The Newcastle Herald can reveal that the NSW Environment Protection Authority (EPA) has taken the decisive step of calling for industry proposals to clean up the abandoned industrial site.

News of the move comes just days after an EPA officer visiting the Maitland plant fell ill from breathing in fumes and a government official admitted ageing tanks at the site could 'fail at anytime'.

The clean-up plans follow a long-running investigation by the Newcastle Herald that revealed in 2018 that Truegain, also known as Australian Waste Oil Refineries, secretly pumped millions of litres of toxic waste into nearby creeks or dumped it on the ground over decades.

More than 40 former workers told how the company would routinely use its Rutherford plant and surrounding waterways as a dumping ground for waste collected from industrial yards, Williamtown RAAF base, airports, service stations, mines and car washes.

It's estimated the clean-up bill, to make the site suitable for future industrial use, will be well in excess of $10 million.

The abandoned refinery, notorious for flooding in heavy rain, contains dozens of ageing tanks containing toxic waste, a large underground storage tank contaminated with PFAS chemicals and a cracked concrete spill containment area.

Industry representatives have been asked to submit proposals on how to tackle the clean up of the site by Friday next week.

The next stage of the process would involve the government determining a budget and issuing a tender for the works.

According to information supplied last week to businesses scoping the works, the "tanks may fail at anytime".

"A risk assessment has been done for the site which showed access should be limited," the report reads. "Gantries are in poor condition and may collapse and tanks may fail at anytime."

According to the EPA, "rough calculations" indicate that a large tank rupture would cause the spill containment area at the site to overflow.

No budget has been set for the clean-up works and a request for funding is expected to go before cabinet in "due course".

"At the moment we are seeking ideas and not limiting ourselves," the EPA document reads. "We are looking to make the site stable and non-polluting. Ultimately, we want the site suitable for industrial zoning."

Police have been called to the trouble-plagued site 38 times since 2015, mainly for vandalism, and the EPA 29 times for spills and odour complaints.

Maitland MP Jenny Aitchison, who has been campaigning to have the site cleaned up for years, described the extent of the pollution as "astounding".

According to the EPA, most of the tanks and equipment on site were bought second-hand by the former owners of Truegain and then put together.

"Previous operations at the premises have left a legacy of contamination which must be cleaned-up to prevent pollution entering the surrounding environment," the document reads.

"The above-ground tanks contain waste oil/hydrocarbons mixtures and wastewater, contaminated with various substances including PFAS. Many of the tanks are in poor condition.

"The above-ground tanks are generally located within bunds, however there are tanker trailers and other tanks on the premises which are not bunded. The bunds are also in poor condition and are full of collected rainwater which has become polluted from leaks/spills in the bunds."

The Kyle St site includes a disused chemical laboratory and up to five million litres of wastewater contaminated with PFAS chemicals - at the heart of the Williamtown red zone environmental scandal - stored in tanks.

In November, the EPA launched debt recovery proceedings against former Truegain director and site owner Robert Pullinger in a bid recoup $1,178,940 it has spent cleaning up and managing wastewater to ensure there are no further leaks to nearby Stony Creek.

According to a consultant's report from 2018, it's estimated the cost of pumping out the tanks and spill containment area each year would be about $1 million.

An EPA warning to residents not to eat eggs, drink milk or consume meat from animals that have had access to Fishery or Wallis creeks - that run to the Hunter River - remains in place after PFAS chemicals, as high as 22 times the recommended drinking water guideline, were found in Stony Creek.

Despite assurances from the government that the site is contained, information provided as part of the request for clean-up proposals indicates otherwise.

"We don't known the status of the underground drains and tank," an EPA document reads.

"We know there is contamination in soil, but we don't know if the contamination is from the surface or an underground source."

The watchdog goes further to detail concerns about pollution during rain.

"When the underground wastewater tank exceeds its storage capacity polluted water collects on driveway areas and could ultimately discharge to an adjacent open storm water drain adjacent to the premises which connects with Stony Creek," it reads.

"There is also the potential for polluted water to seep into the ground through cracks and joins in the handstand surfaces."

Hunter Water disconnected Truegain from the sewage system in February 2016 after it was caught discharging PFAS chemicals and the company went into liquidation six months later.

Ms Aitchison said nothing has changed in more than five years since the plant shutdown.

"Successive government ministers have sat on their hands, with a known pollution PFAS timebomb ticking in our community, and done nothing to remediate the site," she said.

"I understand the polluter pays principle, but I am not willing to gamble the health and safety of my community.

"I want the government to guarantee that the site will be completely safe...it must be made permanently safe."

Environment Minister Matt Kean visited the site in June and slapped a prohibition order on the plant weeks later, describing what he saw at the property as "appalling".