Muddy Run Pumped Storage Project Powerhouse, Pennsylvania

When the Muddy Run pumped storage project opened in 1968 it was the largest pumped storage project in the world. The eight pump/turbines in the plant  generate a total of 1,072 megawatts, from water flowing down from an upper reservoir, water that was pumped up earlier by the same reversible pump/turbines. The upper reservoir is a rambling 1,000-acre lake, 400 feet above the elevation of the river. The lower reservoir, where the powerhouse is located, is a flooded section of the Susquehanna formed by the Conowingo Dam, the last dam on the river before it enters Chesapeake Bay. This section of river also serves as the cooling water pond for the Peach Bottom Nuclear Power Plant, one of the first commercial nuclear plants in the nation. Muddy Run was built to absorb the excess power produced by the nuclear power plant at night, when demand for electricity decreases, returning it to the grid during the day. Both facilities are owned by Constellation Energy, one of the largest power companies in the USA.