Western Hills Sewer Main Rehabilitation (State Highway 2)

Published on 31 March 2025

Wellington Water is undertaking some urgent works to a substantial section of the Western Hill Sewer Main.

These works will be taking place 24/7 for two weeks from 12 April, weather permitting.

About a year ago, it was identified that a section of this pipe was in very poor condition due to hydrogen sulphide erosion.

The original wall thickness was assumed to be around 60mm, and the worst areas indicated a loss of about 37mm. This puts this section of the pipeline at high risk of failure, which could cause significant disruptions on SH2 and impact public health and the Hutt River with wastewater overflows.

Pipe Condition.png

 

To fix the pipeline we are lining it using a ‘cured-in-method'. This means that pipe needs to be taken out of operation, drained and cleaned before we can even start work. A resin impregnated ‘sock’ is pulled through the pipe and cured to harden, with UV lamps.

Sock Pipe.png

This method requires the manholes to be enlarged for access.
As this pipeline is underneath SH2 and there is expected to be disruption to the traffic flow, works are timed over the school holidays and Easter period when the traffic volumes are generally lower.

To ensure the safety of workers and road users, traffic management will be in place between Melling Link and Kennedy Good Bridge.

Western Hills.png

  • One northbound lane will be closed and speed limits will be reduced.
  • One southbound lane will be converted into a northbound lane – this means there will be two northbound lanes and one southbound lane.
  • Block Road will be closed to all traffic except buses and emergency services.
  • There will be no turn out of Tirohanga Road onto SH2.

The traffic layout with two northbound lanes towards Lower Hutt/Upper Hutt and one southbound lane towards Wellington City open best balances the impacts on all lanes and local roads. Southbound traffic is more spread out in the morning and easier to manage. There are also more easily accessible alternative routes for the southbound travelling public which will alleviate the pressure on southbound lanes.

We are working closely with key stakeholders and NZTA to ensure that our work creates as limited disruption as possible.

Huge effort has been put in to make sure that we can complete the project in the two week window. In the event of something outside our control it is likely that it will take some weeks, possibly months, to reorganise workers, plant and equipment and resubmit and get traffic management plans approved, which will impact cost.  This risk has been balanced against the risk that the pipe fails in an uncontrolled way. 

For more information on the project and traffic management details, visit the Western Hills Sewer Main project page. Regular updates will be shared on this project page and Wellington Water's social media channel.

 

 

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