After launching in 2013, the world's largest tunnel-boring machine could finish its trip from Seattle's Sodo to South Lake Union this spring. Here's a look back on the tumultuous dig that's years behind schedule.
Bertha’s end could be near.
The world’s largest tunnel-boring machine is on schedule to break into daylight this spring after a tumultuous dig under downtown Seattle that’s years behind schedule.
The massive drill is part of the state Department of Transportation’s multibillion-dollar plan to replace the aging Alaskan Way Viaduct, which runs about two miles along the city’s waterfront and could buckle in an earthquake.
We’ve spotlighted Bertha’s technical challenges and successes every step of the way.
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Here’s a look back on that coverage, leading to what is expected to be the four-lane, $2.1 billion Highway 99 tunnel’s opening in 2019.
After a trip across the Pacific Ocean, Bertha arrived to Seattle on April 2, 2013, in more than 40 pieces, weighing 6,700 tons.
Crews at the Seattle dock unloaded the drill’s heavy parts over days and hauled them to the tunnel construction zone.
About four months later, the rotary machine started slowly digging out of its launch pit in Sodo, beginning the 1.7-mile trip to South Lake Union.
Workers at the rear of the giant drill began installing decks of the stacked Highway 99 tunnel.
At the time, the tunnel was estimated to open to traffic at the end of 2015.
Bertha hits steel pipe, stalls
The machine was cruising along at the start of December 2013, roughly four months after beginning its underground voyage.
Then, the cutter head on Dec. 3 hit a long steel pipe near South Main Street, which state officials later disclosed was left buried more than a decade ago by one of the Highway 99 project’s own research crews.
Three days later, Bertha overheated and failed to remove dirt, leading to a massive repair effort.
The Highway 99 tunnel contractors, Seattle Tunnel Partners (STP), contend the pipe impact damaged Bertha. Hitachi Zosen, which manufactured Bertha in Japan, says the giant drill would have otherwise made it all the way to South Lake Union as built.
However, the state says the relatively small 8-inch-diameter pipe couldn’t have possibly caused such severe damage to a 57-foot-diameter machine.
A dispute review board later ruled the state should have done more to warn STP about the location of the pipe, but didn’t express an opinion about whether the pipe was to blame for the repair costs exceeding $100 million.
Repairs cause two-year delay
Bertha remained stranded some 1,028 feet into its underground journey from Seattle’s Sodo to South Lake Union after overheating in December 2013.
Crews had to excavate a 120-foot deep vault to rescue and repair the giant drill’s front end, work that started in October 2014.
Meanwhile, the ground in Pioneer Square began sinking.
Bertha’s travails attracted national media attention.
Feeling the heat, some state and local elected officials ducked questions about the boring machine’s boondoggle potential.
“I’m not sure anyone wants to talk about this, because it’s a nightmare. There’s no happy ending,” former Seattle City Councilmember Nick Licata told The Seattle Times.
Bertha started finally digging again in February 2015, chewing toward the repair-access pit.
Then, crews launched a massive effort to retrieve Bertha’s damaged parts.
Crews eventually got Bertha’s scuffed and rusty disc-shaped front end above ground, a 4 million pound load.
Workers disassembled it and made repairs over months, discovering far more damage than they expected.
In turn, the target date for opening the Highway 99 tunnel to traffic was pushed back even more, with projections aiming for March 2018.
Crews had Bertha’s refurbished face stacked and reassembled by August 2015, as others continued working on building the highway.
On-again, off-again progress
Workers finally powered up the tunnel-boring machine on Dec. 22, 2015 after a two-year delay.
Less than a month later, the drill broke through the concrete, repair-access pit and began tunneling again under Seattle’s downtown.
But true to Bertha fashion, problems popped up left and right.
First, the machine temporarily stopped after a barge tilted and damaged a Port of Seattle dock, spilling excavated dirt into the Puget Sound.
Then, a sinkhole formed near the giant drill.
That’s when Gov. Jay Inslee intervened.
He ordered the Highway 99 tunnel contractors, Seattle Tunnel Partners (STP), to suspend Bertha’s drilling in January 2016, stressing the “contractual obligation to Washingtonians to drill the tunnel in the right way.”
Bertha was about 250 feet away from a planned stopping point, before the machine was scheduled to dive under the Alaskan Way Viaduct.
“Look, we’re going under a viaduct. It’s the only arterial right now, north-south along the waterfront. We don’t want it to go down,” Inslee told reporters after making the order.
Digging restarted six weeks later, after a state review committee approved a plan by STP to improve how soil is monitored around the project.
Meanwhile, Sound Transit scrapped using the names “Brenda” and “Pamela” for its boring machines across the city, digging a future light-rail route from Northgate to the University of Washington’s Husky Stadium, to distance those drills from the troubled Bertha.
The downtown drill, though, began its passage underneath the viaduct, showing steady progress.
From that point on, Bertha’s churning remained fairly consistent, with scheduled breaks for crews to inspect and replace the machine’s cutting tools.
So, with Bertha digging as intended, the Japanese firm that built the mammoth machine, Hitachi Zosen, felt comfortable enough to discuss the drill’s major delay.
In July 2016, state leaders mulled estimates that showed Bertha’s problems costing Washington state $223 million in cost overruns. Later, projections cut that total by $80 million due to the machine’s forward momentum.
Still, the Highway 99 tunnel’s opening was pushed back yet again — this time to early 2019.
That would mark a full decade since former Gov. Chris Gregoire chose the deep-bore tunnel option and lawmakers approved legislation to make it happen, sponsored by then-Sen. Ed Murray, now Seattle mayor.
Court disputes over who pays for a potential half-billion dollars in cost overruns could stretch years longer.
Bertha reaches halfway point
At that point, the top of the massive machine was 190 feet below First Avenue downtown, passing Pike Place Market on its left.
By December 2016, Bertha had chewed underneath Blanchard Street in Belltown and was on a gradual climb toward the surface.
Behind Bertha, crews continued pouring concrete for the future highway. They had completed nearly one-third of the tunnel’s upper road deck.
Roughly two months later, the boring machine dug below the Battery Street Tunnel on its homestretch.
A drone captured where the giant drill will eventually break into daylight between Denny Way and Mercer Street, which could happen as early as this spring.
We’ll update this post as Bertha’s journey continues.
Material from The Seattle Times archives contributed to this report.