 An agreement between the two organizations was signed on September 2, 1966, for construction of the project.The Castaic Power Plant is located about from the northern Los Angeles city limits at the upper end of the West arm of Castaic Lake.California State Aqueduct water en route to Southern California is pumped up through the Tehachapi Mountains (by the Edmonston Pumping Plant) to the Tehachapi Afterbay.