How Freeport McMoran recovered an additional 13,600 tonnes of copper from its Arizona heap operation
Freeport-McMoRan’s Safford Mine in Arizona had a problem. Low grades, unique mineralization and fine particle size resulted in a sub-optimal heap operation.
The heap had low and variable permeability, so the mine was not producing enough copper. Freeport McMoran tried wick drains, commonly known as prefabricated vertical drains or PVDs, which are prefabricated strips of flexible polypropylene plastic containing channels and surrounded by a geotextile filter fabric. Water in the soil, under pressure in excess of hydrostatic, flows through the filter fabric of the wick drain and into the channels of the plastic wick drain core where it can flow vertically either up or down and out of the soil.
The results were impressive. The wick drains have reestablished hydraulic connectivity between more permeable zones in the heap, which has allowed leach solution to contact ore that has residual copper value. Draining solution in the heap also increased slope stability and made the heap safer.
Contact American Wick at 800.242.WICK(9425) to learn how wick technology can improve your mine’s production.
The impact of releasing trapped solution from the heap via the wick drains has been profound from a production standpoint. Between the start of wick drain installation in late June of 2012, and the end of May 2013, over 13,600 tonnes of additional copper have been recovered from the Safford Phase I heap. Revenue from this increased production has far exceeded the cost of increased heap monitoring and wick drain installation.