Winter is coming. Isn’t it always in the Midwest? With cold weather fast approaching, we are preparing to manage the snow and ice with plows, shovels, snow blowers, and lots of salt.
The most commonly used deicer is rock salt, otherwise known as NaCl or Sodium Chloride. Rock salt is frequently used as a deicer for many reasons: it Is inexpensive, works well to melt ice and snow, and it has been used for the last 50 years. Winter maintenance is set up to use rock salt since it is relatively safe and easy for maintenance workers to handle. Most people do not think of salt as a dangerous product (after all, it is put on popcorn), and subsequently, do not know the numerous environmental and infrastructure impacts of salt.
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. It is invisible as it dissolves and moves through the environment, and it typically is not given a second thought — but it should.
What is Chloride and Why is it Harmful?
Chloride is found in a variety of products such as road salt, water softening salt, dust suppressants, fertilizer and more. For storm water management, deicing salt is the primary focus. Chloride is a permanent pollutant; it never biodegrades or breaks down. 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.
The United States Environmental Protection Agency (EPA) has set standards for a variety of pollutants and steps need to be taken to keep lakes and rivers below these thresholds to protect aquatic life. Chloride is one of those pollutants and a top pollutant of concern in Minnesota today. According to the EPA chloride is toxic to aquatic life at 230 mg/l (federal chronic standard). Salt will damage fish eggs and small organisms in freshwater. Shockingly, just one teaspoon of salt pollutes five gallons of water to the 230 mg/l threshold.
Chloride also impacts water for human consumption. At 250 mg/l, chloride is a secondary drinking water contaminant, which means water’s taste will be affected.
Alongside water damage, the sodium in salt attacks the soil structure. It works like a water softener where the sodium ions displace the calcium and magnesium ions, weakening the soil integrity. This can increase erosion potential and decrease plant viability on roadsides.
How does Chloride Impact Infrastructure?
In addition to the environmental impacts of chloride, there are also significant infrastructure impacts. According to the Minnesota Pollution Control Agency, infrastructure damages for salt use range from $800 - $3,300 per ton. These are conservative projections based on pre-2014 research and because labor and material prices have recently skyrocketed, so can the projected cost of infrastructure damages. For every ton of salt that a winter maintenance crew loads into their trucks, they should be thinking about the enormous amount of infrastructure damage being created.
How does Chloride Impact Storm Water Ponds?
Storm water ponds are not the answer with a dissolved pollutant like chloride as it travels through these systems and worse yet, causes problems with the ponds ability to trap pollutants.
These ponds have been designed to regulate flow of water and to improve water quality moving from storm water ponds to receiving waters. However, a high salt load flowing into these ponds (common in cold climate areas) shocks the pond. According to the University of Minnesota (Jacques Finlay), this shock causes a release of heavy metals and nutrients stored in the bottom sediments back into the water column where they can move freely into the unprotected receiving waters.
It is imperative to try and provide instant snow- and ice-free roads the public demands. Salt is a trusted friend and an easy tool to get us through the storm. However, long after the snow has melted, salt remains, creating a bleak future for freshwater systems.
Are Clear Winter Pavements Achievable without using Salt?
Instantly clear winter roads are a tall order. Current designs require heavy lifting by winter maintenance professionals; the designs of the future will take away some of this responsibility thus less need for salt. This might be an uncomfortable idea for the storm water community who prides itself on removing pollutants, but chloride source reduction is essential to the freshwater future.
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. Imagine a day when the winter maintenance industry operates at top efficiency but still uses chloride products— the problem does not go away, it simply slows down the growth of the problem. Storm water management has taken on the burden of managing extreme pollutant loads through ever-changing storm water management techniques. The chloride problem cannot be fixed through storm water management alone.
What is Currently Being Done and What is the Solution?
One partial, and highly overlooked, solution to the chloride crisis is the infrastructure design of salted surfaces. It is time for a new era of low salt design. Roads, bridges, roundabouts, parking lots, sidewalks, and all potentially salted infrastructure will benefit from design criteria that look at managing snow and meltwater. Sometimes the answer to a difficult question is simple, but it needs to be seen through a different lens. By capitalizing on the sun’s energy and better managing the prevailing winter winds, nature can be used as an advantage.
If the meltwater footprint can be reduced, the need for salt can also be reduced. Every thaw/freeze cycle creates a salting event. How can design manage these events? If the meltwater footprint can be shifted away from critical stopping and high pedestrian areas, safety can be improved and the need for salt can be reduced.
LSiD™ Low Salt Solutions was introduced to attendees at the 2022 Salt Symposium as a new concept in cold climate infrastructure design. While many community and business leaders may not be thinking about the chloride issue, engineers, architects, and planners should consider addressing this problem and provide sustainable winter infrastructure solutions.
Most infrastructure design and regulations influencing design are focused on handling rain. Minnesota and many other states manage snow nearly as often as they manage rain but the design for snow and ice management is largely ignored. Snow, blowing snow, strategic snow storage, ease of plowing, meltwater sprawl, and refreeze are rarely thought about in the planning or design phase. This oversight has led the winter maintenance industry into the high salt use seen today. Storm water leaders should be engaging with the professionals who design the salted surfaces to change cold climate plan sets for equal performance in winter conditions.
A commitment to cold climate design reduces the need for salt. The freshwater future is calling.
Connie Fortin | Senior Project Manager
Connie Fortin is a senior project manager with Bolton & Menk. Fortin can be reached at [email protected].
