Updated guidance will help ensure SuDS are built and function as designed By SUZANNE SIMMONS of the Construction Industry Research and Information Association (CIRIA)
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WITH THE RELEASE of CIRIA’s new SuDS Manual (C753) we could be forgiven for thinking that guidance on the subject of sustainable drainage systems, or SuDS, was complete. Not so – a good SuDS design can be misinterpreted and let down by poor construction and detailing and that can affect performance and ultimately cause failure. With SuDS becoming more commonplace and the diversity of schemes and applications growing, it is timely to review and update guidance on the construction of SuDS to ensure they are built as designed and provide the performance and benefits required. One of the biggest areas of concern in the SuDS community lies in reputational risk. All too often inexperienced contractors are faced with SuDS projects having never constructed a SuDS scheme before. Assumptions are made and what gets built is not necessarily what was intended by the SuDS designer. The reasons for that can be unclear but the outcomes can be catastrophic for the project and its end users, and importantly it can undermine the reputations of designers and contractors. From the client’s perspective it is imperative that we ensure SuDS are constructed well and that they function as intended. That is why CIRIA is now developing guidance on SuDS and construction. RP1028 Update of SuDS and Construction Guidance is led by landscape consultancy Illman Young and the Environmental Protection Group (EPG Ltd). Lead author Sue Illman said: “Knowing how to build SuDS properly to both good visual and engineering standards is the industry’s last big hurdle. Unless we do, it will seriously undermine its uptake.” Contractors need to understand that in constructing SuDS schemes they are also delivering a multiple range of benefits – not only for the conveyance of surface water but also for water quality, amenity and biodiversity. The new SuDS Manual extols an interconnected relationship between what the authors call the ‘four pillars of SuDS’, where a welldesigned and constructed SuDS can deliver on water quantity, quality, amenity and biodiversity. CIRIA’s author team for RP1028 Update of SuDS and Construction Guidance recently carried out an industry survey that drew significant feedback on contractors’ relationship with constructing SuDS, drawing out information on performance that included the good, the bad and
the ugly. The feedback gained from the research will now feed into the project to shape outputs and target areas most in need of steer. Positive suggestions from respondents that are being considered in the new guidance relate to: • Checking the design prior to commencement – for services, infiltration capacity and confirmation of levels at all stages • Ordering the right materials at the right time • Using the right contractor or specialist contractor • Managing the works on site throughout – including sequencing, site conditions, protecting the works and maintenance • Ensuring that those who sign off have the right expertise to do so. Poor delivery of SuDS may be due to a lack of clear communication and handover; but more often it is due to a lack of understanding and awareness of the critical principals required for SuDS that differ from those for conventional, below-ground drainage. Resolving these issues often begins with having a basic understanding of the principals underpinning the project’s SuDS design philosophy. The new update will take the feedback and suggestions from the construction industry and work them into accessible and easy-to-follow guidance. It will include illustrations, images, step-by-step processes, case studies and handy hints. They will have strong visuals, be easy to read and suitable for contractors to use on site. They will be aimed particularly at those who supervise site operatives. However, the outputs from the research will have wider readership within the construction team, as well as for SuDS designers and approval/adopting bodies who share vital interactions with the construction process and construction team. The guidance will be shaped around the following key stages and processes: • Setting the scene – SuDS: the basics • Pre-construction – understanding the site and its design • Construction planning and programming • Site management and general construction considerations • Constructing and inspecting SuDS. It is anticipated that the outputs from CIRIA’s Update of RP1028 SuDS and Construction Guidance with be released early next year. q • Suzanne Simmons is a chartered landscape architect and the project manager at CIRIA responsible the recent release of its SuDS Manual (C753) and forthcoming CIRIA project RP1028 Update of SuDS and Construction Guidance. If you have any queries on the project, or wish to provide supporting case studies or information, please contact suzanne.simmons@CIRIA.org. Images courtesy of Salix and JPP Consulting
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