The Transbay Tube is the part of BART which runs under the San Francisco Bay in California and is the longest underwater tube for rapid transit in the world. The tube itself is 3.6 miles (5.7 km) long; including approaches from the nearest stations (which are underground), it totals 6 miles (9 km). At a maximum depth of 135 feet (41 meters) below the surface, the Transbay Tube is the deepest vehicular tube in service today.
Transbay Tube | |
|---|---|
| Coordinates | 37°48′32″N 122°18′58″W / 37.8089°N 122.316°W |
| Carries | 4 lines of the BART transit system |
| Crosses | San Francisco Bay |
| Locale | San Francisco, California and Oakland, California |
| Maintained by | San Francisco Bay Area Rapid Transit District |
| Characteristics | |
| Total length | 5.7 km (3.6 miles) |
| History | |
| Opened | 1974 |
| Statistics | |
| Toll | $2.55 (Embarcadero Station to West Oakland Station) |
| Location | |
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The tube was constructed on land, transported to the site then submerged and fastened to the bottom (mostly by packing the sides with sand and gravel). This is in contrast to tunneling, where earth is removed to leave a passage, the method of underground mines, and, for example, the Channel Tunnel between France and England.
Conception
The idea of an underwater tube traversing the San Francisco Bay was originally conceived in October 1920 by Major General George Washington Goethals, the builder of the Panama Canal. The alignment of Goethal's proposed tube is almost exactly the same as BART's Transbay Tube. In 1947, a joint Army-Navy Commission recommended an underwater tube as a means of relieving automobile congestion on the then ten-year old San Francisco-Oakland Bay Bridge.
Construction
Seismic studies commenced in 1959 and construction was started in 1965. The tube itself was finished in 1969. The tracks and electrification needed for the trains was finished in 1973 and it was opened to service in 1974. The tube is made of 57 individual sections that were built on land and towed out into the bay by a large barge. They were then positioned above where they were to sit and lowered into a trench packed with soft soil, mud and gravel for leveling along the bay's bottom. Once the sections were in place, bulkheads at each end of each of the sections were removed and a protective layer of sand and gravel was packed against the sides. It cost approximately $180 million in 1970.
Trivia
The tube appears briefly at the end of George Lucas' film THX 1138. The final climb out to the daylight was actually filmed, with the camera rotated 90 degrees, in the incomplete (and decidedly horizontal) Transbay Tube before installation of the track supports, with the character using exposed reinforcing bars as a ladder.
See also
External links
- BART's Transbay Tube - Detailed history of the tube and primary source of information for this article