Dewatering of planned Key Lake open pits in northern Saskatchewan

CIM Bulletin, Vol. 73, No. 818, 1980

WERNER UNLAND and NICK HOLL, Key Lake Mining Corporation, Saskatoon, Saskatchewan

The paper presents the engineering design and experience gained so far with a dewatering system for an open-pit uranium mine planned at Key Lake in Northern Saskatchewan.The results of hydrogeological investigations preceding engineering exhibit an extensive unconfined overburden aquifer hydraulically connected with the underlying Athabasca Formation and basement rocks, both of relatively low hydraulic conductivity. The overburden aquifer is embedded in a bedrock trough, with the deepest depression between the planned pits. The hydrogeological data were used in a numerical dewatering model simulating groundwater flow at different stages of the pit development.Based on the model results, the engineering design had to provide for different pumping rates, varying between 1.0 and 0.21 m3/sec. This problem was solved by using a double line pressure system. The design concept for the complete peripheral discharge system and the well design used for 26 dewatering wells are discussed.

Keywords: Key Lake mine, Dewatering, Open-pit mining, Saskatchewan, Hydrogeology, Surficial deposits, Groundwater, Wells, Pumping.