Oconee County, SC Environmental Rules: Stormwater Management (2026)

Oconee County's subdivision regulations in Chapter 32, Article VI put stormwater management on the developer, not the county, but subject the design to county review. Sec. 32-216(a) states that while a DHEC land-disturbance permit usually covers the technical information needed, the county will review the information to ensure that all stormwater runoff is removed from proposed developments in perpetually maintained drainage systems designed to avoid damage to personal property, and that the planning director shall not approve any plat of subdivision that fails to make adequate provision for storm or floodwater runoff channels or basins.

Stormwater drainage systems must run separate and independent of any sanitary sewer system, and inlets have to be placed so surface water isn't carried across or around a road intersection unless the county engineer approves routing small volumes around in writing. Subsection (b) lets the planning department or county engineer require the applicant to carry away spring or surface water by pipe or open ditch, built to the county engineer's accepted engineering standards, with swales and ditches designed to minimize erosion. The developer's engineer must certify that drainage facilities can handle the entire upstream drainage area (subsection (c)) and must show there's no adverse impact on downstream drainage facilities (subsection (d)); if a downstream facility would be overloaded, the planning director can withhold subdivision approval until that's fixed.

Floodplain areas crossed by a watercourse get a dedicated stormwater easement, and any subdivision within a mapped floodplain must also comply with the county's separate floodplain ordinance.