15 February 2008
Wonderfonteinspruit — One legacy of South Africa's extensive mineral deposits is the infrastructure and wealth of the country. But another more troubling legacy is emerging as an increasingly urgent problem: environmental contamination from over 100 years of mining that could severely pollute the country's water, affecting the food chain and citizens' health.
The magnitude of the potential problem has government agencies scrambling to coordinate a response to a relatively new issue for the regulatory bodies. "The truth of the matter is that as a nation we don't know how to deal with this problem because it has never happened to us before," said Dr Anthony Turton, a leading water researcher at the Council for Scientific and Industrial Research (CSIR).
"This was always suppressed before because people didn't matter in the pre-1994 South Africa. All we've done so far is see the tip of the iceberg. We certainly don't have any coherent government strategies yet."
But the urgency is real. As more mines close and more tests reveal hazardous contamination levels in sediment and local food samples, there is growing concern about acidic waters emanating from disused mines.
The epicentre of the problem lies southwest of Johannesburg in a valley ringed by mines - both active and closed - where a small river called the Wonderfonteinspruit runs southwest from the mining town of Randfontein to Carletonville and Khutsong, and into the Mooi River, which provides water for Potchefstroom, a large university town.
Over 10 years of scientific studies have established that the sediment in the Wonderfonteinspruit is contaminated with radioactive uranium and high levels of other heavy metals in wastewater discharged from local mines.
By law, wastewater from mines is supposed to be treated to a standard established by the Department of Water Affairs and Forestry (DWAF) before being discharged into waterways, but the evidence of contamination in the sediment means there has not been compliance. The mining companies were not closely regulated during the apartheid years, but environmental activists charge that while laws are now in place, enforcement is not.
Further complicating the enforcement issue is that several different mining companies - DRD, Gold Fields, Harmony - operate in the area and discharge water into the same canals and pipelines, so identifying a specific source of contamination can prove difficult.
A second source of pollution is runoff and wind-eroded particles from slime dams - soil residue from within the mines that often contains radioactive elements and heavy metals. On a recent site visit south of Carletonville, residue from eroding slime dams was observed washing down dirt roads towards drainage canals that empty into the Wonderfonteinspruit.
A 2007 report by the National Nuclear Regulator (NNR) stated: "These slime dams and rock dumps are potentially significant contributors to diffuse contamination."
Wind-blown radioactive dust particles from the slime dams could also pose "significant radiation exposure" through inhalation or by contaminating agricultural crops, while cattle posed a serious problem because they churned up sediment loaded with radioactive elements and heavy metals in the waterways when they went into them.
After the NNR's report was released, the largest mining company operating in the area, Harmony, issued a directive to land and water users in the area, saying that cattle should no longer be watered in the river.
Thus far, the more proactive steps are coming from the local community. The Merafong Council, which includes the town of Carletonville and surrounding district, has put up signs warning people to not use the water and has provided drinking water to informal settlements on the river's banks.
"Although Water Affairs in their latest reports indicate that the water itself is safe, it is a known fact that there are sediments that are contaminated with radiological elements," said Albie Nieuwoudt, Strategic Executive for Economic Development, Planning, and Environmental Management at Merafong.
"That's why we put up the signs. We've just created our own Environmental Management section to look at issues arising from dust and slime dam residue; we've got a duty to protect our citizens."
Frustrations with government
Rene Potgieter, a former peat farmer who now works on the Wonderfonteinspruit contamination issue, said, "We have a group here organised through DWAF where water quality is monitored. I sit on the committee, and on a regular basis we look at what the discharge water qualities are. You just see noncompliance, noncompliance, noncompliance. But all DWAF does is monitor - they don't do anything with those results."
Basically we're just keeping the cattle alive and having to borrow money from the bank. This was supposed to be my legacy to my children, but everything has been stopped. This is horrible
Nieuwoudt said he had heard of NNR reports about vegetable samples but had not seen them yet. "Apparently they found some pollution in some crops. "There are small community farming projects using that water source from boreholes, so we need to be informed."
The NNR has made statements that contradict its own reports, several of which classify food samples as above the accepted limit. On 7 February 2008 it issued a statement about the Wonderfonteinspruit that said, "No evidence has been found indicating unacceptable levels of radioactivity in vegetables, fish and meat samples." NNR's CEO, Maurice Magugumela, has also assured the public that food from the area was safe to eat.
Yet an NNR status report in October 2007 said: "The NNR collected samples of vegetables (onions, asparagus and oats) and fish in the area and sent these for analysis. The projected doses from the samples taken indicate that the total doses from some [of] the samples taken are above the dose constraints and dose limits ... and are of safety concern from a radiological point of view."
When questioned about these discrepancies, Magugumela stated that it was a complex issue and different international measurements were used to determine dosage and when intervention was appropriate.
Acid Mine Drainage
After 100 years of mining in South Africa, the subterranean infrastructure is vast and many neighbouring mines are interconnected for safety reasons. To mine for gold, mining companies must displace the groundwater for the duration of the mining operation by pumping it out. This slurry carries an assortment of naturally present heavy metals to the surface on the slime dams and discharges water.
When a mining company ceases operation, water begins to re-enter the area and reacts with exposed pyrite, a mineral formation, which creates sulphate. Sulphate reacts with water to become sulphuric acid, which then dissolves the heavy metals into the mix as the water rises and eventually "daylights" onto the surface. At this point, the water is considered to be acid mine drainage (AMD) or "mine water decant".
"You get this flow of water that comes up through the springs and it is very low Ph - very acidic - and it is a whole cocktail of heavy metals and potentially radioactive metals," said the CSIR's Turton.
In the Wonderfonteinspruit area the aquifers are in dolomite, a spongy layer of rock through which water moves quickly. The speed of the water is increased by the mining shafts. In August 2002, acid mine water began to appear in the West Rand Mining Basin just above Krugersdorp Game Reserve.
Harmony Gold rapidly built containment dams and channelled the water into Robinson Lake for treatment, but a percentage of the water is unusable even after treatment and is released into the Tweelopie Spruit, a small river in the area.
A 2006 Water Resources Commission report described Robinson Lake as having an exceptionally high uranium concentration after the influx of AMD water. "This extreme concentration is believed to be the result of remobilisation of uranium from a contaminated sediment by acidic water."
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