Tukwila Urban Center Pedestrian and Bicycle Bridge

Tukwila, Washington

Project Size:

Bridge length: 220 feet

Project Status:

Anticipated Completion 2018

Vision
Located along a prominent regional transit corridor, Tukwila is poised for urban expansion. This new pedestrian/bicycle bridge across the Green River connects areas planned for a mix of transit-oriented development in the Tukwila Urban Center with the Tukwila Station, a major transportation hub served by Amtrak and Sound Transit Sounder trains, as well as Metro RapidRide buses. Introducing a signature piece of non-motorized infrastructure, the bridge highlights the importance of such links in today’s transportation network—creating a safe and enjoyable walking and biking experience, and attracting the types and densities of uses envisioned for a regional center.

Site and Program
Situated at a bend in the Green River, just south of I-405, the bridge connects the West Valley Highway on the east to the Green River Trail on the west, less than half a mile east of Southcenter Mall. The project is key to implementing the land use and transportation goals of the Tukwila Urban Center Plan and the Tukwila Comprehensive Plan, which outline a 20-year vision for urban evolution. Previously, the Green River stood as a barrier between the station and nearby places of employment, shopping and housing. Now, the high visibility of the bridge from surrounding neighborhoods invites public engagement, serving as a community landmark and symbol of urban connectivity.

Design
Beginning at the conceptual level, LMN collaborated closely with KPFF, the project engineer, to establish the alignment and selection of a structural system that is both efficient and iconic, addressing the city’s desire to make a bold statement. The bridge is a twin-tied arch spanning 220 feet. The structural system is made from white-painted tube steel. The concrete bridge deck is 13-feet wide with an open grating edge that extends up to six feet on either side, allowing more daylight to reach the water. The bridge’s height, geometry, materials and finishes stand out vividly against the green backdrop of the river’s natural setting. At night, integrated, programmable LED lighting illuminates the arch in a dynamic play of color.

The tied-arch bridge construction creates a strongly curved profile, further enhanced by the plan form, which incorporates gentle curves that widen the bridge surface toward the center of the span. This widening allows for pedestrian overlooks from the bridge in both directions. The railing creates a continuous texture across the span, and features built-in LED pathway lighting. LED uplights graze the hanger cables and arches to create a subtle web effect against the night sky. Gentle ramps at the east and west approaches to the bridge blend the form organically into the landscape, completing the composition. The overall effect conveys simplicity, clarity and lightness.