Along South Yarra’s busy Chapel Street ran two cast iron cement lined water mains dating back to the early 1920s. A burst on one of the mains put it in a high-risk category and it was flagged for renewal.
Delivery partner Interflow was engaged by South East Water to renew both mains to ensure certainty of supply for their customers into the future.
What followed was an award-winning project that demonstrates what can be achieved for our communities and our networks when the status quo is challenged.
South Yarra is vibrant inner-city suburb of Melbourne, south-east of the city’s main business district.
The area surrounding the work zones has seen extensive development in recent years. The street is a mix of shops, cafés and businesses at street level, with apartment buildings towering overhead.
On paper this was a straightforward project. Both mains could be renewed by digging them up and replacing them, working at night to reduce the impact on traffic.
Interflow and South East Water understood that the real marker of success was the impact works had on the 12,000 people and businesses that rely on Chapel Street’s water mains for their supply.
At the time of tender, Interflow submitted an alternate proposal designed to leverage the benefits of trenchless renewal technologies to reduce the impact of the renewal works on residents and the business community.
The two organisations collaborated closely during the project to ensure any proposed solutions balanced community and network needs.
“Our goal is always to deliver a better, more sustainable water network for our customers and community, while minimising disruption,” shared Matthew Snell, General Manager Liveable Water Solutions.
“Through our partnership with Interflow we were able find new, innovative ways to safely deliver this important project and provide ongoing reliability for the South Yarra community and business owners.”
While there are many examples of proactive problem solving during the Chapel Street renewal project, two were key to delivering exceptional customer outcomes.
The west-side 100mm main was to be renewed with a 150mm pipe (to meet growth demands) and the 300mm east-side main with a like-for-like size.
Interflow identified an opportunity to renew the larger eastern water main using a low impact trenchless approach. The challenge: the cast iron pipe had been lined with cement in the late 1970s, reducing its diameter such that preferred methods like slip lining weren’t practical.
“There just wouldn’t have been enough capacity to support the network,” Interflow Project Manager Reece Paulzen explained. “But if we could figure out a way to remove the cement liner, then slip lining would become a viable option”
The inspiration for a bespoke cement liner removal process came from a different part of Interflow’s operations.
“High-pressure water jetting is a normal part of our wastewater services,” said Paulzen. “It’s used to clear significant blockages in sewer pipes, like tree roots, or to grind down junctions that will get in the way of lining.”
“We understood that in theory it should be possible to break down a cement liner in a water pipe too.”
With South East Water’s support, Interflow began trials in their Scoresby yard. The delivery team used some cast iron cement lined pipe removed on another project to test their idea.
What resulted was a process that used ultra-high-pressure water (up to 15,000psi) and custom cleaning heads to pulverise the cement liner. The cement, along with the water, was flushed through removed using a hydro truck.
Afterwards, all 485m of the eastern water main was slip lined with a 280mm (outer diameter) HDPE water pipe.
Chapel Street is a four-lane road with trams operating in both directions and a clearway during peak times. 20,000 vehicles use it daily.
Nightworks are effective for managing traffic impacts, however in this case the effect of noise on residents was a greater concern.
The delivery team realised that by challenging the norm, they could reduce the chance of community fatigue brought on by long project timelines and disruptive works.
Working with the Department of Transport, the team secured a 7am to 10pm working window with permission to occupy the clearway with a site compound outside these times. The process was uncharted territory for both Interflow and South East Water and took 6 months to obtain.
The permit eliminated almost all nightworks and allowed two back-to-back shifts each workday, which were beneficial to both the community and the construction program. Significant time was saved by avoiding the need to establish and demobilise the site at every shift.
A long-term collaborative relationship between Interflow and South East Water was the foundation for success on Chapel Street. By putting community needs first and actively problem solving, the desired outcomes were achieved with minimal impact.
“The Chapel Street renewal project has mitigated the risk presented by an ageing asset,” said Snell. “Now that the project is complete, our customers can be confident that their community will benefit from reliable, high-quality water infrastructure well into the future.”
Innovation brings benefits beyond the problem they are created to solve. For asset owners across the country, the project shows that trenchless solutions can be designed for the most challenging conditions.
Investing upfront in developing these solutions saved South East Water time and money. However, on Chapel Street, it was the community that came out on top.
“We’re all about improving lives,” said Paulzen. “Knowing we made people’s lives easier while we were working, that’s the real win.”
