Uranium contamination of the environment by mines is an ongoing concern for surrounding communities in the Wonderfonteinspruit catchment area (WCA), west of Gauteng.

About 73 000 t of uranium has been extracted during 120 years of gold mining in the WCA, which includes the West Rand and the Far West Rand areas, resulting in uranium pollution, with elevated levels of radioactivity impacting on the area’s surface and groundwater systems, says the Federation for a Sustainable Environment (FSE) CEO Mariette Liefferink.

“Since the 1980s, 450 000 t of uranium has been deposited in the 270 tailings dams of the Witwatersrand’s goldfields and a further 250 000 t of uranium has been deposited in the tailings dams of the West Rand and the Far West Rand goldfields,” she says.

Studies and samples, which have been undertaken by various organisations over the past decade, have indicated that the tailings dams within the WCA currently contain 100 000 t of uranium.

A report by the Water Research Commission (WRC) found that 50 t/y of uranium enters the groundwater from point sources, seepage and stormwater discharges within the West Rand and the Far West Rand goldfields.

Sinkholes, historically filled with uraniferous tailings could also become secondary sources of uranium contamination when mines close and premining flow patterns and volumes are restored.

“The radioactive contamination of surface water bodies in the WCA are caused by long-lasting mine water discharges, seepage and runoff from slimes dams,” Liefferink says.

Findings in a research report, by North West University School of Environmental Sciences and Development’s Professor Frank Winde, show that the radioactive heavy metal uranium may be more of a toxic risk than previously thought, even at comparably low concentrations.

Although uranium loads emitted by larger gold mines in the Far West Rand were reduced, its levels in the water resources of the WCA have increased over the past 15 years. This is due to the contribution of highly polluted water decanting from the flooded mine void in the West Rand, Winde states in his report.

Further, Winde explains that in mined-out areas, such as the West Rand and the Central Rand of the Witwatersrand basin, water flowing out of flooded mine voids may act as another significant source of uranium pollution affecting surface and groundwater.

The report, which explores the impacts that mining has had over the past decade on uranium pollution of water resources in the WCA, says: “The uranium levels in the WCA are comparable to those detected in the Northern Cape, which had been geostatistically linked to abnormal haema- tological values related to increased incidences of leukaemia observed.”

Spreading Out
Airborne pathways, where radon gas and windblown dust disperse outwards from mine sites, and waterborne pathways from ground or surface water, are some of the primary ways in which the contamination of the area takes place, Liefferink says.

A report titled ‘Radiological impacts of the mining activi- ties to the public in the Wonder-fontein Catchment Area’ by the National Nuclear Regulator (NNR), which observed various samplings of dust emissions from slimes dams during windy weather conditions, found that, owing to the small particle size of the slimes, particulate matter can be transported over relatively great distances to land used for agriculture.

The report further noted that the deposition of radioactively contaminated dust on the leaves of vegetable and forage plants could result in radiation exposures exceeding those from the inhalation of contaminated dust.

The use of contaminated mine waste material in construction on the West Rand has also been identified as a means of dispersal of radioactive material into the environment, she says.

Working Towards a Solution
The contaminated areas have been identified and the need for comprehensive monitoring and study as well as epidemiological studies in affected communities are recommended, says Liefferink.

The FSE recommended actions to be undertaken by the NNR within the Witwatersrand gold- fields. These include informing mining communities of the risks and hazards of radioactivity in the area and regular assessments of dose contributions and dust emissions from slimes dams.

It is also recommended that a structure be created to include comprehensive monitoring of groundwater, airborne dust, radioactivity and radon.

“Monitoring and collection of information on waste generation are crucial to better understanding the relationship between radioactive waste management and the quality of life, as well as for the implementation of effective waste-reduction measures,” Liefferink says.

She adds that, although the Chamber of Mines uses the guideline of a 500 m buffer zone surrounding the tailings deposits, where no human settlement is allowed, this has not always been adhered to in the development of new settlements.

In many cases, new developments, such as low-cost housing, are constructed adjacent to tailings dams or on footprints of reprocessed tailings dams.

“Unauthorised entry to mining areas must be prohibited. Contaminated areas must be fenced off and warning signs must be put in prominent places,” she says.

Tailings dams must be vegetated and seepage of water from tailings dams must be controlled to prevent the pollution of ground- and surface water. Con- taminated soil must be removed and replaced with uncontaminated soil to remediate the footprints.

Tudor Dam Dilemma
Thousands of residents of the Tudor Shaft informal settlement, near the Tudor dam in the south-eastern portion of the WCA, near Krugersdorp, are in the process of being relocated to a site that is within a 500 m buffer zone of a tailings dam.

Liefferink says that, after more than eight years of whistleblowing and lobbying as well as presenting hundreds of workshops and distributing hundreds of thousands of pamphlets relating to the contamination, she is relieved the NNR and the Mogale City municipality have acknowledged their responsibility to relocate settlements in contaminated areas to safer locations.

“The soils and sediments at the site are potentially contaminated with radionuclides and there is evidence of sulphate evaporates on the surface of the sediments,” she says.

Another WRC report recorded the Tudor dam’s radioactivity in the soil as between 10 000 Bq/kg and 100 000 Bq/kg. The regulatory limit is 500 Bq/kg.

The Far West Rand, the Central Rand, the Klerksdorp and the East Rand goldfields, have a similar challenge and it is hoped that the relocation of residents of the Tudor Shaft informal settlement will establish a positive precedent for these goldfields, concludes Liefferink.

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