Kowhai Reservoir in Mairangi Bay is small but mighty. Nine metres high and with a diameter of 27meters, Kowhai Reservoir serves a population of 16,500 residents from Browns Bay in the north to Campbells Bay in the south.

It was originally built in 1957 with a dome roof, that due to its age, needed replacing.  Dismantling and replace the roof started in June and has now been completed. Watercare project manager Giorgos Lourmas says the new roof is more robust, built with a steel frame with fiberglass cladding. It is supported by a central column to ensure no excess loads are added to the remaining walls. But the really cool aspect of this project was the dismantling of the roof.

 "We cut open a small hole on the roof and propped the entire roof up with scaffolding. Then it was cut into sixty 3.2m x 3.2m sections that weighted approximately 2.5 tonnes each. These sections were then lifted out with a custom-designed lifting jig by a crane, broken on site and sent to a concrete recycling facility." Says Giorgos.

Since the works were happening in a residential area, this method of dismantling was a lot less disruptive than conventional demolition. It also drastically reduced the risk of damaging the existing structure.

Giorgos says they also used this opportunity to introduce the ability to fully control the reservoir remotely. "Earlier, our operations team would have to send in people to manually isolate the reservoir but with this capability, it can be managed from Newmarket."

The reservoir can hold 4.6 million litres; it is currently being commissioned and will be put back into service in mid-October.