The Escondida copper mine is located in the Atacama Desert in northern Chile, one of the driest deserts on Earth. Escondida is the largest copper mine (by production) in the world. It produces over a million tonnes of copper per year, employs more than 3,500 employees and is one of the biggest private single taxpayers in the Chilean economy.
It is not simple to change water sources and to rely solely on one; careful planning and preparation is critical. Escondida has been planning a transition away from groundwater resources to desalinated seawater since the mid-2000s, achieving permanent cessation of withdrawal from underground aquifers for operational use in January, 2020.
The first large-scale desalination plant for industrial use in Chile was commissioned at Escondida in 2006. The plant, in the Port of Coloso, is designed to produce 525 litres per second and includes a pipeline of more than 180 kilometres to reach the mining operations 3,200 metres above sea level in the Altiplano (High Andes).
Escondida commissioned its second desalination plant, Escondida Water Supply (EWS) in 2017. This resulted in the desalination facility being one of the largest desalination plants in the world. EWS had a design capacity of 2,500 litres per second and includes a twin 42-inch diameter, 180-kilometre pipeline, four high-pressure pumping stations and a reservoir to move water from the Port of Coloso across the Atacama Desert to the mine site. In July 2017, the construction of the Escondida Water Supply Expansion project (EWSE) commenced. The EWSE project added a further three reverse osmosis racks, providing an extra 800 litres per second of desalinated water supply. The project also increased the pumping capacity by incorporating six additional pumps in each of the four pumping stations, allowing a maximum design capacity of 3,800 litres per second for the desalination facility in the future. In early January 2020, EWSE started production. This expansion to the desalination facility was an essential part of BHP's water strategy, to ensure increased water supply for Escondida and to allow the cessation of extraction from the Andean aquifers for operational purposes, which in turn provides more sustainable, resilient and reliable water.
In 2017, Escondida announced it would cease extraction from one of the main aquifers, Salar de Punta Negra. In 2019, Escondida announced it would also reduce water extraction from the aquifer underlying the Monturaqui well field by 70 per cent from FY2020, and that it aspires to cease all groundwater extractions for operational supply by 2030. The implementation of this strategy has since accelerated and, in January 2020, Escondida ceased extraction from its Monturaqui well field - 10 years ahead of target for its aspiration to cease all groundwater extraction. All water use is now supplied by desalinated seawater, other than small quantities of groundwater extracted for pit dewatering to allow safe mining
Additionally, in recognition of the need to reduce the carbon footprint from desalination, the Kelar power generation plant that provides energy to the desalination facility, originally to be coal fired, was redesigned and built as a liquefied natural gas combined cycle plant. The total investment for the new desalination plant was US$3.4 billion.
This water supply strategy is a milestone in the history of mining in Chile, given the ambition and scale of the desalination projects and the level of investment. The strategy conveys a recognition that groundwater resources are limited and important to communities and the environment, and industry cannot rely on such unique resources in the long term. While the strategy had a significant impact on Escondida’s production costs for the short term, we were convinced that today’s challenge is tomorrow’s opportunity. This is key to creating a sustainable future for Escondida.
Escondida is also working on ways to decrease its overall freshwater consumption. It has promoted efficiency initiatives that increase the use of water recovered from its production processes, primarily from the tailings dam, and is investigating technology to reduce overall demand.