After launching in 2013, the world's largest tunnel-boring machine has less than 220 feet to go before finishing its 1.7-mile trip. Here's a look back on the tumultuous dig that's years behind schedule.

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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.

Bertha’s chapters:

Mid 2013: The launch
Late 2013: Bertha hits steel pipe, stalls
2013-2015: Repairs cause two-year delay
Early 2016: On-again, off-again progress
Late 2016: Bertha reaches halfway point

Mid 2013:

The launch

Bertha — nicknamed after Seattle mayor Bertha Knight Landes — left Osaka harbor, Japan, on March 18, 2013, beginning a three-week trip across the Pacific Ocean.

Only a few ships in the world are capable of carrying such a heavy load.

The machine 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.



Late 2013:

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.


Late 2013 – 2015:

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.

That dig captured the attention of archaeologists after workers uncovered a mysterious deposit of shells that officials later determined were from settlers who worked shucking oysters.

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.

The machine churned through 20 feet of concrete in less than two days to reach open air.



Then, crews launched a massive effort to retrieve Bertha’s damaged parts.

In March 2015, one of the world’s strongest cranes hoisted a 270-ton piece of the drill from the pit and set it along Seattle’s waterfront, the first of several lifts for the repairs.

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.

Officials temporarily closed the roadway to traffic in April 2016 as a safety precaution, but they ended the shutdown earlier than planned, citing Bertha’s advancement.

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.



Late 2016:

Bertha reaches halfway point

Bertha passed its halfway point on its 1.7-mile voyage from Sodo to South Lake Union in early October 2016, covering 4,662 feet on the future Highway 99 tunnel’s route.

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.

Bertha was churning under Denny Way at Sixth Avenue North as of early March 2017, following a one-week halt to measure and correct a slight deviation off course.

About two weeks later, the state Department of Transportation said the Highway 99 tunnel contractors, Seattle Tunnel Partners (STP), were making final preparations for Bertha’s break into daylight.

As of March 27, Bertha had less than 220 feet to go.


[Watch: 360-degree look inside Seattle’s future Highway 99 tunnel as Bertha nears exit]


The breakthrough will happen at a pit near the intersection of Sixth Avenue North and Thomas Street, where crews will disassemble the machine’s parts.

You can check the state department’s website for more updates.

To mark the dig’s end, the agency said crews will set up cameras at the pit to record both time-lapse images and a video stream. The public won’t be allowed in the construction zone as a safety precaution.

“We recognize that there is great interest surrounding this stage of the project, and we are working on ways to share this historic moment with the public,” the department said in a blog post.

We’ll update this post as the project continues.


Material from The Seattle Times archives contributed to this report.