\ Workers Still Trying to Free SR 99 TBM

Workers Still Trying to Free SR 99 TBM

SR 99 Alignment Workers for the SR 99 tunnel construction project in Seattle were still trying to find out what is hindering progress of the world’s largest TBM, which has been stuck since Dec. 6. According to the Seattle Times on Dec. 30, workers have drilled six probe holes, spaced 5 ft apart and 110 ft deep, but have yet to encounter any obstacles. The machine has excavated about 1,000 ft of its 1.7-mile long alignment.

Crews are in the process of dewatering the area around the TBM in anticipation of sending workers into the machine to look for possible causes of the stall of the 57.5-ft diameter TBM. According to the report, it is still too soon to tell what impact the delay could have on the anticipated 2015 completion of the project, and as to whether it will impact the $1.44 tunnel construction budget.

The full article can be found here: http://seattletimes.com/html/localnews/2022564294_berthasoggyxml.html

The SR 99 tunnel has already been affected twice by delays, one due to a labor dispute over which party has jurisdiction over the removal of tunnel muck, and another related to a stoppage needed to reconfigure the cutterhead as the TBM was in its startup phase.

On Dec. 20, the this release was posted on the official project website (http://www.wsdot.wa.gov/):

People love a good mystery. That would explain why we’ve been all over the national news this week, and why we’re continuing to be flooded by questions (and suggestions) about what’s blocking Bertha, the SR 99 tunneling machine.

Unfortunately, the only answer we have to offer isn’t very satisfying: we simply don’t know yet.

But we have a plan and we’re working hard to get Bertha moving again. Last week, our contractor, Seattle Tunnel Partners, started drilling wells to pump water out of the ground near Bertha. So far, they’ve removed more than 300,000 gallons. If that sounds like a lot of water, you’re right. It is. And there’s a lot more where that came from.

On Wednesday, crews were able to turn the machine’s screw conveyor and remove some muck from the excavation chamber. As the muck lowered, a crew member was able to take a quick peek through a hatch near the top of the machine. What they saw inside was dirt, sand and cobbles – nothing extraordinary. Because water quickly filled the part of the chamber that was previously occupied by muck, they were only able to look around for a few minutes before they had to close the hatch.

Since our visual inspection yielded no obvious clues about what is going on in front of or inside the machine, our next step is to continue doing what we’ve been doing: lowering the water pressure around Bertha so crews can get a closer look.

Over the holidays, we’ll be drilling more wells, maintaining Bertha and preparing to reconfigure the launch pit so construction of the highway within the tunnel can begin. We’ll continue to update you on our progress, but we don’t expect to know more about what’s blocking Bertha until after the first of the year.

We’ve received a lot of questions about how the stoppage in tunneling might affect the project’s cost and schedule. It’s too early to tell. Our focus is now on addressing this issue safely and in a timely manner so we can resume tunneling as soon as possible.

We hope you have a fantastic holiday season. It’s been a productive year for Bertha and the tunnel team, and we can’t wait to dig into 2014.

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