Gold and copper mining of low grade ore typically involves an open pit circuit with a heap leaching facility. A heap consists of blasted rock placed in a large pile, which is subject to surface irrigation with a reagent to dissolve and transport the metal out of the rock. Pressurized Injections (Hydro-Jex) into the heap leach pad at the Cripple Creek &Victor (CC&V) Gold Mine were also conducted to further enhance the recovery of gold. Hydro-Jex is operated by injecting fluid at very high pressures from a centralized well to targeted zones within the heap. Real-time electrical monitoring, where electrical current and voltage potential measurements were made on a 96-channel system to track the Injections, provided both direct and indirect Information to understand fluid movement during the Injections. Although additional data processing would have provided valuable Information, the strategy of focusing on the monitoring of time series data allowed for a quick turn-around. During this trial application of the Hydro-Jex technology, the timing of wetting front arrivals were noted in real-time by monitoring the electrical current output of the borehole electrodes; a sharp increase in current was a result of an increase in saturation, and hence a decrease in contact resistance with the heap. Flow direction was an important aspect during this project because the Injections were near the slope of the heap and monitoring for stability of the rock pile was a necessary condition of the operating permit. Directionality of the wetting front was determined by mapping the shape of the apparent resistivity contours using a time-lapse mise-a-la-masse methodology. Overall, the monitoring showed no impact to the side slopes and that the recovery of gold could be improved through simple redesign of the well field and Injection timing.


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