NSW Environment Minister Matt Kean also told the same hearing on Tuesday that he wanted the federal government to take more responsibility for the pollution that it caused through the use of toxic firefighting foam at the RAAF base.

In response to questioning from Labor's Adam Searle, EPA executive director of regulatory operations Steve Beaman said it was not possible to put a "completion date" on the clean-up project.

"It will be difficult to put an absolute time on it. We have been very clear, both ourselves and Defence in terms of the timing of this. This is going to be a long-term issue," Mr Beaman said.

"The hydrology of the site is quite unusual being at sea level; there is quite a lot of interconnectedness between the groundwater and the surface water. That's why the primary work by Defence is to remove the hot spot areas, which they have done.

"What they have also done is build the four water treatment plants - Defence is controlling the level of contamination on the base - that's why it's called the ongoing monitoring program. We need to see what effect those have and if they are not having the effect we are after we will keep pursuing Defence to do more."

Mr Beaman said testing of aquatic biota had shown a decrease in PFAS contamination between 2016 and 2020.

"We are starting to see those measures work but they will take time," he said.

Mr Kean said while the EPA had a key role in protecting the community, he believed the federal government should take more responsibility for the clean up.

"They caused the mess. They are the ones sitting on their hands. They should step in and help us help the community," he said.

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He took on notice questions about how much the state and federal governments had spent on the clean-up.

A hearing held as part of last year's class action against the federal government heard many properties in the red zone had lost 20 per cent of their value in the past five years.

While the $86 million settlement provided some compensation to property owners, the pollution legacy meant banks would not lend for projects in the area.

The federal government said at the time that it had spent more than $130 million nationally and treated more than 1.2 billion litres of water by removing the PFAS from firefighting foam and releasing the clean water back into the environment.

Port Stephens MP Kate Washington said the state government had done "appallingly little" to support the residents of Williamtown, Salt Ash and Fullerton Cove to rid their properties and lives of PFAS pollution.

"The NSW EPA is meant to protect people and the environment from pollution. And yet the PFAS-contaminated drains remain untouched and there are no plans to remove or reduce the red zone which is limiting people's lives," she said.

"Despite meeting with affected residents more than a year ago, the minister hasn't acted on their pleas for help.

"Sadly, the revelations from budget estimates today show there's no light at the end of the tunnel for families living in the red zone.

"It's not good enough for the minister to say he might speak to the federal minister for Defence. The time for talk is long passed, residents need meaningful action."

The state government introduced a ban on PFAS foams for firefighting training this week. Further restrictions on their use in fire extinguishers is set to take effect in 18 months' time.

Mr Kean said the new regulations would significantly reduce environmental impacts while allowing emergency agencies to use the products in defined "catastrophic" or "special" situations. "Firefighting foam is the key cause of PFAS contamination in the NSW environment with concentrations detected at airports, Defence sites, emergency service facilities, training facilities, major hazard facilities, and their surrounding environments," he said.

"This ban on PFAS firefighting foam will significantly reduce the impact on our environment but still enable our emergency agencies to fight catastrophic fires that can have devastating impacts on life and property."