In 1972, the U.S. Congress passed the Clean Water Act (CWA). The CWA was enacted to protect and improve the quality of the waters of the United States. Toward this end, the Clean Water Act prohibits the discharge of any pollutants to waters of the United States unless that discharge is authorized by a National Pollutant Discharge Elimination System (NPDES) permit.
Initially, the NPDES program focused on reducing pollutants in discharges of industrial process wastewater and wastewater discharges from publicly-owned treatment works (POTWs). Implementation of pollution control measures have demonstrated that diffuse sources, or nonpoint sources, also contribute to water quality degradation.
In 1990, the U.S. Environmental Protection Agency (EPA) published regulations governing storm water discharges under the NPDES storm water program of the CWA. These regulations established requirements for permitting storm water discharges associated with certain types of industrial activities, construction activities, and municipal areas with a certain population level.
In 1997, EPA issued a municipal separate storm sewer system (MS4) permit to Pima County. In order to ensure that the quality of storm water discharges from the County’s municipal storm sewer system is managed to the maximum extent practicable, Pima County has developed a Storm Water Management Program. The program includes best management practices to minimize storm water pollution, public education and business outreach, and storm water runoff monitoring. The County’s storm water permit area encompasses the urbanized, unincorporated portion of Pima County directly surrounding the City of Tucson (Tucson). Tucson was issued a separate storm water discharge permit at about the same time as the County.
On December 5, 2002, Arizona received authorization from EPA to implement the NPDES permit program on the state level. The state-specific program is called the Arizona Pollutant Discharge Elimination System (AZPDES) permit program. The Arizona Department of Environmental Quality (ADEQ) website contains background information on Arizona’s storm water program, which regulates industrial, construction, and municipal storm water discharges.
