Queensland government mines inspectors continue to work with mine management to ensure gas levels are returned to safe levels before re-entry to the mine is permitted, a spokesperson for the Queensland department of natural resources told ILN.
“On May 29, 2012, the Queensland Government Mines Inspectorate issued a Directive suspending operations at Carborough Downs mine,” he said.
“The directive remains in effect until inspectors are satisfied gas levels have returned to safe levels and appropriate action response procedures for carbon monoxide and other gases are in place.”
The current investigation by mine management and the Mines Inspectorate will identify all factors and necessary corrective actions prior to the resumption of production.
The mine is using several inert gas generators to direct inert gas into the longwall goaf via surface-to-seam boreholes. Both Floxal and Tomlinson boiler units are in use. The Queensland Mine Rescue Service GAG unit is available should it be required.
There is a risk of methane accumulation in the goaf, the spokesperson said.
The mine is enacting strategies to lower the oxygen content in the goaf to minimise any potential further temperature rise and potential ignition of methane. This includes bulldozing cracks on the surface of the mine above the longwall panel.
“Current strategies identified by the mine are aimed at stopping the coal from getting hotter and minimising the risk of spontaneous combustion in the goaf,” the spokesperson said. “If temperature increased, there would be a risk of fire, and for an ignition of methane.”
Ongoing mine atmosphere testing will continue to monitor for methane and other gases. Risk of methane accumulation in the goaf needs to be evaluated as part of risk assessment and management procedures associated with recovery operations.
Elevated levels of carbon monoxide are believed to be associated with accelerated oxidation or self-heating of the coal seam in the longwall goaf.
ILN did not get a response from Vale at the time of publishing.
