Governing Law and Regulations
U.S. Environmental Protection Agency (EPA) Office of Wastewater Management
EPA regional offices
Overview of Municipal Stormwater Discharge Regulation
Polluted stormwater runoff is commonly transported through municipal separate storm sewer systems (MS4s), from which it is often discharged untreated into local water bodies. To prevent such pollution, many MS4s, which are publicly owned or operated stormwater conveyance systems (including municipally owned storm sewer systems, systems operated by universities, local sewer districts, hospitals, military bases, prisons, etc.), are required to obtain coverage under a federal or state stormwater permit. See the national section STORMWATER—GENERAL for more information on the National Pollutant Discharge Elimination System (NPDES) stormwater permitting program.
The existing regulatory definition of an "MS4" is a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains):
- Owned or operated by a state, city, town, borough, county, parish, district, ...