20160742 Ver 1_More Info Received_20180228

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Submit by Anonymous User 2/28/2018 10:04:40 AM (Supplemental Submital)
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• The task was assigned to Montalvo, Sheri A 2/28/2018 10:05 AM

itial Review of Submittal
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20160742 1
Reviewer List:* Kevin Mitchell:eads\rkmitchell
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Project Submittal Interim Form
submtted: 2/28/2018
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Project Contact Information:
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Project Information:
Existing ID #:* Existing Version:*
20160742 2016
Project Name: Cedar Cliff Development Au)aliary Spillway
Upgrade Project
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r No
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Jackson
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Cedar Cliff Geotechnical Investigation Report
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Geological and
Geotechnical Subsurface
Investigation
East Fork Hydroelectric Project and Cedar Cliff
Development (FERC No. 2698)
Tuckasegee, North Carolina
June 5, 2017

06/05/17
06/05/17
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

June 5, 2017 | ii
Contents
1 Introduction .......................................................................................................................................... 1
1.1 Project Location ......................................................................................................................... 1
1.2 Project Description .................................................................................................................... 1
1.3 Field Investigation Purpose ....................................................................................................... 2
1.4 Scope of Work ........................................................................................................................... 3
2 Previous Work ..................................................................................................................................... 4
3 Field and Laboratory Investigation ...................................................................................................... 5
3.1 Boreholes .................................................................................................................................. 5
3.2 Packer Testing .......................................................................................................................... 6
3.3 Concrete and Rock Testing ....................................................................................................... 6
3.4 Borehole Water Levels .............................................................................................................. 6
3.5 Geophysical Reports ................................................................................................................. 7
3.6 LiDAR Imaging of the Auxiliary Spillway ................................................................................... 7
3.7 Geologic Observations and Measurements .............................................................................. 7
3.7.1 Geologic Observations ................................................................................................. 7
3.7.2 Discontinuity Measurements ........................................................................................ 7
3.7.3 Rock Discontinuity Profiles ........................................................................................... 8
3.7.4 Schmidt Hammer .......................................................................................................... 8
4 Geology ............................................................................................................................................... 8
4.1 Regional Physiography and Geology ........................................................................................ 8
4.1.1 Regional Physiography ................................................................................................ 8
4.1.2 Regional Geology ......................................................................................................... 9
4.2 Site Geology ............................................................................................................................ 10
4.2.1 Overburden Lithology ................................................................................................. 10
4.2.2 Bedrock Lithology ....................................................................................................... 11
4.2.3 Structural and Engineering Geology .......................................................................... 14
5 Potential Rock Slope and Fusegate Structure Failure Modes .......................................................... 17
5.1 Potential Rock Slope Failure Modes ....................................................................................... 17
5.2 Potential Fusegate Structure Failure Modes ........................................................................... 17
6 Estimation of Strength Parameters ................................................................................................... 17
6.1 Rock Mass Strength Parameters ............................................................................................ 17
6.1.1 Introduction – Hoek-Brown Criterion .......................................................................... 17
6.1.2 Intact Rock Strength and Rock Modulus .................................................................... 18
6.1.3 Geological Strength Index (GSI) ................................................................................ 18
6.1.4 mi Parameter .............................................................................................................. 19
6.1.5 D Parameter ............................................................................................................... 20
6.1.6 Rock Mass Strength Parameters ............................................................................... 20
6.2 Discontinuity and Interface Shear Strength Parameters ......................................................... 20
6.2.1 Introduction – Barton Shear Failure Criterion ............................................................ 20
6.2.2 JRC Values for the Concrete/Rock Interface and Rock Mass Discontinuities ........... 21
6.2.3 JCS Values for the Rock Mass Discontinuities and Concrete/Rock Interface ........... 22
6.2.4 Basic Friction Angle Values ....................................................................................... 23
6.2.5 Barton Shear Failure Criterion ................................................................................... 23
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

June 5, 2017 | iii
7 Kinematic Analysis and Rock Cut Stabilization ................................................................................. 24
7.1 Kinematic Analysis .................................................................................................................. 24
8 Discussion ......................................................................................................................................... 25
8.1 East (Outer) Wall Auxiliary Spillway Rock Cut ........................................................................ 25
8.2 West (Inner) Wall Auxiliary Spillway and Fusegate Rock Cuts ............................................... 26
8.3 Fusegate Structure Inlet Pipe Trench Rock Cuts .................................................................... 27
8.4 Fusegate Structure Foundation ............................................................................................... 28
8.5 Scouring, Plucking, and Hydraulic Jacking of the Auxiliary Spillway Bedrock ........................ 28
8.6 Rock Spoil – Toe Berm ........................................................................................................... 28
8.7 Rock Spoil – Pyritic Rock Material .......................................................................................... 29
9 Recommendations for Design Phase ................................................................................................ 30
10 References ........................................................................................................................................ 31
11 Limitations ......................................................................................................................................... 35
List of Tables
Table 3-1: Subsurface Investigation Borehole Summary
Table 3-2: Cedar Cliff - Packer Test Results
Table 3-3: Geotechnical Testing Results
Table 3-4: Geotechnical Testing Statistics
Table 3-5: Water Level Measurements
Table 3-6: Televiewer and Field Structural Data
Table 3-7: Joint Roughness Coefficient Field Estimates of Foliation Surfaces
Table 3-8: Schmidt Hammer Field Data
Table 3-9: Schmidt Hammer Unconfined Compressive Strength Statistics
Table 4-1: Left Abutment Continuous Feature Investigation Summary
Table 6-1: GSI Quantification
Table 6-2: Hoek-Brown Input Values
Table 6-3: Hoek-Brown Rock Mass Strength Values
Table 6-4: Barton Shear Strength Input Values
Table 6-5: Barton Shear Strength for Sliding on Foliation Planes – 50 ft
Table 6-6: Barton Shear Strength for Sliding on Foliation Planes – 75 ft
Table 6-7: Barton Shear Strength for Sliding on Foliation Planes – 100 ft
Table 6-8: Barton Shear Strength for Sliding on Joint Planes – 50 ft
Table 6-9: Barton Shear Strength for Sliding on Joint Planes – 75 ft
Table 6-10: Barton Shear Strength for Sliding on Joint Planes – 100 ft
Table 6-11: Barton Shear Strength for Sliding on Concrete/Rock Interface – JRC = 6
Table 6-12: Barton Shear Strength for Sliding on Concrete/Rock Interface – JRC = 10
Table 7-1: Kinematic Analysis Results
Table 7-2: December 2014 Kinematic Analysis Results
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

June 5, 2017 | iv
List of Figures
Figure 1-1: East Fork Hydroelectric Project – Cedar Cliff, Bear Creek, Wolf Creek, and Tanasee Creek
Dams and Vicinity.
Figure 1-2: Tennessee Creek Development - Wolf and Tanasee Creek Dams and Vicinity
Figure 1-3: Bear Creek Development - Bear Creek Dam and Vicinity
Figure 1-4: Cedar Cliff Development - Cedar Cliff Dam and Vicinity
Figure 1-5: Select Proposed Design Cross Sections Layout Plan
Figure 1-6: Left Abutment Rock Cuts Cross Section
Figure 1-7: Auxiliary Spillway Rock Cuts Cross Sections
Figure 1-8: Fusegate System and Inlet Pipe Trench Rock Cuts Cross Sections
Figure 3-1: Cedar Cliff Dam – Boring Location Map
Figure 3-2: Bear Creek Dam – Boring Location Map
Figure 3-3: Tanasee Creek Dam – Boring Location Map
Figure 3-4: Wolf Creek Dam – Boring Location Map
Figure 3-5: Cedar Cliff Dam – JRC and Schmidt Hammer Investigation Lines
Figure 3-6: GEL Seismic Refraction Profile
Figure 3-7: Televiewer Data versus Depth
Figure 3-8: LiDAR Scans
Figure 3-9: Equal Angle Projection for All Televiewer Data (Foliation and Joints)
Figure 3-10: Equal Angle Projection for Televiewer Data in Auxiliary Spillway (Foliation and Joints)
Figure 3-11: Equal Angle Projection for Televiewer Data in Auxiliary Spillway. B-9I, B-10I, B-11I (Foliation
and Joints)
Figure 3-12: Equal Angle Projection for Televiewer Data in Auxiliary Spillway. B-12I, B-13I B-14I
(Foliation and Joints)
Figure 3-13: Equal Angle Projection for Televiewer Data in Primary Spillway. B-21, B-22, B-27, and B-28
(Foliation and Joints)
Figure 3-14: Equal Angle Projection for Field Data Collected 2014-2015 (Foliation and Joints)
Figure 3-15: Equal Angle Projection for Field Data Collected 2017 (Foliation and Joints)
Figure 3-16: Equal Angle Projection for Field Data Collected 2014, 2015 and 2017 (Foliation and Joints)
Figure 3-17: Equal Angle Projection for All Televiewer Data and Field Data (Foliation and Joints)
Figure 4-1: Tectonostratigraphic Terrane Map of the Southern and Central Appalachians
Figure 4-2: Representative Photograph of Biotite Gneiss
Figure 4-3: Representative Photograph of Granite
Figure 4-4: Representative Photograph of Garnet Mica Schist
Figure 4-5: Representative Photograph of Mica Schist
Figure 4-6: Representative Photograph of Schistose Biotite Gneiss
Figure 4-7: Representative Photograph of Pegmatite
Figure 4-8: Representative Photograph of Aplite
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

June 5, 2017 | v
List of Figures (Continued)
Figure 4-9: Representative Photograph of Quartz Feldspar Gneiss
Figure 4-10: Cedar Cliff Site-Wide Lithology
Figure 4-11: B-4 Lithology
Figure 4-12: B-5 Lithology
Figure 4-13: B-6 Lithology
Figure 4-14: B-7 Lithology
Figure 4-15: B-8 Lithology
Figure 4-16: B-9I Lithology
Figure 4-17: B-10I Lithology
Figure 4-18: B-11I Lithology
Figure 4-19: B-12I Lithology
Figure 4-20: B-13I Lithology
Figure 4-21: B-14I Lithology
Figure 4-22: B-15 Lithology
Figure 4-23: B-16 Lithology
Figure 4-24: B-19 Lithology
Figure 4-25: B-20 Lithology
Figure 4-26: B-21 Lithology
Figure 4-27: B-22 Lithology
Figure 4-28: B-23 Lithology
Figure 4-29: B-27 Lithology
Figure 4-30: B-28 Lithology
Figure 4-31: Bear Creek Site-Wide Lithology
Figure 4-32: B-17 (Bear Creek) Lithology
Figure 4-33: B-18 (Bear Creek) Lithology
Figure 4-34: B-24 (Bear Creek) Lithology
Figure 4-35: B-25 (Tanasee Creek) Lithology
Figure 4-36: B-26 (Wolf Creek) Lithology
Figure 4-37: Geotechnical Exploration Sections - Cross Section A-A’
Figure 4-38: Geotechnical Exploration Sections - Cross Section B-B’ and Cross Section C-C’
Figure 4-39: S1 and S2 Foliations
Figure 4-40: S2 Foliation in Mica Schist and Garnet Mica Schist
Figure 4-41: Equal Angle Projection – Poles to Foliation, Fold Girdle
Figure 4-42: F2 Isoclinal Fold
Figure 4-43: F3 Antiformal Fold
Figure 4-44: F3 Antiformal and Synformal Folds
Figure 4-45: F3 Crenulation Fold
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

June 5, 2017 | vi
List of Figures (Continued)
Figure 4-46: First Generation Pegmatite – Boudinage
Figure 4-47: Granite Intruded into S2 Foliation – Concordant Contacts
Figure 4-48: Granite Intrusion Cross-Cutting Foliation
Figure 4-49: Granite Cross-Cutting Granite
Figure 4-50: Biotite Gneiss Xenolith in Granite (Displaced)
Figure 4-51: Biotite Gneiss Xenolith in Granite (Rock Core)
Figure 4-52: Granite, Pegmatites, and Folds
Figure 4-53: Granite Cross-Cutting F3 Fold (Rock Core)
Figure 4-54: Discontinuous Stress Relief Joint
Figure 4-55: Valley-Side Stress Relief Joint
Figure 4-56: Left Abutment Continuous Feature (Close Up)
Figure 4-57: Left Abutment Continuous Feature (Entirety)
Figure 4-58: Stratigraphic Sequences Underlying the Auxiliary Spillway
Figure 4-59: Schistose Sequence 1 in the Auxiliary Spillway
Figure 4-60: Biotite Gneiss and Granitic Sequence 2 in the Auxiliary Spillway
Figure 5-1: Possible Rock Slope Failure Modes in Rock Cuts
Figure 5-2: Photograph of Planar Slide
Figure 5-3: Photograph of Wedge Slide
Figure 5-4: Photograph of Flexural Toppling Slide
Figure 5-5: Photograph of Direct Toppling
Figure 6-1: Barton JRC Chart
Figure 7-1: Kinematic Analysis Lines A-D
Figure 7-2: Kinematic Analysis Lines 1-5 and Lines E-F
Figure 7-3: Kinematic Analysis Alternative 3-2, Sections 1-5
Figure 8-1: Area of Rock Removal on Left Abutment Rock Mass
Figure 8-2: West Wall of Auxiliary Spillway, Potential Hydraulic Conditions
Figure 8-3: Section View of Main Dam and Toe Berm
Figure 8-4: Construction Photograph, April 6, 1951. Downstream Rock Toe
Figure 8-5: Reservoir Rock Spoil Plan and Section

Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

June 5, 2017 | vii
List of Appendices
Appendix A: Previous Work
Appendix B: Borehole Logs and Core Photographs
Appendix C: Shut-In and Packer Testing
Appendix D: Sample Photographs and Laboratory Testing – GeoTesting Express, Inc. Reports
Appendix E: GEL Geophysical Reports and HDR Review of GEL Televiewer Report
Appendix F: Table of Structural Measurements on Investigation Line
Appendix G: JRC Photographs
Appendix H: Petrographic Analyses
Appendix I: Left Abutment Continuous Feature Investigation Worksheets
Appendix J: Strength Parameters – Hoek-Brown Worksheets
Appendix K: Kinematic Plots
Appendix L: Historic Limnological Profiles

Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

June 5, 2017 | 1
1 Introduction
1.1 Project Location
The East Fork Hydroelectric Project (Project) comprises four hydroelectric dams on the East Fork of
the Tuckasegee River in Jackson County, North Carolina. The Project is regulated under the Federal
Energy Regulatory Commission (FERC) License Number 2698. From upstream to downstream, the
Project consists of the Tennessee Creek Development, which includes Wolf Creek Dam (NATDAM
NC00789) and Tanasee Creek Dam (NATDAM NC00335); the Bear Creek Development, which
includes Bear Creek Dam (NATDAM NC00336); and the Cedar Cliff Development, which includes
Cedar Cliff Dam (NATDAM NC00334). The Project reservoirs are surrounded by steep, forested
slopes ranging in elevation from 2,250 feet above mean sea level (ft msl) to 3,800 ft msl (Duke
Energy 2011). A map depicting the Project and its vicinity is presented on Figure 1-1.
1.2 Project Description
The Project was previously owned and operated by Nantahala Power and Light (NP&L), a subsidiary
of the Aluminum Company of America (Alcoa). Duke Power Company purchased NP&L from Alcoa
in 1988 and connected the NP&L system to its electric transmission grid. In 1998, NP&L became a
division of Duke Power Company, now Duke Energy Carolinas, LLC (Duke Energy).

Power generated from the Project begins at the Tennessee Creek Powerhouse, which serves both
the Tanasee Creek and Wolf Creek dams, and continues via the Bear Creek and Cedar Cliff
powerhouses, providing electricity for residential and commercial use. The Project’s four
developments are described below.

The Tennessee Creek Development consists of the Wolf Creek Dam and reservoir (Wolf Creek
Lake), and the Tanasee Creek Dam and reservoir (Tanasee Creek Lake). Construction of the
Tennessee Creek Development began in October 1952; Wolf Creek Dam was completed in March
1955 and Tanasee Creek Dam was completed in April 1955. The two dams are served by a single,
shared powerhouse (Tennessee Creek Powerhouse) that contains one vertical Francis-type
generating unit with an installed capacity of 10.8 megawatts (MW ) (Duke Energy 2011). Tanasee
Creek Lake has a surface area of 40 acres and a maximum normal pool elevation of 3,080 feet. The
Tanasee Creek dam, formerly known as the East Fork Dam, is a rockfill dam with a sloping earth
core; it is 385 feet long, has a maximum height of 140 feet, and has a dam crest width of 25 feet.
The single spillway for Tanasee Creek Dam is located in the right abutment and consists of one
Tainter gate and two erodible fuse plugs. The standalone Tanasee Creek saddle dam was modified
in 1988 to function as a fuse plug. Wolf Creek Lake has a surface area of 183 acres and a maximum
normal pool elevation of 3,080 feet. The Wolf Creek Dam is a rockfill dam with a sloping earth core;
it is 810 feet long, has a maximum height of 175 feet, and has a dam crest width of 30 feet. The
single spillway for the Wolf Creek Dam is located in the right abutment and consists of one Tainter
gate and two erodible fuse plugs. The layout of the Tennessee Creek Development is presented on
Figure 1-2. Additional information about the Tennessee Creek Development can be found in its
Supporting Technical Information (STI) document (Duke Energy 2013a).
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

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The Bear Creek Development consists of the Bear Creek Dam and reservoir (Bear Creek Lake).
Construction of the Bear Creek Dam began in January 1952 and was completed in April 1954. Bear
Creek Lake has a surface area of 476 acres and a maximum normal pool elevation of 2,560 feet.
The Bear Creek Dam is a rockfill dam with a sloping earth core; it is 760 feet long, has a maximum
height of 215 feet, and has a dam crest width of 25 feet. The Bear Creek Dam has one spillway,
which is located on the right abutment and consists of one Tainter gate and two erodible fuse plug
sections separated by a concrete splitter wall. The dam has a single powerhouse containing one
vertical Francis-type generating unit with an installed capacity of 9 MW (Duke Energy 2011). The
layout of the Bear Creek Development is presented on Figure 1-3. Additional information about the
Bear Creek Development can be found in its STI document (Duke Energy 2013b).
The Cedar Cliff Development consists of the Cedar Cliff Dam and reservoir (Cedar Cliff Lake).
Construction of the Cedar Cliff Dam began in October 1950 and was completed in August 1952.
Cedar Cliff Lake has a surface area of 121 aces and a maximum normal pool elevation of 2,330 feet.
The Cedar Cliff Dam is a rockfill embankment with a sloping earth core; it is 590 feet long, has a
maximum height of 173 feet, and has a dam crest width of 25 feet. The primary spillway for the dam
consists of one Tainter gate on the right abutment, while the auxiliary spillway for the dam consists
of two erodible fuse plugs separated by a concrete splitter wall on the left abutment. A minimum flow
powerhouse (generating 500 kilovolt-amperes) was constructed in 2013 and is located adjacent to
the existing main powerhouse, which contains one vertical Francis-type generating unit with an
installed capacity of 6.4 MW (Duke Energy 2011). The layout of the Cedar Cliff Development is
presented on Figure 1-4. Additional information about the Cedar Cliff Development can be found in
its STI document (Duke Energy 2013c).
1.3 Field Investigation Purpose
A geotechnical subsurface field investigation of the Project commenced in August 2016 and
concluded in December 2016. The bulk of the investigation occurred at the Cedar Cliff Dam and
reservoir in support of the future Cedar Cliff Inflow Design Flood (IDF) and Spillway Upgrade Project.
The IDF and Spillway Upgrade Project includes deepening and widening the existing auxiliary
spillway channel and replacing the two existing fuse plugs with a Fusegate system. Approximately
75 percent of the auxiliary spillway channel length will be modified (variable width and depth
increase) through various rock excavation means such as rock splitting and controlled rock blasting.
Sufficient rock excavation and foundation preparation will occur at the existing fuse plug control
section to lower the sill elevation from 2,315 ft msl to 2,305 ft msl. The existing auxiliary spillway
channel control section will be widened from 200 feet to 250 feet, which includes the removal of a
30-foot section of the existing left abutment for placement of the Fusegate structure. The existing
average auxiliary spillway channel width will be increased from approximately 95 feet to 145 feet.
The auxiliary spillway existing channel bottom will be lowered by 15 feet on average. The rock cut
height of the outer (east) channel wall will increase from an average of 127 feet (160 ft max) to an
average of 162 feet (220 ft max). Intermediate benches (25 feet wide) are proposed along the outer
(east) channel wall in order to break up the steep rock cut slopes into 60 feet to 70 feet sections.
Select proposed rock cuts are presented in plan view and cross section on Figures 1-5 through 1-
8. The data obtained from the 2016 subsurface investigation will be used to develop the foundation
design for the planned Fusegate structure, develop the design of the rock cuts for the auxiliary
spillway channel improvements, as well as to investigate and determine the effort required to
excavate the existing rock for widening and deepening of the existing auxiliary spillway channel. The
Cedar Cliff subsurface investigation also characterized conditions near the toe of the dam for the
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

June 5, 2017 | 3
potential location of a permanent rock spoil toe berm comprised of material excavated during the
auxiliary spillway improvements.

Boreholes were drilled in the tailrace at the Bear Creek Dam to evaluate foundation and subsurface
conditions for a proposed underwater weir. The proposed underwater weir would hold the necessary
tailwater elevation to allow the Bear Creek Powerhouse to continue power generation during the
eventual drawdown of Cedar Cliff Lake during the auxiliary spillway modifications.

Boreholes were drilled adjacent to the spillway gates at the Cedar Cliff, Bear Creek, Tanasee Creek,
and Wolf Creek Dams to provide information for future gate modifications.
1.4 Scope of Work
The original HDR Geotechnical Scope of Work (SOW) consisted of three primary tasks, including the
development of the FERC-required Drilling Program Plan (DPP) for drilling near Cedar Cliff Dam, the
implementation of the subsurface exploration plan, and pre-Potential Failure Mode Analysis (PFMA)
investigations identified during the August 2015 Core Team meeting.

The DPP sub-task involved the development of plan/section drawings of the identified boring
locations, development of an exploration work plan, and coordination between Duke Energy and the
drilling company. The DPP was approved by the FERC on September 9, 2016.

The subsurface exploration plan implementation included coordination and planning (Duke Energy
and drilling contractor pre-bid meeting support, DPP coordination, on-site exploration support, boring
layout, drilling observation, and exploration coordination), laboratory testing sampling and
coordination, and the Subsurface Exploration Report (field data reduction, testing results,
geologic/geotechnical condition assessments, and design basis recommendations).

The pre-PFMA investigation tasks that were directly/indirectly established at the conclusion of the
August 2015 Core Team Meeting and reported in Section 11 of the August 2015 Supplemental
PFMA and Core Team Meeting Summary, Cedar Cliff IDF and Spillway Upgrade Study, East Fork
Projects, FERC Project No. 2698, October 2015, were modified in the first quarter of 2016. The
kinematic evaluations of the of the existing left abutment rock knob adjoining the fuse plug spillway
and inner wall of the auxiliary spillway channel (left abutment of main dam) were completed. The
pre-PFMA tasks associated with the August 2015 conceptual layout of the toe berm (crest elevation
at 2,300 ft msl) were deferred due to the significant reduction in size of the proposed 2016 toe berm
(crest elevation at 2,215 ft msl) and pending PFMA. The identified 2015 toe berm pre-PFMA tasks
had included Slope/W model evaluations, Sigma/W evaluations, rock gradation compatibility, and
foundation drainage evaluation.
The completed SOW for the 2016 subsurface investigation of the Project included:
 Review of Project reports and drawings
 Field investigations:
o Geologic observations
o Schmidt hammer testing
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

June 5, 2017 | 4
o Drilling of 26 boreholes at the Cedar Cliff Development (B-4 through B-16, B-19
through B-23, B-27, and B-28)
 Eleven boreholes were logged with optical and acoustic televiewer tools
 Water levels were measured throughout the drilling process
o Drilling of three boreholes at the Bear Creek Development (B-17, B-18, and B-24)
o Drilling of one borehole at the Tanasee Creek Dam spillway (B-25)
o Drilling of one borehole at the Wolf Creek Dam spillway (B-26)
o Seismic refraction survey downstream of the existing Cedar Cliff fuse plugs
 Shut-in and packer testing in one borehole (B-8)
 Selection of rock and concrete samples for geotechnical laboratory testing, including the
following tests:
o Unit weight of concrete and bedrock
o Unconfined compressive strength of concrete and bedrock
o Splitting tensile strength of bedrock
 Selection of rock samples for petrographic analysis
 Analysis of field and laboratory data:
o Development of geologic cross-sections
o Determination of the primary orientation and continuity of rock mass discontinuities in
the auxiliary spillway
o Determination of potential rock slope failure modes based on geologic conditions
 Estimation of strength parameters for concrete and rock mass from the field investigations:
o Compressive strength of concrete at principal spillways
o Rock mass strength parameters for foundation, cut slope, and slope stabilization
design
Details of the field and laboratory investigations are discussed in Section 3 and analysis of the field
and laboratory data are discussed in Sections 4, 6, 7, and 8.
2 Previous Work
The following reports and technical memoranda were utilized in the preparation of this report:
 “Cedar Cliff Development - Alternatives to Increase Spillway Capacity” (Piedmont Olsen
Hensley 1992): The 1992 Piedmont Olsen Hensley Report is included in Appendix A of this
report. The 1992 Piedmont Olsen Hensley Report also exhibited borehole logs (CC-1
through CC-5) from the 1989 Geotechnical Study performed by Hensley-Schmidt, Inc. The
CC-series boreholes were drilled near the primary spillway; the 1989 Geotechnical Study in
its entirety has not been located at this time.
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

June 5, 2017 | 5
 “Geologic Evaluation of Rock-Cut Auxiliary Spillway Alternatives” (HDR Engineering, Inc.
2014): This technical memorandum is included in Appendix A of this report.
 “Auxiliary Spillway – Geologic Evaluation and Kinematic Analysis of the Left Abutment Rock
Mass” (HDR Engineering, Inc. 2016): This technical memorandum is included in Appendix A
of this report.
3 Field and Laboratory Investigation
3.1 Boreholes
The field investigation at Cedar Cliff Dam included drilling 26 boreholes (Figure 3-1) for the purpose
of evaluating rock lithologies, rock quality, and discontinuities in the extent of the proposed cuts . Two
boreholes were drilled in Cedar Cliff Lake (B-6 and B-7) upstream of the existing fuse plugs, one
borehole was drilled in the auxiliary spillway downstream of the existing fuse plugs (B-8), and one
borehole was drilled in the left abutment rock mass (B-4). Twelve boreholes were drilled east of the
auxiliary spillway (B-9V/I, B-10V/I, B-11V/I, B-12V/I, B-13V/I, and B-14V/I). Inclined boreholes (B-9I,
B-10I, B-11I, B-12I, B-13I, and B-14I) were drilled 30 degrees from vertical in a due south direction
to maximize the potential for intercepting the known orientation of discontinuities at the site. Vertical
boreholes east of the auxiliary spillway (B-9V, B-10V, B-11V, B-12V, B13V, and B-14V) were offset
from the associated inclined borehole and drilled to auger refusal at these borehole locations to
classify and delineate the depth of overburden material. Two boreholes were drilled along the
reservoir rim in the location of the proposed new Wet Well (B-5) and Fusegate inlet pipe trench (B-
23). Two boreholes were drilled at the downstream toe of the dam (B-15 and B-16). Six boreholes
were drilled at the principal spillway (B-19, B-20, B-21, B-22, B27, and B-28).
The field investigation at Bear Creek Dam included drilling three boreholes (Figure 3-2). Two
boreholes were drilled in Cedar Cliff Lake in the tailrace of Bear Creek Dam, west of the Bear Creek
Powerhouse (B-17 and B-18). One borehole was drilled at the right abutment of the principal
spillway (B-24).
One borehole was drilled at the right abutment of the principal spillway at Tanasee Creek Dam (B -
25) and one borehole was drilled at the right abutment of the principal spillway at Wolf Creek Dam
(B-26), as shown on Figures 3-3 and 3-4, respectively.
The boreholes were drilled by Terracon Consultants, Inc. (Terracon). Boreholes B-9I, B-10I, B-11I,
B-12I, B-13I, and B-14I were drilled using a track-mounted Acker Renegade drill rig. Boreholes B-4
and B-8 were drilled using a Diedrich D-25 skid rig. All other boreholes were drilled using a Diedrich
D-50 drill rig. Standard Penetration Tests (SPT) were performed in 2- to 5-foot intervals in boreholes
B-5, B-9V, B-10V, B-11V, B-12V, B-13V, B-14V, B-15, B-16, and B-23. All soil boreholes were
advanced using continuous flight hollow-stem augers. Boreholes B-5, B-6, B-7, B-17, B-18, B-22, B-
23, B-25, B-27, and B-28 were drilled using a double barrel (HQ) system equipped with a diamond -
impregnated bit. All other boreholes were drilled using a triple tube wireline core barrel (HQ3) system
equipped with a diamond-impregnated bit. W ater slurry or water-bentonite slurry was used as drilling
fluid. The total depths, survey coordinates, elevations, and other field data for each borehole are
presented in Table 3-1.
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HDR geologists were present on-site to monitor and observe drilling, to prepare initial borehole logs,
photograph the core, and assist with samples for testing. An HDR senior engineering geologist
reviewed the concrete and rock cores, provided additional comments and refinement of borehole
logs, and selected the samples for laboratory testing. Details of each borehole, drilling methods
used, and conditions encountered during drilling are included in the borehole logs. Borehole logs
and photographs of soil samples and rock core are presented in Appendix B.
3.2 Packer Testing
Shut-in and borehole pressure tests were performed in borehole B-8 using a double packer system.
The testing provided an assessment of the uplift pressure and the horizontal hydraulic conductivity at
the locations of the test intervals. The test intervals were selected at 5-foot intervals in the bedrock to
reflect different bedrock conditions. Terracon performed the packer testing with guidance and
measurements provided by HDR.
Shut-in testing is performed by isolating the zone between packers and measuring the resulting
water level over time until the water level is stable. Packer testing involves forcing water under
pressure into the bedrock through the walls of the borehole in order to determine the horizontal
conductivity of the surrounding bedrock. Each depth interval is measured at varying water pressures.
The procedure used for these tests is outlined in the U.S. Bureau of Reclamation (1995).
Worksheets for the shut-in and packer tests are provided in Appendix C and the water level and
hydraulic conductivity results are summarized in Table 3-2.
3.3 Concrete and Rock Testing
Laboratory testing of concrete and bedrock samples consisted of unconfined compressive strength
tests (UCS, performed in accordance with ASTM D7012 Method C), splitting tensile strength tests
(STS, performed in accordance with ASTM D3967), and unit weights (bulk density, pounds per cubic
foot - pcf). The testing was performed by GeoTesting Express, Inc. Unit weights originated from the
respective sample selected for unconfined compressive strength testing. Three UCS tests were
performed on concrete samples; STS tests were not performed on concrete samples. Testing for
bedrock samples was grouped by lithologic classification; bedrock samples selected for UCS and
STS testing were paired, whereby two samples were selected from the same lithology from similar
depth intervals in the same borehole. Bedrock sample quantities are as follows: 18 samples of biotite
gneiss (nine UCS, nine STS), six samples of garnet mica schist (three UCS, three STS), 10 samples
of granite (five UCS, five STS), two samples of mica schist (one UCS, one STS), eight samples of
pegmatite (four UCS, four STS), four samples of quartz feldspar gneiss (two UCS, two STS), and
eight samples of schistose biotite gneiss (four UCS, four STS). Photographs of samples and the
laboratory reports from GeoTesting Express are included in Appendix D. Results of the laboratory
tests and material strength properties are summarized in Table 3-3 and Table 3-4, respectively.
3.4 Borehole Water Levels
Water levels were measured throughout drilling activities and upon completion of each borehole.
Groundwater level measurements in boreholes are summarized in Table 3-5. Packer testing was
performed in borehole B-8 and the results are shown in Table 3-2. Results of the shut-in tests
showed an increase in the water level throughout the duration of the tests. No water takes were
recorded during the pressure testing at the maximum allowed pressure, indicating a relatively tight
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rock mass. This suggests minimal, if any, leakage under the existing Cedar Cliff fuse plugs within the
rock mass.
3.5 Geophysical Reports
GEL Engineering of NC, Inc. (GEL) performed a seismic refraction survey along the toe of the
existing fuse plug structure. The seismic refraction line location is shown on Figure 3-5, the
refraction profile is shown in Figure 3-6, and the full report is in Appendix E. The data from the
refraction line is discussed in Sections 6.1.2 and 6.1.3.

GEL additionally performed geophysical borehole logging in 11 boreholes at the Cedar Cliff
Development (B-4, B-9I through B-14I, B-21, B-22, B-27, and B-28). The geophysical logging
consisted of optical and acoustic televiewer logging and synthetic caliper logs calculated from the
acoustic televiewer travel time data. This data was used to determine the location, orientation, and
aperture of fractures and other features in bedrock. The GEL geophysical logging report, including
the televiewer and caliper logs, is provided in Appendix E.
HDR reviewed and edited GEL’s televiewer fracture data set and substantially reduced the number
of data points. The process by which the data was edited is found in HDR’s 2017 technical
memorandum provided in Appendix E. The combined, edited data set for the 11 boreholes is shown
on graphs of fracture/feature dip versus depth on Figure 3-7. The edited data set was utilized in the
site geologic discontinuity data (Section 3.7.2), in the discussion of structural and engineering
geology (Section 4.2.3), and in the kinematic analyses of the proposed rock cuts for the Cedar Cliff
Development (Section 7).
3.6 LiDAR Imaging of the Auxiliary Spillway
Three-dimensional scanning of the auxiliary spillway was performed by HDR over the course of
three days (November 29 through December 1, 2016) and processed on-site to supplement the
aerial LiDAR data collected by Duke Energy in March 2016. The three-dimensional scans provided
greater channel detail (excluding those areas with scrub brush and tree growth interference) of the
existing side walls and bottom channel of the auxiliary spillway. The scanned data will support
detailed section view development of the existing auxiliary spillway channel during rock cut slope
design. Examples of the processed LiDAR data are shown on Figure 3-8.
3.7 Geologic Observations and Measurements
3.7.1 Geologic Observations
Details of the stratigraphic sequence, including lithology and structures, were noted during two field
reconnaissance investigations in the vicinity of Cedar Creek Dam and a more detailed investigation
of the auxiliary spillway. Geologic observations are discussed in Section 4.2.
3.7.2 Discontinuity Measurements
The orientations of discontinuities, primarily foliation and joints, were measured at rock outcrops
located around Cedar Cliff Dam including on the right abutment, left abutment, auxiliary spillway, and
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primary spillway in September 2014 (HDR Technical Memorandum, “Geological Evaluation of Rock-
Cut Auxiliary Spillway Alternatives” dated December 19, 2014; provided in Appendix A). Additional
structural data was collected in December 2015 on the left abutment rock mass (HDR Technical
Memorandum, “Auxiliary Spillway – Geologic Evaluation and Kinematic Analysis of the Left
Abutment Rock Mass” dated February 23, 2016; provided in Appendix A), and in February 2017
along lines in the auxiliary spillway (Figure 3-5; Appendix F). Observations were made regarding
the spacing, persistence, aperture, and degree of filling of the measured discontinuities.
The structural measurements from the televiewer data and field data are summarized in Table 3-6
and in Figures 3-9 through 3-17. The results and observations are discussed in Section 4.2.3.
3.7.3 Rock Discontinuity Profiles
The surface roughness/waviness of a discontinuity is an important component of rock shear
strength, especially in the case of undisplaced and interlocked features. In order to measure the
surface roughness of foliation planes, 29 foliation plane profiles were measured from seven
photographs along the auxiliary spillway rock cuts. The lengths of the planes and their maximum
amplitudes were estimated from the photographs based on interpretation by a senior engineering
geologist. The locations of the photographs used for the Joint Roughness Coefficient (JRC)
measurements are shown on Figure 3-5 and the photographs and planes measured are included in
Appendix G. The results of the JRC measurements are shown in Table 3-7 and their use in
determining JRC values for shear strength estimations are discussed in Section 6.2.2. Profile
measurements were not made on the dominant continuous joint set (~N37W strike with steep dips;
see Section 4.2.3) due to inaccessibility. Few joints of the dominant continuous joint set are present
in the various rock cuts at Cedar Cliff. The joints were observed to have similar profiles as the
foliation planes.
3.7.4 Schmidt Hammer
The compressive strength of the rock in the walls of a discontinuity is an important component of the
discontinuity’s shear strength. In order to measure the compressive strength of the wall rock,
Schmidt hammer tests were performed on foliation and joint planes in the auxiliary spillwa y
(locations shown on Figure 3-5) following the International Society for Rock Mechanics (ISRM)
(1978) procedure. The tests and results are summarized in Tables 3-8 and 3-9 and are discussed in
Section 6.2.3.
4 Geology
4.1 Regional Physiography and Geology
4.1.1 Regional Physiography
The Project is located in the Blue Ridge physiographic province, a mountainous zone that extends
northeast-southwest from southern Pennsylvania to central Alabama, varying in width from less than
15 miles up to 70 miles. It is characterized by rugged terrain with valleys ranging in elevation from
1,000 feet in the south to greater than 1,500 feet in the north. Several mountain peaks have
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elevations greater than 6,000 feet with relief of up to 3,500 feet. In North Carolina, massive and
resistant gneiss and metasedimentary rocks underlie most of the province with the valleys tending to
follow weak-rock outcrops related to carbonate rocks and fracture or shear zones. Underlying
structural geology has a strong influence on local topography. Drainage is generally to the west;
however, the slopes separating the Blue Ridge from the Piedmont physiographic province are
typically steep and provide the initial run-off (headwaters) for some of the largest streams of the
Piedmont, which drain to the east and southeast.

The Project is in Jackson County, situated in the mountains of southwestern North Carolina. The
terrain varies from nearly level flood plains to almost vertical rock cliffs. The physiography of the
county consists of high, intermediate, and low mountains, floodplains, and low stream terraces. The
county is largely situated within the Tuckasegee River watershed, which drains to the northwest.
4.1.2 Regional Geology
The crystalline rocks of the southern Appalachians occur in northeast-trending parallel geologic
terranes. The Project is within the Tugaloo terrane, which includes rocks of the eastern Blue Ridge
northwest of the Brevard zone as well as the rocks of the western Inner Piedmont southeast of the
Brevard zone (Figure 4-1; Hatcher et al. 2007). The Blue Ridge province is a complex crystalline
terrane consisting of Precambrian gneissic basement core structurally overlain by a vast thickness of
metasedimentary and metavolcanic rocks of Precambrian to lower Paleozoic age (Hatcher 1978a,
1978b). Numerous igneous bodies of mafic to felsic composition intrude into the basement core and
the overlying metasedimentary and metavolcanic sequences. The structure of the Blue Ridge is
controlled by major thrust faults, associated complex polyphase folding, and subsequent brittle
faulting (Hatcher 1978a; Clendenin and Garihan 2007).

The southern Blue Ridge is divided into three belts: 1) a western belt of imbricate thrust sheets
involving upper Precambrian and lower Paleozoic rock and some basement rocks, 2) a central belt
containing most of the basement rocks exposed in the Blue Ridge terrane along with higher grade
upper Precambrian and possible lower Paleozoic metasedimentary rocks, and 3) an eastern belt of
high grade early Paleozoic metasedimentary and metavolcanic rocks (Hatcher 1978a, 1978b;
Hatcher et al. 2007). The eastern belt of the southern Blue Ridge comprises those portions of the
Tugaloo terrane that occur northwest of the Brevard zone (Figure 4-1).

The principal rock unit of the western Tugaloo terrane (eastern Blue Ridge belt) within the Project
region is the Tallulah Falls Formation (TFF). The TFF consists of metagraywacke, pelitic schist,
mafic volcanic rocks, and quartzite; the rocks of the TFF are migmatitic1 in places. These rocks are
intruded by Paleozoic granitoid rocks and overlie 1,000 to 1,200 million years ago (Ma) Grenville
basement in the Toxaway Dome (primarily Toxaway Gneiss; Hatcher 1977). The TFF consists of
four members: 1) the quartzite-schist member, 2) the lower graywacke-schist-amphibolite member,
3) the garnet-aluminous schist member, and 4) the upper graywacke-schist member (Hatcher 1977).
The lower member contains quartzite with interlayered schist. The lower graywacke-schist-
amphibolite member contains metagraywacke (biotite gneiss), amphibolite, muscovite schist, and
biotite schist. Layers of granitic gneiss and pegmatites also occur in the lower member. Overlying
the lower member is the garnet-aluminous schist member. It consists of muscovite-garnet-kyanite

1 Migmatite – Rock consisting of alternating layers or lenses of granitic material in gneisses and schists; related to partial melting of
the rock during deformation and metamorphism and then re-crystallization of the melt during the waning stages of metamorphism.
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schist with interlayered amphibolite, muscovite schist, metagraywacke (biotite gneiss), granitic
gneiss, and pegmatites. It is generally easily recognizable by abundant garnet and kyanite. The
upper graywacke-schist member contains metagraywacke (biotite gneiss), muscovite schist, garnet
muscovite schist, and minor amounts of amphibolite, granitic gneiss, quartzite, calc-silicate rocks,
and pegmatites.

The Toxaway Gneiss, part of the Precambrian basement of the eastern Blue Ridge, is exposed in
the core of the Toxaway Dome (located south of the Project area). It is typically a medium- to
coarse-grained banded biotite-plagioclase-microcline-quartz gneiss with some massive and augen
varieties, which do not appear to be significantly different in composition (Schaeffer 1987, 2016;
Merschat et al. 2003). The Toxaway Gneiss has an Rb/Sr whole-rock isochron age of 1203+54 Ma
(Fullagar et al. 1979). A derived zircon age for the Toxaway Gneiss is 1,150 Ma (Carrigan et al.
2003, in Hatcher et al. 2007).

In the vicinity of the Project, the TFF is intruded by the Whiteside Granite (~466 Ma; located south of
the project), the Rabun Granodiorite2 (340+12 Ma; located south and west of the Project), and the
Looking Glass Granodiorite (~380 Ma? located southeast of the Project; Thigpen and Hatcher 2009).

The migmatitic TFF rocks are metamorphosed to the upper amphibolite facies (Hatcher 1977).
Dominant metamorphic fabric and peak metamorphism in the eastern Blue Ridge is dominantly circa
450 Ma based on metamorphic ages of detrital monazite and zircon grains from TFF rocks (Moecher
et al. 2011; Cattanach et al. 2012). The Grenvillian basement rocks of the Blue Ridge terrane,
including the Toxaway Gneiss, were subjected to granulite facies metamorphism about 1000 Ma
(Hatcher and Butler 1979).
4.2 Site Geology
4.2.1 Overburden Lithology
Overburden material was encountered in all boreholes at Cedar Cliff Dam except B-4 and primarily
consisted of alluvium, in-situ residuum, boulders, and engineered surfaces. These overburden
materials are described herein:
 Alluvium: Alluvium was only observed in boreholes located at the toe of the dam (B-15 and
B-16). It was described as brown and gray, fine to coarse sand with silt with traces of gravel,
roots, and mica. SPT blow counts ranged from 2 blows per foot to 50 blows per one-inch.
This stratigraphic unit ranged in thickness from 16.4 to 18.3 feet and was immediately
underlain by competent bedrock.
 In-situ Residuum: Soil and saprolite were observed in boreholes throughout the site (B-5, B-
8, B-9V/I, B-10V/I, B-11V/I, B-12V/I, B-13V/I, B-14V/I, and B-23). This unit was described as
reddish brown, fine to coarse sand and silt and brownish yellow, low plasticity silt with sand
with traces of mica and clay. SPT blow counts ranged from 7 blows per foot to 50 blows per
zero inches. Soil/saprolite was typically dry to moist. Partially weathered rock was observed
at the surface in boreholes B-21 and B-28 and near the refusal depths of other boreholes. In-
situ residuum thicknesses generally ranged from less than five feet thick up to approximately

2 Granodiorite – A granitic plutonic rock consisting of quartz, plagioclase (oligoclase or andesine), and alkali feldspar (orthoclase)
with biotite, hornblende, or pyroxene as mafic constituents. Contains at least twice as much plagioclase as alkali feldspar.
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thirty feet thick. Residuum east of the existing auxiliary spillway in the area of the proposed
new rock cuts ranged from 5.0 to 16.9 feet thick and overlies slightly weathered bedrock. The
slightly weathered bedrock extends about 5 to 15 feet below refusal depth in the boreholes
east of the existing spillway.
 Boulders: Boulders were encountered above bedrock in boreholes B-6 and B-7. The
thickness of boulder intervals above competent bedrock ranged from 2.6 to 10.4 feet.
Boulders were not sampled during field operations, but the boulders likely originated from the
initial construction of the reservoir in the 1950s; they are assumed to be similar to other site
bedrock lithology described in Section 4.2.2.
 Engineered Surfaces: Boreholes drilled near the primary spillway (B-19, B-20, B-22, and B-
27) encountered pavement, concrete, and grout related to the construction of the spillway
and dam. Concrete and grout also transected rock at depths below the first described
instance of rock.
4.2.2 Bedrock Lithology
The Cedar Cliff Development is underlain by metasedimentary rocks of the TFF (upper portion of the
formation; Thigpen and Hatcher, 2009) that have undergone multiple periods of deformation/folding
and upper amphibolite grade metamorphism and were intruded by several generations of pegmatites
and granitic rocks. Geologic reconnaissance of rock cuts and outcrops near the dam and spillways,
detailed description of the rock core from boreholes, and petrographic analyses of thin section
samples resulted in the identification of the following major lithologies:
 Biotite Gneiss: Biotite gneiss of the TFF constituted approximately 46 percent of the rock
encountered in boreholes across the site (Figure 4-10). It was typically described as medium
dark gray to grayish black, moderately hard to very hard, fine to medium grained, and
primarily weakly foliated with thinly spaced (<1 foot) banding. Feldspar augen were
occasionally observed. A representative hand-sample photograph of biotite gneiss is
presented on Figure 4-2. In thin-section (five thin-sections), the biotite gneiss has a
granoblastic texture with banding defined by elongate quartz crystals, plagioclase, and alkali
feldspar and early formed subparallel biotite. The dominant constituents are quartz,
plagioclase, alkali feldspar, and biotite with minor muscovite, pyrite, and myrmekite3 and
trace amounts of apatite, zircon, sphene, and rutile. Photomicrographs of biotite gneiss are
presented in the petrographic reports for samples B-10I-T5, B-12I-T3, and B-13I-T3 in
Appendix H.
 Granite: Granite comprised approximately 20 percent of the rock encountered in boreholes
across the site (Figure 4-10). Various granite descriptions ranged from white to grayish
black, hard to very hard; fine to coarse grained, and primarily massive/non-foliated. Some
flow banding and weak foliation were observed both in rock core samples and outcrop and
the orientation was generally parallel to the foliation of the gneisses and schists. Both
concordant and cross-cutting contacts between granite and the gneisses/schists were
frequently observed. Xenoliths4 of other site lithologies, particularly biotite gneiss and mica
schist, were common within the granites. Small (<1 millimeter) ‘pinhead’ garnets were

3 Myrmekite - Worm-like intergrowth of quartz in plagioclase.
4 Xenolith – Rock fragments that are foreign to the body of rock in which they occur. An inclusion.
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occasionally observed in the more leucocratic granites. A representative hand-sample
photograph of granite is presented on Figure 4-3. Petrographic analysis of six granite thin-
sections identified two types of granitic rocks and their relative ages were determined by
cross-cutting relationships in rock outcrops and rock core (discussed in Section 4.2.3):
o 1) An early granodiorite with hypidiomorphic granular texture consisting of subhedral
plagioclase with borders corroded by anhedral alkali feldspar and quartz that are
interstitial to the plagioclase and biotite, biotite which forms independent flakes with
ragged edges with subordinate amounts of myrmekite and muscovite in thin-books
with ragged edges generally associated with biotite. Rutile, sphene, and ilmenite are
present in trace amounts (three thin-sections).
o 2) A younger trondhjemite5 with hypidiomorphic granular texture consisting of
subhedral to anhedral plagioclase crystals with borders corroded by quartz and small
amounts of alkali feldspar (1 to 5 percent), which are anhedral and interstitial to the
plagioclase with biotite that forms independent flakes with associated muscovite and
trace amounts of myrmekite, sphene, and apatite (three thin sections).
Photomicrographs of granodiorite and trondhjemite are presented in the petrographic
reports for samples B-13I-T4 and B-12I-T2, respectively, in Appendix H.
 Garnet Mica Schist and Mica Schist: Garnet mica schist and mica schist of the TFF
comprised approximately 12 percent and 7 percent, respectively, of rock encountered in
boreholes across the site (Figure 4-10). Mica schist was typically described as dark gray to
grayish black, moderately hard, fine to medium grained, and very thinly foliated. Garnet mica
schist was described similarly except for the presence of garnet porphyroblasts present in
greater than 5 percent abundance. Such garnets typically ranged from 1 to 5 millimeters,
with few garnets exceeding 10 millimeters. Mica schist and garnet mica schist were
occasionally noted to have crenulated fabric. Upper and lower contacts of schist members
were often described as migmatitic. Representative hand-sample photographs of garnet
mica schist and mica schist are presented on Figures 4-4 and 4-5, respectively. In thin-
section, the garnet mica schist (six thin-sections) has a lepidoblastic texture with schistosity
defined by subparallel muscovite, biotite, and quartz-feldspar rich layers. The primary
minerals are muscovite, biotite with pleochroic inclusions of zircon, quartz, plagioclase, alkali
feldspar, 2 to 4 percent garnet up to 5 mm in diameter that is poikiloblastic with many
inclusions of fine-grained biotite and quartz, with minor feldspar and pyrite (0.05 to 0.2 mm),
fractured and bounded by more or less regular crystal faces, 2 to 6 percent crystalline pyrite
in equant to elongate grains from 0.2 mm to 1.75 mm, and trace amounts of zircon, apatite,
sphene, and kyanite. The mica schist (three thin-sections) is similar to the garnet mica schist
with the exception of less garnet (trace amounts) and less pyrite (<1 to 4 percent). .
Photomicrographs of garnet mica schist and mica schist are presented in the petrographic
reports for samples B-4-T1, B-9I-T2, B-12I-T1, and B-14-T3 in Appendix H. The presence
of pyrite in amounts greater than 1 percent and its potential to produce acid-drainage is
discussed in Section 8.
 Schistose Biotite Gneiss: Schistose biotite gneiss comprised approximately 7 percent of the
rock encountered in boreholes across the site (Figure 4-10). Schistose biotite gneiss was
identified as intermediary between biotite gneiss and mica schist end members. It was

5 Trondhjemite – A granitic plutonic rock consisting of quartz and plagioclase (oligoclase) with no or little amounts of alkali feldspar
(orthoclase) with biotite and hornblende as mafic constituents.
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typically described as medium gray to dark gray, moderately hard to hard, fine to medium
grained, and very thinly foliated. Schistose biotite gneiss was often interlayered with either
biotite gneiss or mica schist. A representative hand-sample photograph of schistose biotite
gneiss is presented on Figure 4-6. In thin-section (two thin-sections), the schistose biotite
gneiss has a granoblastic (xenoblastic) to lepidoblastic texture with poorly to well developed
schistosity defined by parallel bands of biotite/muscovite and feldspar, quartz, and
myrmekite. The amount of feldspar and quartz was dominant, comprising 60 to 75 percent of
the rock, with biotite and muscovite comprising about 25 percent of the rock. Pyrite (in one
thin-section) comprised about 7 percent of the rock and occurs as equant to elongate grains
from 0.2 to 1.5 millimeters in length. Apatite, zircon, sphene, and kyanite occur in trace
amounts. Photomicrographs of schistose biotite gneiss are presented in the petrographic
report for sample B-14I-T1 in Appendix H. The presence of pyrite in amounts greater than 1
percent and its potential to produce acid-drainage is discussed in Section 8.
 Pegmatite: Pegmatite comprised approximately 6 percent of the rock encountered in
boreholes across the site (Figure 4-10). Pegmatite was typically described as white, light
gray, and brownish gray, very hard, medium to very coarse grained, and massive/non-
foliated. Pegmatites were frequently encountered in association with granite bodies, both as
masses distributed within or near granite bodies and along the margins of granite bodies.
Concordant and cross-cutting contacts between pegmatite and the gneisses/schists were
frequently observed. Megascopic perthitic feldspars were sometimes noted within thicker
zones of pegmatite, and few ‘pinhead’ garnets and trace chlorite were also noted in this
lithology. A representative hand-sample photograph of pegmatite is presented on Figure 4-7.
Pegmatite was not selected for thin-section processing and petrographic analysis.
Minor lithologies (<1 percent of site lithology) included:
 Aplite: Aplite comprised approximately 0.8 percent of the rock encountered in boreholes
across the site (Figure 4-10). It was primarily restricted to borehole B-10I, in which it made
up less than 7 percent of that borehole’s lithologic composition. Aplite was described as
medium light to medium dark gray, very hard, very fine to fine grained, and primarily
massive/non-foliated. Few sections of aplite exhibited weak alignment of platy, fine to
medium grained mafic minerals such as biotite. A representative hand-sample photograph of
aplite is presented on Figure 4-8. In thin-section (one thin-section), the aplite has a
granoblastic, massive texture with generally equant quartz and feldspar grains with quartz
grains dominating. Muscovite, biotite, and tourmaline are minor constituents as are trace
amounts of sphene and apatite. The thin-section report is presented in Appendix H.
 Quartz Feldspar Gneiss: Quartz feldspar gneiss comprised approximately 0.9 percent of the
rock encountered in boreholes across the site (Figure 4-10). It was located intermittently
across the site, including in boreholes along the auxiliary spillway (B-10I and B-11I), near the
primary spillway (B-22), and along the reservoir rim (B-23). Quartz feldspar gneiss was
typically described as light gray, greenish gray, and greenish yellow gray, hard to very hard,
fine to coarse grained, and weakly foliated. The weak foliation, greenish hue, and micaceous
character generally distinguished it from pegmatite. A representative hand-sample
photograph of quartz feldspar gneiss is presented on Figure 4-9. In thin-section (two thin-
sections), the quartz feldspar gneiss has a granoblastic texture with porphyroblasts of
microcline and to a lesser extent plagioclase with quartz, minor amounts of biotite and
muscovite, and trace amounts of apatite and chlorite. The thin-section report is presented in
Appendix H.
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 Quartzite: Quartzite comprised approximately 0.5 percent of the rock encountered in
boreholes across the site (Figure 4-10). It was primarily restricted to borehole B-8, in which it
made up approximately 26 percent of that borehole’s lithologic composition. Quartzite was
described as white to light brownish gray, very hard, fine to medium grained, and primarily
massive/non-foliated. In thin-section (two thin-sections), the quartzite has a granoblastic
massive texture comprised of large recrystallized quartz grains with embayed and sutured
grain contacts. Quartz is the major constituent with trace amounts of plagioclase, muscovite,
tourmaline, sphene, zircon, and apatite. The thin-section report is presented in Appendix H.
 Granitic Gneiss: Granitic gneiss comprised 0.4 percent of the rock encountered in boreholes
across the site (Figure 4-10). This lithologic identification was given when an interval had a
granitic appearance, but with diffuse or gradational contacts and discernable foliation. It was
identified in boreholes along the toe of the dam (B-15), the auxiliary spillway (B-10I), and the
primary spillway (B-28 and B-22). Granitic gneiss was typically described as light gray and
grayish black, hard to very hard, fine to medium grained, and weakly foliated. Granitic gneiss
was not selected for thin-section processing and petrographic analysis.
 Calc-Silicate Quartzite: Calc-silicate quartzite was found only in borehole B-10I. It was
described as medium gray and greenish gray, very hard, fine grained, and very thinly
banded. It was noted to have trace pyrite and irregular quartz-rich masses. In thin-section
(one thin-section), the calc-silicate quartzite has a granoblastic texture with alternating
quartz-rich bands and calc-silicate bands that define the foliation (layering). The calc-silicate
bands consist of subhedral to anhedral diopside, scapolite, and idocrase with numerous
inclusions of euhedral to subhedral sphene. Pyrite and zircon are present in trace amounts.
The thin-section report is presented in Appendix H.
Figures 4-11 to 4-30 present the percentage lithology in the twenty six boreholes at Cedar Cliff;
Figure 4-31 presents the site-wide percentage lithology at Bear Creek and Figures 4-32 to 4-34 for
the three boreholes at Bear Creek; Figure 4-35 presents the percentage lithology in B-25 at
Tanasee Creek; and Figure 4-36 presents the percentage lithology in B-26 at Wolf Creek. Geologic
cross-sections showing the distribution of the lithologies in boreholes along the section lines are
presented on Figures 4-37 and 4-38 (location of section lines shown on Figure 3-1).
4.2.3 Structural and Engineering Geology
The TFF at the site is a complex sequence of metasedimentary rocks (amphibolite grade
metamorphism) that have been polydeformed, migmatized, and intruded by at least two generations
of pegmatite and granite. Two generations of foliation and three phases of folds are recognized in
the bedrock of the Project area. The second and third generation of folds control the trends of the
regional foliation as these folding events have obscured the first generation folds. The dominant
foliation (S1) in the metasedimentary sequence is a metamorphic foliation that is planar and
generally parallel to the gneissic compositional layering (Figure 4-39). The second generation
foliation (S2) is more schistose in texture and has a flaser-like habit in garnet mica schist and mica
schist where it overprints the S1 foliation in the schists (Figures 4-39 and 4-40). The two foliations
are parallel to each other; only in one fold (discussed below) were the two generations of foliation
observed at an angle relative to each other. For this reason, all field foliation measurements and
foliation measurements from the televiewer data were not considered separately and are combined
and designated as “S” on the stereonet plots on Figures 3-9 to 3-17 and on the kinematic analysis
stereonets discussed in Section 7. The statistical maximum orientation of the foliations at the Cedar
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Cliff project range from N58E to N68E; 72-81NW depending on the data set/grouping considered
and as shown on Figures 3-9 to 3-17 and listed in Table 3-6.

Upright to overturned, open to isoclinal folds with a range of orientations are present in the Cedar
Cliff auxiliary spillway and other rock outcrops at the site. The folds have hinges that plunge gently to
the southwest as shown in the stereonet plot of poles to foliation measured in outcrops, which show
a well-developed fold girdle (Figure 4-41). No first-generation folds (F1) were recognized at the site
and only one second-generation fold (F2) was recognized. The F2 fold folds S1 and has developed
an axial planar foliation, S2 (Figure 4-42). The most obvious folds in the auxiliary spillway channel
are northeast-trending folds that are typically upright and tight with gently southwest- or northeast-
plunging hinges (Figures 4-39, 4-43, and 4-44); these are considered F3 folds since they
deform/fold both the S1 and S2 foliations. A separate foliation surface related to the F3 folds is not
present in outcrops observed. Smaller amplitude F3 crenulations are seen in the outcrops and are
presumed to be parasitic to larger F3 folds (Figure 4-45).

The earliest generation of pegmatites is parallel to the S1 foliation and in places have been stretched
(boudinage6 structure), probably during the F2 fold phase (Figure 4-46). The second-generation
pegmatite cuts across the earlier pegmatite and foliations (Figure 4-46) and is likely related to a later
stage intrusion of granitic rocks into the TFF rocks. There are at least two stages of granitic intrusion
into the TFF rocks based on cross-cutting relationships and mineralogy (an earlier granodiorite and
later trondhjemite; see Section 4.2.2 and petrographic analysis of thin-sections in Appendix H). The
younger and older granites have been emplaced along the S2 foliation in places with concordant
contacts, have flow banding defined by biotite parallel to the contacts (Figure 4-47); however, both
phases have discordant contacts that cut across the foliations in places (Figure 4-48). The second
granitic intrusion cuts across the earlier granite (Figure 4-49). Both granites contain a number of
xenoliths of TFF rocks (Figures 4-50 and 4-51). The earlier granite cross-cuts F3 folds as shown on
Figure 4-52 (block sample) and in the rock core (Figure 4-53; the later granite also cross-cuts F3
folds). The granitic rocks comprise approximately 20 percent of the rock encountered in the
boreholes at the Cedar Cliff Project site (Figure 4-10).

The rocks underlying the Project are relatively unfractured/unjointed compared to crystalline rocks of
similar metamorphic grade (amphibolite grade) in the region (Burton and Brame 2009; Schaeffer
2016). The primary rock mass discontinuities are foliation(s) and one major joint set. The average
orientations based on all data (field and televiewer) are: 1) N62E; 75NW – Foliation(s)-1m and 2)
N37W; Vertical – Joint Set-2m (Table 3-6; Figure 3-17). Foliation planes are relatively continuous
planar features in the rock mass while the joint set is irregularly and widely spaced at the site. Where
present, Joint Set-2m has exposed lengths in rock cuts of 20 to greater than 100 feet. Subhorizontal
to low dip (<40o), curvilinear to planar stress relief joints are present near the ground surface in some
of the present rock cuts as well as minor discontinuous joints with lengths generally less than 20 feet
(Figure 4-54). High angle stress relief joints are present in the granite knobs on the left and right
side of the auxiliary spillway (Figure 4-55) about 20 feet from the end of Lines 4 and 10 (line
locations shown on Figure 3-5). A number of low angle stress relief joints are present in the
boreholes. Two statistical maximum orientations for stress relief joints were evident in the stereonet
plot (Figure 3-17); 1) N10E; 5SE – Joint Set-3m and 2) N87E; 33NW Joint Set-4m; however, there
is a wide scatter in the orientation of the stress relief joints (Figure 3-17). The televiewer data

6 Boudinage – A structure in which veins (pegmatite veins in this case) set in a yielding matrix are divided/pulled into pillow-like
structures generally due to extension along limbs of folds.
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collected in the boreholes at Cedar Cliff supports the field observations that the bedrock is relatively
unfractured/unjointed (141 joints and stress relief joints in approximately 1,520 feet of televiewer
logging) and indicates that the majority of the joints are stress relief joints located within the upper
30 feet of bedrock (Figure 3-7(b)).

A possible through-going structural feature is located on the west (inner) wall of the auxiliary spillway
(left abutment rock mass). It is a low-angle feature with a strike that varies from EW to N40E with 25o
to 65o N to NW dips. At the base of the west (inner) wall the possible structural feature has a 1- to 2-
inch thick quartz vein with fractured contacts that continue to the top of left wall rock cut (Figures 4-
56 and 4-57). To investigate the extent of this feature, structures logged in borehole B-4 (location
presented on Figure 3-1) and for three depths at the location of B-4 below the cored interval were
evaluated using three-point problem solutions. Three point problems calculate strike and dip of a
feature from the location of the feature measured at three different locations. The type of features in
B-4, the estimated strike-dip direction, and the dip magnitude are summarized in Table 4-1 and the
worksheets are in Appendix I. The first feature that has an orientation within the range of the
measured orientations is Trial 8, while Trials 9 to 12 are also within the range. Neither Trial 8
(lithologic contact) nor Trial 9 (last trial based on the borehole data; intrusive contact) are consistent
with the features of the structure exposed in the spillway cut. This suggests that if the feature is
continuous in the left abutment rock mass, its continuation is below the bottom of the cored interval.
The elevation of the Fusegate structure concrete sill is 2,305 feet. Trials 10 to 12 are approximately
35 to 55 feet below this elevation, suggesting a potential wedge in the rock mass defined by the
structural feature that could be disturbed during the excavation/blasting.

Geologic cross-sections along the top of the spillway cut and along the fuse plugs are presented on
Figures 4-37 and 4-38. The bedrock along the auxiliary spillway channel can be divided into two
sequences based on borehole data and observations of the rock in the spillway: 1) a sequence in
which the dominant lithologies are garnet mica schist, mica schist, and schistose biotite gneiss (~61
percent) along the northern portions of the spillway including the left abutment rock mass and the
Fusegate Structure foundation, and 2) biotite gneiss and granite along the southern portion of the
spillway (~78 percent; Figure 4-58). In Sequence 1 within the spillway where the schistose rocks
predominate, the exposed rock is slightly more weathered than Sequence 2 (compare Figure 4-59
with Figure 4-60) and has relatively low shear strength along the schistosity (foliation) and lower
rock tensile strength leading to an increased potential for planar failures in the spillway east rock cut
near the north end of the fuse plugs (Figure 4-59).

Rock Quality Designation (RQD) is a general indication of rock mass quality and signifies the degree
of jointing or fractures within a rock mass. RQD is calculated by summing the lengths of rock core
greater than four inches over the total length of the core run (ASTM D 6032). RQD was generally
excellent (>90 percent) throughout the site after the first 20 to 30 feet of weathered rock. RQD did
not vary between lithologies. Schistose lithologies experienced more frequent drilling/handling
breaks due to the low shear strength along foliation planes imparted by platy minerals (e.g. mica); in
accordance with ASTM D 6032, only those pieces of rock formed by natural breaks (e.g. joints,
fractures, cleavage planes) were considered in the calculation of RQD. Run recovery was commonly
greater than 90 percent after the first 10 to 20 feet of cored length and was typically 100 percent
after the first 20 to 30 feet of cored length. Recovery and RQD are shown in the geologic logs in
Appendix D.

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5 Potential Rock Slope and Fusegate
Structure Failure Modes
5.1 Potential Rock Slope Failure Modes
There are four principal types of rock slope failures: 1) circular failure in highly jointed or weak rock
mass, 2) planar failure in rock mass with well-developed continuous discontinuities, 3) wedge
failures on two intersecting discontinuities, and 4) toppling, including both flexural toppling due to
steeply dipping discontinuities and direct toppling due to steeply dipping intersections of two
discontinuities with a basal relief discontinuity (Figure 5-1).

The rock at the Cedar Cliff site is a relatively high strength rock mass that is not conducive to rock
mass, circular-type failures. Planar (Figure 5-2), wedge (Figure 5-3), flexural toppling (Figure 5-4),
and direct toppling (Figure 5-5) failures were observed in the existing rock cuts. Similar failures can
and will occur in the new rock cuts associated with the Fusegate structure and auxiliary spillway.
Kinematic analyses of the proposed rock cuts are discussed in Section 7.
5.2 Potential Fusegate Structure Failure Modes
The design of the Fusegate structure and its foundation has not been finalized. When the design is
finalized, potential failure modes related to geologic conditions will be considered and analyzed
using appropriate strength parameters (rock mass and/or shear strength). The development of these
parameters are discussed in Sections 6.1 and 6.2
6 Estimation of Strength Parameters
This section describes the development of two types of strength parameters: 1) rock mass strength
parameters, and 2) shear strength parameters along the rock mass discontinuities and for the
concrete/rock interface of the Fusegate structure. The rock mass criterion is for rock mass failures
that involve both the intact rock and the discontinuities in the rock mass. The criterion also provides
an estimate of the deformation modulus of the rock mass. The global strength or the shear strength
(at the appropriate normal load) of the rock mass is used to estimate the bearing capacity of the
foundation rock (Fusegate structure). The shear strength criterion was developed for sliding on rock
mass discontinuities (for analysis of potential rock slope sliding failures) and sliding on the
concrete/rock interface for the Fusegate structure foundation.
6.1 Rock Mass Strength Parameters
6.1.1 Introduction – Hoek-Brown Criterion
The estimate of the rock mass strength parameters is based on the generalized Hoek-Brown Failure
Criterion (Hoek et al. 2002; Rocscience 2002). This criterion is widely accepted and has been
applied to a large number of projects around the world (Hoek et al. 2002). The Hoek-Brown Criterion
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utilizes four input parameters related to the quality of the rock mass to estimate rock mass strength
parameters:

(1) Intact rock strength (uniaxial compressive strength)
(2) Geological Strength Index (GSI) based on the quantitative method of Hoek et al. (2013)
(3) mi, a parameter based on rock type
(4) D, a parameter to denote the disturbed rock condition and construction application (slope or
tunnel).
6.1.2 Intact Rock Strength and Rock Modulus
The foundation of the Fusegate structure will be constructed on top of the metasedimentary rocks
described in Section 4.2. The boreholes near the structure foundation are B-4, B-6, B-7, and B-8
(Figure 3-1). The predominant lithology in these boreholes is mica schist and garnet mica schist
(Figure 4-11 and 4-13 through 4-15). The seismic refraction line at the base of the existing fuse
plugs (seismic refraction profile presented in Figure 3-6; seismic refraction line location shown on
Figure 3-5) shows a relative low compressional wave velocity for approximately 45 feet of the line,
suggesting primarily mica schist and garnet mica gneiss in this section. For conservatism, the
unconfined compressive strength of mica schist/garnet mica schist (mean = 6,774 pounds per
square inch (psi); standard deviation = 3,275 psi) from laboratory testing (Table 3-4) is used.
Additional conservatism is present in the UCS test results as some of the samples failed along
foliation planes, resulting in lower UCS than would be obtained for tests perpendicular to the foliation
in the schists. The values for the best, low, and high strength estimates are 6,774 psi, 3,499 psi, and
10,049 psi, respectively.

The intact rock modulus is estimated using an empirical relationship (Hoek and Diederichs 2006):

(EQ1) Ei = MR*sigci

Where: Ei is the intact rock modulus
MR is the modulus ratio estimated from empirical data
sigci is the unconfined compressive strength of the intact rock

The MR value for schist is 675+425 and values of 675, 250, and 1,100 are used for the middle, low,
and high strength estimates, respectively.
6.1.3 Geological Strength Index (GSI)
The Geological Strength Index (GSI) value was estimated using the quantitative method of Hoek et
al. (2013). The method is based on Rock Quality Designation (RQD) data from rock coring and the
joint condition ratings of either Bieniawski (1989; 1976) or Barton et al. (1974). The equations for
estimating GSI are:
(EQ2) 𝐺𝑅𝐼=1.5 ∗𝐼𝐶𝑛𝑛𝑑89 +(𝑄𝑄𝐷
2 )

Where: GSI is Geological Strength Index
JCond89 is joint condition index of Bieniawski (1989)
RQD is Rock Quality Designation

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(EQ3) 𝐺𝑅𝐼=2 ∗𝐼𝐶𝑛𝑛𝑑76 +(𝑄𝑄𝐷
2 )

Where: GSI is Geological Strength Index
JCond76 is joint condition index of Bieniawski (1976)
RQD is Rock Quality Designation

(EQ4) 𝐺𝑅𝐼=52𝐽𝑟
𝐽𝑎
1+𝐽𝑟
𝐽𝑎
+(𝑄𝑄𝐷
2 )

Where: GSI is Geological Strength Index,
Jr is Joint Roughness Number
Ja is Joint Alteration Number (Barton et al. 1974)
RQD is Rock Quality Designation

The values of JCond89, JCond76, and Jr and Ja are based on the field observations of
foliation/joints surfaces in the auxiliary spillway channel below the existing fuse plugs and the rock
core from boreholes on the east side of the dam.

The average RQD of the rock core from borehole B-8 is 100 percent. The JCond89 value is 25,
which corresponds to a joint condition of slightly rough surfaces, separation of less than 1 millimeter
and slightly weathered joint walls. The JCond76 value is 20, which corresponds to a joint condition of
slightly rough surfaces, separation of less than 1 millimeter, and hard joint wall rock. The Jr number
is 2, corresponding to a smooth, undulating joint surface. The Ja number is 0.75, corresponding to
tightly healed, hard, non-softening, unaltered wall rock (Table 6-1). The GSI values from the three
relationships range from 88 to 90.

A GSI value of 85 is used for the middle or best estimate. GSI values of 80 and 90 are used for the
low and high strength estimates, respectively. This range of values is consistent with the Hoek-
Brown presumptive values based on rock structure and surface conditions (Hoek, 2002).

The seismic refraction line along the base of the dam shows compressiona l wave velocity lows of
15,000 to 20,000 feet per second from approximately Station 45 to Station 90 to depths of about 25
feet (Figure 3-6; corresponding to increased mica schist and garnet mica schist in borehole B-8).
Palmstrom (1995) found that compressional wave velocities in this range indicate probable rock
mass conditions of slightly to moderately jointed rock masses that generally require small to
moderate rock support in tunnels, lending support to the quantitatively derived GSI value. The higher
compressional wave velocities of greater than 20,000 feet per second of the rock mass along the
southwestern and northeastern portion of the seismic line and below the lower velocity zone indicate
massive rock that generally requires little or no rock support in tunnels (Palmstrom 1995), further
supporting the quantitatively derived GSI values.
6.1.4 mi Parameter
The parameter, mi, was estimated using the range of values calculated by Hoek et al. (2002) for
schist. The range for schist is 10±3. The low, middle, and high strength estimate values are 7, 10,
and 13, respectively.
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6.1.5 D Parameter
The D parameter varies from 0 (undisturbed rock mass) to 1 (highly disturbed rock mass). A D value
of 0.2 is used based on controlled blasting methods similar to those utilized in tunnels or in the
vicinity of structures to minimize disturbance (maintain rock quality). Those controlled blasting
methods will be used to excavate the rock for the Fusegate structure foundation and the selected D
value was used for all strength estimates.
6.1.6 Rock Mass Strength Parameters
The values used to estimate the rock mass strengths are summarized in Table 6-2. The equivalent
Mohr-Coulomb strength parameters were calculated for a failure envelope with a maximum principal
stress of 0.016 kilopound per square inch (ksi) that corresponds to the normal stress (load) of the
heaviest Fusegate on the rock foundation. The rock mass strength estimates are summarized in
Table 6-3. For estimating the bearing capacity of the rock foundation below the Fusegate structure,
the middle global strength estimate in Table 6-3 or the equivalent Mohr-Coulomb parameters
(cohesion and friction angle) of the middle estimate at the appropriate normal load should be used.
The Hoek-Brown worksheets are located in Appendix J.
6.2 Discontinuity and Interface Shear Strength Parameters
6.2.1 Introduction – Barton Shear Failure Criterion
A sliding failure along the concrete/rock contact involves the same mechanisms as shearing of a
rock joint. In rock mechanics, it is generally agreed that there are three potential modes of failure
along a joint or discontinuity:

(1) Asperity override at low normal stress;
(2) A combination of asperity override and failure through asperities at intermediate normal
stresses; and
(3) Failure through asperities at high normal stresses.

The undulations and asperities along the interface of a prepared rock foundation and the concrete
section of a dam have a significant influence on and are an important component of the shear
strength of the interface surface. Studies have shown that surface roughness significantly increases
the shear strength along the surface (Patton 1966; Barton 1973, 1976; Barton and Choubey 1977).
Failure through rock asperities is not anticipated along discontinuities in the metasedimentary rocks
or along the concrete/rock interface due to low normal stresses and high intact rock and rock mass
strengths, although possible failure through asperities in the concrete would result in a small asperity
shearing component of strength.

Patton (1966) demonstrated this increase in strength by simple experiments on “saw-tooth”
specimens. He found that the shear strength is represented by the equation:

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(EQ5) n b itan
Where: is the shear strength
n is the normal stress
b is the basic friction angle
i is the roughness angle (angle of the “saw-tooth”)

This equation is valid only at low normal stresses where the shear strength is influenced by asperity
override.

Barton (1973, 1976) showed that the roughness angle i is dependent on the normal stress acting
across the joint surface. As the normal stress increases, the effect of the roughness angle on the
shear strength decreases, but the asperity shearing component of the strength of the discontinuity
increases. Barton and Choubey (1977) proposed the following empirical shear strength equation for
discontinuity surfaces which takes into account the dependence of the roughness angle i on the
normal stress across the discontinuity:
(EQ6) 



n b
n
JRC JCStanlog10
Where: is the shear strength
n is the normal stress
JRC is the Joint Roughness Coefficient
JCS is the Joint Wall Compressive Strength
b is the basic friction angle

The second term in the friction angle takes the place of i in Patton’s equation (EQ5). Note that (EQ6)
is a frictional relationship and does not rely on any adhesion between the surfaces of the
discontinuities (rock on rock and concrete on rock).

The Joint Wall Compressive Strength (JCS) of (EQ6) is of importance in the determination of shear
strength since the thin layers of rock (or concrete) adjacent to the interface control the strength and
deformation properties of the mass as a whole (Barton and Choubey 1977).
6.2.2 JRC Values for the Concrete/Rock Interface and Rock Mass
Discontinuities
Barton (1990) presented data relating JRC, the amplitude of asperities, and the length of the profile
(Figure 6-1). He showed that the relationship between the variables is consistent over two orders of
magnitude (0.1m to 10m). Utilizing the 29 rock foliation surface profiles described in Section 3.7.3,
the JRC values for foliation along these lines were determined with the chart in Figure 6-1 (and by
visual observation, joints). The scaled JRC values to three lengths of potential failure surfaces (50
feet, 75 feet, and 100 feet) were estimated with the following equation:

(EQ7) 𝐼𝑅𝐶𝑛= 𝐼𝑅𝐶𝑛∗((𝐿𝑛𝐿𝑛⁄)^(−0.02 ∗𝐼𝑅𝐶𝑛)),

Where: JRCn is the scaled value
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JRCo is the estimated value from the rock profile
Ln is the length JRCo is being scaled to
Lo is the length of the rock profile (Barton 1990)

The JRC of the measured lines and the scaled JRC values are summarized in Table 3-7. The
average values are used in the strength estimates. The assumed failure plane lengths (and
corresponding JRC values) are to illustrate the change in shear strength with changing lengths. JRC
values will need to be scaled to estimated failure plane lengths for planar and wedge failures during
the design phase. Strength estimates for the concrete/rock interface assume JRC values of 6 and
10; maximum amplitude of the foundation surface roughness of approximately 0.6 feet and 0.9 feet,
respectively, over a length of 50 feet. (Note: Estimated from Table 6-1; 50 feet is the assumed width
of the concrete sill under the Fusegate structure; if sliding along the concrete/rock interface is
determined to be a potential failure mode during the design of Fusegate structure, the JRC should
be scaled to the appropriate width of the concrete sill assuming a maximum amplitude of 0.6 feet for
the prepared foundation for conservatism.)
6.2.3 JCS Values for the Rock Mass Discontinuities and Concrete/Rock
Interface
The joint wall compressive strength of the rock comprising the walls of a discontinuity is an important
component of the shear strength of the discontinuity. A quantitative method for determining the
compressive strength of discontinuity walls is the Schmidt hammer test (ISRM 1978). Schmidt
hammer testing was performed on foliation and joint planes along the walls of the auxiliary spillway
(Section 3.7.4). Nine tests consisting of 10 rebound measurements (r) each were made on foliation
or joint planes within biotite gneiss (Table 3-8). The five lowest readings of each group were
discarded and the mean rebound value was calculated from the five highest values from each test
(ISRM 1978). The angle and direction of the test was recorded in the field and the appropriate
correction was made in accordance with ISRM 1978. The unconfined compressive strength was
estimated using the mean rebound number (r) and the rock density (γ in pcf) value of 168.4 pcf (see
Tables 3-3 and 3-4) to estimate the unconfined compressive strength (UCS) using the following
equation (Deere and Miller 1966):

(EQ8) log10(σc) = 0.00014*γ*r+3.16

Where: σc is the unconfined compressive strength (in psi)

The Schmidt hammer results are presented in Table 3-9. Schmidt hammer tests were conducted on
both joint surfaces and foliation surfaces in exclusively biotite gneiss lithologies. T he average σc is
20,720 psi for all Schmidt hammer measurements (nine measurements), 20,956 psi for Schmidt
hammer measurements on joint surfaces (six measurements), and 20,248 psi for Schmidt hammer
measurements on foliation surfaces (three measurements). The averages for the joint and foliation
surfaces are statistically the same (2-Sample T-Test, p value = 0.80). These values are higher than
the average (17,453 psi) of nine unconfined compressive laboratory tests on biotite gneiss (Table 3-
4), but not unexpected since the Schmidt hammer was applied perpendicular to the foliation or joint
surfaces whereas the laboratory UCS tests were made with the foliation at an oblique angle to the
applied load. However, based on the presence of schistose biotite gneiss, mica schist, and garnet
mica schist in the metasedimentary sequence, the JCS for foliation planes will be controlled by the
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strength of these rocks and the JCS for joint planes that cross foliation planes will be a composite-
average strength. For the JCS for foliation planes, the average laboratory tested unconfined
compressive strengths for schistose biotite gneiss, mica schist, and garnet mica schist from Table 3-
4 were combined and the average (5,950 psi) is used. For joint planes, JCS was calculated using a
weighted average of biotite gneiss, schistose biotite gneiss, mica schist, and garnet mica schist from
Table 3-4 based on the percentages of footage of each of these rock types encountered in all Cedar
Cliff Development boreholes (Figure 4-10) normalized to 100 percent. The weighted average is
13,240 psi.

For sliding on the concrete sill of the Fusegate structure on rock, concrete with an unconfined
compressive strength of 4,000 psi was assumed for the JCS.

A reduction factor of 2.5 was applied to the above-estimated JCS values (joints, foliation, concrete)
to take into account the scaling effect of JCS with increasing sliding plane length (block size) as
recommended by Barton and Choubey (1977) and Barton (1990) for unweathered surfaces.
6.2.4 Basic Friction Angle Values
Site-specific data is not available for the basic friction angle,b , of the discontinuities in the bedrock
or the concrete/rock interface. Wylie and Norrish (1976) give values of the basic friction angle for
schist (high mica content) of 20 to 27 degrees. Barton (1973, 1976) gives values of the basic friction
of schistose gneiss and granite of 23 to 29 degrees and 31 to 33 degrees, respectively. A value of
23 degrees (lower third of the range) is used to estimate the shear strength of rock on rock along
foliation planes (high mica content) and 30 degrees along joint planes that will cross several
lithologies. EPRI (1992) gives values of the basic friction angle for concrete on rock of 34 to 39
degrees. Based on the EPRI (1992) data, a value of 34° was used to estimate the shear strength of
concrete on rock.
6.2.5 Barton Shear Failure Criterion
The values used to estimate the shear strength along foliation and joints and along the concrete/rock
interface of the Fusegate structure are summarized on Table 6-4. The shear resistance relationship
between normal stress and shear strength for sliding are shown in Tables 6-5 through 6-7 (along
foliation planes), Tables 6-8 through 6-10 (along joints), and Tables 6-11 and 6-12 (along the
concrete/rock interface). These shear strength tables should be changed as required for use in
design of the Fusegate structure and for slope stability/stabilization calculations. The average normal
load on the potential sliding plane beneath the Fusegate structure should be calculated and applied
in (EQ6) along with the appropriate basic friction angle, JRC, and JCS. For calculations of rock slope
stability/stabilization utilizing computer software, the appropriate basic friction angle, JCS, and JRC
(scaled to the failure plane length) should be used based on discontinuity and rock types, and
anticipated failure mode.

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7 Kinematic Analysis and Rock Cut
Stabilization
7.1 Kinematic Analysis
Three discontinuity data sets were evaluated as the project advanced:
 Data Set One: a set of field measurements made in 2014 to look at alternative
spillway locations (HDR Engineering, Inc. 2014; technical memorandum and
kinematic analyses included in Appendix A of this report),
 Data Set Two: additional field measurements made in 2015 and added to the 2014
data set (HDR Engineering, Inc. 2016; technical memorandum and kinematic
analyses included in Appendix A of this report), and
 Data Set Three: additional field data and televiewer data collected during this
investigation, 2016-2017.

The various orientations of the Fusegate Inlet Pipe Trench slope (assumed vertical cuts, Cuts A to
D, Figure 7-1), the cut for the new Fusegate structure in the left abutment rock mass (assumed
vertical cut, analysis Cut E, Figure 7-2), the cut along the west wall of the spillway channel (4V:1H,
analysis Cut F, Figure 7-2), and for the cut along the east (outer) wall of the spillway channel wall
(4V:1H rock cuts, Cuts 1 to 5, Figure 7-2) were analyzed for planar, wedge, and toppling (flexural
and direct) failures utilizing the discontinuity measurements made during the field investigations
(field and HDR screened televiewer data; discussed in Section 3.5 and Appendix E) and using a
stereographic kinematic analysis program (Rocscience Dips V.6.015). Inputs to the analysis include
the discontinuity data set, slope orientation, friction angle of the discontinuities, and lateral limits (for
planar, flexural toppling, and direct toppling). The analysis for each type of failure provides a rough
estimate of “probability/likelihood of failure” related to all planes in the discontinuity data set. The
probability/likelihood of failure given for the four types of potential rock slope failures in Tables 7-1
and 7-2 is determined by the stereographic kinematic analysis as follows (see examples of
kinematic analysis of each mode of rock slope failure in Appendix K):
 Planar sliding – the number of poles to discontinuities that fall within the critical
zone divided by the total number of poles to discontinuities, expressed as a percent.
 Wedge sliding – the number of discontinuity intersections that fall within the critical
zone divided by the number of intersections of all discontinuities, expressed as a
percent.
 Flexural toppling – the number of poles to discontinuities that fall within the critical
zone divided by the total number of poles to discontinuities, expressed as a percent.
 Direct and oblique toppling – the number of intersections of discontinuities that fall
within the critical zone divided by the number of intersections of all discontinuities,
expressed as a percent.

The probability/likelihood of failure was based on the professional judgment of a senior engineering
geologist. The ranges for probability/likelihood of failure are defined as follows:
 Low probability/likelihood – 0 to 20 percent
 Medium probability/likelihood – 20 to 35 percent
 High probability/likelihood – greater than 35 percent
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The kinematic stereonet analyses using Data Set Three are presented in Appendix K and the
results are presented in Table 7-1.

For comparison of the different data sets, Figure 7-3 shows the location of analyzed sections and
Table 7-2 shows the results of the kinematic analysis of the east (outer) auxiliary spillway wall from
Data Set One, provided in Table 1 of the 2014 HDR Technical Memorandum (Appendix A). The
differences in probability/likelihood of failure between Data Set One and Data Set Three are due in
part to the slightly different line orientations between the two analyses (Figures 7-2 and 7-3), but are
primarily due to the differences in the number (N) and type of measurements between the two data
sets. Data Set Three (Table 3-6; N = 527) contains a larger number of structural measurements,
more scatter due to the inclusion of discontinuous joints located in the upper 30 feet of bedrock
(Section 4.2.3), and a large number of foliation measurements from the televiewer data; Data Set
Three kinematic analyses predominantly resulted in low to medium probability/likelihood of failure.
Conversely, Data Set One (Table 3-6; N = 114) is exclusively comprised of structural field
measurements and predominantly resulted in medium to high probabilities/likelihood of failure.

The four types of rock slope failures analyzed in the kinematic analyses have already occurred in
various rock cuts at Cedar Cliff (Section 5) and are readily observed at the site. It is likely the larger
combined data set (i.e. Data Set 3) improperly attenuates the estimated probability/likelihood of
failure. Based on professional geological engineering judgment, the field rock cut data analyses (i.e.
Data Sets 1 and 2) are more representative of large-scale site conditions than the larger combined
data set used in the present analyses; therefore, all proposed rock cuts for the project are assigned
a medium to high probability/likelihood of localized failure. These failures can and will occur during
the initial excavation and at any time after the excavation. Planar failures and flexural toppling
failures along the foliation/bedding will occur, as they have in the present cuts. W edge failures,
defined by foliation and the primary joint and secondary joints, will occur where the relationship
between slope geometry (slope orientation and angle) and the discontinuity orientation is favorable
and may occur along the entire length of these cuts. The wide spacing of the major joint set indicates
that potential direct toppling and wedge failures will be localized over the extent of the cuts, although
the potential occurrence and location will be unknown prior to excavation.
8 Discussion
8.1 East (Outer) Wall Auxiliary Spillway Rock Cut
The results of the field investigations and kinematic stability analyses indicate all rock cuts have a
medium to high likelihood of localized failure. These failures can occur during the initial excavation
and at any time after the excavation. Planar failures and flexural toppling failures along the
foliation/bedding will occur where the relationship between slope geometry and the discontinuity
orientation is indicative, as shown by the kinematic analyses, and may occur along the entire length
of these cuts. The wide spacing of the major joint set (Joint Set-2m; Section 4.2.3) indicates that
potential toppling and wedge failures will be localized over the extent of the cut, although the
potential occurrence and location of such failures will be unknown prior to excavation. Although the
kinematic analyses are an indicator of probability/likelihood of failure, the extent and location of the
discontinuities in the proposed rock cut face is difficult to predict in this geologic system.

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Rockfall protection and stabilization measures will be required on the east (outer) wall of the auxiliary
spillway cut for both the protection of workers during excavation and to ensure the long-term stability
of the cuts in both temporary and permanent applications, respectively. An anchored wire rope
system (such as a Rolled Cable Net Drape System - RCN) is an option for permanent stabilization
on the east (outer) wall cut in the area of rock sequence 1 (Section 4.2.3; Figure 4-58) above the
Fusegate structure to protect it from rockfalls and to maintain it in a safe and operational condition.
Rock bolting of potential large wedges defined by Foliation-1m and Joint Set-2m (Section 4.2.3) and
rock bolting of other blocks identified during excavation will provide long-term stability in rock
sequences 1 and 2 (Section 4.2.3; Figure 4-58). Potential temporary stabilization and protection
measures such as scaling, temporary rockfall barriers, earth berms with a backslope on the
benches, and rock bolts to stabilize rock blocks, or other potential measures may be appropriate in
rock sequence 2.

During the design phase, the size, stability, and rock support (rock bolts) of potential large wedges
should be determined along the kinematic analysis lines (Cuts 1 to 5; Figure 7-2) for each bench so
that appropriate rock bolt support can be applied to any wedges formed by these discontinuities, as
noted during the course of excavation/construction. Additional spot bolts will likely be required during
construction to control blocks defined by stress-relief joints, joints, and foliation. The design and
specifications for both temporary and permanent rock cut stabilization and protection measures
should be adaptable and allow for timely field decisions regarding the appropriate stabilization
method to be applied.

The excavation of the east (outer) side of spillway rock cut should utilize high-production controlled
blasting techniques to reduce rockfall during and post-construction. Pre-splitting should be utilized to
minimize disturbance of the rock mass during excavation.
8.2 West (Inner) Wall Auxiliary Spillway and Fusegate
Rock Cuts
The current design necessitates the removal of approximately 30 feet of rock from the upstream left
abutment rock mass to accommodate the new Fusegate structure (Figure 8-1). This cut and the
rock cut associated with the deepening of the west (inner) spillway channel wall have a low to
medium likelihood of planar, wedge, and toppling failures (Table 7-1). The cut for the new Fusegate
Structure is oriented approximately N55W and a vertical cut was assumed for the kinematic
analyses (Cut E, Figure 7-2). Planar sliding on Joint Set-2m (Section 4.2.3) is likely if joint(s) of that
set are present at the location of the cut. Wedge sliding is also possible if Joint Set-2m is present.
Joint Set-2m was not observed in the rock mass in the area of the cut during the field investigations.
Toppling failure has a low likelihood of occurring in this cut. Spot rock bolts and possibly wire rope
netting may be required for rockfall protection of personnel before and during the construction of the
Fusegate structure.

As discussed in Section 4.2.3, a possible through-going geologic structure is located on the west
(inner) wall of the auxiliary spillway. The feature in the vicinity of borehole B-4, if present, is likely
below the base of the Fusegate structure concrete sill and would define a potential wedge in the rock
mass that could be disturbed during the excavation and blasting. To prevent movement of this
wedge and to provide additional stability to any other blocks or wedges in the rock mass, a series of
vertical rock anchors/bolts should be installed to tie the left abutment rock mass together. The
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bottom of the vertical rock anchors should be below the base of the concrete sill of the Fusegate
structure before any blasting occurs in the area. The type and lengths of anchors should be
determined in the rock stabilization design phase. These anchors will be in addition to the spot rock
bolts that would be installed into the rock mass along the west (inner) channel wall (discussed
below).

The partial removal of the left abutment rock mass (Figure 8-1) should utilize small-scale blasting to
reduce rock mass disturbance, provide good-quality anchorage for the Fusegate structure, and limit
disturbance to the dam. A test blast program should be considered prior to production blasting so
that adjustments can be incorporated into the blasting plan to help minimize disturbance of the left
abutment rock mass. The installation of the anchors/rock bolts discussed above should be installed
prior to any blasting, test or production.

The additional deepening excavation cut along the west (inner) wall of the spillway has low likelihood
of planar, wedge, and toppling failures (Cut F, Figure 7-2; Table 7-1). Planar sliding and large
wedge sliding are unlikely, although small wedges are possible due to intersections either of
Foliation-1m or Joint Set-2m with discontinuous joints. Flexural toppling is unlikely; direct toppling
has a higher likelihood and appears to have occurred in the past on the rock slope on the west
(inner) wall of the auxiliary spillway channel. Discontinuous joints are the base planes and Foliation-
1m and Joint Set-2m form the steeply dipping intersections. Due to the wide spacing of Joint Set 1,
potential direct toppling and wedge failures will be localized over the extent of the cuts, but the
particular locations of such failures will not be known prior to excavation. Protective measures
against local rockfalls will be required during the excavation of the channel along the left abutment
rock mass. The potential toppling and small rock blocks noted are a potential danger to personnel
and can be addressed with the installation of wire rope netting along the rock cut. The potential for
larger toppling or other failures during construction that could affect the stability of the rock mass or
the safety of personnel can be addressed using various approaches, including installation of spot or
pattern rock bolts with relatively short lengths (~10 ft).

The excavation of the west (inner) side of the spillway should utilize high-production controlled
blasting techniques to reduce rockfall during and post-construction. Pre-splitting should be utilized to
minimize disturbance of the rock mass during excavation.

Grouting of the rock mass is not considered a feasible ground improvement for the left abutment
rock mass as there is a potential for grout leakage into the dam filter system that protects the thin
clay core of the dam.
8.3 Fusegate Structure Inlet Pipe Trench Rock Cuts
The rock cuts for the Fusegate structure inlet pipe trench have the potential for toppling, wedge, and
planar sliding failures, although the location of such potential failures will not be known until the
excavation of the cuts (Cuts A to D, Figure 7-1, and Table 7-1). Protection for personnel, such as
wire rope netting as well as spot rock bolts, will likely be required during excavation of the trench and
during construction of the inlet pipe.

Controlled blasting and pre-splitting will be required to control blast damage to the inlet pipe trench
cuts.
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8.4 Fusegate Structure Foundation
The bedrock underlying the Fusegate structure is of sufficient quality and strength to support the
structure. Rock mass strengths and shear strengths (both rock mass and concrete on rock sliding)
for determining the bearing capacity of the rock and for stability analysis of the structure are provided
in Section 6.
8.5 Scouring, Plucking, and Hydraulic Jacking of the
Auxiliary Spillway Bedrock
The strength and relatively unfractured nature of the bedrock in the channel and the east (outer) wall
of the auxiliary spillway mitigates potential hydraulic conditions that may otherwise occur during a
major spilling event. The foliation in the bedrock in the spillway channel effectively strikes
perpendicularly to slightly obliquely across the channel and dips upstream - the optimal orientation to
prevent scour/plucking/hydraulic jacking. Blocks that could be plucked or eroded in the channel floor
are unlikely to be encountered over large areas of the spillway channel floor due to the relatively
unfractured nature of the bedrock. The east (outer) wall of the spillway within rock sequence 1
(Figure 4-58; discussed in Section 4.2.3) will be protected against major scouring/plucking/hydraulic
jacking by an anchored wire net system or some other stabilization method.

The west (inner) wall of the spillway presently exposed has the potential for plucking and hydraulic
jacking due to blast damage sustained during the initial excavation (early 1950s) and by the
orientation of the foliation in the channel wall. The foliation in the bedrock is at an oblique angle to
the wall and the potential for dislodgement and hydraulic jacking by water infiltration along foliation
and other fractures is possible (Figure 8-2).

The potential for rock scour/plucking/hydraulic jacking along the auxiliary spillway walls and channel
floor after the construction of the new Fusegate structure needs to be addressed/analyzed during the
design phase using Annandale’s (1995; 2006) method, the geologic data collected during the site
investigation, and the results of the hydraulic modeling of the proposed spillway channel.

In conjunction with this analysis, the design and construction of a concrete facing along the entire
length of the west (inner) wall of the spillway past the downstream toe of Cedar Cliff Dam should be
considered if rock scour is possible.
8.6 Rock Spoil – Toe Berm
A toe berm is proposed against the downstream face of the main dam. The toe berm is comprised of
rock spoil from the auxiliary spillway’s excavation with an estimated bulk volume of approximately
20,300 cubic yards. The proposed toe berm crest elevation is 2,215 ft msl, which represents a toe
berm height of approximately 30 feet.

Based on the data obtained from boreholes B-15 and B-16 (Figure 3-1), the subsurface below the
location for the potential toe berm is primarily alluvium underlain by sound bedrock. This sequence
will support the approximately 20,300 cubic yards of spoil from the rock excavation as currently
planned.
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Figure 8-3 is based on the Cedar Cliff Development STI, Exhibit F, Sheet F-3, East Fork Project,
Cedar Cliff Development, Dam Sections Drawing (HDR 2013) and shows that the rock spoil toe
berm will rest against the extra-large quarry run rock downstream rock toe (estimated crest elevation
2,200 ft msl). A construction photograph of the upstream/downstream rock toe and upstream
cofferdam as shown in Figure 8-3 is presented in Figure 8-4. The toe berm design should include
adequate foundation drainage and foundation assessment and berm stability and differential
settlement analysis.
8.7 Rock Spoil – Pyritic Rock Material
The present plan calls for spoiling a majority of the rock (approximately 262,900 cubic yards) from
the auxiliary spillway and Fusegate structure rock cut excavations into Cedar Cliff Lake upstream of
the dam, (Figure 8-5) with a lesser amount (approximately 20,300 cubic yards) placed at the
downstream toe of Cedar Cliff Dam.

The petrographic analyses of rock from the site found that the garnet mica schist, mica schist, and
schistose biotite gneiss lithologies contained greater than 1 percent pyrite by volume (2 to 7 percent
pyrite; Section 4.2.2 and Appendix H). The pyrite crystals observed in the thin-sections ranged
from 0.05 to 1.5 millimeters in size and are morphologically crystalline. Approximately 25 percent of
the excavated material will be made up of these three rock lithologies. In Sequences 1 and 2 (see
Section 4.2.3) approximately 60 percent and 14 percent of the excavated material will be these
three lithologies, respectively.

Generally, rocks with greater than 1 percent pyrite by volume or pyritic sulfur in excess of 0.5 weight
percent are considered to be potentially acid-producing (Byerly 1996). Pyrite can react in the
presence of atmospheric oxygen and water to form ferrous sulfate and sulfuric acid (2FeS2 + 7O2 +
2H2O -> 2FeSO4 + 2H2SO4). Sulfuric acid can contribute to acid-drainage and impact environmental
quality through the mobilization of certain metals (Igarashi and Oyama 1999).

Key acid-producing rocks in the Blue Ridge are the graphitic schists of the Anakeesta Formation
(AFm) of the Great Smoky Group (Huckabee et al. 1975; Bacon and Mass 1979; Mathews and
Morgan 1982; Schaeffer and Clawson 1996). The nearest outcrop of AFm is located approximately
20 miles northwest of the Project site. There are no known instances of acid-drainage related to the
metasedimentary rocks of the TFF in the region surrounding the Project.

A factor in the reaction rate of pyrite is the ratio of a crystal’s surface area to volume (Pugh et al.
1981; 1984). Fine grained pyrite will more readily oxidize due to a larger active surface area. Based
on initial analyses and prior knowledge (Schaeffer and Clawson 1996), HDR noted the pyrite found
at the Cedar Cliff site is coarser-grained than the pyrite in the graphitic schists of the AFm (based on
field observations of AFm in rock cuts and initial petrographic review of prepared AFm thin sections)
and therefore less likely to be acid-producing despite the pyrite content.

In addition, atmospheric oxygen is required to drive the oxidation reaction of pyrite to sulfuric acid
(USEPA 1994). Oxygen availability within the reservoir is in in the form of dissolved oxygen, which
typically follows a decreasing trend with increasing water depth. Historic data from Cedar Cliff Lake
limnological profiles (provided in Appendix L) indicate that dissolved oxygen trends in the reservoir
are consistent with other run-of-river reservoirs in the southeastern United States, whereby dissolved
oxygen concentration follows a decreasing trend with increasing depth with defined layers that
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coincide with thermal stratification of the water column. Dissolved oxygen concentration is more
consistent throughout the reservoir profile prior to thermal stratification (occurs in late summer and
early fall) and after reservoir turnover7 (Dobson and Frid 2009).

The location and depth profile anticipated for the project will maximize the height of the water cover
overlying the rock spoil, thus sequestering the material to the lower layer of the reservoir. Restricting
the material to this region of the reservoir where dissolved oxygen is typically limited or non-existent
will inhibit the exposure of the rock spoil to atmospheric oxygen, thereby reducing the potential for
oxidation reaction. Water cover has been noted by several researchers as an effective acid-
generation control measure for mine tailings and mine waste of finer grained pyrite than is observed
in the TFF pyrite-bearing lithologies (Sengupta 1993; Lapakko 1994; Payant and Yanful 1997).
Although the complete submergence of pyrite-bearing materials may not completely halt the
oxidation of sulfide and resultant acid generation, the reaction rate in aquatic environments is
generally reduced, resulting in negligible impact (Sengupta 1993).

Based on water cover acting as an effective inhibiter of acid production, the spoiling of all excavated
rock into the lake should be considered. In addition, this issue should be further studied with
additional research of the literature and documentation of pertinent factors specifically related to
potential acid production of the TFF lithologies.
9 Recommendations for Design Phase
The following recommendations are made:

 The toe berm design should include adequate foundation drainage and foundation
assessment and berm stability and differential settlement analysis.

 Analyze potential scour, plucking, and hydraulic jacking of the bedrock in the spillway
channel using Annandale’s (1995; 2006) method, geologic data collected during this
investigation, and the results of the hydraulic modeling of the proposed auxiliary spillway.

 In conjunction with the scour analysis, Duke Energy should consider extending the concrete
facing/wall from the Fusegate structure along the west (inner) wall of the spillway to near the
downstream toe of Cedar Cliff Dam.

 The potential acid-production of the TFF lithologies and the disposal of the excavated rock in
Cedar Cliff Lake should be further investigated.

 Establish design requirements for both temporary and permanent rockfall stabilization and
protection measures based on potential impacts during construction and long-term
performance of the Fusegate and spillway. Define the rockfall impact zone relative to the
Fusegate structure and its long-term performance in collaboration with the design team.
Consider completing rockfall simulation analyses of the east auxiliary spillway and left
abutment rock mass cuts to help develop the rockfall impact zone. This will help define the

7 Turnover - breakdown of the thermal stratification of a lake. It is driven by decreasing surface water temperatures that result from
cooler fall weather patterns.
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limits where permanent stabilization is required and should be estimated during the design
phase.
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Project, Cedar Cliff Development (FERC No. 2698), Revision 3. December 20, 2013.

Duke Energy Carolinas, LLC. 2013c. Supporting Technical Document No. 2698-BC-01. East Fork
Project, Bear Creek Development (FERC No. 2698), Revision 2. December 20, 2013.

Electric Power Research Institute (EPRI). 1992. Uplift Pressures, Shear Strengths, and Tensile
Strengths for Stability Analysis of Concrete Gravity Dams: EPRI TR-100345, Volume 1,
Project 2917-05, Final Report, August 1992.

HDR Engineering. 2014. Technical Memorandum: Geological Evaluation of Rock -Cut Auxiliary
Spillway Alternatives. Dated December 19, 2014.

HDR Engineering. 2016. Technical Memorandum: Auxiliary Spillway – Geologic Evaluation and
Kinematic Analysis of the Left Abutment Rock Mass. Dated February 23, 2016.

Fullagar, P. D., R. D. Hatcher, Jr., and C. E. Merschat. 1979. 1200 M.Y.-old gneisses in the Blue
Ridge province of North and South Carolina: Southeastern Geology, v. 20, p. 69-77.

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June 5, 2017 | 33
Hatcher, R. D., Jr. 1977. Macroscopic polyphase folding illustrated by the Toxaway Dome, eastern
Blue Ridge, South Carolina-North Carolina: Geological Society of America Bulletin, v. 88, p.
1678-1688.

Hatcher, R. D., Jr. 1978a. Tectonics of the western Piedmont and Blue Ridge, southern
Appalachians: review and speculation: American Journal of Science, v. 278, p. 276-304.

Hatcher, R. D., Jr. 1978b. Synthesis of the southern and central Appalachians, U.S.A., in, IGCP
Project 27, Caledonian-Appalachian Orogen of the North Atlantic Region: Geological Survey
of Canada, Paper 78-13, p. 149-157.

Hatcher, R. D., Jr., Bream, B. R., and Merschat, A. J. 2007. Tectonic map of the southern and
central Appalachians: A tale of three orogens and a complete Wilson cycle, in, Hatcher, R.
D., Jr., Carlson, M. P., McBride, J. H., and J. R. Martinez Catalan, eds., 4-D Framework of
Continental Crust: Geological Society of America Memoir 200, p. 595-632.

Hatcher, R. D., Jr. and J. R. Butler. 1979. Guidebook for southern Appalachian field trip in the
Carolinas, Tennessee, and northeastern Georgia: International Geological Correlation
Program, The Caledonides in the U.S.A., 117p.
HDR Engineering, Inc. of the Carolinas (HDR). 2013. Supporting Technical Information, East Fork
Project, Cedar Cliff Development, FERC Project No. 2698, Rev. 3. December 2013.

Hoek, E., T. G. Carter, and M. S. Diederichs. 2013. Quantification of the Geological Strength Index
Chart. 47th U. S. Rock Mechanics and Geomechanics Symposium, San Francisco,
California, July 23-26, 2013, 8p.

Hoek, E., C. Carranza-Torres, and B. Corkum. 2002. Hoek-Brown Failure Criterion - 2002 Edition.
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Huckabee, J. W., C. P. Goodyear, and R. D. Jones. 1975. Acid rocks in the Great Smokies:
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Igarashi, T. and T. Oyama. 1999. Deterioration of water quality in a reservoir receiving pyrite-bearing
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April 24-29, 1994.

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Mathews, R. C., Jr. and E. L. Morgan. 1982. Toxicity of Anakeesta Formation leachates to shovel-
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June 5, 2017 | 35

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11 Limitations
This study was conducted in accordance with generally accepted geological and geotechnical
practice and is intended for use by Duke Energy Carolinas, LLC and its consultants for the design of
structures related to the Project. This report presents the data collected, analyzed, and conclusions
of the study and was prepared for use by engineers, analysts, and technicians familiar with the
Project.

The conclusions presented are based on a review of pre-existing geological and geotechnical
studies and data obtained from the geologic reconnaissance, observation, and measurements
made; from exploratory boreholes drilled; field geophysics, and laboratory concrete and rock testing
performed as part of this study. The nature and extent of the subsurface conditions may vary
between the boreholes.

Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

Figures

June 5, 2017
#
#
#
#
PATH: C:\USERS\JDVORAK\DOCUMENTS\EAST_FORK\REGIONAL_MAP.MXD - USER: JDVORAK - DATE: 2/24/2017
CEDAR CLIFF DAM, BEAR, WOLF, ANDTANASEE CREEK DAMS AND VICINITY
FIGURE 1-1
0 1 20.5 Miles
/
Aerial Source Data: Sources: Esri, HERE,DeLorme, Intermap, increment P Corp., GEBCO,USGS, FAO, NPS, NRCAN, GeoBase, IGN,Kadaster N L, Ordnance Survey, Esri Japan, METI,Esri China (Hong Kong), swisstopo, MapmyIndia,© OpenStreetMap contributors, and the GIS UserCommunitySources: Esri, HERE, DeLorme, USGS, Intermap,INCREMENT P, NR Can, Esri Japan, METI, Esri
Cedar CliffDam
Bear Creek Dam
Wolf Creek Dam
Tanasee Creek Dam
EAST FORK HYDROELECTRIC
PROJECT
PATH: C:\USERS\JDVORAK\DOCUMENTS\EAST_FORK\TANASEE_WOLF_LAYOUT.MXD - USER: JDVORAK - DATE: 2/24/2017
WOL F AND TANASEE CREEK DAMS AN D VICIN ITY
FIGURE 1-2
TENNESSEE CREEK DEVELOPMENTFERC NO. 2698
DATA SOURCES: Aerial photography from NC One Map (2015)
0 600 1,200 1,800 2,400300Feet
/
DISCLAIMER: Location of Tunnels is approximate
Powerhouse
Spillway
Wolf Creek Dam
Project Extent
Tanasee Creek
Spillway
Tanasee Creek Dam
Wolf Creek Reservoir
Reservoir
Penstock
Tunnels
EAST FORK HYDROELECTRIC PROJECT
PATH: C:\USERS\JDVORAK\DOCUMENTS\EAST_FORK\BEAR_CREEK_LAYOUT.MXD - USER: JDVORAK - DATE: 2/24/2017
BEAR CREEK DAM AND VICINITY
FIGURE 1-3
BEAR CREEK DEVELOPMENTFERC NO. 2698
DATA SOURCES: Aerial photography from NC One Map (2015)
0 440 880 1,320220Feet
/
Powerhouse
Spillway Gate
Fuse Plug
Bear Creek Dam
Project Extent
Bear Creek Lake
Spillway
EAST FORK HYDROELECTRIC PROJECT
PATH: C:\USERS\JDVORAK\DOCUMENTS\EAST_FORK\CEDAR_CLIFF_LAYOUT.MXD - USER: JDVORAK - DATE: 2/24/2017
CEDAR CLIFF DAM AND VICINITY
FIGURE 1-4
CEDAR CLIFF DEVELOPMENTFERC NO. 2698
DATA SOURCES: Aerial photography from NC One Map (2015)
0 300 600 900 1,200150Feet
/
Powerhouse
Principal Spillway
Fuse Plug
Cedar Cliff Dam
Project Extent
Cedar Cliff Lake
Auxiliary Spillway
EAST FORK HYDROELECTRIC PROJECT
SELECT PROPOSED DESIGNCROSS SECTIONSLAYOUT PLAN
LEFT ABUTMENT ROCK CUTS CROSS SECTION
AUXILIARY SPILLWAY ROCK CUTSCROSS SECTIONS
FUSEGATE SYSTEM AND INLETPIPE TRENCH ROCK CUTS CROSS SECTIONS
AA
JRC AND SCHMIDT HAMMER INVESTIGATION LINESA

HDR Project No. 10020225 Task 63

Figure 3-6 – GEL Seismic Refraction Profile: Seismic refraction line along the toe of the
existing Cedar Cliff fuse plugs. From GEL Geophysics, LLC report dated January 26, 2017; in
Appendix E. Location shown on Figure 3-5.

HDR Project No. 10020225 Task 63

(a)

(b)

Figure 3-7 - Televiewer Data versus Depth: (a) Plot of all structural televiewer data dips
versus depth. S is foliation, Jt-SR is Joint-Stress Relief, Jt is Joint. Majority of plotted
S-foliation planes are not fractures, but are tight. (b) Plot of Jt-SR and Jt dips versus depth.
Length

HDR Project No. 10020225 Task 63

Figure 3-8(a)

Figure 3-8(b)

N N

HDR Project No. 10020225 Task 63

Figure 3-8(c)

Figure 3-8(a-c): Examples of the ground LiDAR scanned data. (a) Overview of Cedar Cliff Dam
and the Auxiliary Spillway. (b) Auxiliary Spillway looking upstream. (c) Cross-section of the
Auxiliary Spillway along the center-line of Cedar Cliff Dam. N
!"# !$%"!&’()"*)"(+,-"./%,(()0n("1(" #2"+!113+4,-("+4,,(%"0+5(667(!,8.,).)9"9("927$:91(669./%1-,(;;<==)5>1(66)’?(+-%(+@-*(1,8Figure 3-9: Lower Hemisphere - Equal Angle Projection forAll Televiewer Data (Foliation and Joints)
!"# !$%"!&’()"*)"(+,-".l0%,(()’1(+-%(+"("2(" #3"+!224+5,-("+5,,(%"6+7(889(!,:.,).);";(";)’1-%(+;2(88;.0%2-,(<<=>>)7?2(88)’1(+-%(+@-*(2,:Figure 3-10: Lower Hemisphere - Equal Angle Projection forTeleviewer Data in Auxiliary Spillway (Foliation and Joints)
!" !#$" %&’(!)W(!’*+,!-.$+’’/01/01/01!’!2’!"3!* 224*5+6,’!*5++’$!/*7’889’ +0-+(-(:!:’!:/0:/0:/0:62’688:-.$2,+’;;1<<(7=62’688(&>’*,$’*?,)’2+0Figure 3-11: Lower Hemisphere - Equal Angle Projection for TeleviewerData in Auxiliary Spillway. B-9I, B-10I, B-11I. (Foliation and Joints)
!"# !$%"!&’()"*)"(+,-"./%,((01201201"("3(" #4"+!335+6,-("+6,,(%"0+7(889(!,1.,).):":(":01:1:01:01:3(88:./%3-,(;;2<<)7=3(88)’>(+-%(+?-*(3,1Figure 3-12: Lower Hemisphere - Equal Angle Projection for TeleviewerData in Auxiliary Spillway. B-12I, B-13I, B-14I. (Foliation and Joints)
!" !#$" %&’(!)(!’*+,!-.$+’’/0/0/0/!’!1’!"2!* 113*4+5,’!*4++’$!/*6’778’ +9-+(-(:!:’!:/:/:/:/:51’577:-.$1,+’;;0<<(6=51’577(&>’*,$’*?,)’1’*,$’*+9Figure 3-13: Lower Hemisphere - Equal Angle Projection for TeleviewerData in Primary Spillway. B-21, B-22, B-27, B-28. (Foliation and Joints)
!"!"#$# %&’(!)(!’*+!,&&’’’-.+’!*/0’$!1*2’334’.,’.335,’’5+!,+’667--(28.,’.33(&9’*+$’*:+)’,;Figure 3-14: Lower Hemisphere - Equal Angle Projection for Field DataCollected 2014-2015. (Foliation and Joints)
!"#$ !%&""’()*#+*#),-#.Structural ))/(), -)#,0)&#1,2)334) .)5335/5.))5-#.-)6678829.)33*(:),-&),;-+).<Figure 3-15: Lower Hemisphere - Equal Angle Projection for Field DataCollected 2017. (Foliation and Joints)
!"#$!"%&#"’()*#+*#),-#.(()))/ -)#,0)&#1,2)334) .)335.))55-#.-)667//*28.)33*(9),-&),:-+).;Figure 3-16: Lower Hemisphere - Equal Angle Projection for Field DataCollected 2014, 2015, and 2017. (Foliation and Joints)
!"#$!"%&#"’()*#+*#),-#.(()))/*01&)))#!$)#.# -)#,2)&#3,4)556) .)557.))77*01&)).-)//899*4:.)55*(;),-&),<-+).=Figure 3-17: Lower Hemisphere - Equal Angle Projection for AllTeleviewer Data and Field Data. (Foliation and Joints)

Figure 4-1: Tectonostratigraphic terrane map of the southern and central Appalachians (from Hatcher et al.2007) and
approximate location of the East Fork Project.
Duke Energy | Cedar Cliff IDF and Spillway Upgrades
Representative Lithology Types

Boring: B-14I Depth: 130.9-131.75ft

Figure 4-2: Representative Photograph of Biotite Gneiss
Duke Energy | Cedar Cliff IDF and Spillway Upgrades
Representative Lithology Types

Boring: B-10I Depth: 126.5-127.15ft

Figure 4-3: Representative Photograph of Granite
Duke Energy | Cedar Cliff IDF and Spillway Upgrades
Representative Lithology Types

Boring: B-4 Depth: 31.2-31.55ft

Figure 4-4: Representative Photograph of Garnet Mica Schist
Duke Energy | Cedar Cliff IDF and Spillway Upgrades
Representative Lithology Types

Boring: B-11I Depth: 45.7-46.35ft

Figure 4-5: Representative Photograph of Mica Schist
Duke Energy | Cedar Cliff IDF and Spillway Upgrades
Representative Lithology Types

Boring: B-13I Depth: 109.7-110.6ft

Figure 4-6: Representative Photograph of Schistose Biotite Gneiss
Duke Energy | Cedar Cliff IDF and Spillway Upgrades
Representative Lithology Types

Boring: B-12I Depth: 238.5-239.6

Figure 4-7: Representative Photograph of Pegmatite
Duke Energy | Cedar Cliff IDF and Spillway Upgrades
Representative Lithology Types

Boring: B-10I Depth: 113.6-115.0

Figure 4-8: Representative Photograph of Aplite
Duke Energy | Cedar Cliff IDF and Spillway Upgrades
Representative Lithology Types

Boring: B-11I Depth: 59.85-60.6ft

Figure 4-9: Representative Photograph of Quartz Feldspar Gneiss
Cedar Cliff Lithology Statistics Lithology Footage Percent Biotite Gneiss 811.4 46.3% Granite 345.1 19.7% Garnet Mica Schist 207.4 11.8% Mica Schist 128.7 7.3% Schistose Biotite Gneiss 116.9 6.7% Pegmatite 96.3 5.5% Quartz Feldspar Gneiss 15.5 0.9% Aplite 13.3 0.8% Quartzite 9.2 0.5% Granitic Gneiss 4.7 0.3% Calc-Silicate Quartzite 2.9 0.2% 46.3%19.7%11.8%7.3%6.7%5.5%0.9%0.8%0.5%0.3%0.2%Figure 4-10: Cedar Cliff Site-Wide LithologyBiotite GneissGraniteGarnet Mica SchistMica SchistSchistose Biotite GneissPegmatiteQuartz Feldspar GneissApliteQuartziteGranitic GneissCalc-Silicate Quartzite HDR Project No. 10020225 Task 63

37.3%
31.2%
12.3%
9.3%
9.1%
0.8%
Figure 4-11: B-4 Lithology
Garnet Mica Schist
Biotite Gneiss
Granite
Schistose Biotite Gneiss
Mica Schist
Pegmatite

HDR Project No. 10020225 Task 63
B-4 Lithology Statistics
Lithology Footage (ft) Percent
Garnet Mica Schist 28.0 37.3%
Biotite Gneiss 23.4 31.2%
Granite 9.2 12.3%
Schistose Biotite Gneiss 7.0 9.3%
Mica Schist 6.8 9.1%
Pegmatite 0.6 0.8%

69%
31%
Figure 4-12: B-5 Lithology
Schistose Biotite Gneiss
Aplite

HDR Project No. 10020225 Task 63
B-5 Lithology Statistics
Lithology Footage (ft) Percent
Schistose Biotite Gneiss 3.1 69%
Aplite 1.4 31%

B-6 Lithology Statistics
Lithology Footage (ft) Percent
Garnet Mica Schist 17.5 58.3%
Biotite Gneiss 11.7 39.0%
Mica Schist 0.8 2.7%
58.3%
39.0%
2.7%
Figure 4-13: B-6 Lithology
Garnet Mica Schist
Biotite Gneiss
Mica Schist

HDR Project No. 10020225 Task 63

43.5%
38.0%
14.6%
4.0%
Figure 4-14: B-7 Lithology
Mica Schist
Garnet Mica Schist
Biotite Gneiss
Granite

HDR Project No. 10020225 Task 63
B-7 Lithology Statistics
Lithology Footage Percent
Mica Schist 14.3 43.5%
Garnet Mica Schist 12.5 38.0%
Biotite Gneiss 4.8 14.6%
Granite 1.3 4.0%

43.8%
26.1%
13.1%
9.1%
5.7%
2.3%
Figure 4-15: B-8 Lithology
Mica Schist
Quartzite
Biotite Gneiss
Schistose Biotite Gneiss
Granite
Pegmatite

HDR Project No. 10020225 Task 63
B-8 Lithology Statistics
Lithology Footage Percent
Mica Schist 15.4 43.8%
Quartzite 9.2 26.1%
Biotite Gneiss 4.6 13.1%
Schistose Biotite Gneiss 3.2 9.1%
Granite 2.0 5.7%
Pegmatite 0.8 2.3%

59.7%
19.9%
7.8%
5.3%
3.8%1.4%
1.3%0.9%
Figure 4-16: B-9I Lithology
Garnet Mica Schist
Biotite Gneiss
Pegmatite
Mica Schist
Granite
Granitic Gneiss
Schistose Biotite Gneiss
Aplite

HDR Project No. 10020225 Task 63
B-9I Lithology Statistics
Lithology Footage Percent
Garnet Mica Schist 76.1 59.7%
Biotite Gneiss 25.4 19.9%
Pegmatite 9.9 7.8%
Mica Schist 6.7 5.3%
Granite 4.8 3.8%
Granitic Gneiss 1.8 1.4%
Schistose Biotite Gneiss 1.7 1.3%
Aplite 1.1 0.9%

34.2%
22.9%
18.2%
10.6%
6.8%
4.9%
1.8%0.6%
Figure 4-17: B-10I Lithology
Granite
Garnet Mica Schist
Biotite Gneiss
Pegmatite
Aplite
Mica Schist
Calc-Silicate Quartzite
Quartz Feldspar Gneiss

HDR Project No. 10020225 Task 63
B-10I Lithology Statistics
Lithology Footage Percent
Granite 54.5 34.2%
Garnet Mica Schist 36.5 22.9%
Biotite Gneiss 29 18.2%
Pegmatite 16.9 10.6%
Aplite 10.8 6.8%
Mica Schist 7.8 4.9%
Calc-Silicate Quartzite 2.9 1.8%
Quartz Feldspar Gneiss 0.9 0.6%

55.3%
20.1%
14.2%
5.1%
2.8%
2.5%
Figure 4-18: B-11I Lithology
Granite
Biotite Gneiss
Mica Schist
Schistose Biotite Gneiss
Pegmatite
Quartz Feldspar Gneiss

HDR Project No. 10020225 Task 63
B-11I Lithology Statistics
Lithology Footage Percent
Granite 112.1 55.3%
Biotite Gneiss 40.8 20.1%
Mica Schist 28.7 14.2%
Schistose Biotite Gneiss 10.3 5.1%
Pegmatite 5.7 2.8%
Quartz Feldspar Gneiss 5.1 2.5%

58.4%
22.7%
10.6%
5.2%
3.2%
Figure 4-19: B-12I Lithology
Biotite Gneiss
Granite
Pegmatite
Schistose Biotite Gneiss
Mica Schist

HDR Project No. 10020225 Task 63
B-12I Lithology Statistics
Lithology Footage Percent
Biotite Gneiss 146.5 58.4%
Granite 57.0 22.7%
Pegmatite 26.5 10.6%
Schistose Biotite Gneiss 13.0 5.2%
Mica Schist 8.0 3.2%

59.8%
23.5%
7.4%
6.5%
2.9%
Figure 4-20: B-13I Lithology
Biotite Gneiss
Granite
Pegmatite
Schistose Biotite Gneiss
Mica Schist

HDR Project No. 10020225 Task 63
B-13I Lithology Statistics
Lithology Footage Percent
Biotite Gneiss 167.3 59.8%
Granite 65.8 23.5%
Pegmatite 20.7 7.4%
Schistose Biotite Gneiss 18.2 6.5%
Mica Schist 8 2.9%

72.5%
13.1%
5.8%
4.5%
2.4%1.7%
Figure 4-21: B-14I Lithology
Biotite Gneiss
Schistose Biotite Gneiss
Granite
Mica Schist
Pegmatite
Garnet Mica Schist

HDR Project No. 10020225 Task 63
B-14I Lithology Statistics
Lithology Footage Percent
Biotite Gneiss 233.6 72.5%
Schistose Biotite Gneiss 42.2 13.1%
Granite 18.8 5.8%
Mica Schist 14.4 4.5%
Pegmatite 8 2.4%
Garnet Mica Schist 5.5 1.7%

32.3%
25.2%
24.3%
8.9%
4.6%
4.6%
Figure 4-22: B-15 Lithology
Mica Schist
Schistose Biotite Gneiss
Biotite Gneiss
Granite
Pegmatite
Granitic Gneiss

HDR Project No. 10020225 Task 63
B-15 Lithology Statistics
Lithology Footage Percent
Mica Schist 10.5 32.3%
Schistose Biotite Gneiss 8.2 25.2%
Biotite Gneiss 7.9 24.3%
Granite 2.9 8.9%
Pegmatite 1.5 4.6%
Granitic Gneiss 1.5 4.6%

38.4%
33.2%
19.1%
9.4%
Figure 4-23: B-16 Lithology
Biotite Gneiss
Granite
Mica Schist
Schistose Biotite Gneiss

HDR Project No. 10020225 Task 63
B-16 Lithology Statistics
Lithology Footage Percent
Biotite Gneiss 14.7 38.4%
Granite 12.7 33.2%
Mica Schist 7.3 19.1%
Schistose Biotite Gneiss 3.6 9.4%

Biotite
Gneiss,
100%
Figure 4-24: B-19 Lithology

HDR Project No. 10020225 Task 63
Lithology Footage Percent
Biotite Gneiss 4.6 100%
B-19 Lithology Statistics

Biotite
Gneiss,
100%
Figure 4-25: B-20 Lithology

HDR Project No. 10020225 Task 63
Lithology Footage Percent
Biotite Gneiss 1.3 100%
B-20 Lithology Statistics

95.3%
3.0%1.7%
Figure 4-26: B-21 Lithology
Biotite Gneiss
Pegmatite
Granite

HDR Project No. 10020225 Task 63
Lithology Footage Percent
Biotite Gneiss 28.7 95.3%
Pegmatite 0.9 3.0%
Granite 0.5 1.7%
B-21 Lithology Statistics

93.9%
2.7%2.4%0.9%
Figure 4-27: B-22 Lithology
Biotite Gneiss
Schistose Biotite Gneiss
Quartz Feldspar Gneiss
Granite

HDR Project No. 10020225 Task 63
Lithology Footage Percent
Biotite Gneiss 28.7 95.3%
Pegmatite 0.9 3.0%
Granite 0.5 1.7%
B-22 Lithology Statistics

63.2%
24.1%
12.7%
Figure 4-28: B-23 Lithology
Garnet Mica Schist
Quartz Feldspar Gneiss
Pegmatite

HDR Project No. 10020225 Task 63
Lithology Footage (ft) Percent
Garnet Mica Schist 22.8 63.2%
Quartz Feldspar Gneiss 8.7 24.1%
Pegmatite 4.6 12.7%
B-23 Lithology Statistics

58.7%
32.8%
6.6%
1.9%
Figure 4-29: B-27 Lithology
Biotite Gneiss
Garnet Mica Schist
Granite
Pegmatite

HDR Project No. 10020225 Task 63
Lithology Footage Percent
Biotite Gneiss 15.2 58.7%
Garnet Mica Schist 8.5 32.8%
Granite 1.7 6.6%
Pegmatite 0.5 1.9%
B-27 Lithology Statistics

71.4%
18.7%
5.1%
4.8%
Figure 4-30: B-28 Lithology
Biotite Gneiss
Schistose Biotite Gneiss
Granite
Granitic Gneiss

HDR Project No. 10020225 Task 63
Lithology Footage Percent
Biotite Gneiss 21 71.4%
Schistose Biotite Gneiss 5.5 18.7%
Granite 1.5 5.1%
Granitic Gneiss 1.4 4.8%
B-28 Lithology Statistics

33.9%
27.4%
15.2%
11.8%
5.4%
5.0%
1.4%
Figure 4-31: Bear Creek Site-Wide Lithology
Biotite Gneiss
Pegmatite
Schistose Biotite Gneiss
Quartz Feldspar Gneiss
Granitic Gneiss
Mica Schist
Granite
Bear Creek Lithology Statistics
Lithology Footage Percent
Biotite Gneiss 24.6 33.9%
Pegmatite 19.9 27.4%
Schistose Biotite Gneiss 11.0 15.2%
Quartz Feldspar Gneiss 8.6 11.8%
Granitic Gneiss 3.9 5.4%
Mica Schist 3.6 5.0%
Granite 1.0 1.4%

HDR Project No. 10020225 Task 63

62.2%
16.3%
13.4%
8.1%
Figure 4-32: B-17 (Bear Creek) Lithology
Pegmatite
Schistose Biotite Gneiss
Biotite Gneiss
Granitic Gneiss

HDR Project No. 10020225 Task 63
B-17 Lithology Statistics
Lithology Footage Percent
Pegmatite 19.9 62.2%
Schistose Biotite Gneiss 5.2 16.3%
Biotite Gneiss 4.3 13.4%
Granitic Gneiss 2.6 8.1%

59.7%
2.9%
18.5%
11.5%
4.2%
3.2%

Biotite Gneiss
Quartz Feldspar Gneiss
Schistose Biotite Gneiss
Mica Schist
Granitic Gneiss
Granite

HDR Project No. 10020225 Task 63
B-18 Lithology Statistics
Lithology Footage Percent
Biotite Gneiss 18.7 59.7%
Quartz Feldspar Gneiss 0.9 2.9%
Schistose Biotite Gneiss 5.8 18.5%
Mica Schist 3.6 11.5%
Granitic Gneiss 1.3 4.2%
Granite 1.0 3.2%
Figure 4-33: B-18 (Bear Creek) Lithology

82.8%
17.2%
Figure 4-34: B-24 (Bear Creek) Lithology
Quartz Feldspar Gneiss
Biotite Gneiss

HDR Project No. 10020225 Task 63
B-24 Lithology Statistics
Lithology Footage Percent
Quartz Feldspar Gneiss 7.7 82.8%
Biotite Gneiss 1.6 17.2%

58.4%
41.6%
Figure 4-35: B-25 (Tanasee Creek) Lithology
Schistose Biotite Gneiss
Mica Schist
B-25 Lithology Statistics
Lithology Footage Percent
Schistose Biotite Gneiss 5.9 58.4%
Mica Schist 4.2 42.6%

HDR Project No. 10020225 Task 63

B-26 Lithology Statistics
Lithology Footage Percent
Schistose Biotite Gneiss 2.7 77.1%
Biotite Gneiss 0.4 11.4%
Quartz Feldspar Gneiss 0.4 11.4%

77.1%
11.4%
11.4%
Figure 4-36: B-26 (Wolf Creek) Lithology
Schistose Biotite Gneiss
Biotite Gneiss
Quartz Feldspar Gneiss

HDR Project No. 10020225 Task 63
B
B

HDR Project No. 10020225 Task 63

Figure 4-39 – S1 and S2 Foliations: Dominant foliations (S1 and S2) in interlayered biotite
gneiss and thin mica schist layers folded by F3 tight, open folds.

Figure 4-40 – S2 Foliation in Mica Schist and Garnet Mica Schist: Second generation
foliation (S2) in mica schist and garnet mica schist.
NSEWbmSymbol TYPEQuantityS134S-Ct4Color Density Concentrations0.00 - 2.702.70 - 5.405.40 - 8.108.10 - 10.8010.80 - 13.5013.50 - 16.2016.20 - 18.9018.90 - 21.6021.60 - 24.3024.30 - 27.00Maximum Density26.32%Contour DataPole VectorsContour DistributionFisherCounting Circle Size1.0%Plot ModePole VectorsVector Count138 (138 Entries)HemisphereLowerProjectionEqual AngleTrend & Plunge - S65W;19Analysis DescriptionField Foliation Data - Global Best Fit - Trend & Plunge of FoldsCompanyHDRDrawn ByM. SchaefferFile NameCedar Cliff_Field Foliation Data_Only_02-27-2017.dips6Date2/27/2017, 10:33:50 AMProjectEast Fork ProjectDIPS 6.015 Figure 4-41: Equal Angle Projection - Poles toFoliation, Fold Girdle

HDR Project No. 10020225 Task 63

Figure 4-42 – F2 Isoclinal Fold: F2 isoclinal fold showing folding of the S1 gneissic foliation
(red dashed line) and an S2 axial planar foliation (orange dashed lines) developed in thin mica
schist layers. Blue dashed line is the approximate trace of the F2 fold axial plane intersection
with the rock surface.

Figure 4-43 – F3 Antiformal Fold: F3 antiformal fold in the Cedar Cliff Auxiliary Spillway (red
dashed lines).

HDR Project No. 10020225 Task 63

Figure 4-44 – F3 Antiformal and Synformal Folds: F3 antiformal and synformal folds along
the right wall of the Auxiliary Spillway folds both the S1 and S2 foliation. Northeast-trending fold
axis, slightly overturned to the southeast.

Figure 4-45 – F3 Crenulation Fold: F3 crenulation fold in mica schist layer in the right wall of
the Auxiliary Spillway. Northeast-trending fold axis.

HDR Project No. 10020225 Task 63

Figure 4-46 – First Generation Pegmatite -Boudinage: First-generation pegmatites parallel to
the S1 foliation stretched during the F2 folding event producing boudinage structure. A later
generation pegmatite (top of picture) cross-cuts the boudinage structure. Right wall of the
Auxiliary Spillway.

Figure 4-47 – Granite Intruded into S2 Foliation: Granite intruded along the S2 foliation
(concordant contacts) of mica schist in Borehole B-10I.

HDR Project No. 10020225 Task 63

Figure 4-48 – Granite Intrusion Cross-Cutting Foliation: Granitic intrusion cross-cutting

Figure 4-49 – Granite Cross-Cutting Granite: Granite cross-cutting granite in B-4.

foliation in biotite gneiss.

HDR Project No. 10020225 Task 63

Figure 4-50 – Biotite Gneiss Xenolith in Granite (Displaced): Biotite Gneiss Xenolith in

Figure 4-51 – Biotite Gneiss Xenolith in Granite (Rock Core): Biotite Gneiss Xenoliths in
Granite in the east wall of the Auxiliary Spillway.
Granite in Borehole B-13I.

HDR Project No. 10020225 Task 63

Figure 4-52 – Granite, Pegmatites, and Folds: Granite cross-cutting F3 folds and first-

Figure 4-53 – Granite Cross-Cutting F3 Fold (Rock Core): Granite cross-cutting F3 Fold in
generation pegmatite and all three cut by a second-generation pegmatite.
Borehole B-14I

HDR Project No. 10020225 Task 63

Figure 4-54 – Discontinuous Stress Relief Joint: Planar block slide along a low angle
discontinuous stress relief joint (N31E; 37SE) along the right wall of the Auxiliary Spillway (Left
Abutment Rock Mass).

Figure 4-55 – Valley-Side Stress Relief Joint: Valley-side stress relief joints developed in
granite. Located on the west wall of the Auxiliary Spillway (Approximately 20 ft south of the end
of Line 10 shown on Figure 3-5).

HDR Project No. 10020225 Task 63

Figure 4-56 – Left Abutment Continuous Feature (Close Up): Continuous structural feature
(quartz vein with fractured contacts). Right wall of the Auxiliary Spillway (Left Abutment Rock
Mass). Point 3 used in the 3-Point structural analysis.

Figure 4-57 - Left Abutment Continuous Feature (Entirety): Continuous structural feature
(quartz vein with fractured contacts). Right wall of the Auxiliary Spillway (Left Abutment Rock
Mass). Point 3 and Point 1 (Borehole B-4) used in the 3-Point structural analysis.

HDR Project No. 10020225 Task 63

Figure 4-58 – Stratigraphic Sequences Underlying Auxiliary Spillway: Cedar Cliff Auxiliary
Spillway – Percentages of major rock types in Sections 1 and 2 of the stratigraphic sequence
based on Borehole Lithologies. Actual percentages of the lithologies may vary due to the 3-
Dimensional variation in the continuity and thicknesses of the lithologies and the complex
structure (folding and granitic intrusion).

HDR Project No. 10020225 Task 63

Figure 4-59 – Schistose Sequence 1 in Auxiliary Spillway: Weathering and planar rock
slides in Sequence 1 at the north end of the fuseplug.

Figure 4-60 – Biotite Gneiss/Granitic Sequence 2 in Auxiliary Spillway: Less weathered
rock of Sequence 2 in the east wall of the Auxiliary Spillway.

HDR Project No. 10020225 Task 63

Figure 5-1 - Possible slope failure modes in rock cuts.

HDR Project No. 10020225 Task 63

Figure 5-2 - Photograph of Planar Slide:Planar failure on the east wall of the
Cedar Cliff Auxiliary Spillway.

HDR Project No. 10020225 Task 63

Figure 5-3 - Photograph of Wedge Slide: East cut of the Auxiliary Spillway with areas of previous
planar sliding, potential planar sliding, and a large previous wedge failure controlled by the two
main rock mass discontinuities.

HDR Project No. 10020225 Task 63

Figure 5-4 - Photograph of Flexural Toppling Slide: Foliation and stress relief joints near
Cedar Cliff Dam right abutment. Note the potential for flexural toppling failures and previous
toppling failures related to foliation.

HDR Project No. 10020225 Task 63

Figure 5-5 - Photograph of Direct Toppling: Foliation, high-angle joint, and stress relief joints
near the Cedar Cliff Dam right abutment. Note the location the direct toppling mode failure
associated with the foliation and high-angle joint.

Figure 6-1 - Barton JRC Chart: Relationship between JRC, length of profile, and amplitude
of asperities used to estimate JRC values for foliation and joints at Cedar Cliff (Barton 1990).

HDR Project No. 10020225 Task 63

Figure 7-1 - Kinematic Lines A-D: Location of Kinematic Analysis Sections of
the Fusegate Inlet Pipe Trench

HDR Project No. 10020225 Task 63

Figure 7-2 - Kinematic Analysis Lines 1-5 and Lines E-F: Location of Kinematic Analysis
Sections of the Left Abutment Rock Mass and East Auxiliary Spillway Cuts.
Section 1
Section 2
Section 3
Section 4
Section 5
Figure 7-3 - Kinematic Analysis
Alternative 3-2, Sections 1-5: Rock-cut
auxiliary spillway Alternate 3 and
location of stability analysis sections
(Dec. 19, 2014 HDR Tech Memo
located in Appendix A)

Figure 8-1: Area of rock removal on the left abutment rock mass for the new Fusegate
Structure.

Figure 8-2: West wall of auxiliary spillway channel showing the oblique orientation of foliation in the
bedrock to the direction of flow. Water infiltration along foliation planes could result in hydraulic
jacking and dislodgement of rock blocks (such as the block labeled A) during a spilling event.

Figure 8-3: Section View of Main Dam and Toe Berm

Figure 8-4: Construction Photograph. April 6, 1951. Downstream Rock Toe

Figure 8-5Figure 8-5
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project and Cedar Cliff Development (FERC No. 2698)

Tables

June 5, 2017
Table 3-1: Subsurface Investigation Borehole Summary
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project
Borehole East Fork Project
Location Boring Area Northing Easting Elevation2,3 Orientation Total Depth /
Length1 (ft)
Depth1 to
Refusal (ft)Televiewer Log Notes
B-4 Cedar Cliff Left Abutment Rock Mass 572,331.89 776,893.48 2,345.47 Vertical 77.7 2.0 Yes -
B-5 Cedar Cliff Reservoir Rim 572,736.86 777,087.48 2,349.25 Vertical 32.4 27.9 No -
B-6 Cedar Cliff Upstream of Fuse Plugs 572,453.75 776,828.57 2,297.20 Vertical 40.4 N/A No Barge Boring in Cedar Cliff Lake
B-7 Cedar Cliff Upstream of Fuse Plugs 572,607.02 776,878.82 2,307.30 Vertical 35.5 N/A No Barge Boring in Cedar Cliff Lake
B-8 Cedar Cliff Downstream of Fuse Plugs 572,446.62 776,966.46 2,311.76 Vertical 37.2 1.3 No Boring on Seismic Refraction Line
B-9V Cedar Cliff Auxiliary Spillway Back Wall 572,540.97 777,093.04 2,388.69 Vertical 14.1 14.1 No Vertical Offset for B-9I Boring
B-9I Cedar Cliff Auxiliary Spillway Back Wall 572,544.15 777,093.25 2,388.19 Inclined 30˚; Oriented South 141.6 14.1 Yes Depth = 122.6 ft; Horizontal Distance = 70.8 ft
B-10V Cedar Cliff Auxiliary Spillway Back Wall 572,420.59 777,133.10 2,409.02 Vertical 4.6 4.6 No Vertical Offset for B-10I Boring
B-10I Cedar Cliff Auxiliary Spillway Back Wall 572,423.95 777,133.23 2,408.67 Inclined 30˚; Oriented South 165.9 6.0 Yes Depth = 143.7 ft; Horizontal Distance = 83.0 ft
B-11V Cedar Cliff Auxiliary Spillway Back Wall 572,294.26 777,126.93 2,439.18 Vertical 16.9 16.9 No Vertical Offset for B-11I Boring
B-11I Cedar Cliff Auxiliary Spillway Back Wall 572,297.36 777,127.17 2,438.79 Inclined 30˚; Oriented South 216.5 13.8 Yes Depth = 187.5 ft; Horizontal Distance = 108.2 ft
B-12V Cedar Cliff Auxiliary Spillway Back Wall 572,161.33 777,088.34 2,468.91 Vertical 6.0 6.0 No Vertical Offset for B-12I Boring
B-12I Cedar Cliff Auxiliary Spillway Back Wall 572,164.82 777,088.81 2,468.53 Inclined 30˚; Oriented South 256.0 5.0 Yes Depth = 221.7 ft; Horizontal Distance = 128.0 ft
B-13V Cedar Cliff Auxiliary Spillway Back Wall 572,044.51 777,063.22 2,494.63 Vertical 9.1 9.1 No Vertical Offset for B-13I Boring
B-13I Cedar Cliff Auxiliary Spillway Back Wall 572,048.05 777,063.46 2,494.29 Inclined 30˚; Oriented South 300.9 20.9 Yes Depth = 260.6 ft; Horizontal Distance = 150.5 ft
B-14V Cedar Cliff Auxiliary Spillway Back Wall 571,869.49 777,027.68 2,518.46 Vertical 9.5 9.5 No Vertical Offset for B-14I Boring
B-14I Cedar Cliff Auxiliary Spillway Back Wall 571,880.55 777,024.86 2,517.79 Inclined 30˚; Oriented South 336.0 13.8 Yes Depth = 291.0 ft; Horizontal Distance = 168.0 ft
B-15 Cedar Cliff Toe of Dam 572,103.91 776,576.32 2,184.81 Vertical 50.8 18.3 No -
B-16 Cedar Cliff Toe of Dam 572,147.91 776,479.51 2,185.82 Vertical 54.7 16.4 No -
B-17 Bear Creek Powerhouse Tailrace 568,264.06 783,597.27 2,320.30 Vertical 32.0 N/A No Barge Boring in Bear Creek Tailrace
B-18 Bear Creek Powerhouse Tailrace 568,268.89 783,568.57 2,320.70 Vertical 35.3 N/A No Barge Boring in Bear Creek Tailrace
B-19 Cedar Cliff Primary Spillway 572,409.99 776,274.45 2,340.27 Vertical 10.5 0.0 No -
B-20 Cedar Cliff Primary Spillway 572,415.30 776,241.83 2,340.29 Vertical 10.7 0.0 No -
B-21 Cedar Cliff Primary Spillway 572,444.37 776,297.27 2,339.35 Vertical 30.9 0.8 No -
B-22 Cedar Cliff Primary Spillway 572,443.04 776,229.39 2,340.66 Vertical 35.4 1.0 Yes -
B-23 Cedar Cliff Reservoir Rim 572,686.93 777,047.98 2,349.85 Vertical 50.8 14.0 No -
B-24 Bear Creek Primary Spillway 568,268.10 784,672.74 2,570.53 Vertical 10.0 0.5 No -
B-25 Tanasee Creek Primary Spillway 556,921.15 804,638.62 3,090.66 Vertical 10.7 0.6 No -
B-26 Wolf Creek Primary Spillway 560,202.41 806,064.78 3,091.39 Vertical 10.7 1.3 No -
B-27 Cedar Cliff Primary Spillway 572,459.21 776,224.75 2,345.73 Vertical 32.1 2.5 Yes -
B-28 Cedar Cliff Primary Spillway 572,444.37 776,297.27 2,339.35 Vertical 33.2 3.8 Yes -
Notes:
1. Inclined Holes use the convention of length along corehole (ft) rather than depth. Vertical holes are presented in depth below ground surface.
2. Coordinates for Barge Borings were estimated in the field from a Trimble GeoXT GeoExplorer 2008 Series;
Elevations for Barge Borings were estimated using lake elevations on first day of drilling and depth to bottom of water body.
3. Surveys for non-Barge Borings were performed by Alliance Land Surveying on January 25, 2017.
HDR Project No. 10020225 Task 63 Page 1 of 1
Table 3-2: Cedar Cliff - Packer Test ResultsGeological and Geotechnical Subsurface Investigation East Fork Hydroelectric ProjectBorehole Test No. Depth (ft)Depth of Hole (ft)Water Level (ft)Shut-In Pressure Change (psi)Hydraulic Conductivity, k, (cm/sec)Remarks - Test Interval Description Test InterpretationB-81 29.3 - 34.6 37.2 -0.281.31-Interlayered biotite gneiss and mica schist. Recovery = 100%; RQD = 100% in test interval.No take at 30 psi maximum pressure. Higher maximum pressure required to induce flow (overcome hydraulic head), but not attempted due to shallow depth of the test interval and the potential for opening existing fractures and/or inducing hydraulic fractures in the rock mass.B-82 24.3 - 29.6 37.2 -0.591.27-Interlayered mica schist, quartzite, and biotite gneiss. Recovery = 100%; RQD = 100% in test interval.No take at 30 psi maximum pressure. Higher maximum pressure required to induce flow (overcome hydraulic head), but not attempted due to shallow depth of the test interval and the potential for opening existing fractures and/or inducing hydraulic fractures in the rock mass.B-83 19.2 - 24.5 37.2 -0.341.41-Interlayered schistose biotite gneiss and mica schist. Recovery = 100%; RQD = 100% in test interval.No take at 25 psi maximum pressure. Higher maximum pressure required to induce flow (overcome hydraulic head), but not attempted due to shallow depth of the test interval and the potential for opening existing fractures and/or inducing hydraulic fractures in the rock mass.B-84 14.3 - 19.6 37.2 -0.501.36-Interlayed biotite gneiss and mica schist wth granitic and pematatic intrusions. Recovery = 100%; RQD = 100% in test interval.No take at 25 psi maximum pressure. Higher maximum pressure required to induce flow (overcome hydraulic head), but not attempted due to shallow depth of the test interval and the potential for opening existing fractures and/or inducing hydraulic fractures in the rock mass.B-85 9.3 - 14.6 37.2 -0.25.1.58-Interlayered quartzite, biotite gneiss, and mica schist. Recovery = 100%; RQD = 100% in test interval.No take at 20 psi maximum pressure. Shut-in 20 psi pressure at end of pressure test with pressure increasing to 24.5 psi in five minutes indicating upward flow in the test interval. Higher maximum pessure required to induce flow (overcome hydraulic head), but not attempted due to shallow depth of the test interval and the potential for opening existing fractures and/or inducing hydraulic fractures in the rock mass.B-86 6.2 - 11.5 37.2 -0.100.58-Interlayered quartzite, schistose biotite gneiss, and mica schist. Recovery = 100%; RQD = 100% in test interval.No take at 13 psi maximum pressure. Shut-in 13 psi pressure at end of pressure test with pressure increasing to 15.2 psi in five minutes indicating upward flow in the test interval. Higher maximum pessure required to induce flow (overcome hydraulic head), but not attempted due to shallow depth of the test interval and the potential for opening existing fractures and/or inducing hydraulic fractures in the rock mass.HDR Project No. 10020225 Task 63Page 1 of 11. Blue text indicates an increase in pressure during the shut-in test. 2. Refer to Appendix C for Packer Testing and Shut-In Testing Worksheets.Notes:
Table 3-3: Geotechnical Testing ResultsGeological and Geotechnical Subsurface InvestigationEast Fork Hydroelectric ProjectSample ID Rock Type Depth (ft) Run Test Unit Weight (pcf)Unconfined Compressive Strength (psi)Tensile Strength (psi)Failure Type1NotesIn Conformance with ASTM D4543In Conformance with ASTM D3967B-10I-1 Biotite Gneiss 34.20 - 34.65 RC-6 UCS 167 12,048 1YesB-10I-2 Biotite Gneiss 45.3 - 45.9 RC-8STS3- - 1,470 1YesB-11I-7 Biotite Gneiss 155.85 - 156.31 RC-31UCS2168 18,213 - 1YesB-11I-8 Biotite Gneiss 166.55 - 167.40 RC-34 STS1,290 1YesB-12I-5 Biotite Gneiss 67.10 - 67.55 RC-15 UCS 168 16,329 - 1YesB-12I-6 Biotite Gneiss 67.80 - 68.50 RC-15 STS - - 1,080 1YesB-13I-10 Biotite Gneiss 48.90 - 49.70 RC-6 STS - - 1,120 1YesB-13I-11 Biotite Gneiss 61.05 - 61.50 RC-9 UCS 168 14,288 3Primary failure initiiated along a Foliation Plane with partial intact rock failure.YesB-13I-12 Biotite Gneiss 61.70 - 62.50 RC-9 STS - - 1,600 1YesB-13I-5 Biotite Gneiss 230.20 - 230.65 RC-42 UCS 168 11,402 1 Secondary failure along Foliation Plane. YesB-13I-6 Biotite Gneiss 230.90 - 231.80 RC-43 STS - - 1,130 3 Partial failure along high angle fracture. YesB-13I-9 Biotite Gneiss 48.40 - 48.85 RC-6 UCS 169 16,663 1No4B-14I-1 Biotite Gneiss 34.55 - 35.05 RC-5 UCS 168 22,848 - 1YesB-14I-2 Biotite Gneiss 35.30 - 35.90 RC-5 STS - - 1,430 1YesB-14I-7 Biotite Gneiss 128.30 - 128.76 RC-24 UCS 170 23,472 - 1YesB-14I-8 Biotite Gneiss 130.90 - 131.75 RC-25 STS - - 2,160 1YesB-9I-3 Biotite Gneiss 136.70 - 137.40 RC-29 STS - - 1,500 1YesB-9I-4 Biotite Gneiss 137.42 - 137.88 RC-29 UCS 170 21,813 - 1YesB-19-1 Concrete 9.50 - 10.50 RC-2 UCS 149 5,972T35ASTM C42 ASTM C42 - YesB-20-1 Concrete 1.40 - 2.30 RC-2 UCS 152 6,114T35ASTM C42 ASTM C42 - YesB-20-2 Concrete 5.7 - 6.6 RC-3 UCS 150 6,826T35ASTM C42 ASTM C42 - YesB-10I-3 Garnet Mica Schist 61.10 - 61.55 RC-12 UCS 176 10,16136Primary failure initiated across intact rock; complete failure along a Foliation Plane.YesB-10I-4 Garnet Mica Schist 61.6 - 62.3 RC-12 STS - - 697 1YesB-10I-7 Garnet Mica Schist 155.90 - 156.35 RC-33 UCS 182 2,297 - 2 Failure along Foliation Plane. No4B-10I-8 Garnet Mica Schist 156.65 - 157.40 RC-33 STS - - 652 1YesB-9I-1 Garnet Mica Schist 64.89 - 65.35 RC-12 UCS 180 7,144 - 1YesB-9I-2 Garnet Mica Schist 65.45 - 66.05 RC-12 STS - - 1,150 1YesB-10I-5 Granite 125.95 - 126.41 RC-25 UCS 166 20,717 - 1YesB-10I-6 Granite 126.50 - 127.15 RC-26 STS - - 1,190 1YesB-11I-5 Granite 104.20 - 104.67 RC-20 UCS 167 18,508 - 1YesB-11I-6 Granite 104.95 - 105.65 RC-20 STS - - 1,240 1YesB-13I-1 Granite 293.05 - 293.50 RC-55 UCS 166 21,370 1YesHDR Project Number: 10020225 Task 63Page 1 of 2
Table 3-3: Geotechnical Testing ResultsGeological and Geotechnical Subsurface InvestigationEast Fork Hydroelectric ProjectSample ID Rock Type Depth (ft) Run Test Unit Weight (pcf)Unconfined Compressive Strength (psi)Tensile Strength (psi)Failure Type1NotesIn Conformance with ASTM D4543In Conformance with ASTM D3967B-13I-13 Granite 67.05 - 67.50 RC-10 UCS 166 16,190 1YesB-13I-14 Granite 67.80 - 68.60 RC-10 STS - - 880 1YesB-13I-2 Granite 293.60 -294.30 RC-55 STS - - 1,870 1YesB-14I-10 Granite 171.70 - 172.50 RC-33 STS - - 1,450 1YesB-14I-9 Granite 170.90 - 171.35 RC-33 UCS 164 26,383 - 1YesB-11I-1 Mica Schist 45.10 - 45.51 RC-7 UCS 178 7,494 -26Failure along Foliation Plane. YesB-11I-2 Mica Schist 45.70 - 46.35 RC-7 STS - - 863 1YesB-12I-1 Pegmatite 236.15 - 236.60 RC-50 UCS 163 24,601 1YesB-12I-2 Pegmatite 237.30 - 237.80 RC-50 STS - - 1,000 1YesB-13I-7 Pegmatite 215.35 - 215.80 RC-39 UCS 164 17,943 1YesB-13I-8 Pegmatite 217.30 - 218.30 RC-40 STS - - 1,160 1YesB-13I-17 Pegmatite 144.53 - 144.98 RC-25 UCS 164 15,602 1YesB-13I-18 Pegmatite 144.0 - 144.50 RC-25 STS - - 1,170 1YesB-14I-3 Pegmatite 84.65 - 85.07 RC-15 UCS 163 18,864 - 1YesB-14I-4 Pegmatite 85.35 - 85.90 RC-15 STS - - 645 1YesB-11I-3 Quartz Feldspar Gneiss 59.20 - 59.66 RC-10 UCS 165 24,537 - 1YesB-11I-4 Quartz Feldspar Gneiss 59.85 - 60.60 RC-10 STS - - 1,580 1YesB-23-1 Quartz Feldspar Gneiss 49.70 - 50.15 RC-8 STS - - 1,240 1YesB-23-2 Quartz Feldspar Gneiss 50.30 - 50.75 RC-8 UCS 164 18,319 1YesB-12I-3 Schistose Biotite Gneiss 94.71 - 95.15 RC-21 UCS 179 6,283 - 1YesB-12I-4 Schistose Biotite Gneiss 95.35 - 96.0 RC-21 STS - - 946 1YesB-13I-15 Schistose Biotite Gneiss 109.05 - 109.5 RC-18 UCS 178 4,359 2 Failure along Foliation Plane. YesB-13I-16 Schistose Biotite Gneiss 109.70 - 110.60 RC-18 STS - - 836 1YesB-13I-3 Schistose Biotite Gneiss 281.25 - 281.70 RC-53 UCS 177 3,998 3Failure along Foliation Plane. Tensile crack developed parallal to long axis of core.YesB-13I-4 Schistose Biotite Gneiss 281.80 - 282.70 RC-54 STS - - 902 1YesB-14I-5 Schistose Biotite Gneiss 101.25 - 101.85 RC-19 STS - - 1,160 1YesB-14I-6 Schistose Biotite Gneiss 102.55 - 103.01 RC-19 UCS 176 5,854 - 2 Failure along Foliation Plane. YesNotes: 4Core did not meet ASTM D7012 Method C side straightness tolerance due in irregularities in the sample as cored.1Failure Type: 1 = Intact Material Failure; 2= Discontinuity Failure; 3 = Intact Material and Discontinuity Failure.2UCS: Unconfined Compressive Strength ASTM D7012 Method C.3STS: Splitting (Indirect or Brazilian) Tensile Strength ASTM D3967.5T3 = Type 3 Concrete: Columnar vertical cracing through both ends, no well formed cones.6Failure Type Reclassified by HDR.HDR Project Number: 10020225 Task 63Page 2 of 2
Table 3-4: Geotechnical Testing StatisticsGeological and Geotechnical Subsurface InvestigationEast Fork Hydroelectric ProjectUW (pcf) UCS (psi) UW (pcf) UCS (psi) STS (psi) UW (pcf) UCS (psi) STS (psi) UW (pcf) UCS (psi) STS (psi) UW (pcf) UCS (psi) STS (psi) UW (pcf) UCS (psi) STS (psi) UW (pcf) UCS (psi) STS (psi)149 5972 167 12048 1470 177 3998 902 176 10161 697 166 21370 1870 164 18319 1240 163 24601 1000152 6114 168 11402 1130 178 4357 836 180 7144 1150 166 16190 880 165 24537 1580 164 15602 1170150 6826 169 16663 1120 179 6283 946 182 2297 652 166 20717 1190163 18864 645168 14288 1600 176 5854 1160 178 7494 863 167 18508 1240164 17943 1,160170 21813 1500164 26383 1450168 18213 1290168 16329 1080168 22848 1430170 23472 2160Count =3 3 9 9 9 4 4 4 4 4 4 5 5 5 2 2 2 4 4 4Mean =150.3 6,304 168.4 17,453 1,420 177.5 5,123 961 179.0 6,774 841 165.8 20,634 1,326 164.5 21,428 1,410 163.5 19,253 994SD =1.5 458 1.0 4,509 335 1.3 1,115 140 2.6 3,275 225 1.1 3,804 366 0.7 4,397 240 0.6 3,821 245+1SD =151.9 6,762 169.5 21,962 1,755 178.8 6,238 1,101 181.6 10,049 1,066 166.9 24,437 1,692 165.2 25,825 1,650 164 23,073 1,239-1SD =148.8 5,846 167.4 12,944 1,085 176.2 4,008 821 176.4 3,499 615 164.7 16,830 960 163.8 17,031 1,170 163 15,432 749Min =149 5,972 167 11,402 1,080 176 3,998 836 176.0 2,297 652 164 16,190 880 164 18,319 1,240 163 15,602 645Max =152 6,826 170 23,472 2,160 179 6,283 1,160 182.0 10,161 1,150 167 26,383 1,870 165 24,537 1,580 164 24,601 1,170Notes: 1. UW - Unit Weight pcf - Pounds per Cubic FootUCS - Unconfined Compressive StrengthSTS - Splitting Tensile Strenghpsi - Pounds per Square Inch2. Refer to Table 3-3 for raw data points from the testing program; full testing reports can be foundin Appendix D of the Subsurface Investigation Report. PegmatiteSchistose Biotite GneissMica Schist and Garnet Mica SchistBiotite GneissGranite Quartz Feldspar GneissStatistical SummaryLithologyTest Results Data PointsConcreteHDR Project No. 10020225 Task 63 Page 1 of 1
Table 3-5: Water Level Measurements
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project
Borehole Ground Surface
Elevation (ft msl)
Date of Water Level
Measurement
Depth bgs
(ft)
Water Level
Elevation (ft)
Lake Elevation
(ft)Notes
10/29/2016 30.7 2314.8 --
11/7/2016 42.3 2303.2 --
11/11/2016 43.6 2301.9 --
8/23/2016 20.6 2328.7 --
8/24/2016 20.6 2328.7 --
10/26/2016 Lake Level -2328.6 -
10/27/2016 Lake Level -2328.5 -
10/28/2016 11.5 -2328.4 Below Lake Level, Casing Sealed. Measured Below Lake Elevation
10/29/2016 9.8 -2328.3 Below Lake Level, Casing Sealed. Measured Below Lake Elevation
10/30/2016 4.7 -2328.2 Below Lake Level, Casing Sealed. Measured Below Lake Elevation
10/22/2016 0.0 2311.8 --
10/27/2016 +0.6 2312.4 -Ponded Area Above Ground Surface
8/26/2016 28.8 2359.4 -Measured Immediately Upon Completion
9/6/2016 28.8 2359.4 --
9/8/2016 28.8 2359.4 --
9/15/2016 29.3 2358.9 --
B-9V 2388.7 8/18/2016 Dry ---
9/6/2016 10.5 2398.2 --
9/7/2016 14.1 2394.6 --
9/8/2016 34.4 2374.3 --
9/15/2016 34.1 2374.6 --
B-10V 2409.0 11/14/2016 Dry ---
9/15/2016 31.5 2407.3 --
9/30/2016 32.0 2406.8 --
10/5/2016 33.3 2405.5 --
10/11/2016 33.6 2405.2 --
B-11V 2439.2 9/15/2016 Dry ---
9/19/2016 17.9 2450.6 --
9/20/2016 16.8 2451.7 --
9/21/2016 16.5 2452.0 --
9/22/2016 16.5 2452.1 --
9/27/2016 17.5 2451.0 --
9/29/2016 29.6 2438.9 -Morning after Total Depth Reached; Tooling Removed
9/30/2016 16.7 2451.8 -Measured 15 Hours After Flushing for Televiewer
10/5/2016 17.8 2450.8 --
10/11/2016 16.9 2451.7 --
B-12V 2468.9 8/25/2016 Dry ---
2408.7
2438.8
2468.5
2345.5
2349.3
2307.3
2311.8
2388.2
2297.2
B-5
B-11I
B-12I
B-6
B-4
B-7
B-8
B-9I
B-10I
HDR Project No. 10020225 Task 63 Page 1 of 2
Table 3-5: Water Level Measurements
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project
Borehole Ground Surface
Elevation (ft msl)
Date of Water Level
Measurement
Depth bgs
(ft)
Water Level
Elevation (ft)
Lake Elevation
(ft)Notes
10/4/2016 30.1 2464.2 --
10/5/2016 28.8 2465.5 --
10/7/2016 32.1 2462.2 --
10/10/2016 30.9 2463.4 --
10/11/2016 30.3 2464.0 -Measured 6 hours after Flushing for Televiewer
10/18/2016 40.3 2454.0 --
B-13V 2494.6 10/11/2016 Dry ---
11/3/2016 18.6 2499.2 --
11/8/2016 17.7 2500.1 --
11/11/2016 14.5 2503.3 -Measured 30 Minutes After Flushing for Televiewer
11/12/2016 9.4 2508.4 --
11/16/2016 6.4 2511.4 --
B-14V 2518.5 8/25/2016 Dry ---
9/30/2016 5.0 2179.8 --
10/1/2016 4.7 2180.1 --
B-16 2185.8 9/29/2016 5.8 2180.0 --
10/19/2016 Lake Level -2329.1 -
10/20/2016 Lake Level -2329.1 -
B-18 2320.7 10/10/2016 Lake Level -2329.1 -
B-19 2340.3 11/11/2016 Dry ---
B-20 2340.3 11/8/2016 Dry ---
11/11/2016 12.1 2327.3 --
11/16/2016 12.2 2327.2 --
10/5/2016 6.9 2333.8 --
10/7/2016 12.3 2328.4 --
11/17/2016 15.1 2325.6 --
8/19/2016 5.4 2344.5 --
8/20/2016 16.3 2333.6 -Tooling Removed
8/22/2016 18.3 2331.6 --
8/23/2016 18.7 2331.2 --
B-24 2570.5 11/14/2016 Dry ---
B-25 3090.7 11/15/2016 Dry ---
B-26 3091.4 11/17/2016 Dry ---
B-27 2345.7 11/8/2016 11.2 2334.5 --
11/10/2016 18.7 2320.7 --
11/16/2016 10.8 2328.6 --
Notes:
1. Water level elevations measured from Below Ground Surface unless otherwise noted.
2. Water Levels measured during drilling unless otherwise noted. Special conditions or factors also noted.
2349.9
2339.4
2494.3
2517.8
2320.3
2184.8
2339.4
2340.7
B-23
B-28
B-13I
B-14I
B-15
B-17
B-21
B-22
HDR Project No. 10020225 Task 63 Page 2 of 2
Table 3-6: Televiewer and Field Structural DataGeological and Geotechnical InvestigationEast Fork Hydroelectric ProjectCOMBINED DATAStructureAll Data - Foliation and Joints1 N2 = 308Auxillary Spillway - Joints and Foliation N = 247Auxiliary Spillway - Joints and Foliation, B-9I, B-10I, B-11I N = 47Auxiliary Spillway - Joints and Foliation, B-12I, B-13I, B-14I N = 192Primary Spillway - Joints and Foliation, B-21, B-22, B-27, B-28, N = 61Field Data 2014-2015 N = 114Field Data 2017 N = 105Field Data (2014-2015 and 2017) N = 219Field Data (2014-2015 and 2017) and All Televiewer Data N = 527Foliation (S)N64E; 75NW N64E;75NW N68E; 77NW N63E; 75NW N65E; 72NWN60E: 75NW N58E; 81NWN59E; 78NW N62E; 75NWJt-SR3N6E;5SE N80W; 3NE - N33W; 6NE N48E; 11SE- -N10E; 5SEJt-SRN83E;36NW N83E; 34NW N88E; 35NW N81E; 32NW N86E; 57NW- -N87E;33NWJt-C4/Jt-D5- - - - -N42W; 88NE -N37W; 89SW N37W; VNotes:- FIELD DATA TELEVIEWER DATA4Jt-C: Joint-Continuous (Trace Length > 20 feet)5Jt-D: Joint-Discontinuous (Trace Length < 20 feet)1All Televiewer Data3Jt-SR: Joint-Stress Relief2Number of Structural MeasurementsHDR Project No. 10020225 Task 63 Page 1 of 1
Table 3-7: Joint Roughness Coefficient Field Estimates
of Foliation Surfaces
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project
Field Line/
Location1
Designation
Photograph Line # Length (ft)
Amplitude
(ft)Length (m)Amplitude
(mm)JRC2 JRC
(50 ft)
JRC
(75 ft)
JRC
(100 ft)
Line 1/10 ft JRC1 Line 1 5.6482
0.2593 1.7 79 20 8.4 7.1 6.3
Line 2 4.7123
0.1048 1.4 32 12 6.8 6.2 5.8
Line 3 9.8765
0.1151 3.0 35 6 4.9 4.7 4.5
Line 4 6.0526
0.1677 1.8 51 13 7.5 6.8 6.3
Line 2/46 ft JRC2 Line 1 4.3822
0.0980 1.3 30 12 6.7 6.1 5.7
Line 2 3.8594
0.0630 1.2 19 8 5.3 5.0 4.8
Line 3 8.0689
0.2098 2.5 64 12 7.7 7.0 6.6
Line 4 8.7869
0.5034 2.7 153 20 10.0 8.5 7.6
Line 5 6.9594
0.1126 2.1 34 8 5.8 5.5 5.2
Line 2/23 Ft JRC3 Line 1 5.0167
0.3096 1.5 94 20 8.0 6.8 6.0
Line 2 7.7988
0.2545 2.4 78 14 8.3 7.4 6.9
Line 3 6.5784
0.2345 2.0 71 16 8.4 7.3 6.7
Line 4 7.2137
0.2981 2.2 91 20 9.2 7.8 7.0
Line 3/71 ft JRC4 Line 1 7.6684
0.1283 2.3 39 8 5.9 5.6 5.3
Line 2 5.1156
0.2338 1.6 71 20 8.0 6.8 6.1
Line 3 5.3313
0.2332 1.6 71 20 8.2 6.9 6.2
Line 4 10.8562
0.3992 3.3 122 18 10.4 9.0 8.1
Line3/64 ft JRC5 Line 1 4.8506
0.0851 1.5 26 8 5.5 5.2 4.9
Line 2 8.7868
0.2227 2.7 68 12 7.9 7.2 6.7
Line 3 10.9932
0.3932 3.4 120 18 10.4 9.0 8.1
Line 3/41 ft JRC6 Line 1 5.1322
0.1070 1.6 33 10 6.3 5.8 5.5
Line 2 2.7882
0.1734 0.8 53 20 6.3 5.4 4.8
Line 3 7.8662
0.3263 2.4 99 18 9.2 8.0 7.2
Line 7/99 ft JRC7 Line 1 8.5838
0.2482 2.6 76 14 8.5 7.6 7.0
Line 2 8.8789
0.3180 2.7 97 18 9.7 8.3 7.5
Line 3 10.6508
0.4187 3.2 128 16 9.8 8.6 7.8
Line 4 5.2343
0.3150 1.6 96 20 8.1 6.9 6.1
Line 5 6.2050
0.3883 1.9 118 20 8.7 7.4 6.6
Line 6 16.6015
0.6811 5.1 208 18 12.1 10.5 9.4
Notes:Average =15.1 8.0 7.0 6.4
SD =4.7 1.7 1.4 1.2
+1SD =19.8 9.7 8.4 7.6
-1SD =10.4 6.3 5.7 5.3
1See Figure 3-5 For location of measurements and Appendix G for photographs.
2Estimated from Figure 6-1 (Barton 1990).
3Estimated from EQ7 (See Section 6.2.2: Barton and Bandis 1982).
Estimation of Joint Roughness Coefficient (JRC) of Foliation Surfaces Scaled JRC3
HDR Project No. 10020225 Task 63 Page 1 of 1
Table 3-8: Schmidt Hammer Field DataGeological and Geotechnical Subsurface InvestigationEast Fork ProjectHigh Values Correction FactorFinal ValuesHigh Values Correction FactorFinal ValuesHigh Values Correction FactorFinal Values47 48 47 -0.54 46.46 46 51 54 -2.68 51.32 52 48 52 -2.86 49.1442 47 48 47.46 54 44 56 53.32 50 46 50 47.1444 47 47 46.46 56 50 55 52.32 56 45 56 53.1444 49 47 46.46 52 54 54 51.32 47 47 48 45.1445 44 49 48.46 55 54 54 51.32 46 54 54 51.1447.6= Average =47.0654.6= Average =51.9252= Average =49.14SD = 0.89SD = 0.89SD = 3.16High Values Correction FactorFinal ValuesHigh Values Correction FactorFinal ValuesHigh Values Correction FactorFinal Values52 44 52 -2.68 49.32 49 51 49 -3.41 45.59 46 49 46 -0.09 45.9250 57 54 51.32 49 43 49 45.59 44 48 44 43.9254 54 57 54.32 49 46 49 45.59 38 38 44 43.9246 56 54 51.32 44 47 49 45.59 44 43 49 48.9248 47 56 53.32 49 42 51 47.59 38 40 48 47.9254.6= Average =51.9249.4= Average =45.9946.2= Average =46.12SD = 1.95SD = 0.89SD = 2.28High Values Correction FactorFinal ValuesHigh Values Correction FactorFinal ValuesHigh Values Correction FactorFinal Values45 53 49 -3.51 45.50 49 40 49 -2.50 46.50 56 48 56 -0.15 55.8549 52 53 49.50 50 44 50 47.50 46 45 53 52.8553 48 53 49.50 46 43 46 43.50 40 54 52 51.8543 54 52 48.50 40 45 45 42.50 53 55 54 53.8546 42 54 50.50 43 45 45 42.50 52 44 55 54.8552.2= Average =48.7047= Average =44.50 54= Average =53.85SD = 1.92SD = 2.35SD = 1.58Table 3-8: Schmidt hammer test results on joints and foliation planes in biotite gneiss. Shaded r values removed from average. Location of tests shown on Figure 3-5. T3T6T9Biotite Gneiss - N19E; 51SE - Jt-SR (39-Down) Biotite Gneiss - N37W; 86SW - Jt-D (4-Up)T4Biotite Gneiss - N72E; 84NW - S (6-Down)Biotite Gneiss - N28W; 73SW - Jt-C (17-Up)T7Field ValuesField ValuesField ValuesBiotite Gneiss - N6E; 73SW - Jt-D (17-Up)T1 Field ValuesBiotite Gneiss - NS; 65W - Jt-D (25-Up)T5Field ValuesT8Field ValuesT2Field ValuesField ValuesField ValuesBiotite Gneiss - N49W; 58SW - Jt-D (32-Up) Biotite Gneiss - N53E; 87NW - S (3-Up) Biotite Gneiss - N51E; 77NW - S (13-Down)HDR Project No. 10020225 Task 63 Page 1 of 1
Table 3-9: Schmidt Hammer Unconfined Compressive Strength Statistics
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project
Test Feature5 r1 UW2
(pcf)
UCS3
(psi)
~Dispersion4
(+)
T1 J-SR 47 168.4 18598 7000
T2 J-Disc 52 168.4 24220 10000
T3 J-Disc 49 168.4 20325 8000
T4 J-Disc 52 168.4 24219 10000
T5 J-Disc 46 168.4 17549 7000
T6 S 45 168.4 16186 6000
T7 J 49 168.4 20827 8000
T8 S 46 168.4 17669 7000
T9 S 54 168.4 26889 12000
20,720
3,660
20,956
2,789
20,248
5,799
5 J - Joint; SR - Stress Relief; Disc - Discontinuous; S - Foliation; SD - Standard Deviation
Test locations are presented on Figure 3-5
Table 3-9: Estimated Unconfined Compressive Strength of Bedrock by Schmidt Hammer (ISRM 1978)
2Unit Weight (pounds per cubic foot) of biotite gneiss from laboratory Testing (Table 3-
4).
3Unconfined Compressive Strength Estimate (pounds per square inch).
1Schmidt Hammer Rebound Number.
4Estimated from Deere and Miller (1966).
Unconfined Compressive Strength
Cumulative Average =
Cumulative SD =
Joint Average =
Joint SD =
Foliation Average =
Foliation SD =
CUMULATIVE - JOINTS AND FOLIATION (N = 9)
JOINTS (N = 6)
FOLIATION (N = 3)
HDR Project No. 10020225 Task 63 Page 1 of 1
Table 4-1: Left Abutment Continuous Feature Investigation Summary
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project
Depth of Feature
(ft bgs)
Elevation of
Feature (ft)
Feature
Category Strike Dip Direction Dip
Trial 1 10.6 2334.87 Joint 13.59 103.59 54.84
Trial 2 14.8 2330.67 Vein 10.85 100.85 51.48
Trial 3 22.35 2323.12 Vein 3.66 93.66 44.23
Trial 4 23.6 2321.87 Joint 2.06 92.06 42.88
Trial 5 24.5 2320.97 Joint 0.80 90.80 41.89
Trial 6 37.0 2308.47 Migmatitc 329.16 59.16 28.30
Trial 7 50.3 2295.17 Intrusion 270.02 0.02 30.25
Trial 8 61.0 2284.47 Contact 245.89 335.89 42.29
Trial 9 66.9 2278.57 Intrusion 239.18 329.18 48.38
Trial 10 80.0 2265.47 >Total Depth 230.88 320.88 58.56
Trial 11 90.0 2255.47 >Total Depth 227.40 317.40 63.86
Trial 12 100.0 2245.47 >Total Depth 225.06 315.06 67.75
Notes:
1. Refer to Appendix I for three-point problem worksheets.
2. Three-point problems were computed using standard license Rockworks17 software.
Trial Plane ResultsB-4 Trial Feature
HDR Project No. 10020225 Task 63 Page 1 of 1
Table 6-1: GSI Quantification
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project
HDR Project No. 10020225 Task 63 Page 1 of 1
JCond89 =25
RQD =100
GSI =88
JCond76 =20
RQD =100
GSI =90
Jr =2
Ja =0.75
RQD =100
GSI =88
Bieniawski JCond89
Bieniawski JCond76
Barton et al 1976
Input Values
Table 6-1: Estimates of rock mass Geological Strength Index (GSI) after Hoek and others (2013).

HDR Project No. 10020225-063

Input Values
Estimate sigma c (ksi) GSI mi D MR
Middle 6.774 85 10 0.2 675
Low 3.499 80 7 0.2 250
High 10.049 90 13 0.2 1100
Notes:
sigma c (ksi) – unconfined compressive strength of intact rock, in kilopounds per square inch
GSI – geologic strength index, after Hoek et al. (2013)
mi – parameter based on rock type, after Hoek et al. (2002).
D – parameter denoting disturbed rock condition
MR – modulus ratio estimated from empirical data

Estimate Cohesion (ksi)Friction Angle Tensile Strength
(ksi)
Uniaxial
Compressive
Stength (ksi)
Global Strength
(ksi)
Deformation
Modulus (ksi)
Middle 0.430 56.97 -0.206 2.772 2.975 3716.11
Low 0.183 52.60 -0.101 1.047 1.135 656.89
High 0.798 59.44 -0.350 5.540 5.776 9382.59
Mohr-Coulomb Fit (for sigma 3
maximum of 0.016 ksi)Rock Mass Strength Parameters
Table 6-2: Hoek-Brown Input Values
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project

Table 6-3: Hoek-Brown Rock Mass Strength Values
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project

HDR Project No. 10020225-063

Notes:
JRC – Joint Roughness Coefficient
JCS – Joint Wall Compressive Strength (pounds per square inch)
Fb – Basic Friction Angle (degrees)
Failure Mode JRC JCS (psi) ∅
Rock on Rock – Foliation, 50 ft 8 5950/2.5 = 2380 23
Rock on Rock – Foliation, 75 ft 7 5950/2.5 = 2380 23
Rock on Rock – Foliation, 100 ft 6.4 5950/2.5 = 2380 23
Rock on Rock – Joint, 50 ft 8 13,240/2.5 = 5296 30
Rock on Rock – Joint, 75 ft 7 13,240/2.5 = 5296 30
Rock on Rock – Joint, 100 ft 6.4 13,240/2.5 = 5296 30
Concrete/Rock Interface 6 4000/2.5 = 1600 34
Concrete/Rock Interface 10 4000/2.5 = 1600 34
Table 6-4: Barton Shear Strength Input Values
Geological and Geotechnical Subsurface Investigation
East Fork Project

HDR Project No. 10020225-063

Cedar Cliff - Rock on Rock - Foliation (Gneiss/Schist)
JRC estimates scaled to 50 ft length
UCS (Schistose Biotite Gneiss and Mica Schist) = 5950 psi; Scaling Factor = 2.5

Barton Shear Failure Criterion
Input Parameters
Basic friction angle (PHIB) - degrees 23
Joint Roughness Coefficient (JRC) 8
Joint Compressive Strength (JCS) MPa - psi 16.4 2380
Minimum Normal Stress (SIGNMIN) MPa - psi 0.000 0
Normal Normal Shear Shear App.Friction
Stress Stress Strength Strength Angle
(SIGN) (TAU) (PHI)
psi MPa Mpa psi degrees
0 0.000 0.000 0.0 0.00
5 0.034 0.034 4.9 44.4
10 0.069 0.062 9.0 42.0
15 0.103 0.089 12.9 40.6
20 0.138 0.114 16.5 39.6
25 0.172 0.139 20.1 38.8
30 0.207 0.163 23.6 38.2
35 0.241 0.186 27.0 37.7
40 0.276 0.209 30.4 37.2
45 0.310 0.232 33.6 36.8
50 0.345 0.254 36.9 36.4
60 0.414 0.298 43.3 35.8
70 0.483 0.341 49.5 35.3
80 0.552 0.383 55.6 34.8
90 0.621 0.425 61.6 34.4
100 0.690 0.465 67.5 34.0
120 0.828 0.545 79.1 33.4
140 0.966 0.623 90.4 32.8
160 1.103 0.700 101.5 32.4
200 1.379 0.849 123.1 31.6
Table 6-5: Barton Shear Strength for Sliding on Foliation Planes – 50 feet

HDR Project No. 10020225-063

Cedar Cliff - Rock on Rock - Foliation (Gneiss/Schist)
JRC estimates scaled to 75 ft length
UCS (Schistose Biotite Gneiss and Mica Schist) = 5950 psi; Scaling Factor = 2.5
Barton Shear Failure Criterion
Input Parameters
Basic friction angle (PHIB) - degrees 23
Joint Roughness Coefficient (JRC) 7
Joint Compressive Strength (JCS) MPa - psi 16.4 2380
Minimum Normal Stress (SIGNMIN) MPa - psi 0.000 0
Normal Normal Shear Shear App.Friction
Stress Stress Strength Strength Angle
(SIGN) (TAU) (PHI)
psi MPa Mpa psi degrees
0 0.000 0.000 0.0 0.00
5 0.034 0.031 4.5 41.7
10 0.069 0.057 8.3 39.6
15 0.103 0.082 11.9 38.4
20 0.138 0.106 15.4 37.5
25 0.172 0.129 18.7 36.9
30 0.207 0.152 22.0 36.3
35 0.241 0.174 25.3 35.8
40 0.276 0.196 28.4 35.4
45 0.310 0.218 31.6 35.1
50 0.345 0.239 34.7 34.7
60 0.414 0.281 40.8 34.2
70 0.483 0.322 46.7 33.7
80 0.552 0.363 52.6 33.3
90 0.621 0.402 58.3 33.0
100 0.690 0.442 64.0 32.6
120 0.828 0.519 75.2 32.1
140 0.966 0.594 86.2 31.6
160 1.103 0.668 96.9 31.2
200 1.379 0.813 117.9 30.5
Table 6-6: Barton Shear Strength for Sliding on Foliation Planes – 75 feet

HDR Project No. 10020225-063

Cedar Cliff - Rock on Rock - Foliation (Gneiss/Schist)
JRC estimates scaled to 100 ft length
UCS (Schistose Biotite Gneiss and Mica Schist) = 5950 psi, Scaling Factor =2.5
Barton Shear Failure Criterion
Input Parameters
Basic friction angle (PHIB) - degrees 23
Joint Roughness Coefficient (JRC) 6.4
Joint Compressive Strength (JCS) MPa - psi 16.4 2380
Minimum Normal Stress (SIGNMIN) MPa - psi 0.000 0
Normal Normal Shear Shear App.Friction
Stress Stress Strength Strength Angle
(SIGN) (TAU) (PHI)
psi MPa Mpa psi degrees
0 0.000 0.000 0.0 0.00
5 0.034 0.029 4.2 40.1
10 0.069 0.054 7.9 38.2
15 0.103 0.078 11.3 37.1
20 0.138 0.101 14.7 36.3
25 0.172 0.124 17.9 35.7
30 0.207 0.146 21.1 35.2
35 0.241 0.167 24.3 34.7
40 0.276 0.189 27.3 34.4
45 0.310 0.210 30.4 34.0
50 0.345 0.230 33.4 33.7
60 0.414 0.271 39.3 33.2
70 0.483 0.311 45.1 32.8
80 0.552 0.351 50.8 32.4
90 0.621 0.389 56.5 32.1
100 0.690 0.428 62.0 31.8
120 0.828 0.503 73.0 31.3
140 0.966 0.577 83.7 30.9
160 1.103 0.650 94.3 30.5
200 1.379 0.793 114.9 29.9
Table 6-7: Barton Shear Strength for Sliding on Foliation Planes – 100 feet

HDR Project No. 10020225-063

Cedar Cliff - Rock on Rock - Joint (All Rock Types)
JRC estimates scaled to 50 ft length
UCS (Botite Gneiss, Schistose Biotite Gneiss and Mica Schist) = 13240 psi;
Scaling Factor = 2.5
Barton Shear Failure Criterion
Input Parameters
Basic friction angle (PHIB) - degrees 30
Joint Roughness Coefficient (JRC) 8
Joint Compressive Strength (JCS) MPa - psi 36.5 5296
Minimum Normal Stress (SIGNMIN) MPa - psi 0.000 0
Normal Normal Shear Shear App.Friction
Stress Stress Strength Strength Angle
(SIGN) (TAU) (PHI)
psi MPa Mpa psi degrees
0 0.000 0.000 0.0 0.00
5 0.034 0.048 6.9 54.2
10 0.069 0.088 12.7 51.8
15 0.103 0.125 18.1 50.4
20 0.138 0.161 23.3 49.4
25 0.172 0.196 28.4 48.6
30 0.207 0.230 33.3 48.0
35 0.241 0.263 38.1 47.4
40 0.276 0.296 42.9 47.0
45 0.310 0.328 47.5 46.6
50 0.345 0.360 52.1 46.2
60 0.414 0.422 61.2 45.6
70 0.483 0.483 70.1 45.0
80 0.552 0.543 78.8 44.6
90 0.621 0.603 87.4 44.2
100 0.690 0.661 95.9 43.8
120 0.828 0.776 112.5 43.2
140 0.966 0.889 128.8 42.6
160 1.103 0.999 144.9 42.2
200 1.379 1.215 176.2 41.4
Table 6-8: Barton Shear Strength for Sliding on Joint Planes – 50 feet

HDR Project No. 10020225-063

Cedar Cliff - Rock on Rock - Joint (All Rock Types)
JRC estimates scaled to 75 ft length
UCS (Botite Gneiss, Schistose Biotite Gneiss and Mica Schist) = 13240 psi;
Scaling Factor = 2.5
Barton Shear Failure Criterion
Input Parameters
Basic friction angle (PHIB) - degrees 30
Joint Roughness Coefficient (JRC) 7
Joint Compressive Strength (JCS) MPa - psi 36.5 5296
Minimum Normal Stress (SIGNMIN) MPa - psi 0.000 0
Normal Normal Shear Shear App.Friction
Stress Stress Strength Strength Angle
(SIGN) (TAU) (PHI)
psi MPa Mpa psi degrees
0 0.000 0.000 0.0 0.00
5 0.034 0.043 6.2 51.2
10 0.069 0.080 11.5 49.1
15 0.103 0.114 16.6 47.8
20 0.138 0.148 21.4 47.0
25 0.172 0.180 26.1 46.3
30 0.207 0.212 30.8 45.7
35 0.241 0.244 35.3 45.3
40 0.276 0.274 39.8 44.9
45 0.310 0.305 44.2 44.5
50 0.345 0.335 48.6 44.2
60 0.414 0.394 57.2 43.6
70 0.483 0.453 65.6 43.2
80 0.552 0.510 73.9 42.7
90 0.621 0.567 82.1 42.4
100 0.690 0.622 90.3 42.1
120 0.828 0.733 106.2 41.5
140 0.966 0.841 121.9 41.0
160 1.103 0.947 137.3 40.6
200 1.379 1.156 167.6 40.0
Table 6-9: Barton Shear Strength for Sliding on Joint Planes – 75 feet

HDR Project No. 10020225-063

Cedar Cliff - Rock on Rock - Joint (All Rock Types)
JRC estimates scaled to 100 ft length
UCS (Botite Gneiss, Schistose Biotite Gneiss and Mica Schist) = 13240 psi;
Scaling Factor = 2.5
Barton Shear Failure Criterion
Input Parameters
Basic friction angle (PHIB) - degrees 30
Joint Roughness Coefficient (JRC) 6.4
Joint Compressive Strength (JCS) MPa - psi 36.5 5296
Minimum Normal Stress (SIGNMIN) MPa - psi 0.000 0
Normal Normal Shear Shear App.Friction
Stress Stress Strength Strength Angle
(SIGN) (TAU) (PHI)
psi MPa Mpa psi degrees
0 0.000 0.000 0.0 0.00
5 0.034 0.040 5.8 49.4
10 0.069 0.075 10.9 47.4
15 0.103 0.108 15.7 46.3
20 0.138 0.140 20.4 45.5
25 0.172 0.172 24.9 44.9
30 0.207 0.202 29.4 44.4
35 0.241 0.233 33.7 44.0
40 0.276 0.263 38.1 43.6
45 0.310 0.292 42.3 43.3
50 0.345 0.321 46.6 43.0
60 0.414 0.379 54.9 42.5
70 0.483 0.435 63.1 42.0
80 0.552 0.491 71.2 41.7
90 0.621 0.546 79.1 41.3
100 0.690 0.600 87.0 41.0
120 0.828 0.707 102.6 40.5
140 0.966 0.813 117.9 40.1
160 1.103 0.917 133.0 39.7
200 1.379 1.121 162.6 39.1
Table 6-10: Barton Shear Strength for Sliding on Joint Planes – 100 feet

HDR Project No. 10020225-063

.

Cedar Cliff - Concrete/Rock Interface
JRC =6: UCS (Concrete) = 4000 psi; Scaling Factor = 2.5
Barton Shear Failure Criterion
Input Parameters
Basic friction angle (PHIB) - degrees 34
Joint Roughness Coefficient (JRC) 6
Joint Compressive Strength (JCS) MPa - psi 11.0 1600
Minimum Normal Stress (SIGNMIN) MPa - psi 0.000
Normal Normal Shear Shear App.Friction
Stress Stress Strength Strength Angle
(SIGN) (TAU) (PHI)
psi MPa Mpa psi degrees
0 0.000 0.000 0.0 0.00
5 0.034 0.040 5.8 49.0
10 0.069 0.075 10.8 47.2
15 0.103 0.108 15.6 46.2
20 0.138 0.140 20.3 45.4
25 0.172 0.171 24.9 44.8
30 0.207 0.202 29.3 44.4
35 0.241 0.233 33.8 44.0
40 0.276 0.263 38.1 43.6
45 0.310 0.293 42.4 43.3
50 0.345 0.322 46.7 43.0
60 0.414 0.380 55.1 42.6
70 0.483 0.437 63.4 42.2
80 0.552 0.493 71.5 41.8
90 0.621 0.549 79.6 41.5
100 0.690 0.604 87.6 41.2
120 0.828 0.713 103.4 40.7
140 0.966 0.820 118.9 40.3
160 1.103 0.926 134.3 40.0
200 1.379 1.134 164.4 39.4
Table 6-11: Barton shear strength for sliding on the concrete/rock interface – JRC = 6

HDR Project No. 10020225-063

Cedar Cliff - Concrete/Rock Interface
JRC =10: UCS (Concrete) = 4000 psi; Scaling Factor = 2.5
Barton Shear Failure Criterion
Input Parameters
Basic friction angle (PHIB) - degrees 34
Joint Roughness Coefficient (JRC) 10
Joint Compressive Strength (JCS) MPa - psi 11.0 1600
Minimum Normal Stress (SIGNMIN) MPa - psi 0.003
Normal Normal Shear Shear App.Friction
Stress Stress Strength Strength Angle
(SIGN) (TAU) (PHI)
psi MPa Mpa psi degrees
0 0.000 0.000 0.0 0.00
5 0.034 0.058 8.3 59.1
10 0.069 0.102 14.8 56.0
15 0.103 0.144 20.9 54.3
20 0.138 0.183 26.6 53.0
25 0.172 0.221 32.1 52.1
30 0.207 0.258 37.4 51.3
35 0.241 0.294 42.6 50.6
40 0.276 0.329 47.7 50.0
45 0.310 0.363 52.7 49.5
50 0.345 0.397 57.6 49.1
60 0.414 0.464 67.2 48.3
70 0.483 0.529 76.6 47.6
80 0.552 0.592 85.8 47.0
90 0.621 0.654 94.8 46.5
100 0.690 0.715 103.7 46.0
120 0.828 0.835 121.0 45.2
140 0.966 0.951 138.0 44.6
160 1.103 1.066 154.5 44.0
200 1.379 1.288 186.7 43.0
Table 6-12: Barton shear strength for sliding on the concrete/rock interface – JRC = 10
Table 7-1: Kinematic Analysis Results
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project
Type of Failure %Type of Failure %%Type of Failure %
Planar Sliding Planar Sliding Planar Sliding
All 2.28 All 15.56 1.52 All 3.61
Set 1 -Set 1 16.08 -Set 1 -
Set 2 -Set 2 -13.51 Set 2 18.92
Set 3 -Set 3 --Set 3 -
Set 4 -Set 4 --Set 4 -
Wedge Sliding Wedge Sliding Wedge Sliding
All 14.57 All 44.52 19.57 All 32.07
Flexural Toppling Flexural Toppling Flexural Toppling
All 15.18 All 2.28 3.42 All 1.52
Set 1 16.08 Set 1 --Set 1 -
Set 2 -Set 2 -18.92 Set 2 13.51
Set 3 -Set 3 --Set 3 -
Set 4 -Set 4 --Set 4 -
Direct Toppling Direct Toppling Direct Toppling
Direct Toppling (Int.)9.41 Direct Toppling (Int.)1.41 28.00 Direct Toppling (Int.)12.78
Oblique Toppling (Int.)12.84 Oblique Toppling (Int.)2.96 10.49 Oblique Toppling (Int.)6.25
Base Plane (All)9.11 Base Plane (All)22.77 9.11 Base Plane (All)10.44
Base Plane (Set 1)-Base Plane (Set 1)16.08 -Base Plane (Set 1)-
Base Plane (Set 2)-Base Plane (Set 2)-13.51 Base Plane (Set 2)18.92
Base Plane (Set 3)60.78 Base Plane (Set 3)39.22 62.75 Base Plane (Set 3)37.25
Base Plane (Set 4)-Base Plane (Set 4)22.73 18.18 Base Plane (Set 4)4.55
Type of Failure %Type of Failure %%Type of Failure %
Planar Sliding Planar Sliding Planar Sliding
All 3.98 All 1.71 0.95 All 0.76
Set 1 -Set 1 --Set 1 -
Set 2 37.84 Set 2 --Set 2 -
Set 3 -Set 3 --Set 3 -
Set 4 4.55 Set 4 --Set 4 -
Wedge Sliding Wedge Sliding Wedge Sliding
All 28.67 All 8.19 13.38 All 16.26
Flexural Toppling Flexural Toppling Flexural Toppling
All 2.28 All 4.93 3.23 All 3.23
Set 1 -Set 1 1.93 -Set 1 -
Set 2 18.92 Set 2 -37.84 Set 2 43.24
Set 3 -Set 3 --Set 3 -
Set 4 -Set 4 --Set 4 -
Direct Toppling Direct Toppling Direct Toppling
Direct Toppling (Int.)4.97 Direct Toppling (Int.)8.73 12.94 Direct Toppling (Int.)11.68
Oblique Toppling (Int.)8.01 Oblique Toppling (Int.)12.01 9.87 Oblique Toppling (Int.)7.89
Base Plane (All)12.14 Base Plane (All)8.35 7.59 Base Plane (All)7.59
Base Plane (Set 1)-Base Plane (Set 1)--Base Plane (Set 1)-
Base Plane (Set 2)37.84 Base Plane (Set 2)--Base Plane (Set 2)2.70
Base Plane (Set 3)58.82 Base Plane (Set 3)58.82 43.14 Base Plane (Set 3)35.29
Base Plane (Set 4)27.27 Base Plane (Set 4)--Base Plane (Set 4)-
Notes:
1. Refer to Appendix K for kinematic plots.
Yellow - Low Likelihood (<20%)
Orange - Medium Likelihood (20-35%)
Red - High Likelihood (>35%)
Inlet Pipe Trench - Cut A Inlet Pipe Trench - Cut B Inlet Pipe Trench - Cut C Inlet Pipe Trench - Cut D
N32E/90SE N32E/90NW N10W/90NE N10W/90SE
Type of Failure
Planar Sliding
All
Set 1
Set 2
Set 3
Set 4
Wedge Sliding
All
Flexural Toppling
All
Set 1
Set 2
Set 3
Set 4
Direct Toppling
Direct Toppling (Int.)
Oblique Toppling (Int.)
Base Plane (All)
Base Plane (Set 1)
Base Plane (Set 2)
Base Plane (Set 3)
Base Plane (Set 4)
Left Abutment Rock Mass - Cut E Left Abutment Rock Mass - Cut F Auxiliary Spillway Slope - Cut 1 Auxiliary Spillway Slope - Cut 2
N55W/90NE N20E/70SE N55W/70SW N28W/70SW
Type of Failure
Planar Sliding
All
Set 1
Set 2
Set 3
Set 4
Wedge Sliding
All
Flexural Toppling
All
Set 1
Set 2
Set 3
Set 4
Direct Toppling
Direct Toppling (Int.)
Oblique Toppling (Int.)
Base Plane (All)
Base Plane (Set 1)
Base Plane (Set 2)
Base Plane (Set 3)
Base Plane (Set 4)
HDR Project No. 10020225 Task 63 Page 1 of 2
Table 7-1: Kinematic Analysis Results
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project
Type of Failure %Type of Failure %Type of Failure %
Planar Sliding Planar Sliding Planar Sliding
All 2.66 All 7.59 All 17.27
Set 1 -Set 1 5.14 Set 1 24.76
Set 2 -Set 2 -Set 2 -
Set 3 -Set 3 -Set 3 -
Set 4 -Set 4 -Set 4 27.27
Wedge Sliding Wedge Sliding Wedge Sliding
All 20.37 All 24.68 All 23.95
Flexural Toppling Flexural Toppling Flexural Toppling
All 1.14 All 1.33 All 6.45
Set 1 -Set 1 Set 1 9.32
Set 2 5.41 Set 2 -Set 2 -
Set 3 -Set 3 -Set 3 -
Set 4 -Set 4 -Set 4 -
Direct Toppling Direct Toppling Direct Toppling
Direct Toppling (Int.)1.45 Direct Toppling (Int.)0.56 Direct Toppling (Int.)0.72
Oblique Toppling (Int.)5.65 Oblique Toppling (Int.)3.11 Oblique Toppling (Int.)1.68
Base Plane (All)10.44 Base Plane (All)15.37 Base Plane (All)25.62
Base Plane (Set 1)-Base Plane (Set 1)5.79 Base Plane (Set 1)27.65
Base Plane (Set 2)-Base Plane (Set 2)-Base Plane (Set 2)-
Base Plane (Set 3)41.18 Base Plane (Set 3)41.18 Base Plane (Set 3)35.29
Base Plane (Set 4)13.64 Base Plane (Set 4)22.73 Base Plane (Set 4)50.00
Notes:
1. Refer to Appendix K for kinematic plots.
Yellow - Low Likelihood (<20%)
Orange - Medium Likelihood (20-35%)
Red - High Likelihood (>35%)
Auxiliary Spillway Slope - Cut 3 Auxiliary Spillway Slope - Cut 4 Auxiliary Spillway Slope - Cut 5
NS/70W N30E/70NW N65E/70NW
HDR Project No. 10020225 Task 63 Page 2 of 2
Table 7-2: December 2014 Kinematic Analysis Results
Geological and Geotechnical Subsurface Investigation
East Fork Hydroelectric Project
Type of Failure Northeast Cut Type of Failure Northeast Cut Type of Failure Southeast Cut
Flexural Toppling %Flexural Toppling %Flexural Toppling %
All 19.35 All 18.28 All 3.23
Set 1 -Set 1 -Set 1 4.69
Set 2 70.83 Set 2 70.83 Set 2 -
Toppling %Toppling %Toppling %
Direct Toppling 21.78 Direct Toppling 16.19 Direct Toppling 3.04
Base Plane (All)2.15 Base Plane (All)1.08 Base Plane (All)24.73
Oblique Toppling 26.20 Oblique Toppling 18.85 Oblique Toppling 6.18
Base Plane (Set 2)8.33 Base Plane (Set 2)4.17 Base Plane (Set 1)32.81
Planar Sliding %Planar Sliding %Planar Sliding %
All 1.08 All 0 All 23.66
Set 1 -Set 1 -Set 1 31.25
Set 2 4.17 Set 2 -Set 2 -
Wedge Sliding %Wedge Sliding %Wedge Sliding %
All 11.91 All 19.20 All 41.26
Type of Failure Southeast Cut Type of Failure Southeast Cut
Flexural Toppling %Flexural Toppling %
All 6.45 All 6.45 Notes:
Set 1 7.81 Set 1 7.81 1. Refer to Appendix A for full technical memorandum.
Set 2 -Set 2 -
Toppling %Toppling %Yellow - Low Likelihood (<20%)
Direct Toppling 2.90 Direct Toppling 1.29 Orange - Medium Likelihood (20-35%)
Base Plane (All)39.78 Base Plane (All)35.48 Red - High Likelihood (>35%)
Oblique Toppling 3.20 Oblique Toppling 4.94
Base Plane (Set 1)54.69 Base Plane (Set 2)48.44
Planar Sliding %Planar Sliding %
All 38.71 All 33.33
Set 1 53.13 Set 1 45.31
Set 2 -Set 2 -
Wedge Sliding Wedge Sliding
All 49.99 All 39.58
Alternate 3: Section 1, N56W Alternate 3: Section 2, N28W Alternate 3: Section 3, N32E
Alternate 3: Section 4, N61E Alternate 3: Section 5, N80E
HDR Project No. 10020225 Task 63 Page 1 of 1