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Alaskan Way Viaduct
Seattle’s Alaskan Way Viaduct sits empty as it was closed to traffic from April 29 through May 8. (Via WSDOT Flickr)

Seattle-area drivers will regain access to the Alaskan Way Viaduct in time for the Monday morning commute as Bertha the tunneling machine has made significant — and safe — progress in a critical phase of mining that took it directly beneath the elevated roadway.

The Washington State Department of Transportation announced on Sunday that structural engineers had completed a thorough inspection of the Viaduct and determined that the 63-year-old structure and the ground around it had maintained stability.

The Viaduct was closed to traffic on April 29 for what was intended to be approximately two weeks. The roughly 90,000 vehicles that rely on the road daily moved to other area highways and surface streets, and for 10 days Seattle’s commute times have been more painful than normal.

“Closing a major highway is never easy, and the public deserves a big thank you for their patience and flexibility while this crucial work took place,” Gov. Jay Inslee said in a WSDOT news release. “I would like to thank the WSDOT and STP project teams and construction crews on a job well done. To finish this piece of the project almost a week early is commendable. The planning and flexibility of commuters, along with strong coordination between WSDOT and partner agencies, ensured commuters had access to real-time information that helped them plan ahead.”

SR 99 tunnel
A specially designed truck carries the next 10 tunnel liner segments — one ring’s worth — into the SR 99 tunnel. (Via WSDOT Flickr)

Seattle Tunnel Partners initially planned to keep the highway closed until Bertha had completely cleared the Viaduct by mining a distance of 385 feet at Yelser and Alaskan Way. On Friday, the machine successfully made its way just 15 feet below the roadway’s foundations — the closest it will to come to any structure during its 9,270-foot journey along the waterfront.

An updated progress graphic on the SR 99 closure web site shows Bertha has traveled 312 feet since the Viaduct closed, and the machine has placed 47 of the 59 tunnel rings that make up this phase of the project.

Bertha progress

“Removing traffic from the viaduct was critical to the success of this work, but we don’t want the closure to last a moment longer than it needs to,” Acting Transportation Secretary Roger Millar said in a news release. “The end of this closure marks a new beginning for the SR 99 Tunnel Project. Much work remains, but we are encouraged by the contractor’s performance during this phase of the project. Our shared focus now, as it has been, is on delivering this tunnel to Washington taxpayers.”

Alaskan Way Viaduct
Crews monitor the Viaduct for movement during the closure of the highway. (Via WSDOT Flickr)

GeekWire previously reported on how Bertha would make its way below the Viaduct and what measures engineers had set in place to monitor the highway and the area around it for potential movement. WSDOT expressed confidence in the contractor’s ability to complete the phase and hope in commuters’ willingness to adjust travel routines.

Less-optimistic Seattleites shared fears that the roadway would never withstand having the tunnel churn through the soil surrounding it. And some figured the closure was the end for the Viaduct, and even if it didn’t sink, it wouldn’t reopen again.

On May 3, WSDOT released video from inside the tunnel, shot by a video-equipped drone. The dramatic footage served as a bit of a look-what’s-possible boost for a project that has suffered major setbacks along the way with breakdowns of Bertha.

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