Elevation Certificates in Martinez, CA

Martinez was founded in 1849 on the floodplain of Alhambra Creek, which FEMA's study calls Arroyo del Hambra Creek, and the town has dealt with seasonal flooding ever since. The creek runs through downtown to a tidal wetland at the Martinez Regional Shoreline on the Carquinez Strait. A flood-improvement project on the downtown reach was finished in 1999, but FEMA's countywide Flood Insurance Study still identifies two main problems on the creek. In the lower reach from Muir Station Road to Tahoe Drive there isn't enough channel and bridge capacity, so water leaves both banks and collects in a low area to the west. Further up, the Alhambra Avenue culvert and an old hydraulic structure just upstream of it cause water to spill at the culvert headwall and run east and west along Alhambra Avenue.

The study also maps shallow flooding, less than a foot deep, along Line A, DA-40 east of downtown, where a 10-foot storm drain runs under streets and backyards upstream of Howe Road and then drains through a long culvert under the refinery to tidal marsh. FEMA states plainly that the Martinez storm drain system is not designed for the 1-percent-annual-chance flood and that no other flood protection measures exist or are planned that would affect flooding in the city. For an owner, that means the mapped zones are what lenders and insurers will use for some time, and an elevation certificate is the way to show where a particular building sits. Martinez is FEMA community 065044. Its FIRM is in NAVD88, about 2.7 feet different from NGVD29 on Arroyo del Hambra Creek, which matters with old downtown building records.

Many downtown Martinez buildings are older, with raised wood floors, basements, or crawlspaces, and the certificate has to describe them correctly. We tie into NAVD88 benchmarks with GNSS, then measure with a Trimble S3 total station: lowest adjacent grade, top of the bottom floor (including a basement or crawlspace floor), the next higher floor, flood openings, and machinery and utilities. We photograph each side as FEMA requires and sign Form FF-206-FY-22-152. When the ground at the building is at or above the Base Flood Elevation, we can pursue a LOMA, through eLOMA where eligible. See our elevation certificate service, nearby Benicia and Pittsburg, and our Martinez surveying page.