Gaithersburg, MD Environmental Rules: Stormwater Management (2026)

Gaithersburg operates under the state of Maryland NPDES MS4 permit program and works in coordination with Montgomery County Department of Environmental Protection and the Washington Suburban Sanitary Commission (WSSC). The city's stormwater management ordinance requires all development and redevelopment projects that disturb 5,000 square feet or more of land to implement environmental site design (ESD) practices to the maximum extent practicable. ESD practices include rain gardens, bioretention facilities, permeable pavement, green roofs, and disconnection of impervious surfaces. Projects must treat stormwater quality and control quantity to pre-development levels. Montgomery County administers stormwater management plan review under Chapter 19 of the County Code even for properties within Gaithersburg. A stormwater management concept plan is required early in the development review process. For residential homeowners, downspout disconnection programs and rain barrel installations are encouraged. Discharging pool water, wash water, or chemicals into storm drains is prohibited. Illicit discharge detection and elimination is an active enforcement program. The city participates in Chesapeake Bay restoration efforts and must meet total maximum daily load (TMDL) targets for nitrogen, phosphorus, and sediment. Contact Montgomery County DEP at (240) 777-7770 or Gaithersburg Public Works at (301) 258-6370 for stormwater management questions.