The long-awaited draft National Standards for Sustainable Drainage Systems (SuDS) have just been issued for consultation by the Department for Environment, Food and Rural Affairs (Defra). Early response from the trade association Interpave raises concerns about a loophole enabling developers to avoid SuDS for cost reasons.

The draft National Standards have been developed to meet the requirements of the Flood and Water Management Act 2010, which makes SuDS effectively mandatory.  They stress the importance of source control, water management near the surface, cost-effective operation throughout design life and integration of public space with SuDS. These are all areas where concrete block permeable paving makes an invaluable contribution, signalling the mainstream use of this important SuDS technique. 

As part of the consultation process, Defra proposes working in conjunction with other organisations over the next few months to develop more detailed guidance than the National Standards offer. Interpave has already indicated its willingness to be a part of this process and has in place a wealth of information on permeable paving and SuDS on its information resource www.paving.org.uk. Interpave will also be discussing the draft Standards in more detail during the consultation period. 

However, Interpave is particularly concerned about a proposed ‘get-out clause’ within the draft National Standards. In its current form, this will allow developers to avoid “full compliance with the Standards” where a SuDS scheme “is more expensive than an equivalent conventional design.” This move could significantly reduce our ability to defend against a repeat of the widespread flooding events seen in recent years where increased urbanisation and climate change have led to the sewer network being overwhelmed. Mandatory SuDS is seen by many as an essential component in the fight against repeats of these flooding events and their cost in both financial terms and human suffering.  

The move could also be seen as unnecessary given the cost-effectiveness of SuDS schemes, particularly those incorporating concrete block permeable paving.  Independent research commissioned by Interpave found that: “concrete block permeable pavements proved the most effective paving solution over 40 years” when using a whole life costing analysis. It also demonstrated that fully infiltrating permeable paving had the lowest initial costs wherever it could be used, when compared with various other impermeable paving materials using concrete block permeable paving with conventional drainage systems.