The excavated rain garden at Age UKs Castle Community Centre was designed as a retro-fit project suitable for installation by volunteers. Its primary purpose is to divert all rainfall landing on the Centres roof away from the local combined sewer network, into which it had always drained. This helps reduce the risk of river pollution from Combined Sewer Overflows (CSOs) at times of peak rainfall. Much of the sewer network in older districts of Northwich is of the Combined type and CSO events are an important source of pollutants in the River Weaver and River Dane within the town.

The project represents part of Groundwork CLMs Love My River Northwich programme, which received funding from the Environment Agency for delivery of a series of demonstration SUDs projects in community premises in Northwich during 2018-19. The design has been inspired by the UK Rain Garden Guide, as developed by CIRIA with support from Thames Water and the Environment Agency: https://raingardens.info/wp-content/uploads/2012/07/UKRainGarden-Guide.pdf .

The permeability of the subsoil on site was tested in advance for its suitability for this type of soakaway feature, using methods outlined in the UK Rain Garden Guide. The specific location of the raingarden within the site was chosen carefully in consultation with centre managers and in consideration of locations of other planned garden features: a whole garden design is currently being implemented by centre staff and local volunteers following plans supplied by a qualified garden designer.