Te Kāhui Whakamana Rua Tekau mā Iwa – Pike River Recovery Agency, based in New Zealand, has hired a nitrogen (N2) plant from BOC to assist in the re-entry of the Pike River mine drift that took place in 2010.

The BOC New Zealand plant is made up of several containers of equipment, including compressors and other machinery. It is expected to be in use for about a year and will be shipped from its current location in Australia.

Chief Operating Officer Dinghy Pattinson, said, “This particular plant has been used in Greymouth before – both at Pike River and at Spring Creek. Part of the contract specifies that the company supplying the plant will also provide a back-up liquid N2 system, train our staff in operating the plant and back-up, and have technicians available should anything be amiss.”

The N2 plant works by taking filtered and compressed air which passes through a carbon filter leaving N2-enriched gas. The plant will be set up opposite the administration buildings at the mine site, and N2 fed into the portal 1.1km up the hill via a steel pipeline.

The plan for purging the mine of methane gas is to pump N2 into the mine drift via a pipe through the 30-metre seal, while at the same time drawing the methane out through existing boreholes above the mine, using a “venturi” – which Mr Pattinson describes as akin to a fan, without the blades.

Two plastic pipelines will also be laid up on the hill above the mine portal, to borehole 47 (about 3.5km), so N2can also be pumped into the top end of the mine.

Initially, the plant will be set-up so that tests can be run to ascertain if a stable environment can be achieved within the mine. It is expected to be up and running at the Pike River Mine site at the start of October.

The Pike River mine tragedy

At 3.44pm on Friday 19th November 2010 there was an underground explosion at the Pike River mine. Two men in the mine drift managed to escape. The twenty-nine men deeper in the mine are believed to have died immediately, or shortly afterwards.

There were three more explosions within the mine before it was sealed nine days later. There is currently no access to the mine. The remains of the twenty-nine men who lost their lives have not been recovered.

A Royal Commission conducted an inquiry into what happened at Pike River Mine in 2012. They found that a substantial volume of methane gas, which is found naturally in coal, accumulated within the explosive limits was the immediate cause of the first explosion. The source of the ignition of the initial explosion was not definitely determined but was assessed to be located in the middle of the mine workings.

The Pike River Recovery Agency is working in close partnership with the Pike River families and other key stakeholders to plan for decisions on the manned re-entry of the Pike River mine drift to:

  • Gather evidence to better understand what happened in 2010 with an eye to preventing future mining tragedies and promoting accountability for this mining tragedy;
  • Give the Pike River families and victims overdue closure and peace of mind; and
  • Recover remains where possible.