ROADS/BRIDGES: Bertha completes journey to build tolled tunnel in Seattle

April 5, 2017

The world's largest tunnel-boring machine completed its job to help Seattle replace the Alaskan Way viaduct

As dozens of people looked on Tuesday, Bertha broke through to daylight after a nearly 2-mile dig under Seattle that took almost four years. Seattle is one step closer to replacing the aging Alaskan Way viaduct and moving a 2-mile section of S.R. 99 underground.

Bertha is the largest tunnel-boring machine in the world, and the tunneling project has been a mammoth undertaking. Officials say its completion marks a key milestone in the effort to provide fast and reliable trips along S.R. 99 for cars and freight. They say the route supports the movement of more than $30 billion in cargo each year.

Bertha's job may be done, but it was not all smooth sailing. The tunneling machine overheated in late 2013, causing major delays. The project will also come in hundreds of thousands of dollars over budget. There is an ongoing court battle over who will pay for the cost overruns.

As well as the overruns, critics have questioned the decision to sink millions into a new highway in an era where climate change is such a big issue.

Crews still have to complete the double-decker highway within and install electric, plumbing and safety systems. The old viaduct also has to be demolished and a toll rate still needs to be set.

The state estimates the tunnel will open to traffic in 2019.