December 14, 2016

Tunnel is now 70% complete with Bertha running well, soil ‘behaving'

Photo by Benjamin Minnick [enlarge]

This train delivered 10 segments — enough to build one tunnel ring — to Bertha during a media tour yesterday.

Yesterday crews from Seattle Tunnel Partners placed the 1,000th ring that forms the 1.7-mile replacement tunnel for the Alaskan Way Viaduct. The tunnel is now 70 percent complete.

STP project manager Chris Dixon said crews have built more than a mile of the tunnel and nearly 3,000 feet of the top deck for the double-decker highway since the tunnel machine named Bertha restarted nearly a year ago.

Crews are placing between seven and 10 rings a day, though Dixon said one day they placed 13. When the tunnel is done, it will have 1,426 rings.

Dixon said Bertha is running well and the ground is “behaving.”

“A lot of how the tunnel goes is dictated by the ground conditions,” he said.

STP is on schedule to substantially finish the tunnel in November 2018, and turn it over to WSDOT at that time. Bertha is expected to break through its northern terminus near the Space Needle next June.

WSDOT will make connections to the tunnel and open it to traffic in early 2019, according to the latest schedule.

Bertha was stalled for nearly two years after it overheated in December 2013. Crews had to dig a rescue pit and remove damaged parts of the machine to fix it.

“I think the repair effort was a tremendous feat,” Dixon said.

The top of Bertha is now about 170 feet below the surface, around Third Avenue and Blanchard Street.

STP will stop mining between Christmas and New Year's, but other work will continue during that period.

Dixon said the infrastructure part of the tunnel catches up when Bertha takes a break for maintenance. When Bertha restarts, the machine speeds ahead of the infrastructural work.

WSDOT has posted a link where you can find more information: http://www.wsdot.wa.gov/Projects/Viaduct/.