Research Study for the Development of Dredged Material Disposal Criteria: final report.

The Elutriate Test was designed to evaluate the release of chemical contaminants from hydraulically dredged sediments at the disposal site water column. An evaluation of the factors influencing performance of this test has been conducted. Sediments used were from the Trinity River, Houston Ship Channel Turning Basin, Port Aransas Channel, and Corpus Christi Bay, Texas; Mobile Bay, Alabama; Bridgeport, Connecticut; and Ashtabula, Ohio, Harbor on lake Erie. The oxygen content of the elutriate was found to be one of the most important factors influencing the release of chemical contaminants from dredged sediments during the Elutriate Test. Under toxic conditions, only manganese (II) and ammonium were released in potentially significant amounts to the elutriate from the sediments tested. Little or no release of nitrate, organic nitrogen, total phosphorus, orthophosphate, copper, lead, cadmium, iron, or PCB's occurred. Zinc and selected chlorinated hydrocarbon pesticides, such as the DDT group, were removed from the test water for some sediments. The amounts of ammonium and manganese released are potentially sufficient to cause acute lethal toxicity to some forms of aquatic life in the disposal site water column, under conditions of little or no mixing of disposal site water with the water in contact with the dredged sediments. Since normal disposal practices for hydraulically dredged sediments involve dumping of the dredged sediments in open water, no acute lethal or significant chronic sub lethal effects would be expected in the water column at the disposal site from the chemical contaminants present in the dredged sediments. Bioassay tests using Daphnia magna for Ashtabula Harbor sediments and Palaemonetes pugio (grass shrimp) for the Corpus Christi Bay sediments showed no toxicity in the elutriates to these organisms in the 96-hour period. Some toxicity was found for P. pugio in the elutriate-sediment mixture from the Bridgeport samples. Because of the importance of dissolved oxygen in influencing the performance of the Elutriate Test, a modified test is recommended which employs compressed air agitation during this 30-minute mixing period. Also it is recommended that the amount of sediment present in the elutriate mixture be reduced from 20 percent to 5 percent. This approach would greatly improve the yield of elutriate for chemical analysis and increase the ease of performance of the test without any detriment to interpretation of the test results.