Beacon Hill tunnel is a

public transit Public transport (also known as public transit, mass transit, or simply transit) are forms of transport available to the general public. It typically uses a fixed schedule, route and charges a fixed fare. There is no rigid definition of wh ...

tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...

in Seattle, Washington, carrying

light rail Light rail (or light rail transit, abbreviated to LRT) is a form of passenger urban rail transit that uses rolling stock derived from tram technology National Conference of the Transportation Research Board while also having some features from ...

trains on the 1 Line under Seattle's Beacon Hill between

Rainier Valley Rainier Valley ( ) is a neighborhood in southeastern Seattle, Washington. It is located east of Beacon Hill; west of Mount Baker, Seward Park, and Leschi; south of the Central District and north of Rainier Beach. It is part of Seattle's So ...

and

SoDo Sodo () or officially Wolaita Sodo (, ) is a city in south Ethiopia. The city is a political and administrative center of the Wolaita Zone and South Ethiopia Regional State. It has a latitude and longitude of with an elevation between abov ...

just east of

Interstate 5 Interstate 5 (I-5) is the main north–south Interstate Highway System, Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific coast of the contiguous U.S. from Mexico to Canada. It travels thro ...

. The Beacon Hill Link Light Rail station is approximately underground near the midpoint of the tunnel.

Construction

Construction of the tunnel began in March 2005 and was completed in July 2009.

Obayashi Corporation is one of five major Japanese construction companies along with Shimizu Corporation, Takenaka Corporation, Kajima Corporation, and Taisei Corporation. It is listed on the Tokyo Stock Exchange and is one of the Nikkei 225 corporations. Its h ...

was the general contractor. The twin running tunnels were excavated with a

tunnel boring machine A tunnel boring machine (TBM), also known as a "mole" or a "worm", is a machine used to excavate tunnels. TBMs are an alternative to drilling and blasting methods and "hand mining", allowing more rapid excavation through hard rock, wet or dry so ...

(TBM) built by Mitsubishi, named the "Emerald Mole." The station and crossover tunnels were constructed using the sequential excavation method (SEM), also known as the

New Austrian tunnelling method The new Austrian tunneling method (NATM), also known as the sequential excavation method (SEM) or sprayed concrete lining method (SCL), is a method of modern tunnel design and construction employing sophisticated monitoring to optimize various wa ...

(NATM). Several workers were injured and one was killed during construction of the tunnel. The tunnel was completed at a cost of $309 million, versus Obayashi's bid of $280 million.

References

{{Bridges of Seattle Railroad tunnels in Seattle Link light rail Tunnels completed in 2009 2009 establishments in Washington (state) 1500 V DC railway electrification