pete governor - californiagmw.consrv.ca.gov/shp/apsi_siteinvestigation... · 12/21/1990 · state...

STATE OF CALIFORNIA - THE RESOURCES AGENCY

DEPARTMENT OF COllSERVATIOll DIVISION OF HINES ANO GEOLOGY BAY AREA REGIONAL OFFICE 185 Berry Street, Suite 3600 San Francisco, CA 94107 Phone (415) 904-7707

ATSS 539-7707 Fax (415) 904-7715

James O .. Berkland County Geologist

October 18, 1993

Santa Clara County Planning Dept. Government Center, East Wing, 4th Floor 70 West Hedding Street San Jose, CA 95110

Dear Jim:

PETE ~ILSON, Governor

This is to acknowledge the numerous reports you loaned us from the 1989 earthquake damage file. We copied 11 of these reports for our AP file (marked "AP" on attached list). In addition, 20 reports for sites outside the sszs were considered to be useful because of fault or ground-fissuring data and were copied for our informal consulting file (marked with a·"C".on the ~ttached list). The remaining reports from this set were not copied. All of the original reports from the damage file were returned to you by Perry Wong on 10/13/93.

The set of duplicate reports provided to Perry about two weeks ago have not yet been processed. We will provide you with a list of the reports filed when this work is finished.

Thanks for making these reports available to us.

EWH:ra Enclosed list/ cc: A-P file ;.

Sincerely,

f ,tc:f!f-EARL W. HART Senior Geologist &

Program Manager

APDRESS

Gascoigne Dr. 10716 CU I

Glencoe 10511 LA

C v:']Iillpark Ln. 11534 LA

H\llpark Ln. 11555 LA

Hillpark Ln. 11559 LA '

Holmes 1160 CA

Johansen 10685 LA

Jcihnson Ave. 10409 CU

I Johnson Ave. 10616 CU

i Johnson Ave. 10700 CU

I La Cuesta 302 LA

! LOngwood 15860 LA

i;oyola W. 10501 LA I

i.;oyola W. 10620 LA

Loyola W. 10665 LA

Loyola W. 10795 LA I

!loyola W. 10800 LA

Loyola W. 10811 LA

Lundy 938 LA

Magdalena 11630 LA

Magdalena 11710 LA

Mayfield Ave. 867 PA

OCTOBER 1989 EARTHO!JAKE

DAMAGE INSPECTIONS

NORTH COUNTY

DAMAGE DESCRIPTION

flp damage; minor

house damage; minor

sheetrock breaks, gar slab breakage;severe(from mod 8

fireplace damage; minor

structural displacement; moderate

flp damaged; minor

cosmetic

cosmetic damage

severe damage to flp

minor damage

issue bldg permit; chimney repair

chimney; minor

damage to 2 frplcs; moderate

cosmetic damage

chimney damage; minor

house damage; minor; garage & chimney down; moderate

geologic problem; house to be demolished; severe(orig.

settlement; wall & chimney cracks; moderate (prev minor 6-22-'

superficial damage; minor

house damage; minor

flp damage; fnd cracks; moderate

replace frplc/chimney; fndn cracks; stairway damage; moderat•

. ' '

cW7 f"'.'.':"--------ENG lN E ER lN G GcOLOGY

.. PILE COPY

GEOTECHNICAL INVESTIGATION on

PROPOSED RESIDENCE 11534 Hillpark Lane

Santa Clara County, California for

DR. NORMAN BUYS

,

i! . :; :_.'•. -: .:\

GEOTECHNICAL ENGINEERS AND GEOLOGISTS

l¥.t GEOTECHNICAL ENGINEERS ANO GEOLOGISTS

'••~ r1~1~ltltA Sl~Altt~H •~•:. 1580 NORTH FOURTH STREET, SAN JOSE, CALIFORNIA 95112-4676, (408) 453-1180

Dr. Norman Buys 11534 Hillpark Lane Los Altos, CA 94022

Subject: Proposed Residence 11534 Hillpark Lane

Project No. 6295 21 December 1990

Santa Clara County, California GEOTECHNICAL INVESTIGATION

Dear Dr. Buys:

In accordance with your authorization, TERRASEARCH, INC., , has investigated the geologic and geotechnical conditions at 1 the subject site for a proposed residence. The data used in

the analysis of the project were derived from literature research, air photo study, and subsurface exploration.

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

Sho'uld you have any.questions or require additional information, please contact our office at your convenience.

. Reviewed by:

~)-~ Tom s. Makdissy, G.E. Principal Engineer

Copies: 6 to Dr. Norman Buys

Very truly yours, ~ARCH INC .

Richard R~C.E.G.~ Senior Geologist

4 7~~ ,,,L.,-,,.L / r~

Amer Kelzieh Staff Engineer

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

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


TABLE OF CONTENTS

LETTER OF TRANSMITTAL

GEOTECHNICAL INVESTIGATION

Purpose and Scope Site Location and Description Geologic Setting Site Geology Seismic Considerations

REFERENCES CITED

DISCUSSIONS, CONCLUSIONS AND RECOMMENDATIONS

General Geologic Conclusions and Recommendations Demolition Grading Slopes Foundations Slab-On-Grade Construction Retaining Walls Pavement Areas General Construction Requirements

GUIDELINES FOR REQUIRED SERVICES

LIMITATIONS AND UNIFORMITY OF CONDITIONS

(ii)

Page No.

1-2 2-3 3-4 4-7 7-9

10-11

12-13 13-14 14-15 15-18 18-19 19-20 21-22 22-24 24-25 25-27

28-29

30-31


APPENDIX A

TABLE OF CONTENTS (continued)

Field Investigation Regional Geology (Figure l) Subregional Geology (Figure 2) Site Plan and Geologic Map (Figure 3) Logs of Test Borings (Figures 4 and 5) Log of Test Trench (Figure 6)

- Logs of Test Pits (Figures 7 and 8)

APPENDIX B

Page No.

33 34 35 36 37-38 39 40-41

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

APPENDIX C

Recommended Grading Specifications Guide Specifications For Rock Under

Floor Slabs

(iii)

46-56 57

PURPOSE AND SCOPE


GEOTECHNICAL INVESTIGATION

'The purpose of the investigation for the proposed residence

:located on Hillpark Lane near Los Altos Hills, California,

was to determine the geologic/seismic hazards and geotech

: nical conditions at the subject site. The proposed dwelling

'will replace one that was so severely damaged by the October

: 1989 earthquake. A trace of the Berrocal Fault has been

:shown on regional maps (Dibblee, 1966) as projecting toward I the subject site. The primary intent of this investigation

•was to determine if faulting would have an adverse impact

· upon the proposed dwelling replacement within its "foot

, print."

This investigation included the following tasks:

a. Review of published and unpublished data

pertaining to the site;

b. Stereoscopic examination of black/white,

vertical-angle photographs;

c. Surface reconnaissance by the Engineering

Geologist and Soil Engineer;

d. Excavation of an exploratory trench and two

test pits;

1


e. Drilling of exploratory borings and sampling

the subsurface soil horizons;

f. Laboratory testing of samples obtained from

the .borings; and

g. Analysis of resulting data and preparation of

a report containing geotechnical recommenda

tions for grading and foundations.

SiTE LOCATION AND DESCRIPTION

The subject site is located a few hundred feet east of

R~vensbury Avenue, just southeast of the town limits of Los

AC!. tos Hills. The irregularly shaped lot, which consists of

aibout 1. 5 acres, lies on the south side of ;the southerly

branch of the forked cul-de-sac of Hillpark Lane (see Figure

2). At the time of our investigation, the distressed house

'fas occupied; and the wood retaining wall along the north

west side of the house had been removed. The swimming pool ' in the west side of the lot was filled and did not appear to

pe cracked, however, the deck had been removed from around

the pool. Most of the. house distress appeared to be located

:in the south part of the house. The distress cracks primar-' ily -affected the garage slab and the retaining wall on the

east side of the lower floor of the house. The exiting land

)scaping and associated irrigation lines had not been

removed.

2

I I


The proposed house will mainly remain within the existing

footprint, except that it will be twisted slightly from a

north-south trend to a north-northwest trend.

This site description is based on site examination by the

Engineering Geologist and 8-scale site plans prepared by

Greg Benton, Architect.

GEOLOGIC SETTING

The site is located in the northeast foothills of the Santa

Cruz Mountains near the contact between older metamorphic

rocks of Cretaceous age, Tertiary marine

m.arine Quaternary sediments bordering

P\1blished regional maps include Dibblee

sediments, and non

the Bay flatlands.

(1966), Rogers and

A;rmstrong (1973), Rogers and Williams (1974), and Cotton (1978). Terratech ( 1990) show the site to be near west-

I}Orthwest trending faults that thrusted Franciscan rocks on

the south up over Tertiary marine sediments (including

Monterey Formation) on the north (see Figures 1 and 2).

Rogers and Armstrong (1973) and Rogers and Williams (1974)

~how the subject site to be underlain by Miocene marine

.sediments with a thrust fault 400 feet to the southwest mark

ing· the contact with Franciscan rocks. In more detailed I

mapping within the limits of Los Altos Hills, Cotton (1978)

shows the area immediately southwest of Ravensbury Avenue to

be Miocene marine sediments, with an east-trending thrust

3


fault located about 500 feet south of the site as the Fran-

ciscan contact {see Figure 2). The historically active San

Andreas Fault lies about 3. 7 miles southwest of the site.

No landslides were mapped in the vicinity of the site in

these studies. A recent investigation has been made by

Terrasearch, Inc., (1990), on the lot immediately to the

southeast of the subject lot. '

SITE GEOLOGY

~ite geologic conditions were studied by means of a) stereo-, ;;copic examination of black/white, vertical-angle aerial

photographs, b) surface geologic mapping of the site, and c) I

subsurface backhoe exploration including one trench and two test pits.

,The photographs that were examined were flown on 26 August

!1976 by Pacific Aerial Surveys {Serial Nos. AV-1277-02-12

:and 13) at a scale of approximately 1: 12000. The photo

'graphs were searched for evidence of geologic hazards.

Faults are sometimes ·indicated by tonal and/or topographic ' ;lineaments while landslides sometimes are expressed by

peculiar geomorphic features such as lobes, hummocks, I . 'swales, or scarps. No indications of any landslide features

1were observed on the photos near the subject lot.

A possible fault related lineament was observed. This is a

topographic lineament trending in a northwest direction,

connecting the saddles

Arroyo Oaks Drive, and

indicated on Figure 2.

in the ridges along Old Ranch Road,

Eloise Circle. This lineament is

4

I


The only exposures of bedrock in the lot were at the toe of

the cutslope on the inside edge of the driveway. These

exposures, which are indicated on Figure 3, were all of

soft, fractured, grey to orange-brown claystone and silt

stone typical of the Monterey Formation (Miocene Age) in the

site vicinity.

Trench 1 was excavated roughly parallel to the long dimen

sion of the proposed dwelling and roughly perpendicular to

the trend of faults in the vicinity as indicated in Figure 2.

The excavation was somewhat constrained by the presence of

a.n active gas main· at the north end of the house and an

active septic leach field at the south end of the house.

The trench actually ended up closely paralleling a leach

line that was exposed in the west wall of the trench. I

Fortunately, this line was part of the expansion area and

was inactive. The east side of the trench was a good

exposure of the native soil horizon and extended well into

the bedrock materials. The trench was 84 feet in length and

ranged up to 1 O feet in depth. Bedrock belonging to

~onterey Formation was exposed in the northern two-thirds of

the trench. Between Stations 49 and 61, a contact with hard

dark grey-green Franciscan rock (serpentine and/or green-

stone) was exposed. This contact appeared to be unsheared,

5


and it dipped at a low angle to the southwest. The topsoil

thinned noticeably from the Monterey Formation to the Fran

ciscan Formation.

Test pits 1 and 2 were located about 80 and 50 feet, respec

tively, beyond the south end of the trench (and outside of

the active leach field) in order to trace the contact

between the Monterey and Franciscan units.

exposed a hard, dark grey-green1 metamorphic '

Test Pit 1

rock of the

~ranciscan Assemblage, whereas Test Pit 2 was excavated in

tlaystone and siltstone of Monterey Formation. Test Pit 2 ' could not be extended further west because leach field ' gravels were exposed. The contact between the two units

appears to run irregularly in a north-northwest direction as

~elineated on Figure 3. The subregional relationships shown I

pn Figure 2 indicate a possibility that the contact may run

;subparal le 1 with the aforementioned topographic lineament ' .and connect with a narrow sliver of Franciscan rock that I ~rosses Eloise Circle.

'The "Tus" unit (unnamed Miocene sandstone) that was mapped I

;by Rogers and Williams (1974) and Terratech (1990) was not

!found on the site either in surface mapping or subsurface

, exploration. I

Evidence of seepage or high ground groundwater was observed

at the toe of the cutslope along the driveway. The existing

house reportedly had a problem with seepage in the retaining

wall on the east side of the ground floor. This problem

6


appears to have been mitigated by construction of a second

wall outside of and upslope from the original structural wall.

SEISMIC CONSIDERATIONS

Damage to structures related to fault movement may be

divided into two categories: a) primary deformation such as

displacement of a structure located directly on a fault or

.ground shaking and b) secondary (induced) failure such as

lurch cracking, landsliding, liquefaction, and differential

icompaction.

The hazard of surface fault displacement is low because no

active faults were found within the proposed building "foot-

·print." However, a contact between the Monterey:=and:::Fran-·,

·ct.scan •. f.'.O£Ill=a-i:,iR~=~as_~found_~~.;~"a'~?.lY...Jf§5t -of -the --house,

Although the contact appears to be unsheared, a geotechnical

limitation will 'l:ie present due to the contact between rocks

:of widely differing characteristics. Therefore, it is recom

.· mended that a fJve-'foot""'""setback-..be c·maj._rr~aine<!,,12.~S'f.~~~!1.e

.contact and the house foundations in order to mitigate this

: limitation.

Ground shaking is a complex concept related to velocity,

amplitude, and duration of earthquake vibrations. Damage

from ground shaking is caused by the transmission of earth

quake vibrations from the ground to the structure. The most

7


destructive effects of an earthquake are usually seen where

the ground is unstable and structures are poorly designed

and constructed. The most probable source of significant

seismic shaking is the historically active San Andreas

,Fault, which lies about 3. 7 miles southwest of the site.

,For the San Andreas Fault, the maximum credible earthquake

(based on rupture of the entire Northern California segment)

has been estimated by Wesnousky ( 1986) to have a moment

: magnitude of 7.8, with an average repeat time of 300 years.

,Based on the relationship formulated by Campbell (1985) and

Joyner and Boore (1988), anticipated peak horizontal bedrock

,acceleration at the site would be between 0.5g and 0.6g for

the M.C.E.

The epicenter of the recent Loma Prieta Earthquake was about

:24 miles south-southeast of the site. Although the probabil

, ity of a similar earthquake occurring southeast of the site

is reduced, the probability of an earthquake on the segment

, of the San Andreas Fault that is west and northwest of the

; site may be increased. The U.S. Geological Survey has

;recently (1990) estimated the probability of a strong (magni-

tude 7. 0) earthquake occurring on the Peninsula segment of

the.San Andreas Fault as 23 percent over the next 30 years.

·If such a quake occurred at the point on the fault closest

'. to the site, peak horizontal bedrock accelerations of 0. 4g

may be anticipated at the site using the attenuation rela-

tions formulated by Campbell ( 1985) or Joyner and Boore

( 1988). Other more distant known active faults that may

8


subject the site to lesser shaking are the Hayward and

Calaveras Faults, which are

tively, to the northeast.

located 13 and 18 miles, respec

Structures built on bedrock are

not as severely stressed by seismic motion as those in flat

~reas covered by thick, unconsolidated alluvium because of

the shorter period and smaller amplitude of the seismic

waves. However, the immediate site vicinity may be subject

to a greater than normal amount of seismic wave energy owing

to the presence near the proposed house foundation of a

~ontact between differing bedrock types.

]!.andslides are common during large earthquakes. However,

there is negligible potential for landslides because none

have previously occurred on the site. The secondary hazards

of lurch cracking, liquefaction, and differential compaction

are not significant because of the shallow depth of bedrock.

The site location precludes the secondary hazards of seiche and tsunami.

9


REFERENCES CITED

'Campbell, K.W., 1985, "Strong Motion Attenuation Relations: A Ten-Year Perspective": Earthquake Spectra, Vol. 1, No. 4, August 1985, pp.759-804.

,Cotton, W.R., 1978, "Geotechnical Map Folio of Los Altos .Hills", unpublished compilation of geologic maps for the Town of Los Altos Hills, California.

Dibblee, T.W., Jr., 1966, "Geology of Palo Alto Quadrangle, ,Santa Clara and San Mateo Counties, California", Division of Mines and Geology, Map Sheet 8, Scale 1:62,500.

,Joyner, W.B., and Boore, D.M., 1988, "Measurement, Charac, terization and Prediction of Strong Ground Motion" in Pro-· ceedings of Earthquake Engineering and Soil Dynamics II: GT 1Div/ASCE, Park City, Utah, June 27-30, 1988.

iRogers, T.H., and Armstrong, C.F., 1973, "Environmental : Geologic Analysis of the Monte Bello Ridge Mountain Study :Area, Santa Clara County, California", California Division ~of Mines and Geology, Preliminary Report 17.

1Rogers, T.H., and Williams, J.R., 1974, "Potential Seismic Hazards in Santa Clara County, California", California Divi

jSion of Mines and Geology, Special Report No. 107. ' ! Terrasearch, Inc., 1990, "Geologic/Seismic Investigation on :Proposed Residence, Arroyo Oaks, Santa Clara County, Cali, fornia": unpublished geotechnical report for Dr. Jorge :Huertas dated 7 May 1990 (Project No. 6195).

' j Terra tech, Inc., 1990, "Concentrated Damage From the Loma 'Prieta Earthquake in the Manta Vista Fault Study Area, Santa : Clara County, California": unpublished geotechnical report for Santa Clara County Planning Department dated 31 Octob.er 1990 (their Project No. 4745).

10


REFERENCES CITED (continued)

U.S. Geological Sur:vey, 1990, "Probabilities of Large Earthquakes in the San Francisco Bay Region, California", U.S.G.S. Circular 1053.

Wesnousky, S.G., 1986, "Earthquakes, Quaternary Faults, and Seismic Hazard in California": Journal of Geophysical Research, Vol. 91, No. Bl2, pp. 12,587-12,631, November 10, 1986.

11

<GENERAL


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 or Engineering Geologist prior to contract

bidding or submittal to governmental agencies so that plans

,are reconciled with soil conditions, and sufficient time is

allowed for suitable mitigative measures to be incorporated

,into the final grading specifications.

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

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

i operations on the property. This will give the Soil Engi-

neer or Geologist ample time to discuss the problems that

may.be encountered in the field and coordinate the work with · the contractor.

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-

12


ing the adequacy Of the site preparation, the acceptability

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 rende·r the recommendations of this report invalid.

'5. Exploration trenches and test pits which have been exca

vated for geologic and/or soil investigations have been

loosely backfilled. Soils in any test pi ts and test

trenches beneath all .proposed structural areas should be re-

' excavated and backfilled with engineered fill in accordance

i with the grading requirements as specified in this report.

GEOLOGIC CONCLUSIONS AND RECOMMENDATIONS

6. The proposed building area appears to be underlain

entirely by claystorie and siltstone of the Miocene Formation.

No evidence was found of active faulting within the proposed

building "footprint." However, an unsheared contact with

: very hard and dense Franciscan rocks was found a short

distance west of the existing house. A building setback

distance of 5 feet from this contact should be adhered to in

order to minimize geotechnical effects from the widely

differing rock types.

13


7 · No evidence of slope instability such as old landslide

zones was observed during. the air photo study and the on

site reconnaissance.

8. The

caused at

caused by

, quake.

distressed condition of the house appears to be

least partly by downslope lurching and soil creep

the gravitational effects during last years earth-

9. Owing to the location of the site in an area of possible

seismic "focusing", it is recommended that

tion be given to the structural design.

, the structural design recommendations

recent Terratech (1990) report be given

special considera

We recommend that

contained in the

careful considera-

tion since they are based on actual building performance in

the pertinent geologic area.

DEMOLITION

10. 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,

of items equipment, debris and trash, with the exception

specified by the owner for salvage. The owner

should specify the saving or removal of shrubs or trees on

the site.

located on

carried out.

In addition, all underground structures must be

the grading plans so that proper removal may be

14


11. 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

: be excavated and removed as required by the Soil Engineer

.during grading. The removal of trees shall include the root

· system. 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. 1 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 extend 5 feet beyond the footprint of the structure and

: backfilled to the specifications for engineered fill as

recommended in the "grading" section herein.

GRADING

i 12. Grading activities during the rainy season may be hamp-

ered by excessive moisture. It is recommended that grading

be performed during the dry months to minimize potential

compaction problems.

15


13. Soft fill and/or soft native soils were encountered in

·Borings 1 and 2 in the upper 2 feet beneath the existing

'asphaltic concrete pavement. These soils must be removed

and replaced as engineered fill compacted to a minimum rela-

1 tive compaction of 90% as determined by ASTM 01557-78

Laboratory Test Procedure.

1 14. The surface of the site should be stripped to remove

all existing vegetation and/or other deleterious 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 Engineer. Stripped

'material from the site may not be used as engineered fill

. but may be stockpiled and used later for landscaping pur

; poses. Any existing wood debris should be removed from the I

: site. Any existing loose fill should be excavated to undis-

1 turbed native ground. Materials generated from loose fills

i may be used as engineered fill with the approval of the Soil IE . ngineer provided they are not contaminated by debris.

15. Following site stripping and excavation of any loose

, fill, the top 6 inches of exposed native ground should be

moisture conditioned and compacted to a minimum degree of

compaction of 90%, but not more than 95%, at 3 to 5% above

optimum moisture content, as determined by ASTM Dl557-78

16


Laboratory Test Procedure. After recompacting the native

ground soils, the site may be brought to the desired

finished grades by placing engineered fill in lifts of B

inches in uncompacted thickness and compacted to the rela

tive compaction requirements in accordance with the aforemen

tioned test procedure. All soils disclosed during our inves

tigation, except those within the top few inches of organi

cally contaminated material, would be suitable for use as

engineered fill.

16. 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 requirements:

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%, at slightly above optimum moisture content, as deter-

, mined by ASTM Dl557-7B Laboratory ~est Procedure. All engi

neered fill should be placed in lifts not exceeding B inches

in uncompacted thickness.

17


17. The grading requirements presented herein are an

ral part of the grading specifications presented in

·dix C of this report and should be considered as such.

,SLOPES

integ

Appen-

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

·a surface gradient steeper than 6: l (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. This key

:should be a minimum of 12 feet in width and 3 feet in height

,cut into competent native soil and sloped into the hillside

at a gradient of no less than 5%. Subsequent keyed benches

1 should be not less than l. 5 times the grading equipment

f width and 3 feet in vertical height.

'19 · Cut and fill slopes should not be steeper than 2: 1

'.(horizontal to vertical). All cut slopes should be rounded I

! at the upper extremities. All engineered fills should

extend a minimum of 10 feet laterally from the proposed 1 building foundations.

i 20. Fill slopes must be compacted as the filling operation

; progresses by ( 1) using sheepsfoot".'type rollers in conjunc

tion with proper moisture conditioning, or ( 2) over

constructing the fill slopes and cutting back the looser

18


surface soils to a firm and adequately compacted designed

slope grade. Track-walking of slope

vide adequate soil densities and is

of slope compaction.

surfaces does not pro

an unacceptable method

21. 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

established to carry the surface runoff water away from the

slopes to areas where erosion and sediment can be controlled.

FOUNDATIONS

22. The surface soils at the site range from highly to

critically expansive. It is imperative that the recommenda

tions regarding depth of foundations, provisions to reduce

damage to foundations, and/or exterior slabs, and preventa

tive measures regarding wetting of foundation soils be

followed closely.

I 23. The proposed building structure should be supported on

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

beam type foundation. The piers should have.a minimum diame

ter of 12 inches and should extend a minimum depth of 10

feet into native undisturbed soil or engineered fill. The

piers should be . designed on the basis of skin friction

acting between the soil and that portion of the pier that

19


extends below a depth of 2 feet below the finished grade.

For the soils at the site, an allowable skin friction value

of 450 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 struc-'tures. Reinforcing steel should be provided as necessary

.for structural support and continuity of pier and grade beam.

·Spacing should be determined as ·required by the load distri

bution; but minimum spacing should not be less than 3 pier

diameters, center-to-center. The piers should be designed

;for an uplift adhesion of 300 p.s.f. along the upper 3 feet

. of their shafts, and grade beams should be designed for an

:uplift pressure of 2,000 p.s.f .

. 24 · Where pier foundations are used, a passive pressure

'equivalent to that of a fluid weighing 250 p.c.f. is recom

:mended. The passive pressure can be assumed to act on an

. area encompassing twice the pier diameter along the length

.of the pier below a depth of 2 feet.·

· 25. Piers located within fill placed on a hillside

i subject to lateral loads imposed by the fill. For

:purposes, it is recommended that a lateral load of 50 '

may be

design

p.c.f.

'(equivalent fluid pressure) be assumed against the sides of

. these piers along the upper 4 feet of pier length or the

portion of the pier within the fill, whichever is smaller.

20

SLAB ON GRADE CONSTRUCTION


26. Concrete slab-on-grade floors are not recommended for

living areas at the subject residence. However, for garage

·and other non-living areas, 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 poten-

tial cracking of the slabs-on-grade, the following recommen

dations are made:

a. All areas to receive slabs should be soaked

until a moisture equilibrium condition is

reached in the upper 24 inches. This condi

tion must be verified by the Soil Engineer in

the field.

b. A minimum of 4 inches of gravel or clean

crushed rock material should be placed between

the finished subgrade and all the slabs to

serve as a capillary break between the subsoil

and the slab. See the "Guide Specifications

For Rock Under Floor Slabs", Appendix c ..

c. Slabs should be reinforced with a minimum of

wire mesh. Care should be taken to center the

reinforcement in the slab.

21


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 12 inches into native ground or

compacted fill.

RETAINING WALLS

1 27. If retaining walls are incorporated into the design and

,construction of the proposed dwelling, the following design

parameters should be used. 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 Unrestrained Condition

45 65

Weight (p.c.f.) Passive

Resistance

250 250

Coefficient of Friction

0.30 0.30

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. All surcharge loads and

loads imposed during compaction have to be considered in the

design of the walls.

22


28 · 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 compacteq 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:

23

Sieve Size

l"

3/4"

3/8"

No. 4

No. 8

No. 30

No. 50

No. 200


Percentage Passing

100

90-100

40-100

25-40

18-33

5-15

0-7

0-3

29. The retaining walls should be supported on the founda

tion system as specified under the heading "Foundations."

' PAVEMENT AREAS

30. Preparation of Subgrade: After underground facilities

have been placed in the areas to receive pavement and the

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 speci

fied in this report.

31. 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 pavement areas

24


should conform to the requirements set forth by the latest

,Standard Specifications of the Department of Transportation

of the State of California and/or County of Santa Clara,

,Department of Public Works.

32. Pavement Sections: No specific tests were performed to

, determine the pavement section in the proposed pavement

areas. However, based on our experience with similar soil

·materials, a tentative pavement section of 2. 5 inches of

asphaltic 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

, 33. All finish grades should provide a positive gradient to

: an adequate discharge point in order to provide rapid

: removal 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.

: 34. 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

25

,


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.

, 35. 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.

' , 36. 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. No sprinkler

!heads should be allowed to water closer than 3 feet from the

I perimeter footings;

' 37. '. 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.

38. 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-

26

pacted to

01557-78


95% relative compaction in accordance with ASTM

Laboratory Test Procedure. Backfilling and

compaction of these trenches must meet the requirements set

forth by the County of Santa Clara.

39. Applicable safety standards require that trenches in

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

'of the trench slope back to provide safety for installation

:of lines. If trench wall sloping is performed, the inclina

: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.

:40. 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

i 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.

27

l '


GUIDELINES FOR REQUIRED SERVICES

The following list of

must be provided by

development. These

services are the services required and

Terrasearch, Inc., during the project

services are presented in check list

format as a convenience to those entrusted with their imple

mentation.

The items· listed 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 overempasized. It should be noted, however,

1 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.

28

1 Project No. 6295 21 Decenter 1990

Itan Description RE.>quired Not RE.>quired

1. Provide foundation design pararreters x

2. Review grading plans and specifications x

3. Review foundation plans and specifications x

4. Observe and provide reccmrendations regard-ing dem::Jlition x

s. Observe and provide reccmrendations regard-site stripping x

6; Observe and provide reccmrendations on , noisture conditioning, reroval, and/or pre- x ' canpaction of unsuitable existing soils

7. Observe and provide reccmrendations on the installation of subdrain facilities x

a: Observe and provide testing services on fill areas and/or inported fill materials x

9. Review as-graded plans and provide additional foundation recarmendations, if necessary x

10• Observe and provide canpaction tests on sanitary sev.ers, stoDn drain, water lines x and PG&E trenches

11~ Observe foundation excavations and provide supplarental recarmendations, if necessary x

' prior to placing concrete

12·. Observe and provide noisture conditioning recarmendations for foundation areas prior x to placing concrete

13:. Provide design pararreters for retaining walls x '

14:. Provide geologic observations and recamenda-tions for keyway excavations and cutslopes x during grading

15. Excavate and recanpact all geologic trenches and/or test pits x

16. Observe installation of subdrain behind retaining walls if any) x

29

l

i 1

!



1. It 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. I

· 2. The recommendations of this report are based upon the

: assumption that the soil conditions do not deviate from I

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

: reconnaissance of the I ; sirable conditions be

, the site, TERRASEARCH,

site. Should any variations or unde-

encountered during the development of

INC., will provide supplemental recom-

mendations as dictated by the field conditions.

i 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

field. Subcontractors carry out such recommendations in the

30

[

i I '

I

I

----··-...



(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 with standing, all the foregoing applicable codes

must be adhered to at all times.

31

J

APPENDIX A

Field Investigation

Regional Geology

Subregional Geology

Site Plan & Geologic Map

Logs of Test Borings

Log of Test Trench

Logs of Test Pits

j


FIELD INVESTIGATION

The field investigation was performed on 6 and 19 December

1990 and included a reconnaissance of the site, the drilling

of 2 exploratory borings, and the excavation of 1 test

~rench and 2 test pits at the approximate locations shown on

Figure 3, "Site Plan & Geologic Map."

The borings were drilled to a maximum depth of 18 feet below ' the existing ground surface. The test pits were excavated

to a maximum depth of 11 feet. The drilling was performed

with a truck-mounted rig using power-driven, four-inch diame

ter 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 2-1/2 inch O.D., split-tube sampler. i The sampler was driven into the in-situ soils under the

1mpact 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). Hand sampling was used to obtain

.two samples from the geologic trench ..

:The· samples were sealed and returned to our laboratory for

1testing. 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 contained within this

'appendix.

33

'.

'. jl" • •.

"'

'Ose: Dibblee (1966) SCALE 1"~ lmile

'-TBl~ltA SEARCH 11c. FIGURE NO. 1 - REGI01'."1\!. GSOI.DG'i

34

/ / /

/ /

BASE, Terratech ( 1990)

, ( Jee D o _,i:;i

21 l'eCC"~beJ:· 1990

SCALE' 111 = 200' TBltltA SBAltt~H INt:. ~JGURE NO. 2 - SL"Er£GI0Hl'ili GEDI.DGY

I

I

I

LOG OF TEST BORING

Baring No: 1

Date Drilled: 12/19/90 Elevation: N.A. Logged by: AK

Water Level: NA

BORING 1

Project No: 6295

After: NA ! I I ....-~~~,.....~~~~~~-.~~...-~~~~~~~~~~~~~....,.~~~--.~~..,...~..,..~~.,....~~ ..

I ELEV SA~J1lo:Ff~~rbi_s uses SOIL DESCRIPTION !REMARKS Somple Blows Density Moisture j DEPTH No. foot Dry-pcf Percent

I I

I l I

~o

-

-10

~ ~I ~ ~· ~ Y'). T

2-1/2" of asphal~ic concrete

cc;·srown.· .Ye110wish.tirown.· CH and grey Silty CLAY w/f ine

Sand. moist. soft in the upper 2 feet. then becomes stiff below that

) Yellow Clayey SANO cuttings (FILL) at 4 feet

tL · · · Ta·nn 1·si-i · ·gre·en · ·cerr1erit.ed Silty CLAY w/some Siltstone, moist, hard

No Reco'v _

30

C=2120 1-1 61/10· 106 16 psf; ~=

- tL ···ye·1to·w·£s·h-·tJ·raw·n··c·eme·nt'e·cf ..... 25 deg.

Silty CLAY w/some fine Gravel, moist, hard

Boring terminated ~ 13.5 ft No groundwater encountered

TERRASEARCH, Inc. 37

1-2 38/6' H6 12

Figure Number 4

LOG OF TEST BORING 80RING 2

Soring No: 2

Date Drilled: 12/19/90 Elevation: N.A. Logged by: AK

Water Level: NA

ELEV

.

DEPTH

-0

-5

-10

-15

SOIL Sn.£30LS SAMPLER SYMBa..S

After: NA

uses SOIL DESCRIPTION

- CLi'bark'browri' Siity'CLA'f;' CH moist, soft in the upper

1-1/2 feet. then becomes stiff below that

- cc Green ist1 orciwn cemented Silty CLAY w/some Claystone, Sandstone, and caliche

- cc··· ve'i1 owist1 i:ir'owri i:eiiie'rit:eci Silty CLAY w/some fine Gravel, moist, hard

Boring terminated at 18 ft No groundwater encountered

*sample examined on site

TERRASEARCH, Inc. 38

Project No: 6295

REMARKS Sample Blows Density Moisture No. 1oot Dr)l-pcf Percent

53•

.2-1 70/11" jOO 22

..

Figure Number 5

0

Sarrple

/ .

Projec'c llo. 6294 21 Dece.'llber 1990

Co1_Jper water line )

10/ 20 30 40

Fedium to dark bro ebbly Clayey SILT (FIT...J,)

- -- - -- - -Q_ - - - - - .._ TT-1 Very dark grey-brown Silcy - - - - -..... ________ -

40

CL.1\.Y, rroist, stiff, irregular lower contact I - - ~ _, ,,.,- ... ___ _ .. _ .... -, --- _, ___ ,- .... _-~ ......... _ .. -,_ .... _... ............. "'\. _______ - .... __ - - -- -- -- -- ..__ .. -... -T-2 Ibttled tan/grey fractured CLAYS'IOl'!E:

w/caliche seams and EXJds in U?per 3 to 4'; local irregular EXJlished shears; soft, r.oist

-- (Tm bedrock)

50 60

- - -- - - ---.. --- - - - - - -, _____ ......

I

70

I I

I

I

... - ..-?"'"~- - I ...... ( \ '\

_ -I'Dttlea"Veryoaf'K grey.:- -1 - - - - - - -- - - - - - l?fOWn Pebbly Silty CLl'.Y 1~- -~

80

/ . ,_.,,.. ' .... , ......... )"-" . ' Tan to light grey',

-- ' '----, ~,._--~, .... ___ ,_ .. , calichified Silty ' , -----Sfu"ID -

--X-

Leach line avel

1

N551"1, 30Sl·J

Blue green to grey green foliatied rnetarrorphic rock (Franciscan bedrock), fol~ation parallel to contact; grades harder w/de,lth to near refusal to backhoe

(attitude of 1.msheared contact)

FI URE NO. 6 -:- TRENQ! r.a;

~/--

DEPTH

0-5.5' (A)

5 • 5•• 7 • 5 I

, --------------" .••.···~ ---~-~~---MATERIALS DESCRIPTION

TYPE, COLOR, MOISTURE, CONSOLIDATION, ETC. BEDDING

Verv dark qrev brown to black Pebbly Siltv CLAY; none finn to stiff, 11Dist ('lDDSCJIL)

~'bttlecl grey brown/n-edirnn brown Pebbly Silty Cf,1\Y none

IR\ and Clavev SILT· finn to stiff lmlluviall

7.5-10.0' (C)

~ -

I::ark grey-green Pranciscan bedrock: verv hard,

dense, refusal to backhoe; rock is an aphani~~ __ c ___ _,

homfels with subhorizontal foliation

0 5

-· - ·-t-t- - -t- - ---f--1- - -- -- -1---- -·- -l-- -·- -- _..._ - - -

-- - - -- - ·· - ·- - -- ·--·I- - - - ·- -- - -I-- -

-- - -- ··- - ·t- - - -- - -- -· - - -J.-- -· ·- - - -- - - -

·--··- - -1- - -

-- t- -- - - - -1--!- -· .... 1-- -- -

10 15

-t--- ---· - --

- " , -,,,. - - -· -- - - --1-f- -· - -1- .. ··-1- - - - ·- - - -- - -- -J.-- -- - - ·-1-- ·- ·-

-- -- I- - --t- -·--------

none

ATTITUDES

JOINTS

none

none

none

- -1-t-+-H- - - - - - - -1- --r- -,,,. r-0 . - -- -- - - - -- - - - - - _,_,.. ,..., _..,

I··- - -· -- - --1- . - --1- - ·- _ 1~~1-- _ __ __ _ __ _ __ _ __ I-

~ (i) - - ,_ - I- - - - - - - - - _,_ - - - I- - - - ~ : ~ i.-"= ~ - 1---- ____ ,_-!------>---·I-- ---1--1-----

z ~.~=~~~~=----·--·~'~-=-~~I===-· --·~·-~=~~-~.~ .. ~ 0 ·-1-1-- -~- - -- - -- -+-· - -- -· -- -- - ·- -- ·-· -- - ~ ·-l- ·- - -1-- -- --1-- - - - -t-- -

- t- -

-t-- - --

FAULT or SHEAR

none

subhori-· zontal foliation

-r

. ! ,, •. ,. • .- •

COMMENTS

S. encl of pit is 31' r-rr:-: anc1 7 ' i'J\.\T of f;\I lot =mer

SCALE

HORIZ. 1"=6'

VERT. 1 "=5'

PIT ORIENTATION

· - ----------·---·--1----1---1---- - -------1.,r·-----··--·--~ f--' 1.:trt·1-~:.tt·:r-J~=i:u-1-=r::i::;i::i::i·::--1---·+-+-1---+--+-· 1--":f-~~~j:'.t~++:+~-1----·+-:i· ::-1----+-:i· -++-l--H·-t-1--t-l-t-t-+--+-+-t-+-+-. f---+--,_--+--t-_t-_+_--+-1-t-·1--t--t--t--t--t--t-t-t--H- >- r

- - -I--- -i-----------1--- ·---·-······--- ··· ---· ~-l--1- - 1--------1- --r--------1--1---

~ l- 1-~l.=,~=~=~~~l.-=-·---- .-=:~--==~~=-~·-t-t--~------ --=; ;,~=-·~~=-~------.. -- - --t--~~-=-~~,~~~- 1----·---:·=-----

-liiii!I ~ •

I--~- -I-I-- - - ... - -

-1--1-- - -- --t- ->-- - f--1- -1----f--l-

.. ... ---1-----1-- -- -- - - - -1- -1-1-1---l-I-.

... -1-i- -- -- ·- ··- .. - I- - - - -- -1-1- -··

1-l---l--l--l---l--l----1----l-H---l-H-l--H-t--+-t-t---H--t--H-+-HH--Hl-t--t--t-+-+-+--t-+-~ e- -

I-- - 1-- -- --l- - l--1-- - - ·-1-1- . -1-- - - -- -· .. - -+-- ·- - - ·-· ·- -i- -1- - . 1--1-- -1-1-1- -·1-1-- - . - - -l- - - ·- - - -· - - --

I-- - 1- - -I-- - -1-- 1-- -+-- -- -1-1- - -1- -1- -1- -- - .. 1-- ·- - - --------, ~- -1--::l-

- 1--1-- ·- - -~- - - f- - -· -- - -· - - - .. - I-- -- -1-1-- -

-I-----·+------· .

NATURAL SLOPE

0--20 dcri •

r- ·- _,_ --+--t-+-i-t-t-1 H"-o--r-r--r-t-o--r-t--r-r-i ANGLE -

- -· - -t- -- - --+-- - - ·- - - 10' - T.D.

-· -· r- - f-- -- - - - t- . ..,__ - ·- -

'u '-< 0

l__J.

(1) () rt

i1 .m

"' "' u'

r-"-"-"-"-~~-r~~~~~~-~~~--~~-~~~----~~~~~r-'-·~-------,-=--=-c-=c-------'-'--'--··~-~~.._ ----~-~-·-MATERIALS DESCRIPTION ATT 1 TUDES COMMENTS DEPTH TYPE, COLOR, MOISTURE, CONSOLI DAT ION, ETC. BEDDING JOINTS FAULT or SHEAR

0 1.5' FILL: r'ottled rredium bro\·111 Pebbly Clayey SILT none none '.> to 6 ' o t J:tt!Ei D'We -E encl of pit

(A)

" Pebblv Siltv CLl\Y (tonsoil?) (B)

3. 5-11. o • Light tan to light red brown fractured SILTS'IDI·lE,

(C) very fine Sandstone and minor Claystone: nr:per 4 to

t; I -~1;. '•' ~·. '' ('I'm bedrock\

... 0 5 10

-I m

~ en -I

~ " - -I ,.. - r ,.. ~

0 G>

.. -· - - - -- - - ··- - -- - - - - - - - -- h-e-.-· - -- -- - ·- - - -- - -- - --

1-+--l--+--1-1+-->-+-il-+-H-+l-l-+-+--H-H- ---t-f- --!-!-H--1-1· -- - -- ___ L_ - -

- ..., . - _).,... -

--1 . -

~ z ~ 0

~ N -,..>----- ·-·-·-~ .E1. - :~~:·--= ; --- -.. -----· -- -- -· ·- I- - ..

none

massive? M60Vi, 40W

(?)

15

- ---

none

irreg.

II ~~:~~~ -- ~~.

- ~ ....... - . .... ,, . . - -

none

none

t~l. encl of pit is 55' SSE .from Sl-'7 house corner

SCALE

HORIZ. 1"=5'

'd t·~

0 u. (]) 0 rt

4; - -- -- ,,,. .. -- - -- - - - -· - "" - - - - - - -'- -- -- - ()

VERT 1"=5'

"' !----------- N

' "' PIT ORIENTATION VI

-----·---1-1-- --l-1-1- - - -· - - - ·- -- ->-- -- - U75E

'

NATURAL SLOPE I- -- -- -· _: - - - - -· .. l- -- - - -- --z , ____ ·- --· - . --- . -- - - -1--· -- .

- - - - -1-- - -

·-·- ··--- ---- --1-----·- -· - -- - - - - -- - ~ - - . .. . 15 de-·i.

~ I- - - - - -· -- - - - - ·- - - .. - ----·-·· ------------ ' ,_ -H-1-+-1-- - ·- - - -- - -1--.__ --1-l-+-4-1-1-·- .=._ ~ _._-:._~ ~- - -~--- ~ - ~ _____ ~ ,_:_:-= ANGLE ~ 2 ~ • OJ .. ·- - -- - -- ... ·- -· - 1-'-· - - -- - - - -- - - -- -·

,_ -----·- -·- -~---·- - .. ---- - - -- - -1- - - ----··----·- -- -

i:_ -· -- -~-='=~===-==---=-==--- :=:: ... :::_ -· I· .. -- -- - ,_ - -·· - -__ l_ - - - - - - - - • - - - - . •. .. -- -- . - - -

11' - -- - T.D.

I I

APPENDIX B

Laboratory Investigation

Summary of Laboratory Test Results


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 unconfined compression and 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."

Tre expansion characteristics of the near-surface soils were

evaluated by means of an Atterberg Limits Test performed in

accordance with ASTM D4318.

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.

43

sample Depth Dry No. Density

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

1-1 8.0 106 1-2 13.0 116

2-1 8.5 100

T-1* 2.0 98

T-2* 5.0 101

TABIB I

Pl:oject No. 6295 21 Decanber 1990

Smm3ry of Lalx:n::atary Test IEsul ts

M::listure Att.,rl:era Limits , Unconfined Direct Shear Content Liquid Plasticity CCJrpressive Cohesion Angle of (%Dry Limit Index Strength (p.s.f.) Internal. Weight) ( %) (p.s.f.) Friction

(degree)

16 2,120 25 12

22

23 70 45 10,233

21

*Indicates sample taken in test trench

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pete governor - californiagmw.consrv.ca.gov/shp/apsi_siteinvestigation... · 12/21/1990 · state...

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