Learn More
Contaminated Sediment Management Options
The appropriate sediment management option should be selected
on a case-by-case basis, after careful consideration of the
risks posed by the contaminants, the benefits of the 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 uncontaminated sand and silt to cover the contaminated
area, capping it naturally. Another option is to the 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 monitored periodically to ensure that
the toxic contaminants are not released.
Contaminated sediments also can be managed by removing 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 unexpectedly 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.
Different ways of treating sediment to remove or neutralize
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 remediation 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.
contaminated sediment home |
sources |
locating contaminated sediments
species affected |
protecting sediments from contamination
management options |
preventing contaminated sediment
glossary |
acronyms
|