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With government legislation recently changing 'householders permitted development rights', paving over fronts gardens with impermeable surfaces now requires planning permission. The new legislation sets out that planning permission is required for hard landscaping of all front gardens and driveways over 5m² unless permeable systems are used. Roy Partington Divisional Manager says: The solution is to use a cost effective Porous Paving System that is both aesthetically appealing to the householder and also a product that provides sufficient surface water infiltration through the system. Duoblock provides the solution to both issues, it can be filled with grass or gravel depending on aesthetic requirements and deals with storm water at source. The Duoblock units also provide a suitable load bearing platform to enable trafficking over the system.     Download: DuoBlock Permeable Paving Download: Future Water Strategy

The North East of England is home to one of the British Army's largest Barracks with a military and civilian population of over 12000. As part of a long term modernisation and expansion programme of the site, contractors have installed an innovative below-ground, SUDs [Sustainable Urban Drainage] solution to accommodate surface-water run-off for a total of 9400sqm car parking area. In periods of heavy rainfall, surface water run-off from large areas of impermeable paving can overwhelm drainage systems, leading to flooding. In view of this, groundworks contractor, K Rouse Ltd, chose a combination of conventional channel drainage, feeding into below-ground attenuation tanking designed and installed by SUDS specialists, Stormwater Management Ltd. The purpose of an attenuation tank is to accept and retain surface water run-off during periods of high intensity rainfall, then manage its discharge into the drainage system at a controlled rate. At the site, Stormwater Management designed a 576m³ capacity system comprising 2880 of its FlowBlock modular water storage cells. FlowBlock cells are high strength, lightweight polypropylene units, 1.0x0.5x0.4m with a 95% void ratio. Their modular format allows them to be linked together to form large underground tanks of virtually any predetermined configuration. FlowBlock assemblies are wrapped in either a geotextile or a geomembrane depending on their application and connected to the drainage system. On site, Stormwater Management installed two tanks 40mx10mx0.8m and 40mx8mx0.8m beneath a car park serving the Barracks. The tank dimensions were calculated using the company's in-house drainage design software, which is based on the industry standard Wallingford Procedure. Both tanks were excavated to a depth of 2m deep, graded to line and level, and lined with 1mm thick VFPE impermeable geomembrane. FlowBlock cells were then installed by hand and wrapped in the geomembrane to create a completely sealed system with mechanically welded seams. Flow regulators were installed at the outlet so that discharge rates could be managed to the pre-determined levels. On completion, the attenuation tank was overlaid with a layer of compacted Mot Type 1, and selected as-dug material with a black top wearing and base course, giving a total construction cover of 1200mm. Surface water drainage was achieved through a network of linear drainage channels. The Barracks SUD system was installed in early summer 2007 and has performed as specified over its first full year of use.  

Dramatic changes in weather and increased developments on Greenfield sites have put enormous strain on existing drainage systems, sometimes causing serious flooding. The Government's latest Planning Policy Statement makes it very clear that Local Authorities should be considering SUDS to prevent flooding and the subsequent damage and pollution. Every new building development is now likely to be scrutinised to make sure it's contributing to the Government's targets to increase the sustainability of urban environments. How will SUDS affect me? Your Local Authority will want to know how you intend to tackle the increased rainwater run-off resulting from new buildings and hard landscaping. Essentially they'll want any run-off to be as close to the original amount from the site before development. Fortunately for the builder there are a number of ways of tackling this – one tried and tested method is the FlowBlock system. What is FlowBlock? Flowblock is a polypropylene modular water storage cell that's easy to install and environmentally-friendly. By locking them together you can quickly create underground storage tanks and soakaways – both of which can support a planning application where SUDS are specified. The modules can be used individually for small domestic situations or connected together to create large, high-capacity storage systems. Why use it? One of the key planning objectives in the Government's policy statement is: “reducing flood risk to and from new development through location, layout and design, incorporating SUDS” The FlowBlock system reduces that risk by retaining surface water underground and then gradually releasing it. This helps to avoid the surges that can overwhelm existing drainage systems and cause flooding. FlowBlock has already proven its performance in SUDS across the UK with thousands of cubic metres in widespread use. What's more FlowBlocks are also BBA certified so you know that it is a quality product. How does FlowBlock work? By creating an underground storage chamber with FlowBlocks, rainwater run-off can be restricted in one of two ways. The first is attenuation – in other words the controlled release of stored water in to the main drainage system / watercourse. This is achieved by wrapping the FlowBlock construction in an impermeable geomembrane and fitting a flow control device at the outlet point. The release rate can then be set to suit the capacity of the existing drainage system. The second is by using FlowBlocks to create a soakaway. In this situation the construction is wrapped in a permeable geotextile which allows the stored water to gradually seep back into the ground and replenish the natural water table – often another key consideration in planning applications. Where can I site them? Soakaways have to be placed at least 5 metres away from any foundations but attenuation tanks can be sited almost anywhere. And because they're modular this makes them ideal for awkward shaped areas. FlowBlocks come in two different load strengths; FlowBlock Lite is for pedestrian areas while the standard FlowBlock can be used in heavy-duty situations such as service yards, car parks and other trafficked areas. Can I install FlowBlock myself? The modules are lightweight and easily assembled on site by stacking together using the shear connectors provided. Stormwater management can supply all the relevant materials to you within 24 hours from stock and the blocks themselves come with a 50-year guarantee. However Stormwater also offer a full installation service that will provide you with a 30-year warranty for the installed system.