Landholders learnt on Tuesday that NSW Energy Minister Matt Kean had signed off on the company's Authority to Survey for the proposed pipeline on January 13.

If built, the 413 kilometre pipeline would carve through hundreds of kilometres of agricultural and conservation land between the Narrabri gas project and Newcastle.

Mr Kean's sign-off, which he revealed during a radio interview, will allow Santos to conduct surveys and testing on affected properties even if landholders do not give consent.

The Hunter Gas Landholder Rights Alliance said more than 100 members between Muswellbrook and Maitland were determined to stop the project.

They include Anne McGowan and her husband John Arthur who stand to lose a section of their Reedy Creek property which they had earmarked for the expansion of their organic olive grove.

Ms McGowan said finding out about the decision to allow Santos to conduct survey via the media represented "total disrespect for landholders" by the state government.

"There are other landowners nearby who are worse off than us, but this pipeline will cut through the corner of our property. Because it has a corridor that is at least 30metres wide, it will take out the beautiful old trees that we had preserved there and we won't be able to farm on it in the future," she said.

The pipeline will also cross Reedy Creek at two points and go under the Hunter River.

"Those banks were flooded out, especially in the last flood. What's that going to do to the pipeline's stability," Ms McGowan said.

The government's green light for the survey work came weeks after farmers presented a petition opposing the pipeline signed by more than 200 landholders along the route.

While the survey work represents a major development in the project, Santos will need consent from the majority of landholders before the project is approved for construction.

It is estimated that the pipeline would not be built before 2025 at the earliest.

Mick Fetch said he would chain himself to the gates of his property to prevent Santos representatives entering his Rosebrook property, located on the outskirts of Maitland.

Mr Fetch has been advised that the pipeline may need to run through his property, even though the project did not appear on land title maps that he inspected prior to moving there in 2017.

"It will go across two dams and cut across our current access to the property," he said.

"It will basically mean we will be paying rates on a piece of land that we can't even use."

Mr Fetch said he was waiting to be contacted by Santos representatives.

"They were apparently talking to my neighbour across the road yesterday. They might want to talk to me directly but they will rue the day they tried. I have nothing to say to them and they won't be coming onto my place. I'll be chaining myself to the gate"

Lock the Gate Alliance national coordinator Carmel Flint said the state government's support of the Hunter Gas Pipeline and the Santos gasfield demonstrated an "utter lack of respect" for Traditional Owners and farmers.

"This coal seam gas project will blow NSW's greenhouse gas reduction targets and keep NSW at the whim of gas companies who have been fleecing Aussies with exorbitant prices," she said.

But Business NSW, has argued that the Narrabri gas project and the associated Hunter Gas Pipeline are needed to secure the state's gas supply.

"Without the Narrabri project coming on line, supply will just about disappear, costs will soar and businesses will be forced to close, meaning even more jobs will be lost in NSW," chief executive Stephen Cartwright said.

The Department of Planning and Environment said the decision to allow Santos to conduct survey work was made after consultation and a review of landholder submissions for the Hunter Gas Pipeline.

"The Hunter Gas Pipeline is expected to behave in a respectful and responsible manner, and use their rights of access... only as a last resort," a spokesperson said.

Santos said this week that the company would work with landholders to obtain access and compensation agreements before it applied for a pipeline licence.

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