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MONITORING THE SUCCESS OF SEDIMENT REMEDIATION AT A SITE CONTAMINATED WITH CHLORINATED PESTICIDES, POLYNUCLEAR AROMATIC HYDROCARBONS AND ARSENIC
Citation:
Impact/Purpose:
Spatial and temporal patterns of contaminant distribution in sediment, riverbank soil and fish were monitored before, during, and after dredging at the Baird & McGuire Superfund Site in Holbrook, MA and important monitoring considerations were identified.
Description:
Monitoring the Success of Sediment Remediation at a Site Contaminated with Chlorinated Pesticides, Polynuclear Aromatic Hydrocarbons and Arsenic (Baird & McGuire Superfund Site, Holbrook, MA) Contaminated sediment in the Cochato River adjacent to the Baird & McGuire Superfund Site (Holbrook, MA) was dredged in 1994-1995. Remediation included source control, and in-situ or ex-situ treatment of contaminated ground water, soil and sediment. Contaminants in sediment, riverbank soil, and fish were subsequently monitored. Post-remediation monitoring in 1996, 1997, 1998, 1999, and 2000 included sediment from areas upstream (outside site influence) and downstream of the site. Sediment was sampled in 1999 from the area of sediment excavation, and chemicals of concern (COCs) had declined 87% (arsenic) to >90% (total PAH, total DDT, total chlordane) compared to pre-remediation levels. Upstream, time trend data analysis (using Mann-Kendall test for trend) indicated concentrations remained relatively constant over the period (no trend) except for total PAH (upward trend). Downstream, time trend data analysis indicated COCs had either downward trend or no trend, except for total PAH in riverbank soil (upward trend at background). In 1996 and 1999, fish species were sampled in areas where sediment was monitored. Fish fillets were analyzed for total DDT and total chlordane. Results in 1996 indicated concentrations in fish were unchanged (total chlordane) or increased approximately 2-fold (total DDT) compared to pre-remediation levels. In 1996, concentrations exceeded fish project action limits (PALs) (>10-5 excess cancer risk). However in 1999, concentrations in fish had decreased significantly (down 90% or more) to less than fish PALs (<10-5 excess cancer risk). In conclusion, while fish consumption risks increased immediately following excavation of contaminated sediment, within 4-years the remediation appeared to have fostered a significant reduction in sediment contamination and fish consumption risks.