Tenders are currently out for a new $14.7million water treatment plant for Cromwell and a $2.7million water pipes renewal contract in Alexandra.

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

The water upgrade programme includes a new treatment plant and upgrade of the bore field.

Construction of a new pipeline has already been completed.

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. Those works were advertised for tender in February.

Construction of the new water treatment plant for Cromwell is expected to cost around $14.7 million. SUPPLIED

Group manager Three Waters Julie Muir said in addition to meeting compliance regulations, Cromwell’s water upgrade projects would ensure there was sufficient capacity to meet the area's rapid growth.

The source of Cromwell’s drinking water - a mix of aquifer and lake water - was not changing, therefore, council did 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 was not treated for protozoa which was a requirement of the New Zealand Drinking Standards. 

While the water was 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 was not considered necessary.

Meanwhile in Alexandra, water pipe renewals work would also be starting later this year after a construction contract has been awarded, with priority locations including the Bridge Hill Rising Main and Enterprise Street.

As well as providing water for residential homes and local businesses, the 70-year-old Enterprise St water main was 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 St water main were getting ‘dirty water,' with 11 complaints over several months.

Council investigated and discovered the new ‘softer’ water supply from Lake Dunstan was impacting older galvanised water pipes like Enterprise Street and resulting in discolouration.

Capital projects programme manager Patrick Keenan recently said replacing those ageing water assets with long-term and more sustainable products would provide increased resiliency for the community and would help reduce water clarity issues.

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

Patrick said 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 meant work to replace two higher-risk sections of the Bridge Hill Rising Main could progress this year, while other lower-risk sections will be upgraded in the future.