HomeMy WebLinkAboutBradley Lake Final Supporting Design Report Vol 2 1988Alaska Power Authority
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION
CONTRACT
BRADLEY LAKE
HYDROELECTRIC PROJECT
FEDERAL ENERGY REGULATORY COMMISSION
PROJECT NO. P-8221-000
VOLUME2
DESIGN CRITERIA
Prepared By
STONE & WEBSTER ENGINEERING CORPORATION
MARCH 1988
TABLE OF CONTENTS
TABLE OF CONTENTS
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION CONTRACT
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
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
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, COFFERDAM
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 11
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION CONTRACT
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 Gate Shaft -Sect ions 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 Accelerogram
0216R-4460R/CG 111
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION CONTRACT
VOLUME 1
REPORT
APPENDIX B ATTACHMENTS
B.l Construction Schedule Contract Dates
B.2 Meetings of the Independent Board of Consultants
B.3
Meeting No. 1
Meeting No. 2
Meeting No. 3
Meeting No. 4
Meeting No. 5
Meeting No. 6
Meeting No. 7
Meeting No. 8
Meeting No. 9
Meeting No. 10
Meetings of the
Meeting No. 1
Meeting No. 2
May 12 and 13, 1983
July 11 to 15, 1983
September 25 to 27, 1984
November 4 and 5, 1985 with response of
November 25, 1985
January 28, 1986
May 6 to 8, 1986 with response dated May 21, 1986
August 12 to 14, 1986 with response dated
October 20, 1986
December 8 to 10, 1986
Site Visit by Mr. A. Merritt on December 11, 1986
May 5 to 7, 1987
December 17 and 18, 1987
FERC Board of Consultants
March 6 and 7, 1986
May 28 and 29, 1986 with response dated July 11,
1986
Hydraulic Model 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
Hydraulic Model Test Spillway 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
0216R-4460R/CG lV
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION CONTRACT
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 Vl
Section
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
Figure
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
0216R-4460R/CG
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION CONTRACT
VOLUME 3
DAM AND SPILLWAY STABILITY ANALYSIS
Section Title
SPECIAL STUDIES
Megathrust (a = .55g)
DBE (ah = .375g)
Influence of Downstream Berm
Failed Concrete Face
Varying Embankment Height
Planar Slip Surfaces
La Union Accelerograrn
Parametric Analyses
COFFERDAM
CONCLUSION
CRITICAL CASES
SUMMARY OF CRITICAL FAILURE SURFACES
PREDICTED DISPLACEMENTS
RESPONSE TO VARIOUS EVENTS
BIBLIOGRAPHY
LIST OF FIGURES
Title
Project Location Map
Main Darn Area -General Arrangment
Main Darn Sections
(Not Used)
MCE Response Spectra -Mean and Chosen
Rockfill Friction Angles
Intermediate avlah Ratio
Selected Sliding Surfaces -Main Darn
Critical Acceleration Plots
Permanent Deformation Plots
MCE Response/Displacement Plots
Megathrust Response/Displacement Plots
DBE Response/Displacement Plots
Flow Through Darn Without Face
Darn Height vs. Acceleration and Displacement
Wedge Stability: Sloped Sliding Planes
Wedge Stability: Horizontal Sliding Planes
La Union Response/Displacement Plots
Response Spectrum -La Union E-W Record
Response Spectrum -Taft Record
Arias Intensity
Taft Response/Displacement Plot
Vll
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION CONTRACT
VOLUME 3
DAM AND SPILLWAY STABILITY ANALYSIS
SPILLWAY STABILITY REPORT
Section
1.0
2.0
3.0
4.0
5.0
6.0
7.0
1.1
1.2
1.3
2.1
2.2
2.3
2.4
3.1
3.2
3.3
4.1
4.2
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.6
4.2.7
4.3
4.4
4.4.1
4.4.2
4.4.3
5.1
5.2
5.3
6.1
6.2
7.1
7.2
0216R-4460R/CG
Section Title
INTRODUCTION
PURPOSE
SCOPE
SPILLWAY SAFETY CRITERIA
DESCRIPTION OF PROJECT FEATURES
GENERAL
OGEE SECTION
NON-OVERFLOW SECTIONS
GEOLOGIC CONDITIONS
DESIGN EARTHQUAKE REGIME
SEISMOTECTONIC SETTING
DESIGN RESPONSE SPECTRA
ACCELEROGRAM DEVELOPMENT
STABILITY CRITERIA
GENERAL
LOADS
Deadweight
Ice
Hydrostatic
Earthquake
Wind
Uplift
Temperature
LOADING CONDITIONS
ACCEPTANCE CRITERIA
Stability Requirements
Minimum Allowable Stress
Shear-Friction Factor of Safety
METHODS OF ANALYSIS
STATIC METHOD
FINITE ELEMENT METHOD
SARMA METHOD
STATIC ANALYSIS
STABILITY ANALYSIS
RESULTS
FINITE ELEMENT ANALYSIS
STRESS ANALYSIS
RESULTS
Vlll
Section
8.0
8.1
8.2
9.0
9.1
9.2
10.0
Figure
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
0216R-4460R/CG
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION CONTRACT
VOLUME 3
DAM AND SPILLWAY STABILITY ANALYSIS
Section Title
SARMA ANALYSIS
STABILITY ANALYSIS
RESULTS
CONCLUSIONS
CRITICAL CASES
SUMMARY OF STABILITY CONDITIONS
BIBLIOGRAPHY
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 El 1124
Case IV -Static Analysis-Base El 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
Stresses -Base El 1160
Finite Element Analysis: Case V -Max. Tensile Stresses -
Base El 1160
Finite Element Analysis: Case V Max. Compressive
Stresses -Base El 1160
Finite Element Analysis: Case III -Max. Tensile Stresses
-Base El 11 so
Finite Element Analysis:
Stresses -Base El 1150
Finite Element Analysis:
Base El 1150
Finite Element Analysis:
Stresses -Base El 1150
Finite Element Analysis:
-Base El 1124
lX
Case III -Max. Compressive
Case V -Max. Tensile Stresses -
Case V Max. Compressive
Case III -Max. Tensile Stresses
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 ANALYSIS
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 Summary -Sheet 1
Spillway Stability Analysis Summary -Sheet 2
Spillway Stability Analysis Summary -Sheet 3
X
HYDRAULIC
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION CONTRACT
VOLUME 4
CALCULATIONS
Calculation
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 & POWER TUNNEL
INTAKE ROCK PLUG
ICE FORCE ON DAM PARAPET H-068
INVESTIGATION OF NEED FOR AERATION OF
SPILLWAY FLOW H-077
RIPRAP DESIGN H-079
FILLING BRADLEY LAKE RESERVOIR H-081
0216R-4460R/CG Xl
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 G(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 MODULI FOR POWER TUNNEL TRANSIENT
STUDY G(Ak)-31
DESIGN OF ROCK SUPPORT FOR THE MAIN
POWER INTAKE STRUCTURE G(Ak)-35
PLINTH AND TOE SLAB GEOMETRY -MAIN DAM G(D)-38
0216R-4460R/CG xi i
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION CONTRACT
VOLUME 6
CALCULATIONS
GEOTECHNICAL
GROUNDWATER INFLOW & LEAKAGE INTO POWER
Calculation
No.
TUNNEL G(Ak)-41
EVALUATION OF SHEAR STRENGTH OF ROCK
MASSES AT THE 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
MANIFOLD & PENSTOCK THRUSTBLOCK
STABILITY CONSIDERING SHEAR ZONE
FEATURE
POWERHOUSE CELLULAR SHEETPILE
COFFERDAM STABILITY ANALYSIS
EVALUATION OF CONCRETE LINER
REQUIREMENTS 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 -70
G -86
G(Ak)-89
G(Ak)-90
G(Ak)-93
G -98
G -104
G -106
TABLE OF CONTENTS (Continued)
FINAL SUPPORTING DESIGN REPORT
GENERAL CIVIL CONSTRUCTION CONTRACT
VOLUME 1
CALCULATIONS
STRUCTURAL
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 xiv
Calculation
No.
SDC.1
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
Calculation
No.
SC-191-26
SC-191-27
SC-191-29
SC-201-8A
SC-201-34
SC-205-23
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
LOCAL STRESSES DUE TO GEOMETRY
DISCONTINUITY AT REDUCERS AND MITERED
ELBOWS
REQUIRED THICKNESS OF ELLIPSOIDAL
HEADS FOR PENSTOCK
STRESS ANALYSIS OF POWER
PENSTOCK WYE BRANCH
PENSTOCK ACCESS FLANGE BOLTS
0216R-4460R/CG xvi
SS-261-17B
SS-261-17C
SS-261-17D
SS-261-17F
SS-261-18
SECTION 1.0
CIVIL
DESIGN CRITERIA
4407R/CG
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J .0. No. 15800
GENERAL PROJECT INFORMATION AND
CIVIL DESIGN CRITERIA
REVISION: 2
DATE: March 30, 1988
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE, ALASKA
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
Section
1.0
1.1
2.0
2.1
2.2
3.0
3.1
3.2
3.3
4.0
4.1
4.1.1
4.1. 2
4.1.3
4.1.4
4.1. 5
4.1. 6
4.2
4.2.1
4.2.2
4.2.3
4.2.4
4.2.5
4.2.6
4.2.7
5.0
Attachments
Figure 1
Figure 2
GENERAL PROJECT INFORMATION
AND
CIVIL DESIGN CRITERIA
TABLE OF CONTENTS
Title Page
SCOPE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
SPECIFIC DISCIPLINE CRITERIA........................ 1
GENERAL PROJECT INFORMATION......................... 3
CLIMATOLOGY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
RESERVOIR, DIVERSION, AND TIDAL INFORMATION......... 6
REGULATIONS, CODES, STANDARDS AND GUIDES............ 9
LOCAL, STATE, AND FEDERAL CODES AND REGULATIONS..... 9
INDUSTRY CODES, STANDARDS, AND SPECIFICATIONS....... 9
DESIGN GUIDES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
CIVIL DESIGN CRITERIA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
MATERIALS FOR CIVIL WORKS....... . . . . . . . . . . . . . . . . . . . . 13
Fill Materials...................................... 13
Fences and Gates.................................... 13
Culverts............................................ 14
Drainage Material................................... 15
Earth Retention Structures.......................... 16
Bridges............................................. 17
DESIGN OF CIVIL WORKS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
R&M Design Criteria................................. 17
Earth Retaining Structures.......................... 17
Roads and Surfacing................................. 18
Slopes......................... . . . . . . . . . . . . . . . . . . . . . 18
Culvert Design...................................... 18
Guardrails and Signs................................ 19
Bridge Design....................................... 19
RESTORATION AND RECLAMATION......................... 20
Project Location
Airstrip/Powerhouse Wind Rose Diagram
CIVIL WORKS DESIGN CRITERIA
4407R/CG
Recommended Access Road Criteria
Haulroad Temporary Bridges -Design Criteria
Aggregate and Concrete Supply
Barge Facility Recommended Design Criteria
Recommended Airport Runway Criteria
Clearing and Grubbing Recommended Design Criteria
Basis of Design -Temporary and Permanent Camps
Basis of Design -Utilities
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
1.0 SCOPE
GENERAL PROJECT INFORMATION
AND
CIVIL DESIGN CRITERIA
This document provides general project information and civil design
criteria necessary for preparation of designs, construction drawings, and
specifications for the Bradley Lake Hydroelectric Project. Issued
separately from this criteria are design criteria set by R&M Consultants,
Inc. (R&M) for roads, bridges, camp facilities and the barge and harbor
facilities (attached), and criteria set by Dryden & LaRue, Inc. (D&L) for
transmission systems. Further, criteria for use by specific disciplines on
the Bradley Lake Project have been developed as needed. These criteria
when combined, constitute the Project Design Criteria.
1.1 SPECIFIC DISCIPLINE CRITERIA
The following specific criteria have been developed as of the latest
revision date of this criteria:
Structural Design Criteria:
Part A General Structural Design Criteria
Part B-1 Main Darn Diversion
Part B-2 Main Darn
Part B-3 Spillway
Part B-4 Power Tunnel Lining, Intake
Part B-5 Steel Liner and Penstock
Part B-6 Powerhouse
Part B-7 Tailrace
Part B-8 Substation
Architectural Design Criteria
4407R/CG - 1 -
and Gate Shaft
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
Hydraulic Design Criteria:
Hydraulic Turbines, Governors, and Spherical Valves
Main Dam Diversion
Power Intake, Tunnel and Penstock
Spillway
Tailrace
Middle Fork Diversion
Nuka Diversion
Electrical Design Criteria
Control System Design Criteria
Mechanical Design Criteria
Bradley 115kV Transmission Lines, Basic Design Manual
Geotechnical Design Criteria
4407R/CG - 2 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
2.0 GENERAL PROJECT INFORMATION
The Bradley Lake Hydroelectric Project is a hydroelectric facility being
designed by Stone & Webster Engineering Corporation (SWEC) for the Alaska
Power Authority (APA). The project is located in the southern port ion of
the Kenai Peninsula approximately 27 miles northeast of Homer, Alaska and
approximately 105 miles south of Anchorage, Alaska.
The project initially will develop a nominal 90 MW capacity. The
powerhouse wi 11 be located on Kachemak Bay with a power tunnel to Bradley
Lake. Bradley Lake is a natural lake with existing water level at
Elevation 1080~ with additional catchment from surrounding sources. The
electricity produced will be transmitted via project transmission lines to
interties serving Homer, the Kenai Peninsula, and, via regional interties,
Anchorage and the Rail belt area. Certain aspects of the project will be
designed so as to not preclude the installation of a third unit which would
result in a total project capacity of 135 MW.
The project includes the following principal features:
1. A concrete faced rockfill dam located at the natural outlet of Bradley
Lake.
2. A concrete gravity ungated agee spillway to the east side of the main
dam.
3. A modified horseshoe-shaped diversion tunnel through the right abutment
of the dam, and improvement of the Bradley River channel immediately
downstream of the tunnel and dam. The tunnel will be finished with a
concrete lining upstream of the emergency outlet gates and a steel
penstock downstream of the gates.
4407R/CG -3 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
4. A fully lined power tunnel approximately 19,000 feet long between
Bradley Lake and the powerhouse located on the shore of Kachemak Bay.
5. An intake structure with removable trashrack and bulkhead gates at the
damsite.
6. A main power tunnel gatehouse and gateshaft located near the upstream
end of the power tunnel.
7. Diversion works on the Middle Fork of the Bradley River and at the
terminus of the Nuka Glacier.
8. A steel penstock located at the downstream portion of the power tunnel
to the powerhouse, including approximately 2, 700 feet of steel tunnel
lining.
9. An above ground powerhouse located on the shore of Kachemak Bay,
containing two 45 MW Pelton Turbines generators and associated
equipment, with capabilities for expansion to three units.
10. A tailrace channel discharging into Kachemak Bay, located downstream of
the powerhouse.
11 . A Compact Gas Insulated Substation (CGIS) with three 115kV
transformers, located adjacent to the powerhouse.
12. Docking and water access facilities and an airstrip along the shore of
Kachemak Bay.
13. Maintenance and storage facilities.
14. Permanent and construction camp facilities and utilities.
15. Access roads within the project area.
16. Permanent housing facilities for operating personnel.
4407R/CG - 4 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
17. Two ll5 kV transmission lines with a switching station located at
Bradley Junction. Bradley Junction is the tie point to the Homer
Electric Association transmission line located near Caribou Lake.
Design Work under items 12, 13, 14 and 16 was performed by R&M Consultants
and work under Item 17 will be performed by Dryden & LaRue, Inc. Work
under item 15 will be performed by R&M Consultants and SWEC.
Work for the project will be accomplished under several contracts. The
permanent and construction camps, barge dock, warehouse facilities,
airstrip, roads, diversion tunnel with concrete intake structure, and the
modification to the Bradley River downstream of the proposed dam were
designed for construction and completed under the Site Preparation Contract.
The dam and spillway, the power tunnel and penstock, the permanent release
facilities of the diversion tunnel, the tailrace, and the powerhouse
excavation will be designed for construction under the General Civil
Construction Contract.
The powerhouse and substation structures will be designed for construction
under the Powerhouse Construction Contract.
The Middle Fork and Nuka diversions, the transmission 1 ines and
rehabilitation and mitigation measures will be designed for construction
under subsequent contracts.
2. 1 CLIMATOLOGY
1.
2.
3.
4.
5.
6.
Latitude: N59°45', Longitude Wl50°30'
0 0 Temperature Range: -38 F to +85 F
Seismic Zone: UBC Zone 4 (minimum requirement)
Wind Speed (max design): 100 MPH Coastal, 120 MPH Mountains
Mean Annual Precipitation: Varies 40 to 80 inches
Approximate Annual Snow Fall: Varies 100 to 200 inches
4407R/CG - 5 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
7. Prevalent wind direction as determined from recent studies and wind
rose data indicates highest speed wind velocities come from the NNE
during cold months and from the SW during warmer months. (See Figure 2,
attached)
2.2 RESERVOIR, DIVERSION, AND TIDAL INFORMATION
THE DATA PROVIDED BELOW IS FOR INFORMATION PURPOSES ONLY AND IS SUBJECT TO
FINAL DESIGN MODIFICATIONS
PROJECT DESIGN LIFE: 50 YEARS
A. Dam & Spillway
Dam Physical Information
Type
Dam Crest Width (minimum)
Dam Crest Elevation
Dam Parapet Crest Elevation
Dam Crest Length
Spillway Physical Information
Type
Spillway Crest Length
Spillway Crest Elevation
Reservoir Levels
Maximum Pool to Pass PMF
Normal Maximum Operating
Minimum Operating
Minimum Possible (@ zero inflow)
Minimum Possible (@ zero inflow)
4407R/CG -6 -
Concrete faced rockfill
16 ft.
(Inside of Parapet to edge of
dam)
1190 ft.
1194 ft.
602.5 ft.
Concrete gravity agee section
175 ft.
1180 ft.
1190.6 ft.
1180 ft.
1080 ft.
1068 ft. (Diversion
Tunnel Drawdown)
1055 ft. (Power Tunnel
Drawdown)
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
Tailwater Levels (Downstream Pool Area)
Probable Maximum Flood
Routed Flood of Record
Minimum Operating
Flow Data
Probable Maximum Flood (PMF)
Maximum Lake Inflow (PMF)
Maximum Recorded Lake Outflow
(Natural Channel)
Minimum Recorded Lake Outflow
(Natural Channel)
B. Diversion Tunnel
Flow Section (unlined)
Flow Section (lined)
Approximate Length
Design Maximum Flow
Operational Minimal Flow
C. Main Power Tunnel
Flow Section -Upper power tunnel
-Lower power tunnel
Approximate Length
Design Maximum Flow
4407R/CG - 7 -
1090 ft.
1067 ft.
1061 ft.
23,800 cfs (Routed)
31,700 cfs
5210 cfs
16 cfs
21 ft. (Modified Horseshoe)
17 ft. 6 in. ID Concrete,
10 ft. 6 in. ID Steel
Penstock
400 ft.
4000 cfs (During construction)
100 cfs (Through fish bypass
pipes)
11 ft. internal diameter
(Modified horseshoe
excavation)
11 ft. internal diameter
(Circular excavation)
19,000 ft.
2150 cfs
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
D. Middle Fork and Nuka Diversions
1. Middle Fork Diversion
Design Flow
Approximate Channel Length
2. Nuka Diversion
Nuka River Outlet
Crest Elevation
Dike Height
Dike Length
Upper Bradley River Outlet
Weir Elevation
Weir Length
E. Tidal Levels
800 cfs
1415 ft.
1296 ft.
5 ft. above existing grade
540 ft.
1291 ft.
100 ft.
Elevations will be based on project datum. Refer to the tabulations
below and to Figure 1, attached.
Bear Cove
Bradley Lake
Project
Datum
(Ft.)
Highest Storm Surge* 13.3
Highest Tide (estimated) 11.37
Mean Higher High Water 4.78
Mean High Water 3.97
Project Datum o.oo
Mean Sea Level -4.02
Mean Low Water -12.02
Mean Lower Low Water -13.63
Lowest Tide (estimated) -19.63
* Estimated 50 Year.
4407R/CG - 8 -
Bear Cove
Mean Sea Mean Low Low
Level (MSL) Water (MLLW)
Datum
(Ft.)
17.32
15.39
8.80
7.99
4.02
0.00
-8.00
-9.61
-15.61
Datum
(Ft.)
26.93
25.0
18.41
17.60
13.63
9.61
1.61
o.oo
-6.0
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
3.0 REGULATIONS, CODES, STANDARDS, AND GUIDES
The following standards, codes, specifications, and guidelines shall apply;
use the editions current at the start of the detailed design, unless
specifically noted otherwise.
3.1 LOCAL, STATE, AND FEDERAL CODES AND REGULATIONS
AAC Alaska Administrative Code
OSHA-AK General Safety Code, Vol. I, II, and III, Occupational Safety and
Health Standards, Alaska Department of Labor, Division of
Occupational Safety and Health, 197 3 and as amended in 1983 and
the Construction Code, 1974 and as amended in 1982.
OSHA-US 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 1926/1910), as
they pertain to the work at hand and supplement the State of
Alaska's General Safety Code identified above.
DOT/PF Alaska Department of Transportation and Public Facilities,
Standard Specifications for Highway Construction, 1981.
3.2 INDUSTRY CODES, STANDARDS AND SPECIFICATIONS
AASHTO-HB
ACI MANUAL
4407R/CG
Specifications for Highway Bridges with updates; American
Association of State Highway and Transportation Officials
(AASHTO), 1978 Edition.
Manual of Standard Practice Vol. 1 to Vol. 5, American
Concrete Institute (ACI), 1985.
- 9 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
AISC MANUAL Manual of Steel Construction; American Institute
of Steel Construction (AISC), 8th Edition.
AISI-68 Specifications for the Design of Cold-Form Steel Structural
Members with Commentary; American Iron and Steel Institute
(AISI).
AITC-TM
AITC-100
ASTM
AWS D1.1
AWS D1.4
AWWA
CLFI
Timber Construction Manual; American Institute of Timber
Construction (AITC), 2nd Edition.
Timber Construction Standard Series, AITC, 1972.
American Society for Testing and Materials (ASTM) -various
standards as required.
Structural Welding Code; American Welding Society (AWS), 1985.
Reinforcing Steel Welding Code; AWS, 1985.
American Water Works Association
publications as required.
(AWWA) various
Commercial Standard for Industrial Aluminum and Galvanized
Steel Chain Link Fencing; Chain Link Fence Institute (CLFI).
CRSI-MSP-2-81 Manual of Standard Practice; Concrete Reinforcing Steel
Institute (CRSI), 1981 with 1983 Supplement.
NEC
NESC
4407R/CG
National Electric Code; National Electrical Contractors
Association, ANSI/NFPA No. 70.
National Electrical Safety Code, American National Standard
ANSI C2-1984; Institute of Electrical and Electronics
Engineers (IEEE).
-10 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
NFPA
SSPC
National Fire Protection Association (NFPA) latest
guidelines and requirements.
Steel Structures Painting Council (SSPC) -various guides and
publications.
UBC Uniform Building Code; International Conference of Building
Officials, 1985 Edition.
3.3 DESIGN GUIDES
CRREL U.S. Army Corps of Engineers, Cold Regions Research &
Engineering Laboratory (CRREL) -various publications.
NAVFAC P-355 Cold Regions Engineering, Design Manual; Dept. of the Navy,
Naval Facilities Engineering Command, 1975.
NAVFAC P-355 Seismic Design for Buildings; Technical Manual,
Dept. Army, Navy and Air Force, 1982.
NAVFAC DM-7.1 Design Manual-Soil Mechanics, Foundations, and
APA-DS
EPA-600
4407R/CG
Earth Structures, Dept. of Navy, Naval Facilities Engineering
Command, 1982.
Drainage Structure and Waterway Design Guidelines,
Alaska Power Authority Document by Harza-Ebasco, Susitna
Hydroelectric Project, 1985.
Cold Climate Utilities Delivery Design Manual; United States
Environmental Protection Agency, 1979.
-11 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
APA-BMP
HSDHCP
HCCPH
CPH
UA
4407R/CG
Best Management Practices Manuals, Alaska Power Authority
Document by Frank Moolin and Associates, Inc., Susitna
Hydroelectric Project, 1985.
• Soil and Erosion Control
• Fuel and Hazardous Materials
• Liquid and Solid Waste
• Oil Spill Contingency Planning
• Water Supply
Handbook of Steel Drainage & Highway Construction Products;
American Iron and Steel Institute.
Handbook of Concrete Culvert Pipe Hydraulics; Portland Cement
Associ at ion.
Concrete Pipe Handbook; American Concrete Pipe Association.
Environmental Atlas of Alaska; C.W. Hartman and P.R. Johnson,
University of Alaska, 1978.
-12 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
4.0 CIVIL DESIGN CRITERIA
The majority of the civil design for the Site Preparation Contract has been
prepared by R&M Consultants and controlled by their design criteria.
Certain civil materials, not defined by R&M criteria and used in SWEC
designs, are defined below. Additionally, minor design considerations and
siting information are included. These civil design criteria supplement
the attached Civil Works Criteria. Seismic design criteria stipulated in
the Geotechnical Criteria shall be utilized (as applicable) by all design
disciplines.
4.1 MATERIALS FOR CIVIL WORKS
4.1.1 Fill Materials
Fill material will consist of excavated site or borrow materials meeting
the requirements of the Geotechnical Design Criteria.
4.1.2 Fences and Gates
The substation transformers, local storage areas, safety and hazard related
areas, and security areas will be enclosed with chain link fences.
Permanent tunnel portal openings will be enclosed to prevent animal
intrusion.
Security related areas will be enclosed with 8 ft. high metal chain link
fences with "V" bar type extensions carrying a minimum of two strands of
barbed wire on each bar.
Temporary storage areas and protective enclosures, provided in areas where
hazards to personnel demand restricted access but pose no security related
problems, will be 8 ft. high galvanized chain link fences, without barbed
wire extensions. Safety fences for sewage lagoon, garbage handling and
related areas; and permanent housing yard fencing, will be 6 ft. chain link.
4407R/CG -13 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
Gates will be provided for access. Vehicle access gates will be double
leafed type capable of a 180 degree swing to the outside or they may be of
the semi-cantilever type. Minimum width vehicle gates will be 16 ft.
Personnel gates shall be nominal 3 ft. opening.
Fences, gates, and hardware will be galvanized and will meet the Chain Link
Fence Institute's "Conunercial Standards for Industrial Aluminum and
Galvanized Steel Chain Link Fencing". All fences will be grounded and
gates shall be provided with brass padlocks.
Snow fencing and deflectors shall not be designed, as directed by APA. They
may be added at a later date should experience indicate need at specific
locations.
4.1. 3 Culverts
Materials for culverts will be selected in accordance with the requirements
of the Alaska Power Authority's Drainage Structure and Watercourse Design
Guidelines. Two types of culvert material available are corrugated metal
pipe (CMP) and precast reinforced concrete pipe.
A. Corrugated Metal Pipe (CMP) Culverts
CMP culverts will meet the material requirements of the latest edition
of American Iron and Steel Institute's publication Handbook of Steel
Drainage and Highway Construction Products. Material dimensions will
be: thickness and corrugations per AASHTO/ASTM Standard, and diameter
18 1n. minimum, with cross-road drainage 24 in. minimum. Bituminous
coating of CMP will be as required. CMP and hardware will be
galvanized or aluminum coated, as required. Culverts exposed to salt
water shall be asphalt coated.
4407R/CG -14 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
B. Precast Concrete Pipe
Reinforced precast concrete pipe, if used, will conform to ASTM C76.
Culvert pipes will be no less than 18 inches in diameter, with
cross-road drainage 24 in. minimum.
4.1.4 Drainage Materials
Materials used in construction of drainage facilities will be as specified
and as identified below, and will follow the Alaska Power Authority's
Drainage Structure and Waterway Design Guidelines and Best Management
Practices Manuals. Ditch checks, diversions and controls shall be designed
to suit particular situations.
A. Drainage Pipe
Drainage pipe will be perforated polyvinyl chloride or galvanized
corrugated metal pipe. All pipe shall include joint hardware, flares,
screens, etc.
B. Trench Covers and Manhole Covers
Trench covers for areas not subject to vehicular traffic may be minimum
5/16 inch ASTM A36 galvanized carbon steel checkered plate. Trench
covers located within areas accessible to vehicles and manhole covers
will be cast products rated to minimum AASHTO HS25 wheel loads.
C. Manholes
Manholes may be precast concrete or cast-in-place concrete units as
availability and design allow. Manholes shall have service permanent
ladder rungs.
4407R/CG -15 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
4.1.5 Earth Retention Structures
Earth retention structures may be reinforced concrete retaining walls,
wood, gabions or concrete cribbed walls, bulkheads, sheetpiling, or
reinforced earth retaining structures.
Materials used shall meet the design and specification criteria
requirements developed by the project. Basic earth retention structures
will also meet the following:
A. Reinforced Earth Retaining Structures
Face panels shall be reinforced concrete. Concrete used for reinforced
earth face panels shall have a minimum specified compressive strength
of 4,000 psi at 28 days. Toe bases shall have a minimum specified
compressive strength of 3,000 psi at 28 days.
Straps will be per the manufacturer's recommendations, except that in
corrosive situations, straps will be aluminum alloy 5052-H32.
Fasteners for aluminum alloy straps shall be aluminum alloy 6061-T4 or
better.
B. Gabions
Gabions shall be galvanized steel, as manufactured by Maccaferri, or
equal, with one cubic yard cells.
C. Reinforced Concrete Retaining Walls
Concrete used for reinforced concrete retaining walls shall have a
minimum specified compressive strength of 4,000 psi at 28 days.
4407R/CG -16 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
4.1.6 Bridges
Permanent site bridges designed by SWEC shall consist of ASTM A588 steel
girders with a reinforced concrete deck over corrugated steel deck forms.
Concrete decking shall have a minimum specified compressive strength of
4,000 psi at 28 days. Steel girders shall meet the minimum charpy
requirements of AASHTO for temperatures to minus 32°F (Zone 2).
Temporary site bridges may use ASTM A36 steel girders with timber decking.
4.2 DESIGN OF CIVIL WORKS
4.2.1 R&M Design Criteria
The majority of the civil works has been designed by R&M Consultants and is
controlled by the attached "Civil Works Design Criteria". Additional
criteria may be developed as required in specific discipline criteria.
Where design concerns soil and erosion control and drainage and waterways
structures, the guidelines APA-DS and APA-BMP will be followed. Some
minimal civil design guidance is included below.
4.2.2 Earth Retaining Structures
Excessively long fill slopes or abrupt changes in the contour may require
benches to reduce erosion and the use of earth retention structures.
Benching will, as a minimum, follow the UBC requirements, unless otherwise
controlled by the Geotechnical Design Criteria or the APA Best Management
Practices Manuals. Earth retention structures will be designed to the
earth pressures and formulation identified by the Geotechnical Design
Criteria.
Solid-type walls will be provided with free-draining fill, or a perforated
CMP or PVC heel drain, wrapped with an approved filter fabric, and covered
with a well graded, drainable fill.
4407R/CG -17 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
4.2.3 Roads and Surfacing
A. Access Roads
Access roads required by design will follow the attached "Civil Works
Design Criteria" unless otherwise approved. Selected segments on
temporary haul/access roads may have low speed curves (i.e. less than
100' radius).
B. Road Surfacing
Roads will be surfaced where traffic and load capacity warrant. It is
not anticipated that paving will be used.
Stone surfacing will be used for selected areas. The following depths
of fill shall be used as a minimum:
Access Roads
Substation
Powerhouse Yard Areas
4.2.4 Slopes
6 in. nominal
12 in. nominal
6 in. nominal
Maximum slope heights and angles and considerations of toe treatment and
placement of rock fall benches for excavations in rock and earth will be
determined on a case by case basis in conjunct ion with stability analysis
which will be performed in accordance with the requirements of the
Geotechnical Design Criteria.
4.2.5 Culvert Design
Flow characteristics for culverts shall be provided by design. Design
loads imposed on culverts, minimum fill, etc., will follow AASHTO
Criteria. Design of any culvert will follow the guidelines and design
4407R/CG -18 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
procedures developed by the Alaska Power Authority as stated in the Best
Management Practices -Soil and Erosion Control and Drainage Structures and
Waterway Design Guidelines, and in accordance with industry and AASHTO
Standards.
Additional design guidance is presented in the Handbook of Steel Drainage &
Highway Construction Products, the Concrete Pipe Handbook, and the Handbook
of Concrete Pipe Hydraulics.
4.2.6 Guardrails and Signs
Guardrails shall be in accordance with Alaska DOT Standards for secondary
roadways, with high-strength sections as dictated by circumstances in
individual locations. Guardrails shall be metal single-row rail on metal
posts, with end flares and/or spring sections. Energy absorbtive end
sections and diverters will not be utilized due to the low project speed
limits. Guardrails will be installed only in areas of inordinate risk such
as sharp curves on high fill, and areas where plowing in heavy snow could
result in run-off on high fills. Slopes of less than 10 ft. in height will
generally not be protected, nor will riprapped berm sections.
Signs shall conform to DOT/PF Standards, and shall include all signs
necessary to regulate the expected traffic flow safely. Emphasis shall be
on warning drivers of geometric or conflicting traffic conditions, and will
not include advisory signage as to hazards or conditions which would be
known to a driver who has previously driven the roads.
4.2.7 Bridge Design
Bridges shall be designed in accordance with AASHTO-HB requirements.
Minimum vehicle loading shall be HS25, with impact. Where bridges are
likely to be used for transport of heavy equipment to the powerhouse, the
following axle loading shall also be considered: two-32 kip axles on 4
foot spacing with a minimum 34 foot distance center-to-center of axle pairs.
4407R/CG -19 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
5.0 RESTORA~ION AND RECLAMATION
All exposed and constructed surfaces will be maintained and treated as
necessary to adhere to permit requirements and the Best Management
Practices Manuals. Post-construction rehabilitation will be performed by
separate contract, and a separate criteria will be developed to address
revegetation, waste area sealing, rehabilitation of construction camp
areas, utility abandonment, environmental mitigation and long-term
environmental mitigation efforts.
4407R/CG -20 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
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•u.r 1 BRADlEY LAKE HYDROELECTRIC pOWER PROJECT
ALASKA POWER IUTfHOfffTY
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ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
KENAI PENINSULA BOROUGH, ALASl<A
GENERAL
AIRSTRIP I POWERHOUSE
WIND ROSE DIAGRAM
FIGURE 2
INFDRtviATial &. CIVIL DESIGN CRITERIA
BRADLEY LAKE HYDRO PROJECT
CIVIL WORKS DESIGN CRITERIA
(ORIGINALLY DEVELOPED BY R&M CONSULTANTS)
REVISED MARCH 30, 1988
RECOMMENDED ACCESS ROAD CRITERIA
The access roads are divided into three basic segments according to
function and similarities of construction as follows:
Road Type
Design Speed (mph)
Lane Width (travel
Shoulders
Horizontal Curves
Sight Distance
• Powerhouse to lower camp
• Lower camp to dam
• Martin River borrow access road
Resource Development Road. Two-lane in higher
traffic areas such as powerhouse to lower camp
segment. Single lane between lower camp and dam
and Martin River borrow access.
Single Lane'ir Single Lane'irlr Two-Lane
20 20 20
surf.) 12' 14' 12'
2' 2' 2'
100' m1n R 100' min R 100' min R
300 300 150
* Single lane road from lower camp to dam.
**Single lane road to Martin River borrow site
Vertical Curvature
4407R/CG
To be calculated in accordance with State of Alaska
DOTPF Highway Preconstruction Manual procedure
11-10-5. Value dependent on design speed and grade
difference.
-21 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
Maximum Grades
Super-elevation
Crown Cross Slope
Clearing
Stripping
Surfacing
Culverts
Road Elevation
Desirable 10%, Maximum 14%
Not to exceed 4%
0.03-foot per foot
10' from edge of cut slope or 10' from toe of fill,
or as necessary for sight distance.
5' from edge of cut slope or 10' from toe of fill
2" minus gravel, 6" thick
24" Min. CMP, 16 gage minimum, inlet armored and
flared.
0. 5 feet above SO year frequency waves in tidal
areas
0.5 feet above 50 year flood level of Battle Creek
The following four items apply only to the one-way roads:
Ditch Widening
Curve Widening
Fill Widening
Turnouts
4407R/CG
Ditches on cut side to be widened 4' in rock cuts
20 feet or over in height.
Inside of curves to be widened from 4 feet on a 100
foot radius to 2 feet on a 200 foot radius curve.
Selected fills will be widened with excess cut
materials when available.
Maximum spacing 2600 feet; minimum spacing 500 feet.
150 feet long, 14 feet wide with 50 feet taper at
each end.
-22 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
zs'
3%-
/
SURFACE/'
\......BORROW EMBANKMENT
POWERHOUSE TO LOWER CAMP
STA.495+00 TO STA. 625 +OO
CURVE WIDENING ON INSIDE
OF R200' CURVES OR LESS'·
-~ .... :~,--· ...... ~-
16'
LOVIER CAMP TO DAM
STA. 625 + 00 TO STA. 922 +00
MIN. ROAD ELEV. AND RIPRAP
ARMOR DESIGN BASED ON 50 YR
DESIGN WAVE WITH 0.5 FT FREEBOAR
LCUT SLOPE DEPENDENT
/i ON MATERIAL
/I
I 1/2 ROCK
I 2 SOIL
REVISED 11-1-85
REVISED 7-31-85
FB:
ACCESS ROAD
TYPICAL SECTIONS
GRID:
PROJ .NO: 5510 95
OWC.NO: I
--------------------------------~1
OWN: OEP
CI<O: VJG
DATE: JULY 1985
SCALE: I": 10'
' \ 'Z,·
MARTIN RIVER ACCESS
18'
q_
1
~ , I
l 3o/o-
BORROW FILL
FILL SECTION
•
WHERE
UIRED
, ... // ' .,. '" '~l"t\'1'/
fB:
GRID:
PROJ.NO; 551095
OWG.NO: 2
HAULROAD TEMPORARY BRIDGES -DESIGN CRITERIA
System: Contractor to design
Design Life: 10 year life
Design Vehicle: HS25
Components:
Steel -SO ksi yield meeting minimum charpy requirements of AASHTO
Concrete-strength as dictated by design, 3000 psi min., 4000 psi at
water
Connections -welds as per AWS specification
-structural bolts ASTM A325
Foundations -as dictated by geotechnical evaluation, recommend treated
crib type foundations
Governing Codes: AASHTO -American Association of State Highway and
Transportation Officials
4407R/CG -23 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
AGGREGATE AND CONCRETE SUPPLY
ELEMENTS CONSIDERED ESSENTIAL OR DESIRABLE
1. Floodplain protection dike at Martin River site to be based on a 100
year flood of the Martin River.
2. Aggregate for road surfacing to be produced and placed under the Site
Preparation Contract, plus a stockpile located in quarry area for
maintenance.
3. Riprap for revetment armor on roads to be produced and placed under the
Site Preparation Contract; plus a stockpile located in quarry area for
maintenance.
4. Concrete aggregate to be produced and stockpiled in the construction
camp area for use in subsequent contracts; quantities based on design
requirements for General Civil and Powerhouse Contracts.
4407R/CG -24 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
BARGE FACILITY RECOMMENDED DESIGN CRITERIA
DOCK
System: Sheet pile cell system with gravel embankment
Design Life: 5 years, SO years with damage during major seismic events
Design Loads: Uniform Load 500 psf
Crane Load -65K pad force from 150 ton crane (with 10% impact)
Fork Lift Load -62 ton axle load (with 30% impact)
Barge Berthing and Breasting Forces -to be determined
Truck Loading -HS25
Loader Load -80 ton axle (without impact) from Cat. 988
Components:
Steel sheet piles -ASTM A328 with coal tar epoxy and anode corrosion
protection
Walers -ASTM A36, 36 ksi yield, coal tar epoxy coated
Tie-back rods -ASTM A36, 36 ksi yield, coal tar epoxy coated
Deadman -concrete, f'c = 3000 psi
Fenders -minimum, as necessary due to exposure condition and to
prevent barges from catching on walers
Governing Codes: AASHTO or UBC as applicable
4407R/CG -25 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
Water Depth:
Outward loading face sited at -6 to -7 foot elevation (project datum).
Access criteria developed will allow access by barges of 6 feet draft
during a period 2 hours before and after higher high water for a period
of 12 to 15 days per month. Barges of greater draft can access the
site with careful planning to intercept the highest monthly tides.
Another ramped loading face shall be provided at -3:t foot elevation
(project datum) to allow a more efficient end unloading operation. A
sloped ramp will also be provided for beaching smaller barges and boats.
Staging Area:
The barge access facility shall have sufficient staging area (1 acre_:t)
for temporary storage of freight. No covered or secured staging shall
be provided.
DREDGE DISPOSAL AREA DESIGN
Only minimal dredging to be performed. This dredging (or excavation)
will likely be performed with a backhoe or track mounted excavating
equipment therefore settling ponds (etc.) should not be required.
4407R/CG -26 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
RECOMMENDED AIRPORT RUNWAY CRITERIA
Following is specific criteria developed to date for construction of the
airport.
Item
Runway Length
Runway Width
Runway Safety Area
Length
Width
Building Restriction Line
Clear Zone
Slope
4407R/CG
Criteria
2200 feet (Determined from FAA
advisory circular Figure 4-1. Based
on airport elevation and mean daily
maximum temperature for hottest month
of year.)
60 feet
240 feet beyond each end of runway
30 feet beyond each side of runway
125 feet from centerline
Begins 200 feet beyond end of runway
20:1
-27 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
Transition Slope
Runway Orientation
Vertical Alignment
Runway Elevation
Vertical Curvature
Maximum Longitudinal
Grade Change
Sight Distance
Cross-Section
Transverse Slope
4407R/CG
7:1 extending to 150 feet above runway
elevation
Based on maximum wind coverage and
minimum obstructions within the clear
zone and runway safety area.
50 year storm and wave runup +0.5'
Wi 11 not be less than 300 feet for
each 1% grade change. No vertical
curvature is planned.
Not to exceed 2%, 0% planned.
Any two points 5 feet above the runway
must be mutually visible for the
entire length of the runway.
2% to edge of runway safety area
Riprap provided on bay side of
airfield to protect against wave
damage at 2:1 slope.
4:1 slope on opposite side of runway.
-28 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
CLEARING AND GRUBBING RECOMMENDED DESIGN CRITERIA
Clearing and grubbing specifications shall be modeled after State of Alaska
Standard Specification for Highway Construction, 1981.
This specification basically requires that all surface objects, trees,
stumps, roots and other protruding obstructions be cleared and grubbed.
Stumps outside the construction 1 imi ts can be left cut off not more than
six inches above ground level.
Merchantable timber, 6" DBH, shall be removed off site to a location having
public vehicular access and sold. Proceeds shall be remit ted to APA. If
not sold see "Timber, less than 6" DBH" below.
Timber, less than 6" DBH: The sections shall be disposed of to prevent
bark beetle outbreak.
Preferable method of slash disposal will be chipping or hauling to and
burial in disposal site, or burned. The Construction Contractors are
permitted to use on-site timber for construction of the project.
Clearing and grubbing 1 imi ts for the maximum reservoir level are to the
1200 foot elevation (project datum) contour.
4407R/CG -29 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
BASIS OF DESIGN -TEMPORARY AND PERMANENT CAMPS
Design Criteria
Snow Load: 65 psf
15 year recurrence interval for Seldovia. From "Alaskan Snow Loads",
USACRREL 1973 and adjusted for terrain and climatic conditions.
Wind Load: 30 psf
1985 UBC, Design charts for 100 mph wind adjusted for terrain and
elevation
Seismic Zone: 4
1985 UBC
Environmental
Minimum Temperature:
Maximum Temperature:
Heating Degree Days:
Environmental Atlas Alaska
TEMPORARY CAMP
Location: floodplain of Battle Creek as shown in feasibility reports
Design of camp pad area showing grading, water supply and distribution,
sewage collection and treatment, and aggregate stockpiles.
PERMANENT FACILITIES
Location: Approximately 1000' SW from powerhouse.
Structures: Configured as shown in December 24, 1985 submittal and as
modified January 8, 1986 by APA.
4407R/CG -30 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
Housing
Duplex housing -Two each
Two bedrooms, 1-3/4 baths
Three bedrooms, 1-3/4 baths
Single level
Full finished basement, with partitioned areas, 3/4 bathroom
Provision for addition of carports at later date
Arctic entries
?refinished metal wood grain siding
Ample eaves and wide facias with soffit on bottom of top chord of
trusses
SO year design life
Wood fireplace
Freezer
50'± separation between duplexes
All electric
Office/Dormitory
Exterior dimensions/architectural features same as duplex (2800 sf)
6 private bedrooms
Central bath on 2nd floor
Two bathrooms on 1st floor, shower in women's
One kitchen area (mess/social)
Office area
All electric
50' minimum to closest duplex
Two story
Shop/Garage/Warehouse
Steel building, 14' eave height
All electric
8,000 square feet
4407R/CG -31 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
Water System:
BASIS OF DESIGN -UTILITIES
TEMPORARY CAMP
Design Population: 300
Water Use: 65 gallons/capita/day
Minimum Well Yield: 27 GPM (based on 12 hrs/day pumping)
No. Wells: 2
Well Configuration: 8" gravel packed well with submersible pump.
Well Location: 1 at test well, 1 towards Battle Creek on camp side
of road to darn.
System Configuration: Design for installation of 2 water wells. Camp
contractor is responsible for providing all
facilities downstream from well pump discharge
piping. This will include elevated storage
(hillside location) or ground level storage and
pressure system. Contractor furnished
facilities shall meet the following minimum
standards:
Instantaneous Demand: 270 GPM (1)
Equalizing Storage: 33,000 Gallons (2)
Fire/Flow Storage: None
Emergency Storage: None
(1) "Connnunity Water Systems Source Book" by Hveem
(2) "Suggested Practice for Small Water Systems" by Alaska Department
of Environmental Conservation. This indicated sotrage capacity
may vary depending upon final well capacity.
4407R/CG -32 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
Sewer System:
Design Population: 300
Wastewater Flow: 65 GPCPD
Design Flow: 19,500 gallons/day
Sewage Treatment: Secondary
System Configuration: Aerated lagoons followed by chlorination and a
polishing lagoon, followed by discharge to
Battle Creek. Lagoon detention time will be
approximately 30 days. Lagoon will be divided
into two sections, primary and secondary.
Aeration will be by bubble from pipes placed on
lagoon bottom. Air will be supplied by 3
blowers, arranged and sized so that 100% backup
capacity is available. Chlorination will have a
60 minute detention time. Polishing lagoon
detention time will be approximately 2 days.
Solid Waste
Incinerator adequate to serve temporary camp facilities. Ash residue
will be disposed of at a sanitary landfill.
Water System:
Water Use: 100 GPCPD
Design Population:
Duplexes 2 x 7 = 14
Office/Dorm = 5
PERMANENT CAMP
20 persons
4407R/CG -33 -
GENERAL INFORMATION AND
CIVIL DESIGN CRITERIA
SECTION 2.0
GEOTECHNICAL
DESIGN CRITERIA
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. No. 15500 and 15800
GEOTECHNICAL DESIGN CRITERIA
REVISION: 2
DATE: March 24, 1988
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE, ALASKA
3890R/193R/CM GEOTECHNICAL DESIGN CRITERIA
Section
1.0
2.0
2.1
2.2
2.2.1
2.2.2
2.2.3
2.2.4
2.3
2.4
2.4.1
2.4.2
2.4.3
2.5
2.6
2.6.1
2.6.2
2.6.3
2.7
3.0
3.1
3.2
3.3
3.4
3.5
3890R/193R/CM
TABLE OF CONTENTS
Title
LIST OF TABLES
LIST OF FIGURES
SUMMARY DESCRIPTION
DESIGN CRITERIA
SEISMIC DESIGN
SEEPAGE CONTROL AND DRAINAGE
Foundation Grouting
Seepage Control
Foundation Drainage for Spillway
Tunnel Drainage
TSUNAMI/SEICHE DESIGN
TUNNEL DESIGN
Tunnel Layout
External Loads on Tunnels and Portals
Ground-Support Interaction
ROCK REINFORCEMENT CRITERIA
FOUNDATION DESIGN
Lateral Forces
Sliding and Overturning Resistance
Individual Footings and Superposition
HYDRAULIC CONSIDERATIONS
DESIGN LOADS AND PARAMETERS
DEAD LOADS
BACKFILL LOADS
UPLIFT AND DRAINAGE CRITERIA
SEISMIC LOADS
COEFFICIENTS OF FRICTION
ii
iv
v
1
1
1
2
3
3
3
4
4
4
4
4
5
5
6
6
6
7
8
9
9
10
11
12
13
GEOTECHNICAL DESIGN CRITERIA
Section
3.6
3.6.1
3.6.2
3.6.3
3.6.4
4.0
4.1
4.2
4.3
4.4
Title
TABLE OF CONTENTS
(continued)
DESIGN PARAMETERS
Basic Data for Excavations in Rock
Basic Data for Foundations on In-situ Soil
Basic Data for Foundations on Compacted Fill
Basic Data for Rock Fill
REFERENCES
APPLICABLE CODES, REGULATIONS AND GUIDES
SWEC CORPORATE CRITERIA
BRADLEY LAKE PROJECT REPORTS
GENERAL DESIGN REFERENCES
14
14
16
17
18
19
19
22
23
27
SYMBOLS and ABBREVIATIONS 32
TABLES 34
FIGURES 46
iii
3890R/193R/CM GEOTECHNICAL DESIGN CRITERIA
LIST OF TABLES
Table No. Title Page
1 Seismic Criteria 34
2 Geotechnical Design Criteria and Data for 37
Diversion Tunnel and Permanent Outlet Facility
3 Geotechnical Design Criteria and Data for 38
Diversion Channel Improvement
4 Geotechnical Design Criteria and Data for 39
Powerhouse and Substation
5 Geotechnical Design Criteria and Data for 40
Power Tunnel Intake Structure
6 Geotechnical Design Criteria and Data for Power 41
Tunnel
7 Geotechnical Design Criteria and Data for 42
Penstock and Steel Liner
8 Geotechnical Design Criteria for Power Tunnel 43
Gate Shaft
9 Geotechnical Design Criteria and Data for Main 44
D~
10 Geotechnical Design Criteria and Data for 45
Spillway
iv
3890R/193R/CM GEOTECHNICAL DESIGN CRITERIA
Figure No.
1
2
3890R/193R/CM
LIST OF FIGURES
Title
Mean Horizontal Response Spectrum
Design Accelerogram
v
46
48
GEOTECHNICAL DESIGN CRITERIA
1.0 SUMMARY DESCRIPTION
The Geotechnical Design Criteria include geotechni.cal parameters and
methods of analysis that are required for the design of structures. Major
structures requiring geotechnical engineering include the concrete faced
rockfill dam, ungated concrete spillway, diversion tunnel, power tunnel and
penstock manifold system, and the powerhouse. Pertinent data (including
cross-references to the Structural Design Criteria and Hydraulic Design
Criteria) for the major project structures are listed in Tables 2 through
10.
2.0 DESIGN CRITERIA
2.1 SEISMIC DESIGN
The Bradley Lake Project is located in a seismically active region. A
summary of seismic criteria for the OBE, DBE and MCE is provided in Table
1. All major project structures will be founded on or excavated in rock.
Structures will typically be analyzed by the pseudostatic method where it
yields acceptable results. Dynamic analyses will be performed where
appropriate to predict structure behavior. For the main rockfill dam and
concrete spillway, dynamic analyses utilizing seismic loads will be
performed using the SARMA Computer Program (GT-055).
The main dam and spillway will be designed to retain the reservoir during
and after the MCE. The diversion and permanent outlet facilities will be
designed to be operable after the MCE to either remain in their normally
closed position in the water passageway or to open as may be needed to
effect reservoir drawdown. The intake structure and gate shaft for the
power tunnel will be designed to be operable after the MCE for closure of
the water passageway of the power tunnel.
3890R/193R/CM 1 GEOTECHNICAL DESIGN CRITERIA
While fully embedded installations react in concert with the surrounding
rock mass, the power tunnel will cross the Bradley River and Bull Moose
Faults which have been assumed to be capable of surface and subsurface
rupture. It is considered impossible to design to withstand or accommodate
rock mass rupture. No consideration other than those consistent with
normal pressure tunnel design will be applied. In the event rupture should
occur, the power tunnel will be dewatered and repairs made. Similarly, due
to full embedment in rock, design of penstock and tunnel 1 ining does not
consider seismic criteria. However, the penstock/manifold thrust blocks
are designed for seismic loads.
The excavation for the powerhouse will be designed to place no additional
loads on the powerhouse during the MCE.
The other project structures will be designed for an effective seismic
acceleration consistent with Uniform Building Code Zone No. 4 as a minimum.
The access roads are founded on soil and rock formations. Local soil
failures are anticipated in the tidal flats during significant seismic
events and will be repaired as needed. As mandated by the Alaska Power
Authority, the risk of regional subsidence during seismic events will not
be considered in design of any project features.
2.2 SEEPAGE CONTROL AND DRAINAGE
The dam and spillway foundations and other water retaining structures must
be stable under all conditions of construction and reservoir operation, and
must limit seepage so as to prevent excessive uplift pressure, erosion of
material, and/or loss of water. Uplift pressures will be assumed to act on
100 percent of the area of a foundation or structure with the effects of
drainage considered where applicable. The foundations and structures wi 11
be analyzed for flotation, if applicable.
3890R/193R/CM 2 GEOTECHNICAL DESIGN CRITERIA
2.2.1 Foundation Grouting
Where control of water flow through rock is required, seepage cutoff grout
curtains shall be designed using the following criteria.
For the Main Darn and Spillway Structures, grout curtain shall be designed
to extend a minimum depth below the structure equal to approximately 2/3 of
the maximum design hydrostatic head.
2.2.2 Seepage Control
Where migration of fines and/or piping potential is evident. the design of
drains to provide filter protection shall be based on the following
criteria:
Piping Criteria. Dl5 (FILTER)
D85 (SOIL) < 4 to 5
D15 (FILTER)
0 1s (SOIL) > 4 to 5
Permeability Criteria.
D50 (FILTER)
< 25
Dso (SOIL)
U.S. ARMY COE Criteria,
2.2.3 Foundation Drainage for Spillway
A foundation drainage curtain will be constructed in the spillway area to
relieve uplift pressures. The drain holes will daylight in the spillway
drainage gallery and will be accessible for clean-out. The uplift
pressures under the spillway will be assumed to act across the complete
rock/concrete interface. The reduction of uplift due to drains shall be
according to the Hydraulic Design Criteria.
The spillway apron and training walls will be designed for uplift
conditions and loads due to sudden changes in water level if applicable.
Drainage may be provided to equalize the water pressure on each side of the
structure when differential pressures must be minimized.
3890R/193R/CM 3 GEOTECHNICAL DESIGN CRITERIA
2.2.4 Tunnel Drainage
The tunnel linings will be designed for uplift and ambient hydrostatic
conditions resulting from dewatering of the tunnel for inspection and/or
repairs.
2.3 TSUNAMI/SEICHE DESIGN
It is anticipated that a tsunami will occur within Kachemak Bay during the
project design life. Project structures will be analyzed to determine
tsunami loading effects. Tsunami loads on project structures will be
determined on the basis of anticipated tsunami height, probability and
force effects.
The effects of a seismically generated seiche on the main dam embankment
shall be analyzed. The dam shall be designed to withstand such an event.
2.4 TUNNEL DESIGN
2.4.1 Tunnel Layout
A minimum radius of curvature of 750 ft and preferably 1000 ft for tunnel
alignment will be used for tunnel sections where use of a tunnel boring
machine (TBM) is anticipated. For drill and blast sections where the TBM
is not operating, a minimum radius of 100 ft will be used.
2.4.2 External Loads on Tunnels and Portals
Rock loads are determined from empirical methods. Near the portals, full
rock cover is taken as rock load with load reductions to one-half maximum
cover for sound rock. Within the sections of control blasted tunnels under
plane strain conditions, one-half to one-quarter of the empirical rock load
is applied to the permanent liner.
Rock loads impose moment, shear, and axial stresses in the tunnel 1 ining.
When rock quality is such that horizontal rock loads exist, only the excess
of vertical load will be considered for the moment stress.
3890R/193R/CM 4 GEOTECHNICAL DESIGN CRITERIA
2.4.3 Ground-Support Interaction
Primary rock loads on the power tunnel steel sets will be checked to insure
that excessive deformations will not occur. Both axial and moment loads
will be analyzed. The sets will be monitored during construction to verify
the adequacy of the design.
Hydrostatic loads and secondary rock loads due to long term relaxation of
the rock mass after the steel sets have been installed will be used to
design the tunnel concrete lining. ACI guidelines will be used to
calculate the required concrete thickness and reinforcing steel necessary
to prevent excessive deformations.
2.5 ROCK REINFORCEMENT CRITERIA
Rock slope stability will typically be analyzed using a two-dimensional
sliding plane analysis. For critical locations, three dimensional wedge
stability analyses will be performed. Sliding wedge theory and
pseudostatic horizontal earthquake loads, as applicable, will be used to
calculate the bolt size, bolt lengths and the pattern necessary to maintain
the design factors of safety. General guidelines for rock bolting
underground are based on the rock quality designation (Ref. Table 3-3,
Support Recommendations for Tunnels in Rock based on RQD, COE Ell0-2-2901,
pp. 3-11 to 3-13).
Rock bolts will be loaded no higher than the yield strength of the bar for
the MCE case and will be stressed to no more than 80% of the ultimate
strength of the bar during installation.
Resin anchor bond length will be determined from resin anchorage charts
supplied by the manufacturer using 150% of the ultimate strength of the bar
as maximum anchorage loading. Each rock bolt and anchor installed using
cement grout will have a first stage grout length in rock sufficient to
resist the proof load of the anchor. This length will be calculated using
the nominal diameter of the hole and an allowable bond stress of 160 psi.
3890R/193R/CM 5 GEOTECHNICAL DESIGN CRITERIA
'The quantity of rock mobilized will be calculated by using the pull-out
volume method. Shear resistance between the cone and the surrounding rock
will be neglected. 'The overlapping of adjacent cones will be accounted for
in the calculation. 'The angle of the cone will be taken as 30° from the
bolt axis and the apex of the cone will be at or above the midpoint of the
first stage grout or resin anchor bond length.
2.6 FOUNDATION DESIGN
2.6.1 Lateral Forces
'The magnitude and distribution of static and dynamic lateral earth forces
on structures will be determined by the Mononobe-Okabe method as defined in
GTG 6.15-1.
2.6.2 Sliding and Overturning Resistance
Critical foundations must be designed to resist sliding and overturning due
to lateral earth pressure, wind, dynamic loads (seismic, etc), and waves.
Appropriate loading combinations and minimum allowable factors of safety
against sliding and overturning for structures are presented in the
Structural Design Criteria. 'The applicable rock and soil criteria for
earth, water-retaining and safety-related foundations are presented below.
All other foundations may be designed in accordance with Structural Design
Criteria. 'The following criteria apply only to the soil or rock foundation
material. Factors of safety are not applicable to dynamic analyses such as
the Sarma method. 'The foundation concrete/rock bond strength will not be
included in the Geotechnical determination of factors of safety against
sliding and overturning.
Load Combination
D + Ls
D + Ls + E + Lo
D + Ls + W or I
D + Ls + I + W
D + Ls + E' + Lm
D + Ls + W'
D + Ls + W + T
3890R/193R/CM
Minimum Factor of Safety
Overturning Sliding
2.0 4.0
1.5
1.5
1.2
1.05
1.1
1.05
6
1.5
1.5
1.2
1.05
1.1
1.05
GEOTECHNICAL DESIGN CRITERIA
where
D = Dead loads or their related internal moments and
any permanent equipment loads and hydrostatic
loads (under normal operating conditions)
Ls = Static lateral earth pressure
Lo = Dynamic earth pressure (for DBE)
Lm = Dynamic earth pressure (for MCE)
E = Loads generated by the Design Basis Earthquake (DBE)
E' = Loads generated by the Maximum Credible Earthquake (MCE)
w = Loads generated by the design wind
W' = Loads generated by design storm wave and wind
T = Loads generated by the design tsunami or seiche
I = Loading from design ice buildup or ice cover on water
surfaces
The case of D + Ls + E + T or W or I is not considered a credible case on
this project. During construction, a factor of safety equal to 1.5 will be
used for structures and 1.2 for slopes.
2.6.3 Individual Footings and Superposition
Individual footings shall be designed not to exceed the allowable bearing
capacity of the foundation material. Each footing shall be proportioned to
include the superposition of stresses from the adjacent structures without
exceeding the allowable maximum bearing values.
The superposition of additional vertical stress imposed on "individual"
footings or other foundations from adjacent structures shall be based on
the Boussinesq distribution principle. Settlement analyses will be
performed for all structures founded on soil since settlement may control.
3890R/193R/CM 7 GEOTECHNICAL DESIGN CRITERIA
2.7 HYDRAULIC CONSIDERATIONS
Flow velocities are limited to prevent undue erosion and scour of earth
materials. The following are allowable flow velocities:
Normal Emergency
0Eeration Drawdown
Sound bedrock 20 fps 30 fps
Fractured bedrock 10 15
Riprap lined channels 6 10
Alluvial channels 4 6
Tailrace/mud channels 1 2
For flow velocities in excess of these, additional treatment of the surface
will be required to ensure that erodible zones are protected. Higher
velocities by a factor of two (2 x normal) are allowed in areas where
erosion will not damage project facilities.
Ice loads and wave loads will be as per the Hydraulic Design Criteria.
3890R/193R/CM 8 GEOTECHNICAL DESIGN CRITERIA
3.0 DESIGN LOADS AND PARAMETERS
3.1 DEAD LOADS (p)
The following unit weights for dead loads have been established for the
Bradley Lake Project:
Mass Concrete
Reinforced Concrete
Steel
Water
Ice
Salt Water
Silt -Vertical
-Horizontal
Backfill
145 pcf
150 pcf
490 pcf
62.4 pcf
56 pcf
64 pcf
120 pcf
85 pcf
-Dry 120 pcf
-Moist 135 pcf
-Submerged 85 pcf
Upland and Intertidal Soils
Total 130 pcf
Submerged 68 pcf
Rock (dry)
-Sound 170 pcf
-Moderately Fractured 165 pcf
-Highly Fractured 160 pcf
-Poor 150 pcf
3890R/193R/CM 9 GEOTECHNICAL DESIGN CRITERIA
3.2 BACKFILL LOADS
The static lateral earth pressure against vertical faces of structures with
cohesionless horizontal backfill will be 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 static loading conditions and the simple case of a vertical wall,
horizontal backfill, and no soil-wall friction, the lateral earth pressure
coefficients are:
K tan 2 (45 -0/2) = a
2 K = tan (45 + 0/2) p
Ko = 1 -sin 0
For inclined walls, sloping backfill and soil-wall friction refer to
Geotechnical Technical Guideline GTG-6.15-1, Determination of Lateral
Pressures on Buried Structures in Granular Soils, for applicable equations.
For seismic or dynamic loading conditions both the active and passive
lateral earth pressure coefficients will be calculated according to the
analysis developed by Mononobe-Okabe found in GTG-6.15-1.
Compaction induced pressures, surcharge pressures and water pressures will
be addressed as required following the guidelines presented in GTG-6.15-1.
3890R/193R/CM 10 GEOTECHNICAL DESIGN CRITERIA
The at-rest coefficient of lateral pressure is K = 0. 45 for upland soils
0
and K = 0.60 for intertidal soils. Soils for areas which are surcharged
0
or heavily compacted will use a K
0 = 1.00. Natural soils
evidence of overconsolidation or which have been compacted may
showing
exhibit
higher values of K .
0
The active and passive earth pressure coefficients presented for soil are
also applicable for compacted random and structural fill. The at-rest
coefficient of lateral pressure (K ) for uncompacted select fill is K
0 0
= 0.50. Compaction will be assumed to produce K = 1.0. All fills shall
0
be designed for a constant pressure in the top 6 feet equal to the value at
6 feet in depth.
Where vehicular traffic can run adjacent to the structure, a surcharge
loading of 300 lbs/ft 2 will be applied; areas subject to crane and
stockpile loads will be analyzed individually.
3.3 UPLIFT AND DRAINAGE CRITERIA
Where no foundation drainage is provided, the phreatic surface will be
assumed to be no lower than linear between points of known elevation, such
as headwater and tailwater in the case of water retaining structures.
Where foundation drains are provided, the phreatic surface will be
determined according to the Hydraulic Design Criteria.
3890R/193R/CM ll GEOTECHNICAL DESIGN CRITERIA
3.4 SEISMIC LOADS
The design ground acceleration levels for critical and operating structure
foundations are summarized below (see Structural Design Criteria for
seismic design category). The Maximum Credible Earthquake (MCE) will be
applied to critical structures (water retaining) and the Design Basis
Earthquake (DBE) will be applied to power generating structures. The
maximum vertical ground acceleration level will be no more than two-thirds
of the respective horizontal ground acceleration.
Figure 2 shows the Design Accelerograrn for the analyses. The significant
duration of shaking for the design earthquake shall be the time required to
reach 95% of the Arias Intensity. Shear wave velocities and damping ratios
for rock fill will be derived from an earthquake induced shear strain of
0.1% by means of the Seed and Idriss method (GTG 6.1).
3890R/193R/CM 12 GEOTECHNICAL DESIGN CRITERIA
3.5 COEFFICIENTS OF FRICTION (f)
The following table presents values of coefficients of friction for use in
stability analyses.
Materials
Mass concrete against clean
sound rock
Mass concrete against
fractured rock
Mass concrete against compacted
granular fill
Mass concrete against compacted
select earthfill, semi-pervious fill,
and upland soil
Coefficient of Friction
0.70
0.65
0.55
0.45
Mass concrete against membrane liner (requires
verification if not a porous geotextile)
Static
Kinetic
Formed concrete against compacted
granular fill
Formed concrete against compacted
select earth and semi-pervious fill
3890R/193R/CM 13
0.60
0.50
0.45
0.45
GEOTECHNICAL DESIGN CRITERIA
3.6 DESIGN PARAMETERS
3.6.1 Basic Data for Excavations in Rock
Results from subsurface explorations and geologic inspections have been
used to determine rock quality. Based on these results, rock quality has
been categorized as follows:
Rock Mass Quality
Sound Rock
Moderately Fractured Rock
Highly Fractured Rock
Poor Rock
Allowable Bearing Capacity (qa)
Drill Core
RQD (%)
> 75
50-75
25-50
0-25
Fracture
Spacing
> 3 ft
1-3 ft
2-12 in.
< 2 in.
For foundations on rock, the allowable bearing capacities are as follows:
Poor rock
Highly fractured rock
Moderately fractured rock
Sound rock
= 10 ksf
= 20 ksf
= 40 ksf
= 80 ksf
Values presented for allowable bearing capacity are very conservative
values. Higher loadings may be acceptable dependent on strain
compatibility and settlement considerations.
The allowable bearing capacity is applicable for all combinations of load,
including dead load plus live load, plus seismic loading or wave loading or
wind loading, whichever is greater. Normal safety factors apply in each
case.
3890R/193R/CM 14 GEOTECHNICAL DESIGN CRITERIA
Strength Parameters
For excavations in rock, the unconfined compressive strength follows:
Sound to Poor to
Rock Type Moderately Fractured Hi~hly Fractured
Graywacke 15,000 psi 7,000 psi
Argillite 8,000 psi 4,000 psi
Tensile strength in foundation materials will not be included in resisting
forces, but will be considered in tunnel support design.
Deformation Modulus (E)
For computing deformations in rock excavations and for determining
transient (dynamic) response, the deformation modulus of the rock mass is
as follows:
Poor rock = 500,000 psi
Highly fractured rock = 2 X 10 6 psi
Moderately fractured rock = 4 X 10 6 psi
Sound rock = 8 X 10 6 psi
Poisson's Ratio (v)
The value of Poisson's Ratio for static loading conditions is v = 0.27. For
dynamic loading conditions, Poisson's Ratio of v = 0.35 may be utilized.
Shear Modulus (G)
The shear modulus for rock is computed from the equation:
G = E I 2 ( 1 + v)
3890R/193R/CM 15 GEOTECHNICAL DESIGN CRITERIA
Angle of Internal Friction (0)
Based on the results of detailed studies of rock foundation conditions, as
well as laboratory test data and analyses, the following criteria have been
established.
Discontinuity
Joints
Foliation planes
Slickensided planes
0 Peak (deg) 0 Residual (deg)
50 35
25 20
20 15
For analyses of shear strength through intact rock, an angle of internal
friction,0= 50° will be used.
Friction angles for fault gouge or filled joints, cohesion, and
concrete-bedrock adhesion will be determined on a case-by-case basis.
Concrete to rock bond strength shall be taken as 160 psi allowable design
working strength.
3.6.2 Basic Data for Foundations on In-Situ Soil
Depth of Frost Penetration
A depth of frost penetration equal to 9 ft will be used for the entire
Bradley Lake Project site.
Allowable Bearing Capacity (ga)
Allowable bearing pressures for structures founded on soi 1 vary with the
size and shape of the footing and with the depth of embedment. To aid in
design, the following criterion is given. For footings with minimum
dimension (B) greater than 4 ft and depth of embedment (D) greater than 4
ft, the nominal allowable bearing capacity is 10 ksf for talus soils, 6 ksf
for upland soils, and 3 ksf for intertidal soils. The determination of
bearing capacity for dimensional factors different from above shall be
performed on a case-by-case basis.
3890R/193R/CM 16 GEOTECHNICAL DESIGN CRITERIA
The reconunended bearing value is applicable for all combinations of load,
including dead load plus live load and seismic loading or wind loading.
However, the bearing capacities are not valid for structures below high
water level in the tailrace and lake areas.
Shear Strength Parameters
Cohesion will be taken as zero or will be established on a case-by-case
basis. The angle of internal friction will be taken as 24 degrees for
intertidal soils and as 33 degrees for upland soils in their undisturbed
state.
These values will be decreased somewhat to account for void ratio changes
when the soil is disturbed or used as lightly compacted backfill.
Shear Modulus (G)
For dynamic analyses, a shear modulus value shall be broad-banded by +33
percent.
Poisson's Ratio (v)
For static loading conditions (above the groundwater table) use Poisson's
ratio for soil, v = K /(1 + K ). Below the water table when the soils
0 0
are undrained, use v = 0.45.
For dynamic loading conditions use v 0.5.
3.6.3 Basic Data for Foundations on Compacted Fill
General
This section covers design parameters applicable for select granular fill,
structural fi 11 and random fill placed in conformance with the
specifications.
3890R/193R/CM 17 GEOTECHNICAL DESIGN CRITERIA
Allowable Bearing Capacity (ga)
The criteria given for natural upland soil are applicable for semi-pervious
fill.
The maximum allowable bearing capacity of compacted select earth fill will
be evaluated on a case-by-case basis.
Shear Strength Parameters
Cohesion will be taken as zero and the angle of internal friction will be
taken as 33 degrees for select and structural fill.
Poisson's Ratio (v) and Shear Modulus (G)
The criteria presented for soil are also applicable for all compacted fill.
3.6.4 Basic Data for Rockfill
The main dam will be constructed with four zones of rockfill. The in-place
rockfill materials are assumed to have the following properties:
Shear Wave Velocity:
Friction Angle:
Unit Weight
3890R/193R/CM 18
700-1000 fps
45° to 50°
125 to 150 pcf
GEOTECHNICAL DESIGN CRITERIA
4.0 REFERENCES
4.1 APPLICABLE CODES, REGULATIONS AND GUIDES
Where specific standards and design criteria are not covered in these
criteria, the latest edition of the following codes and standards will
apply:
BATF
COE
COE
COE
COE
COE
Bureau of Alcohol, Tobacco & Firearms (Various regulations
regarding explosives use and blasting)
Engineering and Design (of) Tunnels and Shafts in Rock; U.S.
Army Corps of Engineers, Engineer Manual EMlll0-2-2901
Recommended Guidelines for Safety Inspection of Dams, U.S.
Army Corps of Engineers
Earth and Rock Fill Dams General Design and Construction
Considerations; U.S. Army Corps of Engineers, Engineer Manual
EM 1110-2-2300
Engineering and Design Stability of Earth and Rock-Fill Dams;
U.S. Army Corps of Engineers, Engineer Manual EM 1110-2-1902
Sliding Stability for Concrete Structures; U.S. Army Corps of
Engineers, ETL 1110-2-256, 24 June 1981
NAVFAC DM-7.1 Design Manual-Soil Mechanics, Foundations,
Structures, Dept. of Navy, Naval Facilities
Command, 1982
and Earth
Engineering
NAVFAC DM-9 Cold Regions Engineering, Design Manual; Dept. of the Navy,
Naval Facilities Engineering Command, March 1985
NAVFAC P-355 Seismic Design for Buildings; Technical Manual, Dept. of the
Army, Navy, and Air Force, 1982
3890R/193R/CM 19 GEOTECHNICAL DESIGN CRITERIA
PTI
ASTM Dl557
ASCE
ASCE
ASCE
3890R/193R/CM
Post-Tensioning Manual; Post-Tensioning Institute
American Society for Testing and Materials
1978 Moisture-Density Relations of Soils Using 10-Lb
Rammer and 18 In Drop (Modified Proctor Density)
American Society of Civil Engineers
Current Trends in Design
Embankment Dams; American
Engineers, 1979
and Construction of
Society of Civil
Concrete Face Rockfill Dams -Design, Construction,
and Performance; American Society of Civil
Engineers, 1985
Guidelines for Tunnel Lining Design; American
Society of Civil Engineers, 1984
20 GEOTECHNICAL DESIGN CRITERIA
ASCE
ASCE
ACI 336.2R 1966
ACI 336.3R 1972
ACI 506 1966
ACI SP-45 1974
ACI SP-54 1976
Grouting in Geotechnical Engineering; American
Society of Civil Engineers, 1982
Subsurface Investigation for Design and
Construction of Foundations of Buildings; American
Society of Civil Engineers
American Concrete Institute
Suggested Design Procedures for Combined Footings
and Mats
Suggested Design and Construction Procedures for
Pier Foundations
Recommended Practice for Shotcreting
Proceedings of the Engineering
Conference on Use of Shotcrete for
Structural Support, ASCE/ACI
Foundation
Underground
Proceedings of the Engineering Foundation
Conference on Shotcrete for Ground Support, ASCE/ACI
If there is, or seems to be, a conflict between this design criteria and a
referenced document, the matter shall be referred to the Project Lead
Geotechnical Engineer.
3890R/193R/CM 21 GEOTECHNICAL DESIGN CRITERIA
4.2 SWEC CORPORATE CRITERIA
Required geotechnical calculations for the Bradley Lake Project are
identified in Geotechnical Technical Procedure No. GTP-8.1-0 as follows:
Title
1. Lateral Earth Pressures
2. Relative Motion During Earthquake
3. Settlement Analysis
4. Heave or Rebound of Excavation
5. Bearing Capacity
6. Stability of Structures
7. Design Groundwater Levels
8. Field Packer Test Data
9. Slope Stability
10. Seepage Analysis
11. Foundation Systems
12.
13.
14.
15.
16.
17.
18.
19.
20.
Earth Support System
Rock Support System
Dewatering System
Tunnel Support System
Embankments (includes fill dams)
Analysis of Shoreline Structures
Erosion Protection
Circulating Water Systems
Design of Grout Curtains
Cross Reference
GTG-6.15
GTG-6.4 and GTP-6.1
GTG-6.7
GTG-6.11 and GTP-6.2
GTG-6.8
GTG-6.12 and 6.13
None
GTG-6.19
GTG-6.16 and 6.17
ST-218
None
None
ST-212 and ST-214
ST-218
None
GT-018 and GT-055
None
None
None
Inspectors' Manual
These calculations support the Geotechnical Design Criteria which meet the
requirements of GTP-8.2-0 and GTP-8.3-0. All Geotechnical Technical
Procedures (GTPs) and Geotechnical Technical Guide! ines (GTGs) are
contained in the document:
SWEC, "Geotechnical Division Technical Procedures and Technical
Guidelines", latest version.
3890R/193R/CM 22 GEOTECHNICAL DESIGN CRITERIA
In the cross referenced list above, GT-xxx refers to qualified Geotechnical
Division computer programs, and ST-xxx refers to qualified Structural
Division computer programs used extensively for solution of geotechnical
problems. "Inspectors' Manual" refers to the document:
SWEC, "Inspectors' Manual. Drilling and Grouting Procedures and
Field Techniques".
The following Engineers' master specifications or applicable portions
thereof shall be considered in conjunction with this design criteria.
OOOOO-G002F
OOOOO-G002L
OOOOO-G002M
OOOOO-G002Q
OOOOO-G002S
OOOOO-G002T
OOOOO-G002U
OOOOO-G003E
OOOOO-S203A
OOOOO-S203C
OOOOO-S203E
OOOOO-S203H
Sediment and Erosion Control During Construction
Soil and Rock Excavation
Drilling and Cement Grouting
Earth Fill
Rock Blasting
Rock Reinforcement
Reinforced Shotcrete
Rock Tunnelling
Mixing and Delivering Concrete
Placing Concrete and Reinforcing Steel
Reinforcing Steel
Concrete Testing Services
4.3 BRADLEY LAKE PROJECT REPORTS
In general, the site or region specific design parameters in this design
criteria are based upon the applicable sections of the following documents:
1. Alaska Power Authority documents:
a. Alaska Power Authority (APA), Bradley Lake Hydroelectric
Project Recommended Design Criteria, July 30, 1985.
3890R/193R/CM 23 GEOTECHNICAL DESIGN CRITERIA
b. Best Management Practices Manual, Alaska Power Authority
Document APA-BMP, Susitna Hydroelectric Project, Frank
Moolin and Associates, 1985.
c. Drainage Structure and Waterway Design Guide! ines, Alaska
Power Authority Document APA-D5, Susi tna Hydroelectric
Project. Harza-Ebasco, 1985.
d. McGillivray, J., and O'Hawley, J., Literature Review:
Earthquake-Resistant Design of Dams and Cold Weather
Construction, prepared for Susitna Hydroelectric Project,
Acres American Inc., June 5, 1981.
e. Civil & Facilities Design Criteria, Bradley Lake Project;
R&M Consultants, Inc., Anchorage, Alaska, 1985.
2. Stone & Webster Engineering Corporation (SWEC). Bradley Lake
Hydroelectric Power Project, Feasibility Study, Volume I, SWEC,
Anchorage, Alaska, October 1983.
3. Dryden & LaRue Consulting Engineers (D&L). Feasibility Study of
Transmission Line System, Phase 1, Bradley Lake Hydroelectric
Power Project, D&L, Anchorage, Alaska, August 1983.
4. Government agency reports:
a. U.S. Army Corps of Engineers (COE). Brad 1 ey Lake
Hydroelectric Project, General Design Memorandum. COE,
General Design Memorandum No. 2, February 1982, Volume 1 of
2.
b. U.S. Army Corps of Engineers (COE). Bradley Lake
3890R/193R/CM
Hydroelectric Project, General Design Memorandum. COE,
General Design Memorandum No. 2, February 1982, Volume 2 of
2.
24 GEOTECHNICAL DESIGN CRITERIA
c. U.S. Army Corps of Engineers (COE). Final Environmental
Impact Statement, Bradley Lake Hydroelectric Project, COE,
Alaska District, August 1982.
d. U.S. Army Corps of Engineer (COE). Feasibility Report for
Hydroelectric Power Development of Bradley Lake, Kenai
Peninsula, Alaska. COE, Alaska District, September 1975.
e. U.S. Army Corps of Engineers (COE). Reanalysis of the
Bradley Lake Hydroelectric Project. COE, March 1978.
f. Stephens, C.D., Lahr, J.C. and Rogers, J.A. Review of
Earthquake Activity and Current Status of Seismic Monitoring
in the Region of Bradley Lake Hydroelectric Project,
Southern Kenai Peninsula, Alaska. U.S. Geological Survey,
Open-File Reports 81-736, 82-417, 83-744, and letter
transmittal 10/85.
g. Lahr, John C., letter to Alaska Power Authority, 5 April
1985 (status report on Bradley Lake Hydroelectric Project
Seismic Monitoring Program).
h. Hinton, R.B. Soil Survey of Homer-Ninilchik Area, Alaska.
U.S. Department of Agriculture, Soil Conservation Service,
July 1971.
i. Johnson, F.A. Waterpower Resources of the Bradley River
Basin, Kenai Peninsula, Alaska. U.S. Geological Survey Water
Supply Paper 1610-A, 1961.
j. Soward, K.S. Geology of Waterpower Sites on the Bradley
River, Kenai Peninsula, Alaska. u.s. Geological Survey
Bulletin 1031-C, 1962.
3890R/193R/CM 25 GEOTECHNICAL DESIGN CRITERIA
k. Karl strom, T.V., Quarternary Geology of the Kenai Lowland
and Glacial History of the Cook Inlet Region, Alaska. U.S.
Geological Survey Professional Paper 443, 1964.
1. Pewe, T.L., Quaternary Geology of Alaska. U.S. Geological
Survey Professional Paper 835, 1975.
5. Geotechnical reports:
a. Woodward-Clyde Consultants (WCC). Reconnaissance Geology,
Bradley Lake Hydroelectric Project. Project No. 41193I, WCC,
Anchorage, Alaska, December 1979.
b. Woodward-Clyde Consultants (WCC). Seismicity Study, Bradley
Lake Hydroelectric Project, Project No. 41229A, WCC,
Anchorage, Alaska, March 1980.
c. Woodward-Clyde Consultants (WCC). Geologic Reconnaissance,
Bradley Lake Access Road, Project No.
Anchorage, Alaska, November 1980.
14844A, wee,
d. Woodward-Clyde Consultants (WCC). Report for Design
Earthquake Study, Project No. 14844B, WCC, Anchorage,
Alaska, November 1981.
e. R.W. Beck and Associates (BECK). Sununary Report on
f.
Construction Procedures and Schedule, Bradley Lake Project.
BECK, Seattle, Washington, September 2, 1982.
DOWL Engineers
Mapping Program.
(DOWL). Bradley Lake Project, Geologic
DOWL, Anchorage, Alaska, January 1983.
g. Shannon & Wilson, Inc. (S&W). Bradley Lake Hydroelectric
Power Project, Geotechnical Studies. K-0631-61, S&W,
Fairbanks, Alaska, September 1983.
3890R/193R/CM 26 GEOTECHNICAL DESIGN CRITERIA
h. R&M Consultants, Inc. (R&M). Final Site Conditions Report
of Geotechnical Field Investigations 1984 & 1985 Programs,
Bradley Lake Hydroelectric Project, Volumes 1, 2 and 3, R&M,
Anchorage, Alaska, II, March 1986.
6. Laboratory Testing of Rock Samples, Professor A.J. Hendron, Jr.
& Associates and The Robbins Company, Seattle, Washington, and
Atlas-Copco Jarva.
The majority of the parameters m this Geotechnical Design Criteria were
either obtained directly from the above sources or were developed via
applicable analytical techniques. There are also several parameters that
can be considered "assumed" values and are typically based upon general
empirical data for similar foundation materials. Specific design values for
lateral earth pressure coefficients and shear moduli have been developed
following methods of analyses from Geotechnical Guidelines 6.15 and 6 .1,
respectively.
Other design values have been developed using methods of analyses from
published literature.
4.4 GENERAL DESIGN REFERENCES
General Design References -Geotechnical
Blaster's Handbook, E.I. duPont de Nemours & Co., Inc.
Compressed Air Handbook, Ingersoll-Rand Corp.
Design of Gravity Dams, U.S. Bureau of Reclamation, 1976
Design of Small Dams, U.S. Bureau of Reclamation, rev. reprint 977
3890R/193R/CM 27 GEOTECHNICAL DESIGN CRITERIA
Dictionary of Geological Terms, American Geological Institute, 1962
Welded Steel Penstocks, U.S. Bureau of Reclamation, Engineering Monograph
#3, Revised 1977
Hoek, E. and Bray, J.W., Rock Slope Engineering, Institution of Mining and
Metallurgy, London, 1981
Bentall, R., Methods of Determining Permeability, Transmissibility and
Drawdown, U.S. Geological Survey Water-Supply Paper 1536-I, 1963
Deere, D.V., Technical Description of Rock Cores for Engineering Purposes,
in Rock Mechanics and Engineering Geology, Vol. 1, 1963
Deere, D.V. and Miller, R.P. Engineering Classification and Index
Properties for Intact Rock, Technical Report AFWL-TR-65-116, Air Force
Weapons Laboratory, N.M. 1966
Fermans, Oscar J., Jr., Permafrost Map of Alaska, U.S. Geological Survey,
Miscellaneous Geologic Investigations Map I-445, 1965
Gibbs, Harold J., Estimating Foundation Settlement by One-Dimensional
Consolidation Tests, U.S. Bureau of Reclamation, Engineering Monograph #13,
March 1953
Hendron, A.J., Jr., Mechanical Properties of Rocks, in Stagg & Zienkiewicz
(eds) -Rock Mechanics in Engineering Practice, John Wiley and Sons, 1968
Hoek, E., and Brown, E.T., Underground Excavations in Rock, Institution of
Mining and Metallurgy, London, 1980
Johnston, G.H. (ed), Permafrost Engineering Design and Construction, John
Wiley and Sons, 1981
3890R/193R/CM 28 GEOTECHNICAL DESIGN CRITERIA
Kenney, C., Current Practice and Research on Protective Filters for Cores
of Dams, presented at 1982 Acres Geotechnical Seminar, April 23, 1982
Linardini, V.J., Heat Transfer in Cold Climates, Van Nostrand Reinhold Co.,
1981
Nichols, H.R., Johnson, C.F., and Duvall, W.I., Blasting Vibrations and
Their Effects on Structures, U.S. Bureau of Mines, Bulletin 656, 1971
Obert, L., and Duvall, W.I., Rock Mechanics and the Design of Structures in
Rock, John Wiley & Sons, New York, 1967
Proctor, V., and White, T.L., Rock Tunnelling with Steel Support,
Commercial Shearing Inc., 1977 reprint
Siskind, D.E., et al., Structure Response and Damage Produced by Ground
Vibration from Surface Mine Blasting, U.S. Bureau of Mines Report of
Investigations #8507, 1980
Stagg, M.S., and Engles, A.J., Measurement of Blast-Induced Ground
Vibrations and Seismograph Calibration, U.S. Bureau of Mines Report of
Investigations #8506, 1980
Travis, R.B., Classification of Rocks, in Quarterly of the Colorado School
of Mines, V of 50 #1, January 1955
Zangar, C.N., Theory and Problems of Water Percolation, U.S. Bureau of
Mines, Engineering Monograph #8, April 1953
Winterkorn, H.F. and Fang, H., Foundation Engineering Handbook, VanNostrand
Reinhold Co., 1978
Bickel, J .0. and Keusel, T .R., Tunnel Engineering Handbook, VanNostrand
Reinhold Co., 1982
3890R/193R/CM 29 GEOTECHNICAL DESIGN CRITERIA
General Design References -Seismic
Earthquake Design and Analysis for Corps of Engineers Dams, U. S. Army
Corps of Engineers, ER 1110-2-1806, 30 April 1977
Algermissen, S.T., and Perkins, D. M., 1976. A Probabilistic estimate of
Maximum Acceleration in Rock in the Contiguous United States, U.S.
Geological Survey Open-File Report, 76-416, 45 pp.
Algermissen, S.T., Perkins, D.M., Thenhaus, P.C., Hanson, S. L. and Bender,
B.L., 1982, Probabilistic Estimates of Maximum Acceleration and Velocities
in Rock in the United States, U.S. Geological Survey Open-File Report,
82-1033, 99 pp.
Chakrabarti, S., et al., Seismic Design of Retaining Walls and Cellular
Cofferdams, in ASCE Conference on Earthquake Engineering, Vol. 1, 1970
Hays, Walter W., Procedures for Estimating Earthquake Ground Motions, U.S.
Geological Survey, Professional Paper 1114, 1980
Joyner, W. B., and Boone, D.M., Prediction of Earthquake Response Spectra,
U.S. Geological Survey Open-File Report 02-977
Schnabel, P.B., and Seed, H.B., 1973, Accelerations in Rock for Earthquakes
in the Western United States, Seismol, Soc. Am. Bull, 62: 501-516
Seed, H.B., Murarka, R., Lysmer, J., and Idriss, I.M, 1976, Relationships
of Maximum Acceleration, Maximum Velocity, Distance from Source, and Local
Site Conditions for Moderately Strong Earthquakes, Seismol. Soc. Am. Bull.,
66:221-224
Seed, H.B., and Idriss, I.M., 1982, Ground Motions and Soil Liquefaction
During Earthquakes. Earthquake Eng. Res. Instr. Monogr., Berkeley,
California, 134 pp.
3890R/193R/CM 30 GEOTECHNICAL DESIGN CRITERIA
Seed, H.B., and Whitman, R. V., Design of Earth Retaining Structure for
Dynamic Loads, in Earth Retaining Structure, ASCE
Woodward-Clyde Consultants (WCC). Final Report on Seismic Studies for
Susitna Hydroelectric Project, WCC, Orange, Calif., April 1982
Woodward-Clyde Consul tatnts (WCC). Seismicity Study, Bradley Lake
Hydroelectric Project, WCC, Anchorage, AK, 28 March 1980.
Woodward-Clyde Consultants, (WCC). Report on the Bradley Lake
Hydroelectric Project, Design Earthquake Study, WCC, Anchorage, AK, 10
November 1981.
3890R/193R/CM 31 GEOTECHNICAL DESIGN CRITERIA
A
a v
B
b
Co
c
D
DBE
E
F
FS
f
G
Gd,Gt
Gm
H
Ka
Ko
Kp
L
M
MCE
m
n
OBE
Poe
Ppe
q
qa
RQD
SYMBOLS and ABBREVIATIONS
Area
Horizontal base acceleration
Vertical base acceleration
Width of footing or excavation
Angle between backfill slope and horizontal
Unconfined compressive strength
Unit shear strength at zero normal load
Depth of base of footing below ground surface
Design Basis Earthquake
Deformation modulus
Pseudostatic seismic force
Factor of safety
Final stress in tunnel lining due to rock load
or coefficient of friction
Shear modulus
Unit weight (dry and total) of soil or rock
Maximum shear modulus
Height of fill or rock slope
Active earth pressure coefficient
At-rest earth pressure coefficient
Passive earth pressure coefficient
Length of footing
Bending moment due to rock load
Maximum Credible Earthquake
Mass active during earthquake
Manning's Coefficient
Operational Basis Earthquake
Total soil and water "at rest" for static
and dynamic loading conditions
Total soil and water "passive" lateral force
Surface surcharge
Allowable bearing stress
Rock Quality Designation
3890R/193R/CM 32 GEOTECHNICAL DESIGN CRITERIA
S Section modulus
S Effective vertical stress v
S Effective normal stress n
T Shear Stress
v Poisson's Ratio
w Unit weight of backfill or Terzaghi rock load
0 Angle of internal friction
D dead load
DBE design basis earthquake
E Design Earthquake Load
E' Maximum Earthquake Load
Encap encapsulated
G.S. ground surface
I ice loads
Ls static lateral
earth pressure
CALC Calculation
CDC Civil Design Criteria
GDC Geotechnical Design Criteria
HDC Hydraulic Design Criteria
SDC Structural Design Criteria
Lo dynamic lateral earth pressure (DBE)
1m dynamic earth pressure (MCE)
MCE maximum credible earthquake
N/A not applicable
N/R not required
OBE operating basis earthquake
O.C. on center
T tsunami or seiche loads
TBD to be determined
TOR top of rock
W wind loads
W' storm wind and wave loads
3890R/193R/CM 33 GEOTECHNICAL DESIGN CRITERIA
Horizontal Ground
Acceleration (Peak)
Approximate Mean
Annual Probabi I ity
of Exceeding Specified
Acceleration (based
on 50 year project
I i fe)
Anticipated Downtime
Project Features
Dam
Spillway
Power Tunnel
Powerhouse
rbine/Generator/
Governor
Controls
3889R/CM
Operational Basis (OBE)
up to . 1 g
0.1-0.2
(1-2 chances in 10
of exceeding 0.1g)
Project resumes operation
within hours
fABLE 1
SEISMIC CRITERIA
Design Basis (DBE)
0.1 g to . 35 g
.007
(7 chances in 1000
of exceeding 0.35g)
Inspection and checkout
30 days. Repairs 1 to 6
months
ALLOWABLE DAMAGE LEVEL
Operational
No significant damage
Ope r at i on a I
No damage, requires
integrity check to restart.
Minor adjustments/reset
controls/spares replace-
ments.
Operational
Architectural damage.
No significant structural
damage.
Minor damage, possible
replacement of components
with spare parts
Limited damage, rep I ace-·
ment of components with
spares
Page 1 3
Maximum Credible Basis (MCE)
.35 g to .75 g
.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 col lapse).
Significant architec-
tural damage.
Possible major damage
Possible major damage
Spherical Valves
and Operators
Power Tunnel and
Diversion Tunnel
S I ide Gates and
Operators,
Diversion Tunnel
Powerhouse
rgency Generator
15 kV Sw i t chgea r
and Bus
Main Powerhouse
Transformers
Substation/
Transmission Line
Emergency Lighting
Fire Protection
Environmental
Systems
3889R/CM
(OBE)
Operationa
Operational
Operationa
Operational
Operational
Operational
Operational, minor
damage (I ight bulb
replacement)
Operational
Operational
SEISMIC CRITERIA
(DBE)
Operational
Operational
Operational
Operational
Operational
Potentia I interrupti on
of service
Operational, minor
damage and I ight bulb
replacement
Operational
Operational
Page 2 ot 3
(MCE)
Operational
Ope rat i ona I
Operational by
start. Manual
reconnect ion
required.
Minor damage
Minor damage
manual
cable
be
Out of service, possible
major damage
May require reconnection
to emergency generator
and I ight bulb replace-
ment
Possible damage
Possible damage
Page 3
SEI~~IC CRITERIA
(OBE) (DBE)_ (MCE)
Permanent Camp Operational Operational Potential for archi tee-
Fac i I it i es tural and structural
including Permanent damage
Housing
Barge Dock Operational So i I fa i I u res Major so i I failures
Airstrip possible. Wi II be possible. Wi II be
Access Roads repaired as needed. repaired as needed.
3889R/CM
GEOTECHNICAL DESIGN CRITERIA TABLE 2
P. 1 of 1 FOR: Diversion Tunnel and Permanent Outlet Facility
Reference Criteria: SOC -Part B, Section 1.0
HOC -Main Dam Diversion
Seismic Category: Critical Response Spectrum Figure:
Water Levels: Maximum
Operating PMF
Reservoir El (ft): 1180 1190.6
Internal El (ft): Fluctuates with Reservoir
Reservoir Level of 1068
Design Dead Loads (psf): Rock Loads
Design Live Loads (psf): Consider Crane Access
Rock Loads on Structure Terzaghi Criteria
Foundation Data: Allowable Bearings Capacity 80 ksf
Drainage Slope: 1.0%
Slope Analysis
Failure Angle
Discontinuity Type:
Cohesion, psf
Angle of Internal Friction, degrees
Peak
Residual
Unit Weight Dry (pcf)
2-Dimensional
60°
Joint
1000
50
30
165
Design Load Cases -Per GDC Unless Otherwise Stated
Sliding Overturning
1. D FS: 4.0 FS: 2.0
2. D + E FS: 1.5 FS: 1.5
3. D + E' FS: 1.05 FS: 1.05
MCE
Minimum
Operating
1068
Level, Dry
Wedge
60°
Joint
1000
50
30
165
at
3887R/193R/CM 37 GEOTECHNICAL DESIGN CRITERIA
TABLE 3
P. 1 of 1
GEOTECHNICAL DESIGN CRITERIA
FOR: Diversion Channel Improvement
Reference Criteria: HDC -Main Dam Diversion
Seismic Category: Non-Critical
Water Levels:
Response Spectrum Figure: DBE
Operating Pool Levels (ft):
Flood Pool Level (ft):
Design Live Loads (psf): 300 (traffic)
Slope Protection
Maximum
1067
1081
Minimum
1061
Materials: Blasted Rock, Stone Protection, and Riprap
Slope Analysis: 2-Dimensional Wedge
Discontinuity Type Sliding Surface
Angle of Internal Friction (degrees) Peak: 45
Unit Weight: dry (pcf): 150
3887R/193R/CM 38 GEOTECHNICAL DESIGN CRITERIA
TABLE 4
P. 1 of 1
GEOTECHNICAL DESIGN CRITERIA
FOR: Powerhouse and Substation
Reference Criteria: SOC -Part B, Sections 6.0, 8.0
Seismic Category: Critical Response Spectrum Figure: MCE
Design Live Loads (psf): 300 (traffic)
Groundwater Levels (ft) Mean El: 15 Max El: 18 Min El: -9.0
Foundation Data: Allowable Bearing Capacity 40 ksf
Slope Analysis: 2-Dimensional
Discontinuity Type: Joints
Cohesion, psf 500
Angle of Internal Friction (degrees
Peak 50
Residual 30
Unit Weight: dry (pcf): 165
Design Load Cases -Per GDC Unless Otherwise Stated
Sliding Overturning
l. D FS: 2.0 FS: 2.0
2. D + E + Lo FS: 1.5 FS: 1.5
3. D + I FS: 1.5 FS: 2.5
4. D + E' + Lm FS: 1.05 FS: 1.05
3887R/193R/CM 39 GEOTECHNICAL DESIGN CRITERIA
GEOTECHNICAL DESIGN CRITERIA TABLE 5
P. 1 of 1 FOR: Power Tunnel Intake Structure
Reference Criteria: SOC -Part B, Section 4.0
HOC -Power Intake, Tunnel and Penstock
Seismic Category: Critical Response Spectrum Figure: MCE
Design Live Loads (psf): 300 psf (Traffic)
Groundwater Levels (ft) Fluctuate with Reservoir Level
Foundation Data -Concrete Slab at Portal
Bearing Material: Sound Rock Allowable Bearing Capacity 80 ksf
Slope Analysis 3-Dimensional Wedge
Discontinuity Type:
Cohesion, psf:
Joint Surface
500
Angle of Internal Friction, degrees
Peak 50°
Effective: 30°
Unit Weight: dry (pcf): 165
Design Load Cases -Per GDC Unless Otherwise Stated
Sliding Overturning
1. D FS: 2.0 FS: 2.0
2. D + E FS: 1.5 FS: 1.5
3. D + E' FS: 1.05 FS: 1.05
3887R/193R/CM 40 GEOTECHNICAL DESIGN CRITERIA
TABLE 6
P. 1 of 1
GEOTECHNICAL DESIGN CRITERIA
FOR: Power Tunnel
Reference Criteria: SDC -Part B, Section 4.0
HDC -Power Intake, Tunnel and Penstock
Seismic Category: Critical Response Spectrum Figure: MCE
Design Dead Loads (psf): Rock Loads by Terzaghi Criteria
Design Live Loads (psf): Hydrostatic & Hydraulic Transients
Groundwater Levels (ft) Fluctuate with Reservoir Level
Analysis: Circular
Failure Radius/Angle: Hoop/Arch Analysis
Discontinuity Type Joints
Cohesion, psf 0
Angle of Internal Friction, degrees
Peak so
Effective 30
Unit Weight: dry (pcf):l65
3887R/193R/CM 41 GEOTECHNICAL DESIGN CRITERIA
TABLE 7
P. 1 of 1
GEOTECHNICAL DESIGN CRITERIA
FOR: Penstock and Steel Liner
Reference Criteria: SOC -Part B, Section 5.0
HDC -Power Intake, Tunnel and Penstock
Seismic Category: Critical Response Spectrum Figure: MCE
Design Dead Loads (psf): Rock Cover
Design Live Loads (psf): Groundwater & Hydraulic Transients
Groundwater Levels (ft) Mean El: 40 Max El:60+ Min El:DRY
Analysis 2-Dimensional Wedge
Failure Radius/Angle: Varies
Discontinuity Type Joints
Cohesion, psf 1000
Angle of Internal Friction, degrees
Peak 50
Effective: 30
Unit Weight: dry (pcf):l60
3887R/193R/CM 42 GEOTECHNICAL DESIGN CRITERIA
TABLE 8
P. 1 of 1
GEOTECHNICAL DESIGN CRITERIA
FOR: Power Tunnel Gate Shaft
Reference Criteria: SOC -Part B, Section 4.0
HOC -Power Intake, Tunnel and Penstock
Seismic Category: Critical Response Spectrum Figure: MCE
Design Dead Loads (psf): Rock Loads
Design Live Loads (psf): 300 (Traffic)
Foundation Data
Bearing Material
Soil or Rock Type:
Sound/Mod Frac Rock Allowable Bearing Capacity 80 ksf
Intermixed Graywacke/Argillite
Grade El: 1194 Bottom EL: 1135
Analysis 3-Dimensiona1 Wedge
Failure Radius/Angle: Variable Joint
Discontinuity Type
Cohesion, psf
See Geotechnical Interpretive Report
0
Angle of Internal Friction, degrees
Peak 50
Effective:
Unit Weight:
3887R/193R/CM
30
dry (pcf): 165
43 GEOTECHNICAL DESIGN CRITERIA
TABLE 9
P. 1 of 1
GEOTECHNICAL DESIGN CRITERIA
FOR: Main Dam
Reference Criteria: SOC -Part B, Section 2.0
HOC -Main Dam
Seismic Category: Critical Response Spectrum Figure: MCE
Water Levels:
Reservoir
Tail water
EL (ft):
EL (ft):
Minimum Operating
1090
1061
Design Live Loads (psf): 300 (Traffic)
Ice Loads: 12k/lf; per HDC
Analysis
Failure Radius/Angle:
Circular
Varies
Discontinuity Type Int. Failure
Cohesion, psf 0
Angle of Internal Friction, 48°
Unit Weight: total (pcf): 135 dry (pcf):
Design Load Cases -Per GDC Unless Otherwise
Sliding
1. D FS: 2.0
2. D + I FS: 1.2
3. D + E' +Lm FS: N/ A'/t
4. D + T FS: 1.1
* See Dam Stability Report
Maximum Operating
1180
1067
2-Dimensional Wedge
Varies
Wedge
0
120 min sat'd (pcf):
Stated
Overturning
FS: N/A
FS: N/A
FS: N/A
FS: N/A
PMF
1190.6
1081.7
150 max
3887R/193R/CM 44 GEOTECHNICAL DESIGN CRITERIA
TABLE 10
P. 1 of 1
GEOTECHNICAL DESIGN CRITERIA
FOR: Spillway
Reference Criteria: SOC -Part 8, Section 3.0
HOC -Spillway
Seismic Category: Critical Response Spectrum Figure: MCE
Water Levels:
Reservoir
Internal
EL (ft):
EL (ft):
Minimum Operating
1080
G.S.
Maximum Operating
1180
1180
Design Live Loads (psf): 300 (Traffic where applicable)
Ice Loads: 12 k/lf
PMF
1190.6
1190.6
Groundwater Levels (ft)
Slope Analysis
Max El: 1150
2-Dimensional Wedge
Min El: 1060
Failure Radius/Angle: Varied based on rock joint orientation
Discontinuity Type
Cohesion, psf
Joint
500
Angle of Internal Friction, degrees
Peak 50
Effective: 35 & 40
Unit Weight: dry (pcf): 165
Design Load Cases -Per GDC Unless Otherwise Stated
Sliding Overturning
1. D FS: 4.0 FS: 2.0
2. D + E FS: 1.5 FS: 1.5
4. D + E' FS: N/A"~r FS: N/ A-Jr
* See Spillway Stability Report
3887R/193R/CM 45 GEOTECHNICAL DESIGN CRITERIA
G)
111
0
--i
111
()
I z
()
)> r
0
111
Ul
Gli z
REF WOODWARD· CLYDE CONSULTANT:
REPORT• "DESIGN EARTHQUAKE STUDY'
NOV 10,1981
2.2 5 ..-----.--------.---.-----.---.------.------.--.---·
....-..,
CJ)
..........
cu RESPONSE SPECTRUM
(})1.88 1 ,...,., " FOR HYBRID EARTHQUAKE
z
0
~ 1.501 II ---1--L-L 0:: w
_j w U 1 .13 I II I lt.: ~
£;J_
_J
<t: 0.75 u: .._
w
Q_ 0. 38 1-1------· .
t/)
BRADLEY LAKE HYDROELECTRIC PROJECT
MEAN RESPONSE SPECTRUM FOR MCE
(NEARBY SHALLOW CRUSTAL FAULT)
DAMPING RATIO = 0.05 n
MEAN RESPONSE SPECTRUM
FOR DBE
DAMPING RATIO = 0.05
0.00 L.-. A ---1.
0.00 025 0 50 075 100 1.25 1.50 1.75 2.00 2 25 2.50
PERIOD (SEC)
2.75 3.00
--J2
G)
fTl
()~----------------------------------------------------------------------~ :u ALASKA POWER AUTHORITY GEOTECHNICAL DESIGN CRITERIA -
--i
111 BRADLEY LAKE HYDROELECTRIC PROJECT MEAN HORIZONTAL RESPONSE SPECTRUM
::0
)> KENAI PENINSULA BOROUGH,ALASKA FIGURE 1
0
11
1\)
SECTION 3.0
STRUCTURAL
DESIGN CRITERIA
4002R/0168R/CM
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. No. 15500 & 15800
PART A:
PART B:
STRUCTURAL DESIGN CRITERIA
GENERAL STRUCTURAL DESIGN CRITERIA
SPECIAL REQUIREMENTS AND DESIGN
CRITERIA FOR MAJOR STRUCTURES
STONE & WEBSTER ENGINEERING CORPORATION
DENVER, COLORADO
GENERAL STRUCTURAL DESIGN CRITERIA
STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS
SECTION TITLE PAGE
PART A GENERAL STRUCTURAL DESIGN CRITERIA
1.0 GENERAL A-1
2.0 REGULATIONS, CODES, STANDARDS AND GUIDES A-4
3.0 MATERIALS A-7
4.0 DESIGN LOADS A-10
5.0 STRUCTURAL DESIGN A-23
6.0 TABLES A-33
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
SECTION
PART 8
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
4002R/0168R/CM
STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS
(CONT'D)
TITLE
SPECIAL REQUIREMENTS AND DESIGN
CRITERIA FOR MAJOR STRUCTURES
PAGE
MAIN DAM DIVERSION 81-1
MAIN DAM 82-1
SPILLWAY 83-1
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT 84-1
STEEL LINER AND PENSTOCK 85-1
POWERHOUSE 86-1
TAILRACE 87-1
SUBSTATION 88-1
MIDDLE FORK AND NUKA GLACIER DIVERSIONS 89-1
GENERAL STRUCTURAL DESIGN CRITERIA
4002R/0168R/CM
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. No. 15500 & 15800
STRUCTURAL DESIGN CRITERIA
PART A: GENERAL STRUCTURAL DESIGN CRITERIA
REVISION: 2
DATE: March 25, 1988
STONE & WEBSTER ENGINEERING CORPORATION
DENVER, COLORADO
GENERAL STRUCTURAL DESIGN CRITERIA
SECTION
1.0
2.0
2.1
2.2
2.3
3.0
4.0
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.8.1
4.8.2
4.8.3
4.9
4.10
4.11
4.12
4.13
4.14
4.15
4.16
4.17
4.18
4.19
4.20
5.0
5.1
5.2
5.3
5.4
5.5
4002R/0168R/CM
PART A
GENERAL STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS
TITLE
GENERAL
REGULATIONS, CODES, STANDARDS AND GUIDES
Local, State, and Federal Codes and Regulations
Industry Codes, Standards, and Specifications
Miscellaneous Documents
MATERIALS
DESIGN LOADS
Dead Loads (D)
Live Loads (L)
Snow and Ice Loads (S,I)
Equipment Loads (M)
Hydraulic Loads (H)
Soil and Rock Loads
Wind Loads (W)
Seismic Loads (E)
General Seismic Conditions
General Seismic Forces
Seismic Forces on Elements
Tsunami and Seiche Induced Forces
Thermal Loads (T)
Pipe and Cable Tray Load Allowances
Roof Girder Load Allowance
Column Load Allowance
Bracing Load
Temporary Roof Loads
Crane Impact Allowance
Hoist Trolley Loads
Truck Loads
Vibrational Loads
Construction Loads
STRUCTURAL DESIGN
Load Combinations
Stability Requirements
Steel Design
Concrete Design
Masonry Design
1
PAGE
A-1
A-4
. .l.-4
A-5
A-6
A-7
A-10
A-10
A-10
A-10
A-ll
A-ll
A-ll
A-12
A-13
A-13
A-14
A-17
A-18
A-18
A-19
A-19
A-20
A-21
A-21
A-21
A-22
A-22
A-22
A-22
A-23
A-23
A-24
A-25
A-29
A-32
GENERAL STRUCTURAL DESIGN CRITERIA
SECTION
6.0
Table 1
Table 2
Table 3
Table 4
Table 5
Table 6
Table 7
Table 8
Table 9
Table 10
ATTACHMENTS
TABLES
TABLE OF CONTENTS
(CONT'D)
TITLE
Selected Material Weights
Minimum Live Loads for Floors and Decks
Estimated Equipment Weights
Miscellaneous Equipment Loads
Snow Loads
Wind Pressures -Speed v = 100 mph,
I = 1.0, Exposure B
Wind Pressures -Speed v = 100 mph,
I = 1.0, Exposure C
Wind Pressures -Speed v = 120 mph,
I = 1.0, Exposure B
Wind Pressures -Speed v = 120 mph,
I = 1.0, Exposure C
Wind Load Importance Factors
PAGE
A-33
A-33
A-34
A-36
A-38
A-38
A-39
A-40
A-41
A-42
A-43
Attachment A -Mean Horizontal Response Spectra
11
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-1
PART A
GENERAL STRUCTURAL DESIGN CRITERIA
1.0 GENERAL
This document provides structural design criteria necessary to design the
Bradley Lake Hydroelectric Project. Separate from this criteria are design
criteria set by R & M Consultants, Inc. (R & M) for roads, bridges, camp
facilities, barge and harbor facilities and criteria set by Dryden and
LaRue, Inc. (D & L) for transmission systems. Supplemental to this
criteria are General Project Information and Civil Design Criteria,
Geotechnical Design Criteria, and Hydraulic Design Criteria.
The Bradley Lake Project is being designed by Stone & Webster Engineering
Corporation (SWEC) for the Alaska Power Authority. The project is located
in the southern end of the Kenai Peninsula approximately 27 miles northeast
of Homer, Alaska and approximately 105 miles south of Anchorage, Alaska.
The project will initially develop a nominal 90 MW capacity. The
powerhouse will be located on the Kachemak Bay with a tunnel to Brad:ey
Lake. The existing natural lake level is at elevation 1080. The
electricity produced will be transmitted to Homer, the Kenai Peninsula, and
Anchorage. The project will be designed so as not to preclude the
installation of a third unit with a resulting total project capacity of 135
MW.
The project includes the following principal features:
1. A concrete faced rockfill dam located at the natural outlet of Bradley
Lake;
2. A concrete ungated gravity ogee spillway;
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-2
3. A horseshoe shaped diversion tunnel approximately 400ft long, with
gatehouse and gateshaft, steel penstock, outlet portal structure, and
excavation of the Bradley River channel immediately downstream of the
tunnel and dam;
4. A power tunnel approximately 11 ft diameter by 19,000 ft long between
Bradley Lake and the powerhouse;
5. An intake structure with a removable trashrack and bulkhead gates at
the inlet to the power tunnel;
6. A gatehouse and gateshaft located in the upstream portion of the power
tunnel;
7. Diversion works on the Middle Fork of the Bradley River and at the
terminus of the Nuka Glacier;
8. A steel penstock and steel liner located at the downstream portion of
the power tunnel to the powerhouse;
9. An above ground powerhouse, containing two
Pelton turbines and associated equipment,
expansion to three units;
45 MW generators with
with capabilities for
10. A tailrace channel discharging into Kachemak Bay, located adjacent to
the powerhouse;
11. A Compact Gas Insulated Substation (CGIS) with 115 kV transformers
located adjacent to the powerhouse;
12. Docking and barging facilities and an airstrip at the Kachemak Bay;
13. Maintenance and storage facilities;
14. Both permanent and construction camp facilities;
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-3
15. Access roads within the project site;
16. Permanent housing facilities for operating personnel; and
17. A 115 kV transmission line with intertie switching station at the
Homer-Soldotna transmission system.
Work under items 12, 13, 14, 15 and 16 will be performed by R & M
Consultants and work under item 17 will be performed by Dryden and LaRue,
Inc., (subcontractors to Stone & Webster Engineering Corporation).
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-4
2.0 REGULATIONS, CODES, STANDARDS, AND GUIDES
Unless otherwise stated, the design of all structures shall conform to the
latest editions of the applicable codes and specification listed below.
2.1 LOCAL, STATE, AND FEDERAL CODES AND REGULATIONS
AAC
OSHA-AK
OSHA-US
DOT/PF 1982
4002R/0168R/CM
Alaska Administrative Code, Section 13AACSO,
(incorporates UBC provisions for Alaska State bui !ding
code requirements).
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
1926/1910), as supplement to the State of Alaska's
General Safety Code.
Alaska Department of Transportation
Facilities, Design Standards for Buildings.
and Public
GENERAL STRUCTURAL DESIGN CRITERIA
A-5
2.2 INDUSTRY CODES, STANDARDS, AND SPECIFICATIONS
MSHTO-HB
ACI 302 .1R
ACI 315
ACI 318
ACI 336.3R
AISC
AISI
AWS D1.1
AWS Dl. 4
SJI
UBC
4002R/0168R/CM
1978
1980
1980
1983
1972
Rl980
1980
1968
1985
1985
1986
1985
Standard specifications for Highway Bridges; American
Associ at ion of State Highway and Transport at ion
Officials (MSHTO).
Guide to Concrete Floor and Slab Construction.
Manual of Standard Practice for Detai 1 ing Reinforced
Concrete Structures.
Building Code Requirements for Reinforced Concrete
(ACI 318).
Suggested Design and Construction Procedures for
Pier Foundations.
Manual of Steel Construction (8th Edition)
Specifications for the Design of Cold-Form Steel
Structural Members with Commentary; American Iron and
Steel Institute (AISI).
Structural Welding Code; American Welding Society
(AWS).
Reinforcing Steel Welding Code; AWS.
Standard Specifications, Load Tables and Weight
Tables; Steel Joist Institute (SJI).
Uniform Building Code; International Conference of
Building Officials.
GENERAL STRUCTURAL DESIGN CRITERIA
A-6
2.3 MISCELLANEOUS DOCUMENTS
SEAOC
R & M
D & L
SWEC
Criteria
4002R/0168R/CM
1980 Recommended Lateral
Commentary; Structural
California, 1980 Edition.
Force Requirements
Engineers Association
and
of
Civil & Facilities Design Criteria, Bradley Lake
Criteria Project, R & M Consultants, Inc., Anchorage,
Alaska.
Transmission Facilities Design Crit a, Bradley
Criteria Lake Project, Dryden and LaRue, Inc.
Bradley Lake Hydroelectric Project:
General Project Information and Civil Design Criteria
Geotechnical Design Criteria
Hydraulic Design Criteria
GENERAL STRUCTURAL DESIGN CRITERIA
A-7
3.0 MATERIALS
Materials 1 is ted below and conforming to the referenced ASTM designation
will be specified on the project. For specific design requirements see
Section S.O, Structural Design, and Part B of this criteria.
A. STEEL
Structural Steel
High-strength steels where
specified
Stainless Steel Plate
Stainless Steel Sheet
B. Bolts, Nuts, and Washers
ASTM A36
ASTM AS72, Grade SO
or ASTM AS88, Grade SO
ASTM Al67, Type 304 or
Type 316
ASTM Al67, Type 304 or
Type 316
High-strength Bolts for Joints ASTM A32S, Type 1
High-strength Alloy Bolts for
Joints
Unfinished Bolts for Anchor
Bolts and Miscellaneous
Connections
High-strength Anchor Bolts
4002R/0168R/CM
ASTM A490, with yield
strength between 130 ksi
min and 14S ksi max
ASTM A307, Grade B
ASTM Al93, Grade B7
GENERAL STRUCTURAL DESIGN CRITERIA
c.
D.
E.
F.
G.
H.
I.
J.
Corrosion-resistant Bolts, Nuts
and Washers for Removable
Structural Members
Crane Rail and Standard
Accessories
Steel Floor Grating and
Stair Treads
Roof and Floor Decking
Weld Filler Metal
Checkered Floor Plate
Pipe Handrail
Ladders
Safety Chain
ASTM Al93, Grade B8 Bolts
ASTM Al94, Grade 8 Nuts
ASTM A304 Washers
A-8
ASTM A759, attached with
pressed clips and reversible
fillers for a tight fit.
Joint Bars ASTM A3
ASTM A569, Welded Bar
Grating
ASTM A446 and coated with
zinc coating conforming to
ASTM A525
AWS Dl.l and Table 4.1.1
therein
ASTM A36 with a symmetrical
raised diamond pattern
Sch. 40, ASTM A53 Grade B, or
ASTM ASOO Grade B, of
comparable section and
strength
ASTM A36
ASTM A413, Proof Coil Class
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
K.
L.
M.
N.
0.
P.
Q.
Cement
Aggregates
Reinforcing Steel
Welded Wire Fabric
Pipe and Floor Sleeves
for Penetrations
Steel Studs
Rock Anchors
4002R/0168R/CM
A-9
Type II, low alkali Portland
Cement conforming to ASTH ClSO
ASTM C33
ASTM A615, Grade 60,
including Supplement Sl
ASTM Al85
ASTM A53, Grade B,
Schedule 40 or ASTM A36
plate material
By Nelson Stud Welding Co.,
or equal
See Geotechnic~l Design
Criteria
GENERAL STRUCTURAL DESIGN CRITERIA
4.0
4.1
4.2
4.3
A-10
DESIGN LOADS
DEAD LOADS (D)
Dead loads consist of the weight of all permanent construction.
Refer to Table 1 Selected Material Weights.
LIVE LOADS ( L)
Live loads wi 11 consist of uniform surface loads or equivalent
point loads developed to represent loading effects due to the
movement of materials, equipment or personnel applied on a
temporary basis. Loads will be identified as live loads when
the i tern imposing the load is not rigidly or permanently fixed
to a structure. Live loads are assumed to include adequate
allowance for ordinary impact conditions.
Table 2 in Section 6.0 lists uniform floor live loads to be used
unless otherwise specified .. Uniform floor live loads may be
omitted in regions where actual equipment loads are provided and
exceed the specified floor loading. Where equivalent uniform
live, floor or point loads are used to represent equipment
weights, actual loads shall be checked against assumed loads
when information is available.
Live loads for floors and roofs shall be designated on the
drawings under the applicable floor or roof plan.
SNOW AND ICE LOADS (S,I)
For purposes of design, snow and ice loading wi 11 be consid-
ered to occur for a minimum of 6 months out of the year.
4002R/0168R/CM GENERAL STRUCTIJRAL DESIGN CRITERIA
4.4
4.5
4.6
A-ll
Snow loads as listed in Table 5 are developed for the project
based on the Department of the Army's technical document ETL
1110-3-317 and shall be used for buildings and structures.
Effects of removing half the snow from any portion of the loaded
area shall be investigated for all roofs. This condition
simulates loss of snow from a portion of roof due to natural or
man made causes.
The effects of ice loads on hydraulic structures as specified in
Part B of this Design Criteria shall be considered.
EQUIPMENT LOADS (M)
Selected equipment weights and estimated loads are listed in
Tables 3 and 4. Evaluate known equipment loads for empty weight
(dead weight of equipment), operating weight (full contents),
and operational loadings (torques, etc.). Use Table 2 load
information when equipment information is not available.
Lifting hooks for equipment shall consider a 33 percent increase
in lifting load for impact.
HYDRAULIC LOADS (H)
Hydrostatic and hydrodynamic loads are those imposed on
structures by water due to pressure, flow or earthquake. Refer
to the Hydraulic Design Criteria, the Geotechnical Design
Criteria, and Part B of this Design Criteria for specific loads.
SOIL AND ROCK LOADS
Refer to the Geotechnical Design Criteria for specific loads.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
4.7
A-12
WIND LOADS (W)
Wind loads developed for the Bradley Lake Project are based on
the 1985 UBC formula for wind pressure:
p = C C q I e q s (UBC Chap. 23, Eq. 11-1)
Where:
p =
c = e
c = q
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 standard height of
30 ft as set forth in UBC Table No. 23-F
I = Importance factor as set forth in UBC Section
2311(h).
For applicable design factors refer to Tables 6 through 9.
1. Wind Load Application:
Wind loads shall be applied orthogonally to bui !dings and
structures in only one direction at a time. For tanks or
structures supported on four legs in an elevated posit ion
wind load shall be applied diagonally. Wind loads shall not
be combined with earthquake loadings; however, they shall be
applied in combination with snow loads.
2. Exposure Category and Importance Classification:
Wind pressures for the identified exposure condition of
Tables 6 through 9 shall be multiplied by the appropriate
importance factor developed for the project and listed in
Table 10.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
4.8
4.8.1
A-13
SEISMIC LOADS (E)
General Seismic Conditions
Structures shall be subjected to seismic event loads in
accordance with the following basis of criticality:
Description
Non-Critical
Those structures which house
or support equipment or sys-
tems which, if damaged during
a major seismic event, could
be replaced or repaired within
six months or are not critical
to the continued operation of
the hydroelectric facility.
Critical
Those structures which house
or support equipment or systems
considered critical to the
continued operation of the
hydroelectric facility, and
which would take more than six
months to repair or replace or
would be prohibitive in cost to
repair or replace, if damaged
during a major seismic event.
Structure
All structures not listed
in critical or hazardous
categories.
Main Dam Diversion Tunnel
and Gatehouse
Power Tunnel including
Intake and Gate Shaft
Powerhouse Structures
Penstock
Spherical Valves
Main Dam
Spillway
Substation
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
4.8.2
Hazardous
Those structures which house
or support equipment or systems
containing materials such as
acids, caustics, chemicals or
flammables which, if damaged,
could be hazardous to personnel,
the environment, or to the
continued operation of the hydro-
electric facility.
General Seismic Forces
A. Non-Critical Structures
1. Force Computation
Chemical Tanks,
Fuel Tanks, Pumps,
Caustic and Acid Tanks,
Chlorine Systems,
Transformers
A-14
Non-critical structures shall be designed for effects of
a static horizontal seismic acceleration of 0.35g
represented by:
v = 0.35 w
Where:
V = Total lateral force or shear at base
W =Total dead load, including partition loads and
equipment weight or 25 percent of live load
Unless otherwise stated, allowable stresses may be
increased by 33 percent for this seismic condition.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
4002R/0168R/CM
A-15
2. Force Distribution
Distribution of forces shall follow UBC formula:
(UBC Chap. 23, Eq. 12-5)
Where:
Ft = 0.07TV (Ft need not exceed 0.25 V and may be
considered as zero where T = 0.7 sec, or less);
T = 0.05 hn
---~ (UBC Chap. 23, Eq. 12-3A)
D
F. = Remaining portion of total base shear distributed
l
over the height of the structure including level n
according to UBC formula 12-7;
F = X
Where:
w.w
l X
h.h h
1 n x
(V-Ft)
t
~-::::.I
Level n
D
w h
X X (UBC Chap. 23, Eq. 12-7)
w. h.
l l
= That portion of W which is located at or
is assigned to level i or x, respectively;
=Height in feet above base to level i, n,
or x, respectively;
= That level which is upper most in the
main portion of the structure;
= The dimension of the structure, in feet
in a direction parallel to applied force
(not to be confused with "D" used for
dead load of Section 4.1, herein).
GENERAL STRUCI'URAL DESIGN CRITERIA
A-16
3. Force Applications
Horizontal seismic forces shall be applied orthogonally
to rectangular structures. Application of force shall be
made in each direction separately. Where tanks or towers
are elevated, application of seismic forces shall be made
diagonally and shall consider affects of liquid
movement. Seismic forces shall not be applied
concurrently with wind forces. Under certain
circumstances seismic forces shall consider live load and
effects of snow.
4. Vertical Forces
In addition to seismic effects due to horizontal ground
motion, structures shall be designed for the effects of
vertical seismic acceleration equal to 2/3 the horizontal
acceleration. Except as otherwise stated, horizontal and
vertical accelerations may be considered to act
independently.
B. Critical Structures
4002R/0168R/CM
Development of seismic forces for critical structures shall
follow the recommendations set forth under Part B of this
Criteria. Unless otherwise stated, critical structures
shall be designed for all of the conditions under Section
4.8.2(A) without any increase in allowable stresses, and
additionally for a static horizontal force of:
v = 0.75 w
GENERAL STRUCTURAL DESIGN CRITERIA
4.8.3
A-17
applied in a manner similar to Section 4.8.2 (A.), except
that allowable stresses may be increased by 50 percent for
this seismic condition. Vertical forces shall be applied in
accordance with Section 4.8.2 (A.4).
Where specified, critical structures shall consider
amplification of acceleration in accordance with the Project
Response Spectra (Attachment A).
C. Hazardous Structures
Structures for hazardous material shall be designed in a
manner similar to Section 4.8.2 (B), except that:
a. Spill containment barriers may be designed for a static
force of V = 0.35W with no increase in allowable stresses.
b. Tanks or towers on elevated support legs shall consider
the seismic effects of motion of the mass of liquid con-
tained within the vessel. Calculation and application of
seismic induced forces shall follow Chapter 11 of Navy
document NAVFAC P-355, or Chapter 6 of TID 7024 Nuclear
Reactors and Earthquakes.
Seismic Forces on Elements
Unless otherwise specified in Part B of this Design Criteria,
parts or portions of structures and anchorage of nonstructural
components, such as equipment or architectural items, to the
main structural system shall be designed for lateral forces in
accordance with the following formula:
F = ZIC W p p p
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-18
Where: F = Lateral forces on a part of the structures and in p
the direction under consideration;
I = 1.0 Importance Factor, except for hazardous
materials where I = 2.0;
c = Numerical Coefficient as specified in UBC Table p
No. 23-J;
z = 1.0 (UBC Zone 4);
w = Weight of object under consideration. p
4.9 TSUNAMI AND SEICHE INDUCED FORCES
Refer to Part B for specific applications.
4.10 THERMAL LOADS (T)
Structures exposed to large temperature changes shall be designed to
consider the affect of induced stresses. Design shall consider the
following extreme exposure conditions:
Minimum Temperature
Maximum Temperature
Modified temperature conditions may apply to enclosed structures,
and will be identified in Part B for specific situations.
Change in length (see p. 6-7, AISC Manual) will be based on a
coefficient of expansion of 0.00065/100°F,
0.00055/100°F, for concrete.
for steel, and
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-19
4.11 PIPE AND CABLE TRAY LOAD ALLOWANCES
Areas of heavily concentrated piping or cable tray runs shall be
designed for that increased loading.
A general load allowance shall be applied to the midspan of all
steel framing members to account for miscellaneous pipe and cable
tray loads, as follows:
Member
Girder
Stringer
12 in. depth or less
2 kips
2 kips
The following shall apply:
Over 12 in. depth
6 kips
3 kips
1. Design for the actual loads where information is available.
2. Platform bracing angles, main bracing, beams less than W8, and
channels shall not receive any load allowances and shall not be
hung with pipes or cable trays.
3. Load allowances shall not be added to the reactions at girders
or columns for the purposes of designing connecting members,
however added load shall be used for design of connections.
4. On vertical pipe runs where two hangers are used to carry the
load at a single clamp, the steel support shall be designed to
carry the full pipe load from either hanger.
5. Where heavy pipe loads are hung from steel beams or girders, the
hanger prying action on the beam flange shall be checked.
6. Applicable hydrostatic test loads shall be considered for pipe
supports or supporting structure.
4.12 ROOF GIRDER LOAD ALLOWANCE
Main roof girders spanning over the powerhouse generator floor shall
be designed for a 12 kip contingency load applied uniformly over the
length of the girder.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-20
4.13 COLUMN LOAD ALLOWANCE
A. Vertical Allowance
For preliminary column sizing, a 15 kip load allowance shall be
applied to the tops of columns to take care of hung pipe, ducts,
miscellaneous equipment, and loads not yet defined.
Column loads shall be checked against actual loads. Calculated
reactions shall include thermal, pipe restraint, wind, and
earthquake forces as applicable. If the actual loads exceed the
known loads plus load allowance, the columns shall be reanalyzed
and, if necessary increased in size. The column sizing need not be
adjusted down in size unless loads have been grossly overestimated.
B. Horizontal Support Allowance
Horizontal beams or trusses shall be used to prevent columns from
buckling. Horizontal struts shall be designed for an axial load of
not less than 10 kips or a percentage of the actual column load,
whichever is greater:
Support Column
r
140 max
141 to 200
Column Load Percentage
2
3
Where horizontal support trusses are used, the truss depth should
equal about one-tenth the span and the web system members should be
a minimum 3 1/2 in. by 3 in. by 5/16 in. double angles, or a
T-section of similar properties.
Where wind loads are carried by the same horizontal support system,
the framing shall be designed for either wind or stability loading,
whichever is largest, but the loads shall not be additive.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-21
4.14 BRACING LOAD
Bracing shall be designed for no less than a 10 kip axial load.
4.15 TEMPORARY ROOF LOADS
Roof member sizes may be increased to suit temporary use in lifting
heavy equipment. Such members would become part of the permanent
roof framing. For temporary conditions, a one-third increase 1n
working stresses will be allowed.
4.16 CRANE IMPACT ALLOWANCE
Powerhouse cranes have relatively low hoisting speeds and DC
controls, which provide for more precise handling. Values to be
used for impact and horizontal forces for the powerhouse crane shall
be as follows:
Rated Load, ~cimpact
Tons %
160 10
~n'<Lateral
Force, %
10
~r-:n'<Longi tudinal
Force, %
10
~c Based on maximum wheel loads (Refer to Table 4)
~.Jc Based on rated loads plus trolley weight applied at top of crane
rail, half on each side.
~.:c-:c Based on maximum wheel loads applied at top of rail.
Impact and horizontal forces shall be included in the design of
columns but not the foundation. Side thrust and impact shall not be
considered simultaneously.
Neither earthquake nor wind loads shall be considered acting
simultaneously with crane live loads in designing columns and
foundations. Full wind or seismic shall be considered acting with
crane dead load.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-22
4.17 HOIST TROLLEY LOADS
Supports for hoist monorails shall be designed to include the
trolley, hoist, and monorail loads. Impact for motor-operated
hoists shall be 25 percent of the lifting capacity added to the
hoist and trolley load.
4.18 TRUCK LOADS
Floor areas and bridges subject to truck loads shall be designed, as
a minimum, for 300 psf or an HS25 truck loading plus 10 percent
impact, whichever governs. Wheel loadings for stator or transformer
transport shall consider axle loadings of 32,000 lb per axle with a
minimum 4 ft axle spacing, or an 800 psf uniform live load,
whichever governs.
4.19 VIBRATIONAL LOADS
It is assumed that most equipment will be properly bedded and
anchored or isolated so as to preclude significant vibration induced
loads being imposed on structures, however, specific conditions may
require the application of dynamic loads due to vibrating equipment.
4.20 CONSTRUCTION LOADS
A 25 psf live load shall be added to all floor construction loads to
account for men and equipment during construction. Where
construction conditions are to be evaluated, a O.lOg horizontal
ground accelarat ion shall be applied pseudostat ically for seismic
conditions during construe t ion. Additional construct ion loads may
be applicable for special applications.
A one-third increase 1n working stresses will be allowed for
temporary construction loads.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-23
5.0 STRUCTURAL DESIGN
5.1 LOAD COMBINATIONS
Load combinations for specific structures will be identified in Part
B of this document. Should an area not be identified, and in the
absence of other instructions, the following loading combinations
will be observed:
A. For Dead Load, Live Load, Wind, Seismic and Snow
B.
D + L
D + L + w
D + L + E
D + L + s
D + L + w + 0.50S
D + L + 0.50W + s
D + L + E + 0.50S
A 1/3 iP-crease in allowable stresses may be used for
combinations including wind per the applicable codes; allowable
stresses for seismic conditions shall be as defined herein.
For Equipment Supports
M (empty) + w or E
M (operating) + L
M (operating) + L + (W or E)
M (flooded or testing load)
Critical load combinations may vary for specific pieces of
equipment.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-24
5.2 STABILITY REQUIREMENTS
Specific conditions for individual structures are elaborated in Part
B of the criteria. Where criteria are not given, the following
stability criteria shall apply:
A. Overturning
The factor of safety against overturning shall be at least 1.5,
except that for the extreme seismic event the factor of safety
may be reduced to 1.05.
B. Sliding
The factor of safety against sliding shall be at least 1. 5,
except that for the extreme seismic event the factor of safety
may be reduced to 1.05. The coefficient of friction on rock
shall be in accordance with the Geotechnical Design Criteria.
Passive pressure shall not be used to resist horizontal forces
unless specifically allowed for in the geotechnical design.
C. Flotation
The factor of safety against flotation shall be at least 1.1
under the "construction" condition and 1.5 under "completed"
condition. The stabilizing force shall be the dead weight of
the structure alone. Live load shall not be considered as
assisting resistance.
D. Anchoring Structure
In lieu of the above given factors of safety, structural
anchorage to rock or foundation may be used to resist forces
tending to upset the stability of a structure. The structure
shall be anchored so as to resist the excess overturning moment,
sliding force, and/or flotation force without exceeding the
allowable stresses for the materials used. Type of anchorage
system shall be determined on a case-by-case basis. Refer to
Part B of this criteria.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-25
5.3 STEEL DESIGN
A. Connections
Field connections with high strength bolts shall be bearing type
connections, except for members having reversible wind or
seismic stresses where friction type joints shall be required.
Connections shall be designed to effectively include the prying
action forces where applicable.
Bolted connections of structural steel members shall be made
with 7/8 in. or 1 in. diameter ASTM A325 Type 1, Class E, high
strength bolts; 1 1/8 in. diameter ASTM A490 high strength bolts
may be considered for special applications.
Bracing connection design loads shall be shown on the drawings.
React ions for design of framed beam connect ions shall be shown
on the drawings if they exceed the shear developed from one half
the total uniform load capacity of the beam in accordance with
AISC. In addition, the following minimum connections are
specified for the fabricator's use:
Beam
Depth
(in.)
36
33
30
27
24
21, 18, 16
14, 12
10, 8
7 and under
Number of Bolts in
Outstanding Legs of
Connection Angles
18
16
14
12
10
8
6
4
2
The minimum connection allowed shall be a 2 bolt connection.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-26
Moment connections shall be designed to develop the full plastic
capacity of the beam, unless otherwise specified.
Stairways and girts shall use 3/4 1n. diameter ASTM A307 bolts.
B. Floor Grating and Checkered Plate
Grating for floor areas, walkways and hatches shall be
galvanized and shall have as a minimum 1-1/4 in. deep x 3/16
inch thick bearing bars spaced at 1-3/16 in. Actual depth shall
be controlled by design load and span.
Checkered floor plate shall be a minimum 5/16 in. thick, except
that 1/8 in. thick checkered plate may be used when welded to
the top of grating.
C. Handrail, Guardrail, and Kickplates
Handrail shall be nominal 1-1/2 in. diameter, Schedule 40 pipe.
Post spacing shall not be greater than 8 ft. A top, bottom and
center rail shall be provided at the powerhouse. Guardrail
shall be nominal 2 in. diameter, Schedule 40 pipe and will
otherwise meet the handrail requirements. Pipe handrail and
guardrail connections will be of welded construction.
Four-inch high kick plates shall be provided around all clear
openings greater than 1 in. and along standard handrails.
D. Steel Floor Forms and Roof Deck
Steel floor forms shall be a minimum 1-1/2 in. deep, 20 gauge
roll formed corrugated metal deck. Steel roof deck shall be a
minimum 3 in. deep, 20 gauge roll formed metal deck. Should
slope of roof be adjusted to reduce load, gauge may be reduced
to 22 gauge, if warranted.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-27
Steel floor forms and roof decks shall be attached to supporting
framing by welding with minimum 3/4 in. diameter fusion welds
(puddle), or by use of approved power actuated fasteners.
E. Crane Rails and Stops
Size, weight and shape of crane rails and accessories shall be
per the AISC Manual, based on the rail size specified by the
crane manufacturer. Type of crane stops shall meet the crane
manufacturer's recommendations.
F. Welding Materials
In general, E70XX welding electrodes shall be used.
welding electrodes may be specified where required.
G. Deflections
Special
Deflections shall not exceed the following deflection limitation
ratios multiplied by the span length:
Member Type or Item
1. Primary Structural
Framing member
2. Secondary Structural
Framing member (Purlins,
girts, etc.)
3. Exterior Wall and Roof
panels
4. Metal floor form with
concrete slab
5. Grating
4002R/0168R/CM
Deflection
Limitation
1/240 (maximum)
1/180 (maximum)
1/180 (maximum)
1/360 (maximum)
1/4 in. for 100
psf live load
GENERAL STRUCTURAL DESIGN CRITERIA
Member Type or Item
6. Checkered floorplate
7. Steel Decking
8. Roof Joist (per SJI)
9. Floor Joists (per SJI)
10. Monorails
11. Crane Girders:
Vertical Deflection
Lateral Deflection
H. Minimum Member Sizes
Deflection
Limitation
1/100 (live load)
1/240 (total load)
1/360 (maximum)
1/360 (maximum)
1/500 (maximum)
1/1200 (maximum)
1/400 (maximum)
A-28
Minimum member sizes allowed shall be based on the following:
Minimum Dimensions (in.)
Flange Flange Member or Web
Member Type Width Thickness Leg Depth Thickness
Wide Flange, 4 1/4 6 1/4
S and M Shapes
Channels 2 1/4 6 3/16
Angles 2 1/4 2 1/4
"S" shapes shall be used for monorails.
Minimum size stringer for stairs shall be C9x13.4.
I. Special Material Considerations
Design of structural steel members subjected to fatigue induced
by vibration or repetitive loading shall follow the
recommendations of the AISC Specification S326.
Where cold temperature conditions must be considered, the
metallurgy of the material must be examined and specified for
toughness.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-29
5.4 CONCRETE DESIGN
A. General
Concrete structures shall be designed in accordance with ACI
318-83. Ultimate Strength Design procedures should be used,
unless directed otherwise.
Generally, load combinations follow the reconunendat ions of ACI
318-83, Chapter 9. Special load combinations identified in Part
B shall be used where applicable.
The seismic detailing provisions of ACI 318, Appendix A shall be
considered in the design, for concrete buildings and frame
structures.
B. Concrete
The minimum specified compressive strength to be used for design
shall be as identified in Part B for specific structures. Where
Part B does not apply, a minimum specified 28 day compressive
strength of 4,000 psi shall be used for purposes of design.
Unless otherwise specified, nominal maximum
shall be 1-1/2 inches. Where required
reinforcing steel or placing requirements,
maximum aggregate size may be specified.
size of aggregate
due to conjested
3/4 inch nominal
The minimum
identified
specified concrete
on the drawings
compressive strength
for each structure
shall be
and areas
requiring special concrete mixes shall be clearly shown.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-30
C. Reinforcement
Deformed reinforcing bars having a yield strength (f ) of 60 y
ksi shall be used. In addition, the following shall be observed:
1. Minimum ties shall be No. 4 rebar.
2. All isolated circular columns shall be spirally reinforced.
3. Minimum reinforcing allowed shall be No. 4. Try to keep
rebar sizes below No. ll's.
4. Lengths should be kept to 40 feet maximum.
5. In order to keep the number of different sizes of
reinforcing bars used to a minimum, the following rebar
sizes should be used in design:
main steel: #4, #6, #8, #9, #11
ties: #4, #s
6. Uncoated rebar shall be used except where specifically noted
otherwise. Epoxy coated rebar shall be used only 1n
specified locations.
D. Concrete Cover for Reinforcement
The minimum clear concrete cover for reinforcement shall be as
follows:
Concrete exposed to fresh or salt water 3"
Concrete cast against rock or earth 3"
Exterior walls:
Outside face 3"
Inside face 211
Floor slabs and interior walls 2"
Beams and columns 1-1/2"
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-31
E. Construction Joints
Where possible, roughened construction joints should be used in
lieu of keyed joints. Load transfer thru joints should be
checked in accordance with ACI 318, Section 11.7,
Shear-friction. Keyed joints may be used
warrant.
where shear forces
Construction joints and control joints should be clearly shown
on the drawings.
F. Drilled Concrete Anchor Bolts
Drilled concrete anchor bolts shall be friction type anchors
designed in accordance with Stone & Webster Structural Technical
Standard STS-ACll-2-1.
G. Floor Forms
Metal floor deck used as floor forms must be checked for load
and span limitations. Keep span within deck manufacturer's
recommended limitations wherever possible.
H. Foundations
Foundation depths may be effected due to frost. Depths of
foundations shall be in accordance with the Geotechnical Design
Criteria and calculations. Siting conditions may dictate the
requirements for special insulation procedures.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
5.5
A-32
I. Waterstops
In general, waterstops shall be natural rubber, synthetic
rubber, or polyvinyl chloride, as manufactured by W.R. Meadows,
Inc., W.R. Grace & Co., or equal, or shall be metal waterstops.
Vertical waterstops at contraction joints shall be dumbbell
types, 6 in. or 9 in. as design dictates. Waterstops shall be
capable of resisting the maximum pressures and movements
anticipated. Cellular-type or baffle type waterstops shall not
be used. Flat metal waterstops, 1/ 8" x 8", shall be used in
vertical and horizontal construction joints. Waterstop,
reinforcing steel, and construction joint placement shall be
arranged to avoid interferences.
J. Conduit
No aluminum or aluminized conduit or fittings shall be allowed
for embedment in concrete.
K. Sleeves
Anchor bolt sleeves may be used for equipment anchor bolts.
Unless proximity to edge of concrete dictates use of steel pipe
sleeves, plastic sleeves are preferred and may be Wilson Anchor
Bolt Sleeves, or equal. Anchor bolt sleeves are not required
for column base plates. All anchor bolts shall be accurately
placed with a template prior to placement of concrete.
MASONRY DESIGN
Masonry construction shall not be used unless specifically
approved by the client.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-33
-6.0 TABLES
TABLE 1
SELECTED MATERIAL WEIGHTS
Mass Concrete (For stability) 145
Reinforced Concrete 150
Steel 490
Water 62.4
Ice 56
Sea Water 64
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
A-34
TABLE 2•'r
MINIMUM LIVE LOADS FOR FLOORS AND DECKS
Area DescriQtion AQQrox. Floor El. Live Load Remarks
(ft) (psf)
Powerhouse:
Generator Floor 42 300 Check maximum
equipment loads.
Service Bay Floor 42 800 Check vehicle
wheel loads.
Shipping loads
are 1/2 stator
ring or full
generator rotor
assembly without
coupling shaft.
Minimum HS25
wheel load.
Turbine Floor 21 300
Tailrace Deck 21 150 Check maximum gate
laydown load.
Spherical Valve & 5 300 On rock.
Runner Gallery
Control Room 42 250 Check maximum
equipment load.
Machine Shop 42 250 I'
HVAC Room 60 250
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
TABLE 2 (Continued)-:<
MINIMUM LIVE LOADS FOR FLOORS AND DECKS
Area Description Approx. Floor El.
(ft)
General-Buildings:
Meeting areas, lunch rooms,
locker facilities, office
areas
Stairs and corridors
Miscellaneous walkways
and platforms
Storage Areas, Heavy
Storage Areas, Light
Hatch Covers and Grating:
Generator Floor
Turbine Floor
Others
42
60
42
21
Live Load
(psf)
100
100
50
250
125
300
300
A-35
Remarks
Use for gate
shaft platforms.
Same as adjacent
floor load.
*Live loads shall not tie reduced 1n accordance with UBC procedures.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
TABLE 3
ESTIMATED EQUIPMENT WEIGHTS
(Subject to verification)
Equipment Type
Turbine
Total Weight
Scroll Case Manifold
Rotating Parts
Runner
Shaft
Generator
Total Weight
Heaviest Lift (rotor and shaft with poles)
Stator, one half
Lower Bearing & Bracket
Upper Bearing Bracket
Transformer 115 kV
Transformer with oil
Shipping weight
Spherical Valve
Total weight
Valve rotor and Trunnion
(heaviest part to be handled)
A-36
Estimated Weight
373,000 lbs.
145,000 lbs.
23,100 lbs.
25,100 lbs.
450,000 lbs.
310,400 lbs.
80,000 lbs.
75,000 lbs.
35,000 lbs.
200,000 lbs.
150,000 lbs.
134,000 lbs.
74,700 lbs.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
Equipment Type
Bridge Crane
Total crane weight
Bridge weight
Trolley weight
Tailrace Gate
Control Board
4002R/0168R/CM
TABLE 3 (Continued)
ESTIMATED EQUIPMENT WEIGHTS
(Subject to verification)
A-37
Estimated Weight
165,000 1bs.
90,000 lbs.
75,000 lbs.
12,000 lbs.
23,100 1bs.
GENERAL STRUCTURAL DESIGN CRITERIA
Equipment Type
TABLE 4
MISCELLANEOUS EQUIPMENT LOADS
(Subject to verification)
Powerhouse Bridge Crane
Maximum wheel load (per wheel)
Main hook capacity
Auxiliary hook capacity
Substation Bridge Crane Capacity
Tailrace Gate Hoists Capacity
Machine Shop Hoist Capacity
TABLE 5
SNOW LOADS
Ground Snow Load
Powerhouse Roof
Powerhouse Tailrace Deck
Gatehouse Roofs
Other Building Roofs
and Covered Structures
Other Building Lower Roofs
(potential drifting)
Tailrace Canopy
Local roofing support
Overall structural support
Estimated Load
103,000 lbs.
160 ton
25 ton
3 ton
2 @ 7-1/2 ton
65 psf
85 psf
110 psf
100 psf
85 psf
110 psf
100 psf
50 psf
2 ton
A-38
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
El. Above
Grade (ft)
0-20
20-40
40-60
60-100
100-150
El. Above
Grade (ft)
0-20
20-40
40-60
60-100
100-150
El. Above
Grade ( ft)
0-20
20-40
40-60
60-100
100-150
'l'cSee Notes
4005R/0168R
for
TABLE 6
WIND PRESSURES* (SPEED V = 100 MPH)
I = 1.0, EXPOSURE B, PRESSURE (psf)
CONDITION 1 -PRIMARY STRUCTURAL FRAMING
Walls Roof
Windward Leeward Leeward Windward
or Flat Slope <9:12
+15 -09 -13 -13
+17 -10 -15 -15
+21 -13 -18 -18
+23 -14 -20 -20
+27 -17 -24 -24
CONDITION 2 -ELEMENTS AND COMPONENTS
(Enclosed Building, Roof Slope <9:12)
Canopy
or
Walls Wall Eave
Pressure Suction Parapets Corners Suction Overhang
+22 -20 24 -36 -20 -51
+25 -23 27 -42 -23 -58
+31 -29 34 -52 -29 -73
+34 -32 37 -57 -32 -80
+41 -37 44 -68 -37 -95
CONDITION 3 -ISOLATED OBJECTS & MISC. STRUCTURES
Tanks and Solid Towers Open Frame
Sq/Rect Hex Oct Round Ell ipt. Towers
26 20 15 36
29 23 17 42
36 29 21 52
40 32 23 57
47 37 27 68
Tables 6 through 9
A-39
Inter
End Ridges/
Ridges/ Eaves
Eave w/o
Corners Overhang
-55 -36
-63 -42
-78 -52
-86 -57
-101 -68
Signs, Pole and
Minor Structures
26
29
36
40
47
GENERAL STRUCTURAL DESIGN CRITERIA
El. Above
Grade ( ft)
0-20
20-40
40-60
60-100
100-150
El. Above
Grade (ft)
0-20
20-40
40-60
60-100
100-150
El. Above
Grade (ft)
0-20
20-40
40-60
60-100
100-150
TABLE 7
WIND PRESSURES* (SPEED V = 100 MPH)
I = 1.0, EXPOSURE C, PRESSURE (psf)
CONDITION 1 -PRIMARY STRUCTURAL FRAMING
Walls Roof
Windward Leeward Leeward Windward
or Flat Slope <9:12
+25 -16 -22 -22
+27 -17 -24 -24
+31 -20 -27 -27
+33 -21 -29 -29
+37 -23 -33 -33
CONDITION 2 -ELEMENTS AND COMPONENTS
(Enclosed Building, Roof Slope <9:12)
Canopy
or
Walls Wall Eave
Pressure Suction Parapets Corners Suction Overhang
+37 -34 41 -62 -34 -87
+41 -37 44 -68 -37 -95
+47 -43 51 -78 -43 -109
+50 -46 54 -83 -46 -117
+56 -52 61 -94 -52 -131
CONDITION 3 -ISOLATED OBJECTS & MISC. STRUCTURES
Tanks and Solid Towers Open Frame
Sq Rect Hex Oct Round Ellipt.
44 34 25 62
47 37 27 68
55 43 31 78
58 46 33 83
66 52 37 94
*See Notes for Tables 6 through 9
A-40
Inter
End Ridges/
Ridges/ Eaves
Eave w/o
Corners Overhang
-94 -62
-101 -68
-117 -78
-125 -83
-140 -94
Signs, Pole and
Minor Structures
44
47
55
58
66
4005R/0168R GENERAL STRUCTURAL DESIGN CRITERIA
El. Above
Grade ( ft)
0-20
20-40
40-60
60-100
100-150
El. Above
Grade (ft)
0-20
20-40
40-60
60-100
100-150
TABLE 8
WIND PRESSURES"' (SPEED V = 120 MPH)
I = 1.0, EXPOSURE B, PRESSURE (psf)
CONDITION 1 -PRIMARY STRUCTURAL FRAMING
Walls Roof
Windward Leeward Leeward Windward
or Flat Slope <9: 12
+21 -13 -18 -18
+24 -15 -21 -21
+30 -18 -26 -26
+33 -20 -29 -29
+39 -24 -34 -34
CONDITION 2 -ELEMENTS AND COMPONENTS
(Enclosed Building, Roof Slope <9:12)
Roof
Canopy End
or Ridges
Walls Wall Eave Eave
Pressure Suction Parapets Corners Suet ion Overhang Corners
+31 -29 34 -52 -29 -73 -78
+36 -33 39 -59 -33 -83 -89
+44 -41 48 -74 -41 -104 -111
+49 -45 53 -82 -45 -114 -122
+58 -53 63 -96 -53 -135 -144
A-41
Interior
Ridges
Eaves
w/o
Overhang
-52
-59
-74
-82
-96
CONDITION 3 -ISOLATED OBJECTS & MISC. STRUCTURES
El. Above Tanks and Solid Towers Open Frame Signs, Pole and
Grade ( ft) Sg/Rect Hex/Oct Round/Ell ipt. Towers Minor Structures
0-20 36 29 21 52 36
20-40 41 33 24 59 41
40-60 52 41 30 74 52
60-100 57 45 33 82 57
100-150 67 53 39 96 67
1cSee Notes for Tables 6 through 9
4005R/0168R GENERAL STRUCTURAL DESIGN CRITERIA
El. Above
Grade (ft)
0-20
20-40
40-60
60-100
100-150
El. Above
Grade ( ft)
0-20
20-40
40-60
60-100
100-150
El. Above
Grade ( ft)
0-20
20-40
40-60
60-100
100-150
TABLE 9
WIND PRESSURESic (SPEED V = 120 MPH)
I = 1.0, EXPOSURE C, PRESSURE (psf)
CONDITION 1 -PRIMARY STRUCTURAL FRAMING
Walls Roof
Windward Leeward Leeward Windward
or Flat Slope <9:12
+36 -22 -31 -31
+39 -24 -34 -34
+44 -28 -39 -39
+47 -30 -41 -41
+53 -33 -47 -47
CONDITION 2 -ELEMENTS AND COMPONENTS
(Enclosed Building, Roof Slope <9:12)
A-42
Roof
Interior
Canopy End Ridges/
or Ridges/ Eaves
Walls Wall Eave Eave w/o
Pressure Suction Parapets Corners Suction Overhang Corners Overhang
+53 -49 58 -89 -49 -124 -133 -89
+58 -53 63 -96 -53 -135 -144 -96
+67 -61 72 -111 -61 -155 -166 -111
+71 -65 77 -118 -65 -166 -178 -118
+80 -73 87 -133 -73 -187 -200 -133
CONDITION 3 -ISOLATED OBJECTS & MISC. STRUCTURES
Tanks and Solid Towers Open Frame Signs, Pole and
Sg/Rect Hex/Oct Round/Ellipt. Towers Minor Structures
62 49 36 89 62
67 53 39 96 67
78 61 44 111 78
83 65 47 118 83
93 73 53 133 93
icSee Notes for Tables 6 through 9
4005R/0168R GENERAL STRUCTURAL DESIGN CRITERIA
A-43
TABLE 10
WIND LOAD IMPORTANCE FACTORS
Design
Importance Wind
Area Exposure Factor Speed (mph)
Main Dam Diversion Outlet B 1.0 120
Structures
Main Dam Diversion Gatehouse c 1.15 120
Main Dam Structures c 1.15 120
Power Tunnel Gatehouse c 1.15 120
Powerhouse and Attached Average 1.15 100
Facilities of B+C
Substation Average 1.15 100
of B+C
Nuka Diversion Structures B 1.0 120
Middle Fork Diversion B 1.0 120
Structures
Exposed Coastal Facilities c 1 • Q;'c 100
Miscellaneous Structures B"#'< 1. Ql'c 100~';
~cConsul t the Project Lead Structural Engineer.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
NOTES FOR TABLES 6 THROUGH 9
1. (+) Indicates a load directed inward.
(-) Indicates a load directed outward.
( ) No sign indicates load may be applied in any direction.
A-44
2. A structure with more than 30 percent of any one side open shall be
considered an open structure. See Uniform Building Code for wind
pressures on open structures.
3. Local pressures shall apply over a distance from the discontinuity of
10 feet or 0.1 times the least width of the structure, whichever is
smaller.
4.
s.
Wind forces on cladding connections shall be calculated
multiplying the tabulated loads by a factor of 1.5.
by
Local pressures on structural
considered simultaneously, but
structure loads.
elements,
not in
walls and
combination
roofs
with
may be
overall
6. Local wall and roof pressures shall not be used when computing entire
bent, structural frame, or moment stability of structure.
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
-:. ;o
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RESPONSE SPECTRUM
FOR MODIFIED ACCELEROGRAM
BRADLEY LAKE HYDROELECTRIC PROJECT
REF: WOODWARD· CLYDE CONSULT
REPORT' "DESIGN EARlliQUAKE ST\JOV'
NOV 10,1981
MEAN RESPONSE SPECTRUM FOR MAXIMUM EARTHQUAKE
(NEARBY SHALLOW CRUSTAL FAULT)
MEAN RESPONSE SPECTRUM
FOR DBE
---------~-~ ·---------o.oo 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 )
MODIFIED ACCfH.,.E:ROGRAM
NORMALIZED TO 0.75g-5°/o DAMPING FOR MCE
MEAN RESPONSE SPECTRA FOR MCE & DBE
(LINEAR SCAl-E PLOT)
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(SEMI-LOG SCALE PLOT)
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STRUCTURAL DESIGN CRITERIA
PART B: SPECIAL REQUIREMENTS AND DESIGN CRITERIA
FOR MAJOR STRUCTURES
1.0 MAIN DAM DIVERSION
2.0 MAIN DAM
3.0 SPILLWAY
4.0 POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
5.0 PENSTOCK
6.0 POWERHOUSE
7.0 TAILRACE
8.0 SUBSTATION
9.0 MIDDLE FORK AND NUKA GLACIER DIVERSIONS
4002R/0168R/CM GENERAL STRUCTURAL DESIGN CRITERIA
3162R/CG
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. No. 15500 & 15800
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
PART B, SECTION 1.0
REVISION: 3
DATE: JANUARY 12, 1988
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE, ALASKA
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
SECTION
1.1
1.2
1. 2.1
1. 2. 2
1. 2. 3
1.2.3.1
1.3
1. 3.1
1.3. 2
1. 3. 3
1.4
ATTACHMENT
Figure 1
3162R/CG
PART B-1
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS
TITLE
FUNCTIONAL DESCRIPTION
SUPPLEMENTAL DESIGN CRITERIA
General
Materials
Design Loads and Load Combinations
Loads
ENGINEERING/DESIGN CONSIDERATIONS
Construction Considerations
Special Design Considerations
Design
DESIGN GUIDELINES AND REFERENCES
Hydrodynamic pressures on sloping face
of dam
PAGE
B-1-1
B-1-3
B-1-3
B-1-3
B-1-5
B-1-5
B-1-14
B-1-14
B-1-16
B-1-16
B-1-18
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
PART B-1
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
B-1-1
1.0 MAIN DAM DIVERSION
1.1 FUNCTIONAL DESCRIPTION
3162R/CG
Bradley Lake flows will be diverted by a diversion tunnel to allow
for construction of the Main Dam and other structures located
within the outlet of the lake. The Main Dam Diversion will lower
the existing Bradley Lake water level by approximately 10 feet
below the existing natural level. The water level of the
completed reservoir may also require lowering for purposes of
safety inspection and possible repair, such as after a significant
seismic event. Consequently the diversion tunnel must remain
operational throughout the project life for lowering of the
reservoir under emergency conditions.
Controlled low flow releases of water for fish needs in the Lower
Bradley River must be made available downstream of the dam during
construction and during regular plant operation. This will be
provided by two fish water by-pass lines, installed on either side
of the diversion tunnel along the tunnel invert.
The Main Dam Diversion will be constructed through the right
abutment of the dam. The diversion will consist of an inlet
works, the diversion tunnel (about 400 feet long), a gateshaft
with high pressure control gates and gatehouse, and the outlet
works.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
B-1-2
The inlet works, located at the upstream end of the diversion
tunnel, will be comprised of a concrete structure to support
bulkhead gate guides and a transition structure designed to
transit ion the intake structure cross sect ion from a rectangular
shape to the circular shape of the tunnel. The section of the
tunnel upstream of the control gates will be concrete lined, while
the section of the tunnel downstream of the control gates will
include a 10'-6" diameter steel penstock. The outlet works will
consist of a concrete outlet portal structure. This structure
will house the fish water by-pass manifold and motor operated
control valves and provide controlled access to the tunnel.
A rock plug will be temporarily left in place upstream of the
intake structure to act as a cofferdam during construction. The
steel bulkhead gates will be provided to be used during
construction of the second phase tunnel works and for future
tunnel inspection and repairs. During the first stages of
.construction temporary timber stop logs will be used at the intake.
The tunnel itself will be a rock cut, of modified horseshoe
shape. The upstream section will be lined with concrete to form a
circular shaped inside surface. A circular gate shaft will be cut
vertically down at tunnel station 1+20. Two high pressure gates,
a control gate and a guard gate, housed in a steel transition
structure will be located at the intersection of the tunnel and
the gate shaft. The tunnel shape will constrict at the location
of the gates. The gate shaft itself will be concrete lined. The
downstream portion of the tunnel will be provided with a steel
penstock inside the horseshoe shaped tunnel. This will terminate
at the outlet portal. The two pipes for the fish water by-pass
conduit will be embedded in the invert of the diversion tunnel.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
1.2
1. 2.1
1. 2. 2
3162R/CG
B-1-3
A reinforced concrete gatehouse will be erected over the gate
shaft. Access stairs and hydraulic lines will be located within
the shaft area. Equipment for control and operation of the high
pressure gates will be housed in the gatehouse.
SUPPLEMENTAL DESIGN CRITERIA
General
General design criteria as established Structural Design
Criteria -Part A will apply except as supplemented herein. For
further supportive information, refer to the Hydraulic and
Geotechnical Design Criteria.
Materials
The following materials will be used:
A. Concrete
Concrete with a minimum specified compressive strength of
4,000 psi at 28 days.
B. Rock Reinforcement
See Geotechnical Design Criteria
C. Reinforcing Steel
ASTM A615, Grade 60
D Structural Steels
a. Bulkhead gate guides -ASTM A36 guide plates and ASTM
Al67 Type 316 stainless steel bearing plates
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
B-1-4
b. Bulkhead Gates-ASTM A537, Class 1
c. High pressure gates and gate chamber transition lining -
By vendor
d. Penstock -ASTM A710, with properties as specified in
Steel Liner and Penstock Structural Design Criteria,
Part B-5
e. Structural steel framing -ASTM A36
E. Temporary Stop Logs
a. Wood-pressure treated Douglas Fir-Larch timbers
b. Steel assembly and lifting outfit -to be designed by
Contractor
F Fish Water Pipe
ASTM Al06 steel pipe with Victaulic and/or Dresser couplings.
G. Rock Bolts and Dowels (Anchors)
See Geotechnical Design Criteria.
H. Grouts
Grouts used for injection grouting of rock formations shall
follow the requirements of the Geotechnical Design Criteria.
Grouts used for bedding of structural elements or
equipment shall have a minimum specified compressive
strength of 5,000 psi at 28 days.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
B-1-5
I. Coating Systems
1. Concrete Lining -unsealed,
2. Inlet/Outlet Portal Concrete Structure -unsealed,
3. Bulkhead Gates -coal tar epoxy painting system,
4. Bulkhead Gate Guides -coal tar epoxy painting system on
non-embedded ASTM A36 material,
5. High Pressure Gates -high build epoxy on exposed steel
surfaces,
6. Steel Transitions and Gate Chamber Liner -coal tar
epoxy painting system,
7. Fish Water By-Pass System -coal tar epoxy painting
system on exposed exterior sections,
8. Penstock and supports -coal tar epoxy painting system
(interior and exterior),
9. Gatehouse and outlet portal structure steel framing -
inorganic zinc primer, high build epoxy top coat,
10. Miscellaneous piping -coal tar epoxy painting system on
non-embedded exterior surfaces.
1.2.3 Design Loads and Load Combinations
1. 2. 3. 1 Loads
3162R/CG
A. General Loads
1. Dead Loads,
2. Rock Loads,
3. Hydrostatic Load -External -Tunnel unwatered with
bulkhead gates in place, PMF condition,
4a. Hydrostatic Load -Internal -Tunnel filled to control
gate, PMF condition
4b. Hydrostatic Load -Internal -Tunnel filled to guard
gate, PMF condition,
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
B-1-6
5. Hydrodynamic Load -Gates open, penstock full,
6. Earthquake Load -Horizontal,
7. Earthquake Load-Vertical,
8. Hydrodynamic Load -Earthquake acceleration with normal
maximum headwater elevation,
9. Hoisting Forces
operating gates,
Loads applied while removing or
10. Construction Loads -Additional loads or construction
conditions, applied or anticipated during construction
efforts or imposed during maintenance operations.
11. Ice Loading,
12. Snow Loading,
13. Wind Loading,
14. Live Loading,
15. Temperature,
16. Hydrostatic Load-Tailwater at El 1077,
17. Penstock-vacuum condition
Hydraulic and rock loads shall be as defined in the Hydraulic and
Geotechnical Design Criteria and calculations.
B Gatehouse Live Load
L = 250 psf floor load
C. Hydrostatic Pressures
Hydrostatic loads shall be based on the high water elevation
at Probable Maximum Flood (PMF), El ll90. 6 ft rounded to El
1191 ft, except under earthquake conditions where hydrostatic
loads shall be based on normal maximum headwater level, El
1180. For the profile of piezometric pressures over length of
diversion structure refer to the Geotechnical Design Criteria
and calculations.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
B-1-7
D. Hydrodynamic Loads
Loads imposed on the diversion structure and its parts due to
flowing water shall be considered in combination with rock and
hydrostatic loads, and shall be based on the following:
1. Flow Velocity or Gate Closure. See the Hydraulic Design
Criteria and calculations.
2. Hydrodynamic loads due to earthquake accelerations will
be based on formulation presented in the Bureau of
Reclamation Publication Design of Gravity Dams, 1976
Edition, Page 70, repeated below:
Where:
_(ow"l
c ~[~(z-~)+0tlz-~)]
Pe = Pressure normal to the face;
c = A dimensionless pressure coefficient;
0( = Horizontal earthguake acceleration;
Acceleration of gravity
w = Unit weight of water;
z = Depth of reservoir at section being studied;
h = Vertical distance from the reservoir surface to the
elevation in question; and
C = The maximum value of C for a given slope, as m
obtained from Figure 4-18 page 71 of the Bureau
Publication and as reproduced as Figure 1.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
B-1-8
1.2.3.2 Load Combinations
3162R/CG
For the various portions of the diversion tunnel identified below
, the following minimum loading combinations shall be examined to
produce optimum, conservative design loads (see 1.2.3.1 for
numbered loads):
1. Inlet Portal Structure (Phase I)
Load Combinations
a. 1+2
b. 1+2+12
c. 1+2+10
d. 1+2+3
e. 1+2+4a
f. 1+2+(3 or 4a)+6
Explanation
Normal rock loads combined w/dead
load.
As 1n "a" with snow load buildup.
As in "a" with construction loads
imposed from above.
As in "a" with external hydrostatic
effects.
As in "a" with internal hydrostatic
effects.
Hydrostatic pressure at normal
maximum water (El 1180 feet) with
horizontal earthquake acceleration of
0.75g, with a SO% increase in
allowable stress for steel but not to
exceed 90% of yield; ultimate design
load not to exceed u 0.67
(1.4D+l.7L+l.87E) for concrete with
no increase in allowable stress.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
g. 1+2+(3 or 4a)+7
B-1-9
Hydrostatic pressure at normal
maximum water (El 1180 feet) with
vertical earthquake acceleration of
0.50 g, allowing same stress increase
conditions as in item "f" above.
Vertical and horizontal accelerations
shall not be combined.
2. Bulkhead Gate Guide Structure (Phase I)
Bearing forces induced by loads on bulkhead gates, as
determined from bulkhead gate loading cases given below.
3. Bulkhead Gates (Phase II)
Bulkhead gates shall be designed for the following conditions:
a. 1+3
b. 1+3+6+8
c. 1+3+7+8
Bulkhead gates in position with PMF
hydrostatic load.
Bulkhead gates 1n position with
normal maximum hydrostatic load and a
0.35g horizontal earthquake condition
causing hydrodynamic load, with a 1/3
increase in allowable stresses.
As in "b" above with 2/3 of
horizontal earthquake applied as a
vertical earthquake loading, same
allowable stress increases.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
d. 1+4a+9
B-1-10
Bulkhead gates lifted from slots with
balanced head on gates, or with 10 ft
head differential imposed on gates
during low flow conditions.
NOTE: One set of bulkhead gates will be fabricated for use at
both the Main Dam Diversion Tunnel Intake and at the
Power Tunnel Intake. Hydrostatic loads shall consider
the intake elevations from both structures.
4. Gate Shaft (Phase II)
Use same load combinations as identified for tunnel lining design
with appropriate adjustments for configuration and orientation, as
defined in the Geotechnical Design Criteria and calculations.
5. High Pressure Gate Concrete Chamber Design (Phase II)
Load Combinations
a. 1+2
b. 1+2+(3 or 4a)
c. 1+2+(4a or 4b)+6+8
Explanation
Dead load with normal rock loads.
As in "a" with hydrostatic pressure.
Normal rock and hydrostatic loads,
combined with horizontal earthquake
acceleration of 0.75g, with a 50%
increase in allowable stress for
steel but not to exceed yield;
ultimate design load not to exceed
U = 0.67 (1.4D+l.7L+ 1.87E) for
concrete with no increase in
allowable stress.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
d. 1+2+(4a or 4b)+7
e. 1+2+3+9
f. 1+2+(4a or 4b)+5+9
B-1-11
As in "c" except with vertical
earthquake accelerationh of O.SOg,
same allowable stress conditions.
Normal dead weight and rock loads,
external hydrostatic pressures,
tunnel drained, gate being raised.
Normal loading with gates being
operated with tunnel full.
6. Tunnel Lining (Phase II)
Load Combinations
a. 1+2+3
b. 1+2+(4a or 4b)
c. 1+2+(4a or 4b)+S
d. 1+2+(3 or 4a)+6
e. 1+2+(3 or 4a)+7
Explanation
Tunnel dewatered with normal rock and
piezometric loads.
Tunnel full.
Normal dead and rock loads with gates
open.
Normal dead and
hydrostatic pressure
maximum water, with
rock loads,
normal at
horizontal
earthquake acceleration of 0.75 g,
with a SO% increase 1n allowable
stress for steel but not to exceed
yield; ultimate design load not to
exceed U ~ 0.67 (1.4D+l.71+1.87E)
for concrete with no 1ncrease in
allowable stress.
As in "d" except with vertical
earthquake acceleration of O.SOg,
same allowable stress conditions.
Vertical and horizontal accelerations
to be applied separately.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
B-1-12
7. Penstock and Penstock Supports (Phase II)
a. 1+5
b. 1+5+15
c. 1+5+17
d. 1.4a+6
e. 1+4a+7
f. 1+5+6
g. 1+5+7
Normal dead load with gates open.
As in "a" except with temperature
stresses.
As in "a" except with a full internal
vacuum.
Normal dead load with penstock empty
combined with horizontal earthquake
acceleration of 0.7Sg,
in
with so
percent increase allowable
stresses for ASTM A36 steel but not
to exceed yield; with allowable
stresses as per "Steel Liner and
Penstock Structural Design Criteria,
Part B-5" for the "Emergency
Condition" for ASTM A710 steel;
ultimate design load not to exceed
U=0.67 (1.4D+l.7L+l.87E) for
concrete with no increase in
allowable stresses.
As in "d" except with vertical
earthquake acceleration of 0.50g,
same allowable stresses. Vertical
and horizontal acceleration not to be
combined.
Normal dead load with penstock full
with horizontal earthquake
acceleration of 0.3Sg, same allowable
stresses as in "d".
As in "f" except with vertical
earthquake acceleration of 0.23g.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
B-1-13
8. Outlet Portal Structure (Phase II)
Load Combinations
a. 1+14+16
b. 1+5+14
c. 1+6+14
d. 1+7+14
e. 1+11+12+14
f. l+ll+(O.SO)xl2+13+14
g. 1+10
9 Gatehouse (Phase II)
Load Combinations
a. 1+12
b. 1+9+14
c. 1+13
d. 1+(0.7S)xl2+13
Explanation
Normal dead load and 1 i ve load with
external hydrostatic effects.
Normal dead load with gates open.
As in "a" with horizontal earthquake
acceleration of 0. 75g, same allowable
stress conditions as item "6.d" above.
As in "c" except with vertical
earthquake acceleration of O.SOg.
Normal dead load and live load with
snow build-up and icing (due to spray
freezeup from fish water by-pass line
flow diffusion).
Normal dead load, with ice, SO% snow,
and live load.
Normal dead load and loads due to
construction conditions.
Explanations
Normal dead loads with snow.
Normal dead loads and live loads,
including equipment operation loads.
Normal dead loads with wind.
Normal dead loads with wind and 75%
snow.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
1.3
1. 3.1
3162R/CG
e. 1+6+(0.75)xl2
f. 1+7+(0. 7S)xl2
B-1 14
Normal dead loads, horizontal
earthquake acceleration of 0. 75g and
75% snow load, same allowable stress
conditions as in item "6.d11 above.
Normal dead loads, vertical
earthquake acceleration of 0. SOg and
75% snow load, same allowable stress
conditions as 11 e" above.
In addition to the above design conditions, the stability of the
concrete gatehouse shall be checked against overturning and
sliding. The factor of safety against sliding or overturning
shall be greater than or equal to 1.0, using a static lateral
force coefficient based on the structure 1 S estimated natural
period and in accordance with the Project Design Response Spectrum
(provided as Attachment A to Part A, General Structural Design
Criteria) for a 0. 75g mean horizontal ground acceleration. The
stabi 1 i ty shall be analyzed for dead weight only, and with 75%
snow load.
ENGINEERING/DESIGN CONSIDERATIONS
Construction Considerations
Due to the remoteness of the site and shipping and transportation
limitations, material quality and weight savings will be a prime
consideration when designing the Main Dam Diversion.
Construction of the Main Dam Diversion tunnel will be accomplished
in two phases. The basic proposed sequence of events for the two
phases of construction is as identified below:
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
B-1-15
Phase I:
a. Excavate upstream and downstream tunnel portals. Leave
temporary rock plug in place approximately 30 feet upstream of
the entry portal. Temporary plug to act as a cofferdam with
top of rock at approximately El 1084;
b. Excavate tunnel (by drill and blast);
c. Construct concrete intake structure including gate guide
embedments and fish water by-pass pipes up to the Phase I
limits;
d. Install temporary wood stop logs in intake bulkhead gate guide
structure;
e. Remove rock plug from in front of intake portal;
f. As required by the Hydraulic Design Criteria, remove stop logs
from slots subsequent to a controlled drawdown of the lake
level.
Phase II:
After Main Dam, Spillway, and Power Tunnel are constructed,
a. Excavate gate shaft and outlet portal area (as construction
schedule dictates);
b. Install bulkhead gates at intake portal of diversion tunnel;
c. Install remaining fish water by-pass 1 ines and valves to end
of tunnel and connect to Phase I lines. Temporary lines will
extend from the outlet portal to the river, until the outlet
works are complete and the manifolds for the fish water
by-pass lines can be installed.
d. Establish controlled flow in fish water by-pass lines;
e. Line upstream section of tunnel and gate shaft with concrete.
Complete rock grouting as required.
tunnel downstream of gates, and
structure;
Install steel penstock in
construct outlet portal
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
1.3.2
1. 3. 3
3162R/CG
B-1-16
f. Install gates and gatehouse structure and test gates;
g. Close control gates, flood tunnel, and remove bulkhead gates.
Special Design Considerations
Design and construction of the diversion tunnel is critical to the
construction of the dam and appropriate support structures. Once
completely installed, it must remain operational throughout the
project life to provide a means of lowering the lake reservoir
rapidly due to emergency conditions.
Equipment associated with the diversion tunnel including the gates
and valves must remain functional over the full range of weather
and loading conditions anticipated, including those of major
seismic events.
Gate shaft will be a "dry" shaft. The gate shaft will be provided
with a steel spiral staircase with 1/4 turn landings at
approximate 20 ft intervals and rest platforms to the side at
approximate 40 ft intervals. The shaft will contain hydraulic
lines, ventilation, penstock vents, and support power.
Design
1. Concrete
Concrete design shall be in accordance with ACI 318-83, unless
otherwise specified. Seismic detailing of the concrete
gatehouse shall be in accordance with ACI 318-83, Appendix A.
2. Structural Steel
Allowable stresses and design shall be in accordance with the
AISC Steel Construction Manual. Stresses shall be kept within
elastic range.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
3162R/CG
B-1-17
3. Factors of Safety
The normal factors of safety developed within Part A or this
design criteria shall apply except as may be otherwise
qualified herein. Factors of safety for structures on, in or
anchored to rock shall be developed in conjunction with the
Geotechnical Design Criteria and calculations.
4. Special Physical Considerations
a. Reinforced Concrete -Rebar Clearances
b.
Concrete cover for reinforcing steel shall be in accordance
with ACI 318-83, except as follows:
(1) Tunnel lining-rock contact = 3 inches
(2) Tunnel lining-inside face = 3 inches
minimum
= 4 inches
where erosion
may occur
(3) Intake Portal structure-
exposed faces = 4 inches
(4) Tolerance of intrusion of rock pro-
jection into neat excavation line
shall be no greater than 2 inches.
Protrusions shall not extend over
an area greater than 10% of neat
excavation line nor over a local
area greater than 5 in. x 5 in.
(5) Gatehouse walls (each face) = 2 inches
Corrosion Allowance
(1) Bulkhead gates, control
allowance
(2) Gate guide -no corrosion
and service gates -no corrosion
allowance
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
B-1-18
c. Gatehouse
(1) Use a 1:12 sloped concrete deck roof.
(2) Minimum concrete wall thickness shall be 1 ft.
(3) A rolling steel door shall be provided for vehicle
access.
(4) Interior concrete walls and/or bullet resistant
doors shall be provided to protect gate operating
equipment.
d. Gate Shaft
(1) Concrete lining will be supported by rock
vertically in bond. The bond shear strength
assumed at the rock-concrete interface is f = v
75 psi, except at bot tom 20 ft of shaft where
f = 0. v
(2) The rock may be assumed to provide continuous
lateral support around the periphery of the lining
to prevent outward deflection.
(3) Minimum concrete lining thickness shall be 1 ft.
1.4 DESIGN GUIDELINES AND REFERENCES
3162R/CG
1. EM 1110-2-2901,
Manual, Engineering
Rock, Sept. 1978.
Army
and
Corps of Engineers,
Design Tunnels and
Engineer
Shafts 1n
2.. Guidelines for Tunnel Lining Design, American Society of
Civil Engineers, T. D. O'Rourke, 1984.
3. ACI 318-83, Building Code Requirements for Reinforced
Concrete, American Concrete Institute.
4. Steel Construction Manual -American Institute of Steel
Construction, 8th Edition.
5. Geotechnical Design Criteria, Bradley Lake Hydroelectric
Project.
6. Hydraulic Design Criteria -Main Dam Diversion, Bradley
Lake Hydroelectric Project.
MAIN DAM DIVERSION
STRUCTURAL DESIGN CRITERIA
'i
'o .
ll
~ eo
~ ..
I ... .. 'o lt ~ • • 't
l . ·~
I
0 • ..
tt 'f :. ..
0
cn:s;
.. ·~
~~ f
!,;OH '
Cz "' 'o
(}
~ ..
~0
..
~~
r ... .
= i
t1o \,
oH ttl<: cntt:l
H::tl
G')(/)
zH 0 nz
!,;0
H
~
ttJ ~
H
):1
I~ ',~ I "'·-..,;~ I
............ ~ ~-·
'1', ~
"'> ., . ...... ..
'• ' .,~, ~... . '•.-.. . , TYriCA~ PRE
-I .... ~ ' ~, 'r-....... ......
--....... ~ ....... ............
' .......
.... , --:' ..........
-' ......
I _j J J J ',, ~~
J J J I J '~! ---1 . ---__j J '~~ -----I 1''-1
0 o.t 0-1 u 0.4 o .• o• 0.1
HUIV~l 'Ot"l'llHT Q ('1\
........ !. ............ 1.-'-'.:.;o.:..:;..o.....l
HURt TYPICA~ !iECTION
NOTES
~ •• ca,.t
Wl'>trt:p 1 t\ tHtUwrt 4vt to 1\0I,UflfOI
tortnq.,oktll~. ~tr \Q,tl)
C 11 • flll"lti'\ltOt'I!Ut prtuwrt
~Tt·;2· -"t~ ~·vv~; :f.~ 1
•1'\ttt Clfl 1\ lhf Utlf•C:•tl\l
oOIOli\U froll'l. tP'It cvr•t.
• 1$ I\OriUt11GI Urthq"'U.
OCUitt•f•OOI' ti'l ~ttUM tf tt011! J
• •t the wn1t ••·~M ot ,..,,,.
1~0 liiH IQ. ffJ
l ll Uf>ll\ of ftU''OI' tft)
tt UC:fiOA ¥fl4tr ll"lf
h it Ofi)IJ\ of I"UthOlr' I•
tiU•otiOfl w~'~cJtr C:OI\t,Citrotion
((t)
Agurt 4·18. Hydrodynllmlc pressures upon the sloping race or I dam due to horizontal c:uthquil.kc e(fcct.-288·D·31SS
Extract p 71 Design of Gravity Dams -U.S. Bureau of Reclamation
Figure 1
3027R/166R/CM
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. No. 15800
MAIN DAM
STRUCTURAL DESIGN CRITERIA
PART B, SECTION 2.0
REVISION: 2
DATE: March 25, 1988
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE, ALASKA
MAIN DAM STRUCTURAL DESIGN CRITERIA
SECTION
2.1
2.2
2.2.1
2.2.2
2.2.2.1
2.2.2.2
2.3
2.3.1
2.3.2
2.4
Attachments:
PART B-2
MAIN DAM
STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS
TITLE
FUNCTIONAL DESCRIPTION
SUPPLEMENTAL DESIGN CRITERIA
Materials
Loads and Load Combinations
Loads
Load Combinations
ENGINEERING/DESIGN CONSIDERATIONS
Geotechnical Design
Structural Design
DESIGN GUIDELINES AND REFERENCES
Attachment A -Dam Plan and Section
PAGE
B-2-1
B-2-1
B-2-1
B-2-2
B-2-2
B-2-3
B-2-4
B-2-4
B-2-4
B-2-6
Attachment B -Hydrodynamic pressures on sloping face of Dam
3027R/166R/CM MAIN DAM STRUCTURAL DESIGN CRITERIA
PART B-2
MAIN DAM
STRUCTURAL DESIGN CRITERIA
B-2-1
2.0 MAIN DAM
2.1 FUNCTIONAL DESCRIPTION
2.2
2.2.1
The Main Dam for the Bradley Lake Hydroelectric Project will be a
compacted rockfill dam founded on competent bedrock. The upstream
face of the dam will be faced with a concrete slab. The
downstream face of the dam will be faced with oversized rocks. A
preliminary plan and sect ion of the proposed dam are shown as
Attachment A and are for information only.
The basic reservoir and tai 1 water elevation criteria are
contained in the General Project Information and Civil Design
Criteria. In addition, the FERC Application for License, VoL 4
provides basic physical and stability criteria.
The darn will be provided with a parapet wall extending
approximately four feet above the dam crest.
SUPPLEMENTAL DESIGN CRITERIA
Materials
1. Reinforcing Steel
ASTM A615, Grade 60
2. Welded Wire Fabric
ASTM Al85
3027R/166R/CM MAIN DAM STRUCTURAL DESIGN CRITERIA
2.2.2
2.2.2.1
B-2-2
3. Concrete
• Dam face -f' = 3,000 psi c
• Toe plinth and abutments -f' = 4,000 psi c
• Parapet wall -f' = 4,000 psi (precast or cast in place). c
• Vaults and manholes f' = 3,000 psi c
Loads and Load Combinations
Loads
The following loading conditions will exist:
1. Uplift and Seepage Forces
• At base -Reservoir pressure at upstream toe plinth
• Internal Reservoir pressure at upstream concrete
membrane and tailwater hydrostatic pressure within
embankment
• Upstream concrete face is imperviou~ compared to
rockfi 11. No excess pore pressures develop for
construction or drawdown loading conditions.
2. Silt
• No silt forces (deemed insignificant)
3. Ice, Wind, Hydrodynamic Loads
• Ice Forces -Refer to the Hydraulic Design Criteria and
calculations
3027R/166R/CM MAIN DAM STRUCTURAL DESIGN CRITERIA
2.2.2.2
B-2-3
• Wind -Wind speed of 120 mph, UBC Class C exposure.
Refer to Structural Design Criteria, Part A, Tables 9
and 10 for wind load information.
• Hydrodynamic Loads -Refer to Attachment B, providing
formulation and design chart for hydrodynamic effects
due to earthquake.
• Wave Induced Forces -Refer to the Hydraulic Design
Criteria and calculations
4. Earthquake Forces
Analysis and design of the overall dam shall be as described
in the Geotechnical Design Criteria. Seismic design of dam
elements shall consider a horizontal acceleration applied
statically as described herein.
Load Combinations
The load combinations below are identified where:
D = Normal dead load
H = Hydraulic or Hydrodynamic loads
E = Earthquake induced forces or acceleration due to
earthquake
w = Wind induced forces
R = Rock or earth pressure
I = Ice induced forces
1. Parapet
Case 1 D+H+E Normal maximum operating conditions with
reservoir at EL 1180 ft, but with
earthquake induced forces.
Case 2 D+W+H Normal case with wind induced wave action.
3027R/166R/CM MAIN DAM STRUCTURAL DESIGN CRITERIA
2.3
2.3.1
2.3.2
Case 3
Case 4
B-2-4
Normal case with ice induced forces.
Probable maximum flood condition with
reservoir at EL 1191 ft.
2. Abutments and Dam Toe Plinth
Refer to Geotechnical Design Criteria and calculations.
3. Vaults and Manholes
D+H+R Normal maximum operating condition with
reservoir at EL 1180 ft, with hydraulic
and earth or rock pressures applied as
appropriate.
ENGINEERING/DESIGN CONSIDERATIONS
Geotechnical Design
The Main Dam, as a total mass structure, and the dam face slab
elements and waterstops will be designed as part of the
Geotechnical engineering effort. As such the dam will be
analyzed both dynamically and statically. Factors of safety will
be provided by the Geotechnical Design Criteria.
Structural Design
Concrete elements, with the exception of the dam face slab, will
be designed as part of the Structural engineering effort. Design
of concrete reinforcing shall be in accordance with ACI 318-83
within the guidelines provided by the Geotechnical Design
Criteria and calculations.
3027R/166R/CM MAIN DAM STRUCTURAL DESIGN CRITERIA
B-2-5
The following conditions should be considered in the Structural
design:
1. Parapet Wall
The parapet wall should be designed to permit it to be cast
in place or set as a precast element. The parapet shall be
reinforced and attached to the dam crest in such a manner as
to resist forces generated by general seismic loading, wind
and wave pressures, and ·ice forces. The parapet wall shall
be designed for a static horizontal seismic acceleration
based on crest accelerations from the dam seismic analysis
and as required by the Geotechnical Design Criteria and
calculations. Ultimate design load factors shall be U =
0.67 (1.4D + 1.71 + 1.87E) for seismic applications.
2. Abutment Blocks
Concrete abutment blocks will be structurally analyzed and
designed in accordance with loads and input as required by
the Geotechnical Design Criteria and calculations. The
blocks shall be reinforced and designed to resist forces
generated by seismic loading and hydrostatic forces, as
appropriate.
3. Vaults and Manholes
3027R/166R/CM
Vaults, manholes and cable areas used for instruments and
power cables, etc., shall generally be designed for static
pressures and forces due to hydrostatic conditions and rock
pressures. Where exposed to truck loads, an HS25 truck
loading shall be considered.
MAIN DAM STRUCTURAL DESIGN CRITERIA
B-2-6
4. Dam Toe Plinth
The base along the dam toe (toe plinth) shall be designed to
accommodate thrust forces from the face slab as well as
normal hydrostatic presures, grouting pressures, and seismic
forces. Grouting pressures shall be in accordance with the
Geotechnical Design Criteria and calculations.
2.4 DESIGN GUIDELINES AND REFERENCES
1. Design of Gravity Dams, U.S. Bureau of Reclamation, 1976.
2. Preliminary Supporting Design Report, Vol. 4, Application
for License for Bradley Lake Hydroelectric Project, for the
Federal Energy Regulatory Commission.
3. Building Code Requirements for Reinforced
(ACI 318-83), American Concrete Institute.
Concrete
4. Uniform Building Code, International Conference of Building
Officials, 1985.
5. Geotechnical Design Criteria, Bradley Lake Hydroelectric
Project.
6. General Project Information and Civil Design Criteria,
Bradley Lake Hydrolectric Project.
7. Concrete Face Rockfill Dams -Design, Construction, and
Performance; Edited by J. Barry Cooke and James L. Sherard,
American Society of Civil Engineers, 1985.
3027R/166R/CM MAIN DAM STRUCTURAL DESIGN CRITERIA
~ ~
~ ' ~
\'J ~
~ ~ \) ~ ' ~ r... '-J ~ ~ ~ ~
' \)
~
l,_ ~ ~ "')
~ ~
~ \1 ~ ~ ~
\.... -..; ~~
E L FEET
:;,,o
I
11FV
1160
, 1 4()
1120
1100
~ 108l'
~ 106('
ll040
~,L. ~~~~ " ~ , ..
~~ .. }_
FUR lUfK SEl ctljW
DWG r·c 1918 / ---
)//
16 _hY/
I YPE [l 1 1--__y'///
-f I\ l ~"'-"'_-/ /' ", /~
/ :>?"/
L
~4/// (:F~/"// T'rPE B
J / -FILL
., --EL 1070 J
-~-j_
----~-
]
_,,. '"' '''"'"
I
I
I
I
I
I
I
I
DEl B
(F 7l
1 - 1
SCALE :A
(C-1)
DE T A
( l -61
' FILL / T YPF B
r DET C
(J-8)
TYPE B_ FILL
(COFFERDAM
\;"' 5 '~' '-'"' ;;,-t, ~=z:-'f ';:!' ],,\ :Jiil .-111 o 1 ·--~~ ~
lrl\;..,q,., ,. ....
-TO EL 10700 OR MIN 50' ~-
BE TWEEN EL 1070 ON RIGHT ABUTMENT
AND El 1160 ON LEIT AFlUTMENT
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Extract p 71 Design of Gravity Dams -u.s. Bureau of Reclamation
Flgure 1
:;J:J
t-3
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to
3045/CG
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. No. 15800
SPILLWAY
STRUCTURAL DESIGN CRITERIA
PART B, SECTION 3.0
REVISION: 2
DATE: October 30, 1987
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE, ALASKA
SPILLWAY STRUCTURAL DESIGN CRITERIA
SECTION
3.1
3.2
3.2.1
3.2.2
3.3
3.3.1
3.3.2
3.3.3
3.4
3.5
3045/CG
PART B-3
SPILLWAY
STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS
TITLE
FUNCTIONAL DESCRIPTION
SUPPLEMENTAL DESIGN CRITERIA
Materials
Loads and Load Combinations
ENGINEERING/DESIGN CONSIDERATIONS
Hydraulic Considerations
Geotechnical Considerations
Structural Considerations
DESIGN
DESIGN GUIDELINES AND REFERENCES
PAGE
B-3-1
B-3-2
B-3-2
B-3-2
B-3-2
B-3-2
B-3-3
B-3-3
B-3-4
B-3-5
SPILLWAY STRUCTURAL DESIGN CRITERIA
PART B-3
SPILLWAY
STRUCTURAL DESIGN CRITERIA
B-3-1
3. 0 SPILLWAY
3.1 FUNCTIONAL DESCRIPTION
3045/CG
The spillway for the Bradley Lake Project will be constructed in a
low saddle area to the right of the right abutment of the main dam
(looking downstream). This saddle is formed by a steep rock face
on the right side of the spillway and a knob of rock that
constitutes the right dam abutment and left spillway abutment. The
knob is high enough not to be overflowed during a flood condition.
The spillway will be in line with the main dam axis.
The spillway will have a uniformly shaped ogee crest which will be
175 ft long. The spillway will consist of two concrete overflow
sections, each designed to discharge to a different elevation. The
west spillway apron will be 70 ft wide and will discharge at El
1165, while the east apron of 105 ft width will discharge at El
1135. This design minimizes rock excavation and concrete
quantities required.
Concrete non-overflow sections shall be provided for transition
from the overflow sections to the adjacent rock. Vertical rock
faces at the sides of the spillway aprons and between the aprons
will be provided with concrete walls to prevent erosion of the rock
face.
SPILLWAY STRUCTURAL DESIGN CRITERIA
3.2
3.2.1
3.2.2
3.3
3.3.1
B-3-2
SUPPLEMENTAL DESIGN CRITERIA
Materials
A. Reinforcing Steel
ASTM A615, Grade 60
B. Rock Bolts
See Geotechnical Design Criteria
c. Grout
See Geotechnical Design Criteria
D. Concrete
Mass concrete sections shall be
compressive strength of 3,000 psi at
designed for a specified
28 days (higher strength of
the shell concrete shall be neglected see Section 3.4).
Concrete training walls shall be designed for a specified
compressive strength of 4,000 psi at 28 days.
Loads and Load Combinations
Loads and load combinations shall be as defined in the Hydraulic
Design Criteria -Spillway.
ENGINEERING/DESIGN CONSIDERATIONS
Hydraulic Considerations
The spillway will operate to discharge excess waters from the
lake. In general, the spillway will be designed to accommodate
flows from normal design water level of El 1180 to Probable
Maximum Flood (PMF) level of El 1190.6 (rounded to 1191 for
design). The water leaving the spillway aprons
3045/CG SPILLWAY STRUCTURAL DESIGN CRITERIA
3.3.2
3.3.3
3045/CG
B-3-3
will travel over the existing rock surfaces, and at tailwater
pool level will be deflected by a rock face towards the west into
the downstream pool area.
Refer to the Hydraulic Design Criteria -Spillway for further
discussion of hydraulic aspects of this structure.
Geotechnical Considerations
The spillway and aprons will be established on sound rock. The
downstream end of the spillway apron will be anchored at least
two feet into sound rock. Excavation limits, areas of sound rock
and weak rock, locations where drain holes and grout holes are to
be placed, special requirements for rock-to-concrete interface,
and any anchorage requirements wi 11 be developed in accordance
with the Geotechnical Design Criteria and calculations.
The dynamic sliding stability will be evaluated using the SARMA
method of analysis. Refer to the Geotechnical Design Criteria
and calculations for further geotechnical design parameters and
criteria.
Structural Considerations
The spillway is primarily a hydraulic structure where much of the
design/analysis centers around stability considerations set by
the Federal Energy Regulatory Commission (FERC), Stone &
Webster's Hydraulic Technical Guidelines, Bureau of Reclamation
design criteria, and Board of Consultants' recommendations. For
this reason, a majority of the criteria for stabi 1 i ty analysis
are defined by the Hydraulic Design Criteria -Spillway.
SPILLWAY STRUCTURAL DESIGN CRITERIA
B-3-4
A two dimensional static stability analysis will be performed for
Usual and Unusual Conditions. Additionally, a computer aided
dynamic analysis for the earthquake conditions will be performed
on the spillway ogee structure by the finite element method. For
the dynamic analysis the results from each applied acceleration
(vertical and horizontal) shall be combined by the square root
sum of the squares (SRSS) method. Rock properties shall be in
accordance with the Geotechnical Design Criteria.
3.4 DESIGN
3045/CG
The spillway is a mass concrete structure. The mass concrete
core shall be constructed with a concrete mix with 3 inch nominal
maximum aggregate size and a specified compressive strength of
3,000 psi at 28 days, in order to minimize heat of hydration.
The outer 3 feet of the mass concrete section shall be
constructed with a concrete mix with 1 1/2 inch nominal maximum
aggregate size and a specified compressive strength of 4,000 psi
at 28 days, in order to provide a· durable outer shell. The two
mixes shall be placed such that monolithic action between the
shell and the core is achieved without the use of construction
joints. Lift heights shall be set at 5 ft intervals, except 2.5
ft lift intervals shall be used for the bottom two lifts.
Allowable stresses and factors of safety shall be in accordance
with the Hydraulic Design Criteria -Spillway.
The concrete training walls shall be designed in accordance with
ACI 318-83. Walls shall be vertical and shall be considered as a
nominal 2 feet 6 inches in thickness. Walls cast against rock
shall be bolted to the rock.
SPILLWAY STRUCTURAL DESIGN CRITERIA
B-3-5
Reinforcing will be used on the upstream face of the spillway for
tension, ice, seismic, and temperature considerations.
Reinforcing may also be used on the downstream face to control
temperature cracking.
Minimum clear concrete cover for reinforcing steel shall be as
follows:
Concrete exposed to flowing water
Concrete cast against rock
Exposed concrete surfaces
4 in.
3 in.
3 in.
Additional concrete cover may be required in mass concrete
sections and where reinforced surfaces of the spillway may be
exposed to high impact of water, to the extent consistent with
temperature crack control.
Joints, keyways, and use of waterstops shall be developed with
consideration given to the recommendations of HTG 109-0.
3.5 DESIGN GUIDELINES AND REFERENCES
3045/CG
1. Design Criteria for Concrete Arch and Gravity Dams, 1977,
U.S. Department of Interior, Bureau of Reclamation.
Engineering Monograph No. 19.
2. Structural Design of Spillways and Outlet Works, 1964, u.s.
Department of the Army, EM 1110-2-2400.
3. Waterstops and Other Joint Materials, 1983, U.S.Department
of the Army, EM 1110-2-2102.
SPILLWAY STRUCTURAL DESIGN CRITERIA
3045/CG
B-3-6
4. Gravity Dam Design, 1958, U.S. Department of the Army, EM
1110-2-2200.
5.
6.
Hydraulic Design Criteria
Hydroelectric Project.
Geotechnical Design Criteria,
electric Project.
Spi 11 way, Bradley Lake
Bradley Lake Hydro-
7. HTG 109-0, Stone & Webster Hydraulic Technical Guideline -
Spillways.
8. ACI 318-83, Building Code Requirmeents for Reinforced
Concrete, American Concrete Institute.
9. Federal Energy Regulatory
Guidelines for the Evaluation
FERC 0119-1, July 1987.
Conuni ss ion, "Engineering
of Hydropower Projects,"
SPILLWAY STRUCTURAL DESIGN CRITERIA
3061R/CM
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. No. 15800
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
PART B, SECTION 4.0
REVISION: 2
DATE: January 29, 1988
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE, ALASKA
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
SECTION
4.1
4.2
4.2.1
4.2.2
4.2.3
4.2.3.1
4.2.3.2
4.3
4.3.1
4.3.2
4.3.3
4.4
ATTACHMENTS
Figure 1
3061R/CM
PART B-4
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS
TITLE
FUNCTIONAL DESCRIPTION
SUPPLEMENTAL DESIGN CRITERIA
General
Materials
Design Loads and Load Combinations
Loads
Load Combinations
ENGINEERING/DESIGN CONSIDERATIONS
Construction Considerations
Special Design Considerations
Design
DESIGN GUIDELINES AND REFERENCES
Hydrodynamic Pressure on sloping face of dam
PAGE
B-4-1
B-4-2
B-4-2
B-4-2
B-4-4
B-4-4
B-4-7
B-4-11
B-4-11
B-4-12
B-4-12
B-4-15
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
PART B-4
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
B-4-1
4.0 POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
4.1 FUNCTIONAL DESCRIPTION
3061R/CM
Water from Bradley Lake will be delivered by a power tunnel to
the powerhouse. The water level of the completed reservoir will
range from El 1080 to El 1180 with a Probable Maximum Flood crest
at El 11 90 • 6 ft .
The power tunnel wi 11 be constructed through the left abutment of
the dam. The tunnel will consist of an intake structure,
concrete lined sections, steel lined sections, a gate shaft with
control and guard gates and a gatehouse, and will connect with
the steel manifold and penstock leading to the powerhouse
turbines.
The intake structure, located at the upstream end of the power
tunnel, will be comprised of a concrete structure to support
bulkhead gates, trashracks and guides. The configuration of the
structure will be shaped to provide a gradual transition from a
rectangular cross section to the circular cross section of the
tunnel. The section of the tunnel upstream of the control gates
will be fully concrete lined with an 11 ft finished inside
diameter and will be level. The section of tunnel downstream of
the control gates will be concrete lined to a point within
approximately 3000 ft of the tunnel portal where a steel 1 iner
will be installed with concrete fill behind the liner. This steel
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
4.2
4.2.1
4.2.2
3061R/CM
B-4-2
liner will be matched to the steel manifold and penstock. Refer
to Part B-5 for further discussion of the steel tunnel liner,
manifold, and penstock.
A vertical circular gate shaft will be located approximately 500
ft downstream of the intake. The area of the tunnel at the gate
shaft will accommodate two rectangular high pressure gates (guard
and control gates) housed in a steel lined transition structure.
The gate shaft will be concrete lined, with a reinforced concrete
gatehouse and concrete cap with access hatch erected at the top
of the gate shaft. Access stairs and hydraulic lines wi 11 be
located within the shaft. Equipment for control and operation of
the gates will be housed in the gatehouse.
SUPPLEMENTAL DESIGN CRITERIA
General
Refer to Part A of the Structural Design Criteria for general
structural information. For further supportive information, refer
to the Hydraulic and Geotechnical Design Criteria. Refer to Part
B-5, Steel Liner and Penstock Structural Design Criteria for
design information on the steel liner.
Materials
The following materials will be used:
1. Concrete
Power tunnel intake structure-£' = 4,000 psi at 28 days c
Power tunnel lining-f' = 3,000 psi at 28 days c
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
3061R/CM
B-4-3
Gate shaft lining-f 1 ; 3,000 psi at 28 days c
Reinforced concrete gatehouse,
cap-f' = 4,000 psi at 28 days
foundation, and shaft
c
Gate chamber area, concrete backfill-£' = 3,000 psi at 28 c
2. Rock Reinforcement
See Geotechnical Design Criteria
3. Reinforcing Steel
ASTM A615, Grade 60
4. Welded Wire Fabric
ASTM 185
5. Structural Steels
days
a. Bulkhead guides -ASTM A36 guide plates and
ASTM Al67 Type 316 stainless steel bearing plates
b. Trashrack guides -ASTM A36
c. Trashracks -ASTM A36
d. High pressure gates and gate chamber transition
lining -By vendor
e. Structural steel framing -ASTM A36
6. Rock Bolts and Dowels (Anchors)
See Geotechnical Design Criteria.
7. Anchor bolts
ASTM A307
8. Grouts
Grouts used for injection grouting and crown grouting of
rock formations shall follow the requirements of the
Geotechnical Design Criteria.
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
4.2.3
4.2.3.1
3061R/CM
B-4-4
Grouts used for bedding of structural elements or equipment
shall have a minimum specified compressive strength of 5,000
psi at 28 days.
9. Coating Systems
a. Intake concrete structure -unsealed,
b. Concrete tunnel lining -unsealed,
c. Bulkhead gate guides -coal tar epoxy painting
system on non-embedded ASTM A36 material,
d. Trashracks -galvanized,
e. High pressure gates -high build epoxy on exposed
steel surfaces,
f. Steel Transitions and Gate Chamber Liner -coal tar
epoxy painting system,
g. Gatehouse structural steel framing -inorganic zinc
primer, high build epoxy top coat.
Design Loads and Load Combinations
Loads
A. General Loads
1. Dead Loads,
2. Rock Loads,
3. Hydrostatic Load -External -Tunnel unwatered with
bulkhead gates in place, normal headwater (El 1180)
4. Hydrostatic -Internal -Tunnel filled to guard
gate,
5. Hydrostatic Load -Internal -Tunnel filled to
control gate, PMF condition,
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
3061R/CM
B-4-5
6. Hydrodynamic Load gates open,
7. Earthquake Load-Horizontal,
8. Earthquake Load -Vertical,
9. Hydrodynamic Load -Earthquake acceleration with normal
maximum headwater elevation,
10. Hoisting Forc~s
operating gates,
Loads applied while removing or
11. Construction Loads -Additional loads or construction
12.
13.
14.
15.
16.
conditions, applied or anticipated during construction
efforts or imposed during maintenance operations, such
as contact grouting,
Ice Loading,
Snow Loading,
Wind Loading,
Live Loading,
Temperature,
Hydraulic and rock loads shall be as defined in the
Hydraulic and Geotechnical Design Criteria and calculations.
B. Gatehouse Live Load
L = 250 psf floor load
C. Hydrostatic Pressures
Hydrostatic pressures will be based on the high water
elevation at Probable Maximum Flood (PMF), El 1190.6 ft
rounded to El 1191 ft, except for earthquake conditions
where hydrostatic loads will be based on normal maximum
headwater level, El 1180 ft. For the profile of piezometric
hydraulic grade over length of tunnel refer to the
Geotechnical Design Criteria and calculations. In addition,
refer to the Hydraulic Design Criteria and calculations for
transient pressures and external pressures.
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
3061R/CM
B-4-6
D. Hydrodynamic Loads
Loads imposed on the Power Tunnel and its parts due to
flowing water will be considered 1n combination with rock
and hydrostatic loads, and will be based on the following:
1. Flow Velocity or Gate Closure.
Design Criteria and calculations.
See the Hydraulic
2. Hydrodynamic loads from a free surface reservoir due to
earthquake accelerations will be based on formulation
presented 1n the Bureau of Reclamation Publication
Design of Gravity Dams, 1976 Edition, Page 70, repeated
below:
:pe.::::: Co; 1.0 ~
c cyY'\
2. [1: lz -~) +1/ ~ ( z-~) J
Where: PE = Pressure normal to the face;
C = A dimensionless pressure coefficient
eX = Horizontal earthquake acceleration
Acceleration of gravity
w =Unit weight of water;
Z = Depth of reservoir at section being
studied;
h = Vertical distance from the reservoir
surface to the elevation in question; and
C = The maximum value of C for a given slope, m
as obtained from Figure 4-18 page 71 of the
above Publication and as reproduced as
Figure 1 of this Criteria.
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
4.2.3.2
3061R/CM
B-4-7
Load Combinations
For the various portions of the power tunnel identified below,
the following minimum loading combinations will be examined to
produce worst case design loads (see 4.2.3.1 for numbered loads):
1. Intake Portal Structure
Load Combinations
a. 1+2
b. 1+2+13
c. 1+2+ll
d. 1+2+3
e. 1+2+5
f. 1+2+(3 or 5)+7
Explanation
Normal rock loads combined w I dead
load.
As in "a" with snow load buildup.
As in "a" with construction loads
imposed from above.
As in "a" with external hydrostatic
effects.
As in "a" with internal hydrostatic
effects.
Hydrostatic pressure at normal
maximum water (El 1180 feet) with
horizontal earthquake acceleration
of 0. 75g, with a 50% increase in
allowable stress for steel but not
to exceed yield; ultimate design
load not to exceed U = 0.67
(1.4D+l.7L+1.87E) for concrete
with no increase in allowable
stress.
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
3061R/CM
B-4-8
g. 1+2+(3 or 5)+8 Hydrostatic pressure at normal
maximum water (El 1180 feet) with
vertical earthquake acceleration of
0.50 g, allowing same stress
increase conditions as in item "f"
above. Vertical and horizontal
accelerations shall not be combined.
2. Bulkhead Gate and Trashrack Guide
Bearing forces induced by loads on bulkhead gates and
trashrack, as determined from the bulkhead gate loading
cases and trashrack design information.
3. Bulkhead Gates
Refer to Part B-1, Main Dam Diversion Structural Design
Criteria, under which bulkhead gates are to be designed.
4. Gate Shaft
Use same load combinations as identified for tunnel 1 ining
design with appropriate adjustments for configuration and
orientation, as defined in the Geotechnical Design Criteria
and calculations.
5. High Pressure Gate Chamber Design
Load Combinations
a. 1+2
b. 1+2+(3 or 5)
Explanation
Dead load with normal rock loads.
As in "a" with hydrostatic
pressure.
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
3061R/CM
c. 1+2+4 (or 5)+7+9
d. 1+2+4 (or 5)+8
e. 1+2+3+10
f. 1+2+(4 or 5)+6+10
B-4-9
rock and hydrostatic Normal
loads, combined with horizontal
earthquake acceleration of 0.75g,
with a SO% increase in allowable
stress for steel but not to exceed
yield; ultimate design load not to
exceed U = 0.67 (1.40+1. 7L+ 1.87E)
for concrete with no increase in
allowable stress.
As in "c" except with vertical
earthquake
0.50 g, same
conditions.
acceleration
allowable
of
stress
Normal dead weight and rock loads,
external hydrostatic pressures,
tunnel drained, gate being raised.
Normal dead and rock loads, gate
being opened.
6. Concrete Tunnel Lining
The following load combinations shall be used when designing
reinforced tunnel lining in the region of the intake portal
structure.
Load Combinations
a. 1+2+3
b. 1+2+5
c. 1+2+(4 or 5)+6
Explanation
Tunnel dewatered with normal rock &
piezometric loads.
Tunnel full to control gate.
Normal dead and rock loads with
gate operation.
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
3061R/CM
d. 1+2+(3 or 5)+7
e. 1+2+(3 or 5)+8
Normal dead and
hydrostatic pressure
rock
at
B-4-10
loads,
normal
maximum water, with horizontal
earthquake acceleration of 0. 75 g,
with a SO% increase in allowable
stress for steel but not to exceed
yield; ultimate design load not to
exceed U = 0.67 (1.4D+l.7L+l.87E)
for concrete with no increase in
allowable stress.
As in "d" except with vertical
earthquake acceleration of O.SOg,
same allowable stress conditions.
Vertical
accelerations
separately.
and
to be
horizontal
applied
Other sections of concrete lining for the power tunnel shall
be designed in accordance with the Geotechnical Design
Criteria and calculations.
7. Gatehouse
Load Combinations
a. 1+13
b. 1+10 +15
c. 1+14
d. 1+(0.7S)xl3+14
e. 1+7+(0.75)xl3
Explanation
Normal dead loads with snow.
Normal dead loads plus live
loads, including equipment
operation loads.
Normal dead loads with wind.
Normal dead loads with wind and
75% snow.
Normal dead loads, horizontal
earthquake acceleration of 0.7Sg
and 75% snow load, same allowable
stress conditions as in i tern "6d"
above.
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
4.3
4.3.1
3061R/CM
f. 1+8+(0.75)x13
B-4-11
Normal dead loads, vertical
earthquake acceleration of o. 50g
and 75% snow load, same allowable
stress conditions as "e" above.
* In addition to the above design conditions, the stability of
the concrete gatehouse shall be checked against overturning
and sliding. The factor of safety against overturning or
sliding shall be greater than or equal to 1.0, using a
static lateral force coeffficient based on the structure's
estimated natural period and in accordance with the Project
Design Response Spectrum (provided as Attachment A to Part
A, General Structural Design Criteria) for a 0.75g mean
horizontal ground acceleration. The stability shall be
analyzed for dead weight only, and with 75% snow load.
ENGINEERING/DESIGN CONSIDERATIONS
Construction Considerations
Due to the remoteness of the site and shipping and transportation
limitations, material quality and weight savings will be a prime
consideration in design.
The basic sequence of construction is as identified below:
a. Construct diversion tunnel excavation and diversion tunnel
concrete intake structure;
b. Lower reservoir;
c. Excavate Power Tunnel intake area providing rockfill and
rock plug cofferdams;
d. Excavate tunnel and gate shaft (by drill and blast and/or
tunnel boring machine, TBM);
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
4.3.2
4.3.3
3061R/CM
B-4-12
e. Install concrete intake structure, tunnel concrete 1 ining,
steel liner and penstock;
f. Install the high pressure gates, transition liner, shaft
concrete, and gatehouse structure, and test gates;
g. Close high pressure control gate, remove cofferdams, and
flood tunnel;
h. After Main Dam, Spillway, and Power Tunnel system are
constructed, install bulkhead gates at intake portal of Main
Dam Diversion tunnel, and complete construction of Main Dam
Diversion.
Special Design Considerations
Equipment associated with the Power Tunnel system including the
gates and valves must remain functional over the full range of
loading conditions anticipated, including those of major seismic
events.
Gate shaft will be a "dry" shaft. The gate shaft will be
provided with a steel spiral staircase with 1/4 turn landings at
approximate 20 ft intervals and rest platforms to the side at
approximate 40 ft intervals. The shaft will contain hydraulic
lines, ventilation, sump piping, tunnel refill vent, and support
power.
Design
1. Concrete
Concrete design shall be in accordance with ACI 318-83.
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
B-4-13
2. Structural Steel
Allowable stresses for gatehouses shall be 1n accordance
with the AISC Steel Construction Manual. Stresses shall be
kept within elastic range.
The penstock and steel liner shall be designed in accordance
with the allowable stresses as stated in Part B-5, Steel
Liner and Penstock Structural Design Criteria.
3. Factors of Safety
The normal factors of safety developed within Part A of this
design criteria shall apply except as may be otherwise
qualified herein. Factors of safety for structures on, in
or anchored to rock shall be developed in conjunction with
the Geotechnical Design Criteria and calculations.
4. Special Physical Considerations
a. Reinforced Concrete -Rebar Clearances
Concrete cover for reinforcing steel shall be in
accordance with ACI 318-83, except as called for below.
(1) Tunnel lining-rock contact : 3 inches
(2) Tunnel lining-inside face ; 3 inches
minimum,
4 inches
where
erosion
may occur
3061R/CM POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
3061R/CM
B-4-14
(3) Intake Portal structure-exposed faces = 4 inches
(4) Tolerance of intrusion of rock projection into
neat excavation line shall be no greater than 2
inches. Protrusions shall not extend over an area
greater than 10% of neat excavation line, nor over
a local area greater than 5 in. x 5 in.
(5) Gatehouse walls (each face) = 2 inches
b. Structural Steel -Corrosion Allowance
(1) Bulkhead gates, control and service gates
-no corrosion allowance
(2) Gate guide -no corrosion allowance
c. Gatehouse
(1) Use a 1V:l2H sloped roof
(2) Minimum concete wall thickness shall be
1 ft.
(3) A rolling steel door shall be provided
for vehicle access
(4) Interior concrete walls and/or bullet
resistant doors shall be provided to protect
gate operating equipment
d. Trashracks
(1) Bar clear spacing = 2 in.
(2) Minimum vertical bar thickness shall be
1/2 in.
(3) Differential head = 10 ft
(4) Maximum approach velocity = 2.5 fps
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
(5) Geometry -As per model test sketch
15500-FC-S151A, with three panels per
side
(6) Bars shall be rectangular with a square
leading edge
(7) Net velocities shall consider a 25
percent reduction in net flow area due to
trash accumulation
(8) Hoisting forces shall be considered
B-4-15
(9) Vibration analysis due to vortex shedding shall be
in accordance with SWEC HTG-118.0-1.
e. Gate and Trashrack Guides
(1) Blackouts shall be provided for guide embedments
f. Gate Shaft
(1) Concrete lining will be supported by rock
vertically in bond. The bond shear strength
assumed at the rock-concrete interface is
f ~ 75 psi, except at bottom 20 ft of shaft v
where f = 0. v
(2) The rock may be assumed to provide continuous
lateral support around the periphery of the lining
to prevent outward deflection.
(3) Minimum concrete lining thickness shall be 1 ft.
4.4 DESIGN GUIDELINES AND REFERENCES
1. EM 1110-2-2901, Army Corps of Engineers, Engineer Manual,
Engineering and Design Tunnels and Shafts in Rock, Sept. 1978.
3061R/CM POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
B-4-16
2. Guidelines for Tunnel Lining Design, American Society of Civil
Engineers, T. D. O'Rourke, 1984.
3. ACI 318-83, Building Code Requirements for Reinforced Concrete,
American Concrete Institute.
4.
5.
6.
7.
Steel Construction Manual, American
Construction, 8th Edition.
Geotechnical
Project.
Hydraulic
Design Criteria, Bradley
Design Criteria Power
Institute of Steel
Lake Hydrolectric
Intake, Tunnel and
Penstock, Bradley Lake Hydroelectric Project.
Hydraulic
Project.
Transient Analysis, Bradley Lake Hydroelectric
8. HTG-118.0-1, Design Memorandum -Trashracks at Water Intakes,
3061R/CM
SWEC Hydraulic Technical Guideline.
POWER TUNNEL LINING, INTAKE, AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
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PO\-lER TUNNEL LINING,
INTAKE AND GATE SHAFT
STRUCTURAL DESIGN CRITERIA
3588R/CM
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. No. 15800
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
PART B, SECTION 5.0
REVISION: 2
DATE: December 22, 1987
STONE & WEBSTER ENGINEERING CORPORATION
DENVER, COLORADO
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
PART B-5
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS
SECTION TITLE
5.1 FUNCTIONAL DESCRIPTION
5.2 SUPPLEMENTAL DESIGN CRITERIA
5.2.1 Materials
5.2.2 Design Loads
5.2.3 Allowable Stresses
5.3 ENGINEERING/DESIGN CONSIDERATIONS
5.3.1 Hydraulic and Physical Considerations
5.3.2 Steel Liner Design
5.3.3 Penstock Movement at Spherical Valve
5.3.4 Concrete Thrust Blocks
5.3.5 Fabrication and Testing Requirements
5.4 DESIGN GUIDELINES AND REFERENCES
ATTACHMENTS:
Attachment A -Tunnel Liner Drain System
Sketch 15800-FS-S262A-3 Steel Liner and Penstock -Plan
PAGE
B-5-1
B-5-3
B-5-3
B-5-4
B-5-9
B-5-11
B-5-11
B-5-12
B-5-13
B-5-14
B-5-15
B-5-17
3588R/CM
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
PART B-5
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
5.0 STEEL LINER AND PENSTOCK
5.1 FUNCTIONAL DESCRIPTION
B-5-1
These design criteria are prepared to provide the pertinent data and
parameters that will be applied for the structural analysis and design of
the steel liner and penstock sections of the Bradley Lake Project power
conduit system, and are supplemented by the Hydraulic and Geotechnical
Design Criteria.
These criteria apply to the steel liner, the penstock
(penstock-manifold) and to other appurtenances, such as thrust rings,
stiffener rings, high pressure head covers, etc.
The power conduit for the Bradley Lake Project consists of: 1) an 11 foot
I.D. concrete lined tunnel section; 2) an 11 foot I.D. steel lined section;
and, 3) a steel penstock-manifold branching to three individual penstocks
and an extension, with two penstocks serving the two turbine units of the
90 MW plant, one penstock terminating at the location of the future third
unit, and a tunnel adit extension terminating at a high pressure head cover
which will provide access into the penstock-manifold and tunnel.
The horizontal and vertical configuration of the steel 1 iner and
penstock-manifold systems are shown on Sketch 15800-FS-S262A, included as
part of this criteria. Factors influencing these configurations are:
1. The initial recommendation that the steel liner terminate at a
point where the overhead rock cover is approximately 80 percent
of the maximum normal static head.
3588R/CM
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-2
2. The location of the two unit powerhouse, and considerations for
provisions for a future third unit.
3. The requirement that the penstock-manifold system be kept at the
lowest grade possible, commensurate with the centerline of the
Pel ton turbine runner center! ine located at El 15 (Bradley Lake
Project Datum -BLPD) and to facilitate access to the high
pressure inspection head.
4. Geotechnical restraints relative to rock quality in the area of
the penstock-manifold.
5. Constructability considerations for both the steel liner and
penstock-manifold system.
Based on the above, and as shown on the referenced sketch, the steel liner
and penstock-manifold systems are defined as follows:
1. Steel Liner System
The steel 1 iner begins at the upstream limit of the steel 1 ined
section and extends to the upstream end of the penstock-manifold
at the power tunnel horizontal point of curvature.
2. Penstock-Manifold System
3588R/CM
The penstock-manifold begins at the power tunnel horizontal point
of curvature, located just upstream of the penstock for the
future third unit, and ends with the upstream flange of each
spherical valve. It also includes the manifold extension which
terminates at the access head and is sealed with a flanged
closure head.
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-3
5.2 SUPPLEMENTAL DESIGN CRITERIA
5. 2.1 Materials
1. Steel Plate Material
Shell
Thickness
(inches)
To 1-1/4
The steel material to be used for the penstock-manifold and steel
liner shell plates shall be as follows:
TABLE 85-1
SHELL MATERIAL FOR LINER AND PENSTOCK-MANIFOLD
Minimum Minimum Notch Toughness
Yield Tensile (CVN)
Strength Strength Transverse
ASTM~c Grade Class (ksi) (ksi) -40°F (ft-lbs)
A710 A 3 90 100 25
Over 1-1/4 A710 A 3 75 85 25
to 2, incl.
Over 2 to
4, incl.
A710 A· 3 65 75 25
;'cWith modified steel properties as given herein.
The above material shall also be used for other high pressure
resisting accessories such as pressure test heads, pressure
bulkheads, manholes, flanges, and thrust rings.
Material for miscellaneous steel appurtenances not welded to the
pressure shell shall be ASTM A36.
2. Concrete
Concrete for backfilling behind steel liner, f' = 2,500 psi c
Concrete for backfilling around penstock and manifold,
f' = 2,500 psi c
Concrete for thrust blocks, f' = 4,000 psi c
Concrete for other structures, f' = 4,000 psi c
STEEL LINER AND PENSTOCK
3588R/CM STRUCTURAL DESIGN CRITERIA
3. Reinforcing Steel
ASTM A615, Grade 60
4. Welded Wire Fabric
ASTM Al85
5. Miscellaneous Steel
B-5-4
ASTM A36 (except for materials welded to the pressure retaining
boundary)
6. Anchor Bolts
ASTM A307
7. Rock Bolts and Dowels (Anchors)
See Geotechnical Design Criteria
8. Flange Stud Bolts and Nuts
ASTM A564, Type 630, Hll50
9. Post Tensioned Anchors
ASTM A722
5.2.2 Design Loads
The analysis and design of the penstock-manifold and steel liner systems
shall be based on the following loading conditions:
A. Internal Pressure Loads
1. Normal Static Head -Maximum normal static head without
3588R/CM
transient loads. This is used to determine required length of
steel liner.
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-5
2. Normal Condition -This condition includes Normal Static Head
plus pressure rise due to normal operation such as full plant
load rejection. Maximum pressure shall be 125 percent of Normal
Static Head.
3. Emergency Condition This condition considers unusual
conditions, such as simultaneous needle valve or spherical valve
closure. Maximum pressure shall be 166 percent of Normal Static
Head.
4. Exceptional Condition -This condition considers the effects of
malfunctioning of control equipment in the most adverse manner,
such as the instantaneous break of a Pelton needle valve,
instantaneous loss of governor oil pressure, or the occurrence of
auto oscillations. This loading condition shall not be used as a
basis for design except to provide a determination of stresses.
Maximum pressure is 200 percent of Normal Static Head.
The following internal pressures shall be used for the design of the
penstock-manifold and steel liner systems:
TABLE B5-2
INTERNAL PRESSURE AT CENTERLINE (PSI)
Power
Conduit Members
Penstock-At
Manifold Turbine
Inlet
Steel L-31
Liner through
L-72
Steel L-1
Liner through
L-30
3588R/CM
Normal
Condition
640
640
615
Emergency Exceptional
Condition Condition
845 1020
845 1020
815 975
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-6
B. External Pressure Loads
Design for external pressure loads is required for both the penstock-
manifold and the steel liner systems. These loads are, however, more
critical to the design of the steel 1 iner components. Only hydrostatic
related external loads shall be used in the design of the steel shells and
their appurtenances.
follows:
The loading conditions to be considered are as
1. External Pressure-General: For both the penstock-manifold and
steel liner systems, an external pressure of 75 psi (SO psi with
a safety factor of 1.5) shall be applied to permit pressure
grouting of the shells, if needed.
2. Steel Liner-External Hydrostatic Pressure: For the steel liner
system, an external hydrostatic pressure shall be applied which
will reflect the effects of a column of water whose height is
equal to the rock cover height above the centerline of the power
conduit and the effects of relief drains as given below. Based
on the vertical alignment shown on Sketch 15800-FS-S262A, the
following external hydrostatic pressures are to be used where
relief drains do not provide pressure reduction:
3588R/CM
L-1
L-10
L-20
L-30
L-40
L-50
TABLE BS-3
EXTERNAL HYDROSTATIC PRESSURE
Liner
Sections
through L-9
through L-19
through L-29
through L-39
through L-49
through L-72
External
Hydrostatic
Pressure
(psi)
380
320
230
195
160
117
External
Head
(ft)
877
738
531
450
369
270
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-7
External pressure relief drains will be established around the steel liner
in accordance with the details of Attachment A. Effective drainage and
pressure reduction will be provided from the upstream end of the steel
liner through Liner Can L-63. The 1 ines wi 11 drain into the powerhouse
drainage system. Two drain pipes will follow the Unit 1 penstock branch
line and two drain pipes will follow the Unit 2 branch line. The lines
will be provided with cleanouts.
The installation of drains along the liner cans will reduce the external
hydrostatic pressure and, therefore, will reduce the required liner
thickness. Assuming that the drains are 25 percent efficient and assuming
a design pressure 10 percent higher than the reduced effective pressure,
(i.e. 1.1 x 0.75 p = 0.825x pressure), external hydrostatic pressures shall
be in accordance with Table BS-4.
Liner Section
Ll to L9
LlO to Ll9
L20 to L29
L30 to L39
L40 to L49
LSO to L63
TABLE 85-4
REDUCED EXTERNAL HYDROSTATIC PRESSURES
Undrained External
Pressure (psi)
380
320
230
195
160
117
Reduced Design
Pressure (psi)
314
264
190
161
132
97
External hydrostatic pressure will likely control steel liner thickness
upstream of Liner Can L-24 (where rock support is considered in design).
The external pressures given by 1 and 2 above shall not be considered to
act simultaneously.
3588R/CM
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-8
C. Other Potential Loads
Consideration shall be given to internal and/or external loads that may
develop during the
and
fabrication,
steel liner
install at ion and testing
under this
of the
penstock-manifold systems. Loads category
include, but are not limited to: temperature changes, filling loads, loads
resulting during hydrostatic pressure testing or during the placement of
concrete, and anchoring support loads.
Temperature stresses shall consider stresses during the installation of the
steel 1 iner and penstock-manifold systems (prior to concreting) and those
that would result subsequent to concreting and during plant operation. For
these two conditions, the following temperature criteria shall be used:
1. Prior to Concreting
Mean Ambient Temperature at 55°F
o Increase above ambient
-Exposed to direct sunlight
-Under cover or in tunnel
o Decrease below ambient
-Open environment
-Inside Tunnel
i:::.T
2. Subseguent to Concreting and During O:Qerating
Mean Ambient Tem2erature
0 Increase above ambient
0 Decrease below ambient
Where AT is the variance from
3588R/CM
at 55°F
ambient
~T
0°F
-20°F
temperature.
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-9
5.2.3 Allowable Stresses
For the internal pressure and other associated loading conditions, the
steel liner sections and the penstock-manifold components (except wyes)
shall be designed to resist these loads with an allowable stress based on
Table B5-5. The resulting allowable stresses for ASTM A710, Grade A, Class
3 steel are shown in Table B5-6.
TABLE B5-5
ALLOWABLE STRESS
STEEL LINER AND PENSTOCK-MANIFOLD(!) (2)
Load Condition
Normal Condition
Emergency Condition
Percent of
Minimum
Yield Strength
60%
96%
Percent of
Minimum Ultimate
Tensile Strength
40%
66.6%
( 1) See Design Criteria for special adjustments regarding specific
components.
(2) The governing allowable stress shall be the lesser value as determined
based on yield strength and ultimate tensile strength.
Material
Thickness
(in.)
To 1-1/4
Over 1-1/4
to 2, incl.
Over 2 to
4, incl.
3588R/CM
TABLE B5-6
ALLOWABLE STRESS -ASTM A710, GRADE A, C3
(with material properties as given herein)
Minimum
Ultimate Minimum
Tensile Yield
Strength Strength
(psi) (psi)
100,000 90,000
85,000 75,000
75,000 65,000
Governing Allowable
Stress (psi)
Normal Emergency
Condition Condition
40,000 66,600
34,000 56,610
30,000 49,950
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-10
The stresses resulting in the member(s) analyzed shall be the equivalent
stress based on the Hencky-Mises theory of failure, as shown below:
-u cr X y
where:
erA = equivalent stress, psi
cr and cr are principal stresses, psi X y
The stress
Table 85-5.
n £r: " A shall not exceed the allowable stress given in
The allowable stresses given in Table BS-6 can be used directly for design
of the following: straight pipe sections that are practically free of
secondary stresses; for pipe sections at bends whose centerline radii are
not less than 10 times the pipe diameter; and for cylindrical or slightly
conical pipe (with apex cone angle less than 16 degrees) having adequately
spaced attachments (nozzles, manholes, etc.) which have a maximum dimension
of not more than 1/10 of the pipe diameter.
The allowable stresses given in Table BS-6 shall be reduced by 10 percent
for use in the following: design of the penstock-manifold wyes; for other
complex cylindrical or highly conical pipes, which may be partially
embedded in concrete; for pipes mitered to form bends with radii between 5
and 10 times the diameter of the pipe; for the flanges of high pressure
flange connections; and,
with dimensions greater
for pipes with nozzles, attachments or openings
than 1/10 of the pipe diameter. For these
components, localized stress conditions at highly stressed areas subject to
potential yielding shall be permitted to reach 1.25 times the reduced
allowable stresses, and for flanged connections longitudinal hub stress may
be increased as allowed in ASME Section VIII, Division 1, Appendix 2.
3588R/CM
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-11
Allowable stresses for flange connection stud bolts shall be the lesser of
25 percent of yield strength or 20 percent of ultimate tensile strength,
for the Normal Condition. A two-thirds increase in allowable stress shall
be permitted for the Emergency Condition.
Miscellaneous steel appurtenances constructed with ASTM A36 steel shall be
designed with allowable stresses in accordance with the Manual of Steel
Construction, Eighth Edition, AISC.
5.3 ENGINEERING/DESIGN CONSIDERATIONS
5.3.1 Hydraulic and Physical Considerations
An 11 foot nominal power conduit diameter has been selected for the Bradley
Lake Project. This selection is based on economic diameter evaluation
studies and hydraulic transient analysis.
All penstock-manifold and steel liner cans, including the reducers and the
three manifold wyes, will be configured to hold the inside diameter of the
shell, varying
thickness. The
the outside diameter as required by
inside diameters identified below
design for shell
for parts of the
penstock-manifold and the steel liner shall be used for all layouts and
designs.
1. Penstock -Manifold
0 Manifold Inlet at Steel
0 Manifold Pipe
0 Adit Extension Pipe
0 Penstock Pipes
0 Penstock Reducer Inlets
0 Penstock Reducer Outlets
2. Steel Liner Sections
0 All Sect ions
3588R/CM
Liner 132 inches
108 inches
108 inches
78 inches
78 inches
60 inches
132 inches
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-12
5.3.2 Steel Liner Design
Beginning at Liner Can L-24 (a point where the rock cover is about 0.40 of
the maximum static head above the liner) and ending with the upstream end
of the penstock-manifold (Liner Can L-72), the steel 1 iner sect ions shall
be designed neglecting external support provided by the surrounding
concrete and rock.
For Liner Can L-1 through Liner Can L-23, the steel liner shall be designed
to take into consideration the assistance of the encasing concrete and rock
mass. The following conditions shall apply to the design of this sect ion
of the steel liner:
1. Initial gap between liner and encasing concrete of 0.05 percent of the
radius of the liner. (This gap is approximately that resulting from
about 25°F temperature differential plus the shrinkage of the encasing
concrete taken at 0.05 percent per inch of concrete lining thickness.)
2. Concrete modulus of elasticity of 2.9 x 10 6 psi with a Poisson's
ratio of 0.30.
3. In situ elastic modulus of rock of 5.0 x-10 5 psi with a Poisson's
ratio of 0.27.
The basic approach to design for internal pressure with rock support shall
be as presented in the article "Rock Properties and Steel Tunnel Liners" by
George H. Kruse, (Ref. 1).
3588R/CM
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-13
The steel liner shell thickness, as calculated for internal pressure
related loading conditions, shall be checked for the external pressure
loads as herein defined. The basic approach for the design of the steel
liner shells for external pressure shall be that presented in the paper
"Buck! ing of Pressure-Shaft and Tunnel Linings" by E. Amstutz (Ref. 2).
Also, the papers by S. Jacobsen entitled: "Pressure Distribution 1n
Steel-Lined Rock Tunnels and Shafts", (Ref. 3); "Buck! ing of Pressure
Tunnel Steel Linings with Shear Connectors", (Ref. 4); and, "Steel Linings
for Hydro Tunnels", (Ref. 5), should be considered when the design analyses
show that use of external stiffeners are to be preferred both from a
technical and economic standpoint. The safety factor of the critical
buckling pressure to the design external pressure shall be greater than 1.1.
5.3.3 Penstock Movement at Spherical Valve
Thrust from spherical valve closure must be transmitted back into the rock
mass for sufficient resistance. In order to prevent loading the rock
immediately adjacent to the powerhouse, movement will be permit ted in the
penstock sections between the thrust blocks and the spherical valves. This
section of each penstock will be encased in compressible material. The
following load cases shall be evaluated to determine effects of thrust,
movement and pressure on pipe sections and thrust blocks, and loads induced
on or by spherical valves.
1. Internal pressures
2. Thrust load due to pressure on spherical valve
3. Torsional load due to spherical valve twisting
4. Bending load due to spherical valve trying to lift off foundation
or move laterally due to seismic acceleration. Seismic loading
shall be based on a 1.88g horizontal seismic acceleration
neglecting lateral resistance at the spherical valve foundation,
or a 1.25g vertical acceleration (acting independently), with
allowable stresses as given for the Emergency Condition.
3588R/CM
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
The following load combinations shall be evaluated as a minimum:
Case a:
Case b:
Case c:
Case d:
Internal Pressure + Torsional Load
Internal Pressure + Thrust Load + Torsional Load
Internal Pressure + Thrust Load + Bending Load
Internal Pressure + Bending Load
5.3.4 Concrete Thrust Blocks
B-5-14
Concrete thrust blocks shall be located to resist the thrust loads
developed in the system. Thrust forces, their direction and magnitude,as
well as the loading conditions under which they occur wi 11 be derived by
transient analysis and shall be in accordance with the Hydraulic Design
Criteria and calculations.
Post-tensioned anchors may be used to aid in resisting thrust forces. If
used, the anchors shall be designed for the Emergency Condition at 0.60 of
the guaranteed ultimate tensile strength (GUTS) of the anchor, with anchors
locked-off at 0.70 of GUTS.
Concret~ thrust blocks shall be designed using the ACI 318-83 guidelines
and the following load factors.
1. Normal case: U=l.7 (Normal Thrust Loads)
2. Emergency Case: U=(0.75)(1.7)(Emergency Thrust Loads)
All cases shall use the appropriate strength reduction factors. Estimated
movements of the thrust blocks under load shall be calculated and the
thrust blocks shall be isolated from the powerhouse walls using
compressible material.
3588R/CM
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-15
5.3.5 Fabrication and Testing Requirements
Plate thickness calculated from the stress analyses shall be rounded up to
the nearest 1/16 of an inch for detailing and drawing.
Regardless of the shell thickness calculated to resist internal or external
pressures, a minimum plate thickness shall be provided so as to provide the
required rigidity for fabrication and field handling. This minimum
thickness shall be based on the formulas and approach presented in the
paper "Minimum Thickness for Handling Steel Pipes", by J. Parmakian, (Ref.
6).
All fabrication shall be in accordance with the requirements of ASME Code,
Section VIII, Division 1.
All shop or field fabricated longitudinal welds, for all members, shall be
made as double "V" butt welds with 100 percent of the weld being inspected
using either. the radiographic or ultrasonic method.
All shop fabricated circumferential welds, for all members, shall be made
as double "V" butt welds with 100 percent of the weld being inspected using
either the radiographic or ultrasonic method.
Circumferential field welds for the penstock-manifold, the 300 ft radius
bend of the steel liner and for the next 15 steel liner sections (600 ft)
upstream of the bend shall be made as double "V" butt welds and shall be
100 percent inspected by either the radiographic or ultrasonic method.
Circumferential field welds for the remaining upstream steel 1 iner cans
(1920 feet) shall be made as single "V" butt welds using an external
backing bar and each of these welds shall be 100 percent inspected by the
ultrasonic method, including the areas where a longitudinal weld crosses or
is near a circumferential weld.
3588R/CM
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRIT~~IA
B-5-16
All shop or field fabricated welds for wye members, manholes, flanged
sections and sections where thrust rings and/or stiffeners are attached to
the cans shall be 100 percent inspected by either the radiographic or
ultrasonic method.
All welds shall be 100 percent inspected by the magnetic particle method,
in addition to the above requirements.
The specification shall require that the penstock-manifold system be either
field or shop pressure tested at a pressure of about 1.5 times the pressure
for the Normal Condition, but so as not to exceed a stress on the members
being tested greater than 85 percent of the yield point of the steel used.
The interweld region of the wye sickle beams shall be inspected by the
ultrasonic method after the pressure test, for evidence of lamellar tears.
All full penetration welds inspected by the ultrasonic or radiographic
method may be considered 100 percent efficient for design.
3588R/CM
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
B-5-17
5.4 DESIGN GUIDELINES AND REFERENCES
1. Rock Properties and Steel Tunnel Liners, G.H. Kruse, ASCE Journal of
the Power Division, Vol. 96, No. P03, June 1970.
2. Buckling of Pressure-Shaft and Tunnel Linings, E. Armstutz, Water
Power, Nov. 1970.
3. Pressure Distribution in Steel-Lined Rock Tunnels and Shafts, S.
Jacobsen, Water Power and Dam Construction, Dec. 1977.
4. Buckling of Pressure Tunnel Steel Linings with Shear Connectors, S.
Jacobsen, Water Power and Dam Construction, June 1978.
5. Steel Linings for Hydro Tunnels, S. Jacobsen, Water Power and Dam
Construction, June 1983.
6. Minimum Thickness for Handling Steel Pipes, J. Parmakian, Water Power
and Dam Construction, June 1982.
7. Steel Penstocks and Tunnel Liners, Steel Plate Engineering Data,
Volume 4, AISC, 1984.
8. ACI 318-83, Building Code Requirements for Reinforced Concrete,
American Concrete Institute.
9. Steel Construct ion Manual, American Institute of Steel Construe t ion,
8th Edition.
10. Geotechnical Design Criteria, Bradley Lake Hydroelectric Project.
11. Hydraulic Design Criteria -Power Intake, Tunnel and Penstock, Bradley
Lake Hydroelectric Project.
12. Hydraulic Transient Analysis, Bradley Lake Hydroelectric Project.
3588R/CM
STEEL LINER AND PENSTOCK
STRUCTURAL DESIGN CRITERIA
'DATE
PREP.
CHECK 5
APPR.
A. 5215.9
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4028R/20SR/CG
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J .0. No. 15800
TAILRACE
STRUCTURAL DESIGN CRITERIA
PART B, SECTION 7.0
REVISION: 2
DATE: March 25, 1988
STONE & WEBSTER ENGINEERING CORPORATION
ANCHORAGE, ALASKA
TAILRACE STRUCTURAL DESIGN CRITERIA
PART B-7
TAILRACE
STRUCTURAL DESIGN CRITERIA
TABLE OF CONTENTS
SECTION TITLE PAGE
7. 1 FUNCTIONAL DESCRIPTION B-7-1
7.2 SUPPLEMENTAL DESIGN CRITERIA B-7-2
7.2.1 Materials B-7-2
7.2.2 Loads B-7-2
7.2.3 Load Combinations B-7-2
7.3 ENGINEERING/DESIGN CONSIDERATIONS B-7-3
7.4 DESIGN GUIDELINES AND REFERENCES B-7-3
4028R/205R/CG TAILRACE STRUCTURAL DESIGN CRITERIA
7.0 TAILRACE
PART B-7
TAILRACE
STRUCTURAL DESIGN CRITERIA
B-7-1
7.1 FUNCTIONAL DESCRIPTION
The tailrace is a pool downstream of the powerhouse designed to collect
water released from the turbines and to provide a channel to transport that
water away from the powerhouse. The tailrace further acts as a stilling
basin by reducing the turbulent flow of released water before it flows into
Kachemak Bay.
The flow of water from the powerhouse will be channelized and directed into
the main flow path of the tailrace channel by the discharge chamber walls
constructed as part of the powerhouse substructure. No special flow
characteristics or shape requirements are required for the chamber walls.
The walls will be at right angles to the west wall and will be rectangular
in cross section.
The tailrace will be excavated out of the mudflats immediately to the west
of the powerhouse. Rock adjacent to the powerhouse will be removed to
provide proper channel alignment. The sides and bottom of the tailrace
basin will be riprapped for protection from scouring. The tailrace will
presently be sized for two units.
Design of the tailrace channel will be developed as part of the
Geotechnical and Hydraulic Engineering efforts. As part of the Structural
design, a concrete retaining wall will be required to retain the fill
material just north of the powerhouse and west of the substation. The
retaining wall will connect with the north end wall of the powerhouse.
4028R/205R/CG TAILRACE STRUCTURAL DESIGN CRITERIA
B-7-2
7.2 SUPPLEMENTAL DESIGN CRITERIA
7.2.1
7.2.2
7.2.3
Materials
1. Concrete
f'c = 4000 psi at 28 days
2. Reinforcing Steel
ASTM A615, Grade 60, Epoxy Coated
Loads
D = Dead load (concrete)
L = Live load or surcharge load, use 300 psf surcharge
F = Fill load (backfill), use 120 pcf dry weight
H = Hydrostatic load
E = Seismic load
Load Combinations
The retaining wall shall consider the following load combinations
and factors of safety.
Load Combination Factor of Safety
1. D + F + H 1.5
2. D + F + H + L + E (O.lOg horizontal) 1.5
3. D + F + H + E (0.35g horizontal) 1.3
4. D + F + H + E (0.23g vertical) 1.3
4028R/205R/CG TAILRACE STRUCTURAL DESIGN CRITERIA
B-7-3
7.3 ENGINEERING/DESIGN CONSIDERATIONS
The tailrace retaining wall shall be designed for backfill loads,
groundwater pressures, surcharge loads due to vehicles, and seismic
loads. The minimum factors of safety against sliding or overturning
shall be in accordance with Section 7.2.3, herein. The foundation
reaction shall be within the kern of the base, except for the seismic
condition. Passive pressure against the toe of the retaining wall
shall be neglected. Weep holes (drain holes) shall be provided to
reduce groundwater pressures, however groundwater pressure shall be
assumed at El 11.4 behind the retaining wall, neglecting tailwater
pressure as a resisting force. Lateral soi 1 presures and allowable
bearing pressures shall be in accordance with the Geotechnical Design
Criteria and calculations.
Keyed control joints shall be provided in the retaining wall at a 15
foot maximum spacing to control cracking due to temperature variation.
A guardrail shall be provided at the top of the retaining wall due to
vehicle access at the substation yard.
7.4 DESIGN GUIDELINES AND REFERENCES
1. General Project Information and Civil Design Criteria, Bradley
Lake Hydroelectric Project.
2. Geotechnical Design Criteria, Bradley Lake Hydroelectric Project.
3. Building Code Requirements for Reinforced Concrete, ACI 318-83,
American Concrete Institute.
4028R/205R/CG TAILRACE STRUCTURAL DESIGN CRITERIA
SECTION 4.0
HYDRAULIC
DESIGN CRITERIA
1-352-JVl
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. 15500-Phase I
J.O. 15800 -Phase II
MAIN DAM DIVERSION
HYDRAULIC DESIGN CRITERIA
REVISION: 2
January 30, 1987
HYDRAULIC DESIGN CRITERIA/HAIN DAH DIVEHSION
TABLE OF ·:::mJT2NTS
SECTIOI1 SECTION TITLE FA'.::2 E·J.
1.0 Description
2.0 Oper•ation ';(
3.0 Design Considerations -
4.0 Design Criteria and Paraoeters '
5.0 Selection of Hajor Eq ui pme n t ~ u
..1
1-352-J\-1 HYDRAULIC DESIGN CRITERIA/MAIN DA:1 DIVERS~IJE
1. 0 DESCRIPTION
This doclE!ent presents hydraulic design criteria for tLc ln':.a'":e,
tunnel, control and guard gates, fish flow release facilities, and
Bradley River channel improvements, of the Hain Darn Diversion.
The diversion tunnel will be constructed to pass Bradley Hi ver flmw
downstream from the Lake during construction of the main darn and
associated structures. The tunnel will also provide a per>tBnent
emergency means of lowering the level of the completed reset"toir, a3
required, during the project life. The tunnel facilities Hill aL;o
allovl for minimum downstream flow releases for the maintenance of
aquatic habitat in the Lower Bradley River.
The diversion tunnel will be constructed and operated in two phases.
Phase I
A modified horseshoe shaped diversion tunnel will pass flows up to the
routed flood of record as a free surface flow. With the exception of
the intake structure the tunnel will be left unlined during Pha~e ~
The tunnel will be grouted during Phase I.
The concrete intake structure will be completed during Phase I. It
will include one set of gate slots and the upstream portion of the
fish release piping. The flow section at the portal inlet is
rectangular with an arched ceiling. Transition to the modified
horseshoe shape is provided. Wooden stop logs '4111 be inse;~ted inl:.o
the gate slots during Phase I to regulate the Lake drawdown. /later·
will be discharged from the tunnel into the existing pool located at
the exit of the tunnel. That side of the pool opposite the tunr,ei
'l'lill be riprapped to resist erosion caused by the tunnel discharge
during the construction. Water from the pool will discharge into
Bradley River channel which will be excavated to lower the tailwater
level at the diversion tunnel exit and the main dam toe.
1-352-JW HYDRAULIC DESIGN C:1ITERIA/l1AIN DAM DIVE~SIOH
Page 2
Phase II
Two bulkhead gates will be supplied for Phase !I. They ·r~ill be used
in the upstream gate slots to impound the reservoir. A vertical gate
shaft will be bored near the mid-point of the tunnel. The shaft will
contain two high pressure gates installed in series. The upstreao
gate will function as a guard gate, and the downstream as the control
:;;ate. The upstream portion of the tunnel will be lined 2
concrete liner. A steel penstock will be installed downstream of t~e
control gate and will extend to the tunnel exit. A surface gate hou::"·
will be located on the top of the gate shaft. It will contain
controls, oil systems, and energy sources to operate the gates.
The main purpose of the high pressure gates is to facilitate emergency
rJraHdown of the reservoir at a controlled rate i:1 case of 2.
catastrophic earthquake where damage to the main dam is a susp>:::ct.
Other means such as a fuse plug, gated spillway, hollow cone valve,
rupture head, etc. were also considered. Technical suitability an~
reliability of these alternatives were carefully evaluated versu:.~
their cost. High pressure gates, although costly, provide essential
features not available from other arrangements such as possibility to
control the flow rate, possibility to terminate the drawdmm at ar:J
time, reliability due to dual energy system, etc. Possibility to
eliminate the gates entirely and use the main power tunnel for
emergency drawdown was also examined. This alternative could not be
adopted since the capacity of a two unit powerhouse would be only 25
percent of the diversion tunnel gates and it is likely that the
powerhouse will not be operational after a catastrophic earthquake.
Hinimum downstream flow releases to maintain aquatic habitat in the
Lower Bradley River will be through two steel pipes embedded ir. the
concrete floor of the tunnel. The two pipe intakes will be located
upstream of the tunnel inlet. The intakes will be grated. A
connection for a source of compressed air will be provided for each
pipe as to facilitate back flush of the intake gratings. ~linimuo flow
releases will be controlled by a system of valves and nozzles at the
1-352-JH HYDRAULIC DESIGN CRITERIA/MAIN DAH DIVERSIO~J
downstream end of the pipes at the tunnel outlet. The capability ~us~
i.Je provided to adjust flow releases at fine increr.1ents. To .:t;tain
this increL'lental flow, it will be necessary to manifold eac[, pipe near
the outlet to provide multiple control valves on each pipe. A drain
will be provided for each nozzle to prevent ice formation in a
non-operating nozzle downstream of the control valve. .u. structure
will be built to accommodate the control valves and manifol~s.
2.0 OPERATION
Phase I
The intake structure, unlined tunnel, and downstreaQ channel shall be
designed to pass up to 4,000 cfs in free flow conditions during the
oain dam construction. This is based on uncontrolled passage of La~e
inflo~s due to natural hydrologic events.
During construction of the tunnel, a rock plug will be tewpor::lr'
left in place to act as a cofferdam while the Lake flow is
through the natural Bradley River channel outlet.
Upon completion of Phase I construction, wooden stop logs ~Jill be
inserted into the gate slots. The rock plug will be renoved by
underv;ater blasting and the blasted material will be removed. _:;.
initiate the lake drawdown, the stop logs will be removed sequentia:;_ly
in such a manner that the average monthly flow in the lower .Sracley
3iver is not exceeded by more than 50 percent. During this operaticn,
the numbers of logs in place on each side of the pier shall not differ
by more than one. If an emergency situation in toe tunnel 'r:i:l
require its closure, the stop logs will be lowered back into tt.e
slots. They can be used only for Lake levels at El. 1031 and loHer.
Once the Lake is drawn down the construction of the cofferda~s at the
~ake outlet can proceed.
1-352-JW HYDRAULIC DESIGN CR:TERIA/MAIN DAM D!VERSIOJ
Ps.~.:,e 4
Pi1ase II
Upon completion of the main dam, the reservoir will be impounded 0y
installing the bulkhead gates at the diversion tunnel inlet.
Installation of the bulkhead gates should not be attempted Hhen
diversion flows exceed 500 cfs. Immediately after the bulkhead gat e.;;
are installed, temporary fish release piping will be completed acd
the minimum required flow established. The installation of the i:it:;!'
pressure gates, the tunnel lining, penstock, and outlet structure >Jill
follow. vlhen the emergency discharge guard and control gates are in
place and operational, the upstream portion of the tunnel will be
filled with the high pressure gates closed and the bulkhead gates !·!ill
be removed at balanced head.
It is recognized that after lowering of the bulkhead gates the Lake
level starts rising thus making it increasingly more dif:'icult to
raise the gates under unbalanced head if required. Althougn te:~lcn is
used on seals and bearing blocks, it appears that an unbalanced ad
of 10 feet on the gates would be the maximum head against which the
gates can be raised.
Unbalanced head above 10 feet would produce vertical friction forces
of such a magnitude that the raising of the gates under the:Je
conditions may become unfeasible and unsafe. These gates 1-1ill be
removed when the diversion tunnel system is complete and the h i;:sh
pressure gates are in place. A means will be provided to fill the
upstream portion of the tunnel to equalize the pressure en the
bulkhead gates when they are to be removed.
The water level of the completed reservoir may require lo't~ering to
expose the dam face and associated structures for purposes of safety
inspection and possible repair. It is anticipated that this activity
will be scheduled whenever possible during periods of low reservoir
level, i.e., ~..arch to Hay, and further lowering of the reservoir level
towards El 1080 will be achieved by operating the turbine-generator
units at full load on a continuous basis. Operation of the diversion
1-352-JH HYDRAULIC DES::::GN CRITERIA/HAD! DA~1 DIVERSION
Page 5
tunnel for this purpose should be avoided and reserved for extreme
emergency only. When ·the gate is operated, either closing or opening,
it must pass through a position resulting into a flow rate which may
produce an oscillating flow regime in the discharge pipe. This
phenomenon will disappear when the gate reaches its extreme position,
i.e., closed or open.
Operation of the gate in a partially open position to regulate the
flow should also be avoided. In addition to the oscillating flow a
cavitation damage to the gate lip would be expected.
High flows discharged through the diversion tunnel will cause erosion
of the pool and sedimentation of the silt in the river channel. This
condition may be tolerated during emergency conditions but would be
undesirable otherwise.
In the case of a catastrophic earthquake, the Lake has to be drawn
down at a fast rate in order to reestablish safety of a damaged dam
crest. The design discharge for this mode of operation is that
required to draw down the reservoir in approximately 45 days, yet
limit the average rate of draw down to not more than 2.5 feet/day to
prevent damage to the facing of the main dam. During an emergency
draw down, an average lake inflow of 1500 cfs (two highest flow
months, July and August) and a no flow condition through the
powerhouse are assumed. The diversion tunnel high pressure gates
would be fully open during this entire draw down period.
The gates will be periodically exercised at no flow conditions. Each
gate will be operated in one full cycle (close-open or open-close) at
least once within each three months. To facilitate exercising at no
flow conditions a double gate arrangement is required. In addition
the upstream guard gate will allow inspection and maintenance of the
downstream control gate without installation of the bulkhead gate and
dewatering of the tunnel.
If required the upper tunnel may have to be dewatered for inspection.
Bulkhead gates will be installed at the intake and the tunnel
1-352-JW HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
I
Page 6
dewatered through the control gate "cracked" open. After the
·inspection is completed, the tunnel will be re-watered through the
refill pipe with the control gate closed. The bulkhead gate will then
be removed.
Fish release facilities will be operated so as to pass the required
flow through the two pipes up to the total of 100 cfs. At Lake level3
close to the minimum level ( El. 1080), both pipes will be required to
pass a total of 100 cfs. For higher levels, one pipe may be able tc:
pass the required flow, and the second will remain closed. Each
valve-nozzle pair mounted at a branch pipe from the manifold will be
of a different size. Valves will be either fully closed or fully
open. They will be sized so that by operating various combinations of
nozzles, the flow can be controlled in increments of approximately 5
cfs for any reservoir elevation within the operating range of El. 1080
to 1180. The valves will be motor operated. Flow through the system
will be controlled remotely based on measured flow through the Bradley
River Channel.
3. 0 DESIGN CONSIDERATIONS
Phase I
The tunnel shall be so sized as to pass the maximum construction flood
of 4,000 cfs as an open channel flow with a minimum distance of four
feet between the water surface and crown of the tunnel at all
locations.
The decision to lower the tunnel invert resulted in the need to
excavate the river channel at the tunnel outlet to El. 1060. This
arrangement offers the advantage of reducing the size of the
downstream cofferdam for main dam construction. The elevation of the
top of the upstream cofferdam and other structures acting in a similar
fashion will need to be set at such an elevation as to provide four
feet of freeboard above El. 1086, which is based on the steady state
Lake level while passing 4,000 cfs through the tunnel.
1-352-JW HYDRAULIC DESIGN CRITERIA/MAIN DA~I DIVERSION
I
7
Improvecents to the existi~g Bradley River channel downst~aa~ of t~8
diversion tunnel shall be made to provide sufficient cross-sectional
area and bottom slope to pass 4,000 cfs without causing a backwater
effect in the tunnel at that flow. The channel shall be unlinecl
excavated rock. It will be important to protect the bank opposite to
the diversion tunnel exit against the diversion flow of 4,000 cfs.
The banks along the entire pool, especially at the toe of the main darn
must be protected against spillway flow. Theoretical conclusion;;; ;.;12_.:._
be supplemented by hydraulic model testing. Velocities on the 2o•:lel
will be measured. Based on these velocities, suitable bank protection
will be designed,
Since the entire diversion tunnel will be modeled, Phase ! and Phase
II flow conditions will be confirmed. Specific areas of conce!'n are
vortices at the intake during Phase II operation, and water surface
elevations inside and downstream of the tunnel during Phase ~
operation.
Phase II
Two steel bulkhead gates, installed side by side, will be designed to
close against the diversion flow of approximately 500 cfs. ~he
corresponding flow depth at the gate section is five feet. T0
minimize the total vertical force on the gates during their lo\·rerir:g
and raising, several design features were adopted. Teflon coated
seals and stainless steel sealing surface will be provided. Al;;;o,
teflon coated bearing blocks will be provided. Seals against t~e sill
will be so arranged as to minimize the downpull force while handling
the gates under flow.
The high pressure gates and the penstock will be sized to pass such
flow as to lower the Lake from El. 1180 to 1090 in approxi:nately 45
days with the gate fully open. To assure that the open gate flm·i
section will control the flow the gates Hill have approxinately ,35
percent of the penstock area. Adequately sized piping ~ill be
1-352-Jii HYDRAULIC DESIGN CRITERIA/HAIN DAH DIVERSIOI'i
8
provided downstream of the main gate to facilitate aeratic,n of the
flow. A 6-inch pipe branching off the fish by-pass line and a 3-inch
vent pipe will be provided to fill the tunnel after dewaterinc;. j
rigid support of the penstock is required to raise the natural
frequency of the system well above a potential flow induced forcing
frequency. A continuous iielded steel penstock supported evel'Y 20 feet
is being considered. There will be a Dresser coupling on the upstream
end to eliminate possible stressing of the gate during an eart:1,~t..:al<e.
Downstream of the coupling an anchor block will be located. The
supports downstream of the anchor will be a sliding type t:,;irder
to allow expansion of the pipe in the downstream direction. A four
foot concrete wall at the exit structure will be provided to suppress
vibration of the downstream end of the penstock.
A curtain will be provided on the downstream end of the Phase II
tunnel and penstock to retain natural heat during periods of ::.oH
temperatures. The fish release control structure and the gate house
Hill be provided with minimum heat to prevent freez of the
equipment and allow operation during winter.
Fish Facilities
The fish bypass pipes must be designed to operate under reservoir S:l.
1180 and to withstand static head to El. 1190.6. To limit stress
caused by water hammer to a reasonable minimum, it is recom:ne::ded to
maintain closing time of the control and guard valves at 10 seconds or
more. With the reservoir level at El. 1180, the nozzle exit velocity
will exceed 70 fps. The use of a suitable type of stainles::. steel
nozzle will prevent erosion. Butterfly valves are used for control of
flow. Flow sections of the valve will be selected as to limit the
velocity through the valve to not more than 35 fps. V/hen selecting
the valves, consideration will be given to resistance against erosion
and cavitation.
1-352-J\-l HYDRAULIC DESIGN CRITERIA/HAIN DAt1 DIVERSION
I
Since the flow through the fish bypass piping illust be estatJlished. as
~oon as possible after the bulkhead gates are installed, use of
Victaulic type couplings is recommended to accelerate this activity.
1.!. 0 DESIGN CRITERIA AND PARAHETERS
In addition to the hydraulic criteria given below, refer to Structural
Criteria, Part B, Special Requirements and Design Ct'iteria for Hajcr
Structures, Section 1.0, Main Dam Diversion.
Phase I
Diversion Tunnel -
Cross section: modified horseshoe, see attached sketches
Invert slope: 1 percent
Invert at concrete intake: El. 1068 (extending downstream of
bulkhead gate slot)
Manning's n: 0.015 (concrete)
0.040 (unlined rock)
Diversion Operation -
Discharge:
Velocity:
Lake Level:
Phase II
4,000 cfs (routed flood of record)
~ 30 ft/sec (concrete at intake structure)
~ 20 ft/sec (unlined rock excavation)
< 10 ft/sec (intake approach velocity)
El. 1086 (when passing 4,000 cfs)
Emergency draw down operation -
Initial reservoir level: El. 1180
Lowered reservoir level: El. 1090
Average rate of draw down: 2.5 ft/day.
1-352-JW HYDRAULIC DESIGN CRITERIA/MAIN DAH DIVERSION
Reservoir inflow:
El. 1180 to El. 1080: 1 ,500 cfs
Below 21. 1080: 500 cfs
Velocity in lined tunnel: <30ft/sec
Velocity in steel penstock: ~ 80 ft/sec.
Total draw down time: 45 to 50 days
~ iini:nw:t fish flow releases -
Discharge:
Headwater:
Taihtater:
50 cfs per pipe
El. 1080
El. 1065
5. 0 SELECTION OF MAJOR EQUIPMENT
Page 10
The bulkhead gates will be designed for the hydrostatic load under the
Lake El. 1190.6. The bulkhead gates will be designed to close st
open channel flow of 500 cfs.
The gate shaft will be of a dry well type construction. The guard
gate and the control gate will be hydraulic cylinder-operated slide
gates capable of throttling flow at varying gate openings and should
be of heavy duty construction to resist potential vibrational loading.
The maximum differential static pressure on both the guard and cont:·o2.
gates is that developed by the Lake El. 1190.6. The gates will be 3~
shaped that they produce downpull under all conditions. Allm.;ance
\-!ill be made in the gate design for pulsating hydrodynamic fcrces
whici1 are expected to occur on the downstream side durir.g the gate
closing and opening.
Each gate will be operated by a dual hydraulic oil pressure syster.1.
The systems will be interconnected with a pipe and isolated with a
valve, normally closed. The primary system will consist of a bank of
accumulators sized for one stroke (open) of the slide gate. A low
volume electric motor/pump will be provided for recharging of the
accumulators. The back-up system will consist of a high volume pump
driven by a combustion engine. The accUiilulators, pi.lillps, motor·s, and
1-352-JH HYDRAULIC DESIGN CRITERIA/MAIN DAH Dl'JERSIO~!
?aLe i 1
engir:es 1r1ill be located in the gatehouse at El. 1195. .Separate open
and close pipes for each gate (total of 4 pipes), will run between El.
1195 and the gate operating cylinders. The control gate ':lill be
operated locally from a panel in the gate house or remotely fro~ t~e
power intake gate shaft, where emergency power will also be provided.
1-352-JH HYDRAULIC DESIGN CRITERIA/MAIN DAM DIVERSION
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ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. No. 15800
HYDRAULIC DESIGN CRITERIA
TAILRACE
REVISION:
DATE: FEBRUARY 10,. 1987
TABLE OF CONTENTS
SECTION TITLE PAGE NO.
1.0 DESCRIPTION AND OBJECTIVES
2.0 OPERATION 2
3.0 DESIGN CONSIDERATIONS 3
4.0 DESIGN CRITERIA AND PARAMETERS 3
1-262-JW HYDRAULIC DESIGN CRITERIA:TAILRACE
Page 1
1. 0 DESCRIPTION AND OBJECTIVES
Background
The turbine chamber acts as a body to receive water falling from the
Pelton wheel turbine buckets. Data from various turbine manufacturers
show that the highest water level for full load operation should be
about 9 feet below the runner centerline, or at elevation +6 Bradley
Project Datum, after establishing the runner centerline (see attached
Table 1 for datum relationships). The manufacturers also recommend
that the bottom of the turbine chamber and tailrace be 21 feet below
the runner centerline, i.e. elevation -6.0. These values are used for
the Project design.
Based on the Powerhouse Setting economic study Action Task No. 1 and
Hydraulic Calculation No. H-009, the runner centerline has been set at
elevation 15. The normal maximum tide elevation is at elevation 6.0,
the highest tailrace allowable level for full load turbine operation.
Tide levels above elevation +6 .0 have only a 2.5% exceedance level
(see attached exceedance levels in section 4.0 and Figure 1). For
these high tides the water level in the turbine chamber must be
reduced by the air depression system to enable the full load turbine
operation.
1-262-JW HYDRAULIC DESIGN CRITERIA:TAILRACE
Page 2
Objectives
The tailrace, which is the channel area downstream of the powerhouse,
will be designed to collect the water from the turbines and transport
it away from the powerhouse to Kachemak Bay with minimal backwater
effect at the powerhouse.
Additionally, the tailrace discharge must be designed to minimize ice
formation during freezing conditions. Design considerations for
prevention of ice formation in the tailrace channel shall include a
relatively narrow top width, a moderate flow depth across this width,
and a fairly swift velocity.
Geotechnical Restraints
The tailrace will be excavated in the tidal mud flats, with limited
bedrock excavation near the powerhouse.
The sides and bottoms of the basin in the mudflats will require
protection against uplift from underlying sands which are under
artesian pressures. This protection entails riprapping, sand drains,
or otherwise protecting the entire basin side slopes and bottom. This
treatment will be addressed in the Geotechnical Design Criteria.
1-262-JW HYDRAULIC DESIGN CRITERIA:TAILRACE
Page 3
2. 0 OPERATION
A maximum of 1500 cfs of water will pass through the two turbines and
flow to the tailrace. Turbulent water discharging into the tailrace
will be diffused across the 90 ft wide channel adjacent to the
powerhouse, slowing its velocity in the process. The channel then
spreads out gradually, while the channel bottom elevation rises, until
it is 176 feet wide. At maximum flow the depth of water is 2.15 feet.
The channel conveys water with a velocity of 3. 8 fps and a depth of
2. 15 feet until reaching the slough where the channel ends. The
slough will receive all the tailrace water beyond this area.
3.0 DESIGN CONSIDERATIONS
The tailrace is to be sized for 2 unit operation with a maximum
combined turbine flow of 1500 cfs.
Starting at the downstream edge of the powerhouse from Station 0+00 to
0+40, the tailrace will have a basin width of 90 feet, excavated tc·
elevation -6 adjacent to the downstream edge of the powerhouse as
shown on Figure 2. Since it is believed that this section of the
tailrace will be entirely excavated in rock, no riprap lining is
required.
From Station 0+40 the tailrace will slope upward from elevation -6 to
elevation 3.5 at a bottom slope of 18 Horiz:1 Vert. The tailrace
bottom sides flare at an angle of 14° until a width of 176 feet is
1-262-JW HYDRAULIC DESIGN CRITERIA:TAILRACE
Page 4
obtained. The tailrace side slopes are to be excavated at 4 Horiz: 1
Vert slope. The top of the sides of the tailrace in the section Hill
be raised to elevation 8.0, Figure 3. Since this section of tailrace
will be excavated in tidal soils underlaiden by a zone of sand which
is subject to confined groundwater pressures, drains and riprap
overlayment is required. The actual engineering characteristics of
the sand drains and riprap are addressed in the Geotechnical Design
Criteria. The end width of the channel shall be extended downstream
with the bottom fixed at elevation 3.5, until the tailrace connects
with a natural slough channel, about 900 feet away. Since this
section of the tailrace is relatively shallow (0.5 to 2.5 feet deep)
and the velocities are 3 to 4 fps, the channel will be left unlined.
No special side slope treatment will be required along this channel
length.
4.0 DESIGN CRITERIA AND PARAMETERS
Bradley Project
Tidal Information Datum
High Tide plus Waves ( 5 ft) El. 16.3
High Tide plus Storm Surge El. 13.3
High Tide at Project Elevation El. 11 .37
Mean Higher High Water Elevation El. 4.78
Mean Sea Level Elevation El. -4.02
Mean Lower Low Water Elevation El. -13.63
Lowest Tide at Project El. -19.63
1-262-JW HYDRAULIC DESIGN CRITERIA:TAILRACE
Haximum Tide Level for Operation El.
of Pelton Turbine without the
depression system operating
in turbine chamber
Water Surface Elevation at Channel El.
at Peak Operation 211 feet from
Powerhouse
Backwater at Powerhouse during Peak El.
Operation
TIDE EXCEEDANCE CURVE
PERCENT
EXCEEDANCE
TIDE ELEVATION (FT)
PROJECT DATUM
100%
99%
98%
95%
90%
80%
70%
60%
50%
40%
30%
20%
10%
5%
2%
1%
O%
Shown in Figure 1
-19.6
.:.17.0
-16.0
-14.3
-12.6
-10.2
-8.0
-5.8
-4.0
-2.2
-0.4
1.4
3.7
5.0
6.4
6.8
11.4
Page 5
6.0
5.65
5.92
Size of Basin 90 feet wide at Powerhouse to 40
feet from the Powerhouse
Finish Elevation
1-262-JW
176 feet wide 211 feet from the
powerhouse
-6.0 feet at Powerhouse
+3.5 at beginning of Channel
HYDRAULIC DESIGN CRITERIA:TAILRACE
Page 6
Bottom Slope 18 Horiz:1 Vert
Haximum Discharge (2 units) 1500 cfs
Maximum Velocity in 3 to 4 fps
the Tailrace
Basin Lining -riprap to be determined by Geotechnical
thickness Division
Mannings "n" factor for
riprapped basin 0.04
Mannings "n" factor for
channel excavated in
tidal silt 0.02
Depth at channel outlet 2 to 2.5 ft
Velocity at channel outlet 3.5 to 4.5 fps
1-262-JW HYDRAULIC DESIGN CRITERIA:TAILRACE
Page 7
TABLE 1
RELATIONSHIP OF VERTICAL DATUt1S
Bear Cove Bear Cove Bradley
MLLW MSL Project
Datum Datum
HT 25.0 15.39 11.37
MHHW 18.41 8.80 4.78
MHW 17.60 7.99 3.97
Project
Datum 13.63 4.02 0.00
Origin
(assumed)
MSL 9.61 0.00 -4.02
MLW 1.61 -8.00 -12.02
MLLW 0.00 -9.61 -13.63
LT -6.0 -15.61 -19.63
1-262-JW HYDRAULIC DESIGN CRITERIA:TAILRACE
I I I I
COVE 1 KACHEMAK BAY 1 ALASKA
25+ ---t-----+ -· --t--1 f ---l--·----1 H T 11.3 7
5
__j
20 MHH\v~=~A1 -t·---1--l ·i --. ~
__j
2
'I o~ . I -z ' : ~ u 0-10 _LL L._ HW (12 HOURS ---~ w-= ~ ~ MSL = 9.6 I I I I I > J <!LL I w 0 > .._.. I I __j 0:: ~ 5 .
1
' HOURLY --t-+--~-w CL -·-
w I wr
1 ow w 0 MLLW ·---__j
0 t-0 ~ I I : <t
' 0:: - 5 +-·-+--+ t ---l -1 I l m
.._..
-1 0 -+-----·+--r-~ +-+---+ ·--+-···---+-···-···+ ---. --1---+-----l
MHHW = 1.78
MHW =3.97
MSL =-4.02
MLLW = -13.67
0.01 0.1 0.5 1 2 5 10 20 3040 60 80 90 95 98 99 99.8 99.9 99.99
0 /o EXCEEDENCE
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
KENAI PENINSULA BOROUGH,ALASKA
CUMULATIVE PROBABILITY DISTRIBUTION
FOR TIDE EXCEEDING LEVEL IVEN
AN OBSERVATION LENGTH
FIGURE 1
000LGE3 . v
·.
c
0009GE3 __)) ···~···
. ( I
~···.
)
'•
W)
i 0
0
0
0
(") ....--
(\j
z
.oooc~E3
I
0
L[)
~
\
tUNIT#1 fUNITif2
I POWERHOUSE I
STA 0+00
0.25:1TYP
STA 0+ 40
EL+8
STA
2+ 11
..
(()
..--
60'
EL -6
go'
176 I
E L + 3. 5
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
KENAI PENINSULA BOROUGH,ALASKA
11= 4011
GEOMETRY OF
TAILRACE
FIGURE 3
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. NO. 15800
HYDRAULIC TURBINES, GOVERNORS, AND SPHERICAL VALVES
PERFORMANCE CRITERIA
REVISION 2
DATE: MARCH 28, 1988
00629A-1580072-D1 PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
TABLE OF CONTENTS
Page No.
OBJECTIVES 1
REFERENCES 1
1.0 DESCRIPTION 1
1.1 General 1
1.2 Contract Packaging 2
1.3 Turbine/Generator Sizing 2
1.4 Hydraulic Turbines 2
1.5 Governors 3
1.6 Spherical Valves 4
2.0 TURBINE HEAD 7
2.1 Water Levels and Tunnel Discharge 7
'2 .2 Head Loss Calculation 8
2.3 Design Pressure 9
3.0 OPERATION 10
3.1 Operation of Units 10
3.2 Regulation of Turbines 11
3.3 Operation of Spherical Valves 11
3.4 Sluicing through the Turbine 12
3.5 Flood Operation 13
4.0 DESIGN CONSIDERATIONS 13
4.1 Hydraulic Turbines 13
4.1.1 Runner 13
4.1.2 Shaft -Bearing System 13
4.1.3 Shaft Seal 14
4.1.4 Tailrace Depression System 14
4.1.5 Cooling Water System 15
4.1.6 Spiral Distributor 16
00629B-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
4.2
4.1. 7
4.1.8
4 .1. 9
TABLE OF CONTENTS (Cont'd)
Runner Chamber
Needle Valves
Deflectors
4.1.10 Instrumentation
Spherical Valves
4.2.1 Valve Body
4.2.2 Connection Pipes
4.2.3 By-Pass System
4.2.4
4.2.5
Oil Pressure System
Valve Seals
Page No.
17
17
17
18
18
18
18
19
19
19
006296-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 1
OBJECTIVES
The ma1n objective of this criteria 1s to provide basic guidelines for
selection and preparation of specifications for hydraulic turbines,
governors and spherical valves. The document addresses general configu-
ration of the powerhouse, rating of the units, operation, and special
requirements on selection of the equipment.
REFERENCES
1. FERC License Application for Bradley Lake Hydroelectric Project
2. SWEC: Master Specifications for:
-Hydraulic Turbines and Pump-Turbines
-Spherical Valves
-Hydraulic Turbines and Pump-Turbines Governors
3. Turbine Manufacturer Information and Design Data from:
-Allis Chalmers -Fuji -Kvaerner Brug
-Dominion Bridge -Hitachi -Vevey
-Escher Wyss -Hydroart -Voith
4. Fuji design data furnished under Contract No. 2890033 with APA
5. Hydraulic Design Criteria: Tailrace Channel, Bradley Lake
Hydroelectric Project
6. Structural Design Criteria: Powerhouse, Bradley Lake
Hydroelectric Project
1. 0 DESCRIPTION
1.1 GENERAL
The powerhouse will contain two 45-MW units with provisions to install a
third unit at a later date. Six jet vertical Pelton turbines will be
directly coupled to synchronous a-c generators. Water for the powerhouse
wi 11 be supplied by an 11-foot diameter power conduit, approximately
19,000 feet long. The power conduit manifolds into three branches immedi-
ately upstream of the powerhouse. This arrangement requires a spherical
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 2
valve to be provided for each of the initial two turbines and a pressure
closure head for the future third unit. Each unit will be equipped with
an electric-hydraulic governor.
1.2 CONTRACT PACKAGING
It is considered advantageous that the hydraulic turbines, generators,
governors, and spherical valves be awarded as one contract package
preferably to a hydraulic turbine manufacturer or a consortium of a
turbine and generator manufacturer. This arrangement will reduce inter-
facing problems, contract administration efforts, and assure a better
product in general. Any two or more identical items must be made by the
same manufacturer.
1.3 TURBINE/GENERATOR SIZING
The turbines will be sized so as to provide 135 MW on the high voltage
side of the transformers, with three units operating under mtntmum
operating reservoir El. 1080. The generators will be rated for maxtmum
power output of two turbines operating simultaneously under reservoir El.
1180 and tide below El. 6.0. Combined rating of two generators will be
the maximum output of the two unit powerhouse.
operating conditions of the units at full
TABLE 1, which summarizes
flow under key reservoir
levels, shows turbine rating as point C and generator rating as point K.
1.4 HYDRAULIC TURBINES
Although the design head 1s well within the range normally covered by
Francis turbines, Pelton turbines were selected for their flatter effi-
ciency curve and for preferred regulating features such as lower
overspeed and pressure rise caused by load rejection. Although the Pelton
has the ability to reject the load much faster than Francis turbines, the
rate to accept load will be limited by the possibility of an
underpressure in the power conduit.
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 3
The turbines will be rated at the net head of 920 feet when three units
operate at reservoir El. 1080 to produce 63,500 HP each or the total high r
voltage output of 135 MW. Synchronous speed will be specified at 300 rpm.
Efficiency at this point is expected in the order of 87.6 percent. Data
indicate the average reservoir level at El. 1155 which, with turbine
setting at El. 15 and the head loss of approximately 30 feet for the
average operating flow of 800 cfs, would result in the turbine design net
head of 1110 feet. Peak efficiency of the turbine (top of hi 11 chart)
should occur at, or as close as possible to, this head.
The turbines will be furnished with a welded steel spiral distributor
(spiral case), fully embedded in concrete. The tailrace gate will facili-
tate partial or complete dewatering of the turbine chamber. Runners will
be removable from below through the runner access gallery.
Three bearings will be provided for the turbine -generator shaft system.
These are: (1) turbine guide, (2) generator guide, and (3) combination
thrust/guide bearing on the top of the generator. This arrangement allows
for walking space in the turbine pit.
1.5 GOVERNORS
A digital electronic governor will be used. Control will be of PID type.
The governor will be equipped with automatic needle selection, and
independent speed supervision. Speed, power, and manual limit control
modes will be provided.
Governor electronics will be located in the Main Control Board. A single
panel section for each unit will contain the governor electronics, and
turbine control and monitoring devices. Each governor will be a separate
system and operate independently.
Deflector control will be the cut-in type. All deflectors operating 1n
parallel will continuously follow the edge of the water jet stream. On
small load changes the needles will modulate to control flow. On large
load reductions the deflector cuts in to reduce the flow directed on the
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 4
runner buckets at a fast rate. The needle closure follows at much slower
rate. The result is faster response time to load rejections even with the
long needle closing times required for Bradley Lake.
Each governor will have an independent oil system, consisting of an
accumulator tank, sump tank, dual oil pumps, controls, connecting piping,
and servomotors.
1.6 SPHERICAL VALVES
The spherical valve was selected as the only suitable shut off valve for
the head range experienced on the Bradley Lake Project.
The spherical valve will be rigidly connected to the penstock and will
have a sliding type coupling on the turbine side. A closure section on
the downstream side will accommodate an ultrasonic system for flow
measurement. A by-pass system will be provided to equalize pressure on
both sides of the valve prior to opening.
The plug will be opened by one single action, oil operated secvomotor and
closed by a counter-weight. The downstream operating seal of the valve
will be stainless steel copper alloy fixed type. The upstream
maintenance seal will be water operated.
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
TABLE 1
FULL LOAD DATA UNDER VARIOUS RESERVOIR ELEVATIONS
AND NUMBERS OF UNITS
Operating Point A B c D E
No. of Units 1 2 3 1 2
Reservoir El. 1080.0 1080.0 1080.0 1155.0 1155.0
Runner Centerline El. 15.0 15.0 15.0 15.0 15.0
Gross Head 1065.0 1065.0 1065.0 1140.0 1140 .o
Head Loss, ft 23.7 71.1 140.6 25.3 76.0
Net Head, ft 1041.3 993.9 924.4 1114. 7 1064.0
Tunnel Velocity, fps 7.61 14.88 21.52 7.88 15.39
Loss Coef (HL/Q2) 45.26 35.56 33.62 45.21 35.52
Station Serv. Pwr., MW 1.0 1.5 2.0 1.0 1.5
Total P-H Flow, cfs 723.6 1413.9 2045.3 748.6 1462.9
Turbine Eff, PCT 89.75 89.40 88.0 89.75 89.80
Needle Valv Opng, PCT 100 100 100 100 100
Turbine Flow, cfs 723.6 706.9 681.8 748.6 731.4
Turbine Power Out, kW 57222 53152 46925 63374 59135
Generator Eff, PCT 98.00 98.00 97.80 98.00 98.00
Generator MVA (p£=0.95) 59.0 54.8 48.3 65.4 61.0
Total H-V Output, MW 54.8 102.2 135 .o 60.8 113.8
Page 5
F
2
1155.0
15.0
1140.0
38.6
1101.4
10.96
35.52
1.5
1041.9
90.70
70
520.9
44036
97.85
45.4
84.3
00629C-1580072-D1 PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
TABLE 1
FULL LOAD DATA UNDER VARIOUS RESERVOIR ELEVATIONS
AND NUMBERS OF UNITS
Operating Point
No. of Units
Reservoir El.
Runner Centerline El.
Gross Head
Head Loss, ft
Net Head, ft
Tunnel Velocity, fps
Loss Coe£ (HL/Q2)
Station Serv. Pwr. MW
Total P-H Flow, cfs
Turbine Eff, PCT
Needle Valv Opng, PCT
Turbine Flow, cfs
Turbine Power Out,kW
Generator Ef£, PCT
Generator MVA (pf=0.95)
Total H-V Output, MW
Synchronous speed
Transformer efficiency
Power tunnel diameter
G
1
1190.6
15.0
1175.6
26.1
1149.5
8.00
45.18
1.0
760.3
89.50
100
760.3
66182
98.00
68.3
63.5
(Continued)
H I
2 3
1190.6 1190.6
15.0 15.0
1175.6 1175.6
78.3 155.3
1097.3 1020.3
15.63 22.61
35.50 33.63
1.5 2.0
1485.6 2148.8
89.80 89.65
100 100
742.8 716.3
61930 55439
98.00 98.00
63.9 57.2
119.3 160.2
Power tunnel length, approximately
300
99.5
11
19000
J
1
1180.0
15.0
1165.0
25.9
1139.1
7.96
45.19
1.0
756.8
89.60
100
756.8
65362
98.00
67.4
62.7
K
2
1180.0
15.0
1165 .o
77.6
1087.4
15.56
35.50
1.5
1478.8
89.80
100
739.4
61094
98.00
63.0
117.7
rpm
PCT
feet
feet
Page 6
L
3
1180.0
15.0
1165.0
153.9
1011.1
22.51
33.63
2.0
2139.1
89.55
100
713 .o
54630
98.00
56.4
157.8
00629C-1580072-D1 PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
2.0 TURBINE HEAD
2.1 WATER LEVELS AND TUNNEL DISCHARGE -TABLE 2
Tunnel Discharge -three units, full power,
-three units, full power,
-two units, full power,
Reservoir Levels -Maximum Flood
-Average Operating Level
-Normal Maximum Operating
-Normal Minimum Operating
-Emergency Drawdown Level
Tail race Levels -Highest Tide (estimated)
-Mean Higher High Water
-Mean High Water
-Mean Sea Level
-Mean Low Water
-Mean Lower Low Water
-Lowest Tide (estimated)
Storm surge wave height at the powerhouse:
(50 year recurrence interval)
Sustained wave height at the powerhouse:
El. 1180
El. 1080
El. 1080
Level
Level
El. 11.37
El. 4.78
El. 3.97
El. -4.02
El.-12.02
El.-13.63
El.-19.63
Maximum credible tsunami wave height (estimated)
Notes:
2140 cfs
2045 cfs
1415 cfs
El. 1190.6
El. 1155
El. 1180
El. 1080
El. 1060
Excd'nce
o.o %
5.5 %
8.5 %
50.0 %
87.5 %
93.0 %
100.0 %
El. 13.3
5 feet
25 feet
1. All elevations related to Bradley Lake Project Datum.
Page 7
2. For the tailrace exceedance curve, see Hydraulic Design Crite-
ria: Tailrace Channel.
00629C-1580072-D1 PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 8
2.2 HEAD LOSS CALCULATION
Friction losses 1n the power conduit were calculated for each flow
individually using Darcy-Wei sbach formula. Local losses for ent ranee,
trashracks, p1ers, bends, bifurcations, conversions and diversions were
established and added to the friction losses to determine the total head
loss.
The head loss 1s a significant factor 1n selecting the turbine rating. To
calculate the turbine flow, equations for head loss and energy have to be
solved simultaneously. Output at the turbine shaft must be 3x47.5 MW to
assure the net output of 135 MW on the HV terminals of the transformer.
This conditions must be met while operating under the minimum reservoir
level El. 1080. The following table summarizes the results of head loss
calculations:
TABLE 3
SUMMARY OF HEAD LOSS CALCULATION
No. of Units
Lake Level
Power Tunnel Discharge
Total Head Loss
Head Loss Coeff.
No. of Units
Lake Level
Power Tunnel Discharge
Total Head Loss
Head Loss Coeff.
3
El.1080
2079 cfs
145.3 ft
33.62
1
El.ll80
771 cfs
26.9 ft
45.20
3
El.ll90. 6
2184 cfs
160.5 ft
33.63
2
El.ll80
1505 cfs
80.4 ft
35.50
It was noted that the head loss coefficient varies with number of units
in operation and is almost constant for the entire range of reservoir
elevations.
00629C-1580072-D1 PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 9
2.3 DESIGN PRESSURE
Transient analyses have been performed to determine the max1mum and
minimum pressure in the power conduit and turbine intake during load
rejection and acceptance. The study further identified the most adverse
combination of operating conditions pnor to load rejection/acceptance
leading to the extreme pressure values:
Static Head
Normal Design Pressure
Emergency Pressure
TABLE 4
CONTROLLING PRESSURE HEADS
feet psi
1175 510
1470. 637
1950 845
Extreme Emergency Pressure 2350 1020
The above pressures are defined as follows:
PCT of PCT of
Static Design
Head Head
100 80
125 100
166 133
200 160
a. Normal Design Pressure includes maximum static head plus pressure
rise due to the normal operation, without malfunctioning of any
protective device or equipment component. The worst case would be a
simultaneous load rejection of three units, operating at full flow
at maximum reservoir elevation (El. 1190.6), resulting from a loss
of transmission lines. Based on the results from the transient
analysis the internal design pressure for normal operating condi-
tions was established as 1470 feet of water column (125 percent of
static head). Corresponding needle closing rate would be approxi-
mately 85 seconds.
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
NOTE:
Page 10
During execution of the Transient Analysis Study the Design
Pressure was reduced from 1650 feet (715 psi) to 1470 feet (637
psi). To facilitate this change, the turbine needle closing
rate had to be extended from 60 to 85 seconds. This longer
closing time would not objectionably impair regulation charac-
teristics of the turbines, however, the reduction of the design
pressure would bring over $860,000 worth of sav1ngs of the
penstock and liner steel.
b. Emergency Pressure includes normal operating conditions plus such
events as malfunctioning of the control system allowing simultaneous
needle valve closure, within 2L/a seconds at maximum rate, of three
units operating with s1x jets at the flood reservoir level. The
maximum allowable pressure for this category was established as 1950
feet (166 percent of static head).
c. Extreme Emergency Pressure includes malfunctioning of the control
system in the most adverse manner, such as instantaneous loss of
governor oil pressure, broken needle stem on one or more Pelton
jets, or auto oscillations due to equipment and interrelated systems
associated with the power conduit. The maximum allowable pressure
for this category will be 2350 feet (double the static head).
The spiral distributor, spherical valve, and other pressure vessels
will be designed by the equipment manufacturer using its design
criteria and approach methodology for the above pressure conditions.
Ninety six percent of Yield Tensile Strength (YTS) should not be
exceeded in any equipment component subjected to the Extreme
Emergency Pressure of 1020 psi.
3.0 OPERATION
3.1 OPERATION OF UNITS
The turbine-generator units should be operated with m1n1mum load changes,
especially load acceptance, due to the long opening rate required due to
the extremely long power conduit. Under normal conditions the units will
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 11
be started by an automatic sequence which will ensure orderly
start-up/ shut-down and speed adjustment with slow needle valve mot ion,
thus minimizing pressure variation in the tunnel. From time to time one
or more units may experience a load rejection, full or partial, depending
on circumstances. Simultaneous load rejection of all three units may
occur for var1ous possible system/plant conditions. Under normal condi-
tions the effects of load rejection will be minimized by rapid closure of
the deflectors with the needle valves to follow. If one or more needle
valves on one unit fail to close, the corresponding spherical valve will
close. This arrangement allows the remaining unit(s) to operate without
any restriction.
In the event that one or more needle valves have failed and the spherical
valve fails to close, the high pressure gate in the power intake shaft
would have to be closed. Initiation of gate closure will automatically
start the shutdown of all operating units.
3.2 REGULATION OF TURBINES
The turbines will have two means of regulation and closure: slowly
operating needle valves and fast operating deflectors. The design closing
and opening rate for the needle valves is 85 and 60 seconds respectively
for the three-unit arrangement. Both closing and opening rates for
deflectors are 1.5 seconds. This combination is specifically suitable for
a long power conduit where transient pressure may be a problem. In the
event of a load rejection the deflectors deflect the jet streams away
from the runner without changing the tunnel discharge and creating a
pressure rise. Closure of the needle valves, although completed in. a
considerably longer time (85 seconds) than closure of deflectors, produc-
es a pressure rise of approximately 25 percent above the static head when
three units are operating.
3.3 OPERATION OF SPHERICAL VALVES
Each unit will be equipped with a spherical valve located inside the
powerhouse upstream of the turbine intake. The valve will be capable of
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 12
emergency closure under full flow conditions. The preliminary
closing/opening rate of the valve is 120 seconds. This total closing time
could be reduced if two speeds are used. The valve wi 11 close on an
emergency close and overspeed signal. The spherical valve will be used to
isolate the unit for maintenance or in case of failure of one or more
needle valves. Closure of a spherical valve against flow would also
produce pressure rise. The closure rate for the valves will be so
designed and adjusted that the pressure r1se caused by the valve closure
will not exceed that caused by the combined needle valve closure.
During repairs and maintenance the unit will be shut down, the spherical
valve closed, upstream seal engaged and locked, and the turbine manifold
dewatered. Access to the inside of the turbine manifold will be possible
through a mandoor in the valve closure section between the valve and
turbine intake section.
3.4 SLUICING THROUGH THE TURBINES
The turbines will be able to operate within the lake level range from El.
1080 to El. 1190.6. In case of extreme emergency, the power tunnel may
be used to lower the lake level to El. 1060. If the equipment 1s
operational the units will operate on-line and generate power. For this
type of operation the needle closing and opening times as well as
spherical valve opening and closing times must be considerably extended
over the presently proposed values to prevent subatmospheric pressure 1n
the upper tunnel bend. The tunnel flow might have to be reduced to
prevent vortices at the intake. This issue must be addressed in the
Plant Operations Manual.
In case of damage to the electrical apparatus the units may be able to
spin but can not be synchronized and no power can be generated. Sluicing
with the runner at standstill, generator brakes applied, deflectors in
fully "cut-in" position, and the needle valves open as needed is pre-
ferred over running the unit at runaway conditions. Small to moderate
damage to the turbine, such as erosion to the turbine pit walls as well
as vibration damage to the deflector operating system, is expected. This
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 13
type of sluicing ope rat ion should therefore be used only to prevent
damage of large magnitude such as failure of the dam and should be
limited to the minimum.
3.5 FLOOD OPERATION
Turbine operation will be available during high flood flows, which result
in raising the reservoir level above El. 1180, without limitation.
4.0 DESIGN CONSIDERATIONS
4.1 HYDRAULIC TURBINES
4 .1.1 Runner
Runners will be made of 13-4 type stainless steel. They will be one p1ece
casting. The foundry chosen to cast the runner must demonstrate experi-
ence with similar work. The finished runners will be balanced statically
and dynamically at a reduced speed.
The runner will be removable from below to facilitate fast repa1rs. An
access gallery and a special cart will be required. One spare runner
will be provided for the project.
4.1.2 Shaft-Bearing System
A three bearing shaft system will be provided for each unit: turbine
guide, generator guide, and combination guide/thrust bearing on the top
of generator. There is virtually no vertical hydraulic thrust so the
thrust bearing has to support weight of rotating parts only. All bearings
will be oil lubricated, the oil will be self-circulated. A high pressure
oil pump will be provided for the start-up of the combination bearing.
Coolers for the combination and turbine guide bearings will be provided.
The turbine guide bearing will be sized to support the radial forces
created by a simultaneous operation of three adjacent jets. For this
00629C-1580072-D1 PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 14
reason a bearing cooler must be provided. The cooler will be used rarely.
For the purpose of sizing the cooling system, 30 gpm is assumed as the
max1mum cooling water requirement for the turbine guide bearing.
The same brand and type of oil will be used for the turbine, governor,
and spherical valve, A portable on-line oil purifier will be provided to
serve all these systems. Filling and drainage connections will be
provided.
4.1.3 Shaft Seal
A shaft seal 1s required for the operation when the tailrace chamber is
pressurized. The commonly used carbon ring seals are not suitable for
application at The Bradley Lake Project due to glacial flour suspended 1n
water. The particles may be highly abrasive and cause rapid wear of
stationary and moving seal components in contact.
A non-contact type seal,
water injection, will be
such as labyrinth or cylindrical type without
specified. If required by the manufacturer,
cooling water in the amount of approximately 10 gpm will be available
from the station service system.
4.1.4 Tailrace Depression System
A tailrace depression system will be provided to maintain the water level
in the turbine chamber at El. 6.0, should the tide r1se above El. 6.0.
This is to maintain a minimum required distance of 9 feet between the
runner centerline and the water level in the chamber. Operation of the
system will be infrequent, not exceeding 2.5 percent of the time. The
system will be designed for the max1mum tailrace chamber pressure of 7.0
feet of water column, corresponding to a tailwater level of approximately
El. 13.4. It will allow two foot waves (or the storm surge) on the top of
the highest tide (El. 11.37), or five foot waves plus two foot storm
surge on the top of the maximum tailrace operating level (El.6.0). It is
recognized that the fans will not be able to suppress completely surges
in the tailrace chamber caused by the waves in the tailrace. Should the
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 15
oscillation of the water level 1n the tailrace chamber create intolerable
power swings, the unit will be operated at a lower load or shut down. In
the case that the total of the tailrace level and waves exceeds El. 13.4,
the unit will be shut down.
The tailrace depression system will consist of two fans, one fan serving
each turbine. The system will allow admission of outside air when the
depression system is not in operation.
The system will be controlled automatically. When the level 1n the
tailrace chamber reaches El. 6.0, the corresponding compressor wi 11 be
started. A modulating valve will maintain the water level 1n the
tailrace chamber at El. 6.0.
4.1.5 Cooling Water System
The turbine manufacturer will provide suitable means of collecting fresh
water discharged from the turbines and storing it 1n a sump located
between Units No. 1 and 2. The theoretical m1n1mum amount of water
required for each turbine in operation is about 300 gpm.
The collecting device will be located at high as possible to m1n1m1ze
intrusion of brackish water into the cooling system and to assure re-
quired water quantity in the fresh water sump. Preferred elevation of the
collecting device is at El. 15.0. The lowest acceptable elevation is at
El. ll. 5.
The Specification will call for turbine guaranteed efficiency including a
water collecting device. A model development study will be conducted on a
fully or closely homologous model to determine the elevation, type, and
size of the water collecting device. It is believed that one or more
troughs can be located between elevations El. 11.5 and 15.0 and deliver
the maximum flow of 530 gpm for two turbines at all loads and heads.
Under normal conditions, no ingression of brackish water into the system
is expected when troughs are located within this range.
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 16
Should adjustment of the quantity of water collected by the troughs be
necessary, the troughs can be made smaller or larger, their number
increased or reduced, or their elevation raised or lowered as the case
may be providing that loss of turbine efficiency will not take place. In
any case the troughs must remain above El. 6.0 (higher high tide) to
limit frequency of potential salt water intrusion and to satisfy equation
(1) for any operating conditions.
A two-circuit closed loop cooling water system with heat exchangers will
be provided. Circulating water pumps will pump water from the sump
through a heat exchanger and discharge it to the tailrace. Component
cooling water pumps serving a closed component cooling water loop will
circulate fresh water through the heat exchanger and the equipment
coolers.
4.1.6 Spiral Distributor
The spiral distributor will be of steel welded construction, and will be
designed by the turbine manufacturer to withstand the internal pressure
as per TABLE 4 without contribution from the surrounding concrete.
Branches with flanges will be provided to receive the needle valves. The
distributor will be shipped in sections and assembled by welding 1n the
field. Connection by flanges will be allowed as an alternative.
After assembly and pr1or to concreting, each distributor will be pressure
tested to 150 percent of normal design pressure (1.5 x 637 = 956 psi). A
bulkhead must be provided for the turbine inlet flange since the pressure
test will be carried out without the spherical valve. Bulkheads should
also be used to seal the branches, rather than use the needle valves.
The distributor will be pressurized during concreting to full static head
(1175 feet).
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 17
4.1.7 Runner Chamber
The runner chamber wi 11 be of hexagonal shape, a steel liner, fully
embeded in concrete will be provided. Blackouts will be provided in the
first stage concrete for installation of the liner. The liner will be
heavily ribbed and anchored to the concrete. It will be designed to
withstand a hydrostatic pressure of 50 feet acting from the tailrace and
resulting from the most adverse combination of tide, waves, storm, and
tsunami.
4.1.8 Needle Valves
Needle valves of built in straight flow type will be mounted on the pipes
branching off the spiral distributor. Each valve will have a built in
servomotor and a control unit mounted on the turbine cover. Needle valve
servomotors will be oil to open and oil to close. The needle valves will
be designed to close in case of oil pressure loss. Pressure oil will be
distributed from the governor accumulator tank to the individual control
units and used oil will be piped back to the governor oil sump. Leakage
oil from the servomotor seals will be collected to the powerhouse dirty
water sump.
The needles will be operated symmetrically by the governor in a preset
sequence. The number of jets in operation wi 11 depend on the load and
will also be automatically selected by the governor. Needles in steady
state operation will be in the same opening position resulting 1n the
same discharge and diameter of the water jet stream. Needle closing and
opening times will be adjustable within the range of 60 to 300 seconds.
Closing and opening rates to be used for operation of two units are
expected to be the same, in the order of 60 seconds.
4.1.9 Deflectors
Deflectors will be operated by a single servomotor v1a a common linkage.
Deflector control will be oil to open and oil to close. The deflectors
will have opening and closing rate adjustable within 1.5 to 5 seconds.
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 18
4.1.10 Instrumentation
The ultrasonic method of measurement will be used for continuous flow
moni taring. A four paths system supplied by a preselected manufacturer
will be specified. Two measurement sections will be provided for each
unit.
Four piezometers for head measurement installed at the turbine inlet will
be provided for each unit. All piezometer piping will be stainless steel
tubing and will terminate above El. 21.0.
4.2 SPHERICAL VALVES
4.2.1 Valve Body
The spherical valve body will be a combination of cast and fabricated
construction. The body will be split in halves, flanged and connected by
bolts. The valve body will be attached by suitable bolts to the base
plate. Slotted holes will be provided to allow axial movement of the
valve up to 3/4 inch.
4.2.2 Connecting Pipes
The spherical valve will be rigidly connected to the penstock on the
upstream side. The valve manufacturer will provide a short length pipe
extension on the upstream side made of A710 steel, the same material as
the penstock. The pipe will have a flange for connection to the upstream
face of the valve and will be welded to the downstream end of the
penstock. The length of the pipe will include allowance for trimming. The
valve manufacturer will be responsible for the design of the weld between
the extension pipe and the penstock. The weld will be performed by the
Powerhouse Contractor. The penstock 1s anchored approximately 40 feet
upstream of the valve. The portion of the penstock downstream of the
anchor will be allowed to expand freely which will result in an axial
movement of the valve, calculated for the exposed pipe, extreme emergency
penstock pressure, and the temperature extremes, to be 1/2 inch.
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 19
A closure section will be flanged to the downstream face of the valve and
will have a high pressure sliding type coupling on the turbine side. The
closure section on the downstream side of the spherical valve will
accommodate the ultrasonic system for flow measurement.
4.2.3 By-Pass System
A by-pass system will be provided to equalize pressure on both sides of
the valve prior to opening. An internal by-pass conduit or an external
system tapped between valve seals will be specified to minimize exposed
pressure piping. The by-pass valve will be operated hydraulically, using
governor oil. The valve will have a strong closing tendency and a spring
will be provided to assure that the by-pass valve will close on loss of
governor pressure.
4.2.4 Oil Pressure System
The valve plug will be operated by one single action, oil to open
counter-weight to close servomotor. Governor oil will be used to· open
the valve. In case of governor oil pressure loss the counter-weight will
safely close the valve. An anti-slamming device will be provided in the
servomotor cylinder.
4.2.5 Valve Seals
The downstream operating seal of the valve will be fixed metal-to-metal
(stainless steel to copper alloy) type. It will close and seal by
eccentric motion of the valve rotor. No moveable parts or operating
media (oil, water) will be used. It is believed that this arrangement
will eliminate the possibility of auto-oscilation in the power tunnel.
The upstream seal will be used for maintenance only, will be manually
operated with the valve closed, and will be water operated. The mainte-
nance seal will be equipped with a manually activated mechanical device
to lock the seal 1n engaged position to max1m1ze safety during the
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
Page 20
maintenance period when the spiral distributor 1s dewatered and the
mandoor is open.
00629C-1580072-Dl PERFORMANCE CRITERIA/TURBINES, GOVERNORS, VALVES
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J.O. No. 15800
HYDRAULIC DESIGN CRITERIA
SPILLWAY
REVISION: 3
DATE: JANUARY 27, 1988
STONE & WEBSTER ENGINEERING CORPORATION
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 1
TABLE OF CONTENTS
l.O Description
2.0 Operation
3.0 Design Conditions
4.0 Design Considerations
5.0 Spillway Stability Analysis Criteria
6.0 References
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 2
SPILLWAY DESIGN CRITERIA
1 • 0 DESCRIPTION
The spillway will allow for ungated releases of water when the lake level
is above the spillway crest (El 1180) and will accommodate flood flows
including the Probable Maximum Flood (PMF).
The spillway will be constructed in the low saddle area to the right of the
right abutment of the dam (looking downstream). This saddle is formed by a
knob of rock that forms the right dam abutment and a rock face on the
right. Non-overflow sections will connect the spillway to the rock knob
and to the rock face. The crest of the spillway will be generally in line
with and parallel to the main dam axis.
The geometry of the ogee crest section will be uniform and level. The
spillway will consist of two concrete overflow sections, each designed to
discharge to a different downstream elevation. The spillway apron will be
at El 1165 for 70 feet of width and El 1135 for 105 feet of width. This
design is developed to minimize quantities of rock excavation and concrete
for the construction of the spillway.
Vertical rock cuts at the left and right limits of the apron will be lined
with concrete walls~ 2 feet 6 inches thick to prevent erosion and
undercutting of the rock. The height of walls shall provide a minimum
freeboard of 2 feet above anticipated flow levels.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 3
Similarly the vertical rock face between the upper and lower spillway
aprons will be protected from erosion by a concrete protective wall. These
walls will be tied to the rock with rock bolts.
The natural rock formations downstream of the spillway are considered
suitable to guide water discharged by the spillway into the downstream
pool. Overburden will be removed from this area, but no significant rock
excavation will be required. The rock immediately downstream from the
spillway apron will be excavated to provide a sloped surface away from the
apron to maintain supercritical flow at all high spillway discharges. This
will eliminate the risk of scouring at the apron toe due to hydraulic jump
formation.
2.0 OPERATION
Flow discharges over the spillway will depend on the lake level. The
spillway will be designed to accommodate flows within the range from zero
flow (at or below El 1180) to the Probable Maximum Flood (PMF) flow of
23,800 cfs (at El 1190.6).
Water leaving the spillway apron will follow the existing rock surface and
will be deflected by the end of the east training wall westward into the
downstream pool area, where rip-rap protection and excavated rock surfaces
will provide controlled energy dissipation.
All data will be calculated and confirmed by a model test program.
(Note: Model test for Spillway has been completed and is reported in
Reference 15.)
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
3.0 DESIGN CONDITIONS
Spillway Crest Elevation (ft)
PMF Reservoir Elevation (ft)
PMF Quantity of Flow (cfs)
Spillway Crest Width (ft)
Radius of Abutment Approach (ft)
Slope of Upstream Spillway Face (Min)
Slope of Downstream Spillway Face (Min)
Spillway Apron Length from Lower Ogee
Point of Tangency (ft)
Spillway Nappe Configuration to be based on
1180.0
1190.6
23,800
175
4
3H: lOV
8H: lOV
s.o
Figure 247 on page 374 of Design of Small Dams,
Reference 1. The layout of the spillway is
shown on Dwg. l5800-FC-201A.
4.0 DESIGN CONSIDERATIONS
Hydraulic
Page 4
Routing of the Probable Maximum Flood (PMF) inflow hydrograph through the
lake and spillway shall be performed. This will confirm analytically the
preliminary spillway design data: (1) PMF outflow, (2) spillway crest
elevation, (3) spillway width. The proposed model test will confirm the
spillway design experimentally.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 5
Geotechnical
The top o£ rock elevations are shown on drawing 15800-FY-182A. The
pre£erred alignment o£ the spillway is that the spillway baseline will
generally be an extension o£ the dam baseline to provide for continuity o£
grout and drain curtains.
The rock knob between the dam and spillway is to be levelled to El 1195 to
match the top o£ spillway non-overflow section. A breakwall portion of rock
will be left in place on the upstream side.
Overburden downstream from the spillway will need to be removed so that the
diversion channel will not be affected by deposition of sediment. The
excavation limits will be confirmed by the model tests and calculations.
Rock may have to be removed downstream of the spillway apron to provide a
final grade sloping away from the apron and to avoid flow concentrations.
One line of grout holes will be drilled at a 30° angle from the vertical,
inclined upstream (south). First-stage primary holes (P 1 ) will be
drilled to a depth equal to 2/3 the maximum head (El 1190) at the hole
location and will be spaced on 20 foot centers. Secondary-stage primary
holes (p 2 > will be 1/2 the maximum head and will also be on 20 foot
centers; however, these centers will split the spacing between P1 holes,
reducing overall primary spacing to 10 £oat centers. Where needed,
secondary (S) holes and tertiary (T) holes to 1/3 maximum head will be used
to further reduce the spacing to 5 feet and 2.5 feet, respectively.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 6
Tertiary holes may be drilled off of the curtain centerline if it is
necessary to intersect a particular geologic feature. The minimum depth
for any hole is 30 feet and a fan pattern will be used at the base of the
right abutment. These grout holes will be located upstream of the base
line of the spillway between points "AAA" and "BBB" and slightly downstream
east and west of those points.
One line of vertical drainage holes will be drilled in the rock. The holes
will be 30 feet deep. A fan pattern at the base of the right abutment will
incorporate 40 foot and 50 foot holes. These drainage holes will connect
to the drainage trench in the drainage/inspection gallery located in the
base of the spillway at or near the concrete/rock interface.
A transverse drain outlet pipe will lead from the drainage/inspection
gallery to a point downstream of the spillway apron. The transverse drain
will be provided with cleanout access and with a measuring weir to monitor
flow from drains. The drain pipe shall be double-walled with insulation
between the walls. To prevent freezing due to slow drainage discharge and
to prevent cold air from entering the spillway gallery through the drain
pipe, an automatic siphon and a backwater valve shall be provided at the
upstream end of the drain pipe.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 7
Concrete
The spillway will be constructed of a mass concrete core with a specified
compressive strength of 3,000 psi at 28 days and a 3 ft or more thick outer
shell of concrete as shown on 15800-FC-201A with a specified compressive
strength of 4,000 psi at 28 days. The core and the shell shall be designed
to act monolithically and the higher strength of the shell may be neglected
in the analysis.
may be located
Vertical concrete contraction joints shall be keyed and
at a maximum spacing of sixty feet. Each vertical
contraction joint will have a vertical rubber or PVC bulb type waterstop
which is located near the upstream face of all spillway and non-overflow
sections. Each horizontal construction joint shall have a horizontal
waterstop which is to be joined to the vertical waterstop. The vertical
waterstop at the spillway sections will extend over and down the nappe of
the spillway.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 8
5.0 SPILLWAY STABILITY ANALYSIS CRITERIA
METHOD OF ANALYSIS
A. Overturning Analysis
The static stability analysis will be performed by the gravity method
as presented in the Design of Small Dams (Reference 1) and in
accordance with the requirements of "Engineering Guidelines for the
Evaluation of Hydropower Projectsu (Reference 13). The analysis will
indicate the location of the resultant, area of the base in
compression, and foundation pressure for each loading condition
investigated. Stresses with and without uplift shall be reported.
Stresses should be computed without uplift and the net pressures
determined by adding the uplift pressure at each point to the computed
stress.
Since the seismic coefficient for the project is greater than 0.2g, a
dynamic response analysis will be required. (See References 9 and
13.) The dynamic stress analysis will be performed by the finite
element method of analysis.
B. Sliding Analysis
Sliding resistance of the structure for Usual and Unusual Conditions
will be investigated by means of the shear-friction factor of safety
formula.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Q = CA + N Tan 0
H
where Q = Shear Friction Factor of Safety
c = Unit Cohesion = 300 psi Concrete on Concrete
at Lift Lines
= 160 psi Concrete on Rock
A = Area Base Section in Contact (uncracked
section)
Page 9
N = Summation of Normal Loads Including Uplift
Effect
0 = Internal Friction Angle
45° Concrete at Lift Lines
45° Concrete on Rock
H = Summation Horizontal Shearing Loads
The base o£ the spillway section shall be embedded at least two
feet into rock. However, the passive resistance of this downstream
layer of rock cannot be utilized for sliding resistance since the
supporting rock downstream of the spillway apron is subject to
water scouring and will be excavated to provide a sloping surface
away from the spillway apron.
The ~ynamic sliding stability will be evaluated by the SARMA method
(Reference 14), neglecting cohesion at the rock-concrete interface,
to determine maximum displacement.
3l27R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 10
ACCEPTANCE CRITERIA
The following factors of safety apply to the calculated stress and sliding
within the structure, at the rock-concrete interface, and within the rock,
on an average basis. If higher stresses occur, then a detailed rock
condition analysis will be required.
Loading Cases as Defined on Page 13 and 14
Stresses:
Concrete (3000 psi)
Safety factor
Compression, psi
Tension psi*
Rock (40 ksf=280 psi)
Safety Factor
Compression, psi
Tension, psi*
Sliding:
Case I
Normal
3.0
1000
60
2.0
140
0
Shear -Friction in Concrete
Safety Factor 3.0
(in Concrete and at
Rock/Concrete Interface)
Case II
PMF
2.0
1500
90
1.5
185
0
2.0
On Rock Foundation Joints and Faults
Safety Factor 4.0 3.0
Case III
Earthquake
1.0
3000
270
1.1
250
*
1.0
1.2
Case IV
Construction
2.0
1500
90
1.5
185
0
2.0
3.0
Case V
Low
Reservoir
1.0
3000
270
1.1
250
*
1.0
1.2
*For Usual and Unusual Conditions, tensile resistance is allowed only above
the rock-concrete interface. For dynamic stress analysis by the finite
element method, the tensile stress at the rock-concrete interface shall not
exceed the allowable tensile capacity of the concrete. Tensile capacity of
concrete is increased SO percent above static tensile capacity for dynamic
loading conditions.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 11
Overturning
The spillway will be considered stable against overturning provided that
the calculated stresses for Usual and Unusual Conditions, not including
uplift, meet the allowable compressive stress on the downstream face and
that the calculated stress on the upstream face is greater than:
Minimum Allowable Stress = wh -ft (at the Upstream Face)
where
w = unit weight of water
h = depth below reservoir surface
ft = allowable tensile strength of concrete at lift surfaces
which includes the safety factor as given above for
concrete; zero at rock-concrete interface
This formula is modified from that shown in Design of Gravity Dams, page 31
(Reference 2). For all Usual and Unusual Conditions the calculated stress
on the upstream face shall not be less than zero. If these conditions are
not met, then a cracked section analysis is required utilizing steel
reinforcement to resist tensile stresses.
RESERVOIR OPERATION
Normal Max -
PMF Flood
Minimum
3127R/CG
1180.0'
1190.6'
1080.0' (below base) Minimum for Generation
HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 12
TAILWATER ELEVATION
Minimum
PMF Flood
1060.0'
-Hydrodynamic loads from tailwater assumed
negligible for stability consideration
UPLIFT AND SEEPAGE
At Base
Internal
100% of full reservoir pressure at the upstream
face varying linearly to 50% reservoir pressure at
the drains (Reference 9), 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
.condition 9 uplift pressure· at the upstream face
shall be taken to be 100% of the maximum water
level reservoir pressure.
100% of the full reservoir pressure at the
upstream face decreasing linearly to zero at
downstream face
-For (PMF) Flood Discharge Condition the uplift
should be assumed to vary from 100% normal water
surface headwater pressure plus 50% of head rise
due to flood at the upstream face, decreasing
linearly to zero at the downstream face.
Uplift shall be assumed to act over 100% of base area.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 13
When the computed stress, without uplift, does not meet the minimum
allowable stress (Overturning, p. 10), then the section shall be
assumed to crack and the uplift on that portion of the section not in
compression shall be assumed to be 100% of the upstream head, except
when the non-compressive stress is the result of earthquake forces.
During the earthquake loading condition the uplift is not revised from
that used in the normal operating condition.
Reinforcement may be provided in the concrete at the upstream face to
help resist ice and/or earthquake forces, and will be required when ~
cracked concrete section is assumed.
DEAD WEIGHTS
SILT
ICE
Concrete -145 lbs/it 3
Water -62.4 lbs/ft 3
No silt loads
12 kips/lf applied at El 1179 (based on 28" ice thickness)
(References 1 & 13)
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 14
EARTHQUAKE
Horizontal earthquake loads shall be based on the response spectrtun
given in the Geotechnical Design Criteria with a normalized horizontal
rock acceleration of 0. 75g representing the Maximum Credible
Earthquake (MCE). The construction condition shall consider a
pseudostatic horizontal acceleration of O.lg. Additional reservoir
water loading during earthquake conditions should be based on the
Westergaard added mass approach or other sui table model for reservoir
interaction. Vertical earthquake ground motions are asstuned equal to
2/3 the horizontal motions. Dynamic analysis for seismic affects will
consider the horizontal and vertical seismic forces to act
simultaneously.
TEMPERATURE (AIR)
WIND
Minimum -38° F
Maximum +85° F
Refer to Structural Design Criteria.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 15
LOADING COMBINATIONS
Case I Usual Condition-Normal Reservoir
1. Normal Max. Res. El 1180.0
2. Uplift and Seepage Forces
3. Dead Loads
4. Ice at El 1179.0
Note: Where a cracked section condition occurs due to ice load, the
section shall also be analyzed without ice to determine stresses.
Case II
Case III
Case IV
3127R/CG
Unusual Condition -Probable Maximum Flood (PMF)
1. Max. Res. El 1190.6
2. Uplift and Seepage Forces
3. Dead Loads
Extreme Condition -Earthquake
1. Normal Max. Res. El 1180.0
2. Uplift and Seepage Forces
3 . Dead Loads
4. Ice at El 1179.0
5. Maximum Credible Earthquake (0.75g)
Unusual Condition-Construction Case
1.
2.
3.
Reservoir Water Surface at El 1065.0
Dead Weight
Construction Earthquake (O.lg) or Wind
HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 16
Case V Extreme Condition-Low Reservoir with Earthquake
1. Reservoir below El 1124
2. Dead Loads
3. Maximum Credible Earthquake (0.7Sg)
6.0 REFERENCES
1. "Design of Small Dams", 2nd Ed 1973, Revised Reprint 1977.
Chapter VIII, U.S. Bureau of Reclamation.
2. "Design of Gravity Dams", 1976 Ed., U.S. Bureau of Reclamation.
3. Document No. ER-111-2-1806, "Earthquake Design and Analysis for
Corps of Engineers Dams", April 1977.
4. Code of Federal Regulations, Title 33, Chapter II, Section 222.8,
Appendix D.
5. "Gravity Dam Design", Corps of Engineers, Engineering and Design
Manual EM-1110-2-2200, September 25, 1958.
6. "United States Practice in the Design and Construction of Arch,
Embankment, and Concrete Gravity Dams", Joint ASCE-USCOLD
Committee, 1967.
7 • Creager , W. P. and Jus tin, Joel D. , "Hydroe 1 ec t ric Hand book" ,
Second Edition, Chapter 17, pp. 317-378.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
Page 17
8. Stone & Webster Hydraulic Technical Guideline HTG-108-0, titled
"Concrete Gravity Dams", dated August 25, 1985.
9. Federal Energy Regulatory Commission Guideline titled "Stability
Criteria of Existing Concrete Gravity Dams", dated November 7,
1985.
10. Geotechnical Design Criteria, Bradley Lake Hydroelectric Project.
11. Structural Design Criteria, Bradley Lake Hydroelectric Project.
12. General Project Information and Civil Design Criteria, Bradley
Lake Hydroelectric Project.
13. Federal Energy Regulatory Commission, "Engineering Guidelines for
the Evaluation of Hydropower Projects", FERC 0119-1, July 1987.
14. Seismic Amplification Response by Modal Analysys, "SARMA", SWEC
Program GT-055, Version 01, Level 00, September 1986.
15. Report on Hydraulic Model Study of Bradley Lake Hydroelectric
Project, Colorado State University, January 1987.
3127R/CG HYDRAULIC DESIGN CRITERIA:SPILLWAY
2-464-JJ
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J. 0. NO. 15800
POWER INTAKE, TUNNEL AND PENSTOCK
HYDRAULIC DESIGN CRITERIA
REVISION 1
DATE: JANUARY 30, 1987
HYDRAULIC DESIGN CRITERIA/POWER TUNNEL
SECTION
OBJECTIVES
REFERENCES
1 . 0 DESCRIPTION
1.1 General
1.2 Intake Channel
1.3 Intake Structure
1.4 Intake Tunnel
1 .5 Gate Shaft
TABLE Of CONTENTS
1.6 High Pressure Gates
1.7 Power Tunnel
1. 8 Penstock
1.9 Turbines and Valves
2.0 OPERATION
2.1 Lake Levels and Tunnel Discharge
2.2 Turbines and Generators
2.3 Maintenance of the Tunnel
3. 0 HEAD LOSS
3.1 Preliminary Calculation
3.2 Method for Final Calculation
4.0 TRANSIENT ANALYSIS
4.1 Scope of Analysis
4.2 Load Rejection
4.3 Load Acceptance
Page No.
2
2
2
3
4
4
5
6
7
8
9
9
9
10
11
11
11
12
12
12
15
2-464-JJ HYDRAULIC DESIGN CRITERIA/POWER TUNNEL
Page 1
OBJECTIVES
The main objective of this criteria is to provide basic guidelines for
hydraulic design of the power conduit. The document addresses general
configuration of the conduit, transient analysis as means to determine
the internal design pressure, calculation of head loss, and selection
of equipment. These criteria are supplemented by structural and
geotechnical design criteria on the same subject.
REFERENCES
1. FERC License Application for Bradley Lake H-E Project
2. Gordon: Practical Aspects of Steel Design, GSA 1970
3. Arthur & Walker: New Design Criteria for USBR Penstocks, ASCE 1970
4. Idel 1 chik: Handbook of Hydraulic Resistance, Coefficients of Local
Resistance and of Friction, 1968
5. Steel Liner and Penstock Structural Design Criteria, Bradley Lake
HEP, 1986
6. USBR: Friction Factors for Large Conduits Flowing Full, Eng l-lono
n
7. Escher Wyss: Distributor Pipes, Bulletin
8. USBR: Welded Steel Penstocks, Engineering Monograph 43
9. USBR: Design Standards No.6 -Turbines and Pumps
10. USBR: Air-Water Flow in Hydraulic Structures -Eng Mono #41
11. USBR: Design of Small Dams
12. Crane Company: Engineering Data VC-1900B
13. Davis/Sorensen: Handbook of Applied Hydraulics
2-464-JJ HYDRAULIC DESIGN CRITERIA/POWER TUNNEL
Page 2
1 . 0 DESCRIPTION
1.1 General
The waterways which will supply water from Bradley Lake to the
hydraulic turbines will consist of:
Intake channel
Concrete intake structure including trashracks and bulkheac
gates
Circular shaped intake tunnel, concrete lined I
Dry well type gate shaft including two high pressure sliding
gates
Concrete lined circular tunnel, including inclined shaft
Steel lined circular tunnel
Steel penstock (manifold) including three branches and one
access adit
The powerhouse will contain two 45 MW turbine -generator units with
provision for an addition of a third unit. The turbines are vertical
shaft, impulse (Pelton) type, directly coupled to the generator. Each
turbine will be furnished with a spherical valve.
1.2 Intake Channel
The intake channel will be approximately 250 feet long and 60 feet wide
at the portal. An invert El. 1030 was selected to assure adequate
submergence of the intake and to allow drawing the reservoir down to
El. 1060 as may be required for maintenance of the dam. This
arrangement also results in a flow velocity in the channel of less than
one foot/second dW'ing full power generation and two feet/second \·Then
the reservoir is drawn down below El. 1080. A rock trap is proposed in
front of the intake structW'e. DW'ing construction of the channel and
the power conduit water will be blocked from entering the work area by
an unexcavated rock plug section on the lake side of the channel. Thi~
2-464-JJ HYDRAULIC DESIGN CRITERIA/PO\,IE:i TUNNEL
Page 3
plug will be removed upon completion of the power conduit. Underwater
blasting and clamshell removal of blast material is proposed for tliL;
task. These operations will be done at "no flow" conditions.
Bydraulic model tests of the intake channel and the intake structure
will be undertaken, to confirm the preliminary configuration and
demonstrate acceptable flow conditions. The primary interest ~<ill be
focused on formation of vortices in the vicinity of the inta1~e openin[
while operating at low reservoir levels.
1.3 Intake Structure
The proposed concrete intake structure will form a gradual contracting
transition varying from a rectangular shape at the intake to a circular
section, where it connects with the upper run of the power tunnel as
shown on the sketch 15500-FC-S151A. The invert elevation of the intake
structure and the upper run of the power tunnel will be set at Sl.
1030. A 21-foot long center pier will be provided for structuraJ
purposes. The inner surfaces of the structure will be designed to
minimize hydraulic losses, while maintaining the formwork as simple aB
possible. The entire intake opening will be submerged below t~e
minimum reservoir El.1080 by 20 feet to prevent air entrainment dur~~~
generation.
Trashracks will be installed in slots on the face of the structure.
Flat bars will be used and arranged in panels and supported in the
guides at the sides of the intake structure and at the nose of the
center pier. Clear opening between the bars will be two inches, a
dimension compatible with the vendor data received. Maximum flow D
velocity through the gross trashrack area will not exceed 2.5
feet/second under full generating flow for three unit operation.
Trashrack loss will be calculated in accordance with Reference 11. lio
rakes for trashrack cleaning will be provided. Cleaning, if necessary,
will be done at low reservoir levels.
2-464-JJ I:!YDRAULIC DESIGN CRITERIA/POHER TUNI'!EL
Pase 4
The trashrack panels will be removable for purposes of maintenance.
Services of a diver will be required for trash rack clE-a:1:r:.::; ,,_r;,j
EJaintenance.
Gate slots will be provided immediately downstream of the trashrack3.
Steel bulkhead gates may be lowered into these slots for inspection of
the intake tunnel or in case of emergency. Since the center ,
extends beyond the gate flow section, two sets of slots an<.i t•..:o
bulkhead gates installed side by side Hill be required. The gate slct
opening is to be made identical to that of the diversion tunnel to
facilitate interchangeability of the bulkhead gates. Removable
concrete gate slot covers will be used to close off the top of the
bulkhead gate slot to prevent cross-flow condition and entry of tr·a~•lJ
when the gates are removed. Similarly as with the trash racks, tbt:::
bul:.Chead gates will be accessible only during low reservoir levels.
1.4 Intake Tunnel
The intake tunnel will be concrete lined and its finished floH ~:ectic'n
will be circular, 11-foot diameter. It will be approximately 650 feet
long, connecting the intake structure and the gate shaft. This portion
of the power tunnel is horizontal, with the invert at 21. 0. Ref:ll
and vent piping will be provided. For the purposes of friction loss
calculation absolute roughness of the tunnel inner surface of 0. OOC5
feet will be assumed.
1 .5 Gate Shaft
A vertical, dry well type gate shaft will be located at the end of the
horizontal tunnel run. The gate shaft shall be sized to accanl!lodate
two high pressure gates which will provide a means of eElergency
closure. The flow section at the gates will be rectangular.
Appropriate transitions will be provided upstream and downstream of the
gate to improve local hydraulics. The shaft will be approximately 160
feet deep, of circular cross-section, and concrete lined. r~iameter of
2-464-JJ HYDRAULIC DESIGN CRITERIA/POH:::r. TUU!'!EL
Page 5
the shaft will be sufficient as to allow lift of the gates, leafs, and
related ectuipment through the shaft. An adequate venting systec: ·..;Hl
be provided to above ground level on the downstream side of each gate
to prevent separation of water column. The tunnel venting systew shall
be designed in accordance with Reference 10. An access will be
provided to allow entrance to the circular part of the power tunnel,
downstream of the gates.
1 .6 High Pressure Gates
The gates will be installed in series. The downstream gate will act as
the control gate, it will be used in the event of emergency to close
off the full flow in the tunnel. The upstream gate will act as the
guard gate. It will be used in the event the downstream gate fails or
if there is a need to service the downstream gate. Both gates ,;ill be
closed during tunnel maintenance. A by-pass pipe and a valve will Ol,
provided to fill the tunnel after maintenance 1tTith the control gate
closed.
The gates will be sliding type, approximately 8.5 feet ;ville and 11 feet
high, designed for a static head of 160 feet, full generating flow cf
three turbine-generator units, hydraulic transient conditions and other
forces resulting from operation, such as down pull, etc. Design of botii
gates will be essentially the same. Each gate will be operated by one
hydraulic cylinder, oil actuated, with the design pressure of 2000 psi.
The gate speed will be 1 foot per minute with the total closing/openin~
time of approximately 11 minutes. The cylinders and associated
equipment will be located in the gate house at the top of the well.
A bank of accumulators will be provided as the pressure source for the
hydraulic system. The oil accumulator system will be sized as tc
operate each gate in one full stroke (close) without recharging. One I
electric motor operated pump will be provided.
2-464-JJ HYDRAULIC DESIGN CRITERIA/POH:SR TU!J~!~L
Page 6
Single phase motors will be used. Single phase motors are available in
ratings less than three horsepower. This limitation, will extend the
time required to pressurize the accumulator oil system to approximately
two hours. An additional engine-pump will be provided for back-up.
The gates will be operated locally from a panel in the gatehouse. The
gate closure can be initiated by an "emergency close" signal from the
powerhouse.
Electric power will be drawn from a single phase power cable run from
the permanent camp. This cable will also provide power for heating and
lighting. A communications cable will run in parallel with the power
cable. The gates will close in case of the communication cable
failure. Battery powered emergency lighting will be provided for the
event of the power failure. An independent battery and inverter
back-up system for control power will be provided. Outside receptacle
for emergency connection will be provided. In addition a manual start
diesel generator will be provided for extended outages.
1.7 Power Tunnel
The power tunnel will extend downstream of the gate shaft as an 11 foot
diameter circular concrete lined conduit, approximately 18,000 feet
long. The upper 15,400 feet will be concrete lined and the remaining
2600 feet will be steel lined. An 11-foot nominal diameter will be
used, based on the economic diameter evaluation studies and preliminary
results of the transient analysis. The tunnel will continue
horizontally, downstream of the gate shaft, for about 150 feet to a
bend that connects to a 850-foot shaft, inclined at 55 degrees with
horizontal. The lower bend of the inclined shaft connects to the main
power tunnel run at El. 310. Both the lower and upper bend will be
designed with a centerline radius of 40 feet. The main power tunnel
run will also be 11 feet in diameter and concrete lined. The power
tunnel slopes at a constant slope of 0.01667 between the lower bend and
the powerhouse. The last 2600 feet of the power tunnel will be steel
lined to resist the internal pressure in areas of shallow rock cover.
This arrangement is known as Option A.
2-464-JJ HYDRAULIC DESIGN CRITERIA/POWER TUNNEL
Page 7
The Contractor will be allowed to submit an alternative bid for a
vertical shaft (Option B) or an inclined tunnel with a slope of 6. 6
percent (Option C). The design and the relevant analyses will address
the 11-foot diameter, 55° inclined shaft option. The Contractor Hill be
penalized for increased head loss in the. tunnel, if applicable. The
Contractor will also be allowed to bid a tunnel diameter within thE-
range of 11 to 13 feet. This variation in the tunnel diameter will be
confined between the gate shaft and upstream end of the steel liner.
The Bids will receive an energy evaluation for larger tunnel diameters.
The tunnel will be designed for hydrodynamic forces at bends and
bifurcations. The inner surface of the 11-foot I.D. steel liner will
be painted with coal tar epoxy paint of a non-toxic type to protect
against corrosion. Maximum velocity in the tunnel should not exceed 25
feet/second. Surface roughness for the head loss calculation will be
assumed as 0.0005 feet for concrete and painted steel surfaces.
1.8 Penstock
A steel penstock-manifold system will connect the power tunnel and the
turbine-spherical valve units. The penstock consists of three
bifurcations, interconnecting piping, and three branch pipes. The
inlet diameter of the penstock is 11 feet (I. D.). The diameter of the
pipes between the bifurcations is 9 1 -0" (I. D.). The 9 1 -0" diameter
pipe continues beyond the branch for Unit No. 1 and will be used for
access to the tunnel for maintenance. A high pressure elliptical head
will be bolted on the downstream end of the extension pipe. The
diameter of the branch pipes connecting the individual units will be
6 1 -6 11 I.D. Each branch will be reduced to 5 1 -0" diameter prior to
connecting to the spherical valve. Surface roughness will be the same
as for the steel liner, 0.0005 feet. The branches protrude through the
powerhouse wall and connect to the spherical valves at centerline El.15
(BLPD). The steel liner, penstock and the branch pipes will be fully
encased in concrete. For more details refer to the Structural Design
Criteria for Steel Liner and Penstock.
2-464-JJ HYDRAULIC DESIGN CRITERIA/POWER TUNNEL
t
1.9 Turbines and Valves
The powerhouse will contain two 45-t1\-l units with provisions to inotall
a third identical unit at a later date. Six t, ver-tical ?el t;:m
turbines will be directly coupled to synchronous a-c generators. The
turbines will be sized so as to provide the horsepower required L
generate 45 ~M on the high voltage side of the transformers, with three
units operating under minimum operating reservoir El. 1080. Th0 I
generators Hill be rated for maximum power output of tHo turbines
operating simultaneously under reservoir El. 1180 and tide belo1.,
21.6.0. Combined rating of two generators will be the maximum output of
the two unit powerhouse.
The turbines will have two means of regulation and closure: slouly
operating needle valves and fast ( 1.5 seconds) operating def2.ectoz'::..
:'tis combination is specifically suitable for a long power condui.t
where transient pressure may be a problem. In the event of c::. lo2d
rejection the deflectors operate, deviate the jet streams away fron the
runner without changing the tunnel discharge and thus creatina:; ci
pressure rise. Closure of the needle valves, although completed in
considerably longer time (one minute) than closure of deflectors,
produces pressure rise 30 to 50 percent above the static :1ead. Each
unit will be equipped with a spherical valve located ln~ide thP
powerhouse upstream of the turbine intake. The valve will be capable
of erJergency closure under full flow conditions. The spherical val·.-;::.
will be used to isolate the unit for maintenance or in case of failure
of one or more needle valves. Closure of a spherical valve against
flow would also produce pressure rise, however the closure r<:.te fo::-the
valves will be so designed and adjusted that the pressure rise caus.;;c:;
by the valve closure will not exceed the pressure rise caused by the
turbines.
2-464-JJ HYDRAULIC DESIGIJ CRITERIA/POHE:ii TU:WEL
2. 0 OPERATION
2.1 Lake Levels and Tunnel Discharge
Lake Elevations -Maximum Flood
-Normal Maximum Operating Level
-Normal Minimum Operating Level
-Emergency Drawdown Level
Tunnel Discharge-three units, full power, El. 1180
-three units, full power, El. 1080
-two units, full power, El. 1080
Page 9
El. 1190.6
El. 1180
El. 1080
El. 1060
2150 cfs
2050 cfs
1250 cfs
The turbines will be able to operate within the lake level range from
El. 1080 to El. 1190.6. In case of emergency or for the purposes of
dam inspection, the power tunnel may be used to lower the lake level to
El. 1060. If the equipment is operational, the units will operate on
line and generate power. For this operation needle closing and opening
times as well as spherical valve closing and opening times must be
considerably extended. A procedure on how to operate the turbines
under these conditions will be developed in collaboration with the
turbine manufacturer. For more details on "Sluicing through the
Turbines" see Hydraulic Design Criteria on Hydraulic Turbines,
Governors, and Spherical Valves. During the flood conditions the lake
level will rise above El. 1180, elevation of the spillway crest, and
water will be spilled.
2.2 Turbines and Generators
The turbine-generator units will be operated with minimum load changes
most of the time, due to long power conduit and thus long water
starting time. Under normal condition the units will be started by the
automatic sequence which will ensure orderly start-up/shut-down and
speed adjustment with slow needle valve motion thus minimizing pressure
variation in the tunnel. From time to time one or more units may
experience a load rejection, full or partial, depending on
2-464-JJ HYDRAULIC DESIGN CRITERIA/POWER TUNNEL
Page 10
circumstances. Simultaneous load rejection of all three units may
occur in the event of the transmission lines outage. Under normal
conditions the load rejection will be facilitated by rapid closure of
the deflectors with the needle valves to follow. In case one or more
needle valves fail to close, the spherical valve will close against the
flow. This arrangement allows the remaining units to operate without
any restriction.
In the event that one or more needle valves have failed and the
spherical valve fails to close, the high pressure gate would have to be
closed. Initiation of gate closure should automatically start the
shutdown of all operating units.
During repairs and maintenance the unit will be shut down, the
spherical valve closed, upstream and downstream seals engaged, and the
turbine manifold dewatered. Access to the inside of the turbine
manifold will be possible through a mandoor in the valve closure
section between the valve and turbine intake section.
2.3 Maintenance of the Tunnel
Dewatering of the tunnel for the purposes of maintenance and inspection
will be done through the turbine needle valves. The entire length of
the tunnel could be dewatered with the bulkhead gates installed in the
intake and both high pressure gates opened. The tunnel will be
rewatered in two steps. First the control gate will be closed and the
tunnel portion between the intake and gate shaft will be rewatered
through the refill piping. Then the bulkhead gates will be removed and
the lower part of the tunnel will be filled through the by-pass piping
with the control gate closed. Alternatively the tunnel could be
dewatered only downstream of the high pressure gates. In that case the
bulkhead gates would not be installed.
2-464-JJ HYDRAULIC DESIGN CRITERIA/POWER TUNNEL
?abe 11
3. 0 HEAD LOSS
3.1 Preliminary Calculation
Eead loss in the power conduit was calculated as part of the 3tudy on
determining the economic tunnel diameter under Action Task IJo. ) , c..::
O.:J000352 times the discharge squared. The head loss was ass1.uned to ~;•.:
proportional to the discharge squared for the entire plant oper·at
range. For three units operating at full flow (2150 cfs) and unrler tr18
maximum reservoir level (El.1180) the head loss would be equal to
feet. The geometry of the power conduit is being finalized. As soon
as this activity is completed, final head loss calculation will be
carried out.
The following Table summarizes the results of preliminary calculations.
Lake Level
Power Tunnel Discharge
Turbine Net Head
Total Head Loss
El. 1080
2053 cfs
917 feet
148 feet
1180
2147 cfs
1003 feet
162 feet
The above calculation is valid for three units operating at full flow.
3.2 Method for Final Calculation
The loss calculation will be done for each flow individually.
Darcy-Weisbach formula will be used to determine friction loss, ?~oody
diagram will be used to establish the friction coefficients for various
flows. Absolute roughness of 0.0005 feet will be used for both, steel
and concrete surfaces.
Local losses for entrance, trashracks, piers, bends, bifurcations,
conversions and diversions will be used as suggested by References ( 1)
to ( 13). Trashracks will be assumed as clean for the purpose of head
loss calculation, which will be carried out in accordance ;.ritil
Reference 9.
2-464-JJ HYDRAULIC DESIGN CRITERIA/POHE:1 TU:nEL
Page 12
The head loss is a significant factor in selecting the turbi~e rati~3.
To calculate the turbine flow, equations for head loss and energy hav,2
to be solved si:nul taneously. Output at the turbine shaft rnu.;;t oe
3x47 .5 HvJ to assure the net output of 135 HH on the hv terminals of Lhe
transformer. This conditions must be met while operating under ~-l'·e
minimum reservoir level El. 1080.
11.0 TRANSIZNT ANALYSIS
4.1 Scope of Analysis
Transient analysis is being performed for the proposed power conduit
system. The objectives of the study are to determine the maximun anJ
minimum pressure in the pow·er conduit during load r·ejectio.1 at:d
acceptance. The study will further identify the ll!ost ::~dver·s•:
combination of operating conditions prior to load rejection/acceptance
leading to the extreme pressure values. The study is performed for t•.J'C'
and three units in the powerhouse with total installed capacity of
l~:l and 135 HH respectively. Several governor opening and closing tirr:e:3
were selected for the simulation runs.
Based on the results of the study the internal design pressure for th2
power conduit will be established and preliminary closing and opening,
governor times selected. Wherever the internal pressure governs, it
will be used to calculate thickness of the steel liner and penstc•cL
Halls. The internal design pressure will also be used in the design of
turbines, spherical valves, piping, and associated equipment. The load
acceptance runs will provide information to confirm that ~Tater colvl!!n
separation will not occur. The results will further be used to
establish preliminary governor times and to study the stability of th,.
plant and the power system.
4.2 Load Rejection
The internal design pressure for the power conduit will be ba.sed on
pressure rise caused by load rejection. Various load rejection case.s
2-464-JJ HYDRAULIC DESIGN CRITERIA/FOHER TUHHEL
Pa~e 13
will be divided into categories depending on the probability of t::!P.7_r·
occurence. For each category a different margin between the allo•,;.::bL:
and yield stresses will be established. The lower the probabilHy of
occurence, the narrower the margin. The load rejection case producing
the highest pressure rise will be identified within each category. Tr1e
individual categories are defined as follows:
a. Normal Operating Conditions. These conditions include Jaxir11l_;-
static head plus pressure rise due to the norl!lal opera.tion,
without malfunctioning of any protective device or equipment
component. The worst case, so far identified, would !:le 2
simultaneous load rejection of three units, operating at full
flow at maximum reservoir elevation (El. 1190.6), resulL.~t:
from a loss of transmission lines. Based on the preliminarJ
results fron the transient analysis the internal desi~n
pressure for normal operating conditions i>~as established 22
1470 feet of water column ( 125 percent of static head). (3t:e
Note below). Corresponding needle closing rate '.'IOuld be
approximately 60 seconds. Should the final simulation run~-;
shoH· a pressure higher than 1650 feet, the governor closing
rate will be extended accordingly.
b. Emergency Conditions. This catee;ory will include nor·r~al
operating conditions plus such events as malfunctionir.g of
the control system allowing sirnul taneous needle valve
closure, within 2L/a seconds at maximum rate, of tLree unit~·
operating with six jets at flood reservoir level.
Simultaneous closure of three spherical valves with all three
units failing to close will be also included. Tl1e ma."iwum
allowable pressure for this category was established a.s 195C·
feet (166 percent of static head).
c. Extreme Emergency Conditions. These conditions include
malfunctioning of the control system in the most 3dverse
oanner, such as instantaneous loss of governor oil pressur·e,
2-464-JJ HYDRAULIC DESIGN CRITERIA/POHEF. TU!JNEL
I
Page 14
broken needle stem on one or more Pelton jets, or auto
oscillations due to equipment and interrelated systecs
associated with the power conduit. The maximum allm~able
pressure for this category will be 2350 feet (double the
static head).
The above allowable pressures are related to the location just upstreaw
of the turbine needle valves. To obtain allowable pressures for eac;,
location of the power conduit, a hydraulic grade line must be
established. Output data from the computer program HYDTRAN, used for
the transient analysis will be used for this purpose. These data Hill
be used as input to the Penstock Design Criteria. The following TabJ..e
summarizes the allowable pressures for various categories:
PCT of PCT of
Static Design
feet psi Head Head
Static Head 1175 510 100 30
Design Pressure (see Note) 1470 637 125 100
Emergency 1950 845 166 13 3
Extreme Emergency 2350 1020 200 160
Some load rejection cases experience strong reflected pressure 'Neve
which causes underpressure. Vlith low reservoir elevations the hydraulic
grade line may be close to the upper bend of the inclined shaft. The
study will address this possibility.
4. 3 Load Acceptance
Maximum underpressure is expected to occur if three units are loaded
to full load capacity under the minimum reservoir level at El. 1080.
The Transient Analysis will address partial load acceptance to support
2-464-JJ HYDRAULIC DESIGN CRITERIA/POWER TUNNEL
Page 15
this fact. The most critical location of the power conduit, as far as
underpressure is concerned, is the crown of the upper bend of the
inclined shaft. At this location the distance between hydraulic grade
line and the conduit is the smallest.
The system will be so designed that the hydraulic grade line, for three
unit load acceptance under the reservoir level at El. 1080, will be
above the upper bend. This gives minimum protection of 30 or more feet
above vapor pressure under any conditions. This margin is generally
considered as an ample protection against potential separation of the
water column. To comply with this criteria the needle valve opening
time may have to be extended over presently considered 35 seconds.
Preliminary results indicate that 60 seconds opening rate, the sace as
the closing rate, would be adequate.
Underpressure experienced during the load acceptance would cause
reduction of the head across the turbine and thus delay the unit in
reaching its full capacity. This phenomenon might extend the effective
load acceptance rate. The study will address this topic.
2-464-JJ HYDRAULIC DESIGN CRITERIA/POWER TUNNEL
SECTION 5.0
ARCHITECTURAL
DESIGN CRITERIA
3116/168R/CG
ALASKA POWER AUTHORITY
BRADLEY LAKE HYDROELECTRIC PROJECT
J .0. No. 15800
ARCHITECTURAL DESIGN CRITERIA
REVISION: 2
DATE: March 23, 1988
STONE & WEBSTER ENGINEERING CORPORATION
DENVER, COLORADO
ARCHITECTURAL DESIGN CRITERIA
SECTION
1.0
2.0
2.1
2.2
2.3
3.0
3.1
3.1.1
3.1. 2
3.1. 3
3.1. 4
3.1. 5
3 .1. 6
3 .1. 7
3 .1. 8
3.2
3.2.1
3.2.2
3.2.2.1
3.2.2.2
3.2.2.3
3.2.2.4
3.2.2.5
3.2.2.6
3.2.3
3.3
3.4
3.4.1
3.4.2
ARCHITECTURAL DESIGN CRITERIA
TABLE OF CONTENTS
ITEM
GENERAL
REGULATIONS, CODES, STANDARDS AND GUIDES
LOCAL, STATE, AND FEDERAL CODES AND REGULATIONS
INDUSTRY CODES AND STANDARDS
DESIGN GUIDES
ARCHITECTURAL DESIGN CRITERIA
ARCHITECTURAL MATERIALS
General
Siding
Insulation
Roofing
Hatches, Doors and Louvers
Fireproofing
Interior Finishing
Windows, Glass, and Glazing
ARCHITECTURAL DESIGN
Facility Design/Performance Requirements
Site Data
Siting Condition
Climate/Microclimate Conditions
Aesthetic Requirements
Space and Room Requirements
Security Requirements
Access and Egress
Accessory Requirements
CODE CHECK
COLOR REQUIREMENTS
General Coatings
Siding Coating System
PAGE
1
1
2
2
3
3
3
3
4
4
5
5
6
6
7
7
7
8
8
8
9
10
12
13
13
15
15
15
16
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 1
ARCHITECTUAL DESIGN CRITERIA
1.0 GENERAL
This document provides architectural design criteria and information
necessary to design the Bradley Lake Hydroelectric facility for the
Alaska Power Authority.
The structure of prime consideration from the architectural standpoint
will be the powerhouse, which is a UBC Group B, Division 4 building of
Type II-N construction. This structure will be approximately 80 feet
wide by 160 feet long by 90 feet high and will be located near Sheep
Point on the east shore of Kachemak Bay. A power tunnel will supply
water from Bradley Lake under high head to power two Pel ton type
turbines within the powerhouse. Consideration will 'be given to
extending the powerhouse by an additional 80 feet in length in the
future to house a third unit. Additional structures on the project
which will incorporate these design criteria presently include the
substation, the power tunnel gatehouse, the diversion tunnel
gatehouse, and the diversion outlet portal structure. Refer to the
General Project Information and Civil Design Criteria and the
Structural Design Criteria, Part A, Section 1.0 for principal features
of the project. Those items that are identified by an asterisk (;'()
are criteria set or provided by the Alaska Power Authority.
2.0 REGULATIONS, CODES, STANDARDS, AND GUIDES
Unless otherwise stated, the design of all structures shall conform to
the latest editions of the applicable codes and specifications listed
below.
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 2
2.1 LOCAL, STATE, AND FEDERAL CODES AND REGULATIONS
AAC
OSHA-AI<
OSHA-US
DOT/PF 1982
Alaska Administrative Code, Section 13AAC50,
(incorporates UBC provisions for Alaska State
building code requirements).
General Safety Code, Vol. I, II, and I II,
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 1926/1910), as
supplement to the State of Alaska's General Safety
Code.
Alaska Department of Transportation and Public
Facilities, Design Standards for Buildings.
2.2 INDUSTRY CODES AND STANDARDS
AISC
MANUAL
NFPA
UBC
3116/168R/CG
Manual of Steel Construction; American Institute
of Steel Construction (AISC), 8th Edition.
National Fire Protection Association -Latest
Guidelines and Requirements.
Uniform Building Code; International Conference of
Building Officials, 1985 Edition.
ARCHITECTURAL DESIGN CRITERIA
2.3 DESIGN GUIDES
SWEC
CRITERIA
R&M
CRITERIA
Page 3
Bradley Lake Hydroelectric Project:
General Project Information and Civil Design Criteria
Structural Design Criteria
Mechanical Design Criteria
Electrical Design Criteria
Civil & Facilities Design
Hydroelectric Project, R&M
Anchorage, Alaska, 1985
Criteria, Bradley
Consultants,
Lake
Inc.,
Environmental Atlas of Alaska, by C.W. Hartman and P.R. Johnson,
University of Alaska, 1978.
3.0 ARCHITECTURAL DESIGN CRITERIA
3.1 ARCHITECTURAL MATERIALS
3.1.1 General
To minimize maintenance problems and meet the functional concept of a
minimally maintained facility, all architectural materials specified
or recommended for construct ion shall be considered on the basis of
being maintenance free with a maximum durabi 1 i ty and the economic
minimum of replacement or repair required. In addition, selection of
accessories and materials should be made in such a manner as to
maximize preassembly and minimize construction time, where practical.
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 4
Whenever possible, materials or accessories readily available in
Alaska will be provided. Concrete block walls should be avoided at the
site, if possible.*
3.1.2 Siding
Metal siding shall be insulated, factory assembled, and will consist
of an inner metal liner panel, insulation, and an outer metal face
panel. The panel system shall achieve an R-value meeting the
requirements as given below. Metal panels shall be roll formed from
minimum 22 gauge metal sheets. Metal siding shall be steel, not
aluminum. -:c
3.1.3 Insulation
A. Thermal Insulation
Thermal insulation shall be sufficient to provide the exterior walls
of all occupied structures with a minimum thermal resistance of R-19,
(no greater than U=0.052 BTU/Hr/Sq. Ft./Degree F). Thermal insulation
for the roofs of occupied structures shall provide a minimum thermal
resistance of R-30,(no greater than U=0.034 BTU/Hr/Sq. Ft./Degree F).
The power tunnel gatehouse and diversion tunnel gatehouse shall be
provided with thermal insulation in the exterior walls and ceiling
with a minimum thermal resistance of R-6.
B. Acoustical Insulation
Acoustical insulation shall be used in all interior walls separating
noisy equipment areas from manned areas (such as main plant areas from
control room or lunch room).*
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 5
3. 1. 4 Roofing
Metal roofing systems shall consist of an insulated field-assembled
roofing system, consisting of a steel roof deck covered with a vapor
barrier, then foam or fiberglass insulation and capped with a steel
corrugated standing seam panel fastened to the roof deck and roof
framing. Metal roof deck shall be roll formed from minimum 22 gauge
metal sheets, and face panels shall be formed from minimum 24 gauge
metal sheets. Overlapping panels shall be fully caulked against water
intrusion.
Minimum roof slope shall be 1V:l2H; where feasible a 3V:l2H roof slope
should be considered, for snow shedding.
3.1.5 Hatches, Doors and Louvers
A. Hatches
All hatches located where personnel walk shall have a raised diamond
walking pattern or shall be covered with a non-slip surfacing.
Hatches located on exterior surfaces of heated buildings shall be
insulated.
B. Rolling Steel Doors
Rolling steel doors for the powerhouse shall be motor-operated, steel
doors with the motor located on the warm side of the opening. A
safety chain shall be provided for motor operated rolling steel doors
for manual operation. Exterior rolling steel doors shall be insulated.
Rolling steel doors for the gatehouses shall be chain operated.
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 6
C. Standard Leaf Doors
Exterior doors shall be insulated hollow metal doors. Interior doors
shall be hollow metal or solid wood core doors, as applicable.
D. Fire Doors
All doors in fire rated walls shall bear an Underwriter's Laboratory
fire label.
E. Louvers
Louvers shall be designed to resist the same wind pressures as the
adjacent walls.
3.1.6 Fireproofing
Classification of fire rated assemblies for walls, floors, ceilings,
beams and columns shall be in accordance with the Uniform Building
Code and Stone & Webster guidelines.
Fireproofing of exposed structural steel members at fire rated
enclosures will be a cementitious type except at drywall partition
enclosures where 5/8" Type X drywall will be used. All gypsum
wallboard used in the plant will be 5/811 Type X fire-rated.
3.1.7 Interior Finishing
A. Interior walls will be constructed of gypsum wallboard attached
to metal wall studs. Where a more durable finish is required,
such as in the machine shop, a metal face panel will be used.*
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 7
B. Suspended acoustical tile ceilings will be used in office areas,
control room, and lunch room. The framework for the acoustical
ceiling shall be designed and braced to accommodate seismic
activities.
C. An access floor will be provided in the control room for cable
spreading purposes. All floors in office spaces, control room,
and lunch room shall be faced with sheet vinyl composition tile.
The floors and walls in the locker room wi 11 be faced with
ceramic tile.
3.1.8 Windows, Glass and Glazing
Windows in exterior walls shall be operable, except that fixed windows
shall be used in the control room, and shall be double glazed with
1/2" airspace. -:c Windows in interior walls shall be sound deadening
plastic laminated glass to reduce sound transmission through walls.
3.2 ARCHITECTURAL DESIGN
3.2.1 Facility Design/Performance Requirements
For the purpose of selection of support facilities, the plant
operations staff shall be assumed as follows: The regular staff at
the project will consist of one plant supervisor and three maintenance
personnel. -:c Because of the remoteness of the project, these workers
will be provided with permanent housing near the powerhouse.
Occasionally, maintenance crews will be brought in to provide general
and heavy maintenance and repairs to project facilities. These crews
will be housed in a 6-bedroom dormitory/office building located near
the regular staff quarters.
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 8
The powerhouse will be designed to be operated as a remote control
facility. The prime function of the regular staff will be to monitor
plant functions and perform minor maintenance tasks. The powerhouse
will be designed such that it need not be staffed on a 24-hour per day
basis.
Since the facility is located in a seismically active area, particular
attention shall be paid to adequate attachment of architectural
fixtures, accessories, and equipment. Reference shall be made to the
Structural Design Criteria requirements when specifying or selecting
accessories and when detailing or identifying attachments for these
items.
3.2.2 Site Data
3.2.2.1 Siting Condition
The powerhouse will be built approximately at sea level. The terrain
to the north, east and south of the powerhouse is heavily wooded and
rises gradually. The area to the west consists of mud and tidal flats
and swamp areas with a reach of approximately four miles to bluffs
across Kachemak Bay. The area is currently undeveloped and
inaccessible by land vehicles, but is accessible by air and water. An
onsite access road will be developed to run from the barging
facilities and base camp to the powerhouse site and to the facilities
at Bradley Lake.
3.2.2.2 Climate/Microclimate Conditions
For general climatology, refer to the General Project Information and
Civil Design Criteria.
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 9
A. Heating Design Temperatures
1. Powerhouse
Winter heating design temperature = -l0°F*
Powerhouse interior temperature = 72°F for occupied control
room, lunch room, locker room and office areas,~·c and 65°F for
normally unoccupied areas (with residual equipment heat and -l0°F
outside ambient). Waste heat from the equipment will be used to
heat the Powerhouse. This will be supplemented by auxiliary unit
heaters when the Powerhouse is not operational.
2. Other Structures
Facilities other than the Powerhouse will generally be heated by
local unit heaters. The working environment within manned
facilities should be maintained at 65"F. Insulation and heating
requirements shall be developed to maintain acceptable
temperature levels required to assure full operation of
equipment. Refer to the Mechanical Design Criteria.
3. For additional information, refer to the Project Mechanical
Design Criteria.
B. Lighting
3.2.2.3
The lighting requirements for each facility will be specified in
the Project Electrical Design Criteria. Natural 1 ighting wi 11
augment artificial lighting where appropriate.
Aesthetic Requirements
A clean, but not sterile, appearance is desired. Facilities requiring
little or no manning will still be required to be coordinated so as to
promote reasonable aesthetics.
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 10
All facilities shall be planned so the exterior pattern promotes a
blending with the surrounding area, minimizing visual impact to the
site. All exterior color schemes and wall patterns shall be reviewed
and approved by the Alaska Power Authority.
3.2.2.4
A.
Space and Room Requirements
Personnel Facilities
A control room for the Powerhouse will be situated to overlook
the generator floor and wi 11 house the control panels, SCADA
computer, and communications equipment.~·, An office will be
located adjacent to the control room for the use of the plant
supervisor .-:r A lunch room complete with sink, refrigerator,
stove, microwave, storage cabinets, and counter space will be
provided for the regular staff adjacent to the control room.-:< A
restroom will be provided including one lavatory, one water
closet, and one urinal, and a locker room will be provided
including one semi-circular wash basin, lockers and one shower.~·<
A separate single water closet and lavatory will be available
adjacent to the control room for female personnel and/or
visitorsJt Handicapped facilities will not be provided in the
Powerhouse. ~·t
B. Miscellaneous Support Services
The following support services shall be provided in the
Powerhouse:
1. Local first aid stations
3116/168R/CG
(It is not intended that a separate first aid room be
required. As a minimum, adequate first aid supplies will
be stored within the lunch room.-:r First aid supplies will
be furnished by the Owner.*)
ARCHITECTURAL DESIGN CRITERIA
2. Emergency eye wash and shower located adjacent to
battery room
Page 11
3. Tool boards located at various locations near equipment
which requires frequent maintenance to facilitate work."'•
Specialty tool boards will be provided by the equipment
manufacturers.* Other tool boards, where required, will be
supplied by the owner.*
C. Machine Shop/Tool Room
A machine shop wi 11 be provided in the Powerhouse and wi 11 be
used to repair minor machines and some equipment.* Major repairs
will be accomplished in the warehouse or vehicle shop or will be
made offsi te. A two-ton hoist on monorail shall be provided 1n
the machine shop. 7c The machine shop wi 11 be sized and wired to
accommodate the following owner-furnished equipment*:
1. Metal lathe
2. Drill press
3. Brake press and shear
4. Band saw
5. Grinder
6. Work benches
7. Storage cabinets
8. Tool boards
D. Electrical Shop
An electrical/instrumentation shop area will be provided in the
Powerhouse for repair and servicing of electrical equipment.
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 12
E. Storage Rooms
Storage rooms for files will be provided in the Powerhouse, where
appropriate.
F. Furniture, Equipment, and Appliances
3.2.2.5
The Archi teet shall prepare a list of appliances for purchase
under the Powerhouse Construction Contract. Unattached
furnishings such as office furniture, work benches, storage
shelves and cabinets, etc., wi 11 be supplied by the Owner . .,.~
Security Requirements
Security philosophy shall be reviewed with the Alaska Power
Authority. As a minimum, the following shall be provided:
1. Exterior entrances to all buildings shall be lockable with high
quality deadbol t locks operated from the outside and by turning
from inside. Exterior and security mandoors at the Powerhouse
shall be provided with locksets that have both a key lock and a
push button combination lock.
2. Selected rooms or areas within buildings may require locksets.
3. A master key plan shall be developed to operate all locks within
the facility. Master keys shall be provided to the Alaska Power
Authority.
The remote location of the site precludes the need for guards.
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 13
3.2.2.6 Access and Egress
Egress requirements shall be in accordance with Chapter 33 of the
Uniform Building Code, as applicable, unless a specific variance is
obtained from the State Fire Marshal. The distance between exits
shall not be less than 1/2 of the longest diagonal of the building,
but shall not exceed 150 feet.
Mandoors at the gatehouses shall open inwards, due to potential snow
accumulation at the exterior face. ~·r
3.2.3 Accessory Requirements
The following information is provided to assist in the planning,
design, and detailing efforts on the project:
A. Standard Stairs (Powerhouse)
Nominal stair width shall be 44 inches, unless otherwise noted.*
Handrail height above nosing shall be 34 inches. Handrails on stairs
shall be provided with three rails to match standard handrails at
platforms.
Maximum vertical distance between landings shall be 12 feet.
Treads used outside shall be open grating or safety grip grating.'''
Treads used indoors shall be checked plate steel treads. ~r A safety
nosing shall be provided.
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 14
B. Ladders
Ladders shall be in accordance with OSHA requirements. Maximum height
of ladder without cage above floor or roof shall be 20 feet. Maximum
run of ladder without intermediate platform shall be no greater than
30 feet.
C. Standard Handrails (Powerhouse)
Handrails around open platforms, landings, and floor openings shall be
42 inches high; openings in a handrail shall not permit a 12 inch
diameter sphere to pass through. Standard handrai 1 shall be 1 1/2"
diameter pipe handrail.
D. Louvers, Screens and Hoods
For the Powerhouse, stormproof louvers will be used to reduce rain and
snow infiltration. Bird screens will be provided to prevent nesting
in the louvers (insect screens are not required).
E. Roof Installations
Mounting of equipment on roofs shall be held to a minimum. If a roof
penetration is required, the equipment shall be mounted on a minimum
six-inch high curb, and the penetration shall be fully flashed.
Manufacturer's details should be used whenever possible. In all cases
roof penetrations shall be flashed, including those for pipes and
vents.
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
Page 15
F. Cabinetry and Counters
Kitchen facilities shall include built-in wooden cabinets with plastic
laminate counters.
Locker room lavatory shall be built into a wood vanity with plastic
laminate counter top.
3.3 CODE CHECK
All buildings shall be in conformance with the applicable codes. For
the Powerhouse, a review of applicable code requirements will be made
based on Section 8 of the State of Alaska, Department of
Transportation & Public Facilities (DOT/PF) document Design Standards
Manual for Buildings.
3.4 COLOR REQUIREMENTS
3.4.1 General Coatings
A. Color Scheme
The external color scheme shall be selected to blend the subject
structure with the natural environment.* Color of doors will contrast
with base building color to be easily located.
Generally, interior colors shall be soft, warm colors. The Archi teet
shall develop a color coordinated scheme acceptable to the Alaska
Power Authority, which will evaluate color requirements for at least
the following:
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA
1. All walls and ceilings
2. Structural and miscellaneous steel
3. Color requirements for equipment
4. Safety colors for special areas or equipment
S. Underside of decking and roof
6. Suspended acoustical ceiling
7. Resilient flooring
8. Ceramic floor and wall tiles
9. Countertops and cabinet work
B. Galvanizing
The following items will be hot dip galvanized:
1. Stair treads
2. Open grating
3. Selected plate material
4. Exterior pipe handrail
3.4.2 Siding Coating System
Colors are as follows:
Page 16
Exterior face panels -Sea Foam (1731 by Robertson Siding which
closely matches Desert Beige as used on worker's facilities and
warehouse)*
Interior liner panels -Arctic Ice (5913 by Robertson Siding)
3116/168R/CG ARCHITECTURAL DESIGN CRITERIA