What is stormwater?
Stormwater is rainfall or melted snow that runs off and is often routed to impervious surfaces, such as roadways, rooftops, sidewalks, and parking lots. Impervious, or hard surfaces, prevent the stormwater from naturally soaking into the ground where the soil would filter out pollutants. As it flows, stormwater picks up pollutants from these surfaces. Common pollutants that are picked up include: oil and grease, sediment, nutrients, salt and pet waste.
What is a Municipal Separate Storm Sewer System?
An MS4 is a conveyance or system of conveyances (roads with drainage systems, municipal streets, catch basins, curbs and gutters, ditches, man-made channels, storm drains, etc.) that is also owned or operated by a public entity (which can include cities, townships, counties, military bases, hospitals, prison complexes, highway departments, universities, etc.). MnDOT MS4 resources, NPDES permits and contacts.