The levels of salt in groundwater are related to proximity to roads and the total coverage of pavement and other surfaces that are impervious to water.
From the 2019 Cary report Road Salt: The Problem, The Solution, and How to Get There
In the 1970s, transportation agencies began to recognize that using large quantities of road salt could harm the environment and infrastructure. Since then, much research has been done to document and improve best management practices for maintaining ice-free roads. Remaining on top of the latest equipment and techniques can be challenging. However, organizations such as Clear Roads have improved opportunities for discovering and implementing accessible methods of salt reduction.
Many departments of transportation have begun using a 23% salt brine solution to pre-treat roads before the onset of storms. Estimates suggest that road pre-treatment with brine can yield a 75% savings in total salt applied
Pre-wetting salt before roadway application can reduce salt infiltration to aquifers by 5%. Pre-wetting salt allows it to stick better to the road, which minimizes spray and kick-up of salt grains.
Calibration allows you to measure the exact amount of material you apply, facilitating more accurate and efficient deicing, with less total salt used. You don’t need a regulator to calibrate your equipment.
Calibration procedures – which are readily available in online manuals – should be a standard component of trainings for salt truck operators.
Automated spreader controls allow salt truck operators to program salt application rates so that the amount of salt being applied changes with ground speed, which reduces bounce and scatter. These programs can also account for curves and hills, which require more salt than flat or straight roads. Vehicle location sensors can target salt distribution to a precise location along a route. This kind of information can allow for fine adjustments and keep track of total salt distribution for salt monitoring purposes.
To minimize salt loss and pollution, salt piles should be contained. Municipalities and privately- owned facilities can protect salt investments and the environment by adopting storage best practices. These include building salt storage sites on impervious surfaces, implementing secondary containment measures, completely enclosing salt piles, and regularly inspecting structures for breaks or tears.
Unintended spills and releases of road salt from vehicles are inevitable. Allowing time to clean up spills will reduce unwanted release of salt to the environment. Also, collection systems are now available to promote the recycling of vehicle wash water, which can be used to produce brine for anti-icing applications.
High quality data on road and weather conditions should be shared between transportation officials and weather forecast providers to facilitate targeted, coordinated road salt application. In addition, smart phone apps, cell phone text alerts, and web-based platforms are increasingly allowing travelers to make informed decisions about road conditions before travelling.
Modern plows are designed to reduce the amount of road salt needed to maintain ice-free roads. For example:
Pavement temperature determines whether frozen precipitation will stick and how much salt is needed to maintain safe roads. They can help guide salt application by road crews and inform the public about the safety of road conditions.
Several states adjust levels of service to conditions. For example, the Vermont Transportation Department seeks to provide ‘safe roads at safe speeds’ – not necessarily bare roads. New Hampshire, Ohio, Colorado, and other states define varying levels of service based on traffic volume.
Surveys can help gauge the public’s expectations and comfort level with varying levels of service. For example, after surveying the public, the Minnesota Department of Transportation was able to adjust its practice of maintaining bare pavement during a storm to maintaining bare lanes.
Expanding the practice of adjusting levels of service to match expectations and traffic volume has the potential to drastically reduce the overall amount of salt released into the environment.
Some road service agencies have identified areas of low or no salt near sensitive freshwater bodies such as reservoirs, lakes, rivers, streams, and well fields that feed public water supplies. Educating travelers in these areas is critical.
Alternative salt-based deicers have changed very little in recent years. Interest in agro-based alternatives has expanded greatly although salt is the active ingredient in most of these products. Products include:
Agro-products can lower the freezing point of chloride-based salts and increase the amount of time salts remain on pavement. They can also improve sunlight absorption and reduce the corrosivity of salt solutions. When washed into streams and lakes, many agro-based deicers have an impact, as would be expected when any organic material (such as wastewater) is released into a water body. High levels of organic material can deplete oxygen, stimulate algae, and cause fishkills.
These agro-based deicers also tend to be more expensive. Other alternatives to rock salt include different types of salt or sand, which vary in effectiveness and impact.
Even with an attractive cost-benefit analysis, some municipalities or contractors may not have the financing to cover the costs of new equipment.
Snow maintenance at shopping centers, hospitals, schools, apartment complexes, and private businesses is largely handled by contractors who may have a disincentive to reduce salt use for a variety of reasons.
Public expectation and laws that mandate the level of service required of road service agencies often dictate the amount of salt that is used. For example, Section 12 of the New York Highway Law says that snow and ice should be controlled to provide reasonable passage and movement of vehicles. This ambiguous language can be interpreted widely by travelers and highway crews.
Annual budgeting requirements, especially for some small municipalities, may result in standardized salt use every year, even if conditions in some years don’t warrant use of the standard amount of salt.
In order to assess the efficacy of new technology and practices, data collection and monitoring are needed.
Best Management Practices for Salt Reduction — NH Dept. Environmental Services best management practices documents developed as part of a survey of the best and most applicable technology.
Clear Roads newsletter — National research consortium Clear Roads, which focuses on testing winter maintenance materials, equipment, and methods.
Clear Roads Best Management Practices — Clear Roads manual for road salt winter maintenance.
Snow and Ice Management Association (SIMA) – Trade organization offfering resources and information for private snow and ice management professionals.