Delaware CGP Reauthorization and NPDES Permit Update, February 2026

DNREC Sediment & Stormwater Listserve Update: February 2026 This month's topics:

1. Delaware CGP Reauthorization
2. Post-Construction Stormwater BMP Standards and Specifications Update

3. Link of the Month

4. Delaware Construction General Permit Reauthorization
   The Department of Natural Resources and Environmental Control (DNREC) Division of Watershed Stewardship Sediment and Stormwater Program has revised the Delaware National Pollutant Discharge Elimination System (NPDES) Construction General Permit (CGP). The Delaware NPDES CGP was publicly noticed on December 1, 2025. All comments have been considered, and changes are detailed in the Delaware NPDES CGP Fact Sheet. These documents are noticed in the February 2026 Register of Regulations and are available for review at https://dnrec.delaware.gov/watershed-stewardship/sediment-stormwater/. The reauthorized NPDES Construction General Permit will be effective on March 11, 2026. Additional information will be provided regarding the necessary steps that project owners must undertake to reauthorize existing Notices of Intent (NOIs) under the new permit.

5. Post-Construction Stormwater BMP Standards and Specifications Update
   The safety features portions of Sections 10.0 Detention Practices, 12.0 Constructed Wetlands, and 13.0 Wet Ponds of the Post-Construction Stormwater BMP Standards and Specifications have been revised to state, in non-bold language, that stormwater management systems with a permanent pool, and that are reasonably accessible to the public, should include barriers to restrict public access while not impeding the facility's function or restrict necessary maintenance access. The revised document is available on the Sediment and Stormwater Program website. Note: You may need to use ctrl-F5 or fn-F5 to refresh your browser's cache to see the new version if you have viewed this document recently.

6. Link of the Month
   DNREC staff recently came across a helpful design guide for determining Manning's N value for floodplains produced by NRCS. While older, this guide does provide photographic references associated with Manning's N value. GUIDE FOR SELECTING MANNING'S ROUGHNESS COEFFICIENTS FOR NATURAL CHANNELS AND FLOOD PLAINS If you have a suggestion for an interesting or helpful link, please forward to DNREC.Stormwater@delaware.gov.