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Pike River Recovery Agency chief executive Dave Gawn said they would start installing the emergency portal doors in the next couple of weeks.
Helicopters have been flying in the polythene pipe above the portal. The mine team then drags it into place to connect two 4.5km pipelines, which will be used to pump nitrogen into the top end of the mine.
''We're getting ready to start up the nitrogen plant before Christmas,'' Mr Gawn said.
The mine is about 96% methane and when methane mixes with fresh air, it is potentially explosive.
The plan is to vent the methane by opening the boreholes in the mine workings and at the far end of the drift tunnel. While doing this, nitrogen will be pumped in at the entrance to the drift, behind the sealed wall.
''We want to ensure we have a nitrogen inert atmosphere behind the 30m seal while we install the emergency doors, as it will require a small planned shutdown of the main fan which pushes fresh air into the portal.''
The mining team is training at the New Zealand Mines Rescue Service facility at Runanga and undertaking risk assessments for each stage of work.