Media release

Lower Waitaki Plains Aquifer bores update

Friday 19 October 2018

A water quality test conducted by Otago Regional Council on 18th September 2018 has shown elevated levels of E. coli in a bore feeding from the Lower Waitaki Aquifer.

The below map identifies the bore (bore reference J41/0317).

The results of that test determined elevated E.coli levels at 63 MPN / 100 ml. The recommended level for safe drinking water is that there should be less than 1 MPN / 100 ml. Results from faecal source tracking, showed a high probability the source is cattle (please note this does not exclude sheep). There was no human faecal source detected.

Letters have been sent containing a recommendation that Lower Waitaki Plains residents who source their drinking water from private bores, should assume their source water is contaminated unless they have effective disinfection in place. Residents should expect to receive them this week. The letter will also contain a previously shared brochure on how to protect their bore water.

The brochure is also available on the ORC website here:

The Otago Regional Council has increased its sampling from quarterly to monthly, with faecal source tracking built into the monitoring programme. The next water testing results from the Lower Waitaki Plains Aquifer are expected this week. This will show if the E. coli spike is still prevalent. If it is, it will be further tested for faecal source tracking to determine the source.

In the interim, Public South Health have been notified of the current results.

How long has this been a problem for?
E. coli concentrations exceeding 1 cfu/100ml (colony forming units) have been detected in some of the bores monitored by the ORC (SOE network) since 1999. Although ORC has been talking informally with the community about this for some time, it was determined recently that it was important to formally notify the community of the ongoing risk.

What is E. coli, and what are the potential effects of exposure?
E. coli is a subset of faecal coliforms (bacteria originating in the bowels of warm-blooded animals). E. coli indicate likelihood presence of pathogenic bacteria from the same source. Exposure can have serious and long-term effects and is especially dangerous for children, older persons and people with compromised health. Gastroenteritis symptoms usually develop within 12 to 18 hours and include severe abdominal cramping, vomiting, and diarrhoea.

How can I be sure of safe drinking water?
The only way to be certain of having safe drinking water from the lower Waitaki aquifer is to have drinking water treated. That means disinfection, using chlorination, UV, ozonation, boiling or filtration.

Dr Gavin Palmer - ORC Director Engineering, Hazards, Resource Science & CDEM
027 493 3960

Emma Schranz – ORC Senior Media Advisor - 027 627 5894