The Wainuiomata-Orongorongo catchment area began chlorinating its water supply in 1963.
After the Boxing Day flood in 1962, heavy rainfall in the Wainuiomata and Orongorongo valleys caused significant damage to the intake weirs, allowing mud and silt to enter the city’s water supply before the valve could be shut. In response, construction of a chlorination plant began in 1963 to improve water quality and safeguard public health by disinfecting the supply. This led to the establishment of a permanent chlorination and fluoridation facility by 1964, designed to ensure ongoing treatment to prevent waterborne diseases and support dental health.
