SEATTLE - The search for answers about what's stopping Seattle's big tunnel dig took a step forward Thursday as crews drained water from the giant drill known as Bertha.
The draining was necessary to create a dry space for workers to go through a hatch in the drill face and look around.
When the drilling stopped nearly a month ago, engineers thought Bertha might have struck an unmapped boulder while digging a new tunnel for SR99 beneath downtown Seattle.
But weeks of probing in front of the drill to see what's there ended earlier this week, with engineers finding nothing unexpected.
That might indicate something is stuck in Bertha's cutter face.
Thursday morning, WSDOT engineering manager David Sowers told KIRO 7 workers planned to attempt a "free air intervention" later in the day.
By early evening, project spokespeople said the drill was still being drained.
It was unclear whether workers had been able to open the hatch for an inspection.
More details are expected Friday.