In a civil claim filed last week in BC Supreme Court, Imperial Metals names Knight Piesold Ltd., its original engineering firm, and its successor: Amec Americas Ltd., Amec Earth and Environmental and Amerc Foster Wheeler Americas Ltd. The allegations have not been proven in court.
On August 4, 2014, the Mount Polley tailings dam collapsed, releasing water and mine slurry into local waters.
The mine was shut down, and the dam was rebuilt. The company only recently received a permit to resume full operations using the new tailings dam.
A special technical panel struck by the provincial government determined that the tailings pond collapse was the result of a design flaw that did not take into account an underlying layer of glacial material that made the ground unstable.
However, there were also criticisms that the dam itself was not properly designed and maintained and that too much water was being stored behind it.
Although the volume of water stored behind the dam was not considered a trigger, it did exacerbate the damage by pushing more slurry into rivers and lakes than might otherwise have occurred, the government's technical panel found.
In its civil suit, Imperial Metals alleges that Knight Piesold “acted negligently” in preparing the initial design between 1990 and 1995 by failing to adequately investigate and identify the subsurface conditions.
Knight Piesold was the company’s engineer of record from 1995 to 2011, when it was replaced by Amec.
The company also claims that the dam itself was not properly designed and that it did not have the minimum “factor of safety” required and as a result was “unsafe and at significant risk of failure.”
It claims that Amec failed to “identify and warn” of design errors that Knight Piesold had made, and “deferred” too much to the original work done by Knight Piesold.
In a written statement, Knight Piesold said it can't be blamed for the tailings pond collapse and will soon respond to Imperial Metals' claim.
"Significant design changes were made subsequent to our departure from the project some four years prior to the breach, such that the tailings storage facility at the time of the breach cannot be considered a Knight Piésold design," the company stated. "Knight Piésold is confident that our engineering services were appropriate and that the breach would not have occurred if the facility had continued to be developed and operated in accordance with our design."
Imperial Metals is claiming damages, but has not stated how much it is claiming. Nor would a company spokesman provide an estimate when contacted by Business in Vancouver.
But the total damages could be $100 million or more, based on the cost of remediation and revenue loss from the mine’s shutdown.
The company originally estimated the cost of remediation alone was about $67.4 million.That doesn't include the loss of revenue from the mine being shut down.
