KGHM – which says it is the “world’s largest silver and eighth biggest copper producer” – has started filling the seawater pipeline and pool at its Sierra Gorda mine in Chile. The water is captured from the cooling systems at a thermal electricity plant in Mejillones and is transported through a 142.6 km pipeline. Securing the water supply to the mine is the latest milestone before Sierra Gorda’s mechanical commissioning, planned in mid-2014. When production begins, the Sierra Gorda mine will use 250,000 m3/d of water. On a yearly basis, this equals a capacity of 92 million m3.
The pool holding 750,000 m3 of water – which is equivalent to 300 Olympic swimming pools – will provide the mine with an essential operating reserve. Filling the pool takes place in several stages by means of 24 pumps having a pumping rate of 1,500 litres/s. The whole process will last a month, which will allow testing the integrity of the liner and the safety of infrastructure.
Sierra Gorda will be one of a few mines in the world and the second in Chile operating this kind of water supply system, which is highly efficient and environmentally friendly. As the mine is located in a desert, with extremely dry conditions and scarce water reserves, the pipeline eliminates the risk of exhausting this resource in the region. Instead of being discharged into the ocean, the water, already processed in the electricity plant, will be reused at the Sierra Gorda mine and plant. Additionally the seawater salt will serve to control the emission of dust on the desert by forming a salt surface on the tailings.
The Sierra Gorda project, operated by KGHM International, is a joint venture between KGHM Group (55%), Sumitomo Metal Mining (31.5%) and Sumitomo Corp (13.5%). It is located in the Antofagasta region within the Atacama Desert, which is Chile’s largest copper producing region. It will produce copper, molybdenum and gold ore by open pit methods. Downstream processing will include crushing, grinding, flotation and drying to obtain copper and molybdenum concentrates. “Sierra Gorda is the seventh largest mining project in the world,” KGHM says.