Pike River Inquiry Phase 3: Pike kept pushing on with production

Pike’s critical safety systems were under-designed, the Commission heard this week.

Fire coming from the vent shaft of the Pike River mine

Any remaining doubt that the Pike River mine was an accident waiting to happen ought to have been erased with this week’s evidence from Australian investigator David Reece, who described serious flaws in virtually every aspect of the mine’s design. Reece, who led the Department of Labour’s team of experts investigating the fatal 2010 explosion, cited a raft of warning signs that ought to have alerted the company – and the department itself – of grave risks to those who worked underground.

In the days before the November 19 explosion, mine deputies had reported methane readings of 3-5% on several occasions. On the day of the blast, of 3.5% was recorded in one area. Methane is explosive between 5 – 15%, and above 2% workers are required under the mining regulations to be withdrawn. It’s likely the high readings under-estimated the true levels because Pike’s sensors weren’t capable of measuring concentrations over 5%. Despite the evidence the mine was struggling to control methane levels, Pike kept pushing on with production, including the ramp up of its hydro-mining operation.

Reece’s team established that Pike’s much-vaunted “real time” gas monitoring system included a sensor that hadn’t been working for nearly two months before the explosion, another that wasn’t properly calibrated, and others that produced variable and inaccurate information. Moreover, Pike had not installed a tube bundle monitoring system – standard kit in other underground coal mines – which would have provided much more detailed information about gas levels, including methane concentrations up to 100%.

The ventilation system was inadequate to deal with Pike’s gassy coal, and the positioning of the most critical piece of equipment – the main ventilation fan – was flawed. The fan – commissioned only days before the explosion – was installed underground, which meant that if the mine lost power (as often happened), it would also lose ventilation. Also, because the motor was electrical, it would shut down automatically if gas levels spiked. The back-up fan, at the top of the ventilation shaft, had also been breaking down. Pike’s own consultant had recommended three weeks before the explosion that extra ventilation capacity was urgently needed, but the company kept mining.

Reece said Pike’s efforts to drain methane away from the coal face were inadequate, and its own consultant had strongly recommended that the capacity of the system be increased before mining continued. That didn’t happen. “Stoppings”, which help direct air flow around the mine, were flimsy and poorly constructed.  Stone dusting – used to control the risk of fire fuelled by coal dust – was judged to be inadequate by Pike’s consultants just days before the explosion. Pike’s geotechnical advisors had also urged the company to hold off on plans to increase by 50% the width of the area being hydro-mined until the implications for the mine’s roof stability were properly assessed. Pike went ahead and increased it anyway.

Reece’s team of experts say it may never be known for certain what caused the explosion of November 19, 2010, but they have come up with a series of possible scenarios. Their preferred explanation is that there was a roof collapse in the area that had been mined out by the hydro-monitor – known as the goaf – which sent a slug of accumulated methane down the mine, where it mixed with air to form an explosive concentration. It was then likely ignited by arcing electrical equipment. But Reece agreed that this chain of events – and the other possible scenarios – was “foreseeable and controllable” using existing underground coal-mining techniques.

The commission’s hearings are continuing until the end of next week.