Hebgen Dam under control

 By Andy Malby, editor

For the first time in more than three weeks, authorities in control of Hebgen Dam actually have control of Hebgen Dam.

“Around-the-clock work to reduce and control flow from the damaged intake structure at Hebgen Dam has paid off,” PPL Montana, the company that operates the facility said in a statement Monday. “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.”

The company has been unable to control the flow of water from Hebgen Lake since the afternoon of Aug. 31, when one of four gates on the structure failed and the dam began releasing four times more water than usual into the Madison River.

Last week, PPL engineers discovered 17 missing stoplogs — wooden beams similar to railroad ties that are stacked in the dam’s four bays and used to regulate water flow, PPL spokesman David Hoffman has said.

Engineers began pushing new stoplogs into place, a process that has taken a week and now appears to have stanched the flow from the dam — enough so engineers can determine what went wrong.

Meanwhile, Hebgen Lake has dropped eight feet and the Madison River has been flowing at around 3,400 cubic feet per second. About 850 cfs is normal for this time of year. But flows have dropped by at least 1,000 cfs since the new stoplogs were installed.

“Our plan is working and the river flow is down to about 2,200 cfs,” 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.”

The dam remains safe and stable, according to on-site monitoring equipment, Simonich said. The company will conduct a thorough investigation to determine the cause of the incident.

Meanwhile, the company plans a pair of public meetings this week to discuss the Hebgen Dam situation. The first, on Wednesday, will begin at 7 p.m. at the West Yellowstone Chamber of Commerce Visitor Center, 30 Yellowstone Ave., in West Yellowstone.

The second meeting will take place Thursday. It also begins at 7 p.m., and will be held at the Ennis Fire Station on U.S. Highway 287, one mile north of Ennis.