Prado Dam Failure Could Flood Dozens Of OC Communities
The 78-year-old earthen dam is all that stands between 1.4 million people and floodwaters during the next huge series of Pacific storms.
By Ashley Ludwig, Patch Staff | May 17, 2019 12:59 pm ET
https://patch.com/california/orange-county/prado-dam-failure-could-flood-dozens-oc-communities
ORANGE COUNTY, CA — Federal engineers have raised an alarm that a "significant flood event," such as a series of strong Pacific storms, could breach the spillway of the aging Prado Dam, in Orange County. Such an event has the potential to drown out dozens of downstream communities, from Anaheim's Disneyland to Newport Beach, the Army Corps of Engineers Los Angeles District reported.
After conducting an assessment of the 78-year-old structure earlier this month, the U.S. Army Corps of Engineers announced that it was raising the dam's risk category from "moderate" to "high urgency."
Over 1.4 million people live and work below Prado Dam, with property valued at over $61 billion, including Disneyland and many high-end resorts and properties in Newport Beach.
"Public safety is our number one priority," Col. Aaron Barta, commander of the U.S. Army Corps of Engineers Los Angeles District, said in a recent release. The Corps is currently reviewing all dams in the area and prioritizing the highest risks, of which Prado Dam tops the list. Any modifications to improve the spillway won't begin for at least two years, they said.
Prado Dam was authorized for development in 1936, to protect the populous communities downstream, and was still under construction during the flood in the spring of 1938, when two mighty Pacific storms swept through the region and dumped over a year's worth of rain in just a few days, according to the Orange County Historical Society. During that time, floodwaters swamped significant swaths of Orange County under six-feet of water for several weeks, including Anaheim and what is now Santa Ana.
During a 100-year flood, Prado Dam is the only stopgap between safety and catastrophe for hundreds of thousands of people. In 2005, a leak in the damn during a series of storms forced hundreds to evacuate their homes in nearby Corona. The latest look at Prado Dam has left the Army Corps of Engineers concerned about what another devastating storm would do to the dam.
"Our concern right now is about the concrete slab of the spillway and how well it will perform if water were to spill over the top of the dam," said Lillian Doherty, the Army Corps' division chief, told the Los Angeles Times. "We will determine whether or not it is as reliable as it should be."
Located beside the 91 Freeway, on the border of Riverside and Orange counties, the dam contains little to no water for much of the year. During periods of heavy rain, however, the structure is intended to collect water and prevent flooding along the Santa Ana River.
Doherty said her agency is working with a national team of experts to develop interim and permanent risk-reduction measures at the dam, as well as public outreach strategies to alert the estimated 1.4 million people who live and work in 29 communities downstream.
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