Todd Trepanier, the project manager for the Alaskan Way Viaduct replacement project, confirmed today that Seattle Tunnel Partners (the tunnel contracting team) and Hitachi-Zosen (the firm that built the tunnel boring machine that's currently stuck underground in Pioneer Square) will likely have to replace the entire bearing that turns the cutterhead at the front of the drilling machine, rather than just replacing the seven seals that protect the bearing, which they had hoped was all they would have to do.
STP plans to replace the bearing, which Trepanier said is "about 30 feet in diameter," with a backup that will have to be shipped via boat from Japan.
The tunnel-boring machine has been stalled in place since early December, when it began overheating. Seattle Tunnel Partners (which initially said the stoppage was due to a pipe left in place by a previous project) ultimately said the problem was that Bertha's seals had cracked, and has been working on a plan to dig a circular pit, reinforced on all sides by concrete pillars, to reach the underground cutterhead and bring it above ground, enabling the team to repair the seals on the surface.
In February, STP project manager Chris Dixon said that the repairs could be completed, allowing the tunneling machine to get going again, within six months under an "optimistic" scenario. Under the current plan, Trepanier said, WSDOT is hoping to announce a repair plan publicly by the end of April, which could push that schedule back.
It's not clear how today's news affects that schedule. Trepanier said said STP "has told us it won't be until later in the month that they will pass that information on to us," adding that Dixon would be better able to answer any questions about the current project timeline. "I have not seen anything yet that makes me think it's going to be a big change" from Dixon's initial September estimate, but added, "that will be up to STP to tell us."
Trepanier also noted that the tunneling team is continuing to work on other projects that need to be done on the north and south ends of the tunnel, although much of that work would have been happening even if the tunnel machine was moving forward instead of stuck underground.
Asked why Dixon, who has appeared at a handful of press conferences about the tunnel (but bowed out of the most recent press call at the last minute) hasn't been accessible to answer questions, WSDOT spokeswoman Laura Newborn said, "We are just trying to give [STP] a little space because of how complicated this plan is. When we make the announcement [about the repair plan], Chris will be there. I think he's just reluctant to give out details that might change."