Nubian Avenue Fish Passage Culvert Replacement
The Nubian Avenue fish passage culvert replacement project addressed an undersized private road crossing that was restricting fish passage and affecting stream function along an unnamed tributary to the Funny River. Trihydro worked with the Kenai Soil and Water Conservation District to design a larger, partially buried culvert and realign the upstream channel. Three months after construction, juvenile coho salmon were documented upstream of the new crossing, confirming restored access to habitat.
The Kenai Soil and Water Conservation District needed to replace an undersized culvert that had become a barrier to fish passage along an unnamed tributary to the Funny River. The existing 4-foot culvert was steep and undersized, with a perched outlet that restricted aquatic organism passage and contributed to upstream sediment buildup and channel degradation. The Funny River is a tributary to the Kenai River and provides important habitat for coho salmon.
Fish Passage Culvert Replacement Design
As part of the fish passage culvert replacement, Trihydro completed hydrologic, hydraulic, and geomorphic analyses to evaluate site conditions and guide the design. Using the reference reach conditions and guided by criteria from the U.S. Fish and Wildlife Service Culvert Design Guidelines for Ecological Function, the team developed a solution designed to restore access to upstream spawning habitat and better accommodate natural channel processes.
Culvert Replacement and Channel Restoration
The final design included an 11-foot, partially buried corrugated metal pipe culvert and approximately 200 feet of upstream channel realignment to restore channel form and aquatic habitat. Trihydro delivered the project through a design-build approach with Peninsula Construction, incorporating contractor input during design and cost estimating.
Restoring Coho Salmon Habitat
Three months after construction, the Alaska Department of Fish and Game documented juvenile coho salmon upstream of the new crossing, confirming that the new crossing restored access to upstream habitat and improved connectivity for aquatic species.
