Jasper, DA, Lacy, HWB, Russell, M & Braimbridge, M 2012, 'Landform planning: using science and economics to reduce operating costs and closure risk', in AB Fourie & M Tibbett (eds), Mine Closure 2012: Proceedings of the Seventh International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 13-22, https://doi.org/10.36487/ACG_rep/1208_02_Jasper
(https://papers.acg.uwa.edu.au/p/1208_02_Jasper/)
Abstract: Landforms of mined waste are the most obvious physical remnant of open pit mining operations. Reflecting this, they represent an important element of closure and relinquishment, and should be safe, stable, appropriately vegetated and represent minimal ongoing environmental risk. We review current issues and practice in the construction and closure of landforms, and then discuss the benefits of integrating enhanced understanding of mined wastes and soil materials with engineering and cost optimisation, to create landforms that will constitute low risk at closure.
The goal of landform planning should be to ensure that the right waste materials are put in the right place at the right time, in terms of the environment and the long-term land use, and also in terms of cost. Substantial cost savings can be achieved during construction and at closure by pursuing this goal. Poor outcomes of landform construction include excessive erosion which potentially compromises the integrity of cover layers, poor establishment of vegetation due to unfavourable material properties, poor vegetation development due to inadequate water holding capacity, nutrient deficiencies, or chemical toxicities, and longer term issues such as deep drainage through hostile stored material. Remediation of existing landforms to correct issues such as these is extremely costly.
The nature of the landform surface, in terms of slope configuration, and the nature of the materials themselves, directly affects critical long-term objectives such as resistance to erosion, integrity of encapsulation of hostile wastes, capacity to accept and store rainfall, and to support plant growth. Understanding the timing of material flow by type, and the preferred location for all materials are key elements in determining if a landform plan can be achieved. Formal audits should review landform development and rehabilitation in relation to the plan, and include updated information on waste types and volumes as mining progresses.
Developing a landform that minimises costs, both in operations and at closure, and that also represents the least risk to the surrounding environment can be achieved. Approaches using a block model approach to landform construction are a powerful tool for mine closure in that they create a practical interface for environmental constraints to be combined with, and influence, mining engineering and economics.