Municipal separate stormwater sewer systems (MS4s) that are covered by the NYS Department of Environmental Conservation (NYS DEC) General Permit for Stormwater Discharges from Municipal Separate Storm Sewer Systems (GP-0-15-003) are subject to annual reporting requirements. The June 1st MS4 annual reporting deadline for the March 10, 2020 to March 9, 2021 reporting year is approaching. Failure to submit the report to the NYS DEC office by the designated date will result in a permit violation. Due to COVID-19, the DEC is encouraging electronic submissions of the MS4 Annual Report at

The MS4 annual report summarizes the activities performed throughout the reporting period and includes the status of compliance with the General Permit conditions, an assessment of the progress made towards achieving the goal of reducing pollutant discharge to the maximum extent practicable, and the identified measurable goals for each of the minimum control measures (MCMs).


The MS4 program was developed as part of the National Pollutant Discharge Elimination System (NPDES) Storm Water Program to address sources of storm water runoff that had the ability to negatively impact water quality.  The NYS DEC is responsible for administering New York’s MS4 program as part of the State Pollutant Discharge Elimination System (SPDES).

The goal of the MS4 program is to improve water quality and recreational use. The program is implemented by two phases of EPA’s Stormwater Rule:

  • Phase I: Regulates large MS4s serving populations of 100,000 or more, industrial activity and construction that disturbs 5 or more acres.  MS4s regulated under EPA’s Phase I Stormwater Rule are not covered by NYS DEC’s General Permit.
  • Phase II: Regulates small MS4s that are located within the boundaries of a Census Bureau defined “urbanized area” and construction sites disturbing 1 to 5 acres.  These small MS4s are covered by NYS DEC’s General Permit.

The MS4 General Permit requires regulated small MS4s to develop and implement a stormwater management program (SWMP) to reduce the number of pollutants carried by stormwater during storm events to waterbodies to the maximum extent practicable (MEP). MEP is a technology-based standard established by Congress in the Clean Water Act. The General Permit requires small MS4s to increase the awareness of direct links between land activities, rainfall-runoff, storm drains, and their local water resources. These requirements include educating the community on the pollution potential of common activities. It is important to note that MS4s should not be confused with combined sewer systems since MS4s use separate pipes and are not designed to properly handle polluted water.


In order for a small MS4 operator to obtain coverage under the SPDES General Permit, they must submit an accurate Notice of Intent (NOI) application form to the NYS DEC. The NOI includes an initial outline of planned management practices and identifies the goals to annually assess progress toward implementing an appropriate stormwater management plan.


The NYS DEC has created multiple actions and management practices for different management controls but encourages small MS4s to develop stormwater management programs to best fit local conditions and pollutants. The SWMP shall address the six MCMs listed below:

  1. Public Education and Outreach
  2. Public Involvement/Participation
  3. Illicit Discharge Detection and Elimination
  4. Construction Site Stormwater Runoff Control
  5. Post-Construction Stormwater Runoff Control
  6. Pollution Prevention/Good Housekeeping for Municipal Operations

The main goals of these MCMs are to promote awareness and good practices in order to reduce discharges of anything other than rain water or snow melt to stormwater collection systems.  Please refer to Walden’s blog “Attention MS4’s: Plan Ahead for the June 1st Annual Report Deadline” for additional details on the MCMs.

For localities seeking help regarding compliance with the state and federal stormwater management requirements, the New York State Department of Environmental Conservation and Department of State issued a Stormwater Management Guidance Manual for Local Officials that deals with developing and implementing local stormwater management programs.  


Walden’s stormwater experts can help you prepare the annual MS4 report and address any stormwater issues to help you maintain compliance with the MS4 General Permit requirements.  Call us today at (516) 559-6976 to discuss your stormwater compliance needs.