The damaged Highway 99 tunnel-boring machine has stopped so that crews can clean debris from the 120-foot-deep pit.

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Bertha has taken a break.

After several days of gnawing through concrete to break into a repair pit, the damaged Highway 99 tunnel-boring machine has stopped so that crews can clean debris from the pit’s bottom, the Washington State Department of Transportation said Friday.

The 120-foot-deep pit — from which Bertha is expected to be hoisted for repairs to its damaged seals and main bearing — collected a mixture of concrete, dirt and water when the machine broke into it on Thursday. Crews are using vacuum trucks and other tools to remove the debris, WSDOT said.

Once the pit’s cradle is cleaned, Bertha will start moving again. The machine needs to travel another 35 feet into the vault before crews can start the repair work. WSDOT didn’t say Friday how long the pit cleaning might take. Bertha is tentatively scheduled to be fixed by the end of summer.

The tunneling machine, which had been stalled underground near Pioneer Square since December 2013, resumed mining Tuesday night and has since traveled nearly 22 feet. Bertha’s troubles have delayed the $3.1 billion Alaskan Way Viaduct replacement project by about two years.