Environmental Protection

A worker collects samples using a push core sampler.

EPA Plans Confined Aquatic Disposal Cell for New Bedford Harbor Cleanup

The agency expects this strategy will save money and speed up PCB remediation effort that has been going on for 29 years.

Based on advancements in sampling technology, engineering, and science, the U.S. Environmental Protection Agency has decided to include an underwater Confined Aquatic Disposal (CAD) cell as one part of the clean-up strategy to address lower levels of contamination in the lower harbor. The agency reached this decision after extensive evaluation of the effectiveness, costs, and benefits of using a CAD cell, and with input from the community, including Acushnet, Fairhaven, Dartmouth, and New Bedford, Mass.

Since 1982, EPA has been cleaning polychlorinated biphenyl and heavy metal contamination from the sediment of New Bedford Harbor. While hydraulic dredging and off-site removal of the highest levels of contamination from the upper harbor will continue, the use of a CAD cell will expedite the cleanup in the lower reaches of the harbor south of Sawyer Street. The CAD cell will be located between the Route 195 and Route 6 bridges. Without the use of a CAD cell, harbor dredging alone would not address contamination in the lower area of the harbor for a decade or more.

The use of CAD cells nationally for contaminated sediment disposal is increasing because they isolate contaminants from further impacting local marine food chains. Contaminated sediment is placed deeper than the active biological zone of the harbor bottom into a geochemically stable environment that prevents contaminants from moving. Once the CAD cell is filled and covered, it will remain a depression, rather than a mound, that will be continually reinforced with natural sedimentation.

While the time and cost to complete the harbor cleanup depends on available project funding, the use of a lower harbor CAD cell will reduce the timeframe and cost under all funding scenarios evaluated. The CAD cell is estimated to shorten the timeframe by up to 14 years, depending on the level of funding. The use of the CAD cell also may save $500 million compared to the current remedy at the usual funding rate of approximately $15 million per year.

EPA has discussed the potential use of a CAD cell under the Superfund clean-up process during public meetings since Oct. 2008. Monitoring performed by EPA and the Army Corps of Engineers during New Bedford’s most recent CAD cell project in 2009 showed no impairment to environmental quality from the process. EPA’s long-term monitoring of the lower harbor environment also has shown significant improvement over the time that navigational CAD cells have been used.

The construction of the EPA CAD cell in the lower harbor will not be performed this summer. The technical details, engineering controls, and project plans will be finalized over the coming year, with continued outreach to interested stakeholders. EPA has made competitive grant funding available for a local community group to hire an independent adviser(s) to interpret and explain technical aspects of the harbor cleanup. Questions about the grant process should be directed to Robert Shewack, Technical Assistance Grant coordinator, U.S. EPA, 617.918.1428.

From the 1940s until EPA banned the production of PCBs in the 1970s, two electrical device manufacturing facilities improperly disposed of industrial wastes, which contaminated the harbor bottom for about 6 miles from the Acushnet River into Buzzards Bay. PCBs do not break down naturally, and the greatest risk from the harbor has been the buildup of PCBs within the local marine food chain. While seafood is part of a healthy diet, the risks from contaminated seafood caught in and around New Bedford Harbor has led to restrictions of fishing, shellfishing, and lobstering since 1979 which will remain until annually collected data verifies that levels are decreasing and once again safe.

Source: EPA

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