Conventional culvert designs based on hydraulic capacity often result in high velocities or inadequate water levels that are not conducive for fish migration. For fish-bearing stream crossings, alternative designs need to be developed in order to secure timely approval from Fisheries and Oceans Canada (DFO). Stream simulation is one of those alternatives. It was proposed to, and accepted by, DFO for the Conn Creek Culvert replacement in Fort McMurray, an environmentally sensitive site due to the controversy over Alberta oil sand projects. The existing 4.2 m diameter, 82 m long culvert carries four lanes of Highway 63 traffic across Conn Creek, a tributary to the Athabasca River. As part of the $530 million Highway 63:11 upgrading project, the existing culvert required extension. During the review of the proposed alternatives, DFO cited the high flow velocity within the existing culvert as a barrier to fish passage, resulting in the separation of upstream and downstream habitats. Authorization for the works would need to ensure fish passage was restored. Challenges encountered during the design and construction of the replacement culvert included: Traffic accommodation for a busy highway with over 50K Average Annual Daily Traffic (AADT) Tight construction schedule demanding a quick approval from DFO Providing fish passage for weak swimming fish species across a 120 m span Enabling fish passage by reducing flows and providing velocity refuge while also addressing constructability and economics. Reducing flow velocity in a system that had been significantly altered historically (stream length shortened by removal of large meander sections of the natural stream). Shallow limestone bedrock demanding blasting for closed bottom culvert installation Owner’s concerns of high construction cost and potential scouring of open bottom culvert This paper presents the background of the project, the existing fisheries, and details of the stream simulation design used to satisfy regulatory and project requirements. It is also the authors’ intention to share their experiences and lessons learned in securing a timely approval from DFO on an extremely tight schedule.
