BUTTE — NorthWestern Energy reported Wednesday morning that Tuesday’s dramatic decrease in river flow to the Madison River was due to a malfunctioning outlet gate on the Hebgen Dam.
NorthWestern Energy reports that hydro engineers and personnel have been working around the clock to develop a repair plan. A replacement gate, which was manufactured in Anaconda, has been transferred to the dam and could be installed by Wednesday evening.
“The area of the failure is underwater which is why we have divers there, so they actually have to dive down and work on those components to get the repair complete,” said NorthWestern Energy’s Director of Hydro Operations Jeremy Clotfelter.
The utility claims there are no issues or risks to the structure of the dam, but the malfunctioning gate interferes with NorthWestern’s ability to control the flow of water into the river.
“We have had reports of fish kills and stranded fish in many areas and there’s also a concern of exposing brown trout spawning beds,” said Clotfelter.
The malfunctioning gate was part of upgrades made about 10 years ago to the dam, so an analysis of the failure will follow.
“At this point, we know what failed, but we don’t know why it failed or how it failed, so are first priority here is to restore flow back to the river,” said Clotfelter.