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Failure of B.C.'s mine tailings dams could put thousands of lives at risk, says report

As mine tailings dams grow in size and number, a new analysis warns thousands of lives could be put at risk if they fail
An aerial view of a copper mine tailing pond in the interior British Columbia, Canada.

The scale and pace of the construction of new mine tailings dams could put thousands of lives at risk across British Columbia should they fail, a new report has found.  

The report, conducted by international mining expert Steven Emerman on behalf of BC Mining Law Reform and Skeena Wild Conservation Trust, found nearly half of B.C.’s existing mine sites with tailings storage facilities are likely to have high, very high, or extreme consequences in the event of dam failure. 

Among sites currently inactive or undergoing maintenance, 46 per cent were found to have the potential to cause loss of human life, environmental fallout, or significant economic damage. But for currently operational or proposed tailings dams, that potential jumped to 83 per cent, found the report. 

Emerman said that puts a minimum of 3,000 lives at risk over the coming decades — largely because, in addition to the 172 tailings dams already built in B.C., a mining boom means new dams are getting bigger and taller, rivalling some of the largest in the world.  

“We're moving into a very scary future where tailings dams are getting riskier and riskier,” he said.

Tailings dams indefinitely store vast pools of waste left over from mining. They contain toxic heavy metals like selenium, and other toxins such as arsenic and cyanide. 

In B.C., public data suggests there are about 2.5 billion cubic metres of such liquid mine waste held back from pouring into watersheds and impacting communities. It’s a volume of waste that could fill B.C. Place stadium 943 times. 

Ministry, industry refute findings

A spokesperson for the Ministry of Energy, Mines and Low Carbon Innovation defended the province’s capacity to monitor tailings dam safety, stating that "safety and environmental stewardship are top priorities at all mine sites in British Columbia.” 

“Any new projects in B.C. must undergo a comprehensive Environmental Assessment and are subject to a thorough permit review process that includes cross-border agencies when there are cross-border interests,” said a spokesperson in a written statement. 

The spokesperson pointed to a December 2021 report from the Chief Auditor of Mines that requires mines to: 

  • establish independent tailings review boards; 
  • secure an engineer of record responsible for the design of tailings storage facilities;  
  • and conduct and report on annual dam safety inspections, and carry out regular dam safety reviews. 

Michael Goehring, president and CEO of the Mining Association of British Columbia, said tailings storage facilities are already designed to withstand extreme weather and seismic events. He said any suggestion otherwise is either “wrong or deliberate fear-mongering.” 

“The report fails to consider how B.C. tailings facilities use design and engineering requirements and best available technology to mitigate risk,” he said in an email. 

Goehring also pointed to the 2021 report from the BC Chief Auditor of Mines, stating it found “B.C.’s regulations for mine tailings are among the best in the world.” 

Upstream construction leads to ballooning risk, says report

However, Emerman's analysis of B.C.'s mine tailings dams found a quarter of them were built through upstream construction, a practice where the base of the dam is made up of confined tailings.  

“The advantage of that method is that you need very little construction material because the dam is basically leaning on those confined tailings,” said Emerman, noting such construction methods are banned in many other countries.  

“The disadvantage is that if the tailings liquefy, the dam just falls.” 

That’s what happened in 2014, when the Mount Polley tailings dam failed, pouring over 24 million cubic metres of toxic sludge into the surrounding waterways in North America’s biggest such failure on record. 

In a 2015 review of the disaster, the province found the annual probability a tailings dam will fail in British Columbia was one in 600. 

Those odds might seem small. But they are roughly equivalent to the chances someone in the United States might die from something as unremarkable as a pedestrian incident

“That’s like dams failing every four or five years,” said Emerman. 

New tailings dams pose extreme risk amid changing climate

With another 11 new proposed mines, the volume tailings dams now hold back could increase by 75 per cent. And of those 11 dams, the report found five had a very high or extreme consequence of failure. 

Emerman points to a proposal to raise the Copper Mountain mine tailings dam south of Princeton, B.C., to 255 metres — only 10 metres shy of the world's tallest tailings dam in Peru.  

In another analysis Emerson says he’s currently conducting for the Colville Indian Reservation, he calculated risk of failure of the Copper Mountain tailings dam, which sits upstream of the tribe's land, was on par with what the Mount Polley review found for other dams across B.C. 

In other words, says Emerson, the risk it poses is “unacceptably high.” 

Or take the 162-metre high HVC Highland tailings dam northeast of Merritt. It holds back 1.19 billion cubic meters of tailings, 50 times more than Mount Polley.  

If it were to fail, it would wash down the Lower Fraser River, likely decimating ecosystems until it poured through Metro Vancouver and into the Strait of Georgia. 

“That kind of toxic spill of toxic material is unprecedented in human history... It's hard to predict what exactly is going to happen,” said Emerson. “So we're looking at future with catastrophic events that have no precedent.” 

The HVC tailings dam isn’t the only facility upstream of B.C.’s most populous corridor. The BC Mining Law Reform and Skeena Wild warned the Fraser River basin hosts 27 current and future mine sites each with at least one tailings facility.

Because tailings dams must hold back their contents indefinitely, they can’t be dismantled like a hydroelectric dam. That means that as time goes on, even the best-constructed dams can face ballooning risk. 

Part of that is because climate change is transforming storms that would usually only hit once every 1,000 years into a more regular event. Then there's the looming risk of a catastrophic earthquake, something past research suggests could have a 37 per cent chance of occurring over the next 50 years.

To withstand the forces of flood or violent shaking means constant surveillance.

“It's just like a highway or a bridge — it still has to receive constant maintenance,” said Emerson. “Anything that doesn't receive maintenance is going to fall apart. Eventually, it's going to fail.” 

Over a century, Emerson says the probability of failure climbs to a 50-50 chance; over several hundred years, failure is inevitable.  

A call to look at alternatives

Despite calls to accelerate critical mineral exploration to feed a decarbonizing economy, Emerson says regulators and companies need to “stop and think” about the long-term consequences of their actions.  

“Slow down,” he said. “Don't be in such a rush.” 

Emerson — who has testified before the U.S. Congress and European Parliament on the mining industry — said there are a number of alternatives to building tailings dams. That includes back-filling open pit mines with the waste, reducing overall production of tailings or removing water from the tailings to make them less mobile, and therefore less dangerous to the surrounding area.

“Don’t think of tailings as wet waste product that has to be stored forever. As much as possible, try to convert it into some marketable products, like material for road construction, asphalt — whatever is possible.”

CORRECTION: A previous version of this story said there are about 2.5 million cubic metres of tailings waste stored across B.C. The volume, in fact, is 2.5 billion cubic metres.