Background/Objectives: Thin-layer placement of sediment and amendments has been evaluated as part of the Remedial Investigation/Feasibility Study (RI/FS) as a potential remedial technology for the Berry's Creek Study Area (BCSA), Bergen County, New Jersey.
A Pilot Study (PS) program was implemented in conjunction with a laboratory-based Treatability Study (TS) effort to: (1) evaluate the effectiveness of thin-layer placement of sand with and without amendments to reduce the bioavailability of COPCs in the biologically active zone (BAZ), and (2) reduce uncertainty related to how the system will respond over time to thin-layer placement.
Approach/Activities: The TS component focused on screening of amendments mixed with BCSA sediments (slurries) and measuring reductions in aqueous phase COPC concentrations (mercury, methyl mercury, and PCBs). Results of 2 rounds of TS testing were incorporated into the Pilot Study program designed to evaluate in-field performance of thin-layer placement as a technology. Pilot-scale placements of sand and sand mixed with amendments were constructed on tidal mudflats and in the tidal Phragmites marsh. Amendments included were granular activated carbon (GAC), powdered activated carbon (PAC) as delivered by SediMiteTM, organoclay MRM, zero-valent iron, and sulfur. Feasibility and performance was measured primarily through physical and chemical monitoring of sediments. The physical monitoring program was implemented focused on surveyed elevation data, coring to directly measure thin-layer thicknesses and consolidation, and geotechnical evaluation. Chemical monitoring was conducted to evaluate reductions in BAZ sediment and porewater mercury, methyl mercury, and PCB concentrations. Additionally, benthic community was assessed to determine impacts on community structure.
Results/Lessons Learned: Treatability studies evaluated aqueous-phase reductions in COPC concentrations of BCSA sediment slurries following application of several amendment types. Results of the TS program will be discussed in terms of which amendments exhibited meaningful reductions in aqueous phase concentrations of PCBs, mercury, and methyl mercury. Overall, the physical monitoring of the pilot studies after over 2 years support that the test plots are physically stable, as demonstrated by cores and survey results. Chemical Data collected to date indicates that the thin-layer placements are achieving objectives with no observed effect to the diversity and abundance of the benthic community. The overall findings of the TS/PS program will directly support the Feasibility Study for the BCSA.