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Safer winter roads but at a cost to water quality


By Stacy Gittleman


Rock salt on the roadways can reduce accidents by up to 80 percent. According to the most recent state environmental reports, instate road salt use has doubled since 1975, although road agencies in Michigan have reduced salt application rates per lane mile in recent years. Even with these reductions, when snow and ice melt, the salt that was applied to paved surfaces washes into wetlands, lakes and streams through stormwater conveyance systems. The salt from managing winter storm events combines with other sources of salt from water softening backwash and industrial discharges and drains into ground and surface water, resulting in concentrations that eventually will adversely impact the quality of Michigan’s waters.


High sodium levels in drinking water can affect people with high blood pressure, and high chloride levels in surface waters are toxic to some fish, bugs and amphibians.


As we head into the summer, a time when we enjoy the state's water natural resources for fishing, swimming, canoeing and other recreational activities, it's important to keep in mind that the quality of that water in the summer, and year-round, has a lot to do with how the thousands of miles of roads are winterized.


According to environmentalists, academics and government officials interviewed, the Great Lakes states sit on 20 percent of all of the world's freshwater.  Added to that, Michigan possesses some of the greatest salt deposits in the world, thanks to the remains of a vast, prehistoric subterranean sea. According to the Detroit Salt Company, rock salt in Detroit was discovered in 1895, and by 1914, the mine was hauling up 8,000 tons of rock salt per month through a 1,160-foot shaft, an engineering marvel at the time. The salt was mainly used for the leather and food processing industries. Today, the mine still exists at 12841 Sanders Street in Detroit. The mine spreads out over more than 1,500 acres and has over 100 miles of underground roads and is a major producer of ice melting products for North America.


Because of this natural resource, Detroit was one of the first large cities to use rock salt to winterize its roads. By 1966, Michigan used 150,000 tons of salt per year, and by the 1990s, that amount tripled. Currently, Michigan uses nearly 500,000 tons of rock salt each winter, according to the Michigan Department of Transportation (MDOT).


Beyond Detroit, the dried-up sea, known geologically as the Michigan Basin, stretches in an underground landmass larger than the state’s Lower Peninsula. Because of these vast underground salt deposits, what is happening now is that when the underground aquifers are over-pumped, salty briny water comes to the top and infiltrates some drinking water, getting into the state’s tributaries that feed into Lake Michigan, according to researchers.


A joint study from Michigan State University and the University of Wisconsin-Madison examined chloride levels from 235 of the 300 tributaries that feed into Lake Michigan from samples taken July 10-15, 2018. Traditionally, Lake Michigan naturally contains one milligram of chloride – a mineral which makes up 60 percent of the molecular mass of sodium chloride (NaCl) per liter.


Researchers concluded that because of decades of using rock salt to winterize roads, among other sources of use the mineral, that level of chloride has steadily but gradually climbed up to 15 milligrams per liter. Comparatively, oceans contain 35 grams of salt per liter. The study stated it would take one million metric tons of salt to raise the salinity of the lake by one milligram per liter. Since the 1800s, chloride concentrations in Lake Michigan have been rising from around one to two milligrams per liter to over 15 milligrams per liter by 2020. The study demonstrated that Lake Michigan’s tributaries are dumping 1.08 million metric tons of chloride into Lake Michigan, and estimated that it would take about five million metric tons of salt to raise the lake’s salinity by one mg per liter, which could happen in one to three years from the time the study was conducted.


Anthony Kendall, associate professor at MSU’s Department of Earth and Environmental Sciences, and one of the authors of the study, said while this increase in salinity is troubling, it is not happening fast enough to make Lake Michigan’s 4.918 trillion gallons of water as salty as the oceans.


"This study was not intended to be like a 'barn-burning three-alarm fire warning,'" cautioned Kendall. “We are not putting enough salt on our landscape that will make the Great Lakes as salty as the oceans, because the volume of Lake Michigan is just so huge. The Great Lakes are fresh and will remain fresh, but they will continue to get saltier because we are using salt at a far faster rate than can be flushed out of the Great Lakes system. It is accumulating in our groundwater and our streams and wetlands – everywhere that water is stored. Salt, and how we use it, is something that we need to get a handle on now because our actions have a very long legacy.”


Kendall continued: “Increased levels of salt will in time cause disruptions and problem hotspots in fragile ecosystems which depend on low salt levels to thrive. What’s needed is to further understand local conditions in certain areas along Lake Michigan’s lakeshore that are being negatively impacted by increased chloride in the water.”


Looking forward, Kendall’s graduate students are now compiling data from water samples taken from Lake Superior.


Kendall explained that half of the water that flows into the Great Lakes comes from groundwater streamflow and the other half percolates into the ground from stormwater runoff, eventually getting discharged into surface waters such as streams and rivers. When water from Michigan’s underground aquifers is over-pumped, it pulls salty water to the surface, which will discharge into surface waters like streams and eventually rivers. But that too will take a long time to reach the Great Lakes.


“It’s hard to visualize, but groundwater flows at a very slow rate,” Kendall explained. “For instance, it can take 30 years for groundwater located 1,000 feet from a stream to reach that stream due to the thickness of our aquifers. Whatever salt we put on our roads or comes out of our septic tanks is going to be in the groundwater for a very long time. Salt readily dissolves into water. It takes expensive, energy-intensive methods like reverse osmosis to remove it. So, there is cause for concern as salt levels in our groundwater gradually build up. We need to take action now to do a better job using this vital mineral, so we don’t cause ourselves more trouble in cleaning it up in the future.”


The Michigan Environment Great Lakes and Energy’s (EGLE) Water Resources Division has been monitoring chloride and sulfate levels in the state’s surface waters since 2005. In 2019, EGLE developed water quality standards that quantified acceptable and dangerous levels of chloride in surface waters. Numerical values vary and reflect the amount of time wildlife could be exposed to effluents of chloride or sulfide before severe harm could occur.


Acute chloride levels (over 640,000 parts per billion) pose threats to the mobility and survival of aquatic flora and fauna, and chronic chloride levels (150,000 parts per billion) are more optimal for species survival, growth and reproduction. Respectively, EGLE has set acute sulfate levels at 1,200,000 parts per billion and chronic levels at 370,000 parts per billion.


In February 2021, EGLE enacted its Chloride and Sulfate Water Quality Values Implementation Plan and added the requirement of municipalities and other entities to incorporate documentation of chloride and sulfate values in its surface waters as part of its National Pollutant Discharge Elimination System (NPDES) Permit Program. According to the plan, these numeric values for chloride and sulfate provide a long-overdue benchmark for the continued protection of aquatic life. With the inclusion of chloride and sulfate in its water quality assessment management, all municipalities applying for an NPDES permit must now include measurements and reports of these substances. The permit will specify the sample type, analytical method, and quantification level that shall be used for the collection and analysis of chloride and sulfate.


In managing levels of chloride and sulfate, new additions to NPDES permits include requirements such as implementing best management and good housekeeping practices, source reduction practices, dilution of higher concentrations under USEPA regulations listed in the Clean Water Act, and employee education.


"Developing those water quality values was truly the jumping-off point for us in the state to educate the public and county and local governments as to what salt applications were doing to impact our environment, aquatic life and water quality,” said Kevin Goodwin, an aquatic biology specialist within EGLE’s Water Resources Division that leads EGLE’s biennial water quality reports. “These are quantifiable values that states like Minnesota and Wisconsin have already had in place. Once we developed these values, which are based on years of toxicological information, they provided concrete thresholds that EGLE could better understand where there might be problems around the state. We could also help our current NPDES permittees in the state understand what their water quality is like and whether additional actions are needed.”

The NDPES also regulates the Municipal Separate Storm Sewer Systems (MS4) program, managed by EGLE environmental quality specialist Christie Alwin. MS4 includes examining stormwater and snowmelt runoff in urbanized areas.


Alwin explained that under this program, before any municipality can apply any deicing application on its roads, EGLE requires municipalities to report its strategies for salt application, storage, and after-season requirements such as equipment cleaning and maintenance as well as street sweeping to remove residual salt from the roads. EGLE requires any municipalities which owns and operate roads, as well as county road commissions and MDOT, must hold a permit under this program. As it is difficult or next to impossible to remove salt once it is dissolved in waterways, programs such as the MS4 are a way for EGLE to focus its efforts at the beginning of the salt application cycle.


“Michigan is unique in that we have a statute that specifically addresses salt as a polluting material,” said Alwin. “We begin regulating a salt storage capacity at five tons or more, which if you are a road agency, or even own a shopping mall, you reach this threshold very quickly. EGLE has specific self-storage requirements. Careful salt application begins with properly calibrated equipment and moves forward from there to avoid excessive salting. If there was an accidental release of excessive salt, it is easier to clean it up if the municipality can pinpoint the spill to a particular location on a road. Once the salt has moved on from its location on the road, there can be no remediation efforts at that time. That’s why we are focused on the beginning of the salt application process.”


Out in the field and reporting her findings back to EGLE’s Goodwin is Sally Petrella, a longtime monitoring manager with Friends of the River Rouge. A trained biologist, over the last three years Petrella and a team of citizen scientists have been working off chloride benchmarks set by EGLE to measure the mineral’s levels in different sections of the Rouge watershed to see how they correlate with populations of wildlife such as the mayfly, the rare red side minnow, which makes it's home exclusively in the Rouge watershed, and especially the humble stonefly.


Overall, Petrella said the most important indicator of the health of the Rouge River watershed – which in part comprises the inland lakes tributaries and streams in Bloomfield Township and Birmingham – is the quality populations of aquatic and amphibious and native plant species.


Beginning in the winter of 2020, Petrella said the Friends of the Rouge participated in a national winter saltwater program run by the Izaak Walton League, one of America’s oldest conservation organizations, to understand how chloride levels were impacting the water. They collected water samples from 30 locations along the Rouge using test kits provided by the Walton League and measured the water quality based on EGLE’s new standards, but quantified findings in parts per million, rather than parts per billion. They coupled this data with their work monitoring populations of the stonefly, which lays its eggs in the water in January, at the height of winter salting season.


The citizen scientists first tested for chloride levels in the winter of 2020, and then again in the winter of 2021. Many of the 2021 samples came back at levels exceeding 320 parts per million, and others showed readings of over 150 parts per million of chloride, a level considered to have a chronic long-term impact on freshwater aquatic life. Areas of concern included Tonquish Creek in Wayne County, the main branch of the Rouge that runs in Firefighters Park in Troy, and Murphy Creek, which runs along the property of The Roeper School in Bloomfield Hills.


"We developed a score for bug count and also kept numbers of salt levels on these sites, and what we observed that there was a clear correlation that sites with higher salt levels had lower scores for numbers of stoneflies, as well as mayflies,” said Petrella.


Petrella also remarked that after the dry winter and spring of 2021, “In the winter of 2021, there was a drought, so there was not much flushing of the waterways with rain or snowfall,” she recalled. “We did see elevated salt levels and low counts of stonefly, which we thought would dissipate over time. When we came back to monitor levels in the spring, we were surprised to find continued elevated chloride levels.”


Dry conditions continued into the spring of 2021 until the deluges of that summer. When her volunteers returned to the same sites in the fall of 2021, they expected that all the heavy rain events from that summer would have flushed the Rouge of some of its chloride levels.


“We went back to these sites in the fall and were surprised that we still saw elevated salt levels at these sites. We found elevated levels around Farmington Hills that we were surprised to see because we were way past winter salting season. We also found some hot spots in and around Washtenaw County. We're wondering if there's something else going on, as there could be salt contributions from groundwater because groundwater can have historic salt levels from less recent salt applications, or it could be the fact we have naturally occurring levels of salt where groundwater flows. And that is where we turned to (EGLE), and we are looking into this with them.”


Chris Bobryk, watershed manager for the Clinton River Watershed Council, said his organization has also participated in the Izaak Walton League’s winter salt study. Bobryk said that he and his citizen scientist volunteers also noticed that fluctuating levels of chloride correlate with stonefly populations. Other observations they have noticed include an influx of invasive non-native aquatic plant species such Eurasian watermilfoil which can tolerate saltier water.

Bobryk said that in addition to limiting the amount of salt on roads, sidewalks and parking lots, average citizens can work to abate this problem by helping to build a greener infrastructure by capturing stormwater runoff and holding it in place with rain barrels or rain gardens.


“When increasing chloride levels begin to impact the health of wildlife, that is a good indicator that human health will also be affected,” said Bobryk. “This is why studying the health of these rivers is so important. When we begin to lose species of invertebrates whose habitats are being crowded out by invasive species, that is going to negatively affect the quality of our drinking water. And what happens in the winter in terms of how we put down salt on our roads will eventually affect our bodies of water in summer that we count on for enjoyment and recreation. So we have to keep this issue in the forefront of our minds year round."


Ellen Foley, a researcher and associate professor at Grand Valley State University, is hoping that her efforts of studying one small lake in Kent County can serve as a wakeup call for safeguarding the rest of the state’s some 35,000 inland lakes and ponds. In Oakland County alone, there are 1,200 such bodies of freshwater, according to county officials.


In April 2022, Foley drew her last water sample from Church Lake, a 20-acre private kettle glacier lake in Grand Rapids that teems with fish, turtles and other aquatic life. But just below the surface, Foley said are "concerningly" high levels of chloride that have created a dead zone that chokes the lake of needed oxygen.


“Church Lake takes runoff water from a nearby highway, and I’ve taken some chloride levels in the winter as high as 1,000 milligrams per liter. In spring and summer samplings, we still saw lingering effects of chloride concentrations when the road had not been salted for months. Chloride gets stuck in the environment, and it is very difficult to remove. Though the numbers have fluctuated some, the high levels in the lake are consistent. The high levels of chloride lead to higher nutrients at the lake bottom via a process called internal phosphorus loading. This is an area that up until now has had little research but demands further examination if we are to understand how rock salt is affecting Michigan’s inland lakes.”


Foley said that local officials and others are paying attention to her research findings but are questioning if there is anything that can be done to sacrifice less safe winter driving for the sake of the health of the lake. She said that road salt is somewhat of an “out of sight, out of mind problem” in lakes. But she hopes that through her research on one lake in the state, people will become more aware or think about how salt put out on the roads may be impacting a body of water where they live or enjoy visiting.


“Church Lake’s chloride levels are an extreme version, and in general I do not think people are aware. But if you live on a lake and it is located near a road where salt is applied, chances are the runoff is causing problems there too.”


Another way of measuring salt levels in freshwater lakes is to monitor how well it conducts electricity. Just like certain metals, water can carry an electrical current. The higher the salt level, the more conductive the water, which may indicate that conditions for aquatic life that depend on salt-free water may be declining. A healthy lake system may have conductivity rates of zero to 200 micro Siemens per centimeter – a measure of electrical conductivity.


Jennifer L. Jermalowicz-Jones is the founder of Restorative Lakes Sciences, a 10-year-old consulting firm whose clients range from municipalities to private lake development associations who are looking to remediate the quality of their lakes through better sustainability and conservation practices outlined in laws such as Public Act 451 of 1994, the Michigan Natural Resources and Environmental Protection Act (NREPA), and under federal law from the U.S. Environmental Protection Agency under the federal Clean Water Act.


Jones said her company has been monitoring the conductivity of Wing Lake and Upper Long Lake in Bloomfield Township, and Lake Angelus, between Rochester and Auburn Hills, where conductivity levels have reached between 800-1000 micro Siemens per centimeter.


“We typically like to see conductivity between 200-500, which is ideal for an inland lake,” explained Jones. “We get concerned when we see conductivity numbers over 800. That's when levels have a negative impact on aquatic flora and fauna and once it reaches 1,000, levels are toxic."


To remediate these levels, Restorative Lakes Sciences takes several data sets at certain times of the year and graphs