For four years, Bertha, once the world’s largest tunnel-boring machine, came packed not only with 57.5-ft worth of diameter and over 8,000 tons of girth, but never-ending drama. Now, though, Bertha remains as only a memory.
And a tunnel.
As part of a multi-billion-dollar plan to replace the aging and seismically vulnerable Alaskan Way Viaduct through downtown Seattle, the Washington State Dept of Transportation planned for a 1.7-mile bored tunnel. That plan led to the birth of Bertha from Japan’s Hitachi Zosen.
Bertha’s assembly wrapped up in June 2013 and started boring by the end of July the same year, then scheduled to wrap up its project under the city in December 2015. But just 1,083 ft and less than five months into the route, Bertha overheated thanks to problems with the main bearing seals. It took two years and a repair pit dug in front of where Bertha sat stuck to get the machine back into working order, finally moving forward unencumbered in early 2016.
Since that time, Bertha showed little issue in tunneling under Seattle, breaking through to the disassembly pit near the Space Needle on April 4, 2017. Then, on Aug. 23, the final piece of the disassembled machine was hauled out of the pit, a symbolic end to Bertha.
Since April, crews from Seattle Tunnel Partners have remained busy getting Bertha out of the way so they could finish the double-decker roadway in the tunnel. Pieces of the machine were pulled by crane—the largest pick was 70 tons—and some portions were cut loose from the machine before removal. Other sections of Bertha were hauled through the tunnel’s south portal and the launch pit.
Hitachi Zosen will decide what to do with many of Bertha’s components, although the steel cutterhead unique to the project was already cut up and trucked to a local steel recycler. Other pieces of the cutterhead were donated to the Port of Seattle while cutting tools and the control panel went to Seattle’s Museum of History and Industry.
With Bertha completely out of the way, work can continue uninterrupted on the 9,270-ft tunnel as the latest plans have it opening to traffic in early 2019.
Follow Tim Newcomb on Twitter at @tdnewcomb.