Leaching unit having overhanging and perforated canopy

A leaching unit, for receiving and dispersing water and other liquids when buried within soil or other granular medium, the unit having a top, bottom, length, a first lengthwise end, an opposing second lengthwise end, a width, and a height extending from the top to the bottom, comprising:

• (a) a plurality of pillar assemblies, each spaced apart from the other along the length of the leaching unit by a pillar assembly space, each pillar assembly comprised of
• a multiplicity of spaced apart pillars, each pillar having a length extending in the height direction of the leaching unit, an upper lengthwise end shaped for mating with a canopy made of sheet material, a lower lengthwise end shaped for soil-bearing contact, and a middle portion running between the upper end and the lower end;
• a multiplicity of struts, interconnecting the pillars, each strut having a length extending laterally with respect to the length direction of a pillar, each strut having a width dimension which extends in the same direction as does the length of a pillar;
• wherein each pillar is connected to another pillar within the pillar assembly by at least two of said struts;
• wherein each pillar assembly space is free of struts that interconnect pillars;
• and,
• (b) a canopy, comprised of sheet material, forming the top of the drainage unit, for carrying weight of soil placed on top of the leaching unit during use, the canopy having a top surface and associated top surface area, and a width and length respectively corresponding with the width and length of the leaching unit, the canopy attached to said upper lengthwise ends of a multiplicity of said pillars within each pillar assembly and substantially lying in a plane which runs transverse to the lengths of said pillars;
• the canopy having at each end of the leaching unit a free end of the canopy that extends lengthwise beyond the pillars nearest the free end;
• wherein the first sheet is attached to a plurality of tops of the pillars of each pillar assembly and the second sheet lies on top of the first sheet, optionally fastened thereto;
• wherein the first sheet and second sheet each have a plurality of openings configured for passage of water and gas;
• and, wherein the openings in the second sheet are substantially smaller than the openings in the first sheet, to inhibit passage of particulates from soil overlying the canopy during use through openings of the first sheet.