Municipal Separate Storm Sewer Systems     

Polluted stormwater runoff is commonly transported through Municipal Separate Storm Sewer Systems (MS4), from which it is often discharged untreated into local water bodies. To prevent harmful pollutants from being washed or dumped into an MS4, operators must obtain a National Pollution Discharge Elimination System (NPDES) permit and develop a stormwater management program.

An MS4 is a conveyance or system of conveyances that is:

  • Owned by a state, city, town, village, or other public entity that discharges to waters of the U.S.;
  • Designed or used to collect or convey stormwater (including storm drains, pipes, ditches, etc.);
  • Not a combined sewer; andNot part of a Publicly Owned Treatment Works (sewage treatment plant).

(source: U.S. Environmental Protection Agency)

Check back for updates.For more information, contact District 2 Public Relations Specialist Jeff Goetz at (307) 473-3303.