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The World's Largest Tunneling Machine
The 7,000-ton machine, named after Seattle's first female mayor, is digging a tunnel this summer to replace the city's iconic highway, the Alaskan Way Viaduct.
Seattle's Alaskan Way Viaduct, which runs along the city's waterfront near downtown, is a double-decker highway slated to be replaced with a tunnel. (Photos: FlickrCC/WSDOT)
Last year, a Japanese company began assembling "Bertha," the tunnel-boring machine that will slice through the earth to make room for the underground roadway.
Bertha was transported by ship from Japan to the Port of Seattle earlier this year. At 57.5 feet, she has the largest diameter of any tunnel-boring machine in the world.
Once the pieces of Bertha arrived in Seattle, they had to be re-assembled at the site of the launch pit where the machine will begin its work.
Last year, crews worked on building the launch pit, where Bertha will begin her two-mile underground journey.
Crews lower a 400-ton piece of gear into the launch pit. Workers installed machinery at night so that their colleagues could work on the pit during the day.
Steel supports were installed underground to protect downtown buildings from the reverberations of the machine.
The 80-foot-deep launch pit was completed in May. After Bertha is reassembled in the pit and tested, she'll begin boring the tunnel in the summer.
Crews are installing sensors in downtown Seattle to measure and monitor reverberation that occurs during the tunneling process.
After 14 months of tunneling, Bertha will emerge two miles later here at this retrieval pit.
Pieces of the Bertha tunneling machine, next to the existing Alaskan Way viaduct, which will be demolished once the tunnel is complete.
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