The Upper Hunter community group behind the legal challenge to the extension of Mt Pleasant coal mine near Muswellbrook says it fears for local residents' health after a second court refused to stop the project.
The NSW Land and Environment Court on Monday upheld the Independent Planning Commission's 2022 approval of the 444 million tonne project.
It followed a Federal Court ruling in May that ruled federal environment minister Tanya Plibersec was not legally required to assess risk to the environment from the climate harm of the mine's expansion.
With the two court challenges lost, MACH Energy's Mount Pleasant Optimisation Project is set to become one of the largest open-cut projects in NSW.
Mining is expected to continue until 2048.
Denman, Aberdeen, Muswellbrook and Scone Healthy Environment Group treasurer Tony Lonergan said the result showed that both state and commonwealth environment laws were broken.
"The fact that you can approve a mine that is going to put out a bit more than three quarters of a billion tonnes of CO2 by the middle of the century just seems ridiculous," he said.
"Tanya Plibersek wasn't able to stop it on the federal laws so they are just as deficient as the state laws."
Mr Lonergan predicted that the community would ultimately suffer from increased respiratory illnesses associated with poor air quality.
"I don't see it as anything but a loss for the community," he said.
"The already poor air quality in Muswellbrook is going to be worse. You can't double production without increasing the amount of dust coming from the mine. There are already regular health alerts going out to people who have compromised respiratory systems."
In his judgement, Justice John Robson said there was "no doubt that the continuation of coal mining will contribute to the global total of greenhouse gas concentrations, which affects the climate system".
However, he said the jurisdiction of the court was "confined to ensuring that the commission" met statutory provisions that govern its "functions and relevant powers".
"It is not the function of this court to undertake merits review of the commission's findings. This is a fundamental principle that will be reiterated throughout this judgement," Justice Robson said.
Despite the legal loss, Mr Lonergan said the group would continue to fight against new coal mining approvals.
"We just have to stop approving these new projects," he said.
"We know coal is coming to an end and I think most of the coal miners do too, maybe not as soon as it needs to happen," he said.
"Mt Arthur is closing in six years and Mangoola won't be far behind.
"They (the coal industry) are just trying to drag it out to the detriment of everybody. Coal miner's kids are going to be impacted by the impact of climate change as much as anybody else's kids."
