Dredging may not eliminate contaminants

By RANDOLPH E. SCHMID
ASSOCIATED PRESS WRITER

WASHINGTON -- Contaminated sediments in rivers and bays from coast to coast pose an environmental hazard, and while dredging reduces the sediment it doesn't always solve the problem, the National Research Council reported Tuesday.

Inevitably dredging leaves some contamination behind, and in some cases further treatment is necessary, such as capping with a layer of clean material, the council said.

In addition, the dredging process itself can release some contamination into the environment, said the council, an arm of the National Academy of Sciences.

The study, requested by the Environmental Protection Agency, evaluated 26 environmental dredging projects in rivers, harbors, lakes and bays across the country contaminated by industrial, agricultural and mining byproducts.

Dredging is the most complex and costly method of cleanup, the report said, but has the potential to permanently remove contaminants from the environment.

But some contamination can be left behind, particularly in places with debris such as boulders or cables, or bedrock lying beneath the contaminated sediment - a situation for which the public may have little tolerance.
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