Ice Harbor Navigation Coffer Cells - Walla Walla, Wash.
Due to nitrogen super saturation that causes trauma to juvenile salmon, General Construction built the deflectors to the spillways which direct the flow of water horizontally to reduce the amount of nitrogen gas entrained in the water. Construction work began with the extension of the dam's seven pier noses. A floating crane was used to place a 27 ft x 56 ft steel bulkhead between two of the pier nose extensions where it was bolted in place. The spillways inside the bulkhead forms were dewatered and 7 ft deep rebar dowel holes were drilled into the existing spillway surface. After rebar installation, approximately 230 cu yd of concrete were placed at each of the spillways. The top two feet of concrete was reinforced with steel fibers to help reduce erosion.