Office of Drain Commissioner

What is an MS4?

“Municipal Separate Storm Sewer System” refers to the collection of structures that gather stormwater in an area and discharge it to local rivers, streams, and lakes or infiltrate it back into the ground water supply.

Structures used in this system can vary from catch basins, roadside ditches, retention basins, underground pipes, and open-air drains.

MS4s are an important part of our current infrastructure as they help us manage and move stormwater into areas that can better absorb it.

We must closely monitor this system because the stormwater is untreated. While the water from inside our homes and businesses travels to the wastewater treatment plant in Kalamazoo, stormwater receives no treatment before it enters local rivers, streams and lakes.

To be able to own and operate MS4s, our County needs to meet certain requirements to be able to get a National Pollutant Discharge Elimination System (NPDES) permit.  This particular type of permit allows us to discharge stormwater into local surface waters. We have a Storm Water Management Plan in place in order to make sure the County is taking all necessary steps to keep our stormwater as clean as possible, and to make sure new developments and redevelopment projects properly manage the quantity of stormwater entering local waterbodies.

• EPA MS4 website
• EGLE MS4 resources
• Why you should care about stormwater video
• Check out other organizations in the area that we have partnered with to help promote and protect the clean waters of our county
• Michigan’s Storm Water program
• MS4 Compliance page
• Illicit discharge brochure