Australia: Centenarian sewer gets after-dark upgrade

Mar 08, 2023

Over 100 years since its inception, Brisbane’s S1 Main Sewer has undergone a seven-year upgrade.

By harnessing the power of innovation, Urban Utilities and its delivery partner, Interflow, have given a 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 1.5 m in diameter, the S1 Main Sewer runs a total of 12 km, stretching from Toowong to the Eagle Farm pump station and is buried eight stories beneath the ground. 

Completed back in 1924, the S1 serves well over 750,000 people, carrying 60 percent of the city’s sewage. To put that in perspective, more than 60 Olympic-sized swimming pools of wastewater travels through the system daily.

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

Owner of the asset, Urban Utilities, first awarded the rehabilitation works to leading pipeline infrastructure company, Interflow, back in 2015. Since then, Interflow has relined 40 individual sections (averaging 160 m) 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 for generations to come.

Operating along Brisbane’s bustling CBD

While the S1 Main Sewer lies quietly 20 m 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 key places such as the Brisbane Airport, Port of Brisbane, and Northshore Hamilton. 

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.

 “We developed a portable set up that could be quickly assembled and removed, giving us more time to make progress on relining the S1 within our small nighttime working window from 8pm to 5am,” says John Adamo, Interflow’s Project Manager during the program’s early phases.

“Once we had sewer access, we would mobilise a gantry set up straight over the access chamber using a small crane, which could easily take it on and off the worksite daily.”

“We did something similar for our grouting team, too. We imported a special trailer and built a mobile grout plant on it,” Adamo says. 

Operating as a separate team up the road, the grouting crew would move large bags of cement by forklift and empty them 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 was able to 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 it led the delivery team to seek new solutions in order to adapt.

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

The increasing depth of the sewer meant the relining solution had to be incredibly strong to withstand the extra pressures. Working closely 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,” says Graljuk. “The new solution, called RibSteel, involved clipping stainless steel strips into the outside of the PVC strip in the lined pipe, which makes it exceptionally strong.” 

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

“We did everything on site. The steel arrived flat and was formed to shaped using a roll former, before being 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,” Graljuk says.

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, 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.

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