Deep under Brisbane’s bustling CBD lies Brisbane’s oldest and largest sewer pipeline. Averaging 1.5 meters in diameter, the S1 Main Sewer runs a total of 12km, stretching from Toowong to the Eagle Farm pump station and is buried 8 stories beneath the ground.

Built back in 1915, it’s no surprise that the S1 would eventually need an upgrade to meet the needs of the growing city. The upgrade involved rehabilitating a section of the pipeline between James Street in Fortitude Valley to the Eagle Farm pump station, spanning a 5.7km distance.

To reduce community disruption and minimise traffic impacts on the busy road, work took place at night. 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.

Commencing work in 2015, Interflow relined 40 individual sections (averaging 160m) of pipeline using a spiral-wound lining system. Fast forward seven years, and the S1 Main Sewer upgrade is now complete, with Brisbane’s largest sewer asset ready to serve its community well into the future.

The challenge

Located up to 8 stories below one of Brisbane’s CBD, the project’s biggest challenge was finding a rehabilitation solution that could withstand the extreme underground pressures.

As the depth of the S1 increased, so too did the enormous pressure on the pipeline. Interflow knew they needed to reinforce the lining system for it to withstand the pressure over time.

Given a short working window, the solution also needed to be portable. Provided with a daily working window of 8pm- 5am, all work had to be set up, completed, and moved within that working timeframe to not disrupt Brisbane’s daily peak hour traffic.

The solution

Working closely with technology partner, Sekisui Rib Loc Australia, Interflow identified an innovative way of reinforcing a spiral-wound liner with steel that could be customised to suit the application. The solution, called Ribsteel, involved clipping continuous stainless steel strips into the outside of the PVC strip, which makes it exceptionally strong.

On site, the steel arrived flat and was moulded and coiled as needed under carefully controlled conditions.

The Ribsteel liners were installed during night shifts with no bypass pumping, which allowed Interflow to complete the project without inconvenience to the surrounding community.

Conclusion

The upgrade of Brisbane’s oldest and largest pipeline undertaken below one of its busiest roads, makes it one of the most challenging sewer upgrades to be completed on Australian soil.

With the last line now complete, the S1 Main Sewer is ready for its next chapter. The impressive yet hidden piece of infrastructure will go on to serve the Brisbane community for generations to come.