John Day
John Day Dam is a conventional hydroelectric plant on the Columbia River in Sherman County, Oregon, with 11 operating generating units reported to EIA-860 totaling 1,485 MW of nameplate capacity. The dam is owned and operated by the U.S. Army Corps of Engineers, Portland District, as a federal multi-purpose project. Publicly, the powerhouse is described as housing 16 turbine-generator units with a total installed capacity of 2,160 MW and an overload capacity of 2,485 MW, making it one of the largest hydroelectric facilities in the country. Construction began in 1958 and finished in 1971, and the project impounds the 76-mile-long Lake Umatilla reservoir that reaches upstream to McNary Dam. The dam's navigation lock has a lift of 110 feet, the highest of any lock in the United States. John Day sells its output into the Bonneville Power Administration balancing area and settles at price nodes near the powerhouse. No whole-plant or unit-level retirement is scheduled for the facility.