ST launches tunnel-boring machine for light rail tunnels under Beacon Hill
Sen. Patty Murray today joined Sound Transit in marking a major light rail construction milestone. A massive tunnel-boring machine (TBM) is about to disappear into the side of Beacon Hill as it digs the first of two almost mile-long light rail tunnels.
"The tunnels we're building will serve thousands of commuters every day traveling between Downtown Seattle, the airport and the communities along the way," said Sen. Murray. "Today is a big day in continuing to build the mass transit system that is connecting our region."
The launch of the TBM represents the start of some of the most exciting and technical light rail construction work. The tunnels will tie in with the underground station that is well under construction 160 feet below the surface of Beacon Hill. The work is being done by Obayashi Corporation, Sound Transit's experienced light rail contractor for the Beacon Hill segment. The machine is guided with a sophisticated tracking system that is accurate to within an inch.
"This machine means business," said Sound Transit Board Chair and Pierce County Executive John Ladenburg. "It's not often you meet a piece of equipment as long as a football field with an insatiable appetite for chewing up dirt and rocks and leaving behind a modern mass transit system."
The TBM's rotating head will cut through everything from sand to boulders, depositing excavated material on a conveyor system for removal. In its path the machine will install pre-cast concrete segments forming the lining of the tunnel. Information about the process is available in Projects and Plans>>
"Project after project, we're showing we've got the experience to build a mass transit system," said Sound Transit Board Member and Seattle Mayor Greg Nickels. "Central Link light rail will dramatically expand the regional system that is up and running today, connecting people from communities all around the region. The system benefits everyone and provides a foundation that can continue growing in the years ahead."
Last year Sound Transit and Obayashi Corporation held a "Name the TBM" contest open to kids 12 and under who live in King, Pierce and Snohomish counties. Today, Board members and Sen. Murray recognized 7-year-old Sean Davidson of Issaquah, who submitted the winning name: Emerald Mole.
Construction of Central Link began in late 2003 and currently is now more than one-third complete. Overall, construction bids came in 6 percent below estimates and construction is currently about $200 million under budget. By 2020 the system is projected to carry more than 45,000 riders daily between downtown Seattle and the airport.
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Sound Transit plans, builds and operates regional transit systems and services to improve mobility for Central Puget Sound.