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Unsolved mystery: bacteria in Carterton’s water supply

News from LDR
Carterton’s E. coli readings are proving a mystery to water boffins. The on-off boil water notice has been in place since March 12, after low-level readings of the deadly bacteria. Carterton District Council [CDC] received two other positive readings over the summer. The most recent results have left experts baffled.

Unlike Martinborough, which suffered similar scares two years ago, Carterton’s network has been chlorinated for some time.

E. coli contamination in a reticulated, chlorinated water system was extremely rare, said CDC infrastructure, services, and regulatory manager Dave Gittings.

“There are many excited scientists around New Zealand who are looking into writing a paper on this,” Gittings told the council’s infrastructure committee today.

“This is one of the very few instances around New Zealand that you will find a reticulated system, with highly residual chlorine, that has an E. coli count in it. That is extremely unusual. They’re excited. I’m not so excited.”

Committee chair Russell Keys acknowledged the team’s work to try and get to the bottom of a situation that was “extremely frustrating for yourselves and for the residents”.

“Especially having been picked up for the third time.

“We’ve taken a responsible attitude. We’re going to have to do these notices for the safety of our community. And that’s going to be uppermost in our mind. We’ve got to make sure that no one in the community gets ill over this. If it was a simple thing that we could just track down, I’m sure we will have it done.”

Mayor Greg Lang said the council and experts were “doing the best that we can”.

“There’s very low level, and it’s a responsible approach that we’ve taken to deploy that. We understand it’s inconvenient for many members of the community, but the community’s health is number one.”

CDC would issue a further situation report on Friday.

News from CDC – April 6
The Carterton District Council is taking every action possible to investigate the cause and prevent reoccurrences of last week’s low-level E. coli reading in one of its water samples connected to the urban supply. The boil water notice will remain in effect until the Council is confident that this has been done.

This means Carterton residents and businesses connected to the town water supply are advised to keep boiling all water before being used for drinking, making baby formula, juice, ice, washing fruit and vegetables, other food preparation/cooking needs, or brushing teeth until further notice. While the risk to the community is extremely low, the Council asks that people remain vigilant with boiling water until they are advised otherwise.

The council has commissioned water experts Lutra to produce a high-level model of the town water supply to identify water movement across the reticulation supply. This will assist with trying to identify the cause of last week’s low-level E. coli reading. The Council has also taken the following actions since the first boil water notice was issued on 17 March:

Checked back flow preventers and known industrial connections.
Replaced any valving that has a potential for a fault.
Undertaken additional daily testing to try and isolate where the potential sources may be coming from.
Had external engineers check the water treatment plants.
Checked procedures for sampling by a laboratory expert.
Walked the Kaipaitangata main trunk line to visually identify any potential sources.
Had Leak Detection Services to check if there are any unknown leaks in the network.

A further update will be provided to the community by 5pm Friday. Please continue to boil water before use until the Council has advised otherwise.

At this stage, the Council has not received any official reports of illness associated with this event.

Boiling water before use is the best way to make water safe. The risk of getting sick from drinking the water is low but possible, especially for vulnerable people. Babies, young children, pregnant women, the elderly and people who have weakened immune systems are more at risk of illness. If you get diarrhoea, vomiting and/or a fever, get advice from your doctor or contact Healthline (0800 611 116).
How to boil water for drinking:

Boiling will kill all disease-causing organisms.

Bring water to a rolling boil (where bubbles appear in the centre and do not disappear when the water is stirred) for one minute or boil a full electric jug until it switches off

Cool water (do not use ice cubes to do this) and pour into clean container with a lid

Refrigerate until needed.

If you experience diarrhoea, vomiting and/or a fever, contact your doctor or Healthline (0800 611 116).

www.cdc.govt.nz/boilwaternotice

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