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A plan of action will be drawn up by the national Cabinet once it has received a report from the interministerial committee on rising acid water. Until then, there is no cause for alarm.
THERE is no need to panic about reports of acid mine drainage water levels rising because of this week’s floods in Johannesburg.

Residents can rest assured that Joburg water is safe to drinkResidents can rest assured that Joburg water is safe to drink“There are people who are alarmists, but there is no reason to panic about this,” said the City’s deputy director of communications, Nthatisi Modingoane. “We need to wait and see what is done at a higher level.”
Modingoane was responding to media reports that contaminated water from disused mines was rising fast after heavy rains pounded the city and surrounding areas recently.

“There is an interministerial committee in place, which will submit a report to Cabinet shortly,” said the Department of Water Affairs spokesperson, Themba Khumalo. “The report will cover what plan of action will be taken, and the decision that has been made about what to do will most likely be known next week.”

Toxic water
Acid mine drainage is water that flows over acid-bearing rock which has been exposed through mining. The water turns toxic as it rises to the surface of disused mines and makes contact with air. It contains sulphuric acid, minerals and metals.

In November 2010, it was reported that the government had an expected 20 months in which to build the infrastructure that would prevent the acid water from rising to the surface. Mining houses had the necessary infrastructure in place to pump this water out, but as mines closed, pumping ceased. This resulted in the underground space created by mining, filling with water.

The space was created by the removal of 1 300 million tons of rock, which yielded over 12 million kilograms of gold. Before the floods, the water level was at a depth of approximately 600 metres below ground and rising at a rate of 15 metres per month. At that pace, the water would have spilled on to the surface in two-and-a-half years.

However, according media reports this week, this rate has increased and mines have been given between six and 18 months before this water reaches the surface.

In Gauteng’s eastern basin, water has been rising at a rate of 40 centimetres a day, making it almost seven times the usual rate. In the central basin, where the mines under Johannesburg are found, water is rising at 50 centimetres a day, up from the usual 35 centimetres.

If no action is taken, the Central Rand Gold Mine’s lower levels will flood within six months, with Gold Reef City’s underground museum following suit in 18 months. This water will also corrode the steel and concrete foundations of high-rise buildings, pollute drinking water and kill any crops irrigated with it.

The solution to the dilemma was a simple, if somewhat costly, one, said Professor Terence McCarthy from the School of Geosciences at Wits University in a lecture on the topic in late November 2010. Pumping stations and treatment plants would need to be established. The stations would pump the water to the surface, and the plants would treat the water and then drain it into nearby water systems. This would maintain the water level in the underground spaces at 250 metres below ground.

The Department of Water Affairs had previously agreed to install one new station and upgrade a sludge treatment plant. The Cabinet’s response to the report tabled by the interministerial committee will update this agreement and outline what the authorities plan to do in order to solve the problem.

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