SuDS have been integrated into developments in the UK since the mid 1990’s, yet they are still not mainstream. Many have citied the lack of any formalised route to adoption as being one of the primary reasons for the lack of uptake, along with the unknown requirements for maintenance, when compared with conventional piped drainage systems.
The published draft Sewers for Adoption 8th Edition (SfA 8th Ed) provides a strong indication that Water and Sewerage Companies (WaSCs) across England are in the process of considering a range of vegetated and hard landscape SuDS techniques for adoption, which considerably extend on the existing offering of oversized pipes and tanks. Welsh Government have taken a further step forward with the introduction of the SuDS Approval Body (SAB) and the imminent release of the SuDS Standards for Wales with associated changes in legislation including enactment of Schedule 3 of the Flood and Water Management Act (2010)
There will be detail that will have to be resolved through all of this and a degree of pragmatism will have to be exercised between the authorities. For example – if it reasonable to have one organisation maintaining a 1-2m wide filter strip (cut grass) which conveys flows to a swale which the WaSC would adopt and maintain (cut grass).
It has also been recognised within the Draft SfA Ed8 that it would be a pragmatic step to align hydraulic standards for adoption with those currently being required by Local Planning Authorities and Lead Local Flood Authorities in dealing with National Planning Policy Framework and Non Statutory Technical Standards.
From reading the draft there are a number of points of interest – some of which are outlined below.
- The 5m rule for infiltration is no longer considered a rule – but rather a stop point to check if it is going to be ok to infiltrate close to buildings. The draft specifically references permeable pavement with no additional contributing area as not having any constraints.
- The Draft SfA recognises the inlet capacity of SuDS features to take the significant rainfall intensities being experienced on a more regular basis, when compared with the limited inlet capacity of gully pots.
- From 7th January 2019 in Wales, the National SuDS Standards for Wales will take precedence meaning that the SAB will adopt SuDS serving more than one property (and other exemptions). Therefore the SfA8 is unlikely to have any real relevance in term sof storm drainage (foul drainage will still be applicable) in Wales from start of next year.
- The Draft SfA identifies a requirement for significant freeboard on open SuDS structures (which could double or treble the available storage), but does not infer any requirement for freeboard on closed underground structures.
The implications of these points will have to be explored further and will most likely be tested whenever the Draft SfA is released as final. To achieve the right outcome from the adoption process in terms of the types of SuDS features which will be delivered on sites a degree of pragmatism will have to be exercised as part of vetting submissions for adoption which will require additional upskilling and capacity building by consultants, Local Authorities and WaSCs alike. A good deal of upskilling by WaSCs will also be necessary if they are going to implement SfA and more forward with the correct endeavour.
Whilst not a silver bullet, it is definitely a step in the right direction. All we need is a really well-designed set of standard details that are SuDS compatible rather than conventional drainage to sit alongside the document when it is released and we could be on to a winner.