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Anglo planning to go underground in Chile as glacier-protective step

Anglo American Chile regards the protection of glaciers as being of critical importance and has developed mining methodologies that promote glacier continuation.

Anglo American Chile regards the protection of glaciers as being of critical importance and has developed mining methodologies that promote glacier continuation.

Photo by Anglo American Chile

22nd October 2019

By: Martin Creamer

Creamer Media Editor

     

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SANTIAGO, Chile (miningweekly.com) – Anglo American has plans to go underground at Los Bronces in Chile, where copper mining has taken place for the last 152 years and where large-scale opencast mining takes place currently.

Anglo American Chile, which regards the protection of glaciers as critical, has developed mining methodologies that promote glacier continuation.

The proposed new mine, which will be located 5 km southeast of the current pit, will be 100% underground to avoid surface impact.

In two months, a virtual reality video will be in place at the corporate office of Anglo American in Santiago to enable viewers to step through the proposed underground operation, where the chosen method of mining will be put through its virtual paces.

Known as sublevel open stoping with backfill, the method sets out to uphold the value of the landscape by removing 48-million tonnes of tailings from the environmentally sensitive surface area and using it underground as backfill. Moreover, the design extracts only half to 70% of the ore to ensure surface stability.

However, there may be delay in gaining approval because of amendments made, even though these are climate-positive. This is because current Chile permitting disallows post-submission changes, even if they are environmentally enhancing.

“One of the things we struggle with in Chile is the permitting process. Some of the real problems we have as an industry are that once you get a permit, it’s something that you want to keep closed because if you open it up, you open yourself up to another six years of studies, another three years of approval, regardless of the outcome,” Anglo American Chile CEO Aaron Puna told an international media contingent, of which Mining Weekly Online formed part.

“The reason that’s a challenge is because, if we know there is a way to do something better, we don’t currently have a mechanism to deliver a positive outcome without opening up all those processes and the negative sentiment that goes with it,” said Puna.

Even for something as straightforward as moving a proposed underground tunnel outside of the glacier shadow requires permit withdrawal and a whole series of studies and reviews that take the process back to the start.

BOOSTED BACKFILL

When dried and filled with a cement aggregate, the planned tailings material mix is regarded as the perfect backfill to stabilise the mined out voids.

“It’s the right thing to do – remove the dam, put it into the underground and deliver on our commitment,” Puna reiterated.

But to permit the changes, even though they are enhancements, takes three or four years.

“So, this is our challenge”, and specially recruited to meet it is new Anglo American Chile VP corporate affairs Rene Muga, who outlined Chile’s relatively recent transition to a specific glacier protection legislative focus.

“In Chile, we’re discussing the introduction of a specific glacier protection law, apart from the existing environmental legislation,” Muga told visiting journalists.

Discussions have been ongoing and proposals from senators, government and experts are expected in the coming weeks.

“The issue will be discussed by the Senate as a whole and then come back to the environmental bench of the Senate. So, it’s a process that will take some time, and then it will go to the lower chamber for discussion. It will give us the opportunity to participate more actively in this discussion regarding glaciers in the coming year, or years even,” he said.

The mining industry is represented in those discussions by a council on which Chile’s biggest mining companies are represented.

CONTINUATION OF EMPLOYMENT

Going underground will require a large capital investment and, depending on permit stringency, the first underground ore could emerge between 2025 and 2028 and then ramp up to 150 000 t of copper a year.

The project provides continuation of employment for many employees currently working at the opencast mine. These employees would need to be trained in sublevel open stoping, which is similar to bord-and-pillar mining but with all the voids being backfilled using a material with a higher density than the material extracted.

It would create 2 850 jobs during development and 2 400 jobs during peak operation.

Block-cave mining, which would have been an option in normal circumstances, has been ruled out.

“If there were no glaciers, it would be openpit going into a block cave,” Puna told journalists.

But block-cave would result in unacceptable surface impact.

HIGHER GRADE

The underground ore is of higher grade than the opencast ore, where activity will be reduced and ultimately become at least one-third less than the case now.

The copper output of Los Bronces in 2018 was 370 000 t, with first-half 2019 costs at 135c/lb.

“We’re talking about replacing one-third of the openpit output with underground output,” said Puna.

Tunnel boring machines will be used to bore the underground tunnelling and 18 months will be required for development.

“We’re challenging some of the paradigms and some of the reasons why we can’t do things that are for the better good of the sustainability of the country.

“The measures that we have to take are necessary and they are also the right thing for us to do. We’re completely comfortable with transparency and information purely because we believe it's the right outcome and we’ve got nothing to shy away from in that space.

“As a business, Chile provides Anglo with a fantastic opportunity to really push into this sustainable mining space and it’s aligned with what we as a company are trying to promote,” said Puna.

“The fact that we’ve been relentless in pursuing hydrogen trucks to the point where we didn’t wait for original equipment manufacturers and we’re building that with off-the-shelf materials from a number of different companies and suppliers, and we’re making that work, is really a testament to the direction of the business,” he added.

The world’s largest hydrogen-powered, zero-emission mine haul truck is being developed at Anglo American Platinum’s Mogalakwena mine in South Africa as a means of lowering carbon emission and Anglo's copper operations in Chile are targeting a switch to hydrogen trucks, should their development in South Africa prove successful. The hydrogen will be produced from renewable sources rendering it ‘green’.

“Every truck that we buy in the future, depending on the success of Mogalakwena, will be targeted as a hydrogen truck,” Puna told Mining Weekly Online.

Edited by Creamer Media Reporter

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