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Aging dams vulnerable; engineers learn from structural failures

Hoover gets all the glory, but Nevada is home to more than 650 dams, nearly a quarter of which are classified as “high hazard” because of what could happen if they fail. State records identify 133 dams in Clark County alone, including 67 high-hazard structures, most of them flood detention basins perched above — and built to protect — residential neighborhoods. Dam safety has been thrust into the national spotlight in recent weeks by the ongoing emergency at California’s Oroville Dam and the Feb. 8 collapse of an earthen dam in northeastern Nevada. For years, engineers and safety advocates have warned that the nation’s dams are aging and do not receive nearly enough funding for inspection and rehabilitation.

According to the Association of State Dam Safety Officials, a national nonprofit advocacy group, $60.7 billion in repair work is needed at state and locally owned dams across the U.S. More than $18.7 billion of that work is required at high-hazard dams, it says. Roughly 20 percent of those high-hazard structures do not have emergency plans to protect people and vital infrastructure in the event of a failure, the association says. Nevada is somewhat better off, with less than 10 percent of its high-hazard dams lacking emergency action plans. A high-hazard rating does not reflect a dam’s condition, but rather its potential for death and destruction in the event of a failure. In other words, it’s a measure of what’s downstream, not whether a dam is structurally sound.

State Engineer Jason King is head of the Nevada Division of Water Resources, which oversees dam safety. He said roughly 90 percent of the high-hazard dams in Nevada are in satisfactory condition, the highest rating state inspectors give. King said his department doesn’t keep a ranking of the state’s most hazardous dams. “(But) if we had a top 10 list, I would guess eight or 10 of them are in Las Vegas,” he said.

Thank you, Ron