Very high Clark Fork River flows this spring forced PPL Montana to remove a number of the removable steel spillway beams on its Thompson Falls Dam in order to open larger areas that would allow the greater than normal amounts of flowing debris to safely pass through the dam.
The restoration work to replace those beams will require an unavoidable lowering of Thompson Falls Reservoir to the crest of the dam, an elevation of 2,380 feet (a point 16 feet down from normal full pool). Once the reservoir elevation drops to that point, work will immediately begin on replacing the beams.
The work, expected to take about two weeks, cannot begin until river flows naturally drop below 20,000 cubic feet per second. After completion of the work, the reservoir will be refilled as soon as reasonably possible given the inflows, likely in mid- to late August.
“Our neighbors may want to consider removing docks and boats from the water to avoid damage as the lake elevation begins to drop, and they should be aware of potential submerged hazards that are not normally a concern when reservoir levels are higher,” said David Hoffman, director of external affairs for PPL Montana.
“We apologize for the inconvenience during this busy time of the year on the reservoir, but the drawdown is unavoidable,” he said.
The newly constructed fish ladder will also not be fully operational until reservoir elevations are restored, Hoffman said.
PPL Montana provides safe, reliable 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 megawatts and has offices in Billings, Butte and Helena. PPL Montana and its 500 employees are dedicated to Montana and its communities, supporting educational, environmental and economic development programs across the state. PPL EnergyPlus operates a trading floor in Butte that markets and sells power for PPL Montana in wholesale and retail energy markets throughout the western United States. PPL Montana and PPL EnergyPlus are subsidiaries of PPL Corporation (NYSE: PPL).