Southeast Alaska boasts a migration habitat for seven species of Pacific salmon. As an anadromous fish species, salmon travel throughout the ocean and smaller streams at various times in their lifecycle. On this unique project, proHNS designed a bottomless pipe arch under a residential driveway to serve as a fish passage corridor, replacing two existing perched culverts. The Alaska Department of Fish and Game had classified the previously perched culverts as Red, which meant that the crossing was inadequate for juvenile salmon and provided weak swimming for fish passage. In solving that problem, the new, innovative design vastly improved the creek’s natural ecosystem and subsequently repaired structural damage done to the residential roadway from a washout caused by a storm event in December 2020. proHNS provided initial site inspections, an in-depth hydrologic and hydraulic study, alternative recommendation and selection, a fish passage design following the USFWS geomorphic analog method, and a construction package including plans, specifications, and cost estimates.
Site improvements include:
- Replacement of two 3.5’ high x 4’ wide x 20’ long corrugated metal pipe (CMP) culverts
- Reconstruction of the stream channel to allow for improved fish passage
- Stabilization and revegetation of adjacent streambanks