The first phase of work in a $10 million upgrade of 10 of the district’s drinking water treatment plants is about to get under way.

The first package of work involves the Hinds, Mayfield and Dromore water supplies and Council has chosen civil contractor ARC Projects to construct the buildings that currently house treatment equipment for these three schemes.

The work involves construction of new buildings at each site and the supply and installation of cartridge filtration, UV disinfection equipment, and associated instrumentation. The Dromore site will also get additional tanks to increase the reservoir storage.

The contractor will have access to the sites from later this month with all work expected to be complete by April 2025. The tender price accepted was $1,799,981 plus GST.

Infrastructure and Open Spaces Group Manager Neil McCann said the work was necessary to meet Council’s obligations under the Water Services Act 2021, and to comply with various parts of the Drinking Water Quality Assurance Rules.

“Under these rules, Ashburton, Methven and Rakaia are considered to be level 3 supplies, and have the highest level of rules to follow. Hinds, Mayfield and Dromore are level 2 water supplies and now need a filtration step, a UV disinfection step and a chlorination step.

“So on these level 2 supplies, we’ll be installing cartridge filters and UV disinfection equipment, and we already have the necessary chlorination equipment.”

Upgrades are planned later in the year for Chertsey and Rakaia, and for the four treatment plants on the Ashburton supply (Ashburton Domain, Bridge Street, Argyle Park and Tinwald).

The Ashburton and Rakaia supplies will also need UV disinfection equipment. Methven and Mount Somers do not need upgrading because they have just got new membrane treatment plants.

Tenders for the Ashburton, Rakaia and Chertsey upgrades will be advertised later this year.

The upgrades to the physical buildings include things like upgrading transformers, generators and switchboards to handle the extra power requirements, and optimising plant layouts so that the new equipment doesn’t result in access problems or complicated pipework arrangements.

“In some cases, especially the Ashburton plants, retrofitting large equipment into the existing buildings is not possible, and since the buildings are in sensitive locations the modifications are not straightforward, raising the project costs,” Mr McCann said.

“We look forward to getting the upgrade package under way with this initial work at Hinds, Mayfield and Dromore.”