Coates Engineering Solutions has delivered a comprehensive dewatering and water treatment solution for the revitalisation of Muddy Creek, ensuring construction work stays on track.
In November 2022, Sydney Water commissioned a consortium of engineering groups called Delivering 4 Customers (D4C) to revitalise Muddy Creek at Brighton-Le-Sands in south Sydney.
Despite its name, the creek will become a thoroughfare of native flora and fauna for the suburb to enjoy, but not before extensive work is performed. This includes re-laying the existing concrete canal and installing new sandstone embankments, along with naturalised banks with native plantings, a new elevated pedestrian bridge, and a widening of the creek.
To help with the refurbishment, D4C engaged Coates to design and implement a comprehensive water management solution. This comprised a tidal barrier and bypass pump system to prevent surface water from entering the canal during the works, and a dewatering system to extract and treat groundwater.
Sobin Joseph, water treatment solutions specialist at Coates, explains that a tidal barrier is used to manage the tidal water flowing back into the canal.
“To achieve a flow rate of 60 litres per second, this system incorporates two electrical vacuum pumps to manage high flow – one operational, the other on stand-by – plus submersible pumps for managing low-level flow,” says Joseph.
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Coates installed a kilometre-long bypass system, designed to operate 24/7 and accommodate a flow rate of 90 litres per second, using a combination of 150mm trailer pumps, 6-inch and 4-inch submersible pumps and a flow metre. Backup pumps remain onsite throughout excavation and construction to safeguard the bypass system in the event of breakdown.
“This site and solution are not straightforward, so D4C and Sydney Water needed confidence in a partner like Coates who could design and implement it without fail,” Joseph explains.
“We proposed a few different systems. Once the solution was chosen and commissioned, we had just two weeks to implement all the equipment.”
Conor Harten, project manager at D4C, highlights the critical role of water management in the project.
“If the bypass pumps break down or the treatment plant doesn’t work and water quality is affected, we will have to stop work,” says Harten. “But with stakeholders like local residents and Transport for NSW waiting to get onsite, it’s important that construction work stays on track.”
“So far, it has been a positive experience working with Coates to deliver this project. Their water management solution is working well, and we are receiving good support from the Engineering Solutions team.”
Sydney Water has assured the community that the project will benefit native flora and fauna, while also protecting aquatic wildlife from the drainage of Muddy Creek. This involves carefully treating and monitoring all groundwater and rainwater runoff while the fresh concrete cures. Joseph explains that this process requires constant re-evaluation.
“When we started the project, the soil and groundwater was very acidic,” says Joseph. “Then as they started pouring the concrete, the pH level became more basic.”
“These levels kept changing each week, so we needed our technicians to visit the site regularly to make any required changes to the chemical programming.”
This was made even more challenging by the height of the water table onsite. Joseph explains that keeping the tide at bay was only half of the dewatering solution.
“To safely excavate to depths of 1 to 2 metres in an area where the water table sits less than 1-metre from the surface, a robust dewatering solution is required,” he says. “Onsite water treatment is important for maintaining and improving the quality of groundwater, which contains varying levels of sediment and other contamination.”
Despite all the challenges, Joseph says the project is progressing to plan and Coates’ water treatment solution has adhered to Sydney Water regulations, which require all groundwater to be treated and tested before being discharged.
“Over the past 12 months, our water treatment system has allowed all water quality criteria to be comfortably met,” he says. “The improvement that Coates has been able to achieve has kept water quality within the required range and is visibly obvious in the samples taken from this site.”
The project is expected to be complete by late-2024, when the Brighton-Le-Sands community will be treated to a flourishing creek and marshland – not to mention the wildlife that comes with it.
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