Concerns have been raised about the expansion of a Queensland waste facility.

The facility, which is operated by We Kando Pty Ltd, has been approved to expand to store up to 15 million tonnes of waste from coal seam gas (CSG) operations.

The local Cameby Concerned Citizens Group has called on the Queensland Ombudsman to investigate the approval process, which local farmer Glenn Beasley says “never went to public comment”.

“Basically, in broad terms you are looking at something over 15 million tonnes of CSG waste of which 5 million tonnes is going to be salt.”

He said the proposed dump is situated near a creek that is a tributary of the Condamine River and connects to the Murray-Darling Basin.

This dump will be discharging directly into a sensitive receiving environment," Mr Beasley said.

The Western Downs Regional Council said the approval was consistent with legal advice.

“Council undertakes regular inspections of waste facilities to ensure compliance with town planning development approval conditions,” a spokesperson told the ABC.

Mr Beasley said locals did not believe the authorities.

“People around Chinchilla have absolutely no confidence in industry or government to regulate, monitor and enforce compliance,” he said.

“So when we have a toxic salt dump of this capacity going into the catchment of the Murray-Darling system, the alarm bells have to start ringing.”

Water researcher Dr Stuart Khan from UNSW said the difficulty with CSG water is the high concentration of salt, which does not break down.

“It doesn't matter how well you design it, the salt is there forever,” he said.

“So unless you are going to be maintaining that landfill forever — decades, century, longer — it is eventually going to fail.”

Professor Khan said the risk of water contamination during a big rain event was concerning.

“The skills exist within the industry to be able to design a landfill and operate a landfill with reasonable containment,” he said.

“Whether appropriate risk assessment is going on to properly identify things such as a big wet weather event and how that might be managed when it occurs, I've seen less evidence for.”