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Bertha's Emergence Marks Beginning Of End For Viaduct

The Highway 99 Tunnel was furnished with technology that will keep travelers well-connected when underground.

Bertha the tunnel-boring machine broke through last week, marking the end of the digging phase of the SR 99 tunnel. What next? According to the Washington State Department of Transportation, in the coming weeks contractor Seattle Tunnel Partners will remove the braces in the disassembly pit and move Bertha into the pit. 

The machine will then be taken apart and removed from the tunnel. Like the breakthrough, the process will be fully covered by social media. As owner of the machine, STP will determine which pieces could be salvaged for use on other projects or recycled.

Manufactured in Japan by Hitachi Zosen Corp., Bertha arrived in Seattle in April 2013, and was launched from a pit near the stadiums in July of that year. In December, STP stopped mining after measuring increased temperatures in the machine. An investigation revealed damage to the machine’s main bearing. Repairs were made, and mining restarted in December 2015. The cause of damage to the tunneling machine is in dispute and is currently in litigation.

Work will continue on making the tunnel into a proper thoroughfare, which should be ready by 2019. That year, the Alaskan Way Viaduct will come down after more than 65 years of use.