Foreseeable Flooding Scenario of the Alsace Potash Mine and the StocaMine Underground Final Waste Storage Site (France): A Case Study

Abstract In 1999, a final waste storage site known as StocaMine was established at a depth of about 500 m within the former Alsace potash mines (France). The administrative abandonment procedure for this mine, which was initiated in 2010, provides for the permanent containment of the waste on site. The mining operator launched a large number of studies to assess the potential effect that the presence of this waste could have on current and future populations and environment. The main studies were aimed to describe the likely flooding scenario of the mining operations on the one hand, and of the storage site on the other. This flooding results from the inevitable percolation of water from the Alsace alluvial water table through the 15 abandoned mine shafts. After a few centuries, when the flooding ceases, the continued compaction of underground cavities under the weight of the overlying terrain may induce an effusion of potentially polluted brine at the base of the Alsace alluvial water table. A series of hydrogeological, geochemical, and geomechanical modelling exercises, mostly carried out by the French National Institute for Industrial Environment and Risks ( Institut français de l’environnement industriel et des risques—Ineris ) has thus been implemented to quantify this risk and to propose measures for managing it.