Gaithersburg, MD Environmental Rules: Grading & Drainage (2026)

Gaithersburg regulates grading and drainage through its building code, zoning ordinance, and coordination with Montgomery County permitting. A grading permit is required for any land disturbance that affects the existing drainage pattern, involves cut or fill exceeding specified quantities, or meets the erosion control plan threshold of 5,000 square feet. Grading plans must demonstrate that finished grades maintain positive drainage away from all structures with a minimum slope of 6 inches in the first 10 feet from foundations. Stormwater runoff must not be redirected from its natural drainage pattern onto neighboring properties. When grading changes increase impervious surface, stormwater management requirements apply. Retaining walls exceeding 4 feet in height require engineering design and a separate structural permit. Grading within the floodplain, stream valley buffer, or forest conservation area requires additional approvals from Montgomery County DEP. The city enforces drainage complaint resolution when grading by one property causes water problems on adjacent lots. Downspout drainage, sump pump discharge, and surface water must be directed to appropriate stormwater infrastructure or pervious areas. Contact Gaithersburg Public Works at (301) 258-6370 for drainage complaints or the Building Division at (301) 258-6330 for grading permits.