New Castle County was required by the Environmental Protection Agency (EPA) to obtain an NPDES permit under the Phase I NPDES regulations. Since the Delaware Department of Transportation (DelDOT) owned most of the stormwater outfalls in New Castle County, DelDOT and the County agreed to be co-applicants for the NPDES permit. 12 of the 13 municipalities (the City of Newark being the exception) in the county also joined in. The stormwater regulations are enforced by the Delaware Department of Natural Resources and Environmental Contol (DNREC), which has been delegated the NPDES authority for Delaware by EPA. Under the regulations, New Castle County must develop and implement programs and procedures that reduce the contribution of pollutants to the municipal separate storm sewer system (MS4) to the maximum extent practicable. The definition of “pollutants” goes beyond the usual toxic and hazardous materials to include any non-stormwater material.

New Castle County and DelDOT are responsible for implementation of a Stormwater Pollution Prevention and Management Program covering the following areas:

   • Structural controls and operations
   • Areas of new development & significant redevelopment
   • Roadways
   • Flood control projects
   • Pesticides, herbicides, and fertilizer application
   • Illicit discharges and improper disposal
   • Spill prevention and response
   • Industrial & high risk runoff
   • Construction site runoff
   • Public education
   • Monitoring programs

New Castle County and DelDOT are also responsible to prepare and submit to the EPA and DNREC an annual report on the status of their NPDES program.