What Is an MS4?A Municipal Separate Storm Sewer System (MS4) is a network of structures designed to collect and manage stormwater. The system helps direct stormwater to local rivers, streams, lakes, o

What Is an MS4?A Municipal Separate Storm Sewer System (MS4) is a network of structures designed to collect and manage stormwater. The system helps direct stormwater to local rivers, streams, lakes, or back into the groundwater supply, supporting proper drainage and reducing flooding.Components of an MS4:Catch basinsRoadside ditchesRetention basinsUnderground pipesOpen-air drainsMS4s play a vital role in stormwater management by moving water into areas that can better absorb it. However, because stormwater in an MS4 is untreated, it can carry pollutants directly into local water bodies. Unlike wastewater from homes and businesses, which is treated at the Kalamazoo wastewater treatment plant, stormwater flows untreated into rivers, streams, and lakes.Monitoring and PermitsTo operate an MS4, Kalamazoo County must meet specific requirements under the National Pollutant Discharge Elimination System (NPDES). This permit allows the discharge of stormwater into local surface waters.The County follows a Stormwater Management Plan (PDF) to:Ensure stormwater is as clean as possible before entering local waterbodies.Properly manage stormwater quantity in new developments and redevelopment projects.By closely monitoring the MS4 system and following these guidelines, the County protects water quality and helps maintain a sustainable environment.EPA MS4 websiteEGLE MS4 resourcesWhy You Should Care About Stormwater videoCheck out other organizations in the area that we have partnered with to help promote and protect the clean waters of our countyMichigan's Storm Water ProgramMS4 Compliance pageIllicit Discharge Brochure (PDF)