A Department of Defence trial has removed 98 per cent of PFAS from almost 1500 tonnes of contaminated soil excavated from the Williamtown RAAF Base.
The soil was excavated in November 2019 and transported to RAAF Base Edinburgh outside Adelaide for treatment as part of a world-first soil treatment technology trail.
The soil treatment plant "washes" the contaminated soil in a solution which removes the PFAS. The concentrated PFAS is then destroyed at a licensed facility.
Defence confirmed this week that the trial had been an overwhelming success.
It also confirmed its latest research indicated that Lake Cochran at Williamtown is not a major source of PFAS.
However, the site does allow potentially contaminated surface water to mix with groundwater.
In response, a passive barrier treatment system has been installed at the lake to remove PFAS from surface water before and after it leaves the area.
The project's effectiveness will be assessed over the next 12 months.
"Passive technology treats water in-place rather than pumping it to and from a water treatment plant, allowing water to naturally flow to and from Lake Cochran," a spokeswoman said.
"The Lake Cochran water treatment plant, commissioned in 2017, was an interim measure to reduce the concentration of PFAS in water leaving the lake, while a long-term solution was developed and implemented."
Fullerton Cove resident Lindsay Clout questioned why the two significant developments had not been shared with the community.
He is among a number of red-zone residents who are calling the contamination zone's boundaries to be reviewed and potentially reduced.
"It would be nice if they (Defence) came and told us what's going on," Mr Clout said.
"I have had two clear (groundwater tests) at my property over the past three years."
Meanwhile Defence has agreed to pay for town water for red-zone residents for another 12 months.
The initial three-year initiative was introduced in 2018 to eliminate exposure to PFAS.
"This decision is intended to further assist residents in transitioning household expenses to include water consumption and moving to standard billing processes," the spokeswoman said.