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USE OF SEDIMENT CORE PROFILING IN ASSESSING EFFECTIVENESS OF MONITORED NATURAL RECOVERY
Citation:
BATTELLE. USE OF SEDIMENT CORE PROFILING IN ASSESSING EFFECTIVENESS OF MONITORED NATURAL RECOVERY. U.S. Environmental Protection Agency, Washington, DC, EPA/600/S-08/014, 2008.
Impact/Purpose:
To evaluate the natural recovery of surface sediments contaminated with polycyclic aromatic hydrocarbons and polychlorinated biphenyls, at the Wyckoff/Eagle Harbor Superfund Site off Bainbridge Island, WA, and the Sangamo-Weston/Twelvemile Creek/Lake Hartwell Superfund Site in Pickens County, SC.
Description:
The Sediment Issue summarizes two studies conducted by the National Risk Management Research Laboratory of U.S. EPA to evaluate the natural recovery of surface sediments contaminated with polycyclic aromatic hydrocarbons (PAHs) an polychlorinated biphenyls (PCBs). Natural recovery combined with long-term monitoring defines a process termed monitored natural recovery (MNR). One of the two studies was undertaken to investigate MNR processes and mechanisms was carried out at a marine site (the Wyckoff/Eagle Harbor Superfund Site off Bainbridge Island, WA) in cooperation with U.S. EPA Region 10 and U.S. Army Corps of Engineers. The second study took place at a freshwater site (the Sangamo-Weston/Twelvemile Creek/Lake Hartwell Superfund Site in Pickens County, SC) in cooperation with U.S. EPA Region 4. The natural recovery process evaluated at both study sites relied on vertical contaminant profiling and age dating of sediment cores to assess the history of contaminant accumulation; measure the extent of natural capping; and document contaminant accumulation, compositional changes, and sources over time and space. For the Eagle Harbor site, the investigation revealed that three distinct PAH sources (creosote, urban runoff, and natural background) contributed to the sediment contamination with urban runoff continuing as an on-going source. In addition, no evidence was found to indicate that the study area was being covered by natural deposits of clean, uncontaminated sediments: thus, MNR was not employed as the final cleanup remedy. Conversely, the cleanup plan for the PCB-contaminated Lake Hartwell site relies on natural recovery by the deposition of clean sediment entering the lake. The results of the investigation at this site were used to determine surface sedimentation, surface sedimentation rates, and predictions for the year cleanup goals would be achieved in the surface sediment. Long-term monitoring of the natural recovery process, i.e., MNR, is needed at this site to determine whether recovery of surface sediment continues to occur at predicted rates.