Nui Phao Open Pit Mine Water Management Support (Vietnam)

The Nui Phao Mining Project is a complex poly-metallic deposit located approximately 80 km northwest of Hanoi, Vietnam. The 55.4 Mt greissen-skarn deposit consists of mineralization containing copper, gold, tungsten, bismuth and fluorite. Mine development has been ongoing for approximately ten years with a comprehensive programme of geological and geophysical investigation; and an extensive programme of exploration drilling, sampling and mineral testing. The mine has completed Stage 1 pit excavation (first half of 2012). The Nui Phao Mining Department has contracted DSI and Geotech Vietnam to provide a better understanding of the hydro-geologic properties of the mineral deposit and its surrounding geologic area to better manage mining operations and to plan for control of ground water and surface water both inside and outside the pit as the depth of the pit deepens and mining operations begin in 2013. The objectives of the hydro-geologic study to be performed by DSI for the Nui Phao Mine will be to assist the Mining Department to optimize mining operations through dewatering of the pit to improve mining efficiency and safety. This involved providing a reduction of ground water flowing toward and into the pit before they can become standing water within the pit as well identifying sources of groundwater for operations. DSI and Geotech are providing recommendations for the most technically feasible and economically viable combined technical methods that will accomplish both pit dewatering and pit slope depressurization together with study results. These objectives are being achieved through the development of a comprehensive hydro-geologic database used to power a simple yet robust mathematical model (MODFLOW) of the regional and site-specific hydro-geology of the mine. The database is being augmented by surface hydromet and subsurface ground water instrumentation to monitor key quantitative values of surface water and ground water flow to continuously update the hydro-geologic database in real time.