Three-dimensional geologic modeling and groundwater fl ow modeling of the Töllinperä aquifer in the Hitura nickel mine area, Finland - providing the framework for restoration and protection of the aquifer

Elevated concentrations of sulphate, chloride, and nickel were discovered in water samples taken from the Tollinpera aquifer in western Finland. The area is located adjacent to the tailings area of the Hitura nickel mine. Earlier studies revealed that the groundwater contamination resulted from tailings-derived mine waters leaking from a tailings impoundment area. The tailings area directly overlies the Weichselian esker system, part of which is the Tollinpera classifi ed groundwater area. The observed groundwater and surface water contamination resulted in a need to characterize the subsurface geology in the whole area of the contaminated esker aquifer. The primary sedimentary units were introduced into a three-dimensional (3-D) geologic model of the aquifer made with EarthVision  geologic modeling software. The information obtained from the 3-D geological model was then introduced into a numerical groundwater flmodel made with MODFLOW code, which was calibrated with MODFLOWP code. The results of this study were used to guide the sealing of the tailings impoundment in order to prevent the further contamination of the Tollinpera aquifer. The groundwater flmodel was used to interpret and simulate the fl ow system, and to provide a plan to safely continue water supply to local inhabitants from the unpolluted parts of the aquifer.