SR 520/Montlake to Lake Washington I/C and Bridge Replacement Project

Location: Seattle, WA

Washington State Route 520 (SR 520) is a state highway and major freeway in the Seattle metropolitan area. The 520 corridor is one of two roadways that cross Lake Washington to connect Seattle to the Eastside region of King County. Everyday tens of thousands of people travel on SR 520 to reach offices, schools, industries, entertainment venues, and more. The SR 520 Montlake Project is part of WSDOT’s SR 520 Bridge Replacement and HOV Program to enhance public safety and mobility by replacing the vital urban highway’s aging and vulnerable bridges.

The program also includes major transit, roadway and trail improvements throughout the corridor, along with significant environmental enhancements throughout the region. Built in stages, the improvements extend from I-405 in Bellevue to I-5 in Seattle. SR 520 construction began in 2011 and the corridor’s final improvements in Seattle are scheduled for completion in 2029.

The SR 520 Montlake Project includes demolition and replacement of the south portion of the West Approach Bridge and new construction of pedestrian and transit facilities. The old West Approach Bridge, built in the early 1960s, served as a vital link across Union Bay, connecting Montlake to the Evergreen Point Floating Bridge. Built on hollow columns, the old bridge was vulnerable to earthquakes, and the highway’s location divided the Montlake community. The new eastbound bridge, parallel to the westbound bridge that opened in 2017, will provide safer and more reliable travel and reconnect the Montlake community with a landscaped lid bridge and a pedestrian land bridge over SR 520. Lid construction includes demolition of the existing 24th Ave and Montlake Blvd overpasses, improvements to the Montlake Blvd/SR 520 interchange, new park space, direct-access bus ramps and a transit plaza, and numerous trails to provide multimodal connections across SR 520.

Link to WSDOT’s project website:

Link to WSDOT’s “Construction Corner” website:

Link to WSDOT’s SR 520 Bridge Replacement and HOV Program website:


Contract Value

$476M USD

Prime Consultant

T.Y. Lin International

Project Owner


Contract Format


Completion Date

June 2023

Contract Duration

50 months