Three non-profit groups are looking for answers into the dam malfunction that cut flows and threatened fish pops in the Madsion on Nov. 30 last year. I agree with them. The part that bothers me is that there was no alarm system to alert NorthWesternEnergy when the dam failed. Or if there was an alarm system, it, too, failed. Ten hours passed from the time the dam broke till it was noticed. It took concerned citizens and a sharp-eyed fishing guide to alert the community.

I commend NorthWesternEnergy for fast action in repairing the dam and restoring flows. But allowing the break to go unnoticed for ten hours is unacceptable. Here’s hoping they get their act together.

Groups request independent investigation into Hebgen Dam malfunction

Hebgen dam trout Madison River
TOP: Water spills down a culvert coming from the Hebgen Dam into the upper Madison River on Dec. 1. .Samuel Wilson/Chronicle/Report for America

Three nonprofits are requesting an independent investigation into a Hebgen Dam gate malfunction that led to an abrupt drop in flows along the upper Madison River in late November.

Upper Missouri Waterkeeper, Montana Environmental Information Center and the Madison River Foundation filed a complaint with the Federal Energy Regulatory Commission on Wednesday.

Guy Alsentzer, executive director of Upper Missouri Waterkeeper, said the organizations are asking FERC to take a hard look at the circumstances surrounding the dewatering event and address the economic and ecological consequences, which are still largely unknown.

A broken metal coupler on a gate stem at Hebgen Dam caused flows to plunge from 648 cubic feet per second to 278 cfs in the wee hours of Nov. 30. The sudden change stranded fish in some side channels and exposed brown trout redds.

NorthWestern Energy, the utility that controls the dam, didn’t learn about the loss of flows until 12:19 p.m., according to a Dec. 23 letter from FERC addressing the incident.

Volunteers from the area and staff from Montana Fish, Wildlife and Parks rushed to rescue stranded fish until the gate component was fixed late on Dec. 1.

“As a public utility, NorthWestern Energy must be held accountable for mismanagement of Montana’s natural resources, especially our water,” said Derf Johnson, staff attorney and clean water director at the Montana Environmental Information Center, in a news release.

“NorthWestern needs to fully cooperate with a comprehensive and transparent investigation, mitigate the impacts to the environment, community, and economy, take measures to ensure that this never happens again, and pay to fix the problem out of its shareholders’ pockets,” Johnson said.

If FERC determines that an investigation is warranted, the complaint could trigger a formal process where independent experts analyze the dam and monitoring equipment failures that led to the event, the groups wrote. The regulatory agency would oversee that process.

Alsentzer said the complainants would like to see two types of investigations by independent third-parties take place on NorthWestern Energy’s dime.

They’d like the utility to hire an engineering expert to look at Hebgen Dam’s infrastructure and identify areas of concern, he said. They’d like an ecological expert to determine how the loss of flows impacted the fishery.

The groups want NorthWestern Energy to allocate resources toward ensuring the two permit violations don’t reoccur, and toward addressing the event’s future ecological and economic impacts.

“Two significant flow failures in fifteen years at NorthWestern’s Hebgen Dam sound the alarm call for much needed additional monitoring and redundancy to protect the river ecology and downstream economies that are directly dependent on stable outflows,” Alsentzer said in the release.

Jo Dee Black, a spokesperson from NorthWestern Energy, wrote in an email that an investigation into the Nov. 30 gate failure is now underway, and the utility has submitted reports to FERC about it.

“Since taking ownership in 2014 of 11 dams in Montana, NorthWestern Energy invested hundreds of millions of dollars in the system. Those investments have increased the generating capacity, improved fish passage through the dam system, modernized the infrastructure and provided more recreational opportunities,” she wrote.

NorthWestern Energy completed a $40 million upgrade at Hebgen Dam in 2018, and the component that failed was installed in 2015 as part of that investment. The utility, regulatory agency and others are taking “purposeful steps” to ensure a thorough analysis of the gate component is conducted, Black wrote.

That analysis is based on sound engineering principles, and it will be used to understand why the relatively new gate component failed. It will also be used to establish corrective actions, she wrote.

NorthWestern Energy plans to work with resource agency biologists and others to assess the effects on the fishery, according to Black.

After the gate component failed, NorthWestern Energy violated two permit requirements, according to documents the utility filed with FERC.

A continuous minimum flow of 600 cubic feet per second must be maintained at a U.S. Geological Survey gauge near Cameron, and outflows from Hebgen Dam can’t change by more than 10% in a 24-hour period.

Flows at the gauge near Cameron dropped to 395 CFS during the dewatering event. In addition, outflows from the dam dropped from 648 CFS to 278 CFS within 15 minutes— a 57% reduction in flows.

Fisheries experts from USGS and Montana Fish, Wildlife and Parks told the Chronicle that the event’s impacts on the fishery won’t be known for several months, but they are cautiously optimistic brown trout populations will recover.

Brown trout have been declining in most southwest Montana rivers over the past decade. However, populations haven’t suffered as much in the portion of the Madison River below Hebgen Dam.

“We have committed to our members, to Montanans, and to the Madison River, that we will protect its vital flows and be responsible stewards in maintaining a healthy watershed,” said Jonathan Malovich, executive director of Madison River Foundation, in the news release.

“This is just a single step in the right direction of many more to come to change the way we can all protect and manage the water that flows down the Madison River,” he said.