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24USGS
science for a changing world
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Tracking Contaminants in Santa Monica Bay,
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Offshore of Greater Los Angeles
Santa Monica Bay is a major
recreational and commercial
resource for the Greater Los
Angeles region. Industrializa-
tion and the dramatic increase
of population in the region
over the past 100 years have
strained the bay's resources
and polluted its sediments.
To help evaluate any possible
hazards posed by contamina-
tion, scientists from the U.S.
Geological Survey (USGS) and
local cooperating organiza-
tions are studying the process-
es that modify, transport, and
redeposit sediments within
Santa Monica Bay.
Santa Monica Bay, offshore of Greater Los
Angeles, provides crucial habitat for a rich web
of marine life and supports important com-
mercial and recreational fisheries. The bay and
its beaches attract residents and visitors alike.
More than 45 million people visit the bay's
beaches each year, helping to support a region-
al tourism industry of $10 billion annually.
In the late 1980's, several sewage spills en-
tered Santa Monica Bay, forcing popular beach-
es to be closed. These closures, along with con-
cern over water quality, kept people away from
beaches, even during unseasonably hot weather,
resulting in serious economic losses for beach-
front businesses. Much has since been done
by the city of Los Angeles to reduce spills and
improve overall sewage treatment, but water
quality in the bay is still a concern.
More than 10 million people now live in the
Greater Los Angeles metropolitan area, a dra-
matic increase from 100,000 in 1900. Rapid
population growth, industrialization, and their
consequences, especially the increased need
for waste disposal, have strained the resources
of Santa Monica Bay. As the region grew, in-
U.S. Department of the Interior
U.S. Geological Survey
SUD0CS,
The Los Angeles metropolitan area is the second largest in the United States, with more than 10 million resi-
dents. Pollution that results from this urbanization is straining the resources of Santa Monica Bay, shown here.
(Photo courtesy of Kevin Snavely, City of Los Angeles Bureau of Sanitation.)
dustrial, agricultural, and household contami-
nants increasingly flowed or were washed into
the bay. Many of these pollutants are known
to pose health hazards for people and for fish
and other wildlife. Some of the contaminants
of greatest concern are DDT (dichlorodiphe-
nyltrichloroethane, a pesticide banned in the
United States in 1972 because of its high tox-
icity to fish and reproductive hazard to birds),
PCB's (polychlorinated biphenyls, toxic com-
pounds widely used as insulation in electrical
transformers until the 1970's), toxic metals
(such as lead from industrial applications, fuel
combustion, and tire and brake wear), and
PAH's (polycyclic aromatic hydrocarbons,
chemicals resulting from fuel combustion, oil
spills, or natural oil seeps).
Much work has been done in Santa Moni-
ca Bay to monitor and determine the present
distribution of contaminants. However, in
order to effectively manage the bay in the
future, it is important to also understand
historical sources and sites of contamination
and the processes that modify and redistrib-
ute contaminated sediments within the bay.
To achieve this goal, the U.S. Geological
Survey (USGS), in cooperation with the
Southern California Coastal Water Research
Project (SCCWRP) and the City of Los An-
geles Bureau of Sanitation, is conducting a
detailed study in Santa Monica Bay.
Part of this study has shown that discharge
from creeks draining highly developed areas
of Greater Los Angeles, such as Ballona
Creek, is affecting water quality in Santa
Monica Bay. Pesticides, fertilizers, oil and
gas residue from automobiles, litter, and pet
waste are washed off by rainwater, untreated,
into storm drains and creeks that flow into
the bay. Although the city of Los Angeles is
increasingly diverting storm-water discharge
to the region’s Hyperion Treatment Plant,
much untreated wastewater from storm
drains still reaches the bay.
Because contaminants bind with sediment,
historical contamination in Santa Monica Bay
can be studied by taking cores of the upper few
feet of sea-bottom sediment. Research cruises
in 1997, 1998, and 1999 collected sediment
cores in the bay. [continued on back page]
USGS Fact Sheet 155-02
2003







shaded belief Map of Santa Monica Bay |
- - º -
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- -
Types of instruments armºnºsmºs
Buoy with
light
Temperature
and salinity
|- Sensors,
spaced
5 meters |-
(16 feet) apart ||
Camerato photograph
seabed, sediment trap,
and instruments to
2-measure temperature,
º preSSure,
tº currents, and turbidity.
|Current
measurements
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water column
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Los Angeles
Santa "Santa Monica
Monica
Bay
- of map
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This U.S. Geological Survey (USGS) map shows the sea-floorto-
pography (see caption of map below) of Santa Monica Bay. The bay
is located offshore of the Greater Los Angeles metropolitan area. Primary
drainage into the bay is from Malibu Creek, Ballona Creek, the Hyperion Treat-
ment Plant wastewater outfall, and storm drains located along the shore of the bay.
USGS research cruises collected cores of sea-bottom sediment from sites in the bay in Q
1997 (green diamonds), 1998 (red squares), and 1999 ſpurple dots) to study contamination. In- *
strumented moorings (inset) placed at sites in the bay (yellow triangles) collected information about -
temperature, salinity, and current conditions in the water column and near the sea floor, key parameters - Onshore image compiled from USGS
that are being used to study and model sediment and contaminant transport. Landsat 7 and digital elevation data






























Santa "Santa Monica
Monica
Bay
of map
ſ 5 MILES
| I
0 5 KILOMETERS
Backscatter Map of Santa
-
Los Angeles
This high-resolution image of Santa Monica Bay was created
by U.S. Geological Survey scientists using multibeam acoustic
mapping techniques. Multibeam data are collected by sending a sound
signal toward the sea floor and receiving the reflected signal back at the
source. The strength (backscatter) and timing of the reflected signal can then be
used to map the topography and infer the geology of the sea floor. In this image, white
areas represent a strong reflected signal and indicate harder materials such as rock, shell,
and coarse sand. Dark areas indicate softer materials like mud and silt, which are finer grained - - Onshore image compiled from USGS
and more easily transported. Such fine-grained sediments can readily bind with contaminants. Landsat 7 and digital elevation data
-










Reduced Contamination in Santa Monica Bay
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This sea-bottom sediment core (left) was taken by the U.S. Geological Survey in 1997 near the
Hyperion Treatment Plant outfall. Tests were conducted on samples from the upper 48 centimeters
(191nches) of the core, representing more than a century of deposition. Improved results for sea-urchin
fertilization and amphipod survival, implying lowertoxicity, are seen forsamples youngerthan 1985
when efforts were made to improve sewage treatment and reduce pollution entering Santa Monica
Bay. Upward decrease in the bulk density (here derived from gamma-ray "logging" of the core) is ex-
pected from natural compaction, but low density is also associated with the presence of sewage. The
[continued from front page]
Samples from the cores were dated using the
radioactive isotope lead-210 (*"Pb), which
is a naturally occurring product of the decay
of radon gas and has a short half-life of 22
years. These dates were used to identify five
key timelines within the cores:
1900–Before most development began in
the Los Angeles region.
1945—When development was increasing in
the region.
1970—When pollution of the bay is thought
to have been severe.
1985—When sewage treatment was being
improved following implementation of
the Clean Water Act.
1997—When cores began to be collected.
Using this time framework, it was possible
to analyze cores for historical changes in
manmade contamination sources and types.
This was done by examining:
Contaminants—Measurements were made
of DDT, PCB’s, toxic metals, PAH's, and
other contaminants. Total organic carbon
was measured as an indicator of sewage
discharge.
Toxicity of samples—The toxicity of con-
taminants in samples of bottom sediment
6.9 Printed on recycled paper
increase in bulk density at the top of the core probably represents reduced sewage contamination.
was estimated in the laboratory using sea-
urchin fertilization tests and Survival tests
on amphipods (small crustaceans).
Foraminifera—The abundance and dis-
tribution of foraminifers (microscopic
single-celled animals) in the cores were
examined to provide information about the
environment in which they lived. Changes
or deformities in their tests (shells) were
also noted as indicators of contamination.
Infaunal distributions —The distribution
patterns of burrowing (infaunal) marine
animals in the cores were examined to
determine their relations to sediment tox-
icity results and the physical and chemical
characteristics of the sediment.
To help determine the sources of con-
taminants found in the cores, as well as the
processes that modify, transport, and rede-
posit sediments within Santa Monica Bay,
scientists conducted additional studies that
included:
Mineralogy—The mineral composition of
samples from the cores was studied to pro-
vide information on the sources and trans-
port pathways of sediments. This analysis
was also important because some miner-
als, particularly the clay mineral smectite,
adsorb contaminants.
Eas.T.
Sedimentology—Sediment texture and
grain size in the cores were examined to
help determine the likely distributions of
contaminants, as well as identify various
habitats of bottom-dwelling marine organ-
isms. Grain-size information also provided
critical baseline data for developing sedi-
ment transport models. Additional studies
were done to help reveal how sediment has
accumulated and been deposited in Santa
Monica Bay during the past 10,000 years.
Oceanography—Moorings placed in various
locations in Santa Monica Bay in both El
Niño and non-El Niño years collected in-
formation about temperature, salinity, and
current conditions in the water column
and near the sea floor, key parameters that
influence sediment transport.
The ongoing efforts of the USGS and its
cooperators in studying pollution in Santa
Monica Bay show that contamination and
sediment toxicity in the bay are being re-
duced by improvements in sewage treatment,
especially the ending in 1987 of sewage
sludge discharge from the Hyperion Sewage
Treatment Plant. These studies also reveal
that some chemicals, such as DDT, occur at
depths associated with dates prior to their
manufacture. Most likely, geologic events and
storms, or more commonly, burrowing marine
animals, have reworked the sediment to bury
the contaminants deeper, which makes the
contaminants less likely to enter the marine
food chain. Sediment transport models are
being developed from the new data provided
by analysis of cores taken from the bay. Un-
derstanding the transport of sediment will be
a critical tool for future management of Santa
Monica Bay and its watershed.
Homa J. Lee, Megan McQuarrie,
and Lori Hibbeler
Edited by
Peter H. Stauffer and James W. Hendley II
Graphic design by
Sara Boore and Susan Mayfield
COOPERATING ORGANIZATIONS
City of Los Angeles Bureau of Sanitation
Santa Monica Bay Restoration Project
Southern California Coastal Water Research Project
For more information contact:
U.S. Geological Survey
345 Middlefield Road, MS-999
Menlo Park, CA 94025
(650) 329-5042
http://walrus.wr.usgs.gov
See also Probing the Los Angeles Basin—Insights into
Ground-Water Resources and Earthquake Hazards
(USGS Fact Sheet 086-02).
This Fact Sheet and any updates to it are available on-
line at: http://geopubs.wr.usgs.gov/fact-sheet/fs]55-02/
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