Casper, WY Environmental Rules: Flood Elevation Requirements (2026)

Section 17.20.100(A) of the Casper Municipal Code sets the specific construction standards that apply once base flood elevation data exists for a site under section 17.20.040(B), 17.20.060(A)(8), or 17.20.110(C). Subsection (A)(1) governs residential construction: any new home or substantially improved residential structure must have its lowest floor, including any basement, elevated no less than one foot above the base flood elevation, and a registered professional engineer, architect, or land surveyor must certify to the floodplain administrator that the elevation meets that standard. Nonresidential buildings get an alternative under subsection (A)(2): they can meet the same one-foot freeboard or instead be floodproofed watertight below that level, certified by a licensed engineer or architect who documents the specific floodproofed elevation for the administrator's records.

Subsection (A)(3) covers enclosed areas below the lowest floor used only for parking, building access, or storage: they need at least two flood openings totaling one square inch of net area per square foot of enclosed floor space, with the bottom of each opening no higher than one foot above grade, so floodwater can enter and exit without building up hydrostatic pressure on the walls. Manufactured homes placed in a mapped zone must be elevated on a permanent foundation so the lowest floor sits at least one foot above the base flood elevation and anchored against flotation and lateral movement, per subsection (A)(4).

Recreational vehicles are exempt from the elevation standard only if they stay on site fewer than one hundred eighty consecutive days, remain licensed and ready for highway use, or meet the same permitting and elevation requirements as manufactured homes.