Assessment of open pit dewatering requirements and pit lake formation for Kışladağ gold mine, Uşak-Turkey

Ünsal, Burcu
The main purposes of this research are (1) to quantify the dewatering requirements for Kışladağ gold mine (Uşak–Turkey) in order to provide stable and dry conditions for mining during the operational period, (2) to assess the pit lake formation in post-closure period, and (3) to assess the impacts of these effects on groundwater resources. Following the development of the site conceptual model, a numerical groundwater flow model is set up and calibrated under steady state conditions and sensitivity analyses are conducted. The calibrated model is used as a tool for the determination of groundwater flow rates into the pit, applying two different simulation approaches: steady state and transient. The results show that steady state simulated pit-inflow rate was almost half of the maximum rates calculated by the transient simulations. The average pit-inflow rates however are very close to each other indicating the reliability of the model results. Following the cessation of dewatering activities during the post-closure period, a pit lake is expected to form. Pit lake water balance calculations are conducted to predict the lake levels with time until the equilibrium conditions are reached. The results show that pit lake levels stabilize at 816 m, 585 years after dewatering ceases. The results also show that 829 m is a critical level, below which pit will behave as a sink and for the higher levels, it will be a flowthrough system which may adversely affect the quality of downstream groundwater resources.