MS4 Program

All operators of municipal separate storm sewer systems (MS4s) are responsible for development and implementation of stormwater management plans.

MS4 Program

The stormwater requirements of the federal Clean Water Act are administered under the Pennsylvania Department of Environmental Protection’s Municipal Separate Storm Sewer (MS4) Program. In December 2002, DEP issued a General Permit (“PAG-13”) for use by MS4s that fall under the National Pollutant Discharge Elimination System (NPDES) Phase II program, requiring the implementation of a stormwater management program for minimizing the impacts from runoff. Several extensions have occurred since the expiry of the initial 5 year permit period, the latest of which extended the permit expiration date to midnight on June 11, 2013.

After much debate and extensive delays, the Pennsylvania Department of Environmental Protection released its new permit requirements in late 2011, so all MS4s are working to understand how they are affected and prepare their applications before they are due. For more information, follow MS4 in the Blog.

Under the MS4 Program, permittees are required to incorporate the following six elements (known as minimum control measures, or MCMs) into their stormwater management programs:

  • Public education and outreach
  • Public involvement and participation
  • Illicit discharge detection and elimination
  • Construction site runoff control
  • Post-construction stormwater management in new development and redevelopment
  • Pollution prevention and good housekeeping for municipal operations and maintenance

Each MCM has a series of suggested best management practices (BMPs) associated with it to guide permit holders in program development, tracking, and reporting.

Pennsylvania has close to 1,000 jurisdictions that are considered small municipal seperate stormwater systems (MS4s) and therefore require Phase II permits. To download DEP's list of MS4s, click on the following link:

Municipal Separate Storm Sewer Systems (MS4s) within Urbanized Areas in Pennsylvania


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National Pollutant Discharge Elimination System