Spokane Valley, WA Environmental Rules: Flood Elevation Requirements (2026)

SVMC § 21.30.090(C) sets specific standards for zones where base flood elevation data exists, meaning Zones A1-30, AH, and AE identified under SVMC § 21.30.020 or SVMC § 21.30.070(D)(4). For residential construction, § 21.30.090(C)(1)(a) requires the lowest floor, including any basement, to sit one foot or more above the base flood elevation, a foot of freeboard beyond FEMA's minimum. Fully enclosed areas below that lowest floor are prohibited unless designed to automatically equalize hydrostatic pressure: § 21.30.090(C)(1)(b) requires either a professional engineer's or architect's certification, or, at minimum, two openings with a combined net area of at least one square inch per square foot of enclosed area, with the bottom of every opening no higher than one foot above grade.

Nonresidential buildings have an alternative under § 21.30.090(C)(2): instead of elevating, they may be flood-proofed so that everything below one foot above base flood level is watertight, with walls substantially impermeable to water and structural components able to resist hydrostatic and hydrodynamic loads, certified by a Washington-licensed professional engineer or architect. Applicants choosing flood-proofing must be told that flood insurance premiums will be rated as if the building sat one foot lower than its flood-proofed level. Where elevation data has not been provided, SVMC § 21.30.090(B) still lets the floodplain administrator require the lowest floor be set at least two feet above the highest adjacent natural ground, warning that skipping that two-foot buffer can mean higher insurance rates.