Lehi, UT Environmental Rules: Flood Elevation Requirements (2026)

1 of the Lehi City Development Code sets the elevation floor for residential construction in Zones A1-30, A, and AE: the lowest floor, including a basement, must sit at least one foot above the Base Flood Elevation (BFE), and where a freeboard option applies, it must instead reach the higher freeboard elevation. A registered professional engineer, architect, or land surveyor must submit certified elevation data to the Floodplain Administrator confirming compliance before the structure is approved. 2 sets a parallel one-foot-above-BFE standard for nonresidential construction, or, as an alternative, requires the space below the BFE be built watertight with walls substantially impermeable to water and structural components able to resist hydrostatic and hydrodynamic loads, certified by a registered engineer or architect.

5. Crawlspace foundations below the BFE are capped: the interior grade cannot sit more than two feet below the Lowest Adjacent Grade, and the crawlspace height from floor to the next joist cannot exceed four feet, with flood vent openings sized at a minimum of one square inch per square foot of enclosed area to equalize hydrostatic pressure. The chapter's own definitions section describes freeboard as the added safety margin above the calculated flood level meant to cover unknowns like wave action and watershed urbanization that a bare BFE calculation does not capture.