Contractor Gets Giant Tunnel Machine Back in Action on Seattle Highway Project
SEATTLE, WA The contractor who is developing a tunnel for Seattle, Washington's, Alaskan Way Viaduct project has reactivated "Bertha," the huge tunnel-boring machine that broke down in December 2013.
The Washington State Department of Transportation said that Seattle Tunnel Partners pushed Bertha forward that day in its access pit, digging 6.5 feet ahead in order to build the tunnel's 161st concrete support ring.
The new tunnel work follows an extensive effort to first dig out Bertha, the world's largest-diameter TBM, then rebuild various parts of its cutting system.
Crews are activating the machine in a series of testing phases, as outlined in the video below. It first moved ahead on Dec. 22 to install the 160th tunnel ring at the bottom of the 120-foot-deep pit crews had built to reach and repair the machine.
In all, that TBM will be used to dig through 9,270 feet to build the multilevel, two-mile tunnel that will eventually carry cars and trucks along State Route 99 in downtown Seattle and allow crews to remove the aged viaduct. By late December Bertha had moved through 1,091 feet.
The announcement also said STP was preparing to cut through a concrete wall that is about 15 feet thick.
"Once beyond the wall, crews will begin tunneling through native soils that will serve as the next stage of STP's testing process," said the WSDOT project update.
It also said with tunnel excavation again under way again STP was resuming its operations to remove excavated material by using a conveyor belt that extends from the tunnel to the edge of the Port of Seattle's Terminal 46.
"Material that contains concrete from the access pit wall will be hauled away by truck," it said. "Clean material - which crews will encounter once outside the access pit - will be taken by barge across Puget Sound to a reclamation site near Port Ludlow. There, the soil will be used to fill an old quarry."