The state cautiously allowed Bertha to bore forward last month and the machine has finally reached a pivotal waypoint.

The boring machine is now expected to soon break through a concrete wall at a planned stop. That stop is the last before Bertha will move forward underneath Seattle’s viaduct.

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After moving forward 300 feet within the last three weeks, Bertha has reached Safe Haven 3, a maintenance stop that will service the machine for about a month before it moves again. Bertha has now bored a total of 1,560 feet. The maintenance stop is basically a solid block of concrete that the machine will bore through and rest in while maintenance is carried out.

Bertha was allowed to move forward after state officials ordered a stop to the project because a sinkhole developed in its wake. That incident occurred shortly after the machine began operating again following nearly two years of repairs. The state gave Bertha conditional permission to move forward to prove it could operate safely.

After maintenance is completed at Safe Haven 3, Bertha is expected to be allowed to move forward yet again, this time underneath the viaduct itself, according to the Washington State Department of Transporation blog. The raised roadway will be closed for two weeks during that time.