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De-Icing Chemicals and the ALTO Southern Route: What They Mean for Our Watersheds and Wildlife
Every winter, a high-speed railway must be kept free of ice. The chemicals used to do that job don’t stay on the tracks. On the southern ALTO corridor, they would drain into some of the most ecologically sensitive land in eastern Ontario.
High-speed rail needs its tracks, switches, and overhead wires kept clear of ice all winter. Unlike roads, where a light sprinkle of salt is temporary, a high-speed rail line operates every day — which means chemical de-icing is continuous, systematic, and large-scale across the entire corridor from November through April.
There are two main types of de-icing chemicals used on railways: glycols (similar to antifreeze) and chloride salts (similar to road salt, but applied in larger quantities and more concentrated forms). Both end up in the surrounding environment. Both cause serious harm to aquatic ecosystems. And on the southern ALTO corridor, the geography makes that harm exceptionally difficult to prevent or contain.
The southern ALTO corridor would pass through the Frontenac Arch UNESCO Biosphere Reserve — one of only 19 in Canada, home to the most biodiverse region in the country. Five forest zones converge here. The Frontenac Arch is the last intact forest corridor between the Canadian Shield and the Adirondack Mountains.
East of the Shield, the southern corridor crosses the Napanee Limestone Plain — a karst landscape unlike anything else on the route. Karst is formed when rainwater slowly dissolves limestone over millions of years, creating underground rivers, sinkholes, caves, and fissures.
Karst features documented directly in the corridor include the Roblin Hell Holes (sinkholes, underground streams, a 20-metre escarpment), the Salmon River Alvar (flat limestone pavement with almost no soil), the Moira River Karst, and the Stoco Fen and Stoco Karst Forest, which filter water flowing downstream toward Belleville.
The Frontenac Arch supports the highest density of reptiles and amphibians at risk in Canada. The Thousand Islands area alone holds more diversity of reptiles, amphibians, and invertebrates than any national park in the country. These species are acutely sensitive to the chemicals that de-icing requires.
| Species | Status | What de-icing would do to them |
|---|---|---|
| Gray Ratsnake | Threatened | Ethylene glycol has a sweet taste that attracts wildlife. Ratsnakes hibernate in rock crevices; pooled glycol near tracks is an attractive lethal hazard. Law protects a 1,000 m radius around every known occurrence. |
| Blanding’s Turtle | Threatened | Breeds in shallow wetlands most vulnerable to oxygen collapse from glycol runoff. Produces only ~8 eggs per year and takes 14–20 years to reach reproductive age — one bad chemical event can set a population back by decades. |
| Loggerhead Shrike | Endangered | The Napanee Plain holds one of only two remaining breeding areas in Canada. Total wild Canadian population: approximately 40 individuals. Salt damage to alvar grassland destroys nesting habitat and insect prey. |
| Pugnose Shiner | Threatened | More than 10% of Canada’s entire population lives in the Thousand Islands waterways. Highly sensitive to oxygen depletion from glycol runoff. |
| King Rail | Endangered | Nests in shallow freshwater marshes. Fewer than 30 calling birds were recorded in a 1999 survey. Glycol-induced oxygen depletion in marsh habitat could be catastrophic. |
| Bobolink & Eastern Meadowlark | Threatened (federal) | Salt spray from passing trains kills grassland vegetation within 30–50 metres of track, destroying the hay-field and alvar habitat these birds nest in. |
| Eastern Whip-poor-will | Threatened | Eats insects. Salt pollution reduces invertebrate populations, cutting off its food supply. |
Glycols (propylene glycol and ethylene glycol) are organic compounds — essentially antifreeze. When they drain into water, bacteria start breaking them down. That breakdown process consumes oxygen. In large enough quantities, glycol runoff can strip all the dissolved oxygen from a receiving stream or pond, creating a dead zone where fish, invertebrates, amphibian eggs, and overwintering turtles suffocate.
Cold water holds less oxygen to begin with. Under ice cover, ponds and wetlands have no contact with the atmosphere to replenish what the bacteria consume. Research shows ethylene glycol can persist in cold water for up to 60 days, causing prolonged stress to fish populations long after the original application.
Ethylene glycol smells and tastes sweet, which is why it attracts pets and wildlife. In the Frontenac Arch, this is a direct hazard to Gray Ratsnakes, Blanding’s Turtles, and small mammals emerging from hibernation in spring — just as meltwater pools collect near track infrastructure.
At airports, glycol-laden runoff is collected by engineered drainage systems. On an open track corridor over the Napanee limestone plain, this doesn’t work: the glycol infiltrates through sinkholes and fissures into the karst conduit system before it reaches any collection point. The collection infrastructure that works at Pearson Airport does not work on the Napanee limestone plain.
Chloride salts (sodium chloride, calcium chloride) don’t degrade. Unlike glycol, every gram of salt applied stays in the environment permanently — cycling between soil, groundwater, and surface water indefinitely. This means chloride isn’t a season-by-season problem; it’s a decades-long accumulation that gets worse every year the railway operates.
Environment Canada’s guideline for the protection of aquatic life is 120 mg/L chloride (chronic). Natural background levels in healthy Eastern Ontario streams should be below 5–20 mg/L. Research found that 70% of Ottawa-area stormwater ponds already exceeded the 120 mg/L guideline in summer — when no salt was being applied.
| Ecosystem | Glycol | Salt | Why |
|---|---|---|---|
| Frontenac Arch Shield wetlands | VERY HIGH | VERY HIGH | Highest reptile/amphibian at-risk concentration in Canada; Blanding’s Turtle breeding habitat; Gray Ratsnake hibernacula |
| Napanee limestone alvars | HIGH | VERY HIGH | Thin or absent soil; no buffering; Loggerhead Shrike habitat; globally rare Juniper Sedge; salt destroys alvar vegetation |
| Karst conduit aquifer system | HIGH | VERY HIGH | Rapid unfiltered contaminant transport; municipal drinking water; chloride accumulation is irreversible |
| Salmon River watershed | HIGH | HIGH | 6 endangered species; Roblin Hell Holes karst; only 38% riparian forest cover; drains to Bay of Quinte |
| Bay of Quinte (receiving waters) | HIGH | VERY HIGH | Designated Area of Concern since 1985; four decades of remediation work at risk from cumulative loading |
Japan’s Shinkansen, Finland’s railways, and most European high-speed rail systems use electric resistance heating built into switches, catenary systems, and platform surfaces as their primary winter solution. Given that ALTO will be electrified and Ontario’s grid is approximately 69% non-emitting, electric heating aligns with the project’s own stated climate objectives. In a landscape with this concentration of species at risk and karst vulnerability, the additional electrical cost is a reasonable price for environmental protection.
CMA is non-toxic, biodegradable, and less corrosive than salt. However, it costs approximately 20 times more than sodium chloride. It would be appropriate at enclosed stations and depots where runoff can be collected and treated, but not for open corridor use over karst terrain.
Runway-style glycol collection systems work because airports have engineered drainage that intercepts runoff before it leaves the site. On an open rail corridor over the Napanee karst, contaminants enter the underground system before they reach any collection point. The collection infrastructure that works at Pearson Airport does not work on the Napanee limestone plain.
Road salts were declared toxic to the environment in 2001. Environment Canada’s Code of Practice for road salt management applies by analogy to railway operations.
Section 36(3) prohibits depositing any deleterious substance in waters frequented by fish. Both concentrated glycol and chloride solutions meet this threshold. The Frontenac Arch waterways support multiple fish species at risk.
Prohibits destruction of critical habitat for listed species. Gray Ratsnake habitat regulation protects a 1,000 m radius around every occurrence. Glycol or salt contamination within these zones constitutes habitat degradation — a federal offence.
Enacted June 2025, replacing the Endangered Species Act. Ontario is removing provincial protection for species already covered by federal SARA — making SARA the operative law for species including the Loggerhead Shrike, Bobolink, and Eastern Meadowlark.
Prohibits discharge of materials that may impair water quality. Karst aquifer contamination would threaten municipal drinking water supplies for multiple communities.
A federal-provincial commitment to restore the Bay of Quinte’s impaired uses. Additional chemical loading from HSR directly contradicts four decades of RAP investment.
No chemical de-icing on open track over the karst and Biosphere
The combination of biological sensitivity and hydrogeological vulnerability makes chemical de-icing unacceptable along open corridor sections. Electric heating must be the primary de-icing technology for the Frontenac Arch and Napanee Plain sections.
Prohibit ethylene glycol anywhere on the ALTO corridor
Its sweet taste attracts wildlife, its toxicity to aquatic organisms is well documented, and its 60-day persistence in cold water means winter application creates oxygen crises in receiving waters come spring.
Prohibit sodium chloride and calcium chloride within 2 km of any karst feature, wetland, or watercourse
Chloride is permanent. Natural background levels are already below 20 mg/L in most Eastern Ontario streams. Once chloride enters the karst aquifer, it cannot be removed.
Restrict chemical de-icing to CMA or potassium acetate at enclosed stations only
With engineered runoff collection and treatment before discharge. Annual volumes must be publicly reported.
Require a comprehensive karst investigation before any permits are issued
Using dye tracing, boreholes, ground-penetrating radar, and electrical resistivity to map the underground conduit network beneath the alignment. This takes 2–3 years and must be complete before construction begins.
Establish continuous water quality monitoring
Baseline chloride, BOD, dissolved oxygen, and glycol monitoring at all karst springs, stream discharge points, and municipal wells within 5 km of the alignment — throughout construction and the life of the railway.
Engage Indigenous and conservation partners in oversight
Including the Mohawk Council of Akwesasne, Quinte Conservation, Cataraqui Conservation, the Nature Conservancy of Canada, WCS Canada, and Friends of the Salmon River.
Require a De-Icing Management Plan as a condition of Environmental Assessment approval
With legally binding adaptive management triggers: if monitoring detects chloride above 60 mg/L at any point, chemical de-icing must be immediately curtailed.