Remediation of contaminated sediments presents an on-going challenge in the efforts toward improved water quality and environmental restoration. Faced with this challenge, Mercury Marine recently selected a remedial alternative that included diverting creek flow and removing approximately 5,900 in-situ cubic meters of sediments containing PCBs from an impoundment in Cedar Creek. The regulatory objective was to remove all sediment containing PCBs “to the extent practicable” from an 180-meter stretch of the impoundment.
A remedial investigation was conducted to collect the data necessary to characterize the site and prepare a remedial design. Technical issues involved with dry excavation that were critical to implementing this alternative included: channel diversion, sediment characterization, pond dewatering, wastewater treatment, groundwater infiltration, surface water run-off, and sediment removal, handling and disposal.
Mercury Marine and its engineering staff found sediment removal by dry excavation to be a labor intensive and costly means of remediating the PCB-affected sediments at this site. Before implementing dry excavation at any site, owners, consultants, and regulatory agencies must realize the many limitations of this alternative and give special consideration to site conditions, engineering, and planning.