z:-tctrgmw.consrv.ca.gov/shp/apsi_siteinvestigationreports_ocr/apsi_004033/apsi_004033...nov 05,...

STATE Of CALIFORNIA ~ THE RESOURCES AGENCY

DEPARTMENT OF CONSERVATION DIVISION OF MINES 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

C 0 •:( ~) - (_-

October 18, 1993

1Santa Clara County Planning Dept. :Government Center, East Wing, 4th Floor 70 West Hedding Street

.San Jose, CA 95110

-Dear Jim:

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 attached list). The remaining reports from this set were not

I 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 1/

Sincerely,

Z:-tctr EARL W. HART Senior Geologist &

Program Manager

OCTOBER 1989 EARTHQUAKE

DAMAGE INSPECTIONS

LOS GATOS & SANTA CRUZ MOUNTAINS

ADDRESS

Old Summit Rd. 17850 LG

Old Well Rd 21095 LG

Oneida Ct. 21432 LG

Oi;ieida Ct. 21445 LG

Overlook Rd. 18660 LG



O;verlook Rd. 19190 LG

Panorama Dr. LG

Panorama 20830 LG '

Panorama 20875 LG

Panorama 20900 LG

Pknorama 20910 LG

::; .v Panorama 20930 LG.\

Panorama 20940 LG

' Panorama 20945 LG

Panorama 20955 LG

Panorama 20980 LG

Panorama 20985 LG

Paul Masson Winery SA

DAMAGE DESCRIPTION

flp, roof damaged; minor

house damaged; severe (prev. moderate 7-13-90)

severe; moderate damage combined with structure age VIOLATION FILE

severe; separation; floor uneven; 2/12/90 -

upgraded to severe VIOLATION FILE

house moved 1 "; 6 flp. and 2 baths damaged; moderate

house, chimney, flp. damaged; moderate

house moved 2" SE; fnd rotated; walls leaning; moderate

moderate damage; repaired w/o inspctn or BP 1/31

tank collapsed; concrete pad cracked; severe

pier shifted; moderate

fireplace; moderate

damage to triplex; severe

house fell off piers,repairs w/o permits;severe

separation & settlement problems; severe -

(upgraded from moderate 3/15/91)

house off piers; severe

structure damage; moderate

severe cracking LPG only gas tank; minor

supporting poles shifted; severe

foundation cracks; severe (from mod 5/23/91)

stonework cracks; moderate

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GEOTECHNICAL INVESTIGATION

OLSON/CARROLL RESIDENCE 20930 PANORAMA DRIVE

SANTA CLARA COUNTY, CALIFORNIA

PREPARED

FOR

MS. STEPHENIE S. OLSON MR. GUS F. CARROLL

20930 PANORAMA DRIVE LOS GATOS, CALIFORNIA

NOVEMBER 5 1 1990

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UPP GEOTECHNOLOGY, INC. Engineering Geology • Geotechnical Engineering .

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UPP GEOTECHNOLOGY, INC. Engineering Geology • Geotechnical Engineering

Ms. Stephenie S. Olson Mr. Gus F. Carroll 20930 Panorama Drive Los Gatos, CA 94022

SUBJECT: GEOTECHNICAL INVESTIGATION OLSON/CARROLL RESIDENCE 20930 PANORAMA DRIVE SANTA CLARA COUNTY, CALIFORNIA

Dear Ms. Olson and Mr. Carroll:

November 5, 1990 Project No. 691.01R2 Serial No. 4437

As you requested, we have performed a Geotechnical Investigation of your residence located at 20930 Panorama Drive in an unincorporated portion of Santa Clara County, California. The accompanying report presents the results of our field investigation; laboratory test:i:ng; geologic and ·engineering analyses; and our conclusions and recommendations concerning the soil and foundation engineering aspects of the project.

This report is contingent upon our review of the final Foundation and Drainage Control Plans and Specifications, as well as our observation of the foundation installation during construction, and the installation of the drainage system.

Kindly refer to the text of the report for detailed findings and recommendations. Should you have any questions concerning our report, please call.

Yours very truly,

UPP GEOTECHNOLOGY, INC.

Mark F. Baumann Project Geologist

MFB:RRU:bd Copies: Addressee (3) Ahearn & Knox, Inc. (1) Dennis Burrow (1)

1330 S. Bascom Ave.• San Jose, CA 95128 (408J 275:1336 •FAX: [408J 287·3079

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INTRODUCTION

This report presents the results of our Geotechnical Investigation

of the distress to your residence located at 20930 Panorama Drive

in an unincorporated portion of Santa Clara County, California (See

Figure 1, Site Location Map). We understand that during the October

17, · 1989 Loma Prieta Earthquake, the residence was subjected to

strong groundshaking and experienced moderate distress.

The initial purpose of our investigation was to evaluate the dis

geologic conditions in the area of the tress, explore the

residence, and to

soil and

develop .findings and recommendations for the

foundation engineering aspects of the project. Subsequent to our

investigation, we understand that you have decided to demolish the I

existing house and build another in the same location. Therefore,

we have performed additional analysis, and changed the focus of our

r~port to provide geotechnical recommendations for the new con

struction. We have previously conducted a Preliminary Geotechnical

Investigation, the results of which are presented in this report.

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OB.r scope of services for our Preliminary Geotechnical Investi-

gation and this investigation included a review of existing pub

l~shed and unpublished geologic literature and aerial photographs ' of the subject property and vicinity; consultation with the County

Geologist; site reconnaissance and engineering geologic mapping; a

Distress Survey and Floor Level Survey of the residence; subsurface

investigation; laboratory testing of soil properties; engineering

ahalysis of the data obtained; and the preparation of this report.

This report has been prepared for the exclusive use of Ms.

Stephenie Olson and Mr. Gus Carroll, and their Engineers and Con

tractors for the evaluation of the soil and geologic conditions in

the area of the distressed residence, and the design and

construction of the proposed new residence. our investigations were


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Olson/Carroll Residence Geotechnical Investigation November 5, 1990 Page 2 (of 26 Pages)

conducted in accordance with generally accepted geotechnical engi

neering principles and practices. No other warranty, either ex

pressed or implied, is made.

In the event that any changes in the nature or location of the pro

posed new residence are planned, the recommendations of this report

shall not be considered valid unless such changes are reviewed and

the recommendations of this report modified or verified in writing

by this firm.

This report is issued with the understanding that it is the respon

sibility of the owners, or the owners' representative, to insure

that the information and recommendations contained in this report

are brought to the attention of the Project Engineer, and are

incorporated into the Plans and Specifications of the project. The

owners should also insure that the Contractor and Subcontractors

follow the recommendations during construction.

METHOD OF INVESTIGATION

Geologic literature and aerial photographs were reviewed to deter

mine the prevailing geqlogic conditions on the site and in the

vicinity. On November 27, 1989, our Principal Engineer conducted an

initial site reconnaissance.

On October 15, 1990, engineering geologic mapping was conducted. On

December 27, 1989, our Principal Engineer conducted a detailed Dis

tress Survey of the residence, and observed the conditions in the

crawlspace beneath the living room. On that same date, our Project

Geologist conducted a site reconnaissance, and our Staff Engineer

conducted a Floor Level Survey of the residence. In addition,

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subsurface conditions were investigated on that same date by hand

excavating 2 foundation observation pits along the downhill side of

the residence.

Subsurface information was also obtained on December 27, 1989 and

January 10, 1990 by excavating 2 exploration pits with a tire

mounted backhoe to a maximum depth of 10 feet. Additional sub

surface information was obtained on February 1 and 5, 1990 by

d~illing 3 test borings to a maximum depth of 24.5 feet. Two of the

borings were augered with a truck-mounted 6 inch diameter contin

uous flight auger, and the third was augered with a portable hy-' draulic 6 inch diameter continuous flight auger.

I The locations of the foundation pits, exploration pits, and borings

a.re shown on Figure 4, Partial Site Plan. These locations were

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approximately determined by taping from known points on the Site '

Plan, and should be considered accurate only to the degree implied

by the method used.

The borings were continuously logged by our Staff Geologist in

accordance with the Unified Soil Classification System described. on I

Figure 8, Key to Logs; and a Summary of Field Sampling Procedures

is presented on Figure 9. The logs of the borings are presented on

Figures 10· through 14; the logs of the exploration pits are pre

sented on Figures 15 and 16; and the logs of the foundation pits

are presented on Figures 17 and 18.

The logs show our interpretation of the subsurface conditions on

the date and at the locations indicated, and it is not warranted

that they are representative of the subsurface conditions at other


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locations and times. Also, the stratification lines on the logs

represent the approximate boundaries between soil types, as the

transitions are generally gradual.

Soil sampies obtained from the test borings were retained for

J laboratory classification and testing. The results of moisture con

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tent, dry density, and shear strength tests are shown on the boring

logs. The results of plasticity and less than No. 200 sieve tests

are presented on Figure 19, Plasticity Chart.

GEOLOGY AND SEISMICITY

Geology

According to the Preliminary Geologic Map of the Los Gatos Quad

rangle (Dibblee and Brabb, 1978), the site is underlain by Fran

ciscan sandstone which consists of Cretaceous and Jurassic Age (68

to 208 million years old) greywacke sandstone with minor siltstone

and shale interbeds. According to Bailey et al (1964), minor

conglomerate lenses have widespread occurrence within Franciscan

Formation rocks (see Figure 2, Regional Geologic Map).

According to the Surficial Geology Map, Plate 1 of the Geotechnical

Investigation for the Aldercroft Heic:Jhts Drainage Basin (Baldwin

Consultants, 1986), the site is located in an area underlain by old

landslide debris. According to this map, artificial fill is located

on the downhill side of the building pad, and an active landslide

is located directly below the building site. This map is based on

photogeologic

investigation

questionable.

interpretation and reconnaissance. Our site specific

indicates that the existence of this landslide is

UPP GEorECHNOLOGY, INC.

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Seismicity

The subject property is located in the San Francisco Bay Area,

which is recognized by Geologists and Seismologists as being one of

most seismically active regions in the United States. The 3 major

faults that pass through the Bay Area in a northwest direction have

produced approximately 12 earthquakes per century strong enough to

cause structural damage.

The faults causing such earthquakes are part of the San Andreas

Fault System, a major rift in the earth's crust that extends for at

least 700 miles along the California Coast, that includes the San

Andreas, Hayward, and Calaveras Fault Zones.

The main trace of the San Andreas Fault is located approximately

2, 700 feet southwest of the site; and the Hayward and Calaveras

Faults are located approximately 16 and 18.5 miles northeast of the

site, respectively. In addition, a trace of the inactive Aldercroft

Fault is mapped approximately 200 feet south of the existing resi

dence .

Site Description

The subject property

Santa Cruz Mountains,

northern Coast Ranges.

near the crest of a

SITE CONDITIONS

is located along the ~astern flank of the

a northwest trending range within the

The irregularly shaped property is situated

roughly east-west trending ridgeline on a

southwest facing slope.


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An asphalt driveway leads up to a level building pad on the

northern portion of the property. The building pad is occupied by a

centrally located residence with a swimming pool to the southeast

(right side, when viewed from downslope). An asphalt parking area

is located to the northwest (left) of the residence, where the

driveway meets the building pad. To the northwest of the parking

area, there is a two-story wood framed structure consisting of a

garage and hobby rooms (see Figure 4).

A cut and fill dirt road extends behind the residence, and leads up

to a water tower. The uphill side of the parking area and the dirt

road are retained with an approximately 4.5 foot high masonry re

taining wall. This wall appears to be incorporated into the rear

foundation of the garage and hobby rooms, and extends to approxi

mately the mid-point of th.e residence.

Where this wall ends, the cut slope for the dirt road is approxi

mately 8 feet high, and has an ·approximately 1: 1 (horizontal to

vertical) slope. The natural slope above is approximately 2:1 (see

Figure 5, Geologic Cross-Section A-A').

T,he fill slope on the downhill side of the road is approximately 3

feet high, with a gradient of 1.5:1, and leads down to a similar

retaining wall which extends along the rear of the residence. This

wall ends at approximately the mid-point of the residence, and a

1.5 foot high wall continues to the right side (see Figure 5).

Downhill, in front of the residence, is an approximately 5 foot

high masonry retaining wall. This wall retains fill material for

the residence, swimming pool and decks, and a patio area which


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Olson/Carroll Residence Geotechnical Inve.stigation November 5, 1990 Page 7 (of 26 Pages)

extends along the front of the residence. This wall extends beneath

the living room wing of the residence, and is incorporated into the

foundation for this portion.

Below the lowest retaining wall, there is a level path up to

approximately 10 feet wide with a small amount of fill on the

downhill edge. The slope below the path is arcuate, approximately

40! feet high, and has a gradient of between 1. 5: 1 and 2: 1, and then

abruptly becomes more gentle (see Figure 5). This slope leads down

to a large bench which slopes gently toward the southwest.

The subject residence is an irregularly shaped single story

structure, with a detached room at the left rear corner. The

detached room and a majority of the residence are wood frame

construction, with stucco and wood exterior. The living room and a

small unfinished utility room below the downhill portion of the . living room have masonry walls.

The entire residence is supported on a perimeter concrete spread

footing. The detached room and a majority of the residence have

concrete slab-on-grade floors. The living room has a raised wooden

floor with isolated interior footings (see Figure 6, Construction

Ctoss-Section B-B'). In addition, the downhill corners of the

living room are cantilevered out from the spread footing on the

downhill side of the lower retaining wall (see Figure 7, Floor

Level Survey) .

Distress

Based on an analysis of the data obtained from the October 17, 1989

Earthquake (Stover et al, 1990), the subject site is located in an

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Olson/Carroll Residence Geotechnical Investigation November·s, 1990 Page 8 (of 26 Pages)

area which experienced strong groundshaking, equal to a Modified

Mercalli Intensity of VII, during the October 17, 1989 event.

During our site visits, we observed and noted distress to the resi

dence and property which resulted from this strong groundshaking.

The property surrounding the subject residence experienced distress

in the form of ground cracks or fissures. There was evidence that

there ·were several fissures in the asphalt parking area that

extended from the residence toward the garage/office building.

These fissures had been backfilled by the time of our first site

visit. A fissure was observed along the length of the dirt road be

h~nd the subject residence.

Minor discontinuous and sinuous ground cracks were observed on the

l~rge level bench below the residence, near the southern property

bbundary, and also on the slope above the subject property. These

c.racks appear to be shrinkage cracks, and not related to strong

g:roundshaking.

The patios surrounding both the residence and pool are constructed

of exposed aggregate concrete slabs separated by 1 inch boards. '

Around the residence, these slabs appear to have settled and sepa-

~ated in the downslope direction by up to approximately 1 inch near

the right side of the residence.

the slabs

In the patio area at

have settled towards a

the left

low area front of the residence,

approximately even with the roof support posts. One of the slabs

has been cracked, patched, and re-cracked.

The slabs for the pool patio have separated and tilted slightly in

the downslope direction. In addition, on the uphill side of the


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pool, the exposed aggregate steps that lead uphill have broken away

from a small retaining wall, and shifted downhill by approximately

1 inch.

The 3 masonry retaining walls around the residence,

appear in good condition. Minor hairline cracks were

in general,

observed at

various locations on all 3 walls, however. Moisture staining around

these cracks indicate that they pre-date the October 17, 1989

Earthquake.

Where the lower retaining wall passes beneath the living room, a

square has been cut from the wall near its top to provide access to

the living room crawlspace. There is a prominent vertical crack at ;

the bottom center of this cut-out. The crack is approximately 1/8

inch wide at the top, and extends down through the masonry blocks.

In addition, there is minor separation between this retaining wall

apd the masonry walls of the utility room.

In several locations around the residence, cracks were observed

b'etween the soil and the foundation. These cracks are likely attri

b'uted to the hammering of the foundation against the adjacent soil.

The residence experienced distress in the form of misaligned door

ways and cracks in the sheetrock interior walls and stucco exterior

walls, mainly at points of stress concentration, specifically door

ways and window openings. In addition, there is a vertical crack in

the masonry wall of the living room above the location of the lower

retaining wall. The mason.ry walls of this room were not constructed

by offsetting alternate layers of blocks to form an interlocking


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Olson/Carroll Residence Geotechnical Investigation November 5, ·1990 Page 10 (of 26 Pages)

wall, and the crack formed in the mortar between 2 columns of

blocks.

The most prominent distress was observed in the slab floor of the

hallway at the rear of the residence. The slab is cracked along an

expansion joint for the entire length of the hallway. It appears

that the downhill side has shifted and settled in that direction.

The detached room at the left rear of the residence has a crack in

the stucco along the rear wall, at the junction of the wall and the

footing. The roof of this room is attached to the roof of the resi

dence in front, and it appears that movement of the residence

pulled the top of the detached room in the downhill direction.

Floor Level Survey

In general, the pattern of distress observed coincides with the

results of the Floor Level Survey. The Floor Level Survey indicates

that the floors, in general, slope from the rear (uphill side) of

the residence to the front (downhill side) of the residence. How

ever, the elevation chqnges vary dramatically in different areas. '

I On the left side of the residence, in the kitchen, solarium and

dining room, there is an elevation change .in the slab-on-grade

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floor of approximately 1 inch from the rear to the front wall.

~imilarly, the slab-on-grade floors on the right side of the

residence and the detached room at the left rear of the residence

have an elevation change of approximately 0.5 inches from rear to

front (see Figure 7).


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The slab floors of the rear wing, including the entry and the guest

suite, have an elevation change of approximately 2. 5 inches from

the rear wall to the hallway. The raised wooden floor of the living

room slopes very gently toward the front of the residence to

approximately the mid-point of the room. From there, the floor

slopes toward the left and right front corners, with an elevation '

change of approximately 1.5 inches (see Figure 7).

subsurface conditions

There were 2 exploration pits, 2 foundation pits, and 3 test bor

irigs excavated around the subject residence (see Figure 4). For a

detailed description of the subsurface materials, refer to the logs

of the excavations (see Figures 10 through 18).

Exploration Pits 1 and 2 were excavated across fissures to deter-.'

mine the depth and cause of the cracking. Both pits encountered '

similar sequences of subsurface materials. Sandstone and inter-

bedded sandstone and shale bedrock were encountered at depths vary

ing between 4 and 8 feet in Exploration Pits 1 and 2, respectively.

The bedrock persisted to the bottom of Exploration Pits 1 and 2 to

d~pths of 12 and 10 feet, respectively. '

' The sandstone and shale bedrock are pervasively fractured, and the

fractures have very little clayey in-filling to provide cohesion.

Because of this condition, cave-ins were common during excavation,

and fissures were difficult to trace during logging.

In Exploration Pit 1, the fissure observed on the ground surface

was traceable to a depth of approximately 5 feet, where it appeared


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Olson/Carroll Residence Geotechnical Investigation November 5, 1990. Page 12 (of 26 Pages)

to end in a weathered bedrock zone. In Exploration Pit 2, the fis

sure was untraceable below the ground surface.

Foundation Pit 1 was excavated near the lower left corner of the

living room. Sandy silt fill material with rusted nails and con

crete fragments was encountered to the bottom of the pit at a depth

of approximately 3 feet. The pit exposed a concrete spread footing

for both the fireplace and the residence. The fireplace footing ex

tends to the bottom of the pit. The footing for· the residence,

adjacent to the fireplace, extends to the bottom of this portion of

t~e excavation at a depth of approximately 1.5 feet below the ex

terior grade.

Foundation Pit 2 was excavated at the base of the downhill retain

ing wall. At this location, the top of the wall's concrete spread

footing was exposed. The pit encountered sandstone bedrock to the

~ottom of the pit at approximately 1 foot. The pit exposed another

portion of the footing which extended to approximately O. 7 5 feet

below grade. The total height of the footing is 1 foot.

Boring 1, augered in the dirt road at the rear of the residence,

encountered approximately 9 feet of very stiff clayey silt col

luvium, underlain by bedrock which consists of a medium dense to

dense highly weathered pebble conglomerate. The bedrock persisted

to the bottom of the boring at a depth of 23.5 feet.

Boring 2, augered in the parking area near the left front corner of

the residence, encountered approximately 4. 5 feet of very stiff

clayey silt fill, underlain by dense silty sandstone bedrock. The


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sandstone persisted to the bottom of the boring at. a depth of 15

feet.

Boring 3, augered near the right front corner of the living room,

encountered approximately 3 feet of soft silty clay topsoil/fill,

underlain by approximately 5.5 feet of stiff clayey silt colluvium.

Medium dense to dense. interbedded sandstone, siltstone, and shale

was encountered below the colluvium at a depth of 13. 5 feet. The

bedrock persisted to the bottom of the boring at a depth of 24.5

feet.

~ Plasticity Test conducted on a near surface sample of the

topsoil/fill from Boring 3 indicates that this material is rela

tively non-expansive, with a Plasticity Index of 9% (see Figure '

19) •

Free ground water was not encountered in any of the excavations. It

should be noted, however, that fluctuations in the level of subsur

face water can occur due to variations in rainfall, temperature,

and other factors not evident at the time our observations were

made. : '

DISCUSSION

Aerial photographs dating back to 1939 were reviewed to determine

the pre-development site conditions. The 1939 and 1950 aerial

photographs indicate that the bench on which the existing residence

is located pre-dates development, and appears natural. A few dirt

roads were present above the site, and an airplane runway was con

structed on the ridgeline above the site sometime between 1939 and


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1950. The site was covered with grass and scattered brush and trees

during this time period.

Aerial photographs from 1956 indicate that minor development had

.started. There was a dirt road that leads onto the lower bench, and

then part way up the slope toward the upper bench. This road does

not correspond with the present day alignment of the driveway, how

ever. In addition, a row of trees had been planted along the

northern property lines.

.Foundation Plans for the residence were prepared by Warren D. Reid,

!'Ind dated May 1, 1961. These Plans indicate that the 3 retaining

walls and the swimming pool previously noted were constructed prior

to the residence. In addition, a garage and boiler room were

located in the area currently occupied by the garage and hobby

rooms, and a greenhouse was located farther to the northwest.

Aerial photographs indicate that the residence and a pool house

were constructed by October, 1963.

We understand that during the Lexington Reservoir Fire of July,

'1935, the greenhouse, garage and boiler room, and pool house were

destroyed. The current residents purchased the property shortly

after the fire. A garage and hobby rooms were constructed in the

,location of the destroyed garage. Portions of the original garage

foundation are incorporated into the foundation for the new build

ing. We understand that, because of the unknown condition of the

existing retaining wall at the rear of the building, it was not

utilized for support. We understand that this structure experienced

very minor distress as a result of the October 17, 1989 Earthquake.


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Olson/Carroll Residence Geotechnical Investigation N9vember 5, 1990 Page 15 (of 26 Pages)

The design of the foundation for the structure was based on a

report by Applied Soil Mechanics, Inc. entitled "Soil Investi

gation, Garage Reconstruction & Expansion", dated March 11, 1987.

FINDINGS

11ost of the distress observed at the subject property appears to

have been directly caused by, or exacerbated by, the strong ground

shaking from the October 17, 1989 Earthquake.

Based upon the results of our investigation, it is our opinion that

the distress observed to the residence uphill from the lower

retaining wall was the result of the vertical settlement of the

fill material underlying the residence. The lower retaining wall

does not appear to have been distressed by the earthquake, and has

prevented much lateral movement of the fill material underlying the

residence.

I The floor at the downhill corners of the living room . is canti

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levered, and has no foundation directly under the exterior wall. In

our opinion, the distress observed to this portion of the living

room was the result of structural sag of the inadequately supported

,floor, and should be evaluated by a Structural Engineer.

The residence apparently was constructed on a natural gently slop

ing bench. A retaining wall was constructed near the downhill edge

of the bench; and then, we assume, fill was placed behind the wall

to create the level building pad. No information on the con

struction of the wall was available for our review, however, it

generally appears to be in good condition.

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According to the Plans for the residence, all foundation and wall

excavations were to be backfilled with soil from the excavations,

placed in 12 inch.lifts, and compacted by water saturation. At the

time of construction, hydraulic compaction was common; however,

with time, hydraulically implaced fills may settle.

The Floor Level Survey indicates that the central portion of the

residence has settled relatively uniformly. The guest suite wing

and the detached room are probably not founded on fill material;

and, therefore, have not experienced this uniform settlement. In

addition, the front portion of the living room, which has little

lateral support, has settled, causing the vertical crack in the

block wall above the lower retaining wall .

Many of the concrete slabs in and around the residence have shifted

in the downhill direction. The retaining wall in front of the resi

dence appears to have prevented a great deal of lateral movement of

the subsurface materials uphill, and the shifting of these slabs is

probably .because the fill may be thicker in the downslope

direction.

,In our opinion, the fissures in the asphalt parking area and in the ' dirt road are not related to landsliding .. Exploration pits exca-

·Vated across 2 of the fissures indicated that they were not trace

able into the weathered bedrock material which was encountered

between 6 inches and 1.5 feet below the ground surface. In

addition, our investigation, found only weak evidence suggesting

the landslide directly below the residence, as indicated on the

.Surficial Geology Map by Baldwin Consultants.


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The occurrence of a new landslide within, or adjacent to, the sub

ject property cannot be excluded. A small shallow landslide could

be triggered by strong earthquake shaking, but such a slide prob

ably would not constitute an immediate threat to the integrity of a

residence built in accordance with an appropriately engineered

design.

The long-term stability of many hillside areas, however, is diffi

cult to predict. A hillside will remain stable only as long as the

existing slope equilibrium is not disturbed by natural processes'

or by the acts of Man.

Lpndslides can be activated by a number of natural processes, such

a:S the loss of support at the bottom of the slope by stream

erosion, or the reduction of soil strength by an increase in ground

water level from excessive precipitation. Artificial processes

caused by Man may include improper grading activities; or the

introduction of excess water through irrigation, leachf ields, or

poorly controlled surface run-off. Thus, we recommend that careful '

attention be given to preserve the current 'state of equilibrium.

It should be noted that although our knowledge of the causes and

m:echanisms of landslides has greatly increased in recent years, it

i!s not yet possible to predict with certainty exactly when and ' -

where all landslides will occur.

At some time over the span of thousands of years, most hillsides

will experience landslide movement, as mountains are reduced to

~lains. Therefore, a certain unknown level bf risk is always

present to structures located in hilly terrain. Owners and

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developers of property located in these areas must be aware of, and

willing to accept, this unknown level of risk.

Based upon our site reconnaissance and our review of published geo

logic maps and aerial photographs, no known active or potentially

active faults pass through the subject site. However, it is

reasonable to assume that the proposed improvements will be

subjected to strong groundshaking from a major earthquake on at

least one of the nearby active faults during its design life.

During such an earthquake, the danger from fault offset through any

of the proposed improvements is negligible.

Based on an analysis by Borcherdt, Gibbs and Lajoie (1975), maximum

) anticipated groundshaking intensities are characterized as violent,

and equal to a Modified Mercalli Intensity of approximately IX. It

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should be noted that these values may be revised in the future,

based on data collected during the October 17, 1989 Loma Prieta

Earthquake.

A Modified Mercalli Intensity

damage to specially designed

severe damage and partial

of IX may cause considerable interior

earthquake-resistant structures, -and

collapse in well-built ordinary

st~uctures (Yanev, 1974) (see Table I, Modified Mercalli Scale of

Earthquake Intensities).

RECOMMENDATIONS

We understand that the existing residence will be razed. In our

opinion, from a geotechnical perspective, a new residence may be

constructed in the same location, provided that the recommendations

UPP GEOTECHNOLOGY, tNC.

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Olson/Carroll Residence Geotechnical Investigation November 5, 1990 Page 19 .(of 26 Pages)

contained in this report are incorporated into the design and

construction of the project.

Seismic Intensity

The Structural Engineer should provide seismic design criteria.

Groundshaking equal to a Modified Mercalli Intensity of IX can be ~ anticipated at the site. It should be noted that this design inten-

sity is based on pre-October 17, 1989 data. New data not yet avail-

able may warrant an upgrade of this number.

Foundations

i. Drilled Piers '

Because of the proposed residence's location on a moderately slop

ing hillside and the presence of non-supportive fill material under

portions of the residence, we recommend that the proposed residence

and garage be supported on drilled cast-in-place straight shaft

:friction pier and grade beam foundations.

The pie~s should have a minimum diameter of 16 inches; and should ' .be drilled to a minimum penetration of 8 feet into supportive I material. Supportive material is considered to be the underlying

stiff colluvium and siltstone and sandstone bedrock. The total pier

'length will vary depending on the depth of the fill material, and

.total pier depth may be up to approximately 15 feet. Because of the

variable depth to the supportive material, the construction of the

.piers should be observed by the soils Engineer at the time of

drilling.


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Active pressure on the upper portion of the piers in fill can be

figured on the basis of an equivalent fluid weight of 40 pcf taken

over 2 pier diameters. The portion of the piers in supportive

material may be designed for a skin friction value of 450 psf for

dead plus live loads, with a 1/3 increase for transient loads, in

cluding wind and seismic. Any portion of the piers in fill or the

topsoil/colluvium, and any point-bearing resistance should be

neglected for support.

For resistance to lateral loads, a passive pressure equivalent to a

fluid weight of 400 pcf to a maximum of 2,500 psf may be taken over

1.5 pier diameters for the length of the pier in supportive

material.

As a minimum, a cage of four No. 5 steel reinforcing bars should be

provided full length. Greater steel reinforcement may be required

,by the Structural Engineer.

:Because of the fractured and non-cohesive nature of some of the

bedrock underlying the site, cave-in of the piers may occur. The

:Foundation Contractor should be made aware of this possibility,· and

concrete should be placed soon after excavation.

The bottoms of the pier excavations should be dry and essentially

free of all loose cuttings and soil fall-in prior to the instal

lation of the steel and the placement of the concrete. Any accumu

lated water in the pier excavations should be removed prior to the

installation of the steel and the placement of the concrete.

UPP GEOl'ECHNOLOGY. INC.

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To verify that the piers are founded in material of sufficient sup

porting capacity and have been properly prepared, it is essential

that we observe the pier holes as they are being drilled.

Grade beams should be reinforced with top and bottom reinforcement

to provide structural continuity, and to permit the spanning of

local irregularities. In addition, good structural continuity

should be provided between the grade beam and the piers .

The actual number, size, locations, depth, spacing, and reinforce

ment of both piers and grade beams should be determined by the

Structural Engineer; but, from a soil engineering perspective,

fewer piers with greater diameter, depth, and reinforcement and

larger grade beams with greater reinforcement are preferable .

Settlements under building loads are expected to be within toler

able limits for the proposed construction supported on piers. We

estimate that the total post-construction settlement and differ

ential settlement will be less than 3/4 inch.

2. Retaining Walls

We understand that the existing retaining wall on the downhill side

of the existing residence will remain. The wall will be utilized

for landscaping purposes, and will not be incorporated into the

design of the proposed structure.

We understand that retaining walls are anticipated for a below

grade utility room. The retaining walls should be designed to re

sist both lateral earth pressures, and any additional lateral loads


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caused by surcharge loads on the adjoining ground surface. Retain

ing walls should be supported on foundations designed in accordance

with the recommendations given in this report for the support of

the residence.

We recommend that unrestrained walls be designed to resist an

equivalent fluid pressure from the existing fill material of 40

pcf. Restrained walls with level backfill should be designed to

resist an equivalent fluid pressure of 40 pcf plus an additional

uniform lateral pressure of SH psf, where H = height of backfill

above the top of the wall footing in feet .

Wherever the walls will be subjected to surcharge loads, they

should be designed for an additional uniform lateral pressure equal

to 1/2 or 1/3 the anticipated surcharge load for restrained or

unrestrained walls, respectively. In addition, walls with sloping

backfill should be designed for an additional uniform lateral pres

sure Of 1 pcf for each 3 degrees Of slope inclination.

The preceding pressures assume that sufficient drainage is provided

behind the walls to prevent the buildup of hydrostatic pressures

from surface or subsurface water infiltration. Adequate drainage

inay be provided by means of a backdrain system consisting of an

fipproximately 1 foot thick curtain of drainrock (crushed r'.)ck or

gravel) placed behind the wall.

The drainrock should be separated from the backfill by an appro

priate filter fabric, approved by the Soil Engineer. A 4 inch

diameter ·heavy duty rigid perforated subdrain pipe, approved by the


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Soil Engineer, should be placed with the perforations down on a 2

to 3 inch layer of drainrock at the base of the drain.

The subdrain pipes should be provided with a positive gradient of

at least 2% to an appropriate discharge location downslope,

approved by the Soil Engineer. The subdrain pipes should be pro

vided with clean-out risers at their up-gradient ends, and at all

sharp changes in direction. The subdrain pipes should discharge

onto an energy dissipater at an appropriate location downslope.

Backfill placed behind the walls should be compacted to at least

90% relative compaction, using light compaction equipment. If heavy

compaction equipment is used, the walls should be appropriately

temporarily braced, as the situation requires. If backfill consists

entirely of drainrock, it should be compacted in 2 foot lifts using

several passes with a vibratory plate compactor

3. Slabs-on-Grade

'If concrete slabs are anticipated for areas underlain by the exist

ing fill material, either the fill should be removed and re

compacted, or the slabs should be supported on foundations designed

:in accordance with the recommendations given in this report for the

;support of the residence .

Proposed slabs located in areas underlain by bedrock should be

supported on 6 inches of non-expansive fill compacted 90% of the

relative dry density as determined by the ASTM Test Designation

01557 (latest edition). Slab reinforcement should be provided in

accordance with anticipated use and loading; but, as a minimum,

UPP GEOTECHNOLOGY.1Nc.

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slabs should be reinforced with 6 inch by 6 inch 10/10 gauge wire

mesh tension reinforcement.

The slabs should also be grooved at 10 foot intervals to control

any cracking. Prior to the final construction of the slabs, the

subgrade surface should be proof-rolled to provide a smooth firm

surface for slab support.

4. wooden Decking

We understand that wooden decking is planned for the area in front

of the proposed residence. Because of the steep slope, and the

presence of non-supportive fill material, decks should be supported

.on foundations designed in accordance with the recommendations

given in this report for the support of the residence.

surface Drainage

Control of surface drainage is critical to the successful develop

ment of the project. The results of improperly controlled run-off

include erosion, gullying, and potential slope instability .

Ponding of surface water should not be allowed on pavements or

adjacent to the residence. The proposed residence should be

provided with roof gutters and a positive gradient of at least 2%

should be provided away from the residence.

In addition, surface run-off should not be allowed to flow over the

top of any artificial slope; and should be controlled with either

~ imboard grading, a berm, or a lined V-ditch.

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UPP GEOfECHNOLOGY. INC.

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water collected in any of these drainage devices and paved areas

should not be allowed to discharge freely onto the ground surface.

The water should be conveyed around and away from the residence via

closed conduit; and discharged onto an energy dissipater at an

~ppropriate location downslope .

PLAN REVIEW AND CONSTRUCTION OBSERVATION

We should be provided the opportunity to review final Foundation

Plans and Drainage Control Plans and Specifications in order to

verify that our recommendations have been properly incorporated

into the proposed repair .

.The installation of the foundations, and any earthwork should be

performed under our observation in order to:

1. Verify that the actual soil conditions are similar to those encountered in our investigation

2. Provide us with the opportunity to modify the foundation design, if variations in conditions are encountered

3. Verify that the recommendations of our report are followed during construction .

·Sufficient notification prior to the start of construction is

essential in order to allow for the scheduling of personnel to

insure proper observation. WE SHOULD BE NOTIFIED AT LEAST 2 WEEKS

PRIOR TO THE ANTICIPATED START-UP DATE. IN ADDITION, WE SHOULD BE

GIVEN AT LEAST 2 (WORKING) DAYS NOTICE PRIOR TO THE START OF THOSE

PHASES OF CONSTRUCTION WHICH WE SHOULD OBSERVE.


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The phases of construction to be observed by this firm should

include, but are not necessarily limited to, the following:

1. PIER EXCAVATION: During drilling

2. RETAINING WALL BACKDRAIN: Prior to backfilling, to observe installation

3. RETAINING WALL BACKFILL: To test compaction, unless backfill is entirely of drainrock.

4. SLABS-ON-GRADE: Prior to the placement of the moisture barrier, to observe base preparation, and to test compaction of non-expansive fill

5. SURFACE DRAINAGE: Near completion

* * * * * * * * * *

A List of References, a List of Aerial Photographs, and the follow

ing Figures and Table are attached and complete this report:

FIGURE NO.

SITE LOCATION MAP ............................ . REGIONAL GEOLOGIC MAP ........................ . COUNTY CADASTRAL MAP ......................... . PARTIAL SITE PLAN ... : ........................ . GEOLOGIC CROSS-SECTION A-A' ....•..•••.•....... CONSTRUCTION CROSS-SECTION B-B' .............. . FLOOR LEVEL SURVEY ........................... . KEY TO LOGS .................................. . SUMMARY OF FIELD SAMPLING PROCEDURES .... ~ .... . LOGS OF BORINGS 1 THROUGH 3 .................. . LOGS OF EXPLORATION PITS 1 AND 2 ............. . LOGS OF FOUNDATION PITS 1 AND 2 .............. . PLASTICITY CHART ............................. .

1 2 3 4 5 6 7 8 9

10-14 15 & 16 17 & 18

19

TABLE NO.

MODIFIED MERCALLI SCALE OF EARTHQUAKE INTENSITIES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I


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LIST OF REFERENCES

BAILEY, E.H., IRWIN, W.P., and JONES, D.L., 1964, Franciscan and Related Rocks, and Their Significance in the Geology of Western California, C.D.M.G., Bulletin 183

BALDWIN CONSULTANTS, 1986, Geotechnical Investigation, Relative Slope Hazard Evaluation, Aldercroft Heights Drainage Basin, Lexington Reservoir Burn Area, Santa Clara County, California, unpublished Consultant's report prepared for Santa Clara County

BORCHERDT I R. D. I GIBBS, J. F. I and LAJOIE, K. R., 1975' Maps showing maximum earthquake intensity predicted in the southern San Francisco Bay Region, California, for large earthquakes on the San Andreas and Hayward Faults, U.S. Geological Survey, Miscellaneous Field studies Map MF-709

DIBBLEE, T.w., Jr. and BRABB, EARLE., 1978, Preliminary Geologic Map of the Los Gatos Quadrangle, Santa Clara and Santa Cruz Counties, California, U.S. Geological Survey, Open File Map 78-453

PLAFKER, GEORGE and GALLOWAY, JOHN P. (editors) I 1989, Lessons Learned from the Loma Prieta, California, Earthquake of October 17, 1989, U.S. Geological Survey, Circular 1045: U.S. Government Printing Office, Washington, DC, 48 p .

SANTA CLARA COUNTY, 1988, Santa Clara County Cadastral Maps, Sheet 166

U.S. GEOLOGICAL SURVEY, 1953, photorevised 1980, Topographic Map, Los Gatos 7.5 Minute Quadrangle

YANEV, P., 1974, Peace of Mind in Earthquake Country, Chronicle Books., San Francisco, California

LIST OF AERIAL PHOTOGRAPHS

"BAY AREA TRANSPORTATION STUDY", black and white, dated May 24, 1965, at a scale of 1:12,000, Serial Nos. SCL 18-126 and 127, State of California Highway Transportation Agency, Division of Highways, Aerial Survey Contract No. 676-15.


1 I I I I I I I I I I I I I I I I I I

Olson/Carroll - List of References List of Aerial Photographs November 5, 1990 Page 2 (of 2 Pages)

U.C. SANTA CRUZ LIBRARY, black and white, dated October 13, 1963, at a scale of approximately 1:20,000, Serial Nos. CIV-7DD-3 and 4.

u.c. SANTA CRUZ LIBRARY, black and white, dated June 2, 1956, at a scale of approximately 1:20,000, Serial Nos. CJA-2R-70 and 71.

U.C. SANTA CRUZ LIBRARY, black and white, dated April 1, 1950, at a scale of approximately 1: 20, 000, Serial Nos. CIV-17G-105 and 106.

U.C. SANTA CRUZ LIBRARY, black and white, dated August 1, 1939, at a scale of approximately 1:20,000, Serial Nos. CIV-286-90 and 91.

U.S. GEOLOGICAL SURVEY LIBRARY, black and January 8, 1982, at a scale of 1:20,000, Serial Nos. JSC 10-13 and 14.


white, dated approximately

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I. I_ BASE: IJSGS Topographic Map, IDs Gatos 7. 5 Minute Quadrangle

,_

APPROVED BY SCALE

1" = 2,000'

SITE I.OCATION MAP

OLOON/CARROLL RESIDENCE 20930 Panorama Drive Santa Clara County, california

PROJECT NO. DATE

691.01 November 1990 Figure 1

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Qls Qal Qoa

TKsh vb vd "-s

"=::::::-==--~-_...;>

).... Zl

EXPLANATION

Landslide deposits Alluvium Older alluvium Micaceous Shale, minor thin sandstone Basalt· Fine-grained diorite Franciscan Formation, greywacke

Geologic contact (dashed where approximate)

Strike and dip of bedding

-+- Vertical bedding ··. ·--~ Fault (dashed where

concealed, arrows approximate, dotted where show relative motion)

BASE: Geologic Map of the IDs Gatos Quadrangle, Santa Clara and Santa Cruz Counties, California, DIBBLEE & BRABB, 1978

REGIONAL GEQr.cx;IC MAP

-'trmJ UPP GEOTECHNOLOGY U Engineering Geology• Geoce<hrucal Engrneenng

AP~AOVED BY SCALE

1" = 2,000'

OLOON/CARROLL RESIDFNCE 20930 Panorama Drive Santa Clara County, California

PROJECT NO. OATE

691. 01 November 1990 Figure 2

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• ' ' BASE: Santa Clara County Cadastral Map, Sheet 166, 1988

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APPROVED BY SCALE

1" = 500'

OJUNTY CADASTRAL MAP

QLffiN/CARROLL RESIDENCE 20930 Panorama Drive Santa Clara County, California

PROJECT NO. DATE


~ • I

~1 • FP1

~---"

f'.-ope Y\..t . --------- ---- -----------

EXPLANATION

- Boring location

- Exploration pit location

- Foundation pit location

- Cross-Section location

- Cut slope

- Fill slope and fill limits

- Footprint of proposed residence

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

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BASE: Plot Plan, WARREiiL B. REID - !µA, May 1, 1961 - .I

PARTIAL S~TE PLAN

~Ii] UPP GEOTECHNOLOGY u Engintt•.ngGrolCq(•Gr-ot~Erqneering

O /<:NlliOIL RESIDENCE 2 '930 Panorama Drive

ta Clara County, California

APl'AOV ED SY SC.ALE 0.ATE

1" = 30' 6 1.01 November 1990 Figure 4

~· ,.. ~ •• •• • • "

• ~ ---~ • . ll I

••-

s:: 0

-4= Ill ;:.. ~ -Cl.>

~ .:j:: ~ ~

A N4/£:

l"/10

IYSO bedrock

11.ffO

BASE: Tape and Hand Level survey, UPP GIDI'FDIOOI£GY, INC., February 5, 1990

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GEDILGIC CROSS-SECI'ION A-A'

-lrm'J UPP GEOTECHNOLOGY u £~1ngGro1c>qy•Gto1rctnicAfEngir«rng

O /Cl\RROJL RESIDENCE 20 30 Panorama Drive


I SCALE PRolecT NO. DATE

1" == 20' 69 .01 November 1990 Figure 5

• --• lf

BASE:

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( CMcrel-e i>loclc w;z//

II 11

j ; ~

sh"JinJ ///HS doer

---llRlll!Hllll n II H II II

UUUUllu

-· . .......__, . .....__,, r:,1

~vhf r"60111_/

older lower l"'---.~ref,1ini115 wall ///2~,

If/:::'=!//~ .. .,. . - /7_,._, -- I I;.:;::;--. ,. ,....J...l::::::::;i ~r.· --///-~

(• "ve.:::://f..::::- -::::II/ I ~ - 111 - L-----------1 ~ ;:::

"

Cross-Section Through Center Line of Living Room, WARREN B. REID -AI.A, May 1, 1961

"'1>jj'l UPP GEOTECHNOLOGY UJ Engintt•rngGro10cb•Grot~IE"191"1ttf~ .APl'ROVEO av SCALE

1 11 5'

D

hurl. '

~CCSJN/CARROLL RESIDENCE 0930 Panorama Drive

Santa Clara County, California

ROJECT NO. CATE


r-----===~ o.s 0·5 ~c-h4d

• YOO~ •

•

0 C::=::::::::::=-=l' 0

2.0

ki-\-Che.n •

\.5

•

\.0 l.O

-z.t; • •

• • so\o.:1r i 1.''IYI

• •

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• ~ Data point

•

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~-0

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•

•

•

YDoil/\

•

1.0

I ~0-5 d

..s:;. ).

~

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ALL DATA POINTS NORMALIZED 'ID IJ.:M POINT AT ZERO

(Living roan and detached roan have separate bases fran the rest of the residence)

\ivi W1!j l'OOIV\

Floor Plan and Foundation Plan, WARREN A. REID - AIA, May 1, 1961,

i..s i..s • •

• • Pe~>'O()Y\I\ 25. • • • •

\irro.v~

• • • • • . .

• • • • • •

• • • •

\?~fY00~ •

'2.S

•

• I . • '2..0

FLOOR LEVEL SURVEY

-fi>li1 UPP GEOTECHNOLOGY UJ £~.ngGeotoqy•Geor~IE~ing O /CARROLL RESIDE1'ICE 20 30 Panorama Drive


APll'AOVEO BY SCALE DATE

1" = 10' November 1990 Figure 7

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'

PRIMARY DIVISIONS GROUP SECONDARY DIVISIONS SYM9C1

GRAVELS CLEAN GW Well graded gravels, gravel-sand mixtures. little or no ~ GRAVELS fines.

~ :!!:

MORE THAN HALF CLESS THAN Poorly graded gravels or gravel-sand mixtures, litt~ or a: 0 GP wo 5% FINES) no fines. g iN OF COARSE

FRACTION IS GRAVEL GM Silty gravels. gravel-sand-silt mixtures, non-plastic fines.

Ii! ~~ w LARGER THAN WITH N z z iii NO. 4 SIEVE FINES GC Clayey gravels. gravel-sand-clay mixtures, plastic fines. .....

~ ~ :z: ...... w CLEAN c:i :z: > SANDS SW Well graded sands. gravelly sands. little or no fines.

a:: w SANOS

·~ ~~ iii

MORE THAN HALF CLESS THAN

i= ~ 5% FINES l SP Poorly graded sands or gravelly sands. ~ittle or no fines. OF COARSE

~~ FRACTION IS SANOS SM Silty sands. sand-silt mixtures, non-plastic fines.

SMALLER THAN WITH NO. 4 SIEVE FINES SC Clayey sands, sand-clay mixtures. plastic fines.

w SILTS AND CLAYS ML lnor~anic silts and very fine sands, rock flour, silty or

~ N c 11t(ey fine sands or clayey silts with slight plasticity.

~~ iii g ii w LIQUID LIM IT IS CL lno~:.nic clays of low to medium plasticity, gravelly > c avs. sandy clays, silty clavs. lean clays. w

LESS THAN SC% 0 iii OL Organic silts and organic silty clays of low plasticity. w z ~

!!! 0

~ 0 lno~K: silts, mic~ or diatomaceous fine sandy or -' N SILTS AND CLAYS MH < . s1ltv soils. elastic silts.

~ cc ~

~ ~i LIQUID LIMIT IS CH Inorganic clays of high plasticity. fat clays.

it GREATER THAN 50% .... OH Organic clays of medium to high plasticity, organic silts.

HIGHLY ORGANIC SOILS Pt Peat and other highly organic soils.

UNIFIED SOIL CLASSIFICATION SYSTEM IASTM 0-2487)

U.S. STANDARD SERIES SIEVE CLEAR SQUARE SIEVE OPENINGS 200 40 10 4 J/4' J" 1211

SAND GRAVEL SILTS AND CLAYS

I I COARSE COBBLES BOULDERS

FINE MEDIUM COARSE FINE

GRAIN SIZES

SANDS AND GRAVELS BLO\NS/FOOT t SILTS ANO CLAYS STRENGTH* BLO\NS/FOOT1

VERY LOOSE 0 - 4 VERY SOFT 0 - 1/4 0 - 2

SOFT 1/4 - 112 2 - 4 LOOSE 4 - 10

112 FIRM - 1 4 - 8 MEDIUM DENSE 10 - JO STIFF 1 - 2 8 - 16

DENSE 3:l - so VERY STIFF 2 - 4 16 - 32

VERY DENSE Ov'ER SO HARO OVER 4 OVER 32

RELATIVE DENSITY CONSISTENCY +Number of blows of 140 pound hammer falling 30 inches to drive a 2 inch 0.0. (1-3/8 inch 1.0.)

split spoon CASTM 0-1586!. +Unconfined compressive strength in tons/sq. ft. as determined by laboratory testing or approximated

by the standard penetration test CASTM 0-1586), pocket penetrometer, torvane, or visual observation.

SDI L STRENGTH

KEV TO LOGS

.. UPP GEOTECHNOLOGY OISJN/CARIDLL RESIDENCE

Eng1ntt"1"10C) Geology• Geot«tv'IOI En:J~ing Santa Clara County, califomia PROJECT NO. DATE


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The standard penetration ~esistance (SPT) blow counts are obtained in accordance with ASTM Test Designation D1586. The drive weight assembly consists of a 140 pound weight dropped through a 30 inch free fall. A standard 2 inch outer diameter split-barrel sampler le driven 18 inches, or to practical refusal, and the number of blows are recorded for each 6 inch penetration interval (See Figure A). The blows per foot recorded on the boring logs represent the accumulated number of blows required to drive the sampler the final 12 inches.

Samples holding 2 I 4 inch (See Figure B) and 2.5'X 6 inch liners (see Figure C) are used to obtain nundisturbed n samples. Blow counts are converted to SPT counts by the following relation:

Where:

B = .00051lE D! - D~

B = Equivalent number of blows per foot with a SPT I = Number of blows per foot actually recorded. B = Energy in inch-pounds per blow. Do = Outside diameter of the sampler. D, = Inside diameter of the sampler.

Occasionally a portable power driven sampler holding 1 I 6 inch liners is used for field sampling (see Figure D). Resistance is measured in seconds per foot and does not correlate with the ASTM SPT. Undisturbed samples may also be collected using a Pitcher Barrel sampler (see Figure E). Material recovered over the length of the sampler is shaded. A measure of resistance is not collected with this technique.

m ~ ~ .

~ ·~ SPI' 2" Liner 2.5" Liner 1" Liner Pitcher Barrel

Figure A Figure B Figure C Figure D Figure E

• - lblisturtied Sanple X - Disturbed Sanple

Where obtained, the shear strength of the soil samples using either Torvane (TV) or Pocket Penetrometer (PP) devices is shown on the boring logs in the far right-hand column.

SUMMARY OF FIELD SAMPLIN'.i PROCEDURES

-er., UPP GEOTECHNOLOGY . U e~~Groioq,.•Groc~Erqnttrng

OLSJN/CARRJLL ~ 20930 Panorama Drive Santa Clara County, California

PROJECT NO. o,r.TE


EQUIPMENT 6" Cont. Flight Auqer ELEVATION 1,475.0' LOGGED BY J. Falls

1 DEPTH TO GROUNDWATER N:Jt. El:m.ntem:l. DEPTH TO BEDROCK 9.0' DATE DRILLED 2-1-90

~w . a:~ - ::c

DESCRIPTION AND CLASSIFICATION - ~ t: ,.

IC~-~

>!:::~ DEPTH w ...... ~ "' .... "z"" ~ ~ I- UJ .... z a:"' LJ .. .... !? ~ CW oz .. "'w ~ (FEET) " ~;;; ::ca:-SOIL .. w.,, w-

DESCRIPTION ANO REMARKS COLOR CONSIST. "' zw~ 0 0 "',_

TYPE w~,.

" "' .. -CLAYEY SILT, with abundant angular Reddish Very ML - -

to sub-rounded sandstone gravel, Brown Stiff - 1 -cohesive, hornogenecus, moist, - -trace charcoal fragments L 2 -(Colluvium)

L -

'- 3 -L . }J '-L

I- 5- 19 19 115 1.0*

L -... 6 -L -L 7 -... -L 8 -

·--PEBm.E~, angular to BlI:w1iS1 (M3::litrn - 9 -sub-rounded siltstone and sand- Yellow Dense

-~ ~tone gravel in a clayey silt to to 24 8 111 matrix, heterogenecus, highly Very Dense) -10-

weathered (Bedrock) Dark - -Grey - 11 -

- -- 12 -L -- 13 -

'- - '--

I I ... u -I L - Y. 31 6

~ 15

I. '- -

I ... 16 -L -

I

I. I L 17 -' ... -

'- 18 -

I L -'--

... 19 -L - Y. 24 6

I *.Unconfined Compression Test I- 20

LOG OF BORING NO. 1

I 1

tlJ :~"~!a~.~~?.~C:V OIS.>N/CARROSS RESIIIDO: Santa Clara County, California

PROJECT NO. DATE


I eautPMENT 6" Cont. Flight Auger ELEVATION 1,475.0' LOGGED BY J. Falls

DEPTH TO GROUNDWATER NJt. Eh:o.nteIB::l. OEPTH TO BEDROCK 9.0' DATE DRILLED 2-1-90

z w--: ;<. r DESCRIPTION AND CLASSIFICATION

Ou~ > ~ ;: z"" <r;: I[~-

DEPTH w .. <' »--~

:: ti~ ~z -~ :z~ ~ <w a:"'u SOIL (FEETJ

, w Ui 0 it~ oz~ r"'"

DESCRIPTION AND REMARKS COLOR CONSIST .. Zw~ w- .,a:-

. TYPE "' ~a: .!B. 0 0 ... u "' PEBBLE ~, angular to Brr:wriffi Very.

.

- -

I I

sub-rounded siltstone and sand- Yellow Dense stone gravel in a clayey silt

... 21 -to

matrix, heterogeneous, highly Very ... -weathered (Bedrock} Dark ... 22 -

I Grey - .

' - 23 - 25(7" I Bottcin of Boring = 23.5' ... 24 -

- -I -25-... -

' - 26 -'

I - - .,

I - 27 -

- -' ... 28 -' ... -

"

... 29 -I - --30-

- -1 ... 31 -... --32 -1 - -- 33 -- -] ... 34 -

- -~35 -]

I ... -- 36 -

.... -] -37 ·-

' ' - -' I - 38 -]

... -- 39 -

- -] ....- 40-

] LOG OF BORING NO. 1 (Continued} 0 UPP GEOTECHNOLOGY' OLOON/CARROSS RESIDmCE

E~'"'iil Grolcq;• Grotectnical E~n;i Santa Clara County, califomia

PROJECT NO. DATE

J 1 691.01 November 1990 Figure 11

EQUIPMENT 6" Cont. Flight Auger ELEVATION 1,470.0' LOGGED BY J. Falls

DEPTH TO GROUNDWATER NJt Elxo.nteie:1 DEPTH TO BEDROCK 4. 6' DATE DRILLED 2-1-90

DESCRIPTION ANO CLASSIFICATION "' ~~~~~~~~~~~~~~~~~~--.~~~~-.-~~~r-~iOEPTH ~

DESCRIPTION AND REMARKS COLOR

CU\YEY SILT, with abundant angular Dark to sub-rounded sandstone gravel, Brown cohesive, heterogeneous, -slightly m::iist, trace charcoal fragments (Fill)

SOIL CONSIST. TYPE

Very Stiff

ML

(FEET) "' ~

'- -~ 1 -

'- -

'- 2 -

'- 3 -

SILTY SllNDS'roNE, fine- to mediumgrained sand, m::iderate cernentation, hcrnogenecus, blocky fracturing with 3/4" to 1 1/2" spacing, clayey silt infilling fractures, dark oxide staining on fracture surfaces

--4-- --+--/-~ 4 ~ 36 Ellnrlllih (Dense ~ s

(Weathered Bedrock)

Bottcm of Boring = 15.0'

* Unconfined Compression Test

Yellow and Strong Brown

'- -'- 6 -

'- 7 -

'- -. ~ 8 -

~.:JJ 45

'- -- 11 -'- -~ 12 -

'- -~ 13 -

'-

14}J '-. - 45 15 '- -- 16 -

- -- 17 -

- -- 18 -

- -- 19 -

- --20-

14 16

16

11

LOG OF BORING NO. 2

OLS'.JN/CARROSS RESIDENCE Santa Clara County, California

PROJECT NO. DATE

112

113

121


1.9*

1.8*

3.0*

EQUIPMENT 6" Hollow Stem Auger ELEVATION 1,460.0' LOGGED BY J. Falls

DEPTH TO GROUNDWATER N:t Etm:ntere:l. DEPTH TO BEDROCK 8.5' DATE DRILLED 2-5-90

Zw- ."! l: DESCRIPTION AND CLASSIFICATION "' 2ut:: "';:

> er~-w ~z, ,._

DEPTH ~ < <., Wz >-~ <z~ .. "'~~ !< ~ "'"' (J ~w~ (FEET) ~ ~., oZo.

SOIL < ~ Ui ...J ii: z w- .,o:-DESCRIPTION AND REMARKS COLOR CONSIST. TYPE

., ~~!!?. O· 0 ..

" .,

SILTY CI.A'l, trace sand and fine Brown Soft CL - -gravel, moderate cohesion, hano- to

very moist to wet, RrrliSl - 1 - 2 19 102 0.3* geneous, trace rootlets ('lbpsoil/Fill) Brown ... - 2

- 3 20 91 0.2* 3 - -

OAYEY SILT, with abundant angular Yell.cwifil Stiff ML - -to sub-rounded sandstone gravel, Red ... 4 -x cohesive, hanogeneous, moist - 13 18

--~

: (Colluvitnn) ,__ 5 -

- -- 6 -

' - -- 7 -- -~ 8 -

-sAfillsroNE, fine- to meditnn- Brownish l}Bji.un - 9 -

•grained, poor to moderate Yellow Dense) ... -·cementation, blocky fracturing, and highly weathered (Bedrock) Dark ,.._ 10

Yell.cwifil ... 11 =t Brown - 23 16 103 1.1* - ..

... 12 -' ' - --13 -

-SILTS'IDNE and SHALE, highly Light l}Bji.un -14 -! fractured, clayey silt infilling Yell.cwifil Dense) .

' fractures, very low cohesion Brown to - -1 along fractures, dark oxide Dark -15

I · staining along fractures, Yell.cwifil - -1 weathered (Bedrock) Brown ~ 16 ~ 26 11

' - 17 - •.

- -- 1 B -- -- 19 -- --20 rv

LOG OF BORING NO. 3

tJ ~~.:!o~~.!?.~~ OISJN/CARROSS RESIDENCE Santa Clara County, California

PROJECT NO. DATE


EQUIPMENT 6 11 Hollow Stem Auger ELEVATION 1,460.0' LOGGED BY J. Falls

DEPTH TO GROUNDWATER N:Jt Etm.nt:enrl DEPTH TO BEDROCK 8.5' DATE DRILLED 2.5.90 I

DESCRIPTION AND CLASSIFICATION Zw~

~ J: ou- > a: ~ z l,L a: ;: a:~-DEPTH w <<~ > !::~ J a:1-"' "'z ~z~ • I-"'~

1-w a: "'u SOIL (FEETl

, w(i)O ;z oZ• J: w"

DESCRIPTION AND REMARKS COLOR CONSIST. < ZwJ w- .,a:-"' 0 0 TYPE ~a:~ u I-

"' SILTS'IDNE and SHALE, hicjlly fuc- :. Dark ~ .... -

I I

"b..lrErl, cl.a}ey silt infill:inj :Era::b.n:Es, Yellru:iffi r:ense) vaif kw a:iESim akrg :Era::b.n:Es, Brown

.... 21 )£ 24 11 120 dlik ad.Ce stainirq akrg :Era::b.n:Es, -Vffl.t:tErErl (I£dro::k) - 22 -• -

SANrisroNE, fine-grained, perva- Dark (I::ense) .... 23 ---sively fractured, rroderately Yellafilh - -I cohesive clay infilling frac- Brown - 24 -

" tu:res, slightly rroist, weatheree 33 11 (Bedrock)

l/ .... 25-

.... -

.... 26 -

Bottcm of Boring = 24.5' - -

• • .... 27 -.... -- 28 -• - -

I - 28 -• .... -

i .... 30-.... -~ 31 -

.... -: I- 32 -

.... -,... 33 -

- -I- 34 -

.... --as - ~

.... -

.... 36 -

- -,... 37 :..

i - -~ 38 -- -r 39 -

.... -* U~confined Compression Test

-40-

LOG OF BORING NO. 3 (Continued)

'CIJ UPP GEOTECHNOLOGY OIIDN/Cl\RROSS RESIDENCE

Engu"ft'r•ngGeollOq,l•Gl!ol~E~ng Santa Clara County, California

PROJECT NO. DATE


I I

0

ID

15

- . - ... -· "j/;> ·---=-· . - . ··'fl·-··-·-·· .. :_. . ·-. '-- U/. o,;:;. - @ . . - . - . . ::_-:- :---1· . . - . - ." -- . 0 ' - ._ .. -.;·_ .-._:_-..::---;;

0 ·- . -- 6 - ..::----,_:::.:- .. (!) . .· .. '

· .. ···w··,,. ·, t?o 0 g· . ,.... .

. :.. . . - ~ • 0 0 . t) ,, .. • - A ,,1 .

• t:il ""' • • ,, • '· •.

0 . .,." . . . o . ,,,,1. ·--·

• . I I ' (7;:") • • •

; ii'9 ···~·;:' '.'h~· :-.:~Y1:>:·: . 13~~· . . fu-Yf·: .. . . :::.: :.,· .. 0 · ....

. . ... . /.'.) {T ·.. ;;.<'7

. ~f)t/ .,,.. . ·=;;:; .... ~&-a"'" . u~ · '. ·:··.6 ·o ...

1. SILTY SAND, dark yellowish brown, scattered sandstone gravel, homogeneous, slightly moist, slightly dense, scattered roots (Fill)

2, SILTY SAND, minor clay, dark greyish brown, scattered sandstone gravel, homogeneous, moist, slightly dense, scattered roots and abundant soil pores (Topsoil)

3. GRAVELLY SAND, dark yellowish brown, minor silt and clay, gravel is sandstone up to approximately 4 inches in ~iameter, homogeneous, slightly dense, moist, scattered roots and rootlets (Weathered Bedrock)

4. SANDSTONE, dark yellowish brown, highly fractured, very low cohesion, loose, slightly moist, contact with overlying unit is gradational over approxi-mately 12 inches (Bedrock) ·

LCGGEJ::i BY: M. Baumann, UPP GIDI'EXlINJu:x;y, INC., December 27, 1989

APPROVED BY

' ILG OF.EXPIDRATION PIT 1

SCALE

1" = 5'

OLOON/Cl\RROLL RESIDENCE 20930 Panorama Drive Santa Clara County, California

PROJECT NO. OATE


- - ~ -- ----· -

]

]

I I I I '

~ 1• ,• '

'

I 1,

~ i

10 ....

. (ba~eyock a11d a.-sl"ha II-

~~- ~- -. - - .• - - - • : - - 4 - I.)_..-,,,,,.. €J " . • @ 'iJ'© .· "'·"." ./. . . ., .. I .·· -~:./. (.J 8 ·. · () ,,, .

· ... ~,,; "'/ v . D ~

-~~· ·&.·o.D ·@. 0 · . .,'.

(;? . • ,.,., . • I t' tft• . o_c:...w,_,,,, ·6

0 ·f:i>."''·. V· ~4

'0;B~®~~ ·~ ty.· .. : : ~· ... :·~,?'

- - ·.(:. ~:'/

0-

1. GRAVELLY SAND, yellowish brown, trace clay and sandstone gravel, low cohesion, loose, moist (Colluvium)

2. SANDY GRAVEL, yellowish brown to brownish yellow, trace clay, sandstone and minor shale gravel and cobbles up to 8 inches in diameter, very low cohesion, moist (Weathered Bedrock)

3. INTERBEDDED SANDSTONE and SHALE, dark yellowish brown, highly fractured, very low cohesion, loose, moist (Bedrock)

1.0:;GED BY: M. Baumann, UPP GEDI'EDlR>ILGY, INC., January 10, 1990

·~- r.o::; OF EXPIDRATION PIT 2

.fr jj'/ UPP GEOTECHNOLOGY U Eng1neenng GeolOgy• ~tecm1ca1 Engineering

APPROVED BY SCALE

1" = 5'

Ounil/CARROLL RESIDmcE 20930 Panorama Drive Santa Clara.County, California

PROJECT NO. DATE


]

I I I I I I I I I I -. I I I I I I I

0 •• # foot hi~ •

I> .. 1 • fiup\o.LL • I>

.foo+i"9 " .. •

2 b CY ~

" p

p • " v v I " -:e.;J " .

" @ • . I '\ " .... I

fee+ I I> • • J -111~€i1-

®

1. SILTY SAND, dark yellowish brown, abundant sandstone gravel, homogeneous, moderately cohesive, loose to medium dense, nails and concrete fragments (Fill)

r..o:;GED BY: M. Baumann, UPP GIDl.'EXllN)lO:, INC., December 27, 1989

:UX: OF FOUNDATION PIT 1

..frliil/ UPP GEOTECHNOLOGY U Eng1neer1ng GeolOgy • Geotecmicar Engineering

APPROVED BY SCALE

As Shown

OIB'.JN/CARROLL RESIDmCE 20930 Panorama Drive Santa Clara County, california

PROJECT NO. DATE


I I I I I I I I I I I I I I I I I I I

0-

1-feet

c;i11ck \iloc.~ Y.eh1.i~iY19 wo.ll

. 11/<Ell

1. SANDSTONE, dark brownish yellow, coarse-grained, moderate cementation, dense (Bedrock)

I..a;GED BY: M. Baumann, UPP GED'l'EXliliOICGY, INC., D2cernber 27, 1989

APPROVED BY

bd

r.o::; OF FOUNDATION PIT 2

SCALE·

As Shown

OLS'.>N/CARROLL RESIDENCE 20930 Panorama Driv~ Santa Clara County, California

PROJECT NO. DATE


I

• I I I I I I

• I I I I I iii I I I II

'

I

'

' :

' I I '

i :

I

' ' I

60 y 50

~ CH " "'""''<-..._ "~ '-'

40 , x

/ w CL c ~

JO >- / I-

MH u ;: . rn 20

// or

< ..J OH Cl.

10 ·~ 7 ,

c~~=-~~ / /, ML or OL 4

0 ML .I I

0 10 20 JO 40 50 60 70 80 90 100

LIQUID LIMIT (%)

NATURAL PASSING UNIFIED

KEY BORING SAMPLE LIQUID PLASTICITY LIQUIDITY SOIL SYMBOL NO. DEPTH WATER LIMIT INDEX NO. 200 INDEX CLASSIFICATION

CONTENT SIEVE SYMBOL (feet) % % % %

~ 3 2.5 20 26 9 52 0;3 CL

PLASTICITY CHART

tlJ :~,,~~':~~~~~~': OISJN/CARROLL RESIDENCE Santa Clara County, California PROJECT NO DATE


l I I I.

II.

I III.

I IV.

I v.

I VI.

I I VII.

I I VIII.

I I IX.

I x.

I I XI.

I XII.

I

TABLE I

MODIFIED MERCALLI SCALE OF EARTHOOAXE INTENSITIES

Not felt by people, except under especially favorable circumstances.

Felt only by persons at rest on the upper floors of buildings. Some suspended objects may swing.

Felt by some people vho are indoors, but it may not be recognized as an earthquake. The vibration 1o similar to that caused by the passing of light trucks. Hanging objects swing.

Felt by many people who are indoors, by a few outdoors. At night ao~e people are awakened. Dishes, windows and doors are disturbed.; walls make creaking sounds; stationary cars rock noticeably. The sensation is like a heavy object striking a building; the vibration is similar to that caused by the passing of heavy trucks.

Felt indoors by practically everyone, Outdoors by moat people. The direction and duration ot the shock call be estimated by people outdoors. At night, sleepers are awakened and so•• run out ot buildings. Liquids are disturbed and sometimes spilled. Small, unstable objects and some furnishings are shifted or upset. Doors close or open.

Felt by everyone, and many people are trightened and run outdoors. Walking ls difficult. Small church and school bells ring. Windows, dishes and glassware are broken; liquids spill; books and other standing objects fall; pictures are knocked from walls; furniture is moved or. overturned. Poorly built buildings may be damaged, and weak plaster will crack.

Causes general alar•. Standing upright is very difficult. Persona driving cars also notice the shaking. Damage le negligible 111 buildings or very good design and construction, alight to moderate in veil-built ordinary structures, considerable in poorly built or designed structuree. Some chimneys are broken; lnteriora and turnishlngs experience considerable damage; architectural ornaments £all. S•all slides occur along •and or gravel bank• ot vater channels; concrete irrigation ditches are damaged. Waves tors in the water and it becomes muddied.

General fright a11d near panic. The steerlng or care ls dirCicult. Damage is slight in specially designed earthquake-resistant structures, considerable in well-built ordinary buildings. Poorly built or designed buildings experience partial collapaes. Numerous chimneys tall; the walls or trame buildings are damaged; interiors experience heavy damage. Frame houses that are not properly bolted down may aove on their foundations. Decayed pilings are broken oft~ Trees are damaged. Cracks appear in vet ground and on steep slopes. Changes in the tlov or temperat~re ot springs and vella are noted.

Panic ls general. Interior damage ls considerable in specially deoigned earthquake-resistant structures. Well~built ordinary buildings suffer severe damage, with partial collapaea; trame structures thrown out ot plumb or shifted arr or their foundations. Unreinforced masonr7 bui?ding• collapse. The ground cracks conspicuously and some underground pipes are broken. Reservoirs are damaged seriously.

Most masonry and many frame structures are destroyed. Specially designed earthquake-resistant structures may auffer aerious damage. Soae well-built bridges are destroyed, and dame, dikea and embankments are seriously damaged. Large landslides are triggered by the shock. Water is thrown onto the banka of canals, rivers and lakes. Sand and mud are shltted horizontally on beaches and rlat land. Rail• are bent slightly. Many buried pipe• and conduit• are broken.

Few, if any, masonry structures remain etanding. Other structures are severely damaged. Broad fissures, slumps and slides develop in sort or vet soils. Underground pipe lines and conduits are put completely out of service. Ralls are severely bent.

Damage is total, with practically all works or construction severely damaged or destroyed. Waves are observed on ground surfaces, and all soft or wet soils are greatly disturbed. Heavy objects are thrown into the air, and large rock masses are displaced.

YANEV, P., 1974, Peace of Mind in Earthquake Country, Chronicle Books, San Francisco, California.

z:-tctrgmw.consrv.ca.gov/shp/apsi_siteinvestigationreports_ocr/apsi_004033/apsi_004033...nov 05,...

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