Aquatic Organism Passage Design: Four Years of Experience with HEC26

The Federal Highway Administration released Hydraulic Engineering Circular (HEC) 26 “Culvert Design for Aquatic Organism Passage” in October 2010 to provide and engineering based stream simulation method for designing culverts to promote fish passage. The basis is to provide hydraulic conditions within an embedded culvert similar to those found upstream and downstream of the culvert over a wide range of flow rates. By simulating the depth, velocity, and sediment transport capabilities of the channel through the culvert, it is reasonable to infer that fish capable of passing up and down the channel can also pass through the culvert. Species-specific information on swimming capabilities or behaviors is not required. In the period since its release, FHWA and others have gained experience in the design and performance of these structures. This presentation provides brief background information on the methodology, but focuses on the experience with the method since its introduction. Case examples are presented along with challenges designers faced with the methodology. Areas for potential additional guidance are also discussed