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Tim Olson, PE, Bolton & Menk
Connie Fortin, Fortin Consulting, Inc. now Bolton & Menk
Ben Scharenbroich, City of Plymouth

Public Works professionals are tasked with managing our infrastructure year-round. In Minnesota, this includes four seasons of varying temperature and precipitation that impact safety, equipment choices, and policy.  Each year, we prepare to manage the snow and ice with plows, shovels, snow blowers, and lots of salt.  Sodium Chloride, or NaCl, is the most common deicer used because it is inexpensive, works well to melt ice and snow, and it has been used for the last 50 years.  Liquid deicers, which are mostly chloride-based, have also grown in popularity.  

Our communities have high expectations for clear roads and walkways, and salt is doing the heavy lifting. However, long after the snow has melted, salt remains, creating a bleak future for our freshwater systems.

Chloride Impacts to the Environment and Infrastructure 

Most people don’t completely understand the numerous environmental and infrastructure impacts of salt.  Chloride is a permanent pollutant; it never biodegrades or breaks down. Once salt is applied, the chloride component of salt travels from the road or sidewalk to the water. It may infiltrate through the soil into the groundwater, run across the land, or flow into a pipe to surface water.  Removing chloride from water is very difficult, expensive, and energy intensive. Even if it is removed through processes like reverse osmosis, chloride remains in the waste stream. 

Just one teaspoon of salt pollutes five gallons of water to the United States Environmental Protection Agency (EPA) threshold for aquatic life.  At harmful concentrations of 230 mg/L or more, salt will damage fish eggs and small organisms in freshwater.  Chloride also impacts water for human consumption. At 250 mg/l, chloride is a secondary drinking water contaminant, which impacts its taste.  Alongside water damage, the sodium in salt attacks soil structure. This can increase erosion potential and decrease plant viability on roadsides. 

In addition to the environmental impacts of chloride, there are also significant infrastructure impacts. According to the MPCA, infrastructure damages for salt use range from $800 - $3,300 per ton. These are conservative projections based on research pre-2014 and because labor and material prices have recently skyrocketed, so can the projected cost of our infrastructure damage. 

Are Clear Winter Pavements Achievable without Using Salt? 

For decades, there has been a push to educate winter maintenance professionals about the chloride problem and significant progress has been made to increase scientific strategies in this sector.  This includes chloride training, calibration of salt application equipment, and significant investments in new technology.  Even if public works winter maintenance crews operate at top efficiency, chloride products will still be used to meet the public expectations and level service.  Therefore, the problem only slows, it doesn’t disappear.  

Instantly clear winter roads are a tall order.  Our current roadway, parking lot, and pedestrian mobility designs and policy require heavy lifting by winter maintenance professionals.  Stormwater management has taken on the burden of managing extreme pollutant loads through ever-changing stormwater management techniques. It’s important to remember that chloride cannot be removed from our traditional stormwater best practices and source reduction is essential to clean water.  

What can we do to help?

Most infrastructure regulations influencing design are focused on managing rain.  Minnesota manages snow nearly as often as we manage rain but the design for snow and ice management is largely ignored. Snow, blowing snow, strategic snow storage, plow access, meltwater sprawl, and refreeze are rarely thought about during project planning or design.  This oversight, in part, has led the winter maintenance industry into the high salt use seen today.  Public works professionals and winter maintenance leaders should be engaging with engineers and architects who design the salted surfaces and should expect equal performance in winter conditions.

It is time to revisit cold climate engineering standards and enhance our education focused on safer winter driving, biking, walking conditions without the need for so much salt.  Our freshwater future is dependent on partnerships between public works officials, engineering teams, and community decision makers.  It is time to reduce Minnesota’s dependence on salt!