Black Eagle Dam
| Black Eagle Dam | |
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Black Eagle Dam in 2013
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| Official name | Black Eagle Dam |
| Location | Great Falls, Montana, U.S. |
| Coordinates | 47°31′11″N 111°15′47″W / 47.51972°N 111.26306°WCoordinates: 47°31′11″N 111°15′47″W / 47.51972°N 111.26306°W |
| Construction began | September 1890 (first dam); April 1926 (second dam) |
| Opening date | December 1890 (first dam); September 1927 (second dam) |
| Operator(s) | NorthWestern Corporation |
| Dam and spillways | |
| Impounds | Missouri River |
| Height | 34.5 feet (10.5 m) (second dam) |
| Length | 782 feet (238 m) (second dam) |
| Reservoir | |
| Creates | Long Pool |
Black Eagle Dam is a hydroelectric gravity weir dam located on the Missouri River in the city of Great Falls, Montana. The first dam on the site, built and opened in 1890, was a timber-and-rock crib dam. This structure was the first hydroelectric dam built in Montana and the first built on the Missouri River. The dam helped give the city of Great Falls the nickname "The Electric City." A second dam, built of concrete in 1926 and opened in 1927, replaced the first dam, which was not removed and lies submerged in the reservoir. Almost unchanged since 1926, the dam is 782 feet (238 m) long and 34.5 feet (10.5 m) high, and its powerhouse contains three turbines capable of generating seven megawatts (MW) of power each. The maximum power output of the dam is 18 MW.Montana Power Company built the second dam, PPL Corporation purchased it in 1997 and sold it to NorthWestern Corporation in 2014. The reservoir behind the dam has no official name, but was called the Long Pool for many years. The reservoir is about 2 miles (3.2 km) long, and has a storage capacity of 1,710 acre feet (2,110,000 m3) to 1,820 acre feet (2,240,000 m3) of water.
The dam is a "run-of-the-river" dam because it can generate electricity without needing to store additional water supplies behind the dam.
Black Eagle Falls is the first in a series of five waterfalls which constitute the Great Falls of the Missouri River in the state of Montana in the United States. Before being dammed, water dropped 26.42 feet (8.05 m) over the falls.
Black Eagle Falls formed on a fall line unconformity in the Great Falls Tectonic Zone. The Missouri River in this area flows over and through the Kootenai Formation, a mostly nonmarine sandstone laid down by rivers, glaciers, and lakes in the past. Some of the Kootenai Formation is marine, however, laid down by shallow seas. The river is eating away at the softer nonmarine sandstone, with the harder rock forming the falls themselves.
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Wikipedia