Bertha, the tunnel boring machine (TBM) tasked with building the SR 99 tunnel in Seattle, is finally getting her day in the sun, though it’s hardly the attention her handlers, Seattle Tunnel Partners (STP) and the Washington State Department of Transportation (WSDOT) had planned on.
After being stalled for more than a year just 1,000 feet into her two-mile journey along the Seattle Waterfront, Bertha finally mustered enough energy to push 20 feet through unreinforced concrete into a specially excavated 120-ft deep access pit on February 27. Portions of Bertha’s massive cutterhead and the drive components are now being lifted to the surface for repair, a process that can be monitored from a variety angles via WSDOT’s construction cams.

STP, a joint venture of New York-based Dragados USA and Tutor Perini Corporation, is hopeful Bertha will be back to burrowing by the end of this summer, though WSDOT deputy project administrator Matt Preedy told a March 15 project stakeholders meeting that “if it takes a little bit longer, that’ll be OK because the project manager says it has to be done right.” STP has repeatedly touted Fall 2017 as the completion date for the $3 billion tunnel that will replace the aging, structurally suspect Alaskan Way viaduct.

That’s assuming, of course, Bertha’s repairs proceed as scheduled, and no other surprises materialize in the fill alongside Elliott Bay.
Speaking of the Viaduct, WSDOT told stakeholders that the 60-year old double-deck structure, damaged in the 2001 6.8 magnitude earthquake, remains safe, but close monitoring will continue. The next bi-annual full inspection is set for late March.
While Bertha has been the reluctant focus of Seattle’s construction spotlight, two other TBMs have been quietly munching their way through relatively benign soil to build  twin 3.6-mile tubes for the Sound Transit light rail system’s $2.1 billion Northgate Link Extension. TBM Brenda, which began her journey south from the Maple Leaf Portant near the project’s northern end in July 2014, a key milestone on March 17 by punching her 21.5 ft diameter drill through the last barrier at what will become the line’s Roosevelt Station.

A “sister TBM,” Pamela, is paralleling Brenda’s route and will reach Roosevelt station this summer. Both TBMs will then proceed beneath Seattle’s University District to Husky Stadium and a planned 2017 connection with Sound Transit’s soon-to-be-completed $1.9 billion University Link extension.

Brenda’s and Pamela’s tunnels are being constructed by a joint venture of Jay Dee, Coluccio, and Michels under a $462 million contract. The Northgate Link Extension is scheduled to be operational in 2021.