It may be preferable if surface water falling on hard surfaces is left to infiltrate into the ground rather than flowing into a piped sewer system, a manual published by Water UK has claimed.
The work to develop the manual was led by a group chaired by professor David Balmforth and also included representatives from a broad range of parties with an interest in water and sewerage companies adopting SuDS. Members of the group also included Defra, CIRIA, specialist drainage engineers and SuDS consultants as well as developers.
The report highlights the benefits of using sustainable drainage systems (SuDS), stating: “Not only will this reduce the chances of the sewer pipes overflowing in times of heavy rain, but it could create additional headroom in the sewer system to allow for more housing development.
“Such systems often provide other benefits as well, such as enhancing the amenity value of an area by creating green spaces and absorbing certain pollutants in surface water.
“A number of water and sewerage companies have already taken steps to encourage this approach, but there has until now been no nationally agreed approach on the part of the water and sewerage companies towards the transfer to them (technically called ‘adoption’) of these types of sewer.”
According to the report, best criteria for sewers to be adoptable to developers and those designing surface water drainage include having a channel, an effective point of discharge and the allowance for some infiltration into the system.
Other positive criteria for sewers to be adoptable in such a manner include them being constructed for the drainage of buildings and yards appurtenant to buildings.
Meanwhile, the report also outlines criteria that may ensure sewers are not adaptable to developers and those designer surface water drainage, such as if they are built to manage groundwater or part of the structure of a building or yard.
In addition, the manual highlights examples of systems, components or features which may be adoptable as public surface water sewers, such as detention basins, swales, rills, under-drained swales, ponds and infiltration basins.
In each case, the examples are of systems which carry away surface water from buildings and surrounding land.
Examples of features, components or systems which the report highlights as unsuitable include highway drainage and private drainage features.
News of Water UK’s guide being released comes after local government’s progress in implementing sustainable drainage systems was last week criticised in a report by landscaping experts Illman Young highlighting “underlying failures within the current system”.
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