SITE REMEDIATION AND
EMERGENCY RESPONSE NEWSLETTER
November 2013
No. 182
EPA Finalizes $506 Million Cleanup Plan for Gowanus Canal Superfund Site in NYC
EPA has finalized a plan to clean up the Gowanus Canal Superfund site in Brooklyn, New York. It is thought to be one of the most contaminated bodies of water in the U.S. Cleanup costs are estimated at $506 million.
The plan requires the removal of contaminated sediment, the capping of dredged areas, and the imposition of controls to reduce sewage overflows and other land-based sources of contamination that may impede cleanup.
High concentrations of polycyclic aromatic hydrocarbons (PAHs); polychlorinated biphenyls (PCBs); and heavy metals, including mercury, lead and copper, have been found in the sediment in the Gowanus Canal. In addition, PAHs and heavy metals have been found in the canal water. Despite advisories against eating fish from the canal, people continue to fish in it and eat their catch.
In its cleanup plan, EPA has divided the Gowanus Canal into three segments that correspond to the upper, middle and lower portions of the canal. The first segment runs from the top of the canal to the 3rd Street Bridge. The second segment extends from 3rd Street to just south of the Hamilton Avenue bridge. These two segments contain the most heavily-contaminated sediment. The third segment stretches from the Hamilton Avenue Bridge to the mouth of the canal.
For the first and second segments of the canal, the EPA plan requires dredging approximately 307,000 cubic yards of highly contaminated sediment. In areas where the deep sediment is contaminated with liquid coal tar that bubbles up toward the surface, the sediment will be stabilized by mixing it with cement or similar binding materials.
The stabilized areas
will then be covered with multiple layers of clean material, including an
“active” layer made of a specific type of absorbent material that will remove
PAH contamination that could well up from below, an “isolation” layer of sand
and gravel that will ensure that the contaminants are not exposed, and an
“armor” layer of heavier gravel and stone to prevent erosion of the underlying
layers from boat traffic and currents. Finally, clean sand will be placed on top
of the armor layer to restore the canal bottom as a habitat.
For the third segment of the canal, EPA will require the dredging of
approximately 280,000 cubic yards of contaminated sediment and capping of the
area with active, isolation and armor layers and a layer of sand to help restore
habitat.
The final plan
includes various methods for managing the contaminated sediment after dredging,
depending on the levels of contamination. The methods include transporting the
dredged sediment that is highly impacted by liquid coal tar away from the area
to a facility where it will be thermally treated for the removal of the organic
contaminants and then put to beneficial reuse such as a landfill cover, if
possible. For the less contaminated sediment, treatment includes stabilization
of the sediment at a facility out of the area, followed by beneficial reuse.
In addition, the final EPA plan requires controls to reduce significantly the
flow of contaminated sewage solids from combined sewer overflows into the upper
canal. Without these controls, EPA finds that solid discharges of contaminated
sewage would recontaminate the canal after its cleanup.
EPA has identified many parties potentially responsible for polluting the Gowanus Canal, including National Grid, the city of New York and other private and federal government entities, and it continues to search for more.
To read the EPA Record of Decision for the Gowanus Canal, see: http://www.epa.gov/region02/superfund/npl/gowanus/ and for more information, see SR&ER Newsletter No. 157 of October 2011, No. 153 of June 2011 and No. 151 of April 2011.