Miners have reached the Roscil Plug, near the end of the drift, in the Pike River mine.
It is the Pike River Recovery Agency's final milestone for the year and was reached last night, 349 days after dismantling the 170m barrier.
On November 19, 2010, an explosion at the mine was reported about 3.44pm. Only two people walked out of the mine that day – 29 people were unaccounted for.
Chief operating officer Dinghy Pattinson said around 8pm yesterday, the afternoon shift reached the plug which was installed in early November 2019.
"We've now achieved another milestone, reaching the Rocsil Plug around 2244m up the Pike River Mine drift. This is as far as we go this year, as we close down for Christmas today and restart on Tuesday, 5 January, 2021."
The plug is 10.3m of expanding foam that was pumped down a borehole in late 2019.
It expanded to 35 times its original size to fill the entire width and height of the tunnel.
The plug kept oxygen out of the areas beyond – the last 8m of the drift (the main mine tunnel), roof fall (an area of tunnel that collapsed in following the explosion), and the mine workings (4.3km of tunnels where the coal was extracted – and where the remains of the 29 miners are expected to be).
Pattinson said next year will begin with some final forensic work around the plug area and the installation of a ventilation control device.
The device, VCD2, acts as a wall with an airlock and will be located approximately 2224m up the drift.
Once it is in place, fresh air will be able to be circulated right up to that point in the drift.
Then mine workers wearing long duration breathing apparatus will go through an airlock door in the wall, tunnel through the plug which is about 10m, and recover the last few metres to the roof fall.
They can then carry out the final forensic searches of the drift.
Following that will be the completion of the forensics search and recovery operations at the Pit, Bottom in Stone – a 600m network of tunnels off both sides of the main tunnel, which had previously been "roped off" as a potential crime scene.