A tailings-pond breach in central British Columbia spewed enough waste water to fill 2,000 Olympic-sized swimming pools into the province's pristine waterways and triggered a local state of emergency – but a consultant who worked with the mining company says red flags were raised years earlier.

The spill from Imperial Metals' Mount Polley copper/gold mine in B.C.'s Cariboo region on Monday happened just weeks after the mining company asked provincial authorities for permission to increase the amount of treated waste water it could release from the tailings pond. Ministry officials said in a statement on Tuesday they were considering the request when the breach occurred.

On Tuesday, with the spill appearing to have stabilized, Imperial Metals president Brian Kynoch apologized, calling the event "a gut-wrenching experience."

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"If you asked me two weeks ago if that could happen, I would have said it couldn't happen," he said at a media update in a community hall in Likely, B.C. "I know that for our company, it's going to take a long time to earn the community's trust back."

The tailings dam breached early on Monday morning, prompting the Cariboo Regional District to issue a strict water use ban for the Quesnel Lake, Cariboo Creek, Hazeltine Creek and Polley Lake areas. It was eventually expanded to include the entire Quesnel and Cariboo Rivers systems right to the Fraser River – an arterial waterway known for its large salmon runs. The district advised against humans or livestock drinking the water; it said swimming and other activities "are at your own risk."

According to preliminary data from Environment Canada's 2013 National Pollutant Release Inventory, the Mount Polley mine disposed of substances including arsenic (406,122 kg in 2013), lead (177,041 kg) and mercury (3,114 kg). Mr. Kynoch attempted to alleviate fears of a contaminated water supply, saying the discharged tailings water "is very close to drinking water quality."

"Specifically, mercury has never been detected in our water and arsenic levels are about one-fifth of drinking water quality," he said. "We regularly perform toxicity tests and we know this water is not toxic to rainbow trout."

When asked why then a water ban was put into effect, Mr. Kynoch said it was a precautionary measure.

As many as 300 people have been forced to use bottled water and to avoid bathing or giving pets and livestock tap water as a result of tailings pond burst. Residents' worries go beyond environmental – some say the impact will include lost jobs in tourism and mining.

Darlene Biggs, who owns the High Country Inn in Likely, said businesses in the community are "doomed," and many young residents will not be able to find jobs in the area and will be forced to move away. "It's going to stop our tourism industry," Ms. Biggs said. "It's going to stop the town because none of these kids are going to be able to work here any more. What's going to bring people into Likely? You can't swim in our lake at this point. And you can't fish. It's going to really, really hurt us."

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Brian Olding, president of environmental planning company Brian Olding & Associates Ltd., was hired as an independent consultant in 2011 to review a technical report from Imperial Metals, which at the time was seeking an effluent discharge permit for the Mount Polley mine.

"We went through it and found discrepancies and provided recommendations," Mr. Olding said. Those recommendations included developing a sedimentation pond for testing water from the tailings pond, and a ground water monitoring system so the mine could detect any leaks from the tailings pond.

The mine, under no legal obligation to act on recommendations, did not follow through on all of them, Mr. Olding said. The company did receive an effluent release permit, allowing it to discharge some water, but it was seeking another permit that would allow it to discharge more water by treating it first.

"They know that they have faced a problem – a concern with more water coming in than water going out," Mr. Olding said. "If they had started discharging the water and treating it some time ago, then it would take the pressures off the dam. … Clearly, a buildup of water is not a good thing."

B.C. Energy and Mines Minister Bill Bennett said government and company officials will get to the bottom of what happened and make sure it does not happen again.

"We don't know how bad, we don't know the quality of the water that was in the tailings pond," he said. "I am advised it was fairly high quality water and I hope that turns out to be the case."

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Gerald MacBurney, a foreman at the dam for seven years before he recently quit, said the dam was breached last May and that weakened the whole system.

"When you get a breach, there's more than one spot it breached. It weakened the whole system," he said in an interview. "And that's where it popped, right where it was breached. ... I knew it was going to burst."

An emotional Mr. Kynock flatly denied the claim: "The dam has never failed before," he said.

The Ministry of Environment has completed its water sampling of the area and has shipped samples off for analysis. Results of the tests – which will look at pH levels and the potential presence of metals and other contaminants – could take between two and four days.

The Cariboo Regional District has trucked in water to Likely, said district chair Al Richmond. "We set up a tank [Monday] night and we will fill that up, so that folks can come fill their bottles there."

Mr. Richmond said the district would ask Imperial Metals about Brian Olding & Associates Ltd.'s 2011 report at a meeting on Tuesday.

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"That report identified some concerns. We'll be asking the Mount Polley people what they've done with that report."

With a report from the Canadian Press

On Aug. 4, 2014, an earthen dam containing waste water from the Mount Polley Mine in B.C.'s Cariboo region breached, sending water and fine sand from the tailings pond into Hazeltine Creek. Some of the waste water and debris also spilled into Polley Lake and Quesnel Lake. See below the map for the latest sequence of events:

0 2 KM Quesnel

Lake Polley

Lake Boot Jack

Lake Tailings

pond Hazeltine

Creek 100-metre buffer from debris fan at mouth of Hazeltine Creek Debris fan identified by Ministry of Environment 200-metre buffer Alta. B.C. Williams

Lake Fraser

River Quesnel Detail Prince

George 1 4 5 2 3 Mount

Polley

Mine Tailings

pipeline

0 2 KM Quesnel

Lake Polley

Lake Hazeltine

Creek Tailings

pond 100-m buffer from debris fan Debris fan 200-m buffer Alta. B.C. Williams

Lake Fraser

Lake Quesnel Detail Prince

George 1 4 5 2 3 Mount

Polley

Mine Tailings

pipeline

1. On Aug. 4, a tailings pond dam breach sent 10 million cubic metres of water and 4.5 million cubic metres of fine sand into Polley Lake.

2. The balance of the tailings and water flowed down Hazeltine Creek, which was originally 1.2 metres wide, but is now up to 150 metres wide.

3. A water-drinking and fish-eating ban has been reduced, and now applies to Polley Lake, Hazeltine Creek and a 100-metre radius into Quesnel Lake from the creek's mouth.

4. Debris from the dam breach created an unstable blockage of Polley Lake. Imperial Metals has since installed a pipe to allow for lake drainage to the creek.

5. Work continues on a dike at the dam breach to contain tailings material during rain.

MURAT YUKSELIR/THE GLOBE AND MAIL » SOURCE: GOVERNMENT OF B.C.