As the new year begins, it’s that time again for municipalities to prepare the NYSDEC Municipal Separate Storm Sewer System (MS4) annual reports to meet the State’s June 1st deadline! This reporting requirement applies to municipalities covered by NYSDEC’s General Permit for Stormwater Discharges from Municipal Separate Storm Sewer Systems (GP-0-15-003).  Municipalities that are subject to the Multi Sector General Permit for Stormwater Discharges Associated with Industrial Activity (GP-0-17-004) must comply with different reporting requirements.

An MS4 is a collection of stormwater drainage systems that discharges to surface waters and is: 

  • Owned by a state, city, town, village or other public entity,
  • Designed or used to collect or convey stormwater, and
  • Not part of a sewage treatment plant or publicly owned treatment works (POTW).

The MS4 program requires municipalities to develop and implement a stormwater management program in order to reduce the amount of pollutants carried by stormwater during storm events. As stormwater moves across developed areas, it can pick up garbage, debris, fertilizers, leaves and even other pollutants from parking lots, yards, streets, roofs and other impermeable sources. Polluted stormwater runoff is commonly transported through drainage systems and can often result in discharges into local water bodies. In addition, the MS4 program strives to eliminate illicit discharges (non-permitted discharges such as waste oil, cement truck washdown water, etc.) to the stormwater system.  Many state manuals offer information on best management practices, maintenance schedules, and various checklists that can be used when performing maintenance and inspections.

The annual MS4 reporting period ends on March 9th each year. The annual reports document the steps taken by the municipality towards meeting the following MS4 minimum control measures (MCMs):


Educate the public on the importance of good stormwater management practices, potential Pollutants of Concern (POC), and local areas of concern.


Comply with the “State Open Meeting” Law and local public notice requirements and implement programs to promote community involvement in stormwater management to reduce the presence of POC’s.


Take action to identify and eliminate illicit discharges to the municipal stormwater drainage system.


Establish and enforce a local ordinance requiring implementation of a Storm Water Pollution Prevention Plan (SWPPP) to control runoff from development/construction projects disturbing one acre or more (or a smaller area, depending on the local requirements).


Monitor stormwater runoff from completed development projects within the municipal boundaries that are subject to MCM-4 in order to ensure that the discharge of pollutants is minimized.


Utilize pollution prevention/good housekeeping practices for municipal operations such as street and bridge maintenance, vehicle maintenance and other municipal functions.

The annual MS4 report must be received by the NYSDEC no later than the June 1st deadline each reporting year and be made available for public review, generally by posting on the municipality’s website.  Failure to submit the annual MS4 report may constitute a permit violation which can carry a civil penalty of $37,500 per day per violation. 

Walden works with municipalities to develop and implement MS4 programs to comply with the six (6) MCMs. Walden coordinates MS4 training programs, defines and improves standard operating procedures (SOPs), and conducts workshops on stormwater management, such as the Stormwater Conference we recently hosted. Walden also assists municipalities in stormwater outfall and facility inspections, GIS mapping as well as permit applications.

Act now to make sure your stormwater management program meets the MS4 general permit and reporting requirements.  If you are looking for assistance on the MS4 Annual Report, general MS4 compliance or other stormwater management challenges, please contact Walden Environmental Engineering.