West Covina, CA Environmental Rules: Flood Elevation Requirements (2026)

Under Sec. 9-56(c), residential new construction or substantial improvement in an A Zone, or any other flood zone, must have its lowest floor, including any basement, elevated at least one foot above the base flood elevation established for the site. Once the structure is finished, a registered professional engineer or surveyor must certify the elevation, and the city's building inspector verifies it before the floodplain administrator will accept the documentation. Nonresidential buildings have a second option: instead of elevating, they can be floodproofed below the same one-foot-above-base-flood-elevation line so the structure is watertight, with walls that resist water passage and structural components able to withstand hydrostatic and hydrodynamic loads, certified by a registered engineer or architect.

Any enclosed area below the lowest floor that isn't a basement, such as a garage used only for parking, building access, or storage, must be designed to let floodwater automatically enter and exit so it doesn't build up pressure against the walls. The code sets a specific minimum for that venting: at least two openings with a combined net area of one square inch for every square foot of enclosed area, with the bottom of every opening no higher than one foot above grade, and openings may have screens, louvers, or valves as long as they still let water flow through automatically. Manufactured homes must meet the separate elevation and anchoring standards of Sec. 9-59.