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It was the world's biggest tunneling machine when it first chewed into the loose dirt and gravel on Seattle's waterfront in 2013. With a cutting head nearly 60 feet wide, it had been built in Japan and shipped across the Pacific to dig a two-mile-long double-decker highway tunnel under downtown.
The machine was named "Bertha" in honor of a 1920s-era mayor — the prefatory "Big" always implied, never stated.
But just a few months and a thousand feet in, Bertha came to a grinding halt. Grit was getting into sealed parts of the machine, temperatures were spiking and an engineer likened it to all your dashboard warning lights going on at once.
The cause of the breakdown was in dispute — still is, and will be, for the foreseeable future, as contractors and the state duke it out in court — but the effect was the same: Bertha was stuck.
That's when the machine's hugeness began to look calamitous: You can't just drive a tunneling machine to the shop. If it needs fixing, it needs fixing where it is.
In Bertha's case, that meant digging an 11-story-deep pit to perform Herculean engineering efforts that insiders say were more challenging than the tunnel project itself.
That's all behind Bertha now.
After the two-year pit stop, it went on to complete its journey toward the Space Needle — so smoothly that most Seattleites forgot about it. Many assumed it was still being fixed.
In fact, it's at the finish line.
Earlier today, the 57.5-foot wide cutting head gnashed through the massive retaining wall on the north end of the tunnel, where a live video feed was waiting to capture the moment — and perhaps the off-screen sound of engineers sighing with relief.
KELLY MCEVERS, HOST:
People in Seattle today heard a noise they've been waiting for for four years.
(SOUNDBITE OF ROCKS CRUMBLING)
MCEVERS: It's the crashing and grinding of the giant tunneling machine known as Bertha. Today it dug its way back into the daylight after a two-mile-long trip under the city's downtown. NPR's Martin Kaste explains why this moment came as a huge relief to many people in Seattle.
MARTIN KASTE, BYLINE: If you want to get an idea of what people around here think of Bertha, just stop someone and ask.
For people who don't live in Seattle, what does the word Bertha mean to people around here?
ANN MARTIN: (Laughter).
KASTE: Like, what pops to mind (unintelligible)?
BRAD STOUT: Oh.
KASTE: This is Brad Stout and Ann Martin.
STOUT: (Laughter) It's kind of a debacle, I think.
MARTIN: Yeah, over budget, bad equipment, yeah.
KASTE: The eye rolling is understandable given the near-calamitous breakdown that Bertha suffered in late-2013. The causes are still in dispute. The contractors and the state will be in court for years to settle it. But the repair job was monumental. It involved digging down 11 stories to reach Bertha and rebuild it. Engineers say that fix was more challenging than the tunnel project itself.
(SOUNDBITE OF HORN)
KASTE: Still, it's kind of a shame that everyone focuses on the massiveness of that repair because when you go down into the tunnel, you realize that a functioning Bertha is also pretty impressive.
This is more than just a digging machine. As the five-story-wide cutterhead rotates, it swallows the mud and the debris and sends it all back out on an ever-lengthening conveyor belt. Meanwhile, hydraulic lifts on the machine swing around like the hands of a clock, assembling the sections of the cement wall around the machine. And the whole thing pushes itself forward, carrying with it the cutting head, the control room, even the port-a-potties for the miners who ride onboard, more than 6,000 tons inching along.
CHRIS DIXON: Well, it's like shoving a five-story building through the ground under downtown Seattle.
KASTE: That's Chris Dixon, the contractor's project manager. Over the years, he's often had to face the cameras to deliver grim news. There was a time back in 2014 when some people called on the state to abandon the tunnel altogether to avoid the risk of yet another breakdown and in even worse location - say, right underneath Seattle's historic Pike Place Market. But now it's Dixon's chance to smile.
DIXON: Well, I was asked all kinds of questions during that period. How confident are you? I've always been very confident that we would get the machine repaired, we would resume tunneling and we've - we'd successfully complete the tunnel drive.
KASTE: Of course the tunnel isn't actually ready yet. Contractors still have to build the double-decker highway that's going down there. Plus, the massive cutting head has to be lifted out. They'll have to slice it up into manageable pieces, and there's been some talk of leaving one of those pieces on display somewhere, assuming people in Seattle come around to feeling a little more affection for Bertha now that its work is done. Martin Kaste, NPR News, Seattle.
(SOUNDBITE OF THE FUNK ARK SONG, "HORCHATA") Transcript provided by NPR, Copyright NPR.