Bertha is just about ready to head underground. The last chance to say goodbye is Saturday. (Image courtesy WSDOT)

Big Bertha about to head under downtown Seattle for 14 months

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Say goodbye to Big Bertha. The world's largest tunneling machine is about to disappear under downtown Seattle where she will spend the next 14 months carving out a new route for Highway 99.

The Washington State Department of Transportation is holding a dedication ceremony Saturday so you can get one last look before Bertha goes to work.

"People can walk around. They'll actually be able to walk over the top of Bertha's launch pit and peer down at her, which is really great to see how big she is and understand the scale of the project," says KaDeena Yerkan with WSDOT.

Yerkan says Bertha has a lot of work to do digging up 850,000 cubic yards of dirt.

"If you put it in (CenturyLink) Field, it would be about 100 feet taller than the roof line," says Yerkan.

The soil from the tunnel will come out on a conveyor system to Terminal 46 where it will be barged across Puget Sound to Mats Mats in Jefferson County.

"There is an old quarry there, it's a reclamation site, and so they'll use the dirt to fill in the old quarry," says Yerkan.

Watch Big Bertha's cutterhead spin:

KIRO Radio Staff, Staff report
Straight from the newsdesk.
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