acres Normal Active Storage Capacity, acre-feet 2.5.2 Bradley Lake Dam 1,080 1,180 1,080 1,068 1,190.6 3,820 1,598 284,150· Type Length, feet Concrete Faced Rockfi11 602 Height of Maximum Section (at Axis), feet Top of Dam Elevation, feet 2.5.3 Bradley Lake Spillway Spillway Type Spillway Crest Elevation, feet .Gross Spillway Length, feet Spillway Crest Length, feet 0216R-4430R/CG 2-26 120 1,190 Ungated Ogee 1,180 27() 175 2.5.4 Power Tunnel Length (concrete and steel lined), feet Inside Diameter (concrete lined), feet Intake Invert Elevation, feet 2.5.5 Steel Liner and Penstock -Manifold 2.5.5.1 Liner Type Nominal Diameter, feet Length, feet Material Minimum Yield Strength, psi To 1-1/4 inch thick liner Over 1-1/4 inch to 2 inch thick liner Over 2 inch to 4 inch thick liner 2.5.5.2 Penstock -Manifold Length, feet Inside Diameter at Inlet, feet Material 18,820 11.0 1,030 Embedded 11 2,600 ASTM A710 90,000 75,000 65,000 230 11 ASTM A710 Minimum Yield St~ength, psi (same as liner yield strength) Diameters of Manifold, feet 11 and 9 Diameters of Penstock, feet 6.5 and 5.0 Diameter of Inlet to Powerhouse, feet 5.0 0216R-4430R/CG 2-27 SECTION 3.0 SUITABILITY ASSESSMENT 3.0 SUITABILITY ASSESSMENT This section addresses the geologic and soil .conditions with respect to their suitability to accommodate the Bradley Lake Hydroelectric Project. This section summarizes the results of the geotechnical investigations that were made for the various project areas. A compilation and summary of the various studies and field investigations which have been conducted for the Bradley Lake Hydroelectric Project is presented in the Geotechnical Interpretive Repo=t (GIR) which is included as part of the General Civil Construction docwrents in Volume 6. The GIR provides interpretations of the probable influecce of geqlogic and seismic conditions upon design, construction, and opet:ational requirements. For details· of· the conditions anticipated at specific project facilities, the GIR and its source documents should be consulted. A detailed discussion of the determination of general seismic effects and design criteria is included in Section 7. 3.1 SPECIFIC ASSESSMENTS 3 .1. 1 Dam Site Surficial geology at the site and logs of borings in the area are included in the FERC License Application Volumes 5 through 10, the Final Site Conditions Report of Geotechnical Field Investigations for the Bradley Lake Hydroelectric Project 1984 and 1985 Program, tb.e Supplement-. to the Final Site Conditions Report, and the 1987 GeotechnicaL Exploration Program. 3.1.1.1 Main Dam The main dam area lie~ at ·the head of the Bradlsy River at the outlet of Bradley Lake. The lake outlet is bounded on. the east (right abutment) by a single, large, bedrock knob, an adjacent low saddle, and a cliff that rises to the high hills north of the lake. The wes:t side of the lake outlet (left abutment) is dominated by a large bedrock ridge, located upstream of the dam axis, and several bedrock knobs in the actual abutment area. The 0216R-4431R/CG 3-1 power tunnel intake will be located in the large ridge upstream of the left abutment, the spillway will lie in the saddle adjacent to the dam right abutment, and the diversion tunnel penetrates the large knob separating the right dam abutment from the spillway saddle. The main dam crosses the river between the large rock knob on the east and the smaller knobs on the west. An upstream cofferdam will be constructed to block off lake outflows . during construction of the main dam. The structure is to be located innnediately at the lake outlet, bridging an existing island·. The crest of the main dam is located about 520 ft downstream of the lake outlet. The east (right) dam abutment is a prominent bedrock knob rising to about El 1220 ft. The west (left) dam abutment is a smaller bedrock knob with a ·top elevation of about 1200 ft. The left abutment area has been trimmed down for the 'power tunnel-gateshaft staging area. The downstream face of the dam will encroach upon another, lower, rock knob with an elevation of about 1150 ft. The upstream face slabs of the dam, on the left side of the Bradley River valley, lie in a topographic ravine; the toe of these slabs will form a segmented arc. Surficial deposits in the area of the damsite generally consist of a thin veneer of organic silts and sandy silts up to 2 ft thick where bedrock is not exposed. Notches, open· fractures, and depressions in the bedrock are generally filled with locally-thicker soil cover consisting of colluvium and talus. Larger-scale valleys, gullies, and saddles are filled with significant deposits of colluvium, till and talus that reach depths of 25 ft. Isolated deposits of glacial till have also been noted in drainage areas adjacent to the Bradley River • .Channel deposits in the Bradley River include alluvium deposits of gravels, cobbles, and boulderss with local areas of talus-accumulation, in a random matrix of sands and silty sands. Talus and rubble deposits, 3 to 25 ft thick, are found in this area of the river and are often underlain by-sands. 0216R-4431R/CG 3-2 The soil cover supports grasses and dense, lo·.;-, brushy scrub vegetation consisting primarily of willows and alders, which .are persistent _throughout the darnsite area. With the exception of an occasional ephemeral stream in the gullies and saddles, no perennial surface ·run off (other :than the Bradley River) or springs have been observed. In the areas of thickened overburden, perched groundwater tables are observed at or near sur::?ace. This is probably due to the poor drainage capacities of the dense cverburden materials and to recharge by surface runoff _produced by the hign amounts of precipitation encountered in this area. Numerous lineaments transect the darnsi te area at various orientations. Predominant orientations are N4°-l0°E, and N4"-55°W, all dipping nearly vertically. These lineaments may represent fal!.lts, closely spaced joint sets, and/or lithologic contacts. Jointing is the dominant structural feature manifested in the damsite area, particularly in the right abutment. Predominant joint orientations are NC8°-85°W, vertical + 10° and N20°-35°E, 72°-82°SE. The darn right abutment knob which supports the spillway foundation and is penetrated by the diversion tunnel is, for all ~ractical purposes, composed entirely of massive graywacke. The left abutJlent is geologically more complex than the right abutment. The rockrnass in the left abutment area consists mostly of interbedded/intermixed graywa=ke-argillite with isolated areas of purer argillite and graywacke. !he prominent ridge south (upstream) of the left abutment is mostly massive graywacke. The lithologic contact between the right abutment and left abutment apparently occurs in the stream bed of the Bradley River. It remains uncertain whether the location of the river bed, and perhaps the lithologic contact, is structurally controlled. At the time of the most recent glacial maximum, the river channel and spillway saddle was occupied by a glacier created by the advance and confluence of the Kachemak and Nuka glaciers. Bedrock adjacent to the river channel displays glacial striations and chatter marks, and is, in places, mantled with dense glacial till and ice-transported boulders. 0216R-4431R/CG 3-3 Glacial striations and grooves ar.e evident on exposed surfaces. Borehole DH6 intercepted a 22ft thick layer of argillite, at El 1157, which is not exposed at the surface. Thin soil and locally thick vegetation are found in numerous open fractures and ledges at the rock/dam interfaces. The graywa~ke appears fresh and hard to very hard. No persistent bedding or foliation was noted in the graywacke. The most significant features at the main darn right abutment are the fractures and jointing. Major joints have a west-northwest trend with nearly vertical dips. Spacing generally ranges from less than 1 ft to more than 6 ft, however, less prominent joint sets are observed with spacing up to 20 to 25 ft.. Measured joints show significant trends and dips of approximately N45°W, 78°NE and Nl9°E, 80°SE. Other significant joint trends that have been measured are N55°W-EW, N74°E, N23°-38°E all dipping nearly vertical. A few secondary joint sets are visible on the abutment face~ one set having an apparent dip of 25° to 30° to the south, and another, more obscure set _with an apparent dip approximately 25° to the north. The various intersecting joints give the bedrock a blocky appearance, however, joint-bound failure wedges are not. expected to present ·a significant stability problem in the right abutment of the dam. Similar conditions are anticipated for the spillway foundation. Surficial weathering is generally confined to the upper few feet of rock, however, staining on fracture surfaces in outcrop and in borings indicates that these are potential leakage channels from the reservoir. Boreholes DH6 and RM30 both intersected open jointing and incurred loss of circulation fluids during drilling at depth, and the diversion tunnel has encountered open, silt and sand-filled joints at depth. The overburden_ is to be stripped from the right abutment area and from the notches and grooves in the southwest face. The upstream dam/bedrock interface is to be extensively excavated (cuts in excess of 10-ft deep) by controlled blasting methods to form a· toe plinth-bench with a minimum width of 4 ft. This excavation is detailed on the construction drawings. Backsloping and benching above and·below the toe plinth may be required to 0216R-4431R/CG. 3-4 stabilize the bedrock. Spot bolting and chain-link mesh or welded wire fabric may be required locally to insure worker safety. A single-row grout curtain is planned to consist_. of primary holes up to 95 ft deep at 10-ft centers with secondary and tertiary holes as necessary along the entire length of the toe plinth. In addition special treatment and grouting of open surface joints and fractures may be required. Grout takes are generally expected to be low except in areas of open, stress-relief joints and fractures such as observed in the diversion tunnel and also as noted in borehole RM 30. No other rock stability problems or significant wat~r inflow along joints and fractures are anticipated during construction. Bedrock at the . stream channel (Borehole RM38) is mostly argillite. The effects of weathering and/or poor rock quality penetrate to depths of up to 45. ft. Further up the slope aloJ:?.g the toe plinth excavation (Boreholes RM35-37) the bedrock is primarily mixed graywacke and argillite. The effects of weathering are generally confined to the uppermost few feet. Variable rock conditions may be .encountered, depending on the dominant 1i thology and the ·presence of shears or intense jointing, as evidenced by lineaments projected through the area. Althoug~ most weak surficial rock has been eroded away, the left abutment still has less favorable mechanical characteristics than the right abutment, requiring more deliberate excavation and scaling. At the upstream toe in the stream channel, · o..,erburden thicknesses range from about 3 ft of gravel at the right abutment to approximately 24 ft of talus, cobbles, boulders and gravel near the left abutment. Bedrock in this area is predominantly graywacke with a zcne of mixed graywacke and argillite. Rock quality in the middle of the channel is generally good. Toward the downstream face of the dam and along the middle to west side of the channel, overburden thicknesses range from 6-12 ft of stream gravels, cobbles, and boulders intermixed with tal us blocks. Bedrock is graywacke and· intermixed graywacke and argillite. Rock guality varies considerably and seems to correspond with lineaments projected through the stream channel. 0216R-4431R/CG 3-5 The main dam left abutment is markedly different than the right. abutment in that argillite is more prevalent and the graywacke is mostly intermixed with various percentages of argillite. Contacts between the two major rock types are typically gradational and exhibit boudinage (or pillow-like) structures of graywacke within the argillite. The argillite shows well-developed foliation which trends generally north-south ·(perpendicular to the dam axis) and dips 80°. While the graywacke is generally fresh and hard·, the argillite is only moderately hard, and is less resistant. Weathering is concentrated along foliation planes. The westernmost extremity of the left abutment ties into Hill 1205, which is a mix of argillite and grayW'acke. The downstream face incorporates another knob consisting .mainly of graywacke. Major joint trends and dips in this area are N45°-85°W, vertical, and N35°-75E, 82°SE. The effects of weathering are more pronounced in the marginal quality rock found in the upper 10 ft to 15 ft of Hill 1152 (Borehole DH16). Overburden cover between these two knobs varies from less than two ft to· approximately 10 ft in the saddle. Toward the south, or upstream face of the· left abutment, the soil profile thickens considerably to an apparent maximum of 25 ft to 30 ft of gravels, cobbles, and boulders (composed predominantly of graywacke) in a sandy, silty, gravel matrix. This maximum thickness occurs in the gully area north of the:=intake-ridge. Seismic velocities indicate that the overburden is moderately dense. Several lineaments which are interpreted to be minor faults or fracture zones trend across this area but no changes in 1 i thology were noted in outcrop. The seismic velocity differentials may be attributed to intense fracturing or a joint swarm. On the west side of the river, a more pronounced velocity differential was recorded which may indicate a lithologic change or intense fracturing or weathering~ This lineament may . also correspond to tunnel fracturing projected between Sta. 187+85 to 190+45. Due to the convergence of several lineaments (faults and/or closely spaced joints) in conjunction with the variable lithology, the ravine north of intake ridge at the left abutment represents the poorest quality bedrock in the damsite area. 0216R-4431R/CG 3-6 The overburden will be removed to expose the bedrock surface ~hroughout the entire dam foundation. Overburden thickness at the left abutment is expected to vary between 2 ft on the higher slopes and knobs to as much as 25 ft adjacent to and in the stream channel. O•erburden seismic velocities in the area of the toe plinth approached 3500 fps, suggesting that some ripping may be required to remove dense mater:al such as till, boulders, and talus. In the area of the toe plinth, it nay be necessary to rip or blast (generally not to exceed 10-ft in depc:~) in order to provide a uniform, sound surface for concrete. Dental exc:lvation ·and filling. of open fractures with lean concrete will be required. Jointing, lineaments, and/or faults projected through ·this area indi::ate th,at openings several inches wide (at the surface) may be encountered (e:g Lineaments 1 and 2). . . As in the right abutment, the entire length of the toe plinth will be curtain grouted to a depth of up to 95 ft. In areas of intense fracturing, additional grouting may be· required. Open fra::tures upstream of the toe I . . plinth are to be surface treated along their exposed length and grouted as l . . necessary to further impede groundwater fracture flow under the dam. Under the fill section of the main dam, some rock :-emoval may be required to eliminate anomalous overhangs and surface irregularities. 3.1.1.2 Upstream Cofferdam The present river channel lies between an islcnd and the main dam right abutment. The portion of the flood. plain between the island and the left abutment is plugged, to an elevation approximately 2 ft to 3 ft above normal lake level, with a deposit of tal us, .boulders, sand, gravel, and minor amounts of silt. This is a secondary channel during high water stages. Bedrock exposures at the left and right abutme!lts and on the island are essentially massive graywacke that is faintly weathered and hard. Borehole D-1 on the lef.t abutment encountered 13 ft of r·:mnded ice-scoured boulders and angular, blocky, rock talus up to 6 ft in dimension, all in alluvial sand and gravel~ This boring encountered argillite which is believed to be mixed with graywacke. Borehole RM46, drilled r.:.ear the right abutment and within the main channel of the lake outlet, encoLntered 10 ft of overburden 0216R-4431R/CG 3-7 consisting of gravel, silts, and sands. Some problems with clean "running sands" were encountered while drilling through the channel deposits. Bedrock in this borehole is faintly-weathered, sound graywacke. Another borehole, RM45, located in the middle· of the channel and upstream of the cofferdam, penetrated 47 .ft of overburden as follows: 26 feet of cobbles and rock fragments with a sandy, gravelly matrix; from 26-36.5 ft;, black argillaceous sand with a trac~ of gravel and silt; 36.5-47.0 ft, inter- layered sands .a:nd gravels with scattered silty layers. Running sands were also encountered in this boring. Again, bedrock is faintly weathered ·graywacke but it is highly to intensely fractured. Records from seismic reflection profiles (SP83-SS) show that a bedrock ridge may extend for approximately 50 ft to 100 f~ into the lake but then drops off rapidly lakeward at a slope of 35°-45°. Sediments that are inferred to be coarse sand and gravel 10 to 60 ft thick overlie the bedrock up to 200 ft offshore. ·The cofferdam is to be constructed from locally-derived materials produced by stripping operations, shot rock from road building, and a limited quantity of processed fill·. An existing exploration trench will be widened and will bottom on bedrock to serve as a cutoff trench. The bottom and upstream slope of the trench will be lined with an impervious geomembrane, which will continue up through the above-ground portion of the cofferdam. The downstream slope of the trench will be lined with filter fabric. The dam is essentially a random-fill structure. Construction is expected to be· carried out under wet conditions. The contractor will be advised to schedule the construction of the cofferdam for the months of November through April when.lake levels and flows are normally at a seasonal low. 3.1.2 Reservoir Rim Stability The entire reservoir rim except the Kachemak Delta area at the head of the lake consist.s of bedrock which is either exposed or very thinly mantled by colluvium and talus. The bedrock is insoluble, and development of instability due to solution channeling is not considered to be a concern. ?llere are no known points around the rim at which the bedrock barrier is thin enough to be breached due to increased hydrostatic pressure resulting 0216R-4431R/CG 3-8 · from the. increase in lake level. There are no "known joint or fault blocks of suffiCient size to produce catastrophic waves should sliding or toppling into the lake occur. A talus slide on the north shore of the lake, about 700 feet to the east of the dam, is composed of small angular pieces .nixed with coarse and fine sands. This material is derived from fractured argillite and graywacke and has formed ~ relatively stable slope. Terraced cliffs across the lake, on the north shore, could pose a threat. because of their steepness. However, if fai~ure occurred, most of the material would fall .on the terrace below. The lower cliffs would have minimal rock fall danger or wave production potential because less than 200 .. feet of the cliff face would be exposed when the reservoir is filled. The Kachemak Creek Delta presents the greatest potential for reservoir instability. The potentia~ risk.from.waves.produced as a result of seismic induced submarine sliding of delta sediments was evaluated ("Investigation of Landslide-Induced Wave at Bradley Lake"). The resulting wave had no detrimental effects on the proposed facilities. 3.1.3 · Spillway The spillway lies east of the main dam in a low saddle. The west side of the saddle is bounded by the east (right) dam abutment rock knob. The east side of the spillway saddle is a· steep rock cliff. Bedrock exposed during Site Preparation excavations in the spillway saddle displays glacial striations and chatter marks left by glacial ice that occupied the spillway saddle and Bradley River channel during the last. glacial advance. The bedrock also exhibits a smootll. polished finish that· was perhaps caused by ice s~ouring or by glacial. meltwater flowing through the spillway saddle. The cliff has continuous bedrock exposure ~d the knob has numerous outcrops nea:r the crest elevation of the spillway. All of these outcrops are mapped as graywacke ( 98%) with very mino:r: argi 11 i te (2%) . The rock appears fresh and is hard to very hard. The bottom of the saddle has bedrock outcrops and the rock appears identical to the high cliff and rock 0216R-4431R/CG 3-9 knob. Hence, the saddle does not appear to have been formed in weaker lithology. This implies a structural influence on the formation of the spillway saddle. Overburden depths in the area of the spillway are quite variable, originally ranging from 2 ft on the west flank to 17 ft near the east cliff at the crest of the saddle. Much material at the crest was removed during site preparation work and very little overburden remains. Throughout the spillway area, the soil materials consist of cobbles and boulders (up to 5 ft in dimension) in a silty, sandy gravel matrix. . Very coarse, bouldery, graywacke talus lies below the eastern cliff and extends from· the saddle to the bottom of the spillway. · Borings throughout the spillway area also show a dominance of graywacke. Two boreholes, RM43 and DH7EX, were drilled at an angle across the spillway from west to east. Neither boring penetrated the plane of the cliff east of thE! spillway;· However, these borings and others drilled near the east cliff, show ev1dence of highly to intensely fractured rock with some gouge present. A lineament can be proj~cted on aerial photographs through the area. It is suspected to be a minor fault or a swarm of closely spaced joints. A small gouge zone is visible at the lake edge· and roughly projects along the base of the cliff face perpendicular to the spillway · · baseiine. Several small groundwater seeps were noted on the face of the east cliff. Major joints in and adjacent to the spillway trend and dip N84°W~ 84°S and N25°E, 72°SE. All overburden from the upstream edge of the spillway to the downstream pool (to El. 1060) will be removed. Overburden varies in thickness from 2 ft near the crest to as much as 60 ft (locally) at the downstream pool. ···Due to· .. the presence of geologic structure through the · saddle and the proximity of steep cliffs to the east, the ·overburden is expected to contain talus in addition to glacial till, with some. boulder and cobble size material. The bedrock is expected ·to be locally somewhat fractured, 0216R-4431R/CG 3-10 requiring grouting and limited fill concrete for foundation improvement. Some ripping and limited blasting will be necessary to meet design grade and flow path requirements in the apron area. A grout curtain is designed to transect the up:;tream base of the spillway structure and extend about 235 ft. westward froJJ the right abutment cliff face. The curtain extends eastward approximately 80 ft from the cliff face. This extension is intended to seal a series of joints oriented approximately N48°W. These fractures may conn=ct the reservoir with the downstream pool, so they will be grouted to reduce potential leakage. 3.1.4 Diversion Tunnel/Gate Shaft The Diversion Tunnel is designed for use during dam construction to divert water around the damsi te. It will also serve 3S a low-level lake outlet and will be used for emergency drawdown during commercial operation. The tunnel is positioned between the east (right) dam abutment and the spillway, and is oriented approximately Nl7°W through the area of the main knob. The tunnel intake lies in the lake slightly to the east of the lake outlet (Bradley River) and discharges water into the downstream pool below the dam. The diversion tunnel is straight and at its deepest point lies about 150 ft below the top of the east abutmer.t knob. Rock crops out at the intake, the tunnel outlet, and along much of the tunnel alignment. The diversion tunnel excavation and intake structure construction was completed during the Site Preparation Contract. Diversion was initiated in late May 1987 and has operated satisfactorily =or almosi:: 10 months. The General Civil Construction Contract consists, in part, of excavating and lining the gate shaft and additional excavation and concrete lining in the _tunnel and portals. Borings RM30 and DH6 are located near ·the gate shaft. The bedrock is comprised of predominantly fresh, hard to very hard graywacke, consistent with the remainder of the right abutment, and ir-cludes minor areas of mixed argillite and graywacke. Major joint trends in the vicinity of the shaft are N20°E, N48°W and N84°W with ·dips of 75°SE, 78°NE and 84°SW, 0216R-4431R/CG 3-11 respectively. Occasional downstream-dipping, open joints were also encountered in tunnel excavation. The shaft is to be excavated from El 1195 to the tunnel crown at El 1084+. throughout. Generally sound rock prevails During the Site Preparation Contract, contact grouting of the upstream concrete portal structure was done. During the General Civil Construction Contract a grout ring will be placed just upstream of the gate shaft. This ring grouting, along with the spillway/main darn grout curtain, is expected to be effective in cutting pff fracture leakage through the main knob area. Grouting of open fractures and water seeps, spot bolting of isolated roof instabilities in the .tunnel, and crown shotcreting may be required in the General Civil Construction Contract. In the gate shaft excavation, little water seepage is expected prior to reservoir filling. During reservoir filling, significant joint seepage can be expected to occur before concreting is completed and will necessitate drainage and/or grouting. Primary porosity in the bedrock is virtually non-existent. Joints, fractures, and faults provide the only means for collecting and conducting groundwater. As a result, storage and recharge capacities are limited. 3.1.5 Power Conduit -General A number of borings have been made on the proposed and alternative tunnel alignments. Logs of these borings are included in Appendix H of the License Application, and in the Final Site Conditions Report and Supplement to the Final Site Conditions Report. Laboratory tests and petrographic analyses were made of selected rock cores from various borings and from some surface samples; results of these are also included in those documents. Interpretations based on data derived from the borings, tests, and analyses are incorporated in the Geotechnical Interpretive Report and are sununarized below. Detailed profiles for the three tunnel options, geologic conditions interpretation and construction considerations are presentedin depth in the Geotechnical Interpretive Report. 0216R-4431R/CG 3-12 3.1.5.1 Intake Area Surface reconnaissance reveals that the ·rock is comprised of complexly mixed graywacke and foliated argillite with :ess than 10 percent chert nodules. and layers. The contacts between t~e graywacke and argillite roughly parallel the foliation in the argillite and typically appears to trend N-S to N 20° E and dips steeply. Several small faults and joint sets are present. These features have been described in some detail in the Geotechnical Interpretive Report and its refe:-ence documents. No faults are known to intersect the currently proposed location for the intake portal. It is considered that the intake facilities should not .encounter any significant faults or shear zones. Several mir:or shears have been mapped in the intake area . These are well exposed 3nd are· not known to exceed one to two feet in width. Several of these may be expected to cross the intake channel but are not considered significant to construction or operation of the facility. Geologic conditions are considered to be satisfactory for construction of the proposed in:ake facilities. Excavation of the approach channel (from portal face to approximately Sta. 194+30) and associated surface cuts is expected to be through bedrock. Talus overburden in a till and alluvium/colluvium matrix is expected beyond this point, to Sta. 195+10 at the lake shore. Excavation in the lake bed would be in similar. type overburden. Bedrock excavation is ·anticipated to be in graywacke with minor argillite and is cor:sidered to be sound except in close proximity of the bedrock surface. Surface features in this area include near vertical rock faces, rock pinnacles and large detached blocks. Joint sets which influence slope stability are oriented as follows and are listed in order of decreasing intensity: Set 1) 2) 3) 4) 0216R-4431R/CG . Strike Range N30°-45°E N75°-85°W N40°-55°W · NS+l0° 3-13 Dip Range 60°SE-85°tiW 65°SW-85°tiW 65°NE-75°DE 55°-65°W The intake is designed as an unsupported quarry excavation with 3S ft. high vertical cuts and wide benches down to El. 1090. The overall average slopes vary between S0° and 60° from the horizontal depending on their orientation with respect to the four primary joint sets. The vertical cuts below El. 1090 are supported by patterned rock bolting. 3.1.5.2 Power Tunnel The power tunnel is designed as a minimum 13 ft diameter excavation (minimum ll ft lined I .D.) connecting the intake works at Bradley Lake to the manifold and penstocks at the powerhouse. Lineaments that represent the surface expressions of faults, shear zones and joint swarms were located from field mapping observations and aerial photo interpretations. The major lineaments are shown on the tunnel plates. Detailed lithologic subdivisions based upon outcrop and boring data are shown on Plates 1-4 of the Geotechnical Interpretive Report. Lithologies within rock units are intimately mixed on the scale of fractions of an inch to tens of feet. Rock units are often discontinuous and irregularly sh~ped with a wide range of 1 i thologic proportions within each unit. Lithologies characteristic of different environments of deposition commonly occur adjacent to each other. Compositional (lithologic) layering and the most pronounced structural trends are essentially coincident, striking N-S to NlS 0 E and dipping 90° ± so. This orientation includes the Bull Moose and Bradley River Faults. The trends of other persistent fracture and joint systems are about N4S 0 W, NS0°-70°W and N50°-60°E. The latter orientation is present only between the Bradley River Fault and Bradley Lake. This easternmost section of the tunnel alignment is underlain by interbedded graywacke and argillite. Because of their complex mixing, these rock types have been mapped as a single· unit. The argillite is commonly foliated and occurs as interbeds and pockets that range from less than a foot to as much as 100 feet thick. 0216R-4431R/CG 3-14 Jointing is more apparent along this section of the tunnel alignment than further to the northwest. Several lineaments also cross this section of the tunnel alignmen~ at various orientations. It is suspected that some of these features may be faults, but there is generally insufficient rock exposure to determine whether they represent f:ml ts or major joints. One pair of parallel lineaments, located about 1 ~ 700 feet northwest of the intake structure is particularly suggestive of ~ fault zone. Their origin is uncertain; if they .are the surface expressioo of a fault, the zone may contain highly fractured and crushed rock up to about 200 feet wide along the proposed tunnel alignment. At a distance of approximately 3, 900 feet from the intake, the tunnel alignment crosses the Bradley River Fault zone. The main trace of the fault can be followed for several miles along a trend of about Nl5°E. The fault is mantled by colluvial and glacial deposits, but is believed to be nearly vertical because of its linear topograFhic expression. Exposures elsewhere along the Bradley River Fault h~ve suggested tpat the main fault trace can have a gouge zone of finely pulverizec material that is up to 50 feet wide, with sheared argillite extending another 50 to 75 feet on either side. The Bradley River Fault zone was explored by borings SW83-2 and RM-19. These borings encountered four significant fault planes, enclosing an extent (along tunnel alignment) of about 200 feet, plus adjacent fracture zones for a total of about 900 feet. Alternating zones of graywacke and chert with local zones of cherty argillite and foliated argillite were encountered .. Joint spacings in these materials increase to moderately to widely spaced joints when argillite materials are present in minor amounts. The naterial observed in shear zones is predominantly brecciated argillite rock containing clasts of chert. Locally the rock has been reduced to fault gouge consisting of breccia fragments in a clayey silt matrix." The cherty argillite adjacent to the shear zones is generally very closely jointed and the argillite faces adjoining shear planes are extremely sliekensided, often containing crushed rock fragments (breccia) and gouge •. 0216R-4431R/CG 3-15 The amount and sense· of displacement along the Bradley River Fault zone is not well established. Slickensides rake from 0 to 30° along the fault suggesting a vertical component of up to 400 feet associated with the 1,000 feet of . apparent horizontal displacement. Horizontal offset of a dacite dike tends to confirm this. A multi position, rod-type extensometer was installed in Bo.ring DH-lOEX by the COE. This boring crosses the Bradley River Fault and is located about 1250 feet (380 meters) north of the point where the presently proposed ·tunnel alignment intersects the fault. The extensometer was installed on December 13, 1980. No movement indicative of fault movement was recorded to date of failure of the instrument.· Failure occurred sometime between April 15, 1981 and July 27,'·1981, due to ice-jacking of the instrument head. Northwest of the Bradley River Fault zone, the tunnel alignment crosses the highest 'e-levations and best exposed bedrock exposures along its route. This area is underlain predominantly by foliated argillite, with lesser amounts of massive argillite, graywacke, and a single large dacite dike. Much of the foliated argillite contains nodules and thin discontinuous layers of chert. A few massive lenses of very closely fractured chert up to lOO=feet --w-ide were also found interspersed with the foliated argi 11 ite in this area. The foliation in the argillite and cherty argillite strikes from N-S to N20°E and typically dips greater than about 75 degrees. The primary dacite dike, although not exposed on the alignment itself, appears to cross the proposed tunnel alignment along a N80°E trend with a nearly vertical dip. For tunneling purposes this rock will probably behave similarly to the graywacke. Bedrock outcrops along this segment of the tunnel alignment tend to be widely to very widely jointed. Hundreds of short, linear, soil-filled depressions can be seen in this area, many of which are presumably the surface expression of bedrock joints and/or minor faults. Larger lineaments, also common in this area, present the same problem for attempts to define their structural significance. A series of lineaments, occupying an area about 1,000 feet wide, located east of and subpara11'el to 0216R-4431R/CG 3-16 the Bull Moose fault· zone are possibly t'he. surface expression of smaller faults associated with the main.fault trace, bu= exposures are insufficient to conclusively determine their origin. In spi-te of relatively good rock exposure in this a,rea, it was not . possible to determine conclusively whether these represent minor faults or promi~nt joint sets. In either case, exposures limit the width of these apparent discontinuities at the surface to less than about 10 to 15 feet where· they cross the tunnel alignment. The main trace of the Bull Moose fault zone is located approximately 9,800 feet northwest of the tunnel intake. It is expressed as a narrow, topographic notch with a 200 feet high steep west wall. This are.a is densely vegetated and rock is exposed only in s~all isolated outcrops. · No surface exposures of the crush zone in the fault were found. The tunnel alignment crossing of the Bull ·Moose· Fault ·was explored with borings SW 83-4 and RM-21. Bedrock was encountered essentially at ground surface in each hole.· Random alternating zones. of graywacke, argillite, and chert, as well as mixtures of these lithologies were logged within the depths explored. The shear zone of the Bull Moose. Fault was encountered over a total width of approximately 400 feet a:).ong tunnel alignment. The brecciated argillite . . . and graywacke in this zone is locally shear~C. to silty sand and clayey gouge. The rocks adjacent to the shear zone, argillite above and chert below, are highly fractured with considerable shear deformation. The vertically projected. location of the shear zone encountered in the ' . borings is consistent with th~ mapped location of the fault trace for a near-vertical fault plane that has a tqtal primary ~ault width of 400 feet and an inferred fault zone width (with adjacent fractured a~eas) of about 1400 feet. A multiposi tion, rod-type extensometer was· insta~led in Boring DH-17EX by the COE. This boring ·is located about 500 feet (152 meters) south-southeast of the point of ·intersection a= the proposed tunnel with 021.6R-4431R/CG 3-17 the Bull Moose Fault. · The boring was angled to cross the fault. The installation was made on December 15-17, · 1980. No evidence of fault movement had been noted up to time of instrument failure due to frost jacking at sometime between April 15, 1981 and July 27, 1981. The bedrock exposure is much more limited along this ·segment of the tunnel alignment than it is to the southeast. This is particula,rly true to the northwest where forest and soil cover mantle all but a few small isolated rock outcrops. The available exposures indicate that this section of the tunnel alignment is underlain predominantly by foliated and massive argillite. Cherty argillite and graywacke crop out in relatively small amounts, although boring data indicat·e that these rock types are more common than their surface exposure suggests. The predominance of argillite is also indicated by natural outcrops visible 1000 -1500 feet southwest of the tunnel alignment in a gully which roughly parallels the alignment. The recognizable str.uctural trends in this area conform to those elsewhere along the tunnel alignmenL Foliatfon in the argillites is consistently oriented at N-S to N20°E. Jointing is widely to very widely spaced in most exposures, with a dominant strike of N75-85° North. Based on data from surface mapping, borings, field instrumentation, and laboratory tests it has been concluded that geologic conditions are adequate for construction of the power conduit system. It is further considered that it is feasible and preferable to excavate the tunnel using a tunnel boring machine~ Intact rock is not expected to pose abnormal support requirements. The potential for difficult tunneling conditions appears to be associated with structural discontinuities such as faults, fracture zones, and joint swarms. Exploration data suggest that. ravelling, squeezing, and running ground conditions might be encountered in areas where structural features intersect the tunnel alignment. Mineralogical testing indicates that significant swelling ground conditions should not be antiCipated. In general, increased weathering and poorer rock conditions might be expected 0216R-4431R/CG 3-18 for a tunnel driven along the Option C (hig~) alignment, resulting in greater rock support requirements. However, dt:.e to the shallower depth, while initial· gro_undwater inflows might be greater than the lower options, the overall water quantities should be less. An exception would be at Halfway Lake, where shallower depth could result in much greater inflows. Pressures inducing running or squeezing ground would be expected to be lower, with resultant minor reductions in tunnel:ing difficulty. 3.1.5.3 Access Adit, Penstock and Manifold-Area Geotechnical ·_ investigations in the south ac:cess adi t, penstock, and manifold areas consist. of surface outcrop mapping, three seismic lines, 5 boreholes and one test pit. The penstock area excavations extend eastward from the east wall of the powerhouse excava:ion, so. geotechnical data gathered within the powerhouse site is also generally pertinent. Prior to Site Preparation, overburden consisted of an organic mat overlying 1-2 ft of· colluvial gravels in an organic s:Il t matrix which, in turn, overlie 2-4 ft of till. Underlying the till, a 2-12 ft horizon of intensely weathered bedrock was encountered. Sand and silt fill the interstices between angular gravel and cobble s~ze fragments of dislocated bedrock. The ground overlying the penstock and manifold excavations has been excavated during Site-Preparation. These excavations consist of three benches approximately 14 ft wide. Side slopes ere 1H:4V. The remainder of the excavation consists of tunnels for thrust blocks and 6-1/2 ft I .D. steel penstocks leading to the manifold section. Four rock types are present in the penstock/manifold tunnel sections. They consist of argillite, mixed argillite and graywacke, argillite with chert, and-dacite. The argillite and graywacke are intimately mixed and display mylonitic structure in the form of irregular bar-ds and lenses on the order of 1 in to 1 ft thick. Foliation in the argillite is poorly developed where graywacke predominates and becomes well developed as the argillite proportion increases. The argillite and mixed argillite and chert have well developed foliation. Foliation planes tend to curve around chert nodules and rarely dissect a nodule. 0216R-4431R/CG 3-19 It ·is anticipated that intermixed argillite and graywacke dominate the lithology of this portion of the site. Seismic velocities range from 9,800 fps to 13,670 fps. This reflects the range of relative ·proportions of argillite and graywac~e, and variations in intensity of weathering. The northeastward trend of the predominant joint and foliation planes is transverse to the tunnel excavation. Essentially, all water-bearing planes, so oriented, are expected to readily drain into the tunnel. Long-term construction seepage into the manifold/penstock excavation is not anticipated to exceed 1 gpm per lineal foot of excavation . . . 3. 1 . 6 Powerhouse The Powerhouse site lies atop a 20-25 ft high rock bluff adjacent to the intertidal mud flats and salt marsh.along the eastern·shoreline at the head of Kachemak Bay. The Powerhouse will contain two Pel ton turbine generating units and is to be founded in an excavated rock bench at El 40. Three steel.penstock sections will connect through a manifold to the steel tunnel liner. It should be noted that the power· conduit, manifold, and penstock sections are sized~ and are to· be constructed, for 3-unit operation. However, the powerhouse will initially contain two operating units, with provision for adding a third. The additional foundation excavation for the future third unit will be excavated during the ·General Civil Construction Contract and then backfilled with free-draining fill. A substation will be located to the north of the Powerhouse on a cut and fill bench at El 18. Powerhouse excavations are expected to require dewatering throughout construction, with shallow dewatering wells or sumps likely to be necessary to drawdown· groundwater below concrete placement e'!evation. Inflow for the entire powerhouse is ·expected to run from 150 to 500 gpm at low tide, and up to 500 gpm plus cofferdam leakage at highest tide. 0216R-4431R/CG The tailrace -will be a flared,-excavated _channel 90-175 ft wide extending 210 ft westward into the tidal flats, with an additional 175 ft wide excavated channel at El 3.5 extending to intercept an exist~ng slough at a distance of approximately 900 ft. The flared section of the channel will be lined with geotextile fabric and will be protected with riprap. The entire planned powerhouse work area above the tidal flats has been excavated to bedrock benches during the Site Preparation Contract. Prior to excavation, vegetative cover consisted of Sitka and White spruce trees and a sparse undergrowth of willow and -alder with en organic mc3.t of moss and lichen. A temporary cellular sheet-pile cofferdam ~ill be placed below the powerhouse site on the tidal flats. The sheet p!le sections will be driven through the intertidal sediments to bedrock and form a cut-off extending from the face of the bluff at the extreme northern and southern margins of powerhouse excavation. The cofferdam should effectively reduce groundwater recharge through the sediments and into the excavation area from tidal influences. Seismic data and-borehole observations indicate the top of bedrock surface below the .tidal flats may be rough and irregular. Artesian pressures of up to 6.5 psi have been recorded (~ith an artesian head to El .. 15±) within sediments immediately overlying becrock. Once the saturated sediments within the enclosed cofferdam area are dewatered, the groundwater pressure differential across the cofferdam may result in some leakage under the base of the cofferdam and pumping of the cofferdam enclosed area wi 11 be necessary. Tailrace channel construction may be performed by hydraulic dredging or using conventional equipment. If conventional excavation is chosen it will begin with excavation at the bedrock/overburden contact to provide maximum relief of artesian pressures. It should be noted that the silts and clays ta be dredged are stiff with high initial shear strength, but display a lower residual strength when disturbed in the wet condition. Sensitivity values (ratio of undisturbed 0216R-4431R/CG 3-21 to remolded strength) up to ~.62 were. measured for 7 samples taken from the tidal flats. The undisturbed/unconfined shear str~ngths measured for these samples ranges from 0.1 to 0.7 tsf. Unconsolidated-undrained strength tests (triaxial shear teste-major principal stress), ·for 5 samples taken from . shallow depths in the vicinity of the tailrace, yielded results of 0.36 to 2.27 tsf. Some minor bedrock excavation is necessary to achieve desired grade immediately adjacent to the west wall of the powerhouse. Rock excavation may proceed effectively· by means of drilling and blasting. The existing top of bedrock beneath the intertidal sediments is expected to be rough and irregular; deadfall trees and slopewash material including large talus blocks may be buried iri the sediments. 3.1.7 Borrow Areas A moderately extensive amount of fluvially transported glacial sand and gravel has been deposited in the typical fan shape delta of the Martin River. This material source covers a 288-acre area and was sampled in 11 locations by hand dug test pits to an average depth of 1 foot each. Both laboratory test results and microscopic examination of this material source showed it to be acceptable for concrete aggregate as well as other types of construction materials.· Access to the source is by a temporary haul road approximately 1.5 miles in length from the main Project access road. Riprap was produced from a quarry on the access road. Production was from predominantly argillite, with some graywacke and dacite included. in the overall volume. 0216R-4431R/CG 3-22 SECTION 4.0 GEOTECHNICAL INVESTIGATIONS 4.0 GEOTECHNICAL INVESTIGATIONS 4.1 CHRONOLOGY OF INVESTIGATIONS A number of studies and investigations have oeen ·performed in the last three decades to evaluate the technical and economic feasibility of hydroelectric development on the Bradley River drainage system. Most of these investigations dealt with geologic ·and geotechnical conditions of the area, amassing a comprehensive body of data over the years. The earliest studies were undertaken by the U.S. Geological 3urvey (USGS) and the U.S. ·· Army Corps of Engineers (COE). In the General Design .Memorandum phase the COE was assisted in their inyestigative efforts by·several suqcontractors. Subsequently, overall responsibility for the Bradley Lake project was assumed by the State of Alaska through the Alaska Power Authority (APA). Stone & Webster Engineering Corporation (SWEC) ~as selected as the primary engineering feasibility and design consultant for the project. Additional licensing studies ·were carried out and a Federal Energy Regulatory Commission (FERC) License was granted in 1985. Since that time, detailed design investigations were performed throughout the project area as engineering and design considerations were finalized. 4.1.1 Surveys and Mapping The first concerted effort to develop acc~rate survey control and topographic mapping .was initiated by the COE in .1979-,80.. Horizontal and vertical control. monuments were established, nunerous aerial photo flight lines were flown, and detailed, large-scale topographic mapping was completed ·throughout the project area •. Ttrough these efforts and subsequent surveys by other investigators, a comprehensive file has been established that ·includes 42 ·flight lines with aer.ial photo coverage at various scales, topographic mapping at scales rar..ging from 1 in. = 10 ft to 1 in. = 200 ft, and various hydrographic surveys of Bradley Lake and Bradley River. 0216R-4432R/CG 4-1 4.1.2 Geologic Mapping As part of a regional hydrologic resources ·survey, the first geologic mapping was conducted by the USGS in 1955 and documented by Soward, 1962. This included generalized geologic interpretation at the damsite, diversion areas, and various tunnel routes. Additional, more detailed mapping was done in support of final design. 4.1.3 Seismic Surveys Seismic refraction profiles were initially carried out by the COE in 1969 at the Nuka River diversion area. Since that time nearly 165·seismic lines have been shot throughout the project area. 4.1.4 Test Borings Since 1959, 24i borings and 77 test. pits· have been complet.ed by the various investigators at the project area and along proposed· transmission line routes. 4.1.5 Borehole Instrumentation In 1980 the COE .installed rod extensometers in 4 boreholes, one in the s~illway area and three along the tunnel alignment. Over the long term no conclusive results can be attributed to the recorded instrument response. Updated graphic results are shown in the Supplement to the Final Site Conditions Report. In addition, observation wells (standpipes) and pneumatic piezometers were. installed throughout the project area during the 1984-86 investigQ.tions performed by R&M Consultants (R&M) and Enserch/Golder Associates as part of the Stone & Webster (SWEC) design studies. . 0216R-4432R/CG 4-2 4.1.6 Laboratory Testing Laboratory testing of soil and rock samples ob=ained froin boreholes, test pits and outcrops during the various investigatio11 programs were undertaken for purposes of classification, determination of engineering properties, and testing of aggregate suitability for concrete .·and riprap. In addition, selected rock core. was tested to define general rock strength properties and, more specifically, to ascertain the feasibility:of driving the power tunnel using a tunnel boring machine (TBM). The majority of tests were performed using standard test procedur.es. Hardness and other index. property tests were conducted on rock samples taken along the tunnel. alignment. Due to thei:-. significance with respect to tunnel excavation techniques, a brief description of these tests are provided below: Unconfined Compression Tests Unconfined compressive strength has been commcnly related to the boring characteristics of rock and is an important index property of the rock. Unconfined compressive strength values .. show a fairly large overall variation, even between samples taken at close proximity or in contact with each other. ~is is likely a reflection of the anisotropic nature of the rock. The anisotropy ~s due to unequal stresses imparted upon the rock during diagenesis and minor; banded variations in rock composition. In addition most samples contain lithologic impurities in the form of lenses, veins,. and stringers. These . form structural discontinuities along which fractures ·may occur. Compressive .. strength. values are therefore not directly proportional to hardness test values. Hardness Rebound and abr~sion hardness tests, at times, have been found to be very effective for determination of TBM performance cl::aracteristics. 0216R-4432R/CG 4-3 Rebound Hardness: Shore rebound hardness tests tend to produce widely variable results due to the extremely small point contact area of the scleroscope with which hardness values are measured·. Mineral or clastic grains of variable hardness may be very large compared to the small contact point. Any individual reading is therefore unlikely to be indicative of ·intact ·sample ?ulk properties. An advantage of Shore hardness is the wide· scale (0-140), which provides a ·greater degree of precision for any given reading. Schmidt rebound hardness is measured by the use ·of a concrete test hammer. The hammer has a larger impact. point (0.5 in. dia.) and greater impact energy (0.54 ft-lbs) than the scleroscope. The Schmidt hammer acts upon a greater portion of a sample and readings tend to better reflect the bulk properties of the sample. Abrasion Hardness Abrasion hardness is·measured by determining the weight loss of a rock disc and the related-weight loss of an abrasive wheel which is used to abrade the rock disc sample. Abrasion hardness can be used to estimate TBM cutter wear, however, advances in cutter head design have resulted in the production of much larger rock cuttings through fracturing rather than grinding, which in turn reduces cutter abrasion wear. Total Hardness: . Total hardness (Ht)is computed from the rebound abrasion hardness (H ) , which individually a hardness measure (H ) and r distinctly different physical properties. Both of these properties influence the ·mechanics of rock-fragmentation. The combination of the two hardness indices yields a parameter which proYides an indication of overall physical rock hardness characteristics: Ht = Hr x .(Ha)0 •5 . 0216R-4432R/CG. 4-4 Chercher Abrasivity Chercher abrasivity measures the abrasive effect of a rock sample on a steel pin. The pin has a 3 kg mass bearing on ft as it is drawn a known distance across the rock surface providing an .:.ndication of abrasivi ty of the rock on steel. Point Load Testing This test measures the load at which a rock spe=imen breaks when stressed between two conical points. The recent introduction of larger and improved TBM cutter bearings has allowed increased cutter pressures to be used. Results of point load testing give an indication of optimum cutter pressures. Results of laboratory rock testing indicate a -.,ide range of strength and hardness values for the argillite. Early investigators have classified a fine-grained siliceous variety of graywacke as argillite, which may partially account for the broad range of values ~eported. The presence of a siliceous variety of argillite and variable chert content also contributes to the wide range of values reported. 4.2 BORING LOGS, GEOLOGICAL REPORTS AND LABORATORY TEST RESULTS The following lists the references and documents for the reports that were developed for the Bradley Lake Hydroelectric Project. 1. Application for License. Bradley Lake Hydroelectric Project .. Preliminary Support Design Report.l984. 2. DOWL Engineers (DOWL). Bradley Lake Project, Geologic Mapping Program. . DOWL, Anchorage, Alaska, I3nuary 1983. Appears in Alaska Power Authority FERC Application for License Bradley ·Lake Hydroelectric Project Volume 5 Appendix A. 0216R-4432R/CG 4-5 3. Bechtel Civil, Inc. Geologic Tunnel Log, Diversion Tunnel, Drawing No. TL-01, 4 Sheets, March 1987 .. 4. Bechtel Civil, Inc •. Inc. Geologic Mapping -Powerhouse Excavation, Drawing No. PHL-01, 2 Sheets, April 1987. 5. Bechtel Civil, Inc. Geologic Report -Powerhouse Excavation, Bechtel Transmittal No. BEC-L-SWEC-039, August 1987 . • 6 Dryden & LaRue, Inc. Alaska Power Authority Bradley Lake 115 kV Transmission Lines Basic Design Manual, Dryden & LaRue, February 1986. 7. Dryden & LaRue Consulting· Enginers (D&L). Feasibility Study ~f Transmission Line System, Phase 1, Bradley Lake Hydroelectric Power Project, . D&L, Anchorage Alaska, August 1983. Appears in Alaska Power Authority FERC Application for License Bradley Lake Hydroelectric Project VQlume 5 Appendix B. 8. Golder Associates. Bradley Lake Hydroelectric Project Core Drilling and Hydrofracture Pressure Testing Program, Golder Associates, August 1986. Included with SWEC· Supplement to Final Site Conditions Report. 9 .. Golder Associates. Geological and Geotechnical Site Investiga- tion for the Bradley Lake 115 kV Transmission Lines, Appendix B of ·Dryden & LaRue, Inc., Alaska Power Authority Bradley Lake 115 kV Transmission Lines Basic Design Manual, February 1986. 10. Hager-Richter Geoscience, Inc. X-ray Diffraction Analysis of Nine Samples for the Bradley Lake Hydro Project, February 1987; 11. Hartman, C.W. and P. R. Johnson. Environmental Atlas of Alaska,. Institute of Water Resources, University of Alaska, (Revised) 1984. 0216R-4432R/CG 4-6 12. Hinton, R. B. Soil Survey of Homer-Ninilchik Area, Alaska. U.S. Department of Agriculture, Soil Conservation Service, July 1971. Appears in Alaska Power Authority FERC Application for License Bradley Lake Hydroelectric Project Volume 5 Appendix C. 13. Johnson, F. A. Open File Report, U. S. Geological Survey 1956. 14. Johnson, F.A. Waterpower Resources of the Bradley River Basin Kenai Peninsula, Alaska, USGS Water Supply paper 1610-A, 1961. 15. Lahr, J. C. and Stephens, C. D. 1980 Revie~ of earthquake acti- vity and current status of monitoring io the region of the Bradley Lake Hydroelectric Project, Kenai Peninsula, Alaska: USGS Open-File Report 81-736, 1981. 16. Ocean Surveys, Inc. Subbottom Profiling Investigations, Hydro- electric Power Project Bradley Lake, Homer, Alaska, Ocean Surveys, Wilmington, CA. April 1986. Included with SWEC Supplemental to Final Site Conditions Report. 17. Peratrovich, Nottingham & Drage, Inc. (PND). Test Pit and Gradation Analyses of Martin River Borrow Area, PND, September 1986. Included with SWEC Supplemental to Final Site Conditions Report. 18. R&M Consultants, Inc. Final Site Conditions Report of Geotechnical Field Investigations 198L & 1985· Programs, Bradley Lake Hydroelectric Project. Volume 1, Main Report. R&M, March 1986. 19. R&M Consultants, Inc. Final Site Conditions Report of Geotechnical Field Investigations 1984-& 1985 Programs, Bradley Lake Hydroelectric Project. Volume 2, Appendices to Main Report. R&M, Anchorage, Alaska, March 1986. 0216R-4432R/CG 4-7 20. R&M Consultants, Inc. Final Site Conditions Report of Geotechnical Investigations 1984 & 1985 Programs, Bradley Lake Hydroelectric Project. Volume 3, Appendices to Main Report. R&M, Anchorage, Alaska, March 1986. 21. R&M Consultants, Inc. Final Site Conditions Report of Geotechnical Field Investigations 1984 & 1985 Programs, Bradley Lake Hydroelectric Project. 1984 & 1985 Rock Core Photographs. R&M, Anchorage, Alaska, March, 1986. 22. R&M Consultants, Inc. Barge Access Alternatives Bradley Lake Hydroelectric Project. R&M Consultants, Anchorage, Alaska, October 1985. 23. R&M Consultants, Inc. U.S. C.O.E. Rock Core Relog, R&M Consultants, Anchorage, Alaska. May 1986. Included with SWEC Supplemental to Final Site Conditions Report. 24. Shannon & Wilson, Inc. (S&W). Bradley Lake Hydroelectric Power Project, Geotechnical Studies. K-0631-61, S&W, Fairbanks, Alaska, September 1983. Appears in Alaska Power Authority FERC Application for License Bradley Lake Hydroelectric Project Volume 6 Appendix D. 25. Soward, K. S. Geology of Waterpower Site on the Bradley River Kenai Peninsula, Alaska. USGS Bulletin 1031-C. 26. Stephens, C. D., Lahr, J. C., and Rogers, J. A. Review of Earthquake Activity and Current Status of Seismic Monitoring in the Region of the Bradley Lake Hydroelectric Project, Southern Kenai Peninsula, Alaska: November 27, 1980-November 30, 1981. USGS Open File Report 82:-417, 1982. (Appears in Alaska Power Authority FERC Application for License, Bradley Lake Hydroelctric Project, Vol. 6, Appendix E.) 0216R-4432R/CG 4-8 27. Stephens, C. D.' Lahr, J. c.·' Page, R. A.' and Rogers, J. A. Review: of Earthquake Activity and Current Status of Seismic Monitoring in the Region of the E.radley Lake Hydroelectric Project, Southern Kenai Peninsula, ~laska. December 1981-May 1983. USGS Open File Report 83-744, 1983. 28. Stone & Webster Engineering Corp. (SWEC). Bradley Lake Hydroelectric Power Project, Feasibil::ty Study, Volume I, SWEC, Anchorage, Alaska, October 1983. .Appears in Alaska Power Authority FERC Application for License Bradley Lake Hydroelectric Project Volume 7 Appendix F. 29. Stone & Webster Engineering Corp. Overview for General Civil Contract on the Bradley Lake Hydroelectric Project. Stone & Webster, September.l986. 30. Stone & Webster Engineering Corp. Detailed Fracture Logging of Bradley Lake Project Rock Core. Stone & Webster, 1986. 31. Stone & Webster Engineering Corp. Rock Core Field Logs, 1986. Included With SWEC Suplemental to Final Si~~Cond-itions Report. 32. Stone & Webster Engineering Corp. Supplement to Final Site Conditions Report. Stone & Webster, April 1987. 33. Stone & Webster Engineering Corp., 1987 Geotechnical Exploration Program, Stone & Webster, February 1988. 34. Stone & Webster Engineering Corp. Bid Documents for General Civil Construction Contract ·-Addendum No. 1. Volumes 1-6 including Geotechnical Interpretive Repor~. Stone & Webster, March 1988. 35. Sverdrup & Parcel and Assoc., Inc. (S&P). Feasibility Report for Hydroelectric Power Development of Bradley Lake, Kenai Peninsula, Alaska. Appendix 1, Sections G & G. S&P, September 1975. 0216R-4432R/CG 4-9 36. Tarkoy, P.J. Rock Hardness Index Properties and Geotechnical Parameters for ·Predicting Tunnel Boring Machine Performance. University of Illinois, 1975. Included with SWEC Supplement to Final Site Conditions Report •. 37. U.S. Army Corps of Engineers. Bradley Lake Project -A Recon- naissance Report on Potential Power Developments Together with Auxiliary Possibilities: Office of the District Engineer, Alaska District. u.s.c.o.E, 1954. 38. U.S. Army Corps of Engineers (COE). Bradley Lake Hydroelectric Project, General Design Memorandum. COE, General Design Memorandum No. 2, February 1982, Volume 1 of 2. Appears in Alaska Power Authority FERC Application for License Bradley Lake Hydroelectric Project Volume 8 Appendix G. 39. U.S. Army Corps of Engineers (COE). Bradley Lake Hydroelectric Project, General Design Memorandum. COE, General Design Memorandum No. 2, February 1982, Volume 2 of 2. Appears in Alaska ·Power Authority FERC Application for License Bradley Lake Hydroelectric Project Volume 9 Appendix H. 40. U.S. Army Corps of Engineers (COE). Final Environmental Im- pact Statement, Bradley Lake Hydroelectric Project, COE, Alaska District, August 1982. Appears in Alaska Power Authority FERC Application for License Bradley Lake Hydroelectric Project Volume 10 Appendix I. 41. Woodward-Clyde Consultants, Inc (WCC). Report on the Bradley Lake· Hydroelectric Project Design Earthquake Study. Woodward-Clyde Consultants, November 1981. 42. Woodward-Clyde Consultants, Inc (WCC). Seismicity Study Bradley Lake Hydroelectric ·Project. March 1980. 0216R-4432R/CG 4-10 Woodward-Clyde Consultants, 43. Woodward-Clyde Consultants (WCC). Geologic Reconnaissance, Bradley Lake Access Road, Project Na. 14844A, WCC, Anchorage, Alaska, November 1980. Appears in Alaska Power Authority FERC Application for License Bradley Lake H:1droelectric Project Volume 10 Appendix J. 44. Woodward-Clyde Consultants (WCC). Reconnaissance Geology, Bradley Lake Hydroelectric Project. Project No. 411931, WCC, Anchorage, Alaska, December 1979. Appears in Alaska Power Authority FERC Application for License Bradley Lake Hydroelectric Project Volume 10 Appendix K. 0216R-4432R/CG 4-11 SECTION 5.0 BORROW AREAS AND QUARRY SITES 5.0 BORROW AREAS AND QUARRY·SITES. 5. 1 BORROW AND QUARRY AREAS Several sources of quarry and· borrow material b.ave. been investigated and found to be generally satisfactory for use as construction material. A description of each area and the engineering characteristics of material contained therein is provided. In addition, vari~us rock materials will be by-products of construction activities and may be utilized at the contractor's option, provided . the material is sui table and processed to conform to applicable specifications. 5.1.1 Martin River Borrow Area The Martin River Borrow Area is located within an alluvial fan-delta complex formed by the braided channels of the .. :Martin River. A dike and interceptor ditch constructed during the Site Preparation Contract has diverted water flow from the eastern port ion of the d.el ta where borrow material was extracted. - The minimum dep-th".to_bedrock. in the designated jorrow areas is 45 ft, with greater depths over most of the area.. The· sediments are very permeable and the groundwater table is expected to respond rapidly to the amount of flow in the Martin River. During periods of hig~ flow (June-October) the groundwater table is in close proximity .to the surface and may be contiguous with surface flow at flood stage. 'Wet ·excavation may be the only economic means of extraction in this area. Sediments in the Martin River Delta consist of silt, sand and gravels which are graded both horizontally and vertically. The upper (near-surface) portion of the delta generally contains larger size gravel with less sand than the deeper portion of the delta. The upsl:rearn portion of the delta generally contains coarser material with a grea:er proportion of sand than silt. Sediments in the surfic.ial 20 ft of the U?Strearn portion of the area average approximately 65% gravel and cobbles, .34% sand and 1% silt, with· cobbles up to 8 in. common. 0216R-4433R/CG 5-l Sedimen~s in the downstream portion of the delta average approximately 40% gravel, 58% sand, and 2% silt with fewer cobbles. A large silt lens that contains clay has been identified and located within the site (Pit 2), and other similar lenses may exist in the borrow. area. Isolated zones and occasional logs (deadfall ) cari also be expected to be found buried in the delta sediments as the borrow area is developed. s.1.2· Battle Creek Quarry The Battle Creek quarry is located in the south side of a low rounded hill that lies along the northeast side of the dam access road between Sta. 663+00 to 670+00. Soil cover over. undeveloped portions of the quarry is thin •. Rock within the quarry area consists primarily of massive siliceous argillite that contains some chert. The argillite is cut by a series of dacite dikes, two of which are 10-20 ft wide. ·Minor · amounts of graywacke and metatuff are present. Laboratory testing indicates that the dacite, graywacke, and argillHe are all sui table for riprap material. Engineering calculations-indicate that the quarry site contains sufficient material for purposes of the remainder of the ·work. The site has been partially developed during the Site Preparation Contract and has produced satisfactory dprap material in all size ranges. Groundwater is limited to minor seepage from joints and fractures. 5. 2 OTHER MATERIAL SOURCES Shot rock, tunnel muck and alluvium will be by-products of construction activities and may be utilized at contractor's option-provided the material meets durability and quality requirements and is processed to conform to applicable specifications. 0216R-4433R/CG ·s-2 5.2.1 Shot Rock Shot rock should be available from drill anc blast excavation of the spillway, dam foundation, intake structure, upp:r and lower power tunnel and gate shafts, powerhouse, penstock/manifold and access adit areas. The shot rock excavated from the dam area surfece should be predominantly graywacke, with argi 11 i te primarily coming from sect ions within the upper and lower power tunnel and powerhouse area. S~t rock may be utilized as dam·rockfill, road fill and other lower grades of fill and slope protection with little or no processing required. The graT~acke may be crushed and/or screened for use as higher grade of fill (including Type Bl). Argillite may be utilized for bulk fill but mey break down upon compac- tion. The use of argillite for aggregate may not be practical because extensive testing and processing may be required. Chert and highly siliceous rock is unacceptable for aggregate . 5.2.2 Tunnel Muck Material derived from the power tunnel excavation has not been designated for use as a borrow material. Potential uses will be dependent upon whether drill and blast methods or a tunnel boring machine (TBM) are used. Power tunnel excavation is expected to encounter all rock types. If drill and blast techniques are used, the above discussion regarding the use of shot rock as fill will apply, subject to the generally finer gradation limitations inherent in tunnel muck. If a TBM is utilized the resultant cuttings w·:mld probably not exceed 6 inches in maximum dimension, and most would probably be under 3 in. A very large amount of fines would be included, and water content might be high. Use for construction purposes would likely reqtrire processing. It may be possible to produce fill gradations from cuttings derived from intervals of graywacke or dacite encountered along the turu:el alignment, but this is generally not considered practical. Cuttings derived from intervals of argillite would probably be suitable only for random fill. 0216R-4433R/CG S-3 5.2.3 Alluvium The main dam foundation will be excavated in alluvium, colluvium, and shot rock generated from previous excavations in the upper Bradley River area. The foundation will be excavated to reasonably sound, groutable bedrock. Material to be removed consists of cobbles with frequent boulders up to 10 ft in diameter in a sandy gravel matrix. Silt and clay appear to be present in proportions that decrease with distance from the lake outlet. Most of the gravel, cobbles, and boulders are graywacke. Cobble and boulder sizes :c:ange from 8 in. to 3 ft. It is estimated that approximately 25% of the rock talus could be oversize material which, if used in the main dam, would have to be reduced in size or utilized for riprap. Alluvium in general (as opposed to colluvium) may not meet the angularity requirements for dam fill (Type Bl-BS). 0216R-4433R/CG 5-4 SECTION 6.0 STABILITY AND STRESS ANALYSIS 6.0 STABILITY AND STRESS ANALYSIS 6.1 GENERAL The design analysis has been completed on proj:ct features which are part of the General Civil Construction Contract. These project features are: • Diversion tunnel gate shaft and outlet structure (Section 6.2) • Main Dam (Section 6.3) • Spillway (Section 6.4) • Power Tunnel and penstocks (Section 6.5) • Powerhouse excavation, cofferdam and tailrac: channel (Section 6.6) The stability and stress analysis is being done now on the Powerhouse and other structures that are part of. the Powerhouse Construction Contract. The completed stress and stability analysis of these structures will be included as part of the Final Supporting Design Report for the Powerhouse Construction Contract that will be submitted -for Commission approval in June 1988. 6.2 DIVERSION TUNNEL INCLUDING INTAKE STRUCTURE 6.2.1 Description The diversion tunnel, as shown in Appendix A, Exhibit F on Plate 10, is . designed to pass Bradley Lake flows downstream during construction of the main dam and to provide a means of lowering the level of the completed reservoir at a controlled rate as required du::dng the project life in an emergency condition.· The tunnel facilities will provide minimum downstream flow releases for the maintenance of aquatic habitat in the Lower Bradley River. 0216R-4434R/CG 6-1 The diversion tunnel construction consists of two phases, the Site Preparation phase and the General Civil Construction phase. The first or Site Preparation phase, now completed, consisted 6-f excavating the full length of the tunnel and constructing the diversion tunnel concrete intake structure. The tunnel downstream of the intake structure was left unlined during this initial. phase. The intake structure includes one set of two gate slots and the upstream portion of the fish water bypass piping. Wooden stop logs were provided for use at the intake for this phase of work. Design and analysis for this phase is included in the Final Supporting Design Report for the Site Preparation Contract. General The General Civil Construction phase includes construction of tunnel linings and facilities downstream of the intake. Steel bulkhead gates will be provided during the General Civil Construction Contract to close off flow from the intake structure to permit construction of the remainder of the tunnel structures. A vertical shaft will be excavated 120 feet upstream from the tunnel outlet. The shaft will contain two high pressure gates installed in series. One gate will function as a control gate and the second as a guard gate. The upstream portion of the tunnel is lined with a 15-inch minimum thickness concrete lining. A steel penstock will be installed downstream of the control gate and will extend to the tunnel exit. Minimum downstream flow releases to maintain aquatic habitat in the Lower Bradley River are through two steel pipes embedded in the con-crete floor of the tunnel. The two pipe intakes are located upstream of the tunnel inlet. Minimum flow releases are controlled with valves and a system of nozzles at the downstream end of the pipes at the tunnel outlet. The capability is provided to adjust flow releases in approximately 5 cfs increments. To attain this incremental flow, two pipe manifolds are provided near the tunnel outlet with varying sizes of control valves and outlets. The manifolds are housed in a concrete structure at the tunnel outlet. 0216R-4434R/CG 6-2 The bulkhead gates are designed to close against a maximum diversion flow of approximately 500 cfs. The corresponding flow depth at the gate guides is five feet. To minimize the total vertical force on the gates during their lowering and raising, several design features are adopted. Teflon coated seals, and low friction bearing blocks and stainless steel sealing surfaces . are provided. Bottom seals . are arranged to minimize the gate hydraulic downpull forces. 6.2.2 Design and Analysis The design and analysis of the tunnel liner,. gate shaft, gate house, diversion penstock, and outlet structure wer~ based on the design criteria for the Bradley Lake Hydroelectric Project included in Volume 2 of this Final Supp9rting Design Report for the General :ivil Construction Contract and listed below: Civil Design Criteria Geotechnical Design Criteria Structural Design Criteria Part A Part B, Section 1 Hydraulic Design Criteria General Civil Contract General Civil Contract General Design Criteria Main Dam C.iversion Main Dam Civersion The following calculations are included in Vol1JIIles 4 to 9 of this "Final Supporting Design Report for the General Civil Construction Contract" and in the previously submitted "Final Supporting Design Report for the Site Prep8:ration Contract": Title Hydraulic Calculations Fish Bypass Pipe System Lake Drawdown Bulkhead Gate Operations Flood Routing -Flood of Record through Bradley Lake and Diversion Tunnel Calculation No. H-012~" H-015~" H-015fc H-033 fc Calculations included in "Final Supporting Design Report for Site Preparation Contract" 0216R-4434R/CG 6-3 Title Geotechnical Calculations Ground Water Seepage Loads on ·Diversion Tunnel Liner Design of Rock Bolts for Diversion Tunnel and Gate Shafts Structural Calculations · Main Dam Diversion Tunnel Lining . and Gate Chamber Analysis Main Dam Diversion Exit Portal Stucture Main Diversion and Main Intake Bulkheads Main Dam Diversion Penstock Design 6.3 MAIN DAM 6.3.1 Description Descri_ption G(A)-08 G(A)-58 SC-133-13 SC-134-14 SS-132-2 SS-134-12 A concrete faced rockfill dam was selected as the most technically feasible and economically suitable structure for increasing the storage capacity of the Bradley Lake reservoir. A plan of the dam and associated structures is shown in Appendix A, Exhibit F on Plate 2. The layout and conceptual details of the ·dam are shown in Appendix A, Exhibit F on Plate 3. The dam has a crest 18 feet wide and 602.5 feet long at elevation 1190.0. It has a height above average foundation level of 120 feet. The axis of the dam is approximately 500 feet downstream of the natural lake outlet. This location and the axis orientation were selected to best utilize existing topographic features and to minimize the volume 0216R-4434R/CG 6-4 of rockfill in the embankment. The selected location also makes.effective use of previously obtained geologic data and allows for the development of the embankment within the restricted area of the river. The axis orientation offers good alignment for the upstream toe plinth and results iri toe plinth construction without excessive three dimensional discontinuities. 6.3.2 Foundation Conditions The dam will be founded on bedrock composed main:y of alternating sequences of argillite ·and graywacke. Bedrock outcroppicgs in the damsi te area are all moderately hard to ·hard with slight weathering. The bedrock is considered adequate to support a rockfill dars. Surficial weathering is generally confined to the upper few feet of rock, however, staining on joints and fractures in the rock indicates these are potential leakage paths from the reservoir. .A grout curtain along the upstream toe plinth will provide positive seepage cutoff and control. A detailed description of the abutment and foundation conditions in the dam area is included in Section 3.1.1. 6.3.3 Foundation Preparation and Treatment The dam foundation must be stable under all conditions of construction and reservoir operation, and must limit seepage sc as to prevent erosion of material and loss of water. The embankment wi:l be founded on competent rock. Overburden and unsuitable rock will be excavated from the embankment footprint. The near-vertical right abutment will be sloped back as necessary to provide a positive abutment cont3ct. This excavation will provide a gradual transition.between the embankment and bedrock to minimize the effect of embankment settlement. on the. :oncrete face slabs. Any intensely sheared and altered rock zones exposed during foundation preparation will be treated. Altered rock exposed beneath or immediately upstream or downstream of the concrete toe plintt-will be excavated and the void filled with dental concrete. Additioncl treatment will include 0216R-4434R/CG 6-5 grouting where necessary. Beneath the main body of the embankment, areas of dental excavation will be backfilled with dental concrete, grout or fill. A grout curtain will be constructed with-holes up to 95 ft deep at minimum 10-ft centers along the entire length of the dam toe plinth. The grout holes will be oriented to intersect major rock joint sets. The grout curtain will continue up onto each abutment. 6.3.4 Dam Cross Section and Materials The design of the embankment section shown in -Appendix A,-Exhibit F on Plate 3 is conservatively developed with selected zoned material to withstand hydrostatic, ice, earthquake, and other external loads. -The dam is developed U!$ing five zones of material compacted to form upstream and downstream embankment slopes of 1. 6H: lV. Zone 1, forming the upstream face of the rockfill, ·consists of select 3 inch minus material. This zone will -be placed in 12 foot wide horizontal layers in one foot-lifts and compacted w-ith heavy steel drum vi bra tory rollers. Zone 2 is a highly pervious drainage band at the base of the central section of the dam. This zone is composed-of minus 24 inch material p·laced in 3 foot lifts and compacted with vibratory rollers. Zones 3 and 4 form the major portion of the embankment core. These zones ·are a highly pervious material composed of quarry run minus 36 inch placed in. 36 inch lifts and compacted with vibrator:{ rollers. Zone-5 forms the downstream face of the rockfill. This zone is composed of oversize material from Zones 3 and 4. Materials forming this zone will be pushed or raked into place and does not require compaction. Use of the proper .material gradation iQ. these selected zones, coupled with controlled placement techniques and proper spreading and compaction, will result in an embankment that is strong, den~e and stable. The gradation of the ·material provides a struCtural skeleton in which the larger pieces are in intimate contact with each other and the smaller sized material occupies the voids between larger rock pieces locking both ·into position. At the same time adequate void spaces are provided within the rockfill matrix to 0216R-4434R/CG 6-6 ensure high permeability .for the drainage of s:epage water. The rockfi 11 embankment will be ·constructed in an essentially continuous operation. . . Materials for its construction will be available fr.om the power. tunnel intake excavation. The upstream face of the dam consists of a parapet wall, concrete face slabs and concrete toe plinth. The concrete parapet wall, extending 4 feet •, above the dam crest, is provided with an overhanging top surface to act as a wave deflector. The impervious upstream face is form~d by a series of reinforced concrete slabs. Central face slabs have been designed as. SO foot wide monoliths but may vary from 40 ft to 60 ft in width. Abutment face slabs are narrower and articulated to accept greater deflections. The slabs are designed to have a nominal thickness of 12 inches. Waterstops will be constructed at the perimeter and transition joints of the face slabs. Construction joints within the face slabs do not require waters tops. The concrete toe plinth will be constructed to adjoin with the face slabs. A perimeter joint waterstop will be constructed along the entire toe plinth and face slab juncture to form a . watertight closure.. Ccncrete m:lxes particularly suitable for cold and harsh environments will 'Je used-in the construction of these members to offer -maximum resistance :o freeze-thaw action, ice buildup and stresses resulting from seasonal temperature variations. 6.3.5 Design and Analysis The design and analysis of the main dam were based on the design criteria for the Bradley Lake Hydroe~ectric Project incl~ded in Volume 2 and listed below: Civil Design Criteria· Geotechnical Design Criteria· Structural Design Criteria, Part A Structural Design Criteria, Part B, Section 2 0216R-4434R/CG .6-7 Gene=al Civil Contract I Gene=al Civil Contract Gene=al Design Criteria Main Dam The main dam · has been evaluated for both static and dynamic · slope stability. The stability analysis methods, input .and results for the Main Dam are presented in Volume 3o In addition, the following calculations are included in Volumes 4 to 9: Title Hydraulic Calculations Simplified Dam Break Analyses·· and Water Surface Profiles Wave Runup and Forces on Dam Parapet Protection Against Waves for Upstream Cofferdam and Power Tunnel Rock Plug Ice Force on Dam Parapet Riprap Design ·Filling Bradley Lake Reservoir Geotechnical Calculations Final Stability Analysis: Bradley Lake Main Dam Plinth and Toe Slab Geometry -Main Dam Dam Toe Plinth Loads Main Dam Face Slab Design Toe and Abutment Plinth Dowel Embedment Lengths and Quantities Structural Calculations Dam·Parapet Main Dam Toe Plinth Design Abutment Design 0216R-4434R/CG 6-8 Calculation No. H-046 H-048 H..:..066 H-068 H-079 H-081 G(D)- G(D)- .G(A)- G(A)- 24 38 60 93 G(D)-106 SC-191-26 SC-191-27 SC-191-29 6. 4 SPILLWAY 6.4.1 Physical Description An ungated concrete gravity ogee spillway is located on the saddle feature of th~ right abutment approximately 150 feet east of the main dam and along the same axis alignment. The overall length of the spillway including abutments is approximately 270 feet of which 175 feet is provided for the overflow crest. The height from foundation level to the overflow crest varies from approximately. SO feet to 20 feet. T.:l.e spillway has an upstream sloping face and its concrete abutments will be rounded above the crest for hydraulic efficiency. The crest is shaped 3nd contoured to produce gradually· accelerating flow· on the basis of a 10.5 foot design head. Spillway discharges will be direct~d onto existing rock beyond the spillway apron. A plan of the spillway with elevations and sections is shown in Appendix A, Exhibit F on Plate 4. 6.4.2 Foupdation·Preparation and Treatment The. spillway is founded on competent bedrock with its concrete gravity abutments keyed into the adjacent rock. All overburden and unsuitable rock will be removed from under the spillway and along the· abutments. It is estimated that a maximum thickness of overburc.en to be removed will be approximately 12 feet. A grout curtain will be constructed along the spillway below foundation level and extended from the right to the left abutment. The grout holes will be oriented to intersect major rock joint sets. Secondary and tertiary grout holes will be constructed as required to assure that the grout curtain is continuous. For additional safety, a foundation drainage system is provided downstream of the grout curtain. The system consists of drain holes drilled into foundation rock, a collector trench, and a lateral pipe to discharge 0216R-4434R/CG 6-9 .seepage below the spillway chute. In addition, provisions are made to access the drain holes for pressure monitoring, cleaning, or re-drilling. 6.4.3 Design and Analysis The design and analysis of the spillway were based on the design criteria for the Bradley Lake Hydroelectric Project included in Volume 2 and listed below:. ·. Ci vi 1 Design Criteria Geotechnical Design Criteria. Structural Design Criteria, Part A Part B, Section 3 Hydraulic Design Criteria General Civil Contr.act General Civil Contract General Design Criteria Spillway Spillway The spillway structure has been evaluated for stability under both static and dynamic loading conditions. The stability analysis methods, input and results are presented in the Spillway Stability Report included in Volume 3. In addition; the following calculations are included in Volumes 4 to 9. Title Hydraulic Calculations Spillway Crest Shape Flood Routing-P.M.F. through Spillway Investigation of Need for Aeration of Spillway Flow Geotechnical Calculation Spillway SARMA Displacement Analysis 0216R-4434R/CG 6-10 Calculation No. H-027 H-028 H-077 G(D)-98 Structural Calculations Spillway Static Stability Analysis Finite El~ment Analysis of. Spil_1way for Seismic Load Combined with Deadweight, Ice Thrust, and Water Loads Spillway. Training Wall~ 6. 5 POWER TUNNEL AND PENS~OCKS 6~5.1 Description SC-201-8A _SC-201-34 SC-205-23 The power tunnel, as shown in Appendix A, Exhibit F, Plates 5, 6, and 7, is designed to deliver water from . Br~dley Lake ·to the powerhouse located adjacent to Kachemak Bay. The power tunnel ·consists of an intake structure, an 11 foot I.D. concrete lined tunnel section, a gate shaft with high pressure gates, an 11 ft' I.D. steel lined section and a steel penstock manifold branching to three individual penstocks and an ac·cess extension. The intake structure will be comprised of a concrete structure providing a gradual transition from the tw:o 12'-8" x 29'-6" rectangular cross sectional inlets to the· 11 '-0" diameter c~rcular tunnel . section. The concrete structure is provided with guides for trashracks and for the installation of the bulkh~ad ·gates. The bulkhead _gates. designed for the closure of the diversion tunnel are useable for closure of the power tunnel. The trashracks were evaluated ·for flow induced vibrations. A vertical circular gate shaft will. be located approximately 505 ft downstream of the intake. The area of. the tunnel at the gate shaft _will accommodate two rectangular high pressure gates housed in a steel lined transition structure. One gate will function as. a contt'o,l gate and the .second as a guard gate. The gate shaft will ·be concrete lined, with a concrete gatehouse and .concrete cap with access hatch erected at the top of the gate _shaft. -Access stairs and hydraulic lines will be located within the sha:ft. · Equipment for control and operation of the gates will be housed in the gatehouse. 0216R-4434R/CG 6-11 The c~~crete lined tunnel will extend from the intake structure to the gate shaft and from there downstream to the tie-in with the steel liner at a point where the overhead· rock cover has decreased to approximately 80 . percent of the maxi.mum normal static head, a total length of approximately 15,700 feet. The concrete liner h~s been designed for various load combinations of internal pressure, external hydrostatic pressure, rock load ·and grouting loads. Areas of poor rock quality, such as at fault zones, and where overhead rock cover is less than the. maximum normal static head will be reinforced. The ll 1 -0" diameter. steel liner extends from where the overhead rock cover . ' is approximately 80 percent of· maximum normal static head to the tie-in at . . the penstock manifold, ·a distance of' approximately 2, 700 feet. The annular space between the· steel liner and excavated surface is backfilled with concrete. This backfill toncrete is unreinforced except where concrete liner reinforcing steel is extended around the upstream end of the steel · liner t() provide bar development. Drain pipes are . provided in this backfill concrete to reduce the external hydrostatic pressure on the steel liner. The steel liner has been designed neglecting the support of encasing concrete arid rock except where the overhead rock cover is in excess of 40.percent.of maximum normal static head •. The penstock manifold provid·es · the transition f:t;"om the 11 1 -0" diameter Steel liner tO the 9 I -011 diameter manifOld. header and inClUdeS the wye branches and individuar" ·penstocks. The manifold header terminates at a high pressure flanged closure head which will provide access into the penstock manifold and power: tunnel. The iridividual'penstocks are·6 1 -6"·in diameter downstream of the manifold and reduce to ·5 1 -0" in diameter prior to entering the powerhouse. Three penstocks · are provided, two serving the two turbine·· units and one terminating at the location of the future unit. The penstock manifold wall thicknesses have been designed neglecting the encasing concrete and rock. Thrust blocks are provided on each penstock and adjacent to the closure head to resist transient loading. 0216R-4434R/CG 6-12 6.5.2 Design and Analysis The design and analysis of the power tunnel and penstocks were based on the design criteria for the Bradley Lake Hydroelectric Project included in Volume 2 and listed below: Geotechnical Design Criteria Structural Design Criteria, Part A Part B, Section 4 Part B, Section 5 Hydraulic Design Criteria General Civil Contract General Structural Design Criteria Power Tunnel Lining, Intake, and Gate Shaft Steel Liner and Penstock Power Intake, Tunnel and Penstock The following calculations are included in Volumes 4 to 9: Title Hydraulic Calculation Design Thrusts -Power Penstock near Manifold Geotechnical Calculations Rock Stress in Circular Tunnel Linings External Rock & Ground Water Loads on Power Intake and Gate Shaft Structures Penstock -Manifold Thrust Block Embedment Length and Stability Analysis 0216R-4434R/CG 6-13 Calculation No. H-036 G(A)-04 G(A)-22 G(A)-29 Rock Moduli for Power Tunnel Transient Study Design of Rock Support for the Main Power Intake Structure Groundwater Inflow & Leakage into Power Tunnel Evaluation of Shear Strength of Rock Masses at the Bradley Lake Site Evaluation of External Loads on Power Tunnel Liner Verification of Confinement to Prevent Hydraulic Jacking of the Power Tunnel Power Tunnel Intake Excavation Design Manifold & Penstock Thrustblock Stabili-t¥- Considering Shear Zone Feature Evaluation of Concrete Liner Requirements for Main Power Tunnel Structural Calculations Power Tunnel Intake Power Tunnel Gate Chamber and Lining Design and Analysis Power Tunnel Intake Trash Racks 0216R-4434R/CG 6-14 G(A)-31 G(A)-35 G(A)-41 G(A)"'-47 G(A)-48 G(A)-49 G -70 G -86 G(A)-90 SC-151-16 SC-152-21 SS-153-10 Power Penstock Thrust Rings and Misc. Components Required Thickness of Steel Liner under Internal and'External Pressure Stress Analysisof Flange with 108" Inside Diameter Local Stresses Due to Geometry Discontinuity at Reducers and Mitered Elbows ~equired Thickness of Ellipsoidal Heads for Penstock Stress Analysis of Power Pensto~k Wye Branch Penstock Access Flange Bolts SS-261-16A SS-261-17A SS-261-17B SS-261-17C SS-261-17D SS-261-17F SS-261-18 6.6 POWERHOUSE/SUBSTATION EXCAVATION, COFFERDAM AND TAILRACE CHANNEL 6.6.1 Description The powerhouse/substation excavation, as shown in Appendix A, Exhi~it F, Plates 7, 8, 9, and 14, is d~signed to provide e stable rock foundation of suitable dimensions to accommodate the powerhouse substructure, the .substation switchgear and the transformer basins. The powerhouse cofferdam is designed to provide a temporary water barrier for the powerhouse excavation from the tidewaters of Kachemak Bay. The tailrace, as shown in Appendix A, Exhibit F, Plate 7, is designed to collect water from the turbi:nes and transport it away from the powerh:mse to Kachemak Bay with minimal backwater effect at the·powerhouse. 0216R-4434R/CG 6-15 The powerhouse excavation will consist of vertical rock cuts excavated to a . maximum depth of 49 feet. These cuts are designed to remain intact during . the MCE earthquake (0.7Sg) and are supported with rock bolts and chain link mesh.. The powerhouse concrete substructure will be placed in direct contact with the rock excavation and support system'.· The substation excavation will consist of rock excavations for utility trenches and building and equipment foundation support. These excavations will not require rock bolt support. The powerhouse cofferdam will· consist of a series of interlocking circular . . . cells that. will be driven to bedrock in the Kachemak Bay tidal flats. The cofferdam will ke.ep .the powerhouse excavation protected from periodic high tides. The design will allow a 100-ton crane to operate while located on the cofferdam. The cofferdam is sized to permit haul trucks access across the cofferdam during operation of the 100-ton crane. The tailrace will· be excavated from the tidal mud .flats of Kachemak Bay. The initial. flared segment of the tailrace channel will be riprapped to prevent erosion. 6.6.2 Design and Analysis The design and analysis of the powerhouse/substation excavation, cofferdam and tailrace channel were based on the 'design criteria for the Bradley Lake Hydroe!'ectric Project included in Volume 2 and listed below: Geotechnical Design Cri t.eria General Civil Contract HydrauiiG Design Criteria Tailrace Structural Design Criteria, Part A General Design Criteria Part B, Section 7.0 Tailrace 0216R-~434R/CG 6-16 .I The following calculations are included in Volumes 4 to 9: Title Tailrace Slope Stability and Protection Powerhouse Cellular Sheetpile Cofferdam Stability Analysis _Tailrace Channel -Slope Protection 6.7 POWERHOUSE Calculation No. G(AK)-50 G(AK)-89 H -050 The powerhouse is being analyzed at this time and the ·static and dynamic analyses' will be a part of the Final Supporting Design Report for the Powerhouse Construction Contract. 6 • 8 REFERENCES 1. Newmark, N.M., Effects of Earthquakes on Dams and Embankments. Geotechnique, Vol. 15, No. 2, 1965, pp. 139-160. 2. Sarma, S.K., Response and Stability of Earth Dams During Strong Earthquakes. Misc. Paper GL~79-13, U.S~ Army Engineer Waterways Experiment Station, Vicksburg, MS, 1979. 3. Seed, H.B. and Idriss, I.M., Soil Moduli and Damping Factors for Dynamic Response Analyses. Report No. EERC 70-10, Earthquake Engineering Research Center, College of Engineering, University of California, Berkley, CA, 1970. 4. Stone & Webster Engineering Corporation (SWEC). Slope Stability Analysis (LEASE II) -User's Manual. GT-018, Version 02 Level 00. SWEC, Boston, MA, August 1980. 5. Stone & Webster Engineering Corporation (Sk~C). Seismic Amplification Response by Modal Analysis (SARMA) -User!s Manual (Draft). GT-055, Version 00 Level 00. SWEC, Boston, MA, July 1983. 0216R-4434R/CG 6-17 6. Woodward-Clyde Consultants (WCC). Report on the Bradley Lake Hydroelectric Project Design Earthquake Study. WCC, Anchorage 9 AK, November 1981. 7. U.S. Dept. of the Interior, Bureau of Reclamation, "Design of Gravity Dams," 1976. 8. U.S. Dept. of the Interior, Bureau of Reclamation, "Design of Small Dams," Revised Reprint 1977. 9. National Research Council, Committee on the Safety of Existing Dams, Water Science and Technology Board, Commission on Engineering and Technical Systems, "Safety of Existing Dams Evaluation and Improvement", 1983. 0216R-4434R/CG 6-18 SECTION 7.0 BASIS FOR SEISHIC LOADING 7. 0 BASIS FOR S.EISMIC LOADING 7.1 GENERAL A number. of investigations of have been completed by the.Army Survey (USGS), Woodward-Clyde Engineering Corporation (SWEC). the seismicity Df the Bradley Lake project Corps of Engineers (COE), the US Geological Consultants (WCC) and Stone and Webster The USGS is conducting a continuing seismic monitoring program in the vicinity of the site.· Their most recent summary report is presented in the Supplement to the Final Site Conditions Report. 7.2 SEISMOTECTONIC SETTING The portion of the Kenai Mountains in which the Bradley Lake project area is located is composed· of upper Mesozoic Age metamorphic rocks of the McHugh Complex. Most of these rocks are interpreted as representing two environments of deposition. Clastic graywackes . and associated argillites represent rapid deposition in a relatively high energy near-shore· marine environment, such as occurred in turbidite zon:s on the ~teep continental slopes bordering the ancestral Aleutian Trench. The physical and chemical immaturity of the sediments indicate derivation from a continental terrain, rapid deposition, and little reworking. Vclcaniclastic metatuff (of andesitic or basaltic composition) was probably derived from adjacent island arc vulcanism and deposited on the trench slopes with silt (forming argillite) and silica (forming chert). Soft sediment deformation involving slumping and turbidity deposition mixed some of the sediments. A different environment is postulated for the flow basalts, which have generally metamorphosed to greenstone. Based dn. the chemistry of the basalts, most investigators infer an oceanic basin, plateau, or rise. environment which niay have also contained fine sediments (argillite) and chert. However, some investigators propose that the basalts are also of . ' :trench origin and would therefore be syngenetic with the deposition· of the graywacke and argillite. 0216R-443SR/CG . 7-1 The two potentially contrasting depositional environments, mode of deformation and general lack of continuity of units indicate that the McHugh Complex, including the Bradley Lake area, represents a melange deposit in which rocks have been tectonically mixed, uplifted, deformed, and accreted onto the North American Plate. The primary large-scale expression of the tectonic influence on the project area is the Aleutian Arc-Trench, which lies 185 miles southeast of Bradley Lake, and parallels the prevalent northeast-southwest strike of the prominent tectonic features found in and around the project area. The Aleutian Trench is a result of the northward movement and under- thrusting of the Pacific Plate beneath the North American Plate, at an estimated rate of about 2.4 inches per year. The resultant subduction zone, called 'the Aleutian Megathrust, dips to the northwest and corresponds to a zone of seismic .activity called the Benioff zone. At the project area, the Benioff zone lies about 30 miles beneath the earth's surface. This zone marks the boundary between the two colliding lithospheric plates, is an indicator of substantial regional tectonic activity, and has been the focus of several major historic earthquakes in southern Alaska. -= H,istorically ( 1899 to date), eight earthquakes ranging from Richter magnitude Ms=7.4 to 8.5 have occurred within 500 miles of the site. Great earthquakes (surface wave magnitude M =8 or greater) and large s earthquakes (greater than Ms=7) have occurred historical~y throughout the region and can be expected to occur in the future. Bradley Lake is situated on the overriding crustal block above the subduction zone and between the Castle Mountain fault to the north and the Patton Bay-Hanning faults to the southeast on Montague Island; these faults have documented Holocene or historic surface ruptures. Because of the active tectonic environment activity is probable on other faults, such as those found near or on the project site, located in the overriding crustal block and between the known active faults. 0216R-4435R/CG 7-2 / The Border Ranges Fault marks . the northern. margin and suture line of the McHugh Complex, while· the Eagie River -Tllrust Fault and adjacent Valdez Group rocks mark the 'sout~ern limit of the complex. In the· Bradley Lake area, the Border Ranges Fault lies under Kachen:ak Bay,···and the Eagle River Fault crosses Bradley Lake near 'its head. Both faults· trend northeast-southwest'. Within the project area, the locally · prominent Bradley River, Bull Moose and Battle Creek Faults, as well as a complex network of secondary . fault's, fracture zones, and major joint sets are expressed by lineaments that generally parallel the same regional structural grain. This orientation may · be attributed to the counter-clockwise rotation· tendency of the Pacific plate as it subducts under the North American Plate, causing Iiorthsouth to nor-thwest-southwest oriented f~actures. The Bradley River Fault and the Bull Moose Fault cross the power tunnel alignment about 4,200 ft arid 11,600 ft, respectively, from the intake area at Bradley Lake. The segment of Battle Creek immediately upstream of the temporary construction camp lies within the surface expression of the ·Battle Creek Fault. This fault strikes north-south and dips 65° -68° West., The trace of the fiml t cuts across the base of Sheep Point and continues:..across the south end of the waste disposal/waterfowl qesting area. The proximity and parallel orientation of the Bradley and Bull Moose Faults and associated lineaments, with respect to the two major regional fault systems which flank. the area, suggest they share a common· relationship and response to the tectonic regime of the region. The tremendous forces ope.rating on the area during accretion created large tectonic feature_s, and also imparted _the melange and cataclastic 'structures on the rock, as manl.fested by the intimate shearing and flow mixing of graywacke, argillite, metatuff and chert. This occurs. at scales ranging from tenths of an inch to hundreds of feet·. The compressional stresses inferred to have been responsible for the structure found at the Bradley Lake area do· not appear to ··be active at this time. Although the overall stress regime for the_Southcentral Alaska area 0216R-4435R/CG 7-3 is compressional on a generally northwest-southeast axis, the current configuration of plate boundaries and the location and orientation of the subduction zone suggest that the regional stress regime of the Kenai Peninsula is, at least temporarily, in a low stress situation. This. tends to be confirmed by initial on-site hydrofracture tests which indicate minimum horizontal stress levels not exceeding vertical geostatic stress, and by the very low level of recorded microseismicity. Definitive data on ·the Border Ranges, Eagle River, Bradley River, and Bull Moose Faults is scarce. None of the. studies (initiated in 1952) have noted evidence of recent displacement on these faults. It should be noted that this time frame includes the great Aleutian Megathrust earthquake of 1964. Microearthquake data available· at the time of this report reveals no association between recorded seismicity and the mapped faults in the project area. In fact, the limited seismic activity appeared to be at a depth shallower than the subduction zone. (but well below ground surface), which is thought to be the primary source of seismic activity. . Some evidence has been found to suggest recent activity on the Eagle River Fault near Eklutna, some 125 miles northeast qf the project site. If the Border Ranges or Eagle River Faults are active, it has been concluded that. displacement on either. of them could potentially induce movement on the Bull Moose or Bradley River Faults, or on other associated small faults in the project area. In addition, independent stress-related, fault rupture appears possible on the Bradley River or Bull Moose Fau1 ts, with amounts of predicted slip ranging from 3 in. to 48 in. The probability of measurable displacements occurring on these faults at any time in the next 100 years is estimated in the range of one in 250 to one in 5,000 (Woodward Clyde Consultants, 1981). Several reports on the geologic and seismic setting of the Kenai Peninsula are listed in the Geotechnical Interpretive Report. Five microseismic stations and three strong-motion stat.ions have been installed within and around the Bradley Lake area by the USGS. One microseismic and one strong motion station are monitored at this time. The stations located on the Project .site are currently (1988) being monitored by the University of Alaska -Fairbanks. 0216R-4435R/CG 7-4 7. 3 SEISMI.C DESIGN 7. 3.1 Design Condition The design earthquake ·studies· (Woodward Clyde Consultants, >1980,-1981) · examined possible. earthquake sources and associated. maximum magnitude ·- estimates for each source zone. Probability curves and tabulations of the -relative contributlon from various size earthq1Jakes · were developed. An analysis of ground motion parameters was performed a~d · response spectra curves were formulate~ for a maximum credible earthqua~e (MCE), producing a 0. 75g 'peak horizontal bedrock acceleration. A response spectra curve was also formulated. for a · design ·basis_ earthquake (DBE) produ.cing a peak horizontal bedrock acceleration of 0.35g. The study concentrates on regional faulting; (the Aleutian Megathrust/ Benioff Zone),. and four local faults· (the Eagle River, Border Ranges, Bradley River, ·and· Bull Moose Faults) as the control! ing sources to be considered. Analysis indicated that a magnitude 8.5 event occurring on the megathrust beneath the sfte . and a magnitude_ 7. 5 event occurring on the Bord~r Ranges. or _Eagle River _Fauns,-domiziate the total response spectra for the project design maximum earthquake. Seismic-design parameters were . developed from the horizontal response spectra at the project area. Both maximum expected magnitude and r~currence intervals were considered. Details of the seismic design spectra and design' accelerogram are provided ' - in the Darn Sl:abiiity Report in Volume 3. 02 f6R-4435R/CG 7-5· The summary of the alternative design cases from which the maximum credible and design basis events were Design . Earthquake Peak Horizontal Acceleration Magnitude 7.5 (Local Fault) (g) 0.75 Magnitude 8.5-· 0.55 (Regional Fault) Magnitude 8.5 (Regional Fault Attenuated by Distance) 0.35 7.3.2 Design Criteria selected are detailed below: Peak Velocity (in/sec) 27.6 21.6 10.1 Peak Displacement (ft) 1.6 1.3 0.61 Significant Duration (sec) 25 (MCE) 45 45 (DBE) Earthquakes will affect the. operation of the Bradley Lake Project.· Since the project site is located in a seismically active area, it is desirable for the plant to remain operational during and after minor earthquakes. A horizontal ground acceleration of O.lg has been selected for this operational basis earthquake. Minor damage can be expected during a moderate earthquake corresponding to a horizontal ground acceleration of O.lg to 0.3Sg._ This would involve possible repair to such items as relays and light bulbs. Architectural siding and windows may need minor repair. Most repairs can be performed by plant personnel using spare parts. During a major or extreme earthquake having a horizontal ground acceleration of 0.35g to 0.75g, increased damage may be expected to occur. An inspection of the plant structures and equipment will be required. Since damage may have occurred to the generating equipment, major repairs may be required. 0216R-4435R/CG 7-6 1. \ I I With a ground· acceleration gr~ater than. 0.7Sg,· .which._is ·greater than the mean maximum credible event presently predicted, · increased damage would occur, varying with the· earthquake magnitude and .period. Tabl'e 7-1 is a ' ~ ' ' •• • > • • seismic evaluation which addresses· the project structures 'and ·equipment .. This evaluation·. provides an approximate annual· probability of exceedance, which is based on the . so year projeCt life, and the anticipated plant downtime for inspection and -repair. It is not· _economically prudent to design all structures and ·equipment-for the Maximum. Credible Earthquake event. The critical structures and equipment including the main dain, spillway, low .level outlet gates and operators, power tunnel, power tunnel .intake and intake. gate shaft, intake gates and operators, and spherical valves and operators are designed for t-he Ma.Ximurn Credible Earthquak~. Some repair may be required after the event. However, the_ operating integrity of these-struct.ures and equipment will be maintained during the Maximum Credible Eerthquake. The generating eqt1ipment will be de~igned to remain. operational during ·minor earthquake· events up to a horizontal-_ ·ground . a~ce.lerat.ion .·of 0.1 g.· Minor damage can be ·expected from an earthquake with a horizontal ground acceleration of O.lg· to 0.3Sg.· Major damage -may" be.possible to the generating equipment from an earthquake w:i th a · horizontal ground acceleration of 0.3~g to 0.7Sg •. Unless specifically 'de~ignated otherwise in design criteria or specifications, all major projeCt facilities will ·be .founded on or in rock and design: acceleration values given below are fo-r horizontal acceleration in rock. 0216R-443SR/CG 7-7 Project Facility Main Darn and Spillway Intake Structure and Gate Shaft Diversion and Outlet Facilities Fish Water Bypass System Power Tunnel and Inclined Shaft Penstock and Steel Liner Powerhouse Other (Service buildings, roads and other non-operational facilities.) Design Ground Acceleration(g) 0.75 0.75 0.75 0.35 Fully embedded-Not applicable 0.75 0. 35 (No collapse at 0. 75) U.B.C. Zone 4 standards (min.) The potential for future fault rupture, including sympathetic rupture initiated by Eagle River and/or Border Ranges Fault movements was evaluated for the Bradley River, Bull Moose, and minor faults in the vicinity of Bradley Lake. On this basis, the probability of rupture occurring at the power tunnel over the next 100 years was estimated at approximately 1 in 250 (or one chance in 25,000 of a rupture in any given year) due to movement either on the Bradley River or Bull Moose Faults. Along a minor fault, the probability of rupture is estimated to be approximately one in 5,000 fo~ a 100-year period. 0216R-443SR/CG 7-8 Table 7-1 SEISMIC CRITERIA Peak Horizontal Ground Acceleration Approximate Mean Annual Probabi I ity of Exceeding Specified Acceleration (based on 50 year project I ife) Anticipated Downtime Operational Basis up to.1 g 0.1-0.2 (1-2 chances in 10 of exceeding 0.1g) Project resumes operation within hours Design Basis 0.1 g to .35 g (DBE) .007 (7 chances in 1000 of exceeding 0.35g) Inspection and checkout 30 days. Repairs 1 to 6 months ALLOWABLE DAMAGE LEVEL Project Features Dam Operational Spillway Power Tunnel Powerhouse and No significant damage Substation Structures Turbine/Generator/ Operational Governor 0216R-4438R/CG Operational Architectural damage. No significant structural damage. Minor damage, possible replacement of components with spare parts Page 1 of 3 Extreme Basis .35 g to .75 g (MCE) .0004 (4 chances in 10,000 of exceeding 0.75g) Possibly greater than 6 months Limited structural damage, no structural col lapse. Potential for functional damage. Structural damage (no structural collapse). Significant architec- tural damage. Possible major damage Table 7-1 SEISMIC CRITERIA Operational Basis Controls No damage, requires integrity check to restart. Minor adjustments/reset controls/spares replace- ments. Spherical Valves Operational and Operators Power Tunnel and Operational Diversion Tunnel S I ide Gates and Operators, Powerhouse Operational Emergency Generator 15 kV Switchgear Operational and Bus Main Powerhouse Operational Transformers Substation/ Operational Transmission Line Emergency Lighting Operational, minor damage (I ight bulb replacement) 0216R-4438R/CG Design Basis Limited damage, replace- ment of components with spares Oper·at i ana I Operational Operational Operational Operational Potentia I interrupti on of service Operational, minor damage and I ight bulb replacement Page 2 of 3 Extreme Basis Possible major damage Operational Operational Operational by manual start. Manual cable reconnection may be required. Minor damage Minor damage Out of service, possible major damage May require reconnection to emergency generator and I ight bulb replace- ment Operational Basis Fire ~rotection Operational Env~ronmental Operational Systems (HVAC) Middle Fork Operational Divers-ion Nuka Diversion Opera~ional Permanent Camp Operational Fac iIi ties including Permanent Housing - Barge Dock Airstr-ip , Access Ropds 0216R-4438H/CG Operational Table 7-1 SEISMIC EVALUATION Design Basis Operational Operational Operational Potential-for functibn~l d?mage· Opera-tional_ Soil failures poss i b I e. Wi I I be repaired as needed. Page 3 of 3· Extreme-Basis Possible damage Possible damage Potential for functional damage ~oss i b I e maj'dr damage Potential for archi tec_-- tural and structural damage Major soi I failures possible. Wi I I be . repaired as needed. Modified Mercalli lntensrty Scale (1931. Wood and Neumann) 1. Detected only by sensitive instruments 2. Felt by few persons at rest, especially on upper floors:· delicately suspended objects may swing 3. Felt notlceatlly, but not always recognized as earthquake: standing autos rocx slightly, vibration like oassing trucx 4. Felt indoors oy many, outdoors by few: at night some awatcen: dishes, wrndows, doors dlsturt>ed: motor carS rocx noticeatlly 5. Felt by most people, some breatcage of dishes. windows. and plaster: dlsturt)anca of tall objects 6. Felt by all, many frightened and run outdoors: falling. plaster and chimneys, damage small 7. Everybody runs outdoors: damage to buildings varies depending on quality of construction; noticed by-drivers of automobiles a. Panel walls tl'irown out of frames: fall of walls, monuments, chimneys; sand and mud ejected: drivers of autos dlstui'OEld. 9. Buildings shifted ott foundation, cracxed, thrown out of plumo; ground cracxed: underground pipes broken 10. Most masonry and frame structures destroyed: ground cracked; rails bent: pipes broken 1 1. Few structures remain standing; bridges destroyed: fissures in ground: prpes broken, landslides. rails bent 12. Damage total: waves seen on ground surface: lines ot sight and level distorted: objects thrown up in air Acceteratrons (Mean Ground) 0.01g- 50 1-o.osg- 0.1g- 200 ~ 0 . .2c;- 500 ~ 0.5g- 600 ~ C.6g- 4 5 7 CLASSIFICA.TION OF EARTHQUAKE EFFECTS : 1018 1020 10.21 1022 SECTION 8.0 SPILLWAY DESIGN FLOOD BASIS )· 8.0 SPILLWAY DESIGN FLOOD BASIS Probable Maximum Flood (PMF) for the Bradley Lake basin and for the Middle Fork Diversion basin were computed by the Alaska District,· Corps of Engineers during its· feasibility investigations of the-project in 1979- 1982. The following ·summarizes the methodology, criteria, and results of those studies as presented in its reports entitled "Design Memorandum No. 1, Hydrology" dated June, 1981, and "Design Hemoranduni No. 2, General Design Memorandum", dated February, 1982. The methodology, criteria, and results of the Corps of Engineers flood studies have been reviewed and found to be reasonable and acceptable. Also, the low level outlet or powerhouse hydraulic capacities were not utilized in reducing the PMF discharge, and this approach was retained when designing the Project spillway structure. 8.1 STUDY METHODOLOGY A mathematical model of the Bradley-Lake basin ~as developed to compute the PMF hydrograph. The watershed model was established using the Streamflow Synthesis and Reservoir Regulation (SSARR) computer . program developed by the North Pacific Division, Corps of Engineers. In order to verify the simulation of -the physical and hydrologic characteristics of the basin, several historical floods were reconstituted using the SSARR program. . In addition, . to better establish glacial runoff parameters, the-model was also calibrated ageinst runoff. from Wolverine Glacier, located 25 miles northeast of Seward. Daily streamflow, temperature, and precipitation were available a= Wolverine Glacier, greatly improving the reconstitution. Schematic diagrams of. the basin inodels used for reconstitution of flows for Bradley River a~d Wolverine Creek are .shown on Figure ·F8.1-l at end of Section 8.0. 0216R-4436R/CG 8-1 The Hydrometeorological Branch, National Weather Service (NWS), developed probable maximum storm criteria of the Bradley Lake basin in their report entitled "Study of Probable Maximum Precipitation for Bradley Lake Basin, Alaska," dated May, 1961. Estimates from this· report were reviewed by the NWS in June, 1979 and found to. be still valid. 8.2 WATERSHED MODEL CALIBRATION The SSARR watershed models for both the Bradley Lake basin and the Wolverine Glacier basin were verified by comparing the computed and observed discharge hydrographs at stream gauging stations on Bradley River near Homer and on Wolverine Creek near Lawing. The following events were selected for flood reconstitution studies: • August -September 1974 (Wolverine Creek) • 10-20 August 1958 (Bradley River) • 8-17 September 1961 (Bradley River) • 10-30 September 1966 (Bradley River) The streamflow hydrographs (observed and computed) for the above events for Wolverine Creek and Bradley river are shown o~Eigure F8.2-l and F8.2-2 at end of this section. 8.2.1 Computer Program Application The basins were divided into subbasins as depicted in Figure F8.1~1. These subbasins represent the glacial and nonglacial regions of the basin, with the glacial areas further subdivided into elevation zones in which temperature dependent processes can be simulated. Separate basin characteristics were derived of the glacial and nonglacial areas, and are illustrated on Figure F8.2-3. Snowmelt and precipitation on each of the subbasins were input to the model and losses simulated to obtain the increments of excess water which were converted to surface, subsurface, and base flow. Total runoff is dependent on the Soil Moisture Index (SMI). 0216R-4436R/CG 8-2 8.2.2 Precipitation Data from Homer and Seward were used as indic:s to precipitation. Since these stations showed variation in daily precipitation 1n the basin, station weights were adjusted on a storm-by-stcrm basis to simulate storm runoff volumes. Reconstitutions were therefjre made for individual rainstorms. 8.2.3 Temperature Data from Homer, adjusted for a lapse rate of 2.9°F/l,OOO feet, were used as an index to basin temperature. Melt rates w:re ·based on average daily temperatures. 8.2.4 Snow Since all reconstitutions were for rainfall events occurring in late summer, it was assumed that all nonglacial are.as were snow-free. The snow covered area in each glacial elevation bank wes set at 100 percent, with the snow water equivalent arbitrarily set at 300 inches for each band to simulate the effect of the glacier. The tempen.ture index method was used for computing snowmelt utilizing a consta11t melt rate of 0.098 inches/°F -day. 8.2.5 Losses Losses were simulated for each time period b the program by the Soil Moisture Index (SMI). Runoff is a function of the SMI, which varies for each time period and which is derived from the 3MI for the previous period, runoff generated in the previous period, and the evapotranspiration index. Both glacial and nonglacial areas assumed high r~noff percentage. 0216R-4436R/CG 8-3 8.2.6 Separation of Runoff The separation of total runoff into the components of flow is variable in the computer program. On the nonglacial areas, the portion of water input contributing to base flow decreases as the Base Flow Infiltration Index (BI I) increases. On glacial areas, there were initial minor decreases in percentage of runoff converted to base flow, but base flows were then held constant at 95 percent of total runoff, as it was assumed that most melt and rainfall runoff would flow into crevasses and emerge as subglacial flow. Although termed base flow, r·outing phases and periods were set such that glacial "base flow" still exhibited rapid runoff characteristics. The number of phases and the time of storage per phase used in the routings are: Runoff Component Surface Subsurface No.. of Phases 4 4 Time of Storage/Phase (hrs) 3.3 10.0 Because the basin lacks any extensive soil cover, the surface-subsurface . split for nonglacial areas assumed that most runoff occurs as surface flow. The base, subsurface, and surface flow for each subbasin were routed and combined to yield the total subbasin outflow. Subbasin outflows were combined with other subbasin flows to produce the total runoff hydrograph. 8.2.7 Flood Reconstitutions The Bradley Lake basin, because of its elevation, proximity to the Gulf of Alaska, and exposure to storms moving into the Gulf of Alaska, receives precipitation amounts exceeding those recorded at the coastal weather stations. Because of the difficulties of verifying computed hydrographs in early summer and in assigning proper precipitation weights over an extended 0216R-4436R/CG 8-4 ( period of time, individual storms were reconstituted August-September period (when rainfall :f.s greatest), for the adjusting precipitation weights until computed runoff volumes matched observed runoff volumes. The reconstitutions are shown in Figures F8.2-I and F8.2-2. They follow the· general timing and pattern sufficiently well. to justify application of the method to PMF derivation. Confidence. can be placed in the glacial runoff characteristics . as derived from· :the reconstitution for Wolverine Creek, where ·adequate data were· available .. Runoff characteristics for the nonglacial areas of Bradley Lake were estimated from hydrological reconnaissance studies, and are believed to be fairly reliable due to the impervious character of the basin. 8.3 PROBABLE MAXIMUM FLOOD The ·streamflow recqrds for the Bradley· River ·a,: the lake outlet indicate that the maximum aQnual peak disc;:harge normally occurs between August 1 and October 31 from ·a summer rainfall flood. .The -National Weather Ser·vice estimated that the probable maximum storm woulc occur ·in either August or September. The probable maximum flood· was developed utilizing storm criteria for August developed . by the Hydrometeorological Branch, National Weather Service, with the 100-year storm 'assumed as an antecedent rainstorm. 8.3 .• 1 Computer Program Application· The SSARR model developed from flood reconstitu:ions was used for the PMF determination for Bradley River. The SSARR mod-:1 for PMF determination of the Middle Fork Diversion was developed using basin characteristics derived for the B~adley Lake basin. 0216R-4436R/CG 8-5 8.3.2 Precipitation The Hydrometeorological Branch, National Weather. Service, determined that the Probable Maximum Precipitation (PMP) would be a combination of orographic and nonorographi'c rainfall occurring in either August or September. The rainfall was distributed in 6-hour periods in the manner prescribed by the NWS. The total 72-hour precipitation for the PMF is 41.0 inches with a maximum 6-hour accumulation of 11. 1 , inches. f.,s the NWS indicated that air temperatures during the August PMP are expected to be about 2°F higher than those during the September PMP, the PM:P is forecast for August. A 3-day antecedent rainstorm was assumed to occur before the PMP storm, using 100-year rainfall data taken from U.S. Department of Commerce, Technical Paper No. 47 and Technical Paper No. 52. . The antecedent rainstorm was logged in 12-hour intervals to determine the sensitivity of the PMF to the timing of the antecedent storm. Since the PMF is relatively insensitive to the length of time between storm, a 48-hour lag time between storm was taken as a reasonable time period, and used in the derivation of the PMF. 8.3.3 Snow Snowmelt was handled in the ·same manner as in the flood reconstitutions. The temperature index method was used to compute melt from the glaciers. It was assumed that nonglacial areas were snow-free. The snow water equivalent for each glacial elevation band was arbitrarily set . at 300 inches. A constant melt rate of 0.098 inches/°F-day was used. 8.3.4 Temperatures The NWS report includes the temperatures to be used during the probable maximum storm, and gives.a temperature envelope to be used for the periods before and after the storm. The highest temperatures in the envelope were utilized to maximize snowmelt. 0216R-4436R/CG 8-6 8.3.5 Runoff Separation and Losses Separation of flow and losses during PMF runoff were simulated .in the same ·manner as in the flood-reconstitutions. 8.3.6 Probable Maximum Flood Hydrographs The Corps ·of Engineers PMF -inflow hydrograph :including Nuka runoff and Middle· Fork Diversion flows, developed as described above, was adjusted upward to 800 cfs to include 400 cfs additional inflow from Middle Fork · Diversion. 8.4 SPILLWAY .DESIGN FLOOD The Spillway Design Flood (SDF) for the Bradley Lake basin is the spillway discharge when the PMF is routed .. through the reservoir. The most critical period occurs during late summer. when the reserv::>ir is at maximum level and the probability of receiving the PMP is greatest. _The starting water surface is at spillway crest Elevation .1180.0. The spillway 1s an . uncontrolled ogee type with a crest length of !75 feet, which length was developed to handle the PMF inflow while maint=.ining a maximum reservoir elevation of 1190.6 when the PMF was routed through the spillway. The PMF inflow and routed outflow hydrographs and a plot of the corresponding Bradley -Lake water surface elevations are shown in Figure 8.4-1. The peak inflow is 31,700 cfs and includes flows from the Middle Fork Diversion up to 800 cfs arid Nuka glacial flows. Also, it was conservatively assumed that no water is diver:ed into power generation during this routing. The PMF routed spillway o1!tflow (the Spillway Design Flood) is 23,800 cfs. The channel downstream of the spillway and the riprap protection on the downstream face of thE dam were sized to handle this flow. . 0216R-4436R/CG 8-7. 8.5 MODEL TEST Part of the 1:50 scale hydraulic model constructed by the Colorado State University Engineering Research Center in Fort Collins, Colorado, included the spillway and downstream pool and channel. The model test results showed excellent correspondence between the theoretical spillway discharge rating curve and that which was measured. For the lake at the PMF elevation, the model test ·indicated a flow of 23,8~0 cfs. This is only 29 cfs different from the calculated flow. The observed flow conditions for the spillway at all reservoir elevations were satisfactory. One small eddy shedding zone at the left abutment (seen at high flows) was corrected by developing a more streamlined geometry. The model also showed that the downstream channel was capable of conveying the PMF. The measured velocity and water surface elevations at the downstream face of the dam during PMF testing was used in designing the riprap protection which will be placed there. 0216R-4436R/CG 8-8 i. 1 Bradley .A Lake Surface . Bradley Nonglacial, Bradley Lake · Bradley River at Lake Out let Bradley Glacial Bands t Sign Change (a) BRADLEY RIVER Wolverine Nonglacial Wolverine Glacial Bands • Wolverine Creek · near Lawing . (observed) @ Middle Fork Glacial Bands (b)WOLVERINE CREEK LEGEND 0 BASIN OR SUBBASIN 0 COLLECT POINT ~ RESERVOIR SCHEMA TIC OF SSARR MODEL L---.----------------------------FIGUR.E F8.1-1---~ FLOW CFS 0. 20.00 o.o 1 ALG 71.1 1200 P 2 AUG 7q 1200 P 3 A~G 7a 1200 P a AUG 7q 1200 P 5 AUG 71.1 1200 ,P · 6 A~ G 7 1.1 1 2 0 0 · p· 7 AUG 71.1 1200 P ··8·AeG .. 71.1-1-200.. P 9 AUG 7a 1200 P 10 AUG 71.1 1200 P 11 AUG 7a 1200 P 12 AUG 7a 1200 P 15 AUG 1200 P 16 AUG 1200 P 1 AU 1 00 P 18 AUG 1200 P· 2a 26 3 5 7 1a 1200 P ., p 71.1 1200 p p p • p p p 9 . 10 p • , -Ci) c JJ m , '(X) • 1\) I ....A. 11 13 15 SEP 7a 17 SEP 71.1 1200 19 SEP SEP SEP SEP SEP SEP 27 SEP 28. SEP 29 SEP 1a 1200 11.1 1200 1a 1200 71.1 1200 71.1 1200 71.1 ·1200 71.1 1200 1a 1200 • • • • • • • • • • p • p p p p 100. 26.00 0.50 • • • • • • • • • • • • • • • • • • . p .• • • • • • • • • • p • • • • • p • p • • p PLOT stATioN NAME CHARACTER C-WOLVERINE CREEK FLOW --CALCLLATED A-WOLVERINE CREEK FLO~ --CBSERVED 200. 3oo. aoo. soo. 600. T 32 •. o 0 1 .o 0 • • • • .•...... • • • • • • • • • • • • • • • • • T 38.00 • • • .T T. T. • • • T • . . •. so.oo 5(:.00 :!.00 • • • • • . .. • • T • • • .• ·r • • • • • T • • • T • . ·r T • • • . . • • • • • • • • • p STATION ~Ut'BER CONTROL 700. -~ 62.00 • • • • • • • • • • T. • • • • • • • I T • • • • • • • • • • • • • ·-.. - - • • T 110.0 G 11o.r: a 800. . 6e.oo • • • . . -. • • • • T • • • • • • • • • • • • • • • • • • • • ·-· -··. ·-·-• • .. • ., -G) c :IJ m ., (X) • 1\) I 1\) FLOn CFS 10 AUG 58 1200 11 AUG 59> 1~00 12 AUG ':ill 1200 13 AUG 0:.!:3 1200 11& AUG 58 1200 15 AUG 56 1200 1& AUG 58 1200 17 AUG 58 1200 18 AUG 58 1200 19 AUG 58 1200 20 AUG ':i8 1200 FLOI'l CFS 8 SE.P &1 1200 9 SEP bl 1200 10 SEP &1 1200 11 SE.P &1 1200 12 SEP b1 1200 U SEP &1 1200 1'1 SEP b1 1200 15 SEP &1 1200 1& SEP &1 1200 17 SEP o1 1200 FLOI'l CFS 10 SEP b& 1200 11 SEP &6 1200 12 SE.P 66 1200 13 SEP b6 1200 14 SEP o& 1200 15 SE.P b& 1200 1& SE.P 6& 1200 17 SEP 6b 1200 16 SEP b6 1200 19 tiEP b& 1200 20 SI:.P b6 1200 21 SE.P o& 1200 22 SEP bb 1200 23 SEP bb 1200 24 SEP bb 1200 25 SE.P 6& 1200 2& St:P b& 1200 27 SEP bb 1200 26 SEP && 1200 29 SEP && 1200 30 SEP bb 1200 m ::0 ::0 > m o mo r-...... 0 m $:10 z -< (J'J ::0 0) -t -0) =i <., c m r--t ::0 0- zo 0 m oZ > (J'J 0 :o.,., :tO ..... o:oco ~ C1l m !» :0 o. bOO. o.o 10.00 -----..... . . --:---eJ o. bOO. o.o 10.00 -s-.._ ... -- o. bOO. o.o 10.00 --. . . . . . . . . . . . . . . . • . • . PLOT STATION NAME Ct!ARACTI::R C·FLO~ AT b~ADLEY LA~E. ·-CALCuLATED A-FLOw AT ijKADLEY LAKE --OBtiERVEO 1~00. 1800. 2400. 3000. 3600. T 20.00 30,00 . ""'=' 40.00 SJJ.OO -·--.------. • _c-----e---·-/ r:" . • ,..c. • 0" • PLul STAllON NAME CHARAClE.H bO,OO . • T T • T T C•FLUw AT A•FLO~ AT ~RADLt:t LAKE •• CALCULAIEO ~RADLEY LA~E •• OBSERVED 1200, 1800. ~400, 3000. 3bOO, T 20,00 30.00 '40,00 • .,...c--c---c- • .f!(' • • PLOT STATION NAME CHARACTE.R 50,00 • T .T T bO.OO T. C•FLOW AT SRAOLEY LAKE --CALCULATED A-FLOW AT BRADLEY LAKE •• OBSERVED 1200, 1800. 2400. 3000. 3&00, T 20,00 .30,00 40,00 so.oo 60,00 . . . T • . . . T • -....:._.c-._ • • T . ........._ . . T • '-:C.--. ......_ • T ~ - . : : r-~ . . • • T .--c---__. :"" • • .......c---,.,.,. ;--T • _._r;----. • T ~---• , • T . . ,1 . . l • . ~ ,T . 1 T tiTATION NUMBER CJNTROL 4200, -361:15 70.00 ·• 10.0 Q 10.5 Q 41\00, I& 100, 80.00 STATION NU"'t~ER C:Jio4TROL '1200. ·.So&S 70.00 10.0 Q 10.5 Q 4800. 4 100. BO.OO STAT!Or~· NUMBt:R CDNTRvL to.o Q 10.5 Q 4200, 4800. •3&&5 I& 100. 70,00 80.00 . . 51&00. &000. 90.00 100.00 51&00. bOOO. 90.01) 100.00 • 51&00. &000. 90,00 100.00 . • J I s... ::3 0 ..c: 1.S -;;; 1.0 QJ ..c: t..: .. c ..... I +-I ::3 0. c ..... o.s QJ u ~ s... ::3 Vl >, ItS -o ....... VI QJ ..c: u c .,... I c 0 .,... +-I ItS s... 0 0.. ItS > LLJ 0 0 .15 .10 .OS 0 SURFACE-SUBSURFACE SPLIT 0.5 1.0 1.S 2.0 Surface & Subsurface Input-inches/hour EVAPOTRANSPIRATIO~ INDEX Nonglacial H Glacial_ . J F MA M JJ AS 0 NO Months +-I c QJ u s... QJ 0.. ct-ct- 0 c ::3 a: et- C+- 0 c ::3 0:: SOIL MOISTURE INDEX 100 .I... _!. I ..I-~ Glacial 17 I rTr' "] .,.,_'1:1 (J 50 II ,'1:1 ..,~ ._.::§.> I}. I- - f. . - _j lb .... -~· - +++·1-L..J....J.....J--00 5 10 15 Soil f~oisture Index-inches BASEFLOW INFILTRATION INDEX ';;; 100 +-I J. ~~ Glacial.~LL~+++TTI· '-'-+--..f--.I +-r--. 0 I- tt- 0 +-I c QJ ~ 50 QJ 0.. c ..... 3: 0 ,.... -1.....<.--+W-.,-,--H ·t ~+-.H±1ttt+H+H··- ru_J_--I-l-Hr-t-n-J t•. . It T -±±t·tj t--·~++ftmm=H=:t= ~ ~ t-f-4--+-.t +-t-Th~1:7-tl:ttt+t=1 n-r 1 4- QJ VI ItS co ~T h NJ~!l_~·~f~l_r 1 .LHJ 00 ... ... 4 6 Baseflow Infilitration Index +-I 5i u s... QJ 0.. c ..... ltl SNOW COVER DEPLETION f SOIIIII N I c:C -o f QJ > 8 3: 0 c Vl 6'' I I I I I I 11111111111~ 0 so 100 Accumulated Runoff in Percent MELT RATE INDEX ~ .10 -o I 01 ~ ....... VI QJ ..c: g .OS ..... I QJ +II ItS 0:: +-I ..... 0.1 :::£ 0 0 50 100 Accumulated Runoff in Percent BASIN CHARACTERISTICS FOR SSARR MODEL "---------------------------FIGURE F8.2-3_, . l 3 )-f- f- ~ 30 f- 2 ~-f-. ---c-:; -zO 00 2 1 -o ~-~"":" O::w (30 wo:: O::<t O..z '\. . ·o 0::(1) :x:_ Ill: <00 )_:. f- ~ .. ~ ,... - - f- f-- ~ f- v I I/ I'\ 1/ I/ I; i// ~ ! I I . 1 1\ PROBABLE MAX. FLOOD INFLOW (31.'700Cfs: ! I 1/ I I I I ;\ I' \ SPILLWAY DESIGN OISCHARGE(~800CFS) ' j\ I \ I I \ \ \ ! I \ I I I \ \ . l I ! I' '· 1\ \ \r MAX. WATER SURFACE El£V. 0190.65 FT:) I r--.. \ f'.. ~ \! I I ............ tl '\ I '~ ." ~~ v --~~ I . ~y _.!-f::t'!'"'" l I' I ~~-t---5-~-r-~ . l/ R' ~ ! -~· I ~ l I I l I ! ........ , _j_ ---~-----~--~ -vi I i I I I l7 ., : i I I ; rl \ "...· v v ~ .(, I~ II ~ I>RfCIPIT[TION ! i------~ , .. 75~ ' I .......... ~.: i rt i ; l I I ~ I I I -D I{· 2t ·~ +8 :5t ~ ~ 7?.. "4+ " gs lUI .,(!" l"t 150 Cf' '2. I 17t ta;.tnfll~t,t201~· 210 ZIC. fff 2'10 nz. 2'-t f~ Z 16 i3 14 15 HOOI\S DURATION (DAYS) PROBABLE MAXIMUM AND SPILLWAY DESIGN FLOODS 1195 -f-w w 1190 lL ..._, z 0 1185 f-~ w _.J 1180 w I PROJECT DESIGN FLOOD FIGURE F8.4 -1. SECTION 9.0 BOARD OF CONSULTANTS 9.0 BOARD OF CONSULTANTS 9.1 INDEPENDENT BOARD OF CONSULTANTS An independent Board of Consultants was formed to review the engineering and design of the Bradley Lake Hydroelectric Project. This independent board has met ten times since being formed in 1983. The reports of these meetings and responses to the meetings are included as part of Appendix B Attachment B2 of this report. The board meetings, convened at either the project site or in Anchorage, on the following dates: Meeting 1 May 12 and 13, 1983 Meeting 2 July 11 to 15, 1983 Meeting 3 September 25 to 27, 1984 Meeting 4 November 4 and 5, 1985 Meeting 5 January 28, 1986 Meeting 6 May 6 to 8, 1986 Meeting 7 August 12 to 14, 1986 Meeting 8 December 8 to 10, 1986 Meeting 9 May 5 to 7, 1987 Meeting 10 December 17 and 18, 1987 9.2 FERC BOARD OF CONSULTANTS In February, 1986, the Federal Energy Regulatory Commission approved the use of the Alaska Power Authority Board of Consultants to be the FERC Board of Consultants. The FERC Board has met six times at board meetings and individual meetings at the Hydraulic Laboratory at the Colorado State University in Fort Call ins, Colorado. The reports of these meetings and responses to the meetings are included as part of Appendix B Attachment B3 of this report. The board meetings convened at either the project site, or in Anchorage on the following dates: 0216R-4437R/CG 9-1 Meeting 1 March 6 and 7, 1986 Meeting 2 May 28 and 29, 1986 Hydraulic Lab July 9, 1986 Meeting 3 August 18 and 19' 1986 Hydraulic Lab August 29 and September 25' 1986 Meeting 4 January 27, 1987 Meeting 5 May 26 to 28, 1987 Meeting 6 December 7 and 8, 1987 0216R-4437R/CG 9-2 APPENDIX A DRAWINGS EXHIBIT F KACHEMAK BAY MUD FLAT '~ .. ~~ ~ ..:.!..:!... ,_.., ' I .• 1, I 11._,1 0~~~ \ s n "' I\ .__:::::-:.""1 / " ? / '---.) A~ I < ~# ~ ""u 0 (\j ~ ~ j " ~ )// ?"---. r r r I I ' MIDDLE BRADLEY LAKE ~ f BRADLEY LAKE HYDROELECTRIC PROJECT ~ c L ALASKA POWER AUTHORITY NOTE, ' GENERAL PLAN 1. WASTE MATERIAL WILL BE USED ID CONSTRUCT RQb.OS, AIRSTRIP, STAGING AREA, SWITCHYARD ARE .A, AND OTHER PROJECT FACILITIES AS N'PROPRIATE. 2. ELEVATIONS SHOWN ARE BASED ON Pfi\JJECT DATUM. MEAN SEA LEVEL DATUM • PROJECT DATUM PLUS 4.02 FT. ~=t:~~r}~r0:~ ' \ \ \ • \ \ AI'PROX \ I I TOP OF ROCK .I I 1 \1 I I \I I \, ·''' \ ', ,,,,' ', ,,, '-.:' ~,,,, .... ..:::, ... '\ '~.::~ .... , ,, .... -............. ',,, ,,,, ''''\ ,\1\ ' '\ \ I I ' \\I I' ,1\ I 1 I 1 1 ~\ \o1 \I\ ~' \ 'l,1 I 1 ·~ I, I! 1 1 ~\ \I 101 I I I )<111 ~ ,, ,' I I ''w~ ACCESS ROAD-; I / / WASTE DISPOSAL AREA 8 , EL 1100.0'MAX ~' ~~ ~ 00 ( I '\ WASTE DIS?OSAL AREA ~h EL 1090.0' MA~ 1-, I I I \ ' ,- 1 I I \,, ' ', ', ........ ,\ ' ' ' ' \ 6 'b _./ \ I I \ \ ' \ \ J-' w 2 2 " .1: "' ,J ~'q,"'o "'"' ' I ', I \ r, 1 \J , ..... ' I ' ..... __ / MAXIMUM NORMAL \ ~ OPERATING WATER • C3~1 1 SURF .ACE EL 1180.0' I \ I I I 1 I ~ WASTE DISPOSALN I ~ AREA F 1 I Q EL 10900\ MAX _.~ , ,' G: 11 / I \ I / I r r I I , , I\ I \ I \ \ \ I ' ' I ACCESS ROAD I ' 0 40 80 FEET E! I SCALE A 1•: 40~ . ' ' ......... ' ..... ::::;_:::-,'',, '':--.'_'-, ',, ',, ', '~', ',,, ' ',:., '2', ', '\'',''o<l ......... ..... ', ', ' ' 0..._ '',,,{>, .......... '',~,,' ',',,%, ',,,''-- ' ' ~','', ',~, ' ',~','' ............. ',~~~:-:_==-----, ""' ®CCC STA 0•00 ~ SYMBOLS KEY 8 SURVEY MONUMENT • SEISMOGRAPH INSTALLATION 0 WalK POINT FILL TYPES Bl I 3' PROcESSED CRUSHED SlONE B2 I ~ ROCK FILL.-GAP GRADED DRAIN B3 :l6°MAX ROCK FILL B4 I :l6'MAX ROCK FIL.L 95 I 49'MAX ROCK FLL (OVERSIZE! B II I GRAVEL RQI>.D SURFACING ZONE 1 TYPE 81 FILL CONC FACE SLAB 1'-0' THICK GROJr. CURTAIN ZONE 2 TYPE 82 FILL. ZONE 3 TYPE 83 FILL ~ ~ ZONE 4 TYPE 84 FILL ~ MAXIMUM DAM PROFILE .. .... Jt.Ai.l .. flll 581 1 ·6· PARAPET WALL. ZONE 5 PE 85 FILL ZONE 2 TYPE S2 FILL. 50'·0• 1 i ~ I 1'1 I 1<'">1 I h ~RANS~bNT I I I I I I I I I I I I I I ,J j ~f(~ANSITIONJOINT WIWATERSTOP I \ "' " " " ---.. GMENT A TOE PLINTH .._ ----SEGMENT B 3-3 •uu 'Ill l'll:n -..-.. -..-.. .....__ SEGME_NT C -- REINFORCED / COI'.CRETE FACE SlABS 21 SEGMENT D VIEW LDOKING DOW~EAM----------. ... ... Uiil""iiiiii I lt(:AUi!lllffU1' RIGHT ABIJTMENT PLINTH •• f . t..' ~ ~ ~ DISTAN:E A B c D L., 61~?• 4'-71 8'-1f 8'-0' T JCi()' 2"-41~ 21.3• 2'~3~ L. 41·t0f 5'·10:f 5'-3:f' 5C3f RIGHT ABIJTMENT PLINTH I l I ..,...__-~-GROUT I CURTAIN / / d 2-2 .. ~ 0 ih FLOW-- MEMBRANE LINER FILTER MINUS 3' MARTIN RIVER SORROW MATERIAL t COFFERDAM UPSTREAM COFFERDAM PROFILE o' 2'-9f 10' lid SCAL.£ .,_ F(El A 10'-0' :.: '··.,. ~--~::.::.:· 1 -1 .. •. f(;AI.I • I'll:? BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY CONCRETE.FACED ROCKFILL DAM SECTIONS AND DETAILS PLATE 3 ~ ~;(~o~ /,......../ __ __./ // /./ / J / / I I I ~~"' /-/ \:;\ J/// ~~~o' // -----::..--_.... // / / 1 / I I~/ / // / // ', ~'.::---/1/ //0,// . ...-:;..---:::..~/ <.-//// //1 //1 / //// ', \ \\\~~------I I I I I ,~" //// -----____....../ / / -------;/ I .!\ I I \ '~\\~.::-~/// // (i / .. /--.-</>-' #? f I , ! I \ \~ \\ '---/ / / / / 1 I g 1 / ~~ I I I ) V I / / I \ __ ) \ \ I I I \ 'b~\\'--/ / ( ......--I/ T 1 / J I 1 I ; 1\ I \ ',~\\.:;,-) <....\ \ ( (~YMOI-UI£7' \ II / J I I ' . '~ ' . I I ( \ / PT BBB....,--' ) I I I \ \ \ \ \ I 0 0 ~ I J I I I / \ \ \ \ \ \ I -t~ 1134. 90' t -----"-"-"-\ \ \ I INTERMEDIATE~ " " I \ I '" \ TRAINING WALL-------."' " \ I I \ \ ~ WEST TRAiNING ' I \1 I G' WALL "-" EAST TR,.,INING \ \ 1 ~ / " \\ \ \\ \ WALL I I \ \ ' "l I \ \\ \ II '-\ \ \ \ MONUMENT /'\ \ \ '-....... '-....-"-\ \ \ \ ' '-.... /}/ \ ~'--...... -----"\' "...___ \ "-...._ .......... " \ '.._.._ '\ " ----~-/.// J / I \ \ " "-...... "'-...... --........_ ' '\ "" '--~-~ _....... ./ / // J \ \ ........ ..._ --........_ \ \ '-. "--------/ // ~/ / -......._ ........ " ----~-.::::.----...... \ '\ "\' \_ ----//// / ,--./ (\ ,____ ........ , "-----......:::--...... \ ' "--,?o--////// \ { / '-. --""-' ----...._ "-........._ ,...._.._ ---///~ /; \ \ r '-----..__ "" ...__, ...___ -_,,s '\ "-"-:::::::..:::::::.:::: __ ,....----"/ / /;I'/. 'I \ \\\\\ r---...__ ......._"'"" <::------'--...... ------~ ........ ::__~....,__~6~------/////I flflll;! \ 1 \ \ \ "-"-, "---...__-:::._--':::_:::_-_:--.....,'-.....~------=----=-__=:-_::_ / /// I )I I II ) I 1 f--TOR \ '-...._ '----.... ''~ -....._ '---~ ~ jl I I l I \ ~---....._------------........ ......._ ...__ ....... _____ -~ /;I / ; 1 I I '\ --..-. -......... ...___ '-....._ -----=--'/;! r/ I { I I _ '-'----..:::_''<>o -----'( /// ~., / / I / --..__ --...... ...._ ...._ ~ L--~ ,_ / / / ./ ........ ----........ ...__ ------;/ / // / / -----1 -----:;;:::;: /(~/ // / PLAN-SPILLWAY--110 _______ __.... / ..// NON·OVERFLOW 105'-011 OVERFLOW 52'-6" FIXED LOLNEFI EL 1187.00' ~ VENTILAT!ON~G I ov"" \ I / I v•~• I ~Q • • ';..,. t LADDER SHAFT ,.. _."' ~-_:_-;-/// \---116:<r!l0' ~ - - - -[~ ' r::;:: -L. EL 1160.00' ~"' .. -------• ,. EL 1175.00' \~:=~\ / // EL 1145.00 ;_--r ,""'\ WEST TRAINING WALL EL 1134 -90' [\ .LI!r' -·-· DRAINAGE GALLERY EAST TRAINING WALL INTERMEDIATE TRAINING WALL ELEVATION-LOOKING UPSTREAM :;:;; '[l 1190.00' UIS CREST XC: 2.52' Yc: 1.00' R1: 5.68' R2: 1. 72' UPSTREAM FACE y !~=~EL~~ X ' 1 I =---< -I CREST EL_1_!80.00' X XC Yc F"~ y I SPILLWAY BASELINE X DIS CURVE COORDINAl'ES X PC 1 14.54' 9.54' PI 1 19.04' 1500' PT 1 26.11' 15.00' PC 2 35.41' 35.52' PI 2 42,92 1 45.00' PT 2 54.9 3' 45.00' DIS CREST COORDINATES X 0 1-00' 2.00' J.QO' 4.00' 5.00' 6-00' 7,001 0.00' 9.00' 10.00' 11,00' 12.00' 13.00' 14.00' 15.07' y 0 0.07' 0.24' 0.52' 0.88• 1, 33 1 1.85' 2.4 7' 3.161 3.93' 4. 78' 5. 70• 6.69' 7.76' 8.90' 10.19'TANGENT CURVE INTERSECT ,---------CURVE EQUATION Y•0.0678X 1.848 END OF' SPILLWAY A PROf\! (CAST AGAINST ROCK) OVERFLOW SECTION GEOMETRY NTS ~SPILLWAY BASELINE LOW ~+ 15·-o•~ ----j HIGH PT EL n9~.00' ~c_ ~ EL 1195,08' FLOW ___f:L___!_1§5,00' ~10 F"IL..L CONCRETE NON-OVERFLOW SECTION GEOMETRY NTS 0 20 40FEET I -SCALE A: 1': :201 BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY SPILLWAY PLAN, ELEVATIONS & SECTIONS PLATE 4 "' u ~~ ..J ::> < •o -lw ~ o: ... ~ ~!;?~~ fj~·· i ! . SEE DETAIL BELOW 8 6 Ill 8 0 ~ 8 0 ~ 8 0 \:1 .01~7 SLOP£;-I 8 8 0 6 (:! ;: 71 I 11' -o';. MIN CONC UNED TUNNEL 8 g 7.J 0 0 0 -01 FLOW TUNNEL PROFlLE 0 0 0 CD 50Ct o' 500 1000' 1500' r;3 'oj'"' -;; i PILOT BOREHOLE \ FOR RAISE ~' , .. SCALE' 1'• 500' TI!NNEL 8 ~ ~-'i?SX)' -20Cd NORMAL TRANSIENT PRESSURE GRADIENT] ---------------__ _._ ____ -15001 BliU. M::lOS£ FAULT £STAOC PRESSURE GRADIENT -~ --100d CONCRETE LINING 8 0 "' 8 6 "' g ::io * aj~ s..J CUTOFF GROUT RINGS TUNNEL & STEEL UNER CONC 9 g STEEL PENSTOCK &MANIFOLD \---+--+-+-GROUT HOLES STEEL SET STEEL LINER --f-'lo.-----. .,.., --JJ;,.i"!ll--- ·:-...;-. ~ ~ L..2 L..3 ROCK TRAP INTAIIE DETAIL . .. .. iW6jiiiiM • "'o ~ 'o ·-R 2-2 . ... .. N'=jO!W • tu.tt•nn ": ... • ., SEE EXHIB.'T F-PLATE 6 FOR INTAKE &GATE SHAFT l.IF'f'ER BEND DETAIL .... '• ; ~ ........... " TUNNEL ·r ' . ' :I --.....,... .. •... . . -·-• ·1·; fO' "·•-. .. , • "'.I ; ,;• ,• 3-3 -... .. ~ ES lk.Al.t••n.o .. 2 ~~ f Ti.JNNEL m·· 4-4 ... w----=e::cs c.-u•un MANIFOLD HORSESHOE ~~C~~~t~ON I POWER TUNNEL--------! I L----~ 7-7 .. c:.::=-==-----7...;:: :::::::; =:J ICAU .. f-UI ----··1· ~~ ,5•001667 JJ 8(SIM) LONER BEND DETAIL . ... .. tli1V' I *C.Al.IWfllT '91~ ... ::; DRAINS (TYPJ 6-6 • 4' •• l""lMilWii 225 KAU *flit' STEEL SET 5-5 KAU .. ,Uf '&-GROUT HOLES H:lOP & LONGITUDINAL STEEL REINFORCING TRANSITION TO STEEL LINER ,UPPER & LOWER BENDS & AREAS OF LOW MODULUS ROCK 8-8 . .. tc.At.t•••n BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY POWER CONDUIT PROFILE & DETAILS A ...... :~~;;:..; .;-.;:;;.,;;;; ....... I EXHIBrT F I PLATE s 8221-5 GATE SHAFT VENTILATON DUCT cr EL 1194.0' ~· 2 -,, I 22' 111 '1.1!> 1'-0'NOMINAL 11 CONCRETE LINING ' • II" SPIRAL STAIR BY-PASS rEL.1030' <t. TUNNEL GATE SHAFT CROSS SECTION ~· 11~.1/r~m ~ PLAN GATE CHAMBER •o' to' ~= SCoiUWfU1' ., 1 ;11 ~ EL 1125.0' ~ I II I I ~ I ~~EL 10300' INTAKE CHANNEL ) ' ,• '•'.• ' . n~ LONGITUDINAL PROFILE AIR VENT GATE SHAFT VENTILATION DUCT 0 16 32FEET SCALE ~ "'1'-0" 16 TE SHAFT CAP SLAB TUNNEL AIR VENT ~ GATE HOUSE FLOOR PLAN •tl' rd ~ LADDER TUt-l\IEL AIR VENT TUNNEL REFILL VENT PLAN EL 1053.50 1 o 10' to' ~-·--I ~ A PLOT PLAN-GATE SHAFT La.A----·~ ICAUMt'fll BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY INTAKE CHANNEL & POWER TUNNEL GATE SHAFT SECTIONS & DETAILS STONE & .WEBSTER ENQINEERIHG CORPORATION PLATE 6 1L oP327400 R ~ EL 3.5' HAIN LINK ~ OCKFALL SA~ETY MESH-N 2112220 TON 2112700 THIS EIENC>i ONLY I ROC~ OOWE L S A NO ROCX 80LTS START AT N 2112220 AND CONTINUE TO N21127~ RE~ PLATE a 1 r I I I I I I rlll / f I I CONSTRUCTION STAGING Af?E;A I 1 ~ ~c.;'ci~T\ED ro I I I I I I I I 1 I I I I I I ACCESS ROAD STA. 3• I I I I I I I I I I I J----SOUTH ACCESS I I ADtT I I I I I I I I L.. 4 MARSHAt.liNG YARO / --, ~ 6• 40 100 eo 100 eo .._tlQ!Ul:i ~~ ~~ ~~0~A~~~~G{HE x NUT .. -~-~-----""" ""CCW'SH /£ .,..----------~---------___ ___, ----~ ------ACCESS ERS(2) ZL / .& _.... ''""'""~-----------~~ _ ___.,....~ ~~III'Fl"''_"_... -------------~-'-'"' BENCH B.~ARING PLATE ~,?:("EXCAVATED TOEL180' --------~-~~-------~"""""""l!ne"' --------~~~ fxs"x8'W/1;t• _, ' =·-·-----"0" •• ~ I ~ EL 18.00' POWERHOUSE EXC"' EXCAVATED TO EL " --~ ~vATION ~~--~~~~~~4~0~'::-J:l ____________________________________ ~ & RIPRAP DETAIL EL 16.00' ~W&i EL1800' 0 R "' "' DOUBLE MESH UNDER PLATE TO EDGE OF ROCK-IMPALE ON DOWEL MESH INSTAI.LED BETWEEN DOUBLE PLATES TOP ROW ONL" ROCK BOLT CTYP) ~ ~ ~ 0 0 ~i N ~ 0 0 ~ " N ~. 0 g " N ~, "'I , -, SECTION @ E 327156 SCALE A (PLATE7) "'-.....__ ~~ ......._ 'Y''Iklh..."'-, EL56.0'! ~.,:}', ' -,~.~ --:::;-..... ............. __ EL40.0'] ::--..._..__ -~~-----~~,..._-..._ I • -"-7~~~------ PONER TUNNEL 18 0' PORTAJ... TO EL EXCAVATION NEAT LlNE(TYP) 2-2 SECTION @ N2112650 SCALE A (PLATE 7) -..._ fEXST GRADE ·~ .. , "' I §/ ........... ---')p 4'._-:;.,.,_~ "', ~~ EL40.0 1 ~......_ --~-~-- ----:. ... 'liv..i.\'~ --· 3-3 SECTION@ N2112470 SCALE A (PLATE 7) EXST TOR EL MINUS 9.001 ---,__ ;-£ EXSTGRAOE ·-..,~ -1_ -------~ 1-,~r--:::__ ~---- ---VIm;,'~~'---------::_ ~-~ ---- 4-4 SECTION @ N2112225 SCALE A (PLATE 7) 1.25' (TYP) ELIMINATE BOTTOM ROW WHEN SLOPE HEIGHT IS LESS THAN 15' SUPPORT { it 10 ROCK / DOWEL (TYP) # 8 ROCi< CHAIN LtNK MESH. OVER TUNNEL PORTAL INSTALL UNDER ALL PLATES (PT H TO PT I, PLATE 7 DETAIL B TYPICAL ROCK SUPPORT ABOVE EL 39.0' BENCH NTS ROAD· DETAIL 0 ELVARIES (ROAD CUT) CUSHION B:..AST FACE CHAIN LINK MESH-DETAIL E ** 8 GRADE 60 THREADBAR ROCK DOWELS 10' LONG- DE T E , ,--TERMINATE MESH 2.0' ABOVE / BENCH (TYP) _{ DETAIL C TYPICAL BENCH SUPPORTS SCALE B DETAIL D SCALE B ( PLATE 7 ) 4 ( T YP) 1 0 10 20FEET I 4liiil SCALE B: t•;JQ' 0 20 40 FEET SCALE A: 1"=2C' DRAPE MESH OVER LOWER BOLTS EXCEPT FROM DETAIL E NTS EL 39 0' THIS DRAWING SHOWS BOTH SITE PREPARATION AND PT. H TO PT. I CIVIL CONSTRUCTION EXCAVATION BRADLEY LAKE HYDR OELECTRIC PROJECT ALASKA POWER AUTHORITY CIVIL CONSTRUCTION EXCAVATION AT POWERHOUSE ,&,_ PLATE 8 - I ·---- tt' 4' SlL LINER- fi"·6'¢5TL PENSTOCl< 6'-6" DIA PENSTOCK IN TRENCH NTS ~ STl L11£R TUNNEL 11' OIA STEEL LINER 0 10 20FEET DRAINS t MANIF"OlO • 9'~ STl MANIFOLD 9 1 rp S TL MANiFQD ·TUNNEL MANIFOLD E:NCASEO IN CON<.:RET£ PENSTOCK, MANIFOLD & POWERHOUSE 0 10 20FEET C?(F"UTUREl EL41' HlVH PRE1~dR~EA0 ELLIPSO I -"-""--i \_~'"''"\ -~Pf:'"I$TOCK t;_QI'!(; ENCASED .•1•1--.,--1 EL MINUS 9'* -~~--r-'r ~TTJ""T1--r-"..,..--,--.--,-· t ' l FUTURE UNIT EXCAVATION 0 10 20 FEEl ,, ~------ GATE EL 21 1 ~? ~-lHIGHE~T TIDE Vf -l'i:L 11.4 ~ --RUNNER ACCESS (X)OR ----~El MtNUS 6' a BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY 90 MW PEL TON POWERHOUSE STONE & W!BSTEA ENGINEERING COAPOAJi,TION PLATE 9 _ S7 PROBABLE MAXIMUM FLOOD LEVEL EL 1190.6' 52__ NORMAL MAXIMUM OPERATING RESERVOIR LEVEL EL 118D.O' ROCKFALL BENCH EL 1120.0' EXISTING GROUND LINE (APPROX) RINGS /---EL:Oj5;l· .... "' I I I . _.. I ,..-"' GROUT RINGS--, I I /"EL1096!!>' Ill ~ SLP:t 0 I. SPRINGLINE FLOW -___ ./ ~ rEL1076Q' ------- EXISTING GROUND LINE (APPRQX) ' ' ' ' ' BENCH EL 1062.!!>' E L 106 o.o· EL 1D68.0'7 ,.' ' • _jE~X~C~A~V~A~T~IO~N~---~~~~~~-----tc:=:~~~~~~H---~==t=~==~r======i==~~~::~~~~ ,-------------------------------------------- /< ------28"0 FISHWATER' ' I I ' / / / ' \ I I J I I I I / / BY-PASS PIPE 0 "' ~~:!~ "' "' ~'?~~ 1/)'q'VIr"' Vlr"'VIr"' "' :!t:-"'M DIVERSION TUNNEL SECTION SCALE B SITE PREPARATION CIVIL CONSTRUCTION CONTRACT I CONTRACT EL 1076.0' CONCRETE I CONCRETE 0 .... .... "'- "' ~? V>O ~0 00 ++ 00 ;!;! "'"' .J ww H :> .. >-z u 11. 3: 5j 0 -:!~:!~ VIOVIO fJ ol EL 1068 0' ct .Il!!i!:!~ J FLOW TUNNEL : 0 --'-·' t, -l. l.2 .. i2 \ \ 1 I I I I I I I I I I I \ I \ \ ' \ ' \ ' ,, o,.3 i '""" T-10" MIN r ' E L 1 085.5' PLAN OF TUNNEL SCALE B ..,. '-coNe <r. ! 40'·0" WALL~ 0 20 SITE PREPARATION CONTRACT v.oRK ON THIS DRAWING INCLUDES: • EXCAVATION OF DIVERSION TUNNEL • CONSTRUCTION OF INTAKE OF DIVERSION THIS DESIGN 'NORK IS PRESENTED IN THE SITE PRE~TON CONTRACT FINAL SUPPORTING DESIGN REPORT. GENERAL CIVIL CONSTRUCTION CONTRACT 'NORK INCLUDES: • EXCAVATION & CONSTRUCT ION OF GATE SHAFT • LINING OF TUNNEL DOWNSTREAM OF INTAKE • CONSTRUCTION OF DISCHARGE STRUCTURE ;,,,, EL 1069.38' & FEET BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY CONSTRUCTION DIVERSION SECTIONS AND DETAILS STONE l WEBSTER ENGINEERING CORPORATION PLATE 10 I I I I 1-1 SCALE A 2-2 SCALE A 3-3 SCALE A 4-4 SCALE A FEET 5-5 SCALE A SCALE A' 1",8'· 0" ---__ U ----------------, 1090 1080 1070 / / --:'==~~:-/,.. I , .... ' /,,/ ,.,/ ) ,_ ..... _--,s .J;)'o /,oro~, ........ """.,..-_,-' \ -/ "' ofci"' .,.--J .1'/ ,':fl), / ',"" / _ .... /.Po~ ~ 1 ----/ 1 ,o..::. ~o~ 1£.-- - - -/ ~ // ;..0 / /(1.. / / LIMIT OF 1 I '-'-,/ I \ EXCAVATION \ "\ l 1 I I 1 \ /I 1 I .., I 1 I /1 1 \ " I \( ' \ ~ I / ''..:: ---'' ''--~ / I '' ' \ I --...'-..." ', \ ' \ \ ' \ \ \ I \ l l I " / APPROX EXIST WATER SURFACf APPRO)( TOP OF ROCI< TUNNEL EXCAVATE TO EI:POSE 13EDROCI< ELEVATION OF RIPRAP VARIES WI TOP OF BEDROCK F~M EL1060 TO EL 1080 ·, ' ' ' ............. ' ' ' ', ' ' ,, ' -~ ' ' ' ' ' ' ' ' ', ' ' ' ' ' '• ' ' ' ~ --/ ; / WASTE FILl. OISPO$AL AQE~ A, FILL TO L 1100 MAX PLAN ~_::;;;:;:.--,,00~ w.'":'C,tc":l,'o'<c/ .· ~ ~~~1'6 0 'MAX DIVERSION CHANNEL ', ' ' \ ' \ ' ' \ \ \ '"\\\ I I 1\\\ ., ... ~/ /)) \, ~ ....... / .. /~//I// :_ ........ ~:~~://:// I' I I ( \ ........ ' ........ _::-;:;:--,, ... ', ',', ' ...... .. ,', ', ' ........ , ', ' ' ...... , ' ' ' .......... '' ' ....................... , ,, .. , ' ... ) ',,\\', \ .. ./ I\\ \' ) \ \ \ \ ------"" ) I \ I ~-:::-.::)) 1070 ---_,.,"'/ ------""" lOBO 1070 1060 1050 / APPROX G.S. PROJECTED tV ~~~~~~6..o TO DAYLIGHT EXTEND N AT EXCAVAT~TA 12•44 \ APPROX CHANNEL fXCAVATION LIMITS -+ SLOPE : 0.33 .. ~~· -.st~ STONE 1 PROTECTON } 1-1 NOTE ALL WORK PERFORMED UNDER SITE PREPARATION CONTRACT L-----~-------L--------------L-------------~--------------~--------------L-------------~~ I I I I 1 1 CHAN STA o.oo o.~ t-oo 2·00 J.oo •.oo 5.oo 6-00 '•f e.oo I 9•00 10·00 11.oo 12.oo SECTIONJOETAIL DIVERSION CHANNEL PROFILE , • o J sLoPE r---:B:::R=-A~o=L~E:::Y:-:-:L-:A-:-K::E=-:-:H~v:::o:::R:-:O::-:E::L-:E::-:C::-:T::R:::I-=c-P=R=-o=-J-e=-c=r::::-----1 SECT 1·1 ~H:~e<: ALASKA POWER AUTHOR'TY 0~~~~4~0~--'~0FEET SCALE: 1": 40' MAIN DAM DIVERSION CHANNEL IMPROVEMENTS 8221-29 I l<ACHEMAK BAY CONSTRUCTION UNDER SITE PREPARATION CONTRACT 30---- .00·------ -+.;2111600 ! ?0 TAILRACE--~ (CIVIL CONS T ROCT ION CONTRACT) MARSHALLING YARD SH::lPIWAR(HOUSt. ~~-·~ i EL 40 S TAG!NG AREA 0 !50 l()(l FEET SCALE· p, !>0' -i~ 2U1600 "' "' ~ ~ ---~;~~ --.::- A \--- BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY GENERAL ARRANGEMENT PERMANENT CAMP & POWERHOUSE PLATE 14 r 0 x~ 1,.4 ~-7.";\ / /--'/ ~/// / OPTIOf!fAL -----. x-7.4 1 ' ~ DOCK -__ _, • I ' MAY 9 El<TfNSION 7 \I x-4.8 a E INSTAL 1 ~ \ y CONTRACT~~O \ \ k x-3. 8 \ , ...... _...,....-'\ \ I J x-7.6 x-7,4 )( -2.7 x-2.3 GRACE THIS AREA AS RfQUlRED TO PROVIDE /UNIFORM BOTTOM FOR SARGE GROUNDING. / GRADING Of SILT~ SHALL BE BY CUT ONlV, MINOR FILLING TO OBTAIN GRADE SHAl.l UTllllE MARTIN RIVER BORROW. UNifORJJI TO EXTENO 100' BEYOND FACE OF ON BofH SIDES OF CElLULAR )(" 2.2 I I I I // SHEET PILE CELLULAR 8ULKHEAO EL 16.5 _,/ /' _/ SCOUR PROTECTION x~2.4 / SCOUR PROTECTION 8 x-2.3 sr~= )(-2.3 ~r-----~ X -2.4 J(-2.8 ----~--- f ' j )(-1.6 x·1.5 )( ~t 7 x-1.5 x-1.5 x-1.5 ~· "" ~~~\ r-.2 x.2 >0 0 .,,( ~ ~",' --'<;/< &, ~ '" v---~ ~~c~ -=~r~.~o&~~~~z~~-·--·~~~-~/-~ ~-, ~~~/ "'~'~ \~ I ~~7 ...._ ----.._-------'-""' .. -'x-7.1 ~/ --------------------------. " -----:::::::::: . // .. / --':::===:::----~ '~ ::.::.:::_ /..;-:;::/ / ------------~//. _.-----. -~~--= __ .::::.::::::::=;::./// /~ -~ ~-~-. --.. -~ /~ HORZ.IYERT. CONTROL MONUMENT SHEEP POINT .!t_2111?79 22. E 321160.97 ELEV.• 14.48'PRCJ. OATUM ~~1 ~/\ x-.9 .. -.4 X ·.2 x-.6 x.3 NOTE; END CHANNEL EXCAVATION AT ~ELO'CONTOUR APPROXIMATE STA. 9•60 flELA't'IONSHtP OF YUTIC.U OATUWS )(-2.3 X-:2.5 ~~g:~;:~:Icl~:s 't. ROAD STA. 556 .. 62 .02 • BARGE ACCESS STA. 8 0•00 N 2:111339.43 E 321616.63 x-2"2 x-1.9 x-.9 x-.7 lt -.4 0 / •. 2 X tO 8 0 50 tOO FEET .,...,ALE: 1':50' .... «N'If IUM COVE a:t"'Dlf'.Y ...... .... Yll:OJ£\.1' OoiifUW OUIJII tiAtVIII '" :::-1:~:~ ! .. o ,.. ts.n i 40% l 0 00 """JECT DATUW O'IJGIIIII!I.SS\JNU " 2.1 ... x-1.2 •l• 000 LT •~•o NEW SLOUGH CHANNEL EXCAVATE 10 EL -6.0 N ALL OREOGE MATERIAL REMOY€0 FROM SLOUGH CHANNEL SliALL BE STOCKPILED IN WATERFOWL NESTING AREA A X .1 ... x.9 X .9 x1.2 z.o------ CHANNEL EXCAYAT10!1 INTERSECTION AT EXISTING CHANNEL STA 0• 30 (N2,t1~773• E 322,183*) CONTRACTOR TO FIELO LOCATE NOTE: ALL ELEVATIONS ON THIS OR.AWING ARE PROJECT DATUM. THIS DRAWING SHOWS SITE PREPARATION CONTRACT WORK BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY BARGE STOHl ' WEBSTER ENGINEERING CORPORATION DOCK PLATE 15 327000 PLOT PLAN-POWERHOUSE SUBSTATION tc:AUwtHU Cd ------~---. POWERHOUSE ~ ~ Oi -----«J ----«] -----«1 DEAD TOWE DEAD TOWE ....-:--. ..,.-,. <~ .~--------~---4----+------------~40 ~ '" r""'' '[' ~ ~ ~D \ DISCONNECT SWITCH ON DEAD END TOWERS LINE CROSSING t\ ~ / _l~!V~~~~~~~~I,. ,r-WOODEN H-TOINER DISCONNECT Y SWITCH ,!~ IV (§ \ 'NO DISCONNECT SWITCH ~ ----«JQQI / ti:&SING s ON DEAD E~ERS J" D1.1$bJIJ4.--- ----«loa I 0 - ~~----------r----4-----+------------~vP ~ -----«<(]{]a 327000 PLAN 0 16 32FEET SCALE:?-;: 1'·0" TYPICAL TRANSMISSION STRUCTURE D 10' 20' ~-__;;;;;;j SCALE IN FEE f .& BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY POWERHOUSE SUBSTATION AND BRADLEY JUNCTION STOHE & WEBSTER ENGI,..EERING CORPORA T10N PLATE 16 ~ 11~KV LINES ovue_l. @~ MGSI~ ovus; ~ MGSI~ OYUB~ MGS11 ' OYUB~­MGS\2 •I TO BRADLEY JUNCTION MDS22 ~ 0YUB-r 115KV BUS OYUB-2B /-® OYUB- -" MGS22 OYUB;J-MGS-41 ~ OYU~2 © ... MGS~. OYUB- VT2S OYUB- MOS41 ovue- MDS42 c: OYUB- C VT-48 OYuB-f ~OYUB-OYUB-<§;. OYUB-~YUB MGSJB E MDS31 ~CB 3 MDS32 MGS4B ,~ 115KV BUS OYUB-JB 0 115KV BUS OYUB-4B 1YUB-, ~~ 1YUB-iJ-<E)OYUB-if'-4) OYUB-2YU~T ~ .J--R, 2YCB- MGSi .. ~ MDSIT ..lr -MGS31 J. -MGS32 MG~~ _f -b MDSIT II 1MTX-XM1 + 2MTX-XM1 MN XFMR1 MN XFMR 2 '"'T"' 33.8145.1/563MVA,13.8-115KV 33E'/451/56.3MVA,13.8-115KV 3PH,60Hl,b9•J. )PH.bOHZ.Z; 9•J. l I 6 VT-<8~>--OEGS-Gl 9. 1NP5·ACB10 12COA. l ~ DIESEL GEN ~ 2tlPS-ACB20 ~ 1~COA ~~8>-vr 1GMB-XV1 1GMB-XV2 O GEN llio.. KVA 4BOV. 9 ., ' ST~J\~~1v 1~0011333KVA JPH, 60HZ • "6MS-AC81 JPH, 60HZ XFMR1 T L800·480V GEN BRKR NO 1 ] 0£GS-ACB 301 3000A . f--4 • • ) ONJS-ACB101 ) ONJS·ACB103 1G.'-1S-G1 GEN NO 1 1J 8K V, 3PH ~OHZ 59MVA . 0 95 PF '""'~' ([:-1, NEUTXFMRlb '"ONJS- ACB102 0NJS·XS2 STA SERV XFMfi2 0NJS-U52 480VBUS y 100CV1333KVA u.lu13800·480V T 3PH,60HZ ) ONJS-AC8201 9. 2GMB-XV1 2GMS-ACB1 GEN BRKR NO 2 JOOOA -~ 6 :~8>-vr 2GM8-XV2 2GMS-G1 GEN NO 2 138KV,3PH,60HZ 59MVA,095PF '""''"' (0 NEurxFMR 1U -----------, TO DIAMOND RIDGE ~Tm~cmm "'r "'r UNE1 UNE2 TO ffiADL.EY LAKE BRADLEY JUNCTION ;r,2NP5-ACB40 ;r, 1NPS-A:B30 T 1200A T 1200A T 1 0NPS-XA1 ~PROJECT FACILITIES SERVICE XF MR NO 1 .ZTl KVA,138-12 47KV 3PH,60HZ FEEDER TO PERMANENT PROJECT FACILITIES BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY J1 MAIN ONE LINE DIAGRAM STONE & WEBSTER ENGINEERING CORPORATION PLATE 17 I MARTIN RIVER BORROW AREA r:Ji" «JJ" ~~-::S «:AU Wllfflf -; 0El? Ill TYPICAL MARTIN RIVER B'JRRON AREA DIKE I to" ~· ~I KAlftflfftU BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY PROPOSED MARTIN RIVER BORROW AREA PLATE 18 8221-18 -------------·----------·--_________ j ~80) §_ iii loJ t-eoo ----.... 20 .•· ~~-77) (::~,,[: ·--~~ --(-t6) f.o• ~- "' .., nuQQQ I ~ \',\1\ I ( \: f I =:, ..-----..._ = ~I ~~ ""' c::::::::>~,;., .,," ... -~·_::C)~ II " .. _.,.op ''I? n ••• I,· "'':'IJ ~,~ ~ ·. 1,/• / '-«~ .. ~ TEMP MUC~ DISPOSAL AREA il ~\ TAIUiACE- 1 ~/)[{( /~/ ~ POWISRHOIJSE ~ Pt,A _:r~:0!c.9 ~ SPOIL DISPOSAL & WATERFOWL NESTING AREA APPROX. ELE\l 12.00' (TYP.) CONCRETE DROP BOX • SET TOP AT El 6.0' 2 __ 1;1AXWS E!,..JlA.!:!J ----\---- TYPICAL ROAD SECTION ALONG BLANKET DREDGE DISPOSAL & WATERFOWL NESTING AREA VIATERFOWL NESTING ISLAND SCHEDULE t~'-2.0' RECLAIMED OREDGE MATERIAL--, 0 10' 20' !'lit.~ I SCALE .. FEET 0 200 -400 ""'"'*~ I SCALE IN FEET SEED TOP ANO UPPER C,lOPE S FROM EL 10' JO EL 1'2' • -REVEGETATE I SLOPES (J NESTING , ·-.r .:IA!o. ISLANDS WITH CLUMPS ~ ,ficy' SEDGE-GRASS -1_5'-2.0' ____ v ___ MAX. WS EL n.4 HT ~NORWS EL.6 A BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY WATERFOWL NESTING AREA $TON£ 1c Yti:8STEA Et.IGIIifEERtHG CORPORATIOH PLATE 19 1 ------------- ------------------ ~ z~ r /-----------_______ , / --·----------~. \ / // -----------·-I \ / ----. \ /' -~ \ / /' l \ ------/ .-"' 11/i'l ,-" /' ----------- ----+---------~ ,_ UNE ROAD ASSUMED I ·. EXCAVATIOt< FOR A ~~ TO BE IN ROCK z~~ ""-FILL TO EL31.0' .. __jN 2113,08~.7\0(1"'""'­ / ·~ 327,1~.~0 ' " 0 CURVE 488 AI A2 81 I CURVE D.A.T.A. ,.ADIUS CENTRAL ANGLE ARCLENGTH TAN LENGTH 7~ 21o•oaoo• 274.89 100 17 10' !:>0' 29.99 1~.11 100 12.49'1~ 22.37 11.23 100 20 3 28. 31:),79 18.09 IRADlEY LAKE HYDAOB..EC1l'll PROJECT AI.AIKA POWIR AUTHOIIIU POWERHOUSE ACCESS ROADS A LINE ROAD & 8 LINE ROAD TO SUBSTATION PLATE 20 FIGURES 2.25 ....--.. rn -cu Vl 1.88 z 0 ~ 1.50 0:: w _j w u 1.13 u <( _j <( 0.75 0:: 1--w Q_ 0.38 Vl 0.00 RESPONSE SPECTRUM FOR HYBRID EARTHQUAKE BRADLEY LAKE HYDROELECTRIC PROJECT MEAN RESPONSE SPECTRUM FOR MCE (NEARBY SHALLOW CRUSTAL FAULT) REF: WOODWARD-CLYDE CONSULT REPORT: "DESIGN EARTHQUAKE STUDv' NOV 10,1981 ~ ----·-- MEAN RESPONSE SPECTRUM FOR DBE 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 PERIOD (SEC) MEAN HORIZONTAL RESPONSE SPECTRUM ...___. _______________________ FIGURE F.6.2-5 _ __, MODIFIED ACCELEROGRAM OOTAINED FROM THE FOLLOWING TWO ACCELEnOGHAMS KERN COUNTY EARTHQUAKE 7·21·52 FRIULI, ITALY EARTHQUAKE 9·15·70 IIA004 TAFTLINCOLN SCHOOL TUNNEl, COMP SG9E AND 1·3·169 ITALY SAN ROCCO. COMP EW SCALE FACTOR : 3.50 SCALE FACTOn = 3.18 0.75r-------------------------------------------------------------------------------------------------- ,.... CJI ..... z 0.60 0 0.26 i= < a: w _, ~ o.oo 0 < a z :J -0.25 0 a: C) -0.50 0.00 SEC TO l.Jl SEC OF MODIFIED • 0.00 SEC TO l.:l2 SEC 'OF KERN CO. 2.34 SEC T0.4.JO SEC OF MODIFIED • 2.14 SEC TO 4.10 SEC OF FRIULI 4.32 SEC TO 55.14 SEC OF MOOIFIEO • J.58 SEC TO 5~.40 SEC OF KERN CO. THIS PLOT LIMITED TO FlflST 48.0 SECONDS OF THE MODIFIEO.ACCELEROGAAM -0.75~----~-------~----~------~-------~----~--------~-------~-----~------~------4-----_J o.oo 4,00 8.00 12.00 16.00 20.00 24.00 28.00 32.00 36.00 40.00 44.00 48.00 TIME (sec) DESIGN ACCELERGRAM '--------------------------FIGURE F. 6.2-6 APPENDIX B ATTACHMENTS CONSTRUCTION SCHEDULE CONTRACT DATES ((){)[ T TL If UHB.LII.. ~IS CATERING CONTR -PREAIIARO , C!!fi. I HID IH 1------' ' 19';18 1991 15101H IH lA Ul SIOINL11 IKIBIH IS ' --. CATERING CONTRACT o I CIVIL CONTR -PREAIIARO rlvii.-(~jR·:·mAwiiki-- HOBILIZATION GENERAL SITE 11001< SPILLWAY COffOAH,PH,PENSTOCI< EXC TAILRACE HAIN COffEROAHS H.OAH EXC/CONC.PLINTH H.OAH EHBfV«HENT H.DAH CONCRETE FACE PROCURE ' IILIVER TBH O&S PORTALS l HANFLO J.¥ _____ 1- HOOILIZATIOH ' I ~~. ' ·--:--· HAIN (OffE~ I ~ : ·---+---· H.OAH EXC/CONC.PLINfH . I ~---------------1-.PROCIJIE l DEll~ TBH ~7--· 1'!.0011 E~HEHT ~··--·--+----~------~~----~--+-------4-------·------·· ps2 • 1 TAILI!fl(E ~------:--· H.OAH.CONCR£1£ FACE I or.s PlliTALs , lfN'LD 1 I I ~•-•---... ~-i---• 1 I 01.5 lVfl TlltJEL 3+46 -31+611 ~. 0&5 L WR TUNNEL 3+.(6 -31 +60 ~------------ TBH ASSEHBLY I TBH ASSEHIIl. y I ,!~-------------------·-"1-TBH EXC. 31+68 -177•58 I . I TBH EXC. 31+60 -177•50 ' I ~------------------3-LIIR TNl (~TE LINER LWR TNL CONCRETE LINER LWR TNL STEEL LINER I e!L.-----+ . I lVR TM,. STEEl LINER ~ ~5---------il-:-- 1 HfiFLO .• PENST!lO: INST IT~ST HANFLO,PENSTOCI< INST/TEST ~' VERTICAL TNL EXC VERTICAl TNL EXC VERTIOI.. TNL LINING ~. ' I VERTICAL TNL I.INING IN ' 1 ' 1 Sh••• I of (()()£ TITLE INTAKE CHANNEL EXC INTAKE PORTAl EXC UPR TUNNEL EXC PWR TNL GATE SHAFT EXC UPR TNl/INTAKE CONCRETE INTAKE GATES/TRASHRACK/TEST COHPL SHAFT/GATES/TEST BREACH PLUG/UNDERWATER EXC OIV.TUNNEL SHAFT EXC OIV. TUNNEL COHPLETE m ITTM:prr:K ... 1988 I -----1989 1990 I 8 lSI o I Ill 0 I ,J IE I HI A I HI J I J I A Is I o IN Tl'TIITliiH IRISIOINIO l F I HIll IIi r~ e:_:___ . . ..... ---~-----+·--· INTAi( Ctt'!Hl EXC a·--INT~E PORTAL EXC I 126 •. _ c:::=..::3 -.,. --• lli'R J~l EJ(( m PliR TNL GATE SHRFT EX( ·~~-----+ . I lf'R TNl( 1 NT liKE CONCRE 1 E 132 ~ - I INT~E GATES/l~SHRAC~~lEST 1·----------f.~ CIH'L, Stt'lfl/GfllES/lESl £!6. . . BREACH I'~UG/UNOERWRTER E~C I ~--·• . DIV. TIJ"'El SIR'T EXC ' 137 . ( •-3-3-f-EU---r QIV. TUNNEL C~ElE I elo--. IN 00100 ILl ZA Tl ON I I DEHPBILIZflliON RESERVOIR FILLING DIVERSIONS -PRECONSTRUCTION ttiOOLE FORK DIVERSION NUKA DIVERSION , ~~----------~----------------+ I RESE:RVOIR fiLLING . ~~· ·---------~----·--------3-~----PIVERSI~-PRE~ONSTRUC11!Jl ,11L ___ .,_~ , HIQOLE fOR~ OIYERSIDN 145 I •-----3-,. ~~~ OIVERS!!Jl 58 I I PROCURE TURBINES/GENERATORS I'AOCliiE rlllBft£5/GENERATI;W'S •• _ -------· I -~~ >••••••••••••••••••••••••••••••• I PROCURE .. INSTALL SCAOA ~ " IHSTA..L SQQI . I I I I br:;ll ·----------------------·-------~---· I I I I PWHS CONTRACT -PREAWARO J'VHS ((lfJROCT -~REAWRRO. • I I 1 ~62 1 1 ·---~-------r---HOOILIZATION PROCURE SUBSTATION PROCURE PWHS STEEL & CRANE SUBSTATION • IQIIU2:ATI(If ~65 : :I I PRIJQIRf; SUBSTAT I!Jl ~66 ' J PROCURE; PliHS STEn I. CllfllE ·--1·-------~------~-------~----· I I ~'---::=-.--:::-3------,---­ sUBSTAT I!X4 I I ' L-------------------------------------L-----------~------------------------------------------:_--------------L-------------~~----------------------------~---Sh .. t 2 of ..-. (00[ TJTlE PIIHS BACKFILL ~------------------------~ PIIHS CONCRETE PIIHS SUPERSTRUCTURE PIIHS YARO INSTAll & TEST UNIT INSTALL & TEST UNIT II HECH/ELECTR EQPHT. START -UP UNIT START-UP ~IT II OfHOOILilATION 521 1'.189 .. J. 1998 1991 [1\ 15 Lll.lll. r 12 .. -..... _:_ •••••• ____ ...... _ ... _ ... __ ........ ___ ~~f.,. PIIHS CON(:RrTE ~---~--PWHS YARO ,•511 .... _ ... _____ ---w-... ------------.... -------------....... -----.... INSTIU ' TEST ~IT II . . . ' . ~HIELECTR-E~r:----------~-·----- ' ~---. STfiU -;U' UN IT I ~--. STIJIT-Lf' ~IT II ~-~ PEHOBILIZRTION TR.LINE CLEARING -PREAIIARO IR.LfHE !1EfiUNG -PIIEA~-----~-------~·-• ------------------------~ ~ . TR.LINE CLEARING ~ I ·-----~-.... --.................... ... TR .. UHE ClEARING . I s.:. I TR.LINE -PREAIIARD jOCLUE :-PREINfi;ID -------·---·;· TR.LIN£ PROCUREHENT TR.LINE HOBILIZATION TR.LINE CONSTRUCTION SITE REHAB -PREAIIARD SITE REHABILITATION l~'";._, ~1 f..-ho-c:::: :::::;, Crltt .. l ..... _ ,.__~ . ·-------· ._... t..t. ··- l'rl••--• s,.-t-. Inc. •-·••·•• ...;,.; rroj.ct Si-I IIIJIMIII l'rojut l'lnllttl 3111CTtl fiMI ' ·---··------------·----~-TR.lJNE P~EHENT ~:u~-QlLtlfiTJON ' (iB8 ..... ..: ...... ----~--.......... ::. ....... ----F----- T~.lfHE CONSTRUCT(ON APR BRADLEY LK SCHEDULE tl/88-38 Mo-Adjl BC-03 MST SUMMARY BARCHART tSCHOl E~--------------------•---· SITE REHAB -~ERWRRO Stteet .S of .S Dota Dote• l..all6 l'lot Dot•• 210Cll7 pas .... -----3:-·- SITE ~EHRBILI~RTION ~ UR M15TI'II SOt:IIU • II5TI ----+ t I I L MEETINGS OF THE INDEP&~DENT BOARD OF CONSULTANTS I \<): .. ·::· STONE & WE~Sl~FI ENGINEEHING COF1"01lA1oON Mr. J. Barry Cooke Technical Review Board 5.0 TUNNEL 3 October 20, 1986 SWEC concurs with the Board's opinion on the issue ot the Dispute Review Board. However, SWEC does not oppose its formation (subject to the several recccmended conditions which were discussed) should APA deem it desirable. 5.2 Escrow Bid Documents SWEC's recommendation is against the use of escrow bid documents. 5.3 Bill of Quantities (Bid Schedule) The tunnel bidding approach 18 under project review following input frcc the Technical Review and FERC Boards. 'lbe Alaska Power Authority, following review ot SWEC and Bechtel recommendations, will make a determination of bidding, pay item and contract administration format and procedures to be utilized. The SWEC recommendation will be forwarded to you for information once it has been finalized. The three alternative tunnel arrangements will be bid as options A, B and c, with no •preferred" or "alternate" designations shown, and award will be to the ~owest bidder's option. 6. 0 POWERHOUSE 6. 1 Tail water Depression The specification calls for dynamic dampeners on the fan mounting and ran housing pipe connections, and noise suppressors at inlet and outlet of the air conduit. Also, the air depression system will be used for a relatively short time, only 2.5 percent of the time. That will limit duration of vibration and higb sound level conditions to a minim\11. Also, frequency of maintenance would be considerably lower cccpared to other equipaent which could be used for air depression. 6.2 Cooling Water The specifications will require that the turbine model test include a cooling water trougb in the runner pit, to evaluate the potential of incorporating such a passive collection system at an elevation that will allow gravity collection of water fraD the runner discharge stream. 1-406-JW ~ .. STONE & v<~asr~>< ENGINEERoNG CORP<.:HATH)N Mr. J. Barry Cooke Technical Review Board 6.3 Blasting 4 October 20, 1986 The requirement for a detailed blasting and excavation method, layout and sequence plan for the powerhouse excavation will be very clearly spelled out in tbe specification. As recommended, cushion blasting with local line drilling will be required throughout the powerhouse footprint area. The blasting plan submittal requirements are couidered necessary to retaiD control over contractor plans and procedures. 'I'he ccmment regarding submittal procedure compleXity and sequencing has been received from several reviewers, and the speci.tication is being thorougbly revised to simplify tbe reporting requirements and expedite approvals without relaxing overall QA integrity. 6.4 Rock Anchor Support The rec0111111endation that standard tunnel rock bolts use single-stage resin has been accepted. Two-stage poet-tensioned anchors will be retained tor use in surface excavations, large intersection spans, and key foundation anchors. The seneral tensioning specification will allow torque or impact-torque wrench tightening rather than jack tensioning for all standard {1•) bolts. 1.0 DRILL HOLE EXPLORATION The final bydro.tracture test data and report has not yet been received from the contractor, so full evaluation ot the in-situ test conditions cannot be made at this ti•. The tunnel lining design currently includes a rein.torced concrete section upstream or the steel lining, which Will be designed to limit crack size and therefore control ex.tiltration rates. In response to the apparently low in-situ miniJIIUil principal stress, the contract will include the following provisions to allow tor final definition ot rein.torced versus unrein.torced concrete section limits during construction. o Pay itaa options tor additional reinforced concrete upstream ot the steel liner o Additional llliniJIIUIIl-stress hydrotracture tests to be conducted in the tunnel as tunnelling advances o Cross-hole shear-wave velocity determination in the same holes to be used tor the additional hydrofraoturing o Allowance tor heavy bi-direction rein.torcement at very low modulus zones .· .·• STONE a. WEBSTER ENGINEERING COR"OR.t.TtQN Mr: J. Barry Cooke Technical Review Board 5 October 20, 1986 o Retention ot the end or the steel liner at its present location, based on cover equal to 0.8 times hydrostatic pressure in the tunnel at maxilllWil reservoir level o Pay item allowance for higb-pressure ring compaction grouting in low modulus zones o Detailing ot steel-liner lateral drain system to accommodate potential groundwater intlov conditions, considering the possibility ot low minimum principal stress in the rock It you should have any questions on these responses or follow-up CCIDIIIents, please teel tree to call me. Theodore CritikDa Deputy Project Manager Enclosure TC/LCD/JW co: Dr. Andrew Merritt Mr. Joel B. Justin Mr. Donald 'I'. fing 1-406-JW NOTED UCT ~J 0 19D6 r. Crttllcos \ J. Barry Cooke 1050 Northgate Drive San Ra~ael, CA 94903 (415) 479-6151 Andrew H. Merritt 7726 S.W. 36th Avenue Gainesville, Florida 32608 (904) 372-6153 December 1 O, 1986 Mr. J.J. Garrity Project Manager Stone & Webster Engineering Corporation 800 "A" Street Anchorage, Alaska 99501 BOARD OF CONSULTANTS EIGHTH REPORT BRADLEY LAKE HYDROELECTRIC PROJECT. I.O INTRODUCTION Joel B. Justin 2401 Pennsylvania Ave (17-B) Philadelphia, PA 19130 (215) 232-5502 Donald T. King P.O. Box 2325 Boston, MA 02107 (617) 589-2034 The eighth meeting of the Board o~ Consultants convened in your office on December 8, 9, and 10, 1986. Mr. Barry Cooke, ·Mr. Joel B. Justin and Mr. Andrew Merritt were joined by Mr. A. Stanley Lucks who substituted for Mr. Donald T. King on the Technical Review Board. 2.0 GENERAL The principal task o-r the Board was to review the contract docUDents for the General Civil Contract which included the following: Volume 1 Volume 2 Volume 3 Volume 4 Volume 5 Volume 6 2-1370-JJ Bidding and Contract Documents General Technical Drawings Civil, Structural and Architectural Technical Requirements Mechanical, Electrical and Hydraulic Technical Requirements Drawings Supporting Documents (not available) Mr. J.J. Garrity 2 December 10, 1986 Stone & Webster Engineering Corporation 3.0 REVIEW All the volumes were reviewed by the consultants with the the Stone & Webster staff including Messrs. T. Critikos, L. J. Rosenblad, J .J .H. Plante, D.L. Matchett, and others. and drawing was reviewed. Corrections of organization, references, and details of drawings were noted by the staff. important items of concern are incorporated in the discussions of the project features. 4. HYDRAULIC MODEL support of L. Duncan, Each page drawings, The more following The hydraulic spill way was September 25, observed. model testing of the diversion tunnel outlet and the completed at Colorado State University Laboratory on 1986. The following areas of the model test were The dentated sill at the outlet portal of the diversion tunnel is designed to suppress the oscillatory conditions in the downstream pool. The model tests did show that placing a sill below the tunnel exit does cause a hydraulic jump wbich suppresses the surge conditions in the pool below the tunnel outlet. The Board is of the consensus that the oscillations in the downstream pool are limited in magnitude and although the sill would lessen these oscillations they are not of sufficient magnitude to justify the cost of the sill. Emersency discharges through the diversion tunnel would occur at infrequent intervals if at all. Field reports indicate the rock conditions downstream of the spillway and diveroion tunnel are different than anticipated and a restudy of the spillway and diversion tunnel discharge may be necessary to determine if revisions of energy dissipation facilities is required to satisfy the new field conditions. We believe that the concrete sill could teminate where appropriate and the rock reinforced with dowels to prevent regressive erosion. 5.0 DAM 5. 1 US Cofferdam The upstream cofferdam is satisfactory, but appears to be more conservative than necessary for a low cofferdam. It was explained that this is due to the requirement for emergency unwatering, after a major earthquake. Though the design is satisfactory, it is considered that a more simplified rock::f'ill cofferdam would be equally acceptable, and using that assumption, the Contractor could be allowed to provide an alternate design, including accepting responsibility for pumping. The probability of needing this in the future is remote as is the improbable seismic damage to a low rock:t'ill dam. 2-1370-JJ ' t I· I I i i i l \ \ ' . \. .. , Mr. J .J. Garrity Stone & Webster Engineering Corporation 5.2 Grouting 3 December 1 0, 19 86 We believe that the curtain grouting program as typically shown for the spillway could be simplified by maintaining rows SG1 and SG2 in parallel planes. This will provide for a somewhat wider curtain than if all holes were drilled along the same row; however, it will not be as wide as shown in the present layout. In our opinion, maintaining the rows in parallel planes will be easier to achieve during construction and provide better quality control regarding decisions on closure by additional drilling and grouting. A "wide curtain" cannot automatically be considered to be superior to a "narrow curtain" in the rocks at this site because most pervious zones will occur along open joints where the grout will travel easily over some distance, regardless of the space between rows. The foundation rocks are not considered to be erodible and therefore higher gradients across the curtain are acceptable. The four grouting mixes shown in the specifications vary from 3:1 to 0.75:1, w:c by volume. It is suggested that the 3:1 mix be emitted because of its generally higb sedimentation rate, as has been shown to be the case in many laboratory tests on other projects. For those mixes where bentonite is required, the bentoni,te should be pre-hydrated for at least 24 hours. 5.3 Plinth The plinth is thicker than normal and has two, and rather than the more usual single layer of reinforcing. These requirements resulted from grout uplift design criteria. Though we would accept one upper layer of steel and a thinner plinth, it was agreed to retain the design but not carry the lower plane of reinforcing through the construction joints. The placement of concrete in lengths convenient to the Contractor, and the use or continuous reinforcing in a top layer represents the most satisfactory and economical current practice. 5.4 Perimeter Joint The proposed design, appropriately, does not include a central PVC bulb waterstop. The use of a 1/2 in. filled joint, a surface rubber covered IGAS seal, a base copper seal, and a bedding for the copper seal is the proposed perimeter joint assembly. These general joint features are considered to provide a satisfactory joint. Our views on the details of the joint design are: a. The conveyor belt cover for the IGAS is appropriate for the severe ice conditions. b. Use more IGAS than presently shown. 2-1370-JJ Hr. J.J. Garrity Stone & Webster Engineering Corporation 4 December 10, 1986 c. Attach conveyor belt cover with well anchored 2 in. by 2 in. galvanized angles. d. Use conventional bottom copper water-stop (single fold with premoulded rubber filler). e. Use 1/2 in. wood or premoulded joint filler (an additional waterstop feature is not needed). f. Use asphalt impregnated sand as base for copper seal, in lieu of mortar. g. For compaction in the periueter joint area, where smooth drum vibratory roller compaction is not feasible, a back hoe handled plate vibrator should be specified. 5.5 Vertical Joint D The two joint Ds are adequate and well located. Changes recommended are the same as for perimeter joint in the cases of: (a) use angle iron and conventional copper waterstop and, (b) use wood or premoulded filler. The cement mortar base is appropriate as shown for this joint where negligible offset is likely, in comparison to perimeter joint where sand impregnated asphalt is more adaptable to expected perimeter joint offset. It is not customary or desirable to continue reinforcing through joint D. 5.6 Face Slab Concrete The concrete mix for the face slab is not yet finalized. It is understood that Class "AL" concrete is being considered: 4,000 psi, 1 1/211 aggregate, air entrainment, no flyash, and option of plasticizers. We understand that the goal is to aChieve an impervious and durable concrete. The above specification is satisfactory but not considered the optimum for the face slab. The Board agrees with the specification of 1 1/2 in. aggregate, air entrainment, and optional use of plasticizers. The minimum 28 day strength is usually 3000 psi, to minimize horizontal temperature shrinkage cracks. It is an adequate strength to assure necessary impermeability and durability. The Board recommends the use of flyash to assure maXimum impermeability and durability. 5.7 Rocktill Specifications The rock:t"ill specifications are given principally in Specification 3.10, EMBAHXMENTS AND CCJotPACl'ION. Suggestions were made in the discussions and general agreement was reached. 2-1370-JJ Mr. J .J. Garrity Stone & Webster Engineering Corporation 6.0 TUNNEL 6.1 Steel Lining 5 December 10, 1986 The upstream limit of the steel lining bas been determined based on a height of rock cover equal to 80% of the static bead measured in feet. This criterion is considered to be adequate for general layout and quantity purposes. It is quite probable that the length of lining can be reduced pending the results of additional hydraulic jacking tests. The report on the hydraulic fracturing studies by Golder and Associates was reviewed. This program was done to obtain an initial impression of the character of the rock in the vicinity of the end of the steel liner. The determination of the magnitude of in-situ stress is inconclusive as it appears that the tests were influenced by a zone of highly pervious rock. Further studies will be made during tunnel excavation where better control of the test location with respect to geologic conditions is possible. Plans are being made to define the time during the procurement schedule wherein the decision must be made on the length of lining. 6.2 Feeler Holes It is suggested that the· quantity of percussion feeler holes ahead of the tunnel face be increased to 3000 ft, or 1200 tt over that presently provided for. This will provide coverage for about 15~ of the tunnel. Probing ahead of the tunnel face to locate water bearing, potentially running ground is considered highly desirable for planning the subsequent advancement of the tunnel. 6.3 Support The drawings and specifications were reviewed and various suggestions were made. The bulk ot the support will be provided by resin- encapsulated rock bolts vhich is a commonly used support system. The support in the manifold is considerably heavier due to increased spans and the anticipated rock conditions. Notes will be added to the drawings regarding bolting and excavation sequences for the major intersections. 6.4 Power Tunnel Intake Support The rock support for the intake excavation is shown on Dwg. FY-1528-1. Above elevation 1080 the bolts (1 3/8• diameter) are spaced 10 ft oc. Below 1080, the bolt diameter is reduced to 1• and the spacing is decreased to 4 ft oc. This very close spacing is apparently to retain smaller rock pieces from falling into the tunnel intake. The dense bolt pattern below 1080 appears excessive and should be reviewed. The use of WWF and shotcrete could be used effectively between a wider bolt spacing. 2-1370-JJ Hr. J.J. Garrity Stone & Webster Engineering Corporation 6 December 10, 1986 To provide full encapsulation, any bolt hole not completely filled with resin, can be topped-off with normal thick cement grout. This applies to all bolts on the project where appropriate. 6.5 Drain Pipes for Steel Liner Drawing SWEC FS-t61A-1, "Power Tunnel-Steel Liner-Profile, Sections & Details" was reviewed in detail, and some modifications made. The details are particularly well developed. A remaining decision to be made is whether the drill boles into the drains should go only into the drain pipe or through the drain pipe and into the rock. It was decided to perhaps include a lump sum price for a bole into the pipe and for a hole that extends into rock. The decision will be made after the tunnel is driven and the water conditions are known. 7. 0 POWERHOUSE The rock bqlting shown below elevation 40 consists of type A2, t" diameter bars spaced at 4' oc. The primary reason for this support density is attributed to seismic considerations. As with the intake cut, we likewise believe that the quantity of rock support could be reduced in the Powerhouse costs. This is especially true for the rock pillars between units that vary in height between 11 ft and 27 ft. In addition, the lower row of bolts probably could be eliminated as it is only about 2 ft above grade. The 8 inch horizontal drainage slot proposed to be excavated along the wall at elevation 18.3 ft should be reviewed. Regardless of the caution taken by the Contractor, this excavation could affect the stability of the slope. While it is possible that normal overbreak will provide enough space for the drainage-way without excavation, an alternative solution could be a surface PVC collector system along the inside wall of the Powerhouse which collects water from drilled drain holes. 8. 0 DESIGN CONTINUITY DURING CONSTRUCTION As with any hydroelectric project, a certain amount of conservatism has been included in the design, principally related to seotechnical matters. These include among others, rock support requirements, length of steel liner, grouting, seepage control, etc. Should field conditions permit, reductions in certain items may result, which if recognized early enough, could have beneficial schedule and cost implications. We would endorse any plan that includes continuous representation of the designer in the field as actual conditions are exposed. We view this as an essential aspect of any major project. 2-1370-JJ f:. ' Mr. J.J. Garrity Stone & Webster Engineering Corporation Very truly yours, J. Barry Cooke ~tJ.~ Andrew H. Merritt 2-1370-JJ 7 December 10, 1986 ' I "- ANDREW H. MERRITT. INC. CONSUL. TANT: ENGINEERING GEOL..OGY ANO AF"F"L..IEO ROCK MECHAJI\C,ji, 772 ••• w. 3eT~ AVENUE t{ t c E I v E D Mr. J.J. Garrity Project Manager GAINESVIL..L..E. FL..ORIOA 32808 Stone & Webster Engineering Corporation 800 "A" Street Anchorage, Alaska 99501 VISIT OF DECEMBER 11, 1986 BRADLEY LAKE HYDROELECTRIC PROJEC'l' Dear Mr. Garrity: DEC 1 := 1986 SWEC-ANCHORAGE December 12, 1986 A site visit was made on December 11, 1986 to inspect the rock conditions exposed in the excavations required for the Diversion Tunnel and Powerhouse. I was accompanied by Messrs. R. Wynn and D. Jurich of your staff and Mr. D. campbell, site geologist for Bechtel. On the following day we met in your Anchorage office to discuss my observat- ions and conclusions. The following letter report sliJIJDarizes these discussions. 1 • DIVERSION TUNNEL 1.1 Inlet Portal The lake level was at elevation 1084.5 during the visit and the level of the water downstream of the plug was about the same. The top of the remaining rock plug is at about elevation 1085, or 5 ft below the design level ot 1090. This overexcavation was probably caused more by ripping than overshooting. I was informed that the contractor had drilled well below 1090 in the plug area; however, the Bechtel inspector apparently noted the overdrilling and had the deeper portion ot the holes stemmed. The rock conditions in the plug could not be viewed due to high water. However photos taken earlier suggest that the rook would be rippable as numerous oxidized joint surfaces and weathered zones exist to the base ot the cut. Flow through the plug has been estimated as 50 gpm which is readily controlled with the Contractor's pumping capability. The rock plug has not yet been grouted as required and I was informed that a complete grout plant is not yet available on site. The Contractor has apparently decided that pumping is all that is necessary and does not see the need for immediate grouting. TEL..EX 704?;P79-JJ ANSWERBACK AMROCK UO Mr. J.J. Garrity Stone & Webster Engineering Corporation 1.2 Tunnel 2 December 1 2, 1 9 86 The tunnel has been excavated 200 ft or about one-half of the total length. The rock conditions are generally good although certain aspects, described below, require your attention. Rock bolts have been installed on an as-needed basis. No other form of support has been used. The tunnel is dry. I was informed that the resin encapsulated bolts are being installed and tensioned in a satisfactory manner. Three continuous joints or shear zones were observed in the tunnel. They contained fillings of 6-8 inches of clay gouge or washed-in soil. One fracture was locally open for several teet back from the tunnel wall. The deep open fissures are probably caused by general stress relief and internal erosion of soft materials. Stress relief is normal under such topographic conditions in massive rocks and evidence of open joints was found in one of the exploratory borings made near the outlet portal. The tunnel will be unlined during diversion for a total distance of about 300 ft between the concrete portal structures. It will remain unlined over sane 95 ft upstream of the downstream portal at the completion of the project. As we discussed, the open erodible seams need to be cleaned out and plugged with concrete prior to diversion. Additional rock bolts may be required. The tunnel needs a detailed geologic inspection and mapping to locate all potentially troublesome seams. The specified air and high-pressure rock clean-up method would be useful in defining erodible areas not immediately visible. For the long term, the unlined portion of the tunnel should be carefully inspected regarding permanent treatment. I expect that extra bolting will be required. Shotcrete would be useful to control local fallout. 2. POWERHOUSE EXCAVATION 2.1 Excavation The back slope excavation is nearly complete to the elevation 60 bench. The upper 4-8 ft of surface rock is weathered and loose. The rock between the gabion bench and elevation 60 is generally of good quality and stands well. Only a few local loose zones were noted. No major stability problems were observed. The quality of the blast hole drilling above elevation 60 is acceptable and very little hole deviation was noted. The drill holes 2-1379-JJ \ Mr. J.J. Garrity Stone & Webster Engineering Corporation 3 December 12, l986 show no evidence of overloading and the general aspect of the slope is good. The loading procedures were observed and the Contractor was using small diameter perimeter-row dynamite of the type required in the specifications. Several of the resin-encapsulated rock dowels along the edge of the gabion bench were inspected. Some of the bars were fully encapsulated whereas others showed no evidence of resin on the steel for the upper 3 ft or so that was exposed. I was informed that payment was not being made for these anchors because they had not been installed to the satisfaction of the Construction Manager. There has been scme discussion on the suitability of the resin-encapsulation support system. This has resulted from an impression that the resin is able to flow away from the hole along open joints. If some resin was lost in the first row of anchors (assuming that the necessary number of cartridges was installed in the first place) it could have been in local zones of near-surface rock. Below the gabion bench where the first row of anchors was installed 1 most of the rock joints are tight enough to retain the resin in the holes. The observed blast hole drilling below elevation 60 did not indicate a loss of air-circulation. Based on my observations, I see no reason to conclude that the resin encapsulated system is not suitable for the Powerhouse cuts. The system has been successfully used for a wide variety of rock conditions and is superior to the cement-grout method. 2.2 Geologic Structures One continuous wet clay-filled shear zone was noted in the rock slope. Fortunately it dips into the hillside and presents no slope stability concerns. All new cuts should be mapped as soon as possible after mucking to insure that nothing is found that was not contemplated in the design slope stability analysis. Any shear zone should be projected into the proposed manifold and penstock area due to the size and complexity of the required excavation. Very truly yours, Andrew H. Merritt AHM/JJ 2-1379-JJ J. Barry Cooke 1050 Northgate Drive San Rafael, CA 94903 (415) 479-6151 Andrew H. Merritt 7726 S.W. 36th Avenue Gainesville, Florida 32608 (904) 372-6153 May 7, 1987 Mr. Theodore Critikos Project Manager Stone & Webster Engineering Corporation 800 11 A" Street Anchorage, Alaska 99501 BOARD OF CONSULTANTS NINTH REPORT BRADLEY LAKE HYDROELECTRIC PROJECT I.O INTRODUCTION Joel B. Justin 2401 Pennsylvania Ave (17-B) Philadelphia, PA 19130 (215) 232-5502 Donald T. King P.O. Box 2325 Boston, MA 02107 (617) 589-2034 1987 SWEC-ANCHCRAGE The ninth meeting of the Board of Consultants convened in your office on May 5, 6, and 7, 1987. Mr. Barry Cooke, Mr. Joel B. Justin and Mr. Andrew Merritt were joined by Mr. A. Stanley Lucks who substituted for Mr. Donald T. King on the Technical Review Board. 2.0 GENERAL The principal tasks of the Board was to visit the site and review the construction carried out under the Site Preparation Contract, particularly the diversion tunnel and the initial excavation for the powerhouse, and provide comments on the General Civil Contract bid documents and the Geotechnical Interpretive Report. The visit to the site was made on May 6, 1987. 3. DIVERSION TUNNEL Excavation for the Diversion Tunnel has been completed and concrete had been placed for the inlet portal gate guides, transition lining, and the lining of the initial 25 ft long horseshoe section upstream of the gate shaft. The gate shaft will be constructed as part of the General 2-1889-JJ Mr. Theodore Critikos Stone & Webster Engineering Corporation 2 May 7, 1987 Civil Contract. Grouting along the lined portion of the tunnel had been completed. The tunnel was unlit which prevented a detailed inspection of the rock. Rock conditions along the tunnel were good. Spot and pattern bolting were the only support measures used. Several joints up to 6 in. wide were encountered. These joints had been filled with silts and clays. Four of these joints required cleaning and treatment with dry pack mortar over their entire length. Another two joints were apparently dry packed over part of their length. Specific details of the cleaning and the treatment were not available. While the Diversion Tunnel as constructed appears to be satisfactory for its intended purpose, we recommend that Stone & Webster, Bechtel, and the Contractor conduct a joint preoperational inspection. Special attention is required to insure that all erodible seams have been treated. 4. DAM 4.1 Upstream Cofferdam In our December 10, 1986 report we questioned the need for a design criterion that required a structure to be built that would allow for future unwatering to repair the concrete face. This criterion developed assuming seismic damage in the lower area of the face and resulted in a complex sheet pile design. The Specifications do not permit the Bidder to submit an alternate. We recommend that, upon award, alternate schemes should be evaluated with the Contractor. It is concluded that there is essentially no probability of damage or leakage requiring unwa ter ing and that the Contractor should be given responsibility for design, satisfactory operation, and pumping for a temporary cofferdam. 4.2 Toe Slab The toe slab layout and details are well adapted to the site and represent good current practice. There are appropriately two reference points (lines); one is for rock excavation and will be finalized after overburden is removed; the other is for the concrete placement of the toe slab. The toe slab points (lines) define the contact of the toe slab concrete and the base of the face slab. The final toe slab control points are established after the excavation is made. The specifications thoroughly provide for adequate treatment. 2-1889-JJ foundation Mr. Theodore Critikos Stone & Webster Engineering Corporation 4.3 Grouting 3 May 7, 1987 We continue to believe that stable grout mixes should be used for the curtain. As such, the preferred mixes are 2:1, water: cement by volume and thicker. Current world-wide experience on hydro projects support this opinion. Where we have had the opportunity to observe seepage beneath dams and into tunnels that had recently been grouted, the unsatisfactory performance of the grouting has been attributed to thin unstable grouts. The selection of NX diameter grout holes is acceptable to us. The need for tertiary etc. holes depends on the grout takes in the primary and secondary holes. This is a field decision and difficult to predict in advance; however, it is normal in grouting practice. The principal requirement here is that experienced staff be on hand to evaluate the grouting as works proceeds. The requirement for pressure testing of grout holes can be modified. The selection of stable mixes precludes the need for water tests to determine the "starting" grout mix. Also, in our experience there is no relation between results of water tests and grout takes. Water tests are appropriate for the check· holes that are drilled after specific areas of the curtain are finished. Thorough washing of the grout holes is endorsed -always subject to modification depending on field experience. 4.4 Joints The joint designs and materials were reviewed. We are confident that the joints will perform as watertight joints if constructed as designed and under close inspection. The backup material under the bottom seal of the perimeter joint can be asphalt impregnated sand or concrete mortar, both having been used. We endorse the selection of the concrete mortar alternative. 4.5 Face Slab We consider the face slab design and the concrete specifications for the face slab to be appropriate. The use of continuous reinforcing both ways and use of air entrainment and fly ash are desirable to adapt to the seismic requirements and freeze-thaw conditions, respectively. 2-1889-JJ Mr. Theodore Critikos Stone & Webster Engineering Corporation 4. 6 Rockfill 4.6. 1 General 4 May 7, 1987 We consider the grading, layer thickness, and compaction to be impracticable for the quality of rock observed at the site. A high quality and more economical embankment can be obtained with the modified specifications given below. 4.6.2 Zone 81 The grading curve is satisfactory. The 3 in. maximum size is used in all current dams. The change from 6 and 4 in. maximum to 3 in. maximum is a recent development which facilitates construction and provides a firm and semi-previous zone with grading such as in the Specifications. The 5% upper limit for No. 200 mesh is low, but will probably be met by crusher run graywacke. The specifications are satisfactory, but need not be rigidly enforced. As high as 10-12 percent minus No. 200 would be acceptable. 4.6.3 Zone 83 Zone 83 is the Zone which takes the water loading and a high modulus of compressibility is desired. However, there is no evidence to indicate that the 18 in. layer is required, and the massive graywacke rock is judged to provide excellent rockfill for thicker lifts. Three foot layers are recommended for a Zone 38, that is extended to three-quarters of the base width. The specification could read, "quarry run rock, the maximum size being that which is incorporated in the layer, providing a generally smooth surface for compaction. Not more than 50% should pass a one inch mesh and not more than 10 percent should pass a No. 200 mesh." 4.6.4 Zone 84 Settlement of Zone 84 takes place only during construction. It is a desirable location for loads of fill containing rocks larger than 3 ft, which are to be expected from the graywacke. It is desirable to have greater permeability in this zone than in the upstream Zone 83. Thicker layers in this downstream zone, usually twice the thickness of the upstream zone, is normal practice. 4.6.5 Zone 85 This zone is primarily to give an attractive surface, as such is achieved best by large rock placed to a close tolerance. This is commonly specified to be surface rocks of greater than 2 ft dimension, where the quarry is judged to provide such rock. Dumping loads of 2-1889-JJ Mr. Theodore Critikos Stone & Webster Engineering Corporation selected large rock on the surface, with high points at line, is a practical method. thickness, a ramp is dozed placed. Examples are Chivor, 4.6.6 Zone 82 5 May 7, 1987 previous layer, and dozing them to the or not more than 6 in. beyond the design Where rocks are smaller than the layer to the face and another large rock is Dartsmouth, Areia, Guavio, etc. Coarse rock, as specified, does not provide a trafficable surface that can be spread and compacted. Bottom permeability is not really a requirement upstream from the axis. It is considered that thick layers can provide high horizontal drainage capacity. A suggested practical means of obtaining a drainage zone is to use three 4 ft layers in the base of the dam for the downstream two-thirds of the base width. 4.6.7 Compaction and Seismic Resistance Usual compaction is by 4 passes of a 10 ton vibratory roller for 3 ft and 6 ft layers. For the special earthquake consideration given to this project the 1.6H:1V slopes is the main consideration. The 6 passes of the 10 ton vibratory roller could be retained for the thicker layers. 5. PRESSURE TUNNEL 5.1 Grouting The specifications contain provisions for compaction grouting behind the tunnel lining with the objective of consolidating the de-stressed zone around the tunnel perimeter and prestressing the concrete lining. This work would be done for about 250 ft upstream of the end of the steel lining and elsewhere as required in zones of low modulus rock. We have the following reservations concerning these provisions. First, this type of grouting falls more closely in the category of consolidation grouting. Compaction grouting, as commonly used, involves pumping very thick mortar mixtures into voids in soil to prevent collapse or to jack-up a foundation. The term compaction grouting {and squeeze grouting} should not be used in the tunnel specifications. The use of grouting to improve rock modulus is a procedure that often is the subject of considerable discussion. In our experience it cannot be concluded that a normal consolidation grouting program can be depended upon to significantly improve the modulus, although some improvement may be achieved in some cases. The same comments apply to prestressing the concrete lining. To achieve any sort of prestress, considerable effort is required. It is our opinion that a normally reinforced concrete lining would be all that is required in the areas mentioned above, although depending on the rock conditions, it might not be required for all 250 ft 2-1889-JJ Mr. Theodore Critikos Stone & Webster Engineering Corporation 6 May 1, 1987 upstream of the steel liner. If Stone & Webster believes that grouting to improve rock modulus and prestress the tunnel lining is a design requirement, then the drawings and specifications have to be greatly expanded to define the scope of work required. For example, prestressing requires carefully sequenced grouting in rings, a bond breaker between the rock and lining, and an instrumentation program to monitor lining deflections. It is not a simple process but is titue consuming and costly. We recommend that this design feature be reviewed. Provisions for normal consolidation grouting to control leakage should be maintained. 5.2 Drains Behind the Steel Lining The drill holes will now be drilled one foot into rock to provide drainage to the pipes set into the concrete lining. We accept this feature recognizing that it would be undesirable to do so if the rock in this section of tunnel proves to have high water flows. We consider that the decision can be made readily in the field at the appropriate time. 5.3 Length of Steel Lining The steel lining presently ends at Sta. 31+60. In-situ stress measurements will be made during tunnel driving to assist in determining the final length of the steel. Should these results be more favorable than those obtained in the Golder study, the lining could be reduced with substantial savings to the APA. 6. POWERHOUSE 6.1 Excavation by Site Preparation Contractor The powerhouse and switchyard excavation has been completed to Elevation 18. The quality of the excavation and rock support installed appear to be very satisfactory. No evidence of potential slope instability was noted. The 20ft slopes between benches have been covered with chain-link mesh. The slope angles were designed in accord with the dip of the major rock joints and the exposed geologic conditions confirm the design. Two shear zones are exposed in the slopes: Because of their angles of dip, they pose no threat to the stability of the cuts. Preliminary drawings have been made that show these shears projected into the penstock tunnels and manifold to assess their effect on future excavations. Plans are being made to refine these drawings by making further field measurements. If determined to present future excavation difficulties, the geologic drawings will be included in the Interpretive Report. 2-1889-JJ Mr. Theodore Critikos Stone & Webster Engineering Corporation 6.2 Excavation for Powerhouse 7 May7, 1987 The required cuts for the powerhouse will be made in generally closely jointed rock as anticipated from the original borings and subsequent site work. We recognize that the required powerhouse cuts involve a certain amount of quite detailed excavation for the units, sumps, etc. This is typical in any such work and is the natural result of minimizing the amount of concrete in the powerhouse. As is typical for any excavation, a certain amount of overbreak related to adverse geologic conditions is expected. In an effort to control the overbreak and m1n1m1ze the adverse effects of the jointed rock, the specifications provide for cushion blasting. Maximum bench widths are given as well as upper limits on loading of the perimeter drill holes and the next interior row. The spacing of the perimeter holes is set at 24 inches; closer spacing may be required. The details of cushion blasting were discussed thoroughly at the meeting in Denver on April 10, 1987 and the specifications are being modified accordingly. It is our opinion that cushion blasting should be used and we endorse the limits that will be included in the specifications. The implementation of these requirements will need careful supervision in the field. Control of the drilling and loading is critical. Some geologically related overbreak will occur which should be acknowledged. The Contractor cannot be held responsible for overbreak related to continuous weak geologic features. In conclusion we believe that although the rock conditions are not optimum, there is nothing unreasonable in the design of the required cuts. Caution is certainly required and for this reason the specifications outline carefully controlled blasting methods. 8. GEOTECHNICAL INTERPRETIVE REPORT A. H. Merritt and A. S. Lucks completed their review of the Geotechnical Interpretive Report. The general content and format of the report, as now written, is satisfactory. Minor comments and corrections were marked on copies of the text for incorporation in the final issue. As mentioned above the information obtained from the recent geologic mapping of the powerhouse excavation should be included in the report, particularly the data on the previously unknown shear zone trending N10°W and dipping at 40-60° to the East. 9. DESIGN AND CONSTRUCTION COORDINATION DURING CONSTRUCTION Modifications of the design details and drawings will be required during construction to satisfy detail field conditions. Geotechnical matters will require additions, deletions or substitutions of procedures for the work required. The Construction Manager should also 2-1889-JJ Mr. Theodore Critikos Stone & Webster Engineering Corporation 8 May 7, 1987 communicate with the Design Engineer if there is any doubt of the interpretation of drawings and specifications. We recommend that the Design Engineer be cant inuously represented on site to assist the Construction Manager in the expeditious resolution of any construction problems that may develop. We believe that the close cooperation of the Design Engineer and the Construction Manager is necessary during construction for a safe and economical completion of the project. 10. REVIEW OF GENERAL CIVIL BID DOCUMENTS 10. General We have individually reviewed the General Civil Documents and have made written notes or otherwise commented regarding these documents. We have also reviewed in like manner the Notes of Meeting of Mr. Hendron of the FERC Board and Mr. Merritt and Mr. Lucks of this Board, April 10, 1987, in Denver, Colorado. We have covered all the important comments in the text of this report. 10.2 Escrow Bid Documents In our report of August 14, 1987 we reported that, "we saw no need for escrow of the Contractor's bid documents. The Contract should stand on its own and the Contractor's bid work sheets are not considered to be a factor in determination of change order amount or basis for a claim". We have not changed our opinion and in particular, we strongly disagree with the current version of the contract that allows the escrow bid preparation sheets to be used in the evaluation of the successful bidder. 2-1889-JJ Mr. Theodore Critikos Stone & Webster Engineering Corporation Very truly yours, J. Barry Cooke Andrew H. Merritt 2-1889-JJ 9 May 7, 1987 AGENDA Ninth Technical Review Meeting Stone & Webster Engineering Corporation 800 "A" Street, Anchorage, Alaska 99501 Bradley Lake Hydroelectric Project -Alaska Power Authority May 5, 1987 Introduction and Project Status Site Preparation Contract Status General Civil Construction Contract Bid Documents Turbine-Generator Status N. A. Bishop N. A. Bishop N. A. Bishop J. Hron Dam Break Analysis Tsunami Report Effects of Tsunami on Powerhouse Structure Diversion Tunnel Geological Mapping Powerhouse Excavation Geological Mapping Site Visit Discussion Reservation Information: N. A. Bishop, S. Lucks, and J. Meisenheimer Depart Anch 7:30 AM Arrive Homer 8:15AM Airline: South Central Fl t No. : 2076 Depart Homer 6:30 PM Arrive Anch 7:15 PM Airline: South Central Flt No.: 2083 May 6, 1987 Field Site Visit May 1, 1987 T. J. Hughes T. J. Hughes W. C. Sherman D. M. Jurich D. M. Jurich N. A. Bishop Reservation Information: B. Cooke, J. Justin, and A. Merritt Depart Anch 8:05 AM Arrive Homer 9:15AM Airline: ERA Flt No.: 4872 Depart Homer 7:00 PM Arrive Anch 7:50 PM Air line: ERA Fl t No . : 4881 Discussion General Civil Construction Contract Bid Document Comments L. C. Duncan Technical Review Board Report Participants: J. Barry Cooke -Consultant Joel B. Justin -Consultant Andrew H. Merritt -Consultant Stanley A. Lucks -Engineering Manager James K. Meisenheimer -Environmental & Geotechnical Division Manager Norman A. Bishop, Deputy Project Manager -Engineering & Design and Environmental & Licensing Lance Duncan, Assistant Deputy Project Manager -Engineering & Design Jay Hron -Lead Hydraulic Engineer William C. Sherman -Lead Structural Engineer Dave M. Jurich -Geotechnical Engineer Timothy J. Hughes -Hydraulic Engineer 2-1864-JJ STONE 81 WIEBSTI:R ~ STONE 8 WEBSTER ENGINEERING CORPORATION 5533 GREENWOOD P~AZA BOU~EVARC ENG~Ewooc. Co~ORAco 80 111 ·2113 ADDR.SS AL.I.. CORRESPONDENCE TO P.O. 80X 54045. DENVER. COLORADO 80217-!!14045 80STON CHilRRY 1111.1... N.J. OltNVIlR HOU.TON NllW YORI( OAI.I.AS POFITLANO, Oft A!CtU.,,.ANQ, WA WASHINGTON, D.C~ J. Barry Cooke 1050 Northgate Drive San Rafael, CA 94903 Joel B. Justin 2401 Pennsylvania Avenue Philadelphia, PA 14130 Mr. Theodore Critikos Project Manager Bradley Lake Hydroelectric Project Stone & Webster Engineering Corp. 5555 Greenwood Plaza Blvd. Englewood, CO 80111-2113 TENTH MEETING OF TECHNICAL REVIEW BOARD DECEMBER 17 & 18, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT TilJ-&.-HONil: 303-?41-7700 W.U. YWX' 810.031-0105 w.u. l"lti.I:X: 41·4.&01 Andrew H. Merritt 7726 S.W. 36th Street Gainesville, FL 32608 D. L. Matchett Stone & Webster Engineering Corp. 5555 Greenwood Plaza Blvd. Englewood, CO December 18, 1987 J. 0. No. 15800.72 T2.2 The tenth meeting of the Technical Review Board for the Bradley Lake Project met in the office of Stone & Webster Engineering Corporation at Englewood, Co. on December 17 and 18, 1987. The Board was briefed by the engineering staff of Stone & Webster on the status of the Bradley Lake Project, the modification of the Design and the General Civil Construction Contract Design Addendum. The Technical Review Board reviewed the sixth report of the FERC Board of Consultants dated December 8, 1987. The Technical Board comments are made under the following headings: 1. Conclusions 2. Investigations since previous meeting 3. Main Dam 4. Cofferdams 5. Power Intake 6. Powerhouse Mr. T. Cri tikos 2 December 18, 1987 1. CONCLUSIONS With the contemplated changes, the designs are considered to be finalized for Addenda to the Contract Specifications and Drawings. 2. INVESTIGATIONS SINCE PREVIOUS MEETING The placing of the diversion tunnel in service lowered the reservoir level by about 8 ft. Advantage was taken of this to map newly exposed areas at the dam and at the reservoir perimeter in the vicinity of the power tunnel intake, and to do further investigation work. At the intake shoreline, large blocks of rock were seen. Percussion drill holes indicated that the assumed bedrock contours included large blocks of rock. Bedrock was lower than assumed for design. Moving the intake became necessary. At the dam, the reservoir lowering exposed bedrock and permitted a trench to be excavated. The trench confirmed favorable rock conditions for the cofferdams, and made a more simplified design possible. 3. MAIN DAM Rockfill grading. Grading curves were presented with a broader range of acceptable grading. This proposal is satisfactory, and should make it clear to the bidders that crusher run rock, gravel, or a combination is acceptable for the face zone, and that quarry run rockfill will be acceptable for the dam. Grout Curtain. The grouting beneath the dam and spillway has been simp! ified and now consists of a single-row curtain. Studies are in progress to define the most efficient angle of the grout holes and present conclusions indicate an upstream inclination of 30° from the vertical. Primary holes will be spaced on 10 ft. centers with every second hole drilled to a depth of two-thirds dam height. The remaining primary holes will be drilled to a depth of one-half dam height. The secondary holes will be drilled to 1/3 H. The minimum depth of the curtain will be 30 ft. Tertiary holes will be drilled as required. Tile water pressure tests prior to grouting as well as surge block washing will not be done as originally specified. We concur with these modifications and note that they are consistent with the rock conditions revealed during the Site Preparation Contract. The reduced grouting has cost and schedule benefits. Mr . T. Cri t i kos Landslide Induced Wave. reservoir rim regarding concluded that the rock to such sliding. 3 December 18, 1987 A study was done on the stability of the possible landslide induced waves. It was and overburden conditions were not conducive However the alluvial deposits in the Martin River Delta could liquify during an earthquake and calculations based on assumed "rapid movements" indicated possible development of a 9. 5 ft. wave. This height of wave, if actually occurring at the dam would not exceed the available freeboard. However the geometry of the reservoir and the rock ridge at the intake make it unlikely that the full 9. 5 ft. wave could reach the dam. We agree that no further study on this aspect is required and note that a rockfill dam can take overtopping since such an event is short-lived and the downstream face is armored with large rock blocks. Schedule. The modifications in dam specifications and cofferdams are considered to make dam construction possible in one season. 4. COFFERDAMS With the difficulty of investigating with river flow at the narrow canyon damsite, knowledge of bedrock conditions had been limited. A conservative sheet pile cofferdam scheme was adopted to allow for unknown conditions. The rock exposures, and the results of the investigation trench, made possible by the drawdown from diversion tunnel operation, indicate favorable rock foundation conditions for simplified cofferdam design without sheet piles. 5. POWER INTAKE The operation of the diversion tunnel affected a 8 ft. drop in the lake level making possible additional observations around the intake. An extensive deposit of very large blocks of talus was visible and mapping and probe hole drilling indicated that the intake had to be pushed back further into the rock ridge. The revised open cut in rock will now provide the rock required for the damfill and the excavation can be designed to provide efficient quarrying. It is suggested that the slopes be designed with vertical lifts and wider benches such that the overall slope is in accord with the dip of the joints. This will provide approximate 35 ft. vertical cuts with 20 ft. minimum benches. The wide benches will catch any loose rock and the vertical faces do not permit bouncing of rock and hopping over narrow benches. This slope geometry is common in quarry work such as spillway excavations adjacent to dams and is suitable for the intake. Rock bolting is kept to a minimum because of the security provided by the wide benches. Mr. T. Cri tikos 4 December 18, 1987 6. POWERHOUSE Excavation and Support. The excavation of the powerhouse has been simplified by reducing the number of benches of varying widths and depth. This will facilitate construction and probably reduce future claims related to overbreak. The design basis for the rock bolt support has likewise been reviewed based on rock conditions exposed during the initial contract. A substantial reduction in the number of rock bolts resulted. Twenty bolts were added as tie-downs in the corners of the floor slab. We concur with these revisions. Thrust Blocks-Penstocks and Manifold. A review was made of the stability of the rock masses containing the thrust blocks. This analysis was commented on by the FERC Board. Based upon somewhat conservative assumptions, additional normal force across a supposed irregular horizontal sliding surface was considered necessary. This can be achieved by 6-8 A4 bolts, a type already provided for in the contract documents. We agree with the SWEC conclusions and note that this extra security can be realized at minimal cost. Mr. T. Critikos 5 December 18, 1987 Respectfully submitted, J. Barry Cooke D. L. t1atchett NAME J. Barry Cooke Joel B. Justin ALASKA POWER AUTI!ORITY BRADLEY LAKE HYDROELECTRIC PROJECT TENTH TECHNICAL REVIEW BOARD MEETING DECEMBER 17 & 18~ 1987 ATTENDEES LIST FIRM Consultant, TECH Board Consultant, TECH Board Andrew H. Merritt Consultant, TECH Board *A. s. Lucks *D. L. Matchett *J. J. M. Plante J. K. Meisenheimer *T. Critikos N. A. Bishop *R. A. Joyet >'f:J. Hron *W. Sherman *P. Mayrose *G. Yow *D. Jurich * Part Time SWEC, Engineering Manager & Board Chairman SWEC, Engineering Mgt. Sponsor SWEC, Vice President & Manager of Denver Office SWEC, Environmental & Geotechnical Division Mgr. SWEC, Project Manager SWEC, Deputy Project Mgr/Engr. SWEC, Lead Geotech. Engineer SWEC, Chief Hydraulic Engr. SWEC, Chief Structural Engr. SWEC, Consulting Geologist SWEC, Geotechnical Engineer SWEC, Engr. in Geotech. Div. .. \·. ·. :··· J. Barry Cooke 1050 Northgate Drive San Ratael, CA 94903 (415) 479-6151 Aadrew Merritt 7726 S. V. 36th lveaue GaiDesvllle, Flol'"ida 32608 (904) 372-6153 August 14, 1986 Mr. J.J. Garl'"ity Project Manager Stone & Webster" Engineuiag Col'"por"atio n aoo •1• street lacborap, llaska 99501 :OOlRD OF CO!lSULT.l!ITS SEVENTH REPORT BRADLEY L.ll! B!DROELECTHIC PROJECT Joel B. Justin· 2-01 Peaasylvaaia Ave (17-B) Philadelphia, PA 19130 (215) 232-5502 Doaal.d T. fiag P.o. Box 2325 Boston, Kl 02107 (617) 589-2034 The seveath meeting ot the Board of Consultants convened 1n your ottice oa August 12 and August 14, 1986. August 13, 1986 was spent oa a trip to the site were the Site Preparation Contractor is at work. The aew Board _.bers, Mr. ladl'"ev Merr"itt and Mr. Donald T. l:iag joiDed Mr. Barry Cooke aad Mr. Joel B. Justin who coatinue on the Techaical Reviev Board. August 12, 1986 the Board was briefed by the Stoae & Webster statt on the ch&D&eS ot the or"pDi2:ation ot the oonstructioa oontract troll one tunlkey coatract to se'f'eral contracts. These separate coatracts will be as follows: 1. Supply ot powertouse major equipment including turbiae:s, paerators and goveraors. 2. Major civU contract which includes the daa, spillway, power twmel, iastallatioa ot gates 1n the diversion cmd power tunnel and the excavatioa of the power bouse. 3. The two proposed diversions, the Nuka and the Middle Fork. 4. The povermu• construction a~ installation ot equipment. 5. Substation aDd Transaission line. 2-955-JJ · Kr. J. J. Garrity Stone & Webster Engineering Corporation 1.0 SIT! VISIT 2 August 14, 1986 On August 13, 1986 a viait to the site wu aade by the Board aDd starr members ot Stone & Webster and Bechtel, the Construction Manager for the Project. The site contractor, EDserch, 1s working on access roads, openi.Dg the riprap quarry, the borrov area tor till and concrete aggregate and the camp facilities. Progress ia good to date. The Board .. ber:s and others were able to visit all the project sites including the powerbouse, power tunnel aligD~~ent, 1nt8ke, .Bradley Lake, the dall spillway and river d1 version and the Nuka and Middle Fork Diversions. Helicopters were used for transportation. We also traveled the r:oacb ia.:specting the quarry borrow area, and the construction camp and facilities. 2.0 BIDRAULlC MODEL The hydraulic model or the spillway, spillway channel, stilling basin, diversion tunnel exit, and Upper Bradley River channel, was tested at Fort Collins, Colorado on July 8, 1986. It was det81"211ned that small changes 1n the downstrea.a discharge area contigurat1on will improve the hydrau.llc conditions. The IDOdel will be adjusted and rerun to contirm the expected results. A second model ot the tunnel is under coa.:struction 1n order to evaluate the hydraulic conditions downstream ot the diacbarge ptes under emergeDCy discharge conditions (6000 cts) aDd to determine air quantity and diatribution pattern. 3. 1 General Design The daa design 1s tirwed up 1n ajor aspects 1nclud1ns location of' a.xi:s, initial est1•te ot plinth ref'erence lines, slopes, and tace slab thickDesa. The dravinp and specifications are not developed to a level enabling review at this meetins. 3.2 Grouting We bave rwiewecl the available drawings aDd speciticat1oa.:s and bave the following caameats: Mixes: Current practice on hydroelectric projects ia to select one grout lllix, based on laboratory testing, aDd to do all grouting with this mix. This single mix 1s based on the concept or a stable a1x which exhibits reduced sedi•ntat1on, hisber strength, lJ)od puaapability, and which leads to less contusion 1n the field. We would preter to see this practice adopted for Bradley Lake. 2-955-JJ .. Hr. J.J. Garrity Stone & Webster Engineering Corporation 3 August tit, 1986 Tests: The specifications require water pressure tests in each - bole prior to injection o-r the grout. We do not believe this is necessary because basically there is poor correlation between results ot water tests and eventual grout take. The grouting will be mucb 1110re etticient, and less costly, it grouting proceeds .illulediately alter drilling and cleaning the hole ot cuttings. Number ot Rows: We recommelld that two rows be :shown on the drawings with a quantity of drilling included to provide for a third row over perhaps 2~ ot the length ot the curtain. 3.3 Instrumentation In our opinion, the instrumentation program tor the dam can be limited to IIIODuments along the crest and a weir to measure seepage downstream in the narrow reach near the waterfalls. 3.4 Rigbt Abutment Plinth The excavation drawing tor the rigbt abutment plinth is well developed. Where the plinth crosses the deep gulley, foundation concrete is needed tor the plinth. It should be designed as a surcharged gravity or plug section of concrete with the assumption of no stabilizing force from the rockt'ill. 4 .0 SPILLWAY Stability cmalyses are in progress tor the spillway. Prelillinary results indicate that tor a two-dimensional IIIOdel a substantial tendon tie-down system would be required to resist the design earthquake forces tor the assumption ot a cohesion value equal to zero. For this condition to exist, a continuous horizontal plane ot low shear strength llllSt be postulated to occur below the structure. Ve inspected the rock outcrops at the site during our visit and found no eYidence ot such geologic planes in the rather IllUsive outcrops below the ogee level upstream of the structure. In our opinion a water retention structure would not initially be designed to require a telldon system. It adverse geologic planes were found in the foundation, the grade could be lo~red. Moreover, the variable depth ot the toulldation bloclcs and the narrow section ot the spillway creates a considerable three-dimensional aspect to the structure and would make it behave silllilar to an arch. In conclusion, we see no reason to provide tor a tendon tie-down system in the spillway design. 2-955-JJ ' : ·Hr. J.J. Garrity Stone & Webster Engineering Corporation 5.0 TUHHEL 5. 1 D:Upute Board 4 August 111, 1986 Consideration or a "Diapute Rniev Board• has been suggested. We recognize the •rit ot such a Board tor aajor underground worb. However, tor Bradley Lake we do not consider such a Board to . be necessry. A1110ng the reasons tor the above view are: 1. The tunnel 1.3 only about 20 percent ot the Civil Contract cost. 2. Two well experieaced firms are involved in design and con.tz-act managell!nt. 3. The geological conditions tor the surface structures are considered to be well det'ined. 4. The Dispute Review Board activities would therefore be , . essentially l.iaited to the underground work. Considering the size or the tunnels and ~e general rock conditions at Bradley Lake we believe that any d:Uputes can be well handled using normal practices. 5.2 Escrow Bid Documents We bave no experience with such a practice aDd see no need for Escrow or the Contz-actor•s bid docwaents. The contz-act should stand on its own and the Contractor's bid work sheets are not considered to be a tactor iD determi.Datioa or Change Order amount or basis ror a claim. 5.3 Bill or Quantities Preseat thinking 1a to provide three schedules ror bidding of the twmel: 1) upper and lower tunnels with a vertical shart, 2) the two tunnels but with an iDclined sbart, and 3) one tuanel with a constant 5.5S slope beginning at the eod or the steel lined section and continuing to the intake portal (no shart required). No so-called •basic-bid• 1.3 speci1'ied, award beiDg made to the lowest bid on any one ot the schedules. The anticipated geologic coDdition.s will be described in the Interpretive Geologic Report. The various :support systems will be shown on the drawings. A bill or quantities bas been prepared for each ~~ajor unique section of the waterway providing for unit prices for excavation, support, lining, aDd water handling/mobilization demobilization. A unit price multiplier tor adverse ground conditions, as detel"'llilled by the Construction Manager, will be applied to the unit price for excavation. 2-955-JJ ~ .. Hr. J.J. Garrity Stone & Webster Engineering COrporation 6.0 POW!Rfi)USE 6.1 Tailvater Supp=ession 5 August 1-", 1986 This is an econoaical system wbich is well adapted to Bradley Lake. Its reliable use is well establisbed. Foundation vibration and sound levels are important considerations in the compressor design. 6.2 Cooling Water It is UDderstood that a turbine llllDut'acturer considers that the elevation or a •scoop• on the wheel pit wall would have to be at a distance below the rwmer such that higb tide would tlood it. We agree with Stone & Webster that a scheme can be worked out. 6 .3 Blasting The speciricationa should require the Contractor to submit a detailed plall ror the drilling and shooting or the powerhouse excavation. The nt~~erous ledps aDd. grade changes will require very careful procedures. Cusbion blasting vill be req.uired throughout. We rind that the general blasting requirements regarding submittal ot blast plans, their approval, and subsequent verification in the field to be apparently very complex and. would tettd to lead to inefficient manage•nt and likely delays to the work. These requirements should be streamlined. 6 • .IJ Rock lncbor Support We recoa•ttd that the standard rock bolt required tor the tunnel be tully encapsulated with a unirora setting time resin. A two set-time srst• with intermediate post-teasioniag is not required. 7.0 DRILL HOLI EXPLORATION -The progru or drilling and hydrojacking tests is complete and pre.l..:1lliuary analyses or the results suggests that the minilllUII in-situ rock stress is approxi•tely equal to the overburden pressure. Further boles aDd additional testing are not considered necessary. We recom•al that b.ydrojackiDg testing be done trom within the tunnel during excafttion to deteraine the appropriate length or the steel lining. Bydrojacld.ng would be in lieu or overcoring tests. We believe that no additional exploratory borings are required tor the principal project reatures. 2-955-JJ .· ( ·: .. .... · Hr. J.J. Garrity Stone & Webster Engineering Corporation Very truly ,.ours, J. Barry Cooke ~JJ~ A. Merritt 2-955-JJ 6 August n, 1986 . . ' . ' Same Letter sent to: Dr. Andrew Merritt Mr. Joel B. Justin Mr. Donald T. King Mr. J. Barry Cooke 1050 Northgate Drive San Rafael, CA 94903 TECHNICAL REVIEW BOARD RESPONSES TO SEVENTH REPORT BRADLEY LAKE HYDROELECTRIC PROJECT October 20, 1986 J.O. No. 15800 T2. 1 The report ot the seventh Technical Review Board meeting ot August 12-14, 1986 has been reviewed, and our response to the comments are as follows. Our responses are numbered and titled to match the report dated August 14, 1986, a copy of which is attacl!ed to this letter tor reference. 2.0 HYDRAULIC MODEL The vertical cut in the pool area at the exit tram the diversion tunnel was eliminated, thus making a smooth sloping transition from the spillway discharge channel into the stilling pool. The reason for elilllination ot this vertical cut was to suppress an oscillating hydraulic jump which was developed scae 300 feet downstream from the diversion tunnel exit portal. Observations at the laboratory indicate that this modification did not eliminate the oscillation, but placement ot either a submerged weir or dentated sill in front of the portal did, so the solution to the oscillation appears to rest with control ot the location of the diversion tunnel jump. The rerun of the model was made tor Mr. J. Parmakian on Aucust 29th, and another was be run September 25, 1986 tor other FERC Board members to witness the test. A second model ot the diversion tunnel bas been built and tested and. was also demonstrated on September 25, 1986. The model is to 1:12 scale. It models the hydraulic gates in the diversion tunnel, transition sections, part of the upstream tunnel and two alternatives ot the discharge conduit. The water passages are, except for the upstream transition and pipe, transparent to allow observation ot flow. A copy ot the initial test observation report will be provided at a later date. 1-406-JW Mr. J. Barry Cooke Technical Review Board 3. 1 General Design 2 October 20, 1986 The Board, previously and in the August meeting, has indicated general concurrence with the main dam design approach and geometry, and after viewing the site, was satisfied with the concept and arrangement. The review ot detailed drawings and specifications will be conducted at the next submittal, when the details have been completed. 3.2 Grouting The issue of grouting mix design practice was discussed in depth, with the general conclusions being. that staged and single-mix designs are both in use today, with staged or multiple-mix design still predcminating in U.S. practice. It is SWEC's position as designers that multiple mix ratios are preferable. The range of mixes required is being reviewed to reduce the number ot mixes and consequently simplify field operations. The pressure testing specification for grout boles is being revised to clarity the pressure test requirement, and to eliminate most of tbe pre-grouting pressure. testing. The specification and drawings will show a two-row spillway grout curtain, and a three-row dam curtain with the third row being considered as closure boles. These will be deleted in the field if, based on pressure testa, it appears that the two-row curtain will suffice. 3.3 Instrumentation SWEC concurs that SUM'ey points and a seepage monitoring weir in conjunction with strong-motion seismographic monitoring will suffice tor dam instrumentation. The exact extent of' aligDment and survey monuments 1a being determined at this time. 3.4 Rigbt Abutment Plinth The recommendation to neglect dam till stresses in calculating plinth abutment block and plug section stability is noted and will be followed. 4.0 SPn.LWAY The FERC Board bas withdrawn their concerns about spillway stability, so this subject, as discussed in the TRB report, is now closed with a conclusion tbat a tie-down syste. will not be required and will not be designed, unless unexpected adverse conditions are found in the spillway foundation during excavation. 1-406-JW .. ) MAY 17, 1983 Bradlev Lake Project Dear Sir: We visited the site of Bradley Lake Project on May 12. Discussions were held with you and your staff on May 12 and 13. The present task is to evaluate the feasibility of the project. The following summary is our conclusions and recommendations. 1. We consider the geologic conditions favorable. There do not appear to be any physical conditions which would preclude development or result in excessive unanticipated costs from the estimates now being developed. 2. \~e concur·· completely with the basic layout now being considered. We consider the r_evised int:ake design and location, spillway, powerhouse location, and method of diversion significant improvements. 3. We believe an embankment: dam approximately at the axis now con- sidered to be feasible and apprcipriat:e. We consider a concrete faced rockfill dam sat:isfactory. A rockfill with till core could also be considered. We note, however, such a design is subject to more delays in construct:ion from weather and requires a larger total volume of fill and wider base width than a concrete faced dam. Thus space limitations, considering the location of the intake, cofferdam and topography of the right abutment:, might: result in significant problems in layout and greater costs for the rockfill dam with impervious core. 4. Studies on other projects have shown repeatedly significantly larger costs for concrete gravity dam as compared with an embank- ment dam where both are located along the same axis. At this site an alternative axis located upstream would offer abucnents and crest length height ratio favorable to the use of a gravity arch with probably some saving as compared with a gravity dam at the present axis. tle are not at all certain that space lil::litations would make this feasible considering topography. requirements of the cofferdam and intake to the power tunnel. We believe fea- sibility of this concept could be evaluated from a preliminary layout and suggest this be considered. 5. Examination of the rock indicates a quarry can be developed which will produce excellent rock for a rockfill dam vith minimal zoning required. For estimating purposes for the concrete faced dam we suggest using only three zones: a zone of processed material under the slab, an oversize rock zone on the downstream face, and the remainder quarry run. 6. We concur with the tunnel alignment and suggest the section requir- ing steel lining upstream of the powerhouse be placed as low as is feasible to shorten the length of steel lining and to minimize the hazard of encountering low areas in the rock cover. Rail transport will be necessary in the tunnel which will generally require a grade not to exceed about one percent. 7. We concur with your plan to move the powerhouse into the rock slope to ensure rock foundations and a rock sill in the tail race to control tail water levels at the powerhouse. 8. We concur with your decision to use two units only. · 9. The economics of the project is dominated by the cost of the power tunnel. Preliminary inspection of the rock from the Bull Moose and Bradley River Fault zones indicate that most of the fault zone material is rehealed breccia which shows neither hydrothermal alteration nor iron staining. from surface water. Although these zones will be crossed by the power tunnel; major support problems are not expected but more exploration in the fault zone are neces- sary to substantiate these opinions. To date the cores take in the fault zone do not show the high percentage of core loss and g~uge one would expect in such a major fault zone. The hardness of the rock is very important in determining if a TBM is feasible for this job. It is recommended that abrasion and Schmidt Hammer hardness tests be conducted on representative samples of the: l) argillite, 2) graywacke, 3) chert and 4) argillite with chert bands. Unconfined strengths and sonic velocities of these materials should be determined on the same samples used for the hardness tests. The geologic investigation should emphasize identification of the argillite, grawacke, and chert units in the field such that the percentage of the proposed tunnel in each of the lithologic units can be estimated. The hardness of these units and the length of tunnel in each can then be used to estimate the daily progress of a TBM. The estimate of progress is the most impor~ant factor govern- ing the economics of the power tunnel as well as the project. \ . •• t "' In order to make the estimate more meaningful it would also be helpful to obtain samples from the Terror Lake Tunnel for hardness tests. The rate of progress in that tunnel is presently being recorded and a correlative betYeen hardness and TBM advance costs for the most current TB~f Yould add to the credibility of an esti- mate of TBM rates for the Bradley Lake Project. 10. Undrained shear strength tests should be made of samples of the soils of the tidal flats to provide short term shear strengths of these materials. These data Yould provide a basis for designing slopes of the barge canal and basin. Respectively Submitted, ~.~-~~· A. J. Hendr6n, lr • .ry_ "" t-tt ~f"'". t"-"', / ~-~ W. F. Swiger A.JH/WFW /FH ) July 18, 1983 BRADLEY LAKE HYDROELECTRIC POYER PROJECT Dear Sir: The second meeting of the Board of Consultants convened in your office in Anchorage on July 11 at 8:00am. There ve were briefed on design studies for·the Bradley Lake project. On July 12 and lJ the site vas visited. This included detailed ex- amination of rock. outcrops to correlate descriptions of the various geologic units vith laboratory tests vhich had been made to determine feasibility and rates of progress vhich could be anticipated for excavating the tunnel vith a tunnel boring machine. The proposed exploratory program vas revieved and drill sites visited. Both the Bradley River Fault Zone and Bull Moose Fault Zone vere examined on foot and from the helicopter. The proposed sites of the dam at Bradley Lake and the Paver House vere examined vhile referring to proposed layouts for these structures. Dam Preliminary layouts and typical cross-sections have been developed for the dam considering both a concrete faced rock. filled embankment and a gravity concrete dam. For either, diversion vould be a gravity tunnel through the right (north) abutment. The intake to the paver tunnel vould be in the left abutment just upstream of the dam. Borrov area for the embankment dam vould be the 1270.7 ·rock hill on the left side. a very short haul. We consider the·proposed layouts excellent. They · are well adapted to the geologic and topographic conditions. We note that the embankment dam would permit levering the low level of the lake to about El 1065 or lover thus increasing total generation at little cost without raising the dam. Also the spillvay for the embankment dam is a simple and economical structure, but the concrete chute should be extended further dovnstream to protect the rock. This spillway design should be considered for the concrete gravity dam in studying comparative costs. The proposed cross-sections for the embankment dam is satisfactory. We understand that a brief study vere made of a gravity arch structure. Hovever. constructing the· upstream cofferdam would be difficult and expensive and there were significant problems in providing a suitable intake to the paver tunnel. Accordingly this need not be further considered at this time. Poverhouse The powerhouse is to be located north of the Corps of Engineers cation vhere a rock nose offers possibility of excavating much of tailrace in rock. Topography of the nose is being revieved. lo- t he The 2 present map is not accurate enough to locate a field survey is necessary to locate the tailrace will be entirely in rock. The development is considered satisfactory. the powerhouse and we feel powerhouse such that the basic, proposed plan of Tunnel As previously indicated, the feasibility and rates of progress of using a tunnel boring machine are strongly influenced by the properties of the rock being excavated. Thus to evaluate this it vas necessary to: 1. Classify the rock along the line of the tunnel and determine the amount of each rock type present. 2. Run tests on representative samples of the various rock types. In these tests the Schmidt Hammer Hardness, Abrasion Hardness and Shore Hardness are measured. Total Hardness HT is then defined as HR times the square root of HA where HR is the Schmidt Hammer Hardness and HA is the abrasion hardness. This has been correlated with penetration rates by tunnel boring machines on a number of other projects. Tests were also made on samples of rock from the Terror Lake Project at locations where the penetration rates were known. Penetra- tion rate is the advance in feet per hour of actual operation of the machine. The route of the tunnel vas mapped by geologists of Shannon & Wilson from outcrops along or near the alignment and a map presented showing the distribution and e~tent of the several rock types present. This is based on surface exposures only of course, but the relative amounts of the various types present are considered adequate as a guide to the relative amounts of the various rock types present along the tunnel line. A number of samples of rock from the earlier core borings were selected as being representative of the rock types anticipated. These were tested at the Rock Mechanics Laboratory at the University of Illinois. Attached is a report by Dr. Hendron dated June 21. 1983 summarizing results of the tests on the rock from the Bradley Lake and Terror Lake projects. The tests on Terror Lake samples were conducted because the rates of penetration· with a recently designed Robbins disk cutter machine vere known. For example, the Total Hardness of samples at station 241+59 averaged abouc 115 for three samples and the rate of progress observed vas 7.1 ft/hr. Table 1 attached summarized the geologic studies and rock tests to provide estimated penetration rates for each rock type and the estimat- ed amounts of each type along the tunnel. Also summarized on this table are estimates of widths of fault affected zones. gouge zones and temporary rock support required. These were developed in conference in your office on July 14. This table will provide a basis for compara- tive estimates to develop project capacity. .J J lt is understood that selected samples oi the several rock types will be submitted to manufacturers of tunnel boring machines who will provide independent estimates of penetration rates. These later data will then be combined with Table 1 for use in preparing the final estimate. It should be noted chat Table l was constructed on the assumption that the rock described in the field as "massive argillite" was as hard as the graywacke. In fact the rock described in the field as massive argillite might well be a very fine graywacke or a metamorphosed silicious siltstone. These studies indicate that the tunnel can be excavated using a tunnel boring machine. The rock here is significantly harder than that at Terror Lake and the rate of progress will be slower but should be much faster than drill and blast procedures. The present estimate is based on a tunnel profile with at 1.5% grade connecting to a steeply sloping shaft near the intake. The steeply inclined portion of the tunnel can be raise bored with presently available equipment and the same raise borer can be used to excavate most of the surge tank and the shafts for the intake gate structure. Boring Program The tunnel alignment was shifted northward at the Bradley fault in order to cross the fault zone where the zone appeared to be narrower from field and airphoto observations; we concur in this change and with the present location of the boring relocated to the present position of the tunnel crossing. We also concur with the boring located at the Bull Moose Fault and the elimination of the boring at the powerhouse. The boring at the powerhouse is to be replaced by surface trenches to verify the existence of bedrock. Summary We were very favorably impressed by the proposed layouts and the work accomplished. As indicated in our opinion the tunnel can be excavated using a tunnel boring machine. Penetration rates for a TBM were developed for the several rock types. Respectfully submitted, ~~~~?· A.J. Hendron, Jr. J/%~r W.F. Svi~ ) '· TABLE ROCK CHARACTERISTICS & TUNNELING DATA TUNNEL FROM D/S PORTAL TO LOYER BEND OF INCLINED SHAFT BRADLEY LAKE HYDROELECTRIC POWER PROJECT ALASKA POWER AUTHORITY Length ROCK TYPE (fc) Graywacke & Gra)""acke/Argtllite 4300 Massive Argillite 5000 Foliated Argillite 3500 Foliated Cherty Argillite (includes Dacite) 3550 Chert 5xl0•50 Fault Zones Bull Moose Bradley River Randotn Lineament Gouge Bull Moose 8radley River Random D/S Portal TOTAL LENGTH 350 200 200 200 50 3x5•15 50 17500 ft. *Additional Testing to be done Penetration Delay Hardness Rate (fc/hr) time 130 6* N/A 130* 6* N/A 70 13* N/A lOO(est) 9* N/A 190 3* N/A N/A N/A N/A N/A N/A N/A N/A 130 N/A N/A N/A N/A N/A N/A N/A Drill and Blast Section 60 days Total .. II " II " If Re-steel through fault area #8 @ 12 .. E.W. Temp.Supt Needs Select- ively located 3/4" dia. 6' long Mech.Anc. 2 bolts every 4 feet for 1650 feet =825 bole 2/3 sees io.'F4xl3 Full Circle Sets WF5x19 Full Sets WF4xl3 I J·) .. ,."::) __ ....... , i ... d , ,,. dJ ~ · ""''ron Jr 1 .11 i ""' ~....:; n .. ~ No 4 Coii.,Q• P••• Court PO. Bo• t]~ Sawoy, llllno•• b18/4 Dr. Gary Brierly Stone S Webster. Inc. P.O. Box 5406 Denver, CO 80217 Dear Gary: Phon •. 111 7) J~ t-8101 June 21 • 1983 J352 l•""'cooy. (]11) J~l-&700 14!'•~•: 170l~1'C~oc:t-ntt"t S•v t Caol•. GtOCENfER Enclosed is a summary of Bradley Lake Rock Tests. These include Schmidt Hardness, Shore Hardness, Abrasion Hardness. Unit Weight, Unconfined Compressive Strength. and longitudinal Wave Velocity test results. Calculated values of the total hardness are also included. At present the total hardness values are still the best index to correlate with machine tunnelling progress. In general it appears that the total hardness values of the argillite ranges between 50-100, while the total hardness of the graywacke ranges from 100-150, and the values for the chert-quartzite ranges from 170-200. AJH:jk enc Respectfully submitted, ~J·~@l· Alfred J. Hendron, Jr. -\.!) 2 ~S';)CJf1...1~ i' .q·...,~;,s , t ------1 ( :I --rr c-_. - - --1.1 0 --:;; . ~ v - r .- . ~·r ·-. --· • -r. .J> I r !: ( ~ ,., c -... ..) 4 .. .. SUMMARy OF ~K /ESTJJJ(; R£5UL TS 7£J~"R01\ LA K.f ~ A LAS K" UN II UtJCOllFIN~b IOTAL. LMJ 4 1 TV ~uJ!t L HI\ ~ ... "" CfiMP llE~SI~ ~..;Av~ ":< :;;:;' "' ~ ~ ... LOCATitJAl :SI1M1'L.E [) ES,Rii'IIO.V \N£16HT J/ til\ llun f VEL.(H.Ifp ~ " .... J STRE'.VL1TU :::: ~ Ill: .t> {pc.f) c <I < -.. "" (f\;)Q) ':.. ~ Q::' ot ~ '<( tlr (hi~ c.) "' .::,: .. \1) .... .f2'=t ':::t- ·r-----···--. -··--.... ·-·-... -" ---·· ·-··-·-.. Z1l.tr' A J1 Y"J)ItO ·fJIIRJIAuY -'"'·r"'l f ~.!I '·0" 7 z .Cl+ J1 L Uk. .i b ~ R. 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I 2 , u ' 'J z.. 2.:fltS'I 'b J,'t"3f.t 2,L4B+ J.1t..2.." 2.-+ 1 t S'\ c.. ~, 31.n 1... z r u... 1, q + 3.) ........... ~.------····· .. -..... ··-·.6 .... t \._,; AXI-1\. LoA~ 'rii) ,,oo I I IODO ~00 o---t) A-A G-f] <}--() \.._./ 2.-tt t5J.. A 2.41f·SZ.. B 2.111SZ. c 2. 4Z. f 1-l 'B sr;co A XI IlL Lo"b ys. So>JtC.. VE.Loc.JT'( ., -,;RR.ol?.. Lro<£) ALfisk:A ..... ~ •. ;, -·· . ,,,""!, ••. :-.~· •• ••. ·'·• ··-·· ...... ..:...:_ , •• ·• ··-........ -..J ··-.... .._.. -"""- 1(),('00 .5oAJ I l V CLOc 11·'(' (t•/SfLJ • r 11 ( 15",000 _) _) Dr. A.J. Hendron, Jr. 28 Golf Drive Mahomet, lLL 61853 (217) 351-8701 September 27, 1984 BRADLEY LAKE HYDROELECTRIC PROJECT BOARD OF CONSULTANTS REPORT Dear Sir: W.F. Swiger Box 388 Buhl, Idaho 83316 (208) 543-4593 The third meeting of the Board of Consultants convened in your office in Anchorage on September 25. We were briefed on status and program of the Phase I geotechnical investigations. We visited the site on September 26. Further discussions were held and this report was prepared on September 27. The borings and field studies completed since our second report of July 15, 1983 were reviewed. GENERAL These further studies confirm the earlier preliminary design which served as a basis for the feasibility report for the project. We conclude: 1. The powerhouse location is satisfactory. 2. The axis of the dam is satisfactory and a concrete faced embank- ment dam is economical and preferred. 3. The tunnel can be excavated using a tunnel boring machine. ..... 2 September 27. 1984 4. The thickness of fault zones and of gouge in the Bradley River Fault and Bull Moose Fault are in reasonable agreement with values previously assumed and can be tunneled through. 5. The location and proposed design of the spillway are satisfac- tory. 6. The present geotechnical investigations are directed to develop- ing information necessary prior to proceeding with design. We consider the program reasonable but do make below some sug- gestions regarding priority of the boring work and presentation of data. INVESTIGATIONS The present investigations reviewed by the writers included the geologic mapping., the drilling of exploratory core holes. and the description of the rocks encountered in both the field mapping and the rock cores. Core Holes Due to the li'mfted working time available this fall, it is extremely important to assign priority to the core holes to be completed at the high elevat.ions. In our opinion, first priority should be assigned to Core Holes 9 and 14 to make sure the intake portal is in a location to provide stable slopes. We agree that Hole 9 should be inclined southward across the possible fault and we agree that Hole 14 should be inclined westward and should be revised to a length of 250 feet to compensate for being moved to a location approximately 50 feet higher than the original lo.cation. Core Hole 16 should be the next priority in order to define the depth of rock cover above the tunnel and to define the width of the possible fault zone. The location of Hole 16 should be moved far enough north in the valley in which it is located that it is located on the north side of the hypothesized fault and that it will cross the fault if it is inclined to the south. The present seismic surveys should be used to locate the most advantageous position for Core Hole 16. Core Hole 43 is next in order of priority and is necessary to define the extent of soft ( _) 3 September 27. 1984 materials in the area of the spillway. Core Hole 17 at the gate shaft is next in priority and is essential to furnish information on the quality of rock at the proposed gate shaft location. To provide time for completing the core holes listed this year. it is our recommendation that Core Holes 24 and 72 be deleted from this year t s program. Core Hole 72 is not essential to locate the depth to bedrock at the powerhouse because of the outcrops and because of the planned trenching. Core Hole 24 is not necessary at this time. Early next year it is important to provide enough drill holes to determine the location of the toe slab of the dam in order that the design may be based on a fairly accurate geometry concerning the top of rock. We concur thac two cest trenches be excavated across the powerhouse locacion in order to define the top of rock. The rock discontinuities should also be mapped such that the orientations could be used to indicate orientation critical to any cuts in close proximity to the trenches. We recommend the overcoring and oriented core work be deferred. Field Mapping We have discussed in detail the geologic mapping with R&M Consultants and Stone & Webster personnel. One of the primary purposes of mapping in the areas of any proposed rock cut is to document the orientation of disconti- nuities such that appropriate wedge analyses can be conducted. It is also helpful to describe the continuity and planarity of the surfaces and the smoothness or roughness of these features. Another purpose of the continuous mapping along a Northwest-Southeast direction such as the power tunnel or access road alignment is to get an indication of the percentage of different lithologies which will be encountered by the tunnel. This is important because the tunnel most likely will be bid by a contractor based upon the use of a tunnel boring machine. The rate of progress will be sensitive to the type of rock encountered. According to hardness tests already conducted on this study, the hardness of the various rock types vary considerably and. therefore. .. ' , . 4 September 2i, 1984 any estimate of average tunneling progress is highly dependent upon the percentage of each rock type encountered. lt is also imperative that the rock outcrops in the field be consistently described lithologically such that it can be determined which rock type in the field is represented by certain laboratory core specimens selected for hardness testing. In past mapping and testing of the rock formations at the Bradley Lake site, ther~ have been no ambiguities concerning the descriptions in the field or cores of rock types designated as graywacke, massive chert. or foliated argillite. For these cases, we believe that the description of the field outcrops and rock cores has been consistent. We believe, however, that in past descriptions, the field outcrops described as "massive" argillite, a rock type which all parties agree is very hard and silicious, may be more appropriately described as a very fine-grained graywacke. This is important because this in effect means that a larger percentage of the tunnel will be excavated in graywacke than was indicated in the feasibility report. lt is recommended that these materials be described as very fine-grained graywacke when encountered. Large blocks of this material should also be obtained from the field to enable rock cores to be drilled for hardness tests. If these borderline materials are described as fine-grained graywacke, then the following guidelines should be used in designating the character of the following lithologic bands in field mapping. GRAYWACKE ARGILLITE CHERT ARGILLITE W/ CHERT NODULES DACITE Greater than 75% graywacke, less than 25% argillite. Greater than 75% argillite, less than 25% graywacke. Massive chert. Describe % of chert. 100% dacite. f • ,) s September 27, 1984 It is our opinion that the hardness tests made on rock cores described as massive argillite and foliated argillite and which are presented in Tables 7.4-4 and 7.4-5 (S -A.J. Hendron, SWEC), are tests on samples which are properly described as argillite. This is confirmed by the fact that the hardness values shown for these materials in Tables 7. 4-4 and 7. 4-5 are nearly identical. It is our opinion, however, that most of the field outcrops mapped previously as 11 massive" argillite are silicious and, as discussed above, should be classified as fine-grained graywacke. Probably this inconsistency developed because classifying these rock in hand specimens from outcrop is difficult. It is properly identified as graywacke in cores because the bit cutting through the sand grains, even though they are very fine, results in the gray color typical of graywacke. It is nevertheless unquestionable that, whether this material is called "silicious" or massive argillite as in past mapping or fine-grained graywacke, it is hard, very difficult to break with a hammer and has a hardness more in line with the 125-150 associated with graywacke than with the range of 60-90 associated with argillite and for the purpose of evaluating tunneling progress should be classified as graywacke. It is suggested that the R&M geologists visit several field outcrops previously' mapped as "massive argillite" such that they can calibrate their current descriptions 'W'ith the previous mapping. Several previous core descriptions should also be checked. It is recommended that the current field mapping effort be extended next spring and summer to map the valley just to the southeast of the tunnel alignment from the powerhouse toward the southeast. This mapping should be continued up and over the top along the tunnel to Bradley Lake. The geologists should continue their practice of obtaining samples from designated observation points so that the information is not lose and such that discussion of rock identification can be continued in the office at any time. The current work being done is very well documented in this fashion and is commended. It is suggested that Stone & Webster Engineering make the samples which were tested for hardness at the University of Illinois available to the . • • • l 6 September 27. 1984 R&M geologists. They should describe these samples lithologically in the same manner currently being used. It is also suggested that a thin section of the "massive" chert be studied to possibly refine or change that description. MARTIN RIVER DELTA The Martin River Delta appears to be a good source of road and concrete aggregate. The aggregate should be tested for possible alkali aggregate reaction as soon as possible because of the "cherts" vhich are found in the formation. Respectfully submitted. / \ -..::::::L.Ll;.aL:::::£:::ts:4.....:.l.c::::.....::..LL.::....::......,;: ~) A.J. Hendron. Jr. AJH:WFS :md ) ) November 7, 1985 BRADLEY LAKE HYDROELECTRIC PROJECT BOARD OF CONSULTANTS -REPORT 4 The fourth meeting of the Board of Consultants convened in your office on November 4, 1985. We were briefed on the findings of geotechnical investigations recently completed in 1985, status of laboratory testing programs and schedules for obtaining bids and undertaking the project. Prior to the meeting we were provided studies of certain action items on which our op~n~ons were requested. There was discussion of design of the dam, tunnels, roads, barge facilities and site work. There vas a short discussion of the construction schedule. Action Items A. Lovering of Diversion Tunnel Studies have been made of lowering the Diversion Tunnel to invert elevation 1,068 and excavating the downstream Bradley River Channel to elevation 1,060. We concur with the Engineering studies and their recommendations that these be done. B. Economic Power Conduit Diameter c. BL-D-131 The Engineer's studies indicate 11.0 ft. ID to be the most economic tunnel diameter. We consider this the minimum acceptable diameter, but suggest that the diameter not exceed 12.5 ft. Penstock Safety Evaluation Five proposed alternative schemes of penstock arrangemen.t at .the powerhouse were presented. We concur that Alternative 4 as shown on SK-15500-FS-D with the tunnel and penstock grade lowered to El 20 is the preferred arrangement. 1 2 i-<uvcrnber 7, :'J85 D. Turbine Setting Analysis Economic comparisons were presented of the effects of setting the centerline of the turbines at five different elevations from El 20 to El 10. These showed the originally assumed setting of El 15 (BLPD) to be the most economical. We concur with setting the turbines at El 15 and installing piping for air depression should future experience show it to be desirable. E. Earthquake/Tsunami Review The outline of studies of Tsunami hazards for the powerhouse and seiche and slide hazards in the lake were presented. We concur that these studies are needed and that the approach is appropriate. Power Tunnel Recent failures of unlined or plain concrete power tunnels have occurred due to hydrofracturing in locations where the minimum principal stress . in the rock formations is less than the static pressure .levels in the tunnels. To avoid this problem on the Bradley Lake project we recommend that the steel lining be lengthened to a point where the rock cover is 0. 8 times the static head. We also recommend that a hydrosplitting test be conducted at tunnel grade in a vertical hole cored 50 feet off the centerline at station 24 + 00. The hole should be grouted when the tests are completed. If the minor principal stress, ~3 , determined from the hydrosplitting test is greater than 1.2V H i , then the steel liner should be reduced in ow stat c length such that the end of the steel lining is at station 24 + 00. A transition section of reinforced concrete should extend from the end of the steel lining to station 36 + 00 where the static head and the rock cover are approximately equal. The circumferential reinforcement should be about 0.5 percent or one row #8 bars at 1 ft. center. The longitudinal steel should be the normal shrinkage steel of about 0.3 percent. Additional low modulus zones along the tunnel should also be reinforced such as at fault zones etc. These lengths and locations will only be known when the actual tunnel is driven and should be designated by the engineer between the time the tunnel is driven and when the concrete is poured. The contract must be flexible to accommodate this process. BL-D-131 2 ) Novcmbct: 7, l9t!5 We recommend re-logging of all Corps of Engineers and Shannon & Wilson cores for lithological descriptions consistent with recent R & M logging. This re-logging should be by the same persons who did the recent logging. An attempt should be made to develop a uniform notation in order to minimize the re-logging effort. We recommend the preparation of a preliminary out line of a Geotechnical Report, to be included with the Phase II Contract Documents. This outline should be available for review prior co the next Board meeting and should be discussed at that meeting. An NX core hole should be cored through the prominent lineation at Station 115~. Attempt to cross the lineation in fresh rock about 100 feet below the surface. This will require about 400 feet of angled core hole. R & M to log as above. Preliminary data concerning the material to be tunnel liner were presented to the Board. considered appear to be suitable and we suggest in final selection should be weld-ability. DAM used for penstock and The three materials that the major factor The Board requests they be furnished with existing dynamic analysis of the dam and with details of procedures and parameters being used in any additional analyses being made. The Board would also appreciate being furnished detailed topography of the toe slab contacts, especially along the right abutment. We-shall be interested in reviewing details of joints and waters tops. We prefer rubber with sleeve joints for wate~ stops. Zoning of the dam should be kept to the necessary minimum. We recommend Zone 1 be about 15 feet. wide. This should be well graded material grading from not more than three-inch maxim~ size t.o fines to achieve a permeability of not more than about 10 em/sec. This should be underlain by a Zone 2 which is 15 to 20 feet wide of rock grading to 12-inch maximum. Care must be taken in placing this material to prevent segregation at its contact with the Zone 1 material. These should extend to foundation level. From rock to about 10 feet above the foundation should be select. clean rock. The remainder of the dam may be constructed of quarry run using argillite, graywacke and other rock types as may be present. Rock sufficiently large that it would protrude above the surface of the lift after compaction should be placed in the oversize zone on the downstream slope. The boundary between the oversize and random zones should not be fixed on the drawings. BL-D-131 3 November 7, 19S 5 Spillway The flip bucket must be founded on sound rock. No special treatment in the design of the flip bucket is required to accommodate small spillway discharges; however the flip bucket should be designed to drain. Drainage should be provided under the spillway chute. Power Intake We suggest that the design of the intake be predicted on good hydraulic engineering and constructibility considerations. Adequate space is needed for a substantial rock plug, rock traps and construction access. We believe all rock materials in the intake knob are suitable for the quarry run sections of the dam. We concur that a hydraulic model test of the area is required. Schedule For the next Board meeting revise schedule to: a. Lengthen tunnel boring machine excavation 3 months and revise impacted items. b. Shorten "concrete line power tunnel" 3 months • . c. Add "and erect" to "fab and del 'IBM". Switchyard We agree that the switchyard should be moved to the rock area northeast of the powerhouse. thus avoiding possible liquefiable material in the location north of the powerhouse. Quarry Discussions indicated present plans are to produce 70,000 cy of riprap by quarrying 150,000 cy of dacite dike. We believe that the quarry will yield less riprap size material and that the under-run will not be made-up from the access road rock excavation. Transmission Lines We concur with the conclusion that the number of towers in liquefiable soils should be minimized. Barge Facility We agree with the project team's conclusions regarding the concept and location of the barge unloading facility. BL-D-131 4 ) / November 7, 1985 Road Cuts We agree chat 0.5:1 average slopes for the road cuts are reasonable. For those areas where the road cuts are higher than 30ft., we suggest however, that possible wedges formed by the intersection of only "smooth" discontinuities, as plotted on stereonecs, be checked to see if the lines of intersection of these smooth planes are such that they daylight into the proposed cut. If so. then the cut should be flattened such that daylighting of unstable wedges bounded by "smooth" planes will not occur. Borrow Areas We agree with the testing underway to check the adequacy of these materials for concrete aggregate. We agree with the possible use of low alltali. Type II cement. We concur with the engineer's effort to select borrow area to minimize the chert content. We trust the foregoing discussion covers all of the material covered in our meeting of November 4 and 5, 1985 and suggest the Board reconvene on January 27, 1986. Yours very truly, A. J. Hendron .· BL-D-131 5 -·---- ( '!.'~I"\ ' - November 25. 1985 Mr. A. J. Hendron, Jr. 28 Gulf D1:ive Maboaet, IL 61853 TECHNICAL B.EVIIW BOARD REPORT FOURTH MEETI'NG OF BOARD OF CONSULTANTS BRADLEY I...AKE HlDRO!LECTB.IC PROJECT • J.O. 15500.12 T2.l Attached for your informacion and file is a copy of the report submitted by the Board, following ita fourth meeting with che project. The Board baa ezpreaaed its agreement on several concepts and design conditione presented at the meeting. In addition, the Board has made several recommendations which will be considered in our design. Regarding the above and in reference to the Board's report • we have written co the Power Authority of our intended actions, as follows: Ac cion I cams A. Lovering of Diversion Tunnel -we are proceeding wich the lowering the diversion tunnel by 10 feet and for excavating the downstream Bradley River channel co elevation 1,060. B. Economic Power Conduit Diameter -we are proceeding on che basis of an 11.0 ft power conduit diamecer. C. Penstock Safety Evaluation -we are proceeding on the basis of Alternative 4. with the tunnel and penstoc~ grade lowered to elevation 20. D. ·turbine Secting ~o~e are retaining the originally and. E. liL-0-tJl preferred unit cenccrline setting ac elevation LS (BLPD). Earthquake/Tsunami Revic~o~ studies on these c~o~o areas. ~o~e arc continuing ~o~ich our • 2 Power Tunnel We are extending the steel lined portion of the tunnel to a point where rock cover is 0.8 times the static bead. Potential reduction of this length will be based on hydrosplitting tests conducted at tunnel grade. Also, we will incorporate the Board's recommendation for a reinforced concrete lined tunnel section beginning at the upstream end of the steel lined section and ending at a point along the tunnel where the rock cover is approximately equal to the maxtawa static bead. The Board's recO'IIIIIlendation for reinforcing the concrete liner along the fault zones and at low modulus zones vas considered in our design and shall be retained as a project requirement. We will implement the Board's recommendation for re-logging all Corps of Engineers and SbaD.Don & Wilson corea for lithological description. Also, the Board recommendation for an NX core hole at station 115 :t, and completion of holes RM 15 and RK 23, vill be scheduled for drilling under the Phase I construction contract. These boles will be logged and tested with the assistance of our subcontractor a&M Consultants. An outline of the geotechnical report will be made available to the Board for ita review and comment. Dam. Spillway and Power Intake Reco'IDIIlendations and design related parameters presented by the Board vill be incorporaced in the project design. Schedule The Board baa requested some revisions to the Phase II construction schedule. The schedule pt:asented to the Board showed a potential sequencing and timing of construction efforts believed reasonable, based on information and data known at the time of its preparation. We will present and discuss the Board's comments to the Power Authority. It is our recommend at ion that the Power Authority's Construction Manager review the Phase II construction schedule requirements to ascertain whether any adjustments are necessary at this time. Scheduling of construction activities vill be the responsibility of the selected Construction Contractor and will be subject to Power Authority's approval. We will work vith the Power Authority and its Construction Manager during the review of a project construction schedule. The construction schedule resulting from these efforts shall be presented to the Board in January. 1986. 1f available. 3 Remaining '\opics The Board' a recouaendations aa.d/or cOIIIIU!nts regarding the switcbyard, quarry, cr~sion linea, barge facility. road cuts and borrow areas are being considered and, ae appropriate, will be implemented in the design of these project facilities. Should you have aa.y queatioa..e or require additional information, please lee us ~ow. Theodore Criti~oa Deputy Project Manager TC/JJ Attachment cc: Mr. Bob A. Dortch, R&M Consultants, Inc. Mr. w. Robertson, R&M Consultants, Inc. Mr. Delbert s. LaRue, Dryden & LaRue NOTED N 0 V 2 5 1985 r. Critikos Note: Same letters went to Mr. White, Mr. Sperry, and Mr. Swiger. BL-D-111 ,, . ) \ _) A.J. Hendron, Jr. 28 Gclf Drive Mahomet, IL 61853 (217) 351-8701 January 29, 1986 P. E. Sperry 21318 Las Pilas Rd Woodland Hills, CA 9136~ (818) 999-1525 BRADLEY LAKE HYDROELECTRIC PROJECT BOARD OF CONSULTANTS -REPQRI 5 J. N. White PO Box 2325 Boston, MA 02107 W.F.Swiger Box 388 Buhl, ID 83316 (208) 543-4593 The fifth meeting of the Board of Consultants convened in your office on January 28, 1986. We were briefed on the status of licensing and permits for the work, schedule for the Phase I contract, status of studies previously discussed, review of drawings and work in progress for the Phase I contract, and ·a review of design activities for the Phase II work. Prior to the meeting we were furnished preliminary drawings for the Phase I work and an agenda for the meeting. Also we were furnished a copy of the FERC license, the Mitigation Plan, License Application to FERC -Volume 4 "Preliminary Design Report Design Criteria -Site Preparation Contract and an outline of the Geotechnical Report. PHASE I CONTRACT Barge Unloading Facilities A review of the proposed design of the barge unloading facility was initiated to investigate possible redesigns having lower costs. Suggestions by the CM and R&:M were reviewed. The CM suggested using partial cells to provide a vertical face for unloading. R&:M had proposed limited use of complete cells. A primary concern in design has been response of the structure to earthquake since liquefaction of the underlying loose sands probably would occur. Prevention of this is not economically feasible. Accordingly, it has been agreed this facility will be designed and accepted as a temporary structure for construction only. From our review and discussions we recommend that at least two barge unloading positions be available. Roll-off capability would be desirable. We believe a deck elevation of about El. 16 would be acceptable but a layer of rock should be incorporated near the top of 2-230-JJ 2 January 29, 1986 the cells to minimize wave scour. We believe the partial cells with tie-back sheet pile walls would be significantly more susceptible to collapse under earthquake than complete circular sheet pile cells. Accordingly we recommend full circle cells be used. Possible plans were discussed. We understand R&H will make additional layout studies considering berthing of two barges and dock width necessary for truck turnaround and unloading cranes. Riprap Along Roads Present drawings of road embankments which could be subjected to wave action are to be protected by 2 layer riprap toed into the underlying soil. We suggest such toeing is not to be done. Rather the riprap and filter fabric be placed directly on the existing soil surface and carried out horizontally as considered necessary. Present studies of haul roads for construction of the main dam show the roads entering at the upstream face. This would require several crossings of the toe slab for the face since this toe slab must be in position before the fill can be placed against it. Such crossings pose severe hazards of damaging the water stops. We suggest this be reviewed further considering possibilities such as alternative roads into the dam or use of a movable bridge to span the downstream face of the toe slab. The Board requests they be fUrnished with the assumptions used in the dynamic analysis which will be used to judge the adequacy of the dam slopes under the Maximum Design Earthquake (MDE). The critical wedges considered should be shown; and, the calculated inelastic displacement should be shown for each wedge considered. The basis for the selection of the safe permissable inelastic displacement under the HDE should also be given. The dynamic analysis should be done as soon as possible because any change in the downstream slope would significantly affect the area available to pass the spillway flows or the emergency low level outlet flows. The basis for sizing the riprap at the downstream toe of the dam must be addressed. A hydraulic model study of the area downstream of the dam should be conducted for this purpose. Spillway Based on the review presented, we believe the infrequent use of the spillway does not require elaborate measures to protect the rock downstream of the agee. We therefore suggest the design of the spillway be based on the following principles: 2-230-JJ '. ) ) 3 January 29, 1986 1. The ogee should be straight. 2. The apron should be as short as possible and arranged to flip the flow onto the natural rock. This should be located on sound rock. We recommend a hydraulic model study be conducted to investigate the flow conditions at the downstream end of the emergency outlet tunnel and the flow over the natural rock downstream of the spillway. The principle need for these hydraulic model studies is to investigate flow velocities and wave action along the toe of the dam. BLASTING The Board recommends that the use of •line drillingw (reference Geotechnical Design Criteria, 12-18-85 (page 42) be changed to ftcushion blasting 'With guide boles. • "Cushion Blastingw (page 43) should be redefined to be nominal 3 inch holes drilled on maximum 24 inch centers at the excavation limit, loaded lightly and fired as the last delay of the round. A guidebole, used with cushion blasting, is drilled halfway between each pair of cushion blasted holes. Guide holes are not loaded. Burden on cushion holes should be 1.5 times the spacing (3' burden for the specified 2' loaded hole spacing). Blast hole maximum diameter in the powerhouse/switchyard area should be limited to 4" for excavation above El. 18 and 3" below El. 18. It is suggested that the specification for "smooth wall blasting" in the tunnel (page 43) include that the adjacent blast holes (first row in from the perimeter boles) are drilled parallel to the perimeter holes. This produces a uniform burden on the perimeter holes, resulting in less blast damage to rock outside the excavation limit. Considering the excellent quality of rock expected in the diversion tunnel, this ftsmooth blasting" technique should produce greater than 80% half casts. The specifications could require the contractor to change his blast design when half casts are less than 60% rather than 33% (page 43). The Board understands that the peak particle velocity criteria (page 44) will be revised. Also that Note 5, drawing 171A and Note 7, drawing 171B will be rewritten. There was much discussion on design assumptions and blasting specifications for the excavation below El. 18 in the powerhouse. The Board suggests that additional study be made of the cost of vertical bolting reentrant corners (corners which protrude into the excavation) plus cushion blasting 'With guide holes, vs. directing the contractor to minimize damage to the remaining rock and to backfill all overbreak with structural concrete. Report at next meeting. 2-230'-JJ t, I • January 29, 1986 Design recommendations are: 1. Show neat excavation line on the drawings. 2. Base the design on, and tell the contractor to anticipate overbreak on re-entrant corners of a chamfer of 30 degrees off vertical starting 6 feet either side of a re-entrant corner and extending to a depth of 6 feet below the bench. 3. Tbe factor ot safety of the powerhouse against uplift should be 1.05 times minimum dead weight of the structure. Use tiedown anchors, rather than relying on rock friction, to increase FS against uplift to FERC standards. It was agreed the excavation walls above El. 18 should be vertical. Diversion Tunnel Tbe diversion tunnel upstream of the gate shaft will be concrete lined. Tbis liner should be contact grouted after curing with pressures of about 50 psi. If it is desired to grout some open fracture zones around this tunnel, the grouting should be done after tbe liner is poured. The grout curtain around the tunnel just upstream of the gate shaft should be done by grouting out from the tunnel. Tailrace Further study is needed on both the design slopes and the lining of the tailrace channel. The 2:1 slopes presently proposed need to be justified. It is our judgment that these slopes may not be sufficiently conservative. Fabriform should be considered as an alternate to replace the riprap which is currently the revetment material used in the proposed design. Aggregate Preliminary concrete mix data were presented together with a study by Mr. Van Epps of Stone & Webster. These showed the fine aggregate to be harsh and rather poorly graded. The fine aggregate is too coarse. The fineness modulus is 3.3 which is not within the limits of ASTM C-33. The grading curve shows the material to be deficient in material between 3/8 inch size and No. 16 and in minus 100 sizes. The design mixes showed adequate strength but the mixes were harsh and bled excessively. These mixes would not be pumpable. Further studies are needed of how to assure improved grading to improve workability and to reduce bleeding of the concrete. To minimize problems at this time it is suggested the Phase I contractor produce material from the Hartin Creek borrow area as the available source there dictates. Additional sources should be identified with the 2-230-JJ ) 5 January 29, 1986 intent that blending sand be obtained and furnished by the Phas~ I contractor as necessary for his work. Blending sand could then be obtained and furnished by the Phase II contractor as necessary for his work. fERC Board Meeting The following. list or materials should be sent to the Board as soon as possible to enable review before the March 6 and 1 meeting. Phase I Specifications Phase I Plans Geotechnical Report wjthout Photographs Any other documents to be issued to Phase I bidders It is also required that Stone & Webster propose a definite plan for obtaining adequate quantities of concrete aggregates which satisfy the appropriate fineness modulus values. 2-230-JJ , , . . . . . 6 January 29, 1986 The Board believes the above comments are self-explanatory but should you have questions please contact us and we will respond promptly. Yours very truly, A. J. Hendron / W. F. Swiger 2-230-JJ Mr. D. R. Eberle Project tlanager Alaska PoHer Authority P.O. Box 190869 Anchorage, Alaska 99519-0869 TECHNICAL REVIEH BOARD SIXTH REPORT BRADLEY LAKE HYDROELECTP~C PROJECT :·!ay 2 1 , 1 9 8 6 J. 0. No. 15800 T2. 1 S\EC/APA 711 The report on the sixth meeting of the Technical RevieH Board, comprised of new members Mr. Barry Cooke and Hr. Joel Justin and continuing raember ~lr. Jim White, is attached. We are replying to the thoughts and ccmments of the Board by means of the attached document titled nResponse to Technical Review Board Sixth Report". This document outlines the Stone & Webster thinking or approach on each of the project areas remarked on by the Board. The response represents our nstatus of thinkingn, not a firm or final position on all issues. The issues discussed will be addressed in the up caning Second FERC Board of Consultants' meeting, and the refined concepts will be presented to the Technical Review Board at the Seventh meeting in July. Please feel free to comment on this report, and \Je will be happy to place any item of interest on the weekly design progress review meeting agenda . Theodore Critikos Deputy Project Manager Enclosure TC/LCD/JW 1-280-JW J. Barry Cooke 1050 Northgate Drive San Rafael, CA 9~903 May 8, 1986 Mr. J. J. Garrity Project Manager Joel B. Justin 2~01 Pennsylvania Ave. (17-B) Philadelphia, PA 19130 Stone & Webster Engineering Corporation 800 "A" Street Anchorage, Alaska 99501 BOARD OF CONSULTANTS SIXTH REPORT BRADLEY LAKE RIDROELECIRIC PROJECT J;/e T:L James N. White P.O. Box 2325 Boston, MA 02107 The sixth meeting of the Board of Consultants convened in your office on May 6 through 8, 1986. The new Board members Mr. Barry Cooke and J. B. Justin joined Mr. J. N. White, Chairman of the Board, to continue the Technical Review Board. May 5, 1986 was used for briefing the Board by the Stone & Webster staff on background . information design, licensing and major project features with particular emphasis on the geology and geotechnical tests and mapping. May 7 and 8 were a complete review or details of development and status of design with the development of the design criteria. The staff was well prepared for the presentation and covered all the elements of Phase II of the project. The presentations included Hydraulic Model Tests being done at Colorado State University, which include the power intake tunnel, the spillway and the diversion tunnel. These tests are to be continued to determine the conditions downstream of the spillway and also to include a model for the low level outlet within the diversion tunnel. 2-623-JJ Mr. J. J. Garrity Stone & Webster Engineering Corporation -2-May 8, 1986 The Board is in agreement with the· criteria as proposed for the loads and values as proposed by the Design Staff of Stone & Webster. This includes the criteria of seismic loadings, the maximum probable floods, and other more normal loadings. It was agreed that the rock used in Zone 1 of the Rock Fill Dam should be a crusher run rockfill zone of minus about 3 inches graded material to form the base for the concrete slab. Compaction of Zone 1 and 3 rockfill will be accomplished by the use of 10-20 ton compactors with 4 to 6 passes. The face may be compacted by a vibratory roller of not less than 5 ton static weight or by a machine mounted plate vibrator. The face slab for this low dam and in severe freezing environment may be of uniform 12 inch thickness. The Specification should specify that Zone 1 rockfill near the toe slab be compacted by the plate vibrator. This is particularly necessary up to the right abutment. The right abutment will be cut back to a slope in the range of .25 -.35 H:1V to remove open joints and to regularize the toe slab. The Specifications should include that rockfill placing . procedures maintain the Zone 1 face horizontal and that within the rockfill 1. 3 H: 1V slopes are permitted as required by the Contractors. From the 12 ft horizontal width Zone 1 to the quarry run rockfill the layer thickness should ramp from 1. 25 ft to 3 ft in a distance of not less than 10 ft, except for special detailing near the crest. A discussion of the details of the joints of the concrete upstream slabs resulted in the following suggestions for development of these details. 1. All reinforcing steel in the slab should run vertically through any horizontal construction joints and also horizontally through the vertical joints. The reinforcing will be terminated at the periphery joints. 2. The vertical joints in the concrete slabs should be spaced 40 to 50 feet except for the vertical joint nearest the periphery right abutment joint. This section will be wedge shaped with about 20 feet maximum width adjacent to the right abutment periphery joint. 3. The periphery joint joining the slab to the toe slab will be made of a capped rubber across the joint over a mastic, and held down by bolts on a metal strip. The face slab and toe slab may be separated by pre-molded mastic joint filler, 1/2 or 3/4 in. thick. The copper waterstop at the base of the slab is desirable, but the center bulb waterstop could be omitted. Treatment of the vertical 2-623-JJ .l Hr. J. J. Garrity Stone & Webster Engineering Corporation -3-Hay 8, 1986 joint in the trapezoidal slab section next to the right abutment should be treated in the same as the periphery joints. All other vertical construction joints should be without water stop seals or other joint material. The toe slab reinforcing may be in the top only, a layer on the rock not being necessary. Current practice on length of toe slab pours and joints is to permit lengths dictated by topography or the Contractor's convenience, and to carry reinforcing through construction joints without waterstops. DIVERSION TUNNEL, GATE SHAFT, LOW-LEVEL OUTLET AND FISH RELEASE SYSTEMS -EMERGENCY DISCHARGE The Diversion Tunnel used during construction of the dam will be converted to an emergency discharge tunnel for the completed project. The maximum emergency discharge is estimated as 6000 cfs for the drawdown of the reservoir within 60 day.s. The discharge will be controlled by hydraulically operated dual, tandum gates 10 feet high x 7-1/2 feet wide. The operating controls for these gates are located at the top of the 106 feet shaft, 18 feet in diameter. The Board recommends that the design staff review the discharge· from the gates, provide for air to be distributed around the jet of water from the gates and the gates be arranged to discharge directly into the tunnel. The horseshoe tunnel would be lined with concrete. The fish release discharge of up to 100 cfs will be accommodated in the same manner as shown on Plate 10 with provision.s to accommodate the manifold within the outlet portal concrete. A model study is recommended of the emergency discharge from the gates into the diversion tunnel to evaluate the air inlet to the gate discharge and the flow conditions within the tunnel. The design staff should consider an alternate to the use of the Diversion Tunnel as an emergency outlet. Instead, the penstock manifold could be extended and provided with a Howell-Bunger valve at its terminus to provide this capability. The likelihood of the power tunnel becoming unavailable for this service is very remote, thus we believe the ability to draw the reservoir down will be unimpaired if this alternate is adopted. We also believe the alternate has an advantage that the lake can be drawn down below the foundation elevation of the dam because of the low invert elevation of the power intake. POWER INTAKE AND TUNNEL Reinforcing steel for the concrete lined tunnel should be placed only where weak rock exists. Drain.s behind the steel liner of the tunnel 2-623-JJ ' I. Mr. J. J. Garrity Stone & Webster Engineering Corporation -4-May 8, 1986 should be placed as indicated and discussed with the staff. Special attention of the possibility of running ground in fault areas of the tunnel should be provided in the contract documents. The transient analyses of pressures in the tunnel as provided by the staff are thorough and adequ3te. The Board endorses the omission of a surge tank, which is made possible by full use of the features of multiple nozzle vertical shaft impulse turbines. POWERHOUSE The revised concept of drainage behind the upstream wall of the powerhouse with tie backs at the columns is an improvement. The uplift analysis and the Tsunami protection is based on conventional and reasonable application of current state of the art. Fire protection equipment and facilities particularly in oil handling areas are being provided and some details are to be completed. The penstock arrangements for the power unit is satisfactory and the tailrace excavation in the tidal flats dredged with flat slopes is normal procedure. The design review provided by the staff was thorough and well prepared. We believe the basic project arrangement is sound and the design approaches are conservative. We trust our comments are clear but should you have questions please call us and we will respond promptly. Very truly yours, J. B. Cooke ~N. White 2-623-JJ ) RESPONSE TO TECHNICAL REVEW BOARD SIXTH REPORT The following outlines the Stone & i·iebster Engineering, Inc. (SWEC) position on the comll'lents made by the Technical Review Board ir-its 5-8 ~~Y 1986 meeting report. 1. I·Iodel Test: o Testing will continue on the power intai<e, spillway, and diversion tunnel (unlined, diversion operation code) as planned. Construction of the second phase, to model the spillway, rock apron, downstream pool and dam toe r'iprap areas is underway at this time. 2 • !1a. in Dam : o It was concurred that crusher-run rockfill of 3" minus gradation would be best for the Zone 1 fill (bedding layer) to be placed in 12-20' horizontal depth. Compaction and placement requirements, and topping-out of the dam prior to placing the slab was also in concurrence with current design philosophy. 0 It is agreed that a uniform 12 inch concrete dam facing slab is appropriate and simpler for the contractor. SWEC will confirm that local joint thickening at the toe is not necessary. o The right abutment cutback and special compaction proposed by SWEC was concurred with by the Board. o SWEC believes that keeping the lifts level (within 1 lift) in the upstream/downstream direction is important to quality control, and to minimize abnormal locked-in stress zones. Mr. Cooke's suggestion to provide for ramps and longitudinally oriented slopes in the fill are accepted. If slope:s tran:sver:se to the axis are necessary, they will be limited by specification to the downstream half of the dam, where uneven settlement and stresses are con3idered less likely to adversely impact dam performance. o lbe Board's concurrence with the SWEC proposal for two-way slab reinforcing i:s noted. While independent vertical joints and strip...slabs are the norm, we believe the two-way reinforcing without intermediate joints is beneficial in the severe seiamic and freeze-thaw environment because: a. Fewer joints mean les:s treeze-thaw damage, due to less openings. 1 b. Fewer joints should reduce initial leak~.ge (i.e., ~;hy create an intentional "weak spot" and potentially troublesome point-leakage source). c. Crack control can be by crack inducers, much as for highway paving, allowing shrinkaee cracks to form but only where they need to, rather th~~ intentionally putting in numerous open joints. d. 2-way reinforcing will improve continuity of slab action in the event of an earthquake, ~here individual slabs or panel strips could slump, buckle or otherwise deform relative to each other, introducing sie;nificant seepage along the separated joints. A continuous mid-slab layer of reinforcing will limit differential displacements and distribute deformations, reducing the size or cracks and, therefore, leakage quantity. The perimeter joints will be designed to be more tolerant of shrinkage to compensate for the reduction of joints. o The joint details at the perimeter vertical joint and plinth joint will be detailed with (in order from face of slabe towards rockfill): a. An extension-type cover seal of heavy rubber; b. l1astic sealant; c. A deformable board to handle compress! ve strain redistribution; d. A highly deformable pre-compressed foam sealer to enable entrapment of silt passing through a ruptured joint; and e. A positive embedded metal strip waterstop, with extension capability. o SWEC concurs with the toe plinth slab comments regarding reinforcing and joints. 3. Diversion·Tunnel Low-Level Outlet: o The diversion tunnel will be modelled to simulate the low-level outlet configuration utilizing gates and steel lined outlet structure. o The use of a release valve on the main power tunnel for a low-level outlet has been considered. However, two significant factors weighed against this option: t-279-JW 2 .... - 4. <>. The valve would he unu$ed and subject to r.luch Olt;ner head than the dive,·:·>ion tunnel gates, so much greater expense \>I'Ould be invol•Teci and much ereater inherent risk would be incur:"ed in the event of accidental opening, materials failure due to aging or l!laintenance errors. b. The primary pur~ose of the lo.,-level release gates is to a.ll0\>1 drawdown in the event of a major facility-damaging earthquake. Since damage to the intake slopes, portal or main tunnel (especially at the fault zones) are among the damage that could occur during a major· event, use of the main power tunnel as an emergency release conduit is considered imprudent when other comparable independent means is available. c. The argument for use of the power tunnel to allow for drmo~down below upstream dam toe level applies (in non-generating !!lode) to the current arrangement as well. However, it is planned to eliminate this need by designing the upstream cofferdam as a pez·manent structure. Therefore, by generating and/or releasing water through the low-level release system in the diversion tunnel, it will be possible to operate the plant in a run-of-river mode, and dewater the dam toe by pumping out the trapped water behind the cofferdam (crest elevation 1090). Power Intake and Tunnel o SWEC concurs in the basic philosophy regarding tunnel reinforcing, and the comments represent no change in design philosophy. o Credit for presence of the drains behind the steel liner will be discussed in subsequent meetings. 5. Powerhouse o The powerhouse area comments are accepted and represent no change in design philosopy. 1-279-JW 3 MEETINGS OF THE FERC BOARD OF CONSULTANTS . . Mr. D. R. Eberle Alaska Power Authority 5 December 8, 1987 Stability calculations for the spillway under static and dynamic loadings have been revised to conform to revised guidelines issued by FERC in the spring of 1987. Dynamic stability analyses were done by Finite Element Analyses, STARDYNE, to determine stresses and the SARMA program to evaluate the possibility of sliding. The analyses were based on bedrock accelerations of 0.75g. which is conservative. ~e concur that these studies show the spillway as designed to be safe under static and earthquake loadings. ~e have previously suggested consideration be given to providing for introducing air at the end of the flip bucket under the nappe of the spillway discharge to minimize possible erosion of the rock downstream of the spillway. Preliminary designs were developed for a system of pipes to supply this air. Estimated cost is about $70,000. In view of the very limited number of times there will be significant discharge over this spillway, we do not consider such an expenditure justified. 4.4 GROUTING -MAIN DAM AND SPILL~AY The proposed grouting program for the main dam is being reviewed. ~e concur that the amount of drilling and grouting can be substantially reduced. ~e concur with using a single row curtain generally with Jrovision for additional rows of holes at selected locations such as across zones of close jointing identified near the right abutment in the spillway. ~e suggest the primary holes be located about 20 feet on centers and that these extend to depths equal to at least 2/3 the head of water at the location considered. Intermediate holes should be drilled to give a spacing of 10 feet. Lengths of these intermediate holes and additional holes, as may be found necessary, should be determined from conditions disclosed by the primary holes. 4.5 MAIN DAM As indicated above, the rock under the downstream toe of the dam is sufficiently high that a formal downstream cofferdam will not be required. A berm for a road will be provided along the downstream toe. The slope below this berm will be covered by oversize rock, Zone 5 material, to serve as riprap. ~e concur with this approach but caution that this slope will be subjected to high velocity flow and wave action. If enough rock of adequate size is not available from the dam fill at the time needed, select rock should be obtained from the quarry. Drawing FY-192A-3 shows a gabion wall above the road along the toe of the dam at the right abutment. ~e do not concur with using a gab ion wall at this location and recomend the basic slope of the downstream face be extended to bedrock. 3504R/CG Mr. D. R. Eberle Alaska Power Authority 6 December 8, 1987 The hazard of landslides entering the reservoir in event of severe earthquakes has been reviewed. The only significant hazard is from flow slides due to liquefaction of deltaic materials at the head of the lake. These studies indicate the resulting wave would not overtop the wave wall along the crest of the dam. Review indicates the assumptions made in these studies were conservative. Further, limited overtopping of short duration due to such wave runup would not damage this rock fill structure. Accordingly we concur waves from possible landslides during even a great earthquake will not affect safety. 5.0 POWERHOUSE 5.1 EXCAVATION The excavation plan for the powerhouse has been revised based on new data supplied by the manufacturer of the major equipment. The new plan is simpler than the original and will, in our opinion, be less expensive to construct. We suggest the plans for rock bolt support of this excavation be reviewed to determine whether the number of bolts could be reduced. Consideration should be given using higher strength steel for these bolts in these studies since the cost of the bolts is a small portion of the total cost of such work. 3504R/CG Mr. D. R. Eberle December 8, 1987 Respectfully submitted. A. J. Hendron, Jr. Attachment NAME A. Hendron W. Swiger P. Sperry J. Parmakian D. Eberle J. Stafford N. A. Bishop *R. A. Joyet *P. Mayrose *J. Hron *W. Sherman ic'l'. Critikos E. H. Elwin * Part Time 3504R/CG ALASKA POWER AUTHORITY BRADLEY tAKE HYDROELECTRIC PROJECT SIXTH FERC BOARD MEETING DECEMBER 7 & 8, 1987 A'l"l'ENDEES LIST FIRM Consultant, FERC Board Consultant, FERC Board Consultant, FERC Board Consultant , FERC Board APA, Project Manager APA, Deputy Project Mgr/Engr. __ .;;..SWE..;..;;;;;;.;;;C, Deputy Project Manager SWEC, Chief Geotech. Engineer SWEC, Consulting Geologist SWEC, Chief Hydraulic Eng. SWEC, Chief Structural Eng. SWEC, Project Manager Bechtel, Field Project Engr. REVISED AGENDA Sixth FERC Board Meeting Bradley Lake Hydroelectric Project -Alaska Power Authority Meetinc Location: Stone & Webster Engineering Corporation 5555 Greenwood Plaza Blvd., Englewood, Colorado 80111-2113 December 7, 1987 i 8:30AM I. Introduction N. A. Bishop II. Project Status N. A. Bishop Site Preparation Contract Closeout N. A. Bishop General Civil Construction Contract Bidding Status N. A. Bishop Turbine-Generator Status J. Iiron Powerhouse Construction Contract Status N. A. Bishop III. Design Developments Penstock Thrust Blocks and Manifold J. K. Meisenheimer Powerhouse Excavation and Rock Support R. Joyet Spillway w. C. Sherman Downstream Cofferdam & Maindam Seepage Monitoring System R. Joyet Upstream Cofferdam R. Joyet Power Tunnel Intake Geotechnical Investigation R. Joyet Power Tunnel Intake Relocation N. A. Bishop rv. Other Discussion Investi1ation of Landslide-Induced Waved December 8, 1987 I 8:30 AM V. Discussion General Civil Construction Contract Design Addendum VI. FERC Board Report Preparation 2846R/Qf N. A. Bishop N. A. Bishop RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS SIXTH REPORT --DECEMBER 7-8, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FERC Board of Consultants Comment 6-l: 3.1 THRUST BLOCKS -PENSTOCKS AND MANIFOLD The Board has reviewed the Stone & Webster ·calculations regarding the overall Factor of Safety against sliding for the rock mass within which the thrust blocks are contained. In general these rock wedges are bounded by a horizontal surface coincident with the base of the tunnel and is bounded on the sides by two vertical planes which each diverge at 30° from the axis of the tunnel until they intersect the face of the Powerhouse cut. A vertical plane perpendicular to the tunnel at the upstream end of the thrust block defines the upstream end of the rock wedge. It is our opinion that shearing resistance should not be assumed to act on the vertical planes which form the upstream end and the side planes of the wedge. Thus, the shearing resistance developed to prevent sliding of the entire rock wedge is developed along the horizontal base plane of the wedge. In view of the fact that there have been no mapped ~iscontinuities which coincide with a horizontal plane, shearing along a horizontal plane would probably involve shearing through some intact rock or severe dilation along a complex system of intersecting discontinuities which would yield a high angle of shearing resistance. It is our opinion that at this location the effective angle of shearing resistance along this horizontal surface should be taken as so•. A Factor of Safety should then be computed on the basis. of frictional resistance only on the base of the wedge, and the Factors of Safety should be at least l. 5, l. 25, and 1. 05 for the Normal, Emergency, and Exceptional loadings. If these minimum Factors of Safety are not met, then anchors should be added to the thrust blocks. A preliminary check of the forces involved indicate that anchors will be required. The only other alternative to anchors would be to relocate the thrust blocks deeper into the valley wall where they are under higher effective stresses. Alaska Power Authority Response: The thrust blocks have been designed to meet necessary factors of safety based on assumptions for frictional resistance, shearing resistance, and failure mode. At the FERC Board's suggestion. an additional analysis will be performed to evaluate thrust block stability using the Board's criteria for only normal load and frictional resistance along the base plane of the resistinc wedge, and appropriately lower factors of safety. Anchors will be added to the thrust blocks design should the results of these analysis so indicate. Any such anchors will serve to further increase the reliability and safety of the thrust blocks. 3529R/CG RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS SIXTH REPORT --DECEMBER 7-8, 1987 FERC PROJECT NO. 8221-QOO BRADLEY LAKE HYDROELECTRIC PROJECT FERC BOARD OF CONSULTANTS COMMENT 6-2: 3. 2 INTAKE CHANNEL A low water inspection in front of the intake structure revealed a talus slope and a narrower rock bench between the lake and the intake structure than had been anticipated. On the basis of this newly developed information, the intake structure has been moved northward into the hillside and the cut excavation has been re-designed. Preliminary model tests have been conducted at Colorado State University on the changed geometry at the intake structure and have been found to yield satisfactory flow characteristics. The newly desianed rock excavation for the intake structure will have 10 feet wide benches every 35 feet in vertical height and the slopes in between benches will be l.SV to lH. The new slope design does not call for pattern rock bolts. The Board agrees that the flatter slopes incorporated into the new design will not require pattern rock bolts. A rock trap should be incorporated into the desian, however, and further layout trials will be necessary to accODIDOdate the construction road down to El 1030. The Board enthusiastically supports this design change since it will eliminate pattern rock bolts, it will make the tunnel shorter, and it will provide 330,000 cubic yards of rockfill which can be used in the dam. This is an excellent example of value engineering at its best. Alaska Power Authority Responses: The final design for the intake will accommodate a construction road to El. 1030, and will include a rock trap. 3529R/CG RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS SIXTH REPORT --DECEMBER 7-8, 1987 FERC PROJECT NO. 8221-QOO BRADLEY LAKE HYDROELECTRIC PROJECT FERC Board of Consultants Comment 6-3: 3. 3 PENSTOCX CONNECTION Reference is made to Owg. No. l5800-FS-262A. care must be taken at the time of welding these final closure joints in the steel liner. In order to provide sufficient longitudinal movement and to minimize its effect on the weld shrinkage, most of the concrete encasement on both sides of this penstock cocnection should be deferred until the final closure welds are completed. Alaska Power Authority Response: Colllllent accepted. 3529R/CG RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS SIXTH REPORT --DECEMBER 7-8, 1987 FERC PROJECT NO. 8221-QOO BRADLEY LAKE HYDROELECTRIC PROJECT FERC Board of Consultants Comments 6-4: 3.4 POWER TUNNEL -PORTAL AT POWERHOUSE The downstream portal of the power tunnel has been revised as shown on Drawing 15800-FY-261-A, B, C, D, E and F in Addendum 1. Excavation slopes have been flattened and the long false tunnel eliminated. The excavation downstream of the portal will be crossed by a bridge. We concur with this change. The cut slopes above the portal should be covered by wire mesh to protect the road and portal from rock falls. We recOUI'IH!Ild that the concrete headwall at the portal have a minimum thickness of 1.5 feet. Alaska Power Authority Response: Comment accepted. 3529R/CG RESPONSES !0 FERC BOARD OF CONSULTANTS COMMENTS SIXTH REPORT --DECEMBER 7-8, 1987 FERC PROJECT NO. 8221-000 BRADLEY I..AKE HYDROELECTRIC PROJECT FERC Board of Consultants Comment 6-5: 4. 1 UPS'I'REAM COFFERDAM The upstream Cofferdam has been re-designed to utilize an impervious soil core or/and a PVC membrane. After viewing pictures and profiles of a backhoe trench along the centerline of the Cofferdam, the Board agrees with the new design. The new design is preferable to the previous design which relied on sheet piles as the low permeability element of the design. Alaska Power Authority Responses: No response required. 3529R/CG RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS SIXTH REPORT --DECEMBER 7-8, 1987 FERC PROJECT NO. 8221-QOO BRADLEY LAKE HYDROELECTRIC PROJECT FERC Board of Consultants Comment 6-6: 4. 2 DOWNS'l'REAM COFFERDAM AND SEEP AGE As several board members have already written in individual letters, we agree that the high rock elevation downstream eliminates the need for a downstream Cofferdam. We also agree that for the type of dam on this project that the USGS downstream gaging station is adequate for seepage measurement. Alaska Power Authority Responses: No response required. 3529R/CG RESPONSES 1'0 FERC BOARD OF CONSULTANTS COMMENTS SIXTH REPORT --DECEMBER 7-8, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FERC Board of Consultants CoDIDent 6-7: 4.3 SPILLWAY Additional investigations of foundation conditions under the spillway have been made to 1110re accurately define the rock conditions by excavating two trenches to rock. These showed the rock under the higher portion of the spillway to be slightly lower than previously estimated. This does not affect the design since design slopes will be extended downwards to the rock surface. The initial investigations indicated a possible fault near the right abutment. These further investigations disclose this is a narrow zone of close jointing rather than a fault. This will be sealed by excavating the weathered material, filling with dental concrete, and thoroughly grouting the zone. We concur with this approach but note that final depth of treatment should be determined after excavation. Stability calculations for the spillway under static and dynamic loadings have been revised to conform to revised guidelines issued by FERC in the spring of 1987. Dynamic stability analyses were done by Finite Element Analyses, STARDYNE, to determine stresses and the SARMA program to evaluate the possibility of sliding. The analyses were based on bedrock accelerations of 0.75g. which is conservative. We concur that these stu~ies show the spillway as designed to be safe under static and earthquake loadings. We have previously sugzested consideration be given to providing for introducing air at the end of the flip bucket under the nappe of the spillway discharge to minimize possible erosion of the rock downstream of the spillway. Preliminary designs were developed for a system of pipes to supply this air. Estimated cost is about $70,000. In view of the very limited number of times there will be significant discharge over this spillway, we do aot consider such an expenditure justified. Alaska Power Authority Responses: In view of the Board's comment, spillway aeration will be eliminated. 3529R/CG RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS SIXTH REPORT --DECEMBER 7-8, 1987 FERC PROJECT NO. 8221~00 BRADLEY LAKE HYDROELECTRIC PROJECT FERC Board of Consultants Comment 6-8 4.4 GROUTING -MAIN DAM AND SPILLWAY The proposed grouting program for the main dam is being reviewed. We concur that the amount of drilling and grouting can be substantially reduced. We concur with using a single row curtain generally with provision for additional rows of holes at selected locations such as across zones of close jointing identified near the right abutment in the spillway. We suggest the primary holes be located about 20 feet on centers and that these extend to depths equal to at least 2/3 the head of water at the location considered. Intermediate holes should be drilled to give a spacing of 10 feet. Lengths of these intermediate holes and additional holes. as may be found necessary, should be determined from conditions disclosed by the primary holes. Alaska Power Authority Responses: The design of the main dam and spillway grout curtain will be revised as discussed. The design drawings will be sent to the FERC Board for concurrence prior to issuing them to the bidders. 3529R/CG RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS SIXTH REPORT --DECEMBER 7-8, 1987 FERC PROJECT NO. 8221-QOO BRADLEY LAKE HYDROELECTRIC PROJECT FERC Board of Consultants CoDIDent 6-9: 4.5 MAIN DAM As indicated above, the rock 1.11lder the downstream toe of the dam is sufficiently high that a formal downstream cofferdam will not be required. A berm for a road will be provided along the downstream toe. The slope below this berm will be covered by oversize rock, Zone 5 material, to serve as riprap. We concur with this approach but caution that this slope will be subjected to high velocity flow and wave action. If enough rock of adequate size is not available from the dam fill at the time needed, select rock should be obtained from the quarry. Drawing 15800-FY-192A-3 shows a the dam at the right abutment. at this location and recommend extended to bedrock. gabion wall above the road along the toe of We do not concur with using a gab ion wall the basic slope of the downstream face be 'l'he hazard of landslides entering the reservoir in event of severe earthquakes has been reviewed. 'l'he only sip.ificant hazard is from flow slides due to liquefaction of deltaic materials at the head of the lake. 'l'hese studies indicate the resulting wave would not overtop the wave wall along the crest of the dam. Review indicates the assumptions made in these studies were conservative. Further, limited overtopping of short duration due to such wave runup would not damage this rock fill structure. Accordingly we concur waves from possible landslides during even a great earthquake will not affect safety. Alaska Power Authority Response 'l'he specification will be IDDdified to assure that enough rock of adequate size will be available for the specified Zone 5 material in the downstream dam toe area. 'l'he gabion wall will be eliminated by IDDdifying the access road and small turnaround area adjacent to the diversion tunnel outlet. 3529R/CG RESPONSES TO FERC BOARD OF CONSULTANTS COHMEN'l'S SIXTH REPORT --DECEMBER 7-8, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT Ferc Board of Consultants Comment 6-10: 5.1 POWERHOUSE EXCAVATION The excavation plan for the powerhouse has been revised based on new data supplied by the manufacturer of the major equipment. The new plan is simpler than the original and will, in our opinion, be less e.xpensi ve to construct. We suggest the plans for rock bolt support of this excavation be reviewed to determine whether the number of bolts could be reduced. Consideration should be given using higher strength steel for these bolts in these studies since the cost of the bolts is a small portion of the total cost of such work. Alaska Power Authority Response We will investigate the use of higher strength steel rock bolts in order to further reduce the number of rock bolts. 3529R/CG Dr. A. J. Hendron, Jr. 28 Golf Drive Mahomet, Illinois 61853 (217)351-8701 Mr. P. E. Sperry 21318 Las Pilas Road Woodland Hills, California 91364 Mr. D. R. Eberle Project Manager Alaska Power Authority P. 0. Box 190869 Anchorage, Alaska 99519-Q869 SIX'l'H REPORT -BOARD OF CONSULTANTS BRADLEY LA.1CE HYDROELEC'l'RIC PROJEcr 1. o IN'l'RODUcrioN Mr. John Parmakian 2695 Lafayette Drive Boulder, Colorado ao303 (303)499-5404 Mr. W. F. Swiger Box 388 Buhl, Idaho a3316 December a, 1987 J. o. No. 15800 T2.2 The sixth meeting of the Board of Consultants for the Bradley Lake Hydroelectric Project convened in the offices of Stone & Webster Engineering Corporation in Englewood, Colorado at 8:30 am on December 7, 1987. A list of attendees-and Agenda are attached. We were briefed on the project status, design IIIOdifications and General Civil Construction Contract Design Addendum. This report was prepared in the offices of Stone & Webster in Englewood on December 8, 1987. 2.0 STATUS A. Site Preparation Contract: All work complete and final settlement negotiated with Contractor. Final cost $25.5 million (Engineer's Estimate $34 million). Diversion Tunnel functioning properly. B. General Civil Construction Contract: Specifications and drawings were made available to potential bidders in September a, 1987, but dates. when bids are due have not yet been set. It is now estimated-the earliest bids could be received is April 1, 1988. If this is realized, construction could start about July 1, 1988 with commercial service in September 1991. 35042/CG Mr. D. R. Eberle Alaska Power Authority CUrrent work by Stone & Webster: Revised design Penstock Thrust Blocks Dam and Spillway Grouting 2 Power Tunnel Intake Structure Relocation Addendum (to APA, Bechtel & Consultant for Comments) Contract Drawings Specifications Geotechnical Interpretative Report Bid Items and Quantities Engineer's Estimate December 8, 1987 C. Turbine Generator: The turbine manufacturer has proposed a casing design in which the turbine casing will consist of bolted flange joints. This option will simplify the erection of the casing at the Powerhouse. To ensure that the bolted flange connections are tight it is planned to utilize seal welds at the outer periphery of the flange joints. These welds should be strength welds of sufficient size to insure tightness when the turbine casing is pressure tested at the required test pressure and also during embedment with the casing under pressure. D. Powerhouse Design: Construction contract drawings are 80'%. complete. 95% submittal scheduled for 2-15-88. E. Middle Fork & Nuka Diversions: All dams eliminated, diversion by canals only. Bid documents to be completed April, 1988. 3. 0 POWER TUNNEL 3. 1 THRUST BLOCKS -PENSTOCKS AND MANIFOLD The Board has reviewed the Stone & Webster calculations regarding the overall Factor of Safety against sliding for the rock mass within which the thrust blocks are contained. In general these rock wedges are bounded by a horizontal surface coincident with the base of the tunnel and is bounded on the sides by two vertical planes which each diverge at 30° from the axis of the tunnel until they intersect the face of the Powerhouse cut. A vertical plane perpendicular to the tunnel at the upstream end of the thrust block defines the upstream end of the rock wedge. 3504R/CG .. Mr. D. R. Eberle Alaska Power Authority 3 December 8, 1987 It is our oplnlon that shearing resistance should not be assumed to act on the vertical planes which form the upstream end and the side planes of the wedge. Thus, the shearing resistance developed to prevent sliding of the entire rock wedge is developed along the horizontal base plane of the wedge. In view of the fact that there have been no mapped discontinuities which coincide with a horizontal plane, shearing along a horizontal plane would probably involve shearing through some intact rock or severe dilation along a complex system of intersecting discontinuities which would yield a high angle of shearing resistance. It is our opinion that at this location the effective angle of shearing resistance along this horizontal surface should be taken as so•. A Factor of Safety should then be computed on the basis of frictional resistance only on the base of the wedge, and the Factors of Safety should be at least 1. 5, l. 25, and 1. OS for the Normal, Emergency, and Exceptional loadings. If these minimum Factors of Safety are not met, then anchors should be added to the thrust blocks. A preliminary check of the forces involved indicate that anchors will be required. The only other alternative to anchors would be to relocate the thrust blocks deeper into the valley wall where they are under higher effective stresses. 3. 2 INTAKE CHANNEL A low water inspection in front of the intake structure revealed a talus slope and a narrower rock bench between the lake and the intake structure than had been anticipated. On the basis of this newly developed information~ the intake structure has been moved northward into the hillside and the cut excavation has been re-designed. Preliminary model tests have been conducted at Colorado State University on the changed geometry at the intake structure and have been found to yield satisfactory flow characteristics. The newly designed rock excavation for the intake structure will have 10 feet wide benches every 35 feet in vertical height and the slopes in between benches will be l.SV to lH. The new slope design does not call for pattern rock bolt~ The Board agrees that the flatter slopes incorporated into the new design will not require pattern rock bolts. A rock trap should be incorporated into the design, however, and further layout trials will be necessary to accommodate the construction road down to El 1030. The Board enthusiastically supports this design change since it will eliminate pattern rock bolts, it will make the tunnel shorter, and it will provide 330,000 cubic yards of rockfill which can be used in the dam. This is an excellent example of value engineering at its best. 3. 3 PENSTOCIC CONNEctiON Reference is made to Dwg. No. 15800-FS-262A. Care must be taken at the time of welding these final closure joints in the steel liner. In order to provide sufficient longitudinal movement and to minimize its effect on the weld shrinkage, most of the concrete encasement on both sides of this penstock connection should be deferred until the final closure welds are completed. 3504R/CG Mr. D. R. Eberle Alaska Power Authority 4 3.4 POWER TUNNEL -PORTAL AT POWERHOUSE December 8, 1987 The downstream portal of the power tunnel has been revised as shown on Drawing FY-261-A, B, C, D, E and F in Addendum 1. Excavation slopes have been flattened and the long false tunnel eliminated. The excavation downstream of the portal will be crossed by a bridge. We concur with this change. The cut slopes above the portal should be covered by wire mesh to protect the road and portal from rock falls. We recommend that the concrete headwall at the portal have a minimum thickness of 1.5 feet. 4.0 DAM 4. l UPS'IREAM COFFERDAM The upstream Cofferdam has been re-designed to utilize an impervious soil core or/and a PVC membrane. After viewing pictures and profiles of a backhoe trench along the centerline of the Cofferdam, the Board agrees with the new design. The new design is preferable to the previous design which relied on sheet piles as the low permeability element of the design. 4. 2 DOWNS'IREAM COFFERDAM AND SEEPAGE As several board members have already written in individual letters, we agree that the high. rock elevation downstream eliminates the need for a downstream Cofferdam. We also agree that for the type of dam on this project that the USGS downstream gaging station is adequate for seepage measurement. 4.3 SPILLWAY Additional investigations of foundation conditions under the spillway have been made to a10re accurately define the rock conditions by excavating two trenches to rock. These showed the rock under the higher portion of the spillway to be slightly lower than previously estimated. This does not affect the design since design slopes will be extended downwards to the rock surface. The initial investigations indicated a possible fault near the right abutment. These further investigations disclose this is a narrow zone of close jointing rather than a fault. This will be sealed by excavating the weathered material, filling with dental concrete, and thoroughly grouting the zone. We concur with this approach but note that final depth of treatment should be determined after excavation. 3504R/CG RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 . FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT _ FBCC 5-1 GENERAL CIVIL CONSTRUCTION SPECIFICATIONS FERC Board of Consultants Comment: 3. 1 Geotechnical Interpretive Report A revision of the Geotechnical Interpretive Report will be available for final review on June 15, 1987. It is understood that the "new" shear zones found in the powerhouse excavation will be added to the report. It is also understood that the Geotechnical Interpretive Report and the Bechtel Report on the geology of the powerhouse will both be revised if necessary to be consistent regarding the percentage of argillite and graywacke mapped in the excavation. Response: Comments from the Alaska Power Authority to Stone & Webster on the Geotechnical Interpretive Report (GIR) have been incorporated and the final document is in the processes of being transmitted to each FERC Board member. A description of the new shear zones has been added to the text of the GIR. The text of the GIR and Bechtel Powerhouse Geological Report have been reviewed and revised as appropriate to reflect the percentage of argillite and graywacke mapped at the powerhouse excavation. 1-686-JW RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 5-1 GENERAL CIVIL CONSTRUCTION SPECIFICATIONS (continued) FERC Board of Consultants Comment: 3.2 Main Dam Embankments The various stages of review have resulted in the adoption of a loose lift thickness of 3 feet for all zones of the rockfill dam except the B1 and B5 zones. The B1 zone remains in the specification as a 12-inch maximum compacted lift thickness and the 85 zone is oversize, carefully placed rock on the downstream face which does not require compaction. The specification will require at least six passes of vibratory roller with a minimum 10-ton drum size. Response: This methodology has been adopted. 1-686-JW 2 l 'T'. "'-~ ·--.. -----·---· ... ----------............. --·· ... --· ... ~-- RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 5-1 GENERAL CIVIL CONSTRUCTION SPECIFICATIONS (continued) FERC Board of Consultants Comment: 3.3 Main Dam -Upstream Cofferdam The Board agrees with the designer's intent to provide for a permanent upstream cofferdam for the purpose of possible dewatering and repair in the case of damage from a major earthquake. It is our opinion that an alternate design, possibly submitted by the contractor, should be considered after the award. Response: This methodoiogy has been adopted. 1-686-JW 3 . ·--·-· ·-· ~··--.... , ___ .. __ " .... -··--.. ~ ..... .,. ................... _~ RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 5-1 GENERAL CIVIL CONSTRUCTION SPECIFICATIONS (continued) FERC Board of Consultants Comment: 3.4 Additional Geotechnical Explorations There are two items of geotechnical exploration which should be conducted as soon as possible and made available to bidders during or before the bidding phase. Continuous trenches should be excavated along the alignment of the upstream and downstream cofferdams for the purpose of defining the top of rock. The information obtained from these trenches could possibly result in complete elimination of the downstream cofferdam and reduce the contractor's contingencies for unknown depth to rock at some points along the upstream cofferdam. At least three additional borings are necessary. in the area of the powerhouse to define the position and orientation of the shear zones behind the existing rock cut. Response: The following geotechnical exploration program is being performed at this time: 1. Penstock and Penstock Manifold Thrust Blocks Four bore holes to cross the shear zone; one in the approximate location of each penstock/manifold thrust block. 2. Main Dam Upstream Cofferdam The approximate baseline of upstream cofferdam will be excavated to bedrock. Surveys will be made to profile the top of rock. 3. Main Dam Downstream Cofferdam The approximate baseline of the downstream cofferdam will be excavated to bedrock. Surveys will be made to profile the top of rock. 1-686-JW 4 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT 4. Spillway and Downstream Apron Three trenches will be excavated parallel to the baseline of the spillway to profile top of rock and locate any major discontinuties. 1-686-JW 5 ·I~ f ,..,, •.-.• • • • '"'• ··• •• RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --MAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 5-1 GENERAL CIVIL CONSTRUCTION SPECIFICATIONS (continued) FERC Board of Consultants Comment: 3.5 Compaction Grouting We concur with the present specification for "high pressure compaction" grouting upstream of the steel lining. It is realized that this could be referred to as high pressure consolidation grouting but as long as the term ttcompaction" grouting, as referred to in this specification is defined, the differences are semantic in nature. This special grouting is for water tightness and improvement of modulus in the event of extension fractures due to destressing. The primary intent was not for prestressing the liner although some prestressing may result as a by-product of this grouting. Regardless of the intent, it has been found on other jobs that this type of grouting is beneficial in reducing leakage, it is not necessary to speculate as to the mechanisms which causes the beneficial effect. Response: No response required. 1-686-JW 6 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 5-1 GENERAL CIVIL CONSTRUCTION SPECIFICATIONS (continued) FERC Board of Consultants Comment: 3.6 Monitoring/Testing -Main Dam Embankments Previous experience on concrete face rockfill dams has shown that the lift thickness, type of roller, and the number of passes as specified on the Bradley Lake Project results in adequate rockfill strength and stiffness for dams 150m in height with 1.45:1 slopes. It has been our judgement, based on review of dynamic analyses, that the 1.6:1 slopes adopted for Bradley Lake Dam adequately account for the intense earthquake motions adopted for design. It is our judgement that conservative strength parameters have been used by Stone and Webster in the dynamic·· analysis of Bradley Lake Dam. The best assurance of obtaining good rockfill is thorough, continuous monitoring and control of lift thickness, number of roller passes, vibration frequency of the roller and travel speed of the roller. Records obtained in this inspection provide appropriate documentation of the work done. In-situ dens! ty tests in rock fills are expensive and data obtained are not meaningful. Therefore, we recommend such tests not be made. Response: We have discussed this matter with Hr. Gus Tjoumas, FERC Deputy Director of Inspection and he agrees with the FERC Board that in-situ dens! ty tests are not required. The requirement for these tests have been removed from the General Civil Construction Contract Bid Document. A copy of the Alaska Power Authority's June 15, 1987 letter to Hr. Ron Corso,· FERC Director of Inspections is attached documenting the telephone conversation between Hr. Tjoumas and Hr. Norm Bishop, SWEC. 1-686-JW 7 ~- Alaska Power Authority APA/FERC/0057 June 15, 1987 Hr. Ronald Corso, Director Division of Inspections State of Alosko Federal Energy Regulatory Commission 825 North Capital Street, NE Washington, D.C. 20436 MAIN DAM ROCKFILL DENSITY REQUIREMENTS CONSTRUCTION DOCUMENTATION BRADLEY LAKE HYDROELECTRIC PROJECT This letter documents a June 11, 1987 telephone conversation between Hr. Constantine {Gus) Tjoumas, Deputy Director ot Inspection and Hr. Norm Bishop, Deputy Project Manager for our Bradley Lake Project Design Engineer, Stone & Webster Engineering Corporation. During the Hay 26 through 28, 1987 FERC Board of Consultants Meeting, the Board indicated that in-situ density tests of the rock tills ot the Main Dam were expensive and the density data obtained would not be meaningful. The Board recommended that these tests not be made. The FERC Board stated that the best assurance ot obtaining good rock£111 is thorough, continuous monitoring and control or lift thicknesses, number or roller passes, vibration frequency of the roller and travel speed of the roller. Records obtained in this inspection provide appropriate documentation of the work done. Mr. Tjoumas indicated that qualified engineering inspection, as well as written thorough technical specifications addressing lift thicknesses, number ot roller passes, vibration frequency and travel speed of the roller were essential to obtain a good dam rocld'ill. FERC will conduct its review ot the technical specifications once the General Civil Construction bid documents are submitted for approval. Hr. Tjoumas agreed with the.Board or Consultants that the in-situ rock fill density _.tests were not ~eces~ry. : · FO Sac 190869 ·701 East Tudor Rood . . Anchofoge. Aloslca 995'19-0869 l90n 56'1-7877 2"'!01999-JJ Hr. Ronald Cor:so, Director -Federal Energy Regulatory Coalllission 2 June 15, 1987 APA/FEBC/0057 Hr. Tjoumas discussed some of the Terror Lake Project Dall Rockfill problems and :solutions. Indicating that tbe solutions were worked out during construction as the various lifts of tbe rockfill embankment were placed and as problems were encountered.· The Main Dam specifications have been modified to remove the requirement for in-situ rockfill density tests. It you should wish to discuss this letter, please call. Very truly yours, ALASKA POWER AUTHORITY LJJ/[}L_ David R. Eberle Project Manager DRE/NAB/JJ cc: Mr. Quentin Edson, FERC, Portland, Attn: Mr. Phil Mabini 2-1999-JJ :: ··--:.~ ·---..:-~~----------------- RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 · FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 5-1 GENERAL CIVIL CONSTRUCTION SPECIFICATIONS (continued) FERC Board of Consultants Comment: 3.7 Power Tunnel Support and Reinforcing Present design of the tunnel includes a one foot larger excavated tunnel diameter, in order to accommodate a second layer of reinforcing steel, for 1'ype V liner (Type VIII support) in fault zones (drawing number FY-1610-1). It is strongly recommended that serious consideration be given to not changing the excavated tunnel diameter in these areas. If the entire tunnel is excavated with drill and shoot methods, driving the larger section is no problem. But it is unlikely that the low bidder will figure drill and shoot excavation. Assuming excavation with a tunnel boring machine, the excavation of an oversize tunnel is either uneconomical or possibly unsafe. Perhaps 300' of the 15,000' of tunnel (2%) would need to be oversize to allow space for two layers of reinforcing. It is unlikely that the low bidder would figure to excavate the entire tunnel oversize with a TBM. It would be costly and time consuming to enlarge, and then reduce, the TBM diameter twice, underground. (This would entail adding four to six cutters, removing six muck buckets, enlarging the dust shield and adding to the thickness of the front shoe, the front steering shoes and the gripper pads. The rock shield might also have to be revised. ) Total estimated time for each complete cycle (enlarge plus reduce back to original size) is a m1n1mum of one month. A rough estimate of cost is $1 million per cycle. It would be dangerous to remove the initial supports in this poor ground to enlarge the excavation after the TBH has passed through this type of material. One solution is to reduce the lined tunnel diameter for these short sections, by the minimum amount feasible to provide space for the additional rebar. With proper transitions, the head loss resulting from short, 6-inch diameter reductions are insignificant. Another possibility is to shut the TBM down at the start of each fault and excavate the entire length of faulted material with hand mining methods. Again, it is unlikely that the low bidder will have the time or cost budget to do this. Other possible solutions include: -a. Allowing less clearance on the rebar, probably requiring 1/2" aggregate. 1-686-JW 8 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT b. Place an unstiffened steel liner instead of rebar. Length of each section of this lining probably would be limited to 40 to 60' which will minimize the possibility of buckling of the liner by external water pressure. We have not reviewed the assumptions used in the analysis which resulted in the need for a double layer of reinforcing. We suggest, however, the assumptions regarding rock modulus and external loadings be reviewed. In conclusion, it appears that allowing a smaller lined tunnel diameter for short areas of faulted ground is the best solution for providing space for a second layer of rebar, if required. The next best solution is to place unstiffened steel liner instead of rebar. Responses: We have initiated the necessary engineering and economic studies to of alternate details which will not require the excavated tunnel diameter to be increased locally to acco111110date a second layer of reinforcing steel. We will provide our findings to the Board members under separate correspondence. 1-686-JW 9 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 5-1 GENERAL CIVIL CONSTRUCTION SPECIFICATIONS (continued) FERC Board of Consultants Comment: 3.8 Penstock Thrust Blocks The shape of the penstock thrust blocks should be reviewed to simplify construction. Consideration should be given to supporting the rock for the thrust block excavations using bolts and shot~Jrete rather then steel sets. These thrust blocks must be located in good rock. Bolts and shotcrete can be placed as excavation proceeds. Further, this would provide sound, firm contact between the thrust block and the rock at all points and thus avoid possible problems from the steel sets and blocking interfering with excavation or placing of concrete. Response: The penstock thrust block design will be reviewed as soon as exploratory boring information and excavation as-built data are available. The construction rock support will also be reviewed. Based on present known geological information, steel sets are necessary for temporary rock support. Wood· blocking can be limited, and grout pads utilized, if necessary. The steel sets when encased in concrete should not detract from the thrust block characteristics. 1-686-JW 10 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4-1 ENGINEERING STUDIES AND PRESENTATIONS FERC Board of Consultants Comment: 4.1 Dam Break Analysis Results of a preliminary dam break analysis were presented. Because the Bradley River valley above Kachemak Bay is uninhabited and can confidently be expected to remain so, a simplified analysis embodying very conservative assumptions was done. These assumptions included: 1. Instantaneous breach to ultimate dimension. 2. Very large breach cross section with 42° side slopes. 3. The breach assumed to coincide with maximum estimated high tide. 4. Discharge at the river mouth was assumed equal to the peak dis- charge through the breach. Thus storage and peak flow attenuation along the channel were ignored. Effects in Kachemak Bay were calculated for a number of locations. These showed no impact on any inhabited area nor any significant economic damage. We have reviewed the assumptions, method and results of this study. In our opinion, the study shows the postulated dam break does not pose a hazard to· inhabitants of the region. Accordingly, a more sophisticated analysis is not requireD nor is there a need for an evacuation plan. Response: No response required. 1-686-JW 11 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --MAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4-1 ENGINEERING STUDIES AND PRESENTATIONS (continued) FERC Board of Consultants Comment: 4.2 Tsunami In compliance with the report of the Board dated May 30, 1986, further studies have been made of the probable water levels at the site result- ing from either earthquake or volcanic eruption. These studies were presented in detail. They indicate a water level due to tsunami at the site of El 25 BLPD (29 feet above mean sea level) to have an annual exceedance probability of 0.007. This is the same probability of occurrence as that of the Design Earthquake. The powerhouse structure will be designed to withstand these hydrodynamic loadings. The design approach is considered satisfactory and the recurrence interval used is considered adequately conservative. Response: No response required. 1-686-JW 12 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --MAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4-1 ENGINEERING STUDIES AND PRESENTATIONS (continued) FERC Board of Consultants Comment: 4.3 Geologic Mapping Geology of the diversion tunnel has been mapped in detail at a scale of 1 inch = 4 feet. The mapping shows the crown and both ribs. It was well done and complete. In general, rock conditions are satisfactory. Four open seams were identified. These were cleaned to suitable depth and filled with concrete placed as dry pack. Diversion through the tunnel was established on May 23rd. Accordingly, we could not inspect the tunnel itself. Both portals were examined. Rock conditions and rock bolting of the portals were satisfactory. Excavation at the powerhouse to the El 60, ·El 40 benches and a small portion of the El 18 bench has been completed. The face between the El 60 and 40 benches has been covered by chain link mesh for safety of personnel. This excavation has been mapped and a preliminary geologic map was presented for our review. This mapping confirmed and more definitely located a suspected shear zone near the south end of the powerhouse and shows a previously unidentified shear zone which cuts the portal of the power tunnel. This zone is about 2 to 5 feet wide. It trends about N10°W and dips about 40° east. This shear zone will affect the manifold section of the tunnel and possibly the thrust blocks of the penstocks. Additional investigations should be made to locate this shear zone relative to the penstocks and manifold. Further studies will then be required of the stability of the thrust blocks and manifold sections of the power tunnel. Response: We have initiated an exploratory boring program to define the shear zones relative to the penstock and manifold. Once this information and the as-builts of the powerhouse excavation are available, the review of the penstock thrust block and manifold calculations will be performed. 1.-686-JW 13 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --HAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4-1 ENGINEERING STUDIES AND PRESENTATIONS (continued) FERC Board of Consultants Comment: 4.4 Concrete Tests Approximately 2150 CY of concrete· have been placed to date, the majority use being at the diversion tunnel. The contractor elected to use rich mixes to improve workability and ensure meeting minimum strength requirements. Water/cement ratios were low and test strengths substantially exceeded required values. Despite the rich mixes used, temperatures during and after placement were acceptable. It is anticipated leaner mixes will be used for the dam and tunnel construction: Leaner mixes should be required both for economy and to reduce shrinkage and cracking. Response: The General Civil Construction Contract documents require the Contractor to adhere to ACI requirements and prohibits use of excessively rich cement content mixes. 1-686-JW 14 ' .... _. ·; RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --MAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 5-1 MECHANICAL EQUIPMENT FERC Board of Consultants Comment: 5.1 Eccentric Rotary Sperical Valve Alternate Fuji Electric Co. has proposed two types of spherical valves for the Bradley Lake Project. The two types are: 1. Spherical valve with a sliding ring service seal 2. Eccentric rotary spherical valve. The original SWEC specifications for the spherical valve seals were based on previous similar designs and included provisions such as oil actuated operators to prevent auto-oscillations. However, the background experience on such designs has not been good. The following incidents have occurred: 1. 2. 3. 4. 5. 6. Bersemis No. 2 Power Plant -Canada. After a few years of operation, one of the valve seals set up a condition referred to as auto-oscillation with resulting high pressure, high frequency pressure oscillations in the penstock system. Fortunately, opening the by-pass valve stopped this phenomena. The problem was traced to a clogged filter in the pressure supply line to the seal. Additional automatic filters were installed. Oroville Pumped Storage Power Plant -California. Same phenomena as described for Bersemis. Alternate automatic filters and a separate water supply line with clean water were installed. Northfield Pumped Storage Project -Massachusetts. The control circuit for the spherical valve was set too close to the seals to permit work to be done inside the turbine. Several days later with the turbine mandoor open, the seal opened and the power plant was flooded from the headwater reservoir which fortunately was only partially full. Pfestiniog Pumped Storage Power Plant -Wales. Auto-oscillation of the spherical valve seals occurred during the initial commissioning of one of the units. The oscillation was stopped by opening the spherical valve by-pass. Helms Pumped Storage Project -California. This is intended to be an unmanned power plant. In the event of auto-oscillation of the seals, a computer controlled device will open the by-pass line. Balsam Meadow Power Plant -California (current} • A pressure differential device across the water supply filter will automati- cally open the by-pass line when the filters to the supply line indicate a partially clogged filter. 1-686-JW 15. RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --MAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT In view of the above, the introduction and satisfactory operation of the Fuji concept such as the eccentric rotary spherical valve is a welcome solution to the problems cited above. The concept of using penstock pressure to close the valve and governor oil pressure to open the valve servomotor is acceptable. Redundant operation is also recommended for the spherical valve by-pass line i.e. penstock pressure to close the by-pass valve and governor oil pressure to open the valve servomotor. Responses: Subsequent to the Board meeting, we reviewed the actuation system for the spherical valve with Fuji Electric. Fuji has now proposed an actuator which uses governor oil pressure to open and a counterweight to close the spherical valve. We are reviewing this methodology with Mr. J. Parmakian. 1-686-JW 16 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --MAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 5-1 MECHANICAL EQUIPMENT (continued) FERC Board of Consultants Comment: 5.2 Generator WR2 for Isolated Operation The recommended generator WR2 for isolated operation has been specified in the generator specifications as a minimum. Nevertheless, the governor manufacturer should be required to analy~e the condition of isolated operation to assure that this generator WR is adequate. Response: The governor manufacturer is required to analyze the condition of isolated operation to assure that the generator WR2 is adequate. This is a technical requirement of the specifications. 1-686-JW 17 ·-·f!~· .... · RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FIFTH REPORT --MAY 26-28, 1987 FERC PROJECT NO. 8221-000 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 5-1 MECHANICAL EQUIPMENT (continued) FERC Board of Consultants Comment: 5.3 Turbine: Although the rotational speed and number of jets has been specified, the number of runner buckets is significant. To prevent shock type vibration at the turbine-generator shaft, the number of runner buckets should not be a multiple of 6 or 3 for the 6 jet unit. The diameter of the runner and size of the buckets must be such as not to interfere with the jet streams. Response: We have advised the turbine supplier, Fuji Electric of these your concerns and they will be required to address this in their design. 1-686-JW 18 Mr. D.R. Eberle 5 May 28' 1987 Alaska Power Authority It would be dangerous to remove the initial supports in this poor ground to enlarge the excavation after the TBM has passed through this type of material. One solution is to reduce the lined tunnel diameter for these short sections, by the minimum amount feasible to provide space for the additional rebar. With proper transitions, the head loss resulting from short, 6-inch diameter reductions are insignifi- cant. Another possibility is to shut the TBM down at the start of each fault and excavate the entire length of faulted material with hand mining methods. Again, it is unlikely that the low bidder will have the time or cost budget to do this. Other possible solutions include: a. Allowing less clearance on the rebar, probably requiring 1/2" aggregate. b. Place an unstiffened steel liner instead of rebar. Length of each section of this lining probably would be limited to 40 to 60' which will minimize the possibility of buckling of the liner by external water pressure. We have not reviewed the assumptions used in the analysis which resulted in the need for a double layer of reinforcing. We suggest, however, the assumptions regarding rock modulus and external loadings be reviewed. In conclusion, it appears that allowing a smaller lined tunnel diameter for short areas of faulted ground is the best solution for providing space for a second layer of rebar, if required. The next best solution is to place unstiffened steel liner instead of rebar. 8. The shape of the penstock thrust blocks should be reviewed to simplify construction. Consideration should be given to supporting the rock for the thrust block excavations using bolts and shotcrete rather then steel sets. These thrust blocks must be located in good rock. Bolts and shotcrete can be placed as excavation proceeds. Further, this would provide sound, firm contact between the thrust block and the rock at all points and thus avoid possible problems from the steel sets and blocking interfering with excavation or placing of concrete. 2-1961-JJ Mr. D.R. Eberle 6 May 28, 1987 Alaska Power Authority 4.0 ENGINEERING STUDIES AND PRESENTATIONS 4.1 DAM BREAK ANALYSIS Results of a preliminary dam break analysis were presented. Because the Bradley River valley above Kachemak Bay is uninhabited and can confidently be expected to remain so, a simplified analysis embodying very conservative assumptions was done. These assumptions included: 1. Instantaneous breach to ultimate dimension. 2. Very large breach cross section with 42° side slopes. 3. The breach assumed to coincide with maximum estimated high tide. 4. Discharge at the river mouth was assumed equal to the peak discharge through the breach. Thus storage and peak flow attenuation along the channel were ignored. Effects in Kachemak Bay were calculated for a number of locations. These showed no impact on any inhabited area nor any significant economic damage. We have reviewed the assumptions, method and results of this study. In our opinion, the study shows the postulated dam break does not pose a hazard to inhabitants of the region. Accordingly, a more sophisticated analysis is not required nor is there a need for an evacuation plan. 4.2 TSUNAMI In compliance with the report of the Board dated May 30, 1986, further studies have been made of the probable water levels at the site resulting from either earthquake or volcanic eruption. These studies were presented in detail. They indicate a water level due to tsunami at the site of El 25 BLPD {29 feet above mean sea level) to have an annual exceedance probability of 0.007. This is the same probability of occurrence as that of the Design Earthquake. The powerhouse structure will be designed to withstand these hydrodynamic loadings. The design approach is considered satisfactory and the recurrence interval used is considered adequately conservative. 4.3 GEOLOGIC MAPPING Geology of the diversion tunnel has been mapped in detail at a scale of 1 inch = 4 feet. The mapping shows the crown and both ribs. It was well done and complete. In general, rock conditions are satisfactory. Four open seams were identified. These were cleaned to suitable depth and filled with concrete placed as dry pack. 2-1961-JJ Mr. D.R. Eberle 1 May 28, 1987 Alaska Power Authority Diversion through the tunnel was established on May 23rd. Accordingly, we could not inspect the tunnel itself. Both portals were examined. Rock conditions and rock bolting of the portals were satisfactory. Excavation at the powerhouse to the El 60, El 40 benches and a small portion of the El 18 bench has been completed. The face between the El 60 and 40 benches has been covered by chain link mesh for safety of personnel. This excavation has been mapped and a preliminary geologic map was presented for our review. This mapping confirmed and more definitely located a suspected shear zone near the south end of the powerhouse and shows a previously unidentified shear zone which cuts the portal of the power tunnel. This zone is about 2 to 5 feet wide. It trends about N10°W and dips about 40° east. This shear zone will affect the manifold section of the tunnel and possibly the thrust blocks of the penstocks. Additional investigations should be made to locate this shear zone relative to the penstocks and manifold. Further studies will then be required of the stability of the thrust blocks and manifold sections of the power tunnel. 4.4 CONCRETE TESTS Approximately 2150 CY of concrete have been placed to date, the majority use being at the diversion tunnel. The contractor elected to use rich mixes to improve workability and ensure meeting minimum strength requirements. Water/cement ratios were low and test strengths substantially exceeded required values. Despite the rich mixes used, temperatures during and after placement were acceptable. -It is anticipated leaner mixes will be used for the dam and tunnel construction. Leaner mixes should be required both for economy and to reduce shrinkage and cracking. 5.0 MECHANICAL EQUIPMENT 5.1 ECCENTRIC ROTARY SPHERICAL VALVE ALTERNATE Fuji Electric Co. has proposed two types of spherical valves for the Bradley Lake Project. The two types are: 1. Spherical valve with a sliding ring service seal 2. Eccentric rotary spherical valve. The original SWEC specifications for the spherical valve seals were based on previous similar designs and included provisions such as oil actuated operators to prevent auto-oscillations. However, the background experience on such designs has not been good. The following incidents have occurred: 2-1961-JJ Mr. D.R. Eberle Alaska Power Authority 8 May 28, 1987 1. Bersemis No. 2 Power Plant -Canada. After a few years of operation, one of the valve seals set up a condition referred to as auto-oscillation with resulting high pressure, high frequency pressure oscillations in the penstock system. Fortunately, opening the by-pass valve stopped this phenomena. The problem was traced to a clogged filter in the pressure supply line to the seal. Additional automatic filters were installed. 2. Oroville Pumped Storage Power Plant -California. Same phenomena as described for Bersemis. Alternate automatic filters and a separate water supply line with clean water were installed. 3. Northfield Pumped Storage Project -Massachusetts. The control circuit for the spherical valve was set too close to the seals to permit work to be done inside the turbine. Several days later with the turbine mandoor open, the seal opened and the power plant was flooded from the headwater reservoir which fortunately was only partially full. 4. Pfestiniog Pumped Storage Power Plant -Wales. Auto-oscillation of the spherical valve seals occurred during the initial commissioning of one of the units. The oscillation was stopped by opening the spherical valve by-pass. 5. Helms Pumped Storage Project -California. This is intended to be an unmanned power plant. In the event of auto-oscillation of the seals, a computer controlled device will open the by-pass line. 6. Balsam Meadow Power Plant -California (current). A pressure differential device across the water supply filter will automati- cally open the by-pass line when the filters to the supply line indicate a partially clogged filter. In view of the above, the introduction and satisfactory operation of the Fuji concept such as the eccentric rotary spherical valve is a welcome solution to the problems cited above. The concept of using penstock pressure to close the valve and governor oil pressure to open the valve servomotor is acceptable. Redundant operation is also recommended for the spherical valve by-pass line i.e. penstock pressure to close the by-pass valve and governor oil pressure to open the valve servomotor. 5.2 GENERATOR WR 2 FOR ISOLATED OPERATION The recommended generator WR 2 for isolated operation has been specified tn the generator specifications as a minimum. Nevertheless, the governor manufacturer should be required to analy~e the condition of isolated operation to assure that this generator WR is adequate. 2-1961-JJ Hr. D.R. Eberle 9 Hay 28, 1987 Alaska Power Authority 5.3 TURBINE Although the rotational speed and number of jets has been specified, the number of runner buckets is significant. To prevent shock: type vibration at the turbine-generator shaft, the number of runner buckets should not be a multiple of 6 or 3 for the 6 jet unit. The diameter of the runner and size of the buckets must be such as not to interfere with the jet streams. 2-1961-JJ Hr. D.R. Eberle Alaska Power Authority Respectfully submitted, obn Parmak1an J _;: P. E. 1 A. J. Hendron, Jr. 2-1961-JJ 10 May 28, 1987 NAME A. Hendron W. Swiger P. Sperry J. Parmakian W. Boyle P. Mabini J. Stafford J.J.M. Plante A.S. Lucks N.A. Bishop L. Duncan *T. Hughes *J. Hron *W. Sherman *T. Critikos R.E. Mitchell E.H. Elwin * Part Time 2-1961-JJ ALASKA POWER AUTHORITY BRADLEY LAKE HYDROELECTRIC PROJECT FIFTH FERC BOARD MEETING MAY 26, 1987 ATTENDEES LIST Consultant, Consultant, Consultant, Consultant, FERC FERC FIRM FERC Board FERC Board F'ERC Board FERC Board APA, Deputy Project Mgr/Eng. SWEC, Principal in Charge SWEC, Engineering Manager SWEC, Deputy Project Manager SWEC, Chief Geotech. Engineer SWEC, Hydraulic Engineer SWEC, Chief Hydraulic Eng. SWEC, Chief Structural Eng. SWEC, ProJect Manager Bechtel, Project Manager Bechtel, Field Project Eng. NAME A. Hendron W. Swiger P. Sperry J. Parmakian W. Boyle P. Mabini D.R. Eberle O.L. Johnson R.E. Mitchell E.H. Elwin J.F. Daly N.A. Bishop L. Duncan *T. Critikos J. Stafford * Part Time 2-1961-JJ ALASKA POWER AUTHORITY BRADLEY LAKE HYDROELECTRIC PROJECT FIFTH FERC BOARD MEETING MAY 28, 1987 ATTENDEES LIST FIRM Consultant, FERC Board Consultant, FERC Board Consultant, FERC Board Consultant, FERC Board FERC FERC APA, Project Manager APA, Deputy Proj. Mgr.-Const. Bechtel, Project Manager Bechtel, Field Project Eng. Bechtel, Field Canst. Mgr. SWEC, Deputy Project Manager SWEC, Chief Geotech. Engineer SWEC, Project Manager APA, Deputy Project Mgr/Eng. Dr. A. J. Hendron, Jr. 28 Golf Drive Mahomet, Illinois 61853 (217) 351-8701 Mr. P. E. Sperry 21318 Las Pilas Road Woodland Hills, CA 91364 (818) 999-1525 Mr. D. R. Eberle Project Manager Alaska Power Authority P. 0. Box 190869 Anchorage, Alaska 99519-0869 FIFTH REPORT -BOARD OF CONSULTANTS BRADLEY LAKE HYDROELECTRIC PROJECT 1.0 INTRODUCTION Mr. John Parmakian 2695 Lafayette Drive Boulder, Colorado 80303 (303) 499-5404 Mr. W. F. Swiger Box 388 Buhl, Idaho 83316 (208) 543-4593 May 28, 1987 J . 0. No . 15800 T2.2 The fifth meeting of the Board of Consultants Hydroelectric Project convened in the offices Engineering Corp. at 8:30a.m. on May 26, 1987. attached. for the Bradley Lake of Stone and Webster A list of attendees is We were briefed on the status of construction and scheduling of the project. Comments by various sources on the drawings and specifi- cations for the General Civil Construction Contract were discussed. Presentations were made of studies of the Dam Break Analysis, Tsunami Hazard and geologic mapping of the diversion tunnel and powerhouse ·excavation. Bids received for· supplying the turbine-generators, spherical valves and governor systems were discussed and we were advised of the status of work under this contract. Fuji of Japan, which has been awarded this contract, has proposed supplying a relatively new type of seal for the spherical valve termed an eccentric rotary spherical valve. The site was visited on May 27th where we examined the diversion tunnel area, exposed river bottom, traversed the access road to the dam and examined the excavation for the powerhouse. We were very favorably impressed by the general cleanliness of the work ~reas and the care taken to minimize damage to the surroundings during the work. This report was prepared in the offices of Bechtel Civil, Inc. in Homer on May 28th, 1987. 2-1961-JJ Mr. D.R. Eberle Alaska Power Authority 2.0 STATUS 2 May 28, 1987 A. Site Preparation Contract: Complete except for minor punch list items. A major milestone was reached on May 23, 1987 when diversion was accomplished. The last stop logs were removed from the Diversion Tunnel on 5/25/87 and the entire Bradley River flow is through the Diversion Tunnel. The flow at Riffle Reach, at the Lower Bradley River, was 1750 CFS. This is the combined flow through the tunnel and from the downstream drainage. B. Turbine Generation Contract: $11.4 million Contract awarded to a trading company representing Fuji Electric Company. Engineering and design work released. Other work on hold. C. Transmission Line: Survey and Geotechnical report due 6/15/87. Clearing Contract ready for advertisement. D. General Civil Construction Contract: 99% review comments being incorporated into the documents now. The Geotechnical Interpretative Report will be revised to reflect changes disclosed by the Site Preparation Contract in the Powerhouse Area and will be ready for comments by 6/15/87. The Supporting Design Report will be mailed out for comments on 6/15/87. Power sales agreements are anticipated to be signed by 7/1/87 with Bid Documents available for· bidders 7115/87. Bids will be received late in September. 3.0 GENERAL CIVIL CONSTRUCTION SPECIFICATIONS AND DRAWINGS The Board of Consultants reviewed the 95% documents for the General Civil Construction Contract and written comments were submitted prior to commencement of the Fourth Board Meeting on January 27, 1987. The documents, including the Geotechnical Interpretative Report, were . discussed for two days during the meeting which resulted in additional suggestions for changes. Since the January Board Meeting, Dr. A. Hendron has reviewed a revision of the Geotechnical Interpretive Report on February 28th with Dr. S. Lucks in the Denver office of Stone and Webster. A "final" review of the revised Bid Documents and Geotechnical Interpretive Report was con-ducted by Dr. A Hendron of this Board and Dr. A Merritt of the Technical Review Board with Dr. A. Lucks, Hr. J. Meisenheimer, and Hr. L. Duncan of Stone and Webster in the Denver office of Stone and Webster on April 10, 1987. The members of both the APA FERC Board and the Technical Review Board have been given the opportunity to respond to each of the questions and suggestions raised at the April 10th review session. We are satisfied that the design drawings and specifications, with the modifications as discussed below, are suitable for obtaining bids for construction and will result in a safe and satisfactory project. 2-1961-JJ Hr. D.R. Eberle 3 Hay 28, 1987 Alaska Power Authority As a result of the review mentioned above, many changes have been effected; the following items are either items which remain to be done or items which need comment for emphasis because they are important and have been the subject of comments by both Boards. 1. A revision of the Geotechnical Interpretive Report will be available for final review on June 15, 1987. It is understood that the "new" shear zones found in the powerhouse excavation will be added to the report. It is also understood that the Geotechnical Interpretive Report and the Bechtel Report on the geology of the powerhouse will both be revised if necessary to be consistent regarding the percentage of argillite and graywacke mapped in the excavation. 2. The various stages of review have resulted in the adoption of a loose lift thickness of 3 feet for all zones of the rockfill dam except the B1 and B5 zones. The B1 zone remains in the specifi- cation as a 12-inch maximum compacted lift thickness and the B5 zone is oversize, carefully placed rock on the downstream face which does not require compaction. The specification will require at least six passes of vibratory roller with a minimum 10-ton drum size. 3. The Board agrees with the designer's intent to provide for a permanent upstream cofferdam for the purpose of possible dewatering and repair in the case of damage from a major earthquake. It is our opinion that an alternate design, possibly submitted by the contractor, should be considered after the award. 4. There are two i terns of geotechnical exploration which should be conducted as soon as possible and made available to bidders during or before the bidding phase. Continuous trenches should be excavated along the alignment of the upstream and downstream cofferdams for the purpose of defining the top of rock. The information obtained from these trenches could possibly result in complete elimination of the downstream cofferdam and reduce the contractor's contingencies for unknown depth to rock at some points along the upstream cofferdam. At least three additional borings are necessary in the area of the powerhouse to define the position and orientation of the shear zones behind the existing rock cut. 5. We concur with the present specification for "high pressure compaction" grouting upstream of the steel lining. It is realized that this could be referred to as high pressure consolidation grouting but as long as the term "compaction" grouting, as referred to in this specification is defined, the differences are semantic in nature. This special grouting is for water tightness and improvement of modulus in the event of extension fractures due 2-1961-JJ Mr. D.R. Eberle 4 May 28, 1987 Alaska Power Authority The primary intent was not for prestressing the liner although some prestressing may result as a by-product of this grouting. Regardless of the intent, it has been found on other jobs that this type of grouting is beneficial in reducing leakage, it is not necessary to speculate as to the mechanisms which causes the beneficial effect. 6. Previous experience on concrete face rockfill dams has shown that the lift thickness, type of roller, and the number of passes as specified on the Bradley Lake Project results in adequate rockfill strength and stiffness for dams 150m in height with 1.45:1 slopes. It has been our Judgement, based on review of dynamic analyses, that the 1 . 6: 1 slopes adopted for Bradley Lake Dam adequately account for the intense earthquake motions adopted for design. It is our judgement that conservative strength parameters have been used by Stone and Webster in the dynamic analysis of Bradley Lake Dam. The best assurance of obtaining good rockfill is thorough, continuous moni taring and control of lift thickness, number of roller passes, vibration frequency of the roller and travel speed of the roller. Records obtained in this inspection provide appropriate documentation of the work done. In situ density tests in rock fills are expensive and data obtained are not meaningful. Therefore, we recommend such tests not be made. 1. Present design of the tunnel includes a one foot larger excavated tunnel diameter, in order to accommodate. ·a second layer of reinforcing steel, for Type V liner (Type VIII support) in fault zones (drawing number FY-161D-1). It is strongly recommended that serious consideration be given to not changing the excavated tunnel diameter in these areas. If the entire tunnel is excavated with drill and shoot methods, driving the larger section is no problem. But it is unlikely that the low bidder will figure drill and shoot excavation. Assuming excavation with a tunnel boring machine, the excavation of an oversize tunnel is either uneconomical or possibly unsafe. Perhaps 300' of the 15, 000' of tunnel ( 2~} would need oversize to allow space for two layers of reinforcing. unlikely that the low bidder would figure to excavate the tunnel oversize with a TBM. to be It is entire It would be costly and time consuming to enlarge, and then reduce, the TBM diameter twice, underground. (This would entail adding four to six cutters, removing six muck buckets, enlarging the dust shield and adding to the thickness of the front shoe, the front steering shoes and the gripper pads. The rock shield might also have to be revised.} Total estimated time for each complete cycle (enlarge plus reduce back to original size) is a m1mmum of one month. A rough estimate of cost is $1 million per cycle. 2-1961-JJ February 17, 1986 Hr. Kenneth F. Plumb Secretary ~ Alaska Power Authority Slate at Alaska Federal Energy Regulatory Commission 825 North Capital Street, N.W. Washington, D.C. 20436 FERC BOARD OF CONSULTANTS MEETING FERC PROJECT NO. 8221-000 BRADLEY LAKE HXDROELECIRIC PROJECT Thank you for the prompt approval of Messrs. W. F. Swiger, A. J. Hendron, Jr., and P. E. Sperry as the Bradley Lake hydroelectric Project FERC Board of Consultants. Per your direction, we are initiating the selection · of an electrical/mechanical engineering consultant for FERC's approval. The first FERC Board of Consultants meeting is presently being scheduled for March 6 and 7. The Agenda for this meeting is attached. The purpose of this meeting will be to review and comment on the Site Preparation Bidding Document, Engineer's Drawings and Specifications. The Site Preparation Contract will be issued for bid on or about March 10, 1986 and bids are to be received for this work on April 15, 1986. Construction is scheduled to begin in late Hay 1986, immediately after -a contract award. We will be forwarding for your review and comment the following Site Preparation Contract related documents. a. Five draft copies of the bid documents for the Site Preparation Con tract including technical specifications and design drawings. b. Two copies of the 1985 Geotechnical Investigation Report. c. Five copies of-the Final Design Criteria applicable to the facilities included in the Site Preparation Bid Documents. 2-328-JJ PO Box 190869 701 East Tuaor Roaa Anchorage. Alaska 99519-0869 (907) 561· 7877 Mr. Kenneth F. Plumb Federal Energy Regulatory Commission 2 February 17 1986 d. Five sets of applicable Checked Design Calculations. The above documents will be reviewed as part of the March 6 and 7, 1986 Board of Consultant's meeting. The March 6th and 7th dates were selected by the Board members as the most suitable for an early schedule meeting. However, should these dates present some difficulty or conflict with your requirements, please call me at (907) 561-7877. Very truly yours, .AO::;JfllJ- David R. Eberle Project Manager DRE/NAB/JJ Attachment cc: Mr. John Longacre Mr. W.F. Swiger Mr. A.J. Hendron, Mr. P.E. Sperry Mr. Arthur Martin 2-328-JJ Jr. AGENDA BOARD OF CONSULTANTS BRADLEY LAKE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY Meeting will be held at the offices of Stone & Webster Engineering Corporation, 800 "A" Street, Anchorage, Alaska on March 6 and 7, 1986. Meeting will start at 8:30 AM on scheduled dates. MARCH 6 I 1986 I. INTRODUCIION A. Opening Remarks B. Agenda and Overview of Meeting Discussions II. BID DOCUMENTS FQR SITE PREPARATION CONIRACI III. DESIGN PBAWINGS·FQR SIIE PREPARATION CQNIBACT IV. fEBC SUPPQRTING DESIGN REPQRI FQR SIIE PREfARATION CONIRACI MARCH 1. 1986 V. HYDRAULIC MODEL SIUPY OF DAM SIIE PLAN VI • .a PRELIMINARY ANALYSIS REsuLTS FQR MAIN DAM VII. GUIDELINES FROM BOARD VIII. BOARD fREPARES ANP ISSQES ITS Rf;:(\,'~- 2-329-JJ A.J. Hendron, Jr. 28 Golf Drive Mahomet, IL 61853 (217) 351-8701 Mr. D.R. Eberle Project Manager Alaska Power Authority P.O. Box 190869 P. E. Sperry 21318 Las Pilas Rd Woodland Hills, CA 9136lt (818) 999-1525 Anchorage, Alaska 99519-0869 FIRST REPORT -BOARD OF CONSULTANTS BRADLEY LAKE HIDROELECIBIC PftOJECT W.F.Swiger Box 388 Bubl, ID 83316 (208) 543-4593 March 7, 1986 J.O. No. 15800 T2.2 The first meeting of the Board of Consultants for the Bradley Lake Hydroelectric Project convened in the offices of Stone & Webster Engineering Corporation at 8:30 AM on March 6, 1986. All current members of the Board were present. Preparatory to the meeting we were sent drafts of the Specifications, Bidding Documents and Preliminary Drawings for the. Site Preparation Contract (first phase of project) for review and cOIIIJilent. A list of attendees is attached. It is planned to place this first phase contract for bids on March 10 with bids due on April 15, 1986. The Board presented cOIIIJilents and suggestions on the Specifications, Bid Forms and Drawings. Four of the Board's recommendations are considered especially important. These are: 1. The provisions for changed site conditions and the consistency of wording between these provisions and descriptions of site conditions should be reviewed. 2. It is suggested that Bid Forms and appropriate para2raphs of the Specifications require that the Bidder certify that he baa visited the site, reviewed the Geotechnical Report and viewed the cores. / 3. Environmental considerations require that material excavated under this contract be used in construction in embankments or wasted in specified areas. Side casting . during road construction is not permitted. Since these requirements are unusual in highway construction, the wording of the Specifications should be strengthened to clearly state that side casting is prohibited and that excavation is to be end hauled and used in necessary fill. 2-372-JJ • Mr. D.R. Eberle 2 March 7, 1986 Alaska Power Authority 4. The sheet pile cells of the barge handling facility, once cell closure has been achieved, should be kept flooded to or above the external water levels at all times to maintain positive outward pressure until fill has been placed to above high tide levels. Fill material of relatively clean gravel, as is to be used here, can be placed by dropping from a clam shell or drag line. Care should be taken to keep the top of the fill reasonably level as the fill is placed. In addition to the above a number of comments on wording and details relating to tunnel construction, blasting, grouting and concrete work were made and notes provided to the Design Engineers. The program for hydraulic model studies of the intake to the power tunnel was described. A contract for this work has been placed and construction of the model started. Scale of this model is 1:50. It is anticipated witness testing will start about April 15. The Board is to be kept advised of progress so that individual members may witness the tests on the model. We were advised ot progress on preparation of the Supporting Design Report tor Site Preparation of the final Geotechnical Report and Design Criteria. Preliminary Pvnamic Analysis Cor Main Pam Preliminary results ot the calculations of dynamic displacements under the Maximum Credible Earthquake (M = 7. 5, • 75 g) were presented by Stone & Webster for the main dam. calculations were presented Cor 0 0 angles of shearing resistance of the rockfill ranging from 45 to 50 ; three earthquake records were used for base motion; the amplification ot motion were considered up through the dam; and, two different methods ot calculating the yield acceleration were employed. In the Board's opinion the calculation ot the •yield" acceleration assuming a constant vertical acceleration of 2/3 the maximum horizontal acceleration is too conservative and not realistic. When the horizontal motion record is used ~a. ~alculatin& motion, it is appropriate to calculate the yield acceleration on the basis of the minimum dynamic resistance as defined by Newmark. This will give a yield acceleration slightly less than the yield acceleration Stone & Webster has calculated when assuming the vertical acceleration to be 0 zeso. The ranges ot angles ot shearing resistance considered (45 to 50 ) are reasonable; but more detailed justification is required if values greater than 45° are to be used in the final calculations. The synthetic ground motion record used looks reasonable and appropriate. An attempt should be made to acquire a "rock• record from the recent earthquake in Mexico. The Helena record is from an earthquake ot smaller magnitude than the design earthquake. The Taft ground motion scaled to 0. 75 g is probably conservative since it is 2-372-JJ Mr. D.H. Eberle 3 March 7, 1986 Alaska Power Authority not a rock record. However, it is from an appropriately large earthquake (Kern County earthquake). The Board is primarily interested in the response of critical surfaces such as those shown for Case 2, see Fig. 1. It now appears that the dynamic displacement of these surfaces would be on the order of 1 to 2 ft if the downstream slope remains at 1.6:1. These values are acceptable to the Board but more analysis of other fracture surfaces need to be conducted in order to estimate the deflection of the concrete face as a function of depth below the water surface. The Board wishes to compliment the Engineers on their presentations and their courtesy in making arrangements. We understand the next meeting of the Board is scheduled May 28 through May 30, 1986. Respectfully submitted, A. J. Hendron, Jr. 2-372-JJ iJlED J UN 0 2 198~ L.Dinl. A.J. Hendron, Jr. 28 Golf Drive Mahomet, IL 61853 (217) 351-8701 Mr. D.R. Eberle Project Manager Alaska Power Authority P.O. Box 190869 P. E. Sperry 21318 Las Pilas Rd Woodland Hills, CA 91364 (818) 999-1525 Anchorage, Alaska 99519-0869 SECOND REPORT -BOARD OF CONSULTANTS BRADLEY LAKE HYDROELECTRIC PROJECT 1. Introduction W.F.Swiger P.O. Box 388 Buhl, ID 83316 (208) 543-4593 May 30, 1986 J.O. No. 15800 T2.2 The second meeting of' the Board of Consultants for the Bradley Lake Hydroelectric Project convened in the offices of Stone & Webster Engineering Corporation at 8:30 AM on Hay 28, 1986. All members of the Board as nov conf'igured were present. We were briefed on the status of' the Phase I contract, the construction schedule, and work in progress for the second phase contract for construction of the dam, tunnels and powerhouse. Prior to the meeting we were provided preliminary studies covering the bulk of the material presented. These were very helpf'ul in familiarizing us before the meeting with the materials to be discussed. 2. Status Bids for the Site Preparation Contract were receive~ on April 29th. A letter of Intent to Award bas been sent to the low bidder, but Notice to Proceed is being delayed by negotiations for Nuka water rights with the National Park Services and by a bid protest. The 60~ design package for the General Construction Contract will be submitted in three packages: Powerhouse Dam Tunnel and Miscellaneous Structures July 15, 1986 August 1, 1986 August 15, 1986 Hodel tests of spillway and D/S toe of dam will be ready in July. 3. Construction SchedUle A present Project Summary Schedule, prepared by Bechtel, was presented. The tunnel portion or this schedule appears to be tight. A more detailed schedule is being prepared and copies will be mailed to the Board in June, and will be discussed at the next meeting. 2-686-JJ Mr. D.R. Eberle 2 May 30, 1986 Alaska Power Authority 4. Model Tests The model tests conducted at CSU on the Power Intake, Diversion Tunnel, and the Spillway were observed and reported on by Board Members Swiger and Hendron on April 18, 1986. At that time it was reported that the performance at the Power Tunnel Intake and the Diversion Tunnel were found to be satisfactory but that the discharge coefficient for the spillway was tentatively found to be lower than assumed for design. Ibis point has now been definitely clarified and the discharge coefficient is as assumed in the design. It has been concluded from the model tests that at elevation 1190.65 the spillway will pass a flow of 23,860 cfs, which is adequate for the PMF. The lower discharge coefficient computed on April 18th resulted because of an error of 1 ft in the reservoir elevation in relation to the agee of the spillway. Observation of the model tests also indicated that the flow conditions over the spill way could be improved by extending the piers further upstream. We understand this design change is being made and we are in agreement with this change. The detailed hydraulic model of the area just downstream of the spillway and. toe of the dam is now being planned. We feel this model is necessary and plan to witness this test sometime during the first two weeks of July. 5. Spillway During the meeting the results of a dynamic analysis of the spillway were presented; and a static stability analysis was presented in Part G of Book One available to the Consultants before the meeting. As a result of the combined ice, water, and earthquake loads considered in tbe analysis, tbe engineer has decided to reinforce the upstream portion of the concrete ~ace. The Board is in agreement with this conclusion. The results of tbe static and dynamic analyses also indicate that a drainage gallery would be desirable. The Board agrees with the addition of a drainage gallery because the total base uplift force. due to water pressures without a drainage gallery could be on the order ot 100 kips per lineal ft at ~ne maximum section versus 265 kips per lineal ft for the weight of the structure. The redu~tion of the water pressure at tbe base will enhance the behavior of the spillway under the earthquake loading. It is requested that the possibility of overall sliding in the foundation materials just below the contact with the concrete be considered on any complex system ot the intersection of various joint surfaces, whose lines of intersection would daylight on the sloping surface just downstream of the spillway. The static factor of safety and the dynamic displacement during the maximum probable earthquake along this system should be calculated if such a system is found. If 2-686-JJ Mr. D.R. Eberle 3 May 30, 1986 Alaska Power Authority geologic information is lacking to make a determination of this matter, then such information should be obtained this summer and detailed geology of this area should, in any case, be further developed during construction. The Board feels that it is desirable for the static stability analysis of the spillway sliding in the foundation materials to show at least a Factor of Safety of 1.5 based upon a cohesion of zero and an angle of shearing resistance consistent with the foundation materials just below the base of the structure. Dynamic displacements of this structure should be calculated on the same basis. The drainage gallery should be designed large enough to accommodate the installation of rock anchors should they become necessary at a future date. 6. Piversion runnel Conversion of the diversion tunnel to a low level outlet by installing gates slightly downstream of the midpoint has been discussed previously. We concur with the general arrangement except we are concerned there could be excessive or damaging vibration of the steel discharge pipe downstream of the gates during gate opening or closing. We understand this will be further investigated by large scale model tests. The alternative of free discharge to the concrete lined tunnel should be considered. Since emergency operation without electric power may be necessary, the Engineers have concluded from a study of several alternatives that an oil-gas accumulator bank capable of one opening of the gate should be installed. This bank would be kept charged by a small high pressure pump. A diesel driven high capacity-high pressure pump would also be in5talled a5 back-up. This arrangement could be operated by one man and without out5ide power. The equipment is rugged and could be de5igned to withstand earthquake motions. We concur with the recommendation of the Engineer. A bulkhead gate will be provided to permit removal for maintenance of the guard gate. Thi3 bulkhead gate loll ... 1 ue so des i6ned that it can also be used at the power tunnel. Provision for handling this gate will be discussed later. 1. Powerhouse Stability Analysis Plans and typical sections of the with overall stability analyses. in the rock mass and evaluation of significant reduction in uplift 2-686-JJ powerhouse were presented together Further studies of piezometer data drainage to be provided permitted a pressures. We concur with these Hr. O.R. Eberle 4 Hay 30, 1986 Alaska Power Authority revised uplift values. These new studies indicate adequate resistance to sliding and overturning and acceptable stresses in the concrete and rock. Mechanical and Electrical Equipment Preliminary discussions have been held with potential suppliers regarding turbines, genera tors, overhead bridge crane and the electrical substation. The purpose was to obtain equipment size and operating requirements sufficient for powerhouse layout and preliminary design. Studies of the electrical switchyard layout including stability of the foundations under earthquake has resulted in a decision to use SF h equipment for the switchyard. This equipment is extremely compact and the switchyard can be placed in a structure founded on rock adjacent to the powerhouse. Such an arrangement ensures foundation stability under earthquake, weather protection and protection against salt spray. Further comment will be deferred until the mechanical-electrical consultant joins the Board. Powerhouse Excavation We believe that the easiest, and most fair, way of presenting the excavation lines in the powerhouse, and paying for the overbreak concrete is to: 1. Show neat excavation lines on the drawings 2. Note on the drawings that concrete is paid to neat lines and that the Contractor should include an allowance for anticipated overbreak during excavation and t'or concrete backfill in his bid. 3. In the interpretative geotechnical report, rock jointing in the powerhouse area and the possible overbreak surfaces on walls and corners should bf: JJ.scussed. Note that the quantity of overbreak will be highly dependent on the Contractor's blasting technique. We suggest that the specificat:l on !'or the powerhouse rock blasting describe, as much as possible, that the result desired is to minimize damage to the rock remaining in place. Although we !'eel that the specifications should specify the type of controlled blasting near finished surfaces, such as cushion blasting, pre-splitting, or line drilling, or the maximum depth of lift permit ted above a finished bottom, it is felt that the blasting methods used except at and close to the final surfaces should be the responsibility of the contractor who should be required to employ a qualified blas~ing expert. 2-686-JJ Mr. D.R. Eberle 5 May 30, 1986 Alaska Power Authority Further ideas, on blasting specifications in the powerhouse, will be presented at the next meeting. Results of blasting, by the Site Preparation Contractor in the powerhouse area, will be studied before finalizing the General Construction Contract specifications. Our experience suggests that the 4' x 4' pattern of 1" rock bolts in the powerhouse excavation walls below El. 39 is more than adequate to provide stable walls and safety for the workmen. We suggest this be reviewed. Chain link fabric (2" x 2" 11 gage), not welded wire fabric, should be used to contain rock blocks between the bolts. Tsunami Studies Studies of tsunami hazards at the powerhouse have been completed but the final report is not yet available. These studies indicate a wave height at the site of 10 ft has a recurrence interval of 60 years. Such a tsunami has a significant probability of occurring during the life of the plant. Studies indicate that coincidences of such a tsunami with a very high tide would result in water levels below the turbine room floor level and there would be no damage to the powerhouse or its equipment. The maximum probable tsuanmi event would result in a wave 25 ft high above still water level. Coincidence of such a tsunami with a maximum tide level of El. 11.4 would result in a water level against the powerhouse of El. 36.4. The recurrence interval for the maximum probable tsunami is about 150 to 200 years. However, coincidence of this tsunami with a very high tide is low and thus the recurrence interval for this highest water level would be much longer. Discussion of the effects of such wave loadings on the structure were limited. We request a more complete discussion of the effects of this larger tsunami on the powerhouse and a curve showing annual probability of coincidence of such a maximum probable tsunami with several tide levels. 8. Power Iunnel Intake The model studies indicate the power tunnel intake as now designed has excellent operating characteristics. Modification will not be necessary nor will additional mod~l tests. Trash removal from the intake poses problems because of the depth. of the intake below reservoir levels. Trash rakes would require very long guide structures which would be subject to ice damage. Consider- ation is being given to using a clam shell bucket operating from a barge. We concur that this probably is the most satisfactory method. 2-686-JJ Hr. D.R. Eberle 6 Hay 30, 1986 Alaska Power Authority The diversion tunnel and power tunnel intakes have slots for installing bulkhead gates for use during construction and to permit maintenance of the guard gates. The bulkhead gates are designed such that they can be used at either tunnel. These gates will have to be handled from a barge. We suggest consideration be given to providing a barge which could handle these gates and the clam shell bucket for cleaning the racks. The depths to be reached preclude most cranes. Consideration should be given a catamaran barge equipped with a hoisting tower and a large capacity winch. Design The configuration of the power tunnel, penstocks, and manifold were described. In our opinion this tunnel should be fully lined with concrete. It was observed that the Engineer presently plans on a minimum thickness of 15 inches for the concrete liner. It is our opinion that 12 inches is an adequate minimum thickness for this tunnel. It was also noted that the upper section of the power tunnel between the intake portal and the gate shaft was "reinforced" due to a combination of rock loads and water pressures during a possible unwatering. It is our judgement that this circular tunnel will support those external loads unreinforced at the minimum thickness suggested above. It is emphasized that the Board still feels it is necessary to have a reinforced concrete transition section between the end of the steel lining and the beginning of the plain concrete tunnel liner in the downstream end of the power tunnel. This transition section was omitted from Drawing 15800-FY-l61A. The length of this section should extend upstream to Station 36+00, as the stationing was defined in November of 1985. The limit of the reinforced concrete transition section extends to a point where the static load and the rock cover are approximately equal. Upstream of the reinforced concrete transition section the power tunnel should be unreinforced except for low modulus zones along the tunnel such as fault zones, etc. Th~se portions of tne tunnel should be designated by the engineer between the · time between tunnel excavation and the pouring of the concrete liner. Bidding Approach / There was a preliminary discussion on how to write the specifications and what bid items to include. The earlier decision, to allow the Contractor to select the tunnel profile, from the U/S end of the penstock manifold to the gate shaft, was reaffirmed. This allows a number of options, which raise many questions on how to establish the payment schedule. 2-686-JJ Mr. D.R. Eberle 7 May 30, 1986 Alaska Power Authority The payment schedule should fairly compensate the Contractor while encouraging an innovative approach to the work. The Owner must not be subjected to undue cost due to bid unbalancing and spurious claims for changed conditions. Tunneling conditions are complicated by the unknowns of tunneling through the Bradley River and Bull Moose Fault zones. Each of these fault zones could be as much as 700 to 900 ft wide and a significant portion of these zones could be squeezing ground consisting of gouge and brecciated material and possibly running sand. These conditions should be described in the contract documents. SWEC will prepare a study of the tunnel profile envelope, defining the limits within which the Contractor can construct the tunnel. In addition, a report will be prepared, in cooperation with Bechtel and the Alaska Power Authority, on how to bid the power tunnel. This will include considerations of: 1. Type of specification a. Method vs. Performance (1) Excavation Method (a) Drill and Shoot (b) TBM (2) Design of Initial Support (3) Tunnel Profiles 2. Possible Contract Provisions a. Interpretative Geotechnical Report b. Disputes Review Board c. Escrow Bid Documents 3. Credit/Debit, for tunnel proi'J.le configuration and tunnel size, to the Contractor's bid price. 4. Pay Items a. Unit Prices (1) Excavation (a) Lineal Foot (b) Ground Classification 2-686-JJ Mr. D.R. Eberle 8 May 30, 1986 Alaska Power Authority {2) Initial supports {3) Discharge of groundwater {4) Grouting to minimize inflow of groundwater {5) Feeder/drain holes ( 6) Final Lining (a) Plain concrete (b) Reinforced concrete (c) Steel and concrete (7) Mobilization b. Lump sum(s) 5. Pay quantities for unit price items We suggest that a one day discussion by the Board of this bidding approach be scheduled in conjunction with the hydraulic model testing meeting in July. Construction Concerns A one and two-thirds percent grade may be steep for rail haulage. We suggest giving the Contractor grade options starting at the upstream end of the penstock manifold as long as minimum cover requirements are satisifed. The geotechnical report should note that "squeezing ground" and ":running ground" (both as defined by Proctor & White), as well as TBM settlement in fault gauge, need to be considered in the design of the machine to perform in the fault zones. 10. Jam StabilitY Analyses The most critical wedge to be considered for the performanc~ of the concrete faced rockfill dam is the wedge located above a straight line extended from 1180 elevation on the upstream face down to the downstream toe of the dam. As a result of a review of the Stone & Webster calculations and as a result of our own independent calculations we agree that the present dam configuration with a downstream slope of 1.6:1 results in permissible permanent downstream displacements of the critical wedge described above. These displacements are likely to be on the order of .6 to 2.0 ft and are considered acceptable. These movements are consistent with retaining the reservoir but after this event the concrete face may require repairs. 2-686-JJ Mr. D.R. Eberle 9 Hay 30, 1986 Alaska Power Authority Concrete Face Slaq We concur that a constant thickness face slab is appropriate for this dam. A thickness of 12 inches is adequate providing care is taken in design of the concrete mix, mixing, placing and curing of the concrete to ensure excellent frost resistance and minimal shrinkage. Continuous two way reinforcing within the perimeter joint is acceptable. However, the face will. be placed in vertical strips of 40 to 60 ft width. A form is required on one or both sides of each strip on wbich the screed can ride. Horizontal reinforcing across these joints probably can be accommodated by dowels as is done in highway paving. Joint details are based on recent practice on a number of other dams. In general there has been a tendency during recent years to reduce use of water stops and to place greater dependence on mastic covered by belting for joints subject to movement such as the perimeter joints and adjoining vertical joints. These details have largely been developed in dams located in tropical areas. The dependability of such details for a dam subject to severe frost action and thick ice cover should be reviewed further. We concur with trimming the right abutment to develop a reasonably straight perimeter joint at a slope of about 0.25 H to 1 V. Experi- ence with very steep abutments such as this shows problems because of shear displacement of the face slab relative to the toe plinth under water load. Details of the rock excavation and plio th arrangement should be carefully developed to minimize such displacements. Instrumentation and monitoring should be limited to monuments along the crest and along a horizontal line on the upstream face at 2/3 the height of the dam. Settlement and horizontal displacements of each monument can be determined by surveys at appropriate intervals. Means of measuring seepage through the dam are desirable but means of doing this at a reasonable cost are not immediately apparent. We suggest this be reviewed further. 2-686-JJ Mr. D.R. Eberle May 30, 1986 Alaska Power Authority The basis for our report is the excellent two volume summary assembled by Stone & Webster sent to us prior to the meeting as well as the oral presentations given on May 28th and 29th. We acknowledge the excellent job of summarizing the current status of design as given in the two volumes without which this report could not have been writ ten in the time allotted. Respectfully submitted, ~~-~[· A. J. Hendron, Jr. I W. F. Swiger ~ Alaska Power Authority APA/O'mR/0103 July 11, 1986 Mr. Quentin Edson Regional Engineer State of Alaska Federal Energy Regulatory Commission Portland Regional Office 1120 S.W. 5th Avenue, Suite 1340 Portland, Oregon 97204 Attn: Mr. Phil Mabini FERC BJARD OF CONSULT ANTS S~ND REPORT BRADLEY LAKE HYDROELECTRIC PROJECT Bill Sheffield. Governor The report ot the second FERC Board ot Consultants meeting of May 28 and May 29 bas been reviewed and our response to the comments is as follows. Our responses are numbered and titled similar to the report dated May 30, 1986 wbich we have attached to this letter tor reference. 2. Status The negotiations tor Nuka water rights were successful and, as a result or this Nuka water rigbt a$treement, a Site Preparation Contract was awarded on June 17, ~986 to the low bidder, Enserch Alaska Construction, Inc. Site work has been star~ad, with surveying and Martin River borrow access road construction underway. 3. Construction Schedule The detailed project schedule is being prepared by Bechtel and will be-sent to the Board in July. 4. Model Tests The model test series of April 18, 1986 indicated a need to improve the flow conditions over the spillway. The design 4-o'27 ~B 190869 701 East Tudor Road Anchorage. Alaska (,)9519·0869 (907) 561-787 7 Hr. Quentin Edson Federal Energy Regulatory Commission 2 July 11 , 1 9 86 APA/OTHR/0103 drawings further spillway spillway. of the spillway were modified to extend the piers upstream, and the excavated topography upstream of was lowered to streamline the entrance into the The witness test of the extended model downstream of the spillway, including the toe of dam and the improved river channel, will take place at Fort Collins, Col or ado, on July 8, 1986 with viewing by Messrs. Swiger and Hendron, and Hr. J. Stafford of the Power Authority. · The funds to construct a model ot the diversion tunnel bave been authorized. This model is being constructed at a scale of 1 to 12 and will include two alternate discharge conduits, a steel penstock and a full-diameter concrete-lined option. 5. Spillway The drainage gallery has been located as tar upstream as possible within t.be li.llitation ot keeping the grout curtain under the spillway and not encroaching on the grouted zone with the drilled drain line. The drainage gallery bas been sized at 8 tt. wide by 8 ft. high which will allow for drilling, grouting, and anchoring subsequent to spillway construction it required. The decision on whether to install rock reinforcement anchors would be made as a result of foundation inspection during excavation, so the anchors would be installed prior to concrete placement. Therefore, any deliberate design tor anchors would utilize full length bars without the necessity tor piecing bars such as would be necessary for gallery installation. Subsequent remedial action during project operation could still be conducted trom the gallery, it needed. The possibility ot overall sliding ot the foundation ot the spillway is being considered through reanalyzing the joint data from borings and field mapping. F.nsting exposed areas in the spillway area have been mapped in detail. Detailed mapping will be conducted during excavation to ensure no heretofore unde~ected adverse conditions exist in the foundation. The few observed fractures no~'dipping very steeply dip upstream so as to resist movement of the spillway downstream. However, the conservative assumption ot no cohesion and hypothetical subhorizontal joints will be considered tor a shear friction analysis as required by the board.· Anchors will be required for this case, as it is felt that installation of anchors will satisfy both the design requirements and the board's concern. 4-Q27-DB Mr. Quentin Edson Federal Energy Regulatory Ccmmission 6. Diversion Tunnel 3 July 11, 1986 APA/OTHR/0103 The results ot a mathematical vibration analysis of the downstream diversion pipe conduit indicated that there was a substantial margin between the natural frequency of the water conduit support syatea and potential flow induced vibrations. Despite these results we appreciate the Board's concerns regarding the possibility ot damaging vibration and are proceeding with the model to study the flow conditions downstream ot tbe gate with both the penstock flow pipe and full tunnel arrangements. The results ot a proposed model study will be of a comparative value only. With the proposed modeling technique it will not be possible to simulate potential pipe vibrations directly since the ratio ot stittnesa/dimensions 1a very different between the model and the prototype. However, basic visual observations and pressure measurements within the penstock flow pipe will be made with variable amounts ot air being individually injected tor each alternative to provide a camparison between aerated and non-aerated flow. Operational behavior of penstock pipe and full tunnel alternatives under consideration will also be carefully compared and evaluated. 1. Powerhouse Excavation The concept ot neat-line excavation tor payment is being retained as reccmmanded. Overbreak control will then be contractor responsibility, as he will be in the best position to determine wtlether a higher degree ot blasting control, neat-line shooting with resultant underbreak removal or, overexcavation to elillinate underbreak ruoval costs (but with inherently higher bacld'ill costs) is most expeditious and economical for his purposes. As a result, overbreak excavation and replacement backfill (earth till or concrete, depending on what the final material in the area will be) will not be paid . .-..:; ·.:::.!t quantit~es, but will have to be esti.aated in the cont~actor' s bid quantities and incorporated as a differential or wastage factor in his estimate. This approach will promote tight overbreak control, by providng inoenti ve to reduce contractor costs for backfill and excess waste removal. An absolute overbreak limitation will be set to avoid use ot excavations as a quarry and to avoid surface damage in critical areas. The meuurement and payment section will emphasize the requirement tor close control on overbreak and stipulate tbat overbreak and backfill costs must be put into the unit prices. 4-027-DB Hr. Quentin Edson Federal Energy Regulatory COIIIIIis si on 4 July 11, 1986 APA/OTHR/0103 Emphaais will be placed in the text that overbreak can be expected due to jointing, bedding and foliation, and excavation shape and rock variability. Special attention will be paid in the final specification to explaining the need and purpose for pre-bolting, dowels, tight mesh and controlled blasting. It will be pointed out that blast design overbreak will depend largely on blasting sequence and attention to geologic structure in the layout and loading of' the explosive round, and rapidity of rock support installation when excavating. The type of' controlled blaating and general lift limitations will be specified, but exact loading details, sequence of excavation, powder loads and types etc. will be entirely the contractor's responsibility. Further discussion on detailed blasting specifications will be incorporated in the final specification after the initial submit tal and the receipt of review comments during the next board meeting. The detailed joint analysis tor the powerhouse area is oontinuing, and indicates that while a 4 and/or 5 toot grid of rook bolts will generally be adequate under static loads, a closer spacing may be locally required at protruding corners, areas of rook stress concentration, and on high cuts (up to 39') under seismic loading conditions. The reference to mesh in the meetings was a question of di!'ferences in use ot terminology. The term •mesh• is being used to indicate chain link or twisted wire mesh, whereas •fabric" is used to indicate welded wire fabric. Due to the blocky nature of the rock and expected permanent load-carryiDg requirement tor the mesh, 2 x 2 inch #9 gage galvanized aaesh is being specified instead of' the more normal #11 gage used tor temporary support. TsUDBDli Studies The Tsunami Hazard Report will be issued prior to the next Board meeting, and will include the combined probability of' tsuuami and various tidal levels, and the final qualitative detailed tsunami risk assessment. The probable effect on the powerhouse tor each wave stage and wave loading~ will be shown as part of a separate design criteria tor the powerhouse. Also, the project will investigate the design of the powerhouse for the ma.xiDl\1111 credible tsunami. 8. Power Tunnel It is our understanding that the sentence "tunnel profile envelope, defining the limits within which the Contractor oan construct the tunnel" means a range bounded by: 4~27-DB Mr. Quentin Edson Federal Energy Regulatory Commission 5 July 11, 1986 APA/OTHR/0103 a. Lower Limit: A near-horizontal line at an elevation not lover than the tunnel invert at the downstream end. b. Upper Limit: An envelope ot the minimum pressures created in the tunnel by the most adverse transient conditions. This line is limited by a straight line from gate shaft to end ot steel lining to prevent the contractor from suggesting an intermediate shaft midway down the tunnel. It is to be noted that all operations connected with trash racks and bulkhead gates must be diver assisted. The current design has been based on the requirement for a barge equipped with a hoist tor handling the bulkhead gates. When the lake elevation is too low to access the inlet portal from the barge a mobile crane can be used from a bench at E1.1080. In addition, the Power Authority will consider and evaluate the merits ot providing a catamaran type barge equipped with a clam shell bucket for cleaning ott the trash rack debris, cleaning ot the rock trap in front ot the trash rack and other underwater related work, as part ot the project equipment supply. The use ot a by-pass tor tilling ot the tunnel downstream ot the Higb Pressure Gates will be incorporated into the design. Power Tunnel Design The understanding that design calls tor a 15 inch concrete liner thickness is incorrect. The concrete lined portion is planned at nominal 12 inch thickness. The reference to 15 inches related to the probable minimum concrete backfill thickness around the steel liner, considering necessary clearance to give access for welding liner sections from both sides. The upper section of the tunnel from intake to gate shaft bas been estimated on the basis ot .... "".i .,f'orced seC"tion. Due to the under-reservoir and upstream-of-gate location ot this segment, (with attendant difficulty ot repair in the event ot major distress), and the fact it closely parallels a significant bedrock foriiB tional contact which is expected to be somewhat poorer rock than typical, it was felt that reinforcing would be beneficial from a project reliability standpoint and would be a worthwhile investment when considering mobilization, access and repair costs and the potential lost energy value that would be incurred in the event ot problems. Should field conditions show the rock or segments thereof to be highly competent the reinforcing would be deleted as a field change. We recommend that this protective reinforcing feature be reconsidered by Board, taking into account the value ot the risk mitigation factor. 4..{)27-DB Mr. Quentin Edson Federal Energy Regulatory Commission 6 July 11, 1986 APA/OTHR/0103 The Board's requirement for a reinforced concrete trans! tion section upstream of the steel liner has been previously noted, and is being incorporated on the drawings. The main segment of the power tunnel is being carried as unreintorced concrete except for the fault sections (very low modulus zones), and possibly the bends in the inclined tunnel section where the effective span gets large. Bidding Approach A preliminary dratt letter report regarding bidding procedures and tunnel configuration restraints was provided to the FERC Board members on 8 July. The engineer preferred scheme, contractor options, and measurement-and-payment details presented therein incorporate the optional tunnel/shatt configuration with the v.ariable tunneling conditions pay items. The resultant contract would be in unit price format, with variable tunneling unit prices dependent on defined rock conditions, and fixed support element units and prices which would be applied in variable combinations as conditions mandate. This approach retains maxiiiiWil flexibility to accoiiiDIOdate the changing ground conditions, and payment by measurable instiJ.led work item will avoid the pitfall ot paying by typical support details when specific conditions may mandate v-ariations in support element combinations needed or used. The payment by support elements installed plus per-lineal-toot of excavation class also reduces the chance of bid unbalancing due to unknown ground conditions, and claim and diapute delays will be reduced because readily measured u.nit:s will be the ba:si:s for payment. The contract documents will clearly spell out all the itelllS of work included in each support element, and ground condition terminology will be defined in considerable detail so as to establish the limiting conditions for each class of excavation. Additional considera tiona such a,. htT"'Ieling met!'lod and equipment options, temporary and permanent s•Jpport design, profile limits, interpretive geotechnical report, disputes board, bid aocument, and bid estimate escrow, etc. are discussed in the report as well. Construction Concerns The design for a 1. 667% sloping tunnel grade was based on providing drainage capacity for maximum infiltration potential without exceeding reasonable haulage grades. Unsanded rail friction is expected to run at 20-251 on clean, heavily used rail, and 15-20% for wet, dirty, or muddy rails. This slope results in a grade resistance of 33 pounds per ton of train, which ia not considered excess! ve. The slope adds up to a deceleration capability rate loss of 0.3 mph per second due to 4-027-DB Hr. Quentin Edson Federal Energy Regula tory CCIIImisaion 7 July 11, 1986 APA/OTHR/0103 slope. Thia results in a required looomotive weight (for grade resistance plus normal 0.3 mph/second deceleration criteria) of about 65 pounds traction per ton ot train, or 65 lbs./.15 friction = 433 pounds maxiJII.Uil ot locomotive weight per ton of loaded weight, or no less than a 5:1 load factor. This is fairly normal tor mine locomotives, and is considered to be a fair basis tor the engineer's recOIIUIIended design. Use ot sand would typically allow a 50S increase in friction, so the actual effective load factor would become 7:1 to 11:1, depending on rail condition. We prater to keep with this basic grade as the basis for common bidding because it reduces the inclined Bhatt length 250'! with onl1 2 teet ot added tunnel length, 1a manageable tor normal equipment, and will handle an1 reasonable groundwater intll tration. Th1a basic oontiguration would then be the basis against which cla1118 tor water handling would be measured, and eliminates the risk ot having to paf a water control claim due to reasonably handled intlovs but an inadequate grade causing flooding on the excavated tunnel. The ground coDd.ition terms, including running, ravelling, squeezing, blockf, etc. will be addressed in the specification and the tunnel bid tor1111.t report, as noted above. 10. Dam Stability Analyses The completed dam stabilitJ/wedge anal7ses confirm the data provided to the Board, and the 1 :68 to 1V slope is, therefore, contirmed as final. The final cont'iguration of the downstream cotterdam will be detailed with the cofferdam initial design sutmittal, and will be discussed at the next meeting. Concrete Face Slab The comments on slab thickness and panel dowelling are noted and are being adhered to in final de.Ri~. The use of the flexible cover flap ot belting with ice lc..adings is being considered in deaign and wUl attect materials selection, fastener de~ign and detailing. However, as a back up, a compressed closed-cell neoprene seal under the mastic and a metal waterstop near the bottCIII ot the slab are stil!' included in the joint detail. Final dam layout has revealed that right abutment trimllling to 1H:4V locally, and flatter slopes below the abutment plinth, will provid& a continuous bedrock contact except at one unavoidable spot where a concrete bearing wall or blook will be necessary. The plinth cut slopes selected will be discussed at the next meeting, and have been designed to provide strain distribution in the till and to avoid •bard• spots under the slab. The resultant perimeter joint is straight, with a slight convergence (in plan) f'rCIII the upstream toe to the axis. A much smaller, shorter, 4-Q27-DB Hr. Quentin Edson Federal Energy Regulatory Commission 8 July 11, 1986 APA/OTHR/0 103 transition occurs at the left abutment where a concrete abutment block will be used to eliminate a section of very low dam facing and fill. The resultant rock excavation to accommodate this plinth configuration improvement is not excessive, and virtually all rock .should be usable in the dam fill. The instrumentation design is a detail to be added after the initial submit tal. The problem of measuring through-flow under the dam is aggravated by high tailwater conditions relative to the toe of the dam. Detailed efforts will be made to accommodate flow ~eaauring. Low flows may be directly measurable by means of a weir, but at high flow conditions it is probable that increased seepage will have to be detected (not measured) by piezometers installed in the dam face bedding layer. Survey instrumentation is expected to include 2 sight linea {crest and mid-face as reca~~eoded by the Board), 2 rows or monuments on the downstream face, and a net or four to six reference monuments which will double as construction control, and as construction progress photo camera positions. If you wish to discuss our responses you may call met at 907-561-7877, or you may wi.sh to discuss these responses at the next FERC board meeting which is scheduled for August 18 -21 in Anchorage. An agenda tor the August meeting is being developed and will be issued prior to the pending 111eeting. Sincerely, Hr. David R. Eberle Project Manager DRE/JF/DB ~t-o27-DB Same Letter Sent To: Mr. A. J. Hendron, Jr. 28 Golf Drive Mahomet, IL 61853 Hr. John Parmakian 2965 Layatette Drive Boulder, CO 80303 Hr. P. E. Sperry 21318 Las Pilas Road Woodland Hills, CA 91364 Hr. W. F. Swiger Box 388 Buhl, ID 83316 4-027-DB Mr. David R. Eberle Project Manager Alaska Power Authority P.O. Box 190869 Anchorage, Alaska 99518-0869 HYDRAULIC MODEL BRADLEY LAKE HYDROELECTRIC PROJECT Dear Sir: RECEIVED JUL 11 1986 SWEC-ANCHORAGE July 9, 1986 J.O. No. 15800.72 In accordance with our decision and your letter of June 23 we observed the Hydraulic Model of the Bradley Lake Project. We were accompanied by Mr. John Stafford of your office and Mr. Jay Hron and Dr. Yung Shen of Stone & Webster Engineering Corporation. The model was operated in the following modes: Flow Over Spillway (Diversion Tunnel Closed) 1000 cfs 2000 cfs 5000 cfs 8000 cfs 10,000 cfs 23,800 cfs (Probable Maximum Flow) Diversion Tunnel 10.5 ft. pipe 6000 cfs -reservoir at El. Open tunnel (19'0) 6000 cfs reservoir at Open tunnel (19'0) 4000 cfs reservoir at Open tunnel (19'0) 6000 cfs reservoir at 1180 El. 1080 El. 1080 El. 1180 During spillway operation a large eddy occurs downstream of the dam so that flow along the face of the dam is towards the diversion tunnel. Flow velocities are small, about 5 ft/sec (prototype) at 10,000 cfs over the spillway and 8 to 9 ft. a second at 23,800 cfs. Flow over the spillway was very smooth with some standing waves on the rock below the concrete apron. Wave action against the toe of the dam was small, of the order of 1 ft. or less for flows below 10,000 cfs and only about 5 to 6 ft. at PMF conditions. DRE 2 July 9, 1986 On the right bank downstream of the dam there is a rock knob which rises well above El. 1100. At high flows the main current impinges on and flows around the channel side of this knob. At PMF flows water rises against this knob to about El. 1100 dropping to about El. 1070 as it passes around the knob. There may be some plucking of rock from the knob because of hydrostatic pressures developed in joints in the rock. This would not affect safety in any way, and we do not consider this condition to be of consequence. Alluvial materials tend to accumulate in the center of the eddy downstream of the dam. Rock is low at this location and such deposition is not of concern. At 6000 cfs and full reservoir the 10.5 ft. diameter pipe of the diversion tunnel was flowing full at a velocity estimated to be 69 ft. per second. For the same flow and reservoir level, the open tunnel was about 1/3 full and the discharge with a velocity of about 40 to 45 ft. per second. For both cases an oscillatory condition developed downstream with water building up on the upstream side of the knob described above which then displaces the main current intermittently. As a result water surged up and down against the knob through a range of about 15 ft. This did not significantly affect the eddy downstream of the dam. Velocities along the toe of the dam were less than 8 ft. per second and wave heights against the dam were about 5 ft. These conditions are quite acceptable. The preliminary plans showed an excavation in the rock aligned with the right side of the diversion tunnel portal. Crude fairing of this cut face with a piece of plywood placed to approximate the rock surface before excavation indicated much smoother flow. This suggests this excavation may not be needed. Accordingly we suggest a removable piece with top surface to model rock contours be made and installed in the model to determine whether such an excavation is needed. Flows through the open tunnel for reservoir level of 1080 were stable with little surging for flows of 6,000 and 4,000 cfs. The eddy along the toe of the dam was present but velocities along the tow were reduced to about 4 ft. per second. We believe the need for placing riprap on the right bank upstream of the rock knob and opposite the mouth of the diversion tunnel should be reviewed. In summary, flow conditions observed are considered acceptable. Wave motion and currents along the face of the dam are modest and can easily be protected against even for PMF conditions. ~a·~jy'· A. J. Hendron, Jr. Dr. A.J. Hendron, Jr. 28 Golf Drive Mahomet, Illinois 61853 (217) 351-8701 Hr. P. E. Sperry 21318 Las Pilas Road Woodland Hills, CA 91364 (818) 999-1525 Hr. D.R. Eberle Project Manager Alaska Power Authority P.O. Box 190869 Anchorage, Alaska 99519-0869 THIRD REPORT -BOARD OF CONSULTANTS BRADLEY LAKE HYDROELECTRIC PROJECT 1. INTRODUCTION Mr. John Parmakian 2695 Lafayette Drive Boulder, Colorado 80303 (303) 499-5404 Hr. W. F. SWiger Box 388 Bubl, Idaho 83316 (208) 543-4593 August 21, 1986 J. 0. No. 1 5 800 T2.2 The third meeting of the Board of Consultants for the Bradley Lake Hydroelectric Project convened in the offices of Stone & Webster Engineering Corporation at 8:30 AM on August 18, 1986. Mr. John Parmaldan joined the Board at this meeting. Dr. Hendron was not able to attend because of his wife being ill. Lists of attendees at the meetings on August 18 and 19 are attached. We were brie.fed on the .status of work in progress on the Site Preparation Contract. Also we were advised of the changes in responsibilities for purchasing of equipment and changes in contracts for the remainder of the work. Briefly, purchase of the turbines, generators, spherical valves and gov.·:::-:-~ (as one ~ontract) and of the SCADA equipment will be done by the Alaska Power Authority with Stone & Webster preparing the procw1 ement documents. The second stage contract will be the General Civil Construction Contract. It will cover construction of the main d~m, intake to the power tunnel, power tunnel, manifold and penstock, completion of the diversion tunnel, and excavation of the powerhouse, tailrace and construction of the tailrace cofferdam. A separate contract will be issued for construction of the powerhouse and will include purchase of the remaining mechanical and electrical equipment. Construction of the Nuka Diversion, Middle Fork Diversion and reservoir clearing will be done under separate contract. 2-965-JJ Mr. D.R. Eberle 2 August 21, 1986 Alaska Power Authority 2. STATUS The contract for site preparations was issued on June 17, 1986. The first equipment arrived on the site on July 1. Work has been concentrated on developing the Martin River borrow area and on road construction. A road suitable for heavy truck use has been constructed to the permanent facilities, which are adjacent to the powerhouse. A "pioneer" road to the main dam has been constructed to about Sta. 806. The camp including the mess hall is in service. Road construction, except for drainage structures, is on schedule. The quarry is being opened but no riprap has been placed and this activity is behind the contractor's schedule. There are other portions of the camp including the incinerator which are behind schedule. Despite these schedule slippages, the amount of work accomplished since placement of the contract is indeed impressive. The 60% design packages for General Construction Contract were issued on schedule for review. Model tests of the spillway and river downstream of the dam were observed on July 8. A large scale model of the low level outlet in the diversion tunnel will be observed in September. 3. GEOLOGICAL STUDIES Borings RM 15, RM 22 and RM 23 have been completed. RM 15 is located on the right side of the intake channel to locate possible faults which could affect stability of this wall of the channel. Both faults were confirmed. Further studies on stability of this wall of the · intake channel are underway. The contact between argillite and graywacke is not faulted. RM 22 was drilled at a dip of 45° on Antenna Hill to cross a major lineation. It found 18 ft of fractured rock with RQD values of 30$ to 40% but only about 0.3 ft of fault gauge and breciated rock. This indicates a minor fault at this location. RM 23 was drilled vertically at about ;:"' "'+ downstre"~.m of the end of the steel liner. Hydro fracture tests were made in this boring to investigate in situ rock stresses. Three tests were made with the following preliminary results: Depth 480 ft 540 (tunnel level) 650 2-965-JJ Ratio Horizontal Stress/Vertical Stress 1.0 0.52 0.85 Mr. D.R. Eberle 3 August 21, 1986 Alaska Power Authority Fractures were near vertical indicating the horizontal stress to be the minimum stress. At these several depths the horizontal stresses were significantly lower than water pressures in the tunnel at this location. Horizontal in situ stresses appreciably smaller than the vertical stresses are not co1111110n but have been encountered before at other sites. Such conditions pose special problems for high pressure tunnels since leakage from the tunnel can cause hydrofracture of the rock mass resulting in excessive losses of water from the tunnel and in some cases stability problems in hillsides above the powerhouse. One method ot controlling problems from low in situ stress conditions is to reinforce concrete lined sections of the tunnel to distribute cracking such that individual cracks do not exceed about 0.3 mm in width. This effectively limits leakage even though the tunnel is cracked because leakage through the tunnel wall is proportional to the cube of the crack width. Also, with these small strains the concrete remains effectively interlocked across the cracks. Analyses to determine the amount of reinforcing and crack widths are based on calculations incorporating diameter, water pressures and "elastic" moduli of the rock adjoining the tunnel. Such a single test of in-situ stress is not conclusive since it may represent only a local condition. However, simple hydrofracture tests were made in the Bradley Lake and Bull Moose Fault zones. These showed similar results. Hydrofracture tests at these depths below surface are quite expensive and a number of tests would be required to define conditions over the length of the tunnel. After discussions it. was concluded that: 1. Additional hydrofracture tests will be made in holes drilled from the tunnel as it is driven. 2. "Elastic moduli" of the rock in the tunnel walls will be measured at selected locations using cross-hole procedure::> by measuring shear wave velocities. 3. Based on the above data, , .::.:. f ... ·cement of the tunnel in areas beyond what is already planned will be designed as the tunnel is driven and installed during construction of the lining. Provision for this will be made in the bidding documents. 4. Special care will be needed in designing reinforcement in the Bradley River and Bull Moose Fault Zones. 5. The length of the steel liner but should not be shortened from that presently planned. 2-965-JJ Mr. D.R. Eberle 4 August 21, 1986 Alaska Power Authority 6. Provision should be made in the bidding documents for compaction grouting of the distressed zone around the tunnel if this is found necessary. 7. Subsurface drainage of the hillside above the powerhouse should be reviewed. 4. SPILLWAY Stability analyses of the spillway for the concrete and the concrete-rock contact using the shear-friction factor showed conservative factors of safety at accepted pore pressure assumptions. In its second report the Board requested that a further analysis be made assuming a hypothetical slide plane having zero cohesion or on such planes wbich could be developed by intersecting joint systems. Further geologic studies did not show any critical slide planes under the structure. Accordingly an analysis was made assuming htpothetical slide planes at El 1150 and 1130. A friction angle of 45 and zero cohesion was used. The analysis of El 1150 controlled and showed factors of safety against sliding of 1.9 for normal full pool and 1.4 under PMF flood conditions. A friction angle of 45° is conservative for this type analysis. Dynamic analyses showed calculated displacements of 0.4 ft ignoring arch action or shear along the abutments for the maximum credible earthquake of 0.75 g acceleration. These findings together with the other studies indicate the spillway is adequately stable. An adequate sized aeration slot should be constructed across the spillway apron to minimize possible cavitation and erosion damage under flow conditions. Check optimum location of the aeration slot on the current model at the Colorado State University. This sLot must be drained in such manner that complete drainage is a5sured. It may be feasible to develop the desired aeration by keeping the rock surface downstream of the end of the apron about 4 ft below the lip of the apron. Details ot the training walls must ensure air supply to this area if this is done. 5. POWERHOUSE Design of the rock bolts for support of the walls of the powerhouse excavation has been reviewed. Consideration was given temporary support for construction below El 21 and permanent support between El 21 and El 42. In general these studies showed a pattern of 4 ft on centers both ways would be adequate with closer spacing needed only in certain locations. Further studies of the powerhouse under earthquake loadings are being made and will be reported on in the future. In its second report the 2-965-JJ Mr. D.R. Eberle 5 August 21, 1986 Alaska Power Authority Board requested a recurrence curve for tsunami height at the powerhouse considering coincidence of tides and tsunami waves. This has been completed and is attached. This indicates the probability of a tsunami wave to El 36 is 0.001 occurrences per year. Design of the powerhouse to resist a breaking wave to this level would be prohibitively expensive. However, completely across the bay, shoals at about MLW, extend to 3 miles south of the powerhouse. This shoal would trip the large tsunami wave considered three miles from the powerhouse. Considering the above and the orientation of the powerhouse, a wave breaking against the powerhouse at El 36 is not considered possible. Lower waves could impact the powerhouse but such waves would, even if breaking which is doubtful, impact largely on the substructure rather than on vertical walls. Accordingly it was agreed it would be adequately conservative for tsunami protection to design the powerhouse to withstand a static bay water level of El 36 using normal stresses. The following comments and recommendations should be added in the bidding documents and design studies of equipment as appropriate: 1. Impulse Turbines 2-965-JJ a. Spin balance each turbine runner at 300 rpm at the turbine manufacturer's shop before shipment. This will prevent arguments later during balancing of the complete turbine-generator assembly. b. Pressurize turbine manifold assemblies during encasement to 100 percent of the maximum static head (not 80% as shown in the present specifications). The difference in radial deflection of the manifold due to this increase in embedment pressure is about 0. 001 inch. However, this will assist in preventing cracking of the concrete encasement of the manifold assembly under surge conditions. c. Circulate cooling water through the manifold assembly during concrete enca:h-:.-.. ~-. This t~ill assi.:st in removing the heat of hydration of the concrete and prevent misalignment of the manifold after the concrete sets. / d. The computed reinforcement required in the concrete encasement to withstand the pressure rise is about 1 inch diameter bars at 9 inch spacing. e. The turbine guide bearing should be designed to withstand the unbalanced load on the bearing due to 3 adjacent needle jets operating. Mr. D.R. Eberle 6 August 21, 1986 Alaska Power Authority 2. Generator a. The generator manufacturer should be required to furnish detailed computations for the critical speed of the turbine-generator assembly. These computations must include bearing stiffnesses at all 3 guide bearings which are used in the analysis, i.e., bearings must not be assumed to be rigid. b. The generator manufacturer should also be required to furnish detailed stress analysis for the dove-tail slots in the rotor under runaway speed conditions. c. The generator guide bearings should be designed to withstand the unbalanced load on the bearings due to 3 adjacent needles operating. d. To provide governing stability of t~e power plant for isolated operation, the minimum 6WH of2 the generator should be not less than 10.3 x 10 lb ft . 3. High Pressure Gates a. Gate slot offsets should be utilized to prevent erosion and cavitation damage due to flow impingement into the gate slots. b. The vibration of the gates' and stem under pulsating flow conditions during the closing stroke should be analyzed to ascertain if a resonance condition is present. 4. Governors The governor manufacturer should verify the stability of the plant for :2olated operation of the plant using the increased WR of the generator noted above. The computations indicate that a :;:-..,.:·1ernor WO!.:ld be adequate. 6. ENVIRONMENTAL CONCERNS DORING CONSTRUCTION Bechtel, Construction Manager fo~ the Project, briefed us on the orientation given all employees regarding protection of the environment during construction. They also presented copies of a handoook which is given each employee regarding protection of the environment. We were very favorably impressed by the thoroughness of their approach and by the handbook. 2-965-.JJ Mr. D.R. Eberle 7 August 21, 1986 Alaska Power Authority 7. BID DOCUMENTS -GENERAL CIVIL CONTRACT Partially complete (60%) plans and specifications for the powerhouse and dam were sent us on July 15 and August 1 , respectively. These were reviewed and comments by Hr. Parmakian, Hr. Sperry and Hr. Swiger were given Stone & Webster Engineering Corporation. Comment3 by Dr. Hendron will be mailed. The documents for the tunnel and miscellaneous structure were furnished on August 18. Comments on these will be fUrnished at a later date. It was agreed that a nearly complete set of plans, specifications, and the Geologic Interpretive Report will be sent the Board on December 1. The next meeting of the Board will convene on December 15 for a detailed review of these documents. There has been considerable discussion on the approach to bidding the construction of the power tunnel. This has not at this time been fully resolved. 2-965-JJ Mr. D.R. Eberle 8 August 21, 1986 Alaska Power Authority We were favorably impressed by excellent progress on the site preparation construction. We also wish to acknowledge with thanks the brierings given on the designs and .specirications under preparation and the on-time issuance of preliminary (60%) drawings and specirications. Respectfully .submitted, ATTENDEES THIRD FERC BOARD MEETING BRADLEY T~KE HYDROELECTRIC PROJECT ALASKA POWER AUTHORITY Meeting of August 18, 1986 The FERC: Messrs. P. Mabini W. H. Allerton The FERC Board: Messrs. W. F .. Swiger J. Parmakian P. E. Sperry The Alaska Power Authority: Mr. J. C. Stafford• Mr. D. R. Eberle* Stone & Webster Engineering Corporation: Messrs. s. A. Lucks D. L. Matchett J. J. Garrity• L. Duncan J. Hron• T. Critikos *Part time. 2-967-JJ 3 0 r-.... m «:r ~~oz.. l:' .J CQ 1C' ~ 0 ~ o.or __ 1!1 u 9. ~ "' ~ 8. :t 0 ~ .;:; (u > i5 lu 7 ~ \J "' 'l( "'· f.u 6-""-... , u. ,.._ u; ~· Q.DOS". .. u -o l:u ~"' ,... ... -,. a:: ... 4 "'"' "'" J o., ..J._. ~ -· ::1''5 -:::1 ...... "'" z 3 !AI z ., ~ ....,. - ·.J ~.~'-~~~~~~~~~~~~~~~~~~~~~~~~~~~--~--~--~ ~ . -· PLEASE NOTE: This letter dated October 28, 1986 supersedes Letter No. SWEC/APA 1003 dated October 21, 1986. Mr. D.R. Eberle Project Manager Alaska Power Authority P.O. Box 190869 Anchorage, Alaska 99519-0869 FERC BOARD OF CONSULTANTS THIRD REPORT BRADLEY LAKE HYDROELECTRIC PROJECT JJMPlante/DLMatchett Gen Files/DOC JJGarrity/Chron TCritikos, JBK T2.2 NABishop LDuncan JHron R.Krohn JYa1e JNowak October 28, 1986 J • 0. No. 1 5 80 0 . 1 2 T2.2 SWEC/APA 1003 We have reviewed the third FERC Board of Consultants Report on the August 18-20, 1986 meetings and our responses and ccmments to the Board's August 21, 1986 Report follow. We have m.mbered and titled the responses and ccmments sequentially with the Board's Report, copy of which is attached for your reference. 1. INTRODUCTION Although no specific recommendations are made within this section, it should be noted that during the previous FERC Board Meetings the Board had expressed concurrence with the proposed changes to the Power Authority's Management Plan for separate purchases of equipment as well as changes to the Construction Contracts for the remainder of the work. As you are aware, Stone & Webster favors the contractual methodologies outlined by the FERC Boa;.::! "'-::::--,rt. 2. STATUS Relative to the Board's visit to the project site on August 20, 1986 no specific recommendations were made. As noted by the Board's Report certain portions-of the work on the permanent facilities and riprap placement are behind schedule, however overall they were impressed with the amount of work accomplished toda t~. In concert with the Construction Manager, Bechtel, and we are pursuing this matter with the Contractor in order to prevent any delays in completing this phase of construction work. 2-1138-JJ w/enc w/enc w/enc w/enc w/enc w/enc w/o enc w/o enc w/o enc Mr. D.R. Eberle Alaska Power Authority 2 October 28, 1986 APA 1003 This section of the Board's report also mentions the model tests of the spillway and river downstream of the dam which members of the FERC Board witnessed on July 8, 1986 at the Colorado State University in Fort Collins, Colorado. A separate report was prepared by the Board to note their observations. On September 25, 1986 the low level outlet model was demonstrated for FERC Board members Messrs. W. F. Swiger and A.J. Hendron. A report on their observations was also received. Our responses to the Board's reports on the model testing will be addressed in a separate letter within the next two weeks. 3. GEOLOGICAL STUDIES This section of the FERC Board's report addressed the status and findings of the Geotechnical investigations and includes a number of recommendations which precipitated from the meeting. We are continuing our evaluation of results of the latest boring program particularly the field borings RM 15, RM 22 and RM 23. Our studies are centered on evaluating the geologic similarity to other existing data as well as the impacts of the latest data on our current designs. To date, our findings show no significant design changes are necessary. We are awaiting the final hydrofracture test data and report from the drilling contractor, therefore full evaluation of the in-situ test conditions a.s related to the tunnel lining cannot be made at this time. Currently our tunnel lining design includes a reinforced concrete section upstream of the steel lining which· is designed to limit crack size and therefore control exfiltration rates. Consistent with the Board's discussion and recommendations relative to the apparently low in-situ minimum principal stress, our designs as well a.s provisions of the construction contract will include the following in order to establish final definition of reinforced versus unreinforced concrete section limits of the power tunnel: 1. Additional minimum-stress hydrofracture tests will be conducted during construction of the tunnel a.s tunnelling advances. 2. Cross-hole shear-wave conducted in the same hydrofracturing. velocity holes as determinations ~.;!11 be used for the additional 3. Provisions will be included in construction bidding documents for pay item options for additional reinforced concrete upstream of the steel liner, including the fault zones. 2-1138-JJ --'-.. '' • ••-- -'>.J'' •'-._I''' • >.J ""'-" • Mr. D.R. Eberle Alaska Power Authority 3 October 28, 1986 APA 1003 4. Designs will include heavy bi-directional reinforcement at very low modulus rock zones including the Bradley River and Bull Moose Fault Zones. 5. Retention of the end of the steel liner at its present location, based on cover equal to 0.8 times hydrostatic pressure in the tunnel at maximum reservoir level. 6. Contract provisions will include bid item for high pressure ring compaction grouting in low modulus zones 7. Subsurface drainage above the powerhouse includes design of a steel-liner lateral drain system to accommodate potential groundwater inflow conditions. 4. SPTI.LWAY This portion of the Board's Report addressed the results of our additional stability analyses of the spillway which were undertaken at the request of the FERC Board during their meeting on May 28-30, 1986. The analysis results showed critical (break-free) accelerations of 0.35g or above for all design cases, with a 45° friction angle and zero cohesion assumption. The maximt.m free-body computed surface displacement, disregarding any beam or arch action, for the design earthquake response is 0.16 feet with no combined vertical component, or 0.6 feet with a vertical component equal to 2/3 of the horizontal component, applied simultaneously. These results are within the design allowables and therefore, failure of the spillway in the design earthquake is highly improbable and stability is fully adequate. The FERC Board agreed withour conclusions on the stability of the spillway. The FERC Board Report recommends that an adequate size aeration slot be constructed across the spillway apron to m1n1mize possible cavitation and erosion damage. They further recommended that the optimum location of this slot be determined from the spillway model tests. We met with and discussed the matter with FERC Board member Mr. John Parmakian and Colorado State n .. ;,.,.,..sity per:o,nnel during a model demonstration test on August 29, 19~6. Mr. Parmakian indicated that the present spillway model scale is not suitable to permit testing the aeration slots suggested by the Board's report and that a larger model would be necessary. We have investigated available literature and results of past installations of aerated slots in spillway aprons and believe that for this spillway aer.a tion slots may not be necessary since the apron velocities are not of the magnitude to require aeration. We will review additional published literature on this subject and present our findings and recommendations at the next FERC Board meeting for further discussion on this matter. 2-1138-JJ .. --- Mr. D.R. Eberle 4 October 28, 1986 APA 1003 Alaska Power Authority 5. POWERHOUSE This section of the FERC Board Report focused on the design of the - powerhouse. Relative to the rock bolt design for supporting the powerhouse excavations, we will be doing additional evaluations during our design and report to the Board at a later date. After considerable discussion of the subject of tsunami probabilities and wave heights, the FERC Board concluded that it was not necessary nor cost effective to design the powerhouse to resist a breaking wave. They reccmmended the powerhouse be designed for a static bay water level of El. 36 using normal stresses. Our studies on the tsunami loading seem to indicate that in. addition to the static loading, hydrodynamic loading should also be considered in the design of the downstream powerhouse wall. We will continue to review this matter and prepare a presentation for a future Board Meeting to present our findings for powerhouse design loadings for tsunami condition. The Board's Report also contained a number of recommendations related to the powerhouse equipment design. Following are our responses to the FERC Board comments and recommendations for inclusion in bidding documents and design studies of equipment: 1. Impulse Turbines 2-1138-JJ a. We will include a specification requirement to spin balance the Pelton runners in the manufacturer'::s shop. However, we believe that balancing at a lower speed than the operational speed of 300 rPD should be allowed, as discussions with turbine manufacturers indicate that a lower speed can be used to satisfactorily balance the runner. Spin balancing the runners at a speed of 300 rpm would be an unnecessarily costly specification requirements. b. We agree with the Board's recc:mmendation that the manifold assemblies should be pressurized to 100S of maximum static bead during encasement and will include this requirement in the bidding documents. c. We concur with the Board's recc:mmendation that cooling water to be circulated through the manifold assembly during concrete curing. Bidding documents will include this requirement. d. our designs for the manifold assembly includes reinforcing the concrete encasement as required for strain compatibility due to the water pressure rise. We will check the Board's suggested reinforcement spacing for adequacy. Hr. D.R. Eberle 5 October 28, 1986 APA 1003 Alaska Power Authority e. Specifications for the turbine will require that all guide bearings be designed for 3 adjacent needle jets operating. 2. Generator 2-1138-JJ a. Critical speed computations will be required of the generator manufacturer in the Turbine-Generator specification. The computations of bearing_ stiffness at all three guide bearings will be a specification requirement. b. We concur with the Board's recommendation and the specifications will require the generator manufacturer to supply calculations indicating the stresses for the rotor dovetail slots under runaway conditions. c. We also concur with the Board's recommendation that the generator guide bearings be capable of withstanding the unbalanced load on bearings under the conditions of three adjacent jets operating. d. We have reviewed the Board's recommendation for providing governing stability of the power 2 plant for isolated operation that the minimum WR 6 of th2 generator should n'2t be less than 10.3 x 10 lb-ft (10.3 million lb-ft ) and have the following comments: ( 1) The generator specifications ~o~ill include requirements that the ~anufacturer furni~h generators with a minimum WR of 8 million lb-ft . lbe manufacturer will also be required ~o furnish costs of gen~ators with a minimum WR of 10.3 million lb-ft • The reasoning here is that ~o~e believe that gen~ators with a minimum inertia of 8 million lb-ft is the minimum required for stability, and that the costs associ~ted with the higher inertia of 1n ~ million lb-ft needs to be evaluated before adoption. (2) Contacts with generator manufacturers indicates that 2he inertia value shoul~ be between 6 million lb-ft and 8.3 million lb-ft for the Bradley Lake Project generators. To provide gen2rators with an inertia value of 10.3 million lb-ft would involve almost doubling the inertia of the generators. The investment for the higher inertia does not seem to warrant the higher costs to maintain plant stability. A cost/benefit analysis will be presented for further discussion before a final determination is made for the generator inertia. Mr. D.R. Eberle 6 October 28, 19 86 APA 1003 Alaska Power Authority 3. High Pressure Gates a. We concur with the Board's comment. The specifications for these gates will require an offset in the gate slot area to prevent erosion and cavitation damage. b. Specifications for the gates will require vendor calculations for possible resonance conditions in the hydraulic slide gate cylinder stem and system. 4. Governors The governor manufacturer will be required to perform a stability analysis to determine the maximum stable load when the unit is operating isolated based on the governor and turbine-generator to be provided. Specifications will also require that the governor manufacturer simulate operation and demonstrate stability for supply of an isolated resistive load as well as parallel operation with an infinite system. 6 . 0 ENVIRONMENTAL The FERC Board members were favorably impressed with the environmental procedures implemented at the site and made no additional recommendation. 7 .0 BID DOCUMENTS -GENERAL CIVTI. CONTRACT The comments received from the FERC Board on the 60% design review will be incorporated into the 90% submittal. Those which are not accepted will be reviewed with the Board members at the next meeting. The General Civil Construction contract 90% review package will now be distributed on or about December 15, 1986. Copies of this submittal will be made available to the FERC Board members at the same time, for review prior to the next Board meeting. This will be a complete submittal package and will contain all final review specification sections and drawings including the Inte~pretive Geotechnical Report. To allow adequate time for a thorough review of the documen~,s, the next FERC Board meeting has been rescheduled to January 27-29, 1987. In regards to the closing statem~~t of FERC Board's Report concerning the approach to bidding format for the power tunnel construction we are continuing to review this matter with the Power Authority and Bechtel. At the next Board Meeting we will have completed a bid schedule for the power tunnel for the Board's comments. 2-1 138-JJ Mr . D. R . Ebe r 1 e Alaska Power Authority 7 October 28, 1986 APA 1003 We trust that we have addressed all of the FERC Board's comments. If you have any questions on our responses, please let us know. Theodore Critikos Deputy Project Manager TC/JJ Attachment 2-1138-J J NOiED -· . i STONE & WEBSTER ENGINEERING r:~ORATIOH Mr. D.R. Eberle Project Manager Alaska Power Authority P.O. Box 190869 Anchorage, Alaska 99519-0869 TRIP REPORT HYDRAULIC MODEL TESTnfG BRADLEY LAm HYDROELECTRIC PROJECT JJMPlante/DLMatcQ.4"rt Gen Files/DOC 1 JJGarrity/Chron TCritikos/JUk 15800.08 WP 06E-la2 NABishop LDuncan WCSherman oJBron RDulin DBlanchette September 12, 1986 J.O. Ho. 15800.08 WP 06E-1a2 SWEC/APA 857 Enclosed tor your information and recorda is a copy ot the Trip Report on J. Bron'a visit to the Colorado State University on August 29, 1986. The purpose ot thia trip was to Witness teats ot the Diversion Tunnel Model and retest the Basic Model atter modification. Baaed on the latest lllodel teat results we Will deaign (and retest it necessary) a submerged weir or a flip buokat to suppress the osCillating flow in the stilling pool. Diversion Twmel Model tests proved the adequacy ot the 10.5 ft. diameter pipe solution. Therefore, we are proceeding with the design accordingly. Details ot the spillway aeration slots were discussed at this opportunity. Mr. J. Parllald.an found the scale ot the &.sic Model (1 :50) too saaall tor aeration slot teats and suggested a new larger spUlway 11odel be built. Based on previous quotations troaa CSU we expect that the cost to build &4d teat suob. a IIOdel would be $30,000 to $40,000. It is our estiate that the model test results would be available within two months. Our present sob.edule would not permit . changes to drawings at that time should any be necessary. 3-319-FS STONE & WEBSTER ENGINEERtNf-' "'ORPORATION I Hr. D. R. Eberle Alaska Power Authority 2 September 12, 1986 SWEC/APA 857 We are reviewing relevant literature to establish precedent tor aeration slots having been used tor a low head spillway similar to that ot Bradley Lake Project. Also, the need to model test the slots is being investigated. It you have questions or need additional intormation please call me or Jay Hron. Theodore Critikos Deputy Project Manager Enclosure TC/JH/FS 3-319-FS NOT!D SEP 111986 J. HRON NOTED S E P 1 2 1986 r. Crmkos TRIP R.BPOBT HYDRAULIC !«)DEL TESTING BRADLEY LAm HYDROELECTRIC PROJECT Trip to Colorado State University Hydraulic Laboratory Fort Collins, Colorado August 29, 1986 PURPOSE Present tor: J.O. No.·-15800.08 WP 06E-1b FERC Board ot Consultants Mr. John Parmakian CSU Laboratory Statt: Dr. J. F. Rutt Mr.AladdinShaikh Stone & Webster Engineering Corporation (SWEC) Mr. J. Bron The purpose ot this trip was to Witness tests ot the Diversion Tunnel Moclel inalucSiDg two clitterent discharge pipes and retest the Basic Model atter elimination ot the vertical cut at the tunnel exit. ITINERARY J. Bron picked up Mr. J. Pa.rmald.an at his Boulder home and arrived at CSU shortly atter 8:00 a.m. Atter a short discussion, the Diversion runnel Moc:lel With 11.5 tt. di&Eter discharge pipe was tested. Later in the morning, exchange ot the discharge pipes ot the Diversion Model was started and in the •antilla the Buic Model With 20 tt. horeshoe tunnel was tested.. 1 group trom the Denver ottice led bi Messrs. Lucks and Matchett visited. the laboratory at about 9:30 a.m. and stqed until noon. In the attemoon the 10.5 tt. diameter diaabarge pipe alternative ot the Diversion Tunnel Model was tested.. The Basic Moc:lel was also tested With the 10.5 tt. dia.ter pipe. Testing was completed at 4:00 p.a. J. Hron d.roYe Mr. J. Parmald.an back to his home. DIVERSIOH TUNHEL MODEL -17.5 tt. Diameter Pipe The lloclel was tested. in Freude similitude. Full reservoir level and. 5500 eta d.isobarge were mocleled.. A sta0.1.e, well d(o..; .. ined. jet tlow was observed tor all pte poSitions at the exit troll the 7 x 10 tt. section. the jet tlov, atter leaving the rectangular section bent downwards and struck the bottaa ot the tunnel approximately 30 feet dovnstreu trca the enlarge•nt .· Fr011 this point, the water run-up on the walls ot the tunnel, struck its crown and tilled. the entire flow area with well aerated tlov. Some energy was dissipated., atter the tlow touched the bottaa ot the tunnel, 1D a torm ot undeveloped. hydraulic juap. the supercritioal flow continued through the rest ot the pipe and outSide ot the tunnel as later observed on the Basic Model. 3-313-FS 1 The tlov pattern was silllilar but attenuated ror partial gate openings. Almost no air was admitted through the air vent pipe downstream ot the control gate sinoe sutticient amount ot air waa drawn through the discharge pipe trom the tailrace. Air could flow underneath or the jet where a 2 tt. step provided a gap, tree of water droplets. Operation ot either gate produces the same tlov pattern. It both gates are partially open and the upstream gate is lover than the downstream gate, a tree surface flow is established starting at the lip ot the upstream gate and the entire downstream gate is in the air. It the downstream gate is lover and controls the flow, the upstream gate is tully subErged and no vortices or bubbles are observed. No effect ot tailrace level on flow in the pipe was observed. The tailrace level was varied traa the invert ot the pipe to its oenterline. DIVERSION TUNNEL MODEL -10. 5 Di&Eter Pipe Again, the model waa tested in Freude silllilitude with tull reservoir level simulated. Testa started with 5500 cts and the air admission pipe tully open. The tunnel discharge pipe flows full under these conditions with so• air bubbles running along the crown or the pipe. This air waa drawn through the vent pipe and slot downstream ot the gates. When the air admission pipe was closed, the discharge pipe was clear without bubbles or air pockets. Closure ot both gates was tested with and without air admission. Also, the upstream gate was operated alone and in combination with the ctire downatreu gate. The same observation as tor the 17.5 tt. diameter pipe was made regarding interaction ot the gates. The gate in a lower position controls the flow, the other gate is es881ltially ineffective. Closure ot the dovnstreu gate waa tested under full reservoir level with 5500 cts discharge, with and without air valve open. With air drawn in, the lip ot the gate formed tree surface tor all gate positions except •tully open•. The water surface sloped upwarcla to the crown ot the pipe and the remainder ot the pipe flowed full. Large amounts ot air wu drawn throush the air vct pipe. With the sate moving down, the tree water surtaoe waa extended dovnstreu and the length or the pipe flowing tull was s,etting shorter. At approximately 75~ gate opening, tree surface flov waa established within the entire pipe. 1o abrupt transition was noted. No air was drawn after the f'ree surtaoe flow waa established. Opening ot the gate was the exaot reverse ot .the closing cycle. Withou1~ admission a pressure tlow regi.M in the pipe waa mai.ntained troaa 100S down to about 25~ gate opening. The water waa clear, without any air bubbles. Downstream race of the gate was tully submerged. At 25~ gate position the pressure flow suddenly changed !Dto a tree surface flow wbiah remained until tull gate closure. During gate opening, a tree surface flow was preMD.t traa 0 to approx. 75~ gate position apparently with air drawn through the pipe froaa the tailrace. At 75~ gate opening tew slugs or water passed throup the pipe, the pipe tilled with clear water and pressure flow waa established. These conditions remained until the gate was tully open. 3-313-FS 2 ( With both gates tully open and with the vent pipe open the· discharge through the pipe was gradually reduoed starting with 5500 eta. At approximately 2500 eta the air bubbles increased in size, rev slugs or water IIOVed along the top ot the pipe and the f'low changed f'rom pressure to a f'ree surface type. Free surface started forming at the ez:l.t ot the pipe and progressed upatreu. lfo Significant f'low inatabili ties or f'low surges were obaened. When the discharge was turther reduced, the tree surface f'low regime continued until zero f'low. Increase or f'low (although pbysioally me ani nglaaa) was the exact reverse or the process. Tailrace ef'f'eat on the pipe with tree surface f'low was examined. Ho •backwater• etf'ect was obaened until the exit or the 10.5 f't. diameter pipe was tully submerged. BASIC MODEL ( 1 :50) The model was retested atter tbe vertical cut downstream ot the tunnel exit was reaoved. The f'low surges are still present, especially when tbe 10.5 rt. diameter discharge pipe was installed and f'ull discharge established. A 1 x 1 i.a.ah, 9 in. long prism was located perpendicular to the tunnel f'low approximately 150 teet downstream ot the tunnel portal. 'l'bia forced a hydraulic j'tap and stabilized the f'low regillle in the pool. Without the prislll the bydraulia jump did not tully develop and was fluctuating in the upstream -downstreu direction. SPn.LWAY Location and size or aeration slots on the spillway apron was discussed. Mr. J. Parrlald.an f'ou.a.d the scale of' the Basic Model ( 1 :50) too small and tbus not suitable tor this type ot testa. A new larger spillway 11odel would be required tor testing or aeration slots. The moat appropriate scale ot this new model would be 1 :15 or larger. Dr. Rutf' inf'ormed J .iron that a Sllll.l f'lip bucket was installed on the spillway apron at El. 1155 to eli1111.a.ate aroaatlow between the aprons. The f'l1p bucket was reaoved :since it did not pr<Xluce the expected illl:provement. Statio pressure was measured on the vertical wall, under the water curtain. Above-atmospberio pressure was recorded. Based on this intormation and obsenation ot t.be IIOdel it is reaOIIUD8nded that the arrangement or the step between ap.i'OilS is lett as is. With the concrete li.a.ing properly rook bolted to the vertical wall a po~aibility or wall or rook failure is suttieiently remote. JBron:FS 3-313-FS 3 ,, • i I l I I ~ ~ , 1 > ,. •. '•' ... A. J. Hendron, Jr. P.O. Box 125 #4 College Park Court Savoy, IL 61874 217-351-8701 1-t-. 0. A. Eberle Project Manager Alaska Power Authority P. 0. Box l9J869 Anchorage, Alaska 99519-0869 Interim Report -Board of Consultants Bradley Lake Hydroelectric Project W. F. Swiger P 0. Box 388 RECORD COPY Buhl, Idaho 83316 208-543-4593 September 25, 1986 RECEiVEQ BY .\tASKA cr:'l!'' ~ .. , :'"'~··'I *&S OCT 14 P 4 ; 19 Board Members A. J. Hendron Jr. and W. F. Swiger observed hydraulic model tests on the diversion tunnel as modified as a low lev~l outlet on Sept. 25, 1986. Accompanying us were tot-. Merritt and tot-• .Justin, Consultants, and Mr. Matchett, tot-. Critikos, and 1-t-. Dulin of Stone & Webster Engineering Corp. Trree tests were made, two with the concrete 1 ined tunne 1 and one with the 10.5 ft pipe downstream of the gates. A test on each tunnel configur- ation was run with water level at full reservoir, El 1180, and flow controlled by slowly closing and then opening the gate again slowly, stopping at various partial gate openings to observe and measure flows. For the third test, on the concrete lined tunnel, the head was varied from full pool to El 1090. The gate was then lowered to 0.05 gate opening. Flow conditions under all gate openings were acceptable for both con- figurations. Flow in the steel penstocks showed some surging at 0.9 gate opening. Conditions appeared somewhat more favorable for the concrete lined pipe than for the steel penstock but we consider either configuration can be designed to perform satisfactorily. Flow lSldef"' the gate was stable and quite good. We ere cancer-ned that the 3/8 inch thickness now being considered for the steel pipe is inadequae ccnsidering panel type vibrations between supports. This problem is not amenable to analysis in the absence of measured pressure fluctuations. Acca-dingly if the steel pipe is to pa .. ~;.c;i.E!!"~ ~~ ~~~TtOi:' that additional test's be made using electrically re!=&Qfed: ~esSy:e t:i=ensc::i:.Jcet:'S.:-'_: s~~:~ I cu?icS: \ I I f----1--- [ . .. ... . Mr. D. R. Eberle September 25, 1986 Page ·2 at a number of cross-sections. These transducers should be mounted flush with the inside wall of the pipe. These data would then provide data for evaluating the wall thickness. Also the top of the tunnel just upstream of the aeration slot should be about 3 inches lower than the top of the tunnel just downstream of the slot to improve air mixing. If the concrete lined tunnel is to be used, the bottom of the gate should be raised to about 4 to 4.5 feet above the tunnel invert. Also the air inlet should be modified to admit air to both sides of the jet near the top of the tunnel and immediately downstream of the point of sudden enlargement. With adequate air around the jet cavitation or erosion of the concrete should not be significant In summary, either configuration can be designed to work. we feel that there is less uncertainty with the concrete alternative. Additional testing will be required for final design of the steel pipe penstock, if used. A~/WF"S:mb Yours very truly, ~8·~~· A • J. Hendron J-:t 1 i dt" U' I W. F. Swi~f Dr. A.J. Hendron, Jr. 28 Golf Drive · Mahomet, Illinois 61853 (217) 351-8701 Mr. P. E. Sperry 21318 Las Pilas Road Woodland Hills, CA 91364 (818) 999-1525 Mr. D.R. Eberle Project Manager Alaska Power Authority P .0. Box 190869 Anchorage, Alaska 99519-0869 FOURTH REPORT -BOARD OF CONSULTANTS BRADLEY LAKE HYDROELECTRIC PROJECT 1.0 INTRODUCTION Mr. John Parmakian 2695 Lafayette Drive Boulder, Colorado 80303 (303) 499-5404 Mr. W. F. Swiger Box 388 Buhl, Idaho 83316 (208) 543-4593 January 29, 1987 J .0. No. 15800 T2.2 The fourth meeting of the Board of Consultants for the Bradley Lake Hydroelectric Project convened in the offices of Stone & Webster Engineering Corporation at 8:30 AM on January 27, 1987. A list of attendees is attached. After a short briefing on the status of the project, comments on the 95% documents for the General Civil Construction Contract were discussed for two days, followed by a presentation on the design of spillway aeration, diversion t~nel penstock vibration analysis and considerations of generator WR . There was a short discussion of dynamic balancing of the turbine runner and the hydrofracture tests. Cores from the major faults ( RH 21 ' a;::::. :..... 982 t and ;.M 19' 515 I to 628') were inspected. 2.0 STATUS The Site Preparation Contract was 75% completed vs. 85% scheduled. Major items of work remaining are the sheetpile cells, completion of permanent facilities and the diversion tunnel concrete. The powerhouse excavation is 90% complete. The diversion tunnel was holed through December 20, 1986. Transmission line center line survey was completed in December, 1986. Bids for transmission line for geotechnical investigations were opened January 28, 1987 and bids for supply of the turbine-generators were opened January 29, 1987. 2-1545-JJ Hr. D.R. Eberle Alaska Power Authority 2 January 29, 1987 The General Civil Construction Contract will be advertised February 17, 1987 and bids received April 22, 1987 with award in early June. 3.0 BID DOCUMENTS -GENERAL CIVIL CONTRACT Prior to the meeting copies of the proposed Specifications Geotechnical Interpretive Report and Bid Drawings for. the General Civil Construction Contract were furnished us for review and comment. Written comments were sent you prior to the meeting. These were further discussed in the meeting and items of special interest are further discussed and certain modifications which were recommended are discussed later in this report. We were favorably impressed by the Geotechnical Interpretive Report. Some changes in wording have been recommended. With these changes we feel this report will be of material assistance in obtaining best economy in completing this project. We are satisfied that the design of work to be done under these Specifications and Drawings is appropriate to the condition and needs of the project and will result in a safe and usable facility. 3.1 DAM 3. 1.1 Toe Plinth Treatment of weathered zones, shears, open or filled joints, etc. in the foundation rock should be modified to ensure sufficiently low seepage gradients and filter zones of adequate length to limit and discharge such seepage as may occur without erosion or piping. 3.1.2 Zone 1 of Embankment As written, the fine limits for grading of the Zone material are too fine. These grading requirements should be revised. 3.1.3 Materials and Placement for Zones 2, 3, and 4 a. Gradation Requirements 1'he present specif~.~ation 2-1545-JJ requirements for the materials in Zones 2, 3, and 4 are restrictive. The contractor may perceive that processing of these materials is required. It is our opinion that the materials in each of these zones can be properly specified in terms of the maximum allowable size and the percentage smaller than 1" in size. Thus this requirement can be obtained with pit run materials passed over a properly sized grizzly. Mr. D.R. Eberle Alaska Power Authority 3 January 29, 1987 b. Compaction -The current specification is a method specifi- cation where the lift thickness and the number of passes of a designated roller are prescribed. We agree with this method. It is our opinion that the compaction of the rockfill as specified will result in rock fill with an adequate stiffness and strength to perform under the maximum design earthquake at the designed slopes. We feel that ring tests to determine the dry dens! ty of the rock fill as placed are not necessary; furthermore, it is not clear to the board that a dry unit weight of 130 pcf is a measure of the adequacy of the rockfill. c. Lift thickness -the lift thickness specified for zones 2, 3, and 4 ranges from 18" to 24". Each lift is to be compacted with 6 passes of a 10 ton vibratory roller. It is our opinion that adequate compaction can be achieved by using a 24" lift thickness for all of these zones. There are many higher concrete faced rockfill dams in the world in seismically active areas where 1 meter thick lifts are used with 4 passes of 5 ton vibratory rollers. The Bradley Lake compaction requirements are more conservative than normal practice and is agreed to by this board in view of the high design accelerations adopted for this project. 3.1.4 Face Slab Concrete mixes for the face slab should be directed towards producing good quality concrete with high resistance to freeze-thaw damage and minimum shrinkage. To this end, consistent air entrainment is necessary. Use of fly ash is desirable provided uniformity and compatibility with the air entraining agent can be assured. Cement content should be limited to minimize shrinkage and we consider 3,000 psi at 28 days adequate for this service. The temperature of concrete when placed should not exceed 70°F. 3.2 SPILLWAY The cement content in the concrete of the spillway should be limited as much as feasible to minimize shrinj......_&. ...:..:1 crackinr;. Stresses in this structure are low and strength is not a concern, especially in the interior. Near surface concrete should contain sufficient cement and entrained air to ensure good frost resistance. Fly ash in the. mix is desirable if uniformity and compatibility with the air entraining agent can be assured. Concrete ~;emperatures when placed should not exceed 70°F under any condition and careful consideration should be given to limiting placing temperature to 55°F, as frequently as required for mass concrete. 2-1545-JJ Hr. D.R. Eberle Alaska Power Authority 3. 3 POWER TUNNEL 3.3.1 Compaction Grouting 4 January 29, 1987 Compaction grouting should be done for a distance of at least 250 feet upstream of the end of the steel liner. The objective is to consolidate the rock of the destressed zone and prestress the concrete liner in this critical zone. Also compaction grouting should be done in selected areas along the tunnel to improve the rock modulus and restore initial stress conditions such as in fault zones. Sleeves should be set through the concrete of the lining for these grout holes so rebar will generally not be cut by drilling. Specifications for this work should: a. Provide for grouting to pressures of at least 500 psi. b. Consolidate a zone to 1. 5 times tunnel diameter extending radially from the tunnel. c. Require at least 8 holes in each ring with grout ring spacings not to exceed 12 feet. d. Require drilling at such angles relative to tunnel 1 ine to cut rock joints at favorable angles. e. Start of grouting should be delayed at least 2 months after placement and until the concrete has cooled to near ambient of surrounding rock but must precede drilling of drain holes for the longitudinal drains of the steel liner. 3.3.2 Seismic Tests and Hydrosplitting Tests It is our feeling that the seismic testing and hydrosplitting tests conducted in the power tunnel must be conducted under the direction of the Construction Manager or the Engineer. The Engineer must be able to participate in the selection of the subcontractor to conduct these tests. We would prefer that the present specification be revised to strengthen the Engineer's position it· ... i,e select ... on of these subcontractors. The determination of shear wave velocities with depth behind the tunnel wall with sufficient accuracy to define the destressed zone requires refined capabilities which only a few firms possess. / The purpose of the shear wave velocity tests are to aid in the selection of those zones of the plain concrete tunnel lining which need to be reinforced in areas of poor rock quality. The shear wave velocity profiles can be used as a tool in determining the amount of required reinforcement. 2-1545-JJ Hr. D.R. Eberle 5 January 29, 1987 Alaska Power Authority The hydrosplitting tests are required in the area near the end of present 600 ft transition zone of reinforced concrete. The results of the hydrosplitting tests will be used to justify the adequacy of the present length of the transition section or they will be used as a basis to extend the transition section further into the mountain. The present design lengths of steel and reinforced concrete lined section of the power tunnel illiDediately upstream of the powerhouse appear to be adequate to provide for the apparent low minor principal stress measured in RH 23. Nevertheless the compaction grouting mentioned above is thought to be a prudent defensive measure to reduce the probability of migration of water axially along the destressed zone around the tunnel. It is suggested that for those sections of the power tunnel where fault zones and gouge are encountered, that the engineer design the final liner configuration which will be required to handle the high internal pressure. These typical sections should be shown in the plans and specifications. Thought should also be given to the ranges of measured shear wave velocities which will require the placement of reinforcement in sections of tunnel which are presently shown as unreinforced. 3.4 TEMPORARY SUPPORTS In Volume 6 of the Bid Documents there are presently four types of . ground, based on RQD, for determining temporary or ini tia1 tunnel supports. It is suggested that "squeezing ground" and "running ground" be added to the four classifications given in the specifi- cations. It is possible that either or both of these conditions could be encountered in the fault zones and both could be worse than the "poor rock" classification given in the current bid documents. An inspection of the gouge zones recovered from core borings does not indicate that highly plastic clays are present which would result in "swelling" ground and this classification need not be included. 4.0 GENERAL SEISMIC DESIGNS -EQUIPMENT The general seismic design requirements ~u. t::\~uipment ai·'d conservative and comprehensive but may require analys~s or testing which ar~ not necessary or available. Compact equipment such as motors, pumps and hydraulic cylinders are heavily built to meet service, and shipping and installation loads. Seismic loadings are well within the normal design loads. The principal concern with such equipment is that anchor bolts, footings and structures on which they are supported are adequate. For equipment mounted in rigid structures at or below ground level, design for the supports should be based on inertial forces as determined by the peak ground acceleration for the appropriate earthquake. For locations above grade, design of supports 2-1545-JJ Mr. D.R. Eberle 6 January 29, 1987 Alaska Power Authority may be based on the peak of the appropriate response spectra or a reduced value based on the spectra if the frequency of the equipment and its supports are determined. Equipment such as switch boards, cable trays, electric buses, OCB and controls and their supports require dynamic analysis and testing as necessary to ensure function and safety during earthquake. It is recommended that a careful review be made of the several systems; and, where each element is installed to identify equipment and systems requiring only anchorage and equipment or other systems including piping requiring dynamic analysis or testing. 5.0 STABILITY OF PENSTOCK BLOCKS The thrust blocks for the penstocks behind the powerhouse are one of the most important elements of the design. The board requests detailed calculations concerning the-overall sliding stability of each thrust block and all or any two of the thrust blocks taken as a group. All possible modes of failure should be considered. It is our opinion that the Factor of Safety against sliding should be greater than 1.0 without the calculated benefit of a cohesive resistance while using reaslistic angles of shearing resistance on the sliding surfaces assumed. 6.0 ENGINEERING PRESENTATIONS 6.1 AERATION OF SPILLWAY Studies of the hazard of cavitation of the spillway to evaluate the need for aeration were presented. These showed aeration slots would not be required to prevent cavitation of this spillway. We concur. We do, however, suggest that rock Just downstream of the end of the spillway bucket be left about 2 to 3 feet lower than the edge of the bucket and an air slot be provided in the training walL This will provide air under the jet which will help reduce erosion of the rock downstream of the spillway. 6.2 DIVERSION TUNNEL PENSTOCK VIBRATION ANALYSIS During the closing or opening cycle of the 7. 5 foot by 10 Jl foot hydraulic operated slide gate, pressure pulsations are generated by water passing under the gate lead. Model tests on similar gates indicate that the highest objectionable frequency of these pressure pulsations occurs at about the 0.15 gate opening and is negligible in magnitude when the slide gate is fully open. Downstream of the control gate there is a transition which connects with a 120 foot long 10-foot 6-inch diameter penstock supported by ring girders. In order to safeguard against a reasonance vibration 2-1545-JJ Mr. D.R. Eberle 7 January 29, 1987 Alaska Power Authority condition in the penstock due to the pressure pulsations originating at the partial opening of the gate, it has been recommended to increase the penstock pipe shell thickness from 3/8 inch to 1/2 inch. This will increase the natural vibration frequency of the penstocl{ and result in an ample safety factor against vibration resonance at part gate operation. The Board concurs in the recommendation to increase the pipe shell thickness to 1/2 inch. 6.3 REQUIRED GENERATOR INERTIA (WR 2 ) FOR ISOLATED OPERATION The generator specifications presently include a 2requirement that th2 manufacturer furnish generators with a minim~ WR of 8 million 1~-ft and to furnish costs of generators with a WR of 10 million lb-ft . The governor specifications require the govern~r manufacturer to recommend a value for the required generator WR to insure stable isolated operation for one and two unit operation. Further discussions on this subject should be withheld until the governor manufacturer's recommendations are received. In the event that the selected tunnel co_rtract results in a larger tunnel diameter, the required generator WR should be reanalyzed. 6.4 DYNAMIC BALANCING OF TURBINE RUNNER The requirement is to insure that the turbine runner is dynamically balanced to acceptable tolerances for the normal rotational speed and also for the runaway speed of the unit. There are two acceptable procedures.. . One, which is· used by ,some manufacturers, is to spin balance the unit at full rotational speed and also at runaway speed. The second is a slow speed static and dynamic balancing procedure. The latter requires very careful measurements and computations. These are described in the brochure on slow speed balancing which was supplied by the Board. / 2-1545-JJ Mr. D.R. Eberle 8 January 29, 1987 Alaska Power Authority Respectfully submitted, ~J·~9"· A.J. Hendron, Jr. Attachment 2-1545-JJ RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT TABLE OF CONTENTS FERC BOARD OF CONSULTANTS COMMENTS (FBCC) FBCC 4 - 1 DAM TOE PLINTH FBCC 4 - 2 DAM EMBANKMENT -ZONE FBCC 4 - 3 DAM EMBANKMENT GRADATION REQUIREMENTS -ZONES 2, 3 and 4 FBCC 4 - 4 DAM EMBANKMENT COMPACTION ZONES 2, 3 and 4 FBCC 4 - 5 DAM EMBANKMENT LIFT THICKNESSES ZONES 2,. 3 and 4 FBCC 4 -6 DAM FACE SLAB CONCRETE FBCC 4 - 7 SPILLWAY CONCRETE FBCC 4 - 8 POWER TUNNEL COMPACTION GROUTING FBCC 4 - 9 POWER TUNNEL SEISMIC AND HYDROSPLITTING TESTS FBCC 4 -10 POWER TUNNEL TEMPORARY SUPPORTS FBCC 4 -11 EQUIPMENT SEISMIC DESIGNS FBCC 4 -12 PENSTOCK BLOCK STABILITY FBCC 4 -13 SPILLWAY AERATION FBCC 4 -14 DIVERSION TUNNEL PENSTOCK VIBRATION ANALYSIS FBCC 4 -15 GENERATOR INERTIA (WR 2 ) FBCC 4 -16 TURBINE RUNNER DYNAMIC BALANCING Page 2 3 4 5 6 7 9 10 11 13 14 15 16 17 18 19 o Each FERC Board of Consul.tants Comment (FBCC) is immediately followed with comments by the Alaska Power Authority. o The first number in the designation "FBCC 4-1" signifies the number of the FERC Board of Consultant's Report (i.e. Report No. 4), the second number is a SWEC assigned number identifying a specific comment/recommendation contained in the report which requires an action/response. 3-537-FS ·~ J. RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 - l DAM TOE PLINTH FERC Board of Consultants Comment: 3. 1 DAM 3.1. 1 Toe Plinth Treatment of weathered zones, shears, open or filled joints, etc. in the foundation rock should be modified to ensure sufficiently low seepage gradients and filter zones of adequate length to limit and discharge such seepage as may occur without erosion or piping. SWEC Response: The design drawings have been modified to show typical details for the special treatment of weathered zones, shears, open or filled joints, etc. in the foundation rock. The specifications include descriptions and bid schedule items for the special treatment where it may be required. The specifications require that the overburden be removed over the entire length of the. toe plinth prior to the start of concrete placement so that a thorough geologic surface inspection can be performed. Once the weathered zones; shears, open and filled joints, etc. are field located, the special treatment for each surface and subsurface feature will be selected a~~ ;~0 ~4lled. ~is work will be conducted under the supervision of Bechtel's site geolog1st and construction engineers, with input from Stone & Webster's site geotechnical engineers. 3-537-FS 2 J FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 - 2 DAM EMBANKMENT -ZONE 1 FERC Board of Consultants Comment: 3.1.2 Zone 1 of Embankment As written, the fine limits for grading of the Zone 1 material are too fine. These grading requirements should be revised. SWEC Response: Revisions have been made to the specifications. A error in B1 gradation has been corrected. 3-537-FS 3 ' ----·--··----~-......... ,.,""'"'"·•··--··· ••••• ••••• •: .............. .,.. ................................... !* .. "-*• ........ ...,..,~ ................ ·•·. -.~ .. -.. """""""""-... · .... ..,; ...... __ ..: •• ~- RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 - 3 DAM EMBANKMENT GRADATION REQUIREMENTS -ZONES 2, 3, AND 4 FERC Board of Consultants Comment: 3.1.3 Materials and Placement for Zones 2, 3, and 4 a. Gradation Requirements The present specification requirements for the materials in Zones 2, 3, and 4 are restrictive. The contra~tor may perceive that processing of these materials is required. It is our opinion that the materials in each of these zones can be properly specified in terms of the maximum allowable size and the percentage smaller than 1" in size. Thus this requirement can be obtained with pit run materials passed over a properly sized grizzly. SWEC Response: The specification.requirements concerning gradation have been modified to clarify material processing. The specifications require the removal of oversize material as can be performed by the Contractor through the use of a bar grizzly, and limits the remainder of the gradation .bY means of limits on percent passing one inch and #200 sieves. 3-537-FS 4 ,I, .. ~ J. RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 - 4 DAM EMBANKMENT COMPACTION -ZONES 2, 3 AND 4 FERC Board of Consultants Comment: 3. 1. 3 b. Materials and Placement for Zones 2, 3 and 4 (Cont'd) Compaction -The current specification is a method specifi- cation where the lift thickness and the number of passes of a designated roller are prescribed. We agree with this method. It is our opinion that the compaction of the rockfill as specified will result in rock fill with an adequate stiffness and strength to perform under the maximum design earthquake at the designed slopes. We feel that ring tests to determine the dry density of the rock fill as placed are not necessary; furthermore, it is not clear to the board that a dry unit weight of 130 pcf is a measure of the adequacy of the rockfill. SWEC Response: We· agree with the Board comments. However, we wish to use ring tests in the early dam lifts to serve as an indicator test to confirm the dam design calculation assumptions. Four or five ring tests early in f~ll placement are expected to accomplish the necessary design confirmation. 3-537-FS 5 ·1 J ---·-·---------------------- RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 - 5 DAM EMBANKMENT LIFT THICKNESSES -ZONES 2. 3 AND 4 FERC Board of Consultants Comment: 3.1.3 Materials and Plac~ment for Zones 2. 3 and 4 (Cont'd) c. Lift thickness -the lift thickness specified for zones 2, 3, and 4 ranges from 18" to 24". Each lift is to be compacted with 6 passes of a 10 ton vibratory roller. It is our opinion that adequate compaction can be achieved by using a 24" lift thickness for all of these zones. There are many higher concrete faced rockfil1 dams in the world in seismically active areas where 1 meter thick lifts are used with 4 passes of 5 ton vibratory rollers. The Bradley Lake compaction requirements are more conservative than normal practice and is agreed to by this board in view of the high design accelerations adopted for this project. SWEC Response: After further discussions with the FERC Board of Consultants, Stone and Webster's Technical Review Board and internal SWEC reviewers, we have adopted 18 inch lifts for the B3 Zone and 24 inch lifts for the . B4 Zone. We understand that this approach is now acceptable to all reviewers. 3-537-FS 6 ,t, ; J RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 -6 DAM FACE SLAB CONCRETE FERC Board of Consultants Comment: 3. 1.4 Face Slab Concrete mixes for the face slab should be directed towards producing good quality concrete with high resistance to freeze-thaw damage an·d minimum shrinkage. To this end, consistent air entrainment is necessary. Use of fly ash is desirable provided uniformity and compatibility with the air entraining agent can be assured. Cement content should be limited to minimize shrinkage and we consider 3,000 psi at 28 days adequate for this service. The temperature of concrete when placed should not exceed 70°F. SWEC Response: The specifications have been revised to require fly ash and a compatible air entraining agent as part of the concrete mix design for the toe plinth, abutment blocks and face slab. The cement content will be limited within ACI guidelines to minimize shrinkage. Concrete mixes will be designed, batched, and tested by the Contractor using the fly ash and air entraining agent. Sources for fly ash and the air ent~aining agent will be subject to the approval of the Construction Manager and Design Engineer and will require advance compatibility testing by test mixing. A careful review by the Constructio!; i·-·:.~ ... r of the fly ash chemical certifications will be made to assure consistent chemistry. 3-537-FS 7 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT The Dam face slab concrete specification requires a compressive strength of 3,000 psi at 28 days. The temperature of concrete being placed is specified not to exceed 70°F. For structural considerations, the plinth, abutment blocks and parapet concrete is specified at 4,000 psi. The specifications prohibit the intentional addition of excess cement, thereby avoiding excess heat and cracking problems. 3-537-FS 8 ,I, • ' / RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 - 7 SPILLWAY CONCRETE FERC BOARD OF CONSULTANTS COMMENT: 3.2 SPILLWAY The cement content in the concrete of the spillway should be limited as much as feasible to minimize shrinkage and cracking. Stresses in this structure are low and strength is not a concern, especially in the interior. Near surface concrete should contain sufficient cement and entrained air to ensure good frost resistance. Fly ash in the mix is desirable if uniformity and compatibility with the air entraining agent can be assured. Concrete temperatures when placed should not exceed 70°F under any condition and careful consideration should be given to limiting placing temperature to 55°F, as frequently as required for mass concrete. SWEC Response: The specifications have been revised to require fly ash and a compatible air entraining agent as part of the concrete mix design for the spillway core mass concrete. The cement content will be limited within ACI guidelines to minimize shrinkage. Concrete mixes will be designed, batched and tested by the Contractor using the proposed fly ash and air entraining agent. Sources for fly ash and the air entraining agent will be subject to the approval of the Construction Manager and Design Engineer. A car-efu~ review by the Construction Manager of the fly ash chemical certifications will be made to assure consistent chemistry. The outer 3'0" concrete shell of/the spillway is specified to have air entrainment and a maximum water/cement ratio not to exceed 0.45. The temperature of concrete being placed at the spillway is specified not to exceed 55°F. 3-S37-FS ' J 9 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS ~OURTH REPORT -BOARD OF CONSULTANTS ~ERC PROJECT NO. 8221-000 JANUARY 29, 1987 _-.BR..;;A=D;..;;L=E-.Y..;;L;;;.;.;A;;;.;;K:;;.E..;;HY=D;;.;.RO;;.;;E;;..=L:..;;;;E~CT;;.;;R=I;...;;C_;;..;PR..;..;O;...;;J..;;;.EC-.T:;.._ ___ _ ~BCC 4 - 8 POWER TUNNEL COMPACTION GROUTING FERC BOARD OF CONSULTANTS COMMENT: 3.3 POWER TUNNEL 3.3.1 Compaction Grouting Compaction grouting should be done for a distance of at least 250 feet upstream of the end of the steel liner. The objective is to consolidate the rock of the destressed zone and prestress the concrete liner in this critical zone. Also compaction grouting should be done in selected areas along the tunnel to improve the rock modulus and restore initial stress conditions such as in fault zones. Sleeves should be set through the concrete of the lining for these grout holes so rebar will generally not be cut by drilling. Specifications for this work should: a. Provide for grouting to pressures of at least 500 psi. b. Consolidate a zone to 1.5 times tunnel diameter extending radially from the tunnel. c. Require at least 8 holes in each ring with grout ring spacings not to exceed 12 feet. d. Require drilling at such angles relative to tunnel line to cut rock joints at favorable angles. e. Start of" grouting should be delayed at least 2 months after placement and until the concrete has cooled to near ambient of surrounding rock but must precede drilling of drain holes for the longitudinal drains·of the steel liner. SWEC Response: The changes recommended by the Board ~l~ :v. grout pre~sures up to 500 psi. However, we are concerned about the affect such pressures may have on the integrity of the concrete liner and personnel safety during grouting operations. An operator error could crack the concrete liner or buckle the adjacent steel liner. ~urther review of this recommendation and its potential safety considerations will be undertaken by SWEC. 3-537-FS 10 J RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 - 9 POWER TUNNEL SEISMIC AND HYDROSPLITTING TESTS FERC Board of Consultants Comment: 3.3.2 Seismic Tests and Hydrosplitting Tests It is our feeling that the seismic testing and hydrosplitting tests conducted in the power tunnel must be conducted under the direction of the Construction Manager or the Engineer. The Engineer must be able to participate in the selection of the subcontractor to conduct these tests. We would prefer that the present specification be revised to strengthen the Engineer's position in the selection of these subcontractors. The determination of shear wave velocities with depth behind the tunnel wall with sufficient accuracy to define the des tressed zone requires refined capabilities which only a few firms possess. The purpose of the shear wave velocity tests are to aid in the selection of those zones of the plain concrete tunnel lining which need to be reinforced in areas of poor rock quality. The shear wave velocity profiles can be used as a tool in determining the amount of required reinforcement. The hydrosplitting tests are required in the area near the end of present 600 ft transition zone of reinforced concrete. The results .of the hydrospli t ting tests will be used to justify the adequacy of the present length of the transition section or they will be used as a basis to extend the transition section further into the mountain. The pr~sent design lengths of steel and reinforced concrete 1 ined section of the power tunnel immediately upstream of the powerhouse appear to be adequate to provide for the apparent low minor principal stress measured in RH 23. Nevertheless the compaction grouting mentioned above is thought to be a prudent defensive measure to reduce the probability of migration of water axially along the destressed zone around the tunnel. It is suggested that for those section::: :-:"' .. ~o.e power tr,nel where fault zones and gouge are encountered, that -:he engineer design the final liner configuration which will be required to handle the high internal pressure. These typical sections should be shown in the plans and specifications. Thought should also be given to the ranges of measured shear wave velocities which will ~equire the placement of reinforcement in sections of tunnel which are presently shown as unreinforced. 3-537-FS 11 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT SWEC Resoonse: The Alaska Power Authority has requested SWEC to enter into a contract with a qualified firm to perform these tests. SWEC will supervise the tests. Development of field criteria for special lining design and/or compaction grouting will be developed prior to start of tunnelling. 3-537-FS 12 ,I, • ' RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 -10 POWER TUNNEL TEMPORARY SUPPORTS FERC Board of Consultants Comment: 3.4 TEMPORARY SUPPORTS In Volume 6 of the Bid Documents there are presently four types of ground, based on RQD, for determining temporary or initial tunnel supports. It is suggested that "squeezing ground" and "running ground" be added to the four classifications given in the specifications. It is possible that either or both of these conditions could be encountered in the fault zones and both could be worse than the "poor rock" classification given in the current bid documents. An inspection of the gouge zones recovered from core borings does not indicate that highly plastic clays are present which would result in "swelling" ground and this classification need not be included. SWEC Response: The four types of ground in the Bid Documents, based on RQD, for determining temporary or initial tunnel supports have been modified to include "squeezing ground" and "running ground" as special cases of poor rock. Swelling ground has been excluded because recent fault gouge testing showed no evidence of clay mineral susceptible to swelling. 3-537-FS 13 J RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4-11 EQUIPMENT SEISMIC DESIGNS FERC Board of Consultants Comment: 4.0 GENERAL SEISMIC DESIGNS -EQUIPMENT The genera! seismic design requirements for equipment are conservative and comprehensive but may require analyses or testing which are not necessa~y or available. Compact equipment such as motors, pumps and hydraulic cylinders are heavily built to meet service, and shipping and installation loads. Seismic loadings are well within the norma! design loads. The principal concern with such equipment is that anchor bolts, footings· and structures on which they are supported are adequate. For equipment mounted in rigid.structures at or below ground level, design for the supports should be based on inertia! forces as detel"!Dined by the peak ground acceleration for the appropriate earthquake. For locations.above grade, design of supports may be based on the peak of the appropriate response spectra or a reduced value based· on the spectra if the frequency of the equipment and its supports are determined. Equipment such ·as switch boards, cable trays, electric buses, OCB and controls and their supports require dynamic analysis and testing as necessary to ensure function and safety during earthquake. It is recommended that a careful review be made of the several systems; and, where each element· is installed to identify equipment and systems requiring only anchorage and equipment .or other. systems including piping requiring dynamic analysis or testing. SWEC Response: We have revised the specification for seismic design requirements for each equipment system. A detailed equipment list has been developed in . the specification which clearly identifies each piece of equipment and/or system, and states the seismic design criteria to be met. Dynamic analysis or testing is specified where required for critical equipment. Testing or analysis is not required for non-critical items. / 3-537-FS 14 , RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 -12 PENSTOCK BLOCK STABILITY FERC Board or Consultants Comment: 5.0 STABILITY OF PENSTOCK BLOCKS The thrust blocks for the penstocks behind the powerhouse are one or the most important elements of the design. The board requests detailed calculations concerning the overall sliding stability or each thrust block and all or any two of the thrust blocks taken as a group. All possible modes of failure should be considered. It is our opinion that the Factor of Safety against sliding should be greater than 1.0 without the calculated benefit of a cohesive resistance while using reaslistic angles of shearing resistance on the sliding surfaces assumed. SWEC Response: The structural and geotechnical calculations for the penstock thrust blocks will be sent under separate cover for the Board's review. We wish to discuss these calculations and the Board's recommendation at the next meeting. 3-537-FS 15 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 -13 SPILLWAY AERATION FERC Board of Consultants Comment: 6.0 ENGINEERING PRESENTATIONS 6.1 AERATION OF SPILLWAY Studies of the hazard of cavitation of the spillway to evaluate the need for aeration were presented. These showed aeration slots would not be required to prevent cavitation of this spillway. We concur. We do, however, suggest that rock just downstream of the end of the spillway bucket be left about 2 to 3 feet lower than the edge of the bucket and an air slot be provided in the training wall. This will provide air under the jet which will help reduce erosion of the rock downstream of the spillway. SWEC Response: We are making the suggested design change. 3-537-FS 16 ' RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 -14 DIVERSION TUNNEL PENSTOCK VIBRATION ANALYSIS FERC Board of Consultants Comment: 6.2 DIVERSION TUNNEL PENSTOCK VIBRATION ANALYSIS During the closing or opening cycle of the 7.5 foot by 10.0 foot hydraulic operated slide gate, pressure pulsations are generated by water passing under the gate lead. Model tests on similar gates indicate that the highest objectionable frequency of these pressure pulsations occurs at about the 0.15 gate opening and is. negligible in magnitude when the slide gate is fUlly open. Downstream or the control gate there is a transition which connects with a 120 foot long 10-foot 6-inch diameter penstock supported by ring girders. In order to safeguard against a reasonance vibration condition in the penstock due to the pressure pulsations originating at the partial opening or the gate, it has been recommended to increase the penstock pipe shell thickness from 3/8 inch to 1/2 inch. This will increase the natural vibration frequency of the penstock and result in an ample safety factor ·against vibration resonance at part gate operation. The Board concurs in the recommendation to increase the pipe shell thickness to 1/2 inch. SWEC Response: The diversion tunnel penstock will have a pipe shell thickness of 1/2 inch. 3-537-FS 17 1 RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 -15 GENERATOR INERTIA (WR 2 } FERC Board of Consultants Comment: 6.3 REQUIRED GENERATOR INERTIA (WR 2 } FOR ISOLATED OPERATION The generator specifications presently include ~?requirement that th~ manufacturer furnish generators with a min~ W~ of 8 million ~b-ft and to furnish costs of generators with a WR of 10 million lb-ft . The governor specifications require the govern~r manufacturer to recommend a value for the required generator WR to insure stable isolated operation for one and two unit operation. Further discussions on this subject should be withheld until the governor manufacturer's recommendations are received. In the event that the selected tunnel c~ntract results in a larger tunnel diameter, the required generator WR should be reanalyzed. SWEC Response: The Power Authority has elected to purchase a generator inertia of 10 million lb-ft2 because of the relatively low cost based upon the Turbine/Generator bids. The Alaska Power Author! ty has delayed the bid advertisement for the General Civil Construction Contract until late Hay 1987. Since General Civil Construction bids will not be reviewed until late July, it may not be possible to decrease the WR 2 because of the progression of the genera tor manufacturer's final design waich is scheduled to be near completion by the end of June, 1987. 3-537-FS 18 ·1 J RESPONSES TO FERC BOARD OF CONSULTANTS COMMENTS FOURTH REPORT -BOARD OF CONSULTANTS FERC PROJECT NO. 8221-000 JANUARY 29, 1987 -BRADLEY LAKE HYDROELECTRIC PROJECT FBCC 4 -16 TURBINE RUNNER DYNAMIC BALANCING FERC Board of Consultants Comment: 6.4 DYNAMIC BALANCING OF TURBINE RUNNER The requirement is to insure that the turbine runner is dynamically balanced to acceptable tolerances for the normal rotational speed and also for the runaway speed of the unit. There are two acceptable procedures. One, which is used by some manufacturers, is to spin balance the unit at fUll rotational speed and also at runaway speed. The second is a slow speed static and dynamic bal~cing procedure. The latter requires very carefUl measurements and computations. These are described in the brochure on slow speed balancing which was supplied by the Board. SWEC Response: The turbine manufacturer is required by specification to spin balance the turbine runner at 300 rpm. 3-~37-FS , ' 19 • J