PCBs, Dredging and Resuspension: Setting a Standard for the Hudson River Remediation

In February 2002, the United States Environmental Protection Agency (USEPA) issued a Record of Decision (ROD) for the Hudson River PCBs Superfund Site. In the ROD, USEPA identified several remedial action objectives, including the following:Reduce PCB levels in sediments in order to reduce PCB concentrations in river (surface) water that are above applicable or relevant and appropriate requirements for surface water;Reduce the inventory (mass) of PCBs in sediments that are or may be bioavailable; andMinimize the long-term downstream transport of PCBs in the river.In selecting its cleanup remedy, USEPA required that performance standards for resuspension during dredging, production rates during dredging, and residual sediment contamination after dredging be established. USEPA tasked TAMS/Earth Tech and Malcolm Pirnie with the development of a technically sound standard designed to protect downstream water users as well as the anticipated long-term recovery of the river.Recognizing the need to respond quickly to sediment resuspension events while at the same time satisfying the need to confirm the release of PCBs and not just sediment, two sets of criteria and monitoring frameworks were created. At near-field stations (within a few hundred yards of the dredge), suspended solids are monitored in real-time, providing rapid feedback to the dredge operator. Far-field monitoring at 1 mile or more downstream is performed periodically by collecting samples for PCB analysis to determine concentration and load. The criteria reflect considerations of PCB water quality and PCB loads, with the purpose of protecting public water supplies and the long-term recovery of the river.