Cromwell Water Treatment Upgrade
Alpha Street - Current Construction Update
Apex Water has established their site office, located along the lakefront adjacent to the existing water treatment plant building.
Key updates:
- Motor Control Centre (MCC) building on Alpha Street lakefront began in November 2025 and is now 90% complete
- A new bore has been successfully drilled and is currently undergoing above-ground upgrades and connection to the newly installed main
- The main water pipeline at the Alpha Street Lakefront borefield has been completed, including all electrical cabling and fibre connections.
- Reinstatement works are planned for the second quarter of 2026.
- Construction of the borehead buildings began in early 2026. Bore site B, a combined building housing two bores, is expected to be completed by the end of May 2026. Bore site A, which will house one bore within a single building, is planned for completion in July 2026.
- Commissioning of the new infrastructure is scheduled to begin in May 2026 and is expected to take one to two months, with completion anticipated by July 2026.
Please note that detours will be in place along the Dunstan Trail while works are underway. Please follow all signage and directions on the track.
McNab Road - Current Construction Update
Key updates:
- Construction of the new water treatment plant began in early November 2025. The building is expected to be completed in May 2026, after which commissioning will begin.
- Power cables have been installed alongside McNab Road. Both transformers are now installed and power is live on site.
- Structural and civil works are continuing across the site.
- Commissioning of the water treatment plant is planned for May 2026, with completion of the main works expected in early August 2026.
If you would like to know more about this project, check out the FAQs or email the project team at waterprojects@codc.govt.nz.
New water treatment plant buildings panels being stood up
Constructing Cromwell’s water future now
Cromwell is growing, and we all know why – it’s a great place to live. But with a growing population, increased employment and more people visiting every year comes an associated increased need for services like safe and reliable drinking water.
The Central Otago District Council (CODC) is undertaking a significant programme of work to provide a fully compliant water supply for Cromwell. Council’s water upgrade projects will provide the increased capacity needed to meet the growth needs of the rapidly growing population in Cromwell and surrounding areas.
The programme involves construction of a new pipeline, a new treatment plant and an upgrade of the bore field. Council is pleased to report that the pipeline is now complete, and we’re moving forward with stage two of the programme; awarding Apex Water the tender to design and construct Cromwell’s new water treatment plant and borefield upgrades.
People may be wondering if Cromwell’s water will taste or feel differently to what it does now as a result of the new pipeline, upgraded bores and new treatment plant. "While the Council are certainly not expecting significant changes to your water, we are upgrading how water is treated. But the Council is confident that if there are any changes, they would be minor as the source of your water is remaining the same," CODC’s Water Services Customer and Compliance Team Leader, Philippa Bain said.
The current Cromwell treatment plant supplying water to Bannockburn, Cromwell, Lowburn, Ripponvale and the southern part of Pisa Moorings treats its water with chlorination.
“All water supplies need to be chlorinated to treat bacteria. This provides treatment for bacteria, but not protozoa which can cause illnesses such as acute gastrointestinal illness. The new water treatment plant will provide ultraviolet treatment; this is an upgrade and will treat Cromwell’s water for protozoa.” Ms Bain said.
CODC’s Capital Projects Programme Manager Patrick Keenan said that the current treatment plant has not treated Cromwell’s water for protozoa. In 2022, legislation changed the approach councils need to take to treat their water supplies with a greater emphasis on protozoal treatment.
“A fair portion of the costs of upgrading work on New Zealand’s water treatment plants in recent times has been in response to the addition of water treatment protozoal requirements,” Mr Keenan said. “We’re pleased to be upgrading the treatment of Cromwell’s water to not only future proof the supply of drinking water for a growing population, but also to manage the risk of protozoa and meet our legislated obligations.”
Cromwell’s water source meets drinking water aesthetic values and is therefore not deemed ‘hard’ enough for consideration of treatment investment.
“The Council has had community feedback and questions about ‘hard’ water versus ‘soft’ water,” Mr Keenan said. “We’ve been asked why we aren’t treating the water to ‘soften’ it. This is mainly because along with the initial expenses such as the cost of the softener and installation, there are higher ongoing operational and maintenance costs.”
“I think it is also important to stress that hard water isn't necessarily ‘bad’ water, any more than soft water is 'good' water. Some people like a degree of hardness in their water, others may have a preference for softer water.”
Ms Bain said that water hardness happens because of certain minerals in the water.
“The main ones are calcium and magnesium, which come from rocks like limestone and chalk. These minerals get into the water naturally from the ground. When water falls as rain, it is ‘soft’ and free of minerals. It picks up minerals as it passes through rock, sand and soil, so most water drawn from an aquifer will be ‘hard’. Hard water is high in mineral salts, especially calcium and magnesium”.
Council anticipates Stage 2 of the Cromwell Water Upgrade Programme to be completed in late 2025.
Latest news article on this project: Lakeside water upgrade ramps up in Cromwell
If you would like to know more about this project, check out our FAQs or email the project team at waterprojects@codc.govt.nz
