Willmott Dixon Construction have been looking for a better environmental solution to prevent silt and sediment entering drainage systems. Common issues with the ‘Witches Hat’ type gulley sock are that they are held in place by nipping the fabric at four points at the grate, however on hinged grates only two securing points can be achieved which allows sediment to pass. These products generally fail as the weight of water and sediment then causes them to rip.
To resolve this issue, Willmott Dixon turned to one of their Mandated Goods Partners to look for an alternative solution. This is how they began using a prototype gulley protector called: ‘Nappy Trap’.
This is a low profile rubber mat weighing 7kg that sits over a drain/gulley using its own weight to create a seal with the ground. The outer perimeter of the product provides the first stage of filtration by filtering out the larger sediment and debris. Water flows through the product until it arrives at the centre section which has a 150 micron mesh that prevents non-compliant sediment entering the gulley. The outer perimeter is visible, which ensures maintenance is easy and any captured sediment or debris can be simply swept away.
Nappy Trap is built to withstand the most arduous site conditions, including being driven over by site traffic. Ultimately two versions of the product will be available; one designed for kerb side gullies and one for gullies situated in an open area. It is fully re-usable, can be easily washed down after use and is manufactured from locally sourced, recycled materials.
Monitor report. Willmott Dixon. South Yorkshire. February 2020.