Stormwater

What is Stormwater?

Stormwater is rain or snowmelt than runs off of surfaces to waterways or waterbodies. As the water runs off the surface it can pick up pesticides, fertilizers, oils, metals, pathogens, salt, sediment, trash, and other pollutants making stormwater runoff is a leading source of water pollution. 

What is an MS4?

A municipal separate storm sewer system (MS4) is a conveyance or system of conveyances (roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, storm drains, etc.) that is owned or operated by a public entity (which can include cities, townships, counties, military bases, hospitals, prison complexes, highway departments, universities, sewer districts, etc.). MS4s in Minnesota are regulated by the Minnesota Pollution Control Agency and must satisfy the requirements of the MS4 general permit. The MS4 general permit is designed to reduce the amount of sediment and other pollutants entering state waters from stormwater systems. Local public entities that own or operate a MS4 play a key role in preventing stormwater runoff from harming Minnesota’s valuable water resources. Entities regulated by the MS4 general permit must develop a stormwater pollution prevention program and adopt best practices. The Washington County Stormwater Pollution Prevention Program (SWPPP) can be downloaded here. The SWPPP is required to have six minimum control measures: public education and outreach, public participation/involvement, illicit discharge detection and elimination, construction site stormwater control, post-construction stormwater management, and pollution prevention/good housekeeping. To provide comments or feedback on the SWPPP please click here.

What measures can I take to prevent stormwater pollution?


Washington County’s MS4 is managed by the Department of Public Works.