Too many urban myths have grown up around the use of SuDs, argues Alex Stephenson, Operations Director Hydro International and Chair of the British Water SuDS Focus Group.
In the Summer of 2007 devastating floods claimed 14 lives, caused £3.2 billion worth of damage, and affected 48,000 homes and 6,000 businesses in Britain.
Two thirds of the floods were attributed to surface water flooding and they turned out to be a major driver for change in the way stormwater drainage schemes would be planned and implemented in England and Wales. Only now, nearly five years later, is the full impact of those changes really starting to be felt by the building industry.
The floods prompted the Government to commission Sir Michael Pitt’s seminal review and his recommendations were embodied in the Flood and Water Management Act (FWMA) 2010. The Act brought in radical changes to make Sustainable Drainage Systems (SuDS) compulsory in new developments and remove the automatic right of a developer to connect to a public sewer.
Right now, the Government is consulting on proposed National Standards for SuDS. The Standards will be the basis by which new Local Authority SuDS Approval Bodies (SABS) will approve Sustainable Drainage schemes on developments and redevelopment greater than one property.
Whilst the proposals are extremely positive, there have been some concerns about the speed of implementation of the proposals. Already delayed until October 2012, it’s possible they may even be put back until April 2013.
My impression is that only about a third of Lead Local Flood Authorities (LLFAs) have the people they need in post for SABS and the delays have made it more difficult for them to get the necessary funding.
It will be the SAB’s role to work closely with developers and contractors from the earliest stages of a project. So, to do their job, the standards must drive through consistent sustainable outcomes across the land, but with such a varying picture ‘on the ground’, there is real cause for concern.
I know some developers and contractors are concerned that the new regime will just mean more cost and another level of planning and red-tape. But my message would be: ‘don’t panic’. The situation may not be what it at first seems.
The problem is that a number of ‘urban myths’ have grown up around SuDS:
Firstly: that they are only ‘green’ or ‘soft’ features. Not true. In fact, true SuDS are made from a treatment train which can be selected from a broad ‘toolbox’ of engineered and more ‘natural’ components. This is the principle of Engineering Nature’s Way, which I believe offers a practical, achievable and clearly-understandable way forward.
Secondly: that they will make projects more expensive. Concerns about the potential extra costs of installing SuDs were probably behind a late addition to the standards: a clause that can exempt developers from installing SuDS schemes on the grounds of “disproportionate cost”. This has been seen as something of a ‘loophole’ and in my view, is unnecessary. By applying SuDS principles – as outlined in the standards – and the full toolbox of SuDS techniques, there should be very few schemes that would fall through the net. If this clause really does deliver a ‘get out of SuDS free card’ for ill-informed developers – or even local authorities – it could compromise the whole spirit of the Act.
The third ‘urban myth’ for SuDS is that one proprietary product is a good as the next one – no matter what is specified on the drawing. Now that all SuDS schemes are subject to approval by the SAB on the basis of a submitted engineering design, this is a dangerous assumption. If a contractor changes from a specified product, it could change the engineering performance on the site with potentially disastrous consequences. Changing from the specified flow control device, for example, could increase the flood storage capacity required. At best, this would be unprofessional, and at worst, could lead to a costly call-back to site following a flood.
The Standards introduce a new requirement for treatment of surface water to remove silts, sediments and pollutants. The stated need for three or four levels of treatment may set alarm bells ringing as contractors contemplate the earthworks involved in ponds, reed beds, swales and basins – not to mention the land take that could otherwise be used for development. Again, things may not be as bad as they seem: Compact treatment devices use vortex separation technologies to provide a low-maintenance, no-power solution incorporating several treatment levels in one. Using vortex flow controls can be used to reduce the storage requirements significantly and consequently the overall project costs.
There is still time to respond to the Defra consultation on the National Standards which ends on March 13. Visit www.engineeringnaturesway.co.uk for more news and comment on the National Standards.
