Field Testing of Activated Carbon Mixing and In Situ Stabilization of PCBs in Sediment

We conducted the first field-scale test of in-situ activated carbon (AC) amendment for contaminated sediment remediation. Using commercial equipment devices, AC was successfully incorporated into the test plots to a nominal 1 foot depth at a dose of 2-3 %. In-situ bioassays with Macoma nasuta showed the benefit of AC treatment, though at 18 months post-treatment the insitu assay results were confounded due to newly deposited sediment. Ex-situ M.nasuta bioassays showed about 50 % reduction in PCB biouptake with 2 % of AC dose. Field-exposed AC retained a strong stabilization capability to reduce aqueous equilibrium PCB concentrations by as much as 95 %, which supports the long-term effectiveness of AC in the field at least up to 18 months. Neither PCB resuspension from the test plots nor adverse impacts to the benthic community were observed. Scaling-up the AC treatment method results in possible total cost savings of 70 to 75 % less than sediment dredging and disposal for the Hunters Point South Basin test site. If ongoing contaminant sources are eliminated and freshly deposited sediments are clean, in-situ AC amendment of contaminated sediments can provide a suitable method for reducing contaminant exposure to the water column and biota. The original document contains color images. Performed in cooperation with the University of Maryland, Baltimore County, MD, and the U.S. Army Engineer Research and Development Center, Mobile, AL.