All night long with the S1 main sewer

Brisbane residents slept through the night while Urban Utilities and Interflow upgraded Queensland’s oldest and largest sewer, the S1. How did they do it?

Brisbane residents slept through the night while Urban Utilities and Interflow upgraded Queensland’s oldest and largest sewer, the S1. How did they do it?

Over 100 years since its inception, Brisbane’s S1 Main Sewer underwent an ambitious seven-year upgrade. By harnessing the power of innovation, Urban Utilities and its delivery partner, Interflow, have given new life to a hidden but essential piece of infrastructure.

Deep under Brisbane’s bustling CBD lies Brisbane’s oldest and largest sewer pipeline. Averaging 1.5m in diameter, the S1 Main Sewer runs 12km, stretching from Toowong to the Eagle Farm pump station and is buried eight stories beneath the ground.

Built in 1915, the S1 serves more than 750,000 people, carrying 60 per cent of the city’s wastewater. To put that in perspective, more than 60 Olympic-sized swimming pools of wastewater travel through the system daily.

A lot has changed in Brisbane over the past 100 years, so it’s no surprise that the S1 would eventually need an upgrade to meet the growing city’s needs. The works involved rehabilitating a section of the pipeline between James Street in Fortitude Valley to the Eagle Farm pump station, spanning a 5.7km distance.

The region’s water and wastewater service provider, Urban Utilities, first awarded the rehabilitation works to pipeline infrastructure company, Interflow in 2015. Since then, Interflow has relined 40 individual pipeline sections (averaging 160m) using a spiral-wound lining system.

Fast forward seven years, and the S1 Main Sewer upgrade is complete. Brisbane’s largest sewer asset is ready to serve its community well into the future.

The project was so impressive that it recently won the Infrastructure Project Innovation Award (Metro) at the Queensland Water Awards, hosted by the Australian Water Association.

Operating in Brisbane’s bustling CBD

While the S1 Main Sewer lies quietly 20m below ground, the same can’t be said for the bustling corridor of Kingsford Smith Drive located directly above. The busy road is a primary freight route linking Brisbane’s CBD to places such as the Brisbane Airport, Port of Brisbane, and Northshore Hamilton.

Work took place at night to reduce community disruption and minimise traffic impacts on the busy road. This meant all traffic lanes could operate undisrupted during peak travel periods. It also meant crews needed to move on and off the busy road each night to allow full lane access in the morning.

Interflow developed a portable set-up that could be assembled and removed quickly. It gave the teams more time to focus on relining the S1. This was critical, as the overnight working window was from 8 pm to 5 am.

Once Interflow had sewer access, the team would mobilise a gantry straight over the access chamber using a small crane. Such an arrangement could be moved on and off the worksite with ease.

A similar process was organised for the grouting team. A trailer was imported specifically for the project, and Interflow built a mobile grout plant on the trailer.

Operating as a separate team up the road, the grouting crew would move large bags of cement by forklift. They would empty the bags into a mixer before blending it with water. The grout was then sent down the access chamber and injected between the lining and the old pipe to secure it in place.

By making their set-up portable, Interflow could work in the peak of the night within a small working window, allowing little disruption to Brisbane’s traffic network.

Going deeper underground

On projects of this scale, it is not unusual for conditions to change along the way. In this case, the delivery team sought new solutions to adapt.

“As we moved further through the sewer, the pipelines were getting deeper,” Interflow’s Development Manager, Boris Graljuk, said. “This meant there were more external forces on the pipeline.”

The increasing sewer depth meant the relining solution had to be strong to withstand the extra pressures. Working with technology partner Sekisui Rib Loc Australia, Interflow identified an innovative way of reinforcing a spiral-wound liner with steel.

“Spiral lining is performed by winding an interlocking strip of PVC into an existing pipe to form a smooth, continuous pipe,” said Graljuk. “The new solution, called RibSteel, involved clipping stainless-steel strips into the outside of the PVC strip in the lined pipe. That makes it exceptionally strong.”

Interflow had to make sure this solution was suitable for the S1 upgrade. The teams at Interflow conducted a series of rigorous tests in their workshop to ensure it would be reliable in the challenging conditions. Once both Interflow and Urban Utilities were satisfied that RibSteel was up to the task, Graljuk and the team took the process to the site.

“We did everything on site,” Graljuk said. “The steel arrived flat and was formed to be shaped using a roll former. This was before it was coiled into the same diameter as the liner. Once it was formed, we could pass it down to the winder and insert it into the profile.”

Beginning the next chapter of the S1’s history

The upgrade of Brisbane’s oldest and largest pipeline, undertaken below one of its busiest roads, made it a challenging project.

With the last line complete, the S1 Main Sewer is ready for its next chapter. The upgraded infrastructure will continue to serve the Brisbane community for generations to come.

To learn more about Interflow, visit

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