Despite this week’s scare about soil settlement in Pioneer Square, excavation continued Tuesday at the access vault that will be used to reach stalled tunnel machine Bertha.
Seattle Tunnel Partners removed three feet and has now reached 84 feet depth, for the 120-foot deep shaft, the Washington State Department of Transportation said Tuesday afternoon. Progress can be seen on the project’s pit-cam.
Groundwater is still being pumped from around and beneath the ring-shaped vault, so that wet soil (under four times atmospheric pressure) won’t surge upward through the bottom of the ring. “Seattle Tunnel Partners’ engineers have determined that continuing excavation to 84 feet, an additional 3 feet from the current depth, will not affect when and how the dewatering wells could be turned off,” the WSDOT update said.
But it’s unclear whether the wells need to be turned off. And STP worked Monday and Tuesday at what appears to be normal pace. Every few feet, its engineers examine the pit walls, and ground pressures, before okaying the next step downward. The contracting team has no comment.
Meanwhile, workers began to install the red, vertical trusses that will support a gantry crane. This crane will lift the front end of Bertha to street level for repairs.
On Monday, the state said soil has settled about 1 inch beneath the Alaskan Way Viaduct as well as 30 Pioneer Square buildings. (Tuesday morning’s Seattle Times story is here.) WSDOT examined one of the potentially affected Pioneer Square buildings as of midday Tuesday, said state spokeswoman Laura Newborn.
The Viaduct doesn’t show damage and it remains safe to drive, project leaders say.
The hotline to report problems or damage is 1-888-AWV-LINE.