PPL Montana able to control river flow

Around-the-clock work to reduce and control flow from the damaged intake structure at Hebgen Dam has paid off. Crews have replaced a number of stoplogs in one of the structure’s bays and are now controlling the flow of the Madison River using the intake structure’s control gates.

Stoplogs, which are 12 inch by 12 inch wooden beams similar to railroad ties, are stacked in the dam’s bays and are used to regulate water flow. A problem with the dam’s intake structure was discovered on Aug. 31 and later determined to be isolated to stoplogs in Bay 4 of the structure.

As a result, river flow increased to 3,400 cubic feet per second — typical of springtime levels — and water elevation in Hebgen Lake has dropped below the minimum recreational level. River flow this time of year is usually between 800 and 900 cubic feet per second.

“Our plan is working and the river flow is down to about 2,200 cubic feet per second,” said Pete Simonich, manager of generation assets for PPL Montana. “We are continuing to insert new stoplogs, and are maintaining flow with the control gates. We are starting to gradually reduce river flows to normal over the next three days to protect fish habitat.

“We appreciate everyone’s patience and understand the inconvenience this has caused those who use the river and the lake for recreational activities,” he said.

Water turbulence presented a challenge as PPL Montana employees, structural engineers and experts in dam construction worked to determine the safest and most effective approach to repair the intake structure and stem the river flow.

The dam remains safe and stable, according to on-site monitoring equipment.

PPL Montana is communicating with local, state and federal officials and those who depend on the river for business and recreation as work continues on the intake structure. The company will conduct a thorough investigation to determine the cause of the incident.

Hebgen Lake, which is created by the dam, is a reservoir just north of the Idaho border that stores water for the Madison-Missouri river system where there are eight PPL Montana hydroelectric dams.