SR 520 - Montlake Project

Project overview

The construction now underway for the SR 520 Bridge Replacement and HOV Program is the Montlake Project. This project is the first stage of all remaining SR 520 improvements in Seattle – what we call the “Rest of the West.” To get the most up-to-date information on current SR 520 construction activities or planned travel restrictions, visit our Construction Corner.

Project news

  • Construction of the SR 520 Montlake Project has moved into high gear with contractor crews preparing a work zone for building a Montlake lid over the highway, an improved Montlake Boulevard interchange, and other corridor enhancements. Read more about this work in our Aug. 1 news release. Because some of the work needs to occur at night, we applied for a project-long noise variance from the city of Seattle. Learn about the conditions for our nighttime work by reading our noise-variance application (pdf 1.2 mb) and the city's decision granting the variance. (pdf 4 mb) 

Needs and benefits

SR 520’s 1960s-era west approach bridge, supported by hollow columns, is at risk of failure in a severe earthquake. In addition, the highway’s old, four-lane segment in Seattle is typically at capacity during peak periods. Now that we’ve completed reconstruction of the highway’s Eastside segment and replaced the old floating bridge, we are moving forward to complete the remaining SR 520 safety and mobility improvements from Lake Washington to I-5.

The end result

  • A new, seismically stronger West Approach Bridge South, parallel to the completed West Approach Bridge North, to carry three lanes of eastbound traffic past Montlake Boulevard East to the new floating bridge
  • A community-connecting highway lid and transit hub at Montlake Boulevard East
  • A rebuilt SR 520 / Montlake Boulevard East interchange
  • A bicycle-pedestrian “land bridge” over SR 520, east of the Montlake lid, connecting the Arboretum and points northward, including the University District

Montlake Project key improvements in the Montlake area

map of SR 520 Montlake Project key elements, including a lid over the highway, a transit hub, and a bicycle and pedestrian land bridge over the highway.

View a larger image (pdf 9 mb)

Project benefits

  • A safer highway for motorists and transit riders by replacing the old, structurally vulnerable west approach bridge
  • Improved regional mobility from the addition of transit/HOV lanes across Lake Washington, direct-access ramps for buses and carpools to and from a regional transit hub on the Montlake lid, and added lane capacity at the Montlake Boulevard East interchange
  • More nonmotorized-travel options from a new north-south bicycle and pedestrian land bridge over SR 520, connecting Arboretum trails with local and regional bicycle/pedestrian routes in Montlake and the University District
  • New community open space and trail connections from construction of a landscaped Montlake lid
  • Fewer traffic backups thanks to wider highway shoulders that allow disabled vehicles to pull over without blocking traffic
  • A cleaner, healthier environment from the creation of treatment systems for SR 520 stormwater runoff

Montlake Market update

WSDOT acquired the Montlake Market and 76 gas station property in June 2019 to enable permanent improvements to the SR 520 corridor, provide space for detours to keep traffic flowing in Montlake during construction, and efficiently stage the work. WSDOT and the market’s operators are discussing a lease that would keep the market open until Jan. 1, 2020, after which the market building will be removed. In addition, under a directive from the state Legislature, we are discussing the possibility of the market’s owners operating a smaller, temporary market or food service in Montlake during the approximate four years of Montlake Project construction. Once Montlake Project construction is complete, WSDOT will sell the remaining, unimproved portion of the market property – a sale that will happen about six years sooner than we’d previously planned. You'll find more information by reading our answers to market-related questions (pdf 105 kb) we received during our 2019 online survey and from our November 2018 public meeting (pdf 250 kb).

Relocation of wireless-communications structure

A company named Crown Castle currently operates a wireless-communications facility – called a “monopole” – on the Montlake Market property. The pole serves two wireless carriers. There are also two facilities on the roof of the market that serve two additional wireless carriers. In order to maintain emergency 911 service and uninterrupted cell phone service for the Montlake area, Crown Castle is working with WSDOT to remove its wireless equipment from the Montlake Market property and erect a new, temporary wireless structure on the nearby WSDOT Peninsula. The new pole will be able to accommodate all four wireless-service providers (AT&T, Sprint, T-Mobile and Verizon) that currently use the Montlake Market property. Please read our Q&A document (pdf 185 kb) for additional information.

More Montlake Project information

  • The city of Seattle granted WSDOT a noise variance for the upcoming Montlake Project. More information on the variance (document #3030792) is available on the city of Seattle's website. You also can read our Q&A (pdf 539 kb) on the variance.

Project design

Our website’s planning-documents webpage contains extensive information about the Seattle Community Design Process and other project-design initiatives and reports. There will be more design work for future Rest of the West projects, with additional opportunities for public comment.

Montlake Project design rendering

Artistic rendering of a Montlake lid transit hub

Artistic rendering of the transit hub on a planned SR 520 highway lid in Montlake.


  • Fall 2018: Select contractor
  • Summer 2019: Begin construction
  • 2023-2024: Complete project construction

Temporary traffic shift

As crews start removing the old west approach bridge from Lake Union to build the West Approach Bridge South, all SR 520 traffic will shift onto the West Approach Bridge North, opened in 2017. During this interim construction period, the West Approach Bridge North will carry two general-purpose lanes of traffic in both the eastbound and westbound direction.

map of SR 520 Montlake Phase traffic shifts

View larger image (pdf 2 mb)


This project, with a $455 million contract cost, is part of the remaining $1.6 billion in SR 520 improvements from Lake Washington to I-5 – the “Rest of the West.” These improvements are funded by the 2015 Connecting Washington transportation legislation. For more information on SR 520 funding, visit the Budget and Performance page.

A commitment to fair contracting

WSDOT is committed to meeting the governor's voluntary goal of providing 26 percent of the contract value for Connecting Washington transportation projects – including the SR 520 Montlake Project – to minority-owned, women-owned, veteran-owned and disadvantaged small businesses. Learn more about the SR 520 Diversity and Inclusion Program.


Here are some resources you can use to stay informed about this project:

If your organization is interested in receiving a project briefing or presentation, please contact us.