Acid river rocks the Cradle of Humankind

Acid river rocks the Cradle of Humankind

April 14 2005

By Alameen Templeton, Indenpendent Online (IOL)

South Africa's renowned Cradle of Humankind in Gauteng, home to one of the world's richest hominid fossil sites, is under threat from highly acidic water pollution, a leading geologist has warned.

The department of water affairs and forestry (DWAF) has issued directives to owners of worked-out mines in the area to address the threat or face criminal prosecution or other sanction.

Although the mine owners in Mogale City on the West Rand - Harmony, DRDGold and Atomaer - have agreed to co-operate, they have protested at being singled out for attention, arguing there are other role-players who are contributing to the pollution.

Ferdi Dippenaar, spokesperson for Harmony Gold Mining Company, said on Wednesday night that several factories and the local sewerage works, as well as a plethora of informal settlements that had sprung up around the mines, were contributing to the contamination.

The Cradle for Humankind incorporates the Sterkfontein Caves, made of dolomite rock, which is extremely susceptible to acidic water.

Archaeological excavations in the ancient cave system have over the past 70 years revealed a treasure trove of the oldest human fossils ever found, including Mrs Ples and Little Foot.

The Cradle was named a World Heritage site five years ago and since then has become a major tourist draw-card.

But Professor Tim Partridge, of Wits University, has warned that highly acidic mine water is starting to decant from vast underground lakes that have started filling up around the worked-out mines into the Tweelopiesspruit, which feeds into the Sterkfontein underground water system.

"As water enters caves such as Sterkfontein, which has underground reservoirs in dolomite, it can result in serious damage, with a pH of well under 3, which is a huge problem if it continues."

"Pollution will extend further and further into the World Heritage site, which is a huge no-no. The main danger is the sensitive nature of the area and the delicate cave formations that could be destroyed - apart from the fact that the local farmers use the water for irrigation and drinking," he said.

Partridge believes the mine workings, dating back to the early 1900s, have pierced the continental divide which separates the southern drainage system, taking water to the Vaal River, from the northern system that drains water to the Limpopo.

This could be seen from the increased outflow into the Tweelopiesspruit, which meanders down through the Krugersdorp Nature Reserve to the caves in the north, he explained.

Although mines were forced to pump water out of the water table in years gone by so that they could access their ore bodies, this had ceased over the past few decades, and the water table was rising back to its old level - hundreds of metres higher than where it was during the heyday of mining, he said.

Because the southern drainage system was higher than its northern neighbour, the southern system was putting pressure on the entire water body - which was being contaminated as it worked its way through the old mineshafts - effectively squeezing it out to the Sterkfontein system in the north.

Partridge said he had visited the area with DWAF officials, and "we have a fundamental agreement on the nature of the problem, and the question now is what must be done about it."

"If they do nothing, then the pollution front will migrate slowly down the valley."

He said the total disintegration of the cave system would be an "extreme view", but that extensive and irreversible damage to the system was still a major concern.

Dippenaar said Harmony was spending R1-million a month to clean and contain the contamination. Samples taken from around the Harmony site confirmed its claim that the contamination was not coming from the mine. This had been reported to the DWAF, he said.

DRDGold spokesperson James Duncan said the mine was aware of the problem and was looking forward to participating in a stakeholders' meeting set for next week.

Marius Keet, the DWAF's regional director, said the department was being forced increasingly to confront the mines about groundwater contamination, because many of them had closed down in the past decade.

This was causing groundwater to fill the disused mineshafts and become increasingly polluted.