What is an MS4?
MS4 stands for Municipal Separate Storm Sewer System. An MS4 entity owns or operates a system for collecting and conveying stormwater. The purpose of the MS4 program is to maintain and benefit water quality in creeks, streams and waterways by reducing pollutants in stormwater runoff.
MS4 program is an unfunded federal mandate. It is the result of the 1987 amendments to the Clean Water Act (CWA), commonly referred to as the Water Quality Act of 1987. In these amendments, Congress mandated that the U.S. Environmental Protection Agency (U.S. EPA) address non-point source pollution associated with stormwater runoff.
In response to the Congressional action, EPA developed the MS4 program to permit the discharge of the stormwater from the MS4s. In essence, EPA defined urban stormwater (previously considered a non-point source) as a point source with numerous physical locations (or points) of discharge.
MS4s are permitted under the National Pollutant Discharge Elimination System (NPDES) program through either the U.S. EPA or the states; in Indiana, through the Indiana Department of Environmental Management (IDEM). MS4 permits are granted in five-year cycles at the end of which the permit must be renewed. The City of Bluffton filed it’s Notice of Intent to IDEM on April 2, 2023. This notifies IDEM of the intent to comply with the requirements of the MS4 General Permit to discharge stormwater run-off.