The perils of Pike River re-entry from an expert

Guest Post

One of the unfortunate aspects of the recent NZ election has been the spectacle of politicians using the terrible and avoidable Pike River tragedy as a political football. NZ First and Labour could be accused of playing upon the emotions of the bereaved Pike River families in a disturbing fashion for political gain. A re-entry to the Pike River mine has been claimed as a “major policy” in the same statements announcing such policies as a rise in the minimum wage, free tertiary education for a year, immigration control and house building targets etc. etc.

Let’s take a look at some of the many risks which the Pike River re-entry “major policy” actually entails.   

Severe tunnel/excavation instability

When the disaster occurred in 2010 there were several major explosions over 4 days. The last explosion ignited the coal which generated very high temperatures within the mine workings and even damaged some of the steel above the workings. Mine workings are developed into a rock mass which has a 3 dimensional insitu stress field (pressure within the rock). When the tunnels are opened up the stress redistributes around the opening and “attempts” to break that rock so that it falls into the opening or closes the gap. Miners use a combination of rock bolting, steel supports, wood supports or filled packs of various sorts to prevent that process. The effects of the multiple blasts and extreme heat will have seriously damaged the support systems and made the rock around the workings very unstable. Conditions will have continued to deteriorate in the 7 years since the disaster and that will have been accentuated by the Hawera Fault which crosses the main access drift before the coal seam.  Here is a quote from the royal commission report on the disaster;

“Construction of the drift took much longer than anticipated, as did mine roadway development. Delays were caused by a downthrust between faults, called a graben, which created a zone of sandstone instead of coal, and the collapse of the bottom section of the ventilation shaft during construction. The collapse meant that a bypass had to be built to reconnect to the upper part of the shaft about 50m above pit bottom”

In other words – tricky rock conditions even before the blasts.

Methane/Coal dust explosion

Methane is explosive between 5% and 15% in air. It needs that mix and a source of ignition to set it off. Methane has been building up steadily in the workings over the last 7 years as it seeps out of the coal seam. Coal dust has also been accumulating in the same time frame. The problem might be that inadvertently introducing air back into the workings now (as the re-entry takes place) could rapidly return the methane mix to explosive with hot spots igniting it again. This will result in another massive explosion – it may be followed by an even more powerful coal dust explosion which would damage the roof even further. It would be like standing in a shotgun barrel (explosive forces take the path of least resistance) when the shot is taken. That is not a place to be at any time.

Four separate remote control robots which have entered the workings failed to return. They are designed for extreme conditions, they don’t have to breathe or keep a normal body temperature. This is also a terrible reality which must be considered when we wonder if there are any remains of the poor souls who are entombed in the mine through no fault of their own.

If a brave team of mine rescuers or other personnel die in an attempt to re-access Pike River, then who will be held accountable for their deaths? Would it be unfair to demand an answer to that question before the re-entry? The best thing for the Pike River mine is to declare it as a grave.

 

-Billy Bro


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As much at home writing editorials as being the subject of them, Cam has won awards, including the Canon Media Award for his work on the Len Brown/Bevan Chuang story. When he’s not creating the news, he tends to be in it, with protagonists using the courts, media and social media to deliver financial as well as death threats.

They say that news is something that someone, somewhere, wants kept quiet. Cam Slater doesn’t do quiet and, as a result, he is a polarising, controversial but highly effective journalist who takes no prisoners.

He is fearless in his pursuit of a story.

Love him or loathe him, you can’t ignore him.

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