2. Municipal Separate Storm Sewer System (MS4) and How it Affects Water Quality

The Municipal Separate Storm Sewer System (MS4) is a public-owned stormwater drainage system designed to convey stormwater.  MS4 structures include inlets, conveyance pipes, manholes, and outfall pipes.  The important point to remember is that the MS4 flows untreated to streams, lakes, rivers, and ponds.