Fly Through the Massive Tunnel They’re Carving Under Seattle

AUTHOR: AARIAN MARSHALL. TRANSPORTATION  DATE OF PUBLICATION: 05.06.16.

05.06.16 TIME OF PUBLICATION: 7:00 AM.

 

LIFE HAS NOT been entirely kind to Bertha, the largest tunnel boring machine in all of North America. About two years ago, the machine, which measures 57 feet tall and 325 feet long, started excavating a two-mile tunnel under downtown Seattle. Seven months later, it ground to a halt, stuck. It had moved all of 1,000 feet.

 

Bertha is the key tool in Seattle’s $3.1 billion Alaskan Way Viaduct, a subterranean highway that will replace an aging, and seismically unsound, surface road. (Sixty-three people died when a similar freeway in Oakland collapsed during the 1989 Loma Prieta quake, so you can understand the urgency of the project.)

 

Construction crews spent two years digging a 120-foot access shaft to reach and repair Bertha’s cutterhead, which was jammed with pipe and other debris. The machine was up and running by December 2015, not long after the new highway was originally slated to open.

Two workers walk through the SR 99 tunnel toward Bertha. WASHINGTON STATE DEPARTMENT OF TRANSPORTATION

 

To prove that Bertha is making progress, the Washington State Department of Transportation sent a camera-carrying drone through more than 1,000 feet of newly excavated tunnel. The film provides a fascinating look at an epic project and the machine making it possible. Despite its immense side, Bertha is weirdly elegant for something that’s effectively a Brobdingnagian earthworm.

 

So far Bertha has excavated 1,455 feet. Only 7,845 to go. At this rate, it’ll be done by 2031. (Seattle is now planning for April 2018.)