Ohlander B., 6th ICARD International conference on acid rock drainage Cairns, Queensland 14-Jul-0314-Jul-03, Carlsson E., Correge O., Holmstrom H., Lindvall M., Peinerud E.K., Widerlund A., Ohlander B., 6th ICARD International conference on acid rock drainage Cairns, Queensland 14-Jul-0314-Jul-03, Carlsson E., Correge O., Holmstrom H., Lindvall M., Peinerud E.K., and Widerlund A.
Poorly buffered tailings from the mine have been deposited in five impoundments located along a valley. The tailings area has been remediated by applying a combination of till cover and flooding. A new method has been applied to parts of the area involving raising the groundwater table to saturate the tailings. A water-covered downstream impoundment has been subjected to liming to increase the pH and reduce metal mobility, and is functioning as a trap for metals released from the till-covered impoundments upstream. Measurements of the progressive changes in water quality confirm the effectiveness of the system approach used in the design of the remediation programme. The sulphide oxidation rate has decreased in the till-covered impoundments and, as predicted, there is an out-flush of old weathering products which will continue for at least five years before equilibrium is reached. The groundwater in the till-covered impoundments has high concentrations of Fe, S, Mg and In, but the concentrations of metals such as Cu, Cd and Pb are much lower than before the till cover was applied. The limed pond is an efficient metal trap, with concentrations as high as 2.76% Zn and 0.28% Cu in the calcite-gypsum sludge in the tailings., Poorly buffered tailings from the mine have been deposited in five impoundments located along a valley. The tailings area has been remediated by applying a combination of till cover and flooding. A new method has been applied to parts of the area involving raising the groundwater table to saturate the tailings. A water-covered downstream impoundment has been subjected to liming to increase the pH and reduce metal mobility, and is functioning as a trap for metals released from the till-covered impoundments upstream. Measurements of the progressive changes in water quality confirm the effectiveness of the system approach used in the design of the remediation programme. The sulphide oxidation rate has decreased in the till-covered impoundments and, as predicted, there is an out-flush of old weathering products which will continue for at least five years before equilibrium is reached. The groundwater in the till-covered impoundments has high concentrations of Fe, S, Mg and In, but the concentrations of metals such as Cu, Cd and Pb are much lower than before the till cover was applied. The limed pond is an efficient metal trap, with concentrations as high as 2.76% Zn and 0.28% Cu in the calcite-gypsum sludge in the tailings.