Bertha (tunnel boring machine)
Bertha is a 17.5 meters (57 ft)-diameter tunnel boring machine built specifically for the Washington State Department of Transportation's (WSDOT) Alaskan Way Viaduct replacement tunnel project in Seattle.[1] It was made by Hitachi Zosen Sakai Works in Osaka, Japan, and the machine's assembly was completed in Seattle in June 2013. The name Bertha, after Seattle's only female mayor, Bertha Knight Landes, was chosen by a panel (that included the Governor and Transportation Secretary) from submissions from kindergarten through 12th graders, who were asked to submit female names with Washington state heritage.[2]
By December 6, 2013, Bertha had tunneled 1,019 ft (311 m), or 11%, of the total 9,270 ft (2,830 m) length of the tunnel,[3] stopping about 60 ft (18 m) below ground between South Jackson Street and South Main Street.[4] However, on that day the machine's progress was halted by an unexpected impediment.[5] After a month's investigation, WSDOT announced that the machine's cutting blades had encountered an 8 in (200 mm) diameter, 119 ft (36 m) long 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.[6][7] Because the machine cannot cut through metal, the pipe damaged several of Bertha's cutting blades, necessitating blade replacement before the machine could proceed.[7] The pipes' locations were known to WSDOT and the agency thought they had been removed. As of now it is unclear if the state agency or one of its contractors is responsible for the left-behind pipes, or who is responsible for allowing the tunneling to proceed without their removal.[6][7]
In early February 2014, as Bertha was preparing to continue drilling, workers discovered it was overheating and that a damaged main bearing seal needed to be replaced. Multiple options were discussed to fix the problem, but Bertha is expected to be out of commission until March 2015.[8] In December 2014, workers were digging a pit in order to lift Bertha's front end up to street level for repairs.[9] As of March 30th, 2015, Bertha's drill head has been almost fully removed from the pit.
References
- ↑ Tunneling toward a new SR 99, Washington State Department of Transportation, 2012
- ↑ Yerkan, KaDeena (December 10, 2012), SR 99 tunneling machine tweets her name: Bertha, Alaskan Way Viaduct Replacement Program, Washington State Department of Transportation
- ↑ Washington State Department of Transportation, Tracking Bertha, the SR 99 tunneling machine, archived from the original on December 19, 2013, retrieved January 5, 2014
- ↑ Associated Press (December 11, 2013), "Seattle tunnel-boring machine Big Bertha still stuck; obstruction could be boulder, rail car", The Oregonian
- ↑ Kirk Johnson (2013-12-20). "'The object’`': Something deep and mysterious has blocked the world's biggest tunnel boring machine under Seattle". National Post. Archived from the original on 2013-12-20. Retrieved 2013-12-21.
- ↑ 6.0 6.1 Lindblom, Mike (January 3, 2014), "Bertha's nemesis: 119-foot steel pipe; Highway 99 contractors revealed Friday what’s been blocking Bertha, the giant tunnel machine: The obstruction is steel pipe, left buried by a state groundwater study in 2002", Seattle Times, retrieved January 5, 2014
- ↑ 7.0 7.1 7.2 Johnson, Kirk (January 3, 2014), "Drilling and other equipment last month in Seattle, where a tunnel-boring machine was blocked", The New York Times, retrieved January 5, 2014
- ↑ http://www.wsdot.wa.gov/Projects/Viaduct/Contents/Item/Display/1601
- ↑ "Actually, digging continued Tuesday at Bertha’s repair pit". The Seattle Times. December 9, 2014.