Rodriguez Fish Passage Project
Client: County of San Luis Obispo
Waterways was contracted by the County of San Luis Obispo Public Works Department (Utilities Division) to provide assessment, design and construction observation services for the improvement of fish passage conditions and the protection of a waterline in Arroyo Grande Creek at the Rodriguez Bridge crossing. Our work also included preparation of a design report and response to comments from NMFS fish passage engineers.
Just upstream of Rodriguez Bridge there was an exposed concrete encased water supply line within the bed of Arroyo Grande. Channel scour on the downstream side of the encasement had nearly undermined the encasement, potentially leading to structural failure of the pipeline, and leaving a 3 foot hydraulic drop that created a partial barrier to fish passage.
The designs for fish passage improvements and pipeline included installation of a roughened channel. The channel was reconstructed for approximately 250 feet, using imported rock to provide a smooth transition in the stream profile and hydraulic conditions conducive to fish passage. Two pools and a woody debris structure were incorporated into the project to provide resting and rearing habitat. Additionally, boulder weirs were installed to maintain pool scour and grade control through the project area.
Steelhead were not found in the project reach during pre-construction field surveys. However, steelhead were observed both upstream and downstream of Rodriguez Bridge, and near the installed woody debris structure during post-construction monitoring. The project has greatly improved fish passage conditions and is meeting established success criteria.