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SR 520 - I-5 to Lake Washington

A map of the Montlake area. State Route 520 is highlighted in orange. 
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Rest of the West timeline

Rest of the West overview


Last updated: February 2018

The 2015 Legislature approved funding for SR 520's planned improvements from I-5 to Lake Washington -- the "Rest of the West." These improvements include highway lids in Seattle's Montlake and Roanoke neighborhoods, the south half of a new west approach bridge, a new Portage Bay Bridge, and a second drawbridge over the Montlake Cut. WSDOT is preparing to begin the first phase of construction, known as the Montlake Phase, in late 2018.

Final traffic management plan for the Montlake area
Check out the final Neighborhood Traffic Management Plan (pdf 4.3 mb) for the Montlake Phase. This plan, developed by WSDOT and the city of Seattle, includes a refined list of traffic-calming measures planned in the Montlake area, as well as a summary of public feedback and an overview of other city projects in the vicinity.

You ask, we answer
We receive a lot of questions about what's ahead for SR 520 reconstruction in Seattle. Read our latest FAQs (pdf 161kb), updated Oct. 20, to learn the latest.  

Montlake Phase noise variance
On Jan. 17 we resubmitted our application with the city of Seattle for a  noise variance for the upcoming Montlake Phase of SR 520 construction. More information on the application is available on the city of Seattle's website. You also can review our Feb. 15 noise-variance presentation (pdf 3mb) given at a city of Seattle public meeting, or read our Q&A (pdf 539 kb) on the variance.

Why is WSDOT pursuing this project?
This project, in phases, will complete all planned safety and mobility improvements on SR 520 from Lake Washington to I-5.

The End Result

  • A safer highway for motorists and transit riders from the replacement of structurally vulnerable bridges.
  • Improved regional mobility from the addition of dedicated HOV lanes across the entire SR 520 corridor, in both directions.
  • Greater transportation options with the completion of a regional, cross-lake bicycle/pedestrian path along the entire corridor.
  • A healthier environment from the creation of treatment systems for highway runoff and other mitigation projects.

Project Benefits

Future improvements to the highway’s western segment in Seattle include:

  • A new, seismically stronger West Approach Bridge South to carry three lanes of eastbound traffic past Montlake Boulevard to the new floating bridge.
  • Community-connecting highway lids in Seattle’s Montlake and Roanoke neighborhoods.
  • A new, seismically stronger Portage Bay Bridge.
  • A landscaped, 30-foot-wide bicycle and pedestrian crossing over I-5.
  • A second bascule bridge across the Montlake Cut to provide additional capacity and safer north-south travel on Montlake Boulevard.
  • A bicycle-pedestrian “land bridge” over SR 520 connecting the Arboretum and points northward.
  • Related mitigation and trail-improvement projects in Seattle parks, natural areas and communities.

What is the project timeline?

The 2015 Washington Legislature fully funded the remaining improvements to SR 520 between I-5 and the new floating bridge. The upcoming phases of construction, in order, are:

Montlake Phase

  • Elements: West Approach Bridge South, Montlake lid and interchange, and land bridge over the highway
  • Timeline: construction planned to begin in late 2018; estimated duration: 4-5 years

Portage Bay Phase

  • Elements: Portage Bay Bridge, Roanoke lid, and I-5 connections
  • Timeline: construction to begin in approximately 2020-2022; estimated duration: 6 years

Montlake Cut Crossing Phase

  • Elements: second bascule bridge over the Montlake Cut
  • Timeline: construction to begin as early as 2024; estimated duration: 3 years

The first two phases are each planned to be delivered as design-build contracts. The type of contract for the final phase will be determined in the future. 

This graphic (pdf 1 mb) shows the project phasing for the Rest of the West.

Financial Information

  • In the 2015 Connecting Washington transportation legislation, the state Legislature authorized $1.64 billion in funding to complete SR 520 improvements from Lake Washington to I-5 – the “Rest of the West.” For more information on SR 520 funding, visit the Budget and Performance page.

How can I get more information?

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