Urban water safe, WDC says

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Oamaru people can drink water with confidence.
The Waitaki District Council says Oamaru’s urban water supply is perfectly safe and there is no chance of a repeat of the situation in Havelock North, where thousands of residents were hit by a gastro bug and E. coli was detected in the town’s water supply on August 12.
Following the outbreak in the Hawke’s Bay town, which led to more than 4000 people being struck down by the bug, the Waitaki District Council has produced a guide which ranks the safety of the district’s urban and rural water supplies.
It said Havelock North’s water supplies were sourced directly from a deep aquifer via a bore and were not treated before being reticulated to users.
Many water supplies, including the Oamaru supply, are chlorinated.
The council’s water guide said chlorination ensured some protection in the reticulation, so if water was contaminated after treatment at the source, about 30 minutes of contact time with chlorine disinfected the water adequately.
As a result, a “minimum level” of chlorine residue was maintained in drinking water.
Supplies considered by the council to be “very safe”, that were chlorinated and had “multiple barriers” such as filtration and ozone treatment, to ensure safety, were the Oamaru (including Enfield, Weston and Kakanui), Waihemo (including Palmerston, Goodwood and Dunback) and Duntroon supplies.
The Kurow and Lower Waitaki supplies, sourced from bores, were chlorinated and UV treated, and classed as “safe”, as was Otematata’s supply, which is UV treated and bank-filtered.
However, bank filtration, where water is filtered though a lake or river bank, did pose “some risk” of recontamination in the supply.
Supplies that posed “some safety risk” were the Hampden-Moeraki, Herbert-Waianakarua, Stoneburn and Omarama supplies, which were sourced through river intakes via a bore and were chlorinated.
The Hampden-Moeraki and Herbert-Waianakarua supplies are to be joined by pipe to the Oamaru supply as part of a council project. Upgrades of the Stoneburn and Omarama supplies are also planned.
Other supplies with some safety risk that were filtered and chlorinated were the Awamoko, Kauru Hill Tokarahi and Windsor supplies.
Supplies not safe to drink, not chlorinated and with permanent boil water notices in place are the Lake Ohau, Bushy Creek and Awamoko supplies.
Waitaki District Council assets group manager Neil Jorgensen said water supplies were tested regularly, depending on the size of the source, either daily or two times a week, in line with required New Zealand drinking water standards.
“At the Oamaru plant, there is continuous monitoring … If chlorine levels drop, we take action before unsafe levels are reached.
“We’re in quite a different situation to Havelock North because they were not treating their water … there are results that come back with E. coli in rural supplies from time to time. That’s when things are introduced like boil water notices.”
He said there was no risk of Oamaru’s water supplied being contaminated with E. coli, because of the level of treatment that took place.
The council regularly updates the status of water supplies through its website.