Civil Engineering

I-405 Corridor

Location: Seattle, Washington

Interstate 405 in Washington is the backbone of the transportation network that connects communities east of Lake Washington to Seattle and Interstate 5. The 30-mile stretch carries from 300,000 to 600,000 people a day, making it one of the most congested corridors in the state. With population expected to grow by more than 50 percent in the next 20 years, more traffic problems are inevitable.

The program combined a transportation study and an environmental impact statement (EIS) into what has been called the most comprehensive transportation analysis in the state’s history. The multimodal transportation study identified 150 separate projects over a 227-square-mile area, estimated to cost $7.8 billion. The decision-making process involved multiple stakeholders and a rigorous public involvement program. More than 100 DEA staff members worked on the project.

Project Awards

  • 2002 Vision 2020 Award, Puget Sound Regional Council
  • 2003 Gold Award, Studies Research and Consulting Engineering Services Category, ACEC Washington
  • 2003 President's National Environmental Excellence Award