Bertha tunneling update: One-third complete, ready to dig under downtown buildlings



SEATTLE -- The Bertha boring machine has reached a big milestone.  It has successfully made it under the Alaskan Way Viaduct without a hitch, and will soon start digging under downtown buildings.

Given all the problems that have beset Bertha, there’s a big sigh of relief that no sinkholes or other problems emerged.

“We’ve completed the 4 percent downgrade from the south portal,” said Chris Dixon, who works for the contractor, Seattle Tunnel Partners.  “Now we’re climbing at 1.6 percent as we proceed to the north portal.”

Project managers said Tuesday that they have stopped the machine for a short period of time to perform routine inspections before firing it up again and plowing forward.  Because of the intense air pressure where the machine is operating, workers have to enter hyperbaric chambers to do the repairs.



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Officials hope to restart as soon as they can.  There’s lots of lost time to make up, if possible.  The machine is still only a third complete and well over a year behind schedule.

Engineers say the soil from this point forward is much more compact and will be easier to dig through than the sloppy fill dirt along the waterfront that gummed up the blades.