The Castaic pumped storage plant is located at the northern fringe of Los Angeles, and is the fourth largest pumped storage project in the nation. Pyramid Lake, the upper storage reservoir, is filled from above, and below by water from the California Aqueduct, part of the California State Water Project, which carries water from northern California, to the south. Water flows out of Pyramid Lake through the Angeles Tunnel, a seven mile long underground conduit, 30 feet in diameter, into penstocks that feed the Castaic Power Plant, which generates more than 1,550 megawatts at its peak from the plummeting water. Water emerging from the plant enters the Elderberry Forebay, which connects to the adjacent Castaic Lake, the official terminus of the west branch of the California Aqueduct, and a major reservoir of Los Angeles’ drinking water. When the six primary turbines at the Castaic Plant reverse, usually at night when demand for power is at its lowest, they pump water backwards through the penstocks, up more than 1,000 feet in elevation and more than seven miles through the Angeles Tunnel, back into Pyramid Lake.
