26 ASK THE MANUFACTURER - BURDENS
needs to work around those features rather than trying to fi nd somewhere to put them once the houses have already been designed.
ooking at it early allows you to consider how much land is reuired, what the costs are and what you want the development to look and feel like. If you leave it until the end, your options become much more constrained, and you can end up trying to shoehorn drainage features into whatever space is left. It should be part of the wider design process, with the developer, designer, contractor and relevant specialists working together, rather than treating drainage as something that is added at the end.
WHAT ADVICE WOULD YOU GIVE TO DEVELOPERS WHO WANT TO TAKE A MORE PROACTIVE APPROACH TO HOLISTIC STORMWATER MANAGEMENT BUT ARE UNSURE WHERE TO START? Gillies: Start as early as possible. oncept planning, detailed design and construction all need to be considered as part of the same process.
The earlier SuDS are embedded into a scheme, the more cost-effective the whole process can be. If you wait until construction is under way, you may have to go back, make changes and alter specifi cations, which costs both time and money.
It’s also about getting the right people around the table. If everyone works together from the outset, you can look at the different solutions available and make sure the fi nal approach is practical to install, cost-effective and appropriate for the site.
WHAT ABOUT MAINTENANCE – WHO MAINTAINS SUDS INSTALLATIONS, AND WHAT HAPPENS IF MAINTENANCE ISN’T FACTORED INTO DESIGN? Taylor: aintenance is absolutely critical, particularly for systems that are buried underground and out of sight. We’ve seen drawings for attenuation tanks where there isn’t suffi cient access for inspection or maintenance. If you can’t get into a system, how are you going to clean it and keep it performing properly The same principle applies to above-ground drainage. ou can see existing schemes where road gullies or channel drainage have become blocked because they haven’t been maintained. The design may have been perfectly adeuate, but if the system isn’t looked after, its performance will decline. With underground attenuation, silt,
fi nes and oils can build up over time, reducing the available storage capacity and potentially causing problems further down the network. So access for
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inspection, cleaning and maintenance needs to be considered as part of the original design, rather than treated as an afterthought.
WHAT ARE GEOSYNTHETICS AND WHY DO THEY PLAY AN IMPORTANT ROLE IN SUDS? Gillies: Geosynthetics are typically man-made polymers used as value-engineered alternatives to traditional construction methods. One of their key functions is fi ltration, which makes them particularly well suited to SuDS applications.
They’re still relatively underused when people are considering SuDS. or example, grass and gravel pavers made from recycled plastics can provide a permeable surface that allows rainfall to pass through naturally, removing the need for some traditional drainage infrastructure.
They can also be used as part of the layers beneath the surface, alongside geotextiles, sub-base materials and, where reuired, geogrids. Non-woven geotextiles, for example, provide strong fi ltration properties. The wider benefi t is that geosynthetics can reduce the volume of traditional stone reuired, as well as reducing installation time and the need to mobilise heavy plant. That can have a signifi cant impact on time, cash and carbon.
WHY IS THERE AN ISSUE AROUND PRODUCTS IN THE MARKET WITHOUT CLEAR ACCREDITATION? Gillies: Developers need confi dence that the products they’re specifying are going to perform as intended. There are products on the market where the information provided may be based on a manufacturer’s data sheet rather than being supported by the appropriate declaration of performance or relevant standard. That can make it diffi cult for specifi ers to understand exactly what they’re getting and how the product compares with an established standard. or example, Burden’s ztex W non-woven geotextile meets the BS standard. aving the appropriate standards, accreditations and supporting documentation gives designers and contractors greater confi dence in the performance and suitability of the product.
WHAT OTHER PRODUCT TYPES HAVE SEEN RECENT INNOVATION THAT IS HELPING RESIDENTIAL SUDS PROJECTS ACHIEVE SUCCESS? Taylor: There have been developments across a number of product categories. With modular attenuation systems,
for example, manufacturers have been increasing the void ratio of some products, allowing them to hold more water within the same overall volume. That can help reduce the footprint of a tank. We’re also seeing more use of rain gardens and planters at individual properties, permeable paving and tree pits. There are developments in crate systems too, including shallower options that can provide greater fl exibility where depth is restricted.
The important thing is that developers and engineers don’t necessarily have to accept the fi rst solution presented to them. There may be another product or approach that reduces the footprint, eliminates the need for additional tanks or makes the installation easier.
WHAT IS THE EXPERTISE THAT BURDENS CAN BRING TO PROJECTS TO ASSIST SPECIFIERS IN SAVING ‘TIME, CASH & CARBON’? Graham: Our role is to bring together technical, logistical and product knowledge to help contractors fi nd the right solution for the scheme. We’re not simply there to sell a particular product. Sometimes the right solution may actually mean we sell less, but if it’s the right solution for the customer and the project, that’s what we should be doing. We’ve seen projects where changing the design has dramatically reduced the number of deliveries reuired, while also reducing cost and carbon. In one example, a design change reduced the number of wagon movements from around to around while achieving the same overall solution.
That’s the value of looking at the whole project rather than simply pricing what’s on a drawing. ndrew and ark can look at a design and ask whether there’s a different way of achieving the same outcome, whether the footprint can be reduced, whether installation can be simplifi ed or whether the amount of material and site movements can be reduced. We’re effectively acting as the link between the developer, contractor and manufacturer, bringing those different areas of expertise together. Ultimately, it’s about understanding what the customer is trying to achieve and fi nding a solution that works technically, commercially and practically.
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