Geohydrological risks associated with abandoned uranium mines: The case of Cunha Baixa Mione (Central Portugal)

This paper addresses the hydrogeological risks associated with the now abandoned and most important Portuguese deposit, the Cunha Baixa uranium mine. The operation lasted from 1966 to 1993 and the ore was mined by open pit and underground methods. For low-grade ore heap leaching techniques were used. As this operation was located in farmlands the focus of research was the determination of the influence of the former mining activity on the quality of ground and surface water, identifying the contaminants and their diffusion. It was found that the observed contamination of water and soils is mainly due to acid drainage coming from the mine. Acid generation potential and acid neutralizing potential were carried out from rock samples of the open pit and the mine's surrounding. The role of the microorganisms (Thiobacillus) were also investigated in laboratory tests. The results of this study will form the basis for recommendations to reduce or eliminate the environmental impacts of the former mine. (author)