South East Water sought to renew the two water mains on Chapel Street, between Toorak Road and Alexandra Avenue, South Yarra.

The area had experienced significant growth and is home to many residents and businesses. Collectively, the two mains serve a customer base of around 12,000 people.

The east-side water main had previously experienced a burst, causing considerable disruption to the public, community, and businesses. South East Water made the decision to extend the scope to include the mains on both sides of the road to ensure certainty of supply for its customers for generations to come.

Interflow and South East Water collaborated closely during the project to ensure the solutions balanced community and network needs.

On the west side, 560m of DN100 cast-iron cement lined pipe (CICL) was renewed with a new DN225 PVC pipe by open trench lift and relay. On the east side, 485m of DN300 CICL pipe was renewed with a 280mm outer diameter HDPE pipe by slip lining, facilitated by a custom process to remove an in-situ cement liner.

The Chapel Street renewal project has mitigated the risk presented by a distressed asset and provided future generations with reliable, high-quality water infrastructure.

The challenge

The key challenge on this project was reducing the impact of works, particularly noise, in one of Melbourne’s most populated areas.

Works like this on busy roadways are usually contained to nightworks to reduce the impact on traffic. In this case, the impact of noise on residents and business owners was a greater concern. As well as disrupting people during sleeping hours, nightworks would have left a very short working window and prolonged the duration of works.

In addition, ground conditions were extremely rocky, meaning excavation was a difficult and noisy activity. Finding a trenchless alternative to digging and relaying the mains was crucial to minimising the impact on the area’s 12,000 customers. The DN300 eastern main appeared a good candidate for slip lining – the catch: the pipe had been lined in cement leaving a smaller than expected internal diameter.

The solution

Working with the Department of Transport and Planning, the team was able to secure a 7am to 10pm working window, with permission to permanently occupy the clearway with a site compound outside these times. This eliminated almost all nightworks which was hugely beneficial to the community.

The permit process took almost 6 months and included the creation of Traffic Guidance Schemes and Traffic Management Plans.

Inspired by their sewer pipe cleaning process, Interflow created a bespoke system that could break down the cement liner and allow it to be flushed out. The innovative removal of the cement liner in the eastern main facilitated the slip lining approach, and in turn, reduced the potential for undesired impact on the community.

Conclusion

Seeking to restore two pipelines in Melbourne’s highly populated Chapel Street, Interflow and South East Water worked together to upgrade both mains while reducing the impact on the community and stakeholders.

Through implementing trenchless methodologies and obtaining a large day time working window, both the eastern and western sides of Chapel Street were upgraded, providing the community with a reliable water asset for generations to come.