Water & Wastewater Treatment

In the know Getting to grips with… sustainable drainage systems the volume of water discharged to the drainage network or local watercourse. SuDS intercept and hold back (attenu- ate) excess surface water runoff, then manage it through temporary storage, infiltration, evapotranspiration or reuse. Storage may be achieved with above-ground features such as reten- tion ponds or by using underground geosynthetic modular systems. Designers may need to consider the most efficient way to minimise storage volumes e.g. by use of optimising vortex flow controls. At the same time, a good SuDS management train should also remove pollutants by filtering or separating out silt/sediment, litter and hydro- carbons from surface water prior to discharge into the watercourse. Removal can be achieved through natural features such as filter strips or swales, as well as by manufactured devices such as hydrodynamic vortex separators. O€en a combination of above- ground landscaped features and man- Top FIve TIps For suDs BesT pracTIce 1 Start early: SuDS plans should be incorporated right from the start of a project, preferably during master- planning and guided by the Local Plan. Close working relationships are needed from the start between landscape architects, drainage designers, developers, Lead Local Flood Authorities (LLFAs), water companies and the Environment Agency. 2 Engage the community: Getting local people passionate and involved in sustainable surface water manage- ment has been shown to be highly effective in achieving successful schemes. 3 Use the full SuDS toolbox: Create a surface water management train using the most appropriate 'natural' and manufactured components, taking into account the space available for storage, the ground conditions, the level of pollutants present, the level of infiltration that is possible, and so on. 4 Plan predictable and repeatable maintenance. The new planning rules for England place a much greater responsibility on developers to show how SuDS schemes will be maintained effectively throughout their life. Ensuring that SuDS continue to perform requires skilled ground maintenance, as well as following manufac- turers' schedules for inspection and maintenance of proprietary systems. 5 Insist on quality contractors: Construction of a SuDS infrastructure can require a different skillset for con- tractors from conventional drainage approaches. Especially for natural SuDS features, incorrect construction can mean the drainage does not perform as designed from the outset. ufactured devices come together to achieve the best results. Increasingly the focus will be on demonstrating how the system can remain effective and continue to perform as designed through appropriate ownership and maintenance. Who is Most Likely to Build SuDS? Although much recent attention has been on developers and housebuild- ers, SuDS are also regularly built by highways authorities and by water companies, who can build, own and maintain SuDS to prevent flooding and over-capacity of their sewer networks. Indeed, water companies are a key stakeholder in surface water control and treatment, as the sewer network may be the last line of defence for poorly-designed or maintained SuDS features. Water companies also argu- ably have a pivotal future role to play in SuDS retrofitting to enhance our urban environments. What Design Guidance Is Avail- able for SuDS? The need for everyone involved to share and learn from best practice is fundamental to future acceptance and successful delivery of sustainable drainage systems. Many local authori- ties, and some water companies, have developed their own design guidance which provide excellent sources of reference. CIRIA's expected update to C697, the SuDS manual will be more important than ever in providing a national framework for best practice. Industry resources such as the En- gineering Nature's Way and Susdrain websites provide a good source of ref- erence, industry news and comment, as well as policy updates and links to resources such as design guidance and online design tools. Manufacturered components can play a crucial role in SuDS alongside natural elements. Pictured below: A Hydro Downstream Defender Vortex Separator being installed 36 | MArCH 2015 | WWT | www.wwtonline.co.uk

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