46 STREET WORKS & UTILITIES


DECEMBER 2013


www.highwaysmagazine.co.uk


“The concept behind SUDS is to replicate the natural systems and processes, using cost-effective solutions with low environmental impact to drain surface water run-off in a controlled way”


Formpave has supplied over 2,000m2


of paving to Barratt Homes’ Hanham Hall development


Encouraging natural drainage


Hanson Formpave’s head of design, John Lloyd, looks at why permeable paving and sustainable urban drainage systems (SUDS) – such as the fi rm’s Aquafl ow system – are a cost-effective way of combatting fl ood risk and why forthcoming changes to legislation mean they are increasingly being specifi ed for roads to be adopted by local councils


Many green spaces are being covered with hard standing surfacing, which leads to natural drainage being prevented causing increased surface run-off and fl ooding.


Drainage systems with only limited capacity, and increasing urbanisation causing rapid run-off have put a tremendous strain on storm water management. This means sewers and culverts become overloaded during periods of heavy rain, leading to contamination of streams and rivers.


With local authorities responsible for managing the risk of fl ooding from surface water, groundwater and ordinary watercourses, increasing focus is being given to whether or not our existing drainage infrastructure can cope and what can be done to make sure that it does.


While SUDS can reduce the risk of fl ooding and help control the amount of water that enters the drainage infrastructure, their use has not yet been mandatory. This is potentially set to change as next year – under The Flood and Water Management Act 2010 – county or unitary local authorities will be required to establish a SUDS approving body (SAB).


The SAB will have to adopt and maintain approved SUDS that serve


more than one property. And with new developments, the SABS are required to adopt the roads once satisfi ed that the SUDS is constructed and functions correctly. The body can adopt either at its own initiative or at the developer’s request. Highway authorities will then become responsible for maintaining SUDS in adopted roads to national standards.


The act will apply to all new schemes requiring planning permission, and will compel house builders to consider SUDS at the earliest stage of a project’s development. Under the old legislation everyone has a right to connect their drains to sewers; the act removes this right and approval will be required before a connection can be made. If local authorities do not adopt the road, they will have to justify why they are not implementing SUDS on new developments.


The concept behind SUDS is to replicate the natural systems and processes, using cost-effective solutions with low environmental impact to drain surface water run-off in a controlled way. This is done through collection, storage and cleaning before the water is slowly released back, either into the watercourses or directly into the ground.


Hanson Formpave offers a design service to suit individual requirements. The service offered by our engineers


includes technical and professional advice, preparation of draft proposals and validation of the client’s own designs. All designs that have been provided or approved by Formpave are covered by the company’s professional indemnity insurance and benefi t from 16 years’ experience in designing permeable paving systems.


Formpave’s Aquafl ow system allows water to drain through the permeable paving blocks and upper fi lter layer, which cleans the water before being stored within the sub base for release back into the environment.


It is cost-effective and, unlike other SUDS, the system only requires builders to typically dig to a depth of 480 millimetres rather than a comparable British standard depth of 680mm, saving valuable time and money, as well as reducing waste for disposal.


The installation of a permeable paving SUDS will also eradicate surface pooling and puddles while allowing for water to be harvested for use in fl ushing toilets, washing cars and watering landscaped areas. In a nutshell, Formpave Aquafl ow tackles the issue of urban drainage while retaining an attractive fi nish suitable for both domestic and commercial application.


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