Using solid wall HDPE pipe, as well as state-of-the-art profile wall HDPE pipe, culverts rehabilitated actually outperform the original structures. The low resistance of flow (Manning’s N of 0.009) of HDPE pipe allows for greater flows. The use of gasketed or fused joints assures a watertight seal, easily meeting the requirements of ASTM D3212. Also, HDPE is of the most corrosion- and abrasion-resistant pipe materials available. Which means you can fix it, forget it.