“A recent inrush incident at an underground mine has been directly linked with prolonged rainfall creating a large surface accumulation of water,” chief inspector of coal mines Gavin Taylor said in a safety alert.

“The water percolated slowly into old underground workings through planes of weakness.

“This situation is not unusual but recent rainfall, not experienced for many years in the Queensland coalfields, could result in substantial volumes of water entering mines from surface accumulations, directly or via aquifers and in amounts never experienced before.

“The result can be that water management systems are unable to cope with water increases larger than that which they were designed to handle.”

Underground coal mines were strongly advised to ensure they have sufficient pump capacity and standby equipment to overcome a possible inrush incident.

Other recommendations were to:

• Consider in detail the impact of such rainfall and if it is possible that connectivity to larger bodies of water has increased.
• Consider what impact your operations may have on another mine.
• Ensure that the amount of water pumped from each part of the mine is identified, along with its probable source.
• Establish a “fingerprint” for the mine in terms of volumes pumped and the variation with the seasons, in much the same way that ventilation patterns are set to provide early warning of a spontaneous combustion event.
• Consider the likely flow-path of water, above, into and then out of the mine and the potential for free-flow becoming artificially or inadvertently dammed by materials or structures constructed in the mine, or known to exist behind sealed areas.

Last month torrential rainfall caused water to seep underground into Xstrata’s Ulan longwall mine in New South Wales.

Production is still down at the mine, which remains focused on removing water from the underground workings.