On one side the Brandy Hill Quarry in the NSW Hunter region wants to clear 52 hectares of bushland - which animal conservationists insist is prime koala habitat - to expand operations and increase its production to 1.5 million tonnes per year.

On the other side Landcare wants to create a wildlife corridor on part of Mr Gilmour's 12-hectare property to protect the national icon and its habitat, as well as other native animals.

The number of koalas that rely on the habitat the quarry land provides has put residents and the quarry at odds.

Quarry owner Hanson pointed to six-year-old survey results in its application, which found koalas and their droppings on the site, but there weren't many. A subsequent report said there would likely be a significant impact on the koala.

Frustrated residents dispute the count and say there are between 200 and 400 koalas in the area who rely on an extensive habitat, which includes the quarry land, to survive.

They have posted videos and photos on social media as evidence and there have been more than 30 sightings in recent weeks.

"How is it that Landcare knows this is an issue and wants to protect the habitat and yet the state government is happy to tick the approval box?," Mr Gilmour said.

"When are we going to start listening to the experts? Think of the koalas and the habitat we lost in the bushfires. Koalas need to eat the leaves on certain trees to survive."

The fate of the quarry expansion rests with Federal Environment Minister Sussan Ley and her department.

Residents want Ms Ley to have a current koala survey that's independent, and takes in the population in the area, before she makes a decision.

They have united through a Facebook page called 18 Days to Save Port Stephens koalas, and it has gained more than 1800 supporters in under two weeks.

"This hub of koalas like to move through a large territory and are very active and mobile," page founder Chantal Parslow Redman said.

A decision is expected on September 8.

Supporters protested outside the quarry on Sunday to voice their concerns, while others took to social media to have their say.

"There is a lot of conflicting information about the impact this expansion will have on the koala, and its habitat, and that needs to be cleared up. We need an updated, and independent report," Ms Parslow Redman said.

"A lot can change in six years, we need an accurate picture."

Quarry owner Hanson conducted a 2014 koala survey in August and November as part of the application process and followed that with a targeted koala habitat assessment and survey.

A 2019 report, which was requested by the NSW Department of Planning and Environment, cited December 2014 survey results and said the impact on the koala was "likely to be significant" at a local, state and national level and that "the clearing of 45.8 hectares of koala habitat will adversely affect habitat critical to the survival of the species".

The state government gave the project the green light - and fast-tracked it - not long after a NSW government inquiry, which was chaired by environmental activist and Greens MLC Cate Faehrmann, revealed the koala could be extinct by 2050 without urgent action.

Under a condition of consent, issued by the Independent Planning Commission, the quarry must use buffer lands to "screen the project from the surrounding residential areas and assist in maintaining vegetation and biodiversity values.