Health & Science
The golden touch
by Marilyn Head
Using new technology, the Australian city of Bendigo has made gold mining more profitable and more environmentally sustainable. There are lessons for those who want to revive mining in the Coromandel – and those who don’t.
The Environmental Court’s recent ruling that mining cannot be deemed a prohibited activity has not daunted the Thames-Coromandel District Council, which is confident of finding other ways to stop it. To quote Mayor Philippa Barriball, “People will be walking on water before there’s mining in the Coromandel.”
Across the Tasman, however, in the Victorian city of Bendigo, a far different mood prevails. For the past 10 years, the city has embraced a revival of its gold-mining industry based on new technology that has made the industry both more profitable and more environmentally sustainable. Are there lessons for Thames-Coromandel?
“Absolutely,” says geologist Ashley Franklyn, who runs the Coromandel Gold Stamper Battery. “The mining technology coming out of Aussie is world-beating stuff. But what we’re doing is extraordinary, too. The open-cut mine at Waihi is a classic example of how well it can work if you do it properly.
“Even the Golden Cross mine has been a world-class example of how to shut down a mine – the bush, farmland and rivers are all regenerating and the tailings pond has been stabilised, thanks to the exceptional technology of the underdrainage system.”
Mining, says Franklyn, is always going to be unsustainable in the sense that you can’t put it back, “but there’s no reason why we can’t get sustainable environments back out of these mining operations. We can use them to clean up the hillsides, put the soil back and have sustainable forestry or farming resources.”
He would like to see less hypocrisy (“the most vehement protesters turn up with gold bars through their noses and then claim it’s recycling”) and more recognition of the opportunities that mining offers both the community and the environment.
So, what has Bendigo’s experience been?
“The whole issue here,” says Rod Hanson, chief operating officer of Bendigo Mining Ltd (BML), “has been getting the geological model right and understanding the mining conditions, so we can be confident it’s workable. We’re mining below the existing shafts and treating the whole field as one big system. Historically, the hundreds of shafts operating in the heart of Bendigo were owned by separate companies – that small scale is not economic any more.”
Nor is the hand-held, dynamite-blasting, cyanide-leaching technology of the past, with its legacy of injury, death and environmental degradation. Mining today is an extremely sophisticated process that draws on technologies beyond the wildest dreams of the old diggers. The gold-bearing quartz veins are precisely located and assayed before the rock is safely drilled by gargantuan purpose-built machines, blasted with an exact amount of ammonium nitrate and fuel oil (ANFO) and taken to the surface in trucks capable of carrying 50 tonnes each.
After processing, most of the waste is taken back underground to backfill the holes; some is kept on the surface for reuse in general construction. The extracted gold amounts to less than a teaspoonful for every tonne of rock.
“Most of the gold in quartz can be removed by gravity,” says Hanson, “and the balance, about 10 percent, is removed by froth flotation – fine floating particles of gold are skimmed off, dissolved in cyanide and the gold is then easily removed from the solution.”
(“Mention cyanide processing,” says Franklyn, “and all hell breaks loose, but cyanide is completely destroyed by sunshine and water and doesn’t pose a long-term threat.”)
BML’s projected total investment of $375 million to recover 95 percent of the estimated 13 million ounces of gold remaining is driven by anticipated gross revenue of $360 million for each of the 25 years of productive mine life.
For Bendigo, it’s more than just big money that’s going into its 100,000-strong community. Mining is a high-tech industry that attracts highly skilled and highly paid engineers, scientists, technicians and operators. That employment profile complements the generally lower-paid jobs that service Bendigo’s other gold-mining industry – tourism – and contributes to the diversity of the city’s cultural and intellectual life.
And the mines? Coming from either end of the goldfield, two gently sloping “declines” or tunnels will eventually meet in the middle, about 750m beneath the surface, under the city. Apart from the chimney-like ventilation shafts built to disperse exhaust and blasting fumes from below, the mines will be all but invisible. The processing plant is contained in a vast artificial pit about three kilometres from Bendigo, hidden from sight and sound by a bunker clad with what Hanson wryly refers to as “the local religion” – the box ironbark trees indigenous to the region.
Though the remark indicates that there’s no less love lost between miners and environmentalists in Bendigo than there is in Coromandel – each treats the other with extreme suspicion – there is a world of difference in the Australian attitude to mining in general. This is understandable, perhaps, since the Australian economy still thrives on it. Aussie environmentalists, backed by legislation similar to the Resource Management Act, have still been able to get the mining industry to pay for environmental projects far in excess of simply “making good” any damage, and have ensured extensive consultation to forestall potential problems. Bendigo will end up with five times the area of native vegetation, more usable land and cleaner river water, with far less visual and aural pollution than a normal busy city street would offer.
As Bendigo gets richer by $2 million a week, it may be worth contemplating a change in attitude.
