Feasibility of Fish Passage at Alameda Creek Diversion Dam

8.0 Conclusion8 CONCLUSIONThis technical memorandum identifies conceptual-level fish passage options at ACDD and assessesthe feasibility of implementing passage to benefit steelhead when populations are restored to theAlameda Creek Watershed. The analysis finds that a fish ladder combined with installation ofscreens is a technologically feasible option for providing volitional passage for steelhead at ACDD.This analysis finds a fish ladder around ACDD on the right bank of Alameda Creek, in conjunctionwith implementing screens at ACDT and fish screen bypass flows on the left side of the dam to be themost feasible method for providing volitional passage (ACDD Fish Ladder Option, Section 7.1). Theperformance of a fish ladder would depend upon passage conditions for immigrating steelhead in theLittle Yosemite reach of Alameda Creek (see Sections 2.3.1 and 6.1). If Little Yosemite significantlylimits immigrating steelhead from reaching a fish ladder at ACDD, trap and haul from below LittleYosemite to above ACDD (Ohlone Trap and Haul Option, Section 7.2) could also provide passage,although long-term success of such passage would depend on ongoing institutional commitment andfunding. Screening and fish screen bypass flows to protect steelhead from entrainment in the ACDTwould be required with any type of fish passage and bypass flows would provide safe downstreampassage for emigrating steelhead.The estimated total capital cost of components associated with a fish ladder passage option and a trapand haul passage option are of a similar order of magnitude ($23.7 and $21.7 million, respectively), inboth cases more than half of which is the estimated cost of fish screens at the ACDT (Section 5.1).Including estimated water costs, the order-of-magnitude capital and operating and maintenance costfor fish passage with screening at ACDD, annualized over a period of 30 years, is estimated atapproximately $4 million annually for either a fish ladder or trap and haul passage option. In bothcases, more than $3 million of the estimated annual cost is associated with screens. A significantportion of the annual cost of passage at the ACDD is estimated to be lost water diversion opportunity(Section 5.2).Facilitating steelhead passage at ACDD would provide access to likely suitable steelhead spawningand juvenile rearing habitat above the diversion dam, and specific engineering solutions to providepassage are technologically feasible. Based on the limited detailed data available regarding habitatconditions in the Upper Alameda Creek Basin (see Section 6.1), it is unknown whether habitat aboveACDD is sufficient to support a self-sustaining population once steelhead gain passage at the BARTweir and re-enter the Upper Alameda Creek Basin. If habitat is not sufficient to support a selfsustainingpopulation above ACDD, provision of passage could still contribute to a steelheadmetapopulation in the Alameda Creek Watershed, if additional subpopulations are established in otherreaches. Detailed surveys of potential steelhead habitat above ACDD, in cooperation with upstreamlandowners, would allow for a more accurate assessment of the potential biological benefit ofsteelhead passage at ACDD.The volitional passage option of a fish ladder is generally preferred compared to non-volitionaloptions such as trap and haul. However, it is currently not known definitively whether adequatenumbers of immigrating steelhead would be able to reach the ACDD if a fish ladder was constructed.Given the substantial costs potentially associated with either passage option (see Section 5), and theuncertainty of passage conditions at Little Yosemite, it is important to understand which option wouldprovide the greatest benefit to the species. When steelhead return to the base of Little Yosemite, itwill be possible to observe and directly evaluate passage at this feature. The results of theseobservations could be used to refine analysis regarding providing immigration passage for steelheadat ACDD.ACDD Passage June 2009 Page 8-1