by: Graham Johnson Updated:SEATTLE, Wash. —
Plans to repair Bertha, the world's largest tunnel-boring machine, have been delayed another month.
Contractors for Seattle Tunnel Partners say connecting huge 10-foot-diameter pilings to form the wall of a repair shaft has proven more complicated and slower than expected.
Building the wall of the circular repair shaft, which will be 80 feet wide and 120 feet deep, must be finished before excavation can begin.
STP had planned to have the wall finished around now, but on Monday announced that work will continue through August.
This means Bertha likely won't tunnel into the repair shaft until November.
Contractors said they had three months of cushion built into the schedule.
Although that cushion has dwindled to two months, contractor Chris Dixon said Monday he remains confident that tunneling will resume in March 2015.
The Washington State Department of Transportation is less confident.
Project administrator Todd Trepanier said Monday the delay "has increased our concern in their ability to start mining at the end of March."
Contractors face financial penalties for delivering the tunnel late.
As part of the work to build the walls of the shaft, contractors have increased the number of pilings from 73 to 84.
Dixon said that's not because anything has gone wrong.
He said shaft design has evolved during construction, an approach planned all along.