page_title: Seven Oaks Dam
section_title: History
hierarchical_section_title: Seven Oaks Dam / History
caption_attribution_description: English: Map of the 100-year floodplain of the Santa Ana river with flood control structures labelled
context_page_description: Seven Oaks Dam is a 550-foot high earth and rock fill embankment dam across the Santa Ana River in the San Bernardino Mountains, about 4 miles northeast of Redlands in San Bernardino County, southern California. It impounds Seven Oaks Reservoir in the San Bernardino National Forest.
  The dam was proposed in response to major floods in the mid–20th century, and was constructed between 1993 and 2000. Seven Oaks is a dry dam that serves mainly for flood protection to Orange, Riverside and San Bernardino Counties, although it also used to impound water for groundwater recharge. One of the largest embankment dams in the United States, the dam was built by the U.S. Army Corps of Engineers and is owned and operated by local flood control districts.
context_section_description: The USACE began an ambitious effort to improve levees and dams on the Santa Ana River system known as the Santa Ana River Mainstem Project. Among the works proposed under the project were an expansion of the massive Prado Dam, which despite filling to capacity did not fully prevent heavy flooding damages in Orange County, and the construction of the $530 million "Mentone Dam" across the Santa Ana north of Mentone in San Bernardino County. However, the Mentone Dam site was controversial because it would affect groundwater recharge, was aesthetically unpleasing and lay on unstable sediment deposits directly above the San Andreas Fault. In response to public opposition, the USACE replaced the Mentone proposal with the $304 million Upper Santa Ana River Dam, later to be called Seven Oaks Dam, in a bedrock canyon one mile (1.6 km) upstream in the southern San Bernardino Mountains.
  The contract for Seven Oaks Dam was awarded in 1994 and construction work began in May. A system of conveyor belts totaling 3.5 miles (5.6 km), with a capacity of 3,400 short tons (3,080 t) per hour, was built to transport materials to the dam site. Fill used in the embankment was excavated from the Santa Ana River canyon directly below the dam, the alluvial fan of the river north of Mentone, and a cut in a ridge directly southeast of the dam that now serves as the dam's spillway. The dam was built in ten alternating zones of dirt, rock and clay that ultimately totaled 38,000,000 cubic yards (29,000,000 m³). When completed and dedicated in January 2000, the Seven Oaks Dam was the 12th highest dam in the world and was one of the last major dams built in the United States. At $450 million, the final cost of the dam significantly exceeded the USACE's projected cost. The federal government shouldered 70.47% of the total cost, while Orange County paid 27.09%, San Bernardino County 1.71%, and Riverside County 0.73%.
caption: USACE map showing major works of the Santa Ana River Mainstem Project
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