New design and construction guidance for the sewage sector replaces SfA7
New Ofwat codes for adoptable sewers came into force in England from April 2020 replacing all versions of Sewer for Adoption. This new guidance is for use by developers when planning, designing and constructing foul and surface water drainage systems intended for adoption by English water and sewage companies under a section 104 agreement. It differs from the outgoing Sewers for Adoption guidance as compliance will be mandatory.
The new code only applies to Water Companies in England, Scotland, Wales and Northern Ireland all continue with the guidance in place. The adoption code is significant as it provides the mechanism by which water companies can secure the adoption of a wide range of SuDS components that are compliant with the document. There are however some notable exceptions to the adoptable components including green roofs, pervious pavements and filter strips. These components may form part of the drainage design but will not be adopted by the WaSC.
It is hoped that this new mandatory code will help to enable more sustainable new developments that also deliver a range of multi-functional benefits to communities. It has the potential to deliver better managed and more integrated surface water systems that align more closely with government and regulatory policy and incorporate the four pillars of SuDS including amenity, biodiversity and water quality.
The new code states that the layout of the whole development including the drainage layout should be considered at the earliest stages of the design as it is fundamental to the performance and affordability of the drainage system as well as the wider urban design including the character of the development, amenity, biodiversity, connectivity and use of the site.
Other key points in relation to the design and construction of new surface water drainage systems include:
- The successful design requires the designer to liaise with a variety of stakeholders from the earliest stages in the design of the development.
- The location of adoptable drainage components should take account of the need to provide appropriate access to each component for maintenance.
- Health and safety risks should be assessed and managed in accordance with Ciria C753 SUDS manual and a copy of the principle designers risk assessment submitted to the water company.
- Provided there is provision for the flows to reach a particular feature, surface SuDS features designed to take 1 in 100 year rainfall event plus climate change will normally be adoptable.
Martin Lambley, product manager for Stormwater Management said
“Since the Pitt report in 2008, the uncertainty the over adoption of SuDS has acted as a barrier to their implementation. I hope that the new DSG will help to remove this barrier and increase the use of SuDS in new developments. SuDS are not only important in ensuring the flood resilience of our cities but will also improve the environment by increasing biodiversity and air quality, ultimately making them healthier places to live and work.”
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