Rocky Mountain Power Submits Proposal for Oneida Hydroelectric Pumped Storage Project

Rocky Mountain Power, a division of PacifiCorp, has filed its Initial Consultation Document with the Federal Energy Regulatory Commission as a preliminary step to evaluate feasibility of a pumped hydroelectric facility at its existing Oneida hydroelectric project.

The document filed with the FERC for the proposed Oneida pumped storage facility includes information on the proposed process and schedule, a description of the project, the existing environment and known potential impacts of the project, and details of studies proposed to fill identified information gaps.

PacifiCorp’s proposed Project would consist of:

• A new upper reservoir.
• The existing lower Oneida reservoir.
• Pipes to connect the upper and lower reservoirs to a new powerhouse and pumping station.
• A new powerhouse and pumping station located northwest of the existing Oneida powerhouse that would contain two pumping and turbine-generator units with a total rated capacity of 200 megawatts.
• A transmission line connecting the new project substation to PacifiCorp’s existing Oneida substation and associated facilities.

The filing begins the process to consult with FERC and evaluate the feasibility of the project. A final decision on whether to construct the project has not yet been made. The full initial consultation document is available on the company’s website.

Pumped storage hydroelectric projects take advantage of natural geographic terrain where an upper and lower reservoir can be constructed with a system of pipes connecting the two. A pumping and generating unit is used to both move water into the upper reservoir and generate electricity when water is released from the upper reservoir back to the lower reservoir. Water is pumped into the upper reservoir during times of lower electric demand, which can then be released downhill through the pumping and generating unit and into the lower reservoir as utility system needs indicate. Pumped storage hydroelectric projects have unique attributes, including longer plant lives and significantly greater energy delivery capability compared with chemical batteries. This makes these resources attractive for integrating wind and solar energy resources and maintaining and enhancing the reliability of the electric system.

The Oneida project is part of the company’s Bear River Hydroelectric Project, FERC Project No. 20. The project is located in Franklin and Caribou counties northeast of Preston, Idaho. The Bear River Project includes the Soda, Grace, and Oneida developments and was issued a 30-year license by FERC on December 22, 2003.

The Oneida project was built in stages between 1913 and 1920 and has a generating capability of 30 megawatts. It is located about 18 miles northeast of Preston, Idaho. The Oneida Dam is constructed of both a concrete structure 111 feet high and 387 feet long and an earthen embankment dam that is 40 feet tall and 1,100 feet long. The reservoir has an active storage capacity of 10,880 acre-feet and a surface area of 480 acres at a maximum full pool elevation of 4,882.90 feet.