1999 Northparkes Air Blast
Case Study
On 24 November 1999, an air blast killed four mine workers at the North Parkes Mine located in central NSW.
The copper and gold mine was in maintenance shutdown, with approximately 65 workers underground. At approximately 2.50pm, a catastrophic event occurred over a period of four minutes, where approximately 5.5 million cubic metres of rock (14,500,000 tons) collapsed from the roof into the void, creating an air blast which travelled through the underground workings of the mine.
The force of the air blast was such that roof bolts and metal mesh were bent, motor vehicles were destroyed, and four workers were killed. Two of the workers killed were contractors employed to conduct drill and hydraulic fracturing procedures on the roof of the cave void. It appears the other two men, employees at the mine, had gone down the mine to examine the activities taking place.
The Coroner found that the only reason the air gap void reached the size it did on that day, was because the mine was maintaining a production rate far greater than the rate at which the ore was falling from the cave roof.
North Parkes is the first block caving mine in Australia.
The Coroner found that the production rate took precedence and that the mine had not followed guidelines for the maximum height of the air gap set down by block caving experts when the mining initially commenced.
The Coroner also found that the mine should have been aware that the position of the bulkhead, as a safeguard against air blast, had been compromised and no longer served its purpose before the incident.
One of the Coroner’s recommendations was that any mine operator intending to employ the process of block cave mining identify and analyse the elements of all the risks associated with its block cave operations. Mine operators should also develop and maintain hazard management procedures for the management of the void above the muckpile, the height of the muckpile above the extraction level, and the air blast hazard, including all appropriate controls for the air blast at all openings or potential openings into the caving zone.
As result of the incident, there is a greater understanding of the risk involved in block cave mining in Australia and managing the risks of air blast. Air blast is a principal mining hazard in NSW.
This incident claimed the lives of 4 people:
Colin Lloyd Jones; Stuart Osman; Ross Bodkin; and Michael House.