Western Hills Sewer Main Rehabilitation

At this stage, the scope of this project is for the urgent renewal of a 590m wastewater pipeline which is jointly owned by Hutt City Council and Upper Hutt City Council that is in poor condition. 
 
This is the main pipeline serving approximately 50,000 people including Western Hills in Lower Hutt and Upper Hutt. 

• Primary objective: Providing reliable services to customers. 
• Secondary goal: Minimising public health risks associated with wastewater and stormwater.

There are no indications of imminent failure with the pipe and we’re regularly monitoring its condition.  

• In the short term, we have a contingency plan in place to ensure we’re keeping the disruptions to a minimum if a pipe failure occurs prior to the repair. 
• And in the longer term, we have a preferred option to rehabilitate the pipeline that will minimise transportation disruption on SH2.

If a pipe failure occurs before the repair, there may be some environmental and transportational impacts depending on the failure and the effectiveness of our operational response.

We’ll be working closely with Hutt City Council, Upper Hutt City Council, Greater Wellington Regional Council and NZTA to determine the best approach. We will communicate with the public to ensure they are aware of the approach, timelines, and any impacts of the work. 

Works will commence on 12 April 2025 with crews operating 24/7 to get this work completed. We expect the works to be completed within two weeks, weather dependent.

As the wastewater pipeline is underneath State Highway 2 (crossing north of Melling), critical works to line a section of this pipeline will cause significant traffic disruptions, especially during peak times. 

To ensure the safety of our workers and road users, traffic management will be in place. 

• The works are expected to take place 24/7 for about two weeks from 12 April, depending on weather conditions.

• Traffic management will be between Melling Link and Kennedy Good Bridge.

• One northbound lane will be closed and speed limits will be reduced.

• To balance the traffic impacts on all lanes and local roads, one southbound lane will be converted into a northbound lane - there will be two northbound lanes towards Lower Hutt/Upper Hutt and one southbound towards Wellington City.

More details on the traffic management will be available soon. Please be patient with us and plan ahead during this time.

This traffic management plan best balances the impacts on southbound and northbound traffic, as well as local roads in the area.

The decision to convert one of the two southbound lanes into a northbound lane is based on the following factors:  

• The morning peak traffic is more spread out whereas northbound traffic in the evening is more concentrated, creating a much narrower peak.  

• There are more easily accessible alternative routes for the southbound travelling public, including Eastern Hutt Road, SH58 via Haywards and local Hutt roads, which alleviates the pressure on southbound lanes. 

• The layout and spacing of the intersections mean it’s more challenging managing northbound traffic queues, which is why an additional lane is needed. 

This is an option we’ve looked into. However, due to significant health and safety risks with switching the layout twice a day for two weeks for workers, traffic controllers, and the travelling public, we decided to keep the traffic management layout consistent over the duration of the project

Even at times in the day when traffic volumes are lower, switching between traffic layouts would be disruptive as this could take between an hour to an hour and a half. There’s also a significant cost to switching the traffic layout over the duration of the works.

We opted for a layout to have two northbound lanes towards Lower Hutt/Upper Hutt and one southbound lane towards Wellington City open because this best balances the impacts on both lanes as well as local roads in the area. 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.

This finding further highlights the ageing infrastructure in the Wellington region and the importance of our existing programme of work for condition assessment our council owners fund us to do which support the prioritisation of pipe repairs and renewals throughout the region.

In this case, the condition assessment has identified that the pipe is in worse condition than anticipated, so has enabled repairs to be developed prior to the assets failing.