Issues of the Environment: Assessing damage caused by winter road salt
- Michigan roads would become dangerous and the economy would grind to a halt without efficient processes to deice roadways. Keeping Michigan’s roads clear typically involves applying millions of tons of salt over the cold season. Ann Arbor, for example, applies between 3500-7500 tons of salt in an average winter.
- All that salt washes into local rivers and streams, which eventually empty into the Great Lakes. Researchpublished in December 2021 by Michigan State’s Department of Earth and Environmental Science and the University of Wisconsin’s Center for Limnology show the salinity in Lake Michigan is incrementally increasing by a milligram every couple of years. They found 1 million tons of salt have been flowing into Lake Michigan annually.
- It is becoming apparent that all that road salt is building up gradually in freshwater lakes, rivers, and aquifers. In Lake Michigan, the researchers found concentrations of chloride (an element in salt) have increased dramatically since the 1800s, from 1-2 milligrams per liter of water to 15.
- According to the CDC, too much dietary salt can increase the risk of stroke, heart disease, and high blood pressure. Thus far levels are below limits known to harm human health. Short term episodes of “salt shock” can kill wildlife and plants, and even low concentrations can alter ecosystems, corrode pipes, and damage vehicles. The Huron River Watershed Council does some monitoring of chloride levels in the local watershed, and rising salinity has been detected at low levels.
- Alternatives to road salt, including sugar beet byproducts which are plentiful in Michigan, have proven less effective and can damage ecosystems because the sugar that replaced salt increases bacteria in waterways. Synthetic de-icers are costly. (Calcium magnesium acetate is used on the Zilwaukee Bridge to prevent oxidation and costs 50 times more than calcium chloride mined from under Detroit.) (Source: *directly quoted* https://www.greatlakesnow.org/2022/01/road-salt-michigan-lakes/)
- Since 2020, Ann Arbor and Washtenaw County have been experimenting with special mixes of salt brine, a wet solution of chloride salts that is spread on roads when icy conditions are anticipated. It is also budget-friendly because less salt is used. Critics of salt brine say it can be more corrosive to vehicles, but the mix used by Washtenaw County is thought to be similar to traditional road salt. A 2019 study in the journal Environmental Science & Technology showed that using salt brine decreased chloride runoff into streams by 45 percent. In 2020, the state reported decreasing salt usage to less than 325,000 tons— the least amount of salt used since the early 2000s. (Sources: https://www.wpr.org/study-finds-more-1m-tons-salt-flowing-lake-michigan-each-year; https://www.mlive.com/news/ann-arbor/2020/02/ann-arbor-now-using-salt-brine-to-combat-ice-snow-on-city-streets.html)
- Unless heated or solar roads can be made economical and safe, chemical deicers or road salts will likely be applied for the foreseeable future. Anthony Kendall, Research Assistant Professor at Michigan State University, says ongoing research will help monitor environmental distress and researchers will continue to look for feasible alternatives.
David Fair: When the freezing rain and snow falls, we are certainly glad for the crews that hit the roads and plow and salt, as grateful as we may be, there is a price to be paid. I'm David Fair, and welcome to Issues of the Environment on 89 one WEMU. Traditional road salt is made of halite. It's the mineral form of sodium chloride as it is naturally mined, and it does work well on our roads, sidewalks, and driveways. But then, it gets plowed or shoveled into our lawns and onto the sides of roadways and ultimately runs off into our waterways. Did you know that more than a million tons of road salt ends up in the Great Lakes every year? If you're like me, you're thinking, "That can't be good." Well, let's find out more together. Our guest today is Anthony Kendall, and he is a research assistant professor in earth and environmental services at Michigan State University. And thank you so much for making time today.
Anthony Kendall: Oh, absolutely. Thank you, David.
David Fair: Am I right? This is not good.
Anthony Kendall: Well, certainly, it's something that we need to be aware of. So, the the amount of road salt that gets into the Great Lakes is certainly impressive. And the one thing I would definitely say, in support of our Great Lakes, is that they are wonderful freshwater resources that, even with all of these salt additions, they are very much freshwater lakes, and we can be proud of that resource. But we definitely need to be aware of how much salt is getting into those lakes and aware also of how that salt is moving elsewhere across the landscape, including in our rivers, our groundwater, our lakes, and our streams.
David Fair: And I did want to scale it down to that for a moment. Like, in Ann Arbor, the city applies between 3500 and 7500 tons of salt in an average winter. As you mentioned, that runs off into all of the creeks and tributaries of the Huron River, which runs right into Lake Erie. The inland lakes are being impacted throughout the county and country as well. What does that do to the salinity of the water?
Anthony Kendall: In some places, especially if there are smaller bodies of water surrounded by really intensely salted areas, like major roads and urban subdivisions and things, we could see salt concentrations in those waters get high enough that they start to negatively affect the ecosystems. And what I mean there is that our freshwater lakes and wetlands have adapted over millennia to handling water that's very low in salt. So, unlike the ocean where salt is ever present and indeed in our own bodies, we're basically walking bags of salt water, these ecosystems have evolved to have very low levels of salt. And what happens is the tiny creatures at the bottom of the food chain--the plankton and the phytoplankton we call them are tiny little algae that float in the water column and harvest energy from the sun--they start to have problems reproducing and and thriving in these saltier environments because they are freshwater species. And so, if you take the bottom rung of that ecosystem and you impair it, then everything that depends on consuming those and then eating further and further that food chain can suffer as well. So, that's the basic issue is that what it creates is problems for the other creatures in the ecosystem, once salt concentrations rise.
David Fair: WEMU's Issues of the Environment and a conversation with MSU research assistant professor Anthony Kendall continues. If we don't change course, Anthony, what are the longer term impacts of increased salinization to these other species, to our waters, and perhaps our drinking water supply?
Anthony Kendall: Sure. So, getting back first to the Great Lakes. In the very long term, our Great Lakes are tremendous freshwater resources and are likely to stay that way for centuries. What the concern is is localized places, even among the Great Lakes shoreline and then, of course, in our inland waters where we have too much chloride--part of that halite mineral that you mentioned--coming into the water, we could see the quality of the water decreased to a point where the ecosystems start to suffer. So, the species that are most sensitive may end up disappearing from those waters, and it would change their essential nature. Now, what it turns it into is something that we would certainly recognize in other places of the country. And even there are a few saltwater marshes naturally occurring in the Great Lakes because of geology. But they wouldn't be the areas that we know right now, and there certainly isn't all of the wetlands or all of the lakes and streams, but certain ones would be affected. And that's part of what we're actively studying is trying to identify where are the inland waters that are most under threat and what might we do in terms of reducing the amount of chloride that gets into ground and surface water to help those areas into the future.
David Fair: I've read scientific estimates that show on our planet, we're seeing between 10,000 and 100,000 species go extinct every year. If unchanged, will our salt usage expedite the impact on plants and animals?
Anthony Kendall: Oh, it's certainly possible. I don't know about it in terms of extinction, but one of the concerns that ecologists have, in addition to extinction, is the elimination of species locally or regionally and the impact that that can have on ecosystems that are all essentially interconnected. So, I don't know that we would be extincting more species, but we would create pressure on them. That would be one of many challenges that those species would be facing.
David Fair: So, let's talk alternatives. The first thing that came to my mind is something I've used before. I've used it because it works really well. But I've also had a feeling in my gut that it probably is worse for the environment. I'm talking about calcium chloride. What do you have in terms of research to tell us about that?
Anthony Kendall: So, calcium chloride is a more effective salt in terms of its function at lower temperatures, and so, it actually can be a really great alternative. The problem is is it's not the sodium in the sodium chloride that's the problem. It's the chloride here. So, even in a calcium chloride formulation, we still are putting chloride down on our pavement, and it's eventually getting into the waterways. Now, the amount that's used can be different, so I'm not entirely positive of whether it's better or worse. But what the major uses are both road salt application and septic tank use. So, people who rely on private drinking water wells that hold water that needs to be softened will use salts containing chloride to improve the quality and taste of that water. So, anywhere where we have an intense concentration of salted roads and septic tank and private drinking water well use are areas that we could say, well, could reductions happen in terms of maybe not, maybe not stopping what we're doing, but looking at alternatives that are less that use less chloride to achieve the benefit.
David Fair: Once again, our guest on 89 one WEMU's Issues of the Environment is MSU research assistant professor Anthony Kendall. Anthony, since 2020, the city of Ann Arbor has been experimenting with some special mixes of salt brine, but it's used a little differently, typically applied before the ice or snow arrives to prevent potential buildup in advance. It is apparently cheaper, but in heavy winter events, probably isn't as effective. Is that being viewed as any kind of long-term viable solution?
Anthony Kendall: I think that is how MDOT and its participating county departments of transportation are viewing it is one part within their toolkit that to deal with road salting and to both reduce costs, as well as to make it better and more benign for the environment. I certainly know that, in major urban areas, you'll see salt brine being applied to the sidewalks beforehand, and you'll see, you know, the residual of that dried on the sidewalk. And when the snow and ice comes, that it can actually help clear those sidewalks more quickly and with less salt later.
David Fair: What about organics like sugar beet byproducts? That's in abundant supply in Michigan.
Anthony Kendall: I have read a little bit about that. That's not my direct area of research, but they tend to be less effective and less available on a broad basis. But there may be regional solutions that are more appropriate for certain areas. For instance, in the Upper Peninsula, there are many places where road salt isn't used at all and sand applications are used. And this is common even in more rural parts of southern counties. So, where you can find and identify both local sources of inexpensive materials that satisfy the need, and it might not be completely clear roadways all of the time, but perhaps, you know, salting or sanding turns on the roads or hills and that sort of thing. So I think that both to reduce costs as well as to make this more benign. These county departments of transportation are looking to other sources.
David Fair: I know some people who have heated driveways. I suppose that technology could be applied on a wide scale basis. But those same people told me what it cost, and it floored me. If we can't afford to fill potholes, I assume developing and implementing that technology for an entire state has already been ruled out of consideration.
Anthony Kendall: Yeah. The costs of heated roadways per mile makes it beyond the reach of any but the most intensively trafficked areas. So, that's more of a local solution, or one that might work in areas like major cities where there are power plants that produce essentially waste heat that then needs to be distributed. That can be a solution. For instance, on Michigan State's campus, they do use heated sidewalks in certain locations to actually help the power plant function more efficiently by distributing that waste heat.
David Fair: Well, as our time together winds down, I think we've made it quite clear that road salt and chemical de-icers are going to be a part of our foreseeable future. So, as a researcher, what will you be monitoring now and what red flags will you be looking for?
Anthony Kendall: We're going to be looking over the next couple of years for places across the landscape where we have a high concentration of salt use and of septic tank usage, so homes that don't send their wastewater back to a wastewater treatment plant. Those are places where we're going to then say we need to keep an eye on our surface water bodies to make sure that those waters stay fresh, and, as we find problems, engage local communities to see what solutions might work there, because this is a problem that can occur everywhere. But, it's the local communities that will need to find particular solutions that work best for them.
David Fair: A lot of conversations to be had. I thank you for the one we've had today, Anthony.
Anthony Kendall: OK, yes. Thank you, David
David Fair: That is MSU research assistant professor Anthony Kendall, our guest on Issues of the Environment. I'm David Fair, and this is 89 one WEMU FM and HD One Ypsilanti.
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