| Muddy Run Pumped Storage Facility | |
| Coordinates: | 39.847°N -76.2915°W |
| Country: | United States |
| Status: | O |
| Construction Began: | 1964 |
| Opening: | 1968 |
| Cost: | $73 million (1968) |
| Operator: | Constellation Energy |
| Res Name: | Muddy Run Reservoir |
| Res Capacity Total: | 11 billion U.S. gallons (41.57 GL, 33,700 acre-feet, 1000 acres) |
| Lower Res Name: | Conowingo Pond |
| Lower Res Capacity Total: | 1 trillion U.S. gallons (3790 GL, 310,000 acre-feet, 9000 acres) |
| Plant Hydraulic Head: | 410feet |
| Plant Pumpgenerators: | 8 × 134 MW reversible Francis type |
| Plant Capacity: | 1072 |
| Plant Annual Gen: | -361 GW·h (2016) |
| Website: | Muddy Run Pumped Storage Facility |
Muddy Run Pumped Storage Facility is a pumped-storage hydroelectric generation facility in Drumore Township, Pennsylvania, United States. Constructed by the Philadelphia Electric Company and completed in 1968,[1] Muddy Run was the largest pumped-storage facility in the world. Muddy Run has a capacity of 1,071 megawatts.[2] The facility is operated by the Susquehanna Electric Company, a subsidiary of Constellation Energy.
The facility's upper reservoir is the 1000acres Muddy Run Reservoir, with a full pool elevation of over, and a usable storage capacity of 1466e6ft3. Muddy Run Reservoir was created by damming Muddy Run with a long, high, rock-filled dam.[1] The lower reservoir is the Conowingo Reservoir, created in the Susquehanna River by the Conowingo Dam, with a normal pool elevation of . The power house uses excess grid capacity during off peak hours to pump water from the Conowingo Reservoir into the upper reservoir through four 25feet diameter, 343feet vertical 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.
The Muddy Run 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".[3]
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.