Feasibility of Fish Passage at Alameda Creek Diversion Dam

Feasibility of Fish Passage at Alameda Creek Diversion DamTrap and haul was also evaluated, and was determined to be potentially suitable for steelhead passageat ACDD due to its ability to move immigrating fish past ACDD, and past Little Yosemite. LittleYosemite is a high-gradient reach of Alameda Creek with exposed bedrock and large bouldersapproximately 2 miles downstream of ACDD that may limit the ability of future steelhead to accessthe reach immediately below the diversion dam. Trap and haul at ACDD would involve trappingimmigrating adult steelhead below the dam (or below Little Yosemite) and hauling them to a releasesite above ACDD. Trap and haul would not require collection or relocation of emigrating steelheadbecause fish screen bypass flows would provide safe downstream passage at ACDD and LittleYosemite is not expected to significantly affect potential steelhead emigration. Due to the uncertaintyof passage conditions at Little Yosemite, trap and haul is retained in the analysis as a technologicallyfeasible option for providing passage.Fish ladders were determined to be suitable for use at ACDD, contingent upon steelhead being able toimmigrate through Little Yosemite. The advantage of fish ladders over fish lifts and trap and haul isthat they provide volitional passage with minimal handling and associated stress to the fish, comparedto other fish passage methods. Two potential ladder configurations were evaluated for use at ACDD,a short fishway that would provide an exit for fish immediately above ACDD, and a long fishway thatwould provide an exit for fish approximately 400 feet farther upstream, above the hydrologicinfluence of the dam. Both fishways would involve construction around ACDD on the right bank ofAlameda Creek; the near-vertical rock wall and presence of existing facilities limit the feasibility ofconstructing a fish ladder on the left bank of the channel. Although both configurations arepotentially feasible, a long fishway that joins Alameda Creek upstream of the hydraulic influence ofACDD may offer greater control over the flows that pass down the fishway than a short fishway thatjoins Alameda Creek immediately upstream of the dam. Therefore, the long fishway concept iscarried forward for further analysis in the technical memorandum.Design components that were determined to be suitable for providing fish passage at the ACDD basedon the first tier of analysis were then evaluated based on estimated capital, operations, andmaintenance costs. The estimated total capital cost of design components associated with a fishladder passage option and a trap and haul passage option are of a similar order of magnitude($23.7 and $21.7 million, respectively), more than half of which is the estimated cost of fish screensat the ACDT. Including the estimated water costs, the order-of-magnitude capital and operating andmaintenance cost for fish passage with screening at ACDD, annualized over a period of 30 years, isestimated at approximately $4 million annually for either a fish ladder or trap and haul passageoption. In both cases, more than $3 million of the estimated annual cost is associated with screens. Asignificant portion of the annual cost of passage at the ACDD is estimated to be lost water diversionopportunity cost.This memorandum also presents preliminary analysis of the potential biological benefit of providingpassage for steelhead at ACDD. Portions of Alameda Creek above ACDD do not have perennialflow; therefore, above ACDD fish habitat is limited during the dry season. A comprehensive surveyof available habitat above ACDD has not been conducted, and it is unknown whether spawning andjuvenile rearing habitat above ACDD is sufficient to support a self-sustaining population. If thequantity and quality of habitat are not sufficient to support a self-sustaining population above ACDD,provision of passage could still contribute to a steelhead metapopulation in the Alameda CreekWatershed, if additional subpopulations are established in other reaches.CONCLUSIONSAn effort to establish steelhead access above the ACDD would have a reasonable probability ofsuccess based on this preliminary analysis. While a fish ladder is a technologically feasible option forACDD Passage June 2009Page ES-2