Abstract: Ocean Dumping of Dredged Material--Major Environmental Considerations in Site-Selection Procedures

David D. Smith, Willis E. Pequegnat

Dredged-material disposal in the ocean totals about 75.4 × 10⁶ cu m annually and comprises 80% of all United States wastes dumped at sea. Excluding beach replenishment activities, there are now about 150 ocean-disposal sites for dredged material; these average less than 7.5 km offshore. Potential environmental restrictions on these nearshore sites warrant consideration of deep-water sites on the outer shelf, slope, and possibly the abyss.

Environmental considerations in ocean disposal-site selection are twofold: (1) factors which control the behavior of dredged material dumped at sea, such as currents, internal waves, temperature/density structures, bottom topography, animal activity, and near-bottom water chemistry; and (2) effects of the dredged material on the water column, the biologic community, and the seafloor, including turbidity, increased oxygen demand, release of chemical constituents, and burial of benthic fauna.

Clearly, fisheries and areas of high biologic productivity or special biologic significance are generally unacceptable as disposal sites. Conversely, areas of very poor biologic productivity are likely candidate areas for such sites. Most ocean areas adjacent to the United States probably fall somewhere between these two extremes. Thus, effective selection of optimum sites requires a multistep procedure involving: (1) developing site-selection criteria based on the two sets of environmental considerations; (2) using these criteria to examine offshore areas and delimit areas favorable and unfavorable for disposal sites; and (3) within the favorable areas, selecting specific disposal sites, on the basis in part of detailed environmental studies of the candidate areas.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC