Power and Water has asked drilling companies to look for clean water to supply Katherine.
A long-delayed tender for works to discover if new bores can be found to supply the town was launched this week.
The “Katherine - Katherine Alternative Water Source - Groundwater Investigations - Investigation Bore Drilling, Construction and Testing” has come more than a year after the town’s water was found to exceed health standards.
Health Minister Natasha Fyles famously held a press conference in Darwin on April 3, 2017 to outline a lowering in national limits for PFAS chemicals meant Katherine was at times in breach.
Two bores used to supply the Katherine water treatment plant along with the Katherine River remain well above health standards.
Those bores are no longer in use and the application of water restrictions and an emergency water treatment plant flown in from the US means the town’s drinking water is today well under those standards.
Dangerous chemicals which have leached into the Katherine water supply from firefighting foams used at Tindal RAAF Base between 1988 and 2004.
Previously the Federal allowable limit for the PFAS group of chemicals was 0.5 micrograms per litre, now it is 0.07.
The plant’s bores regularly produce results of 0.2 and some tests produced a result of 0.33.
At the time, bore water blended with river water was found to be 0.079 and tap water was found to be 0.05, perilously close to the new standard.
Authorities are now searching for “clean” bores on the north side of the Katherine River and evaluating a bigger treatment plant for Katherine which removes all the PFAS.
An added complication was a surprisingly high PFAS result found at the Katherine Town Council’s bore at the civic centre.
The tender closes on May 11.
The tender’s background documents state:
“For many years the town of Katherine been supplied with water from two sources; surface water extracted from Donkey Camp Weir on the Katherine River, and groundwater pumped from bores located within the Katherine water treatment and office complex on Drome Hill.
“Water testing in 2017 indicated that groundwater used to supply Katherine has been impacted by PFAS chemicals that are thought to have originated as a result of past firefighting activities on Tindal air base. The Department of Defence has commenced detailed environmental studies to better understand the magnitude of the problem.
“Selection of a preferred long term water supply strategy is still being determined. Demand management options are being implemented, and options for the treatment of existing PFAS impacted bore water are being considered. However the evaluation of alternative groundwater source option/s is also considered prudent, and is the major objective of this project.
“On the basis of a recently completed desktop feasibility assessment the most promising source would likely be new groundwater source, most likely from a new borefield to be established north of the Katherine River outside of the area potentially impacted by PFAS. This project seeks to undertake groundwater investigation works to evaluate the potential for the establishment of a new, alternative groundwater source north-west of the Katherine River.”
At least three test bores are to be drilled.