Taum Sauk Hydroelectric Power Station

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Taum Sauk Hydroelectric Power Station
The rebuilt upper reservoir of the Taum Sauk plant, nearing completion in this photo, is the largest roller-compacted concrete dam in North America.
Location of Taum Sauk Hydroelectric Power Station in Missouri
Country	United States
Location	St. Francois Mountains, Missouri
Coordinates	37°32′08″N 90°49′05″W / 37.53556°N 90.81806°W / 37.53556; -90.81806
Purpose	Power
Status	Operational
Construction began	1960 (1960)[1]
Opening date	December 20, 1963 (1963-December-20), April 15, 2010 (2010-April-15)[2][3]
Construction cost	US$45.9 million (1963) US$490 million rebuild (2010)
Owner(s)	Ameren Missouri (previously AmerenUE, formerly Union Electric)
Operator(s)	Ameren Missouri
Upper dam and spillways
Type of dam	Gravity dam
Height (foundation)	125 feet (38 m)
Length	6,800 feet (2,100 m)[4][5]
Elevation at crest	1,601 feet (488 m)
Width (crest)	25 feet (7.6 m)
Width (base)	150 feet (46 m)
Dam volume	3,200,640 cubic yards (2,447,060 m3)
Spillways	1
Spillway type	Broad crested weir
Spillway capacity	5,358 cubic feet per second (151.7 m3/s)
Upper reservoir
Total capacity	4,350 acre-feet (5,370,000 m3)[6]
Surface area	54.5 acres (22.1 ha)
Maximum water depth	120 feet (37 m)
Normal elevation	1,597 feet (487 m)
Lower dam and spillways
Type of dam	Gravity dam
Impounds	East Fork Black River
Height (foundation)	60 feet (18 m)
Height (thalweg)	55 feet (17 m)
Length	390 feet (120 m)
Elevation at crest	750 feet (230 m)
Width (base)	75 feet (23 m)
Spillways	1
Spillway type	Ogee crest
Spillway capacity	70,000 cubic feet per second (2,000 m3/s)
Lower reservoir
Creates	Lower Taum Sauk Lake
Total capacity	6,350 acre-feet (7,830,000 m3)
Catchment area	88 square miles (230 km2)
Surface area	395 acres (160 ha)
Normal elevation	749.5 feet (228.4 m)
Power Station
Coordinates	37°31′14″N 90°50′04″W / 37.52056°N 90.83444°W / 37.52056; -90.83444
Operator(s)	Ameren Missouri
Commission date	December 20, 1963 (1963-December-20), April 15, 2010 (2010-April-15)
Type	Pumped-storage
Hydraulic head	860 feet (260 m)
Pump-generators	2 × 225 MW reversible Francis type
Installed capacity	450 MW
Capacity factor	5–8%[1][7]
Overall efficiency	70%
Storage capacity	8 hours (3600 MW·h)
2017 generation	-148 GW·h
Website Taum Sauk Energy Center

The Taum Sauk pumped storage plant is a power station in the St. Francois mountain region of Missouri, United States about 90 miles (140 km) south of St. Louis near Lesterville, Missouri, in Reynolds County. It is operated by Ameren Missouri.

The pumped-storage hydroelectric plant was constructed from 1960–1962 and was designed to help meet daytime peak electric power demand.^[8] It began operation in 1963. Electrical generators are turned by water flowing from a reservoir on top of Proffit Mountain into a lower reservoir on the East Fork of the Black River. At night, excess electricity on the power grid is used to pump water back to the mountaintop.

The Taum Sauk plant is an open-loop pure pumped operation: unlike some other pumped storage sites, there is no natural primary flow into the upper reservoir available for generation. It is therefore a net consumer of electricity; the laws of thermodynamics dictate that more power is used to pump the water up the mountain than is generated when it comes down. However, the plant is still economical to operate because the upper reservoir is refilled at night, when the electrical generation system is running at low-cost baseline capacity. This ability to store huge amounts of energy led its operator to call Taum Sauk "the biggest battery that we have".^[9] An unusual feature is the upper reservoir which is constructed on a flat surface, requiring a dam around the entire perimeter.

On December 14, 2005, a catastrophic failure in the upper reservoir dam put the plant out of operation until it was rebuilt, recertified, and reopened on April 21, 2010.^[10] The new upper reservoir dam, rebuilt from the ground up, is the largest roller-compacted concrete dam in North America.^[11]