Posey and Webster Street tubes

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

Posey and Webster Street tubes
Overview
LocationAlameda, California and Oakland, California
Coordinates37°47′16″N 122°16′38″W
Route SR 260
(Signed as SR 61)
CrossesOakland Estuary
Operation
OpenedOctober 27, 1928 (Posey tube)
1963 (Webster St. tube)
OperatorCalifornia Department of Transportation
Technical
Length3,545.1 feet (1,080.5 m)[1]
No. of lanes2 per each tube
Tunnel clearance14.67 feet (4.47 m) (Posey tube)
14.83 feet (4.52 m) (Webster St. tube)
Route map

The Posey tube is the second-oldest underwater vehicular tunnel in the US, preceded only by the Holland Tunnel.

Construction

Posey Tube
Posey tube entrance in Alameda

The Posey tube, completed and opened to traffic on October 27, 1928, was named after George Posey, who was the Alameda County Surveyor during the tunnel's planning and construction, and also chief engineer on the construction project. The Posey tube replaced a swing bridge that interfered with maritime traffic. The ventilation buildings that house the exhaust and fresh air fans are built in an art deco style.[2]

The ventilation of toxic vehicular exhaust fume design was modeled on that of the Holland Tunnel's ventilation system, and Ole Singstad (who had designed the pioneering ventilation system of the Holland Tunnel) consulted.[3]

Webster Street Tube
Webster Street tube entrance in Oakland

In order to deal with increased traffic between Oakland and Alameda, a second tube, the Webster Street Tube, was constructed west of and parallel to the Posey Tube starting in 1960.[4] It was completed and opened to one-way southbound (into Alameda) traffic in 1963.[5] The Posey Tube was converted to one-way northbound (into Oakland) traffic.

References
  1. Baughn, James. "Posey Tube". Bridgehunter. Retrieved 19 March 2019.
  2. "Building Spotlight: Historic Posey Tube and 2016 Renovation Plan". Jack London Improvement District. Retrieved 2017-06-12.
  3. Saga in Steel and Concrete, pp. 191–202 Archived 2015-09-26 at the Wayback Machine
  4. California Highways and Public Works, Official Journal of the Division of Highways, Department of Public Works, State of California, Vol.39, Nos.3-4, March-April, 1960, p.11-12
  5. "Webster Dt. Tube", California Highways and Public Works, March-April 1963, pp.10-14
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