The company has existing approval to extract the panels of 415 to 417, but is seeking to modify the subsidence management plan.

The key change is to reduce the panel widths by 54 metres to 260.9m wide, increasing the size of the associated pillars to improve stability.

The proposed variations were outcomes of earlier community and government consultation, which also led to a decision against extending panel 414 to avoid extraction underneath Sunnyside Swamp.

Given the soft roof of the Lithgow seam, Centennial said in its application that pillar extraction mining could be extremely hazardous, so could not be considered a safe alternative option to mining these coal reserves.

Centennial said the only other alternative would be sterilising the reserves, about 11.7 million tonnes of coal which impact production rates, jobs and the export potential from the resource.

The mine aims to install its longwall equipment into panel 415 in December.

The federal application was made to meet the requirements of the Environment Protection and Biodiversity Conservation Act.

Centennial is a subsidiary of Thai energy giant Banpu Minerals.