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~TATE o~ CAllFQl<!NlA-THE: 1u:50URCE5 AGENCY

D[PAl\!MfNT 0~ CONSERVATION

DIVISION OF MINES AND GEOLOGY SAN FRANCISCO DISTRICT OFFICE FERi;tV &UILDING

SAN FRANCISCO, CA 94111

(Ph on~ 415....o.557-0633) Af County Engineer Facilities Engineering Geology Section ROom 403 A 550 South Vermont Avenue Los Angeles, Ca. 90020

Attention: Art Keene

Dear Art,

December 16, 1982

EDMUND G. B'!OWN JR., Gon•rm.:ir

We are placing on open file the following report, reviewed and approved by the County of Los Angeles in compliance with the Alquist-Priolo Special Studies Zones Act:

Report of seismic investigation, 8555 Elizabeth Lake Road, Leona Valley, Los Angeles County, CA; by J.D. Merrill; August 5, 1982.

Sincerely yours,

f'a,,_( -4/ J/-~1.,,.,,f" EARL W. HART Office of the State Geologist CEG 935

EWH:mc

cc: A-P file./

Et.IGINlE:RING GEOl..OGV SECTION

t21.l) 7a8-2161 0 ' ' 0 Dirt. Office _.;.?~'c..:.1.-----F NF __ , ___ _

GEOLOGIC REVIEW SHEET

COUNTY OF LOS ANGELES DEPARTMENT OF ENGINEER-FACILITIES

55050_ VERMONT AVE-, LOS ANGELES. CA 90020

PLAN CHECK NO. OR DATE Of REPORTISI

SHEET I OF I

DISTRIBUTION: ~ist. Engineer /Geologist .! Soils Engineer .L Geol. Sect. File _ Grading Section _L 'i4k ,,..,,,/_ ,

Review of:

Action:

OJGrading P_C_ No.~-;­

OBuilding P.C. No.----·-------­DGeologic Site Inspection Only P_C_ No. __ ~---DG•ologic Report Dated _...s__'.".'.!'.--:- "'- +:k __ ?;--: s-- Z-,_ CiJS'oilsReportDated /t-2-3-?2- ___________ _

DGeology & Soils Report Dated --------

D Plan i• geologically approved

w4 approved geologically subject to conditions below

~~09 Code requirements met ( t :et)

DSec. 308{b) 3c & e code requirements met {not met)

D Plan is not approved for reasons below

::!Submit plans for recheck

Remarks: •­c-.,

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1. DA consulting Dsoils engineering, Oreport(s) is required

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2. 91\ii recommendations of the consulting design or shown as notes on the plans..

~~logist, Bfuiis engineer Je 11.,;.,-v~. -------

must be i~e

3. DThe plan must be specifically approved by the Ocon5Ultant geologist, Dconsultant soils engineer by Dletter-.eport and/or Omanual signature(s) with date(s) prior to approval by the Geology Section_

4. UJ.trfilrading inspections must be made by the coosulting [gg'eOiogist,.t/"<./) ~-engineer. Dlnspection reports must be submitted to the Geol0gy Section for review ~y.

5. ~gh grading must be appro-.d by a !afiilat geology report. Gfirlai" soils engineering report prior to approval ~ the_Ge.:t,:sv Section. , DAn As·Built Geologic Map mu'1 be included in the final geology report. S•bu., 'f

1-o G-ed· ; (_...,,,. ,._., -fr; .... ~?P J- ,..,...._{' ~ -L 1 J-" ~ .,/I ~ --4..... b '1 ~ 141 ~ 6. DFoundation and/or wall excavations must be tnspected arid approved by the-Cor'ISOlting '-ged!ogist. Osoils

engineer. prior to the placing of steel or concr~te_

J_ DThe C.Ounty Engineer Soils Engineering Section's Dappro1Jal is required D requirements attached

Oconditions of approval are attached D approval attached (dated--------- -·--)

8_ DShow all PfOposed tentative corrective devices (e.g. bunre ... stability fills, subdrains, etc) on the plan .

9. Add items ________ _,___ and ----"'-------- . above, as notes to the plan.

Prepared by __________________ _ Reviewed by I ~-!<' ~ Date .l -?' "

7&Ci.:)0 ~ P$ 3-82

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OCT 2 7 1982 Report of Seismic Investigation 8555 Elizabeth Lake Road Leona Valley District Los Angeles County, California

Project 25Ul2 August 5 , l 9S2

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@rn®rP~ffiQJ11 ~OO®o consulting engineering geologists

18432 OXNARD STREET

Report of Seismic Investigation 8555 El\zabeth Lake Road Leona Valley District Los Angeles County, California

Ray Urwil l er 11829 La Cima Drive Whittier, California 90603

Dear Mr. Urwiller:

TARZANA, CALIF. 91356

John O. Merrill, President

August 5, 1g32

Project 25812

(213) 881 ·2063

ocr 2719sz

In accordance with instructions from James W. Price, Architectural Engineer,

an engineering geologic investigation was conducted on subject property to identify

geologic and seismic conditions that may bear.on proposed grading and residential

development to be served by a private sewage disposal system. This report is

based on observation and measurement of surficial deposits and bedrock that crop

out on and adjacent to the property and which are exposed in low cut slopes on the

property and in two backhoe trenches. Geologic data have been plotted on a. Geologic

Sketch Map prepared with tape, compass and hand level. Earth materials.exposed

in th~ backhoe trenches are illustrated on Section A.

This report is prepared in conformance with requirements ·of the Alquist-Priolo

Special Studies Zones Act of 1972 (Sec. 2622, Public Resources Code) and imple­

ments the suggested outline for geologic reports on faults and Note 44, Form and

Content of Geologic and Seismic Reports by California Division of Mines and Geology.

This report emphasizes applicable elements of the county Building Ordinanc~ and

the recommendations of the project consultants. It is intended to be understood

by reasonably well educated persons, but to avoid misunderstanding of terms and

~ useage the reader is directed to the Glossary of Geology, 3rd edition, 1974.

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GEOPLAN, Inc. CONSIJLTING ENGINEERING GEOLOGIStS

Project 25812 Page 2 August 5, 1982

The purpose of this report is to prov1de geologic data that may be incorporated

in the grading plan and in the design of foot1ngs and buildings. Persons utilizing

this report are cautioned that notwithstanding the straightforward appearance of

conditions it is possible that latent defects are concealed by earth materials

and that such defects, if present, are beyond the scrutiny and evaluation of the

engineering geologist.

To supplement field exploration review was made of data contained in our files

describing the results of surface and subsurface exploration on nearby and adja­

cent properties, Further, published reports and maps were reviewed along with

stereographic aerial photographs. 'A list of references is appended.

Location and Topographic Expression:

Subject property is a rectangular parcel comprising about 2~ acres fronting

along the north side of Elizabeth Lake Road, midway between 90th Street West, and

Bouquet Canyon Road, Leona Valley District, Los Angeles County.

Leona Valley is characterized by a scattering of single family residences,

small fanns and ranches. Terrain is smooth, but varies from nearly hort~ontal

on the valley floor to moderately steep on the flanking slopes.

Subject property comprises part of the south-facing flank of a low, rounded

ridge that rises about 120 feet above the grade of Elizabeth Lake Road. The south

half of the property has been modified by nominal grading that included excavation

of the access .roadway and cut/f11 l grading of the small pad at the location of the

proposed residence. The pad is about 25 feet higher than street grade, and is at

the break 1n slope north from which the slope steepens to about 2~:1, rising an

additional 100 feet to the r1dgecrest.

~ A minor swale has been eroded in the slope illll1ediately above the building site,

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GEOPLAN, IM. CONSULTING E't,;GINEEAING GEOLOGISTS

Project 25812 Page 3 • August 5, 1gs2

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but ow1ng to the limited areal extent of the slope there has been no sign1f1cant

tributary flow. Runoff generated by incident rainfall has eroded some minor gullies

on the filled part of the pad and on the access roadway, but these can be elimihated

when the site fs landscaped. subsurface exploration reveals that ground water is

more than 15 feet beneath the surface at the building site and in the gently sloping

area 75 feet south from ft, where an unsubstantiated report noted water at a depth ,.

of about 11 feet shortly after the intense rains of 1977;.78. Fluctuation is conrnon,

by contrast with the perennially shallow ground water in alluvium that comprises the

floor of Leona Valley south of Elizabeth Lake Road, an area traversed by the east­

flowing Amargosa Creek,

Geologic Elements:

Minor grading has produced a thin wedge of fill on the downslope side of the

bu1l ding pad and a b 1 anket- like depos 1 t just upslope from the access drf veway. F11 l

generated ~Y pad grad1ng is fairly evident and was exposed in the exploratory trench,

but blanket fill nearer Elizabeth La.ke Road reputedly was placed about 15 years ago

as part of grading an agr1cul tura 1 /poultry raising operation that exists' on adjacent

property to the east. The old fill is obscure, 1f 1t is present, and forms a ridge

that appears to have been produced by faulting. However, backhoe trench 2 was exca­

vated at the break in slope on the north side of the low ridge/f11 l where· it pene­

trated unconsolidated, sandy alluvi.um that exhibits no evidence of faulting.

Unconsolidated residual soil/colluvium forms a southward-thickening wedge

that ranges from a film on slopes north of the building site to about 14 feet

thick beneath the pad and to an estimated 25 feet thick beneath Elizabeth Lake

Road (see structure section A, which includes the illustrated logs of the backhoe

• trenches). Residual soil/colluvium consists of medium to fairly coarse grained;

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GEOPLAN. Inc. CONSULTING ENGINEERING GEOLOGISTS

Project 25812 Page 4 August 5, 1982

dark brown silty sand derived from terrane comprised of tan and red arkose. The

base of the unit is made up of numerous hard blocks of buff and red arkose comparable

with the outcrops that comprise the low hills to the north. Colluvium is moder~tely

CQR1)act and dense and should provide competent foundation for the proposed

structure.· Percolation tests indicate that it is highly adsorptive {percolation

test: results appended), and that it ~an be relied upon to adsorb seioiage effluent

effectively.

The buff arkose member of the Anaverde formation {map symbol Tab) underlies

subject property. This crudely bedded to massive, hard, well cemented sedimentary

rock is made up of detritus shed from the nearby granitic terrane •. It is poorly

sorted and clasts exhibit little rounding such that the unit would better be

termed an arkosic breccia as many clasts range to several feet in largest dimension •

Locally the buff arkose is well bedded, but at subject property is appears to have

been ·deposited under high energy conditions, and there is no discernible bedding.

However, well bedded strata that crop out about 500 yards west suggest that the

buff arkose dips southerly at 50-75 degrees.

A recently graded pad about 75 feet north from the northeast corner of.the

parcel exposes the red arkose member {Tar), suggesting that the section is right

side up and thAt the brown shale section, if present, is concealed beneath residual

soil and colluvium near Elizabeth Lake Road.

Subject property is bounded on the south by the San Andreas fault, and on the

north by the Portal fault which, together with innumerable subsidiary faults,

define the San Andreas fault zone (see plate 4, Regional .Geologic Map).

Despite the complex geologic structure of Leona Valley as shown on the

• regional geologic map by Evans {1976) outcrops of the Anaverde formation exhibit

little structural deformation and are judged to .be grossly stable, with deterto~

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GEOPLAN, Inc. CONSUi.TiNG ENGINEERING GEOLOG1~:1s

Project 25812 Pa(l' 5 • August 5, lg82

ration be1ng limited to granular ravel1ng. Because there is practically no

residual soil/colluvium upslope from the building area and because the tributary

watershed is small, there is no likelihood·of mudflow.

There has been comparatively.little seismic activity along the San Andreas

fault between Tejon Pass and Cajon Pass, but the probability that strong ground

motion will be generated by an earthquake along this segment of the fault cannot

be disregarded. The seismic investigation has indicated no evidence of an active

fault beneath the building site or within 50 feet north or south from it. The

principal trace is about 80 feet south from the building pad, as indicated by

Kahle, et _!l {1977), and as shown on the Geologic Sketch Map.

Estimates of maximum credible earthquake along the San Andreas range to as

high as 8.3, measured histor1cal events range ilo higher than 7.1 (El Centro, 1940),

• and average slightly more than 6. An event in the range of M 6 - M 6.5 occuring

within 10 miles of the site could cause total ground acceleration of about 0.32g,

of which the horizontal component would be about 2/3, or about 0.2g.

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Geoplann1ng Analysis:

It 1s concluded from the engineering geologic 1nvestfgation and analysis of

data that proposed grading and residential development are feasible within the

framework of applicable elements of the County Building Ordinance and the recom­

mendations of the project consultants. The site is not affected by.landslide and

the implementation of the development will have no adverse affect on neighboring

property,

1) According to the grading plan the dwelling will be constructed on a cut/

fill pad. Ow1ng to the fairly soft character of surface soil/colluvium and the

existing fill it is reconmended that all f111 and .the upper 5 feet of residual

soil/colluvium be stripped and replaced as compacted fill with emphasis on keying

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GEOPLAN, Inc. CONSULTING ENGINEEFllNG GEOLOGISTS

Project 25812 Page·6 August 5, 1982

and benching, under control of the soil engineer. Alternatively, footings could

be deepened to penetrate bedrock, but the cost would likely exceed the recom­

mended grading. Although not shown on the grading plan a·:shallow swale rises

beyond the top of cut slope, north of the pad. It fs reconmtended that the "pro­

tective ditch" along the top of cut slope be widened to 10 feet and deepened to

3 feet at the flow line where it spans the mouth of the ravine. All flow from the

structure and pad should be directed down the driveway to Lake Elizabeth Road.

3) Percolation tests and exploratory excavations indicate that the leach

field of the private sewage disposal system may be located slightly lower and west

from the building site (see sketch map), where geologic elements are identical to

those at 'the percolation test sites.· The leach field should comprise an area

of 340 sq. ft. , or 225 sq. ft. for leach trenches, and an area of equival~nt sf:z:e

should be reserved for future needs.

4) . The site is not subject to liquefaction as ground w11ter is in fractures

in bedrock, below the bottom o:f. __ the residual s.oil/colluvium.

5) No active ·fault was iclentiffed on the property, but there is an a_namolous,

1i near feature in the south end of the lot_, about 85 feet so1Jth _ _from the 0fu_ture

building site. ·Despite a reputed origin by grading, this area is classified as a

Restricted Use Area, with respe.ct to habitable structures. The restriction does

not apply to the proposed leach field or leach trenches, however.

Thank you _for this .opportunity to be

questions regarding this report •

JDM:sh

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GEOPLAN, lno. CONSULTING ENGINEEFll,.,,G GEOLOGISTS

Project 25812 August 5, 1982

REFERENCES

1. Evans, J.G. (1976); Geologic Map of the San Andreas Fault Zone, Leona Valley,

California: U.S. Geological Survey, Misc. Field Studies Map MF 766.

2. Kahle, James E., Smith, Drew P., and Beeby, David J. (1975); Geology of the

Leona Valley Segment of the San Andreas fault Zone, Los Angeles County,

California: California Division of Mines and Geology, Open File Report 77-2 LA.

3. Ross, Donald C. (1969); Map Showing Recently Active Breaks Along the San

Andreas Fault Between Tejon Pass and Cajon Pass, Southern California: U.S.

Geological Survey, Misc. Geologic Investigations Map 1-553 •

4~ Dibblee, Jr., Tom W. (1961); Geologic Map of the Bouquet Reservoir Quadrangle,

Los Angeles County, California: U.S. Geological Survey, Mineral Investigations,

. Field Studies Map MF-79.

5. U.S. Department of Agriculture (ASCS); Stereographic Aerial Photographs

AXJ-15-W-171, 172 (9-28-59) .

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JOHN 0. MERRI~~ COfllSULTING E:NGfN'E:E:RfN'G Gf0LOG!.S1$

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PERCOLATION TEST

Project 2581'2 Test Pit No. I Client k'~ !j. u,l-1d.~ I le I Date 1-t'5_- g 2 Tested by JP

TIME f:!.T

DEPTH 6H AMT DESCRIPTION Of EARTH MATERIALS (TI (HI llllATER . .

/"'157 . B.25 ?..,nf ... .. .

t,.75 • n-40 ..fa,,.A J,l.i..; dari:::_ 6rl'.Jwn;ka.J.e-14e>Z

14oG · '·" we.oJ.-/,,,, r{,J,J> ~it.1e ,,../,.,_ . /Li I I tl.o I I

14/C:. l.d' .o A),, f,: .,.;.. r / ri; ./ ,,r,,,. .I't;Bhz,A 2'.d h,.I llr'~ /423 3,0 5 ,;, -1-D ./.-,, r./. • I

1430 ?.:~ 2.0 ' ;,, .

CALCULATIONS LOCATION Of TEST Pt.T .

Assume /{)&)C 7al.Seffii::. fa,.,k ' Scale:

e'7"rt ./i,rnivla ·,. T+6.Z4 wh~~ r; f1~e(utr'1) for ..sk-7f: 9feve

1f ./,,

J,."' ~ tf rP"'-t ? It, fc b fh ,;,c /, See ste.f..ci Ma P. F 7..-nin.·. 7+~.24 _ ei.45 z9 -

o. 4~x1ooe> :zz 5 ~1 . ./'I /,ac£ z frenol.es

".!' 22?:fo/ = llJ-+-s1.fl leach - l,efd

JOHN 0. MERRILL CON51Jl 11NG ENGINEERING GeO~OGISTS

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PERCOLATION TEST

Project 25812 Test Pit No. 2 Client 'f;?,;;t A Urwi lier Date 7/;~/P,2 Tested by JP , ,

' TIME

6.T DEPTH aH AMT DESCRIPTION OF EARTH MATERIALS CT I CH I WATER

rat G q,z5 ,. __ / ' ' ',

142t. 7.75 • /'I_ a.o -.Ji}l'I,(. JI '4 : ,,/_,rJ:: /,_ ... •µ· ,... ~,,,rre- - ·

1434 r,._o /e.-r;,_, I - L,./ ,,.~t,er1:1;.1f..-. · r"cf1: 14.-40 5.2S ,/ ,..,,,. . ( '

1447 4.2&:, ;.fl. {

/454 7 .. ;,., 3-25 &fl '

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CALCULATIONS LOCATION OF TEST PIT

A s-su_,e 1otJ07at s-erlic. f.a,..,f: . Scale:

f!1o¥1 /;,rll((,)/a,,_ 7+--&· 24., wt.~rc z-3 .

r; flme{m1n)w~fer level drop Jr()""' ?It. fo t .ft. in. = 7rn1;, , 1-f-b-24 "' 0 .45 ~ee rkefoh ~p .. , . 0.4~itooo,, 225 s-z.11 kac/, ·

2.. =-- !/·r~h .

or z2~ +zt?: 3374- s1 . .f /, z. ~ /e,pc.£.hetd

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GECJLOG!C SK.£lCI-/ lv1AP . . I /

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GEC>PLAAl,JNC Pro/ec/2?812 8/!o/82

MAPS ;:;iL...t:,.t::,.,....] V /"'\l...rJ..i.C...., .1 "-"4V,f'""'\..a...'A ... , ..

CALIFORNIA-LOS ANGELES CO. 7.5 MINUTE SERIES (TOPOGRAPHIC)

S.E/.C. BOUQUET t:l£SERY(JlR IS' QUADRA.ti!OU:

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