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Sustainable Drainage

Wales is now perhaps leading the world in requiring joined up thinking in drainage design.  Drainage systems are core to sustainable development. They can hugely improve the environment where we live, work and play.

SuDS systems must address 4 core areas:  water quantity (flooding), water quality (pollution), biodiversity (wildlife and plants) and amenity. Such systems that do address these 4 core objectives are then known as Sustainable Drainage Systems (SuDS).

SuDS usually manage rainfall close to where it falls. The Welsh Government guidance has the Hierarchy Standard S1 of SuDS. This is the Surface Water Runoff destination Standard:

  • Priority Level 1: Surface water runoff is collected for use
  • Priority Level 2: Surface water runoff is infiltrated to ground
  • Priority Level 3: Surface water runoff is discharged to a surface water body
  • Priority Level 4: Surface water runoff is discharged to a surface water sewer, hiughway drain, or another drainage system
  • Priority Level 5: Surface water runoff is discharged to a combined sewer. 

Wales then has Fixed Standards S2 to S6, covering Design Standards and the Build and Maintain Standards. 

All new housing applications (for more than one dwelling) in Wales need to incorporate Sustainable Drainage within their design that must be be approved by a SuDS Approval Board.

At Celtic Water we have assembled a collection of Proprietary Treatment Devices (PTD) to assist Designers required to meet standard S3 for Medium and High Pollution Hazard Levels sites (as per Table G3.1). These PTD are especially useful for meeting the Mitigation Indices (MI) cited in the UK wide SUDS Manual by CIRIA.  Flawed as CIRIA C753 is at providing the ability to compare rates of TSS removal, the SuDS manual is becoming more widely used by Designers.  (Note that C753 never defines the Particle Size Distributions of the TSS it refers to through the document).

We work with our suppliers and will be happy to discuss Proprietary Treatment Devices and their associated MI in an open and transparent manner.