d-7°470gmw.consrv.ca.gov/shp/apsi_siteinvestigationreports_ocr/apsi_000463/apsi_000463...mar 09,...

STATE OF CALIFORNIA~ THE RESOURCE:S AGENCY

DE~.4RTMENT OF CONSERVATION

DIVISION OF MINES AND GEOLOGY DIVISION HEADQUARTERS RfSOURCES BUJlDING. ROOM 1341

1416 NINTH Stfl:EET

SAC:RA.MENTO, C:A 9.1814

Oi1trlc;t Offic:11tll~ t.OS AHGEl~5 SACRAMENTO

===-~~ ~=·

' \ d-7°470 EDMUND G. BROWN JR:., G"o'lte1nar

Jtmip•ro .Serra Bldg., Rm. 1065 107 South 8rogdway

R~~ourc;e&. liUdg., Rm. l 18 1416 Ninth Street

SAN FstANCISCO Fi:trry Building 9 ... 111

"""" 9581~

Hr. Robert W. Brown Senior Building Inspector C 1 ty of Fremont City Government Building Fremont, California 94538

Dear Mr. Brown:

(415) 557-0413

June 22, 1977

We are placing on open file the following reports, reviewed and approved by the City of Fremont in compliance with the AlquistPriolo Special Studies Zones Act:

Soil and geologic investigation on lands of Silveria (Tract 3754), Fremont, California; by Terrasearch; August 23, 1976; with supplement of May 19, 1977.

Soil and geologic investigation on Tract 3690, Starlite Way and Hackberry Street, Fremont, California; by Terrasearch; March 9, 1977; with supplement of April 1, 1977.

Sincerely yours,

EARL W. HART Office of the State Geologist CEG 935

EWH/mkr

cc: A-P file (2) •/ D.W. Carpenter

.r;; ""i::i,~ , . --City of Fremont City Governrnent Building Fremont, California 94538

June 20, 1977

State Division of Mines and Geology Room 1009, Ferry Building San Francisco CA 94111

ATTN: Earl W. Hart, Office of State Geologist

RE: Soil and Geologic Investigation for Tract 3690, Fremont, California

Gentlemen:

Enclosed for your file are the Soil and Geologic Investigation and our consultant's review for the subject tract,

Very truly yours,

/-,.,,~-,_t~,L~ __ ...• -

ROBERT W. BROWN Senior Building Inspector (415) 791-4142

RWB:erm

Enc. (1) Terrasearch, Inc. - Soil and .Geologic Investigation (2) David w. Carpenter, Alameda County Engineering Geologist letter

l( : '·''

Mr. Robert v. Brown Senior Building Inspecto'E' City of F'E'etll<mt City Govem~nt Buil.dins Fremont. CA 94538

De•r Mr: Brown1

March 31. 1977

As authorized by the City of l'nilllOUt. the Soil end Geologic In"stigatioll repol"t ;n:-epand by Tenasearch I11c. for T~ct 3690 has been revi.wed for confol"l!IUU'lce with pr.:iTistans of the Alquist-Pl"1olo Act. the l'eVieor consisted of a careful etudy of the nport.aod a field 1nspection of the tract eits.

It is f1i!1 p'E'Ofe.seiouel opinioll that the repon: prepared by Ternsearch lnc. ~fo- to l;bA nqv.i~.of the Alql.ii.st-Prtolo Act. It may be Wiled by the City of Fresmt && a bA111a for fUtQnl actioll!J pertaining to Tract 3690.

\

I.op of the test trezidi ad a test pit P-1. shaw the puse.nca of poekets of looaa, debris-bearing fill up to ,almu.t thnie feat to. depth. Sita inspection showed that thin. fills al.so blanket othsr portions of the au.hdivisioa 1trcia.

'1'b• presence of these filled ai:-eas 111ay e:.:plaio the .linear awale Which pal'allels the sMtero boundary of the sllbdivieicm adjacent to the Hetch-U.11:dly equeduct. Shallow filling has raised pol"tionft of the llllbdivision arc.a laartng a 1-ar area at natlll"U ~ade edjac..it to th• ll<i.~t.

' ' .. , : ': ,, ' ' " : . ' ' . ' . ' ~ ... ' -,.,... " .

'l'h• .fill.a ~ not •PP-r to pose a 11ro1>lem if rutdenus 1n the subdivision •?'& iiulfported .b)'\!"·i>1•1'. and grade beam ayat= •= reCClllliUmdcd b7 the aoil. engineer.

· .. ;However. thE:,y wmiHJ.'~esent in:oblei!lll for conventional foundation$ since they do not appear to h~i~¥"'f:K,Com;>acted md contain scrcp llll!tal and othef.' unsuitable con9titue:nt:s~ '1'berefon. :f,;tU yleomwded that u a condition of appT<Wal of thia eubdivtaion, · . the •oil e11g:l.1leef .be nqu.ired to cel'tify the remova.1 of ell fill 1118tariela or re~mpacticn of the· fills with 4euual of .unsuitable ccnetituenta. if tba developet: pl.ans a foundeti<m ,•)'Stai other thau pier md grade bemL ·

• ' I l

~····,

•,

. ' Mr. Robert V. Erown Mar. 31, 1977

Co11t11 for this review ara $96.00. n1ese vill be char11:ed againat the tnmt accowt estnblished by Harrison Romes vith the Al.o.i::eda County Euilding Inspection Department. · I havo appt'ecieted thia opportt<nitl' to provicle geological 1'evie11 s~rvices for tho City of Frenont and vould ba pleased to do so again if desit'ed ~1 th• City of Frell!Ont.

DWCrdl

•

·.~ . ~.""". .. .;."!''

Very tTilly you:ra,

DAVID W. CARPENTER ALAM!mA COUNTY

JnlG!?llIBRING GEOLOGIST LG. 1248 C.E.G. #13!1

'·

•

r

''.'!.;:~·''

' . , i

I i

···~· ·~ 1·--

•

•

•

•

•

•

•

•

•

•

•

SOIL & GEOLOGIC INVESTIGATION on

TRACT 3690 Starlite Way and Hackberry Street

Fremont, California

for

MORRISON HOMES Pleasant Hill, California

By

TERRASEARCH, INC,

Project No. 1715-E March 1977

•

•

•

•

•

•

•

•

•

•

•

TERRASEARCH, INC.

SOIL, FOUNDATION ANO GEOLOGICAL ENGINEERS

1\\80 NORTH FOURTH STREET SAN JOSE, CALIFORNIA 95112 (•08) 287-9460

Project No. 1715-E l April 1977

Morrison Homes P. 0. BOX 23172 Pleasant Hill, CA 94523

Attention: Mr. Barney Knox

Subject: Tract No. 3690 Starlite Way & Hackberry Street Fremont, California SUPPLEMENT TO SOIL AND GEOLOGIC INVESTIGATION

Gentlemen:

In accordance with your request, we have reviewed the subject Soil and Geologic Investigation Report prepared by our firm and dated __ 9 March 1977 in order to provide the following additional slab-on-grade and foundation criteria•

Concrete slabs-on-grade in living areas may be poured monolithically with spread footing foundations. It is feasible to support the foundations on properly designed structural slabs using post-tensioning .

Should post-tension slab foundations be desired to support the proposed structures, .the following criteria should be followed:

1. The slabs should be thickened at the edges so as to penetrate a minimum of 8 inches beneath final grade .

2. The slabs should be underlain by a layer of sand acting as a cushion. The cushion should be a minimum of 2-inches thick.

3. The slab should be underlain by a moisture barrier such as a plastic diaphragm. The diaphragm may be placed under the sand cushion .

SAN JOSE SACIAMl!NTO

•

•

•

•

•

•

•

•

•

•

•

Project No. 1715-E l April 1977

4. The s1ab,should be designed for a cantilever of 3 feet along the outer edge of the slab. The outer edge of the slab should be designed for a deflection of one inch in both directions .

5. Any exterior concrete flatwork such as steps, patios, or sidewalks may be designed either as part of the slab. or completely independent of the slab. If the flatwork is designed independently of the slab, waterproof joints should be provided between the flatwork and the structural unit.

If post-tension concrete slab-on-grades are utilized in the construction ot the proposed structures, the grading reco:rmiendations presented in the original report may be modi!ied as follows:

1. Compact the fill to a relative compaction o! no more than 85% and no less than 80% for the top one foot of fill and 85% to 90% below one foot of finish grade based on the ASTM Test Procedure Dl557-70 •

2. Moisture content should be no less than 4% wet of optimum. The subgrade soil should be saturated a minimum of one foot below finished grade before the slabs are poured.

3. The Soil Bngineer should verity the subgrade saturation of the subgrade soil before the slabs are poured. A minimum of one week of saturation is required before the slabs may be poured.

Should you have any questions or desire additional information, please contact our office at your convenience •

Reviewed by:

~~ Principal Engineer

TM:DY:ld

Copies: 9 to Morrison Homes

Very truly yours, TERRASEARCH, !NC.

Project

2 to MacRay & Somps (Union City)

2

•

•

•

•

•

•

•

•

•

•

•

TERRASEARCH, INC.

SOIL, FOUNDATION ANO GEOLOGICAL ENGINEERS

1580 NORTH FOURTH STREET SAN JOSE, CALIFORNIA 95112 (408) 287·9-tGO Project No. 1715-E 9 March 1977

Morrison Homes P. o. Box 23172 Pleasant Hill, CA 94563

Attention: Mr. Barney Knox

Subject:

Gentlemen:

Tract No. 3690 Starlite Way and Hackberry St.reet Fremont, California SOIL AND GEOLOGIC INVESTIGATION

In response to your authorization, TERRASEARCH, INC., has conducted a soil and geologic investigation at the site of your proposed project in Fremont, California .

The investigation consisted of subsurface exploration, aerial photograph interpretation, a research of literature, and laboratory testing. Analysis of the data resulted in the conclusion that the subject site is not crossed by a trace of an active fault and that some special considerations in foundation design and grading will be required because of the expansive nature of the near-surface soils.

Soil and geologic conditions do not preclude the development of the site for the construction of one or two-story, wood-frame single-family residences. This feasibility does not include economic factors and is based on the provision that design and construction will be accomplished in accordance with the recommendations of the enclosed report.

Should you have any questions, please contact our office .

Reviewed by:

th:rtHo~/J!i.E. Project ~i~::r CM:DY:ld

Copies: 10 to Morrison Homes

Very truly yours, TERRASE~CH, INC.

~ Curtis Messing Senior Enginee

, E.G. ng Geologist

1 to MacKay & Somps (Union City)

SAN JOSE SACltMIENTO

•

•

•

•

•

•

•

Project No. 1715-E 9 March 1977

TABLE OF CONTENTS

LETTER OF TRANSMITTAL

SOIL AND GEOLOGIC INVESTIGATION

Purpose and Scope Site Location and Description Geology (Regional) Regional Seismic History

GEOLOGIC FIELD INVESTIGATION

General Site Conditions Trenching Conclusions and Recommendations

REFERENCES

DISCUSSIONS, CONCLUSIONS AND RECOMMENDATIONS

General Grading Foundations Concrete Slab-on-Grade Construction Pavements General Construction Requirements

LIMITATIONS AND UNIFORMITY OF CONDITIONS

• APPENDIX A

•

•

•

Field Investigation Site Plan (Figure 1) Late Cenozoic Deposits (Figure 2) Special Studies Zone Map (Figure 3) Aerial Photograph (Figure 4) Log of Test Trench (Figure 5) Log :of Test Pits (Figure 6) Logs of Test Borings (Figures 7 through 9)

(ii)

Page No •

1-2 2-3 3-5 5-6

7 7-9 9-10

10-12

13

14 15-16 17-18 18-20 20-21 21-22

23

25 26 27 28 29 30 31 32-34

•

•

•


TABLE OF CONTENTS

APPENDIX B

Laboratory Investigation Summary of Laboratory Test Results (TABLE !)

• APPENDIX C

Recommended Grading Specifications Guide Specifications for Rock Under Floor Slabs

•

••

•

•

•

•

• (iii)

36 37

39-43 44 .

•

•

•

•

•

•

•

•

•

•

•


SOIL AND GEOLOGIC INVESTIGATION

Purpose and Scope

This report presents the results of our soil and geologic in-

vestigation for the proposed residential development in Fremont,

California. The purpose of the soil investigation was to

evaluate the subsurface soil conditions underlying the site

and to make recommendations concerning soil and foundation en-

gineering aspects of the site development. A geologic study

was conducted for this site in an effort to define any geologic

hazards, seismic or otherwise, that may exist on this site •

The investigation consisted of:

1. A review of literature concerning the site

and general area.

2. A study of aerial photographs of the site and

surrounding area .

3. A visual reconnaissance and field mapping

program by both the Engineering Geologist

and Soil Engineer •

1

•

•

•

•

4.

5.


The drilling of test borings including a

sampling program .

A trenching program on the site which con-

sisted of excavating more than 190 linear

feet of trench to a minimum depth of 9.5

feet.

6. The testing of soil samples obtained during

• the field exploration.

•

•

•

•

•

•

7. An analysis of data gathered and publishing

of a soils and geologic report .

Based on the results of the field investigation and laboratory

testing, recommendations are presented concerning grading,

geologic hazards, foundations and concrete slab-on-grade con-

struction .

Site Location and Description

The proposed 9-acre subdivision is located east of the inter-

section of Starlite Way and Hackberry Street in Fremont,

California. The "L"-shaped property is bordered on the east

by Starlite Way and Lands of the City of Fremont, on the

northeast by Hetch-Hetchy Water Line, on the south by an exist-

ing subdivision, and on the southwest by Hackberry Street •

2

•

•

•

•

•

•

•

•

•

•

•


At the time of our field exploration, the site was covered with

a low growth of grass. The site drains towards the south with

approximately 30 feet of drainage relief. A small slab of

asphalt was noted in the eastern corner of the site. A 2-foot

deep depression was also noted directly north of this asphalt

slab.

The location and description is based upon the site reconnais-

sance by the Soil Engineer and on a "Tentative Map" prepared

by MacKay & Somps which is the basis for our "Site Plan",

Figure No. 1.

Geology (Regional)

The site itself is underlain by alluvial deposits of Pleisto-

cene Age and is very close to the contact with a poorly lithi~

fied bedrock of Plio-Pleistocene Age.

The alluvial deposits have been described by Helley as Older

Alluvial fan deposits which, in this area, consist of weathered

poorly-consolidated, poorly-sorted silt, sand and gravel.

These deposits are reported to be less permeable and more poor

ly drained than younger alluvial fan deposits. Concentrations

of continental vertebrate and fresh water invertebrate fossils

are found locally. The maximum thickness of this unit is un-

known .

3

•

•

•

•

•

••

•

•

•

•

•


Dibblee (1972) has identified the bedrock unit which underlies

the hills to the east of the site as the Santa Clara Formation .

However, Burkland and Associates (1974), after an extensive

study, have stated that this formation is similar to the

Orinda Formation of Radbruch (1969), as noted in Northern

Contra Costa County, east of the Hayward Fault. Noting that

Dibblee's contribution is, for all practical purposes, a pre~

liminary map, the exact relationship between these two rock

units is not clear at this time.

The site is located partially within the State of California

Special Studies Zone to the east (see Figure 3, "Special Studies

Zone Map"). Three splinters of the Hayward Fault zone have

been located by Dibblee (1972) as being approximately 750 to

1,400 feet to the east of the site. These active faults trend

in a northwest direction approximately parallel to the site's

eastern boundary and divide the Plio-Pleistocene Santa Clara

Formation into two blocks.

The State of California has located a fourth splinter of the

Hayward Fault approximately 2,000 feet southeast of the site

at the Santa Clara-alluvium contact. This fault, as mapped,

4

•

•

•

•

•

•

•

•

•

•

•


terminates in the alluvium at this point. This contact has been

found faulted less than one mile to the north of the site near

Gable Drive, according to a recent investigation by Burton Rose

(1976). His study did not evaluate seismic risk for this trace,

but it is generally considered active •

Although Dibblee has mapped the contact between the poorly

lithified Plio-Pleistocene Santa Clara and Pleistocene alluvial

sediments as depositional, this contact is now considered to

be faulted in other areas. Dibblee notes landslides throughout

much of the Diablo Range but has not mapped landslides in the

hills directly adjacent to this site.

Regional Seismic History

The site is located within the seismically active San Francisco

Bay Region. Within the vicinity of the site, three active

splinters of the Hayward Fault have been included on the State

of California's Special Studies Zone Map. The site is located

within the sphere of influence of at least two other active

faults, the Calaveras, 3 miles northeast of the sitei and the

San Andreas, approximately 17 miles to the west of the site .

5

•

•

•

•

•

••

•

•

•

•

•


Seismic events do occur at recurrent intervals along these

active fault zones. The California Division of Mines and Geo-

logy (1973) has reported the latest notable historical events

as having occurred in 1836 and 1868 along the Hayward Fault

zone, and in 1906 and 1957 along the San Andreas Fault zone •

These events produced earthquakes of magnitudes of 7.0 and 7,5

in the Hayward Fault zone and magnitudes of 8.3 and 5.3 in the

San Andreas Fault zone, respectively. The epicentral distance

of these notable events from the site were approximately 1 and·

7 miles, respectively, for the Hayward Fault, and 79 and 34

miles, respectively, for epicenters at Olema and the Daly City

area along the San Andreas. It should be noted that the general

nature of the historic movement along known active faults has

been rioht lateral with a small vertical comoonent .

6

•

•

•

•

•

•

•

•

•

•

•


GEOLOGIC FIELD INVESTIGATION

General

The extent of this investigation was limited to that portion of

the site which falls within the Special Studies Zone boundary

in the eastern portion of the site. The surface conditions of

the site were investigated by air-photo interpretation and field

mapping. The subsurface conditions at the site were investigated

by trenching in an northeast-southwest direction between the

site boundary on the east and the Special Studies Zone boundary

·on the west. In .this manner, any northwest-southeast trending

faults could be intercepted. Also, three exploratory borings

were drilled to a minimum depth of 20 feet. All exploratory

work was performed under the direct supervision of members of

our geology and engineering staff.

Site Conditions

Due to the absence of surface exposures on the site, field map-

ping was confined to observations in landforms and lateral sur-

face soil changes •

7

•

•

•

•

•

••

•

•

•

•

•

Project No. 1715-G 9 March 1977

Aerial photographs flown in April, 1973, were stereographically

examined. These photos reflect a scale of approximately

l"=l,000' and revealed strong geomorphic evidence for recent

fault movement in this area, see Figure No. 4, "Aerial Photo-

graph."

The courses of natural streams to the east of the site are

deeply incised at the mountain front and_ .. appear to turn north

at a point along a line trending roughly north-south. This

apparent right lateral displacement of stream courses is, most

likely, due to right lateral displacement across the Hayward

Fault. This apparent trace of the fault is approximately

1,500 feet to the east of the site.

A shallow linear surface depression was noted approximately

200 feet from the eastern boundary of the site. This linear

feature parallels the Hetch Hetchy water line and was probably

caused during fill consolidation following the construction

of the water line.

Stream drainage patterns in the hills to the east of the site

are generally oriented along the strike of the bedrock. Several

recent landslides are apparent in the aerial photographs within

8

•

•

•

•

•

•

•

•

•

•

•

Project No. 1715-G 9 March 1977

the drainage basins of the streams to the east of the site.

It can be expected that an influx of sediment may be trans-

ported and deposited along the stream systems during periods

Of landslide movement in this basin .

Due to the gentle slope gradients within the vicinity of the

site, all natural slopes are considered stable and the occur

ance of landslide movement is virtually nil on this site .

Trenc;:hinq

The absence of sharp, lateral, lithologic contrast, which is

generally related to faulting, was confirmed through trenching.

One exploratory trench and two exploratory test pits were exca-

vated on the site in an east-west direction. The "Log ©f

Test Trench and Test Pits" are shown on Figures No. 5 and

No. 6.

The site is overlain by a 2 to 3 foot layer of dry friable organic

chocolate-brown to black topsoil which is moderately to highly

expansive. Relatively wide and numerous expansion cracks are

found to a depth of 3.8 feet. Immediately below this topsoil lay-

er is a chocolate-brown silty clay which grades to mottled green-

brown and chocolate-brown stiff clay toward the west of the

9

•

•

•

•

•

•

•

•

•

•

•


trench. These clays contain minor amounts of rounded to well-

rounded quartzite and metamorphic pebbles. Toward the west of

the trench T-1 (see Figure No. 5 ), chert and quartzite pebbles

become subrounded to subangular. Below these clays, there

occurs a thin, interbedded tan and chocolate-brown silty,

pebbly clay with 5 to 10% rounded to subrounded friable light

tan sandstone pebbles, and well-weathered friable medium to

light tan siltstone pebbles and rounded quartzite pebbles •

Throughout all these units, there occur numerous expansion

cracks which have filled with calcite and randomly oriented

expansion cracks. Occasionalinvertebrate fossils are found

within these units. The sediments observed in the trenches are

likely equivalent to what Helley et al (1972) have mapped as

"Older Alluvial Fan Deposits" which are lower Pleistocene in

age .

Conclusions and Recommendations

The following conclusions are based upon the data obtained and

evaluated during the course of the investigation:

1. There is no evidence that the Hayward Fault crosses the

property •

10

•

•

•

•

•

•

•

•

•

•

•


2. From the data gathered in test trenches and borings, the

nearest fault trace is beyond the eastern boundary of the site .

3. The most likely location of the active traces of the Hayward

Fault is to the east of the site with the closest trace being

some 750 feet to the east. Other active trac.es are located to

the east of Interstate 680 and possibly under the freeway.

4. Geomorphic evidence indicates regional movement has occurred

in recent times within the vicinity of the site.

5. There is no evidence that any landslide movement has occur-

red within the site on any natural slopes.

6. There may be a periodic increase in sediment load in the

small drainages entering the site due to possible landslide

movement in drainage basins to the east.

7. In general, there were no geologic conditions recognized

within this site that should prevent development as proposed.

Estimated Secondary Ground Effects of Earthquakes: The

effects during an earthquake in the San Francisco Bay Area

during a credible earthquake are based upon estimates made

11

•

•

•

•

•

•

•

•

•

•

•


in the San Jose area, directly to the south which, in turn,

were determined by computer models (Cooper-Clark, 1974) .

The borings at the site indicate that no saturated, loose sands

are located within considerable depth at the site. Therefore,

the potential for shallow liquefaction is low.

All factors indicate that the geologic conditions are such as

to produce low accelerations of long periods which would have

a tendency to produce temporary lurch cracking within the site.

The actual effects on structures would be dependent upon the

structures and the earthquake signature. One and/or two-story

frame structures designed in accordance with current design

criteria should survive a seismic event with minimal damage .

12

•

•

•

•

•

••

•

•

•

•

•

REFERENCES


1. California Division of Mines and Geology, "Environmental Geological Analysis of the South County Study Area, Santa Clara County, California", by J.W. Williams, Preliminary Report No. 18, 1973.

2. California Division of Mines and Geology, "Special Studies Zones for the Milpitas Quadrangle, June, 1974.

3. Dibblee, Thomas w., "Preliminary Geologic Map of the Mil-. pitas Quadrangle, Alameda and Santa Clara Counties, California", U.S.G.S. Open Map File, 1972 .

4. Helley, E.J.; Lajoie, K.R.; and Burke, D.B., "Geologic Map of Late Cenozoic Deposits, Alameda county, California", U.S.G.S. Misc. Field Studies Map, MF-429, 1972.

5. Porter, Ed, "Soil and Geologic Investigation on Lands of Arai", dated September, 1976.

6. Porter, Ed, "Soil and Geologic Investigation on Tract 3738", Fremont, California, dated 1976.

7. Rose, Burton, "Geologic Report on Tract 3623", dated 4 February 1976 .

13

•

•

•

•

•

·-•

•

•

•

•

Project No. 1715-E 9 March 1977 ,

DISCUSSIONS, CONCLUSIONS ANb RECOMMENDATIONS

General

1. The site is suitable for residential-type development pro-

vided the recommendations presented in this report are incor-

porated into the project plans and specifications.

2. All grading and foundation plans should be reviewed by th·e

Soil Engineer prior to contract bidding •

3. The Soil Engineer should be notified at least two working

days prior to any site clearing or grading operations on the

property in order to observe the stripping of contaminated

material and to coordinate the work with the grading contractor

in the field .

4. Field observation and testing during the grading operations

must be provided by representatives of TERRASEARCH, INC., to

enable them to form an opinion regarding the adequacy of the

site preparation, the acceptability of fill materials, and the

extent to which the earthwork construction and the degree of

compaction comply with the specification requirements. Any

work related to grading performed without the full knowledge

and under the direct observation of the Soil Engineer will ren

der the recommendations of this report invalid.

14

•

•

•

•

•

•

•

•

•

•

•

Grading


5. Before any grading is done, the surface of the site should

be stripped to remove existing vegetation and other deleterious

materials. The depth of stripping should be determined in the

field at the time of grading. lt is estimated that stripping

depths of 3 to 5 inches may be necessary. Any undesirable

items which do not meet the requirements of engineered fill

(basements, old building foundations, septic and other buried

tanks, leach fields, etc.) should be removed. Any existing fill

and rubble should be excavated and removed in their entirety.

The resulting excavations should be backfilled with engineered

fill. Stripped material from the site may not be used as en-

gineered fill .

6. Following site stripping, the top 8 inches of exposed sub-

grade soil in both areas to be cut and filled should be scari-

fied and compacted to a minimum degree of compaction of 85% but

not more than 90% and at a moisture content of at least 3% above

the optimum moisture content as determined by ASTM Dl557-70

laboratory test procedure. The degree of compaction is defined

in the attached "Recommended Grading Specifications." After

15

•

•

•

•

•

••

•

•

•

•

•


stripping and recompacting, the site may be brought to the

desired finished grades by placing engineered fill. All soils

encountered during our investigation, except those within the

top few inches of organically contaminated material and any ex-

isting fill, would be suitable for use as engineered fill when

placed at the recommended moisture content.

7. Native materials used in fills should be compacted to a

minimum degree of compaction of 85% but not more than 90% and

at a moisture content of 3% above the optimum moisture content

as determined by ASTM Dl557-70 Laboratory Test Procedure .

8. Import material to be used as engineered fill must be ap-

proved by the Soil Engineer and should meet the requirements

of the attached grading specifications. Import engineered fill

should be compacted to a minimum degree of compaction of 90%

as d~f~ned on the attached specifications. All engineered fill

should be placed in lifts not exceeding 8 inches in uncompacted

thickness .

16

•

•

•

•

•

•

•

•

•

••

•

Foundations


9. The near-surface site soils are highly expansive. It is,

therefore, recommended that the proposed structures be sup-

ported on a pier and grade beam foundation. Recommendations

to support the structure on spread footings founded on the

native soils are also provided. All foundations should be

designed in accordance the recommendations of this report.

Alternate A - Pier and Grade Beam Foundations

10. It is recommended that the proposed residential structures

be supported on a drilled friction pier and grade beam founda-

tion. The piers will derive their support from peripheral

friction developed in the in-situ soils. For design purposes,

the allowable friction should not exceed 500 p.s.f. due .to dead

plus live loads with an increase of one-third allowed for

temporary, wind or seismic loads. The top 18 inches should be

neglected from the design friction capacity of the piers be-

cause of the potential soil shrinkage away from the top of the

piers.

11. The piers shall be of reinforced cast-in-place concrete

with a minimum diameter of 10 inches and a minimum depth of

54 inches below the existing ground surface. A minimum spac-

ing between piers of 3 times the pier diameter should be

maintained .

17

•

•

•

•

•

••

•

•

•

•

•


12. The grade beam reinforcing will be dependent on the pier spac-

ing and the structural loads to be supported but, in no case,

should less than two No. 4 bars be used, one on top and one on

the bottom of the beam. The topsoil should be sloped away from

the foundations to provide rapid runoff of the surface water •

It is recommended that the grade beam be constructed so that

the width of the beam is constant, top and bottom .

Alternate B - Spread Footing Foundations

13. Should it be desired that the proposed residential structures

be supported on spread footing foundations bearing on native

soil, the footings should extend a minimum depth of 24 inches

below the lowest adjacent finished grade, At this depth, design

allowable bearing pressures should not exceed 2,000 p.s.f. due

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

3,000 p.s.f. due to all loads including wind or seismic. The

native soil should be presoaked until all shrinkage cracks are

effectively sealed.just prior to pouring foundations and slabs-

on-grade .

Concrete Slab-on-Grade Construction

14. The near-surface soil at the site is highly expansive.

Therefore, it is expected that the concrete slabs-on-grade will

18

•

•

•

•

•

•


experience cracking. Because of the potential expansion, con-

crete slabs-on-grade in living areas may be utilized for struc-

tures supported on deep spread footings only. To reduce the

cracking for slabs-on-grade, the following recommendations are

made:

a. All areas to receive slabs should be soaked

to saturation prior to the placing of concrete.

This work should be done under the observation

of the Soil Engineer,

b. Slabs should be provided with tool joints as

expansion joints. Such joints should extend

along the middle of the slab in both directions.

c. Slabs at door openings should be constructed

• with a curl or thickened edge extending six

inches into native ground or compacted fill.

d. Concrete slabs must be poured structurally in-

• dependent of the foundations. A 30-pound felt

strip, expansion joint material or other posi-

tive separator should be provided around the

• edge of all floating slabs to prevent bond to

the foundation. No dowel of any kind should

• be used.to tie any slabs-on~grade to adjacent

.foundations. A positive bond break should be

used between all garage slabs and foundations,

• 19

•

• Project No. 1715-E 9 March 1977

e. Where floor covering is anticipated, measures

e should be provided to prevent damage due to

moisture condensation. If visqueen is used, 2

inches of moist sand placed over the visqueen

• will minimize damage to the moisture barrier

and help the curing of the slab.

f., Slabs should be underlain by a four-inch minimum

• layer of gravel or clean crushed rock.

g. Slabs should be reinforced with a minimum of

wire mesh; however, due to the difficulty of

•• proper placement of wire mesh within the

center of the slab, the equivalent bar rein-

• forcing is preferable. Single-unit slabs

should not be more than 200 square feet of

equal dimensions .

• 15, Porch columns supporting overhanging roofs should be struc-

turally independent of porch slabs •

• Pavements

16. Recommended section thicknesses are summarized on the

table below, based on an R-Value of 5. Several traffic indices

• were assumed in the design. Pavement sections corresponding

to traffic indices different from those shown will be provided

upon request .

• 20

•

•

•

•

•

•

•

•

•

•

•

Traffic Asphaltic Index Concrete

4 2 3

5 2.5 3

6 2.5 3

7 3 4

8 3 4

Class 11 Aggregate Base

(inches)

8 6

6 9

6 6

6 6

6 6


Class II Aggregate Subbase

(inches)

6

10 8

12 9

16 14

NOTE: (1)

all layers in compacted thickness Cal-Trans Standard Specifications

17. All pavement construction and materials used should con-

form to applicable sections of the latest edition of the Cal-

Trans: Specifications, State of California, Department of

Transportation. The top 6 inches of native subgrade beneath

pavements should be compacted to a minimum degree of compaction

of 90% and at a moisture content at least 2% above optimum

as determined in the laboratory .

General Construction Requirements

18. All final grades should be provided with a positive gradi-·

ent away from all foundations in order to provide rapid removal

21

•

•

•

•

•

•

•

•

•

•

•


of t.he surface water runoff away from the foundations to an

adequate discharge point. No ponding of water should be

allowed on the pad or adjacent to the foundations.

23. The use of continuous roof gutters is recommended. The

downspouts from the roof gutters should be provided with ade-

quate drainage to carry storm water away from the structures

and to reduce the possibility of soil saturation adjacent to

the buildings .

22

•

•

Project No. l715rE 9 March 1977

LIMITATIONS AND UNIFORMITY OF CONDITIONS

• 1. The recormnendations of this report are based upon the

assumption that the soil conditions do not deviate from those

disclosed in the borings and from a reconnaissance of the site.

e If any variations or undesirable conditions are encountered

during the development of the site, TERRASEARCH, INC., should

be notified so that supplemental recormnendations may be given •

• 2. This report is issued with the understanding that it is the

responsibility of the owner, or his representative, to ensure

•• that the information and reco!Tllllendations 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 Contractor and Subcontractors

carry out such reco!Tllllendations in the field .

•

•

• 23

•

•

•

•

•

•

•

•

•

•

•

•

APPENDIX A

Field Investigation

Site Plan

Late Cenozo.ic Deposits

Special Studies Zone Map

Aerial Photograph

Log of Test Trench

Log of Test Pits

Logs of Test Borings

•

•

•

•

•

•

•

•

•

•

•


ENGINEERING FIELD INVESTIGATION

The engineering portion of the field investigation consisted

of a site reconnaissance by the Soil Engineer and the drilling

of 3 test borings at the approximate locations shown on Figure

No. 1, "Site Plan." The test borings extended to depths rang-

ing from 20 to 25 feet below the existing ground surface.

Drilling was performed a truck-mounted. rig using power-driven

6-inch diameter continuous flight augers. As the drilling pro-

ceeded, undisturbed core samples were obtained by means of a

3-inch 0.D. modified split-tube sampler. The sampler was hydrau

lically pushed into the in-situ soils.

The samples were sealed and returned to our laboratory for

testing. Two disturbed near-surface samples were also obtained .

The stratification of the soils, description, location of un-

'disturbed soil samples and selected test results are shown on

Figures 7 through 9 .

25

•

•

•

•

•

•

•

•

•

•• Tl~l~l~A S8Al~t~H HK.

•


\ ' ,..\

SITE

MAP

l . ~deep

Oepre>sion

'I' lndlcaj·es Approx. Test Eloring Locations ..,. • " • Pi1· Locutions

• " Trench t.ocahon

FIGURE NO. 1 - SITE PLAN

26

I

I

EXPLA.~ATION

'1;

I\,'

; :: ,,·., :. -~.

·.· Younger alluvial fan d@posits \ ,,

';'<. '•

Qb; interfluvial basin deposits; mainly organie-~ich clay and.silty Contain modern· fresh~wat.er gastropods and pe:lt:!:~}"'POds. Sunnyv.alt:!: 1

Bayshote Soil Series of U.S. Soil Conservation Set'Vice (1968) are thri!!s~ de.posi t:e

clay that 'loCai'ly . · Willows, ·and de:ve.loped on.

~ Qyfo, fluvial d~posits at the outer edge of young alluvial fans (Qyf); fonns leveea ~ between basin deposits (Qh) and characterized by variable grain size:. Ha.inly fine

: o sa.nd 1 silt, and silty clay. Cle.':lr Lake, Castro, and Campbell Soil Series of U.S. ·Soil; ~ Cvnservation Service (19~8) are dcv~lope:d on these deposits ~ Qyf, young alluvial fan deposits grading headward to terrace and levee ·deposits of

ehannel~ incised in Qof. Consista of moderately well sorted fine sand and silt with minor gravel beds be~oming more abundant toward fan heads. Locally contains abotiginal artifacts and skeletal remains. The weakly developed Yolo, Garret~on. and Cortina. Soil Series of U.S. Soil Conseivdtion S~rvice (1968) are developed on these deposits

Qobm

• Older San Francisco Bay mud

'

).. Qobm.1 si!mi consolids.t~d orga.ni~-ri~h clay depoaite; underlies younget" San Ftancis:co a:ay O::

?11\!d of Nichols and Wright (1971) and young alluvial fan deposits; ~xtends landward to<( maxi~1.m1 elevation of 10 feet above mean sea level. The ~istinctive Alviso Soil S@ries:z: of U,S. Soil Conservation Service (1968) is developed on these deposits C::·

UJ

~· Qof <(

fmffB~ 5 Old~r alluvial fan d@posits

Qof~ older fan deposits bordering uplands; at fan heads incised by channel~ partly filled by Qyf: at outer margins overlap~ed by younger alluvial fan de:po~ita, Qyf 1

Qyfo. and Qb. ~ainly coarse sand ~nd g~avel wt th local accumulations of middle and late Pleieto~ene vertebra~e foaaila. Th~ strongly deve:lope:d Zamora, Pleasanton, San Ysidro, Arbuckle, Cropley, and Rincon Series of U.S. Soil Conservation Setvice (1968) are developed on th~ee deposits

Older digsected alluvi&l fan deposita

Isolated alluvial de:posits fonni.ng moderately dissected fans (Qofd1) and highly dissected fans (Qofd

2); c.onsist of coarse to very c.oarsi:!: highly weather~d gravels.

Hillgate, Sa:r;atogd;and Posi.tas Soil Series of U.S. Soil Con~etvation Service (1968) have very strongly develop~d soil profil~e which are slightly @roded (ofd1) or deeply eroded with strl.vp•d soil hotbon.• (ofd2l

'

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

SCALE 1:62500

Project 9 March

No. 1715-E 1977

I ~ j 4MILES :,=="'======='-.========-=---.- - - ===--=====>

~llni rEEY ---...

FIGURE NO. 2- LATE CENOZOIC DEPOSITS

27

.~) I

............ .. , ,, 4.··

' , .. . '\ ' .... • ' •t•"····

MAP EXPLANATION •

Potentially Active Faults

-Faults considered to have been active during Quaternary time; solid line where accurately located, long dash where approximately located, short dash where inferred, dotted where concealed;. query(?) indicates additional uncertainty. Evidence of historic offset indicated by year of earthquakeassociated event or C for displacement caused by creep or possible creep.

Aerial photo lineaments (not field checked); based - -- · -· - on youthful geomorphic and other features believed

to be the results o'i"Quaternary faulting.

6---o 1

---~----0 - . - ....•

Speclal Studies Zone Boundaries

These are delineated as straight-line segments that connect consecutively numbered turning points so. as to define one or more special s.tudies zone segments.

Seaward projection of zone boundary.

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

•

••

•

•

•

•

• 28

Project No. 1715-E 9 March i977

6000 ~OOQ FEET ., .. .:.:..==:::J

FIGURE N0.3-SPECIAL STUDIES ZONE 1\AI'

Project Mo. 1715-E 9 Morch 1977

J

J

J

J

J

)

J

•

) ,..

sea le : t '= 1000' :t -·---=-=-=--=----:-:---- -. ---- -- -=----= ·--)

[ FIGURr: ~;-_-4 ~~ i;~Pho·i·oqraph

)

J

)

J

l

)

)

)

I

)

)

,-

.,. . 1" < 1oco1_t_ sc_n. n~.

" 1715. E. Project "0 · 9 March 1977

-------·----'".er i;lPh~~:~graph _____ _ ---·-··----~-IG-Ul<': •;u._ <1_-_/4._ ___ ·--·---·-b --:-: .. -:---., ~i~~..-.~., -.. _,. I _________ ... ---· ... 'l ,.., '? i' ~J.o1 ... J [:.,... ·----11'.""'l"l· .. !"", ·. 'l ·. · .. ' ... i;.•)+'.4Jt.l - -' liij .. .i. ""~--·-_!'·_·_· .. --·-·-·· ---

-, I I i

OVER IZED ~·

DOCUME T HAS. BEENP LLED ANDSC NNED WITHT EMAP

FIL .

• 30

•

•

•

•

• 'lO

I •

•

•

•

•

P-1 Pro'ect 1715-E 9 March 1977

Black CLAY, dry w/organics and numerous expansion cracks

'20 lO 0

I I FILL area, loose w/debris

Chocolate-brown to black CLAY w/trace of rounded metamorphic pebbles and caliche deposits, slightly moist to moist, stiff

P-2 Ill 0

I I Black CLAY, expansive w/organics, trace of Sand, numerous expansion cracks

-95

-90

I

-too

-95

- -90

Black CLAY w/trace of Sand, moist, stiff w/ many expansion cracks filled w/caliche deposits

-ss

Seo I e : I" ~ 51

1 Horiz. ~ Vert .

FIGURE NO, 6 - LOG OF TEST PITS

• Project No. 1715-E 9 March 1977

LOGGED BY BG DATE DRILLED 3/3/77 BORING DIAMETER 6 " BORING NO. '

• - · 1-1 - 2 -- -- 4 -• - - -- 6 -- -- 8 -- --10 -• - --12 -- --14 -

• - --16 -- --18 -- --20 •• - -- -- -- -- -- -. - -- -... -... -... -... -. ... -... -- -- -. -. -. - -- .. - -- -- -. - ., - -

-- -

•

- / ~,

I(

1-2 ,r 0

U' J'y y

J '

/~ ,j'

~ ~

SOIL DESCRIPTION

Dark brown Silty CLAY, moist, hard

T T

Brown

White specks

Boring terminated at 20 feet.

.

L06 18 CH

06 20

.

.

MISC. LAB

RESULTS

I FIGURE NO. 7 - LOG OF TEST BORING

32

•

•

•

•

•

•

•


LOGGED BY BG DATE DRILLED 3/3/77 BORINO DIAMETER 6" BORING NO. 2

SOIL DESCRIPTION

- - ~ Dark brown silty CLAY, moist, hare , - 2 -- _:..-1 1 - 4 - . - . -- 6 -- -2-2 - 8 -- --10 -- . --12 -- --14 -- --16 -- --18 -- -... 20 -... -... 22 -... -

' '/.A.A

-~ y· ~

vv

,

... 24 - :,i

T Brown

T White specks

T Light brown

CH

.

.

01

94

17

16

MISC, LAB

RESULTS

~,· T Trace of small gravels

... -1-~f..:t.i+-~~~~~~~~~~~~~~~~--11----1~-+~-+~-+-~-+-~~~~--1

,... - Boring terminated at 25 feet . - -- -- -- -- ~

- -. - -- -- -- -- -- -. - -- -- -- -- -- -. - -- -- -- -

T FKlURE NO. 8 - LOG OF TEST BORING

• 33

•

•

•

•

•

•

•

•

•

•

•

.

LOGGED BY BG DA TE DRILLED JLJt:ZZ

= 18.-

J ~b .8 ~~

SOIL OESCRIF>TION

i:iJ "'


BORING DIAMETER fi II BORING NO. 3

a~ -j1i ~j b e"i MISC.

"B~ ,...,. "jg .....: :I LAB i~ ...J ~ c! ~ t; z:.

~ "ili ·-"' ' ., z:. ca. :i "" RESULTS :55

_:g :I "' m.., C>'tf Cl

.. - :;,i:oark ~ JI

brown Silty CLAY, moist, hard .... 2 -

y CH ,_ -

- 4 - 3-1 05 19

- -,_ 6 - - y Brown y

~T - -8 - 3-2 .06 16 -- -

-10 -~T

White Specks

- .--12 -- -""14 -

tT - --16 - Trace of small gravels - --1s - ~ - --20 - - Boring terminated at 20 feet. - -.... -- -- -- -- -.... -- -- -- -.... -.... -- -- -- -- -- -- -- ...,

- ...,

- -- -- -- -- -- -- -

'rl~lflfA s1~Alft~u •N•:. I FIGURE NO. 9 - LOG OF TEST BORING

34

.

•

•

•

•

•

••

•

•

•

•

•

APPENDIX B

Laboratory Investigation

Summary of Laboratory Test Results

•

•

•

•

•

•

•

•

•

•

•


LABORATORY INVESTIGATION

Laboratory tests were made to evaluate the strength, compres-

sibility and expansion potential of the soils. Moisture

content and dry density determinations were made on represen-

tative soil samples. The results of these tests are shown

on the corresponding sample locations of the "Logs of Test

Borings", and on TABLE I.

The strength parameters of the foundation soils were determined

by unconfined compression tests. The expansion characteristics

of the existing near-surface soils were evaluated by means of

Atterberg Limits (Liquid and Plastic Limits). The results of

the tests are shown on TABLE I •

36

•

• Hole Depth Dry No. . Density

(ft.) (p.c.f.)

• 1:..1 1 106 1-2 5 106

• 2-1 2 101 2-2 6 94

3-1 3 105 3-2 7 106

•

••

•

•

•

•

•

TABLE I


Summary of Laboratory Test Results

Moisture Atterberg Limits Unconfined Direct Content Liquid Plasticity Compressive Cbhesion

(%Dry wt.) Limit Index Strength (p.s.f.) (%) (p.s.f.)

18 59 36 20

17 4,100 16

19 16 3,500

37

Shear Angle of Internal Friction {deilree~

•

•

•

•

••

••

•

•

•

•

•

APPENDIX C

Reconunended Grading Soecifications

Guide Specifications for Rock Under Floor Slabs

. .

•

•

•

•

•

•

•

•

•

•

•

. '


RECOMMENDED GRADING SPECIFICATIONS for

TRACT 3960 Fremont, California

1.1 General Description

1.11 These specifications have been prepared for the grading and site development of the proposed residential development located in the warm Springs District in Fremont, California. TERRASEARCH, Inc., hereinafter described as the Soil Engineer, should be consulted prior to any site work connected with site development.

1.12 The Soil Engineer should be notified at least.two working 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.

1.13 This item shall consist of all clearing or grubbing, preparation of the land to be filled, filling of the land, spreading, compaction and control 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. The property owner, or his representative, shall designate the person or organizations that will be responsible for these items of work.

1.14 The contents of these specifications shall be integrated with the soil report of which they are a part; therefore, they shall not be used as a self-contained document •

2.1 Tests

2.11 The standard test used to define maximum densities of all compaction work shall be the ASTM test procedure Dl557-70. All densities shall be expressed as a relative compaction in terms of the maximum dry density obtained in the laboratory by the foregoing standard procedure .

39

•

•

•

•

•

•

•


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

3.ll All trees, roots, debris, vegetable matter, and organic topsoil shall be removed from all structural areas. The depth of organic topsoil to be removed will be determined in the field by the Soil Engineer but in general will vary from 3 to 6 inches.

3.12 All soil deemed soft or unsuitable by the Soil Engineer shall be removed. Any existing fill and rubble shall also be excavated and removed.

3.13 All underground structures shall be removed. from the site ·such as old foundations, abandoned pipe lines, septic tanks and leach fields. \

3.14 The final stripping and excavation shall be approved by the Soil Engineer during construction before further grading is started.

3.15 After the site has been cleared, stripped and scarified, it shall be disked or bladed until it is uniform and free from large clods. The exposed native subgrade soils which are expansive shall be compacted to a minimum degree of compaction of 85% but not more than 90% and at a moisture content of at least 3% above the optimum moisture content as determined in the laboratory. Fill can then be placed to provide the desired finished grade. The Contractor shall obtain the Soil Engineer's approval of subgrade compaction before any fill is to be placed.

e 4. l Materials Used for Fills

•

•

•

4 .11 All fill material shall b.e approved by the Soil Engineer. The material shall be a soil or soil-rock mixture which is free from organic matter or other deleterious substances. The fill material shall not contain rocks or lumps over six inches in greatest dimension and not more than 15% larger than 2-1/2 inches.

·Materials from the site below the stripping depth may be suitable for use in fills. The soil Engineer shall determine the suitability of materials for use as engineered fill .

40

•

• Project No, 1715-E 9 March 1977

4.i'2 Import material required must be approved by the Soil Engineer prior to transporting it to the project and must meet the requirements of Section 4.11. In addition, import material

e •hall. have a Plasticity Index not greater than .12.

•

•

•

•

•

•

•

•

5.1 Placing, Spreading and Compacting Fill Material

5.11 The fill materials shall be placed in uniform lifts of not more than 8 inches in uncompacted thickness. Each layer shall be thoroughly blade-mixed during the spreading to obtain l:lniformity of material in each layer. 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 •

5.12 After each layer has been placed, mixed and spread evenly, import material shall be compaCted to a relative compaction of not less than 90%. Expansive native soils shall be compacted to a minimum degree of compaction of 85%, but not more than 90%, and at a moisture content of at least 3% above the optimum moisture content as determined in the laboratory. The degree of compaction is the ratio of the dry density of the constructed fill to the maximum determined by the ASTM Laboratory Test Procedure Dl557-70 .

5.13 Compaction shall be by sheepsfoot rollers, multiplepneumatic tired rollers or other types of acceptable compacting rollers. Rollers shall be of such design that they will be able to compact the fill to the specified density. Rolling shall be accomplished while the fill material is within the specified moisture content range. Rolling of each layer shall be continuous over its entire area and the roller shall make sufficient trips to ensure that the required density has been obtained. No ponding or jetting shall be permitted.

· S.14 Field density tests shall be made in each compacted layer by the Soil Engineer in accordance with ASTM Test Procedure 01556-64 or ASTM Test Procedure D2922-71. When sheepsfoot rollers are used for compaction, the density tests shall be taken in the compacted material below the surface disturbed by the roller. When these tests indicate that the density of any layer of fill, or portion thereof, is below the required compaction the particular layer, or portion thereof, shall be reworked until the required compaction has been obtained .

41.

•

•

•

•

•

•

•

•


5.15 No soil shall be placed or compacted during periods of rain nor on ground which is not drained of all free water. Soil which has been soaked and wetted by rain or any other cause shall not be compacted until completed drained and until the moisture content is within the limits hereinbefore described or approved by the Soil Engineer. Prior approval by the Soil Engineer shall be obtained before continuing grading operations.

6.1 Pavement

6.11 The proposed subgrade under pavement sections, native soil and/or fill, shall be compacted to 90% relative compaction at a moisture content of at least 2% above optimum, for a depth of 6 inches.

6.12 All pavement construction and materials used shall conform with the applicable sections of the latest edition of the CalTrans Specifications for Pavements, State of California, Department of Transportation.

7.1 Utility Backfill

7.11 Where any opening is made under or through the perimeter foundations for such items as utility lines and trenches, the openings must be resealed so that they are watertight to prevent the possible entrance of outside irrigation or rain water into the underneath portion of the structures. The utility trenches extending under the perimeter foundations and concrete slabs-ongrade floors shall be backfilled with native engineered fill and compacted to the requirements for engineered fill. No ponding or jetting will be permitted.

8.1 Subsurface Line Removal

8.11 The methods of removal will be designated by the Soil Engineer in the field depending on the depth and location of the lines. One of the following methods will be used.

8 .• 12 Remove the pipe and compact the soil in the trench accord-• ing to the applicable portions or Sections 5.1 and 7,1

•

•

8.13 The pipe shall be crushed in the trench. The trench shall then be filled and compacted according to the applicable portions of Sections 5.1 and 7.1

42

•

•

•

•

•

•

•

•

•

•

•


8.14 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 .

9.1 Unusual Conditions

9.11 In the event that any unusual conditions, not covered by the special provisions, are encountered during the grading operations, the Soil Engineer shall be immediately notified for directions .

43

•

•

•

•

•

••

•

•

Definition


GUIDE SPECIFICATIONS FOR ROCK UNDER FLOOR SLABS

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 adobe, vegetable matter, loam, volcanic tuff, and other 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.

Grading

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 grading:

Sieve Size

3/4" No. 4 No. 200

Percentage Passing

100 10-35

0-2

e Placing

•

•

Subgrade, upon which gravel or crushed rock is to be placed, shall be prepared as outlined in the accompanying Soil Report •

44

d-7°470gmw.consrv.ca.gov/shp/apsi_siteinvestigationreports_ocr/apsi_000463/apsi_000463...mar 09,...

Documents