The State Route 99 tunneling machine has been sitting idle since Friday. A DOT spokesperson says they are not sure if the obstruction is natural or man-made.
According to the Washington State Department of Transportation, the tunnel contractor is taking into account the high groundwater table and historic fill soil at the digging site.
The Seattle Times reports there’s to more to the job than just finding and removing a clog. Crews will likely have to use concrete grout or another hard substance to fill the resulting gap. Bertha requires firm surroundings as it drills ahead, so it can stay on a precise path.
Officials say it could take several days to restart the project. The machine is currently about 60 feet deep and is half-way between Jackson and Main streets.
Since its start on July 30th, Bertha has dug out more than 1,000 feet. That is about one-eighth of the tunnel’s total distance.