Sustainable Urban Drainage Systems - (SUDS) Project Guidelines

Building Regulations

The Building Regulations Approved Document H3, Rainwater Drainage, which came into effect on 1 April 2002, prioritises drainage requirements. In short, it requires that rainwater from the roof of a building or from a paved area may either be gathered for reuse or be discharged into one of the following, listed in order:

• an adequate soakaway or some other adequate infiltration system; or, where that is not reasonably practicable
• a watercourse; or, where that is not reasonably practicable
• a sewer

In other words, the traditionally preferred method of rainwater disposal, ie totally discharging to a sewer, may now only be considered after other forms of reuse or drainage have been considered. The Building Regulations also provide guidance on the construction of rainwater harvesting systems for the first time

Environmental Guidelines

Stormwater runoff from impervious surfaces often carries a high pollutant load that has a detrimental effect on the bodies of water into which it discharges. Sediment has been identified as one of the most widespread pollutants impairing the water quality of rivers and streams. To mitigate the problem, planning and environmental guidelines such as PPG25 (Planning Policy Guidance No. 25) are becoming more stringent. Developers and authorities are required, through UK building regulations, to consider sustainable urban drainage systems as priority solutions rather than more conventional drainage systems.

Recent research shows that typically up to 80% of sediment; 60% of phosphorous and; 80% of nitrogen can be removed from rainwater through porous paving , and grass/gravel porous paving systems. This natural treatment provides the ideal opportunity for rainwater conservation and re-use for a variety of non-potable applications e.g. toilet/urinal flushing, irrigation, laundry, process water, vehicle washing, refrigeration, coolant use, etc.

Planning

Implementing SUDS contributes significantly towards achieving sustainable development. Many planning authorities will expect planning applications, whether outline or detailed, to demonstrate how a more sustainable approach to drainage is to be incorporated into development proposals. Planning authorities will set a limit to the rate of stormwater flow from a site via sewers as a condition of planning consent. In recognition of this, Local Plans increasingly state that all applications should, in the first instance, aim to incorporate SUDS into development proposals. SUDS are also considered suitable for mitigating adverse impacts and supporting water conservation objectives.