The purpose of the Municipal Separate Storm Sewer System (MS4) program is to maintain and enhance water quality in the United States.
Untreated or uncontrolled stormwater is the number one cause of impairment to our local waterways. Polluted run-off is often transported through municipal stormwater systems, where it is eventually discharged, untreated into water ways.
In 1987 an amendment to the clean Water Act resulted in the EPA addressing non-point source pollution in stormwater runoff. As runoff moves, it picks up and carries away natural and man-made pollutants, depositing them into lakes, rivers, streams, wetlands, costal water and even our underground sources of drinking water.
Arizona Department of Environmental Quality administers the MS4 program. Part of the program requires the City of El Mirage to have a permit to discharge stormwater into water ways. The Permit requires the City to design a Stormwater Management Plan that reduces pollutants with six elements termed “Minimum Control Measures”.