Working Toward a Low Salt Diet
By Susannah Wood
As winter started up in earnest in late fall, drivers around town began to see scatterings of greenish chunks on the roads before any bad weather had actually arrived. Was this something new? Why was it being applied before the snow and not after? Turns out, there’s a good reason, a very good reason: using less salt to keep our roads safe.
Rock salt (sodium chloride) continues to be the cheapest and most widely used treatment for winter roads. The problem is salt doesn’t go away, never breaks down into something else, remains in ground water—perhaps for decades, contaminates streams and settles into lakes perhaps forever, since the salty water sinks to the bottom, being heavier than fresh water. It has become a worldwide problem in countries where snow and ice are part of winter. Road salt has invaded wells, lakes and ground water across the northern tier of the United States at rates that are climbing steeply. Of the 18 million tons of salt put on the nation’s roads each year, about 70 per cent ends up in our waterways and ground water. A study done by the USGS found that half of the water samples taken across the northern United States were above the chronic toxic level for aquatic life (230mg/litre).
So far this winter, we in Norfolk have used nearly 1,400 tons of pre-treated salt. That works out to about 31 tons per mile of road.
A quick chemistry refresher: sodium chloride is made up of two ions bonded together, a positively charged sodium ion and a negatively charged chloride ion. When wet, the two ions part company. Because chloride has a negative charge and most of the ions contained in earth do too, chloride ions do not attach themselves to other particles but instead move quickly through the ground and into whatever water they encounter. Sodium ions do bond with negative ions so do not travel far, but tend to replace other important soil nutrients such as magnesium and potassium.
Here in Norfolk, John Allyn, of Louis Allyn &Sons, Inc., reports that two wells have become too salty for drinking. (At one well, Allyn was able to work around the problem with a longer steel casing, but more often the only solution is an expensive reverse osmosis system.) While wells closest to roads or downstream from roads are most vulnerable, cracks in bedrock can allow salt to travel surprising distances.
Too much sodium is a health problem for some people on salt-restricted diets, but too much chloride is particularly damaging to aquatic life, from microscopic invertebrates to amphibians, to fish. It interferes at a cellular level with the uptake of water and nutrients, affects reproduction in amphibians, causes deformation in salamanders, and disturbs the delicate moisture balance of their porous skins. It retards oxygenation in lakes, stressing vegetation and fish.
What can we do? At this point, researchers agree that the only real option is to use as little salt as possible while keeping the roads safe for travel. In 2014 Norfolk Now’s article on road salt described the “de-icing” of roadways. Now, the aim is “anti-icing,” putting salt down first before a storm to prevent a strong bonding of ice and snow to pavement so that much less salt is needed after the storm arrives. The town formerly used Magic Salt and now uses ClearLane. Both are proprietary products that combine sodium chloride and a by-product of the liquor industry. Only the luminous green is new. The town has also invested in a new, computerized truck, which varies the amount of salt dispersed as the speed of the truck changes. John Allyn, head of the Public Works Department and a half-cousin of the other John Allyn, reports that the trucks are calibrated at the start of each season so that the crews know how much the trucks are spreading. Record-keeping is an important part of best practices and Allyn tracks salt use pretty closely, he says, though he admits a couple of big storms one right after the other can make it hard to keep up with. The staff goes to periodic training sessions to brush up on new advances and recommendations. One practice Norfolk does not follow is to put liquid brine on the roads prior to a storm. Studies have shown that brining can cut down even more dramatically the amount of salt used overall, but it requires a different truck set-up, in addition to brine-making and -storing capabilities—costs larger communities can better afford.
Norfolk also takes no special approach to treating roads near wetlands and ponds, where salt could be especially damaging to aquatic species. Victoria Kelly of the Center for Ecosystem Studies recommends that towns consider using magnesium chloride acetate in such vulnerable areas.
It may be that if we were to look at the real cost to roads, vehicles and bridges as well as the danger to aquatic life and wells, investing in more costly technology would be worth it, even in a small town. The road budget in Norfolk is the second biggest item after the school budget. Rebuilding even a small bridge will cost in the hundreds of thousands of dollars. We spend roughly $425,000 on road repair each year, much of that damage caused by the corrosive effects of salt. Finland now uses potassium formate, a much more environmentally benign substance that is not corrosive. While it is much more expensive than sodium chloride because it is made, not mined, it could save enormous infrastructure costs. Researchers continue to try to find affordable and less harmful alternatives; Iowa even tried out garlic salt in 2008.
The New Hampshire Department of Environmental Services estimated that private contractors are responsible for half of the road salt used each winter. In response, New Hampshire created the Green Snopro program to train and certify participating contractors and their employees, and to provide liability protection. Connecticut could follow their lead, perhaps figuring out how to extend such protection to towns and municipalities. Fear of liability is a very real and pressing worry to public works departments, business owners and private contractors.
Rethinking our approach to paving could provide another way to cut back. Porous asphalt, in use for many years for parking lots and driveway, requires very little salt treatment and has a much longer life, offsetting its higher initial cost. Because it allows water to trickle through, there is no freeze-thaw cycle to crack the paving apart.
Maybe as drivers we should to learn to deal with snowier roads and slower driving. In the late 1950s and early 1960s, I remember the sound of chains clunking along a snowy road. The “bare road” approach did not become the norm until Texan Lyndon Johnson declared it national policy in the mid-60s. In Finland, for example, they require drivers to take a winter driving course, and Quebec requires snow tires from Dec. 15 to March 15.
As individuals we can also be smarter about salt use. Of course, shoveling is the first step. Then use as little salt as possible. For sodium chloride, sprinkle about one handful per square yard; for calcium chloride, it’s about one handful per three square yards. If you have not had your well tested recently, especially if it is near a road or relatively shallow, it’s a good idea to do so. Torrington Area Health District will give you the results in about a week.
Photo by Wiley Wood: One of six trucks used by the Public Works Department as snow plows and salt spreaders. Behind the truck is a shed containing 250 tons of newly delivered salt.