1999 WACA Awards - Public Works

At Beacon Rock State Park a box culvert was combined with a bridge deck to allow traffic to pass above while salmon swim below.

The Public Works category winner was a box culvert/bridge project at Beacon Rock State Park near Camas. The project was designed to improve access to the park's day-use area. The jobsite consisted of a one-lane trail sharing space beneath a railroad trestle with Woodward Creek.

The project's challenge was to combine a box culvert with a bridge deck to allow vehicular traffic to share the underpass with the creek. Since the creek is a habitat for salmon, the culvert was designed with a natural rock bottom. The design required piles to be driven to support the load of the entire structure. Extra piles were driven at the end of the trestle since there was no way to drive pile beneath it.

Under the trestle, engineers designed an elevated concrete tie beam to transfer loads to the additional piles at the trestle ends. The tie beams have to be elevated to avoid disturbing the original footings for the trestle.

At the north end where the water enters the structure, the piles needed to support the north deck were "columnized" by encasing them with concrete. Also, to protect them from debris in the creek, the columns were thickened from 24 inches to 30 inches and a 4,000 psi concrete mix was used.

The design team included: Washington State Parks Department, owner; Exeltech Engineering, structural engineer; Bergerson Construction, general contractor; and Aphis Ready Mix & Concrete Pumping, ready mixed supplier.

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