The $80 million tunneling machine known as 'Bertha' resumed mining Tuesday beneath the Seattle waterfront for the first time in about seven weeks.
The machine moved forward about two feet, allowing contractors to resume building the next tunnel ring, which was underway when the machine stopped on December 6.
Once that is done, Seattle Tunnel Partners will begin an evaluation of the machine, which will determine when full-scale mining can resume, according to the Washington State Department of Transportation. The tunneling machine stopped after it chewed into a steel pipe and began to encounter unusual resistance.
Bertha has advanced about 1,000 feet along the 1.7 mile tunnel route.
In an update posted online Monday night, WSDOT said the next milestone for Bertha is a safe haven about 500 feet ahead of the current location. The contractor said the third and final safe haven is a controlled environment used for maintenance before the machine moves beneath the Alaskan Way Viaduct and downtown Seattle.
The state plans to close SR 99 while tunneling is underway beneath the viaduct.