The mere mention of a snowflake in the seven-day forecast has the Washington region scrambling to stockpile food and toilet paper rations from the neighborhood grocery store. Our collective aversion to snow also places great pressure on local departments of transportation to vaporize every snowflake that touches a road surface.
However, the salt that gets spread on our roadways, driveways, parking lots, and sidewalks each winter is putting the quality of our drinking water at risk.
Salt pollution is a national problem
Every winter nationwide we dump more than 20 million tons of sodium chloride (salt) onto our roadways, parking lots, driveways, and sidewalks. Road salts are increasingly contributing to poor water quality in our streams, rivers, and lakes across the country.
According to the US Geological Survey (USGS), de-icing was the primary use of salt (46 percent) in 2008. By comparison, the entire food processing industry, agriculture, and direct consumption was less than 10 percent of the sodium chloride market in that same year.
While the corrosive impacts to road infrastructure and vehicles are well known, we are only recently learning more about the long term impacts to local water quality. Researchers at the University of Minnesota observed rising concentrations of chloride in streams and lakes around the state, and estimate that 70 percent of road salt applied around the Twin Cities remains in the watershed.
Salty water is toxic to humans. The saltier your water is, the more water your kidneys need to filter out the salt. This is why you can't drink seawater: filtering out the salt requires more water than you drink, so your kidney uses water from elsewhere in your body. You get more dehydrated with every drink you take, until you die.
Rising chloride concentrations in streams and lakes harm freshwater aquatic life and also have potential consequences for local drinking water supplies. Recent studies have even shown that exposure to this pollutant can have an effect on circadian rhythms in certain species, which may create a cascading effect on entire ecosystems
Research is ongoing to determine if our own circadian rhythms could be affected by increased salinity levels in drinking water, which could lead to other health complications such as diabetes, obesity, heart disease, and depression.
USGS found average chloride concentrations exceed toxic levels in 84 percent of urban streams and rivers in the northeast and the frequency of these occurrences nearly doubled in the last two decades. Road salt and winter de-icing are identified as the primary driver. Researchers in Upstate New York reached similar conclusions and directly attributed the rapid growth of cities and suburbs to rising chloride levels in area streams.
Once road salt washes off roads and other surfaces and enters our waterways, it becomes very difficult to remove from drinking water supplies. Many public and private drinking water systems were not designed to remove high concentrations of chloride from source water and may require expensive upgrades to treat salty water. Predictably, the costs of these upgrades are likely to be passed on to water customers in the form of higher water utility rates.
Chloride concentrations increasing in our region, too
These water quality trends are also being observed here in the Washington region. Every winter 750,000 tons of road salt is dropped in the Potomac River watershed, which is the primary drinking water source for the region. Researchers have noticed chloride concentrations increasing in area streams and rivers. Fairfax Water and the Potomac River Basin Drinking Water Source Protection Partnership have identified road salt as an emerging concern for drinking water quality in the region.
We walk a fine line balancing public safety, environmental issues, and economic concerns during a snowstorm. Economic analysts estimate winter storms can cost cities and their surrounding suburbs hundreds of millions of dollars per storm when government offices are closed, transportation routes are impacted, and employees have difficulty getting to work.
Fortunately, the departments of transportation in Maryland, Virginia, and District of Columbia are aware of the environmental impact to area streams and water quality and have taken measures to reduce the amount of road salt while improving the de-icing efficiency of each application through a variety of strategies (and also saving our hard-earned tax dollars).
Local municipalities are also exploring ways to reduce their impact on our waterways. The highway operations department in Frederick County, Maryland, along with many counties in the region, uses a salt brine to pretreat roads. This reduces the amount of rock salt needed after a storm.
Area roadways are the responsibility of departments of transportation, but sidewalks, driveways, and parking lots are the responsibility of home and business owners or property management companies.
Here are some winter tips for homeowners, businesses, and property managers to reduce the amount of salt used during the winter, saving you money while protecting the quality of our drinking water.
Be salt wise this winter!
- Shovel: The more snow you shovel from sidewalks and driveways, the less salt you need to apply. Shovel immediately after it snows (or periodically during a prolonged event) to prevent the snow from turning to ice.
- Scatter: When applying salt, leave space between salt grains (think fertilizing your lawn). A coffee mug of salt is enough to treat a 20-foot driveway or 10 sidewalk squares.
- Switch: While not very common in DC, salt loses its effectiveness when surface temperatures fall below 15 degrees (F). Consider switching to alternative de-icers or use sand for traction.
- Read the label: “Salt” is a general term for any de-icing agent, but not all salt is created equal. Calcium magnesium acetate is considered the most environmentally friendly option for de-icing. However, it can be expensive. Magnesium chloride is a more economical alternative and still considered a better alternative to sodium chloride.
- Speak out: Talk to your government representatives, homeowners association, property manager, or landlord about their use (or overuse) of de-icing agents.
- Review: Finally, for property managers who may contract out snow clearing, review your agreements and work with your contractors to pay by the square footage cleared rather than by the number of bags of salt used. You may be inadvertently incentivizing the application of more salt than is necessary to remove snow and ice from parking lots and sidewalks.