Evolution of Leach Pad Designs

By Scott Elfen, Global Practice Lead, Earth Sciences, Ausenco

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 demand for raw materials such as precious metals, copper, nickel, and other base metals.

In order to respond to this demand, and to be successful financially, socially and environmentally, heap leaching has evolved quickly in the last decade, overcoming a number of challenges. These challenges include: volatile commodity/market scenarios, environmental considerations (e.g. stricter regulations and regulators), lower ore grades, productivity/efficiency rates, increases in energy costs, water availability etc.

Response to the aforementioned challenges has led to a series of improvements making the process feasible even in extreme geographical locations where success would not have been possible before. It has driven major changes and new approaches in the design of heap leach pads, leading to more aggressive designs within stricter environmental and social restrictions and requirements.

Successful heap leach projects are incorporating new materials, new technology (monitoring, instrumentation), new designs for leach pads, and lessons learned. These improvements allow designers to design fit-for-purpose heap leach pads in order to meet each client’s needs, location/project variables, and to protect project economies by lowering costs and/or increasing recoveries.

At Ausenco, we have designed hundreds of heap leach pads around the global in various challenging environments. This experience allows us to address the unique issues for a project surrounding the main construction items that drive costs of a typical leach pad project such as earthworks, liner system, solution collection system, and overliner and to look for alternative technologies for reducing water loss, as well as considering the use of alternative stacking and reclaiming equipment. With advances in technology, the future of heap leaching will see even more opportunities and innovative solutions.

Pierina Gold Mine Heap Leach Project

The Pierina Gold mine project in Peru is located at an elevation of 4,100 metres. Ausenco has been working on this project for over a decade, providing our client with innovative design solutions for the leach pad and best in class construction monitoring support services in a very challenging environment.

Through partnership with our client we help meet their goals of sustainable economic development and protecting the environment. During this time we developed some industry firsts including: placement of the leach pad liner system on near vertical slopes; high head internal leach pad pregnant solution pond with vertical caisson pumping system; leach pad raincoat and surface water management system providing increase stream flow below the project, and one of the first compartmentalised valley-fill heap leach leak detection system.

Ausenco’s scope of services included:

  • Heap leach pad design for seven phases
  • Resident engineering and construction quality assurance for 1.3 million square metres
  • Feasibility studies
  • Geotechnical and geological engineering
  • Saturated and unsaturated flow models
  • Conventional and static liquefaction studies
  • Geotechnical monitoring of all civil facilities
  • Annual safety inspection of dams
  • Closure planning
  • Injection well design
  • Water modelling including water balance and water surplus management.

To find out more about our innovative heap leach facility design solutions visit here. #AskAusencoHow