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The New Bedford Harbor Superfund Site Long Term Monitoring Program (1993-2009)
Citation:
NELSON, W. G. AND B. J. BERGEN. The New Bedford Harbor Superfund Site Long Term Monitoring Program (1993-2009). ENVIRONMENTAL MONITORING AND ASSESSMENT. Springer, New York, NY, 184(12):7531-7550, (2012).
Impact/Purpose:
Many recent reviews of EPA’s Superfund sediment program, most recently the NRC in 2007, have cited the lack of comprehensive, long-term site monitoring as one of the major flaws at these sites. New Bedford Harbor, MA (NBH), is one of the most highly contaminated marine PCB Superfund sediment sites in the United States. A long-term monitoring program (NBH-LTM) was developed and initiated in 1993 by AED staff to document the effects and effectiveness of remedial activities in NBH. It incorporates all of the elements called for in the NRC report, including pre-remedial monitoring, a sample design that enables rigorous statistical data analyses, benthic community condition variables, consistency, and flexibility. In addition to baseline sampling in 1993, monitoring has been repeated four times in the last sixteen years. This manuscript describes the program and an overview of the results. Briefly, there is a decreasing spatial gradient in sediment PCB concentrations from the northern boundary (upper harbor) to the southern boundary (outer harbor) of the site. Along this same transect, there is an increase in biological condition (e.g., benthic community diversity). Temporally, the contaminant and biological gradients have been maintained since the 1993 baseline collection; however, since the onset of full-scale remediation in 2004, PCB concentrations have decreased throughout the site and one of the benthic indices has shown significant improvement in the lower and outer harbor areas. The NBH-LTM has been able to rigorously document the effects of remedial dredging to date (i.e., only about 25% complete), will continue to do so as clean-up continues, and has been used as a monitoring blueprint for other Superfund sites around the country.
Description:
New Bedford Harbor (NBH), located in southeastern Massachusetts, was designated as a marine Superfund site in 1983 due to sediment contamination by polychlorinated biphenyls (PCBs). Based on risks to human health and the environment, the first two phases of the site cleanup involved dredging PCB-contaminated sediments from the harbor. Therefore, a long-term monitoring program (LTM) was developed to measure spatial and temporal chemical and biological changes in sediment, water, and biota to assess the effects and effectiveness of the remedial activities. A systematic, probabilistic sampling design was used to select sediment sampling stations. This unbiased design allowed the three segments of the harbor to be compared spatially and temporally to quantify changes resulting from dredging the contaminated sediments. Sediment was collected at each station and chemical (e.g., PCBs, metals), physical (e.g., grain size), and biological (e.g., benthic community) measurements conducted on all samples. This paper describes the overall NBH-LTM approach and the results from the five rounds of sample collections. Briefly, there is a decreasing spatial gradient in sediment PCB concentrations from the northern boundary (upper harbor) to the southern boundary (outer harbor) of the site. Along this same transect, there is an increase in biological condition (e.g., benthic community diversity). Temporally, the contaminant and biological gradients have been maintained since the 1993 baseline collection; however, since the onset of full-scale remediation, PCB concentrations have decreased throughout the site and one of the benthic community indices has shown significant improvement in the lower and outer harbor areas.