Alex Stephenson looks at the myths surrounding SuDS
New regulations are set to make the use of Sustainable Drainage Schemes compulsory for development and redevelopment serving more than one property as part of far-reaching measures to improve flood risk management and control in England and Wales.
Developers and contractors will need to understand their obligations in designing and installing SuDS-compliant schemes, in future, and will need to work closely from the early stages of planning with new Local Authority teams – to be known as SABS (SuDS Approving Bodies) to ensure the drainage scheme is designed in accordance with new National Standards.
Some developers and contractors are naturally nervous about the proposals, worried that they may put extra time and cost pressure onto developments.
The good news is there is no need to worry and there are plenty of opportunities for Builders’ Merchants to supply SuDS-compliant products to control the quantity and quality of surface water according to the requirements.
The problem is that a number of ‘urban myths’ have grown up which could have a tendency to discourage the correct specification of products and techniques to design efficient and cost-effective SuDS schemes. It’s important for merchants to understand the myths, so that they can advise customers accordingly.
The first myth is 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.
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.
A significant 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. This is the most important one to bust from the Builders’ Merchants perspective.
It’s important because it influences the way merchants should advise customers. Let’s take the example of a vortex flow control device such as the Hydro-Brake Optimum™.
Changing from the specification to a cheaper product will change the engineered performance of the site, and could increase the flood storage capacity required, meaning more contracting costs and more land-take.
Changing to an alternative product without adjusting the design accordingly at best would be unprofessional on the part of the customer. At worst, could lead to a costly call-back to site following a flood.
Alex Stephenson is director of Hydro International UK Stormwater Division and chair of the British Water SuDS Focus Group. www. Engineering Nature’s Way.co.uk – a means of sharing knowledge and experience about SuDS.