Beacon Hill tunnel (Seattle)

Beacon Hill tunnel is a public transit tunnel in Seattle, Washington, carrying light rail trains on the 1 Line under Seattle's Beacon Hill between Rainier Valley and SoDo just east of Interstate 5.[1] The Beacon Hill Link Light Rail station is approximately 165 feet (50 m) underground near the midpoint of the tunnel.

Beacon Hill tunnel
Sound Transit Light Link Rail Beacon Hill West Portal.jpg
Tunnel's west portal under an elevated portion of Interstate 5
LocationSeattle, Washington
Coordinates47°34′37″N 122°19′12″W / 47.577°N 122.320°W / 47.577; -122.320Coordinates: 47°34′37″N 122°19′12″W / 47.577°N 122.320°W / 47.577; -122.320
StartSoDo, Seattle, Washington
EndRainier Valley, Seattle, Washington near Mount Baker station
OwnerSound Transit
TrafficLink light rail (1 Line)
Length1 mi (1.6 km)
Tunnel clearance21 ft (6.4 m)[1]
Width21 ft (6.4 m)[1]


Construction of the tunnel began in March 2005 and was completed in July 2009. Obayashi Corporation was the general contractor. The twin running tunnels were excavated with a tunnel boring machine (TBM) built by Mitsubishi, named the "Emerald Mole."[2] The station and crossover tunnels were constructed using the sequential excavation method (SEM), also known as the New Austrian tunnelling method (NATM).[3]

Several workers were injured and one was killed during construction of the tunnel.[4]

The tunnel was completed at a cost of $309 million, versus Obayashi's bid of $280 million.[5]


  1. ^ a b c Beacon Hill Station and Tunnel factsheet (PDF), Sound Transit, 2008[permanent dead link]
  2. ^ Carl Molesworth (June 5, 2006). "Inside the Emerald Mole". Pacific Builder and Engineer. Archived from the original on 2008-02-14.
  3. ^ "Sound Transit digs a cutting-edge tunnel". DJC. Retrieved 2009-09-17.
  4. ^ Levi Pulkkinen; Larry Lange (February 7, 2007), "Worker killed in Sound Transit tunnel: Second accident in three months at light rail site", Seattle Post-Intelligencer
  5. ^ Eric de Place (October 2009), Sightline Report: Cost Overruns For Seattle-Area Tunnel Projects (PDF), Sightline Institute, retrieved 2013-04-04[permanent dead link]