What is an MS4?

Understanding Your Local Stormwater System

Our District’s stormwater systems play a key role in keeping our neighborhood safe and clean. These systems are called MS4s, short for Municipal Separate Storm Sewer Systems.

Unlike wastewater systems, MS4s are designed to carry only stormwater, not sewage. When it rains, water flows over streets, rooftops, and lawns, picking up debris, oil, and other pollutants. MS4s collect the runoff through drains and ditches, then carry it to local waterways like creeks, rivers, and lakes.

Because of this, it is critical to keep pollutants out of our drains to protect our environment and water supply.

Since MS4s discharge directly into rivers, lakes, and other U.S. waters, they must follow federal clean water regulations under the National Pollutant Discharge Elimination System. 

MS4s each develop a stormwater management program (SWMP) that helps them decide how to reduce the discharge of pollutants from its sewer system. 

SWMPs address the following topic areas: 

• Construction Site Runoff Control 

• Illicit Discharge Detection and Elimination 

• Pollution Prevention/Good Housekeeping 

• Post-Construction Runoff Control 

• Public Education and Outreach 

• Public Involvement/Participation 

• Program Effectiveness 

• Total Maximum Daily Loads

  
  

  

  
  

  For more information on MS4s click here: https://www.wcfmud.com/ms4