Wednesday, July 17, 2024


Interflow successfully rehabilitated the problematic culvert section again using Channeline segmental liners

Mooloolaba is a coastal suburb of Maroochydore in the Sunshine Coast Region of Queensland, Australia. It is located 97 km north of the state capital, Brisbane. A large concrete box culvert in Mooloolaba suffered severe spalling and corrosion, necessitating urgent renewal. The culvert, located at Amarina Avenue, was constructed in 1975 and passed beneath a busy street, carrying run-off from the Sunshine Motorway to the Mooloolaba Canal. The culvert’s structural damage posed a risk of collapse, requiring immediate action.

The Sunshine Coast Council’s Stormwater Management Asset team conducted an inspection in 2020, revealing the deteriorated condition of the culvert. Flood modelling indicated that reducing flow capacity was not a viable option. Traditional methods, such as lining the culvert with smaller sections or excavation and replacement, would compromise flow capacity or cause significant disruption, including road closures and relocation of utilities.

Contractor Interflow proposed an innovative and sustainable solution to renew the culvert. The company imported custom-designed and manufactured glass reinforced plastic box sections from Channeline. These sections, with thinner walls and a smoother interior surface, were specifically engineered to maintain flow capacity while addressing the structural issues. The installation process involved slipping the new sections into the existing culvert and filling the small annulus gap with grout, eliminating the need for excavation and minimising community disruption.

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The implementation of the alternative solution was highly successful. Over a 12-day period, the large concrete box culvert was renewed without any environmental incidents or significant community disruption. The smooth internal surface of the Channeline sections reduced friction, ensuring that flow carrying capacity was maintained, despite a slight loss in internal cross-section. The renewed culvert is expected to have a service life of over 50 years, providing a long-term solution to the complex culvert problem. This project demonstrated the effectiveness of sustainable and innovative approaches in addressing complex culvert issues. By thinking outside the box and utilising custom-designed materials, Interflow achieved exceptional results, exceeding the required outcome while minimising disruption and costs for the Sunshine Coast Council. Such solutions offer valuable alternatives for similar infrastructure renewal projects in the future.

Penrith Project
Penrith is a town in New South Wales, Australia, located in Greater Western Sydney
some 55 kilometres west of the Sydney central business district on the banks of the
Nepean River, on the outskirts of the Cumberland Plain.

The Penrith Water Recycling Plant (WRP) processes a daily volume of 24 million litres of wastewater. The existing culvert structure consisted of a precast reinforced concrete box culvert placed on a reinforced concrete base, with internal dimensions measuring 1,800 mm wide by 900 mm high.

Issues arose when surcharges occurred in the culvert structure due to high levels in the oxidation ponds, leading to increased pressure within the structure. These surcharges, combined with the poor condition of the culvert, posed risks to the local environment, and caused damage to above-ground infrastructure. To address these concerns, Sydney Water enlisted the expertise of Interflow to rehabilitate two downstream sections of the culvert using their patented Rotaloc system, covering a total length of approximately 67 m.

During the project, an additional 78 m of culvert were included in the scope of the works. However, upon inspection, it was discovered that the culvert did not maintain a consistent shape throughout. Between the two internal headwalls, a portion of the culvert tapered down to around 50% of its original height before gradually increasing back to its full capacity.

A 30 m section of the Penrith WRP Culvert 1 presented an unconventional shape and size, which traditionally would have required costly and time consuming replacement.

Calculations indicated that applying the twin Rotaloc methodology to this section would result in an unacceptable hydraulic capacity. The consideration of stainless-steel sleeving was dismissed earlier due to cost and weight concerns associated with each section. Thus, the delivery team needed to explore alternative solutions that were cost-effective, expedient to install, and ensured an acceptable flow level through the culvert.

Interflow successfully rehabilitated the problematic culvert section again using Channeline segmental liners, a versatile solution that can be customised to fit any shape and size. Channeline possesses superior flow-through characteristics, making it an ideal choice for Sydney Water’s culvert problem.

To ensure the efficacy of the design, a timber template was constructed and a trial installation was conducted before proceeding to full manufacturing. Since person-entry into this section of the culvert was prohibited, each Channeline segment was carefully winched into place and securely sealed.

The combined application of Channeline and Rotaloc has resulted in a rehabilitated culvert with an expected lifespan exceeding 100 years. Additionally, the culvert now possesses sufficient hydraulic capacity to sustain the Water Recycling Plant’s operations well into the future. Interflow effectively addressed the challenges presented by the Penrith Water Recycling Plant culvert by thinking outside the box and offering a cost-effective, efficient, and reliable resolution.


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