Council commits to replacing water infrastructure

Ageing pipes a priority for replacement in Alexandra

Water pipes will be renewed in priority locations following approval by the Central Otago District Council (CODC).

At the meeting on Wednesday (29 January 2025), the Council agreed to progress work replacing the pipes as part of the 2025-2026 renewals.

Priority locations include the Bridge Hill Rising Main and Enterprise Street.

A third site, Northland Street in Ranfurly, will also see water pipes replaced this year under a separate contract.

CODC Capital Projects Programme Manager Patrick Keenan said that Bridge Hill’s water pipe was a critical piece of infrastructure linking Bridge Hill to the wider Alexandra water supply network and providing water to many nearby properties.

“The Bridge Hill Rising Main is nearly 100 years old. This water main dates right back to when Aronui Dam was used as the town water supply. Some sections had to be laid above ground due to the sometimes difficult and rocky conditions.”

Council approval means work to replace two higher-risk sections of the Bridge Hill Rising Main can progress this year, while other lower-risk sections will be upgraded in the future.

As well as providing water for residential homes and local businesses, the 70-year-old Enterprise Street water main is the main source of drinking water for Dunstan High School, Terrace Primary School and several early childcare facilities.

Last year, Council was told that some people getting water from the Enterprise Street water main were getting ‘dirty water’. Council investigated and discovered that the new ‘softer’ water supply from Lake Dunstan was impacting older galvanised water pipes like Enterprise Street and resulting in discolouration.

With a budget of $2.7 million, Mr Keenan said that replacing these ageing water assets with long-term and more sustainable products would provide increased resiliency for the community and will help reduce water clarity issues.

Central Otago Mayor Tamah Alley said the ability for people to drink water straight from the tap was important to Council.

“This project is an example of our continued commitment to investing in critical infrastructure."

Water pipe renewals work will start later this year after a construction contract has been awarded.

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New water treatment plant for Cromwell a step closer

The Central Otago District Council (CODC) is moving forward with a major programme aimed at providing a fully compliant water supply for Cromwell.

The water upgrade programme includes construction of a new pipeline (already completed), a new treatment plant, and an upgrade of the bore field.

Recently, Council approved the next phase of the project, building a new water treatment plant at the reservoir site on McNab Road and upgrading the bores between Lake Dunstan and the Alpha Street recreation reserve. These works are set to be advertised for tender in February.

CODC Group Manager Three Waters Julie Muir said that in addition to meeting compliance regulations, Cromwell’s water upgrade projects will ensure there is sufficient capacity to meet the areas rapid growth: The source of Cromwell’s drinking water - a mix of aquifer and lake water - is not changing, therefore, Council does not expect water from the new water treatment plant to taste or feel too differently. However, Council would be changing how drinking water was treated, she said.

“In addition to chlorination, which is currently used to treat the water, the new treatment plant will also use ultraviolet light treatment.

“Ultraviolet light treatment effectively treats water for protozoa, a class of parasitic microorganisms that can cause acute gastrointestinal illness.”

Currently, Cromwell’s water is not treated for protozoa which is a requirement of the New Zealand Drinking Standards. While the water is not compliant, there has been no change in the risk profile of the Cromwell water supply. For this reason, a long-term precautionary boil water notice is not considered necessary. Council will continue to utilise tools such as boil water notices to manage specific events which result in an elevated risk.

While Council did consider upgrading and retrofitting the existing water treatment plant, electrical switchboard and communications building, it ultimately decided to relocate these services to a new site. This decision would help reduce costs and enhance security. The future of the existing buildings will be considered at a later stage.

Construction of the new water treatment plant for Cromwell is expected to cost around $14.7 million, with completion anticipated by the end of the year.

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Water treatment solution supported by Council

New water treatment solutions are in the pipeline for Ranfurly and Patearoa following the approval of over $3 million in funding to upgrade their treatment plants.

The Central Otago District Council (CODC) Ranfurly and Patearoa treatment plants source their water from ‘surface water sources’ — the East Ewe Burn and Sowburn River. One of the challenges with surface water is its vulnerability to turbidity (dirty water) following heavy rainfall. Both plants had faced turbidity issues in the past, CODC Capital Projects Programme Manager Patrick Keenan said.

During high turbidity events, both towns’ drinking water has occasionally been non-compliant, leading to boil water notices: Additionally, both treatment plants needed upgrades to meet the requirements of the New Zealand Drinking Water Standards.

“Currently chlorination occurs which treats bacteria, and ultraviolet light treatment needs to be added to provide treatment for protozoa , a class of parasitic microorganisms that can cause acute gastrointestinal illness”.

Mr Keenan said that with the recently approved funding, the upgrades to the water treatment plants should be completed by the end of 2025 as required by Taumata Arowai, the governments water services regulator. “While water conservation may still be necessary during high turbidity events, we are confident that our solution — chlorination, with the additional combination of cartridge filters and ultraviolet treatment — is an affordable and effective option to meet New Zealand’s Drinking Water Standards.”

Council Group Manager Three Waters Julie Muir advised that while the water is not currently compliant for protozoa treatment, there has been no change in the risk profile of the Ranfurly and Patearoa water supplies. For this reason, a long term precautionary boil water notice is not considered necessary. Council will continue to utilise tools such as boil water notices to manage specific events which result in an elevated risk.

Council expects to begin construction of the water treatment plant upgrades following procurement in March and complete the work before the end of the year.