Gnangara aquifer at risk from airfield’s toxic firefighting foam
14 August 2018
Perth’s most important water supply is at risk of contamination from toxic firefighting foam, according to Department of Defence documents.
A recently released Defence report on the use of per- and poly-fluoroalkyl (PFAS) substances used in firefighting foams at the Gingin satellite airfield found the toxic substances had contaminated a shallow aquifer within the boundaries of the airfield.
It also found contamination was slowly migrating in the groundwater, away from areas where the firefighting foam was used in training exercises.
“Further away from the central area of the site, significant dilution and dispersion of PFAS in groundwater is apparent, one exceedance of the investigation criteria was reported,” the report said.
The Gingin airfield sits above part of the Gnangara mound, which supplies almost half Perth’s water and is only 7.5km from two major bores used by the Water Corporation to draw water.
While the report says there is no evidence contamination has spread beyond the borders of the airfield, it recommends further studies to “consider the risk to the Gnangara underground water pollution control area from off-site migration of PFAS in groundwater”.
More studies were also needed to judge the potential impact of the presence of PFAS on the health of people who used the base.
“PFAS concentrations in the water supply to the site (derived from the central on-site abstraction bore) exceed the human health criteria for drinking water and recreational water use,” the study said.
The Defence Department played down the results of the study, saying it had found no evidence contamination had migrated beyond the boundaries of the airfield.
“Defence is working with the Western Australian Water Corporation to test their bores South-West of the Site boundary. These bores are outside the investigation area and the testing is being done as a precautionary measure,” the spokesperson said.
The State Government confirmed it was watching the situation closely but a spokeswoman for Water Minister Dave Kelly said there was no concern about a threat to Perth’s water sources.
She said initial sampling of Water Corporations nearest bores had found no sign of PFAS, but an ongoing monitoring program would be put in place.
“The report itself finds that the underlying Leederville aquifer (from which a portion of the public water supply is drawn) is not currently at risk,” she said.