Tunnel on hold: Damaged Bertha won’t dig again for at least 6 months

SEATTLE -- The Alaskan Way Viaduct will be closed in both directions for inspections this weekend.

Bertha in the launch pit (Courtesy: WSDOT)

That will happen as we learn the tunnel that will replace it faces more delays. The boring machine won't be chewing up dirt again for at least six months.

This tunnel project has seen setback after setback. The machine, nicknamed Bertha, hasn’t been running normally since December.

And at 10 p.m. Friday, the Alaskan Way Viaduct closed down so engineers can take a closer look at how the fragile structure is reacting to the work underground.

Bertha is stuck and the timeline for completing the Highway 99 tunnel keeps pushing further and further past the 2015 deadline.

“We would be obviously pleased to start tunneling earlier than that, but this isn’t the time to try to accelerate things or take shortcuts,” said Chris Dixon, who is with the contractor for the project, Seattle Tunnel Partners.

A series of broken seals means the biggest tunnel-boring machine in the world can’t push on.

Now Seattle Tunnel Partners, and Bertha’s Japanese manufacturers, are coming up with a plan to repair the damage.

“These things do happen on tunnel projects,” said Dixon. “We’re really testing the limits of the state-of-the-art for tunnel-boring machines.”

Contractors plan to dig a giant shaft between 11 and 20 meters wide and more than 100 feet deep so they can either fix the seals underground or bring the cutting head to the surface.

“We know that the seals need to be replaced. They’re still investigating the condition of the main bearing to see what needs to be done there,” Dixon added.

Sitting above Bertha is the Alaskan Way Viaduct, which will eventually be demolished.

The structure survived the magnitude 6.8 Nisqually earthquake 13 years ago, but officials worry another one could cause serious damage.

The viaduct has settled nearly a half-inch since tunneling began – and starting this weekend, engineers will be taking careful measurements to see if it’s sinking any further.

The survey work is part of ongoing, scheduled inspections.

“They want to make sure there’s no additional cracking or stress or widening of existing distress, or signs of any new distress in the bridge,” said Matt Preedy with the Washington State Department of Transportation.

Business owners on South Washington Street say the benefit of a new waterfront trumps what they call minor setbacks with Bertha.

“Years after it’s constructed and finished, nobody’s going to remember that,” said David Bovard, owner of Pioneer Pet Feed and Supply.

For decades, the Alaskan Way Viaduct has stood in the way of a clear view of the Puget Sound.

“We gotta take care of it, we gotta get the viaduct down before it falls down,” said Sake Nomi’s owner, Johnnie Stroud.

Bertha’s manufacturer is supposed to come back to the table in 10 days with detailed plans on exactly how they plan to repair the boring machine