Online open house launches for upcoming Portage Bay Bridge & Roanoke Lid Project

By Shoshana Wineburg

Critical transportation improvements are headed to Seattle’s Portage Bay and north Capitol Hill neighborhoods as we gear up to start the SR 520 Bridge Replacement and HOV Program’s next big project: replacing Seattle’s aging Portage Bay Bridge, building a landscaped lid in north Capitol Hill, and completing the improved SR 520 all the way to I-5. After multiple years of planning and stakeholder collaboration, the project is forging ahead on multiple fronts to break ground for construction in 2024.

One important step is engaging with neighbors who live close to the construction area – the people who’ll be most affected by our work. That’s why we’ve launched a new Portage Bay Bridge & Roanoke lid project online open house. The open house includes information about what the community can expect and asks for neighbors’ feedback on reducing construction effects like noise, vibration, and traffic.

Like other bridges in the region, the 1960s-era Portage Bay Bridge is supported by hollow concrete columns that could collapse in a severe earthquake. This project will replace the aging Portage Bay Bridge with two parallel, three-lane bridges for eastbound and westbound traffic. The new bridges also improve travel for busses and carpools and extend the SR 520 Trail from Montlake to I-5. In addition, the project will build a “lid” over SR 520 that reconnects Seattle’s Roanoke Park and north Capitol Hill neighborhoods. The lid will include three acres of open green space with trail connections and viewpoints of the city and Portage Bay.

A visualization of a new, replacement Portage Bay Bridge between Seattle’s Montlake neighborhood and I-5. It will have two parallel, three-lane bridges, one for eastbound and one for westbound, improving travel in this busy area.

Another important feature of the new bridge is a system for capturing and treating highway runoff to keep roadway pollutants out of Portage Bay. The replacement SR 520 bridges over Union Bay feature a similar system for capturing and treating highway runoff.

The initial design for the Portage Bay Bridge and Roanoke lid began more than a decade ago, starting with the 2011-2012 Seattle Community Design Process (PDF 31MB). Additional community involvement over the years helped refine the project’s key features.

A visualization of a landscaped lid over SR 520 between 10th Avenue East and Delmar Drive East. The lid will have about three acres of green space, four viewpoints, and multiple connections to the SR 520 Trail and other paths.

The Portage Bay project is part of the larger SR 520 Bridge Replacement and HOV Program, which is rebuilding SR 520 between I-405 and I-5. The program is enhancing public safety by replacing the highway’s three aging bridges, all at risk of collapse. We’re also improving travel by adding a lane in each direction for buses and carpools on SR 520 between Seattle and King County’s Eastside cities. In addition, we created new, nonmotorized travel options by building a wide bicycle and pedestrian trail across Lake Washington – opened in 2017 – that connects to local and regional paths on both sides of the lake.

If you live close to the Portage Bay or Roanoke Park, be sure to check out our online open house to share your feedback!

The project will extend the regional SR 520 Trail from Montlake over Portage Bay to the new Roanoke lid and build a 30-foot-wide bicycle and pedestrian crossing over I-5. Once the Portage Bay project is finished,
the SR 520 Trail will extend from Redmond to I-5 in Seattle.

Learn more!

• Want to know more history about how community feedback influenced the design of the new bridge? Check out the 2014-2015 Westside Design Refinements (PDF 60MB) and this summary of our 2019 community and stakeholder engagement (PDF 5MB).
• Have other questions about the project? Visit the 520 Construction Corner to read our project FAQ.
• Curious about how we are addressing environmental effects on the Portage Bay shoreline? Check the Seattle Services Portal as well as our website’s environmental page to read how we’re protecting our region’s natural resources.