The
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