An anonymous “concerned citizen” called the Memphis field office of the Tennessee Department of Environment and Conservation in January to lodge a complaint: water was running from a nearby lake onto his property. A few days later, a dam safety inspector uncovered a 25-by-40-foot breach developing in the earthen dam on neighboring land — one that could ultimately “cause total failure of the structure,” according to a notification letter sent to the owner. They advised the owner to permanently drain the pond or repair it.
But the letter was a courtesy, not a command.
This “farm pond,”an earthen dam used to hold water for agricultural purposes, qualifies as “high-hazard,” which means if it were to fail, at least one death would likely result. Its structural problem was caught before that happened, thanks to a worried neighbor and a vigilant state regulator — though it had no emergency action plan and no required state or federal oversight to ensure it was fixed.
“I have no idea what their status is — it’s a concern,” said Terrell Hendren, who oversees safety inspections for state-run dams in Tennessee. “Personally, I wish we could regulate [farm ponds].”
Dams can take many forms: The largest ones in Tennessee, operated by the Tennessee Valley Authority and federally regulated, are made mostly from reinforced concrete and provide electricity, flood control, and navigation. But more than half of dams in the U.S. are privately owned by farmers, companies, and landowners; they’re often smaller and made from earth and rock. One of the most common types are farm ponds, and Tennessee’s Safe Dams Act of 1973 exempts all 170 of them from regulation. Over 40% are considered high-hazard.
The exemption exists in part to protect private landowners from being subject to the same rules as larger, public-purpose dams. However, that means owners determine safety requirements without an obligation to plan emergency response. Private dams in Tennessee also have no spillway requirements, which outline how water is safely released in the event of a structural failure or flood.
People may not even know they’re buying property, living, working, or commuting in the vicinity of a dam, potentially in harm’s way. Private dam regulations are a patchwork of rules that vary by state. Several, including Texas, have some kind of exemption for regulating them, according to a 2019 congressional report on the federal role in dam safety. Alabama has no dam safety legislation at all.
“We don’t like those exemptions,” said Bill McCormick, president-elect of the Association of State Dam Safety Officials. “We advocate in those states to say this is a mistake with respect to public safety.”
An investigation last year by the Associated Press found that over 1,680 dams in the U.S. are considered high-hazard because they are aging or don’t have emergency action plans. Tennessee has about 123 dams regulated by the state that are in the high-hazard category and built before 1970, according to the U.S. Army Corps of Engineers database.
The state’s private dams are, on average, 60 to 70 years old. As dams in Tennessee and across the country are increasingly stressed by extreme weather like rainfall and flooding, there’s a renewed urgency to make them safer and update guidelines. Hendren acknowledged that Tennessee still uses the National Oceanic and Atmospheric Administration’s (NOAA) 1999 guidance on climate and weather conditions to determine spillway requirements, which are central to dam safety.
Aging dams that were state-of-the-art when they were built should be checked for adequacy in view of the increases in our scientific knowledge, McCormick said. Recognizing that most states were relying on decades-old data, the Association of State Dam Safety Officials, submitted testimony to Congress in February underscoring “a clear need for NOAA to resume a leadership role toward developing 21st century national standards for estimating extreme rainfall … in a changing climate, in order to ensure consistent public safety in the future, across all states.”
An influx of people and businesses add more layers of risk. The South is the fastest urbanizing region in the country, and Tennessee has for years been above the national average for population growth, mostly due to an influx of migration from other states. Urbanization means both more people potentially living and building downstream from dams — and also more concrete. “Once you start paving roads and parking lots runoff is much greater, so inflow to dams can be much greater,” said Martin McCann, director of the National Performance of Dams Program at Stanford University.
Some states are starting to address these challenges. A 2018 study in Colorado and New Mexico, which looked at the effects of extreme precipitation on dams, demonstrated a clear need to consider higher maximum rainfall levels when assessing safe dam practices in new construction and in the rehabilitation of old dams. Colorado did so after the study was published. McCormick, who also oversees dam safety there, said the study shows how the industry is “waking up” to climate change effects and how they could impact dam infrastructure.
McCormick said an update might include changing the design criteria for spillways; this could reduce erosion problems that cause many earthen dams to fail. New strategies are needed to address these risks, but every dam is different, in structure, size, age, and purpose. While calculating weather conditions into new dams is fairly simple, it can be more challenging — and expensive — to retrofit existing dams. That’s often unaffordable for private dam owners who sometimes rely on their own pockets or fees from housing authority associations.
McCormick says the dam safety organization’s advocacy efforts are an attempt to push for more uniform guidance at a national level, to mitigate the current patchwork of rules. The organization offers resources and training, and advocates for legislation and funding. “It’s an awareness and a funding issue,” he said.
There is a more immediate way to lessen some of the risk surrounding aging and unregulated dams: Ensure all high-hazard dams have an updated emergency action plan, which details what steps owners should take in the event of an incident and includes contact information for area officials and people living downstream. The plan should also include an updated flood inundation map.
The emergency action plan is “a big deal,” McCann said. “Trivial though it sounds, even very simple things like phone numbers, names of people, have to be updated every year.”
The database of Tennessee’s state dam inspections shows a rigorous level of inspections and compliance, with only two dams cited as “out of compliance” and being remediated as of early April. Hendren said emergency plans “have got to be a living organism” to ensure public safety. He has sufficient manpower to manage inspections, but many of the emergency action plans are “antiquated” and keeping them updated requires more resources and funding that most states don’t have.
This means the system largely relies on members of the public to do their own research about whether they are near a private dam or in a flood zone, using publicly available — though not always easily accessible — inundation maps.
Until regulations change to prioritize emergency action plans for both state-regulated and private dams, the risk of incidents and failures creeps up. Failures of farm ponds without loss of life have happened in Tennessee, Hendren said, but there’s no reporting requirement, so exact numbers are unknown.
The owner of the Memphis-area dam with the breach risk responded in an email to the state regulator, assuring them he had “lowered the water level by about 2 feet, to below the breach level.” The Memphis inspector, Cliff Caudle, confirmed that the lake could refill, again threatening a breach. “There are at least two homes in the near downstream,” he said. Those living nearby, and motorists, “could be impacted by a catastrophic failure of the dam.”
For now though, there’s nothing more he can do.
Melanie Faizer is a senior lecturer in journalism at the University of Tennessee in Knoxville, where she teaches courses in reporting, editing, and media entrepreneurship. She previously worked for Bloomberg News.