SOMBA K'E/YELLOWKNIFE - The freeze system is fully operational and freezing has begun on the outside of arsenic trioxide Chamber No. 10 as of the last week of March, according to the Department of Indian and Northern Affairs (INAC).

"It is great news that we are actually seeing the freezing begin. Giant Mine is in our backyard, and we care about implementing a permanent solution," said a spokesperson who asked not to be identified due to constraints from Ottawa put on the department in communicating to the media in the midst of the federal election campaign.

Benny Nordahn, a mine system officer with INAC's Giant Mine Remediation Project, inspects the progress of the frozen shell forming around Chamber No. 10 during the last week of March. - photo courtesy of Indian and Northern Affairs Canada

There are about 237,000 tonnes of arsenic trioxide dust underground at Giant Mine, which is somewhat soluble in water and deadly poisonous if ingested. It's the by-product of more than 50 years of smelting at the mine.

The full frozen shell at Chamber No. 10 is expected to be complete by early 2012. There are 14 underground arsenic trioxide chambers which will be frozen in place pending an environmental assessment, with Chamber No. 10 being part of an optimization study which is gathering information on the project, such as power requirements, rate of freezing and other project management data.

Once the environmental assessment by the Mackenzie Valley Environmental Impact Review Board is complete, which could be as early as next year, INAC will proceed with cleanup of the mine site.

Kevin O'Reilly, of Alternatives North, said the way the government arrived at the freeze optimization study is questionable.

"I think it's probably worthwhile testing it, but the way in which it was hived off really amounts to project-splitting which is not a good idea," he said.

"There's a lot of resources that were invested into doing that study. I'm surprised it took them as long as it did to get it up and going," he said.

The cleanup plan, along with a water licence application, was submitted to the Mackenzie Valley Land and Water Board in 2007, according to the spokesperson. In 2008, the City of Yellowknife submitted the plan for an environmental assessment to the review board. The freeze optimization study was exempt from the assessment in 2008; work on it began in 2009.

The decision to go with the "frozen block method" was made after exploring a total of 56 options, which were first whittled down to 19, then three and finally to the freezing plan.

The spokesperson said the air in the underground tunnel is heated, so the temperature is approximately 5 C.

"In the actual 10-feet wall, the temperature currently varies between -2 C and -5 C. The goal is to reach a minimum temperature of -10 C on the surface of the wall."

According to the spokesperson, biodegradable food-grade glycol coolant is being pumped from the freeze system on the surface, through the pipes.

The end goal of the project is to have all the cleanup finalized in eight to 10 years, including the capping of the tailings ponds, demolishing the buildings, establishing a new water treatment system, freezing all 14 arsenic trioxide chambers and decommissioning the mine.

O'Reilly said he wondered if there are any plans for ongoing research and development into other technologies to deal with the arsenic trioxide dust underground.

The spokesperson said through the environmental assessment process, the question has been asked if freezing the arsenic is reversible. The spokesperson said although it is reversible, the frozen block method is a "permanent solution."

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