Rio’s unit Coal & Allied has started an appeal against the NSW Land and Environment Court’s decision to overturn the 2012 Development Consent for the extension of the mine, disagreeing with residents of Bulga, near the Warkworth coal mine, that expansion of the mine will affect the community.

Rio Tinto Energy chief executive Harry Kenyon-Slaney said that it is unlikely the legal system can deliver an outcome in time to avoid affects on the production at the mine.

"We are committed to doing everything we can to avoid the loss of production and associated jobs for our workforce of 1300 people at Mount Thorley Warkworth mine and that is why we are proceeding with this appeal," Kenyon-Slaney added.

The Warkworth Extension is the continuation of operations at the mine, within the footprint of Coal & Allied’s existing mining tenements and on land owned by the company.

The NSW Department of Planning recommended approval and referred it to an independent Planning Assessment Commission, which conducted public hearings before approving the project on behalf of the NSW government in February 2012.