Santos' plans to treat and dispose of coal seam gas wastewater from its $2 billion project in northern NSW would pose a "significant environment risk" and face rejection, government agencies said.

The company has been told by the Division of Resources and Energy (DRE) to resubmit plans for the Leewood Produced Water and Beneficial Reuse Project "with the required information" by June 5 or the application "will be refused".

Santos has been told to resubmit plans for the Leewood Produced Water and Beneficial Reuse Project in northern NSW. Credit:Dean Sewell

Among the litany of demands, the NSW Environment Protection Authority wants to know what Santos plans to do with the expected 500,000 litres of brine produced daily from the Narrabri Gas Project, which had the potential to exhaust storage capacity after three years of the five-year venture.

"In the absence of a detailed commitment for the lawful disposal of brine, the EPA has concluded that this issue presents a significant environmental risk and is unable to support this proposal in its current form," the agency said.