The Ottawa Riverkeeper is calling on the City of Ottawa and other municipalities to identify areas to restrict the use of road salt, after a new study found high levels of chloride in water samples that are harming aquatic wildlife and the environment across the national capital region.
The non-profit organization conducted a five-year study on the application of salt on roads and sidewalks in Ottawa and Gatineau, looking to determine chloride levels in fresh-water streams. Chloride is a key component of road salt.
“Unfortunately, the impact of road salt on aquatic ecosystems can only be described as devastating,” the Ottawa Riverkeeper said in its report.
“Chloride concentrations are rarely within the range to ensure there is minimal impact on urban aquatic organisms. Most devastating is that for most streams in Ottawa, the concentration of chloride after a trigger event is, on average, above the acute toxicity threshold, and high enough to cause immediate harm to aquatic organisms.”
Between the winters of 2019-2020 and 2023-24, community scientists collected more than 500 water samples at 45 different locations across Ottawa and Gatineau. The report says only 10 per cent of samples were below the safe level for chloride, while 45 per cent exceeded the threshold for “acute toxicity.”
The samples with the highest toxicity were found at Green’s Creek and Nepean Creek during the winter of 2021, along with one at Carp River and two at Nesbitt Creek.
The report says the highest chloride values occurred during the winter months, with February having the highest median concentrations, while the lowest chloride concentrations were found in the summer.
“With no snow events during this period of the year, the summer chloride concentrations suggest that road salt remains in the environment after the winter season and the application of road salt has ended,” the report says. “Previous studies have shown that salt can be retained in the soil and become reintroduced into aquatic ecosystems throughout the year.
“It is critical to note that the use of road salt impacts water bodies negatively throughout the year, not just during winter.”
The Ottawa Riverkeeper is recommending municipalities identify areas to restrict the application of road salt and develop and regularly update its Road Salt Management Plans. The organization also wants cities and property owners to ensure the road salt application is effective.
“The overuse of road salt is a complex issue with many actors contributing to the problem,” the report says. “A broader cultural shift is needed to solve it, and these recommendations suggest ways to begin.”
Last week, Ecology Ottawa and transit users raised concerns with CTV News Ottawa about a large amount of salt at transit stops. Ecology Ottawa called for a review of the city’s salting practices during the winter.
“Salt is toxic. So, it pollutes our streams,” William van Geest with Ecology Ottawa said. “Ottawa Riverkeeper has shown that consistent levels of high toxicity throughout the year. It pollutes the soil, making it difficult for things to grow. And it’s also deleterious for the infrastructure. It makes it break down.”
The City of Ottawa has expanded a pilot project to test sidewalk machine salt controllers to monitor salt use during the winter. Twelve machines are being used to test the sidewalk salters.
“These controllers monitor and adjust salt application rates in real-time based on vehicle speed and surface conditions, ensuring precise calibration and optimal use,” Christopher Paquette, program manager of Operational Research and Projects, said in a statement to CTV News Ottawa.
“Equipped with GPS and automated reporting capabilities, the controllers improve operational control and provide valuable real-time data.”
According to data provided by the City of Ottawa, the city has used 51,530 metric tonnes of salt between Dec. 1, 2024 and Jan. 6, 2025. In the same period in the winter of 2023-24, the city used 15,253 metric tonnes of salt, but in 2022-23, it used 50,043.
Full report:
With files from CTV News Ottawa’s Ted Raymond and Peter Szperling
