Elevation Certificates in Oakley, CA

FEMA's Contra Costa County Flood Insurance Study is direct about Oakley: the northern portion of the city is subject to Delta flooding via the San Joaquin River. The study explains the setting. The Delta was reclaimed with about 1,100 miles of levees that divide it into roughly 120 tracts called islands, much of the land sits below the water on the other side of those levees, and Delta islands have usually flooded from structural failure of a levee before it was overtopped. Every island has flooded at least once since levee building began in the 1860s. For a home near the river edge, the question an elevation certificate answers is how the floor and the ground at the foundation compare with the mapped Base Flood Elevation, not whether the levee looks solid.

The south side of Oakley is shaped by Marsh Creek. The lower reaches of the Marsh Creek channel run through the city, part of the Marsh-Kellogg Watershed Plan that built the Marsh Creek detention reservoir south of Brentwood and improved 36 miles of channel on Marsh, Sand, and Deer Creeks to carry a 2-percent-annual-chance flood. FEMA did not compute floodways for any Oakley streams, and in tidal reaches it started its flood calculations at mean higher high water. The countywide FIS also lists levee segments along the Contra Costa Canal in Oakley among its certified and accredited levees, and another Oakley levee among the structures flagged for later flood hazard revision. Oakley is FEMA community 060766, and all elevations on its FIRM are in NAVD88.

Our survey ties to NAVD88 benchmarks using GNSS, then a Trimble S3 total station picks up the building: lowest and highest adjacent grade, the top of the lowest floor, any garage or crawlspace, flood openings, and mechanical and utility equipment. We take the required photographs and sign FEMA Form FF-206-FY-22-152. If the lowest adjacent grade is at or above the BFE but the house is shown inside the flood zone, we can prepare the Letter of Map Amendment data and file through eLOMA when the request qualifies. Read more on our FEMA elevation certificate page, or see Brentwood, Antioch, and Discovery Bay.