Failed tailings pond at B.C. mine creates fear of long-term environmental damage

It could be days before residents of a remote part of British Columbia learn whether their water is safe to drink or even bathe in after a massive spill from a breached mine tailings pond dumped millions of litres of toxic water into local waterways.

The giant containment pond for the Mount Polley copper and gold mine ruptured early Monday morning, sending an estimated five million cubic metres of water and sludge into neighbouring Polley Lake and Hazeltine Creek, which runs into salmon-rich Quesnel Lake six kilometres downstream.

The Cariboo Regional District quickly issued a notice banning water use covering several lakes and creeks, including the Quesnel and Cariboo River systems as far as the Fraser River. District chairman Al Richmond told Yahoo Canada News between 200 and 300 residents of the community of Likely and surrounding area are affected.

"We've got a long expanse of river frontage but largely uninhabited for the most part," he said in an interview Tuesday. "We do have ranches along the way that water cattle and there's concern about using that by anyone drawing water directly from the river."

The regional district is trucking drinking water into two watering stations until it's determined local sources are safe, Richmond said.

The flow of water, rocks, trees and mud along swollen Hazeltine Creek also threatened a bridge on the only road to Likely, Richmond said.

The scale of the spill, reportedly equivalent to 2,000 Olympic-sized swimming pools, is raising concerns about the potential environmental damage if significant amounts of poisonous sludge have contaminated local water sources.

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Officials from the B.C. Ministry of Environment were on the scene Tuesday, along with staff from Imperial Metals, the Vancouver-based company that operates the Mount Polley mine.

"My understanding there was still some flow coming out of there," said Richmond. "They were only just able to get able to get in to try and do some more stabilization today."

No one from Imperial responded to a request from Yahoo Canada News for comment. The company posted a statement on its web site saying the breach had "stabilized" and expressing concern for the health and safety of its employees and local residents. It promised to "mitigate immediate effects and understand the cause" of the breach.

The earthen dam at the head of the 3.3-square-kilometre tailings lagoon "operated within design limits and specifications," the company's statement said. "Monitoring instruments and onsite personnel had no indication of an impending breach."

Water samples have been taken and Richmond said the province has promised the results will be returned quickly.

"Our main focus at the regional district is public safety and in particular the water quality," he said. "Those who take water from the river need to know whether they can continue to do so."

Imperial said in its statement that water in the tailings pond was not acidic but highly alkaline, which Richmond noted is also the case with lakes in the Cariboo region.

Tailings ponds are repositories of the waste products of the mining and milling of minerals. Water is used to cover the material to keep it from polluting the air.

A 2013 report filed with Environment Canada showed the Mount Polley mine deposited more than 400,000 kilograms of arsenic and related compounds into the pond, as well as 177,000 kg. of lead, almost 21,000 tonnes of manganese and 3,114 kg. of mercury. Large quantities of Phosphorus, selenium, vanadium, cadmium and cobalt were also disposed of.

There had been concerns about the vast tailings pond for several years, said Brian Olding, a Vancouver environmental-planning consultant hired by the company and two local First Nations to look at a plan to discharge its growing volume of water.

"It's a big one," Olding said in an interview. "It’s a net precipitation site, which means more water is coming into the lagoon than is going out of the lagoon."

The company had tried to control the buildup by using some of the water for dust control at its open-pit mine and to fill voids in mined-out areas. It's also been increasing the height of the dam but eventually decided some water had to be released into neighbouring Hazeltine Creek.

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Olding's firm was hired to review Imperial's 1,500-page application to the Environment Ministry for an effluent-discharge permit.

Olding's recommendations for developing a safe discharge plan included building a sediment pond to capture solids from the tailings lagoon. It would be connected to a secondary pond stocked with rainbow trout, a "canary in the coal mine" species that would signal any potential problems with the discharged water.

The company obtained the discharge permit in 2012 but never proceeded with many of the recommended elements in Olding's non-binding report, said Aaron Higginbottom, resource manager of the Williams Lake Indian Band, one of the First Nations that commissioned the report. Imperial will be allowed to discharge 76,000 cubic metres this year, he said.

It's too early to say what caused the tailings pond dam to fail. The region had a lot of rain in July and parts of June, said Richmond, and that could be a factor. Nor is the dam's growing height necessarily the culprit, said Higginbottom.

"They say an accident takes a number of factors for it to happen," he said. "No dam's failure has ever occurred because of one thing."

But Higginbottom noted the company was in the process of increasing the dam's height again when breach occurred.

Olding said it's not possible to call the accident predictable but the tailings pond was nearing its capacity.

"I don't know what caused the breach in the dam, no one does," the consultant said. "But I think that a water-management strategy was required, was recommended.

"It can be done safely and I think there's an onus on the government to ensure the correct monitoring of tailing lagoons as well as receiving water environment is done very thoroughly.

"I don't think they overlooked it. I think they're under resourced."