‘Business as usual’ is not an option for mines
Province should move away from storing waste in tailings ponds, engineering panel says
An expert engineering panel recommended Friday a major shift for the mining industry after it determined the Mount Polley tailings dam collapsed because of a design failure.
The panel concluded “business as usual” cannot continue and the industry must move away from storing mine waste under water behind earthen dams.
The B. C. governmentappointed panel pointed to the Greens Creek, Alaska, mine that uses filtered tailings, sometimes called dry stacking, saying it is the “prime candidate” to eliminate the risk of tailings dam failures. There is no dam and no water stored on the tailings. That mine also uses a synthetic liner to prevent leakage, a practice not common in B.C.
The panel noted that dry stacking is more expensive than water storage.
While B.C. Energy and Mines Minister Bill Bennett endorsed some of the panel’s recommendations, he had a muted response to the call to move away from storing finely ground rock that contains potentially toxic metals under the conventional method used in the province. There are no examples of dry stacking in B.C.’s 60 operating and closed mines.
In its 156-page report, the panel said that simply put, dam failures are reduced by decreasing the number of dams that can fail.
The report said the number of tailings dams could be reduced by storing waste below ground in mined-out pits or as backfill for underground mines. But surface storage using filtered tailings is a prime candidate for best available technology, the report added.
“It’s not enough to tweak around the edges of what we’ve been doing and say we promise to do better — that won’t cut it,” said panel member Steve Vick, a U.S. geotechnical engineering consultant. “In order to get there, we can’t continue to use technology that is fundamentally 100 years old,” said Vick.
The panel — chaired by University of Alberta professor emeritus Norbert Morgenstern and University of B.C. professor Dirk van Zyl — said the industry must move to a “zero rate” of acceptable failure.
Bennett said he did not disagree with the zero rate measure.
He said independent dam review boards ( used in the Alberta oilsands, which add another level of scrutiny) would be made mandatory and regulations will be brought in that likely make dam design criteria more prescriptive.
But Bennett said the use of dry stacking has to be balanced against whether you could build the mine with that technology and whether it is appropriate.
He said, for example, a large mine like Teck’s Highland Valley Copper outside of Kamloops could not be built with dry stacking.
“I think we will eventually get to some project where our engineers are saying the only way to safely manage tailings is to dry stack,” Bennett said in an interview.
“What I don’t want to do is say that every single new mine will have to use dry stack tailings, because it’s not necessary and the panel didn’t say it was necessary,” added Bennett.
Provincial and national mining industry representatives also put up resistance to the panel’s call for methods such as dry stacking.
Pierre Gratton, president of the Mining Association of Canada, said dry stacking is not an appropriate option in circumstances where you have acid-generating rock, and where underwater disposal is the best technology for preventing acid generation.
“It also doesn’t work well in very wet locations,” he said.
But Gratton said that industry “fully accepts” it should continue to look at better, safer long-term storage options.
Added Scott Broughton, chairman of the Mining Association of B.C.: “I think that describing (dry stacking) as one of the next best practices that industry should embrace is not necessarily joining all the dots properly, and failed to highlight that we have a very, very high best practice of conventional earth-filled tailings dams as an industry in British Columbia.”
Imperial Metals vice-president of corporate affairs Steve Robertson said the panel’s finding of the cause of the breach agreed with the company’s finding in its own investigation.
Opposition NDP leader John Horgan said the report proves the disaster was preventable, because it shows the company and government had numerous chances over the years to reconsider building the dam too high.
Yet Horgan also said he’s not sure he’d support forcing B.C.’s mining industry to consider dry storage and covered facilities like Alaska’s. He said the public interest would be better protected by more inspectors and oversight, rather than forcing certain building solutions.
University of Victoria Environmental Law Centre legal director Calvin Sandborn said the panel findings showed the province’s environmental assessment is not looking closely enough at mine designs.
First Nations in the area of the Mount Polley mine — including the Williams Lake Band and the Soda Creek Band — said they were reserving comment until they had a chance to review the report in detail.