A massive mining wastewater spill in the interior of British Columbia highlights a new global trend: tailing dams that hold waste are not only getting bigger, but posing greater risks to watersheds and communities downstream.
Drawing upon recent industry reports and presentations made by engineers living in the province, it’s clear that the complexities of the industry have multiplied and with them, risks to water are escalating.
Increased global mining production of substances such as iron ore, gold, copper and nickel along with rising metal prices has tripled the value of the industry from $200 billion to $600 billion over the last decade.
But due to declining ore quality, the sheer volume of waste produced by the industry, which can contain substances such as arsenic, lead and cyanide, is increasing.
Every year, the industry digs and moves as much solid rock (several thousand million tonnes per year) as all earthen materials transported by natural geological processes, such as landslides and erosion.
Because of the challenge of peak metals and high global demand, the mining industry faces a number of somber risks, as reported by Andrew M. Robertson of Robertson GeoConsultants at a recent mining conference.
It must not only dig deeper for poorer quality ores, but create larger and taller dams of tailings waste.
As a result, the dykes that contain the waste have been growing higher and larger every year. The average height of a tailings dam has grown from 120 metres in the 1960s to 240 metres today. They also contain more water than ever before, reported Robertson.
In addition, the growing size of mines means that the industry is “increasingly dominating regional water supply and quality. Our structures to control water have become large and threatening,” reads Robertson’s presentation.
Every 30 years, the volume of water and tailings produced by the industry increases tenfold, said Robertson. Meanwhile, the area of waste deposits increases fivefold and the height of dams grows twofold. “We are not dam building — we are terraforming,” he told a Tailings and Mine Waste conference in 2011.
Booms add risk
Across the world, the rate of dam failures containing mining waste now averages 1.7 a year. That’s a much higher rate than conventional hydro dams.
Norbert Morgenstern, a world authority on the structures, has reported that the reliability of tailing dams is “among the lowest of earth structures.” In addition, he has said, “well-intentioned corporations employing apparently well-qualified consultants is not adequate insurance against serious accidents.”
In 2010, Morgenstern noted an interesting fact: tailing dams that received regular third party inspections rarely failed.
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