Numerical Simulation of Brine Migration in the Vicinity of a Potash Mine

by Uwiera, Michelle

The development and results of a 3-D site-specific groundwater flow and transport study of the Potash Corporation of Saskatchewan Incorporated Cory Division Potash Mine (PCS Cory Mine) and surrounding area are presented. The mine is located approximately 10 km southwest of Saskatoon, Saskatchewan, Canada. The objectives of the study are to simulate, analyze and predict the extent of brine migration, originating from the PCS Cory Mine Waste Management Area (WMA), in the groundwater flow system.

The hydrogeology of interest to the study is Late Cretaceous to Quaternary in age. A 3-D finite element mesh representing the hydrogeology of the study area is constructed. The FEMWATER code is used to simulate steady-state and transient groundwater flow and solute transport processes. Calibration of the model using observed hydraulic heads is reported.

Fifty years of brine plume migration at the PCS Cory Mine WMA, beginning in 1969, are simulated. Detailed analysis of the position and concentration of the brine plume in the surficial stratified deposits, the Floral Aquifer, the Judith River Aquifer and in vertical cross-sections are conducted for the years 1979, 1986, 1995 and 2019. Analysis of the base case model indicates that after 50 years of simulated brine transport, the contaminant plume migrated past the freshwater bypass ditch in the surficial stratified deposits and infiltrates the Floral Aquifer reaching concentrations in excess of 100 g/L.

Sensitivity studies indicate that the engineered containment devices are ineffective at inhibiting brine plume migration. These studies also show that brine mounding in the tailings pile is a critical control on plume migration to the Floral Aquifer and in vertical section. Varying the coefficient of tortuosity has little effect on brine migration.