The NSW Department of Planning, Industry and Environment had recommended the project be approved, saying its environmental effects were acceptable.

But those opposed to the expansion - 5000 people signed a petition - have vowed not to be bowed. Both Kiama and Shellharbour councils oppose the plan and Shellharbour Mayor Marianne Saliba said people could register to have their say at the IPC meeting.

"I know this issue has generated interest in our community," Cr Saliba said. "This is an opportunity for people to share their thoughts directly with the commissioners who will be making the determination on this application."

Read more: 5000 residents draw a line in the sand at Minnamurra

Registrations close on October 21.

Independent MLC Justin Field said the community had supported Boral's existing operations at Dunmore - "but this expansion goes too far and they have got the community offside".

"Sand mining right alongside the Minnamurra River and clearing critically endangered vegetation is totally unacceptable," he said. "It's an environmental risk and will have a negative impact on the amenity of this beautiful area.

"This campaign has brought together everyone who cares about the river including environmentalists, fishers, members of the local communities, and regular visitors but Boral have just rejected community concerns out of hand."

Both councils were concerned about clearing native vegetation, as well as the potential impact on the Minnamurra River and the wetlands to the east of the site.

Public submissions had also raised fears of damage to the Minnamurra River, a popular recreation spot, and the effects of land clearing.

The Planning Department's report said Boral's proposal involved clearing 4.5ha of Bangalay Sand Forest, which is a listed endangered ecological community (EEC) under the Biodiversity Conservation Act 2016. But it said this was only a "very small proportion" of the EEC.

Boral already had consent permission to extract 800,000 tonnes of sand until 2030 - about 7.5 per cent of the Sydney industry's construction needs - but Boral said it needs more.

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