Dismantling the Roaster: The Latest on Giant’s Massive Remediation Project

267,000 tonnes of arsenic contaminated waste will be frozen and sealed in 15 underground vaults onsite | Photos courtesy Aboriginal Affairs and Northern Development Canada

Over the past two years, workers in yellow hazmat suits have been dismantling the Giant Mine roaster complex piece by piece. The roaster — “arguably… one of the most contaminated structures in Canada,“ according to the remediation project’s deputy leader Natalie Plato — spewed hundreds of thousands of tonnes of arsenic trioxide gas into the air for 50 years, blanketing the mine site and blighting the surrounding area.

The break-up work on the roaster is now mostly done, Plato told the City’s Municipal Services Committee on Monday. Three thousand tonnes of arsenic-impacted waste from the complex, “about the same mass as 1400 F150 trucks,” has been bundled into some 7000 hazardous material bags, most of which have been loaded into around 310 shipping containers that are now sitting in one of the mine’s tailings ponds.

Plato’s comments came during the first of three public sessions this week hosted by the Giant Mine remediation team. There will be a meeting for Yellowknives Dene members in the N’Dilo gym on Wednesday evening and another for the general public on Thursday in Northern United Place.

The next phase of the massive remediation project, in which 237,000 tonnes of arsenic contaminated waste will be frozen and sealed in 15 underground vaults, isn’t slated to start for another four or five years.

“I couldn’t give you a definite time frame now,” said Craig Wells, the project’s director with Aboriginal Affairs and Northern Development. “Once we get the water license approved [in four or five year’s time]… we’d be looking at [another] 10 to 12 years of really active remediation… then we’d get into long-term care and maintenance.”

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Workers drilling as a part of the underground stabilization project. Det’on Cho Corp. was recently awarded an $18-million contract to stabilize the pits and tunnels

Avoiding disaster

In the meantime, there’s plenty of work to be done on the site, said Wells. Two issues in particular need to be dealt with swiftly to avert a potential disaster.

One is the Site C headframe, the rickety wooden symbol of the mine’s past. Like the Robertson Headframe, its days are numbered.

“We’re looking at removing the structure because it’s at risk of collapsing,” said Wells. “Power to the mine and water, communications, basically everything runs under C Shaft, so if the headframe were to collapse it would be a pretty catastrophic incident to the site and would have a huge impact on worker safety.”

The other major issue is stabilizing a number of the tunnels and open pits that are at risk of, or are already, crumbling into dangerous sinkholes. Det’on Cho Corporation was recently awarded an $18-million contract to stabilize the pits and tunnels using a kind of concrete-like substance that’s pumped into the spaces.

One area of particular concern is the Site C Pit, which is at risk of being flooded by nearby Baker Creek. Over the long term, the remediation team may have to reroute Baker Creek around the mine site, said Wells. In the short term, a subterranean chamber under the creek has been filled, and “we’re going to prop up the pit wall, with a buttress… so there’s no risk of flooding,” said Wells. “If it gets into the pit it may get into the mine, and that would result in contaminating the water.”

The C-Shaft Headframe. The original timber frame is deteriorating and a collapse would be catastrophic

One spill, 26 recommendations, 312,000 days of work

So far the project has seen relatively little escape of contaminated material, said Plato. All the water from the project is put into tailing ponds that are treated and tested in a water treatment plant. There’s been no indication that arsenic levels in the water are dangerously high, said Plato.

“We did have one reported spill last season, we believe from water,” she said. “When the roaster came down, we had to do a lot of wetting to keep the dust down, so a lot of the material was saturated. There was some water around the container which was promptly dug up and placed in a secure container.”

An environmental assessment came out last August, which had 26 recommendations that will be guiding work leading up to the big freeze. Wells and Plato say they’ll continue consultation with community members in the coming years, and are working to “employ and train aboriginal and northern workers so we have a sustainable workforce to manage both the clean-up of the site and all the monitoring and maintenance we’ll have to do after.”

Despite the unequivocal environmental disaster that is Giant Mine, Yellowknife’s one-time business engine may yet continue to prime our economy even into its afterlife.

According to a 2010 assessment report, which doesn’t even include work leading up to the big freeze, there’s over 2,496,000 person hours of work to be done during the implementation phase – which comes to roughly 312,000 eight-hour days of well-paid work remedying past woes.

Remediation workers deconstructing the roaster.  In the 1940s, as much as 22,000 pounds of poisonous gas was pouring from the buildings every day, in which the arsenic-rich mineral Arsenopyrite was processed to reveal its gold


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