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What happens next for Bertha, Seattle’s waterfront tunnel

Bertha is aiming for this wall at the end of its journey near 6th Avenue and Thomas Street. (WSDOT)

Update: Tuesday is finally the day the massive tunnel boring machine, Bertha, is expected to emerge from under downtown Seattle, KIRO Radio reports.

For the machine’s last hurdle, Bertha must to chew through a concrete retaining wall before emerging.

Bertha is now 30 feet from completing her journey.

The boring machine has traveled 78 feet in April and a total of 9,181 feet overall.

Check back for updates.

What’s next?

What happens after Bertha completes its journey? A portion of the giant boring machine will move on, while the rest will be destroyed.

Related: Timeline of Bertha’s journey under Seattle

The massive cutting disc, the outer shell of the machine, and the ring-shaped bearing will most likely be melted down for recycling, The Seattle Times reports. That will likely be a local job and could be handled by Nucor in West Seattle. Nucor has already been removing steel from portions of the viaduct that have been torn down and re-purposing it for use inside the tunnel.

But the rest of Bertha has a different fate.

Plenty of work left

In her final days, Bertha will break through a concrete wall at Sixth Avenue and Thomas Street before she slowly moves into a pit. The Seattle Times reports that steel plates have been laid to form a cradle for the machine at the bottom of the north portal pit.

Inside that pit, Bertha will be broken down into smaller pieces to be loaded onto trucks and shipped away. Bertha weighs more than 6,000 tons, so this process can take a while. The cutterhead will be lifted from the pit in eight pieces, according to The Times. It weighs about 2,000 tons and it is expected to take up to five months for it all to be removed. Those pieces will be further disassembled in order to travel on Seattle streets that have a 20-ton limit.

Meanwhile, the rear portion of Bertha will be broken down and moved in the other direction, two miles through the tunnel it just bored, to the south portal. Much of the machine is reusable, such as hoses, mechanical arms, and motors.

But after Bertha is no longer in Seattle, there is more than a year’s worth of work left in its 9,270-foot-long wake. Crews will spend the rest of 2017 and all of 2018 finishing construction of the two-level roadway inside the tunnel, which will eventually be the highway that replaces The Alaskan Way Viaduct. Crews will also have to construct the roadways and ramps that will connect SR 99 to the tunnel at both ends.

The tunnel is expected to open in early 2019 — three years after initially planned.

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