The Pike River re-entry team steps through the double airlock doors at 10am today, watched by families of the 29 men who died in the 2010 tragedy.
In 2010 the West Coast coal mine exploded, killing 29 men whose bodies have never been recovered.
The Pike River Recovery Agency has completed its year-long preparations, including cutting through the mine drift's concrete seal and ventilating the access tunnel.
Today's entry attempt will be a low-key event for families after they requested privacy. It comes after an eight-year battle by families to gain re-entry to the drift after being told numerous times by the previous government that it was too dangerous.
The re-entry team will walk through a door on the other side of the concrete seal and spend a short amount of time examining the scene. Any evidence pointing to why the mine exploded will be handed to the police.
Bernie Monk - father of Michael, one of the miners who died in the Pike River mine and who for years acted as the families' spokesperson, said there was a still a lot of work required before actual re-entry into the drift would take place, and so far there had been no indication of exactly when that might be.
"They're taking the first wall down today and then there's a lot of work to get up to the next seal and then the actual re-entry into the drift will take place after that.
"It could be a couple of weeks before they get down to the next seal. I don't know about that, but that's my opinion."
He remained positive however, and said it was a big day for the families.
"We're all meeting at the gate, the families that can make it back ... there won't be the big contingent of the families that were there last time due to a lot of them got to work, got to travel huge distances - some come from overseas - so you know the people that are there will be representing them.
"It's pretty low key because I think everyone's hyped up ... media and people around New Zealand, they just want to do it, you know. And I think with the work that's got to be done to get everyone up there's an enormous job so just keeping it a family affair I can understand."
He said he had seen too many failed attempts to enter the mine to believe it would definitely happen this morning.
"We've been down this track before - we've nearly been there and it hasn't happened and unfortunately the other day when I know it was going to happen it didn't - so I'll believe everything when I see it happening today."
He said he was very confident it would be safe.
"Time's not in essence and safety is a priority so I know that they'll work from day to day gauging all of these elements before they go ahead."
Earlier this month the plan to re-enter the access tunnel was called off after high levels of oxygen were detected, making entering potentially unsafe.
The problem was identified as a tube for monitoring equipment that had been leaking into the area, and has since been fixed.