Work was halted on December 6, 2013 after the machine overheated and shut down [70] approximately 1,083 feet (330 m) into the planned 9,270-foot-long (2,830 m) route. Investigations later revealed the seal system that protects the machine’s main bearing had been damaged. Three days prior to stopping, the machine mined through an 8-inch-steel well-casing used to help measure groundwater in 2002 around Alaskan Way, drilled as part of the planning phases of the project.[71] Whether this pipe had anything to do with the machine’s failure is at the center of legal dispute between WSDOT and the contractor, Seattle Tunnel Partners.[72] This delay lasted for more than two years as the workers had to dig a 120-foot (37 m) vertical shaft down to Bertha’s cutting head to repair it. Settling was discovered in Pioneer Square that may be related to this additional excavation.[73]
Tunnel boring had resumed on December 22, 2015.[74][75] The tunnel boring was halted 23 days later on January 14, 2016, after a 30-foot-wide (9.1 m) sinkhole developed on the ground in front of the machine, causing Governor Jay Inslee to halt drilling until the contractors can perform a root cause analysis to show that the machine can be run safely.[76] Even though contractors filled the hole with 250 cubic yards (190 m3) of material, the ground above the tunnel-boring machine continued to sink, according to the Washington State Department of Transportation. The tunneling restriction was lifted on February 23, 2016, and tunneling resumed that day.[77] Bertha passed under the Alaskan Way Viaduct in early May, closing the roadway for 11 days as the machine had 15 feet (4.6 m) of vertical clearance under the structure’s pilings.[78] On April 4, 2017, the tunnel boring machine broke through to the recovery pit on the north end of the tunnel, completing the excavation process.[79] The boring machine was dismantled and removed from the site over the next four months.[80]
Back of tunnel boring machine and partially completed tunnel with concrete walls in place in 2017
Dirt produced by tunnel construction was sent to fill a CalPortland quarry in nearby Port Ludlow.[81]
As I said in my prior post...I love what the Big Dig did for Boston even if I don’t agree with the way it was funded and executed.
Right in the middle of the Big Dig project, our family was visited by an old friend who lived in California. He was involved in large construction projects, not like the big dig, but larger than individual large office buildings.
When he got off the plane in Boston, he was astonished looking at the city. Apparently there are special cranes that you only see at very large projects, and most of the time you only see one or two (according to him). He knew of what he spoke, and he said the most of those kinds of cranes he had ever seen in one spot at one time was four.
At that time, I recall he said he counted twelve of them!
I don’t know what they used them for, but I do know that huge earthmoving machines were routinely lowered through vertical tunnels hundreds of feet down, often with inches to spare around the device as it was lowered.
Pretty impressive stuff.
One of the last things to be done after the tunnels were completed was to actually remove the elevated roadway, a rusty green eyesore that cut the city in half. They apparently accomplished that in a comparatively short time frame.
My wife and I had not gone into Boston for months, and we took the train in...when we got off and walked around the corner near what is called “City Hall Plaza ( a real eyesore of a building in and of itself) we had our breath taken away.
The Expressway was gone. Just gone. You only saw blue sky, where there had formerly been that crappy POS highway that caused so much irritation and traffic misery for decades.
That was pretty cool.
from wiki
“As of 2019, litigation is ongoing over which parties are responsible for the $642 million repair to the tunnel boring machine.[83][84] Fragments of the steel well casing struck in December 2013 and cited as a possible cause of Bertha’s breakdown were stored as evidence at the construction site and subsequently went missing in 2014.[83][85] Detailed journal entries kept by the tunnel contractor’s deputy project manager between December 2013 and February 2014 also went missing”
In reading about it at the time, I thought that the real reason for the problems with the boring machine was that they never assembled it at the factory and tested it. It was assembled for the first time in the dig hole.