Project news

We’ve created a new set of webpages, called the SR 520 Construction Corner, to help keep the public informed on what to expect from SR 520's reconstruction and how the work will affect travel in and around the corridor. To get the latest on SR 520 construction, including planned highway closures, we recommend bookmarking the Construction Corner or saving it in your web browser's "favorites" folder.

Overview

Now that we’ve completed reconstruction of SR 520’s Eastside corridor, built a new floating bridge on Lake Washington and completed the first of two parallel bridges across Union Bay, we are focused on completing the remaining SR 520 improvements from Lake Washington to I-5. These phased improvements, which we call the "Rest of the West," include:

the second of two, parallel west approach bridges.

landscaped highway lids in Seattle's Montlake and Roanoke neighborhoods.

a new bicycle and pedestrian land bridge over SR 520.

a new, reversible bus/carpool connection between SR 520 and Seattle’s South Lake Union area.

a new Portage Bay Bridge.

a second bascule bridge over the Montlake Cut.

Why is WSDOT pursuing these projects?

SR 520’s 1960s-era bridges are structurally vulnerable and at risk of failure in a severe storm or earthquake. In addition, the highway’s old, four-lane segment is typically at capacity during peak periods. The projects we'll construct, in phases, for the Rest of the West will complete all planned safety and mobility improvements on SR 520 from Lake Washington to I-5.

The end result

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

A bicycle-pedestrian “land bridge” over SR 520 connecting the Arboretum and points northward, including the University District

Mitigation and trail-improvement projects in Seattle parks, natural areas and neighborhoods

Project benefits

A safer highway for motorists and transit riders by replacing structurally vulnerable bridges

Improved regional mobility by adding dedicated transit/HOV lanes across the entire SR 520 corridor, in both directions, and direct-access ramps to and from a regional transit hub on the Montlake lid

Greater transportation options by completing a regional, cross-lake bicycle/pedestrian path along the entire corridor, with connections to local trails on both sides of Lake Washington

Safer, more efficient north-south travel through Montlake from a second bascule bridge across the Montlake Cut

Quicker, safer travel between the Eastside and Seattle’s South Lake Union neighborhood from a new SR 520 transit/HOV connection via the I-5 express lanes

A healthier environment by creating treatment systems for highway runoff, along with other mitigation project

Timeline for Rest of the West projects

We are constructing the remaining SR 520 improvements in phases between the new floating bridge and I-5. The phased projects are:



Montlake Project

Elements: West Approach Bridge South, Montlake lid and interchange, bicycle/pedestrian land bridge over the highway

West Approach Bridge South, Montlake lid and interchange, bicycle/pedestrian land bridge over the highway Timeline: construction began in summer 2019; estimated duration: 4-5 years

SR 520 / I-5 Express Lanes Connection Project

Elements: new, reversible transit/HOV connection between SR 520 and Seattle’s South Lake Union neighborhood, running on the I-5 express lanes

new, reversible transit/HOV connection between SR 520 and Seattle’s South Lake Union neighborhood, running on the I-5 express lanes Timeline: construction estimated to begin in 2021*; estimated duration: 3 years

* Following passage of I-976, Gov. Inslee directed WSDOT to postpone projects not yet underway. This provides the governor and the Legislature flexibility during the 2020 legislative session to address the funding gap in the 2019-21 transportation budget. Learn more about the delay and related projects. (pdf 256 kb)

Montlake Cut Bascule Bridge Project

Elements: second bascule bridge over the Montlake Cut

second bascule bridge over the Montlake Cut Timeline: WSDOT will conduct additional coordination with community stakeholders and agency partners regarding the scope of this project

Portage Bay Bridge and Roanoke Lid Project

Elements: Portage Bay Bridge, Roanoke lid, I-5 bicycle and pedestrian crossing

Portage Bay Bridge, Roanoke lid, I-5 bicycle and pedestrian crossing Timeline: construction estimated to begin in 2023; estimated duration: 6 years

Project design

Our website’s planning-documents webpage contains extensive information about the Seattle Community Design Process and other project-design initiatives and reports for the Rest of the West projects.

Funding