Inside Bellevue’s Future Light Rail Tunnel
An excavator removes soil underneath 110th Avenue.
Image: Lizz Giordano
Progressing 3.5 to 5 feet a day on average, crews working on the East Link light rail tunnel have completed 700 of the 2,000 feet of tunnel that will eventually connect the future East Main and Downtown Bellevue stations under 110th Ave.
Due to the short tunnel length, approximately one-third of a mile, the tunnel is being constructed using the Sequential Excavation Method (SEM) rather than using a tunnel boring machine. As the soil is removed in small sections, pressurized concrete, known as shotcrete, is sprayed onto the tunnel's sides. Steel lattice girders are added to give additional support as the shotcrete is drying. A waterproof layer will then be added, followed by a thicker layer of shotcrete.
A video by Sound Transit shows the tunnel excavation process in detail.
Crews have worked twenty-four hours a day, six days a week since construction began in late February. Work is expected to continue through the end of 2018.
Image: Lizz Giordano
Workers examine the soil before steel lattice girders are placed.
Image: Lizz Giordano
A piece of shotcrete.
Image: Lizz Giordano
A dump truck removes soil from the south portal of the tunnel. The tunnel's depth will vary from 12 to 60 feet below the surface.
Image: Lizz Giordano
Chad Frederick, construction manager for Sound Transit.
Image: Lizz Giordano
The tunnel is 27 feet, 10 inches tall and 34 feet wide. A wall will eventually separate the two tracks.
Image: Lizz Giordano
The SEM method can minimize impacts on neighboring homes and businesses.
Image: Lizz Giordano
Image: Lizz Giordano