geotechnical investigation 2000-2070 bryant street san

GEOTECHNICAL INVESTIGATION

2000-2070 Bryant Street

San Francisco, California

Prepared For:

Nick Podell Company

22 Battery Street, Suite 404

San Francisco, California 94111

Prepared By:

Langan Treadwell Rollo

501 14th Street, 3rd Floor

Oakland, California 94612

Blaire L. Banagan, P.E.

Project Engineer

Lori A. Simpson, G.E.

Principal/Vice President

28 March 2014

750615602

28 March 2014

Ms. Linsey Perlov

Nick Podell Company



Subject:

Geotechnical Investigation

2000- 2070 Bryant Street


Langan Project No.: 750615602

Dear Ms. Linsey Perlov:

We are pleased to present our geotechnical investigation report for the proposed residential

development to be constructed at 2000-2070 Bryant Street in San Francisco, California. Hard

copies of this report will be furnished upon request.

The project site is rectangular with plan dimensions of about 200 by about 325 feet. It is bound

by Bryant Street on the east, Florida Street on the west, 18th Street on the north, and a

community garden and two buildings on the south (two-story and three-story structures, both

of wood-framed construction). The location of the project site is shown on the Site Location

Map, Figure 1. The site is occupied by a one- and two-story concrete and brick building, a two-

story wood frame building with a basement, two two-story wood frame buildings, a one-story

metal and wood frame building, asphalt paved areas, concrete paved areas, and lawn areas.

The sidewalk elevation ranges from approximately 23 to 26 feet (San Francisco City Datum,

SFCD) (north to south) along Bryant from approximately 21 to 19 feet SFCD (north to south) on

Florida Street. Interior portions of the existing building have raised floors, ramps, or staircases

to accommodate the grade changes between Bryant and Florida Streets.

Based on our review of architectural plans prepared by BDE Architecture, we understand the

proposed development consists of a six-story residential building comprised of five levels of

light-framed construction over a one-level concrete podium with parking, residential, and retail

uses. We also understand that the new building will encompass the entire footprint of the site

and will be constructed at grade to minimize excavation depths. The planned finished floor

elevation for most of the building is Elevation 21.5 feet SFCD and steps up to match existing

grades along Bryant Street (finished floor at about Elevation 27.5 feet SFCD) and down to

match existing grades on Florida Street (finished floor at about Elevation 19 feet SFCD).

Subsurface conditions at the northern portion of the site consist of poor quality fill containing

weathered serpentinite underlain by a Marsh deposit and the Colma formation. The marsh

deposit contains continuous layers of potentially liquefiable material and is judged to have a

Geotechnical Investigation

2000- 2070 Bryant Street


Langan Project No.: 750615602

28 March 2014

Page 2 of 2

high potential for lateral spread during a large earthquake. At the southern portion of the site,

subsurface conditions consist of medium dense to dense sand fill (with debris in the upper

several feet) underlain by medium dense to very dense sands and stiff to very stiff clays and

silts, the Colma formation, and stiff clays and medium dense to very dense sands. Thin,

continuous layers of potentially liquefiable material were encountered; however, the predicted

settlement is small, and we judge the potential for lateral spreading is low. Groundwater was

measured at the site between Elevations 7 and 14½ feet SFCD during our exploration.

We conclude that the proposed development can be supported on a mat foundation bearing on

improved soil or engineered fill. At the northern portion of the site, the mat can be supported

on improved soil that has been treated in place to mitigate the liquefaction/lateral spread

potential. At the southern portion of the site, the mat can be supported on engineered fill or

improved soil that has been designed to improve the fill, as discussed in the report.

The recommendations contained in this report are based on a limited subsurface exploration

program. Consequently, variations between expected and actual soil conditions may be found

in localized areas during construction. We should be retained to observe excavation, ground

improvement, mat subgrade preparation, and compaction of backfill, during which time we may

make any changes to our recommendations, if deemed necessary.

We appreciate the opportunity to assist you with this exciting and challenging project. If you

have any questions, please call.

Sincerely,

Langan Treadwell Rollo

Blaire L. Banagan, PE Lori A. Simpson, GE

Project Engineer Principal

750615602.03_BB_Letter_2000_2070 Bryant Street_SF

Geotechnical Investigation 28 March 2014

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TABLE OF CONTENTS

1.0 INTRODUCTION ............................................................................................................. 1

2.0 SCOPE OF SERVICES .................................................................................................... 2

3.0 FIELD EXPLORATION .................................................................................................... 3

3.1 Borings ............................................................................................................... 3

3.2 Cone Penetration Tests ..................................................................................... 4

3.3 Laboratory Testing ............................................................................................ 5

4.0 SUBSURFACE CONDITIONS ......................................................................................... 5

4.1 Groundwater ...................................................................................................... 6

5.0 GEOLOGY AND SEISMICITY ......................................................................................... 7

5.1 Regional Geology ............................................................................................... 7

5.2 Regional Seismicity and Faulting ..................................................................... 8

5.3 Seismic Hazards ............................................................................................... 10

5.3.1 Fault Rupture ........................................................................................ 10

5.3.2 Liquefaction and Associated Hazards ................................................. 11

5.3.3 Lateral Spreading ................................................................................. 14

5.3.4 Cyclic Densification .............................................................................. 15

6.0 DISCUSSION AND CONCLUSIONS ............................................................................ 15

6.1 Ground Improvement ...................................................................................... 16

6.1.1 Drilled Displacement Columns ............................................................ 16

6.1.2 Deep Soil Mixing (DSM) ....................................................................... 17

6.2 Foundations and Settlement .......................................................................... 17

6.3 Groundwater .................................................................................................... 19

6.4 Floor Slabs ........................................................................................................ 19

6.5 Corrosion Potential .......................................................................................... 19

6.6 Construction Considerations .......................................................................... 20

7.0 RECOMMENDATIONS ................................................................................................. 21

7.1 Site Preparation and Grading ......................................................................... 21

7.1.1 Site Clearing ......................................................................................... 21

7.1.2 Subgrade Preparation .......................................................................... 21

7.1.3 Fill Placement and Compaction ........................................................... 22

7.1.4 Utilities .................................................................................................. 23

7.1.5 Temporary Slopes ................................................................................ 24

7.2 Foundation Support ........................................................................................ 24

7.2.1 Mat Foundation .................................................................................... 24

7.2.2 Ground Improvement .......................................................................... 26

7.3 Below�Grade Walls .......................................................................................... 27

7.4 Floor Slab ......................................................................................................... 29

7.5 Shoring and Underpinning .............................................................................. 31

7.6 Construction Monitoring ................................................................................. 31

7.7 Site Drainage .................................................................................................... 32

7.8 Corrosion Design ............................................................................................. 32

7.9 Seismic Design Criteria ................................................................................... 32


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TABLE OF CONTENTS (Cont.)

8.0 FUTURE GEOTECHNICAL SERVICES ......................................................................... 33

9.0 LIMITATIONS ............................................................................................................... 33

10.0 REFERENCES .............................................................................................................. 34


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LIST OF FIGURES

Figure 1 Site Location Map

Figure 2 Site Plan

Figure 3 Map of Major Faults and Earthquake Epicenters

in the San Francisco Bay Area

Figure 4 Modified Mercalli Intensity Scale

LIST OF APPENDICES

Appendix A Logs of Borings and Cone Penetration Tests

Figures A#1 Logs of Borings B#1 through B#4

through A#4

Figure A#5 Classification Chart

Figures A#6 Logs of Cone Penetration Tests CPT#1 through CPT#7

through A#12

Figure A#13 Classification Chart for Cone Penetration Tests

Appendix B Laboratory Test Results

Figure B#1 Plasticity Chart

Figure B#2 Plasticity Chart

Figure B#3 Consolidation Test Report

Figure B#4 Particle Size Analysis



Appendix C Corrosivity Test Results


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GEOTECHNICAL INVESTIGATION

2000�2070 Bryant STREET


1.0 INTRODUCTION

This report presents the results of the geotechnical investigation performed by Langan

Treadwell Rollo for the proposed development to be constructed at 2000#2070 Bryant Street in

San Francisco, California. We previously performed a geotechnical investigation for the 2070

Bryant Street site and presented our results in a report dated 10 July 2013. We understand

that the 2070 and 2000 Bryant Street sites will be developed as one project. Therefore, this

report combines data generated for both sites and presents conclusions and recommendations

regarding the geotechnical aspects of the proposed development for the entire site.

The project site is rectangular with plan dimensions of about 200 by about 325 feet. It is bound

by Bryant Street on the east, Florida Street on the west, 18th Street on the north, and a

community garden and two buildings on the south (two#story and three#story structures, both

of wood#framed construction). The location of the project site is shown on the Site Location

Map, Figure 1. The site is occupied by a one# and two#story concrete and brick building, a two#

story wood frame building with a basement, two two#story wood frame buildings, a one#story

metal and wood frame building, asphalt paved areas, concrete paved areas, and lawn areas.

The sidewalk elevation ranges from approximately 23 to 26 feet1 (north to south) along Bryant

from approximately 21 to 19 feet (north to south) on Florida Street. Interior portions of the

existing building have raised floors, ramps, or staircases to accommodate the grade changes

between Bryant and Florida Streets.

Based on architectural plans prepared by BDE Architecture titled “Background Set” dated 27

February 2014, we understand the proposed development consists of a six#story residential

building comprised of five levels of light#framed construction over a one#level concrete podium

with parking, residential, and retail uses. We also understand that the new building will

encompass the entire footprint of the site and will be constructed at grade to minimize

excavation depths. The planned finished floor elevation for most of the building is Elevation

================================================1 Elevations in this report are referenced to the San Francisco City Datum and were obtained from a site survey

provided by Martin M. Ron Associates.


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21.5 feet and steps up to match existing grades along Bryant Street (finished floor at about

Elevation 27.5 feet) and down to match existing grades on Florida Street (finished floor at about

Elevation 19 feet).

The structural loads for the new development were unknown at the time of this report.

Based on our discussion with the architect, we also understand that the adjacent site currently

occupied by the community garden is being developed; a six#story building is planned.

2.0 SCOPE OF SERVICES

Our scope of services, outlined in our proposals dated 20 March 2013 and 29 October 2013,

consisted of exploring the subsurface conditions at the site and performing laboratory tests and

engineering analyses to develop conclusions and recommendations regarding:

• soil and groundwater conditions at the site

• site seismicity and seismic hazards, including ground rupture, liquefaction, lateral

spreading, and cyclic densification

• the most appropriate foundation type(s) for the proposed structure

• design criteria for the most appropriate foundation type(s), including values for vertical

and lateral capacities

• estimated foundation settlement

• excavation and shoring (if needed)

• floor slabs

• below#grade walls

• ground improvement

• seismic design criteria in accordance with California Building Code 2013 (CBC)

• development of site#specific response spectra using ground motion response analysis (if

deemed necessary)


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• fill quality and compaction criteria

• construction considerations.

3.0 FIELD EXPLORATION

We explored the subsurface conditions at the combined site by drilling four borings, designated

B#1 to B#4, and advancing seven cone penetration tests (CPTs), designated CPT#1 to CPT#7 at

the locations shown on the Site Plan, Figure 2.

Prior to beginning our field investigation, we obtained drilling permits from the City of San

Francisco Department of Public Health (SFDPH) and multiple street#use permits from the City

of San Francisco Department of Public Works (SFDPW), which allowed us to work in the

streets adjacent to the property. We checked boring and CPT locations for the presence of

underground utilities by contracting with a private utility locating service; we also contacted

Underground Service Alert (USA), as required by law, before commencing our field exploration.

Upon completion, borings were backfilled with cement grout in accordance with SFDPH and

SFDPW requirements.

3.1 Borings

From 18 to 19 April 2013 and on 30 January 2014, Pitcher Drilling Company of Palo Alto,

California drilled three borings, designated as B#1, B#2 and B#4, to depths ranging from about 70

to 91½ feet using truck#mounted, rotary#wash drilling equipment. On 22 April 2013, Clearheart

Drilling of Santa Rosa, California drilled one boring designated B#3, to a depth of about 50 feet

using a limited#access, track#mounted drill rig equipped with hollow stem augers. During

drilling, our field engineer logged the borings and collected representative samples of the soil

encountered for classification and laboratory testing. The boring logs are presented in

Appendix A on Figures A#1 through A#4. The soil encountered was classified in accordance

with the soil classification chart on Figure A#5.

Soil samples were obtained using four samplers:

• Standard Penetration Test (SPT) sampler with a 2.0#inch outside and 1.5#inch inside

diameter, without liners

• Sprague & Henwood (S&H) split#barrel sampler with a 3.0#inch outside diameter and

2.5#inch inside diameter, lined with 2.43#inch inside diameter brass tubes.


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• Dames & Moore piston sampler with 2.5#inch outside diameter and a 2.43#inch

inside diameter brass tubes

• Shelby tube sampler with a 3.0#inch outside diameter and 2.875#inch inside diameter

The SPT and S&H samplers were driven with a 140#pound, downhole safety hammer falling

30 inches. The samplers were driven up to 18 inches, and the hammer blows required to

advance the samplers every six inches of penetration were recorded and are presented on the

boring logs. A “blow count” is defined as the number of hammer blows per six inches of

penetration or 50 blows for six inches or less of penetration. The driving of samplers was

discontinued if the observed (recorded) blow count was 50 for six inches or less of penetration.

The blow counts required to drive the SPT and S&H samplers were converted to approximate

SPT N#values using a factor of 1.2 and 0.7, respectively to account for sampler type and

hammer energy and are shown on the boring logs. The blow counts used for this conversion

were: 1) the last two blow counts if the sampler was driven more than 12 inches, 2) the last

one blow count if the sampler was driven more than six inches but less than 12 inches, and

3) the only blow count if the sampler was driven six inches or less.

The Dames & Moore brass tubes and shelby tube were pushed hydraulically into the soil to

obtain relatively undisturbed samples of the soft cohesive soil. The pressure required to

advance the sampler is shown on the logs, measured in pounds per square inch (psi).

3.2 Cone Penetration Tests

On 16 April 2013, 22 April 2013, 28 January 2014, and 1 February 2014 Gregg Drilling &

Testing, Inc. of Martinez, California, advanced seven CPTs designated CPT#1 through CPT#7.

The CPTs were advanced by hydraulically pushing a 1.4#inch diameter (ten square centimeters),

cone#tipped probe into the ground. The cone on the end of the probe measures tip resistance,

and the friction sleeve behind the cone tip measures frictional resistance. Electrical strain

gauges within the cone measure soil parameters continuously for the entire depth advanced.

Soil data, including tip resistance, was transferred to a computer while conducting each test.

Accumulated data was processed by computer to provide engineering information, such as the

types and approximate strength characteristics of the soil encountered. The CPT logs showing

tip resistance, friction ratio, equivalent SPT N#value, in#situ stress, shear strength, and soil

behavior type as a function of depth are presented in Appendix A on Figures A#6 through A#12.

A classification chart for the CPTs is included as Figure A#13.


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3.3 Laboratory Testing

All samples recovered from the field exploration program were examined for soil classification,

and representative samples were selected for laboratory testing. The laboratory testing

program was designed to correlate and evaluate engineering properties of the soil at the site.

Samples were tested to measure organics, consolidation, moisture content, dry density,

plasticity, and percent fines. Results of the laboratory testing are included on the boring logs

and in Appendix B on Figures B#1 through B#5.

4.0 SUBSURFACE CONDITIONS

The site is approximately 400 feet east of the historical Mission Creek drainage area at the

bottom of Potrero Hill. The adjacent Mission Creek area was reclaimed by placing fill starting in

the 1880s.

The results of the investigation at the proposed project site indicate that the northern portion of

the site is underlain by about 10 to 24 feet of fill. The fill consists of a heterogeneous mix of

gravel, sand, silt, and clay and contains weathered serpentenite with significant rock fragments.

The granular portions of the fill (sand and gravel) are generally loose to medium dense and the

cohesive portions (silt and clay) are soft to medium stiff. At the southern portion of the site, we

encountered 12 to 15 feet of fill generally consisting of medium dense to very dense silty

and/or clayey sand and sand. In boring B#2, about 3 feet of clay fill with varying sand and gravel

content was encountered over the medium dense to very dense sandy fill, and both borings

B#2 and B#3 encountered traces of concrete and brick debris in the upper several feet of the fill.

At the northern portion of the site, the fill is underlain by soft to medium stiff, compressible

sandy clay and sandy/clayey silts and loose to medium dense clayey sand, silty sand, and

clayey silty sand extending to approximate depths between 28 and 44 feet below the ground

surface (bgs). We believe this soil forms a marsh deposit associated with the Mission Creek

drainage. In boring B#4 the marsh consists of two layers; a layer of sandy clay and silty sand is

bound between the upper and lower marsh deposits. Results of consolidation tests performed

on samples of the marsh deposit near and at the project site indicate that the marsh deposit is

normally to over consolidated 2. Laboratory testing performed on the marsh deposit indicates

================================================2 A normally consolidated soil is one that has not historically been subjected to overburden or other pressures

greater than those that are currently present. Additional loading through fill placement or net building load

increase will begin a new cycle of consolidation where reduction in volume of the soil will result as pore

pressures dissipate. An overconsolidated clay has experienced a pressure greater than its current load.


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that the fines content ranges between approximately 33 and 55 percent with the plasticity

index of the fines content ranging between 7 and 19. At the southern portion of the site, the fill

is underlain by medium dense to very dense sand with varying fines content and stiff to very

stiff silts and clays.

The marsh deposit to the north and medium dense to very dense/stiff to very stiff material to

the south are underlain by the Colma formation. The top of the Colma formation was

encountered at depths ranging from 27 to 44 feet below ground surface and extends to the

maximum depths explored of 69 and 49 feet in borings B#1 and B#3, respectively, and to

approximately 67 and 78 feet in B#2 and B#4, respectively. The Colma formation encountered in

our borings consists of medium dense to very dense sand with varying amounts of clay and silt.

According to our CPTs, the upper portion of the Colma formation classifies as very stiff fine#

grained material with very stiff to hard silts and clays and thin layers of medium dense to dense

sands. The Colma deposit typically increases in density with depth, except for an

approximately 4#foot#thick medium dense layer of clayey silty sand encountered in boring B#1 at

a depth of approximately 58 feet. Laboratory testing on this sample indicates a fines content of

about 28 percent with a plasticity index of 7.

Borings B#2 and B#4 in the northern portion of the site were drilled past the Colma formation.

At B#2 a thin layer of very stiff clay was encountered below the Colma formation. The clay is

underlain by about 2½ feet of medium dense clayey silty sand, which is underlain by very

dense sand to the maximum depth explored of about 75 feet bgs. Laboratory testing on a

sample of the medium dense sand indicates a fines content of about 13 percent with a

plasticity index of 4. At the location of boring B#4, the Colma formation is underlain by a five#

foot thick layer of clayey peat underlain by hard, gray clay. The clay is extends to the maximum

depth explored of about 91½ feet bgs.

4.1 Groundwater

Groundwater was encountered during auger drilling prior to switching to rotary wash in borings

B#2 and B#3 at depths of about 12 and 17 feet (Elevations 7 and 7½ feet), respectively.

Groundwater was not measured in B#1 and B#4. Dissipation tests performed in CPT#1,CPT#2,

and CPTs 5 through 7, indicate groundwater is at depths of about 9 and 16 feet (Elevations 14½

and 9 feet) bgs, respectively. Fluctuations in groundwater levels are expected and occur due to

many factors including seasonal fluctuation, tides, underground drainage patterns, regional

fluctuations, and other factors.


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5.0 GEOLOGY AND SEISMICITY

The regional geology and seismicity were evaluated as part of this investigation. The evaluation

was based on our review of published reports, our experience in the project area, and the

results of field investigations.

5.1 Regional Geology

The site is in the northeast portion of the San Francisco peninsula, which lies within the Coast

Ranges geomorphic province. The northwesterly trend of ridges and valleys characteristic of

the Coast Ranges is obscured in San Francisco, except for features such as Russian Hill,

Telegraph Hill, Hunters Point, and Potrero Hill. San Francisco Bay and the northern portion of

the peninsula lie within a down#dropped crustal block bounded by the East Bay Hills and the

Santa Cruz Mountains. The San Francisco Bay depression resulted from interaction between

the major faults of the San Andreas fault zone, particularly the Hayward and San Andreas faults

east and west of the bay, respectively (Atwater, 1979).

San Francisco’s topography is characterized by relatively rugged hills formed by Jurassic# to

Cretaceous#aged bedrock (Schlocker, 1974). The bedrock consists of highly deformed and

fractured sedimentary rocks of the Franciscan complex. The present topography resulted

mainly from east#west compression of coastal California during the late Pliocene and

Pleistocene epochs (Norris and Webb, 1990).

The low#lying areas of the San Francisco peninsula are underlain by Quaternary sediments

deposited on eroded Franciscan bedrock. Sediment deposition within the prehistoric bay

margin was influenced by oscillating late#Quaternary sea levels that resulted from the advance

and retreat of glaciers worldwide. The resulting sequence of alternating estuarine and

terrestrial sediments corresponds to high and low sea#level stands, respectively. In contrast,

Quaternary sediments in the plains landward of the bay are predominantly terrestrial.

By late Pleistocene time, the high sea level associated with the Sangamon (about

125,000 years ago) interglacial resulted in deposition of the Yerba Buena Mud (Sloan, 1992).

The Yerba Buena Mud was deposited in an estuarine environment similar in character and

extent to the present bay. Sea level lowering associated with the onset of Wisconsin glaciation

exposed the bay floor and resulted in terrestrial sedimentation, such as the Colma formation,

on the Yerba Buena Mud. Sea level rose again starting roughly 20,000 years ago, fed by the


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melting of Wisconsin#age glaciers. The sea re#entered the Golden Gate about 10,000 years ago

(Atwater, 1979). Inundation of the present bay resulted in deposition of estuarine sediments,

called Bay Mud, which continue to accumulate.

Historical development of the San Francisco Bay area resulted in placement of artificial fill

material over substantial portions of modern estuaries, marshlands, tributaries, and creek beds

in an effort to reclaim land (Nichols and Wright, 1971).

5.2 Regional Seismicity and Faulting

The major active faults in the area are the San Andreas, San Gregorio and Hayward Faults.

These and other active faults of the region are shown on Figure 3. For each of the active faults

within 50 kilometers (km) of the site, the distance from the site and estimated mean

characteristic Moment magnitude3 [2008 Working Group on California Earthquake Probabilities

(WGCEP) (2008) and Cao et al. (2003)] are summarized in Table 1.

TABLE 1

Regional Faults and Seismicity

Fault Segment

Approximate

Distance from

Site (km)

Direction

from Site

Characteristic

Mean Moment

Magnitude

N. San Andreas – Peninsula 10 West 7.23

N. San Andreas – 1906 Event 10 West 8.05

N. San Andreas – North Coast 15 West 7.51

San Gregorio Connected 17 West 7.50

Total Hayward 19 Northeast 7.00

Total Hayward#Rodgers Creek 19 Northeast 7.33

Mount Diablo Thrust 35 East 6.70

Total Calaveras 36 East 7.03

Rodgers Creek 36 North 7.07

Monte Vista#Shannon 39 Southeast 6.50

Green Valley Connected 40 East 6.80

Point Reyes 42 West 6.90

West Napa 47 Northeast 6.70

================================================3 Moment magnitude is an energy#based scale and provides a physically meaningful measure of the size of a

faulting event. Moment magnitude is directly related to average slip and fault rupture area.


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Figure 3 also shows the earthquake epicenters for events with magnitude greater than 5.0 from

January 1800 through January 1996.

Since 1800, four major earthquakes have been recorded on the San Andreas Fault. In 1836 an

earthquake with an estimated maximum intensity of VII on the Modified Mercalli (MM) scale

(Figure 4) occurred east of Monterey Bay on the San Andreas Fault (Toppozada and Borchardt

1998). The estimated Moment magnitude, Mw, for this earthquake is about 6.25. In 1838, an

earthquake occurred with an estimated intensity of about VIII#IX (MM), corresponding to a Mw

of about 7.5. The San Francisco Earthquake of 1906 caused the most significant damage in the

history of the Bay Area in terms of loss of lives and property damage. This earthquake created

a surface rupture along the San Andreas Fault from Shelter Cove to San Juan Bautista

approximately 470 kilometers in length. It had a maximum intensity of XI (MM), a Mw of about

7.9, and was felt 560 kilometers away in Oregon, Nevada, and Los Angeles. The most recent

earthquake to affect the Bay Area was the Loma Prieta Earthquake of 17 October 1989, in the

Santa Cruz Mountains with a Mw of 6.9, approximately 93 km from the site.

In 1868 an earthquake with an estimated maximum intensity of X on the MM scale occurred on

the southern segment (between San Leandro and Fremont) of the Hayward Fault. The

estimated Mw for the earthquake is 7.0. In 1861, an earthquake of unknown magnitude

(probably a Mw of about 6.5) was reported on the Calaveras Fault. The most recent significant

earthquake on this fault was the 1984 Morgan Hill earthquake (Mw = 6.2).

The 2008 WGCEP at the U.S. Geologic Survey (USGS) predicted a 63 percent chance of a

magnitude 6.7 or greater earthquake occurring in the San Francisco Bay Area in 30 years. More

specific estimates of the probabilities for different faults in the Bay Area are presented in

Table 2.


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TABLE 2

WGCEP (2008) Estimates of 30�Year Probability

of a Magnitude 6.7 or Greater Earthquake

Fault

Probability

(percent)

Hayward#Rodgers Creek 31

N. San Andreas 21

Calaveras 7

San Gregorio 6

Concord#Green Valley 3

Greenville 3

Mount Diablo Thrust 1

5.3 Seismic Hazards

During a major earthquake on a segment of one of the nearby faults, strong to very strong

shaking is expected to occur at the site. Strong shaking during an earthquake can result in

ground failure such as that associated with soil liquefaction4, lateral spreading5, and cyclic

differential compaction6. We used the results of our borings and CPTs to evaluate the potential

for these phenomena to occur at the site. The results of our evaluation are presented below.

5.3.1 Fault Rupture

Historically, ground surface ruptures closely follow the trace of geologically young faults. The

site is not within an Earthquake Fault Zone, as defined by the Alquist#Priolo Earthquake Fault

Zoning Act and no known active or potentially active faults exist on the site. Therefore, we

conclude the risk of fault offset at the site from a known active fault is low. In a seismically

active area, the remote possibility exists for future faulting in areas where no faults previously

existed; however, we conclude the risk of surface faulting and consequent secondary ground

failure is low.

================================================4 Liquefaction is a transformation of soil from a solid to a liquefied state during which saturated soil temporarily

loses strength resulting from the buildup of excess pore water pressure, especially during earthquake#induced

cyclic loading. Soil susceptible to liquefaction includes loose to medium dense sand and gravel, low#plasticity

silt, and some low#plasticity clay deposits.

5 Lateral spreading is a phenomenon in which surficial soil displaces along a shear zone that has formed within an

underlying liquefied layer. The surficial soil is typically displaced in “blocks” that are transported downslope or

in the direction of a free face by earthquake and gravitational forces.

6 Cyclic soil densification is a phenomenon in which non#saturated, cohesionless soil is densified by earthquake

vibrations, resulting in ground surface settlement.


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5.3.2 Liquefaction and Associated Hazards

When a saturated, cohesionless soil liquefies during a major earthquake, it experiences a

temporary loss of shear strength caused by a transient rise in excess pore water pressure

generated by strong ground motion. Flow failure, lateral spreading, differential settlement, loss

of bearing, ground fissures, and sand boils are evidence of excess pore pressure generation

and liquefaction. The site is located within a liquefaction hazard zone as designated by the

California Geological Survey (CGS) seismic hazard zone map for the area titled State of

California Seismic Hazard Zones, City and County of San Francisco, Official Map, dated 17

November 2001. CGS has recommended the content for site investigation reports within

seismic hazard zones be performed in accordance with Special Publication 117A titled

Guidelines for Evaluating and Mitigating Seismic Hazard Zones in California, dated September

11, 2008. Our evaluation of site seismic hazards was performed in general accordance with

these guidelines.

The level of ground shaking that may occur at the site during future earthquakes is uncertain

because the location, recurrence interval, and magnitude of future earthquakes are not known.

A peak ground acceleration (PGA) of 0.58 times gravity was used in our liquefaction analysis.

This PGA was calculated using the procedures specified in the provisions of 2013 California

Building Code (CBC)/ ASCE 7#10 for the Maximum Considered Earthquake, using site class D.

We used a Moment magnitude of 8.05, which is the maximum Moment Magnitude for the San

Andreas Fault, located about 10 kilometers from the site as shown on Table 1. Groundwater

levels used in our liquefaction analysis varied and were based on groundwater level elevations

measured at nearby exploration points.

We used the results of borings B#1, B#2, and B#4 and the CPTs to evaluate the liquefaction

potential at the site. Boring B#3 was not used in our evaluation because it was drilled using

hollow stem auger equipment, which is less reliable in evaluating liquefaction. The liquefaction

analysis was performed in accordance with the methodology presented in the publication titled

Proceedings of the NCEER Workshop on Evaluation of Liquefaction Resistance of Soils,

prepared by the National Center for Earthquake Engineering Research (NCEER), dated 31

December 1997, and in Youd et al. (2001). The susceptibility of sand to liquefaction under

seismic loading was evaluated in general accordance with the procedure presented by Seed

and Idriss (1982). Our liquefaction analysis using the boring and CPT data indicates that the

majority of the relatively shallow, loose material in the fill and marsh deposit that was


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encountered at the northern portion of the site, some thin layers of medium dense material

encountered beneath the fill at the southern portion of the site, and some discontinuous,

isolated medium dense layers encountered at the top, within and below the Colma Formation

at relatively deeper depths are susceptible to liquefaction (FSliq<1.3) during the maximum

considered earthquake, as defined by the provisions of 2013 CBC/ASCE 7#10.

We estimated liquefaction#induced settlement using the procedure outlined in the NCEER

report. The strain potential of any potentially liquefiable layers was estimated in accordance

with the method developed by Tokimatsu and Seed (1984), which relates (N1)60,CS values to

strain potential. For CPTs, the tip resistance (qC1N)CS was converted to an (N1)60,CS value

assuming the ratio (qC1N)CS/(N1)60,CS (blows/foot) is equal to five. This value is consistent with

published values for clean sand. The estimated liquefaction#induced settlement from our

borings and CPTs is summarized in Table 3.


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TABLE 3

Estimated Liquefaction�Induced Settlement

Project Area

Boring / CPT

Approximate

Elevation of

Top of

Liquefiable

Soil Layers

(feet)

Approximate

Thickness of

Liquefiable

Soil Layers

(feet)

Estimated

Settlement

(inches)

Total

Estimated

Settlement

(inches)

Northern

Portion

B#1

1 6 2¼

3 #8 4 ½

#38 4 ¼

B#4 6½ 9½ 1¾ 1¾

CPT#1

2½ 2½ ¾

1¼ #1½ ½ ¼

#3½ 3 ¼

CPT#3

4 12 2¼

2½ #10 1 <¼

#15 ½ <¼

CPT#5 4.5 2½ ¼

¾ #9 3 ½

CPT#6

10 10 1½

2½ #9 2 ½

#14 1 <¼

#17 3½ ½

CPT#7

11 10½ 1¾

3½ #1½ 2 ½

#5 6 1¼

#16 1 <¼

Southern

Portion

B#2 #50½ 2½ ½ ½

CPT#2

½ ½ <¼

¼ #1 ½ <¼

#5½ ½ <¼

CPT#4

4½ 1 <¼

½ #1 1½ <¼

#6 2 <¼


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On the basis of our liquefaction analyses, we conclude that up to about 3½ inches of

liquefaction#induced total and differential settlement may occur at the northern portion of the

project site. The majority of the potentially liquefiable layers are relatively shallow and within

the marsh deposit; however, potentially liquefiable material was also encountered near the top

and near the bottom of the Colma formation. Because of the relatively shallow groundwater

table and shallow liquefiable deposits, we conclude ground failure, such as lurch cracking

and/or the development of sand boils, could occur in the northern portion of the site. The

ground#surface settlement will likely be larger than estimated in areas where these types of

ground failure occur.

At the southern portion of the site, we conclude that about ¼ to ½ inch of liquefaction#induced

total and differential settlement may occur. The majority of the liquefiable layers are thin and

were encountered within the medium dense to very dense/stiff to very stiff material

encountered beneath the fill; however, potentially liquefiable material was also encountered

near the top and near the bottom of the Colma formation. Because the potentially liquefiable

deposits are relatively thin and deep, the potential for ground failure, such as lurch cracking

and/or the development of sand boils at the southern portion of the site is low.

5.3.3 Lateral Spreading

Lateral spreading is a phenomenon in which a surficial soil block displaces along a shear zone

that has formed within an underlying liquefied layer. The surficial blocks are transported

downslope or in the direction of a free face, such as a bay or a channel, by earthquake and

gravitational forces. Lateral spreading is generally the most pervasive and damaging type of

liquefaction#induced ground failure generated by earthquakes.

According to Youd, Hansen, and Bartlett (2002), for significant lateral spreading displacements

to occur, the soils should consist of saturated cohesionless sandy sediments with (N1)60

blowcounts less than 15, where liquefaction of the soils is likely to occur based on standard

liquefaction analysis. At northern portion of the site, we encountered continuous zones (2½ to

10 feet) of potentially liquefiable material with (N1)60 less than 15 blowcounts within the fill and

marsh deposit. If this portion of the site is not mitigated against liquefaction, there are

sufficient zones of liquefiable material present within the fill and marsh deposit to induce lateral

spreading. This has the potential to cause significant damage to shallow or deep foundations.


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Therefore, we conclude the soil beneath the northern portion of the site should be improved to

mitigate the liquefaction and lateral spread potential. The estimated boundary of the zone of

potential lateral spread at the northern portion of the site is shown on the Site Plan, Figure 2.

At the southern portion of the site, we encountered relatively thin, continuous zones of

potentially liquefiable soils with (N1)60 less than 15 blowcounts within the medium dense to

very dense/stiff to very stiff material encountered beneath the fill. However, given that these

potentially liquefiable zones are very thin (< 4 inches) with high fines content, we judge that the

potential for lateral spreading to occur at the southern portion of the site is low.

5.3.4 Cyclic Densification

Cyclic densification refers to seismically-induced differential compaction of non-saturated

granular material (sand and gravel above the groundwater table) caused by earthquake

vibrations. Approximately 13 to 24 feet of loose fill was encountered in our borings and CPTs

at the northern portion of the site during our investigation. Unless mitigated, these non-

saturated granular layers could settle up to one inch due to strong shaking from a large

earthquake.

6.0 DISCUSSION AND CONCLUSIONS

On the basis of the results of our subsurface investigation, laboratory testing and engineering

analyses, we conclude the proposed development is feasible from a geotechnical engineering

standpoint. The primary geotechnical issues associated with the proposed development

include:

presence of shallow, debris-laden fill

presence of potentially liquefiable soils and potential for liquefaction-induced settlement

to occur during a moderate to major earthquake at the site

potential for significant lateral spreading at the northern portion of the site in the event

of liquefaction

construction considerations.

Our discussion and conclusions regarding these and other issues and their impact on the

design and construction of the proposed structure are discussed in the following sections.


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6.1 Ground Improvement

A heterogeneous mix of loose fill overlying marsh deposits blankets the northern portion of the

site. The loose, unsaturated fill is susceptible to cyclic densification, and the loose saturated fill

and marsh deposit has a high liquefaction and lateral spread potential during a large earthquake.

In addition, the soft, compressible sandy clay layers within the marsh deposit could undergo

significant static settlement (consolidation) under the weight of the new development. If not

mitigated, these conditions could cause significant damage to the proposed development,

resulting in poor building performance. Therefore, we recommend mitigating these potential

hazards at the northern portion of the site using ground improvement, which includes deep soil

mixing (DSM) or drilled displacement columns (DDC). Soil improvement methods can also be

used to transfer the support of building loads through the column elements to deeper, more

competent soil.

The approximate area requiring ground improvement, labeled as the zone of potential lateral

spread, at the northern portion of the site is shown on the Site Plan, Figure 2. The delineation

between lateral spread and no lateral spread potential is based on limited exploration within the

footprint of the new building. To better define the portion of the north side of the site that

requires site improvement, additional CPTs should be performed following demolition of the

existing development.

Deep soil mixing (DSM) and drilled displacement columns (DDC) are installed under design#

build contracts by specialty contractors. DSM or DDCs will need to be designed to mitigate the

lateral spreading potential by using a sufficient replacement ratio of cement mixtures to soil.

The ground improvement method should also be designed to adequately transfer the building

loads to a competent bearing layer because of potential settlement between column elements

associated with consolidation and liquefaction. At a minimum, the DSM elements or DDCs

should extend at least three feet below the top of the bearing layer. The estimated elevations

to the top of the bearing layer at the locations explored are shown on the Site Plan, Figure 2.

DDC and DSM are discussed in the following sections.

6.1.1 Drilled Displacement Columns

DDCs are constructed by using a displacement auger to create a soil shaft that is filled with

CLSM (Controlled Low Strength Material) injected under pressure as the displacement auger is

withdrawn from the hole. Because of the installation pressures, DDCs vary between 20 to

24 inches in diameter. Strength of the CLSM is on the order of 500 psi at 28 days, depending

on the foundation load requirements. Installation of DDCs produces minimal soil cuttings


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because the soil is displaced during column installation. The purpose of the drilled

displacement columns is to eliminate the lateral spread potential and transfer building loads to a

deeper bearing stratum. The structure can then be supported on a shallow foundation bearing

on the DDC columns. DDCs can also be constructed to resist uplift loads by drilling them

deeper into the bearing layer and installing a central bar.

Because DDCs inject the CLSM under pressure, there is the potential for soil heave near the

column. To eliminate the potential to damage nearby improvements, DDCs may need to be set

back a horizontal distance from adjacent structures.

6.1.2 Deep Soil Mixing (DSM)

Mechanical deep soil mixing is used to treat soil in#place with cement grout using mixing shafts

consisting of auger cutting heads, discontinuous flight augers, or blades/paddles to create

below ground deep soil elements. Deep soil mixing may be installed in a variety of patterns

including cellular blocks, a grid pattern, or columns/panels. Typical minimum replacement ratios

(ratio of treated soil to building footprint) are on the order of 30 to 50 percent. The structure

can then be supported on a shallow foundation bearing on the improved soil.

The deep soil mixing should be installed in a pattern that will eliminate the potential for

liquefaction and lateral spreading and transfer building loads to a deeper bearing stratum with a

sufficient replacement ratio. A cellular block of continuous DSM walls composed of overlapping

DSM columns or panels may be needed to create an effective buttress for lateral spreading.

Resistance to lateral loads will be developed in friction along the contact area between the soil#

cement shafts and the base of the shallow foundation

The installation of DSM systems typically does not create soil spoils; however, it does transport

cementitious grout spoils and some soil cement mix spoils to the ground surface. DSM

systems typically produce little to no vibrations, such that damage to the adjacent structures

would not be a concern. However, structures should be monitored throughout DSM

installation and DSM operations should cease if unacceptable movement is measured.

6.2 Foundations and Settlement

Once the ground improvement is in place, the northern portion of the building can be supported

on a mat foundation bearing on the improved soil. Based on our experience with sites with

similar soil conditions, we anticipate static settlement of a properly constructed mat foundation


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supported on DDC or DSM will be limited to ¾ inch or less under the weight of the anticipated

building loads with differential settlement dependent upon the loading and rigidity of the mat.

The estimated static settlement should be confirmed by the design#build contractor.

Because the ground improvement will only mitigate the liquefaction/lateral spread potential to

the top of the dense Colma formation, additional seismically#induced total and differential

settlement associated with deeper liquefiable and compressible layers within and below the

Colma formation of up to ½ inch may occur at the northern portion of the site, as discussed in

Section 5.3.2.

The subsurface conditions encountered at the southern portion of the site generally consist of

12 to 15 feet of fill comprised of medium dense to dense sand with varying fines content over

stiff to very stiff silts and clays. In general, this fill appears to be relatively consistent between

points of exploration. However, the upper two to three feet of fill is in poor condition and

contains debris. We judge that the fill is adequate to support the southern portion of the

building bearing on a mat foundation; however, to reduce erratic settlement associated with the

upper portion of the fill, the top three feet of fill beneath the planned foundation elevation

should be overexcavated and recompacted as engineered fill. Also, areas to receive new fill

should be overexcavated to a depth of three feet and recompacted prior to placement of new

fill.

We anticipate static settlement of a properly constructed mat foundation bearing on at least

three feet of engineered fill should be about 1 to 1¼ inches with differential settlement

dependent upon the loading and rigidity of the mat. We estimate about half of these

settlements will occur during construction. In addition to the static settlement, seismically#

induced settlement may occur across the southern portion of the site during a major

earthquake, as discussed in Section 5.3.2.

The subsurface conditions encountered in B#2, B#3, CPT#2, and CPT#4 appear to be

representative of conditions at the southern portion of the site, and we conclude the building in

this area be supported on a mat foundation bearing on at least three feet of engineered fill over

the existing medium dense to dense sand fill. However, we also conclude additional

exploration be performed within the building footprint following demolition of the existing

development to confirm the uniformity of the existing fill.

Alternatively, the mat on the southern portion of the site could also be supported on improved

soil. We understand that there may be environmental costs associated with disturbing and


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excavating the fill. In addition, overexcavation adjacent to existing structures may require

underpinning of adjacent foundations. By improving the fill on the south side of the site with

DDCs or DSM, the need for additional exploration will be eliminated, and the soil is treated in

place to avoid costs associated with, underpinning and exposing the upper portions of the fill.

The replacement ratio and minimum depth of soil improvement methods in areas to improve

the fill are expected to be less than in areas treated to reduce liquefaction and lateral spread

potential. If ground improvement is chosen for this area, the design, pattern, and placement of

soil improvement methods on the southern portion of the site will need to consider the

proximity of the adjacent structures. DDCs displace soil and inject grout which could result in

soil heave near the column. To eliminate the potential to damage nearby improvements, DDCs

may need to be set back a horizontal distance from adjacent structures.

6.3 Groundwater

Groundwater levels were measured during our field investigation at approximate elevations

ranging between 7 and 14½ feet. The measured groundwater is below existing site grades and

the anticipated finished floor of the new building, assuming the building will be constructed to

match existing grades at the site. Therefore, we do not anticipate encountering groundwater

during mass grading of the site. However, groundwater may be encountered in deeper

excavations, such as elevator pits and utilities.

6.4 Floor Slabs

In general, the floor slab will be a mat slab bearing on either improved soil or at least three feet

of engineered fill above the measured groundwater level. Moisture barriers are typically used

in areas where moisture is not desirable including lobby and storage areas. A moisture barrier

may not be necessary in areas beneath the parking areas, provided it is acceptable that

moisture and efflorescence (white powdery calcium or chloride staining) will occur over time.

Although not shown on the plans, we anticipate that elevator pits will be part of the new

development. If the elevator pits extend below the measured groundwater levels, they should

be designed for hydrostatic uplift. The mat foundation for the elevator pits may also need to be

waterproofed.

6.5 Corrosion Potential

Corrosivity testing was performed on a sample from a depth of 5½ feet in Boring B#2 and a

depth of 3 feet in boring B#4. The sample of soil was tested in accordance with Caltrans and


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ASTM protocols by Environmental Technical Services (ETS) of Petaluma, California and CERCO

analytical of Concord, California. The corrosivity test results are presented in Appendix C.

6.6 Construction Considerations

The fill at the site consists mainly of sand, gravel, and clay that can be excavated with

conventional earth#moving equipment such as loaders and backhoes. The granular nature of

the fill will likely make it difficult to maintain neat vertical cuts for utilities and foundation

elements, and prepared subgrade for foundations will likely become disturbed with

construction traffic. Site preparation and grading may be difficult if performed during the rainy

season.

Serpentinite was encountered in the fill. Serpentinite often contains naturally occurring

asbestos, and it may be difficult and costly to dispose of, whether it contains asbestos or not.

The fill may contain heavy metals and petroleum hydrocarbons. Handling and disposal of the fill

material should be performed in accordance with a site mitigation plan (SMP) that includes

health and safety criteria; preparation of an SMP is not within the scope of this investigation.

Although only trace amounts of concrete and brick debris were encountered in our borings,

greater amounts and larger pieces of brick, concrete, and other rubble may be encountered in

the fill. Installation of ground#improvement elements or excavations may be difficult in some

areas of the site.

Excavations below the measured groundwater level should be dewatered as needed to install

utilities and compact soil. Because the fill is granular, there is a potential for significant water

inflow into any excavation. Prior to dewatering, the groundwater should be tested to evaluate if

it can be discharged directly to the storm drain system or if it must be treated on#site prior to

discharge.

If ground improvement is performed in the southern portion of the site, the ground#

improvement design#build contractor should consider the neighboring structures when

designing the appropriate ground#improvement method. If overexcavation and recompaction of

the fill is performed adjacent to existing structures, underpinning or design of shoring to

support the excavation and loads from adjacent structures will be required. A pre#construction

survey and monitoring program should be undertaken prior


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to construction to monitor any effects to the surrounding buildings during construction. The

survey should include documenting the condition of the surrounding structures, including a

crack survey, prior to, during, and following ground#improvement installation or underpinning or

shoring installation.

7.0 RECOMMENDATIONS

Recommendations regarding site preparation, foundation design, ground improvement, floor

slabs, below#grade walls, and seismic design are presented in the following sections.

7.1 Site Preparation and Grading

This section presents earthwork recommendations for site preparation and grading.

7.1.1 Site Clearing

Site demolition should include the removal of all slabs, foundations, retaining walls, pavements,

utilities, and other below#grade improvements that will interfere with the proposed

construction. Where utilities that are removed extend off site, they should be capped or

plugged with grout at the property line. It may be feasible to abandon utilities in#place by filling

them with grout, provided they will not impact future utilities or building foundations. The utility

lines, if encountered, should be addressed on a case#by#case basis.

If an excavation extends below the groundwater during demolition activities, the portion of the

resulting excavation below the groundwater level should be filled with ¾#inch crushed rock. If

fine#grained soil is exposed at the base of the excavation, it may be necessary to place a

reinforcement fabric (Mirafi 500X or equivalent) over the base of the excavation prior to

placement of the rock to prevent the rock from being pushed into the fine#grained soil. Once a

firm base is established above the groundwater level, compacted fill can be placed on the

crushed rock. The crushed rock should be wrapped in filter fabric, such as Mirafi 140NC (or

equivalent) to reduce the potential fines infiltrating into the voids between the crushed rock

particles.

7.1.2 Subgrade Preparation

At the northern portion of the site, the mat will be supported on improved ground. In the case

DDC is the chosen ground improvement option, the mat should bear on at least 12 inches of

Class 2 aggregate base over the DDC columns and be compacted to 95 percent relative


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compaction7. In the case DSM is the chosen ground improvement option, the mat can bear

directly on DSM ground, provided the soil subgrade between the DSM columns is stable and

suitable for a working surface. 12 inches of Class 2 AB compacted to at least 95 percent

relative compaction or a rat slab should be placed if the unimproved soil subgrade is weak and

unstable.

At the southern portion of the site, the mat foundation should bear on improved ground or at

least 3 feet of engineered fill. To provide 3 feet of properly compacted fill, the upper 2½ feet

beneath the mat subgrade should be overexcavated, and the material exposed at the bottom of

the overexcavation should be scarified to a depth of at least 6 inches, moisture conditioned to

near the optimum moisture content, and compacted to at least 95 percent relative compaction.

If soft areas are encountered at the bottom of the overexcavation, the soft material should be

removed and replaced with either crushed rock or engineered fill. If the material is wet, the

upper 12 inches should be scarified and aerated to reduce its moisture content so that it can be

compacted to the required compaction. The remaining 2½ feet of fill should be placed in 8#

inch#loose lifts, moisture conditioned to near the optimum moisture content, and compacted to

at least 95 percent relative compaction. Also, in areas to receive new fill beneath the mat, the

existing fill should be overexcavated as stated above prior to placement of the new fill. After

recompaction of fill or improvement of soil, the subgrade should be proof rolled to provide a

smooth, non#yielding surface.

7.1.3 Fill Placement and Compaction

From a geotechnical standpoint, concrete generated by demolition may be crushed and reused

as fill provided it is free of organic material and rocks or lumps greater than three inches in

greatest dimension. Where crushed concrete is used, particles between 1½ and 3 inches in

greatest dimension should comprise no more than 30 percent of the fill by weight.

Alternatively, concrete may be crushed to meet the requirements of Caltrans Class 2 aggregate

base (“recycled AB); in this case, the recycled AB may be used where AB is recommended.

Onsite fill is suitable for reuse as backfill, provided it is acceptable from an environmental

standpoint and meets the requirements for general fill. All material to be used as fill, including

on#site soil, should be non#corrosive, free of organic matter or other deleterious material,

contains no rocks or lumps larger than four inches in greatest dimension, has a liquid limit of

less than 40 and a plasticity index lower than 12, and is approved by the Geotechnical Engineer.

================================================7 Relative compaction refers to the in#place dry density of soil expressed as a percentage of the maximum dry

density of the same material, as determined by the latest ASTM D1557 laboratory compaction procedure.


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Fill should be placed in horizontal lifts not exceeding 8 inches in uncompacted thickness,

moisture#conditioned to moisture conditioned to near the optimum moisture content, and

compacted to at least 95 percent relative compaction.

It should be noted that if earthwork occurs in city streets, fill placement and compaction should

be in accordance with City and County of San Francisco Standard Specifications; however,

jetting should not be permitted.

The Geotechnical Engineer should approve all sources of fill at least three days before use at

the site. The grading contractor should provide analytical test results or other suitable

environmental documentation indicating the imported fill is free of hazardous materials at least

three days before use at the site. If this data is not available, up to two weeks should be

allowed to perform analytical testing on the proposed import material. A bulk sample of

approved fill should be provided to the geotechnical engineer at least three working days before

use at the site so a compaction curve can be prepared.

7.1.4 Utilities

All trenches should conform to the current OSHA requirements for work safety.

The thickness and type of bedding material required for utility conduits will depend on the soil

conditions at the utility trench bottom. As a minimum, bedding should have a thickness of at

least D/4 (with D equal to the outside pipe diameter) below the bottom of the pipe, and a

minimum thickness of four inches. Clean sand, rod mill, or pea gravel bedding material are

acceptable for use as bedding materials. Below the groundwater level, bedding material should

consist of either Caltrans Class 2 permeable rock or ¾#inch crushed rock wrapped in filter fabric

(Mirafi 140NC or equivalent). Underground utilities should be located above an imaginary plane

inclined downward at 1.5:1 (horizontal to vertical) from the bottom edge of shallow foundation

elements, or foundations will need to be deepened.

Backfill for utility trenches and other excavations is also considered fill, and it should be

compacted according to the recommendations presented in Section 7.1.3. If imported clean

sand or gravel is used as backfill, however, it should be compacted to at least 95 percent

relative compaction. Jetting of trench backfill should not be permitted. Special care should be

taken when backfilling utility trenches in pavement areas. Poor compaction may cause

excessive settlements, resulting in damage to the pavement section.


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Where utility trenches extend from the exterior to the interior limits of a building, lean concrete

should be used as backfill material for a distance of two feet laterally on each side of the

exterior building line to reduce the potential for the trench to act as a conduit for external water

to enter the building footprint.

Utilities should be designed to accommodate the predicted settlement and differential

settlement where they connect into new structures. Flexible connections and hangers should

be considered.

7.1.5 Temporary Slopes

Excavations deeper than five feet entered by workers should be shored or sloped for safety in

accordance with the Occupational Safety and Health Administration (OSHA) standards (29 CFR

Part 1926). Inclinations of temporary slopes should not exceed those specified in local, state or

federal safety regulations. As a minimum, the requirements of the current OSHA Health and

Safety Standards for Excavations (29 CFR Part 1926) should be followed. The Contractor

should determine temporary slope inclinations based on the subsurface conditions exposed at

the time of construction. However, temporary slopes less than 10 feet high should be inclined

no steeper than 1½:1 (horizontal to vertical).

If temporary slopes are open for extended periods of time, exposure to weather and rain could

result in sloughing and erosion. In addition, we recommend all vehicles and other surcharge

loads be kept at least 10 feet away from the tops of temporary slopes and the slopes be

protected from either excessive drying or saturation during construction.

7.2 Foundation Support

7.2.1 Mat Foundation

The proposed mat should gain support on improved ground or engineered fill. At the southern

portion of the site, where the proposed mat may bear on at least three feet of engineered fill,

we recommend an average allowable bearing pressure of 2,000 pounds per square foot (psf)

for dead plus live loads. Concentrated stresses may occur at interior columns and at the edges

of the mat. Mat foundations may be designed to impose a maximum dead plus live load

pressure equivalent to an allowable bearing capacity of 4,000 psf. The allowable bearing

pressures can be increased by one#third for total design loads, including wind and seismic

loads. The allowable bearing pressures for dead plus live and total design loads include factors

of safety of about 2.0 and 1.5, respectively. To design the mat at the southern portion of the

site bearing on engineered fill using the modulus of subgrade reaction method, we recommend


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a modulus of 22 kips per cubic foot (kcf). After the mat analysis is completed, we should

review the computed settlement and bearing pressure profiles to check that the modulus value

is appropriate. It may be necessary to perform additional analysis and refine the modulus value.

For a mat bearing on improved soil, (at the northern portion of the site and possibly the

southern portion) we cannot provide specific design recommendations or settlement estimates

because soil improvement is typically performed by design#build contracts by specialty

contractors. However, the mat on improved soil will have a greater allowable bearing capacity

and a higher modulus than the mat on engineered fill. On the basis of our experience we

estimate DDC or DSM can provide an improved allowable bearing capacity of between 3,000

and 6,000 pounds per square foot (psf), depending on the soil type pattern, and spacing. Once

a soil improvement technique has been chosen, the design capacity should be verified by test

sections. Ground improvement recommendations are provided in Section 7.2.2.

The allowable bearing pressure can be increased by one#third for total design loads, including

wind and seismic loads. The allowable bearing pressures for dead plus live and total design

loads include factors of safety of about 2.0 and 1.5, respectively. To design a mat bearing on

improved soil using the modulus of subgrade reaction method, we recommend a modulus on

the order of 70 to 80 kcf. The values are based on the estimated allowable bearing pressures

and the settlement we anticipate based on our experience with this type of foundation system.

The actual value should be confirmed by the design#build contractor.

Lateral loads may be resisted by friction along the base and by passive pressures against the

embedded vertical faces of the mat. For calculating the lateral resistance, we recommend an

allowable equivalent fluid pressure (triangular distribution) of 250 pounds per cubic foot (pcf) be

used for design. Because we understand a vapor mitigation system will be installed, we

recommend a coefficient of base sliding of 0.2 against the bottom of the mat. The values

include a factor of safety of 1.5 and may be used in combination without reduction.

In general, the mat excavation should be free of standing water, debris, and disturbed materials

prior to placing concrete. Except where DDC or DSM are supporting the mat, if loose or soft

soil is encountered at the mat subgrade, the weak soil should be overexcavated to expose

more competent material. The excavated material should be replaced with engineered fill,

structural concrete, or sand#cement slurry with a minimum 28#day compressive strength of at

least 50 pounds per square inch (psi). The bottoms and sides of excavations should be wetted

following excavation and maintained in a moist condition. We should check foundation


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excavations prior to placement of reinforcing steel to confirm suitable bearing material is

present. We should recheck the condition of the excavations just prior to concrete placement

to confirm the excavations have not become disturbed and are sufficiently moist.

7.2.2 Ground Improvement

A qualified, design#build, specialty contractor, who has previously successfully performed

ground improvement in similar subsurface soil conditions, should perform the ground

improvement. We recommend they be presented with our report and they design the ground

improvement system, including installation method, the depth, size and spacing of the DDC or

DSM elements within the recommended improvement zone limits, the strength of the

element, and the quality control requirements. We should be retained to provide technical

input and review the design prior to construction.

On the northern portion of the site, we recommend that the ground improvement be designed

to mitigate the lateral spreading potential and adequately transfer the building loads to a

competent bearing layer. The approximate elevations to the top of the soil improvement

bearing layer at the northern portion of the site are shown on the Site Plan, Figure 2. At a

minimum, the ground improvement in the northern portion should extend at least three feet

into the bearing layer. If ground improvement is selected on the southern portion of the site,

we recommend the ground improvement methods be designed to improve the fill. We

recommend the soil improvement in the southern portion extend a minimum of 10 feet bgs.

DDC or DSM should have a compressive strength of at least 400 pounds per square inch (psi)

and be designed using a factor of safety of at least 2 for the compressive strength. To mitigate

the effects of liquefaction and thus the potential for lateral spreading, we judge a replacement

ratio between 40 and 50 percent should be used in the northern portion of the site. To improve

the fill in the southern portion of the site, we judge a replacement ratio of about 30 percent

should be used.

To confirm that lateral spreading has been mitigated and the fill has been improved using

DDCs, we recommend a preliminary study with test sections be implemented. For DDCs, Pre#

and post#improvement borings (using SPT sampling) or CPTs should be advanced between

columns to confirm the ground has been sufficiently improved. The CPTs or borings should be

performed at least two weeks following installation of the test section to allow for pore

pressure dissipation and soil improvement.


2000�2070 Bryant Street 750615602


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The improved soil between columns should have minimum and average SPT blow counts

[(N1)60,CS] , over three consecutive SPTs, of at least 20 and 30 blows per foot, respectively. If

CPTs are used for quality control (QC), the improved soil should have minimum and average tip

resistances [(qc1N) CS] , over an interval of 3 feet, of at least 80 and 120 tons per square foot

(tsf), respectively. The acceptance criteria may need to be reevaluated depending on the soil

types encountered. Improvement of the fill and liquefiable material should be verified at the

test sections prior to continuing improvement throughout the site.

DSM does not densify the soil, but rather improves the soil in place, such that CPTs or SPTs

are not a recommended QC measure. For QC of a DSM#improved zone, we recommend

monitoring the grout pumping and mixing/penetration rate and obtaining wet samples of the in#

situ soil#cement mixed material for laboratory testing. We recommend a minimum unconfined

compressive of 200 psi for the soil#cement mix. In addition, at least two columns should be

cored. Continuous coring should be performed within the outer third of the element.

We should be involved throughout the ground improvement contractor bidding and selection

process and provide additional detailed recommendations and input on specifications and

procedures.

7.3 Below�Grade Walls

The walls of below#grade structures should be designed as restrained walls. The walls should

be designed to resist both static lateral earth pressures and lateral pressures caused by

earthquakes. We used the procedures outlined in (Sitar, et. al., 2012) to compute the seismic

active pressure. The more critical condition of either at#rest pressure or active pressure plus a

seismic increment (total pressure) should be checked. At#rest and total equivalent fluid

pressure for the Design Earthquake (DE) level of shaking for the site, both for level backfill, are

presented in Table 4 for fully drained and undrained conditions.


2000�2070 Bryant Street 750615602


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TABLE 4

Lateral Earth Pressures

Below Grade Wall

Level Backslope

Drainage Condition

Drained Undrained

Static

Pressure

At�rest

Pressure

(pcf)

Total Pressure

Active plus Seismic

Pressure Increment

(pcf)

Static

Pressure

At�rest

Pressure

(pcf)

Total Pressure

Active plus Seismic

Pressure Increment

(pcf)

65 70 95 100

If surcharge loads are present above an imaginary 30#degree line (from the horizontal) projected

up from the bottom of a retaining wall, a surcharge pressure should be included in the wall

design. Where vehicular traffic will pass within 10 feet of retaining walls, traffic loads should

be considered in the design of the walls. Traffic loads may be modeled by a uniform pressure

of 100 psf applied in the upper 10 feet of the walls.

A backdrain can be provided behind below#grade walls to prevent the buildup of hydrostatic

pressure. One acceptable method for backdraining basement and retaining walls is to place a

prefabricated drainage panel against the backside of the newly cast wall. If temporary shoring

is used, the panel may be placed directly on the shoring prior to casting the wall. The panel

should extend down to a perforated PVC collector pipe or an equivalent “flat” pipe (such as

AdvanEdge) at the base of the wall or shoring; where walls are above the groundwater level,

the drain should extend to a pipe at the design groundwater level. The PVC pipe should be

bedded on and covered by at least 4 inches of Class 2 permeable material (per Caltrans

Standard Specifications) or drain rock, and the aggregate material should be surrounded by filter

fabric (Mirafi 140NC or equivalent). If a flat pipe surrounded by a filter fabric is used, it is not

necessary to surround it with rock. A closed collector pipe should be sloped to drain to a

suitable outlet. If water is collected in a sump, a pumping system may be required to carry the

water to the storm drain system. We should review the manufacturer's specifications for

proposed prefabricated drainage panel material and drain pipe to verify they are appropriate for

the intended use.


2000�2070 Bryant Street 750615602


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To protect against moisture migration, below#grade walls should be waterproofed, and water

stops should be placed at all construction joints.

Wall backfill should be compacted to at least 95 percent relative compaction. If heavy

equipment is used, the wall should be appropriately designed to withstand loads exerted by the

equipment and/or temporarily braced.

7.4 Floor Slab

The floor slab will be a mat slab that will extend across the entire site and bear on subgrade

prepared in accordance with our recommendations in Section 7.1.

Moisture is likely to condense on the underside of the mat slab, even though it will be above

the measured groundwater levels. Consequently, a moisture barrier should be installed

beneath the slabs if movement of water vapor through the slabs would be detrimental to its

intended use. A typical moisture barrier consists of a capillary moisture break and a water

vapor retarder. In general, a moisture barrier is not required beneath parking garage slabs,

provided it is acceptable that moisture and efflorescence (white powdery calcium or chloride

staining) will occur over time. Moisture barriers are typically used in areas where moisture is

not desirable. Parking garage slabs may be underlain by at least 6 inches of Class 2 aggregate

base compacted to at least 95 percent relative compaction.

If the depths of the elevator pits are within 30 inches of the measured groundwater, the

elevator pits should be waterproofed. We recommend a waterproofing consultant be retained

to determine the most appropriate system for this project and to provide input regarding

waterproofing details. Installation of waterproofing should be performed in accordance with

the manufacturer’s requirements.

The capillary moisture break should consist of at least four inches of clean, free#draining gravel

or crushed rock. The vapor retarder should meet the requirements for Class C vapor retarders

stated in ASTM E1745#97. The vapor retarder should be placed in accordance with the

requirements of ASTM E1643#98. These requirements include overlapping seams by

six inches, taping seams, and sealing penetrations in the vapor retarder. The vapor retarder

should be covered with two inches of sand to aid in curing the concrete and to protect the

vapor retarder during slab construction. The particle size of the gravel/crushed rock and sand

should meet the gradation requirements presented in Table 5.


2000�2070 Bryant Street 750615602


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TABLE 5

Gradation Requirements for Capillary Moisture Break

Sieve Size Percentage Passing Sieve

Gravel or Crushed Rock

1 inch 90 – 100

3/4 inch 30 – 100

1/2 inch 5 – 25

3/8 inch 0 – 6

Sand

No. 4 100

No. 200 0 – 5

=

The sand overlying the membrane should be dry at the time concrete is cast. Excess water

trapped in the sand could eventually be transmitted as vapor through the slab. If rain is forecast

prior to pouring the slab, the sand should be covered with plastic sheeting to avoid wetting. If

the sand becomes wet, concrete should not be placed until the sand has been dried or

replaced.

Concrete mixes with high water/cement (w/c) ratios result in excess water in the concrete,

which increases the cure time and results in excessive vapor transmission through the slab.

Therefore, concrete for the floor slab should have a low w/c ratio # less than 0.50. If approved

by the project structural engineer, the sand can be eliminated and the concrete can be placed

directly over the vapor retarder, provided the w/c ratio of the concrete does not exceed 0.45

and water is not added in the field. If necessary, workability should be increased by adding

plasticizers. In addition, the slab should be properly cured. Before the floor covering is placed,

the contractor should check that the concrete surface and the moisture emission levels (if

emission testing is required) meet the manufacturer’s requirements.

We understand a liquid boot may be installed under the floor slab. If a liquid boot is installed as

part of the environmental program, the need for a capillary break/vapor retarder system is

eliminated.


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7.5 Shoring and Underpinning

Excavations will be required in areas where the fill is removed and replaced with engineered fill.

If temporary slopes are used for the excavation, they may be constructed no steeper than 1½

to 1 (horizontal to vertical). Where space does not permit an open#cut excavation with sloped

sides, the temporary excavation faces can be retained using cantilevered soldier#pile#and#

lagging walls. Cantilevered shoring should be designed to resist an equivalent fluid weight of

65 pounds per cubic feet (pcf). Passive resistance may be calculated using an equivalent fluid

pressure of 300 pcf. Passive pressures include a factor of safety of 1.5. Penetration of soldier

piles should be deep enough to maintain lateral stability. At#rest pressures should be assumed

to act over one pile diameter; passive pressures may be assumed to act over three diameters.

The shoring system should be designed by a licensed civil engineer experienced in the design

of retaining systems, and installed by an experienced shoring specialty contractor. The shoring

engineer should be responsible for the design of temporary shoring in accordance with

applicable regulatory requirements. Control of ground movement will depend as much on the

timeliness of installation of lateral restraint as on the design. We should review the shoring

plans and a representative from our office should observe the installation of the shoring.

If hand#excavated, end bearing piers are used to underpin the adjacent buildings, the piers

should be designed using a minimum allowable bearing pressure of 2,000 pounds per square

foot (psf) for dead plus live loads. We should observe the underpinning pier excavations to

check that the exposed soil can support the design bearing pressures. Piers should extend at

least two feet below the bottom of the excavation and below loose fill and debris. Piers should

be designed to resist an at#rest soil pressure caused by soil against the underpinning; an

equivalent fluid pressure of 65 pcf should be applied against the embedded portion of the pier.

Passive resistance may be calculated using an equivalent fluid pressure of 300 pcf which

includes a factor of safety of 1.5.

7.6 Construction Monitoring

A monitoring program should be established to evaluate the effects of the construction on the

adjacent buildings and improvements. The conditions of the existing buildings and

improvements within 50 feet of the site should be photographed and surveyed prior to start of

construction and monitored periodically during construction. A thorough crack survey of the

adjacent buildings, especially those surrounding the proposed excavation should be performed

by a surveyor prior to start of construction and immediately after its completion.


2000�2070 Bryant Street 750615602


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7.7 Site Drainage

Drainage control design should include provisions for positive surface gradients so that surface

runoff is not permitted to pond, particularly adjacent to structures, or on roadways or

pavements. Surface runoff should be directed away from foundations and below#grade walls.

7.8 Corrosion Design

All below grade improvements should be properly protected against corrosion. A corrosion

expert should be consulted during the design phase for the most economical and effective

corrosion protection.

7.9 Seismic Design Criteria

As previously mentioned in Section 5.3, potentially liquefiable soils where encountered at the

site during our investigation. According to the 2013 California Building Code (CBC), seismic

design should be based on a site#specific response analysis for sites underlain by potentially

liquefiable soils. However, we evaluated the average shear wave velocities within the top

75 feet at the site taking into account the approximate shear wave velocities of the liquefied

soil layers and found that the average shear wave across the site fell within the range of a site

class D site. Also, we are recommending ground improvement to mitigate the lateral spread

potential at the northern portion of the site, which will further increase the average shear wave

velocity across the site. Therefore, for seismic design in accordance with the provisions of

2013 CBC/ASCE 7#10, we recommend the following:

• Risk Targeted Maximum Considered Earthquake (MCER) SS and S1 of 1.500g and

0.653g, respectively.

• Site Class D

• Site Coefficients FA and FV of 1.0 and 1.5, respectively

• Maximum Considered Earthquake (MCE) spectral response acceleration parameters at

short periods, SMS, and at one#second period, SM1, of 1.500g and 0.979g, respectively.

• Design Earthquake (DE) spectral response acceleration parameters at short period, SDS,

and at one#second period, SD1, of 1.000g and 0.653g, respectively.


2000�2070 Bryant Street 750615602


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8.0 FUTURE GEOTECHNICAL SERVICES

Prior to construction, we should review the project plans and specifications to check their

conformance to the intent of our recommendations. During construction, the Geotechnical

Engineer should observe excavation, ground improvement, mat subgrade preparation, and

compaction of backfill. These observations will allow us to compare the actual with the

anticipated subsurface conditions and check that the contractor's work conforms to the

geotechnical aspects of the plans and specifications.

9.0 LIMITATIONS

The conclusions and recommendations presented in this report result from limited engineering

studies and are based on our interpretation of the geotechnical conditions existing at the site at

the time of investigation. Actual subsurface conditions may vary. If any variations or

undesirable conditions are encountered during construction, or if the proposed construction will

differ from that described in this report, Langan Treadwell Rollo should be notified to make

supplemental recommendations, as necessary.

=


2000�2070 Bryant Street 750615602


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10.0 REFERENCES

Atwater, B.F., (1979), “Ancient Processes at the Site of Southern San Francisco Bay:

Movement of the Crust and Changes in Sea Level, published in San Francisco Bay: The

Urbanized Estuary; Investigations into the Natural History of San Francisco Bay and Delta with

Reference to the Influence of Man,” Pacific Division, American Association for the

Advancement of Science, San Francisco, California, Conomos, T.J, ed., pp. 31#45.

Bonilla, M.C., (1998), “Preliminary Geologic Map of the San Francisco South 7.5#Minute

Quadrangle and part of the Hunters Point 7.5#Minute Quadrangle, San Francisco Bay Area,

California.”

California Division of Mines and Geology, (1996), “Probabilistic Seismic Hazard Assessment for

the State of California.” DMG Open#File Report 96#08.

California Division of Mines and Geology, (1997), “Fault Rupture Hazard Zones in California,”

CDMG Special Publication 42.

California Division of Mines and Geology, (1997), “Guidelines for Evaluating and Mitigating

Seismic Hazards in California,” California Department of Conservation, Division of Mines and

Geology, Special Publication 117.

California Division of Mines and Geology, (2001), “Seismic Hazard Zone Report for the City and

County of San Francisco,” California Department of Conservation, Division of Mines and

Geology, Seismic Hazard Zone Report 043.

Cao, T., Bryant, W. A., Rowshandel, B., Branum D. and Wills, C. J., (2003), “The Revised 2002

California Probabilistic Seismic Hazard Maps.”

Helley, E.J., and Herd, D.G., (1977), Map showing faults with Quaternary displacement,

northwestern San Francisco Bay region, California: U.S. Geological Survey Miscellaneous Field

Studies map MF#881, scale 1:125,000.

Jennings, C.W., (1994), “Fault Activity Map of California and Adjacent Areas,” California

Division of Mines and Geology Geologic Data Map No. 6, scale 1: 750,000.

Lienkaemper, J. J., (1992), “Map of Recently Active Traces of the Hayward Fault, Alameda and

Contra Costa counties, California.” Miscellaneous Field Studies Map MF#2196.

Nichols, D.R., and Wright, N.A., (1971), “Preliminary Map of Historic Margins of Marshland,

San Francisco Bay, California,” U.S. Geological Survey Open File Report OFR#71#216.

Norris, R.M., and Webb, R.W., (1990), “Geology of California,” John Wiley & Sons, Inc.

San Francisco Building Code, (2010).


2000�2070 Bryant Street 750615602


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Schlocker, J., (1974), “Geology of the San Francisco North Quadrangle, California.”

Sloan, D., (1992), “The Yerba Buena Mud � Record of the Last Interglacial Predecessor of

San Francisco Bay, California,” Geological Society of America Bulletin, v. 104, pp. 716#727.

Sitar, et al, (2012), “Seismically Induced Lateral Earth Pressures on Retaining Structures and

Basement Walls.” Geotechnical Engineering State of the Art and Practice Keynote Lectures

GeoCongress 2012 Geotechnical Special Publication No. 226.

Toppozada, T. R. and Borchardt G., (1998), “Re#Evaluation of the 1836 “Hayward Fault” and the

1838 San Andreas Fault earthquakes.” Bulletin of Seismological Society of America, 88(1), 140#

159.

Townley, S. D. and Allen, M. W., (1939), “Descriptive Catalog of Earthquakes of the Pacific

Coast of the United States 1769 to 1928.” Bulletin of the Seismological Society of America,

29(1).

Tokimatsu, K. and Seed, H.B., (1984). “Simplified Procedures for the Evaluation of Settlements

in Clean Sands,” Earthquake Engineering Research Center Report UCB/EERC#84/16, University

California, Berkeley.

Treadwell & Rollo, Inc., (2005), “Final Geotechnical Investigation, Alabama Street Housing,

San Francisco, California.” 23 August.

Wesnousky, S. G., (1986), “Earthquakes, Quaternary Faults, and Seismic Hazards in California,”

Journal of Geophysical Research, 91(1312).

Working Group on California Earthquake Probabilities (WGCEP), (2008), “The Uniform California

Earthquake Rupture Forecast, Version 2,” Open File Report 2007#1437.

Yanev, P., (1974), “Peace of Mind in Earthquake Country,” Chronicle Books, San Francisco,

California.

Youd, L.T., Hansen, C.M., and Bartlett, S.F., (2002), “Revised Multilinear Regression Equations

for Prediction of Lateral Spread Displacement,” Journal of Geotechnical and Environmental

Engineering, Vol. 128, No. 12, December 1.

=

FIGURES

0 1/2 Mile

Approximate scale

1/4

Project No. FigureDate 75061560203/25/14 1

SITE LOCATION MAP

SITE

Base map: The Thomas Guide San Francisco County 2002

2000-2070 BRYANT STREETSan Francisco, California

CPT-3

[-18']

CPT-4

[-8']

B-1

[-12']

B-2

[-8']

B-3

[-18']

CPT-2

[-23']

CPT-1

[-15']

CPT-6

[-20]

B-4

[-23]

CPT-5

[-15]

CPT-7

[-20]

Approximate scale

0 40 Feet

Reference: Base map from a drawing titled "Site Survey of a Portion of Assessor's Block No. 4022 for Nick Podell Company,by Martin M. Ron Associates, dated 06-28-13.

Date Project No. Figure

SITE PLAN

San Francisco, California2000-2070 BRYANT STREET

275061560203/25/14

Approximate location of boring by Langan TreadwellRollo, January 2014

Approximate location of cone penetration test byLangan Treadwell Rollo, January and February 2014

Approximate location of boring by Treadwell & Rollo,April 2013

Approximate location of cone penetration test byTreadwell & Rollo, April 2013

Elevation of top of bearing layer

Site boundary

Zone of potential lateral spread

EXPLANATION

B-1

CPT-1

[-14']

B-4

CPT-5

Project No. Figure Date

MAP OF MAJOR FAULTS ANDEARTHQUAKE EPICENTERS IN

THE SAN FRANCISCO BAY AREA

375061560203/25/14


SITE

Project No. FigureDate

I Not felt by people, except under especially favorable circumstances. However, dizziness or nausea may be experienced.Sometimes birds and animals are uneasy or disturbed. Trees, structures, liquids, bodies of water may sway gently, and doors may swing very slowly.

II Felt indoors by a few people, especially on upper floors of multi-story buildings, and by sensitive or nervous persons.As in Grade I, birds and animals are disturbed, and trees, structures, liquids and bodies of water may sway. Hanging objects swing, especially if they are delicately suspended.

III Felt indoors by several people, usually as a rapid vibration that may not be recognized as an earthquake at first. Vibration is similar to that of a light, or lightly loaded trucks, or heavy trucks some distance away. Duration may be estimated in some cases.

Movements may be appreciable on upper levels of tall structures. Standing motor cars may rock slightly.

IV Felt indoors by many, outdoors by a few. Awakens a few individuals, particularly light sleepers, but frightens no one except those apprehensive from previous experience. Vibration like that due to passing of heavy, or heavily loaded trucks. Sensation like a heavy body striking building, or the falling of heavy objects inside.

Dishes, windows and doors rattle; glassware and crockery clink and clash. Walls and house frames creak, especially if intensity is in the upper range of this grade. Hanging objects often swing. Liquids in open vessels are disturbed slightly. Stationary automobiles rock noticeably.

V Felt indoors by practically everyone, outdoors by most people. Direction can often be estimated by those outdoors. Awakens many, or most sleepers. Frightens a few people, with slight excitement; some persons run outdoors.

Buildings tremble throughout. Dishes and glassware break to some extent. Windows crack in some cases, but not generally. Vases and small or unstable objects overturn in many instances, and a few fall. Hanging objects and doors swing generally or considerably. Pictures knock against walls, or swing out of place. Doors and shutters open or close abruptly. Pendulum clocks stop, or run fast or slow. Small objects move, and furnishings may shift to a slight extent. Small amounts of liquids spill from well-filled open containers. Trees and bushes shake slightly.

VI Felt by everyone, indoors and outdoors. Awakens all sleepers. Frightens many people; general excitement, and some persons run outdoors.

Persons move unsteadily. Trees and bushes shake slightly to moderately. Liquids are set in strong motion. Small bells in churches and schools ring. Poorly built buildings may be damaged. Plaster falls in small amounts. Other plaster cracks somewhat. Many dishes and glasses, and a few windows break. Knickknacks, books and pictures fall. Furniture overturns in many instances. Heavy furnishings move.

VII Frightens everyone. General alarm, and everyone runs outdoors.People find it difficult to stand. Persons driving cars notice shaking. Trees and bushes shake moderately to strongly. Waves form on ponds, lakes and streams. Water is muddied. Gravel or sand stream banks cave in. Large church bells ring. Suspended objects quiver. Damage is negligible in buildings of good design and construction; slight to moderate in well-built ordinary buildings; considerable in poorly built or badly designed buildings, adobe houses, old walls (especially where laid up without mortar), spires, etc. Plaster and some stucco fall. Many windows and some furniture break. Loosened brickwork and tiles shake down. Weak chimneys break at the roofline. Cornices fall from towers and high buildings. Bricks and stones are dislodged. Heavy furniture overturns. Concrete irrigation ditches are considerably damaged.

VIII General fright, and alarm approaches panic.Persons driving cars are disturbed. Trees shake strongly, and branches and trunks break off (especially palm trees). Sand and mud erupts in small amounts. Flow of springs and wells is temporarily and sometimes permanently changed. Dry wells renew flow. Temperatures of spring and well waters varies. Damage slight in brick structures built especially to withstand earthquakes; considerable in ordinary substantial buildings, with some partial collapse; heavy in some wooden houses, with some tumbling down. Panel walls break away in frame structures. Decayed pilings break off. Walls fall. Solid stone walls crack and break seriously. Wet grounds and steep slopes crack to some extent. Chimneys, columns, monuments and factory stacks and towers twist and fall. Very heavy furniture moves conspicuously or overturns.

IX Panic is general.Ground cracks conspicuously. Damage is considerable in masonry structures built especially to withstand earthquakes; great in other masonry buildings - some collapse in large part. Some wood frame houses built especially to withstand earthquakes are thrown out of plumb, others are shifted wholly off foundations. Reservoirs are seriously damaged and underground pipes sometimes break.

X Panic is general.Ground, especially when loose and wet, cracks up to widths of several inches; fissures up to a yard in width run parallel to canal and stream banks. Landsliding is considerable from river banks and steep coasts. Sand and mud shifts horizontally on beaches and flat land. Water level changes in wells. Water is thrown on banks of canals, lakes, rivers, etc. Dams, dikes, embankments are seriously damaged. Well-built wooden structures and bridges are severely damaged, and some collapse. Dangerous cracks develop in excellent brick walls. Most masonry and frame structures, and their foundations are destroyed. Railroad rails bend slightly. Pipe lines buried in earth tear apart or are crushed endwise. Open cracks and broad wavy folds open in cement pavements and asphalt road surfaces.

XI Panic is general.Disturbances in ground are many and widespread, varying with the ground material. Broad fissures, earth slumps, and land slips develop in soft, wet ground. Water charged with sand and mud is ejected in large amounts. Sea waves of significant magnitude may develop. Damage is severe to wood frame structures, especially near shock centers, great to dams, dikes and embankments, even at long distances. Few if any masonry structures remain standing. Supporting piers or pillars of large, well-built bridges are wrecked. Wooden bridges that "give" are less affected. Railroad rails bend greatly and some thrust endwise. Pipe lines buried in earth are put completely out of service.

XII Panic is general.Damage is total, and practically all works of construction are damaged greatly or destroyed. Disturbances in the ground are great and varied, and numerous shearing cracks develop. Landslides, rock falls, and slumps in river banks are numerous and extensive. Large rock masses are wrenched loose and torn off. Fault slips develop in firm rock, and horizontal and vertical offset displacements are notable. Water channels, both surface and underground, are disturbed and modified greatly. Lakes are dammed, new waterfalls are produced, rivers are deflected, etc. Surface waves are seen on ground surfaces. Lines of sight and level are distorted. Objects are thrown upward into the air.

75061560203/25/14 4

MODIFIED MERCALLI INTENSITY SCALE2000-2070 BRYANT STREET


=

APPENDIX A

Logs of Borings and Cone Penetration Tests

20.9

20.6

19.9

GRAB

GRAB

S&H

SPT

S&H

S&H

S&H

D&M

SPT

D&M

S&H

GC

SC

SC

CL

SC-SM

CL

SP-SC

4

6

4

4

2

125psi

2

200psi

28

35.9

44.5

54.5

38.5

33.3

533

232123

014

011

111

121723

4 inches Asphalt Concrete (AC)2 inches Aggregate Base (AB)2 inches concreteCLAYEY GRAVEL with SAND (GC)red-brown, moist, fine- to coarse-grainedangular gravel, fine- to coarse-grained sandgreen-gray [SERPENTINITE FILL]

loose, serpentinite fragments up to 2.5 inches indiameter

limited recovery likely due to rocks in fill largerthan sample diameter

CLAYEY SAND (SC)brown and gray, loose, moist, fine-grainedLL = 25, PI = 10, see Figure B-1

CLAYEY SAND (SC)dark gray, loose, moist to wet, fine-grained sand

SANDY CLAY (CL)dark olive-gray, very soft, wet, fine-grained

CLAYEY SILTY SAND (SC-SM)dark olive-gray, loose, wet, fine-graind

strong hydrocarbon odor

LL = 22, PI = 7, see Figure B-1gray with orange-brown mottling, very looseCLAYEY SILTY SAND (SC-SM) (continued)SANDY CLAY (CL)orange-brown, soft, wet, fine-grained sand

SAND with CLAY (SP-SC)olive-brown with orange-brown mottling, mediumdense, moist, fine-grained

FIL

LM

AR

SH

DE

PO

SIT

S

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft

Hammer type: Down Hole Safety

Boring location:

Date started:

Drilling method:

Hammer weight/drop: 140 lbs./30 inches

E. Toth

Date finished: 4/18/13

See Site Plan, Figure 2

4/18/13

Rotary Wash with Automatic Trip, 6-inch auger to 15 feet

Sampler:

Ground Surface Elevation: 20 feet2

Sprague & Henwood (S&H), Standard Penetration Test (SPT), Dames & Moore (D&M)

Logged by:

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

SAMPLES

LABORATORY TEST DATA

MATERIAL DESCRIPTION

Log of Boring B-12000-2070 BRYANT STREETSan Francisco, California

Figure:

PAGE 1 OF 3

750615602Project No.:

PROJECT:

A-1a

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

28.3

SPT

SPT

SPT

SPT

SPT

SPT

SP-SC

SC-SM

37

47

84

91

60/5"

29 28.1

171714

91425

242941

374729

3250/5"

141311

SAND with CLAY (SP-SC) (continued)

dense

olive-brown, very dense

SAND (SP) (continued)

with orange-brown mottling, clay seams

CLAYEY SILTY SAND (SC-SM)olive-gray with red-brown mottling, mediumdense, wet, fine-grained, interbedded lenses ofcemented sand, oxidizedLL = 25, PI = 7, see Figure B-1

CO

LM

A F

OR

MA

TIO

N

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

SAMPLES LABORATORY TEST DATA



Figure:

PAGE 2 OF 3


PROJECT:

A-1b

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

SPT

SPT

SC-SM

SP

60/6"

60/3"

50/6"

4250/3"

CLAYEY SILTY SAND (SC-SM) (continued)

SAND (SP)olive, very dense, wet, fine-grained, trace fines

CO

LM

A F

OR

MA

TIO

N

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90




Figure:

PAGE 3 OF 3


PROJECT:

A-1c

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

Boring terminated at a depth of 69.3 feet below ground surface.Boring backfilled with cement grout.Groundwater obscured by drilling method.

1 S&H and SPT blow counts for the last two increments wereconverted to SPT N-Values using factors of 0.7 and 1.2,respectively to account for sampler type and hammer energy.

2 Elevations based on San Francisco City datum and Site Surveydated 06-28-13.

PP 1,600

16.2

18.9

GRAB

GRAB

S&H

SPT

S&H

D&M

SPT

SPT

CL

SC

CL

SP-SM

36

32

14

300psi

44

41

13.5

122428

111413

6812

81225

151618

6 inches Asphalt Concrete (AC)5 inches concreteSANDY CLAY with GRAVEL (CL)dark brown, moist, fine sand, angular gravel,trace concrete and brick debris

CLAYEY SAND (SC)brown and gray, moist, fine-grained

dense

olive-brown, clayey sand

(04/19/12, 9:00 a.m.)SANDY CLAY (CL)olive-brown with orange-brown mottling, stiff,moist to wet, fine-grained sand

SAND with SILT (SP-SM)olive-gray, dense, wet, fine-grained

FIL

L 110

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft


Boring location:

Date started:

Drilling method:


E. Toth



4/19/13

Rotary Wash with Automatic Trip, 6-inch auger to 13.5 feet

Sampler:

Ground Surface Elevation: 19 feet2


Logged by:

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

SAMPLES




Figure:

PAGE 1 OF 3


PROJECT:

A-2a

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

20.1

21.1

SPT

SPT

SPT

SPT

SPT

SP-SM

SP-SC

35

42

35

80

73

10.5

12.7

101415

91421

91019

142938

222734

SAND with SILT (SP-SM) (continued)

SAND with CLAY (SP-SC)olive-brown with orange-brown and blackmottling, dense, wet, fine-grained

very dense

increase clay content

CO

LM

A F

OR

MA

TIO

N

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52




Figure:

PAGE 2 OF 3


PROJECT:

A-2b

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

PP 2,000

30.9

SPT

SPT

SPT

S&H

SPT

SP-SC

CL

SC-SM

SP

68

60/4"

107/9.5"

19

66

12.9

323027

4650/4"

253950/3.5"

41017

6550

SAND with CLAY (SP-SC) (continued)

dark gray, 4 inch clay lens at 54.5

gray-brown with orange-brown mottling, ironoxide staining

no oxidation

SANDY CLAY (CL)dark gray, very stiff, wet, fine-grained sand,interbedded seams of sand

CLAYEY SILTY SAND (SC-SM)dark gray, medium dense, wet, fine-grainedsandLL = 22, PI = 4, see Figure B-1

SAND (SP)dark gray, very dense, wet, fine-grained,interbedded lenses of sandy clay

CO

LM

A F

OR

MA

TIO

N

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78




Figure:

PAGE 3 OF 3


PROJECT:

A-2c

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

Boring terminated at a depth of 75 feet below ground surface.Boring backfilled with cement grout.Groundwater encountered at 12.3 feet below ground surface duringdrilling.PP = pocket penetrometer



23.2

18.8

S&H

SPT

S&H

DIST

SPT

SPT

S&H

SP-SC

SP

CL

SP-SC

SP

CL

SC

22

38

16

26

24

29

30

11.8

16.7

101517

131517

7914

111522

8911131212

111924

8.5 inches concrete

SAND with CLAY (SP-SC)brown, moist, fine-grained, trace concrete debris

medium dense

SAND (SP)brown, dense, moist, fine-grained

SANDY CLAY (CL)olive-brown with red mottling, very stiff, moist,fine-grained sand

(04/22/13, 8:10 a.m.)

SAND with CLAY (SP-SC)olive-brown, medium dense, wet, fine-grained

SAND (SP)olive-brown, medium dense, wet, fine-grained


SANDY CLAY (CL)orange-brown with black mottling, very stiff, wet,fine-grained sand

CLAYEY SAND (SC)orange-brown with black mottling, dense, wet,

FIL

L

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft


Boring location:

Date started:

Drilling method:


E. Toth



4/22/13

Hollow Stem Auger with Automatic Trip

Sampler:

Ground Surface Elevation: 24.5 feet2


Logged by:

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

SAMPLES




Figure:

PAGE 1 OF 2


PROJECT:

A-3a

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

SPT

SPT

SPT

SPT

SC

SP-SC

29

28

67

60/4"

101311

41112

203125

3550/4"

fine grained

olive-brown with orange mottling, medium dense

with black mottling

SAND with CLAY (SP-SC)olive-brown with red and black mottling, verydense, wet, fine-grained, iron oxide staining

gray-brown

CO

LM

A F

OR

MA

TIO

N

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60




Figure:

PAGE 2 OF 2


PROJECT:

A-3b

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

Boring terminated at a depth of 49.3 feet below ground surface.Boring backfilled with cement grout.Groundwater encountered at 17.3 feet below ground surface duringdrilling. by drilling method.



39.2

20.0

14.4

17.9

25.2

GRAB

S&H

S&H

S&H

SPT

S&H

S&H

ST

SC

SM

GP-GC

GP-GM

CL

7

8

16

22

15

6

41.1

9.5

6.7

7.1

455

347

1311124135

91111

235

0-350psi

6 inches concreteCLAYEY SAND with GRAVEL (SC)red-brown, moist, fine to medium grained sand,subangular to angular gravel, trace wood debris

color change to light brown

orange-brown, loose, moist, decrease clay andgravel content

SILTY SAND with GRAVEL (SM)brown and gray, loose, moist, angular tosubangular gravel, trace sand[crushed serpentinite]LL = 59, PL = 38, PI = 21, see Figure B-2Sieve Analysis, see Figure B-4

gravel up to 2" in diameter observed in cuttingsloss of drilling fluid, advance casing to 15 feet

GRAVEL with CLAY and SAND (GP-GC)gray, olive gray sand with yellow mottling,medium dense, wet, subangular gravelLL = 41, PL = 25, PI = 16, see Figure B-2Sieve Analysis, see Figure B-5

loss of drilling fluid, advance casing to 20 feet

GRAVEL with SILT and SAND (GP-GM)gray-brown, medium dense, wet, subangular toangular gravel[crushed weathered serpentinite]LL = 38, PL = 31, PI = 7, see Figure B-2Sieve Analysis, see Figure B-6

SANDY CLAY (CL)black, medium stiff, wet, trace organics

LL = 36, PL = 17, PI = 19, see Figure B-2

grayConsolidation Test, see Figure B-3

FIL

LM

AR

SH

DE

PO

SIT 100.2

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft

Hammer type: Automatic Safety

Boring location:

Date started:

Drilling method:


P. Brady

Sprague & Henwood (S&H), Standard Penetration Test (SPT)



1/30/14

Rotary Wash

Sampler:

Ground Surface Elevation: 21.5 feet2

Logged by:

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

SAMPLES




Figure:

PAGE 1 OF 4


PROJECT:

A-4a

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

23.7

24.9

S&H

SPT

DIST

SPT

SPT

SPT

SPT

CL

SM

SC

SP

23

28

11

78

95

50

29.8

44.8

81223

7815

245

152736

192950

121933

SANDY CLAY (CL) (continued)yellow-brown, very stiff, wet, trace fine gravel

SILTY SAND (SM)yellow-brown, medium dense, wet, fine grainedsandPI = Non-Plastic, see Figure B-2

CLAYEY SAND (SC)olive gray, medium dense, wet, trace fine tomedium gravel

LL = 24, PL = 16, PI = 8, see Figure B-2

SAND (SP)olive-gray, very dense, wet, trace silt, fine tocoarse grained sand

increase in gravel content

MA

RS

H D

EP

OS

ITC

OL

MA

FO

RM

AT

ION

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60




Figure:

PAGE 2 OF 4


PROJECT:

A-4b

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

24.2

SPT

SPT

SPT

SPT

SPT

S&H

PT

CL

60/5"

102/10"

114/10"

58

14

33

4.3

3050/6"

3835

50/4"

3545

50/4"

102424

248

102027


color change to yellow-brown

gray

CLAYEY PEAT (PT)black to dark brown, stiff to very stiff, wet, tracefine sand, trace shell, root structureorganic matter = 25.73%

CLAY (CL)gray, hard, wet

CO

LM

A F

OR

MA

TIO

N

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90




Figure:

PAGE 3 OF 4


PROJECT:

A-4c

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

S&H CL41213029

CLAY (CL) (continued)hard, trace fine grained sand, trace fine angulargravel

Typ

e of

Str

engt

hT

est

She

ar S

tren

gth

Lbs/

Sq

Ft

Dry

Den

sity

Lbs/

Cu

Ft

Fin

es%

Nat

ural

Moi

stur

eC

onte

nt,

%

Con

finin

gP

ress

ure

Lbs/

Sq

Ft

Sam

pler

Typ

e

Sam

ple

Blo

ws/

6"

SP

TN

-Val

ue1

LIT

HO

LOG

Y

DE

PT

H(f

eet)

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120




Figure:

PAGE 4 OF 4


PROJECT:

A-4d

TE

ST

GE

OT

EC

H L

OG

750

615

602

.GP

J T

R.G

DT

3/3

1/1

4

Boring terminated at a depth of 91.5 feet below ground surface.Boring backfilled with cement grout.Groundwater not measured during drilling.



Project No. FigureDate 03/25/14 A-5

CLASSIFICATION CHART

Major Divisions Symbols Typical Names

GW

GP

GM

GC

SW

SP

SM

SC

ML

CL

OL

MH

CH

OH

PTHighly Organic Soils

UNIFIED SOIL CLASSIFICATION SYSTEM

Well-graded gravels or gravel-sand mixtures, little or no fines

Poorly-graded gravels or gravel-sand mixtures, little or no fines

Silty gravels, gravel-sand-silt mixtures

Clayey gravels, gravel-sand-clay mixtures

Well-graded sands or gravelly sands, little or no fines

Poorly-graded sands or gravelly sands, little or no fines

Silty sands, sand-silt mixtures

Inorganic silts and clayey silts of low plasticity, sandy silts, gravelly silts

Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, lean clays

Organic silts and organic silt-clays of low plasticity

Inorganic silts of high plasticity

Inorganic clays of high plasticity, fat clays

Organic silts and clays of high plasticity

Peat and other highly organic soils

Clayey sands, sand-clay mixtures

Range of Grain Sizes

Grain Sizein Millimeters

U.S. Standard Sieve Size

Above 12"

12" to 3"

Classification

Boulders

Cobbles

Above 305

305 to 76.2

Silt and Clay Below No. 200 Below 0.075

GRAIN SIZE CHART

SAMPLER TYPE

Co

arse

-Gra

ined

So

ils(m

ore

than

hal

f of s

oil >

no.

200

siev

e si

ze

Fin

e -G

rain

ed S

oils

(mor

e th

an h

alf o

f soi

l<

no.

200

sie

ve s

ize)

Gravels(More than half ofcoarse fraction >no. 4 sieve size)

Sands(More than half ofcoarse fraction <no. 4 sieve size)

Silts and ClaysLL = < 50

Silts and ClaysLL = > 50

Gravel coarse fine

3" to No. 43" to 3/4"

3/4" to No. 4

No. 4 to No. 200No. 4 to No. 10No. 10 to No. 40

No. 40 to No. 200

76.2 to 4.7676.2 to 19.119.1 to 4.76

4.76 to 0.0754.76 to 2.002.00 to 0.420

0.420 to 0.075

Sand coarse medium fine

C Core barrel

CA California split-barrel sampler with 2.5-inch outside diameter and a 1.93-inch inside diameter

D&M Dames & Moore piston sampler using 2.5-inch outside diameter, thin-walled tube

O Osterberg piston sampler using 3.0-inch outside diameter, thin-walled Shelby tube

PT Pitcher tube sampler using 3.0-inch outside diameter, thin-walled Shelby tube

S&H Sprague & Henwood split-barrel sampler with a 3.0-inch outside diameter and a 2.43-inch inside diameter

SPT Standard Penetration Test (SPT) split-barrel sampler with a 2.0-inch outside diameter and a 1.5-inch inside diameter

ST Shelby Tube (3.0-inch outside diameter, thin-walled tube) advanced with hydraulic pressure

SAMPLE DESIGNATIONS/SYMBOLS

Sample taken with Sprague & Henwood split-barrel sampler with a 3.0-inch outside diameter and a 2.43-inch inside diameter. Darkened area indicates soil recovered

Classification sample taken with Standard Penetration Test sampler

Undisturbed sample taken with thin-walled tube

Disturbed sample

Sampling attempted with no recovery

Core sample

Analytical laboratory sample, grab groundwater

Sample taken with Direct Push sampler

Sonic

Unstabilized groundwater level

Stabilized groundwater level

750615602


CONE PENETRATION TEST RESULTSCPT-1

Project No. Figure750615602 A-6Date 03/25/14

Terminated at 43.9 feet.Groundwater encountered at elevation 14.5 feet.Date performed 04/16/13.Ground surface elevation: 23.5 feet, City of San Francisco Datum.

v

v 'E f fect ive vert icals t ress,

T otal vert ical s t ress,

Undrained S hearS t rength, s

u


55

45

35

25

15

5

0 200 400 600qc (ts f)

55

45

35

25

15

5

0 1 2 3 4 5 6 7 8 9R f (percen t)

55

45

35

25

15

5

0 20 40 60 80S P T (N )

55

45

35

25

15

5

0 10 20 30 40 50Ø (deg)

55

45

35

25

15

5

0 1 2 3 4 5 6 7 8S u (ts f)

55

45

35

25

15

5

v v, ',



Terminated at 51.5 feet.Groundwater encountered at elevation 9 feet.Date performed 04/16/13.Ground surface elevation: 25 feet, City of San Francisco Datum.

v




u


55

45

35

25

15

5

0 200 400 600qc (ts f)

55

45

35

25

15

5

0 1 2 3 4 5 6 7 8 9R f (percen t)

55

45

35

25

15

5

0 20 40 60 80S P T (N )

55

45

35

25

15

5

0 10 20 30 40 50Ø (deg)

55

45

35

25

15

5

0 1 2 3 4 5 6 7 8S u (ts f)

55

45

35

25

15

5

v v, ',



Terminated at 44.9 feet.

Date performed 04/22/13.Ground surface elevation: 20 feet, City of San Francisco Datum.

v




u


55

45

35

25

15

5

0 200 400 600qc (ts f)

55

45

35

25

15

5

0 1 2 3 4 5 6 7 8 9R f (percen t)

55

45

35

25

15

5

0 20 40 60 80S P T (N )

55

45

35

25

15

5

0 10 20 30 40 50Ø (deg)

55

45

35

25

15

5

0 1 2 3 4 5 6 7 8S u (ts f)

55

45

35

25

15

5

v v, ',



Terminated at 45.6 feet.

Date performed 04/22/13.Ground surface elevation: 19.5 feet, City of San Francisco Datum.

v




u


55

45

35

25

15

5

0 200 400 600qc (ts f)

55

45

35

25

15

5

0 1 2 3 4 5 6 7 8 9R f (percen t)

55

45

35

25

15

5

0 20 40 60 80S P T (N )

55

45

35

25

15

5

0 10 20 30 40 50Ø (deg)

55

45

35

25

15

5

0 1 2 3 4 5 6 7 8S u (ts f)

55

45

35

25

15

5

v v, ',


2000-2070 BRYANT STREETSan Francisco, California CONE PENETRATION TEST RESULTS

CPT-5Date performed 01/28/14.Ground surface elevation: 23 feet, City of San Francisco Datum.

03/25/14 A-13

CLASSIFICATION CHART FORCONE PENETRATION TESTS

GR

EG

G

Project No. FigureDate

ZONE SOIL BEHAVIOR TYPE

123456789

Reference: Lunne, T., Robertson, P.K., and Powell, J.J.M., 1997.

Sensitive Fine GrainedOrganic Material

SILTY CLAY to CLAYCLAYEY SILT to SILTY CLAYSILTY SAND to SANDY SILT

SANDS to SILTY SANDGRAVELLY SAND to Dense SAND

Very Dense SAND to CLAYEY SANDVery Stiff, Fine Grained

Qt = (qt – svo)/s’vo = Normalized Cone Resistance qt = qc + (1-a)u2 = Corrected Cone Resistance qc = Measured Cone Resistance a = 0.8 = Area Ratio of Cone u2 = Pore Pressure Measured Behind Cone During Test svo = Total Vertical Stress s’vo = Total Effective Vertical Stress F = fs/(qt – svo) x 100% = Normalized Friction Ratio fs = Measured unit Sleeve Friction Resistance

Note Testing Performed in Accordance with ASTM D5778-95

Normalized Friction Ratio, F= x 100%fs

q t vo

f 1

Nor

mal

ized

Con

e R

esis

tanc

e, Q

t

7 8

9

3

2

6

5

4Inc

reasin

g

OCR & ag

e

I = 2.6

c

1000

100

10

1 0.1 1 10

Normally Consolidated

s

Increasin

g

Sensitivity

Increasi

ng

OCR, age,

cementati

on

1

Increasing Ic

750615602


=

APPENDIX B

Laboratory Test Results

ML or OL

MH or OH

Symbol Source

Natural

M.C. (%)

Liquid

Limit (%)

CL - ML

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80 90 100 110 120

LIQUID LIMIT (LL)

Description and Classification% Passing

#200 Sieve

Plasticity

Index (%)

Project No. FigureDate 03/25/14 B-1

PLASTICITY CHART

PLA

ST

ICIT

Y IN

DE

X (

PI)

Ref erence:

ASTM D2487-00

750615602

2000-2070 BRYANT STREET


B-1 at 11 feet

B-1 at 23.5 feet

B-1 at 59 feet

B-2 at 69.5 feet

CLAYEY SAND (SC), brown and gray

CLAYEY SILTY SAND (SC-SM), dark

olive-gray

CLAYEY SILTY SAND (SC-SM), olive-gray

with red-brown mottling

20.9

19.9

28.3

30.9

35.9

33.3

28.1

12.9

25

22

25

22

10

7

7

4CLAYEY SILTY SAND (SC-SM), dark gray

ML or OL

MH or OH

Symbol SourceNatural

M.C. (%)Liquid

Limit (%)

CL - ML

0

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80 90 100 110 120

LIQUID LIMIT (LL)

Description and Classification% Passing#200 Sieve

PlasticityIndex (%)

Project No. FigureDate 03/25/14 B-2

PLASTICITY CHART

750615602

2000 BRYANT STREETSan Francisco, California

PLA

ST

ICIT

Y IN

DE

X (

PI)

Ref erence:ASTM D2487-00

B-4 at 11 feet

B-4 at 16.5 feet

B-4 at 21 feet

B-4 at 26 feet

B-4 at 35 feet

B-4 at 42 feet

SILTY SAND with GRAVEL (SM), brown and gray

GRAVEL with CLAY and SAND (GP-GC),gray

GRAVEL with SILT and SAND (GP-GM),gray-brown

SANDY CLAY (CL), black

SILTY SAND (SC), yellow-brown

CLAYEY SAND (SC), olive gray

39.2

14.4

17.9

25.2

23.7

24.9

41.1

6.7

7.1

--

29.8

44.8

59

41

38

36

--

24

21

16

7

19

--

8

Sampler Type: Shelby Tube Condition Before Test After Test Diameter (in) 2.42 Height (in) 1.00 Water Content wo 23.1 % wf 15.8 % Overburden Pressure, po 2,240 psf Void Ratio eo 0.65 ef 0.43 Preconsol. Pressure, pc 3,200 psf Saturation So 96 % Sf 100 % Compression Ratio, Cc 0.125 Dry Density d 102 pcf d 118 pcf LL PL PI Gs (assumed) Classification SANDY CLAY (CL), gray Source B-4 at 27 feet


03/25/14 750615602

2.70

CONSOLIDATION TEST REPORT

Date Project No. Figure B-3

0

5

10

15

20

25

0.1 1.0 10.0 100.0Vo

lum

etric

Stra

in (p

erce

nt)

Pressure (ksf)

0

200

400

600

800

1000

0.1 1.0 10.0 100.0

Cv

(ft2

/ yea

r)

0

10

20

30

40

50

60

70

80

90

100

100 10 1 0.1 0.01 0.001GRAIN SIZE (millimeters)

50 5 0.5 0.05 0.005

3 11/2 3/4 3/8 4 8 16 30 40 50 100 200 Ref erence: ASTM D422

U.S. Standard Sieve Size (in.) U.S. Standard Sieve Numbers Hydrometer

% Cobbles % Grav el %Sand % Fines

Symbol

Coarse Fine

Sample Source

ClaySiltFineMediumCoarse

0.00.0 0.00.00.00.0 0.0

Classification

PE

RC

EN

T FI

NE

R B

Y W

EIG

HT

Project No. FigureDate B-4

PARTICLE SIZE ANALYSIS

B-4 at 11 feet SILTY SAND with GRAVEL (SM), brown and gray

03/25/14 750615602


0

10

20

30

40

50

60

70

80

90

100


50 5 0.5 0.05 0.005

3 11/2 3/4 3/8 4 8 16 30 40 50 100 200 Ref erence: ASTM D422



Symbol

Coarse Fine

Sample Source


0.00.0 0.00.00.00.0 0.0

Classification

PE

RC

EN

T FI

NE

R B

Y W

EIG

HT


PARTICLE SIZE ANLYSIS

B-4 at 16.5 feet GRAVEL with CLAY and SAND (GP-GC), gray

03/25/14 750615602

2000 BRYANT STREETSan Francisco, California

0

10

20

30

40

50

60

70

80

90

100


50 5 0.5 0.05 0.005

3 11/2 3/4 3/8 4 8 16 30 40 50 100 200 Ref erence: ASTM D422



Symbol

Coarse Fine

Sample Source


0.00.0 0.00.00.00.0 0.0

Classification

PE

RC

EN

T FI

NE

R B

Y W

EIG

HT


PARTICLE SIZE ANLYSIS

B-4 at 21 feet GRAVEL with SILT and SAND (GC-GM), gray-brown

03/25/14 750615602


=

APPENDIX C

Corrosivity Test Results

DISTRIBUTION

1 copy: Ms. Linsey Perlov

Nick Podell Company



:

QUALITY CONTROL REVIEWER:

Richard D. Rodgers, G.E.

Managing Principal

geotechnical investigation 2000-2070 bryant street san

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