Social, Economic and
Sustainable Design Considerations
National finalist
Gold Award

WHPacific

Project: Monte Cristo Bridge
Client: Snohomish County




Photo courtesy of WHPacific
The Monte Cristo Bridge has timber decking to allow rain to fall through, avoiding the need for stormwater pipes and catch basins.

WHPacific designed a low-cost bridge structure and recommended the project sequencing that allowed Snohomish County to reestablish access across the south fork of the Stillaguamish River. Heavy flows there caused a large section of the riverbank supporting the Monte Cristo Grade Road to wash away in 2003.

The project site lies near the border of the Mount Baker-Snoqualmie National Forest, a delicate natural environment that required special attention to potential environmental impacts. Other challenges included budget limits, aesthetics, pedestrian safety, future maintenance needs and a schedule imposed by the Federal Emergency Management Agency.

Several techniques helped resolve the complex set of challenges:

Constructing the bridge solely from one side of the river and using the existing south abutment was possible due to the use of lightweight trusses.

Using timber planks for bridge decking to allow rain to fall through, eliminating the need to construct stormwater pipes and catch basins.

Designing for future migration of the river channel, leading to the strategic placement and design of the center pier and north abutment.

Selecting materials such as weathering steel trusses to complement the setting and keep future maintenance costs low.

Integrating a pedestrian refuge into the design, allowing pedestrians and vehicles to use the single-lane crossing simultaneously.



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