NPDES/MS4

The NPDES permit program addresses water pollution by regulating point sources that discharge pollutants to waters of the United States.

Created in 1972 by the Clean Water Act, the NPDES permit program is authorized to state governments by EPA to perform many permitting, administrative, and enforcement aspects of the program.

The United States Environmental Protection Agency’s (EPA) National Pollutant Discharge Elimination System (NPDES) municipal stormwater program regulations were published in 1990. These regulations were implemented in two phases. In 1990, Phase I established requirements for stormwater discharges associated with 11 categories of industrial activity, and for large (population >250,000) and medium (population >100,000) municipal separate storm sewer systems (“MS4”). In Maryland, ten jurisdictions and the State Highway Administration (SHA) were required to apply for coverage under individual MS4 stormwater permits. 

In 1999, Phase II expanded the stormwater permitting program to smaller municipalities located in Census-defined urbanized areas as well as State and federal agencies. The Phase II program, which is described in 40 Code of Federal Regulations §122.34, relies on a general permit (vs. an individual). These permits require implementation of six minimum control measures:

1. Public education and outreach
2. Public involvement and participation
3. Illicit discharge detection and elimination
4. Construction site stormwater runoff control
5. Post construction stormwater management
6. Pollution prevention and good housekeeping