One of the biggest challenges cities face during winter is managing snow and ice buildup on roads. Snow can melt from the pavement’s warmth and then refreeze into ice, creating dangerous conditions for drivers. Over the winter, roads can become increasingly hazardous for drivers as snow and ice accumulates.
The primary method for managing snow and ice is through plowing. Physically plowing removes snow and ice, clearing roads for safer travel. The second tool is to salt the roads. Snow plows scatter rock salt or spray liquid brine to prevent ice from forming on pavement. While this practice helps create clear roads and even maintain summer-like road conditions during wintertime, it comes with a significant environmental cost.
A Quick History of Road Salting
Road salting started in the 1940s and has rapidly increased since then. When salt is applied, it dissolves into chloride and sodium ions, preventing refreezing on the pavement. Ultimately, these dissolved chlorides wash off the roads and into the surrounding environment. Since the 1940s, we have consistently and increasingly been polluting our land and rivers with chloride.
The rise in road salt is primarily driven by two factors: increased urbanization of our landscape, which means more roads to salt, and public expectations for consistently clear winter roads. For instance, people expect to drive as fast and carefree in the winter as they do in the summer. In fact, one of the most common complaints to local officials is dissatisfaction with winter road conditions. This demand has led to large quantities of road salt being applied every winter season.
Road Salt in Rivers and Streams
Salt is applied to roads each snow and ice event. As the snow and ice melt, the salt-laden runoff flows into rivers, streams, and lakes. This continues all winter long, causing chloride levels to spike in the winter. Chloride concentrations gradually diminish as salt washes downstream in spring and summer. It often takes well into the summer for chloride concentrations to get back to “normal.” However, over time, this “normal” baseline concentration is increasing. Spring and summer chloride concentrations are not decreasing as much as before, leading to a higher average year-round concentration in our waterways.
Chlorides in Groundwater
Our rivers and lakes are getting saltier, and unfortunately, so is our groundwater. In regions like Will County, where drinking water comes from shallow and sandstone aquifers, the impact is particularly concerning. These uncontained aquifers recharge with rainfall, which makes them a sustainable water source, but it also makes them more susceptible to contamination. Unfortunately, the aquifers that we rely on for our drinking water are being recharged with salty runoff from our roads. Over the years, chloride has been detected deeper in the groundwater supply. Recent measurements show chloride reaching over 300 feet deep into the aquifers.
Road Salt Damages Infrastructure and the Environment
Excessive salt use damages both infrastructure and ecosystems. Salt is highly corrosive to metal and can cause rapid rusting. Concrete also suffers from salt exposure; small holes, or “pitting,” form, allowing rainwater to seep in, which causes cracking and chipping. Since we build most of our roads, bridges, and buildings from steel and concrete, we are weakening them with corrosive chemicals every time we salt the roads.
Salt is also highly toxic to plants and animals. Landscaped areas along roads and sidewalks suffer from salt burn when the salt concentrations are too high. Plants die off and are often replaced by salt tolerant invasive species. Salt hurts aquatic organisms in local rivers and lakes too. As chloride concentrations rise in the water, fish, insects, and aquatic plants struggle to survive.
Additionally, salt degrades drinking water quality. As rivers, lakes, and aquifers become saltier, our freshwater sources face long-term risks. 20% of the world’s freshwater supply resides in the Great Lakes region where we live. As we continue to pollute this fresh water with salt, it eventually will no longer be fit for human use or support natural ecosystems.
The Path Forward: Responsible Salt Use
Given the threat of the salinization of our land and water, it is clear we must do something to reduce our salt use. Many public agencies are optimizing their winter road maintenance practices. Groups like the Salt Smart Collaborative provide technical training aimed at decreasing salt usage without compromising safety. Despite these efforts, however, optimizing current practices alone may not be enough to stop the salinization of our rivers and drinking water.
To make a meaningful impact, we may need to reconsider how we approach winter road maintenance. This could mean relying more on plowing and accepting that, during icy conditions, we might all need to drive a little slower.
Written by Alex Handel, The Conservation Foundation
