To avoid Cromwell drinking water being deemed non-compliant the Central Otago District Council will vote next week on whether to install a temporary ultraviolet treatment system to ensure the town’s drinking water remains safe, following delays in the construction of a new water treatment plant.
The Cromwell water supply, which draws from bores near Lake Dunstan, does not have a protozoa barrier in place - a critical requirement under New Zealand’s Drinking Water Quality Assurance Rules.
In a report to council from Three Waters group manager Julie Muir it says while the supply is largely sourced from the aquifer during low demand, higher summer demand means more water is drawn from the lake, increasing the risk of protozoa contamination.
Originally scheduled for completion by December 2025, the new water treatment plant is now expected to be operational in May 2026. The report shows this leaves a five-month gap where the water supply could be non-compliant, placing the community at risk of a boil water notice - a scenario that could significantly impact local residents, food businesses, retirement homes and medical facilities.
In response, the Central Otago District Council will consider the installation of a containerised UV treatment system leased from Queenstown Lakes District Council at a full council meeting on Tuesday.
The unit, no longer needed in Queenstown, will provide the required protozoa barrier until the permanent plant is complete. The lease cost is $500 per month, with the total estimated cost for transport, installation, and operation expected to be $360,000.
Council staff have been working with Taumata Arowai, New Zealand’s water regulator, who has made it clear that critical barriers like UV treatment are essential for public safety.
Recent high-profile cases across the country have highlighted the risks of operating bore-sourced water supplies without proper protozoa treatment, with boil water notices imposed in several communities.
The only other option the council will consider is providing tanker water supply with a boil water notice in place until May 2026, but the report makes it clear that supplying water tankers to Cromwell’s 4500 connections - spanning Bannockburn, Cromwell, Lowburn and Pisafor up to six months is logistically and financially unfeasible with costs exceeding $360,000.
The estimated $360,000 cost for the (UV) treatment system would be covered within the existing $14.7 million budget for the Cromwell water treatment upgrade project, which is forecast to come in under budget.
- Allied Media
