The Emerald Mole begins burrowing beneath Beacon Hill

Sen. Patty Murray recently joined Sound Transit in marking a major light rail construction milestone last week before a massive tunnel-boring machine (TBM) began to disappear into the side of Beacon Hill. The TBM is currently digging the first of two, near 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," Sen. Murray noted.

The launch of the tunnel-boring machine represents the start of some important technical light rail construction work. The tunnels will tie in with the underground station that is currently under construction 160 feet below the surface of Beacon Hill. The work is being done by Obayashi Corporation, Sound Transit's light rail contractor for the Beacon Hill segment.

"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 on the process is available at

"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. Board members and Sen. Murray recently recognized 7-year-old Sean Davidson of Issaquah, who submitted the winning name: Emerald Mole.

Construction of Central Link began in late 2003 and is now more than one-third complete. Overall, construction bids came in six 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 Seatac airport.

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