Moa Point Sludge Pipelines
Update 20 May
With work progressing well on the project we want to update you on what will be happening in the coming weeks.
The liner has been installed in the first of the 1.8km sludge lines through the tunnel. This week work is being completed to reconnect the high-pressure pipeline to the network at each end of the tunnel and put it through a comprehensive testing programme.
The liner for the second pipe has arrived from Germany and this week the crew will be preparing for its installation next week. The pipe needs to be thoroughly cleared of all debris before the protective “sock” is pulled through and then the liner itself.
The process to pull the sock and liner through will be the same as for the first pipe. A four-tonne capacity winch, normally used for drawing power cables between pylons, will be set up on the Kilbirnie side while on the Island Bay side the liner is unspooled from large drums.
As with the installation of the first liner, we cannot give a precise timing on when the pull will happen as it depends on how long it takes to ensure cracks and other damage to the pipe is remediated and it is thoroughly cleaned. This can be a long process. If you would like email updates around this time, please send your address to Suzanne (contact details below).
We are very conscious of the odour that residents have been having to put up with during the repair process. The demisters we have installed at both ends of the tunnel are the best technology available internationally to counter the odours, but we appreciate they are limited in what they can achieve on some days. In response to feedback from residents, we are now running the demisters 24/7. When we have crews working in the tunnel or directly at the head wall in Kilbirnie, however, these misters may have to be temporarily switched off to avoid soaking the workers.
We are aware of the significant impact on some residents from this project, and how much more difficult that was during the earlier lockdown periods when people were not able to leave their homes - we apologise for this. It is not possible to do the work without the noise and smell, but we are committed to doing everything we can to mitigate these intrusions.
Once the liner has been successfully installed in the second tunnel, the same process of reconnecting and testing the pipe will need to be undertaken.
We will also be constructing a chamber on the Kilbirnie side, which will provide access to the joints between the liner and standard pipeline. This will allow inspections of the joints in future, without the need for excavation.
Once all work has been completed on the Kilbirnie side, the community garden will be reinstated.
We are not expecting to have to work late or on Sundays to deliver the rest of the project, although we may have to on occasion because of unforeseen circumstances.
If you have any questions about this work, please contact:
Suzanne at Brian Perry Civil, firstname.lastname@example.org or 027 607 2498
Update 30 April
With the repairs deemed “essential work”, significant progress has been made over the past five weeks. All possible precautions have been undertaken to protect both the safety of workers on site and members of the public and this will continue with the move to Alert Level 3.
At both ends of the tunnel the sludge pipes have been broken out of their concrete casings and an entry platform constructed. To achieve the safest, most resilient solution to repairing the pipes, a woven polyester liner will be pulled through both pipes, then expanded into shape. The liners have been manufactured in Germany, as they cannot be made in New Zealand. The specialist technicians needed to install and set the liners have travelled from Europe, and will arrive in Wellington later this week after their quarantine period in Auckland.
Breaking the pipes out has been noisy and at times smelly, and we appreciate residents’ patience with this work. To address the odour issues we have installed a “fogging” system at both the Kilbirnie and Island Bay ends. It’s a small pump with high-pressure nozzles that emit a mixture of water and an odour neutralising product that has no fragrance.
On Friday (1 May) work will begin setting up the site for the installation of a liner next week. A pipe will be laid across Adelaide Road (by the Dover Street intersection) through which the liner will be pulled. A “speedbump” will be created on each side of the pipe so that traffic can continue to use Adelaide Road. It will take a few days for the crew to install patches and ensure the pipe is clean and dry for the new liner.
A specialist heavy duty winch will be set up in Leonie Gill pathway, Kilbirnie, to pull the liner through. It will be noisy and inconvenient for residents, but it is an essential part of completing this important infrastructure repair project. It is expected that the liner will be pulled through early next week. The process will involve up to 18 hours of continuous work – it cannot be stopped and started again, so it is likely to require working through the night.
Once installed the liner will be tested and connections made at both ends. The whole process will need to be repeated in a few weeks when the second liner arrives from Germany.
We appreciate the cooperation we have received from residents. Please continue to practice social distancing around our sites and do not approach workers. If you have any queries or concerns please contact Suzanne Pollard – email@example.com or 027 607 2498. If you would like to receive weekly updates about the project, please send your email address to Suzanne.
Update 30 March
During the heightened national response to Covid-19, our top priority is providing clean drinking water and safe wastewater treatment to our communities, which has meant prioritising essential project work. Read more here.
Thanks once again to the local community for their support and understanding as we continue this essential work during the lockdown period. Work on this project has been delayed due to the international Covid-19 response, but will continue over this time. Read more here.
Update 5 February
Thanks to the local community for their continued patience and understanding as we continue with our trucking operations from the Moa Point treatment plant and the Southern Landfill.
We will be adjusting the route due to Island Bay’s Day in the Bay this weekend, with the trucks following an alternative route along State Highway 1 and up through Brooklyn (pictured below). Trucks will use this route from 6am-6pm on Saturday and Sunday, with trucks following the existing route outside of these hours. We expect about 5 to 6 trucks each way per hour during this period.
From Thursday through to Sunday, we will also be staggering the truck movements, as well as reducing the number of trucks on the road.
We apologise for any inconvenience this additional traffic may cause, but we are working to prevent the need to discharge the sludge into Cook Strait while we work to repair the pipeline to the Southern Landfill.
Update 29 January
We are continuing with our investigations into the tunnel and sludge pipelines. As part of these investigations, we are testing air valves along the pipelines in the tunnel.
As air valves are located along the pipeline, these investigations may result in noticeable odour areas surrounding the tunnel that runs under Mt Albert. We apologise for any odour issues that arise as part of this work.
Update 28 January
We have begun CCTV through the Mt Albert tunnel, which is an essential part to our investigations, helping us to understand the extent of the fault and look into solutions for the long term repair.
Trucks continue their operations 24/7, transporting sludge from the treatment plant to the landfill. The drivers have been greeted with a positive response from the community, with the sign pictured appearing on the route to the landfill.
We will be sharing weekly updates on the Moa Point situation as works continue. However, we will provide further updates should anything change.
Update 27 January
Trucks continue to work around the clock, transporting sludge from Moa Point to the landfill. We have managed to reduce the number of trucks and still continue to keep up with demand, meaning we are avoiding discharge into the Cook Strait.
We understand truck movements may be inconvenient to residents along the route, and we thank them for their understanding. We are briefing truck drivers to ensure they are keeping themselves and the public safe by reducing their speed.
The picture below shows an example of the sludge/slurry that is taken to the landfill for dewatering. This process removes the water, which then is piped back to the treatment plant through the wastewater network. The leftover solids are then put in the landfill.
Update 24 January
The trucking operations that have been operating this week, continue to prevent sludge from being discharged into the Cook Strait. The alternative operation means trucks on 24 hour rotation collect the wastewater treatment byproduct at the Moa Point Treatment Plant, taking it to the landfill at Carey’s Gully.
The operation was today refined by reducing the amount of trucks on the road and splitting them into two shifts of 6-7 trucks each. These trucks are continuing to keep up with demand, and are operating efficiently.
The fault in the pipeline was located yesterday, and we are continuing to plan a repair with a temporary bypass, as well as a long term fix. The location appears to be about 200m inside the tunnel under Mt Albert.
We are working with the local community at Moa Point, and are holding a community meeting on Sunday to update them on the project and address any concerns residents may have.
We will provide further update on Monday 27 January.
Update 23 January
Trucking operations are continuing as an alternative to the sludge pipeline between Moa Point Treatment Plant and the landfill at Carey’s Gully.
The pipeline failed last week, and a repair could be a month away or longer. No wastewater or sludge was discharged to the environment as a result of the failure, which occurred in a wastewater tunnel beneath Mt Albert.
Investigations have located the point of failure and work is under way to plan a repair with a temporary bypass, as well as a long term fix. It will be a complex job, because wastewater also flows within the tunnel towards Moa Point, making for dangerous working conditions.
With the pipeline out of action, there is a risk that if the trucking option is interrupted for 24 hours or more, some sludge may need to be discharged via the long outfall pipe that carries treated wastewater out to Cook Strait.
When the plant was built, the intended alternative to pumping sludge to the landfill in the event of a significant failure was to discharge it via the long outfall. Public expectations have changed since then however, and Wellington Water and teams of contractors are making every effort for this not to happen.
The trucking system is keeping up with daily demand, but because treatment operations at the plant and the landfill were not designed to load and unload sludge from trucks, there remains a risk that we may have to discharge sludge from the outfall.
Wellington Water is also working across a number of other options for the pipeline repair and to manage the sludge volumes.
- The treatment plant discharges over 70 million litres of treated water a day.
- Just over a million litres of sludge is produced at the plant a day. This is being transported by truck to the landfill.
- The sludge pipeline from the treatment plant to the landfill runs for 9km. It consists of two pipes, which operate one at a time, to allow for maintenance. It is highly unusual that they both have failed.
Investigations are under way for repairs to two pipes that convey a wastewater treatment byproduct – generally known as sludge – from Moa Point Treatment Plant to the council’s Southern Landfill in Carey’s Gully.
The pipes were installed in the mid-1990s, when the treatment plant was built (prior to that, wastewater was discharged to the sea at Moa Point via a short outfall pipe). They were designed to last for 80 years or more, and we believe these repairs are the result of an installation defect.
Only one pipe is operating at a time, but in this case, repairs are necessary on both. The pipes are under very high pressure when operating, and pass through a tunnel beneath Mt Albert. This is where the repair will be carried out.
While we carry out the repairs trucks will be used to convey sludge from the plant to the landfill. About a million litres of sludge a day is generated at the plant, and trucks may need to operate around the clock from time to time.
A similar repair, also due to a defect in the concrete in which the pipes are embedded, was carried out in 2013 and took about five weeks to complete.
We’ll provide more information on the repair timeline and truck schedule as we learn more.