Beyond the border: Canadian studies consider permeable pavement, climate change impacts on deicing operations

Reprinted from MnLTAP News, November 17, 2025

The 2025 Salt Symposium highlighted two studies from Canada, one comparing salt applications on permeable and asphalt surfaces and another considering the impact of climate change on municipal operations. Hosted by Bolton & Menk, the August 5 Salt Symposium brought together professionals from throughout the world to share research, projects, and approaches for chloride management.

Permeable pavement achieves safe friction levels faster than asphalt

From the mouth of the Credit River in Mississauga, Ontario—one of Canada’s largest cities—winter salt runoff easily flows into connecting waterways. This helps explain why Credit Valley Conservation (CVC), the community-based conservation authority for the Credit River Watershed, reports high chloride concentrations in its area waters.

“We have a great interest in salt management, and we also want to make sure we are applying best management practices on our property,” said Lorna Murison, coordinator of real-time water quality monitoring for CVC.

As a result, CVC developed a salt management plan that recommends using liquid deicer instead of sand on parking lots. “Liquids are one of the best methods we have to reduce salt use,” Murison said. The recommendation, though, spurred concerns that liquids would infiltrate permeable surfaces immediately without doing the job, and a research project was born.

For the project, CVC delineated separate asphalt and permeable plots in a parking lot to test four products, as well as a control plot with no application, and measured the time it took to regain bare pavement after shoveling the plots and applying product. Researchers choose solid rock salt, fusion-treated salt with solid salt and beet juice, liquid salt brine, and a fusion of liquid salt brine and beet juice to hand apply. Among the key study findings:

Conventional asphalt takes less time to regain bare pavement than permeable pavement; however, permeable pavement achieves safe friction levels faster than conventional asphalt.
Slushy conditions on the conventional asphalt may look like bare pavement, but moisture remains on the pavement, reducing friction.
There was no conclusion on whether one product performed better than another, but all were effective.
In some cases, anti-icing and shoveling alone were enough to achieve safe friction levels.

While liquid salt brine resulted in bare pavement on asphalt in around an hour—the quickest of all products—it took up to eight hours to achieve bare pavement on permeable surfaces. Measuring friction, though, told a different story.

“We found bare pavement is not really the best way of evaluating the safety of the permeable surface,” Murison said. “Even though there was a thin layer of snow left behind, the surface was still quite dry, and the friction was actually higher than what you would measure on wet asphalt.”

It comes down to the melting pattern. The applications’ impact on asphalt continues to spread out as the snow melts, melting a larger area but leaving more moisture. Applications on permeable surfaces spread out in rings until reaching and infiltrating a crack, which stops melting.

There is still much to learn, including the amount of infiltration on permeable surfaces, the impact of equipment application versus hand application, and the effect on different types of permeable pavements. But the study did show that no matter the surface, liquid products do reduce salt without compromising friction.

“We wanted to know if you could use a product that contains less chloride and still achieve the same friction levels, and we were finding that you can,” Murison said.

Data and municipality perspectives reinforce climate change

Salt Symposium participants also learned about research from Canada that looked at the impact of climate change on winter deicing operations and the perceptions of municipal staff dealing with changing conditions.

“Municipalities are observing climate change and are experiencing complications in their winter maintenance operations,” said Wyatt Weatherson, a PhD student in the Environmental Applied Science and Management Program at Toronto Metropolitan University.

Weatherson interviewed staff from five municipalities and collected data from three. His goal was to better understand how changing weather conditions influence deicer use in the Lake Simco Region Conservation Authority area in Ontario.

“If climate change is becoming a greater concern to municipalities and conservation authorities in the context of winter maintenance operations, we now need to understand what the implications are of these risks and for salt applications practices,” Weatherson said.

Municipalities reported substantial changes to winter weather events, with fewer and less frequent sustained snowfalls, more freeze-thaw cycles, more overnight flash-freeze conditions (which can mean more black ice formation), and more impactful major storms. They also face additional challenges: a lack of digitized records, equipment procurement issues, and operators with different levels of experience.

To support reducing their salt application, three of the five municipalities in the study are moving ahead with data modification. One is upgrading its equipment for brine application, while another is reworking its entire program.

When Weatherson compared the available salt application data with annual snowfall, he didn’t correlate a trend between them. “That indicates to us that there is a fair amount of operator decision making or management decision making within the municipality that’s leading to an increased amount of salt being used relative to the amount of snowfall that we are seeing.”

The finding reinforces the importance of a standardized approach to training, as well as the value of ongoing data collection that helps municipalities track and compare salt application under different circumstances.

The concerns that come with a changing climate will likely remain for municipalities. An analysis of climate data for the study revealed that precipitation is increasing, falling three to six more days each month over the last 10 years. The analysis did not show any clear pattern in the change of precipitation mix.

The research provides a better understanding of municipal perspectives, compares those perspectives to available data, and offers evidence that supports municipal concerns over climate change. Results identify common challenges and could help facilitate discussion about possible solutions. Additionally, future research to collect and analyze sub-daily winter weather and salt application data will help to evaluate the influence of mixed precipitation events on salt use.

“This work is showing us that we are seeing climate change, and it’s confirming what we are hearing from municipal staff,” Weatherson said.

—Darlene Gorrill, contributing writer