It’s that time of year again - temperatures have dropped below freezing, and the wintery weather has blown in. Departments of Transportation, state, local and city road crews are being kept on their toes, applying roadway treatments and safe passage for all of us. It is estimated that the US spends approximately $2.3 billion annually to keep highways free of snow and ice, and roughly 20% of transportation department budgets goes toward winter road maintenance. Over 43% of the mined salt is applied for winter deicing efforts, when in comparison only 4% is applied to our food. In the US, over 19 million tons of road salt is annually spread over our highways, roads, parking lots and sidewalks to keep us safe.
Currently, there are not many environmentally safe, effective and inexpensive alternatives to road salt. Sand and chip stone is likely the most environmentally friendly, however, these materials do not deice. These materials are often ground down by vehicle wear into smaller, finer particles over time. Once a thaw occurs, they are washed into our storm drains and waterways which is not desired.
Sodium chloride (salt), is only effective at temperatures above -18° C and, therefore, when colder temperatures get this cold, sodium chloride is not the salt type applied. Other chemical deicers are typically chloride-based salts of calcium, potassium, or magnesium, with some being effective at temperatures as low as -34° C. There are also non-chloride chemicals available including calcium magnesium acetate, potassium acetate, and urea. Newer liquid byproducts from the food or beverage industry, such as beer waste and beet juice, are mixed with rock salt and applied to roadways. The newer organic products come with other environmental issues. For example, as these byproducts like beet juice or beer waste wash into our waters, they naturally breakdown, consuming oxygen from the water, the same way algal blooms do, which can have negative environmental impacts.
Bottom line, deicers are polluting our waters, while keeping our streets safe during winter travel. When snow and ice melts, all roadway treatments are washed into our catch basins, eventually washing into our lakes, streams, wetlands and groundwater. Once present in water, there is no easy way to remove chlorides. No existing stormwater treatment system exists to capture and retain salts, or chlorides. Chlorides may be loosely retained in soils or in water, but will continue to flush through the system as more water enters, building up at the downstream end of the watershed, or within groundwater. Chloride from deicing salts also has the potential to increase the mobility of metals loosely attached to sediments, as does other deicing chemicals, calcium and magnesium. Additionally, research indicates the toxicity of available metals increases from the use of salts.
In high concentrations, chlorides can be harmful to our freshwater aquatic life. Chlorides also have negative and destructive impacts on our infrastructure, as they corrode metal and pit concrete, rust metal vehicle components, kill non-salt tolerant vegetation, and are harmful to soil, pets, and wildlife, as well as contaminate our groundwater and drinking water supplies.
Since there are no treatment mechanisms for road salt, the best way to reduce road salt in the environment is to reduce the amount you put on to start with, which is why many municipalities investing in training maintenance staff an private contractors on the most efficient use of road salts.
So with doctors and dieticians alike telling many of us to reduce our salt intake, this winter, consider taking these same recommendations into account in your area of influence as it relates to impervious surfaces. Less is more when it comes to applying deicers.