Sustainable Drainage Systems SUDs Soakaways
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Sustainable Drainage Systems SUDs are a modern approach to drainage and are generally concerned with surface water disposal. Planning Policy Guidance Note 25 and Requirement H3 of the building regulations encourage the use of SUDS.
There are a number of definitions which could be used to best describe SuDS. However, the most appropriate is a sequence of management practices and control structures designed to drain surface water in a more sustainable fashion than some conventional techniques. Others include how the built environment attempts to mimic the natural drainage of the land and the storage and safe handling of surface run-off of rain to slow down the volume on sewer.
The need for SUDS is nationally recognised and we’re fully in favour of properly implemented SUDS, and where appropriate, we play our part in designing a SUDS solution where it is suitable to form part of the wider public sewer network.
The government is preparing national guidelines for the implementation of SUDS together with a model framework for their maintenance. Depending on the specifics of a site, responsibility is expected to fall to the most appropriate relevant authority.
Correct implementation of SUDS will reduce the rate and volume of surface water draining into the public sewer network by allowing the water to drain naturally into the ground or slowing discharge into the public sewer. This in turn protects the public sewer from overload and the environment from pollution.
Where surface water would have traditionally drained into a combined foul and surface water sewer, the use of SUDS prevents relatively clean surface water from passing unnecessarily through the waste water treatment process. The use of certain types of SUDS for highway drainage has the advantage of inbuilt pollution control, for example the vegetation in grass swales can be effective at filtering oil and grit out of the surface water runoff from the highway.
The statutory sewerage undertaker is responsible for the public sewer network. their role in the disposal of surface water is defined by the Water Industry Act 1991. A sewer is a conduit that is provided for domestic sewerage purposes, serving more than one curtilage and has a proper outfall (e.g. a watercourse is a proper outfall but a soakaway is not). A public sewer is a sewer that is the responsibility of the sewerage undertaker. Legislation defines what can form part of the public sewer.
Unfortunately, many types of SUDS, such as soakaways and ponds cannot be adopted as part of the public sewer network. Where there is a need to restrict the rate and volume of surface water draining into the sewer network, use of an underground on-line storage tank is the favoured method (Paragraph 1.13, Water UK/WRC PLC 2001 Sewers for Adoption 6th Edition). Consequently, where SUDS, for example a detention pond, is proposed to form part of the public sewer network, special arrangements are necessary that are usually subject to a private agreement.