How does the world’s largest tunneling machine work? Take a look

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SEATTLE – The world’s largest tunneling machine, Bertha, is a complex machine. Now, residents around the sound are getting a look at how it works.

An animated video created by Bertha’s manufacturer, Hitachi Zosen Corp., illustrates how the machine will dig a two-mile long tunnel beneath downtown Seattle.

The tunnel will be a replacement for the aging State Route 99 Alaskan Way Viaduct. Bertha arrived in Seattle from Japan on April 2, and its 41 different pieces were transported to a storage area near the 80-foot-deep pit where tunneling will start this summer.

Assembly crews are placing the rear end of the machine in the launch pit first, to be followed by Bertha’s front end and her massive green cutterhead.

Tunneling will begin after Bertha is fully reassembled and tested, a process that takes about two months.

You can follow Bertha’s progress on twitter at @BerthaDigsSR99.

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