Sound Transit installing tunnel monitoring equipment

Publish Date

Construction crews building the East Link Extension tunnel in downtown Bellevue will begin installing monitoring equipment along the tunnel alignment as early as the middle of this week. The equipment will monitor tunnel excavation activities as they occur. The equipment will be installed in a number of locations along the tunnel alignment over the next several months. Tunnel excavation is anticipated to begin this fall.

What to expect:

Crews will be installing various types of monitoring equipment. You may observe the following as this work occurs:

  • Hours: Work will occur during daytime hours. Specific hours will vary depending on the specific location and will be kept to mid-day as much as possible. 
  • Drilling activities: Drilling and vacuuming is required as part of the equipment installation. Drilling will sound similar to a truck running with occasional hammering sounds and the vacuuming will make noise while soil material is being removed. 
  • Sequencing: The installation will begin at the south tunnel portal and gradually move north towards the north tunnel portal. 
  • Equipment: Drill rig, trucks, traffic signage and cones, vacuum trucks. 
  • Access: Lane closures along Main Street and 110th Avenue NE will be necessary as the equipment is installed on public streets. Signage and flaggers will be used as necessary when travel lanes, sidewalks or parking areas are affected during this work.

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Downtown Bellevue tunnel alignment

Why is monitoring important?

Early detection of ground or building movement is a key component of safe and successful tunnel construction.

For more information

Contact Blake Jones, Sound Transit Community Outreach at 206-398-5470 or

For issues that need immediate attention after normal business hours, call Sound Transit's 24-hour construction hotline at 888-298-2395.