Ralston Afterbay Sediment Removal and Trash Rack Installation Project

The Ralston Afterbay Sediment Removal and Trash Rack Installation Project, managed by the Placer County Water Agency, addresses sediment accumulation caused by the 2022 Mosquito fire in the Tahoe National Forest near Foresthill, California. This accumulation has impacted the safe operation of the Ralston Afterbay Dam low level outlet and the Ralston-Oxbow Tunnel Intake, which is critical for water delivery to the Oxbow Powerhouse. The project involves the mechanical dredging and physical removal of approximately 40,000 cubic yards of sediment. This process will utilize a crane to deploy three to five barges into the afterbay, with an excavator operating from one of the barges to remove the material. Removed sediment will be transported via truck to the EBRL Sediment Disposal Area, located approximately 10 miles from the site. Following the removal of the sediment, the project includes the replacement of the existing steel trash rack with a new structural trash rack on the dam's low level outlet to ensure continued operational cycling despite future sedimentation. The project is classified under NAICS code 237990 and is exempt under CEQA Guidelines Sections 15301(b) and 15304(c)(g) as it consists of minor alterations and maintenance with no significant expansion of capacity.