Each of the 1,618 slabs will sit on custom-built rubber pads sourced in part for their durability and vibration-absorbing properties. The rails in this part of the tunnel will rest on a “floating slab,' a series of extra-dense concrete slabs that each weigh 11,000 lb. Some of the most interesting and complex work are the roughly 7,400 ft of tracks beneath the University of Washington. Building a cross passage every 1,000 ft along the alignment ensures that riders will never be further than 500 ft from a cross passage, a bit more than a city block. Using two tunnel boring machines-weighing 600 tons each-JCM excavated more than 500,000 cubic yd of soil, yet kept community impacts to a minimum.Ĭrews hand dug 23 cross passages that connect the two parallel tunnels. Tunneling began in 2014 and finished in 2016.įacing challenging ground and water conditions, along with urban construction constraints, Sound Transit and Northgate Link tunneling contractor JCM (a joint venture of Jay-Dee Contractors, Coluccio, and Michels) clocked more than 2 million staff hours, successfully completing two parallel tunnels on budget and on time. One of the project’s major accomplishments are the twin tunnels for the underground portion of the extension. Construction on the project began in 2012 following six years of planning. Voters approved the Northgate Link extension in 2008 as part of the Sound Transit 2 ballot measure.

Planning for the extension began in 2006. The station will also provide easy access via a pedestrian bridge to North Seattle College. The elevated station at Northgate is close to the headquarters of the Kraken, Seattle’s new NHL team, and its three NHL regulation skating rinks, which are expected to attract 800,000 visitors a year. The underground Roosevelt Station connects to a vibrant neighborhood and nearby Green Lake. The underground station in the University District is conveniently located near the University of Washington campus, home to nearly 50,000 students. The first 3.5 miles of the extension are underground, and the final 0.8 miles, ending at Northgate station, are elevated. The 4.3-mile extension connects to Sound Transit’s existing 20-mile light-rail system, extending it northward from the current terminus at the University of Washington Stadium. By: John Gallagher After 15 years of planning, design, and construction, Sound Transit’s Northgate Link extension will open on Oct 2, 2021.

Northgate link station