LOS ANGELES — By the time Bertha reaches downtown Seattle, hopefully next year, it may lose the title of world’s largest tunnel-boring machine.
Despite local anxiety about the current seven-month stall — and a complicated repair ahead — the tunneling industry worldwide continues to burrow undaunted.
German company Herrenknecht is manufacturing a machine 57 feet, 9 inches in diameter near Hong Kong. That’s 5 inches wider than the $80 million Hitachi Zosen machine that stalled in December while drilling the Highway 99 tunnel.
The new champ will bore part of a road tunnel connecting the northwestern New Territories district to the Hong Kong airport, on Lantau Island.
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This follows boring of the giant Sparvo tunnel in Italy, and one now being drilled under the Bosporus, to link Asia to Europe. Herrenknecht says it has even designed a 62-foot tunnel-boring machine (TBM) for a proposed bore in St. Petersburg, Russia.
“The latest innovations underscore the high potential of further development in mechanized tunneling,” said Karin Bäppler, a senior executive at Herrenknecht, at the North American Tunneling Conference in Los Angeles this week.
What’s driving the growth, she said, is a new demand for tunnels big enough to contain stacked highways.
In Seattle, thousands of citizens didn’t even want a tunnel, though a majority of voters said yes in a belated advisory ballot. Some cherish the views from the elevated but old Alaskan Way Viaduct. Others are bitter the city missed a chance to scrap the highway and kick the car habit.
Bertha’s repairs and delay costs could exceed $125 million, an amount contractor Seattle Tunnel Partners (STP) has sought from the Washington State Department of Transportation (WSDOT), which denied the request. It may take years before the question of who pays what share is definitively settled.
Cost overruns here won’t chill other projects, said numerous officials gathered in L.A. A few mentioned “rumors in the industry” that STP’s goal of a March restart would slip. But mainly the key point was that, eventually, just about every tunnel gets finished. One tunnel’s flaws become the next region’s lesson.
Jamal Rostami, engineering professor at Penn State, said: “You’re going to have cost overruns. It’s almost inevitable. This is normal in the project, as it would be on any capital project. When you’re pushing the envelope, there are unknowns that come in. They need to be worked out.
“If you look at the tunneling industry throughout the world, they’ve been going up to larger TBMs,” he added. Only 15 years ago, the largest was 12 meters wide (39 feet), and now they’re approaching 18 meters, he said.
So, how does Chris Dixon, STP project director, feel about his machine being surpassed?
“Haven’t heard about that,” he said Friday.
Matt Preedy, deputy Highway 99 administrator for WSDOT, said, “It’s never been about being the world’s biggest,” adding it was only a matter of time before a larger drill came along.
Regardless, the industry seems fascinated with the width record, which gives Bertha its celebrity.
Shannon & Wilson, a Seattle geotechnical firm, showed video in its L.A. booth that mapped the location where Bertha stalled.
Joe O’Carroll of Parsons Brinckerhoff, the state’s design consultant, rolled an animation of the Seattle route longer than he planned — so his talk could end with a reassuring image of the cutterhead turning.
“That picture is something we want to see happening, for everybody in our industry, as soon as possible,” he told the audience.
Martin Herrenknecht, the German firm’s founder, yearned for the Highway 99 challenge in 2010, but failed to win the job. A year ago, he publicly questioned STP’s choice of machine designs, as reported by Tunneltalk.com: “I wish you good luck, but you will have problems,” he said.
The Seattle project should have used a slurry-type machine to soften the soil, plus a rock-crushing device, he said. The article lightheartedly noted Herrenknecht was “about to lose the record for the largest machine in world.”
Meanwhile on the Seattle waterfront, crews steadily build a ring-shaped access shaft, where a crane will reach down 120 feet, and hoist Bertha’s entire 2,000-ton front end to street level for repairs. These include a new, heavier bearing, and steel plates to reinforce it.
Dixon said if everything goes perfectly, the machine might be reassembled and bore again as early as December — three months before his official March goal. But that’s possible only if the machine doesn’t require lengthy tests, he said.
WSDOT isn’t grasping at this sort of news, since STP is in the early phase of making an access shaft.
“It’s too early to say,” Preedy said.
Mike Lindblom: 206-515-5631 or firstname.lastname@example.org On Twitter @mikelindblom