Evaluation of historic and contemporary rehabilitation performance to optimise rehabilitation planning, methodologies and outcomes

Abstract

Mine rehabilitation methodologies, objectives, success measures and stakeholder expectations often evolve over the life of a mining operation, as rehabilitation activities are completed, and as a site- and area-specific knowledge base is built. This may result in different rehabilitation outcomes depending on the age of the rehabilitation, the nature of the underlying spoil material, the design of the constructed landform, adoption of differing erosion control techniques, changes in topsoil management, and differences in the species mixes that were sown. As with anything that varies over the life of an operation, there is potential for knowledge to be lost due to turnover in personnel who manage the rehabilitation process. Given this, it is important to review rehabilitation outcomes in order to capitalise on an operation’s investment in progressive rehabilitation, monitoring and trials. Conducting such a review can provide a valuable contribution towards improved rehabilitation planning and optimisation of practices over time. In particular, such a review can provide insight and assurance that the rehabilitation methodologies employed will: 1) result in positive rehabilitation outcomes; and 2) achieve the intended post-mining land use outcomes. In this case study, such a historical review of rehabilitation practices and outcomes was completed for Anglo American’s Capcoal Complex in Central Queensland. The Capcoal rehabilitation appraisal utilised personnel with extensive rehabilitation knowledge and experience to undertake a detail review of rehabilitation records, trial outcomes, monitoring results, processes, prescriptions and procedures in order to build a concise record for each rehabilitated area. The information was evaluated and formatted to enable upload into the site geographic information system platform. The desktop evaluation was then followed by a detailed site inspection to evaluate historic and contemporary rehabilitation areas that were representative of differing rehabilitation ages, prescriptions, spoil/soil types, and rehabilitation objectives. The site visit built on knowledge obtained from direct interviews with former site personnel, as well as internal and external stakeholders to obtain insights into contemporary rehabilitation practices, perceptions on rehabilitation success to date, and desired rehabilitation outcomes. External stakeholders’ views were sought on their expectations on rehabilitation outcomes and preferred post-mining land use objectives for differing site domains. The review culminated in refinement of rehabilitation prescriptions based on rehabilitation success from the historical record, confirmed with observations at the site, and combined with a knowledge of industry best practice methodologies appropriate to the site. Remedial actions were suggested for areas that may not be on a trajectory to achieve a desired relinquishment outcome. Documented outcomes included revisions to the recommended site rehabilitation prescriptions, amended post-mining land use mapping, and further refinement of post-mining land use outcomes. Finally, potential rehabilitation knowledge gaps that were identified were highlighted and opportunities for adoption of innovative technology were suggested. This case study showcases a methodology that can be applied at other mining operations to extract maximum value from their historic and contemporary rehabilitation performance and can optimise progressive rehabilitation methodologies for the site.