The Stormwater Program manages activities that potentially result in polluted runoff from urban areas discharging into the New York City (NYC) water supply in both the east-of-Hudson (EOH) and west-of-Hudson (WOH) watersheds. The pollutants of concern in stormwater primarily consist of fine sediment (turbidity), phosphorus and nitrogen (nutrients), and microbial pathogens. Other pollutants in stormwater runoff include oil and grease, floatables, dissolved metals, and toxic organics (Debo and Reese, 2002; Smullen et al., 1999).
Implementation of the Stormwater Program of the Watershed Protection Program predates issuance of the 1997 filtration avoidance determination (FAD) because federal, state, and New York City Department of Environmental Protection (NYC DEP) stormwater regulations were promulgated in the early 1990s to control pollutants discharging from municipal drainage systems. These regulations require treatment of stormwater runoff from new urban development as well as sediment-laden runoff from disturbed land at construction sites. The Stormwater Program is a mature program consisting of (1) the mandatory federal/state stormwater regulations for new development, and (2) the Stormwater Retrofit Program specifically targeting NYC’s water supply watershed as obligated by the FAD.
PROGRAM DESCRIPTION
Stormwater treatment is accomplished through the installation of stormwater control measures (SCMs) such as detention, retention, and bioretention ponds and grassy swales, as well as more recent green infrastructure, which incorporates SCMs into landscaped urban developments including rain gardens and green roofs (NRC, 2009; NYC DEP, 2010a). During construction activities, erosion prevention and sediment control (EPSC) devices such as silt fences, rock check dams, and hay are commonly used to treat construction site runoff. Acceptable SCMs and EPSC devices are found in standard design guidance documents provided by the New York State Department of Environmental Conservation (NYS DEC), such as the New York State Stormwater Management Design Manual (NYS DEC, 2015) and New York State Standards and Specifications for Erosion and Sediment Control (Blue Book, NYS DEC, 2016). In addition, NYC DEP has created a similar design document for standard practices, Guidelines for the Design and Construction of Stormwater Management Systems (NYC DEP, 2012). Estimated reductions in pollutants per SCM or EPSC device are based on published review data summarized in the National Pollutant Removal Database for Stormwater Treatment Practices (Winer, 2000, 2007) and the International Stormwater BMP Database (Clary et al., 2017).