{{Short description|Rapid transit tunnel in California, US}} {{About|the rail tunnel|the road tunnel|Caldecott Tunnel}} {{Use mdy dates|date=April 2025}} {{Use American English|date=February 2025}} {{Infobox tunnel |name = Berkeley Hills Tunnel | image = East portal of Berkeley Hills Tunnel, March 2018.JPG | image_size = 300px | alt = An angular concrete structure | caption = East portal structure of the Berkeley Hills Tunnel | official_name = | other_name = Caldecott BART Tunnel |line = {{ric|BART|Yellow|name=yes}} |location = [[Alameda County]], [[California]] |coordinates = Oakland portal:<br />{{Coord|37|51|05|N|122|14|17|W|format=dms|display=inline|type:landmark_region:US-CA}}<br />Orinda portal:<br />{{Coord|37|52|29|N|122|11|16|W|format=dms|display=inline|type:landmark_region:US-CA}} | os_grid_ref = | status = | system = [[Bay Area Rapid Transit]] | crosses = [[Berkeley Hills]], [[Hayward Fault]] |start = [[Rockridge (BART station)|Rockridge Station]], [[Oakland, California|Oakland]] |end = [[Orinda (BART station)|Orinda Station]], [[Orinda, California|Orinda]] |stations = None | startwork = 1965 | opened = {{start date and age|1973|5|21}} | closed = <!-- or |closes for future dates --> | rebuilt = | reopened = <!-- or |reopens for future dates --> |owner = [[Bay Area Rapid Transit|San Francisco Bay Area Rapid Transit District]] |operator = [[Bay Area Rapid Transit|San Francisco Bay Area Rapid Transit District]] | traffic = |character = [[Rapid transit]] | engineer = | construction = [[Drilling and blasting|drill-and-blast]] | length = |linelength = {{convert|3.1|mi|km|abbr=on}} | tracklength = | notrack = 2 | gauge = {{RailGauge|5ft6in}}<br />([[Indian gauge]]) | el = [[Third rail]], 1000 [[Volt|V]] [[Direct current|DC]] | speed = | hielevation = | lowelevation = | height = {{convert|16.8|ft|m}}<ref>{{cite web | url=http://sonic.net/~mly/www.geolith.com/bart/figure12.html | title=Figure 12}}</ref> | width = | grade = 1.2% (2% max)<ref name="CompositeReport">{{cite web |title=The Composite Report Bay Area Rapid Transit |url=https://archive.org/details/compositereportb1962pars |website=Archive.org |publisher=Parsons Brinckerhoff / Tudor / Bechtel |access-date=23 July 2018 |pages=19, 20}}</ref><ref name=geolith /> | map = | extra = }} The '''Berkeley Hills Tunnel''' is a [[tunnel]] which carries [[Bay Area Rapid Transit]] (BART) {{lnl|BART|Yellow}} 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]].{{citation needed|date=October 2025}}
The tunnel bores through the Berkeley Hills east of Berkeley and Oakland a distance of {{convert|3.1|mi|km}}<ref name=geolith /> through a variety of rock strata, most of which are soft and porous. The earthquake-active [[Hayward Fault]] bisects the tunnel about {{convert|900|ft|m}} inside the west portal (Oakland side). There are 2 bores, each {{convert|17.5|ft|m}} in diameter,<ref name=geolith>{{cite web|last1=Rogers & Peck|title=Engineering Geology of the Bay Area Rapid Transit (BART) System, 1964-75|url=http://sonic.net/~mly/www.geolith.com/bart/#berkeley-design|website=Index of /~mly/www.geolith.com|publisher=Geolith Engineering|accessdate=22 June 2017}}</ref> spaced {{convert|50|ft|m}} apart. Pedestrian cross-tunnels are spaced every {{convert|1000|ft|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.<ref>{{cite web |url=https://www.seaonc.org/civicrm/event/info?reset=1&id=179 |title=August Monthly Meeting: Caldecott BART Tunnel Creep Repair - SEAONC |archive-url = https://web.archive.org/web/20171201042318/https://www.seaonc.org/civicrm/event/info?reset=1&id=179 |archive-date = 2017-12-01 |accessdate = 2018-11-05 |website=www.seaonc.org }}</ref> The work, which includes excavating the tunnel walls and realigning the tracks, is expected to cost $60 million.<ref>{{cite web |url=https://www.bart.gov/sites/default/files/better-bart/RepairStructures2018.pdf |title=BART Board Workshop |publisher=San Francisco Bay Area Rapid Transit Agency |date=February 2018 |accessdate=April 28, 2019 }}</ref>
==Construction== Construction of the tunnel began in early February, 1965. The bores were holed through by March, 1967, and construction completed in July, 1968.<ref>[http://sonic.net/~mly/www.geolith.com/bart/#geo "Engineering Geology of the Bay Area Rapid Transit (BART) System, 1964-75", Geolith Consultants, 2000, archived from a defunct website]</ref> The tunnel was opened for revenue service on May 21, 1973, with the Concord line.<ref name=history>{{BART History}}</ref>
Material removed in the construction of the tunnel was used as fill for a concurrent expansion of the [[Port of Oakland]].<ref>''Berkeley Gazette'', October 24, 1966, p.13</ref>
==Incidents== On December 4, 2013, a BART train suffered mechanical braking problems and made an emergency stop in the tunnel near [[Rockridge (BART station)|Rockridge station]]. Eleven people were treated for [[smoke inhalation]].<ref>{{cite news |url=http://news.kron4.com/news/breaking-news-bart-train-stopped-in-caldecott-tunnel/ |title=BART Brake Smoke Causes Injuries in Caldecott Tube |last=Shields |first=Brian |newspaper=KRON4 |date=December 4, 2013 |accessdate=2013-12-05 |archive-url=https://web.archive.org/web/20140302035535/http://news.kron4.com/news/breaking-news-bart-train-stopped-in-caldecott-tunnel/ |archive-date=March 2, 2014 |url-status=dead }}</ref>
==See also== *[[List of tunnels in the United States]]
== References == {{reflist}}
{{Bay Area Rapid Transit}} {{Bay Area tunnels}}
[[Category:Berkeley Hills]] [[Category:Yellow Line (BART)]] [[Category:Railroad tunnels in California]] [[Category:Tunnels in the San Francisco Bay Area]] [[Category:Transportation buildings and structures in Alameda County, California]] [[Category:Transportation buildings and structures in Contra Costa County, California]] [[Category:Rail transportation in Oakland, California]] [[Category:Tunnels completed in 1973]]