Posted by: Saving Water SA (Cape Town, South Africa) - partnered with Water Rhapsody conservation systems – 21 July 2010

Millions of litres of highly acidic mine water is rising up under Johannesburg and, if left unchecked, could spill out into its streets some 18 months from now, Parliament’s water affairs portfolio committee hears.

The last working mine still pumping out water in the Eastern Basin was Grootvlei

The acid water is currently about 600 metres below the city’s surface, but is rising at a rate of between 0.6 and 0.9 metres a day, water affairs deputy director water quality management Marius Keet told MPs.

“[It] can have catastrophic consequences for the Johannesburg central business district if not stopped in time. A new pumping station and upgrades to the high-density sludge treatment works are urgently required to stop disaster,” he warned.

Speaking at the briefing, activist Mariette Liefferink, from the Federation for a Sustainable Environment, said the rising mine water posed an “enormous threat”, which would become worse if remedial actions were further delayed.

“This environmental problem is second [in South Africa] only to global warming in terms of its impact, and poses a serious risk to the Witwatersrand as a whole. At the rate it is rising, the basin [under Johannesburg] will be fully flooded in about 18 months”

She said the rising mine water had the same acidity as vinegar or lemon juice, and was a legacy of 120 years of gold mining in the region.

Acid water is formed underground when old shafts and tunnels fill up. The water oxidises with the sulphide mineral iron pyrite, better known as fool’s gold. The water then fills the mine and starts decanting into the environment, in a process known as acid mine drainage.

Keet said the problem was not just confined to Johannesburg, which is located atop one of several major mining “basins” in the Witwatersrand, known as the Central Basin. Continue reading Johannesburg CBD threatened by rising acidic water