Validating WRD conceptual models and implications for mine closure an semi arid environments: a high level assessment using field data

摘要

The prediction of how waste materials will evolve geochemically within waste storage facilities in semi arid environments requires a coherent and detailed understanding of the mechanisms that control oxidation reactions, and seepage generation. As part of a large scale investigation to improve the understanding of waste rock geochemistry at macro scale in semi arid environments O'Kane Consultants (OKC) has had the opportunity to lead two large scale waste rock storage facilities (WRSF) drilling programs at different sites in Western Australia. A range of WRSFs were investigated to include both active facilities and historical closed facilities of around 10-30 years in age. These investigations included approximately 2,000 m of sonic drilling, the recovery and detailed analysis of over 2,000 samples of core material and the installation of over 200 sensors at depths between 5 and 140 m within the waste which have provided over 5 million points of monitoring data to date and are still actively generating data.The quantity and quality of materials testing and in situ monitoring data collected has provided OKC the opportunity to determine the specific factors related to in situ field conditions that act as the main controls on geochemical evolution of waste materials in semi arid environments. Data has been used to develop a detailed conceptual model for the geohydrology of WRDs within a semi arid environment. In addition OKC has developed field calibrated analytical AMD loading models.The extensive data gathered as part of the assessment has allowed OKC to determine the geochemical, hydrological and geophysical evolution of the waste rock facilities as a result of 10-30 years of exposure. This valuable site data has been used to both back test the results of predictive models made for the waste facilities, and to optimise predictive models for future scenarios.