engineering geology, inc. - california€¦ · 16/05/1988 · engineering geology, inc....

ALLAN E. SEWARD ENGINEERING GEOLOGY, INC.

n:mOISTl!:H.ED GEOI~OGlST Ci71

'K.NOINEEffiNO Ot!iOLOOIST 246

SINCE 10:S8

July 15, 1988 Job N'f?:1 @,-1025-4

Valencj.a Company 23823 West Valencia Blvd. Valencia, CA 91355

Attention: Mr. Mark Subbotin

Subject:

Reference:

Gentlemen:

GEOLOGIC REPORT - Addendum No. 1 Vesting Tentative Tract 44832 Valencia, California

GEOLOGIC REPORT Vesting Tentative Tract 44832 Valencia, California Dated May 16, 1988 JN: 8-1025-4

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This report has been prepared at the request of the County

Geologist, Mr, Robert Larson,

LOCATION OF ALQUIST-PRIOLO SPECIAL STUDIES ZONE

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The location of the northern boundary of the Alquist-Priolo

Special Studies Zone is illustrated on the Tentative Tract

Map included in the above-referenced report. This boundary

is based on the Special Studies Zones Map for the San Gabriel

Fault (Newhall Quadrangle) issued by the State of California.

24523 CHESTNUT STR~RTt NEWHA.T..il..i, CALIFORNIA Ql 321

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Tnis. Mnp i5. Not a Survey of the Property.

NEWHALL QUADRANGLF. 1 ~ 2000'

LOCATION MAP

JOI N~Mllll !J-1025-4

ALLAN E. Engineering

SEWARD Geology

Valencia Company July 15,1988

Job No.: 8-1025-4 Page 2

The pertinent portion of the Alquist-Priolo Special Studies

Zone boundary was transferred from the state map to a

"400-scale" map based upon topographic prominences and the

intersection of the Special Studies Zone boundary with Bouquet

canyon Road. The boundary was then transferred from the

"400-scale" map to the Tentative Tract Map based upon the

Zone 7 California Coordinate System.

In an effort to allow for any inaccuracies in the transferring

process, our exploratory excavation was extended for a distance

of 70 feet north of the transferred boundary. In addition,

our trenching program was surveyed and staked in the field.

As noted on page 7 of our referenced report, this firm has

been involved in extensive geologic studies along the San

Gabriel F'ault Zone in the near vicinity of Tentative Tract

44832. These studies have resulted in the definition of a

"main zone" of deformation within bedrock exposures located

to the northwest and southeast of the subject tract. The

boundaries defined for this main zone of deformation include

a minimum 50 foot setback on either side. '

The southern boundary of Tentative Tract 44832 illustrated on

the map included in our referenced report was specifically

re-located to the north in order to be coincident with the

northern boundary of the main zone of deformation.

LOCATION MAP

Location Maps are provided in our reports in order to assist

the County Geologist in locating the general area of the

subject property. They are not intended as a ·survey of the


Job No.: 8-1025-4 Page 3

propertyi the illustrated project boundaries on them should

not be used as a basis for the transfer of geologic data.

A review of the Location Map included in our original report

dated May 16, 1988 indicates that the project boundaries

illustrated on that map have been plotted somewhat to the

south of their actual location.

An updated Location Map illustrating project boundaries

provided to us by our Supervising Civil Engineer (Sikand

Engineering Associates) is included herein.


Job No.: 8-1025-4 Page 4

CONCLUSIONS

The boundary of the Alquist-Priolo Special Studies Zone

illustrated on the Tentative Tract Map included in our original

report dated May 16, 1988 has been reviewed and found to be

satisfactory. A revised Location Map based upon information

provided to us by the project Supervising Civil Engineer is

included with this addendum report.

If you have any questions regarding the contents of this

letter or if any further clarification is required, please

give us a call.

Respectfully Submitted

£~/ Allan E, Seward Certified Engineering Geologist 246

Christopher J. Sexton Project Geologist

Enclosure:

Distribution:

Location Map

(2) Valencia Company Attention: Mr. Mark Subbotin

(2) L, A. County Department of Public Works Geology Group Attention: Mr. Robert Larson

(1) Sikand Engineering Associates Attention: Mr. Ron Horn

(1) R. T. Frankian and Associates Attention: Mr. R. T. Frankian

• . ·" l 21&? SlATE OF CALIFORNIA-THE RESOURCES AGENCY

c .. ·1? T' GEORGE O!:;UKMEJIAN, Gov.mor

DEPARTMENT Of CONSERVATION

DIVISION OF MINES AND GEOLOGY 8A Y AREA REGIONAL OFF ICC 380 CIVIC DRIVE. SUITE 100

PLEASANT ... Ill, CA 9.4523-1997

PHON" (413) 6-*5920 ATSS .599--'920

County of Los Angeles Department of Public Works 900 South Fremont Avenue Alhrunbra, California 91803-1331

Attention: Mike Johnson

August 15 1 1988

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

Geologic report, vesting Tentative Tract 44823, Valencia, CA, by Allan E. Sewardi 6/15/88.

Geologic report, Vesting Tentative Tract 44832, Valencia, CAJ by Allan E. Seward; 5/16/88; with addendum of 7/15/88.

EWH:slf

cc: A-P file(2)

Sincerely,

Earl w. Hart, CEG 935 senior Geologist &

Program Manager

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COUNTY OF LOS· ANGELES DEPARTMENT OF PUBLIC WORKS

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THOMAS A. TIDt:MANSON, Director

July 25, 1988

Mr. Earl Hart Department of Conservation Division of Mines and Geology 380 Civic Drive Pleasant Hill, California 94523-1997

Dear Mr. Hart;

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ADDH .. :S~ ALL CORA.ESl'UNJ>l-:NCE T01 P.O. BOX 1460

ALHAMBRA, CAI.IFOHNIA 91802·1460

IN REPLY PLEASE

REFER TO FllE L-4

Please find enclosed reports pertaining to Tentative Tracts 44823 and 44832. The San Gabriel Fault A-P Zone, transects these tracts. These reports are for your files.

Very truly yours,

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~rt A. Larson District Geologist

9:HART

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SUB DI,V:y>ER

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COUNTY OF LOS ANGELES DEPARTMENT OF COUNTY ENGINEER-FACILITIES

ENVIRONMENTAL. DEVELOPMENT .DIVISION

ENGINEERING GEOLOGY SECTION TENTATIVE LAND DIVISION REVIEW

?-'Cr · e1>1. C, I s· The Regional Planning Commission, developer and engineer are advised that:

j:>Q_ PRIOR TO APPROVAL OF TENTATIVE OR PARCEL MAPS:

( l An engineering geologic report will be required ---

( l Sufficient evidence must be submitted to show that the sustained use of private sewage disposal system is possible without inducing a geologic hazard. The Health Department and developer are advised that geologic conditions within this tract may severely limit or prohibit the use of private aewage disposal system that will introduce water into the subsurface.

( ) Special Conditions ~------------------

Ge 0(03 y ve,?o.,. /s c(q ./eel 7//s/86' ,F:., 5//G/(9$ ltqve bee-vi v-ev1'ew,.c/ o.11cl Dt.Ae o.ck,n~vlecf9.,,o/,

Reviewed by~~ Date ~4/9£

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c ENGINEERING bEOLOl!Y GROUP L.A. COUNTY DEPARTMENT OF PUBLIC WORl<S

TRACT No. i/./B :3 z_ TENTATIVE MAP DA TE ""'R~~~t/~, _51,.,_,,_//,_,~'-'T-/1..,,'!f'.~!l~

PARCEL MAP NO._~--'- LOCATION t/q /,...µ,.., :.._ PRIOR TO FILING THE FINAL LAND DIVISION MAP,

THE FOLLOWING CONDITIONS MUST BE FULFILLED:

tllf The final map must be approved by the Engineering Geology Group to assure that all geologic factors have been properly evaluated.

j;a_A grading plan must be approved by the Engineering Geology Group. This grading plan must be based on a detalled engineering geology report and/or soils engineering report and must be specifically approved by the geologist and/or soils engineer and show all recommendations submitted by them. It must also agree with the tentative map and conditions as approved by the Planning Commission. All buttresses over 25 feet high must be accompanied by calculations.

D A detailed engineering geologic report (and soils engineering report) must be approved.

~All geologic hazards associated with this proposed development must be eliminated.

!Ji!" or delirieate a restricted use area approved by the consultant geologist to the satisfaction of the Engineering Geology Group and dedicated to the County the right to prohibit the erection of buildings or other structures within the restricted use areas.

D Specific recommendations will be required from the consultant(s} regarding the suitability for develop" ment of all lots designed essentially as ungraded site lots. A report will be filed with the State Real Estate Commissioner indicating that additional geologic and/or soils engineering studies may be required for ungraded site lots by the Engineering Geology Group.

D Special Conditions:

f1! INFORMATION APPLICABLE TO THIS DIVISION OF LAND:

~The subdivider is advised that approval of this division of land is contingent upon the installation and use of a sewer system.

D The Health Department is advised that there is no assurance at this time that geologic and soil con· ditio~s wil I al low the sustained use of private sewage disposal on each lot.

D The Real Estate Commissioner will be advised that, due to adverse geologic conditions Which exist on the land division, a final geologic report approved by the Engineering Geology Group will be filed with the Commissioner concurrently with the filing of the final land division map.

fl( A geology and/or soil engineering report may be required prior to approval of building or grading plans.

D Approved without conditions.

D Special Conditions:

By~i~~ CONSULTANT: &an 6-,'oM

Date: g//~{f O' 7 7-/=98 :;--1G -BB

REPORT(S) 7- 2 z-i?z 76Q.202R - 6-7;!1 - P5 7-85

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ALLAN E. SEWARJ) ENGINEERING GEOLOGY, INC.

BEQlBTI!:Ill·:D (J1'~n1~o<H:o:t'1' Cj7J

ENOINl!:Jl~HINO OEOL0013T 2<1.CJ.

May 16, 1988 Job No.:

Val enc;,_, Company 23823 West Valencia Boulevard Valencia, CA 91355

Attention: Mr. Mark Subbotin

Subject: GEOLOGIC REPORT

Gentlemen:

Vesting Tentative Tract 44832 Valencia, California

This report presents our opinions on the existing geologic

conditions present on Tentative Tract 44832 and their affects

on the proposed residential development.

This investigation was performed in March through May, l.988.

SCOPF. OF INVES'l'IGATION

This investigation included the following:

1.

2.

3 •

4 .

Review of reports compiled by this office ln the general area.

Heview of the CDMG, Geologic Map of California, Los Angeleo Sheet (1969).

Review of USGS Bulletin 753 by Kew (1924).

Review of USGS Professional Paper 334-H by Winterer and Durhilm (1962).

24.5:.'.a ClI~-::S'fN'lJT f:oiTH.~ET, NEWI-i.ALL, CALllf'ORNl.J\. 91321 805 2Uri-Ci072

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Tni~ Map i1 Not a Survt?y of tht! Property,

NEWIIALL QUADRJ\,NGLE Scale: 1" ; 2000~

LOCATION MAP

ALLAN E. SEWARD Engineering Geology

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Valencia Company May 16, 1988

Job No,: 8-1025-4 Page 2

5.

6.

7.

8.

9.

Review of seismicity references listed in Appendix A.

Review of USGS Open File Report, Water-Resources Investigation Using Analog Model Techniques in the Saugus-Newhall Area, Los Angeles County, California by Robson (1972).

Review of water well data on file with the Los Angeles County Flood Control District.

Review of water well data on file with the Valencia Water Company.

Review of the following aerial photographs:

Year Photo Agency

1928 E-172, 17 3' 174 Fairchild

1963 24 & 25 Horizon Surveys

1968 4-95, 96 & 97 United States Department Of Agriculture

1980 1280-61, 62 United States Department of Agriculture

1980 123 & 124 American Aerial

10. Excavation and geologic logging of a single exploratory backhoe trench. This trench extended a lineal distance of 500 ft., and reached a maximum depth of approximately six feet. The end-points of this trench were surveyed in the field and arc plotted on the Geologic Map included with this report.

11. The Vesting Tentative Map (dated March 28, 1988) for Tentative Tract 44832 has been utilized as a base map for this study. This map was prepared at a Scale of 1"m100' by Sikand Engineering Associates, and was provided to this office for use in preparing this report. We make no representations regarding the accuracy of this base map.

12. Geologic analysis, conclusions and recommendations based upon the existing site conditions and future use intended.

13. Preparation of Location Map, Geologic Map, Geologic Trench Log and this report.

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


SITE DESCRIPTION

•

Job No.: 8-1025-4 Page 3

Vesting Tentative Tract 44832 consists of 20.s acres located

in Valencia approxirnately 1/3 rni. northwest of Bouquet Junction.

Access to the property is availa.ble via dirt roads which adjoin

Newhall Ranch Road (recently constructed).

'l'he site grades evenly from an elevation of approximately 1148

in the western po:ction to app:coximately 1162 in the eastern

portion, No topog:caphic p:cominences are present.

In the past the site has been farmed with row crops; cu:c:i:-ently

it is plowed and leveled.

PROPOSED DEVELOPMENT

It is our unde:i:-standing that you propose to develop Vesting

Tentative T:cact 44832 for residential purposes utilizing

condominiums. No significant cut or fill slopes are currently

proposed.

GEOLOGY

General

Vesting Tentative Tract 44832 is located in the Transverse

Range geologic province of Southern California just north of

San Gabriel Fault. This fault forms the boundary between the

Soledad Basin to the north and the Ventura Basin to the south.

Both the Ventura Basin and the Soledad Basin have been downwarped

in the geologic past to allow the accumulation of thousands of

feet of Cenozoic sediments.



Job No.: 8-1025-4 Page 4

Portions of the San Gabriel Fault have recently been classified

as active by the State Geologist, and arc. now included within

an Alquist-Priolo Special Studies Zone (Newhall Quadrangle).

The southern 1/3 of Vesting Tentative Tract 44832 is located

within this Special Studies Zone.

Bedrock

Saugus Formation {TQs)

Bedrock beneath Vesting Tentative Tract 44832 consists of

Plio-Pleistocene, non-marine sediments of the Saugus Formation.

These sediments include light-gray to reddish-brown and pale

yellowish-brown massive sandstones, pebble conglomerates and

red mudGtoncs.

The Saugus }'ormation is not exposed within the boundaries of

Vesting Tentative Tract 44832, and will not be encountered

during the proposed grading operations,

Surfic)_al Deposits

Recent Alluvium (Qal)

Bedrock beneath vesting Tentative Tract 44832 is overlain by

approximately 150 ft. of Recent Alluvium consisting of lensing,

interbedded silt, sand and gravel deposited by the Santa Clara

River. For a complete description of alluvial materials and a

discussion of their engineering characteristics refer to the

report by the project Geotechnical Engineer, R.T. Frankian &

Associates_.



ENGINEERING GEOLOGY

Fills

Job No.: 8-1025-4 Page 5

Fills will be placed under the observation of the project

Geotechnical Engineer, R.T. Frankian & Associates.

Sewage Disposal

It is our understanding that sewage disposal will be by public

sewers ...

Drainage

Drainage from the Santa Clara River flood plain falls under

the jurisdiction of the Los Angeles County Department of Public

Works.

Surface runoff from the future graded areas should not be

allowed to run over any natural, cut or fill slopes. Runoff

from future structures and pads should be collected and channelled

to the streets via non-erosive devices. Water should not be

allowed to stand or pond anywhere on the graded pads.

Rippabil it:y

The Recent Alluvium which underlies Vesting Tentative Tract

44832 is generally granular and relatively unconsolidated.

Grading operations can be performed using conventional grading

equipment.



Landslides

Job No.: 8-1025-4 Page 6

No landslides have been recognized as existing on or posing a

hazard to Vesting Tentative Tract 44832.

Building Setbacks

Building Setbacks from ascending and descending slopes should

be in accordance with standards set forth in Section 2907.1

of the County Building Code.

Ground Water

During this investigation the Santa Clara River was flowing to

the south of the subject site.

Our review of ground water data obtained from wells in the

immediate area (See Water Well Location Map, Table I and Table

II) indicates that the historic high ground water surface in

the vicinity of Vesting Tentative Tract 44832 has been recorded

on the order of 10 to 15 ft. below the ground surface. In

February of 1971, during the San Fernando Earthquake, the

ground water surface beneath the subject site was at a depth

of approximately 20 ft. below the ground surface.

Recent readings in local water wells indicate that the ground

water surface is presently located at a depth of 15 to 20 ft.



FAULTS-SEISMICITY

General

Job No.; 8-1025-4 Page 7

During a seismi.c event there are three common forms of geologic

hazard that are related to the earthquake;

1. Ground Rupture or Displacement

2. Ground Failure (liquefaction, landslides, failures, etc.)

3, Ground Shaking.

Ground Rupture

Although new faults may well develop during a seismic event.

significant ground rupture is generally expected to occur

along pre-existing fault breaks. Ground rupture cannot be

prevented; therefore, mitigation of the ground rupture hazard

involves identifying major faults and avoiding construction

over their surface trace. Recognition and mapping of these

pre-existing fault breaks is accomplished by excavating a

suitable trench, and geologically inspecting the trench walls

with an emphasis on identifying faults and fault-related features.

Extensive geologic investigations have been carried out by

this firm within the local bedrock exposures to the northwest

and southeast of vesting Tentative Tract 44832. These studies

have have resulted in the definition of concentrated "main"

zone of deformation for the San Gabriel Fault; however lack

of bedrock exposures makes it very difficult to locate this

Zone with a high degree of accuracy in the immediate vicinity

of the Vesting Tentative Tract 44832,



Job No.: 8-1025-4 Page 8

In the interests of providing a reasonable level of safety

regarding ground rupture hazard on Vesting Tentative Tract

44832 the main zone of deformation was projected between the

nearest known bedrock exposures, and the southwestern boundary

of the project was located to the north of this projected zone

(See Geologic Map). The Alquist-Priolo Special Studies Zone

Boundary extends beyond this main zone of deformation and

approximately 400 ft. into the site.

In order to evaluate the possibility of recent fault breaks

extending north of the projected boundaries of the main fault

?.one (and hence within the boundaries of the Vesting Tent«tive

Tr«ct 44832), approximately 500 lineal feet of exploratory

trench was excavated in the southwestern portion of the subject

site perpendicular to the projected trace of the San Gabriel

Fault zone. No evidence of fault rupture or seismicity-related

ground failure (liquefaction features) were recognized within the

Recent Alluvium exposed in this exploratory trench (See Geologic

Trench Log No. 1).

Ground Failure

The project Geotechnical Engineer, R.T. Frankian & Associates,

has evaluated Vesting Tentative Tract 44832 relative to the

potential for liquefaction. A complete discussion concerning

liquefaction is included in their report dated July 27, 1987.



Ground Shaking

General

Job No,: 8-1025-4 Page 9

The current state-of-the-art for earthquake resistant design

related to the shaking phenomena is based upon empirical

correlations. These correlations are based upon statistical

analysis of available data from past earthquakes; however, in

many cases the statistical distributions are not well-defined,

and the upper bounds are interpreted projections.

According to Hay (1980), the seismic empirical relations most

frequently used are the following;

1. Earthquake recurrence

2. Magnitude and Modified Mercalli intensity

3, Peak ground acceleration and Modified Mercalli intensity

4. Magnitude and length of fault rupture

5. Peak acceleration, distance, and magnitude

6. Modified Mercalli intensity and distance

7. Duration of shaking and magnitude

8, Peak velocity and distance

9. Site-independent response spectra

10. Site-dependent response spectra.

In our current evaluation, we have utilized the published data

relating rupture length to magnitude and then correlated magnitude

to probable horizontal peak bedrock acceleration.


Valencia Company Muy 16, 1988

Faults

Job No.: 8-1025-4 Page 10

Based upon our review of published literature, the following

active faults could have an impact on the subject site:

1. San Andreas Fault

2. San Fernando/Santa Susana/Sierra Madre Pault Zone

3. San Gubriel Fault.

The maximum credible earthquake is defined as "the maximum

earthquake that appears capable of occurring under the presently

known tectonic framework. It is a rational and believable event

that is in accord with all known geologic and seismologic facts"

(CDMG, 1975).

The values for maximum credible earthquakes for the San Andreas

and San Fernando/Santa Susana/Sierra Madre Fault Zone included

in this report are based upon data published by the USGS. On

the San Gabriel Fault, a maximum length of potential surface

rupture is assumed to be 31 miles. This is based upon the

truncation of the San Gabriel fault plane by the 1971 San

Fernando Earthquake to the southeast and basement complex

north of Violin Canyon to the northwest. Based upon this 31

mile length, the projected maximum credible earthquake that

the San Gabriel Fault could generate would be 6.6M. This is

based upon Bonilla and Buchanan's world-wide data for strike-slip

faults and Schlemrnon's North American data on all types of faults.



Peak Bedrock Acceleration

Job No.: 8-1025-4 Page 11

Table III summarizes our interpretation of the horizontal peak

bedrock accelerations that could be anticipated as determined

using the maximum probable earthquakes along faults likely to

effect the subject site. The maximum probable earthquake is

defined as the largest earthquake which is likely to occur

during a 100-year interval (CDMG - 1975).

Of the three faults named above, the southern San Andre<is

Fault is considered to pose the greatest threat to the subject

site for two reasons:

1. The probability of movement along this fault is considered to be much higher than that of movement along the other faults.

2. The ground motions expected to be generated during a maX.imum probable event along the southern San Andreas Fault far exceed those expected during maximum probable events along other local Southern California faults.

A maximum probable magnitude is not given for the San Gabriel

Fault. A seismic event along the San Gabriel Fault is not

considered likely in the next 100 years.

Repeatable High Ground Accelerations

Many studies have indicated that a single peak acceleration of

a seismic event is not indicative of the associated ground

motion; therefore, the peak acceleration is of little value in

structural design, Studies by Ploessel (1974) indicate that

the Repeatable High Ground Acceleration (RHGA) will more closely

approximate a "design acceleration" than a maximum peak

acceleration. The Repeatable High Ground acceleration is

calculated as 65% of the peak bedrock acceleration.



Job No.: 8-1025-4 Page 12

In summary, the site is subject to shaking and associated

ground motions from earthquakes on nearby and distant faults.

This is characteristic of all Southern California.

Neither the Time, Location, or Magnitude of an earthquake can

be accurately predicted at this time.



LIMITATIONS

Job No.: 8-1025-4 Page 13

This report has been prepared for the exclusive use of Valencia

Company and their design consultants for the specific site

discussed herein. This report should not be considered

transferable. Prior to use by others. we should be notified,

as additional work may be required to update this report.

In the event that any modifications in the design or location

of the proposed development, as discussed herein, a,re planned,

the conclusions and recommendations contained in this report

will require a written review with respect to the planned

modifications.

This study was conducted according to generally accepted

engineering geologic practice for studies of this magnitude.

Our conclusions and recommendations are based upon the data

available and our interpretation of that data based upon

experience and background. Hence, our conclusions and

recommendations are professional opinions and are not meant

to be a control of nature; therefore, no warranty is herein

expressed or implied.

It should be noted that faulting is normally confined to the

area immediately adjacent to a known fault, or within a few

feet of the last fault movement. Regardless of what criteria

are used however, absolute assurance against future fault

displacement cannot be obtained in tectonically active areas.

New f<ml ts can form as the orientation and magnitude of

deformational forces in the earth's crust chang<;l with time.

This report should not be duplicated without the writt"'n consent

of this firm.

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Conclusions and Recommendations

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ALLAN E.' SEWARD ENGINEERING GEOLOGY



CONCLUSIONS AND RECOMMENDATIONS

Job No.: 8-1025-4 Page 14

1. In compliance with Section 309 of the County Code, it is

the finding of this firm that the proposed grading and

proposed lot on Vesting Tentative Tract 44832 will be

safe from geologic hazard, and will not adversely affect

adjacent property, provided our recommendations are

incorporated in the Grading Plan and implemented during

construction.

2. The current and past ground water conditions in the immediate

vicinity of Vesting Tentative Tract 44832 are summarized

in Table I and Table II.

3. No historically active earthquake faults traverse Vesting

Tentative Tract 44832, The active San Gabriel Fault

projects immediately outside the southwestern boundary of

the property.

4. Table III summarizes the geo-seismic parameters of the

three active faults that could potentially affect the

subject site.

5. All fills will be placed under the observation of the

project Geotechnical Engineer, R,T. Frankian & Associates.

6. Excavation of the on-site materials may be performed

using conventional grading equipment, Heavy ripping will

not be required,

7. The potential for liquefaction within the alluvial materials

is being evaluated by the project Geotechnical Engineer.



Job No.: Page 15

8-1025-4

8. Water should not be allowed to stand or pond on the graded

pads, but should be collected and channelled to the future

streets.

9. It is our understanding that sewage disposal will be by

public sewers.

10. All constructed slopes should be planted as soon as practical

following their construction,

11. The location and dimensions of our exploratory backhoe

trench (Sec Geologic Map) should be noted relative to

future building plans. If this exploratory excavation is

not removed by future grading operations, then any

foundations which may traverse it should be evaluated by

the project Geotechnical Engineer.

12. It is recommended that the owner of the subject property

review the findings of this report with adjacent property

owners so that any impact arising from the proposed

construction can be evaluated.

13. We should review and geologically approve the grading

plans prior to submittal to Los Angeles County.

14. Future grading within the boundary of the Alquist-Priolo

Special Studies Zone should be conducted under continuous

geologic inspection.



Job No.: 8-1025-4 Page 16

This opportunity to be of service is appreciated. If you have

any questions concerning this report, please give us a call.

Respectfully submitted

Allan E. Seward Certified Engineering Geologist 246

Christoper J, Sexton Project Geologist

Enclosures: Geologic Map (In Pocket)

Geologic Trench Log No, 1 {In Pocket)

Location Map

APPENDIX

Water Well Location Map

Water Table Data {Los Angeles Flood Control District) - Table I

Water Table Data (Valencia Water Company) - Table II

Geoseismic Parameters - Table III

References

Distribution: (2) Valenc;ia Company Attention: Mr. Mark Subbotin

(2) L.A. County - Dept. of Public Works Geology Group Attention: Mr. Bob Sousa

(1) L.A. County - Dept. of Public Works Valencia Regional Off ice Attention: Mr, Dick Brundige

(1) Sikand Engineering Associates Attention: Mr. Ron Horn

(2) R.T. Frankian & Associates Attention: Mr, R.T. Frankian

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Appendix

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WATER· WELL LOCATION MAP

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I TO$ /1 /.

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ol Nj

• 7057C

8-1025-4

SCALE 1"=2000'

RECENT ALLUVIUM

QUATERNARY TERRACE DEPOS 1 TS

SAUGUS fORMATJON

GEOLOGic CONTACT

WATER WELL LOCATION (WELL MONITOREP BY VALENCIA

WATER COMPANY)

WATER WELL LOCATION (WELL MONITOREU·B~ Los ANGELES

COUNTY ~LOOD CONTROL DISTRICT)

DATE: May 16, 1988 OflAIJ'JN SY: CJS :A=. v ISE D:

I Valencia Company Job No.: 8-1025-4

I May 16, 1988

I TABLE I

I WATER TABLE DATA

I Wells Monitored by

I Los Angeles Flood Control District

Historic High Historic Low Feb.

I Well No. Elev. Elev. Date Elev. Date 1971 Recent

I 7026 D 1090 1084

I 11/28/83 986 09/25/65 1076 1080

7027 A 1097 1050 11/15/68 948 02/24/64 1050

I 7036 1104 1088 04/19/79 1047 07/10/68 1085

I 7037 c 1117 1099 10/30/85 1024 09/07/65 1091 1099

I 7038 B 1138 1112 11/23/83 1003 08/25/65 1102 1111

I 7077 B 1179 1166 04/28/81 1062 08/25/66 1102 1158

I 7067 D 1157 1148 04/1/7 0 1046 08/25/65 1146 1140

I I I I I

11 I I I I I I I I I I I I I I I I I I


well No.

Q

N

S-2

TABLE ll

WATER TABLE DATA

wells Monitored by Valencia water Company

Job No.; 8-1025-4

Recent water Surf ace Elev.

1155

1130

1118

Elev. Date

1133

1109

1099

6/87

4/87

3/99

I

:1

I 'I

•• I I I I I I I I

TABLE I I I !

GEO - SE IS!1I C PAR~.METERS Vesting Tentative Tract 44832 .

Valencia, California

.·

I PEAK BEDROCK ACCELERATION AT

DISTANCES .ESTIMATED MAXIMUM EARTHQUAKES; SUBJECT SITE*** TO .

F.'IULT MAXIMUM HISTORICAL Max. Credible Max. Probable' Max. Max. CLASSIFICATION FAULT (km) EARTHQUAKE MAGNITUDE Magnitude .. Magnitude Credible Probable

i .

'• ! I .

Active San Andreas 31* 8.o± 0.5 {1875) 8.25 8.25 0.62+ 0.62+ ..

.

I I

' Active San Fernando, 12* 6.4 ( 19 71) 7.7 6.4 0.6 0.4

.Santa Suzanna, :

Sierra Madre Fault Zone

Active San Gabriel 15** --- 6.6 --- 0. 5 ---

+ Mean plus 2 Standard Deviations !

* CDMG Prel. Report 13 (1973) - Distance is to the closest Epicenter of Energy Release

** Distance to Estimated Focus ALLAN E. SEWARD *** Can be modified by structural design of structures ENGINEERING GFOLOGY

and/or thickness of surficial alluvial sediments JOB NUM8ER! 8-1025-4

. I DATE: 5/16/88

DRAWN BY: .

SCALE: RE VlS:ED: .

.



REFERENCES

Job No.: 8-1025-4

Bonilla, M.G., (1982), Evaluation of Potential ing and Other Teceonic Deformation:

Surface FaultUSGS Open File

Report 82-732.

Boore, David M.. et al. (1978), Estimation of Ground Parameters: USGS Circular 795.

California Division of Mines and Geology (1973), Guidelines To Geologic and Seismic Reports: CDMG Notes 37.

California Division of Mines and Geology (1975), Recommended Guidelines for Determining the Maximum Credible and the Maxi.mum Probable Earthquakes: CDMG Notes 43.

California Division for Evaluating CDMG Note 49.

of Mines and Geology (1975), Guidelines the Hazard of Surface Fault Rupture:

Cotton, W.R., and Seward, A.E., (1984), Engineering Geologic Investigation of the San Gabriel Fault: Prepared for The Newhall Land ,md Farming Company, on file with the Los Angeles County Department of Public Works, Geology Group, under PM 12009.

Greensfelder, R.W,, (1974), Maximum Credible Rock Acceleration From Earthquakes in California: CDMG Map Sheet 23,

Hart, E.W., (1985), Fault CDMG Spec, Pub. 42,

Rupture Zones in California:

Hays, Walter w., (1980), Procedures for Estimating Earthquake Ground Motions: USGS Prof. Paper 1114.

Plocssel, Mr. Ground Geology,

R., and Slosson, J.E., (1974), Repeatable High Accelerations from Earthquakes: California Vol. 27, No. 9, pp. 195-199.

Sieh, Kerry (1978), Andreas Fault:

Earthquake Recurrence CDMG California Geology.

Intervals, San

Slemmons, David B., (1977), State-of-the-Art for Assessinq Earthguake Hazards in the United States: U.S. Army Office, Chief Engineer, Misc. Paper S-73-1, Report No. 6


V<ilencia Company May 16, 1988

Slemmons, David B., (1981), E<irthguake Microzonation: University of Nevada, U.S. 1981 (Preliminary Draft).

Geologic Mackay - China

Job No.: 8-1025-4

Considerations for School of Mines, Workshop, January,

Stitt, Leonard T., and Yeats, Robert S. (1983), Geology Seismic Hazard, and Ground Rupture Hazard of the S<in Gabriel and Holser Faults, Eastern Ventura and Western Soledad Basins, California, Final Technical Report: USGS Contract Number 14-08-001-19138.

U.S. Geological Survey (1981), Scenarios of Possible Earthquakes Affecting Major California Population Centers, with Estimates of Intensity and Ground Shaking: USGS Open File Report 81-115,

Wallace, R.E., (1970), Earthquake Recurrence Intervals on The San Andreas Fault: GSA Bulletin Vol. 81, 2875-2890,

Yerkes, R,F,, and Lee, W.H.K,, Earthquake Activity and Quaternary Deformation of the Western Transverse Ranges, California.: USGS Circular 7 99-A, B.

engineering geology, inc. - california€¦ · 16/05/1988 · engineering geology, inc....

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