Hebgen Dam

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.[2] Montana Power Company originally built the dam, PPL Corporation purchased it in 1997 and sold it to NorthWestern Corporation in 2014.

Hebgen Dam
The damaged Hebgen Dam in 1959
Location of Hebgen Dam in the United States
Official nameHebgen Dam
LocationGallatin County, Montana
Coordinates44°51′49″N 111°20′08″W
Opening date1914
Owner(s)NorthWestern Corporation
Dam and spillways
Type of damConcrete-core, earthen embankment
ImpoundsMadison River
Height85 feet (26 m)
Length721 feet (220 m)
Spillway typeChute, gate-controlled
Reservoir
CreatesHebgen Lake
Total capacity325,000 acre⋅ft (0.401 km3)[1]
Catchment area905 square miles (2,340 km2)
Surface area21 square miles (54 km2)

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, 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.[3] 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.[4]

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.[5]

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See also

1959 Hebgen Lake earthquake

References
  1. "HEBGEN LAKE IS 65 MILES AROUND". Montana Standard. 19 August 1959. Archived from the original on 8 March 2012. Retrieved 11 July 2010.
  2. "Hebgen Lake". PPL Montana. Retrieved 11 July 2010.
  3. "Hebgen Lake". Montana Official Travel Site. Retrieved 11 July 2010.
  4. Tuholske, Lily. "Yellowstone Earthquake at the Madison River." Distinctly Montana. September 9, 1998. Accessed March 18, 2018.
  5. "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.

"Yellowstone earthquake at the Madison River." Tuholske, Lily. "Yellowstone Earthquake at the Madison River." Distinctly Montana. September 9, 1998. Accessed March 18, 2018.</ref>


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