Transbay Tube

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Transbay Tube
Toward the Transbay Tube.jpg
View into the Transbay Tube
Overview
Line
Location San Francisco Bay, California, US
Coordinates Oakland portal:
37°48′32″N 122°18′58″W / 37.80889°N 122.31611°W / 37.80889; -122.31611
System Bay Area Rapid Transit
Start Embarcadero Station, San Francisco
End West Oakland Station, Oakland
No. of stations None
Operation
Opened 16 September 1974 (1974-09-16)[1]
Owner San Francisco Bay Area Rapid Transit District
Operator San Francisco Bay Area Rapid Transit District
Character Rapid transit
Technical
Line length 3.6 mi (5.8 km)
No. of tracks 2
Track gauge 5 ft 6 in (1,676 mm)
(Indian gauge)
Electrified Third rail, 1000 V DC
Highest elevation Sea level
Lowest elevation 135 ft (41 m) below sea level

The Transbay Tube is an underwater rail tunnel which carries Bay Area Rapid Transit's four transbay lines under San Francisco Bay between the cities of San Francisco and Oakland in California. The tube is 3.6 miles (5.8 km) long; including the approaches from the nearest stations (one of which is underground), it totals 6 miles (10 km) in length. It has a maximum depth of 135 feet (41 m) below sea level.

The tube was constructed on land, transported to the site, then submerged and fastened to the bottom (mostly by packing the sides with sand and gravel). This immersed tube technique is in contrast to bored tunneling, where rock is removed to leave a passage.

The Tube was the final segment to open in the original BART plan.[2] All BART lines except the Richmond–Fremont line operate through the Transbay Tube, making it one of the busiest sections of the system in terms of passenger and train traffic. During peak commute times, over 28,000 passengers per hour travel through the tunnel[3] with headways as low as 2.5 minutes.[4] BART trains reach their highest speeds in the Tube, almost 80 miles per hour (130 km/h), more than double the average 36 miles per hour (58 km/h) speed in the remainder of the system.[5]

Conception and construction[edit]

Early concepts[edit]

The idea of an underwater rail tunnel traversing San Francisco Bay was suggested by the San Francisco eccentric, Emperor Norton, in a proclamation that he issued on May 12, 1872.[6][7] Emperor Norton issued a second proclamation on September 17, 1872, threatening to arrest the city leaders of Oakland and San Francisco for neglecting his earlier proclamation.[8]

Official consideration to the idea was first given in October 1920 by Major General George Washington Goethals, the builder of the Panama Canal. The alignment of Goethals's proposed tube is almost exactly the same as today's Transbay Tube, and called for building on bay mud, which anticipated some of the seismic design aspects of the finished Transbay Tube. Goethals's proposal was estimated to cost up to US$50,000,000 (equivalent to $663,300,000 in 2015) in 1921.[9] A competing bridge-and-tunnel proposal was advanced in July 1921 by J. Vipond Davies and Ralph Modjeski, closer to the alignment of a proposed Southern Crossing, between Mission Rock and Potrero Point in San Francisco due east to Alameda. Davies and Modjeski were critical of the ventilation issues that would arise from a long combined automobile and rail tunnel, indirectly endorsing the idea of a dedicated tunnel for electric rail traffic.[10] The Davies and Modjeski proposal was joined by twelve other proposed projects to cross the Bay in October 1921, several of which featured rail service through long tunnels.[11][12]

In 1947, a joint Army-Navy Commission recommended an underwater tube as a means of relieving automobile congestion on the then-ten-year-old Bay Bridge.[13] The recommendation was issued in a report undertaken to determine the feasibility of the Reber Plan.[14][15]

Construction[edit]

Brochure from November 9, 1969, when a portion of the Tube was open for pedestrian traffic

Seismic studies commenced in 1959, including boring and testing programs in 1960 and 1964, and the installation of an earthquake recording system on the Bay floor. The Tube's route was modified after preliminary surveys were unable to identify a continuous bedrock profile, requiring more precise boring and probing of the Bay floor.[16] The route was deliberately chosen to avoid bedrock as much as possible so the tube was free to flex, avoiding concentrated bending stresses.[17]

Design concepts and route alignment were completed by July 1960.[18] A 1961 report estimated the cost of the Transbay Tube at US$132,720,000 (equivalent to $1,050,970,000 in 2015).[19] Construction was started on the Tube in 1965, and the structure was completed after the final section was lowered on April 3, 1969.[20] BART sold commemorative bronzed aluminum coins to mark the placement of the final section.[21] Prior to being fitted out, the Tube was opened for visitors to walk through a small portion on November 9, 1969.[22] The tracks and electrification needed for the trains were finished in 1973, and the tube was opened to service on September 16, 1974,[23] five years after the originally-projected completion date, after clearing California Public Utilities Commission concerns regarding the automated dispatch system.[24] The first test run was performed by a train under automatic control on August 10, 1973. Train No. 222 ran from West Oakland to Montgomery Street in seven minutes at 68 to 70 miles per hour (109 to 113 km/h) and returned in six minutes at the full speed of 80 miles per hour (130 km/h), carrying approximately 100 passengers including BART officials, dignitaries and reporters.[25]

The tunnel is set in a trench 60 feet (18 m) wide with a gravel foundation 2 feet (0.61 m) deep. Lasers were used to guide the dredging of the trench and the laying of the gravel foundation, maintaining route accuracy of within 3 inches (76 mm) for the trench and 1.8 inches (46 mm) for the foundation.[26] Construction of the trench required dredging 5,600,000 cubic yards (4,300,000 m3) of material from the Bay.[27]

The structure is made of 57 individual sections that were built on land at the Bethlehem Steel shipyard on Pier 70[28][29] and towed out into the bay by a large catamaran barge.[30] After the steel shell was completed, water-tight bulkheads were fitted and concrete was poured to form the 2.3-foot (0.70 m)-thick interior walls and track bed. They were then floated into place (positioned above where they were to sit), and the barge was tethered to the Bay floor, acting as a temporary tension leg platform.[31] The section was ballasted with 500 short tons (450 t) of gravel before being lowered into a trench packed with soft soil, mud, and gravel for leveling along the Bay's bottom. Once the section was in place, divers connected the section with the sections that had already been placed underwater, the bulkheads between placed sections were removed and a protective layer of sand and gravel was packed against the sides.[21][30] Cathodic protection was provided to resist corrosive action from the Bay's salt water.[27]

The same catamaran barge was later used to set the tunnel sections of the second (eastbound) Hampton Roads Bridge–Tunnel.[32]

The project cost approximately $180 million in 1970 (equivalent to $1.91 billion in 2015[33]),[34][35] with $90 million of that cost being spent on construction, the remainder going towards laying rails, electrification, ventilation and train control systems.[36]

Configuration[edit]

Approximate route of Transbay Tube (shown in yellow). View directed south; Treasure Island in left foreground, San Francisco (Financial District) on the right, and Oakland/Alameda in the left background.

The western terminus of the Tube directly connects to the downtown Market Street Subway near the Ferry Building, north of the Bay Bridge. The tube crosses under the western span of the Bay Bridge between the San Francisco Peninsula and Yerba Buena Island, and emerges in Oakland along 7th Street, west of Interstate 880.[37][citation needed]

The Tube has 57 sections; each section ranges from 273 to 336 feet (83 to 102 m) long.[26] The average length of each section is 328 feet (100 m), measured along the tunnels' bore; sections are 48 feet (15 m) wide, 24 feet (7.3 m) high, and weigh approximately 10,000 short tons (9,100 t) each.[20] To conform with the route, 15 tube sections were curved horizontally, 4 were curved vertically, 2 had horizontal and vertical curves, and the remaining 36 sections were straight.[26] Each section of the Tube cost approximately US$1,500,000 (equivalent to $9,680,000 in 2015), based on the US$90,000,000 (equivalent to $580,750,000 in 2015) construction contract.[38] The steel shell is 0.625 inches (15.9 mm) thick,[39] and has just enough strength to support its own weight and resist hoop stresses; an external consultant, Professor Ralph Peck, convinced project engineer Tom Kuesel that thin shells were adequate because the soil loads would naturally form an arch.[17]

Typical section of the Transbay Tube

The tube consists of two tunnels and a central maintenance/pedestrian gallery. Each tunnel has a bore approximately 17 feet (5.2 m) in diameter, with the track centerline offset 8 inches (200 mm) towards the outside from the bore centerline. The tunnels flank a gallery which contains maintenance and control equipment in the upper gallery, including a pressurized water line for firefighting. Each tunnel has 56 doors opening into the lower gallery, spaced approximately 330 feet (100 m) apart, numbered consecutively from the San Francisco side of the tube. The doors are locked from the gallery side and can be opened inwards (toward the gallery) from the tunnel through emergency hardware. Between doors, the tunnel has narrow 2.5-foot (0.76 m) wide walkways adjacent to the gallery space.[40]

The upper section of the gallery space is also used as a duct, moving 300,000 cubic feet per minute (8,500 m3/min) of air under forced circulation.[41] The tunnels are vented to the atmosphere at the San Francisco and Oakland ends and are vented to each other (through the upper gallery) with remotely-operated dampers 6 feet (1.8 m) long by 3 feet (0.91 m) high over every third door.[40]

Each end of the tube is secured to the vent structures with a patented sliding seismic joint[42] which allows six degrees of freedom (translation along and rotation about three axes). As-designed, the joints allow movement of up to 4.25 inches (108 mm) along the tube's axis and up to 6.75 inches (171 mm) vertically or laterally.[43]

Seismic retrofitting[edit]

The 3.6-mile (5.8 km) Transbay Tube has required earthquake retrofitting, both on its exterior and interior. The total cost of seismic retrofits was estimated at US$330,000,000 (equivalent to $413,400,000 in 2015) in 2004.[44]

A 1991 study, commissioned at the recommendation of the Governor's Board of Inquiry in the wake of the 1989 Loma Prieta earthquake,[45] found the seismic joints would "likely remain intact and functional after the next earthquake."[46] However, settling of the Tube within its trench and the Loma Prieta quake had reduced the allowable movement of the seismic joints to as little as 1.5 inches (38 mm).[43][47]

The 1991 study was followed by a more detailed BART Seismic Vulnerability Study, published in 2002, which concluded the fill packed around the tube might be prone to soil liquefaction during an intense earthquake, which could allow the buoyant hollow tube to break loose from its anchorages or cause movement that would exceed the capacity of the sliding seismic joints.[43][48] Retrofitting work required the fill to be compacted, to make it denser and less prone to liquefaction.[44] Compaction started in Summer 2006 at the east end of the Tube, on property belonging to the Port of Oakland.[49] A 2010 paper concluded the distance the Tube would rise due to liquefaction was limited based on model testing of potential liquefaction mechanisms, and questioned the justification for the compaction effort.[50]

On the interior of the tube, BART began a major retrofitting initiative in March 2013, which involved installing heavy steel plates at various locations inside the tube that most needed strengthening, to protect them from sideways movement in an earthquake. A vehicle was custom-built to handle the 4-short-ton (3.6 t), 2.5-inch (64 mm) thick plates; once hoisted in place, the plates were bolted to the existing concrete walls and welded together, end-to-end.[51] The contract for US$7,735,000 (equivalent to $7,973,000 in 2015) was awarded to California Engineering Contractors for installation.[52] In order to complete this work during 2013, BART closed one of the two bores of the tube early midweek (Tuesdays, Wednesdays and Thursdays), resulting in delays of 15-20 minutes. The work, originally estimated to last approximately 14 months, was completed by December 2013, after only 8 months of construction.[53][54]

Incidents and issues[edit]

January 1979 fire[edit]

On January 17, 1979 at approximately 6 p.m., an electrical fire broke out on a San Francisco-bound seven-car train (Train No. 117) as it was passing through the tube.[55][56] One firefighter (Lt. William Elliott, 50, of the Oakland Fire Department) was killed[57] by smoke and toxic fume inhalation (generated from burning plastic materials) during the effort to extinguish the blaze. The forty passengers and two BART employees aboard the stricken train were rescued by another train passing in the opposite direction.[58][40] The poor communication and coordination observed during the January 1979 fire played a key role in developing National Fire Protection Association transit industry guidelines (NFPA 130, Standard for Fixed Guideway Transit and Passenger Rail Systems).[55]

Figure 1: Cutaway of Transbay Tube, a diagram of the rescue, from NTSB RAR-79-05

The cause of the fire was traced to a short circuit on Train No. 117. The collector shoe assemblies on the number five and six cars broke after striking a line switchbox cover which had fallen off a prior train (Train No. 363), resulting in a short circuit and fire.[40]

Earlier that day, San Francisco-bound ten-car Train No. 363 had made an emergency stop in the Transbay Tube at approximately 4:30 p.m., reporting smoke and a possible fire. Troubleshooting without an external inspection revealed No. 363 had broken derail bars on the number six and eight cars, and an engaged parking brake on the number nine car. After clearing the derail bar circuits and manually releasing the parking brake, No. 363 was cleared to proceed, and upon reaching the end of the line in Daly City, was taken out of service for inspection.[40]

The train following No. 363 was dispatched to run in "road manual" mode, where the train is operated by the onboard engineer, rather than by the computerized central control system. That train reported seeing derail bar debris between the tracks near where No. 363 had stopped, but the tracks remained clear and available for service. The train immediately following also ran in "road manual," but subsequent trains were dispatched through the Tube in automatic mode, including No. 117, the tenth train to enter the westbound Tube after No. 363.[40]

No. 117 came to an emergency stop at 6:06 p.m., just after entering the Transbay Tube, with the operator reporting thick smoke which kept him from determining the exact location. Central operations shut down power to the third rail, but restored it 40 seconds later in an effort to uncouple the lead portion of the train from the burning cars. This was unsuccessful, and vent fans were turned on at 6:08 p.m. to attempt to clear the smoke, and the third rail was again powered down at 6:15 p.m. A BART supervisor who had been riding on the train helped gather passengers in the lead car, including one blind passenger.[40]

The Oakland Fire Department responded to the West Oakland station, where nine firefighters and two BART policemen boarded Train No. 900 running in "road manual." No. 900 was forced to stop at approximately 1 mile (1.6 km) into the Tube to remove an auxiliary box cover and a derail bar from the track, and eventually stopped approximately 200 feet (61 m) behind No. 117, where the train operator reported the rear car was on fire with heavy black smoke. Upon reaching No. 117, the responders were separated by the smoke, with one policeman and seven firefighters proceeding into the gallery between the tunnels, and the others were forced to return to No. 900 by the smoke. However, the group in the gallery had left the doors open to the tunnel for the others to follow.[40]

Train No. 111 with over 1,000 passengers on board had been holding at the last San Francisco stop, Embarcadero. At 6:21 p.m., No. 111 moved in automatic mode into the eastbound tunnel adjacent to the stricken No. 117 to rescue passengers, who had been led along the smoke-filled westbound tunnel into the gallery. After the rescued passengers boarded No. 111, firefighters searched No. 117 for any remaining passengers, informing central dispatch at 6:59 p.m. that all passengers had been transferred from No. 117 to No. 111. No. 111 immediately proceeded in automatic to West Oakland to transfer passengers to hospitals, but upon accelerating, smoke was drawn from the westbound tunnel through the open doors into the gallery. By this time, more firefighters had responded through the Oakland vent structures, having donned portable oxygen masks with 30-minute supplies.[40] Since the doors to the eastbound tunnel were locked from the gallery side, with smoke filling the gallery, the keyholes were obscured and the firefighters were unable to evacuate to the eastbound tunnel.[55]

The force of the draft from the departing No. 111 knocked the firefighters in the gallery down, and the firefighters began to make their way eastward in the gallery as a single-file human chain, through thick smoke. By this time, their portable oxygen masks were starting to run low, and Lt. William Elliott began to have trouble, requiring assistance from his fellow firefighters. Upon reaching a clear section of the tunnel, another train was dispatched from West Oakland in "road manual" to rescue the firefighters. After the rescue train returned to West Oakland, the firefighters were taken to area hospitals for treatment. Elliott had exhausted his oxygen supply, and died of smoke inhalation and cyanide poisoning.[40]

The fire was declared under control at 10:45 p.m., although the fires were not yet fully extinguished. At approximately 6 p.m. on the following day, January 18, Oakland firefighters responded to flare-up in the gutted train at BART's storage yard.[55] BART would spend US$1,100,000 (equivalent to $3,590,000 in 2015) in tube repairs and safety improvements on top of losing US$1,000,000 (equivalent to $3,260,000 in 2015) in revenue due to the loss of tube service.[59]

BART proposed new evacuation plans to the San Francisco and Oakland fire chiefs by February,[59] but BART service through the Transbay Tube did not resume until April 1979, with California Public Utilities Commissioner Richard D. Gravelle warning "the patrons of BART who utilize its services should be fully aware that the instant order [to reopen service] does not in any way provide a guarantee of safe service."[60] Both the Oakland and San Francisco fire departments criticized BART officials for failing to relinquish control of the emergency situation to the fire departments.[55]

Earthquakes[edit]

As a precaution, BART's emergency plans dictate that trains stop during an earthquake, except for trains in the Transbay Tube or the Berkeley Hills Tunnel, which proceed to the nearest station. The lines are then inspected for damage, and resume normal operation if no damage is found.[61]

The largest to date was the 1989 Loma Prieta earthquake. During the 1989 earthquake, a train passing through the Tube was ordered to stop, although the operator reported no apparent motion.[62] After inspection, the tube was found to be safe, and was reopened just six hours later, with regular service resuming system-wide twelve hours after the quake.[62][63] Many area highways were damaged by the event, and with the Bay Bridge closed for a month due to a section of the upper deck falling onto the lower deck on a truss section of the east span, the Transbay Tube was the only passable direct way between San Francisco and Oakland.[45]

Pedestrians[edit]

On occasion, pedestrians have entered the Tube through the Embarcadero station, prompting shutdowns and delays in transbay service.[64][65]

Noise[edit]

According to a 2010 survey by the San Francisco Chronicle, the Transbay Tube is the noisiest part of the BART system, with sound pressure levels inside the train reaching 100 decibels (comparable to a jackhammer).[66] The noise, which according to BART "has been compared to banshees, screech owls, or Doctor Who's TARDIS run amok" is exacerbated by the concrete enclosure and the fact that tracks are curved when the tunnel crosses beneath the San Francisco–Oakland Bay Bridge, causing a high-pitched screeching sound.[66] In 2015, after replacing 6,500 feet and grinding down (smoothing) 3 miles of rail in the tube, BART reported a reduction of noise and positive feedback from riders.[67]

Marine traffic[edit]

Ship traffic passing through the Bay can damage the anodes used in the Tube's cathodic protection system when dropping anchor. Since the anodes protrude from the filled trench surrounding the Tube, they are more vulnerable to damage. Marine traffic is restricted from dropping anchors when over the Tube, but BART conducts routine inspections for anode damage.[68]

The Tube was closed briefly on January 31, 2014, after a drifting freighter dropped anchor near the Tube at 8:45 a.m. to maintain position. The Coast Guard notified BART officials the anchor appeared to be close to the Tube at 11:55 a.m., based on the ship's position, leading to a suspension of Tube service for approximately 20 minutes while inspections were conducted. No damage was found, and the Tube was reopened at 12:15 p.m. Harbor pilots later noted the ship had anchored 1,200 feet (370 m) southwest of the Tube.[69] Two trains that had been passing through the Tube were stopped in place while the inspection was conducted. Trains were delayed by 15 to 20 minutes, with normal service resuming around 1 p.m.[39]

Future[edit]

In 2007, as BART celebrated the 50th anniversary of its creation, it announced its plans for the next 50 years. Its vision includes a new separate four-bore Transbay Tube beneath San Francisco Bay that would run parallel to and south of the existing tunnel. The new tunnel would emerge at the Transbay Transit Center to provide connecting service to Caltrain and the planned California High Speed Rail (HSR) system. The four-bore tunnel would provide two additional tunnels for BART trains, and two tunnels for conventional/high-speed rail (the BART system and conventional US rail use different and incompatible rail gauges and operate under different sets of safety regulations). In the terminal, there would be 6 tracks: 4 for HSR and 2 for Caltrain.[70]

In media[edit]

During construction, the Transbay Tube was also used briefly as a shooting location for the ending of George Lucas's film THX 1138. The final vertical climb out to daylight was actually filmed, with the camera rotated 90°, in the incomplete (and decidedly horizontal) Transbay Tube. The scene was filmed before installation of the track supports, with Robert Duvall's character using exposed reinforcing bars as a ladder.[citation needed]

The television adaptation of Terry Brooks' Shannara series of books, The Shannara Chronicles, is partly set in the Bay Area, and part of the journey/quest routes the protagonists through the Transbay Tube.[71]

One of the early sections of Dead Space features a sound sample taken from a ride through the Transbay Tube.[72][73]

See also[edit]

References[edit]

  1. ^ "BART Tube Link Opens". Pittsburgh Post-Gazette. AP. 17 September 1974. Retrieved 20 August 2016. 
  2. ^ Strand, Robert (14 September 1974). "San Francisco gets its space age underwater trains". The Dispatch. UPI. Retrieved 20 August 2016. 
  3. ^ "The Case for a Second Transbay Transit Crossing" (PDF). Bay Area Council Economic Institute. February 2016. p. 7. 
  4. ^ Mallett, Zakhary (September 7, 2014). "2nd Transbay Tube needed to help keep BART on track". San Francisco Chronicle. 
  5. ^ Minton, Torri (17 September 1984). "BART: It's not the system it set out to be". Spokane Chronicle. AP. Retrieved 20 August 2016. Hitting speeds close to 80 mph only in the 3.6-mile tube under the bay, the trains average 36 mph for safety reasons, [BART spokesman Sy] Mouber said. 
  6. ^ Norton I (June 15, 1872). "Proclamation". The Pacific Appeal. p. 1 – via California Digital Newspaper Collection. Believing Oakland Point to be the proper and only point of communication from this side of the Bay to San Francisco, we, Norton I, Dei gratia Emperor of the United State and Protector of Mexico, do hereby command the cities of Oakland and San Francisco to make an appropriation for paying the expense of a survey to determine the practicability of a tunnel under water; and if found practicable, that said tunnel be forthwith built for a railroad communication. Norton I. Given at Brooklyn the 12th day of May, 1812. 
  7. ^ Lumea, John (2016). "Bridge Proclamations". The Emperor's Bridge Campaign. Retrieved 8 September 2016. 
  8. ^ Norton I (September 21, 1872). "Proclamation". The Pacific Appeal. p. 1 – via California Digital Newspaper Collection. Whereas, we issued our decree, ordering the citizens of San Francisco and Oakland to appropriate funds for the survey of a suspension bridge from Oakland Point via Goat Island; also for a tunnel; and to ascertain which is the best project; and whereas, the said citizens have hitherto neglected to notice our said decree; and whereas, we are determined our authority shall be fully respected; now, therefore, we do hereby command the arrest, by the army, of both the Boards of City Fathers, if they persist in neglecting our decrees. Given under our royal hand and seal, at San Francisco, this 17th day of September, 1872. NORTON 1. 
  9. ^ "San Francisco Bay Bridge Project Revived by New Plans". Engineering News-Record. 87 (1): 16–17. 7 July 1921. Retrieved 8 September 2016. Howe & Peters, consulting engineers of San Francisco, have been working for nearly two years as Pacific Coast representatives of George W. Goethals, in getting together data on the construction of a subway for both vehicular and rail traffic, which would connect the foot of Market St. with Oakland Mole. Tentative plans on this project, made public some months ago, call for a shield-driven concrete tube, similar to the type General Goethals recommended for the New York-New Jersey tube under the Hudson River.
    Provision would be made for two decks, the upper for use of motor vehicles and the lower for electric trains. [...] The gradient would be kept below 3 per cent so freight could be handled easily. The depth of water along the route the tube would follow does not exceed 65 ft. and soundings taken at various points indicate that its entire length would be in blue mud. Not only would mud facilitate driving by the shield method, it is pointed out, but it would constitute a cushion to safeguard the tube from possible disalignment due to earthquake shocks.
    [...]If the results of such a survey confirm the rough estimates, it is suggested that the construction of the entire 3.5-mi. concrete tube would be between $40,000,000 and $50,000,000.
     
  10. ^ "Features of San Francisco Bay Bridge Report". Engineering News-Record. 87 (7): 268–269. 18 August 1921. Retrieved 8 September 2016. Any high bridge between Yerba Buena Island and San Francisco would naturally land on Telegragh Hill [sic]. It would not only involve very long and costly spans, even if piers were permitted in the channel, but would land the traffic in a section of the city already quite congested, and from which a proper distribution would be impracticable. Any tunnel on this location would have to be constructed at great depth in an unknown rock formation, as the water depth is too great for tunneling under air pressure, and the length would consequently be so great as to involve an extremely difficult problem in ventilation for vehicular traffic. We there fore consider this plan as impracticable. Any continuous tunnel across the bay, on any location, while practicable for purely electrically operated railroad traffic, would involve most serious ventilation problems for vehicular traffic, and enormous expense if constructed for all classes of traffic. 
  11. ^ "Thirteen Projects Submitted for San Francisco Bay Bridge". Engineering News-Record. 87 (18): 739. 3 November 1921. Retrieved 8 September 2016. 
  12. ^ Scott, Mel (1985). "ELEVEN: Seeds of Metropolitan Regionalism". The San Francisco Bay Area: A Metropolis in Perspective (Second ed.). Berkeley, California: University of California Press. p. 178. ISBN 0-520-05510-1. Retrieved 8 September 2016. 
  13. ^ Bay Area Rapid Transit District (n.d.). "History of the Tube". Bay Area Rapid Transit District. Archived from the original on March 29, 2013. 
  14. ^ H.Res. 529
  15. ^ Report of Joint Army-Navy Board on an additional crossing of San Francisco Bay (Report). Presidio of San Francisco, California. 1947. 
  16. ^ Aisiks, E. G.; Tarshansky, I. W. (23–28 June 1968). "Soil Studies for Seismic Design of San Francisco Transbay Tube". Vibration Effects of Earthquakes on Soils and Foundations (ASTM STP 450). Seventy-first Annual Meeting of the American Society for Testing and Materials. San Francisco, California: American Society for Testing and Materials. pp. 138–166. Retrieved 7 September 2016. 
  17. ^ a b Rogers, J. David; Peck, Ralph B. (2000). "Engineering Geology of the Bay Area Rapid Transit (BART) System, 1964-75". Geolith. Retrieved 17 August 2016. 
  18. ^ Parsons Brinckerhoff-Tudor-Bechtel (1960). Trans-bay tube: engineering report (Report). San Francisco Bay Area Rapid Transit District. Retrieved 7 September 2016. 
  19. ^ Parsons Brinckerhoff-Tudor-Bechtel (June 1961). Engineering Report to the San Francisco Bay Area Rapid Transit District (PDF) (Report). San Francisco Bay Area Rapid Transit District. p. 21. Retrieved 7 September 2016. Use of a precast concrete tube with metal shell for the underwater crossing between shore points is recommended. 
  20. ^ a b "Final Section Of Transit Tube Lowered Into San Francisco Bay". Lodi News-Sentinel. UPI. 4 April 1969. Retrieved 18 August 2016. 
  21. ^ a b "BART Tunnel Completion Moves Near". Lodi News-Sentinel. UPI. 31 March 1969. Retrieved 20 August 2016. 
  22. ^ "BART Tube Is Opened For Sunday Visitors". Lodi News-Sentinel. UPI. 10 November 1969. Retrieved 20 August 2016. 
  23. ^ Leavitt, Carrick (16 September 1974). "After three year wait BART goes down the tube". Ellensburg Daily Record. UPI. Retrieved 20 August 2016. 
  24. ^ "Bay Area Rapid Transit System to Open Last Link". The Times-News. AP. 27 August 1974. Retrieved 20 August 2016. 
  25. ^ "Bay tube run made by BART". Lodi News-Sentinel. UPI. 11 August 1973. Retrieved 20 August 2016. 
  26. ^ a b c Frobenius, P.K.; Robinson, W.S. (1996). "3: Tunnel Surveys and Alignment Control". In Bickel, John O.; Kuesel, Thomas R.; King, Elwyn H. Tunnel Engineering Handbook (Second ed.). Norwell, Massachusetts: Kluwer Academic Publishers. p. 35. ISBN 978-1-4613-8053-5. Retrieved 20 August 2016. 
  27. ^ a b "Bay Tube is quake proof". Lodi News-Sentinel. UPI. 12 January 1978. Retrieved 18 August 2016. 
  28. ^ Wilson, Ralph (2016). "History of Potrero Point Shipyards and Industry". Pier 70 San Francisco. Retrieved 20 August 2016. 
  29. ^ "Bethlehem built section of the BART Tubes at Pier 70". Bethlehem Shipyard Museum. 2016. Retrieved 20 August 2016. 
  30. ^ a b Walker, Mark (May 1971). "BART—The Way to Go for the '70s". Popular Science. New York, New York: Popular Science Publishing Company. 198 (5): 50–53; 134–135. Retrieved 20 August 2016. 
  31. ^ Gerwick Jr, Ben C. (2007). "5: Marine and Offshore Construction Equipment". Construction of Marine and Offshore Structures (Third ed.). Boca Raton, Florida: CRC Press. pp. 139–140. ISBN 978-0-8493-3052-0. Retrieved 20 August 2016. 
  32. ^ "Building some of the world's longest immersed-tube tunnels". Skanska (blog). 21 January 2014. Retrieved 20 August 2016. 
  33. ^ United States nominal Gross Domestic Product per capita figures follow the Measuring Worth series supplied in Johnston, Louis; Williamson, Samuel H. (2016). "What Was the U.S. GDP Then?". MeasuringWorth. Retrieved April 10, 2016.  These figures follow the figures as of 2015.
  34. ^ Godfrey Jr., Kneeland A. (December 1966). "Rapid Transit Renaissance". Civil Engineering. American Society of Civil Engineers. 36 (12): 28–33. 
  35. ^ "Transit system safety studied". Lawrence Journal-World. AP. 23 January 1975. Retrieved 17 August 2016. 
  36. ^ "Mayors open Transbay Tube". Lawrence Journal-World. AP. 20 September 1969. Retrieved 17 August 2016. 
  37. ^ "Bay Tube Gets Longer". Reading Eagle. UPI. 16 December 1968. Retrieved 17 August 2016. 
  38. ^ "Exclusive Club 120 Feet Deep Offshore In San Francisco Bay". Ellensburg Daily Record. UPI. 12 March 1969. Retrieved 20 August 2016. 
  39. ^ a b Bender, Kristin J.; Alund, Natalie Neysa (31 January 2014). "BART: No damage after container ship's anchor drops near Transbay Tube". The Mercury News. San Jose, California. Retrieved 9 September 2016. 
  40. ^ a b c d e f g h i j Railroad Accident Report: Bay Area Rapid Transit District fire on train No. 117 and evacuation of passengers while in the Transbay Tube (PDF) (Report). National Transportation Safety Board. 19 July 1979. Retrieved 17 August 2016. 
  41. ^ "Bay Area Rapid Transit System". American Society of Mechanical Engineers. 24 July 1997. Retrieved 17 August 2016. 
  42. ^ US granted 3517515, Warshaw, Robert, "Tunnel construction sliding assembly", published 30 June 1970, issued 17 July 1968, assigned to Parsons Brinckerhoff Quade & Douglas, Inc. 
  43. ^ a b c "Seismic retrofit for BART's Transbay tube". TunnelTalk. March 2004. Retrieved 19 August 2016. 
  44. ^ a b "Transbay Tube Earthquake retrofit keeps farmers market in place". Bay Area Rapid Transit (Press release). 16 October 2006. Retrieved 6 September 2016. 
  45. ^ a b Housner, George W. (May 1990). Competing Against Time: The Governor's Board of Inquiry on the 1989 Loma Prieta Earthquake (Report). State of California, Office of Planning and Research. pp. 19; 25; 36–37; 39. Retrieved 7 September 2016. The impacts of the earthquake were much more than the loss of life and direct damage. The Bay Bridge is the principal transportation link between San Francisco and the East Bay. It was out of service for a [sic] over a month and caused substantial hardship as individuals and businesses accommodated themselves to its loss. [...] The most tragic impact of the earthquake was the life loss caused by the collapse of the Cypress Viaduct, while the most disruption was caused by the closure of the Bay Bridge for a month while it was repaired, leading to costly commute alternatives and probable economic losses. [...] On the other hand, the Board received reports of only very minor damage to the Golden Gate Bridge, which is founded on rock, and the BART Trans-bay Tube, which was specially engineered in the early 1960s to withstand earthquakes. [...] Two facts stand out: the importance of the Oakland–San Francisco link, and the volume of traffic borne by the San Francisco–Oakland Bay Bridge—approximately double that of the Golden Gate Bridge, and almost equal to the combined traffic carried by all four other bridges. For automobile traffic, the Golden Gate and Bay bridges are essentially nonredundant systems, with alternative routes via the other bridges being time consuming to a level that seriously impacts commercial and institutional productivity. [...] The critical role played by the BART Trans-bay Tube in cross-bay transportation is clear, as is the fact that the South Bay bridges (San Mateo and Dumbarton) accommodated most of the redistribution of vehicular traffic. [...] Engineering studies should be instigated of the Golden Gate and San Francisco–Oakland Bay Bridges, of the BART system, and of other important transportation structures throughout the State that are sufficiently detailed to reveal any possible weak links in their seimic resisting systems that could result in collapse or prolonged closure. 
  46. ^ Parsons Brinckerhoff Quade & Douglas, Inc. (November 1991). Transbay Tube Seismic Joints Post-Earthquake Evaluation (Report). San Francisco Bay Area Rapid Transit District. 
  47. ^ Cabanatuan, Michael (17 April 2004). "SAN FRANCISCO - OAKLAND / BART warns of possible leaks in Transbay Tube in big quake". San Francisco Chronicle. Retrieved 7 September 2016. 
  48. ^ Bechtel Infrastructure Corporation; Howard, Needles, Tammen & Bergendorff (2002). BART Seismic Vulnerability Study (Report). San Francisco Bay Area Rapid Transit District. Retrieved 7 September 2016. 
  49. ^ "BART awards first major construction contract to earthquake strengthen the Transbay Tube". Bay Area Rapid Transit (Press release). 16 October 2006. Retrieved 6 September 2016. 
  50. ^ Chou, J.C.; Kutter, B.L.; Travasarou, T.; Chacko, J.M. (August 2011). "Centrifuge Modeling of Seismically Induced Uplift for the BART Transbay Tube". Journal of Geotechnical and Geoenvironmental Engineering. American Society of Civil Engineers. 137 (8): 754–765. doi:10.1061/(ASCE)GT.1943-5606.0000489. 
  51. ^ Jordan, Melissa (20 March 2013). "Late-night work over next 14 months will strengthen Transbay Tube against a quake". Bay Area Rapid Transit (Press release). Retrieved 6 September 2016. 
  52. ^ "Next stage of Transbay Tube retrofit set to launch". Bay Area Rapid Transit (Press release). 26 January 2012. Retrieved 6 September 2016. 
  53. ^ "Transbay Tube Retrofit Work Wraps Up Early Ending Late Night Single Tracking" (Press release). Bay Area Rapid Transit District. December 2, 2013. Retrieved February 5, 2014. 
  54. ^ Cabanatuan, Michael (2 December 2013). "Transbay Tube retrofit, and late-night delays, end". San Francisco Chronicle. 
  55. ^ a b c d e "3: Case Studies". Making Transportation Tunnels Safe and Secure. Washington, DC: Transportation Research Board. 2006. pp. 42–44. ISBN 978-0-309-09871-7. Retrieved 17 August 2016. 
  56. ^ Chisholm, Daniel (1992). "5—The Fruits of Informal Coordination". Coordination Without Hierarchy: Informal Structures in Multiorganizational Systems. Berkeley, California: University of California Press. ISBN 9780520080379. Retrieved 17 August 2016. 
  57. ^ "BART train burns in tunnel; one killed". Eugene Register-Guard. AP. 18 January 1979. Retrieved 17 August 2016. 
  58. ^ "Fire shuts down BART 'tube'". Lodi News-Sentinel. UPI. 19 January 1979. Retrieved 17 August 2016. 
  59. ^ a b "BART cancels request to reopen bay tube". Lodi News-Sentinel. UPI. 12 February 1979. Retrieved 20 August 2016. 
  60. ^ "BART resumes tube service for first time since fatal fire". Eugene Register-Guard. AP. 5 April 1979. Retrieved 17 August 2016. 
  61. ^ "BART to participate in statewide earthquake drill Thursday" (Press release). San Francisco Bay Area Rapid Transit District. 14 October 2015. Retrieved 7 September 2016. 
  62. ^ a b Jordan, Melissa (2014). "Behind the Scenes of BART's Role as Lifeline for the Bay Area". San Francisco Bay Area Rapid Transit District. Retrieved 7 September 2016. Donna “Lulu” Wilkinson, an experienced train operator, was barreling through the Transbay Tube at 80 miles per hour in the cab of a 10-car train when the quake hit.
    “I didn’t even feel it,” she recalled. She was about halfway through to San Francisco when she got the order to stop and hold her position.
    It was routine procedure (and remains so) to do a short hold after any earthquake, even smaller ones, and passengers were familiar with that routine. “They didn’t panic,” she said. “I got on the intercom and told them we were holding for a quake and would be moving shortly.”
    The design and strength of the tube, an engineering marvel sunk into mud on the bottom of the bay, had insulated the train and its passengers from feeling the earth’s movements.
     
  63. ^ Annex to 2010 Association of Bay Area Governments Local Hazard Mitigation Plan "Taming Natural Disasters" (PDF) (Report). Association of Bay Area Governments. 2010. p. 8. Retrieved 7 September 2016. BART's success in maintaining continuous service directly after the 1989 Loma Prieta earthquake reconfirmed the system's importance as a transportation "lifeline." While the earthquake caused transient movements in the Tube there was no significant permanent movement and BART service was uninterrupted except for a short inspection period immediately following the quake. With the closure of the Bay Bridge and the Cypress Street Viaduct along the Nimitz Freeway, BART became the primary passenger transportation link between San Francisco and East Bay communities. Its average daily transport of 218,000 passengers before the earthquake increased to an average of 308,000 passengers per day during the first full business week following the earthquake. 
  64. ^ "Man Walking In Transbay Tube Prompts Temporary BART Shutdown". CBS SFBayArea. 15 October 2012. Retrieved 17 August 2016. 
  65. ^ Alund, Natalie Neysa (11 August 2013). "BART trains back on track after man found walking in Transbay Tube". Oakland Tribune. Retrieved 18 August 2016. 
  66. ^ a b Cabanatuan, Michael (2010-09-07). "Noise on BART: How bad is it and is it harmful?". SFGate. Retrieved 2016-04-22. 
  67. ^ "Riders notice a quieter ride following first of two tube shutdowns". www.bart.gov. 2015-08-13. Retrieved 2016-04-22. 
  68. ^ Reisman, Will (12 May 2013). "BART working to protect Transbay Tube from elements, ships". San Francisco Examiner. Retrieved 9 September 2016. 
  69. ^ Williams, Kale; Ho, Vivian (1 February 2014). "BART tube reopened after anchor scare". San Francisco Chronicle. Retrieved 9 September 2016. 
  70. ^ Cabanatuan, Michael (June 22, 2007). "BART's New Vision: More, Bigger, Faster". San Francisco Chronicle. p. A1. Retrieved April 17, 2008. 
  71. ^ Dowd, Katie (10 March 2016). "MTV show uses BART's Transbay Tube as the key to saving the world". San Francisco Chronicle. Retrieved 17 August 2016. 
  72. ^ Veca, Don (audio director); Napolitano, Jayson (interviewer) (7 October 2008). Dead Space sound design: In space no one can hear interns scream. They are dead. (Interview). Original Sound Version. Retrieved 18 August 2016. 
  73. ^ Dead Space Dev Diary #3 -- Audio on YouTube (starts at 4:30)

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