SEATTLE — Enough of the State Route 99 tunnel has been completed that workers and visitors ride a wheeled people mover to reach the digging machine, Bertha.
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More than a half mile of the 1.7 mile tunnel is excavated and lined with concrete rings.
With Bertha stopped for a few weeks for planned maintenance on Wednesday, the Washington State Department of Transportation invited reporters to see the progress of the project, which was delayed for more than two years after Bertha broke down in 2013.
The newest part of the tunnel is round and open, but at each step back toward the beginning of the tunnel, the double-decker roadway visibly takes shape.
Crews build foundations first, then walls of the roadway.
Farther back, the lower northbound roadway and the upper southbound roadway are already separated.
At the tunnel entrance, the space feels close to finished.
Chris Dixon, of Seattle Tunnel Partners, said crews have performed 44 pressurized work sessions, called hyperbaric interventions, to inspect the cutterhead and replace tools.
So far, crews have replaced 33 tools, three times what they did at the last maintenance stop.
Dixon said it was not yet clear when the maintenance would be completed and tunneling resume.
Dixon said no problems with Bertha have been discovered during inspections.
"We have no concerns, whatsoever, with the machine," Dixon said.
Cox Media Group
