Mt Albert high-pressure sludge pipeline repair
The Mt Albert high-pressure sludge pipeline repair is a critical project for Wellington’s wastewater network, and one that Wellington Water is committed to progressing during lockdown.
Repairing these pipelines is a significant technical challenge, because the bursts occurred deep beneath Mt Albert so it is not practical to excavate the pipes. In this context, the polyester sleeve solution which has been developed is the safest and most durable option for this repair.
Wellington Water has worked with a specialist engineering firm in Germany to design and manufacture the sleeves specifically for the Mt Albert pipes. Given the importance of the installation, and the fact this will be the largest-scale implementation of this technology in Australasia to date, bringing in experienced international expertise for this operation was a key component of our arrangements with the manufacturer.
Unfortunately, the unprecedented impact of Covid-19 restrictions around the globe has delayed the project.
The manufacturer has worked extremely hard, while complying with their government restrictions, to produce and freight the liners as soon as possible. Each liner is approximately two kilometres long when fully extended and weighs about three tonnes. The first liner is complete, the second liner we expect to be ready this week (commencing 6 April).
We have worked closely with WCC and the Government to secure special permission for the international experts to be brought into the country in these extraordinary circumstances. The team of six people are booked to fly from Germany to New Zealand, with a planned arrival in the middle of this month. That number includes cover, in case any of the group were to become sick or injured, to ensure the work can be completed.
On arrival, they will be placed in isolation in self-contained accommodation, with food and other essential items delivered to them.
Once their quarantine period is complete and the liners have arrived in Wellington, installation will begin. At this stage the earliest that would be is early May, meaning the repair could be completed by mid-May, however there remains considerable uncertainty due to the disruption caused by the Covid-19 pandemic.
Update 21 March 2020
Wellington Water has worked with a leading international engineering firm to develop an innovative solution to repair the high pressure sludge pipelines between the Moa Point Wastewater Treatment Plant and the Carey’s Gully landfill. However the global response to the Covid-19 pandemic will delay its installation.
The repair presents a significant engineering challenge, as it must be completed within the 1.8 km section of the pipelines running through a tunnel deep beneath Mt Albert. The solution that has been developed is a polyester woven liner which will be winched from one end of each pipe to the other, then expanded to essentially act as a new pipeline within the old.
The liner will be installed through the full length of the pipelines under Mt Albert, where they are most inaccessible. This will be the largest-scale deployment of this technology in Australasia.
Once in Wellington, the estimated timeframe for installation of the pipe liner is eight days.
Wellington Water CEO Colin Crampton says due to restrictions on business imposed this week by the German government, delivery of the liner by the supplier has been pushed back.
“This is a high-quality, robust and resilient solution that will get the pipelines back up and running, and reduce the risk of further bursts. It’s a high-tech specialist product which is not manufactured in New Zealand. Unfortunately, due the importance of protecting their workforce and community from the spread of Covid-19, production at our supplier’s factory has slowed.”
Mr Crampton says that current estimates are for the liners to arrive in Wellington by mid-May.
“We appreciate the ongoing patience and understanding of the communities in the area. Trucking operations are not ideal from anyone’s perspective, but they are successfully keeping millions of litres of wastewater from flowing into Cook Strait,” says Mr Crampton.
Mr Crampton says the long-term approach should be to decommission the underground sludge pipelines entirely.
“The solution we have developed has a working life of 10 years. This provides an opportunity for Wellington City Council to receive advice on what is the best way to manage sludge going forward. We are now developing alternative options for Council to consider which would enable us to stop disposing of sludge into the landfill entirely.”