Rolling Out the Road Salt: Protecting Our Safety & Environment
Here in Michigan, we’re all familiar with the wonders and woes of snow and ice. As lovely as it looks accumulating on the trees and blanketing the ground, no one is a fan of it on our roadways or sidewalks, where it can pose significant risks to all of us as we try to go about our usual routines on a potentially slippery or icy surface. To keep everyone safe as they travel – be it on foot, by bike, car, or bus – organizations responsible for transportation in colder climates across the country rely on road salt to help melt the ice. In the United States, an estimated 20 million tons of road salt is used annually to keep our roads and sidewalks safe. But why do we use road salt, specifically? It’s similar to the table salt you use in your kitchen, a natural mineral also known as halite, and is composed of sodium-chloride that helps to break up and melt ice under most conditions. When salt is sprinkled on top of ice, it reduces the temperature at which the liquid water freezes. Known as freezing point depression, this disrupts the water molecules’ ability to stick together and form ice.
So where do we find 20 million tons of salt each year? Road salt is typically mined from the same underground deposits as table salt, which were left behind by evaporated prehistoric oceans. The largest of these mines in the United States is actually located in Michigan, operated by the Detroit Salt Company. Once the salt has been mined, additives can be mixed in to prevent the salt from compacting while it’s stored and to make it easier to spread over icy ground. From there, individual states and their municipalities determine how much salt they need to purchase to make it through the year, storing it in large covered areas until the first sign of flurries, when it will be distributed by snow plows and trucks according to their best practices.
How & Why Do We Use Road Salt?
The use of road salt in the transportation sector has been around almost as long as cars and roads themselves. The first documented use was in 1938 when the state of New Hampshire used it as a cheap and effective way to de-ice their roads. Due to its success and relative cost-effectiveness, it became a nationwide practice by the winter of 1941-1942.
The tri-county region of Clinton, Eaton, and Ingham counties is no different; one of our highest priorities is providing residents with access to safe and reliable transportation. As you might imagine, Michigan’s winter accumulation of snow and ice can create hazardous road conditions, amplifying the need to mitigate slippery roads or parking areas with salt or another de-icing alternative. According to our regional crash data over the last ten years, approximately 15 percent of all crashes in the tri-county region can be attributed to icy, snowy, or slushy road conditions.
Our region includes nearly 5,500 miles of interstates and county roads, all of which are owned and/or managed by their respective county or one of the 38 individual cities and villages throughout the three counties. Each of these jurisdictions sets their own procedures regarding snow removal according to their unique budgetary and environmental considerations. For example, the City of Lansing is responsible for the snow removal and salting of over 400 miles of streets, and in 2019, maintained their own fleet of 12 salt trucks and 17 plow trucks.
In addition to maintaining their own salt trucks and salt stores, each jurisdiction determines its own snow removal procedures. In Eaton County, the road commission first clears the primary roads, then hard-surfaced (paved) secondary roads, and finally low-traffic subdivision streets and gravel roads. Depending on conditions, local agencies may focus their snow removal and salting efforts on conflict points – like street intersections, stop signs, left turns, hills, and corners – where traction is critical.
Typically, road crews are dispatched for plowing and salting when conditions are right for ice and snow, or just as it starts to accumulate. To maximize efficiency, many communities supplement their salt distribution with brining and pre-wetting practices. Brining, or anti-icing, refers to the application of a liquid salt brine to the pavement prior to a weather event. This prevents ice and snow from bonding to surfaces in the first place, making it easier to remove. Pre-wetting is the process of applying a liquid de-icer (usually brine) to the salt prior to spreading, helping salt stick to pavement rather than bouncing or blowing away. This allows road crews to apply less salt and speeds up the melting process, which also improves the performance of the salt in colder temperatures since it’s not as effective at depressing the melting point of ice at temperatures below 15°F.
How Does Road Salt Impact Our Environment?
While road salt plays a crucial role in keeping people safe on the roads during the winter, it’s not a perfect solution. Excess de-icing salt can negatively impact our natural environment – harming plants and trees, animals, and other wildlife – especially aquatic ecosystems. As the snow and ice melt, that water flows from roads and parking lots into storm drains that discharge directly into our rivers and streams. On its way, the runoff carries dissolved or small pieces of road salt with it, increasing the salinity – or concentration of dissolved salt – in receiving waters and the aquatic ecosystems they support.
Salt in these high concentrations can become harmful to fish, aquatic bugs, amphibians, and even aquatic vegetation. Elevated levels of chloride and sodium can stunt growth, disrupt reproduction, and impact the ability of freshwater species to regulate fluid transfer. It can also contribute to biological dead zones, as salinity impacts how ponds and lakes mix when the weather cools and surface water temperature changes, resulting in salty concentrations near the bottom that can start to change the composition of the entire water system and make it impossible for aquatic life to survive.
Though the specific impacts of road salt usage near our regional freshwater ecosystems can be more difficult to track given their widespread scope, evidence of these higher chloride concentrations has been documented, revealing road salt’s contribution to high salt concentration in our waterways. A 2015 study conducted by Michigan State University found that chloride levels in the Red Cedar River spiked as a result of snow melt, more than doubling the average levels recorded throughout the year. Studies like these help and encourage us to learn more about the effects and presence of these chemicals in our local water systems, particularly as they are connected to our drinking water resources.
In the tri-county region, our communities depend on local groundwater resources for their drinking water, delivered either by their local water utility or a private drinking well. Aside from concerns about road salt runoff in our local rivers or surface water, it’s also important to consider the impacts to our unseen water resources. During a recent study of the groundwater in Ingham County, high levels of chloride were recorded in a sample in Williamston Township near Meridian Road, where changes in traffic patterns caused by a new highway exit on northbound I-69 resulted in increased road salt usage between 1980 and 2016. The results of the study indicate that the impact of road salt can extend deep underground and over a significant amount of time, making it essential for public water suppliers and well owners to regularly test their water. Chloride levels in your drinking water are particularly important to monitor as high salt concentrations can present complications for people with health conditions like high blood pressure.
Unfortunately, once salt has entered our groundwater resources, there’s no easy way of getting it out. The best approach to protecting our drinking water from increased salt levels is by preventing it – that means reducing the amount of salt we apply whenever possible.
What Can We Do to Curb the Impacts of Road Salt?
Communities across the country (including our own!) are making efforts to reduce their salt usage or find alternatives that are considered more environmentally friendly, while still prioritizing safety and keeping costs down. During the winter of 2016-2017, the City of Lansing experimented with a beet byproduct instead of road salt, until they found that the material would be too expensive when ordered in bulk and “not as effective as [they] hoped.” Other communities across North America have tested alternatives such as cheese brine, pickle juice, or potato juice solutions. In addition to pre-wetting and brining, the Ingham County Road Department uses yet another approach – distributing sand in lightly trafficked areas. While sand doesn’t melt the ice, it helps create traction on the roads that aren’t visited as regularly by salt trucks.
That said, non-salt solutions for one community may not be possible or as effective for another given the many challenges they must consider, such as retrofitting salt trucks to distribute alternative substances, budgetary constraints, varying levels of traffic, or even negative impacts to their built infrastructure. Because of these fluctuating needs, road salt has largely remained the cheapest and most effective method of de-icing. Improvements in salt truck technology and driver education have also led to a more efficient use of salt; newer trucks are able to automatically adjust how much salt is dumped based on vehicle speed, preventing the loss of 20-30% of salt bouncing off the roads.
When it comes to salt usage, most people believe that it’s a problem for municipalities to solve and that road crews are the bulk of the issue. While road crews are certainly the most visible users, over half of all road salt purchased is sold to private homeowners and businesses to de-ice millions of driveways, parking lots, and sidewalks, often to prevent safety and liability issues. Furthermore, communities who fall under state and federal stormwater rules are required to train staff on proper salt application, calibrate their trucks, and protect their stockpiles from rain and wind. Homeowners and businesses, on the other hand, are not subject to the same requirements. By adopting similar best management practices of municipal operations, home and business owners can play a major role in reducing salt pollution.
So, what can you do to be part of the solution? First, it’s important to shovel quickly and keep up as the snow falls. This makes it easier to move the snow and can prevent ice from forming, eliminating the need for salt entirely. You should also know that using more salt does not necessarily equate to more ice melting. To avoid distributing more salt than you need, use a handheld spreader to maintain a consistent application of less than four pounds per 1,000 square feet, or roughly four full coffee mugs spread over half a tennis court. If salt is still visible on dry pavement, it’s no longer serving its purpose and should be swept up to keep it from washing away.
As mentioned previously, most salt is ineffective below 15°F, so don’t bother applying it if temperatures are already too low. Instead, use sand to provide some traction, or try an alternative product. If you hire someone to perform your snow removal, ask them about their application and storage methods and encourage them to follow best management practices. Reducing salt usage isn’t just good for the environment, it can also save you money!
As our local road crews, municipalities, and community leaders continue to do their part in finding a balance between protecting the public’s safety and our environment, it’s important that we support their efforts in our personal usage of road salt. Snowy and icy winters in mid-Michigan aren’t going away anytime soon, so it’s up to all of us – homeowners and business owners alike - to continuously reevaluate our de-icing practices and continue researching the best, most cost-effective options for each of our community’s unique needs. Whether it’s testing out pickle brine on your driveway this season, or shoveling sooner than you would have before, we can all can take action to help keep our freshwater resources clean and free from salt!