Tunnel boring machine completes first Beacon Hill light rail tunnel

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The 300-foot-long machine drilling twin Link light rail tunnels through Beacon Hill in Seattle broke through the east side of the hill today. The “hole-through” completes the machine’s first 4,300 foot trip.

“You can see the light rail system taking shape all over the region,” said Seattle Mayor and Sound Transit Board member Greg Nickels. “With this milestone we’re on track for light rail service to the airport in 2009 and with the voter’s approval in November, we’ll be ready to add 50 more miles to the system.”

Obayashi Corporation launched the tunnel boring machine (TBM) in January 2006 and excavated more than 50,000 cubic yards of soils as it made its way through Beacon Hill. In its path the 100-yard-long machine installed more than 800 pre-cast concrete segments forming the lining of the tunnel. In June the machine will be transported back to the west side of Beacon Hill to begin drilling the second tunnel. The first tunnel is for southbound trains, the other northbound.


The tunnels tie in with the Beacon Hill station 160 feet below the surface. Both the tunnels and underground station are being built by Obayashi along with the elevated Mt. Baker Station at Rainier and McClellan avenues.

"This is a breakthrough in every sense of the word. It's proof Sound Transit has the expertise to handle the most complex and technical challenges and it demonstrates we're ready to expand the regional transit system outlined in the Roads and Transit package," said Sound Transit Board Chairman and Pierce County Executive John Ladenburg.

In November the region’s residents will vote on major expansions of light rail, Sounder station and ST Regional Express bus services as part of the Roads & Transit ballot measure. The plan would expand light rail services across a regional system stretching more than 70 miles, adding fast, frequent and reliable service to the Bellevue, Redmond, Mercer Island, Northgate, Shoreline, Mountlake Terrace, Lynnwood, 164th St./Ash Way, Des Moines, Federal Way and Tacoma areas.

Construction of Central Link began in late 2003 and currently is more than 70 percent complete and on schedule to begin service between downtown Seattle and Sea-Tac International Airport in 2009.



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Sound Transit’s regional network of express buses, commuter rail, light rail and transit facilities connects communities in King, Pierce and Snohomish counties.