Seattle’s Northgate Link Extension Now Open for Service

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McMillen Jacobs Associates, a multidisciplinary engineering and consulting firm specializing in underground and water resources projects, is proud to have played a significant role in the recently completed Northgate Link Extension Light Rail project in Seattle, Washington. Completed under budget and ahead of schedule, this project aims to increase light rail ridership, improve travel time, and add transit capacity to the congested Interstate-5 corridor.

Northgate Link connects Sound Transit’s University Link light rail segment to the Northgate business/retail center and forms part of a system connecting four major urban centers to the existing Central Link (which extends from downtown Seattle to SeaTac airport). It consists of 4.3 miles (6.9 km) of double-track light rail, 3.5 miles (5.6 km) in twin bored soft-ground tunnels and .8 miles (1.3 km) in retained cut fills and elevated structures. Precast segments were used for the tunnels.

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The project also includes two underground transit stations (U District and Roosevelt), one elevated station (Northgate), a portal structure, and 23 cross passages. Both underground stations were designed as bottom-up excavations, and the cross passages are sequential excavation method structures. The project was constructed in an area characterized by dense, urban neighborhoods and complex subsurface and groundwater conditions, which required optimizing the location and alignment of the underground elements.

“Working with the Project Team for the past 10+ years has been tremendously rewarding. Riding the first train with Don Davis, Lacey Mehlert, and the entire Sound Transit team was pure joy. We’re grateful to have been of service to the agency and deeply thank the 90 folks from McMillen Jacobs who put in the hard yards during Final Design,” said Dan Adams, McMillen Jacobs Corporate Development Officer

As the prime consultant, McMillen Jacobs provided project management, tunnel and underground structure design, estimating and scheduling, and geotechnical engineering services. The team included more than 30 firms, including key teaming partners WSP, KPFF Consulting Engineers, Hewitt Architects, and LMN Architects. In 2018, Northgate Link received the Tunnel Achievement Award for Project Excellence from TBM: Tunnel Business Magazine, in partnership with the 11th annual Breakthroughs in Tunneling Conference.

McMillen Jacobs Associates has a long history of successfully designing and managing complex rail mass transit projects in major urban centers, dating back to the 1960s with the planning, design, and construction of the Bay Area Rapid Transit and Washington Metro Area Transit Agency systems. Additional signature projects include Sound Transit’s University Link, San Francisco’s Central Subway, Vancouver’s Evergreen Line Rapid Transit, Los Angeles County Metropolitan Transit Authority’s Gold Line Eastside Extension, and Ottawa Light Rail.

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