The new technology of the Rainbow Dam near Great Falls

Aug 2, 2013

The new Rainbow Dam power plant generates 60 megawatts of electricity, the old plant (left) generated 36 megawatts.
Credit Dan Boyce

PPL Montana is now operating a completely renovated Rainbow Dam, just a few miles northeast of Great Falls.

The $230 million project marks the biggest investment in energy generation in the state since the Colstrip coal-fired power plant was built about 30 years ago.

PPL Montana Director of External Affairs David Hoffman said the new power house generates almost twice as much electricity as the old one. It’s enough to power about 45-thousand homes.

Construction on this renovation started back in 2009 and went fully online this past April.

The old system had eight, quickly-spinning, twin turbines and any fish that happened to swim through them was a goner.

Hoffman said those 8 twin-turbines have been completely replaced by a new bigger, slower, single turbine. 

“(It’s) estimated to be about 95 percent less fish mortality for fish that may pass through that,” he said.

PPL predicts the new power station and turbine at Rainbow Dam should be able to last as long as the old system did—about 100 years.