Parallelepiped-shaped monoblock plant for the treatment of first rain waters realized in extruded polypropylene (PP) sheet, fully recyclable material, thermoweled with continuous  wire and carry suitably reinforced to withstand the pressures siltation and ensure walkability. It 'consists of six compartments, screening, primary oil removal / grit removal, floodway, water accumulation of 1st  rain, oiling lamellar pack, the grilling is done internally by a panel grilling PP with 20mm spacing. The plant is equipped with rain sensor, electric lifting pump for lifting 1st rain waters, automatic shut-off valve and the electrical protection and control with timer for a delayed start of 24/48 hours after the last meteor event. Access to compartemnt is guaranteed by  manholes for inspection and proper maintenance. All manufactured articles have inlet and outlet pipes suitably dimensioned, equipped with suitable double lip gaskets .