BART's tunnels and tubes
E-mail from: Craig Fleming, Concord, California BART Electrician
Berkeley Hills Tunnel (BHT):
On the Central Contra Costa County Line (C-Line), between Rockridge and Orinda Stations, bores through the Berkeley Hills east of Berkeley and Oakland a distance of 3.2 miles through hard rock. The earthquake-active Hayward Fault bisects the tunnel about 1000 feet inside the west portal (Oakland side). There are 2 bores, each about 22 feet in diameter, spaced 50 feet apart. Pedestrian cross-tunnels are spaced every 1000 feet for emergency evacuation in case of fire, etc. There is a ventilation structure at the east portal with roll-down doors that can close off the tunnel end to allow air to be sucked out or blown in. Boring was completed in February 1967 after 465 work days. The tunnel was opened for Revenue Service in 1974.
Trans-Bay Tube (TBT):
On the Mission-Market St. Line (M-Line) going from Oakland to San Francisco, the TBT consists of 57 tube sections, each averaging 330 feet long. The tube is 3.8 miles long, with support structures for ventilation, electrification, etc. at both ends. Each tube section has two bores 22 feet in diameter for train traffic separated by service tunnels in the middle, designated the upper and lower galleries. The upper gallery is a ventilation passage, with remotely controlled louvers connecting it to the train bores every third tube.The lower gallery has doors to the train bores at the midpoint of every tube, and contains a pedestrian/service cart passageway, small electrical substations, pump stations, etc. The TBT is 135 feet below sea level at its deepest point. Basic tube construction was completed in 1969 after three years work, and was opened for Revenue Service in 1975. Construction cost was 180 million dollars.The seismic joint at the San Francisco Vent Structure moved 1/8 of an inch during the 1989 7.1 earthquake, it was designed for up to eight inches of movement.
Thanks for your interest!
This page was last modified on July 10, 2000