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The Posey Tube is an underwater tunnel connecting the cities of Oakland and Alameda, California, running beneath the Alameda-Oakland Estuary. Completed and opened to traffic on October 27, 1928, it is named for George Posey, Alameda County Surveyor during the tunnel's planning and construction, and also chief engineer on the construction project.
To deal with the increased traffic between Oakland and Alameda, the parallel Webster Street Tube was completed and opened in 1963. Currently, the Posey Tube carries Oakland-bound traffic under the Estuary, while the Webster Tube carries traffic bound for 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.
Posey and Webster Street Tubes
| | Bridge Name | Webster Street Tube | | image |  | | Carries | 2 lanes of California State Route 260 | | Crosses | Oakland Estuary | | Locale | Alameda, California and Oakland, California | | Maint | California Department of Transportation | | Id | idge |
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