Washington’s State Route 520 is part of the National Highway System, important to the national economy, defense and mobility. But a six-mile east-west corridor in Seattle, connecting Interstate 405 in Bellevue to Interstate 5, was aging. The old SR520 approach bridge was built on hollow columns and vulnerable to earthquakes. It was at capacity at peak hours. And its location divided the surrounding Montlake community. 

Replacing the section was a controversial, multimillion undertaking. MIG helped bring stakeholders together, creating a revised design that met the City’s vision for an “entry experience” with improved nonmotorized connections and open space within the constraints of constructability—reducing cost, time and risk. 

When completed in 2024, the section will provide a safer and seismically stronger eastbound bridge, improve mobility with more transit and carpool lanes, offer more bicycle and pedestrian options, result in fewer backups thanks to wider shoulders for disabled vehicles, and contribute to a healthier environment through new stormwater systems. And the three-acre landscaped lid over the highway provides new community open space and trail connections that help restore the Montlake neighborhood fabric.