Innovative tree root trial helping protect SA sewers

A new trial looking to prevent thirsty tree roots impacting South Australian sewers is now underway across metropolitan Adelaide, as part of efforts by SA Water to reduce customer sewer overflows and protect the natural environment.

As part of the innovative pilot, a thin layer of high-density plastic liner made from 100 per cent re-used material has been installed below ground between problematic trees and a sewer connection at four customer properties.

The first stage of the trial is targeting properties which have experienced higher than usual sewer blockages caused by tree root intrusion.

SA Water Innovation Specialist Alex Czura said the liners aim to restrict roots moving towards the pipes, without impacting the tree’s health.

“Tree root intrusion is the leading cause of blockages at customer’s sewer connection points, and when caught up with cooking fats, oils and other foreign objects flushed down the toilet or sink, can lead to everything that goes down coming back up,” Alex said.

“Most sewer blockages can be cleared by cleaning the inside of the pipe, without the need for any excavation. However in some cases, tree roots continue to grow, making it difficult to prevent further blockages occurring at the same location.

“We devised a trial to dig an environmentally-friendly barrier around the base of a tree using hydro vac excavation and a root sawing method, which causes minimal disturbance to the tree itself, while preventing the growth of thirsty roots towards nearby sewer connections.

“With the dig needed to install the barrier just 150 millimetres wide, the end result also reduces the need to excavate large areas of kerbing, footpath and residential driveways, often required for replacing damaged customer connections.

“This project represents our proactive approach to protecting pipes and customer connections, rather than reactively managing an incident after it’s occurred.”

Throughout the three-year trial period, SA Water will use CCTV to monitor wastewater pipes at regular intervals, helping to assess the viability of expanding root barrier technology to other suitable locations around South Australia.

“While it’s early days, initial works show the installation of root barrier technology comes in at just one-third the cost of a traditional wastewater connection replacement, and takes less than a quarter of the time. This may allow us to improve sewer services for three times as many properties, for the same cost,” Alex said.

“We will also use this project to work with local councils and landscape architects to provide our expertise on the most suitable trees and plants to grow near our water and wastewater networks which support tree canopy coverage for greening and cooling, while also protecting our underground infrastructure.

“This is an exciting initiative that can help us save time and money while continuing to deliver the safe and reliable wastewater services that our customers expect.”

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