Pike River mine re-entry options

Photoshopped image credit: Pixy

Andrew Little has received the report from the Pike River Recovery Agency [PRRA] laying out the three options for the Pike River mine re-entry that we first heard about last June. Quote.

The Agency has identified three safe and feasible re-entry options to recover the drift:?

  • Drive a small tunnel to create a ventilation circuit;
  • Single entry, using the existing main drift access tunnel as the sole means to ventilate the main drift;
  • Single entry with a large diameter borehole.

“I am satisfied that the Agency has been robust in developing the options,” Little said.

Workshops have included technical experts, and partners including New Zealand Police, Mines Rescue, WorkSafe and the Department of Conservation.

The Pike River Families and their representatives have been also included at every stage. The families have shown extraordinary patience and tenacity, and their contribution has been crucial.” End of quote.

Lack of adequate ventilation was a major contributing factor to the 2010 explosions and is obviously the biggest consideration in all three options on the table.?

Pike River Mine Image credit NewstalkZB

The Agency took longer than expected to finalise their report. ?Reducing the costs associated with working in difficult terrain was challenging. It took them longer than expected and, given the large army of experts with differing opinions, added to the time taken to sort through the alternatives.

Former Chief Mines Inspector Tony Forster commented on the Agency’s preferred recommendation for re-entry when he discussed their three options at a mining workshop last June. Quote.

?What I?ve seen is a very robust process,? he said of the PRRA recommendation. ?I?d be the first to tell the families the process was flawed and there were fatal risks involved in this project, and it?s far from that. This is an example of?new thinking that has been brought to the table.?

The tunnel is predicted to be around 2m-wide, and will provide a?new means of entry to and exit from the mine,?which would otherwise consist of the single vertical shaft that was damaged in the explosion.??

The government is considering another two options, one of which involves creating a short drift to establish a second entry point to the mine.??End of quote.

Forster favours the tunnel option for safety reasons. The tunnel is probably the most expensive option but it does provide the security of a second means of escape which is standard mining practice.

Of the other two options, using the existing main drift access tunnel would be the cheapest.? This could be done relatively safely by first sending in a robot with a camera and then controlling the gas in the mine by injecting nitrogen, but this option lacks that all-important second exit.

The third option of using a large diameter borehole may be cheaper than the tunnel.? But this option is a bit like playing Russian roulette with the ground conditions; good ground conditions would mean easy going and controlled costs but encountering difficult ground conditions would slow the project down and easily blow the budget.

Little says there will be a cost blowout on his previous estimates.?Whaleoil?previously indicated re-entry cost estimates could be in the region of triple the original $23 million budget.??Quote.

“Little told Newshub Nation at the weekend that re-entry would “almost certainly” require more funding, which he would seek from Cabinet.

Up to $23 million has been budgeted over three years.

“Once I have the agency’s report … my independent ministerial adviser’s report, and the decision from Cabinet on the funding, then I’ll make a decision. That’ll be mid-November,” Little told Newshub.” End of quote.

It seems full speed ahead, but already both the original cost estimate and the timeline have been blown out of the water.? Little has admitted that he will need more money and a December re-entry looks highly unlikely.


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