The Kori Chaca gold mine is the “little” brother of the Kori Kollo mine. Like his older borther, Kori Chaca is an open-pit mine owned by the private company Inti Raymi (EMIRSA). Although the concentration of gold is particularly low, EMIRSA decided to start this project in 2004 because for this new project the company could recover a big part of the facilities of Kori Kollo. A peak in the gold price during the first years after its opening has been advantageous for EMIRSA and thus the mine has stayed open for a lot longer than initially planned. Despite the low gold concentrations, huge profits were made. Due to its unusual location, CEPA and CORIDUP are closely monitoring this case, and so are we.
The Kori Chaca mine is situated on the Andean plateau (Altiplano), in the department of Oruro. The biggest criticism of the project lies in the fact that the site is located less than 5 kilometers Southwest of the city centre of Oruro. This means that the site is situated in the urban zone of this big city and making the construction of the mine unlawful. Nevertheless EMIRSA obtained the licenses to extract gold from the Vincutaya hill. The site borders the Iroco mining district, a district where mining activities have already been taking place for hundreds of years.
Since 1994, six foreign companies have explored the Iroco site: Free Port, BHP, Cameco, Austrabol, Vista Gold and Newmex. However, none of these found the potential gold output high enough to start exploiting the site. EMIRSA did, however, have an interest in the extraction of the 0,8 grams of gold that one metric ton of ore on average contains, and obtained the concession rights in 2001. They acquired the environmental license in 2004, after which the construction of the mine started, with the objective of extracting 224,000 ounces of gold in four years’ time. In 2008 the decision was made to extract an additional 2.8 tons of ore (mix of gold and silver). By the end of 2013, the closing phase of the mine started.
The kori-Chaca mine is an open-pit gold mine, which in this case means that every day an average of 20,000 tons of material has been excavated from an ever-deeper hole, 24 hours a day, 6 days a week. These tons of materials are then grinded and piled on leaching platforms. Up to now, the platforms have been sprayed non-stop with a mixture of water and cyanide to extract the gold particles. About 60 to 70 tons of cyanide is used on a daily base. Moreover, the mine has an excessive water usage, according to official numbers (‘Ficha ambiental’) the mine uses up to 6240m³ water per day and an additional 25000m³ drinking water per year.
By the end of 2013 EMIRSA started the closing phase of the Kori Chaca mine. No new rocks are being excavated. Without any warning, EMIRSA filled up the hole, which had reached a depth of about 110 meters, with water from the bordering Desaguadero River. The leaching platforms will continue to be sprayed on for three years after closure, to continue the extraction of gold.
The Kori Chaca project has several consequences for its surroundings. Besides the noise and dust disturbances, the risky transport of the highly toxic cyanide and the dumping of the contaminated waste rock, the biggest problems are related to water:
- While digging the mining pit there is a continuous supply of groundwater in the pit. To keep the pit dry, the (saline) groundwater is pumped up and stored in big evaporation lakes. Because of the composition of the subsoil, this water contains high concentrations of heavy metals. The water evaporates after which a salt-encrusted surface(with heavy metals) remains. In periods of heavy rainfall these evaporation lakes receive big amounts of water, which can cause the embankments to break. The released water then enters the Desaguadero River, which takes the salt and heavy metals to the Poopó lake. Along the way, the river can also overflow its banks and leave behind contaminated silt.
- The pumping of groundwater to keep the mine dry also has an influence on the reserves of groundwater that seep into the pit from kilometres away. Various communities, downstream of the mine, complain about dried out or salinized groundwater wells.
- The inadequate storage of the contaminated waste rock causes the release of heavy metals, which infiltrate into the soil and thus contaminate the groundwater.
There is much confusion now about what will happen with the mining area and with EMIRSA. According to EMIRSA they have moved out of Oruro completely and don’t have further plans to continue mining. However, rumours have it that they plan to obtain concession rights for neighbouring mountains to continue extracting gold there. Another option is that smaller mining cooperatives will extract gold there, and EMIRSA could act as wholesaler. Whatever the future holds, it remains important to continue monitoring the case.