NPDES MS4 Permit

Stormwater regulations adopted by the Environmental Protection Agency (EPA) in November 1990 led to the 1993 issue of a National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS4) Discharge Permit to Prince George's County, Maryland. This permit is administered by the State of Maryland's Department of the Environment.

County Permit
According to 40 Code of Federal Regulations (CFR) ┬ž122.26, owners of storm sewer systems serving populations greater than 100,000 were required to apply for Phase I NPDES MS4 permit coverage. The County permit has been renewed 3 times, in 1999, 2004 and 2014. The latest permit renewal outlined more stringent requirements than those imposed in previous permit renewals.

Permit Conditions
Previous permit conditions mandated the County to:
  • Develop geographic information system mapping on a watershed basis.
  • Develop management programs to address runoff from new and significant redevelopment, construction site discharges, illegal storm drain system connections, and road maintenance operations.
  • Maintain legal authority to control storm drain system pollution.
  • Provide education and outreach regarding stormwater pollution.
  • Use a combination of chemical, physical and biological monitoring to characterize urban stormwater.

The new permit increased the impervious area treatment goals from 10% to 20% of the total impervious area that the County is regulating. Additionally, the 2014 permit augmented the permit conditions to include:

  • Litter and trash reduction strategies.
  • Implementation of environmental site design (ESD) technologies for new and redevelopment projects to the maximum extent practicable (MEP).
  • Development of watershed restoration plans to address stormwater waste load allocations (WLA) established under the EPA approved total maximum daily loads (TMDL) estimates.

The overall goals of the County's five-year NPDES municipal stormwater permit program are to control stormwater pollutant discharges by implementing Best Management Practices (BMP) and programs, show a reduction of pollutants pursuant to EPA approved TMDLs and improve water quality. The County evaluates and documents progress toward improving water quality within its jurisdiction on an annual basis and submits a report to MDE. To view this report as well as other reports the County has developed, see the links provided below.

  • Select the following link to access the latest NPDES MS4 annual report that has been submitted to MDE (2015 NPDES MS4 Annual Report).
  • Select the following link to access the Watershed Restoration Plans and supporting documents that were developed to show the County's strategy to improve water quality (Watershed Restoration Plans and supporting documents), please note that you will be taken to an external site that is not managed by the County).