Company to conduct design and engineering work to prepare for permanent repairs

PPL Montana crews have safely and successfully secured the intake structure at Hebgen Dam, reducing flows to normal levels for this time of year as the company prepares the site for winter and makes plans for permanent repairs.

“By no means are we done with this project, but we have completed the work necessary to stem the flows into the Madison River before the winter freeze,” said David Hoffman, director of External Affairs for PPL Montana. “Steel plates have been installed in all four bays as an added measure to control water flow into the Madison.”

PPL Montana crews have been working at the dam since Aug. 31 when a problem with the intake structure developed. The problem was determined to be the result of missing stoplogs in one of the structure’s four bays. Stoplogs, timbers similar to railroad ties, are stacked in the dam’s bays and used to regulate water flow from the intake structure.

The malfunction led to flows more typically seen during spring snow melts. However, the recent work, including replacing missing stoplogs, has reduced flows to less than 700 cubic feet per second, which is normal for this time of year. The elevation of Hebgen Lake is slowly beginning to rise.

“With the early snowfall in the Madison Valley, we’re hopeful that nature will replenish Hebgen Lake during the spring runoff,” Hoffman said. “This lake has proven itself resilient, even in times of prolonged drought. There is a pretty big watershed above Hebgen Lake.”

PPL Montana will conduct a thorough investigation to find the cause of the incident and complete design and engineering work to determine the best course to make permanent repairs.

The dam remains stable, as verified by on-site monitoring equipment.

Hebgen Dam creates Hebgen Lake, a reservoir just north of Yellowstone National Park that stores water for the Madison-Missouri river system. PPL Montana owns and operates eight hydroelectric facilities on the Madison and Missouri rivers.

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).