Lining inadequate or failing structures with corrugated metal material or plastic pipe uses little of the available area, thereby preserving the maximum amount of the original opening. Due to the hydraulic efficiency of Contech products, often a smaller structure provides the same hydraulic capacity as the original because of the low Manning “n” factors of A-2000 and A2 Liner PVC pipes and HEL-COR and ULTRA FLO CMP pipes. Existing pipes and arches are generally lined with structures of the same shape, though slightly smaller in size. Rectangular openings can be lined with round, elliptical or pipe arch structures. Corrugated metal structures can fit almost any existing shape.