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April 28, 2014
Sound Transit is preparing to launch the first of two tunnel boring machines that will dig a 3.6-mile light rail tunnel between the University of Washington and Northgate.
The first machine will start digging in June, and the second one will start later in the summer. One machine will dig a northbound tunnel and the other will dig the southbound tunnel. One of the machines was used to tunnel between downtown and Capitol Hill, said Sound Transit spokesman Bruce Gray.
The boring machines were manufactured by The Robbins Co. and Hitachi Zosen Corp., which manufactured Bertha as well as the TBM used for the downtown-to-Capitol Hill tunnel. Bertha got stuck last December under the waterfront in Seattle and is not expected to start digging again until March of 2015 after repairs are completed.
Jay Dee Contractors of Livonia, Mich., Frank Coluccio Construction Co. of Seattle and Michels Corp. of Brownsville, Wisc., formed a joint venture, JCM, to be the general contractor for the University District to Northgate tunnel. JCM was the contractor for the downtown to Capitol Hill tunnel.
The University District to Northgate tunnel and station excavations is the largest contract in Sound Transit's history, valued at $440 million, Gray said.
The machines are scheduled to be done by mid 2016. Crews will then install tracks and other systems.
Service between UW and Northgate is projected to open in 2021.
Both machines will start at the same place — near Northeast 95th Street — and end up at the UW station near Husky Stadium where they will be taken apart. Gray said by the time the machines arrive, the Husky Stadium station will be open.
Gray said the machines that will dig the Northgate extension are much smaller than Bertha — 21 feet in diameter versus more than 57 feet for Bertha's cutterhead. Gray said 21-foot cutterheads are a standard size for transit projects all over the world.
The contractors successfully dug the downtown-to-Capitol Hill tunnel using one of these machines.
The Northgate light rail extension is expected to carry passengers between downtown and Northgate in 14 minutes. There will be stations at Northeast 45th Street and Brooklyn Avenue Northeast in the University District; at Northeast 65th Street and 12th Avenue Northeast in Roosevelt; and at Northgate on Northeast 103rd Street.