[miningmx.com] — THE deadline for preventing rising acid mine drainage to cause a massive ecological disaster in the Central Witwatersrand has come and gone – because of government’s indecision.
Acid mine drainage will, according to a scientific model, rise to the ecologically perilous level of 150 metres below the surface by 2012 – and after the end of October this year nothing humanly possible can be done to avoid this.
From February 2012 onwards, acid mine effluent will rapidly start to erode dolomite structures in Johannesburg and the near East Rand, and shortly thereafter the water will poison boreholes and fountains – as has been happening on the West Rand in the Cradle of Humankind, the Krugersdorp Game Reserve and the Sterkfontein caves since September 2002.
Some weeks later the first acid water will emerge above ground at Cinderella East, an old, abandoned shaft less than 100 metres from Rondebult Road in Boksburg – very close to Boksburg’s central business district.
According to the model, the effluent there will be 57 megalitres (million litres) a day – four times that on the West Rand, where 15.7 megalitres is being discharged every day.
Proposals to avoid this disaster have been in government’s hands for more than two years, but nothing has been done. A plan to avoid the crisis should have been implemented by October.
The model for the calculation was compiled by various scientists, mainly geohydrologists, over more than 15 years.
Marius van Biljon, who has an MSc degree in geohydrology, started doing these calculations in the Western Witwatersrand in the mid-90s, at the behest of the old JCI. By 1998 he had computed that in October 2002 the first mine water would flow from the old Swartrif shaft near the Epol plant in Randfontein.
His calculation was out by two weeks, because the water started to flow out in September 2002, and is today the cause of massive pollution of river systems in the Krugersdorp Game Reserve, Cradle of Humankind and Sterkfontein Caves.
It is also poisoning farm dams and other natural water sources.
Van Biljon was later employed by Golder & Associates, one of the world’s largest and best-known environmental consultancy firms, to develop precisely the same model for the Central and Eastern Witwatersrand basin.
Mining plans for every single shaft were obtained. These were digitised, enabling calculations of total volumes created by underground mining activity. The group then calculated water inflows, scientifically termed recharge. This they used to develop models to arrive at the rate at which the acid water was rising.
The model showed that the water would reach the critical environmental level (CEL) by February 2012, said Van Biljon. The CEL is the point at which the acid water will reach the low-lying dolomite, destroy it and cause sinkholes – in the Central Basin, right in the centre of the country’s most populous areas.
At the important south-western vertical shaft of the old ERPM mine in Germiston, the CEL has been established to be about 150 metres below the surface.
The rate at which the water is rising in five shafts in the Central Basin is measured every week by ERPM’s ventilation division, using measuring instruments beneath old skips which are sent down to the water in the different shafts. The data are used to test the accuracy of Van Biljon and Golder & Associates’ model.
To date the model’s accuracy has proved to be above 95%.
Scientists involved in compiling the model have until now been unwilling to comment on it for ethical reasons, but remarks by Trevor Manuel, the Planning Commission Minister in the Presidency, greatly alarmed them.
In August this year Manuel said that what was needed was a national conversation on an empirical basis, because the idea that acid mine drainage would run through the streets of Johannesburg “next week’ and that we would all need to wear Wellington boots, was totally ludicrous.
Perhaps not in Johannesburg, but it is exactly what will happen in Boksburg, another scientist who wished to remain anonymous, told Sake24.