Seven Oaks Dam
Its construction at the base of the San Bernardino Mountains was a major component of the Santa Ana River Mainstem Project, costing $464 million and meant to protect the more than 2 million citizens of Orange, Riverside and San Bernardino counties from flooding. To accomplish this, the dam releases only 7,000 cubic feet per second (cfs) of the 85,000 cfs flowing into it, giving it 350-year flood protection. The rest of this flood control project consisted of raising the already existing Prado Dam downstream and building additional channels.
Seven Oaks Dam is the world’s 10th-largest earthen dam – composed of soil, clay, sand and rocks – at 2,980 feet long. It sits half a mile away from the North Branch and one mile from the South Branch of the San Andreas Fault and is engineered to endure up to a magnitude 8.0 earthquake.