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Porgera Mine Explosives Explosion

On 2nd . August 1994, Dyno Wesfarmers Limited (DWL), Papua New Guinea (PNG), explosive manufacturing facility at the Porgera Gold Mine was totally destroyed by two explosions, with the loss of eleven lives. Extensive damage was done to nearby mine facilities and numerous mine employees suffered other injuries. Two out of thirteen DWL employees survived the first explosion because they were working inside storage containers at the time.

The mine is situated at an altitude 7700ft. in a remote and rugged part of the Enga Province of PNG, which produced 35,977 kg of gold from both open-cut and underground mining operations in 1993. The explosive facility consisted of  the following plant and equipment:

• sensitive manufacturing and packaging;
• non-electric detonators
• (Nonel) assembly and testing; ANFO and
• ANFOPs manufacturing;
• Bulk Emulsion manufacturing with delivery by a Triple T (TTT) bulk truck.

Main storage facilities were suitable for:

• 40 Containers of Ammonium Nitrate/ Sodium Nitrate;
• 20,000 l oxidising solution;
• 25,000 l fuel phase;
• 85,000 l of un-sensitised bulk emulsion in two tanks (some government agencies now class this substance as an explosive product of other than Class 1); and
• up to 10,000 l of fuel oil stored approximately 18 m from the fore-mentioned product storage tanks.

All finished explosive products, including Nonel detonators and elemented caps, were stored in underground magazines.

The first explosion occurred at about 09:45hrs on 2nd August 1994, at which time the following operations were taking place:

• manufacturing of ANFO,
• packaging of S.D. Emulite 100 (capsensitive) explosives,
• loading Ammonium Nitrate into the Bulk Explosives truck, and
• assembling of non-electric detonators.

Approximately 4,300 kg of explosives consisting of 120 x 25 kg bags of ANFO on the 4x4 canter truck, 25-30 kg ANFO in the Coxon Mixer, 1250 kg of cap-sensitive explosives in the Emulite 100 explosives production line and hopper, plus a small quantity of Emulite 100 explosives chubs 30x400mm in the cooling tray.

All fatalities are believed to have occurred in this first explosion, which destroyed the manufacturing plant, office and main plant shed. Fires on the bulk truck, around and underneath the bulk emulsion and process oil tanks subsequently led to the second explosion, just after 11:00 hrs. This explosion involved approximately 70-75t of emulsion matrix and between 10-15 t of emulsion and ammonium nitrate in the bulk truck.