SEE IT: Tunneling machine Bertha breaks through concrete wall into access pit

Big Bertha breaks through wall into access pit for repairs

SEATTLE -- The front end of the tunnel boring machine Bertha punched through a 20-foot-thick wall around noon Thursday.

Crews restarted Bertha on Tuesday night working to get the boring machine to the access pit. From there, the process of repairing the tunnel boring machine will get underway.

Video released by the Washington State Department of Transportation shows the moment Bertha broke through the wall, sending a cloud of dust into the air.

The machine can only move a few feet at a time before it overheats. Bertha is expected to keep moving forward in increments of about 6.5 feet.

When the front end of the machine is fully exposed in the rescue pit crews will then start fixing the machine.

WSDOT says Seattle Tunnel Partners informed them that the process of taking the machine apart and hoisting the cutter head to the surface will take "significant time and effort."

Bertha still needed to go another 40 feet as of Thursday afternoon.

Once Bertha reaches the pit, crews plan to remove the front of the machine and pull it out of the pit so it can be repaired.

The tunnel, which will run about 2 miles under the city, is designed to replace the Alaskan Way viaduct, damaged in a 2001 earthquake. The project is two years behind schedule.