On May 21, 2013, the Minnesota Pollution Control Agency’s Citizens’ Board unanimously approved reissuance of the Municipal Separate Storm Sewer System (MS4) permit, a general NPDES permit that regulates stormwater discharge from Minnesota counties, cities, townships and other government entities in urbanized areas. The new permit is designed to provide greater protection of Minnesota waters than its 2006 predecessor, and will require regulated entities to update their existing stormwater programs to address the new requirements. The permit and a summary of the new requirements are available on MPCA’s website. The following excerpt outlines the purpose of the MS4 program:

According to the 1996 National Water Quality Inventory, stormwater runoff is a leading source of water pollution. Stormwater runoff can harm surface waters such as rivers, lakes, and streams which in turn cause or contribute to water quality standards being exceeded.

Stormwater runoff can change natural hydrologic patterns, accelerate stream flows, destroy aquatic habitats, and elevate pollutant concentrations and loadings. Development substantially increases impervious surfaces thereby increasing runoff from city streets, driveways, parking lots, and sidewalks, on which pollutants from human activities settle.

Common pollutants in runoff include pesticides, fertilizers, oils, metals, pathogens, salt, sediment, litter and other debris are transported via stormwater and discharged – untreated – to water resources through storm sewer systems.

The Stormwater Program for MS4s is designed to reduce the amount of sediment and pollution that enters surface and ground water from storm sewer systems to the maximum extent practicable. Stormwater discharges associated with MS4s are regulated through the use of National Pollutant Discharge Elimination System (NPDES) permits. NPDES permits are legal documents. Through this permit, the owner or operator is required to develop a stormwater pollution prevention program (SWPPP) that incorporates best management practices (BMPs) applicable to their MS4.

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