The construction materials giant has applied to modify its Dunmore development consent to expand the quarry by 8 hectares to enable the extraction of another 21 million tonnes of hard rock, plus another 8 million tonnes from digging further.

But the company has said it is likely approval from the Commonwealth will be needed because the Illawarra Zieria is regarded as a Matter of National Environmental Significance.

Read more: Vegetation clearing at Primbee halted until council-EPA meeting

Zieria granulata is a shrub that grows up to 6m high and is covered with small wart-like growths called glandular tubercles. Like the Boronia plant to which it is related, these tubercles give a strong aroma when crushed.

The Illawarra Zieria is found only in a small area from Wollongong to Nowra, primarily between Oak Flats and Toolijooa.

The NSW Office of Environment and Heritage lists Zieria granulata as threatened by land clearing for agriculture, quarrying, road construction and residential development.

Boral, which recently purchased a section of quarry land from the Rail Infrastructure Corporation, says the new section is easier to access than previous dig areas.

Its scoping report from November 2021 said the work would also disturb 7ha of an endangered ecological community identified as Melaleuca armillaris Tall Shrubland in the Sydney Basin Bioregion, but offsets would be calculated.

"A Biodiversity Development Assessment Report (BDAR) will be prepared to support the modification report," it states.

"Targeted spring survey work has commenced and additional survey work will be undertaken in early 2022 to inform the BDAR. Along with results analysis, BDAR reporting will also cover a final credit calculation for the proposed modifications offsetting requirements."

Boral will this year submit an updated modification plan and technical reports for exhibition, which will supersede the scoping report.