Following an initial SuDS assessment for Ellen’s Court, Furzen Lane in Waverley, GeoSmart were commissioned to update the findings of our report following the client’s revised site layout plans. The initial report included an assessment of the SuDS hierarchy, runoff calculations and proposed outline drainage strategy.
Recent legislation changes to rural proposed developments proved a challenge for the client to secure planning permission, given the necessary requirement for a drainage assessment. By collaborating with Emily Temple from ET Planning (based near Reading), we were able to successfully satisfy the Local Authority by ensuring our updated run-off rates and volumes were managed for the lifetime of the development. This included the 1 in 100 year storm event and 40% allowance for climate change.
Given the low potential to infiltrate to ground (as shown by GeoSmart’s SD50 Map© and indicated during in-situ percolation testing) and limited opportunity connect into the nearby sewer, our recommendation was to discharge into a surface water course identified by a GeoSmart consultant during a site visit.
The surface water course was located off-site on land adjacent to the west, therefore discharge would be subject to consent following a feasibility assessment and formal agreement from third party landowners and the Local Authority.
The final SuDS scheme included an attenuation volume of 43.4 m³ stored within SuDS features prior to discharging to the nearby surface water course at a restricted rate of 2.28 l/s (Greenfield QBAR runoff rate). The features included lined permeable paving (with underlying aggregate material) and conveyance swales, to attenuate flows prior to discharge off-site.