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TOOLS FOR ASSESSING MONITORED NATURAL RECOVERY OF PCB-CONTAMINATED SEDIMENTS
Citation:
Mills*, M A., R C. Brenner*, J M. Lazorchak, J SchubauerBerigan, P dePercin*, T. Lyons,T.M., F H. McCormick, E Kleiner*, P T. McCauley*, AND D L. Lattier. TOOLS FOR ASSESSING MONITORED NATURAL RECOVERY OF PCB-CONTAMINATED SEDIMENTS. Presented at The Seventh International Symposium - In situ and On-site Bioremediation, Orlando, FL, 6/2-5/2003.
Description:
Management of contaminated sediments poses many challenges due to varied contaminants and volumes of sediments to manage. dredging, capping, and monitored natural recovery (MNR) are the primary approaches at this time for managing contaminated sediment risks. Understanding how well these approaches manage risk in different environments is critical for choosing appropriate remedies to predictably reduce risk to human and ecological receptors. MNR of sediments is a risk management option that relies on natural environmental processes to permanently reduce risk, and includes careful assessment, modeling, and monitoring to ensure success.
To address the chemical, physical, and biological monitoring issues associated with MNR of contaminated sediments, a site where MNR had been selected as the remedial action was essential. An appropriate site was identified in Lake Hartwell, near Clemson, SC. A collaborative project, involving several EP A ORD Laboratories, EP A Region 4, and contractor support (Battelle Memorial Institute), was established to address multiple issues involved at Lake Hartwell. Generally, the collaboration consisted of:
NRMRL-Cinc.: Physical, chemical, and biological characterization of sediment, water, and air; biotic vs. SPMD studies; groundwater surface water interactions; project management
NERL-Cinc.: Biological monitoring (fish/plankton/macro invertebrates); project management
NERL-Athens: Modeling studies
Region 4-Atlanta: Project authorization/local coordination via EP A Remedial Project Manager
Region 4-Athens: Logistics and sampling support. .
To evaluate how the physical, chemical, and biological processes involved with MNR relate to risk management, a mechanistic understanding of these processes is needed. Empirical relationships are not sufficient to allow extrapolation to additional sites, contaminants, or remedial actions. To examine these processes, a mass balance approach was taken at Lake Hartwell. Site characterization and monitoring have been conducted at the site for 3 years to evaluate effective tools for characterizing the contaminants. As a synopsis:
Year 2000 - PCB characterization and sediment age dating of deep cores in 5-cm increments were conducted at 10 stations along the centerline of the lake and most of its northern tributaries.
Year 200 I -PCB characterization and age dating of deep sediment cores in 5-cm increments were conducted at three stations across the lake
(bank to bank), plus PCB characterization of the overlying water column and the atmosphere at the air-water interface was performed. Year 2002 - Biological and surrogate monitoring tools were developed and evaluated to assess recovery of the entire Lake Hartwell ecosystem including indigenous fish, clams, plankton, and macro invertebrates; physical/chemical transport mechanisms for PCBs from the sediment to the water column were evaluated; additional sediment, water, and air monitoring was conducted.
Year 2003 and 2004 (Planned)- The physical, chemical, and biological processes database will be expanded to provide more refined model inputs (mechanistic and data); andmonitoring and assessment tools for use at other contaminated sites will be optimized.