On September 30, 2013, the United States Environmental Protection Agency (EPA) issued a record of decision documenting its final selection of a remedy for cleanup of the Gowanus Canal Superfund Site. The Site consists of the entire length of Gowanus Canal in Brooklyn. It borders several residential neighborhoods, including Gowanus, Park Slope, Cobble Hill, Carroll Gardens and Red Hook, with housing located within one block of the canal. The cleanup remedy selected by EPA will address both contaminated sediments in the canal and continuing sources of contamination outside of the canal. EPA estimates that it will take another three years to complete design of all of the elements of the remedy, and six years thereafter to implement the remedy. However, EPA acknowledges that some elements of the remedy may not be completed within six years and additional interim measures may be required.

Contaminated sediments will be addressed by the dredging of shallow sediments and capping of deeper “native” sediments with multiple layers of clean material, including an active layer to remove contamination that could well up from below, an isolation layer to ensure that the contaminants are not exposed, and an armor layer to prevent erosion of the underlying layers from boat and traffic currents. In the most contaminated portions of the canal, EPA will conduct targeted in situ stabilization of native sediments to prevent the upward migration of contaminants before installing the multiple layer cap.

The cleanup plan acknowledges that some bulkheads may need to be replaced in conjunction with the dredging and capping activities. Some bulkhead replacements will be undertaken and funded by the federal government as part of the cleanup, but in some cases the cost of bulkhead replacement will have to be covered by the owners of property adjoining the canal. Owners of property that needs bulkhead replacement should consider negotiating with EPA to get the costs covered as part of the cleanup.

EPA has identified two major continuing sources of contamination into the canal: contamination from three former manufactured gas plants; and combined sewer overflows (CSOs), which are discharges of untreated domestic sewage and contaminated stormwater from combined sewer systems. Contamination from the three former manufactured gas plants is currently being addressed by the New York State Department of Environmental Conservation and will be monitored by EPA as part of the remedy for cleanup of the canal. 

The cleanup requires the City to reduce CSOs from two major sewer outfalls that discharge into the upper portion of the canal by outfitting both outfalls with retention tanks to reduce the volume of contaminated sewage discharges. The locations of the retention tanks have not yet been identified, although EPA suggests that one tank could be installed in a portion of Thomas Greene Park, bounded by Third Avenue and Nevins, DeGraw Street and Douglass Streets, near the northern portion of the canal, and another tank could be installed at the NYCDOT Department of Transportation storage lot located at 2nd Avenue and 5th Street. EPA has stated that the capacity of the tanks will need to accommodate projected additional loads to the combined sewer system as a result of current and future development near the canal and estimates that the tanks will be approximately 8-million and 4-million gallons in size.