The Supertunnel

A Look Back at Seattle’s Supertunnel

Official SR 99 Tunnel Project site photographer Catherine Bassetti’s 184-page hardcover book, Building Seattle’s State Route 99 SupertunnelJourney from Light to Light documents one of Seattle’s largest public works project.

If you’ve resided in Seattle over the last eight-to-ten-years, you’ve probably heard of, dealt with roadblocks, driven through, or even worked on Seattle’s State Route 99 (SR 99) Tunnel Project, also known as the Alaskan Way Viaduct. It’s hard to believe that two years have already passed since the tunnel opened to traffic on February 4, 2019. To mark the occasion, we partnered with official site photographer Catherine Bassetti to revisit one of Seattle’s largest public works projects.

January 2014: The tunnel launch site, where “Bertha” began her journey.

The underground drive of the SR 99 tunnel began in July of 2013 with “Bertha” (the world’s largest diameter boring machine at the time) and took the next six years to complete. From start to finish, an average of 200 union carpenters worked in a variety of capacities to complete this high-profile project. The tunnel itself is a single tube that measures 9,270 feet long and 57.5 feet wide, carrying a double-decker highway that is 32 feet wide with two lanes in each direction.

The design-build contractor, Seattle Tunnel Partners (STP), hired Bassetti as the official on-site progress photographer starting in January 2014. She continued to document everything concerning the project in the six years it took to complete. A life-long resident of the Pacific Northwest, Bassetti’s career began overseas in fashion photography, photojournalism, and advertising. When she returned to the Pacific Northwest her business evolved into documenting the development of her native Seattle, a small contribution to the city where her family has a history of architectural achievements. 

“I’ve had a long, multi-faceted career and I would say this was one of the most challenging, yet rewarding of all assignments. Many who labored on the tunnel refer to it as a once-in-a-lifetime project. With such a volume of material, I began thinking of a photographic coffee table book, but this eventually grew into a longer, more inclusive endeavor, which the complex and historic tunnel deserves,” said Bassetti. 

“The size of [this project] was mind-boggling,” said Northwest Carpenters Union Representative Jesse Scott-Kandoll. “We drilled under a major city and had an average of 200 carpenters and close to 60 divers working on the project with multiple contractors just from our union.”

As Bassetti spent years photographing the SR 99 tunnel, she captured statements from all six of the participating unions, insights from key management, planning and civic leaders, and intimate first-hand stories from crew members that evolved her coffee table book into an oral and pictorial history of one of Seattle’s largest public works projects.

July 2014: View of the Cut and Cover zone progress, and mouth of the tunnel.
January 2015: Interior view of SR 99 Tunnel Project.
January 2015: Aerial view of the Alaskan Way Viaduct and Seattle waterfront.
March 2015: The TBM “Bertha” is rescued and lifted to be repaired.
July 2016 – Crews began construction of the interior roads while the TBM was under repair.
April 2017: Members of the crew celebrate “Bertha’s” successful exit at North Portal.
October 2017: Cement pour on upper road deck interior.
Fall 2018: Near completion of the dual road decks.
October 2017: Interior completion of lower road deck.
2019: Evening view of the completed southern roadways and tunnel northbound entrance.

Interested in learning more about Catherine Bassetti and the 184-page hardcover book, Building Seattle’s State Route 99 SupertunnelJourney from Light to Light?

Check out her website:

All photographs in this article are copyrighted and being published with permission of Catherine Bassetti.

Did You Know?

PNWRCC has many women in our crafts and leadership positions.

Margaret Ellings became the first woman initiated into the United Brotherhood of Carpenters in October 1935. The establishment of a women’s committee within the United Brotherhood of Carpenters is one of the most important developments in the union’s recent history. Visit


Sign up for mobile alerts

Mobile alerts from Northwest Carpenters. Periodic messages. Msg & data rates may apply. Text STOP to 91990 to stop receiving messages. Text HELP to 91990 for more information.
Terms & Conditions