Tunnel-boring machine Bertha approaching South Washington Street, WSDOT says

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SEATTLE — Bertha, the State Route 99 tunneling machine, has traveled about 110 feet since the contractor, Seattle Tunnel Partners, resumed mining on Feb. 23., the Washington State Department of Transportation said Thursday.

The machine has tunneled a total of 1,391 feet and is approaching South Washington Street, WSDOT said.

Crews are mining north to a planned maintenance stop just south of Yesler Way. Once there, WSDOT said, they could spend several weeks performing final maintenance before the machine tunnels beneath the Alaskan Way Viaduct.