The heap leaching process is a technology that has been used for over four centuries to obtain metals from raw ores. The development of the global industry and developing technology during the last century has led to an accelerated-growth demand for raw materials such as precious metals, copper, nickel, and other base metals. In this challenging scenario, during the last couple of decades, the mining sector has been able to increase extraction, processing, and production rates with the utilization of new technology, software, equipment, machinery, materials, knowledge, and experience. In the heap leaching process, a series of improvements have been made during the last decade, adapting to more challenging market scenarios, reducing environmental risks, increasing production rates, reducing costs, increasing efficiency – and making the process feasible even in extreme geographic locations where success would not have been possible before.

Since the 1980s Chile has been the world’s largest copper producer, producing over 30% of total global production. Ausenco (formerly Vector Engineering) has participated in the design of nearly 70% of the heap leach projects in Chile, witnessing and actively being part of the evolution of leach pad designs from the early 2000s to the present. This paper reviews the most critical aspects and elements of the construction and operation of the most recent heap leach pad designs in the Chilean mining sector, and provides a comparison with the “old fashioned” design.

This paper discusses several issues such as location, earthworks, overliner materials, liner system, leak prevention and monitoring systems, leach collection and recovery systems, and pond covers, among other issues. In addition, operational issues are discussed, such as the evolution of the stacking and reclaiming mechanized equipment, and solution application, as primary operational aspects. Finally, all of these improvements are analyzed in terms of mining trends in Chile, and of the impact of some of the new technologies on costs, timelines, and recovery.

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