MTGL Somerville Geohazards Ltr.pdf - Centinela Valley Union High
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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
Page 2
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.
Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23
Lawndale, California MTGL Log No. 11-443
Page 3
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
Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23
Lawndale, California MTGL Log No. 11-443
Page 4
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
Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23
Lawndale, California MTGL Log No. 11-443
Page 5
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.
Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23
Lawndale, California MTGL Log No. 11-443
Page 6
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.
Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23
Lawndale, California MTGL Log No. 11-443
Page 7
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
Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23
Lawndale, California MTGL Log No. 11-443
Page 8
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
Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23
Lawndale, California MTGL Log No. 11-443
Page 9
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.
Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23
Lawndale, California MTGL Log No. 11-443
Figure 1
SITE LOCATION MAP Not to Scale
Base Map: Google Earth
SITE
Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23
Lawndale, California MTGL Log No. 11-443
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
Lawndale H.S. – Somerville Strip Acquisition MTGL Project No. 7052A23
Lawndale, California MTGL Log No. 11-443
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
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