Winner — Most Improved Business: Anglo Platinum Paardekraal Tailings Dam
Five years ago the Paardekraal Tailings Dam, 5km north-east of Rustenburg, was a dust bowl. Leaders from the neighbouring communities of Boitekong, a suburb of Rustenburg, and Mfidikwe village approached Anglo Platinum mine bosses concerned about the impact of dust on their health.
The environmental monitoring data from the mine also measured unacceptably high levels of dust. ‘We called a number of community meetings to explore solutions,†said Andre Britz, the mine’s environmental manager.
‘We held educational workshops on health and environment with our neighbours. The problem was that the tailings dam had large bare surfaces exposed to wind,†said Britz. ‘This caused significant dust in dry, windy months, especially August and September.â€
After community consultation, a comprehensive plan to combat dust was drawn up which included planting grasses and irrigation. The plan has five key components:
Greening with grass
At first, the sides of the tailings dam were sparsely vegetated with only one species of grass. Fraser Alexander, the company’s tailings management contractor, was commissioned to implement a better sidewall vegetation programme.
A greater diversity of grasses was introduced. ‘We have been aided by the fact that platinum tailings are less toxic than gold tailings so vegetation grows more readily,†said Britz.
Arsenic and cyanide are not part of the platinum extraction process. Anglo Platinum has also taken further steps to reduce the toxicity of the dumps by removing all the sulphur. This is converted to sulphuric acid and sold on to fertiliser companies.
The absence of sulphur means that there is no potential to cause acid mine drainage. The presence of acids means that heavy metals are moblised to pollute water and air.
Dust-busting
Anglo Platinum bought three Bell 18 000 litre bowsers (water trucks) with modified water cannons for suppressing dust on the roads around the tailings dams and terraces.
Exposed areas of the side walls are being irrigated to ensure they remain damp during windy periods. It was not a cheap exercise: with inflation, the bowsers almost doubled in price: costing R1.4-million in 2003 and R2.2-million by 2008. But the improved water monitoring has resulted in significant savings.
From 2007 to 2008 the company reduced its water use by one million cubic litres (36.2 to 35.2-million cubic litres). Anglo Platinum has recently been using greater amounts of second-class (waste) water. Its use increased by 43%. This means Anglo Platinum reduced the amount of potable water used for operations.
Potable water use at the Rustenburg concentrators decreased by 22% during 2008. This was as a result of the partial replacement of potable water by waste water from the Rustenburg municipality. The use of this waste water has increased by 17% year on year. Groundwater use has decreased by 9%.
Water recycled from internal sewage works, tailings return dams and underground work increased from 24-million m3 (2007) to 25.3-million m3 (2008). Water use for primary activities from managed operations decreased by 8%.
To cap it all
Wind speeds reach their peak at the crests of the tailing dams and this was the part that is difficult to cover. Where vegetation was not possible, a dual capping programme was implemented.
Inert slag from the company’s smelting operations, which is denser than tailings, was placed on the crest walls, and then a capping dust suppressant was applied to form a hard pan seal.
A large volume of dust was also caused by vehicles driving over active benches and haulage roads. Haulage roads were capped with a special dust suppressant.
‘Sprinkle-cleaning’
During Rustenburg’s dry winters, dust continued to be a problem, so an array of sprinklers were used to keep areas wet without using excessive water.
Four different systems were examined and a system chosen on the basis of efficiency and water saving.
The water used for dust suppression is process water from the tailings water reticulation system. The Paardekraal Tailings Dam is the first dam in the country to use this system.
Cleaner air
The last major aspect looked at ways of reducing the movement of people and vehicles on the tailings dam. The number of access roads was reduced and only capped roads are
allowed to carry vehicle traffic.
Anglo Platinum operates a dust bucket monitoring system across 21 sites at its Rustenburg operations. Monitoring points close to the Paardekraal Dam have shown decreasing dust levels over the past three years.