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Acid mine water threatens Cradle of Humankind

Posted by: Saving Water SA (Cape Town, South Africa) – partnered with Water Rhapsody conservation systems – 18 April 2010

A massive study is under way to investigate the impact of toxic acid mine water and other dangerous sources of pollution to the world-famous Cradle of Humankind World Heritage Site.

Australopithecus sediba was discovered two years ago.

It is here where the nearly two million-year-old hominid skeleton, Australopithecus sediba, was discovered two years ago, and unveiled to global wonder last week.

But in recent years, several scientists have slammed authorities for failing to protect ancient hominid fossils, including the Sterkfontein Caves. These are made of dolomite rock and vulnerable to acidic water from historic mining operations on the West Rand.

Peter Mills, the acting director of research and planning at the Cradle of Humankind World Heritage Site, told the Saturday Star the management authority had commissioned the Council for Scientific and Industrial Research and the Council for Geosciences “to understand the flow of water through the Cradle”.

As gold mines on the West Rand have ceased operating, the water table has returned to pre-mining levels, bringing with it a rising tide of toxic water, characterised by heavy metals and radioactive uranium, as well as high levels of sulphates.

Since 2002, more than 15 million litres of this acidic water has been decanting daily and flowing into the Tweelopie- spruit, through the Krugersdorp Game Reserve, into the Blaauwbankspruit which feeds into the Cradle of Humankind.

Some of it has been pumped and partially treated by the local mines, but large amounts continue to flow untreated into the system. And since another decant started in January, millions more litres pour out every day and pass through underground dolomite.

This week, the DA’s shadow minister of environmental affairs, Gareth Morgan, called on environment minister Buyelwa Sonjica to commit to addressing the unqualified volume of “untreated acid mine drainage (AMD) flowing in the Zwartkrans Compartment, which threatens the Cradle of Humankind and the drinking water of 11 000 people”.

Mills said the study, which will also probe pollution from farming, sewage and development, would be wrapped up by August.

“We know there is an impact of acid mine drainage

“The whole idea is to have a monitoring system in place… to understand the flow of water through the area.

“We can see what the surface water is doing but we have no clue what is happening underground. People say we aren’t doing anything but we never said AMD wasn’t a problem. We don’t know whether caves in the system are getting acid water where there are fossils.”

There is scant evidence that the existing set-up is threatening the fossils on the site.

“The World Heritage Site as 52 000ha of real estate is under threat from AMD but the actual fossil sites in that boundary, apart from Bolts farm, the AMD doesn’t appear to be reaching them.

We know AMD is reaching there (Bolts Farm). Again, we don’t know at what levels.

“What we don’t know and what the specialists don’t agree on is what the impact is. You have some specialists that say the acid water eats away at the dolomite but you get other just as reputable scientists who believe the deposits from the AMD actually seal the cavities and prevent cave genesis.

“When the water leaves the mine the pH is 3 (highly acidic). By the time it passes through the Krugersdorp Game Reserve, the condition is slightly improved and it gets diluted under heavy rains. A lot disappears into the aquifer. That is what everyone is concerned about because no one knows where it goes to. Some say it’s to the west of the site and some say it filters through.”

Garfield Krige, a water scientist who has led studies on the mine decant into the Tweelopiespruit, said the discovery of Australopithecus sediba will refocus attention on the AMD threat to the Cradle.

“The fossil find is the best thing that could have happened. It’s got everybody’s attention. Now maybe somebody will start to take notice of the plight of the Cradle of Humankind. The place is riddled with fossils in direct line of the AMD.

“A lot of plans have been made and money spent but nothing has happened… Don’t forget this was predicted in 1996. We’ve proved a tremendous amount of the acid mine water finds its way into the groundwater. We’ve proved the water has corrosive properties and eats away at the dolomite.”

He added the volumes of water flowing from the latest decant are so huge that the formerly-dry Rietspruit is now flowing constantly into the Blaauwbankspruit.

Ecologist Mike Buchanan believes the mines should stop pumping the water to allow the groundwater table to restore itself.

The AMD should then be laundered to drinking water standards before being sent back into the deep aquifer.

– Sheree Bega
Source: Iol

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