SuDS Drainage Design for Two New Homes on a Brownfield Site Near Chepstow
Two new dormer bungalows near Chepstow needed a SuDS drainage scheme to satisfy Welsh Water’s 5 l/s discharge condition and the local authority’s planning requirements. WCI Consulting Engineers delivered the full design package.
Summary
- 40% minimum reduction in peak runoff - planning condition requirement
- 1:100yr plus 30% climate change - design standard applied
- 5 litres per second - Welsh Water's maximum permitted discharge rate
Project in numbers
40%
Minimum reduction in peak runoff
1:100yr plus 30%
Climate change - design standard applied
5 litres per second
Welsh Water's maximum permitted discharge rate
Overview
Planning permission for two new dormer bungalows near Chepstow required a SuDS drainage scheme compliant with both Welsh Water’s connection conditions and the Forest of Dean planning authority’s requirements – on a site where infiltration had already been ruled out.
The Challenge
The originally designed infiltration scheme had been shown to be unviable due to poor soil porosity. Welsh Water granted connection on the condition that discharge was limited to 5 l/s. The scheme needed to make efficient use of drainage already installed on site.
The WCI Solution
WCI calculated greenfield runoff rates, determined attenuation storage requirements and specified flow control equipment. A drainage layout was developed making full use of the existing on-site drainage, with attenuation infrastructure and flow controls specified and documented for planning submission. A maintenance and management plan was prepared to support the planning authority’s long-term requirements.
The Outcome
A fully documented SuDS scheme was delivered for planning submission, compliant with both Welsh Water’s discharge condition and the local authority’s requirements.
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