"Accurate answers put a sound footing under the next stage of research. That usually involves experimenting with typical material under controlled conditions and measuring the results. Some of the work may be done in the laboratory, but the most realistic results come from field trials, say with test heaps or experimental dumps. Individual experiments investigate one or two variables at a time.

"The results are used to build predictive models to help us estimate what will actually happen with the full sized dumps of the future. A range of options for the mining sequence and for waste rock handling can then be fed into the model, to see which options give the best overall outcome."

Rio Tinto has developed a protocol, a set of guidelines, for assessing ARD risks at any site. It draws attention to all the ARD related factors that have to be considered at site level, and calls on site operators to take stock of what they know and, where necessary, what has done about them. The first aim is to bring into focus innate risks posed by the nature of the mineral deposit and the mining operation.

That aim been achieved in a preliminary way by screening 59 operations and six advanced exploration prospects for innate hazards. Geology counts for most in the scoring process, followed by the scale of disturbance by mining, and the sensitivity of environments on the receiving end of water discharges. Other factors are scored to give overall totals that are a measure of the degree of hazard at each site.

  PAGE 7 OF 8

 

Review is published by Rio Tinto,
6 St James' Square, London
SW1Y 4LD, England
Telephone +44 (0)20 7930 2399
Editor: Cherry DeGeer