Berkeley Hills Tunnel

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Berkeley Hills Tunnel
An angular concrete structure
East portal structure of the Berkeley Hills Tunnel
Overview
Other name(s)Caldecott BART Tunnel
Line
LocationAlameda County, California
CoordinatesOakland portal:
37°51′05″N 122°14′17″W / 37.85139°N 122.23806°W / 37.85139; -122.23806
Orinda portal:
37°52′29″N 122°11′16″W / 37.87472°N 122.18778°W / 37.87472; -122.18778
SystemBay Area Rapid Transit
CrossesBerkeley Hills, Hayward Fault
StartRockridge Station, Oakland
EndOrinda Station, Orinda
No. of stationsNone
Operation
Work begun1965
Constructeddrill-and-blast
OpenedMay 21, 1973; 46 years ago (1973-05-21)
OwnerSan Francisco Bay Area Rapid Transit District
OperatorSan Francisco Bay Area Rapid Transit District
CharacterRapid transit
Technical
Line length3.1 mi (5.0 km)
No. of tracks2
Track gauge5 ft 6 in (1,676 mm)
(Indian gauge)
ElectrifiedThird rail, 1000 V DC
Tunnel clearance16.8 feet (5.1 m)[1]
Grade1.2% (2% max)[2]

The Berkeley Hills Tunnel (also called the Caldecott BART Tunnel) is a tunnel which carries Bay Area Rapid Transit's Antioch–SFO/Millbrae line through the Berkeley Hills between Rockridge station and Orinda station.

Design[edit]

While the tracks run in the median of California State Route 24 on both sides of the tunnel, the Berkeley Hills Tunnel allows the tracks to take a straighter alignment offset to the north of the Caldecott Tunnel.

The tunnel bores through the Berkeley Hills east of Berkeley and Oakland a distance of 3.1 miles (5.0 km)[2] through a variety of rock strata, most of which are soft and porous. The earthquake-active Hayward Fault bisects the tunnel about 900 feet (270 m) inside the west portal (Oakland side). There are 2 bores, each 17.5 feet (5.3 m) in diameter,[2] spaced 50 feet (15 m) apart. Pedestrian cross-tunnels are spaced every 1,000 feet (300 m) 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.

By 2017, cumulative minor damage from fault creep had significantly reduced the tunnel's cross section, to the point where BART determined it was necessary to plan for repair and mitigation against future creep.[3] The work, which includes excavating the tunnel walls and realigning the tracks, is expected to cost $60 million.[4]

Construction[edit]

Boring was completed in February 1967 after 465 work days. The tunnel was opened for revenue service in 1973.

Material removed in the construction of the tunnel was used as fill for a concurrent expansion of the Port of Oakland.[5]

Incidents[edit]

On December 4, 2013, a BART train suffered mechanical braking problems and made an emergency stop in the Berkeley Hills Tunnel near Rockridge station. Eleven people were treated for smoke inhalation.[6]

See also[edit]

References[edit]

  1. ^ "Figure 12".
  2. ^ a b c Rogers & Peck. "Engineering Geology of the Bay Area Rapid Transit (BART) System, 1964-75". Index of /~mly/www.geolith.com. Geolith Engineering. Retrieved 22 June 2017.
  3. ^ "August Monthly Meeting: Caldecott BART Tunnel Creep Repair - SEAONC". www.seaonc.org. Archived from the original on 2017-12-01. Retrieved 2018-11-05.
  4. ^ "BART Board Workshop" (PDF). San Francisco Bay Area Rapid Transit Agency. February 2018. Retrieved April 28, 2019.
  5. ^ Berkeley Gazette, October 24, 1966, p.13
  6. ^ Shields, Brian (December 4, 2013). "BART Brake Smoke Causes Injuries in Caldecott Tube". KRON4. Retrieved 2013-12-05.