B09__Amendment_0002_Attachment__1_GEOTECHNICAL_INVESTIGATION_REPOR.pdf

FINAL GEOTECHNICAL INVESTIGATION REPORT

Replace Failing Wawona Campground

Restroom Leach Fields with Connection to

Wawona Wastewater System Yosemite National Park | March 5, 2019

Architecture

Planning

Conservation

20170255.001A/FRE18R87819R1 Page ii of v Revision No. 1: March 5, 2019 Original Report: November 30, 2018 ©2019 Kleinfelder

KLEINFELDER 3731 W. Ashcroft Ave., Fresno, CA 93722 p| 559.486.0750 f| 559.442.5081

GEOTECHNICAL INVESTIGATION REPORT

SEWER LINE AND LIFT STATION IMPROVEMENTS

YOSEMITE NATIONAL PARK

WAWONA, CALIFORNIA

Project No. 20170255.001A

Prepared for:

Architectural Resources Group Pier 9, The Embarcadero, Suite 107 San Francisco, California 94111

March 5, 2019

Copyright 2019 Kleinfelder

All Rights Reserved

ONLY THE CLIENT OR ITS DESIGNATED REPRESENTATIVES MAY USE THIS DOCUMENT AND ONLY FOR THE SPECIFIC

PROJECT FOR WHICH THIS REPORT WAS PREPARED.

20170255.001A/FRE18R87819R1 Page iii of v Revision No. 1: March 5, 2019

A Report Prepared for:

Ms. Kitty Vieth

Architectural Resources Group Pier 9, The Embarcadero, Suite 107

GEOTECHNICAL INVESTIGATION REPORT

SEWER LINE AND LIFT STATION IMPROVEMENTS

YOSEMITE NATIONAL PARK

WAWONA, CALIFORNIA

Prepared by:

Adam AhTye, EIT Staff Engineer

Reviewed by:

Stephen P. Plauson, PE, GE Principal Geotechnical Engineer

KLEINFELDER, INC.

3731 W. Ashcroft Avenue Fresno, California 93722

(559) 486-0750

20170255.001A/FRE18R87819R1 Page i of v Revision No. 1: March 5, 2019

Project No. 20170255.001A

Ms. Kitty Vieth

Architectural Resources Group Pier 9, The Embarcadero, Suite 107

Phone: 415.421.1680

Subject: Geotechnical Investigation Report

Sewer Line and Lift Station Improvements

Wawona Campground, Yosemite National Park

Wawona, California

Dear Ms. Vieth:

Kleinfelder is pleased to present the results of a geotechnical investigation for the proposed Wawona Campground sewer line and lift station improvements to be located in Yosemite National Park, Wawona, California. It is understood that a new sewer pipeline and three (3) new lift stations are to be installed at the campground and along Highway 41 (also referred to as Wawona Road) from the camp ground to Chilnualna Road. The purpose of this study was to evaluate the subsurface conditions along the proposed pipeline in order to characterize the subsurface materials likely to be encountered during construction.

Based on the results of our field investigation, laboratory testing, and review of surface topography, it is Kleinfelder’s professional opinion that the proposed lift stations and pipeline installation are feasible as currently envisioned. Specific recommendations regarding the geotechnical aspects of project design and construction are presented in the following report.

Kleinfelder appreciates the opportunity to provide services for this project. If you have questions regarding this report or if we may be of further assistance, please contact the undersigned.

Respectfully submitted, KLEINFELDER, INC.

Adam AhTye, EIT Stephen P. Plauson, PE, GE Staff Engineer Principle Geotechnical Engineer

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TABLE OF CONTENTS

Section Page

1 INTRODUCTION

1.1 GENERAL

1.2 PROJECT DESCRIPTION

1.3 SCOPE OF SERVICES

2 FIELD INVESTIGATION AND LABORATORY TESTING

2.1 SITE DESCRIPTION

2.2 FIELD EXPLORATION

2.3 SAMPLING PROCEDURES

2.4 LABORATORY TESTING

3 SITE CONDITIONS

3.1 SURFACE CONDITIONS

3.2 EARTH MATERIALS

3.3 GROUNDWATER CONDITIONS

4 GEOLOGIC CONDITIONS

4.1 SEISMICITY AND FAULTING

4.2 SITE CLASS

4.3 DESIGN EARTHQUAKE LEVEL

4.4 SEISMIC DESIGN CRITERIA

4.5 LIQUEFACTION

5 EARTHWORK

5.1 GENERAL

5.2 SITE PREPARATION

5.2.1 Demolition of Existing Pavements

5.2.2 Stripping

5.2.3 Disturbed Soil, Undocumented Fill and Subsurface Obstructions

5.2.4 Over-excavation

5.2.5 Scarification and Compaction

5.2.6 Construction Considerations

5.3 ENGINEERED FILL

5.3.1 Materials

5.3.2 Compaction Criteria

5.4 TEMPORARY EXCAVATIONS

5.4.1 General

5.4.2 Excavation and Slopes

5.4.3 Construction Considerations

5.5 TRENCH BACKFILL

5.5.1 Materials

5.5.2 Compaction Criteria

6 DESIGN RECOMMENDATIONS

6.1 GENERAL

6.2 FOUNDATIONS

6.2.1 Vertical Bearing Pressures and Settlements – Miscellaneous Surface Improvements

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6.2.2 Bearing Pressures and Settlements – Mat/Slab Foundations

6.2.3 Lateral Resistance

6.2.4 Design and Construction Considerations

6.3 POLE FOUNDATIONS

6.3.1 Allowable Vertical Axial Capacity and Settlements

6.3.2 Lateral Resistance

6.3.3 Design and Construction Considerations

6.4 RETAINING STRUCTURES

6.5 EXTERIOR CONCRETE SLABS-ON-GRADE

6.5.1 Subgrade Preparation

6.5.2 Conventional Slab Design

6.6 PIPELINE THRUST

6.7 CORROSION POTENTIAL

6.8 SITE DRAINAGE

7 ADDITIONAL SERVICES

7.1 PLANS AND SPECIFICATIONS REVIEW

7.2 CONSTRUCTION OBSERVATION AND TESTING

8 LIMITATIONS

FIGURES

Figure 1 – Site Vicinity Map Figure 2 – Boring Locations Map

APPENDIX A – LOGS OF BORINGS

Figure A-1 – Graphics Key Figure A-2 – Soil Description Key Figure A-3 to A-14 – Boring Logs B-1 through B-12

APPENDIX B – LABORATORY TEST RESULTS

Figure B-1 – Laboratory Test Result Summary Figure B-2 – Sieve Analysis Figure B-3 to B-4 – Direct Shear

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1 INTRODUCTION

1.1 GENERAL

This report presents the results of a geotechnical investigation conducted for the proposed

Wawona Campground sewer line and lift station improvements to be located in Yosemite

National Park, Wawona, California. The purpose of this investigation was to evaluate the subsurface conditions near the proposed improvements and to characterize the subsurface materials likely to be encountered during construction activities. The approximate locations of the improvements are shown on Figure 1, Site Vicinity Map

This report includes recommendations related to the geotechnical aspects of project planning, design, and construction of the proposed pipeline and lift station improvements. Conclusions and recommendations presented in this report are based on the subsurface conditions encountered in the exploratory borings drilled for this investigation and review of published geologic data referenced in this report. Recommendations presented herein should not be extrapolated to other areas or used for other projects without prior review. The approximate locations of the exploratory borings are shown on Figure 2, Exploration Location Map.

1.2 PROJECT DESCRIPTION

It is understood that the project consists of the design and construction of three (3) new lift stations to replace the six (6) failing leach fields for the Wawona Campground restrooms. One

(1) lift station will be designed for each Campground Loop (Loop A, B, and C) to collect sewage from 2, 1, and 3 restroom facilities; respectively. Each lift station is anticipated to include a wet well, overflow tank, generator, and electrical/control box with sunshade. Additionally, approximately 2.6 miles of sewer pipeline will be constructed to direct the sewage disposal from the Wawona Campgrounds to a sewer line in Chilnualna Road that is connected to the Main

Central Lift Station. Appurtenant improvements are anticipated to include underground utilities, hardscape, and landscape.

1.3 SCOPE OF SERVICES

The purpose of this investigation was to explore the subsurface conditions at the site location and provide comments and recommendations to aid in design. This report includes the following:

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• A description of the proposed project, including a site vicinity map showing the approximate location of the site and a site plan showing the approximate locations of the exploration points for this study

• A description of the site surface and subsurface conditions encountered during the field investigation, including boring logs

• Comments on groundwater conditions encountered and potential impact on design and construction

• A summary of the field exploration and laboratory testing programs

• Discussion of the regional geology and site seismicity, including liquefaction potential and seismically induced settlement

• Recommendations for site preparation and earthwork, including the use of on-site soils for engineered fill and recommended import fill specifications

• Recommendations for foundation design including bearing capacity of foundation soil for sustained loading and total combined loading including embedment depths and anticipated settlements

• Recommendations for frictional coefficient and passive pressure for lateral loads

• Recommended earth pressures for use in design of retaining structures

• Recommendations for axial frictional capacity of drilled pier footings

• Recommendations to aid in design of concrete building slabs-on-grade, including modulus of subgrade reaction

• Recommendations for resistance of lateral loads of pipelines, including thrust blocks and friction along the pipe

• Comments on the corrosion potential of on-site soils to buried metal and concrete

• Comments to aid in the design of site drainage

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2 FIELD INVESTIGATION AND LABORATORY TESTING

2.1 SITE DESCRIPTION

The proposed lift stations and pipeline alignment are located within the Wawona Campground and along Highway 41 (also referred to as Wawona Road) in Yosemite National Park, Wawona, California. One lift station is proposed at each campground loop and connects to a pipeline which traverses from northwest to southeast, running along the Wawona Campground Road from Campground Loop C to Highway 41, where it continues along Highway 41 southeast toward Chilnualna Road. The project site is shown on Figure 1.

2.2 FIELD EXPLORATION

The subsurface conditions along the alignment were explored on November 1 and 2, 2018 by drilling twelve (12) borings to depths of 1.5, 2.5, 3, 5.5, 11.5, and 12.5 feet below the ground surface. The borings were drilled using a CME-55 truck-mounted drill rig equipped with hollow-stem augers. All of the borings encountered auger refusal due to gravel, cobbles, and bedrock except for Boring B-8. The approximate locations of the exploratory borings are shown on

Figure 2, Boring Locations Map.

A Kleinfelder professional maintained logs of the borings, visually classified the soils encountered according to the Unified Soil Classification System (American Society for Testing and Materials International [ASTM] D2488 visual-manual procedure) and obtained both disturbed and relatively undisturbed samples of the subsurface materials. The Graphics Key with the Unified Soil Classification System descriptive criteria is presented on Figure A-1 in

Appendix A. Following laboratory testing, the field visual classifications were revised, as appropriate, based on ASTM D2487. A Soil Description Key is presented on Figure 2 and logs of borings are presented on Figures A-3 through A-14.

2.3 SAMPLING PROCEDURES

Relatively undisturbed samples were obtained from the borings at selected depths by driving a

2.5-inch inside diameter (I.D.), split-barrel, California sampler containing stainless steel and brass liners into undisturbed soil with a 140-pound automatic hammer free-falling a distance of

30 inches. The California sampler was in general conformance with ASTM D3550. Soil sampled

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Disturbed samples were also obtained at selected depths by driving a 1.4-inch I.D. Standard

Penetration Test (SPT) sampler into undisturbed soil with a 140-pound automatic hammer free-falling a distance of 30 inches. The SPT sampler was used in sandy and gravelly soils and when sufficient recovery could not be achieved with the California sampler. The SPT sampler was in general conformance with ASTM D1586.

Blow counts were recorded at 6-inch depth intervals for each driven sample attempt and are reported on the logs. Blow counts shown on the boring logs have not been corrected for the effects of overburden pressure, rod length, sampler size, or hammer efficiency. Sampler size correction factors were applied to estimate the sample apparent density noted on the boring logs. The consistency terminology used in soil descriptions for cohesive soils is based on field observations (see Figure A-2). Relatively undisturbed soil samples obtained from the borings were packaged and sealed in the field to reduce moisture loss and disturbance and returned to

Kleinfelder’s laboratory for further testing. After the borings were completed, they were backfilled with cement grout.

2.4 LABORATORY TESTING

Laboratory tests were performed on selected samples recovered from the borings to evaluate physical and engineering properties. The geotechnical laboratory testing included the following tests:

• Unit Weight (ASTM D2937)

• Moisture Content (ASTM D2216)

• Sieve Analysis (ASTM C136)

• Direct Shear (ASTM D3080)

Unit weight, moisture content, and direct shear test results are summarized on the boring logs presented in Appendix A. The results of other laboratory tests are included in Appendix B.

Samples of near-surface soil encountered at the site were also subjected to chemical analysis for the purpose of corrosion assessment. Sunland Analytical of Rancho Cordova, California performed the tests under subcontract to Kleinfelder. The samples were tested for:

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• Soluble Chlorides and Sulfates (ASTM D516)

• pH (ASTM D4972)

• Minimum Resistivity (ASTM G-57)

These test results are summarized in Section 6.7 “Corrosion Potential” and in Appendix B

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3 SITE CONDITIONS

3.1 SURFACE CONDITIONS

At the time of the field reconnaissance, the project site consisted primarily of asphalt concrete pavements along Highway 41 and the Wawona Campground Road, and bare soil with light to moderate seasonal vegetation at various locations where drilling in the roadway was inaccessible. The site topography appeared to consist of rolling terrain throughout the entire project length.

3.2 EARTH MATERIALS

The natural earth material consists of Early Crustaceous aged surficial deposits consisting of

Bass Lake Tonalite, with small areas consisting of Early Crustaceous aged El Capitan Granite and Holocene aged alluvium. The general soil profile encountered by the subsurface exploration consisted of silty sand and poorly graded sand with varying amounts of gravel underlain by various sized cobble and gravel ranging from 1.5 to 11.5 feet below ground surface

(bgs). Auger refusal occurred in all of the borings except for Boring B-8 at depths ranging from

1.5 to 11 feet bgs. The granular soils generally had a relative density of medium dense to very dense.

The above is a general description of the earth material profile. A more detailed representation of the stratigraphy at the specific exploration locations is provided on the boring logs in

Appendix A.

3.3 GROUNDWATER CONDITIONS

Groundwater was not encountered during the subsurface investigation. Groundwater in the

Sierra Nevada mountains is found in seasonal, shallow, and perched aquifers consisting of weathered materials (decomposed rocks) along the bedrock surface and through a complex system of joints and fractures within the bedrock. Depth to groundwater in the foothill and mountain areas varies with the local topography and depth to the decomposed rock/bedrock interface. Additionally, irregularities in the underlying bedrock may trap pockets of perched water. Localized groundwater may occur during wetter periods, within lower elevations of the project, and trench and lift station excavation, which could affect design and construction.

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Therefore, the contractor should be prepared to control and, or remove surface and groundwater from the work area as needed.

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4 GEOLOGIC CONDITIONS

4.1 SEISMICITY AND FAULTING

The project site is located in an area characterized by relatively low historic seismic activity.

The site is not located in an Alquist-Priolo Earthquake Fault Zone as established by the Alquist-

Priolo Fault Zoning Act (Section 2622 of Chapter 7.5, Division 2 of the California Public

Resources Code).

Based on review of published data and a current understanding of the geologic framework and tectonic setting of the proposed development, the primary source of seismic shaking at this site is anticipated to be the San Andreas Fault, which is located at a distance of 180.23 km from the site.

4.2 SITE CLASS

Based on the field investigation, the subsurface exploration consisted of silty sand and poorly graded sand with varying amounts of gravel to the depth of exploration, 11.5 feet bgs. The granular soil had a relative consistency of medium dense to very dense. The site soil is classified as Site Class D as presented in Table 20.3-1 of the American Society of Civil

Engineers (ASCE) 7-10. Site Class D is defined as a stiff soil profile with shear wave velocities between 600 feet/sec and 1,200 feet/sec, or Standard Penetration Resistance (N) between 15 and 50 blows/foot, or the undrained shear strength (Su) greater than 1,000 psf for the upper 100 feet.

4.3 DESIGN EARTHQUAKE LEVEL

In accordance with Section 1803A.5.11 of the 2016 CBC, the design peak ground acceleration

(PGAM) for evaluation of liquefaction was based on ASCE 7-10, Equation 11.8-1

(PGAM=FPGAPGA), where PGAM is the MCEG peak ground acceleration adjusted for Site Class effects, PGA is the mapped MCEG peak ground acceleration, and FPGA is the site coefficient interpolated from Table 11.8-1 of ASCE 7-10. Based on this procedure, a code based peak ground acceleration of 0. 303g is recommended for evaluation of liquefaction.

A probabilistic seismic hazards analysis (PSHA) procedure was performed using the 2014

USGS Unified Hazards Tool to estimate the earthquake magnitude. The program allows user input of the project site coordinates and produces the expected peak ground motions for the site

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Tool based on a probability of exceedance of 2 percent in 50 years determined a peak ground acceleration of 0.363g and a weighted magnitude of MW = 6.02.

4.4 SEISMIC DESIGN CRITERIA

Seismic evaluation of the building and equipment structure improvements will utilize the 2016

California Building Code (CBC) (based on ASCE 7-10). For code-based design using the 2016

CBC, the estimated Maximum Considered Earthquake (MCE) mapped spectral accelerations for

0.2 second and 1 second periods (Ss and S1). Associated soil amplification factors (Fa and Fv), and peak ground acceleration (PGA) are presented in Table 4.2-1. Corresponding site modified

(SMS and SM1) and design (SDS and SD1) spectral accelerations, PGA modification coefficient

(FPGA), PGA (PGAM), and risk coefficients (CRS and CR1) are also presented in Table 4.4-1. The

Site Class and Seismic Design Category is D.

TABLE 4.2-1

GROUND MOTION PARAMETERS

2016 CBC/ASCE 7-10/AWWA D100/D103

Parameter Value Reference

SS 0.611g 2016 CBC Section 1613.3.1

S1 0.231g 2016 CBC Section 1613.3.1

Site Class D 2016 CBC Section 1613.3.2

Seismic Design Category D 2016 CBC Tables 1613.3.5 (1) and (2)

Fa 1.311 2016 CBC Table 1613.3.3(1)

Fv 1.937 2016 CBC Table 1613.3.3(2)

SMS 0.801g 2016 CBC Section 1613.3.3

SM1 0.448g 2016 CBC Section 1613.3.3

SDS 0.534g 2016 CBC Section 1613.4.4

SD1 0.299g 2016 CBC Section 1613.4.4

PGA 0.224g ASCE 7-10 Figure 22-7

FPGA 1.352 ASCE 7-10 Table 11.8-1

PGAM 0.303g ASCE 7-10 Section 11.8.3

CRS 1.022 ASCE 7-10 Figure 22-17

CR1 1.122 ASCE 7-10 Figure 22-18

TL 6 s ASCE 7-10 Figure 22-12

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4.5 LIQUEFACTION

In order for liquefaction of soils due to ground shaking to occur, it is generally accepted that four conditions will exist:

• The subsurface soils are in a relatively loose state,

• The soils are saturated,

• The soils are granular,

• Ground shaking is of sufficient intensity should occur to act as a triggering mechanism.

Geologic age also influences the potential for liquefaction. Sediments deposited within the past few thousand years are generally much more susceptible to liquefaction than older Holocene sediments; Pleistocene sediments are even more resistant; and pre-Pleistocene sediments are generally immune to liquefaction (Youd, 2001).

Saturated granular sediments can experience liquefaction if subject to seismically induced ground motion of sufficient intensity and duration. Based on the ground shaking which may be expected at this site, the relative soil density, soil type, and depth to groundwater, liquefaction and associated seismically induced settlement is considered unlikely.

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5 EARTHWORK

5.1 GENERAL

Based on the laboratory data, field exploration, and geotechnical analyses conducted by

Kleinfelder for this study, it is geotechnically feasible to construct the proposed lift stations and pipeline, as currently envisioned. The proposed lift stations and pipeline can be constructed using conventional grading and foundation construction techniques.

Due to the presence of relatively shallow cobble, boulders and granitic bedrock of various weather and strength, ripping or other aggressive demolition techniques will likely be necessary to facilitate the pipeline, lift station, and eqiuipment foundations.

Recommendations regarding site grading are presented in subsequent sections of this report.

All reference to relative compaction, maximum density, and optimum moisture is based on

ASTM Test Method D1557.

5.2 SITE PREPARATION

5.2.1 Demolition of Existing Pavements

Where not to remain, existing asphalt concrete pavements, underground utilities, and other unsuitable structures encountered during the site preparation should be entirely removed.

Following removal of asphalt concrete pavements and any underground utilities, disturbed soils should be mitigated as described in Section 5.2.3.

5.2.2 Stripping

At the time of the site reconnaissance, light to moderate growth of seasonal vegetation was present on the site. It is likely the amount of surface vegetation will vary with time. Any surface vegetation and any miscellaneous surface or subsurface obstructions should be removed from the project area, prior to any site grading. Based on site observation, stripping will likely involve the upper 1 to 2 inches of surface soil.

Surface strippings should not be incorporated into fill unless they can be sufficiently blended to result in an organic content less than 3% by weight (ASTM D2974). Stripped topsoil, with an organic content between 3% and 12% by weight, may be stockpiled and used as non-structural

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5.2.3 Disturbed Soil, Undocumented Fill and Subsurface Obstructions

Initial site grading should include a reasonable search to locate soil disturbed by previous activity, any undocumented fill soils, abandoned underground structures, or existing utilities that may exist within the area of construction. All surface obstructions should be removed from the project area. Any areas or pockets of soft or loose soils, void spaces made by burrowing animals, undocumented fill, or other disturbed soil that are encountered, should be excavated to expose firm native material approved by a representative of the Geotechnical Engineer.

5.2.4 Over-excavation

Over-excavation is typically reserved for soils that, in their natural state, will not provide adequate bearing for structures. The native soils at the project site should provide adequate bearing for the proposed improvements. Therefore, provided the recommendations in Sections

5.2.2 and 5.2.3 are followed, no general over-excavation is required.

5.2.5 Scarification and Compaction

Following any required over-excavation and any other removals, the exposed subgrade soil in areas to receive engineered fill or to support project improvements should be scarified to a minimum depth of 8 inches, uniformly moisture conditioned at, or above optimum, proof rolled to detect soft or pliant areas, and compacted to the requirements for engineered fill (Section 5.3).

Soft or pliant areas should be mitigated in accordance with Section 5.2.3.

5.2.6 Construction Considerations

Should site grading be performed during or subsequent to wet weather, near-surface site soils may be significantly above optimum moisture content. These conditions could hamper equipment maneuverability and efforts to compact site soils to the recommended compaction criteria. Discing to aerate, chemical treatment, replacement with drier material, stabilization with a geotextile fabric or grid, or other methods may be required to mitigate the effects of excessive soil moisture and facilitate earthwork operations. Any consideration of chemical treatment (e.g.

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5.3 ENGINEERED FILL

5.3.1 Materials

All engineered fill soils should be nearly free of organic or other deleterious debris and less than

3 inches in maximum dimension. The on-site soil exclusive of debris, may be used as engineered fill, provided it contains less than 3 percent organics by weight (ASTM D2974).

Should any imported material be used for engineered fill, it should be sampled and tested by a represented of the project Geotechnical Engineer prior to being transported to the site. Table

5.3-1 provides general criteria for imported soil.

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TABLE 5.3-1

SOIL MATERIALS TEST PROCEEDURES

Gradation Test Procedures

Sieve Size Percent Passing

ASTM1 Caltrans2

76 mm (3 inch) 100 C136 202

19 mm (¾ inch) 80 – 100 C136 202

No. 4 60 - 100 C136 202

No. 200 20 – 50 C136 202

Plasticity

Liquid Limit

Plasticity Index

< 40 < 25 D4318 204

Soluble Sulfates

< 1500 ppm - 417

Soluble Chloride

<250 ppm - 422

Resistivity

>1000 ohm x cm - 532

Notes:

American Society for Testing and Materials Standards (latest edition) State of California, Department of Transportation, Standard

Test Methods

(latest edition)

5.3.2 Compaction Criteria

Soils used as engineered fill should be uniformly moisture conditioned to at, or above optimum moisture, placed in horizontal lifts less than 8 inches in loose thickness, and compacted to at least 90 percent relative compaction. The relative compaction of the subgrade in the top 12 inches of pavement areas is recommended to be increased to 95 percent relative compaction.

Discing and/or blending may be required to uniformly moisture-condition soils used for engineered fill.

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5.4 TEMPORARY EXCAVATIONS

5.4.1 General

All excavations must comply with applicable local, State, and Federal safety regulations including the current OSHA Excavation and Trench Safety Standards. Construction site safety generally is the responsibility of the Contractor, who shall also be solely responsible for the means, methods, and sequencing of construction operations. The information provided is a service to the client. Under no circumstances should the information provided be interpreted to mean that Kleinfelder is assuming responsibility for construction site safety or the Contractor's activities; such responsibility is not being implied and should not be inferred.

5.4.2 Excavation and Slopes

The Contractor should be aware that slope height, slope inclination, or excavation depths

(including utility trench excavations) should in no case exceed those specified in local, State, and/or Federal safety regulations (e.g., OSHA Health and Safety Standards for Excavations, 29

CFR Part 1926, or successor regulations). Such regulations are strictly enforced and, if they are not followed, the Owner, Contractor, and/or earthwork and utility subcontractors could be liable for substantial penalties.

All excavations should be constructed and maintained in conformance with current OSHA requirements (29 CFR Part 1926) for a Type C soil (Silty Sand).

5.4.3 Construction Considerations

Heavy construction equipment, building materials, excavated soil, and vehicular traffic should be kept sufficiently away from the top of any excavation to prevent any unanticipated surcharging.

If it is necessary to encroach upon the top of an excavation, Kleinfelder can provide comments on slope gradients or loads on shoring to address surcharging, if provided with the geometry.

Shoring, bracing, or underpinning required for the project (if any), should be designed by a professional engineer registered in the State of California.

During wet weather, earthen berms or other methods should be used to prevent run-off water from entering all excavations. All run-off should be collected and disposed of outside the construction limits.

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5.5 TRENCH BACKFILL

5.5.1 Materials

Pipe zone backfill (i.e., material beneath and in the immediate vicinity of the pipe) should consist of soil compatible with design requirements for the specific types of pipes. It is recommended that the project designer or pipe supplier develop the material specifications based on planned pipe types, bedding conditions, and other factors beyond the scope of this study. Randomly excavated on-site soil from the near surface of the site will likely be Class III material per ASTM

D2321.

Trench zone backfill (i.e., material placed between the pipe zone backfill and finished subgrade) may consist of native soil which meets the requirements for engineered fill.

5.5.2 Compaction Criteria

All trench backfill should be placed and compacted in accordance with recommendations provided for engineered fill. Reduced compaction (85% minimum) could be specified for trench zone backfill in non-structural areas located a distance equal to the depth of the trench from any structures, pavements, and appurtenant improvements. Mechanical compaction is recommended; ponding or jetting should not be used.

Table 5.5-1 provides estimated geotechnical parameters for designers to consider in evaluating pipe zone backfill criteria that is compatible with pipe types and deformation tolerances. Data are presented for site soil and imported Class II or Class III (per ASTM D 2321) soil. Use of site soil as backfill will be very labor intensive to provide adequate placement and compaction under and around pipes.

TABLE 5.5-1

PIPE ZONE BACKFILL PARAMETERS

Soil Stiffness Modulus (psi) Backfill Density (pcf)

E’n

(Trench

Sidewall)

E’b (Backfill) 85%

Compaction

90%

Compaction 85%

Compaction

90%

Compaction

3,000 900 1350 123 130

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E’n represents the modulus for the undisturbed natural soil and is based on relative density and data by Howard (1996). E’b is the modulus for backfill derived from random excavation of on-site soil and is based on data by Hartley and Duncan (1982) and Watkins and Anderson (2000). The design E’ will be dependent upon the pipe diameter and trench width, which dictates the relative influence of E’n and E’b. Methods by Howard (1996) are suggested for evaluating the design E’.

Kleinfelder can furnish a recommended design E’, if provided with pipe diameter and specifications for trench construction.

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6 DESIGN RECOMMENDATIONS

6.1 GENERAL

Based on the laboratory data, field exploration, and geotechnical analyses conducted for this study, it is geotechnically feasible to construct the proposed improvements as currently envisioned. Provided that the recommendations presented in this report are incorporated into the project design and construction, use of shallow spread reinforced concrete footings and reinforced concrete mat/slab foundations bearing on undisturbed native soil or approved engineered fill are considered appropriate for support of the lift station and miscellaneous surface improvements. Pole footings may also be an appropriate foundation alternative for support SCADA equipment, light poles, and sunshades associated with the project improvements.

The following recommendations are based on the assumption that the recommendations in

Section 5, “Earthwork,” have been implemented. Recommendations regarded the geotechnical aspects of building design are presented in subsequent sections.

6.2 FOUNDATIONS

The foundation soil is anticipated to have a low expansive potential. Therefore, foundation embedment should be consistent with frost penetration, structural or architectural considerations, and the 2015 International Building Code (IBC). At a minimum, frost penetration dictates that foundations be embedded at least 18 inches below the ground surfaces exposed to freezing conditions. Footings should be placed on a level bearing surface. Where footings are placed on sloping ground it will be necessary to step the foundation to provide a level bearing surface in accordance with the 2015 IBC. If competent bedrock is exposed in the footing excavations that prevents level bearing or limits developing lateral resistance due to limited embedment, the structural engineer should provide a foundation pinning detail to develop the necessary resistance. Pinning into the bedrock is often accomplished through the use of No. 5 rebar epoxied into the competent bedrock. If pinning to bedrock is required, we recommended that we observe and approve rock pinning locations. Foundation bearing, pinning details to the bedrock, and reinforcement shall be designed by a structural engineer and should consider both structural and or architectural considerations.

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6.2.1 Vertical Bearing Pressures and Settlements – Miscellaneous Surface Improvements

It is assumed that miscellaneous surface improvements associated with the lift stations including the generators, electrical/control boxes, and sunshades may be supported on conventional spread footings.

Generally two geotechnical issues determine the design bearing pressure for conventional spread footing foundations; (1) strength of the foundation soil and (2) tolerable settlement. For light loads, bearing may be dictated by code required minimum footing geometry or constructability considerations.

The available bearing capacity, based only on the shear strength of the soil will be dependent upon the footing geometry. Presented in Table 6.2-1 are the bearing expressions for the allowable available bearing capacity (shear strength considerations only) for static loading (D.L.

+ L.L.), total combined loading (D.L. + L.L. + Transient loading, such as wind or seismic), and unfactored ultimate bearing.

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TABLE 6.2-1

AVAILABLE ALLOWABLE BEARING

Available Allowable Bearing (psf)

Static Loading 700 B + 1,340D

Total Combined Loading 1,045 B + 2,000 D

Ultimate Loading 2,090 B + 4,015D

Note: B is the footing width and D is the footing embedment in feet.

The above expressions are appropriated for design using the Basic and alternate Load

Combinations in Section 1605.3 of the 2015 IBC.

Analysis, based on Schmertmann, determined the following estimated static settlement based on a range of assumed design bearing and estimated structural loads. The estimated settlements presented in Table 6.2-2 are based on the assumption that the sustained load of footings is equal to 80 percent of the total load. The design bearing presented in Table 6.2-2 is based on a footing embedment depth of 1-foot below lowest adjacent grade.

TABLE 6.2-2

ESTIMATED SETTLEMENT

Footing Type Loading

(DL +LL)

Design Bearing

(psf) Estimated Settlement (inch)

Strip To 3 kips/ft To 2,270 Less than 0.25

Square To 30 kips To 3,500 Less than 0.25

The available bearing pressure due to shear strength is high. Therefore, an allowable bearing pressure of 2,000 psf could be considered as an alternative to maximizing bearing utilizing the equations in Table 6.2-1. The simplified allowable bearing pressure could be increased 50 percent for evaluating transient loads, such as, wind or seismic. If deemed necessary by the design engineer, Kleinfelder can provide the estimated settlement for other loading conditions.

The foundation soil is anticipated to have a low expansive potential. Therefore, foundation embedment and reinforcement should be consistent with structural or architectural considerations and the 2015 IBC. A modulus of subgrade reaction, Kp (Bp = 1 foot), of 270 pci can be used for undisturbed on-site soils or engineered fill. The subgrade modulus is applicable to consideration of static loads with deformations within an elastic range.

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6.2.2 Bearing Pressures and Settlements – Mat/Slab Foundations

It is anticipated that the proposed lift stations and generators may be supported on mat/slab foundations. The available bearing capacity for mat foundations, based only on shear strength of the soil, will be dependent upon the geometry of the mat foundations. The bearing expressions presented in Table 6.2-1 are also suitable for design of mat supported improvements.

Considering the depth and dimension of the proposed lift station, the available allowable bearing associated with soil strength is extremely high (exceeds 10,000 psf). The actual contact pressure associated with the lift station is anticipated to be significantly less than the available bearing. Therefore, the foundation soils are capable of supporting the proposed mat supported improvements.

For lift station embedment of 15 to 20 feet, no appreciable settlement is anticipated for contact pressures on the base of the lift station up to approximately 1,800 to 2,000 psf due to overburden relief. The estimated settlement of the lift station is approximately 0.1-inch per additional 1,000 psf of additional bearing in excess of 1,800 to 2,000 psf due to overburden relief.

The foundation soils are essentially granular; therefore, settlement is expected to occur rapidly with load application. Differential settlement across mat foundations is anticipated to be less than 50 percent of the total settlement. If deemed necessary by the design engineer, Kleinfelder can provide the estimated settlement for other loading conditions.

The weight of the concrete should be included in evaluating the contact pressure at the base of mat/slab footings. The weight of embedded concrete can be reduced by the unit weight of soil times the depth of embedded concrete. The unit weight of soil for use in analysis is 110 psf.

The foundation soil is anticipated to have a low expansive potential. Therefore, foundation embedment and reinforcement should be consistent with structural or architectural considerations and the 2015 IBC.

6.2.3 Lateral Resistance

Lateral loads applied to foundations can be resisted by a combination of passive lateral bearing and base friction. The allowable and ultimate passive pressures and frictional coefficients for the footings are presented in Table 6.2-3.

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TABLE 6.2-3

PASSIVE PRESSURES AND FRICTIONAL COEFFICIENTS

Allowable

Ultimate Static

Total

Combined

Frictional Coefficient 0.45 0.54 0.67

Passive Pressure (psf/ft of depth) 340 450 680

Lateral Translation Needed to Develop Passive Pressure

0.004 D 0.008 D 0.023 D

Note: D is the footing depth

If the deflection resulting from the strain necessary to develop the passive pressure is beyond structural tolerance, additional passive pressure values could be provided based on tolerable deflection. The passive pressure and frictional resistance can be used in combination. The allowable values already incorporate a factor of safety and, as such, would be compared directly to the driving loads. If analytical approaches require the input of a safety factor, the ultimate values would be used.

6.2.4 Design and Construction Considerations

Prior to placing steel or concrete, footing excavations should be cleaned of all debris, loose or soft soil, and water. All footing excavations should be observed by the project Geotechnical

Engineer just prior to placing steel or concrete. The purpose of these observations is to check that the bearing soils actually encountered in the foundation excavations are similar to those assumed in analysis and to verify the recommendations contained herein are implemented during construction.

6.3 POLE FOUNDATIONS

6.3.1 Allowable Vertical Axial Capacity and Settlements

Structures such as scata equipment, light poles and sunshades may be supported by pole foundations. Should design incorporate the use of pole foundations, Table 6.3-1 provides expressions for the allowable and ultimate axial capacity using friction to resist axial loads. If the design of the pier foundations includes end bearing to resist axial loads, the design may utilize the bearing capacity expressions given in Table 6.2-1, up to an allowable bearing capacity of 2,000 psf for static loading (D.L. + long term L.L.). The end bearing capacity may be

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TABLE 6.3-1

ALLOWABLE AXIAL CAPACITY

Frictional Resistance for Vertical

Loads in Compression (lbs)

Static Loading 55 DL2

Total Combined Loading 75 DL2

Unfactored Ultimate Capacity 115 DL2

Note: 1) D is pier diameter in feet and L is embedment length in feet.

2) The allowable uplift resistance would be 70 percent of the compressional resistance.

The total settlement of pole foundations designed in accordance with the above recommendations using the friction capacity should be less than 0.002 times the footing diameter in inches. If design incorporates end bearing to resist axial loading, the estimated settlement would increase to approximately 0.018 times the pier diameter in inches. The concrete mix and reinforcement for drilled pier/caisson foundations should be designed by the project structural engineer.

6.3.2 Lateral Resistance

Methods by ASHTO and Caltrans can be used to evaluate the lateral capacity of pier footings.

The allowable passive pressure to resist lateral loads on isolated piers for use in these methods may be taken as 580 psf per foot of depth of embedment. The passive pressure may be increased by one-third for the total combined loads, including wind and seismic. The passive pressure values already consider arching and, as such, should not be increased further.

The allowable passive pressure provided above would not be appropriate for use in place of the values given in Table No. 1806.2 of the 2015 IBC if pier foundation design utilizes the pole formulas in the CBC. If design uses the pole formulas in the CBC, the appropriate class of material in Table 1806.2 would be No. 4 (Silty Sand). Based on the strength of the on-site soils, a lateral bearing pressure of 200 psf/ft of embedment below the site grade may be used in place of the value given in Table 1806.2.

The passive pressure only considers soil strength. Tolerable pole footing deflection may govern the design lateral resistance. If provided with pole footing geometry, lateral load, and loading eccentricity, we can provide the estimated pole head deflection.

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6.3.3 Design and Construction Considerations

The concrete mix and reinforcement for the pole foundations should be designed by the project structural engineer.

Prior to placing steel or concrete, footing excavations should be cleaned of all debris, loose or soft soil, and water. All footing excavations should be observed by the project Geotechnical

Engineer just prior to placing steel or concrete. The purpose of these observations is to check that the bearing soils actually encountered in the foundation excavations are similar to those assumed in analysis and to verify the recommendations contained herein are implemented during construction.

Based on the subsurface conditions at the time of exploration, pole footing construction may encounter granular soils of sand, gravel, and cobble sediment and potentially groundwater as well as granitic bedrock of various weathering and strength. The sand, gravel, and cobble sediments will likely require temporary casing to maintain bore-hole stability. The pole installation contractor should exercise care in drilling and be prepared to use temporary casing of the pole footing excavation if caving or sloughing becomes problematic.

Placement of reinforcement shall be performed in such a way as to avoid disturbance to the sidewalls of the pier boring. Concrete shall be placed using tremie methods to displace the drilling fluid. Care should be exercised to maintain the tremie pipe below the concrete surface to avoid folding of drilling fluid into the concrete. To assess the relationship between the tremie pipe and concrete surface, during the concrete placement, the depth to concrete should be monitored with a weighted tape measure to ensure that the concrete placement occurs below the concrete surface. The volume of concrete placed in the pier should be measured and compared to the intended volume to be placed. The purpose of assessing the placed concrete volume is to ensure that the pier has been paced as a homogeneous mass.

6.4 RETAINING STRUCTURES

The lateral earth pressure against retaining structures will be dependent upon the ability of the wall to deflect. Presented in Table 6.4-1 are the active, at-rest, and braced lateral earth pressures. The active pressure is applicable to walls able to translate 0.0005 radians at the top or bottom. The at-rest soil pressure is applicable to retaining structures that are fully fixed against both rotation and translation. Walls restrained from translation at the top and bottom, 20170255.001A/FRE18R87819R1 Page 25 of 29 Revision No. 1: March 5, 2019 but able to deflect 0.0005 radians between the restrained points should be designed for the braced lateral pressure.

TABLE 6.4-1

LATERAL EARTH PRESSURES FOR ON-SITE SOIL

Loading Conditions Lateral Earth Pressures (psf) Earth Pressure

Coefficient Drained Undrained

Active Pressure (psf/ft of depth) 34 13 psf + Hydrostatic 0.28

Braced Pressure (psf) 22 8 psf + Hydrostatic 0.18

At-Rest Pressure (psf/ft of depth) 53 20 psf + Hydrostatic 0.44

H in the expression represents the retained height in feet (measured from finished grade to bottom of footing). The “Drained” earth pressures presented above assume saturated conditions. The earth pressures do not include hydrostatic pressures; therefore, wall should be adequately drained to prevent the build-up of hydrostatic pressure if the “Drained” values are used for retaining wall design.

Should retaining walls be influenced by surcharge loads (e.g. vehicle, snow, etc.), the surcharge against the walls can be evaluated by multiplying the surcharge pressure by the earth pressure coefficient. Surcharge loads should be modeled as a uniform pressure against the wall by multiplying the surcharge load by the earth pressure coefficient.

The resultant of the active earth pressure can be assumed to act at a 17-degree angle downward from horizontal with no heel extension and at a 34-degree angle downward from horizontal if a heel extension is utilized. The resultant of the earth pressures against braced walls or walls fully fixed against both rotation and translation shall be assumed to act horizontally.

Retaining wall foundation design can utilize the passive pressures and sliding resistance given in Table 6.2-3 and allowable bearing capacity given in Section 6.2-1. When utilizing the available allowable bearing capacities of Table 6.2-1 the value for static loading would represent the average bearing for the footing and the value for total combined loading would represent the allowable maximum toe pressure.

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6.5 EXTERIOR CONCRETE SLABS-ON-GRADE

6.5.1 Subgrade Preparation

Slabs-on-grade should be supported on recompacted soils or engineered fill placed as described in Section 5.3 of this report. The slab subgrade, to a depth of 12 inches should have a moisture content within 2 percent of optimum immediately prior to pouring the slab.

6.5.2 Conventional Slab Design

There are no geotechnical considerations (e.g. expansive soil), which would require special design of slabs. Therefore, the thickness and reinforcement of slabs-on-grade should be determined by structural considerations and should be designed by the project structural engineer or designer. A modulus of subgrade reaction, Kp (Bp = 1 foot), of 360 pci may be used for elastic analysis of slabs on properly compacted subgrade.

6.6 PIPELINE THRUST

The lateral thrust on pipelines can be resisted by friction between the pipe and native or imported backfill soil and lateral bearing on thrust blocks. The allowable frictional resistance between the pipe and backfill comprised on-site soil or select sand, is given in Table 6.5-1.

TABLE 6.5-1

FRICTIONAL COEFFICIENTS

Pipe Material Allowable Frictional Coefficient

Sustained Loading Test Loading

Smooth Plastic or Steel (native soil or imported sand backfill)

0.20 0.24

The lateral load on shallow thrust blocks (block height greater than 70 percent of depth to center of pipeline) poured against undisturbed soil can be resisted by the passive lateral bearing provided in Table 6.2-3.