Resources Safety 100 Plain Street EAST PERTH WA 6004 Department of Consumer Email: [email protected] Phone: + 61 8 9222 3333 and Employment Protection Website: www.docep.wa.gov.au/ResourcesSafety Fax: + 61 8 9325 2280 2 Reactive mineralisation, containing sulphide material including pyrite and chalcopyrite, was present in the rock in which the magazine was excavated. Marcasite was also identified — a material that could react with ammonium nitrate in the explosive stored in the magazine and cause self-ignition as a result of the chemical reaction. ANFO was known to have spilled in the magazine prior to the incident. ANFO is known to interact with sulphides to cause an exothermic reaction. The chemical reaction may have a long induction period with little observable temperature increase. However, once sufficient catalysing species have built up, the reaction rate increases rapidly, generating sufficient heat to cause self-ignition. Ammonium nitrate is also an oxidising agent, which evolves its own oxygen during chemical reaction. This made it impossible for the dry powder fire extinguishers to smother the fire. Water application is the primary suppression method recommended in explosives manufacturers’ material safety data sheets. A number of empty 500 kg bulk ANFO bags were allowed to accumulate in the magazine, stacked in close proximity to full ANFO bags. This would have provided an additional fuel source and assisted in the propagation of the fire. A number of personnel authorised to enter the working party magazine were found to be smokers and routinely carried cigarettes and lighters into the magazine. However, there was no evidence from witness statements or previous inspections and audits that personnel had been smoking inside or in the vicinity of the magazine immediately prior to the incident. The working party magazine was being utilised to supply several jumbo development headings concurrently. Consequently, a quantity of explosives in excess of six tonnes was being stored in one area for this purpose. There was no regular shift supervisory inspection carried out in the working party magazine on the shift the incident took place or on the shifts immediately prior to the incident. The explosives management plan for the mine did not detail the storage requirements mandated by legislation and regulation. The explosive management plan required weekly contractor inspections and monthly principal employer audits of magazines. Records revealed that the inspections and audits were not being carried out at this frequency. Dry chemical powder fire extinguishers were provided both inside and outside of the locked gates of the magazine. Personnel were not able to use these extinguishers due to their proximity to the fire. Fire extinguishers were sourced from mobile equipment to fight the fire. There was no water hose provided outside the locked magazine. The water hose inside the magazine could not be utilised when fighting the fire as the smoke had become too intense by the time the gate was unlocked. The area was force ventilated using a compressed air fan. The direction of the ventilation hampered attempts to put out the fire. Consequences Personnel involved in fighting the fire suffered from smoke inhalation. They did not don their self rescuers but were able to quickly reach fresh air in the main decline after their attempts to extinguish the fire failed. The fire and subsequent explosion caused significant damage to services, ventilation doors and machinery up to a kilometre away. Communications were lost underground as a result of damage to the leaky feeder during the explosion. Communications were re-established after half an hour using hand held line-of-sight two way radios, which were brought down the shaft. The location of the working party magazine and the siting of force ventilation fans serving an adjacent, blind incline development heading were such that a jumbo operator wearing a self-rescuer had to
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