SEATTLE — The state Department of Transportation and contractors building a highway tunnel under downtown Seattle are trying to find out what has blocked their tunnel-boring machine.
The machine called Bertha ran into something Friday and was shut down Saturday about 1,000 feet into the 1.7 mile project and 60 feet below South Jackson Street and South Main Street.
The $80 million machine is designed to break up boulders, so what it hit is a mystery. It may be a huge boulder left by the last ice age. Others think it could be a buried rail car from pioneer days when the area was filled in.
Engineers are considering drilling down to the object as one of the ways to break up or remove the obstruction.
The 58-foot diameter tunnel is scheduled to be completed by the end of 2015, creating a four-lane route for Highway 99 traffic between South Lake Union and the area south of downtown near the Seahawks and Mariners stadiums.