Chemical analysis has identified the Cadia Hill goldmine as a potential source of some of the lead found in samples collected from nearby residential rainwater tanks in central west New South Wales, the mine’s management has said.
The NSW Environment Protection Authority has been investigating the goldmine – one of the largest in the world – since May, when it issued Newcrest’s Cadia Holdings Pty Ltd with a draft pollution prevention notice and a draft licence variation regarding its management of emissions of dust and other pollutants. It followed local residents, including children, reporting heavy metals in their blood and rainwater tanks.
Under the new licence conditions, Cadia Valley Operations was required to engage a qualified independent consultant to provide an interpretation report of the lead isotope sampling results from a community water tank testing project that the mine had conducted in March and April.
NSW Health also undertook independent testing of household water supplies and did not return any unsafe results. The EPA is currently conducting another round of water testing of both rain and bore water used at more than 60 properties. It also plans to take samples from creeks and dams.
Cadia Valley Operations general manager, Mick Dewar, told Guardian Australia that preliminary test results showed a “slight overlap” with the characterisation of the mine’s lead isotope and the lead found in samples collected from local residents’ rainwater tanks.
“We’ve got some preliminary [results] back and identified the samples that overlapped,” he said. “Out of an abundance of caution, we looked at that and said, let’s assume if it overlaps, it’s ours.”
Dewar said the overlapping lead isotopes were found in the samples with “the lowest lead concentrations” of all those where lead was present.
“The highest concentrations in the tanks actually set far off the Cadia characterisation,” he said, suggesting the lead in those tanks came from another source.
Dewar said the samples had been sent to the University of South Australia for lead isotopic fingerprinting, which is a tracing technique used to identify the possible sources of the lead.
The results were then sent to Prof Brian Gulson at Macquarie University, an expert on lead analysis. Gulson submitted his draft report to Cadia but the company is yet to release the results.
“We sent them 50 to 60 samples from the Cadia ore from all different sorts of areas, so they can characterise the lead from our ore,” he said. “Then we sent them the sediment samples and any water samples that returned lead as well.”
The samples used in the analysis were collected by independent testing laboratory ALS from 145 residences in the area earlier this year. Dewar said they collected water samples from kitchen taps and rainwater tanks, as well as sediment and “sludge” samples from the bottom of rainwater tanks.
Guardian Australia understands that three of the water samples taken from kitchen taps exceeded the level of lead listed in the NSW health guidelines. Dewar said they had “slightly more readings out of lead” in the samples collected from rainwater tanks but did not specify how many.
According to the mine’s latest licence conditions, Gulson’s report must be completed and submitted to the EPA by 14 July and published on the company website.
It comes as the NSW EPA announced late on Friday that it had received interim results from Cadia from the first round of dust emissions monitoring from the Vent Rise 8 outlet – the mine’s main vent, which is also known as the “crusher vent” because it extracts air from where the ore is crushed deep underground.
The head of the regulator characterised the preliminary test results from May as containing “completely unacceptable” levels of air pollution which failed to meet the clean air standards.
In June the EPA called on the mine to immediately comply with the Protection of the Environment Operations (Clean Air) regulations. Cadia has since made operational changes which it says are aimed at reducing the discharge of dust from the ventilation system serving the underground mine.
“The interim results appear to show that operational changes at the Cadia mine have reduced the discharge of total solid particle from underground operations through Vent Rise 8,” the EPA said in a statement this week.
“Cadia reported that the concentration of total solid particles at the time of testing on 28 June 2023 was below the requirements set in the Clean Air Regulation. The EPA is reviewing the data and is seeking further information from Cadia.”
The results only relate to the quantity of dust. A full chemical analysis, which will detail the makeup of the dust, will take a further 28 days.
Guardian Australia understands that Cadia did not submit the chemical analysis results for the dust samples taken from VR8 in May, when it was expelling between up to 570 milligrams a cubic metre of dust – more than 11 times the regulatory limit for air pollution. An earlier report, prepared by Ektimo for Newcrest in May 2022, found VR8 was emitting lead at a rate of 1.3 grams a minute.
Responding to questions from Guardian Australia about more recent chemical analysis results, Newcrest said that the latest report prepared by Ektimo, and submitted to the EPA on Wednesday 5 July, shows that Cadia is operating in compliance with clean air regulations, the Protection of the Environment Operations Act 1997 and its Environment Protection Licence.
“We submitted our latest results, they were taken on the 28th of June yesterday to the EPA,” Dewar said. “In terms of dust concentration, they were within compliance.”
The EPA said it has also requested that Cadia undertake further testing to confirm the impact of the operational changes made to reduce dust emissions and will await further emissions testing results over the coming weeks.
The next formal results from the emission test on 12 July will be due on 19 July, and the full metal report from testing on 28 June will be due on 26 July.
• This article was amended on 9 July 2023 to state that the water samples used in the chemical analysis were collected by ALS independent testing laboratory, not Cadia staff.
