What has stopped the drill bit is unknown. Engineers have to investigate. Don’t panic, yet.
The Transportation Department and contractors building a highway tunnel under downtown Seattle are trying to identify the mystery object that has blocked their tunnel boring machine.
The machine called Bertha ran into something Friday and was shut down Saturday about 1,000 feet from the start. The $80 million machine is designed to break up boulders, so there’s speculation about what it hit.
WSDOT says the latest trouble started Friday when Bertha’s five-story tall cutter head felt some resistance, then stopped. WSDOT says engineers with Seattle Tunnel Partners, the company in charge of building the viaduct replacement tunnel, have been consulting with other experts to identify the obstruction – whether it’s natural or manmade.
They say Bertha wasn’t damaged in any way. They’re keeping her idle until they decide whether crews need to dig the obstruction out from above or if Bertha can charge through it.
This is the latest pause in a project that’s had a few hurdles. The area contains fill so the blockage could be a boulder transported by glaciers in the past. It could also be a buried train car or boat though that is unlikely. Previous surveys did not identify anything large and metal buried here.
They may be too deep to use conventional remote sensing equipment to try to ascertain how big it is. But, these stories, they tend to make the monster fans a bit worried…
Drano won’t work to unclog this blockage. Hopefully crews will know what it is by tomorrow.
(13-Dec-2013) They are drilling wells to lower groundwater pressure (by pumping the water out) so they can send people in to the tunnel to inspect the machine. Gee, robots would come in handy right now!
(20-Dec-2013) Covered by the NYTimes. Still no word but people are hoping for something more spectacular than a boulder. Under Seattle, a Big Object Blocks Bertha. What Is It? – NYTimes.com.