The world’s biggest tunnel boring machine will remain stuck along the Seattle waterfront until March 2015 — six months later than an earlier Sept. 1 restart goal.
Seattle Tunnel Partners will take until late summer just to dig a deep repair shaft lined with vertical concrete pillars. Then comes one of the biggest challenges: to drive the damaged drill about 45 feet forward into the circular pit, even though its main bearing is contaminated by grit, and the front end overheated in a late-January test. The drill known as Bertha has moved only four feet since Dec. 6.
Chris Dixon, STP’s project director, said the four-lane tunnel could still open to traffic by November 2016, from Sodo to South Lake Union. The state and STP originally planned a December 2015 startup.
But the makers of the 57.3-foot diameter drill haven’t issued a full repair plan yet, he said. Hitachi does know it will completely replace the bearing.
Preliminary plans call for workers to peel away the steel skin or “shield” for the cylindrical machine, then to hoist the rotary cutter head, the drive axle, and the bearing all together. This would total more than 2,000 tons, and require special lifting devices, Dixon said. So the bearing would actually be replaced at surface level, next to the old Alaskan Way Viaduct.
The state Department of Transportation continues to maintain that STP is responsible for the costs of repair and delay, said Todd Trepanier, Highway 99 program administrator. Dixon said the costs will be negotiated, based on language in the sophisticated contract. It is currently worth $1.44 billion.
Workers this week are injecting grout between buried pillars that STP previously installed, to form a protective wall alongside the Viaduct, and another fronting Elliott Bay. The grout should make the walls watertight. That way, groundwater won’t drain out of Pioneer Square and cause historic buildings or the Viaduct to settle.
Trepanier acknowledged that project isn’t moving along as quickly as the public or DOT hoped. “What we are envisioning, is to get this tunnel complete,” he said.