In 2009, SCPPA acquired the Tieton Hydropower Plant from Tieton Hydropower, LLC. pursuant to an Asset Purchase Agreement. Per this agreement, Burbank and Glendale receive 100% of the energy that is generated. The Tieton Hydroppower Project consists of a "run-of-the-reservoir" hydroelectric generation facility inclusive of a powerhouse and 21-mile transmission line.
The Tieton Hydropower Project powerhouse is located near Rimrock Lake in Yakima County, approximately 40 miles west of the city of Yakima, Washington. This territory is owned by the United States and is incorporated into the existing outlet foundation of the Bureau's Tieton Dam. The transmission line that runs from the property connects to the PacifiCorp Tieton Substation which is owned by PacifiCorp.
By May snowmelt filled the reservoir to 100% capacity and generation set a new record high for that month, last set in 2012. In June, reservoir capacity ranged from 98-100%. In mid-June the flow rates dropped below two-unit levels and remained there the rest of the summer. Generation remained steady at this rate. By August the reservoir had been depleted to 76% of capacity and the USBR announced that it will begin the annual "flip-flop" operation in the Yakima Basin by gradually reducing flows out of Cle Elum Reservoir in the upper Yakima River basin and increasing flows from Rimrock Reservoir affecting flows in the Tieton and Naches Rivers. The purpose of the "flip-flop" operation is to achieve and maintain relatively low flows in the upper Yakima, Cle Elum and Bumping rivers where the Chinook salmon spawn. These lower flows are closer to natural flow conditions and are therefore more helpful to successful spawning and incubation of salmon eggs. this operation also reduces impacts on irrigation water supply by allowing for lower flow releases throughout the winter to improve reservoir storage.