The Independent Planning Commission approved Boral's submission to expand the Dunmore sand mine in November 2020, allowing it to extract 1.35 million tonnes of sand from two new pits over three to four years.

The discovery of Aboriginal artefacts on the site stopped work, which led to the Illawarra Local Aboriginal Land Council lodging an application to stop the project under section nine of the Aboriginal and Torres Strait Islander Heritage Protection (ATSHIP) Act while the site was assessed.

In a letter to the land council outlining her decision, Ms Ley said she was satisfied that the area had been occupied by Aboriginal people in the past and there were "sites of moderate-high archaeological significance".

But that wasn't enough to get the application over the line.

"I am not satisfied that the area is a significant Aboriginal area, because I am not satisfied the area is of particular significance to Aboriginal people in accordance with Aboriginal tradition," Ms Ley wrote.

"As a consequence, I find it is not open to me to make a declaration to protect the specified area."

Illawarra Local Aboriginal Land Council CEO Paul Knight was unimpressed with the decision.

"It's a pretty disappointing position that's been put forward by the minister," Mr Knight said.

"It actually doesn't reflect the position that we put forward in terms of recognising the significance about landscape to Aboriginal people.

"The challenge that we have here is you've got a non-Aboriginal minister determining whether it's significant to Aboriginal people and that is flawed in itself."

He noted that went against the Dhawura Ngilan statement on Aboriginal heritage - which Ms Ley signed off on - that said Aboriginal people should actually be determining the importance of Aboriginal cultural heritage.

He added that it had been hard to "articulate the significance" of the site due to the land being in private ownership, which meant First Nations people had not been able to access the place for a long time.

Mr Knight said the fight wasn't over; the council had also lodged a second application under a different section of the ATSHIP Act, but which would have the same result of stopping activities on the site.