This overflowing dam swept away a family's legacy. It's a growing risk across the US

A few miles outside Mankato, Minnesota, painted blue and white with a vintage Pepsi sign hanging out front, the Rapidan Dam store stood for more than 50 years.

That’s how long Jenny Barnes and her family owned the store, set just back from the landmark dam on the Blue Earth River. Their store was a local favorite, but they’ve also had tourists from as far away as Alaska. Work has always started early here; on a typical night, shortly after midnight, Barnes would be busy preparing and baking pies for the next day.

That’s where she was at 1:32 a.m. on June 24 when she heard the first explosion. She looked outside and saw not fire, but water.

"We noticed water in the parking lot,” she said. She had lived alongside the Blue Earth River for 50 years, and never seen water that high.

The explosion, Jenny and her neighbors believe, was the sound of a transformer breaking. Rapidan Dam, an earth-and-concrete structure and electrical generating station, built in 1910, had begun to overflow.

The past week of rainy days had brought as much precipitation as that part of Minnesota normally sees in an entire summer. Now, water was pouring past one edge of the dam and downstream, toward the store.

In the dark, Barnes and her husband tried to rush toward the dam but found the way hindered by rising water. It had already passed the parking lot and was rising toward her childhood home next door. She knew her father and brother were inside, asleep.

Federal inspection reports show the dam was rated in “poor” condition as of its 2022 inspection, the second-worst possible rating.

The next inspection wasn’t due until 2025, so its condition this year isn’t known. But the records also show one other thing, something Barnes already innately understood: The dam’s hazard rating, meaning the amount of damage it would cause if it failed, was “significant,” meaning if the dam fails, the flood is likely to harm the environment, or structures.

In 2022, a USA TODAY investigation identified more than 3,000 U.S. dams in poor or unsatisfactory condition that are likely to destroy property or kill people if they fail. Another 7,000 dams had no condition rating, even though they’re in places where they endanger lives and structures. All of them are also predicted to face stress from increasingly severe rainfall .

Upmanu Lall, a professor of Engineering at Columbia University and director of the Columbia Water Center, has raised concerns over dam safety in the U.S. According to Lall, approximately 500 dams have failed across the country since 2000.

Often, worries boil down to the broad idea of climate change. “That’s become the bogeyman for everything,” Lall said. “The real issue here is we are not paying attention to these issues, not addressing them, and not putting the money in to address them.”

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Most of those failures, he said, were because of “overtopping” — in essence, water backs up more quickly than the dam can release it, until it flows over the top or sides uncontrolled.

"When you talk to regulators or engineers," Lall said, "they’ll tell you that these dams are engineered to withstand the probable maximum precipitation.” That benchmark for dam design predicts the most intense rainfall, and builds a dam prepared to face it.

At Rapidan Dam, the rainfall happened not just in one storm, but as a cumulative rainfall over several days.

“It's definitely an extreme,” said Tyler Hasenstein, meteorologist from the National Weather Service in Chanhassen. “It was about a summer average, about as much rain fell in the week prior to when all of the flooding started happening.”

Like so many other dams, Rapidan – which is run by Blue Earth County – saw overtopping after intense rainfall . The rain, though, was not the only problem.

The dam, built as a generating plant, had seen its powerhouse equipment damaged in a 2019 flood. Since then, according to a memo a Blue Earth County official sent to federal regulators, the power plant itself was inoperable. The dam’s spillway gates had been locked open to let water flow freely past.

But the three years before 2024 had been dry. A large amount of fallen dead trees had accumulated in the river valley upstream. Instead of those logs washing away slowly, the heavy rainfall that week pushed years’ worth of debris downstream all at once.

The result was dead tree trunks blocking five of the gates at Rapidan Dam, choking off the flow through the open gates and backing up water at the same time an extraordinary amount of rainfall was rushing downstream.

Dams fail across country

Summer rainfall has triggered dam failures, overflows or near-misses across the country.

In early July, the Little Wolf River overflowed Manawa Dam west of Green Bay, Wisconsin, after a morning that brought almost 6 inches of rain. The overtopping caused major flooding downstream and triggered the evacuation of a 1,400-person town even though the federal dam inventory lists its hazard rating as low. That dam was listed in satisfactory condition as of 2019.

Later that month, local officials in Nashville, Illinois, warned of an imminent dam failure after a 6-inch rainfall as the Nashville City Reservoir Dam overtopped. Some residents reported waist-high water in the flooding at the time. (That dam’s condition was listed as not available in the most recent records, but its hazard level is high, meaning it is likely to be deadly if it breaks.)

Two dams breached in early August in Bulloch County, Georgia, as heavy rain fell from Tropical Storm Debby.

Lall emphasized that many recent dam failures have been triggered by relatively moderate rainfall, raising critical questions about current dam design standards and their ability to cope with even ordinary weather conditions.

He likens a dam and reservoir to a bucket. If it starts out empty, it can take a significant amount of rain and not overflow.

But if the bucket is already full, he said, “even a modest amount of rain can lead to a quick overflow.”

In several dam disasters in recent years, “they were just keeping water levels high, and when it rained more than a little bit, they overtopped,” he said. “That's the more common story of what's actually going on.”

The results mean more families may face sudden disasters like the one that swept through Jenny Barnes’ life that rainy June night.

“You knew things were going to happen,” she said, “but never in a million years.”

How Rapidan Dam overflowed

At Rapidan Dam, the people around Barnes saw the disaster unfolding, too. Jeremy Jordan, who lives nearby, says he used to work on the dam’s power plant as a fill-in employee. He said he could see the debris clogging the dam’s outlet in the days before the flood, and claims the operators didn’t do enough to keep those outflows open.

“They knew the water was going to climb higher.  They knew they had significant blockage in the gates,” he said.

In memos to energy regulators, Ryan Thilges, the Blue Earth County public works director, described how county employees had been monitoring the dam daily. They saw masses of downed trees lodged against a bridge just upstream, and noted that some logs that broke free managed to work their way through the open spillway gates.

Blue Earth County officials had reported efforts to remove debris the Friday before the incident. However, contractors hesitated, citing concerns for worker safety and placing equipment on the dam. It would have required operators to go directly on top of the structure to clear the debris— a risk they weren’t willing to take.

County Administrator Bob Meyer also told USA TODAY that his team was closely monitoring the dam throughout the weekend. On Sunday, June 23, staff went to the site after reports that the reservoir was filling up.

Meyer said the dam, even in normal operation, doesn’t retain much water. Its hydroelectric systems failed during an earlier flood, so the gates are now left fully open.

Meyer said inspections over the weekend showed sufficient water flow through the gates. He said the masses of trees had been clogged against a bridge piling, and that once those logs began clogging the dam, it was too dangerous to operate heavy equipment above the rushing water to try to clear them.

“There was significant risk to human life,” Meyer said. “And so to me, it was a natural disaster.”

Under an emergency action plan, with notifications issued as water flows reached critical thresholds. On Friday, June 21, alerts were triggered when flows hit 10,000 cubic feet per second. By Sunday, June 23, with flows reaching 15,000 cubic feet per second, another set of notifications went out. Then, early on Monday, June 24, at around 3 a.m., residents downstream were alerted to the potential for a dam failure. "We followed that emergency action plan," Meyer said.

As the water rose, it reached the edges of the dam. The east side, as described in the county’s memo, is solid rock, but the west side of the dam is pure topsoil and easily eroded.

Lall, the Columbia University expert, believes the Rapidan flood was an operational and infrastructure failure. “This is obviously an operational maintenance issue. They should not have had this happen.”

In what felt like seconds, the river claimed the Barnes's family's two acres of property.

With only 15 minutes to salvage 15 years’ worth of belongings, Barnes saw her community start to rally. Neighbors and firefighters came together to retrieve clothes, family picture books and their business’s paperwork.

As the water continued to pour past the dam, the county took another emergency measure. It bought the structure of the Rapidan Dam store from Jenny Barnes’ family. On Friday, just a few days after Barnes first heard the explosion, the county had crews demolish the store and haul it away, to prevent it from becoming dangerous debris downstream.

Word of the devastation quickly spread through the community. In the days following the flood, neighbors rallied around the Barnes family, launching a fundraising campaign with "Dam Store Strong" shirts and donations to the family.

As the flood abated, the Rapidan Dam Store was gone – its vintage sign, its 50 years of memories.

Rapidan Dam remains in place, but the Blue Earth River now rushes around it in the new channel it scoured from the earth. County officials are now debating whether to leave the eroded dam in place, tear it down or replace it.

As for Jenny Barnes’ family, the Rapidan Dam Store is set to reopen in a building in downtown Mankato.

Looking back, though, Barnes knows that some things are gone forever. Cherished childhood keepsakes, irreplaceable documents.

"It's a huge loss,” she said. “A house that you grew up in. There are things, memorable things, that money can't replace."

This article originally appeared on USA TODAY: This overflowing dam swept away a family's legacy. It's a growing risk across the US