A salt in our freshwaters: Understanding the barriers to better winter road salt management in Ontario to clear the road toward healthier aquatic ecosystems

Finally, winter has come; it is December in Ontario once again. For many, this means a break for the winter holiday season, and time spent in celebration with families and friends. But for the winter maintenance industry, the busiest time of year is just beginning. While we spend our time inside (or perhaps outside, enjoying a beach getaway) in an attempt to avoid the cold weather, winter maintenance operators will spend much of their time over the next several months working hard to keep our roads, sidewalks and parking lots clear of snow and ice. The work the winter maintenance industry conducts is critical for public safety. Not only are they responsible for clearing snow following major winter storms, but they also are out on the roads applying de-icers such as brine and road salt in advance of, and in response to, snow, rain, freezing rain, and rain-on-snow events, as well as specific requests from local residents who have observed potentially hazardous conditions. 

The importance of this work cannot be understated, particularly in such a car-centric society as North America. In Ontario, we rely on our roads and highways to facilitate the transport of our food, goods, and services (like emergency medical services, or the emergency plumber when your pipes freeze). Thus, it is critical that roads remain clear from the build-up of potentially hazardous snow and ice. The most versatile tool at the disposal of winter maintenance operators for this task is road salt. Most widely used in Ontario, to the tune of approximately 1.5 million tonnes on public roads each year, Canada applies a total of approximately 7 million tonnes of winter de-icers to public roads annually. But here’s the kicker: that only accounts for public roads. Why? Because we simply do not know how much road salt is applied to parking lots. Though several attempts have been made to understand how much salt is being used on these other surfaces, the actual salt application on these surfaces is rarely tracked. Estimates suggest that total salt application to parking lots is as much as we apply to roads alone. 

This blind spot presents a serious challenge: throughout much of Southern Ontario, chloride concentrations have been steadily increasing for many decades. Chloride, the common constituent ion amongst commercially available winter de-icers (e.g., NaCl rock salts and brines) causes growth defects and even death among aquatic organisms at various concentrations. Worryingly, many monitoring studies have found that chloride concentrations in our streams, groundwaters, and wetlands are exceeding the long-term guideline for exposure of aquatic life to chloride. Set by the Canadian Council of Ministers of the Environment in 2011, the long-term guideline is set at 120 mg/L of chloride. A higher (640 mg/L) acute guideline is set for short-term exposures. Based on dozens of ecotoxicological studies, the federal chronic and acute guidelines exist to preserve the health of aquatic organisms from potentially lethal side effects from the exposure to high chloride concentrations. 

But the guidelines don’t stop chloride concentrations from increasing. As my Master’s research (supervised by Dr. Claire Oswald at TMU, and Dr. Jim Roy at Environment and Climate Change Canada (ECCC)) showed, this guideline is exceeded more than 90% of the year (yes, even during the summer months) in urban and urbanizing streams, and the more urbanized streams can experience short-term maximum chloride concentrations over 9000 mg/L – that’s approximately ⅓ as salty as the Atlantic ocean. In comparison, Lake Ontario typically sits at around 30 mg/L. 

But why does this matter? Many people look to the winter months with concern about road safety, and using road salt is often the fastest and easiest way to achieve safe, bare pavement conditions. Indeed, safety is a main driver for the expectation of bare pavement on our roads, sidewalks and parking lots, so much so that it is enshrined in provincial legislation (e.g., Ontario’s Minimum Maintenance Standards). However, there is no legislation for the type or amount of de-icers to be used. While there are countless studies that show chloride has negative impacts on aquatic ecosystems and organisms health, we continue to rely on the cheapest, most easily applied material available: sodium chloride (NaCl) rock salt. Given the costs of alternative de-icers and the new application equipment, staff training, and supporting infrastructure needed to adopt them, the impairment of water quality from winter de-icers is an unfortunate, but largely unavoidable, cost of having safe roads in the winter months.

Yet, there have been attempts to control road salt use to varying degrees, but these have been voluntary in nature. Most notably, the Code of Practice for the Environmental Management of Road Salts, developed by ECCC in 2004, has resulted in the development of municipal salt management plans, the adoption of best management practices for road salt application and storage, and overall reductions in the application rates of salt in Canadian municipalities. Through hard work and dedication, many municipalities have built covered salt storage facilities, optimized their salt application rates, and purchased new equipment with rate-controlled salt spreaders, as recommended by the 2004 Code of Practice. However, my discussions with municipalities suggests that there are a number of challenges preventing further reductions: 

1. Municipalities are growing outwards, with urban sprawl creating more roads that require salting – this is an issue that is far greater than the winter maintenance industry alone can address.
2. Legislated minimum maintenance standards, while helpful for setting clear minimum expectations, are not sufficient to avoid legal liability for damages resulting from motor vehicle accidents – this forces municipalities to respond to winter conditions by applying more salt than they otherwise would need to, to prevent liability in possible future lawsuits. 
3. Conversely, the absence of minimum maintenance standards for parking lot maintenance, or any legislative mechanism to limit legal liability for contractors, is likely a primary reason why parking lots are so commonly over-salted – there is no provincial guideline for salt application in parking lots, so property owners and their contractors often over-apply salt to reduce their risk of liability from slips and falls.
4. Climate change may be driving more frequent freeze-thaw cycles, and is changing the types of winter precipitation we receive – this could create situations where more road salt is needed to combat black ice formation on roads and parking lots. A shift to more rainfall in the winter months would also force more frequent salt applications to compensate for the loss of salt that is washed off roads during rain events.

To begin addressing these challenges, it is important to first engage with those responsible for conducting this delicate balancing act each year. My doctoral research, supervised by Drs. Claire Oswald and Carolyn Johns, seeks to: 1) Engage with municipal winter maintenance managers to understand how climate change is influencing their operations and try to identify learning opportunities for other municipalities. 2) Conduct a case study of several municipalities in the Lake Simcoe watershed to understand how road salt application is influenced by different winter storm event conditions at the annual and event-scales. Conducted in collaboration with the Lake Simcoe Region Conservation Authority (LSRCA), these two objectives are part of a broader effort to model future road salt use and chloride concentrations in the Lake Simcoe watershed. 3) Engage with policymakers in Ontario and New Hampshire to understand how limited liability protection for winter maintenance contractors in New Hampshire was developed and implemented, and understand the pathways to implementing similar legislation in Ontario. This work has been generously funded through the Geoffrey F. Bruce Fellowship in Canadian Freshwater Policy. Together, these projects will help to support long-term planning by municipalities and conservation authorities, and shed light on possible strategies for achieving reduced road salt application across Ontario. Despite the many efforts of Canadian governments and public servants at the municipal, provincial and federal levels, many Canadian freshwater ecosystems are perpetually under stress from the winter application of de-icers. With the anticipated transition from heavy snowfall to more freezing rain and frequent freeze-thaw cycles in Ontario, the need for road salting will continue; in the face of urban sprawl and more frequent freeze-thaw cycles, the case may even be that demand increases in the short and medium terms. Indeed, climate change presents a great deal of uncertainty around future demand for salt use, and serves as a primary motivator of my research. However, there is still hope for freshwater ecosystems: by leveraging the expertise of municipal winter maintenance staff and their historical data, as well as looking to success stories in other jurisdictions, we can set Ontario on a path to clear roads with less salt. You, the reader, can help as well: by wearing the right footwear, driving the right speeds, and being smart about salt (external link)  on our front doorsteps, we can all help keep salt out of our freshwaters.