2020 Local Hazard Mitigation Plan

City of Irvine

Dam Failure

Description

Dam failure can result from several causes such as earthquakes, rapidly rising floodwaters, and structural design flaws. These hazards can occur instantaneously or very gradually, depending on the source of the failure. Inundation associated with these events have the potential to cause loss of life, damage property, and other ensuing hazards, as well as the displacement of persons residing in the inundation path. According to the California Division of Safety of Dams (DSOD), a dam falls under their jurisdiction if its height is greater than six feet and impounds more than 50 acre-feet of water, or its height is greater than 25 feet and impounds 15 acre-feet of water. Based on these criteria, 1,537 dams fall under DSOD jurisdiction, 40 of which are located within Orange County.

Location and Extent 29

The City of Irvine has seven dams that have the potential to inundate areas of the City if failure were to occur. Of these dams, three of them are located within the City’s planning area, while the other four are located outside of the City limits. Descriptions of these dams are provided, below: • Rattlesnake Canyon Reservoir: located on Rattlesnake creek in the eastern portion of the City, this 79-foot-high earth-filled dam is owned by Irvine Ranch Water District. Built in 1959, this facility impounds 1,480 acre-feet of recycled water primarily used for irrigation. • Sand Canyon Reservoir: located adjacent to the Strawberry Farms Golf Club in the western portion of the City, this 58-foot-high earth-filled dam is owned by Irvine RanchWater District. Built in 1912, this facility impounds 768-acre feet of recycled water, primarily used for irrigation. • Syphon Canyon Reservoir: located in the northeastern portion of the City, this 59-foot-high earth- filled dam is owned by Irvine Ranch Water District. Built in 1966, this facility impounds up to 535- acre feet of recycled water, primarily used for irrigation. • Peters Canyon Reservoir: located north of the City of Irvine (approximately 3 miles west of Santiago Dam), this 50-foot earth-filled dam is owned by the County of Orange. Built in 1932, this facility impounds up to 626-acre feet of water. • Santiago Dam: located northeast of the City of Irvine, this 136-foot high earth-filled dam is jointly owned by Irvine Ranch Water District and Serrano Water District. Built in 1931, this facility impounds approximately 25,000 acre-feet of water, creating the largest freshwater lake contained wholly within Orange County (Irvine Lake). • San Joaquin Reservoir: located west of the City (in neighboring Newport Beach), this 224-high earth-filled dam is owned by Irvine Ranch Water District. Built in 1966, this facility impounds over 3,000 acre-feet of recycled water, primarily used for irrigation. • Villa Park Dam: located north of the City, this 118-foot-high earthen filled dam is owned by the Orange County Flood Control District. Built in 1963, this facility has the capacity to impound over 15,000 acre-feet, which is primarily used for flood control purposes. • Prado Dam is located approximately 25 miles northeast of the City, along the Santa Ana River in Riverside County. This dam facility poses a great risk to northern Orange County cities. Given the

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