Advance rates depend on the class of rock being mined and with a range of conditions throughout the tunnel, rates will continue to vary, the company said.

In an effort to improve advance rates, mine contractor McConnell Dowell during January introduced a robotic arm shotcreting machine to support the roof more efficiently.

At April 23, the tunnel had advanced 641m of the total 2300m to the coal seam. Rock conditions at the Hawera Fault located at 2100m are expected to substantially improve and the company is anticipating improved progress rates beyond this point.

As of yesterday, linear progress of the tunnel was reduced as excavation focused on development of a loading position for a conveyor. Conveyor installation and operation is expected to increase efficiency of rock removal from the tunnel.

Access roads at the project are almost completed and site building has commenced with all other major contracts on schedule.