Wake County, NC Environmental Rules: Stormwater Management (2026)

Wake County operates as a regulated Municipal Separate Storm Sewer System (MS4) under the federal Clean Water Act's NPDES Phase II program (40 CFR Part 122) because portions of the unincorporated county lie within a U.S. Census Bureau Urbanized Area centered on Raleigh. In North Carolina, EPA has delegated NPDES permitting to the state; permits for MS4s, industrial stormwater, and construction stormwater are issued by the North Carolina Department of Environmental Quality (NCDEQ), Division of Energy, Mineral and Land Resources (DEMLR). NCDEQ-DEMLR issues an NC NPDES MS4 General Permit that Phase II MS4s in NC — including Wake County — typically use as their coverage instrument.

Locally, the Wake County Watershed Management Division (within the Environmental Services / Planning, Development & Inspections side of County government) is the lead implementing agency for unincorporated Wake County. Watershed Management reviews development projects and issues permits to help prevent flooding, excessive erosion, and water pollution. It conducts site inspections during construction and after, verifying proper land grading and the function of stormwater control measures (SCMs). Its four core service areas are erosion control and sedimentation management, floodplain management, stormwater plan review and permitting, and water resources planning.

Development in unincorporated Wake County must comply with the Wake County Stormwater Design Manual, which sets the County's post-construction water-quality treatment, peak-flow control, and channel-protection standards. Construction activity that disturbs one acre or more (or less than one acre if part of a larger common plan of development) also requires coverage under the NC NPDES Construction General Permit (NCG010000) issued by NCDEQ-DEMLR, with the project's erosion and sediment control plan reviewed under N.C. Gen. Stat. § 113A-50 et seq., the NC Sedimentation Pollution Control Act. Wake County is one of the local-government implementers under the NC Sedimentation Pollution Control Act, meaning erosion and sediment control plan review and inspection for projects in unincorporated Wake County are performed at the County rather than directly by NCDEQ in most cases.

Inside the corporate limits of Wake County's municipalities — Raleigh, Cary, Apex, Garner, Holly Springs, Fuquay-Varina, Wake Forest, Knightdale, Wendell, Zebulon, Morrisville, and Rolesville — stormwater plan review, MS4 obligations, and post-construction standards are handled by the municipality under its own NCDEQ MS4 permit, with the municipality's own stormwater design standards layered on top of (or in lieu of) the County manual. The Wake County program described here therefore applies to unincorporated Wake County, not to areas inside city or town limits.

As an MS4, the County also implements the federal NPDES Phase II Illicit Discharge Detection and Elimination (IDDE) minimum control measure: non-stormwater discharges to the County storm sewer system (any discharge that is not composed entirely of stormwater) are prohibited, except for categorical allowable non-stormwater flows expressly listed in the NPDES Phase II rule (such as landscape irrigation, uncontaminated groundwater, and firefighting flows). Examples of prohibited illicit discharges include motor-vehicle fluids (oil, gasoline, antifreeze, transmission fluid), commercial car-wash wastewater that flows off-site, paint and paint-wash water, sanitary sewage and septage, industrial process wastewater, contaminated swimming-pool water, pet waste deliberately swept into the drain, and grass clippings or leaves blown or swept into the drain.