Highly toxic and acidic water from Johannesburg’s Gauteng mine is at dangerous levels and could put the city at risk if it is not pumped out, according to an environmental report.

A joint report by the departments of Water Affairs and Mineral Resources and Environmental Affairs, dated March 2009, disclosed that the mine’s acidic water is projected to hit the city in 2012, according to The Times.

It says that drastic efforts need to be taken to plug disused mine shafts and drain the mine before the toxic water hits the city, at a rate of 70 megalitres a day.

Gauteng’s toxic mine water is rising at a rate of 15m a month and will flow into rivers and low-lying areas affecting farming and the city’s water supply.

The polluted water, currently 800m underground, can cause structural damage to buildings and severely affect human health as it contains heavy metals and salts.

It also threatens the Cradle of Humankind World Heritage Site, the report says.

Toxic water used to be treated and pumped off East Rand Proprietary Mines before it was liquidated in 2008.