Crews have filled in about 80% of nine voids leftover from a 2-mile tunneling job through Seattle’s Beacon Hill. Japan’s Obayashi Corp. did not discover the voids while boring the parallel, 1-mile tunnels as part of its $280-million contract, which has since increased to $312 million. Owner Sound Transit contends the contractor is at fault.
The new, $2.6-billion, 16-mile Link Light Rail from downtown Seattle south to Seattle-Tacoma International Airport required tunnels and a station 180 ft deep beneath Beacon Hill. Obayashi in 2004 won the contract to bore the 21-ft-dia tunnels. During tunneling from 2006 to 2008, the tunnel-boring machine hit pockets of flowing, “cohesionless” sand, causing Obayashi to excavate more material in some areas than needed, says Bruce Gray, Sound Transit spokesman.