Coates keep water clean at Spirit of Tasmania Quay

As a proven shoring and water management solution provider, Coates was chosen to support BMD Constructions in delivering a stormwater pollution solution for the recently constructed Spirit of Tasmania ferry terminal at Corio Bay in Geelong, Victoria, featuring gross pollutant traps.

One of the most important methods of preventing water pollution is to excavate and install gross pollutant traps (GPTs) to filter out rubbish or harmful debris. This is precisely what BMD Constructions entrusted Coates to do at the Spirit of Tasmania port, which opened in late 2022.

As BMD Constructions was responsible for all the landside civil construction at the quay, this encompassed stormwater management.

“When rain falls in any paved areas – such as the large parking and marshalling areas at the quay – the water needs to be properly drained and channelled into the waterways,” explained Coates Engineering Solutions Specialist John Palavras. “A network of drains achieves this, but the water needs a filtration system to remove litter or other objects that might pollute it.”

According to Palavras, BMD Constructions chose Coates to help with this aspect of the project because of the company’s proven working history in delivering custom shoring solutions.

“We’ve worked with BMD on many engineering projects, particularly sheet piling and slide rail shoring,” said Palavras. “The project had some challenges, particularly since it had to be delivered to a strict timeline. But they trusted we could do it, and we delivered.”

Challenges of installing gross pollutant traps (GPTs)

One of the challenges in installing GPTs at the Spirit of Tasmania’s terminal was its waterside location. When excavation is performed close to or below the water level, it increases the risk of flooding and collapse. It is why a robust shoring solution and dewatering strategy was required.

“It was quite tricky to manage the water during the excavation process, as we had some tanks that were five metres wide and about two and a half metres below ground level,” said Palavras. “As you can imagine, we experienced many issues as we dug down with water coming back up on us and with ground stability. We had to come up with a shoring system that was safe and adequate to suit these dimensions.”

All the GPTs required concrete bases to hold them securely in place. This was a challenge in the context of the wet conditions.

“If the bases didn’t have enough time, or a dry enough environment to cure, the tanks wouldn’t sit securely in the pit,” Palavras explains. “The pressure was on Coates to keep the pits dry throughout this process, giving the slabs the time they needed to harden.”

GPT plans need adjusting

Originally, BMD had planned to use sheet piling for most of the gross pollutant traps (GPTs) excavations, but as the team began the process, they realised that it would take too long considering the conditions. Instead, the Coates and BMD teams worked collaboratively to devise an alternative solution that combined slide rail shoring and sheet piling. One of Coates’ engineered shoring solutions – slide rail rolling strut shoring – was used.

“Slide railing isn’t watertight, but the further we got from the water’s edge, the more we used this technique. And when we encountered water, we could quickly install localised pumps to keep the excavation sites safe and dry,” Palavras said. “This proprietary, engineered slide rail system won’t suit every application, but it worked well for this client and on this particular site.”

The site also relied on sheet piling to support the installation of GPTs near the water. Coates’ proprietary hydraulic Mega Brace and waler beams are used to brace the excavation horizontally.
“For the largest GPT, which was located on the northwest side closest to Corio Bay, this was necessary as it gave the support required for those larger dimensions,” Palavras elaborates. “As the ground conditions were so challenging for this excavation, we designed a system that incorporated walers positioned at four different levels, braced with Mega Brace hydraulic rams. Our 100t mechanical system propping provided additional support, and wellpoint dewatering was used to manage water within the excavations.”

Despite the tight deadline and weather conditions – as much of the work was carried out during the winter months of 2022 – Coates completed their project scope on time. Palavras attributes this efficiency to Coates’ value of acting as ‘One Team’.

Coates perfect partner for turnkey solutions like gross pollutant traps

“We can deliver a turnkey package where every aspect is done in-house. We’re not outsourcing anything. From the first enquiry to the engineering design, we’ve got the equipment and skillset to install, commission and deliver an end-to-end solution,” he said. “That mitigates a lot of risk for the client, as they don’t have multiple contractors coming in providing separate services, such as one company for transport, one for dewatering, one for propping and so on.”

Laurence Leeming, Senior Project Engineer for BMD Constructions, believes having Coates as a partner for the GPT installation was instrumental in BMD completing the project within the deadline.

“As we needed a reliable solution and quick turnaround, we knew Coates was the best provider to work with. The guys on the ground were easy and professional to deal with. We had some trouble getting the shoring to connect with what we already had in the ground, but they worked well with us to resolve the issue,” said Leeming. “Coates was also quick with turnarounds for pricing and sourcing equipment, keeping us on schedule. We also found it much easier to deal with one company for shoring and dewatering solutions.”

Palavras also complimented the fact that BMD communicated their scope of works and targets clearly from the outset of the project – so that both organisations could work together as ‘one team’.

“Communication is key. Having a clear message from the top down as to what the project is about and what needs to be delivered is critical to the project’s success,” he summarised. “We were happy to work with BMD to fulfil these works in time for the terminal’s opening on 23 October 2022.”

For more information, visit https://www.coates.com.au/