Feasibility of Fish Passage at Alameda Creek Diversion Dam

7.0 Evaluation of the Biological Benefit of Two Passage Options7 EVALUATION OF THE BIOLOGICAL BENEFIT OF TWOPASSAGE OPTIONSIn the evaluation of passage, it is important to note that fish passage is almost always“technologically” feasible. That is, it is almost always possible to catch fish and relocate them,combined with sufficient financial investment, engineering determination, and organizationalcommitment. Perhaps more important is whether the cost, including the time, money, and loss ofthese resources for other efforts, as well as unintended effects on non-target fishes and otherenvironmental consequences, is worth the benefits that fish passage achieves. Given that fish passageis almost always technologically feasible, it is important to focus the evaluation of fish passage on theability or likelihood of successfully meeting the biological goals of fish passage.As outlined in Section 3, the typical goals of fish passage are to:■■■■■Provide access to additional quantity of habitat to increase natural production;Contribute to species recovery through increased overall natural production;Provide access to historical habitat;Protect or enhance the genetic integrity and/or distinctness of stocks; andReduce risk of extinction through increased natural production and creation of additionalindependent populations.This section examines the potential for success of fish passage for steelhead at ACDD. As describedin Section 6.4, whether fish ladder design components or trap and haul design components are moreappropriate for fish passage at ACDD cannot be determined with certainty until the ability ofimmigrating steelhead to pass Little Yosemite at high flows has been tested, or passage has beenprovided at that potential barrier. Therefore, both a ladder option and a trap and haul option arecarried forward through this analysis, where the potential goals and success criteria for fish passageare used to evaluate the likelihood for success of each conceptual fish passage option.7.1 ACDD FISH LADDER OPTIONThis section evaluates the likelihood of the ACDD Fish Ladder option to meet the goals of fishpassage. As identified in Section 5.3, an ACDD Fish Ladder option would include the following twodesign components:■■Long FishwayFish ScreensImmigrating adult steelhead arriving at ACDD would enter the fishway and climb the ladder aroundACDD on the right bank of Alameda Creek. Steelhead would exit the fishway upstream of ACDD.Screening at the ACDT would prevent fish from being entrained in the diversion tunnel, and a fishscreen bypass would allow emigrating juveniles and post-spawn adults safe downstream passage atACDD.The potential for this option to meet each of the stated goals of fish passage is addressed below. Thedegree to which a fish ladder at ACDD would effectively pass immigrating steelhead depends largelyon passage conditions at Little Yosemite. Therefore, for the analysis in this section it is assumed thatimmigrating steelhead are able to pass Little Yosemite, either because it is not a complete barrier toupstream migration or because passage at that barrier has otherwise been provided.ACDD Passage June 2009 Page 7-1