Attenuation systems for sustainable drainage project

Timeworn agricultural land is fast being used as the new source of development land for housing projects, such as the new Lewis Civil Engineering scheme for Taylor Wimpey Homes, which sees the development of 475 homes on an old dairy farm on the A48, near Cowbridge, Wiltshire. A new primary school and associated infrastructure are also part of the development, with a new roundabout being constructed on the A48 as part of the link road. When the Darren Farm project was granted planning permission there were conditions relating to flooding and infrastructure issues, which has resulted in a three-line attenuation tank being installed, using 1500mm dry weather flow pipes from Marshalls CPM. Lewis Civil Engineering were ideally matched to this type of scheme as they had initially specialised in deep sewer and water main pipelines when the company began in 1984. Les Vile, Specifications Manager for Marshalls CPM believes that the precast concrete dry weather flow pipes are perfect in areas that are prone to flooding as they can reduce over-pumping costs by up to 15% and are used in large capacity surface water or foul tanks. “Using the precast dry weather flow pipes concentrates the water flow into a channel at the bottom of the attenuation system, increasing the water flow velocity and preventing the settlement of solids or water in the tank. When flooding or high flow levels are in action, the open channel overflows, stimulating the full volume of pipe. This enables the water and sewage to move freely, during both high and low flow levels, eliminating blockages in the system.” Jo Wallace-Blaker, Trading Manager said, “using a precast solution reduces on-site construction time as well as the need for confined space working and heavyweight concrete has the ability to withstand ground movements and water jetting. By installing concrete pipes, a contractor can make cost savings on both pipe bedding materials and a reduction in vehicle movements on-site. As well as the attenuation pipe system, we have also supplied Hydro-brake chambers as part of the sustainable drainage system (SuDS). Aligning modern drainage systems with the natural water processes of the land.”

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