Feasibility of Fish Passage at Alameda Creek Diversion Dam

Feasibility of Fish Passage at Alameda Creek Diversion DamHabitat surveys were conducted in August and September 2006, to assess existing habitat conditions forO. mykiss in a reach of Alameda Creek that stretches upstream from Camp Ohlone for approximately3.9 miles (Hagar and Paine, 2008). All life stages of rainbow trout were seen consistently throughout thewetted portions of the survey reach, which provide suitable spawning and rearing conditions for steelhead.Steep boulder falls present fish passage obstacles at three locations, one of which may be impassable at allbut extreme high flows. The creek was intermittent beginning approximately 0.3 mile upstream of CampOhlone, through an alluvial valley, before surface flow reappeared approximately 1.3 miles fartherupstream. A more confined reach with flow supporting rainbow trout populations continued upstream forthe remaining 2.3 miles surveyed. Low summer stream flows and warm water temperatures weredetermined to be the most likely limiting features of habitat for salmonids in this reach.While the above data do not provide a complete picture of habitat availability above ACDD, suitablesteelhead spawning and rearing habitat is present. A fish ladder at ACDD would only succeed inproviding access to upstream habitat if steelhead achieve volitional upstream passage through LittleYosemite (see Section 2.3.1 for a description of Little Yosemite). If observations of future populations ofsteelhead at Little Yosemite indicate that it presents a significant barrier to immigration, trap and haulcould provide access above ACDD. Trap and haul would involve collecting immigrating adults belowLittle Yosemite at the confluence with Calaveras Creek, and releasing them above ACDD. Unless fish arealso released immediately above ACDD, this could result in excluding adult steelhead from potentialspawning habitat between the confluence and ACDD.Detailed data are limited regarding habitat conditions in the approximately 3 miles of Alameda Creekthat lie between the Calaveras Creek confluence and ACDD. The 2002 aerial survey described abovefound that 1.8 of the 3 miles were dry, and it was estimated that 1.1 of the 1.2 wetted miles hadpotential to support rearing juvenile steelhead (Entrix, 2003). During the SFPUC spawning surveys,no spawning fish or redds were observed in this reach, although suitable spawning gravels and adultrainbow trout were observed (SFPUC 2009c; Brian Sak, pers. comm., 2009b), and rainbow troutredds were observed in the adjacent reach of Alameda Creek immediately below the confluence withCalaveras Creek (Brian Sak, pers. comm., 2009b). Based primarily on the stream lengths, as well asthe proportion of the reaches that are intermittent, and based less on the limited spawning surveys thathave been conducted, it appears that spawning and rearing habitat above ACDD is more extensivethan that between ACDD and the Calaveras Creek confluence.6.2 POTENTIAL FOR SUSTAINABILITYAlthough the primary scope of this investigation is to assess the technological feasibility of providingsteelhead passage at the ACDD, a preliminary analysis of the associated potential benefit of passageis also presented (see Section 7). In this section, the potential for establishing a sustainable steelheadpopulation in the Upper Alameda Creek Basin through provision of fish passage at ACDD is assessedqualitatively based on literature review of similar passage projects, analysis of existing data, andapplication of basic ecological theory. While the data required to make an accurate assessment of thepotential for sustainability are not available, this rough analysis provides some preliminary indicationof the potential for a steelhead population above ACDD to achieve sustainability. The assessmentconsidered fish survival during fresh water residency, the amount of spawning and juvenile rearinghabitat that passage would make accessible, the ability of adults to immigrate to newly availablespawning habitat, the ability of juveniles to emigrate from upstream rearing habitat, and maintaining aminimum viable population size. Success is defined as the ability for fish passage and associatedfacilities to maintain a sustainable population of anadromous steelhead in the Upper Alameda CreekBasin, but the potential for passage to contribute to a steelhead metapopulation in the greaterAlameda Creek Watershed is also considered.ACDD Passage June 2009 Page 6-2