Equipment Type

Made It! Drone's Video View of Bertha's Breakthrough

Bertha's 57.5-foot cutterhead lost a few teeth along the way, but of course, heavy construction isn't for sissies.

April 05, 2017

Around noon Tuesday, Bertha the massive tunneling machine used to cut a five-story-tall, double-decker highway tunnel under downtown Seattle, finished her job.

A year ago, SR 99 tunnel crews were about to face their biggest challenge: a trip beneath the Alaskan Way Viaduct they were working to replace. Today, with the viaduct and more than 9,270 feet of new tunnel safely behind them, there was nothing left to face but daylight as the SR 99 tunneling machine chewed its way into a pit near Seattle Center.

ABOVE: Bertha the Tunneling Machine and Bertha Landes, the first woman mayor of a major American city.

Bertha’s 1.7-mile drive beneath Seattle came to a successful end Tuesday afternoon, 64 years to the day since the viaduct first opened to traffic. Led by the Washington State Department of Transportation, and designed and built by contractor Seattle Tunnel Partners, the tunnel project will move a two-mile section of SR 99 underground when it wraps up in early 2019. Crews will then demolish the viaduct, clearing the way for the city’s new waterfront.

“Machine was right on alignment, broke through at the exact spot it was supposed to,” said Chris Dixon, with the contractor Seattle Tunnel Partners. 

Crews will spend the next several days removing steel support braces that stand between Bertha and the interior of the 90-foot-deep disassembly pit. When the braces are gone, crews will drive the machine into its final position and begin cutting it into pieces for removal. As owner of the machine, the contractor will determine which pieces could be salvaged for use on other projects or recycled.

STP still has significant work to complete before the tunnel opens. Crews must finish building the double-deck highway within the circular walls that were built by crews inside the tunneling machine. Mechanical and electrical systems, plumbing and safety features also must be installed.

Over the next several years, the City of Seattle’s Waterfront Seattle project will build new public space and a surface boulevard in the place of the double-deck viaduct, which is scheduled for demolition in 2019.

Below is footage of Bertha's breakthrough, captured by a drone flying above the disassembly pit.

Why is her name Bertha?

Naming tunneling machines after women is a long-running tradition within the tunneling industry and WSDOT chose to follow in that tradition. Bertha’s name was chosen as part of a contest for Washington students and the proposed names had to have significance to Washington state heritage, life, nature, transportation or engineering. Elected mayor of Seattle in 1926, Bertha Knight Landes was the first woman to lead a major American city.

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