Pelton Round Butte Selective Water Withdrawal Project and Fish Collection Facility
Summary
Portland General Electric (PGE) and the Confederated Tribes of the Warm Springs Reservation of Oregon (CTWS) successfully completed construction of a first-of-its-kind fish bypass/intake structure at the 465-MW Pelton Round Butte Hydroelectric Project near Madras, Oregon. In addition to restoring downstream passage of anadromous fish, this 273-foot tall structure – all but five feet of it underwater – allows management of temperatures in the lower Deschutes River to achieve natural patterns while maintaining existing generating capacity.
Project completion means that, for the first time in more than 40 years, Chinook salmon, steelhead and sockeye salmon have the opportunity to complete their life cycles in the Deschutes River basin. During its first year of operation in 2010, more than 100,000 fish have passed through the structure. This project is a culmination of modeling and design efforts that began over 15 years ago, and reflects a close partnership between the licensees, resource agencies, engineering; fabrication; and construction firms.
Background
The 440-foot high Round Butte Dam, with 340-MW capacity, was constructed in 1964 as the uppermost, largest, and last dam in the 3-dam hydroelectric complex. Round Butte Dam impounds Lake Billy Chinook, which is fed by three rivers: the Deschutes, the Metolius, and the Crooked. All three dams were originally constructed with fish passage facilities in the 1950s and 1960s.
The bypass and intake structure was one of the central elements of an historic 50-year relicensing agreement for the Pelton Round Butte Project. The new federal license was issued in 2005. Officially known as the Selective Water Withdrawal Project, the structure is the only known floating surface fish collection facility coupled with power generation in the world. It was designed to reflect the latest scientific data about fish migration patterns, especially biologists’ greater understanding of the critical role river currents play in helping juvenile salmon and steelhead to make their downstream journey to the Pacific Ocean.
The structure itself is a marvel of engineering. It stands 273 feet tall — just 25 feet short of the Statue of Liberty — with all but the top five feet of the structure sunken in the waters of Lake Billy Chinook, located just east of the Cascade Mountains about 1,932 feet above sea level. The success of this project serves as an important advancement in the area of fish migration and biology, and will serve as a model for future efforts aimed at restoring fish passage around the nation.
In addition, the project means that, with time, the Tribes will be able to once again harvest sockeye and Chinook salmon, an important part of their cultural heritage. The success of this project has also spawned a series of projects and innovations upstream, which will not only provide improved spawning and rearing habitat and improved fish passage, but also improved educational and recreational opportunities for the residents of the region.
Challenge
At a cost of $108 million, and with no historical precedent to confirm the system would successfully resolve migration problems, moving forward with the device represented a leap of faith, especially as traditional systems hadn’t been as successful as hoped in the past. As complicated and difficult as the engineering challenges of this project were, PGE and the Tribes faced an equally daunting task: obtaining support for this project from more than 22 stakeholder organizations and agencies with a diverse and sometimes competing range of objectives, including the National Marine Fisheries Service, the Oregon Department of Environmental Quality, the Oregon Department of Fish and Wildlife and the U.S. Department of the Interior.
Following issuance of the new license, the next challenge was to take the concept to design, and ultimately to fruition. The SWW is unique in that it is the only known floating surface fish collection facility coupled with power generation in the world. Using the structure to satisfy water quality requirements contributes to the uniqueness, as does the size of the structure and the construction methods. Adding to the challenge was the fact that the reservoir could not be drawn down to allow construction in “the dry,” requiring assembly of components on site in a size-constrained construction area.
Innovation
PGE and the Tribes began efforts to develop a design to meet the objectives in the mid-1990s. This effort involved collaboration between the project owners, more than 22 local, state and federal agencies, environmental groups and engineering/consulting firms. Research included utilizing Doppler radar to measure stream flow of the three rivers in various parts of Lake Billy Chinook, and the development of 3-D hydrodynamic and temperature computer models to evaluate reservoir conditions based on varying flows through the structure. The final design was the result of value-engineering analysis and computer modeling, and finally, construction of a 1:20 scale physical model at ENSR/AECOM in Seattle Wash. PGE’s engineering department and the engineering firms of CH2M Hill, EES Consulting, and ENSR/AECOM were instrumental in arriving at the final design.
Results
The SWW reestablishes salmon and steelhead runs above Round Butte Dam as part of a comprehensive plan to restore anadromous fish runs while maintaining water flow for both fish collection and power generation, provides a source of certified green power for the region, secures a 50-year federal license to produce low-cost hydropower, supports the local economy with continued jobs, and improves water quality in reservoirs and rivers.
To support the returning fish, PGE and the Tribes have set aside $21.5 million to restore habitat in areas ranging from the Metolius, upper Deschutes and Crooked Rivers above the dams to Trout Creek and the Warm Springs Reservation below the dams. To date, nearly 30 projects have been completed that provide improved water quality, aquatic and terrestrial habitat; and fish passage, and increased stream flows in the upper Deschutes basin.
Many utilities and agencies in the region are looking at the Selective Water Withdrawal as an example of incorporating fish passage while not adversely affecting hydro power generation.
Stakeholder Quotes
“PGE has raised the bar for US hydropower operators by addressing the recreational and natural resource objectives of the National Forests and providing tangible benefits to their public visitors.” –Rod Bonacker, Deschutes/Ochoco National Forest, Special Projects Coordinator
