The excavation of Seattle’s Sound Transit’s East Link light rail tunnel has been completed.
The 605m tunnel was constructed using sequential excavation method (SEM) using an excavator and cutting equipment to remove 55,000m³ soil in small sections. Following the removal of soil, crews have sprayed 6881m³ of shotcrete and installed 479 arc-shaped lattice girders. The tunnel is between 3.6m to 9.1m below the surface.
Contractor Atkinson Construction used observational methods and numerical modelling to adapt its excavation to different ground conditions in different areas of the tunnel. With excavation complete, Atkinson will begin constructing the tunnel’s final concrete lining, a process that is expected to take another year to complete.
Sound Transit board member Claudia Balducci said: “Today is a breakthrough in every sense of the word. This tunnel is the culmination of over a decade of vision, hard work and tenacity by local and regional leaders, planners, workers and many, many members of the public who all insisted on a great transit connection through downtown Bellevue. East Link, and this tunnel, will connect our communities, support our economy and provide a fast and reliable way to get out of traffic for people all over the region.”
When completed the East Link will extend light rail 22.5km from downtown Seattle to downtown Bellevue and the Overlake area of Redmond with 10 stations.
By the end of 2018, all segments of the East Link extension will be under construction, and the entire line will be operational in 2023.