North America’s largest tunnel-boring machine will soon see the light of day, all while resting on a newly poured cradle.

Bertha, the tunneling machine that has sat idle since December 2013, nears a spring repair date in an effort to have it continue tunneling the new State Route 99 under downtown Seattle. But before Bertha can move into repair position, contractor Seattle Tunnel Partners must prepare a place to fix Bertha.

Last week, Seattle Tunnel Partners finished the 120-ft-deep pit used to access and repair Bertha. The final scoop of soil taken from the pit just over a 1,000 ft into the tunneling route completes approximately 20,000 cubic yards of material removed ever since excavation for the pit started in mid-October.

With excavation complete, next comes concrete. Crews can now start construction on the concrete cradle at the bottom of the pit, used to support Bertha after it moves through the pit’s southern wall, a 20-ft-thick mass of concrete.

Seattle Tunnel Partners plans to have Bertha tunnel through the concrete wall. If the machine struggles with the wall, crews will instead open up the concrete from inside the pit to allow Bertha free movement into the access pit.

Once resting on the concrete cradle, a gantry crane will hoist the front end of the machine to the surface for repairs.

All the while, a dewatering system to control groundwater in the pit will continue to work.

With the project falling well over a year behind schedule, crews have also started prepping for the first roadway concrete pour for southbound lanes.

Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.