Stomor Ltd has been working on proposals for a 43-unit residential development at Gardiners Close on behalf of their Client, The Anderson Group. Stomor were commissioned to prepare a Flood Risk Assessment and Transport Assessment in support of the planning application, providing feasibility and planning advice associated with access and drainage for the site. Stomor’s appraisal of the site constraints identified potential issues associated with the discharge of surface water from the development. Clayey soil conditions meant that soakage rates were unsuitable for infiltration, no watercourses were present in the immediate vicinity of the site, and levels across the site were too flat to allow a gravity drainage solution to the public surface water drainage network. As the site is in a Critical Drainage Area, legislative requirements demanded coherent problem solving. To meet a challenging brief set by the Lead Local Flood Authority (LLFA), an integrated drainage solution was developed incorporating surface drainage features to provide water quality treatment and water storage for extreme storm events, underground storage to address water authority requirements and a pumped outfall with limited discharge rate to minimise the surface water runoff into the public sewer. The proposed systems were modelled using Micro Drainage software to demonstrate the hydraulic performance of the system. Modelling confirms that sufficient surface water attenuation has been provided to minimise flood risk within the site and surrounding areas for all storms up to and including the 1 in 100 year event with allowance for 30% increase in rainfall intensity due to climate change. Engagement with the LLFA enabled Stomor to prepare a compliant drainage strategy, meeting demanding requirements for Sustainable Drainage Systems (SuDS) within a complex site. Despite a number of site constraints, Stomor’s rigorous approach in the preparation of planning documents was rewarded when the site gained planning permission in September 2015.
5th January 2016
Civil Engineering Design, Flooding & Drainage