Modem open cut and underground mining in the tropics inevitably expose
partially weathered and unweathered rocks to oxygen and water, leading
to weathering and the release of solutes and often acidity as well.
Historical monitoring data can demonstrate these phenomena. Three case
studies from open cut mines in the north of the Northern Territory
illustrate the deterioration in quality of pond water receiving drainage
from waste rock dumps. The potential for deterioration of water quality was not recognised in
many mine Environmental Impact Statements prepared and accepted in
the 1980s. The examples documented indicate the importance of
adequately planning for this near inevitable process. Retrofitting a mine
water management system to 'no' or minimal release can be very difficult
and expensive, and may not be feasible, leading to downstream pollution.
The characterisation of acid and solute production potential of ore and
waste rock, and improved dumping strategies and water management are
very important to minimise the environmental impact of mining in the
tropics.