Chemical experts have warned a Queensland council that a plan to dump millions of litres of PFAS-tainted water into the sea off the Sunshine Coast is "insanity".

Key points: The council's plan involves building a pipeline to funnel the contaminated water from the Sunshine Coast airport construction site into the ocean at Marcoola

The council's plan involves building a pipeline to funnel the contaminated water from the Sunshine Coast airport construction site into the ocean at Marcoola Chemical experts say there is no known way for PFAS to break down, meaning it would stay in the water and contaminate fish

Chemical experts say there is no known way for PFAS to break down, meaning it would stay in the water and contaminate fish The Sunshine Coast Council says it will not be releasing the water into the ocean if it is not safe to do so

The Sunshine Coast airport was inundated during heavy rainfall earlier this year, leaving more than 125 million litres of PFAS-contaminated water at the site.

PFAS is a potentially dangerous chemical found in firefighting foam.

The Sunshine Coast Council's proposed plan involves building a pipeline to funnel the contaminated water from the airport construction site and into the nearby ocean at Marcoola.

The pumping was due to begin this weekend, but the council said that had been pushed back while it waited for final approvals, and the commissioning of a water treatment plant at the site.

The plan to pump excess water has infuriated residents and has chemical experts worried.

Dr Mariann Lloyd-Smith, a chemical law expert and adviser to the National Toxic Network, said the notion of pumping PFAS-tainted water was "insanity".

Dr Lloyd-Smith said there was no known way for PFAS to break down, meaning it would stay in the water and contaminate fish.

"The idea that you would knowingly release diluted PFAS is naive," Dr Lloyd-Smith said.

The council's plan involves pumping water from the airport construction site into the ocean at Marcoola. ( ABC News: Tara Cassidy )

Council needs to 'screw their head on'

Concerned resident and lobby group member, Levi Allan, said a large part of the Sunshine Coast community was against council's proposal.

"Our community does not want toxic chemicals in our oceans," Mr Allan said.

"We've got two petitions that have accumulated 17,000 signatures of people who are against this already.

"I think they [Sunshine Coast Council] need to screw their head on and think about the people they're in place to look after."

When questioned if the lobby group had an alternative suggestion to dumping the contaminated water, Mr Allan said that was the council's responsibility.

"I think our council are meant to be the ones in there looking for alternative solutions to this, and if they need the community to do their jobs for them, then they shouldn't be in the position they're in," Mr Allan said.

Residents lobby group Levi Allan with Greens spokesman Daniel Bryar at Marcoola Beach. ( ABC News: Tara Cassidy )

'The best we can do'

The council said the estimated amount of PFAS in the water would not exceed 0.5 grams in 125 megalitres of water — the equivalent of one-tenth of a teaspoon in 50 Olympic-sized swimming pools.

Deputy Mayor Tim Dwyer said no water released from the site would pose any risk to the environment or the community, and the council was working closely with the state environmental regulators.

Cr Dwyer said dry weather had reduced the amount of water on the site, and that even if it was able to build the pipe, it might not need to be used.

"We're hoping we don't need to end up enacting that process but we need to put it in place in case it's required," he said.

"If the dry conditions continue, we might find we don't need to pump it out to the ocean."

The Sunshine Coast Council said it would not be releasing the water into the ocean if it was not safe to do so.

"The levels that have been tested and are required of us has us well below the requirement that the science tells us," Cr Dwyer said.

"That's the best we can do to tell you the truth — in some cases the water on the site is a better quality than water outside of the site."

The plan to pump excess water has infuriated residents and has worried chemical experts. ( ABC News: Tara Cassidy )

'We don't really have a major issue'

In August, when the council announced the water would be released, project director Ross Ullman said the concentration of PFAS was lower at the Sunshine Coast airport than at other airports.

"In relation to the very, very low PFAS concentration. — and we have to make very, very clear this is a very, very low concentration — at other airports around Australia they are more than a million times higher, so by comparison we don't really have a major issue," Mr Ullman said.

Mr Ullman also told a press conference in August the water had already been released gradually into the Maroochy river in smaller amounts, for months.

"We have been releasing into the Maroochy River — we have been releasing into the Maroochy River at very, very low levels of concentration, much lower than a number of other environmentally approved releases in south-east Queensland," he said.

Earlier this year, Councillor Jason O'Pray released a video of him drinking water from a drain he said contained contaminated water from the airport site.

"This is rain water, this is fresh water, this is clean water," he said between sips.

"It's safe for our environment, it's safe for our fish life — it's actually safe for the human touch and human consumption."

Construction site Sunshine Coast airport expansion near Marcoola Beach. ( ABC News: Tara Cassidy )

'Utter lack of transparency'

Greens spokesperson Daniel Bryar said he was not willing to take council's word the contaminated water would not do harm to the environment.

"One of the issues we have with this council is their complete and utter lack of transparency in a lot of things," Mr Bryar said.

Mr Bryar said so far council had failed to consult with residents and the scientific community about its decision.

"The best we've got is someone drinking the water saying it's okay — where's the science, where's the testing, where's the evidence?" Mr Bryar said.

With Sunshine Coast Council comparing the level of contamination to other airports like Brisbane, Mr Bryar said Australian standards were low.

"The science we have in Australia has been largely looked down upon by the international community and Australia has a very low level of concern for the chemicals in question," Mr Bryar said.

"In other developed nations there's a very high level of concern.

"The chemicals don't break down so that means when you release them into the environment, they stay in the environment for a very long time.

"Any amount of organic chemicals being released into the environment needs to be thoroughly tested."