Bertha more than halfway through tunnel dig; WSDOT calls it big 'milestone'

SEATTLE -- A rare look underground 6th and Thomas was offered Monday where Bertha is expected to end her dig next spring.

The site is also the place crews are building one of two operation centers that will monitor the tunnel once it replaces the Alaskan Way Viaduct.

On Monday, WSDOT said Bertha is more than halfway done digging the tunnel.

The tunnel is currently underneath First Avenue between Pike and Pine Street, a place almost always packed with tourists.

“I just like that we can walk everywhere,” Jared Robinett said.

What Jared and his wife, Alexa, can’t see is Bertha, 190 feet beneath them. The giant tunnel-boring machine has been working underneath downtown Seattle since 2013.

“It makes me a little nervous," said Colleen Wilke, who opened up Shug’s Soda Fountain and Ice Cream several months ago near First Avenue and Pine, the halfway mark of Bertha’s nearly 2-mile dig.

“Fifty percent is a major milestone for the project, but I do not want to distract that there is 50% to go,” WSDOT's Joe Hedges said.

Hundreds of boulders two to eight feet in diameter could be in the way of Bertha’s cutterhead. Moving forward, the soil underground will be turning from clay to sands and gravel, which are more abrasive.

“There is a lot of unknowns, a lot of uncertainties. What we need to do is be consistent with our approach,” Hedges said.

Once Bertha is finished digging, it will rest in a pit 10 stories underground near 6th and Thomas, close to the Space Needle.

“The machine will come in here and sit on the cradle,” said Chris Dixon, who is with the contractor, Seattle Tunnel Partners. If the dig continues without any hiccups, Bertha is expected to punch through the hole in the pit sometime in May.

At that point, crews will continue to build the double-decker highway, the operation centers and other infrastructure that will help replace the viaduct. The project could last until January 2019.

“They say it’s going to open in 2015 and now it’s 2019; what does that mean, 2022?" asked Seattle resident Heman Hill.

Some are frustrated with the project’s three-year delay and $60 million cost overrun so far. But WSDOT is feeling encouraged over the progress they’ve seen during the past six months.

“Everything is going according to plan, as we’ve been going up First Avenue, almost zero ground movement,” Dixon said.

Shug’s owner says she can attest to that.

“Can’t feel the vibrations, that’s interesting to know,” Wilke said.

The tunnel was supposed to be completed in December 2015 now the completion date is expected to be January 2019.

Bertha was delayed for almost two years because the machine broke down, leading to the delay and cost overruns.