NPDES MS4 Permitting

The National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) Program is mandated under the federal Clean Water Act.  In North Carolina, the EPA has delegated MS4 Program oversight to the Department of Environmental Quality (DEQ).  An NPDES MS4 permit is required for all MS4 owners and operators that are located in a U.S. Census Bureau designated Urbanized Area, or are designated under state rules [Ref. 15A NCAC 02H .0151].

NPDES MS4 permits require the implementation of a comprehensive stormwater management program to reduce pollutants in stormwater runoff to the Maximum Extent Practicable (MEP).  The MEP is based upon implementation of six Minimum Control Measures (MCMs) throughout the MS4s jurisdictional area:

  • Public Education & Outreach
  • Public Involvement & Participation
  • Illicit Discharge Detection & Elimination
  • Construction Site Runoff Controls
  • Post-Construction Site Runoff Controls
  • Pollution Prevention & Good Housekeeping for Municipal Operations

Some development activities occurring within the unincorporated area of a county (outside of permitted MS4 areas) are considered to be “urbanizing areas”, and are subject to the MS4 Post-Construction Site Runoff Control requirements [Ref. 15A NCAC 02H .1017].   These urbanizing areas lie within a U.S. Census designated Urbanized Area or the municipal sphere of influence around an MS4 [Ref. 15A NCAC 02H .1016].  In these areas, a stormwater post-construction permit is required for development that disturbs one acre or more of land.  The counties with urbanizing areas are called “Tipped Counties” because they are subject (or tipped in) to just the post-construction portion of the MS4 requirements, but they do not receive MS4 permits.  Post-Construction stormwater permitting for development in these areas may be performed by either the county, local government or DEQ:

The evolution of the NPDES MS4 Program from inception through 2011 is summarized in the MS4 Background Information Document.  This document was included with notification letters that DEQ sent to potential MS4s/candidate coverage areas in 2011.  In 2014, the cities of Statesville, Lexington and New Bern were also notified that they are subject to NPDES MS4 permitting. 

In 2018, the EPA began a statewide compliance and enforcement initiative in North Carolina.  In 2019, MS4 Permit compliance audits were incorporated into the NPDES MS4 Permitting Program as a routine component of the permit renewal process, and an MS4 Audit Schedule was instituted for renewal of 20% of the MS4 permits each year.   

    If you have questions, please contact Jeanette Powell, MS4 Program Coordinator, at 919-707-3620 or

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