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Mine Method Base Open Pit Mining
Process Routes Base Concentration (+Au), Base Open Pit Mining,SX/EW
Commodities Copper, Molybdenum, Gold, Silver
Geological Province Coquimbo Region
State Region IV (Coquimbo)
Country Chile
Latitude 24°16'17" S
Longitude 69°4'13" W
Project Status Production
Likelihood Producing
Startup Year 1990
Closure Year 2067
Operator BHP
Ownership Rio Tinto Group 30.00%, BHP 57.50%, Mitsubishi Corporation 7.00%, International Finance Corporation 2.50%, JX Nippon Mining & Metals 2.00%, Mitsubishi Materials Corporation 1.00%
Our Appraisal
Escondida is a tier-one copper asset with the world’s largest production scale, forecast at over 1.0Mtpa of copper for more than 50 years. The mine also is estimated to contain the world’s largest tonnage of contained copper, with 51Mt in Reserves grading 0.6% copper. The mine is expected to produce copper until around 2070. The operation encompasses two open pits that feed concentrator plants and two leaching operations. Major capital investments have been made through 2011 to 2017 to maintain the very high copper output as ore grades decline. Despite recent increases in labour costs, declining grades and facility degradation, Escondida’s cash costs remain competitive, ranking near the industry average on AME’s cash cost curve.
Site Introduction

Escondida is located at high altitude in the Chilean Andes, 160km SE of Antofagasta. Through a series of expansions it has become the largest copper mine in the world, with annual production capacity of 1.2Mtpa. Along with the five expansions there has been an introduction of two SX/EW facilities. The mine produces concentrate for smelting and refining from its open pits, and cathode via SX/EW.

There are two open-cut pits (Escondida and Escondida Norte), two concentrator plants with 3.4Mtpa copper concentrate production capacity, and two solvent extraction plants with a nominal capacity of 330ktpa copper cathode. A third concentrator (Organic Growth Project 1) with 55Mtpa ore processing capacity was commissioned in 2015. It was to replace the 44Mtpa Los Colorados concentrator. In August 2015, BHP Billiton indicated all three concentrators would be utilised to support production as grade declines and expects 1.2Mtpa of payable copper production over the decade from 2016.

Operation History

Construction of the mine started in August 1988, and the first batch of ore was processed in November 1990. In 1993, the US$76m phase one expansion was completed with the incorporation of a new ball mill. This increased ore throughput capacity to 45.6ktpd. The phase two expansion commenced in 1994 to increase the Los Colorados plant capacity to 54.6ktpd of sulphide ore by adding an additional ball mill, and a concentrator ammonia leaching plant in Coloso to produce 80ktpa of copper cathodes. In 1996, the phase three expansion was completed and ore throughput capacity was increased to 105ktpd of sulphide ore through the addition of a SAG mill, two ball mills, additional flotation capacity and filters.

In 2002, the Laguna Seca concentrator plant was commissioned with the capacity to process 110ktpd of sulphide ore. At the same time, the Laguna Seca tailings dam was built to dispose of the tailings from both concentrators, and recover process water for reuse. The investment for this expansion reached US$1bn.

In 2005, Escondida produced its first batch of cathodes through the process of bioleaching low-grade sulphide ore. This project also included the construction of a seawater desalination plant in Coloso.

In 2007, a new oxide leach pad started operations, replacing the original pad, which had reached its maximum design height.

In 2012, the Organic Growth Project 1 (OGP1) was approved with budgeted expenditure of US$3.8bn. It proposed the replacement of the Los Colorados concentrator with a new 152ktpd plant. The project provided additional processing capacity and allowed access to higher-grade ore. The new concentrator was completed in 2015 at a capital cost of US$4,279m.

In February 2012, the Oxide Leach Area Project (OLAP) was also approved with budgeted expenditure of US$721m. It involved the creation of a new dynamic leaching pad and mineral handling system, including overland conveyors. The new pad was expected to maintain oxide leaching capacity at the existing level following the exhaustion of the heap leach in 2014. The OLAP was brought into production in the December Quarter of 2014. The actual capital cost was US$899m.

In 2013, BHP Billiton and Rio Tinto approved a combined US$3.4bn expenditure on a new desalination plant to reduce the operation's reliance on the region's aquifers. The plant consists of a new 2,500L per second seawater desalination facility, which will provide an alternative water supply to Escondida as water usage was to increase on completion of the 152ktpd OGP1 copper concentrator. The new facility is expected to be commissioned in 2017.

In August 2015, during commissioning of the OGP1 concentrator, BHP Billiton stated that the three concentrator strategy, with the commissioning of the desalination plant, is expected to offset grade decline and support a strong recovery in production. AME's production forecast assumes the Los Colorados concentrator is retained and all three concentrators with a combined capacity of 145Mtpa of sulphide ore are available.

BHP plans to delay the dismantling of the Los Colorados concentrator and spend US$180m on revamping its facilities in order to prolong its operating life until at least 2030, to maintain copper production capacity in response to declining grades. The preserved throughput from Los Colorados added to the existing Laguna Seca and OGP1 concentrators, and the leach-SX/EW capacity, will enable Escondida to produce 1.2Mtpa of payable copper for a decade from 2016 at minimal capital cost. The Los Colorados concentrator was put into care and maintenance in March 2016, pending the completion of the desalination plant. BHP expected the revamped Los Colorados concentrator to be operational by mid-2017.

In December 2015, BHP Billiton was reviewing the long-term sulphide leach strategy. It may decide to divert the sulphide ore feed to the higher value concentrator stream. AME continues to forecast long-term production at Escondida on the basis that the Sulphide Leach Reserves will continue to be processed by leaching and SX/EW, pending further information.

Production was halted in February and March 2017 during a 44-day strike that started after the existing labour agreement expired. The strike ended despite BHP and the workers’ union being unable to reach a labour agreement. The union and its 2,500 members used a legal provision, Article 369 of the Labour Code, which permits workers to return to the previous agreement for 18 months. Existing benefits and working conditions are maintained. When negotiations commence in June 2018, new labour laws will be in effect including a requirement that existing benefits in the current collective agreement are offered in the new agreement. Commissioning of the Escondida Water Supply project and the planned ramp-up of the Los Colorados Extension project were delayed until the September 2017 quarter as a result of the industrial action and delayed mobilisation.


Escondida owns mining concessions in accordance with the current mining laws and national constitution of Chile. Escondida owns 155,000ha of surface rights. These cover the current and foreseeable Escondida requirements. Surface rights are renewed by the existing owner on an annual basis.

Escondida's main mining concessions are Alexis 1 AL 1424 (02201-1299-3), Catita 1 AL 376, Colorado 501 AL 977(02201-1180-6), Guillermo 1 AL 368 (02201-1216-0), Amelia 1 AL 1049, Costa 1 AL 1861 (02201-1215-2), Donaldo 1 AL 612 (02201-1217-9), Paola 1 AL 3000 (02201-1324-8), Ramon 1 AL 640 (02201-1280-2) and Rola 1 AL 1680 (02201-1300-0).