CA_.PRA.SEKI.10(10)_Sequoia_National_Park,_Geotech._2012.pdf

SEQUOIA AND KINGS CANYON

NATIONAL PARK

CA PRA SEKI 10(10)

Draft Final Geotechnical Investigations Report

Report No. CA-PX-SEKI-12-01

Geotechnical Services Branch Technical Services

August, 2012 i

TABLE OF CONTENTS

SECTION ONE - INTRODUCTION

1.1 BACKGROUND AND LOCATION

1.2 SCOPE AND PURPOSE

SECTION TWO - GEOLOGY AND SEISMICITY

2.1 REGIONAL GEOLOGY

2.2 SEISMIC DESIGN PARAMETERS

2.3 GEOLOGICAL HAZARDS

SECTION THREE - SUBSURFACE INVESTIGATION

3.1 FIELD EXPLORATION

3.2 SUMMARY OF SUBSURFACE EXPLORATION

3.3 LABORATORY TESTING

3.4 CUT AND FILL SLOPES

SECTION FOUR - ANALYSIS AND RECOMMENDATIONS

4.1 CAST-IN-PLACE RETAINING WALL DESIGN RECOMMENDATIONS

4.1.1 Retaining Wall Bearing Resistance

4.1.1.1 Strength Limit State

4.1.1.2 Service Limit State

4.1.1.3 Extreme Event Limit State

4.1.2 Lateral Earth Pressure

4.1.3 Global Stability Analysis

4.1.4 Earthwork Recommendations

4.1.5 Erosion and Corrosion Protection

4.2 CANTILEVER VIADUCT DESIGN RECOMMENDATIONS

4.2.1 Geotechnical Axial Resistance

4.2.2 Lateral Load Analysis

4.2.3 Micropile Grout

4.2.4 Settlement

4.2.4 Group Effects for Axially Loaded Micropiles

4.2.5 Load Testing of Micropile

4.3 DISCLAIMER/LIMITATIONS CLAUSE

SECTION FIVE: REFERENCES

ii

TABLES

TABLE 2.1: Summary of Seismic Parameters for Earthquake with 1000-Year Return Period TABLE 2.2: Summary of Design Response Parameters for Class C TABLE 3.1: Summary of Proposed Structures with Number of Borings per Structure TABLE 3.1: Rock Quality based on RQD Values TABLE 3.2: Summary of Test Hole Borings by Structure TABLE 3.3: Summary of Laboratory Index Tests of Select Soil Samples TABLE 3.4: Unconfined Compression Strength Test Results TABLE 3.5: Electro Chemical Test Results.

TABLE 3.6: Summary of the Field Results from Each Cut Slope TABLE 4.1: Estimated Material Properties for Design TABLE 4.2: Resistance Factors for Wall Foundation Design TABLE 4.3: Factored Bearing Resistance of Overburden Materials TABLE 4.4: Footing Elevation Recommendation for Fill Wall #1 (679+08 to 682+60) TABLE 4.5: Footing Elevation Recommendation for Fill Wall #2 (683+69 to 685+80) TABLE 4.6: Footing Elevation Recommendation for Fill Wall #3 (689+70 to 690+80) TABLE 4.7: Footing Elevation Recommendation for Fill Wall #4 (691+45 to 696+40) TABLE 4.8: Footing Elevation Recommendation for Fill Wall #5 (703+30 to 704+80) TABLE 4.9: Footing Elevation Recommendation for Fill Wall #6 (712+00 to 714+40) TABLE 4.10: Recommended Wall Backfill Parameters for Design TABLE 4.11: Strength and Unit Weight Parameters Used in the Stability Analysis TABLE 4.12: Calculated Static and Seismic Factors of Safety for Global Stability TABLE 4.13: Cantilevered Viaduct Locations TABLE 4 14: Factored Geotechnical Capacity for Various Bond Lengths TABLE 4.15: Soil and Rock Strength Parameters for LPILE Analysis

FIGURES

FIGURE 2.1: Five-Percent-Damped Design Response Spectrum Corrected for Class C Soil

APPENDICES

APPENDIX A: Project Location Maps, Boring Log Sheets, and Site Photographs APPENDIX B: Borehole Logs APPENDIX C: Laboratory Test Results APPENDIX D: Global Stability Analysis APPENDIX E: Photographs

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 1

SECTION ONE - INTRODUCTION

1.1 BACKGROUND AND LOCATION

This report provides geotechnical recommendations for the reconstruction and rehabilitation of a one-mile long section along Generals Highway, located between Deer Creek Ridge (Stations 675+50) and Eleven Range (Station 725+00). Generals Highway was constructed in early 1930 and is the primary artery through Sequoia and Kings Canyon National Park, in Tulare County, California. The narrow winding roadway traverses the canyon slopes with steep cuts excavated in schist and granite bedrock and steep sidcast fills to provide nine-foot lane width. This segment is currently in a poor condition with several failures, short sight distance, and drainage issues and does not meet FHWA design standards. A project location and vicinity maps are presented in Figures A1 and A2 of Appendix A.

Central Federal Lands Highway Division (CFL) of the Federal Highway Administration (FHWA) has been involved in the design and reconstruction of Generals Highway since 1993.

Reconstruction began at south Park entrance and has been completed to Amphitheater Point with reconstruction currently underway from Amphitheater Point to Deer Creek Ridge. A segment between Wolverton to Little Baldy trailhead was also rehabilitated in 2009. This project (SEKI 10(10)) will complete the reconstruction and rehabilitation of the most difficult and highly sensitive (through the Giant Sequoias) 28-mile segment along Generals Highway between the south Park entrance and Little Baldy trailhead.

This report is presents geotechnical recommendations for the final 4R reconstruction phase of the Generals Highway project CA PRA SEKI 10(10). Proposed roadway design criteria will include vertical and horizontal alignment improvements to accommodate ten-foot paved travel lanes with minimal shoulders. Cut slopes will be avoided as much as possible but spot slope scaling to achieve slope stability may be required. New retaining walls and shoulder stabilization will be required to gain the desired roadway width. For consistency with previous projects along the roadway and for cost effectiveness, all widening will be accomplished by installing reinforced cantilever fill walls or cantilever viaducts with varying face treatments. Existing historic stone masonry retaining structures will be preserved to the maximum extent possible with minor modifications to achieve required safety standards.

1.2 SCOPE AND PURPOSE

The scope of work included geotechnical investigation, analysis, and recommendations for use in design and construction of six walls and two cantilever viaducts. This involves several tasks including drilling, geological mapping, laboratory testing, data interpretation, and engineering report preparation. Specifically, this investigation is to determine the subsurface soil profiles at wall locations and provide AASHTO LRFD based recommendations on bearing resistance, global stability, and earth pressures. This report presents the findings of the subsurface investigation programs and provides geotechnical recommendations for the design and construction of retaining walls at structure locations along the alignment. The stationing in this report is based on the preliminary 50 percent project plans, September 2011.

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SECTION TWO – GEOLOGY AND SEISMICITY

2.1 REGIONAL GEOLOGY

During the Triassic/Jurassic Periods an oceanic plate was subducted under the North American plate in this region. As a result, vast magma chambers formed at depth through melting of subducted plate materials. The melting of the crustal materials created hot plutons or masses of magma that traveled upwards towards the earth’s surface. Large masses of plutons that coalesce are termed batholiths. Batholiths are defined as a continuous intrusive igneous rock that covers an area larger than 100 square miles. Batholiths are typically composed of felsic or intermediate granitic rock types. The Sierra Nevada Mountains are collectively known as the Sierra Nevada Batholith that is parallel to this past subduction zone for hundreds of miles. The formation of the metamorphic rock in the area was the result of island arcs, which typically drift on the oceanic plates, which collided into the North American plate. This collision process is thought to have changed or modified the subduction of the oceanic plate into a point of plate convergence resulting in uplift of the sedimentary and volcanic rock. The heat and pressure of the collision and uplift created metamorphic rock from the marine rocks of the oceanic plate and volcanic rocks of the island arcs. This time of mountain building is referred to as the Nevadan orogeny.

During this time the proto-Sierra Nevada Mountains and the Great Basin to the east were formed.

During the Cretaceous Period, the proto-Sierra Nevada Mountains were eroded to low lying features several thousand feet high. The erosion process exposed the upper sections of the granitic plutons, which were previously at depth, and left the metamorphic remnants derived from the oceanic plate and island arcs along the flanks and tops of the batholiths.

During the Oligocene Epoch the Sierra Nevada Mountains began to rise and tilt towards the west. Presently, active uplift appears to be occurring with height gains coinciding with earthquake activity along active fault zones at the eastern base of the Sierra Mountains. The uplift is almost matched by erosion that has deposited thousands of feet of sediment in the valley basins west of the Sierras.

Glacial ice ages accompanied global cooling about 2.5 million years ago and the ice quarried large sections of the mountains. The glaciers and associated rivers sculpted and shaped the mountains that we see today exposing metamorphic rock that has been intruded by the younger granitic rock that forms the core of the Sierra Nevada Mountains.

Moro Rock, outside of the project area, was reported to be a starting zone for a massive debris-avalanche that occurred in the Pleistocene. The exact age is unknown, but Hospital Rock appears to have fallen from Moro rock during this event and subsequently was inscribed by pictographs by native residents. Material from this debris avalanche is not found within the project area, however the Generals Highway trends across part of the resulting deposit where it turns uphill away from the Kaweah River near Buckeye Flat.

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 3

The project area crosses the following three geologic units:

1. JTra Amphibolite-Jurassic and/or Triassic aged massive and schistose amphibolite derived from mafic volcanic rocks.

2. JTbs Calc-silicate schist-Jurassic and/or Triassic aged calc-silicate schist adjacent to granitic plutons; includes tactite and marble.

3. Kgf Giant Forest Granodiorite-Cretaceous aged medium-grained, equigranular, hornblende-rich granodiorite with abundant mafic inclusions.

In general, the bedrock outcrops along the project area is mainly divided into granite and metamorphic schist. Large sections of decomposed and/or shear zones of metamorphic schist were also observed during the field investigation.

2.2 SEISMIC DESIGN PARAMETERS

The project area is not included in the zones covered by the Alquist-Priolo Fault Zoning Act as detailed in their mapped earthquake fault zones and listings of affected cities and counties.

Active faults are located on the east margins of the southern Sierra Mountains. These are known as the Owens Valley and Independence faults. No known active faults underlie or are closely associated with the project site.

The American Association of State Highway and Transportation Officials (AASHTO) criteria for seismic design allows for some structural damage to occur when the structure is subjected to 1000-year strong ground motion. For Extreme Event I Limit State Design an earthquake load and resistance factor of 1.00 should be used during the LRFD design of structures.

Recommended seismic response parameters for the Sequoia National Park Project CA SEKI 10(10) design are based on the AASHTO LRFD Bridge Design Specifications, 5th Edition, 2010 and represent horizontal peak ground acceleration with 7% probability of exceedance in 75 years (approximate 1000-year return period). The 1000-year return period data for the project site located at 36.541º latitude and -118.784º longitude, was obtained in accordance with the AASHTO ground motion maps for the probabilistic horizontal acceleration values corresponding to specific peak ground acceleration (PGA) and the spectral coefficients, namely the short- and long- period ground acceleration (Ss and S1 respectively) for a certain soil profile at the bridge site.

Subsurface profiles similar to the ones encountered at the project site with soil layers overlaying bedrock that significantly differ in stiffness and density, will have amplified ground motion and resonant period governed by the layer thickness and shear wave velocity of the materials. The damage potential of strong ground motions with respect to a structure is typically affected by the period of the earthquake motion and the resonant period of both soils the soil and the structure.

Although the shear wave velocities of the soils were not measured, based on a representative subsurface profile at the project site, the average-time-weighted shear velocity for the top 100 feet (Vs100) of the subsurface materials can be estimated between 1,200 and 2,000 feet per second therefore the site soils are classified as Class C according to the site class definitions specified in Table 3.10.3.1-1 of AASHTO.

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A seismic hazard analysis to establish ground motions for seismic design was conducted. The recommended spectral acceleration coefficient values for probabilistic design with a return period of 1000 years were calculated using the computer program provided with the AASHTO TRFD Bridge Design Manual developed by the USGS (2008) entitled “Seismic Design parameters,” version 2.10 and are summarized in Table 2.1.

TABLE 2.1:- Summary of Seismic Parameters for Earthquake with 1000-Year Return Period.

Horizontal Peak Ground Acceleration, (PGA) 0.179g

Horizontal Response Spectral Acceleration at Period of 0.2 sec, (Ss) 0.428g Horizontal Response Spectral Acceleration at Period of 1.0 sec, (S1) 0.167g

Site Factor at Zero-Period of Acceleration Spectrum, (Fpga) 1.20 Site Factor at Short-Period Range of Acceleration Spectrum, (Fa) 1.20 Site Factor at Long-Period Range of Acceleration Spectrum, (Fv) 1.63

Factored Horizontal Peak Ground Acceleration, (As) 0.215 Factored Horizontal Response Spectral Acceleration at Period of 0.2 sec, (SDs) 0.513 Factored Horizontal Response Spectral Acceleration at Period of 1.0 sec, (SD1) 0.273

Seismic Zone Zone 2

The 5% damped design response spectrum for a total period of 2.00 seconds was calculated (Table 2.2) and is plotted in Figure 2.1. This spectrum is calculated using spectral acceleration coefficients listed in Table 2.2.

FIGURE 2.1:- Five-Percent-Damped Design Response Spectrum Corrected for Class C Soil

0.1

0.2

0.3

0.4

0.5

0.6

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Sp ec tr al

A cc el er at io n, S a ( g)

Period, T (seconds)

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TABLE 2.2:- Summary of Design Response Parameters for Class C.

TIME, sec Sa, g Sd, in REMARKS

0.000 0.215 0.000 T = 0.0, Sa = As

0.106 0.513 0.057

0.200 0.513 0.201 T = 0.2, Sa = SDs

0.531 0.513 1.414

0.600 0.454 1.598

0.800 0.341 2.130

1.000 0.273 2.663 T = 1.0, Sa = SD1

1.200 0.227 3.195

1.400 0.195 3.728

1.600 0.170 4.260

1.800 0.151 4.793

2.000 0.136 5.325

Based on an acceleration coefficient (SD1, the seismic response motion acceleration at 1.000 second) value of 0.273g calculated as Fv.S1, the bridge is assigned a seismic performance Zone 2 in accordance with Table 3.10.6-1 in AASHTO (0.15 ≤ Fv.S1 ≥ 0.30). Seismic zones reflect the variation in seismic risk in different parts of the country and should be used for permitting different requirements for design. Seismic design forces in the lateral direction for retaining walls shall be determined by dividing forces obtained from Article 3.10.8 by the appropriate response modification factor, R, specified in Table 3.10.7.1-1 in AASHTO

2.3 GEOLOGICAL HAZARDS

Ground motions caused by an earthquake are influenced not only by the distance from the fault planes, but also by the geology and soils found at the site. Amplified ground motions are expected in areas underlain by thick soil layers. Intense ground motions may trigger landslides, debris flows or rock falls especially following heavy rains when soils are saturated. Several slopes in the vicinity of the project sites have experienced minor landslides, but it is not known if they were primarily caused by ground motions or loss of soil shear strength caused by heavy precipitations. Observed rocks that rolled out onto the roadway are generally less than 24-inches in diameter. In general, areas composed of weak, highly fractured, steeply dipping rock are especially subject to erosion, mass wasting, and sediment production resulting in debris flow reaching the roadway.

Highly fractured bedrock with steeply dipping joint sets and large boulders encountered in the wall foundations occasionally may require additional treatment.

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SECTION THREE – SUBSURFACE INVESTIGATION

3.1 FIELD EXPLORATION

A site-specific investigation program based on anticipated subsurface conditions and the proposed design was developed. This subsurface investigation program was conducted at the project site to evaluate subsurface conditions and determine soil/rock properties for design and construction of proposed retaining walls and cantilever viaducts. The field program consisted of drilling 23 test holes, station 675+55 to station 726+00. Borings B-1 through B-20 were drilled at proposed fill wall locations and borings B-101 through 103 were drilled at cantilever viaducts locations. The borings were drilled in May 2011 by Technicon drilling company using two CME 55 drill rigs, one for drilling through the overburden and one for rock coring. The borings were logged on-site by geotechnical personnel from Central Federal Lands (CFL). During the field investigation, one or more borings were advanced at each proposed reinforced concrete fill-wall and cantilever viaduct locations along the project alignment. All borings were located between the existing center line and the edge of the outboard lane. Table 3.1 shows the location of each structure and the number of borings advanced per structure.

TABLE 3.1:- Summary of Proposed Structures with Number of Borings per Structure.

STRUCTURE TYPE AND NUMBER BEGIN

STATION

END

STATION

LENGTH,

ft

MAX.

HEIGHT,

ft

NUMBER

OF

BORINGS

Cantilever Viaduct #1 676+15 676+80 65 NA 2 Cantilever Viaduct #2 697+75 698+08 33 NA 1

Reinforced Concrete Fill Wall #1 679+20 683+20 400 12 5 Reinforced Concrete Fill Wall #2 683+70 686+00 230 14 3 Reinforced Concrete Fill Wall #3 689+70 690+90 120 8 2 Reinforced Concrete Fill Wall #4 691+40 696+38 498 13 5 Reinforced Concrete Fill Wall #5 703+30 704+70 140 14 2 Reinforced Concrete Fill Wall #6 712+00 714+40 240 10 3

Total Number of Borings 23 Stationing is based on 50% Plans

Drilling was performed with the objective to obtain and log sufficient subsurface data required for the design of the proposed structures and to collect soil and rock samples for laboratory testing. The following best-practice subsurface investigation guidelines (based on FHWA subsurface investigations for structures) were followed to determine location, depth, and minimum number of exploration borings required for each structure:

• a minimum of one exploration boring was advanced along each structure

• a maximum spacing between borings 100 feet

• boring locations were alternated between the edge of the roadway and near the roadway center line along each structure

• borings were advanced to a minimum depth that is twice the maximum wall height listed in the table above or 10 feet in bedrock. For viaduct locations the boring depths were a minimum of 40 feet.

Boreholes were strategically located to characterize soil variability along each structure.

Representative stratigraphic subsurface profiling is used to depict a vertical distribution of the

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 7 major subsurface layers exhibiting distinct characteristics for engineering design. A summary of borehole data are shown in Table 3.2. Borehole stationing and offset are based on the preliminary 50 percent project plans produced in September, 2011.

TABLE 3.2:- Summary of Borings by Structure.

BORING

NO.

BORING

DEPTH,

ft

STATION OFFSET*

GROUND

ELEVATION,

ft

BEDROCK

ELEVATION,

ft Cantilever Viaduct #1 (676+15 to 676+80)

B-102 41.0 676+20 5-ft LT 4900.0 4893.0 B-103 41.0 676+75 7-ft LT 4903.6 4896.6

Cantilever Viaduct #2 (697+75 to 698+08) B-101 36.0 697+90 4-ft LT 5051.4 5034.1

Reinforced Concrete Fill Wall #1 (679+20 to 683+20) B-9 21.0 679+25 3.5-ft LT 4920.4 4908.4 B-10 21.0 680+25 3-ft LT 4925.6 4914.6 B-11 20.5 681+25 2-ft LT 4931.5 4921.0 B-12 21.0 682+25 2-ft LT 4938.3 4927.3 B-13 20.0 683+00 4.5-ft LT 4943.2 4936.7

Reinforced Concrete Fill Wall #2 (683+70 to 686+00) B-14 26.0 684+00 4.5-ft LT 4948.3 4937.3 B-20 24.5 685+00 5-ft LT 4955.8 4951.8 B-19 26.0 686+00 2-ft LT 4963.3 4956.8

Reinforced Concrete Fill Wall #3 (689+70 to 690+90) B-18 19.0 690+00 4.5-ft LT 4992.8 4974.8 B-17 16.0 690+90 10.5-ft LT 5000.1 4991.1

Reinforced Concrete Fill Wall #4 (691+40 to 696+38) B-16 26.0 692+00 1-ft LT 5007.6 4989.1 B-15 21.0 693+00 2-ft LT 5015.2 5007.2 B-8 24.0 694+00 5-ft LT 5022.3 NE** B-7 24.5 695+00 5-ft LT 5029.8 5012.3 B-6 25.5 696+00 2-ft LT 5037.2 NE**

Reinforced Concrete Fill Wall #5 (703+30 to 704+70) B-5 16.0 703+50 5-ft LT 5090.6 5087.1 B-4 25.0 704+50 5.5-ft LT 5098.0 5092.0

Reinforced Concrete Fill Wall #6 (712+00 to 714+40) B-3 21.0 712+00 4-ft LT 5154.9 NE** B-2 20.5 713+00 4.5-ft LT 5162.8 NE** B-1 19.5 714+05 4.5-ft LT 5171.0 5159.0

*Offset is from proposed roadway centerline. **NE-Bedrock not encountered.

Boring location plans and cross sections are provided in Appendix A. Photos of the drill rig set up at each boring location and recovered core samples are located in Appendix E.

Drilling was conducted using an ODEX casing advancer system in overburden soils and HQ-3 triple- tube wireline coring systems in bedrock to yield maximum core recovery. The ODEX system is a casing advancer system that utilizes an eccentric under reamer to cut a drilled hole ahead of the bottom of the casing. The casing is then simultaneously advanced by a percussive drilling force applied to either the top or bottom of the casing. As the hole is advanced, the drill cuttings are removed by air and travel up the inside of the casing in the annular space between

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 8 the casing inside diameter and the drill rod outside diameter. This drilling method was selected in lieu of auger drilling due to the anticipation of high frequency of cobble and boulder size rock fragments within the overburden soils. Water was used during the core drilling and as a result it was difficult to detect ground water in the borings. At selected depths in the overburden Standard Penetration Tests (SPT's) were driven. SPT's were performed in accordance with AASHTO T 206 using an automatic hammer of 80 percent efficiency. Disturbed samples for visual identification and laboratory classification were recovered. The number of blows required to drive the sampler is a measure of the soil standard penetration resistance and is related to soil density. Samples were obtained in the overburden soils at 5-foot intervals using a standard 2-inch outside diameter split-spoon sampler. The number of blows required to drive the split-spoon sampler for three consecutive 6-inch intervals, or a total of 1.5 feet, was recorded on the boring logs. The initial 6-inch increment is considered a seating drive. The number of blows required for the second and third increments are totaled to provide the soil SPT resistance known as the N-value. SPT's taken in soils with gravel and cobbles typically result in high, un-conservative N-values and should not be relied on for design. For LRFD design requirements, numerous correction factors to the measured N-value are necessary to account for hammer efficiency, procedural variation in practice and increasing effective overburden stress with depth.

Laboratory testing on representative soil samples recovered during subsurface exploration were conducted in accordance with appropriate AASHTO specifications to obtain engineering properties necessary for design. A summary of laboratory test results on soil and rock samples are shown in Section 3.3 in Tables 3.4 and 3.5 respectively. The sampling sequence within the borings is summarized on the final boring logs attached in Appendix B and the laboratory test results is presented in Appendix C.

Percent core recovery and rock quality designation (RQD) were also determined for each core run to provide a quantitative basis of the rock mass conditions. Core recovery is the ratio of the length of recovered material to the total length of the core run, presented as a percentage. The RQD is a modified core recovery percentage and is defined as the ratio of the cumulative length of rock core pieces that are 4 inches in length or greater to the total length of the core run (ASTM D-6032). Percent core recovery and RQD designations provide a qualitative indication as to the competency and structural integrity of the investigated rock mass. Table 3.3 provides a rock quality description based on measured RQD Values.

TABLE 3.3:- Rock Quality based on RQD Values.

MEASURED RQD VALUES DESCRIPTION OF ROCK QUALITY

0-25% Very Poor 25-50% Poor 50-57% Fair 75-90% Good

90-100% Excellent

Intact rock core samples with an approximate length to diameter ratio of 2.0 or greater were selected from different rock units for laboratory testing to determine the unconfined compressive strength (UCS), in accordance with ASTM 2938 and D4543.The UCS test results were incorporated onto the boring logs and are also presented in Table 4.2 in Section Four.

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3.2 SUMMARY OF SUBSURFACE EXPLORATION

Field test results were recorded on field logs and appropriate data sheets at the time of the geotechnical investigation. The data sheets and logs contain information concerning the boring methods; samples attempted and recovered; indications of the presence of various materials such as gravel, cobbles and boulders, organic matter, and loss of water circulation. Also included in the boring logs are laboratory test results and visual interpretations by the field personnel of the conditions based on the performance of the drilling equipment and samples/cuttings brought to the surface.

Specific site descriptions are based on field observations, subsurface characterization information, and may vary in material type and strength with distance away from test boring locations. This variability is due to topography and land forming process.

Groundwater elevations were not measured during the subsurface investigation due to the use of water during the wireline coring process. Fluctuations in the ground water level due to seasonal precipitation and climatic effects are, however, expected. The following is a detailed description of materials encountered at each structure location. A summary of the boring information for each structure is also provided in Table 3.2.

CANTILEVER VIADUCT #1

Viaduct #1, located between station 676+15 and station 676+80, is 65-feet long. Two borings (B- 102 and B-103) were advanced at this location to the depth of 41 feet.

Boring B-102, located at Station 676+20 about 5 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 7 feet and cored using the HQ-3 wireline rock core system to a total depth of 41 feet from a starting elevation of 4,900.0 feet. The subsurface materials encountered were asphalt pavement and base course and yellow brown silty sand, gravels and rock fragments to a depth of 6 feet overlying one foot of light gray brown weathered schist from a depth of 6 to 7 feet, light gray to gray, strong, slightly to moderately weathered quartzite from a depth of 7 to 25 feet, and gray to light green, predominantly decomposed to moderately weathered serpentinite from a depth of 25 to 41 feet. Calcium infilling was encountered at a depth of 11 feet and some quartz infilling, healed fractures were encountered at a depth of 31 feet. A moderately weathered and high angle to vertical fracture zone was also encountered from a depth of 21.25 to 22.25 feet. An SPT N-value of 98 was recorded in the overburden soil layer but is high and unreliable due to the presence of gravels and rock fragments. Core recovery in the bedrock ranged from 0 to 100 percent and the RQD ranged from 0 to 90, both generally increasing with depth. Due to the fracturing patterns in the quartzite and serpentinite, there was no circulation of drilling fluids. UCS of a bedrock sample, obtained from 30 to 31 feet deep, was 3,020 pounds per square inch. The sample failed along visible fracture planes (joints).

Boring B-103, located at Station 676+75 about 7 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 11 feet and cored using the HQ-3 wireline

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 10 rock core system to a total depth of 41 feet from a starting elevation of 4903.6 feet. The subsurface materials encountered were asphalt pavement and base course and yellow brown silty sand with rock fragments to a depth of 7 feet overlying gray, soft to medium strong, decomposed to moderately weathered schist from 7 to 36.5 feet, light gray to gray quartzite from 36.5 to 39.5 feet, and olive green to gray schist from 39.5 to 41 feet. A clay seam was encountered at a depth of 16 feet and a decomposed seam just below at a depth from 17 to

18.5. Micaceous foliation was present at a depth of 21 feet. No SPT’s were recorded in the overburden soil layer due to the presence of large rock fragments. Core recovery in the bedrock ranged from 38 to 100 percent and the RQD ranged from 0 to 60 with an average of

25. Due to the fracturing patterns in the schist, there was no circulation of drilling fluids.

UCS of a bedrock sample obtained from 23 to 24 feet was 4,520 pounds per square inch with failure along the visible fracture planes.

CANTILEVER VIADUCT #2

Viaduct #2, located between station 697+75 and station 698+08, is 33-feet long. One boring was advanced to the depth of 36 feet.

Boring B-101, located at Station 697+75 about 4 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 8 feet and cored using the HQ-3 wireline rock core system to a total depth of 36 feet from a starting elevation of 5,051.4 feet. The subsurface materials encountered were asphalt pavement, base course and brown silty sand and gravels and rock fragments to a depth of 6.5 feet overlying gray weathered schist from

6.5 to 8 feet, dark gray predominantly decomposed to moderately weathered schist from 8 to 11 feet, tan decomposed granite (DG) from 11 to 17.3 feet, and gray, medium hard to hard granodiorite from 17.3 to 36 feet. A heavily weathered zone was encountered at a depth from

21.5 to 22.5 feet as reflected by the UCS of core taken from this zone. The driller noted there were zones of easy drilling in the last core run between 31 feet 36 feet although the core recovery and RQD were relatively high. An SPT N-value of 8 was recorded in the overburden soil layer. Core recovery in the bedrock ranged from 2 to 100 percent and the RQD ranged from 0 to 95, both increasing with depth. Water circulation through the bedrock was good with the exception of lost drilling fluid circulation at a depth of 28.5 feet. UCS of bedrock samples obtained from 17.4 to 18.2 feet and 21.5 to 22.5 feet was 10,550 pound per square inch and 2,920 pounds per square inch, respectively.

FILL WALL #1

Fill wall #1, located between station 679+20 and station 683+20, is 400-feet long with a maximum height of 12 feet. Five borings (B-9 through B-3) were advanced to depths ranging from 20 to 21 feet.

Boring B-9, located at Station 679+25 about 3.5 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 12 feet and cored using the HQ-3 wireline rock core system to a total depth of 21 feet from a starting elevation of 4,920.4 feet. The subsurface materials encountered were asphalt pavement, base course and yellow brown silty sand, gravel, and rock fragments to a depth of 7 feet overlying yellow brown to dark yellow

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 11 brown decomposed granite from 7 to 12 feet, and gray to white strong to very strong slightly weathered granodiorite from 12 to 21 feet. An SPT N-value 36 was recorded in the overburden soil layer. Core recovery in the bedrock was 100 percent and the RQD ranged from 72 to 97. Due to the fracturing patterns in the granodiorite, there was no circulation of the drilling fluids. Occasional quartz inclusions were encountered at a depth from 16 to 21 feet. UCS of a bedrock sample obtained from a depth of 16 to 17 feet was 21,170 pounds per square inch.

Boring B-10, located at Station 680+25 about 3 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 12 feet and cored using the HQ-3 wireline rock core system to a total depth of 21 feet from a starting elevation of 4,925.6 feet. The subsurface materials encountered were asphalt pavement, base course and yellow brown silty sand, gravel, and rock fragments to a depth of 10 feet overlying brown gray weathered rock (gneiss) from 10 to 11 feet and light gray to gray, strong, slightly weathered gneiss from 11 to 21 feet. An SPT N-value of 20 was recorded in the overburden soil layer. Core recovery in the bedrock ranged from 96 to 100 percent and the RQD ranged from 58 to 76. Due to the fracturing patterns in the gneiss bedrock, there was no circulation of the drilling fluids. UCS of a bedrock sample obtained from 12.5 to 13.4 feet was 5,610 pounds per square foot.

Boring B-11, located at Station 681+25 about 2 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 12 feet and cored using the HQ-3 wireline rock core system to a total depth of 20.5 feet from a starting elevation of 4,931.5 feet. The subsurface materials encountered were asphalt pavement, base course and yellow brown silty sand and rock fragments to a depth of 5.5 overlying yellow brown weathered schist from 5.5 feet to 10.5 feet, and gray to white strong slightly weathered granodiorite from 10.5 to 20.5 feet. An SPT N-value of 91 was recorded in the overburden soil layer. Core recovery in the bedrock ranged from 43 to 89 percent and the RQD ranged from 0 to 78. Poor circulation was consistent throughout the granodiorite bedrock.

Boring B-12, located at Station 682+25 about 2 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 8 feet and cored using the HQ-3 wireline rock core system to a total depth of 21 feet from a starting elevation of 4,938.3 feet. The subsurface materials encountered were asphalt pavement, base course and dark yellow brown silty sand and rock fragments to a depth of 6 feet overlying brown gray weathered granodiorite from 6 to 7 feet, gray to white medium strong slightly to moderately weathered gneiss from a depth of 7 to 11 feet, and gray gneiss from a depth of 11 to 21 feet. A weathered zone of gneiss (RQD = 0) was also encountered at a depth from 16 to 17 feet and reoccurred at a depth from 19 and 21 feet. No SPT’s were recorded in the overburden soil layer due to the presence of rock fragments. Core recovery in the bedrock ranged from 67 to 100 percent with very low RQD values (RQD = 0 to 14). Good circulation was consistent throughout the drilling in bedrock.

Boring B-13, located at Station 683+00 about 4.5 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 7 feet and cored using the HQ-3 wireline rock core system to a total depth of 20 feet from a starting elevation of 4,943.2 feet. The subsurface materials encountered were asphalt pavement, base course and dark yellow brown

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 12 silty sand and rock fragments to a depth of 2 feet overlying brown gray weathered granodiorite from 2 to 6.5 feet, and gray to white strong slightly weathered gneissic granodiorite from 6.5 to 20 feet. Predominantly decomposed zones with clay infilling were encountered between approximately 17 and 20 feet in depth. No SPT’s were recorded in the overburden soil layer due to encountering rock at a depth of 2 feet. Core recovery in the bedrock ranged from 95 to 100 percent recoveries and the RQD ranged from 13 to 80 with an average of 43. Good circulation of drilling fluids was consistent throughout the drilling in bedrock. UCS of a bedrock sample obtained from 14 to 15 feet was 8,540 pounds per square foot with failure along the visible fracture planes.

FILL WALL #2

Fill wall #2, located between station 683+70 and station 686+00, is 230-feet long with a maximum height of 14 feet. Three borings (B-14, B-19, and B-20) were advanced to depths ranging from 24.5 to 26 feet.

Boring B-14, located at Station 684+00 about 4.5 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 12 feet and cored using the HQ-3 wireline rock core system to a total depth of 26 feet from a starting elevation of 4,948.3 feet. The subsurface materials encountered were asphalt pavement, base course and light yellow brown silty sand and rock fragments to a depth of 3 feet overlying yellow brown weathered and fractured schist from 3 to11 feet, and gray medium strong, slightly to moderately weathered gneiss from 11 to 26 feet. Large quartz inclusions were encountered at a depth of 17 feet.

Refusal (10 blows for no penetration) was encountered for an SPT taken from 2 to 3 feet due to the presence of schist. Core recovery in the bedrock ranged from 25 to 100 percent and the RQD ranged from 0 to 58 with an average of 22. Due to the fracturing patterns in the gneiss, there was no circulation of drilling fluids while drilling in the bedrock.

Boring B-20, located at Station 685+00 about 5 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 7 feet and cored using the HQ-3 wireline rock core system to a total depth of 24.5 feet from a starting elevation of 4,955.8 feet. The subsurface materials encountered were asphalt pavement, base course and yellow brown silty sand, gravel, and rock fragments to a depth of 4 feet overlying gray, medium strong to strong slightly weathered gneissic granodiorite from 4 to 24.5 feet. A seam of clayey sand was encountered from a depth of 10 to 10.5 feet. No SPT’s were recorded in the overburden soil layer due to the presence of rock fragments and encountering shallow bedrock. Core recovery in the bedrock ranged from 47 to 100 percent and the RQD ranged from 0 to 64, very poor from a depth of 4 to 11 feet and fair from 11 to 24.5 feet. Good circulation was consistent throughout bedrock. UCS of a bedrock sample obtained from 16- to 17-feet was 10,200 pounds per square inch with moderate to vertical fractures.

Boring B-19, located at Station 686+00 about 2 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 8 feet and cored using the HQ-3 wireline rock core system to a total depth of 26 feet from a starting elevation of 4,963.3 feet. The subsurface materials encountered were asphalt pavement, base course and yellow brown silty sand, gravel, and rock fragments to a depth of 6.5 feet overlying gray, strong, slightly

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 13 weathered gneissic granodiorite from a depth of 6.5 to 26 feet. An SPT N-value 11 was recorded in the overburden soil layer. Core recovery in the bedrock ranged from 20 to 100 percent and the RQD ranged from 0 to 75 with an average of 34. Good circulation was consistent throughout bedrock. UCS of a bedrock sample obtained from 23.8 to 25 feet was 8,960 pounds per square inch with failure along the visible fracture planes.

FILL WALL #3

Fill wall #3, located between station 689+70 and station 690+90, is 120-feet long with a maximum height of 8 feet. Two borings (B-17 and B-18) were advanced to depths ranging from 16 to 19 feet.

Boring B-18, located at Station 690+00 about 4.5 feet to the left of proposed centerline, was advanced using only the ODEX system to a total depth of 19 feet from a starting elevation of 4,992.8 feet. The subsurface materials encountered were asphalt pavement, base course and brown silty sand and rock fragments to a depth of 18 feet overlying brown gray schist from 18 to 19 feet. Representative soil samples were classified as SM, with fines in excess of 15 percent. Three SPT N-values were recorded in the overburden soil layer ranging from 6 to

26. No competent bedrock was encountered.

Boring B-17, located at Station 690+90 about 10.5 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 6 feet and cored using the HQ-3 wireline rock core system to a total depth of 16 feet from a starting elevation of 5,000.1 feet. The subsurface materials encountered were brown silty sand and rock fragments to a depth of 4 feet overlying yellow brown to gray, granodiorite from 4 to 16 feet with a tan decomposed zone from 7 to 9 feet. No SPT’s were recorded in the overburden soil layer due to the presence of rock fragments. Core recovery in the bedrock ranged from 60 to 87 percent and the RQD ranged from 20 and 92 with an average of 58. There was good circulation throughout the bedrock with the exception of lost drilling fluid circulation around a depth of 14 feet. Unconfined compressive strength (UCS) of bedrock measured in the laboratory on a sample obtained from 6 to 7 feet was 14,670 pounds per square foot.

FILL WALL #4

Fill wall #4, located between station 691+40 and station 696+38, is 498-feet long with a maximum height of 13 feet. Five borings (B-6 through B-8, B-16, and B-17) were advanced to depths ranging from 21 to 26 feet.

Boring B-16, located at Station 692+00 about 1 foot to the left of proposed centerline, was advanced using the ODEX system to a depth of 8 feet and cored using the HQ-3 wireline rock core system to a total depth of 26 feet from a starting elevation of 5,007.6 feet. The subsurface materials encountered were asphalt pavement, base course and brown silty sand and rock fragments to a depth of 8 feet overlying gray medium strong to strong slightly weathered granodiorite from 8 to 13.8 feet, a decomposed zone of granodiorite from 13.8 to

18.5 feet, and back into gray granodiorite from 18.5 to 26 feet with some zones of more weathered rock. No SPT’s were recorded in the overburden soil layer due to boulders. Core

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 14 recovery in the bedrock ranged from 67 to 100 percent and the RQD ranged from 0 to 80 with an average of 45. Due to the fracturing patterns in the granodiorite and decomposed granodiorite zone, drilling fluid circulation was lost at approximately 9.5 feet in depth. UCS of two bedrock samples obtained from 8.0 to 9.1 feet and from 24.5 to 26.0 feet were 18,850 and 17,230 pounds per square inch, respectively.

Boring B-15, located at Station 693+00 about 2 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 12 feet and cored using the HQ-3 wireline rock core system to a total depth of 21 feet from a starting elevation of 5015.2 feet. The subsurface materials encountered were asphalt pavement, base course and brown silty sand and rock fragments to a depth of 8 feet overlying gray medium strong to strong, slightly weathered granodiorite from 8 to 21 feet. Very hard drilling was encountered at a depth of approximately 9 feet which caused the casing shoe to snap off at 12 feet. A quartz infilled seam was encountered at a depth of 14 feet dipping approximately 60 to 70 degrees. No SPT’s were recorded in the overburden soil layer due to boulders. Core recovery in the bedrock ranged from 88 to 92 percent and the RQD ranged from 83 to 92 with an average of

88. Due to the fracturing patterns in the granodiorite, circulation was lost at approximately 15 feet in depth; causing no water return. UCS of a bedrock sample obtained from 12 to 13 feet was 17,820 pounds per square inch.

Boring B-8, located at Station 694+00 about 5 feet to the left of proposed centerline, was advanced using only the ODEX system to a total depth of 24 feet from a starting elevation of 5,022.3 feet. The subsurface materials encountered were asphalt pavement, base course and brown silty sand, with gravel to a depth of 9 feet overlying light brown to dark brown decomposed granite (DG) from 9 to 24 feet. Representative soil samples of the overburden classified as SM. An SPT N-value of 6 was recorded in the overburden soil layer and SPT N-values in the DG ranged from 28 to refusal (50 blows for 6 inches).

Boring B-7, located at Station 695+00 about 5 feet to the left of proposed centerline, was advanced using only the ODEX system to a total depth of 24.5 feet from a starting elevation of 5,029.8 feet. The subsurface materials encountered were asphalt pavement, base course and brown gray silty sand with gravel and rock fragments to a depth of 17.5 feet overlying dark gray schist from 17.5 to 24.5 feet. A weathered zone was encountered from a depth of 21 to 22.5 feet. Representative soil samples of the overburden classified as SM. SPT N-values in the overburden soil ranged from 2 to 15.

Boring B-6, located at Station 696+00 about 2 feet to the left of proposed centerline, was advanced using only the ODEX system to a total depth of 25.5 feet from a starting elevation of 5,037.2 feet. The subsurface materials encountered were asphalt pavement, base course and brown gray silty sand and gravel and rock fragments to a depth of 25.5 feet. Bedrock was not encountered but notably harder drilling started at a depth from 15.5 to 25.5 feet.

Representative soil samples of the overburden classified as GM and SM. Five SPT N-values were recorded in the overburden soil layer ranging from 18 to 53 but tended to be a somewhat high due to the presence of gravels.

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 15

FILL WALL #5

Fill wall #5, located between station 703+30 and station 704+70, is 140-feet long with a maximum height of 14 feet. Two borings (B-4 and B-5) were advanced to depth of 16 and 25 feet.

Boring B-5, located at Station 703+50 about 5 feet to the left of proposed centerline, was advanced using the ODEX system to a depth of 5 feet and cored using the HQ-3 wireline rock core system to a total depth of 16 feet from a starting elevation of 5,090.6 feet. The subsurface materials encountered were asphalt pavement, base course and brown gray silty sand and rock fragments to a depth of 3.5 feet overlying dark gray to green, medium strong, moderately weathered schist and serpentinite from 3.5 to 16 feet. No SPT’s were recorded in the overburden soil layer due to the presence of shallow bedrock. Core recovery in the bedrock ranged from 80 to 100 percent and the RQD ranged from 33 to 67 with an average of

45. Circulation of drilling fluids became poor with increasing depth.UCS of a bedrock sample obtained from 10.3 to 11.0 feet was 16,760 pounds per square inch.

Boring B-4, located at Station 704+50 about 5.5 foot to the left of proposed centerline, was advanced using the ODEX system to a depth of 8 feet and cored using the HQ-3 wireline rock core system to a total depth of 25 feet from a starting elevation of 5,098.0 feet. The subsurface materials encountered were asphalt pavement, base course and brown gray silty sand with gravel and rock fragments to a depth of 6 feet overlying dark gray, hard to soft, predominantly decomposed to moderately weathered schist. Quartz infilled seam was encountered at a depth of 21.5 feet. An SPT N-value of 16 was recorded in the overburden soil layer. Core recovery in the bedrock ranged from 20 to 90 percent and the RQD ranged from 0 to 29 with an average of 10. Due to the fracturing patterns in the schist, drilling fluid circulation was lost at a depth of approximately 15.5 feet.

FILL WALL #6

Fill wall #6, located between station 712+00 and station 714+40, is 240-feet long with a maximum height of 10 feet. Three borings (B-1 through B-3) were advanced to depths ranging from 19.5 to 21 feet.

Boring B-3, located at Station 712+00 about 4 foot to the left of proposed centerline, was advanced using the ODEX system to a depth of 8 feet and then cored using the HQ-3 wireline rock core system to a total depth of 21 feet from a starting elevation of 5,54.9 feet.

The subsurface materials encountered were asphalt pavement, base course and red brown silty sand with gravel and rock fragments to a depth of 21 feet. Bedrock was not encountered.

No SPT’s were recorded in the overburden soil layer due to boulders. No return of drilling fluids was observed throughout the overburden to the depths explored.

Boring B-2, located at Station 713+00 about 4.5 feet to the left of proposed centerline, was advanced using only the ODEX system to a total depth of 20.5 feet from a starting elevation of 5,162.8 feet. The subsurface materials encountered were asphalt pavement, base course and red brown silty sand and rock fragments to a depth of 17 feet overlying yellow brown

Final Geotechnical Investigations Report CA PRA SEKI 10(10) Page 16 decomposed granite (DG) from 17 to 20.5 feet. Representative soil samples of the overburden classified as SM. SPT N-values were recorded in the overburden soil layer ranging from 6 to 8.

Boring B-1, located at Station 714+05 about 4 foot to the left of proposed centerline, was advanced using the ODEX system to a depth of 14 feet and cored using the HQ-3 wireline rock core system to a total depth of 19.5 feet from a starting elevation of 5171.0 feet. The subsurface materials encountered were asphalt pavement, base course and red brown silty sand with gravel and rock fragments to a depth of 12 feet overlying dark gray to green serpentinite from 12 to 19.5 feet. Representative soil samples of the overburden classified as SM. Two SPT N-values were recorded in the overburden soil layer ranging from 3 to 8.