High levels of road salt in Pa., N.J., Del. pollute streams months past winter

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Road salt used last winter, and possibly decades ago, is still contaminating waterways across the region. In many cases, the levels exceed federal standards for maintaining healthy aquatic life and safe drinking water, according to a recent citizen-science survey.

During the first two weeks of October, hundreds of volunteers fanned out across the region to test salt levels in 1,200 locations, mostly small streams. Led by Stroud Water Research Center, the citizen scientists, from dozens of partner groups, wanted to know how much of the road salt spread during past winter storms remains months, or even years later.

The results were stark. Of more than 700 locations sampled, 61% exceeded aquatic life thresholds set by the Environmental Protection Agency. Sixty-four “hotspots” had levels greater than 230 milligrams per liter, a guideline set by the EPA at which water begins to taste salty. Sixty percent of samples blew past the accepted healthy drinking water standard for those on a low-salt diet of 50 milligrams per liter.

The nationwide effort was coordinated locally by the Stroud Center in Chester County. Known as the “Fall Salt Snapshot,” it marked the first time this type of data was collected during several weeks in October, rather than the annual winter salt snapshot conducted in January. The winter snapshot has revealed some local waterways that were twice as salty as seawater.

“We’re addicted to what road salt gives us,” said John Jackson, a senior scientist at Stroud. “It’s cheap and it really makes it possible to drive fast and safely in the winter.”

But Jackson said environmental and health costs have not been part of the conversation.

“If we continue to use road salt at the rate we’re using it, then every winter we’re going to take freshwater out of the ground as a normal cycle and replace that fresh water with saltwater. That’s what we’ve been doing for 50 years. That’s why our streams are salty in July and August, September, October, November, December, before we ever apply any more salt.”

The amount of road salt used each year in the U.S. has doubled since 1975, according to Penn State, resulting in a current annual estimated use of 15-32 million metric tons of road salt.

Pennsylvania’s streams are often fed by groundwater more than rain water, making them vulnerable to damage by salt that has run off and accumulated in aquifers.

That salt depletes the oxygen in the waterways, which affects aquatic life, especially the insects that provide food for fish, like mayflies, stoneflies and caddisflies, said John Barbis, a board member of Valley Forge Trout Unlimited, which participated in the project.

“Most people perceive that when salt is applied to the road during a snowstorm or an ice storm, rain comes in, washes it down into the stream, and then that’s rushed out to a bigger stream, and then down to the ocean, and it disappears,” Barbis said.

“That’s only part of the story. What may be the bigger part of the story is that a lot of that salt gets deposited on the ground, and when the rain washes it, not necessarily into the stream but into puddles and other areas, and then that salt-laden water can soak into the earth, it now seeps down into the groundwater.”

Months, years or even decades later, that salty ground water will feed small streams.

Barbis pointed to data from some streams in the Exton area that are near large shopping centers.

“Those areas have salt concentrations that are probably three to four times above what we would normally expect from regular groundwater,” Barbis said.

Both Jackson and Barbis say their groups don’t advocate for the elimination of road salt.

“Because we need to get around, we need the roads safe after a snowstorm,” Barbis said. “But there are ways of applying salt, applying brine to the roads, doing it in a very judicious way, where we can limit how much salt is then transferred to the groundwater and then to the stream.”