B09_Amd_1_Geotech_Investigation_Crane_Flat_Water_System_0001.pdf

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GEOTECHNICAL INVESTIGATION

CRANE FLAT WATER SYSTEM

YOSEMITE NATIONAL PARK, CALIFORNIA

Prepared for Kennedy/Jenks Consultants, Inc.

5190 Neil Road, Suite 210 Reno, NV 89502

Prepared by Condor Earth Technologies, Inc.

21663 Brian Lane Sonora, CA 95370

209.532.0361

June 19, 2009 Condor Project No. 5655

Copyright © 2009, Condor Earth Technologies, Inc.

All Rights Reserved

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TABLE OF CONTENTS

1.0 INTRODUCTION .•••.•...•.••...•..•.•.....•...•...••••.•••...•..•..•.•....•..•.•••..•..•.•.•.•.•.•...•..•.•........•.•.•..•.......•••.••....•• 1

2.0 PROJECT DESCRIPTION ••.•..•..•.•.•.•.......••.•.•..•.•...••••••....•.•.•.•..•......•.....•......••.•.•.•.•..•.••.•.•...•.••••••.•... l

3.0 SCOPE OF WORK •..•..•.•...••..•.•..•.......•..•.•.••.•.••...•....•.•.....•..•..•..•...•.••...•.••••.•...••........•..••......•.••...•...••• 2

4.0 SITE GEOLOGY •.•...••.......•..•..•..•..•.••••.•..•.•...•.•.••.•.•.••.••..•.••.•.•.•..•..••............•.......•.........••.••.....•.••.••.•• 3

5.0 SUBSURFACE INVESTIGATION METHODS •.••.•.•..••.•.•••..•.•..•.•.•...•...••.•.••.....•.••.•.•..•.•...•..•...•....• 3

6.0 SITE AND SUBSURFACE CONDITIONS .•.•..•.•....•..•.••.•.•.•....•.•..•••..•..••.•....•...•.•••.•...•.•.••..••........•.. 4

6.1 PHASE 1 WATER LINE ALIGNMENT

6.1.1 Crane Flat Gas Station to Crane Flat Campground Access Road

6.1.2 Crane Flat Campground

6.2 PHASE 2 WATER LINE ALIGNMENT

6.2.1 Crane Flat Gas Station to the Yosemite Institute

6.2.2 Yosemite Institute to the Existing Water Tank

6.3 SUBSURFACE CONDITIONS

7.0 CONCLUSIONS •.•••.••.....•.•.....•....•..•.......••.•..•••.•..•..•...••.••....•.•.•.•..•.•.••....•.•..•.•••••.•.....•.•..•.••.•.•..•..•..•••.• 7

7.1 GENERAL ....................................................................................... .. ............. ..................................... ?

7.2 GEOLOGIC HAZARDS

8.0 RECOMMENDATIONS ...•....••.•.•..........•.•.••.•.••....•...•.••.•.•..•.....•..•...•.•..•......•••.•.•.....•.•...........•......•.•.. 8

8.1 PIPEZONE MATERIALS

8.2 TRENCH BACKFILL MATERIALS

8.3 EXTERNAL PIPELINE LOADS

8.4 MODULUS OF SOIL REACTION (E') ........................................................................................ ... 1 0

8.5 THRUST RESISTANCE

8.6 AGGREGATE BASE AND PAVING .. .. .......................................................................................... 1 0

8.7 WET WEATHER EARTHWORK CONSIDERATIONS

8.8 DRAIN"AGE AND EROSION CONTROL

9.0 .ADDITIONAL SERVICES ..•..•.•..•.•.••....•.•..••.•.••••...•..•.••.•..•.•.........•••.•..•.•.•..•..•.....•..•.•..•••......•..•.•••.. 12

10.0 LIMITATIONS •..••.•.••.•••........•..•.•.••.•...•.•.•..•.••.•...•..•..•.•.••.•..•.•...•.•.•.•.•.•..•....•.••.••.•.•......•....•..•••...•..••.. 12

11.0 CLOSURE ...•••••••....•.••••.•..•..•..•..•.•..•.•.•••...•..•.••.•......•....•.••.•.........••.••.•••...•.......•.••••.•...•.•.....•.••..•..•••.•.. 13 ii "-CONDOR l

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FIGURES

Figure 1 Figure 2 Figure 3 Figure4

APPENDIX A

Vicinity Map Site Plan Aerial Location Map Surface Geologic Map

Soil Boring Logs

APPENDIXB

Laboratory Test Results

APPENDIXC

Pavement Calculations

ATTACHMENTS

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1.0

GEOTECHNICAL INVESTIGATION

CRANE FLAT WATER SYSTEM

YOSEMITE NATIONAL PARK, CALIFORNIA

INTRODUCTION

This report presents the results of a geotechnical investigation performed by Condor Earth Technologies, Inc. (Condor) for the proposed underground water pipe installation at Crane Flat in Yosemite National Park, California. We performed our work in accordance with our December 23, 2009 Proposal and the May 5, 2009 Subcontract with Kennedy/Jenks Consultants, Inc. (hereinafter "KJC").

The purpose of our work was to investigate and evaluate site and subsurface conditions and to develop geotechnical recommendations for design and construction of the Crane Flat water system for use by other design professionals and by contractors.

Figure 1, Vicinity Map, shows the approximate location of the proposed water pipe alignment. The site is approximately 11 miles west of the center of Yosemite Village. The water pipe alignment follows the gravel and dirt road shoulders of Big Oak Flat Road and Tioga Road, Crane Flat Campground access roads, and dirt roads leading to the water well site on the northwest side of Crane Flat and the water tank site off Tioga Road. The approximate coordinates of the site are 37.756864° north latitude and -119.800314° west longitude.

2.0 PROJECT DESCRIPTION

The project will involve construction of over 15,000 feet of 6-, 8-, and 1 0-inch diameter water pipe buried about 4.5- to 5-feet deep. Water line construction will be completed in two Phases. Figure 2, Site Plan, shows the water pipe alignment and the Phase 1 and Phase 2 limits. The existing water pipes along the alignment generally are outside of the areas of the new pipes. The existing water pipes will be abandoned in accordance with recommendations provided by KJC.

Phase 1 construction will involve the installation of 6- and 8-inch diameter water pipe along the access roads in the Crane Flat Campground and extending to the campground entrance on the south side of Big Oak Flat Road (Highway 120). Comfort stations and fire hydrants along the Crane Flat Campground access roads and in campground loops A, B, D and E will be connected to the new water line. Eight-inch diameter water pipe will also be installed during this Phase of construction along the south shoulder of Big Oak Flat Road from the campground entrance to the intersection of Tioga Road. The water pipe will then extend north across Big Oak Flat Road and terminate on the west shoulder of Tioga Road directly south of the Crane Flat gas station entrance off Tioga Road. An 8-inch water pipe will extend across Tioga Pass to the Crane Flat gas station. This water pipe will transition to a 6-inch diameter pipe in the immediate area of the gas station.

Phase 2 construction will involve the installation of an 8- and 1 0-inch diameter water line. The water line will extend from the Crane Flat gas station area westward along the south shoulder of Tioga Road to the Tuolumne Grove parking lot. Prior to the water line reaching the Tuolumne Grove parking lot, a southwest extension of the water line consisting of an 8-inch diameter pipe will connect to a pump house located at a site identified as the YCC Camp. Tioga Road then curves to the northeast and east beyond the Tuolumne Grove parking lot. The 1 0-inch water line will continue along the outboard shoulder of Tioga Road from this point and terminate at an existing 50,000-gallon aboveground water tank located

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Geotechnical Investigation Crane Flat Water System Kennedy/Jenks Consultants, Inc.

Page2 directly northeast of Crane Flat Meadow. All portions of the Phase 2 water line route will support both a 10-inch water line and various configurations of 1- to 4-inch diameter electrical conduit installed in the water line trench to provide electricity and control panel wiring conduit for a shutoff valve located at the water tank.

If the design or location of the project varies significantly from this description, then Condor should re evaluate the recommendations in this report.

3.0 SCOPE OF WORK

To develop geotechnical recommendations for design and construction of the project, the following tasks were completed:

• Attended a site meeting on December 18, 2008 to review the proposed water line alignment with David Engelstad, PE, Project Manager, Yosemite National Park.

• Attended a site walk on May 7, 2009 prior to the start of the subsurface investigation to mark geotechnical boring locations to allow Underground Services Alert (USA) to be notified that drilling activities would occur along the proposed water line alignment

• Prepared a site-specific safety plan.

• Prepared a field investigation work plan.

• Notified USA North on May 8, 2009 that drilling work was scheduled to begin on May 20, 2009.

• Directed and coordinated with Subdynamics Utility Locating Service to mark underground utilities in the immediate area of the proposed geotechnical boring along the proposed water line alignment.

• Coordinated with Force Traffic Control personnel to erect and maintain appropriate traffic control for the drilling of soil borings within public road right-of-ways along the water line alignment. ·

• Completed a site and subsurface investigation along the proposed pipe alignment on May 20 to May 22, 2009. Seventeen geotechnical borings were drilled along the proposed water pipe alignment by Taber Drilling to allow a Condor Geologist to characterize subsurface soils, describe subsurface conditions and geology, and collect disturbed and undisturbed soil samples.

• Coordinated drilling work with a Yosemite National Park Archeologist that allowed selected samples of drilling cuttings to be evaluated for the presence of artifacts.

• Completed laboratory testing of selected samples obtained from the geotechnical borings.

• Contacted Dena Traina, PE, of KJC to secure data and reports generated by KJC or its subcontractors related to geologic studies and subsurface investigations completed in the Crane Flat area of Yosemite National Park.

Completed a review of a Condor Earth Technologies, Inc. Onsite Wastewater System Subsurface Investigation Report completed in July 1999 for the Yosemite Institute.

Reviewed a report titled "Summary of Soil Testing and Assimilative Capacity Analysis";

completed by Northstar Engineering in June 2004 for the Yosemite Institute.

Reviewed Yosemite Institute monitor well head survey data compiled by the Condor Earth Technologies, Inc. Survey Division in 2004 and updated in 2009.

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• Reviewed state and federal agency published reports and web-based information regarding geologic and subsurface data related to the Yosemite National Park.

• Prepared a report that presents our findings, conclusions regarding excavation difficulty, suitability of excavated material for use as backfill, and recommendations for bedding and backfill material properties and compaction, as well as geotechnical design parameters for the pipeline.

4.0 SITE GEOLOGY

Figure 4, Surface Geologic Map, shows the site plotted on a geologic map. As mapped, Cretaceous period, late Sanotonian age Arch Rock Granodiorite (Kar) lies beneath the site. The rock encountered in our subsurface investigation, and that exposed on the ground surface in various locations, is granodiorite (Figure 2, Site Plan). Colluvium and/or residual soil (generally sandy silts and silty sands) associated with the granodiorite was encountered in most of our borings. Quaternary-period, Holocene-epoch alluvial deposits (Qal) also are located along the proposed water line alignment. The areas have been identified as Alluviwn/Shallow Groundwater Area on Figure 2. These deposits are located in the grass covered areas of Crane Flat north and northwest of the Crane Flat gas station and on the Tioga Road and Crane Flat Campground main access road. Early Paleozoic, Cambrian- to Ordovician-period metasedimentary rock (Pzme) has been mapped in the area of the Crane Flat Campground. However, no metasedimentary rocks were observed on the surface near the water line alignment or in the borings.

5.0 SUBSURFACE INVESTIGATION METHODS

The Condor subsurface investigation consisted of drilling borings at various locations along the alignment of the proposed water line, logging individual borings, recording blow counts, and perfonning laboratory tests on samples retrieved. A trailer-mounted CME 45 solid-stem auger drilling rig was used to drill 17 borings on May 20 and 21, 2009, designated B-1 through B-17. The borings were drilled at the approximate locations shown on Figure 2. All the borings extended to an approximate depth 6 feet except boring B-9, where refusal was encountered at 4 feet. Appendix A contains the logs for these borings.

Our field representative retrieved samples of soil and rock from the borings using either an auto hammer driven California Modified sampler or a Standard Penetration Test (SPT) sampler. The samples retrieved consisted of both disturbed samples as well as relatively undisturbed liner samples that have dimensions of about 6 inches long and 2.5 inches in diameter. The liners were driven by an auto-hammer with a 140 pound hammer and a 30 inch drop.

Our field representative logged the soil conditions encountered in the borings using the visual/manual procedure and the Unified Soil Classification System (USCS). In addition, we evaluated the pertinent engineering properties of the rock encountered according to the system described in Appendix A. A Yosemite National Park Archeologist also examined selected cuttings from the borings during drilling.

The field representative checked the borings for groundwater during drilling. After the borings were completed, they were backfilled with clean cement slurry. Boring spoils were spread around the individual boring locations.

We examined and tested the samples in our laboratory and our subcontracted laboratories. We performed moisture content, dry density, sand equivalent, sieve analysis including 200 wash, unconsolidated undrained triaxial compressive strength, R-value, and corrosion. Appendix B contains the test results.

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6.0 SITE AND SUBSURFACE CONDITIONS

Geotechnical Investigation Crane Flat Water System Kennedy/Jenks Consultants, Inc.

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The proposed Crane Flat water line alignment will be constructed in two phases designated Phase 1 and Phase 2. The following sections provide descriptions of site and subsurface conditions for the Phase 1 and Phase 2 water line alignments.

6.1 PHASE 1 WATERLINE ALIGNMENT

The Phase 1 water line alignment will extend south from the Crane Flat gas station along the south shoulder of Tioga Road to the Tioga Road and Big Oak Flat Road intersection. The water line will then cross Big Oak Flat Road and proceed along the west shoulder of the road to the entrance of the Crane Flat Campground. The water line will then proceed south along the west shoulder of the main campground access road and extent to Loop E of the campground. Eastern extensions of the main water line will be constructed to provide water service to existing comfort stations in campground loops A, B, D, and E. Figure 2, Site Plan, shows the locations of the borings along the proposed water line alignment.

The Phase 1 water line alignment will be constructed in areas corresponding to the locations of borings B-1 through B-9 and borings B-12, and B-13.

6.1.1 Crane Flat Gas Station to Crane Flat Campground Access Road

The topographic relief along the proposed Phase 1 water line alignment from the Crane Flat gas station to the Crane Flat Campground entrance is relatively level. Gravel and soil covered road shoulders of Tioga Road and Big Oak Flat Road (HWY 120) constitute the surface materials covering this portion of the water line alignment. Outcrops of granodiorite were observed along this portion of the water line alignment. A 20-foot high fill spanning Crane Creek was observed approximately 200 feet east of the Crane Flat Campground and Big Oak Flat Road intersection. Examination of the fill slopes indicates the material consists of silty sands and sandy silts. Asphalt concrete is the surface material of the roads. Road subgrade material was observed to consist of fine to medium sand and silt with fine gravel ranging in size from !4- to ~-inch diameter. Cutbanks exposing colluvial soils consisting of silty sand and sandy silt with scattered cobbles and boulders were observed along . the proposed water line alignment. These approximately 2 horizontal to 1 vertical (2H: 1 V) cut banks slopes are 2 to 4 feet high. Shallow groundwater conditions were encountered in the area of boring B-13 near the Crane Flat gas station.

6.1.2 Crane Flat Campground

Slight to moderate slopes were observed along the water line alignment located along the west shoulder of the Crane Flat Campground main access road. Soil with some gravel-covered areas constitutes the surface material of this shoulder. Granodiorite outcrops were observed along the proposed water line alignment from the Crane Flat Campground and Big Oak Flat Road intersection to a point approximately 1 ,000 feet south of this intersection. Shallow soils overlying hard granodiorite at 4 feet were encountered in boring B-9 near the campground entrance. A 3-foot deep fill with a boulder base was observed approximately 50 feet south of boring B-9. This fill spans a wet area. Another fill was observed in the vicinity of boring B-5. This fill spans a small intermittent drainageway located directly south of the intersection of campground Loop A and the main campground access road. Cutbanks exposing colluvial soils consisting of silty sand and sandy silt with scattered cobbles and boulders were observed along the proposed main campground access road water line alignment. The 2H: 1 V cut banks slopes were observed to be 2 to 4 feet high.

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Moderate slopes were observed on the portions of the individual water line alignments that will extend east from the main access road to comfort stations located in campground loops A, B, D, and E. Fills of 3 to 4 feet high were observed at the upper portions of the water line alignments to the comfort stations located in campground loops A and B. These fill materials consist of silty sand and sandy silt. The lower portions of the water line alignments were along slightly sloping to level road shoulder areas.

Granodiorite outcrops were observed downslope of these proposed water line alignments. Large mature pines were observed along the lower portions of these proposed water line alignments.

Asphalt concrete is the surface material of the roads in the campground. Road subgrade material was observed to consist of a fine- to medium-grained sand with silt and fine gravel ranging in size from ~- to %-inch diameter. Large, mature pine trees were observed along the proposed water line alignments in the campground.

6.2 PHASE 2 WATER LINE ALIGNMENT

The Phase 2 water line alignment will extend northwest from the Crane Flat gas station along the south shoulder of Tioga Road to the existing water tank located approximately 3,000 feet up slope and east of the Yosemite Institute. Figure 2, Site Plan, shows the locations of the borings along the proposed Phase 2 water line alignment. The Phase 2 water line alignment will correspond to the locations of borings B-10, B-11, and B-13 through B-17.

6.2.1 Crane Flat Gas Station to the Yosemite Institute

The proposed Phase 2 water line will be constructed in existing road shoulder and subgrade areas of Tioga Road and in a short section of dirt road leading to a well and pump located at a site identified as the YCC Camp. The topographic relief along the proposed Phase 2 water line alignment from the Crane Flat gas station to the Yosemite Institute, including the dirt road leading to the well at the YCC Camp, is level to slightly sloping. Gravel and soil covered road shoulders constitute the surface materials along the alignment. Outcrops of granodiorite were observed in the areas along Tioga Road shown on Figure 2.

Six-foot high fills were observed spanning Crane Creek approximately 100 feet southeast ofboring B-14;

a wet area east of the YCC Camp; and a wet area approximately 100 feet north of the dirt road/Tioga Road intersection. The fills overlay areas identified on Figure 2 as Alluvium/Shallow Groundwater Area.

Examination of the fill slope indicates the material consists of a base of boulders overlain by silty sands and sandy silts.

Asphalt concrete is the surface material of Tioga Road. Subgrade material was observed to consist of fme to medium sand and silt. Cutbanks exposing colluvial soils consisting of silty sand and sandy silt with scattered cobbles and boulders were observed along the proposed water line alignment. These 2H: 1 V cutbanks slopes are 2 to 6 feet high. The dirt road leading to the YCC Camp had a surface cover of gravel that transitioned to a dirt surface. Slight slopes and 1- to 2-foot high cutbanks were observed along this portion of the proposed water line alignment. Large, mature pine trees were observed along this portion of the proposed water line alignment.

6.2.2 Yosemite Institute to the Existing Water Tank

Moderate to steep slopes were observed along the water line alignment from Yosemite Institute to the water tank site. Gravel-covered areas constitute the surface material of the Tioga Road shoulder. Four to 6-foot high fills spanning intermittent drainageways were observed approximately 100 feet east ofboring B-16. A 10- to 12-foot high fill was observed directly west of boring B-17. Examination of these fill slopes indicates the material consists of silty sands and sandy silts. Asphalt concrete is the surface material of Tioga Road. Road subgrade material was observed to consist of a fine to medium sand with l l l .1 l

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Page6 silt. Cutbanks exposing colluvial soils consisting of silty sand and sandy silt with scattered cobbles and boulders were observed along the proposed water line alignment. The 2H: 1 V cut banks slopes were observed to be 4 to 16 feet high.

6.3 SUBSURFACE CONDITIONS

All borings were drilled in existing road right-of-ways along road shoulder areas. Surface materials encountered in all borings consisted of an undocumented fill consisting of a loose to dense gravelly silty sand (SM) extending to depths of between 0.5 and 1 foot below the ground surface (bgs). These surface fill materials generally overlaid colluvial soils consisting of loose to dense silty sands with fine gravel (SM) or sandy silts with fine gravel (ML) extending to depths of 2.5 to 6 feet below the ground surface (the maximum depth explored). The colluvium generally contained limited quantities of roots and small gravels. In several of the borings, the colluvium was underlain by residual soils consisting of loose to dense poorly-graded silty sand (SM) with occasional small granodiorite gravels. The colluvium/residual soil horizon was encountered between 2.5 and 6 feet bgs. The residual sand was derived from the weathering of the underlying granodiorite bedrock.

Drilling refusal on the granodiorite bedrock was encountered in only one boring, B-9, near the entrance to the Crane Flat Campground. The drilling refusal was encountered at a depth of approximately 4 feet bgs. It should be noted, however, that the upper surface of the granodiorite bedrock throughout the Crane Flat area is uneven, as evidenced by the surface exposures of the granodiorite along the proposed water line alignment (Figure 2, Site Plan). Shallow, hard, fresh, granodiorite bedrock should be anticipated to be encountered at various points in the water line trench along the entire length of the proposed water line alignment.

Thicker undocumented fills were noted along the proposed water line alignment during Condor's site reconnaissances. These fills were estimated to be 4 to 20 feet deep. The fills were observed in areas spanning drainageways, portions of the Crane Flat Campground loop roads directly downslope from the main campground access road, and directly west of boring B-17. The fills consisted of gravelly silty sand (SM) or gravelly sandy silt (ML). With the exception of the campground loop road fills, and the fill in the vicinity of boring B-17, the undocumented fills correspond to the areas identified on Figure 2, Site Plan, as Alluvium/Shallow Groundwater Area.

Alluvial soils underlie the proposed water line alignment at the areas designated as Alluvium/Shallow Groundwater Area on Figure 2. The alluvial soils generally should not be encountered in these areas to the depth of excavation for the pipeline due to the depth of the toad base fill, with the exception of the fill in the area of boring B-5 and downslope from boring B-9. These undocumented fill areas are approximately 4 feet deep which, given the proposed 5-foot depth of the water line trench will place the water line directly on alluvial soils. Examination of the surface exposures of these alluvial soils indicates they are a gravelly sandy silt (SM).

Shallow groundwater was encountered in borings B-6, B-12, B-13, and B-14. Boring B-6 is located in Loop A of the Crane Flat Campground. This boring location is down slope from an intermittent drainageway. The shallow groundwater at 4 feet bgs appears to be the result of snow melt flowing down the intermittent drainageway. We would expect the groundwater level to be at shallower depths than 4 feet during and immediately after snow has melted and/or during heavy rainfall events. Shallow groundwater also was encountered at 2 to 4 feet bgs in borings B-12, B-13, and B-14; this groundwater appears to be the result of snow melt water accumulating in the grass-covered areas of Crane Flat and then flowing to the south from this area. The grass-covered areas appear to have, in the past, supported a small lake that has undergone eutrophication. Fine- and coarse-grained materials have filled this small

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Page7 lake. During and immediately following the snow melt and/or immediately following heavy rainfall events, we anticipate groundwater levels in colluvial soils away from the filled areas will be shallower than noted in the borings.

7.0 CONCLUSIONS

7.1 GENERAL

Based on the surface mapping and subsurface data, we anticipate that ground conditions exposed along the proposed Phase 1 and Phase 2 water line route generally will consist of loose to dense granular soils;

i.e., silty sands and sandy silts with varying but limited quantities of small gravels and organics (mainly roots). Most of the soil materials consist of colluvium and residual soils, and/or fill materials historically derived from these soils, that will be relatively easy to excavate with standard equipment (i.e., backhoe or excavator). Generally, the materials that will be generated during the trench excavations will be suitable for re-use as trench backfill. In addition, based on testing of these materials, they could also be used for pipe bedding material. However, in the area of boring B-9, we encountered shallow dense residual soil, and refusal in hard granodiorite bedrock at a depth of approximately 4 feet. Such hard bedrock likely will be encountered in other areas of the approximately 5-foot deep pipeline excavation due to the undulating nature of the rock. Heavy duty excavation equipment configured with a hoe ram may be required to excavate shallow exposures of the granodiorite. Figure 2 shows the areas where granodiorite outcroppings were noted near the water line alignment.

7.2 GEOLOGIC HAZARDS

There are no known active or potentially active faults at the site, and the site is not located in a State of California Earthquake Fault Zone. Therefore, ground rupture at the site from fault movement is not considered a significant hazard.

Rockfall is a condition where seismically induced shaking will cause rock outcrops and surface boulders to dislodge and travel d9wnslope. Typically, rockfalls occur in moderately- to steeply-sloping topography. A portion of the proposed water line alignment along Tioga Road, approximately 400 feet northeast of the Yosemite Institute, and extending to the existing water tank location is bounded on the north by moderate to steep slopes with exposed rock outcrops and scattered boulders. This portion of the water line alignment has a moderate risk of seismically induced rockfall hazard. However, the proposed water line will be buried, which will protect the water line from rockfall induced damage. The rockfall hazard to the water line, therefore, is low.

Liquefaction is a condition where a significant loss of strength and stiffness of soil occurs from pore pressures generated by cyclic loading, typically from earthquake shaking. Soil types susceptible to liquefaction include saturated, very loose to medium dense sand, with varying amounts of silt. Our evaluation indicates that these materials exist along the proposed water line alignment. These soils pose a moderate risk of liquefaction or significant seismically induced settlement. However, the materials generally are anticipated to be relatively thin along the pipeline alignment, and liquefaction-induced settlement should be limited and tolerable.

Recommendations for grading and excavation, pipe zone bedding and backfill, trench zone and final backfill, as well as geotechnical design information and parameters for the pipeline, are provided in the following sections.

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8.0 RECOMMENDATIONS

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The proposed pipeline project will consist of the excavation and emplacement of pipelines, manholes, and appurtenant structures. The contractor should be responsible for the stability of all temporary excavations and should comply with applicable OSHA regulations (California Construction Safety Orders, Title 8). All open cuts should be periodically monitored for evidence of incipient stability failures. The following paragraphs describe nomenclature used in this report, and bedding and trench backfill recommendations follow.

Nomenclature for zonation of pipeline trenches, used herein, is as follows:

• The pipezone is defined as that cross-sectional area extending from the subgrade to 12 inches above the top of the pipeline.

• The trench zone is that cross-sectional area of the pipeline trench extending from the top of the pipezone to the bottom of the structural pavement section, foundations systems, or the ground surface.

8.1 PIPEZONE MATERIALS

Pipezone materials are defined, herein, as those select earth materials used as pipeline bedding and shading within the pipe area. Pipezone materials should consist of clean sand, gravel, or crushed aggregate having a minimum sand equivalent (SE) of 30 and a maximum particle size of % inch. It is noted that much of the materials encountered in our borings, and that will be excavated for the pipelines, may be suitable for pipe bedding material. Organic-laden soils or those with oversize materials encountered during construction should be segregated and prevented from being used within the pipezone. The pipezone materials should extend from at least 0.5 feet below the pipe to 1 foot above. The bedding materials for manholes should extend at least 0.5 feet below the manhole bottoms.

All pipezone materials should be properly placed and compacted in order to achieve a minimum of 90 percent relative compaction based on ASTM Test Method D1557 or equivalent, as approved by the Project Geotechnical Engineer. The pipezone materials should be mechanically compacted and jetting or flooding should not be allowed. Care should be provided to reduce the potential of leaving voids beneath the pipeline haunches. We recommend that the Contractor establish a "test" section of pipeline to prove that their proposed compaction methods achieve the specified relative compaction in the pipeline bedding, the pipeline haunch area, and in the pipezone materials placed above the pipeline. Compaction tests should be performed in those areas to estimate the relative compaction obtained using the proposed procedures. In addition, excavations should be made in the pipeline haunch area to observe if the Contractor's methods leave voids in this critical area. We recommend that this test section be performed in alluvial areas having relatively shallow groundwater and soft subgrade conditions.

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We recommend that pipezone materials be placed with moisture content within 3 percent of optimum moisture content. Compaction tests should be performed on the pipe bedding prior to placement of the pipeline within the trench, and on the pipezone materials placed along the haunches and on top of the pipeline. Once appropriate placement methods are established and shown to be effective under actual field conditions, we recommend at a minimum that testing and confirmation of adequate compaction of materials within the pipezone is as follows:

• Pipe bedding should be tested at 200-foot intervals along the alignment.

• Pipezone materials placed along the haunches of the pipeline should be tested at intervals of no greater than every 200 lineal feet, randomly selecting which side of the pipeline haunch area to test.

• Pipezone materials above the springline and over the pipeline should each be tested at intervals no greater than every 200 lineal feet for every 2-foot lift.

• For short runs of pipeline, such as into the various campground loops, several tests should be taken in the pipe bedding and pipezone materials for each short run.

Those areas found to have inadequate compaction (below 90 percent relative compaction based on ASTM 01557), or having voids, should be reworked and retested until the specifications are met.

Corrosion testing of two representative samples of the subsurface materials at the site, and that could be used for pipezone materials, is presented in Appendix B.

In lieu of the recommended pipe zone materials noted above, a pipezone backfill alternative could consist of the placement of "flowable fill," also called controlled low strength materials (CLSM; see 2007 California Building Code), consisting of plastic soil-cement slurry materials.

8.2 TRENCH BACKFILL MATERIALS

Trench. backfill materials are defined, herein, as those materials placed above the pipezone and below other specified backfill materials, such as structural pavement sections. Earth materials encountered in our subsurface exploration can be used for trench backfill provided they are free of organics, debris, and other deleterious materials, and contain no particles greater than 3 inches in diameter.

We recommend that backfill materials placed above the pipezone materials be compacted and tested to a minimum of90 percent relative compaction, as determined by ASTM 01557, in undeveloped areas (open fields), and 95 percent compaction in developed areas (under roadways or shoulders, pad areas, areas of future development, etc.). The backfill materials should have a moisture content within 3 percent of optimum moisture content. We recommend that compaction tests be performed at intervals of 200 lineal feet or less along the alignment, at no greater than 2-foot vertical intervals between the pipezone and the top of the trench zone. Those areas found to have inadequate compaction (below 95 percent relative compaction based on ASTM D1557), or having voids, should be reworked and retested until the specifications are met.

8.3 EXTERNAL PIPELINE LOADS

External loads on pipes will consist of loads due to the overlying earth materials, loads due to construction activities, loads due to traffic, and other post-construction land uses. It is recommended that the pipe be designed to resist the imposed loads with a factor of safety and an amount of deflection, as recommended by the pipeline manufacturer.

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Geotechnical Investigation Crane Flat Water System Kennedy/Jenks Consultants, Inc.

Loads on the pipe due to the overlying soil will be dependent upon the depth of placement, type and method of backfill, configuration of the trench, the depth of groundwater, and whether any additional fill will be placed above the pipeline, on the ground surface. The earth loads on the pipe can be estimated using formulas developed by Marston (1930) and Spangler (1982). Trench conditions will likely occur along the alignment, and there is a low probability that embankment conditions will be present. Trench conditions are defined as those in which the pipe is installed in a relatively narrow trench, cut in undisturbed ground, and covered with earth backfill to the original ground surface. Embankment conditions are defined as those in which the pipe is covered with fill above the ground surface or when a trench in undisturbed ground is excavated so wide that trench sidewall friction does not affect the load on the pipe. When using Marston's formulas, the unit weight of the native backfill materials should be assumed to be 130 pounds per cubic foot (pet), with a buoyant unit weight of 70 pcf.

8.4 MODULUS OF SOIL REACTION (E')

Flexible and semi-rigid pipes typically are designed to withstand a certain amount of deflection from applied earth loads. Those deflections can be estimated with the equations developed by Spangler (1982).

The modulus of soil reaction (E') value for the project was obtained from average values provided by Howard (1996)- an E' of2,000 pounds per square inch (psi) is recommended.

8.5 THRUST RESISTANCE

Where the proposed pipeline changes direction abruptly, resistance to thrust can be provided by mobilizing frictional resistance between pipe and the surrounding soil, by use of a thrust block, by use of restrained pipe joints, or by a combination of the above. To design thrust resistance by mobilizing frictional resistance, we recommend that a coefficient of lateral earth pressure at-rest, Ko, of 0.9 be used in conjunction with a coefficient of friction of 0.20 for PVC pipelines. Those frictional values include a factor of safety of 1.5 and are based on the assumption that a sand with an SE of 30 or greater will be placed as pipe bedding and within the pipezone, in accordance with recommendations presented in Section 8.1. In addition, the pipe bedding, pipezone and native soils materials are considered granular, non-cohesive materials. ·

8.6 AGGREGATE BASE AND PAVING

Where asphalt concrete (AC) is disturbed or removed for the placement of the pipeline, it should be replaced in accordance with the recommendations of this section. We based our pavement design recommendations on the Cal trans Flexible Pavement Design Method as presented in Chapter 600 of the California Department of Transportation Highway Manual, Fifth Edition. We included the use of safety factors in the calculations of the required gravel equivalent for AC. Two R-value tests were performed on samples of the near-surface soils along the pipeline route, indicating R-values of 59 and 72. Taking into account likely variations and weaker areas, we used an R-value of 50 for design. The table below presents the recommended pavement design sections for various traffic indices (Tis) and a design R-value of 50.

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Geotechnical Investigation Crane Flat Water System Kennedy/Jenks Consultants, Inc.

Table 1 Crane Flat Water Line, Phase 1 and Phase 2

Recommended Pavement Sections (Subgrade R-value = 50) St d d Fl 'bl A h It C t P t an ar ex1 e sp1 a onere e avemen

Recommended AC Thickness Recommended AB Thickness Traffic Index (inches) (inches)

5 2.5 6.0 6 3.5 6.0 7 4.0 6.0 8 5.0 6.0

AC = Asphalt Concrete AB =Class 2 Aggregate Base rock (minimum R-Value = 78)

Page II

The AC pavement design computations were based on the Caltrans Flexible Pavement Design Method as presented in Chapter 600 of the Caltrans Highway Manual, Fifth Edition, and includes the use of safety factors in the calculations of the required gravel equivalent (GE) of the AC layer. Copies of the design calculations are attached for review. Pavement construction should conform to the requirements of the Caltrans Standard Specifications, latest edition.

8.7 WET WEATHER EARTHWORK CONSIDERATIONS

If earthwork operations are performed during the rainy season, or if areas containing wet soil are encountered during other seasons, drying of fill may be required to facilitate compaction. If desired, we can provide supplemental recommendations for wet weather work and alternatives for drying the soil. To facilitate compaction, water will be required to moisten dry backfill during periods of dry weather. Water should be available during excavation operations, as necessary.

8.8 DRAINAGE AND EROSION CONTROL

We recommend that appropriate temporary and permanent erosion-control measures be implemented to reduce erosion. Soil on graded slopes should be fertilized, mulched, and planted as soon as possible after grading with erosion-resistant vegetation. These plants should be watered lightly at appropriate intervals until growth is established. The project Civil Engineer should determine the actual erosion control requirements.

Trench plugs (seepage collars) should be placed to reduce the potential for erosion of the bedding sand from groundwater flowing in the trench, particularly where the gradients are high. Due to the granular nature of the soils at the site, trench plugs may be appropriate even where little gradient exists. We recommend that trench plugs be designed and constructed at the increments shown in the following table.

Table 2 Crane Flat Water Line, Phase 1 and Phase 2

T h PI I t rene ue; ncremen s Recommended Spacing of Trench Plugs

Slope Inclination (feet) 0-5H:1V 200

5H:1V- 4H:1V 125 4H:1V -3H:1V 100 3H:1V- 2H:1V 75 l l l

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The plugs should extend at least 2 feet beyond the trench bottom and sidewalls, and at least 1 foot above the top of the bedding. Where the gradient is great, gravel pocket drains should be considered on the upgradient side of each plug to reduce the build-up of hydrostatic pressures that could result in heaving of the ground surface. Each drain should consist of at least 1 cubic foot of free-draining gravel per foot of trench width wrapped completely in filter fabric (Mirafi 140N or equivalent). A solid PVC pipe should extend from the gravel to a suitable discharge point, and should slope at least 1 percent to drain.

9.0 ADDITIONAL SERVICES

Condor should review the project plans and specifications to check that the intent of our recommendations have been incorporated in the project design.

Because subsurface conditions at this site are highly variable, it is not possible to include all construction details related to geotechnical aspects of the project. Geotechnical recommendations depend on the possible need for adjustment in the field during construction. The adjustments depend on conditions revealed during construction that could previously only be assumed from site investigation. Therefore, Condor, or another qualified representative, should perform geotechnical observation and testing services during trench excavation to check that the intent of our recommendations were followed during construction, and that the geotechnical aspects of the work are performed in accordance with the approved plans and specifications. Also, we should check for any subsurface conditions that vary from the conditions we encountered during our subsurface investigation and develop supplemental geotechnical recommendations, as necessary.

The geotechnical engineer of record should be on site periodically to perform observations and provide oversight during trench excavation and backfill. These observations should be supplemented with periodic compaction testing of the trench backfill materials to establish conformance with the recommendations contained in this report.

10.0 LIMITATIONS

The geotechnical conclusions and recommendations presented in this report are intended for planning and design of the proposed water line, as described in this report. These conclusions and recommendations may not apply if:

• The report is used for a different site or project.

• The recommendations presented in this report are not followed.

• Any other change is made that materially alters the proposed project.

The analyses and recommendations presented in this report are based upon the published and unpublished geologic and soils reports and maps, field reconnaissance mapping, logging soils exposed in 17 individual borings, collecting disturbed and undisturbed samples from the borings, and laboratory test results obtained from the samples collected from the borings. Subsurface conditions may, and usually do, vary between and around the boring locations. Should varied conditions be discovered during construction, additional exploration, testing, analysis, and development of supplemental recommendations may be required. Any person associated with this project who observes conditions or features of the site or its surrounding areas that are different from those described in the report should report them immediately to Condor for evaluation.

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Implementation of our reconunendations requires an adequate testing and observation program during construction. If this testing and observation is not performed by Condor, as discussed in various sections of this report, then the geotechnical engineer of record responsible for observation and testing should thoroughly review this report and should agree with its conclusions and reconunendations or, otherwise, provide alternative reconunendations.

This report was prepared in accordance with the generally accepted standards of geotechnical engineering practice that exist in Northern California at the time the report was written. No other warranty, express or implied, is made. It is the owner's responsibility to see that all parties to the project, including the designers, contractors, and subcontractors, are made aware of this report in its entirety.

Changes in the standards of practice in the field of geotechnical engineering, changes in site conditions such as a new fire line route than described in this report, new agency regulations, or modifications to the proposed project warrant professional review of this report. Because of this, there is a practical limit to the usefulness of this report without critical professional review. It is suggested that 2 years be considered a reasonable time for the validity of this report.

11.0 CLOSURE

We appreciate the opportunity to submit this geotechnical report. Please contact us if you have any questions.

Respectfully submitted, Frederick Maurer, Jr., GE No. 2035 Engineering Services Manager esley P. Greenwood, PG No. 8669 Associate Geologist

P:\5000_prj\5655 Crane Flat Water Line\Report\Crane flat Water Line Geo Investigation Tracked.doc

"-CONDOR

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REFERENCES

Adams, M., Wert, S., 2004, Yosemite National Institutes Crane Flat Campus Wastewater System Improvements, Summary of Soil Testing and Assimilative Capacity, Northstar Engineering, Letter Report, 5 pages.

California Water Resources Control Board Geotracker Page, 2009, State of California. 15 June 2009 http://geotracker.swrcb.ca.gov.

California Geological Survey Library Page, 2009, State of California Department of Conservation, 15 June 2009, http://www.conservation.ca.gov/cgs/library/Pages/index.aspx.

California Department of Transportation Highway Design Manual Page, 2009, State of California, 17, June 2009, http://www .dot.ca.gov/hg/oppd/hdmlhdmtoc.htm.

California Department of Water Resources Teclmical Reference Page, 2009, State of California, 18 June 2009, www. water .ca.gov/damsafety/techreference/ geologic index.cfm.

Crum, M.R., 1999, Report of Findings - New Septic System at the Crane Flat Facility, Yosemite National Park, Condor Project No. 2728, Condor Earth Technologies, Inc., Report, 21 pages.

Harden, D.R., 1998, California Geology, Prentice Hall, 479 pages.

Hill, M., 2006, Geology of the Sierra Nevada, California Natural History Guides, University of California Press, 468 pages.

Huber, N.K., Bateman, P.C., and Wahrhaftig, C., 1989, Geologic Map of Yosemite National Park and Vicinity, California, U.S. Geologic Survey Miscellaneous Investigations Series Map 1-1874, 1:125,000.

Koningsmark, T., 2007, Geologic Trips Sierra Nevada, GeoPress, 319 pages.

Natural Resource Conservation Service Soil Survey Page, 2009, U.S. Department of Agriculture, 16 June 2009, http:/ /websoilsurvey.nrcs. usda.gov/app/W ebSoilSurvey.aspx.

Parrish, J.G., et.al., 2008, Guidelines for Evaluating and Mitigating Seismic Hazards in California, California Geologic Survey, Special Publication 117 A, 108 pages.

Peck, D.L., Wahrhaftig, C., and Clark, L.D., 1966, Field Trip: Yosemite Valley and Sierra Nevada Batholith, in Geology of Northern California, California Division of Mines and Geology, Bulletin 190, pages 487-502.

United States Geologic Survey, The Geologic Story of Yosemite Valley Page, 2009, USGS, 16, June 2009, http://geomaps.wr.usgs.gov/parks/yos/topobk.html.

United States Geologic Survey, Bedrock Geology of the Yosemite Valley Area, Yosemite National Park, California Page, 2009, USGS, 16, June 2009, http://geomaps.wr.usgs.gov/parks/yos/l 1639.html.

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United States National Parks Service, Yosemite Geology Page, U.S. Department of the Interior, 2009, National Park Service, 16 June 2009, http://www.nps.gov/yose/naturescience/geology.htm.

Wilcox, L.A., 1982, Roadside Geology of the Eastern Sierra Region, Geologicial Society of the Oregon Country, Publication No. 19,42 pages.

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PROJ. LAT.: N37.756864"

PROJ. LONG.: W119.800314"

PROJ. MN. ELEV.: ±6150 FT. TO ±6300 FT.

USGS QUAD NAME: ACKERSON MTN.

USGS QUAD DATE: 1992

VICINITY MAP

GEOTECHNICAL INVESTlGA llON

CRANE FLAT WATER SYSTEM

FIGURE

~=--=--?::i+.';-----1 YOSEMITE NAllONAL PARK, CAUF'ORNIA ~=-:-:-----f 5655F1 l l

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' CAMPGROUND\

LOOPE \

CAMPGROUND

LOOPD

CAMPGROUND

LOOPC

(E) GAS STATION

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0 600

SCALE IN FEET

LEGEND

-.._._/\ PROPOSED WATER PIPE ROUTE

-+- BORING LOCA TlON

.. GROUNDWATER WELL

® GRANODIORITE OUTCROP

_./. ALLUVIUM/SHALLOW

';/ GROUNDWATER AREA

_,--/PERRENIAL STREAM

_,-·../ INTERMITIENT STREAM

' \ \ - FILL AREA

' ' B-17 \ ' ' \

VPHASE2

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{E) WATER TANK~

::i c;') .,..

tiQIE.;_

ALL OTHER WATER AUGNMENT AREAS

NOT DESIGN A TED AS · GRANODIORITE

OUTCROPS OR ALLUVIUM/SHALLOW

GROUNDWATER AREAS ARE COLLUVIUM

SOILS CONSIS11NG OF SILTY SAND OR

SANDY SILT WllH FINE GRAVEL AND SCA mRED COBBLES AND BOULDERS.

N I ..

1-------til\ u c b "' "' 1-;:;;----:-;---- --1 ;

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NORTH

AERIAL LOCATION MAP

GEOTECHNICAL…