Gear Island Water Treatment Plant sits beside the Hutt River at the eastern end of Petone foreshore. The plant was commissioned in 1935 and, like Waterloo, treats water from the Waiwhetu aquifer.
Water is drawn from three wells at Gear Island. This water is safe to drink without treatment due to the filtering effect of the aquifer. Microbiological contaminants cannot survive because the water is underground and in an airtight environment for more than 12 months. This water is naturally quite acidic, so we add lime to reduce acidity. We also add fluoride for optimal dental protection.
The Gear Island water treatment plant is able to produce 27 million litres of water per day, but since 1999 it has been used as a standby facility and is typically only run on one or two days each month, to maintain operational readiness.
Monitoring of the aquifer had shown that taking larger volumes of water during periods of drought creates zones of lower water pressure around our wells.
Because the Gear Island wells are close to Wellington harbour, there is a greater risk of salt water being able to infiltrate the aquifer. Since 1999, abstraction of water from the aquifer has been concentrated further inland, at Waterloo.
When the Gear Island Water Treatment Plant is operating, it usually supplements the supply to Wellington's business district and southern and eastern suburbs.