Officials: Bertha, World's Largest Tunnel Machine, Will Be More Robust

Jun 17, 2014

Two workers walk through the first rings of the tunnel toward Bertha, the SR 99 tunneling machine.
The guts of Bertha, the tunnel boring machine.
Credit Flickr Photo/WSDOT (CC-BY-NC-ND)

The builders of the tunnel machine stuck beneath the Seattle waterfront don’t just plan to repair the world’s largest tunnel machine.

Hitachi Zosen plans to add tons of steel and other improvements to make sure the machine known as Bertha doesn’t break down again beneath the heart of downtown Seattle.

Bertha broke down in December, just a thousand feet into a new highway tunnel designed to replace the Alaskan Way Viaduct.

Project officials declined to discuss why on Monday afternoon. But they’re moving ahead with efforts to dig up the front of the giant machine and replace its main bearing and seals with ones to be shipped from Japan in August.

Chris Dixon, who heads the project for Seattle Tunnel Partners, says the new, improved Bertha will be less vulnerable to dirt getting inside its bearings.

“Whatever repairs they carry out to fix the seal problem, we expect them to go above and beyond so we have a machine we are 100 percent confident can tunnel the remaining 8,000 feet under the city,” he said.

Hitachi Zosen plans to ship 2,000 tons of parts from Japan in a special semi-submersible cargo ship in August.

Dixon calls the manufacturer’s schedule “very aggressive.”

Todd Trepanier with the state transportation department says he’s skeptical the repair work can be done in time to let tunneling resume by the end of March.