Willapa Hills Overpass

Location: Chehalis, Washington

Cost: $2.2 million

Completion: August 2023

Owner/Developer: Washington State Parks & Recreation

Architect: Not applicable

Engineer: Otak

General Contractor: Tapani

Submitting Company: Tapani

Subcontractors: Clark Crane, Foresight Surveying, Greyrock Drilling & Piledriving, Northfork Asphalt Paving, Purcell, RT General Construction, Specialized Landscaping, Unlimited Fence

The Willapa Hills State Park Trail Overpass in Chehalis, Washington, rising above a once-dangerous roadway crossing, features an S-shaped weathering steel truss that is not only functional but adds a touch of architectural beauty to the landscape.

Locals and visitors now can traverse a scenic 28-mile trail, free from the hazards of busy highways. For Chehalis residents, this overpass isn’t just a bridge it’s a pathway to enhanced recreational opportunities, greater connectivity and safer travels.

The three-span S-shaped weathering steel truss supports a 10-foot-wide concrete deck over a busy roadway crossing. At the eastern end, an overlook area provides scenic views of the area. The bridge approaches adhere to ADA standards and provide a gradual 5 percent grade spanning 400 feet onto the bridge. Custom railing and fencing ensure fall protection. Locally sourced stone accents adorn the abutment wing walls and overlook area. Landscaped embankments soften trail entrances, blending grasses and shrubs to integrate the structure into its natural setting.

Project contractor Tapani encountered several challenges on the project, including permitting and material procurement. Tapani overcame permitting obstacles by collaborating to obtain permit approvals and implementing a strategic phasing plan, increasing manpower and size of equipment. Wall material and steel procurement challenges were overcome by resequencing the project scopes. The bridge abutments had a long lead time and were delayed by three months. Tapani adjusted the wall system slightly to facilitate the final completion of retaining walls after finishing the abutments.

Another challenge was the settlement of a retaining wall. To enhance stability and avoid re-constructing the wall post settlement, Tapani installed a facing along the wall a cost effective and functional solution.

Several new construction methods were used on the project, most notably the utilization of S curves for the bridge, which required careful placement with a crane equipped with air hoists. Tapani noted that what made the project unique is the elegant design of the overpass combined with public safety.

Collaboration was key to the project’s success, with Tapani working closely with Washington State Parks & Recreation and the engineer.

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