David Reece, an expert in mine design and ventilation, was giving evidence at phase three of the Royal Commission inquiry into the Pike River mine tragedy, which is seeking to determine the likely causes of the explosion.
Reece was apart of an expert team working for the Department of Labour to help identify the possible cause of the explosion.
The commission heard Pike, due to its particular gassy nature had to be prudent in mitigating the build-up of gas in the mine, best done by the mine’s ventilation system.
However Reece said placing the mine’s ventilation system underground at the base of the mine in a “high hazard” area was a concern.
“It’s highly unusual” he said. “It’s certainly not something that I have come across and it’s not something that would be contemplated in this situation for an underground mine.”
Reece said it was very hard to protect an underground fan from an event such as an explosion, ultimately resulting in it not working.
“If you get a situation where you’ve had a fire or an explosion it’s still your primary means of controlling the atmosphere in the mine and giving people maximum chance of escape,” he said.
In his written submission, Reece came to the conclusion the ventilation system at Pike River was not satisfactory for the amount of mining activity taking place.
He said there were a number of reasons for arriving at this conclusion but a give away had been “simply reading the deputy’s report and seeing that they were struggling with ventilation.”
“It was really a case of having to cut back on the extent of operations to match the ventilation and the gas that they were struggling with,” he told the inquiry.
The commission heard the fan, which was only commissioned a month before the explosion, had immediately run into problems with power to the electric motor tripping as a result of ongoing faults with the liquid cooled.
Methane or gas drainage, another way in which the build up of gas can be mitigated, also came under criticism from Reece who said the gas drainage system at Pike River was under designed.
Reece said the drainage system was unreliable, often giving poor or inconsistent gas flow readings.
“The thing that particularly concerned us and was quite perplexing was the gas detectors in the main shaft itself and we found that there were initially two detectors in there and they were reading quite different numbers,” he said.
“It was concerning that that wasn’t resolved.”
Reece said the issue with methane detectors was that they could be “poisoned” by high levels of methane, resulting in them becoming unreliable.
He “suspected” the poisoning of methane detectors was happening at Pike River.
Reece said he had a “fundamental” problem with the Alimak raise, which was being used as a second means of exit from the mine.
To make the second egress safer, Reece said it needed a hoist.
“That’s where I would’ve gone and the reason I say that is because it’s a significant issue to climb out 105/110 metres of vertical shaft as it is, let alone under breathing apparatus,” he told the commission.
He said, ideally, this should have been done in 2009.
Yesterday the commission heard the deadly explosion at Pike River was more than likely caused by a significant roof collapse in the goaf of the mine, causing an accumulation of methane to come into contact with an ignition source.
Reece said it was originally thought that the ignition point could have been in a section of the mine known as the Spaghetti Junction.
However, Reece said the explosion was likely to have ignited further into the mine than the Spaghetti Junction because the two survivors wouldn’t have survived the 1700-2000 degrees Celsius temperature from the gas explosion.
“Had it been close to them, they simply wouldn't have survived,” Reece said.