The community around College Park in London wanted a focal point for the neighbourhood. Following extensive consultations, it was decided to close the carriageway outside the Kenmont School and make the area an informal gathering area to be used by all the public, especially the parents of children at the school.
Various designs were proposed, and with the advice from the London Borough of Hammersmith and Fulham, and in partnership with Thames Water, it was decided to provide a landscaped area including a Sustainable Urban Drainage System (SuDS) system as well as benches and general landscaping.
The existing combined foul sewage and storm water sewer system for this area of London had become inadequate due to the growing population and an increase in the frequency of stormwater events. This was exacerbated by a lack of permeable surfacing. There was a high risk of surface water flooding.
A new street design was undertaken that included the removal of road gully drains and replacement with rain gardens, tree planting using GreenBlue Urban Soil Cell Systems, and a dished central area to hold excess flow.
Now stormwater is diverted into the rain gardens and StrataCell™ tree pits, where it is filtered through AborSoil Hydro soil medium which removes much of the pollutant loading. The water is then slowly returned to the combined sewer via a control orifice.
For up to a one-in-ten year rainfall event, the water returns to the combined sewer at a greenfield runoff rate, massively helping the sewer network.
In the event of a larger rainfall event, some of the rainwater can be stored above-ground in the dished area, and some can pass over to alternative inlets to cope with the exceedance flow. Typically, only 50% of the water that enters this type of SuDS system ever reaches the sewer system, as the planting and trees retain a lot of the water and use it for their own requirements.