Seattle tunnel sees progress
Work continues even as ‘Bertha’ machine stalled
SEATTLE – Walking down the center of the concrete rings that form the five-story-tall Seattle tunnel, 60 feet below the city’s downtown streets, you pass piles of rebar, elaborate strands of pipes, busy welders and black tubing attached high on the wall.
Each of the rings that form the tunnel is made up of 10 curved concrete sections that fit together like puzzle pieces and line up one in front of the other. They’re designed to hold back saturated soils and glacial deposits. And they’re numbered. You pass ring 56, 57, 58 as you get closer to Bertha, the tall state-of-the-art earth-moving machine that sits silently as it awaits repairs.
Bertha drilled 1,000 feet, about 10 percent in, and had placed 149 of those rings when it broke down in December — stalling efforts to replace a major thoroughfare through the city. The tunnel is designed to replace the Alaskan Way Viaduct along State Route 99 — damaged in 2001 by a 6.8 magnitude earthquake that rattled Seattle — and open up the waterfront.
When complete, it will have placed 1,445 rings, said Matthew Preedy, deputy program administrator with the Washington State Department of Transportation.
Seattle Tunnel Project Manager Chris Dixon told a group of reporters who were invited Thursday to tour the tunnel for the first time that the machine stopped working when the seals became overheated. When later asked if the breakdown involved a pipe, he said: “Everyone knows we hit a pipe,” but added, “That’s not a subject of discussion today.”
Seattle Tunnel Partners filed a claim with WSDOT in March asking for compensation because the machine broke when it hit a 119-foot-long steel well casing that had been installed by WSDOT in 2002. The state denied the claim, arguing the pipe was clearly marked in the plans and the breakdown was STP’s responsibility.
While that debate continues and Bertha repair work moves forward, Dixon said they’ve taken advantage of the down-time by beginning work on the interior structure that will support the double-decker roadways.
“We’re looking for every opportunity to advance other work — shortening the amount of work that needs to be done once the tunnel’s complete,” he said. “We had planned on getting in 2,000 feet with the tunnel before we started the interior structure, but since we’re stopped we saw this as a good opportunity to get in there and start building.
“So by the time we resume tunneling in March of next year, we plan on having about 450 feet of the interior structure built.”