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MS4 Toolbox

According to the federal law commonly known as Stormwater Phase II, permits are required for stormwater discharges from Municipal Separate Storm Sewer Systems (MS4s) in urbanized areas and those additionally designated by the Department. Owners or operators of such MS4s must be authorized in accordance with the State Pollutant Discharge Elimination System (SPDES) General Permit for Stormwater Discharges from Municipal Separate Storm Sewer Systems.

This page contains information and reference material that will aid in the implementation of a Stormwater Management Program (SWMP) and provide assistance in meeting the permit and program requirements.

Program Assistance Documents

Stormwater Assessment and Design Modeling Tools (Appendix D) (PDF) (326 KB)-the document summarizes modeling tools that may be used to implement NYS stormwater design standard requirements and assess MS4 Stormwater Management Plans.

Local School District Decision Tree for MS4 Designation - information will help a school district evaluate its MS4 designation

Decision Tree for MS4 Waiver I (PDF) (16 KB)-the document will help MS4s evaluate eligibility for Waiver I.

Reference and Google Earth Maps

Google Earth map of Impaired Waterbodies Applicable to MS4s (requires Google Earth to be installed on your computer) --This map highlights impaired waterbodies that are applicable to the waiver eligibility criteria.

Owner/operators may use this reference tool to determine if their MS4 (system) discharges into an impaired waterbody listed on the Priority Waterbodies List (PWL) in order to make a determination about waiver eligibility. Discharge to the impaired waterbodies listed on this map does not necessarily subject the MS4 to the requirements for discharges to an impaired waterbody (Part III.B of GP-0-10-002). The owner/operator should review Appendix 2 of the general permit (GP-0-10-002) to confirm permit requirements, as well as, verify the information in this map with the NYS Waterbody Inventory/Priority Waterbodies List.

Google Earth map of Estimated Populations within Urbanized Areas for MS4s (requires Google Earth to be installed on your computer)--This is a map of the 2010 urbanized areas in NYS identified by the U.S. Census Bureau. The map includes estimated populations (based on the 2010 U.S. Census Data) within the 2010 urbanized areas for MS4s. The instructions, Decision Tree for MS4 Waiver Criteria (PDF) (966 KB) and the map may be used to to help MS4s to their eligibility for a waiver.

Visit DEC's Google Maps and Earth web page for general information about Google Earth and for instructions on how to download Google Earth.

Overview of the Minimum Control Measures (MCM)

The permit requires development of a Stormwater Management Program (SWMP) that includes the six required program components, or the six minimum control measures (MCMs).

1. Public Education and Outreach

This includes the distribution of educational materials and outreach activities that inform the public about the impacts of polluted stormwater runoff can have on water quality.

2. Public Participation/Involvement

Provide opportunities for citizens to participate in the development, implementation, review and revision of the stormwater management program. This includes publicizing public hearings and encouraging citizens participate in the stormwater management program process.

3. Illicit Discharge Detection and Elimination

Develop, implement and enforce a plan to detect and eliminate illicit discharges. This includes developing and maintaining a map of outfall locations and their receiving waterbodies, mapping the storm sewershed, prohibit illicit discharges through laws or ordinances, and inform the public about the hazards associated with illegal discharges and the improper disposal of waste.

4. Construction Site Runoff Control

Develop, implement and enforce an erosion and sediment control program for construction activities that disturb greater than or equal to one acre of land.

5. Post-construction Runoff Control

Develop, implement and enforce a plan that addresses stormwater runoff from new development and redevelopment projects and incorporates enforceable mechanisms. Applicable controls could include preventative actions (e.g., protecting sensitive areas) or the use of structural controls (e.g., grassed swales or porous pavement).

6. Pollution Prevention/Good Housekeeping

Develop and implement a program to prevent or reduce pollutant runoff from municipal operations. The program must include municipal staff training on pollution prevention measures and activities to reduce the amount of pollutants in stormwater (e.g., regular street sweeping, reduce the use of pesticides or street salt, or frequent cleaning of catch-basins).


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