A plastic infiltration unit comprising: a top deck which extends in a plane, the top deck having an underside, at least one pillar extending in a direction from the top deck for supporting the top deck, wherein the top deck comprises at least one first integrated connector and the at least one pillar comprises at least one second integrated connector, for temporarily holding in position the plastic infiltration unit with another identical plastic infiltration unit comprising at least one other pillar, the at least one other pillar comprising at least one other second integrated connector, wherein the plastic infiltration unit and the other plastic infiltration unit are connectable, so that in a coupled arrangement, the at least one pillar of the other identical plastic infiltration unit is held in position at the underside of the top deck of the plastic infiltration unit, characterised in that: the at least one first integrated connector is a male connector comprising a pin extending from the underside of the top deck, in that: the at least one second integrated connector is an at least one female connector comprising an opening provided in a distal end of the at least one pillar, and in that: the at least one pillar comprises a foot having an underside located at the distal end of the at least one pillar, and the opening is provided in the underside of the foot, so that the pin and the opening in the underside of the foot temporarily connect, in use, the plastic infiltration unit with said other identical plastic infiltration unit, so that the at least one pillar of the other plastic infiltration unit is temporarily connectable to the underside of the top deck of the plastic infiltration unit. a top deck which extends in a plane, the top deck having an underside, at least one pillar extending in a direction from the top deck for supporting the top deck, wherein the top deck comprises at least one first integrated connector and the at least one pillar comprises at least one second integrated connector, for temporarily holding in position the plastic infiltration unit with another identical plastic infiltration unit comprising at least one other pillar, the at least one other pillar comprising at least one other second integrated connector, wherein the plastic infiltration unit and the other plastic infiltration unit are connectable, so that in a coupled arrangement, the at least one pillar of the other identical plastic infiltration unit is held in position at the underside of the top deck of the plastic infiltration unit, characterised in that: the at least one first integrated connector is a male connector comprising a pin extending from the underside of the top deck, in that: the at least one second integrated connector is an at least one female connector comprising an opening provided in a distal end of the at least one pillar, and in that: the at least one pillar comprises a foot having an underside located at the distal end of the at least one pillar, and the opening is provided in the underside of the foot, so that the pin and the opening in the underside of the foot temporarily connect, in use, the plastic infiltration unit with said other identical plastic infiltration unit, so that the at least one pillar of the other plastic infiltration unit is temporarily connectable to the underside of the top deck of the plastic infiltration unit.