REGIONAL

Hebgen Dam malfunction causes dramatic drop in river flows, strands fish NorthWestern Energy works to repair dam and restore flows

BY GABRIELLE GASSER

HEBGEN LAKE – Volunteers and Montana Fish, Wildlife and Parks staff gathered on the morning of Dec. 1 to rescue fish on the upper Madison River after a malfunction in the Hebgen Dam caused a significant drop in flows.

A gate component on Nov. 30 failed on the dam’s outlet structure, according to a Dec. 1 press release from dam operator NorthWestern Energy, which decreased the opening for the outtake of water at the bottom of the gate. The gate malfunction interferes with NorthWestern Energy’s ability to control river flows which led to the river dropping to a third of normal.

NorthWestern Energy said at a Dec. 1 press conference that the failure occurred between 2 and 3 a.m. on Nov. 30 based on United States Geological Survey data that showed a sharp drop in flows at that time. Equipment at the site did not notify NorthWestern Energy of an issue at that time, and Clotfelter said NorthWestern Energy became fully aware of the problem mid-morning Nov. 30.

“The indicating equipment worked as it’s designed to do,” Clotfelter said. “It’s just that the failure occurred in a matter that the indicating equipment would not pick up.”

According to a Nov. 30 press release from FWP the impacts to the fishery are still unclear. Morgan Jacobsen, information and education program manager with FWP, said that the impact will take a while to become fully known.

“It is significant for sure,” he said. “There is still water in the channel but it is a significant drop.”

FWP issued a full fishing closure on Nov. 30 for the upper Madison River from Ennis Lake to Hebgen Dam. As of EBS press time, the closure was still in place.

FWP staff and volunteers moved stranded fish along the upper Madison River into the main channel on Dec. 1. Jacobsen said that the biggest concern was spawning trout. The Madison River brown trout are currently spawning, meaning their fertilized eggs are being deposited into spawning beds in the river called redds. As low flows lead to dried up channels, redds are left exposed.

“At this point, the biggest potential impact to those redds is going to be low temperatures at night,” Jacobsen said.

Kelly Galloup, owner of Galloup’s Slide Inn located on the upper Madison River, witnessed the impacts of the low flows firsthand. When he walked out to the river the morning of Dec. 1, Galloup estimated he saw 200 people on the river trying to save the stranded trout.

“It’s quite heart wrenching to walk out there and see all of that,” Galloup said. “It’s just dry. It’s just frightening.”

NorthWestern Energy spent Nov. 30 trouble shooting the failure, according to Clotfelter, and a new gate component was fabricated overnight in Anaconda. On the morning of Dec. 1, contract divers were on site at Hebgen Dam and were able to support the gate from above to prevent it from closing any further.

As of the Dec. 1 press conference, the replacement gate was en route to the dam and Clotfelter was hopeful that the repair could be completed quickly.

“If current efforts are successful, flow could be restored back this evening,” he said.

If the new part does not fix the issue, Clotfelter said NorthWestern Energy has the option to transfer flow to a different gate as an alternative solution.

As of EBS press time, river flows were holding steady at approximately 250 cubic feet per second according to USGS data.

Moving forward, Clotfelter said NorthWestern Energy will focus on studying the failure as well as impacts to the Madison River and the fish.

“On the failure itself, Federal Energy Regulatory Commission will be very involved in working with us to help identify the why and the how of the failure and to identify those corrective actions that we can implement to prevent reoccurrence,” he said. “And then on the resource side, certainly there will be efforts to understand the impact, and to see what could be done to help offset that going forward.”

Travis Wilson, a diver from Associated Underwater Services, preps to go into the river to look at the component that failed on Hebgen Dam. PHOTO COURTESY OF NORTHWESTERN ENERGY