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As Seattle’s Alaskan Way Viaduct sat free of cars overhead and drivers attempted to move around the city during the roadway’s planned 2-week closure, a new drone video Tuesday showcased again what all the fuss is about. A view inside the SR 99 tunnel won’t get much better than this until you’re actually able to drive through it.

A few days before the tunneling machine Bertha began a phase of its big dig that is taking it beneath the Viaduct, the Washington State Department of Transportation flew a video-equipped drone north into the tunnel to show construction progress.

The 4-minute video captures what has been built behind nearly 1,600 feet of mining along Seattle’s waterfront. There is no sound in the video and no workers are present as WSDOT says it was shot between shifts to avoid disruption. Text overlays provide information throughout.

SR 99 tunnel
A screen grab from video inside Seattle’s SR 99 tunnel as the drone arrives at Bertha’s cutterhead. (Via WSDOT)

The northbound lanes are the lower portion of the future double-deck roadway. Early on, the drone makes its way to the top of the tunnel to show the southbound lanes. The exterior walls of the tunnel are made up of curved concrete rings that are installed by Bertha as the machine moves forward. The roadway itself is built by construction crews.

A yellow tube used to carry fresh air to the tunneling machine is visible along the top of the tunnel. The drone eventually catches up to the back of Bertha’s trailing gear which is five stories tall and houses all of the equipment crews need to support Bertha’s operation. It takes another 300 feet to reach the machine’s rotating cutterhead.

There is an astounding amount of machinery and infrastructure in place along the way and we can only imagine what the entire operation looks like teeming with workers. Still photos released in March provided a bit of the dramatic scale by featuring a couple tiny people.

Alaskan Way Viaduct
The Alaskan Way Viaduct sits empty during closure of the roadway to enable the tunneling machine to pass beneath it. (Via WSDOT Flickr)

WSDOT issued an update on Bertha’s progress on Tuesday, reporting that Seattle Tunnel Partners have installed 17 rings since mining resumed on Friday. Crews have excavated 117 feet of the approximately 385 feet of tunnel that must be completed before the Alaskan Way Viaduct reopens to traffic. A map tracks the progress, below.

Bertha map



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