Summer weather slows Pike River work

File picture / Martin Hunter

Work to fully seal the ventilation shaft at the former Pike River Mine is nearing completion.

Sealing the shaft is an essential step in the $7.2 million project to allow exploration of the main entry tunnel, which no one has seen since the November 2010 explosion that killed 29 men trapped inside the mine.

The shaft needs to be sealed to fully stabilise the mine environment.

The bottom 40m to 50m - originally about 100m deep - is filled with rock from an earlier collapse. The remaining area being filled in this phase of the project is about 700 cubic metres in volume.

A tough resin layer has been placed over the area of collapsed rock and topped with a layer of concrete. An expanding foam material is now being placed, which will fill almost to the surface. A reinforced-concrete cap is the final part of this stage.

Solid Energy, which now owns the mine and is undertaking the work, said today the early part of summer had not been as favourable, which meant fewer work days on the vent shaft platform, an area which could only be reached by helicopter.

As well, challenges with the materials being used had made progress slower than had been hoped.

However, preparation for the next stage is well advanced.

Three drill holes will be cut, two into the area of the tunnel where a temporary expanding-foam seal will be placed and another into the lowest point of the former mine's main workings to allow water to be pumped out.

This is a safety measure, aimed at reducing the amount of water which might enter the tunnel above the temporary seal.

The project does not include entry into the actual mine workings beyond the rockfall.