Loudoun County, VA Environmental Rules: Stormwater Management (2026)

Loudoun County is a Virginia Stormwater Management Program (VSMP) authority under the Virginia Stormwater Management Act (VA Code §62.1-44.15:24 et seq.) and implements regulations through Loudoun Codified Ordinances Chapter 1096 (Stormwater Management). Thresholds: land-disturbing activity of 10,000 sq ft or more requires a VSMP permit; within Chesapeake Bay Preservation Areas (RPAs), threshold drops to 2,500 sq ft per Ord. Ch. 1220. Applicants must submit a stormwater management plan demonstrating water quality treatment (phosphorus reduction per state nutrient credit standards) and quantity control (detention, retention) consistent with Virginia Runoff Reduction Method. Standard BMPs: bioretention, bioswales, permeable pavement, stormwater ponds, constructed wetlands. Loudoun's Facilities Standards Manual (FSM) Chapter 5 details engineering requirements. Ashburn's massive data center development ('Data Center Alley', largest concentration on earth) is a major stormwater compliance area — campus-scale detention ponds, green roofs, and underground storage systems are common. MS4 (Municipal Separate Storm Sewer System) permit with EPA/DEQ covers county stormwater discharges. Illicit discharges (oil, chemicals, paint, concrete washout) to storm drains are prohibited under Ch. 1096-30 and VA Code §62.1-44.5. Post-construction stormwater facilities must be maintained by property owner or HOA per recorded maintenance agreement — failure to maintain triggers enforcement including repair at owner expense.