CHB District council will have to file its second "transgression" report over drinking water standards in ten months, after the detection of E.coli at Takapau's water treatment plant — even though the result came from a "false sample".
On Monday last week, the council released a statement to notify residents that the "lowest reading of E.coli detectable" had been found at the Takapau plant on Friday, January 19.
However council also said both it and the Hawke's Bay District Health Board (HBDHB) were confident there was no E.coli present in the water, given the concentration levels of chlorine in Takapau's already treated water supply.
That confidence was backed up when samples taken on both the Sunday and Monday came back clear.
In accordance with new national Drinking Water Standards, council had to wait for three days of clear results before it could declare a return to "business as usual".
Council chief executive Monique Davidson said it appeared that the positive result came from a "false sample", which she said could have been caused by cross-contamination picked up at the site or in the laboratory.
She said the typical response would be to treat the water, but Takapau's water supply, like all of CHB, was treated to a "very high" standard through the use of chlorine and other measures.
"The fact that the water is chlorinated should be a cause for comfort [for residents]."
"The minimum requirement of chlorine concentration in potable water, as set out by the Drinking Water Standards, is 0.2 ppm (parts per million).
"At the time of sampling the chlorine concentration was 0.34ppm. at the treatment plant and 0.47ppm in the reticulation [system]."
Mrs Davidson said the HBDHB was satisfied that E.coli could not survive at those concentrations, but the incident would still be regarded as a transgression by the health board and treated as such, similar to when it had to issue a boil water notice to residents at Porangahau and Te Paerahi last March.
She said a "transgression report" about the Porangahau incident had been completed by council staff and a subsequent meeting had been held with the HBDHB, "which was satisfied that CHBDC had reacted in a responsible and satisfactory manner to ensure the safety of the potable drinking water supplies."
To protect against potential contamination of the district's water supplies, council will soon be contacting the owners of 148 properties in CHB telling them they need to spend at least $2000 each to install backflow preventers.
The testable devices stop the back flowing (syphoning) of water from a source back into council's water network.
Of those properties, council estimates that 20 will require larger commercial devices which cost around $2500, while the other 148 require smaller devices that cost around $2000.
Council has decided that property owners will foot the bill for installing the devices as well as an annual testing charge of $306, and pay to replace the devices at the end of their 30-year lifespan.
Mrs Davidson said the properties were spread across the district and included a number of farms, but the majority were commercial businesses.
"There is a potential risk of backflow contamination from a number of properties in the district and therefore council believes that this risk should be addressed."
"Whilst backflow prevention is not a new requirement, there is no doubt that following the Havelock North inquiry [into the 2016 gastro outbreak], there will certainly be a stronger focus on drinking water compliance requirements."
Council has yet to start contacting the property owners but Mrs Davidson wanted the work to start in the "near future".
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