Most of Marlborough’s drinking water is safe to drink.

The Blenheim supply, which delivers water to 10,700 households, is protozoa compliant with UV treatment in place to ensure cryptosporidium and giardia doesn’t enter supplies. Picton and Seddon’s water supply to 1,775 and 210 households respectively are also compliant.

Taumata Arowai, New Zealand’s water regulator, has written to 27 councils around the country, including Marlborough, outlining the Water Services Act 2021 which states suppliers must use a multi-barrier approach to managing risks to protect drinking water from contamination.

Head of Regulatory Steve Taylor said Taumata Arowai expected protozoa barriers to be in place by the end of 2024 for surface water sources and the following year for bore water.

Currently Blenheim’s water supply is protected with ultraviolet light disinfection Council’s Operations and Maintenance Engineer Stephen Rooney said. This means all households supplied from the Blenheim supply are protected from protozoa and bacteriological contamination.

Water supplies in Marlborough at risk include rural households in the Awatere Valley, Havelock, Renwick and Riverlands Industrial Estate, affecting about 4750 people.

Seddon already has a compliant treatment plant and Wairau Valley’s just completed water treatment plant, which cost $2.6m, is delivering compliant water to the community as it goes through a commissioning phase.

Ultra filtration systems and UV filters were installed in the Wairau Valley treatment plant – the same as are being installed in the new Renwick plant, which has cost about $8.7m and due for completion next year.

The Renwick plant will have membrane filtration to provide protozoal compliance while bacterial compliance will use UV and chlorine.

There is a plan in place to install barriers on the remaining three supplies before the end of 2025 with land already set aside in Havelock and Riverlands.

Given the Awatere was a rural scheme plans were to install point of entry treatment devices at each household.

Havelock and Riverlands Industrial Estate are budgeted for in Council’s current Annual Plan at $8.145m and $8.515m respectively. “Taumata Arowai will soon require water suppliers to install residual disinfection (chlorination) on supplies where none exists. This is going to affect Blenheim and Riverlands’ water supplies,” Stephen said.

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