The Queensland Department of Mines and Energy (DME) has released a safety bulletin urging all mines to complete a comprehensive assessment of the risk of falling from height, after several fatal accidents have occurred in the past few years involving workers driving or falling over the edge of excavations at mines and quarries.
These incidents involved a variety of equipment performing different tasks at different locations. All were potentially fatal.
One fatal accident involved a small open cut copper mine in north Queensland, where an air trac drill rig toppled over the edge of a narrow bench and came to rest approximately 20 m below. The driller was killed. The accident investigation concluded at least seven simultaneous defences failed and contributed to the accident.
Each of the failures related to mine design.
The bench was too narrow for safe operation, particularly to allow construction of adequate safety bunds on the edge of the bench for the equipment being used.
The compromised narrow bench design was to compensate for a narrowing orebody and the steeply sloping terrain. For operating expediency and because of the narrowness of the bench, this control was replaced by an inadequate procedural control of daily inspections by the supervisor.
The bench floor contained a number of loose rocks which were not cleaned off the bench.
These ultimately became an unstable operating platform for the air trac.
The air trac was operated beyond its limit of stability. The boom was fully extended and swung to the side towards the bench edge.
The operator was inexperienced, having only had two months experience on an air trac and less than three months experience at a mine. This, combined with the fact that the supervisor had not assessed the risk of the air trac operating on a narrow bench on loose rocks, particularly with the boom fully extended, directly led to the fatality.
According to the safety bulletin, all mines and quarries should complete a comprehensive risk assessment that includes consideration of existing site conditions, particularly topography, geology, and environmental conditions; mine design, taking into account geotechnical considerations, minimum bench width, bench height, batter angle, overall pit gradient, haul road width and gradient, ramp width and gradient, and drainage.
Inspector of Mines