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The Gowanus Canal is a 100-foot wide, 1.8-mile long canal in the New York City (NYC) borough of Brooklyn, Kings County, New York. The Canal is bounded by several communities, including Park Slope, Cobble Hill, Carroll Gardens and Red Hook. The Canal empties into New York Harbor. The adjacent waterfront is primarily commercial and industrial, currently consisting of concrete plants, warehouses and parking lots.
The Gowanus Canal was built in the mid-1800s and was used as a major industrial transportation route. Manufactured gas plants (MGP), paper mills, tanneries and chemical plants operated along the Canal and discharged wastes into it. In addition, contamination flows into the Canal from overflows from sewer systems that carry sanitary waste from homes and rainwater from storm drains and industrial pollutants. As a result, the Gowanus Canal has become one of the nation's most seriously contaminated water bodies. More than a dozen contaminants, including polycyclic aromatic hydrocarbons, polychlorinated biphenyls and heavy metals, including mercury, lead and copper, are found at high levels in the sediment in the Canal.
What Is Being Done to Clean Up the Site?
The Gowanus Canal has been heavily contaminated throughout its existence. No environmental remediation has been undertaken, to date. Remedial efforts are currently underway at three former MGPs along the Canal. These plants are believed to be sources of much of the PAH contamination in the Canal – the former Fulton MGP site, the former Citizens Gas Works MGP site and former Metropolitan Gas Light Company MGP site. National Grid is the PRP for the former MGP sites.
In April 2009, the EPA proposed putting the Gowanus Canal on the National Priorities List. While the community and many elected officials supported the listing, New York City and some development interests did not. New York City proposed an alternate approach that would have depended heavily on the assumption of long-term Congressional funding to the U.S. Army Corps of Engineers (COE). After consulting extensively with the many stakeholders who expressed interest in the future of the Gowanus Canal and the surrounding area, the EPA determined that Superfund designation was the best path to the cleanup of this heavily contaminated and long-neglected urban waterway. EPA placed the site on the National Priorities List on March 4, 2010.
EPA, in conjunction with New York City and National Grid, performed supplemental field work to characterize the nature and extent of contamination in the canal; determine the human health and ecological risks from exposure to contamination in the canal; identify the sources of contamination to the Canal, including ongoing sources of contamination that need to be addressed so that a sustainable remedy can be developed and implemented; and determine the physical and chemical characteristics of the canal that will influence the development, evaluation and selection of cleanup alternatives. This work, which supplemented previous studies carried out by the COE and National Grid, included a bathymetric (underwater depth) study, sediment sampling, monitoring well installation, groundwater, surface water, air, sediment and fish tissue sampling, sewer system sampling, and an investigation of hundreds of pipes that lead to the canal. A remedial investigation report was released to the public on February 2, 2011 and a public meeting was held on February 23, 2011 to discuss the results of the study. A feasibility study which developed and evaluated remedial alternatives for mitigating human and ecological risks in the Canal was released the public on December 30, 2011, followed by an informational public meeting held on January 24, 2012. Nearly 200 people were in attendance.
On December 27, 2012, the EPA released a Proposed Plan describing its proposed remedy for the site. The Proposed Plan recommended removing all of the contaminated sediment that has accumulated as a result of industrial and sewer discharges from the bottom of the canal by dredging. The dredged areas would then be capped. EPA also recommended controls to prevent CSOs and other land-based sources of contamination from compromising the cleanup. On January 23, 2013, and January 24, 2013, EPA held public meetings to present the Proposed Plan, including the preferred remedy, and respond to questions and comments from the 200 attendees at the first meeting and 100 attendees at the second meeting. A ROD, selecting a remedy for the site, was signed on September 27, 2013.
In 2014, EPA issued an order to National Grid (the company that acquired the legal liability for the three former MGP sites), NYC, and more than 30 other PRPs requiring them to design the selected remedial action in the Canal. EPA issued a second order to NYC requiring it to design the CSO retention tanks and certain other elements of the remedial action.
In June 2016, EPA finalized an agreement with the City that secured the design of the larger of two CSO retention tanks, including both the tank’s size and location. It also requires New York City to undertake activities to prepare that location for the tank installation and to pay EPA’s oversight costs. Prior to finalizing the agreement, EPA accepted comments from the public for 45 days and attended two community meetings to explain the proposal. The consent order allows New York City to locate an eight million-gallon retention tank in New York City’s preferred location, known as the “Head-of-Canal” location, but it also holds the city to a strict schedule with monetary penalties imposed if violations of the schedule occur. Also, EPA can require New York City to place the tank in the Thomas Greene Park location instead if certain activities do not occur on schedule, including if New York City is not able to acquire the land at the Head-of-Canal location within approximately four years. Locations for staging and other work related to the construction of the eight million-gallon retention tank will be acquired by New York City as part of the ongoing design phase of the project. The first phase of the tank design (site preparation and demolition) DEP was submitted on June 30, 2017. The design related to addressing support of excavation, excavation, deep foundation and associated elements of the tank is due on April 30, 2019. The design addressing above-ground structures and appurtenances, mechanical fit-out and conveyances for the tank is due on September 30, 2019.
Pilots are being performed by National Grid to provide information necessary to complete the full-scale dredging and capping design for the upper canal, from Butler Street to 3rd Street. National Grid commenced a 4th Street basin marine debris removal pilot in October 2016; the work was completed in November 2016. Dredging and capping pilots in the 4th Street turning basin commenced in October 2017 with the dredging of approximately 2,000 cubic yards of sediment so that the equipment barges could move into the basin. The banks of the 4th Street turning basin are being stabilized with bulkheads to conduct the dredging and capping pilots. The dredging is to begin in early January 2018. The dredging will take at least two months. It will be followed by placing a cap. The pilots are expected to be completed by late spring 2018.
National Grid’s 35% design for the upper portion of the canal was submitted in October 2016. The 65% design was submitted in mid-November 2017. It is anticipated that the design will be completed by February 2019.
On October 24, 2017, National Grid completed the 35% design for the Fulton former MGP cutoff wall (to prevent the migration of coal tar to the canal).
EPA’s Involvement at the Site
EPA added the Gowanus Canal to the Superfund program’s National Priorities List on March 2, 2010.
Based upon the results of an extensive investigation of the contamination in the Canal and public comment on a proposed remedy, in September 2013, signed a Record of Decision (ROD), EPA finalizing a plan to clean up the contaminated sediment that has accumulated as a result of industrial and combined sewer overflow (CSO) discharges. The plan divides the canal into three segments. The first segment runs from the top of the Canal to 3rd Street, the second segment from 3rd Street to just south of the Hamilton Avenue Bridge and the third segment runs from the Hamilton Avenue Bridge to the mouth of the Canal. Approximately 300,000 cubic yards of highly-contaminated sediment will be dredged from the first and second segments. For the third segment, approximately 281,000 cubic yards of contaminated sediment will be dredged. The plan also calls for removing contaminated material that was placed in the 1st Street turning basin decades ago and restoring about 475 feet of the former basin. A portion of the 5th Street turning basin underneath the 3rd Avenue bridge and extending about 25 feet to the east of the bridge will be dredged and restored.
In dredged areas of the Canal where contamination exists in the native sediment, multiple layers of clean material will placed. The multilayer cap will consist of an “active” layer made of a specific type of clay that will remove 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 canal currents. Finally, sufficient clean sand will be placed on top of the “armor” layer to fill in the voids between the stones and to establish sufficient depth in order to restore the canal bottom as a habitat. In the middle and upper segments of the Canal where the native sediment is contaminated with coal tar, the sediment will be stabilized by mixing it with concrete or similar materials. The stabilized areas will then be covered with the multiple layer cap as described above.
The remedy also includes the construction of retention tanks to reduce the volume of contaminated sewage solid discharges from the CSOs at two major outfalls in the upper portion of the Canal be outfitted with retention tanks.
The cost of the cleanup plan is estimated to be $500 million.