Where Has All the Road Salt Gone

As the days begin to warm, and the last remnants of snow have disappeared, thoughts of Winter fade into the distance. Many now deal with the post-Winter clean-up. The debris, dirt, dust, and remnants left behind after several months of snow and ice cover. There are some remaining signs of the road salt and sand used to battle the ice. Most of it however, washed from roads and walkways by the melting snow and April rains.

If you live in Canada, chances are you have come to appreciate the benefits of road salt. Either while driving after a spell of freezing rain, or when negotiating stairs and sidewalks covered in ice and snow, we respect the inherent danger, and welcome the relative safety when salt has been applied.

However, you likely have mixed feelings. It is troubling when seeing the corrosive impacts on your expensive automobile, stains on your foot-ware, pitted cement on your new interlocked walkway or garage floor. Perhaps you have witnessed a limping dog with salt crystals stinging his paws. And, road salt is not a derivative of table salt, it contains a range of toxic additives and impurities. Animals are attracted to salt taste and there are reports of sickness and cancer related deaths to pets and wildlife.

The primary salt type used for de-icing purposes is sodium chloride, which is composed of 40 percent sodium and 60 percent chloride. Other components in road salt like ferrocyanide, which is used for anti-caking, and impurities like phosphorus and iron, can represent up to 5 percent of the total product by weight. The sodium, chloride, ferrocyanide and impurities make their way into our environment through the runoff. They find their way onto vegetation and into the soil, groundwater, storm-drains, and surface waters for further transport to lakes and rivers.

Chloride is completely soluble and very mobile. Chloride is toxic to aquatic life and negatively impacts vegetation and wildlife. There is no natural process by which chlorides are broken down, metabolized, taken up, or removed from the environment. Higher salinity water is denser and so builds from the lake bottom. We may be unaware of a growing salinity problem as it lies undetected in the depths of fresh water lakes. In 2008, New Hampshire listed 19 water bodies impaired by chloride; in 2010 that number increased to 40. Trends show that chloride levels continue to rise with increasing use of road salt.

The use of salt has increased significantly over the last few decades. A growth in population and urbanization, an expanded road and sidewalk network, more traffic, liability concerns, and, higher service expectations of our municipalities in the battle against ice, have led to a significant increase in road salt use. The latest estimate is that 30 million tonnes of road salt are dispensed each year on public roads and walkways (excludes private use of road salt). 30% of that amount is used on Canadian roads each year.

A recent study by the Cary Institute of Ecosystem Studies as reported in the Proceedings of the National Academy of Sciences, has raised the alarm about the increasing salinity of our fresh water lakes. Co-Author Dr. Sujay Kaushal from the University of Maryland uses the term “fresh water salination syndrome’. According to the study, 37% of the entire US continental fresh-water drainage area has significantly increased in salinity over the last 10 years. In addition to salinity, the alkalinity of the water is changing. The same area has had a 90% increase in alkalinity levels. Not all of the salt impact comes from road salt. Other sources of salt runoff come from irrigation of high-potassium fertilizers and mining waste. However, this is more prevalent in the mid-West, whereas the main contributor in the North East is road salt.

The salinity and alkalinity issue of our fresh water supply gives rise to other concerns. Water of this type is corrosive. When drawing from these water sources for municipal water requirements, the municipal infrastructure may deteriorate and be in need of costly rehabilitation. If not addressed, the drinking water supply can become contaminated with heavy metals. A high-profile case-in-point was the well-documented contamination of the Flint Michigan water system. The water crisis received prominent attention during the last US Federal election. In 2014 the city started to draw water from the Flint river. The high salinity and alkalinity of the Flint river water system resulted in the leaching of lead from the city’s water infrastructure into the drinking water supply.

In the USA, road salt is not regulated by EPA. This leaves municipalities to address the issue. There is evidence both in US and Canada, that municipalities are actively trying to reduce consumption of road salt. Motivated by their environmental policies and demands of their constituency, they also have concerns for the municipal water supply, as well as increasing road salt costs and issues related to availability. Broader public awareness of the fresh water salination syndrome is also growing. Social media has been active with news of potential alternatives to road salt. There have been a number of reports where some municipalities have undertaken trials with beet juice and cheese brine as alternatives.

In Switzerland, a road salt alternative technology has been developed and effectively deployed for the last eight years. It utilizes an engineered wood chip, specially coated with a pH neutral formulation of which magnesium chloride is the active ingredient. The coating sets the chip into the ice or snow which then re-freezes to lock the chip in place. The result is a surface with traction and grip. The Swiss are now licensing the technology elsewhere and it is gaining notoriety in Europe and Scandinavia. With an abundance of forest residuals in the North East of North America, this technology looks promising as a possible component of a municipal salt reduction strategy.

Although there are road salt alternatives, changing the way things have been done for decades comes slowly. Support for alternatives begins with awareness and motivation. This Summer, we will once again enjoy and appreciate the bounty of our fresh water lakes and rivers. It is unlikely that any will disagree that preserving these is of paramount importance and serves as motivation for change.

(References to studies and data in this article are available upon request. Please inquire through the Contact Us page.)