“The changes respond to the economic challenges facing the Australian coal industry and Glencore’s revised production figures for the year, which will be reduced by 15 million tonnes,” Glencore said in a statement.

“Discussions between Thiess and their employees are ongoing.”

Mt Owen, situated in the Upper Hunter Valley, currently has about 400 workers. The mine produced 4.5 million tonnes of saleable coal in 2014.

A spokeswoman for Thiess declined to elaborate on how many jobs would be affected by the changes when asked by ICN.

Thiess’ involvement at Mt Owen Mine extends back to 1994 when it built the mine complex. It then assumed responsibility for all mining activities.

The mine processes up to 15Mtpa of ROM, of which 7.8Mtpa is mined by Thiess from the Mt Owen North Pit.

Mt Owen’s deposit is complex, comprising multiple seams of coal dipping up to 45 degrees, with mined thickness between 0.4 and 11m. Thiess also mines to a depth of 270m below the surface, with the challenge of minimising truck hours and maintaining ‘mass balance’ on site to ensure enough dump space for the overburden.

To overcome these complexities, its technical team created Dump Planner software. This allows the mine planning team to run a range of scenarios and develop a mine plan that increases plant hours and scheduling, and achieves mass balance.

In addition, the team has developed industry-leading specialised terrace mining and through-seam blasting techniques, leading to higher reserve recovery.

Last month Thiess said its mine rehabilitation achievements with Glencore at Mt Owen coal mine had received international recognition.

The delegates of the International Mining for Development Centre inspected mined areas nearly 20 years after they were rehabilitated.

IM4DC is a partnership between the Federal Government, the University of Western Australia and the University of Queensland and is designed to deliver best practice to developing nations as they build their mining industries.

UQ Director of UQ’s Centre for Mined Land Rehabilitation David Mulligan said Mt Owen represents best practice.

“Mt Owen is certainly a leader in rehabilitation for the coal industry and it has been for many years,” Mulligan said.