THE most recent tests show Katherine’s tap water remains below the maximum allowable limit for chemical contamination.
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Power and Water tests in February found the town’s tap water was 0.04 micrograms per litre of the worrying PFAS chemicals.
The chemicals have leached from the Tindal RAAF Base where they were used in firefighting foams a decade ago.
The new limit adopted nationally this week is now 0.07, down from 0.5.
A test of the town’s water in October last year remains the highest at 0.05.
Authorities say the town’s two bores, used at the water treatment plant, remain the biggest concern.
The February test found the bore water was 0.27, down from 0.331 in October, but still well above the safe level.
The contaminated bore water is used every day at the treatment plant to mix with Katherine River water, Power and Water say the average “mix” rate is 76 per cent river water to 24 per cent bore water.
The NT Health Department says Katherine drinking water remains safe to use.
Authorities are working with the Department of Defence to find a solution to the town’s complete reliance on bore water during very limited times of the year, often at the end of the dry season.
A Power and Water spokesman said “We can't say exactly when we may need to switch to 100 per cent bore water as it depends on the river water quality and supply infrastructure.
“Over recent years it has been necessary to switch to 100 per cent bore water on rare occasions.
“In the past nine years, 100 per cent bore water has been used on nine occasions,” the spokesman said.
“Historically, duration of use of 100 per cent bore water has been from a few hours up to a few days. For example, the most recent was in 2015 – from December 2-4.”
Power and Water said it is “conducting ongoing testing” for PFAS in the Katherine region
“Our testing is specific to the management of town drinking water and includes results from our production bores, at the intake from the river and from the reticulated tap water,” a spokesman said.
Health Department environmental health director Xavier Schobben said Katherine’s PFAS contamination levels are “not comparable” to other contaminated sites at Oakey and Williamtown.
Mr Schobben said other than warnings about crocodile safety it was still safe to swim in the Katherine River.
“However, being a natural water body, microbiological water quality will fluctuate in the river, so care should be taken to minimise ingestion of untreated river water while swimming,” he said.
He said it was safe to bathe in the town's treated water and even to still brush your teeth in it.
The NT Primary Industry Department’s director of biosecurity and animal welfare Michelle Rodan said the department has assessd the impacted area and found there was “little commercial horticulture or
cattle production” present.
There are currently no restrictions on domestic or international trade in agricultural products.
The department will be contacting Katherine residents with a Property Identification Code, indicating they keep livestock, to provide more information.
The Northern Territory will continue to work with University of Queensland’s National Centre for Environmental Toxicology (which leads studies in this area), along with our interstate counterparts and the Department of Defence to better understand the potential impact of PFAS in the environment as new information becomes available.