Skip to main content

SR 520 – Portage Bay Bridge and Roanoke Lid Project – Project overview

Overview of the Portage Bay Bridge and Roanoke Lid Project

The Portage Bay Bridge and Roanoke Lid Project will complete SR 520’s east-to-west reconstruction from I-405 to I-5. Like the highway’s other 1960s-era bridges, the Portage Bay Bridge was built with hollow concrete columns and could collapse in a severe earthquake. This bridge’s replacement will be built to current seismic standards. The project also will build a landscaped lid over SR 520 between 10th Avenue East and Delmar Drive East and extend the highway’s transit/HOV system to I-5 and the SR 520 Trail to the Roanoke Lid.

Conceptual rendering of new Portage Bay bridges, looking southwest
Conceptual rendering of new Portage Bay bridges, looking southwest

Project benefits

  • Safer travel from replacement of the old, structurally vulnerable Portage Bay Bridge with two parallel, seismically stronger bridges
  • Improved regional mobility with completion of the SR 520 Program’s transit & HOV enhancements between Redmond and I-5
  • Greater transportation options through an extension of the regional SR 520 Trail across Portage Bay, a new bicycle and pedestrian crossing over I-5, and connections to the city of Seattle’s non-motorized trail networks
  • A community-connecting highway lid between 10th Avenue East and Delmar Drive East, with landscaped open space on top
  • Improved water quality from a new system for treating SR 520 stormwater runoff
  • Wider highway shoulders that allow disabled vehicles to pull over without blocking traffic
Conceptual rendering of a new Roanoke lid, looking north from the end of Federal Avenue E
Conceptual rendering of a new Roanoke lid, looking north from the end of Federal Avenue E

Project timeline

  • Fall/Winter 2022
    Publish Request for Qualifications (RFQ) from contractors
  • January 2023
    Publish Request for Proposals (RFP) from contractors
  • Summer/Fall 2023
    Award design-build contract
  • 2024
    Begin construction
  • 2030
    Complete construction

Major project elements

Map of major project elements
  • Portage Bay Bridge: Two new parallel bridges built to modern seismic code will replace the existing Portage Bay Bridge. There will be one bridge for eastbound traffic, one for westbound traffic, and improved travel for busses and carpools.
  • Roanoke lid: A new lid over SR 520 between 10th Avenue East and Delmar Drive East that will reconnect the neighborhoods on both sides of SR 520. The lid will create approximately three acres of new community open space.
  • Bicycle and pedestrian connections: An extension of the regional SR 520 Trail across Portage Bay, a new bicycle and pedestrian crossing over I-5, and connections to the city of Seattle’s non-motorized trail networks.

Project contracting

This project will be a design-build contract, which means WSDOT completes the preliminary design of the project and then hires a firm to complete the final design and plans and construct the project.

Key advantages to the design-build process include:

  • The designer and builder can closely collaborate at the same time. As a result, complicated projects find innovative solutions faster.
  • This design and build collaboration saves time and can significantly shorten the overall project timeline.

WSDOT is committed to providing equitable contracting opportunities to minority-owned, women-owned, veteran-owned and disadvantaged small businesses (MSVWBEs). Our goal is to provide 26 percent of our transportation projects’ contract value to these firms. See our equal opportunity in contracting webpage for more information and resources for working with WSDOT.