TRACE AMOUNTS of the contaminants at the centre of the Williamtown scandal have been found in Grahamstown Dam, the region’s main drinking water supply.

Low levels of the chemicals have also been discovered for the first time in two additional pumping stations within the Tomago Sandbeds, on top of the three that have already been embargoed by Hunter Water.

However the organisation has downplayed the developments, stressing the concentrations are all well below the safe limits and pose no risk to human health.

It also denied any link between the presence of the chemicals in those locations and the contamination seeping into the water table from the nearby RAAF Base.

Six months worth of water quality monitoring reports obtained by the Newcastle Herald show that the chemicals perfluorooctane sulfonate (PFOS) and perfluorohexane sulfonate (PFHXS) were discovered in Grahamstown Dam in June, July and September.

The combined concentration detected on those occasions was .004, .004 and .008 micrograms per litre respectively. Earlier this year, Food Standards Australia and New Zealand set a safe level for the two chemicals combined in drinking water of .07 micrograms per litre.

Hunter Water’s other drinking water plants at Dungog, Anna Bay, Lemon Tree Passage and Gresford all returned nil detects. Over the six months, there was one detect at the Nelson Bay water treatment plant of .005 micrograms per litre.

But the Hunter Water spokesperson said the detects at Grahamstown dam were no cause for alarm.

“With PFAS chemicals being persistent in the environment and having a legacy of use in a range of products over decades, it’s expected to find trace level concentrations in the water supply.”

The spokesperson said the detects at Grahamstown were likely to be due to run-off from the urban area at Medowie, fed into the dam via a canal at Campvale. He said the region’s hydrology made it “impossible” for the contaminants to be travelling from the RAAF base.

“It would require water to literally flow uphill, even in wet conditions,” he said. “This fact is based on decades of modelling and backed up by regular testing.”

The Tomago Sandbeds were comprehensively tested in June, ahead of their potential use over summer.

Two pumping stations – numbers 8 and 14 – returned concentrations higher than in the dam but below safe limits, at .038 and .024 micrograms per litre respectively.

The Hunter Water spokesperson admitted the levels were “above what we tend to pick up throughout the network” and “warrant close monitoring into the future.”

But they were unrelated to the contamination at the base, he said. He suggested the contaminants at pumping station 8 could be due to Defence activities at Radar Hill, while at station 14 they were likely to be due to the proximity to the Salt Ash weapons testing range.

The sandbeds have not been used since 2015.

“Any decision to use water from any of the bores in the Tomago Sandbeds will be made in consultation with NSW Health and the Williamtown Expert Panel, and will follow stringent water quality tests,” the spokesperson said. “We regularly test all water supplied to our community. The results are available online and consistently show our water is safe.” 

Since the Tomago Sandbeds were last tested in 2015, advances mean smaller quanitites of the chemicals can now be detected.

“Hunter Water’s independent laboratory can detect PFAS at a concentration of .002 micrograms per litre. This is the equivalent of one tenth of an eye drop in an Olympic-sized swimming pool,” the spokesperson said.

Hunter Water also found a spike in the contaminants at its Farley wastewater treatment works, believed to be the result of unauthorized discharges by Rutherford company Truegain.