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Portage Bay Bridge and Roanoke Lid Project: Environmental Online Open House – Project background

Building the “Rest of the West” in Seattle

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 – a series of four projects we call the “Rest of the West.”

Last year’s I-976 ballot initiative and the COVID-19 pandemic have had significant effects on state revenue. In response, WSDOT is developing recommendations for the Governor and the Legislature to reduce WSDOT operating programs and defer some capital investment. Currently, we don’t know how this will affect SR 520 project timelines and scopes. We will keep you apprised as we learn more.

Map outlining the four SR 520 construction projects in Seattle that make up the so-called "Rest of the West." The projects extend from the west shore of Lake Washington, near Madison Park, west through Montlake and Portage Bay to Interstate 5.
The four SR 520 construction projects that make up the "Rest of the West."

“Rest of the West” project benefits

  • Safer travel from replacement of the old, structurally vulnerable Portage Bay Bridge with two parallel, seismically resilient bridge structures.
  • Improved regional mobility with completion of the final SR 520 stretch of dedicated transit/HOV lanes, in each direction, between Redmond and I-5.
  • Greater transportation options from a completed regional bicycle and pedestrian trail along the entire SR 520 corridor, and a new, 30-foot-wide shared-use crossing over I-5.
  • A community-connecting highway lid between 10th Avenue East and Delmar Drive East, with landscaped open space.
  • New and improved local, nonmotorized connections on the Roanoke lid and surrounding area.
  • Improved water quality from a new system for treating SR 520 stormwater runoff.
  • Fewer traffic backups from wider highway shoulders that allow disabled vehicles to pull over without blocking traffic.

Follow-up from 2019 Portage Bay Bridge Project community workshops

Last summer and fall, we hosted a series of community workshops where we heard feedback on the importance of maintaining the stair connection between Boyer Avenue East and Delmar Drive East. Due to the new bridge’s footprint, WSDOT will need to remove these stairs during project construction.  We recognize that the stairs are an important community connection, and we’re working with the city of Seattle to develop a replacement stair connection. We’re also exploring accessible on-street improvements for an alternate route between Boyer and Delmar.

We also heard support for a trail connection between the Bill Dawson Trail and West Montlake Park. While WSDOT will not construct this trail connection as part of the Portage Bay project, the project's design allows for another group to integrate this connection in the future.

In addition, throughout the workshops, community members emphasized their interest in various neighborhood improvements, including projects that may be proposed as potential mitigation measures in the shoreline permit application. You’ll find more information on these potential projects in the Shoreline Permit section of this online open house. Note that the projects of interest related to traffic impacts are not covered at this time. You’ll have opportunities for feedback on potential construction impacts and neighborhood traffic impacts during our development of a Community Construction Management Plan and a Neighborhood Traffic Management Plan.

Key elements of the Portage Bay Bridge and Roanoke Lid Project

Overhead map of the SR 520 corridor between Montlake and Interstate 5. The map points out key features of the Portage Bay Bridge and Roanoke Lid Project, including the lid, two parallel replacement bridges over Portage Bay, and a shared-use path on the south bridge.

This project will complete improvements to the SR 520 corridor between Montlake and I-5.

Conceptual illustration of a new Portage Bay Bridge, looking southwest across Portage Bay, with lily pads covering the water.
Conceptual illustration of a new Portage Bay Bridge, looking southwest across Portage Bay.
  •  The Portage Bay Bridge
    • Builds a new, seismically resilient bridge to replace the old 1960s structure that is built on hollow columns
    • Adds a new transit/HOV lane in each direction from Montlake to I-5
    • Provides noise-reduction measures such as quieter concrete pavement and a 45-mile-per-hour speed limit on the new Portage Bay Bridge
A conceptual design of a new Roanoke freeway lid over SR 520, as viewed from a Federal Avenue overlook. People are standing and sitting at the overlook in the foreground, looking northwest toward the landscaped Roanoke lid in the background.
Conceptual image of a new Roanoke freeway lid, as viewed from an overlook at Federal Avenue.
  • The Roanoke lid
    • Provides new community open space
    • Reintegrates neighborhoods on both sides of SR 520
    • Creates approximately 3 acres of new, accessible passive-use community open space
    • Creates three new viewpoints and improves the existing Bagley Viewpoint on the northeast side of the lid
Design rendering of the gateway to the future Roanoke freeway id neighborhood open space at the southeastern corner of East Roanoke Street and 10th Avenue East. The rendering shows walkers and cyclists on a wide, paved walkway, looking southeast toward grassy open space and trees.
Conceptual illustration of the gateway entry to a Roanoke freeway lid
at the southeast corner of East Roanoke Street and 10th Avenue East.
  •  Bicycle and pedestrian connections
    • Extends the regional SR 520 Trail across Portage Bay
    • Provides a new nonmotorized shared-use path over I-5 at East Roanoke Street
    • Builds on and connects to the city's network of nonmotorized trails

Timeline update

  • The WSDOT team is refining the project’s conceptual design in preparation for a design-build contract. The team’s project timeline includes the following steps:
    • Winter 2021/2022: Issue request for proposals (RFP)
    • 2022: Award contract
    • 2023: Begin construction, with estimated construction duration of six years

For more information on other Rest of The West projects, including the Montlake Project and the SR520/I-5 Express Lanes Connection Project, visit the SR 520 Program webpage.


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