It’s nearly the season for road salt, and last year alone the city of Kalamazoo used 5,000 tons of it. While surface deicers keep the city’s roads ice-free and safer, all that road salt is polluting our urban lakes.
Road salt, or sodium chloride, is the most inexpensive and readily available surface deicer for slick roads. But after it has done its magic melting the ice and snow, where does it go? It runs off into city storm sewers and, in the case of Kalamazoo, ultimately ends up in urban lakes, such as Woods and Asylum lakes, changing the aquatic ecology.
Such was the unplanned discovery by students of Carla Koretsky, a professor in Western Michigan University’s Geosciences Department and Environmental & Sustainability Studies Program, and Heather Petcovic, a WMU associate professor of earth science education in the Geosciences Department. The pair launched an undergraduate class in 2009 to give students a professional field experience that included taking and analyzing water samples.
Koretsky, who became dean of WMU’s Lee Honors College in 2013, says she sought to use “new techniques of authentic learning” because she “had observed that geoscience graduates who learned only in the classroom don’t have the field and lab skills they need to be employed in the environmental industry.”
In the class, Koretsky says, she and Petcovic told their students, “Congratulations, you’ve graduated and been hired. And you’ve been presented with a problem: A lake in your community has water quality issues about which residents have been unhappy for a number years.”
The lake in question was Woods Lake, bordered by Oakland Drive, Parkview Avenue and various residential roadways. “It’s a beautiful lake for teaching,” Koretsky says. “It’s intricate, with a lot of connections between biology, chemistry, physics and weather patterns. It’s a kettle lake, formed by glaciers, 40 or 45 feet deep in the middle and very steep-sided, with only 26 acres of surface area — a good lake to study the way water moves through the hydrological system.”
Local residents had been concerned about the lake’s quality because of turbidity (lack of water clarity), accrued sediment, excessive nutrient buildup (eutrophication) and invasive aquatic plants. The apparent cause of these problems was phosphorous-rich sediment from stormwater sewer outlets constructed in the 1960s that direct roadway runoff into the lake.
In the 1990s, the Woods Lake Association, a neighborhood organization of shoreline residents, went to city officials to seek solutions. Frank Wolf, president of the association at the time, says city officials “responded favorably” and commissioned an extensive report by Kieser & Associates, a Kalamazoo-based scientific research and environmental consulting company. The report, completed in 1997, confirmed “many water quality problems including … accumulation of numerous pollutants from roadway runoff.”
The report led to construction of a dry detention basin and treatment wetlands at the west end of the lake to help catch and hold pollutants. Financed with money from federal Clean Water Act grants and the city of Kalamazoo, the system went into service in 2003.
“The system is working as planned and is helping to keep phosphorous levels in the lake from increasing,” Wolf says.
In addition, the neighborhood association educated lakeside residents on practices to reduce pollution from their yards, such as not raking leaves into the lake, cleaning up pet waste and properly disposing of motor oil.
Koretsky says the Kieser & Associates study was a major factor in her selection of Woods Lake for the students’ fieldwork. “Your job,” she says she told her students in 2009, “is to go out there and assess the effectiveness of the storm water collection system.”
Unexpected discovery
Equipped with three canoes, the latest field and lab techniques and state-of-the-art water-sampling equipment, the students “measured everything they could with the tools they had,” Koretsky says. And they found something they didn’t expect: Salt. A lot of it.
The students’ samples showed Woods Lake had concentrations of 200 to 250 parts per million (ppm) in the lake’s deeper waters, a level that, according to Koretsky, the U.S. Environmental Protection Agency says is “the chronic toxic threshold for many freshwater organisms.”
“I looked at the students’ data and thought they made a mistake,” Koretsky says, “because those numbers were way, way, way too high based on my geochemical intuition and the known geochemical makeup of the area. I checked their standards and ran the tests again. Sure enough, the data came back with a high number.”
In addition, an exhaustive, 15-month study of Woods Lake by graduate student Ryan Sibert in 2010 and 2011 determined that the water in Woods Lake did not mix, top to bottom, in the spring and fall, as is typical of similar lakes. This stratification of layers — salty water toward the bottom and non-salty water toward the top — is the result of salt water’s greater density, which prevents or inhibits the strata from mixing.
“This mixing action is important for the biology of the lake because it delivers oxygen from the top to the bottom and nutrients from the bottom to the top,” Koretsky explains. Failure of the lake to mix, or “turn over,” seasonally causes the bottom to remain deprived of oxygen and very salty.
The students then addressed the next obvious question: Where is the sodium chloride coming from? It turned out it was from the same source that is guilty of pouring high phosphorous loads into the lake: nearby roadways, via the city’s storm sewer system, as well as surface runoff from residential driveways and sidewalks.
But, unlike phosphorous, salt isn’t being stopped by the detention pond built at the west end of the lake. “Salt is very soluble — it goes where the water goes,” Koretsky says. In this case, it goes into the depths of Woods Lake.
And Woods Lake is not alone. Asylum Lake, situated a mile west-northwest of Woods Lake, was also found to have excessively high levels of sodium chloride.
From September 2012 to March 2014, WMU graduate student Davina “Allie” Wyman conducted a field study of Asylum Lake, which receives stormwater runoff from Stadium Drive, South Drake Road and US-131. Wyman reported that Asylum Lake contains “maximum chloride concentrations of 334 ppm” — a level even higher than that of Woods Lake.
To make sure they weren’t mistaken, the WMU studies utilized Brewster Lake, a rural lake at Pierce Cedar Creek Institute, in Barry County, as a control water body for data comparison. They found that Brewster Lake’s salt levels were only a few parts per million, much lower than the concentrations found in Woods Lake and Asylum Lake.
‘Not a priority’
Shortly after the studies were completed, Koretsky and her students shared their findings with both the Asylum Lake Preservation Association and the Woods Lake Association.
The residents with property adjoining Woods Lake seemed to have mixed reactions to the students’ findings, Wolf says.
“We can see that the lake has a problem with sediment, phosphorous and algae,” he says. “But the salt, so far, is confined to the lower depths and hasn’t visibly affected water quality.”
He points out that the lake, which has two parks on its shores, is “heavily used” for swimming, kayaking and canoeing and has a good fishery, including largemouth bass and sunfish. “With all the forces that impact an urban lake, just holding our own is a good accomplishment,” says Wolf, who has monitored water quality parameters on the lake since the 1990s.
After Koretsky and her students shared their findings with the two lake associations, Wolf says he shared the findings informally with City Commissioner Jack Urban. “But city officials are more concerned with the budget and payroll,” Wolf says. “The salt issue isn’t upsetting anybody. It’s not a priority.”
And, indeed, Urban acknowledges the city does have higher priorities. These include, he says, safe neighborhoods, sidewalk and street repairs, insufficient revenue to maintain services at their current levels, land owned by nonprofit entities that don’t pay property taxes, and lack of economic recovery of the tax base from the 2008–09 recession.
“The city commissioners are very hesitant to spend money on things that people don’t regard as absolutely essential,” Urban says. “This issue of salt in Woods Lake (or any other urban lake) is pretty far down on the list right now.”
Yet, that doesn’t mean that this economic and environmental issue is completely off the table or that efforts are not being made to reduce use of road salt here or across the nation.
“From the 1940s to the 2000s, the increase of salt applied to roads (nationwide) was exponential,” Koretsky says. “The rate of usage is still rising, but at a lesser rate now, and the increase is mostly due to more subdivisions and more roads being built. We’re salting more length of road, not using more salt per mile.”
John Paquin, environmental programs manager for the Environmental Services Division of Kalamazoo’s Department of Public Services, says the same is true locally. And while he says the city’s first priority in winter is to keep roads safe, he adds, “Our field services management team is pretty innovative regarding how they achieve that — how much salt to use, how much sand to use. They keep up on weather reports and have learned that certain techniques are more effective than others, depending on the temperature, to enhance the effectiveness of snowplowing and deicing. They are aware of and sensitive to the environmental concerns associated with excess salting or sedimentation, so they utilize various strategies for the projected conditions. And they’ve used alternatives.”
One alternative is sugar beet juice. Robert McClenney, the city’s field services manager, says road crews have mixed beet juice with road salt under certain conditions since 2010. McClenny says in the past six years, the city has used beet juice when it is available and the temperature is right, which reduced the amount of salt applied during that time by 30 percent.
Urban, a retired chemical engineer who worked for the former Upjohn Co. and the former Pharmacia, explains how beet juice works on ice. “What makes ice melt is the number of ions or the number of molecules per cubic centimeter in the slush that’s melting,” he says. “Sugar can do the same thing as sodium chloride, but it has bigger molecules. So it takes a lot more beet juice, it costs a lot more, and it’s more labor-intensive because you need more trips back to the salt depot to reload the trucks.”
In addition to beet juice costing more than sodium chloride, deicing products derived from agricultural byproducts “have the potential to adversely affect water quality if allowed to enter surface waters … (due to) high levels of organic materials,” says an online Frequently Asked Questions sheet posted by the Michigan Department of Environmental Quality. “… Fish kills, impaired biological communities, and noxious growths of bacterial slimes can result.” So beet juice or other agricultural byproducts aren’t the definitive answer either.
Another alternative, Koretsky says, is calcium magnesium acetate. “CMA has no chloride in it. It’s effective, but not as effective as chloride, and it’s about 200 times more expensive. The economy being what it is, that’s a major problem.” CMA is also biodegradable and, like beet juice, could potentially exacerbate eutrophication in lakes.
Applying greater quantities of sand to roads is also a possibility. But sand doesn’t wash away easily, and it clogs drains and causes turbidity. In addition, driving on sand can launch fine particles into the air that cause health issues for people with respiratory problems.
No simple solutions
So what is the solution?
Koretsky somewhat jokingly suggests rerouting storm sewers — an expensive mitigation scenario also mentioned in Kaiser’s 1997 report — then quickly acknowledges that in the current economy that isn’t going to happen.
Urban says that baskets containing ion exchangers could be installed in sewer lines to capture and remove sodium ions and chloride ions from runoff, but he notes that the baskets would need to be removed, recharged and reinstalled periodically. “That would be very labor-intensive and expensive,” he says, and is therefore not likely to happen.
Nor has desalinization technology advanced as an efficient and economical option to remove salt from small urban lakes.
Yet, doing nothing and letting water-borne sediments just run downhill isn’t the answer either. The often-criticized dictum from the 1970s that “dilution is the solution to pollution” doesn’t hold up in this case.
Koretsky notes that saline content in all of the Great Lakes, with the exception of Lake Superior, is increasing, with road salt suspected as a major contributing factor.
But solutions have to start somewhere, and perhaps the first step is awareness that a problem exists. The WMU students who discovered the high saline content in Woods Lake and Asylum Lake are now publishing their reports in scientific journals worldwide. Koretsky speaks about this research at international conferences. Residents around Woods Lake and city officials know about the problem, and road crews are applying lower volumes of sodium chloride deicers.
This winter Koretsky’s colleague Kathryn Docherty, WMU assistant professor of biological sciences, will begin studying the microbial community in Woods Lake to determine how much methane is being produced at different water depths due to the lack of oxygen caused by the salt. Methane is a potent greenhouse gas believed to be a significant cause of climate change.
Paquin points out that municipalities, both local and throughout northern climes, are partnering with county, state and federal agencies to share ideas, insights and innovations. And Koretsky wonders if homeowners and businesses, armed with the knowledge of the effects of road salt, might choose to apply less salt or utilize appropriate alternatives when deicing their properties.
Urban suggests that people simply drive more cautiously on snow and ice. “Fifty years ago we put chains on (the tires of) our cars. It was kind of a bother, but we did it,” he says.
And while the idea of everyone taking a “snow day” when winter storms hit might seem desirable, that concept doesn’t work for people who drive emergency vehicles — fire trucks, police cars, ambulances. Even in stormy weather, those public servants must go to work. And they need roads that are free of ice and snow in order to do their jobs quickly, efficiently and safely — for the greater public good.
At the same time, preservation of our natural resources, especially water, is essential to life. Therefore, most of the people interviewed for this article say that finding a balance between human and environmental needs seems to be the best available solution. They hope that awareness of the lake pollution caused by road salt will lead to someone, somewhere, creating a heretofore unheard-of solution.
