The management of Stormwater has become increasingly important in recent years, with climate change creating unexpected rainfall events resulting in localised flooding. Stormwater is the runoff from rooftops and roadways and other “sealed” surfaces and by its very nature it washes the area over which it travels picking up pollutants such as debris and hydrocarbons on its way. These pollutants have to be dealt with but also the volume of water has to be managed.
This management can take many forms; either by infiltration into the ground using soakaways or by attenuation (the temporary storage of the water until the storm has passed). Both these methods reduce the impact of storms on the UK’s beleaguered sewer system and help reduce flood risk dramatically adding to the sustainability of building schemes.
Where the surrounding ground is insufficiently permeable to allow the volume of water to infiltrate away naturally, the insertion of a soakaway structure as part of a SUDs scheme (StormMaster) with a permeable geotextile surround) will help this process dramatically by providing an underground void for temporary storage of the stormwater whilst it infiltrates into the surrounding soil.
Attenuation means to temporarily store stormwater for a period of time, normally until the worst of the storm has passed, the water is then released to the sewer network.
This process uses a “sealed” storage box (attenuation tank) created from our the StormMaster system with both a geotextile and geomembrane surround as part of a SUDs scheme.
The stormwater is collected by normal road gullies and routed to the sewer in the usual way, but is passed through a “control manhole” that only allows a controlled volume of flow through to the mains. The water then backs up in the manhole and is fed into the temporary attenuation storage system and over a period of time this stored water continues to exit the system through the control manhole at a regular rate thus preventing flooding downstream. These systems tend to be commercial rather than private schemes and are a common method of a SUDs scheme.