SR 520 Eastside Transit & HOV Design-Build

Lead designer for $365 million, 2.5-mile, 100,000 AADT urban highway improvement project to provide needed congestion relief through an integrated, multimodal operational system, as well as reconstruction of a complex urban corridor. SR 520 is a busy regional corridor that connects several communities, including Bellevue, Kirkland, and Redmond, to downtown Seattle.

Project elements include transit and high-occupancy vehicle (HOV)/managed lane improvements, four interchanges, two in-line transit stations, and three urban lids, totaling approximately 300,000 square feet. The project’s unique lidded overpasses provide overcrossing connectivity, as well as unique community amenities such as open space gathering areas, ADA-accessible pedestrian and bicycle facilities, and transit-user transfer facilities.

Aiding the project’s emphasis on connectivity, the design included three pedestrian bridges with lengths up to 78 feet, three pedestrian tunnels with lengths up to 280 feet, and a bike/pedestrian regional trail parallel to the highway. The project team also minimized environmental impacts to existing wetlands, improved fish passage, and restored habitat as part of the project’s environmental stewardship goals.

A multiphase traffic control plan was developed to maintain existing traffic during peak hours and transit station and interchange ramp access throughout. Design of the west end of the project was coordinated to operate with the connection to the existing floating bridge, as well as to connect with the new floating bridge.