The decision to freeze about 237,000 tonnes of toxic arsenic trioxide dust underground at the former Giant Mine in Yellowknife remains the chosen solution for now — and possibly for the next 100 years — but a researcher at Queen's University says he and his team have a technology that could render all that toxic dust inert in five years.
"Freezing arsenic underground is a good solution, but in general it's not a permanent solution," says Dr. Ahmad Ghahreman, a Queen's University assistant professor in the department of mining.
"Imagine if for any reason you have a power loss … the water body around the arsenic is not frozen anymore and then your arsenic starts to release into the environment."
Ghahreman says a new process to treat arsenic trioxide and render it into inert could work, and would be relatively affordable compared to another well-established — but prohibitively expensive — hydrogen peroxide treatment.
The new process, which costs about 40 per cent less than the hydrogen peroxide treatment, uses a column of activated charcoal and air to convert an arsenic trioxide solution into an arsenic five-oxide solution, leaving a deposit of "immobilized" arsenic that does not require further treatment.
He says it could work in Yellowknife, rendering the frozen block solution obsolete.
"You remove that arsenic [trioxide] from underground. You convert it to a more stable mineral, which is roughly 10,000 to 100,000-times less soluble, and then you even don't have to worry about that compound anymore. It's so stable, even in the rain, the arsenic will remain in the mineral and will not get into underground waters."
Ghahreman said a test at Queen's University has been running at over 99 per cent effectiveness.
But the process has never been tested in a working or retired mine setting outside a lab. Ghahreman said there is a natural reluctance in the mining industry for a company to want to be the first to try anything new.
"The challenge with the mining industry is that all the companies want to be second, no one wants to be the first," he said.
Ghahreman said he like to see the government take the lead and bring the project to Yellowknife for a real-world test, "taking material to run a small plant … and prove the concept works fine with the material we have in Yellowknife."
He said if the process would work in Yellowknife, it could take less than five years to treat all the arsenic underground at Giant Mine.
He said it would cost about $200,000 to run a small field test in Yellowknife to prove the process works.
Significant hurdles to concept
The Giant Mine Oversight Board is the public organization tasked with, among other things, monitoring the state of the art in mine clean-up and making recommendations for better solutions to the frozen block method, if any are developed.
"It is certainly possible that this research could lead to a possible treatment approach at Giant Mine," said Dr. Kathleen Racher, chair of the Giant Mine Oversight Board, in an email to CBC.
"However, there are at least two very important factors that would need to be considered: the very large quantity of impure arsenic trioxide dust at Giant that is in a powder form and research to date has shown this arsenic dust is not easily dissolved into solution; and transferring the dust from the underground chambers to above-ground treatment remains a significant technological hurdle."
Racher said Ghahreman has not made a proposal to the board, and Ghahreman's research was not included in the board's recent "State of Knowledge" report. But Racher said the board was aware of his work and continues to monitor current research at Queen's University and elsewhere.
Racher said the board is still developing its research program and a formal review process of new and future technologies, but until that's in place any proposals like Ghahreman's will have to wait.
"The board has not and will not turn any formal proposals away but it will make it clear that they will be held until the research program is fully functional before being evaluated," she said.