Stormwater-Municipalities: What you need to know

Clean Water Act (CWA), 33 USC 1251 to 1387 and regulations at 40 CFR 122 and 40 CFR 124

National Pollutant Discharge Elimination System (NPDES): 33 USC 1342

Municipal separate storm sewer systems (MS4s): 40 CFR 122.26(b)(8)

Phase I MS4s: 55 Federal Register (FR) 47990 (11/16/90)

Permit applications: 40 CFR 122.26(d)

MS4 General Permit Remand Rule: 81 FR 89320 (12/9/2016)

Phase II MS4s: 64 FR 68722 (12/8/1999) and 40 CFR 122.32 to 122.37

Permit applications: 40 CFR 122.33

Waivers: 40 CFR 122.32(d)

Stormwater management programs: 40 CFR 122.34

Shared responsibilities: 40 CFR 122.35

U.S. Environmental Protection Agency (EPA) Office of Wastewater Management

EPA regional offices

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, ...