SA Water removes half-tonne tree root from sewer

Resembling a fantasy creature, a giant half-tonne tree root mass has been removed from the sewers in Adelaide’s north-east, preventing potential community interruption and sewage overflows.

The five-kilometre-long, 675-millimetre-diameter sewerage pipe travels beneath suburban streets and reserves between Bridge Road in Walkley Heights and Kelly Road in Pata Vista, with a large number of trees in the area.

SA Water crews carefully attached several lifting slings to the cluster’s main roots before fixing them to an excavator’s arm, which guided the mass out of the concrete sewer chamber.

Colin Bell, SA Water Senior Manager of Field Operations, said other sections along the pipe also had extreme root intrusion, while some yielded around 200 kg of wet wipes.

SA Water was first alerted to the potential invasion after a substantial blockage occurred in another section of pipe in Walkley Heights, where what appeared to be a tree was discovered growing in the sewers.

“Typically, areas in the foothills or surrounded by natural spaces experience a higher number of blockages, due to tree roots breaking into pipes in search of water and blocking the flow of sewage to our treatment plants,” Bell said.

“In fact, thirsty tree roots are the leading cause of sewer blockages within our network across South Australia.”

The mass in Modbury weighed around half a tonne and measured five metres in length, so the team needed to break it down into smaller pieces for transport and disposal.

A lot of behind-the-scenes work went into preparing for the job, with investigations along the pipe finding several sections impacted by tree roots and at risk of further blockages.

To reduce the risk of blockages downstream when removing the mass, crews proactively cleaned around 500 metres of that part of the pipe every night over a number of weeks to reduce any potential disruption to the community and take advantage of lower flows in the network.

The cleaning also yielded a few more surprises, such as 200 kg of wet wipes and several metres of rope.

“There’s a range of preventative measures we have invested in to reduce the risk of blockages from tree roots, with the community able to access our Healthy Pipes online tool to help people plant the right tree in the right place on their property, along with our ongoing sewer cleaning program and innovative tree root barrier trial,” Bell said.