Newcrest chief executive Greg Robinson said the project had been eight years in the making and expertise had been sought from as far as Chile.

“In designing and building the panel cave, we learned a lot from the Ridgeway block cave, so it was a nice starting point to have that,” he said.

“Each mine [Cadia Hill, Ridgeway and Cadia East] has demonstrated the ability of Newcrest, and in part the local people around Orange, to demonstrate that can-do Australian spirit to push the technical boundaries of mine development.”

Cadia East will be the largest metalliferous mine in Australia once it reaches its peak of 26 million tonnes a year.

Constructed 1.2 kilometres underground, panel cave one is already producing 10 million tonnes a year. 

Panel cave two is currently under construction and is expected to come online in March next year and $340 milllion will be spent to target commercial production in 2015.

Newcrest head of mining operations Geoff Dunstan said caves were created by pumping high-pressure water into the rock to create extra cracks.

The rock’s own weight crushes it to the size of a small car as it drops to the extraction level.

“[The surface has] been cleared in preparation for the cave coming through so we don’t get trees in the draw points,” Mr Dunstan said.

Front-end loaders then take the ore from the draw points to the underground crushers where it is reduced to the size of a football. 

The ore is then brought to the surface for further processing and transport.

Cadia Valley Operations general manager Tony McPaul said construction had been a challenge.

“Getting some of that equipment underground through 6.5 by 6 [metre] or a 5.5 by 6 [metre] decline was no mean feat in itself,” he said.

danielle.cetinski@fairfaxmedia.com.au