In-Situ Copper Recovery

In-situ means “in the natural or original position.” In the simplest terms, in-situ recovery (ISR) involves removing the selected minerals or metals without digging up the host rock. This creates many environmental and economic advantages over conventional extraction.

In-situ extraction is not new. It has been used successfully for decades primarily for the extraction of uranium and potash. The most common approach for extracting copper deposits, however, remains either excavating massive open pits or the sinking of shafts and tunnels deep underground. These conventional extraction methods have the potential to leave long lasting environmental legacies that may never go away. As technology has advanced, ore deposits like the Gunnison Copper Project have been identified for development as in-situ mines. This is a much less invasive approach that has been used safely and effectively for more than 50 years.

The unique characteristics of the Gunnison Copper deposit make in-situ extraction possible. The oxidized copper deposit is located below the water table, a rare geological occurrence that exists more so in Arizona than anywhere else in the world. The deposit also is naturally highly fractured and most of the copper is located on the surface of the open fracture veins, providing all of the necessary conditions for in-situ recovery.

Extraction is conducted via a closed loop system of delivery and recovery wells. Each delivery well is surrounded by four recovery wells; each recovery well is in turn surrounded by four delivery wells. A weak acid solution is delivered into the copper ore body, essentially under gravity pressure. The acid dissolves the copper, creating a copper-rich solution that is then pumped to surface where it is processed in a Solvent-Extraction Electrowinning plant (SX/EW). These plants typically produce 100-pound sheets of pure copper cathode.

The well field is divided into several extraction areas, consisting of numerous delivery and recovery wells. Each extraction area will operate for several years. When the copper is depleted, the area is rinsed with water to remove any remaining solutions. Control and monitoring wells are positioned around the extraction area to protect and maintain water quality. By virtue of the deposit's geological location and conditions, plus the multi-layer control mechanisms in place during extraction, the Gunnison Copper Project will not contaminate any surrounding water wells. Additionally, the Gunnison Copper Project will not affect any wells located downstream from the site.