Kowhai Water Reservoir Roof Replacement

Client: Cassidy Construction

Fit-for-purpose roof and coating solution for ageing reservoir

Kowhai Water Reservoir in Mairangi Bay is a vital Watercare asset, holding 4.6 million litres of water and serving 16,500 North Shore residents. At 63 years old, the reservoir shell and much of the pipework was still serviceable, but the reinforced concrete roof had deteriorated to the point where it was becoming unsafe.

Cassidy Construction were contracted to carry out the upgrades, and engaged GRIT to work with them and Watercare on a design for the new roof, below-ground chambers and associated pipework. Importantly, the design had to comply with Watercare’s design standards to ensure the upgrades met their specific safety and service life requirements.

Meeting specific design requirements

A robust steel structure and roof sheeting system, supported by the reservoir walls and a central concrete column, would replace the ageing concrete dome roof. GRIT’s durability in design and safety in design assessments proved that the design could be built, operated and maintained safely, and would meet Watercare’s service life expectations.

Our team also provided guidance and specifications for the coating systems that would be used for the structural steel. Considering several options, we recommended a system that would be safe for potable water applications, and robust enough to withstand the structure’s transport and installation, along with providing the required durability. The result is an asset that will stand the test of time, providing a reliable service to North Shore residents for many years to come.

“An enjoyable professional engagement - GRIT were very approachable and demonstrated a desire to work with us to get the best outcome. Very happy with the service provided. ” — Jason Yukich - Project Manager, Cassidy Construction.