Round Butte Dam is located about 90 miles southeast of Portland, Oregon, on and adjacent to the Warm Springs Reservation. Portland General Electric determined that a selective water withdrawal and fish bypass structure was necessary to ensure the survival of Summer Steelhead and Spring Chinook Salmon in the Upper Deschutes, Metolius, and Crooked rivers. Partially due to unusual currents in Lake Billy Chinook, the downstream fish passage facilities constructed in the 1960’s failed to work properly.
The new system is a 270-foot structure which was delivered to the site in pieces and assembled both in and on the water. Associated Underwater Services provided the underwater assembly and installation, topside support, and underwater survey and inspection. AUS used the long-range Falcon “Sea Eye” with sonar capabilities to guide and monitor the underwater activities. Barnard Construction was the general contractor, assisted by Dix Corporation. The project involved drilling and grouting 11 piles 50 feet into the lake bottom, 320 feet below the water surface. A Selective Water Bottom Structure was submerged to a depth of 270 feet and attached to the existing powerhouse intake. A floating Selective Water Top Structure was positioned directly above the Bottom Structure and connected by the 40-foot diameter Vertical Steel Conduit.