Road salt making Ottawa-area waterways 'toxic' to wildlife, report finds

A five-year study that involved taking hundreds of water samples in the National Capital Region has found that the vast majority were "toxic" to wildlife due to road salt levels, according to a new report.

The findings were released Monday by Ottawa Riverkeeper, a local non-profit which advocates for the sustainable use of the Ottawa River.

Starting in the winter of 2019-2020, the group worked with community scientists to study how much road salt ends up in local rivers. 

"Unfortunately, the impact of road salt on aquatic ecosystems can only be described as devastating," the report said.

It issued four recommendations targeted at cities, large property owners and regular individuals in the hope that the effects of road salt — which last throughout the year — can be mitigated.

'Shocking' revelations

Larissa Holman, Ottawa Riverkeeper's director of science and policy, said they became curious about the impact of road salt after learning about the harms other cities were experiencing.

Community scientists in Ottawa gathered about 500 water samples from 45 locations at streams in populated areas — streams that feed into the Ottawa River and "support the wildlife and the organisms" that are part of the watershed, Holman explained.

According to the report, only 10 per cent of the samples collected over the five years had safe levels of chloride (the key component of road salt). 

It was a "shocking" revelation, Holman said.

"Almost everywhere we were testing, at one point or another, the water that supports freshwater ecosystems was toxic to those organisms that live there," she said.

High chloride levels even continued into the summer, long after snow clearing and road salting had stopped, the scientists found.

The report also compared Ottawa and Gatineau's five worst streams, finding that none of the samples taken in Ottawa were safe although some were safe in Gatineau.

Ottawa Morning7:08Report: Road salt use “devastating” aquatic ecosystems within Ottawa River watershed

The Ottawa Riverkeeper spent five years monitoring road salt use in Ottawa and Gatineau. We hear what they found.

Holman attributed the difference to Ottawa being a denser city with more frequent road salt applications and cleanings.

Road salt also seeps into soil and eventually reaches the groundwater, causing the salinity of above-ground water to rise slowly and consistently over time, according to Philippe Van Cappellen and Jovana Radosavljevic, ecohydrologists at the University of Waterloo.

It's usually the main driver of drastic changes to salinity of water in urban areas, said Radosavljevic, who has been studying how urbanization over time has affected the overall ecosystem of a lake in Richmond Hill, Ont.

'Big mind shift' needed

The report's four recommendations are:

1. That municipalities and large property owners should take provincial guidelines about road salt more seriously and maintain and upgrade their equipment where necessary.
2. That they should also have road salt management plans.
3. That sensitive ecosystems which can't tolerate any road salt must be identified and protected.
4. That individuals should educate themselves about how to use road salt appropriately.

In the report, Ottawa Riverkeeper said it had shared its data with the City of Ottawa and had trained snow-clearers how to salt properly.

Holman explained that, after the temperature drops below –7 C, road salt isn't very effective — and it's almost useless if it drops to –10 C, so using sand and gravel is important.

"That's a really big mind shift away from what we see in some of these commercial spaces or really urbanized spaces where road salt is applied in quite large amounts," she said. 

Van Cappellen said it's not "very realistic" to completely stop using road salt or to entirely replace it, and that officials need to "start to think in terms of a circular salt economy" where the salt in the water, soil, and skies are all taken into account.

He suggested other solutions, like collecting salty water from highways to reuse as road salt, using excess heat from buildings to heat sidewalks and roads, and adjusting liability laws so that individuals and property owners don't over-salt out of fear of being sued. 

Read the full report