The application to double the mine's annual yield and extend its lifespan to 2048 was described as the biggest coal mine expansion plan, in terms of its greenhouse gas footprint and the amount of coal to be extracted, to come before the Independent Planning Commission (IPC) since it began in 2018.

While Hunter Valley residents battled rising floodwaters, which Prime Minister Anthony Albanese has linked to climate change, the issue of climate change was also raised early in the IPC hearing on Thursday.

Shortly after NSW Planning Department senior planning officer Steve O'Donoghue made his presentation, Commissioner Chris Fell AO asked whether climate change had been factored into mine's expansion plans. "Climate change has brought about quite a few changes to our weather and I wonder if these have been taken into account," Professor Fell asked.

Mr O'Donoghue outlined some ways in which climate change had been factored in, such as the impact on air quality of wind speed and direction, but said he needed to take the question on notice, "keeping in mind" that the mine was set to close in 2048, two years before the state's net zero emissions target of 2050.

Presenters included residents who have lived in the region for more than 30 years, as well as health professionals, and representatives of the equine industry.

Muswellbrook resident Beverley Atkinson told the IPC she was concerned about the future of young people who were attracted to work in the Hunter's coal mines without thinking ahead.

"Mines are ... poaching our school students before their dreams can evolve, and turning tradies, nurses, teachers, and waiters, none of them with truck licences, into stressed high-earners within weeks.

"They're even offering $10,000 to sign up. This leaves vacant essential jobs in the community and families uprooted. The Mt Pleasant mine expansion is just as poisonous to a healthy economy as it is to our beautiful valley, and the timeless gift of the Castle Rock Ridge. I ask the IPC to leave it intact ... and allow the mine to rehabilitate after 2026."