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Optimum cover design for waste rock storage areas

Argunhan, Çidem
Developments in mining sector in Turkey necessitate examination of mine effects to the environment in a more extensive way. In this context, cover designs became important for waste rock storage and heap leach areas. Especially, cover design is applied in most of the waste rock areas in order to prevent exposure of minerals in waste rock storage area which may result in unwanted consequences such as acid rock drainage. In this study, North Waste Rock Storage Area in Kışladağ Gold Mine located in Uşak in Western Turkey is modeled to investigate various cover designs and suggest an optimum cover to prevent any damaging consequences. SEEP/W and VADOSE/W softwares are used to model flow in unsaturated zone in order to design an effective (optimum) protective cover. SEEP/W software is used to model bedrock where waste rock storage area will be located under steady state condition. The soil water characteristics and parameters used in the model for saturated and unsaturated conditions were taken from in literature. Accuracy of input data is checked during calibration for steady state condition with SEEP/W. Bedrock is modeled under transient condition with climate boundary condition for 20 years with VADOSE/W. Waste rock was then stored on the bedrock and model was rerun under transient conditions. Climate data such as temperature, relative humidity, wind speed and precipitation data are input to the model and runoff, evaporation and recharge values are simulated. Using the data obtained type of cover and parameters such as permeability and thickness of the material were decided. At the last stage of modeling, cover design and climate boundary condition were assigned on the waste rock and model was re-run. The effectiveness of the cover design for minimizing the ingress of water and air that cause acid rock drainage is checked and recommendations were made so that the impacts to groundwater from the waste rock storage areas during closure period are minimized.