Thinking outside the box

Tailor-made solution for an unusual box culvert at Penrith water recycling plant.

The rehabilitation of aging infrastructure presents unique challenges, often requiring innovative solutions to extend asset life while minimising disruption. This was precisely the case at the Penrith water recycling plant in New South Wales, where high water levels in the oxidation ponds caused the culvert structure to become pressurised, leading to surcharges. These surcharges, combined with the deteriorating condition of the culvert, posed a risk to the surrounding environment and were also causing damage to the aboveground infrastructure. The culvert was a precast reinforced concrete box structure set on a reinforced concrete base, with internal dimensions measuring 1800mm in width and 900mm in height.

What initially seemed like a straightforward relining project quickly revealed itself to be a far more complex challenge.

A 30m section of the culvert presented an unexpected anomaly: a non-standard shape where the structure tapered down to approximately 50 per cent of its original height before expanding back to full capacity. Traditionally, a complex section like this would have been dug up and replaced – but this is a costly, disruptive and time-consuming process. Calculations showed that applying the twin Rotaloc methodology to this section of culvert would have resulted in a hydraulic capacity that was lower than acceptable; and stainless steel sleeving was also considered but ruled out earlier because of the associated cost and the weight of each section.

Faced with these challenges, Interflow turned to Channeline for a solution that would deliver durability, precision, and efficiency. Channeline’s bespoke glass reinforced plastic (GRP) lining system provided the perfect answer to this complex problem. Unlike conventional relining methods, Channeline’s liners are individually designed and handcrafted to ensure a precise fit within existing structures – regardless of shape, size, or dimensional variations. This unique manufacturing approach proved to be invaluable in addressing the Penrith culvert’s irregular geometry.

The Channeline advantage

The unique advantage of Channeline is its ability to accommodate complex shapes and non-standard dimensions, thanks to the company’s bespoke design and manufacturing processes. This was particularly crucial for the Penrith culvert, which was not only non-circular (box) shaped, but also had a significant change in internal diameter over the affected section.

There is really no theoretical limit to the shapes and sizes that Channeline liners can come in. For this project, a transition liner was created to facilitate a seamless shift between the changing diameter. This seamless shift decreases turbulence within the pipeline, and continues to ensure optimal set up, cross-sectional area, and flow effectiveness.

A successful installation

The rehabilitation process began with a trial installation using a timber template to verify the liner’s fit within the culvert’s unique shape. This preliminary step confirmed that the bespoke Channeline solution would fit seamlessly inside the structure. Then, with precision manufacturing complete, the custom liner was delivered and installed. Person-entry into this section of culvert wasn’t permitted, so each segment was winched into place, then sealed.

Following installation, asset owners can be assured that the structure will remain structurally sound and efficient for generations to come, thanks to Channeline’s 150-year design life.

The future of infrastructure rehabilitation

This project serves as a powerful example for asset owners across the industry, highlighting the value of embracing innovative technologies and flexible problem-solving approaches. By thinking beyond traditional rehabilitation methods and leveraging Channeline’s bespoke GRP solution, the delivery team achieved a cost-effective, long-lasting, and hydraulically efficient outcome. The success of this project reinforces the importance of considering all available options before resorting to costly and disruptive excavation or replacement. As infrastructure ages and complex challenges arise, adopting emerging solutions like precision-engineered GRP lining can extend asset life, minimise environmental impact, and deliver significant financial savings.

For more information, visit channeline.com