Elevation Certificates in Union City, CA

Union City sits on the historic floodplain of Alameda Creek, and the creek's plumbing explains most of its flood mapping. The Alameda County Flood Control District describes the 12-mile Alameda Creek Flood Control Channel, built by the Army Corps of Engineers in the 1970s, which runs through Union City and Fremont across the creek's old flood plain to the bay. When the channel was built, Alameda Creek was diverted south of its historic route. Old Alameda Creek still flows in its original natural channel as far as Cann Park in Union City, where a gated culvert lets water move from the main channel into Old Alameda Creek when water is high. Dry Creek comes out of the hills and meets the main channel, and the District's Zone 5 lines drain residential neighborhoods near the south bay ponds.

Union City's ADU checklist shows how flood rules reach small projects. If a lot is inside a FEMA Special Flood Hazard Area, a detached ADU may exceed the normal 16-foot height limit in order to meet FEMA flood-safety requirements, as long as it keeps an 8-foot maximum ceiling height and meets 4-foot side and rear setbacks. That exception only makes sense with real numbers: the Base Flood Elevation for the lot, existing grade where the unit will sit, and the proposed floor elevation. A surveyed elevation certificate after construction then documents that the finished floor actually landed where the design said it would.

Our process in Union City is the standard FEMA one done carefully. We tie a benchmark on the FIRM's vertical datum with GNSS, then measure the lowest adjacent grade, lowest floor, garage, any crawlspace, and machinery and utilities with a Trimble S3 total station. We photograph each building face as FEMA requires and deliver a signed FEMA Form FF-206-FY-22-152. For an existing home that turns out to sit above the BFE even though the map shows it in the SFHA, we can prepare a letter of map amendment and submit through eLOMA when eligible. Union City work is scheduled as a mobilization from our base in Lotus. See our elevation certificate service, the Fremont and Newark pages, and our Union City area page.