Canadian Mining Journal

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Why mine closure matters and why it gets ignored

Trends in mine closure from the Progressive Mine Forum



If you want to clear a room of miners, there are few better ways than to raise the topic of mine closure.

At least, that’s sort of what happened at the Progressive Mine Forum in Toronto in late October. The inaugural event, organized by The Northern Miner, was dedicated to discussing innovation in mining. After a day of roundtables discussing CSR, Big Data in exploration, and innovation in mine development, operations and finance, about half the audience got up and left when it came time for the final topic of the day – mine closure. (Watch the Mine Closure portion of the event.)

While mine closure may not be a sexy topic, it is an urgent one.

“It’s the single most important thing that our industry does,” said Douglas Morrison, president and CEO of the Centre for Excellence in Mining Innovation. “Nobody in the public could care less what our productivity levels are, what the return on investment is. They absolutely care what we do with our waste streams – waste water and solid waste. This is where our industry interacts with the public.”

In other words, if this is what the public is most interested in, mining companies should also be interested – if only out of self-preservation. How the industry deals with mine waste, mining among regular Canadians.

But this isn’t the only reason mine closure is so important.

It’s a costly part of mining that far too many miners neglect.

“The reality is when you look at mine closure in the overall life cycle of a mine, it’s actually the longest phase of a mine,” said Steven Woolfenden, director of environment for Iamgold. “I’m managing some legacy sites that are 30, 40, 50 years old and there is no end to that management – it will be in perpetuity.”

The cost, Woolfenden added, is often underestimated.

“Most people really don’t pay much attention to it because when you do the costing on mine closure, it’s pushed so far out and discounted so much that it doesn’t really impact it. But when you get there, and you actually have a closed mine, it costs you a lot of money.”

The roundtable, moderated by CMJ, looked at advances in mine closure and evolving best practices, and how to get the topic more top of mind in the industry.

A new concept

Ken Bocking, principal in the mine waste division at Golder Associates, pointed out that mine closure is acutally a pretty new concept.

“I started (in mine closure) in 1992. Why? Because that’s when the law came in in Ontario,” Bocking said.

“Until that time, basically mines would live out their useful life and then many of the operators just walked away.”

Now, mine operators need to have a thought-out closure plan and put up financial assurance so that there is funding in place for closure if they do walk away.

However, the industry hasn’t really implemented closure at many sites: “There’s not very many mines that have been completely closed to the point where the company can walk away and the land can be returned to the Crown,” Bocking noted.

“So I think that’s where it needs to go next.”

Waste management alteratives

The current standard approach to tailings and waste management is sub-aqueous deposition – where tailings and waste are held in a tailings pond under water to prevent the sulphides in the material from reacting with oxygen in air and causing acid mine drainage.

“It involves storing a large volume of water behind the dam,” Morrison said. “That’s also where all the risk is. If you didn’t have water behind the dam, and you had a breach of your containment system that unsaturated tail would actually go nowhere.”

In the wake of the Mount Polley tailings dam breach in 2014, there have been calls for the mining industry to move to dry-stacking, which involves filtering the tailings and stacking them up like a landfill.

However, it is very expensive to build and operate a filter plant and then to haul and place the tailings. “I think there will be places where because of special circumstances (dry-stacking is) justified, but it’s not going to be a general solution because of its cost,” Bocking said.

Another alternative to sub-aqueous deposition is separation and sequestration.

“The fact is 80% of the material in any metal mining tail is benign – it’s clay and other solid materials,” Morrison says. “We could depose of that 80% with very, very low-cost systems and that product could be laid out and we could actually be having alternative land use on that product very quickly.”

Morrison noted that the current approach takes the 20% of problematic tailings and mixes them in with the 80% of benign material – making 100% of the waste problematic.

At its old Doyon mine site in Quebec, where its new Westwood mine sits, Iamgold is looking at treating old mine waste. The company hopes to strip the sulphur out of the Doyon tailings so it can be reused at Westwood. Currently, Iamgold spends quite a bit of money to treat water at the site.

The company is hoping to prove to regulators that the option is viable. If not, it will have to dig up other material to use. “If we can use our tailings, it’s probably about cost neutral, but it’s a much better, more sustainable practice in the long run,” Woolfenden says.

In northern Ontario, the company is investigating the use of biosolids from the Ashbridge’s Bay sewage plant in Toronto as a growth medium for rehabilitation at its Chester mine.

Progressive closure

There are many advantages to progressive closure, the practice of conducting closure activities during operations. For example, if a particular tailings cell is no longer used, it can be closed out while others are still in operation.

One advantage to progressive closure is the opportunity to practice and verify your closure technique, says Bocking.

“There’s also financial advantages because the financial assurance that you put up, if you then progressively do some of that closure, you can claim some of that back so you’re liberating some of your financial assurance and putting it back in your pocket.”

Progressive closure, which is made much easier if companies separate the benign tailings and waste from the reactive, Morrison noted, can also serve to reassure the public about responsible waste management practices in mining, because they don’t have to wait 50 years to see the result.

Despite the advantages, progressive closure doesn’t seem to be on the radar for many executives and general managers.

“One of the things we’ve been challenged with regards to progressive reclamation is the question of why do it now, why pay for it now vs. just kicking it down the road?” Woolfenden said.

In order to make the case to decision makers, Woolfenden says KPIs (key performance indicators) need to be developed.

“Most of them don’t seem to have KPIs with respect to progressive reclamation. They’re all on ounces produced, cost reductions, various other metrics,” he says.

When the numbers are calculated, progressive reclamation really does save money over doing it all later.

“When we look at the numbers in our ARO (asset retirement obligation) calculations and our LOM plannings, it does benefit the balance sheet when you can actually get these liabilities off of them,” Wolfenden said. “I’m not a finance guy but we used financial numbers to sell the argument (within Iamgold) and it worked.”

Perhaps other companies are also becoming believers. Modelled on an Australian initiative, a number of majors and smaller companies have created a North American Mine Closure Group to collaborate on best practices, including progressive reclamation, Woolfenden noted.

It’s also considered good practice for companies to incorporate the concept of design for closure earlier – in the development stage.

Environmental monitoring

As long as sites can’t be fully remediated, environmental monitoring is necessary.

While in the past, a five-year monitoring period after closure was considered acceptable, that’s no longer the case, Bocking said. “The regulators and the industry are, I think, agreeing now that we need longer monitoring periods and more thorough monitoring.”

A lot of monitoring equipment can now be automated, and drone and virtual reality technology can be used in some elements of monitoring and inspections.

The industry should be making use of same technology being used on farms for autonomous monitoring, said Morrison.

“When you look at the quality of data that farms produce and the precision with which they apply the various chemicals and the other things that they need to do vs. how we’ve continued to monitor our tailings facilities, we’re a long long way behind.”

CEMI is working with a group at McMaster to commercialize a technique that can remotely monitor dissolved metals in water down to tiny concentrations, he added.

In another example of new monitoring technology, Iamgold and other miners are working with the Biodiversity Institute at the University of Guelph to apply genomics to the environmental effects monitoring programs that are required during operations.

Rather than send people into the field to take samples and deliver them to a lab that isn’t always accurate in testing, the companies can simplify the collection process at a fraction of the cost and time with a PCR (Polymerase Chain Reaction) machine onsite. “You can actually just take a water sample… and you will have the data as to what species are in that river and in what relative abundance,” Woolfenden said.


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1 Comment » for Why mine closure matters and why it gets ignored
  1. Effective restoration of mining disturbances is an essential part of the mining industry. I have developed cost-effective closure treatments that can be used at mines and I have presented papers at the various Mine Closure conferences.

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