Pike River mine re-entry will take months

Wednesday, 22 May 2019

The Pike River re-entry crew steps into the mine drift. (Video first published on May 21, 2019)

The Pike River re-entry team will spend the next six to eight weeks moving in 20-metre stages to rebuild the tunnel wall.

The Pike River Recovery Agency has started recovering the mine drift more than eight years after 29 men died in a series of explosions at the West Coast mine.

After removing the concrete wall located 30m from the entrance, the team will clear the tunnel of any debris to allow machinery to be moved further into the mine.

The re-entry team inside the Pike River mine drift on May 21, 2019.

Agency chief operating officer Dinghy Pattinson said the 'real work' began after the ceremonial opening of the doors witnessed by families on Tuesday.

The journey down the Pike River mine drift.

* Pike River re-entry finally a reality after eight-year battle

* A proud moment for the Pike River families

Pike River Recovery Agency chief operating officer Dinghy Pattinson, mine deputy Kirk Neilson and geotechnical engineer Chris Lee after they entered Pike River mine drift on Tuesday.

* Pike River re-entry team breaks through into mine drift

* Invercargill sister of Pike River mine victim pleased re-entry has begun

Pattinson says the real work to re-enter the mine is now beginning.

* Pike River widow 'full of nerves' for mine drift re-entry

The doors had been kept in an airlocked galvanised steel chamber behind a 88-centimetre thick concrete wall.

The team was able to breach the seal by cutting the concrete around the door until it was exposed and could be opened.

Prior to re-entry, methane was cleared from the mine by pumping nitrogen into the portal. A 1m hole was then cut into the seal to allow ventilation ducting to pass through.

The team will now spend up to eight weeks rebuilding the previous seal 170m down the drift, which Pattinson helped build in 2011.

It was built to help put out fires in the mine, but was left open when the entry seal was put in by Solid Energy in 2016.

'It's only built of lightweight concrete that was pumped in. We've got to bring it up to an engineered design that's fit for purpose even though it's only going to be there for six to eight weeks' Pattinson said.

The atmosphere will be monitored for a week before the rest of the 30m wall is removed so machinery like loaders can be driven into the tunnel.

'It will take up to eight weeks to do all that work between the two walls and we've still got a lot of planning to do to go beyond the 170 [metre point],' Pattinson said.

The mine will be ventilated up to the rockfall that blocked the mine workings at the end of the 2.3-kilometre tunnel, before the 170m seal is removed.

The area of most interest to investigators looking for what caused the 2010 explosions is known as Pit Bottom in Stone, which holds electrical equipment and is located 1.8km into the tunnel. It is also where Daniel Rockhouse was when he survived the blast of the first explosion.

'We will advance incrementally and do all our forensics in 20m stages – 20m at a time, then we will build a wall. That will allow us to forensically examine all the stuff that is … [there] and that will take some time,' Pattinson said.

The re-entry teams will then breach the temporary concrete wall beyond Pit Bottom in Stone and enter the last section of drift, which has been unexplored since the 2010 explosions. Robots had previously travelled up to the 1.4km point, where survivor Russell Smith's loader was left when he escaped the mine.

Pattinson said he expected the re-entry to be completed by the end of the year.

He has not ruled out having to use breathing apparatus as they approached the rockfall.

The re-entry team will bring out any equipment, including Smith and Rockhouse's loaders, and other forensic items they find. If any human remains are found in the final section of drift, the team will retreat and police will decide whether to send their own staff in to recover the remains.