Arvada, CO Environmental Rules: Flood Elevation Requirements (2026)

S. Title 29, Article 20, and adopts FEMA's Flood Insurance Studies and DFIRMs for both Jefferson County (dated January 15, 2021) and Adams County (dated September 28, 2018), reflecting Arvada's position across the two counties. Section 4-1-2-7(B)(3) sets the residential freeboard standard: new construction and substantial improvement of any residential structure in the Regulatory Floodplain must have its lowest floor, including the basement and any mechanical equipment or attendant utilities, built at or above two feet over the base flood elevation. In Flood Zone AO, the two-foot freeboard is measured above the depth number shown on the DFIRM, with a two-foot minimum if no depth number is listed; if neither a base flood elevation nor depth number exists at all, the flood protection elevation defaults to four feet above the highest adjacent grade.

Nonresidential structures get a lighter one-foot freeboard option under Section 4-1-2-7(B)(4), or may instead be flood-proofed watertight and certified by a Colorado-registered professional engineer. Manufactured homes placed in Zones A1-30, AH, or AE face the same two-foot freeboard plus anchoring to resist flotation, collapse, and lateral movement. Every project in the Flood Fringe Sub-Zone must go through a Floodplain Development Permit reviewed by the Floodplain Administrator under Section 8-3-5-6 before construction, and critical facilities must also clear the two-foot freeboard with continuous non-inundated emergency access where practicable.