This latest dredging effort started in May 2011 and focused on the northern cove on the Acushnet side of the Harbor and off-shore from the Titleist facility on Hadley Street in New Bedford. Approximately 11 acres of sediment were dredged this year, resulting in the removal of more than 21,600 cubic yards of contaminated sediment. Dredging activities will resume again in Summer 2012.
The dredged material was pumped directly into a floating pipeline connecting the dredge to EPA’s desanding building located at Sawyer Street, approximately one mile south of the dredged area. Booster pumps, located along the shoreline, helped pump the dredged sediment through the floating pipeline to the desanding facility.
At the desanding facility, coarse material was separated from the finer sediment producing a total of 4,300 tons of sand. A submerged pipeline carried the remaining sediment another 1.4 miles south to the dewatering facility at Hervey Tichon Avenue and Herman Melville Boulevard. At the dewatering facility, specialized presses squeezed the excess water out of the dredged sediment. Approximately 33 million gallons of water were treated to stringent standards and then discharged back into the harbor. About 19,200 tons of dewatered sediment were transported by truck to a trainload facility in Worcester, MA and then by rail for disposal in a licensed PCB-landfill in Michigan.
In addition to the eight seasons of full-scale harbor dredging, many other areas of PCB contaminated harbor sediment have been cleaned up to date, including:
– 19 acres capped in 2005 south of the hurricane barrier;
– seven acres cleaned north of Wood Street in 2002-2003;
– two acres dredged in 2002 for a business relocation;
– five acres of the most highly contaminated sediment dredged in 1994-1995.
The New Bedford Harbor Superfund site includes all of New Bedford Harbor and parts of the Acushnet River and Buzzards Bay. The harbor is contaminated with PCBs, the result of past waste disposal practices at two capacitor manufacturing plants – one located on the shore of the Acushnet River, the second located on the shore of the outer harbor. PCB wastes were discharged directly into the harbor, as well as indirectly through the City’s sewer system. EPA added the harbor to its National Priorities List (known as the Superfund list) in 1983, making the site eligible for federal Superfund cleanup money.
An estimated 900,000 cubic yards of sediment are slated to be removed, roughly equivalent to 175 football fields each filled three feet deep.
Under the current level of funding of $15 million per year, the selected remedy, which includes dredging with off-site disposal, confined disposal facilities (CDFs), and a Lower Harbor Confined Aquatic Disposal (CAD) Cell, will likely take 40 years to complete at a cost of $1.2 billion, EPA continues to evaluate measures to reduce the cost and time it will take to complete the remedy.
Source: epa, November 7, 2011