Fluoridating Rotorua’s drinking water supply

In July 2022, the Ministry of Health directed Rotorua Lakes Council (RLC) to fluoridate drinking water across two of its ten supply zones – the Central supply, sourced from the Karamū Tākina Spring, and the Eastern supply, sourced from the Waipa Spring.

Together, these two supplies serve around 52,800 people, delivering an average of 28 megalitres of drinking water per day and up to 45 megalitres at peak demand. Raw water from Karamū Tākina is pumped to the Matipo and Utuhina reservoirs serving the Central zone, while water from the Waipa Spring feeds the Tarawera Reservoir for the Eastern zone. Both supplies already underwent individual chlorination and UV treatment before the fluoridation work began.

RLC engaged Pattle Delamore Partners (PDP) to support the implementation of the Ministry’s directive, from the initial funding application through to construction and commissioning.

PDP’s first task was to assemble the technical information needed for RLC’s Ministry of Health funding application. This covered an overview of both water supplies, a proposed fluoridation system design, safety-in-design considerations and cost estimates for procurement.

A key early decision was selecting the right fluoridation agent. After assessing options including powder Sodium Fluoride and Sodium Fluorosilicate, liquid Hydrofluorosilicic Acid (HFA) was selected as the preferred chemical. The decision reflected factors including water demand at each site, chemical handling and operational requirements, independent fluoride dosing checks, consistency with chemicals used at other RLC sites, and the physical constraints of each location.

With the funding application supported, PDP developed specimen designs proposing fluoridation dosing stations at Karamū Tākina Spring for the Central supply, and at Tarawera Reservoir for the Eastern supply. Each proposed system included a ventilated chemical storage and dosing building, a chemical receiving and delivery area, bulk storage for a minimum one-month HFA supply, a dosing system, a fluoride analyser, and electrical and control system integration.

PDP also prepared a schedule of quantities, engineer’s cost estimates, technical specifications and tender documentation compliant with NZS 3916:2013, enabling RLC to procure the work through a design-and-construct contract.

PDP’s involvement extended beyond design. Our team provided monitoring, supervision and quality assurance support throughout construction – reviewing the contractor’s detailed design, offering remote technical assistance during the build, and signing off Ministry of Health requirements at commissioning.

The result is a fluoridation system that now delivers the health benefits of fluoridated water to tens of thousands of Rotorua residents across both supply zones.

Key aspects:

• Concept and detailed design work supporting RLC’s funding applicationand agreement with the Ministry of Health
• Specimen designs covering fluoridation layout, dosing and analyserlocations, chemical delivery, storage and dosing buildings, and processdiagrams
• Schedule of quantities and engineer’s estimate of anticipated costs
• Technical specifications and tender documentation compliant with NZS3916:2013
• Technical assistance, installation inspections and commissioning sign-off.