Hillandale CDP (part), Montgomery County, Maryland Environmental Rules: Grading & Drainage Rules (2026)

Montgomery County requires a grading permit from the Department of Permitting Services (DPS) for earth disturbance activities that alter existing topography or drainage patterns. This includes excavation, filling, grading, and any work that changes the direction or volume of stormwater runoff. The grading permit process requires a site plan showing existing and proposed grades, drainage patterns, stormwater management, and sediment control measures. The applicant must demonstrate that grading will not adversely affect drainage on neighboring properties. In Special Protection Areas (SPAs) such as the Clarksburg and Upper Paint Branch watersheds, enhanced standards apply including water quality plan approval and monitoring. Work within the 100-year floodplain requires a floodplain district permit under Chapter 19, Article IV, and must demonstrate no rise in base flood elevation. Stream buffer requirements prohibit most disturbance within 100 feet of perennial streams (expanded to 125 feet in SPAs). Montgomery County also has a forest conservation law (Chapter 22A) that may require tree save plans and reforestation for projects involving grading on forested land. All grading must comply with geotechnical requirements; sites with steep slopes (25 percent or greater) or unstable soils require geotechnical investigation reports. DPS coordinates with DEP, Parks, and Planning for multi-agency review of complex grading projects.