Cromwell Water Treatment Upgrade

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; detailed design, procurement and construction of a new treatment plant at the reservoir site and upgrading the bores.

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 because 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.

If you would like to know more about this project, check out our FAQs on the CODC website or email the project team at waterprojects@codc.govt.nz