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Low-Salt Formula Safeguards the City's Arteries And its Side Streets, Sidewalks and Watersheds Too
November, 2007
By Barbara Carss
The return of cold weather and slippery conditions marks the launch of the City of Toronto's latest pilot project to test alternatives to sodium chloride road salt for de-icing. This year staff in the Transportation Services division is concurrently reviewing the City's winter services program for pedestrian routes such as sidewalks, crosswalks, bus shelters and wheelchair accessible ramps to assess maintenance and service requirements across the city.
"We are doing that to respond to what we feel is a growing demand for attention to pedestrian-ways, particularly along public streets," says Peter Noehammer, a Director of Transportation Services with the City of Toronto. Currently about 20% of the winter maintenance budget is allocated to sidewalks, with the much larger remaining share spent on roadways.
Toronto has been a leader among Canadian municipalities for its salt management plan, which was completed in 2002 in response to Environment Canada's 2001 report on the impact of road salt on the environment. (In 2004, Environment Canada introduced the Code of practice for the environmental management of road salts, encouraging municipalities and other public agencies to prepare salt management plans. For more information, see the web site at www.ec.gc.ca/nopp/roadsalt.)
Over the past five years the City of Toronto has steadily increased its reliance on and capacity to apply a salt brine mixture to roadways. The brine dilutes the amount of road salt required and can be applied in advance of a storm so that a slip retardant is already present when the snow and/or freezing rain falls. In 2002, just three City trucks were equipped to apply the brine, but last winter there were 96 such trucks in service, and there are plans to have more than 200 trucks equipped by the winter of 2008.
To date, the City has no vehicles that can apply liquids on sidewalks. Instead, sidewalk tractors with plows push away the snow, while a mixture of salt and sand is dispersed from a spreader towed behind the tractors. However, a future pilot project may test the feasibility of new equipment and/or application methods. "The City of Barrie has used liquid application on sidewalks and we do want to try that as well," Noehammer notes.
ALTERNATIVES COME WITH QUALIFICATIONS
Pilot projects for the winter of 2008 will focus on alternatives to sodium chloride. For example, a product derived from sugar beets will be used to coat the salt applied to roads and sidewalks. This will test the effectiveness of the alternative solution and reduce the overall amount of salt in use.
"The practicality of alternatives really depends on what climatic zone you are in," Noehammer observes. "In Toronto, the winter temperature is in the range that still makes sodium chloride the most effective and most economical to use on sidewalks."
Snow removal contractors suggest that organic based de-icing solutions are best suited for temperatures below -13º C (9º F) when sodium chloride can no longer effectively melt snow and ice. However, southern Ontario winters tend to be milder, especially in recent years, and the organic solutions come with a cost premium.
"Since there has been some talk of banning road salt we've been using alternative methods to some extent, but we're finding they don't work as well," reports Dean Schofield of Landmark Landscaping, who is a member of the Snow & Ice Management Association. "There is a lot of experimentation involved in trying to get the right formula and the right amount, and if you miscalculate it can be a costly mistake."
Magnesium chloride remains effective to a temperature of about -20º C (-4º F) and proved a reliable de-icing agent when tested in a Toronto pilot project during the winter months of 2004-05, but is considered prohibitively expensive for widespread application. Tests also suggested that it might have accelerated spalling of concrete, which would make it impractical for sustained use.
Sand - a longtime standby, particularly in municipalities that experience colder winters - also creates environmental concerns. Sand must be swept up and disposed of at the end of the winter or, worse still, it washes into drains and storm sewers where it can cause clogs and carry contaminants into the watershed.
SAFETY PRIORITIES
As Environment Canada's voluntary code of practice emphasizes, safety is a paramount concern. In a climate where snow and/or freezing rain is a frequent occurrence, roadways and sidewalks must be safely navigable. Salt management plans are a way to define and implement best practices for salt storage, snow clearance, de-icing and snow disposal, but not necessarily to replace salt.
"We notice that we are using less salt since we introduced the salt management plan, but that could be partly because of the winters we've had," Noehammer says. "Chlorides in soils and watersheds take a long time to pass through and we don't have a good amount of data yet to indicate whether levels are going up or down. Intuitively, we think that if we are using less salt, there should be less negative environmental impact and, intuitively, we think that by using less salt we would have less corrosive impact on structural steel."
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