Balsam Meadow Eastwood Powerhouse, California

The Eastwood Powerhouse is the power plant and pumping station for the Balsam Meadow Pumped Storage Project, one of just a few dozen pumped storage hydroelectric projects in the USA, and one of two in the Southern Sierra. An upper reservoir, the Balsam Forebay, is filled by water pumped up to it from the lower reservoir, Shaver Lake, though a 7,500-foot-long tunnel bored through solid rock, by a pump inside the Eastwood Powerhouse. When water flows back down, the pump reverses, becoming a turbine that generates up to 200 megawatts of electricity, for the grid, during periods of peak demand, during the day. The powerhouse is located in a cavity carved out of solid granite, 1,000 feet underground. Construction for the project started in 1983 and ended in 1987, when the upper reservoir at was filled. Balsam Meadow was the last part of the larger Big Creek Hydroelectric Project, which was developed by Southern California Edison between 1913 and 1987 to provide power for Los Angeles.