Open Cut » Environment
Several open-cut mines in the Bowen basin are at or near the end of their operational lives. When mining companies seek regulatory 'sign-off' for these sites, or to obtain certification of rehabilitation that has been completed progressively, they are required among other things to nominate an end-use that is demonstrably sustainable. These requirements are mandated by regulations and in accord with mine approval documents. The area of land disturbed by mining in the Bowen Basin and requiring an end-use to be designated already exceeds 150,000 ha and is set to increase substantially. In addition to the need for end-use decisions at these existing mines, planning for the many new mines proposed for the region will also require early assessment of end-use options, a process that is consistent with recent industry codes, promptings from research and the weight of the business case.
This report describes an approach to end-use risk assessment using a Bayesian Network modelling framework. Separate risk models are developed for key hazards of surface erosion and bushfires. Rudimentary models for risks of weeds and feral animals are also presented. The models are generically instructive, highlighting the crucial role of site specifications (the characteristics of the underlying spoil and of the topsoil applied, plus a suite of factors under the control of mining companies). The nature of the vegetation type established on the rehabilitated site also shapes the impact of the modelled hazards.
In contrast to traditional approaches that assess the risks of a final outcome, the approach taken in this research also identifies and quantifies the roles of the factors that drive risk outcomes. This knowledge is particularly valuable where key drivers are controllable by management. The focus is thus directly on site construction factors, land management factors, and circumstantial factors, reducing reliance on mere descriptors of resulting ecosystems (completion criteria) that are only presumed to be suited to a low-risk end-use.