mtgl somerville geohazards ltr.pdf - centinela valley union high

Geotechnical Engineering Construction Inspection

Materials Testing Environmental

OFFICE LOCATIONS

ORANGE COUNTY

CORPORATE BRANCH

2992 E. La Palma Avenue

Suite A

Anaheim, CA 92806

Tel: 714.632.2999

Fax: 714.632.2974

SAN DIEGO

IMPERIAL COUNTY

6295 Ferris Square

Suite C

San Diego, CA 92121

Tel: 858.537.3999

Fax: 858.537.3990

INLAND EMPIRE

14467 Meridian Parkway

Building 2A

Riverside, CA 92518

Tel: 951.653.4999

Fax: 951.653.4666

INDIO

44917 Golf Center Pkwy

Suite 1

Indio, CA 92201

Tel: 760.342.4677

Fax: 760.342.4525

OC/LA/INLAND EMPIRE

DISPATCH

800.491.2990

SAN DIEGO DISPATCH

888.844.5060

www.mtglinc.com

April 5, 2012

MTGL Project No. 7052A23

MTGL Log No. 12-443

Centinela Valley Union High School District

14901 S. Inglewood Avenue

Lawndale, CA 90260

Attention: Ms. Preeti D'Souza, Assistant Project Manager

Subject: PRELIMINARY GEOLOGIC HAZARD ASSESSMENT REPORT

Somerville Strip Acquisition - Lawndale High School

14901 S. Inglewood Avenue, Lawndale, CA 90260

Dear Ms. D’Souza:

In accordance with your request and authorization, MTGL, Inc. has completed a

Preliminary Geologic Hazard Assessment for the subject site. We understand that the

school district will use the information presented herein to evaluate the feasibility of

acquiring the subject property. The following report presents a summary of our

preliminary findings and conclusions based on a limited reconnaissance investigation

that includes information obtained from our past subsurface geotechnical investigations

conducted at Lawndale High School.

The scope of our services included review of readily available geologic, seismic, ground

water and geotechnical published literature and preparation of this report summarizing

our findings and presenting our conclusions regarding on geologic hazards for the

subject property. Many of the requirements of 5 CCR § 14010 and § 14011 cannot be addressed at this time and is beyond the scope of this assessment. A site specific geotechnical

investigation consisting of drilling the site to obtain subsurface soil samples for laboratory

analysis will be required. Based on our scope of work for a preliminary geologic hazard

assessment, our findings are as follows:

Code Description Remarks

5 CCR § 14010(f) Pursuant to Education Code Section

17212 and 17212.5, the site shall not

contain an active earthquake fault or

fault trace

The site does not contain an

active earthquake fault or fault

trace

5 CCR § 14010(i) The site is not subject to moderate to

high liquefaction or landslides The seismic hazard evaluation

of the Inglewood quadrangle

(CDMG, 1999) indicates the

site area is not within a zone

of liquefaction.

Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23

Lawndale, California MTGL Log No. 11-443

Code Description Remarks

5 CCR § 14011 (g)(1)

Comply with Ed. Code §§ 17212

and 17212.5, with particular

emphasis upon an engineering

investigation made of the site

to preclude locating the school

on terrain that may be

potentially hazardous.

A site specific subsurface geotechnical

investigation consisting of a field exploration

(drilling) and laboratory analysis of the soil

samples will be required to specifically address

these items. This investigation should be

conducted once the property is acquired and

comply with Ed. Code §§ 17212 and 17212.5.

Our general finding based on our research is

presented in the accompanying report.

5 CCR § 14011 (g)(1)(A)

Nature of the site including a

discussion of liquefaction,

subsidence or expansive soils,

slope stability, dam or flood

inundation and street flooding

Based on our research and review of available

maps and data, the potential for liquefaction is

low. Expansive soils will most likely be

encountered in the near surface soil profile.

Topographically, the site is essentially planar,

thus slope stability is not expected to be a

factor. The site is designated as FEMA Zone X,

and is considered a minimal flooding hazard

located outside the 500-year flood level. The

potential for street flooding will need to be

determined by the design civil engineer.

Our general findings are based on a review of

available maps and data. Actual conditions of

the specific site relative to the requirements of 5

CCR § 14011 (g)(1)(A) will require a site

specific subsurface geotechnical investigation

consisting of a field exploration (drilling) and

laboratory analysis of the soil samples.

5 CCR § 14011 (g)(1)(B)

Whether the site is located within

a special study zone as defined in

Ed. Code § 17212

The site is not located within a special study

zone as defined by Ed. Code § 17212.

5 CCR § 14011 (g)(1)(C)

Potential for earthquake or other

geologic hazard damage

The potential for earthquake or other geologic

hazard damage must be evaluated by a site

specific geotechnical investigation.

5 CCR § 14011 (g)(1)(D)

Whether the site is situated on or

near a pressure ridge, geological

fault or fault trace that may

rupture during the life of the

school building and the student

risk factor

Generally, based on our research, the site is not

situated on or near a pressure ridge, geologic

fault or fault trace.



SITE DESCRIPTION

The subject site is located adjacent to the northeastern portion of the existing campus at Lawndale

High School in the city of Lawndale, California. The property, known as the Somerville Strip is

approximately 25 feet wide and 417 feet long oriented in an east-west direction. The property is

undeveloped and is currently covered with grasses. The property abuts a warehouse and asphalt

parking lot used for storage of large delivery trucks. The approximate location of the property is

illustrated on the accompanying Site Location Map (Figure 1).

Topographically, the location of the subject property is essentially planar and elevations are

essential coincident with the adjacent high school access driveway, on the order of 65 to 67 feet

above mean sea level.

LOCAL AND REGIONAL GEOLOGIC CONDITIONS

The site lies within the Los Angeles Basin within a low lying coastal plain area located between the

Transverse Ranges to the north and the Peninsular Ranges to the south. Generally, the Los Angeles

basin is included within the Peninsular Ranges geomorphic province. The site is approximately 3

miles inland from the shore of the Pacific Ocean at an elevation of approximately 66 feet MSL.

According to Norris and Web, the site is located within the Southwestern block of the Los Angeles

Basin. The Southwestern Block is the westernmost part of the Los Angeles basin and is bounded

on the east by the Newport-Inglewood fault zone. This easterly boundary is characterized by a

series of low-lying hills created through a combination of faulting and folding. The northern

boundary is the Santa Monica fault zone and the western and southern boundaries are the Pacific

Ocean. This portion of the basin contains up to 14,000 feet of sediments overlying rock belonging

to the Franciscan Formation of late Jurassic or late Cretaceous age.

In General, the Peninsular Ranges geomorphic province is composed of an elongated series of

mountainous ridges and peaks rising in places to altitudes of more than 10,800 feet above sea level.

The province extends southwestward about 900 miles from the Transverse Ranges and the Los

Angeles basin to the tip of Baja California. The largest part of the Peninsular Ranges province, the

continental borderland, is submerged beneath the Pacific Ocean. The exposed part of the province

varies between 30 and 100 miles wide. This province been uplifted, tilted seaward, and sliced

longitudinally into subparallel blocks by young steeply dipping northwest-trending fault zones.

The dominant controlling structure of the Peninsular Ranges geomorphic province is faulting.

Major onshore faults include the San Jacinto and Elsinore and offshore faults include the Newport-

Inglewood and the Coronado Bank. These faults exhibit generally right lateral and dip-slip

movement and the major faults are steeply dipping.

FAULTING AND SEISMICITY

Faults are one of the most widespread geologic hazards to development in California. Faults of

most concern are those designated as active, which have shown surface displacement with the last

approximately 11,000 years and potentially active, which have shown surface displacement within



the last approximately 1.6 million years. The site is within 25 miles of number of other active and

potentially active faults in the seismically active southern California region; therefore, the potential

for future strong ground shaking at the site is high. The site and site region will likely experience

future earthquakes of moderate to large size. Some of the near-future earthquakes on nearby (less

than about 50 miles) active faults may be greater than Richter magnitude 8.0. The site is not

located within the Alquist-Priolo Earthquake Fault Zone. A brief discussion of the closest and most

significant faults and fault zones within the site vicinity is given below.

The site is centrally located within a diffuse fault zone area called the Compton thrust. The

Compton thrust extends from Santa Monica on the northwest approximately 25 miles south along

the western margin of the Los Angeles Basin into southern Orange County. The Compton thrust is

part of a larger complex fault system that includes detachment and ramp structures underlying the

Elysian Park and Palos Verdes hills. This fault zone is expected to be capable of generating a 6.8

magnitude earthquake and is believed to have generated multiple earthquakes between magnitudes

7.0 –7.4 within the last 14,000 years (Leon, L.A. in Journal of Geophysical Research, Vol. 114,

B12305, 14 PP., 2009).

Newport-Inglewood-Rose Canyon (north Los Angeles basin section) fault zone is located

approximately 3.7 miles southwest of the site. The fault zone is composed of a northwest trending

line of en-echelon faults extending from the Los Angeles basin to San Diego. This fault, located

both on and off shore has been active in Holocene time. The most recent movement identified has

been in the Huntington Mesa area within the last 11,700 years.

The Palos Verdes Fault zone (San Pedro Shelf section) is located approximately 6.0 miles

southwest of the site. This fault is believed to be a northerly extension of the Coronado Bank fault

zone and generally exhibits high angle right-lateral and reverse movement. Expected magnitude is

in the 6 to 7 range. Studies have shown that this fault has been active in late Holocene (less that

8,000 years).

Numerous additional faults are present within the Los Angeles basin and with 25 miles of the site

and it is reasonable to assume that the site will be subjected to future severe seismic ground shaking

from movement along one of the faults listed above or from any number of nearby faults. There are

no mapped faults within the boundaries of the subject property.

LIQUEFACTION POTENTIAL

Liquefaction is a phenomenon where earthquake induced ground vibrations increase the pore

pressure in saturated, granular soils until it is equal to the confining, overburden pressure. When

this occurs, the soil can completely loose its shear strength and enter a liquefied state. The

possibility of liquefaction is dependent upon grain size, relative density, confining pressure,

saturation of the soils, and strength of the ground motion and duration of ground shaking. In order

for liquefaction to occur three criteria must be met: underlying loose, coarse-grained (sandy) soils, a

groundwater depth of less than about 50 feet and a nearby large magnitude earthquake.

The seismic hazard evaluation of the Inglewood quadrangle (CDMG, 1999) indicates the site area is

not within a zone of liquefaction. Based on previous analyses performed for Lawndale High



School based on subsurface exploration, sampling and material testing, the potential for

liquefaction is anticipated to be very low.

LAND SUBSIDENCE

Subsidence of the ground surface is a phenomenon generally associated with deep alluvial basins

like the Los Angeles Basin that can occur when significant amounts of groundwater or petroleum

oil and gas are removed over long time periods. Based on historic and recent groundwater levels at

the subject site, the potential for significant land subsidence occurring at the site is low. Similarly,

given the relatively small amount of oil currently being removed from the Lawndale Oilfied, the

potential for significant land subsidence occurring at the site is low.

SURFACE AND GROUNDWATER CONDITIONS

There are no impoundments of surface water observed on or adjacent to the subject site or with the

immediate site area. According to the California Division of Mines and Geology (1998), historic

high groundwater levels in the immediate site vicinity are shown to be in approximately 40 feet

below surface elevations. Previous investigations performed at Lawndale High School in 2011 and

2012 encountered perched groundwater conditions at approximately 35 feet below the ground

surface.

FLOODING POTENTIAL

The site is included within the FEMA Zone X, Other Flood Areas. This zone is a designation of a

minimal flooding hazard and located outside the 500-year flood level.

TSUNAMI AND SEICHE HAZARD

The site is not located within an area mapped by the California Geological Survey as subject to

inundation by tsunami. Given the inland location of the site at an elevation of approximately 66

feet MSL, within a densely developed area, the inundation hazard posed by tsunami is considered to

be low. Seiches are not considered to be a hazard due to the absence of above-ground tanks or

reservoirs located immediately up gradient from the site.

DAM INUNDATION HAZARD

No dams or reservoirs are located within the immediate site vicinity. The two closest reservoirs to

the site are the Upper Hollywood Reservoir located 15.9 miles north of the site and the Whittier

Narrows Dam located 18.2 miles northeast of the site. Numerous other dams and reservoirs are

located north and northeast of the site within the surrounding foothills and mountains generally

between 25 to 35 miles from the site.

Review of a Dam Inundation Map prepared by Los Angeles County Department of Regional

Planning (see references) shows the school site is located outside of potential dam inundation areas.



LANDSLIDES

The site is not located in a hillside area where earthquake induced landslides would cause

permanent ground displacements. No reported occurrences of landslides or debris flows are known

to have affected the site. Therefore, the potential for landslides and mudflows is considered to be

very low at the site.

ASBESTOS, RADON AND OIL FIELDS

The site or local region does not contain naturally occurring serpentine rock which is directly

associated with the presence of asbestos fibers, therefore the potential for exposure to asbestos at

the site is considered very low.

The county of Los Angeles has on overall rating of Moderate Potential for naturally occurring

Radon gas according to the EPA. Radon testing was performed by the Department of Health

Services within the subject property zip code of 90260. Four locations were tested within the zip

code and no Radon gas levels were above the action level of 4 pCi/l, therefore the potential for

exposure to naturally occurring Radon gas at the site is low.

The site is located adjacent to the Lawndale Oil Field. According to the Division of Oil, Gas and

Geothermal Resources’ online mapping system, there are approximately six actively producing oil

wells within approximately 0.45 miles north-northeast of the subject property. Numerous

abandoned and plugged wells are located north and easterly adjacent to the site. No oil wells are

located on the subject property and the potential for exposure to naturally occurring hydrocarbons at

the site is considered low.

HIGH PRESSURE PIPELINES

The Southern California Gas Company operates and maintains two high-pressure gas transmission

lines within the site vicinity. The closest gas transmission line is located under Rosecrans Avenue,

approximately 1,730 feet to the north. A second gas transmission line is located under Hawthorne

Boulevard, approximately 3070 feet to the east of the site. The Southern California Gas Company

is currently is currently implementing its Pipeline Safety Enhancement Program to improve pipeline

maintenance and overall safety.

CONCLUSIONS

Based on our review of the published literature, it is our opinion that there are no known geologic

hazards that would preclude the safe development of the site for use as expansion of the existing

high school. Due to proximity of the site to regional active and potentially active faults, the site

will most likely experience moderate to high levels of ground shaking from future regional seismic

events within the projected life of any proposed improvements. A site-specific geotechnical

investigation will need to be performed in order to make specific recommendations for future

foundation design and mitigation of any soil or geologic hazards at the site.



LIMITATIONS

The findings, conclusions, and recommendations contained in this report are based published data

and on observed site conditions. No subsurface exploration, materials sampling or laboratory

testing were performed.

This report was prepared for the exclusive use and benefit of the owner, architect, and engineer for

evaluating the design of the facilities as it relates to geotechnical aspects. It should be made

available to prospective contractors for information on factual data only, and not as a warranty of

subsurface conditions included in this report.

Our investigation was performed using the standard of care and level of skill ordinarily exercised

under similar circumstances by reputable soil engineers and geologists currently practicing in this or

similar localities. No other warranty, express or implied, is made as to the conclusions and

professional advice included in this report.

We appreciate this opportunity to be of continued service and look forward to providing additional

consulting services during the planning and construction of the project. Should you have any

questions regarding this report, please do not hesitate to contact us at your convenience.

Respectfully submitted,

MTGL, Inc.

Michel Vasconcellos, CEG 2411 Isaac B. Chun, GE 2649

Engineering Geologist Vice President | Engineering Manger

Attachments: Site Location Map Figure 1

Regional Geologic Map Figure 2

Seismic Hazards Fault Map Figure 3

Seismic Hazards Zone Map Figure 4



REFERENCES

California Department of Health Services, Radon Data Base for California, October 2002.

California Division of Oil, as and Geothermal Online Mapping System.

California Division of Mines and Geology, 1997, Fault-Rupture Hazard Zones in California,

Special Publication 42.

California Division of Mines and Geology, 1998 Seismic Hazard Zone Report for the Inglewood

7.5-Minute Quadrangle, Los Angeles County, California.

California Geological Survey, 2008, Guidelines for Evaluating and Mitigating Seismic Hazards in

California, Special Publication 117.

Churchill, R.K. and Hill, R.L., 2000, A General Location Guide for Ultramafic Rocks in California

– Areas More Likely to Contain Naturally Occurring Asbestos: California Division of Mines and

Geology OFR 2000-19 (ftp://ftp.consrv.ca.gov/pub/ dmg/pubs/ofr/ofr_2000-019.pdf).

Federal Emergency Management Agency, September 26, 2008, Flood Insurance Rate Map, Los

Angeles County, Panel 1790 of 2350, FEMA Map 06037C1790F.

Jahns, R.H., 1954, Geology of Southern California: CDMG Bulletin 170, Guidebook No. 3.

Jennings, C. W., Geologic Map of California, Long Beach Sheet, 1962.

Miller, C.A., 1989, Potential Hazards from Future Volcanic Eruptions in California: United States

Geological Survey Bulletin 1847.

Treiman, J.A., and Lundberg, M.Matthew, compilers, 1999, Fault number 127a, Newport-

Inglewood-Rose Canyon fault zone, north Los Angeles Basin section, in Quaternary fault and fold

database of the United States: U.S. Geological Survey website,

http://earthquakes.usgs.gov/regional/qfaults.

Treiman, J.Jerome, compiler, 1998, Fault number 130, Redondo Canyon fault, in Quaternary fault

and fold database of the United States: U.S. Geological Survey website,

http://earthquakes.usgs.gov/regional/qfaults.

Treiman, J.Jerome, and Lundberg, M.Matthew, compilers, 1998, Fault number 128c, Palos Verdes

fault zone, San Pedro Shelf section, in Quaternary fault and fold database of the United States: U.S.

Geological Survey website, http://earthquakes.usgs.gov/regional/qfaults.

U.S. Geological Survey, Earthquakes Hazard Program/Quaternary Fault and Fold Database,

http://gldims.cr.usgs.gov/qfault/viewer.htm



Yerkes, R.F., McCulloh, T.H., Schoellhamer, J.E., and Vedder, J.G., 1965, Geology of the Los

Angeles Basin California - An Introduction, US Geological Survey Professional Paper 420-A.

FIGURES



Figure 1

SITE LOCATION MAP Not to Scale

Base Map: Google Earth

SITE



Figure 2

REGIONAL GEOLOGIC MAP Scale: As Shown

Source: California Division of Mines and Geology, Seismic Hazard Zone Report for Inglewood, 7.5 Minute Quadrangle,

1999.

Description of Units in Immediate Site Vicinity:

Qva/Qyf – Younger Alluvium

Qoa – Older Alluvium

Qoe – Older Eolian Deposits

SITE



Figure 3

SEISMIC HAZARDS FAULT MAP Scale: As Shown

Source: California Division of Mines and Geology, Special Studies Zone for Inglewood, 7.5 Minute

Quadrangle, 1999.

SITE

Seismic Special Studies Zone



Figure 4

Source: California Division of Mines and Geology, Seismic Hazards Zone for Inglewood, 7.5 Minute

Quadrangle, 1999.

SEISMIC HAZARDS ZONE MAP Scale: As Shown

SITE

mtgl somerville geohazards ltr.pdf - centinela valley union high

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