SOMBA K'E/YELLOWKNIFE - In the city's only attempt to test the temperature of the mine water at the now defunct Con Mine last June, the company contracted to do the tests snagged and lost a probe, which two sources close to the story say was worth about $80,000.

A probe on a steel cable was snagged and lost beneath Robertson headframe when a contractor tried to test water temperatures in the mine last June. The city hasn't made any further attempts to test water temperatures. - image courtesy of the City of Yellowknife

Weatherford Canada, which works in the oil and gas industry, was conducting a test to confirm temperatures recorded in a 2009 geothermal energy feasibility study that says the water filling up the now defunct Con Mine is between 33 C and 71 C at 1,900 metres.

The city needs to know the temperature of the water as part of its research for the proposed $60.4 million Con Mine community energy system, which, if completed, will heat 39 downtown buildings with a mixture of wood-pellet boilers and geothermal heat generated by the earth below the mine.

Weatherford said it isn't commenting on the job at this time because it's currently an unresolved billing issue.

When asked whether the cost of the probe would fall on the city, Bob Long, the city's senior administrator, said, "We didn't lose the probe. It's a company that we hired and they lost their probe."

He said as far as he's concerned, the city won't be at a loss.

Mayor Gord Van Tighem couldn't confirm or deny what the probe was worth. "As far as their instrumentation materials cost, that wouldn't be something we would necessarily have knowledge of or need knowledge of, as long as they have the stuff required to do the contract they were given, then everybody's happy," he said, pointing out that the contract wasn't completed.

He said he couldn't say how much Weatherford was being paid to do the testing.

Ron Connell, manager of environmental and reclamation for Newmont - the company that owns Con Mine - said to his knowledge the probe was worth $80,000. A source close to the story, who asked to remain anonymous, confirmed that number.

When the probe got snagged, it was on the end of a steel cable, which was attached to a cable reel on the back of a truck, said Connell. Full force was exerted to reel the wire in, but it wouldn't budge, he said.

"It got caught on something - nobody knows what because it was about 3,000 feet down - and they couldn't get it to come back up, so they ended up cutting the guy wire."

Connell said pulling any harder would have been a safety risk because the cable could have snapped and recoiled.

He speculated that the probe could have been caught on a collapsed beam in the shaft or on steel mesh that is starting to come loose from the shaft walls.

"That's about the only thing I can think of," he said. "But at this moment in time, it's purely speculative. We don't know what happened and we do intend to investigate when it warms up a little."

The city hasn't made any further attempts to the test the water temperatures.

Long said tests will be done in the summer, after the city has chosen a private partner - currently they are considering three that have not yet been named.

Although the city doesn't yet have concrete numbers, Long said based on the feasibility report done by University of British Columbia professor Mory Ghomshei, there is no question there is enough heat to make the project work.

The business case for the project, conducted by Vancouver-based Compass Resource Management, shows that the project is viable if the water temperatures are 20 C or higher.

The difference between 20 C and 30 C - the temperature used as the base case - is how much energy will come from the mine.

To generate geothermal energy, warm water would be pumped to the surface, passed through a heat exchanger, and then the cooler water would return to the mine, far below the surface.

Long said the important thing for the city to determine is the sustainable rate for reheating the water.

There is a point where it hits a diminishing return, he said, and the city needs to determine what that point is in order to design the system.

"That data will be used to determine the size of the heat pump (and) the capacity of some of the other boilers."

To avoid another lost probe, Long said the city will likely do further testing by drilling a hole into one of the drifts, rather than using the mine shaft.

There will be three holes drilled to pull water out of the mine for the system anyway, said Long, so it just makes sense to go about the testing in that way.

"We think that's probably a more practical way to do it."

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