About 150 properties connected to the Mount Somers water supply are being advised there will be a late-night water shutdown for three hours on Thursday 15 February.

The shutdown, from 10pm until 1am the following morning, is part of installing new water mains on Ashburton Gorge Road to connect to the new Mount Somers water treatment plant.

Residents are advised to store water, though a potable water tanker will be parked at Mt Somers Springburn School before and during the shutdown if needed.

Work on the new $4.6m membrane treatment plant is on track, with commissioning programmed for May.

The plant is a smaller version of the new Methven water membrane treatment plant that opened late last year, ending the need for boil water notices that were often issued after heavy rain.

A new building is currently under construction to house treatment equipment for the Mount Somers plant, and new soakage fields, settling ponds and drainage pipework have been completed.

The upgrade includes eight new tanks which will increase storage capacity from 125 cubic meters to 240 cubic meters.

Group Manager Infrastructure and Open Spaces Neil McCann said the short shutdown on 15 February is needed so water from the Mount Somers supply intake could be fed to the new building.

“We’re really pleased at how this project is tracking and this will be the first of several improvements for the Mount Somers supply.

“We are also proposing money be put aside in the Long Term Plan to investigate a supplementary water source, to support future growth in the town, and assist when demand increases during dry periods.”