Mine tailings integrated investigations: The case of Rio tailings (Panasqueira Mine, Central Portugal)

Abstract

Mining generates huge quantities of waste materials from ore extraction and milling operations, which accumulate in tailings and open impoundments. The risks associated with mine tailings have different nature, namely stability, rupture, surface and groundwater contamination, acid mine drainage (AMD) and precipitation of secondary minerals. In fact catastrophic failure of tailings impoundments has occurred, transporting slurry, dissolved metals and fine reactive metal particles to the environment. Often deposition conditions of old mine tailings are unknown and monitoring is deficient or even inexistent. Thus, in order to prevent accidents it is necessary to establish the internal structure, that is, mapping tailings impoundment, internal sediment structures – limits and stratigraphy – seepage and pathway locations, bedrock depth and topography estimates and actual deposition conditions of the tailings. Owing to the complexity of the problem, only integrated approaches can investigate and monitor comprehensively the characteristics and evolution of mine tailings and its impacts on the environment. As this is a multidisciplinary problem, strategies should consider integrated studies such as Geophysics, Geochemistry and borehole surveys. However data from these sources must be interpreted together, in a GIS database, to provide better models and an enhanced overall knowledge of the studied structures. It is proposed to test and validate such a methodology in a case study, Panasqueira mine, central Portugal and to contribute to the decision-making process of environmental and civil protection agencies with responsibilities in the assessing, prevention, mitigation, and controlling the potential and actual effects of tailings spills on the environment.