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Experts from the manufacturer in Japan are due in Seattle next week to explain exactly how to repair “Bertha,” the stalled tunnel boring machine.

The earth moving work beneath downtown Seattle somehow damaged bearings behind the massive cutter head of the world’s largest boring machine.

“We will be constructing a shaft to access the TBM from the front to do the repairs,” said Chris Dixon with the contractor Seattle Tunnel Partners, which owns the $80 million machine, told reporters.

The other option was to access the damaged section from behind Bertha.

It was manufactured by Hitachi Zosen Corp. which has built more than 1,300 tunneling machines, according to the Washington State Department of Transportation.

The boring machine has excavated just more than 1,000 feet of the nearly two-mile tunnel. Tunneling stopped Dec. 6 when the machine overheated and it has barely moved since.

Contractors discovered damage to seals that allowed dirt and moisture to get into bearings. Representatives of Hitachi Zosen are due to meet with the contractors next week to provide details of the configuration of the repair shaft to be built in front of, or around, Bertha.

It’s not clear when that work might begin.

Because of delays in the tunneling, there will be layoffs.

“We are taking steps to reduce or workforce during this stoppage period,” Dixon told reporters Friday. “I don’t know the exact numbers or what layoffs have occurred thus far.”

It will takes months to make repairs to the tunneling machine. Dixon said contractors have not been told, but he assumes repairs will require removal of the massive cutter head.