In August 2014, an opal miner lost his life when he fell into a blind Caldwell shaft on the opal fields. The shaft location was not clearly identified or guarded, having been covered with corrugated iron and excavated soil. The covering collapsed under the miner’s weight.
Other shafts in the vicinity were also covered in a variety of unsatisfactory ways or left open or exposed without identification or edge protection.
Caldwell shafts are sunk during exploration drilling to provide ventilation and access/egress from underground workings on the opal fields. Often these shafts will be in-situ when a claim is pegged. Without adequate identification and guarding, these shafts present a major hazard.
- the shaft was covered and soil from excavation or noodling placed on top, obscuring the shaft’s existence
- the coverings used may have degraded and/or were incapable of supporting a person’s weight
- mounded ground collapsed during noodling or when walked on work occurred underneath the covered shaft which enabled the ground to collapse and cause engulfment. Vibration or failure of the cover due to corrosion or the weight placed upon it could have been responsible.
- when pegging a claim, ensure all existing shafts are identified and made safe
- steps should be taken to protect shaft edges by using earthen bunds or the placing of open mesh, capable of supporting a person, over the shaft opening
- on surrendering a claim, ensure all shafts are clearly identified and protected in such a way that alerts a person of their presence
- when noodling or climbing mounds, use a rod to penetrate the ground to identify where a shaft may be covered
- maintain regular contact with companions to monitor each other’s safety when on the opal fields
- do not place heavy vehicles on top of shaft coverings.
Bunding (moulding of earth around the outer edges) and guarding creates awareness of the shaft’s location
A correctly guarded Caldwell shaft.
An unguarded Caldwell shaft.