The unique landfill site and the mine void backfilling as solutions for the environmental safety of the abandoned mine areas

abandoned mining districts of Sardinia in which contaminated materials both from mining excavations and mineral processing plants are accumulated. Remediation solutions based on the relocation of the materials in new and engineered dumps or on materials treatment are not appropriate due to the huge volume of the deposits (the whole amount has been estimated in 70 Mm3). It appears particularly workable the use of a small number of the compromised major sites as “accumulation centres” in which materials from the other smaller abandoned areas of the same district, can be placed. This strategy has important advantages related to some typical elements of the mining areas i.e. the presence of tailing basins, often having significant surface extension, and the existence of mining voids both on the surface and underground. The use of these surfaces and volumes as “accumulation centres” introduces important technical matters referred mainly to the need of ensuring pollutants containment, to the embankments stability and to the safety condition of surface and underground voids during and after backfilling operations. The paper discuss the issues related to the selection criteria of the sites to be used as “accumulation centre” and proposes some technical solutions aimed at obtaining their permanent and global safety conditions.