Two fuel tanker fires decades ago and the Medlow Bath Rural Fire station have been pinpointed as the likely sources of PFAS or 'forever chemicals' in the Blue Mountains water supply.
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An investigation by WaterNSW concluded that a tanker accident in 1992 and another in 2002 near Medlow Bath township were treated with fire fighting foam containing the chemicals.
Analysis of samples taken from those areas show the chemical compound signature was "consistent with the historical use of aqueous fire fighting foam", the report concluded.
Such foam is no longer used. Fire and Rescue NSW and the Rural Fire Service began phasing it out in 2000 and fully discontinued its use by 2007.
The investigation into the contamination was sparked by findings last year of high levels of the chemicals, called PFAS, in Medlow and Greaves Creek dams at Medlow Bath. They are called forever chemicals because they do not break down in the environment. Exposure to PFAS has been linked to increased incidence of some cancers.
After the contamination was discovered, both dams were disconnected from the water supply from that area, which flows to the homes of more than 41,000 residents from Mt Victoria to Springwood.
In a statement issued with the report, just released, WaterNSW said: "Medlow Dam and Greaves Creek Dam ... will remain disconnected from the Blue Mountains water supply system. The dams will only be returned to the raw water supply network once WaterNSW is confident appropriate permanent mitigation measures are in place."
It added: "With these disconnections in place and according to the most recent monitoring results, NSW Health and Sydney Water have advised drinking water in the Blue Mountains meets the existing Australian drinking water guidelines and is safe to drink."
WaterNSW enlisted independent specialist advice in the investigation which included taking more than 250 samples from 37 different locations, including all accessible tributaries and streams within the watershed of the Great Western Highway.
"The findings indicate PFAS concentrations are higher in the upper Adams Creek catchment than further downstream in the Medlow/Greaves catchment. This suggests that any contamination may be moving downstream into the Medlow/Greaves catchment via rainfall and surface water runoff, and previous water transfers between dams," the statement said.
The findings of the investigation were reviewed by the NSW PFAS Technical Advisory Group and the Environmental Protection Authority (EPA).
The EPA has recommended that a detailed site investigation should now be undertaken consistent with the National Environment Protection Measure 1999. The WaterNSW investigation will help inform potential remediation options.
