Alaskan Way Viaduct and Seawall Replacement
Seattle, Washington, United States
Client: Washington State Department of Transportation
Parsons Brinckerhoff Role: General Engineering Consultant, Project Visualization (3D Modeling, Interactive Application Development, Virtual Design & Construction)
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As general engineering consultant, Parsons Brinckerhoff served for 10 years as lead strategic advisor assisting the Washington State Department of Transportation (WSDOT) in eliminating its greatest public safety risk—the seismically vulnerable viaduct running along the Seattle waterfront. The project included preparation of an environmental impact statement and bid documents in connection with replacing the viaduct, which runs more than 2 miles (3.2 kilometers) and carries 110,000 vehicles daily. In addition, conceptual design was prepared for replacement of the 6,500-foot-long (1,980-meter) Elliott Bay Seawall.
The $3.1 billion replacement program includes approximately 1 mile (1.6 kilometers) of new elevated roadway in the south end connecting to a bored 56-foot-diameter (17-meter) tunnel approximately 2 miles long (3.2 kilometers) with a stacked interior roadway beneath the downtown. The Parsons Brinckerhoff team developed the design-build technical requirements and specifications for the tunnel, the largest ever constructed by tunnel boring machine technology.
The team also led a rigorously inclusive public involvement program to help define and communicate project goals and develop political consensus. Project visualization proved to be an invaluable tool to inform the public and as a design tool to determine the viability of proposed concepts. Parsons Brinckerhoff drew upon CAD and geospatial data to develop digital 3D and Building Information Models for all of the major parts, pieces and processes of the project.
Tunnel construction began in late 2011 under a design-build contract. Completion is scheduled for late 2015.