United States         EPA 823-F-93-009
Environmental Protection  May 1993

Office Of Water (WH-585)
Questions And
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          J What are sediments?
Sediments are the unconsolidated materials at the bottom of
water bodies such as lakes, rivers, estuaries, and oceans.
Sediments consist of mineral particles, organic material, and
water.  Mineral particles are most familiar to us as clay, silt,
sand, and gravel.  Organic material in sediments results from
the activities of living organisms. Some organic material is
solid, like plant debris, while other organic material is
dissolved in the water in sediments. Water is a large compo-
nent of the sediments, occupying as -much as 60 percent of its
volume by filling in the spaces between the*particles.  Certain
kinds of contaminants are attracted to the organic material
that can coat sediment particles.  Contaminated sediments are
those that "contain chemical substances at concentrations that
pose a known or suspected environmental or human health
threat," according to the National Research Council.
           I How are they contaminated?
Contaminants are introduced into aquatic systems through
many routes including runoff from cropland, lawns, and
urban areas; chemical spills; municipal and industrial plant
discharges; and airborne pollutants.  Common contaminants
are pesticides, herbicides, polychlorinated biphenyls (PCBs),
polycyclic aromatic 'hydrocarbons (PAHs), and metals such as
lead, mercury, and arsenic.  Once these pollutants are in the
water, they tend to accumulate in sediments.  Problem
sediments most often contain toxic levels of long-lived
contaminants like metals that can directly kill aquatic life, or
contaminants like pesticides that can have long-term effects
on wildlife health and reproduction. Mercury and PCBs also
pose risks to human consumers of contaminated seafood.
            | How extensive is the problem?
Answer   .
The extent of contaminated sediments is still unknown
because comprehensive assessments have not been com-
pleted. ,A great deal of work has focused on marine sedi-
ments in harbors and waterways. Over 50 sites on coastal
areas have been identified as contaminated including Boston
Harbor, Hudson-Raritan estuary, Long Island Sound,  Puget
Sound, Oakland estuary of San Francisco Bay, and the South-
ern California Bight. Recently, attention has been directed to
freshwater sites.  In the Great Lakes, 43 "Areas  of Concern"
have been found to contain toxic pollutants in sediments.
Contaminated sediments also have been identified at 85
wildlife refuges, which pose potential problems for managing
wildlife resources. As a result of toxic contaminants in sedi-
ments and overlying water, more than 1,000 fish consumption
advisories have been issued in the  U;S. The list of contami-
nated sites of both marine
and freshwater
is likely to
grow  as 'we
look in more
and more locations.

             Why do we care?
Sediments are important because they are the home to a wide
variety of aquatic life, such as worms, clams, crustaceans, and
insects.  These benthic or bottom-dwelling organisms are key
links in the aquatic food web leading from nutrients in the
water and sediment to fish and wildlife.  Sediments can serve
as a "reservoir" from which fish and benthic organisms take up
contaminants.  These contaminants may then be passed along
the food chain to larger fish, birds, and mammals until they  •
accumulate to levels that may be toxic to them or to humans.
People also may be exposed to contaminants directly through
contact with sediments during recreational activities.  Thus,
people such as fisherman, hunters, waders, and swimmers
could be affected by contaminated sediments.
          J What can be done?
Once sediments are polluted, measures must be taken to
contain; or treat contaminated material to minimize exposure
to humans or wildlife. Contamination in sediments can be
greatly reduced by pollution prevention efforts and cleanup
activities.  In order to identify existing problem areas requirir.
cleanup, states and the EPA are developing sediment quality
criteria and bioassays to measure sediment toxicity
and bioaccumulation potential.

In .general, contaminated sediments can either be left in place
•or removed. If left in place, the contaminated sediments can
be buried by natural sedimentation, covered by clean sedi-
ments or sand, degraded through natural processes, or treate
in place through technologies currently under development.
Covering or burying are good options when the risk posed b
the sediments is not too large, and when the contaminated
area is in a relatively undisturbed environment.

The other main option is to remove or dredge sediments.
These sediments can be buried in a depression or hole in the
sediment bottom, contained behind a berm along the shore-
line, or itaken out of the water altogether for upland disposal
or treatment. If the removed sediments are highly contami-
nated with organic chemicals, they may have  to be  inciner-
ated, which can be extremely expensive.- A recent evaluation
of Superfund Records of Decisions
identified 49 sites where remedial
actions were selected for
contaminated sediment.
At 30 sites, excavation
and treatment were selected,
and at 19 sites, excavation and
containment were chosen.

 Examples and locations
 of current Superfund
•'• remediation sites
 with contaminated
 sediments and
 selected remedial
 are shown.
            | Who is responsible?
 There is no single agency or group with a unique mandate to
 address contaminated sediments.  Rather, responsibility falls
 to several agencies, primarily at the federal level through a
 number of laws and regulations. Some of these laws are the
 Clean Water Act (1970, 1987), Superfund (1980, 1987), and
 Marine Protection, Research and Sanctuaries Act (1972).
 However, none were written specifically to deal with con-
 taminated sediments.
Offsite Disposal
Onsite Containment
Under Study
 The most comprehensive federal program to manage con-
 taminated sediments has been initiated by the EPA, which has
 established a Sediment Steering Committee chaired by the
 Office of Water. This committee will coordinate EPA's assess-
 ment, prevention, remediation, and dredged material manage-
 ment programs. The Army Corps of Engineers also plays an
 important role through its oversight of dredging  activities.
 Others important players include the National Oceanic and
 Atmospheric Administration and the Fish and Wildlife Service.
 States are just beginning to take a more active stance through
 their respective environmental agencies.  Presently, only one
 state (Washington) has legally-binding sediment standards.

              What can I do to help?
 Preventing further sediment contamination is the responsibil-
 ity of every person. The'small amount of cleaners, solvents,
 motor oil, and other toxic materials dumped down the drain
 of a single household may seem insignificant.  But when
 thousands of people contribute to this pollution, the effect is
 substantial.  Therefore it is important to explore "environmen
 tally friendly" alternatives to household cleaners, recycle youi
 motor oil, and dispose of paint cans, household chemical
 containers, and garden insecticides'in a responsible manner.
 Many towns and counties sponsor hazardous waste disposal
 centers - please make  use of them. You can also support
 local water quality protection legislation in your area.
             Where can I get more information?
Local, state, and federal agencies can give you more informa-
tion on local regulations as well as the locations and status of
sites with contaminated sediments. Your state health depart-
ment can give you information on fish consumption adviso-
ries. Information can also be obtained from EPA's Office of
Water and Office of Science and Technology at
(202) 260-7049.

The EPA's Emergency Planning and Community Right-To-
Know Hotline (800-535-0202) is a good number to call, and
the Superfund Hotline  is a useful information resource on
sites listed under Superfund (800-424-9346). For sites listed
in your state, contact your state's environmental agency.
Your local library can also be an excellent source of informa-
tion as well as local environmental groups.