Management 'deliberately ignored' gas build up in Pike River mine, investigation suggests
Wednesday, 6 October 2021
A police investigation into the Pike River tragedy has uncovered evidence of a build-up of gas in the mine in the months before the explosion – and that management knew and deliberately ignored it.
Bosses also failed to install monitoring equipment that could have warned of the dangers, and the system that was in place could have warned of the possibility of an explosion, but was not properly maintained.
The revelations were made by police in an update to families of those killed on the progress of their ongoing criminal investigation into the disaster that killed 29 men in 2010.
The investigation was reopened following the Government’s decision to recover the mine access tunnel, or drift, in a $50 million project that has been completed.
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The update to relatives, seen by Stuff, says the investigation has progressed with new and reassessed information, witnesses re-interviewed and a “vast quantity” of material recovered from the drift.
“It has become clear that gas content in the mine during October and November 2010 was high. There is evidence that management knew this and some evidence that they actively chose to ignore it,” it says.
“Furthermore, they either omitted or chose not to instal gas monitoring devices that would have warned them of the dangers with absolute clarity.”
The gas monitoring system it did have could have given sufficient warning that an explosion could happen, but it was not properly maintained or monitored, and its data was improperly interpreted.
The update says police and recovery teams found evidence of “significant explosive forces” around an area of the drift called Pit Bottom in Stone, which holds equipment that was damaged.
However, it said the damage was not believed to be caused in the first explosion because one of the survivors was in Pit Bottom in Stone.
The West Coast coal mine blew up for the second time on November 24, five days after the first explosion, and police ruled out any chance any of the 29 men inside were still alive.
Some relatives allege the second explosion was caused by a conveyor belt being turned on, but a police investigation in 2019 found no evidence of that.
The update says police have recovered two large pieces of the main fan that were blown 200 metres down the drift, one of which weighed more than a tonne.
They consulted experts who believed the first explosion happened further into the mine because one of the survivors was in Pit Bottom in Stone during the first explosion.
In order to find the location of the first explosion, police decided to drill up to six boreholes into the mine workings.
The update says two boreholes have already been drilled, but one missed its target. The other was drilled into an area of the mine known as the goaf, where mining was taking place.
A large quantity of methane expelled from a roof fall in the goaf was one of the possible causes of the explosion suggested by the Royal Commission in 2012.
The families’ update says a camera found no fire or heat damage in the goaf area.
Experts told police it was likely the second, third and fourth explosions happened in the area of the main fan, and the first explosion happened further into the mine, far enough away from the goaf for it to have survived relatively unaffected.
The next borehole would be drilled into the area of the main fan, which has been widely considered a possible ignition source for the explosion.
There are 12 staff working full-time on the Pike River investigation, as well as an expert panel and imaging staff.
The Pike River Recovery Agency is rehabilitating the area and winding down operations after it hands the mine site over to the Department of Conservation for inclusion in the Paparoa National Park.