The National Pollutant Discharge Elimination System (NPDES) seeks to end the discharge of all types of industrial, municipal, and agricultural waste from point sources into American waters. These point sources include industrial facilities and publicly owned treatment works (POTWs), as well as runoff from urban areas.

The NPDES was established by the Federal Water Pollution Control Act Amendments of 1972 and was expanded under the Water Quality Act of 1987. Most NPDES programs are administered by the states, under the direction of the Office of Wastewater Management of the U. S. Environmental Protection Agency (EPA).

Nationwide more than 400,000 facilities are required to obtain NPDES permits. NPDES permits usually license a facility to discharge a given amount of a pollutant under specific conditions, although permits also are granted for other types of waste disposal. Permits are required only for facilities that discharge directly...