Wellington - Many people had hoped the spectacular rescue of Chilean miners last month and that of two Australians in 2006 after lengthy periods underground showed that it would be possible for 29 miners in New Zealand to survive after an explosion on Friday.
On Wednesday, with the miners trapped below ground in the Pike River mine on the South Island for six days, a second explosion shook the pit and officials said no one could have survived. They never had the same chance of survival as their colleagues.
The 33 Chileans were working in a copper mine. The Australians were mining gold at Beaconsfield, Tasmania. In both cases they were trapped by falling rocks as their mines collapsed and they did their jobs in an atmosphere of relatively clean air.
The New Zealanders, by contrast, worked a coal mine and they became victims of two explosions caused by poisonous gases released as an inevitable result of drilling for coal.
The only consolation for relatives as the nation joined them in mourning on Thursday was an expert's view that if the miners were not killed immediately by the first explosion, they probably succumbed peacefully to a creeping concentration of colourless, odourless carbon monoxide before Wednesday's second blast.
The blasts were caused by methane, which occurs naturally along coal seams, and reaches a potentially explosive level when it accounts for 5 to 15 per cent of the atmosphere.
The first tests taken after a 162-metre borehole broke through into the mine a few hours before Wednesday's explosion revealed a concentration of 95 per cent methane, high levels of carbon monoxide and little oxygen.
The cause of Friday's explosion - estimated to have produced a temperature of more than 1,200 degrees Celsius - remains a mystery as company chief executive Peter Whittall said that no drilling or other equipment had been used at the time.
Regular testing of air samples showed the volatile atmosphere did not dissipate and it is believed the second explosion was sparked by still-smouldering coal or the spontaneous combustion that can occur under such circumstances.
This volatility continues and is a major obstacle to recovering the men's bodies. Australian mine disaster expert David Cliff said rescuers would need to be sure of methane levels under 1 per cent over four to five hours of sampling before they could contemplate going in.
Whittall has pledged to try to recover the bodies, but experts warned it could take weeks or prove impossible to bring them out along the 2,2-kilometre long access tunnel that runs at a slight incline into the pit set in the hillside.
Groups of the men were known to be in three or four different locations in the mine. It is not known how much damage the second explosion caused to the tunnel, but it is believed the ventilation system designed to disperse gas is severely affected.
Whittall rejected claims during the week that the mine was unsafe and had long been plagued with methane problems. But he conceded it was “a quite complex geological environment that would always throw up challenges.”
A US expert, Davitt McAteer, who is investigating an explosion at a West Virginia mine in April which also killed 29 men, was quoted by Christchurch's The Press newspaper as saying, “There's no real excuse for accidents to happen.”
He said the technology existed to eliminate the threat from methane and dust. “The fact is, for whatever reason, we are not doing that.” - Sapa-dpa