Road salt, spread on highways during winter storms, was measured this year at one Philadelphia-area stream at more than triple the level deemed toxic to aquatic life, and above the maximum level at 23 other nearby waterways, according to newly released data.
The ample use of salt has become a major environmental issue in recent years as more and more road crews pre-salt or brine roads before expected winter storms. Homeowners and businesses also add salt to driveways and parking lots.
The salt makes its way into freshwater streams.
“It makes streams more toxic to the life living in it,” said Emily Bialowas, of the Izaak Walton League, a national conservation nonprofit that organized the testing.
Levels above 230 parts per million of chloride can be toxic to that life, she said. Chloride measurements are a proxy for sodium levels. Table salt is sodium chloride. But salt can change chemically when dissolved in water, so chloride is an indicator of its presence.
One location on Darby Creek in Berwyn reached at least 800 parts per million in March.
High levels of sodium can pose a threat to people on restricted diets. The Philadelphia Water Department and other water companies that draw from rivers normally do not remove sodium, though they do test for it.
This year marked the first time the Izaak Walton League coordinated testing in the Philadelphia area for a full winter season.
Volunteers fanned out through various area waterways including the Darby, Pennypack, and Poquessing Creeks, as well as other streams that drain into the Delaware. Tested areas included downtown Philadelphia, Berwyn, Havertown, Upper Darby, Southampton, Elkins Park, and Camden. Volunteers took readings for chloride.
Bialowas said her organization, which is based in Gaithersburg, Md., recruited volunteer testers in Philadelphia through social media. Organizers were surprised at the large response.
“This is only our first full year,” Bialowas said. Testers checked early in the season before major storms to get a baseline. They then continued testing into March.
“We’ve seen some pretty high levels,” she said.
Though the tests were conducted January through March, high chloride levels were still detected long after the worst storms had passed. Salt in water gets flushed out and flows, ultimately, out to the sea. However, studies in recent years say concentrations are remaining high even after winters have passed.
“Our last readings from the Philly area were still not close to zero and that was in March,” Bialowas said.
The streams and creeks have not been tested since.
Ryan Neuman, a coordinator with the Tookany/Tacony-Frankford Watershed Partnership, said the testing and reporting program is an important new tool. The Izaak Walton League supplies the testing strips. Citizen scientists upload the data to Water Reporter, a social media app for watershed organizations, such as Neuman’s.
“Some of the higher readings that came from our area weren’t surprising,” Neuman said. “We’ve seen from a lot of our other work that salt levels are high in some of our creeks.”
Julie Slavet, executive director of the Tookany/Tacony-Frankford Watershed Partnership, said the organization has 25 regular citizen volunteer scientists to help with testing, and is mounting an education campaign to help communities understand the impact of salt in the water.
Other area groups participating in the testing included Pennypack Streamkeepers, Darby Creek Valley Association, Delaware River Watershed Initiative, Lower Merion Conservancy, Wissahickon Valley Watershed Association, Ambler Environmental Advisory Council, various watershed stewards, and local teachers.