A directive issued by an inspector of coal mines required the orderly withdrawal of workers and the suspension of all underground operations while mine management deals with the situation.
It also requires mine management to review and validate the effectiveness of “trigger” levels used to activate its current action response plan to deal with this type of gas situation.
A spokesperson for Vale told ILN: “Vale can confirm that a controlled withdrawal of personnel from the underground workings of its Carborough Downs mine occurred on May 29 as a precautionary measure.
“In response, site management is currently adjusting the mine’s Trigger Action Response Plan (TARPS). Upon completion, these will be provided to the Mines Inspectorate for their review and approval.
“It is anticipated that with the Mines Inspectorate consent, a resumption of normal underground workings will occur in the near future.”
A spokesperson for the Queensland Department of Natural Resources and Mines told ILN the directive would remain in place until inspectors are satisfied gas levels have returned to safe levels and appropriate response procedures for carbon monoxide are in place.
“The Mines Inspectorate is closely monitoring the company’s actions and two mines inspectors are at Carborough Downs (May 30) to assist in the review process,” the spokesperson said.
“This action follows notification on May 25 by Carborough Downs operator, Vale, that it had detected elevated levels of carbon monoxide in a longwall area of the underground mine.
“The elevated carbon monoxide levels are believed to be associated with accelerated oxidation, or self-heating, of the coal seam in the longwall.
“Workers were withdrawn from the affected area and mine management implemented its incident response procedures and gas sampling as required by Queensland mine safety and health laws.
“Through its Trigger Action Response Plan (TARP), mine management has been injecting inert nitrogen into the affected longwall area to reduce oxygen levels in the mine atmosphere and minimise any potential for an underground fire or explosion.
“The Mines Inspectorate continues to provide help and advice to the mine,” the spokesperson said.
“On May 29, the Mines Inspectorate concluded that risk could become unacceptable by relying on the current TARP and directed the mine to cease using the plan until it is thoroughly reviewed.
“Workers will be allowed to re-enter the mine once carbon monoxide readings return to safe levels and the Mines Inspectorate is satisfied the mine has an appropriate and effective Trigger Action Response Plan in place for elevated gas levels.”