Louisville and Jefferson County Metropolitan Sewer District's (MSD) Water Quality-based Wet Weather Program Exemplifies EPA's Watershed Approach

The U.S. Environmental Protection Agency (EPA) realized in the late 1980s and early 1990s that to control pollutant discharges to the nation's waters, more would be required than just regulation of traditional point sources from municipal, commercial, and industrial wastewater treatment plants. Various EPA studies and assessments since then have indicated that urban wet weather discharges, whether they are from point or non-point sources, are one of the largest threats to water quality and public health. EPA has stated that urban wet weather discharges such as combined sewer overflows (CSOs), storm water runoff (MS4), sanitary sewer overflows (SSOs), and non-point source runoff must be addressed in a coordinated and comprehensive fashion consistent with a watershed approach. Louisville and Jefferson County Metropolitan Sewer District (MSD), about the same time as EPA, also believed that a watershed approach was necessary to make positive water quality improvements at the lowest costs across its 300-square-mile service area, which serves approximately 800,000 people.