Open-textured soil or granular material Gravel or similar surface on a sub-base. Typically used in locations where very low volumes of light weight traffic, such as cars, will be present and a low cost solution is required. There is little design and the use is restricted to locations such as pedestrian areas, driveways on private property and temporary car parks.
To read more follow the link below https://www.susdrain.org/delivering-suds/using-suds/suds-components/source-control/pervious-surfaces/pervious-surface-types/porous-surfacing-options.html
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