Elevation Certificates in Suisun City, CA

Suisun City sits where the Fairfield creeks meet tidewater, at the head of Suisun Slough on the edge of Suisun Marsh, which FEMA's Solano County study describes as the largest contiguous marsh in the continental United States. The Suisun Channel connecting the city to Suisun Bay still carries barge traffic. FEMA's Flood Insurance Study describes the core problem simply: Suisun Slough is tidal, so the worst flooding comes when very high tides arrive at the same time as large creek outflows, and restrictive outlets into the sloughs cause water to pond in low-lying areas while high tides delay drainage for days.

The city's flood history is unusually well documented in that study. Suisun City flooded in 1940, 1950, 1955, 1963, 1966, 1967, 1969, 1970, and 1973. In December 1955 water rose to waist depth in a residential development when high tides slowed drainage. In January 1967 floodwater covered a third of the streets and was about 2 feet deep in the southern part of town, and in 1970 a high tide combined with overflow from Laurel Creek and Union Avenue Creek. The part of the city south of State Highway 12 relies on sumps that pump storm water into tidal channels, and low, discontinuous levees along Marina Channel and near Suisun Slough guard against minor flood tides. The city's floodplain ordinance sets primary, secondary, and tertiary floodplain zones along its streams. Suisun City is FEMA community 060372. For houses in the older low-lying neighborhoods and around the waterfront, the elevation of the floor relative to the Base Flood Elevation drives flood insurance cost more than anything else, and the elevation certificate is how that number gets documented.

We tie to NAVD88 benchmarks with GNSS and measure the building with a Trimble S3 total station: lowest adjacent grade, highest adjacent grade, the top of the lowest floor, any garage or crawlspace, flood openings, and HVAC and utility equipment. We take FEMA's required photos and sign Form FF-206-FY-22-152. If the ground at the structure is at or above the BFE but it is still mapped in the zone, we can prepare a Letter of Map Amendment and file through eLOMA where eligible. Read more on our elevation certificate service page, and see Fairfield and Rio Vista.