Road salt is corroding pipes and water supplies as cities contend with aging infrastructure
Calgary’s recent water main rupture highlights how sodium chloride from road‑salt use is corroding infrastructure and raising chloride in waterways across Canada.
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By Torontoer Staff
Calgary moved this week to ease emergency water restrictions after crews repaired a second major rupture in 18 months on the Bearspaw South Feeder Main, the pipe that delivers up to 60 per cent of the city’s potable water. Investigators say the line was weakened by chloride-driven corrosion, and city officials warned the section could fail again before a permanent fix is in place.
The Calgary failure exposed a tension that affects municipalities nationwide: the same sodium chloride that dramatically reduces winter road collisions is accelerating corrosion in buried infrastructure and raising chloride levels in soil and freshwater.
How salt degraded a major Calgary water main
Investigators found that the failing portion of the Bearspaw South Feeder Main, built with concrete, steel and high-tensile wire wrapping, showed signs of hydrogen embrittlement and stress corrosion attributable to elevated chloride in surrounding soils. The section was designed for a 100-year service life but began to fail about 50 years in.
We have a ticking time bomb underneath our streets.
Mayor Jeromy Farkas
A city-commissioned inquiry into the June 2024 blowout cited political and bureaucratic factors in the pipe’s poor condition, but it gave little weight to sodium chloride, the chemical used on roads that investigators say saturated local soils and corroded metal components.
A national problem in numbers
Canada applies roughly seven million tonnes of sodium chloride to public roads each winter. Calgary alone spreads between 40,000 and 50,000 tonnes. Researchers have estimated that the hidden costs of salt-related damage to roads, bridges, vehicles and water infrastructure amount to about $5-billion a year.
- Toronto’s Gardiner Expressway requires major renewal after decades of corrosion.
- Montreal replaced the Champlain Bridge after 57 years, citing salt-related deterioration.
- A parking-structure collapse in Elliot Lake in 2012, which killed two people, was linked in part to corrosion.
Environmental and public-health implications
Salt keeps roads safer in winter: a widely cited Marquette University study found road salting can reduce collisions by about 90 per cent. But chloride accumulates in soils and waterways, altering ecosystems and complicating water treatment.
Salt is important for safety, but it goes into our water system, destroys our vegetation, kills aquatic life and corrodes our vehicles and infrastructure.
Kamal Hossain, associate professor in transportation engineering, Carleton University
The Canadian Council of Ministers of the Environment sets 120 milligrams per litre as a threshold for aquatic protection, but urban waterways often exceed that by a wide margin. Queen’s University aquatic ecologist Shelley Arnott notes that many organisms show adverse effects at chloride concentrations between 5 and 40 mg/L, suggesting current guidelines may not fully protect freshwater life.
Is that where we want to go, lakes that are full of algae and lacking in diversity? I do not think so.
Shelley Arnott, Queen’s University
Chloride levels have risen steadily in many water bodies despite reduction efforts. For example, Lake Simcoe has increased by roughly 0.7 mg/L per year since the 1970s. Along parts of the Bearspaw main that failed, chloride concentrations spiked by as much as 15 times over a decade.
Alternatives, reductions and barriers
Municipalities and contractors are experimenting with alternatives and application changes. Some jurisdictions use pre-wetted brines, variable application systems that adjust salt by speed and conditions, and organic or food-industry by-products such as beet juice. Results vary, and some alternatives can carry their own ecological risks.
Private snow-removal contractors often apply excess salt because of liability fears, said Joe Salemi of Landscape Ontario. Municipal crews face similar pressures, and the bulk of winter safety practice remains focused on immediate road safety rather than long-term environmental impacts.
Just being named in a lawsuit usually means spending $20,000 or $30,000 in a lawsuit.
Joe Salemi, executive director, Landscape Ontario
Experts call for a mix of measures: better targeted application, improved monitoring of groundwater and soil chloride, procurement and contracting rules that limit unnecessary application, and public education about non-chemical winter choices such as winter tires.
It’s a wicked problem. There’s no clear solution.
Wyatt Weatherson, PhD student, Toronto Metropolitan University
What governments must weigh
Municipalities must balance immediate road safety with long-term infrastructure resilience and environmental health. Without coordinated policy and investment in alternative practices and water-treatment capacity, chloride will continue to corrode buried assets and stress aquatic ecosystems while cities rely on salt to keep traffic moving.
Calgary’s recent pipe failures demonstrate the stakes. As crews complete temporary repairs, officials and municipalities across Canada face growing pressure to reduce environmental chloride and to account for the downstream costs of winter road maintenance.
infrastructureroad saltwaterCalgaryenvironment
