Caldecott Tunnel Excavation Completed | 511 Contra Costa

Caldecott Tunnel Excavation Completed

On September 21, 2012 – almost exactly two years from the start of tunneling – all excavation of the Fourth Bore was completed. An update on tunnel progress with photographs and additional information can be downloaded from our website (PDF).

The tunnel now measures almost 10 meters (33 feet) high and 13 meters (43 feet) wide for its entire length. Crews are currently working around the clock to complete the installation of a waterproof membrane to prevent groundwater seepage, as well as a rebar cage and final lining arch, which will provide both flexibility and strength in the event of an earthquake. The final lining, which requires a total of 69 concrete pours, or “lifts,” is what motorists will see as they travel through the tunnel.

Although we are pleased with the significant progress to date, there is still much work to be done before the tunnel is ready for traffic in late 2013. This work includes paving of the roadway inside and outside of the tunnel, completion of the portal arch on the tunnel’s eastern end, as well as the installation, configuration and integration of electrical, drainage and ventilation systems. These operational and safety systems will be controlled from the new state-of-the-art Operations and Maintenance Control building. Crews will also construct a permanent sound wall in Oakland measuring 2.5 meters (eight feet) high and 161 meters (528 feet) long.

When the tunnel is completed, its eastern and western portals will be adorned by medallions. The medallion designs will be influenced by artwork provided by young residents in Alameda and Contra Costa counties.

For detailed information on the progress of the Fourth Bore’s construction, please see the Fall Project Update, which is available for download here (PDF). Please continue to visit the website for updates on tunnel progress.

Over the next three months, Caltrans and its partners, the Contra Costa Transportation Authority and the Alameda County Transportation Commission, will host ceremonies for participants in the medallion design contest in both Alameda and Contra Costa Counties, and the Caldecott Tunnel project team will mark the 75th anniversary of the Caldecott Tunnel’s first two bores. If you have friends or neighbors who would like to stay updated on the project, please ask them to sign up for these email alerts at

The Caldecott Fourth Bore Project is a partnership between the Federal Highway Administration, the California Department of Transportation, the Metropolitan Transportation Commission, the Contra Costa Transportation Authority, and the Alameda County Transportation Commission. 

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