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UV failure led to E.coli contamination

Emergency water bladders, on Cork St behind the Waihinga Centre, will stay in place until Martinborough’s water supply is confirmed clear. PHOTO/HAYLEY GASTMEIER

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It appears that a failure of the ultra violet system used to treat Martinborough’s water was the cause of the town’s E.coli contamination.

South Wairarapa District Council relies on the UV treatment to kill 99.9 per cent of bacteria entering the water network.

It treats water collected in bores on land near the Ruamahanga River off New York St West.

The treated water is then piped through the town, with reserves pushed up to the reservoirs off Hinakura Rd.

A boil water notice has been in effect for Martinborough for 12 days, after E.coli was first detected in a water test near the primary school and then in subsequent tests near the reservoirs.

A statement from the council said a “temporary malfunction” of the UV disinfection system was the most likely cause of this event.

This came after “a risk assessment of all the possible causes of contamination, [and] an in-depth review of past data”.

The council said it was carrying out work to fix the UV system to ensure it did not fail in future.

The council’s four reservoirs are being emptied, cleaned and disinfected with chlorine.

Tests at the site have been clear of E.coli since the reservoirs were flushed with chlorine on February 4.

“The next step is to flush the whole network with water.

“The timing of this, and what it means for residents, will be communicated later this week, however, it is likely that network flushing will cause some discolouration of the water.

“Residents may need to run taps until the water runs clear.”

Clear test results on three consecutive days are required before lifting the boil water notice will be considered by the council and Regional Public Health.

Mayor Viv Napier apologised to residents and businesses for the inconvenience.

“Now that we have an understanding the likely cause of contamination, we can have more confidence that we’re taking the right steps to prevent it from happening again.”

Safe drinking water is available from the emergency bladders that have been placed around the township.

The council has received comments from Martinborough residents that the water provided smelled “strongly of chlorine”.

This was because the water in the bladders came from the Masterton water supply, which is chlorinated.


  1. Complaints are important sources of information which help corporates and communities identify and solve problems. For example, Martinborough’s residents recently complained their drinking water tastes of chlorine. Water imported from Masterton to replace water supplies contaminated with E.coli a bacteria associated with dairy and sewage.

    The question which needs answering is why is the groundwater supply contaminated? Groundwater is generally the safest and most secure source of water. Contaminated groundwater, especially groundwater used for drinking water is a very, very serious problem.

    The recent Havelock groundwater contamination was one of most devastating cases in the OECD. Have we leaned nothing? Somebody, somewhere has knowingly, intentionally and willfully kept this information secret. I’m complaining.

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