Steady progress into the re-entry of Pike River mine has been made four weeks to the day since it began - and eight-and-a-half years since the mine was sealed off.
Twenty-nine men died in an explosion at the mine on the West Coast on November 19, 2010.
The first crucial junction in the re-entry effort has been safely reached, Pike River Recovery Agency CEO Dinghy Pattinson said, and a team of three men, led by Mr Pattinson, are currently at the 170-metre seal - "the target for the first stage," of re-entry.
Mr Pattinson told TVNZ1's Breakfast this morning, "When [the seal] was built in 2011, it was done by the mine's rescue in an environment that was full of methane and everyone had to wear breathing apparatus, so it wasn't done to an engineered design, so we've had to design from a firm in Australia of how we can bring that up to a fit-for-purpose design. We've achieved that. We've finished that last Friday."
The seal, which Mr Pattinson helped to create and place in the mine in 2011, is now safe and sound, meaning crews "can now start opening up a 30-metre wall and remove that completely."
Its removal will allow for their machinery and equipment to "get in and remove all the infrastructure between the two walls."
On the other side, Mr Pattinson said, was a note left there in 2011 vowing to return.
"It was left on behalf of New Zealand Mines Rescue and our Australian counterparts who helped us at the time of the explosion, and that note said we would be back and we’re on our way back.
"We've got back-to-back wall, and now we've just got to get beyond that wall."
Mr Pattison also revealed that the other side of the 170-metre wall is "mainly nitrogen – 98 per cent nitrogen, and less than two per cent oxygen."
"The idea of that wall is to keep that atmosphere away from us while we’re working up to the wall in that first 170 metres, and then, once we've got our plan finalised, we'll go through that 170-metre and start working our way up that tunnel."
He said the removal of the infrastructure is necessary in order to carry out ventilation trials "just to confirm our plan, how we're going to take the fresh air up the rest of the tunnel."
"Once we've proven that and we get our plan the go ahead to go further, we'll then bring fresh air up that tunnel so we have fresh air way up the tunnel in advance of us.
"Morale is high. The guys up in the mine site – all they ever wanted to do was get back into that tunnel, and now they're back in there.
"There is a long way to go yet and things are going well, and we've just got to keep that and safety is our number one priority, so if things take a little bit more time at times, then that’s just what it is."