Knight Pisold designed the tailings containment facility for the Canadian-owned Omai gold mine in Guyana. Before the accident, it had handed off operational responsibility to the mining company, which then hired another engineering consultant, the Canadian firm Golder Associates. The Omai tailings dam collapse spilled an estimated 2.9 million cubic metres of toxic waste into the Essequibo River, the country’s biggest and most important watershed. (Some estimates run higher.) Guyana’s President Cheddi Jagan, whose government held a five per cent share of the mining venture — it was the poor country’s largest private sector employer — and had been championing its economic benefits, called it “the country’s worst environmental disaster.”.... A subsequent inquiry found no criminal liability and a civil class action suit was later dismissed..... It’s worth noting, perhaps, that by comparison the Mount Polley tailings dam failure, which B.C.’s Mines Minister Bill Bennett has equated with a simple natural landslide, spilled 14.5 million cubic metres — about five times as much contaminated waste as at Omai — into the Fraser River system, B.C’s biggest and most economically important watershed. The most hazardous component in the Guyana accident was cyanide. The accident at Mount Polley released sediments contaminated mostly with arsenic and heavy metals.... In one eerie foreshadowing of the current situation near Quesnel Lake, Knight Pisold warned the mine operator in Guyana when it handed off responsibility that modifying the tailings containment structure to increase volume might exceed its designed capacity and safety margins. The Guyanese newspaper Stabroek News reported from the inquiry into the Omai tailings dam collapse that “Knight Pisold has told foreign media that the dam failed at a height at which they were no longer responsible, having been replaced at the end of 1992 by Omai’s current dam consultants, Golder Associates.” After Knight Pisold had ended its relationship with the Omai mine, the dam was raised significantly, and subsequently failed. At the Mount Polley mine, Knight Pisold says that in 2011 it warned both the B.C. mine’s owners, Imperial Metals, and the provincial government that its original engineering was designed to accommodate a significantly lower water volume than was reportedly present when the dam breached. “Knight Pisold informed Imperial Metals that we would not continue as the engineer of record for the Mount Polley Mine on Feb. 10, 2011, and subsequently ceased to perform that role,” the company said in a statement posted to its website last week. “During the time we acted as engineer of record, the tailings storage facility at Mount Polley operated safely and as it was designed.”...... However, the company says, the tailings containment was designed to accommodate “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.” Knight Pisold says that it wrote the B.C. government in 2010, just before leaving the operation, to warn that “the embankments and the overall tailings impoundment are getting large and it is extremely important that they be monitored, constructed and operate properly to prevent problems in the future.” kaieteurnewsonline/2014/08/20/engineering-firm-in-collapsed-omai-tailings-pond-fingered-in-another-failure/
Posted on: Mon, 19 Jan 2015 04:07:47 +0000
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