Construction Advisory for Gowanus Canal Combined Sewer Overflow Storage Tanks

August 1, 2024

The Department of Environmental Protection (DEP) is making great progress constructing the underground storage tanks that will capture eight million gallons of sewage and rainwater that would otherwise overflow into the Gowanus Canal during rainstorms. This important project complements USEPA's on-going Superfund dredging project and will significantly improve the health of the neighborhood. DEP's project will also create new public waterfront open space and amenities for the Gowanus community. The construction site is located along the eastern side of the Canal, bounded by Butler Street, Nevins Street and Degraw Street.

DEP broke ground on the project in March 2023. On July 25, 2024, DEP's construction crews completed the deep underground perimeter wall that will support the removal of soil necessary to build the tanks. This is a major project milestone. The next two months will be a period of transition, as crews take apart the large construction equipment and remove it from the site and build a groundwater treatment system for use in the next phase of work beginning in October.

During this transition period, there will be no excavation of soil, but contractors will be injecting grout into the ground for added groundwater control. Work hours will continue as Monday through Saturday, 6:00 AM to 2:00 AM, but night shift activities will be significantly ramped down during this transition. Community air monitoring (described below) will continue during all working hours.

In October 2024, work is scheduled to begin on the excavation of soil within the perimeter underground wall to make way for the eight-million-gallon tank. That excavation will extend only 60 feet in depth-much shallower than the excavation for the underground perimeter wall. DEP expects to encounter much less contaminated soil due to the shallow nature of the excavation. The community air monitoring will remain active during all working hours, and the odor mitigation measures (described below) will resume during the next phase of excavation.

Working with the US EPA, DEP implemented a robust community air monitoring program (CAMP) to monitor emissions and protect residents and construction crews while DEP undertakes this important project. The monitoring program includes eight automatic monitoring stations around the perimeter of the construction site that operate continuously during working hours to monitor air quality for particulate matter and chemicals, including petroleum. The CAMP data, which is updated daily, is available on DEP's website.

To control nuisance odors that arise during periods of excavation, excavated soils are sprayed with non-toxic, odor neutralizing foam and stockpiled soil is foamed and/or tarped during times of inactive construction. A misting system is also used to neutralize and mask odors. The mist is primarily water with a non-toxic odor neutralizing agent and added fragrance. During periods of excavation, DEP performs at least six daily odor inspections (three on the day shift and three on the night shift) of the site's perimeter and the surrounding community. The tank site is one of several potential sources of odors in the community. Additional inspections are conducted immediately after receipt of any community odor complaints.