The failure of the outer slope of one of the paddocks of a tailings dam, resulted in a significant decrease in the area available for tailings deposition. Overloading of the remaining five paddocks resulted. To maintain the stability of the existing dam whilst construction of new disposal facilities was in progress, three techniques were investigated; horizontal, push-in drains at the dam toe, a rock buttress around the operational paddocks, and vertical de-watering wells installed on the first terrace, or ‘step-back’ of the dam. De-watering wells proved most effective, and 165 wells were installed. A monitoring programme included regular determination of the water level in each well, and the installation of piezometers at selected locations around the dam. These observations were used to optimise the use of the five remaining paddocks, thus ensuring stability of the dam during the transfer of deposition operations to two new tailings dams
