Idaho State Highway 21 Five Mile Creek Fish Passage Project

This senior design project is the evaluation and design of a replacement for a culvert on Five Mile Creek, near Lowman in central Idaho, which has been identified as a barrier to safe passage of endangered fish. Near the confluence of Five Mile Creek and the South Fork of the Payette River, the 72” diameter culvert has been identified as a barrier to fish passage, specifically for bull trout and red branded trout, by the Federal Fish Passage Coordination Group (FFPCG). The culvert has an excessive gradient which creates a velocity too large for fish to swim against. Design includes consideration of a bridge or larger culvert, costs, environmental impact analysis, structural and geotechnical design parameters, traffic control planning and hydraulic analysis of the creek. Structural and geotechnical considerations include a bridge design to span the creek, meeting the Association of State Highway and Transportation Officials (ASHTO) loading requirements, and foundation design that does not exceed soil bearing capacity. Plans will also be provided for rehabilitating the creek bed below the new passage structure to simulate natural conditions