Tom Warne Report, 5 August 2013
Seattle is using the world’s biggest drill to bore the Highway 99 tunnel under downtown in the replacement project for the replacement of the Alaskan Way Viaduct.
Nicknamed Bertha, the massive drill will begin the most tenuous portion of the journey – a 1.7-mile section under the old viaduct section at Pioneer Square. Engineers in Seattle have experience in drilling tunnels through the Brightwater Sewer tunnel nearby and the Beacon Hill light-rail tunnel.
The opening ceremony was held on July 20 for the drill, which cost $80 million and measures 57 feet, 4 ¾ inches.
In late 2014, the machine will re-emerge at South Lake Union, with road-deck construction in progress following the drill. The four-lane toll tunnel is scheduled to be open to traffic a year later, in December 2015. In the months following the opening, the waterfront section of the viaduct will be demolished.