The Highway 99 tunnel project is reaching a milestone, or maybe a 1/20th milestone.
An empty barge could be seen Tuesday morning, moored alongside Terminal 46 for the first time. That makes tunnel watchers wonder whether boring machine Bertha has already advanced far enough to reach clean soil, which can be ferried from Seattle to the Mats Mats quarry near Port Ludlow.
The barge is just hanging around for a couple days, so that an overhead loading spout — nicknamed the elephant trunk — and the barge positions can be calibrated, says spokeswoman KaDeena Yerkan of the state Department of Transportation.
So far, Bertha has traveled about 250 feet, after an 18-foot push on Monday. That’s close to what engineers expect for the early, difficult waterfront phase of the tunnel from Sodo to South Lake Union. But for now, the machine is still churning through shallow fill dirt that’s been reinforced with concrete grout. Trucks are taking this unclean soil to processing sites, until the drilling operation reaches better soil. It’s going to take another 250 feet, and at least a couple weeks, to reach clean soil, Yerkan said.
By early 2014, Bertha should pass under the Alaskan Way Viaduct and achieve speeds of 35 feet a day through downtown, taking most of the year to complete the 1.7-mile dig.
“Things are continuing to progress well,” Yerkan said Tuesday afternoon.
The recent advance follows a four-week delay caused by a clogged conveyor screw and a labor dispute, shortly after the drilling began July 30. Union dockworkers have ceased picketing T-46, but there’s still no long-term agreement to resolve the demand from the International Longshore and Warehouse Workers Local 19 that they should perform the four muck-loading jobs that are currently being done by building-trades workers.