Bertha (tunnel boring machine) explained

Bertha
Classification:Tunnel boring machine
Application:State Route 99 tunnel
Dimensions:Length: 326feet
Diameter: 57.5feet
Free Label:Cost
Free Text:$80 million
Free Label1:Launched
Free Text1:July 30, 2013
Free Label2:Disassembled
Free Text2:August 2017

Bertha was a 57.5feet tunnel boring machine built specifically for the Washington State Department of Transportation's (WSDOT) Alaskan Way Viaduct replacement tunnel project in Seattle, Washington, United States.[1] It was made by Hitachi Zosen Sakai Works in Osaka, Japan, and the machine's assembly was completed in Seattle in June 2013. Tunnel boring began on July 30, 2013, with the machine originally scheduled to complete the tunnel in December 2015.

On December 6, 2013, work was halted approximately 1083feet into the planned 9270adj=midNaNadj=mid route because of an unexpected impediment. It was thought that several cutting blades were damaged by striking a steel pipe that had been used to measure groundwater in 2002 around the Alaskan Way Viaduct. However, subsequent investigation revealed that portions of the main bearing seal system were damaged, causing the bearing to overheat during operation.[2] Over the next two years, a recovery pit was dug from the surface in order to access and lift the machine's cutterhead for repair and partial replacement in 2015.

Bertha resumed tunnel boring on December 22, 2015, but was stopped in early January 2016 after a tethered barge in Elliott Bay damaged nearby piers and a sinkhole opened near the project site. Governor Jay Inslee halted all work on the tunnel on January 14, 2016, citing concern over public safety after the sinkhole incident. Digging briefly resumed on February 23, but was halted again for maintenance and inspections before resuming full operations on April 29.[3]

In December 2015, WSDOT had estimated that the tunnel would be completed and open to traffic in early 2018.[4] The estimate was revised in July 2016 to open in early 2019 with an estimated $223 million in cost overruns stemming from the two-year delay.[5] Tunnel boring was completed on April 4, 2017, with Bertha's cutterhead breaking through into a disassembly vault at the tunnel's north portal in South Lake Union.[6] The final disassembled pieces of the boring machine were removed in August 2017, and the finished tunnel opened to traffic on February 4, 2019. Bertha's components were not reusable and were scrapped.

Name

The name Bertha, after Seattle's first female mayor, Bertha Knight Landes, was chosen by a panel (that included the Governor and Transportation Secretary) from 150 submissions from kindergarten through 12th graders, who were asked to submit female names with Washington state heritage.[7] The winning entry, which was submitted by two elementary schools in Poulsbo and Hoquiam, was selected in December 2012.[8]

Some media have also referred to the machine as "Big Bertha".[9] [10]

In March 2016, regional transit agency Sound Transit decided to drop names for its own tunnel boring machines, used for smaller light rail tunnels, citing unwanted association and confusion with Bertha, especially the machine "Brenda" used on the Northgate Link Extension and University Link Tunnel.[11] [12]

Design and assembly

Bertha was designed and manufactured by Hitachi Zosen Sakai Works of Osaka, Japan, and was the world's largest earth pressure balance tunnel boring machine,[13] at a cutterhead diameter of 57.5feet across. The machine was 326feet long and weighed .[14] The machine itself cost $80 million and was owned by Seattle Tunnel Partners (STP), the project contractors.[15] STP is a joint venture of New York-based Dragados USA, a wholly owned subsidiary of Dragados, S.A., the construction division of ACS Group of Spain; and Tutor Perini Corporation, based in Sylmar, California.[16]

Hitachi Zosen held a completion ceremony for the machine, performed at the same time as the naming ceremony, in Osaka, Japan, on December 20, 2012.[17] Test assembly and shakedown on Bertha in Japan indicated issues with the main-drive unit and tolerances that required repairs in February 2013.[18] [19] Bertha was shipped to the Port of Seattle in 41 sections, arriving on April 2, 2013.[20] [21]

Bertha had a special pre-programmed melody that played for workers inside the machine and those monitoring the tunnel-borer.[22]

Excavation

Dedication and first section

The machine began excavation of the 1.7adj=midNaNadj=mid route on July 30, 2013, with completion of the bore scheduled in 14 months' time and the tunnel opening to traffic in December 2015.[23] [24] [25] Over 5,000 members of the public, along with Governor Jay Inslee, were present for the machine's dedication a week prior to the beginning of excavation.[26] [27]

Damage to cutterhead and two-year delay

By December 6, 2013, Bertha had tunneled 1019feet, or 11%, of the total 9270feet length of the tunnel,[28] stopping about 60feet below ground between South Jackson Street and South Main Street.[29] The machine's progress was halted on that day by an unexpected impediment.[30] After a month's investigation, WSDOT announced that the machine's cutting blades had encountered an 8adj=midNaNadj=mid, 119adj=midNaNadj=mid steel pipe, one of several well casings left over from a previous 2002 drilling project that had assessed groundwater conditions and soil stability in the area in case of another earthquake, such as the 2001 Nisqually earthquake, which led to a need for the replacing of the Alaskan Way Viaduct in the first place. Because the machine cannot cut through metal, the pipe damaged several of Bertha's cutting blades, necessitating blade replacement before the machine could proceed. The pipes' locations were known to WSDOT and the agency thought they had been removed, while STP admitted in a 2019 lawsuit that they had knowledge of the pipe prior to excavation.[31] [32] [33] [34]

In early February 2014, as Bertha was being prepared to resume operation, workers discovered it was overheating and that a damaged main bearings seal needed to be replaced. Multiple options were discussed to fix the problem, but Bertha was expected to be out of commission until March 2015.[35] In December 2014, workers began digging a 120adj=midNaNadj=mid pit in order to lift Bertha's front end up to street level for repairs,[36] but were delayed when groundwater pumping caused visible damage to nearby South King Street and some of its neighboring buildings.[37] The front end of the machine, including the damaged cutter head, was successfully lifted onto the surface on the morning of March 31, 2015.[38] STP estimated that fixing Bertha would delay the opening of the new tunnel by an additional nine months to August 2017,[39] which was later extended to March 2018 after additional damage was discovered in June 2015.[40] [41]

On May 18, 2015, WSDOT reported to the Seattle City Council that the damage to the bearing and seals was worse than had been previously reported. Further inspection after the cutting head was removed and disassembled showed damage to the cutter head drive gears, so a new estimate of the repair time and cost was prepared.[42]

The front end of the machine was lowered back into the access pit for reassembly in a four-lift process beginning with the repaired cutter drive on August 24, 2015.[43] [44] [45]

In June 2015, STP sued to force insurers to payout on the $85 million insurance policy to cover repairs needed after Bertha's cutting teeth were damaged in a collision with a steel pipe in December 2013. In August 2015, a consortium of eight insurers filed a lawsuit against STP in order to avoid a $143 million payout to cover the cost of repairs to the boring machine. The insurers claimed that the tunnel-boring machine's capabilities were inadequate for the project and should be excluded.[46]

It is unclear what triggered the damage to Bertha's main bearing. Problems with the seal system appear to date back to the machine's initial testing in Japan, when the seal assembly was damaged and required repairs.[47] However, Hitachi Zosen general manager Soichi Takaura later stated that "there was nothing wrong with the seals in the original machine", noting that Bertha appeared to function properly before striking the well casing. WSDOT disputed this, and stated that the well casing was not responsible.[48]

Resumption of digging and subsequent activities

On December 22, 2015 at 12:30 a.m., the machine resumed digging 1.5feet through sand poured into the recovery pit. By January 4, Bertha had traveled 1098feet of its planned 9270adj=midNaNadj=mid route from SoDo to South Lake Union.[4] On January 6, 2016, Bertha broke through the concrete access vault and began digging through normal soil.[49] [50] Digging was halted once again on January 12, 2016, after a barge carrying excavated dirt tipped over in Elliott Bay, spilling its load and damaging a dock at the Port of Seattle's Terminal 46.[51] The same day, a sinkhole formed within the tunnel's work zone approximately 35feet north of the access pit; the hole was filled with 250cuyd of concrete by contractors the following day and was not expected by WSDOT to delay the resumption of digging later in the week.[52] [53]

On January 14, 2016, Governor Jay Inslee ordered drilling on the tunnel to stop, invoking a contract clause in the tunnel agreement that allowed the state to suspend work based on unsafe conditions for project personnel or the general public.[54] Before excavation of the tunnel could resume, WSDOT requested that STP complete and deliver an analysis of what caused the January 12 sinkhole and what modifications to tunneling operations could be made to prevent further ground-level problems.[55] [56]

Digging resumed on February 23, after a WSDOT review determined that new soil monitoring practices were sufficient, allowing the machine conditional permission to bore through 160feet of material and finish the initial testing phase of the machine.[57] By March 14, Bertha had finished its 300feet bore to a "safe haven" located ahead of the Alaskan Way Viaduct;[58] allowing WSDOT and STP to prepare for a two-week closure of the viaduct in late April as the machine passed under the vulnerable structure while closely monitored.[59] Following a month of maintenance and inspections, Bertha resumed tunneling on Friday, April 29, 2016,[3] and crossed 15feet under the closed viaduct in an 11-day closure in early May that ended earlier than scheduled.[60]

In June 2016, the tunnel reached its lowest point, 115feet under Madison Street in downtown.[61] A maintenance stop from June 23 to July 18 was conducted under Spring Street, replacing 33 of the cutterhead's teeth.[62]

By September 30, 2016, Bertha had tunneled 4635feet, surpassing the halfway mark of the planned 9270NaN distance.[63] the tunnel length reached 70% completion.[64]

Tunnel boring was completed on April 4, 2017,[6] and the finished tunnel opened to traffic on February 4, 2019.[65] Practically none of Bertha's components were reusable, and most of its steel was melted and recycled.[6] The final, disassembled pieces of Bertha were removed from the tunnel portal in August 2017.[66]

Zone advancement

Bertha's digging route was divided into 10 zones, representing different types of soil or progress under city landmarks.[67]

ZoneDate reachedDays since entering the previous zone
Zone 3May 26, 2016[68] n/a
Zone 4June 16, 2016[69] 21
Zone 5August 1, 2016[70] 46
Zone 6August 29, 2016[71] 28
Zone 7November 3, 2016[72] 66
Zone 8December 1, 2016[73] 28
Zone 9January 27, 2017[74] 57
Zone 10March 9, 2017[75] 41

Controversy

The two-year stoppage of Bertha has been criticized as an example of a political boondoggle by opponents.[76] [77]

In January 2015, two Republican state senators introduced a bill in the Washington State Legislature to kill the project, citing Bertha and its delay in particular. The bill was never heard in the state senate and failed to pass the Senate Transportation Committee.[78]

See also

External links

Notes and References

  1. Web site: 2012 . Tunneling toward a new SR 99 . . May 19, 2015 . December 10, 2012 . https://web.archive.org/web/20121210035623/http://www.wsdot.wa.gov/Projects/Viaduct/About/Tunneling . dead .
  2. News: Newcomb . Tim . February 10, 2014 . Damaged Main Bearing Seals Cause of Bertha Overheating, Shutdown . . April 4, 2017.
  3. News: Demay . Daniel . April 29, 2016 . Bertha inches ahead, viaduct closure begins, traffic slows . . April 30, 2016.
  4. News: Lindblom . Mike . January 4, 2016 . Tunnel machine Bertha expected to bust out of vault this week . . January 4, 2016.
  5. News: Lindblom . Mike . July 21, 2016 . Bertha's woes grind on: more delay, higher cost for Highway 99 tunnel . . July 21, 2016.
  6. News: Lindblom . Mike . April 4, 2017 . Bertha's breakthrough just 'halftime' for tunnel project . . April 6, 2017.
  7. Yerkan . KaDeena . December 10, 2012 . SR 99 tunneling machine tweets her name: Bertha . dead . https://web.archive.org/web/20141110124014/http://www.wsdot.wa.gov/News/2012/12/10_sr99_tunnel-machine-name.htm . November 10, 2014 . Washington State Department of Transportation . May 19, 2015.
  8. News: Cohen . Aubrey . December 10, 2012 . World's largest tunneling machine gets name, face, voice . . April 29, 2016.
  9. News: Grayson . Wayne . April 4, 2013 . Big Bertha, world's largest tunnel-boring machine, arrives in Seattle . . January 15, 2016.
  10. News: Dahl . Timothy . January 8, 2016 . Seattle's Big Bertha Tunneling Machine Is Finally Back on Track . . January 15, 2016.
  11. News: Bush . Evan . March 28, 2016 . Thanks to Bertha, Sound Transit nixes nicknames for its own tunnel machines . . April 18, 2016.
  12. News: Sullivan . Chris . March 18, 2015 . Bad news Bertha overshadows successful sisters . MyNorthwest . April 18, 2016.
  13. Web site: The World's Largest EPB Shield Tunneling Machine . . April 29, 2016.
  14. News: December 25, 2013 . Big Bertha – world's largest tunnel boring machine – facing big Seattle challenge . . April 29, 2016.
  15. News: Wilhelm . Steve . April 2, 2013 . Bertha tunnel-boring machine arrives to make big splash in Seattle . Puget Sound Business Journal . April 29, 2016.
  16. Web site: . SR 99 Bored Tunnel Alternative Design-Build Project . June 12, 2017 . https://web.archive.org/web/20170220221540/http://www.wsdot.wa.gov/nr/rdonlyres/35fae5c0-c79f-496d-9354-dec2e4e98819/0/sr99boredtunnel_stp.pdf . February 20, 2017 . dead .
  17. News: December 21, 2012 . Becoming Bertha: the journey begins for the world's largest tunneling machine . WSDOT Blog . Washington State Department of Transportation . April 29, 2016.
  18. Web site: Testing of the SR 99 tunneling machine continues in Japan . WSDOT Blog . Washington State Department of Transportation . 16 February 2019 . January 23, 2013.
  19. Web site: SR 99 tunneling machine problem nearly fixed . WSDOT Blog . Washington State Department of Transportation . 16 February 2019 . February 11, 2013.
  20. News: Lindblom . Mike . April 2, 2013 . Mammoth tunnel drilling machine arrives in Seattle . . April 29, 2016.
  21. April 1, 2013 . World's largest tunneling machine arrives by ship in Seattle April 2 . Washington State Department of Transportation . April 29, 2016.
  22. News: Raftery . Jillian . April 29, 2016 . Did you know Bertha whistles while she works? . MyNorthwest . . April 29, 2016.
  23. Yerkan . KaDeena . July 30, 2013 . Bertha starts digging: tunneling underway in Seattle . Washington State Department of Transportation . December 5, 2015.
  24. News: Lindblom . Mike . July 30, 2013 . Bertha's excavation mission beginning under downtown . . December 5, 2015.
  25. News: Aitchison . Sarah . July 17, 2015 . State officials skeptical Bertha contractor can deliver on new deadline . . December 27, 2015.
  26. Yerkan . KaDeena . July 20, 2013 . Bon voyage party for Bertha draws 5,000 to SR 99 tunnel site . Washington State Department of Transportation . December 5, 2015.
  27. News: Jarvis . Brooke . July 31, 2013 . Bon Voyage, Big Bertha! Seattle Digs a Cave For the Future . . December 5, 2015.
  28. Yerkan . KaDeena . December 10, 2013 . WSDOT Statement on SR 99 Tunneling Machine . Washington State Department of Transportation . May 19, 2015.
  29. Newborn . Laura . December 13, 2013 . Tunnel crews lowering groundwater to get a closer look at what's blocking Bertha . Washington State Department of Transportation . May 19, 2015.
  30. News: Johnson . Kirk . December 20, 2013 . 'The object': Something deep and mysterious has blocked the world's biggest tunnel boring machine under Seattle . . December 21, 2013.
  31. News: Lindblom . Mike . January 3, 2014 . Bertha's nemesis: 119-foot steel pipe . . January 5, 2014.
  32. News: Lindblom . Mike . December 13, 2019 . Contractor ordered to pay Washington state $57M over tunnel-boring machine Bertha;s big stall . The Seattle Times . December 18, 2019.
  33. News: Johnson . Kirk . January 3, 2014 . Prosaic Pipe Stymied Seattle's Big Bertha . . January 5, 2014.
  34. Newborn . Laura . January 4, 2014 . Progress made on SR 99 tunnel blockage . Washington State Department of Transportation . May 19, 2015.
  35. Newborn . Laura . April 21, 2014 . SR 99 tunneling machine to resume digging in March 2015 . Washington State Department of Transportation . May 19, 2015.
  36. News: Lindblom . Mike . December 9, 2014 . Actually, digging continued Tuesday at Bertha's repair pit . . May 19, 2015.
  37. News: Lindblom . Mike . December 8, 2014 . New delay in Bertha rescue as engineers study sinking soil . . May 19, 2015.
  38. News: Lindblom . Mike . March 31, 2015 . Bertha's mammoth cutter head emerges from tunnel vault . . May 19, 2015.
  39. News: Lindblom . Mike . December 22, 2014 . New estimate of tunnel opening: August 2017 . . May 19, 2015.
  40. Newborn . Laura . July 17, 2015 . Seattle Tunnel Partners submits new schedule for completing SR 99 Tunnel Project . Washington State Department of Transportation . July 17, 2015.
  41. News: Lindblom . Mike . July 17, 2015 . New Bertha start date to resume digging is Nov. 23 . . July 17, 2015.
  42. News: Lindblom . Mike . May 18, 2015 . Bertha repair will take longer – there are lots of broken parts . . May 19, 2015.
  43. News: August 24, 2015 . Aug. 24 project update: Seattle Tunnel Partners planning to lower Bertha into the access pit today . Washington State Department of Transportation . August 26, 2015.
  44. News: DeMay . Daniel . August 24, 2015 . Bertha going back underground . . August 26, 2015.
  45. News: Lindblom . Mike . August 24, 2015 . Crews start moving Bertha's rebuilt cutter drive back into pit . . August 26, 2015.
  46. News: August 30, 2015 . Case information . August 30, 2015.
  47. News: Lindblom . Mike . Garber . Andrew. Bertha's big troubles started in Japan. 3 May 2017. . February 25, 2014.
  48. News: Lindblom . Mike . Bertha's builders: Tunnel borer started out 'perfect'. 3 May 2017. . July 20, 2016.
  49. Web site: January 7, 2016 . Jan. 7 project update: Bertha exits the access pit . Washington State Department of Transportation . January 7, 2016.
  50. News: Bush . Evan . January 7, 2016 . Bertha making progress, tunnels 73 feet since repairs . . January 7, 2016.
  51. News: Lindblom . Mike . January 12, 2016 . Bertha stops digging again, but this time it's because of a barge . . January 12, 2016.
  52. News: Lindblom . Mike . January 13, 2016 . Sinkhole adds to Bertha's problems, but drilling to resume . . January 13, 2016.
  53. News: DeMay . Daniel . January 13, 2016 . While Bertha halts over barge issues, sinkhole opens near access pit . . January 13, 2016.
  54. News: Lindblom . Mike . January 14, 2016 . Inslee orders tunnel dig halted as soil sinks above Bertha . . January 14, 2016.
  55. Web site: January 14, 2016 . Jan. 14 project update: Tunneling on hold pending safety review . Washington State Department of Transportation . January 14, 2016.
  56. News: Stewart . Ashley . January 14, 2016 . Gov. Inslee halts Bertha work after sinkhole forms near project . Puget Sound Business Journal . January 14, 2016.
  57. News: Lindblom . Mike . February 23, 2016 . She's ba-ack! Yes, Bertha's on the move once again . . February 23, 2016.
  58. News: Lindblom . Mike . March 14, 2016 . Tunnel machine Bertha moves 300 feet, reaches 'safe haven' . . April 18, 2016.
  59. News: Lindblom . Mike . April 11, 2016 . Viaduct closure coming once Bertha's ready to dig . . April 18, 2016.
  60. News: Demay . Daniel . May 11, 2016 . Viaduct closure ends, Bertha to make pit stop . . May 15, 2016.
  61. News: June 13, 2016 . June 13 project update: Bertha passes the half-mile mark . Washington State Department of Transportation . June 15, 2016.
  62. News: Lindblom . Mike . July 19, 2016 . Bertha restarts early — with 33 new teeth (out of 750) . . July 20, 2016.
  63. October 3, 2016 . Bertha Passes Halfway Point . Washington State Department of Transportation . October 3, 2016.
  64. News: Dyer . Oxley . 'Finish line in sight' for Bertha under Seattle . MyNorthwest . December 15, 2016 . December 15, 2016.
  65. Web site: New tunnel? No problem? It was an easy, light-traffic day Monday on Highway 99. 2019-02-04. The Seattle Times. en-US. 2019-03-06.
  66. News: Lee . August 23, 2017 . From disassembly pit, crews haul away last bits of Bertha . . August 26, 2017.
  67. Web site: Follow Bertha . February 10, 2017 . February 10, 2017.
  68. Web site: Bertha is now tunneling under buildings in downtown Seattle . May 27, 2016 . February 26, 2017.
  69. Web site: Distance update: Bertha has traveled a total of 2,886 feet. She's now in Zone 4 of the tunnel drive. . June 16, 2016 . February 10, 2017.
  70. Web site: Bertha is now in Zone 5 of the tunnel drive . June 16, 2016 . February 10, 2017.
  71. Web site: Monday tunneling update: Bertha has reached zone 6 . August 29, 2016 . February 10, 2017.
  72. Web site: Bertha is past Stewart St. & the 1-mile mark . November 3, 2016 . February 10, 2017.
  73. Web site: #BalloonsOverBertha at 2nd/Lenora. Now past 6,000 ft., Bertha digs into Belltown and Zone 8 of the tunnel drive . December 1, 2016 . February 10, 2017.
  74. Web site: Yesterday's progress update: Bertha has reached Zone 9 of the tunnel drive! . January 27, 2017 . February 10, 2017.
  75. Web site: March 9, 2017 . March 9 project update: New 360-degree video takes you inside the tunnel as Bertha enters Zone 10 . Washington State Department of Transportation . March 9, 2017.
  76. News: Lindblom . Mike . September 18, 2014 . Seattle tunnel tops U.S. green group's 'boondoggle' list . . January 14, 2016.
  77. News: Roberts . David . June 5, 2015 . Seattle's unbelievable transportation megaproject fustercluck . . January 14, 2016.
  78. News: Connelly . Joel . January 27, 2015 . Bertha: Off the hook in the Legislature but not out of mind . . January 14, 2016.