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SR 99 tunnel
A worker is visible inside the SR 99 tunnel is this view looking south from the back end of the tunneling machine Bertha. (WSDOT via flickr)

The slow crawl of Bertha, the tunneling machine making its way below Seattle’s Alaskan Way Viaduct, hasn’t been without its share of frustrating setbacks. But when there is a glimpse at signs of progress, it’s easy to be impressed by the feat of engineering.

The Washington State Department of Transportation posts photos from a variety of road projects around the state on its flickr page. The SR 99 Tunnel Project has a dedicated album which currently has 146 images in it dating back to a photo of former Gov. Christine Gregoire signing a bill to replace the Viaduct.

Along with the official Bertha Twitter feed and WSDOT’s Viaduct replacement website, readers are offered unique access to a construction project transforming the way traffic will move through Seattle.

This month there have been a few stunning shots from inside what will become the new waterfront tunnel. A lone worker is shown dwarfed inside the massive project in a shot dated March 14 (above). Another image looks north at the back end of Bertha and shows the framework for the future double-deck roadway.

SR 99 tunnel
Steel hooks on both sides of the circular wall of the tunnel will become part of the foundation that will support the decks and walls of the future roadway inside the tunnel. (WSDOT via flickr)

Before and after images from November 2015 and this month show the tunnel after Bertha moved a distance of 470 feet.

SR 99 tunnel
(WSDOT via flickr)

The WSDOT project website also has a Follow Bertha page which includes a map showing the great distance the machine still has to travel before it reaches the finish line. Bertha was fired up on July 30, 2013, and has been plagued by breakdowns and delays along the way. As of mid-March, Bertha has moved 1,560 of the 9,270 feet it needs to bore underground.

SR 99 tunnel
A map shows Bertha’s entire route divided into zones which are unique because of a certain soil type or a noteworthy location beneath the city. (Via WSDOT)

On March 14, Bertha reached a planned maintenance stop near Yesler Way, according to WSDOT. Workers will spend up to a month inspecting the machine and performing planned maintenance, including inspecting the cutterhead and replacing cutting tools, among other things. After the work is completed, the machine will move beneath the Alaskan Way Viaduct, forcing a closure of the elevated roadway for approximately two weeks.

SR 99 tunnel
Light at the end of the tunnel? The circle in the middle of the square wall marks the spot where Bertha will break through at the end of her trip under downtown Seattle. On the floor of this pit, crews are building the cradle Bertha will rest upon while being disassembled. (WSDOT via flickr)
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