The NSW Environmental Protection Authority responded to community concerns last month following complaints of visible foam residue surrounding the Williamtown RAAF Base.
New testing results have shown a mystery foam residue in Moors Drain near Nelson Bay Road appears to have pulled the chemical perfluorooctane sulfonate (PFOS) from the water into the foam, creating a higher concentration of the chemical.
EPA Regional Director Adam Gilligan says the levels found aren't indicative of PFOS levels in the surrounding environment and no action is necessary at this stage, despite the levels being more than 1280 times the safe level for drinking water in the United States.
"The levels within the foam residue are quite high however it is a very small amount that's concentrated within that foam residue and we're expecting that to dissipate back into the environment."
The defence department will continue to monitor the area and Mr Gilligan says work on strategies to reduce contaminates leaving the base in surface water will also continue.
"What we've found is that water in that vicinity had levels that we would expect within the investigation area of around two micrograms per litre. However the foam residue itself had quite high levels, around 90 micrograms per litre. We're satisfied these levels don't reflect the overall levels in the environment in the area."
