Berkeley Hills Tunnel


The Berkeley Hills 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

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 through a variety of rock strata, most of which are soft and porous. The earthquake-active Hayward Fault bisects the tunnel about inside the west portal. There are 2 bores, each in diameter, spaced apart. Pedestrian cross-tunnels are spaced every 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. The work, which includes excavating the tunnel walls and realigning the tracks, is expected to cost $60 million.

Construction

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.

Incidents

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.