Public Safety and the Environment: Solving the Road Salt Dilemma

When the Bow River Basin Council (BRBC) was established as a Watershed Planning and Advisory Council under Alberta’s Water for Life Strategy shortly after 2000, it brought together the people and processes necessary to help make the difficult tradeoffs between social, economic and environmental interests. Today, the BRBC’s municipal members are faced with very difficult tradeoffs: Do we increase the use of road salt to further reduce accident frequency? Do we reduce the amount of salt used to protect the aquatic environment? Does road salt in runoff limit the reuse of stormwater as we enter extended periods of drought with less water available for a healthy economy?

Stormwater reuse has been a key issue for the Calgary Metropolitan Region Board (CMRB) since its initial studies supporting a Regional Servicing Plan began in 2019. At that time, the CMRB published a Stormwater Reuse Backgrounder that identified water reuse case studies around the world. The CMRB correctly identified stormwater reuse as a potential solution for reduced water availability under climate change scenarios (and, in fact, stormwater runoff was already contributing to the Bearspaw and Glenmore reservoirs).

More than 5 million tonnes of salt are applied to roads across Canada resulting in elevated levels of sodium and chloride in soils, vegetation and the aquatic environment. The reduction of salt in runoff is a priority for the Federation of Canadian Municipalities, which has a Green Municipal Fund Program supporting studies to reduce salt impacts.

Undoubtedly, salt application benefits commuters during icy conditions. Studies across the US have shown that the application of salt can reduce accident frequency by 85%. A 10% improvement in the surface friction of a road can yield a 20% reduction in crashes. And on four-lane roads, before-and-after analysis has shown a 93% reduction in crashes after de-icing. Calgarians benefit immensely from The City’s Snow and Ice Control (SNIC) Policy.

On the flip side, road salt increases chloride concentrations in runoff. Chloride is a highly soluble and mobile ion that spreads rapidly throughout a water body. It is also toxic to wildlife and can be incredibly persistent because nothing naturally breaks down chloride in the environment. High chloride levels can also inhibit the growth/reproduction of aquatic species, impact food sources, and disrupt amphibian osmoregulation. In addition, high chloride levels can lead to oxygen depletion by creating an oxygen-deficient layer that is harmful to aquatic life. A comprehensive 5-year scientific assessment published by Environment and Climate Change Canada determined that, in sufficient concentrations, road salts pose a risk to plants, animals and the aquatic environment.

Excess salt in the environment also impacts riparian landscapes. Salinity affects almost all aspects of plant development including germination, growth and reproduction. High salinity can cause ion toxicity, osmotic stress, nutrient deficiency and oxidative stress on plants, thereby limiting water uptake. There are also impacts on agrarian landscapes. In Eastern Canada, downstream landowners have successfully been awarded compensation for crop losses, the cost of soil/plant analysis, and for the diminution of property value resulting from road salt contamination. Closer to home, Alberta’s Ministry of Environment and Protected Areas has monitored water quality in Fish Creek at its mouth to the Bow River for 20 years through its Tributary Monitoring Network. Although sample frequency is too limited to yield a conclusive trend, 10% of samples analyzed from December through to February showed chloride levels exceeding Alberta Water Quality Guidelines for acute toxicity (see Table 1). Perhaps equally problematic is the fact that chloride measurements often exceed levels considered acceptable for long-term chronic exposure. Acute guidelines are never to be exceeded; chronically high chloride levels can cause permanent damage to the ecosystem.