‘Future Water’ - the new water strategy for England – will have a major impact on the application and adoption of permeable paving for highways and other areas.
Governmental planning policy guidance throughout the UK clearly requires use of sustainable drainage system (SUDS) on all developments wherever possible and also encourages planners to take a central role in coordinating their acceptance by all.
This requirement is supported by Building Regulations and other governmental guidance, including the Manual for Streets and Code for Sustainable Homes.
Concrete block permeable paving is a unique SUDS technique with important attenuation and pollution source control characteristics, but it can also be used in isolation to achieve sustainable drainage demands.
Along with other SUDS techniques, there has been some confusion over responsibilities and adoption limiting take-up of permeable paving by developers, an issue which the Government is now determined to address with a consultation process as part of its water strategy.
As a result, surface water management plans will be required to co-ordinate activity, clarifying responsibilities for SUDS and their adoption by local authorities.
Future Water also calls into question the automatic ability to connect new development surface water drainage to the public sewer, strengthening pressure for on-site solutions such as concrete block permeable paving.
Finally, major changes for domestic paving are proposed which will, for the first time, require planning permission for paving to front gardens of existing homes, unless permeable systems are used.
And it can be expected that in many cases permission will not be granted if permeable paving is a viable alternative.
Concrete block permeable paving is fundamentally different to other SUDS techniques and it is important to understand how it works.
In conventional pavements rainwater is allowed to run across the surface to gullies that collect and direct it into pipes, removing it as quickly as possible. In contrast, permeable paving acts as the drainage system as well as supporting traffic loads.
It allows water to pass through the surface, between each block, and into the underlying permeable sub-base, designed specifically for this role, where it is stored and released slowly, either into the ground, to the next SUDS management stage or to a drainage system.
As well as new-build, concrete block permeable paving can also be retrofitted, for example during refurbishment work or as part of a planned operation to reduce storm-water runoff and improve water quality.
It is capable of handling rainwater from roof drainage and impervious pavements as well as the permeable paving itself.
In general a 2:1 rule applies, with permeable paving able to handle runoff from up to double the area of impermeable surfaces. With a minimal maintenance requirement, similar or even lower whole life costs than conventional paving in various materials with piped drainage have been demonstrated in recent independent research.
The highway infrastructure in a development is usually adopted by the local authority without charge.
However, some SUDS techniques may still be considered as ‘unusual drainage systems’, raising maintenance issues – an approach not justified in the case of concrete block permeable paving.
Unlike most SUDS techniques falling outside the immediate highway area, it simply provides a sustainable alternative to conventional paving with piped drainage, but on the same footprint.
So, at adoption it will itself become the highway, justifying the same approach as conventional highways and associated drainage.
While concrete block permeable paving is popular as part of a management train comprising various SUDS techniques it can equally be used in isolation or to improve conventional drainage systems.
Comprehensive technical guidance is available from Interpave’s at www.paving.org.uk. So, even without the new water strategy, concrete block permeable paving can be considered mainstream technology that can be specified and adopted with confidence.
