A fresh snowpack can bring a feeling of natural beauty to even the most densely developed, highly urbanized area. For many towns and cities, when that snow piles on several inches deep, a series of policy changes go into effect. Schoolkids cheer to have the day off; some workers might experience mixed feelings about their career status at being designated non-essential personnel and being given the day off to help reduce the risks of incidents on the roads. Motorists unwary enough to have parked and left their vehicles on emergency snow routes can look forward to a level of anxiety rarely experienced by law abiding citizens when they contemplate retrieving their cars after they’ve been towed to the impoundment lot. Road clearing crews gear up and hit the streets, laying down road salt, sand, and various chemical deicers.
As the snow continues to descend, piling up in depth from inches to feet, many cities are forced to come to a virtual halt. Commerce shuts down, and, for safety reasons, residents are often prohibited from driving at all. As the plows course the streets, it soon becomes impossible to clear much more than a narrow corridor, and this only on the main streets, to provide access for emergency vehicles. Finally, something intriguing begins to happen: Snow begins to gradually disappear by the truckload.
At night, and sometimes 24 hours a day, trucks can be seen hauling the graying soot-encrusted piles from the roadside.
Then, one day, it’s all gone. At least it is out of sight. However, no longer a concern of the highway department, snow remains a concern for water-quality managers. They know that somewhere in the metropolitan area, there is a pile of heavily contaminated snow, driven from city streets and parking lots, slowly melting well into spring, and in some cases into the summer season.
According to the Minnesota Pollution Control Agency (MPCA) stormwater manual, snowmelt has special characteristics and contaminants not usually present in precipitation from rainfall events. Most notably, it’s cold, and as a result “BMPs are prevented from working as intended because of ice, cold water, highly concentrated pollution and lack of biological activity.”
The MPCA manual explains, “BMP design criteria addressing only rainfall runoff might not work well during cold periods,” and says this becomes a major problem because in cold climate regions “a substantial percentage of annual runoff volume and pollutant loading can come from snowmelt.”
A central problem with snowmelt runoff is that water volume in the form of snow and ice builds for several months and suddenly releases with the advent of warm weather in the spring, or during short interim periods during the winter. Along with this, the distribution of pollutants potentially released into the environment during the melt vary by type over time, depending on how they interact with the physical characteristic of snow and the environment, as the snow melting process advances.
Water-soluble contaminants are the first to begin leaching through the snow piles. These may include salts applied by road-clearing crews, but according to Torsten Meyer, a University of Toronto researcher who conducted a number of simulations of melting snow, “By the time snow has turned black with muck and grime, many harmful chemicals—including those from pesticides, car exhaust, telecommunications wiring insulation, water repellent, clothing, paints, or coatings—may have already seeped out of the snow and into the surrounding groundwater or surface water.”
Furthermore, according to the MPCA, the conventional pollutants of concern for most urban runoff situations are supplemented in meltwater runoff by additional contaminants added during the winter. The solids, nutrients, and metals present during the summer are joined by increased polycyclic aromatic hydrocarbons (PAHs) and hydrocarbons from inefficient and increased fuel combustion. Other contaminants include salt and increased solids from antiskid applications and cyanide compounds used as an anticaking additives to salt. Fortunately, the manual states, “pesticide and fertilizer runoff and organic debris (leaves, grass clippings, seeds) are less of a concern during the winter.”
Meyer believes his laboratory models of snow piles contaminated with organic pollutants can demonstrate what happens when that snow begins to melt. “During the winter months, contaminants accumulate in the snow,” he says. “When the snow melts, these chemicals are released into the environment at high concentrations.”
In his study, published in 2011, he wrote, “There is a peak contaminant flush at the very beginning of the melt.” With the advent of spring “comes this deluge of pollution.” What makes it so problematic, he says, is that this is also the time many aquatic organisms and the ecological systems they depend upon are most active and vulnerable. For example, for migratory fish and shellfish such as oysters, the snowmelt season corresponds with mating season and spawning activity in streams, wetlands, and estuaries.
Meyer’s findings have obvious real-world implications, such as how municipalities choose their snow dumpsites. He says cities and towns “should be very careful to select well-contained sites to protect against that early flush of pollutants.”
Case by Case
Kelli Buscher is the engineering manager and the administrator of the Surface Water Quality Program for the South Dakota Department of Environment and Natural Resources (SD DENR). She says South Dakota has a lot of experience clearing snow-bound roads. Generally speaking, she says, most of the state gets about 2.5 to 3 feet of snow during an average year.
“The exceptions are the communities in the Black Hills, Lead and Deadwood, which get 197 and 101 inches, respectively, on average.” She counts the runoff effects from snow as “different from rain.”
“There are very different runoff events with snow than with rain. In some cases, our snow just slowly melts away all winter long; and other times we get dumped on, and three days later the snow is gone. You can have a much quicker runoff; you have the potential for erosion and other damage.”
Although she has seen communities take snow from roadways and dispose of it “right over the shore or right into creeks,” it’s a practice the SD DENR discourages. “As you’re moving snow, you’re also moving a lot of pollutants that can be carried away if there is not a buffer between the snow pile and the flowing waterway,” she explains. “We were actually seeing some real water-quality issues because of snow being piled right by a river. You’d pick up gravel and other dirt and debris. We also see a lot of petroleum products—kind of an oily sheen coming off that snow from the vehicles.”
But there is a solution, Buscher says. “A lot of the time just having a vegetated buffer between the snow pile and the creek is enough to filter out the pollutants.” However, she notes, “A better scenario would be to use something like a fairground to dispose of snow and store it in the middle of town away from a flowing creek.”
According to Buscher, for the 15 largest communities in South Dakota, the principles and main directives for dealing with snow disposal can be found in each of the covered municipality’s MS4 permit. “We expect them to manage snow and other municipal activities to minimize pollutants,” she says. “We want it away from storm sewers and we want it away from flowing creeks.”
She says that objective is facilitated in great measure by the rural setting of much of South Dakota. “We’re lucky—we have a lot of open space where we can store that snow, so most communities don’t have much of a problem finding places to dispose of snow.”
Although it doesn’t happen very often, she says there are times when snow gets misplaced. “If we get a complaint, we talk with the city about options they have for better managing the snow.”
Some communities, though, face perennial challenges finding ways to deal with snow disposal. “In one city in the Black Hills, all of the roads in town are on very steep slopes, and they receive a very large amount of snowfall every year,” says Buscher. “They really have a challenge trying to find places to pile the snow. And that’s the community that we’ve seen pile it right in the creek at times. We’ve been working with them to stop that, but their options are limited by the terrain.”
She says cities facing similar circumstances sometimes “have to be creative” to protect the waterways, some of which bring commerce directly to the communities as prized high-quality cold-water fisheries. In the case of the Black Hills town, she notes, after consultation with the SD DENR, the town made a few changes in how it handles snow disposal.
“Rather than putting all of the snow in one spot, some of it is going on the fairgrounds and a couple of other spots, but that means they have to haul it farther.” In spite of the cooperation on efforts to mitigate the practice, she says, “Some of it is still going near the creek.”
Planning for the Worst-Case Scenario
Larry Hajna, a spokesperson for the New Jersey Department of Environmental Protection (NJDEP), says New Jersey encourages municipalities to dispose of snow in upland areas and “away from ecologically sensitive areas and areas that could be damaged by road salt.”
After a particularly heavy snow emergency some years back, Hajna says, some municipalities “just figured, ‘We can just dump it into the water.’ That wasn’t a good thing.”
He adds, “We realize that, especially in urban areas, it’s really tough to get the streets cleared, so we adopted a set of procedures” to guide snow disposal activities. “It’s not the kind of thing that would kick in with a normal six- to eight-inch snowfall, but would kick in with a 20-inch snowfall, or a series of snowstorms that keep adding up and blocking roads and storm drains.”
The New Jersey guidelines suggest that public and private entities work together to select appropriate snow disposal sites, and they outline a plan of action for each community. The first step is obtaining “an estimate, based on historic snowfall records and experience, of the amount of snow disposal capacity needed for the season,” so that an adequate number of disposal sites can be selected and prepared. The guidelines recommend marking or delineating potential sites for snow disposal, such as municipal open space parking lots or lawns.
In preparing these sites, the NJDEP recommends “placing a silt fence or equivalent barrier on the down gradient side of the snow disposal site and maintaining a 50-foot vegetative buffer strip” between the disposal site and adjacent water bodies. Clearing debris from the site prior to snow disposal and again after the snow melts is a vital maintenance procedure.
Recognizing that innovations in snow disposal, such as mechanical snow melters, may be employed by municipalities and businesses, the NJDEP offers guidance on how they may be deployed. In addition to complying with the requirements of federal agencies, municipalities, counties, and other local agencies regarding any discharges to storm drain systems, the NJDEP prohibits direct discharges of melted snow from mechanical melting devices into water bodies. Regulations require that a “filter bag or similar filtration device” be used to remove suspended solids and debris. Any discharge released from the device to the storm drainage system must also be visibly clear and not contain floating or solid materials, and it must be absent of any visible sheen.
In the worst-case scenario of a massive snow emergency, when all land-based disposal options have been exhausted, and upon stringent application requirements, the NJDEP may permit disposal of snow from public roadways and essential facilities such as hospitals, fire departments, police departments in a waterway, provided the snow is “not obviously contaminated with road salt, sand, and other pollutants.”
A Roadmap for Snow Disposal
With the increasing global temperature, the precipitation in some regions has presented a slowly increasing trend. “In general, an increase of the mean precipitation between 30 degrees North and 70 degrees North has been observed, and this is also true for the area between zero degrees south and 70 degrees South southern latitude,” writes Hui Zhu in the 2012 paper “Snowmelt Runoff: A New Focus of Urban Nonpoint Source Pollution,” published in the International Journal of Environmental Research and Public Health. In it he argues for greater attention and focus worldwide on the potential effects of urban snow runoff.
He writes, “Due to global climate change, the snowfall has increased gradually in individual regions, and snowstorms occur more frequently, which leads to an enhancement of snowmelt runoff flow during the melting seasons.”
Massachusetts in recent years has been no stranger to snowmelt runoff. Although Massachusetts has a long experience with heavy snowfall, for Beth Card, deputy commissioner with the Bureau of Policy and Planning for the Massachusetts Department of Environmental Protection (Mass DEP), keeping up with the problem under changing climate conditions means finding ways to prepare for even more-intense winter precipitation.
Widely variable weather patterns are a phenomenon Lealdon Langley, director of the Wetlands and Waterways Program at MassDEP, has observed on the local scene in Massachusetts. “Two years ago we had record-breaking snow, and this year we had a record low snowfall,” he says. “We do see more severe peaks and valleys, and really big storms followed by drought. I can’t answer how to plan when these storms will come, but we can plan for the best places to put snow.”
He adds, “The first and primary goal of government in a snow emergency is to public health and safety, to remove snow from roads and emergency parking areas.”
In an average year, most snow removed from roadways is disposed of at the roadside, says Langley, “except for the big parking lots or big intersections, where they have to physically remove it. If you have a cold winter with a lot of snowfall, then that problem becomes more acute because it starts to gobble up parking areas and streets, making it more challenging from a safety perspective to get clear line of sight and those kinds of things on roadways.”
Even with historical experience of extremely cold winters associated with New England, in 2015 the Boston area was virtually paralyzed by a series of winter storms that brought 65 inches of snow in 28 days. Several of the region’s municipalities, in the fight to keep up with the volume of snow cleared from roadways, were forced to obtain emergency permission from the MassDEP to begin dumping snow piles in the ocean.
Card concedes, “With storms of the magnitude seen in recent times, you quickly run out of places to put the snow.”
She says the experience revealed the importance of planning ahead and knowing in advance “where you had the most capacity to place snow after a significant snowfall.”
She says the disaster contributed other teaching moments as well. “From a regulatory agency standpoint, we learned we needed to have very clear direction on what happens if we run out of those available spaces, and what are the next steps and what are the next options and what regulatory tools do we have available.”
As a result of lessons learned from the 2015 season, she notes, “Our process now, for the middle of a snow emergency, is very streamlined; there is one phone number that a municipal official needs to call to get guidance on where that city or town may be able to place snow in the absence of another upland location.”
She says, “We worry about snow from at least two angles. Snow that is plowed and picked up brings oil and debris and anything in the way of the plow blade. And we worry about access to disposal sites and the impact of equipment and operations near a drinking water supply.”
Langley adds that the special concern with snow is that, as a solid, it can be moved from place to place, a process that “tends to concentrate any contaminants it might contain at the disposal site.”
Confronting this issue head on after the massive 2015 New England snowstorm, MassDEP introduced a new tool to help municipalities in choosing sites for disposal of large volumes of snow. The online mapping tool assists municipalities and businesses in identifying possible locations to potentially dispose of snow, should the need arise. The disposal locations depicted on these maps are also intended to aid MassDEP and the Massachusetts Emergency Management Agency in providing assistance to communities with snow disposal in the event of severe winter storm emergencies.
There are several different layers displayed on the map corresponding to resource areas, hydrology, and land use. Langley says the tool can be used to show “where those jurisdictions are that are regulated under the wetlands protection act; it allows people to plan to stay outside of those areas.”
Safely moving and storing snow to melt off gradually is “largely an avoidance exercise,” says Langley. To assist in this, the tool provides physical identification of sensitive resources such as shellfish beds, salt marshes, vegetated wetlands, and water bodies to guide disposal activities. Langley points out that it is important to exercise caution around stormwater infrastructure when seeking sites to dump snow.
Although locations where there is a working stormwater management system may be capable of handling meltwater, he says, “You’ve got to think about where those pollutants go once it melts.”
Drinking water mapping of Zone II areas documented in the mapping tool provides municipalities with “a lot of the groundwater hydrology, known subsurface information, that we can provide to people to help them avoid importing polluted snow into Zone II areas,” says Langley. By giving officials at the municipal level a tool that they can use, “it puts them in the drivers seat and allows them to consider local issues in making those choices.”
With this tool, Langley says, “You don’t have municipalities going out there and trying to figure out where these resources are on their own. We’ve done that for them. We’ve collected all that resource information on places to avoid and provided that to them.”
Although Card says one of the big challenges in developing the tool was trying to decide “what information to include, while at the same time making it user friendly,” she adds, “One of the things that helped us is that now most municipalities have a GIS department and professionals that know how to use it.”
She is confident also that the tool will be put to good use when it’s needed. “Our experience is that most folks at the municipal level are trying to do the right thing,” she says.
Thinking back over the mountains of snow that he’s seen moved around the roads during the colder months of the year, and the discolored heaps of half-melted residue peppering the landscape at the intersection of environmental health and public safety, Langley says, “People are surprised by the amount of pollutants that are collected and concentrated when snow disposed of in a central location.” Langley believes this is an important educational process that should also be pursued: explaining to the public why it’s important and why they should care about it.
But he acknowledges the predominant public concern during massive storms. “You only have to live on a street that doesn’t get plowed to realize how much it cramps your style.” However, he says, “It’s not all of one or all of another; you have to make the roadways safe and also protect water resources from contamination, so it’s a bit of a collaboration.”
