ULTRA
Resin Bound Knowledge Base
Resin Bound Knowledge Base
Information - SuDS (sustainable urban drainage systems)
The acronym SuDS refers to sustainable urban drainage systems. These are systems which are designed to align modern drainage systems with natural water processes. The aim is not to prevent flooding in the areas in which they are incorporated but to help prevent drains and sewers exceeding their capacity and enhance ground water quality.
It is important to distinguish between a SuDS compliant surface and a permeable surface. SuDS compliance is often used to incorrectly promote a resin bound surface when in reality it would be more relevant to refer to the products permeability.
Why SuDS?
In urban areas many of the surfaces are sealed by paving and buildings which means that rain water has to be diverted to drainage networks. In heavy rainfall the drainage systems may be overwhelmed by the surface water and this can result in localised flooding.
The water that is diverted is discharged into local watercourses such as streams and rivers however this water has often picked up pollutants from sealed surfaces or from sewers which release contaminated water.
Sustainable urban Drainage Systems are designed to alleviate the problems by decreasing flow rates to watercourses and by improving water quality. Provision for SuDS and the national standards required for their design, construction, maintenance and operation is included in the Flood and Water Management Act 2010.
Permeability
Permeability refers to the capacity of a porous surface to allow water to pass through it. One of the key benefits to a StarScape ULTRA resin bound surface over other traditional paving options is that it is highly porous and allows for the free draining of rain water. This can reduce the chance of flooding and pollution. As water passes through the surface it traps pollutants below and many pollutants are then broken down by natural processes.
Soak-away
A soak-away is the term used for an area in which water can sufficiently drain naturally as opposed to being directed into the local watercourse through drains. Gardens, lawns and areas which allow water to naturally drain are soak-aways. Replacing or covering an existing driveway or pathway of a residential property with a non-permeable surface that directs water to a soak-away does not typically require planning permission.
The infiltration rate of a natural soak-way will usually be adequate for a pathway or standard domestic driveway however, larger areas and commercial installations may require a constructed soak-away. A constructed soak-away consists of a large hole that is back-filled with gravel and rubble to allow surface water to quickly drain back into the ground. These can easily be constructed using soak-away crates or a granular (large particle) stone infill with a geotextile membrane.
Cut out
The term ‘cut out’ refers to a process in which an existing driveway has large slots cut through the surface. These are then back-filled (often with the rubble of the material which has been removed) in order to allow rain water to flow through the resin bound surface and escape via the slots. This can also be done by drilling holes into the base course. Star Uretech do not recommend this installation method as it does not always achieve adequate draining and the overall strength of the base course is compromised.
Summary
The use of a permeable resin bound surface does not necessarily imply SuDS compliance due to its permeability. It should to be used in conjunction with permeable basecourses or soakaways to achieve SuDS compliance. Consider a non-permeable tarmacadam driveway on which surface water is directed towards a lawn and allowed to soak away beneath the garden. This is a SuDS compliant surface, but it isn’t a permeable surface. If you now consider a permeable resin bound surface laid on top of a non-permeable tarmacadam driveway that directs water to a drain. This is not a SuDS compliant surface. It is possible to create a SuDS compliant surface using any type of paving however a resin bound surface offers a very simple, cost effective, decorative option. Regardless of SuDS compliance, replacing or covering an existing driveway or pathway with either a permeable surface or non-permeable surface which directs water away from drainage networks, will not typically require planning permission.
● A hard surface with a total area of less than 5m² installed to the front of a property does not typically require planning permission.
● Replacing or covering an existing driveway or pathway to the front of a property with a permeable surface does not typically require planning permission.
● Replacing or covering an existing driveway or pathway to the front of a property with a non-permeable surface which directs water away from drainage networks and to a natural soakaway (such as a garden, grassed area or naturally draining trench) does not typically require planning permission.
Dependant on the overall construction of a driveway or pathway, both permeable and non-permeable surfacing products can be used as part of a complete SuDS compliant installation. Using a porous product such as a resin bound surface is the simplest way to avoid the requirement of planning permission and a highly effective way of reducing flooding and water pollution.
IMPORTANT: The following statements are found in the explanatory memorandum to the town and country planning order 2008:
Householder Permitted Development: Permitted development is development that can be undertaken without the need to apply for planning permission. These rights have existed for many years and provide the freedom for householders to make improvements or alterations to their homes without the cost and delay of applying for planning permission. It also removes the need for local authorities to determine a large number of routine proposals.
Paving of Front Gardens: the consultation paper proposed that householders should continue to be able to pave over their front gardens under permitted development. Responses to the consultation showed that there was a significant desire for greater control over this type of development to address concerns about water run-off, visual impact and loss of habitat. In the light of this and concerns that the floods of summer 2007 were in part the result of surface water run-off building up in paved areas, the permitted development rights will in the future be framed so that a surface installed to the front of the property should not, in itself, lead to surface water run-off. This can be achieved by the use of porous materials or by using more “traditional” materials and ensuring that any runoff is directed to an area that allows the water to drain away naturally, for example, a garden border. The provision makes clear that the restriction applies to any installed area of more than 5m². Given the regulatory nature of the proposal, a separate Impact Assessment has been prepared on this issue and is attached.
Class F – Hard Surfaces Permitted Development subject to: • Any surface installed in the front garden of more than 5m² to be either porous or to run-off to a porous or permeable surface. From 1 October householders who wish to hard surface more than 5m² of their front gardens so as to make the area impermeable would need to seek planning consent from their local planning authorities. Those who opt for permeable solutions, whether by using permeable materials or ensuring permeability where impermeable surfacing is used (e.g. by installing a soak-away) will not be required to seek planning permission.
More information regarding SuDS regulation can be found on the government website:
● www.gov.uk/government/publications/best-management-practices-for-urban-drainage
Natural clay
This map highlights areas of the England in which natural clays can be found in large quantities. Our testing, calculations and quoted ratings for permeability are all based upon normal, low-clay soil conditions and as with any groundworks, the type and quality of the natural base (sub-base) should be established as suitable prior to installation of a permeable surface.
If a sub-base is laid on natural soil which contains high levels of clay this will provide neither sufficient load bearing ability nor an adequate infiltration rate for the rainwater. In these circumstances an additional 100mm of the natural soil should be removed and replaced with an additional 100mm of the sub-base. This will provide more structural support for the asphalt and a greater storage capacity for surface water.
Porosity
Porosity is the property of the resin surface that is an indication of the ability for water to flow through it. High porosity will allow water to pass rapidly through the surface and prevent the build-up of surface water whilst a low porosity will result in pooling and the potential for flooding.
The figures below show the approximate water flow-rate for a StarScape ULTRA surface:
► StarScape ULTRA at 20mm depth with 1mm to 3mm aggregate: 1,035 (Litre/m²/minute)
► StarScape ULTRA at 20mm depth with 3mm to 6mm aggregate: 1,675 (Litre/m²/minute)
► StarScape ULTRA at 20mm depth with 50/50 aggregate blend: 1,220 (Litre/m²/minute)
► StarScape ULTRA at 20mm depth with 6mm to 10mm aggregate: 3,940 (Litre/m²/minute)
StarScape ULTRA is a high-quality aliphatic resin with a viscosity specifically formulated to produce a highly porous, bound surface which allows a high volume of water to pass through the matrix of the completed installation. There are two factors that determine a resin bound surface’s porosity and this is the ratio of aggregate particle sizes and the level of resin required to provide a suitable matrix strength. A low-quality resin system will require a greater quantity of resin to bind the aggregate and this often results in a low porosity surface and potential drainage issues. The use of StarScape ULTRA and our approved aggregate blends produces a highly porous surface which can be used incorporated in to a SuDS compliant installation.