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Firm that designed tailings pond warned about possible issues

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by Russell Hixson last update:Oct 8, 2014

The international consulting engineering firm that designed the Mount Polley tailings pond claims it warned the owner, as well as the government that the pond and embankments were getting too large and needed to be monitored extremely closely.
Firm that designed tailings pond warned about possible issues

Earlier this month, billions of litres of water mixed with potentially toxic mining waste breached the earthen wall and continues to spill.

Knight Piésold Consulting initially designed the facility that was built in 1995.

According to the company, inspection records show that while it was the engineer of record, there were no issues.

The consulting company informed Imperial Metals that it would not continue as the engineer of record for the mine in February 2011.

"During the time we acted as Engineer of Record, the tailings storage facility at Mount Polley operated safely and as it was designed," noted the company in a release.

"The original engineering done by Knight Piésold Ltd. accommodated a significantly lower water volume than the tailings storage facility reportedly held at the time of the breach. Significant engineering and design changes were made subsequent to our involvement, such that the tailings storage facility can no longer be considered a Knight Piésold Ltd. design."

The company also noted that in 2011 it wrote a letter to Mount Polley Mining Corporation and to B.C.'s chief inspector of mines warning that "the embankments and the overall tailings impoundment are getting large and it is extremely important that they be monitored, constructed and operated properly to prevent problems in the future."

While the flow of water at the spill has significantly decreased, the pond continues to leak.

According to the Ministry of Mines, Imperial Metals has 300 workers constructing a temporary dike.

The dike is being built in a horseshoe shape just on the inside of the breach to stabilize the tailings material and keep it inside the impoundment when it rains.

The Imperial Metals estimates that it will take about three weeks to complete.

Imperial Mines has also begun pumping water out of Polley Lake both down Hazeltine Creek into Quesnel Lake and back into Wight and Springer Pits, two open pits on the mine.

The ministry states that the controlled release will significantly lower the potential risk of another breach.

An uncontrolled release of the stored water in Polley Lake could cause additional risks to human health and a further delay in possible rescinding of the drinking water advisory currently in place.

In addition, progress continues to be made booming debris with tug boats in Quesnel Lake to prevent it from reaching bridges.

Recent reports suggest that about 80 per cent of the debris is contained in Mitchell Bay and will be forwarded to Fraser Mills haul-out site.

The Likely Bridge is not at risk.

While a series of tests has shown the water to be safe, a water quality advisory notice remains in place for those near Polley Lake, Hazeltine Creek, Cariboo Creek and all parts of Quesnel Lake.

This includes the communities of Winkley Creek, Abbott Creek, Mitchell Bay and the East Arm of Quesnel Lake.

Interior Health will continue to evaluate water samples as they arrive and will update the communities as more information becomes available.

The cause of the breach is still unknown.

Ministry of Environment conservation officers are investigating the breach.

Ministry of Energy and Mines inspectors also are investigating, two of whom have been monitoring the site by helicopter.

last update:Oct 8, 2014

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