Wednesday, October 04, 2017

Sound Transit East Link tunneling now at 30% completion

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Sound Transit East Link tunneling now at 30% completion Sound Transit

Construction of Sound Transit's East Link light-rail tunnel has reached 30 percent completion, according to the transit agency. Excavation is expected to progress at approximately three to four feet per day.

Sound Transit is utilizing Sequential Excavation Method (SEM) to build the tunnel due to the short tunnel length and to minimize the impact of tunnel construction on neighboring homes and businesses. Sound Transit explains that SEM removes soil in small sections or bites using an excavator and support equipment. As soon as soil is removed, shotcrete is sprayed on the tunnel's perimeter and lattice girders made from steel reinforcing bar provide additional structural support for the tunnel.

Crews are excavating at the south portal site at 112th Ave. Northeast and Main. When complete, the tunnel will be approximately one-third of a mile long, running between the future East Main and Downtown Bellevue stations under 110th Ave. Northeast, turning east near Northeast 6th Street. The tunnel will be 27 feet, 1- inches high and is being constructed12-60 feet below the surface.

Sound Transit says the tunnel's inclusion in East Link project was enabled by city of Bellevue in-kind contributions of $100 million, including property and permits, formalized in a Memorandum of Understanding executed by the Sound Transit Board in April 2015.

East Link will extend light rail 14 miles from downtown Seattle to downtown Bellevue and the Overlake area of Redmond via Interstate 90, with 10 stations. All segments of the East Link extension are currently under construction and the entire line will be operational in 2023. The following year Sound Transit will open a 3.7-mile extension further east to new stations in Southeast Redmond and downtown Redmond under funding approved in November 2016.