April 3 project update: Bertha on the verge of breakthrough

Posted on Apr 3 2017 2:00 PM

After churning through 9,240 feet of Seattle soil, the SR 99 tunneling machine is only 30 feet away from daylight. Bertha’s five-story-tall cutterhead is expected to reach the edge of the disassembly pit’s five-foot-thick wall later today, setting the stage for her breakthrough near Seattle Center.

Crews will spend this evening making final preparations. Then, early tomorrow, the massive machine will begin mining through the wall and into the pit where it will be disassembled. Machine operators will proceed slowly through the wall, so it may take several hours for the cutterhead to emerge.

The breakthrough will occur in several stages, as shown in the graphic below. The first two images show what is planned for tomorrow. Removing the braces will take several days, and it will be weeks until the machine is in its final position in the disassembly pit:

How to watch

Bertha's breakthrough will be streamed live on our Follow Bertha page . The camera feed will be available later today, and will remain on through tomorrow's breakthrough. We also have a new time-lapse camera that will capture images of breakthrough, and of crews disassembling the machine after it emerges in the pit. For safety reasons, the public will not be allowed in the construction zone during the breakthrough, and there will not be any public event.

We’ll continue to provide regular updates via social media as the big moment approaches.