ST. LOUIS — Early last week, floodwaters in rural Minnesota pushed debris against a more than century-old dam and then a path has been carved out around itwhich washed away so much of the riverbank that most of a house collapsed into the river. Several days later, heavy rains damaged a dam that held drinking water for Houston, prompting officials to issue a warning of possible failure.
“Something like this could happen, and it has happened, all over the country,” said Del Shannon, former president of the American Society on Dams.
There are approximately 90,000 major dams in the United States. According to data from the U.S. Army Corps of Engineers, at least 4,000 are in poor or unsatisfactory condition and could cause loss of life or simply harm the environment if they fail. They need inspections, upgrades and even emergency repairs.
It’s a tricky problem, in part because dams in the U.S. are on average about 60 years old. It requires costly maintenance to counter decades of wear and tear from degrading dams, and resources to fix problems are often scarce, Shannon said.
Blue Earth County owns the Rapidan Dam, a 1910 hydroelectric dam in Minnesota that still exists, but has been demolished. badly damaged last week by the second-worst flood in its history. The dam has not produced power since previous floods wiped out that small source of revenue. The county of about 70,000 people considered spending $15 million on repairs or removing the dam at a cost of $82 million.
“The amounts we’re talking about … are significant amounts for a county of our size,” said County Administrator Bob Meyer.
A federal inspection in May found no major problems at the Rapidan Dam, which is not considered a major hazard to people if it fails completely. A federal investigation is now expected. Debris clogged the dam during the floodforcing the river to flow around it. The damage was likely unrelated to the dam repairs, Meyer said.
Dams are designed to withstand a lot of stress, but sometimes a flood is too much and causes damage, says Martin McCann Jr., director of the National Performance of Dams Program at Stanford University. Climate change could make the problem worse in some parts of the country. A warming atmosphere holds more moisture, so heavy rains can release more water.
In Texas, officials said flooding has damaged the spillway at the Lake Livingston Dam about 65 miles (105 kilometers) northeast of Houston. They assured the public that the dam is not in immediate danger of failing.
The vast majority of dams are safe, and even when one fails, fatalities are rare. But large dams hold back enormous amounts of water and energy, so they have enormous potential for destruction downstream. That’s why even rare failures are such a concern for state and federal regulators.
For example, in 2017 there was heavy rainfall the overflow is damaged at California’s Oroville Dam, forcing nearly 190,000 residents downstream to evacuate. And after storms in 2020, the Edenville Dam in Michigan. Water rushed downstream and overwhelmed another dam, causing it to collapse as well.
John France, an engineering consultant who led teams investigating both incidents, said that when many dams were built decades ago, engineers knew less about how to design them to withstand flooding. And while many dams were built far from populated areas, circumstances changed as cities and towns spread.
“The danger is gradually increasing,” France said.
After his teams’ investigations, he’s seen some improvements. The Federal Energy Regulatory Commission, which licenses hydroelectric dams, has added more thorough inspections that review a dam’s design and construction to find weaknesses. Some states have considered including these reviews, and France hopes FERC’s broader approach will extend to state regulatory programs.
Most dams are privately owned, and the need for resources is enormous — repairing many of the nation’s major dams alone could cost $34 billion, according to a report from the Association of State Dam Safety Officials. Minnesota, for example, regulates about 1,000 dams and helps provide some funding, but officials said there is “a mismatch between demonstrated need and available funds.” The Biden administration’s infrastructure bill provided a rare boost to upgradesDam owners are responsible for the safety of their dams and can be held liable if something goes wrong.
“We’re one step away from having bake sales to help dam owners,” joked John Roche, a board member of the Association of State Dam Safety Officials. State officials are trying to help owners find grants to help pay for improvements. Help is there, but there’s more need.
In southeastern Nebraska, the Nemaha Natural Resources District covers eight counties and collects about $4 million a year from a small property tax. With that money, it maintains about 380 structures, the vast majority of which are dams, including Wilson Creek Dam 9-C, a roughly 840-foot-long (255-meter-long) earthwork built in the 1960s for flood control.
“Funding is probably our biggest challenge,” said district Executive Director Kyle Hauschild.
After a bad inspection in 2022, the district rushed to fix a rusty spillway at the Wilson Creek Dam. The district keeps a maintenance list and prioritizes older structures, but if the public doesn’t see a problem with a dam, it usually forgets about it, Hauschild said.
States have limited power to pressure owners to fix problems. Roche said regulators try to work together, but if that doesn’t work, they can pressure owners by launching more confrontational enforcement proceedings.
“It takes a lot of dedication to keep enforcement actions going, as they can often take years to resolve,” Roche said.
In Colorado, officials consider whether a dam poses a threat to people and how serious its flaws are, helping them prioritize monitoring and funding.
If an owner doesn’t make needed upgrades, officials can wield a “regulatory hammer” and force owners to store less water behind their dams, relieving pressure and ensuring safety. That can trigger action — less water in a reservoir can hurt dam owners’ ability to deliver water to the communities they serve, according to John Hunyadi, who oversees Colorado’s dam safety department.
But in many states, officials cannot order the worst-off owners to remove their dams, France said.
“All state bodies should have that authority,” he said, adding that if an owner refuses, the state should be able to do it itself.
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Hanna reported from Topeka, Kansas.
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