… and what is its impact on the environment?
When snow and ice hit the streets and roads of Durango and La Plata counties, the only thing standing between a safe commute and a winter wrecking derby are road maintenance crews who plow the roads and spread sand and de-icing agents.
It’s de-icing agents that raise environmentally-conscious eyebrows and ask the question – what agents are being used and what impact are they having on the environment?
The first part of the question is simply answered. The state, county and city of Durango all use sand derived from crushed rock. Durango and the state also use magnesium chloride and ice slicers. La Plata County avoids magnesium chloride and relies on ice slicers.
The second part of the question is more complicated in that it goes down the proverbial rabbit hole of degrees – how much is too much, resulting in damage to water, plants and animals – and how little is the environment to make roads safer without harming them?
Again, the simple answer is that too much de-icer will harm the environment, and those who live in it — even though city, county and state officials say they use small and dilute amounts — are monitored to make sure they’re not harming the environment.
“We are very conservative in our use of magnesium chloride through our stormwater management program,” said Allison Baker, Durango’s director of public works. “We have a stormwater master plan and an MS4 permit through the state that requires constant monitoring throughout the year. And we monitor at multiple points across the city.”
Municipal Separate Storm Sewer System (MS4) permits are issued to discharge urban stormwater into streams, rivers, and lakes. The process is designed to keep Colorado’s waters clean enough to support recreational use and aquatic life.
Magnesium chloride can be extracted from brine or seawater. It is an inorganic compound of the salt family. It is used for low-temperature de-icing and helps prevent ice from bonding to the pavement, allowing snow to clear the road more easily.
A research paper published by the Colorado Department of Transportation in 2001 stated that magnesium chloride may contribute to the mobilization of trace metals from soil to surface and groundwater, but noted that field evidence for this effect is limited. There is also the possibility of increased salinity of rivers, streams, lakes and groundwater. Chloride de-icers also have the potential to deplete oxygen in streams near roads where they are applied and may result in the death of fish and other aquatic life. However, fluid assumed to occur in runoff from roads reduces the likelihood of these effects.
The paper states that chloride-based de-icers can damage “terrestrial vegetation” up to 650 feet away, but that magnesium chloride does not attract wildlife because the main chemical attractant is sodium.
“Several years ago, CDOT completed a study on the effects of magnesium chloride on the roadside environment and found that the product did not significantly harm aquatic or plant life,” CDOT representative Lisa Schwantes said in an email. Durango Herald. “CDOT requires all vendors and suppliers of liquid road treatment products to meet the specifications designated by the study.”
La Plata County does not use a liquid de-icing agent such as magnesium chloride, said county road maintenance supervisor Mike Canterbury.
“La Plata County uses an environmentally safe product called Ice Slicer,” he said. “We mix 10% ice slicer into our sanding material. We use 100% ice slicers in isolated areas like dangerous hills, curves and intersections.”
A supplier of ice slicers, Envirotech Services Inc. Claimed to be a more environmentally friendly alternative to road salt because less is required, resulting in less chloride in the environment. They describe it as “complex red salt containing sodium chloride, calcium chloride, magnesium chloride, potassium chloride, and inert materials such as clay.”
Durango uses both magnesium chloride and ice slicers because they actually serve different purposes, Baker said.
“The ice slicer we use specifically relates to traction, where magnesium chloride is used to prevent ice from building up and to help us remove it during plowing,” Baker said. “So they are not equivalent products.”
Baker and Joey Medina, who is in charge of Durango’s roads, are both new to their positions, so more research needs to be done on how long magnesium chloride has been used in Durango, Baker said. But it has been in use for at least the last three years that he is aware of and has been in common use throughout the United States for the last 10 years
“Magnesium chloride is a salt substitute,” Baker said. “It does much less damage to vehicles over time than sodium chloride, which used to be used. It’s not a new technology, it’s been around the country. It’s very effective.”
La Plata County’s current contract price for ice slicer is $126.40 per ton when mixed with sand. The county used 200 tons last winter. Baker and Medina have not broken down those numbers to indicate the application or mixing process, but they said they will next year. They provided purchase data showing magnesium chloride at $1 per pound and ice slicer at $104.50 per gallon.