Horry County, SC Stormwater Regulations

Horry County operates under a Phase II Small MS4 NPDES permit, with enforcement driven by rapid development in the Myrtle Beach metro area. The county manages stormwater through its Stormwater Management department. State penalties from SCDES reach $10,000 per day, and the county enforces local ordinances covering construction runoff and post-construction BMP maintenance.

Primary source: South Carolina Department of Environmental Services (SCDES)

Permit Requirements

Horry County follows the state NPDES Construction General Permit (SCR100000) requirement for land disturbance of one acre or more. Given the volume of construction in the Myrtle Beach metro area, SCDES processes a high number of permit applications for Horry County projects annually.

The county reviews stormwater management plans as part of its development approval process. New subdivisions, commercial centers, and resort developments must demonstrate adequate stormwater management before receiving construction approval. Post-construction BMPs must be designed to SCDES standards and maintain water quality and peak flow control.

OCRM permits are required for development within the coastal critical area, which includes beachfront properties, tidal creeks, and marsh areas along the Grand Strand. The City of Myrtle Beach and other beachfront municipalities may have additional permitting requirements for construction near the beach.

Inspection Obligations

Construction site inspections are required at least weekly and within 24 hours of rainfall events producing 0.5 inches or more. With the volume of active construction in Horry County, both self-inspections by permit holders and oversight inspections by county staff occur frequently.

Post-construction BMPs must be inspected annually by the property owner or responsible party. Horry County tracks permitted stormwater facilities and conducts its own compliance inspections. The county's stormwater department focuses on facilities that have been flagged through complaints, previous violations, or age-based risk assessments.

The county's illicit discharge detection program monitors storm sewer outfalls for non-stormwater discharges. Given Horry County's hospitality industry and the seasonal population surge during tourist season, the IDDE program is particularly important for maintaining water quality at beach access points and recreational waterways.

Penalty Structure

SCDES enforces state-level stormwater violations with civil penalties up to $10,000 per day per violation under the SC Pollution Control Act. High-profile violations on large development sites or discharges affecting swimming beaches receive heightened enforcement attention.

Horry County enforces its local stormwater ordinance through notices of violation, compliance orders, and fines. The county's enforcement process starts with notification and a compliance deadline. Failure to correct violations leads to escalated enforcement, potentially including stop-work orders and referral to SCDES.

Construction sites with visible sediment discharge to ditches, creeks, or the Intracoastal Waterway receive immediate attention from both county and state inspectors. The tourism-dependent economy amplifies the consequences of water quality violations.

Key BMPs

Horry County's flat coastal plain, sandy soils, and high water table influence BMP design. Common BMPs include:

• Wet detention ponds - The standard BMP for residential subdivisions and commercial developments. Horry County has thousands of permitted stormwater ponds across the county.
• Bioretention systems - Used in commercial and higher-density residential projects. Require underdrains in areas with high water table or poorly draining soils.
• Swale systems - Common along roadways and in residential developments. Provide conveyance and filtration through vegetated channels.
• Permeable pavement - Applied in parking areas for commercial and resort properties. Sandy subsoils generally provide good infiltration, but high groundwater can limit effectiveness.
• Dune and beach management - Specialized BMPs for beachfront properties that address coastal erosion, sand transport, and stormwater discharge to the beach.

Local Ordinances

Horry County's stormwater ordinance implements the requirements of its MS4 permit and addresses the unique challenges of managing rapid development. The ordinance requires stormwater management plans for new development, maintenance agreements for permanent BMPs, and compliance with the county's IDDE program.

The City of Myrtle Beach, North Myrtle Beach, and other municipalities within Horry County have their own stormwater ordinances that may be stricter than county requirements. Projects within municipal limits should verify local standards with the respective city or town.

Horry County's experience with Hurricane Florence (2018), which caused record flooding along the Waccamaw River, has influenced stormwater policy. The county has increased emphasis on flood resilience in development reviews and is updating its stormwater management standards to account for more intense rainfall patterns.