Washington County, MD Environmental Rules: Stormwater Management (2026)

1 of the county's Stormwater Management, Grading, Soil Erosion and Sediment Control Ordinance requires stormwater management (SWM) measures for any development or redevelopment that disturbs 5,000 square feet or more of total land area, with narrow exemptions for agricultural land management, minor additions to existing single-family homes, and activities the State regulates directly. A sets the core design standard: SWM plans "shall be designed using ESD sizing criteria, recharge volume, water quality volume, and channel protection storage volume criteria according to the Design Manual," with the MEP (maximum extent practicable) standard met only when channel stability is maintained, predevelopment groundwater recharge is replicated, and nonpoint source pollution is minimized.

H requires overbank flood protection volume to be calculated using the 10-year frequency storm event, with the 100-year event used only if the Director of the Division of Plan Review and Permitting (DPRP) directs it. I imposes a physical setback: where a structural stormwater measure with an embankment is to become public infrastructure, a minimum 10-foot setback from the top of cut, or 15 feet from the toe of the embankment, is required to the closest property line. N requires a Stormwater Pollution Prevention Plan for land uses generating elevated pollutant loads.