The East Link light rail tunnel excavation is nearly complete, Sound Transit announced last week. Crews are expected to begin construction on the Bellevue Downtown Station later this month.

“We are on the verge of a breakthrough in many senses of the word,” Sound Transit Boardmember Claudia Balducci said in a statement. “As the tunnel nears completion, we are moving ever closer to seeing light rail fully constructed, connecting the eastside to the rest of the region and giving our residents and visitors a fast, reliable, traffic-free way to get around.”

Tunnel work began in February 2017 and is on pace to be finished in just 15 months, five months ahead of schedule.

East Link tunnel, East Link

East Link tunnel excavation. Courtesy Sound Transit via Vimeo.

Instead of a tunnel-boring machine or a “cut-and-cover” trench-digging system, workers are using the Sequential Excavation Method (SEM), which utilizes an excavator and other cutting equipment to remove soil in small chunks. According to Sound Transit, this method allows for continuous monitoring and reduces traffic disruption, noise, and dust impacts to surrounding areas.

The tunnel begins near 112th Avenue Northeast and Main Street and covers one-third of a mile, running under 110th Avenue Northeast and turning east near Northeast 6th Street.

Tunnel Facts:

  • Length: 1,985 linear feet, approximately one-third of a mile
  • Height: 27 feet, 10 inches
  • Width: 34 feet
  • Depth: 12-30 feet below the surface
  • Volume of soil removed: 72,000 cubic yards
  • Number of lattice girders used: 479
  • Volume of shotcrete used: 9,000 cubic yards

The tunnel excavation is being paid for largely with $100 million of in-kind contributions from the City of Bellevue. Once the overall East Link project is completed, there will be 10 stations and 14 miles of light rail from downtown Seattle to downtown Bellevue and the Overlake region of Redmond, across I-90. The system is expected to become fully operational in 2023.

By 2040, after several other light rail projects are completed in the region, trains will carry approximately 600,000 riders daily, according to a Sound Transit statement.

Watch a timelapse video of the Bellevue tunnel construction here.