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

Chapter 15.27 of the Logan Municipal Code sets the elevation rules, and section 15.27.170 is the core standard wherever base flood elevation data has been provided. For residential construction, the lowest floor including any basement must sit two feet (2') above the base flood elevation. A registered professional engineer, architect, or land surveyor submits a certification to the floodplain administrator that the standard is satisfied. Nonresidential buildings have two paths: elevate the lowest floor two feet above the base flood level, or design the structure and its utility and sanitary facilities to be watertight with walls substantially impermeable to water for at least two feet above that level. The floodproofing route requires a registered engineer or architect to certify the design, and the Floodplain Administrator keeps a record of the elevation to which the structure is floodproofed.

Manufactured homes in the flood zones follow the same two-foot rule and must be anchored to resist flotation, collapse, and lateral movement. Fully enclosed areas below the lowest floor that are used only for parking, building access or storage need at least two openings with a total net area of not less than one square inch for every square foot of enclosed area, and the bottom of every opening can be no higher than one foot (1') above grade.

Where flooding is shallow, in AO and AH zones with base flood depths of one to three feet, section 15.27.190 requires the lowest floor to be elevated two feet above the depth number on the FIRM, or at least two feet above the highest adjacent grade if no depth number is specified. Section 15.27.210 sets critical facilities two feet above the base flood elevation or at the height of the 500-year flood, whichever is higher. Subdivision and site plans under 15.27.180 must identify the base flood elevation, and lots and parcels of one acre or smaller are excused from determining it unless they are in a subdivision, multi-family, commercial or industrial development, or manufactured home park.