MOD18R78466_Bridalveil_Falls_Report_5-17-18_Amd3_0003.pdf

20184025.001A/ MOD18R78466 Page i of iv May 17, 2018 © 2018 Kleinfelder www.kleinfelder.com

May 18, 2018 Kleinfelder Project No. 20184025.001A

Mr. John N. Roberts John Northmore Roberts & Associates 2927 Newbury Street, Suite B Berkeley, CA 94703

Subject: Geotechnical Services Report Proposed Bridalveil Fall Rehabilitation

Yosemite National Park, California

Dear Mr. Roberts:

Kleinfelder is pleased to present the results of our geotechnical services performed for the proposed Bridalveil Fall Rehabilitation in Yosemite National Park, California. The accompanying report includes background information regarding the anticipated construction, the purpose of our services, and scope of services provided. In addition, discussions regarding our investigative procedures and the site conditions encountered during our field exploration are presented. Finally, geotechnical conclusions and recommendations are provided for use in preliminary project design. The appendix of the report includes logs of borings and a summary of laboratory tests.

We appreciate the opportunity of providing our services for this project. If you have questions regarding this report or need further assistance, please contact us.

Respectfully submitted, KLEINFELDER, INC.

Brock E. Campbell, GE, No. 2995 Project Geotechnical Engineer

Reviewed by:

Nathan L. Dahlen, PE, No. C71344 Senior Engineer http://www.kleinfelder.com/

20184025.001A/ MOD18R78466 Page ii of iv May 17, 2018

GEOTECHNICAL SERVICES REPORT

PROPOSED BRIDALVEIL FALL REHABILITATION

YOSEMITE NATIONAL PARK, CALIFORNIA

KLEINFELDER PROJECT NO. 20184025.001A

MAY 18, 2018

Copyright 2018 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.

http://www.kleinfelder.com/ JBoudreaux Text Box

20184025.001A/MOD18R78466 Page iii of iv May 17, 2018

A Report Prepared for:

Mr. John N. Roberts John Northmore Roberts & Associates 2927 Newbury Street, Suite B Berkeley, CA 94703

GEOTECHNICAL SERVICES REPORT

PROPOSED BRIDALVEIL FALL REHABILITATION

YOSEMITE NATIONAL PARK, CALIFORNIA

Prepared by:

Brock E. Campbell, GE, No. 2995 Project Geotechnical Engineer

Reviewed by:

Nathan L. Dahlen, PE, No. C71344 Senior Engineer

KLEINFELDER

1224 Sixth Street Modesto, CA 95354 Phone: 209.577.4333 Fax: 209.575.3444

May 18, 2018 Kleinfelder Project No. 20184025.001A

20184025.001A/MOD18R78466 Page iv of iv May 17, 2018

TABLE OF CONTENTS

Section Page

1 INTRODUCTION

2 FIELD AND LABORATORY INVESTIGATIONS

2.1 FIELD DESCRIPTION

2.2 LABORATORY INVESTIGATION

3 SITE CONDITIONS

3.1 SURFACE CONDITIONS

3.2 SUBSURFACE CONDITIONS

4 GEOLOGIC CONDITIONS

4.1 REGIONAL GEOLOGY

4.2 CBC SEISMIC DESIGN CRITERIA

4.3 LIQUEFACTION

5 CONCLUSIONS AND RECOMMENDATIONS

5.1 GENERAL

5.2 CONCRETE FLOOR SLAB – NEW RESTROOM AREA

5.2.1 Subgrade Preparation

5.2.2 Capillary Break

5.2.3 Additional Considerations

5.3 EXTERIOR FLATWORK

5.4 SPREAD FOUNDATIONS

5.5 LATERAL RESISTANCE

5.6 PAVEMENTS

5.6.1 Subgrade Preparation

5.6.2 Asphalt Pavement Sections

5.7 EXCAVATION COMMENTS

5.7.1 General

5.7.2 Sloped Excavations

5.7.3 Shored Excavations

5.7.4 Existing Structures, Pipelines, etc

5.7.5 Trench Backfill

5.7.6 Pipe Bedding and Pipe Zone Backfill Placement

5.7.7 Filter Fabric Envelope

5.8 FOUNDATIONS AND THRUST BLOCKS FOR PIPELINES

5.9 SOIL CORROSION

5.10 SITE DRAINAGE

5.11 GENERAL EARTHWORK

5.11.1 Site Stripping

5.11.2 Subgrade Preparation

5.11.3 Temporary Excavations

5.11.4 Fill Materials

5.11.5 Engineered Fill

5.11.6 Wet/Unstable Subgrade Mitigation

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6 ADDITIONAL SERVICES

6.1 PLANS AND SPECIFICATIONS REVIEW

6.2 CONSTRUCTION OBSERVATION AND TESTING

7 LIMITATIONS

FIGURES

SITE VICINITY MAP

BORING LOCATION MAP

APPENDIX A

BORING LEGEND AND LOGS ............................................................................. A-1/A-9

APPENDIX B

LABORATORY TEST RESULTS ........................................................................... B-1/B-4

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1 INTRODUCTION

1.1 GENERAL

This report presents the results of a geotechnical investigation for the proposed Bridalveil Fall

Rehabilitation, generally located in the western portion of Yosemite Valley (Figure 1, Site

Vicinity Map). The purpose of the investigation was to explore and evaluate the subsurface conditions at various locations along the proposed reconstructed parking lot, new comfort station, and utility connections for the new comfort station.

The project involved the drilling of seven (7) vertical exploratory borings to a maximum depth of about 3.5 feet. The approximate locations of the borings are shown on Figure 2, Boring

Location Map.

This report includes recommendations related to the geotechnical aspects of project design and construction. Conclusions and recommendations presented in this report are based on the subsurface conditions encountered at the location of the exploration and the provisions and requirements outlined in the “Additional Services” and Limitations” Sections of this report.

Recommendations presented herein should not be extrapolated to other areas or used for other projects without prior review.

1.2 PROPOSED CONSTRUCTION

It is understood the rehabilitation project includes the reconstruction of the existing parking lot with a new entry with turning lanes along Wawona Road, a new larger comfort station with flush toilets, utility connections for the flush toilets (water, power, and sewer) to the Pohono Bridge approximately 1.25 miles away from the site, new accessible loop trails including about 700 linear feet of elevated pathways and bridges capable of spanning about 40 feet, an enlarged overlook at the base of the fall, potential accommodation for tour buses along Southside Drive, and other related trail improvements.

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1.3 PURPOSE AND SCOPE OF SERVICES

The purpose of this investigation was to explore the site subsurface conditions, and provide recommendations and opinions regarding the following:

A description of the proposed project, including a vicinity map and a site plan showing the approximate boring locations.

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

A summary of the field exploration and laboratory testing data.

Recommendations for site preparation and earthwork grading including a discussion concerning the use of on-site soils for engineered fill, recommendations for import fill specifications, and over-excavation requirements (if any).

Recommendations for allowable bearing and settlement for shallow spread footings for the structure.

Parameters for lateral capacity of foundations.

Recommended subgrade preparation for concrete building slabs-on-grade.

Recommended minimum flexible pavement sections, based on a range of traffic conditions.

Seismic design parameters and other requirements for site based on 2016 CBC.

Comments on regional and local groundwater levels.

Comments on the general corrosion characteristics of the site soils.

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2 FIELD AND LABORATORY INVESTIGATIONS

2.1 FIELD DESCRIPTION

The field exploration was conducted on March 19 and 20, 2018, and consisted of drilling seven

(7) exploratory test borings along the project site. The test borings were explored with a hand auger. The borings ranged in depth from 1-foot to up to 3.5 feet below the existing ground surface. The approximate locations of the test borings are indicated on the Boring Location Map, Figure 2, located at the end of this report. The borings were located in the field by visual sighting and/or pacing from existing site features; therefore, the locations shown on Figure 2 should be considered approximate

The soils encountered in the test borings were visually classified in the field and a continuous log was recorded. Boring logs are presented in Appendix A and graphically illustrate the materials encountered at the boring locations. Samples were collected from the test borings at selected depths by placing into sealable plastic bags.

2.2 LABORATORY INVESTIGATION

Laboratory tests were performed on selected samples to evaluate certain physical characteristics and engineering properties. The following laboratory test data were used to develop the design geotechnical parameters:

• Direct Shear (ASTM D3080)

• Grain-Size Distribution (ASTM D422, without hydrometer)

• Resistance Value (California Test Method No. 301)

The percent passing the #4 and #200 sieve test results are shown on the boring logs in Appendix

A. The other test results are provided in Appendix B.

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3 SITE CONDITIONS

3.1 SURFACE CONDITIONS

The borings were generally located in unpaved areas surfaced with soil and organic material, mostly leaf litter. At the time of exploration, 1 to 4 inches of snow was covering the project area.

The snow at the auger locations was removed before exploration was begun.

3.2 SUBSURFACE CONDITIONS

The subsurface conditions described here are general observations determined from the explorations. Details of each are located in the boring logs located in Appendix A. Subsurface soils are predominately silty sands with gravel and poorly graded sands with gravel.

The borings were checked for the presence of groundwater during and immediately following drilling operations. Groundwater was not encountered in the borings to the maximum depth explored of approximately 3 .5 feet 8 below existing ground surface. Groundwater elevations and soil moisture conditions within the project area will vary depending on seasonal rain and snow fall, irrigation practices, land use, and/or runoff conditions not apparent at the time of our field investigation. The evaluation of such factors is beyond the scope of this investigation.

Groundwater depths are generally shallower near creek and stream channels and directly adjacent to the Merced River (2 to 4 feet below ground surface) (fbgs), than at other locations in

Yosemite Valley (4 to 15 fbgs).

Detailed descriptions of the subsurface conditions encountered during our field investigation are presented on the Logs of Borings in Appendix A.

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4 GEOLOGIC CONDITIONS

4.1 REGIONAL GEOLOGY

The project site and its vicinity are located in the western portion of the Yosemite Valley in an upper portion of the Merced River Canyon. This area is in the central portion of the Sierra

Nevada Batholith. The Sierra Nevada Mountains were initially formed by uplifts, which occurred during the Jurassic and Cretaceous periods of geologic time (greater than 65 million years ago).

Renewed uplift began in the Sierra Nevada during the late Tertiary time and is continuing today.

The Yosemite Valley was formed during glacial episodes over the past million years.

Sediments underlying the Valley consist of about 1,000 feet of boulders, cobbles, gravels, sands, and silts deposited by lakes, streams, and receding glaciers. The boundary colluvium along the edges of the Valley was derived from rockslides and debris flows. The site is underlain by several hundred feet to over 1,000 feet of soils that consist of either Holocene alluvium or river deposits of the Merced River. These sediments overlie granitic bedrock.

Faulting and seismic ground shaking are usually associated with known fault systems. There are no known fault systems which cut through the local soils in or near the site and the site is not located in an Alquist-Priolo Earthquake Fault Zone as defined by Special Publication 42 published by the California Geologic Society (CGS). However, during the formation of the

Coast Range and Sierra Nevada Mountains, numerous faults and shear zones developed in the mountain ranges bordering the Central Valley and Sierra Nevada. Most of these fault zones have not moved during the last 2 million years and are currently considered inactive.

4.2 CBC SEISMIC DESIGN CRITERIA

The parameters provided below are based on the 2016 CBC. The 2016 CBC is based on the

2015 IBC and ASCE 7-10. The Risk-Targeted Maximum Considered Earthquake (MCER) mapped spectral accelerations for 0.2 second and 1 second periods (SS and S1) were estimated using Section 1613A of the 2016 CBC. The mapped acceleration values and associated soil amplification factors (Fa and Fv) based on 2016 CBC are presented in the table below.

Corresponding site modified (SMS and SM1) and design spectral accelerations (SDS and SD1) are also included.

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Table 4.2-1

Ground Motion Parameters Based on 2016 CBC

Parameter Value Reference

SS 0.652g 2016 CBC Section 1613.3.1

S1 0.232g 2016 CBC Section 1613.3.1

Site Class C 2016 CBC Section 1613.3.2

Fa 1.139 2016 CBC Table 1613.3.3(1)

Fv 1.568 2016 CBC Table 1613.3.3(2)

PGA 0.240g ASCE 7-10 Figure 22-7

SMS 0.743g 2016 CBC Section 1613.3.3

SM1 0.364g 2016 CBC Section 1613.3.3

SDS 0.495g 2016 CBC Section 1613.4.4

SD1 0.243g 2016 CBC Section 1613.4.4

FPGA 1.160 ASCE 7-10 Table 11.8-1

PGAM 0.278g ASCE 7-10 Section 11.8.3

CRS 1.018 ASCE 7-10 Figure 22-17

CR1 1.102 ASCE 7-10 Figure 22-18

TL 6 seconds ASCE 7-10 Figure 22-12

Seismic Design Category D ASCE 7-10 Table 11.6-1 and 11.6-2

Based on the information provided in Section 4.1, and using Table 20.3-1 of ASCE 7-10, the project site is categorized as Site Class C. Site Class C is defined as a stiff soil profile with average shear wave velocities within the upper 100 feet between 600 ft/s and 1,200 ft/s, average SPT 15<N<50, or average 1,000 psf <Su < 2,000 psf.

Based on Figure 22-7 of ASCE 7-10, the mapped geometric mean peak ground acceleration

(PGA) for the project site is 0.240g. Using Equation 11.8-1 and Table 11.8-1 of ASCE 7-10 and

FPGA of 1.160, PGA adjusted for site class (PGAM) for the project site is 0.278g.

4.3 LIQUEFACTION

During previous investigations by Kleinfelder in Yosemite Valley, liquefaction analysis used procedures by Youd, et al (2001), and considered the relative density and fines content of the granular sediments. Analyses indicate the potential for liquefaction is marginal within the Valley, considering the relative density of the cohesionless soils encountered. Isolated areas, generally deeper than 30 feet, may be subject to liquefaction. Based on procedures by Tokimatsu and

Seed (1987), the seismically induced cyclic stress in the majority of Valley subsurface soils would not generally result in any significant settlement

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5 CONCLUSIONS AND RECOMMENDATIONS

5.1 GENERAL

Based on our findings, it is our professional opinion that the site should be suitable from a geotechnical standpoint for support of the proposed Bridalveil Falls Rehabilitation project provided the recommendations contained herein are incorporated into the project design. Given the subsurface conditions encountered and anticipated structural loads, the near-surface soil should be essentially non-expansive and should provide adequate support for shallow spread, continuous, or mat foundations and roadway improvements. Specific conclusions and preliminary recommendations regarding the geotechnical aspects of design and construction are presented in the following sections.

5.2 CONCRETE FLOOR SLAB – NEW RESTROOM AREA

5.2.1 Subgrade Preparation

We assume that dead and live loads supported by the proposed support building floor slab and equipment pads will be relatively light. Based on these premises, all areas to support the concrete floor slab or engineered fill should be scarified to a depth of at least 12 inches, uniformly moisture conditioned to between 1 and 4 percentage points above the optimum moisture content, and compacted as engineered fill to a minimum of 90 percent of the maximum dry density as determined by the ASTM D1557 test method.1 Additional criteria regarding general earthwork are presented in Section 5.11.

5.2.2 Capillary Break

It is understood the restroom building will be built above typical highwater mark for the area, so groundwater should not rise near the surface and adversely impact the structural performance of the floor slab. If portions of the restroom building floor slab will be covered with moisture-sensitive flooring, it has been common practice and industry standard in the project area to

This test procedure should be used wherever relative compaction, maximum dry density, or optimum moisture content is referenced within this report.

20184025.001A/MOD18R78466 Page 9 of 24 May 17, 2018 place a capillary break consisting of at least 4 inches of free draining crushed gravel on the finished subgrade soil that, in turn, is overlain by a flexible sheet membrane, such as

StegoWrap™, Moistop Plus™, or an equivalent meeting the requirements of ASTM E1745, that serves as a water and/or moisture vapor retarder. The crushed gravel should be graded so that

100 percent passes the 1-inch sieve and less than 5 percent passes the No. 4 sieve. Care should be taken to properly place, lap, and seal the membrane in accordance with manufacturer’s recommendations to provide a vapor tight barrier. Tears and punctures in the membrane should be completely repaired prior to placement of concrete. Until recently, the local practice and American Concrete Institute (ACI) standard has been to place a 1- to 2-inch thick layer of relatively dry, fine-to medium-grained “clean” sand over the membrane to promote uniform curing of concrete and to protect the membrane. ACI has now revised their standard and this layer of sand is no longer recommended. To compensate, a lower water cement ratio and improved curing methods are suggested. If the design engineer still prefers to specify a sand cushion, we suggest that the moisture content of the sand not exceed 4 percent by dry weight. If the sand becomes overly wet, it should be removed and replaced with suitable sand.

The capillary break should not replace in whole or in part the Subgrade Preparation recommendations discussed in the previous subsection.

Over the past few years, problems with wet, curled, and loose floor coverings have become an issue. Accordingly, prior to placement of floor coverings, moisture emissions through the concrete and the pH and relative humidity of the concrete should meet the manufacturer’s recommendations and requirements. A guide for preparing concrete floors that will receive moisture-sensitive floor covering is presented in ASTM F710. Since Kleinfelder is not a floor moisture proofing consultant or expert, it is our professional opinion that these standards should be incorporated into the project design and construction unless otherwise revised by a qualified specialist with local knowledge of slab moisture protection systems, flooring design, and other potential components that may be influenced by moisture and/or moisture vapor.

In areas where the restroom building is not covered with floor coverings or supports moisture-sensitive equipment, it is common to replace the gravel and capillary break with at least 4 inches of Class 2 aggregate base. We recommend that the equipment pads also be underlain by 4 inches of Class 2 aggregate base. The aggregate base should be compacted to at least 95 percent relative compaction. The aggregate base provides added support for concentrated vehicle and/or storage loads and less deflection at the slab joints caused by vehicle or other equipment traffic. The moisture-proofing specialist and Structural Engineer should approve this slab support prior to final design and construction.

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5.2.3 Additional Considerations

The project Structural Engineer should provide the final design floor slab thickness and reinforcement requirements. Care should be taken to place, consolidate, and cure concrete in accordance with ACI standards and criteria

5.3 EXTERIOR FLATWORK

Following site stripping, as a minimum all areas to support exterior concrete flatwork, i.e., sidewalks, patios, and the like, should be scarified to a depth of 6 inches, uniformly moisture conditioned to between 1 and 4 percentage points above the optimum moisture content, and compacted as engineered fill to a minimum of 90 percent of the maximum dry density as determined by the ASTM D1557 test method. Additional criteria regarding general earthwork are presented in Section 5.11.

The near-surface soil conditions do not necessarily warrant the placement of aggregate base below flatwork from a geotechnical standpoint. Flatwork, however, tends to perform better during and following construction with less maintenance if it is underlain by a layer of Class 2 aggregate base. The aggregate base serves to provide a firm/uniform surface directly below the flatwork where surcharge stresses are highest. As a result, we have found that flatwork supported on aggregate base tends to experience less stress cracking and movement or deflection at joints. If considered, the aggregate base should have a thickness of at least 4 inches and be compacted to at least 90 percent relative compaction. In areas where concrete flatwork will support construction equipment and/or vehicle traffic, we suggest that the aggregate base be increased to a thickness of 6 to 8 inches and be compacted to at least 95 percent relative compaction.

5.4 SPREAD FOUNDATIONS

The proposed structure may be supported on shallow, reinforced concrete spread footings founded on undisturbed native soil, engineered fill, or a combination of both. A net allowable bearing pressure of 2,000 pounds per square foot (psf) for dead plus sustained live loading may be used to size column and continuous footings supported by these materials. A one-third increase in the allowable bearing pressure may be applied when considering short-term loading due to wind or seismic forces.

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Even though computed footing dimensions may be less, continuous bearing wall and column footings should have minimum widths of 12 and 24 inches, respectively, to facilitate hand cleaning of the footing excavations and reduce the potential for localized punching shear failure.

All footings should be embedded at least 12 inches below the lowest final adjacent subgrade

At this depth, foundations should be supported below the critical zone of seasonal moisture fluctuations where soil shrink-swell cycles are most severe. In addition, perimeter continuous foundations would serve as a horizontal moisture break, reducing the potential for seasonal or man-made wetting and drying below the structure. Accordingly, continuous foundations should extend the entire perimeter of the building.

Total settlement of an individual foundation will vary depending on the plan dimensions and location of the foundation and the actual load supported. Based on the anticipated foundation loads and dimensions, we estimate maximum total and differential foundation settlements due to structural loads should be less than ½ inch. Similar foundations underlain by Engineered Fill will experience less settlement.

Prior to placing steel or concrete, footing excavations should be cleaned of all debris, loose or soft soil, and water. If shrinkage cracks appear in the footing excavations, the excavations should be thoroughly moistened to close all cracks prior to placement of concrete. All footing excavations should be observed by a representative of the project geotechnical engineer just prior to placing steel or concrete to evaluate whether the recommendations contained herein are implemented during construction.

The structural engineer should evaluate footing configurations and reinforcement requirements to account for loading, shrinkage, and temperature stresses. As a minimum, continuous footings should be reinforced with at least two No. 4 reinforcement bars, one top and one bottom, to provide structural continuity and permit spanning of local subgrade irregularities.

5.5 LATERAL RESISTANCE

Resistance to lateral loads (including those due to wind or seismic forces) may be determined using an at-rest coefficient of friction of 0.45 between the bottom of cast-in-place concrete foundations and the underlying soils. Lateral resistance for foundations can alternatively be

Within this report, subgrade refers to the top surface of undisturbed native soil, native soil compacted during site preparation, or engineered fill.

20184025.001A/MOD18R78466 Page 12 of 24 May 17, 2018 provided by the passive soil pressure acting against the vertical face of the spread and/or continuous foundations. The passive pressures available in undisturbed native soils and engineered fill may be taken as equivalent to pressures exerted by fluids weighing 350 and 450 pounds per cubic feet (pcf), respectively. The top 12 inches of soil should be neglected when evaluating passive resistance unless the area adjacent the foundation is protected by concrete or pavement. These two modes of resistance can be combined. However, since horizontal movement is required to mobilize passive resistance, the allowable at-rest frictional resistance should be reduced by 50 percent.

Lateral resistance parameters provided above are ultimate values. Therefore, a suitable factor of safety should be applied to these values for design purposes. The appropriate factor of safety will depend on the design condition and should be determined by the project Structural

Engineer. Depending on the application, typical factors of safety could range from 1.0 to 1.5 depending on the loading condition.

5.6 PAVEMENTS

5.6.1 Subgrade Preparation

Following site stripping, all subgrade soils to support pavements should be scarified to a minimum depth of 12 inches below the finished subgrade elevation, uniformly moisture conditioned to between 1 and 4 percentage points above the optimum moisture content and compacted as engineered fill to at least 95 percent of the maximum dry density as determined by the ASTM D1557 test method. The subgrade soils should be in a stable, non-pumping condition at the time aggregate base materials are placed and compacted.

5.6.2 Asphalt Pavement Sections

Two (2) R-values were sampled for this project. The result of the laboratory test indicates that the subgrade soils tested should exhibit good support characteristics for pavements as represented by two R-values of 72.

Pavement sections (determined in units of inches rounded up to the nearest ½-inch) are presented in Table 5.6.2-1 and are based on a maximum Caltrans design R-value of 50, current

Caltrans design procedures, TI’s ranging from 4 to 8, and our assumption that Caltrans

20184025.001A/MOD18R78466 Page 13 of 24 May 17, 2018 construction tolerances are acceptable. Pavement sections include a Gravel Equivalent Safety

Factor of 0.20 per Caltrans highway design criteria.

The project owner and/or civil engineer should review the pavement sections and evaluate the suitable TI’s for this project

Table 5.6.2-1

Asphalt Pavement Sections

Traffic Index Asphalt Concrete

(inches)

Class 2 Aggregate Base

(inches)

4 2½ 4

5 3 4

6 3½ 4

7 4 4½

8 5 4½

The pavement sections provided above are contingent on the following recommendations being implemented during and following construction.

• All trench backfills, including utility and sprinkler lines, should be properly placed, and adequately compacted at above optimum moisture content to provide a stable subgrade. All backfill within the streets should be completed prior to lime treating the street subgrade.

• Aggregate base material should conform to the specifications stated in Section 26 of the Caltrans Standard Specifications and be compacted as engineered fill to at least

95 percent relative compaction.

• Asphalt paving materials and placement methods should conform to Section 39 of the Caltrans Standard Specifications, latest edition.

• Adequate drainage (both surface and subsurface) should be provided such that the subgrade soils and aggregate base materials are not allowed to become wet.

Pavement sections should be isolated from intrusion of water at all locations where pavements are adjacent to irrigated landscaping or areas that may pond water. For long-term performance, pavement edge drains should be placed to collect water and

The traffic index (TI) is a measure of traffic wheel loading frequency and intensity of anticipated traffic. For comparison, TI’s of between 4 and 5 are often suitable for design of automobile parking areas, TI’s of between 5 and 6 are commonly used for design of fire truck access lanes and areas subject to channelized flow with light delivery trucks, and TI’s greater than 6 are common for design of pavements supporting light to moderate bus and truck traffic.

20184025.001A/MOD18R78466 Page 14 of 24 May 17, 2018 to convey it to a storm drain or other drainage facility. As an alternative, but one that tends to be less effective, edge barriers, such as concrete curbs, polyethylene membranes and the like, should be placed that extend a minimum of 4 inches below the aggregate base and into the subgrade soil. Additional details regarding these systems can be provided upon request.

• Periodic maintenance should be performed to repair degraded areas and seal cracks with appropriate filler.

5.7 EXCAVATION COMMENTS

5.7.1 General

We anticipate that trench excavations will extend to a maximum depth of about 10 feet. Based on experience, it is our professional opinion that the subsurface soils within the project area can be readily excavated using conventional earth moving equipment. Somewhat slower excavations should be anticipated within the dense to very dense, hard, and partly cemented soils. This report does not represent a study of the excavatability of the subsurface materials that may be encountered within the limits of the proposed project. The contractor should independently evaluate the condition of the subsurface materials in order to select the appropriate excavation equipment and techniques. Furthermore, the contractor should be aware of past development and activities within the project area and that active and abandoned utility lines, wells, and/or other buried objects may be encountered within the proposed excavation locations. Excavation and removal of these features, if encountered, will require special consideration by the contractor.

All excavations must comply with applicable local, state, and federal safety regulations including the current Cal OSHA Excavation and Trench Safety Standards. Construction site safety generally is the sole responsibility of the Contractor, who shall also be solely responsible for the means, methods, and sequencing of construction operations. We are providing the information below solely as a service to our 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.

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General recommendations for site preparation and earthwork construction are presented in the following sections of this report. All references to compaction, maximum density and optimum moisture content are based on ASTM D1557, unless otherwise noted.

5.7.2 Sloped Excavations

It is anticipated that silty sand with gravel and poorly graded sand with gravel will be encountered near the surface of the project. We anticipate the sand and gravel soils may require sloped excavations (if possible) and/or sheeting to prevent caving or sloughing. We note that it has generally been our experience that excavations in existing pavement areas can be somewhat more stable due to the bridging capability of surrounding pavement sections. Any excavations extending into these soils are susceptible to caving, loss of ground, and undercutting of overlying soils during or soon after excavation. The contractor should be prepared to protect existing utility lines and any other structures should caving soils be encountered adjacent to the line or structures.

The following table provides maximum temporary slope inclinations for the various soil conditions that maybe encountered. Maximum slope inclinations used in construction should be based on the weakest soil layer encountered.

Table 5.7.2-1

Maximum Slope Inclination

Soil Type

Maximum Slope Inclination

(Horizontal to Vertical)

For Excavation Depths of 10 Feet or Less

Medium-Dense to Dense Silty Sand and

Poorly Graded Sand 1½:1

The above table was developed under the assumption that temporary excavations will not extend below groundwater, will not be left open or exposed for a period greater than five days, and will not be exposed to direct rainfall, runoff, or surcharge loading. Heavy equipment, construction materials, excavated soil, and vehicular traffic should not be allowed within 1/3 the slope height from the top of any excavation. During wet weather, earthen berms or other methods should be used to prevent runoff water from entering all excavations. All runoff water should be collected and disposed of outside the construction limits.

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Excavated slope height, slope inclination, or excavation depths (including utility trench and wet well 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.

5.7.3 Shored Excavations

In areas where existing site features interfere with temporary sloped excavations, we anticipate that excavations will be shored. As indicated earlier, the soils anticipated to be encountered will likely vary, with interbedded layers and strata of potentially caving or sloughing sands and gravels. Accordingly, the Contractor should exercise care during excavations. Where temporary sloped excavations are not possible and potentially caving sands and gravels are encountered, excavations likely will require continuous or solid-type shoring during excavation.

Furthermore, the sand may not stand vertically long enough to move shoring into place following excavation. Shoring should be removed as backfilling progresses. The Contractor should have a California licensed structural engineer design the required shoring systems prior to earthwork activities.

Shoring should be designed to resist the earth pressure exerted by the retained soil plus any additional lateral force due to surcharge loading, i.e., construction equipment, foundations, roadways, etc., at or near the shoring. The following equivalent fluid earth pressures are recommended assuming a maximum shoring height of 10 feet, a level ground surface, an effective soil unit weight of approximately 120 pounds per cubic foot (pcf), and a fully drained soil condition:

Table 5.7.3-1

Lateral Earth Pressures

EARTH PRESSURE CONDITION Lateral Earth Pressure (pcf)

Active 35

At-Rest 55

Passive 350

The above values can also be used in design of pipeline thrust blocks with the same assumptions noted in the previous paragraph.

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5.7.4 Existing Structures, Pipelines, etc.

Temporary sloped excavations should not encroach on adjoining buildings, walls, or other structures within an area defined by an imaginary 2½(h):1(v) line drawn outward and downward from the closest edge of the structure. Furthermore, sloped excavations should maintain a minimum 1-foot separation from adjacent pipelines and pipeline backfill. Where the stability of a structure may be endangered by excavation operations, support systems such as shoring, bracing, or underpinning may be required to provide structural stability and to protect personnel working within the excavation.

5.7.5 Trench Backfill

All trench backfill in building or other structural areas should be placed and compacted in accordance with the recommendations provided for engineered fill (*see Section 5.11.5). During backfill, mechanical compaction of engineered fill is recommended, and jetting should not be used. Where access for compaction testing in deep trenching operations is limited by trench stability, safety, and other access concerns, a cementitious slurry mixture such as lean concrete, Controlled Low Strength Material (CLSM) or Controlled Density Fill (CDF) may be used for backfilling as long as adequate pipe anchoring measures to prevent pipe floating are employed. The slurry should be adequately vibrated into position under the spring line of the pipe.

5.7.6 Pipe Bedding and Pipe Zone Backfill Placement

Pipe bedding and pipe zone backfill materials for pipelines should meet manufacturer’s recommendations for material type, gradation, and thickness. If used, clean crushed rock bedding and initial backfill materials should be overlain by a non-woven filter fabric to prevent migration of fines into the voids in the material.

Bedding materials should be compacted to a firm and unyielding condition prior to placement of pipes. Initial backfill materials placed around the pipe zone should be placed in a manner to eliminate voids beneath the pipe. Clean crushed rock should be suitable for this use. If used, clean crushed rock materials should be placed in lifts less than 2 feet in loose thickness and be compacted using vibratory plate equipment until it is firm and unyielding. It is recommended that

20184025.001A/MOD18R78466 Page 18 of 24 May 17, 2018 placement of the bedding and pipe zone backfill material be observed by a representative of the geotechnical engineer during construction to verify proper placement and compaction.

Compaction of the soil in the haunch area significantly increases the support for the pipe. For reinforced concrete pipe, literature indicates increasing the percent compaction of the soil in the haunch areas increases the bedding factor about 2-1/2 times for embankment conditions and about 1-1/2 times for trench conditions (reference: ACPA Design Data No 9). Methods such shovel slicing and/or using small compaction equipment consolidates the bedding material in the haunch to (1) help the pipe remain true to line and grade and (2) provide uniform circumferential support to the pipe which is essential for the total load factor to be realized.

Consideration could also be given to the use of cementitious slurry mixtures such as lean concrete, Controlled Low Strength Material (CLSM) or Controlled Density Fill (CDF) for bedding and initial backfill around the pipes. In general, we recommend cementitious slurry mixtures have a 28-day compressive strength between 50 and 200 psi.

5.7.7 Filter Fabric Envelope

To reduce the potential for migration of the trench backfill soil into the voids in crushed rock bedding and initial backfill, a non-woven filter fabric should be placed between backfill soils and the underlying crushed rock. Filter fabric should be laid-out over the top of the crushed rock and up the side of the trench at least 1 foot and overlapped according to the manufacturer’s recommendations.

5.8 FOUNDATIONS AND THRUST BLOCKS FOR PIPELINES

Lateral loads may be resisted by a combination of friction between the foundation bottoms and the supporting subgrade, and by passive resistance acting against the vertical faces of the foundations. An allowable coefficient of sliding friction of 0.45 between the foundation and the supporting subgrade may be used for design. For allowable passive resistance, an equivalent fluid weight of 350 pcf acting against the side of the foundation may be used. This value is based on a safety factor of at least 1.5. This value generally corresponds to a lateral deflection of less than about ½-inch. Passive resistance in the upper 12 inches of soil should be neglected unless the area in front of the footing is protected from disturbance by concrete or pavement.

The allowable friction coefficient and passive resistance may be used concurrently.

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5.9 SOIL CORROSION

It is important to note that our scope does not include corrosion engineering and that detailed corrosion test results are not included in this report. A qualified corrosion engineer should be retained to design protective systems that may be required.

5.10 SITE DRAINAGE

Foundation and slab performance depends greatly on how well runoff water drains from the site.

Accordingly, positive drainage should be provided away from the structure toward appropriate drop inlets or other surface drainage devices without ponding. The drainage should be maintained both during construction and over the life span of the project. Landscaping after construction should not promote ponding of water adjacent to the structures.

5.11 GENERAL EARTHWORK

The following presents recommendations for general earthwork criteria. Previous sections should be reviewed for specific or supplemental earthwork recommendations.

5.11.1 Site Stripping

Prior to general site grading, surface vegetation and debris should be removed and disposed of outside the construction limits. Deep stripping may be required where concentrations of organic soils or roots are encountered during site grading. The depth of stripping and/or discing should be determined in the field by a representative of Kleinfelder prior to earthwork. Upon approval of the owner and/or landscape architect, any stripped topsoil (less any debris) may be stockpiled and placed in landscape areas. This material, however, should not be incorporated into any engineered fill.

It is possible that underground utility lines or buried objects will be encountered within the areas of construction. If encountered, these items should be removed and disposed of off-site.

Existing utility pipelines that extend beyond the limits of the proposed construction and will be abandoned in-place should be plugged with cement grout to prevent migration of soil and/or water. All excavations resulting from removal activities should be cleaned of loose or disturbed material and dish-shaped with sides sloped 3:1 (3 horizontal to 1 vertical) or flatter to permit access for compaction equipment.

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5.11.2 Subgrade Preparation

Previous sections discuss specific subgrade preparation recommendations related to the concrete floor slab, equipment pads, and foundations. Where not specifically addressed by these previous sections, all subgrade areas that will receive engineered fill should be scarified to a depth of at least 12 inches, uniformly moisture conditioned to between 1 and 4 percentage points above the optimum moisture content and compacted as engineered fill to at least 90 percent of the maximum dry density as determined by the ASTM D1557 test method.

In-place scarification and compaction may not be adequate to densify all disturbed soil within areas grubbed or otherwise disturbed below a depth of about 6 inches. Therefore, overexcavation of disturbed soil, scarification and compaction of the exposed subgrade, and replacement with engineered fill may be required to sufficiently densify all disturbed soil.

5.11.3 Temporary Excavations

Construction site safety generally is the sole responsibility of the Contractor, who shall also be solely responsible for the means, methods, and sequencing of construction operations. 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). Flatter slopes and/or trench shields may be required if loose, cohesionless soils and/or water are encountered along the slope face. Heavy construction equipment, building materials, excavated soil, and vehicular traffic should not be allowed within a lateral distance equal to one-third the slope height from the top of any excavation. During wet weather, earthen berms or other methods should be used to prevent runoff water from entering all excavations. All runoff water, seepage and/or groundwater encountered within excavations should be collected and disposed of outside the construction limits.

5.11.4 Fill Materials

The existing soils encountered in our borings, minus organics, debris, and/or other deleterious materials, should be suitable for use as engineered fill in the proposed structure areas. All import fill soils should be nearly free of organic or other deleterious debris, essentially non-

20184025.001A/MOD18R78466 Page 21 of 24 May 17, 2018 plastic, and less than 3 inches in maximum dimension. In general, well-graded mixtures of gravel, sand, non-plastic silt, and small quantities of cobbles, rock fragments, and/or clay are acceptable for use as import fill. All imported fill materials to be used for engineered fill should be approved by the project Geotechnical Engineer prior to being transported to the site. General guidelines for import fill are provided in the following table.

Table 5.11.4-1

Import Fill Guidelines

Gradation (ASTM C136)

Sieve Size Percent Passing

3-inch 100

No. 4 50 – 100

No. 200 15 – 70

Plasticity (ASTM D4318)

Liquid Limit Plasticity Index

Less than 30 Less than 12

Organic Content (ASTM D2974)

Less than 3 percent

Trench backfill, or bedding placed outside existing or future right-of-ways could consist of native or imported soil that meets the requirements for fill material provided above. However, in very moist conditions, coarse-grained sand and/or gravel should be avoided for pipe bedding or trench zone backfill unless the material is fully enclosed in a geotextile filter fabric such as Mirafi

140N or an equivalent substitute. In a very moist or saturated condition, fine-grained soil can migrate into the coarse sand or gravel voids and cause “loss of ground” or differential settlement along and/or adjacent to the trenches, thereby leading to pipe joint displacement and pavement distress.

Trench backfill recommendations provided above should be considered minimum requirements only. More stringent material specifications may be required to fulfill bedding requirements for specific types of pipe. The project Civil Engineer should develop these material specifications based on planned pipe types, bedding conditions, and other factors beyond the scope of this study.

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5.11.5 Engineered Fill

All fill soils, either native or imported, required to bring the site to final grade should be compacted as engineered fill. Import fill or native subgrade soil should be uniformly moisture conditioned to between 1 and 4 percentage points above the optimum moisture content, placed in horizontal lifts less than 8 inches in loose thickness, and compacted to at least 90 percent of the maximum dry density as determined by the ASTM D1557 test method. Additional fill lifts should not be placed if the previous lift did not meet the required dry density or if soil conditions are not stable. Discing and/or blending may be required to uniformly moisture condition soils used for engineered fill. The contact between existing soils and engineered fill beneath the building or equipment pads should be no steeper than 4:1 within approximately 3 feet of planned finished subgrade. All trench backfill in building or other structural areas should be placed and compacted in accordance with recommendations provided above for engineered fill.

5.11.6 Wet/Unstable Subgrade Mitigation

If site grading is performed during or following extended periods of rainfall, the moisture content of the near-surface soils may be significantly above optimum. This condition, if encountered, could seriously delay grading by causing an unstable subgrade condition. Typical remedial measures include discing and aerating the soils during dry weather, mixing the soils with dryer materials, removing, and replacing the soils with an approved fill material, stabilization with a geotextile fabric or grid, or mixing the soils with an approved hydrating agent such as a lime or cement product. Our firm should be consulted prior to implementing any remedial measure to observe the unstable subgrade condition and provide site-specific recommendations.

If construction is to proceed during the winter and spring months, one way to reduce the exposure of the pad and potential repairs is to leave the subgrade at least 1 foot above the proposed subgrade elevation, cutting it down immediately before placing the capillary break and floor slab. The cut areas should be proof-rolled at the discretion of the geotechnical engineer to identify whether undercutting of any remaining wet/unstable soils is required. Cut soils can be placed in landscape areas or disced and aerated (dried) during dry weather for placement in pavement, future pad, or other areas.

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6 ADDITIONAL SERVICES

6.1 PLANS AND SPECIFICATIONS REVIEW

It is recommended Kleinfelder conduct a general review of plans and specifications to evaluate that the earthwork and foundation recommendations have been properly interpreted and implemented during design. In the event Kleinfelder is not retained to perform this recommended review, no responsibility will be assumed for misinterpretation of the

6.2 CONSTRUCTION OBSERVATION AND TESTING

It is recommended that all earthwork during construction be monitored by a representative from

Kleinfelder, including site preparation, placement of all engineered fill and trench backfill, construction of slab and pavement subgrades, and all foundation excavations. The purpose of these services would be to provide Kleinfelder the opportunity to observe the soil conditions encountered during construction, evaluate the applicability of the recommendations presented in this report to the soil conditions encountered, and recommend appropriate changes in design or construction procedures if…