The contamination of the Katherine River downstream of the high level bridge was a shock to many people.
Precise results have not been released but the Monday meeting was told that results are above drinking water guidelines (0.07 micrograms per litre) and below recreation limits (0.7).
It remains safe for swimming but not safe for drinking.
The interim results released on Monday night will be followed by the draft results next month and the full results in April.
Interim results have showed the “plume” of PFAS chemicals is leaking from Tindal into the groundwater under Katherine and into the river.
Monday’s results confirmed what most local people believed, that the Tindal Aquifer empties approximately at the Hot Springs area.
Previous tests have found the hot springs safe to use (0.04).
Power and Water was at pains to say the river water it takes upstream at Donkey Camp for the town’s supplies is clear of this plume.
Its bores remain contaminated at about 0.2 but because of water restrictions and the hastily flown in treatment plant add-on, it has not used bore water for some time.
Power and Water is looking west of the river in the supposed safe zone for clean supplies.
All but three of 27 bore results from the west-side have been clear of PFAS.
Most notably was the bore result at the Katherine Civic Centre (0.2) which is still being investigated.
It was a deep bore near the river and so were the positive results.
The latest results summary show:
- PFAS is leaching to groundwater and spreading in runoff from the Fire Training Area and Fire Station at Tindal.
- PFAS is flowing in Tindal Creek and in groundwater to the Katherine River.
- PFAS has been detected in the Katherine River downstream of the Stuart Highway.
Better news for the district’s farmers was the 57 fruit and vegetable tests found “very occasional detectable PFAS”.
Eggs (39 tests) could be a problem if drinking bore water and fish (98 samples) bioaccumulate PFAS, particularly in their livers.
Test results on other animals are still to come.
The national “trigger value” for fish is 5.2 micrograms per kilogram based on a young child (2-6 yrs) eating 0.5 kg of fish per week.
“End of dry season results from Katherine River (under Stuart Hwy bridge and Galloping Jack’s) were above the trigger value,” defence consultants Coffeys said.
“Results suggest eating fish from Katherine River (at least downstream of Donkey Camp) should be minimised to reduce exposure.”
Questions from Monday night’s meeting which remain unanswered.
Are ongoing upgrade works at Tindal RAAF Base further disturbing contaminated soil which is leaching even more PFAS from the base?
Should modelling be done to estimate how much PFAS Katherine residents have been exposed to in their drinking water over the past two decades?
Fish need to be tested in the Daly River downstream of Katherine River because of potential impact on Territory economy?
Monday’s Defence presentation and summary can be found here.