Hebgen Dam
Hebgen Dam is a concrete-core earthen embankment dam in the western United States, located on the Madison River in southwestern Montana. The dam is tall and in length; its purpose is to store and regulate water for other downstream reservoirs and hydroelectric power plants. Montana Power Company originally built the dam, PPL Corporation purchased it in 1997 and sold it to NorthWestern Corporation in 2014.
History
Hebgen Dam was built across the Madison River in 1914 by Montana Power Company to create Hebgen Lake.During the 7.5 magnitude 1959 Hebgen Lake earthquake in mid-August, the dam was damaged, primarily due to intense ground movement that led to water surging over the dam crest four different times. It was repaired several weeks later. The epicenter of the quake was determined to be beneath the bottom of Hebgen Lake. Seismologists reported it to be the fourth largest quake recorded in the United States up to that time.
On August 30, 2008, two of the dam's four hydraulic gates failed, releasing per second of water into the Madison River. The normal discharge of the dam is per second and the gate failure caused a 1-foot rise in the river.
On November 30, 2021, the hydraulic gates failed again causing downstream flows to rapidly drop. Nearby locals quickly organized an effort to rescue stranded fish trapped in pools in the side channels. An ongoing lawsuit against Northwestern Energy claims that NWE failed in its requrirement to keep streamflows above 150 CFS.