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The New Year Brings a New Stormwater MS4 Permit

Authored by David Hanny | January 4, 2024

It has been more than 10 years since the New York State Department of Environmental Conservation (NYSDEC) Municipal Separate Storm Sewer Systems (MS4) Permit has undergone substantive change.  Several factors, including opposition by environmental groups and changes to the Federal USEPA stormwater rules, delayed the issuance of the NYSDEC MS4 Permit.  The time has come with the issuance of the new MS4 Permit (GP-0-24-001) that became effective on January 3, 2024.  The new MS4 Permit has significant changes that will affect the 500+ municipalities and non-traditional MS4s across New York.

A MS4 is a stormwater conveyance system owned or operated by the State, County, Town, City, Village, or other public body.  According to the Federal Clean Water Act, discharges of stormwater from a regulated MS4 must be permitted.  Municipalities are automatically designated as regulated MS4 based on population density and proximity to an urbanized area.  Additional non-traditional MS4s, including select Authorities, Districts, and transportation agencies are also required to comply with the Permit.  Regulated MS4s are required to develop (and now update) a comprehensive Stormwater Management Program Plan (SWMP).  The SWMP must meet the Permit’s 6 minimum control measures focusing on:

  • Public Education and Outreach
  • Public Involvement/Participation
  • Illicit Discharge Detection and Elimination (an illicit discharge is any non-stormwater contribution to the drainage system that may contain contaminants or pathogens)
  • Construction Site Stormwater Runoff Control
  • Post-Construction Stormwater Management, and
  • Pollution Prevention and Good Housekeeping.

Key changes for the new MS4 Permit enhance many of the prior requirements including:

  • Completion of a comprehensive stormwater system map that includes stormwater outfalls (discharge points), interconnections, storm-sewershed boundaries, monitoring locations, stormwater management practices (publicly and privately owned), municipal facilities, and stormwater infrastructure (pipes, open channels, flow direction, catch basins and manholes);
  • Advancing Enforcement Response Plans for municipalities to address violations within their MS4;
  • Increased public education and outreach measures to target focus areas, and to stress illicit discharge prevention;
  • Increased public involvement/participation requirements including making the SWMP and reporting documents available for annual public review and comment;
  • Public reporting of illicit discharges, additional inventorying of stormwater outfalls, prioritizing outfalls for increased inspection requirements, and development of an illicit discharge trackdown and elimination program.
  • Detailed inventories of active construction projects including new requirements for municipal inspections.
  • New inspection and maintenance requirements for both public and private permanent stormwater management practices (i.e. stormwater ponds and other drainage features);
  • Requirements for municipal facility inventories to assess the potential for pollutants to be generated from municipal operations (highway garages, parks, waste/recycling operations, salt storage facilities, municipal buildings, etc.);
  • Development of Stormwater Pollution Prevention Plans (SWPPPs), site assessments, inspections and monitoring for high-priority municipal operations;
  • Implementation of catch basin inspection programs.

The MS4 Permit includes several other new requirements, along with detailed implementation schedules that will represent the biggest change to municipal stormwater programs in the last decade.  The requirements and schedules for implementation vary based on MS4 status (newly designated MS4s vs. previously permitted MS4s); Traditional vs. Non-Traditional Operators; and classification of the receiving waters within your community (i.e. Enhanced Requirements for Impaired Waters and Watershed Improvement Requirements).

The first step for compliance is the submittal of an electronic Notice of Intent (eNOI) to the NYSDEC to obtain Permit coverage. To maintain compliance, previously permitted MS4s must submit an eNOI to the NYSDEC by February 27, 2024.  From there, the SWMP must be updated and implemented within the designated Permit timeframes.

For more information regarding the NYSDEC’s MS4 Permit, or questions regarding stormwater management issues, please contact our Vice President of Environmental, David Hanny, CPESC, CPSWQ, LEED AP at