At the San Manuel copper mine in southeastern Arizona, recovery of copper from the oxidized portion of this porphyry mineral resource is being achieved through a large in situ leaching operation using weak sulfuric acid solution. In the past, this activity was coordinated with open pit and underground mining, but in today's economic climate only the in situ operation continues. The acid solution (20 grams/liter) is injected into wells (unpressurized at varying depths up to several hundred meters), usually at rates of only a few tens of gallons per minute. The copper-bearing pregnant leach solution (PLS) is recovered either in...

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