GROUNDWORKS 63


USE THE RIGHT CHANNELS TO LIGHTEN THE LOAD


When it comes to specifying drainage channels, there are vital factors that enable a system to meet requirements of a housing development project. Rob Butcher of ACO Water Management looks at the standards that must be upheld from the earliest stages of the project.


M


any areas of the building design process have guidelines in place to help housebuilders and developers avoid confusion. There is, however, still some misunderstanding around drainage. Coming in January 2024, Schedule 3 of the Flood Act will see changes to the legal requirements around drainage systems across England, making sustainability mandatory across new schemes. Because of this, it is vital that all involved in property building and development understand drainage channel specifi cation, though the reality is that many are unaware of some crucial points.


In fact, the results of an ACO survey of 100 highways and infrastructure engineers strongly pointed towards a lack of clarity around the key factors that need to be taken into account when designing drainage schemes. Only 1% of survey respondents said that they do not face barriers in SuDS schemes, and fewer than half claim to fully understand load class specifi cation requirements. So, what is the needtoknow on load class specifi cation


LOAD CLASS


An often-overlooked aspect is drainage channel load classes, defi ned by S EN1433. In cases where the wrong load class is specifi ed, the risk of  ooding is increased. This is because the channel may sustain signifi cant damage if it is unable to bear the load from traffi c passing over it. When drainage channels fail, costly repairs are incurred as well as devastating losses to businesses and homes. In some cases, such as roads where people are travelling at high speeds, the collapse of a drainage channel can result in fatal accidents.


It is the anticipated use that determines load class, ranging from A 15 to F 900. This covers pedestrian use (A 15) through to heavy industrial and military installations (F 900).


Sometimes it is wrongly assumed that residential developments only need A 15, however, if vehicles are going to be driven over drainage channels, A 15 will not be suffi cient and will break prematurely. To be certain that the correct load class is specifi ed, it is of course always best to consult an expert.


n areas with fastmoving traffi c, it may be better to use a monolithic drainage channel. This means the channel and grating comes as a single, one-piece design and there is less risk of the grating coming loose and posing a danger to


vehicles and pedestrians.


One point to keep in mind is that the load class is based on the combination of the grating and channel. For example, a channel with a B 125 rating, when used with an A 15 rated grating, automatically becomes an A 15 channel and should only be used in areas where pedestrians and cyclists are likely to be going over it. The load class specifi cation should also take into account whether vehicles will likely be turning as they pass over the drainage structure. The turning motion can increase the pressure applied and therefore a different load class may be required to ensure safety. It is because of nuances like this that drainage experts should be involved with a project right from the design stage.


SOMETIMES IT IS WRONGLY ASSUMED THAT RESIDENTIAL DEVELOPMENTS ONLY NEED AN A 15 LOAD CLASS, HOWEVER, IF VEHICLES ARE GOING TO BE DRIVEN OVER DRAINAGE CHANNELS, IT WILL NOT BE SUFFICIENT AND WILL BREAK PREMATURELY


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