AUTHORITIES are still figuring out how to keep Katherine’s drinking water safe.
Chemical contamination levels have likely already spiked above the new federal maximum limits for PFAS, the family of chemicals which have leached from the Tindal RAAF Base into the town’s water supply.
Power and Water Corporation officials have released new testing results for Katherine which shows average results of 0.05 (micrograms per litre) for PFAS.
The new maximum allowable limit is 0.07.
The two bores which supply the Katherine water filtration plant returned average results of 0.14 and previous tests produced results of 0.33.
Power and Water now tests Katherine’s water weekly.
The NT Health Department says Katherine’s water is still safe to drink.
Katherine River supplies are used to mix with the bore water to drop the overall contamination level below 0.07.
Power and Water’s general manager for water services, John Pudney, said the issue of Katherine’s water supply was occupying a lot of the water authority’s time.
Laboratories can take 10 days to return test results so any “spiking” on one result would not lead to an immediate warning.
“It would only be for a short time and the PFAS limits are really about a whole of life exposure, not one result here or there.”
Mr Pudney said the authority was already operating the Katherine plant “differently” with chemical contamination in mind.
He said it may be possible to upgrade the Katherine plant given the contamination issue would last for many years.
But he said infrastructure fixes like reverse osmosis or activated carbon were expensive.
Historically, Katherine has been reliant on its bore supply for several days or sometimes several weeks of a year at the end of dry seasons when the river was low.
Normally, between 70 per cent to 90 per cent of its drinking water is sourced from the Katherine River and is blended it with groundwater from two production bores.
There may be times during the first rains of the wet season that bacteria levels peak in the Katherine River and it becomes highly turbid and reliance on bore water increases.
Mr Pudney said the authority was considering whether added treatment of the river water might solve the issue short term.
The authority might also top its storage tanks with treated water before the river cannot be used to make it through the short period.
The town could be placed on water restrictions during this period so treated “safe” water is not wasted on gardens and lawns and is reserved for household use.
Mr Pudney said restrictions would be a “worst case”.
“We are learning about this issue, residents and us,” Mr Pudney said.
“There is a lot of work going on behind the scenes on this, you can assure Katherine people of that.”