In order to increase the safety and survival rate of migrating salmon and steelhead trout in the Columbia River, the U.S. Army Corps of Engineers – Portland District (USACE) contracted a joint venture led by Kiewit Pacific Co., a subsidiary of Kiewit Corporation, to construct the Bonneville Fish Bypass – transporting fish around the Bonneville Dam.
This best-value project involved moving underwater obstructions to make room for features of the work, which included 25 massive boulders weighing up to 100 tons each. Crews then excavated a 24,000 cu. yd. bowl in the river bottom and lined it with 90,000 sq. ft. of precast concrete block and wire mesh mat assemblies positioned underwater by dine operations. The channel is supported on a foundation of 31 stacked hollow precast concrete boxes, each weighing 150 tons. Once in position, 12,000 cu. yd. of tremie underwater concrete fill were placed. Ultimately, a 3,000-ft.-long, high velocity concrete chute with 25-ft.-high walls was created to transport fish through the powerhouse gate and into the new channel outfall. Additional quantities included 60,000 cu. yd. of structural excavation and backfill.
The project won an Excellence in Concrete Award from the Oregon Concrete and Aggregate Producers Association. Additionally, the team's performance was rated "outstanding" by a USACE Performance Evaluation – the highest level of commendation.