Preliminary results of an extensive 11-week investigation by Grant PUD and its consultants have determined that the primary contributing factor to a fracture developing within the dam’s spillway was a mathematical error during the pre-construction design of Wanapum Dam. Repairs to the spillway are likely to occur throughout the summer allowing the utility to potentially raise the reservoir behind Wanapum Dam at the end of 2014 by an additional 19 feet to an operating elevation of 560-562 feet above sea level. Under the current reservoir elevation, Wanapum Dam continues to generate electricity at about 50 to 60 percent of its capacity and is passing spring runoff flows in coordination with other dam operators on the river.
Adult fish passage continues through modified fish ladders at Wanapum Dam. Grant PUD ended trap and haul fish operations at Priest Rapids Dam because fish have successfully been using the modified ladders. Initial monitoring shows successful passage through the modified ladder and the drawn-down reservoir upstream is similar to that found under normal operating conditions. Juvenile salmon and steelhead passageis now underway at Wanapum and Priest Rapids Dams. Juvenile passage at Wanapum Dam is accommodated through the dam’s fish bypass unit, spillways and advanced turbines, which all remain functional under the current reservoir elevation. Passage at the upstream Rock Island Dam has also been accommodated for the expected late season reservoir levels through extensions to their adult fish ladder entrances. As of May 26th a total of 17,087 adult spring Chinook and 275 adult steelhead had reached Rock Island Dam (Fish Passage Center 2014).
