The Blenheim-Gilboa Pumped Storage Power Project is a pumped-storage hydroelectricity plant in the Catskill Mountains of New York State. The plant is part of the New York Power Authority, and can generate over 1,000,000 kilowatts of electricity, all of which is sent to New York City in the case of a power crisis in the city. It is to be used only for emergency situations; i.e., in case another powerplant shuts down, or in case the other powerplants can't provide enough electricity. There are two reservoirs that are involved in the project, both with a capacity of 5 billion gallons (over 71.6 million m³); one at the foot of Brown Mountain in the Schoharie Valley, and another one at the top of the mountain. The project's power station has a maximum production capacity of 1,057 MW.

The reservoir at the foot of the mountain was created by impounding the Schoharie Creek downstream from the village of Gilboa, New York. Water from this reservoir is sent through an aqueduct up the mountain to the upper reservoir to be stored until it is needed. When power is needed, the water is sent back down the mountain into the lower reservoir, where it enters a powerplant on the banks of the lower reservoir, and spins a series of turbines in the powerhouse. (This structure is almost completely underwater, and only five feet of it can be seen above water when the reservoir is full). The water is sent back into the reservoir, flows over the dam that holds the reservoir back, and continues down the rest of the Schoharie Creek.

The Blenheim-Gilboa Visitors Center is housed in a restored 18th century dairy barn, and features exhibits and interactive displays that demonstrate the science of energy and electricity, and how power is made and used. Admission to the center is free. The historic Lansing Manor House is a historic house museum adjacent to the Visitors Center. The Visitors Center, Lansing Manor House and the Power Project are located near Mine Kill State Park.

Blenheim-Gilboa Hydroelectric Power Station
Country	United States
Locale	Catskill Mountains
Owner(s)	NYPA
Reservoir information
Reservoir capacity	19,000,000 m3 (5.0×109 US gal)
Power generation information
Installed capacity	1,057 MW

Muddy Run Pumped Storage Hydroelectricity is a pumped-storage hydroelectric generation facility in Drumore Township, Pennsylvania, USA. When completed in 1968, Muddy Run was the largest pumped-storage facility in the world. The facility is operated by the Susquehanna Electric Company, a subsidiary of Exelon Generation.

The facility's upper reservoir is the 1,000 acre (400 ha) Muddy Run Reservoir, with a full pool elevation of over 500 feet (150 m), and a usable storage capacity of 1,466,000,000 cubic feet (41.5 hm³) or 33,650 acre-feet. Muddy Run Reservoir was created by damming Muddy Run with a 4,800 foot (1,500 m) long, 250 foot (76 m) high, rock-filled dam. The lower reservoir is the Conowingo Reservoir, created in the Susquehanna River by the Conowingo Dam, with a normal pool elevation of 109 feet (33 m). The power house uses excess grid capacity during off peak hours to pump water from the Conowingo Reservoir into the upper reservoir through four 25 foot (7.6 m) diamter, 343 vertical foot (105 m) shafts. During peak power demand periods, the water is allowed to flow back from the lake through the shafts to the eight turbines causing the pumps to act as generators. Muddy Run has a capacity of 1,071 megawatts.

The Muddy Run Pumped Storage Hydroelectricity electrical machinery was designed by the noted engineer Eugene C. Whitney of Westinghouse Electric Company, who designed the machinery for the Grand Coulee Dam #3 powerhouse. Whitney "was present when the machines were first to be started. The operator was reluctant to take the first step. Gene said, 'Call your boss.' The boss said, 'If Gene says to start the machines, start them.' So they did, and water rose from the lower Susquehanna River to the upper reservoir, 400 feet above".

The upper reservoir extends into Martic Township. The area around the upper reservoir is operated as a park, complementing the nearby Susquehannock State Park. Susquehannock State Park has an overlook trail with a good view of the Muddy Run facility.

Engineering studies began in October 1964, with early site preparation starting three years later. In 1972 its 1,080-megawatt pumped storage hydroelectric plant became operational as the largest such facility in the world.

The Northfield Mountain pumped storage hydroelectric plant was built entirely underground, and located about 5.5 miles (8.9 km) up the Connecticut River from Turners Falls Dam. A stretch of the Connecticut River, extending some 20 miles (32 km) north from this dam to the Vernon Dam, Vermont, serves as the station's lower reservoir. During periods of lower electrical power demand, the plant pumps water from this lower reservoir to a man-made upper reservoir. At times of high demand, water is released to flow downhill from this upper reservoir through a turbine generator, where it then collects in the lower reservoir to be stored until again pumped to the upper reservoir.

Northfield Mountain's upper reservoir covers 300 acres (1.2 km²) at 800 feet (240 m) above the river, with total storage of 5.6 billion gallons of water. Its underground powerhouse lies at 700 feet (210 m) below the surface and is accessible through a 2,500-foot (760 m)-long tunnel; it includes four large reversible turbines, each of which can pump about 20,000 gallons of water per second and generate 270,000 kilowatts of electricity.

The "lower reservoir" noted above is a pool along the Connecticut River above Turner's Falls Dam. Since the dam at Turner's Falls was raised in the early 1970s for Northfield Mountain, the banks of the Connecticut River have been re-adjusting to the new water level.

Raccoon Mountain Pumped-Storage Plant is a pumped-storage hydroelectric underground power station in Marion County, just west of Chattanooga in the U.S. state of Tennessee.

The facility is owned and operated by the Tennessee Valley Authority (TVA). Construction was started in 1970 and was completed in 1978.

Water is pumped from Nickajack Reservoir on the Tennessee River at the base of Raccoon Mountain to a storage reservoir built at the top of the mountain. The reservoir at the top of the mountain covers 528 acres (214 ha), with a dam that is 230 feet (70 m) high and 5,800 feet (1,800 m) long, the largest rock-fill dam ever built by TVA. It takes 28 hours to fill the upper reservoir. During periods of high electric demand, water can be released from the reservoir through a tunnel drilled through the center of the mountain, driving electric generators in an underground hydroelectric plant. The Raccoon Mountain Pumped-Storage Plant has a capacity of 1600 megawatts of electricity and can generate for up to 22 hours. The plant is used most every day and serves as an important grid balancing in the TVA system.

The Raccoon Mountain Pumped-Storage Plant facility is a popular recreation spot for hiking, walking, running, road and mountain biking.

Raccoon Mountain Pumped-Storage Plant
Status	Operational
Construction began	1970
Commission date	1978
Owner(s)	Tennessee Valley Authority
Power station information
Primary fuel	Water
Generation units	4 x Pump-generator
Power generation information
Installed capacity	1600 MW

The 1,566 MW Castaic pumped-storage hydroelectric plant is located at the other end of the lake. Castaic Lake serves as the lower reservoir, while Pyramid Lake serves as the upper. When demand for electricity is high, usually during the afternoon, water is withdrawn from Pyramid Lake and released into Castaic Lake. At night, when demand is low, water is pumped back into Pyramid Lake. The sale of peak electricity reduces the Department of Water Resources' overall electric costs for operating the California Aqueduct.

Castaic Dam is a dam near the city of Castaic, California. It is an earth-fill dam, though its surfaces are covered with boulders and cobble-sized rocks to prevent erosion. Although located on Castaic Creek and forming Castaic Lake, Castaic Creek provides little of its water. The lake is the terminus of the West Branch of the California Aqueduct, part of the State Water Project. The dam was built by the California Department of Water Resources and construction was completed in 1973. The lake has a capacity of 325,000 acre-feet (401,000,000 m³) and stores drinking water for the western portion of the Greater Los Angeles Area.

The Ludington Pumped Storage Power Plant is a hydroelectric plant and reservoir in Ludington, Michigan. It was built between 1969 and 1973 at a cost of $315 million and is owned jointly by Consumers Energy and Detroit Edison and operated by Consumers Energy. At the time of its construction, it was the largest pumped storage hydroelectric facility in the world.

Ludington Pumped Storage Power Plant consists of a reservoir 110 ft (34 m) deep, 2.5 miles (4 km) long, and one mile (1.6 km) wide which holds 27 billion US gallons (100 million m³) of water. The 1.3 mi² reservoir is located on the banks of Lake Michigan. Because impervious bedrock is more than 800 feet below the reservoir, the builders had to line the reservoir with a layer of asphalt and clay to prevent water seeping into the ground.

The Ludington Pumped Storage Power Plant consists of six reversible turbines that can each generate 312 megawatts of electricity for a total output of 1872 megawatts. Water is delivered from the upper reservoir to the turbines by six penstocks each 1100 feet long that taper from 28 to 24 feet in diameter.

At night, during low demand for electricity, the turbines run in reverse to pump water 363 ft (110 m) uphill from Lake Michigan into the reservoir. The plant takes advantage of the natural steep sand dune landform of eastern Lake Michigan. During periods of peak demand water is released to generate power. Electrical generation can begin within 2 minutes with peak electric output of 1872MW achieved in under 30 minutes. Maximum water flow is over 33 million gallons per minute.

This process helps level the load of coal-fired power plants on the grid. It also replaces the need to build natural gas peak power plants used only during high demand. The Ludington Pumped Storage plant is connected to three 345,000 kv Transmission lines, all owned and maintained by METC, a subsidiary of ITC Holdings.

Ludington Pumped Storage Power Plant project was given the 1973 award for "Outstanding Civil Engineering Achievement" by the American Society of Civil Engineers.

Consumers Energy discussed plans in 2008 to extend the life of the facility and upgrade the pumps to increase efficiency by up to 9%. Consumers Energy also planned to tap the wind power resources along the eastern Lake Michigan shore with wind farms. Because wind is an intermittent power source and may inconveniently deliver large amounts of power during periods of low electric demand, pumped storage facilities are desirable to have on the same grid with large-scale wind farms. The available pumped storage capacity, along with the wind characteristics, partly determine the maximum contribution wind power can make to the overall electricity use in a region.

Consumers Energy and Detroit Edison announced an $800 million upgrade on February 7 2011. The six year project would begin in 2013 and extend the plant's life by at least forty years and upgrade the generating capacity from 1,872 megawatts to 2,172 megawatts.