Mining experts are gathered in Greymouth to look at the risks involved in the three re-entry options for the Pike River Mine, and 1 NEWS has explained the options using a 3D graphic.
The bodies of 29 men remain in the West Coast mine following an explosion on November 19 2010. Re-entry would allow experts to search for the bodies and gather evidence about the disaster.
The project is so unique the army have been called on to help with planning.
The graphic shows the lie of the land above the mine and two distinct areas of the mine underground.
The mine drift, or access tunnel, starts from the entrance to the mine and runs 2.29 kilometres to what's known as the workings.
The workings are where the coal was being extracted and were the last locations of the 29 miners. The workings area contains a network of more than four kilometres of tunnels.
The first re-entry option is going in through the current entrance as it is now, with no secondary exit.
The second is the same but with a large bore hole made to provide a means of escape.
The other option is to create a new two-metre by two-metre tunnel about 200 metres long from up on a hill, to connect with another area for ventilation and a second exit.
Safety is the biggest priority and the findings will be reviewed over the next month.
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