The mining company last month applied to modify development consent for the mine, by increasing the maximum height of a section of the northern emplacement by one metre, among other changes.

The plans are currently before the Department of Planning, Industry and Environment, with a dozen residents making a submission on the application.

Resident Libby Laird, a longstanding opponent of the mine, said in her submission that if that were signed off, the "massive soil hill" would tower over surrounding hills that are just 353 m tall. What is now the soil hill was just 300 metres tall before the mine, she said.

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She said allowing the heap to grow further would cause "unacceptable" dust and health impacts - "including silicosis potential concerns".

The mine already causes "unacceptable" pollution, she said.

"The air pollution assessment confirms lived experience that there are many recent exceedances of the 24-hour average limit for PM10 particle pollution at the four air pollution monitoring stations nearby," she said in a submission.

"On some days, the surrounding areas are experiencing average air quality where PM10 concentrations are several times the purported limit. This is unacceptable."

Roselyn Druce, another opponent, said the dirt pile would actually grow about 16m, despite being marked as one metre in the modification report, because the report said it could grow to "up to" 455m tall.

"It will take the best part of 100 years to grow a 'forest' on this overburden - if ever," her submission said.

"It is most likely that much of this 'hill' will end up downstream before any real vegetation can prevent rills and gullies forming."

A spokesperson for Whitehaven Coal said the company had consulted with a range of stakeholders including state government agencies, the local council and community among others.

"We will respond to all submissions received on the proposal, including through the formal Response to Submissions process and address all community feedback," the spokesperson said.

"Maules Creek's compliance with applicable air quality criteria is publicly available and this data set also illustrates the correlation between air quality at the mine and regional dust events."

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Half of the 12 submissions into the development application supported the proposal.

Residents also complained the modification would increase the size of the mine's void, which will remain forever once the mine has exhausted local coal resources.

Supporters of the modification, some of them current or former employees of the company, said the proposed modification would allow the mine to continue to operate and employ people for many more years.

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