JOHANNESBURG (miningweekly.com) - More medium-term and long-term solutions, including desalination, are needed to combat the water quality and treatment challenges on the old Witwatersrand gold mines, says the Council for Geoscience's Henk Coetzee.
In an address to the thirty-fifth International Geological Congress, Coetzee sketched a picture of how water issues have come to the surface in this gold-rich area over the years.
He said it was vital to educate the next generation of mine water specialists, as a lot of institutional memory had been lost.
“This is a long-term process and we need to maintain the expertise in future,” said Coetzee, a specialist scientist and geophysicist.
Coetzee told the congress in Cape Town that the Witwatersrand has produced one-and-a-half billion ounces of gold over the decades, making up half of the gold ever produced globally.
Gold production in South Africa peaked in the 1970s and has declined since then. Easy- and cheap-to-mine gold has already been mined while mines today are deeper and more expensive to operate. Coetzee said South Africa accounted for about 5% of global gold production today.
In most cases, the underground mine extended beyond the natural discharge level of water, while mines were often interconnected. As mines developed, it was easier to access a mine from a neighbouring one. In the Johannesburg area, 48 km of mines were connected to each other.
Coetzee explained that, as mines closed, they ceased pumping water from underground. As each mine closed, it would stop pumping, and then the mines would flood. Individual mines flooded, with adjacent mines left to manage extraneous water with a State subsidy, although this only helped in part.
It took until 2002 for the first discharge of water to surface from the mines of the West Rand goldfields. Over the next eight years a programme was put in place in a bid to manage the situation.
“The programme is still in place to look into aspects of water quality but the volume of water to be managed is still poorly constrained,” said Coetzee.
He said building sustainability was difficult in the area for various reasons.
“If we want to pump water, pumps are expensive and require energy. Pumps, as well as water treatment plants, need a lot of maintenance.” But Coetzee said human factors were often the dealbreaker or dealmaker. Information on water resources in the gold mining area was often unreliable and accompanied by poor communication.
He said it could be difficult to convey complex information to policymakers. Biases also come into the picture, with emotional investment in a solution and the possibilities of financial gain, also hurdles. Competing government priorities were also a challenge.
Coetzee said that, in the short-term, the pumping and neutralisation of water from the mines is under way, but desalination is the next step.
Rain gets into the surface water system, with seepage of contaminated water into rivers and groundwater. As rainfall patterns differ, any long-term solution needs to take variability of flow into account, not just day to day, but at the scale of events, seasons and long-term processes.
“Lowering the water level after it has risen to the surface requires much greater pumping capacity than maintaining a water level, but it eliminates the cost of pumping and the risks associated with maintenance of complex systems,” said Coetzee.
He said it was vital to educate and inform affected parties, including national, provincial and local government, as well as regulators; develop expertise for the future and apply lessons from the past to current and future mining projects.