While working on the Shasta Constructors team, Gallaway Enterprises recently completed a sophisticated fish passage project on State Route 1 at Dunn Creek in Mendocino County. Dunn Creek crossed State Route 1 through a nine-foot diameter structural steel plate pipe culvert. There was a six-foot vertical drop downstream of the culvert, creating a barrier to fish passage, including the Federal and State listed Coho salmon (Oncorhynchus kisutch) and the Federal listed Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss).
The fish passage project was accomplished by removing the existing culvert and constructing a 134-foot long concrete slab bridge. The bridge would allow for the installation of rock weirs in the stream channel, providing grade control and allowing for all life stages of fish to pass. In addition to fish passage, the weirs and grade control measures would prevent head cutting upstream, resulting in the reduction of potential downstream water quality degradation due to sediment transport. To accomplish the project Gallaway Enterprises staff developed a dewatering and fish relocation program and provided constant monitoring. Krishnan Nelson, Senior Ecologist, used a variety of nets and an electro-shocker to relocate numerous salmonids. Working with Shasta Constructors, Gallaway Enterprises developed innovative methods for preventing fish from re-entering the work areas due to unexpected influxes of ground water. The project was recently completed in late 2013.