The project’s goal is to produce 180,000 copper cathodes tpy starting from low grade ore leaching, known as marginal material. The project’s life is estimated in 40 years. The share that corresponds to the stock participation of BHP Billiton on the project makes a total of 103,500 tons.
The marginal material, with grades generally between 0.3 and 0.7% copper, found under the cut-off grade for concentrators and currently stored in the present dumps of the mine, will be bio leached in piles, process known as Run of Mine. The resulting solutions will be treated in two new solvent extraction plants (SX).
* Process description:
1.- Leaching in ROM piles: this process consists of the formation of ROM piles in which copper is dissolved by leaching, due to the oxidation assisted by bacteria, with air presence and in favourable temperatures for its activity. The leaching piles will be fed with both the marginal material currently stored and the material to be produced in the future. Such material will be transported in trucks from its current storage area in the case of the ore produced in the future.
The marginal material appearing before the piles are ready or when there is no enough surface with available plastics sheeting, will be stored in a separate way, and later, will be part of the piles feeding.
2.- Solvent extraction: The SX plants will be located in the south west end of the first leaching pile and will be located so that the solution coming from the plants can flow by gravity from the SX plants into refine pools.
There will be six pools. Two of them will be used for the refine going to irrigation (with a maximum capacity of 54,000 m3 each); two extra pools will be used for the PLS or solution of piles collecting (with a maximum capacity of 108,000 m3 each); and two emergency pools, generally empty whose estimated capacity will be 300,000 m3 each. A system to detect potential infiltrations will be installed under the PLS and refine pools.
The process solution pools will have impervious plastic sheeting formed by two geo-membrane liners; the lower geo-membrane liner will be 1 mm thick; the upper geo-membrane liner will be 2 mm thick. The copper solution flow to the SX Plant will be about 6,000 m3/h, to do that, three settler-mixer trains will be needed. The trains’ amount will be defined in the basic engineering stage. During such engineering stage, the technology with the advantage of using only one train to process all the PSL flow will be defined. The flow will increase up to 12,000 m3/h, when the new SX plant is built.
3.- Electrowinning: From the SX aisles, a rich electrolyte solution will arrive at the EW plant, about 1,100 m3/h which will deposit the copper to later become poor electrolyte. Subsequently, the poor electrolyte comes back to the SX circuit to extract more copper.
The new SX plant capacity will be 100,000 copper metric tons per year at a current density of 290 A/m2. The plant will have a ventilation system consisting of the acid mist extraction, which complies with the regulations currently in force. The plan capacity will increase up to 200,000 tpy between the year 2006 and 2010 depending on the ore availability. Besides, special functioning conditions for the cathodes transportation, the temporary waste storage area and the Desalination Plant operation are stipulated. The power supply in the mine area will need 60 Mw which will be doubled, the estimated power increase will require a transmission line of 220 kV whose extension will be no more than 2 kms. | 
