May 9 – Spence Mine (BHP)

We left San Pedro monday morning and traveled west to the Spence copper cathode project. Spence is located 60 km to the east of the city of Calama and is owned by BHP Billiton. The mine began production in 2007 and processes both sulphide and oxide ore, grading at 1.4% Cu, via heap leach.

Once we arrived at the mine we were treated to lunch in the cafeteria and a tour of the camp facilities. The camp included a full gymnasium, workout room, movie theatre and entertainment space. Workers are on a 7/7 rotation and appeared very comfortable in this world-class facility.

Open pit mining is conducted at a rate of 200,000 – 250,000 tpd of material moved. The mining fleet consists of four P&H 4100 shovels and forty CAT 793C trucks. Additionally the site has six CAT 994 loaders and a Bucket Wheel excavator to service the leach pads. Oxide ore is leached on one pad with sulphuric acid while sulphide ore is bio-leached with bacteria on a separate pad.  Everyday approximately 60,000 t of ore (at a 4:1 stripping ratio) is placed on/removed from the leach pads, which are leached in a continuous fashion.

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Next we visited Spence’s truck shop which we all agreed was the cleanest shop any of us had visited. Also of interest was the fact that every type of oil/lubricant/hydraulic fluid that was needed to work on the trucks was available to each bay through a series of pressurized lines.

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Spence currently performs 5 blasts a week at a bench height of 15 m. Two pits are currently being mined and they will eventually merge into a single pit. Blasts are limited to less than 900,000 t due to the community of Sierra Gorda being located 50 km to the south of the mine. The mine is actively trying to reduce the number of blasts per week to 4 in order to minimize the total amount of ground vibration felt collectively from all mines in the region. The mine life is currently until 2025 however plans are to build a flotation plant in the next five years. At this time they will be through the deposit’s oxide cap and into the sulphide zone which makes up the bulk of the deposit. This flotation plant will extend the mine’s life an additional 50 years. The final pit is estimated to 1 km x 1 km and 850 m deep.

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Finally we visited Spence’s electrowinning facility. Here the pregnant solution is processed into copper cathodes. Spence produces roughly 200,000 t per year of copper cathodes. Production costs are roughly $1.6 per pound of copper produced. The picture below shows Spence’s automated electrowinning plant.

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The employees at Spence were great hosts to their Canadian copper cousins. They were very proud of their mine and, as we have found all over this country, they were very proud of the mining culture in general in Chile. Our tour ended up being much more detailed than originally planned and as such it ran quite over time, however they graciously offered us dinner. After dinner we loaded back on our bus and headed for Calama. We checked into our hotel Los Domos de Calama and settled into bed, off to Chuquicamata tomorrow.

– Davis Kelly

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