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46 www. bus- ex. com July 09 Constructive cyclones

Cyclone Projects & Consulting T here are two inevitabilities about mining for certain types of minerals such as gold, platinum and chrome: they consume vast amounts of water and produce equally large quantities of waste. For example, one source reckons that for each kilogram of gold recovered, 240 kg of cyanide and 250,000 litres of water have been consumed and over 3,000 tonnes of solid waste and 25 tonnes of CO2 produced. It follows then that not only is tailing management an expensive part of the process, it's also one that needs to be handled with considerable responsibility. Environmentalists in the remotest parts of the world are there to pressurise mine operators. In the deserts of southern Africa, there is also the practical need to recover scarce water resources with the utmost efficiency. The mineral extraction process, in essence, requires rock to be crushed and ground small enough so that the minute ore particles can be extracted either by chemical or mechanical means. Depending on the particle size, the tailings left behind are referred to as slurry or slime: the former contains a proportion of grit where the grains can be as large as 1.6mm while the latter is predominantly composed of much smaller particles of less than 300 microns. Historically, tailings were simply discharged directly into streams and rivers. In the West this form of disposal has been outlawed since the 1930s but in some parts of the world it still continues, particularly where the terrain is diffi cult or the rainfall high. Such blatant disregard for the environment at mines in Papua New Guinea and Indonesia have gone a long way to creating hostility for the mining industry at large as well as burdening the community with enormous environmental liabilities and costs to remedy the situation. More efficient extraction techniques are now allowing lower grade ores to be mined, creating greater quantities of waste in the process. Tens or even hundreds of thousands of tonnes of tailings a month are not untypical and if storage can only be done on the surface, they call for huge dams to be employed that can stretch several hundred hectares with walls rising to 30 metres or more in order to store them. As the tailings have no commercial value, they are a burden to the mine operator, but they do have the potential to cause problems so their management is not something that can be taken lightly. The exact nature of the dam design and construction depends to a large extent on the geography in question, but since 1998, Cyclone Projects & Consulting [ CP& C] of Krugersdorp in the Gauteng province of South Africa has been offering a process of dam construction known as cycloning. The business was established by a South African engineer, G. J. van Ryssen, who had a quarter of a century July 09 www. bus- ex. com 47 Often the ancillary elements of a larger system provide some of the more interesting engineering solutions, as Dan Bailey discovers when investigating mining in southern Africa Constructive cyclones