Last week thousands of community objectors were left dumbfounded when the Independent Planning Commission (IPC) announced that it had reached agreement with the proponent, Australian Pacific Coal (AQC), during a pre-trial conciliation conference.

Community representative, Kirsty O'Connell, of Friends of the Upper Hunter Inc, said: "This effectively meant that unless a third party applied to join the case, the company would receive its five year extension and the case would never see the light of day."

Australian Pacific Coal had proposed in 2018 to reopen the safety plagued Dartbrook underground mine near Aberdeen after 13 years in care and maintenance and three deaths at the site.

It advised investors via the Australian Stock Exchange that its objective was to use the underground mine to generate cashflow while it developed plans for an open cut mine at the site. AQC has never retracted that advice.

Last year, the IPC consented to the company changing its method of mining (to board and Pillar) and the coal transfer within its existing approval to December 2022 but refused its application for a five year extension to 2027. This year Australian Pacific Coal launched a merit appeal in the NSW Land and Environment Court against the IPC's determination.

As is usual, the parties participated in mandatory conciliation ahead of going to Court. As part of this process, AQC presented changes to its earlier proposal but in a shock result the IPC agreed to the 11th hour proposal from the company.

Ms O'Connell said the decision was a slap in the face for community.

"This proposal attracted more local community objections than any other coal mine modification in the State's history. We presented evidence from world leaders in social impact assessment and climate change while other groups including the HTBA and thee Upper Hunter Shire Councillors presented extensive expert evidence against the proposal. The NSW Government completely ignored all of that and through it's Independent Planning Commission, washed its hands of its duty of care and reached agreement with Australian Pacific Coal," she said.

"They were effectively saying 'we don't care about making the State's worst air quality even worse, we don't care how this impacts the health and livelihoods of local people, we don't care about increasing the mining-related water shortfall in the Hunter River and we're not interested in preserving the economic diversity of the Upper Hunter."

When asked whether the community conceded that at least it was given the opportunity to join the proceedings before the agreement was ratified, Ms O'Connell said:

"FOTUH and the wider community never dreamed that the Government would reach agreement on a proposal from a completely inexperienced proponent where significant technical issues had been raised by world leading experts," she said.

"It would have cost tens - if not hundreds - of thousands of dollars to join the case - not to mention a huge amount of time - all so that we could shoulder the Government's responsibility for them.

"We honestly thought that on balance, with such a weak proposal that was riddled with problems, that we could count on the IPC to do the right thing and take the matter through to the Land and Environment Court.

After the shock IPC announcement, the HTBA gave notification on Monday that it would seek permission to join the proceedings and requested a stay on the completion of the case. If they succeed, every aspect of the initial decision could be overturned, sending AQC back to the drawing board. If they fail, AQC's 11th hour proposal will be rubber-stamped without any thorough environmental scrutiny.

The matter will return to the NSW Land and Environment Court on Thursday where it is expected that the HTBA will need to outline each of the key elements of its case for the Court to consider whether it will allow HTBA to join the proceedings. Australian Pacific Coal is expected to fight the application.