mill capacity has been necessary to compensate for the gradual move of mining into the lower grade primary ore zone. The concentrate goes to the Caletones smelter further down the valley. This is equipped with two Teniente converters with slag furnaces, three Pierce Smith converters and six anode furnaces feeding two anode and one fire refined casting wheels. Tailings are flumed down the valley to dams on flatter ground. An independent company, Minera Valle Central, retreats old and current El Teniente tailings and extracts some 12,000 tonnes p.a. of copper in concentrate. Sewell Sewell, the original mine camp and known as the 'city of stairs' because it looked as though it had been poured down the mountain, has become a UNESCO World Heritage Site. It was founded in 1906 by William Braden to house his mine workers and had a population of around 15,000 at its peak. It was closed down in the late 1980s as all the workers moved down to Rancagua. El Abra Codelco sold a 51% interest in its El Abra deposit in 1994 to Cyprus-Amax (now part of Freeport McMoRan Copper and Gold) who then developed it. Production started in 1996. It is a porphyry copper with an extensive capping of leachable oxide and sulphide mineralisation. Production over the next three years is expected to be in the 152,000 to 168,000 tonnes copper p.a. from the 227,000 tonnes p.a.capacity SX/EW plant. It is planned to exploit the underlying sulphides starting in 2010 which should extend the mine life by over 10 years. Other projects The Gabriela Mistral ("Gaby") Project is an oxide copper project located 120 km south of Calama. Reserves are estimated at 580 million tonnes of oxide ore grading 1.41% copper and there is underlying sulphide mineralisation but this is not being considered at present. A 14-year open pit leaching and SX/EW operation producing about 150,000 tonnes of copper annually is planned. Startup was in 2008 marking the milestone to be the first mine in the world to introduce the full autonomous trucks from [Komatsu]. Leaching of tailings with the potential to produce and additional 30,000 to 50,000 tonnes p.a. between 2011 and 2014 is being investigated, as is wind power. An 'exotic copper' orebody, "Vicky" has also been found in the Gabriela Mistral area with potential estimated resources of 80 million tons of oxide ore with a copper grade of 0.6%. A 44,000