Mining’s a dusty job, but Vale has implemented a process for dust suppression that is proving to be effective at keeping the pesky substance at bay.
It doesn’t pose any ill effects to human health, but the dust can be a nuisance, said Glen Watson, Vale’s senior environmental specialist in Sudbury, which is why the company has worked over the decades to fine-tune its dust-control program.
“Years ago, if we weren’t doing dust control properly, in a community like Lively or the highway stretch between Lively and Creighton Mine you could see the dust blowing across the highway on a windy day,” Watson said. “That’s a very rare event now. We do a fine job of dust control up there and we get better at it all the time.”
A fine, sandy dust is left after water drains through the waste slurry that is collected in tailings ponds as a result of the mining process, and it’s this material that Vale strives to restrict to its property.
Dust control falls to a crew of eight seasonal employees working under Mark Palkovits, Vale’s land reclamation supervisor. The team monitors conditions and applies dust-control measures when required.
In the “Cadillac” approach to dust control, which offers longer-term results, hay is distributed across the tailings field and then “crimped” into the surface of the tailings, Watson said. The crew uses regular farm equipment to distribute the hay, which is purchased from local farmers and delivered daily.
But under certain conditions, a product called Entac, manufactured by Hamilton-based EnsSolutions, offers a faster, more effective approach, such as when the weather forecast calls for high winds, or when tailings are due to be released and the crew knows that cover is needed.
Entac is a tall-oil pitch emulsion derived from the process of pulping pine trees. It’s environmentally benign, non-toxic, and is good at keeping the dust down.
“If the wind’s coming from a certain direction and we know we have to get in that area—and we know in a couple of days they’re going to putting fresh tailings there—then we’re going to use Entac because it’s a lot faster, and it’s a bit cheaper than the straw because there’s a lot fewer resources required to do that,” Watson said.
Spring and fall pose particular challenges to the company. The cycle of freezing and thawing reduces snow cover, which is becoming more of a problem as less snow accumulates each winter.
The emulsion can be distributed via hydroseeders—large trucks with huge tanks on them. Helicopters are called in to spray the substance in areas the maintenance crew can’t reach by ground, or when the area is too soft for the farm machinery, Watson said.
“Typically we’ll cover 200 to 300 acres in the spring and 200 to 300 acres in the fall,” Watson said. “We’ve done up to 400 acres with the helicopters.”
When the company ceases to use an area for depositing tailings, that’s when the crew will take a more permanent approach to dust suppression, revegetating the area with tree seedlings grown in Vale’s own greenhouse.
Revegetation helps slow the release of the highly acidic leachate that results from tailings.
“Water and oxygen are not getting to the tailings, so you’re slowing down the process and promoting growth on the surface,” Watson said.
Revegetation additionally increases biodiversity while beautifying the area.
Watson said the company is continually seeking cheaper, more effective solutions to dust control and honing its processes, since it can be expensive, time-consuming and dangerous for the people operating the equipment.
Vale isn’t the only company to employ these measures—it’s popular amongst mining and aggregate businesses—but the company has taken a forward-thinking approach to the issue, serving as an example to others.
“Vale has pioneered processes,” Watson said. “Companies from around the world have come to see how we’ve revegetated the surface of the tailings and what sort of amendments did we need to do.”