Bertha (tunnel boring machine)
Bertha, at 17.5 meters (57 ft) in diameter, is the largest tunnel boring machine in the world as of 2013[update], built specifically for the Washington State Department of Transportation's (WSDOT) Alaskan Way Viaduct replacement tunnel project in Seattle. 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 including the Governor and Transportation Secretary from submissions from kindergarten through 12th graders, who were asked to suggest names of a female who had significant Washington state heritage.
On December 6, 2013, the machine's progress was halted by an unexpected impediment. 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 previous drilling done in 2002 to assess groundwater conditions and soil stability in the area in case of another earthquake, like the 2001 Nisqually earthquake which led to the need for a replacement for the Alaskan Way Viaduct. 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 were supposed to have been removed; as of yet it is not known if the state agency or a contractor is responsible for the pipes having been left behind or for tunneling having proceeded without their having been removed. As of 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, stopping about 60 ft (18 m) below ground between South Jackson Street and South Main Street. In early February 2014, as Bertha was preparing to continue drilling, workers discovered that it was overheating and subsequently that a main bearing seal had been damaged and required replacement. Multiple options were discussed to fix the problem, but Bertha is expected to be out of commission until March 2015.
- Foley, Amanda (3 April 2013). "Big Bertha arrives in Seattle". Tunneling Journal. Retrieved 21 December 2013.
- Tunneling toward a new SR 99, Washington State Department of Transportation, 2012
- KaDeena, Yerkan (December 10, 2012), SR 99 tunneling machine tweets her name: Bertha, Alaskan Way Viaduct Replacement Program, Washington State Department of Transportation
- 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.
- 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
- 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
- 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