Capping Contaminated Dredged Material,

Capping contaminated dredged material with clean material to reduce the ecological impact of dredged material disposal in open water has been utilized by the New England and New York Districts. Monitoring of capped disposal sites has shown that capping is technically feasible and that the caps are stable under normal tidal and wave conditions OConnor and OConnor 1983 Science Applications, Inc. 1982. Bioaccumulation studies conducted in the field have been inconclusive as to the ability of capping to prevent contaminant uptake by organisms OConnor and OConnor 1983. In the New York Bight, a mussel bioaccumulation study at the capping site showed low body burdens which could have been due to bioconcentration of contaminant for ambient water as much as from the nearby sediments OConnor and OConnor 1983. In Long Island Sound, mussels were also suspended in the water column at the sand and silt capped sites of the Stanford-Norwalk capping project. Concentrations of Co, Cu, HG, Zn, and V fluctuated in the mussels over time, but these changes were thought to be unrelated to the caps because no differences in spatial concentration were detected Morton and Kemp 1980. Determining the ability of caps to isolate contaminated dredged material from the water column has, therefore, proven to be a difficult field problem Morton and Kemp 1980 OConnor and OConnor 1983. Contaminants that organisms encounter and bioaccumulate in the water column can originate from many sources other than dredged material.