Stormwater management is necessary to reduce combined sewer overflows (CSO) in combined sewer areas of the city and to reduce pollution in waterways in the municipal separate storm sewer system (MS4) areas of the city. New York City manages stormwater through “gray” infrastructure, including tanks and pipes, or “green” infrastructure (GI) practices which mimic the way the natural environment handles stormwater. GI practices typically manage stormwater via infiltration through soil and evaporation through vegetation. GI practices can also provide co-benefits such as reduced flooding, improved air quality, attractive streetscapes, traffic calming, and more.
Both public and private projects must comply with the Unified Stormwater Rule (USWR) requirements; review the USWR. The treatments described here can be utilized to comply with USWR requirements. Site-specific design for projects in the right-of-way subject to USWR must be reviewed and approved by DEP and DOT.
Using natural components, such as plants, stones, and soils, to mitigate the impacts of stormwater runoff is an ecologically responsible and economical technique to employ within the right-of-way. DEP, together with DOT, Parks, and DDC, developed standardized designs, specifications, siting criteria, and protocols to site GI practices within the right-of-way. These standards, along with other helpful guidance, can be found on DEP's Green Infrastructure web page. Please also refer to the NYC Stormwater Design Manual.
The following sections describe specific city-led strategies for managing stormwater in targeted areas that have the greatest need. These practices will be built and maintained by the City within areas of combined sewer (CSO) and separately sewered (MS4) areas. The City is continuing to build GI and will site the appropriate standard treatment based on visible site conditions (grading, location of catch basins, tributary drainage area, pedestrian volumes, built fabric context) as well as subsurface conditions (permeability, site contamination, water table, etc.). Additionally, city-led projects will install GI practices based on appropriate USWR requirements.
Private entities or community groups must follow USWR requirements as well and are encouraged to build standard green infrastructure treatments beyond those requirements where feasible. Treatments other than City standards are generally discouraged and will require more intensive review. Non-standard treatments will also require a maintenance agreement with DOT.
For information on existing and planned green infrastructure, review DEP’s interactive map.