This replacement of a 1930s bridge ties together south and west Seattle for vehicular, pedestrian and bicycle traffic and serves maritime traffic on the Duwamish River. It is unique in being the world's first hydraulically operated, double-leaf concrete swing bridge.

During demolition of the old foundations and construction of the swing bridge, environmentally sensitive steps, including an "air curtain," were taken to protect the native salmon and steelhead. The air curtain absorbed up to 80 percent of the pressure caused by in-water blasts.

Among its engineering and structural innovations are the concrete box leaf design, the movable hydraulic system and the high-strength concrete. The hydraulic system lifts and rotates 7,500-ton leaves in open and closed positions. By increasing the vertical clearance, the bridge has succeeded in achieving one of the project's primary goals: reducing bridge openings.

The new low-level bridge has been a financial success and has proven cost effective in maintenance costs and as an investment in a new bridge with a longer life span.

CREDITS...

• City of Seattle, Engineering Department
• Anderson Bjornstad Kane Jacobs, Inc.
• Tudor Engineering, Inc.
• Parsons Brinkerhoff Quade & Douglas, Inc.
• Hamilton Engineering

JURY COMMENTS...

As the first example of its type, the West Seattle Low-Level Bridge uses an innovative, technical solution to allow use of concrete construction. This elegant design, mirroring the high-level bridge located above, created a technical design challenge.