An MS4 is a municipal separate storm sewer system that conveys stormwater from inlet to outfall. This may include roads with drainage systems, municipal streets, catch basins, curbs & gutters, ditches, man-made channels and storm drains.
The City of Forest Lake is designated as an MS4. This mandate required the City of Forest Lake to obtain an NPDES permit and prepare a SWPPP by February 2007. In spring 2021, the City of Forest Lake renewed its MS4 permit and will modify their stormwater ordinance and SWPPP to meet the requirements of the new MS4 Permit over the next 12 months.