Geotechnical aspects of decommissioning tailings storage facilities (TSF) in mining districts of Southern Spain

Abstract Production practices in the mining industry during the last century have left numerous inactive facilities that current administrations have to deal with. In the case of tailings storage, the risk of pollution dispersion or large-scale damage caused by stability failures requires specific actions. In southern Spain, 28 abandoned tailings dams in the mining districts of Mazarrón, Cartagena and La Unión and 59 in the mining districts located in Andalucian Provinces, have been classified as hazardous for potential pollution risk, according to European regulations. In this document, we gather the experiences of 23 case studies in tailing decommission projects planned during the 2010-24 period, focusing on the most recent case of the San Cristobal-II tailings dam (SC-II). The actions conducted consist essentially of sealing, introduction of drainage elements, slope reprofiling and surface revegetation. The geotechnical characterization and monitoring conducted during decommissioning have emphasized that action must focus on pore water pressure control throughout all the phases of the project. The analysis of the actions involved in the decommissioning projects shows some positive experiences but also the need to improve in-depth geotechnical data acquisition, to ensure long-term safety while optimizing the decommissioning costs.