After hearing local submissions, the hearing will move to the Sydney Land and Environment Court.

The Ironstone Community Action Group has instituted the proceedings, with the support of the Environmental Defenders Office (EDO).

Two solicitors acting on behalf of the action group have lodged an appeal as a 'merits appeal - class 1', as a result of widespread community objection by individuals and groups to a proposed extension of the Duralie coal mine, and to future mining operations in general.

The NSW Planning Department has approved Gloucester/Duralie Coal's mine extension until December 31 2021 and authorised the surrender of all conditions of consent, including the 'no direct river discharge' condition.

"One of our concerns is that Duralie Coal will directly discharge their dirty mine water waste into Mammy Johnsons River or indirectly discharge it into Coalshaft Creek or other creeks and gullies, called 'first flush protocol," Ironstone action group secretary Amanda Albury said.

"We believe this is extremely alarming for the health of water quality and fauna in the creek and river systems."

Coalshaft Creek flows directly to Mammy Johnsons River (a tributary of the Manning River), the Karuah River and Port Stephens-Great Lakes Marine Park.

Ms Albury said Duralie Coal in one of its many submissions over the last two-and-a-half years had listed heavy metals, diesel fuels and explosive residue possible in its discharged water.

"The Commonwealth government is also responsible for approving Duralie Coal and not protecting endangered, threatened and vulnerable species," Ms Albury said.

Protection of the habitat of giant barred frogs will be another of the issues to be raised in the court hearing, she said.

Other issues will include air pollution and dust emanating from blasting and mined areas, as well as the cumulative effect of mining on residents' health, effects on the tourism industry, agriculture and businesses.

Ms Albury has called for all concerned individuals, organisations and businesses to gather outside the court house in a show of support for the action. The case was to begin in Gloucester today but has been delayed until Thursday.