US Patent 7938597 Subsurface drainage system and drain structure therefor

A subsurface drainage assembly for directing fluid drainage from a surface is disclosed. The subsurface drainage assembly includes a plurality of drain structure panels linked together in a manner that permits movement of one drain structure panel relative to the adjacent drain structure panel. The drain structure panels have a laterally extensive backing grid and a plurality of spaced apart tubular support members projecting therefrom. The tubular support members are tapered so that the tubular support members are nestable with the tubular support members of an identical drain structure panel when the drain structure panels are stacked.