Good progress on water upgrade

Saturday June 02, 2018 Written by Published in Hot on the Rock
The Turangi valley water intake site where work is progressing in the Te Mato Vai project Stage 2 upgrades. 18052919 The Turangi valley water intake site where work is progressing in the Te Mato Vai project Stage 2 upgrades. 18052919

Extensive work by the McConnell Dowell construction team is progressing well at the Turangi, Avana and Papua water intake sites as part of improving Rarotonga’s water network.

 

The Stage 2 intake upgrade works requires 10 of the 12 existing water intake sites in Rarotonga to be upgraded to deliver the Te Mato Vai project.

At the Turangi water intake, which contributes about 21 per cent of Rarotonga’s total water supply, the construction team, which includes around 14 local workers, is progressing well after recent deluges on the island with the construction timeframe for these new treatment and filtration facilities expected to take around 17 months.

Works at the intake include earthworks as well as transportation of materials to the site set deep in the Turangi Valley where the area is being prepared in advance for foundation works for the proposed facilities including the construction of a new stainless steel storage tank.

The stainless steel tank will store water after it has made its way from the stream via a new intake structure which will provide better protection from debris and rocks entering the pipework. 

Water will then pass through a settlement tank which enables sediment and solids to settle to the bottom of the tank. Then automatic valveless gravity filters will purify the water by removing particles and any residual sediment as the last step before the water goes into the storage tank. 

Water from the storage tank will then be transported via a trunk main pipeline to the ring main pipeline for distribution to homes and businesses. A water storage tank also helps with managing water needs during peak usage times.

The Turangi intake site will have one stainless steel storage tank, capable of holding approximately 2.4 million litres of water. This storage tank will measure 20m in diameter with a height of 8.5m, and be partially buried in the ground.

At the Avana intake, vegetation clearing and earthworks have been ongoing at the site along with the start of construction. The Avana intake is the biggest provider of water for Rarotonga, contributing 27 per cent of the island’s water supply, with the construction timeframe for the new treatment and filtration facilities at the site expected to take approximately 20 months.

Repairs have been required to the Avana and Turangi access roads after the major rainfall and storm events in Rarotonga. A number of stream crossings have also been required to be repaired and have been undertaken by McConnell Dowell and local contractors Mike Rennie Builders to continue to provide reasonable access for vehicles into the Avana and Turangi intake sites.

At the Papua water intake site, the focus has been on replacing the trunk main. The existing trunk main from the new intake site facilities to the new ring main will be entirely replaced with a new 1.3km long trunk main, being a 200mm diameter polyethylene PE pipe and steel pipe at river crossings. Replacement of the first 580m is being done now and is nearly complete.

All facilities constructed at the water intakes will be built according to Australia, New Zealand and World Health Organisation Standards and will also need to meet all Te Mato Vai Project Specification and Environmental Protocols enforced by the National Environment Service. Professional engineers and construction personnel are supervising the work to ensure standards are met.

Meanwhile, local company Landholdings Ltd has been working on the last of the ring main commissioning works this month.

The Te Mato Vai Project Management Unit would like to say meitaki maata to everyone for their patience around the work sites and for the disruptions to water supply that have occured. All of the new ring mains on both the Arametua and Aratapu around the island are now live, meaning water is running through these new pipes to your home or business. Some final decommissioning works are still in progress, but work is almost complete.

If you have any questions on the project or to share your views, call the Te Mato Vai Project Management Unit on 28851.

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