The Project

Kaitoke Bulk Water Main

The Kaitoke bulk water main provides all of Stokes Valley’s water, all of Porirua City’s water, and forms part of the major water supply to 40% of Wellington City’s water.

The pipeline needs replacing because it’s nearing the end of its operational life. Over the years, the soil conditions have corroded the pipeline and atmospheric corrosion has deteriorated the above ground section of pipeline across the Silverstream road bridge along Fergusson Drive. The pipeline is also primarily located deep below State Highway 2, which makes access to undertake any required inspections or maintenance more difficult and disruptive to road users.

Background

Half the water supply for the Wellington urban area comes from the 8900-hectare Hutt Water Collection Area, which takes in the headwaters of Te Awa Kairangi / Hutt River at the southern end of the Tararua Range.

Rainwater collects in tributary streams that flow into Te Awa Kairangi / Hutt River. Wellington Water has a weir (low dam) at Kaitoke, just north of Upper Hutt, where water is taken from the river, strained to remove sticks, leaves and silt, and piped through tunnels to the Te Mārua Water Treatment Plant.

The network begins at the treatment plant, where water is transported along bulk mains – large water pipelines, similar to a state highway which carries the bulk of the water into the city.

Resilience

Regional resilience is a priority for Wellington Water and Greater Wellington Regional Council. This includes reducing the time it takes to restore water to customers after a major event, with the goal of providing 80 percent of our customers, within 30 days of a reasonable seismic event, at least 80 percent of their water needs.

Strengthening the bulk water network in Te Awa Kairangi / Hutt River area is crucial to the protecting supply of water to Porirua, and minimising the length of time water can be restored to other areas of the region.

Timeline

 

When

What

December 2020 to March 2021 

Ground investigations to inform detailed design

First half 2021 to Q3 2021

Construction of Kingsley main 

July 2020 to July 2021

Detailed design and consenting of the Silverstream pipe bridge, including public consultation 

Second half 2021 to early 2023

Construction of the Silverstream pipe bridge and connecting pipework