Town meetings provide update on Hebgen Dam

About 60 people attended town meetings last week to discuss the improving situation at PPL Montana’s Hebgen Dam in southwestern Montana near the west entrance to Yellowstone National Park.

About 20 people attended Wednesday (9/24) night’s meeting in West Yellowstone, which is about 20 miles upstream of the dam, and about 40 came to the meeting Thursday (9/25) night in Ennis, which is about 50 miles downstream along the Madison River.

PPL Montana representatives were joined by agency partners from the Montana State Department of Environmental Quality; Montana Fish, Wildlife and Parks; Montana Department of Natural Resources and Conservation; U.S. Forest Service; and the U.S. Bureau of Land Management.

“We appreciated the opportunity to talk with our neighbors in the Madison Valley, answer questions and explain the next steps at Hebgen Dam, now that we have the water flows under control,” said David Hoffman, director of External Affairs for PPL Montana.

“People have vacation properties on the lake, fishermen from all over the country come here to catch trophy trout, and business owners and river guides depend on the lake and river for their livelihoods, so there’s much at stake here,” he said.

By placing new stoplogs in Bay 4 of the intake structure, PPL Montana crews have safely and successfully stemmed the flows into the Madison River to less than 800 cubic feet per second.

River flows, which are being controlled using the intake structure’s control gates, are usually between 800 cubic feet per second and 900 cubic feet per second this time of year. However, additional work will be performed in the coming weeks to reinforce the remaining logs to reduce the probability of another failure through the winter months.

Stoplogs, 12-inch-by-12-inch timbers similar to railroad ties, are stacked in the dam’s bays and used to regulate water flow.

PPL Montana crews have been working at the dam since Aug. 31 when a problem with the intake structure was discovered and later determined to be the result of missing stoplogs in Bay 4.

The malfunction increased river flows to 3,400 cubic feet per second, typical springtime levels, and caused the lake elevation to drop. Part of PPL Montana’s Project 2188 license obligation is keeping an eye on valuable river and reservoir resources in the Madison Valley, and company representatives met regularly with state and federal agencies over the past several weeks to discuss regulatory, public recreation and natural resource issues.

The people who attended the meetings received an overview of the dam’s construction and heard about PPL Montana’s next steps at Hebgen Dam. The next steps include:

• Conducting a thorough investigation of what suddenly caused the loss of stoplogs in one of the bays of the intake structure.
• Engineering a long-term solution to replace all the timber stoplogs currently in service in the intake structure.
• Designing and installing a secondary shutoff system that would control water flow in the event of a future problem with the intake structure.

“There’s still a lot of work to do,” Hoffman said. “Once the causes of the malfunction are made known through this investigation, we will take appropriate actions to prevent reoccurrence.”

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.