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SOIL, FOUNDATION AND GEOLOGICAL ENGINEERS

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on PRO~~fpj;~PrNT ;~~~··l) ' .:·,·~·~iJ', ~

13575 Lake Chabot Road San Leandro, California

for SIGNATURE PROPERTIES

By

TERRASEARCH, INC .

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·-~ GEOTECHNICAL ENGINEERS AND GEOLOGISTS

,.~ 'l~l~ltltA S~Altt~H INt:. 15e<I NORTH FOURTH STREET, SAN JOSE, CALIFORNIA 95112-4676, (408) 453-1180

Project No. 6063 18 December 1989

Signature Properties 6612 OWens Drive Pleasanton, CA 94566

Attention: Mr. Jim McKeehan

Subject:

Refs;

Gentlemen:

San Leandro Rock Quarry 13575 Lake Chabot Road San Leandro, California GEOTECHNICAL ENGINEERING INVESTIGATION

l) Geologic/Seismic Investigation Report By TERRASEARCH, INC. Dated August 2, 1989

2) Environmental '.resting Results By TERRASEARCH, INC. Dated July 24, 1989

3) Fault Location Investigation By Cleary Consultants, Inc. Dated December 27, 1977

In accordance with your authorization, TERRASEARCH, INC., has investigated the geotechnical conditions at the subject site of the proposed residential development in San Leandro, California .

The accompanying report presents our conclusions and recommendations based on our investigation. Our findings indicate that the site is physically suitable for the proposed construction provided.the recommendations of this report are carefully followed and are incorporated into the plans and specifications •

I 11840 DUBLIN BOULEVARD, DUBLIN, CALIFORNIA 94568, (415) 833-9297

2349 NORTH WATNEY WAY, BLDG. A, FAIRFIELD, CALIFORNIA 94533, (707) 422-3292

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Should you have any questions relating to the contents of this report or should additional information be required, please contact our office at your convenience •

Reviewed by:

~~~~. Principal Engineer

Very truly yours, TERRASEARCH, INC.

~~.e/ • :' : . ~. ·~·; 1! . t11Hiibiinr

Staff Engineer

Copies: 6 to Signature Properties

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Project No. 6063 18 Decmeber 1989

TABLE OF CONTENTS

LETTER OF TRANSMITTAL

GEOTECHNICAL ENGINEERING INVESTIGATION

Purpose and Scope Proposed Development Site Location and Description Soil Conditions Liquefaction Potential Evaluation

DISCUSSIONS, CONCLUSIONS AND RECOMMENDATIONS

General Demolition Grading Slopes Drainage Remedial Measures and Mitigation of

Existing Slide Foundations Slab-On-Grade Construction Retaining Walls Pavement Areas General Construction Requirements

GUIDELINES FOR REQUIRED SERVICES

LIMITATIONS ANO UNIFORMITY OF CONDITIONS

APPENDIX A

Field Investigation Site Plan (Figure 1) Logs of Test Borings (Figures 2 through 8) Typical Landslide Reconstruction Detail

(Figure 9) Landslide Buttress Detail (Figure 10) Typical Subdrain Section (Figure 11)

(iii)

Page No .

1 1 2-3 3-4 4-5

6-7 7-8 8-11

11-13 13-14 14-15

15-17 17-19 19-21 21-22 22-24

25-26

27-28

30 31 32-38 39

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Project No. 6063 18 Decmeber 1989

APPENDIX B

TABLE OF CONTENTS (continued)

Page No.

Laboratory Investigation 43 Summary of Laboratory Test Results (TABLE I) 44

APPENDIX C

Recommended Grading Specifications Guide Specifications For Rock Under

Floor Slabs

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GEOTECHNICAL ENGINEERING INVESTIGATION

Purpose and scope

The purpose of the investigation for the proposed residen

tial development on Lake Chabot Road in San Leandro, Cali

fornia, was to determine the surface and subsurface soil

conditions at the subject site. Based on the results of the

investigation, criteria were established for the grading of

the site, the design of foundations for the proposed struc

tures, and the construction of other related facilities on

the property. Our investigation included the following:

a. Field reconnaissance by the Soil Engineer;

b. Drilling and sampling of the subsurface

soils;

c, Laboratory testing;

d. Analysis of the data and formulation of con-

clusions and recommendations;

e. Preparation of this written report .

Proposed Development

The proposed development consists of single-family houses,

appurtenant streets, and retaining walls .

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Site Location and Description


The subject site lies just east of the City of San Leandro

on the upslope (south) side of Lake Chabot Road. The sub

ject property is in County Territory, but its western boun

dary is the easterly City Limit (see Figure l). The proper

ty extends about 1,500 to 1,700 feet south from the road and

is about 2, 0 00 feet wide.

acres .

The parcel includes about 59

The quarry which the property contains was first started in

the 1880's on the north end of a northwest trending ridge.

Nearly the entire property was quarried, and very few natur

al slopes remain. The native slope immediately above Lake

Chabot Road is densely forested and ranges between 1: 1 and

2:1 (horizontal to vertical) in inclination. A grass

covered, 2:1 slope near the south border of the site is the

only other significant remaining natural slope .

As a result of the quarrying operation, overburden material

was disposed of on site. It appears that the western por

tion of the site still contains the bulk of this fill. The

fill appears to have been placed as uncontrolled fill •

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Total relief on the site is about 500 feet, with elevation

ranging from about 305 feet at the northwest corner to 805

feet at the southeast corner. Most of the cutslopes have

been finish-graded. The major north-facing slope on the

south side of the site is cut at between 1.5:1 and 2:1 with

benches every 25 to 30 vertical feet, However, a 60-foot

high cut at the center of the site has no benches and has an

inclination of about 1: 1. Other unfinished quarry slopes

near the center of the site are nearly vertical and 50 to 75

feet high. Some small trees have been planted on the cut

slopes, but most of the vegetation consists only of grass

and low weeds. About a dozen man-made structures are pres

ent in the north part of the site. These include a resi

dence, an office, several barns and sheds, and crushing/

screening facilities.

This description is based on a site reconnaissance by the

Engineering Geologist and a 100-scale topographic plan by

Bissell & Karn, Inc., dated April, 1987.

Soil Conditions

The on-site surface and subsurface conditions in the upper

layer overlying bedrock vary over the site depending on

whether the borings were made in cut, fill, or undisturbed

soil. The majority of the underlying soil is considered low

to medium expansive except for some of the near-surface

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soils encountered in the undisturbed native soil. The soils

encountered consisted of reddish-brown, dense

gravelly clayey sands or gravelly sandy clays,

soil horizon, bedrock was encountered.

to hard,

Below the

No groundwater was encountered at the time of exploration .

Fluctuations in the groundwater table are anticipated with

variations in the seasonal rainfall.

A more thorough description and stratification of the soils

encountered are shown on the "Logs of Test Borings". The

results of the laboratory tests are presented in TABLE I,

Results. " The approximate "Summary of Laboratory Test

locations of these borings

Plan", Appendix A.

are shown on Figure 1, "Site

Liquefaction Potential Evaluation

Liquefaction occurs primarily in relatively loose, satur

ated, cohesionless soils. Under earthquake stresses, these

soils become "quick", lose their strength and become incap

able of supporting the weight of the overlying soils or

structures,

The data used for evaluating liquefaction potential of the

subsurface soils consisted of: the penetration resistance,

the soil description, the relative density of the materials,

and the groundwater conditions.

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Based on the data obtained and in view of the cohes.ive type

soil characteristics, it is our opinion that the near-sur

face soils are not prone to liquefaction .

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~neral


DISCUSSIONS, CONCLUSIONS AND RECOMMENDATIONS

1. The site is suitable for the proposed residential devel

opment provided the recommendations presented in this report

are incorporated into the project plans and specifications.

2. All Grading and Foundation Plans for the development

designed by the project Civil Engineer must be reviewed by

the Soil Engineer prior to contract bidding or submittal to

governmental agencies so that plans are reconciled with soil

conditions, and sufficient time is allowed for suitable miti

gative measures to be incorporated into the final grading

specifications.

3. TERRASEARCH, INC., should be notif1ed at least two work

ing days prior to site clearing, grading, and/or foundation

operations on the property. This will give the Soil Engi

neer ample time to discuss the problems that may be encount

ered in the field and coordinate the work with the con

tractor.

4. Field observation and testing during the grading and/or

foundation operations must be provided by representatives of

TERRASEARCH, INC., to enable them to form an opinion regard

ing the adequacy of the site preparation, the acceptability

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of fill materials and the extent to which the earthwork con

struction and the degree of compaction comply with the speci

fication requirements. Any work related to the grading and/

or foundation operations performed without the full know

ledge and under the direct observation of the Soil Engineer

will render the recommendations of this report invalid .

Demolition

5. Prior to any grading, demolition of the site should be

completed. Demolition should include the complete removal

of all subsurface structures, concrete, septic tanks, gas

and oil tanks (if any), storm inlets, foundations, asphalt,

machinery, equipment, debris and trash, with the exception

of i terns specified by the owner for salvage. The owner

should specify the saving or removal of shrubs or trees on·

the site, In addition, all underground structures must be

located on the grading plans so that proper removal may be

carried out.

6. Excavations made by the removal of any structure should

be left open by the demolition contractor for backfill in

accordance with the requirements for engineered fill. The

removal of underground structures should be done under the

observation of the Soil Engineer to assure adequacy of the

removal and that subsoils are left in proper condition for

placement of engineered fills. Any soil exposed by the demo

lition operations, which is deemed soft or unsuitable, shall

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be excavated and removed as required by the Soil Engineer

during grading. The demolition operation should be approved

by the Soil Engineer prior to commencing grading operations.

Any resulting excavations should be properly backfilled with

engineered fill under the observation of the Soil Engineer.

Should the location of any localized excavation be found to

underlie any structure, backfill should be compacted to a

minimum relative compaction of 95% or the excavation widened

to include the footprint of the structure and backfilled to

the specifications for engineered fill as recommended in the

"grading" section herein.

Grading

7. Areas containing uncontrolled fill are shown on Figure 1.

The depth of this fill varies from 2 to 20 feet as depicted

on the "Site Plan." The shallow fill has been subjected to

activity during the life of the quarry operations and

appears to be in a dense condition. The depth of fill in

the area designated as deep fill varies from north to south

with the maximum depth in the area of Boring 1. Therefore,

prior to grading on the site, the area of uncontrolled deep

fill should be excavated to native ground. The native

ground shall be properly prepared, scarified, moisture con

ditioned, and compacted to a minimum relative compaction of

90% based on ASTM Test Procedure Dl557-78 .

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8. Subexcavation in the area designated as shallow uncon

trolled fill is not contemplated at this time. However,

should the material be found to be loose or organics are

encountered during the grading operation, mitigation

measures need to be implemented as required by the Soil Engi

neer in the field .

9. The surface of the site in areas to be filled should be

stripped to remove all existing vegetation and/or other dele

terious materials. It is estimated that stripping depths of

4 to 6 inches may be necessary, however, the actual depth of

stripping should be determined in the field by the Soil Engi

neer. Stripped material from the site may not be used as

engineered fill but may be stockpiled and used later for

landscaping purposes. Any existing wood debris should be

removed from the site. Any existing loose fill should be

excavated to undisturbed native ground. Materials generated

from loose fills may be used as engineered fill with the

approval of the Soil Engineer provided they are not contamin

ated by debris.

10. Following site stripping, the top 6 inches of exposed

native ground should be scarified and compacted to a minimum

degree of relative compaction of 90% slightly above optimum

moisture content as determined by ASTM Dl55 7-7 8 Laboratory

Test Procedure . After stripping and recompacting the native

subgrade, the site may be brought to the desired finished

grades by placing engineered fill in lifts of 8 inches in

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uncompacted thickness and compacted to the relative compac

tion requirements in accordance with the aforementioned test

procedure. All soils disclosed during our investigation,

except those within the top few inches of organically contam

inated material, would be suitable for use as engineered

fill when placed and compacted at the recommended moisture

content.

11. If the 'overburden expansive soil is not needed for

later use as topsoil around the structures, then it is recom

mended that this material be buried underneath deep fill so

that one type of foundation is used over the entire site.

12. Should select import material be used to establish the

proper grading for the proposed development, the import

material should be approved by the soil Engineer before it

is brought to the site and should meet the following require

ments:

a. Have an R-Value of not less than 25;

b. Have a Plasticity Index not higher than 12;

c. Not more than 15% passing the No. 200 sieve;

d. No rocks larger than 6 inches in maximum size.

Import material meeting the requirements stated above should

be compacted to a minimum relative compaction of at least

90% as determined by ASTM 01557-78 Laboratory Test Procedure.

All engineered fill should be placed in lifts not exceeding

8 inches in uncompacted thickness.

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13. All exploratory trenches and test pi ts that were exca

vated for the geologic and environmental investigations

(References 1, 2, and 3) were loosely backfilled. There

fore, all pits affecting proposed foundations, streets,

curbs, or other grade features should be re-excavated and

backfilled with engineered fill in accordance with the grad

ing requirements of this report, These trenches and pi ts

should be shown on the grading plan by the Civil Engineer .

Slopes

14. Where fill is to be placed on an existing slope having

a surface gradient steeper than 5: 1 (horizontal to verti

cal), the surface soils are to be removed and these areas

keyed and benched horizontally into competent soil materials

prior to placement of engineered fill. A toe key excavation

should be placed at the base of all such fills. The width

and depth of the keyways will be determined by the Soil Engi

neer during the grading operations based on soil conditions.

Subsequent keyed benches should be not less than 1. 5 times

the grading equipment width and 3 feet in vertical height .

15. Cut and fill slopes may experience severe erosion when

grading is halted during rainy weather. Before work is

stopped, a positive gradient away from the slopes must be

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established to carry the surface runoff water away from the

slopes to areas where erosion and sediment can be con

trolled.

16. Concrete or asphalt-lined drainage facilities should be

installed above all cut and fill slopes greater than 15 feet

in vertical height or where the natural drainage is directed

toward the slopes from the large drainage areas above. The

purpose of the drainage facilities is to divert the excess

surface runoff water from the slopes and, consequently, mini

mize sloughing or erosion of the slope surface.

17. After the completion of the slope grading, erosion pro-

tection must be provided . Slope planting, preferably with

deep-rooted native plants, must be completed on all exposed

surfaces of cut and fill slopes. Graded slopes should not

be left exposed through a winter season without the comple

tion of erosion control measures and slope planting .

18. Cut and fill slopes should not be steeper than 2:1 (hor-

izontal to vertical) .

may be constructed at

vertical).

Cutslopes made in competent bedrock

a gradient of 1-1/2:1 (horizontal to

19. Fill

progresses

slopes must be compacted as the filling operation

by (1) using sheepsfoot-type rollers in conjunc-

tion with proper moisture conditioning, or (2) over-construc

ting the fill slopes and cutting back the looser surface

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soils to a firm and adequately compacted designed slope

grade. Track-walking of slope surfaces does not provide

adequate soil densities and is an unacceptable method of

slope compaction.

Drainage

20. The slope gradients are based on strength characteris

tics of the materials under conditions of normal moisture

content that would result from rain water falling directly

on the slope but do not take into consideration the addition

al seepage forces from springs or subsurface water areas.

Areas of observed seepage, as discovered during grading oper

ations, should be provided with subsurface drains below the

surface of the slope as directed by the Soil Engineer. Sub-

surface drainage facilities may include gravel blankets,

rock-filled trenches, horizontally-drilled drains, or perfor

ated pipe within filter gravel as shown on Figure 11 •

21. It will be necessary to install subsurface drains

beneath the fills to be placed in the swale areas, particu

larly, where boggy areas were encountered and in all other

seepage areas where disclosed during the grading operations.

This is necessary in order to provide drainage to these

areas and to ensure stability of the fills and provide a

stable base for placement of fill, where required. It is

recommended that all subsurface drains be installed accord

ing to the "Recommended Grading Specifications. " No ponding

of storm water is to be permitted on cut or fill pads during

prolonged periods of inclement weather .

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22. The location of the subdrains will be defined by the

Soil Engineer during the revision of the Grading Plan. The

final location, addition, or deletion of subdrains will be

determined in the field by the Soil Engineer during the grad

ing operations .

23. Drainage benches should be provided at 30-foot inter

vals of vertical height for cut and fill slopes. For slopes

over 30 feet high, the benches should be placed at the mid-

point of the slope. Intermediate benches are not required

for slopes less than 30 feet in height. Drainage benches

should also be provided at all locations of changing slope

gradient. Minimum 6-foot wide benches are recommended with

lined "V" type swales or interceptor ditches leading to a

controlled discharge point. Caution must be exercised so

that the uphill lip of the concrete or asphalt swale is prop

erly backfilled to prevent infiltration of surface water

beneath the ditch which may result in saturated soils and a

slope failure.

Remedial Measures and Mitigation of Existing Slide

24. The slide mapped on the Site Plan within the area to be

developed are shallow and are located in areas where fill is

contemplated . Therefore, the entire unstable area must be

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excavated and the material generated from the excavation

incorporated in the fill. No unusual procedures are re

quired for this phase of work. Should subdrains be deemed

necessary during the removal of the unstable mass, they will

be implemented as deemed necessary in the field based on

soil and site conditions .

25. The minor slides mapped on existing cutslopes above the

area of development are considered "popouts" and are small

in nature. These slides do not seem to pose any hazard to

the development. Any mitigation at this time shall consist

of removing any debris that may have deposited on the

benches below to ensure that those benches will carry sur

face runoff as they were originally intended to do. Should

any slide repair be contemplated, the method of mitigation

is shown schematically on Figure 9.

Foundations

26. The proposed building structures can be satisfactorily

supported on either a spread footing foundation system or a

pier and grade beam system provided that the site is pre

pared as previously recommended.

27. Spread footings may be used where soil conditions are

uniform over the entire building pad. The footings should

have a minimum depth of 18 inches below the lowest adjacent

pad grade (trenching depth). Design bearing pressures for

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footings should not exceed 2,000 p.s.f. due to dead loads,

2,200 p.s.f, due to dead plus live loads, and 2,500 p.s.f .

due to all loads which include wind or seismic. Perimeter

footings are to be reinforced with a minimum of two No, 4

bars, one at the top and one near the bottom of the footing.

Additional reinforcement will be as determined by the founda

tion design engineer and in accordance with structural

requirements.

28. To accommodate lateral building loads, the

resistance of the foundation soil can be utilized.

passive

Where

spread footings are used, the passive soil pressures can be

assumed to act against the front face of the footing below a

depth of one foot below the ground surface. It is recom-

mended that a passive pressure equivalent to that of a fluid

weighing 250 p.c.f. be used. For design purposes, an allow

able friction coefficient of 0.35 can be assumed at the base

of the spread footings .

29. Should cracks develop in the foundation trenches before

the placing of concrete, the trenches should be soaked until

all cracks are effectively sealed. The Soil Engineer should

observe the soaking in the field prior to the concrete being

poured, if deemed necessary.

30. As an alternative foundation system, it i.s recommended

that the proposed building structures be supported on a

drilled cast-in-place friction pier and perimeter grade beam

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type foundation. The piers should have a minimum diameter

of 12 inches and should extend a minimum depth of 6 feet

into native or compacted soil. The piers should be designed

on the basis of skin friction acting between the soil and

that portion of the pier that extends below a depth of one

foot below the finished grade. For the soils at the site,

an allowable skin friction value of 500 p. s. f. can be used

for combined dead and live loads. This value can be

increased by one-third for total loads which include wind or

seismic forces. Reinforced concrete grade beams should be

used to support the perimeter walls and, if desired, certain

bearing walls of the building structures. Reinforcing steel

should be provided as necessary for structural support and

continuity of pier and grade beam. Spacing should be deter

mined, as required, by the load distribution but minimum

spacing should not be less than 3 pier diameters, center-to

center •

Slab-on-Grade Construction

31. It is expected that the concrete slabs-on-grade may

experience some cracking due to the nature of soils present

on the site. To reduce the potential cracking of the slabs

on-grade, the following recommendations are made:

a. All areas to receive slabs should be wetted

until a moisture equilibrium condition is

reached as deemed necessary by the Soil Engi

neer .

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b.

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A minimum of 4 inches of

crushed rock material should

the finished subgrade and

gravel or clean

be placed between

all the slabs to

serve as a capillary break between the subsoil

and the slab. See the "Guide Specifications

For Rock Under Concrete Slabs", Appendix C.

Slabs should be reinforced with a minimum of

wire mesh . Care should be taken to center the

reinforcement in the slab.

d. All slabs should be properly reinforced to

meet structural design criteria. The rein

forcement shall be placed in the center of the

slab unless otherwise designated by the design

engineer .

e. Slabs at door openings should be constructed

with a curl or a thickened edge extending a

minimum of 6 inches into native ground or

compacted fill

f. Slabs supporting floor coverings should be

provided with measures to prevent condensation

caused by temperature differentials from harm-

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ing floor coverings. One way to protect the

floor covering is to place a waterproof mem

brane between the granular layer and the floor

slab. In addition, two inches of wetted sand

should be placed over the membrane to minimize

puncture and facilitate curing of the concrete .

The sand and the membrane are to be placed

over the 4-inch layer of gravel or clean sand

and crushed rock recommended herein .

Retaining Walls

32. If retaining walls are incorporated into the design and

construction of the proposed

parameters should be used.

dwellings, the following design

The retaining walls should be

designed to resist lateral pressures exerted from a media

having an equivalent fluid weight as follows:

Gradient of Back Slope

Flat 2:1

Equivalent Fluid Weight (p.c.f.)

Unrestrained

45 65

Passive Resistance lp.c.f.)

250 250

Coefficient of Friction

0.35 0.35

In addition, restrained retaining walls should be designed

to resist an additional uniform pressure of 100 p.s.f. for

the entire height of the wall .

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33. The above criteria are based on fully-drained condi

tions. For these conditions, we recommend that a filter

material blanket be placed behind the wall. The blanket

should be a minimum of 12 inches thick and should extend

the full height of the wall to within 12 inches of the sur

face. If the excavated area behind the wall exceeds 12

inches, the entire excavated space behind the 12-inch blan

ket should consist of compacted engineered fill or gravel

blanket material. A 4-inch perforated drain pipe should be

installed in the bottom of the filter blanket and should be

underlain by at least 4 inches of filter type material.

Adequate gradient shall be provided to discharge water that

collects behind the wall to an adequately controlled dis

charge system away from the structure foundations and nearby

engineered fills. A filter fabric may be required in con-

junction with the filter material. The granular crushed

rock or gravel filter material should meet the following

gradation;

Sieve Size Percentage Passing

l" 100

3/4" 90-100

3/8" 40-100

No. 4 25-40

No . B 18-33

No. 30 5-15

No. 50 0-7

No . 200 0-3

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34. The retaining walls should be supported on a spread

footing system and should be a minimum of 2 feet below adja

cent pad grade.

Pavement Areas

35. Preparation of Subgrade: After underground facilities

have been placed in the areas to receive pavement removal of

excess material has been completed, the upper 6 inches of

the subgrade soil shall be scarified, moisture conditioned

and compacted to a minimum relative compaction of 95% in

accordance with the grading recommendations specified in

this _report .

36. Aggregate Base: All aggregate base material placed

subsequently should also be compacted to a minimum relative

compaction of 95% based on the ASTM Test Procedure Dl557-78 .

The construction of the pavement in the parking and traffic

areas should conform to the requirements set forth by the

latest Standard Specifications of the Department of Transpor

tation of the State of California and/or City of San

Leandro, Department of Public Works.

37. Pavement Sections: No specific tests were performed to

determine the pavement section in the proposed parking

areas. However, based on our experience with similar soil

materials, a tentative pavement section of 2-1/2 inches of

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asphal tic concrete on 8 inches of aggregate base material

may be utilized. When the subgrade is established, the

necessary samples can be obtained; and an accurate pavement

section can be designed at that time.

General Construction Requirements

38. All finish grades should provide a positive gradient to

an adequate discharge point in order to provide rapid remov

al of surface water runoff away from all foundations. No

ponding of water should be allowed on the pad or adjacent to

the foundations. Surface drainage must be provided as

designed by the project Civil Engineer and maintained by the

property owners at all times .

39. Liberal lot slopes and drainage must be provided by the

project Civil Engineer to remove all storm water from the

pad and to prevent storm and/or irrigation water from seep

ing beneath the houses. Should surface water be allowed to

seep under the structures, foundation movement resulting in

structural cracking will occur. In addition, all site drain

age must be provided as designed by the project Civil Engi

neer and maintained by the property owners at all times to

minimize foundation movement.

40. Where roof gutters are used, downspouts from the

gutters should be provided with closed pipe conduits or

splash blocks to carry storm water away from the structures

and graded areas and, thus, reduce the possibility of soil

saturation adjacent to the foundations and engineered fills •

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41. Flower beds or planters should be avoided adjacent to

the building foundations. Should planters be constructed,

foliage requiring little irrigation should be installed to

prevent water from affecting the foundation .

42. Utility trenches extending under building areas should

be backfilled with native on-site soils or approved import

materials. Backfill should be properly compacted to ensure

against water migration underneath the structure •

43. Utility trenches extending underneath all traffic areas

must be backfilled with native or approved import material

and compacted to a relative compaction of 90% to within 6

inches of the subgrade. The upper 6 inches should be com

pacted to 95% relative compaction in accordance with ASTM

Dl557-78 Laboratory Test Procedure. Backfilling and

compaction of these trenches must meet the requirements set

forth by the City of San Leandro.

44. Applicable safety standards require that trenches in

excess of 5 feet must be properly shored or that the walls

of

of

the trench slope back to provide safety for installation

lines. If trench wall sloping is performed, the inclina-

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Project No. 6063 lB December 1989

tion should vary with the soil type. The underground

contractor should request an opinion from the Soil Engineer

as to the type of soil and the resulting inclination.

45. With respect to state-of-the-art construction or local

requirements, utility lines are generally bedded with granu

lar materials. These materials can convey surface or subsur

face water beneath the structures. It is, therefore, recom

mended that all utility trenches which possess the potential

to transport water, i.e., backfilled with granular material,

be sealed with a compacted impervious cohesive soil material

or lean concrete where the trench enters/exits the building

perimeter. This impervious seal should extend a minimum of

2 feet away from the building perimeter .

46. The high cutslopes along the southeastern boundary of

the development may experience some raveling with the pas

sage of time. It may be desirable to construct a debris

bench and a cyclone fence at the toe of the slope to ensure

that no debris encroaches on the road .

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GUIDELINES FOR REQUIRED SERVICES

The following list of services are the services required and

must be provided by Terrasearch, Inc., during the project

development. These services are presented in check list for

mat as a convenience to those entrusted with their implemen

tation.

The i terns 1 i sted are included in the body of the report in

detail. This list is intended only as an outline of the

required services and does not replace specific recommenda

tions and, therefore, must be used with reference to the

total report .

The importance of careful adherence to the report recommenda.

tions cannot be overemphasized. It should be noted, however,

that this report is issued with the understanding that each

step of the project development will be performed under the

direct observation of Terrasearch, Inc •

The use of this report by others presumes that they have

verified all information and assume full responsibility for

the total project .

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• Item Desci:iption R=quired l'bt Requii:ed

• 1. Provide foundation design·para!T);Oters x

2. F2view grading plans and specifications x

3 • Review foundation plans ar:d specifications x

4. Cbserve and provide reccmuendations regard-iflj demolition x •

s. Cbserve and provide r-eccmnendations regard-in:J site stripping x

6. Cbserve and provide reccrnnendations on rroisture conditioning, ranoval, and/or pre- x • canpaction of unsuitable existing soils

7. Observe ar:d provide recarmendations on the installation of subdrain facilities x •

8. Observe arrl provide testing services on fill areas and/or imp:irtea fill materials x

9. Review as-graded plans arrl provide additional foundation reccmnendations, if necessai:y x •

10. Observe arrl provide canpaction tests on x sanitary sewers, storm drain, watei: lines, and PG&E trenches

11. Cbserve foundation excavations and provide I supplemental recarmendations, if necessary, x • pdor to placing concr-ete

12. Observe and provide moisture conditioning x recarrnendations foi: foundation areas prior

• to placing concrete •

13. Provide design parameters for retaining v.alls x 14. Provide geologic observations and recan112nda-

tions for keyway excavations and cutslopes x during grading • 15. &cavate and reccrnpact all geologic ti:enches x and/or test pits

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LIMITATIONS AND UNIFORMITY OF CONDITIONS

1. lt should be noted that it is the responsibility of the

owner or his representative to notify TERRASEARCH, INC., in

writing, a minimum of two working days before any clearing,

grading or foundation excavations can commence at the site.

2. The recommendations of this report are based upon the

assumption that the soil conditions do not deviate from

those disclosed in the borings and/or test pits and from a

reconnaissance of the site. Should any variations or unde-

sirable conditions be encountered during the development of

the site, TERRASEARCH, INC., will provide supplemental recom

mendations as dictated by the field conditions.

3. This report is issued with the understanding that it is

the responsibility of the owner, or his representative, to

ensure that the information and recommendations contained

herein are brought to the attention of the Architect and

Engineer for the project and incorporated into the plans and

that the necessary steps are taken to see that the Contrac

tor and Subcontractors carry out such recommendations in the

field .

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LIMITATIONS AND UNIFORMITY OF CONDITIONS

(continued)

4. At the present date, the findings of this report are

valid for the property investigated. With the passage of

time, significant changes in the conditions of a property

can occur due to natural processes or works of man on this

or adjacent properties. In addition, legislation or the

broadening of knowledge may result in changes in applicable

standards. Changes outside of our control may render this

report invalid, wholly or partially. Therefore, this report

should not be considered valid after a period of two ( 2)

years without our review, nor should it be used, or is it

applicable, for any properties other than those investi

gated .

5. Not withstanding, all the foregoing applicable codes

must be adhered to at all times .

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APPENDIX A

Field Investigation

Site Plan

Logs of Test Borings

Typical Landslide Reconstruction Detail

Landslide Buttress Detail

Typical Subdrain Detail

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FIELD INVESTIGATION

The field investigation was performed on 5 December 1989 and

included a reconnaissance of the site and the drilling of 7

exploratory borings at the approximate locations shown on

Figure 1, "Site Plan."

The borings were drilled to a maximum depth of 28 feet below

the existing ground surface. The drilling was performed

with a truck-mounted rig using power-driven, six-inch diam

eter continuous flight augers. Visual classifications were

made from the auger cuttings and the samples in the field.

As the drilling proceeded, undisturbed core samples were

obtained by means of a 2-inch, Q.D., split-tube sampler.

The sampler was driven into the in-situ soils under the

impact of a 140-pound hammer having a free fall of 30 inches.

The number of blows required to advance the sampler 12

inches into the soil were adjusted to the standard penetra

tion resistance (N-Value) .

The samples were sealed and returned to our laboratory for

testing. Classifications made in the field were verified in

the laboratory after further examination and testing .

The stratification of the soils, descriptions, location of

undisturbed soil samples and standard penetration resistance

are shown on the respective "Logs of Test Borings", Appen

dix A .

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• )1'/ "' ' ' I ~ ~.

·{_____ ~ · .

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j -,.,_

l ./

=

Approximate lill'.its of s..liallow uncontrolled fill

1'.pproxirnate limits of deen tmcontrolled fill

Landslic1.e C.e.1:-iris

APPROXIMATE LOCATION OF TEST BORINGS

T~lfl~A S~Al~t:H INt:. FIGURE NO. ~ - SI''l'!. "!1\N

ProJect No. 6063 18 DccG."lbe_r 1989

---~- ... LOGGED BY D?) DA TE DRILLED 12/5/89 BORll'KI DIAMETER 6" BORING NO, l •

15 j$ ....:,!? b ~ ~8_ 3i;;: ~~ MISC.

.8 :3 .,; ~ "ii! ...: .!!b "2;;: ..._, "' LAB s SOIL DESCRIPTION .o - <!' [ i .r ~ ~ .. . "' C>. ~ ;;:::: "iii • - Q '-! .- ... .. ..

~ C>.

:i ""' RESULTS

c .:i"' ..., "' .. _s;: "' "' =>- a> ..... C',f Q u • -~1~~

-Seddish-brown Gr'1velly S.1\ND w/Silt,

- - ''< medium d1?nse, noist (FTI.L) Sli/ l-l

~). 16 -- 9 ... - ,.. - . i;1~: - - J1~if} ... 5- :~~f~

1-2 ~1 SP.me as al:ove 14 -- 9 - -~~

•

·.t.-..,.\~ - f~~:~~ .... ,;i.. - -

I - - EeCXJITEs looser

. 10 · Y•

•

l-3 %~ 10 - 7 - . ·~· .. - - h~~~: - - .~:"!j.:

~{~· . -. 15-

1-4 :~ 5~ l?.-'.' l'l -

•

• - - ~ Greyish-brrn·m, loosely cer:ented SAfID-

i:::::;:::: S'Jl'.)NE w/some rocks, VG!:'} dense, T'Dist ... - ::;:::;::

:::;::::: . -

~ 20- 1-: 84 t-b • m::; reo::ivery •

. - 2oring terminated at 20.5 feet. lb groundwater enoountered. - -

• - -- -

. 25..

- -• - -- -- -. -•

Tl~l~l~A Sl~Al~t~H INC. I FlOURE NO. 2 - If)'.; OF ri~.ST BORING

32

•

• LOGGEO BY ~.!B PA TE PRILLEP 12/5/89 BORINC) PIAMETER 6" BORING NO. 2

• ~g -b .:2 ,g 8. 11i -= .!e

~ 'i MISC • .,; 21 ·u;. . ~l:> .8 al Ji ....... ..,. "' - => LAB .&£ SOIL DESCRIPTION .o

~~ -:;; z:. ~ i == .... -... §!? -;; ·a .... ·- -0 .. ' .. z:. C>. ~ .... RESULTS

~ ... - 50: => "' c :::> - "" ... o-8:_ u c

•

:;~-,.~~-

Bl:'"OV.1'J.J Clayey SJ-IND •·7/f.i.lt a..."'1d Gravel - - -~-t-~-

2-' ~.$)· (weathered bedrock) , very dense, '1Dist SW 80 104 9 - - r..: ~"-Z"·

""" ... - ~~·j<

'-f.;i; .,,,, - ··-.:,;l· - -~··'J

~r.

"' 5 - •, -~-

but becanes rredium ~: SP.lnte as atove, - 2-2

,. dense, nnist 23 Bag sariple ... < r.

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- - ·;~J ~.ti'." '.(._v:

- - 1-·.I" -!J.-?. -~::.I

- - 1'.\:. - 10 - -·~~~:

2-3 ~:~- 56 102 11 rerrolded

- - ~! Bro,1Jl"l Silty Sk'ID Fjheavv GrE!Vel , SN c>O . 1! fl"'64 degrees - t~' very de-..nse, rroist ·yl (scme Gravel -..H ... - i•--r is rernved) :~~; . . ; .. ... - :i~ib

.,1~1· ... is- I ;<

2-4 l.1 SillOO as above 1 but less dense -:ir.: lH s ·~:1 ~--

~: - - ~I

• ~ ·1·

... - . \i~· f ) ·r11f

... - 'iit! lf?.e

... - ·Vf {1\ eJi Be=ros very dense ... 20- 2-5. ·l;l 102 8

- - Eoring terminated at 20.5 feet. ... tb groundwater encountered. -

• ... -- -- 25-

-• - .

- -- -... -•

TEl~l~A Sl~Al~tH INC. I rJOORE NO. ~ - IDG O:' TI:ST l'Olc'.I!"G J

33 •

Pro1eet tb. (,(,63 18 Dx.ernt>?x 1~8~

• LOGGED BY DR DA TE: DRILLED 12/5/89 BORING DIAMETER 6" BORING NO.

3

• ::::: ~8. ~! §Ii -:£ ~

!!! ~ MISC. ..!!~ i ll~ ...... ...,. .,; ~ '!1j _,

"' LAB 5 SOIL DESCRIPTION ~ ... .o ., .

-:;:; ~ Q. ~ ~-~ -~ o~ ·- --cl ., . .,

~ ... j~ RESULTS ~ ... ..... -~ "' iii 0 ::=> - i:D .....

<.> O'c... 0

• I 13rovm Sandy GRAVEL w/traee of Silt and GW

t- - Clay (i~eathered Sandstone), VP_ry der1se, 3-1 97 115 13

" rrol.st ,_ - .. .:.• - " ;.~{f~Y .

- - Eorl.ng te=inated at 3.5 feet. .. 5 - lb grounC:Viater p_nccuntered.

.. -

• .. -,_ -

- -

" -

• - -- -

- -

- -

• - -- -- -- -

• - -

- -,_ -

,_ .

• . -- .

. -

. -• . .

- -- -- -•

T~•~•~A s•~••~•~n ••c. I FIOURE NO. 4 - LOG OF '"EST !30RD<G

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!'rOJ8Ct ~Jo. 6063 lH I:ecernber l'!B'!

------- -------------------------------------------, LOGGED BY ,\Y DATE DRILLED 12/5/89 BORING DIAMETER

~8. :d .8 --"' ~~ - [ <>- n .. "' 0

' -ti. - - /.·

4-1 ;. - - ~

- - ~¥

~ - -V;ii - 5 -"''*

4-2 - -

- -

~ - -- -.10 -

'"15 -

~20 -

-

--

" -

- -- -

- -

SOIL DESCRIPTION

Beddish-brown Sandy CLAY wjhce.vy Co:ravel, dense, rrnist

Becomes less rroist

1'annish-brown weathered (fractured) S.l\NLS'IONE w/Si.lt (cuttings are very noist Sandy Clay, very dense, rroist)

~an Silty S.""-"lD w/fractured rocks, very dense, !:'Dist

cuttings are crushed rock

Boring terminated at 23.5 feet. Ko groundwater en=untered.

~~ ~1i ll~ ...... ...,. i= '; -~ - :1: :>- eQ..,

u

CL 50

93

111

6'' BORING NO. 4

-b ... !!! 'i :i MISC. "ih .

"' - "' .o ~ <..?

-.;; i!:' LAB - -"i ·-"" RESULTS i'::'"'" :i _., g.~ 0

112 14

110 13

104 15

TBl~l~A Sl~A·~·~H INC. I FlOURE NO. 5 - LOG OF TEST !'DPJNG

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T>ro-ject No. 6063 18 December 1989

~---,--- ----~---------------------..,..,,.--------;:----,

G" BORING NO. S LOGGED BY _c.K DATE DRILLED 12/5/89 BORING DIAMETER

0 = z: i!t .c ~.i!> Ci. ~ "' c tl.,

-

.

- -

--

-10 -

-

--

15 ..

.

--

... 20 -

--

-

... 25 -

-~ -... 30 -

.8 !!. ...,

SOIL DESCRIPTION

Heddish-brown Sandy CLAY w/Gravel, dense, m::iist

Recorres nure ('.ravelly

Dark brown Sandy Clay w/Gravel, dense, TIDist .

Very hard drilling

lbri_ng terrrinate:i at 28 feet. No groundwater encountered •

CH

3"

CL

115 13

lo::'

---

MISC. LAB

RESULTS

Ur51 0 I=28

Tt~•~•~A s1~A•~•~n ••c. I FlOURE NO. 6 - lffi OF TEST BOP.ING

36

ProJect Lb. 6053 18 tecembcr 1989

• I,oc,GED BY Al-( DA TE DRILLED 12/5/89 BORING DIAMETER 6" BORING NO. 6

•

g ~

~-. ., b 0 ~~ -- ~}'. MISC. :::: ~!. _1: .; ~ ·;;;

-=- ~b .8 ~.g ...... ...,. "'-: :::> LAB [ SOIL DESCRIPTION i :::: ....;~

., . .., ~ Q. ~ ;;::: "jjj Q '-! ·-..,. ., .,,

~CL ;i,.. RESULTS Q ~ ... .,, "' .. - Si; :::> "' :::> - lrl ... o-tf (..'> Q

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~· Brown Sandy CLAY w/fine Gravel, hard - - drilling, da."1j) CL 9Z V; - - '.%. - Ji

at. - -

- 5 - I -

- ~· ~ -l%3 - - Vill

.. 10 - I ~· - -

~ I Very hard drilling - -

- - ~ - - ;~ Dark brown Clayey SAND w/fine Gravel, SD/ ..is - o-1 very dense, damp (REFUSAL) S(~ Jl? llG ~ 0 - -

- - Boring terminated at 16 feet. No qroundwater encountered.

- -• - -

-20 --

- -• --- -- -

• --

- -... -•

TB•~•~• s1~••~•~n IN& I FIOURE NO. 7 - LOG OF 'T'RST BORil'lG

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• --

• ---

• -... ... I-

• ----

• ----

• ---

-•

---• -

--•

•

oroject N:::>. 6063 18 December 1989

LOGGED BY_ H'. DATE DRILLED 12/5/89 BORING DIAMETER BORING NO. ~

:~Q~ - ~~:0

~~ - ::~·

•,y.JI.' ;;/!/-

- y· :~-- t 7-1 ~

s- ff.. ~·

- ":jj: ~;t'.

'!-~?:.· . ,:ft .

~ -7-2

I

10 - " ~I - ~ - Xt .1!.1. -

-

is--

----------

--

-

SOIL DESCRIPTION

IX>c:cUsh-brovm Clayey SAl\1D vi/Gravel, rredium dense, noi.st (FILT,) S? I

SC

t:ark greyish-brown Silty CJ..AY w/scrre organics, hard, noist (11ATIVE) CJ,/

B::>ring terminated at 13 feet (refusal) . No groundwater encountered .

CH

18

37

99 15

84 15

MISC. LAB

RESULTS

rerrolded 0"1200 l)Sf

,0=64 degrees (some gravel rerrovo::l J

T•~·~·~A Sl~A·~·~H INC. I FIGURE NO. 8 - LOG OF TEST BOP-.ING

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• • • • • • • • • • Project No. 6063 18 December 1989

TYPICAL IJ\NCGLIDE PECDl'lSTPlJCI'IC'.N DETAIL

Existing Ground Surface

Lined Di le h -----.--------------.

Subdroin

Slide Plane

T~l~RA S~Al~CH 111e. FIGURE NO. 9

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/,_. '/,' ,,,., , . " Slide

Project ;Jo. 6063 lR DecS'lber 1989

LANDSLIDE BUT'rRESS DETAIL

40

Minimum 6' bench (see general slope st~bility requirements}

FIGURE NO. 10

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Project Kb. 6063 18 Dec£l'lber .l 98'l

TYPICAL SUBDl<AIN SECTION

As directed by the Soil Engineer

during installation

3' minimum

.. .,

'·

Embankment Material

. .... I::'•' I ' ........ .

•• ·~' 0- ,· • ' -- ~ ... I" ~ . .!! ..... ~ .' .

0 •• • •. ~

. .

.,

Permeable material as specified in the Grading Specifications of this report

6'' perforated pipe with the holes turned down

Note: Bottom of subdrain trench and pipe should be sloped at least 2 percent

TEl~l~A SEAltl~H 111c. F'IGURE NO. 11

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APPENDIX B

Laboratory Investigation

Summary of Laboratory Test Results

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LABORATORY INVESTIGATION

The laboratory testing program was directed towards provid

ing sufficient information for the determination of the engi

neering characteristics of the site soils so that the recom

mendations outlined in this report could be formulated.

Moisture content and dry unit weight tests were performed on

undisturbed soil samples in order to determine the consist

ency of the soil and moisture variation throughout the ex

plored soil profile and estimate the compressibility of the

underlying soils .

The strength parameters of the foundation soils were deter

mined from direct shear tests performed on selected

undisturbed soil samples .

Field penetration resistance (N) assisted in the determina-

tion of the strength parameters of the soils. The standard

penetration resistances are recorded on the respective "Logs

of Test Borings."

The expansion characteristics of the near-surface soils were

evaluated by means of Atterberg Limits Tests performed in

accordance with ASTM D-423 and D-424 .

A summary of all laboratory test results is presented on

TABLE I of this appendix and on the respective "Logs of Test

Borings", Appendix A .

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• Project &:>. 6063 18 Decanter 1989

• TllBLE I

• Surrmary of Ial:x:iratpry Test Results

Sample Depth Dry MJisture Atterllero Limits Diiect 511ea;r lib. Dansity content Liquid Plasticity Cohesion Angle of

Limit Index Internal

• Friction ill...l rp.c.f.) (% pzy ~ight) (%) (p.s.f.) (degree)

1-1 2.0 9 1-2 6.0 9 1-3 11.0 7

• 1-4 16.0 124 19

2-1 2.0 104 9 2-3 11.0 102 11 0 64 2-4 16.0 114 9 2-5 20.0 102 8

• 3-1 1.5 115 13

4-1 2.0 112 14 4-2 6.0 110 13 4-3 11.0 104 15

• 5-1 6.0 115 13 51 28 5-2 16.0 102 9

6-1 15.5 116 8

• 7-1 5.0 99 15 1,200 64 7-2 10.0 84 15

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• APPENDIX C

The Grading Specifications

Guide Specifications For Rock Under Floor Slabs

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THE GRADING SPECIFICATIONS on

SAN LEANDRO ROCK QUARRY 13575 Lake Chabot Road

San Leandro, California

1. General Description

1.1 These specifications have been prepared for the grading

and site development of the subject residential development .

TERRASEARCH, INC., hereinafter described as the Soil Engi

neer, shall be consulted prior to any site work connected

with site development to ensure compliance with these speci

fications .

1.2 The Soil Engineer shall be notified at least two work

ing days prior to any site clearing or grading operations on

the property in order to observe the stripping of surface

contaminated material and to coordinate the work with the

grading contractor in the field.

1. 3 This specification encompasses all clearing or grub

bing, preparation of land to be filled, filling of the land,

spreading, compaction and control of the fill, and all sub

sidiary work necessary to complete the grading of the filled

areas to conform with the lines, grades, and slopes as shown

on the accepted plans. The Soil Engineer is not responsible

for determining line, grade elevations, or slope gradients .

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The property owner, or his Engineer, shall designate the

person or organization who will be responsible for these

items of work.

1. 4 The contents of these specifications shall be inte

grated with the soil report of which they are a part, there

fore, they shall not be used as a self-contained document.

2. Tests

The standard test used to define the maximum densities of

all compaction work shall be the ASTM Test Procedure D1557-

78. All densities shall be expressed as a relative compac

tion in terms of the maximum dry density obtained in the

laboratory by the foregoing standard procedure,

3. Clearing. Grubbing, and Preparing Areas to be Filled

3. 1 All vegetable matter, trees, root systems, shrubs,

debris, and organic topsoil shall be removed from all struc

tural areas and areas to receive fill. The depth of organic

topsoil to be removed will be determined in the field by the

Soil Engineer but, in general, is expected to vary from 4 to

6 inches.

3.2 All soil deemed soft or unsuitable by the Soil Engineer

shall be removed. Any existing debris or excessively wet

soils shall be excavated and removed as required by the Soil

Engineer during grading .

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3. 3 All underground structures shall be removed from the

site such as old foundations, abandoned pipe lines, septic

tanks, and leach fields.

3. 4 The final stripped surface shall be approved by the

Soil Engineer during construction and before further grading

is started.

3.5 After the site has been cleared, stripped, excavated to

the surface designated to receive fill, and scarified, the

native subgrade soils shall be moisture conditioned and com

pacted to the requirements of engineered (structural) fill.

Fill can then be placed to provide the desired finished

grades • The contractor shall obtain the Soil Engineer's

approval of subgrade compaction before any fill is placed.

Final grade within cut areas shall be prepared as above to

provide uniform compaction of disrupted surface soils .

4. Materials

4 .1 All fill material shall be approved by the Soil Engi

neer. The material shall be a soil or soil-rock mixture

which is free from organic matter or other deleterious sub

stances. The fill material shall not contain rocks or lumps

over 6 inches in greatest dimension and not more than 15%

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larger than 2-1/2 inches. Materials from the site below the

stripping depth are suitable for use in fills provided the

above requirements are met.

4. 2 Materials existing on the site are suitable for use as

compacted engineered fill after the removal of all debris

and organic material. All fill soils shall be approved by

the Soil Engineer in the field.

4.3 Should import material be required, it must be approved

by the Soil Engineer prior to transporting it to the project

and must meet the requirements as specified in the report.

5. Placing. Spreading and Compacting Fill Materials

5.1 Before compaction begins, the fill shall be brought to

a water content that will permit proper compaction by either

a) aerating the material if it is too wet, or b) spraying

the material with water if it is too dry. The fill mater

ials shall be placed in uniform lifts of not more than 8

inches in uncompacted thickness. Each layer shall be spread

evenly and shall be thoroughly blade mixed during the spread

ing to obtain uniformity of material in each layer.

5.2 After each layer has been placed, moisture conditioned,

mixed and spread evenly, either import material or native

material shall be compacted to a relative.compaction of not

less than .90% slightly above the optimum moisture content as

determined by ASTM Test Procedure 01557-78 .

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5. 3 Compaction shall be by acceptable compacting rollers .

Rollers of such design that they will be able to compact the

fill to the specified density. Rolling shall be accomp

lished while the fill material is within the specified mois

ture content range. Rolling of each layer shall be continu

ous over its entire area and the roller shall make suffi

cient trips to ensure that the required density has been

obtained and that adjacent areas are overlapped •

5.4 Field density and moisture tests shall be made in each

compacted layer by the Soil Engineer in accordance with ASTM

Test Procedure D1556-64, D2922-81, or D3017-78. When footed

rollers are used for compaction, the moisture and density

tests shall be taken in the compacted material below the

surface disturbed by the roller. When these tests indicate

that the moisture or density of any layer of fill, or por

tion thereof, does not meet the required specifications, the

particular layer, or portion thereof represented by the

test, shall be reworked until the compaction requirements

have been met .

5.5 No soil shall be placed or compacted during periods of

rain nor on ground which contains free water. Soil which

has been soaked and wetted by rain or any other cause shall

not be compacted until completely drained and until the mois-

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ture content is within the limits approved by the Soil Engi

neer. Approval by the Soil Engineer shall be obtained prior

to continuing the grading operations.

6. Payement

6 .1 The proposed subgrade under pavement sections, native

soil and/or fill shall be compacted to a minimum relative

compaction of 95% at slightly above optimum moisture content

for a depth of 6 inches .

6 .2 All pavement materials and construction methods used

shall conform to the applicable sections of the latest edi

tion of the Cal-Trans Specifications for Pavements, State of

California, Department of Transportation and/or the City of

San Leandro, Department of Public Works.

6. 3 It is recommended that soils at

level be tested for a pavement design

the proposed subgrade

after the preliminary

grading is completed and the soils at the site design sub

grade levels are known .

7. Subdrains

7.1 Subdrains shall be provided where seepage is discovered

and at any other location where recommended by the Soil

Engineer .

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8. Subdrain Installation


8.1 Provide and install perforated PVC pipes or perforated

metal pipe and filter material for subdrains.

8.2 Use Class II material as specified in Section 68-1.025

of the Standard Specifications of the State of California.

9. Utility Trench Backfill

9.1 The utility trenches extending under concrete slabs-on

grade shall be backfilled with native on-site soils or

approved import materials and compacted to the requirements

pertaining to the adjacent soil. No ponding or jetting will

be permitted.

9. 2 Utility trenches extending under all pavement areas

shall be backfilled with native or approved import material

and properly compacted to meet the requirements set forth by

the City of San Leandro, Department of Public Works.*

NOTE: Requirements of City to be added .

9. 3 Where any opening is made under or through the perim

eter foundations for such items as utility lines and

trenches, the openings must be resealed so that they are

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watertight to prevent the possible entrance of outside irri

gation or rain water into the underneath portion of the

structures.

10. Subsurface r.ine Removal

10.1 The methods of removal shall be designated by the Soil

Engineer in the field depending on the depth and location of

the line. One of the following methods will be used .

10.2 Remove the pipe and fill and compact the soil in the

trench according to the applicable portions of sections

pertaining to compaction and utility backfill .

10.3 The pipe shall be crushed in the trench. The trench

shall then be filled and compacted according to the appli

cable portions of section 5.1 .

10. 4 Cap the ends of the line with concrete to prevent

entrance of water. The length of cap shall not be less than

5 feet. The concrete mix shall have a minimum shrinkage .

11. Unusual Conditions

In the event that any unusual conditions not covered by the

grading specifications are encountered during the grading

operations, the Soil Engineer shall be immediately notified

for additional recommendations •

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12. General Requirements

Dust Control


The contractor shall conduct all grading operations in such

a manner as to preclude wind blown dirt and dust and related

damage to neighboring properties. The means of dust control

shall be left to the discretion of the contractor and he

shall assume liability for claims related to wind blown

material .

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GUIDE SPECIFICATIONS FOR ROCK UNDER FLOOR SLABS

Definition

Graded gravel or crushed rock for use under slabs-on-grade shall consist of a minimum thickness of mineral aggregate placed in accordance with these specifications and in conformity with the dimensions shown on the plans. The minimum thickness is specified in the accompanying report .

Material

The mineral aggregate shall consist of broken stone, crushed or uncrushed gravel, quarry waste or a combination thereof. The aggregate shall be free from deleterious substances. It shall be of such quality that the absorption of water in a saturated dry condition does not exceed 3% of the oven dry weight of the sample.

Gradation

The mineral aggregate shall be of such size that the percentage composition by dry weight, as determined by laboratory sieves (U.S. Sieves), will conform to the following gradation:

Sieve Size Pe,;:centage Passing

3/4" 90-100 No. 4 25-60 No. 8 18-45 No. 200 0-3

Placing

Subgrade, upon which gravel or crushed rock is to be placed, shall be prepared as outlined in the accompanying soil report.

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0312 ~') 11~~gmw.consrv.ca.gov/shp/apsi_siteinvestigationreports_ocr/apsi_0… · 18/12/1989...

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