The science surrounding the impact of the controversial Shenhua coal mine in the Liverpool Plains district of New South Wales is far from settled, according to a ground water engineer.

"I don't think the project is risk free," University of New South Wales Water Research Laboratory's Doug Anderson told Landline.

"I like to think of ground water modelling as an impressionist painting.

"It looks really good at a distance, but when I get up close and look at it I see all the broad brush strokes and all the imperfections."

Chinese government-owned company Shenhua Watermark recently received conditional Federal Government approval to build a 10-million-tonnes-a-year coal mine in the Liverpool Plains district, about 300 kilometres north-west of Sydney.

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The mine would be restricted almost solely to ridge country, avoiding the highly productive black soil plains that are considered to be some of the best farming country in Australia.

A key point of controversy is how the mine will affect ground water supplies.

Shenhua argues its mine will take about 194 megalitres of water a year away from agriculture during the project's 30-year operation.

That translates to a reduced flow of less than half a per cent to registered bores within 10 kilometres of the mine.

But Mr Anderson, who was asked to peer review the water modelling by mine opponents, said it was difficult to make accurate predictions.

"There's always uncertainties in ground water modelling because the geology is always uncertain, so there always is some risk, " he said.

Doubts about the water modelling are being highlighted by mine opponents.

"To build a mine anywhere on the Liverpool Plains is completely insane," local farmer and head of the Caroona Coal Action Group Tim Duddy said.

"And if ever you were talking about an area where unacceptable risks were posed, this would be it."

Gunnedah businesses keen for mine to go ahead

But many businesses in the nearby township of Gunnedah want the mine to go ahead.

"Agriculture has been declining a fair bit in the past few years," deputy head of the local chamber of commerce and industry Peter Jones said.

Key facts: Shenhua's coal mine The open-cut coal project is valued at $1.2 billion

The open-cut coal project is valued at $1.2 billion 10 million tonnes of coal will be extracted a year

10 million tonnes of coal will be extracted a year The mine has a 30-year life, with extraction expected to end in 2046

The mine has a 30-year life, with extraction expected to end in 2046 159 million tonnes of coal will be mined over 30 years

159 million tonnes of coal will be mined over 30 years The project is 280km by rail from the Port of Newcastle, from where the coal will be exported

The project is 280km by rail from the Port of Newcastle, from where the coal will be exported Mining operations will run 24 hours a day, seven days a week

Mining operations will run 24 hours a day, seven days a week There will be five blast events a week once mining operations are established

There will be five blast events a week once mining operations are established The project is expected to employ 600 construction staff and another 400 to run the mine Source: NSW Planning and Environment and Shenhua Watermark

"[The mine] will give people confidence, it will bring developers into the area, and obviously there will be employment opportunities."

But Mr Jones agreed it was essential to get the science around ground water right.

"I think [businesses] are still keen to have a mine here, but they want to see it done properly."

Doug Anderson said it was essential to have more information about the history and present state of the aquifers before mining ever took place.

"Without that information, you end up in a circular argument — did the mine cause the impacts, or was it an agricultural pumping bore?"

That is exactly what is happening some 30 kilometres south of the proposed Shenhua site.

The coal mine at Werris Creek is pumping water out of its pit, while less than three kilometres away a bore on Bill Ryan's property has run dry.

"Since the mine started, it has slowly declined ... and now it's totally out of water," Mr Ryan said.

He lodged a complaint with NSW Water, which found no breach of the legislation.

In a statement to Landline, the Werris Creek Coal company said the likelihood of damage to the aquifer arising from mine blasting is "extremely remote".

A bore on Bill Ryan's property has run dry. ( Supplied )

"The onset of drought conditions in 2012, and rainfall recharge not keeping pace with groundwater extraction for surrounding uses not related to mining, are the major factors implicated in declining water levels," the company said.

The complaints by Bill Ryan and his neighbours have been taken up by Federal Agriculture Minister Barnaby Joyce, who has also described the Shenhua mine proposal as "ridiculous".

His Cabinet colleague and Environment Minister Greg Hunt said farmers could be assured the mine would be subject to the toughest environmental rules in Australia history.

"It is not unreasonable, it is entirely appropriate, it is a tougher standard than has previously been applied because I want to make sure there is absolute community confidence," Mr Hunt told the ABC.

The final stages of approval lie with the New South Wales Government.

Landline's story will be broadcast this Sunday at noon on ABC TV