New York City’s Municipal Separate Storm Sewer System (MS4) Stormwater Management Program is a multiagency effort led by the Department of Environmental Protection (DEP) to reduce pollution in stormwater runoff in the MS4 Area of NYC. This MS4 Map represents the known MS4 outfalls and drainage areas as of August 1, 2020 and provides additional data relevant to the MS4 Permit. The MS4 map only shows areas draining to the Municipal Separate Storm Sewer System. DEP also maintains combined sewer and sanitary sewer systems; these service area delineations are not represented on this map. More information about the MS4 Stormwater Management Program is available at www.nyc.gov/dep/ms4

Citywide Outfalls

The dataset represents the locations of combined sewer overflow (CSOs) outfall locations in NYS. Combined sewers collect stormwater runoff, domestic sewage and industrial wastewater in the same pipe and bring it to a wastewater treatment facility. They are designed to overflow during heavy rain events, causing excess water to be discharged directly into a waterbody. The public is advised to avoid contact while recreating within waterbodies with a CSO during or following rain or snowmelt. There are about 800 CSO outfalls in New York State. This is a decrease from about 1,300 in 1993, due to CSO abatements completed by the permittees.Service is updated annually and was last updated 11/6/2024.For more information or to download layer see https://dec.ny.gov/environmental-protection/water/water-quality/combined-sewer-overflow1. The NYS DEC asks to be credited in derived products. 2. Secondary Distribution of the data is not allowed. 3. Any documentation provided is an integral part of the data set. Failure to use the documentation in conjunction with the digital data constitutes misuse of the data. 4. Although every effort has been made to ensure the accuracy of information, errors may be reflected in the data supplied. The user must be aware of data conditions and bear responsibility for the appropriate use of the information with respect to possible errors, original map scale, collection methodology, currency of data, and other conditions.

The information submitted is in accordance with New York State Department of Environmental Conservation's (NYSDEC's) guidance, "Outfall and System Mapping For Illicit Discharge Detection and Elimination (IDDE) in NY (August 2005). Most outfalls were mapped using Trimble GeoXT GPS units, capable of sub-meter accuracy, with either post-processing or real-time corrections. New York State Department of Transportation (NYSDOT) record plans were used to determine outfall locations when they occurred in closed systems or were inaccessible. All of NYSDOT mapped outfalls meet the NYSDEC 45-meter positional accuracy requirement as per 6 NYCRR Part 750. For further information, see Data Quality Positional Accuracy statement. NYSDOT Stormwater Outfalls along or near State Highways and NYSDOT facilities in designated urban areas. Mapping is required by the NYSDEC General Permit for Stormwater Discharges from Municipal Separate Storm Sewer Systems (MS4s), GP-02-02. Publication Date: April 4, 2008, updated as needed. The original point dataset was clipped to the Mohawk watershed counties. The projection remains in UTM 18N, NAD 83.View Dataset on the Gateway