The world’s largest boring machine that has sat mostly idle for about two years moved Tuesday morning.

Bertha crept forward near Pier 48, before installing a tunnel ring at the bottom of the 120-foot-deep repair pit.

Seattle Tunnel Partners plans to tunnel “a short distance further” in the tunnel before work stops for the holiday. Crews will return Jan. 4.

After the holidays, the plan is to mine out of the access pit toward a planned maintenance stop 450 feet to the north. During that boring, tunnel rings will be placed and tests on the machine will continue to be run.

Related: Timeline of Bertha and Seattle tunnel project

Once the machine reaches the maintenance stop, final preparations will be made before Bertha mines beneath the Alaskan Way Viaduct. The viaduct will be closed for about two weeks while Bertha makes its way underneath.