A major $30 million water project to secure Whangārei's urban water supply for decades to come is almost ready to start flowing.
Whangārei District Council water services manager Andrew Venmore said the project has been a major undertaking in the 10 years since the decision was made to upgrade the current treatment plant at Whau Valley.
The plant currently produces about 60 per cent of the city's water supply, boosted by smaller treatment plants at Poroti Springs and Maunu Springs.
The new plant, which cost $30m, will increase the water supply from 15,000 cubic metres to 22,000cu m per day.
New filtration systems and the latest technology is being used in the new building at 213 Whau Valley Rd, about 500 metres from the old treatment plant.
Venmore said the new building became necessary as the old one did not meet earthquake standards and the plant was at least 68 years old.
The new plant has been designed to better cope with major rain events, which is the main challenge for the city.
Raw water will be taken from the existing Whau Valley Dam and the Hatea River.
Venmore said water quality at the sources could change significantly in different seasons and the new treatment plant incorporates new measures to cope with poor water quality.
These include clarifiers to create a process to bind larger particles and draw them out of the water, as well as two sets of filters to further purify the water.
Testing of the new components is under way to make sure all parts of the treatment plant are working correctly, and staff plan to start blending the new water between the two plants for a few weeks to phase in the new system.
He said, all going well, the new system should be operating fully by May and the old system would be switched off.
It was likely the old plant would be dismantled.
Once the new Whau Valley plant is operating, the next project is to upgrade the Poroti treatment plant.
"The Poroti upgrade will really put us in a good position for growth and resilience as we will be able to treat more water than before, including taking water from the Wairua River which we are not currently using," Venmore said.