Boring of the tunnel with the diameter "Bertha," at the time the world's largest-diameter tunnel-boring machine, began on July 30, 2013, and at the time was expected to be completed in 14 months. After three weeks of drilling, the project was estimated to be two weeks behind schedule; problems with fiberglass near the front of the drill and a labor dispute with a local longshoreman's union were blamed. Work was halted on December 6, 2013 after the machine overheated and shut down  approximately into the planned 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 a hollow, 8-inch steel well-casing and pipe used to measure groundwater in 2002 around Alaskan Way, which was drilled as part of the planning phases of the project. The unexpected discovery of the pipe was blamed by the contractor for the work stoppage in litigation, but STP later admitted to its knowledge of the pipe's location prior to the start of tunnel boring. This delay lasted for more than two years as the workers had to dig a 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. Tunnel boring had resumed on December 22, 2015. The tunnel boring was halted 23 days later on January 14, 2016, after a 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. Even though contractors filled the hole with 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. Bertha passed under the Alaskan Way Viaduct in early May, closing the roadway for 11 days as the machine had of vertical clearance under the structure's pilings. 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. The boring machine was dismantled and removed from the site over the next four months. Dirt produced by tunnel construction was sent to fill a CalPortland quarry in nearby Port Ludlow. In July 2016, WSDOT estimated that the tunnel would be completed and open to traffic in early 2019. An estimated $223 million in cost overruns were reported as a result of the two-year stoppage.