In situ leach (ISL) mining of uranium involves the drilling thousands of boreholes spaced between 20 and 30 m apart, into the ore body in the underground aquifer.
Approximately two-thirds of the boreholes are for injection of a leach solution into the ore body and one-third for recovery of the pregnant mine-solution.
The leach solution consists of ground water to which a little sulphuric acid and oxidising chemicals are added. This takes 1-2 months to dissolve the uranium and is then pumped to surface by the recovery boreholes.
In the processing plant, only uranium is removed from the mine-solution. The remaining water is recharged with a little acid and oxidant and repeatedly recycled back into the ore body. As a result, the aquifer in the mine area becomes contaminated with high-grade dissolved uranium, dissolved radionuclides and dissolved heavy metals.
Large-scale use of the aquifer water by farming makes the likelihood of escape of the toxic mine solution beyond the mine area into the rest of the aquifer, high.
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