Yose Cormier
Northern News Services

Yellowknife (May 30/03) - The Giant Mine remediation project team looked at four criteria in choosing the method of managing the arsenic trioxide still found underground.

They were: is it feasible? What is the risk to workers and the public? What is the long-term risk? and what is the cost?

The teams' final two choices were frozen block, and removal and cement encapsulation.

The GNWT, though, wants more information on a third option - deep disposal.

Frozen block

The idea is that the arsenic dust located in 15 chambers 250 feet below ground would be frozen solid.

The bedrock surrounding the chambers would be frozen using a proven technique.

This option has a low long-term risk and a low risk to worker safety.

The cost to perpetuity of this option is estimated at $90 million and $120 million.

Removal and cement encapsulation

The arsenic dust is extracted from the underground chambers and processed into a more stable form.

The dust would be mixed with cement and aggregate and the resulting mixture stored in a landfill.

The long-term risk for this option is low and the risk to worker safety is moderate.

The cost to perpetuity of this option is estimated at $230 million to $280 million.

Deep disposal

The arsenic dust is extracted and relocated dry and wet into an area geologically secure from ground water transfer deep inside the mine.

New vaults would have to be excavated and prepared.

The long-term risk is low and the risk to worker safety is moderate.

The cost to perpetuity of this option is estimated at $190 million to $230 million.

Source: Summary of preferred arsenic trioxide management levels provided by the GNWT