Modelling of mine flooding and consequences in the mine hydrogeological environment: flooding of the Koenigstein mine, Germany

Abstract.

The approach to modelling of flooding of the underground mines and hydrogeological consequences in the downstream aquifers of the mine followed in the WISMUT Decommissioning and Reclamation Programme is illustrated for the case of the uranium underground leach mine in Koenigstein, near Dresden, Germany. The modelling of the present and future quantity and quality of the water in the mine workings (source of the potential groundwater contamination) and of the contaminant transport in the hydrogeological environment of the mine is central to finding the optimal courses of action for a safe (i.e. controlled) flooding of the mine and for decision-making regarding water-treatment strategy. The results gained in two large scale in-situ flooding experiment lasting over several years and the models developed, calibrated and validated on this basis for the mine flooding is presented. The modelling of the migration of reactive multi-component contaminants in the hydrogeological environment of the mine proved to be useful for the identification of the significance of the geochemical processes. Because of the problems of up-scaling the commonly inadequate database and limited accuracy of the data available, and because of the inherent uncertainty of approximations used in the reactive transport model, the assessment of the environmental impact caused by long-term migration of contaminants downstream of the mine had to be done using a simplified conventional, non-reactive, single component transport model that provided conservative results. For simulation of the mine flooding, it is recommended to use a concurrent monitoring and modelling approach and step-wise forward calculations that do not exceed the length of each preceeding observation period.