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East Link tunnel excavation is underway in downtown Bellevue

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Behind the construction sound wall, crews are busy excavating at the south tunnel portal site located at 112th Avenue Northeast and Main Street. A video of the construction progress at the the tunnel portal and route through downtown Bellevue can be viewed here.

Because of the short tunnel length (approximately 2,000 feet long, or approximately one-third of a mile), and to minimize impact on neighboring homes and businesses, Sound Transit is constructing the tunnel using the Sequential Excavation Method (SEM) rather than a tunnel boring machine or digging a large trench that is later covered. SEM removes soil in small sections or bites using an excavator and cutting equipment. As soon as soil is removed, pressurized concrete, called shotcrete, is sprayed on the tunnel's sides, celling and floor. Lattice girders provide additional structural support for the tunnel.

SEM minimizes disruptions to surface streets, homes and businesses while also reducing noise and dust. Sound Transit used SEM to successfully dig its Beacon Hill light rail station. 

Sequential Excavation Method graphic

What to expect:

  • Approximately two years of excavation followed by finish work inside the tunnel.
  • Work began at the south tunnel portal and will advance north at a projected rate of 3 – 4 feet per day.
  • Tunnel excavation occurs on a 24/7 timeline with truck hauling occurring during daytime hours.