Gear Island water treatment plant

Gear Island water treatment plant sits beside the Hutt River at the eastern end of the Petone foreshore. The plant was commissioned in 1935 and, like Waterloo, treats water from the Waiwhetu aquifer.

Gear Island is able to produce 27 ML/d from 3 bores located at the edge of the Shandon Golf Course, 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.

When the Gear Island Water Treatment Plant is operating, it usually supplements the supply to Wellington's business district and southern and eastern suburbs.

Gear Island treatment process

  1. The treatment process at the Waiwhetu aquifer is slightly different than the rivers, as it is an underground zone of water-holding sand, gravel and boulders beneath the Hutt Valley. Water takes more than 12 months to pass through the aquifer to our wells and is naturally filtered while underground.
  2. Gear Island draws water from three bores along the Shandon golf course.
  3. Once the bores extract the water it is then pumped to Gear Island treatment plant where the water at Gear Island is aerated to remove carbon dioxide and caustic soda is added to adjust the pH and alkalinity of the water.
  4. Flouride and Chlorine are then added. The amount of fluoride is measured and dosed to target a range from 0.7mg/L to 1.0mg/L. The amount of Chlorine is measured and dosed to target a minimum residual of 0.2 parts per million at the far end of our distribution system.

Since 1999 the Gear Island water treatment plant has only been used as a standby facility and is typically only run on one or two days each month, to maintain operational readiness.