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Tue May 21 2024

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Perth makes savings with plastic sewers

4 Apr The Scottish city of Perth is getting a £107m investment in drainage and has opted for composite sewers instead of concrete.

Steel reinforced composite sewers being laid in Perth
Steel reinforced composite sewers being laid in Perth

Morrison Water Services and Aecom, operating as Caledonia Water Alliance, began work on the Perth sewer project in May 2023 for Scottish Water. The team has now taken delivery of

520 metres of reinforced steel composite pipes from Lancashire-based manufacturer Aquaspira.

Usually built using concrete pipe for strength, the steel composite option has saved 5,000 tonnes in transport weight and an estimated 234 tonnes of carbon.

It is also reckoned to reduce site installation time by approximately eight to 10 weeks, since the plastic pipes require less excavation. The smaller size and lighter weight has decreased the amount of excavation required by 28%, according to Aquaspira.

The amount of money saved was not revealed.

A spokesperson for Caledonia Water Alliance said: “We specified the Aquaspira pipes and access units because it would provide a lower carbon solution, minimise the footprint and shorten programme time.

“An accredited and adoptable solution is vital and Aquaspira provides this, the added benefit is that the 2.6 metre sections of pipe, coupled with the push-fit access solution, help with the ease of installation.

“We’ve been delighted with the product and time savings. Lightweight and strong, the pipes can be handled more swiftly and safely, with much smaller machines and need about a quarter less excavation as well.”

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Perth needs new sewers to manage the expected 50% growth in its population, particularly to the north and west of the city. The project will also improve the network’s resilience to and capacity for intensive rainfall, particularly in the low-lying areas near the Tay between Muirton and the city centre. The project is set to complete in January 2025.

Scottish Water’s senior project manager, David Lavery, said: “While we are adapting our infrastructure to a changing climate, we also need to play our full part in addressing its causes. Scottish Water has set a challenging target to go beyond net zero emissions across all of our work by 2040, including the delivery of our significant investment programme. Finding lower carbon ways to build new infrastructure is a crucial part of that journey.”

“Modern sewers of this scale would ordinarily be built using concrete pipe to achieve the required strength, but manufacturing and transporting these across long distances generates significant carbon emissions. The composite steel pipe being used has a lower carbon cost and is much lighter, while having higher strength than could be achieved using plastic pipe at this scale.”

Aquaspira director Mark Stanway said: “In addition to the 2.25-metre diameter steel-reinforced pipes, our solution also includes prefabricated access units. These push-fit solutions reduced the installation of each manhole from an average of four days to around an hour, delivering dramatic cost and time savings to the job, as well as providing a far more environmentally friendly and safer solution.

“Ultimately, we reduced the number of vehicle movements to site by over 65%, as well as cutting the amount of bedding and backfill. The project is now running ahead of programme, partly due to the installation efficiencies of the pipe and access units, helping to reduce disruption for the local community.”

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