​Water treatment upgrades for Patearoa and Ranfurly now underway​

Work is underway on major upgrades to the water treatment plants in Patearoa and Ranfurly, with both projects scheduled for completion in December 2025.

Central Otago District Council is undertaking these critical improvements as part of planned infrastructure upgrades that have been in development since 2021, aiming to address ongoing issues with protozoa treatment.

The $4.2 million budget allocated in Council's 2024 Annual Plan and 2025 Long-term Plan allows for the treatment upgrade and necessary supporting works.

Why the upgrades are needed

The upgrades will include the installation of protozoa barriers at both facilities, to ensure compliance with New Zealand Drinking Water Quality Assurance requirements and provide more reliable, safe drinking water. The water source for both towns is prone to high turbidity, particularly after heavy rainfall, which can compromise water treatment effectiveness and require boil water notices to protect public health.

“Following direction from Taumata Arowai in April, Council has committed to closely monitor the Patearoa and Ranfurly drinking water supplies while these upgrades are being undertaken,” Patrick Keenan, CODC Capital Projects Programme Manager said.

What's being installed

After evaluating all options, including building entirely new treatment plants (which would have cost approximately $15 million for Patearoa and $21 million for Ranfurly), Council has opted for cartridge filter and ultraviolet (UV) protozoa barriers as the most cost-effective solution.

This technology uses ultraviolet light to neutralise harmful microorganisms including protozoa, providing a sustainable and efficient treatment solution.The UV treatment system will replace the existing treatment processes to deliver safe drinking water that meets New Zealand Drinking Water Standards.

What this means for residents

Once this work is completed, residents in both communities should see fewer boil water notices. While these improvements will greatly enhance water safety, it's important to understand that these upgrades won't solve all water quality issues. During severe weather events Council may still need to issue the occasional boil water notice as a safety precaution.

Getting the work done

Following a competitive tender process, the contract to construct the protozoa barriers was awarded to Fulton Hogan on 28 May 2025. Council has worked closely with Fulton Hogan’s design team to develop a cost-effective and practical upgrade plan, with the concept design now approved and coming in well under the initial $4.2 million budget.

Estimated investment:

• Ranfurly upgrades will be approximately $1.7 million
• Patearoa upgrades will be approximately $1.6 million

"These upgrades represent a significant investment in the long-term water security of our communities," Mr Keenan said. "While residents may experience some temporary inconvenience during the upgrade period, the end result will be safer drinking water that meets national standards."

The protozoa barriers are part of a nationwide strategy to prevent outbreaks of waterborne illnesses and ensure all New Zealand communities have access to safe drinking water.

Council will continue to provide updates to residents throughout the construction period.