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Road de-icing technology under pressure to go green

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by Ian Harvey last update:Sep 19, 2016

Ask a Canadian what they hate most about winter and driving is probably going to be one of the top five items. Winter driving conditions can be treacherous and unpredictable even when the sun is shining and the asphalt seems dry. For 70 years or more the go-to solution has been sodium chloride, also known as white salt, either in granular form or in a brine spray.
Several companies, environmental groups and industry stakeholders are looking at alternatives to road salt, such as products made from magnesium chloride, calcium chloride, potassium chloride and other trace minerals in order to reduce some of the adverse effects road salt is having on equipment, concrete, road surfaces and aquifers.
Several companies, environmental groups and industry stakeholders are looking at alternatives to road salt, such as products made from magnesium chloride, calcium chloride, potassium chloride and other trace minerals in order to reduce some of the adverse effects road salt is having on equipment, concrete, road surfaces and aquifers. - Photo: Oregon Department of Transportation/Wikimedia Commons

However, it can come with a price, states one industry expert. White salt buildup can be damaging to vehicles, equipment, concrete, road surfaces and aquifers.

Also, white salt is ineffective below -20 C and refreezes, while storage of snow and ice after removal causes problems during melting since there's usually road salt mixed in.

The alternatives, however, are seen as expensive and there's been a general resistance to adopting technology based on calcium chloride or magnesium chloride, says Greg Baun, of Innovative Surface Solutions, an Ajax, Ont. company that imports and distributes de-icing solutions across North America.

Its products are made of magnesium chloride, calcium chloride, potassium chloride, sodium chloride and other trace minerals. The ingredients are mixed with water to form a solution that is sprayed on the roads for de-icing.

It's more effective and less environmentally harmful, says Baun.

"The difference with magnesium chloride is that it's a lot more forgiving," he explains. "And it has a lower refreezing point."

The company can also mix in carbohydrates like corn syrup that add viscosity to the solution, making it sticky so that it can adhere to the road surface more efficiently, he adds. White salt is commonly mixed with beet sugars, for example, for the same reason.

"One of the big problems with white salt is that it is toxic to humans," says Baun. "You shouldn't breathe it in and that's what happens with the residue dust."

Colorado, for example, has switched mostly to magnesium chloride because of those concerns and two years ago Environment Canada raised concerns around the use of white salt on roads, he states.

The Canadian consensus among road organizations involved with Environment Canada on the issue is to identify salt-vulnerable areas and adjust the application of white salt accordingly.

Environment Canada has set national standards based on its 2004 Code of Practice for the Environmental Management of Road Salts and plans to monitor progress through 2024.

It targets road organizations using more than 500 tonnes of road salt a year or who have salt-vulnerable areas in their territory. The plan is currently focused on getting organizations to voluntarily join and is initially targeting safe storage and application technology.

"Road managers today are set in their ways and they don't want to have any problems or experiment," says Paul Johnson, operations manager with Wellington County, which sits between Mississauga and Kitchener, Ont. west of Toronto. "They've been in it too long."

Johnson says the county uses a magnesium chloride mix applied as a liquid, rather than salt.

Part of the reason for the switch is because his patch includes areas that are salt vulnerable and there is obvious evidence of salt getting into the drinking water aquifers.

"A lot of the concern and the committees we're working with have come out of what we learned from Walkerton," he says, referring to the 2000 public health crisis in which E. coli contaminated drinking water, killing seven people.

It's not just salt on roads, Johnson says; salt is applied on sidewalks at 40 times the rate of roads and that's a problem for the underlying soil and water too, not to mention shoes and clothing.

Johnson is also working with other stakeholders to raise the profile around overuse of road salt and investing in alternatives as well as storage issues.

Switching to magnesium chloride might seem initially more expensive in terms of raw materials, says Baun, but it's just one factor in de-icing. The equipment remains the same, the magnesium mix is less likely to freeze up in the tanker trucks and there's a lot less damage to road surfaces, concrete and metal infrastructure, he says.

Baun says there are some signs that things are changing slowly as white salt users come under pressure from Environment Canada and local conservation authorities looking to preserve the quality of their water and adhere to Ontario drinking water regulations.

Under the Ontario Clean Water Act local municipalities must develop a water source protection plan to guard against contaminants from faulty septic tanks, leaking fuel tanks, fertilizer run-off, pesticides and road salt.

Bill Thompson is with Lake Simcoe Region Conservation Authority, one of 36 conservation agencies in Ontario working on water source protection plans. He says road salt is showing up in aquifers, rivers and lakes across the province.

"In Simcoe we're finding it in the rivers feeding the lake and in the ground and the levels don't go down much in the summer. So it's not just a winter issue. The salt is sticking around," he says. "In looking at the data since 1970 there's been a shocking increase in salt levels in Lake Simcoe."

Road salting alone isn't the only issue, he adds. Parking lots, sidewalks and other surfaces are often over salted.

"There's no silver bullet," he says. "Sodium chloride or magnesium chloride, once they separate it's the chloride which is the problem. Magnesium chloride is 75 per cent chloride, while sodium chloride is 66 per cent, so there's more chloride, even though it's more effective."

He says alternatives aren't a solution alone, but it appears treated salt that is made partly by mixing magnesium chloride with sodium chloride is more effective and less damaging.

"How you apply it is also important, so they are looking at more efficient application using less salt to do the same work," he says. "We had this a few years ago with farmers and fertilizer. The run-off of fertilizer was getting into the water. So we worked with the farmers and now they use precision farming techniques — less fertilizers but applied at the right time, the right place, in the right amount. Road managers need to start doing the same thing."

last update:Sep 19, 2016

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