The Royal National Agricultural and Industrial Association (RNA) and Lendlease are redeveloping the historic Brisbane Showgrounds into a vibrant, year-round destination. The RNA Redevelopment Project is 1.5 km from Brisbane’s CBD on 22 hectares of land. It is the largest brownfield development in Australia and will take approximately 15 years to complete.
To service the current and future needs of the development, the trunk sewer works needed to be upgrade. This external sewer connection included a 646 m gravity trunk sewer main, part of which was a 29.6 m long railway crossing and connections to ageing sewer infrastructure in dense, busy inner-city areas.
Lendlease partnered with WSP for the design of the gravity trunk sewer. Our team provided extensive technical inputs to identify a broad range of design options and recommendations to balance the objectives and needs of Lendlease and Queensland Urban Utilities. We completed and submitted the concept, preliminary, detailed design and construction tender drawings and specifications to Queensland Urban Utilities for approval.
Challenging the Status Quo
The typical approach to deliver trunk sewer works would have been to excavate a jacking reception shaft in the intersection of Ann and James Streets. This would have closed at least two lanes to the city traffic for weeks to months. Instead, our team challenged the status quo and proposed the use of direct blind bore construction in the dense urban environment.
This methodology delivered minimal impacts to the surrounding communities, environment and existing infrastructure. A MicroTunnel Boring Machine (MTBM) does not require a retrieval pit at the end of the 70 m microtunnelling drive. The team dismantled the MTBM and retrieved it in segments via an existing 1.2 m diameter maintenance hole in Ann Street. The direct blind bore of a mild steel enveloper allowed a carrier pipe to be installed and connected to the existing maintenance hole, thereby reducing the construction and public safety impacts at the Ann/James Streets intersection.
Innovation for a Safe Working Environment
To provide a safe and unique dry environment for staff working in the live sewer connection, our team developed and constructed a water-tight and gas-tight working platform within the existing maintenance hole.
We designed the platform to withstand substantial upward forces during peak wet weather flow events when the sewer becomes surcharged well above the level where the work was being undertaken. Nearby works on the Kingsford Smith Drive caused unforeseen higher water levels in the sewers, which impacted our project. Despite this, our innovative platform kept workers safe and dry.
Assessing Ageing Infrastructure
A 100-year old maintenance hole on Ann Street needed to remain operational during the trunk sewer works. We set up real time vibration monitoring to assess the impact of connection. We did so with a finite element structural model analysis based on concrete strength test data from samples collected during the condition assessment. This analysis was critical to the connection methodology we adopted to ensure there was no damage to the existing maintenance hole.
Maximising Community Benefits
By adopting the blind bore construction method, the team minimised the construction impacts on the community and the environment. This meant we avoided daytime traffic restrictions on busy streets, removed the public safety risks associated with deep trench construction and delivered the project ahead of schedule. As the team retrieved the MTBM at the end of the project, it can also be used again for similar projects.
The RNA Redevelopment Project has a future-proofed sewerage infrastructure and can continue its exciting regeneration of the Brisbane Showgrounds. Once the regeneration project is complete, more than 15,000 people will live, work and play in the thriving urban village. The project is expected to deliver AU$300 million per annum in economic benefits to Queensland.