Using Technology to Reduce Costs and Help the Environment During Road Salting
Lake Champlain Sea Grant and UVM Extension partnered with the town of Hyde Park Highway Department to offer a free training for municipal employees and others who manage snow and ice on roads and other surfaces in winter. The workshop was held at the Hyde Park Highway Department garage on October 26. In all, 67 people representing 19 different Vermont communities participated. Using Hyde Park’s snow and ice management techniques as an example, participants in the workshop learned about technologies that can help minimize use of road salt. These practices maintain public safety and, while there is an initial investment cost, they can ultimately reduce costs and benefit the environment.
Since 2020, with support of their select board, Hyde Park staff, led by Road Foreman Mark French, have taken steps to update their road salting equipment to use new technologies. This has helped them reduce road salt use by about 50 percent. The technologies the Hyde Park team has incorporated include purchasing equipment that allows them to make a salt-water mixture, called brine, using the brine to prewet dry rock salt before it is applied to the road, calibrating equipment and measuring salt use during each storm, and using temperature sensors on their trucks.
Prewetting salt happens “at the spinner,” which means the rock salt is wet with the 23.3 percent brine solution on the truck just before the salt is spread onto the road. This allows the salt to stick better to the road, keeping it in place where it is needed to prevent ice from forming on the road. When the salt is not prewet, it tends to bounce off the road, requiring additional salt to be added to replace that which bounced off the road. Any salt that bounces or later washes off the road can in turn damage vegetation, enter waterways where it can be toxic to fish and other aquatic life, and cause changes in soil properties such as allowing heavy metals that come from cars to move through the soil.
Monitoring pavement temperatures with the on-truck sensors allows Mark and his colleague Ryan Nolan, to know when it makes sense to salt or not. For instance, if they observe that pavement temperatures are 35F and the forecast calls for a sunny and warming day, they know that ice won’t form on that surface and can opt out of salting the road. On the other end of the temperature scale, rock salt (which is sodium chloride) only works down to pavement temperatures of about 15F. So, if Mark or Ryan observe that pavement temperatures are lower than that, they can save salt by not spreading it as it won’t be able to keep ice from forming at such temperatures.
Mark shared that “salt is immediately activated by the salt brine,” so its beneficial work of keeping roads ice free starts to happen right away when pre-wet salt is spread. When dry rock salt is spread on roads or other surfaces, it must mix first with water to begin to lower the freezing point of water and keep those surfaces ice-free. As water molecules try to bond with one another to form ice, sodium and chloride (which break apart into separate molecules when in water) get in between the water molecules. This process keeps ice from forming. When pavement temperatures are below 15F, there isn’t water available in liquid form to mix with the sodium chloride, explaining why salt doesn’t work to keep surfaces ice-free at lower temperatures.
Finally, calibrating equipment is important, as it allows Mark and Ryan to track how much salt is going out at any moment in time. Their goal is to only put out what’s needed to keep ice from forming on the road, so if they know how much is going out at any given setting on their controls, they can be sure to put enough out to keep roads safe, but not too much.
The practices that Hyde Park implements are not the only ones that can help reduce the use of salt. For instance, South Burlington uses plows with multiple rubberized segments. The individual segments can do a better job scraping snow and ice off of surfaces to prepare them to add salt. They also have secondary plows on some trucks, which also help to clean the surface. No matter if it’s professionals adding salt or individuals at their homes, the idea is that salt should only be added to clean surfaces, not to snowy or icy ones, as it can do its job to prevent ice formation on surfaces only when in contact with those surfaces.
Mark also shared that, “whoever is spreading salt needs to be educated in salt use.” It is important that snow fighters understand how salt works to keep surfaces free from ice. This includes understanding the temperatures at which sodium chloride works, what happens to dry or prewet salt when it hits the pavement and how that can be affected by traffic or other road conditions, and having awareness of what happens in the environment when salt finds its way into waterways, soils, and vegetation.
As users of roadways, residents in communities throughout the Lake Champlain basin and beyond can help snow fighters do their jobs by supporting budgets that keep road and sidewalk surfaces in good shape and that allow municipalities to invest in new snow and ice management technologies, both of which can help them to reduce their use of salt.
Communities interested in learning more about the use of different technologies to reduce the use of salt can visit the Lake Champlain Sea Grant website where a suite of videos are posted. If you have questions about how salt works, or ideas for future road salt reduction trainings, videos, or other resources contact Kris Stepenuck at kstepenu [at] uvm.edu.