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REMEDIAL DREDGING AND EFFECTIVE ENVIRONMENTAL PROTECTION: EXAMPLES FROM THE NEW BEDFORD HARBOR, MA SUPERFUND SITE
Citation:
Nelson, W G. AND B J. Bergen. REMEDIAL DREDGING AND EFFECTIVE ENVIRONMENTAL PROTECTION: EXAMPLES FROM THE NEW BEDFORD HARBOR, MA SUPERFUND SITE. Presented at Coastal Zone 2001, Cleveland, OH, July 16-18, 2001.
Description:
Currently, there is an on-going national debate questioning whether remedial dredging can be conducted without causing environmental harm. Two common assertions are that: 1) dredging contaminated sediment will do more harm than good, and 2) natural processes will eventually mitigate the environmental damage. In the case of the New Bedford Harbor (NBH) Superfund site remediation, neither assertion is true. Data collected during various activities at the NBH site (e.g., a pilot dredging study, hot spot sediment remediation, long-term monitoring, and a new dredge technology evaluation) demonstrate that it is possible to dredge extremely PCB- contaminated sediment while protecting the environment. The pilot study and hot spot remediation data indicate that, with proper planning and monitoring, water-column concentrations, net PCB flux, acute and chronic biological toxicity, and bioaccumulation can all be controlled effectively.
Relative to leaving sediments in place for natural remediation, the pilot study showed that the highest water-column PCB concentrations occurred during storm events, not dredging activities. Furthermore, the long-term monitoring data and other recent sediment cores both provide evidence that, even after 25 years of clean sediment deposition (i.e., cessation of PCB inputs), most of the contamination remains in the upper sediment layer, where it is bioavailable and subject to continued natural resuspension and transport. Finally, a new dredging technology recently tested in NBH demonstrated that emerging technologies can make remedial dredging more efficient, cost-effective, and environmentally safer.