When work stoppages and delays start getting measured in years instead of months you know you have a less-than-desirable situation on hand. Such is the case with the 1.7-mile bored tunnel under downtown Seattle as part of the larger Alaskan Way Viaduct replacement project.
Amidst recent concerns over ground settlement in the area around the digging of an access pit to reach the front of North America’s largest-diameter tunnel-boring machine, updated timelines show massive delays—as was expected—in the completion of the tunnel. The access pit is needed to reach the front of the machine in order to fix it.
Original projections by Seattle Tunnel Partners when the project started called for the tunnel to open to traffic in December 2015. But that was long before the machine—dubbed Bertha—stopped tunneling in December 2013.
Bertha has sat idle for over a year now, with even the restart date slowly slipping further into the future.
Each month, Seattle Tunnel Partners updates the Washington Dept. of Transportation on the schedule, including the extra workdays the contractor believes they are entitled to as a result of the tunneling stoppage and other delays. The latest schedule now shows that tunneling will resume in late April 2015. If that date gets met, don’t expect the tunnel to open to traffic until August 2017.
And, of course, that’s a best-case scenario.
Already the August 2017 date is a pushback from the November 2016 date the contractor was targeting since the tunneling stoppage materialized.
Even with this August 2017 date as the latest from the contractor, WSDOT says in a statement, “We cannot endorse a project completion date until the work is further along.”
A more accurate completion date “will likely come into greater focus only after the access pit is complete and the tunneling machine has demonstrated it can successfully mine.”
Crews near completion on the access pit, with over 90 feet of the needed 120 ft dug. Currently contractors have taken a break from excavation in order to remove five piles from inside the pit. These three-ft-diameter piles don’t provide structural support, but act as plugs to hold grout in place. To access these grouted areas and complete the grouting process, the piles must be removed. Excavation will continue after this roughly two-week process.
Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.