Investigations into the Tinwald bore, including a $50,000 options report, are being advanced by Ashburton District Council’s Three Waters Committee.
It follows recordings of higher-than desired levels of nitrate.
Committee chair Russell Ellis said via a statement that councillors were not comfortable with nitrate levels consistently over half the maximum allowable value (MAV) set by the Health New Zealand.
“Work is planned in the 2028-29 financial year but we would like that to happen earlier, given general community concerns about nitrate in drinking water.”
Health New Zealand has also begun a high level review of the MAV, which sits at 11.3mg/L, and will report to the water regulator Taumata Arowai by the end of the year.
Three Waters manager Ulrich Glasner said nitrate levels in the Tinwald bore were expected to reach the MAV in 3-5 years.
He said there was $1.129m in the 2028-29 budget for Tinwald bore nitrate management, and another $1.1m in the following years to investigate and add another bore for the Ashburton water supply.
Tinwald’s drinking water is mostly supplied from Ashburton, via a pipe under the existing State Highway 1 bridge, and another pipe will be added to the new second bridge; the Tinwald bore augments supply as required.
Glasner said the Tinwald bore work could be progressed separately or as part of the wider investigation into additional sources for the Ashburton network.
A recent report by consultants Aqualinc looked at deepening the Tinwald bore to about 200m to access a different layer of aquifer water, but it was uncertain how successful that would be, based on data from other bores in the area.
District councillors said they wanted to move faster on the Tinwald bore and asked for an issues and options report, that would form the basis of a workshop later in the year.
The report will study in depth issues that are present at the bore and seek to identify options that could address those issues.
Glasner said the cost of the report, which would be done by specialists, was about $50,000 and would be paid for by cost savings in water services contracts earlier this year.
