An aggregate replacement device may be used to replace rock aggregate in underground drainage systems. An aggregate replacement includes a structure having a proximal face, a distal face, a bottom face and two side faces with a plurality of openings. The two side faces and bottom face have a proximal edge, a distal edge and two side edges. The proximal face and distal face are coupled to the proximal edges or distal edges of the two side faces and bottom face to form an obtuse angle. A first of the side edges of the side faces is coupled to the side edges of the bottom face. A coupler and a locking device are coupled to a second of the side edges of the side faces. The coupler and locking device couple the structure to a second structure with the second of the side edges of the side faces abutting.