Bertha won’t be the world’s largest tunneling machine much longer. Industry leaders say the Seattle stall won’t stop demand for big highway tubes.
By Mike Lindblom, June 27, 2014
Mud spills from a clamshell scoop Friday near the stalled Highway 99
tunnel-boring machine. Crews are building a ring-shaped shaft 120 feet
deep and 83 feet in diameter to reach the buried drill. They push steel
tubes into the soil and extract the muck within, making room for
concrete to be poured down the tubes. As of Friday morning, 31 of the 80
new pillars that will form the shaft were completed. In September, the
tunnel drill is supposed to grind through the south side of the shaft
into open air, where a crane is to lift the entire 2,000-ton cutter
drive to the surface for repairs.
LOS ANGELES — By the time Bertha reaches downtown Seattle, hopefully
next year, it may lose the title of world’s largest tunnel-boring
Despite local anxiety about the current seven-month stall — and a
complicated repair ahead — the tunneling industry worldwide continues to
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.
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
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
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
“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
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.