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Researcher taking samples on a boat

Sediment Sampling at the New Bedford Harbor Superfund Site

Challenge

New Bedford Harbor, one of the nation’s largest Superfund cleanup sites, was placed on the Environmental Protection Agency (EPA)’s National Priorities List in 1983. Battelle has worked with the EPA and the U.S. Army Corps of Engineers New England District (USACE NAE) at the site in various capacities since the 1980s to support site cleanup efforts.

The site was heavily contaminated with polychlorinated biphenyls (PCBs) resulting from the manufacture of electrical devices. The EPA found that PCB contamination in the sediments at the harbor bottom had built up in the local food chain and presented significant risks to both human health and the environment.

Remedying the problem requires dredging and disposal of more than 900,000 cubic yards of PCB-contaminated sediments from the bottom of the harbor as well as cleanup of the surrounding wetlands—a project still in progress today. EPA and USACE needed objective, accurate data to monitor the impact of the dredging operation over time and make confident decisions for ongoing cleanup efforts. 

Solution

During the 80s and 90s, Battelle performed physical and chemical modeling to characterize PCB transport patterns. These models helped to inform the creation of the initial cleanup plan in 1998. Since then, Battelle has continued to provide support for field collection, laboratory analysis, database management and strategic planning under four USACE-NAE contracts. 

Between 2014 and 2017, the Battelle team provided a broad range of services, including:  

  • Water quality monitoring using sensors and weekly boat-based sample collection during dredging season.
  • Collection and characterization of more than 1,000 sediment cores from subtidal areas of the Upper and Lower Harbors Sediment to characterize PCB contamination before, during and after dredging.
  • Collection of more than 600 sediment cores in intertidal areas including saltmarshes, mudflats, beaches and residential properties to delineate the horizontal and vertical extent of intertidal areas requiring excavation.
  • Verification/confirmatory sampling to assess whether additional dredging is needed at compliance demonstration areas (CDAs) and to demonstrate compliance with the target cleanup levels. 
  • Analysis of more than 2,000 samples for rapid PCB characterization and confirmatory analysis. The lab developed and validated modified analytical methods for more accurate analysis of sediment cores.
  • Completion of passive sampler studies in the Upper and Outer Harbor areas to understand the flux of contamination from sediment to water. 
  • Management of the project database, which contains more than 800,000 records.
  • Strategic planning support for developing the final cleanup approach, including evaluation of current conditions, development of planning areas, and determination of the sequence of final remediation activities.
  • A plume tracking study to assess the presence, extent and concentration of suspended sediment plumes resulting from disposal of navigational dredged material by the City of New Bedford into the city’s confined aquatic disposal (CAD) cell. 

Outcome

Data from the sediment sampling and water quality monitoring programs have been used to inform decisions about dredging, fishing restrictions and other aspects of the cleanup. As of April 2017, approximately 450,000 pounds of contaminated sediments have been dredged and disposed of from the Upper Harbor, along with 82,000 pounds of sediments from the Lower Harbor.