SR 520 I-5 Express Lanes Connection Project

Plans and progress

Over the last decade, Seattle’s population and employment boomed, especially in the South Lake Union neighborhood. At the same time, the Eastside’s technology-driven cities continued to see rapid growth. These two factors underscore the importance of a safe, reliable transit/HOV link between Seattle and the Eastside via SR 520. This project addresses this issue by extending SR 520’s new transit/HOV system onto the I-5 express lanes, creating a direct bus and carpool connection between SR 520, South Lake Union and downtown Seattle.

This project is a central part of the larger, ongoing SR 520 Bridge Replacement and HOV Program that is reconstructing the SR 520 corridor from I-405 in Bellevue to I-5 in Seattle. We’ve already completed several phases of the program, including:

• Floating Bridge and Landings Project: Building the world’s longest floating bridge on Lake Washington between Seattle and the Eastside, and constructing the bridge’s 44 smaller pontoons in Tacoma.
• Pontoon Construction Project: Constructing the floating bridge’s 33 largest pontoons in Aberdeen, Washington.
• Eastside Transit and HOV Project: Rebuilding the highway’s Eastside segment between I-405 and Lake Washington’s east shore.
• West Approach Bridge North Project: Completing the first of two parallel west approach bridges over Union Bay, between the floating bridge and Seattle’s Montlake neighborhood.

The Montlake Project, currently under construction, is completing the second of two parallel west approach bridges over Union Bay. This project also is building a new landscaped lid between Montlake Boulevard and 24th Avenue East, and a bicycle and pedestrian land bridge to the east of the lid.

When the corridor’s reconstruction is fully completed:

• All of SR 520’s major bridges will be replaced with stronger structures.
• The bus/carpool lanes and a regional bicycle/pedestrian path will extend from I-5 in Seattle east to Redmond
• Travelers will have safer access ramps and improved connections to transit, local streets, and local and regional shared-use trails.

Project benefits

• Safer, more reliable bus and carpool travel between the Eastside, the South Lake Union area, and downtown Seattle from a new, reversible transit/HOV lane that connects SR 520 and the I-5/Mercer Street interchange.
• Earlier-than-planned Eastside/South Lake Union transit service via the reversible I-5 express lanes connection; the connection could open as early as late 2023 for transit instead of the originally expected opening in 2029.
• A more efficient phasing of SR 520 construction that minimizes contractor overlap in the Montlake area while keeping regional and local traffic moving during construction.

Project design

The SR 520/I-5 Express Lanes Connection Project’s design was developed through years of coordination between WSDOT, the city of Seattle, partner transit agencies and design professionals. Visit the maps and drawings tab for renderings of key project elements.

A commitment to equitable contracting

WSDOT is committed to meeting the governor's voluntary goal of providing 26 percent of the contract value for Connecting Washington transportation projects to minority-owned, women-owned, veteran-owned and disadvantaged small businesses (MSVWBEs). See more on equal opportunity in contracting for more information and resources for working with WSDOT.

Construction on the SR 520/I-5 Express Lanes Connection Project is expected to last into fall 2023. The work includes building a new, elevated reversible HOV access ramp between SR 520 and the I-5 express lanes, constructing 23 retaining walls, and electrical and real-time traffic signage work. The prime contractor, Walsh Construction, has open contracting opportunities on the project for qualified MSVWBE firms for landscaping, hydroseeding, and Vactor truck operations. Subcontractors interested in working on this project should contact:

• John Currier, Walsh Construction/Inclusion Manager, at jcurrier@walshgroup.com or 206-661-1657
• Regina Glenn, WSDOT’s Megaprograms Diversity and Inclusion Manager, at GlennRe@consultant.wsdot.wa.gov