February 10, 2025

National Finalist: Gold Award
Transportation

Photo from ACEC Washington [enlarge]

The design raised the road above the floodplain, mitigated debris flow and landslide hazards, and restored a salmon-bearing creek.

Shannon & Wilson| WSP

Index-Galena Road Flood Repair Project

Snohomish County

The Index-Galena Road Flood Damage Repair Project, initiated after record flooding in November 2006 destroyed a key section of road, was a critical effort to restore access to the upper North Fork Skykomish River valley in the Cascade Mountains. This route is vital for local and recreational traffic, but the flooding had caused significant damage, leaving an unsustainable detour of up to 40 miles over rugged, gravel roads. Restoring the road became a priority for Snohomish County.

The project, led by the Shannon & Wilson | WSP team, not only restored the road but also addressed future flood risks, enhanced river conditions for wildlife, and minimized environmental impacts. The design raised the road above the floodplain, mitigated debris flow and landslide hazards, and restored sensitive habitat areas. The project’s challenges included steep terrain, complex soil and rock conditions, active debris flows, and harsh winter weather, which required innovative design solutions.

Key elements of the project included a box culvert vented ford and diversion berms to mitigate debris flow hazards, and a 180-foot-long bridge to restore a salmon-bearing creek. The bridge was designed to blend with its surroundings and could be retrofitted in the future to accommodate river migration. Despite the challenging environment, the project was completed on time and under budget, meeting Snohomish County design standards with a remarkably small footprint.

The Index-Galena Project is an exemplary model for restoring access in environmentally sensitive mountainous areas, especially in light of future climate-related risks. The project demonstrated engineering excellence by adapting existing technologies to create a sustainable, low-impact solution that ensures long-term access to an important recreational area while preserving the natural environment.

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