Fremont, CA Environmental Rules: Flood Elevation Requirements (2026)

Fremont Municipal Code Chapter 18.200 (Flood Damage Prevention) sets the city's freeboard standard. Under Section 18.200.080(a)(3)(A), new construction and substantial improvement of any structure must have the lowest floor, including the basement, elevated to the minimum elevation required by the Fremont Building Standards Code (Chapter 15.10) but no lower than one foot above the base flood elevation shown on FEMA's flood insurance rate maps (FIRMs). Nonresidential structures can instead floodproof under subsection (a)(3)(C): walls watertight below one foot above base flood elevation, structural components able to resist hydrostatic and hydrodynamic loads, and certification by a registered engineer or architect.

In Zone AO, the lowest floor must sit above the highest adjacent grade at least as high as the FIRM's depth number plus one foot of freeboard, or three feet if no depth number is listed. Every completed structure needs its lowest-floor elevation certified by a registered professional engineer or surveyor and verified by the floodplain administrator under subsection (a)(3)(A). The city engineer serves as floodplain administrator (Section 18.200.060(b)) and reviews every development permit application in the special flood hazard area, drawing on the FEMA Flood Insurance Study for Fremont dated August 3, 2009, and its accompanying FIRMs.

Fully enclosed areas below the lowest floor that are subject to flooding need automatic flood-venting: a minimum of two openings on different walls with a combined net area of at least one square inch per square foot of enclosed area, with opening bottoms no higher than one foot above grade (Section 18.200.080(a)(3)(D) and (F)). Manufactured homes fall under the same one-foot freeboard floor and must be anchored to a permanent foundation system under subsection (d). Subdivision applicants on any lot and other development on parcels over five acres must identify the base flood elevation and the elevation of every proposed structure's lowest floor on final plans under subsection (c).