NPDES construction permit requirements in South Carolina

Any construction project that disturbs one acre or more of land in South Carolina must obtain NPDES permit authorization before breaking ground. For most construction sites, that means coverage under the SCDHEC Construction General Permit. Understanding what the CGP requires, and what SCDHEC looks for when they visit a site, is the foundation for maintaining a compliant project from initial disturbance through final stabilization.

The one-acre threshold applies to the total disturbed area of a common plan of development or sale, not just the immediate construction footprint. A subdivision that disturbs land in phases still requires permit coverage if the total development plan disturbs one acre or more. Each individual lot disturbance does not need to meet the threshold independently.

Smaller sites (under one acre) may still require permit coverage if they are part of a larger common plan, or if the local jurisdiction has its own stormwater requirements that apply at a lower threshold. Anderson, Greenville, Charleston, and Columbia counties each have local programs that may impose requirements beyond the state CGP.

Coverage under the CGP requires the operator to develop and implement a Stormwater Pollution Prevention Plan before land disturbance begins. The SWPPP identifies all potential sources of stormwater pollution on the site, describes the BMPs installed to control that pollution, and establishes the inspection and maintenance schedule for those BMPs.

The BMPs required on a typical construction site include perimeter controls (silt fence or equivalent), inlet protection at all storm drain inlets, sediment basins or traps for larger drainage areas, stabilized construction entrances, and slope stabilization on all disturbed areas not under active construction. The specific BMPs required depend on site conditions, drainage patterns, and proximity to receiving waters.

The CGP sets a fixed inspection schedule: at minimum once every seven calendar days during active land disturbance, and within 24 hours of a rainfall event of 0.5 inches or greater. Both schedules run independently. A rain event inspection does not reset the seven-day clock.

In South Carolina, SWPPP inspections must be conducted by a Certified Erosion Prevention and Sediment Control Inspector (CEPSCI). The inspector must assess the condition of every installed BMP, document deficiencies, and record corrective actions taken. Corrective actions must be completed within seven calendar days of the inspection that identified the deficiency.

The inspection record must be kept on site or immediately accessible and produced for SCDHEC inspectors on request. SCDHEC conducts site inspections and looks specifically at whether the inspection record is current, whether BMPs are installed and functioning as designed, and whether corrective actions have been completed within the required timeframe.

SCDHEC field inspectors typically arrive unannounced. They will request the SWPPP and inspection record first. A site with failed BMPs and a complete, current inspection record that documents the deficiency and shows a corrective action in progress is in a better compliance position than a site with intact BMPs and an inspection record that is two weeks behind.

Common findings on SCDHEC site inspections include: silt fence that has been undercut or overtopped without a corrective action entry in the inspection record, sediment basins that have reached 50% capacity without a noted maintenance action, inlet protection that has been removed or damaged, and stabilization on areas that have been inactive for 14 or more days without temporary cover.

NPDES permit coverage continues until the site reaches final stabilization. Under the SCDHEC CGP, final stabilization means 70% permanent vegetative cover on all disturbed areas of the site, or permanent pavement, concrete, or other cover over all disturbed ground. The operator must submit a Notice of Termination to SCDHEC once the site achieves final stabilization.

Sites with phased stabilization, where sections of the site achieve final stabilization at different times, must maintain coverage and inspections for any section that has not yet reached the stabilization threshold. The inspection record should identify which sections are stabilized and which remain active.

Drone documentation covers every BMP location on a construction site in a single flight. The deliverable is organized for direct use in the SWPPP inspection record: GPS-tagged photos by BMP category and location, written condition summaries using the same pass/deficiency/corrective-action language that goes into the inspection log, and a timestamped flight record.

For GCs and environmental consultants managing multiple permitted sites across South Carolina, drone coverage makes the 7-day inspection schedule and 24-hour rain event requirement maintainable during peak construction season. SC Drone Services covers construction sites statewide. Upstate SC sites are handled by our Upstate partner, Upstate Drone Services.