MS4 STORMWATER DEFINED
- MS4 refers to Municipal Separate Storm Sewer System, a publicly owned system of conveyances (like pipes, curbs, and ditches) that collect stormwater and other drainage, not part of a combined sewer or a wastewater treatment plant.
- MS4 regulations are part of the EPA’s National Pollutant Discharge Elimination System (NPDES) to prevent pollutants from entering local water bodies.
- Permitted towns must implement a stormwater management program that includes six “minimum control measures,” such as public education, pollution prevention, and illicit discharge detection.

