Brad Cornelius didn’t know what to make of the letter he received at home in late December warning that the levels of “total trihalomethanes” in his water exceeded state standards.
Like other public water systems, South Hero Fire District 4 is required to test its water every three months for the toxic by-products of chemical disinfectants, including trihalomethanes. The results are reported to the Department of Environmental Conservation; if there is a violation of state standards, the water district must let its customers know immediately.
That job often falls to the volunteers who run small water districts and use jargon-heavy templates from the state to let residents know about violations.
“This is not an emergency,” the South Hero district’s letter cautioned Cornelius and 370 other users, before adding that “some people” who drink water containing trihalomethanes over a long period of time “may experience problems with their liver, kidneys, or central nervous systems, and may have an increased risk of getting cancer.”
Cornelius, whose two children are 9 and 12, was spooked. He purchased enough bottled water to last his family a few days and took to a town Facebook group to compare notes.
“This is unsettling,” one neighbor posted.
“Ken is doing the best he can,” Cornelius told Seven Days, referring to the fire district’s chair, Ken Little. “But I’m frustrated. We are paying for water that we can’t necessarily safely drink.”
Cornelius and his neighbors are not alone in their confusion and concern. The number of public drinking water systems in Vermont with elevated levels of disinfection by-products has notably increased in recent years. And while the problem is fixable, it requires expertise and expensive equipment that districts run by volunteers can’t always provide.
“Climate change is going to continue to impact how we operate our treatment plants.” Joe Duncan
Scientists link the trend to climate change. Extreme flooding and warmer winters mean more organic matter is being washed into rivers and lakes. When chlorine is added to ensure drinking water is pathogen-free, it interacts with the organic material in a way that creates toxic chemicals such as trihalomethanes.
State health officials say most Vermonters have nothing to worry about — the risk comes only from long-term exposure to trihalomethanes. Still, these situations could affect many of the public drinking water systems that serve 60 percent of Vermonters.
“Climate change is going to continue to impact how we operate our treatment plants,” said Joe Duncan, general manager of the Champlain Water District, the state’s largest, which draws water from Shelburne Bay and distributes it to 83,000 people. “The resources and the technology and the level of operation necessary are just going to get more and more complex.”
Bridget O’Brien, radiological and toxicological analyst for the Vermont Department of Health, said all treated drinking water contains some level of disinfection by-products.
The trouble isn’t dealing with sediment and other visible pollutants, which water systems can filter out. Instead, “This is an interaction at a very small, molecular scale,” said Ben Montross, drinking water program manager at the state Department of Environmental Conservation.
About 400 public water systems statewide test for disinfection by-product, and it’s not only systems that depend on Lake Champlain water that have been affected. The city of Rutland, which draws from Mendon Brook, has had to manage elevated levels for years.
A flood’s effect on water systems is not necessarily immediate, making it difficult to measure. “It’s not as simple as saying there was a storm on this day and it had this quantifiable effect on our drinking water,” Montross said. “This is happening on a watershed scale.”
The number of violations in Vermont has been on the upswing. None were noted in 2022. But the next year, seven violations were logged across six water systems. Preliminary data for 2024 count 25 violations across 12 water systems, according to Montross.
Below a certain threshold, the state considers the by-products to pose no health risk. But when consumed at elevated levels over long periods of time, they can lead to cancer.
“We’re talking about exposure over a number of years,” O’Brien cautioned. “Because we have regulations, those health risks are unlikely.”
Standards are set state by state. Indrajit Kalita, a researcher at Boston University who studies disinfection by-products, said Vermont’s limits are in line with national regulations. However, his research shows that a slightly lower threshold would provide an “added margin of safety” for consumers.
The state advises pregnant women, young children and immunocompromised people to consider switching to bottled water when limits are exceeded, as just happened in South Hero. O’Brien, the health department analyst, said home carbon filters such as Brita have been shown to remove disinfection by-products.
Water plant managers can also employ strategies to address higher-than-acceptable levels. One option is to switch from chlorine to monochloramine, a related disinfectant that kills bacteria but results in fewer by-products.
That’s what the Champlain Water District did in 2006. “We’ve been able to keep the process under control through careful adjustments,” Duncan said. However, installing a monochloramine disinfection system is costly.
Another option is to install a carbon filter at a water plant to remove much of the organic matter before the water is treated with chlorine. Like the monochloramine solution, carbon filtration is expensive.
The Grand Isle Consolidated Water District, which serves about 1,600 people, invested in a carbon filter system in 2015 after a number of disinfection by-product violations. For almost a decade, the upgrade worked. But last fall the numbers went up again. Janine Banks, a water district commissioner, blames increased flooding.
The water district board decided to replace the aging carbon filters to see whether that solved the problem. Easier said than done. “It’s not something you can just call and schedule to have happen next week,” Banks said. Changing the filters costs north of $25,000 and requires sending water samples to a lab.
With a staff of more than 40 people, the Champlain Water District hasn’t had a disinfection by-product violation in decades. Duncan is acutely aware that part of the reason is that his team has the workforce and resources to respond quickly when a potential problem arises.
Meanwhile, Little, who is retired, dedicates hours of unpaid work each week to dealing with issues related to the South Hero district’s water treatment. While the district outsources management to a private company, rapid response and decision making fall to a five-person volunteer board.
“Nobody runs for this position,” Little said with a laugh. “But it’s pretty important.”
It’s a reality that worries experts who foresee a future in which water quality management becomes increasingly complex.
“There’s a real lack of capacity,” said Liz Royer, executive director of the Vermont Rural Water Association. “Small towns and fire districts are struggling to even complete applications for funding that might help them.”
In South Hero, the path forward is not entirely clear. In 2018, the fire district invested more than half a million dollars in system upgrades which included changing the chemical treatment process. Just like Grand Isle’s upgrade, the solution seemed to work until last year.
Last week, Little discussed a permanent solution with Ray Solomon, an environmental scientist at the state Agency of Natural Resources. Solomon offered some possible next steps but warned in an email that “none of these alternatives are simple and all would require professional engineer design.”
For now, Little is monitoring the treatment plant and answering his neighbor’s questions.
Cornelius, meanwhile, has purchased a $700 carbon filtration system for his family’s home. It is supposed to reduce disinfection by-products in drinking water by more than half.
“It’s a lot of money,” he said. “But for peace of mind, I think it’s worth it.”
The original print version of this article was headlined “Something in the Water | Increased flooding creates problems for public drinking water systems around Vermont”
This article appears in Jan 29 – Feb 4, 2025.
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