Yarra Valley Water provides water supply and sewerage services to a population of 1,500,000 people in the eastern and northeastern metropolitan region of Melbourne across an area exceeding 4,000 square kilometres.

Yarra Valley Water owns some 8,200 km of sewer mains. They range in size from DN150 to DN1800 and are constructed from various materials including concrete, earthenware/vitrified clay, brick, cast iron, steel, asbestos cement, PVC and polyethylene.

The oldest sewers, still in operation, were constructed in 1901 and the average age of sewerage assets is 60 years. So far, Interflow has renewed over 100 km of these sewers by installing structural liners.

Much has changed in the Trenchless Technology industry since the start of Yarra Valley Water’s sewer rehabilitation program.

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“For a developing industry like pipeline rehabilitation, it’s important that a client is willing to trial innovations if it can be shown that these are likely to provide benefits,” said Interflow Southern Region Manager David Dodemaide. “Yarra Valley Water has been an important partner in the advancement of the industry in Australia.”

Interflow, as the exclusive Australian installer of the Rib Loc range of spiral wound liners, is in the unique position of providing a sewer lining technology that was developed in Australia. Over the years a ‘partnering’ relationship has developed between manufacturer, installer and client that has seen world leading technology incorporated into sewer rehabilitation projects. This has made sewer rehabilitation more practical and extended it into areas previously considered too difficult or impossible.

When reticulation sewers were originally laid through back yards of residential developments several decades ago, little thought was given to the difficulties their locations would cause when rehabilitation was to be eventually required.

For Yarra Valley Water, renewal of reticulation sewers has been complicated not just by their locations but also by the ‘gentrification’ of inner Melbourne suburbs. Hawthorn, for example, is a suburb with expensive houses, many with large, well planned gardens.

Sewer rehabilitation in such areas offers a stern test of Yarra Valley Water’s commitment to provide services while minimising inconvenience to its customers.

This commitment was particularly tested when two sewers running through the back yards of several luxury houses in Hawthorn caused flooding due to blockages from root infiltration. The access point for the sewers was at the back of one of the properties, on a newly paved area in the garden next to the tennis court.

“We have to be careful when we work in anybody’s back yard,” said Interflow Project Engineer Peter Pandoleon. “But this was a particularly difficult situation.

“All the equipment had to be carried in by hand and we had to be careful not to cause any damage to the tennis court, or the garden. Fortunately we were able to line both of the pipelines from the one manhole, so we only had to set up once.”

But the complications didn’t end there. Typically installation of Rib Loc Expanda Pipe requires access at both ends of the line. However on this project the two pipelines ended in a dead end and a 300mm diameter inspection shaft respectively.

It was decided to wind the liners and expand ‘blind’. This was a risky process, but success would mean that expensive and difficult excavations under trees in well manicured gardens could be avoided.

“Installation took longer than usual,” said Peter, “but we lined both pipelines in a day, so we only needed one visit to the premises.”