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Municipal Separate Storm Sewer Systems or MS4

The MS4 is:
1. The Federal Environmental Protection Agency's effort to keep streams and oceans clean; and
2. Part of the National Pollutant Discharge Environmental System (NPDES).
Polluted stormwater runoff is a leading cause of impairment to the nearly 40 percent of surveyed U.S. water bodies which do not meet water quality standards. Over land or via storm sewer systems, polluted runoff is discharged, often untreated, directly into local water bodies. When left uncontrolled, this water pollution can result in the destruction of fish, wildlife, and aquatic life habitats; a loss in aesthetic value; and threats to public health due to contaminated food, drinking water supplies, and recreational waterways. Mandated by Congress under the Clean Water Act, the NPDES Stormwater Program is a comprehensive two-phased national program for addressing the non-agricultural sources of stormwater discharges which adversely affect the quality of our nation's waters.
To learn more about NPDES in relation to the City and County of Honolulu and Mililani Waena Elementary see below: