Commerce City, CO Environmental Rules: Flood Elevation Requirements (2026)

Sec. 21-4400(7) of Commerce City's Land Development Code sets the elevation standard for structures the floodplain overlay district does allow. Since residential structures are prohibited in the floodplain outright, the freeboard requirement applies to permitted nonresidential structures: their lowest floor, including any basement, must either be elevated to one foot above the base flood elevation, or, together with attendant utility and sanitary facilities, be flood-proofed so the structure is watertight below that elevation with walls substantially impermeable to water. A flood-proofed structure must also have structural components capable of resisting hydrostatic and hydrodynamic loads and the effects of buoyancy, and a licensed engineer or architect must certify to the floodplain administrator that the design meets accepted standards of practice.

Critical facilities face a stricter freeboard: Sec. 21-4400(7)(b) requires their lowest floor or floodproofing, together with attendant utility and sanitary facilities, to sit at least two feet above the base flood elevation, and new critical facilities must have continuous, non-inundated access for evacuation and emergency services during a 100-year flood event where practicable. Sec. 21-4400(9) applies a parallel one-foot freeboard rule to structures on land removed from the floodplain by fill, measured against the base flood elevation that existed before the fill was placed, for both the lowest floor and mechanical, electrical, heating, and plumbing equipment.