Long Term Monitoring of Activated Carbon Amendment to Reduce PCB Bioavailability in Sediments at an Active Shipyard
Gunther Rosen | Space and Naval Warfare Systems Center Pacific
The primary objectives of this project relate to demonstration of long term stability and effectiveness of activated carbon (AC)-based amendment as in situ treatment for persistent organic contaminant-impacted sediments, specifically polychlorinated biphenyls (PCBs), while ensuring the amendment does not adversely affect benthic ecological resources. The primary objectives include evaluation of (1) long-term effectiveness of AC amendment to reduce bioavailable concentrations of PCBs in biota and available concentrations of PCBs in porewater (2) long-term stability of the AC amendment with observations of the lateral and vertical extent, uniformity, and persistence in surface sediments; (3) long-term potential for adverse impacts to the benthic community due to the remedy; and (4) promoting technology transfer through commercial availability and acceptance of the technology.
This project will focus on long-term performance associated with a recently completed Environmental Security Technology Certification Program (ESTCP) demonstration project ( ER-201131; PI Dr. Bart Chadwick) which involved amendment placement and three years of post-remedy monitoring of an AC-based amendment (AquaGate+PACTM) for the sequestration of PCBs at Pier 7 at the Puget Sound Naval Shipyard & Intermediated Maintenance Facility (PSNS & IMF). The technologies included are the AC-based amendment itself, which was specifically formulated for successful application in deep water environments, coupled with a comprehensive monitoring program to evaluate the performance of the amendment. The monitoring will generally follow the design used for the pre- and post-installation monitoring in the previous demonstration project (Kirtay, Chadwick et al., Final Report for ESTCP Project ER-201131), which included physical, chemical, and biological parameters using a suite of largely in situ technologies to evaluate the stability, effectiveness, and potential for adverse impacts to the benthic community. Physical parameters assessed in this project will characterize the lateral and vertical extent, stability, and content of the AC amendment in surface sediments, to evaluate changes in these parameters over time resulting from natural sedimentation, benthic mixing, ship and tug activity; and/or increased sediment cohesiveness. Chemical parameters include monitoring concentrations of PCB congeners in surface sediment to evaluate changes in bulk concentrations as well as monitoring the reduction in contaminant availability via in situ passive sampling (magnitude and sustainability of the bioavailability reduction). Biological parameters will include assessing the reduction of PCBs in clam and polychaete tissues and assessing changes in benthic community richness, abundance, evenness, and diversity 7 years post placement of the remedy. As discussed below, the earlier results of the first monitoring events, as reported in ER-201131, indicated immediate and sustained performance of the AC in reducing PCB availability by approximately 70% to 90%, without adverse effects on the native benthic invertebrate community.
The primary expected benefit of this project is to build confidence in the long-term performance of AC amendments to remediate sediments under conditions associated with active Department of Defense harbors. The primary keys to building this confidence are providing data demonstrating whether or not: (1) the short-term performance observed at these sites continues to persist over periods extending to the range of 5-10 years; (2) the amendment technology results in significant adverse benthic community effects over these extended periods; and (3) the approach is implementable and cost effective at scale based on how long the remedy will persist in the environment. The research team believes the effort described in this project will help significantly to address these remaining uncertainties. (Anticipated Project Completion - 2020)