What’s in Imperial Metals’ Mount Polley tailings? Should you be worried?
WATCH: Experts are just beginning to assess the environmental impacts of the tailings pond breach at the Mount Polley mine and as Linda Aylesworth reports, we’re learning more about what chemicals may be in the tailings.
The bad news: Spilling five million cubic metres of tailings represents a massive failure of a mine-waste storage method designed to be safe and secure for decades (and on whose safety guarantee permission to develop mines is supposed to rest).
The good news: It’s rare – “very rare,” says University of British Columbia groundwater hydrologist Leslie Smith.
“Any breach at all would be a rare event.”
The big uncertainty: Just about everything – what was in the suspended solids in the mass of spilled sludge; how far it went; whether it can be cleaned up; how much risk it poses right now; and what impact it will have on the environment, animals and humans – from spawning salmon to drinking humans – over the long term.
The tailings are what’s left over when Imperial Metals is done extracting, in this case, gold and copper from its Mount Polley mine. And any risk posed by the wall of slurry that flowed out of the tailings pond Monday comes down to what’s in it – what’s in the water, and what’s in the solids muddying it up.
“You can’t assume that every pond … is toxic,” Smith said. “The impact of the release has to be assessed. We can’t assume it’s terrible; we can’t assume it’s benign.”
Indeed, Imperial Metals has said the water in its tailings pond “is not toxic” and is “very close to drinking water. … The water itself is relatively benign.” The suspended solids that spilled along with it, however, may be another story.
The first good news: According to Imperial Metals, the tailings water was alkaline, not acidic, with a pH of 8.5 (7 is neutral; anything below 7 is acidic). Most metals dissolve faster in acidic water, so alkaline tailings are a good thing.
But it still isn’t clear how much of a risk the spilled tailings pose, or even how far they reached.
An Environment Canada filing from Mount Polley Mine lists all the substances disposed of in the tailings pond – including manganese, cadmium, phosphorous and mercury. But to get a really good idea of the massive spill’s impact and toxicity, you’d need to know how mobile those substances are.
In the immediate term, the biggest concern is what was in the water itself, Smith said.
“If you’re a fish in Quesnel Lake, what you’re going to be exposed to first is what was in the tailings pond water, not what was in the tailings themselves,” he said.
But in the longer term, any suspended solids left in the environment could cause problems.
“Those will start to weather and potentially release metals and we need to figure out what the concentrations of that would be,” he said. “Every mining company I know knows what’s in their pond.”
Cleanup, if it’s feasible, could be pretty basic: Think “truck and shovel,” Smith said, to recover any solids.
In the minds of environmental groups who’ve been fighting the development of similar mines from B.C. to Newfoundland, Monday’s massive breach proves there’s no safe way to dispose of the gunky leftovers from open-pit mines.
“A spill like that is devastating,” said Leila Darwish, B.C. and Yukon organizer for the Council of Canadians. And for many, the uncertainty’s the worst part.
“People don’t know the extent of the contamination, how far its moved into different water systems … what’s going to happen to that sludge.”
Darwish hopes the fallout from this spill will give ammunition to communities that oppose mining development near them.
“The safe thing would be not to have these mines,” she said. “What we’re risking is too high.”
“I don’t think there’s a need for a general panic but we have to learn what happened here … and how we can improve. Because this is not acceptable.”
Substances listed as disposed “on-site” in Imperial Metals’ 2013 Mount Polley Mine report (Note: We still don’t know how mobile these solids were, how much was in water, and how much spilled as solids in Monday’s massive breach)
- Phosphorus – 41,640 tonnes
- Manganese – 20,988 tonnes
- Copper – 18,413 tonnes
- Vanadium – 5,047 tonnes
- Zinc – 2,169 tonnes
- Cobalt – 475 tonnes
- Nickel – 326 tonnes
- Antimony – 14 tonnes
- Arsenic – 406,122 kg
- Lead – 177,041 kg
- Selenium – 46,136 kg
- Cadmium – 6,487 kg
- Mercury – 3,114 kg