The State Route 99 tunnel, also known as the Alaskan Way, is a tunnel located of the Seattle city, in Washington (United States). The SR 99 tunnel is a single tube that it has two lanes in each direction with a total distance of 3,2km that it crosses the city of Seattle.
The largest-diameter tunnel boring machine, nicknamed Bertha, was used in the development of this project. Work began in April 2017 but didn't open until February 2019. Part of seconday linning support was manufactured by Caldibe, including among other elements, transporting gantries.