Attachment 4 - 20220404_2020-1204 Mather (612-163) 100_ CD Specs - Volume 1 (04-04-2024).pdf

Project Manual for

VISN 21

DESIGN SOCIAL WORK

AND

EXPAND CLINICAL SPACE

3551 FEMOYER STREET

MATHER, CALIFORNIA 95655

CONSTRUCTION DOCUMENT SUBMISSION

December 4, 2020

VOLUME 1

DENISE GROVES, NETWORK CONTRACTING OFFICER (NCO 21)

CONSTRUCTION TEAM II

3801 MIRANDA AVENUE

PALO ALTO, CA 94304

Project Number – 612‐163 Contract Number – VA261‐17‐C‐0044

Romanyk Consulting Corp. Copyright © 2016

PRIVILEGED AND CONFIDENTIAL PROPRIETARY INFORMATION

Design Social Work and Expand Clinical Space Mather, CA December 04, 2020

Project Number 612-163

SECTION 00 00 00

SEALS PAGE

ROMANYK CONSULTING

REBECCA OLSON, AIA

ILLINOIS LICENSE NO.

001.011034

IMEG

CALIBRE

00 00 00 - 1

GEOTECHNICAL INVESTIGATION REPORT

MATHER SOCIAL WORK BUILDING

PETER A. MCCUEN BLVD. AND FEMOYER ST.

MATHER, CALIFORNIA

KLEINFELDER PROJECT # 20181864.001A

OCTOBER 2, 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.

20181864.001A/SAC18R85032 Page i of iv October 2, 2018 © 2018 Kleinfelder

20181864.001A/SAC18R85032

Page ii of v October 2, 2018

October 2, 2018 Project No. 20181864.001A

Mr. Gary Clough Romanyk Consulting Corp.

3308 Preston Road, Suite 350-164 Plano, Texas 75093

Subject: Geotechnical Investigation Report Mather Social Work Building Peter A. McCuen Boulevard and Femoyer Street Mather, California

Dear Mr. Clough:

This report presents the results of Kleinfelder’s geotechnical investigation for the proposed Mather

Social Work Building located at the southeast corner of Peter A. McCuen Boulevard and Femoyer

Street in Mather, California. The purpose of our investigation was to explore and evaluate the subsurface conditions at the site in order to develop geotechnical engineering conclusions and recommendations for project design and construction.

It is Kleinfelder’s professional opinion that construction for the proposed project is geotechnically feasible using conventional earthmoving equipment and shallow spread foundation systems with an allowable bearing pressure of 3,000 psf, provided settlement tolerances and specific grading recommendations can be incorporated into the design. Recommendations for design of foundations, site grading, pavements, and other geotechnical considerations are presented in this report. The recommendations presented in this report should be incorporated into project design and construction. We identified the following key geotechnical considerations/recommendations during our study.

• Soft and potentially compressible layers of clay were encountered across the site up to a depth of 5 feet. Therefore, Kleinfelder recommends overexcvataion to a depth of 5 beneath all footings and extending at least 2 feet beyond the edge of all footings. The overexcavated materials can be re-used, and should be compacted to the requirements presented in the attached report.

• Cobbles were encountered during the field exploration; the Contractor should anticipate and provide construction equipment capable of working with cobbles, boulders, and cemented soils.

Page iii of v October 2, 2018

• In general, near-surface, on-site soils similar to those encountered in our borings meet the requirements specified for non-expansive engineered fill. Medium plasticity clay soils may also be encountered below a depth of approximately 3 feet, and these soils would not meet the criteria for non-expansive engineered fill.

We appreciate the opportunity of serving you on this project and look forward to discussing our report with you should there be any questions concerning our data or findings. Please feel free to contact our office at (916) 366-1701.

Respectfully submitted, KLEINFELDER, INC.

Hadi Fattal, EIT Staff Engineer

Don Adams, PE Project Manager

Rebecca L. Money, PE, GE Principal Geotechnical Engineer

Page iv of v October 2, 2018

TABLE OF CONTENTS

Section Page

1 INTRODUCTION

1.1 GENERAL

1.2 PROJECT DESCRIPTION

1.3 PURPOSE AND SCOPE

2 FIELD EXPLORATION AND LABORATORY TESTING

2.1 FIELD EXPLORATION

2.2 LABORATORY TESTING

2.3 CORROSION TESTING

3 SITE AND SUBSURFACE CONDITIONS

3.1 SITE CONDITIONS

3.2 REGIONAL AND LOCAL GEOLOGY

3.2.1 Area and Site Geology

3.2.2 Faulting and Seismicity

3.3 SUBSURFACE CONDITIONS

3.4 GROUNDWATER CONDITIONS

4 CONCLUSIONS AND RECOMMENDATIONS

4.1 GENERAL

4.2 SEISMIC DESIGN

4.2.1 2016 CBC Seismic Design Parameters

4.2.2 Seismically Induced Settlement

4.3 SITE PREPARATION

4.3.1 Site Preparation, Stripping, and Grubbing

4.3.2 Excavation Characteristics

4.3.3 Scarification and Compaction

4.3.4 Overexcavation at Foundations

4.4 WET WEATHER CONSTRUCTION/UNSTABLE SOIL CONDITIONS

4.5 TEMPORARY EXCAVATIONS

4.6 ENGINEERED FILL

4.6.1 Compaction Criteria

4.7 TRENCH BACKFILL

4.7.1 Subgrade Preparation

4.7.2 Materials

4.7.3 Compaction Criteria

4.8 SPREAD FOUNDATION RECOMMENDATIONS

4.8.1 Allowable Bearing Pressures

4.8.2 Lateral Resistance

4.8.3 Settlement

4.8.4 Construction Considerations

4.9 RETAINING WALLS

4.9.1 Lateral Earth Pressures

4.9.2 Seismic Earth Pressure

4.9.3 Wall Drainage

4.9.4 Backfill Placement

4.9.5 Construction Considerations

4.10 INTERIOR CONCRETE SLABS SUPPORTED-ON-GRADE

4.10.1 Subgrade Preparation

4.10.2 Rock Capillary Break

4.10.3 Interior Concrete Slabs-On-Grade Construction Considerations

4.11 MOISTURE PROTECTION

4.12 EXTERIOR CONCRETE SLABS SUPPORTED-ON-GRADE

4.12.1 Subgrade Preparation

4.13 PAVEMENTS

4.13.1 General

4.13.2 Asphalt Concrete Pavements

4.13.3 Portland Cement Concrete Pavement Sections

4.13.4 Unstable Subgrade

4.13.5 Variations in Subgrade Materials

4.14 SOLUBLE SULFATES AND CORROSIVE SOILS

5 ADDITIONAL SERVICES

6 LIMITATIONS

7 REFERENCES

FIGURES

1 Site Vicinity Map 2 Boring Location Map

APPENDICES

A Exploratory Borings B Laboratory Testing

C Laboratory Testing by Others

20181864.001A/SAC18R85032 Page v of v October 2, 2018

Page 1 of 36 October 2, 2018

1 INTRODUCTION

1.1 GENERAL

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

Social Work Building to be located at the southeast corner of Peter A. McCuen Boulevard and

Femoyer Street in Mather, California. The purpose of this investigation was to evaluate the subsurface conditions at the site and develop geotechnical engineering recommendations to aid in project design and construction. This report includes conclusions and 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 locations of our explorations. Recommendations presented herein should not be extrapolated to other areas or used for other projects without our prior review.

1.2 PROJECT DESCRIPTION

Kleinfelder understands the proposed project consists of the construction of a new two-story, 14,540 square-foot social services building for the VA Northern California Health Care System in

Mather, California. Additional site improvements will include the installation of underground utilities, construction of parking lot pavements, concrete flatwork, site lighting and landscaping.

We anticipate the building will be supported on shallow, reinforced concrete spread foundations with concrete slab-on-grade floors with column loads between 100 and 200 kips.

Grading plans were not available for our review at the time this report was prepared. However, we anticipate site earthwork will consist of cuts and fills of about one to three feet in vertical extent.

1.3 PURPOSE AND SCOPE

The purpose and scope of our study was outlined in the task order dated August 29, 2017 and included the following:

• Review provided geotechnical reports and as-built information.

• Perform utility clearance tasks

Page 2 of 36 October 2, 2018

• Drill 3 borings to a depth of 30 feet, or practical refusal, with a truck mounted drill rig using hollow stem augers. Obtain samples and log borings. Backfill borings with lean cement.

Note that as the project developed, the scope was revised and approved to drill 2 borings to a target depth of 30 feet and 2 borings to a target depth of 5 feet.

• Containerize excess cuttings in drums and dispose of them off-site, assuming soil is nonhazardous. Note that based on the final location of the project, the soil cuttings were approved to be spread on site.

• Perform Laboratory Testing

• Provide this geotechnical report

Our scope of services did not include the assessment of site environmental characteristics, particularly those involving hazardous substances.

Page 3 of 36 October 2, 2018

2 FIELD EXPLORATION AND LABORATORY TESTING

2.1 FIELD EXPLORATION

Four exploratory borings were advanced at the site on July 27, 2018 by Taber Drilling of West

Sacramento, California. The soil borings (B-1 through B-4) were advanced using four-inch diameter, solid-stem augers to depths between about 13 and 23½ feet below existing site grades.

The approximate locations of the borings are shown on Figure 2.

Prior to subsurface exploration, Underground Service Alert (USA) was contacted to provide utility clearance, as required by law. In addition, a private utility locator was retained to confirm that the boring locations were not in conflict with known underground utilities.

A Kleinfelder engineer supervised the field operations and maintained a log of each boring. The soils encountered in the borings were visually classified in the field in general accordance with

ASTM D2487. Logs of the borings are presented in Appendix A. Samples were obtained from the borings by driving a 2.5-inch inside diameter (I.D.), split-barrel, “California” type sampler containing stainless steel liners into undisturbed soil with a 140-pound automatic hammer free-falling a distance of 30 inches. The California sampler is in general conformance with ASTM

D3550. In addition, a 1.4-inch I.D. Standard Penetration Test (SPT) sampler was driven in general accordance with ASTM D1586 test procedures. The SPT sampler was used without liners. Soil samples may have experienced some disturbance due to hammer impact, retrieval, and handling.

The blow counts were documented for each 6-inch interval for a total of 18 inches per sample, unless otherwise noted. The apparent density and consistency terminology used in the soil descriptions are based on sampler blow counts and field observations, respectively (see Figure

A-1). Soil samples were collected in 6-inch long stainless-steel tubes within the California Sampler and were capped in the field to reduce moisture loss and disturbance. Disturbed samples (e.g.

SPT) were placed in plastic bags and sealed. Bulk samples were collected of near surface soils at relatively continuous intervals from auger cuttings. All samples were returned to the Kleinfelder

Sacramento laboratory and select samples were subjected to further evaluation and testing.

Following completion of the exploratory drilling, boreholes were backfilled with soil cuttings.

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2.2 LABORATORY TESTING

Laboratory testing was performed on select soil samples recovered from the borings to assist in soil classification and to evaluate engineering parameters for foundation design. The testing program developed by Kleinfelder included sieve analyses, Atterberg limits, R-value, Triaxial compression (TXUU), as well as corrosion testing (see Section 2.3). Most of the laboratory test results are summarized on the boring logs in Appendix A. Results of the individual tests are included in in Appendix B.

2.3 CORROSION TESTING

Two soil samples were submitted to Sunland Analytical of Rancho Cordova, California to perform laboratory tests to evaluate corrosion potential. Tests included pH, electrical resistivity, soluble sulfates, and chlorides. Results of soil corrosion potential testing are discussed in Section 4.13, Soil Corrosivity, and laboratory test results are provided in Appendix C. The soil corrosivity test results may be used by a qualified corrosion engineer in designing an appropriate corrosion control plan for the project.

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3 SITE AND SUBSURFACE CONDITIONS

3.1 SITE CONDITIONS

The proposed building is located in a relatively flat area near the intersection of Femoyer Street and Peter A. McCuen Boulevard (see Figure 1). The project site is bordered by Femoyer Street to the west and undeveloped property to the east, north and south. At the time of our field explorations, the surface conditions at the site were relatively level and vegetation consisted of dry seasonal grasses.

3.2 REGIONAL AND LOCAL GEOLOGY

The Mather area is situated within the southeastern portion of the Sacramento Valley, which is part of the Great Valley geomorphic province of California. The Great Valley province is a large northwestward trending, asymmetric structural trough that has been filled with as much as six vertical miles of sediment. The valley trough is situated between the Sierra Nevada Mountains to the east, the Coast Range Mountains to the west, Klamath Mountains to the north, and the

Cascade Range to the northeast. The Sierra Nevada and Coast Range mountain ranges were initially formed by uplift that occurred during the Jurassic (about 146 to 199 million years) and

Cretaceous (about 65 to 146 million years) periods. Renewed uplift began in the Sierra Nevada during late Tertiary period and continues to this day. The deepest and oldest sediments that occupy the structural trough are marine sediments deposited before the uplift of the Coast Range

Mountains. A mix of marine and continental deposits formed over these older units as seas advanced and retreated in the Sacramento and San Joaquin Valleys. The upper and youngest sediments in the valley are continental deposits consisting of alluvial fan deposits and flood basin, natural levees, stream channel, terrace, lake, and marsh deposits. The general geologic framework of the Sacramento Valley is described and illustrated in studies by Helley and Harwood

(1985) and others.

The Sacramento Valley comprises the northern portion of the 400-mile long, 50-mile wide Great

Valley alluvial plain. Prior to construction of modern flood control features (e.g., dams, levees), the Sacramento River and its major tributaries were confined mostly by natural levees, which are low ridges of sandy and silty sediment deposited during above flood-stage conditions. When the river and its tributaries flooded their natural levees, higher-energy sediment was deposited in the

Page 6 of 36 October 2, 2018 adjacent areas along the river channel while fine-grained sediments were deposited in lower-energy environments (e.g., topographically-lower flood basins, abandoned river channels) father from the river channel, resulting in highly variable deposits.

The western and eastern margins of the valley area bordered by Coast Range and Sierra Nevada derived alluvial fans. These fans are highly variable and stratigraphically complex. The

Sacramento River and its major tributaries traverse the Sacramento Valley floor between these two fans, flowing south/southwest from the Klamath Mountains in the north to the Sacramento-

San Joaquin Delta and San Francisco Bay.

3.2.1 Area and Site Geology

The surficial geologic deposits in the project area have been mapped and complied by Gutierrez

(2011), Helley (1979), and Helley and Harwood (1985), who differentiated the Quaternary deposits into Pleistocene (between 2.6 million and 11,700 years old) and Holocene (11,700 years old to modern [USGS, 2010]) ages and also into type of alluvial deposit. These geologic maps generally agree that the project site is underlain by middle to late Pleistocene alluvial deposits.

The alluvial deposits were generated through the erosion of bedrock units from the Sierra Nevada

Mountains and transported westward to the project area by the American River and other prominent creeks/sloughs emerging from the Sierra Nevada and converging with the Sacramento

River. These alluvial sediments located to the east of the Sacramento River channel are mainly comprised of the Modesto (late Pleistocene to early Holocene) and Riverbank (Pleistocene) formations, along with other young Holocene deposits. The Modesto formation is the youngest unit and it consists of tan and light-gray gravelly sand, silt, and clay. The Riverbank formation is older than the Modesto and it consists generally of weathered reddish gravel, sand, and silt.

Based on mapping by Gutierrez et al. (2011), the project site is underlain by the middle to late

Pleistocene age Riverbank formation which is described as arkosic alluvium, with sand and silt, forming alluvial terraces, and dissected alluvial fans along streams on the southeast side of the

Sacramento Valley. Helley and Harwood (1985) describe the Riverbank in the project area as unconsolidated but compact, dark-brown to red alluvium composed of gravel, sand, silt and with minor clay.

Page 7 of 36 October 2, 2018

3.2.2 Faulting and Seismicity

The project lies in an area with few mapped faults. An active fault is a fault that has experienced seismic activity during historic time (since roughly 1800) or exhibits evidence of surface displacement during Holocene time (California Geological Survey [CGS], 2018). The definition of

“potentially active” varies. A generally accepted definition of “potentially active” is a fault showing evidence of displacement that is older than 11,800 years (Holocene age [USGS, 2010]) and younger than 2.6 million years (Pleistocene age). However, “potentially active” is no longer used as a criterion for zoning by the CGS. The terms “sufficiently active” and “well-defined” are now used by the CGS as criteria for zoning faults under the Alquist-Priolo Earthquake Fault Zoning

Act. A “sufficiently active fault” is a fault that shows evidence of Holocene surface displacement along one or more of its segments and branches, while a “well-defined fault” is a fault whose trace is clearly detectable by a trained geologist as a physical feature at or just below the ground surface. The definition “inactive” generally implies that a fault has not been active since the beginning of the Pleistocene Epoch (older than 2.6 million years).

Based on the data provided by CGS (2000 and 2018), the project area is not located within an

Alquist-Priolo Earthquake Fault Zone (AP Zone) established by the CGS around active fault traces. The nearest zoned fault is the West Tahoe-Dollar Point fault located approximately 113 kilometers northeast of the project site (Jennings et al., 2010).

Some significant regional faults include the Foothills Fault System to the northeast and the Great

Valley Fault System to the west. These faults are not zoned by the CGS. However, the Great

Valley fault has been the source of the recent earthquakes, most notably, the magnitude 6.5 1983

Coalinga Earthquake and the magnitude 6.1 Kettleman Hills earthquake.

3.3 SUBSURFACE CONDITIONS

Borings were explored to depths ranging between about 13 and 23 ½ feet below the ground surface. Near surface soil consisted of alternating layers of silt, silty sand, sand, and gravel in the upper 2 to 4½ feet. A soft, potentially compressible layer of lean clay was encountered in Borings

B-1 and B-4 to depth of approximately 5 feet. Below these near-surface soils, all borings generally encountered a medium stiff to very stiff lean clay extending to depths ranging from about 8 to 13 feet. Very dense gravels were encountered below the clay layer in Borings B-2 and B-3 to the maximum depth explored of 23½ feet. Although not visible in our explorations, the gravel layers

Page 8 of 36 October 2, 2018 normally contain abundant cobbles. There is a potential for cobbles up to 12 inches in maximum dimension to be encountered in the gravel units based on our experience in the project area.

3.4 GROUNDWATER CONDITIONS

Permanent groundwater was not encountered in our subsurface explorations at the site.

According to the State of California Department of Water Resources Water Library, recent regional permanent groundwater levels at the project site vary from approximately 70 feet to 80 feet below grade. It should be noted that groundwater and soil moisture conditions within the area will vary depending on rainfall, irrigation practices, and/or runoff conditions not apparent at the time of our field investigation. It is common for seasonal seepage to develop at the interface between the surficial soils and the denser/less permeable soils at depth.

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4 CONCLUSIONS AND RECOMMENDATIONS

4.1 GENERAL

From a geotechnical standpoint, the proposed construction is considered feasible provided the recommendations presented in this report are incorporated into the project design and construction. Soft, potentially compressible soils were encountered to depths of approximately 5 feet which will require overexcavation during construction of the footings described in Section

4.3.4. The following sections discuss conclusions and recommendations with respect to geotechnical design of the project.

4.2 SEISMIC DESIGN

4.2.1 2016 CBC Seismic Design Parameters

The site is located at latitude 38.5726 degrees North and longitude -121.29119 degrees West.

Based on the subsurface conditions encountered, a Site Class D should be used in seismic evaluations at the site following the requirements of Chapter 20 of ASCE 7-10.

Using the above information, Kleinfelder estimated code-based seismic design parameters consistent with the 2016 CBC using the U.S. Geological Survey (USGS) web-based application

(available at http://geohazards.usgs.gov/designmaps/us/application.php). These design parameters are presented in Table 1, below and include the Risk-Targeted Maximum Considered

Earthquake (MCER) mapped spectral accelerations for periods of 0.2 and 1 second (e.g. SS and

S1), mapped peak ground acceleration (PGA) for Geometric Mean Maximum Considered

Earthquake (MCEG), and the mapped long-period transition period (TL) as well as associated soil amplification factors (Fa and Fv), and corresponding site modified (SMS and SM1) and design spectral accelerations (SDS and SD1). Based on these values a Seismic Design Category of D should be used for design at this site.

http://geohazards.usgs.gov/designmaps/us/application.php)

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TABLE 4.1

2016 CBC Seismic Design Parameters

Parameter Value Reference

SS 0.546 2016 CBC Section 1613A.3.1

S1 0.261g 2016 CBC Section 1613A.3.1

Site Class D ASCE 7-10 Chapter 20

Fa 1.363 2016 CBC Table 1613A.3.3(1)

Fv 1.879 2016 CBC Table 1613A.3.3(2)

SMS 0.744g 2016 CBC Section 1613A.3.3

SM1 0.489g 2016 CBC Section 1613A.3.3

SDS 0.496g 2016 CBC Section 1613A.4.4

SD1 0.336g 2016 CBC Section 1613A.4.4

Seismic Design Category D 2016 CBC Tables 1613A.3.5 (1) and (2)

PGA 0.178 ASCE 7-10 Figure 22-7

FPGA 1.443 ASCE 7-10 Table 11.8-1

PGAM 0.257g ASCE 7-10 Section 11.8.3

CRS 1.154 ASCE 7-10 Figure 22-17

CR1 1.141 ASCE 7-10 Figure 22-18

TL 12 sec. ASCE 7-10, Figure 22-12

4.2.2 Seismically Induced Settlement

A common secondary hazard of strong ground shaking is the potential for soil liquefaction or seismically induced dynamic settlement of the subsurface soils. Based on the depth to groundwater, age of the deposits, sampler blow counts, as well as the relatively low peak ground acceleration (PGA) expected at the site, liquefaction nor dynamic settlement should not pose a significant risk to the proposed structures.

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4.3 SITE PREPARATION

4.3.1 Site Preparation, Stripping, and Grubbing

Site preparation should include the stripping and removal of existing vegetation, abandoned underground utilities, debris, loose, soft, or saturated materials, and other deleterious materials from the areas to be graded. We estimate the depth of stripping to be approximately 1 to 3 inches over the majority of the site. Deeper stripping or grubbing may be required where existing structures, pipes, concentrations of organic soils or tree roots are encountered during site grading.

Stripped topsoil (minus any debris) may be stockpiled and reused for landscape purposes.

However, this material should not be incorporated into any engineered fill.

After site clearing, we recommend over-excavation be conducted within the footing lines and proposed foundations by excavating the soil to a depth of approximately 5 feet below current site grade. The over-excavation should extend laterally a minimum of 2 feet on all sides of the foundations. The bottom of the excavation should be scarified and recompacted, and backfilled with moisture conditioned and compacted native soils.

We recommend that any existing utilities within the footprint of the proposed building be removed or rerouted.

All excavations resulting from removal activities should be cleaned of loose or disturbed material

(including all previously-placed backfill) and dish-shaped (with sides sloped 3(h):1(v) or flatter) to permit access for compaction equipment. These excavations should be cleaned of loose or disturbed material and should be backfilled with engineered fill placed and compacted under observation by the Geotechnical Engineer as recommended in the original report and in the project plans and specifications.

4.3.2 Excavation Characteristics

The borings drilled at the site were advanced using a truck-mounted, solid-flight auger drill rig.

Drilling was completed with easy to moderate effort through the fill and native soil deposits.

Conventional earth moving equipment equipped for excavation in dense gravels with cobbles should be capable of performing the excavations required for the proposed project. Although not encountered in our explorations, cobbles may be present and range from about 3 to 12 inches in

Page 12 of 36 October 2, 2018 maximum dimension. Very few small boulders up to about 22 inches in maximum dimension may also be present in the gravel units.

4.3.3 Scarification and Compaction

Following site stripping and any required grubbing and/or removals, we recommend all areas to receive engineered fill or to be used for the future support of structures or concrete slabs supported-on-grade be scarified to a depth of 8 inches, uniformly moisture-conditioned and compacted as follows:

• Clay subgrades should be moisture conditioned to a minimum of two percentage points above the optimum moisture content and compacted to between 88 and 92 percent of the maximum dry density as determined by ASTM Test Method D1557

• Non expansive soil subgrades should be moisture conditioned to a minimum of the optimum moisture content and compacted to a minimum of 90 percent of the maximum dry density as determined by ASTM D1557.

The upper twelve inches of pavement subgrades should be compacted to at least 95 percent relative compaction. The adequacy of compacted fill should be based on the material being properly mixed, uniformly moisture conditioned, and stable under construction equipment. If any of these criteria are not met, the fill material may not be acceptable.

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 8 inches. Therefore, over-excavation of disturbed soil, scarification and compaction of the exposed subgrade, and replacement with engineered fill may be required to sufficiently densify all disturbed soil.

4.3.4 Overexcavation at Foundations

The bottom of the foundation excavations for the proposed structure should be over-excavated to a depth of 5 feet plus 2 feet minimum on either side of the footing, or as directed by the

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

Page 13 of 36 October 2, 2018

Geotechnical Engineer during construction. The bottom of the excavation should be scarified and recompacted. The excavation should be backfilled with native soil or engineered fill in lifts

The proposed foundations may be founded on existing soils that are scarified to a depth of at least 8 inches, uniformly moisture conditioned to at least 2 percent above the optimum moisture content and be compacted to at least 90 percent relative compaction, based on ASTM D1557.

4.4 WET WEATHER CONSTRUCTION/UNSTABLE SOIL CONDITIONS

Should grading be performed during or following extended periods of rainfall, the moisture content of the near-surface soils may be significantly above the optimum moisture content. Additionally, it is common to encounter wet, unstable soils upon removal of site pavements or flatwork as a result of subsurface moisture becoming trapped beneath relatively impervious asphalt concrete or portland cement concrete surfaces. These conditions could seriously impede grading by causing an unstable subgrade condition. Typical remedial measures include the following:

• Aerate – Drying the unstable subgrade would involve disking or ripping the wet subgrade to a depth of approximately 24 inches and allowing the exposed soil to dry. Multiple passes of the equipment (likely on a daily basis) will be needed because as the surface of the soil dries, a crust forms that reduces further evaporation. Frequent disking will help prevent the formation of a crust and will promote drying. This process could take several days to several weeks depending on the nature of the material, the depth of ripping, the number of passes, and the weather.

• Remove & Replace plus Geotextile Fabric – The subgrade could be over-excavated 12 to

24 inches below existing grade and be replaced with aggregate base or coarse gravel underlain by woven geotextile such as Mirafi 500X or approved equal. The final depth of removal will depend upon field conditions exposed once the over-excavation begins. The geotextile fabric should be placed in accordance with the manufacturer’s recommendations.

• Lime Treat – The unstable subgrade could be stabilized by mixing the upper 12 to 18 inches of the subgrade with lime. For estimating purposes, lime application rates of 4 percent for high calcium quick lime may be used. Final application rates should be determined in the field at the time of construction in consultation with the project geotechnical engineer. Lime treatment should be performed by a specialty contractor

Page 14 of 36 October 2, 2018 experienced in this work and should be performed in accordance with Caltrans Standard

Specifications. Lime treated areas will have a high pH level (pH over 10) that will need to be removed from landscape areas. As runoff from lime treated soils will also have an elevated pH level, the use of lime should be addressed by the project Storm Water

Pollution Prevention Plan (SWPP).

The above recommendations are intended to stabilize unstable subgrades. If deeper earthwork activities (i.e. over-excavations and trenching) are planned during adverse weather conditions, additional measures may be necessary. In addition, material removed from over-excavations and trenches may be at a high moisture content and require stabilization prior to reuse as backfill.

Kleinfelder should be consulted prior to implementing any remedial measure to observe the unstable subgrade condition and provide site specific recommendations.

4.5 TEMPORARY EXCAVATIONS

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 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.

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. Flatter slopes and/or trench shields may be required if loose, cohesionless soils and/or water are encountered along the slope face.

Excavations for utility trenches are anticipated to be possible using conventional rubber-tired backhoes. However, some difficulty in excavating will probably be encountered in the variably cemented onsite soils. Any excavation may become unstable and should be evaluated to monitor stability prior to personnel entering the trenches. Shoring or sloping of any trench wall may be necessary to protect personnel and to provide stability.

Page 15 of 36 October 2, 2018

Heavy construction equipment, building materials, excavated soil, and vehicular traffic should not be allowed within 1/3 the slope height from the top of any excavation. Where the stability of adjoining buildings, walls, or other structures is 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. 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 runoff water from entering all excavations. All runoff water and/or groundwater encountered within the excavations should be collected and disposed of outside the construction limits.

4.6 ENGINEERED FILL

All engineered fill soils should be nearly free of organic materials, debris, or other deleterious materials, essentially non-plastic, and have a maximum particle size less than 6 inches in maximum dimension. Trench backfill should have a maximum particle size less than 3 inches. In general, well-graded mixtures of gravel, sand, non-plastic silt, and small quantities of clay are acceptable for use as non-expansive engineered fill. Specific requirements for non-expansive engineered fill (onsite or imported), as well as applicable test procedures to verify material suitability are provided in Table 4.2.

TABLE 4.2

Non-Expansive Engineered Fill Requirements

Fill Requirement Test Procedures

Gradation ASTM1 Caltrans2

Sieve Size Percent Passing

6 inch3 100 C136 202

3/4 inch 70-100 C136 202

No. 4 50-100 C136 202

No. 200 5-70 C136 202

Plasticity

Liquid Limit Plasticity Index

<30 <12 D4318 204

Organic Content

Less than 3% D2974 ---

Expansion Index

Less than 20 --- D4829 ---

Page 16 of 36 October 2, 2018

TABLE 4.2

Non-Expansive Engineered Fill Requirements (Cont.)

Fill Requirement Test Procedures

Corrosion Potential

Soluble Sulfates <1000 ppm -- 417

Soluble Chlorides <200 ppm -- 422

Minimum Resistivity >1000 ohm-cm --- 643 1ASTM International Standards (latest edition) 2State of California, Department of Transportation, Standard Test Methods (latest edition) 3Trench backfill should have a maximum particle size of 3 inches.

In general, near-surface, on-site soils similar to those encountered in our borings meet the requirements indicated above for non-expansive engineered fill. Medium plasticity clay soils may also be encountered below a depth of approximately 3 feet, and these soils would not meet the above criteria for non-expansive engineered fill. These soils can be used for backfills beside foundations and in utility trenches provided they are adequately moisture-conditioned during placement (see section below entitled Compaction Criteria). These soils should not be used under foundations.

All imported fill materials to be used for engineered fill should be sampled and tested by the project

Geotechnical Engineer prior to being transported to the site. All onsite fill materials to be used for non-expansive engineered fill should be sampled and tested by the project Geotechnical Engineer prior to use.

4.6.1 Compaction Criteria

Non-expansive soils used for engineered fill should be uniformly moisture-conditioned to a minimum of 1 percent above the optimum moisture content, placed in horizontal lifts no more than

8 inches in loose thickness, and compacted to at least 90 percent relative compaction.

Where used for general engineered fill or trench backfill outside of foundation areas, on-site clay soils should be adequately processed, and uniformly moisture-conditioned to a minimum of 2 percent above the optimum moisture content, placed in horizontal lifts less than 8 inches in loose thickness, and compacted to between 88 and 92 percent relative compaction. On site sands and gravels should be uniformly moisture-conditioned to a minimum of 1 percent above the optimum moisture content, placed in horizontal lifts no more than 8 inches in loose thickness, and compacted to at least 90 percent relative compaction.

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4.7 TRENCH BACKFILL

The materials encountered in the borings generally appear suitable for trench backfill, except for coarse-grained gravelly soils containing cobbles. Any gravelly soils to be used for trench backfill fill should be processed to remove particles over 3 inches in maximum dimension. If soft or unstable trench bottoms are encountered, these areas may require removal and replacement with additional bedding material.

4.7.1 Subgrade Preparation

Prior to placement of utility bedding, the exposed subgrade at the base of the trench excavations should be examined to detect soft, loose, or unstable areas. Loose materials at trench bottoms resulting from excavation disturbance should be removed to firm material. If soft or unstable areas are encountered, these areas should be over-excavated to a depth of at least 1 foot, or to a firm base, and be replaced with additional bedding material. Where excavations cross existing trench backfill materials, the need for and extent of over-excavation or stabilization measures should be evaluated by the Geotechnical Engineer on an individual basis.

4.7.2 Materials

Trench zone backfill (i.e., material placed between the utility and finished subgrade) should consist of native material or imported soil with a maximum particle size of less than one inch in maximum dimension. Trench zone backfill (i.e., material placed between the pipe zone backfill and finished subgrade) may consist of native or imported soil which meets the requirements provided in the ENGINEERED FILL sections of this report.

If import material is used for pipe zone backfill, we recommend it consist of compacted washed sand, Caltrans Class 2 aggregate base material, or clean crushed rock. If the on-site clay is used for pipe zone backfill, lateral support for the pipes will be reduced. Due to the potential for soil migration into the relatively large void spaces present in clean gravel materials, these materials should be completely surrounded by a non-woven filter fabric such as Mirafi 140N or approved equal. Recommendations provided above for pipe zone backfill are minimum requirements only.

More stringent material specifications may be required to fulfill local codes and/or bedding requirements for specific types of pipes. We recommend the project Civil Engineer develop these material specifications based on planned pipe types, bedding conditions, and other factors beyond the scope of this study.

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Where utility trenches pass beneath perimeter building foundations, a trench plug should be provided to prevent water from entering beneath the building through relatively permeable trench backfill materials. The trench plug may consist of a zone of lean concrete beneath the footing that completely surrounds the utility and engages the trench wall soils. The plug should be at least

12 inches in thickness.

4.7.3 Compaction Criteria

All trench backfill should be placed and compacted in accordance with recommendations provided above for engineered fill. Within pavement areas, trench backfill should be compacted as recommended above for pavement subgrades. Mechanical compaction is recommended.

Ponding or jetting should be avoided, especially in areas supporting structural loads or beneath concrete slabs supported-on-grade, pavements, or other improvements.

4.8 SPREAD FOUNDATION RECOMMENDATIONS

4.8.1 Allowable Bearing Pressures

The foundations should satisfy two independent criteria with respect to foundation soils. First, the foundation should have an adequate safety factor against bearing failure with respect to the shear strength of the foundation soils. Second, the vertical movements of the foundation due to settlement (both immediate elastic settlement and consolidation settlement) should be within tolerable limits for the structure. Based on the criteria and loads anticipated for the proposed building, we recommend it be supported on shallow spread footings.

Reinforced concrete spread foundations may be supported on firm native soils or engineered fill.

As discussed above in Section 4.3.4, footing lines should be overexcavated 5 feet below existing grade and recompacted with engineered fill to the appropriate footing depth. For this structure, perimeter spread footings should be continuous. They should also be a minimum of 12 inches wide and embedded a minimum of 18 inches below the lowest final adjacent subgrade . Interior column or wall foundations may be continuous or isolated. Isolated footings should be a minimum

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

Page 19 of 36 October 2, 2018 of 24 inches wide and embedded a minimum of 18 inches below the lowest adjacent building pad subgrade. This does not include gravel courses or slabs-on-grade that are placed on the building pad subgrade.

An allowable bearing pressure of 3,000 pounds per square foot (psf) may be used for design of spread foundations with the above minimum dimensions. The allowable bearing pressure provided above is a net value. Therefore, the weight of the foundation (that extends below grade) may be neglected when computing footing contact pressures. The allowable bearing pressure applies to dead plus live loads, includes a calculated factor of safety of at least 2, and may be increased by ⅓ for short-term loading due to wind or seismic forces.

4.8.1.1 Subgrade Modulus

A modulus of subgrade reaction, KV1 = 150 pounds per cubic inch (based on a one square foot bearing plate) can be used for slab subgrades prepared as recommended in this report. The subgrade modulus is applicable for consideration of static loads with subgrade deformations within an elastic range. The subgrade modulus should be adjusted for the actual slab size using appropriate formulas or software.

4.8.2 Lateral Resistance

Resistance to lateral loads (including those due to wind or seismic forces) may be provided by frictional resistance between the bottom of concrete foundations and the underlying soils, and by passive soil pressure against the sides of the foundations. An allowable coefficient of sliding friction of 0.30 may be used between cast-in-place concrete foundations and the underlying soil.

Allowable passive pressure in engineered fill or undisturbed native soil may be taken as equivalent to the pressure exerted by a fluid weighing 345 pounds per cubic foot (pcf). Passive pressure should be neglected in the top 12 inches of soil unless confined by slabs or pavements.

This value was derived with a factor of safety of about 1.5 and generally corresponds with a lateral deflection of about ½ inch. Passive resistance and sliding friction may be combined provided that the sliding friction component is reduced by 50 percent.

4.8.3 Settlement

Total settlement of an individual foundation will vary depending on the plan dimensions of the foundation and the actual load supported. Based on our field exploration, as well as pertinent

Page 20 of 36 October 2, 2018 experience in the area, we anticipate settlement to be less than ¾ of an inch. We anticipate these total settlements will be reduced to less than about ½ inch if the shallow foundations are founded on native soil or on engineered fill placed on native soil as recommended in this report. Settlement of all foundations is expected to occur rapidly and should be essentially complete shortly after initial application of the loads.

Foundation settlement and bearing capacity should be checked once the structure loads and final configuration are available.

4.8.4 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 to verify the recommendations contained herein are implemented during construction.

Footings may experience an overall loss in bearing capacity or an increased potential to settle where located in close proximity to existing or future utility trenches. Furthermore, stresses imposed by the footings on the utility lines may cause cracking, collapse and/or a loss of serviceability. To reduce this risk, footings should not extend below a 2 horizontal to 1 vertical plane projected upward from the closest bottom corner. Utility trenches should not cross under footings.

4.9 RETAINING WALLS

4.9.1 Lateral Earth Pressures

Subsurface structures and retaining walls should be designed to resist the earth pressure exerted by the retained, compacted backfill plus any additional lateral force that will be applied due to surface loads placed at or near the wall or below-grade structure. Recommended design criteria for retaining walls and subsurface structures are presented below. These values are based on the on-site soils, meeting the requirements for non-expansive engineered fill, using a friction angle of 35 degrees and unit weight of 135 pounds per cubic foot (pcf). If imported materials are used for wall backfill, the material should have similar properties, otherwise the lateral earth pressure behind the wall could be different from the values presented in Table 4.3 below.

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TABLE 4.3

Lateral Earth Pressures for Retaining Walls

Backfill Configuration Earth Pressure Equivalent Fluid Density (pcf)

Drained

Level Active

At Rest

Level Passive 345

Surcharge factor, Ka = 0.3 x surcharge pressure for active case Surcharge factor, Ko = 0.5 x surcharge pressure for at-rest case

Passive resistance should be neglected within the upper 1 foot of soil unless the passive pressure area in front of the footing is protected by concrete or pavement and is not disturbed by excavation or other means.

An allowable coefficient of sliding friction of 0.40 may be used between cast-in-place concrete foundations and the underlying undisturbed native soil, engineered fill or rock. Passive pressure available in engineered fill or undisturbed native soil may be taken as equivalent to the pressure exerted by a fluid weighing 345 pounds per cubic foot (pcf).

Lateral resistance parameters provided above are allowable values derived with a factor of safety of at least 1.5. Therefore ultimate values may be calculated by multiplying the above values by the factor of safety. Allowable passive and sliding resistance may be combined without reduction.

4.9.2 Seismic Earth Pressure

Considering the site PGAM of 0.17 g, retaining walls at the site need not be designed using an additional seismic earth pressure, as recommended by Atik and Sitar (2010) and Seed and

Whitman (1970).

4.9.3 Wall Drainage

The above-recommended lateral earth pressure values do not include lateral pressures due to hydrostatic forces. Therefore, wall backfill should be free draining and provisions should be made to collect and dispose of excess water that may accumulate behind earth retaining structures.

Otherwise the walls should be designed for the undrained condition.

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Wall drainage may be provided by a zone of free-draining gravel surrounded by a non-woven geotextile or by prefabricated drain panels. In either case, drainage should be collected by perforated pipes and directed to a sump, storm drain, weep hole(s), or other suitable location for disposal. We recommend drain rock consist of durable stone having 100 percent passing the 1-inch sieve and less than 5 percent passing the No. 4 sieve. The drain zone should extend from the base of the wall stem to within 2 feet of the top. The top 2 feet of backfill should consist of engineered fill.

The non-woven geotextile should have an equivalent opening size (EOS) based on the U.S.

Standard Sieve of 70, a minimum flow rate of 110 gallons per minute per square foot of fabric, and a minimum puncture strength of 110 pounds. Products such as Mirafi 140N or approved equal can meet this specification.

4.9.4 Backfill Placement

All backfill should be placed and compacted in accordance with recommendations provided above for Engineered Fill in Section 5.3.5. Light equipment should be used during backfill compaction to minimize possible overstressing of the wall.

4.9.5 Construction Considerations

Properly compacted retaining wall backfill may experience some settlement or deflection after construction. This is a result of normal deflection of the wall and settling of relatively deep-engineered fills. This post-construction “settling in period” will vary with wall type, size, and construction and should be taken into account in overall site design.

4.10 INTERIOR CONCRETE SLABS SUPPORTED-ON-GRADE

4.10.1 Subgrade Preparation

Prior to constructing interior concrete slabs supported-on-grade, surficial soils should be processed as recommended in the SITE PREPARATION and ENGINEERED FILL sections of this report. Scarification and compaction may not be required if floor slabs are to be placed directly on undisturbed engineered fill or native soil compacted during site preparation, and if approved by the project Geotechnical Engineer during construction.

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