May 5 – Andina Mine

Today we left at 5am to visit the Andina Mine, located 80km northeast of Santiago at an elevation of 3500-4200m above sea level. Andina is a combined open-pit and block caving operation. We toured the open pit which sees a total of 230,000 tonnes of material per day moved with a fleet of 30 trucks. The pit has a 2:1 strip ratio and an average head grade of 0.7% Cu. This is considered as Codelco’s smallest operation.

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In order to get this tour we were required to do extensive medical tests which included a blood test, electrocardiogram and chest x-ray. The Andina division of Codelco has impressively strict safety regulations to ensure everyone is fit to visit high altitudes. Luckily nobody was severely affected by the altitude and we managed to get through the tour without any fainting.

For the first part of the visit we traveled to La Mirador to meet with the general foreman and get some views over the open-pit mine. Three loaders and two shovels are currently operating on multiple pit phases including a pushback of a 600 meter high wall.

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Due to the high risks of avalanches and steep terrain, the Andina mill is located underground. Haul trucks feed two primary crushers on the surface which convey material to an ore bin underground. Large underground chambers house the SAG, grinding, and flotation circuits. Copper concentrate is produced and is piped down to the bottom of the mountain pass in slurry form. It is then dewatered and trucked to the Ventanas smelter on the coast. The biggest challenge of having the mill located underground is the complex ventilation system that is required to deal with dust.

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Part of the unique history of Andina is how the tailings management plans have changed over the years. Initially the tailings dam was located near the open pit operation for ease of tailings disposal. At one point in the 1990’s, Andina nearly suffered a breach of the tailings dam when central Chile was undergoing heavy rain during an El niño event. After that event, Codelco moved the tailings dam to a valley that is approximately 45km west of the mine. This location provides significantly more space for tailings disposal and also moves the dam away from the Santiago-area water shed and any glacial discharge. When we arrived in Santiago on May 2nd, we were able to get some aerial photos of the tailings dam before the plane landed.

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