Repair of the Mt Albert high-pressure sludge pipeline is a critical project for city council Wellington’s wastewater network in New Zealand, 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 the council’s 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’s restrictions, to produce and freight the liners as soon as possible. Each liner is about two kilometres long when fully extended and weighs about three tons. The first liner is complete, while the council expects the second liner to be ready in the first week of April.

The council has worked closely with Wellington City Contact 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 owing to the disruption caused by the Covid-19 pandemic.

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.

“The solution we have developed has a working life of ten years. This provides an opportunity for Wellington City Council to receive advice on what is the best way to manage sludge going forward,’ concludes Wellington Water CEO Colin Crampton.