The NSW EPA launched its investigation at the end of last year, when the Department of Industry, Land and Water raised concerns over Santos’ water use approval for irrigation activity.

“The EPA has examined the site and has found no environmental damage occurred or is likely to occur as a result of the irrigation,” an EPA spokesperson said.

“It is expected that the investigation will be finalised soon. Santos has stopped irrigation while the investigation is underway.”

A Santos spokesperson said the company had “all necessary approvals in place to irrigate at Leewood”, however it was working with the government to “clarify some administrative issues”.

The Leader asked Santos to explain what the administrative issues were, but received no response.

Labor MLC Daniel Mookhey, raised the investigation in parliament with Regional Water Minister Niall Blair, who took the question on notice.

“People in northwest NSW have every right to ask for the proactive release of this information,” Mr Mookhey said.

“It shouldn’t take a question in parliament or questions by the media to find out that the EPA has launched an investigation.

“With Liberal ministers openly campaigning from the floor of parliament for CSG mining in the Pilliga, the perception that they're withholding information about an EPA investigation is deeply worrying.”

NSW Greens resources spokesman Jeremy Buckingham said the community had a right to be concerned about what may happen if Santos is given approval for 850 gas wells.

“Again and again we see breaches of licences and pollution incidents when it comes to coal seam gas,” he said.

“Unfortunately the EPA has a record of being a toothless tiger, regularly making excuses for polluters or issuing only paltry fines that these big companies just see as a cost of doing business.

“When I visited the mature coal seam gas fields in Wyoming, USA, it was common to see salty water being irrigated onto fields – a practice they called ‘land farming’. Only salt tolerant weeds would grow, while the river banks were caked with a crust of white salt. We must avoid the US experience at all costs.

“Disposal of salt and waste water has always been a massive issue for coal seam gas and Santos have yet to outline a convincing solution – its intractable.”