By Mike Allen
Do we know what we are really paying for the salt that is used to keep the ice off our roads in winter? The question has had little public attention in recent years. But a clear and careful public accounting could very well lead to major changes in the way we cope with winter ice.
What is the cost to our trees, grass and other green things of the brine from the melted snow and salt that seeps into the soil and sickens or even destroys them? How much is the corrosive action of the calcium and sodium chlorides damaging our roads and bridge infrastructure, and what will the repairs cost? Indeed, what role if any did these de-icing chemicals play in the recent collapse of bridge structures in Minneapolis and Montreal, and even in the damage to the tunnel structure under a downtown Montreal’s thoroughfare? Knowledgeable observers say these questions are begging for answers.
On the surface, salt application is the cheapest way to remove ice from our streets and make them safe in winter. But some argue that this is a delusion, that it is imperative that damage to both our infrastructure and the greenery in our landscapes be part of the cost calculation. Public officials appear to be turning a blind eye to these costs, leaving the public very much in the dark about the potential problem.
The choice for local governments is to use the chlorides and then replace their decaying roadways or to use a more expensive but far more benign chemical. They usually choose the former, and a main reason is that they can recover much of the capital replacement cost from the senior governments. Whatever the calculation, however, the public is entitled to have the full picture, including all cost calculations, made openly available – including studies carried out by other administrations – so the issues can be openly debated.
Most Canadian towns and cities continue to treat their roads with salt – using calcium chloride to prevent ice formulation and sodium chloride to melt existing ice. As a federal environmental study revealed a few years ago that adds up to nearly three million tons of the chlorides annually being released into the environment. They then become widely dispersed.
In our landscapes, the brine pentrates susceptible parts of woody and perennial plants. Evergreen trees and shrubs turn rust brown; deciduous trees and shrubs develop aberrant growths on their branches. The branches soon die, and the damaged trees themselves slowly succumb. We see these sick and stressed trees, but scarcely take note there is a problem.
There are alternatives to this salt, and while the products themselves are more expensive they are not corrosive and will not damage vegetation. The main products are calcium magnesium acetate, sodium acetate and potassium acetate. In Canada, the federal government uses acetate-based de-icing agents for most of its airports.
The purchase cost of CMA can be between 12 and 20 times the cost of sodium chloride salt, but the chloride can be up to 20 times more corrosive. In New York state a few years ago the Energy, Research and Development Authority estimated the annual cost of corrosion damage to vehicles, highways, bridges and below ground utilities to be about $1.4 billion. The agency said a mid-range estimate of the extra cost of CMA, compared to sodium chloride, equalled about half that $1.4 billion amount. The agency based its figures on a $650-a-ton price for CMAs and $50-a-ton price for sodium chloride.
Indeed, U.S. states have been far more aggressive than Canadian administrations. Several U.S. states have either banned use of the chlorides or severely limit their use. In Canada, the more widespread response to concerns about salt use appears to have been to amend management practices, as in the city of Toronto, so that lesser amounts are used.
Canadian administrations need to do some brutal calculations of their own and, using the best knowledge and investigative techniques available today, come up with a full assessment both environmentally and on an overall cost basis of the impact of chloride salts, and the comparative costs and benefits of shifting to CMA or some other similarly benign replacement.
*Originally published on Manitoba Gardener Fall 2007 issue. |
