Posey and Webster Street Tubes

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Posey Tube
Posey Tube
Carries 2 lanes of CA 260 Southbound
(Signed as CA 61)
Crosses Oakland Estuary
Locale Alameda, California and Oakland, California
Maintained by California Department of Transportation
Opening date October 27, 1928
Coordinates 37°47′16″N, 122°16′38″W
Webster Street Tube
Webster Street Tube
Carries 2 lanes of CA 260 Northbound
(Signed as CA 61)
Crosses Oakland Estuary
Locale Alameda, California and Oakland, California
Maintained by California Department of Transportation
Opening date 1963

The Posey Tube and the Webster Street Tube are two parallel underwater tunnels connecting the cities of Oakland and Alameda, California, running beneath the Alameda-Oakland Estuary. Currently, the Posey Tube carries Oakland-bound traffic under the Estuary, while the Webster Tube carries traffic bound for Alameda.

The Posey Tube, completed and opened to traffic on October 27, 1928, was named after George Posey, Alameda County Surveyor during the tunnel's planning and construction, and also chief engineer on the construction project. The Webster Street Tube opened in 1963 to deal with the increased traffic between Oakland and Alameda. Both are immersed tubes, constructed by sinking precast concrete segments to a trench in the Estuary floor, then sealing them together to create a tunnel.

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