Bite by bite, tunnelers will push through layers of glacial deposits to build a crucial section of Sound Transit's $2.4-billion, 14-mile light rail system that will eventually connect downtown Seattle to the Seattle-Tacoma International Airport. The Beacon Hill segment consists of two parallel 4,300-ft-long, 18.8-ft-dia tunnels to be built with a 335-ton earth pressure balance tunnel-boring machine. For the station, two vertical shafts, 50 and 30 ft in diameter, will connect to platforms located about 160 ft below grade.
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