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Spalding Bridge Scour Repair project also wins Washington AGC award

The scour repair project on the Clearwater River Bridge in Lewiston, recognized for an AASHTO Innovation Initiative and winner of an AASHTO President’s Award for Environment, also was a winning entry for West Company (Airway Heights, Wash.) in the Washington State Associated General Contractors “Build Northwest” awards in the Inland Chapter.

The Build Northwest awards were presented in Dec. 2014 in Spokane, Wash.

The bridge was one of the 10 most scour-critical bridges in the entire state — meaning it was at risk of failure due to erosion. The project was a unique effort to combat erosion around the bridge’s piers, and involved a complex set of environmental considerations.

The concrete-deck, steel-girder bridge was built in 1962, is more than 1,200 feet long and approximately 33 feet wide. The project was completed under budget and two weeks ahead of the Sept. 30, 2014, deadline.

The project also enhanced fish habitat. The bridge spans the Clearwater, a body of water vital to the area’s recreation and commerce, so minimizing impact to the river was critical. Crews also had to reduce the effects of construction on endangered fish such as bull trout, Snake River Basin steelhead and Snake River fall Chinook salmon. Also unique were the nearly 2,700 lbs. of articulated riprap per mat placed at the river’s bottom to shield the piers against further erosion from water flow at the pier. After work was done, nearly 400 of the heavy concrete A-Jacks mats were placed on the riverbed to continue to provide armor against erosion. Research indicates that voids in the mats provide a support system for the river gravels and help to promote fish habitat. The mats, made of more than 30 individual units, were secured with corrosion-resistant steel cables.