Olympia, WA Environmental Rules: Flood Elevation Requirements (2026)

The City of Olympia adopted its floodplain rules in OMC chapter 16.70, and the elevation standards sit in § 16.70.050(B). Where base flood elevation data is provided by the Flood Insurance Study and FIRM, or is obtained from other sources under § 16.70.040.C.2, the lowest floor of a new or substantially improved residential structure in an AE, A1-30 or other mapped A zone must be elevated one foot or more above the base flood elevation, called the BFE. Mechanical equipment and utilities must be waterproof or elevated at least one foot above the BFE.

Nonresidential buildings in those zones follow the same one foot rule for the lowest floor, and their mechanical, sanitary and utility equipment must be waterproofed or elevated at least one foot above the BFE, or as required by ASCE 24, whichever is greater. A nonresidential building that does not meet the elevation rule can instead be dry floodproofed so that it is watertight below one foot or more above the base flood level, or to the ASCE 24 level if that is higher, with a certification from a registered professional engineer or architect. Manufactured homes must be set on a permanent foundation with the lowest floor one foot or more above the BFE.

Where a site is in an Unnumbered A zone and no BFE is available or reasonably obtainable, the structure must be reasonably safe from flooding, and in all cases the lowest floor must be at least two feet above the Highest Adjacent Grade. In coastal V and VE zones, the bottom of the lowest horizontal structural member must be at or above the BFE plus one foot, or the ASCE/SEI 24-14 Table 4-1 level, whichever is more restrictive.

A substantial improvement is a repair, reconstruction or improvement whose cost equals or exceeds 50 percent of the market value of the structure, so a large remodel of an existing building triggers the same elevation rule as new construction. Under § 16.70.040.A.2 the permit application must show the lowest floor elevation in relation to mean sea level NAVD88 on a current FEMA elevation certificate, and under § 16.70.040.C.3 the Building Official records the actual as-built elevation of the lowest floor of every new or substantially improved structure.

A variance from the elevation standard under § 16.70.040.C.6 is confined to new construction and substantial improvements on a small or irregularly shaped lot contiguous to and surrounded by lots with existing structures built below the base flood level. The applicant is given written notice that the lowest floor will be below the BFE and that flood insurance cost will be commensurate with the increased risk.