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Combined attenuation system meets flood prevention requirement


Combined attenuation system meets flood prevention requirement

Flood prevention was a key requirement of planning permission for a 475-home development on agricultural land in the Vale of Glamorgan. The project also includes a new primary school and a roundabout being constructed as part of a link road.

The main contractor, Lewis Civil Engineering, specialises in deep sewer and water main pipelines and worked closely with Marshalls CPM. Precast concrete dry-weather-flow pipes are suited to areas prone to flooding as they can reduce over-pumping costs by up to 15 per cent.

A three-line attenuation tank using 1500mm dry weather flow pipes was specified. This was combined with Hydro-Brake Optimum flow-control chambers, as part of the sustainable drainage system (SuDS), which Marshalls CPM also supplied.

Les Vile, specifications manager for Marshalls CPM said: “Using the precast dry-weather-flow pipes concentrates the flow of stormwater into a channel at the bottom of the attenuation system. This increases velocity and prevents the settlement of solids or water in the tank.

“When flooding or high-flow levels are in action, the open channel overflows, utilising the full volume of pipe. This means stormwater can move freely during both high-flow and low-flow events, eliminating blockages throughout the system.”

Jo Wallace-Blaker, Marshalls CPM’s trading manager said, “There are multiple benefits to using a precast concrete solution like the one deployed here. It reduces onsite construction time, in turn reducing health and safety risk.

“In addition, heavyweight concrete has the ability to withstand ground movement and water jetting, making the system more resilient. By aligning modern precast drainage with Hydro-Brake flow control as part of the SuDS, it has been possible to mirror the natural watercycle at this site.”