Coates keeps Sydney canal dry for restoration

One Sydney canal needed specialist attention. How do you keep the tide at bay while refurbishing a waterway for the local community?

How do you keep the tide at bay while refurbishing a waterway for the local community? Learn how Coates Engineering Solutions delivered a comprehensive dewatering and water treatment solution for D4C to keep construction work 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. However, extensive work is needed. 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 solution included 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.

“A tidal barrier is used to manage the tidal water that moves back into the canal,” says Coates Water Treatment Solutions Specialist Sobin Joseph.

“To achieve a flow rate of 60L/s, this system incorporates two electrical vacuum pumps to manage high flow – one operational, the other on standby – plus submersible pumps for managing low-level flow.”

Building a bypass for Sydney canal

Coates installed a kilometre-long bypass system designed to operate 24/7 and accommodate a flow rate of 90 litres per second. The system uses a combination of 150mm trailer pumps, 4- and 6-inch submersible pumps, and a flow meter. Backup pumps remain on site throughout excavation and construction to safeguard the bypass system in case of a 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.”

D4C Project Manager Conor Harten 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 on site, 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.”

Supporting community in Sydney canal project

Sydney Water has promised the community that the project will benefit native flora and fauna while protecting aquatic wildlife from the draining of Muddy Creek. This involves carefully treating and monitoring all groundwater and rainwater runoff while the fresh concrete cures. Joseph says this process requires constant re-evaluation.

“When we started the project, the soil and groundwater were very acidic. Then, as they started pouring the concrete, the pH level became more basic,” he said.

“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 due to the height of the water table on site. Joseph explains that keeping the tide at bay was only one-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. “On-site water treatment is important for maintaining and improving groundwater quality, which contains varying sediment levels and other contamination.”

Despite all the challenges, Joseph says the project is progressing to plan. 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 achieved 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 completed 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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