Ivan Arriagada
President
EDC Mining Limited
Mike Arriagada
Mike Arriagada
Sr. Mechanical Engineer
EDC Mining Limited
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View from the Top

Building Access to Deeper Deposits

Mon, 10/21/2013 - 13:21

Q: How did EDC get started, and which of EDC’s projects are you most proud of?

IA: One of the reasons the company was started was because generally speaking mines are getting deeper and deeper. Development by ramp was the traditional way of reaching bigger depths in Mexico, but as the mines got deeper, constructing ramps became more expensive. Peñoles was one of the first companies we developed new shafts for. When they had to put in their first shaft at Milpillas, in around 2005, the only companies that could do this type of work were foreign companies, mostly from Canada, the US, South Africa and Australia. At the time, I was working with a Canadian cementation mining company and we got the contract. While we were constructing the shaft, Armando Sánchez, one of the Directors at Peñoles, had the vision of developing a contractor in Mexico that could do this type of work. Ricardo Cárdenas from Minería Castellana agreed to do the job as long as we provided the engineering and the expertise. I decided to take the plunge and left Wardrop Engineering to set up EDC.

On the El Saucito project of Fresnillo we were the first Mexican company to build a shaft in Mexico. The need for shafts had not yet existed, but the ore bodies here started at 600m below the surface, which would require 11km of ramp just to reach them. As a result, it was no longer economical to build a ramp. Time was also was a big factor since the rate of advancement was about 70m or 80m per month for a ramp while we were advancing 60m per month sinking a shaft straight down.

EDC stands for Engineering, Design and Construction. We are a certified company with professional engineers, but apart from that we do the design and construction as well, and we provide the supervision on the projects we undertake. We build circular concrete shafts, and they are maintenance free. Thus, for a mining company, even if the initial cost is elevated building a shaft with us entails a long term economic gain.

Q: EDC specializes in double post mining. How does this technique work?

IA: Our double post mining project, which is underway in the Madero mine, is going to be a success. With all the safety concerns in mining, and the present geology of the most important ore bodies – with rocks and sandstones – this new method could contribute a lot. The process is like constructing a parking lot from the top down. You open the top layer, pour in a concrete floor, and drill in order to insert posts for the floor that would go underneath. Next, you drill the following slice, mine the rock, backfill it with cement, and build the floor and posts for the third slice. In this way, when you go underneath again, you have a concrete layer over you, which means that there is no need for rock bolting or similar processes. Furthermore, when you are drilling the posts for your next floor, you will know whether you have ore or waste, so you are assessing the geology right there.

MA: Double post mining can be compared to room and pillar mining; instead of leaving 20% of the ore as your pillars you use prefabricated concrete posts, which allows you to remove 100% of the ore. Also, you are working under a reinforced concrete roof, so it eliminates some of the safety hazards involved with underground mining.

IA: Recovering all of the ore extends the life span of the mine. The cost is also reduced after you get underneath the first concrete floor, because you do not have to do any ground support and you can carry all the ventilation through the stopes.

Q: EDC is also evaluating narrow vein mining, what do you see as the main opportunities for this technology in Mexico?

IA: We are trying to innovate narrow vein mining, too. We are in contact with a friend in British Columbia who has developed a system for narrow vein mining, and we are currently helping him put it into operation. Barrick was interested and they were going to try it in Tanzania, but they decided to put the project on hold because of the changes in the economic situation. We are hoping to introduce this system soon; most of the silver and gold mines in Mexico are narrow veins, so it is an idea worth trying. We have seen the prototype for this new, safer system and we know it will work. With the proposed system you can turn with the veins and follow them, thus making sure you get minerals instead of chunks of waste.