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To assist MS4s with understanding their obligations regarding impaired waters, DEP has prepared an MS4 Requirements Table. The Table consists of two parts – one for Municipal MS4s (PDF) and one for Non-Municipal MS4s (PDF). See also the MS4 Requirements Table Instructions (PDF) for understanding and using the Table and for methods to provide comments.

DEP has developed a supplement to the MS4 Requirements Table which is titled Pollutant Aggregation Suggestions for MS4 Requirements Table (PDF) (the Aggregation Table). The Aggregation Table helps permittees interpret the content of the MS4 Requirements Table by grouping the impaired surface waters into separate watersheds. See the Pollutant Aggregation Suggestions for MS4 Requirements Table Instructions (PDF) and FAQ (#17) for further explanation.

DEP has also developed a web-based GIS application that provides an improved visual representation of the information contained in the MS4 Requirements Table and the Aggregation Table.




  • Statewide MS4 Land Cover Estimates (PDF)
    This document contains percent impervious and pervious cover, both inside and outside of urbanized areas, for each municipality with an MS4 in PA, which may be used to develop pollutant loading estimates for Pollutant Reduction Plans and TMDL Plans.
  • PA Stormwater Manual DRAFT Compliance Spreadsheet (XLSX)
    Use of the Chesapeake Bay Performance Standards curves to calculate BMP pollutant load removals requires an estimate of the stormwater pre-to-post development volume increase. The pre-to-post volume increase is most easily calculated using this spreadsheet.


  • Quick Resource Guide for Winter Maintenance BMPs (PDF)
    Educational booklet from the Southwestern Pennsylvania Commission (SPC) Water Resource Center to provide information to municipalities on how to improve winter maintenance operations
  • The Latest Evolution of Stormwater (PA Township News March 2017)
    An informative article on the preparation of Pollutant Reduction Plans with commentary from local government officials, consultants and DEP.