Engineers warned this week that new national standards for sustainable drainage systems would be used by developers to avoid installing them in projects.
The standards are proposed in the Flooding and Water Management Bill, currently being finalised by the Department for the Environment, Food and Rural Affairs (Defra). The Bill states that sustainable urban drainage systems (Suds) should be used “where practicable” instead of surface water automatically discharging into the existing sewer network.
“An area of concern is the ‘where practicable’ element,” said Hydro International director Alex Stephenson. “Does that give people the opportunity to ignore Suds altogether?”
The comments were made at a round table discussion about the new Bill held in London last week and organised by NCE and Hydro International.
Defra head of non-agricultural diffuse pollution team Vicky Dawe acknowledged the concern and said a hierarchical system will apply with approval being easiest for schemes that fit flooding, water quality and amenity criteria: “We need to frame them in a way that developers are comfortable with and don’t immediately leap to the bottom of the hierarchy.”
“There is this issue about where practicable. Practicable means sometimes you have clay soil, sometimes you might have a chalk fissure, sometimes you are on contaminated land,” she explained.
Ground conditions play a major role in determining the suitability of a suds system. However she said that suds would not always be appropriate. “ There will be exclusion tests and cost benefits tests and if we get that right, then I think we have got a good system on our hands.”
In the proposed legislation local authorities will become the approval body for suds and must adopt new systems that meet the national standards. Consultants said they hoped that the standards would improve continuity within the approvals process.
“The biggest problem for us as a consulting engineer is explaining to a client why we have to do something in one part of the country when in another part of the country we don’t have to,” said Arup associate director David Schofield.
Consultation for the Bill closed in July and an amended version is expected before the end of the year. It will be made law in the 2010 Parliamentary session.