Permanent repairs and upgrades to the release gate at Hebgen Dam in Montana will begin later this summer and are expected to be complete by mid-September, according to NorthWestern Energy.
On Nov. 30, 2021, a stem coupling on the release gate failed, causing the gate to partially close. An investigation, called a root cause analysis, was completed. The findings and corrective actions were reviewed and approved by the Federal Energy Regulatory Commission, the federal licensing authority for NorthWestern Energy’s Missouri-Madison Hydroelectric Project.
The work taking place at Hebgen Dam will implement the corrective actions identified through the root cause analysis. However, NorthWestern Energy did not indicate exactly what repairs would take place.
Outflow from Hebgen Dam will continue over the spillway until work is completed on the dam gate, according to a release.
Hebgen Dam, near West Yellowstone, Mt., U.S., is located at over 6,500 feet in elevation. Construction of the dam, a 700-foot-long earth embankment with a concrete core wall, was completed in 1914. A concrete-lined and gated spillway was constructed near the right abutment. A small powerhouse was constructed to provide local power service, but by the 1950s it was no longer operating. As a flow-control and storage reservoir, the 386,000-acre-foot volume of Hebgen Lake provides a benefit to the 11 downstream hydroelectric plants on the Madison and Missouri rivers in Montana.
The Missouri-Madison consists of nine developments on the Madison and Missouri rivers in southwestern Montana and develops hydropower along a 324-mile stretch of the two rivers.
NorthWestern Corporation, doing business as NorthWestern Energy, provides electricity and/or natural gas to about 753,600 customers in Montana, South Dakota, Nebraska and Yellowstone National Park.
