Washington County, MD Landscaping Rules: Rainwater Harvesting (2026)

Under the county's Stormwater Management, Grading, Soil Erosion and Sediment Control Ordinance, every land-disturbing development project must first apply ESD planning techniques "to the Maximum Extent Practicable" before any structural best management practice (BMP) can be considered (Section 3.6.1). Rainwater harvesting is one of thirteen ESD treatment practices the Division of Plan Review and Permitting (DPRP) will approve to satisfy the minimum control requirements of Sections 3.5 and 3.6.2, alongside options such as rooftop disconnection, rain gardens, dry wells, micro-bioretention and infiltration berms (Section 3.6.1.A.b).

Any harvesting system, like every other ESD practice, must be designed to the county's Design Manual and the current Washington County Standards and Specifications for Public Works Construction, and it cannot conflict with existing state law or other local ordinances or policies (Section 3.6.1.A.d). Because underground cisterns are common for this practice, the county's construction-inspection checklist requires the Verifying Professional to confirm during final grading that the top elevation of an underground storage tank sits below the frost line, and to certify the tank's water tightness before the county will accept the installation (Section 3.15, Rainwater Harvesting inspection checklist).

If a harvesting system is deeded to the county for public ownership and maintenance, the developer must also record the lot corners and follow the county's Policy on Construction of Infrastructure for Acceptance and Ownership (S-3) before conditional acceptance is granted. Rainwater harvesting is optional, not mandated: a project can meet its stormwater obligations through any qualifying combination of the listed ESD practices, so a builder who prefers rooftop disconnection or a rain garden instead faces no penalty for skipping harvesting altogether.