Appendix D-1 Geotechnical Report - Hayward · 4. Obtaining a drilling permit from Alameda County...

Appendix D-1

Geotechnical Report

BERLOGAR STEVENS & ASSOCIATES

DESIGN LEVEL GEOTECHNICAL INVESTIGATION

PROPOSED RESIDENTIAL DEVELOPMENT

TENNYSON PROPERTY - APN: 078C-0461-001-13

TENNYSON ROAD EAST OF MISSION BOULEVARD

HAYWARD, CALIFORNIA

FOR

The Grupe Company

3255 West March Lane

Stockton, California 95219

October 17, 2017

Job No. 3823.102


Design Level Geotechnical Investigation

Proposed Residential Development

Tennyson Property - APN: 078C-0461-001-13

Tennyson Road East of Mission Boulevard

Hayward, California

TABLE OF CONTENTS

INTRODUCTION ....................................................................................................................................... 1 Purpose And Scope................................................................................................................................................. 1 Project Understanding ............................................................................................................................................ 1 Site Location and Description ................................................................................................................................ 2

GEOLOGY .................................................................................................................................................. 3 Regional And Local Geology ................................................................................................................................. 3 Artificial Fill ........................................................................................................................................................... 4 Landslide Deposits ................................................................................................................................................. 4 Faulting ................................................................................................................................................................... 4

SITE INVESTIGATION ............................................................................................................................ 4 Field Exploration .................................................................................................................................................... 4 Geotechnical Laboratory Testing ........................................................................................................................... 5 Subsurface Conditions ............................................................................................................................................ 6

Soils ................................................................................................................................................................. 6 Bedrock ........................................................................................................................................................... 6 Groundwater .................................................................................................................................................... 6

GEOLOGIC AND SEISMIC HAZARDS ................................................................................................ 7 Fault Rupture .......................................................................................................................................................... 7 Seismic Shaking and Seismic Design Parameters .................................................................................................. 7 Earthquake-Induced Landslide Potential ................................................................................................................ 9 Liquefaction Potential ............................................................................................................................................ 9

CONCLUSIONS AND RECOMMENDATIONS .................................................................................... 9 General ................................................................................................................................................................... 9 Site Design Considerations ................................................................................................................................... 10

Building Setbacks from Slopes ..................................................................................................................... 10 Surface Drainage ........................................................................................................................................... 10 Subsurface Drainage ..................................................................................................................................... 11 Bioretention Areas ......................................................................................................................................... 11

Slope Stability ...................................................................................................................................................... 12 Static Slope Stability ..................................................................................................................................... 12 Pseudo-Static Slope Stability ........................................................................................................................ 12

Graded Slopes ....................................................................................................................................................... 13 Cut Slopes ..................................................................................................................................................... 13 Fill Slopes ...................................................................................................................................................... 13 Erosion Protection ......................................................................................................................................... 15

Remedial Grading ................................................................................................................................................. 15 Residual Soil Removal .................................................................................................................................. 15 Uncontrolled Fill ........................................................................................................................................... 15 Differential Fill on Building Pads ................................................................................................................. 15 Landslide Repair ........................................................................................................................................... 16 Foundation Decoupling Section .................................................................................................................... 16

Expansive Soils .................................................................................................................................................... 16 Excavation Characteristics ................................................................................................................................... 16 Fill Materials ........................................................................................................................................................ 16 Site Preparation And Grading............................................................................................................................... 17


Utility Trenches .................................................................................................................................................... 19 Trenches Adjacent to Building Foundations ................................................................................................. 19 Excavation ..................................................................................................................................................... 19 Groundwater Considerations ......................................................................................................................... 20 Backfill .......................................................................................................................................................... 20

Building Pad Pre-soak .......................................................................................................................................... 21 Landscaping and Landscape Irrigation ................................................................................................................. 21 Building Foundations ........................................................................................................................................... 22

Foundation Decoupling ................................................................................................................................. 22 Post-Tensioned Slab-On-Grade Foundation Design Parameters ................................................................... 23 Additional Design and Construction Considerations .................................................................................... 23

Moisture Vapor Transmission through Interior Slabs-On-Grade ......................................................................... 24 Retaining Walls .................................................................................................................................................... 24

Conventional Concrete or Concrete Masonry Retaining Wall ...................................................................... 24 Mechanically Stabilized Earth Retaining Wall ............................................................................................. 26 Wall Surcharge .............................................................................................................................................. 27 Retaining Wall Backdrains ............................................................................................................................ 27 Retaining Wall Backfill ................................................................................................................................. 28

Concrete Flatwork ................................................................................................................................................ 28 Structural Pavement.............................................................................................................................................. 29

Flexible Pavement ......................................................................................................................................... 29 Materials ........................................................................................................................................................ 30 Seepage Cut-Off And Pavement Section Drainage ....................................................................................... 31

ADDITIONAL GEOTECHNICAL ENGINEERING SERVICES ...................................................... 31 Remedial Grading Plan ......................................................................................................................................... 31 Review of Plans and Specifications ...................................................................................................................... 31 Earthwork and Paving Observation and Testing .................................................................................................. 31

LIMITATIONS ......................................................................................................................................... 32

PLATES

Plate 1 – Vicinity Map

Plate 2 – Site Plan

Plate 3 – Fill Slope and Keyway Detail

Plate 4 – Typical Subdrain Details

Plate 5 – Pavement Edge Drain Detail

Plate 6 – Foundation Decoupling Detail

Plate 7 – Retaining Wall Backdrain Detail

Plates 8-11 – Slope Stability Analysis

APPENDICES

Appendix A – Boring Logs and Boring Log Key

Appendix B – Exploratory Test Pit and Trench Logs - BSA

Appendix C – Exploratory Trench Logs - Engeo

Appendix D – Geotechnical Laboratory Test Results

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PROPOSED RESIDENTIAL DEVELOPMENT

TENNYSON PROPERTY - APN: 078C-0461-001-13


HAYWARD, CALIFORNIA

INTRODUCTION

PURPOSE AND SCOPE

The purpose of this study was to further investigate the geologic and geotechnical subsurface

conditions at the site and to provide geotechnical conclusions and recommendations based on

those conditions for use in the design and construction of the proposed project. The scope of our

services was in general accordance with our proposal of February 2, 2017 and included the

following:

1. Review of conceptual site plans prepared by Wood Rodgers, Inc. (provided by E-Mail

on June 7, 2017).

2. Site reconnaissance by a member of our engineering staff.

3. Marking of borings and test pit locations, and USA North notification.

4. Obtaining a drilling permit from Alameda County Public Works Agency-Water

Resources.

5. Exploration of subsurface conditions by drilling soil-test borings and the excavation of

test pits.

6. Geotechnical laboratory testing to assess the physical properties of selected soil

samples collected during the field exploration.

7. Engineering analysis.

8. Preparation of this report.

PROJECT UNDERSTANDING

It is our understanding that the current concept is for a residential development with multi-family

attached structures. Concept drawings for the site depict a terraced site with two levels. The

upper level of the development will have a single loaded street, with a double-loaded street at the

lower level. The conceptual plans show retaining walls or retaining walls with slopes above the

wall between the two levels of the site. Grading of the site will result in both cut and fill slopes

with slope heights up to about 20 feet. Retaining walls are also shown along the southeast side of

the site to maximize the density given the site constraints and the need to limit slope inclinations as

discussed below. The conceptual plans show duplex and triplex buildings. The structures are

expected to be two- to three-story wood-frame buildings, constructed at-grade and supported by

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structural concrete slab-on-grade foundations. Structures of this type are generally relatively lightly

loaded; a uniform bearing pressure of 400 pounds per square foot (psf) is assumed.

The project will also include construction of new underground utilities and roadways. Site access

will be by way of a new roadway from Tennyson Boulevard, located to the west of the site,

entering the site at the northwest corner of the property. A culvert or bridge will be required to

cross an existing drainage at the northwest end of the planned development.

There are two designated wetland areas north of the proposed area of development. The wetland

areas and the area of the property located to the east of the proposed development, which

contains a third wetland area, will remain as open-space.

SITE LOCATION AND DESCRIPTION

The project site lies on the west flank of the East Bay Hills on a low ridge of foothills

overlooking the broad alluvial plain about six miles northeast of the San Francisco Bay. The

approximately 15½-acre, roughly triangular-shaped southwest sloping property (Assessor’s

Parcel Number 078C-0461-001-13), which was previously referred to as the “Ersted Property,”

is located about 450 feet east of Mission Boulevard and south of the former La Vista Quarry in

Hayward (Vicinity Map, Plate 1). The parcel is about 1,500 feet deep and is elongated in a

northeastern direction, narrowing toward the northeast. A narrow strip of undeveloped land

separates the site from commercial buildings along Mission Boulevard to the southwest.

The United States Geologic Survey 7½-minute Hayward quadrangle topographic map (USGS,

1980) indicates that the property ranges from an elevation of about 50 feet above mean-sea-level

(msl) in its southern corner to about 265 feet in its northwestern corner. The area identified by

BSA as potentially developable (BSA 2017) is generally located between elevation 110 feet and

165 feet msl. The site slopes down to the west and south with slopes ranging from as steep as

about 2-¼ Horizontal to 1 Vertical (2-¼ H:1V) to as flat as about 8H:1V. The property has been

extensively modified by grading or quarrying in the central area of the parcel. Quarry activities

resulted in the removal of the natural soil cover in the central and northeast eastern portions of

the site. The grading activities also resulted in varying amounts of artificial fill. Surface

drainage is concentrated in two incised drainage courses near the northern and southern

boundaries of the property.

Existing vegetation within and adjacent to the development area is predominantly dense seasonal

grasses with a few scattered palm and willow trees. Two wetlands areas have developed along

the northwestern side of the site. It appears that water diverted to the site during past quarry

operations upslope of the site, water currently directed toward the site from subdrains installed

during grading of the upslope site, and current construction of the extension of Tennyson Road

are contributing factors in the development of the wetlands. A linear stand of eucalyptus trees is

located along the southwestern property line.

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GEOLOGY

REGIONAL AND LOCAL GEOLOGY

The City of Hayward and the subject property are located within the Coast Ranges Geomorphic

Province. The province consists of a series of discontinuous northwest trending mountain

ranges, ridges, and intervening valleys characterized by complex folding and faulting. Geologic

and geomorphic structures within the San Francisco Bay Area are dominated by the San Andreas

fault system, a right-lateral strike-slip transform boundary that extends from the Gulf of

California in Mexico, to Cape Mendocino in Humboldt County, California. It forms a portion of

the boundary between two independent tectonic plates. To the west of the San Andreas fault

system is the Pacific plate, which moves north relative to the North American plate, located east

of the fault system. In northern California, movement across this plate boundary is concentrated

on the San Andreas fault. However, a portion of the movement is also distributed across a

number of faults including the Hayward, Calaveras, San Gregorio, Paicines, Zayante-Vergeles,

and Quien Sabe among others. Together, these faults are referred to as the San Andreas fault

system.

The project site is underlain by basement rock consisting of a complicated mixture of

metamorphosed rocks of the Franciscan Complex derived from deformed and accreted seafloor

rocks. Structurally adjacent to or unconformably overlying the Franciscan are marine

sedimentary rocks of the Great Valley Group deposited during Jurassic and Cretaceous time.

The Great Valley Group in the area of study on the site is mantled by alluvial fan and colluvial

materials shed from the hills to the east. Mapping by Graymer and others (1995) of the USGS

indicates that the portion of the site proposed for development is underlain by the Jurassic Age

Knoxville Formation of the Great Valley Group. These two bedrock units date to the Jurassic to

Cretaceous Periods. Their rocks were extensively fractured and sheared, and some were slightly

metamorphosed by subduction processes that stopped operating in this part of California several

million years ago.

The sedimentary rocks, consisting of conglomerate, sandstone, and shale, are generally assigned

to the Knoxville Formation, and the volcanic rocks, consisting of slightly metamorphosed basalt

(greenstone), are assigned to the Franciscan Complex. The Knoxville Formation is comprised

mainly of dark, greenish-gray silt or clay shale with thin sandstone interbeds. Thick pebble to

cobble conglomerate beds are present in the lower part of the Knoxville Formation. Exposures

of the Knoxville Formation are generally weak to moderately strong, highly fractured to crushed,

and thinly bedded. Franciscan Complex rocks are more or less sheared and metamorphosed

graywacke, shale, mafic volcanic rock, chert, ultramafic rock, limestone, and conglomerate.

Highly sheared sandstone and shale forms the matrix of a mélange containing blocks of many

rock types, including sandstone, chert, greenstone, blueschist, serpentinite, eclogite, and

limestone (USGS, 2000).

Residual soil, which is residual natural soil derived by weathering of the underlying parent

bedrock, overlaps the bedrock and underlies the valley floor west of the site where elevations are

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below 50 feet. The residual soils generally consisted of dark brown to red-brown, dry, medium-

stiff to stiff silty clay and sandy clay.

ARTIFICIAL FILL

Artificial fill is present along and upslope of a ridge that crosses the proposed development area.

The fill generally consists of clay soils that likely were removed from the area to the east during

previous grading or quarry activities.

LANDSLIDE DEPOSITS

A landslide was identified in the vicinity of the south corner of the proposed development area,

as shown on the Site Plan, Plate 2. Mitigation of the landslide and its potential impact on

development of the site are discussed below.

FAULTING

Approximately one-half of the property is located within a State of California Earthquake Fault

Hazard Zone (CGS, 1982) for the Hayward fault. The southwest limit of the Earthquake Fault

Hazard Zone as it crosses the site is shown on the Site Plan, Plate 2. The main trace of the

Hayward fault is mapped crossing the site near the property’s eastern property line (California

Geological Survey, CGS, 1982; Graymer, 1995; Crane, 1988; Dibblee, 1980; Radbruch-Hall,

1974; Herd, 1978; Lienkaemper, 2006). The area proposed for development is not within the

state designated Fault Hazard Zone. However, previous geologic investigations at the site and

surrounding properties (BSA, Engeo, Makdissy, Soil Engineering Consultants, Earth System

Consultants, Judd Hull) indicate the presence of fault traces south of the hazard zone (Site Plan).

Fault traces located within exploration trenches and those inferred by site reconnaissance and

aerial photograph interpretation were mapped by those consultants, with revisions or updates

made as subsequent investigations were completed. The most recent work was completed by

BSA in April 2017. Based on that work, BSA mapped traces of two splay faults crossing the

southwestern portion of the site. We recommended setbacks from the faults with a

“Development Zone,” located between the setback limits. The setback limits are shown on the

Site Plan, Plate 2.

SITE INVESTIGATION

FIELD EXPLORATION

BSA conducted two supplemental fault ground-rupture potential investigations of the site. Field

exploration during those investigations, conducted in December 2016 (BSA, 2017a) and March

2017 (BSA, 2017b), included excavation of 12 exploratory trenches with depths of excavation

that were generally between 5 and 7 feet below the ground surface (bgs) and locally as deep as

17-½ feet. The excavations for the exploratory trenches were completed using a Caterpillar 312

excavator with a three-foot bucket.

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Five test pits were excavated for this geotechnical investigation following completion of the

second set of six exploratory trenches excavated for the fault investigation in March 2017. The

excavations for the test pits were completed using a Caterpillar 312 excavator with a three-foot

bucket.

Five borings were drilled on March 21, 2017, by Pitcher Drilling using a track-mounted drill rig

with hollow-stem augers. Borings were extended to depths of between 11-½ and 31-½ feet bgs.

Soil sampling and penetration resistance testing were performed in the borings beginning just

below the surface and at intervals of approximately 5 feet to the maximum depth of exploration.

In addition, two shallow hand-augered borings were advanced to log surficial soil deposits. A

member of our staff visually classified the soils in the field as the drilling progressed and

recorded a log of each boring. Sampling was conducted using either a 2½-inch inside diameter

Modified California sampler with 6-inch long liners or a 2-inch outside diameter, 1⅜-inch inside

diameter Standard Penetration Test (SPT) split-spoon sampler (smooth inside bore with no

provisions for use of liners). The samplers were driven 18 inches with a 140-pound hammer

falling 30 inches. The number of blows required to drive the sampler the last 12 inches of the

18-inch drive are shown as blows per foot on the boring logs. Soil samples from the borings

were transported to our laboratory for further examination and testing.

The logs of the borings, which are based on field classifications as well as the results of

laboratory tests, are presented in Appendix A along with a key for the classification of the soil.

Visual classification of the soils was made in general accordance with the Unified Soil

Classification System (ASTM D2487). The test pit and exploratory trench logs are presented in

Appendix B. The boring, test pit and trench logs depict subsurface conditions at the locations

explored at the time of exploration. Subsurface conditions may vary with the passage of time

due to changes in groundwater levels or other factors. Some variations in subsurface conditions

should be expected between points of exploration. The locations of the borings, test pits and

exploratory trenches are shown on the attached Site Plan, Plate 2. The boring locations plotted

were determined based on readings obtained using a hand-held GPS device (accuracy ± about 10

feet). The locations of the exploratory trenches and test pits excavated by BSA were determined

by survey conducted by Wood Rodgers, Inc. The locations of trenches excavated for fault

investigations conducted by others are considered to be approximate.

GEOTECHNICAL LABORATORY TESTING

Soil samples from the borings were transported to our laboratory for testing. Laboratory tests

were performed on selected soil samples to evaluate their physical characteristics and

engineering properties. Laboratory testing included moisture, density, Atterberg Limits, grain

size analyses, unconfined compressive strength and triaxial compression tests performed on

selected samples. Laboratory test results are presented in Appendix D with some of the results

also included on the boring logs.

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SUBSURFACE CONDITIONS

Soils

The property has been extensively modified by grading or quarrying in the central area of the

property, which extends into the northeastern portion of the development site. This previous

activity resulted in artificial fills overlying the mapped geologic deposits. The fill soils range in

depth from about 1 to 3 feet below the existing surfaces. Fill soils are also present at test pit and

trench locations with fill ranging from about 5 feet to as much as 18 feet in depth. Refer to the

trench logs for additional information regarding fill depths. These soils are uncompacted.

The surficial soils covering the site consist of residual soils derived from weathering of the

bedrock deposits at the site and the hillside to the east. The soils are predominately moderately

to highly expansive clays with varying amounts of sand and some gravel. The soils are medium

stiff in the upper few feet and increase in stiffness below. More detailed subsurface information

is contained in the boring logs in Appendix A and the trench logs in Appendix B.

Bedrock

The materials below the residual soils consist of highly to completely weathered bedrock

materials that present as soils within the depths of excavation at the trenches. Less weathered

bedrock consisting of clayey siltstone was encountered in Boring B-2 at a depth of 24 feet bgs.

The siltstone is friable, highly fractured to crushed and partially decomposed. A layer of

gravelly sand was encountered at a depth of 23-½ feet in Boring B-6. The sand is dense. Below

the gravelly sand we encountered bedrock consistent with highly weathered clay shale. The

material was noted to be friable and crushed.

Groundwater

During the course of development of the La Vista project (at the site of the former La Vista

quarry) which is located immediately upslope of the subject project site, BSA personnel

observed several springs in the vicinity of quarry cut slopes as excavations were made to grade

the site and in the construction of Tennyson Road adjacent to this project. An extensive array

network of subdrains was installed. Recent observations of the subdrain outfalls revealed steady

flows, confirming that shallow groundwater is present in the area upslope of the subject site.

Groundwater seepage was observed at exploratory trenches T-7, T-9 and T-10 in the northeastern

area of the proposed development, northeast of the aforementioned ridge. The water level

stabilized at a depth of about 4 feet below the ground surface (bgs) over night.

The borings were monitored for visible signs of free groundwater during and immediately after

completion of drilling each boring. Groundwater was encountered in one boring, Boring B-6, at

a depth of 24 feet bgs. Groundwater was not evident in the other borings.

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The depth to groundwater can be expected to fluctuate both seasonally and from year to year.

Fluctuations in the groundwater level may occur due to variations in precipitation, irrigation

practices at the site and surrounding areas, climatic conditions, pumping from wells and other

factors not evident at the time of our investigation.

GEOLOGIC AND SEISMIC HAZARDS

The Alquist-Priolo Earthquake Fault Zoning (formerly Special Studies Zone) Act (AP Act) was

signed into California law on December 22, 1972. The intent of the AP Act is to mitigate the

hazard of surface faulting ground-rupture to structures for human occupancy by prohibiting the

siting of most structures for human occupancy across traces of active faults. The Seismic Hazard

Mapping Act (SHMA) was enacted by the California legislature in 1990. The purpose of the

SHMA is to minimize loss of life and property through the identification, evaluation and

mitigation of seismic hazards, specifically the hazards of liquefaction, or earthquake-induced

land sliding. These Acts require the California State Geologist and the Department of

Conservation, California Geological Survey to identify and map areas prone to earthquake-

induced ground failures and "Zones of Required Investigation" to reduce the threat to public

health and safety and to minimize the loss of life and property posed by earthquake-induced

ground failures.

FAULT RUPTURE

The potential for ground-rupture to occur with activity on a fault is one of the hazards associated

with faulting. Seismic shaking is also a fault-related hazard, as discussed below. As discussed

above, extensive investigation of the site has been conducted to evaluate the potential for fault

ground-rupture on the site. In keeping with the California Code of Regulations and the

subsurface exploration findings of our previously completed fault ground-rupture investigations,

BSA recommended a fault ground-rupture setback from the splay fault found in our exploratory

trenches. Given the maturity of the shear zone at the Hayward fault, the corresponding low

probability that ground rupture will occur at locations not previously ruptured, the secondary

nature of the splay faults exposed in our trenches, and the direct method of fault location, it is our

opinion that the potential for ground-rupture to occur within the development zone shown on the

Site Plan, Plate 2 is low.

SEISMIC SHAKING AND SEISMIC DESIGN PARAMETERS

The site is located in a region of high seismicity. There are several major faults within the

greater San Francisco Bay Area that are capable of causing significant ground shaking at the site.

The most notable of these are the Hayward, Calaveras and San Andreas faults. The site will

likely be subject to at least one moderate to severe earthquake and associated seismic shaking

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during the useful life of the planned development, as well as periodic slight to moderate

earthquakes. The probability of one or more earthquakes of magnitude 6.7 (Richter scale) or

higher occurring in the San Francisco Bay Area is evaluated by the Working Group on California

Earthquake Probabilities on a periodic basis, as are the probabilities of earthquakes of varying

magnitudes on each of the major faults. The faults with the greater probability of a moment

magnitude of 6.7 or higher earthquake between 2014 and 2044 are the Hayward fault at 14.3

percent, the Calaveras fault at 7.4 percent and the San Andreas fault at 6.4 percent. Some degree

of structural damage due to strong seismic shaking should be expected at the site, but the risk can

be reduced through adherence to seismic design codes.

We are providing the following 2016 California Building Code seismic design criteria from the

U.S. Geological Survey Earthquake Hazards Program U.S. Seismic Design Maps application.

Seismic design parameters were obtained from the U.S. Seismic Design Maps, determined with

consideration of the 2010 ASCE 7-10 (w/March 2013 errata) publication, site location of

latitude: 37.6355 N and longitude: 122.0500 W, site soil classification C, and risk category

I/II/III.

Site Coefficients and Risk-Targeted Maximum Considered Earthquake

Spectral Response Acceleration Parameters

Site Class D

Mapped Spectral Acceleration for Short Periods, Ss 2.442 g

Mapped Spectral Acceleration for 1-Second Period, S1 1.016 g

Site Coefficient Fa 1.0

Site Coefficient Fv 1.5

Acceleration Parameter SMS 2.442g

Acceleration Parameter, SM1 1.524 g

Acceleration Parameter, SDS 1.628 g

Acceleration Parameter, SD1 1.016 g

Long-Period Transition Period, TL 8 seconds

Seismic Design Category D

Additional Parameters for Sites with Site Design Categories D through F

Peak Ground Acceleration, PGA 0.943

Site Coefficient, FPGA 1.0

Peak Ground Acceleration – geometric mean, PGAM 0.943

Risk Coefficient at 0.2 s Spectral Response Period, CRS 0.981

Risk Coefficient at 1.0 s Spectral Response Period, CR1 0.957

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EARTHQUAKE-INDUCED LANDSLIDE POTENTIAL

The site is not located within the zone of required investigation for potential ground

displacement triggered by an earthquake as identified by the California Geologic Survey on the

State of California Seismic Hazard Zones map for the Hayward Quadrangle, issued 2003.

Review of the Landslide Hazard Identification Map No. 37 (DMG 1996) indicates that the area is

unmapped due to extensive grading activities. Mapping by Wentworth et. al. (USGS 1997)

shows the site in an area with few landslides if any landslides. More specifically, the mapped

zone is described as “Few Landslides - contains few, if any, large mapped landslides, but locally

contains scattered small landslides and questionably identified larger landslides; defined in most

of the region by excluding groups of mapped landslides but defined directly in areas containing

the 'Many Landslides' unit by drawing envelopes around areas free of mapped landslides. As

discussed below, we did map one small landslide above a drainage along the southeast property

line. We also conducted slope stability analyses to assess the stability of natural and graded

slopes.

LIQUEFACTION POTENTIAL

The site is not located within the zone of required investigation for liquefaction potential as

identified by the California Geologic Survey on the State of California Seismic Hazard Zones

map for the Hayward Quadrangle, issued 2003.

CONCLUSIONS AND RECOMMENDATIONS

GENERAL

Based on the information collected during this investigation and prior investigations, it is our

opinion that development of the site is feasible from a Geotechnical Engineering perspective,

provided that the recommendations contained in this report are incorporated into the design and

construction of the project. The primary geotechnical concerns with the site are:

Stability of natural, and proposed cut and fill slopes.

Expansive near-surface soils.

Existing uncompacted fill at exploratory excavations and associated with past grading

activities.

Shallow groundwater conditions requiring subsurface drainage.

Our detailed design and construction recommendations pertaining to site clearing and

preparation, site earthwork, foundations, retaining walls, concrete slabs-on-grade (flatwork) and

pavements are presented below.

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SITE DESIGN CONSIDERATIONS

Building Setbacks from Slopes

Residential structures should be setback from top slopes a minimum of 10 feet. Residential

structures should be setback from toe slopes a minimum of 10 feet.

Surface Drainage

The area to the east of the proposed development, which will remain as undeveloped open-space,

drains toward the proposed development. A drainage ditch should be constructed slightly

upslope of the planned cut slope along the northeast side of the proposed development.

Surface water should not be allowed to collect on or adjacent to structures or pavements

anywhere on the site during or after construction. Final site grading should provide surface

drainage away from structures, pavements and slabs-on-grade to reduce the percolation of water

into the underlying soils. Surface drainage on residential lots should comply with Section 1804,

Subsection 1804.3 of the California Building Code. If recommended surface gradients cannot be

met or where there are landscape areas around the structures that cannot drain freely through

sheet flow, area drains should be considered. Even with the recommended gradients there is a

potential that ponding conditions may develop adjacent to the buildings over time. Where

positive drainage around buildings cannot be established and maintained as part of the site

grading and paving design, area drains should be provided around the structures in landscape and

possibly within the areas of concrete flatwork where it abuts the structures.

Surface drainage should be directed away from the top of cut and fill slopes by sloping the

ground surface at least 2 percent.

Rainwater collected on the roofs of the buildings should be transported through gutters,

downspouts and closed pipes, which discharge away from the buildings and preferably into the

storm water management system such as the bioretention facilities. Roof runoff should not be

allowed to drain into landscape area in close proximity to the perimeter of the buildings.

Pavement areas should be sloped and drainage gradients maintained to carry surface water off

the site. Ideally all pavements will be designed with a crown to allow for drainage toward the

pavement perimeter. A cross slope of 2 percent is recommended in asphalt concrete pavement

areas to provide surface drainage and to reduce the potential for water to penetrate into the

pavement structure. Recommendations for control of seepage water entering pavement

structures and pavement section drainage are presented in the Structural Pavements section of

this report.

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Subsurface Drainage

During our field investigation, groundwater was encountered as shallow as 4 feet below the

ground surface in the north and northeast areas of the of the planned development area, in the

vicinity of the proposed road and cut slope. This relatively shallow groundwater could adversely

affect future cut slope stability and pavement subgrade in addition to creating a surface water

nuisance. We recommend a deep subdrain be installed along the northeastern and northern

bounds of the proposed development. The subdrain should begin at the east end of the site at the

top of the ridge above the cut slope, continue northwesterly along the top of the cut slope and

then continue along the roadway to the west end of the site where the road crosses the wetland

area. The subdrain should be installed to a depth of 10 feet along the northeastern side of the

project, with the depth of installation reduced to 5 feet below the ground surface along the

northern bound of the development.

Additional subsurface drains are recommended where fill slopes and retaining walls will be

constructed as discussed in more detail below. Site conditions, particularly at cut slopes along

the northern and northeastern bounds of the development area should be monitored for

indications of groundwater seepage by a representative of the Geotechnical Engineer. If seepage

appears at cut slopes or excavations for underground utilities, additional subdrains will be

required.

Bioretention Areas

Bioretention swales and basins should be located at least 5 feet away from foundations,

roadways, and exterior concrete flatwork. Bioretention swales and basins in close proximity to

foundations have the potential to undermine the foundation or cause a reduction in the soil

bearing capacity. Bioretention swales and basins located in close proximity to roadways and

exterior concrete flatwork can cause settlement of these structures as well as cracking associated

with lateral extension of these structures with lateral movement of the supporting soils. Where a

5-foot separation is not practical or possible due to site constraints, bioretention areas located

within 5 feet of foundations, pavements or concrete flatwork should be constructed with

structural side walls capable of withstanding the loads from the adjacent improvements. In the

case of a building foundation in close proximity to a bioretention area, a deepened foundation

edge designed as a retaining structure may be an option. Precast units may be an expedient

method of installing bioretention facilities that are capable of supporting concrete flat work,

roadways and foundations.

Bioretention basins or swales should not be constructed in proximity to the top of a descending

slope unless the basin or swale is fully lined to preclude stormwater infiltration into the site

above the slope. Bioretention areas located within 5 feet of building foundations or pavements

should also be lined with impermeable liners. A perforated drain pipe should be provided within

the swale or basin when a liner is installed or where the site soils have a low permeability rate

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and infiltration capacity (i.e. the clay soils at the subject site). The perforated pipe should lead to

a solid-wall pipe to convey accumulated water to a suitable point of discharge.

SLOPE STABILITY

Slope stability analyses were performed to evaluate the stability of the existing hillside slope

below the proposed development with a 15-foot high fill slope at the southwest side of the site

and a 20-foot high cut slope between the lower and upper terraces. The fill and cut slopes were

models at inclinations of 2 ½-H:1V. The slope profile is shown on Plates 8 and 9. Our slope

stability analyses were performed using the program Slope/W. Analyses were performed using

models based on Morgenstern-Price and Bishop methods of slices for circular shaped failure

surfaces. The slip circle calculated to have the lowest factor of safety against failure is referred

to as the critical failure surface.

Soil strength parameters were developed based on the soils exposed in our borings and trenches,

the results of geotechnical laboratory testing on samples collected during this investigation as

well as the results of geotechnical laboratory testing during our previous investigations of the

former La Vista Quarry site surrounding the subject site, and engineering judgement. The soil

parameters used in the analyses are shown on Plates 8 and 9.

Static Slope Stability

For the analysis of static slope stability, we utilized static strength parameters and programmed

the stability program to search for the critical failure surface. We analyzed a 15-foot high fill

slope at an inclination of 2 ½-H:1V above a natural slope at 3H:1V and a 20-foot high cut slope.

Based on this search, the program determined that the most critical failure surface initiates

behind the top of slope and propagates down through the upper bedrock unit that presents as soil

due to it crushed and highly weathered state, and the less weathered bedrock to a depth of about

60 feet. The critical failure surface for this analysis had a factor of safety 3.1 for the fill slope

and natural slope below, which indicates that the slope should be stable.

Pseudo-Static Slope Stability

The pseudo-static slope stability analysis involves applying a horizontal acceleration coefficient

to the static slope stability model to evaluate the slope for dynamic stability during an

earthquake. We performed the pseudo-static slope stability analyses in general accordance with

guidelines provided in the California Geological Survey’s SP 117A (2008). A seismic

coefficient (k) of 0.49 was used to evaluate slope stability under seismic shaking conditions.

This coefficient was determined using the simplified methods of Blake et al. (2002), a PGA of

0.94g, a Magnitude of 6.8, a distance of less than 10 km and a threshold displacement of 5

centimeters. For this analysis, the critical failure surface was a circular failure that initiated at

the top of the levee, propagated down through the levee fill and below the levee to the top of the

underlying sand layer and terminated in the middle of the channel. The calculated factor of

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safety for this critical failure is 1.04, which indicates that instability resulting in displacement

greater than 5 cm at the top of slope should not occur during this event.

GRADED SLOPES

Cut Slopes

We recommend that cut slopes generally be constructed at slope gradients no steeper than

3H:1V, except for cut slopes less than about 10 feet in height which should be no steeper than 2-

½H:1V. We recommend that all cut slope exposures be carefully examined by an engineering

geologist for evidence of potential instability. Cut slopes are not anticipated to exceed a height

of 25 feet. Mid-slope benches are not required for slopes less than 30 feet high.

Due to variations in the geologic deposits across the site and in the immediate vicinity of the site

we recommend that all cut slopes should be observed by an engineering geologist during grading

for evidence of potential instability. Where adverse bedrock structure or zones of geologic

weakness are encountered in cut slopes during grading, remedial measures such as flattening the

slope or slope reconstruction may need to be performed. If very highly expansive claystone

bedrock or cohesionless sandstone bedrock is exposed in the cut slope, these areas may need to

be reconstructed with a buttress constructed using suitable engineered fill material. The project

Geotechnical Engineer should develop specific remedial alternatives as cut slope conditions are

exposed during grading. We also recommend that an engineering geologist perform annual

reviews of the cut slopes after development.

Based on the data obtained, there are no specific zones of bedrock we now recommend for

remedial treatment. However, this may be a limitation of the data. It would be prudent to expect

some remedial slope buttressing could be needed following inspection of the actual exposed cut

slopes.

Surface drainage should be installed up slope of cut slopes to intercept surface runoff. Runoff

should be collected in a concrete lined v-ditch and should be conveyed to a suitable point of

discharge.

Fill Slopes

The stability of planned fill slopes depends on proper placement and construction of keyways

and benching, subsurface drainage, fill compaction and slope gradients. We recommend that fill

slopes with a height of 15 feet or greater be constructed at slope gradients no steeper than 3H:1V.

Slopes up to a height of 15 feet may be constructed at a maximum gradient of 2-½H:1V. If used

for fill slope construction, residual soils and landslide debris should be properly blended with

bedrock materials. In general, blending should consist of one part weak soils to three parts

minimum bedrock materials.

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Fill slopes are not anticipated to exceed a height of 25 feet. Mid-slope benches are not required

for slopes less than 25 feet high. In the event that 25 feet or greater in height is planned, a

drainage ditch should be constructed on a bench placed at mid-slope. Benches should be at least

8 feet wide with a concrete-lined V ditch to conduct runoff.

Fill slopes should have a 20-foot wide geogrid reinforced keyway. Wider keyways may be

required as determined in the field by the Geotechnical Engineer. Keyways should extend a

minimum of 8 feet below the existing ground surface (as measured at the downslope side of the

keyway) into the bedrock or firm soil, and slope down and back into the hillside at a 5 percent

gradient. The final depth of keyways should be determined by the Geotechnical Engineer in the

field during grading. Five layers of geogrid reinforcement (Tensar TX-7, or a similar approved

equivalent), extending across the full width of the keyway, with the first layer at the bottom of

the keyway, and then 2-foot vertical spacing thereafter is recommended. Engineered fill is to be

composed of cut bedrock materials. Plate 3, Fill Slope and Keyway Detail, contains a schematic

of typical fill slope construction.

The keyway should contain a subdrain, and intermediate subdrains should be placed on benches

where appropriate, as determined by the Geotechnical Engineer in the field during grading.

Benches should be constructed into the hillside, approximately one equipment width, as the fill is

being placed. The benches should slope slightly down and back into the hillside and should be

constructed below the recommended depth of residual soil removal. Plate 3, Fill Slope and

Keyway Detail, contains a schematic of typical bench construction. Subdrain pipes should

typically be at least 6 inches in diameter at the back of the keyway, with 4-inch diameter pipes

for drains on intermediate benches. Subdrains should be surrounded by and be underlain by at

least 6 inches of Class 2 Permeable Material, as defined in Section 68-2.02F(3). The subdrain

can daylight below the fill slope to an appropriate outfall structure protected with cobble and

boulder sized rip rap.

Subdrains should consist of PVC perforated pipe conforming to ASTM Designation 03034, Type

SDR 35 for fill depths less than 30 feet. Perforations should be placed facing down. Subdrains

should typically be at least 6 inches in diameter. Subdrain laterals less than 200 feet in length

can be constructed using 4-inch diameter pipe. All subdrains should be surrounded by and be

underlain by at least 6 inches of Class 2 ''Permeable Material," as defined in Section 68-2.02F(3)

of the Caltrans Standard Specification (2015). Subdrain trenches should be at least 18 inches

wide and at least 4 feet deep, unless otherwise recommended. Final trench configurations should

be approved by the Geotechnical Engineer. Subdrain trenches should be capped with 2 feet of

engineered fill or topsoil, depending upon the subdrain location. Typical subdrain details are

presented on Plate 4. Subdrain systems should be discharged into observable storm drain

structures (inlets, manholes, ditches) where possible. Elsewhere, subdrains may discharge to

suitable open-space locations.

The grading contractor should survey the locations of all subdrains and submit the latitude,

longitude, and elevations to the Civil and Geotechnical Engineers as grading progresses.

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Some areas of seepage may develop after grading and house construction are completed.

Additional subdrains will likely be needed in these areas should seepage develop.

Erosion Protection

All cut and fill slopes should be planted with deep-rooted, fast growing grasses before the first

winter to reduce erosion. On a preliminary basis, some irrigation of slopes could be performed;

however, specific details regarding irrigation systems, locations and discharge should be

reviewed by BSA.

REMEDIAL GRADING

Remedial grading activities will be required to prepare the site to receive fill and to provide

proper support for fill slopes and for structures. The details of remedial grading should be

developed and a Remedial Grading Plan should be prepared after the site and grading plans have

been prepared. Subsurface drainage plans should be prepared in conjunction with the

preparation of the Remedial Grading Plan. The Remedial Grading plan should address the

following:

Residual Soil Removal

Remove the upper 4 feet of residual soil in fill areas and replace with engineered fill. Remove

residual soil in at-grade and cut areas if present within 4 feet of finish grade and replace with

engineered fill.

Uncontrolled Fill

Uncontrolled fill in the northeastern area of the site not removed during design cuts and residual

soil removal should be removed and replaced with engineered fill.

Exploratory trenches and test pits excavated within the planned development area by BSA and

Engeo were backfilled with loosely placed uncontrolled fill. As discussed under Site Preparation

and Grading, uncontrolled fill should be removed and, if required to establish site design grades,

may be replaced as engineered fill. The approximate locations of the trenches and test pits are

shown on Plate 2. Logs for the exploratory excavation made by BSA are included in Appendix

B. Trench logs for excavations performed by Engeo are included in Appendix C.

Differential Fill on Building Pads

Cut/fill transitions should not be present with building pads. In addition, differential fill

thickness within building pads should be limited to 10 feet. Over-excavation in portions of the

building pads may be required to comply with these recommendations.

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Landslide Repair

A landslide is present at the southern tip of the proposed development, in the location of a

proposed fill slope. Repair of the landslide should be performed concurrent with grading for the

fill slope. A keyway will be required in this area for support of the fill slope. Any landslide

debris not entirely removed by the required grading for the keyway and fill slope should be

removed and the area then reconstructed as the fill slope is constructed.

Foundation Decoupling Section

A double layer of plastic, to be placed 3 feet below pad grade, is recommended at the building

locations. See “Foundation Decoupling” in the Building Foundations section below for

additional details.

EXPANSIVE SOILS

The near-surface residual soils and underlying highly to completely weathered bedrock is

moderately to highly expansive. Expansive soils shrink and swell with changes in moisture

content, especially seasonally. During the summer months, expansive soils can dry out and

desiccate, with shrinkage cracks extending several feet deep. During the winter months,

expansive soils can absorb excessive moisture and swell. In order to mitigate for expansive

soils, moisture conditioning and compaction of expansive soils will need to be controlled as

discussed below under Site Preparation and Grading. Additionally, foundations for residential

structures should be designed for expansive soil conditions. Presoaking of the building pad

subgrades prior to concrete placement will also be required.

EXCAVATION CHARACTERISTICS

Exploratory excavations were completed using a Caterpillar 312 excavator with a three-foot

bucket. Excavation depths were generally limited to about 8 feet but did extend as deep as about

18 feet at the north end of Trench T-11. The materials encountered were readily excavatable

with the equipment in use. Bedrock consisting of clayey siltstone was logged at a depth of 24

feet in Boring B-2. The material is friable, highly fractured to crushed and partially decomposed

into clayey silt. In general, we anticipate that the site will be excavatable using conventional

equipment for mass grading.

FILL MATERIALS

The on-site soil is generally suitable for engineered fill, provided it is free of debris, significant

vegetation, rocks greater than 6 inches in largest dimension and other deleterious matter. Use of

on-site soils and import soil for fill or backfill within 5 feet of the back of retaining walls should

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be limited to those soils with a Plasticity Index of 20 or less. In addition, clay soils should not be

used as backfill at mechanically stabilized earth (MSE) walls. Granular soils are recommended

for backfill at MSE walls, as discussed in the Retaining Walls section of this report.

SITE PREPARATION AND GRADING

1. The Geotechnical Engineer should be notified at least 48 hours prior to site clearing,

grading and backfill operations. The procedure and methods of grading may then be

discussed between the contractor and the Geotechnical Engineer.

2. Boulders present within the area to be graded will need to be removed and placed outside

of the development area.

3. Vegetation within the area to be graded is predominately seasonal grasses with occasional

brush. Surface vegetation present at the time of grading should be stripped down to the

soil surface. Vegetation should not be tilled or ripped into the site as a way of disposal.

Should dense roots be present in the upper few inches of the soil or where dense organic

matter is present, the top soil will need to be stripped from the site and stockpiled for use

in future landscape areas. Organic laden soils should not be placed in compacted fills.

4. Existing uncontrolled fill up to about 3 feet in depth was encountered at exploratory

trenches and test pits excavated to the northeast of an existing ridge crossing the

development area. Fill up to about 6 feet in depth was encountered where exploratory

trenches crossed the ridge. Uncontrolled fills identified during grading operations that

are not removed as part of the planned grading of the site will need to be removed.

Determination of the quality, and full lateral and horizontal extent of the fill present on

the site was beyond the scope of this investigation. Thus, monitoring of the site during

clearing and grading operations will be required to see that the uncontrolled fills are

removed. The existing fill soils should be cleared of any over-size material (cobbles

greater than 6-inches and boulders), debris or deleterious materials as they are excavated

so that the soils can be reused as engineered fill.

5. Exploratory excavations made for fault ground-rupture studies were backfilled with

uncontrolled fill. The uncompacted fill should be re-excavated and then be replaced as

engineered fill in accordance with the recommendations presented below.

6. Residual soils blanketing the site should be removed to a depth of 4 feet below existing

grade.

7. Landslide debris not removed as a part of the design grading, including recommended

excavations for residual soil removal, keyway constructing at fill slopes and site benching

to receive fill, should be removed down to stiff undisturbed soils.

8. Following the clearing and stripping operations and removal of uncontrolled and poorly

compacted fills, residual soil and landslide deposits, the exposed surface should be

scarified to a depth of about 12 inches, moisture conditioned, and recompacted to provide

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a surface ready to receive fill. If zones of soft or saturated soils are encountered,

excavations may be required to remove those soils. This should be determined in the

field by the Geotechnical Engineer. After the soil subgrades have been properly

prepared, the areas may be raised to design grades by placement of engineered fill.

9. Fill and backfill should be placed in thin lifts (normally 8 to 12 inches in loose lift

thickness depending on the compaction equipment), properly moisture conditioned, and

compacted as recommended below.

10. In general, fill soils should be compacted to no less than 90 percent relative compaction

at a moisture content not less than 3 percentage points (“3 percent”) above the optimum

moisture content. Where fill depths exceed 20 feet, fills deeper than 20 feet below design

grade should be compacted to no less than 92 percent at no less than 3 percent above

optimum moisture content. Where fill within the upper 5 feet of the site will be

comprised of moderately to highly expansive clay soils (PI>20) compaction of clay soils

in building pad and concrete flatwork areas should be between 85 and 90 percent relative

compaction at a moisture content at least 5 percent over optimum moisture content.

Where fill within the upper 5 feet of the site will be comprised of low plasticity fine-

grained soils and granular soils, those soils should be compacted to at least 90 percent at

a moisture content of at least 3 percent above the optimum moisture content. Where

previously compacted building pads become disturbed, they should be reprocessed to

meet the compaction and moisture requirements. These soils should be uniformly

moisture conditioned to at least 5 percent above optimum moisture content and

compacted prior to concrete placement.

11. Prior to subgrade preparation, utility trench backfill in the pavement areas should be

properly placed and compacted. All pavement subgrades should be scarified to a depth

of 12 inches below finished subgrade elevation, moisture conditioned to at least 2 percent

above the optimum moisture content, and compacted to at least 95 percent relative

compaction. Subgrade preparation should extend a minimum of 2 feet laterally behind

the face of the curb. Compacted subgrade should be stable and non-yielding under the

weight of a fully loaded 10-wheel water truck prior to placement of the aggregate base

section. Areas deemed to be exhibiting signs of instability as assessed by the

Geotechnical Engineer should be reworked and/or stabilized until a well-compacted non-

yielding surface is achieved. Subgrade soils should be maintained in a moist and

compacted condition until covered with the complete pavement section.

12. Aggregate base for roadways should conform to the requirements for ¾” Class 2

aggregate base in Sections 26 of the Caltrans 2010 Standard Specifications. The

aggregate base should be placed in thin lifts in a manner to prevent segregation,

uniformly moisture conditioned, and compacted to at least 95 percent relative compaction

to provide a smooth, unyielding surface. ASTM test procedures should be used to assess

the percent relative compaction of soils and aggregate base.

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13. Engineered fill is material that is properly moisture conditioned, placed and compacted in

accordance with the recommendations presented herein, as observed and documented by

a representative of the Geotechnical Engineer.

14. Earthwork observations and soil density test services should be carried out by a

representative of the Geotechnical Engineer during site clearing, grading and backfill

operations to assist the contractor in obtaining the required degree of compaction and

proper moisture content and to allow for documentation that the project requirements

have been met. Where the compaction and/or soil moisture content are outside the range

required, additional compaction effort and/or adjustment of moisture content should be

made until the specified compaction and moisture conditioning is achieved.

15. Relative compaction (“compaction”) refers to the in-place dry density of the soil or

aggregate base expressed as a percentage of the maximum dry density for soils and

aggregate base tested as determined in the laboratory. ASTM test methods should be

used to evaluate the relative compaction of processed subgrade below general fills,

completed subgrade and aggregate base. In-place dry densities and moisture contents of

compacted soils should be determined in accordance with ASTM test method D6938

("Test Methods for Density of Soil and Soil-Aggregate In-place by Nuclear Methods

[Shallow Depth]"). Maximum dry density and optimum moisture content should be

determined by ASTM D1557 laboratory compaction test procedure.

UTILITY TRENCHES

Trenches Adjacent to Building Foundations

To maintain the desired support for foundations, utility trenches running parallel or near-parallel

to building foundations should be located away from the foundation such that the base of the

trench excavation is located above an imaginary plane having an inclination of 1 Horizontal to 1

Vertical (1H:1V), extending downward from the bottom edge of the foundation toward the

trench location. Where trench locations are restricted and must be in close proximity to

foundations, footings or slab edges located adjacent to utility trenches should be deepened during

the design of the project as necessary so that their bearing surfaces are below an imaginary plane

having an inclination of 1H:1V, extending upward from the bottom edge of the adjacent utility

trench. As an option to the use of a deepened foundation, the trench can be backfilled with

controlled low strength material, such as sand-cement slurry, unless the use of sand-cement

slurry is prohibited by the City of Hayward or the utility company.

Excavation

All excavations should conform to applicable state and federal industrial safety requirements.

Safety in and around utility trenches is the responsibility of the general and underground

contractors. Where necessary, trench excavations should be shored in accordance with current

CAL-OSHA requirements to ensure safety.

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The contractor is cautioned that shoring or sloping back of trench walls may be required in some

areas even with trenching limited in depth to 4 to 5 feet based on our experience during

exploratory trenching of the site. In general, trench sidewalls should be sloped no steeper than 1

Horizontal to 1 Vertical (1H:1V) in stiff to hard cohesive soil and no steeper than 1-½H:1V in

granular soils. Where weaker soils are encountered in the upper 4 to 5 feet of the site or trenches

will extend deeper than 5 feet, trench sidewalls should be sloped no steeper than 1H:1V in stiff to

hard cohesive soil, no steeper than 1-½H:1V in moist granular soils and no steeper than 2H:1V in

dry granular soils. Flatter trench slopes may be required if seepage is encountered during

construction or if exposed soil conditions differ from those encountered in in our borings,

trenches and test pits. Heavy construction equipment, building materials, excavated soil, and

vehicular traffic should not be allowed within 5 feet of the top (edge) of the excavation.

Groundwater Considerations

As noted above, shallow groundwater was encountered in the northeastern area of the site, which

appeared to be a perched water zone. At the time of this investigation, groundwater was with

about 4-feet of the ground surface. Underground contractors should be prepared to dewater their

trenches and may need to stabilize the base of their excavations. Should unstable conditions be

encountered at the base of the trenches, BSA should be contacted to discuss stabilization options.

Backfill

Materials type and placement procedures for utility bedding, shading and backfill materials

should meet local agency and/or other applicable utility providers’ requirements. In the absence

of a specific agency or utility company requirement, utility lines should be bedded and shaded

with open-graded crushed rock or well-graded sand and gravel to at least 6 inches over the top of

the pipe. The bedding and shading material should conform to the pipe manufacturer’s

requirements. Open-graded gravel should be densified prior to placing subsequent backfill

materials; well-graded sand and gravel should be compacted to no less than 90 percent relative

compaction prior to placing subsequent backfill materials. Where open-graded gravel is placed

as bedding, shading or backfill, the gravel should be fully wrapped or encapsulated using non-

woven geotextile filter fabric such as Mirafi 140N or equivalent.

From a geotechnical perspective, utility trench backfill above the bedding and shading materials

(beginning 6 inches above the top of pipe) may consist of on-site soils with a PI of 20 or less,

that have been processed to remove rock fragments over 3 inches in largest dimension, rubbish,

vegetation and other undesirable substances. Backfill materials should be placed in level lifts

about 4 to 12 inches in loose thickness, moisture conditioned and mechanically compacted. Lift

thickness will be a function of the type of compaction equipment in use. Thinner lifts (4- to 6-

inch lifts) will be required for manually operated equipment, such as wackers or vibratory plates,

and thicker lifts possible where a sheepsfoot wheel is used on the stick of an excavator. Jetting

should not be used for densification of backfill on this project.

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Trench backfill consisting of fine-grained soil (clays and silts) should be moisture conditioned to

between 3 and 5 percent above optimum and compacted to at least 90 percent relative

compaction where the soil PI is 20 or less. Where sand is used as backfill, it should be moisture

conditioned to slightly above the optimum moisture content and compacted to at least 93 percent

relative compaction. Trenches in pavement areas should be capped with at least 12 inches of

compacted, on-site soil similar to that of the adjoining subgrade. The upper 12 inches of trench

backfill for trenches located in streets should be compacted to at least 92 percent for moderately

expansive soils and to no less than 95 percent relative compaction for soil that have a low

expansion potential. The expansion potential of backfill soils should be assessed by the

Geotechnical Engineer during the construction process.

BUILDING PAD PRE-SOAK

The upper 12 to 18 inches (depending on the depth of drying that has occurred) of the subgrade

soils should be pre-soaked to at least 5 percent above optimum moisture content prior to

constructing foundations. The pre-soaked pads should not be allowed to dry out to less than the

recommended moisture content before concrete is placed. Subgrade moisture should be checked

by a BSA representative prior to concrete placement.

LANDSCAPING AND LANDSCAPE IRRIGATION

Fluctuations in near-surface soils’ moisture content due to seasonal changes and irrigation, as

well as the effects of landscaping can have an adverse impact on the foundations. According to

the Post-Tensioning Institute (PTI), “watering should be done in a uniform, systematic manner

as equally as possible on all sides to maintain the soil moisture content consistently around the

perimeter of the foundation.” Areas of soil that do not have ground cover may require more

moisture as they are more susceptible to evaporation. Ponding or trapping of water in

localized areas adjacent to the foundations can cause differential moisture levels in subsurface

soils.

Tree roots have the potential for causing uplift and possible distress to concrete slabs-on-grade,

including building foundation slabs-on-grade and pavement. If trees are to be planted around or

in close proximity to the buildings, the selection of the types of trees to be planted and the

construction details for building foundations and slabs, as well as for pavements should be based,

at least in part, on the consideration of future damage due to the presence of trees.

Whenever possible, trees should be located out from the building perimeter at a distance equal to

or greater than the anticipated radius of the canopy of a mature tree. This would place the trees

out from the buildings such that the buildings would not be within the drip line and dense root

zone of the tree. Where trees are to be planted close to buildings or pavements, tree wells with

root barriers extending to a minimum depth of 3 feet should be considered. Trees in close

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proximity to foundations will require more water in periods of extreme drought and in some

cases a root injection system may be required to maintain moisture equilibrium to reduce the

potential for the trees to impact the foundations. The project landscape architect should be

consulted to determine if there are any low water demand trees that will work within the planned

project to reduce the potential impacts of trees on foundations and pavement.

BUILDING FOUNDATIONS

With highly expansive soils and the potential for slight ground distortion resulting from proximal

fault rupture and strong seismic shaking, we recommend the use of post-tensioned (PT) slab-on-

grade foundations and “decoupling” of the foundations from the underlying soils. Post-tensioned

slab-on-grade foundations should be structurally designed to resist or distribute the stresses that

are anticipated to develop as the result of supporting soil movement. Movement may be

associated with expansive soil volume change and seismic-induced ground movement.

Foundations in all areas of the site should be capable of withstanding differential movement of

2½ inches of vertical displacement of the ground surface across the span of the structure.

Foundation Decoupling

To decouple the foundations from the effects of lateral ground distortion, foundations should be

supported by engineered fill constructed over two layers of 15 mil sheet plastic. Projections for

deepened sections in the foundation, such as those commonly associated with anchor bolts at

holdowns for shear walls, or steps in the foundation, should not penetrate the doubled plastic

sheets.

Based on our recent work on the La Vista site located upslope of the subject project site, working

with the foundation designer, the grading contractor and the developer, we developed a

decoupling detail that allowed for installation of the doubled plastic sheets as part of the grading

operation. This eliminated the need to re-excavate the site to install the plastic sheeting below

the lowest foundation projection into the building pad after rough grading had been completed.

Plate 6, Foundation Decoupling Detail, shows the recommended method to decouple the post-

tension concrete slab foundations (PT slabs) from the ground. A double layer of sheet plastic

(15-mil minimum) should be placed at the bottom of engineered fill building pads, with the

plastic placed on smooth, stable (non-yielding) continuous flat pads. The plastic sheeting should

be at least 6 inches below the lowest protrusion below the bottom of the PT slabs. Absent

specific foundation design requirements, we recommend that the plastic sheeting be installed at a

depth of 3 feet below the bottom surface of the post-tensioned concrete slab-on-grade

foundations if it is to be installed during rough grading. Ideally, the plastic should extend to the

building perimeter or slightly beyond. In the absence of identified building footprints on each

lot, the plastic sheeting should extend to the limits of the designated building envelopes. Prior to

installing the plastic sheeting, the grading contractor should consult with the Civil Engineer to

confirm that the pad grades shown on the rough grading plans were set with consideration of the

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slab thickness and a 4-inch thick capillary break. We anticipate a minimum post-tension slab-

on-grade thickness of 15-inches.

Post-Tensioned Slab-On-Grade Foundation Design Parameters

Moderate to highly expansive soils are present on the site. Post-tensioned foundations should be

designed in accordance with the design provisions as presented in the document Design of Post-

Tensioned Slabs-On-Ground, third edition, published by the Post-Tensioning Institute (PTI),

with consideration of Addendums No. 1 and No. 2. PT concrete foundation design parameters

based on expansive soil parameters as well as consideration of the potential ground movement

associated with seismic-induced ground distortion.

Allowable Bearing Capacity (may be increased by 1/3 for seismic

and wind loads at the discretion of the Structural Engineer)

1,500 psf

Passive Equivalent Fluid Pressure (neglect the upper foot if the

ground surface is not confined by slabs or pavement)

300 pcf

Base Friction Coefficient 0.30

Edge Moisture Variation Distance

Center Lift

Edge Lift

8.0 feet

4.1 feet

Differential Swell

Center Lift

Edge Lift

2.48 inches

3.97 inches

Slab Minimum Thickness (in) 15 inches

Additional Design and Construction Considerations

Perimeter columns located outside of the main structure, such as those required for covered

terraces or second floor areas projecting out beyond the building footprint should not be founded

on spread footings that are structurally separated from the PT slab-on-grade foundation.

Perimeter columns should be supported by the PT slab-on-grade foundation.

Even where increased stiffness is provided at the foundation level, some distortion may occur in

the structures with bending of the slabs. This will need to be considered by the Structural

Engineer. The above recommendations may not prevent all damage to the proposed residential

development in the event of a major earthquake resulting in ground distortion and strong to

violent shaking of the structures. Adherence to the above recommendations and the current

building code during design and construction of the development should reduce such potential

damage. The recommendations are not intended to be a guarantee that significant structural

damage will not occur in the event of a maximum magnitude earthquake; the intent is to

provide design input for use in design of a foundation that will not undergo catastrophic

failure leading to structural collapse or cause loss of life in a major earthquake.

October 17, 2017

Job No. 3823.102

Page 24


MOISTURE VAPOR TRANSMISSION THROUGH INTERIOR SLABS-ON-GRADE

A vapor retarder should be installed immediately below the concrete in accordance with Section

1907 of the California Building Code. Sand should not be placed over the vapor retarder.

Guidelines for capillary break installation and for installation of the vapor retarder are provided

in ASTM E1745. A standard specification for the vapor retarder material is presented in ASTM

E1643. The details of the materials and installation of a vapor retarder and capillary break

should be determined by the project designers. A minimum 4-inch section of gravel is suggested

for the capillary break.

RETAINING WALLS

Retaining walls can be of conventional cantilever or gravity type walls, or mechanically

stabilized earth (MSE) retaining walls with geogrid. Conventional retaining walls can be

supported on shallow foundations where the area in front of the wall is relatively flat and level.

If walls are to be constructed above slopes, deep foundations, such as drilled, cast-in-place

concrete piers may be required. Where retaining walls are free to rotate at least 0.1 percent of

the wall height at the top of the backfill, as with a cantilever wall, the walls may be designed

using an active lateral earth pressure. Walls that are incapable of this deflection or walls that are

fully constrained against deflection, should be designed for an equivalent fluid at-rest pressure.

Retaining wall and wall foundation design parameters are presented below.

Conventional Concrete or Concrete Masonry Retaining Wall

Retaining Wall Design Parameters

Active Equivalent Fluid Pressure *

Level backfill (drained conditions)

Sloping backfill 3H:1V (drained conditions)

Sloping backfill 2H:1V (drained conditions)

55 pcf

65 pcf

75 pcf

At-Rest Equivalent Fluid Pressure (Level backfill and drained

conditions) 90 pcf

Seismic Load for retained height (H) of 6 feet or greater

Line Load applied at 0.33H above the wall base 32H

2

Surcharge Load, where applicable Designated by

Structural Engineer

* Values listed are applicable for backfill or retained soils within a distance H

from the back of wall having a Plasticity Index of 20 or less. High Plasticity

soils should not be used as backfill.

October 17, 2017

Job No. 3823.102

Page 25


Retaining Wall Shallow Foundation Recommendations

Allowable Bearing Capacity (may be increased by

1/3 for temporary seismic and wind loads at the

discretion of the Structural Engineer)

2,000 psf

Allowable Passive Equivalent Fluid Pressure

Level ground surface in front of the wall

Sloping surface in front of the wall.

250 pcf

Ignore the upper 2’ of embedment

Ignore the upper 3’ of embedment

Allowable Base Friction Coefficient 0.30

Minimum Footing Depth 24 inches below lowest adjacent

grade *

* Where footings are constructed in proximity to descending slopes, the base

of the footing should be at a depth sufficient to provide a minimum of 10

feet of soil in front of the base of the at the base of the footing as measured

laterally out to the face of the slope.

Drilled cast-in-place concrete pier foundations designed to resist both lateral and vertical loads

can be used to retaining walls located above descending slopes.

Drilled Cast-In-Place Pier Foundation Design Parameters

Allowable Skin Friction – Vertically Down

(may be increased by 1/3 for seismic and wind loads;

neglect the upper 2 feet in calculating pier capacity)

400 psf

Allowable Skin Friction – Uplift

(may be increased by 1/3 for seismic and wind loads;

neglect the upper 4 feet in calculating pier capacity)

250 psf

Passive Equivalent Fluid Pressure, acting on 1.5 pier

diameters

(neglect the upper 4 feet in calculating the lateral capacity)

350 pcf

Minimum Pier Spacing (center to center) At least 3 pier diameters

apart

The piers should be drilled and poured on the same day. If the drilled pier holes are to be left

open overnight for production purposes, the drilled pier holes should be covered; however, the

potential for caving increases with time. Groundwater may seep into the pier holes. The

contractor should be prepared to case the drilled holes. Any water that accumulates in the holes

should be removed prior to concrete placement.

October 17, 2017

Job No. 3823.102

Page 26


Mechanically Stabilized Earth Retaining Wall

MSE Retaining Wall Preliminary Design Considerations

Backfill Soil

Soil Friction Angle (soil classified as SM, SC, SP, GM, GC)

Unit Weight (Wet) (soil classified as SM, SC, SP)

Unit Weight (Wet) (soil classified as GM, GC)

Maximum fines content (passing #200 sieve)

30°

125 pcf

140 pcf

20%

Retained Soil

Soil Friction Angle (soil classified as CL, CH, SC)

Soil Cohesion (soil classified as CL, CH, SC)

Unit Weight (Wet) (soil classified as CL, CH, SC)

16°

700 psf

125 pcf

Allowable Base Friction Coefficient 0.25

Allowable Bearing Capacity (may be increased by one-third for temporary

seismic and wind loads at the discretion of the Structural Engineer). 2,000 psf

Minimum Embedment 16 inches below

lowest adjacent

grade*

* The base of MSE walls should be setback from descending slopes. This

may require the construction of a bench on an existing slope with the bench

extending 10 feet out from the base of the wall.

MSE wall design responsibility is commonly assigned to the MSE wall installer or the MSE wall

supplier, under subcontract to the general contractor. Design of MSE walls requires specific

information including allowable soil bearing capacities, soil strength parameters (phi angle and

cohesion) for the backfill in the reinforced zone as well as the retained soils beyond the

reinforced soil zone, soil unit weights for specific soils in the reinforced zone and retained zone.

The values presented are intended for preliminary design purposes only. The soil friction values

are intended to be maximum values unless specific soils are specified for the reinforced soil zone

and retained soil zone immediate behind the reinforced soil zone. Additional information

required for design is the intended soil reinforcement, height of the wall, backfill condition (level

or sloping), and preload loads. The design must consider sliding, overturning and both internal

and global stability. Global stability is often overlooked; global instability is a common cause of

MSE wall distress or failure. A factor of safety of no less than 1.3 should be considered for

global stability.

We should review the MSE wall design, plans and specifications to confirm that: appropriate

input values were used in the design; stability (both global and internal) requirements are met;

complete materials specifications are provided for the wall facing, soil reinforcement (geogrid),

wall drainage, backfill soils at the reinforced soil zone including minimum soil friction angle and

soil unit weight.

October 17, 2017

Job No. 3823.102

Page 27


Wall Surcharge

The above recommended lateral pressures do not include any surcharge loads due to loads or

structures placed above the wall. The surcharge effect from loads adjacent to the walls should be

included in the wall design. The surcharge load for restrained walls should be based on one-half

of the applied load above the wall distributed over the full height of the wall. The surcharge load

for walls free to deflect should be based on one-third of the applied load above the wall

distributed over the full height of the wall.

To prevent excess lateral forces from being applied to the retaining wall, heavy compaction

equipment (such as loaders, dozers, or sheepsfoot rollers) should not be allowed within a

horizontal distance of about 5 feet behind the top of the retaining wall. The backfill directly

behind the retaining wall should be compacted using light-weight equipment such as self-

propelled vibrating rollers or hand operated equipment (jumping jack compactors or vibratory

plates). For backfill of the retaining wall using self-propelled vibrating rollers, an additional

uniform lateral pressure of 200 psf should be added over the entire height of the retaining wall.

Retaining Wall Backdrains

The above recommended lateral pressures are based on drained conditions. All walls retaining

more than 2 feet of soil should be provided with a backdrain to prevent hydrostatic pressure

build-up. The backdrain should consist of a subdrain pipe placed at the base of the wall with a

vertical drain constructed or installed behind the retaining wall. Subdrain pipes should be SDR

35 perforated pipe, typically at least 4 inches in diameter, installed with the perforations facing

down. All subdrain pipes should be surrounded by and be underlain by at least 4 inches of Class

2 Permeable Material, as defined in Section 68-2.02F(3) of the State of Caltrans Standard

Specification (2010). The vertical drain should extend from the Class 2 Permeable Material

encapsulated subdrain pipe at the base of the wall to about 1 foot below the finished grade

behind the retaining wall. The vertical drain should consist of Class 2 Permeable Material and

should be at least 12 inches thick. Alternatively, a geo-composite drain, such as Miradrain 6200

or approved equivalent, may be used in lieu of the Class 2 Permeable Material vertical drainage

blanket for walls other than MSE walls. The geo-composite should drain into the subdrain pipe

as shown on Plate 7. The upper 1 foot of wall backfill above the backdrain should consist of

compacted site soils. The subdrain pipe should tie into a solid pipe leading to a suitable gravity

discharge or storm drain system.

Where slopes are located above retaining walls, surface water draining toward the wall should be

collected in a lined concrete ditch located at the back of the wall. Surface water should not be

allowed to percolate into the retaining wall backfill. The concrete ditch should direct the water

into a closed pipe to be conveyed to a suitable discharge point.

Even with the presence of a wall drain, dampness may occur at the face of the walls. If this is

objectionable, waterproofing of the walls should be considered.

October 17, 2017

Job No. 3823.102

Page 28


Retaining Wall Backfill

Backfill soils for concrete or masonry walls should have a PI of 20 or less for soil placed within

the lateral distance equal to the height of the wall.

Backfill soils at the reinforced soil zone behind MSE walls should be primarily granular with a

maximum fines content (passing the #200 sieve) of 20 percent and a minimum friction angle of

34 degrees. Backfill should be compacted as discussed in the section “Site Preparation and

Grading,” above.

Laboratory testing of backfill soils should be performed prior to and during backfilling

operations to confirm that the soil friction angle requirement for soils used as backfill in the

reinforced soil zone is met and to confirm soil unit weights are within the specified range.

Backfill should be compacted to not less than 90 percent relative compaction. Over-compaction

should be avoided because increased compactive effort can result in lateral pressures

significantly higher than those recommended above. To prevent excess lateral forces from being

applied to the retaining wall, heavy compaction equipment (such as loaders, dozers, or

sheepsfoot rollers) should not be allowed within a horizontal distance of about 4 feet behind the

top of the retaining wall. The backfill directly behind the retaining wall should be compacted

using light-weight equipment such as self-propelled vibrating rollers or hand-operated equipment

(jumping jack compactors or vibratory plates). Backfill should be placed and compacted

according to the requirements for engineered fill contained in the “Site Preparation and Grading”

section.

CONCRETE FLATWORK

With the exception of slabs subject to vehicular loads, it is our opinion that, from a Geotechnical

Engineering standpoint, exterior concrete slabs-on-grade, such as sidewalks and patios, can be

placed directly on the prepared subgrade. The use of aggregate base as support for concrete

flatwork should be avoided except in traffic areas where required as part of a structural section,

or where required for compliance with a City standard.

Exterior concrete flatwork such as sidewalks, walkways and driveways will be subject to

differential soil movements due to the expansive soils. A minimum slab thickness of 5 inches

and reinforcing steel should be considered for improved slab performance. Steel reinforcement

(rebar as opposed to wire mesh) should also be considered to reduce cracking and the potential

for tripping hazards to develop between adjacent concrete panels due to expansive soil

movement and/or tree roots. Minimum recommended reinforcement is No. 4 steel reinforcing

bars at 18 inches on-center each. The minimum recommended steel will not prevent the

development of slab cracks but will aid in keeping the construction joints relatively tight and in

reducing the potential for differential movement between adjacent panels.

October 17, 2017

Job No. 3823.102

Page 29


In addition to steel reinforcement, frequent construction or crack control (contraction) joints

should be provided in all concrete slabs where cracking is objectionable. Deep, scored joints

spaced no more than 6 feet apart should be considered to control shrinkage cracking. Scoring of

contraction joints should extend slightly deeper than one-quarter the slab thickness to be

effective.

Where exterior concrete slabs-on-grade are planned, we generally recommended that exterior

slabs-on-grade (i.e. sidewalks) be cast free from adjacent footings or other edge restraint. Using

a strip of ½-inch thick asphalt impregnated felt or other commercially available expansion joint

material between the slab edges and the adjacent structure may accomplish this. Where there is a

concern that a trip hazard could develop due to differential movement between the exterior slab-

on-grade and the adjoining foundation, or where concrete flatwork abuts embedded curbs,

consideration may be given to tying the slab to the foundation or to the curb with reinforcing

steel (rebar) dowels. Where the residential structures are to be constructed at a distance of 10

feet to 15 feet from the top of a descending slope, there is a potential for concrete flatwork

constructed in the area between the building foundation and the top of slope to move laterally

slightly over time due to the effects of expansive soils. Securing the flatwork by tying it to the

foundation or other methods should be considered.

With the on-site clay soils having a moderate to high expansion potential, it is important that

these soils be properly moisture conditioned during grading operations and that the moisture

content is maintained until the concrete has been placed. The moisture content of the subgrade

soils should be checked several days prior to the placement of concrete, or baserock where

required, to allow for presoaking where needed. Where moderately to highly expansive soils are

present and the soil moisture content is less than 5 percent above optimum, the subgrade should

be presoaked to at least 5 percent over optimum moisture content prior to placing concrete. Even

with proper site preparation there will be some effects of soil moisture change on concrete

flatwork.

The above recommendations, including soil moisture conditioning, contraction joints and steel

reinforcement are intended to help reduce the potential for distress in concrete flatwork, but may

not totally eliminate distress.

STRUCTURAL PAVEMENT

Flexible Pavement

The Caltrans flexible pavement design method was used to develop the recommended pavement

sections presented below. Highly expansive soils are present in the upper several feet of the site.

Soils with high expansion potential, as exhibited by a Plasticity Index (PI) in excess of 25 and

with a high clay fraction and low sand or silt content typically have an R-value on the order of 5.

The pavement section recommendations presented below are based on a subgrade R-value of 5.

October 17, 2017

Job No. 3823.102

Page 30


FLEXIBLE PAVEMENT SECTIONS

Subgrade R-Value = 5

Traffic Index

Asphalt

Concrete

(inches)

Class 2

Aggregate Base

(inches)

Total Section

Thickness (inches)

5.0 3.0 10.0 13.0

4.0 7.5 11.5

5.5 3.0 12.0 15.0

4.0 10.0 14.0

6.0 3.5 13.0 18.5

4.0 11.5 15.5

6.5 4.0 14.0 18.0

7.0 4.0 15.5 19.5

8.0 5.0 17.5 22.5

Materials

Class 2 Aggregate Base should conform to the requirements found in Caltrans Standard

Specifications Section 26. The aggregate base should be placed in thin lifts in a manner to

prevent segregation, uniformly moisture conditioned, and compacted to at least 95 percent

relative compaction (using ASTM test methods) to provide a smooth, unyielding surface. Where

the completed aggregate base section is exposed to periods of rainfall or extensive construction

traffic prior to paving, the baserock should be proof-rolled with a loaded 10-wheel truck to locate

any soft or yielding areas.

The asphalt concrete should comply with Caltrans Standard Specifications for ½” maximum,

Type A for the surface course and ¾” maximum, Type A asphalt concrete for the base course

where the asphalt concrete is placed in two lifts. Asphalt concrete should be placed and

compacted in accordance with the specifications presented in Section 39 of the 2010 Caltrans

Standard Specifications. To achieve proper compaction of asphalt concrete placed against

concrete gutters and to reduce the potential that poorly compacted asphalt concrete pavement

will drop below the concrete surface as the asphalt concrete is further compacted under the

effects of vehicle traffic, the asphalt concrete should be placed such that the compacted surface is

approximately ¼-inch above the concrete surface (excluding spill type gutters). If the paving

machine screed is allowed to ride on the concrete gutter during asphalt concrete placement and

the roller operator has the roller on the concrete during the compaction process, the asphalt

concrete surface will appear to be compacted but will settle over time. This will result in water

entering into the pavement structure, which can lead to accelerated pavement failure.

October 17, 2017

Job No. 3823.102

Page 31


Seepage Cut-Off And Pavement Section Drainage

Maintaining a drained condition at the pavement section is important to reduce the possibility of

premature pavement failure due to saturation of the aggregate base and softening of the subgrade

soils. Where cross-sloped pavements are planned with a spill-type curb and gutter section or a

vertical curb at the upslope side of the pavement, in the absence of a requirement for a Class 2

Aggregate Base section below the curb, a deepened curb section extending 3 inches below the

aggregate base/subgrade contact should be considered to act as a seepage cut-off to reduce the

amount of water that enters the pavement structure. A pavement edge drain should be

constructed under the catch-type curb and gutter along both sides of the roadway where crowned

along the centerline, and along the low side of cross-sloped pavements. These subdrains will

drain water that may collect and saturate the aggregate base, which could cause premature

pavement failure. A pavement edge drain detail is provided on Plate 5 of this report.

ADDITIONAL GEOTECHNICAL ENGINEERING SERVICES

REMEDIAL GRADING PLAN

BSA should review the grading plan when it is near completion so that we can assist with the

development of a remedial grading plan. It has been our experience that a remedial grading plan

aids in the contractors’ understanding and implementation of the recommendations presented in a

geotechnical report.

REVIEW OF PLANS AND SPECIFICATIONS

Prior to construction, our firm should be provided the opportunity to review the geotechnical

aspects of the project structural, civil and landscape plans, and specifications, to determine if the

recommendations of this report have been implemented in those documents.

EARTHWORK AND PAVING OBSERVATION AND TESTING

To a degree, the performance of the proposed project is dependent on the procedures and quality

of the construction. Therefore, we should provide observations of the contractor's procedures

and the exposed soil conditions, and field and laboratory testing during site preparation and

grading, placement and compaction of fill, underground utility installation, and foundation and

pavement construction. These observations will allow us to check the contractor's work for

conformance with the intent of our recommendations and to observe unanticipated soil

conditions that could require modification of our recommendations. We would appreciate the

opportunity to meet with the contractors prior to the start of site grading, underground utility

installation and pavement construction to discuss the procedures and methods of construction.

This can facilitate the performance of the construction operation and minimize possible

misunderstanding and construction delays.

October 17, 2017

Job No. 3823.102

Page 32


LIMITATIONS

The conclusions and recommendations presented herein are based on the assumption that the

data collected is representative of the subsurface conditions across the site. Site and subsurface

conditions described in this report and presented on the boring, test pit and trench logs are those

existing at the times of our field explorations and may not necessarily be representative of such

conditions at other locations or times. It is not warranted that the logs are representative of such

conditions elsewhere or at other times. This geotechnical investigation has been conducted in

accordance with professional geotechnical engineering standards current at the time of service

and in the geographic area of the site; no other warranty, expressed or implied, is offered or

made.

The conclusions and recommendations presented in this report are based upon the project

information provided to us by The Grupe Company, information obtained from published

geologic reports and maps, unpublished geotechnical reports by others as identified in this report,

subsurface conditions encountered at the borings, exploratory test pits and trench locations, the

results of geotechnical laboratory testing, engineering analyses and professional judgment. It is

not warranted that such information, interpretation of the data, and the conclusions and

recommendations based on the interpretation of that data, will not be superseded by future

Geotechnical Engineering developments. In addition to advancements in the field of

Geotechnical Engineering, the International Building Code and the California Building Code are

revised periodically. Those revisions can impact interpretation of subsurface soil conditions and

regional seismicity, and may necessitate revisions to the recommendations presented in this

report.

This geotechnical investigation has been conducted, and the opinions, conclusions and

recommendations presented in this report were developed, in accordance with accepted

Geotechnical Engineering practices that exist in the San Francisco Bay Area at the time this

report was prepared. No warranty, expressed or implied, is offered, inferred or made, by or

through our performance of professional services.

The information provided herein was developed for use by The Grupe Company for the project

as described herein. In the event that changes in the nature, design or location of the proposed

project are planned, it is found during construction that subsurface conditions differ from those

described herein, or revisions are made to the Building Code that are related to Geotechnical

Engineering, the conclusions and recommendations in this report shall be considered invalid,

unless the changes are reviewed and the conclusions and recommendations are confirmed or

modified in writing by BSA. In light of this, there is a practical limit to the usefulness of this

report without critical review. Although the time limit for this review is strictly arbitrary, it is

suggested that two years from the date of this report be considered a reasonable time for the

usefulness of this report.


PLATES

JO

B N

UM

BE

R: 3

82

3.1

02

D

AT

E: 6

-8

-1

7 B

Y: C

C

BASE: PORTION OF U.S.G.S. 7.5 MINUTE TOPOGRAPHIC QUADRANGLE,

HAYWARD, CALIFORNIA

PLATE 1

SITE

N

0 2000

1"=2000'

VICINITY MAP

TENNYSON


HAYWARD, CALIFORNIA

FOR

THE GRUPE COMPANY

FAULT "A"

FAULT "B"

FAULT "C"

FAULT "D"

SUSPECTED

FAULT "E"

??

? ?

T-4B

T-4

T-9

T

-3

T

-

1

3

T

-1

4

T

-1

5

T

-

2

B

T

-

2

T

-

2

A

T

-

2

C

T

-

1

T-3

T-2

T-4

?

?

?

?

?

?

?

?

?

?

?

E

N

G

E

O

F

A

U

L

T

1

E

T

-

1

E

T

-

2

E

T

-

3

37

T

R

7

T

R

8

T

3

(1

9

7

5

)

T

1

(

2

0

1

2

)

T

4

(

1

9

7

5

)

L

2

(

2

0

1

2

)

T

1

(1

9

7

5

)

HAYWARD

CONCENTRATED

FAULT

ZONE

(BGC, 2001)

62

32

29

21

29

21

36

66

40

?

?

?

?

B

S

A

F

A

U

L

T

A

B

S

A

F

A

U

L

T

B

T-1

T

-5

T

-

4

T-2

T

-

3

T

-

6

T

-

7

T

-

8

T

-

9

T

-

1

0

T

P

-

1

T

-

1

1

T

-

1

2

T

P

-

2

T

P

-

3

T

P

-

4

T

P

-

5

1

'

B-6

B-5

B-4

B-3

B-2

B-1

1

N

JO

B N

UM

BE

R: 3823.102 D

AT

E: 6-20-17 D

RA

WN

B

Y: C

C

PLATE 2

0 50

1"=50'

SITE PLAN

TENNYSON

TENNYSON ROAD

EAST OF MISSION BOULEVARD

HAYWARD, CALIFORNIA

FOR

THE GRUPE COMPANY

Berlogar Stevens & Associates

SOIL ENGINEERS * ENGINEERING GEOLOGISTS

PROPERTY LINE

CROSS SECTION LOCATION

BORING LOCATION

DEVELOPMENT AREA

TRENCH LOCATION

(BSA, 2017)

TEST PIT LOCATION

(THIS STUDY)

APPROXIMATE TRENCH

LOCATION (C&A 2012)

T-12

ET-3

T-16

T-4

37

66

T4 (1975)

TR8

L2 (2012)

APPROXIMATE TRENCH LOCATION

(ENGEO, 2005)


(BERLOGAR GEOTECHNICAL

CONSULTANTS, 2001)


(EARTH SYSTEMS CONSULTANTS, 1980)


(JUDD HULL & ASSOCIATES, 1975)


(SOIL ENGINEERING CONSULTANTS, 1973)

SOUTHWESTERN LIMIT OF EARTHQUAKE

FAULT HAZARD ZONE

(STATE OF CALIFORNIA, 1982)

APPROXIMATE FAULT LOCATION

(BERLOGAR STEVENS & ASSOCIATES

(2017)


(BERLOGAR GEOTECHNICAL

CONSULTANTS, 2001)


(ENGEO, 2013)


(ENGEO, 2005)

EXPLANATION


(SOIL ENGINEERING CONSULTANTS,

1973)

STRIKE AND DIP OF SHEAR (ENGEO,

2005)

STRIKE AND DIP OF SHEAR

(SOIL ENGINEERING CONSULTANTS,

1973)

TP-5

1'1

B-6

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206.6

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213.4

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214.3

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186.7

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66.3

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63.8

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144.3

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144.1

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147.6

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116.8

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DIRT PILE

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BUILDING MATERIALS

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PIPES

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DEBRIS

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272.6

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273.7

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272.5

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271.5

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270.5

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269.4

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273.9

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274.3

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271.2

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271.4

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271.8

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270.5

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270.6

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PIPES

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DEBRIS

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DEBRIS

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DEBRIS

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OBSCURED

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50

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55

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60

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65

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110

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115

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Proposed Retaining Wall location ( Detail TBD)

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Proposed Stepped Retaining Wall location ( Detail TBD)

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Proposed 3:1 Manufactured Slope location ( Detail TBD)

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Proposed 2-3:1 Manufactured Slope location ( Detail TBD)

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APN 078C-0461-001-13

BENCHES 5 FEET

(TYPICAL)

(SEE NOTE 2)

TOPSOIL, COLLUVIUM,

OR SLIDE DEBRIS

(TO BE REMOVED)

8 FEET

MINIMUM

ORIGINAL

GRADE

INTERMEDIATE BENCH

(SEE NOTE 1)

KEYWAY

20 FEET MINIMUM

(SEE NOTE 3)

SUBDRAIN

(SEE NOTES 4,5)

SUBDRAIN

(SEE NOTES 4,5,6)

ENGINEERED

FILL

20 FEET

(MAXIMUM)

GEOGRID REINFORCEMENT

(TENSAR TX-7 OR APPROVED

EQUIVALENT, 2 FOOT VERTICAL

SPACING, 20 FEET LONG)

JO

B N

UM

BE

R: 3823.102 D

AT

E: 6-9-17 D

RA

WN

B

Y: C

C

PLATE 3

FILL SLOPE AND KEYWAY DETAIL

NOTES:

1. INTERMEDIATE BENCHES SHOULD BE SPACED EVERY 25 VERTICAL FEET ON SLOPES HIGHER THAN 30 FEET.

2. WHERE NATURAL GRADE IS STEEPER THAN 7:1, BENCH INTO STIFF SOIL OR BEDROCK AS DETERMINED BY SOIL

ENGINEER.

3. KEYWAY SHOULD EXTEND AT LEAST 8 FEET BELOW EXISTING GRADE AT TOE OF SLOPE OR 4 FEET INTO STIFF

SOIL OR BEDROCK WHICHEVER IS DEEPER, AS DETERMINED BY THE SOIL ENGINEER. KEYWAY WIDTH SHOULD

BE A MINIMUM OF 20 FEET OR 1/2 OF THE FILL SLOPE HEIGHT, WHICHEVER IS GREATER.

4. NECESSITY OF KEYWAY SUBDRAIN AND INTERMEDIATE BENCH SUBDRAINS TO BE DETERMINED BY THE

GEOTECHNICAL ENGINEER.

5. SUBDRAIN, IF NECESSARY, SHOULD DISCHARGE VIA A CLOSED PIPE TO STORM DRAIN OR SUITABLE OUTFALL.

6. SUBDRAIN, IF NECESSARY, SPACING MAXIMUM 20 FEET VERTICAL OR AS DETERMINED IN THE FIELD BY

GEOTECHNICAL ENGINEER.

NOT TO

SCALE

4 FEET

MINIMUM

6 INCHES

6 INCHES

KEYWAY AS APPROVED BY

THE SOIL ENGINEER

18 INCHES MINIMUM

CLASS 2 PERMEABLE

MATERIAL (NOTE 1)

PERFORATED PIPE

(NOTE 2)

TRENCH SUBDRAIN

KEYWAY SUBDRAIN

18 INCHES MINIMUM

4 FEET

MINIMUM

CLASS 2 PERMEABLE

MATERIAL (NOTE 1)

PERFORATED PIPE

(NOTE 2)

JO

B N

UM

BE

R: 3823.102 D

AT

E: 6-9-17 D

RA

WN

B

Y: C

C

PLATE 4

TYPICAL SUBDRAIN DETAILS

NOTES:

1. CLASS 2 PERMEABLE MATERIAL AS GIVEN IN STATE OF CALIFORNIA STANDARD SPECIFICATIONS.

2. PERFORATED PIPE PLACED PERFORATIONS DOWN, PVC PIPE WITH A MINIMUM DIAMETER OF SIX (6) INCHES,

CONFORMING TO ASTM D-3034 SDR 35, FOR DEPTHS LESS THAN 30 FEET, AND SDR 23.5 FOR DEPTHS GREATER

THAN 30 FEET.

NOT TO

SCALE

CLASS 2

PERMEABLE

MATERIAL

ASPHALT CONCRETE

CURB AND GUTTER

8 INCHES

MINIMUM

SUBGRADE

12 INCHES MINIMUM

ASPHALT CONCRETE

CURB AND GUTTER

12 INCHES

SUBGRADE

GEOTEXTILE WRAPPED

DRAINAGE COMPOSITE

(i.e. Multi-Flow, AdvanEdge)

CLASS 2

AGGREGATE BASE

4 INCHES

MIN.

CLASS 2

AGGREGATE BASE

3 INCH

DIAMETER SDR

23.5 OR PVC

SCHEDULE 40

PERFORATED

PIPE

JO

B N

UM

BE

R: 3823.102 D

AT

E: 6-9-17 D

RA

WN

B

Y: C

C

PLATE 5

PAVEMENT EDGE DRAINS

SCALE N.T.S.

NOTES:

1. FOR CROWNED STREETS, PAVEMENT EDGE DRAIN TO BE INSTALLED ON

BOTH SIDES OF STREET. FOR FIXED CROSS SLOPE STREETS, PAVEMENT

EDGE DRAIN TO BE INSTALLED ON LOW SIDE OF STREET.

ALTERNATIVE A:

1. PERFORATED PIPE TO BE SURROUNDED BY AT LEAST 2 INCHES OF CLASS

2 PERMEABLE MATERIAL.

2. PERFORATED PIPE TO DISCHARGE INTO CATCH BASIN/DRAIN INLET.

3. PERFORATED PIPE TO BE LOCATED BELOW EXISTING SHALLOW

UNDERGROUND UTILITIES WHERE THEY CROSS.

ALTERNATIVE B:

1. DRAINAGE COMPOSITE MAY BE PLACED DIRECTLY AGAINST CUT BANK AT

THE PAVEMENT STRUCTURE EDGE SHOWN.

2. DRAINAGE COMPOSITE TO DISCHARGE INTO CATCH BASIN/DRAIN INLET.

3. DRAINAGE COMPOSITE TO BE LOCATED BELOW EXISTING SHALLOW

UNDERGROUND UTILITIES WHERE THEY CROSS.

ALTERNATIVE A ALTERNATIVE B

GARAGE

ANCHOR

BOLT

ANCHOR

BOLT

ENGINEERED FILL

2 LAYERS 15 MIL

PLASTIC SHEETING

3 FEET BELOW

BOTTOM OF PT SLAB

MINIMUM

6 INCHES

MAXIMUM

2-1/2 FEET

(TYPICAL)

VAPOR RETARDER

TO BUILDING

PERIMETER

OR LIMITS OF

DESIGNATED

BUILDING

ENVELOPE.

4 INCH

CAPILLARY

BREAK

4 INCH

CAPILLARY

BREAK

4 INCH

CAPILLARY

BREAK

JO

B N

UM

BE

R: 3823.102 D

AT

E: 6-9-17 D

RA

WN

B

Y: C

C

PLATE 6

FOUNDATION DECOUPLING DETAIL

12 INCHES

MIRADRAIN (PLASTIC TO WALL)

PERFORATED PIPE

(ENCAPSULATE WITH

CLASS 2 PERMEABLE

MATERIAL)

12 INCHES

FINISH GRADE

JO

B N

UM

BE

R: 3823.102 D

AT

E: 6-16-17 D

RA

WN

B

Y: C

C

PLATE 7

RETAINING WALL BACK DRAIN DETAIL

Cross-Section 1 – Slope Stability Analysis – Static Condition

PLATE 8

JOB

NU

MBE

R: 3

823.

100

D

ATE

: 6-

16-2

017

Cross-Section 1 – Slope Stability Analysis – Pseudo-Static Condition

JOB

NU

MBE

R: 3

823.

100

JOB

NU

MBE

R:D

ATE

: 6-

16-2

017

PLATE 9


APPENDIX A

Boring Logs and Key to Boring Logs

11

12

30

9

15

CL

CL

CL

SILTY CLAY, gray-brown, moist to wet, stiff to very stiff, trace fine-to coarse-grainedsand, trace fine gravel

SANDY CLAY, light gray-brown, moist, very stiff to hard, fine-to coarse-grained sand,crushed rock fragments, trace fine gravel below 4-1/2 feet, hard drilling

SILTY CLAY, gray-brown, moist, stiff, trace fine-to medium-grained sand, limonitestains

Bottom of borehole at 11.5 feet.

NOTES

GROUND ELEVATION 161 ft

LOGGED BY ROV

DRILLING METHOD Hollow Stem Auger 2.5" I.D. Split Barrel

DRILLING CONTRACTOR Pitcher Drilling

DATE STARTED 3/21/17 COMPLETED 3/21/17

GROUNDWATER: No Groundwater Encountered

DE

PT

H(f

t)

0

5

10

PLA

ST

ICIT

YIN

DE

XP

LAS

TIC

ITY

IND

EX

LIQ

UID

LIM

IT

DR

Y U

NIT

WT

.(p

cf)

FIN

ES

CO

NT

EN

TP

AS

SIN

G #

200

Modified CaliforniaSampler

StandardPenetration Test

SA

MP

LER

BLO

WC

OU

NT

US

CS

MATERIAL DESCRIPTION

MO

IST

UR

EC

ON

TE

NT

(%

)

PAGE 1 OF 1BORING NUMBER B-1

ELE

VA

TIO

N(f

t)

160

155

150

CLIENT The Grupe Company

PROJECT NUMBER 3823.102

PROJECT NAME Ersted - Tennyson Property

PROJECT LOCATION Hayward, CA

Berlogar Stevens & Associates5587 Sunol BoulevardPleasanton, CA 94566

BE

RLO

GA

R N

O G

RO

UN

DW

AT

ER

- G

INT

ST

D U

S.G

DT

- 6

/20/

17 1

4:13

- S

:\PR

OJE

CT

S\3

823.

102\

3823

.102

BO

RIN

GS

.GP

J

A-1

94

113

113

15

20

32

20

27

CL

CL

CL

SILTY CLAY, gray-brown, moist, stiff, trace fine-to coarse-grained sand

below 3 feet, stiff to very stiff

SILTY CLAY, light cream-gray-brown, moist, very stiff, trace to some fine-tocoarse-grained sand, fine gravel

SILTY CLAY, gray-brown, moist, hard, trace fine-to coarse-grained sand, trace finegravel

25.0

19.0

17.0

NOTES


LOGGED BY ROV





DE

PT

H(f

t)

0

5

10

15

20(Continued Next Page)

PLA

ST

ICIT

YIN

DE

XP

LAS

TIC

ITY

IND

EX

LIQ

UID

LIM

IT

DR

Y U

NIT

WT

.(p

cf)

FIN

ES

CO

NT

EN

TP

AS

SIN

G #

200


SA

MP

LER

BLO

WC

OU

NT

US

CS


MO

IST

UR

EC

ON

TE

NT

(%

)


ELE

VA

TIO

N(f

t)

145

140

135

130






BE

RLO

GA

R N

O G

RO

UN

DW

AT

ER

- G

INT

ST

D U

S.G

DT

- 6

/20/

17 1

4:13

- S

:\PR

OJE

CT

S\3

823.

102\

3823

.102

BO

RIN

GS

.GP

J

A-2

11143

100

60-6

CL SILTY CLAY, gray-brown, moist, hard, trace fine-to coarse-grained sand, trace finegravel (continued)

CLAYEY SILTSTONE, gray-brown, friable, highly fractured to crushed, partiallydecomposed into clay/silty clay


16.0

DE

PT

H(f

t)

20

25

30

PLA

ST

ICIT

YIN

DE

XP

LAS

TIC

ITY

IND

EX

LIQ

UID

LIM

IT

DR

Y U

NIT

WT

.(p

cf)

FIN

ES

CO

NT

EN

TP

AS

SIN

G #

200

SA

MP

LER

BLO

WC

OU

NT

US

CS


MO

IST

UR

EC

ON

TE

NT

(%

)


ELE

VA

TIO

N(f

t)

125

120






BE

RLO

GA

R N

O G

RO

UN

DW

AT

ER

- G

INT

ST

D U

S.G

DT

- 6

/20/

17 1

4:13

- S

:\PR

OJE

CT

S\3

823.

102\

3823

.102

BO

RIN

GS

.GP

J

A-3

CL

GC/CL

SILTY CLAY, dark gray-brown, moist, medium stiff

CLAYEY GRAVEL/GRAVELLY CLAY, light gray-brown, moist, medium dense todense/very stiff


NOTES


LOGGED BY KK


DRILLING CONTRACTOR Hand Auger



DE

PT

H(f

t)

0

5

PLA

ST

ICIT

YIN

DE

XP

LAS

TIC

ITY

IND

EX

LIQ

UID

LIM

IT

DR

Y U

NIT

WT

.(p

cf)

FIN

ES

CO

NT

EN

TP

AS

SIN

G #

200

SA

MP

LER

BLO

WC

OU

NT

US

CS


MO

IST

UR

EC

ON

TE

NT

(%

)


ELE

VA

TIO

N(f

t)

115






BE

RLO

GA

R N

O G

RO

UN

DW

AT

ER

- G

INT

ST

D U

S.G

DT

- 6

/20/

17 1

4:13

- S

:\PR

OJE

CT

S\3

823.

102\

3823

.102

BO

RIN

GS

.GP

J

A-4

20

23

33

34

CL

CL

CL

CL

SILTY CLAY, gray-brown, moist, stiff, trace fine-to medium-grained sand,

SILTY CLAY, light gray-brown, moist, stiff to very stiff, trace fine-to coarse-grainedsand, trace fine gravel

SILTY CLAY, light gray, moist, very stiff, white and gray-brown mottling

SANDY CLAY, light green-gray, moist, very stiff, fine-to coarse-grained sand, tracefine gravel


NOTES


LOGGED BY ROV





DE

PT

H(f

t)

0

5

10

PLA

ST

ICIT

YIN

DE

XP

LAS

TIC

ITY

IND

EX

LIQ

UID

LIM

IT

DR

Y U

NIT

WT

.(p

cf)

FIN

ES

CO

NT

EN

TP

AS

SIN

G #

200



SA

MP

LER

BLO

WC

OU

NT

US

CS


MO

IST

UR

EC

ON

TE

NT

(%

)


ELE

VA

TIO

N(f

t)

125

120

115






BE

RLO

GA

R N

O G

RO

UN

DW

AT

ER

- G

INT

ST

D U

S.G

DT

- 6

/20/

17 1

4:13

- S

:\PR

OJE

CT

S\3

823.

102\

3823

.102

BO

RIN

GS

.GP

J

A-5

8613

14

21

19

35

CL

CL

CL

SILTY CLAY, gray-brown, moist, stiff, trace fine-to medium-grained sand

SILTY CLAY, white-gray, moist, stiff, trace medium-to coarse-grained sand, tracefine-to coarse gravel, caliche stains

below 5 feet, mixed with green-brown rock fragments

SILTY CLAY, gray-brown, moist, stiff, white and black mottling


21.0

NOTES


LOGGED BY ROV





DE

PT

H(f

t)

0

5

10

15

PLA

ST

ICIT

YIN

DE

XP

LAS

TIC

ITY

IND

EX

LIQ

UID

LIM

IT

DR

Y U

NIT

WT

.(p

cf)

FIN

ES

CO

NT

EN

TP

AS

SIN

G #

200



SA

MP

LER

BLO

WC

OU

NT

US

CS


MO

IST

UR

EC

ON

TE

NT

(%

)


ELE

VA

TIO

N(f

t)

115

110

105






BE

RLO

GA

R N

O G

RO

UN

DW

AT

ER

- G

INT

ST

D U

S.G

DT

- 6

/20/

17 1

4:13

- S

:\PR

OJE

CT

S\3

823.

102\

3823

.102

BO

RIN

GS

.GP

J

A-6

105

113

18

37

38

43

40

CL

CL

CL

SILTY CLAY, dark gray-brown, moist, stiff, trace fine-to coarse gravel

SILTY CLAY, light to medium gray-brown, moist, very stiff, some fine-tocoarse-grained sand, trace fine gravel

below 14 feet, medium brown

SANDY CLAY, red-brown, moist, hard, fine-to coarse-grained sand, trace fine-tocoarse gravel, some silt

18.0

13.0

NOTES


LOGGED BY ROV





DE

PT

H(f

t)

0

5

10

15

20(Continued Next Page)

PLA

ST

ICIT

YIN

DE

XP

LAS

TIC

ITY

IND

EX

LIQ

UID

LIM

IT

DR

Y U

NIT

WT

.(p

cf)

FIN

ES

CO

NT

EN

TP

AS

SIN

G #

200


SA

MP

LER

BLO

WC

OU

NT

US

CS


MO

IST

UR

EC

ON

TE

NT

(%

)


ELE

VA

TIO

N(f

t)

115

110

105

100






BE

RLO

GA

R N

O G

RO

UN

DW

AT

ER

- G

INT

ST

D U

S.G

DT

- 6

/20/

17 1

4:13

- S

:\PR

OJE

CT

S\3

823.

102\

3823

.102

BO

RIN

GS

.GP

J

A-7

113

53

46

65

CL

SC

SANDY CLAY, red-brown, moist, hard, fine-to coarse-grained sand, trace fine-tocoarse gravel, some silt (continued)

CLAYEY SAND with GRAVEL, light to medium gray-brown, saturated, dense, fine-tocoarse-grained sand, fine-to coarse gravel

CLAYSTONE (highly weathered bedrock), green-brown, friable, crushed, lowhardness


12.0

DE

PT

H(f

t)

20

25

30

PLA

ST

ICIT

YIN

DE

XP

LAS

TIC

ITY

IND

EX

LIQ

UID

LIM

IT

DR

Y U

NIT

WT

.(p

cf)

FIN

ES

CO

NT

EN

TP

AS

SIN

G #

200

SA

MP

LER

BLO

WC

OU

NT

US

CS


MO

IST

UR

EC

ON

TE

NT

(%

)


ELE

VA

TIO

N(f

t)

95

90

85






BE

RLO

GA

R N

O G

RO

UN

DW

AT

ER

- G

INT

ST

D U

S.G

DT

- 6

/20/

17 1

4:13

- S

:\PR

OJE

CT

S\3

823.

102\

3823

.102

BO

RIN

GS

.GP

J

A-8


APPENDIX B


Exploratory Trench and Test Pit Logs

A

A

SOUTH END

0+00 0+10 0+20 0+30 0+40

NORTH END

B

C

D

E

B

CALCIUM CARBONATE

LIGHT BROWN CLAY SEAM

CALCIUM

CARBONATE

VEIN

RELIC BEDDING (?)

CALCIUM CARBONATE

STRINGERS

FAULT

E-W 53°N

CLAY GOUGE

A

SOUTH END

0+00 0+10 0+20 0+30 0+40 0+50 0+60

NORTH END

0+70 0+80

ANGULAR COBBLES OF

SERPENTINITE

SERPENTINIZED BASALT

BOLDER

SHEAR INFILLED

WITH CALCIUM

CARBONATE

SEEPSHEAR INFILLED

WITH CALCIUM

CARBONATE

N48°W 90°

1/2 INCH GOUGE SEAM

N48°W

SHEAR WITH CALCIUM

CARBONATE

B

B

C

C

C D

E

D

D

CAVING

A

A

G

B

C

D

E

F

H

F

I

COMPLETELY

WEATHERED

BASALT, BLACK

E-W 27°N

ON SOUTH SIDE OF

TRENCH

HIGHLY FRACTURED,

HIGHLY WEATHERED,

VOLCANIC ROCK

SEEP

SEEP

SOUTH END

0+00 0+10 0+20 0+30 0+40 0+50 0+60 0+70 0+80

NORTH END

0+90

CARBONATE RICH CLAY

VEIN, GRAY-BLUE TO BLUE,

SATURATED, VERY SOFT

F

I

G

CLAY, WHITE, WET,

VERY STIFF, SOFT

FAULT

E-W 27°N

CLAY, BLUE, WET TO

SATURATED, VERY SOFT

0+600+700+80

NORTH END

0+50

SOUTH END

0+00 0+10 0+20

NORTH END

CALCIUM CARBONATE

VEIN N80°W 32°E

A

B

C

?

?

?

A

A

A

B

C

D

E

F

G

H

H

J

K

B

I

POCKET PENTROMETER >3

COMPLETELY WEATHERED

SERPENTINITE CLAY,

GREEN, WET, SOFT TO

MEDIUM STIFF

CARBONATE VEIN,

N55°W 88°N

CARBONATE VEIN,

N57°W 27°E

SOUTH END

0+00 0+10 0+20 0+30

0+40 0+50 0+60

0+70 0+80

0+90

1+00 1+10 1+20 1+30 1+40

NORTH END

SOUTH END

0+00 0+10 0+20

0+30 0+40 0+50 0+60

NORTH END

0+70

A

A

B

C

C

D

E

F

G

ANGULAR COBBLES

VOLCANIC ROCK

ROUNDED VOLCANIC

AND LIMESTONE

COBBLES, FRACTURED

N48°E 25°N

JO

B N

UM

BE

R: 3

82

3.1

01

D

AT

E: 3

-1

7-1

7 D

RA

WN

B

Y: C

C

PLATE 4

TRENCH LOGS

TRENCH T-7 THROUGH T-12

TENNYSON

HAYWARD, CALIFORNIA

FOR

THE GRUPE COMPANY



0 5

1"=5'

TRENCH T-7

LOG OF NORTH WALL

TREND N28°E

TRENCH T-8

LOG OF NORTH WALL

TREND N34°E

TRENCH T-9

LOG OF NORTH WALL

TREND N18°E

TRENCH T-9

PARTIAL LOG OF SOUTH WALL

TRENCH T-10

LOG OF NORTH WALL

TREND N40°E

TRENCH T-11

LOG OF NORTH WALL

TREND N25°E

TRENCH T-12

LOG OF NORTH WALL

TREND N-S

GROUND SURFACE AND BOTTOM OF TRENCH

GEOLOGIC CONTACT, SOLID WHERE SHARP, DASHED

WHERE APPROXIMATE

CLAYEY SAND, MIXED MEDIUM TO DARK BROWN, SLIGHTLY

DAMP, LOOSE (FILL)

SILTY CLAY WITH ANGULAR ROCK FRAGMENTS, MEDIUM TO

LIGHT RED-BROWN, STIFF TO VERY STIFF

CLAY WITH SCATTERED COBBLES, MEDIUM TO DARK

BROWN, MOIST, VERY STIFF, SCATTERED VEINS OF

CALCIUM CARBONATE CUTTING THROUGH RELIC BEDS(?),

COBBLES ARE ROUNDED TO WELL-ROUNDED BASALT,

SLIGHTLY WEATHERED WITH THIN WEATHERING RIND

GRAVELLY CLAY, WHITE TO LIGHT GRAY, DRY, STIFF TO

VERY STIFF, CALCIUM CARBONATE BEDS MIXED WITH

BLACK CLAY

CLAY, MEDIUM BROWN, MOIST, STIFF TO VERY STIFF

T-7 EXPLANATION

A

B

C

D

E



WHERE APPROXIMATE

SANDY CLAY, MEDIUM YELLOW-GRAY TO DARK

ORANGE-GRAY, MOIST, STIFF, SAND IS CALCIUM

CARBONATE NODULES, SOME DECOMPOSED QUARTZ

GRAVEL

SANDY CLAY, LIGHT TO MEDIUM GRAY, CALCIUM

CARBONATE RICH, DRY, STIFF TO VERY STIFF

BASALT, DARK GREEN BROWN, COMPLETELY WEATHERED,

SERPENTINIZED

CLAY WITH MINOR GRAVEL, RED TO ORANGE-BROWN,

MOIST, STIFF TO VERY STIFF, GRAVEL IS WELL-ROUNDED

QUARTZ, MANY VERTICAL CALCIUM CARBONATE

STRINGERS NEAR TOP OF UNIT

CLAY WITH PERVASIVE CALCIUM CARBONATE, MOTTLED

VERY DARK GRAY AND WHITE, DRY TO MOIST, VERY STIFF

T-8 EXPLANATION

A

B

C

D

E



WHERE APPROXIMATE

SILTY CLAY, RED-BROWN, MOIST, STIFF

SANDY CLAY WITH SCATTERED GRAVEL, MEDIUM

RED-GRAY-BROWN, MOIST, STIFF TO VERY STIFF

GRAVELLY SANDY CLAY, MEDIUM TO DARK BROWN, SOME

CALCIUM CARBONATE STRINGERS, DRY TO MOIST, VERY

STIFF, GRAVEL IS ANGULAR BASALT

SANDY CLAY, DARK GRAY TO BLACK, DRY, MEDIUM STIFF

CALCIUM CARBONATE, LIGHT GRAY TO WHITE, DRY,

FRIABLE, SLICKS ON CAVED SURFACE

SANDY CLAY WITH GRAVEL, RED-BROWN, MOIST

SANDY CLAY, MEDIUM BROWN, MOIST, SOFT TO MEDIUM

STIFF, RAGS, WOOD DEBRIS AT STATION 0+70 (FILL)

SANDY CLAY WITH GRAVEL, DARK BROWN, MOIST, VERY

STIFF, GRAVEL IS ANGULAR BASALT

SILTY CLAY, RED-BROWN, DRY TO MOIST, VERY STIFF

T-9 EXPLANATION

A

B

C

D

E



WHERE APPROXIMATE

SILTY CLAY, DARK GRAY-BROWN, MOIST, VERY SOFT TO

SOFT

SILTY CLAY, MEDIUM TO DARK GRAY TO BLACK, MOIST TO

WET, STIFF TO VERY STIFF, CAVED IN CONCODIAL BLOCKS

6-10 INCH MAXIMUM DIAMETER

SILTY TO SANDY CLAY, MEDIUM BROWN, MOIST, STIFF,

REMNANT BEDDING PARALLEL TO CALCIUM CARBONATE

VEIN

T-10 EXPLANATION

A

B

C



WHERE APPROXIMATE

SILTY CLAY, DARK GRAY TO BLACK, MOIST, SOFT

SILTY CLAY, DARK GRAY-BROWN WITH WHITE MOTTLING,

MOIST, STIFF TO VERY STIFF, MOTTLING IS CALCIUM

CARBONATE UP TO 1 INCH DIAMETER

SILTY CLAY, MEDIUM ORANGE-BROWN, MOIST, STIFF

CLAY, BLUE-GRAY WITH WHITE NODULES AND STREAKS OF

CALCIUM CARBONATE, MOIST, STIFF

SILTY CLAY, MEDIUM ORANGE-BROWN, DRY, VERY STIFF

CLAY WITH SILT AND GRAVEL, MEDIUM OLIVE-BROWN TO

BROWN-GRAY, DRY, VERY STIFF TO HARD, GRAVEL IS

ANGULAR SILTSTONE, SOME CALCIUM CARBONATE

NODULES UP TO 2-1/2 INCH DIAMETER

SANDY CLAY WITH GRAVEL, MEDIUM TO LIGHT GRAY, DRY,

VERY STIFF, GRAVEL IS WELL ROUNDED AND BROKEN

VOLCANIC ROCK (BASALT?)

SILTSTONE, HIGHLY TO COMPLETELY WEATHERED, HIGHLY

FRACTURED

SILTY CLAY, ORANGE-BROWN, DRY, VERY STIFF TO HARD

SILTY CLAY, DARK GRAY AND BROWN, DRY, HARD,

CONTAINS STRETCHED CALCIUM CARBONATE STRINGERS

CLAYSTONE, ORANGE-BROWN, DRY, HARD, CONTAINS

CALCIUM CARBONATE NODULES APPROXIMATELY 1/2 INCH

DIAMETER

T-11 EXPLANATION

A

B

C

D

E



WHERE APPROXIMATE

SILTY SANDY CLAY, DARK GRAY TO BLACK, DRY TO MOIST,

STIFF

CLAY, LIGHT GRAY TO WHITE, MOIST, STIFF

SILTY CLAY, MEDIUM OLIVE-BROWN, DRY, VERY STIFF

SILTY CLAY WITH COBBLES, DARK GRAY-BROWN, DRY,

VERY STIFF, ABUNDANT CALCIUM CARBONATE NODULES

UP TO 1/2 INCH DIAMETER

CLAY, GREEN-GRAY, MOIST TO WET, STIFF

CLAY, BLACK, MOIST, SOFT

SILTY CLAY, ORANGE-BROWN, MOIST, STIFF TO VERY STIFF

T-12 EXPLANATION

A

B

C

D

E

145

ELE

VA

TIO

N IN

F

EE

T

150

155

160

ELE

VA

TIO

N IN

F

EE

T

135

140

145

ELE

VA

TIO

N IN

F

EE

T

135

140

145

ELE

VA

TIO

N IN

F

EE

T

140

145

150

ELE

VA

TIO

N IN

F

EE

T

140

145

150

145

ELE

VA

TIO

N IN

F

EE

T150

155

140

145

ELE

VA

TIO

N IN

F

EE

T

150

140

ELE

VA

TIO

N IN

F

EE

T

150

155

160

ELE

VA

TIO

N IN

F

EE

T

125

130

135

140

145

ELE

VA

TIO

N IN

F

EE

T

145

150

155

160

165

ELE

VA

TIO

N IN

F

EE

T

140

145

150 ELE

VA

TIO

N IN

F

EE

T

150

155

160

145

F

G

H

I

F

G

H

I

J

K

F

G

SILTY CLAY, DARK

GRAY-BLACK TO DARK

BROWN, MOIST, SOFT TO

MEDIUM STIFF (COLLUVIUM)

(POCKET PENTROMETER 1.5)

SILTY CLAY, MEDIUM BROWN, MOIST,

SOFT TO MEDIUM STIFF (COLLUVIUM)


CLAY, DARK GRAY TO BLACK WITH

WHITE MOTTLING, MOIST, STIFF,

ABUNDANT CALCIUM CARBONATE

NODULES UP TO 1 INCH DIAMETER

(GRADATIONAL CONTACT ABOVE)

SILTY CLAY, LIGHT

TAN-BROWN, MOIST, STIFF

(SHARP CONTACT ABOVE)

SILTY CLAY, DARK GRAY-BLACK

TO DARK BROWN, MOIST, SOFT

TO MEDIUM STIFF, ANGULAR

QUARTZ GRAVEL NEAR BASE

(COLLUVIUM)

CLAYEY GRAVEL, LIGHT BROWN,

MOIST, DENSE, GRAVEL IS

QUARTZ AND VOLCANIC

SILTY CLAY, DARK

GRAY-BLACK TO DARK



SILTSTONE, MEDIUM BROWN-GRAY,

HIGHLY WEATHERED, VERY CLOSE

FRACTURING, WEAK, ROCK FRAGMENTS

HAVE WEATHERING RINDS AND IN PLACES,

COMPLETELY WEATHERED, SOME

SERPENTINIZED ROCK WITH NOA FIBERS

SILTY CLAY, DARK

GRAY-BLACK , MOIST,

STIFF (COLLUVIUM)

(POCKET

PENTROMETER 1.5)


WHITE MOTTLING, MOIST, CALCIUM

CARBONATE NODULES UP TO 1 INCH

DIAMETER WITH CLUSTER OF 3 INCH,


CLAY, BLUE-GRAY, MOIST,

STIFF TO VERY STIFF

SILTY CLAY, MEDIUM

ORANGE-BROWN, MOIST, VERY STIFF



WHITE MOTTLING, MOIST, CALCIUM

CARBONATE NODULES UP TO 1 INCH

DIAMETER WITH CLUSTER OF 3 INCH,


SILTY CLAY, DARK

GRAY-BLACK TO DARK




SILTY CLAY, LIGHT

BLUE-GRAY, MOIST,

VERY STIFF

TP-3

TREND N18°W

TP-1

TREND N23°E

TP-2

TREND N18°W

TP-4

TREND N5°W

TP-5

TREND N29°E

EL

EV

AT

IO

N IN

F

EE

T

155

160

165

170

EL

EV

AT

IO

N IN

F

EE

T

155

160

165

150

EL

EV

AT

IO

N IN

F

EE

T

140

145

EL

EV

AT

IO

N IN

F

EE

T

110

115

120

EL

EV

AT

IO

N IN

F

EE

T

125

130

135

GRAPHIC TEST

PIT LOGS

TENNYSON

HAYWARD, CALIFORNIA

FOR

THE GRUPE COMPANY



JO

B N

UM

BE

R: 3823.101 D

AT

E: 3-17-17 D

RA

WN

B

Y: C

C

PLATE 5

0 5

1"=5'

EXPLANATION

GROUND SURFACE AND TEST PIT LIMITS

GEOLOGIC CONTACT, SOLID WHERE

SHARP, DASHED WHERE GRADATIONAL


APPENDIX C

Engeo

Exploratory Trench Logs

1

2

24

25

26

27

26

28

1

29

1

16

17

13

15

18

17

13

15

1

16

15

13

19

161

1522

22

24

23

16 1

1

2

3

4

5

6

7

8 10

9

11

12

12

14

1

13

16

1513

17

15

1

16

17

13

1

2

35 4 32

33

34

1

2

32

33 31

30

3

4

1

2

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

31

32

33

34

35

24

25

26

27

28

29

30

19

20

21

22

23


APPENDIX D

Geotechnical Laboratory Test Results

Berlogar Stevens & Associates Pleasanton, CA

Final Moisture Content, %: 19.4 19.0

Graph of Shear Stress vs Normal Stress

Sh

ear S

tress (

psf)

Normal Stress (psf)

Peak Cohesion, (C' ), psf: 736 Peak Friction Angle, (Ф'peak), Degrees: 15.7

Initial Dry Density, pcf: 110.9 112.1

Initial Moisture Content, %: 15.8 15.8

Peak Shear Stress, psf: 1,158 1,722

Summary of Results

Normal Stress, psf: 1,500 3,500 0

Maximum Dry Density, pcf: 0.0 Minimum Required Compaction, %: 0.0

Optimum Moisture Content, %: 0.0 Minimum Compacted Moisture Content, %: 0.0

Material Description: Silty Clay Dark Gray Invoice Number: 15192

Sample Type: Undisturbed Test Type: CD Shear Rate, inches/min.: 0.00099

Sample ID: B2 at 20-1/2ft Date Tested: 04/04/17

Direct Shear - ASTM D-3080

Project Name: Tennyson Project Number: 3823.102

y = 0.2818x + 735.72

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

Peak Friction Angle




Sh

ear S

tress (

psf)

Normal Stress (psf)

Peak Cohesion, (C' ), psf: 470 Peak Friction Angle, (Ф'peak), Degrees: 29.4




Summary of Results

Normal Stress, psf: 1,000 2,500



Material Description: Sandy Clay Dark Red Brown Invoice Number: 15192



Direct Shear - ASTM D-3080


y = 0.5635x + 469.61

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

Peak Friction Angle


Direct Shear Worksheet ASTM D-3080


Material Description: Sandy Clay with Gravel Yellow Brown Dark Brown Mix Invoice Number: 15192




Summary of Results

Normal Stress, psf: 1,500 4,000 0







Sh

ear S

tress (

psf)

Normal Stress (psf)

Peak Cohesion, (C' ), psf: 37.5 Peak Friction Angle, (Ф'peak), Degrees: 42.5

y = 0.9142x + 37.568

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500

Peak Friction Angle

Sample ID.: B2 at 10-11ft

Sample Description: Silty Clay Light Olive Gray with Caliche

1 2

749 2002

112.5 117.1

19.2 17.8

Total

Stress

Effective

Stress

Cohesion (psf) 950 700

Friction Angle (degrees) 12.7 17.4

Consolidated Moisture Content (%)

TRIAXIAL COMPRESSION TEST - TXCU - ASTM D4767

Specimen

Consolidaiton Pressure

Consolidated Dry Density (pcf)

y = 0.3125x + 0.7

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00

Shea

r St

ress

(ks

f)

Normal Stress (ksf)

Effective Stress

y = 0.225x + 0.95

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00

Shea

r St

ress

(ks

f)

Normal Stress (ksf)

Total Stress


Sample Description: Sandy Clay with Gravel Red Brown

1 2

504 1498

111.1 116.0

18.2 17.9

Total

Stress

Effective

Stress





Specimen



y = 0.4x + 0.62

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00

Shea

r St

ress

(ks

f)

Normal Stress (ksf)

Effective Stress

y = 0.34x + 0.93

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00

Shea

r St

ress

(ks

f)

Normal Stress (ksf)

Total Stress


Sample Description: Sandy Clay Red Brown

1 2

504 2002

116.6 120.7

16.8 15.1

Total

Stress

Effective

Stress





Specimen



y = 0.23x + 0.98

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00

Shea

r St

ress

(ks

f)

Normal Stress (ksf)

Effective Stress

y = 0.1375x + 1.25

0.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00

Shea

r St

ress

(ks

f)

Normal Stress (ksf)

Total Stress


Pe

rc

en

t P

as

sin

g

Sieve Opening, mm

Tested By: gs Reported By: G. Suckow

04/03/17

Project Name: Tennyson Sample ID: B6 at 25ft Project Number: 3823.102

Invoice Number: 15192 Sample Description: Clayey Sand with Gravel Date Tested:

0

10

20

30

40

50

60

70

80

90

100

0.00.11.010.0100.0

Gradation

3823.102

4/5/2017

15192

G. Suckow

SymbolASTM D4318 Plasticity

Index:

41

Gradation Test Data ASTM D 422

Sample ID Description

Comments: Date:

Project Name: Tennyson

Tested By: Reported By:gs

Project No:


B6 at 2-1/2ft CH Silty Clay Gray

Invoice Number:

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.11101001000

COBBLES SILT/CLAYGRAVEL SAND

coarse coarse medium finefine

12" 3" 1 1/2" 3/4" 3/8" #4 #8 #16 #30 #50 #100 #200

3823.102

4/12/2017

15206

G. Suckow


Index:

43


TP1 at 6ft CH Silty Clay with Sand Dark Gray Brown

Invoice Number:



Comments: Date:



Project No:

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.11101001000



12" 3" 1 1/2" 3/4" 3/8" #4 #8 #16 #30 #50 #100 #200

3823.102

4/12/2017

15206

G. Suckow


Index:

23



Comments: Date:



Project No:


TP4 CL Sandy Clay Light Olive Gray

Invoice Number:

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.11101001000



12" 3" 1 1/2" 3/4" 3/8" #4 #8 #16 #30 #50 #100 #200

Date Tested:

63 22

E2 e3 e4 3c 1m 1e

35 24 18 13

13.82 13.61 13.69 13.61 11.46 11.68

18.77 18.45 19.74 19.89 13.17 14.03

16.91 16.58 17.39 17.44 12.87 13.61

60.2 63.0 63.5 64.0 21.3 21.8


Tested By: kk Reported By: G Suckow

Liquid Limit: Plastic Limit: Plasticity Index: 41

Classification: CH Fat Clay

Material Description: CH Silty Clay Gray Invoice Number: 15192

Summary of Test Results

Sample ID: B6 at 2-1/2ft 04/05/17

Atterberg Limits Test Data ASTM D 4318


Dry Soil + Tare Mass, (g):

Moisture Content, %:

Liquid Limit Plastic Limit

Tare ID:

Number Of Blows:

Tare Mass, (g):

Wet Soil + Tare Mass, (g):

0

10

20

30

40

50

60

10 20 30 40 50 60 70 80 90 100

Pla

sti

cit

y I

nd

ex (

PI)

Liquid Limit (LL)

Liquid Limit - Plasticity Chart

CH

MH & OH

CL

ML & OL

"A" Line

25 56

57

58

59

60

61

62

63

64

65

66

10 100

Flow Curve

Mo

istu

re C

on

ten

t(%

)

Number of Blows

25

cl-ml

Date Tested:

63 20

e1 e2 e3 e4 1 1e 1o

34 26 19 16

13.72 13.78 13.60 13.66 11.54 11.48 11.61

16.67 19.22 20.10 21.19 14.29 13.99 14.67

15.57 17.12 17.53 18.19 13.78 13.53 14.25

59.5 62.9 65.4 66.2 22.8 22.4 15.9




Classification: CH Fat Clay

Material Description: CH Silty Clay with Sand Dark Gray Brown Invoice Number: 15206


Sample ID: TP1 at 6ft 04/13/17






Tare ID:

Number Of Blows:

Tare Mass, (g):


0

10

20

30

40

50

60

10 20 30 40 50 60 70 80 90 100

Pla

sti

cit

y I

nd

ex (

PI)

Liquid Limit (LL)


CH

MH & OH

CL

ML & OL

"A" Line

25 57

58

59

60

61

62

63

64

65

66

67

10 100

Flow Curve

Mo

istu

re C

on

ten

t(%

)

Number of Blows

25

cl-ml

Date Tested:

42 19

6i 6l 6p 6f 1a 1d 1k

34 26 21 15

13.80 13.71 13.71 13.63 11.62 11.69 11.61

19.28 20.23 21.64 20.95 15.23 14.75 14.63

17.78 18.33 19.23 18.64 14.65 14.25 14.16

37.7 41.1 43.7 46.1 19.1 19.5 18.4




Tare ID:

Number Of Blows:

Tare Mass, (g):


Sample ID: TP4 04/13/17



Material Description: CL Sandy Clay Light Olive Gray Invoice Number: 15206



Classification: CL Lean Clay



0

10

20

30

40

50

60

10 20 30 40 50 60 70 80 90 100

Pla

sti

cit

y I

nd

ex (

PI)

Liquid Limit (LL)


CH

MH & OH

CL

ML & OL

"A" Line

25 37

38

39

40

41

42

43

44

45

46

47

10 100

Flow Curve

Mo

istu

re C

on

ten

t(%

)

Number of Blows

25

cl-ml

A B C

439

<5 0 0

22.2

106.2

56 0 0

248.1

0.0

<5 Specification:

29


0Resistance Value ( R ) :

% Moisture at Test:

Dry Density at Test, pcf:

0Expansion Dial, (0.0001"):

Expansion Pressure, psf:

Expansion Pressure at 300 psi: psf

R-Value at 300 psi Exudation Pressure:

Sample ID: 04/18/17

Area Sample Represents:

Material Description:

Invoice Number: 15200

Reported By:Silty Clay with Sand Dark Brown with Caliche G Suckow

TP2 at 6 to 8-1/2ft Date Tested:

Exudation Pressure, psi

Sample oozed from under mold by definition RV<5

Specimen Data

DSpecimen

Comments:

Resistance Value ( R ) Value Test

ASTM D2844 and CalTrans CTM 301


-20

-10

0

10

20

30

40

50

60

70

80

90

10001002003004005006007008009001,0001,1001,2001,3001,4001,5001,6001,7001,800

R-V

alue

Exudation Pressure (psi)

0 4 8 12 16 20 24 28 32

94.2 24.6

Load, lbs:

Percent Strain,

%:

Load, lbs:

Percent Strain,

%:0.0 - 86.1 5.74.7 0.2

21.3 0.6 27.2 0.8 32.9 1.0 38.8 1.1 44.2 1.3 50.9 1.5 56.7 1.7 61.4 1.9 70.2 2.3 75.7 2.7 81.1 3.1 85.2 3.4 88.5 3.8 90.8 4.2 92.2 4.6 92.2 5.0 90.2 5.4

Comments:

Summary of Results

Max. Stress, psf: Strain at Failure, %: Dry Density, pcf: Moist. Content, %:

0.000 0 0.300 2,541

Test Data

Strain Gauge Reading, inches: Stress, psf: Strain Gauge

Reading, inches: Stress, psf:

Sample ID: 4/3/2017

Sample Description:

Unconfined Compressive Strength of Cohesive Soils: ASTM-D2166


B2 at 4ft Date Reported:

Silty Clay Dark Gray Brown Plastic Invoice Number: 15192

0.020 0.380 0.010 147 0.340

0.040 845 0.460 0.030 663 0.420

0.060 1,201 0.540 0.050 1,020 0.500

0.080 1,569 0.620 0.070 1,365 0.580

0.100 1,885 0.700 0.090 1,745 0.660

0.140 2,307 0.780 0.120 2,147 0.740

0.180 2,576 0.860 0.160 2,461 0.820

0.220 2,723 0.200 2,665 0.900

0.260 2,743 0.240 2,754

Sketch of Failure

0.280 2,673

Sample Data

Sample Diameter, inch: 2.420

Wet Sample Mass, (g): 740.9Sample Height, inch: 5.230

Wet Density, pcf: 117.4

Tare ID: 411Tare Mass, (g): 73.9

Tare + Wet Sample Mass,(g): 814.5 Drilling FractureTare + Dry Sample Mass, (g): 668.2


Tested By: gs

3823.102


Sample ID: 4/3/2017

Stress vs Strain Curve


Project Name: Tennyson Project Number:

Tested By: gs Reported By: G Suckow


0

1000

2000

3000

4000

5000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Str

es

s (

ps

f)

Strain (%)

112.9 17.1

Load, lbs:

Percent Strain,

%:

Load, lbs:

Percent Strain,

%:0.0 - 114.7 5.118.3 0.2 119.4 5.828.6 0.3 123.7 6.536.8 0.5 127.6 7.244.4 0.7 130.8 7.851.2 0.9 133.5 8.557.0 1.0 135.8 9.262.7 1.2 138.4 9.966.0 1.4 139.9 10.670.0 1.5 141.3 11.273.2 1.7 142.5 11.979.8 2.0 143.8 12.685.2 2.4 144.7 13.389.9 2.7 144.8 14.095.1 3.1 144.8 14.799.2 3.4 145.0 15.3103.1 3.7 106.3 4.1 109.3 4.4 111.5 4.8

Comments:

Summary of Results


0.000 0 0.300 3,407

Test Data



Sample ID: 4/3/2017

Sample Description:




Silty Clay Light Olive Gray Plastic Caliche Invoice Number: 15192

0.020 892 0.380 3,6220.010 572 0.340 3,522

0.040 1,381 0.460 3,7740.030 1,146 0.420 3,709

0.060 1,766 0.540 3,8600.050 1,589 0.500 3,823

0.080 2,038 0.620 3,9170.070 1,940 0.580 3,905

0.100 2,253 0.700 3,9290.090 2,158 0.660 3,926

0.140 2,604 0.780 3,9280.120 2,447 0.740 3,934

0.180 2,886 0.860 3,8690.160 2,738 0.820 3,900

0.220 3,107 0.200 3,000 0.900 3,844

0.260 3,270 0.240 3,192

Sketch of Failure

0.280 3,324

Sample Data





Tare + Wet Sample Mass,(g): 1,009.2Tare + Dry Sample Mass, (g): 872.6


Tested By: gs

3823.102


Sample ID: 4/3/2017






0

1000

2000

3000

4000

5000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Str

es

s (

ps

f)

Strain (%)

105.3 17.5

Load, lbs:

Percent Strain,

%:

Load, lbs:

Percent Strain,

%:0.0 - 16.4 0.2 26.7 0.3 36.8 0.5 47.0 0.7 54.9 0.8 61.9 1.0 66.5 1.2 70.8 1.3 75.0 1.5 78.7 1.7 85.0 2.0 89.8 2.3 93.6 2.7 95.6 3.0 95.6 3.4 94.0 3.7 91.0 4.0 89.0 4.4

Comments:

Summary of Results


0.000 0 0.300

Test Data



Sample ID: 4/3/2017

Sample Description:



B6 at 3-1/2ft Date Reported:

Gravelly Clay Gray Brown Invoice Number: 15192

0.020 833 0.380 0.010 513 0.340

0.040 1,462 0.460 0.030 1,146 0.420

0.060 1,918 0.540 0.050 1,704 0.500

0.080 2,187 0.620 0.070 2,057 0.580

0.100 2,423 0.700 0.090 2,313 0.660

0.140 2,745 0.780 0.120 2,608 0.740

0.180 2,903 0.860 0.160 2,852 0.820

0.220 2,834 0.200 2,893 0.900

0.260 2,665 0.240 2,734

Sketch of Failure

0.280

Sample Data





Tare + Wet Sample Mass,(g): 997.6Tare + Dry Sample Mass, (g): 865.4


Tested By: gs

3823.102


Sample ID: 4/3/2017





B6 at 3-1/2ft Date Reported:

0

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2000

3000

4000

5000

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Str

es

s (

ps

f)

Strain (%)

Appendix D-1 Geotechnical Report - Hayward · 4. Obtaining a drilling permit from Alameda County...

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Transcript of Appendix D-1 Geotechnical Report - Hayward · 4. Obtaining a drilling permit from Alameda County...