Jim Hatfield

Washington state trees are dying where calcium chloride has been applied on nearby roads.

Have you been wondering why Calgary roads are now wet at -15 C, why far more road lines have vanished, why your vehicle, boots and shoes look excessively dirty and why it takes longer for snowbanks to melt?

That’s because the city is now spraying winter roads with calcium chloride — a liquid salt more potent than the commonly used rock salt — because it is more cost-effective, melts ice at colder temperatures and is hailed as being more eco-friendly than common salt. But the liquid spray can seep into nooks and crannies of your vehicle eating away at unprotected parts. It also burns roadside trees, pits aluminum and pollutes groundwater and soil.

“Calcium chloride’s environmental rating is high, meaning it has a high impact on watersheds,” says Kevin Mercer, executive director of RiverSides Stewardship Alliance in Toronto, where they’ve been spraying calcium chloride for several years.

While calcium and sodium chlorides are both considered detrimental to the environment, calcium chloride’s effects on infrastructure is much worse, says Mercer. “On an infrastructure-basis sodium chloride gets a bit more of a pass because calcium chloride is so absolutely corrosive.”

Last year, Calgary crews began spraying the roads with the anti-icing chemical using retrofitted trucks. As well, calcium-chloride-treated sand is now applied to city roads. In all, Calgary plans to use 1.2 million litres of the chemical this winter season — 50 per cent more than the 800,000 litres used last year.

City officials say they are careful in using calcium chloride. “We don’t just arbitrarily use this stuff; there are pretty strict mandates as to how you can use it as far as environmental concerns,” says Dan Jones, the city’s roads operations manager. The city’s “extensive salt management program” includes electronically monitoring how much chemical is used on roads and it’s stored in tent structures designed to prevent wind erosion and run-off.

Officials in Washington state, where calcium chloride has been sprayed on mountain roads since the early 1990s, have noticed trees are slowly dying along the roadside where the de-icer has been applied.

“In some areas we do see symptoms of what we call conifer browning,” says Jim Hatfield, a pathologist with the Wenatchee-Okanogan National Forest. “It’s a browning and dying of entire needles or portions of needles on the trees, typically within 30 feet of the edge of the roads where the material has been applied.”

Conifer trees, including fir, pine and spruce, seem to be more susceptible than broadleaf trees because the chemical is absorbed through the needles, says Hatfield. State transportation department officials responsible for applying the de-icer contend the trees recover during the summer. However, Hatfield says there is evidence trees can’t cope with multiple-year burning. “What seems to be going on is that the trees become so weak after several years that they just fully die,” he says.

Calcium chloride also slowly damages cars and trucks. It’s a hygroscopic substance, meaning it attracts moisture and, along with its heating properties, it remains in a liquid form longer than traditional road salt. The corrosive liquid seeps into small vehicle areas and can eat away at unprotected metal parts.

“If there’s a rock chip or scratch and it’s ignored, salt gets on the wounds and the oxidization gets going and the rust gets worse every year,” says Emilio Elia, owner of Auto Protectors. Nuts, bolts and moving parts that aren’t stainless steel, galvanized or treated are particularly vulnerable, he adds.

Calcium Chloride is commonly used as an additive in swimming pool water, which in turn tends to be corrosive on equipment, pumps and metal fittings.

The chemical is also used on roadways to hold dust down, which introduces a potentially more dangerous side effect: concealing traffic lines. “For paved roads it may grab airborne dust and stick to the road,” says Stephen Hu, senior chemical engineer for Tiger Calcium, the company that sells the de-icer to Calgary. This could make traffic lines invisible for drivers, says Hu.

However, the city points out that the chemical doesn’t corrode traffic lines. “If you were to do a study on traffic lines, the paints they use is a whole science in of itself,” says Dan Jones, the city’s roads operations manager.

In 2001, Environment Canada recommended all road salts be listed as toxic substances under the Canadian Environmental Protection Act. The federal agency’s five-year study determined road salts were toxic to surface and groundwater, can poison birds and threaten aquatic life.

Salts are damaging to ecosystems because they don’t dissolve or breakdown once in the soil or water, says Mercer, who has sat on the federal government’s road salts advisory group since 2000. “Every ton of road salt poured onto the streets of Calgary will remain either in the soil or the water bodies of water in Calgary or downstream,” he says.

Once in the ecosystem, calcium chloride breaks down into two components: calcium and chloride. Both upset the natural balance of water tables and kill aquatic life, says Mercer. “You won’t find acres of fish floating upside down, but you will find is that over time you’ll lose your aquatic species particularly the tiny things that everything feeds on.”

Calgary’s water resources department, which tests the city’s waterways for the presence of chlorides and other contaminants every four weeks, say tests have not shown an increase in calcium chloride in Calgary’s waters. Yet, the city is closely monitoring chloride levels and its effects on storm water equipment. “It’s an area that’s under a lot of scrutiny and a lot of interest,” says Bert van Duin, senior development engineer, “but the reality is we’re still trying to find more information about as to how sensitive the drainage systems are to the presence of chlorides.”