Council investigating Methven water colour

Residents connected to the Methven water supply are being encouraged to continue boiling their water, as Ashburton District Council investigates discolouration in the supply that has been detected today.

Council issued a precautionary boil water notice for the scheme on Tuesday 20 February due to high levels of turbidity (cloudiness) in the supply. Today, the water is presenting with a yellow discolouration, and Council Assets Manager Andrew Guthrie says this is being looked into.

“Although we aren’t yet certain of the cause, it is expected that it will relate to the recent heavy rainfall events in the catchment where the Methven water supply is sourced. We will provide more information when we know more, and in the meantime we’d urge residents to please continue boiling their drinking water, and any water used in food preparation or for hygiene purposes.”

The precautionary boil water notice was issued on Tuesday last week as the deluge from Cyclone Gita began increasing turbidity levels. Metservice reports that Methven received more than 100 millimetres of rain during the event.

“During periods of very heavy rain, turbidity of the source water increases to a level which reduces the effectiveness of the UV equipment that we use to treat the water. Since the end of last week, turbidity has returned to a lower level, however a colour is now evident and this is also affecting the UV system. We are unable to lift the notice until water has returned to normal.

“Boil water notices are necessary during these times because we cannot be certain that treatment equipment is fully effective. The Methven supply typically copes with some heavy rainfall events, however when the amount of rainfall reaches the levels we saw last week, that’s when turbidity levels may become a problem.

“The current treatment system design was based on a very stable water source that existed prior to the gallery upgrading. The treatment system is challenged by these very high rainfall events and we have been actively investigating options that will address this particular issue. However, it is extremely complex and we need to be sure that any further investment in equipment is going to do the job required.”

The Methven precautionary boil water notice will remain in place until further advised.​

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Page reviewed: 26 Feb 2018 4:56pm