The damaged Hebgen Dam in 1959
|Official name||Hebgen Dam|
|Location||Gallatin County, Montana|
|Dam and spillways|
|Type of dam||Concrete-core, earthen embankment|
|Height||85 feet (26 m)|
|Length||721 feet (220 m)|
|Spillway type||Chute, gate-controlled|
|Total capacity||325,000 acre⋅ft (0.401 km3)|
|Catchment area||905 square miles (2,340 km2)|
|Surface area||21 square miles (54 km2)|
The Hebgen Dam is a concrete-core earthen embankment dam on the Madison River in the U.S. state of Montana. The dam is 85 feet tall and 721 feet long. The dam's 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.
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, the dam was damaged, primarily because of such intense ground movement that water surged over the dam crest four different times, but it was fixed several weeks later. The epicenter of the quake was determined to be 20 miles (32 km) 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 3,400 cubic feet (96 m3) per second of water into the Madison River. The normal discharge of the dam is 900 cubic feet (25 m3) per second and the gate failure caused a 1-foot rise in the river.
- "HEBGEN LAKE IS 65 MILES AROUND". Montana Standard. 19 August 1959. Retrieved 11 July 2010.
- "Hebgen Lake". PPL Montana. Retrieved 11 July 2010.
- "Hebgen Lake". Montana Official Travel Site. Retrieved 11 July 2010.
- Tuholske, Lily. "Yellowstone Earthquake at the Madison River." Distinctly Montana. September 9, 1998. Accessed March 18, 2018.
- "Dam Failures, Dam Incidents (Near Failures)" (PDF). Association of State Dam Safety Officials. Archived from the original (PDF) on 5 July 2010. Retrieved 11 July 2010.
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