The classifications do not measure the stability of the dams or likelihood of them bursting, but rather estimate the hypothetical loss of life and damage to surrounding areas if a worst case scenario failure occurred with no controls in place.Extreme risk, the worst of CDA’s classifications, means the potential loss of life exceeded 100 people and there would be major environmental, cultural, infrastructure and economic damage.
The risk from the company’s Australian dams was to its employees and it is understood the company has taken it seriously enough to relocate employee offices at its Mt Whaleback mine.Three extreme risk dams in joint ventures not operated by BHP were also identified in South America. BHP’s extreme risk dams are all built using the upstream method, where dam walls are raised sequentially from the crest. It is the same method used in Vale’s Brumadinho dam in Brazil, which collapsed in January and killed more than 200 people. The disaster prompted the country to ban the method.
Mr Currie told investors Brumadinho strengthened its resolve to collaborate to eliminate tailings risk from our sector.“The taskforce will be accountable for further enhancing our focus on tailings including the continued improvement and assurance for BHP’s global tailings storage facilities, progressing our technology efforts and leading ongoing participation in the setting of new international tailings management standards,” he said.
At BHP’s Pilbara iron ore mines it has temporarily relocated employees from offices currently in the ‘inundation zone’ while it looks at building a barrier to protect them.A similar barrier is being engineered at Olympic Dam and emergency drills have been run to test the effectiveness of emergency evacuation and response. A BHP spokeswoman said its Mount Whaleback mine in the Pilbara, the home of one of its extreme classified dams, had extensive controls in place.
Earlier this year the International Council on Mining and Metals, an industry trade group including BHP, announced it would set new standards for tailings dam design and maintenance by the end of the year.
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