Geotech_Report.pdf

Copyright © 2010 By ENGEO Incorporated.

This Document May Not Be Reproduced In Whole Or In Part By Any Means Whatsoever, Nor May It Be Quoted Or Excerpted Without The Express Written Consent Of ENGEO Incorporated

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GEOTECHNICAL REPORT

SAN FRANCISCO VETERANS AFFAIRS

CLINICAL EXPANSION FOR MENTAL

HEALTH CARE AND SLEEP LAB UNIT

SAN FRANCISCO, CALIFORNIA

Submitted to:

Mr. Sanjiv Singh eCIFM Solutions, Inc.

3130 Crow Canyon Road, Suites E and F San Ramon, California 94583

Prepared by:

ENGEO Incorporated

October 4, 2010 Project No. 9069.000.000

GEOTECHNICAL

ENVIRONMENTAL

WATER RESOURCES

CONSTRUCTION SERVICES

332 Pine Street, Suite 300 San Francisco, CA 94104 (415) 284-9900 Fax (888) 279-2698 www.engeo.com

Project No.

9069.000.000

October 4, 2010

Mr. Sanjiv Singh eCIFM Solutions, Inc.

3130 Crow Canyon Road, Suites E and F San Ramon, CA 94583

Subject: A/E Design Service for Project 662-607

Clinical Expansion for Mental Health Care and Sleep Lab Unit Veterans Hospital, San Francisco, California

GEOTECHNICAL EXPLORATION

Dear Mr. Singh:

With your authorization, we have conducted a geotechnical exploration for the proposed expansion of the Mental Health Care and Sleep Lab Unit at the San Francisco Veterans Affairs Hospital in San Francisco, California. The accompanying report presents the results of our site exploration, the analysis of the geotechnical and geologic data accumulated during the study and the geotechnical recommendations for design of the proposed building and associated improvements. Based on our findings, it is our opinion that the currently proposed development is feasible from a geotechnical standpoint provided the recommendations included in this report are followed.

We are pleased to provide our services to you on this project and look forward to consulting further with you and your design team.

Sincerely, ENGEO Incorporated

Leroy Chan, PE Donald Bruggers, GE lc/deb/jf:gex eCIFM Solutions, Inc. 9069.000.000 San Francisco Veterans Hospital October 4, 2010

TABLE OF CONTENTS

Letter of Transmittal

Page

1.0 INTRODUCTION

1.1 PURPOSE AND SCOPE

1.2 SITE LOCATION AND DESCRIPTION

1.3 PROPOSED DEVELOPMENT

2.0 GEOLOGY AND SEISMICITY

2.1 REGIONAL GEOLOGIC HISTORY

2.2 GEOLOGIC SETTING

2.3 PREVIOUS STUDIES

2.4 SITE SEISMICITY

3.0 FIELD EXPLORATION

3.1 LABORATORY TESTING

3.2 SUBSURFACE CONDITIONS

3.3 GROUNDWATER

4.0 DISCUSSION AND CONCLUSIONS

4.1 SEISMIC HAZARDS

4.2 SITE-SPECIFIC GROUND MOTION ANALYSIS

4.2.1 Ground Rupture

4.2.2 Ground Shaking

4.2.3 Soil Liquefaction

4.2.4 Liquefaction-Induced Settlement

4.2.5 Lateral Spreading

4.3 CORROSION POTENTIAL

4.4 ADDITIONAL POTENTIAL GEOLOGICAL HAZARDS

5.0 RECOMMENDATIONS

5.1 GRADING

5.2 DEMOLITION AND STRIPPING

5.3 SUBGRADE PREPARATION

5.4 FILL MATERIALS

5.5 PLACEMENT OF FILL

5.5.1 Underground Utility Backfill

5.5.1.1 General

5.5.1.2 Structural Areas

5.5.2 Landscape Fill

5.6 SLOPES

5.6.1 Gradients

5.7 FOUNDATIONS

5.7.1 Spread Footings

5.7.2 Slab-on-Grade Construction

5.7.3 Secondary Slab-on-Grade Construction

5.8 SURFACE DRAINAGE

5.8.1 Subsurface Drainage

5.9 PAVEMENT DESIGN

5.10 PLAN REVIEW AND CONSTRUCTION OBSERVATION SERVICES

6.0 LIMITATIONS AND UNIFORMITY OF CONDITIONS

SELECTED REFERENCES

FIGURES

APPENDIX A – ENGEO, Boring Logs APPENDIX B – ENGEO, Laboratory Test Data APPENDIX C – Site Specific Spectra APPENDIX D – Guide Contract Specifications

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1.0 INTRODUCTION

1.1 PURPOSE AND SCOPE

The purpose of this report is to provide geotechnical engineering recommendations for the design and construction of the proposed project. The scope of our services included reviewing available literature and geologic maps for the immediate area, a subsurface exploration consisting of three exploratory borings, laboratory testing of materials sampled during the field exploration, geotechnical data analyses, and report preparation summarizing our recommendations for the proposed site development.

We prepared this report exclusively for eCIFM Solutions and their design team consultants.

ENGEO should review any changes made in the character, design or layout of the development to modify the conclusions and recommendations contained in this report, as necessary. This document may not be reproduced in whole or in part by any means whatsoever, nor may it be quoted or excerpted without the express written consent of ENGEO.

1.2 SITE LOCATION AND DESCRIPTION

The project is located on 4105 Clement Street in San Francisco, California. The tentative plan provided by eCIFM Solutions shows the proposed building expansion located east of Buildings 8 and 9 on the San Francisco Veterans Affairs Hospital campus. The project site currently consists of an asphalt-paved driveway with the eastern portion of the site occupied by a one-story maintenance/storage building and a portable trailer daycare center. The topographic relief at the site is relatively flat (Figure 1).

1.3 PROPOSED DEVELOPMENT

Based on the project team discussions and the tentative plans provided by eCIFM Solutions, it is our understanding that the proposed structure will consist of a multi-story building that would be part of the expansion associated with the existing Mental Health and Sleep Aid unit. At the time of this report, the location and type of structure has not been determined.

2.0 GEOLOGY AND SEISMICITY

2.1 REGIONAL GEOLOGIC HISTORY

The site is located on the San Francisco Peninsula, on the western side of the California Coast Ranges geomorphic province. The Coast Ranges are a complex series of linear mountain ranges that lie more-or-less parallel to the coast and to the San Andreas Fault System. The Coast Ranges are composed primarily of Jurassic and Cretaceous-age rocks that accumulated on the sea floor and were later scraped off when the ocean plate on which they originated was subducted beneath North America. These older rocks include a tectonic mix of sandstone, chert, altered basalt referred to as greenstone, and serpentinite, collectively referred to as the Franciscan Complex.

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While Franciscan bedrock is exposed in the hills and cliffs of San Francisco, the flanks of the hills are blanketed with thin to thick layers of colluvium and alluvium (weathered material washed downslope from the bedrock exposures). Valleys are filled with water-laid stream deposits.

2.2 GEOLOGIC SETTING

The project site is situated on the northwestern corner of the San Francisco Peninsula in the San Francisco North Quadrangle. Review of the geologic map of San Francisco North prepared by Schlocker (1958) found that intensely sheared rocks of the Franciscan formation underlie the property. This mapped unit generally includes rock fragments rounded by shearing and embedded in a soft matrix. The site is also adjacent to deposits of Quaternary-age dune sand consisting of clean, well-sorted, fine- to medium-grained sand, underlain by weathered Franciscan bedrock.

In addition, there are three visible inactive fault traces in the vicinity of the site and two mapped landslide scarps to the north of the site. One of the faults runs to the north of the site; however, the site is not situated in a mapped Alquist-Priolo Earthquake Fault Hazard Zone.

2.3 PREVIOUS STUDIES

Prior to beginning the field portion of our exploration, we reviewed available geotechnical engineering reports for the site and vicinity. ENGEO previously performed geotechnical site investigations for the Building 16 Annex and Building 22. Historic aerial photographs dating back to 1946 were also reviewed as part of this study. Aerial photography suggests that buildings at the site date back prior to 1946.

2.4 SITE SEISMICITY

No active faults are mapped across the project footprint and the site is not located within a State of California Earthquake Fault Zone for active faults. The San Andreas and San Gregorio faults are located approximately 3 miles and 6 miles, respectively, to the southwest of the site (Idriss, 1994). The Hayward and Calaveras faults are located approximately 15 miles and 21 miles, respectively, to the northeast. Each of these faults is considered a major active fault and has produced earthquakes within the last 200 years. The maximum earthquake for the region can be expected from the San Andreas Fault, a major active fault within the Bay Area. Figure 4 shows the site in relation to the faults in the region.

In addition, the Working Group on California Earthquake Probabilities (2007) estimates there is a 21 percent probability that a magnitude Mw = 6.7 or greater earthquake will occur on the northern portion of the San Andreas Fault while they estimate a 31 percent probability of the same magnitude event occurring on the Hayward/Rogers Creek Fault within 30 years of their study (2007 – 2037).

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3.0 FIELD EXPLORATION

The field exploration for this study was conducted on September 9, 2010, and consisted of three exploratory borings advanced to depths up to 27 feet below grade. The boring locations are shown on the Site Plan, Figure 2. We located the borings relative to existing features and the locations should be considered accurate only to the degree implied by the method used. The purpose of the borings was to log the subsurface materials in each borehole and to obtain representative samples of underlying native soil and bedrock deposits for laboratory testing.

All test borings were drilled using a truck-mounted B-24 drill rig equipped with 4-inch-diameter continuous flight augers. An ENGEO Engineer logged the borings in the field and collected soil samples using either a 2½-inch-inside-diameter (I.D.) California-type split-spoon sampler fitted with 6-inch-long brass liners or a 2-inch-outside-diameter (O.D.) Standard Penetration Test split-spoon sampler. The penetration of the samplers into the native materials was field recorded as the number of blows needed to drive the sampler 18 inches in 6-inch increments. Blow count results on the boring logs are recorded as the number of blows required for the last one foot of penetration. The samplers were driven with a 140-pound safety hammer falling a distance of 30 inches. A rope and cat-head system was used to lift the safety hammer during our exploration.

The field logs were used to develop the report boring logs presented in Appendix A.

The logs depict subsurface conditions within the borings at the time the exploration was conducted. Subsurface conditions at other locations may differ from conditions occurring at these boring locations. Stratification lines representing the approximate boundaries between soil types and the transition may be gradual.

3.1 LABORATORY TESTING

Following drilling, samples were reexamined in the ENGEO laboratory to confirm field classifications. Representative driven samples were tested for the following physical characteristics:

TABLE 1

Characteristic Test Method Location of Results Within This Report

Atterberg Limits ASTM D-4318 Appendix B

Natural Moisture Content ASTM D-2216 Appendix B

Unit Weight ASTM D-2937 Appendix B Unconsolidated Undrained Triaxial Compression ASTM D-2850 Appendix B

Sulfate Testing Caltrans 417 Appendix B

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Laboratory test results from samples recovered are included on the boring logs in Appendix A and on the laboratory test data in Appendix B as noted above. If the unit weight laboratory test results indicated a degree of sample disturbance possibly due to handling and transport, they were not taken into consideration for analysis and design.

3.2 SUBSURFACE CONDITIONS

In general, the project area is currently covered by asphaltic concrete (AC) over an aggregate base (AB) of varying thickness. In general, the subsurface conditions encountered within the project area consist of 7 to 17 feet of loose to medium dense sand and clayey sand. Laboratory testing found that this soil has a Plasticity Index that is non-detected, which is indicative of a soil with low potential of expansion. Underlying this layer of sand, our borings encountered stiff to hard sandy clay. This material overlies Franciscan bedrock. The Franciscan bedrock encountered generally consists of sandstone or graywacke, with some sheared and weathered claystone and sandstone. All of the exploratory borings performed during this study terminated due to drilling refusal.

3.3 GROUNDWATER

No groundwater was encountered at the site during our field exploration with the exception of Boring 1-B1 to the north of the study area where groundwater was encountered at a depth of 18½ feet. It should be recognized that fluctuations in the level of groundwater may occur due to variations in rainfall, irrigation practice and other factors not evident at the time observations were made.

4.0 DISCUSSION AND CONCLUSIONS

Based on a review of the findings of the subsurface exploration and laboratory test results, we conclude that the proposed improvements are feasible from a geotechnical standpoint, provided that the recommendations included in this report, along with other sound engineering practices, are incorporated in the design and construction of the project.

4.1 SEISMIC HAZARDS

Seismic hazards can generally be classified as primary and secondary. The potential primary seismic hazard resulting from a nearby moderate to major earthquake is ground rupture, also called surface faulting. Common secondary seismic hazards include ground shaking, soil liquefaction, liquefaction-induced settlement, dynamic densification, lateral spreading, expansive soils, flooding, earthquake-induced landslides, regional subsidence or uplift, and tsunamis and seiches.

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4.2 SITE-SPECIFIC GROUND MOTION ANALYSIS

The project hospital structure is not under OSHPD jurisdiction and there are no site-specific ground motion procedures stipulated by current Federal design standards. However, at the request of the project structural engineer, the ground motions were developed in accordance with the 2007 CBC and the requirements outlined in Code Application Notice (CAN) File No. 2-1802A.6.2 and CAN 2-1614A.1.2. CBC Section 1614A.1.2 requires that a ground motion hazard analysis be performed in accordance with ASCE 7 Chapter 21. Consequently, we undertook a site-specific ground motion hazard analysis as outlined below.

We developed a site-specific probabilistic MCE acceleration response spectrum for 5 percent damping with a 2 percent probability of exceedance in a 50-year period. To perform this probabilistic analysis, we utilized the computer software EZFrisk. We performed our analyses using faults within a 100-kilometer radius. We utilized recently published Next Generation Attenuation (NGA) relationships for shallow crustal earthquakes on the West Coast of the United States, which have been used by the USGS in their recent seismic mapping project. Specifically, we utilized NGA relationships by Boore and Atkinson (2008), Campbell and Bozorgnia (2008), and Chiou and Youngs (2007). The results of the three NGA relationships were averaged for use in our analyses. We then scaled these results to the maximum direction of ground motion using scaling factors published by Huang et al. (2008).

We also developed a site-specific deterministic MCE acceleration response spectrum for 5 percent damping using the 84th percentile spectral response acceleration calculated for faults within the same radius and using the same NGA relationships used to develop the Probabilistic MCE. We performed this search using EZFrisk. We scaled this spectral acceleration to represent the maximum direction of ground motion as with the Probabilistic MCE. The highest spectral response acceleration values calculated by EZFrisk were for a seismic event on the San Andreas Fault with a Moment Magnitude of 7.9. This spectrum was then compared to the minimum deterministic values as discussed in Chapter 21.2.2 of ASCE 7-05.

We developed our recommended Design Spectrum by comparing the lesser of the Probabilistic MCE and the Deterministic MCE spectra and by taking 2/3 of the controlling spectrum. The lowest of the two spectra was then compared to 80 percent of the mapped spectrum developed in accordance with Chapter 11 of ASCE 7-05. The “Recommended Design Spectrum” shown on Appendix C shows the spectrum developed as discussed above. The spectral acceleration values are also provided.

Below is the table with the spectral acceleration values of the “Recommended Design Spectrum” for the short period and long period at the site.

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TABLE 2

Coefficient

(2 Percent Probability Of Exceedance In A 50-Year Period) Value

Site Class C

Design, 5% Damped, Spectral Response Acceleration from Site- Specific Analysis at Short Periods, SDS 1.240

Design, 5% Damped, Spectral Response Acceleration from Site- Specific Analysis at a Period of 1 second, SD1

1.010

4.2.1 Ground Rupture

No known active faults have been mapped across the area of the planned structure. We therefore conclude that the potential for ground rupture is low.

4.2.2 Ground Shaking

An earthquake of moderate to high magnitude generated within the San Francisco Bay Region could cause considerable ground shaking at the site. To mitigate the ground-shaking effects, all structures should be designed using sound engineering judgment and the latest California Building Code (CBC) requirements as a minimum. Seismic design provisions of current building codes generally prescribe minimum lateral forces, applied statically to the structure, combined with the gravity forces of dead-and-live loads. The prescribed lateral forces are generally considered to be substantially smaller than the actual peak forces that would be associated with a major earthquake. Consequently, structures should be able to: (1) resist minor earthquakes without damage, (2) resist moderate earthquakes without structural damage but with some nonstructural damage, and (3) resist major earthquakes without collapse but with some structural as well as nonstructural damage. Conformance to the current building code recommendations does not constitute any kind of guarantee that significant structural damage would not occur in the event of a maximum magnitude earthquake; however, it is reasonable to expect that a well-designed and well-constructed structure will not collapse or cause loss of life in a major earthquake (SEAOC, 1996).

4.2.3 Soil Liquefaction

Soil liquefaction is a phenomenon where saturated, cohesionless, loose soils experience a temporary, but essentially total, loss of shear strength when subjected to the reversing cyclic shear stresses caused by earthquake ground shaking.

Based on the findings from the subsurface exploration and review of the City and County of San Francisco Seismic Hazards Zones map (Figure 5), we conclude that the soil profile under the site has a low potential for liquefaction. Based on the foregoing discussion, we conclude that the risk for liquefaction at the site is low.

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4.2.4 Liquefaction-Induced Settlement

As previously stated, site soils have a low potential for liquefaction; therefore, liquefaction-induced settlement is expected to be insignificant.

4.2.5 Lateral Spreading

Lateral spreading is a failure within a nearly horizontal soil zone, commonly associated with liquefaction, which causes the overlying soil mass to move toward a free face, or down a gentle slope. As previously stated, site soils have a low potential for liquefaction; therefore, lateral spreading is expected to be insignificant.

4.3 CORROSION POTENTIAL

An evaluation of possible corrosion impacts to site improvements was conducted on a near-surface soil sample (Appendix B). As reported in the attached analytical result, the sample contained a sulfate concentration of 3 mg/kg. The criteria presented in the 2007 California Building Code (CBC) show that the test result is classified in the “negligible” sulfate exposure range. Cement type, water-cement ratio and concrete strength are not specified by the CBC for this range. We recommend that Type II cement be used in foundation concrete for structures within the project site. Additionally, concrete should incorporate a maximum water cement ratio of 0.50 and a minimum compressive strength of 3,000 psi. Structural engineering requirements for strength design as well as the results of the resistivity may result in more stringent concrete specifications.

The 2007 CBC provides the following guidelines to mitigate sulfate attack on concrete in contact with soil.

TABLE 3

Sulfate In Soil Sulfate

Exposure mg/kg (%) Cement Type

Maximum Water- Cement

Ratio

Minimum F’c (Psi)

Negligible 0 – 1,000 0.00 – 0.10 --- --- ---

Moderate 1,000 – 2,000 0.10 – 0.20

II, IP(MS),

IS(MS), P(MS),

I(PM)(MS),

I(SM)(MS)

0.50 4,000

Severe 2,000 – 20,000 0.20 – 2.00 V 0.45 4,500

Very Severe Over 20,000 over 2.00 V plus pozzolan 0.45 4,500

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4.4 ADDITIONAL POTENTIAL GEOLOGICAL HAZARDS

Based on topographic and lithologic data, the risk from regional subsidence or uplift, tsunamis, inundation due to embankment failure or seiches, and volcanic eruption is considered low to negligible at the project site.

5.0 RECOMMENDATIONS

5.1 GRADING

All grading and site development plans should be reviewed by the project Engineering Geologist and the Geotechnical Engineer. When detailed grading plans are available, we can provide specific corrective grading procedures for the site including a quantitative analysis of the grading scope.

The project Geotechnical Engineer or qualified representative should be present during the site work to observe demolition, site preparation, grading operations and subdrain placement. The Geotechnical Engineer should be notified a minimum of 72 hours prior to the commencement of any grading or stripping operations at the site. This is to provide time to coordinate the work with the Grading Contractor. After the grading operations commence, geologic observation of cut areas should be made at frequent intervals. This is advised so that revised geologic recommendations can be incorporated into updated grading plans as grading proceeds.

Ponding of stormwater, other than within engineered detention basins, should not be permitted at the site, particularly during work stoppage for rainy weather. Before the grading is halted by rain, positive slopes should be provided to carry the surface runoff to storm drainage structures in a controlled manner to prevent erosion damage.

5.2 DEMOLITION AND STRIPPING

All existing pavement, concrete slabs, and debris in the area of the improvements should be removed prior to grading. Care should be taken with existing utility trenches. All excavations from demolition and stripping below design grades should be cleaned to a firm undisturbed soil surface as determined by the Geotechnical Engineer or their qualified representative in the field at the time of site preparation. This surface should then be scarified, moisture conditioned and compacted prior to placement of new fill. All excavations should be backfilled with compacted engineered fill. The requirements for the placement of backfill materials are the same as for engineered fill.

5.3 SUBGRADE PREPARATION

Following demolition, stripping of surface soils and excavation of loose fills, all areas to receive fill and slabs-on-grade should be overexcavated, moisture conditioned and compacted to the requirements for engineered fill presented below so as to create a zone of engineered fill at least

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24 inches thick. The finished subgrade should be firm and non-yielding under the weight of compaction equipment.

5.4 FILL MATERIALS

Onsite material is suitable to be used as fill material provided it is processed to remove concentrations of organic material, debris, and particles greater than 6 inches in maximum dimension.

Imported fill materials should meet the above requirements and have a plasticity index less than 18. Allow ENGEO to sample and test proposed imported fill materials at least 72 hours prior to delivery to the site.

5.5 PLACEMENT OF FILL

After removal of loose soil, the exposed non-yielding surface should be scarified to a depth of 12 inches; moisture conditioned and recompacted to provide adequate bonding with the initial lift of fill. The bottom of the excavation for foundation elements should be compacted to assure stabilization of the underlying material. All fills should be placed in thin lifts. The lift thickness should not exceed 8 inches or the depth of penetration of the compaction equipment used, whichever is less.

The following compaction control requirements should generally be applied to all fills (assumes that fills consist of native sandy granular non-expansive soils):

Test Procedures: ASTM D-1557

Required Moisture Content: At least 1-percentage point above optimum moisture content.

Minimum Relative Compaction: Not less than 95 percent of maximum dry density.

Relative compaction refers to in-place dry density of the fill material expressed as a percentage of the maximum dry density as determined by ASTM D-1557-91. Optimum moisture is the moisture content corresponding to the maximum dry density.

It is important that all site preparation, including demolition and stripping be done under the observation of the Geotechnical Engineer or his/her qualified field representative and should be carried out according to the requirements contained herein.

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5.5.1 Underground Utility Backfill

5.5.1.1 General

The contractor is responsible for conducting all trenching and shoring in accordance with CALOSHA requirements. Project consultants involved in utility design should specify pipe-bedding materials.

5.5.1.2 Structural Areas

Place and compact trench backfill as follows:

1. Trench backfill should have a maximum particle size of 6 inches.

2. Moisture condition trench backfill to or slightly above the optimum moisture content for nonexpansive soils and to at least 3 percent above the optimum moisture content for expansive soils. Moisture condition backfill outside the trench.

3. Place fill in loose lifts not exceeding 12 inches.

4. Compact fill to a minimum of 90 percent relative compaction (ASTM D1557).

Where utility trenches cross underneath buildings, we recommend that a plug be placed within the trench backfill to help prevent the normally granular bedding materials from acting as a conduit for water to enter beneath the building. The plug should be constructed using a sand cement slurry (minimum 28-day compressive strength of 500 psi) or relatively impermeable native soil for pipe bedding and backfill. We recommend that the plug extend for a distance of at least 3 feet in each direction from the point where the utility enters the building perimeter.

Jetting of backfill is not an acceptable means of compaction. We may allow thicker loose lift thicknesses based on acceptable density test results, where increased effort is applied to rocky fill or for the first lift of fill over pipe bedding.

5.5.2 Landscape Fill

Process, place, and compact fill in accordance with Sections 5.4.2, except compact to at least 85 percent relative compaction (ASTM D1557).

5.6 SLOPES

5.6.1 Gradients

Construct final slope gradients to 2:1 (horizontal:vertical) or flatter. The contractor is responsible to construct temporary construction slopes in accordance with CALOSHA requirements.

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5.7 FOUNDATIONS

We understand that a new expansion may be constructed to connect to the existing mental health and sleep-aid structure to the west. Foundation plans of the adjacent Building 8 were not available for us to review. Based on our experience, it is likely that the adjacent building is supported on shallow spread footing foundation. We should review the foundation plans of the new and existing buildings so that we may provide supplemental recommendations, as necessary.

5.7.1 Spread Footings

The proposed building expansion may be supported on a spread footing and slab-on-grade foundation system. The spread footings should be a minimum of 12 inches wide and should be founded at least 18 inches below the lowest adjacent grade. Footing trenches should be cleared of loose soil and rock fragments prior to steel and concrete placement. It is important that footing trenches not be allowed to desiccate prior to placing concrete.

Geotechnical design criteria for use in footing sizing are as follows:

Minimum depth of footing embedment: 18 inches below the lowest adjacent grade.

Minimum footing width: 12 inches

Maximum allowable footing pressure: 3,500 psf dead plus live loads. Increase by one-third when considering total loads including wind or seismic loads.

Resistance to lateral loads can be obtained from a combination of passive earth pressures against the face of the foundation and soil friction along the base of the foundation. To resist lateral loads, a passive pressure corresponding to an equivalent fluid weighing 350 pounds per cubic foot (pcf) and a base friction factor of 0.4 times net vertical dead load should be used. Lateral resisting pressures in the upper one foot should be neglected if the footings are not confined by slab or pavement. Independent column footings should be structurally tied together to reduce the effects of differential settlement.

5.7.2 Slab-on-Grade Construction

The subgrade material under slabs-on-grade should be uniform and properly moisturized engineered fill. The upper 24 inches of subgrade should be moisture conditioned and compacted per recommendations in the fill placement section of this report. The subgrade should be thoroughly soaked prior to placing the concrete and should not be allowed to dry prior to concrete placement.

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When buildings are constructed with concrete slabs-on-grade, water vapor from beneath the slab will migrate through the slab and into the building. This water vapor can be reduced but not stopped. Vapor transmission can negatively affect floor coverings and lead to increased moisture within a building. When water vapor migrating through the slab would be undesirable, we recommend the following to reduce, but not stop, water vapor transmission upward through the slab on grade. The structural engineer should design the slabs-on-grade (steel size and spacing and slab thickness) for their intended use but we recommend a minimum slab thickness of 5 inches.

1. Where moisture transmission through the slab will be detrimental to floor coverings, install a vapor retarder membrane directly beneath the slab. Seal the vapor retarder at all seams and pipe penetrations. Vapor retarders shall be Class A vapor retarder in accordance with ASTM E 1745 “Standard Specification for Plastic Water Vapor Retarders used in Contact with Soil or Granular Fill under Concrete Slabs.” Vapor retarders should be installed and sealed as recommended by the manufacturer and at all seams and pipe penetrations.

2. Concrete shall have a concrete water-cement ratio of no more than 0.5.

3. Provide inspection and testing during concrete placement to check that the proper concrete and water cement ratio are used.

4. Consider moist cure slabs for a minimum of 3 days.

The Structural Engineer should be consulted as to the use of a layer of clean sand (less than 5 percent passing the U.S. Standard No. 200 Sieve) placed on top of the vapor retarder membrane to assist in concrete curing. In our past experience, we have observed that concrete slabs retain moisture and may take several months to fully hydrate. Provide sufficient time to air dry floor slabs before floor covering application, such as vinyl floor tile and wood flooring placement. Alternatively, apply a floor sealant over the concrete to minimize moisture from accumulating under the flooring. Also, the use of a lower water/cement ratio and higher strength concrete will reduce the amount of water in the slab and help expedite the hydration time.

5.7.3 Secondary Slab-on-Grade Construction

This section provides guidelines for secondary slabs such as exterior slabs, walkways, and steps.

Secondary slabs-on-grade should be constructed structurally independent of the foundation system. This allows slab movement to occur with a minimum of foundation distress.

Slabs-on-grade should be designed specifically for their intended use and loading requirements.

As a minimum requirement, slabs-on-grade should be reinforced for control of cracking. Slab reinforcement should be designed by the Structural Engineer. In our experience, welded wire mesh is generally not sufficient to control slab cracking. Therefore, we recommend the Structural Engineer consider using a minimum of No. 3 bars for design of the slab reinforcement.

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Slabs-on-grade should have a minimum thickness of 4 inches with a thickened edge extending at least 6 inches into compacted soil to minimize water infiltration. A 4-inch-thick layer of clean crushed rock or gravel should be placed under sidewalk and driveway slabs. As an alternative to providing a 6-inch-thick edge, a minimum 5½-inch-thick slab could be placed over 4 inches of clean crushed rock or gravel.

5.8 SURFACE DRAINAGE

The project site must be positively graded at all times to provide for rapid removal of surface water runoff away from the foundation systems and to prevent ponding of water under floors or seepage toward the foundation systems at any time during or after construction. Ponded water will cause undesirable soil swell and loss of strength. Care should be exercised to provide that landscape mounds or walkways will not interfere with this requirement. Area drains may be needed to comply with these requirements in some instances.

Ponding of stormwater must not be permitted during prolonged periods of inclement weather. As a minimum requirement, unpaved finished grades should have slopes of at least 3 to 5 percent and hardscaped areas should have slopes of at least 1 to 2 percent within 5 feet of the exterior walls and at right angles to them to allow surface water to drain positively away from the structure. All surface water should be collected and discharged into the storm-drain system in accordance with the City of San Francisco requirements. Landscape mounds must not interfere with this requirement.

All roof stormwater should be collected and directed to downspouts. Stormwater from roof downspouts should be carried away in closed conduits to collection points designed by the Civil Engineer.

5.8.1 Subsurface Drainage

Based on our site exploration and current grading concepts for the site, we do not anticipate that subdrainage systems will be necessary. We recommend that ENGEO will review the site grading plans to further evaluate the need for subdrainage systems as well as observe the earthwork operations during site grading.

5.9 PAVEMENT DESIGN

For budgeting purposes, we provide the following pavement design based on an estimated a resistance ("R") value of 5 for the onsite near-surface soils. The following preliminary flexible pavement sections have been determined for Traffic Indices of 4.5, 5, 6, and 7 based on an assumed R-value of 5 according to the method contained in Topic 608 of Highway Design Manual by CALTRANS.

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TABLE 4

Alternative I Alternative II

Traffic Index AC (inches)

AB

(inches)

AC

(inches)

AB

(inches)

ASB*

(inches)

4.5 3.0 8.0 3.0 4.0 5.0

5.0 3.0 10.0 3.0 4.0 7.0

6.0 3.5 13.0 3.5 6.0 8.0

7.0 4.0 16.0 4.0 7.0 10.0 Notes: AC is asphaltic concrete

AB is aggregate base Class 2 Material with minimum R-value = 78 ASB is aggregate subbase with minimum R-value = 50

* A minimum 12-inch-thick section of lime-treated subgrade can be substituted for ASB provided equivalent R-values can be obtained

The Traffic Index should be determined by the Civil Engineer or appropriate agency. These sections are for estimating purposes only. We recommend R-value testing be performed following site grading to determine the as-built pavement subgrade characteristics for final pavement section evaluation. Pavement construction and all materials should comply with the requirements of the Standard Specifications of the State of California Division of Highways, County requirements and the following minimum requirements:

• All pavement subgrades should be scarified to a depth of 12 inches below finished subgrade elevation, moisture conditioned to at least 1-percentage point above optimum, and compacted to at least 95 percent relative compaction and in accordance with applicable City and County requirements. These specifications may be modified depending on the materials actually exposed at roadway subgrade levels.

• Subgrade soils should be in a stable, non-pumping condition at the time aggregate baserock materials are placed and compacted.

• Adequate provisions must be made such that the subgrade soils and aggregate baserock materials are not allowed to become saturated.

• Aggregate baserock materials should meet current Caltrans specifications for Class 2 aggregate baserock and should be compacted to at least 95 percent of maximum dry density at a minimum moisture content of optimum.

• Asphalt paving materials should meet current Caltrans specifications for asphalt concrete.

• All concrete curbs separating pavement and irrigated landscaped areas should extend into the subgrade and below the bottom of adjacent aggregate baserock materials.

- 15 -

5.10 PLAN REVIEW AND CONSTRUCTION OBSERVATION SERVICES

It is important to the success of this project that the recommendations contained in this report be carefully implemented in the field. ENGEO should be retained to review the project plans and specifications to confirm that they meet the intent of the recommendations contained in this report.

We recommend that ENGEO be retained to provide soil engineering services during the earthwork phases of the work. This is to check for compliance with the design concepts, specifications and recommendations, and to allow design changes in the event that subsurface conditions differ from those anticipated prior to the start of construction.

At the completion of the earthwork and foundation construction aspects of the work, we will provide documentation of construction activities observed by ENGEO along with a statement regarding the adequacy of the work observed.

6.0 LIMITATIONS AND UNIFORMITY OF CONDITIONS

This report is issued with the understanding that it is the responsibility of the owner to transmit the information and recommendations of this report to developers, owners, buyers, architects, engineers, and designers for the project so that the necessary steps can be taken by the contractors and subcontractors to carry out such recommendations in the field. The conclusions and recommendations contained in this report are solely professional opinions.

The professional staff of ENGEO Incorporated strives to perform its services in a proper and professional manner with reasonable care and competence but is not infallible. There are risks of earth movement and property damages inherent in land development. We are unable to eliminate all risks or provide insurance; therefore, we are unable to guarantee or warrant the results of our services.

This report is based upon field and other conditions discovered at the time of preparation of ENGEO’s report. This document must not be subject to unauthorized reuse that is, reusing without written authorization of ENGEO. Such authorization is essential because it requires ENGEO to evaluate the document’s applicability given new circumstances, not the least of which is passage of time. Actual field or other conditions will necessitate clarifications, adjustments, modifications or other changes to ENGEO’s documents. Therefore, ENGEO must be engaged to prepare the necessary clarifications, adjustments, modifications or other changes before construction activities commence or further activity proceeds. If ENGEO’s scope of services does not include on-study area construction observation, or if other persons or entities are retained to provide such services, ENGEO cannot be held responsible for any or all claims arising from or resulting from the performance of such services by other persons or entities, and from any or all claims arising from or resulting from clarifications, adjustments, modifications, discrepancies or other changes necessary to reflect changed field or other conditions.

SELECTED REFERENCES

American Concrete Institute, 2005, Building Code Requirements for Structural Concrete

(ACI 318-05) and Commentary (ACI 318R-05).

Blake, T. F., 2000, EQFAULT, A Computer Program for the Deterministic Prediction of Peak

Horizontal Acceleration from Digitized California Faults.

Bonilla, M.G., 1998, Preliminary Geologic Map of the San Francisco South 7.5’ Quadrangle and

Part of the Hunters Point 7.5’ Quadrangle, San Francisco Bay Area, California: a Digital Database, U.S. Geological Survey, Open File Report OF-98-354.

Boore et al., 1997, in Blake, T.F., 1996, EQSEARCH computer program, referenced as personal communication to Blake, p106.

California Department of Transportation, 1992, Highway Design Manual.

California Geological Survey (CGS), 1997, Guidelines for Evaluating and Mitigating Seismic

Hazards in California, Special Publication 117, March.

Frankel, Arthur D. et al. Documentation for the 2002 Update of the National Seismic Hazard

Maps, Open-file Report 02-420.

International Code Council, 2007 California Building Code.

Ishihara, K., 1985, Stability of Natural Deposits during Earthquakes: Proceedings Eleventh

International Conference on Soil Mechanics and Foundation Engineering, San Francisco.

Ishihara, K., 1985, Stability of Natural Deposits during Earthquakes: Proceedings of the Eleventh

International Conference on Soil Mechanics and Foundation Engineering.

SEAOC, 1996, Recommended Lateral Force Requirements and Tentative Commentary.

WGCEP, 2007; Earthquake Probabilities in San Francisco Bay Region 2002-2031;

U.S. Geological Survey; Open-File Report 03-214.

LIST OF FIGURES

Figure 1 - Vicinity Map Figure 2 - Site Plan Figure 3 - Regional Geologic Map Figure 4 - Regional Faulting and Seismicity Figure 5 - Seismic Hazard Zone Map

F I G U R E S

1-B1

1-B2

1-B3

1-B3

ORTIGALITA

G

REENVILLE

SAN

G

R

EG

O

RIO

SAN ANDREAS

HAYW

ARD

POINT REYES

SAN ANDREAS

CO

NCO

RD

G R

EEN

VALLEY

V

AC

A

SAN JOAQUIN

ORTIGALITA

TOLAY

RODG

ERS CREEK

C O

R D

E

LIA

M

IDW

AY

SILVER CREEK

SAN JOSE

MONTE VISTA SHANNON

BERROCAL

ZAYANTE

VERGELES

SARGENT

DUNNIGAH HILLS

M

AACAMA

CALAVERAS

CARNEGIE CORAL HOLLOW

W

EST NAPA

BENNETT VALLEY

H U

N

TIN

G C

R

EEK - BERRYESSA

ALEXANDER-REDW

OOD HILL

GEYSER PEAK

COLLAYOMI

ANTIO

CH

BEAR M

O

UNTAINS

BEAR MOUNTAINS

M

ELONES

BEAR M

OUNTAINS

TAHO

E - SIERRA FRONTAL

G R

E A T V A L L E Y F A U L T

G R E A T V A L L E Y F A U L T

Santa Cruz Santa Clara

Merced

San Mateo Mariposa

Alameda

Stanislaus

Contra Costa San Joaquin

Marin Tuolumne

Calaveras Solano

Amador Sacramento

NapaSonoma Alpine

Yolo El Dorado

Lake

San Francisco

SAN ANDREAS

APPENDIX A

Boring Logs

A P P E N D

X

3/4 "41040

MORE THAN HALF

COARSE FRACTION

IS LARGER THAN

NO. 4 SIEVE SIZE

OH - Highly plastic organic silts and clays

For fine-grained soil with >30% retained on the #200 sieve, the words "sandy" or "gravelly" (whichever is predominant) are added to the group name.

For fine-grained soils with 15 to 29% retained on the #200 sieve, the words "with sand" or "with gravel" (whichever is predominant) are added to the group name.

FI

N

E -G

R A

IN

E

D S

O

IL

S M

O R

E

TH

A N

H A

LF

O

F M

A T'

L S

M A

LL

E

R

TH

A N

S

IE

V

E

C O

A R

S E

-G R

A

IN

E D

S O

IL

S

M O

R E

T H

A N

H A

LF

O

F M

A T'

L

LA

R G

E R

T H

A N

SI

EV

E

SILTS AND CLAYS LIQUID LIMIT 50 % OR LESS

U.S. STANDARD SERIES SIEVE SIZE

SILTS AND CLAYS LIQUID LIMIT GREATER THAN 50 %

PT - Peat and other highly organic soils

KEY TO BORING LOGS

CH - Fat clay with high plasticity

SC - Clayey sand, sand-clay mixtures

GP - Poorly graded gravels or gravel-sand mixtures

Grab Samples

Dusty, dry to touch

Solid - Layer Break

LINE TYPES

WET Visible freewater MOIST Damp but no visible water

DRY

Groundwater level during drilling

MOISTURE CONDITION

* Unconfined compressive strength in tons/sq. ft., asterisk on log means determined by pocket penetrometer

(S.P.T.) Number of blows of 140 lb. hammer falling 30" to drive a 2-inch O.D. (1-3/8 inch I.D.) sampler

12"3"

No Recovery

Bag Samples

GRAIN SIZES

CLEAR SQUARE SIEVE OPENINGS

MAJOR TYPES

NR

Continuous Core

S.P.T. - Split spoon sampler

Dashed - Gradational or approximate layer break

Modified California (3" O.D.) sampler

GROUND-WATER SYMBOLS

California (2.5" O.D.) sampler

SAMPLER SYMBOLS

Stabilized groundwater level

Shelby Tube

SANDS WITH OVER

12 % FINES

GM - Silty gravels, gravel-sand and silt mixtures

HIGHLY ORGANIC SOILS

GRAVELS WITH OVER

12 % FINES

GRAVELS

DESCRIPTION

MH - Elastic silt with high plasticity

OL - Low plasticity organic silts and clays

GW - Well graded gravels or gravel-sand mixtures

CLEAN SANDS WITH

LESS THAN 5% FINES

OVER 4

STRENGTH*

FINE

RELATIVE DENSITY CONSISTENCY

SANDS

MORE THAN HALF

COARSE FRACTION

IS SMALLER THAN

NO. 4 SIEVE SIZE

CL - Inorganic clay with low to medium plasticity

ML - Inorganic silt with low to medium plasticity

SM - Silty sand, sand-silt mixtures

SP - Poorly graded sands or gravelly sand mixtures SW - Well graded sands, or gravelly sand mixtures

GC - Clayey gravels, gravel-sand and clay mixtures

LOOSE

SILTS

AND

CLAYS

VERY DENSE

0-4

BLOWS/FOOT SILTS AND CLAYS

SOFT

VERY SOFT

STIFF

HARD

2-4 1-2

1/4-1/2 0-1/4

CLEAN GRAVELS WITH

LESS THAN 5% FINES

1/2-1

VERY STIFF

VERY LOOSE

DENSE

MEDIUM DENSE

(S.P.T.)

GRAVELSAND

FINE COARSE BOULDERS

SANDS AND GRAVELS

4-10

OVER 50

30-50 10-30

MEDIUM STIFF

MEDIUM COARSE

COBBLES

113.9

124.4

Grades to orange-brown.

D E

P

TH

0.

G P

J E

N G

E O

IN

C

.G D

T

/2 8/

D ep th in

M et er s

D ep th in

F ee t

17.6

12.6

SANDSTONE, dark gray, very weak, slightly weathered. 65/6"

4" AC

6" AB

SAND (SP), light brown, moist, medium dense, fine to medium grains, poorly graded.

Grades to brown.

SANDY CLAY (CL), dark brown, moist, stiff, fine to medium grains.

Grades to grayish brown mottled with orange-brown. Stiffer drilling.

Fi ne s C on te nt p as si ng si ev e)

Atterberg Limits

A. Hargrove / L. Chan West Coast Exploration Solid Flight Auger 140 lb. Rope and Cathead

P la st ic

L im it

Li qu id L im itDESCRIPTION

D ry

U ni t W ei gh t

(p cf

Geotechnical Exploration SFVA Mental Health Expansion

San Francisco, CA 9069.000.000

DATE DRILLED:

HOLE DEPTH:

HOLE DIAMETER:

SURF ELEV ():

Lo g

S ym bo l

S tre ng th

V al ue

S tre ng th

T es t T yp e

9/9/2010 Approx. 27½ ft.

4.0 in.

LOGGED / REVIEWED BY:

DRILLING CONTRACTOR:

DRILLING METHOD:

HAMMER TYPE:

S am pl e

Ty pe

LOG OF BORING 1-B1

W at er L ev el

M oi st ur e C on te nt d ry w ei gh t)

P la st ic ity In de x

B lo w C ou nt

/F oo t

M oi st ur e C on te nt d ry w ei gh t)

D ep th in

F ee t

D ep th in

M et er s

S am pl e

Ty pe

LOG OF BORING 1-B1

D

E P

TH

0.

G

P J

E N

G E

O

IN

C .G

D T

/2

8/

Bottom of boring at approximately 27.5'.

Groundwater encountered at 18.5' during drilling.

50/1"

SANDSTONE, dark gray, very weak, slightly weathered.

LOGGED / REVIEWED BY:

DRILLING CONTRACTOR:

DRILLING METHOD:

HAMMER TYPE:

D ry

U ni t W ei gh t

(p cf

DATE DRILLED:

HOLE DEPTH:

HOLE DIAMETER:

SURF ELEV ():

DESCRIPTION

S tre ng th

V al ue

9/9/2010 Approx. 27½ ft.

4.0 in.

S tre ng th

T es t T yp e

Lo g

S ym bo l

Fi ne s C on te nt p as si ng si ev e)

P la st ic ity In de x

B lo w C ou nt

/F oo t

W at er L ev el

Atterberg Limits

A. Hargrove / L. Chan West Coast Exploration Solid Flight Auger 140 lb. Rope and Cathead

Geotechnical Exploration SFVA Mental Health Expansion

San Francisco, CA 9069.000.000

P la st ic

L im it

Li qu id L im it

Bottom of boring at approximately 18'.

Groundwater not encountered during drilling.

SAND (SP), light brown, moist, loose, fine to medium grains, poorly graded.

LO

G

G

E O

TE

C

H N

IC

A

L

0.

G

P J

E N

G E

O

IN

C .G

D T

/2

8/

D ep th in

M et er s

D ep th in

F ee t

50/5"

114.784.48

Rock fragments in bottom of sampler.

CLAYEY SAND (SC), light brown, moist, very dense, fine to medium grains.

75/3"

4" AC

4" AB

CLAYEY SAND (SC), dark brown to black, moist, fine to medium grains. (FILL)

P la st ic

L im it

P la st ic ity In de x

B lo w C ou nt

/F oo t

W at er L ev el

Fi ne s C on te nt p as si ng si ev e)

Atterberg Limits

M oi st ur e C on te nt d ry w ei gh t)

Geotechnical Exploration SFVA Mental Health Expansion

San Francisco, CA 9069.000.000

Li qu id L im itDESCRIPTION

9/9/2010 Approx. 18 ft.

4.0 in.

DATE DRILLED:

HOLE DEPTH:

HOLE DIAMETER:

SURF ELEV ():

Lo g

S ym bo l

A. Hargrove / L. Chan West Coast Exploration Solid Flight Auger 140 lb. Rope and Cathead

S am pl e

Ty pe

LOG OF BORING 1-B2

LOGGED / REVIEWED BY:

DRILLING CONTRACTOR:

DRILLING METHOD:

HAMMER TYPE:

U nc on fin ed S tre ng th (ts

f) *f ie ld a pp ro x

D ry

U ni t W ei gh t

(p cf

2.5" AC

4" AB

SAND (SP), brown, moist, medium dense, fine to medium grains, poorly graded.

SANDY CLAY (CL), brown, moist, very dense, some oxidation, some rock fragments.

Bottom of boring at approximately 25'.

Groundwater not encountered during drilling.

LO

G

G

E O

TE

C

H N

IC

A

L

0.

G

P J

E N

G E

O

IN

C .G

D T

/2

8/

D ep th in

M et er s

102.32.9

NP

50/4"

64/6"

P la st ic

L im it

D ep th in

F ee t

B lo w C ou nt

/F oo t

W at er L ev el

Fi ne s C on te nt p as si ng si ev e)

Atterberg Limits

M oi st ur e C on te nt d ry w ei gh t)

Geotechnical Exploration SFVA Mental Health Expansion

San Francisco, CA 9069.000.000

Li qu id L im itDESCRIPTION

9/9/2010 Approx. 25 ft.

4.0 in.

DATE DRILLED:

HOLE DEPTH:

HOLE DIAMETER:

SURF ELEV ():

Lo g

S ym bo l

A. Hargrove / L. Chan West Coast Exploration Solid Flight Auger 140 lb. Rope and Cathead

S am pl e

Ty pe

P la st ic ity In de x

LOG OF BORING 1-B3

LOGGED / REVIEWED BY:

DRILLING CONTRACTOR:

DRILLING METHOD:

HAMMER TYPE:

U nc on fin ed S tre ng th (ts

f) *f ie ld a pp ro x

D ry

U ni t W ei gh t

(p cf

APPENDIX B

Laboratory Test Data

P E N D I

B

Dark brown SAND with silt. 14 20 NP SP-SM

9069.000.000

MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS

Project No. Client: Remarks:

Project:

Plate

Sample Number: 1-B3 @ 4

P

LA

S

TI

C

IT

Y

IN

D E

X

LIQUID LIMIT

0 10 20 30 40 50 60 70 80 90 100 110

CL-ML

CL or OL

CH or OH

ML or OL MH or OH

Dashed line indicates the approximate upper limit boundary for natural soils

W A

T E

R C

O N

T E

N T

18.7

18.9

19.1

19.3

19.5

19.7

19.9

20.1

20.3

20.5

20.7

NUMBER OF BLOWS

5 6 7 8 9 10 20 25 30 40

LIQUID AND PLASTIC LIMITS TEST REPORT

SFVA Mental Health Expansion - San Francisco, CA

(no specification provided)

PL= LL= PI=

D85= D60= D50= D30= D15= D10= Cu= Cc=

USCS= AASHTO=

see boring logs #4 #10 #20 #40 #60

#100 #140 #200

100.0 100.0 99.8 92.0 42.7 6.7 3.8 3.1

0.3847 0.2955 0.2685

0.2185 0.1793 0.1636

1.81 0.99

SP

1-B1 @ 4 09/21/10

SFVA Mental Health Expansion - San Francisco, CA

9069.000.000

Soil Description

Atterberg Limits

Coefficients

Classification

Remarks

Sample No.: Source of Sample: Date:

Location: Elev./Depth:

Client:

Project:

Project No: Plate

SIEVE PERCENT SPEC.* PASS?

SIZE FINER PERCENT (X=NO)

P E

R C

E N

T

FI

N E

R

GRAIN SIZE - mm.

0.0010.010.1110100

% Cobbles Coarse

% Gravel…