Reducing Road Salts Use

Reducing the ecosystem impacts of road salts in Ontario requires a comprehensive and integrated approach. This approach includes implementing best management practices concerning storage and application, reducing the amount of salt through improved application techniques, integrating alternative products into current practices, and introducing policies to achieve social change.

Best Management Practices

Environment Canada’s Code of Practice recommends the voluntary development of salt management plans that will implement best management practices (BMPs) within road authorities that are using more than 500 tonnes of road salts annually, or applying salt in environmentally vulnerable areas. These BMPs focus on three areas: storage, application and snow disposal.

Storage sites have historically been a large source of chloride contamination through runoff. The BMPs are thus designed to eliminate this source of contamination on both existing and new storage sites.

BMPs for application are designed to minimize the amounts of salt used by targeting delivery based on specific conditions in specific places. This targeting includes using calibrated spreaders to ensure even distribution of the salt and determining when to salt, and how much salt to apply through the use of road weather information systems, infrared thermometers and road surface friction sensors. Perhaps the most important improvement in road salts application came with the introduction of pre-wetting and anti-icing techniques. Pre-wetting is the practice of using a liquid to wet salt prior to spreading. This technique improves the ability of the salt to stick to the surface of the roadway and enables it to melt ice quicker. Anti-icing involves spreading product prior to the storm event, which prevents ice from forming and assists in the rapid melting of snow and ice.

In many urban centres, snow is removed to a snow disposal site – or snow dump. By depositing snow in one location, road authorities are concentrating the potential contaminants, including road salts, oil, grease and heavy metals. Therefore BMPs include taking precautions to ensure that snow dumps are not located near environmentally sensitive areas and are able to contain and treat runoff if necessary.

Implementing BMPs has the potential to greatly reduce the amount of road salts loadings to the ecosystem. However, participation is completely voluntary and any salt management plans developed under the Code of Practice are not reviewed or approved by Environment Canada.

Alternative Products

A tremendous amount of research has been dedicated to exploring alternative deicing products that have less ecological and economic impacts than traditional road salts. Non-chloride based alternatives include acetate and formate products.

Calcium magnesium acetate (CMA) is the most widely studied alternative to road salts. Its effectiveness is in the same range as sodium chloride, decreasing below -7oC. CMA does not directly melt ice or snow, but breaks the bond between snow particles and the road surface enabling it to be ploughed more efficiently. As such, CMA is not a good deicer on its own, but is an effective anti-icer when applied ahead of an event. CMA contains no chlorides and is biodegradable. It is also less corrosive than chlorides and demonstrates low toxicity in aquatic environments, but may deplete oxygen in some aquatic habitats. CMA is ideal for areas such as bridges or parking decks that are vulnerable to corrosion, and for roadways in environmental sensitive areas. The initial cost of CMA is significantly higher than that of road salts.

Liquid potassium acetate can be used as an anti-icer, deicer, or as a pre-wetting agent. It is chloride-free, biodegradable, non-corrosive and has a low toxicity. It is effective at temperatures lower than -26oC. It is an ideal alternative for use in vulnerable areas, where environmental damage or corrosion is a key concern. Liquid potassium acetate is particularly well-suited for FAST-systems – fixed automatic spray technology that are used on bridges, exit ramps and other elevated structures.

Sodium acetate is used in solid or liquid form, primarily as a deicer and anti-icer on airport runways. As with other acetate products, sodium acetate is chloride-free, biodegradable, with low toxicity. It is considered an environmentally friendly alternative to urea, which has been a common airport deicer.

Both sodium formate and potassium formate have been primarily used as airport runway deicers, however, recent studies show promise for the increased use of potassium formate as a highway deicer. Potassium formate biodegrades rapidly and is less harmful to groundwater then traditional road salts applications.

Policy Changes – Supporting Social Change

As discussed earlier, road authorities have the ability to dramatically reduce the amount of road salts entering the ecosystem by implementing salt management plans that incorporate BMPs. These efforts can be complemented and enhanced through provincial government educational and regulatory programs. By altering public demand for winter road maintenance, changes in the necessity for bare pavement policies and reduced road salts demand should result. Two societal factors are highlighted: mandatory snow tire installations on automobiles, and winter speed limits.

Due to the current popularity of all-season radial tires, it is estimated that only a minority of Ontario drivers use winter tires. The reduced use of winter tires is part of the reason road authorities maintain “bare pavement” objectives. Research demonstrates that reduced winter speed limits and increased winter tire use will reduce the incidence of accidents on winter roads, which will then reduce the need for reliance on road salts alone to achieve the goal of winter road safety.