South Africa faces £100m bill for acid water threat

South Africa will spend some 1.2 billion rand (£100 million) to clean up acidic water threatening to spill from abandoned gold mines around Johannesburg, a report said yesterday.

The toxic chemical cocktail has been building up in mine shafts dug more than a century ago to tap one of the world's largest gold deposits, and stretches miles under the city.

"The problems posed by acid mine drainage will have implications far into the future, with impacts likely to continue for many years," said a report by a team of experts, issued by the water ministry.

Their report recommends building pumping, treatment and monitoring stations with pumps in place under Johannesburg by March next year, just months before the acid water is expected to reach environmentally critical levels.

The budget is estimated at 441.7m rand for capital expenditure, 121.2m for annual operating cost and 626.3m for long-term costs related to preventing water from flowing into the mines, the ministry said.

Acid water has plagued derelict mine-workings globally for decades but most of the damage has been in remote areas.

The problem for Johannesburg is that it was built over its mines and the land at risk is occupied by some of South Africa's biggest firms and its most densely packed communities.

The toxic liquid has already been flowing from mines to the west of the city in what is know as the Western Basin. Acid mine water is now about 500 metres below the surface in the Central Basin under Johannesburg, rising an average of 59 centimetres a day, and is about 700 metres below the surface in the Eastern Basin, the report said.

Water in shafts and tunnels has been reacting with rocks formed about 2.8 billion years ago and triggering reactions that produced sulphuric acid, heavy metals, toxins and radiation.