Elevation Certificates in Antioch, CA

FEMA elevation certificates and LOMA elevation data for homes and buildings in Antioch, Contra Costa County, prepared and signed by a California licensed land surveyor.

Elevation certificates from $1,000 · (510) 543-2220

Elevation Certificates in Antioch: Local Conditions

Antioch's flood zones come from two different kinds of water. Along the north edge of the city the San Joaquin River is tidal, and FEMA's Contra Costa County Flood Insurance Study starts its water-surface calculations for East and West Antioch Creek at mean higher high water on the river. Inland, the mapped flooding is mostly creek and culvert driven. The study describes water backing up behind culverts at Contra Loma Boulevard and L Street on West Antioch Creek, flooding north of the Union Pacific Railroad and north of West 10th Street when culvert capacity is exceeded, and shallow flooding averaging about 3 feet near Contra Loma Boulevard and Whately Court. Markley Creek and several smaller branches are mapped as well.

Lake Alhambra is its own case. FEMA notes that low-lying areas around the lake on East Antioch Creek flood because the North Lake Drive bridge at the lake outlet, combined with high tides, keeps water from draining out, and no floodway is delineated for the lake because of its impoundment effect. If you own near the lake, near a creek channel, or close to the river and your lender says you need flood insurance, an elevation certificate is the document that shows where your floor and the ground around your house actually sit relative to the Base Flood Elevation (BFE). Antioch is mapped on the countywide FIRM (community 060026), first effective in June 2009 and revised in 2015 and 2017. All flood elevations on it are in NAVD88; older Antioch plans in NGVD29 differ by about 2.4 feet on East Antioch Creek, so a datum mix-up on an old drawing can make a house look higher or lower than it is.

Our field work starts with a GNSS tie to published benchmarks on NAVD88, carried to the building with a Trimble S3 total station. We measure the lowest adjacent grade, the top of the lowest floor, any garage or crawlspace floor, flood vents, and the HVAC and utility equipment, take the required building photos, and deliver a signed FEMA Form FF-206-FY-22-152. When the lowest adjacent grade comes out at or above the BFE but the house is still drawn inside the Special Flood Hazard Area, we can prepare the data for a Letter of Map Amendment (LOMA) and submit it through eLOMA when the case qualifies. More on the process is on our elevation certificates page. Nearby pages: Pittsburg, Oakley, and our Antioch survey area page.

Full service details, process, and deliverables: FEMA Elevation Certificates & LOMA · All surveying in Antioch: Antioch land surveying

What's Included

Signed and sealed by a California Professional Land Surveyor
Completed on FEMA Form FF-206-FY-22-152, with the required photographs
Elevations tied to a published benchmark on the flood map’s vertical datum
eLOMA submission as a licensed professional when the building qualifies
Construction-stage ECs for permits: construction drawings, building under construction, and finished construction
Sacramento region, Central Valley, Delta, and Bay Area

Our Process

Address & Flood Map Check

Send the address and the reason you need the certificate: lender letter, insurance quote, building permit, or a LOMA. We pull the effective FIRM panel, flood zone, and Base Flood Elevation before quoting, and tell you up front if a LOMA looks possible.

Benchmark Tie

We tie the site to a published benchmark on the vertical datum the flood map uses, with GNSS and a total station. Every elevation on the certificate is measured from that tie, not estimated from a contour map.

Building Measurement

We measure the top of the bottom floor, the next higher floor, the garage slab, the lowest and highest adjacent grade, the lowest machinery and equipment, and the flood openings, and take the photographs the form requires.

Signed EC, and the LOMA if It Qualifies

You receive the completed, signed Elevation Certificate as a PDF. If the lowest adjacent grade is at or above the Base Flood Elevation, we prepare the LOMA request and submit it to FEMA, through eLOMA when the building meets its criteria.

Elevation Certificates in Antioch: FAQ

FEMA's Contra Costa County study says the low areas around Lake Alhambra flood because the North Lake Drive bridge at the outlet, together with high tides on the river, keeps the lake from draining. Whether a particular house is actually below the Base Flood Elevation is a question an elevation certificate answers with measured numbers.

Usually not. Older plans are often on the NGVD29 datum, while the current FIRM uses NAVD88, and the two differ by roughly 2.4 feet along East Antioch Creek. Lenders and insurers need a certified FEMA elevation certificate measured on the map datum.

If the lowest ground touching the house is at or above the Base Flood Elevation, FEMA can issue a Letter of Map Amendment that removes the structure from the Special Flood Hazard Area. FEMA charges no review fee for a LOMA, and we can file eligible cases through eLOMA. If the ground is below the BFE, a LOMA won't work, and the elevation certificate is then used for insurance rating.

Need Elevation Certificates in Antioch?

Elevation certificates start at $1,000. Call (510) 543-2220 with the Antioch address and we'll check the flood map and give you a fixed price.

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Private licensed surveyor, not affiliated with FEMA • Homeowners welcome • Response within 24 hours

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