Seven Oaks Dam

Seven Oaks Dam is a single purpose flood control project constructed by the U.S. Army Corps of Engineers, Los Angeles District. The project is located on the Santa Ana River in the upper Santa Ana Canyon about 8 miles (13 km) northeast of the City of Redlands, in San Bernardino County, California. Authorization for the project construction is contained in the Water Resources Development Act of 1986. Construction was completed on November 15, 1999.

It cost $250 million to construct and at the time of its completion in November 1999, it ranked as the 10th largest earthfill dam in the United States.

Construction of the Seven Oaks Dam began in August 1994. When it was completed, the height of the dam was 550 ft (168 m) and was over 2,200 ft (670 m) wide at its base; 43,000,000 yd³ (33,000,000 m³) of earth and rock were required to build it. The dam sits virtually on top of the San Andreas Fault and is designed to withstand a |magnitude 8.0 earthquake. The dam forms Seven Oaks Reservoir, which has a capacity of 147,970 acre-feet (182,521,000 m³).

The project is planned to operate in tandem with Prado Dam, also located on the Santa Ana River 40.3 miles (64.9 km) downstream, to provide flood protection to Orange County, California. During the early part of each flood season, runoff will be stored behind the dam in order to build a debris pool to protect the outlet works. Small releases will be made on a continual basis in order to maintain the downstream water supply. During a flood, Seven Oaks Dam will store water destined for Prado Dam for as long as the reservoir pool at Prado Dam is rising. When the flood threat at Prado Dam has passed, Seven Oaks will begin to release its stored flood water at a rate which does not exceed the downstream channel capacity. At the end of each flood season, the reservoir at Seven Oaks will be gradually drained and the Santa Ana River will flow through the project unhindered.

The water control manual for Seven Oaks Dam is scheduled for completion in November, 2001.