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EPA Issues Order for Gowanus Canal

Tuesday, April 6, 2021

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In an effort to control contaminated solids discharges at the Gowanus Canal Superfund site in Brooklyn, New York, the U.S. Environmental Protection Agency ordered the City of New York to construct and operate two combined sewer overflow retention tanks.

The administrative order was issued on March 30 and is a key component of the Gowanus Canal cleanup.

Previous Orders, Clean Up Plan

In September 2013, the EPA issued its final cleanup plan for the Gowanus Canal Superfund site, which included dredging contaminated sediment that has accumulated on the bottom of the canal as a result of industrial and sewer discharges. Following these efforts, the dredged areas planned to be capped.

As part of the plan, the EPA also instructed that controls be put in place to prevent combined sewer overflows, or CSOs, and other land-based sources of contamination from compromising the cleanup.

At the time of announcing the final plan, the EPA was conducting and overseeing engineering design work needed for the site cleanup, as canal design work was expected to continue for another two years, followed by the start of cleanup operations.

Jim.henderson, CC-Zero, via Wikimedia Commons

In an effort to control contaminated solids discharges at the Gowanus Canal Superfund site in Brooklyn, New York, the U.S. Environmental Protection Agency ordered the City of New York to construct and operate two combined sewer overflow retention tanks.

In 2014 and 2016, the EPA issued additional orders requiring that the city find a location for and design the two tanks. In April 2016, the EPA announced a proposed agreement with the City of New York establishing a location for two sewage and storm water retention tanks.

As part of the proposed agreement, the EPA planned to set out a schedule for the design of the larger of the two tanks and required the city to undertake activities to prepare that location for the tank installation, and to pay EPA oversight costs. Specifically, the proposed administrative settlement agreement and order allowed New York City to locate an 8 million-gallon retention tank in the “Head-of-Canal” location, however, the city could also place the tank in the Thomas Greene Park location should the schedule fail to be carried out effectively.

“Cleaning up the Gowanus Canal is a daunting task which not only involves dredging toxic sediment, but also building huge retention tanks to reduce the amount of raw sewage that flows into the canal,” said Judith A. Enck, former EPA Regional Administrator, at the time. “Getting these tanks installed is a key component of the cleanup. The New York City Parks Department prefers not to have a large sewage retention tank permanently located in a city park. The EPA is also committed to preserving urban parkland and therefore spent time working with the City of New York about an alternate location. This proposed location meets the EPA’s twin goals of cleaning up the canal while also protecting urban parkland.”

The Agency points out that more than a dozen contaminants, including polycyclic aromatic hydrocarbons, PCBs and heavy metals such as mercury, lead and copper, had been found at high levels in the sediment in the Gowanus Canal. PAHs and heavy metals were also found in the canal water, which are commonly formed during the incomplete burning of coal, oil, gas, wood, garbage or other organic substances. PCBs and PAHs are suspected of being cancer-causing and PCBs can have neurological effects, as well.

In its cleanup plan, the EPA estimated that a reduction of 58% to 74% of these discharges would be needed to maintain the effectiveness of the cleanup, and that the new tanks were being designed to achieve that goal.

By June, the EPA announced that it had finalized the agreement with the City of New York, securing the design of the larger of two combined CSO retention tanks. The city was given four years to acquire the land at the Head-of-Canal location. Locations for staging and other work related to the construction of the eight-million-gallon retention tank was to also be acquired by the city as part of the ongoing design phase of the project.

In January 2020, the EPA announced the issuance of an administrative order requiring the start of the cleanup of the Gowanus Canal Superfund site. A major milestone for the project, the order covers both the cleanup of the upper canal—denominated as Remediation Target Area (RTA) 1—and the 1st Street turning basin, following years of detailed engineering, scientific studies and design work.

As outlined in this order, work would involve full-scale dredging and capping of RTA 1, as well as restoration of the 1st Street turning basin. Work was estimated to cost $125 million and would take roughly 30 months to complete.

“We’ve come a long way to achieve this significant milestone in cleaning up the Gowanus Canal. With pilot dredging tested, full-scale dredging, capping and restoration of the canal can proceed, starting with the first third of the canal,” said U.S. Representative Nydia M. Velázquez at the time. “We are on an ambitious timeline for cleanup as compared to other Superfund sites throughout the nation. Most importantly, we are cleaning up Gowanus the right way, in a manner respectful of community needs, and responsible parties are shouldering the cost. I would like to thank all the EPA regional staff for their tireless work for the health and benefit of Brooklyn and New York.”

The RTA 1 remediation is the first of three areas of the Canal that were targeted for cleanup, while the restoration of the contaminated filled-in former 1st Street turning basin plans to serve as the primary wetlands area for mitigating or offsetting incremental encroachment into the Canal. This area is planned to be created by constructing deeper, and more robust bulkheads along the Canal as to allow dredging to take place at the required depths. The start of dredging required by the order was scheduled for September 2020, contingent on completion of bulkhead upgrades.

The following year, state officials introduced what was titled the Unified StormWater Rule (USWR), which if approved, would apply to construction within the city’s Gowanus area as part of its rezoning plan, as well as citywide.

The rule applies to projects on lots sized 20,000 square feet of more and would require developers to install a detention tank capable of capturing more than the 10-year rainfall. The rule also requires the tank to have a one-inch maximum diameter for the tank’s orifice, where water would exit. Ideally, the rule would help achieve greater water retention in the area and promote a slower release of stormwater into the Gowanus canal.

The proposal’s introduction is just a step in reducing combined sewer overflows, as the local Councilmember Brad Lander-supported Gowanus Neighborhood Justice Coalition has issued several other demands with the proposal, most notably the reduction of overflows into the canal to zero.

What’s Happening Now

Following years of research, proposals and orders, the EPA is now ordering the City of New York to construct and operate two CSO retention tanks to control contaminated solids discharges at the Gowanus Canal Superfund.

“This order will ensure that EPA’s cleanup efforts will not be undermined by uncontrolled combined sewer overflow discharges that have contributed to the chemical contamination of this waterway and impacted this community for the past century and a half,” said EPA Acting Regional Administrator Walter Mugdan. “To ensure the integrity of the dredging work, the retention tanks will control New York City’s sewer outfalls over the long-term.”

According to the order, the city is required to construct one 8 million-gallon tank, located at the head of the canal, and one 4 million-gallon tank, located at a New York City Department of Sanitation Salt Lot near the middle of the canal.

The order also requires the city to, among other things:

  • Ensure that developers comply with municipal stormwater regulations within the Gowanus area to prevent additional sewer volume from impairing the effectiveness of the CSO tanks;
  • Provide treatment for separated stormwater discharges;
  • Perform monitoring of sewer solids discharges to ensure protection of the dredging remedy;
  • Perform associated maintenance dredging, if determined by EPA to be necessary;
  • Construct a bulkhead on City-owned property to prepare for the second phase of dredging work; and
  • Adhere to an overall schedule for remaining tank design work and construction.

Regarding the contaminated sediment removed from the canal, the EPA reports that sediment containing high levels of liquid tar will be thermally treated at an offsite facility and disposed, while less-contaminated dredged sediment will be processed at an offsite facility into a beneficial use product, such as landfill cover. Certain areas of the native sediment, below the original canal bottom, that contain mobile liquid tar and are too deep to excavate, will be mixed with cement and solidified to prevent the migration of the tar into the water of the canal.

Following dredging and solidification of areas of the native sediment, construction of a multilayer cap in dredged areas will isolate and prevent migration of any dissolved chemicals remaining in the deep native sediments.


Tagged categories: Cleanup; Environmental Controls; Environmental Protection Agency (EPA); EPA; Infrastructure; NA; North America; Program/Project Management; Sewer systems; Stormwater; Tanks; Tanks; Tanks and vessels; Wastewater Plants; Water/Wastewater

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