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Municipal Stormwater

Program Updates

  • PRP and TMDL Plan Final Reports
    A Pollutant Reduction Plan (PRP) / TMDL Plan Final Report template has been posted to eLibrary. Permittees with PRP and/or TMDL Plan requirements must submit a completed PRP/TMDL Plan Final Report as an attachment to the first Annual MS4 Status Report that is due following completion of the 5th year of permit coverage.  DEP encourages use of the template to ensure the report is complete. Instructions for completing the PRP/TMDL Plan Final Report are included within the Annual Municipal Separate Storm Sewer System (MS4) Status Report Instructions.

  • PAG-13 General Permit for Discharges of Stormwater from Small Municipal Separate Storm Sewer Systems Extension
    As announced in the September 24, 2022 issue of the Pennsylvania Bulletin (52 Pa.B. 6107), the Department is extending for 24 months the availability of the current NPDES PAG-13 General Permit. This notice does not extend any deadlines that are contained in the PAG-13 General Permit, including the date by which implementation of Pollutant Reduction Plans (PRPs) and Pollutant Control Measures (PCMs) must be achieved. The existing PAG-13 in effect at this time will expire on March 15, 2023. With the 24-month extension, permittees who are operating under PAG-13 may continue to operate until March 15, 2025; the submission of a Notice of Intent (NOI) to remain covered under a renewed PAG-13 is anticipated by that date. More information on the PAG-13 can be found in the MS4 FAQ document (see FAQs # 78 – 82).
  • Waiver Application
    Permittees with waivers of PAG-13 coverage or individual permit coverage set to expire in 2023 must submit a waiver application (3800-PM-BCW0100E) along with the PAG-13 NOI or individual permit application at least 180 days prior to the expiration date of the waiver. Updated waiver application forms are available in eLibrary.
  • MS4 Frequently Asked Questions (MS4 FAQs) provides general information on the MS4 program as well as concepts relevant to Pollutant Reduction Plans (PRPs) and TMDL Plans. Periodic updates to the MS4 FAQ are published as needed.


Municipalities and other entities such as universities and prisons that meet certain standards must obtain NPDES permit coverage for discharges of stormwater from their municipal separate storm sewer systems (MS4s). In Pennsylvania, there are two Large MS4s, no Medium MS4s, and 1059 Small MS4s.

MS4s must apply for NPDES permit coverage or a waiver if they are located in an urbanized area as determined by the latest Decennial Census by the U.S. Census Bureau, or if they are designated as needing a permit by DEP. EPA has posted Urbanized Area Maps from the 2010 census data.

For NPDES permits issued after 2017, MS4s that discharge to surface waters impaired for certain pollutants or that discharge to waters in the Chesapeake Bay watershed were required to develop Pollutant Reduction Plans (PRPs) or TMDL Plans. See the PRP/TMDL Plans webpage for further information.

NPDES Permits

Small MS4s that are required by federal regulations to obtain NPDES permit coverage may, if eligible, apply for coverage under the NPDES General Permit for Stormwater Discharges from Small MS4s (PAG-13) (3800-PM-BCW0100) that is currently in effect. Small MS4s that are ineligible for PAG-13 General Permit coverage may apply for an individual permit (3800-PM-BPNPSM0200).

Permit coverage is generally for a 5-year term. To renew coverage for a new term, MS4 permittees must submit an individual permit application or a NOI to discharge under the statewide General Permit prior to the expiration date of coverage, as specified in the permit. The MS4 can, if it chooses, elect to apply for an individual NPDES permit in lieu of continued coverage under the reissued General Permit.

DEP has developed a reporting tool that can be used to search NPDES-permitted and waived MS4s in Pennsylvania.


DEP's regional offices inspect MS4s to determine if the MS4 is meeting its permit obligations. The inspections are documented on a MS4 inspection report. DEP also reviews the Annual Status Reports (3800-FM-BCW0491) submitted by MS4s to DEP.

Contact Us

For questions on MS4 NPDES permits and compliance in Pennsylvania, contact DEP’s Bureau of Clean Water (BCW) at or 717-787-5017.