The water reservoirs in Martinborough, close to where low levels of E.coli have been detected. PHOTO/HAYLEY GASTMEIER
Chlorine decontamination carried out by council
Chlorine may blacken water
Martinborough’s water reservoirs were chlorinated on Monday after further tests for E.coli came back positive.
Water pipes in the surrounding area were also flushed out with the chemical in a bid to kill the bacteria.
About 70 affected properties, east of Todds Rd, were warned of “blue/black” water coming through their taps as a result of a chemical reaction between the chlorine and manganese, a mineral occurring naturally in Martinborough’s water.
South Wairarapa District Council has had a boil water notice in place since Friday, after routine tests found “low” levels of E.coli at sites near Martinborough School and the town’s water reservoirs.
Follow-up tests cleared the school site of the bacteria.
But council infrastructure and services group manager Mark Allingham said E.coli was detected again in samples taken near the reservoirs, off Hinakura Rd.
“Two came back with a low positive [E.coli] result and one was negative.
“That’s enough for us to confirm that there is an issue.”
The risk of getting sick from drinking the water is low but possible, so the chlorination went ahead after consultation with Regional Public Health, Allingham confirmed on Monday.
No E.coli has been detected in samples taken in the township, and a Wairarapa Hospital spokesperson confirmed there had been no reports of illness to date as a result of the contamination.
Council staff went door-to-door informing the affected residents of the plan to chlorinate, with the council saying in a statement to the Times-Age that the flushing would hopefully be a one-off.
Three clear samples over three consecutive days will be needed before the boil water notice can be lifted.
The council anticipates the notice will remain in place for at least two more days as further tests are carried out.
Many councils in New Zealand chlorinate their water supplies but SWDC does not because of the presence of manganese.
The “blue/black” reaction means the water is not aesthetically pleasing but is okay to drink.
Allingham said an option for the future was to remove the manganese so the water could be chlorinated.
He explained that Martinborough’s town water supply was collected in bores on land near the Ruamahunga River off New York St West.
It is sterilised through a UV disinfectant system before it is pushed through the township and up to the reservoirs.
Testing is carried out approximately every six days, with at least one sample taken from each of the sites at the reservoir, council office, primary school and an address on Ferry Rd.
Residents were told to run taps for 10 minutes after chlorination until water cleared.
The council had began talks with Wellington Water about becoming a shareholder of the organisation, which manages the water for five local authorities
A report to councillors in November last year stated that SWDC would be in a better position to respond to catastrophic events if it joined Wellington Water.
Allingham said Wellington Water had been working closely with the council over the past few days, offering help and resources.
The council says all drinking water in Martinborough must be boiled before being used for drinking, cooking, making up formula, juices, ice, washing fruits and vegetables, or brushing teeth.
Emergency water bladders, with multiple tap stations, will stay in place until the town water supply is confirmed clear.