New powerhouse dedicated at PPL Montana hydro facility

PPL Montana dedicated a new 60 MW powerhouse July 10 at its Rainbow Dam hydroelectric facility near Great Falls. This marks the completion of a $245 million redevelopment project, which replaced a century-old powerhouse and increased the hydroelectric facility’s power generation capacity by 70 percent.

In addition to the new powerhouse, the redevelopment project included the replacement of 23 miles of 100-kV power lines, substation upgrades at PPL Montana’s five Great Falls hydroelectric plants, and installation of a new Crooked Falls switchyard.

The enhancements will strengthen the reliability and efficiency of electrical systems connecting PPL Montana’s Great Falls facilities to NorthWestern Energy’s grid.

Construction of the new facility began in October 2009 and was completed earlier this year. The project required the removal of more than 500,000 tons of earth and rock. More than 50,000 cubic yards of concrete were poured, and 7 million pounds of rebar went into the new powerhouse.

Incentives made available through the American Recovery and Reinvestment Act of 2009 helped make the project possible.

PPL Montana’s Rainbow Dam, which began operation in 1910, is 1,055 feet long and 29 feet high. The new powerhouse sits about 2,500 feet downstream from the dam and 200 feet from the old powerhouse. Water flows down a 2,500-foot power canal and through a 25-foot diameter penstock to the new turbine generator. The turbine’s slower rotation, wider flow passages and fewer rotating surfaces make it easier for fish to pass through unharmed.

PPL Montana provides energy from coal-fired power plants at Colstrip and Billings, as well as 11 hydroelectric plants along West Rosebud Creek and the Missouri, Madison, Clark Fork and Flathead rivers. It has a combined generating capacity of more than 1,200 MW and has offices in Billings, Butte and Helena.

PPL Montana and PPL EnergyPlus are units of PPL Corp.

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at

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