Tunnel-boring machine Bertha set to restart journey

by: KIRO 7 STAFF Updated:


The tunnel-boring machine called Bertha came to life after almost two years of repair work and is set to restart its journey under Seattle.


  • Tunnel to replace Alaskan Way Viaduct after 2001 earthquake
  • Project delayed in December 2013 after Bertha overheated
  • The front of the machine had to be pulled out of an access pit to be fixed
  • It has since been reattached

The contractor, Seattle Tunnel Partners, announced Tuesday Bertha successfully moved forward and installed a tunnel ring at the bottom of the 120-foot-deep pit.

Project manager Chris Dixon says the next several hundred feet of excavation will give them the information they need to make final adjustments before tunneling under the viaduct and downtown Seattle.

It should move more on Wednesday.

Dixon says after the holidays, the contractor plans to mine out of the access pit toward a maintenance stop 450-feet to the north. It's expected to reach the viaduct in March.

Here’s a Q&A refresher on what went so wrong with Bertha, how much it costs, and what happens next. 

Why did Bertha come to a halt?

The cause of the breakdown is under investigation and will likely be at the center of a legal dispute between state officials and the contractor over liability.

The machine’s cutting teeth struck a 119 foot pipe, eight inches in diameter, on December 3, 2013.

The machine overheated and came to a halt three days later. In investigating the overheating, contractors discovered the cutter head was clogged and found pieces of the pipe. A subsequent investigation discovered damage to the seal system protecting the main bearing.

The pipe was a steel well casing installed by a previous contractor for WSDOT and its role in Bertha’s problems is in dispute.

In 2014, contractors suggested that chewing through the pipe set off a chain reaction that led to the breakdown.

In 2014, state officials suggested there might have been other factors, such as the machine being operated incorrectly, that contributed to the machine overheating.

Another theory is that problems re-surfaced that were first identified during testing in Japan by Bertha’s manufacturer, Hitachi-Zosen.

“When someone tells you what they think caused the damage you're only hearing one of six or seven causation theories that were out there,” Chris Dixon of Seattle Tunnel Partners told the Seattle City Council in December 2015.

WSDOT contends the steel pipe was well documented in material it provided to STP. STP contends it was not properly warned about the pipe, and requested $125 million in additional compensation related to the breakdown. WSDOT denied that request.

Who is in charge of the tunnel project?

The project was initiated by Washington’s previous Governor Chris Gregoire.

The Washington State Department of Transportation is working with Seattle Tunnel Partners (STP), a consortium of Dragados USA and Tutor Perini.

How much progress has Bertha made?

Bertha tunneled 1,023 feet before becoming stranded underground. The entire tunnel drive from SODO to South Lake Union will be 1.7 miles.

Workers then had to dig an access pit in front of Bertha to pull major components above ground for repairs.

Contractors successfully lifted the machine's cutter head and drive unit out of a 120-foot pit in March 2015.

STP and manufacturer Hitachi Zosen spent most of the rest of the year fixing the machine and then lowered it back down into the pit.

WSDOT released video of the cutter head rotating in a test on Nov. 24, 2015.

When will the tunnel machine finish its trip under Seattle and break-through to the other side?

January 2017 is the new anticipated break-through date, according to the contractor’s schedule. April 2018 is when the tunnel is supposed to open for traffic.

Why so many restart dates?

After the halt, STP initially announced September 2014 as a restart, then pushed it back several times. Building the access pit and the repair effort itself proved complicated.

When was the tunnel supposed to open?

According to the contract with STP, the four-lane toll tunnel was supposed to open to traffic at the end of 2015.

How much money is being lost?

WSDOT says it expects to lose $78 million, according to insurance fillings.

The $78 million cost reflects extra spending on administrators, engineers, consulting firms and office space associated with a two-year delay.

An expert review panel, hired by the Washington Legislature, made a worst-case prediction in April 2015 that Bertha's breakdown will cost the state $317.5 million.

The panel also identified $329.6 million in potential funding to cover those costs.

They include $124.2 million in contingency funds, $50.4 million in penalties from STP for delivering the tunnel late, $85 million in insurance payments and $70 million in savings on projects after the tunnel is done that the state thinks will cost less than first expected.

"From what we know today, those issues could be resolved with the funds currently available within the program budget," panel chair Patricia Galloway told KIRO 7.

Soon after that report, state legislators declined to extend the contract for the expert review panel, fearing that its access to both WSDOT and STP could put the state at risk in future litigation.

The overall program budget for replacing the viaduct is $3.1 billion and the value of the contract with STP is $1.35 billion.

What does this mean for taxpayers?

Despite the expensive breakdown, taxpayers might not be on the hook for extra money. Read the full report released in April for the reason why.

Separately, WSDOT filed a lawsuit against STP in October:

“Filing this lawsuit ensures WSDOT will have a right to make legal claims in the future. This lawsuit does not prevent STP from pursuing claims under the terms of the design-build contract,” WSDOT said in a statement.

WSDOT says the design-build nature of its contract with STP protects taxpayers because the contractor and Bertha’s manufacturer are on the hook for the cost of repairs.