MS4 Operators are required to develop stormwater management programs aimed at reducing the discharge of pollutants affecting water quality under the final SPDES General Permit issued by the New York State Department of Environmental Conservation.

The final SPDES General Permit governs the functioning of stormwater management systems for some 500 MS4 operators across the state, including municipalities (e.g., cities, towns, villages, counties, state agencies, and other institutions.) The permit takes effect on January 3, 2024.

MS4s are small municipal separate stormwater sewer systems located within the boundaries of an urbanized area, as defined by the U.S. Census Bureau, and are regulated under the U.S. Environmental Protection Agency’s (EPA) Phase II Stormwater Rule. This stormwater map shows the automatically designated areas in New York identified by the U.S. Census Bureau.

The Phase II Rule requires MS4 Operators to develop a Stormwater Management Program (SWMP) which includes six minimum control measures that, when implemented together, are expected to reduce the discharge of pollutants to the maximum extent practicable. The overall goal of the program is to improve water quality and recreational use of waterways.

The six goals of the minimum control measures are:

1. Public Education and Outreach. The MS4 Operator must develop and implement an education and outreach program to increase public awareness of pollutant generating activities and behaviors. This requirement is designed to inform the public about the impacts of stormwater on water quality, the general sources of stormwater pollutants, and the steps the general public can take to reduce pollutants in stormwater runoff.
2. Public Participation/Involvement. The MS4 Operator must provide opportunities to involve the public in the development, review, and implementation of the SWMP. This MCM is designed to give the public the opportunity to include their opinions in the implementation of this SPDES general permit.
3. Illicit Discharge Detection and Elimination. The MS4 Operator must develop, implement, and enforce a program which systematically detects, tracks down, and eliminates illicit discharges to the MS4. This MCM is designed to manage the MS4 so it is not conveying pollutants associated with flows other than those directly attributable to stormwater runoff.
4. Construction Site Runoff Control. The MS4 Operator must develop, implement, and enforce a program to ensure construction sites are effectively controlled. This MCM is designed to prevent pollutants from construction-related activities, within the automatically and additionally designated areas, as well as promote the proper planning and installation of post-construction stormwater management practices.
5. Post-construction Runoff Control. The MS4 Operator must develop, implement, and enforce a program to ensure proper operation and maintenance of post construction SMPs for new or redeveloped sites. This MCM is designed to promote the long-term performance of post-construction SMPs in removing pollutants from stormwater runoff.
6. Pollution Prevention/Good Housekeeping. The MS4 Operator must develop and implement a pollution prevention and good housekeeping program for municipal facilities and municipal operations to minimize pollutant discharges. This MCM is designed to ensure the MS4 Operator's own activities do not contribute pollutants to surface waters of the state.

DEC’s Division of Water’s operative enforcement guidance document directs staff to take enforcement action against non-compliant MS4 Operators for a number of different categories of violations of the SPDES General Permit. These enforcement actions can result in the imposition of significant civil penalties and detailed compliance schedules.

MS4 Operators should be reviewing the requirements of the recently issued SPDES General Permit with qualified attorneys and technical consultants in order to update and align their compliance strategy with the requirements of the new permit.