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Thompson Falls Reservoir Levels to Drop; Recreation Users Advised to Use Caution, Remove Docks and Boats

May 29, 2018

Butte, Mont. – May 25, 2018 – Very high Clark Fork River flows this spring forced NorthWestern Energy to release a number of the removable steel spillway beams on its Thompson Falls Dam. The action, aimed at allowing greater-than-normal amounts of water and debris to safely pass through the dam, will create recreational impacts on the reservoir above the dam in coming weeks.

NorthWestern is advising its neighbors around the reservoir and other users to consider removing docks and boats from the water to avoid damage as the reservoir elevation drops and use caution navigating the shallow reservoir.

The restoration work to replace the spillway beams will require an unavoidable lowering of the reservoir to the crest of the dam, an elevation of 2,380 feet (a point 16.5 feet down from full pool). Once the reservoir elevation drops to that point, work will immediately begin on replacing the beams.

The replacement work, expected to take about two weeks, cannot begin until river flows drop below 20,000 cubic feet per second. The flow was at 98,700 cubic feet per second on May 24, 2018.

We apologize for this inconvenience, but the drawdown is unavoidable. After completion of the work, the reservoir will be refilled as soon as reasonably possible given the inflows, likely to be late July to mid-August.

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About NorthWestern Energy (NYSE: NWE)
NorthWestern Energy provides electricity and natural gas in the Upper Midwest and Northwest, serving approximately 709,600 customers in Montana, South Dakota and Nebraska. More information on NorthWestern Energy is available on the company's website at  

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Butch Larcombe
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