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Delaware Department of Transportation

Stormwater Management

Stormwater Permit

Under the Clean Water Act and the National Pollutant Discharge Elimination System (NPDES) program, the U.S. Environmental Protection Agency (EPA) regulates the water quality of stormwater runoff that discharges into local waterways. Stormwater runoff is transported through municipal separate storm sewer systems, referred to as MS4. To prevent harmful pollutants from being washed or dumped into an MS4, the EPA requires an NPDES permit and a Stormwater Management Program (SWMP) that includes the following program elements:


  1. Construction Site Runoff Control
  2. Illicit Discharge Detection and Elimination
  3. Pollution Prevention/Good Housekeeping
  4. Post-Construction Runoff Control
  5. Public Education and Outreach
  6. Public Involvement/Participation
  7. Program Effectiveness
  8. Total Maximum Daily Loads

The MS4 program is divided into phases that are based on population. The 1990 Phase I regulations require that medium and large cities with a population of greater than 100,000 obtain NPDES permit coverage for stormwater discharges. The 1999 Phase II regulations require that small urban areas obtain similar NPDES permit coverage for stormwater discharges.

DelDOT has a Phase I Permit that covers all of New Castle County, and a Phase II Permit that covers the urbanized areas of Kent and Sussex Counties.

Phase I NPDES Permit Requirements

All of New Castle County was required by the U. S. Environmental Protection Agency (EPA) to obtain an NPDES permit under the Phase I NPDES regulations. New Castle County, 12 municipalities, and DelDOT are jointly responsible for implementing a Stormwater Pollution Prevention and Management Program under this permit.

Phase II NPDES Permit

DelDOT also has a Phase II NPDES permit for stormwater discharges in the urbanized areas of Kent and Sussex Counties. This includes areas of Dover in Kent County and Delmar in Sussex County.

Annual Reports

DelDOT is required to submit annual reports summarizing its Phase I and Phase II permit activities to the EPA and the Delaware Department of Natural Resources and Environmental Control (DNREC). Annual reports are available upon request.



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