36C10F18R0581-079.pdf

Geotechnical Engineering Report

Sacramento Valley National Cemetery Phase 2

VA Project Number 921PC2007

5810 Midway Road

Dixon, Solano County, California

August 16, 2017

Terracon Project No. NB17P044

Prepared for:

Anderson Engineering of Minnesota, LLC

Minneapolis, MN

Prepared by:

Terracon Consultants, Inc.

Sacramento, California

Terracon Consultants, Inc. 50 Goldenland Cour t , Suite 100

P [916] 928 4690 F [916] 928 4697 terracon.com

13605 1st Avenue N #100, Plymouth, MN 55441

Attn: Mr. Mike Brandvold

E: MBrandvold@AE-MN.COM

Re: Geotechnical Engineering Report

Sacramento Valley National Cemetery Phase 2

VA Project Number 921PC2007

5810 Midway Road

Dixon, Solano County, California

Dear Mr. Brandvold:

Terracon Consultants, Inc. (Terracon) has completed the geotechnical engineering services for the above referenced project. This study was performed in general accordance with our master subcontract agreement for professional services dated May 9 th, 2017. This report presents the findings of the subsurface exploration and provides geotechnical recommendations concerning earthwork and the design and construction of Phase 2 of the proposed expansion to the

Sacramento Valley National Cemetery.

We appreciate the opportunity to be of service to you on this project. If you have any questions concerning this report, or if we may be of further service, please contact us.

Sincerely, Terracon Consultants, Inc.

Nicholas Novotny, G.I.T. Rob Holmer, G.E.

Staff Geologist Geotechnical Engineer 2672

Office Manager

Enclosures cc: 1 – Client (PDF)

1 – File

Sacramento Valley National Cemetery Phase 2 ■ Dixon, Solano County, California August 16, 2017 ■ Terracon Project No. NB17P044 ■ VA Project Number 921PC2007

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TABLE OF CONTENTS

EXECUTIVE SUMMARY ............................................................................................................. i

1.0 INTRODUCTION

2.0 PROJECT INFORMATION

Project Description Site Location and Description Previous Investigations

3.0 SUBSURFACE CONDITIONS

Geology Typical Profile Corrosion Potential Groundwater Seismic Considerations

3.5.1 Seismic Design Parameters

3.5.2 Faulting and Estimated Ground Motions

3.5.3 Liquefaction

4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

Geotechnical Considerations Earthwork

4.2.1 Subgrade Preparation

4.2.2 Potential Volumetric Shrinkage During Grading

4.2.3 Non-Expansive Structural Fill Material Requirements

4.2.4 Compaction Requirements

4.2.5 Grading and Drainage

4.2.6 Exterior Concrete Flatwork Design and Construction

4.2.7 Earthwork Construction Considerations

Foundations

4.3.1 Foundation Recommendations

Floor Slab

4.4.1 Design Recommendations

4.4.2 Floor Slab Construction Considerations

4.5 Cantilever Retaining Walls

Pavements

4.6.1 Subgrade Preparation

4.6.2 Design Considerations

4.6.3 Estimates of Minimum Pavement Thickness

4.6.4 Pavement Drainage

4.6.5 Pavement Maintenance

5.0 GENERAL COMMENTS

Sacramento Valley National Cemetery Phase 2 ■ Sacramento, California August 16, 2017 ■ Terracon Project No. NB17P044

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APPENDIX A – FIELD EXPLORATION

Exhibit A-1 Location Diagram

Exhibit A-2a Boring Location Diagram

Exhibit A-2b Estimated Groundwater Elevation

Exhibit A-3 Field Exploration Description

Exhibit A-4 to A-44 Boring Logs

APPENDIX B – LABORATORY TESTING

Exhibit B-1 Laboratory Testing

Exhibit B-2 Atterberg Limits Results

Exhibit B-3 to B-12 Unconfined Compression Testing

Exhibit B-13 to B-20 Consolidation Testing

Exhibit B-21 to B-22 Corrosivity Test Results

Exhibit B-23 to B-31 R-Value Test Results

Exhibit B-32 to B-38 Laboratory Compaction Test Results

APPENDIX C – SUPPORTING DOCUMENTS

Exhibit C-1 General Notes

Exhibit C-2 Unified Soil Classification System

Exhibit C-3 USGS Seismic Design Maps Detailed Report

Exhibit C-4 Liquefaction Analysis Figures

August 16, 2017 ■ Terracon Project No. NB17P044 ■ VA Project Number 921PC2007

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EXECUTIVE SUMMARY

A geotechnical investigation has been performed for Phase 2 of the proposed Sacramento Valley

National Cemetery expansion to be located at 5810 Midway Road in Dixon, Solano County, California. Fourty-two (42) geotechnical borings were drilled to an approximate depth of 10 to 41½ feet below ground surface (bgs). This report provides geotechnical recommendations for the proposed development at the site.

Based on the information obtained from our subsurface exploration, the site is considered suitable for development of the proposed project provided the geotechnical engineering recommendations included in this report are implemented in the design and construction. The following geotechnical considerations were identified:

Subgrade soils encountered in our borings are described as alluvial deposits generally consisting of stiff lean sandy clays and medium dense to dense silty to clayey sands. Highly plastic fat clays were encountered intermittently throughout the site.

Groundwater was encountered in our borings at a depth of 9½ to 15½ feet while drilling and

7½ to 12½ feet 24 hour after completion of drilling.

Laboratory test results indicate the near surface clays have low to moderate expansion potential, with small isolated areas exhibiting high expansion potential. These soils will experience volume changes with fluctuating moisture content. Concrete flatwork should be underlain by a layer of aggregate base or non-expansive engineered fill, and the native clays should be in a moist condition immediately prior to casting concrete. As a minimum, flatwork shall be reinforced with No. 4 rebar at 18 inches on center.

The proposed structures associated with this project may be supported by spread footings bearing on native firm soils or engineered fill. Foundation shall penetrate at least 24 inches below surrounding site grades.

Building slabs shall be supported by 18 inches of non expansive engineered fill or 18 inches of lime treated subgrade.

Pavements for the parking and drive areas of the Phase 2 expansion should consist of the following: Auto Parking (TI = 4.5) 3 to 3½ inches AC; 8 inches AB or 5 inches PCC; 6 inches

AB, Auto drives (TI = 5.5) 3½ to 4 inches AC; 10 to 11 inches AB or 5½ inches PCC; 6 inches

AB, Truck/Delivery (TI = 6.5) 4 to 4½ inches AC; 13 to 14 inches AB or 6 inches PCC; 6 inches AB.

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The 2016 California Building Code (CBC) Seismic Site Classification for this site is D.

Close monitoring of the construction operations discussed herein will be critical in achieving the design subgrade support. We therefore recommend that Terracon be retained to monitor this portion of the work.

This summary should be used in conjunction with the entire report for design purposes. It should be recognized that details were not included or fully developed in this section, and the report must be read in its entirety for a comprehensive understanding of the items contained herein. The section titled GENERAL COMMENTS should be read for an understanding of the report limitations.

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GEOTECHNICAL ENGINEERING REPORT

SACRAMENTO VALLEY NATIONAL CEMETERY PHASE 2

VA PROJECT NUMBER 921PC2007

5810 MIDWAY ROAD

DIXON, SOLANO COUNTY, CALIFORNIA

1.0 INTRODUCTION

This report presents the results of our geotechnical engineering services performed for Phase 2 of the proposed Sacramento Valley National Cemetery expansion to be located at 5810 Midway

Road in Dixon, Solano County, California. The Location Diagram (Exhibit A-1) is included in

Appendix A of this report. The purpose of these services is to provide information and geotechnical engineering recommendations relative to:

subsurface soil conditions groundwater conditions earthwork foundation design and construction seismic considerations pavement design potential volumetric shrinkage during grading operations floor slab design and construction liquefaction potential concrete flatwork design and construction

Our geotechnical engineering scope of work for this project included the advancement of fourty-two (42) geotechnical borings drilled to an approximate depths of 10 to 41½ feet below the existing ground surface (bgs).

Logs of the borings along with a Boring Location Diagram (Exhibit A-2) are included in Appendix

A of this report. The results of the laboratory testing performed on soil samples obtained from the site during the field exploration are included in Appendix B of this report. Descriptions of the field exploration and laboratory testing are included in their respective appendices.

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2.0 PROJECT INFORMATION

Project Description

Item Description

Site layout See Appendix A, Exhibit A-1 and A-2: Location Diagram and Boring

Location Diagram.

Proposed Improvements

The proposed development for the 50-acre Phase 2 of the

Sacramento Valley National Cemetery Expansion is planned to include 9,000 crypt full casket gravesites, approximately 8,500 traditional in-ground cremains, approximately 11,500 columbaria niches, 100x150’ hybrid burial section to accommodate 300 no vault burial sites, one committal service shelter, and additional asphalt paved roadways, concrete flatwork, and landscaping areas. The proposed project will also include additional cortage lanes and parking for the existing cemetery.

Construction

We assume the proposed committal service structure may consist of concrete, masonry, wood, or metal stud construction founded on a shallow foundation system with slab on grade floors.

Maximum foundation loads

■ Maximum Column Loads: up to 150 kips (assumed)

■ Maximum Wall Loads: less than 3 kips/ft. (assumed)

■ Maximum Floor Loads: less than 100 psf (assumed)

Maximum allowable settlement Columns: 1-inch (assumed)

Walls: ¾ inch over 40 feet (assumed)

Grading Minor cuts and fills on the order of approximately 3 feet are anticipated.

Site Location and Description

Location The project site is located at 5810 Midway Road in Dixon, Solano

County, California.

Existing site features

The entire Sacramento Valley National Cemetery includes over 560 acres and is planned to be constructed in 6 phases. Phase 1 is currently constructed and includes approximately 63 acres. The site is currently developed with two committal service shelters, one administrative building, asphalt paved roadways, concrete flatwork, landscaping areas, and gravesites.

Surrounding developments

The entire 560-acre cemetery site is roughly bordered by highway 80 to the west, Midway Road to the north, Batavia Road to the east, and farmland to the south. The existing Phase 1 is located in the middle

1/5 of the property. The Phase 2 project is located adjacent to and west of Phase 1.

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Current ground cover Native vegetation and exposed native soils and gravel paved access roads. Row crops are present in the western portion of the site.

Existing topography

Existing topography is relatively flat with elevation changes on the order of 3 to 4 feet across the site. Relative elevations at the western portion of the site are generally lower than elevations at the eastern portion of the site.

Previous Investigations

Multiple previous investigations have been prepared for the Sacramento Valley National

Cemetery site. In 2002, URS prepared a Final Geologic & Seismic Hazards Assessment Report

(2002a), a Final Environmental Assessment Report (2002b), and a Limited Phase II

Environmental Site Assessment (2002c). A previous Geotechnical investigation was prepared by

España Geotechnical Consulting for Phase 1 of this expansion (EGC Project Number L160, report dated 1/12/2005). A Geotechnical Evaluation Report was prepared for a 19-acre expansion of

Phase 1 by Ninyo & Moore (Project No. 402733001, report dated March 7, 2016). These reports have been reviewed in preparation of this report.

3.0 SUBSURFACE CONDITIONS

Geology

The site is situated within the Great Valley Geomorphic Province in California, which is comprised of a large sedimentary basin dominated by floodplain and alluvial fan processes. The Great Valley

Geomorphic Provence extends south to the Transverse Range Provence, and is bounded to the west by the Coast Ranges, to the north by the Klamath Mountains, and to the east by the Sierra

Nevada Batholith.

The native soils underlying the site are considered to consist of alluvial deposits (Qal) and older alluvial deposits (Ooal) as described on the Geologic Map of the area1. According to the CGS map, both alluvial units are mid to late Quaternary in age (2.6 million years ago and present). The younger, late Quaternary aged alluvial deposits generally consist of unconsolidated flood-plain deposits of sand, silt, gravel, and clay irregularly interstratified. The older alluvial deposits mainly consist of flood-plain and alluvial fan deposits, formed adjacent to previously mountainous areas, and consisting of commonly unconsolidated, and irregularly interstratified sand, gravel, silt or clay. The total thickness of the alluvial deposits at this location was not determined during our investigation.

1 Sims, J.D., Fox, K.F., Bartow, J.A., and Helley, E.J., 1973, Preliminary Geologic Map of Solano County and parts of Napa, contra costa, Marin, and Yolo Counties, California: U.S. Geological survey, Miscellaneous field Studies Map MF- 484, Scale 1:62,500

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Typical Profile

Our geotechnical engineering scope of work for this project included the advancement of fourty-two (42) geotechnical borings drilled to an approximate depth of 10 to 41½ feet below the existing ground surface (bgs).

Near surface soils across the site generally consisted of interbedded medium stiff to hard lean to fat clay and loose to dense clayey sand with some poorly graded sand layers. Soils below a depth of 25 to 30 feet bgs, generally consisted of medium dense to very dense silty sand and stiff sandy silt with variable gravel. Near surface sand and clay soils exhibiting weak cementation were encountered across the site. Cemented soils generally were encountered at depths of approximately 2½ to 7½ feet bgs.

Specific conditions encountered at each boring location are indicated on the individual boring logs.

Stratification boundaries on the boring logs represent the approximate location of changes in soil types; in-situ, the transition between materials may be gradual. Details for each of the borings can be found on the boring logs included in Appendix A of this report.

Laboratory tests were conducted on selected soil samples and the test results are presented in

Appendix B. The near surface clays have low to high plasticity, and had the following measured liquid limits, plastic limits, and plasticity indices.

Sample Location Depth

(feet bgs)

Liquid Limit

Plastic Limit

Plasticity

Index (%)

Percent

Fines (%)

Boring B-01 10 to 11½ 55 20 35 91

Boring B-02 5 to 6½ 37 15 22 50

Boring B-04 1 to 2½ 25 16 9 59

Boring B-07 7½ to 9 39 19 20 68

Boring B-11 1 to 2½ 52 19 33 84

Boring B-12 12½ to 14 46 26 20 --

Boring B-15 10 to 11½ 37 18 19 86

Boring B-18 2½ to 4 35 15 20 65

Boring B-20 1 to 2½ 41 13 28 73

Boring B-23 12½ to 14 39 19 20 58

Boring B-27 5 to 6½ 43 15 28 63

Boring B-29 1 to 2½ 42 18 24 81

Boring B-34 1 to 2½ 44 16 28 56

Boring B-35 1 to 2½ 31 14 17 --

Boring B-35 5 to 6½ 44 18 26 79

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Depth

(feet bgs)

Liquid Limit

Plastic Limit

Plasticity

Index (%)

Percent

Fines (%)

Boring B-36 5 to 6½ 44 18 26 65

Boring B-38 1 to 2½ 29 14 15 69

Boring B-39 1 to 2½ 41 23 18 65

Boring B-40 1 to 2½ 38 20 18 76

Corrosion Potential

Results of soluble sulfate testing indicate that type II cement may be used for concrete on and below grade. Foundation concrete may be designed for moderate sulfate exposure in accordance with the provisions of the ACI Design Manual, Section 318-14, Section 19.3.2.

Laboratory soil pH, sulfate content tests, and laboratory resistivity tests were conducted on six (6) selected soil sample recovered from borings B5, B12, B27, SB2, SB5, and SB7 at depths of 1 to

5 feet to assess the corrosivity risk of the soils at the site. Laboratory test results indicate that on-site soils have the following sulfate, chloride, electrical resistivity, red-ox potential, and pH values:

Corrosivity Test Results Summary

Boring

Sample

Depth

(feet)

Soil

Description

Soluble

Sulfate

(mg/kg)

Soluble

Chloride

(mg/kg)

Electrical

Resistivity

(Ω-cm)

Red-Ox

Potential

(mV) pH

B-5 1 Sandy Lean

Clay 61 50 10,670 +582 9.98

B-12 2½ Clayey Sand 26 225 1,261 +582 9.09

B-27 1 Sandy Lean

Clay 110 150 3,783

+596 8.58

B-36 1 Lean Clay 187 100 1,649 +666 7.69

B-39 5 Clayey Sand 29 58 1,164 +640 7.97

B-41 1 Sandy Lean

Clay 51 68 1,358

+672 7.85

The results of the laboratory test are provided in Appendix B of this report and are also discussed herein.

The resistivity of the laboratory tested samples were determined to be 1261, 3783, 10670, 1,649, 1,164, and 1,358 ohm-cm. The resistivity value indicates that the samples tested exhibit a mild to high corrosive potential to buried metal pipes.

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Evaluation of the test results is based upon the guidelines of J.F. Palmer, “Soil Resistivity

Measurements and Analysis”, Materials Performance, Volume 13, January 1974. The following table outlines the guidelines for soil resistivity for corrosion potential.

Corrosion Potential of Soil on Steel

Soil Resistivity (ohm-cm) Corrosion Potential

0 to 1,000 Very High

1,000 to 2,000 High

2,000 to 5,000 Moderate

> 5,000 Mild

The sulfate test results indicates the water soluble sulfate concentrations at the corresponding boring locations ranged from 26 to 187 mg/Kg. According to ACI Code 318-14, Section 19.3.2, sulfate concentrations less than 150 ppm are considered negligible when considering corrosion to concrete, with concentrations of 150 to 1,500 ppm considered moderately corrosive to concrete. Of the six samples analyzed, only one sample obtained from boring SB-5 exhibited a sulfate concentration within the moderate range.

The six samples tested exhibited pH values of 8.58, 9.09, 9.98, 7.69, 7.97, and 7.85. Laboratory testing indicates soils in the undeveloped area may require some amendment to reduce pH levels to tolerable levels. pH values in the area of the proposed cortage lane expansions were generally more neutral.

Groundwater

The boreholes were observed while drilling and 24 hours after completion for the presence and level of groundwater. Groundwater was encountered during drilling at depths ranging from 9 ½ to

15½ feet bgs during drilling and 7¼ to 12½ feet bgs after 24 hours. Groundwater was not encountered in our test borings drilled at the location of the proposed cortage lane expansion. At the time of our investigation, irrigation canals bordered the site to the south, east, and west. Two ponds are also present at the site within the existing cemetery and to the adjacent southeast.

Based on the depth to groundwater measured in our borings and the surface elevations of our test borings surveyed by Anderson Engineering of Minnesota, we have prepared an estimated groundwater elevation contour map presented in Appendix A of this report, Exhibit A-2b.

These observations represent groundwater conditions at the time of the field exploration and may not be indicative of other times, or at other locations. Groundwater conditions can change with varying seasonal and weather conditions, and other factors. The evaluation of these factors is beyond the scope of this study.

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Seismic Considerations

3.5.1 Seismic Design Parameters

DESCRIPTION VALUE

2016 California Building Code Site Classification (CBC) 1 D

Southeast Corner Latitude/ Longitude N 38.4102° / W -121.8739°

Northwest Corner Latitude/Longitude N 38.4164° / W -121.8838°

Ss Spectral Acceleration for a Short Period 1.346 to 1.371 g

S1 Spectral Acceleration for a 1-Second Period 0.472 to .480 g

Sds Design Spectral Acceleration for a Short Period 0.879 to 0.914 g

Sd1 Spectral Acceleration for a 1-Second Period 0.481 to 0.486 g

Site Coefficient Fa 1.000

Site Coefficient Fv 1.528 to 1.520

1 Note: The 2016 California Building Code (CBC) requires a site soil profile determination extending to a depth of

100 feet for seismic site classification. The current scope does not include the required 100-foot soil profile determination. Borings extended to a maximum depth of 41½ feet, and this seismic site class definition considers that similar soils continue below the maximum depth of the subsurface exploration.

3.5.2 Faulting and Estimated Ground Motions

The site is located in Northern California, which is a seismically active area. The type and magnitude of seismic hazards affecting the site are dependent on the distance to causative faults, the intensity, and the magnitude of the seismic event. The table below indicates the distance of the fault zones and the associated maximum credible earthquake that can be produced by nearby seismic events, as calculated using the USGS Earthquake Hazard Program 2008 interactive deaggregations.

Characteristics and Estimated Earthquakes for Regional Faults

Fault Name Percent Contribution

Approximate

Distance to Site

(kilometers)

Maximum Considered

Earthquake (MCE)

Magnitude

Great Valley 06, (Midland) alt 1

13.70 4.87 6.74

Great Valley 04b Gordon

Valley

10.43 15.33 6.79

Hunting Creek Berryessa 4.49 29.80 7.12

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Characteristics and Estimated Earthquakes for Regional Faults

Fault Name Percent Contribution

Approximate

Distance to Site

(kilometers)

Maximum Considered

Earthquake (MCE)

Magnitude

Great Valley 04a Trout

Creek

2.17 19.15 6.95

The mapped Maximum Considered Earthquake (MCE) peak ground acceleration at the subject site is expected to be between 0.491 to 0.498 g with a mean modal magnitude of 6.54 per the

ASCE 7-10 standard with July 2013 errata.

The site is not located within an Alquist-Priolo Earthquake Fault Zone based on our review of the

State Fault Hazard Maps.2 However, the site is located in a zone of moderate liquefaction risk according to the U.S. Geological Survey Liquefaction Susceptibility maps3.

3.5.3 Liquefaction

Liquefaction is a mode of ground failure that results from the generation of high pore-water pressures during earthquake ground shaking, causing loss of shear strength. Liquefaction is typically a hazard where loose sandy soils exist below groundwater. The California Geologic

Survey (CGS) has designated certain areas within California as potential liquefaction hazard zones. These are areas considered at a risk of liquefaction-related ground failure during a seismic event, based upon mapped surficial deposits and the likely presence of a relatively shallow water table. The project site is not located within a mapped potential liquefaction hazard zone as indicated by the CGS. However, the project site is located within a zone of moderate liquefaction hazard by the United States Geological Survey.

Subsurface materials generally consisted of interbedded lean to fat clay to clayey sand to a depth of approximately 25 to 30 feet overlying silty sand to sandy silt to the total depth of exploration of

41½ feet bgs. Groundwater was observed throughout the site at depths ranging between 7¼ and

14 feet bgs in the borings at the time of field exploration. Two (2) test borings were advanced to depths of 41½ feet bgs at the site to assess liquefaction potential of subgrade soils.

Based on the location to nearby faults and subsurface conditions encountered, we believe the site is at low to moderate risk for liquefaction during a seismic event. The liquefaction study we performed utilized the Simplified Procedure originally developed by Seed and Idriss (1971) and most recently refined by Idriss and Boulanger (2008). This analysis was based on the soils data

2 California Department of Conservation Division of Mines and Geology (CDMG), “Digital Images of Official Maps of Alquist-Priolo Earthquake Fault Zones of California, Northern Region”, CDMG Compact Disc 2000- 0003, 2000.

3 United States Earthquake Hazards Program Liquefaction Susceptibility Program (https://earthquake.usgs.gov/learn/topics/geologicmaps/liquefaction.php)

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Peak Ground Acceleration (PGA) of 0.498 was used. Calculations utilized current groundwater depths. Liquefaction potential analysis was calculated from a depth of 0 to 40 feet below the ground surface. Liquefaction potential analysis is attached in Appendix C of this report.

Based on the calculation results, total seismically-induced settlement of saturated sands is expected to be approximately 1 inch. The consequences of one-dimensional settlement may be largely mitigated by the presence of a thick non-liquefiable layer above the potentially liquefiable soils (Ishihara 1985, Naesgaard et al. 1998, Bouckovalas and Dakoulas 2007). It is our opinion that the presence of stiff clay soils (non-liquefiable layer) found beneath the existing ground surface to a depth of approximately 10 to 20 feet may act as a bridging layer that redistributes stresses and therefore results in more uniform ground surface settlement. Therefore, seismically-induced differential settlement at the ground surface is anticipated to be uniform and ½ inch or less.

4.0 RECOMMENDATIONS FOR DESIGN AND CONSTRUCTION

Geotechnical Considerations

The site appears suitable for the proposed construction based upon geotechnical conditions encountered in the borings and our current understanding of the proposed development. Our findings indicate the proposed structures can be supported on a shallow spread footing foundation system bearing on native soils or engineered fill.

Native clay soils tested in our laboratory are classified as lean to fat clays with low to high expansion potential. Fat clays with high expansion potential were encountered intermittently throughout the site. Due to the high expansion potential of the upper materials, floor slabs of the proposed structures should be underlain by a minimum of 18 inches of non-expansive structural fill or lime treated clay soils. The native clay soils are not considered suitable for use as non-expansive structural fill on the project. Non-expansive structural fill should be comprised of low volume change materials.

This report provides recommendations to help mitigate the effects of soil shrinkage and expansion. The severity of cracking and other cosmetic damage such as uneven floor slabs will probably increase if any modification of the site results in excessive wetting or drying of the expansive soils.

The native soils underlying the site are sensitive to increases and decreases in moisture content.

Planters and other surface features which could retain water in areas adjacent to the building should be sealed. If site layout design requires landscape areas within 10 feet from the perimeter

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Geotechnical engineering recommendations for foundation systems and other earth connected phases of the project are outlined below. The recommendations contained in this report are based upon the results of data presented herein, field exploration, engineering analyses, and our current understanding of the proposed project.

Earthwork

Site grading on this project will likely consist of minor cuts and fills on the order of one to three feet. The following presents recommendations for site preparation, excavation, subgrade preparation and placement of engineered fills on the project.

Earthwork on the project should be observed and evaluated by Terracon. The evaluation of earthwork should include observation and testing of engineered fill, subgrade preparation, foundation bearing soils, and other geotechnical conditions exposed during the construction of the project.

4.2.1 Subgrade Preparation

Strip and remove vegetation and any other deleterious materials within the footprint of the proposed building. Exposed native soils should be free of mounds and depressions which could prevent uniform compaction.

The depth of scarification of subgrade soils and moisture conditioning of the subgrade is highly dependent upon the time of year of construction and the site conditions that exist immediately prior to construction. If construction occurs during the winter or spring, when the subgrade soils are typically already in a moist condition, scarification and compaction may only be 8 to 10 inches.

If construction occurs during the summer or fall when the subgrade soils have been allowed to dry out deeper, the depth of scarification and moisture conditioning may be as much as 18 inches.

The subgrade soils shall be moisture conditioned and recompacted as specified in Section 4.2.4.

4.2.2 Potential Volumetric Shrinkage During Grading

Some volumetric shrinkage of onsite soils should be anticipated during grading and compacting operations for this project. During our investigation, seven (7) soil samples were collected at an approximate depth of 24 inches and tested for maximum dry density in accordance with ASTM

D1557.

Maximum dry unit weights and optimum water contents for the soil samples collected are summarized in the table below:

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Maximum Dry Unit Weight

(pcf) Optimum Water Content (%)

Boring No. B-2 121.3 10.1

Boring No. B-11 127.9 8.9

Boring No. B-17 120.0 10.2

Boring No. B-27 116.4 13.3

Boring No. B-28 113.0 11.5

Boring No. B-39 117.4 11.3

Boring No. B-40 116.1 12.3

We anticipate that most areas to receive engineered fill will be compacted to a minimum of 90 to

95% relative compaction as specified in Section 4.2.4 of this report. Based on the results of our subsurface investigation and laboratory analysis, we estimate that the upper 24 inches of material could result in volumetric shrinkage on the order of 3% to 15% during grading.

Actual volumetric shrinkage during construction will be based on a host of factors, including variable strata thickness and uniformity, compaction method and equipment utilized, compaction of underlying strata, stripping losses, and uncharacterized changes in topography at the site. It should be noted that shrinkage estimates presented above are based on limited data and should be considered approximate.

4.2.3 Non-Expansive Structural Fill Material Requirements

We recommend concrete slab on grade floors be underlain with either 18 inches of non-expansive structural fill material or 18 inches of lime-treated native subgrade. Exterior concrete sidewalks and other flatwork shall be underlain by 12 inches of non expansive structural fill material or lime-treated native subgrade. All non-expansive structural fill materials from any source (either on-site or imported) should be inorganic soils free of vegetation, debris, and fragments larger than three inches in size. Pea gravel or other similar non- cementitious, poorly-graded materials should not be used as fill or backfill without the prior approval of the geotechnical engineer.

On site or Imported soils for use as compacted non-expansive structural fill material within the proposed building areas should conform to low volume change materials as indicated as follows:

Percent Finer by Weight

Gradation (ASTM C 136)

3”

No. 4 Sieve ..................................................................................... 50-100

No. 200 Sieve ................................................................................. 20 - 40

Liquid Limit ....................................................................... 30 (max)

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Plasticity Index ................................................................. 12 (max)

Maximum expansive index* .............................................. 20 (max)

*ASTM D 4829

Non-expansive structural fill should be placed and compacted in horizontal lifts, using equipment and procedures that will produce recommended moisture contents and densities throughout the lift. Fill lifts should not exceed ten inches in loose thickness.

4.2.4 Compaction Requirements

Recommended compaction and moisture content criteria for fill materials are as follows:

Material Type and Location

Per the Modified Proctor Test (ASTM D 1557)

Minimum

Compaction

Requirement

Range of Moisture Contents for

Compaction Above Optimum

Minimum Maximum

Approved non-expansive structural fill soils:

Beneath foundations: 90% -1% +3%

Beneath floor slabs & exterior sidewalks or concrete flatwork:

90% -1% +3%

Utility trenches (structural areas): 90% -1% +3%

On site Soils:

90% 2% +4% Bottom of excavation receiving fill:

Miscellaneous backfill: 90% 2% +4%

Beneath non-expansive structural fill supporting concrete floors, sidewalks and other exterior flatwork:

88% - 92% +1% +4%

Utility trenches (Landscape areas): 90% 0% +4%

Beneath asphalt pavements: 95% 0% +2%

Beneath concrete pavements: 95% 0% +2%

Aggregate base (beneath pavements): 95% 0% +2%

Engineered fill materials should be placed in horizontal, loose lifts not exceeding 8 inches in loose thickness.

4.2.5 Grading and Drainage

All final grades must provide effective drainage away from the building during and after construction. Water permitted to pond next to the building can result in greater soil movements than those discussed in this report. These greater movements can result in unacceptable differential floor slab movements, cracked slabs and walls, and roof leaks. Estimated movements

Responsive ■ Resourceful ■ Reliable 14 described in this report are based on effective drainage for the life of the structure and cannot be relied upon if effective drainage is not maintained.

Exposed ground should be sloped at least 2 percent away from buildings extending a minimum of 10 feet beyond the perimeter of the building. After building construction and landscaping, we recommend the Civil Engineer/Surveyor verify final grades to document that effective drainage has been achieved. Grades around the structure should also be periodically inspected and adjusted as necessary, as part of the structure’s maintenance program.

Planters located within 10 feet of the structure should be self-contained to prevent water accessing the building and pavement subgrade soils. Locate sprinkler mains and spray heads a minimum of 5 feet away from the building line. Collect roof runoff in drains or gutters. Discharge roof drains and downspouts onto pavements which slope away from the building or extend down spouts a minimum of 10 feet away from the structure.

Downspouts, roof drains or scuppers should discharge into catch basins and tight lines or extensions when the ground surface beneath such features is not protected by exterior slabs or paving. Sprinkler systems should not be installed within 5 feet of foundation walls. Landscaped irrigation adjacent to the foundation system should be minimized or eliminated.

4.2.6 Exterior Concrete Flatwork Design and Construction

Near surface clay soils tested in our laboratory are classified as lean to fat clays with low to high expansion potential. We recommend that exterior concrete flatwork be underlain by a minimum of 12 inches of non-expansive structural fill, lime-treated native subgrade. Aggregate base may also be used, if desired.

Compacted subgrade composed of on-site clayey soils will expand with increasing moisture content; therefore, exterior concrete slabs and sidewalks may heave, resulting in cracking or vertical offsets. The potential for damage would be greatest where exterior slabs are constructed adjacent to the building or other structural elements. To reduce the potential for damage caused by movement, we recommend:

exterior slabs should be supported directly on 12 inches of non-expansive structural fill, lime-treated subgrade, or aggregate base;

strict moisture-density control during placement of subgrade fills;

maintain proper subgrade moisture until placement of slabs;

placement of effective control joints on relatively close centers and isolation joints between slabs and other structural elements;

provision for adequate drainage in areas adjoining the slabs;

use of designs which allow vertical movement between the exterior slabs and adjoining structural elements.

and reinforce slabs with a minimum No. 4 bars at 18 inches on center.

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4.2.7 Earthwork Construction Considerations

Weakly cemented soils were encountered in our borings at variable depths of 2½ to 7½ feet across the site. We anticipate conventional heavy equipment is suitable to grade the site;

however, a ripping tooth may be required for excavations in some areas and extra time should be budgeted for grading in this stratum. At the time of our study, moisture contents of the surface and near-surface native soils ranged from 5 to 25 percent. Based on these moisture contents, some moisture conditioning, including wetting and/or drying, will likely be needed for the project.

Upon completion of filling and grading, care should be taken to maintain the subgrade moisture content prior to construction of the floor slab and exterior sidewalks and flatwork. Construction traffic over the completed subgrade should be avoided to the extent practical. The site should also be graded to prevent ponding of surface water on the prepared subgrades or in excavations.

If the subgrade should become desiccated, saturated, frozen, or disturbed, the affected material should be removed or these materials should be scarified, moisture conditioned, and re-compacted prior to floor slab and pavement construction.

Surface water should not be allowed to pond on the site and soak into the soil during construction.

Construction staging should provide drainage of surface water and precipitation away from the building and pavement areas. Any water that collects over or adjacent to construction areas should be promptly removed, along with any softened or disturbed soils. Surface water control in the form of sloping surfaces, drainage ditches and trenches, and sump pits and pumps will be important to avoid ponding and associated delays due to precipitation and seepage.

Groundwater was encountered in our borings at depths ranging from 7¼ to 15½ feet bgs during our exploration. Estimated groundwater elevations are presented in Appendix A, Exhibit A-2a.

Groundwater may impact utility construction if excavations extend at or near these depths. If groundwater is encountered during construction, some form of temporary or permanent dewatering may be required. Conventional dewatering methods, such as pumping from sumps, should likely be adequate for temporary removal of any groundwater encountered during excavation at the site. Well points would likely be required for significant groundwater flow, or where excavations penetrate groundwater.

All excavations should be sloped or braced as required by OSHA regulations to provide stability and safe working conditions. Temporary excavations will probably be required during grading operations. The grading contractor, by his contract, is usually responsible for designing and constructing stable, temporary excavations and should shore, slope or bench the sides of the excavations as required to maintain stability of both the excavation sides and bottom. All excavations should comply with applicable local, state and federal safety regulations, including the current Occupational Health and Safety Administration (OSHA) Excavation and Trench Safety

Standards.

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Construction site safety is the sole responsibility of the contractor who controls the means, methods and sequencing of construction operations. Under no circumstances shall the information provided herein be interpreted to mean that Terracon is assuming any responsibility for construction site safety or the contractor's activities; such responsibility shall neither be implied or inferred.

Foundations

In our opinion, the proposed structures can be supported by a shallow, spread or isolated pad footing foundation system bearing on native soils. Design recommendations for shallow foundations for the proposed structures are presented in the following paragraphs.

4.3.1 Foundation Recommendations

DESCRIPTION RECOMMENDATION

Foundation Type Conventional Shallow Spread Footings

Bearing Material Native Soils or Engineered Fill

Allowable Bearing Pressure 2,500 psf

Minimum Plan View Dimensions Walls: 12 inches; Columns: 24 inches

Minimum Embedment Below Finished Grade 24 inches

Total Estimated Settlement 1-inch

Estimated Differential Settlement ¾ inch over 40 feet

Ultimate passive pressure5

Compacted structural fill or native clay 350 pcf, equivalent fluid density

Ultimate coefficient of sliding friction5 0.35

Finished grade is defined as the lowest adjacent grade within five feet of the foundations. The allowable foundation bearing pressures apply to dead loads plus design live load conditions. The design bearing pressure may be increased by one-third when considering total loads that include transient conditions, such as wind or seismic. The weight of the foundation concrete below grade may be neglected in dead load computations. The spread footing foundation excavation sides must be nearly vertical and the concrete should be placed neat against these vertical faces for the passive earth pressure values to be valid. If the loaded side is sloped or benched, and then backfilled, the allowable passive pressure will be significantly reduced. Passive resistance in the upper 1 foot of the soil profile should be neglected. If passive resistance is combined with base friction to resist lateral loads, the passive resistance should be reduced by 50 percent.

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Foundations should be reinforced as necessary to reduce the potential for distress caused by differential foundation movement. To ensure footings have adequate support, special care should be taken when footings are located adjacent to trenches. The bottom of such footings should be at least 1 foot below an imaginary plane with an inclination of 1.5 horizontal to 1.0 vertical extending upward from the nearest bottom edge of the adjacent trench.

Foundation excavations and bearing soils should be observed by the geotechnical engineer. If the soil conditions encountered differ significantly from those presented in this report, then supplemental recommendations will be required.

Floor Slab

4.4.1 Design Recommendations

Floor slab support1 Either 18 inches of non-expansive engineered fill or 18 inches of lime-treated native subgrade.

Modulus of subgrade reaction

150 pounds per square inch per inch (psi/in) (The modulus was obtained based on our experience with similar subgrade conditions.)2

Aggregate base course/capillary break

4 inches of ¾ inch gravel for slabs with floor coverings which may be sensitive to moisture vapor migration or compacted Aggregate Base (Caltrans Class 2) for slabs which may not be considered sensitive to moisture vapor.

1. Upon completion of grading operations in the building area, the recommended subgrade moisture content and density should be maintained to construction of the building floor slabs.

2. This value is for a small load area (1 sq. ft. or less) such as for forklift wheel loads or point loads and should be adjusted for large loaded areas.

If floor slabs are to be supported by chemically treated subgrade soils, the following recommendations should be utilized:

Native sandy clay soils should be scarified to a depth of 18 inches, moisture conditioned and compacted per the compaction requirements in Section 4.2.4.

Once building pads are brought to grade, the upper 18 inches of subgrade should be thoroughly mixed with high calcium quick lime and compacted. The amount of lime to be used should be determined by laboratory testing at least three weeks prior to the start of any grading operations. For budgeting purposes, we recommend assuming a spread rate of 7½ pounds of lime for a 18 inch deep treated section.

Lime treatment should be performed in accordance with Section 24 of the Cal

Trans Standard Specifications, latest edition.

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The use of a vapor retarder should be considered beneath concrete slabs on grade that will be covered with wood, tile, carpet or other moisture sensitive or impervious coverings, or when the slab will support equipment sensitive to moisture. When conditions warrant the use of a vapor retarder, the slab designer should refer to ACI 302 and/or ACI 360 for procedures and cautions regarding the use and placement of a vapor retarder.

In areas of exposed concrete, control joints should be saw-cut into the slab after concrete placement in accordance with ACI Design Manual, Section 302.1R-37 8.3.12 (tooled control joints are not recommended). To control the width of cracking (should it occur), continuous slab reinforcement should be considered in exposed concrete slabs.

4.4.2 Floor Slab Construction Considerations

Interior trench backfill placed beneath slabs should be compacted in accordance with recommendations outlined in the Earthwork section of this report. Other design and construction considerations, as outlined in the ACI Design Manual, Section 302.1R are recommended.

On most project sites, the site grading is generally accomplished early in the construction phase.

However as construction proceeds, the subgrade may be disturbed due to utility excavations, construction traffic, desiccation, rainfall, etc. As a result, the floor slab subgrade may not be suitable for placement of rock and concrete and corrective action will be required.

We recommend the area underlying the floor slab be rough graded and then thoroughly proof-rolled with a loaded tandem axel dump truck prior to final grading and placement of aggregate base rock.

Particular attention should be paid to high traffic areas that were rutted and disturbed earlier and to areas where backfilled trenches are located. Areas where unsuitable conditions are located should be repaired by removing and replacing the affected material with properly compacted fill. All floor slab subgrade areas should be moisture conditioned and properly compacted to the recommendations in this report immediately prior to placement of the aggregate base rock and concrete.

4.5 Cantilever Retaining Walls

Cantilever retaining walls at the site may be supported by spread footings constructed in accordance with the recommendations provided in section 4.3 Foundations.

The lateral earth pressure recommendations given in the following paragraphs are applicable to the design of rigid retaining walls such as cantilever or gravity type concrete walls.

Reinforced concrete walls with unbalanced backfill levels on opposite sides should be designed for earth pressures at least equal to those indicated in the following table. Earth pressures will be influenced by structural design of the walls, conditions of wall restraint, methods of construction

Responsive ■ Resourceful ■ Reliable 19 and/or compaction and the strength of the materials being restrained. Two wall restraint conditions are shown. Active earth pressure is commonly used for design of free-standing cantilever retaining walls and assumes wall movement. The "at-rest" condition assumes no wall movement. The recommended design lateral earth pressures do not include a factor of safety and do not provide for possible hydrostatic pressure on the walls.

Earth Pressure Coefficients

Earth Pressure

Conditions Backfill Type

Equivalent

Fluid Density

(pcf)

Surcharge

Pressure, p1 (psf)

Earth

Pressure, p2

(psf)

Active (Ka) Imported Sandy

Soil/granular 35 (0.29)S (35)H

At-Rest (Ko) Imported Sandy

Soil/granular 55 (0.46)S (55)H

Passive (Kp) Imported Sandy

Soil/granular 350 - -

Applicable conditions to the above include:

For active earth pressure, wall must rotate about base, with top lateral movements of about

0.002 H to 0.004 H, where H is wall height

For passive earth pressure to develop, wall must move horizontally to mobilize resistance

Uniform surcharge, where S is surcharge pressure

In-situ soil backfill weight a maximum of 120 pcf

Horizontal backfill, compacted between 90 and 95 percent of modified Proctor maximum dry density, unless otherwise noted

Loading from heavy compaction equipment not included

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No hydrostatic pressures acting on wall

If dynamic loading from seismic ground motions is needed to be accounted for in the wall design, use 12 pcf applied via normal triangular distribution extending from bottom of footing.

No safety factor included

A coefficient of friction of 0.35 may be used for sliding resistance; however if passive resistance is combined with base friction to resist lateral loads, the passive resistance should be reduced by 50 percent.

Backfill placed against structures should consist of granular soils. For the above values to be valid, the backfill must extend out and up from the base of the wall at an angle of at least 45 and 60 degrees from vertical for the active and passive cases, respectively.

To control hydrostatic pressure behind the wall we recommend that a drain be installed at the bottom of the wall with a collection pipe leading to a reliable discharge. The drainage should consist of either a composite drain such as Miradrain 6200, Mirafi G100W, or Amerdrain Totaldrain or a 12-inch thick free draining gravel blanket. Free draining gravel should consist of Caltrans Class II permeable material or ¾ inch clean gravel wrapped in Mirafi 140N filter fabric or equivalent. The drainage should extend from the bottom of the wall to within 12 inches of the top of the wall. The drainage should be capped with 12 inches of compacted cohesive soil. The collection pipe should be a minimum 4-inch diameter perforated Schedule 40 PVC or ABS drain pipe and should slope to an existing drainage system or to a positive gravity outlet. If construction will take place below grade and positive drainage is not feasible, the drainage may be eliminated provided the walls are designed to account for hydrostatic pressures.

Pavements

4.6.1 Subgrade Preparation

We recommend the moisture content and density of the top 12 inches of the subgrade be evaluated and the pavement subgrades be proof rolled within two days prior to…