Over five years, Spiire worked in close consultation with Melbourne Airport to design a ‘holistic’ stormwater solution for an area of the airport prone to flooding and poor quality water. The Airport Drive Extension and Steele Creek North Stormwater Enhancement Project, which was awarded the prestigious Stormwater Australia Excellence in Infrastructure Award last year, encompassed four aspects of water management to create a sustainable water system for years to come: flood mitigation, water conveyance, improved water quality and the recycling of stormwater.
Completed in 2015, it included the installation of a system to recycle water from the airport within the Steele Creek North catchment area, providing an additional water supply as well as improving the quality of the water that is discharged. It also included other aspects of water management, including retention systems, infiltration measures and rainwater harvesting to improve water quality in receptor water systems.
In his early consultations with Melbourne Airport, Spiire Project Manager and Design Lead Leigh Holmes says the project quickly developed into something more than just mitigating the risk of flood. He says it had to be designed with the four aspects of water management as the priority, and the foundation of the outcome.
“The Steele Creek North catchment, which is approximately 430 hectares, incorporates long-term carparks, buildings and the airport’s business park. It is one of the only catchments that is discharged downstream into neighbouring residential areas, so prior to development the airport needed a strategy to mitigate the risk of flooding downstream,” Mr Holmes says.
Spiire entered into a design and construction contract with John Holland, who subcontracted some of the work including the main civil earthworks which featured the trenchless boring. The project contract included a 100,000 m3 flood retention basin to protect residents downstream and a 7,000 m2 sedimentation basin with a rain garden, one of the largest in Australia.
The rain garden allowed the runoff from the airport area to be treated to best-practice standards, as well as mechanically treating the catchments stormwater. The project is one of Victoria’s largest stormwater harvesting projects, producing over 130 ML of treated water per year, which is supplied to airport operations and the surrounding areas.
“Put simply, we designed a system that collected all the stormwater, cleaned it and then filtered it back into the end users like the airport’s toilet system, irrigation at the Essendon Football Club’s new facility in Tullamarine, car washing facilities and cooling towers at the airport which use a lot of water,” Mr Holmes says.
“In regards to the cooling towers, we were looking for a constant demand for water and wanted to push the boundaries of how the treated water could be utilised. There was obviously concern around using the water in cooling towers.
“So, we went through a series of risk workshops, operations and maintenance workshops to make sure that everyone knew how to mitigate the risks and ultimately produce a consistent end product that was safe to use in such an important piece of the airport’s infrastructure.
“Stormwater is a highly variable water source and we had challenges working out the best treatment train for that system. Specifically, there were some issues around stability which we solved by adding coagulants,” he says.
Mr Holmes says the project included several challenges, including that it could not disrupt the airport’s operations. This was solved – in part – by the use of microtunnelling. He says the design and construction team also had to innovate to overcome time constraints, with just 18 months to complete the design and construction.
“There are so many services in the construction area, not to mention the airport had to operate 24/7, so it was imperative that we maintained access while the water infrastructure was being constructed. We found boring was a solution because it mitigated the risk to operations at the airport.
“However, the main challenge was speed of delivery. We had 18 months to turnaround the design and construction to the end product, which we overcame by communicating and working openly with John Holland, as well as using some innovative construction techniques to speed things up.
“One of these, was the installation of a 5 ML underground storage tank, which we installed using a precast method. We used Humes’ StormTrap® system, which involved surrounding it with a liner and pouring 5 ML worth of culvert systems in there, which enabled a quicker turnaround.”
The project not only reduced the airport’s water consumption, but dramatically improved the water quality of the Steele Creek North catchment. Mr Holmes says it completed under external pressures from community and environmental groups concerned with the affect the project would have on the area.
“There was quite a few issues with water quality downstream too, with organisations such as the Friends of Steele Creek, the EPA regularly monitoring the water, trying to fix what was going on there. As a result we put together a strategy to help improve the water quality too,” he says.
Mr Holmes and Spiire are currently working with Melbourne Airport on planning for future works on the site.
For more information visit the Spiire website.
This article was featured in the March 2017 edition of Trenchless Australasia. To view the magazine on your PC, Mac, tablet, or mobile device, click here.
If you have a project you would like featured in Trenchless Australasia contact Assistant Editor Nick Lovering at nlovering@gs-press.com.au