Bertha’s front-end parts have been reassembled so that Highway 99 tunnel work can resume.

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After months of repairs, the front-end pieces of tunnel-boring machine Bertha have been stacked and reassembled — a small milestone in the effort to revive the stalled Highway 99 tunnel dig.

Crews accomplished an 814,000-pound lift on Saturday to set the circular bearing block onto the round cutter head, which temporarily rests face down.

In the coming days or weeks, the entire cluster, totaling 4 million pounds, will be rotated a quarter turn and lowered by crane into a deep access vault. Workers will need additional time to connect Bertha’s front end to the rear power lines, conveyors and other parts which await underground.

The world-record, 57-foot 4-inch diameter drill overheated and stopped Dec. 6, 2013. Seattle Tunnel Partners (STP) and machine maker Hitachi-Zosen later found that the outer bearing seals and some gear teeth were broken. Bertha’s outer and inner bearings, which surround a drive ring, have been replaced with bearings that feature stiffer seals, to resist future contamination.

The refurbished front end, which looks like a steel wedding cake, was supposed to be lowered a week ago. But some parts were flawed by a few millimeters and needed to be remanufactured, said an update post Monday by the Washington State Department of Transportation (WSDOT).

Before the front end goes back down, workers must reattach most of the 24 electric motors that rotate the drive gears from behind, a task STP previously estimated to take a week. Each motor weighs 8,000 pounds.

The Dutch heavy-lift company Mammoet successfully raised the 4-million pound load in March. Jeroen van Kooperen, its project manager for Bertha’s lift, has said “taking it out is not that hard, but putting it back in will be,” because of the challenge of lowering a live load, without swinging, toward its precise target.

STP still says it can meet its latest goal of restarting the dig Nov. 23, according to WSDOT, though the state does not verify this schedule will hold up.

The allocation of cost overruns between contractors, insurers or taxpayers is yet to be determined, though an expert panel has estimated at least $300 million will be in dispute.

In other news, Highway 99 will be closed in the South Lake Union area this weekend to realign the detour lanes of Aurora Avenue North, at the $2 billion tunnel’s future north portal.