Los Angeles Contaminated Sediments Task Force Dredge Material Management Program Feasibility Study - Sediment Washing Bench Scale Studies

The multi-agency Los Angeles Basin Contaminated Sediments Task Force (CSTF) was established in 1998 to develop a long-term management plan by 2003, for dredging and disposal of contaminated sediments from coastal waters in Los Angeles County. The plan's goal is to include measures to identify environmentally preferable, practicable disposal alternatives, promote multi-use disposal facilities and beneficial re-use, and support efforts for watershed management to control contaminants at their source. To identify the most appropriate sediment disposal alternatives, four pilot and/or bench scale studies were conducted and led by one of the CSTF executive members, the Los Angeles District Army Corps of Engineers. This paper describes sediment washing, one of the four bench scale studies. A literature search and bench scale study were completed at the ERDC Waterways Experiment Station, to evaluate the feasibility of washing dredge material to remove chlorides and other salts prior to upland disposal and/or reuse. Current management practices in Southern California prohibit upland disposal of marine sediments because of concerns that salts will leach from the sediments and impair groundwater resources. The current study focuses on two approaches for sediment washing: passive-gravity washing and cake washing. While the primary objective is to evaluate salt removal, changes in bulk sediment and leachate chemical concentrations will also be evaluated.