The Challenges of Dewatering at the Victor Diamond Mine in Northern Ontario, Canada

Abstract

The costs and efficiency of dewatering are particularly important at De Beers Canada’s Victor diamond mine in northern Ontario, where the bottom of the water-bearing carbonate country rocks is near the bottom of the planned pit, which limits the available drawdown in the perimeter wells. Most of the inflow to the wells comes from a limited number of discrete zones in the carbonate rocks, resulting in low hydraulic efficiencies. The variable hydrogeologic conditions require efficient pumping over a wide range of yields and lifts, and there are logistical issues associated with the isolated setting and the extreme cold winter temperatures. The hydrogeology of the Victor mine area was characterised over three winter field seasons using packer tests, pumping tests, step-drawdown tests, and downhole logging to define the lateral and vertical variation in the hydraulic conductivity of the carbonate aquifer. Based on these data, wells were designed and submersible pumps with variable frequency drives were installed. Two 3-D numerical groundwater flow models were constructed, one a ‘sub-regional’ model to provide input to the mine feasibility study and permitting process and the other a near-pit ‘window’ model to simulate groundwater conditions in the immediate vicinity of the mine. These models are used in tandem to direct design of the dewatering system, evaluate its effectiveness, and to predict long-term environmental effects.