disclosed is a foldable arched conduit suitable for use as drain tubing , culverts and the like . the conduit has the cross section of a parabolic arch with a flat base . the arched portion of the conduit comprises a pair of rigid corrugated plastic walls jointed at the apex area by a hinge . the base is constructed from a flexible sheet material which may contain apertures for liquid ingress and egress . for shipment , the rigid walls are folded inward about the hinge with the flexible sheet being folded between the rigid walls in order to present a generally flat configuration . after folding , the conduit may be conveniently rolled or length placed in parallel stacks for reducing the storage and / or shipping space required . at installation , the conduit may be unrolled along the installation site and then caused to expand into its unfolded shape .