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It's getting cold down there
Giant Mine's freeze optimization study underway

Katherine Hudson
Northern News Services
Published Tuesday, February 8, 2011

SOMBA K'E/YELLOWKNIFE - After a dark and bumpy 15-minute drive into the depths of Giant Mine, the manager of the mine's clean up explained the progress of the freeze optimization study Monday, the first step toward the Giant Mine Remediation Project.

NNSL photo/graphic

Martin Gavin, manager of the Giant Mine Remediation Project for the Department of Indian and Northern Affairs (INAC), stands outside the concrete wall of an arsenic chamber in Giant Mine Monday morning. There are about 237,000 tonnes of arsenic trioxide dust stored underground at the site, which is the by-product of more than 50 years of operation. - Katherine Hudson/NNSL photo

All 14 underground arsenic trioxide chambers will be frozen in place pending an environmental assessment, said Martin Gavin, who heads up the remediation project for Indian and Northern Affairs Canada. There are about 237,000 tonnes of arsenic trioxide dust, which can be deadly if ingested when mixed with water, the by-product of more than 50 years of smelting at the mine.

The study is in its conditioning stage, according to Gavin, with the facility pumping a super-cooled liquid through pipes around Chamber 10, one of 14 arsenic trioxide chambers, freezing rock around the area, locking in large storage pockets of arsenic trioxide dust held there.

The actual freezing began in mid-December with the development of one freeze optimization study pipe every four metres extending back in the rock around Chamber 10, creating a frozen shell. The last of the pipes will be operational in the next few days, according to Gavin.

"The coolant comes out of a plant and is sent here and it withdraws the heat from the rock," said Gavin.

He said the team of workers has been checking the pipes for leaks by pumping air through as well as checking alarms systems, switches and sensors along the 8 kilometres of piping.

The official opening of the study will be some time in March or April.

"It's very exciting. It started with a concept and it's going to be a reality in a very short period of time," said Gavin.

He said the study will go on for years, with the mine continuing to use data from the first chamber that is frozen.

"If we know how long it takes for the freeze wall to expand and become established, then that's our project management data and we know to plan the bigger project," said Gavin.

"So with any project, you realize increased efficiency is approximately 10 per cent after you do it the second time and it diminishes from that point, in this case if we save 10 per cent of what would have been an operational cost, saving somewhere in the vicinity of $20 million of taxpayers' dollars ... It allows us to use this to learn from to do things efficiently in the fixture and it supports us through the environmental assessment process."

Once the environmental assessment is concluded in a year or two, Gavin said the designs and implementation strategies will be stable and the project will move forward with the remediation plan led by the Mackenzie Valley Environmental Impact Review Board.

"From the point that the underground piece starts, the surface piece will also be going on. It's essentially two project thats are working together under one big project. The surface and the underground have to work cooperatively," he said.

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

"The mine will need to operate with ventilation for a number of years after that so we can come down and look at these things and then after that, up to 10 years, there will be a significant period of time where there's actually care and maintenance of the project systems that have just been put in," said Gavin.

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