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Contaminated Sediments: An Overview 1
Major Contaminants of Sediments . 4
Sources of Contaminants 5
Locating Contaminated Sediments 6
Species Affected by Contaminated Sediments , 8
Protecting Sediments Through Legislation 10
Solving the Problem 11
Contaminated Sediment Management Options 12
Preventing Sediment Contamination 14
Glossary 15
Acronyms 18
Note: Drawings on pages 11 and 14 courtesy of the University of Wisconsin-Extension and Wisconsin Department of Natual
Resources.
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Introduction to Contaminated Sediments
Sediments are loose particles of sand, clay, silt, and other
substances that settle at the bottom of a water body. They
come from eroding soil and from decomposing plants and
animals. Wind, water, and ice often carry these particles
great distances.
Many of the sediments in our rivers, lakes, and oceans
have been contaminated by pollutants. Some of these
pollutants, such as the pesticide DDT and
the industrial chemicals known as poly-
chlorinated biphenyls (PCBs), were
released into the environment long ago.
The use of DDT and PCBs in the United
States was banned in the 1970s, but these
chemicals persist for many years.
Other contaminants enter our waters every
day. Some flow directly from industrial
and municipal waste dischargers, while
others come from polluted runoff in urban
and agricultural areas. Still other contami-
nants are carried through the air, landing in
lakes and streams far from the factories and
other facilities that produced them. In cases like this, the
sediment may serve as a contaminant reservoir or source
of contamination.
Experts believe that contaminated sediments are a
widespread and serious problem. Areas of concern are
found on the Atlantic and Pacific coasts, the Gulf of
Mexico and the Great Lakes, and along inland waterways.
Contaminated sediments affect small creatures such as
worms, crustaceans, and insect larvae that inhabit the
bottom of a water body in what is known as the benthic
environment. Some kinds of toxic sediments kill benthic
organisms, reducing the food available to larger animals
such as fish.
Some contaminants in the sediment are taken up by
benthic organisms in a process called bioaccumulation.
When larger animals feed on these contaminated organ-
EPA scientists use research vessels like the
R/V MUDPUPPYto study contaminated sediments.
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Introduction to Contaminated Sediments
When
contaminants
bioaccumulate in
trout, salmon,
ducks, and other
food sources, they
pose a threat to
human health.
isms, the toxins are taken into their bodies, moving up the
food chain in increasing concentrations in a process
known as biomagnification. As a result, fish and shell-
fish, waterfowl, and freshwater and marine mammals, as
well as benthic organisms, are affected by contaminated
sediments.
Species that cannot tolerate the toxic contaminants found
in some sediments simply die, reducing the variety of
organisms, also known as biodiversity, in the affected
environment. Animals that survive exposure to contami-
nated sediments may develop serious health problems,
including fin rot, tumors, and reproductive effects.
When contaminants bioaccumulate in trout, salmon,
ducks, and other food sources, they pose a threat to human
health. In 1998, fish consumption advisories were issued
for more than 2,506 bodies of water in the United States.
Possible long-term effects of eating contaminated fish
include cancer and neurological defects.
Contaminated sediments do not always remain at the
bottom of a water body. Anything that stirs up the water,
such as a storm or a boat's propeller, can resuspend some
sediments. Resuspension may mean that all of the animals
in the water, and not just the bottom-dwelling organisms,
will be directly exposed to toxic contaminants.
Every year, approximately 300 million cubic yards of
sediment are dredged to deepen harbors and clear shipping
lanes in the United States. Roughly 3-12 million cubic
The propeller of a passing boat can churn sediments and resuspend
contaminants in the water.
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Introduction to Contaminated Sediments
yards of these sediments are so contaminated they require
special, and sometimes costly, handling. If dredging to
improve navigation cannot be conducted because sedi-
ments are contaminated, the volume of shipping on these
waterways will decline.
No single government agency is completely responsible
for addressing the problem of contaminated sediments. A
variety of laws give federal, state, and tribal agencies
authority to address sediment quality issues. Private
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industry and the public also have roles to play in contami-
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Between 1 and 4 percent of the sediments dredged annually in the United States are contaminated.
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Introduction to Contaminated Sediments
Major Contaminants of
Sediments
Five major types of pollutants are found in sediments:
Nutrients, including phosphorous and nitrogen
compounds such as ammonia. Elevated levels of
phosphorous can promote the unwanted growth of
algae. This can lead to the amount of oxygen in the
water being lowered when the algae die and decay.
High concentrations of ammonia can be toxic to
benthic organisms.
Bulk Organics, a class of hydrocarbons that includes
oil and grease.
Halogenated Hydrocarbons or Persistent Organics,
a group of chemicals that are very resistant to decay.
DDT and PCBs are in this category.
i
Polycyclic Aromatic Hydrocarbons (PAHs), a group
of organic chemicals that includes several petroleum
products and byproducts.
Metals, including iron, manganese, lead, cadmium,
zinc, and mercury, and metalloids such as arsenic and
selenium.
Metals, PAHs, and organics listed above are toxic to
| various plants and animals, including people. These
contaminants tend to biomagnify as they travel up the
food chain. All have been linked to health problems in
people.
Pesticides applied by airplanes and chemicals emitted into the air from
smokestacks can contaminate water and sediments.
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Introduction to Contaminated Sediments
The origins of sediment contamination can be divided into
point and nonpoint sources of pollution. Point source
pollution comes from a specific, identifiable source such
as a pipe. Nonpoint source pollution cannot be traced to a
specific spot.
Point sources include municipal sewage treatment plants,
overflows from combined sanitary and storm sewers,
stormwater discharges from municipal and industrial
facilities, and waste discharges from industry.
Nonpoint sources include stormwater runoff from hazard-
ous and solid-waste sites; runoff from croplands, livestock
pens, mining and manufacturing operations, and storage
sites. Atmospheric deposition is another source of
nonpoint pollution.
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Introduction to Contaminated Sediments
Locating Contaminated
Sediments
Water pollution is a significant problem in the United
States. In the 1970s, a host of measures were taken to
improve water quality, including bans on the use of DDT
and PCBs. Major water quality legislation in the 1970s
included the Federal Water Quality Pollution Control Act
Amendments of 1972 and the Clean Water Act (CWA) of
1977. Water quality began to improve, but by the early
1980s scientists realized that many toxic contaminants
remained in sediments and that they could be resuspended
by storms, ships, or even passing aquatic animals.
In 1985 and 1987, the EPA Office of Water began to
document the extent and severity of sediment contamina-
tion. Surveys showed that the types and levels of contami-
nation varied greatly at sites throughout the country.
More recently, under the Water Resources Development
Act of 1992 (WRDA), Congress directed EPAin
consultation with the National Oceanic and Atmospheric
Administration (NOAA) and the Secretary of the Army
to conduct a comprehensive national survey of data on
sediment quality. In response, EPA undertook the Na-
tional Sediment Quality Survey (NSQS), a compilation
of data on sediment quality.
EPA submitted to Congress its first survey report on
sediment contamination in 1998. The survey found that
there is contaminated sediment in all
regions and every state. The affected water
bodies include streams, lakes, harbors,
near-shore areas, and oceans. Some of the
most contaminated sediments are found in
the Great Lakes and in the harbors of
Boston, Los Angeles, Chicago, Detroit,
and Puget Sound. All of these water bodies
have been impacted throughout the years
by heavy shipping traffic, contamination
from upstream sources, and local munici-
pal and industrial discharges.
Although the NSQS is an important step in
the identification and analysis of contain!-
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Introduction to Contaminated Sediments
nated sediments, the study does Have its limits. For
example, many of the data in the inventory were collected
before experts had identified all of the important factors
that affect sediment contamination.
Today, scientists realize that the size of a sediment grain,
the amount of organic carbon in the sediment, and other
characteristics determine the bioavailability of contami-
nants. Unfortunately, this important information is not
always available in historical sediment data. EPA believes
that better data on sediment quality and direct measure-
ments of chemical concentrations in edible fish tissue are
needed. Efforts to gather this information are underway.
EPA's Environmental Monitoring and Assessment
Program (EMAP), NOAA's National Status and Trends
Program, and EPA's Great Lakes National Program
Office are among the programs monitoring sediments
more comprehensively. They are collecting data on the
physical and chemical characteristics of sediments, the
bioavailability of contaminants, levels of contaminant
residues in the tissues of aquatic organisms, and the health
of benthic communities.
Even if toxic chemicals and metals are present in sedi-
ments, they may not be harmful. Bioavailablity is a
measure of how likely it is that the contaminants will
actually affect living organisms. Many factors affect the
bioavailability of contaminants. These factors include the
acidity/alkalinity of the water and the presence or absence
of sulfur in the sediment.
To assess the ecological and human health risks posed by
contaminated sediments at a site, it is not enough to
measure the types and amounts of pollutants present.
Scientists may conduct field surveys to assess the
health of benthic communities and the levels of
contaminants found in the resident fish species. They
may run chemical tests to assess the factors that affect
bioavailability, and often times conduct biological
tests by actually exposing benthic organisms to the
contaminated sediment and observing the results.
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Introduction to Contaminated Sediments
Species Affected by
Contaminated Sediments
Sediments are home to a wide variety of aquatic life,
including worms, clams, mussels, crustaceans, and
insects. Field observations suggest, and laboratory tests
confirm, that contaminated sediments can be lethal to
benthic organisms such as crustaceans and insect larvae.
These creatures occupy important positions on the food
chain that leads up to larger fish like trout, bass, and
salmon and to fish-eating wildlife such as mink, pelicans,
cormorants, and bald eagles.
If the smaller animals lower on the food chain die due to
toxic contaminants in the sediment, the larger animals
further up the chain will lose their supply of food. On the
other hand, if the smaller animals accumulate toxic
contaminants in their tissue and survive, the larger
animals may take hi dangerous levels of toxins when they
eat the smaller ones.
People can be exposed to dangerous levels of toxic
^St.'bJh?^^:* contaminants when they eat animals high on the food
chain, such as salmon and trout. There also is the potential
for exposure to toxic contaminants through direct contact
with contaminated sediments. Anglers, hunters, waders,
and swimmers could be at risk.
Concerned about biomagnification, the increased accumu-
lation and concentration of contaminants at higher levels
of the food chain, many consumers wonder whether they
should continue to eat fish. The answer is not a simple yes
or no. Fish is a good source of protein and other nutrients,
and commercial seafood typically comes from unpolluted
areas. But, people should avoid eating unsafe amounts of
fish that might be contaminated. Anyone planning a
recreational fishing trip, or who regularly eats fish caught
from one body of water, should check with the state health
department to learn if any fish-consumption warnings or
advisories are in effect. Some advisories highlight groups
that are at special risk, including young children, the
elderly, pregnant and nursing women, and individuals
whose immune systems are impaired. The fact sheet
Update: Listing of Fish and Wildlife Advisories (EPA-
nants in sediments.
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Introduction to Contaminated Sediments
823-F-98-009) contains more information on fish con-
sumption.
EPA's database, Listing of Fish and Wildlife Advisories
(LFWA), contains all available information on current
fish-consumption advisories in the United States and
Canada. It also contains wildlife advisories for other
species such as frogs and turtles. The database is available
on the Internet at www.epa.gov/OST/fish/.
Please note that not all fish and wildlife advisories are
related to contaminants in sediment; some advisories are
due to contaminants in other places, like water itself.
In 1996, fish consumption advisories were issued for more than 2,100 bodies of water in the United States. Possible long-
term effects of eating contaminated fish include cancer and neurological defects.
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Introduction to Contaminated Sediments
Protecting Sediments
Through Legislation
jJU'ji No single agency is completely responsible for addressing
Ulf the problem of contaminated sediments. More than ten
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federal laws give EPA, the U.S. Army Corps of Engineers,
NOAA, and other federal, state, and tribal agencies
authority to address sediment quality issues.
Some of the most important sources of sediment quality
actions are the Clean Water Act and the Comprehensive
Environmental Response Compensation and Liability Act,
which established the Superfund program. Other relevant
statutes include the National Environmental Policy Act;
the Clean Air Act; the Coastal Zone Management Act; the
Marine Protection, Research, and Sanctuaries Act; and the
Great Lakes Critical Programs Act of 1990.
These laws address sediment quality:
By identifying areas contaminated with chemicals.
By restricting or eliminating further discharge of
pollutants into water bodies.
By implementing a remediation strategy that will most
effectively reduce the risk associated with the contami-
nated sediment.
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Introduction to Contaminated Sediments
The first step in solving the problem of contaminated
sediments is understanding that they present
risks to public health and to the environment
Just as water quality has been a major concern
for the past 30 years, sediment quality needs
to become a priority as well.
The second step is preventing the discharge of more toxic
contaminants into sediments. The government, private
sector and the public can work together to protect and
improve water quality by preventing toxic substances
from entering the waterways. One piece- of good news is
that sediments closer to the surface of a water body
generally have fewer contaminants than do deeper
sediments. This suggests that discharges of toxics have
dropped over the past decade or two.
In the third step, federal, state, and local government, the
regulated community, environmental advocacy groups,
and interested members of the public work together to
identify all existing problem areas. Biological and
chemical tests are run to determine how widespread and
serious the contamination is at each site. Based on the
results, priorities can be set for sediment management.
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ductic
ated Sediments
Contaminated Sediment
Management Options
The appropriate sediment management option should be
selected on a case-by-case basis, after careful consider-
ation of the risks posed by the contaminants, the benefits
of remediation, and the costs. Contaminated sediments
may either be left in place or removed. Contaminated
sediments should not be removed from a site if doing so
would cause more harm than simply leaving them in
place. In some cases, experts determine that leaving
sediments in place poses lower risks to the environment
than removing them. If sediments are left in place,
however, measures must be taken to limit the danger they
pose to people and wildlife. Long-term biological and
chemical monitoring should be established to measure any
change in contaminant levels over time and the associated
biological response.
Contaminated sediments can be managed by waiting for
new deposits of ^contaminated sand and silt to cover the
contaminated area, capping it naturally. Another option is
to cap the contaminated site artificially by depositing a
layer of clean clay, sand, gravel, or other material on top
of it. If contaminated sediments are capped rather than
treated or removed, the area around them must be moni-
tored periodically to ensure that the toxic contaminants are
not released.
Contaminated sediments also can be managed by remov-
ing the sediment. Cleaning up contaminated sediments
can be expensive. If authorities decide to remove them,
they must choose the kind of dredge most appropriate to
site conditions. Sometimes, dredging uncovers unexpect-
edly high concentrations of contaminants beneath surface
sediments.
After the sediments are dredged, they must be disposed of
safely. Often they are placed in a Confined Disposal
Facility (CDF), usually a diked area built in shallow
water. Sometimes a CDF is built on dry land. Highly
contaminated sediments may be placed in a special kind of
CDF that works like a hazardous waste landfill.;
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Introduction to Contaminated Sediments
Different ways of treating sediment to remove or neutral-
ize contaminants are being developed. They include
isolating the contaminants from the rest of the sediments
by separating the smallest grains (since contaminants tend
to stick to them), and separating the oily part of the
sediment (which contains most toxic organic compounds).
Sometimes sediments are incinerated to destroy organic
contaminants. At other times, setting agents such as
cement are added to solidify the sediments and prevent
contaminants from being released into the environment.
Bacteria and fungi may be added to break down, or
biodegrade, certain contaminants; this process is called
bioremediation. Advanced treatment approaches such as
these are promising, but often expensive.
Because contaminants often come from numerous sources
over a long period of time, determining who must pay for
clean-up can be a problem. The cost of sediment remed-
iation cannot be borne by government alone. Appropriate
authority should be used to encourage voluntary clean-ups
or compel responsible groups to clean up the sediments
contaminated by their activities.
Efforts to manage contaminated sediments have already
begun in some areas of the country, but many need further
evaluation. Dealing with this problem is essential to
prevent damage to wildlife, drinking water, public health,
commerce, and recreation.
Cleaning up
contaminated
sediments can be
expensive. Highly
contaminated
sediments may be
placed in a special
Confined Disposal
Facility that works
like a hazardous
waste landfill.
Excavating "in the dry" behind a coffer dam is one way to control the resuspension of
contaminated sediments.
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Introduction to Contaminated Sediments
Preventing Sediment
Contamination
Preventing further sediment contamination is everyone's
responsibility. Many people overlook one major source of
water contaminants: individual households. The small
amounts of cleaners, solvents, motor oil, and other toxic
materials dumped down the drain or onto the lawn or
driveway of a single household may seem insignificant.
When thousands or millions of households
release toxic substances in this way,
however, the effect is substantial. The
contaminants flow into sewage treatment
plants, which are not designed to remove
chemicals. Thus, the contaminants enter
the water cycle and may end up in
sediments.
The proper, safe disposal of household cleaners and
other chemicals Is an important safeguard against water
and sediment contamination.
14
You can help by exploring environmen-
tally friendly alternatives to household
cleaners, by recycling motor oil, and by
responsibly disposing of paint cans,
household chemical containers, and
insecticides.
Many towns and counties sponsor hazardous waste
disposal centers. Please use them.
As a citizen, encourage
your town, county, or state
to enforce environmental
protection laws and to
pursue watershed-based
management. Remind your
representatives in govern-
ment and your fellow
citizens that contaminated
sediments affect not only
wildlife, but can seriously
harm people, too.
Another way you can help is by passing this message
about contaminated sediments to others. For additional
copies of this brochure, please contact the EPA Water
Resources Center at (202) 260-7786 or by e-mail at
center.water-resource@epa.gov.
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Introduction to Contaminated Sediments
This glossary includes terms used in this document and
others frequently used in discussions of contaminated
sediments.
Aquatic living or growing in or on the water.
Benthic Environment the environment at the bottom
of lakes, rivers, esturaries, or oceans.
Bioaccumulation the process in which a substance is
taken up by an aquatic organism through any route,
including respiration, ingestion, or direct contact with
water or sediment.
Bioavailability the ability of a substance to affect
organisms.
Biodegrade to decompose a substance by living
organisms.
Biodiversity the presence of many species of organ-
isms, plant and animal.
Biomagniflcation the increased accumulation and
concentration of a contaminant at higher levels of the food
chain; organisms higher on the food chain will have larger
amounts of contaminants than those lower on the food
chain, because the contaminants are not eliminated or
broken down into other chemicals within the organisms.
Bulk Organks a class of hydrocarbon compounds
including oil and grease.
Contaminated Sediment soil, sand, organic matter, or
minerals that accumulate on the bottom of a water body
and contain toxic or hazardous materials at concentrations
that may adversely affect human health or the environ-
ment.
Dredging removal of material from the bottom of a
water body by excavation or similar removal activity.
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Introduction to Contaminated Sediments
Ecological relating to the interrelationships of organ-
isms and their environment.
Endangered referring to an endangered species;^ any
species in danger of extinction throughout all or a signifi-
cant portion of its range/habitat
Geologic referring to the history and structure of the
solid portion (rocks, soils, and minerals) of the earth.
Halogenated Hydrocarbons/Persistent Organics a
group of chemicals that are very resistant to decay. The
banned pesticide DDT and PCBs fall into this category.
Metalloids metalloids are nonmetallic elements, such
as arsenic and selenium, with some of the chemical
properties of metals.
Metals metals include elements with a metallic luster
and are found on and beneath the earth's surface, such as
iron, manganese, lead, cadmium, zinc, nickel, gold and
mercury.
Nonpoint Source Pollution pollution sources that are
diffuse, without a single identifiable point of origin,
including runoff from agriculture, forestry, and construc-
tion sites.
Nutrients substances such as nitrogen and phosphorus
compounds necessary for growth and survival. Elevated
levels can cause unwanted growth of algae, and can result
in the lowering of the amount of oxygen in the water when
the algae die and decay.
I
Point Source Pollution point source pollution refers to
the pollution that comes from a specific, identifiable
source, such as a pipe or channel.
Pollutant a chemical or biological substance in a form
that can be incorporated into, onto, or be ingested by
aquatic organisms, consumers of aquatic organisms, or
users of the aquatic environment.
Polycyclic Aromatic Hydrocarbons (PAHs) a group
of organic chemicals that includes several petroleum
products and their derivatives.
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Introduction to Contaminated Sediments
CAA Clean Air Act
CDF Confined Disposal Facility
CERCLA Comprehensive Environmental Response Compensation and Liability Act
CWA Clean Water Act
CZMA Coastal Zone Management Act
EPA U.S. Environmental Protection Agency
GLCPA Great Lakes Critical Programs Act of 1990
LFWA Listing of Fish and Wildlife Advisories
MPRSA Marine Protection Research and Sanctuaries Act
NEPA National Environmental Policy Act
NOAA National Oceanic and Atmospheric Administration
NSQS National Sediment Quality Survey
OW EPA Office of Water
USAGE U.S. Army Corps of Engineers
WKDA Water Resources Development Act
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Introduction to Contaminated Sediments
Sediment loose particles of sand, clay, silt, and other
substances that settle at the bottom of a body of water.
Sediment can come from the erosion of soil or from the
decomposition of plants and animals. Wind, water, and ice
often carry these particles great distances.
Toxic Substance a substance that can cause short-term
or long-term damage to biological tissue following contact
or absorption. Routes of exposure of the substance include
ingestion, inhalation, or assimilation into any organism,
either directly from the environment or indirectly by
ingestion through food chains.
Water Column A hypothetical "cylinder" of water
from the surface of a water body to the bottom and within
which physical and chemical properties can be measured.
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