What exactly is the Municipal Separate Storm Sewer System (MS4)?
The MS4 includes the conveyance or system of conveyances designed or used for collecting or conveying storm water that is not a combined sewer or part of a publicly owned treatment works. It includes roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains. These drainage systems typically dump their water (and any associated pollutants) directly into streams, bays, and/or the ocean.
