• Greymouth-born Gerry Morris is a former coal-mining journalist and author.

The dramatic release of 13 hours of underground footage by the police relating to the Pike River tragedy is more sad raking of the tragedy's embers, instigated by a small minority of the 29 families.

Pike re-entry is a subject that has become highly charged on both sides of the argument, especially at political levels and across the country, with everyone seemingly having a view on a complex tragedy that has so many sad threads.

Nearly seven years on from November 19, 2010, global mining tragedies tell us emphatically the passage of time after an underground mining disaster markedly increases the complexity of victim recovery which in turn, decreases the probability of successful recovery.

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Every New Zealander wishes to see all victims of Pike returned to their families for a respectful burial. An abandoned underground mine is not morally acceptable as an eternal resting place for these 29 men.

It remains a sad fact that mining all over the world, in Australia, Europe, South Africa, the USA and China have underground mines as eternal tombs for victims of mine disasters. Strongman Number One mine near Greymouth is a tomb for two victims of the 1967 disaster that killed 19.

Some of the Pike victims' families commissioned an experts' report to support their case for re-entry and have lobbied hard to get this report accepted.

Prepared by United Kingdom coalmining experts, Dr David Creedy and Robert Stevenson, the report A method for safe reentry of Pike River Mine Drift, has been used to make the case for re-entry into the 2.3km stone access tunnel to the mine, known as the Drift.

The five-page UK report contrasts with the extensive bevy of reports commissioned by Pike's owner Solid Energy, using New Zealand underground mining experts, and published in their hundreds of pages on their website.

Solid Energy's work using extensive local knowledge, is perceived to be too conservative compared with the UK opinion. History repeats in a sense as on the day after the first explosion at Pike, on November 20, 2010, seven of the 13 New Zealand certificated underground mine managers were there ready to assist only to be sidelined by the government agencies.

Both sides partially agree, based on footage obtained by robots and borehole cameras, that structurally, the drift could be entered as it is likely to be in good condition for the first 2km, given the installed level of structural supports and roof bolts. Even after four explosions, it is likely to be intact.

From footage obtained from cameras inserted down boreholes near the in-bye end of the drift, damaged infrastructure from pipes and conveyor belts obstructing the roadway is seen up to 1m deep in places.

Compounding this is the methane rich, potentially explosive atmosphere in the drift that is the core problem for re-entry. The Pike Royal Commission identified the last working locations of the Pike 29 as beyond the drift, in the actual workings of the mine, beyond Spaghetti Junction, where a huge rockfall blocks access.

There is a belief that a group of miners were exiting the mine at the time of the first blast in an underground transporter, a Driftrunner, and maybe caught in the large rockfall at Spaghetti Junction, the point where the drift meets the mine workings.

One of the two survivors from Pike's first explosion, Daniel Rockhouse, was within 500m of Spaghetti Junction and it is this stretch of the drift where the speculation is focused. There is no advocacy from the majority of Pike families to go beyond this point and enter the actual mine workings.

In addition to the gas ignition risk that would be caused by activity at the top end of the drift, a similar danger is the geological structure where the coal seam intersects with the stone drift.

The Hawera fault lies near where the seam starts adjacent to a known fall at Spaghetti Junction. Given the increase in earthquakes across the South Island there is significant stress on the adjoining strata.

The mine has been on fire at various stages and any form of re-ignition arising from re-entry activity into the drift, can not be dismissed. The UK experts say the workings have been gas-filled, therefore oxygen free for four years, which removes spontaneous combustion concerns, a view not shared by New Zealand experts.

In any analysis of the risk of re-entry at Pike, history reminds us of the many rescue workers killed attempting recovery of coalmine disaster victims. In a Pike-sized mine at Crandall Canyon in Utah in 2007, six miners were killed in the mine and 10 days later, three rescue workers were killed attempting recovery. The six miners remain entombed.

Like Pike, the Crandall Canyon inquiry found the mine was destined to fail because the company made critical miscalculations, and again like Pike, the US Department of Labour was faulted for lax oversight of the mine and mismanaging the failed rescue attempt.

The re-entry of the drift at Pike is recognised in mining circles globally, as not straightforward. The UK experts' report commissioned by some of the Pike families, is full of unproven, hopeful assumptions.