Pulacayo Project Feasibility Study - Apogee Silver

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Pulacayo 1 000 t/d Phase I Feasibility Study - NI 43-101 Technical Report 090644-3-0000-20-IFI-100 25.1.3 Hydrogeology An in-depth study on the hydrogeological conditions has not been completed on this project thus far but seeing that this mine is in current operation and was in operation for many years, underground mine water is not expected to pose a risk to future mining operations. It is known that old workings are flooded, but the current level of this water is significantly below the planned lowest level in the new mine. However, this needs to be monitored regularly to see if there is a trend of rising water. If that occurs, a dewatering scheme will have to be implemented. 25.1.4 Paste Backfill The mine design at present includes 100% cemented paste backfill, which is a conservative approach. Backfill testing has been completed to ascertain a suitable mix design, which includes 6% cement content. In addition, a reinforced plug at the bottom of each backfill section has been designed and will be constructed prior to backfilling taking place. 25.1.5 Metallurgy and Mineral Processing As the material to be processed are mainly sulphides, a flotation method to improve and optimize the level of lead, zinc and silver recovery was selected. Challenges related to flotation selectivity and low lead concentrate grades were due to the presence of mixed, intertwined galena-sphalerite assemblage. The selectivity issue was overcome by selecting an adequate reagents suite. The consistency of the results obtained at the laboratory level, combined with higher recoveries, led to the selection of the conventional differential flotation. Bulk flotation did not render adequate performance (recovery and grade). Reclaimed process water was pre-treated with activated carbon in order to obtain higher lead concentrate grades as the carbon adsorbs the dissolved copper ions (Cu 2+ ) present in the water, which causes pre-activation of sphalerite and pyrite. The straightforward conventional selective lead-silver flotation (locked cycle tests) show that good lead recoveries of between 88% and 93% can be achieved with a large variation in head grade from 1.5% Pb to 4.3% Pb. The silver recoveries range between 67% and 93.5% with a variation in head grade of between 136 g/t Ag and 375 g/t Ag. Saleable lead and zinc concentrates can be produced from the Pulacayo ore using conventional mineral processing techniques including crushing, milling and differential flotation. For tailings disposal the underflow from the tailings paste thickener will be either sent to the TSF or used as paste fill for underground stope support. The paste thickener overflow water will be reclaimed for the plant process water. Results from metallurgical test work carried out in four stages have been used to guide process plant design. The Feasibility Study process comprises crushing, milling and classification, differential lead and zinc flotation, tailings disposal (tailings storage facility and cemented paste fill plant) and concentrate dewatering. Although a significant amount of test work has been completed, additional variability metallurgical tests for process flow circuit TWP Sudamérica S.A. Av. Encalada 1257 Of. 801, Santiago de Surco Lima 33, Perú (51-1) 4377473 Page 289
Pulacayo 1 000 t/d Phase I Feasibility Study - NI 43-101 Technical Report 090644-3-0000-20-IFI-100 validation are required. The “name-plate” capacity of the designed processing facility is 1,000 t/d. 25.1.6 Environmental and Permitting The development of the Pulacayo Project poses certain significant challenges with respect to environmental management, including passive contamination from previous activities. This issue is covered in the environmental Baseline Study. The Environmental Impact Study (EIA) was filed and submitted to government entities for review, categorization and approval in January 2013. This study includes the outcome of a public consultation meeting held in December 2012 with the representatives of communities within the area of influence of the project. The result of this meeting was positive. The environmental practices described in the current Environmental Impact Study will be implemented in the project, whilst the permit extension process continues. The communities will participate in these activities in order to create awareness. While this in progress, Apogee would continue with further engineering and procurement activities. Apogee has land tenure, surface rights agreements, permits for water supply and discharge and exploration permits, required to carry out exploration activities including the development of an exploration access drive. 25.1.7 Water Management The main supply of water in the region is the Yanapollera reservoir. The Yanapollera reservoir stores water from the snowmelt, run-off and ground water springs in the upstream Cosuño nevado (snow-capped mountain peak) and distributes the water to local users. At present, the reservoir has three users: A mining cooperative located in the Pulacayo town, the Pulacayo population and the town of Uyuni. The actual water demand of these users from Yanapollera is still somewhat uncertain, and their water demands are supplemented by ground water and other sources. The hydrologic model evaluated the likelihood of a water deficit over the Life of Mine. This model included a sensitivity analyses on input parameters, to account for the lack of longterm site data normally recommended for model validation. The results of this work indicate that the Yanapollera reservoir alone should not be relied upon for process and potable water related to mine operation, as this would leave a statistically significant chance of a water deficit during the Life of Mine. This probability can be reduced or eliminated by constructing a water storage reservoir, and/or by supplementing the water supply with ground water sources. Investigation and design of the aforementioned items is currently underway. The spring and summer months will see demand for water to suppress dust as well as to wash plant and other mine equipment. The bulk of such water should come from clean water run-off captured by drains located around the periphery of site. 25.1.8 Infrastructure The 115 kV power line is one of the first activities to be developed, as the electrical equipment involved are considered long-lead items. Power line procurement and construction can take as much time as needed for the plant construction itself. TWP Sudamérica S.A. Av. Encalada 1257 Of. 801, Santiago de Surco Lima 33, Perú (51-1) 4377473 Page 290
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Pulacayo Project Feasibility Study - Apogee Silver

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