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Dams putting many at risk

 

Shared from the 11/11/2019 The Denver Post eEdition FLOOD CONTROL

Thousands of aging structures are rated as unsatisfactory or poor condition

By David A. Lieb, Michael Casey and Michelle Minkoff The Associated Press

On a cold morning last March, Kenny Angel got a frantic knock on his door. Two workers from a utility company in northern Nebraska had come with a stark warning: Get out of your house. Just a little more than a quarter-mile upstream, the 92-year-old Spencer Dam was straining to contain the swollen, ice-covered Niobrara River after an unusually intense snow and rainstorm. The workers had tried but failed to force open the dam’s frozen wooden spillway gates. Fearing the worst, they fled in their truck, stopping to warn Angel before driving away without him. Minutes later, the dam came crashing down, unleashing a wave of water carrying ice chunks the size of cars. Angel’s home was wiped away; his body was never found.

State inspectors had given the dam a “fair” rating less than a year earlier. Until it failed, it looked little different from thousands of others across the U.S. — and that could portend a problem.

A more than two-year investigation by The Associated Press has found scores of dams nationwide in even worse condition, and in equally dangerous locations. They loom over homes, businesses, highways or entire communities that could face life-threatening floods if the dams don’t hold.

A review of federal data and reports obtained under state open records laws identified 1,688 high-hazard dams rated in poor or unsatisfactory condition as of last year in 44 states and Puerto Rico. The actual number is almost certainly higher: Some states declined to provide condition ratings for their dams, claiming exemptions to public record requests. Others simply haven’t rated all their dams due to lack of funding, staffing or authority to do so. Built for flood control, irrigation, water supply, hydropower, recreation or industrial waste storage, the nation’s dams are more than a half-century old on average. Some are no longer adequate to handle the intense rainfall and floods of a changing climate. Yet they are being relied upon to protect more and more people as housing developments spring up nearby.

“There are thousands of people in this country that are living downstream from dams that are probably considered deficient given current safety standards,” said Mark Ogden, a former Ohio dam safety official who is now a technical specialist with the Association of State Dam Safety Officials.

“Most people have no clue about the vulnerabilities when they live downstream from these private dams,” said Craig Fugate, a former administrator at the Federal Emergency Management Agency. “When they fail, they don’t fail with warning. They just fail, and suddenly you can find yourself in a situation where you have a wall of water and debris racing toward your house with very little time, if any, to get out.”

Since the Sept. 11, 2001, terror attacks, the U.S. government has cited national security grounds in refusing to include dams’ conditions in its inventory, which was updated most recently in 2018. But the AP was able to determine both condition and hazard ratings for more than 25,000 dams across the country through public records requests.

 The tally includes some of the nation’s most well-known dams, such as Hoover Dam along the Colorado River, but mostly involves privately owned dams. Many are used for recreation.

The AP then examined inspection reports for hundreds of high-hazard dams in poor or unsatisfactory condition. Those reports cited a variety of problems: leaks that can indicate a dam is failing internally; unrepaired erosion from past instances of overtopping; holes from burrowing animals; tree growth that can destabilize earthen dams; and spillways too small to handle a large flood. Some dams were so overgrown with vegetation that they couldn’t be fully inspected.

Georgia led the nation with nearly 200 high-hazard dams in unsatisfactory or poor condition, according to the AP’s analysis.

Among them is Reservoir No. 1 in Atlanta, a 180 million-gallon water supply dating to the late 1800s that has been out of service much of the past few decades. The city made repairs and brought it back online in 2017, only to shut it down again after leaks were noticed.

If the dam were to catastrophically fail, the water could inundate more than 1,000 homes, dozens of businesses, a railroad and a portion of Interstate 75, according to an emergency action plan.

The Atlanta Watershed Management Department declined the AP’s request for an interview about the reservoir and instead asked for questions in writing. When those were submitted, it declined to answer them.

One of the most common problems for aging dams are spillways incapable of handling an extreme rainfall event.

If water can’t escape quickly enough through spillways, it could flow over the top of a dam, which increases the probability of rapid erosion that can cause it to collapse.

The spillway at the 107-year-old Willett Pond Dam near the Boston suburb of Norwood is capable of handling just 13% of the water flow from a serious flood before the dam is over-topped, according to a recent state inspection report. If the dam were to give way, it could send hundreds of millions of gallons of water into the heart of the city of nearly 30,000 people.

“We are not talking of just flooding someone’s house. We are talking about covering their house,” said Murray Beach, who lives on the shore of the 220-acre privately owned lake and belongs to a citizens group that has lobbied for years for the spillway to be repaired.

 

 

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