Lakes are getting saltier, study finds
Winter’s last chilly gasps yielded to spring warmth a while ago, but an unfortunate part of its legacy lives on in the region’s ponds and lakes now beckoning boaters and swimmers.
Rock salt and salt brines, applied to help keep roads clear of snow and ice, linger in the environment long after they have served their public safety purpose, blurring the line between fresh and salt-water bodies.
“We have a legacy of salt in the environment built up over the last 70 years,” said Hilary Dugan, researcher at the University of Wisconsin-Madison’s Center for Limnology and co-author of a recent study quantifying salt levels in Northeast lakes. “You get a strong pulse when the snow melts that can push levels extremely high, but there’s also a lot of salt stored in the soil surrounding lakes that continues to act as a reservoir supplying salt to lakes.”
Dugan’s study, published in the Proceedings of the National Academy of Sciences in April, quantified salt concentrations in 371 North American lakes, including some in Connecticut. The largest study of its kind, it found a dozen lakes with levels exceeding the Environmental Protection Agency’s threshold for aquatic water quality, and virtually all lakes showing long-term trends of increasing saltiness since the 1970s.
The study also confirmed what may seem an obvious point: the most urbanized lakes surrounded by the most pavement have the highest salt levels, and the most rural lakes tend to have the lowest. But even very rural lakes have been getting saltier.
“The more impervious surface around a lake, the higher the risk,” Dugan said. “We don’t have an alternative to using road salt, but we need to be aware that if you use road salt, it’s going to end up in the environment.”
The salt, she said, stays in lakes and ponds for varying time periods, depending on the size and the amount of water moving from the source streams to the outflow. Generally, larger lakes hold salt longer — for periods of months or years.
Chris Bellucci, supervising environmental analyst for water protection and land reuse for the state Department of Energy and Environmental Protection, said the study is consistent with water quality test data from Connecticut lakes, as well as rivers and streams.
“It’s a wake-up call that we need to pay attention to how much salt we’re using,” he said. “Once it’s applied, it doesn’t go away. It’s a balance between public safety and the environment.”
Ponds and lakes around the state are sampled at least once every five years, and while none are yet showing levels at the EPA threshold, the trend is worrisome, he said. State and town highway crews and private contractors are reducing salt use with better equipment, mixes of salt-molasses and salt-lignin (an organic tree extract) that adhere better to roads, and limited applications around public drinking water reservoirs and other sensitive areas. But more education is needed, he said.
“It’s something we need to make people aware of,” he said.
Lakes monitored in East Lyme, Salem
Data collected by DEEP for two southeastern Connecticut lakes demonstrates what’s being found statewide. At Pattagansett Lake in East Lyme, testing in 2016 showed a salt concentration of 28.4 mg/liter — well below the EPA threshold level of 230 mg/liter, but saltier than a fresh water lake should be.
At Gardner Lake in Salem, where a state park draws thousands each summer to its swimming beach and boat launch, water quality tests showed similar results. Two rural southeastern Connecticut lakes in Dugan’s study, Wyassap Lake and Spalding Pond, both in North Stonington, salt measured at 10 mg/liter.
At Rogers Lake in Lyme and Old Lyme, the lake authority is aware of the growing concern about salt in lakes and is hoping to sponsor some water quality testing to measure it, said Dennis Overfield, chairman of the group. Since the lake’s 4,200-acre watershed is more than 90 percent forest, he expects salt levels will be relatively low.
“But we need data, because this can be an issue with runoff from the roads,” he said.
Michael Dietz, associate extension educator with Connecticut Sea Grant and the Department of Extension at the University of Connecticut, has worked on several studies looking at impacts of salt, including in groundwater that supplies drinking water wells, with hydrogeology Professor Gary Robbins of UConn’s Department of Natural Resources and the Environment. The effect on fresh water bodies, he said, has been a decline in amphibian and plant species most sensitive to salt, and increases in invasive species that fill the void. Even trees are being weakened by high salt in the environment.
“Everything is trending upward for salt in lakes, rivers and groundwater,” Dietz said. “There are generally no good findings in these areas.”
Both he and Dugan said the findings point to the need to reduce salt use as much as possible, and to rely more on pushing snow off the road mechanically rather than trying to melt it as soon as possible. Private contractors who clear parking lots at stores, offices and condominiums, in particular, Dietz send, tend to over apply.
“They apply so much because they’re so concerned about lawsuits from slips and falls,” Dietz said. “But you can apply twice as much salt without getting twice as much protection from slips and falls.”
A program in New Hampshire, he noted, trains contractors in how to use less salt. In exchange for completing it, the contractors can’t be sued for slip and fall injuries.
“The best thing you can do is to try to minimize the use of salt,” he said.
Less salt in Groton
At Groton Public Utilities, several of the reservoirs that supply drinking water abut major roadways including Interstate 95 and Route 117. Rick Stevens, manager of water utilities, said the upward creep of salt showing up in water tests caused the utility to contact the town road crew and the state Department of Transportation to ask for reduced salt use around the reservoirs. The DOT this year also cleaned out clogged detention basins that collect runoff, he said. This summer, the utility will clean out a clogged basin on Route 117 near the Smith Lake reservoir.
“We also gave maps of the watershed to all the plow drivers,” he said, so they can limit salt use in the most sensitive areas.
The utility is also trying to get the word out to local contractors to reduce salt use, and now routinely reviews plans for new parking lots and roadways to ensure they’re designed properly to allow for reduced salt use.
While retention ponds can collect other contaminants before getting into waterways, Dugan noted, “they aren’t super effective for salt,” so the best solution is to use less.
“Salt stays dissolved in the water,” she said. “Nothing takes it out.”
Salt, said Richard Canavan of Pomfret, past president of the Connecticut Federation of Lakes and senior environmental scientist with Tighe & Bond, is one of several stressors on lakes. In recent years, invasive plants and algae blooms have been attracting the most attention, but there is growing awareness about the hazards of salt, he said.
“Better road maintenance and proper drainage can reduce the amount of salt we use,” he said. “Salt is a slow stressor that’s changing the ecology of lakes and ponds. If you can use less salt, you should.”
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