Toronto’s unmeltable snow piles become a toxic hazard

Most peaks require tens of millions of years to develop. Toronto’s latest “mountain” appeared in a matter of days.

Rising above a stand of evergreens, it lacks any limestone or granite core. There are no spires, cornices, or headwalls—only layers of snow blended with road salt, antifreeze, oil, coffee cups and misplaced keys. It serves as the final repository for the weather forces that have battered the city in recent weeks and poses a serious environmental threat.

In late January, Toronto experienced what many specialists described as the most intense single‑day snowfall on record for the city. In certain locations, almost 23 inches fell, driven by a clash of weather systems. By mid‑February the municipality had already cleared 264,000 tonnes of snow from 1,100 km (680 miles) of streets, sidewalks and bike paths.

A comparable storm struck New York City at the end of February, depositing more than 25 inches of snow in some areas during a two‑day event accompanied by hurricane‑strength winds.

Metropolitan areas that endure harsh winters have long faced the reality that snow cannot remain on thoroughfares or walkways. The usual remedy is to haul the snow—sometimes for weeks—to storage sites on the urban fringe.

Toronto now hosts six such snow piles scattered across the city. Most are kept out of sight to discourage illegal dumping. One location on the north‑western edge of the city, however, is clearly visible to motorists on the highway. It can accommodate 144,000 cubic metres of snow on a two‑acre plot.

Reaching almost 100 feet—about the height of a ten‑storey building—it looks like an Italian marble quarry, with yellow excavators working in unison against the ashen drifts. Vents of steam rise from large melting units, roughly the size of shipping containers, that gradually shrink the pile. Operators work long shifts; during severe storms the equipment runs around the clock, seven days a week.

“Certainly there’s a need to clear snow to reduce hazards on roads and sidewalks, especially from a public‑safety standpoint,” said Donald Jackson, a professor of ecology at the University of Toronto. “But the challenge lies in what they’re trying to balance against: the ultimate impact on aquatic ecosystems.”

Canada’s largest city has spent more than C$1 billion over the past decade to restore the mouth of the Don River, reviving its natural flood‑control functions and a riparian ecosystem once thought lost.

The city reports using a range of measures to keep contaminants such as automotive oil from entering water bodies, yet salt remains a pervasive problem, passing through most storm‑water treatment processes.

Toronto has already applied over 130,000 tonnes of salt this season, and municipal authorities are confronting a shortage—even though the world’s largest salt mine lies less than 150 miles west of the city.