ATTACHMENT_6_-_APPENDIX_A_-_GEOTECHNICAL_ENGINEERING_REPORT.pdf

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Geotechnical Engineering Report Livermore French Camp CBOC and CLC Veterans Administration Project French Camp, California

Prepared for:

Ms. HyeMyoung Kim HDR Architecture, Inc.

560 Mission Street, Suite 900 San Francisco, California 94105

December 11, 2015 Project No. 11005.001

Geotechnical Engineering Report Livermore Veterans Administration CBOC and CLC Project i

TABLE OF CONTENTS

1.0 INTRODUCTION

1.1 General

1.2 Project Understanding

2.0 SITE CONDITIONS

2.1 Surface Description

2.2 Geologic Setting

2.3 Subsurface

2.3.1 Field Explorations

2.3.2 Subsurface Conditions

2.3.3 Groundwater

2.4 Laboratory Testing

3.0 GEOTEHNICAL DESIGN RECOMMENDATIONS

3.1 Discussion

3.2 Spread Footing Design

3.3 Floor Slabs

3.4 Seismic Design Criteria

3.4.1 Liquefaction

3.5 Retaining Structures

3.6 Pavement Design

4.0 CONSTRUCTION CONSIDERATIONS

4.1 Site Preparation

4.1.1 Stripping and Grubbing

4.1.2 Proofrolling

4.1.3 Wet-Weather/Wet-Soil Conditions

4.2 Excavation

4.3 Permanent Slopes

4.4 Structural Fill

4.4.1 Borrow Material

4.4.2 Import Granular Material

4.4.3 Trench Backfill

4.4.4 Stabilization Material

4.4.5 Retaining Wall Backfill

4.4.6 Trench and Retaining Wall Drain Backfill

4.4.7 Footing and Floor Slab Base Course

4.4.8 Aggregate Base Course

4.5 Drainage Considerations

5.0 CONSTRUCTION OBSERVATION

6.0 LIMITATIONS

7.0 REFERENCES

ii

SUPPORTING DATA

Figures Figure 1 Vicinity Map Figure 2 Boring Locations Figure 3 Settlement Plate Detail and Specification

Appendix A – Summary Logs Table A-1 Terminology Used to Describe Soil Table A-2 Key to Test Pit and Boring Log Symbols Figure A1 through A13 Logs for Borings B-1 through B-13 Figure A14 through A15 Logs for Cone Penetration Tests CPT-1 and CPT-2

Appendix B – Laboratory Test Results

Figure B1 Liquid and Plastic Limits Test Report Figure B2 Particle-Size Distribution Report Figure B3 Compaction Test Report Figure B4 California Bearing Ratio Figure B5 Corrosivity Test Summary Figure B6 Consolidation Test

Appendix C – Site-Specific Seismic Hazard Analysis

Figure C1 Seismic Response Spectra

1.0 INTRODUCTION

1.1 General

This report presents the results of Allegiance Group LLC’s (Allegiance), geotechnical investigation for the proposed Veterans Administration (VA) CBOC and CLC buildings on the VA French Camp site (subject property) located in Stockton, California. The project location is provided on Figure 1, Vicinity Map.

1.2 Project Understanding

Allegiance understands that the proposed project will consist of the construction of two structures including an approximate 150,000-square-foot, one- to four-story building (CBOC) and a single story building (CLC) as shown on Figure 2, Boring Locations. Parking areas, access roadways, and utilities will be part of the development. Based on information provided by the structural engineer, Robert Graff of Degenkolb, maximum static column and perimeter foundation loads for the four-story CBOC structure will be on the order of 525 kips and approximately 14 kips per linear foot, respectively. Maximum column and perimeter foundation loads for the single story portion of the CBOC will be on the order of 175 kips and 2 to 3 kips per lineal foot, respectively. At this time, the scope of grading work is unknown. Maximum column and wall loads for the CLC will be less than about 70 kips and 2 to 3 kips per lineal foot, respectively. The purpose of our services was to evaluate subsurface conditions at specific locations within the site and provide geotechnical recommendations for design and construction of building foundations and pavements.

2.0 SITE CONDITIONS

2.1 Surface Description

The proposed buildings will be constructed on the field situated to the north of the San Joaquin General Hospital located on South Manthey Road in French Camp, California. The subject property is bordered by San Joaquin General Hospital to the south, South Manthey Road to the east, agricultural fields to the west, and several farm buildings to the north. The proposed building site is essentially level, at an elevation of approximately 17 feet above mean sea level (AMSL).

2.2 Geologic Setting

The subject property is located within the central valley of California. The Central Valley is bounded by the Pacific Coast Range to the west and the Sierra Nevada Range to the east.

The mountain ranges were elevated by accretion, faulting, and volcanic processes. Since the development of the mountain ranges, the valley has filled in with alluvial deposits. The Sacramento Valley to the north and the San Joaquin Valley to the south make up the Central Valley. The northern and southern valleys are separated by the Sacramento-San Joaquin River Delta. The site is located near the southern extent of the Sacramento-San Joaquin River Delta. The San Joaquin River is approximately 2 miles west of the site.

The project site geology is mapped as Pleistocene Modesto Formation (Atwater, 1982).

Atwater describes the Modesto Formation as consisting of eolian loose sands and fluvial loose sand and silt. Geologic mapping by Bartow (1991) suggests that the Modesto formation thickness in the vicinity of the site is roughly 300 feet thick before encountering the Great Valley sequence. The Great Valley sequence is described as Tertiary to Jurassic age sedimentary rock, serpentinite, and blueschist.

2.3 Subsurface

2.3.1 Field Explorations

Thirteen borings were drilled to depths between 11.5 and 101.5 feet below the existing ground surface (bgs) at the approximate locations shown on Figure 2. Borings B-1 through B-13 were completed by Precision Sampling of Stockton, California, using an ATV-mounted drill rig. Mud-rotary methods were used to drill B-1 through B-6 in the vicinity of the proposed new buildings; hollow-stem auger methods were used to drill B-7 through B-13 in the roadways and parking areas for pavement design. Fugro Consultants of Hayward, California, performed the Cone Penetration Tests (CPT), using a truck-mounted CPT rig. CPT-1 and CPT-2 were located in the vicinity of the proposed CBOC building. The explorations were completed January 9 through 13, 2012.

The subsurface conditions encountered were logged and field-classified in general accordance with the Visual- Manual Procedure (ASTM D 2488). In-situ standard penetration tests (SPT, ASTM D 1586) were performed at regular 2.5-, 5.0- and 10.0-foot intervals in the borings. Disturbed soil samples were collected using a split-spoon sampler and packaged in moisture-tight bags. Thin-wall Shelby tube push samples were also collected from B-2, B-3, and B-5. The borings were backfilled with grout in accordance with local regulations. San Joaquin County Environmental Health Department personnel were present during the backfilling of each boring. The soil samples were re-examined in the laboratory to supplement field classifications.

Interpreted boring logs are provided in Appendix A – Summary Logs.

2.3.2 Subsurface Conditions

General subsurface conditions encountered in the borings consist of a thin layer of topsoil underlain by alluvium to the termination depth in all of the borings. A summary of the encountered units is described below.

TOPSOIL: The topsoil consists of very loose to loose, brown, silty fine sand, and is dry to moist. The topsoil layer ranges from 0.6 to

1.0 feet in thickness.

ALLUVIUM The alluvium consists of alternating layers of coarse-grained and fine-grained soils. The coarse-grained alluvium consists of very loose to dense silty fine to medium sand. The fine-grained alluvium consists of medium stiff to hard clay to fine sandy silt.

All borings were terminated in this unit.

2.3.3 Groundwater

Thin zones of perched groundwater were encountered between 26 and 70 feet bgs in the borings. The perched groundwater was typically encountered where sandy soils overlaid less permeable clayey soils. Ground surface elevations at the borings were estimated to the nearest foot from Google Earth.

2.4 Laboratory Testing

Laboratory tests included natural moisture contents, Atterberg limits, particle-size analysis, and consolidation testing. A California Bearing Ratio (CBR) test was performed on the near-surface soil to assist in the pavement design. Chemical tests including pH, percent sulfates, chlorides, and soil resistivity were performed to evaluate soil corrosivity. Laboratory test results are provided in Appendix B - Laboratory Test Results. Results for select tests are included on the boring logs presented in Appendix A.

3.0 GEOTEHNICAL DESIGN RECOMMENDATIONS

3.1 Discussion

Based on our investigation and experience with similar soils and seismic design criteria, the buildings can be founded on spread footings. However, certain design and construction procedures are recommended. Detailed recommendations for building foundations are discussed later in this report.

A tilled zone was encountered in all thirteen borings. We understand that minor grading will be required for the site. Due to the high organic content of the tilled zone, we recommend that the organic layer be stripped and removed from the site or stockpiled and used for landscaping purposes. Approximately 6 to 12 inches of organic material is present. A layer of 6 inches of imported granular material should be placed below the building slab-on-grade. The top approximately 10 to 17 feet of the site is covered with alluvial sand. Because this soil is non-plastic to low plasticity, problems with swelling soils are not anticipated.

3.2 Spread Footing Design

The CBOC building, in our current opinion, can be supported on spread footings. Preliminary loads provided to us for the CBOC were on the order of 900 kips, which would result in estimated settlement on the order of 2 to 3 inches. As a result, site preloading/surcharging was being considered for the CBOC. Footings for the CLC building support lighter loads and preliminary recommendations were for support on spread footings without surcharging, that is on normally prepared foundation subgrade. However, we understand the current maximum static column loads are on the order of 525 kips for the CBOC; therefore, surcharging would not be required.

Updated analyses using the loads described in Section 1.2 – Project Understanding, of this report, indicate total settlement of about 1 inch, which includes about ½ inch of long-term creep settlement. This estimate was based on an allowable bearing pressure of 2,500 pounds per square foot (psf) and requires that, following stripping, the ground surface be moisture conditioned and compacted using a large (minimum 5-foot diameter) vibratory roller and completing a minimum of four overlapping passes covering the proposed building footprints.

If higher bearing pressures or greater column loads are desired, then the building area should be preloaded. Based on our analysis, total post-construction settlement following preloading would be less than 1 inch, with post-construction differential settlement of less than 0.5 inch over a 30-foot span.

A preloading program for the CBOC building would consist of placing fill over the proposed building footprint. We estimate 8 feet of fill would be required for a period of 30 to 60 days.

The full height of the preload fill should extend beyond the exterior footing edge at least 10 feet. In addition, the single story portion of the CBOC building should be surcharged with a 4-foot preload fill. Consolidation should be monitored using settlement plates. A settlement plate detail is shown on the Settlement Plate Detail and Specification - Figure 3. Settlement plates should be surveyed initially, prior to placing the surcharge, and at regular intervals during and after surcharge placement. Survey data should be reported to the geotechnical engineer, who will determine when estimated remaining settlements are within the project tolerances.

Continuous-wall and isolated-spread footings should be at least 18 and 24 inches wide, respectively. Footings should be sized for an allowable bearing pressure in accordance with those values presented in Table 1. These are net bearing pressures and the weight of the footing and overlying backfill can be disregarded in calculating footing sizes. The recommended allowable bearing pressure applies to the total of dead plus long-term-live loads. Bearing pressure may be increased by a factor of two for short-term/transient loads, such as those resulting from wind or seismic forces for footings with widths greater than 5 feet and a minimum factor of safety of 1.5 for footings with widths of less than 5 feet.

Table 1: Allowable B earing P res s ure Footing Width

(feet) Allowable Bearing

Pressure (ksf) Preloading Required?

ALL 2.5 NO

< 5 4 YES

≥ 5 3 YES

Lateral loads on footings can be resisted by passive earth pressure on the sides of the structures and by friction at the base of the footings. An allowable passive earth pressure of 300 pounds per cubic foot (pcf) may be used for footings confined by native soils and new structural fills. Adjacent floor slabs, pavements, or the upper 12-inch depth of adjacent unpaved areas should not be considered when calculating passive resistance. For footings in contact with native sand soils, use a coefficient of friction equal to 0.4 when calculating resistance to sliding.

An Allegiance geotechnical engineer (or their representative) should confirm suitable bearing conditions and evaluate all footing subgrades. Observations should also confirm that loose or soft material, organics, unsuitable fill, and old topsoil zones have been removed. Localized deepening of footing excavations may be required to penetrate any deleterious materials.

The footings should be founded below an imaginary line projecting at a 1 horizontal to 1 vertical (1H:1V) slope from the base of any adjacent, parallel, utility trenches. The footings must be embedded so that a minimum of 10 feet of horizontal distance is between the face of the footings and any adjacent, parallel slope.

3.3 Floor Slabs

The entire site is covered with approximately 15 feet of loose to medium dense sand over medium stiff to hard clay, underlain by alternating layers of sand, silt, and clay. After the loose material within and extending 5 feet beyond the edge of the building footprint is moisture conditioned and compacted, the soils are adequate to provide slab support with a modulus of subgrade reaction, k, of approximately 250 pounds per cubic inch (pci). A minimum 6-inch-thick layer of aggregate base should be placed and compacted over the prepared subgrade.

3.4 Seismic Design Criteria

Allegiance understands that the seismic design criteria for this project are based on the 2012 International Building Code (IBC). Allegiance completed a site-specific seismic analysis in general accordance with the American Society of Civil Engineers (ASCE) Minimum Design Loads for Buildings and Other Structures, 7-10, Chapter 21, as presented in the Site-Specific Seismic Hazard Analysis, Appendix C. As discussed in Appendix C, the IBC 2012 spectra can be used. The seismic design criteria, in accordance with the IBC, 2012, are summarized in Table 2.

Table 2: 2012 IB C S eis mic Des ign P arameters

Parameter Short Period 1 Second

Maximum Credible Earthquake Spectral Acceleration Ss = 0.97 g S1 = 0.35 g

Site Class D

Site Coefficient Fa = 1.11 Fv = 1.70

Adjusted Spectral Acceleration SMS = 1.08 g SM1 = 0.59 g

Design Spectral Response Acceleration Parameters SDS = 0.72 g SD1 = 0.40 g

Design Spectral Peak Ground Acceleration 0.29 g - Acceleration due to gravity

The seismic design accelerations for the liquefaction hazard analysis are based on the 2008 USGS National Seismic Hazard maps for the California region.

3.4.1 Liquefaction

Liquefaction analyses for the project site was completed using data collected from our borings and CPT probes. The two percent in 50-year design earthquake is a moment magnitude 6.6. Our analysis indicates no liquefaction potential in the sand and silt layers encountered in the top 50 feet. This is due to the depth to the groundwater and soil type and consistency (dense sand and stiff to hard clay layers in the top 50 feet).

3.5 Retaining Structures

Our retaining wall design recommendations are based on the following assumptions: (1) the walls consist of conventional, cantilevered, retaining walls; (2) the walls are 10 feet or less in height; (3) the backfill is drained; and (4) the backfill is flat. An evaluation of our recommendations will be required if the retaining wall design criteria for the project varies from these assumptions.

Unrestrained site walls retaining native soils or structural fill should be designed to resist active equivalent earth pressures of 35 pcf, where supporting slopes are flat. For slopes of up to 2H:1V, the equivalent pressure should be 50 pcf. If retaining walls are restrained from rotation prior to being backfilled, an at-rest earth pressure of 55 pcf should be used for flat backfill. For embedded building walls, a superimposed seismic lateral force should be calculated based on a dynamic force of 6.5H2 pounds per lineal foot of wall, where H is the height of the wall in feet, and applied at 0.6H from the base of the wall. If other surcharges (e.g., slopes, foundations, etc.) are located within a horizontal distance from the back of a wall equal to twice the height of the wall, then additional pressures will need to be accounted for in the wall design. A traffic surcharge equivalent to 250 psf should be used for design of walls where driveways and parking areas are present. This can be applied as an area surcharge load or an additional two feet of wall height. Allegiance should be contacted for appropriate wall surcharges based upon actual magnitude and configuration of the applied loads.

A passive pressure equivalent of 300 pcf can be used for static conditions and 170 pcf for seismic conditions.

These design parameters have been provided assuming back-of-wall drains will be installed to prevent buildup of hydrostatic pressures behind all walls.

A minimum 24-inch-wide zone of granular drain backfill material, extending from the base of the wall to within 6 inches of finished grade, should be placed against the back of all retaining walls. Perforated collector pipes should be embedded at the base of the granular drain backfill material. Granular drain backfill material specifications are provided in Section 4.4. The perforated collector pipes should discharge at an appropriate location away from the base of the wall. The discharge pipe(s) should not be tied directly into stormwater drain systems unless measures are taken to prevent backflow into the wall’s drainage system. Retaining wall backfill specifications are presented in Sections 4.4.5 and 4.4.6.

Footings for retaining walls should be proportioned using the recommendations presented for spread footings in Section 3.2 – Spread Footing Design of this report. For foundations in contact with the native sand, structural fill, select granular materials, or compacted gravels, use a coefficient of friction equal to 0.40 when calculating resistance to sliding.

Settlements of up to one percent of the wall height commonly occur immediately adjacent to the wall, as the wall rotates and develops active lateral earth pressures. Consequently, Allegiance recommends that construction of flat work adjacent to retaining walls be postponed at least four weeks after backfilling of the wall, unless survey data indicate that settlement is complete prior to that time.

3.6 Pavement Design

The areas of the site for proposed pavement are covered with loose sand. The subgrade should be prepared in accordance with Section 4.1 – Site Preparation of this report. Old asphalt, topsoil, grass, and other loose material should be removed and replaced with compacted structural fill wherever necessary. The required layer of aggregate base should be placed and compacted over the prepared subgrade. Aggregate base course recommendations are provided in Section 4.4.8.

Our pavement design recommendations are based on the following assumptions:

• A resilient modulus of 20,000 pounds per square inch (psi) was based on California Bearing Ratio (CBR) testing for the fine sand.

• A resilient modulus of 40,000 psi was assumed for the aggregate base rock.

• Initial and terminal serviceability index of 4.2 and 2.5, respectively.

• Reliability and standard deviation of 85 percent and 0.45, respectively.

• Structural coefficient of 0.42 and 0.14 for the asphalt and aggregate base rock, respectively.

• Equivalent Single-Axle Loads (ESALs) values as follows are assumed applicable to the pavements at the site:

− Parking Lots – 10,000 ESALs − Driveways – 50,000 ESALs

Construction traffic should be limited to non-building, unpaved portions of the project site or haul roads. Construction traffic should not be allowed on new pavements. If construction traffic is to be allowed on newly constructed road sections, an allowance for this additional traffic will need to be made, and the design pavement section thickness increased.

The thicknesses shown in Table 3 are intended to be the minimum acceptable.

Table 3: Minimum P avement S ections

Traffic Loading (ESALs)

Asphalt Cement (inches)

Base Rock (inches)

10,000 2.5 6

50,000 3 6

The asphalt cement (AC) binder should be Performance Grade Asphalt Cement in accordance with Caltrans 39-1.02 – Materials. The AC should consist of ½-inch RHMA-G dense, hot-mix asphalt. The minimum and maximum lift thicknesses should be 2 and 4 inches, respectively. The AC should be compacted to a minimum of 92 percent of the maximum theoretical density (Rice value) of the mix, as determined in accordance with ASTM D 2041.

The recompacted sand soils will have an effective modulus of subgrade reaction of 400 pci.

For this soil and the anticipated traffic loads, a concrete pavement section should consist of 6 inches of concrete over 6 inches of crushed aggregate base.

4.0 CONSTRUCTION CONSIDERATIONS

4.1 Site Preparation

The site should be stripped of any organic material before any improvements take place.

Trees and shrubs should be removed from all fill areas. In addition, root balls should be grubbed out to the depth of the roots, which could exceed 3 feet bgs. Depending on the methods used to remove the root balls, considerable disturbance and loosening of the subgrade could occur during site grubbing. Allegiance recommends that soil disturbed during grubbing operations be removed to expose firm, undisturbed subgrade. The resulting excavations should be backfilled with structural fill.

Following stripping, the soils within the building footprint should be moisture conditioned to near optimum moisture and compacted using a large (minimum 5-foot diameter) vibratory roller and a minimum of four overlapping passes.

If any abandoned foundation elements or utilities from past site use are encountered during construction, they should be removed throughout the buildings, pavements, and other improvement areas. Underground utility lines, vaults, basement walls, or tanks should also be removed or grouted full if left in place. The voids resulting from removal of foundation, buried tanks, etc., or loose soil in utility lines, should be backfilled with compacted structural fill. The base of these excavations should be excavated to firm subgrade before filling, with sides sloped at a minimum of 1H:1V to allow for uniform compaction.

Materials generated during demolition of existing improvements should be transported off-site or stockpiled in areas designated by the Owner. Asphalt, concrete, gravel fill, and base rock materials may be crushed and recycled for use as general fill.

4.1.1 Stripping and Grubbing

Trees and shrubs should be removed from all building, pavement and improvement areas. Stripped material should be transported off-site for disposal or used in landscaped areas.

4.1.2 Proofrolling

Following stripping, moisture conditioning and compaction as recommended, and prior to placing structural fill, pavement, or building improvements, the subgrade should be evaluated by proofrolling. The subgrade should be proofrolled with a fully loaded dump truck or similar heavy, rubber-tire, construction equipment to identify soft, loose, or unsuitable areas. A member of Allegiance’s geotechnical staff should observe the proofrolling. Soft or loose zones identified during the field evaluation should be compacted to an unyielding condition or be excavated and replaced with structural fill.

4.1.3 Wet-Weather/Wet-Soil Conditions

Trafficability on the near-surface soils may be difficult during or after extended wet periods or when the moisture content of the surface soil is more than a few percentage points above optimum. Soils that have been disturbed during site preparation activities, or soft or loose zones identified during probing or proofrolling, should be removed and replaced with stabilization material.

Track-mounted excavating equipment may be required during wet weather. The thickness of the haul roads and staging areas will depend on the amount and type of construction traffic. The material used for haul roads should be stabilization material (Section 4.4.4). A 12- to 18-inch-thick mat of stabilization material is sufficient for light staging areas. The stabilization material for haul roads and areas with repeated heavy construction traffic typically needs to be increased to between 18 to 24 inches. The actual thickness of haul roads and staging areas should be based on the Contractor’s approach to site development, the amount and type of construction traffic, and is the Contractor’s responsibility. The stabilization material should be placed in one lift over the prepared, undisturbed subgrade and compacted using a smooth-drum, non-vibratory roller. Additionally, a geotextile fabric should be placed as a barrier between the subgrade and stabilization material. The geotextile should meet Caltrans 88-1.02O

– Subgrade Enhancement Geotextile. The geotextile should be installed in conformance with Caltrans 19-8 – Subgrade Enhancement Geotextile.

4.2 Excavation

Subsurface conditions at the project site consist of predominately alluvial fine sand in the top 10 to 15 feet. Excavating this soil may be readily accomplished with conventional earthwork equipment.

Trench cuts in the native fine sand should be sloped at 1H:1V, to a depth of 10 feet provided groundwater seepage is not present and with the understanding that some sloughing may occur. The trenches should be flattened to 1.5H:1V if excessive sloughing occurs or seepage is present. Please note that these conditions may only be valid during the dry months of the year.

Use of temporary earth-shoring (that is, temporary ground support) is recommended for cuts extending below groundwater seepage or if vertical walls are desired for cuts deeper than one foot. Please note that perched groundwater was observed in the sand layers at a depth of 26 feet bgs in most of the explorations at the time of exploration. If shoring or dewatering (that is groundwater removal) is required, we recommend that the type and design of the shoring and dewatering systems be the responsibility of the Contractor, who is in the best position to choose systems that fit the overall plan of operation. These excavations should be made in accordance with applicable Occupational Safety and Health Administration (OSHA) and State regulations.

4.3 Permanent Slopes

Permanent cut and fill slopes up to 10 feet tall may be constructed at inclinations of up to 2H:1V. However, cut slopes over 10 feet tall should be limited to 2.5H:1V or should be partially supported by a retaining wall. Slopes that will be maintained by mowing should not be constructed steeper than 3H:1V. Newly constructed fill slopes should be over-built by at least 12 inches and then trimmed back to the required slope to maintain a firm face.

Access roads and pavements should be located at least 5 feet from the top of cut and fill slopes. The setback should be increased to 10 feet for buildings, unless special foundation considerations are implemented. Slopes should be planted with appropriate vegetation to provide protection against erosion as soon as possible after grading. Surface water runoff should be collected and directed away from slopes to prevent water from running down the face of the slope.

4.4 Structural Fill

Fills should be placed over subgrade that has been prepared in conformance with the Site Preparation and Wet-Weather/Wet-Soil Conditions sections of this report. A wide range of material may be used as structural fill; however, all material used should be free of organic matter or other unsuitable materials and should meet the specifications provided in the Standard Specifications, State of California, Department of Transportation-2010 (Caltrans) depending on the application. A brief characterization of some of the acceptable materials and our recommendations for their use as structural fill is provided below.

4.4.1 Borrow Material

Borrow material for general structural fill construction should meet the requirements set forth in Caltrans 19-7– Borrow Material. The native alluvial material may be used as structural fill if processed properly, but if clay is present it may be difficult to dry the clay to near optimum moisture for adequate compaction. In order to adequately compact the native soils, moisture conditioning of the soil to within ±3 percent of the optimum moisture content will be required. When used as structural fill, native soils should be placed in lifts with a maximum uncompacted thickness of 6 to 8 inches and compacted to not less than 92 percent of the maximum dry density, as determined by ASTM D 1557. If suitable common borrow material is not available, use of selected general backfill, as specified in Caltrans 6-2-Material, should be considered.

4.4.2 Import Granular Material

Imported granular material used during periods of wet weather or for haul roads, building pad subgrades, staging areas, etc., should be pit or quarry run rock, crushed rock, or crushed gravel and sand and should meet the specifications provided in Caltrans 19-7– Borrow Material. However, the imported granular material should also be fairly well graded between coarse and fine material and have less than 5 percent by weight passing the US Standard No. 200 Sieve.

Imported granular material should be placed in lifts with a maximum uncompacted thickness of 8 to 12 inches and be compacted to not less than 95 percent of the maximum dry density, as determined by ASTM D 1557. During the wet season or when wet subgrade conditions exist, the initial lift should be approximately 18 inches in uncompacted thickness and should be compacted by rolling with a smooth-drum roller without using vibratory action.

Where imported granular material is placed over soft-soil subgrades, we recommend a geotextile be placed as a barrier between the subgrade and imported granular material. Depending on site conditions, the geotextile should meet Caltrans 88-1.02O– Subgrade Enhancement Geotextile. The geotextile should be installed in conformance with Caltrans 19-8-Subgrade Enhancement Geotextile.

4.4.3 Trench Backfill

Trench backfill placed beneath, adjacent to, and for at least 2 feet above utility lines (i.e., the pipe zone), should consist of well-graded granular material with a maximum particle size of 1.5 inches and less than 10 percent by weight passing the US Standard No. 200 Sieve, and should meet the standards prescribed by Caltrans Division VII, Drainage for the type of pipe specified. The pipe zone backfill should be compacted to at least 90 percent of the maximum dry density, as determined by ASTM D 1557, or as required by the pipe manufacturer or local building department.

Within roadway alignments or beneath building pads, the remainder of the trench backfill should consist of well-graded granular material with a maximum particle size of

2.5 inches, less than 10 percent by weight passing the US Standard No. 200 Sieve, and should meet the requirements for specific surface loading or other criteria of the backfill zone. This material should be compacted to at least 92 percent of the maximum dry density, as determined by ASTM D 1557, or as required by the pipe manufacturer or local building department. The upper 2 feet of the trench backfill should be compacted to at least 95 percent of the maximum dry density, as determined by ASTM D 1557.

Outside of structural improvement areas (e.g., roadway alignments or building pads), trench backfill placed above the pipe zone may consist of general fill materials that are free of organics and materials over 6 inches in diameter and meet Caltrans 19-7– Borrow Material. This general trench backfill should be compacted to at least 90 percent of the maximum dry density, as determined by ASTM D 1557, or as required by the pipe manufacturer or local building department.

4.4.4 Stabilization Material

Stabilization rock should consist of imported granular material that is well-graded, angular, crushed rock consisting of 4- or 6-inch-minus material with less than 2 percent passing the US Standard No. 4 Sieve. The material should be free of organic matter and other deleterious material.

4.4.5 Retaining Wall Backfill

Backfill material placed behind retaining walls and extending a horizontal distance of H, where H is the height of the retaining wall, should consist of selected granular material meeting Caltrans 19-3.02B. We recommend the selected granular wall backfill be separated from general fill, native soil, and/or topsoil using a geotextile fabric that meets the requirements provided in Caltrans 88-1.02B–Filter Fabric.

The wall backfill should be compacted to a minimum of 95 percent of the maximum dry density, as determined by ASTM D 1557. However, backfill located within a horizontal distance of 3 feet from the retaining walls should only be compacted to approximately 90 percent of the maximum dry density, as determined by ASTM D 1557. Backfill placed within 3 feet of the wall should be compacted in lifts less than 6-inches thick using hand-operated tamping equipment (such as a jumping jack or vibratory plate compactors). If flat work (sidewalks or pavements) will be placed on top of the wall backfill, we recommend that the upper 2 feet of material be compacted to 95 percent of the maximum dry density, as determined by ASTM D 1557.

4.4.6 Trench and Retaining Wall Drain Backfill

Backfill in a 2-foot zone against the back of retaining walls and for subsurface trench drains should consist of granular drain rock meeting the specifications provided in Caltrans 19-3.02C-Pervious Backfill Material. The granular drain rock should be wrapped in a geotextile fabric that meets the specifications provided in Caltrans 88- 1.02B-Filter Fabric.

4.4.7 Footing and Floor Slab Base Course

Imported granular material placed at the base of retaining wall and building footings and floor slabs should be clean, crushed rock or crushed gravel, and sand that is fairly well-graded between coarse and fine. The granular materials should contain no deleterious material and have a maximum particle size of 1.5 inches. The imported granular material should be placed in one lift and compacted to not less than 95 percent of the maximum dry density, as determined by ASTM D 1557.

4.4.8 Aggregate Base Course

Imported granular material used as aggregate base course (base rock) along roadway alignments should be clean, crushed rock or crushed gravel, and sand that is fairly well-graded between coarse and fine. The base aggregate should meet the gradation defined in Caltrans 26-Aggregate Bases, depending upon application. The base aggregate should be compacted to not less than 95 percent of the maximum dry density, as determined by ASTM D 1557.

4.5 Drainage Considerations

The Contractor shall be made responsible for temporary drainage of surface water and groundwater, as necessary, to prevent standing water and/or erosion at the working surface.

Allegiance recommends removing only the foliage necessary for construction to help minimize erosion.

The ground surface around the structures should be sloped to create a minimum gradient of 2 percent away from the building foundations for a distance of at least 5 feet. Surface water should be directed away from all buildings into drainage swales or into a storm drainage system. “Trapped” planting areas should not be created next to any building without providing means for drainage. The roof downspouts should discharge onto splash blocks or paving that directs water away from the building, or into smooth-walled underground drain lines that carry the water to appropriate discharge locations at least 10 feet away from any buildings.

5.0 CONSTRUCTION OBSERVATION

Satisfactory pavement and earthwork performance depends on the quality of construction. Sufficient observation of the Contractor's activities is a key part of determining that the work is completed in accordance with the construction drawings and specifications. We recommend that a representative from Allegiance be retained to observe general earthwork, stripping, structural fill placement, foundation subgrades, temporary shoring, and subgrades and aggregate base rock for floor slabs and pavements. A representative from Allegiance should confirm suitable bearing conditions and evaluate foundation subgrades prior to placement of any structural fill for the new structures.

Subsurface conditions observed during construction should be compared with those encountered during the subsurface explorations. This is important since variable material is present throughout the site. Recognition of changed conditions requires experience. Therefore, qualified personnel should visit the site with sufficient frequency to detect whether subsurface conditions change significantly from those anticipated.

6.0 LIMITATIONS

The opinions, comments, and conclusions presented in this report are based upon information derived from our literature review, field exploration, laboratory testing, and analyses. Conditions between or beyond our exploratory borings may vary from those encountered. It is possible that soil, rock, or groundwater conditions could vary between or beyond the points explored. If soil, rock, or groundwater conditions are encountered during construction that differ from those described herein, the client is responsible for ensuring that Allegiance is notified immediately so that we may re-evaluate the recommendations of this report.

Unanticipated soil and rock conditions and seasonal soil moisture and groundwater variations are commonly encountered and cannot be fully determined by merely taking soil samples or soil borings.

Such variations may result in changes to our recommendations and may require that additional expenses to attain a properly constructed project. Therefore, we recommend a contingency fund to accommodate such potential extra costs.

The scope of services for this subsurface exploration and geotechnical report did not include environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous substances in the soil, surface water, or groundwater at this site.

If there is a substantial lapse of time between the submission of this report and the start of work at the site, if conditions have changed due to natural causes or construction operations at or adjacent to the site, or if the basic project scheme is significantly modified from that assumed, it is recommended that this report be reviewed to determine the applicability of the conclusions and recommendations. Land use, site conditions (both on- and off-site), or other factors may change over time and could materially affect our findings. Therefore, this report should not be relied upon after three years from its issue, or in the event that the site conditions change.

This report is for the exclusive use of the Client for design of the development, as described in our proposal for this particular project, and is not to be relied upon by other parties. It is not to be photographed, photocopied, or similarly reproduced, in total or in part, without express written consent of the Client and Allegiance. It is the addressee's responsibility to provide this report to the appropriate design professionals, building officials, and contractors to ensure correct implementation of the recommendations

Allegiance appreciates the opportunity to provide our geotechnical services on this important project.

Please contact us with any questions regarding our services.

Sincerely, PBS Engineering and Environmental Inc. / for Allegiance Group, LLC

Ryan White, PE, GE (OR) Senior Engineer

Arlan H. Rippe, PE (OR), GE (OR), D.GE Senior Engineering Consultant

RW/AR/rg

9/30/17

7.0 REFERENCES

ASCE (American Society of Civil Engineers). (2010). Minimum Design Loads for Buildings and Other

Structures, ASCE/SEI 07-10.

Atwater, Brian F., (1982). Geologic Maps of the Sacramento – San Joaquin Delta, California, US Geological Survey Miscellaneous Field Studies Map 1401, Sheet 17 of 21 sheets.

Bartow, J. Alan (1991). The Cenozoic Evolution of the San Joaquin Valley, California, US Geological

Survey Professional Paper 1501, 40 pp, 2 pl.

Caltrans (2010). Standard Specifications, State of California, Business, Transportation, and Housing

Agency, Department of Transportation.

IBC. (2012). International Building Code. Country Club Hills, IL: International Code Council, Inc.

NCEER (National Center for Earthquake Engineering Research). (2001, October). Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of Soils. Journal of Geotechnical and Geoenvironmental Engineering.

US Department of Veterans Affairs. (August 2013). Seismic Design Requirements, H-18-8. Office of Construction & Facilities Management, Strategic Management Office.

USGS (US Geological Survey). (2011). US Geological Survey Web site:

http://earthquake.usgs.gov/hazards/qfaults/

USGS (US Geological Survey). (2008). Earthquake Hazards Program – Interactive Hazard Maps:

National Seismic Hazard Maps.

FIGURES

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MAY 2012

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APPENDIX A

Summary Logs

A-1

A1.0 GENERAL

Allegiance explored subsurface conditions at the project site by completing a combination of pavement cores, borings, and cone penetrometer test probes (CPTs). The approximate locations of the explorations are shown on Figure 2. The procedures and techniques used to advance the borings, collect samples, and other field techniques are described in detail in the following paragraphs. Unless otherwise noted, all soil sampling and classification procedures followed applicable ASTM standards.

A2.0 Borings

A2.1 Drilling Precision Sampling of Stockton, California, drilled the mud-rotary and hollow-stem auger borings using truck-mounted drill rigs. Fugro Consultants, Inc., advanced the CPTs.

Explorations were observed by a subcontracted geologist from PBS Engineering and Environmental who located the general areas for the explorations and, for borings, maintained a detailed log of the subsurface conditions and materials encountered during the course of the work.

A2.2 Sampling Disturbed soil samples were taken in the borings at selected depth intervals. The samples were obtained using a standard 2-inch outside diameter (OD), split-spoon sampler following procedures prescribed for the Standard Penetration Test (SPT). Using the SPT, the sampler is driven 18 inches into the soil using a 140-pound hammer dropped 30 inches. The number of blows required to drive the sampler the last 12 inches is defined as the standard penetration resistance, or N-value. The N-value provides a measure of the relative density of granular soils such as sands and gravels, and the consistency of cohesive soils such as clays and silts. The disturbed soil samples were examined by the PBS geologist and then sealed in plastic bags for further examination and physical testing in our laboratory.

Relatively undisturbed samples were collected at selected depth intervals in 3-inch OD, thin-wall Shelby tubes by hydraulically pushing the tube into the undisturbed soil at the bottom of the borehole. The soils exposed at the ends of the tubes were examined and classified.

After field classification, the ends of the tubes were sealed to help preserve the natural moisture of the sample. The sealed tube was returned to our laboratory for physical testing.

A2.3 Boring Logs The logs show the various types of materials that were encountered in the borings and the depths where the materials and/or characteristics of these materials changed, although the changes may be gradual. Where material types and descriptions changed between samples, the contacts were interpreted. The types of samples taken during drilling, along with their sample identification number, are shown to the right of the classification of materials. Standard penetration resistances (N-values) and natural water (moisture) contents are shown further to the right. Measured groundwater levels and the dates of the readings are plotted in the column to the right. The groundwater levels are only for the dates shown and likely vary from time to time during the year.

A-2

A3.0 MATERIAL DESCRIPTION

Initially, soil samples were classified visually in the field. Consistency, color, relative moisture, degree of plasticity, and other distinguishing characteristics of the soil samples were noted.

Afterward, the samples were re-examined in the laboratory, various standard classification tests were conducted, and the field classifications were modified where necessary. The terminology used in the soil classifications and other modifiers are defined in Table A-1, Terminology Used to Describe Soil.

A4.0 Cone Penetrometer Tests (CPT)

A4.1 Fie ld Procedures Before the start of testing, the truck is jacked up and leveled on four pads to provide a stable reaction for the cone thrust. During the test, the instrumented cone is hydraulically pushed into the ground at the rate of about 2 centimeters per second (cm/s), and readings of cone tip resistance, sleeve friction, and pore pressure are digitally recorded every second. As the cone advances, additional cone rods are added such that a “string” of rods continuously advances through the soil. As the test progresses, the CPT operator monitors the cone resistance and its deviation from vertical alignment.

For CPT soundings in which seismic data were collected, conventional CPT testing is temporarily halted at 5-foot intervals to collect seismic data. A Seismograph integrated with the CPT is used to record the arrival time of seismic waves generated by striking a steel beam positioned at least 10 feet from the cone rods and coupled to the ground surface by the weight of the beam and operator to prevent the beam from moving when struck.

Each side of the beam is struck several times, and each signal produced by a blow is closely examined for signal and noise content, after which the waveform is selected and the arrival time of the shear wave is determined and recorded. After a complete set of seismic data are recorded, the cone is advanced to the next depth, and the procedure is repeated until the hole is complete.

A4.2 CPT Logs In accordance with the ASTM standard, the vertical axis is designated for the depth, while the horizontal axis displays the magnitude of the test values recorded. Recorded values include tip and shaft resistance and pore pressure. Final plotting scales are determined after all the tests are completed, and take into consideration maximum test values and depths recorded for the project. This information is used to calculate the friction ratio and is correlated to material types, which are presented graphically in a column to the right.

Terminology Used to Describe Soil and Rock

Soil Descriptions

Soils exist in mixtures with varying proportions of components. The predominant soil, i.e., greater than 50 percent based upon total dry weight, is the primary soil type and is capitalized in our log descriptions, e.g., SAND, GRAVEL, SILT or CLAY. Lesser percentages of other constituents in the soil mixture are indicated by use of modifier words in general accordance with the Visual-Manual Procedure (ASTM D2488-93). “General Accordance” means that certain local and common descriptive practices have been followed. In accordance with ASTM D2488, group symbols (such as GP or CH) are applied on that portion of the soil passing the 3-inch (75mm) sieve based upon visual examination. The following describes the use of soil names and modifying terms used to describe fine- and coarse-grained soils.

Fine - Grained Soils (More than 50% fines passing 0.074 mm, #200 sieve) The primary soil type, i.e. SILT or CLAY is designated through visual – manual procedures to evaluate soil toughness, dilatency, dry strength, and plasticity. The following describes the terminology used to describe fine - grained soils, and varies from ASTM 2488 terminology in the use of some common terms.

Primary soil NAME, adjective and symbols Plasticity Description

Plasticity Index (PI)

SILT

ML & MH

CLAY

CL & CH

ORGANIC

SILT & CLAY

OL & OH

SILT Organic SILT Non-plastic 0 - 3 SILT Organic SILT Low plasticity 4 - 10

Clayey SILT Silty CLAY Organic clayey SILT Medium Plasticity >10 – 20 Clayey SILT CLAY Organic silty CLAY High Plasticity >20 – 40 Clayey SILT CLAY Organic CLAY Very Plastic >40

Modifying terms describing secondary constituents, estimated to 5 percent increments, are applied as follows:

Description % Composition Trace sand, trace gravel 5% - 10% With sand; with gravel 15% - 25%

Sandy, or gravelly 30% - 45%

Borderline Symbols, for example CH/MH, are used where soils are not distinctly in one category or where variable soil units contain more than one soil type. Dual Symbols, for example CL-ML, are used where two symbols are required in accordance with ASTM D2488.

Soil Consistency.