SEATTLE — Bertha, the machine digging a 1.75 mile tunnel under Seattle to replace a waterfront bridge with an underground roadway, is reaching the end of its journey.
State transportation officials say Bertha should break through a five-foot concrete wall on Tuesday.
Crews will break down the boring machine as others prepare the inside of the tunnel to handle double-decker lanes of highway that will replace the Alaskan Way Viaduct, which was damaged in a 2001 earthquake. The $3.1 billion tunnel project is scheduled to open in 2019, four years behind schedule.
The original completion date was the fall of 2015.
Opponents of the project continue to be skeptics about whether it will serve its purpose.