ST. LOUIS — Early last week, floodwaters in rural Minnesota pushed debris against a dam greater than a century old and carved a path around it, eroding the riverbank so badly that almost all of a house collapsed into the river. Just a few days later, heavy rains damaged a dam that stores drinking water for Houston, forcing authorities to issue a warning of a possible breach.
“Something like this could happen, and it has happened across the country,” said Del Shannon, former president of the U.S. Society on Dams.
There are about 90,000 major dams within the United States. At least 4,000 of them are in poor or unsatisfactory condition and will cause lack of life or harm to the environment in the event that they fail, in keeping with data from the U.S. Army Corps of Engineers. They have to be inspected, upgraded and even emergency repairs.
That's a difficult problem, partially because dams within the U.S. are about 60 years old on average. Protecting the dams from many years of damage and tear requires costly maintenance, and resources to repair the issues are sometimes scarce, Shannon says.
Blue Earth County owns the Rapidan Dam, a 1910 hydroelectric dam in Minnesota that also stands but was badly damaged last week within the second-worst flood in its history. The dam has not produced electricity since previous floods dried up that small income. The county of about 70,000 residents had considered spending $15 million on repairs or demolishing the dam at a price of $82 million.
“The dollar amounts we’re talking about are large amounts for a county our size,” said County Administrator Bob Meyer.
A government inspection in May found no major defects within the Rapidan Dam, which doesn’t pose a significant threat to the general public within the event of a complete failure. A government investigation is now expected. During floods, debris clogged the dam and compelled the river to flow around it. The damage was likely not related to the dam's need for repairs, Meyer said.
Dams are designed to resist great stress, but sometimes one flood is simply too much and causes damage, says Martin McCann Jr., director of the National Performance of Dams Program at Stanford University. Climate change could exacerbate the issue in some parts of the country. A warming atmosphere retains more moisture, allowing heavy rainstorms to release more water.
In Texas, officials said flooding had damaged the spillway of the Lake Livingston Dam about 65 miles northeast of Houston. They assured the general public that the dam was not in imminent danger of breaking.
The overwhelming majority of dams are protected, and even when one fails, fatalities rarely occur. But large dams store enormous amounts of water and energy and subsequently have enormous potential for destruction downstream. That's why even rare problems are of such concern to state and federal regulators.
In 2017, for instance, heavy rains damaged the spillway on the Oroville Dam in California, forcing nearly 190,000 downstream residents to evacuate. And after storms in 2020, the Edenville Dam in Michigan burst. Water rushed downstream and overwhelmed one other dam, causing it to fail as well.
John France is an engineering consultant who led the teams that investigated each incidents. He said that when many dams were built many years ago, engineers had less knowledge about how you can withstand flooding. And although many dams were built removed from populated areas, circumstances modified as towns and villages spread.
“The danger is gradually increasing,” France said.
After his teams' research, he has seen some improvements. The Federal Energy Regulatory Commission, which issues hydroelectric licenses, has been conducting more thorough inspections that search for weaknesses within the design and construction of dams. Some states have already considered implementing such reviews, and France hopes FERC's more comprehensive approach will probably be expanded to state oversight programs.
Most dams are privately owned and there is a large need for resources — repairing lots of the nation's major dams alone could cost $34 billion, in keeping with a report from the Association of State Dam Safety Officials. Minnesota, for instance, regulates about 1,000 dams and contributes among the funding, but officials said there may be “a gap between demonstrated need and available funds.” The Biden administration's infrastructure bill provided a rare push for improvements. Dam owners are chargeable for the protection of their dams and might be held liable if something goes unsuitable.
“We're one step away from having bake sales to help dam owners,” joked John Roche, board member of the Association of State Dam Safety Officials. State agencies are attempting to assist owners find grants so that they can afford improvements. There is help, but the necessity is even greater.
In southeastern Nebraska, the Nemaha Natural Resources District covers eight counties and collects about $4 million annually in a small property tax. It uses that cash to take care of about 380 structures – the overwhelming majority of that are dams – including Wilson Creek Dam 9-C, an 840-foot-long earthen structure in-built the Sixties for flood control.
“Funding is probably our biggest struggle,” said district general manager Kyle Hauschild.
After a poor inspection end in 2022, the district rushed to repair a rusty spillway on the Wilson Creek Dam. The district keeps a maintenance list and prioritizes older structures, but when the general public doesn't see an issue with a dam, it tends to ignore it, Hauschild said.
States have limited power to pressure owners to repair problems. Roche said regulators attempt to work cooperatively, but when that doesn't work, they may also pressure owners through more confrontational enforcement proceedings.
“It requires great care to pursue enforcement actions as they can often take many years to resolve,” Roche said.
In Colorado, regulators consider whether a dam poses a threat to humanity and the severity of its deficiencies to assist them set review and funding priorities.
If an owner doesn't make the required improvements, authorities can hit with a “regulatory hammer,” forcing owners to store less water behind their dams to cut back pressure and ensure safety. That can trigger motion — less water in a reservoir, for instance, can affect dam owners' ability to deliver water to the communities they serve, said John Hunyadi, who oversees dam safety in Colorado.
But in lots of states, authorities cannot order the worst owners to demolish their dams, France says.
“All government agencies should have that authority,” he said, adding that the state must have the facility to accomplish that itself if a property owner refuses.
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