Stormwater Management

WHAT IS A MS4? There are approximately 7,250 permitted Municipal Separate Storm Sewer Systems (MS4s), that exist nationwide, operating under a National Pollutant Discharge Elimination System (NPDES) MS4 permit. The NPDES MS4 permit requires, permittees to develop and implement a comprehensive Storm Water Management Program (SWMP) that must include pollution prevention measures, treatment or removal techniques, monitoring, use of legal authority, and other appropriate measures to control the quality of storm water discharged to the storm drains and thence to waters of the United States.

See for more details.

An illicit discharge is anything that is not composed entirely of stormwater. Examples of illicit discharges include yard debris, household cleaners, oil, pesticides, and paint. To report an illicit discharge, contact Inframark at

For more information about the District's MS4 Plan